I have two circuits and i want to adjust the photo-transistor and IR-LED separately.
I will mount them side by side for hand waving in front of them.
Does the bottom circuit also work to adjust the sensibility of the photo-transistor?
I did not jet check the resistor values.
Does the bottom circuit also work to adjust the sensibility of the photo-transistor?
I did not jet check the resistor values.
Yes.
Resistors look O'K to me.
The inputs of unused op amps must always be connected to a low impedance voltage source within the active region, and the op amp output should be set to a valid value.
Otherwise the amp may oscillate or create other problems with the circuit. See this application note.
But it is an comparator and as always it is not easy to figure out what to do.
From the TI datasheet:
All pins of any unused comparators should be tied to the negative supply.
But then i was reading:
The inputs of an LM339 quad or LM393 dual comparator are still active when they are connected to ground. A comparator usually oscillates when both inputs have the same voltage. So you do not want both inputs connected to ground.
Connect the (-) input to ground and connect the (+) input to a positive voltage to set the output high (no current at the output).
check the datasheet to see if the Lm393 is OPEN COLLECTOR output. If so, you need a pullup resistor.
It looks like open collector to me.
datasheet
Definitely open-collector - useful for wired-and gates with the outputs. Everyone should have
some LM393's or LM339's (the quad version) in stock.
Note that the usable range is from ground up to 1.5V below the positive supply, so watch for
that
