Maintain current

[ridelong]

Jaxom,

You can remove the zener and 135 ohm. They setup a stable reference voltage for the divider.

[h2ocommuter]

Jaxom,
I found the same thing, so I called and they told me to change a couple of letters around and they were there at a 5 to 10 pack quantity. I ordered enough parts for a min, of three ( Shunt potentiometer ) Or pwm and where I had to get more, I won't have to order them next time.

1 10 10 0 0 1N5349BTPMSCT-ND 0.39000 $3.90
2 3 3 0 0 CT2201-ND 2.71000 $8.13
3 3 3 0 0 LM339NFS-ND 0.47000 $1.41
4 3 3 0 0 IRL1404ZPBF-ND 3.67000 $11.01
5 5 5 0 0 20.0XBK-ND 0.09800 $0.49
6 5 5 0 0 20.0KXBK-ND 0.09800 $0.49
7 3 3 0 0 CMF133QFCT-ND 0.29000 $0.87
8 10 10 0 0 1460PH-ND 0.16600 $1.66
9 5 5 0 0 10MQBK-ND 0.05400 $0.27
10 10 10 0 0 CMF49.9KQFCT-ND 0.25700 $2.57
11 3 3 0 0 CMF1.00KQFCT-ND 0.29000 $0.87
12 6 6 0 0 CMF24.9KQFCT-ND 0.29000 $1.74

You will be able to figure out where the changes are.

[h2ocommuter]

ridelong,
If you could express what to do in this circumstance: I intend on using 6 volt big truck batteries to power my electrolizers in many applications for sale. so I wonder if I need to do somthing different besides changing the 20 meg to eclude the 49.9 k so it is only touching the 2 and 5 pins? Hope I said that right.
I don't know how many amps I willl be pulling, I am just now building my first "whoper"
I hope to produce 2 gal min gas continually. I want to keep my temp to ngt 135 deg.
So I will have to let you know the progress.

[Jaxom]

Good deal...thanks for the info. The FETs and other stuff have already been shipped (should be here tomorrow) so I'll probably just source the resistors locally for the sake of time. I'll keep this info handy for the next time around though.

Also, 2gal/min is a lot of HHO...you'll have to really push some current to get that from a 6v supply. I'd expect a current draw of at least 150-180 amps.

[ridelong]

h2ocommuter,

The circuit that I published on this thread will only handle 30 amps. Also it was designed to work on 12 volts. It won't work on 6 volts. It would probably fry the fet on 6 volts because there would not be enough gate drive.

To do this circuit for 6 volts would require a total redesign.

I would need the maximum current, operating voltage spread (for example 12 to 14.4 volts).

With that data, I could find what will work for you

[h2ocommuter]

Thanks ridelong

Thats ok,

Normal big trucks have 4, 6V batteries. so i thought of using just one of them.
No prob, I don't need to use just one it was just a thought. no biggie...

Thanks for the offer.

[donnylynn]

Here is a link to the schematic of the current feedback pwm.

http://www.mikecramer.com/images/ebay/ifeedpwm.jpg

In your circuit you use a resistor to sense current. What if you put a series ammeter there instead? Is it possible to use it as a sense resistor? or does the voltage across it change with respect to current? I know that somehow the ammeter divides off a percentage of the current to create a voltage to drive the meter mechanism, but dont know the specifics of how it works. Just thinking of performing 2 functions with one part. I was considering this ammeter from harbor freight.

http://www.harborfreight.com/cpi/cta...emnumber=95778

[ridelong]

donnylynn,
The ammeter will act as a resistor in the circuit.

The problem will be scaling. The resistor in the schematic will develop 10 mv/amp across it. The pot voltages are set to match the resistor voltage. The current can be determined by the voltage across the resistor (100 mv=10 amps).

If the ammeter is not close to .01 ohm, the pot scaling will not be known.

[Jaxom]

Well I finally got this thing assembled. Digi-Key messed up my order and sent me surface-mount ICs so I had to wait for the right parts to come in. It's not tested yet, but it's built and modified for progressive control based on a 0-5v input with the output range adjustable between 0-10 and 0-60 amps (0v=0A, 5v=[5-30A adjustable] on each of two output channels.) The whole unit measures 4"x4"x1", not counting the adjustment knob, and it's a simple 5-wire hookup. I still need to find a box to put it in.

[ridelong]

Jaxom,

Glad to hear you finished it.

It will be interesting to see what the setup does for mpg.