Need help adding a on off IR LED/Phototransistor as switch

  • Thread starter mac37m
  • Start date
  • #1
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I'm building a small project and would like some assistance from you folks.
I have this motor 5rpm -12vdc and I'm using a Class 2 plug in transformer (input 12VDC 60Hz 23W - output 12VDC 1000mA) to power it up.

I would like to add a IR LED/Phototransistor between the two to act as a on off switch.
when a solid item goes between the LED and phototransistor it will stop or turn the motor off
and when it's clear it will turn on.
the distance of the IR LED/Phototransistor will be about two inches.



project_1.JPG


thanks in advance.
 

Answers and Replies

  • #2
25
0
for a small application like this motor, you should invest in an arduinio. By doing this all you really have to worry about is a handful of line of code, and the usage of a NPN transistor, a flyback diode (to prevent current surge damaging electronic components when the motor stops)

if you go this way, this youtube video should help out:
http://www.youtube.com/watch?v=js4TK0U848I&feature=relmfu
 
  • #3
dlgoff
Science Advisor
Gold Member
4,050
2,072
With discrete components, you can do it this way (motor in place of lamp),

transwitcho.gif


with the switch & resistor replaced by a photo-transistor and operational amplifier.

photdet.gif


For details on how this works see:

Transistor Switches
Photodiode Light Detector
Phototransistors
 

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