I’m helping my son’s school club with building a Kid’s ride on car that can be controlled remotely from a PC wirelessly. We plan to use Arduino for the controller. I have no previous experience with hobby electronics, only industrial experience. Thanks!
The components are as follows: Any help with potential issues or things we have missed would be appreciated.
]Mabuchi RS-550PF-8021 6-12V DC motor max current 37/75A, stall current 75/150A (for drive)/:m]
][font=Arial]Servo - Hitec HS-755HB (1/4 Scale) (for steering )[/font][font=Arial]ROB-12625 (from Sparkfun)[/font]/:m]
][font=Arial]Motor Driver 15A IRF7862PBF (for drive motor)[/font][font=Arial]ROB-09107 (from Sparkfun)[/font]/:m]
][font=Arial]Arduino Mega 2560 R3[/font][font=Arial]DEV-11061 (from Sparkfun)[/font]/:m]
][font=Arial]SparkFun Ardumoto - Motor Driver Shield (for steering servo)[/font][font=Arial]DEV-09815 (from Sparkfun)[/font]/:m]
][font=Arial]Arduino Wifi Shield 101[/font][font=Arial](from Arduino)[/font]/:m]
][font=Arial]Hangar 9 12V 7Ah Battery/Charger Combo[/font][font=Arial](from Amazon)[/font]/:m]
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Hi,
If we understand correctly, you want to build a small remote car that could transport children is that it?
If this is the case, the servo for steering seems a bit weak for this application. We do not have all the details of the project so maybe there is a gearbox system which makes it ok. We have gearbox systems if you ever need more strength.
The motor driver also seems to be a bit weak for this application. A 30A or more motor driver would be best. We have this 30A Motor controller which is fairly inexpensive for the power. We also have other high power motor drivers.
Any Arduino should do. The Mega is good but a Uno would also work well. We also have a wide variety of Arduino Wifi Shields.
We hope this will help.
Best regards,
No one will ride in the car. It’s just used for the wheels, frame and motor with gear drive. The car was donated and we are trying to do this on a limited budget. We only need to be able to go slowly down hallways and into classrooms.
The controller you recommend has enough power for the 75A stall current at 6V?
Thanks for the reply!
Hi,
By looking at the motor Specs of the RS-550PF, the current at maximum efficiency is 14.7A@12V. Rule of thumb is to go for about 1/4 of the Stall current. 148@12V / 4 is 37Amps. The 30 amps driver should do. If you want more power, you can always go with another driver but they will be much more expensive.
Best regards,
Ok, so I could run it all from the 12 V battery (I’ve been told lipo or deep cycle would be better)? I also thought of using a 6V battery for the drive and servo motors to limit the current and then a lower power 12 V battery for the controller, but not sure how that would work with the servo.
I was told I don’t need a servo driver shield board and can run it tied to battery power with PWM output from the Mega or Uno. Just not sure about the shared negative with 2 different batteries, tie them together?
Thanks again! I appreciate your time and knowledgeable information.
Hi,
You could definitely run it all from a 12V battery if this is what you have on hand. For the servo, you can either use a separate battery like you mentioned or use a power regulator to step down the 12V to 6V.
You can control the servos directly from the Arduino, but you will need to cut the wires to connect the servo power to your 6V source. The Arduino cannot supply enough power to the servos.
The following example shows how to do this with a 9V battery and a 5V regulator. In your case, it would be 12V and either a 6V regulator or another battery connected instead of the regulator. All grounds must be tied together.
We hope this will help.
Regards,
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Thanks for the reply again. More details as follows.
I thought of the servo as the best alternative for the steering, direct link with horn to the steering sway bar under the car. Seems the Arduino needs 7-12 VDC to operate (decided to go with Uno instead), and can become unstable when <5V, reason for the 12V supply. The motor was originally powered by a pot under the go pedal, no solid state controls, using a 6V rechargeable NiCd battery that came with the car.
I’m thinking to go with 2 higher power 12 VDC batteries in parallel, and then use the SBEC, hobbyking.com/hobbyking/stor … ouse_.html , to regulate the voltage as needed to 5 to 6VDC for the servo. I plan to use your motor controller, 30A rated RB-Cyt-133 for the drive motor to run the drive motor at 6V. I’ll run the servo as you mentioned from the Arduino for the PWM signal and then powered with the SBEC.
This would be used in school hallways, moving between classrooms during the day, as a kid would.
At this point, I could use the following:
Best option for 12V batteries (inexpensive with good run times)
Best Arduino WIFI shield model for school WIFI (good coverage within school)
Advice for wiring - will I need a breadboard - with recommendations?
Wiring kit options - simple…for motor and controller.
Thanks again,
Jroono
Hi,
You should drive your motors at 12V. They are optimal at 12 and it is less complicated than to regulate power for them.
For the batteries, we have this 2800mAh NiMh battery pack. We do not recommend plugging them in parallel. In your case, you should maybe look for Sealed Lead Acid batteries like the one used in kid cars, motorcycles or alarm systems. They will probably be cheaper and you should have enough space.
For the wifi shield, we have the official Arduino WiFi Shield which is always a good option because there is a lot os support documentation. We also have this less expensive DFRobot WiFi Shield which is also great because it has an external antenna so probably a better range.
Breadboards are good for prototyping but you may prefer soldering if you want to use this for a long period of time.
As for wiring, it is pretty simple. You just need to make sure your wires are big enough between the driver and the motors. We cannot guarantee a certain gauge but we think AWG 18 should work.
For the rest, regular AWG 22 wires , servo wires or anything you have on hand will do.
We hope this helps,
