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photodiode

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fogus

New Member
Hi! Can someone tell me how to set up a photodiode to, for example, make a motor spin when it is activated.

-fogus
 

kizzap

Member
the simplest way to do it would be to use a transistor with the photodiode attahed to the base of the transistor. if the motor is small it may be ale to be run only one transistor but if the motor is quite large it may pay to use a second transistor that is controlled by the first one.

if you need a schematic i may be able to draw one up for you.
 

mattg2k4

New Member


ExpressSCH doesn't have a symbol for phototransistors (at least I don't think it does) so I labeled them for you using regular transistors.

The second schematic is for higher power motors. For a small motor, you'll be able to get by with the first one.[/img]
 

kizzap

Member
yeah he's post exactly what i was describing so i don't see a point to post another picture up.

and mattg2k4 when posting up a thing for a photodiode you just use the normal symbol for a diode and just label it as being a phototdiode.

Kieran
 

Phasor

Member
Be careful when switching a motor (or other inductive load) this way - put a flyback diode across the motor, otherwise, when you switch it off, the motor can generate a high voltage (momentarily), and the transistor can be destroyed.

I had a similar issue in a friend's car the other day - his in-car electronic thermometer was resetting itself every time he used his air horn (his new toy...). A 1N4004 across the horn solenoid fixed it 8)
 
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