engineer1000
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I want to use a din mounted opto coupler .I want to switch a relay with it. I have put the coil between 24V and collector of opto output. The relay coil is 445ohms so current will be 54mA. The output from the opto is 3-48Vdc 100ma so I'm not exceeding the current requirement.
Any circuits I see use a second transistor to do the switching, what is the reson for this?