Maintain current

[stevo11]

Its ALIVE!!! Its ALIVE!!!! (My Gene Wilder impresion, young frankenstien) I started to type this, sat down and ate lunch. Came back from lunch to test it again and when i turn the amps up it will not come back down. I am also measuring amps with an DM set to 10a and at its lowest pot setting runs at 2.48 - 2.60. when i turn pot all the way up it goes to 3.45. I am not sure but when i turn on the pwm is it running 24.8 amps and when maxxed 34.5 amps?

TY for all the help, yall been great.



Stevo

[stevo11]

Ok, i just searched for the breakdown and found it on Ridelong schematic, 10mv=1amp, i new i saw it somewhere.



Stevo

[ridelong]

Actually, the 339 is an open collector output, so it is fine to ground all the unused pins. I just put inputs only out of habit.

[ridelong]

stevo11,

You can measure across the 25 watt, .01 ohm resistor with a voltmeter set to 200 mv or 2000 mv (2 volt).

On 200 mv scale, if it reads 143.5 mv, it means 14.35 amps.

On the 2000 mv scale, if it reads 144 mv, it means 14.4 amps.

Hope this helps.

BTW, the lowest pot setting should be betweem 3 and 5 amps. The highest setting is around 30 amps.

[stevo11]

I have attempted to build this pwm 6 times, one i had going for a little while and the others basically failed.

I have enough parts left for 1 more attempt and I dont want to waste them. I am looking for someone to build it for me please. Any takers out there?



Stevo

[galkaen]

Ridelong

Would you be kind and post a picture of your finished unit, please. Even if it is made on a perf board it would be of great help to see the actual connections.

Thanks in advance:
Galkaen

[ridelong]

Galkaen,

Here it is.

It's drawing 10.64 amps.

http://www.mikecramer.com/images/iproto.jpg

[h2ocommuter]

I have attempted to build this pwm 6 times, one i had going for a little while and the others basically failed.

I have enough parts left for 1 more attempt and I dont want to waste them. I am looking for someone to build it for me please. Any takers out there?



Stevo

Stevo,
I believe I should get my next one right but I am going over the last one untill I find the problem; My mistake I am sure.

I have an issue I am going to scrutinize untill I decern the answer.
I like the example of ridelongs and I will be able to get a better concept of what it could look like.

I am courious as to the what looks like a heat sink but I don't see the mosfet. thats ok I will have this one done in a couple of days the last one took 3 to 4 days. ( I had no clue) LOL

I am having fun but strugling to get it right.

[ridelong]

h2ocommuter,

The black thing is the heatsink for the fet.

The fet is mounted horizontally on the heatsink with the legs pointing toward the terminal strip.

The gate lead is the closest pin to the perf board.

Hope this helps.

[h2ocommuter]

Stevo,
I believe I should get my next one right but I am going over the last one untill I find the problem; My mistake I am sure.

I have an issue I am going to scrutinize untill I decern the answer.
I like the example of ridelongs and I will be able to get a better concept of what it could look like.

I am courious as to the what looks like a heat sink but I don't see the mosfet. thats ok I will have this one done in a couple of days the last one took 3 to 4 days. ( I had no clue) LOL

I am having fun but strugling to get it right.

I had put the 20 ohm and the20k in the reverse places, at that piont I was getting a consistant voltage to the cell but no adj. were poossile, So at that piont I put a jumper wire across the sweep "between the 49,and the 20k" and that was not the answer and I had no out put to the cell at all, so I shorted the ground directly to the ammeter on the cell and adj the sweep and I poofed the 339 I think. I tore it down and found the 20 ohm and the 20k mixed up and my heat sink was rather big and I had atached the .01 to it with big wires and I pulled the mosfet apart. I replaced it with a scavengered one but I could not redeem the unit. I am going to build another.


Happy just to learn this stuf. And thanks to all.....