Simple transistor switch

[Techno10]

This project is using the parts from a recordable greeting card to drive two motors that can run off a 9v battery. This greeting card also has a moving part that is a small flat motor, so I cut the motor off and measured the voltage 1.2v. I need that voltage to turn on a transistor which will turn on the 9v for the motors. So I practice with a 1.5v AA battery connected to the base of a transistor and it works, but only turns the motors slowly, if I hook up a 9v to the base then the motors will turn fast like they should. The transistor is a NPN NTE47. Is this the wrong transistor or what?

 

[andyy07]

This project is using the parts from a recordable greeting card to drive two motors that can run off a 9v battery. This greeting card also has a moving part that is a small flat motor, so I cut the motor off and measured the voltage 1.2v. I need that voltage to turn on a transistor which will turn on the 9v for the motors. So I practice with a 1.5v AA battery connected to the base of a transistor and it works, but only turns the motors slowly, if I hook up a 9v to the base then the motors will turn fast like they should. The transistor is a NPN NTE47. Is this the wrong transistor or what?

Hi.

I suppose you would need something like this. You can replace the 2N3906 with one that can handle more current like S8550...

 

[Mike odom]

The NTE47 is a good transistor. Very high gain. But it only has a 200mA collector current.

If you're trying to sink the motor( -) to ground, then maybe you have too big a resistor on the gate input to the transistor (especially if it works with 9v). Since you hooked up 6x (9v vs 1.5v) the voltage and it worked, try 1/6 the resistor with the 1.5v input.

Your base current will be (1.5v - .7v) / R. This current needs to be about 1/10 your collector current.
If you can get it to run, let it run for a while and see how hot the transistor gets.

 

[Techno10]

The NTE47 is a good transistor. Very high gain. But it only has a 200mA collector current.

If you're trying to sink the motor( -) to ground, then maybe you have too big a resistor on the gate input to the transistor (especially if it works with 9v). Since you hooked up 6x (9v vs 1.5v) the voltage and it worked, try 1/6 the resistor with the 1.5v input.

Your base current will be (1.5v - .7v) / R. This current needs to be about 1/10 your collector current.
If you can get it to run, let it run for a while and see how hot the transistor gets.

I don't have a resistor on it, maybe if I used a different transistor with a higher collector current?

 

[Mike odom]

I don't have a resistor on it, maybe if I used a different transistor with a higher collector current?

Then you are using it to source current? If you are pulling the - to ground to run the motor, you would blow the transistor up by connecting 9V to the base w/o a resistor.
Do you have a schematic of what you are trying to do.

I would not say you need a higher collector current if you got the thing to run... it may be in your drive circuit.

 

[Techno10]

How about just using a small relay
CPC1017N, I have a input of 1.2 vdc and this should switch on/off the 9v.