Guys, I want to activate a 24V relay, with a coil current of 100mA and I want to isolate it from the ATmega328 output, to have the 5V ground isolated from the 24V ground.
Initially I thought of an optical coupler, I have a 4N35 here, but it does not support 100mA, so it would have to trigger a transistor and the transistor would trigger the relay.
Does anyone have a circuit with this scheme, I am in doubt about how to drive the transistor through the optocoupler in the 24V line.
One of the main features of a relay is that it isolates the controlling voltage from the switched circuit - so why do you want to provide this extra, double isolation?
It's just that I have a 24Vc source that triggers the optocouplers at the input of the circuit and I want to use it to also trigger the relays and I don't want to join the GND of this source with the GND of the 5V, because this source has some wires connected to it that run through a long way.
100mA is a large current for a 24V relay, can you post more information about the relay? Brand name and part number? Datasheet?
Using google you will find several.......
See if this helps.
or this:
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