Servers by jDrones

Motor driver connection

(Anthony Johnson) #28

David, The docs show 6 wires but you are right there are only 4. so I assumed the other two were ground and maybe that was a mistake. Looking at the rover from the pin side with top as top I connected the ground to the top set of pins on 1 and 3 and then connected 7,11 to the next two down on 1 and 13,15 to the next two on 3. I think I will remove the ground for now and see if that helps. Is it possible that connecting the top pins on 1 and 3 to ground may have caused the power problem that burned out the pixhawk? Something caused the APM power module to draw excess power through the pixhawk.


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(James Pattison) #29

@khancyr can you chip in here?
The key confusion seems to be pwm (3 wire plug) vs relay (2 wire plug) motor control setup, and I’ve provided the wiki link to that.

(David Boulanger) #30

I can’t read the brushed motor controller where the wires go in. I don’t think this should be set up as a relay output. Doesn’t this motor controller take a PWM signal and translate it to voltage for the brushed motors

(James Pattison) #31

I read a data sheet on this thing.
This isn’t a “normal” esc. It’s just a H-bridge, so basically there’s 2 pins for each motor controlling direction (ie high-low for forward, low-high for reverse, or similar).
There’s a pwm for speed as well, but it isn’t normal range (0-255 not 1000-2000).
It should work as brushed-with-relay.

(Anthony Johnson) #32

This youtube video tells it all.

(Anthony Johnson) #33

Hi James the video explains a normal set up and there are in fact 3 pins (my mistake as using th pi I was only controlling direction not speed. I am trying to establish which pins go from this to which pins on 1 and 3 of the pixhawk? After that there are set ups to do as you say in mission planner

(Anthony Johnson) #34

Ok based on all your feedback and my failure to spot I did not control speed on Rasp pi 0 I now see that there are in fact three connectors from the n298 bridge that need to go to the pixhawk. One cable is for speed that is the end pin on the bridge. The other two are direction. SO now coming back to the pixhawk, how to connect this?

(David Boulanger) #35

Looks like Aux 5 and 6 are for the relay pins.

(James Pattison) #36

By default, yes, 5 & 6. You’ll need to assign 2 more pins to relay (two for each motor), plus the speed pins.
All 6 of those are connected to the signal row on the Pixhawk. You’ll need to add a ground wire too.

(David Boulanger) #37

I don’t think they all go to the middle row. This may have been the problem. Signal is the bottom row I believe. I’ll take a look at one of my Pixhawks,

(James Pattison) #38

Crap. I shouldn’t answer this on the bus.
My bad. All 6 are signals. Bottom row.

(Anthony Johnson) #39

Hi thanks but confused (of course) as the inline docs for Rover and Skid Steering say that they should go 3 and 3 to pins 1 and pins 3. Now we have established that it is three its just getting the right ones in the right pins? I guess the critical one is the speed pin as the other 2 if you get it wrong will just need reversing (if say the rover goes backwards instead of forwards).

(David Boulanger) #40

If SERVO1_FUNCTION is 73 and SERVO3 is 74 then the speed pins would go to the signal pin on output 1 and 3. Looks like you can also assign more of the aux outputs with the RELAY_PINx parameter. I’ve never set up a brushed system so this is all marginal advice at best.

(David Boulanger) #41

Maybe something like this would be easier. These come in different Amp capacity. Just throwing this out there.

(Anthony Johnson) #42

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.

(Anthony Johnson) #43

I found this at a decent price and it says works with tanks, cant find a dual motor on Amazon

(Anthony Johnson) #44

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?

(Anthony Johnson) #45

The motors are spec’d 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
  • Locked-rotor current: 2.3 A

(David Boulanger) #46

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.

(Anthony Johnson) #47

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 “motor driver” 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 don’t 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 can’t 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.