Asked — Edited
Resolved Resolved by Jeremie!

Continuous Servo Calibration Or Hbridge Question?

Edited Original Post:

Good Afternoon,

I am trying to get a Roli to work for a school club and after spending the majority of my afternoon on this issue I have yet to find a solution for my issue.

Issue: The right side (looking at robots back) continuous rotation servo DC Motor begins turning counterclockwise (reverse) as soon as the robot connects to a computer.

Troubleshooting: I have...

  • confirmed connections both to the primary control unit and internally on the HBridge based on what I am seeing online -attempted to operate the unit with the HBridge switch both up and down
  • attempted to determine if there was a way to "calibrate" the servo DC motor through the HBridge PWM Movement panel

Notes: -I can get it to stop turning by using the manual controls within the HBridge PWM Movement Panel by selecting forward which counters the reverse motion. -I have access to another unit (still in box) which I plan to take the servo DC motor from to determine if the servo motor is faulty

Sys Specs: Windows 7, 2Gb Ram, 64 Bit OS, & 2.4Ghz Intel Core 2 Duo

I am missing something here and have watched many videos, read many tutorials and articles and attempted to search the forum. Maybe I am using the wrong terminology in my searches? Any help would be greatly appreciated. Should I switch to a personal home computer with windows 10 to see if that makes a difference in the initial commands issued to the bot upon connection?

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Hi @cslater,

Can you show us a couple photos of your internal and EZ-B H-bridge wiring?

You won't need to use a different computer. It seems to be wiring related to me.

Just as a minor correction, Roli has DC Gear motors for it's treads. They aren't called servos because they don't have positional feedback built-in.


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Thanks for the tip on the DC Motors, I will try to use that in some searches on the forums as well. Didn't realize I was calling them the wrong thing. I will modify my original post as well.


Thanks for the pictures @cslater!

Your wiring looks good! Next question, do you have the latest version of ARC and are you using the Roli Example that comes with ARC? If so, have you changed any of the pin assignments in the PWM H-Bridge control?


I was using the Roli project but will have to check to see if the version is the most recent. Our computers are managed and therefore the most recent install was about two months ago. However, I don't have the ability to upgrade without bringing it back to our IT department. I don't know what you mean about pin reassignment though so I am gong to answer "Im not sure". Is that through the HBridge control panel? Ill try to bring the gear home tomorrow to continue troubleshooting (forgot it when I left for the weekend!). I really appreciate the help/time so far, Thanks!


Sorry for the lack of response @cslater I haven't had a chance to get back onto forum until now. Yes, you are correct, the gear icon on the H-bridge PWM Movement Panel will show you the pin assignment.

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I'm assuming that the pin assignment hasn't been changed but if you are using a computer that has been used by other students the example file could have be modified and saved. This is what it should look like:

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If it all matches you can now rule out software settings and wiring and the only thing left to check would be the H-Bridge hardware itself.


Thanks for your continued help @Jeremie, I have confirmed that the pin assignment is as you posted with your screen shot. I have also removed all peripheral servo's (arms, neck) and the camera in hopes of seeing if anything was causing interference but the same issue is still occurring.

Would you be able to describe what I would need to do to review the HBridge or point me to a tutorial you would recommend on the subject? Ill continue to look into this issue in the meantime now that you have been able to confirm wiring and pin assignment.

Again, thanks a lot for your continued help, it is greatly appreciated as I am new to this.


Great @cslater thanks for checking that. Another you could try (if you have some spares) is replacing the 6 wires temporarily with some other wires to eliminate the wiring harness as the possible issue. If the results are the same then you can check the H-Bridge itself.


It sounds like the hbridge is damaged in your Roli. To reduce diagnostic time and get you up and running, use the Contact Us to have your Roli replaced. Include the link to this conversation thread so customer support can reference it.

We’ll get you running shortly:) in the meantime, unpack that other Roli


Morning Everyone,

The school brought over the second Roli which allowed me to troubleshoot the issue further. I got the base unit hooked up (no arms/neck) and ran the basic project and had no issues with the second Roli in regards to movement commands through the HBridge Movement panel; this confirms no software issues present on the device I am using.

I then switched out the wiring harnesses on the machines and noted that the second Roli with the harness in question had no issues; ruling out the wiring harness from the original bot.

After switching the wiring harness and having the same result I decided to also test the controller unit. When I placed the EZ-Bv4 from the second unit into the original unit, the movement commands responded as expected, ruling out any HBridge issues. I then placed the EZ-Bv4 from the original unit into the second unit and experienced the same issues in regards to auto-movement (counterclockwise) on the right hand DC motor.

This leads me to believe the issue lies with the actual controller and not the HBridge or wiring harness as originally suspected.

@Jeremie, thanks for the support early on in reviewing my wiring and making suggestions.

@DJSures, Does the offer still stand to send in the Controller rather than the HBridge? Will I need to send in the whole unit or just the controller? I have contacted Tech Support but am awaiting a reply.

Alternatively, does anyone have a suggestion for the controller? I have attempted to use the reset button but that does not rectify the issue.

Thanks again for the continued support, the problem has been narrowed down to a specific part with your help!


Hi cslater! Way to troubleshoot this issue!

I haven't seen any communications from you about this issue yet in did you try to get in touch with us?

For warranty discussion, click Product Warranty in Contact Us to get in touch with us about the controller.

Speak soon!


@Herr, I thought that originally as well but after switching the controllers between the units I ruled out the fuse being the issue.

@Chelsea, I have just submitted a ticket through Warranty. My original ticket must have not went through properly. Thanks!


@Jeremie Thanks for your initial help and review.


No prob @cslater, great work finding the issue!