a friend has this question ......

Hi Guys,

I’ve got a problem with an electronics project that I’m trying to solve. I’m hoping one of you can give me some guidance.

I am trying to get one circuit board to pass a signal to a second circuit board. The 2nd board has a trigger pin for digital signals that is set up to accept 3.3v/5v trigger either as an edge signal or a level signal. The first board is signalling an event by changing a pin’s voltage from 2.46V to 4.72V.

Any idea how I can connect the 1st to the 2nd? I’m assuming I have to somehow change the 4.72V to 5V for this to work. Does the fact it only goes down to 2.46V, rather than 0V, in non-signal mode an issue?

Thanx in advance. Bill

by davecason
February 03, 2018

Do you have a schematic for the output of the first board? In other words what is the source and sink current? Also is polarity the same? When first board output goes hi does the second board input require hi?

by mikerogerswsm
February 03, 2018
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Answer by mikerogerswsm

Buffer the signal with a comparator. Connect one input to 3.5 volts and the other to the first board via say 10k. then the comparator output will drive your second board. The comparator schematic looks like this: https://www.electronics-notes.com/images/op-amp-comparator-circuit-diagram-01.svg The output may require a pull-up resistor to +5V.

+1 vote
by mikerogerswsm
February 04, 2018
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