I decided to build a simple (I thought) circuit that when I pushed one temporary push button an electric motor would go forward and when I let off the motor would stop. Then when you pressed the second push button the electric motor would go backwards.
I decided to use four transistors to do the job. I tested all of the transistors that I have scavenged off of old circuit boards and found four of them that were the same. I am not sure whether they are PNP or NPN, but when I apply current to the base, current flows from the emitter to the collector.
I set up the circuit so that the first push button connects the positive to the bases of two transistors. then I connected the positive to the emitter of the first transistor, then from the collector to the electric motor. Then I connected from the negative of the motor to the emitter of the second transistor, then from the collector of the second transistor to the negative.
When I tested this first part of the circuit nothing happened. Using my voltmeter I measured the voltage across the motor leads and when there was power applied to the circuit but the button was not pushed it measured 0.3 volts. when I pushed the button It went to 0.4 volts.
I discovered that when I bypassed the second transistor (between motor and negative) the circuit worked. then I replaced the second transistor with another one but it didn't work either.
After that I decided to reconnect the second transistor and bypass the first one. when I tested that, the transistor started smoking, melting and stinking.
When I first thought of this Idea it sounded really good and I thought It would work, but apparently I don't quite understand how transistors work.
Any help is appreciated, and if there is a better or easier way to reverse power to an electric motor I would really like to know about it.
Thanks
I decided to use four transistors to do the job. I tested all of the transistors that I have scavenged off of old circuit boards and found four of them that were the same. I am not sure whether they are PNP or NPN, but when I apply current to the base, current flows from the emitter to the collector.
I set up the circuit so that the first push button connects the positive to the bases of two transistors. then I connected the positive to the emitter of the first transistor, then from the collector to the electric motor. Then I connected from the negative of the motor to the emitter of the second transistor, then from the collector of the second transistor to the negative.
When I tested this first part of the circuit nothing happened. Using my voltmeter I measured the voltage across the motor leads and when there was power applied to the circuit but the button was not pushed it measured 0.3 volts. when I pushed the button It went to 0.4 volts.
I discovered that when I bypassed the second transistor (between motor and negative) the circuit worked. then I replaced the second transistor with another one but it didn't work either.
After that I decided to reconnect the second transistor and bypass the first one. when I tested that, the transistor started smoking, melting and stinking.
When I first thought of this Idea it sounded really good and I thought It would work, but apparently I don't quite understand how transistors work.
Any help is appreciated, and if there is a better or easier way to reverse power to an electric motor I would really like to know about it.
Thanks
