| Electronics > Beginners |
| Simplest circuit to connect/diconnect a wire. |
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| Ian.M:
No optocoupler is needed if you can link PIR 0V to bell 0V. You only need the optocoupler if you need isolation. OTOH an ordinary BJT output optocoupler could replace the N-MOSFET with its output transistor collector directly pulling down the P-MOSFET gate. |
| David Cutcher CEG:
You've given limited information. The least expensive source of push buttons is old equipment, or junk electronics, from garage sales. An old computer keyboard (of the right style) will provide you with 80 push buttons, all momentary normally open momentary. To buy one individually would be about $.50 each. But depends what you want. David Cutcher "Certified Evil Genius" |
| Ian.M:
WTF??? The O.P. wants to get away from the existing push button, not add 80 more of them! @hgg, I think we were all assuming it needed to switch a lot of current to power the RF transmitter module. If its only a logic signal power MOSFETs would be over-kill. If you can guarantee to wire the load side the right way round, an ordinary BJT output optocoupler would probably work OK. If you get it wrong, 10uA wont do any damage to it so if you cant identify the Vcc wire to hook up to its collector, just swap the output wires till it works! If it rings continuously, you may find it needs a pulldown resistor to bell 0V on the load side to deal with any leakage current when the optocoupler is off - 100K would probably be suitable. |
| hgg:
Ian.M thank you, I will try that. |
| SilverSolder:
--- Quote from: hgg on April 20, 2019, 02:04:52 pm ---SilverSolder, I thought of that [reed relay] as well, but I don't have any available at the moment. It also needs 10mA. --- End quote --- It only needs 10mA for the few seconds that someone presses the bell - the rest of the time it uses nothing, and has no leakage. |
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