Do you have an oscilloscope?

The voltages you measured before don't quite add up - unless you're operating from a battery that's discharging the whole time you're experimenting.

What do you measure from ground to the source of M1, ground to drain of M1, gate of M1, and then the low side of L1?

From your prior measurements, I'm suspecting that perhaps M1 is turning on only partway, but I need more info to be certain.

 

Do you have an oscilloscope?

Yes but I don't have any leads for it.

The voltages you measured before don't quite add up - unless you're operating from a battery that's discharging the whole time you're experimenting.

I am using a fully charged battery but i'm not charging it while expermenting. Shoud I be?

What do you measure from ground to the source of M1,
1.2v
ground to drain of M1,
12.2v
gate of M1,
4.7v
and then the low side of L1?
1.7v

Hope this helps, Thanks

 

So, it looks like M1 isn't turning on all the way. Any Ideas what would be preventing this? maybe C6 neeeds to be a different value? any Ideas are appreciated.

 

Well, it would help a lot if you had a probe or two for your O-scope. I bought a few 100MHz probes on E-bay for around $10 each. They're not great, but certainly more than adequate for this task.

M1 needs to turn on a time or two before C6 gets fully charged. If the 555 timer isn't oscillating, that would be one cause.

 

I don't know why I didn't think to look on ebay for probes. I'll have to check 'em out and check the timer. Thanks

 

I got the probes for my O-scope and the output of the timer is flatlined. I've checked the resistors and they are correct as well as the circuit as per the drawing.
Any Ideas would be appreciated

 

OK. The 555 timer portion is probably the easiest part of the thing to fix. There's C1, R1, and the control voltage.

Are you getting any voltage/signal on pins 2, 3, and 5?

Are you reading ground on pin 1? Do you have voltage on pins 4 and 8?

 

OK. The 555 timer portion is probably the easiest part of the thing to fix. There's C1, R1, and the control voltage.

Are you getting any voltage/signal on pins 2, 3, and 5?

I am 3,5 are the same voltage and signal and same waveform as 8 and .3vdc. I'm not real good at the o-scope thing yet, but the wave form looks like a shallow dish then it rises to a little hill then to a much larger one. pin 2 looks like a shallow sine wave but it all positive.

Are you reading ground on pin 1? Do you have voltage on pins 4 and 8?

Yes pin 1 is grounded. pin 8 has .26v and pin4 has 11.84 vdc. I need to charge the battery.

 

I am 3,5 are the same voltage and signal and same waveform as 8 and .3vdc.

Pin 3 is the output from the 555. It should be roughly a square wave, varying between nearly 0v and about 1.3v to 1.7v less than pin 8.

I'm not real good at the o-scope thing yet, but the wave form looks like a shallow dish then it rises to a little hill then to a much larger one. pin 2 looks like a shallow sine wave but it all positive.

Pins 2 and 6 should have identical waveforms on them (they should be connected together). They should look roughly like a sawtooth wave, who's points are approximately 1/3 and 2/3 of the voltage level on pin 5.

Yes pin 1 is grounded. pin 8 has .26v and pin4 has 11.84 vdc.

Pin 8 is a problem. It needs to be adjusted so that the pin 3 output is nearly 0v when low, and nearly 5v when high. Since the output of the 555 timer has a Darlington pair that pulls the output high that has a voltage drop of somewhere between 1.2v and 1.8v, you'll need to supply pin 8 of the timer with between 6.2v and 6.8v. The easiest way to do this would be to use an LM317 adjustable 1.5A regulator; adjust the regulator's output while looking at the pin 3 output.

Note that the MCP14628 requires a Vcc of 4.5v to 5.5v; nominally 5v.

I need to charge the battery.

Yes, you certainly do. Lead-acid batteries begin to sulphate at about 12.5v. Sulphation greatly shortens their life. I suggest using an automatic charger of no more than 6A capacity to keep the battery charged. Giving the battery a high current charge will raise it's internal temperature very significantly, causing greatly increased chemical activity and shortening battery life.

 

I changed the 7805 to a 7806 regulator before I got your reply and it works. will this be to much voltage for the MCP14628? It does a good job in producing the hydrogen The only problem I hve now is I can seem to adjust the current. I used a 1k trimpot for R9. I might have the op-amp hooked up wrong. I didn't sue pins 1,5,or 8. 1 and 5 are offset null here is the data sheet of you need it.
http://www.fairchildsemi.com/ds/LM/LM741.pdf
Thanks again for all your help.

 

I changed the 7805 to a 7806 regulator before I got your reply and it works. Will this be to much voltage for the MCP14628?

Yes, that's too much voltage for the MCP14628. Use the 7805 regulator to supply it, and the 7806 to supply the 555 timer.

It does a good job in producing the hydrogen. The only problem I hve now is I can't seem to adjust the current. I used a 1k trimpot for R9. I might have the op-amp hooked up wrong. I didn't sue pins 1,5,or 8. 1 and 5 are offset null here is the data sheet of you need it.
http://www.fairchildsemi.com/ds/LM/LM741.pdf

You cannot use an LM741 opamp for this circuit. You must use an opamp that can reach the lower rail (ground) for the input. You might get by with an LM324.

 

[QUOTEYou cannot use an LM741 opamp for this circuit. You must use an opamp that can reach the lower rail (ground) for the input. You might get by with an LM324.[/QUOTE]

Ahh man, I don't know why I spaced that I talked to you about it earlier in this thread. Ok I can get another. The one I'm looking at says it has a negative rail and is described here :http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMtOXy69nW9rM5wfe4h9MwciRN/6SkgMXRg=
Will I be able to use this one?
Thanks

 

That's an LM358 in a SMT package.

You'd be better off with an LM2904 in a DIP package. The LM2904 is basically the same as an LM358, but is for a broader temperature range.
http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMtCHixnSjNA6JEg9YovI8%2bdHXSu5CYHL7Q=

You'll need to wire the unused opamp as a voltage follower to keep it's output from being in constant saturation. Wire the inverting input to the output, and the noninverting input to a voltage divider across the opamp's supply pins. A couple of 5k or 10k resistors would work just fine.

 

Right on, I was trying to do everything in smt cause thats how the MCP14628 came and I couldn't find on in a dip package. Thanks for the advice on the unused op-amp I woulnd't of know to do that.

 

OK.

So, here's an LM2904 in an SMT package:
http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMtCHixnSjNA6JBn1Gc5N1erpLR3nGnHosc=

Roughly the same price, but better temp specs.

 

Nice, thanks a ton for your help. I'll get some stuff coming and try it all again.

 

Well I got it all together and I can't adjust the amps at all. It's putting out a constant 80 amps. I'm looking for connection problems, but can seem to find any other problem that would cause this.
Thanks for you help.

 

I'm not sure if My o-scope is working right, it hasn't been calibrated since '87. But I can't seem to locate the waveform for the gates. I can still see it on the old "PWM". What else can I do?

 

I think you have a problem with the grounding.

R4 (the 2-foot length of AWG-10 stranded wire) should be connected to the battery, and so should the remaining grounds. So, you need at least two seperate wires.

If your board is very far away from the ground, that could present problems, too.

Take some photos of what you have and post them.

 

I had R4 going to the positive side of the cell which also is on the source of M2, and the drain Of M2 to the negative side. Also source is connected to the battery - and drain of M1 is to battery +. I'll send the schematic I made on Eagle as well. R8 is an 82k resistor. Thanks