Voltage-variable capacitor doesn't work in LTSpice

Joerg

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Mar 16, 2015, 8:26:49 PM3/16/15

to

Gentlemen,

Setting up voltage-controlled resistors is easy: R=(V(X)+0.01) or
whatever. Works, always did. Doing the same with a capacitor fails with
this error message:

Error on line 6 : c1 n002 0 c=(v(x)+0.01)
Unable to find definition of model "c"

* Unknown parameter "x"
WARNING: Less than two connections to node X. This node is used by V4.
Fatal Error: Missing capacitance value for "C1"

Both sims attached. What gives? Ideas how to make it work? Disregard the
values that wouldn't make sense for the cap here, this is just to find
the principal reason why the control method doesn't work with capacitors.

Variable resistor:

Version 4
SHEET 1 880 680
WIRE -80 -32 -256 -32
WIRE 64 -32 0 -32
WIRE 320 -32 64 -32
WIRE 64 0 64 -32
WIRE -640 16 -640 -48
WIRE -256 16 -256 -32
WIRE 320 16 320 -32
WIRE -640 112 -640 96
WIRE -256 112 -256 96
WIRE 64 112 64 80
WIRE 320 112 320 80
FLAG -256 112 0
FLAG -640 112 0
FLAG -640 -48 X
FLAG 64 112 0
FLAG 320 112 0
SYMBOL voltage -256 0 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value 2.048
SYMBOL res 48 -16 R0
SYMATTR InstName R1
SYMATTR Value R=(V(X)+0.01)
SYMBOL res -96 -16 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R2
SYMATTR Value 2.49k
SYMBOL voltage -640 0 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V4
SYMATTR Value PULSE(0 1 1n 1m 2m 1m 5m 1)
SYMBOL cap 304 16 R0
SYMATTR InstName C1
SYMATTR Value 1p
TEXT -472 -96 Left 2 !.tran 5m

Variable capacitor:

Version 4
SHEET 1 880 680
WIRE -80 -32 -256 -32
WIRE 64 -32 0 -32
WIRE 320 -32 64 -32
WIRE 64 0 64 -32
WIRE -640 16 -640 -48
WIRE -256 16 -256 -32
WIRE 320 16 320 -32
WIRE -640 112 -640 96
WIRE -256 112 -256 96
WIRE 64 112 64 80
WIRE 320 112 320 80
FLAG -256 112 0
FLAG -640 112 0
FLAG -640 -48 X
FLAG 64 112 0
FLAG 320 112 0
SYMBOL voltage -256 0 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value 2.048
SYMBOL res 48 -16 R0
SYMATTR InstName R1
SYMATTR Value 100k
SYMBOL res -96 -16 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R2
SYMATTR Value 2.49k
SYMBOL voltage -640 0 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V4
SYMATTR Value PULSE(0 1 1n 1m 2m 1m 5m 1)
SYMBOL cap 304 16 R0
SYMATTR InstName C1
SYMATTR Value C=(V(X)+0.01)
TEXT -472 -96 Left 2 !.tran 5m

--
Regards, Joerg

http://www.analogconsultants.com/

Jim Thompson

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Mar 16, 2015, 8:48:16 PM3/16/15

to

On Mon, 16 Mar 2015 17:26:44 -0700, Joerg <ne...@analogconsultants.com>
wrote:

>Gentlemen,
>
>Setting up voltage-controlled resistors is easy: R=(V(X)+0.01) or
>whatever. Works, always did. Doing the same with a capacitor fails with
>this error message:
>
>Error on line 6 : c1 n002 0 c=(v(x)+0.01)
> Unable to find definition of model "c"
>
> * Unknown parameter "x"
>WARNING: Less than two connections to node X. This node is used by V4.
>Fatal Error: Missing capacitance value for "C1"
>
>Both sims attached. What gives? Ideas how to make it work? Disregard the
>values that wouldn't make sense for the cap here, this is just to find
>the principal reason why the control method doesn't work with capacitors.
>
>
>Variable resistor:
>

John Larkin

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Mar 16, 2015, 8:54:40 PM3/16/15

to

On Mon, 16 Mar 2015 17:26:44 -0700, Joerg <ne...@analogconsultants.com>
wrote:

>Gentlemen,
>
>Setting up voltage-controlled resistors is easy: R=(V(X)+0.01) or
>whatever. Works, always did. Doing the same with a capacitor fails with
>this error message:
>
>Error on line 6 : c1 n002 0 c=(v(x)+0.01)
> Unable to find definition of model "c"
>
> * Unknown parameter "x"
>WARNING: Less than two connections to node X. This node is used by V4.
>Fatal Error: Missing capacitance value for "C1"
>
>Both sims attached. What gives? Ideas how to make it work? Disregard the
>values that wouldn't make sense for the cap here, this is just to find
>the principal reason why the control method doesn't work with capacitors.
>
>

Here's one I did a while back... can't remember why.

https://dl.dropboxusercontent.com/u/53724080/Circuits/Caps/Nonlin_Cap_Sweep.asc

What's annoying is that Q is a function of voltage, not C.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

Joerg

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Mar 17, 2015, 10:29:15 AM3/17/15

to

On 2015-03-16 5:48 PM, Jim Thompson wrote:
> On Mon, 16 Mar 2015 17:26:44 -0700, Joerg <ne...@analogconsultants.com>
> wrote:
>
>> Gentlemen,
>>
>> Setting up voltage-controlled resistors is easy: R=(V(X)+0.01) or
>> whatever. Works, always did. Doing the same with a capacitor fails with
>> this error message:
>>
>> Error on line 6 : c1 n002 0 c=(v(x)+0.01)
>> Unable to find definition of model "c"
>>
>> * Unknown parameter "x"
>> WARNING: Less than two connections to node X. This node is used by V4.
>> Fatal Error: Missing capacitance value for "C1"
>>
>> Both sims attached. What gives? Ideas how to make it work? Disregard the
>> values that wouldn't make sense for the cap here, this is just to find
>> the principal reason why the control method doesn't work with capacitors.
>>
>>
>> Variable resistor:
>>
> [snip]
>
> See VVC.zip and VVR.zip on the Device Models & Subcircuits Page of my
> website for the proper notation.
>

One is Altium and on PSpice. I checked the VVC for Altium in Notepad
(can't open it in the viewer) but it seems it's only a LUT version. I
need a real voltage control.

Joerg

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Mar 17, 2015, 10:30:52 AM3/17/15

to

On 2015-03-16 5:54 PM, John Larkin wrote:
> On Mon, 16 Mar 2015 17:26:44 -0700, Joerg <ne...@analogconsultants.com>
> wrote:
>
>> Gentlemen,
>>
>> Setting up voltage-controlled resistors is easy: R=(V(X)+0.01) or
>> whatever. Works, always did. Doing the same with a capacitor fails with
>> this error message:
>>
>> Error on line 6 : c1 n002 0 c=(v(x)+0.01)
>> Unable to find definition of model "c"
>>
>> * Unknown parameter "x"
>> WARNING: Less than two connections to node X. This node is used by V4.
>> Fatal Error: Missing capacitance value for "C1"
>>
>> Both sims attached. What gives? Ideas how to make it work? Disregard the
>> values that wouldn't make sense for the cap here, this is just to find
>> the principal reason why the control method doesn't work with capacitors.
>>
>>
>
> Here's one I did a while back... can't remember why.
>
> https://dl.dropboxusercontent.com/u/53724080/Circuits/Caps/Nonlin_Cap_Sweep.asc
>
> What's annoying is that Q is a function of voltage, not C.
>
>

Yes, I'd rather control C directly with a voltage. Why does LTSpice
refuse this? Maybe I'll have to ask over at the Yahoo forum, after
figuring out the dreaded login there. With that was a NG as well.

John Larkin

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Mar 17, 2015, 11:22:57 AM3/17/15

to

On Tue, 17 Mar 2015 07:30:53 -0700, Joerg <ne...@analogconsultants.com>
wrote:

I used to use ECA under DOS, a great netlist-based simulator. It
always converged and cruised through divide-by-zero and other errors.
It let you express any voltage, current, or R/L/C value as a simple
expression of anything else.

--

John Larkin Highland Technology, Inc

picosecond timing laser drivers and controllers

Jim Thompson

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Mar 17, 2015, 11:28:49 AM3/17/15

to

On Tue, 17 Mar 2015 07:29:15 -0700, Joerg <ne...@analogconsultants.com>
wrote:

Sorry. I had forgotten that "VVC" is a varicap model.

"Real" voltage control is trivial to do. Tell me the desired
expression... C = f(V) and I'll knock it for you in a few minutes ;-)

Joerg

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Mar 17, 2015, 1:14:29 PM3/17/15

to

ECA224 was a great little simulator. I loved it. When starting
self-employed in 1989 I bought a PSpice license. I still have the
cloth-covered binders, IBM-style. Those were the days when I entered a
SPICE schematic in ASCII, pounding out the netlist in IBM EasyWriter. It
felt real manly just like cooking over wood fire. Scared clients though
because they couldn't see the schematic.

John Larkin

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Mar 17, 2015, 1:27:31 PM3/17/15

to

On Tue, 17 Mar 2015 10:14:30 -0700, Joerg <ne...@analogconsultants.com>

Here's an ECA netlist. I may have the hand-drawn schematic around here
somewhere. It would be a nuisance to reverse-engineer it from the
netlist.

' VARIAN L701 GRADIENT DRIVER MODEL L701.CKT
'
' BY JOHN LARKIN
' HIGHLAND TECHNOLOGY, INC
' SAN FRANCISCO
'
' SEPTEMBER 15, 1993
'
' THIS VERSION INCLUDES...
'
' 3 AMP PEAK DRIVE
' SIMPLE TRANSCONDUCTANCE OUTPUT STAGE
' WITH THERMAL TAILS
'
' FIRST, DO THE AD1862 20-BIT DAC...
'
VDAC 0 0 -3
RDAC 1 0 1u
'
' HERE'S THE SHUNT AND PREAMP...
' SHUNT .05R X GAIN 20 = 1V/AMP
'
R10 10 0 .05
U2 10 12 OP278
* 11 0
R11 11 12 1900.013
R12 12 0 100
'
' AND THE ERROR AMP...
'
U3 0 15 OP278
* 20 0
R5 1 15 2K
R13 11 15 2K
'
' LOOP COMPENSATION PARTS...
'
RZ 15 16 10K
CZ 16 20 1.5N
'
' THIS IS THE OUTPUT TRANSCONDUCTANCE AMP...
' R21:C21 IS 15 KHZ ROLLOFF
' TRANSCONDUCTANCE IS 3 AMPS/10 VOLTS = 0.3 SIEMENS
'
R21 20 21 1K
C21 21 0 15N
IAMP 21 0 0.3
RAMP 30 0 10K

' SIMULATE THE THERMAL HOOK OF THE OUTPUT
' DARLINGTON. ASSUME...
'
' CHIP THERMAL TAU = 20 mSEC
' THETA = 2 DEGC/WATT
' POWER PULSE = 25 WATTS
' EMITTER RESISTOR = 1 OHM
' TRANSISTOR VBE 5 mV/DEGC
' THERMAL HOOK 250 mV/3V = 1/12

R90 21 90 12K
C90 90 0 2U

'
' AND THE GRADIENT COIL LOAD...
'
LM 30 31 15U
RM 31 10 1.2

--

John Larkin Highland Technology, Inc

picosecond timing precision measurement

Jim Thompson

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Mar 17, 2015, 2:31:52 PM3/17/15

to

On Tue, 17 Mar 2015 10:14:30 -0700, Joerg <ne...@analogconsultants.com>
wrote:

[snip].

>>
>
>ECA224 was a great little simulator. I loved it. When starting
>self-employed in 1989 I bought a PSpice license. I still have the
>cloth-covered binders, IBM-style. Those were the days when I entered a
>SPICE schematic in ASCII, pounding out the netlist in IBM EasyWriter. It
>felt real manly just like cooking over wood fire. Scared clients though
>because they couldn't see the schematic.

I started out with Berkeley Spice on a VAX, pencil-drawn schematics,
number the nodes, write the netlist with a text editor... my son
Aaron, while still a teenager (now 45 :-), wrote me a netlist version
control so I could back up to a previous netlist easily if I made a
change that malfunctioned.

When PSpice first came out I continued that procedure until MicroSim
Schematics arrived, which I still use to this day. I absolutely hated
OrCAD Crapture.

Jim Thompson

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Mar 17, 2015, 4:06:40 PM3/17/15

to

On Mon, 16 Mar 2015 17:26:44 -0700, Joerg <ne...@analogconsultants.com>
wrote:

[snip]

Here you go...

.SUBCKT VControlledCap CAP+ CAP- VC+ VC- PARAMS: C1=1nF C2=100pF
C_C1 CAP+ N_1 {C1}
R_NOF1 VC+ 0 1G
R_NOF2 VC- 0 1G
V_IM1 N_1 CAP- 0
G_G2 CAP+ CAP- VALUE {C2/C1*V(VC+,VC-)*I(V_IM1)}
.ENDS VControlledCap

When VC=,VC1 is zero, cap value is C1

When VC=,VC1=+1, cap value is C1+C2

When VC=,VC1=-1, cap value is C1-C2

I'll post this to my website in a few days... honey-do projects abound
;-)

Jim Thompson

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Mar 17, 2015, 4:24:39 PM3/17/15

to

On Tue, 17 Mar 2015 13:06:35 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Mon, 16 Mar 2015 17:26:44 -0700, Joerg <ne...@analogconsultants.com>
>wrote:
>
>[snip]
>
>Here you go...
>
>.SUBCKT VControlledCap CAP+ CAP- VC+ VC- PARAMS: C1=1nF C2=100pF
>C_C1 CAP+ N_1 {C1}
>R_NOF1 VC+ 0 1G
>R_NOF2 VC- 0 1G
>V_IM1 N_1 CAP- 0
>G_G2 CAP+ CAP- VALUE {C2/C1*V(VC+,VC-)*I(V_IM1)}
>.ENDS VControlledCap
>
>When VC=,VC1 is zero, cap value is C1
>
>When VC=,VC1=+1, cap value is C1+C2
>
>When VC=,VC1=-1, cap value is C1-C2
>
>I'll post this to my website in a few days... honey-do projects abound
>;-)
>
> ...Jim Thompson

Typos galore, lagging/leading shift key, text should say...

When VC+,VC- is zero, cap value is C1

When VC+,VC- = +1, cap value is C1+C2

When VC+,VC- = -1, cap value is C1-C2

Joerg

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Mar 17, 2015, 8:04:43 PM3/17/15

to

On 2015-03-17 1:24 PM, Jim Thompson wrote:
> On Tue, 17 Mar 2015 13:06:35 -0700, Jim Thompson
> <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>
>> On Mon, 16 Mar 2015 17:26:44 -0700, Joerg <ne...@analogconsultants.com>
>> wrote:
>>
>> [snip]
>>
>> Here you go...
>>
>> .SUBCKT VControlledCap CAP+ CAP- VC+ VC- PARAMS: C1=1nF C2=100pF
>> C_C1 CAP+ N_1 {C1}
>> R_NOF1 VC+ 0 1G
>> R_NOF2 VC- 0 1G
>> V_IM1 N_1 CAP- 0
>> G_G2 CAP+ CAP- VALUE {C2/C1*V(VC+,VC-)*I(V_IM1)}
>> .ENDS VControlledCap
>>
>> When VC=,VC1 is zero, cap value is C1
>>
>> When VC=,VC1=+1, cap value is C1+C2
>>
>> When VC=,VC1=-1, cap value is C1-C2
>>
>> I'll post this to my website in a few days... honey-do projects abound
>> ;-)
>>
>> ...Jim Thompson
>
> Typos galore, lagging/leading shift key, text should say...
>
> When VC+,VC- is zero, cap value is C1
>
> When VC+,VC- = +1, cap value is C1+C2
>
> When VC+,VC- = -1, cap value is C1-C2
>

Thanks, Jim. Couldn't make a go of it yet, it errors with "Port(pin)
count mismatch between the definition of subcircuit "vcontrolledcap" and
instance: "xc1" ... The instance has fewer connection terminals than the
definition"

Jim Thompson

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Mar 17, 2015, 9:19:43 PM3/17/15

to

On Tue, 17 Mar 2015 17:04:42 -0700, Joerg <ne...@analogconsultants.com>
wrote:

Read the help files about how to make a symbol in LTspice by
highlighting the .subckt line.

John Larkin

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Mar 17, 2015, 10:05:10 PM3/17/15

to

On Tue, 17 Mar 2015 17:04:42 -0700, Joerg <ne...@analogconsultants.com>
wrote:

I bet you could build a variable c-multiplier with a capacitor and a
multiplier, or an e source with the right expression.

--

John Larkin Highland Technology, Inc

picosecond timing laser drivers and controllers

Ralph Barone

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Mar 17, 2015, 10:22:18 PM3/17/15

to

If you dynamically change the value of a capacitor, do you end up with
discontinuities in the stores charge on that cap?

John Larkin

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Mar 17, 2015, 10:44:27 PM3/17/15

to

I guess the only way to change the voltage across a voltage-dependant
capacitor is to apply current, which takes power, so energy is
conserved. A varicap doesn't violate conservation of energy.

If a c value depended on something independent of the terminal
voltage, you could apparently violate COE. Imagine a charged
parallel-plate capacitor connected to nothing. If you yank (yank!) the
plates apart, c goes down, Q is conserved, V goes up, and more energy
is stored in the cap. Pulling the plates apart took mechanical work,
which is where the added energy came from.

In my proposed c-multiplier, the e source can do work.

Joerg

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Mar 18, 2015, 10:09:55 AM3/18/15

to

Guys, I do not want to change the capacitance by changing the voltage at
the cap terminals. I want to change the capacitance by a mathematical
expression where the control function is a rail (or a voltage) in some
other distant land in the schematic. I still do not understand why this
works perfectly for a resistor value but it does not for a capacitor
value. For the resistor I do not have to make some other model with more
terminals, I can just key in expressions such as "R=V(X)" in the value
field where X is a rail somewhere else that I assign the label "X".

Jim Thompson

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Mar 18, 2015, 11:32:43 AM3/18/15

to

On Tue, 17 Mar 2015 17:04:42 -0700, Joerg <ne...@analogconsultants.com>
wrote:

To learn how to do this, search LTspice Help for "automatic symbol"...

VControlledCap.asy

Version 4
SymbolType BLOCK
RECTANGLE Normal -64 -40 80 40
WINDOW 0 8 -40 Bottom 2
WINDOW 3 8 40 Top 2
WINDOW 39 8 64 Top 2
SYMATTR Prefix X
SYMATTR Value VControlledCap
SYMATTR ModelFile C:\Projects\Expments\BehavioralComponents\ASY Copy
of VControlledCap.net
SYMATTR SpiceLine C1=1nF C2=100pF
PIN -64 -16 LEFT 8
PINATTR PinName CAP+
PINATTR SpiceOrder 1
PIN -64 16 LEFT 8
PINATTR PinName CAP-
PINATTR SpiceOrder 2
PIN 80 -16 RIGHT 8
PINATTR PinName VC+
PINATTR SpiceOrder 3
PIN 80 16 RIGHT 8
PINATTR PinName VC-
PINATTR SpiceOrder 4

Jim Thompson

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Mar 18, 2015, 11:35:15 AM3/18/15

to

On Wed, 18 Mar 2015 07:09:56 -0700, Joerg <ne...@analogconsultants.com>
wrote:

[snip]
>>
>

>Guys, I do not want to change the capacitance by changing the voltage at
>the cap terminals. I want to change the capacitance by a mathematical
>expression where the control function is a rail (or a voltage) in some
>other distant land in the schematic. I still do not understand why this
>works perfectly for a resistor value but it does not for a capacitor
>value. For the resistor I do not have to make some other model with more
>terminals, I can just key in expressions such as "R=V(X)" in the value
>field where X is a rail somewhere else that I assign the label "X".

My previously posted subcircuit VControlledCap does exactly as you
want.

I have just now posted VControlledCap.asy so you can get the pinout
correct >:-}

Jim Thompson

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Mar 18, 2015, 12:29:11 PM3/18/15

to

Voltage-Controlled Capacitor Spice Model now on my website.

See VControlledCap.zip on the Device Models & Subcircuits Page.

Includes Library File (.LIB), LTspice Symbol (.ASY), and a JPEG
showing how it was developed.

John Larkin

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Mar 18, 2015, 1:31:13 PM3/18/15

to

On Wed, 18 Mar 2015 09:28:57 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>Voltage-Controlled Capacitor Spice Model now on my website.
>
>See VControlledCap.zip on the Device Models & Subcircuits Page.
>
>Includes Library File (.LIB), LTspice Symbol (.ASY), and a JPEG
>showing how it was developed.
>
> ...Jim Thompson

I don't have time to play with this just now, but one quick question:

Given that C is a variable capacitor, set C to 1F and charge it to 1
volt. Now change C to 0.5F. What is the new voltage?

--

John Larkin Highland Technology, Inc

picosecond timing precision measurement

DecadentLinuxUserNumeroUno

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Mar 18, 2015, 1:40:24 PM3/18/15

to

On Wed, 18 Mar 2015 10:30:44 -0700, John Larkin wrote:

> On Wed, 18 Mar 2015 09:28:57 -0700, Jim Thompson
> <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>
>>Voltage-Controlled Capacitor Spice Model now on my website.
>>
>>See VControlledCap.zip on the Device Models & Subcircuits Page.
>>
>>Includes Library File (.LIB), LTspice Symbol (.ASY), and a JPEG showing
>>how it was developed.
>>
>> ...Jim Thompson
>
> I don't have time to play with this just now, but one quick question:
>
> Given that C is a variable capacitor, set C to 1F and charge it to 1
> volt. Now change C to 0.5F. What is the new voltage?

How many 1 farad capacitors are you aware of?

Oh and would not a 1F charged cap dump into a 0.5F cap and fully charge
it? If that answer is yes, then the voltage would be the same...
slightly less even, all elements considered.

You thought it would morph the EMF into something else?

John Larkin

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Mar 18, 2015, 1:54:56 PM3/18/15

to

On Wed, 18 Mar 2015 17:40:06 +0000 (UTC), DecadentLinuxUserNumeroUno
<DL...@DecadentLinuxUser.org> wrote:

>On Wed, 18 Mar 2015 10:30:44 -0700, John Larkin wrote:
>
>> On Wed, 18 Mar 2015 09:28:57 -0700, Jim Thompson
>> <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>>
>>>Voltage-Controlled Capacitor Spice Model now on my website.
>>>
>>>See VControlledCap.zip on the Device Models & Subcircuits Page.
>>>
>>>Includes Library File (.LIB), LTspice Symbol (.ASY), and a JPEG showing
>>>how it was developed.
>>>
>>> ...Jim Thompson
>>
>> I don't have time to play with this just now, but one quick question:
>>
>> Given that C is a variable capacitor, set C to 1F and charge it to 1
>> volt. Now change C to 0.5F. What is the new voltage?
>
> How many 1 farad capacitors are you aware of?

In LT Spice, you can use any C value. 1F is the generic capacitor. I
usually normalize theoretical circuits to 1F, 1H, 1 ohm. [1]

In real life, Digikey will sell you 1F caps. Or 5000F caps. But not
variable 1F caps.

>
> Oh and would not a 1F charged cap dump into a 0.5F cap and fully charge
>it? If that answer is yes, then the voltage would be the same...
>slightly less even, all elements considered.
>
> You thought it would morph the EMF into something else?

I'd like to know if Jim's model conserves charge, or conserves energy,
or conserves voltage. Or whatever it does.

[1] I do find myself picking standard values, like 39nF instead of 40
nF, and worrying about leakage and stray capacitance and power
dissipation, when none of these matter in Spice.

Jim Thompson

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Mar 18, 2015, 2:33:44 PM3/18/15

to

On Wed, 18 Mar 2015 10:30:44 -0700, John Larkin

<jla...@highlandtechnology.com> wrote:

>On Wed, 18 Mar 2015 09:28:57 -0700, Jim Thompson
><To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>
>>Voltage-Controlled Capacitor Spice Model now on my website.
>>
>>See VControlledCap.zip on the Device Models & Subcircuits Page.
>>
>>Includes Library File (.LIB), LTspice Symbol (.ASY), and a JPEG
>>showing how it was developed.
>>
>> ...Jim Thompson
>
>I don't have time to play with this just now, but one quick question:
>
>Given that C is a variable capacitor, set C to 1F and charge it to 1
>volt. Now change C to 0.5F. What is the new voltage?

I haven't tried that. Since it _is_ a capacitor, it'll depend on
whether a simulator treats capacitors as charge-controlled devices or
otherwise.

Jim Thompson

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Mar 18, 2015, 2:53:39 PM3/18/15

to

Voltage-Controlled Resistor Spice Model Updated

See VVR.zip on the Device Models & Subcircuits Page of my website

Includes Library File (.LIB), LTspice Symbol (.ASY), PSpice Symbol
(.SYM)and a JPEG showing how it was developed.

Syd Rumpo

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Mar 18, 2015, 2:54:10 PM3/18/15

to

On 17/03/2015 00:26, Joerg wrote:
> Gentlemen,
>
> Setting up voltage-controlled resistors is easy: R=(V(X)+0.01) or
> whatever. Works, always did. Doing the same with a capacitor fails with
> this error message:
>
> Error on line 6 : c1 n002 0 c=(v(x)+0.01)
> Unable to find definition of model "c"
>
> * Unknown parameter "x"
> WARNING: Less than two connections to node X. This node is used by V4.
> Fatal Error: Missing capacitance value for "C1"
>
> Both sims attached. What gives? Ideas how to make it work? Disregard the
> values that wouldn't make sense for the cap here, this is just to find
> the principal reason why the control method doesn't work with capacitors.
>

<snip>

This is what I did for a time-varying capacitance. In the component
'Value' field, I put Q=(4p/(0.25 +(time*5)))*x which swept the
capacitance from 16pF downwards controlled by the internal variable 'time'.

I can't remember why you need the Q and the x, but you do, and it took a
good while to find out - it seems you can't just vary the capacitance
directly. Replace time with a voltage and the appropriate scaling and
you should be good to go.

Cheers
--
Syd

Joerg

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Mar 18, 2015, 4:36:27 PM3/18/15

to

Tried it and that completely bungled the linearity when the cap is
inside a resonant circuit. At least no more error messages which is
good. Well, maybe I just do it in hardware then, firing up the old
Weller. I'd have to buy a bag of varicaps but those are cheap.

John Larkin

unread,

Mar 18, 2015, 4:46:51 PM3/18/15

to

On Wed, 18 Mar 2015 13:36:27 -0700, Joerg <ne...@analogconsultants.com>
wrote:

Are you trying to sim a VCO? Simulating oscillators is always tedious.

You could use a diode model, which does include variable capacitance.

https://dl.dropboxusercontent.com/u/53724080/Circuits/Caps/Cap_Sweep.asc

Try to get the Skyworks sample kit. It has a lot of varicaps, and many
other cool things.

John Larkin

unread,

Mar 18, 2015, 5:00:51 PM3/18/15

to

On Wed, 18 Mar 2015 18:54:11 +0000, Syd Rumpo <use...@nononono.co.uk>
wrote:

Q is charge and X is the cap voltage.

Q = (expression) * X

just means that (expression) is the capacitance. Seems silly to me.

http://ltwiki.org/LTspiceHelp/LTspiceHelp/C_Capacitor.htm

I tried a capacitor that changes value abruptly at 0 volts, like the
example. That works. If I try to change C abruptly at a non-zero
voltage, the sim crashes. Some conservation thingie was violated.

Joerg

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Mar 18, 2015, 5:03:06 PM3/18/15

to

No, it's a circuit where a capacitive sensor is employed and I want to
mimic the sensor output. The capacitor itself will be inside a somewhat
resonant circuit so it has to behave like a real and clean capacitor.

> You could use a diode model, which does include variable capacitance.
>
> https://dl.dropboxusercontent.com/u/53724080/Circuits/Caps/Cap_Sweep.asc
>

But that's a voltage-controlled voltage source. I'd need a real cap.

> Try to get the Skyworks sample kit. It has a lot of varicaps, and many
> other cool things.
>

I'd need the old AM tuning diodes, tons of capacitance. What I need is a
variable range of several hunded pF around a base of 1000pF or slightly
above. Or I have to make Jim's method work but so far no luck. Could
have to do with the durn Windows 7 restrictive file writing "privileges".

If we had all our hardware going I wouldn't need this. It is intended to
give a SW engineer a fake signal in file format that he can plug into
his algorithms so he doesn't have to wait for HW to be done.

I can somehow kludge it with a voltage-variable resistor because in
contrast to capacitors that works in LTSpice. But it won't be pretty.

Lasse Langwadt Christensen

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Mar 18, 2015, 5:13:08 PM3/18/15

to

http://powerelectronics.com/site-files/powerelectronics.com/files/archive/powerelectronics.com/mag/504PET07.pdf

-Lasse

Jim Thompson

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Mar 18, 2015, 5:15:25 PM3/18/15

to

On Wed, 18 Mar 2015 14:03:07 -0700, Joerg <ne...@analogconsultants.com>
wrote:

[snip]
>>
>

>No, it's a circuit where a capacitive sensor is employed and I want to
>mimic the sensor output. The capacitor itself will be inside a somewhat
>resonant circuit so it has to behave like a real and clean capacitor.
>
>

[snip]

I take it you haven't tried my subcircuit?

Jim Thompson

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Mar 18, 2015, 5:17:47 PM3/18/15

to

On Wed, 18 Mar 2015 14:13:02 -0700 (PDT), Lasse Langwadt Christensen
<lang...@fonz.dk> wrote:

[snip]
>
>http://powerelectronics.com/site-files/powerelectronics.com/files/archive/powerelectronics.com/mag/504PET07.pdf
>
>-Lasse

Same way I did my varicap models and Joerg's voltage variable one.
(The varicap model uses a Table to handle the non-linearity of a
varicap.)

Joerg

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Mar 18, 2015, 5:44:36 PM3/18/15

to

On 2015-03-18 2:15 PM, Jim Thompson wrote:
> On Wed, 18 Mar 2015 14:03:07 -0700, Joerg <ne...@analogconsultants.com>
> wrote:
>
> [snip]
>>>
>>
>> No, it's a circuit where a capacitive sensor is employed and I want to
>> mimic the sensor output. The capacitor itself will be inside a somewhat
>> resonant circuit so it has to behave like a real and clean capacitor.
>>
>>
> [snip]
>
> I take it you haven't tried my subcircuit?
>

I have not given up yet but so far I got all kinds of error messages.
The next step would be to try it on an XP machine where I'd have to get
LTSpice going again. XP was IMHO the last known good OS and I've had
error message in other software caused by Windows 7 (meaning they didn't
happen on an XP machine).

Jim Thompson

unread,

Mar 18, 2015, 5:50:14 PM3/18/15

to

On Wed, 18 Mar 2015 14:44:39 -0700, Joerg <ne...@analogconsultants.com>
wrote:

What kind of error messages?

If you use the LTspice _symbol_ I made, you need to open the .ASY file
with a text editor and change the path to wherever you've located the
subcircuit definition library.

The latest version, on the website, shows how more clearly.

John Larkin

unread,

Mar 18, 2015, 5:56:08 PM3/18/15

to

On Wed, 18 Mar 2015 14:03:07 -0700, Joerg <ne...@analogconsultants.com>

Would something like this work?

https://dl.dropboxusercontent.com/u/53724080/Circuits/Caps/Modulated_Cap_1.asc

The cap is modulated by voltage ZZ, which in this case makes the cap
ramp from 1F to 20F. That in turn sweeps the LC ringing frequency
down.

Jim Thompson

unread,

Mar 18, 2015, 7:14:48 PM3/18/15

to

On Wed, 18 Mar 2015 14:55:54 -0700, John Larkin
<jla...@highlandtechnology.com> wrote:

[snip]

>
>Would something like this work?
>
>https://dl.dropboxusercontent.com/u/53724080/Circuits/Caps/Modulated_Cap_1.asc
>
>The cap is modulated by voltage ZZ, which in this case makes the cap
>ramp from 1F to 20F. That in turn sweeps the LC ringing frequency
>down.

<http://www.analog-innovations.com/TankTest_Greenshot_2015-03-18_16-10-12.jpg>

Jim Thompson

unread,

Mar 18, 2015, 7:32:46 PM3/18/15

to

On Wed, 18 Mar 2015 16:14:44 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Wed, 18 Mar 2015 14:55:54 -0700, John Larkin
><jla...@highlandtechnology.com> wrote:
>
>[snip]
>>
>>Would something like this work?
>>
>>https://dl.dropboxusercontent.com/u/53724080/Circuits/Caps/Modulated_Cap_1.asc
>>
>>The cap is modulated by voltage ZZ, which in this case makes the cap
>>ramp from 1F to 20F. That in turn sweeps the LC ringing frequency
>>down.
>
><http://www.analog-innovations.com/TankTest_Greenshot_2015-03-18_16-10-12.jpg>
>
> ...Jim Thompson

It would be trivial to add tabular data to this model to characterize
a non-linear transducer.

I just need to scratch my head and remember how to have a subcircuit
call external tabular data so I can make it a generalized transducer
model ;-)

Joerg

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Mar 18, 2015, 7:34:08 PM3/18/15

to

On 2015-03-18 2:50 PM, Jim Thompson wrote:
> On Wed, 18 Mar 2015 14:44:39 -0700, Joerg <ne...@analogconsultants.com>
> wrote:
>
>> On 2015-03-18 2:15 PM, Jim Thompson wrote:
>>> On Wed, 18 Mar 2015 14:03:07 -0700, Joerg <ne...@analogconsultants.com>
>>> wrote:
>>>
>>> [snip]
>>>>>
>>>>
>>>> No, it's a circuit where a capacitive sensor is employed and I want to
>>>> mimic the sensor output. The capacitor itself will be inside a somewhat
>>>> resonant circuit so it has to behave like a real and clean capacitor.
>>>>
>>>>
>>> [snip]
>>>
>>> I take it you haven't tried my subcircuit?
>>>
>>
>> I have not given up yet but so far I got all kinds of error messages.
>> The next step would be to try it on an XP machine where I'd have to get
>> LTSpice going again. XP was IMHO the last known good OS and I've had
>> error message in other software caused by Windows 7 (meaning they didn't
>> happen on an XP machine).
>
> What kind of error messages?
>
> If you use the LTspice _symbol_ I made, you need to open the .ASY file
> with a text editor and change the path to wherever you've located the
> subcircuit definition library.
>

And there is the first problem. Windows 7 no longer allows writes to the
program directories. Well, it does but secretly stashes them some place
else but then access become an issue. I'll get to the ground of that,
hav to for my CAD as well, just not right now. The usual, swamped in
work plus honey-do stuff.

And, we had to get a Mexican Burger at one of our favorite watering
holes. Along with an Old Republic red ale.

> The latest version, on the website, shows how more clearly.
>
> ...Jim Thompson
>

--

Regards, Joerg

http://www.analogconsultants.com/

Jim Thompson

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Mar 18, 2015, 7:38:45 PM3/18/15

to

On Wed, 18 Mar 2015 16:34:10 -0700, Joerg <ne...@analogconsultants.com>

wrote:

>On 2015-03-18 2:50 PM, Jim Thompson wrote:
>> On Wed, 18 Mar 2015 14:44:39 -0700, Joerg <ne...@analogconsultants.com>
>> wrote:

[snip]

>>>
>>> I have not given up yet but so far I got all kinds of error messages.
>>> The next step would be to try it on an XP machine where I'd have to get
>>> LTSpice going again. XP was IMHO the last known good OS and I've had
>>> error message in other software caused by Windows 7 (meaning they didn't
>>> happen on an XP machine).
>>
>> What kind of error messages?
>>
>> If you use the LTspice _symbol_ I made, you need to open the .ASY file
>> with a text editor and change the path to wherever you've located the
>> subcircuit definition library.
>>
>
>And there is the first problem. Windows 7 no longer allows writes to the
>program directories.

I have LTspice installed in a directory outside of Program Files. I
haven't "upgraded" to Win7 yet. I hope I can still get away with
that.

>Well, it does but secretly stashes them some place
>else but then access become an issue. I'll get to the ground of that,
>hav to for my CAD as well, just not right now. The usual, swamped in
>work plus honey-do stuff.

I appreciate the problem ;-)

>
>And, we had to get a Mexican Burger at one of our favorite watering
>holes. Along with an Old Republic red ale.

Aha! The most important interruption >:-}

>
>
>> The latest version, on the website, shows how more clearly.
>>
>> ...Jim Thompson
>>

Joerg

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Mar 18, 2015, 7:39:37 PM3/18/15

to

Thanks, John, that actually seems to work. Beats me why mine didn't
because the only difference was that I called "ZZ" "Y" instead.

John Larkin

unread,

Mar 18, 2015, 7:46:48 PM3/18/15

to

On Wed, 18 Mar 2015 16:39:38 -0700, Joerg <ne...@analogconsultants.com>

Well, that's what you need an expert for!

It may matter about whitespace in the Q equation; it doesn't seem to
like any.

Well, I may find this useful in the future.

George Herold

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Mar 18, 2015, 7:47:53 PM3/18/15

to

Well, energy conservation seems silly... if you are changing C,
moving plates around, someone has to provide the energy.
And I assume charge or voltage depends on how it's hooked up.

George H.

Joerg

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Mar 18, 2015, 8:02:37 PM3/18/15

to

On 2015-03-18 4:38 PM, Jim Thompson wrote:
> On Wed, 18 Mar 2015 16:34:10 -0700, Joerg <ne...@analogconsultants.com>
> wrote:
>
>> On 2015-03-18 2:50 PM, Jim Thompson wrote:
>>> On Wed, 18 Mar 2015 14:44:39 -0700, Joerg <ne...@analogconsultants.com>
>>> wrote:
> [snip]
>>>>
>>>> I have not given up yet but so far I got all kinds of error messages.
>>>> The next step would be to try it on an XP machine where I'd have to get
>>>> LTSpice going again. XP was IMHO the last known good OS and I've had
>>>> error message in other software caused by Windows 7 (meaning they didn't
>>>> happen on an XP machine).
>>>
>>> What kind of error messages?
>>>
>>> If you use the LTspice _symbol_ I made, you need to open the .ASY file
>>> with a text editor and change the path to wherever you've located the
>>> subcircuit definition library.
>>>
>>
>> And there is the first problem. Windows 7 no longer allows writes to the
>> program directories.
>
> I have LTspice installed in a directory outside of Program Files. I
> haven't "upgraded" to Win7 yet. I hope I can still get away with
> that.
>

Win 7 is a royal pain in the you-know-what. I needed a new PC because of
simulation speed and they didn't offer XP anymore :-(

>> Well, it does but secretly stashes them some place
>> else but then access become an issue. I'll get to the ground of that,
>> hav to for my CAD as well, just not right now. The usual, swamped in
>> work plus honey-do stuff.
>
> I appreciate the problem ;-)
>
>>
>> And, we had to get a Mexican Burger at one of our favorite watering
>> holes. Along with an Old Republic red ale.
>
> Aha! The most important interruption >:-}
>

Yeah, but now I have to bicycle lots of extra miles to work off the
calories.

>>
>>
>>> The latest version, on the website, shows how more clearly.
>>>

Thanks. I'll still try that but meantime John's version worked on my PC.
It doesn't need any custom symbols. I originally tried it almost the
same way but mine produced error messages while John's doesn't.

Lasse Langwadt Christensen

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Mar 18, 2015, 8:03:49 PM3/18/15

to

tried right-click "run as administrator" ?

you can put stuff the program directory you just have to copy and say yes to a UAC prompt

-Lasse

Joerg

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Mar 18, 2015, 8:05:25 PM3/18/15

to

Yup :-)

> It may matter about whitespace in the Q equation; it doesn't seem to
> like any.
>
> Well, I may find this useful in the future.
>

I think I know what it could have been. I had a voltage rail called "X"
left in the schematic and it must have not liked that.

Joerg

unread,

Mar 18, 2015, 8:18:53 PM3/18/15

to

I did that and then it put it into some extra directory and marked the
file with a yellow padlock. I can't stand such behavior of an OS that MS
calls "professional".

Jim Thompson

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Mar 18, 2015, 8:25:50 PM3/18/15

to

The simulation I posted ala Joerg's transducer demonstrates energy
changes (AM modulation) and the FM modulation you'd expect from the
capacitor changing value.

I'm musing how to set up an old fashioned "pump" frequency multiplier
;-)

Ralph Barone

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Mar 18, 2015, 10:19:11 PM3/18/15

to

Which is where I was heading with my question about conservation of charge.
Perhaps changing the capacitance breaks something inside the sim related to
continuity of charge.

Ralph Barone

unread,

Mar 18, 2015, 10:19:11 PM3/18/15

to

Jim Thompson <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
> On Wed, 18 Mar 2015 14:03:07 -0700, Joerg <ne...@analogconsultants.com>
> wrote:
>
> [snip]
>>>
>>
>> No, it's a circuit where a capacitive sensor is employed and I want to
>> mimic the sensor output. The capacitor itself will be inside a somewhat
>> resonant circuit so it has to behave like a real and clean capacitor.
>>
>>
> [snip]
>
> I take it you haven't tried my subcircuit?
>
> ...Jim Thompson

Jim, can I assume that your subcircuit switches capacitance between two
values based on a voltage? I suspect Joerg's desire is for something that
is a mite less "binary".

John Larkin

unread,

Mar 18, 2015, 11:56:58 PM3/18/15

to

On Wed, 18 Mar 2015 17:05:28 -0700, Joerg <ne...@analogconsultants.com>

Try this one:

https://dl.dropboxusercontent.com/u/53724080/Circuits/Caps/Modulated_Cap_2.asc

the peak inductor current triples from start to end, so the stored
energy in the tank goes up almost 10:1.

--

John Larkin Highland Technology, Inc

picosecond timing laser drivers and controllers

Jasen Betts

unread,

Mar 19, 2015, 2:01:01 AM3/19/15

to

On 2015-03-18, DecadentLinuxUserNumeroUno <DL...@DecadentLinuxUser.org> wrote:
> On Wed, 18 Mar 2015 10:30:44 -0700, John Larkin wrote:
>
>> On Wed, 18 Mar 2015 09:28:57 -0700, Jim Thompson
>> <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>>
>>>Voltage-Controlled Capacitor Spice Model now on my website.
>>>
>>>See VControlledCap.zip on the Device Models & Subcircuits Page.
>>>
>>>Includes Library File (.LIB), LTspice Symbol (.ASY), and a JPEG showing
>>>how it was developed.
>>>
>>> ...Jim Thompson
>>
>> I don't have time to play with this just now, but one quick question:
>>
>> Given that C is a variable capacitor, set C to 1F and charge it to 1
>> volt. Now change C to 0.5F. What is the new voltage?
>
> How many 1 farad capacitors are you aware of?

I've seen maybe 10 or 20 examples for sale retail. seen adverts for more.

> Oh and would not a 1F charged cap dump into a 0.5F cap and fully charge
> it? If that answer is yes, then the voltage would be the same...
> slightly less even, all elements considered.

"change", not "charge"

> You thought it would morph the EMF into something else?

conservation of matter and all that.

--
umop apisdn

John Larkin

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Mar 19, 2015, 11:37:10 AM3/19/15

to

I you make an instantaneous change in C, LT Spice conserves charge, so
doesn't conserve energy. Spice doesn't need to conserve energy.

Joerg

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Mar 19, 2015, 4:30:43 PM3/19/15

to

That probably only works in the cyber world :-)

> I you make an instantaneous change in C, LT Spice conserves charge, so
> doesn't conserve energy. Spice doesn't need to conserve energy.
>

SPICE has weirdnesses. When I tried to massage the stimulus pulse for
the cap values using LC the capacitor action flatlined. The stimulus
itself looks ok, it's just that the formula in the cap seems to choke.
So I had to restrict it to RC. Beats me why but for now it's good enough.

Thanks again for all the hints. I got it to run and produce a useful WAV
output for the software engineer. 60 cardiac cycles. Ba-bump .. ba-bump
.. ba-bump .. ba-bump .. ba-bump ............... *BEEEEEEEEEP* .... just
kidding ...

John Larkin

unread,

Mar 19, 2015, 5:55:45 PM3/19/15

to

On Thu, 19 Mar 2015 13:30:47 -0700, Joerg <ne...@analogconsultants.com>

This is fun:

https://dl.dropboxusercontent.com/u/53724080/Circuits/Current_Sources/Isink_NAN.asc

LTS doesn't mind zero value resistors or caps, but it doesn't like L=0
in this circuit.

--

John Larkin Highland Technology, Inc

picosecond timing precision measurement

Tom Swift

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Mar 19, 2015, 6:41:57 PM3/19/15

to

Joerg <ne...@analogconsultants.com> wrote:

[...]

> Thanks again for all the hints. I got it to run and produce a useful
> WAV output for the software engineer. 60 cardiac cycles. Ba-bump ..
> ba-bump .. ba-bump .. ba-bump .. ba-bump ............... *BEEEEEEEEEP*
> .... just kidding ...

Another method might be to search google for 'heart sounds'. You will
find many examples of normal and abnormal sounds to work with. Find a
site that allows you to download the file in MP3 format, such as

http://depts.washington.edu/physdx/heart/demo.html

A normal heart sounds like

http://depts.washington.edu/physdx/audio/normal.mp3

Download it and listen in VLC to see if it's what you want. Then search
google for MP3 to WAV converters. Watch out for ones that want you to
download a 'download management' file. Skip those ones. There's a good
online site at

http://audioformat.com/mp3-to-wav

In this case, the normal.mp3 file is 154,227 bytes, and the WAV file is
850,220 bytes. There seems to be some mashup at the beginning, but
otherwise it sounds exactly like the MP3 file. You can probably edit it
and trim the part you want or extend it.

You can find all kinds of abnormalities to listen to. I have a young and
very pretty doctor who just gave me a complete physical. I have
absolutely no idea how she can memorize all those different sounds. There
are hundreds of them. But maybe you can put them in your device and have
them detected automatically.

Joerg

unread,

Mar 19, 2015, 7:57:14 PM3/19/15

to

On 2015-03-19 2:55 PM, John Larkin wrote:
> On Thu, 19 Mar 2015 13:30:47 -0700, Joerg <ne...@analogconsultants.com>
> wrote:
>
>> On 2015-03-19 8:37 AM, John Larkin wrote:

[...]

>>
>>> I you make an instantaneous change in C, LT Spice conserves charge, so
>>> doesn't conserve energy. Spice doesn't need to conserve energy.
>>>
>>
>> SPICE has weirdnesses. When I tried to massage the stimulus pulse for
>> the cap values using LC the capacitor action flatlined. The stimulus
>> itself looks ok, it's just that the formula in the cap seems to choke.
>> So I had to restrict it to RC. Beats me why but for now it's good enough.
>>
>> Thanks again for all the hints. I got it to run and produce a useful WAV
>> output for the software engineer. 60 cardiac cycles. Ba-bump .. ba-bump
>> .. ba-bump .. ba-bump .. ba-bump ............... *BEEEEEEEEEP* .... just
>> kidding ...
>
>
> This is fun:
>
> https://dl.dropboxusercontent.com/u/53724080/Circuits/Current_Sources/Isink_NAN.asc
>
> LTS doesn't mind zero value resistors or caps, but it doesn't like L=0
> in this circuit.
>

But it works if you give the inductor 1 femtohenry. Nothing in the world
could ever have such a low inductance.

Joerg

unread,

Mar 19, 2015, 8:16:09 PM3/19/15

to

On 2015-03-19 3:41 PM, Tom Swift wrote:
> Joerg <ne...@analogconsultants.com> wrote:
>
> [...]
>
>> Thanks again for all the hints. I got it to run and produce a useful
>> WAV output for the software engineer. 60 cardiac cycles. Ba-bump ..
>> ba-bump .. ba-bump .. ba-bump .. ba-bump ............... *BEEEEEEEEEP*
>> .... just kidding ...
>
> Another method might be to search google for 'heart sounds'. You will
> find many examples of normal and abnormal sounds to work with. Find a
> site that allows you to download the file in MP3 format, such as
>
> http://depts.washington.edu/physdx/heart/demo.html
>
> A normal heart sounds like
>
> http://depts.washington.edu/physdx/audio/normal.mp3
>
> Download it and listen in VLC to see if it's what you want. Then search
> google for MP3 to WAV converters. Watch out for ones that want you to
> download a 'download management' file. Skip those ones. There's a good
> online site at
>
> http://audioformat.com/mp3-to-wav
>
> In this case, the normal.mp3 file is 154,227 bytes, and the WAV file is
> 850,220 bytes. There seems to be some mashup at the beginning, but
> otherwise it sounds exactly like the MP3 file. You can probably edit it
> and trim the part you want or extend it.
>

The problem is that I need the aortic pressure signal and not the sound.
I've mimicked it with an asymmetrical RC sawtooth for now, good enough
to test the software initially.

> You can find all kinds of abnormalities to listen to. I have a young and
> very pretty doctor who just gave me a complete physical. I have
> absolutely no idea how she can memorize all those different sounds. There
> are hundreds of them. But maybe you can put them in your device and have
> them detected automatically.
>

It comes with experience of maybe she has a knack for it. As a kid I was
pretty good at diagnosing car engine troubles by ear. Until a kablouie
kind of accident in the army messed up my hearing.

Once I told my dad a valve on his new 5-cylinder Audi may be bad,
probably an exhaust valve. So he brought it to the dealer. They laughed.
"Phhht ... it's brand new and besides, what does a kid know?". My dad
insisted. So they did a compression test and sure enough it failed the
test on one cylinder. Major engine tear down and its exhaust valve had a
deep V-cut burned into it from the side, totally toast. It was a
warranty repair.

Tom Swift

unread,

Mar 19, 2015, 8:38:40 PM3/19/15

to

Joerg <ne...@analogconsultants.com> wrote:

> The problem is that I need the aortic pressure signal and not the
> sound. I've mimicked it with an asymmetrical RC sawtooth for now, good
> enough to test the software initially.

Cool! That signal appears to be much more complex. Good thing you're doing
it and not me!

Joerg

unread,

Mar 20, 2015, 10:12:12 AM3/20/15

to

Let's hope you and I never need the equipment that this is for but it'll
be good it's there, just in case.

Ultimately I'll feed in a WAV file with real data once I obtain data in
a non-proprietary format, which won't be too long now. Meantime I can
fake events by sprinkling in random error signals via PWL and running
them through analog circuitry.

Tom Swift

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Mar 20, 2015, 12:36:06 PM3/20/15

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Joerg <ne...@analogconsultants.com> wrote:

> On 2015-03-19 5:38 PM, Tom Swift wrote:

>> Cool! That signal appears to be much more complex. Good thing you're
>> doing it and not me!

> Let's hope you and I never need the equipment that this is for but
> it'll be good it's there, just in case.

You must be at the point now where you walk into a Doctor's office or
operating room, look around and say to yourself. "I designed that, and
that, and that...."

Pretty good insurance in case you ever get sick. They're fixing you with
your own stuff!

You should post a list of all the instruments you have designed so we can
be sure they use nothing else when they want to cut us open:)

Joerg

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Mar 20, 2015, 1:34:13 PM3/20/15

to

On 2015-03-20 9:35 AM, Tom Swift wrote:
> Joerg <ne...@analogconsultants.com> wrote:
>
>> On 2015-03-19 5:38 PM, Tom Swift wrote:
>
>>> Cool! That signal appears to be much more complex. Good thing you're
>>> doing it and not me!
>
>> Let's hope you and I never need the equipment that this is for but
>> it'll be good it's there, just in case.
>
> You must be at the point now where you walk into a Doctor's office or
> operating room, look around and say to yourself. "I designed that, and
> that, and that...."
>

Not anymore, I moved largely away from med tech. This is the only major
med project I am involved in right now and for the foreseeable future.
Much of that market got jinxed by Obamacare and I saw it coming, so
branched out into industrial electronics and stuff.

> Pretty good insurance in case you ever get sick. They're fixing you with
> your own stuff!
>
> You should post a list of all the instruments you have designed so we can
> be sure they use nothing else when they want to cut us open:)
>

When it comes to intravascular ultrasound, yes, then I'd like to be
diagnosed with one of our machines if that is ever necessary. Because it
is the only fully electronic system on the planet and I sure would not
like them to snake a catheter with a spinning shaft up into my coronary
blood vessels. Not that it's inherently too unsafe but it kind of scares
me. Plus IMHO our image quality is better and more consistent.

John Larkin

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Mar 20, 2015, 2:32:13 PM3/20/15

to

On Thu, 19 Mar 2015 16:57:15 -0700, Joerg <ne...@analogconsultants.com>

wrote:

>On 2015-03-19 2:55 PM, John Larkin wrote:
>> On Thu, 19 Mar 2015 13:30:47 -0700, Joerg <ne...@analogconsultants.com>
>> wrote:
>>
>>> On 2015-03-19 8:37 AM, John Larkin wrote:
>
>[...]
>
>>>
>>>> I you make an instantaneous change in C, LT Spice conserves charge, so
>>>> doesn't conserve energy. Spice doesn't need to conserve energy.
>>>>
>>>
>>> SPICE has weirdnesses. When I tried to massage the stimulus pulse for
>>> the cap values using LC the capacitor action flatlined. The stimulus
>>> itself looks ok, it's just that the formula in the cap seems to choke.
>>> So I had to restrict it to RC. Beats me why but for now it's good enough.
>>>
>>> Thanks again for all the hints. I got it to run and produce a useful WAV
>>> output for the software engineer. 60 cardiac cycles. Ba-bump .. ba-bump
>>> .. ba-bump .. ba-bump .. ba-bump ............... *BEEEEEEEEEP* .... just
>>> kidding ...
>>
>>
>> This is fun:
>>
>> https://dl.dropboxusercontent.com/u/53724080/Circuits/Current_Sources/Isink_NAN.asc
>>
>> LTS doesn't mind zero value resistors or caps, but it doesn't like L=0
>> in this circuit.
>>
>
>But it works if you give the inductor 1 femtohenry. Nothing in the world
>could ever have such a low inductance.

Weird, but that little current sink, with L=0, runs at home but gets
NAN crashes when I run it at work. Must be some different Spice
setting.

Tom Swift

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Mar 20, 2015, 6:05:10 PM3/20/15

to

Joerg <ne...@analogconsultants.com> wrote:

> On 2015-03-20 9:35 AM, Tom Swift wrote:

>> You must be at the point now where you walk into a Doctor's office or
>> operating room, look around and say to yourself. "I designed that,
>> and that, and that...."

> Not anymore, I moved largely away from med tech. This is the only
> major med project I am involved in right now and for the foreseeable
> future. Much of that market got jinxed by Obamacare and I saw it
> coming, so branched out into industrial electronics and stuff.

Just out of curiosity, why would Obamacare affect the med tech business?
There would still be a need for equipment, and as far as I can tell, the
equipment cost would not change. What happened to ruin the business?

k...@zzz.com

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Mar 20, 2015, 7:51:35 PM3/20/15

to

On Fri, 20 Mar 2015 10:34:18 -0700, Joerg <ne...@analogconsultants.com>
wrote:

Just the idea of a catheter snaking around inside scares me. Not much
choice, though. Fortunately, my doc uses the wrist as the entry point
(when possible). Don't know anything about spinning stuff, though.

k...@zzz.com

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Mar 20, 2015, 7:52:13 PM3/20/15

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Med device tax, for one.

Joerg

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Mar 21, 2015, 10:35:42 AM3/21/15

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Lesson learned: Go home when you want to solve a really tough problem.
No kidding, I solved one (a difficult safety feature that I am sure the
Federales will insist on) yesterday on a 36mi mountain bike ride. Then
around mile 30 a large rock got kicked up by the front wheel and hit me
in the right shin at a delta-V of 15-20mph. It still hurts.

Joerg

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Mar 21, 2015, 10:45:57 AM3/21/15

to

Several things, the most important ones being:

1. A new 2.3% medical device tax, as Keith said. This gets creamed off
the top from gross revenue, not from profits. So a start-up that
naturally won't be able to make profits for the first few years will
have to fork over an additional tax. More established companies that run
only a slim profit got that wiped out.

2. Culling of services and fees. In order to finance this gigantic
welfare expansion the president and his people thought it smart to
simply cut reimbursements and such. If a doctor can barely break even,
how do they think he or she will do if they cut down another 21% or
whatever?

Anyhow, this has predictably resulted in a souring of the investment
climate and it has become much tougher to find funding for a medical
device start-up. While I participate in the development of an idea that
did manage to get funded I also found in my other consulting work that
the pocket books in med devices for R&D and thus also for consulting
work are now a lot tighter. They are not in fields such as oil, gas,
industrial and so on. Therefore, that's where my work mainly headed.

Joerg

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Mar 21, 2015, 10:51:54 AM3/21/15

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This is for the more serious stuff such as snaking up ultrasound
catheters or stents riding on balloon catheter tips. They go in through
a cut in the femoral artery where they place a temporary lockable port,
just during the procedure.

Get a ton of exercise, don't smoke, don't eat bad stuff and you might
never need this done. But for some people the conditions are heredetary,
not much they can do about it. A friend of ours just got a whole new
heart valve delivered and installed with such a procedure. They didn't
have to crack his chest for open heart surgery, a procedure he might not
have survived due to other medical conditions.

John Larkin

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Mar 21, 2015, 11:22:22 AM3/21/15

to

On Sat, 21 Mar 2015 07:35:48 -0700, Joerg <ne...@analogconsultants.com>

I get all my best ideas in the shower. Luckily, our water heater has
an 80 gallon tank.

--

John Larkin Highland Technology, Inc

picosecond timing laser drivers and controllers

k...@zzz.com

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Mar 21, 2015, 11:48:00 AM3/21/15

to

On Sat, 21 Mar 2015 07:52:02 -0700, Joerg <ne...@analogconsultants.com>

More serious than a triple bypass? ;-) He does angioplasty and stents
through the wrist. Don't know about ultrasound. If at all possible
he doesn't use the femoral artery. That has a lot of complications
that the wrist doesn't have. It's a straight run from the right wrist
(or elbow) to the heart.

>Get a ton of exercise, don't smoke, don't eat bad stuff and you might
>never need this done. But for some people the conditions are heredetary,
>not much they can do about it. A friend of ours just got a whole new
>heart valve delivered and installed with such a procedure. They didn't
>have to crack his chest for open heart surgery, a procedure he might not
>have survived due to other medical conditions.

Pretty much a genes thing. My brother had a couple of stents a week
before I had the catheterization/ He, too, should have had a triple
bypass but they blew it so he'll have to wait a year for the surgery.
Another brother died of sudden death syndrome. He was the one who was
anal about all the exercise and diet stuff. He swam two miles three
times a week and did a couple of hours at the gym 7 days. Didn't help.

I got the whole zipper deal. In addition to the three cabbages, I got
a maze. ;-) All in all, it beats cancer, which other than a little
skin cancer (my mother, in her 90s), no one in my family on either
side has had.

Tom Swift

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Mar 21, 2015, 12:37:39 PM3/21/15

to

Thanks for taking the time to post, Joerg. That is a very alarming
picture, and I'm glad you got out in time.

Joerg

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Mar 21, 2015, 3:29:30 PM3/21/15

to

Bigger stuff usually only fits through the femoralis. It's pretty
routine. One of the cardiologists said that he feels like a glorified
plumber.

>> Get a ton of exercise, don't smoke, don't eat bad stuff and you might
>> never need this done. But for some people the conditions are heredetary,
>> not much they can do about it. A friend of ours just got a whole new
>> heart valve delivered and installed with such a procedure. They didn't
>> have to crack his chest for open heart surgery, a procedure he might not
>> have survived due to other medical conditions.
>
> Pretty much a genes thing. My brother had a couple of stents a week
> before I had the catheterization/ He, too, should have had a triple
> bypass but they blew it so he'll have to wait a year for the surgery.
> Another brother died of sudden death syndrome. He was the one who was
> anal about all the exercise and diet stuff. He swam two miles three
> times a week and did a couple of hours at the gym 7 days. Didn't help.
>

But it still does other things. I bet he feels really good after
exercise. When I came home from a 36mi hard mountain bike ride yesterday
night I felt like a Viking warrior on a horse.

> I got the whole zipper deal. In addition to the three cabbages, I got
> a maze. ;-) All in all, it beats cancer, which other than a little
> skin cancer (my mother, in her 90s), no one in my family on either
> side has had.
>

Alzheimer's can be much worse. Many of these people know full well that
they are losing their brains but it can be agonzingly slow. Some know
exactly want they want to communicate but can't get it out. For years.

Joerg

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Mar 21, 2015, 3:38:09 PM3/21/15

to

I hope some day we'll get real healthcare reform but that cannot come
from the current administration. Obamacare completely missed the boat.
For example, there are no provisions in that law to open the
chargemaster to patients and everyone else and also to cut ambulance
chasers out of the deal.

The chargemaster secrecy alone is huge. Case in point: Eye exam was
needed. So we inquired and at one out-of-network doctor the procedure
with prescription would have cost about $70. Called the HMO to see what
they charge. To out great surprise since we have a high-deductible plan
they said that it's no charge at all, like preventative care. So we
went. _Then_ we got a statement for $163. I called. "Oh, sorry, you were
given wrong information but it's your responsibility to check the
coverage". Which we can't because most of it isn't disclosed. This is
despicable and a serious cancer in US health care.

Joerg

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Mar 21, 2015, 3:40:00 PM3/21/15

to

Oh, oh, the guys in Sacramento will come down on you now. Drought
legislation is in the making. We already started early last year to cut
the water consumption during showers to a minimum. Like not running the
water while soaping up.

John Larkin

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Mar 21, 2015, 3:41:48 PM3/21/15

to

On Sat, 21 Mar 2015 12:38:13 -0700, Joerg <ne...@analogconsultants.com>
wrote:

Obamacare sold out to all the big stakeholders, to get it to pass. I
suspect that it was actually designed to fail.

>
>The chargemaster secrecy alone is huge. Case in point: Eye exam was
>needed. So we inquired and at one out-of-network doctor the procedure
>with prescription would have cost about $70. Called the HMO to see what
>they charge. To out great surprise since we have a high-deductible plan
>they said that it's no charge at all, like preventative care. So we
>went. _Then_ we got a statement for $163. I called. "Oh, sorry, you were
>given wrong information but it's your responsibility to check the
>coverage". Which we can't because most of it isn't disclosed. This is
>despicable and a serious cancer in US health care.

Yup. Published price lists should be mandatory. There's no other
business that can charge whatever they want after the product is
delivered.

k...@zzz.com

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Mar 21, 2015, 6:50:07 PM3/21/15

to

On Sat, 21 Mar 2015 12:29:37 -0700, Joerg <ne...@analogconsultants.com>

I can believe that. My cardiologist doesn't do anything past the
plumbing. If more is needed he passes it off to the surgeon. He's
good but real surgery is not his specialty.

>
>>> Get a ton of exercise, don't smoke, don't eat bad stuff and you might
>>> never need this done. But for some people the conditions are heredetary,
>>> not much they can do about it. A friend of ours just got a whole new
>>> heart valve delivered and installed with such a procedure. They didn't
>>> have to crack his chest for open heart surgery, a procedure he might not
>>> have survived due to other medical conditions.
>>
>> Pretty much a genes thing. My brother had a couple of stents a week
>> before I had the catheterization/ He, too, should have had a triple
>> bypass but they blew it so he'll have to wait a year for the surgery.
>> Another brother died of sudden death syndrome. He was the one who was
>> anal about all the exercise and diet stuff. He swam two miles three
>> times a week and did a couple of hours at the gym 7 days. Didn't help.
>>
>
>But it still does other things. I bet he feels really good after
>exercise. When I came home from a 36mi hard mountain bike ride yesterday
>night I felt like a Viking warrior on a horse.

Drugs do the same thing, in the same way. Dopamine, Serotonin, and
Endorphins.

>> I got the whole zipper deal. In addition to the three cabbages, I got
>> a maze. ;-) All in all, it beats cancer, which other than a little
>> skin cancer (my mother, in her 90s), no one in my family on either
>> side has had.
>>
>
>Alzheimer's can be much worse. Many of these people know full well that
>they are losing their brains but it can be agonzingly slow. Some know
>exactly want they want to communicate but can't get it out. For years.

Agreed.

Joerg

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Mar 21, 2015, 7:01:47 PM3/21/15

to

On 2015-03-21 3:50 PM, k...@zzz.com wrote:
> On Sat, 21 Mar 2015 12:29:37 -0700, Joerg <ne...@analogconsultants.com>
> wrote:
>
>> On 2015-03-21 8:48 AM, k...@zzz.com wrote:
>>> On Sat, 21 Mar 2015 07:52:02 -0700, Joerg <ne...@analogconsultants.com>
>>> wrote:
>>>

[...]

>>>> Get a ton of exercise, don't smoke, don't eat bad stuff and you might
>>>> never need this done. But for some people the conditions are heredetary,
>>>> not much they can do about it. A friend of ours just got a whole new
>>>> heart valve delivered and installed with such a procedure. They didn't
>>>> have to crack his chest for open heart surgery, a procedure he might not
>>>> have survived due to other medical conditions.
>>>
>>> Pretty much a genes thing. My brother had a couple of stents a week
>>> before I had the catheterization/ He, too, should have had a triple
>>> bypass but they blew it so he'll have to wait a year for the surgery.
>>> Another brother died of sudden death syndrome. He was the one who was
>>> anal about all the exercise and diet stuff. He swam two miles three
>>> times a week and did a couple of hours at the gym 7 days. Didn't help.
>>>
>>
>> But it still does other things. I bet he feels really good after
>> exercise. When I came home from a 36mi hard mountain bike ride yesterday
>> night I felt like a Viking warrior on a horse.
>
> Drugs do the same thing, in the same way. Dopamine, Serotonin, and
> Endorphins.
>

But with exercise it only happens after reaching a certain endurance
level. When I started intense biking 1-1/2 years ago I was huffing and
puffing after 15 mile of hills and my only thought was "Get me off of
this bike!". Now it's different.

[...]

Tom Swift

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Mar 21, 2015, 7:02:16 PM3/21/15

to

Joerg <ne...@analogconsultants.com> wrote:

> The chargemaster secrecy alone is huge. Case in point: Eye exam was
> needed. So we inquired and at one out-of-network doctor the procedure
> with prescription would have cost about $70. Called the HMO to see what
> they charge. To out great surprise since we have a high-deductible plan
> they said that it's no charge at all, like preventative care. So we
> went. _Then_ we got a statement for $163. I called. "Oh, sorry, you were
> given wrong information but it's your responsibility to check the
> coverage". Which we can't because most of it isn't disclosed. This is
> despicable and a serious cancer in US health care.

From the discussion, I understand med tech companies aren't making much
money, and are laying off people. Doctors are barely able to scrape by.

From Wikipedia, "According to the World Health Organization (WHO), the
United States spent more on health care per capita ($8,608), and more on
health care as percentage of its GDP (17.2%), than any other nation in
2011."

http://en.wikipedia.org/wiki/Health_care_in_the_United_States

So who is making all the money in health care? Is it the hospitals with
their obscene chargemaster lists?

Reinhardt Behm

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Mar 21, 2015, 7:03:26 PM3/21/15

to

On 22.03.2015 03:29, Joerg wrote:
>
> But it still does other things. I bet he feels really good after
> exercise. When I came home from a 36mi hard mountain bike ride yesterday
> night I felt like a Viking warrior on a horse.

So you needed some mead? ;-)

--
Reinhardt

Joerg

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Mar 21, 2015, 7:13:38 PM3/21/15

to

Almost. On the way back I had a Strong Blonde Ale at one of my bicycle
"gas stations":

http://placervillebrewingco.com/wp-content/uploads/2014/02/frontslider1.jpg
http://placervillebrewingco.com/wp-content/uploads/2014/02/beer2light.jpg

Eight volts, woohoo ...

k...@zzz.com

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Mar 21, 2015, 7:18:33 PM3/21/15

to

Like most statistics, it doesn't tell the entire story.

>
>So who is making all the money in health care?

Insurance companies? Lawyers? Congresscritters?

>Is it the hospitals with

Nope, they're going broke too. Obamacare is putting the small
regional hospitals out of business. The large city hospitals seem to
be doing OK, but...

>their obscene chargemaster lists?

Who pays the rates on the "obscene chargemaster lists"? Insurance
companies certainly don't and those without insurance don't (pay
anything). Who's left?

Joerg

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Mar 21, 2015, 7:21:37 PM3/21/15

to

On 2015-03-21 4:02 PM, Tom Swift wrote:
> Joerg <ne...@analogconsultants.com> wrote:
>
>> The chargemaster secrecy alone is huge. Case in point: Eye exam was
>> needed. So we inquired and at one out-of-network doctor the procedure
>> with prescription would have cost about $70. Called the HMO to see what
>> they charge. To out great surprise since we have a high-deductible plan
>> they said that it's no charge at all, like preventative care. So we
>> went. _Then_ we got a statement for $163. I called. "Oh, sorry, you were
>> given wrong information but it's your responsibility to check the
>> coverage". Which we can't because most of it isn't disclosed. This is
>> despicable and a serious cancer in US health care.
>
> From the discussion, I understand med tech companies aren't making much
> money, and are laying off people. Doctors are barely able to scrape by.
>

That is true for many.

http://www.californiahealthline.org/road-to-reform/2013/more-doctors-are-quitting-medicare-is-obamacare-really-to-blame

Some are retiring early. Others don't take Medicare and/or patients. I
know people who've had serious difficulties finding a doctor that had
time to treat them and was willing to.

> From Wikipedia, "According to the World Health Organization (WHO), the
> United States spent more on health care per capita ($8,608), and more on
> health care as percentage of its GDP (17.2%), than any other nation in
> 2011."
>
> http://en.wikipedia.org/wiki/Health_care_in_the_United_States
>
> So who is making all the money in health care? Is it the hospitals with
> their obscene chargemaster lists?
>

Lawyers, liability insurers, unionized workers and hospitals, mostly. A
nurse makes more money than an engineer in many places. The health
"system" in the US has gone beyond absurd. Which is why many people with
non-urgent or elective surgeries go to Thailand and other places to have
it done.

k...@zzz.com

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Mar 21, 2015, 7:21:40 PM3/21/15

to

On Sat, 21 Mar 2015 16:01:54 -0700, Joerg <ne...@analogconsultants.com>

Not sure that it matters. The drugs and effects are the same. If you
don't exercise for several days, you'll have withdrawal symptoms, too.
Drugs don't addict the user on first use, either.

Tom Swift

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Mar 21, 2015, 8:58:08 PM3/21/15

to

Thanks for the link:

http://www.californiahealthline.org/road-to-reform/2013/more-doctors-are-
quitting-medicare-is-obamacare-really-to-blame

The article linked to another article in the NewYorker, "Cowboys and Pit
Crews":

http://www.newyorker.com/news/news-desk/cowboys-and-pit-crews

This was a very enjoyable read - thank you.

But the problem is once you start reading about these issues, you quickly
get overwhelmed with the complexity. There doesn't seem to be a single
string that if you pull on it, out will come the solution. Given all the
different factors - politics, liability, social, and plain greed, there
may be no solution.

Medical tourism may be the answer for those who can afford it, but many
cannot. Possible solutions abound, for example the free health care
enjoyed by Canadians. But it is doubtful anything like this could be
introduced in the US.

I know many people in health care are very idealistic about helping
others. But when it starts affecting your family, you have to make a
choice.

I guess you can consider yourself lucky to have got out when you did.

Clifford Heath

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Mar 21, 2015, 11:21:51 PM3/21/15

to

On 22/03/15 10:02, Tom Swift wrote:
> So who is making all the money in health care? Is it the hospitals with
> their obscene chargemaster lists?

At some point, professional indemnity insurance costs more than health
insurance (with reduced liability). It seems likely that the USA is well
past that point.

Life is dangerous. Not everything that happens to you is "someone else's
fault".

Joerg

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Mar 22, 2015, 10:27:30 AM3/22/15

to

On 2015-03-21 5:58 PM, Tom Swift wrote:
> Joerg <ne...@analogconsultants.com> wrote:
>
>> On 2015-03-21 4:02 PM, Tom Swift wrote:
>
>>> So who is making all the money in health care? Is it the hospitals
>>> with their obscene chargemaster lists?
>
>> Lawyers, liability insurers, unionized workers and hospitals, mostly.
>> A nurse makes more money than an engineer in many places. The health
>> "system" in the US has gone beyond absurd. Which is why many people
>> with non-urgent or elective surgeries go to Thailand and other places
>> to have it done.
>
> Thanks for the link:
>
> http://www.californiahealthline.org/road-to-reform/2013/more-doctors-are-
> quitting-medicare-is-obamacare-really-to-blame
>
> The article linked to another article in the NewYorker, "Cowboys and Pit
> Crews":
>
> http://www.newyorker.com/news/news-desk/cowboys-and-pit-crews
>
> This was a very enjoyable read - thank you.
>
> But the problem is once you start reading about these issues, you quickly
> get overwhelmed with the complexity. There doesn't seem to be a single
> string that if you pull on it, out will come the solution. Given all the
> different factors - politics, liability, social, and plain greed, there
> may be no solution.
>

The key points are missing in most publications (sometimes because they
are not "PC") and those are that, before doing anything to our medical
system, we must get rid of the parasites in it and also make it at least
as transparent as the process of buying groceries. If a cardiologist has
to pay north of $100k just in liablility insurance just to be able to
practice that is sick. If people cannot find out before committing what
a procedure costs that is never going to work in the long run.

> Medical tourism may be the answer for those who can afford it, but many
> cannot. Possible solutions abound, for example the free health care
> enjoyed by Canadians. But it is doubtful anything like this could be
> introduced in the US.
>

I wouldn't want it. Socialized medicine results in the usual, waiting
lists. Except people die on those kinds of waiting lists. Wealthier
Canadians often quietly carry a Mayo Care card or something similar in
their pockets. That way they can avoid the mediocre performance of their
country's health system and skip across the border for top notch
treatment. While at Mayo I was astounded how many Canadian patients were
there, their accents gave them away. Problem is, if our system turns
sour we have no border to skip across for medical care. We'd have to
cross an ocean and with a heart condition that may not be possible.

> I know many people in health care are very idealistic about helping
> others. But when it starts affecting your family, you have to make a
> choice.
>
> I guess you can consider yourself lucky to have got out when you did.
>

It would have been ok to get out later but it would have created a lull
in assignments. I'd have used that for mountain biking :-)

I didn't get out completely, still doing one medical project and that is
a very challenging one. When it's tough, it's fun.

Joerg

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Mar 22, 2015, 10:34:07 AM3/22/15

to

I do. That is because it isn't the endorphins, it's the experience. On
Friday I used my mountain bike to go to Placerville, a 36mi ride and
often through gnarly terrain. I met many horses, dogs, had a fox travel
in front of me on the trail for a while, saw beautiful birds, pretty
flowers, a few chats with ranchers. Then there is the experience of
achievement. For example, for the first time ever I was able to hammer
up a particular uphill stretch staying in the pedals. I and almost
anyone I know used to walk the last part of it.

> Drugs don't addict the user on first use, either.
>

Because they can't give you any of the above.

k...@zzz.com

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Mar 22, 2015, 12:47:40 PM3/22/15

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On Sun, 22 Mar 2015 07:34:01 -0700, Joerg <ne...@analogconsultants.com>

You're wrong. It's the drugs.

>> Drugs don't addict the user on first use, either.
>>
>
>Because they can't give you any of the above.

Wrong again. It's *exactly* the same process. Your brain likes the
endorphins, no matter how you get them (whether it be dope, exercise,
or chocolates).

Joerg

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Mar 23, 2015, 12:22:18 PM3/23/15

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Nope. For me it's mostly the memories of the last ride. For example, I
do not net much fun out of a tough ride along one of the main county
roads here and there isn't much of an "endorphin high" afterwards. But
when coming back from a similarly strenuous trail ride it's completely
different. I feel good and can't wait to go back there. This is because
of the whole experience and has little to do with body-produced substances.

k...@zzz.com

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Mar 23, 2015, 8:50:12 PM3/23/15

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On Mon, 23 Mar 2015 09:22:15 -0700, Joerg <ne...@analogconsultants.com>

Where do you think those happy thoughts came from? You're ADDICTED!
;-)

Joerg

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Mar 24, 2015, 2:56:32 PM3/24/15

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It's probably from the Strong Blonde Ale, Guinness or Hefeweizen at an
outdoor pub on the way back.