I am building a small controller (Based on Arduino Pro Mini) for a signage/advertisement display which is basically a large marble run.
as the marble goes through the run it will pass over a few beam break sensors and micro switches
these will in turn trigger a few flashing lights (and stepper motors but these are not what need help with)
attached is three schematics showing how i was intending to do the two different inputs (switch and Beam Break ) and the FET output.
I have used Opto-isolators so that my triggering voltage can be 24V (or 12V) thus lensing the chance of interference and to provide protection to the Micro controller incase of wiring mistakes during install
currently the FET outputs will just flash however if possible i might implement PWM dimming
the break line shows where the field wiring is (5m ish from the case to the sensors, buttons)
Optos are http://newzealand.rs-online.com/web/...ucts/667-5073/
Fets are http://newzealand.rs-online.com/web/...ucts/325-7580/
Beam break switch http://newzealand.rs-online.com/web/...ucts/642-4301/
my questions are
do i need the resistors labels r1,r2 and r2?
if R1 is needed should it be in the case or should it be with the sensor (purple arrow)
for my inputs i am switching the Positive (common ground) both at the 24V side and the 5v arduino side, i have seen a lot of circuits where pins are switched low (thus have pull up resistors )
is either way better then the other when you have the choice (with the output of course i do not have the choice as i im using N-Channel Fets)
i assume i need a capacitor inline with the 24v for the fet output stages, how do i calculate what this should be? and work out what type it should be?
can anyone seen any potential problems with the over all design of these input and output stages?
are the Optos on the outputs over kill?
any help/ advice would be very much appreciated