555 power supply not working
Imbanon
Yeah, another thread about this supply.. http://www.ledsales.com.au/kits/nixie_supply.pdf
I know I could and should have made that Maxim power supply, but I
didn't. So now I'm stuck fixing this with loads of spare parts I've
got... except for the FETs..
Anyways, the supply isn't working. The first one I made worked just
fine for 15 minutes, powering 6 IN-14 at 170 volts (multiplexed). Then
I set it to 200 volts (to get RMS of 2mA), which worked for 5 minutes,
and then smoked and failed.
I made another on a quick PCB, which just smoked immediately when I
switched it on. The same thing happened to the newest, breadboarded
one.
The MOSFET seems to overheat instantly and smoke out. Having nothing
to lose (except the molten hole in the breadboard), I left it powered,
to see the diode smoking next. Aparently, its still in working order
(so says the multimeter).
Heat sinking FET only makes it last longer in not working state before
it smokes.
I tried replacing inductors, 555s, diodes, transistors..
What the F**K do I do people? Losing my head here!
And yeah, I'm powering it at 12 volts, tried 5. Output is always 3-6
volts.
Thank you for any help provided!
Imbanon
Per Jensen
Do you have around 100nF of decoupling directly across the power pins of the 555 ?
Gimme a link to the shematic you used.
// Per.
Imbanon
As posted, http://www.ledsales.com.au/kits/nixie_supply.pdf
I used exactly the same parts, made exactly the same PCB. I really
don't know what's wrong with it. I test all my parts before using them
(except the 555s, FETs and inductors). All new.
Could it be the cheap-chinese factor? I've heard they like to sell
fake MOSFETs
Thanks a lot
Imbanon
On Nov 18, 8:55 pm, Per Jensen <elektronikbik...@gmail.com> wrote:
> Which kind of FET and Diode are you using ?
>
> Do you have around 100nF of decoupling directly across the power pins of the 555 ?
>
> Gimme a link to the shematic you used.
>
> // Per.
>
> On 18/11/2011, at 20.43, Imbanon wrote:
>
>
>
>
>
>
>
> > Hi all.
>
Quixotic Nixotic
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JS Design
Imbanon
good as a broken nixie. Now I'm afraid of using them, they are my last
x)
I can't test the inductors, but they should be 100uH, 1watt max. I
can't test them, nor do they have any markings on them. Just plain
black cover.
The diodes are UF4004. I suppose they should work..
Can I use some other inductor, like 220uH?
Also, how do I check if my 555 is oscillating without an oscilloscope?
Thanks!
On Nov 18, 10:29 pm, Quixotic Nixotic <nixot...@blueyonder.co.uk>
wrote:
> 
Adam Jacobs
It doesn't need to be fast. I use a dual-channel tektronix 100mhz scope
that was built in the 80's. There are even PC based storage scopes now.
-Adam
Tony Adams
the 12v supply, it will still work and produce 180-200v out for test
purposes.
Don't bother putting another mosfet in just yet, you need to fid out
why it's being fried first.
Probably either the mark/space ratio is too long or it's being driven
on permanently. What's the DC voltage on pin 3?.
You could try connecting one pin of a small cap, maybe .1u to pin 3
and connecting your meter probe to the other pin, if it's oscillating
you should get a reading therough the capacitor. Or try a cheap AM
radio next to it, you may pick up harmonics.
I would check around the feedback circuit and Q2, beyond that you
really need a scope to see what the gate drive looks like. It could be
very long rise/fall times though if they're failing almost instantly
it's probably just the 555 output is stuck high.
Tony.
Tony Adams
next.'
If the mosfet was fried before then, the diode should just have been
sitting there with nothing to do. I assume it's not connected to the
rest of the clock?.
Power it up with a 15R series resistor, no mosfet and come back with
some voltages.
Tony.
threeneurons
|
| I can't test the inductors, but they should be 100uH, 1watt max....
| The diodes are UF4004. I suppose they should work..
|
| Can I use some other inductor, like 220uH?
Are using the parts provided by that kit, or are you just using the
schematic ? This is very important for us to know !
Not all inductors are the are same. 1W ?. That's not a typical
inductor rating. Its usually current (amps, milliamps), for maximum DC
current, and/or maximum saturation current. A supply like this should
be able to handle 500mA (half amp), at the very minimum. Any old pile
of crap from your junk bin just won't do.
Make sure its a UF4004, and not to be confused with a 1N4004. The "UF"
means its an "ultra fast" switching rectifier, in the ballpark of 50
to 100nS (10^-9sec). A 1N4004 ("jelly bean" rectifier) switches much
slower by orders of magnitude. An "order of magnitude" is equal to
10x, 2 orders = 100x, ...
The inductance isn't super critical. What is critical, is that it can
handle the current. Use power inductors.
If you have a scope, test the frequency first. Just hook up the 555,
but leave off the FET and coil, and the feedback parts going back to
pin-5. Leave pin-5 disconnected from everything. Turn it ON, and check
the frequency at pin-3. It calculates to 31KHz, with the schematic's
part values. See if its in the ballpark of 30KHz (20KHz to 40KHz). If
one of those parts is too big, then the frequency will be too low, the
symptoms you describe will happen..
chuck richards
It's like being in the dark and not being able to see.
I shopped around, went to hamfests, etc. Eventually found
a nice little 10 mHz scope made by BK Precision. I paid
70 bucks for it, and it is still a reliable workhorse.
It is not very fancy, but it is dual trace.
You'll be amazed how much easier things are when you
have an oscilloscope and can see stuff such as a 555 output.
Chuck
>
>
>---- Original Message ----
>From: ad...@jacobs.us
>To: neoni...@googlegroups.com
>Subject: Re: [neonixie-l] Re: 555 power supply not working
>Date: Fri, 18 Nov 2011 15:34:46 -0800
>
>>If you're going to make a hobby out of electronics, buy an
>oscilloscope.
>>It doesn't need to be fast. I use a dual-channel tektronix 100mhz
>scope
>>that was built in the 80's. There are even PC based storage scopes
>now.
>>
>>-Adam
>>
>>On 11/18/2011 3:31 PM, Imbanon wrote:
>>> Also, how do I check if my 555 is oscillating without an
>oscilloscope?
>>>
>>> Thanks!
>>>
>>
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>>
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Imbanon
I know I need an oscillosope, It's just that I can't afford one as a
student. Saving for one for a while now..
I'm gonna test it tomorrow with a friend's sope and tell you how it
goes.
As for the components, they are not from a kit. I bought them
separately from ebay.
I don't know the current for the inductor (asked the guy, he only knew
the wattage - 1W). It was this one here
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330452969986
And the diodes are (I hope UF4004, at least I hope), these here
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330553568765
Hopefully I will test 555s tomorrow and let you know, gotta go now
Thanks again!
Imbanon
Nick
mind me saying so, you are very new to all this and getting the
pinouts on FETs, ICs, transistors etc. wrong is easy to do.
Secondly, inductors are not measured in Watts - lots of other things,
yes, Watts, no. They will have a saturation current - personally, that
inductor "looks" a bit small - a larger one (still 100uH but with a
higher current rating) might be better.
Thirdly, I'd really check hard that your 555 is oscillating and on the
pin you expect - if its locked on, then that might explain why your
FET caught fire (it'd be shorting your input supply to ground through
the tiny inductor, which would then cook too). It happens... Check
every pin on the 555 is going where you expect. Check the feedback
transistor pinout is actually what you expect. Make no assumptions at
all about anything being above suspicion.
Get another pair of eyes to check your wiring - its easy even for
experienced engineers to get "blind" to obvious mistakes (obvious to
others, that is). Get a second opinion, and let them check it from the
original schematic - don't let them assume anything.
If you've never played with a 555 before (the world's most popular
IC), trying doing some simple stuff like flashing an LED at 1Hz (lots
of schematics out there for that) - boring maybe, but you'll learn an
awful lot...
Cheers
Nick
Adam Jacobs
The 555 designs work well for a lot of people, but if there is no specific reason why you're using that design (other than that you have most of the parts already) then I you might consider switching to Mike's MC34063 mk1.5 design.
I would not try the max1771 designs if you are not able to make the 555 design work. The max1771 is notoriously picky about layout.
-Adam
Charles MacDonald
> You'll be amazed how much easier things are when you
> have an oscilloscope and can see stuff such as a 555 output.
Just looking at e-bay and they have several scopes under 100 bucks, (of
course reading fine print is important there.) I was only looking at
e-bay canada, if you are in the US their are likely more that the seller
will only ship to the US.
I was surprised that both 10 and 100 Mhz units were all over the price
map. Have a look for some less popular brands like Hitachi,
telequipment, Leader or Kikusui Oscilloscope
--
Charles MacDonald Stittsville Ontario
cm...@zeusprune.ca Just Beyond the Fringe
http://users.trytel.com/~cmacd/tubes.html
No Microsoft Products were used in sending this e-mail.
Imbanon
post my real reply.
On Nov 19, 11:05 pm, Charles MacDonald <cm...@zeusprune.ca> wrote:
> On 11-11-19 02:27 PM, chuck richards wrote:
>
> > You'll be amazed how much easier things are when you
> > have an oscilloscope and can see stuff such as a 555 output.
>
> Just looking at e-bay and they have several scopes under 100 bucks, (of
> course reading fine print is important there.) I was only looking at
> e-bay canada, if you are in the US their are likely more that the seller
> will only ship to the US.
>
> I was surprised that both 10 and 100 Mhz units were all over the price
> map. Have a look for some less popular brands like Hitachi,
> telequipment, Leader or Kikusui Oscilloscope
>
> --
> Charles MacDonald Stittsville Ontario
> cm...@zeusprune.ca Just Beyond the Fringehttp://users.trytel.com/~cmacd/tubes.html
Imbanon
Imbanon
theory. The rest I've had a lot of practise in college and at home as
much as I can.
Anyways, I've got my hands on an oscilloscope! It's a friend's UNI-T
UT81B.
Did some testings, and came with a frequency of around 22kHz. But I'm
not sure what to expect with peak to peak voltage. For some strange
reason, I can only measure it in 100mV on volts/div, which then
exceeds the screen. If set to the next step of 200mV, the somewhat
triangular waveform takes a really small unrecognisible form with low
amplitude. I cannot say what the amplitude is. I could only measure it
with 3.3V input, which is then Um=0.72V. (see pics below)
DC voltage on pin3 is 5.8 volts.
I did testings on 5 different ICs, on 2 separate circuits and a PCB,
input voltage 11.8. All gave the same results.
Imbanon
The power supply is an old PC supply, and it does have a short circuit
protection. At some point before the circuit failed, I noticed the
slower fan speed of the PC supply, which usually happens when it tries
to provide max amperage (15A at 12V). So maybe the circuit really did
shorted through the coil, but the supply didn't detect it as a true
short because of the tiny resistance in the coil, which is apparently
enough for this to happen.
Imbanon
cannot get all the parts I need, such as power inductors. I tried
ordering from Mouser, but gave up. The shipping prices are insane -
around $20 for a few parts worth $5.
Pics;
100mV V/div, 20uS T/div http://imageshack DOT us/photo/my-images/
851/100mvvdiv20ustdiv.png/
200mV V/div, 20uS T/div http://imageshack DOT us/photo/my-images/
155/200mvvdiv20ustdiv.png/
So what do I do now? Test the diodes? Replace the diodes (which I
believe are ok, they did deliver on the first prototype), inductors?
Thank you all for your time.
Imbanon
Adam Jacobs
instead of $5 worth of stuff. :D
-Adam
Imbanon
Anyways, I just tried the frequency measuring function on the scope.
On the breadboard I got 32kHz which is great. On the other hand, I've
got only around 21kHz on the PCB which is 100% copied from the PDF
instructions.
unpleasant_persona
assuming you are using +/-10% tolerance resistors you may see a range
of 27.5-33.6kHz and that's not even accounting for the cap, C2. If
you're actually using 20% resistors your range can vary as low as
25.25kHz. So 21kHz is still a little low but not outside the realm of
reason. A quick experiment would be to swap resistors in your
breadboard ans see what variance you get there but I doubt this is
your problem.
Another thing that's important to check is your feedback node:
collector of Q2. If the base is never being brought above ~0.7V then
your oscillator won't shut off when it should and you'll end up with
move than the desired 170V at the output. I'm not sure how far it can
run away but it would certainly lead to components being fried because
your FET drain would see higher and higher voltages before the diode
turns on, potentially damaging the FET.
Try disconnecting the diode on your breadboard and applying a 12V DC
to the output node (where you expect 170V) and see what voltage you
measure at the base of Q2. Do this with the oscillator unpowered (no
12V where it usually goes, just where it usually doesn't). You should
see about (0.7/170)*12 = 49.4mV. If its much higher than that you are
likely getting too great of an output voltage and it's burning out you
FET.
Just a though. I haven't built this circuit yet but I've spent the
last few evening learning about it in detail.
If I've said anything grossly in err someone should correct me! :)
Cheers,
Steve
unpleasant_persona
order them separate. If they were ordered separately you may want to
make sure you got the 400V ones and not the 20/40V...
I'm guessing since you said you installed a heatsink that you got the
correct one in the TO-220AB package (the big standup kind).
Imbanon
> Just a quick question: your FETs, are they from the kit or did you
> order them separate. If they were ordered separately you may want to
> make sure you got the 400V ones and not the 20/40V...
Got them separate. No kit, just plane copying the schematic and the
board. Pretty sure it's the right one. It is the TO-220AB package.
Also, I got my hands on the college scope, and measured it right this
time. 11.5volts on the 555 output (12v input), 30kHz, really nice
square waveform.
> Try disconnecting the diode on your breadboard and applying a 12V DC
> to the output node (where you expect 170V) and see what voltage you
> measure at the base of Q2. Do this with the oscillator unpowered (no
> 12V where it usually goes, just where it usually doesn't). You should
> see about (0.7/170)*12 = 49.4mV. If its much higher than that you are
> likely getting too great of an output voltage and it's burning out you
> FET.
Measured 54.7mV. I guess that is fine.
I can't measure the voltage between the base and the emitter on Q2
yet. Don't want to put in another FET and burn it like the other 3. I
want it to be the last thing.
So I would say that the problem really is in the cheap chinese
components! And hopefully, I will get a replacement soon! :)
And just one question. I checked the shipping prices from Mouser and
Digi-key. They were both between $100 and $120 for a single item. Is
it always like this (I am in Europe).
JohnK
If you really get stuck I can mail parts to you from Australia. For example
check this supplier :- http://au.element14.com/
John K.
----- Original Message -----
From: "Imbanon" <imba...@gmail.com>
To: "neonixie-l" <neoni...@googlegroups.com>
Sent: Friday, November 25, 2011 11:17 AM
Subject: [neonixie-l] Re: 555 power supply not working
...clip....
So I would say that the problem really is in the cheap chinese
components! And hopefully, I will get a replacement soon! :)
And just one question. I checked the shipping prices from Mouser and
Digi-key. They were both between $100 and $120 for a single item. Is
it always like this (I am in Europe).
...clip...
Charles MacDonald
> And just one question. I checked the shipping prices from Mouser and
> Digi-key. They were both between $100 and $120 for a single item. Is
> it always like this (I am in Europe).
>
International shipping is always a grey area. You may do better with a
European distributor. Best way to find them is probably by starting at
a semi makers site. and look for that brands distributors for your part
of the world.
unpleasant_persona
> > to the output node (where you expect 170V) and see what voltage you
> > measure at the base of Q2. Do this with the oscillator unpowered (no
> > 12V where it usually goes, just where it usually doesn't). You should
> > see about (0.7/170)*12 = 49.4mV. If its much higher than that you are
> > likely getting too great of an output voltage and it's burning out you
> > FET.
>
> Measured 54.7mV. I guess that is fine.
54.7mV is good, it means that you'll come in somewhere under 170V and
not way over. So your FET will be safe from that perspective.
Another point that someone in the thread had made was to ensure that
your diode wasn't a general purpose diode but something quick (not
sure if signal diode is the right term here). If it is too slow the
drain voltage on the FET can still get quite high before the diode has
a chance to forward bias and conduct any appreciable current.
> I can't measure the voltage between the base and the emitter on Q2
> yet. Don't want to put in another FET and burn it like the other 3. I
> want it to be the last thing.
When you do end up finally powering up with your FET back in the
circuit you'll probably want to have a look at the CTRL pin (collector
of Q2) to make sure that it does go low on occasion. Otherwise your
oscillator is always be going.
I would expect that the oscillator would stop for a bit and then
restart.
Like I said. I haven't built one of these yet but I plan too very
shortly and I'm really interested in knowing what ends up being the
root of your problem.
Steve
John Rehwinkel
> Digi-key. They were both between $100 and $120 for a single item. Is
> it always like this (I am in Europe).
In Europe, you'd likely do better ordering from RS, Farnell, or even Jaycar or Futurlec.
- John
Tidak Ada
eric
-----Original Message-----
From: neoni...@googlegroups.com [mailto:neoni...@googlegroups.com] On
Behalf Of John Rehwinkel
Sent: vrijdag 25 november 2011 22:13
To: neoni...@googlegroups.com
Subject: Re: [neonixie-l] Re: 555 power supply not working
Per Jensen
We have a local warehouse in Copenhagen, and if it's in stock there you can pick it up at the counter and pay by cash, but if it's not in stock, you'll have to order it online and pay for shipping to your home address.
// Per.
threeneurons
> Measured 54.7mV. I guess that is fine.
>
> I can't measure the voltage between the base and the emitter on Q2
> yet. Don't want to put in another FET and burn it like the other 3. I
> want it to be the last thing.
Making too big of a deal over the FET. Unless you're really cranking
out some current (over 30mA out), a FET like the IRF730 will do just
fine.
I'm betting the coil is too puny, current wise. Its probably
saturating under 200mA (in), and the rest of the current over that is
just going up as heat, instead of adding to the magnetic field. Also,
I wouldn't be surprised if the Chinese are making their own UF4007s,
by getting 1N4007s and re-stamping them.
Imbanon
especially the diodes.
Can't wait to fix the supply. Haven't seen my nixies illuminating the
desk for a while now..
Imbanon
Got some news on the supply!
I got some replacement parts (big thanks to Threeneurons here), and
got it all working as intended. I replaced the diode and the FET, I
left the cheap chinese coil on, and it all worked like a charm. So I
guess I'll be pointing my blame finger on the diode..
Finally, I can now continue the second part - coding :)
So thank you all for your help, you've all been very helpful!
unpleasant_persona
Matzenegger
Huggermugger
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Frank Bemelman
Krzysztof Więckowicz
Check te voltage divider at the outpup. Are resistors properly placed?
Dnia 2012-07-29 19:41 Huggermugger napisał(a):
----- Original Message -----From:Matzenegger
Matzenegger
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Matzenegger
That was it, just a bad inductor... Kind of ashamed now, but happy you helped me get this beauty working!
Thanks! :D
Sam
