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Need to replace some SSR with real relays. I have a footswitch rigged up that has an LED in the box that i want to maintain. Previous setup used the footpedal to ground an LED connected to a PNP transistor base. Emitter to power, collector to control pin of logic chip that then controlled the SSRs.
Here's what I propose after reading some about controlling relays. The same PNP controlling two more NPNs that control the relays. The collector of the PNP is now connected to the base of two NPNs through current limiting resistors. The Collectors go one of each relay control pin, the other relay control pin to power. The relays are 6V at 25mA, so with a 2N5089 with gain of about 400, with twice the amount of necessary current: 6V / ((25mA/400hFE)*2) = 48K for the NPN base resistors. The 2N5089 should be fine supplying 25mA to the relays.
This should work fine right? Do I need a pulldown resistor from the collector of the PNP to ground to set a 0V state to shut off the NPNs?
Thanks,
Mike
Here's what I propose after reading some about controlling relays. The same PNP controlling two more NPNs that control the relays. The collector of the PNP is now connected to the base of two NPNs through current limiting resistors. The Collectors go one of each relay control pin, the other relay control pin to power. The relays are 6V at 25mA, so with a 2N5089 with gain of about 400, with twice the amount of necessary current: 6V / ((25mA/400hFE)*2) = 48K for the NPN base resistors. The 2N5089 should be fine supplying 25mA to the relays.
This should work fine right? Do I need a pulldown resistor from the collector of the PNP to ground to set a 0V state to shut off the NPNs?
Thanks,
Mike
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