HHO Generator Project - help needed

hho control box



I have a PWM to control the current for a 12volt DC hydrogen generator up to 30 amps.
The PWM has a 10K variable pot on the board with three connection points (soldered to board) I want to remove this pot and wire it inside the vehicle and leave the board under the hood where I can put a heat sink and fan on it to cool it. I will be running it at from 15-20 amps but as the generator heats up so will the current draw go up so I want to be able to reduce it from inside the vehicle. Can I use plain 22 gauge wire twisted or shielded? Not sure about the resistance increase either or gauge of wire to use. The wiring and pot will be approximately 8 feet from the board (physically about 5 feet but to route it around and to the control box I’ll put it inm, it will be about 8-10 feet of 3 wires).

Thanks
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Detailed question. Deserves an answer.

A wire dimensioning/diameter problem usually can be easily solved using a wire gauge calculator (just google it there are plenty).
Usually the longer the wiring the thicker it should be - even though there will not be high current as it's just a poti (variable resistor) to an ADC for the \[\mu\]Controller. Unfortunately this means the pin voltage (thus the poti wire voltage level too) will not be higher than 5V, if not even only 3V. Another reason to better use too thick a wire than too small.

The wire size calculator should give you a good idea. Nevertheless I'm not sure about noise immunity - after all the analogue signal is going to be converted to a digital value (by the ADC hardware), and you don't know if there is any filtering or if it is enabled in software or not. So a cap for smoothing the signal could be necessary (signal to ground). Anyone correct me if I'm wrong?

It would help to see a schematic. We don't know if the pot's just controlling DC, or if the PWM signal's going through it.

The pot resistance normally ranges 5k-10K. A filter capacitor connected between center pin and ground will solve noise problem 9 if it is not already there. Small thickness wires may have near 10 ohm resistance and thick wire be of 1-2 ohm. Practically either will do.

1.

Links to charts of wire gauges showing resistance per wire length:

http://amasci.com/tesla/wire1.html



http://www.powerstream.com/Wire_Size.htm

2.

Will an engine be running at the same time as you operate the hydrogen generator? If so, there is the possibility that unshielded wires could be affected by alternator noise, ignition noise, spark plug noise, etc. I don't know for sure, it's just something to be on the lookout for.

3.

as the generator heats up so will the current draw go up so I want to be able to reduce it from inside the vehicle.

Click to expand...

If you wish to experiment, you can add a temperature sensor, so it will adjust operation automatically.
You'll need a few additional components. Probably a transistor or op amp.