Transistor help

Thread Starter

timplett

Joined Jan 20, 2009
19
I want to use a transistor to power a motor but I need the motor to run when there is 0 volts to the base and shut off when the base receives voltage. How do I do this?
 

mik3

Joined Feb 4, 2008
4,846
Use PNP transistor instead of a NPN one. What is the voltage and current ratings of the motor?
 

Thread Starter

timplett

Joined Jan 20, 2009
19
I am not exactly sure of the size motor I will be using yet for this project. It will be 12 volts and I think under 10 amps.
 

SgtWookie

Joined Jul 17, 2007
22,201
If it's more than a few Amperes, you'd be better off using an N-channel power MOSFET; they're much more efficient power-wise than using transistors. A P-channel power MOSFET could be used, but they are typically less efficient than their N-channel counterparts.

Once you figure out what your input signal will look like, and how much power your motor will require, we can be of more help.
 

Thread Starter

timplett

Joined Jan 20, 2009
19
I am planning on using a monostable 555 circuit as was suggested to me by mik3 so the output of the 555 will be the input to the base of the transistor. As far as the motor as I said I am not completely sure yet but lets say 5-10 amps @ 12VDC. If anything it may be less than 5 amps, but not significantly.
 

mik3

Joined Feb 4, 2008
4,846
Use a n channel MOSFET driven by a BJT as to turn it on/off fast and not allow it to spend much time in the linear region and dissipate much heat.
 

Thread Starter

timplett

Joined Jan 20, 2009
19
I was actually just doing some further research on the 555 and stumbled across a monostable circuit with the output normally on. Does this make it simpler at all?
 
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