I have a TIP42 transistor and I am trying to drive a Car Window Regulator motor at 19v. My wiring path is as such:
Power + to emitter
Motor + from collector
Motor - to GND
Power - to GND
I have a capacitor between the Emitter and Collector.
Now to my problem. If I connect the base back to the 19V power supply positive, the transistor turns on and the motor drives. If I remove it the motor stops. This is how it's supposed to be. My problem is that I cannot seem to turn the transistor on and off with the Arduino. If I connect pin 13 to the base and the Arduino GND to the same common ground as the other two, nothing happens. Actually that's not true, I have blown both pins 12 and 13 on my Arduino. I hope it's just the chip since I have spares and not the board. I just can't seem to figure out what I'm doing wrong. I have a ULN2003 but only one of them. I have been tempted to try using that but I don't want to fry it because I need it for other things.
The specs on the TIP42 are as follows:
Collector to Emitter 40V
Collector to Base 40V
Emitter to Base 5V
Current 10A
Am I just wiring it wrong? It is a PNP transistor. Do I need to but a resistor in the Base path? If so, why?
To turn off a PNP transistor the base must be less that 0.7V of the emitter.
You can only get 5V from an arduino so it can not turn off. What is more ad you have found you are subjecting the arduino to the full voltage of the supply and so you are blowing it up.
You need an NPN transistor to drive the base of your PNP.
Do I need to but a resistor in the Base path? If so, why?
I have a TIP120 NPN but it has been kicking my butt as well.
Here is the wiring for it:
Power + to Motor +
Motor - to collector (middle pin)
Emitter to GND
Diode between Emitter and Collector
Power - to GND
As soon as I connect the Power -, the motor runs. If I short the Base pin to either side, it doesn't matter. The motor always runs. Is it possible the transistor is bad? I believe I already ruined my one ULN2003. It has a max current draw of .5A and I am fairly certain this motor is drawing considerably more than that.
If I change from a 19V supply to a 9V supply, everything works like it should. Does this make sense?
At this point I am just going to use the 9V. All I have to do is let the motor unwind a cable attached to a spring loaded Umbrella. Since I don't have to wind it back up, I don't need full power on the motor anyway.
I would eventually like to make this work bi-directionally which will require some form of h-bridge so need to understand what I'm missing here.
Mike, you were right, a simple resistor on the base and I was in business. Everything worked like a charm. You saved my wife's Christmas show!
The only negative is that I now have an Ardiuno with two bad outputs on pins 12 and 13 and it is overheating severly indicating a short somewhere. I can live with the bad outputs but I need to find and isolate the short(s) in the board. It isn't the chip, I have spares and replaced it and it still does the same thing.
The upside is that I understand transistors a lot better than I did before.
Mike, you were right, a simple resistor on the base and I was in business. Everything worked like a charm. You saved my wife's Christmas show!
The only negative is that I now have an Ardiuno with two bad outputs on pins 12 and 13 and it is overheating severly indicating a short somewhere. I can live with the bad outputs but I need to find and isolate the short(s) in the board. It isn't the chip, I have spares and replaced it and it still does the same thing.
The upside is that I understand transistors a lot better than I did before.
Replace the 328 immediately(*) - its not a short, the overheating means its severely damaged, probably in latchup-mode
and it could burn out the regulator, its polyfuse, melt the IC holder. And sa I'm sure you're aware Arduino pins should
never be taken above 5.5V or below -0.5V (!)
(*) Lots of Arduino suppliers sell 328 chips pre-loaded with an Arduino bootloader - this is what you need.
I have already replaced the Chip and this did not eliminate the overheat. The chip itself is not overheating it is other components on the board. I don't have one in front of me at the moment to tell you which component it is but it is around the crystal and regulator. It actually gets too hot to touch.
I have one more chip that I could try but I replaced the chip once and uploaded a simple blink and disconnected everything from it to make sure that I didn't damage it as well. Since the Pin 13 LED won't come on anymore and I cannot get an output from 12 or 13, I am thinking that something is shorting to ground. I used this one as the 'remote' with a 9V battery and it burned through that battery in about 30 minutes with only an occasional output to an Xbee. When I say occasional, I mean once every 3 or 4 minutes. I have access to a clamp on ammeter at work. I was thinking about comparing the two boards I have from the source and seeing what I get.
What sort of arduino board is it? Do you get overheating with USB power or jay external power? You could have damaged something in the power switch over circuits.
