Transistor Help, Cannot get transistor to amplify power
DiablodeMorte
Posts: 238
I just first want to say I feel like an idiot for not being able to figure out such a simple electronic component.
But, shame aside, I still have my problem which is: I cannot get a transistor to amplify power.
Look at the attachment for my set up.
When I set the vdd to vdd(it's a floating wire) the pwr light(Board of Education) flickers and the motor strains alittle. After about a second the pwr light comes back strong and the motor is no longer moving/straining. I try again and nothing happens this time. I think I killed the transistor. What is wrong w/ my circuit? The motor was previously run on 4 transistors using the 9volts in the battery pack(which I have connected to the Board of Education). I think they were used for directional control on the cheap. When I connect the motor directly to vss and vcc the motors turns with ease, when I try my way the motor barely moves. What gives?
Any help will be greatly appreciated.
-DiablodeMorte
P.S. I would love it if someone could also give me a schematic for directional control using transistors for the motor. :P
P.S.S. Transistor PDF: http://www.fairchildsemi.com/ds/2N/2N5088.pdf
But, shame aside, I still have my problem which is: I cannot get a transistor to amplify power.
Look at the attachment for my set up.
When I set the vdd to vdd(it's a floating wire) the pwr light(Board of Education) flickers and the motor strains alittle. After about a second the pwr light comes back strong and the motor is no longer moving/straining. I try again and nothing happens this time. I think I killed the transistor. What is wrong w/ my circuit? The motor was previously run on 4 transistors using the 9volts in the battery pack(which I have connected to the Board of Education). I think they were used for directional control on the cheap. When I connect the motor directly to vss and vcc the motors turns with ease, when I try my way the motor barely moves. What gives?
Any help will be greatly appreciated.
-DiablodeMorte
P.S. I would love it if someone could also give me a schematic for directional control using transistors for the motor. :P
P.S.S. Transistor PDF: http://www.fairchildsemi.com/ds/2N/2N5088.pdf
Comments
There should be a resistor between Vdd and the base of the transistor. You could be destroying the transistor.
Twisted Pair....
A transistor is a current amplifier. What you're showing is an NPN junction transistor. You normally connect the emitter to ground and the base to a current source, not an essentially infinite source, but one limited to the maximum base current specified in the datasheet for the device. Just to confuse things, a typical transistor often used for switching, the 2N2222, doesn't have a maximum base current in the datasheet. The maximum collector current is 1A. The transistor minimum gain is 40 (hFE). So: Ic / hFE = 25ma. I would probably assume that 100ma is a good maximum base current. Anyway, you put current into the base and the collector circuit will conduct current (collector to emitter) up to the maximum collector current and dependent on the base current times the gain of the transistor.
Now, the base will accept current up to the point where the transistor melts anytime the base voltage is greater than about 0.7V. You have to limit this to something reasonable. There are lots of ways to do this. One way is to use a resistor. Use Ohm's Law (E = I R) to figure the right value. Do remember that most microprocessor I/O pins can provide about 20ma and more is not better (for the microprocessor).
For directional control, search the Wikipedia for articles on an H-Bridge (Google "Wiki H-bridge").