
Mulberry
USA
Asked
— Edited

Evening All
I'm working with H-Bridges and am having trouble finding the controls to regulate speed. I've followed the tutorial which directs me to use the PWM slider to regulate speed however I can't locate this control. When I open the Control tab this is all I see:
Any suggestions? My board interface is different from the one in the tutorial.
Thanks,
Daniel
Here's an example
My method uses one jumper to both PWM pins - this is an old photo done before the speed control was in ARC. While it will work with one on PWM and both speeds set the same it doesn't work correctly so 2 jumpers are required as DJ has said, or use a different control (one without speed or even the custom panel and script it for a single speed control)
The tutorial I linked to should also explain to you how a H-Bridge works etc. and give you a better understanding, one you understand how things work they are much easier to work with
Daniel
Thank you!
Daniel
You have PWM, they have jumpers connected to 5V which need removing. These are indicated by the yellow box I have added to the photo below.
Then take 2 Digital ports and connect the signal to the ENa and ENb pins (the outer 2 pins, they do have labels on the board) as indicated by the 2 white lines I have shown in the photo below.
Edit: Posted that at the same time you replied
What are these motors going to move on your robot? Is this by any chance a full sized B9?
Have fun, Dave Schulpius
Yep. Its me from San Francisco
I'm slowly getting there
Daniel
Welcome to the EZ life. Glad to see you here. you are good to love it.
What are the amps each of the motors pull. make sure your hbridge is rated to handle them. What hbridge are you using here?
I'm using the H bridges sold through EZ Robot. They're rated at 2.5. The heaviest motor I'm using is a Dewert and they're rated at 1-2 amps. At least that's what I found on the B9 Builder's Club. As far as I can tell that's correct...I hope.
Daniel
>>>>>>>>>>>>>>>>>>>>>>>>
I've come up with why I'm destroying h-bridges. I installed another working one and got things working properly with the H-Bridge movement control in ARC. Push an arrow, push Stop, push the other arrow and the motor would reverse nicely. I did that a few times and all went well until....... I decided to switch the motor direction back and forth without pushing the "Stop" button. Well, it did change direction a few times nicely but then it just locked on in one direction again and would not respond. Remember, I'm supplying 24vdc through the H-Bridge to the DC motor (which is OK).
The problem happens when I reverse the motor quickly and it sends a serge back into the H-Bridge causing damage. I read that this is normal and dammage happens when there is no protection diodes to block the back shock. Seems that the back voltage ( counter-electromotive force also known as back electromotive force) can be as high as twice the supply voltage. So the answer is to surround the motor with Protection Diodes and a of course a fuse. The best type of diode to use is a very quick switching diode and they recommend a Shottky diode rated just above (not below) the value of the supply voltage and rated above the current you will pull. In my case I need a 30v, 3 amp diode sense my supply voltage is 24vdc and my motor pulls just above 2 amps under load (a 1N5821 is just right). Well, now to build the circuit and see if it helps. They also suggest adding caps to save the motor and add more power smoothing. Here is a drawing of how it should look:
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Here's a picture of one of the diode protection boards I made to keep the flyback voltage away from my h-bridge. It's the little tan one on the left:
Most people building small robots with small DC motors will not have this problem. I'm running a couple small DC motors that turn my Radar and Ears and have no protection diodes. No problems with them. It the bigger DC motors that turn my robots waist and bend the hips that were blowing my H-Bridges. I suspect this has been the problem of a few people on this forum that has had problems with one side of their H-bridge not working and it not being a faulty product. Perhaps it was working properly till Flyback voltage took it out. Well never know though.
Hope this helps.
Dave Schulpius
While I'm here