modified 9 years ago

Coil switch.

01:32:37

Small test circuit for driving a relay and led

published 9 years ago

BillyT

9 years ago

As you have allready noticed, the relay's pull in voltage needs to be less than the rated power supply voltage, and the led resistor would be better if it was about 150 ohms.

rich11292000

9 years ago

Your relay is going to put a voltage surge on the led.

separateness

9 years ago

Would a flyback make it better? In reality i am going to be using a uln2003 to drive a dpdt ea2 signal relay to divert a guitar signal to some effects pedals. The uln has a com pin that , when tied to Vcc works as a flyback, i believe. The actual pull in voltage is 3.75VDC. this seems reasonable to you fellas?

rich11292000

9 years ago

The built-in flybacks protect the chip and anything "upstream" of the chip. With the relay and led "downstream" in parallel, the led will still take some of the voltage spike. A fly back diode should directly connect to the coil, utilizing the shortest path possible.

rich11292000

9 years ago

I would rather switch from the ungrounded conductor instead of the grounded conductor. Having components tied to a clean ground vs a noisy power supply, also static.

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