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Need help choosing parts for and configuring a unique RC car


#1

Hello all. I’ve created a bit of an adventurous project for myself, and I need help choosing the right parts to use, and minorly with configuring them. It will require some backstory, so prepare yourself. Skip to the end for a Tl;DR if you please.

A while back in middle school I competed in a junior solar sprint competition. It’s like a mini drag race for solar cars. The idea is you start with a kit including a solar panel, motor, and a few other things, and you make a car that can travel some distance the fastest. I loved the idea, and tirelessly honed mine to perfection. The car went incredibly fast for its size because it was extremely light, with the solar panel making up ~2/3 of the weight. Thanks to the hard work I won first place. For winning, I got the parts to make my own small solar array: 30 1x6 panels that put out 0.5V and ~1 Amp each, plenty of tabbing and bus wire, and a flux pen. Since then, the car has just been sitting on a shelf in a box doing nothing. So, a couple weeks ago I thought why not put it to some use by modifying it so I could remotely control the speed and turning (as for the competition it traveled in a straight line). This turned out to be much more intricate than I previously anticipated. After deliberation and discussion with friends, I decided it would be much less of a hassle to just create a new car using the kit I won.

Now onto the car itself. The goal here is to construct a car that has these basic features: remote speed and directional control, a solar array as the primary power supply, and the lightest weight possible as to increase the speed. For the steering, I’ve designed a simple lightweight mechanism powered by the smallest servo I could find. For speed control, I thought including a potentiometer between the solar panels and motor was the simplest solution. I’m willing to, despite the redundancy, include a small battery to power these mechanisms as long as the motor’s power comes from the solar panels.

The problem here is number three; I have to make the car as light as possible. I’m part of a robotics club at my school, and have worked with motors and servos plenty, so I know how to rig them up normally in this environment where weight is minor. However, since even a few ounces can slow down the car I am consulting you people as to the most efficient way to configure one small servo and a digital potentiometer. My price point is $50 for the parts needed for this, but if needed I can accommodate more from other parts of my budget. The remote part I’ll work on once I can figure this out. So far I’ve looked at the boards sold on this site and some Arduino boards, but I’m new to this field, and was overwhelmed by the possibilities.

TL;DR: I’m building a solar powered RC car. I figured out efficient ways to control the steering and speed, but need help configuring them in a lightweight manner. Once I have that done I’ll move on to the ‘remote’ part.

Thanks for whatever help you guys can provide.


#2

Hello.

There certainly are a lot of options for a project like that. It might be helpful to look at some of the recent line following robot posts on our blog to get an idea of how some of the engineers here built some small robots for a line following competition for a robot club we host.

If you look through the posts, you’ll find Amanda’s line following robot: Newbie, which uses a servo to steer the front wheels. Most of the other robots use differential steering, which uses two independent motors to spin one wheel faster than the other to turn the robot. A lot of these differential steering robots use a ball caster to support the platform in addition to the two drive wheels.

To control the amount of power to the motors, it is common to use a motor driver in combination with a microcontroller like an Arduino. We have a large selection of motor drivers, but the best one for your application will depend on the voltage and current required by the motors. For a microcontroller platform, Arduino is relatively friendly for beginners. Our A-Star 32U4 Micro board can be programmed from the Arduino IDE, is very compact, and is relatively inexpensive. I recommend looking at the “Fade” tutorial for the Arduino IDE since the PWM method it uses to control power to an LED will be the same method generally used to control power to the motors with a motor driver.

Finally, if you are using individual solar cells, you might be able to boost their output voltage to power something like a microcontoller with one of our step-up voltage regulators, though it can be a bit tricky to determine a power budget for your system so that the power drawn by your motors does not prevent the other electronics systems from working.

Those are just a few thoughts. If you have any specific questions after going through those links, feel free to post them.

-Nathan


#3

I actually do have a questions.

I’ve been looking though the parts each link described and I’m still a bit confused. I’ve never built a robot from scratch; My robotics club is part of FTC, and as per league rules, we are constrained to the TETRIX kit. I know the basic parts needed (i.e. a central unit to communicate with, and controllers for the motor and servo), but I see parts like “Dual Motor Driver Carrier”, “Motor Driver IC”, and “A-Star 32U4 Mini LV”, and I have no idea what I’m doing.

Really, what I need is something like a tree diagram that shows me exactly what circuit boards I need and what I need to connect them to to control a motor/servo.


#4

Hello.

In general, our parts are not as modularized as something like the TETRIX system. There can be many ways to set up a system to do something, so connections can be made in different ways to accomplish different goals. If you look at the product pages for these products (for instance, our DRV8833 Dual Motor Driver Carrier), you will find some more documentation, often including a minimal wiring diagram.

A “Motor Driver IC” is an integrated circuit that can be used to drive a motor. We generally refer to the printed circuit boards that use these ICs with a minimal amount of other supporting components as motor carrier boards and our “Dual Motor Driver Carrier” boards are boards that can control two motors independently, either because they have a motor driver IC that can control two motors or because they have two single motor driver ICs.

The “A-Star 32U4 Mini LV” is an Arduino-compatible microcontroller board. It has a microcontroller on it with many input/output pins that you can control with code written in the Arduino integrated development environment (IDE). Essentially, it runs the code that you write to control your robot.

If you have not looked through those blog posts I linked to last time, I encourage you to do that. We also have some community project posts on our blog with links to information about projects our customers have built.

-Nathan


#5

I’ve done some more searching, and found a product that enticed me: the Wixel Programmable USB Wireless Module. I was wondering, can I control 1 servo and 1 motor with just this board, or would I need to also include something like the DRV8833 Dual Motor Driver Carrier to do so? From the research I did I am fairly certain I only need the former, but I wanted to ask to be sure.


#6

Hello.

If you are just getting started with microcontrollers, I would definitely recommend an Arduino compatible board instead of the Wixel, which is intended for more advanced users. You would probably need to write your own code for the Wixel to control your robot; you can get an idea of how much effort that would take by looking at the “Writing Your Own Wixel App” section of the Wixel User’s Guide to see if this is something you would feel comfortable doing. Also, while it is possible to control a servo using the Wixel without additional hardware, you would still need a motor driver like the DRV8833 to control a brushed DC motor.

The Arduino boards have much more sample code and documentation available online, and are more beginner-friendly. Additionally, if you need wireless capability or the ability to control a motor, there is a wide selection of hardware (shields) that can be easily mounted to the Arduinos.

-Nathan