Asked — Edited
Resolved Resolved by Steve G!

12 V Motor With H-Bridge

Afternoon All

Can anyone confirm the H Bridges in the tutorials are still not suitable for 12 volt motors even with the new EZ boards? I want to avoid the headache of using a Pololu H bridge. The wiring and configuration are a nightmare :D This is for a simple waist rotation, not high speed.




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The question with an H-brisdge is always amps not volts (well , not entirely, but virtually any H-bridge on the market can easily handle 12 volts). We need to know how many amps the motors draw at stall, then you add a percentage for good measure, and that will tell you what to get.

The EZ-B store has an easy to use 2.5 amp controller (although it requires 6 digital ports for 2 motors with PWM). Sabertooth has H-bridges that support from 5 to 60 amps and just use one digital port since they use a serial protocol. For a single motor, you can also look at R/C escs.



The Pololu H bridges work (I actually had one going last year) but I've been unable to get any others to work. I've gone through 4 (and they aren't cheap) just for this one function. The issue is either my soldering and/or port connections. At least with the bridge in the tutorials the directions are clear. With any other H bridge I'm flying blind.


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As Alan has said, it's not the voltage you need to consider so much, it's the amps again (as explained in your servo thread). Just to add, as well as the stall draw, the weight of what the motor is moving as well (in your instance, the weight from the waste upwards). There are 10, 15, and 20 amp motor controllers with H-Bridge available on eBay and Amazon which are reasonably priced and not that much different to wire up than the L298 H-Bridge.

I know because I did exactly this for two 12v drive motors. Bench testing the motors drew 1.2 amps. Stalling the motors (physically holding them with my hand) spiked to 2.1 amps. Fitted to the chassis with the full weight of the robot on top, when driving the motors drew 2.4 amps with a stall spike of 5 amps. A two channel £20 ($35) 10 amp motor controller fixed my issues and still works well today (no soldering required). If your using one motor, a single channel H-Bridge is all you need which should be cheaper.

So to answer your initial question, you can in fact use the H-Bridge in the tutorials with 12 volt motors, but it depends how many amps the motors draw. Test the amp draw with a multi meter. If you don't have one you should get one as they are a good investment.

Motor controller I currently use.

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Wiring for the H-Bridge motor controller I linked to in the above post. As mentioned this is a two channel H-Bridge motor controller for two motors, but one motor can be used.

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I have a related question, if i may. I'm using the H bridge that EZ-R sells and it works very well. I am using the the EZB battery (7volt +-) . Is it ok to use a separate 12vdc battery and just tie the grounds together? My motors are 12 volt as well and just run a little slower with the lower voltage. (current isn't a problem).


@Steve B, yes, that is the main purpose of an H bridge, providing different voltage and/or amps than the signaling device (EZ-B in this case) can handle.



@ Alan Thanks! I was pretty sure that that was the case. I'm just a little gun shy...this is my second h-bridge, eek

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Don't worry about being a lil gun shy. I was exactly the same as you when I wired my first H-Bridge controller up (the one in the pics above). As you say, as long as you have the common ground in place and the little white regulator button in the correct position (I think it's push down), then your golden.:)


Thanks Steve

I'll check out your recommendation and look at the amps. This is a 12 v Dewert motor to slowly rotate the main robot body on a smooth Lazy Susan. Nothing continuous.


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No problem. If you Google the motor you have, you might find a spec sheet telling you the current draw. That will give you an idea of what motor controller you can use.


Daniel, Is this the same Dewert motor the B9 club uses and talks about? if so it's a 24v motor. However that's OK as it can easily run at 12v DC only it will turn slower with less torque.

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These motors pull a ton of amps at start up and throw current back into the controller when reversed. When I first started trying to control them I burnt up two of the H-bridges sold here in the EZ Robot store. They are nice h-bridges but wont handle the flyback current produced by this motor when it reverses. Last time we spoke I mentioned this issue and is why I recommended the Pololu h-bridge as it's much better and natively protected from this electrical phenomenon. Your going to keep burning up controllers unless you use one that is good at protecting it's self from over voltage and reverse voltage. eek

EDIT: I just reread your last few posts. Are the H-Bridges you burnt up the Pololu I recommended? I have used them with this motor with no issues. I can help you with the connections and would also be willing to solder the needed parts to it if you want the help. :)


Yep. The issues are with the Pololu and H Bridges in general. The soldering seems straightforward but for some reason I can't get the bloody things to work. I've gone through several. The issue must lie with connecting to EZ (ports). I've tried with and without a PWS. I suspect there is something quite obvious that I'm missing. My EZ in the leg section will control waist rotation and soil tester. Over the weekend I stripped out my power block and fuse wiring and am starting from scratch. I'm fine with the slow rotation from the Dewert with 12 volts. That's how I ran it before when I had an H bridge that worked. Once I upgraded to the latest EZ board that set-up failed despite mirroring the same ports.



I've continued work with my Pololu motor controller with the H_bridge control with PWM but to date I'm only able to get motor rotation in one direction. I've tried dozens of port setting permutations but no luck. If anyone has used a similar setup would they be willing to share images of their EZ board connections and port settings? This is about my only block to finishing my build.

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Believe it or not the damn thing's working. The port configuration makes no sense to me but I don't care. I've taken photographs, drawn a circuit diagram, and made every conceivable steps I could to record the connections.

Man we're talking weeks here.........

Thanks to everyone who gave advice. I'm now going to start drinking.


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That's great news. So glad you got it finally working the way you want. Enjoy the drink, you deserve it.;)


Great Daniel. I knew you would get it if you kept at it.

In know you have it working now but just to run through the connections:

In a typical application: **The motor power supply is connected at the bottom of the board (where is says + - Motor Supply). in your case 12vdc. **The motor it's self is attached to the right side of the board (where it says Out A and Out B). On a typical DC motor it would not matter which lead goes to A or B. You can swap these if you want the motor to go the other way. **The control connections go to the left side of the board. You would want to attach one signal pin of an EZB Digital port to the PWM pin, The Black Ground pin of EZB's Digital port to GND. Now you need to be careful on the next connection. This motor control board requires 5vdc be delivered to the 5+ pin. The center power pin of any digital port on EZB will deliver what ever voltage your powering EZB at. If your feeding 12 vdc to power EZB then you have 12vdc at the center pin of any digital port. If your attaching this feed through 12vdc to the little Pololu board at the 5+ pin it sill shut down or burn up. You need to step down the voltage or use an alternate power source to get a stable 5vdc feeding the 5+ pin on the left side of the Pololu motor controller. **You will also need two more wires attached to INa and INb. These would in turn attach to two different signal pins on EZB's digital ports. These will turn on when you call for them and set the direction of the motor.

So on EZB you'll have: 3 wires connected to the digital signal ports 1 wire to the ground of a digital port 1 one to the center power pin of a digital port that must be regulated to 5vdc

**Now in ARC you would have to make sure you set the PWM port to te wire that is attached to the PWM of the Pololu and move ot up over 40 by either using the PWM control or in a script. **Only then can you turn on or off the Digital port (one at a time) either in a script or a control that either attaches to INa or INb and the motor will turn the way you want or stop.

Hope this helps.

Chears and bottom s up! I'll hava a rum and coke. :)


I think I understand Dave. I'm currently using a 6 v battery pack to power the Pololu ( this was just for determining my ports) but in my final connections I need a source at 5 v either with a voltage regulator stepped down from 12v or battery source.



Yep, that's right. I don't know if the 6vdc supply was causing problems with the Pololu that needs 5vdc but somehow you have managed to get it to work. Good work!


Oh the drama. When I re-activated my EZ and connected, none of my H-Bridges worked. eek

All port settings are the same, I get a clean connection to the board, read power going in via my test meter but yet no responses.

Now I understand you're only allowed 1 H-bridge per project so I created multiple projects, each with their own H-bridge, however I used the same EZ. Perhaps the problem is I can only use a single bridge per EZ itself. Not a big issue because I have several.

Anyone care to chime in?



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Just to correct you, you can in fact use 2 H-Bridge's on a single project. It's only one Movement Panel your allowed to have. This would mean that a Movement Panel would control one H-Bridge, while you would have to script the other one. Or you could script both and use a custom movement panel. Using two h-Bridges is not done to often as it uses up more ports, and to set up two H-Bridges in ARC is a little bit more complex than adding the H-Bridge movement panel, but it can be done with a little extra work.


Yes, Steve's correct. You can have as many H-Bridges or motor controllers as you want on any one project. You just need to write scripts to control them all. You don't even have to have a Movement Panel installed.

Don't know why your h-bridges are not responding. When strange things like this happen to me I shut down the robot and EZB, reboot the computer and restart ARC, the robot and EZB. Also check to see the H-Bridges are getting power and the connections are tight.


Writing script may be the next evolution but I think for now I'll use my many EZ's.

BTW Dave. You have 3 running you said. I'm assuming you connect to all 3 at the same time and just have multiple project windows. Have you encountered any issues?



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No problem. When you get around to it, scripting the H-Bridge motor controllers won't be too difficault. I mentioned that you can only use one Movement Panel per project to control one motor controller, but with scripts you can use a custom Movement Panel to control two H-Bridge motor controllers (which of course would depend on how you wish to use them in a project).

A few months back now, I asked about using multiple motor controllers in one project and got some great advice. Have a look here as you may find it useful.:)


Hi Daniel, I have many motor controllers operating in my B9 and only one project controlling the entire robot and all the controllers. I now have two EZB's controlling every sensor, light and control board through that one project. There's no reason why you need to be running several projects to control your B9 unless you want more then one movement panel. BTW, I have no movement panels at all installed in my project.

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No problem. Did you get everything sorted in the end, and if so, what did you end up doing about the motor controllers?


When selecting an H-Bridge for two motors beyond the EZ-Robot store, be careful to verify that it will work with two motors. I and a few others newbies have accidently purchased H-Bridges that said Dual H-Bridges assuming it's for dual motors when in fact they were for a single motor and dual directions (which all of them are).




An h bridge by nature moves a DC motor in two (dual ) directions. You can buy h bridges that can control two different motors and move each of them in opposite directions. This includes the one sold here in the ez store. I think you may be a little confused. Maybe it's just the way you wrote your post.


Hi Steve

Until I learn to write script I'll use multiple EZs and just not activate a few functions. I need to get this build out of the garage :-)