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how to make an electronic relay switch? Answered

So I'm making this thing for my friend and i wanted to flash 27 LEDs with a 555 timer, thing is, you cant power 27 LEDs with that so i was going to use a relay switch to turn on a different power supply but it cant even power my smallest relay switches so i was wandering if anyone could tell me how to make a simple switch that can be turned on by a 555. 


Add a transistor between the 555 and the relay. Don't forget to protect the transistor with a diode. If you use something like an IRL540, you would connect the gate to the output of the 555, the source to the ground line, and your transistors to the source line of the transistor. No relay needed at all for this application.

Is there any way i could use a C945 cause i have a lot of those?

Yes, put a 470 ohm from the 555 to transistor base, emitter to ground, collector to the load. It'll handle 60V, at up to ~100mA. Its not got a brilliant gain though.


Not quite, the LEDs are connected to the POSITIVE supply - and that can be >>> the 555 supply.



6 years ago

A 556 is a dual 555 timers that can handle 300 ma each
Any way why 27 ?


12V- complimentry556.png

Could you build this with two 555s instead of a 556 and could you just make 3 rows of 9 LEDs instead of 10 rows of 4?

a 556 is a pair of 555s on the same chip. Weather you use a 556 or 2x 555 doesn't matter.

You can line the LEDs up however you want. You don't have to mount the LEDs in 10 rows of 4 you just have to wire them that way. Really you don't even have to wire them that way. There are many configurations you could wire them in but you will need to know the right resistor value to use in each grouping so you don't blow the LEDs. Just take the voltage, number of LEDs, and the specs of the LEDs and enter into the LED resistor calc liked below. That will give you several different wiring options and the resistors you need to achieve that setup.


But like i said how the LEDs are wired together doesn't dictate where the LEDs are placed. You can run longer wires to the LEDs and spread them out how you want.