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I am wiring up a kids ride-on toy (Powerwheels) to control both speed and steering with an Arduino. The ultimate goal is to have the Arduino take analog inputs from the driver (steering and acceleration) as well as digital inputs from a Radio Control source. The Arduino will combine these inputs such that the Radio inputs override the driver, but otherwise the driver is free to operate the vehicle.

The vehicle is driven by 2 motors, Fisher Price part 00968-9015. From what I can find on the internet they are 12v DC brushed motors that run @ 1.25amps with no load, and supposedly hit 70 amps during stall.

I plan to drive the motors with the Actobotics Dual Motor Controller in split mode. Channel 1 will operate Steering with a 4" Stroke 25 lb Thrust Heavy Duty Linear Actuator from #ServoCity. Channel 2 would operate the above mentioned set of Fisher Price motors.

I have 2 SLA batteries that are connected in parallel for longer run time while maintaining a 12v output. The positive(+) terminal goes through a 30Amp DC circuit breaker before going to the rest of the system.

I'm a software engineer so programming the Arduino isn't a concern, but the I have to admit I'm out of my comfort zone with wiring and electronics. I could use any input on the wiring of this project. If I'm wiring something wrong, or should be using other/different components - suggestions are welcome!

Question 1: Can I run two 12v motors in parallel on channel 2 of the Actobotics Dual Motor Controller from #ServoCity? (can Channel 2 handle that load)

Question 2: Will the parallel 12v SLA batteries (as shown) be sufficient to run both motors, the Linear Actuator and an Arduino without any problem or is there a more appropriate power configuration? I would like to avoid making the worlds slowest Powerwheels car.

Thanks!

#Actobotics #ServoCity

CarPlan

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  • $\begingroup$ Just wanted to add links to the parts I'm using. I'm not certain of the specs on the motors, just model number. 30A Inline Circuit Breaker amazon.com/gp/product/B01H3DKGFK/… Dual Motor Controller: servocity.com/actoboticsr-dual-motor-controller-assembled Linear Actuator :servocity.com/hda4-2 Radio receiver (could by any, but here's one I was considering) horizonhobby.com/product/radios/spektrum-trade-up/… $\endgroup$ – DontPanic May 20 '18 at 2:08
  • $\begingroup$ the linear actuator is powerful enough to sever fingers .... it is not suitable in a toy $\endgroup$ – jsotola May 20 '18 at 4:39
  • $\begingroup$ @jsotola lots of things are dangerous when mishandled. Do you mean a 25lb actuator is more than is required to actuate a front wheel assembly, or that in your view, using any sort of actuator is too dangerous for a toy? $\endgroup$ – DontPanic May 20 '18 at 5:45
  • $\begingroup$ you need to use an actuator that has "slip" ... the linear actuator is usually worm gear driven (i think), it has a lot of power and it cannot he moved by pushing on it .... the one you have may have different mechanics than what i am thinking of ..... in the end, the design is up to you and i am sure that you will test it fully before handing it to your child, so i have no concerns .... i do not know what kind of an actuator would be best, maybe an enclosed rack and pinion arrangement, or a spool and cable $\endgroup$ – jsotola May 20 '18 at 6:00
  • $\begingroup$ This is an interesting point, I had not considered behavior when movement is impeded. I'll have to look into these other actuator ideas, thanks! $\endgroup$ – DontPanic May 20 '18 at 6:04
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I suspect that you will need a more powerful motor controller. This one is a 10 amp controller, and I suspect that the motors will have a higher stall amperage than that.

The RoboClaw 2x30 amp motor controller is the minimum I'd use, and can be bought from the same place (I use ServoCity as well). I might go up to the 45 amp version. I build robots that are much lighter than this car (with kid) and i use the 45 amp version. But I often over-build so that my bot's don't set themselves on fire.

For steering I think I'd use a small electric motor like this one for the steering. I'd either use a belt that could slip or a 3d-printed gear that would break if there was too much resistance. Or I'd find the plans for a slip-clutch to make sure that the motor won't use more torque than X, where X is an experimentally determined value. I'd put the steering motor behind the dash panel so that the kids can't get their fingers caught in the belt or gear.

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  • $\begingroup$ I was concerned the board might be insufficient, so thank you for saving me some melting circuitry! The steering mechanism, whatever it is, will be under the body of the vehicle, with no opportunity for kids to get near it. One of the reasons I liked the Linear Actuator was having positive feedback about the exact position in the stroke. I'm not sure how to use a slipping belt drive and have certainty of position of the wheels without adding additional sensors of some kind. With car steering you expect when you center the steering wheel that the actual wheels would also be centered... $\endgroup$ – DontPanic May 20 '18 at 17:05
  • $\begingroup$ Are you able to comment on the wiring in my diagram? I'd appreciate a more veteran opinion. Do I have anything hooked up an an inappropriate way? Short circuits, insufficient voltages, improper pin, missing ground etc? $\endgroup$ – DontPanic May 20 '18 at 17:22
  • $\begingroup$ You're treating this like a giant R/C car. I've worked with R/C controls and don't like them. Getting a 50 Hz PWM with a varying duty cycle seems wrong to me when working with digital electronics. I would use a digital signal, perhaps even Bluetooth or WiFi, though some of the inexpensive radio modules work fine. This is probably just because digital is what I'm used to. One advantage of WiFi is that you could run a Raspberry Pi with a webcam and have it stream from the POV of the car. $\endgroup$ – NomadMaker May 22 '18 at 5:23
  • $\begingroup$ I can't comment on the 12V SLA batteries because you aren't giving us enough information. What size (amp-hours) are the batteries. With a digital signal you could also send information on the battery charge back so you could determine when to bring the car in and recharge. $\endgroup$ – NomadMaker May 22 '18 at 5:28

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