Hey there all,
I have a simple hbridge setup to run 6v (4 AAAs) to the motors on a little hacked rc car. The RC car has only 4.5v (3 AAs) but when I control it with with it's factory controls on the 4.5v it has more power/ speed than it does on the 6v through the hbridge. What is going on here? do I have to use bigger transistors? Other than using npn and pnp when needed I didn't really pay any attention to the specifics of the transistors as I pulled them out of the pack of 2222s, 3904s, 4401s for the npns and 2907s, 4403s, 3906s. I also have some random diodes, does that matter with a low voltage project like this? I used this http://www.electronics-tutorials.ws/blog/h-bridge-motor-control.html
but I used 100 ohm and 1k ohm resistors instead and the transistors are ether 4007, 4004, 4001, or 4002.
can someone straiten me out here
Hey there all,
Could you click on the 'Modify' button of your first post, and replace the link with a normal link, http://www.electronics-tutorials.ws/blog/h-bridge-motor-control.html
Those TIP102 and TIP107 transistors can drive a lot more current than the transistors you used. Perhaps you have already blown a few transistors.
Do you really think it would have blown a transistor on such a low voltage circuit? Wouldn't the Hbridge stop working properly? it seems to work fine but it is only putting out about 85% of what the factory setup can do
If you can make the motor run in both directions, the transistors are not blown. However, I think they are not up for the job.
Do you have a multimeter ?
You could run the motor 100% in one direction and measure the voltages.
After that run the motor 100% in the other direction and measure again.
That way you should able to determine why you don't get the full power to the motor.
Current gain of a transistor reduces substantially as they reach their max current ratings, often dropping as low as 10,
so under-rated transistors are going to be very poorly performing in an H-bridge circuit. Many of the stock transistors
you mention are good to 0.4A or something like that, motors tend to pull at least that under load, so you won't have
much gain headroom. Replacing the 470 ohm base resistors with 180 ohm or so might help (don't overload Arduino
Bottom line is the transistors in the H-bridge should be reaching saturation.
Do you really think it would have blown a transistor on such a low voltage circuit?
If you exceed the current rating, certainly!