Hi everyone. I've learned a lot from this site and have received help before with regards to BJTs, which I now understand.
I've been trying a uC in my car, despite all of the horror stories, etc. but that has somehow failed and I'm trying to replicate the circuit's functions using a simple 556 timer instead. Here's what I want to happen:
Timer is connected to permanent 12v supply. When a 12v trigger occurs from another source, I need a 12VDC relay to switch an external load for at least 5 seconds, and then switch back to normal operation (COM to NC pins on relay).
Attached is a schematic of what I have come up with so far. There is a TVS diode to protect the circuit from transient voltages: breakdown V is 18.9V MAX, so should protect the timer from excessive supply voltages.
I've fabricated multiple PCBs and wasted quite a bit of money so far on circuits that don't work, so I'd be very grateful if anyone could point out any errors I may have before I actually go ahead with this one.
Thanks for any help in advance.
I've been trying a uC in my car, despite all of the horror stories, etc. but that has somehow failed and I'm trying to replicate the circuit's functions using a simple 556 timer instead. Here's what I want to happen:
Timer is connected to permanent 12v supply. When a 12v trigger occurs from another source, I need a 12VDC relay to switch an external load for at least 5 seconds, and then switch back to normal operation (COM to NC pins on relay).
Attached is a schematic of what I have come up with so far. There is a TVS diode to protect the circuit from transient voltages: breakdown V is 18.9V MAX, so should protect the timer from excessive supply voltages.
I've fabricated multiple PCBs and wasted quite a bit of money so far on circuits that don't work, so I'd be very grateful if anyone could point out any errors I may have before I actually go ahead with this one.
Thanks for any help in advance.
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