My brother and I built a dual motor controller. We're trying to add a heater to the vw. He's rigged up tubing that goes around the exhaust pipes into a device that fits behind the back seat. It runs fluid through the tubing and then through an old oil cooler. A fan blows through the oil cooler and should (in theory) heat the passenger compartment.
I used the 555 based PWM controller from the Nov Nuts & Volts. I modified it to use a 556 so that we could control two motors separately (the fan and the pump).
My brother hooked it up today. Here is what he said:
So, here is the original schematic:Hey, it was all working for about a min, then it started smoking, then i turned it off. I took it apart to look, and the timing IC had melted partially, and there was a little chunk taken off of it
<img src="http://img363.imageshack.us/img363/7945 ... 6ug.th.jpg" alt=" - " />
Here is how the pins on the 555 (left column) corelate to pins on the 556:
<img src="http://img363.imageshack.us/img363/3186 ... 9vk.th.jpg" alt=" - " />
And here is my finished diagram:
<img src="http://img363.imageshack.us/img363/8003 ... 5cj.th.jpg" alt=" - " />
The transistors are T1P42 pnps. The diodes are 1N4148s. The potentiometers are 100K linears. The resistor connected to the base of the pnp is a 1k ohm. The resistors connected in series with the potentiometer are 6.8k ohm. The capacitors are 1uF non-polarized electrolytics.
The pump is rated at 3amp, the fan doesn't have a rating but it's not too high powered. I estimate 2 amps or less (likely far less).
The circuit is fused at 10amp and didn't blow. There's a relay connected to a switch that turns the whole circuit on and off. The circuit is built on a perf board and crammed into a hobby box.
Any idea why the smoke?
<small>[ November 22, 2005, 08:10 PM: Message edited by: Matt Nuzum ]</small>