Author Options:

Guide to RC? Answered

So don't tell me to go and buy a small RC car, and hack it. I want to know how to MAKE one! Like, totally MAKE!
Where can I find out where to make a simple 2-4 channel RC thingermabob with a range of about 50 feet? I just don't get it, everywhere I look, they make these huge units. My helicopter is 6 channels and the circuit board is no bigger than 2x2, and only has 2 IC's on it. Why can't I find instructions for some small and simple like the circuits you find in RC car! What about Zip Zaps! Their circuit boards are tiny, and work better then the huge circuits you find online!




Best Answer 5 years ago

I suggest starting by making a simple, single channel IR remote and receiver with arduino so that you can pick up the basics of how the data is being transmitted. Infrared and Radio remotes are very similar in how they communicate, the major difference is that one uses pulses of light and the other uses electromagnetic waves. IR is the simpler (and cheaper) of the two choices and thus a great place to begin IMO. Once you get that part down it will be easy to plug in a radio module like the xbee for better range and outdoor use.

If you aren't married to using arduino, I highly recommend getting some picaxe chips to make your own remote and receiver. The chips have a built in IR remote function and the circuitry involved is relatively simple.

What frollard has said about deciding how much you want to build yourself is absolutely spot on. If you want to make the remote and receiver from individual components you will need to do a massive amount of research, especial if you want to use radio. It would be a rewarding build, and I'm sure you would learn a ton if you chose this route, but it would be time consuming.

However, if you just want to make your own remote/receiver and gain a general understanding of how it works, and have it done this year,  your best bet would be an xbee / arduino combo. I personally have this badass, ps2/xbee remote project on my to do list which is exactly that:

If you want to buy tiny, toy helicopter style transmitters/receivers you can find them on micro-airplane hobby sites, like these:

I do know of some instructions and schematics for making such tiny boards, but they are not in English (google translate works fairly well on them.)

And finally, I'm not sure exactly which instructions your looking at where people are connecting iPads to arduinos, but my first guess is that they use bluetooth. If not that then they are likely plugging an infrared LED into the headphone jack so it can be used like a regular ol' IR remote.

Well thanks tom! I'm about to make these ibles on the IR remote. IR is prolly what I'm going to have to use.

So what about hacking other peoples projects? Now that you guys totally discouraged me from ever trying to make because of my electronic skill set, how do I go about hacking the RC stuff I get from the store?? Any tips, and good practices I can use to get the best out of using another circuit to control my project? Say this, I by a 4 channel RC toy from the store, and I want it to be able to power my big robot. The output of from the reciever board is NOT going to be powerful enough to control the big drive engines. I had two ideas. I could hook it up to a transistor, and make it work like a switch, and, I was thinking I could use Arduino to detect the high voltage, and then have it respond?? Sound good?

Well hey, first off, please don't be put off because of the electronic skills needed. Toying around and experimenting is exactly how you learn and build those skills. This is again why I think starting with IR is a good idea, it covers most remote control concepts and is cheap to play with.

As for hacking into stuff, it does help to have an overall idea of how the remote works. For the most part, all of the RC toys you get from the store will contain the following:
• A radio receiver that picks up the signal being transmitted from the remote control.
• A microcontroller chip that decodes the digital signal and converts it to control signals for the motors.
• An amplifier that uses the control signal to turn the motors on and off. These are usually transistors or MOSFETs that are arranged in an H-bridge that is connected to the motor. (I believe brushless motors are slightly different, I'm not sure.)

I would go about hacking into a toy RC by first opening it up and finding the biggest transistors on the board, there should be at least 4, and following the traces from them back to the microcontroller. The pins that are connected to the transistors/mosfets will be the control pins and this can be confirmed by testing them with an multimeter, logic analyzer, or oscilloscope.

To drive a larger motor that consumes more amps, you would buy, or make your own h-bridge using transistors/mosfets that were able to handle it. The control signal from the microcontroller would then be disconnected from the original H-bridge and connected to your new, high powered one (with optoisolators to protect the uC.) Since I don't know exactly how to design an H-bridge from scratch, I would find the max amperage of my motors, lets say 25 amps, and google for "25 amp h-bridge schematic" and see what came up.

Do you already have a motor and RC, or where you thinking about buying one?

PS. I'm a tinkerer, not an expert. The reason I have such bizarrely specific information is because I've recently been spending a lot of time learning this stuff myself. I've never actually hacked into an RC car, but I did consider it and looked into how it was done. End the end I decided that it would be easier to buy premade parts like an xbee and a motor control board that I could configure to do exactly what I wanted rather than deal with the unknowns that come with modifying an existing toy.


Well that's something to think about.
So the 4 big transistors would get turned on by the microcontroller, which gets controlled by the RC. So I'm going to be looking to trace back the middle pin of the transistor back to the microcontroller? So if I can identify which pins on the micro controller go HIGH when I push certain buttons I'm good??
Never thought of it that way! I could also use my Arduino to detect those inputs, and then, have it do something besides driving a car ;-)

I've got a small RC car that goes only forward and backward; I'd thought I'd start out that. Then I have another one that goes in all four directions.
So try tracing the traces back?? Wow, Ok, I'll tell you how it goes!

Oh yeah, you got the idea. Do be aware that the middle pin of the transistor isn't always the base. If the transistor has a part number on it you can look it up, or you can try to guess by referencing an h-bridge schematic. Your small RC car that goes forward and reverse (variable speed?) most likely has only one H-bridge connected to the motor and two control sign from the uC; one turns the motor on and off, the other sets the direction.

You should also be aware of Pulse Width Modulation (PWM). See, if you hook a motor right up to a battery it will only have one speed, full on. Most RC cars have different speeds and go slower or faster depending on how far you push the control stick.

To vary the speed, the uC turns the motors on and off very quickly. The less time the motor is on compared to off, the slower the motor turns. So, one of the signals out of the uC and going to the h-bridge will be a varying high/low signal at a frequency probably around 10kHz., this is the speed control. The other control pin will change from low to high when you change from forward to reverse (or high to low, whichever.) An oscilloscope would be super useful here, but you should be able to find the right pins with just a multimeter.

And, definitely yes you can use your arduino to detect the inputs, the only things to consider are what voltage the uC's control is, and connecting both of the grounds together. Arduino likes 5v signals, but you often run into 3.3v ones. Here is some good info on dealing with that: http://www.cellbots.com/how-to/handling-3-3v-to-5v-logic-level-conversion/

If you get stuck try reading up a bit on H-bridges and PWM and I'm sure you'll make progress.

Yes, one of my cars has variable speed. I'm sure that would be interesting to try to get that working!

Thanks for explaining this all to me!

Thanks for sharing such a nice blog but as every one have different choice.So one think different then other.I also interested in rc toys and get different from online toy shop.If you need best rc toy shop visit here or search on google and get as per choice.

It all comes down to how much of the proverbial wheel you are willing to reinvent.

It needs:
  • controls
  • remote transmit and receive
  • on board control to interpret those signals
  • power management/batteries/charger?
  • motor drivers
  • steering (servo generally)
  • motors and gearboxes
  • cases to hold all the components together
  • suspension
  • wheels
  • drivetrain to connect the motors to the wheels
  • outer body to make it look awesome

TOTALLY MAKE would involve making the ICs, refining the silicon to make the transistors...layering the copper on the board before etching out the circuit...molding or milling or 3d printing the plastic parts.  That is mostly unreasonable.

The next reasonable level would be to assemble commonly available components into boards, assemble them on available chassis designs.  This depends on your electronics and engineering ability.

Most of the items in the 'you need' section are available as modules with standard interconnects - sourcing and putting them together isn't hard, just generally more expensive.  A microcontroller prototyping platform (like arduino) could reasonably connect to an xbee radio, turnigy motor drivers, king lithium batteries, some beefy brushless motors....

The reason people say to hack existing stuff is the hard work has been done.  You can pick ANY combination of the above options to suit your fancy. 

Hmm, yeah I was thinking about using an Arduino, but I don't have an iPad or Android that everybody uses to control it. Are there some computer programs [MAC] for this? I wasn't totally sure how they were able to connect the Arduino to the Ipad. Any tips??

Presumably just with a USB lead. You USUALLY use a PC to talk to Arduinos. Developing code for an arduino on an android device would be entertainingly fiddly .

Nobody has ported gcc to android yet - so you can't compile from droid yet :(


Who uses an ipad to control an arduino? definitely not everybody. As I said, you need controls. That can be a tablet if you so desire - but also as I mentioned controls connected to a uC in the transmitter can give the instructions to the bot - it doesn't need to be a computer or tablet.