circuit design help: momentary switch activates/cancels electronic switch
matthewuw
I have a momentary switch. When I press it, I want to switch something
on (light bulb) and have it stay on even though momentary switch was
released. maybe 500 mA draw.
When I press it again, it turns the light bulb off. How do I do this?
This is in a 12VDC circuit.
Thanks!
Ken Taylor
it for a push-on/push-off momentary action one?
Ken
"matthewuw" <pro...@gmail.com> wrote in message
news:1129097288.4...@o13g2000cwo.googlegroups.com...
ehsjr
There are a number of ways to do this. Do you want
to learn, or are you just interested in having
a circuit that will do it?
Ed
matthewuw
What I asked for is actually only part of the functionality, but I see
it as a building block to start with and was hoping I might figure the
rest out on my own.
matthewuw
momentary switch, but doesn't function like one. I have to use a
momentary switch, no option because of existing hardware.
Terry Pinnell
This should do it.
http://www.terrypin.dial.pipex.com/Images/Momentary1.gif
There are many circuits for a 'toggle' or flip-flop, but that's the
simplest/cheapest I know of.
--
Terry Pinnell
Hobbyist, West Sussex, UK
Fred Bloggs
Did you simulate that?
Ken Moffett
@o13g2000cwo.googlegroups.com:
I've tried this and it works. Simple and cheap. Sub in a 12vdc supply and a
12v relay.
Fred Bloggs
You can use a miniature SCR bistable:
View in a fixed-width font such as Courier.
.
. 12V
. |
. +--------------+--+----+--------------+-----+
. | | | | | |
. | +-------------|--------------------------+
. | | | | | | | |
. | | | | | +-----+ | |
. [10M] [1K] | [1K] | | | | |
. | | | | | | -|-----|-----|---
. | | | | | | | | | | |
. | | | | | | | \ COM NC |
. | 0.0022 | | | |< - | / |
. +---||---|--------+--| ^ | \ |
. | | | |\ | | / |
. | | | 2N2907| | | | NO |
. | | | | | -|------------|--
. | | [100K] [3.3K] | | |
. | | | | +-----+ |
. | | | | | |
. | +-----+--||---|--------------+ |
. | | 100U 16V | | |
. | | non- | | |
. | | polar | | |
. | | | | |
. | | | | |
. o | SCR1 | SCR2 | |
. -| SW --- | --- |
. o \ /-+-[1K]-|<|-+-|>|-[1K]-+--\ / LAMP
. | --- | | | --- |
. | NTE5400| | | | | NTE5400 |
. | | | | | | |
. | |[10K] [3.3K] [10K] | |
. | | | | | | |
. | | | | | | |
. +--------+--+----------+----------+---+------------+
. |
. ---
. ///
.
Fred Bloggs
View in a fixed-width font such as Courier.
.
. 12V
. |
. +--------------+--+----+--------------+-----+
. | | | | | |
. | +-------------|--------------------------+
. | | | | | | | |
. | | | | | +-----+ | |
. [10M] [1K] | [1K] | | | | |
. | | | | | | -|-----|-----|---
. | | | | | | | | | | |
. | | | | | | | \ COM NC |
. | 0.0022 | | | |< - | / |
. +---||---|--------+--| ^ | \ |
. | | | |\ | | / |
. | | | 2N2907| | | | NO |
. | | | | | -|------------|--
. | | [100K] [3.3K] | | |
. | | | | +-----+ |
. | | | | | |
. [470] +-----+--||---|--------------+ |
Terry Pinnell
>Did you simulate that?
No, but maybe I'll have a crack at it when I get some time. Meanwhile,
I've put together this scan from my original source: "Elektor 302
Circuits", ~1985
http://www.terrypin.dial.pipex.com/Images/MomentaryScan1.jpg
which explains its working.
And I'm pretty sure I breadboarded it successfully a decade or two
ago.
Jim Thompson
See "TogggleFlopAncient.pdf" on the S.E.D/Schematics page of my
website.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Fred Bloggs
Here is a less parts intensive version of the same thing, consumes about
50uA in the off state:
View in a fixed-width font such as Courier.
.
. 12V
. |
. +-------------+-----+--------+-----+
. | | | | |
. | o | | |
. | -| SW | | |
. | o | +----+ |
. | | | | | |
. | +------+ | | -|-----|---------
. | | | | | | | | |
. | [10M] === | | | \ COM |
. | | 0.022U | - | / |
. | -+- | | ^ | \ |
. | /// | | | | / |
. | | [1.5K]| | | NO |
. | [820] | | -|------------|--
. [100K] | | | | |
. | | | +----+ |
. | | | | |
. +--------+--------||---|-----+--------+ |
. | | 10U 16V | | |
. | | non- | | |
. | | polar | | |
. [100K] | | | |
. | | | | |
. | SCR1| | SCR2 | |
. | --- | --- |
. | \ /-+-[1K]-|<|-+-|>|-[1K]-+--\ / LAMP
. | --- | | | --- |
. | NTE5400| | | | | NTE5400 |
. | 2N5060 | | | | | 2N5060 |
. | |[10K] [270] [10K] | |
Fred Bloggs
Terry Pinnell wrote:
> Fred Bloggs <nos...@nospam.com> wrote:
>
>
>>Did you simulate that?
>
>
> No, but maybe I'll have a crack at it when I get some time. Meanwhile,
> I've put together this scan from my original source: "Elektor 302
> Circuits", ~1985
> http://www.terrypin.dial.pipex.com/Images/MomentaryScan1.jpg
> which explains its working.
>
> And I'm pretty sure I breadboarded it successfully a decade or two
> ago.
>
Thanks- I think I recall that article now, clever.
Fred Bloggs
Jim Thompson wrote:
> On 11 Oct 2005 23:08:08 -0700, "matthewuw" <pro...@gmail.com> wrote:
>
>
>>Here is the application:
>>
>>I have a momentary switch. When I press it, I want to switch something
>>on (light bulb) and have it stay on even though momentary switch was
>>released. maybe 500 mA draw.
>>
>>When I press it again, it turns the light bulb off. How do I do this?
>>This is in a 12VDC circuit.
>>
>>Thanks!
>
>
> See "TogggleFlopAncient.pdf" on the S.E.D/Schematics page of my
> website.
>
> ...Jim Thompson
A little before my time, but those were the days...toggle on release.
Ken Moffett
news:Xns96EE4ED9...@24.94.170.94:
I looked back at the circuit again and noted something they had left out.
The relay in their circuit was a 12vdc for the 24v supply. So for a 12v
supply you would choose a 5vdc or 6vdc DPDT relay. The resistance of R1,
R2, and relay's coil would all be approximately equal.
matthewuw
you...but like I said early on, this is a learning experience for me.
It has occured to me that I don't want to worry about contact bounce
and that in reality, this will fit my application much better if there
are 2 momentary switches. pressing one of them turns the system on and
pressing the other turns the system off. i can probably adapt this
setup somehow from some of the provided circuits, so I will look into
it. this might actually simplify the circuit too i would think.
THANKS!
Terry Pinnell
How much simpler can you get than the circuits posted? Have you tried
any of them yet?
Hey, how about an even simpler approach: a single toggle switch? No
buttons, no electronics. AC or DC power supply in at one side, and out
of the other to whatever you want to control. Its explanation is as
follows: when you switch it one way, the circuit is powered on. When
you switch it the other way, the circuit is powered off again. Very
reliable, parts easily obtained. What's more, it has another advantage
over a button-based approach: the status of the circuit is always
visibly obvious (providing the two switch positions have been marked
accordingly, e.g. 'On' and 'Off' or whatever.) This advantage over
buttons applies even if the load has failed somehow (lamp filament
burned out, motor stalled, etc).
Fred Bloggs
View in a fixed-width font such as Courier.
.
.
. 12VDC>---+-------+-----+-------+
. | | | |
. | | | 12VDC |
. | | --RELAY---
. | | |\ COM|
. | - |/ |
. | ^ |\ |
. | 1N4001 |/ NO |
. | | ----------
. | | | |
. o +-----+ +-----+
. -| SWon | | |
. o | | |
. | | | |
. +----[2.2K]---|-------+ |
. | | |
. [2.2K] | |
. | | LAMP
. | ||- |
. +-------+--||< IRF510 |
. | | ||- |
. o === | |
. -| SWoff 0.1U | |
. o | | |
. | | | |
. +-------+-----+-------------+
. ---
. ///
.
.
.
Fred Bloggs
IF your load is inductive, non-resistive, or capacitive then something
like this would be better:
View in a fixed-width font such as Courier.
.
. 12VDC>-------+----+---+-------+-----+-------+
. | | | | | |
. | | | | | 12VDC |
. | | | | --RELAY---
. | | | | |\ COM|
. | [10K] | - |/ |
. | | | ^ |\ |
. | | | 1N4001 |/ NO |
. | | | | ----------
. >| | | | | |
. 2N3906|--+---|-[10K]-+-----+ |
. /| | | |
. | o | |
. | -| SWon | |
. | o | +-------+
. | | | | |
. | | | - |
. | | | ^ |
. | [2.2K] | 1N4001 LAMP
. | | | | |
. | | ||- +-------+
. +--------+-------+--||<IRF510 |
. | | | ||- |
. | o === | |
. [10K] -| SWoff 0.01U | |
. | o | | |
. | | | | |
. +--------+-------+-----+-------+
. ---
. ///
Fred Bloggs
Allowing for pressing both switches simultaneously, make this change:
View in a fixed-width font such as Courier.
.
. 12VDC>-------+----+---+-------+-----+-------+
. | | | | | |
. | | | | | 12VDC |
. | | | | --RELAY---
. | | | | |\ COM|
. | [10K] | - |/ |
. | | | ^ |\ |
. | | | 1N4001 |/ NO |
. | | | | ----------
. >| | | | | |
. 2N3906|--+---|-[10K]-+-----+ |
. /| | | |
. | o | |
. | -| SWon | |
. | o | +-------+
. | | | | |
. +--------+ | - |
. | | ^ |
. | | 1N4001 LAMP
. [1K] | | |
John Fields
wrote:
---
This is the standard way to do it: (View in a fixed-pitch font like
Courier)
+V
|
S1| O +V
PRESS ON >--| |
| O---+ | O-------->NO
| |K1A O |K1B O--->COM
| +--> | +--> |
[COIL]- - -|- - - -|
|
S2 O|
PRESS OFF >-----|
O|
|
GND
S1 is a Single-Pole Single-Throw Normally Open (FORM 'A') momentary
switch which can handle the relay coil current, S2 is a Single-Pole
Single-Throw Normally Closed (FORM 'B') momentary switch which can
handle the relay current, and the relay is a DPSTNO or a DPDT relay.
One set of contacts is used to latch the relay in the energized
position when S1 is pressed, and the other set is used for external
purposes.
When S1 is pressed, current flows through the relay coil, which
attracts the armature of K1A to the normally-closed contact. When
they touch, another path to +V will be established for the coil,
latching the relay. S1 can then be released and the relay will
remain energized.
When S2 is pressed, the path to ground for the current will be
broken, the magnetic field around the relay coil will collapse, and
the contacts will spring back to their non-energized state.
--
John Fields
Professional Circuit Designer
Rich Grise
> Fred Bloggs wrote:
>> [op wrote:]
>>> Okay, thanks for all the replies. Sorry to change things up on
>>> you...but like I said early on, this is a learning experience for me.
>>> It has occured to me that I don't want to worry about contact bounce
>>> and that in reality, this will fit my application much better if there
>>> are 2 momentary switches. pressing one of them turns the system on and
>>> pressing the other turns the system off. i can probably adapt this
>>> setup somehow from some of the provided circuits, so I will look into
>>> it. this might actually simplify the circuit too i would think.
>>
>> IF your load is inductive, non-resistive, or capacitive then something
>> like this would be better:
>> View in a fixed-width font such as Courier.
[circuits snipped]
Boy, that sure is a lot of stuff, when it could be done with an RS
flip-flop.
Cheers!
Rich
John Fields
---
For your lamp load:
+12V>-----------+--------+---------+
| | |
S1| O | |
PRESS ON >--| | |
| O---+ | |
| |K1A O |
| O--> | K1B O
[COIL]- - -|- - - - -|
| O--> |
S2 O| |
PRESS OFF >-----| [LAMP]
O| |
| |
GND>------------+-------------+
Spehro Pefhany
Does RS even sell chips any more?
;-)
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Rich Grise
> On Fri, 14 Oct 2005 15:20:24 GMT, the renowned Rich Grise
> <ri...@example.net> wrote:
>
>>On Fri, 14 Oct 2005 12:41:23 +0000, Fred Bloggs wrote:
>>> Fred Bloggs wrote:
>>>> [op wrote:]
>>>>> Okay, thanks for all the replies. Sorry to change things up on
>>>>> you...but like I said early on, this is a learning experience for me.
>>>>> It has occured to me that I don't want to worry about contact bounce
>>>>> and that in reality, this will fit my application much better if there
>>>>> are 2 momentary switches. pressing one of them turns the system on and
>>>>> pressing the other turns the system off. i can probably adapt this
>>>>> setup somehow from some of the provided circuits, so I will look into
>>>>> it. this might actually simplify the circuit too i would think.
>>>>
>>>> IF your load is inductive, non-resistive, or capacitive then something
>>>> like this would be better:
>>>> View in a fixed-width font such as Courier.
>>
>>[circuits snipped]
>>
>>Boy, that sure is a lot of stuff, when it could be done with an RS
>>flip-flop.
>>
>>Cheers!
>>Rich
>
> Does RS even sell chips any more?
>
> ;-)
>
LOL!
But, just because I'm in a bluff-calling mood, yes:
http://support.radioshack.com/productinfo/DocumentResults.asp?sku_id=276-2816&Name=High-Speed%20CMOS%20Logic%20ICs&Reuse=N
(mind the wrap)
Cheers!
Rich
Fred Bloggs
Spehro Pefhany wrote:
>
> Does RS even sell chips any more?
>
> ;-)
>
>
Only the analog stuff, LM339, LM324, TL082, 555, 556, LM386, LM317,
7805, 7812, maybe some others, transistors, diodes, resistors, caps,
etc...but no digital IC's whatsoever available in the stores.
matthewuw
toggle switch?"
--------------------
if you can find me toggle switches that fit inside the switch housings
on my motorcycle handlebars, that would be great. please post link. :)
Fred Bloggs
A rocker switch would be best for light circuit control on a motorcycle.
These come in momentary also and can be controlled by thumb. One way
using readily available parts is shown below. When the rocker momentary
is moved to BATT position, voltage is applied through D1 to RLY1 and R1
to the transistor base turning both components on. D2 prevents load
current from flowing through the miniature switch. When RLY1 activates,
BATT is thrown onto the load ckt through the COM-NO contact closure, and
BATT is also applied through D2 to RLY1 and R2 to the TIP31 base drive.
SW1 can now be released and the circuit remains latched on. When SW1 is
moved to the GND position, junction of R1-R2 is pulled to GND removing
TIP31 base drive and turning it off. D1 prevents current flow from the
RLY1 NO ckt from flowing to GND. RLY1 cuts off, removing voltage from
the load and RLY1. The SW can now be released and the circuit remains
off. D3 suppresses RLY1 coil inductive flyback, and D4 kills transients
from the load wiring. R3 is a leakage drain resistor for the TIP31.
View in a fixed-width font such as Courier.
.
. +---+ +-----------------------------+---->
. | | | |
. -+- | | | TO LAMP_CKT
. /// | | +---->
. GND | |
. +-----------------------WTHR_PROOF_ENCL---+
. | | | |
. | +---------+ | |
. | | | |
. | | 1N4001 | 1N4001 |
. | +-----|>|-----+---|>|---+ |
. | | D4 | D2 | |
. | | | +-----|--------+ | +---------+
. | | | | | | | | |
. | | ------- | | | | |
. | | |NO COM| | | | | |
. | | RLY1 | | | | | | SW MOM |
. | | | | | | | | ROCKER |
. | | | | | | | | +-----+ |
. | | +--|-/\/\- |---+ | | | | | |
. | | | ------ | +--|-------+ | o--|-+- BATT
. | | TIP31 | D3 | 1N4001 | | / |
. | +-E C--+---|>|--------+--|<|---+--|---------|--o |
. | | B 1N4001 | D1 | | | \ |
. | | | | | | | o--|---- GND
. | [1K] | R1 R2 | | | | |
. | |R3 | 120 120 | | | +-----+
. | +---+----/\/\--+--/\/\--+ | | SW1
. | 3W | 3W | |
. | +-----------------+ |
. | |
. +-----------------------------------------+
Rich Grise
matthewuw
http://www.google.com/search?q=motorcycle+handlebar+switch
Good Luck!
Rich "
-------------------------------
Thanks for the reply rich. I already have nice switch housings and
swiches that fit in them and look nice. they are momentary switches.
the switches are already in place...the bike wiring is all custom and
right now I am working though turn signals and running lights and such.
I am not sure how google would help me at all in the case since i spent
a LONG time on google before I posted here.
Will post what I came up with when I am done with it.
John Fields
wrote:
---
If the switches are Normally Open, you could use another small SPDT
or SPSTNC relay to supply the normally closed contacts you'd need
for the circuit I posted earlier. Or, you could use an RS latch, a
transistor, and a SPSTNO relay to do the trick instead. Want a
schematic?
roma
> Here is the application:
>
> I have a momentary switch. When I press it, I want to switch
something
> on (light bulb) and have it stay on even though momentary switch was
> released. maybe 500 mA draw.
>
> When I press it again, it turns the light bulb off. How do I do
this?
> This is in a 12VDC circuit.
>
> Thanks!
>
http://members.shaw.ca/roma/switching.html , all kinds of electronic
switching for low volt/current applications .
roma