need help with constant current PWM conversion from 12v to 24v

SgtWookie

Joined Jul 17, 2007
22,230
All photos you posted are blurry. It looks like the camera moved when the exposure was being taken. Difficult to make out anything.

Apparently, you used the latest Cadsoft Eagle. I'm running 4.16r2, and it can't read version 5 or later.
 

SgtWookie

Joined Jul 17, 2007
22,230
Is there a certain part you want to see or should I just try the same pics again?
Try the same pics again, but hold the camera more steady - and a bit further away. If you have a tripod, use it.

I'm using eagle 5.6.0
Ok. In that case, do a screen print (Ctrl+PrintScr), paste it into MS Paint, crop, save it as a .PNG file and upload it.

Do the same thing with the .sch file.

My Eagle is registered, and I don't want to spend the money to upgrade to v5.6.
 

Thread Starter

samuraimarc

Joined Mar 28, 2009
48
Ok my computer at work doesn't have paint on it, so I'll get it done when I get home.
My eagle isn't registered but they still let you up grade just run it as freeware. and you can keep your old version it won't over write it if you save the download to your documents and load it from there.
I don't have a .sch file just the .brd file.
I'll get the pics and .brd file switched and get it back to you about 5:00 MST
Thanks
 

Thread Starter

samuraimarc

Joined Mar 28, 2009
48
I followed your schematic to make the first one, then made the upgrades after I got the dual op-amp. I'm not familiar with the program just self tought. I started using it to make the old "ZFFPWM" board and just drew the board. never used the schematic part of it.
 

Thread Starter

samuraimarc

Joined Mar 28, 2009
48

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SgtWookie

Joined Jul 17, 2007
22,230
Do you know of a good online course for learning more about how to use an O-scope?
Here's a decent basic tutorial:
https://www.cs.tcd.ie/courses/baict/bac/jf/labs/scope/
Another: http://www.williamson-labs.com/scope-main.htm#top
Tektronix tutorials: http://www.tek.com/learning/oscilloscopes/

Navy NEETS publications: http://www.tpub.com/neets/
See module 16, topic 6.
Oops, they now want you to pay to download at that site. Download it free here:
http://jacquesricher.com/NEETS/
The O-scope tutorial begins on 6-1, which is the 179th page.

BTW, sorry I haven't made any progress on your stuff. I've been out of town for nearly two weeks, don't have much of my stuff available, and just have short periods of time to be on the computer. I won't be back home again for several days yet.
 

Thread Starter

samuraimarc

Joined Mar 28, 2009
48
Hey no problem, I'm very thankful for all the help ou've given me so far. A few more days will give me the chance to go through the tutorial and be able to give you better answers or figure it out for my self even.
 

Thread Starter

samuraimarc

Joined Mar 28, 2009
48
Ok I found the real problem. M1 was blown and shorted causing the high amperage draw. I replaced it and went in for another test and got nothing. I hooked it up exactly like the diagram and R4 is going to the battery. I get 12.2v at the gates but the O-scope shows a very tiny ripple. I have a pulse coming from the 555 timer but it seems I have no real path for flow through the cell.
Any Ideas?
 

SgtWookie

Joined Jul 17, 2007
22,230
Ok I found the real problem. M1 was blown and shorted causing the high amperage draw.
Well, part of the mystery solved. ;) Oh, I'm back home BTW. Was a heck of a drive. :rolleyes:
I replaced it and went in for another test and got nothing. I hooked it up exactly like the diagram and R4 is going to the battery.
How about the other grounds in the circuit? Do they also go to the battery, but on wires separate from R4?
I get 12.2v at the gates but the O-scope shows a very tiny ripple.
12.2v relative to what? Ground? Or the source terminal of the MOSFET?

You have to realize that when measuring the voltage on the MOSFET's gate, the only reference you can use is the source terminal. If the gate is near 0v, the MOSFET will be turned off. If the gate is near 10v, the MOSFET will be turned ON.
I have a pulse coming from the 555 timer but it seems I have no real path for flow through the cell.
What is the P-P voltage of the pulse from the 555 timer?
 

Thread Starter

samuraimarc

Joined Mar 28, 2009
48
Well, part of the mystery solved. ;) Oh, I'm back home BTW. Was a heck of a drive. :rolleyes:
Welcome home

How about the other grounds in the circuit? Do they also go to the battery, but on wires separate from R4?
All of the other grounds are tied together and go to the battery, so i have two grounds going the the pwm.

12.2v relative to what? Ground? Or the source terminal of the MOSFET?
Ground. got nothing from source to gate.

You have to realize that when measuring the voltage on the MOSFET's gate, the only reference you can use is the source terminal. If the gate is near 0v, the MOSFET will be turned off. If the gate is near 10v, the MOSFET will be turned ON.
Rookie mistake:rolleyes:


What is the P-P voltage of the pulse from the 555 timer?
P-P? positive to positive? 8.12v using Fluke processmeter 789
did you get a chance to look at the pics?
Thanks
 

SgtWookie

Joined Jul 17, 2007
22,230
P-P means peak-to-peak. :)

I've been looking at your board a bit. It appears that you placed all of the parts on layer 1 (top), but made all of the traces on layer 16 (bottom), and then mirrored the board when you printed it out. This makes things a bit confusing.

I'm going to have to reconstruct what you've done to see if errors were made.
 

Thread Starter

samuraimarc

Joined Mar 28, 2009
48
ok, sorry bout that. I haven't completed the schematic yet. I've gone over it about a 100 times comparing it to your scematic but there could be something I'm not seeing.
I'm thinking that maybe the mcp14628 got hit when the mosfet shorted out. I think it's that or the op-amp is wrong.
 

SgtWookie

Joined Jul 17, 2007
22,230
The schematic really should've been created first, as I previously mentioned. Cadsoft Eagle really isn't terribly difficult once you get familiar with it, but the learning curve is rather steep.

Since you started off by creating a board, it will be very difficult and frustrating to create a schematic from the board.

I'll simply start from my schematic, using components physically sized similar to what you have, and go from there to see if I can re-create what you've done.
 

SgtWookie

Joined Jul 17, 2007
22,230
Here is what I have so far hope it helps
Are you using an OPA2344U for the op amp?
Are you using IRF512s for the MOSFETs?

Where is your regulator?

I dunno, you started out saying that you built it exactly like I had it in my schematic. Now it seems that you changed quite a few things, and I'm still trying to make heads or tails out of what you did on the PCB. I don't see C6 anywhere, which is a pretty important part.
 
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Thread Starter

samuraimarc

Joined Mar 28, 2009
48
SgtWookie;152166]Are you using an OPA2344U for the op amp?
I'm using the LM2904DMR2G op-amp that you suggested.

Are you using IRF512s for the MOSFETs?
I used a couple of n-channel mosfets I had an abundance of: IXTH240n055t

Where is your regulator?
The regulator's are the six square holes at the top I could'nt find the right one's so i measured and placed the holes where I needed them. You can see them in the pics I took.

I dunno, you started out saying that you built it exactly like I had it in my schematic. Now it seems that you changed quite a few things, and I'm still trying to make heads or tails out of what you did on the PCB. I don't see C6 anywhere, which is a pretty important part.
C6 and c2 are the same thing as the regulators couldn't find the right package to put it on the schematic. I can try to use paint and draw where all this stuff goes but I assure you it's there.

I changed out the MCP14628 and it bubbled for about 5 seconds then nothing. I couldn't get any readings. Thanks
 
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