Hi, I am building a circuit in which the output of an LM 339 comparator activates the coil of a 5V relay to close the switch. I tested the comparator and it works perfectly by itself. So does the relay, by itself.
In the schematic below you can see that in this state the comparator outputs 5V. The problem is, when I connect the comparator output to the coil of the relay the voltage at the output of the comparator drops from 5V to 0.555V. I would like to know why this is and how can I fix it?
I am thinking it might be because the output resistance of the LM 339 is much higher than the input resistance of the relay coil, and thus a voltage divider is created where most of the voltage is dropped across the comparator and 0.555V is dropped across the relay coil. Am I right?
If so, I could probably use either an emitter follower buffer or an op amp voltage follower to raise the input resistance of the relay.
In the schematic below you can see that in this state the comparator outputs 5V. The problem is, when I connect the comparator output to the coil of the relay the voltage at the output of the comparator drops from 5V to 0.555V. I would like to know why this is and how can I fix it?
I am thinking it might be because the output resistance of the LM 339 is much higher than the input resistance of the relay coil, and thus a voltage divider is created where most of the voltage is dropped across the comparator and 0.555V is dropped across the relay coil. Am I right?
If so, I could probably use either an emitter follower buffer or an op amp voltage follower to raise the input resistance of the relay.
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