Making a ground trigger with a transistor

I have a device thats activates with a ground pulse to one of its pins. I am making a pcb to do this wirelessly but currently using a pcb relay to connect the ground. Pin 87 is grounded and when the relay is activated it connects to pin 30 which then activates the device. Can this be done with something less bulky like a transistor rather than a relay. I cant seem so figure it out.

If you must do it in hardware, it sounds like an NPN transistor, say 2n3904 and base resistor, say 1k May work. But are both pins on the same mcu device? If so, can’t you do this with code?

I want to play it safe and use something else instead of the arduino that can handle more than 40mA. I can try it but i just worry about burning the board

ataveras64:
I want to play it safe and use something else instead of the arduino that can handle more than 40mA. I can try it but i just worry about burning the board

If there is any doubt about it, and you are considering a specific scenario, then show a schematic. Especially so if you are mixing logic level voltages. You could also google for "low side transistor switch" since you appear to want to pull a pin down to ground.

ataveras64:
I have a device thats activates with a ground pulse to one of its pins. I am making a pcb to do this wirelessly but currently using a pcb relay to connect the ground. Pin 87 is grounded and when the relay is activated it connects to pin 30 which then activates the device. Can this be done with something less bulky like a transistor rather than a relay. I cant seem so figure it out.

This is a pretty standard thing to do with an NPN transistor, as 6v6gt suggests. The mpu output pin goes to a 1k resistor, the resistor to the base of the transistor, the transistor emitter to ground, and the transistor collector to the pin you want to pull low. The current you can pass in this manner depends on the transistor (and also base current) but 40 mA should be no problem. If you do something really wrong it's likely that you'll destroy the transistor rather than the mpu, which is a decided advantage.
S.

What is the voltage between pin 30 and pin 87?

JCA34F:
What is the voltage between pin 30 and pin 87?

Yes, the open cct. voltage.

And, what current flows through a wire connection when the pins are connected to each other.

An OptoFET might work if there is need for 100% isolation.

This sounds a lot like it's an automotive relay.

  • Do you have a link?
  • Could you show a circuit diagram of what you tried?
  • What's the application?

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