Inexpensive relay need for LED project

I have a circuit that turns on an LED. Outputs approx 3v. Instead of turning on the LED, I want to trip a relay. On the other pole I will have a separate LED circuit consisting of a 9V battery, resistor, and set of 4 LEDs.

What I need is a cheap relay capable handling the above requirements.

Thoughts?

Latch

0 YT2095 over 13 years ago

are you asking where to buy the relay from? or a cct to drive said relay from the bits you have?
Farnell will likely sell such a relay, and to drive it you`ll need a simple NPN transistor like a BC108 or 2N2222A2N2222A, and resistor for the base so the 3V doesn`t overdrive it, and a bias resistor to pull it low.
probably a good idea to have a reverse biased diode across the relay coil too.
that`s about it really

edited to add: and don`t forget to make both grounds common for both power supplies.
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