-I want to start-stop a Dc motor just start-stop. Is there any electrical switch for wires?
-I used npn transistor which is BC237b with 9V battery, it worked perfectly until it burned. Which transistor I should use?
-I need a electrical switch between 2 wires(9V battery's positive or negative wires).
Which transistor depends on which motor and power supply. The BC237 is rated for an absolute maximum
of 0.1A (ie 50mA would be a sensible working current level), which is considerable less than many tiny
motors take...
So what load current and stall current does your motor need/take?
It's 6-12V standard DC motor.
I connected it to 9V battery, I'm trying to start-stop with arduino's pwm pins
Hi,
You need to use a MOSFET to control your motor, its more efficient and the MOSFET runs cool.
The MOSFET needs to be N-CH Enhance Mode, logic level type.
Tom.... 
PawPaw-:
standard DC motor.
Is there such a thing?
I cant find my standard motor handbook, what are the standard full load and stall currents?
?? If you want to simply start/stop a DC motor, you can install a cheap on/off rocker switch between the pwm board and power supply.
PawPaw-:
It's 6-12V standard DC motor.
No such animal, there is no "standard motor", each has different voltage and current
requirements, rated speed, torque and so forth. All these details can matter, so provide all
the information you have. You can (and should always) measure the motor's winding
resistance with a multimeter, that's always good to know as that sets a limit on the stall
current.
Hi,
I did an image search and found this, may be it, generic motor case.
But Amazoooooonn don't give any specs.
But in their Q and A, (why do you have to ask for the specs, I NEVER use Amazoooon)
Question:
What's the max current draw of this motor?
Answer:
Depends on your load and Voltage. If it's 6 volts, at no load it's about 400 mA. I was operating with a load that cut the rpm's in half (a fan) and it was about 1.7 amps. So I'd say somewhere between 0.5-1.5 amps. Use a variable voltage supply with your load to figure it out, or a multi meter
By Cory Z. on October 11, 2015
Hope it helps. OP hasn't even said where he got the motor.
Tom....