I have two motors connected to two TIP3055 transistors. Both motors are 9v DC exactly the same. Battery is 9.6 800 mah. My question is the following: When I do the digitalWrite of both motors to High on motor spins for more time than the other. I'm doing digitalWrite(MotorDer, HIGH); digitalWrite(MotorIzq, HIGH); then a delay of 1000 and then I stop them. Still one spins for a bit more than the other. Not sure if I have something wrong here. Help is appreciated.
TIP3055 transistors are not that small, your circuit seems confused (emitter on the
middle leg? Really? - free-wheel diode between Vcc and GND - no, wrong...)
Hi Mark. Sorry, I sent the incorrect layout. This is the correct one. Please let me know if this seems right.
TIP3055 is about the poorest performing power transistor in existence. Any reason
for not using a modern device, in particular a power MOSFET?
Hard to know for sure but most likely as as first guess the motors are not exactly the same, one might be older or more used. Those toy motors are pretty open, with use the bearings will get dirty and this will slow it down and make it stop much faster.
Although still possible, I think its far less likely that a defect in a transistor would cause that type of difference in performance if they are the same model, it usually works or horribly fails, or half works then horribly fails.
One has cleaner ball bearings, spins faster, takes longer to slow down.
Thanks for the replies. It really helps a lot. The TIP3055 was the best transistor they had in Radio Shack. I guess that is what I got for going to radio shack for parts (but it's close from home). Could you recommend a good MOSFET transistor, and abusing the question, could you recommend a good MOSFET H Bridge?
Thanks,
Leo
Swap the motors and see if the problem moves with the motor or not.
When I started here I loved Fritzing, thinking that the "photo look" was such a good idea. I was annoyed when longer-standing members and / or those experienced in electronics asked for proper schematics.
But I soon realised why: Fritzings are not good for others to understand the circuit from. They're good in tutorials to show the physical layout and aid correct setup of a project. I would really recommend you post schematics, either from the schematics mode of Fritzing, hand-drawn, or from a utility like Express.
That said..... you have no resistors on the base of the transistors afaics.(I don't know if that contributes to your problem or not, but something's going to POP.
Could you recommend a good MOSFET transistor, and abusing the question, could you recommend a good MOSFET H Bridge?
pololu.com is a good place for motor drivers - MOSFETs there are so many, its a more
useful thing to find a good electronics supplier and then search their site.
Energy efficiency aside, was there ever a problem determined with the transistors?
I can't fathom telling someone still learning to use transistors to go out and buy motor driver boards designed for much larger motors.
You'll use more batteries as is, maybe less speed then you could have, but unless you plan to really move to the next level I'd be happy with what seems to work.
Thanks all. Turns out it was the transistor. Used another one and it's working fine now. Both motors work the same. I will change the transistors for a MOSFET H BRIDGE though as I now want the ability to go backwards-.
By used another one and its working fine, did you replace it with a different model or a new one of the same type?
Comparing transistors to each other is like night and day, even if there from different batches. How well they work is based on the Beta or gain. They are current devices, 5mA for one might work just fine, 5mA for another might do squat for the same load/motor.
If your in the saturation zone it rarely matters, but if its not saturated you will diminished current flow through the transistor.
I'm not saying the transistor wasn't defective, but I wouldn't assume that its defective just because a different one worked better.