R.G. Keen's Blog

Parts list for remote button pusher

Posted in Uncategorized by rgkeen on May 23, 2011

OK, I got a few requests for the parts list, so here it is:
Tr1 = wall-wart, 8Vac to 12Vac, or 10Vdc to 15Vdc output; this is very non-critical, as the other parts are designed to work with a wide range here.
DB1 = 1A/100V Diode Bridge Example: DF01S (Fairchild); this replaces the four diodes in the full wave bridge.
IC1 = 78L05 5V 100ma regulator
C1 =470uF/25V capacitor
C2 = 0.1uF 25V (or more) ceramic capacitor
D1 = 1A/100V (or more) diode
R1 = 1/4W 2.2K
IC2 = Microchips Technology TC54VN2702EMB713 (2.7V trip point, open drain)
R3 = 220 ohms 1/4W
ISO1 = transistor output optoisolator: example Fairchild FOD852

Notice that the specified TC54 part is an OPEN DRAIN output, so the schematic must be rearranged so that R3 attaches to the +5V supply to the TC54, and the cathode side of the LED in the optoisolator attaches to the output pin of the TC54. This is slightly different from the more generic schematic shown in the first posting.

The usual cautions apply here: you’re messing with AC power issues (although the wall wart keeps you out of the worst of it) and also messing with the power system on your computer. Don’t even try this unless you know and accept the risks of doing this, and have the skills to do this right. I have built one of these, and mine works. I may have made mistakes or omissions here; I don’t think so, but it’s always possible. You take responsibility for how your unit turns out if you build this.


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