Tuesday, May 26, 2009

Something I Worked Out While Driving My Truck

OK so this is probably not going to have any pictures, but I need to get this down somewhere. I was thinking about Chase's Eclipse, and how the relay circuit I built was pretty big since I used relays instead of an IC. The reason I chose to go with relays in the first place is because I couldn't figure out a way to get an IC to tie into a real-life circuit. What I mean by "real life" is a circuit that has voltage AND current. And yes, I know that there is a little bit of current in an IC, but never enough to really work with. Definitely not enough to trip a relay. So the question I had always wondered, was how do you get a circuit at 5 volts and almost zero current to do anything useful?

I think the solution involves finding a field-effect transistor with a cutoff voltage (or "cuton" if it exists) of 5V. Then, tying the IC output to the gate of the FET and using the source and drain as the "switch" for the main circuit. FETs can usually handle exponentially more current from source to drain and only need a voltage at the gate to turn them on or off. I think this is a perfectly good solution to minimize the scale of Chase's circuit and increase reliability. (Relays wear out after about 500,000 operations.)

But any way, last night Chase and I were working on the Eclipse and remembered that the rear center plate that actually says ECLIPSE is the stock plate, and it's tinted red. So no matter what color the lights are on the inside, on the outside they'll be red. So this pretty much negates the need for the circuit whether it's built from ICs and FETs or from relays. We're still going to put 7000 mcd white LEDs back there, only they're just going to be wired straight into the brake lights and that's it.

More on that later.

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