Maybe something like this would be easier. These come in different Amp capacity. Just throwing this out there.
I guess the advantage being that this comes with a preconfigured 3 pin connector that plugs right in to pixhawk pin set 1 or 3. so buy two of these to replace the existing h-bridge? I would have to find out which one suits the motors I guess or is as close to the existing h-bridge specs. I just wish the image in the ardupilot rover manual for connections to skid steering were a bit more precise or accompanied by detailed pinout descriptions as its not a problem connecting individual pins as long as your sure of where. Burning out the pixhawk was not a result I had expected as I thought the APM power module would ensure the pixhawk could not burn by only allowing 5 volts.
I found this at a decent price and it says works with tanks, cant find a dual motor on Amazon
https://www.ebay.co.uk/p/RC-Car-Hobbywing-QuicRun-1060-60a-Brushed-ESC-Electronic-Speed-Controller-Hot-UK/764007312
The reason I thought to look for a dual motor is that would be an exact replacement for the bridge. The problem with two units might be powering them as right now I have power from a bank of AA rechargeable (8). I suppose with the individual motor controller route I would need lipos one for each controller/motor pair?
The motors are specād as * Rated Voltage: 6 V
- Operating Voltage Range 2~7.5V
- Gear reduction ratio: 45:1
- D output shaft diameter: 4 mm
- No-load speed: 133 RPM @ 6 v
- No-load current: 0.13 A
- Locked-rotor torque: 4.5 kg.cm
- Locked-rotor current: 2.3 A
Well if your motors are 7.5 volt max how are you using 8 rechargeable batteries with them. What you need, and your controller you gave the link to may work if you had 2, is probably just one 2s LiPo battery. The LiPo plugs into the pixhawk power module. it gives nice clean 5.3 volts to the pixhawk. The heavy wires coming out of the power module would go to the motor speed controllers. Well actually a 2s LiPo is 8.4 volts fully charged. And know it occurs to me that your 8 rechargeable batteries are probably wired in a combination of series and parallel. I seem to remember being told 4 or 5 years ago that the input voltage to the power module needed to be above 6 volts or it could cause problems.
David, Thanks a lot for your help here. But if you go to the rover docs on ardupilot and look at the image in skid steering the thing called āmotor driverā looks a lot like a l298 bridge. For some reason the docs do not recommend an esc although it says 3 types of esc supported ?? you would think they would give you a clue. I donāt know how to reach out to the person who documented or who made this work so hard to find out. I have been looking at the hobbywing quicrun 0860 which supports dual brushed motors. Its a bit overkill maybe. I just got the replacement pixhawk and am pleased that that set up ok in mission planner. I may try the bridge again now I know about the speed jumpers on the bridge and if I canāt get that working will get the quicrun. The bridge of course uses 8 AA but then steps it down for the motors. From replies here it seems I would connect the speed pins to the bottom rail of 1 and 3 on the pixhawk and I guess the others can be adjusted by testing if it runs backwards etc.
OK David after a lot of reading and careful checking I discover that most of the two motor controller are in fact not going to work as they have only one set of controls. i.e they expect the wheels to be in synch all the time. With skid steering I need both motors to be working separate on turns. So back to your idea, should have listened but at least I now know why 
SO I will work on two esc. I have tried the h298 bridge and connected it up to the pixhawk but nothing happens. I connected on pin group 1 and 3 with the pin controlling speed at the bottom. I though that was it but although I got the pixhawk fired up and GPS points set the motors wonāt start. One problem I seem to have is that pixhawk seems to expect a go command from some rc controller which I am not using as I intend eventually for this to be autonomous.
There is an arming parameter that means either you arm the vehicle with a rc controller or it will self arm if it is comfortable with a number of things checking out.
Tony,
I wrote quite a lot of the Rover wiki. I guess itās this page that is confusing? The āMotor Driverā in that picture is, I think, a RoboClaw brushed motor driver which accepts a PWM input from the flight controller. So itās basically an ESC.
Itās very possible that the red and black wires going from the motor driver to the motors are not coming out of the correct place on that board so perhaps we should fix that picture.
Hereās a more specific wiki page that deals with setting up Brushed Motors.
Thanks I looked at the wiki page but didnāt help a lot. The roboclaw is very expensive. Where I am at is this the devastator tank comes with very simple brushed motors that the L298n H Bridge can drive effectively and has as I had it working using a hand controller using a pi 0w to drive it. I have just realised belatedly that my frustration with getting it working may well be connected to my poor understanding of drones and rovers that need to be told to start using a rc transmitter/receiver, despite the fact the pixhawk has an arming switch of sorts. My motors wonāt run connected to main out 1 and 3 but now I am wondering if its just that the tank is not getting a āgoā as I donāt have a receiver transmitter installed. Most frustrating as I am trying to build an autonomous rover that will start and run without rc and looking at the recommended models I have to spend Ā£150 just to say āgoā. . Anyway if the h bridge has to be replaced with esc then I am concerned about compatibility between esc available and motors. I was about to get two hobbywing eagle esc and drew back as I am not sure they match the motors installed.
An L298 H-Bridge needs a PWM signal for speed and a two pin/bit input to set forward/reverse/brake/float. It can not work with just a PWM signal. I once used an H-Bridge for a rover and put an arduino in between the autopilot (an APM2.6, if I remember correctly) and the H-Bridge to translate the PWM signal in PWM+2bit. The pixhawk supports motor drivers with a single pin to set forward/reverse (brushed with relay), but a two pin H-Bridge is not supported. Any brushed car ESC should be able to drive the motors of that chassis. The motors usually come in 6V or 12V variants and you just have to make sure that the ESC supports the voltage. H-Bridges usually take a higher voltage, but less current and most rc hobby car ESCs lower voltage and higher current. Be careful to not overvolt the motors too much, the brushes will burn up in no time or weld themselves to the rotor if the motor stalls. If you power everything with 6 NiMh cells, you should not have a problem with the motors or with a car ESC.
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This is the item on the to-do list to add support for the two input brushed motor drivers. @khancyr says that itās already supported but I donāt know really.
Thank you for the clarity on this. So the bridge is not supported, now I know. The idea of replacing the pi 0w instead of the Arduino might work but I really do not want to program it to support the pixhawk or add another variable unless you have your python code handy . So I will look for an esc that will support the two tank motors. I got an email from rchobbystore in uk saying they had some small brushed esc coming in next week at Ā£6.50 each so that might be a solution. They said "They should be perfect for the job. Rated up to a 20A with forward,
reverse and a brake option which can be disabled for a tank.
I can let you know when there are here. They should be around Ā£6.50 ea.
I will be testing them here with various brushed motors before releasing
them on the website so I will check the suitability for tank control.
i.e. forward and reverse speed similarity."
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Hi!
The brushed Esc work on pixhawk?