Relay switching circuit please

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I need a simple circuit that will allow me to activate a 5 volt relay (max 200m coil) lusing a momentary action PCB mount tactile membrane (keyboard) type switch. I want the relay to remain on until the power supply is switched off, and then revert to the off position, ready to be activated agian by the switch.

Power supply for the circuit willbe +5V.

This relay will be used to force a NEC CDROM to read the TOC of a CD. Currently a simple microswitch on the CD transport tray does that job but I have converted the CDROM to top loading and do not want to use the microswtch.

Can anybody help?

Cheers,

Joe Newbold
 
Hi Frank,

I think I see what you mean (I am not an EE by the way). Does using a relay with N.O. contacts mean that the relay is open until I depress the momentary switch, and then, when the switch is dpressed, the contacts remain closed until power off?

Cheers,

Joe
 
Joe,

This is the circuit. Pardon the sloppy drawing. I did it in MS Paint.
 

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A very easy way to do this without any other electronics, is to use the membrane switch to close the relay using the 5V. Also wire the 5V through one of the spare contacts (if it is for instance a double relay) back to the coil of the relay. This way the relay will "keep itself on" until the 5V drops away.

I've built a couple of circuits using this technique, from car engine immobilizers to keypad security locks.

Hope this helps.

Regards
Paul
 
psmithmx said:
A very easy way to do this without any other electronics, is to use the membrane switch to close the relay using the 5V. Also wire the 5V through one of the spare contacts (if it is for instance a double relay) back to the coil of the relay. This way the relay will "keep itself on" until the 5V drops away.

I've built a couple of circuits using this technique, from car engine immobilizers to keypad security locks.

Hope this helps.

Regards
Paul


That's exactly what I told him.
 
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