Introduction: Hack an RC Car's Unused 3rd Channel!

Picture of Hack an RC Car's Unused 3rd Channel!
So, as we all know most remote control (RC) cars use only 2 channels on their remote control: one for forward and backward, another for left and right. What you may not know is that there is an unused third channel on most RC cars! Cheap cars such as the New Bright line found at places like WalMart and Target use a standard chipset (RX-2/TX-2) found in many many remote control vehicles.  Today we will be hacking that third, unused channel.  On the RX-2/TX-2 datasheet, that third channel is called the "Turbo Mode".

This Instructable showcases a couple of example projects I made to test out if I could take advantage of this unused "Turbo Mode" and operate a gun turret remotely. I built two vehicles - one using a fully automatic battery powered Nerf gun and another using a battery powered squirt gun with an electric pump.

EDIT: I originally titled this "Hack an RC car's unused 5th channel!" but I've since been informed that it's actually just three channels.  The forward/backward and left/right controls are just two channels!  If you see me refer to a 5th channel, just imagine I said three, okay?

EDIT #2: (5/28/13) I recently made another project and Instructable very similar to this one. I mounted an Airsoft machine gun on the top of an RC car! Here's the link to see a full video tutorial to make it: https://www.instructables.com/id/Airsoft-Gun-on-an-RC-Car-Hack/

Helpful Guides:

Step 1: Supplies List

Picture of Supplies List
I was amazed to find that between your local Walmart, Target, and RadioShack one can find all the parts necessary for this project!  In fact, this project is so quick and easy that you can do it in mere minutes if you know what you're doing.

You will need:

From Target, WalMart, Toys 'R Us, or wherever: From RadioShack:

Step 2: About Driving DC Motors...

Picture of About Driving DC Motors...

Okay, so check out page 6 of the datasheet I included.  You can see that if you put in a button or switch in the controller that shorts pin 6 to ground you will activate the third "Turbo" channel.  This causes the receiving chip to output 3v on its pin number 12.

Now, we can't just power a DC motor directly from that RX chip.  First of all, the voltage probably isn't high enough.  Second of all, the amount of current needed to power the motor is absolutely not going to be provided by that little chip (I measured 1 Amp for the Nerf gun!).  We need something else to take that 3v signal from the chip and use it to turn the DC motor in whatever toy you're hacking on and off and power it directly from the battery.  That something is the TIP120 transistor.

The two tutorials I listed in the introduction of this Instructable pretty much spell it all out.  I made up a drawing of the circuit, but basically it is just a circuit that takes the 3v signal from the RX-2 chip and switches the battery power on and off for the motor.  The diode, pointing AWAY from ground toward the transistor, is to help prevent back voltage from the motor frying the RX-2 chip.

Step 3: Go Crazy With It and Make Some Stuff!

Picture of Go Crazy With It and Make Some Stuff!

Now for the really fun part - go make some stuff!  The motor in the previous step's diagram is just whatever motor you find in some toy.  In my case, it was a Nerf gun and a squirt gun.  Included are some pictures and stuff of what I made, just check out the captions for each picture for more info.

I put in a beefier battery to give myself some more playtime and the car some extra "oomph".  Original battery was 6v and lasted a measly 15 minutes.  This one is 7.2v NiMH and is 2800mAh.  Just solder a connector to the battery terminals of the car, hook in your new battery, and you're good to go!  So far as I know the little DC motors in both the car and the toys I used can handle the extra voltage without any issues.  If someone out there is more knowledgeable about this topic then I'm all ears!

Comments

HamishM15 (author)2017-02-10

Is it possible to run a servo from this?

daniex611 (author)2015-07-23

Is is possible to add another back/forward motor onto pin #6? I want to repurpose an old RC car and possibly build a small dynamic RC sub. If this is possible, how could I do this? I would need to be able to reverse the motor, so i know that i would need 3-way switch to control the motor. This new motor would be for dive planes to bring the sub down and the usual backwards/forwards motor for the drive. the left/right would stay the same for the rudder. If you could help me with this that would be awesome! Thanks in advance.

iteepu made it! (author)2015-05-31

Great idea! I combined it with the alcohol powered rocket launcher by theconstructor.

artrjc (author)2015-04-27

I know how to make it work right, but to go in both directions you need another RC unit whiches uses the other half - like 27MHz virses 49MHz.

oldsmarracin (author)2015-02-14

could one use a 2n2222 transistor i tried but i may be doing something wrong

gunman15 (author)2014-01-11

I am going to have to do this, do you know of a way to attach a live feed cam to it also.

mk2001 (author)gunman152015-02-02

Yes but it involves wifi.

mohamedbenayad (author)2014-10-19

HELLO

ARE TX2C/RX2C SAME TX2B/RX2B?

lukeD (author)2014-09-02

I am currently trying to do it with the tx2c, I got the right datasheet but nothing seems to work, anyone got ideas for me?

lukeD (author)2014-08-29

THANK YOU A LOT!
In my case I am going to mod my rc boat, im planning to make a feeding boat for carp fishing. The third channel will be used to flip a box or someting (filled with food for carp fishing, to say it simply) so al the stuff in it will fall out of it. That way I'll be able to feed the carp on just the right spot (wich isn't the case if you throw it by hand).

Nice and clearly Idle!

Itchyzombie (author)2014-03-17

I'm a 12 year old and I'm proud to say, I did it. :)

if you need help search up the ic on your car, my New Bright was different so thats what I did.

I put a breadboard on top of the hull instead, for my arduino and stuff.

cplnerf (author)2013-07-01

is there any cheap way to send live video feed through? Do you know of any app and cheap camera pair that will work over bluetooth on an iPhone?

4lifenerdfighter (author)2013-06-15

Is the third channel analogue like the other two? Can you choose the strength of the water?

ldrago808 (author)2013-06-06

Where does the other end of the battery connect to?

Sergeant Sarcasm (author)2013-06-01

Great way to build a RC north korean nuke launcher truck!

gravityisweak (author)2013-05-17

So the TX-2 Turbo chip is in the remote. The RX2 chip is in the car, is that correct? Let's say I don't care about the car moving forward or backward anymore, and just wanted to make a stationary mounted nerf gun that I could remote control to shoot at people walking up my driveway. Would it make the project any simpler? I'm pretty interested in figuring out how to use cheap remote control car guts as on/off switches for random objects.

cplnerf (author)gravityisweak2013-05-29

just wire the gun up to one of the drive motors, make sure you know what your are doing though

tman27 (author)2013-05-20

That is f@&&!/&! Awesome

robo10302 (author)2013-03-23

Hello,can you please help me?on the receiver the IC is the same(RX-2B) But on the transmitter my IC is (TX-2E),will you please give me some suggestions on schematic of this IC?Its a different car:)

katman101 (author)2012-11-19

i love you in the least weirdist way possible

ivanjacob (author)2012-04-14

are you selling them?

I've thought about it - the whole project takes like 15 minutes at most :D

cplnerf (author)Brian Henderson2012-09-10

its taken me forever

cplnerf (author)2012-08-16

PLEASE HELP
i am using the same rc hummer but i got it last year. The circuit board is almost idenical to the picture. the problem is the led on the remote just remote just stays on continuously. there are no wrong connections on the remote. i used the 6th pin from the top on the left connected to a switch that is connected to the ground or negative terminal. its the right negative terminal too. when i press right it goes right/back and left = left/back forward rarely works and the gun does not work either. my remote led will act normal but it goes back to troubled after a minute.(it could be because of slight shaking) i am using 6 recharged AA batterys each outputting 1.2 volts adding up to 7.2 volts and the same with the 6 volt rechargeable battery
PLEASE HELP

Brian Henderson (author)cplnerf2012-09-05

If you disconnect the switch you put in, does it fix the problem? Sounds like you hooked it up right. Another possibility - the pin that the gun assembly is connected to might be different from the one I used. Do you know how to use a voltmeter? You might try pressing each direction on the remote control and seeing which pin gets voltage with each direction.

cplnerf (author)Brian Henderson2012-09-07

i have the exact same car and chip set though the only difference is i got mine last year

cplnerf (author)Brian Henderson2012-09-06

thank you so much but the remote works out of randomness now that i took the button out but it turns out the turbo pin on the remote was completely desoldered when it took it out but the remote did work at times and the led that indicated a signal going out did go on.
now i have to use another remote.
i will try using a multimeter.
do you have any tips on soldering the tiny pins?, i have a regular solderer and a pencil tip (?) (thin tip?) solderer.

Ilija Miljkovac (author)2012-04-14

do you mind if i take this idea and ann something like a live action camera+something to control it from a computer?And if yes do you know what that can be

It's not controlled with a computer but I made something kind of like that. Here's the video I made a while back: RC Drone video

I'm currently working on a pan tilt assembly controlled by a Wii nunchuk controller and an Arduino. I need to get an XBee radio or something similar to make it all wireless.  I might as well turn it into a full blown robot at this point though and let the Arduino drive the car while I'm operating the camera/turret assembly.

cplnerf (author)Brian Henderson2012-08-15

it would be beast! if you combined this with your rc camera car!!

Brian Henderson (author)2012-04-13

Hmm, this fully automatic Airsoft gun for $20 at Walmart looks promising...  

http://www.walmart.com/ip/Crosman-AS-Pulse-M74-Dual-Power-Mini/13916909

cplnerf (author)Brian Henderson2012-08-15

PLEASE HELP
i am using the same rc hummer but i got it last year. The circuit board is almost idenical to the picture. the problem is the led on the remote just remote just stays on continuously. there are no wrong connections on the remote. i used the 6th pin from the top on the left connected to a switch that is connected to the ground or negative terminal. its the right negative terminal too. when i press right it goes right/back and left = left/back forward rarely works and the gun does not work either. my remote led will act normal but it goes back to troubled after a minute.(it could be because of slight shaking) i am using 6 recharged AA batterys each outputting 1.2 volts adding up to 7.2 volts and the same with the 6 volt rechargeable battery
PLEASE HELP

Find a Fully Automatic Nerf Gun, and name the resultant project F.A.N.G...

Yes please! F.A.N.G. is so much better than what I came up with :)

hey you and the dude who made the nerf tank should get together you could have a ramp on his tank for the ankle biter or fang so if the nerf tank battery dies FANG is there to protect it all you have to do is just drive it down the ramp.

freeza36 (author)Brian Henderson2012-04-13

Sounds like a fun idea.

cplnerf (author)2012-08-15

PLEASE HELP
i am using the same rc hummer but i got it last year. The circuit board is almost idenical to the picture. the problem is the led on the remote just remote just stays on continuously. there are no wrong connections on the remote. i used the 6th pin from the top on the left connected to a switch that is connected to the ground or negative terminal. its the right negative terminal too. when i press right it goes right/back and left = left/back forward rarely works and the gun does not work either. my remote led will act normal but it goes back to troubled after a minute.(it could be because of slight shaking) i am using 6 recharged AA batterys each outputting 1.2 volts adding up to 7.2 volts and the same with the 6 volt rechargeable battery
PLEASE HELP

Eddie4 (author)2012-07-24

this is a really cool project
if stores sold it as a kit they would make alot of money

Nicbur (author)2012-07-22

Sorry, I know this comment is a little behind. I was trying to do the same thing with an air-soft gun and ran into a problem that when I turn it on I can steer and use the car fine but once I fire the gun and then try to move forward/ steer the gun triggers even though I didn't hit that switch and as it tries to move the gun uses all the power so it just lurches about 1/4 of an inch. I'm using a car that used to be able to transform and replaced that motor with that of the guns. The only difference is, it lacks a small green circle that was attached to both ends that said 473 on it. I was wondering if you could help solve my problem or tell me what that is?
Thanks a lot, Nic.

Ihackedyouraccount (author)2012-07-01

Hey there is a circuit diagram app for the iPad. Although it will cost you $10 it's worth it I love it I think it's called I circuit

Gydoko (author)2012-04-17

Thank you for posting this! i learned much of it (of 3 channels instead of 5, and i watched an old remote, and its 6th pin wasn't connected to something...
im gonna try something...

Elmardus (author)2012-04-15

Nice tutorial, but that about the 5 channels is not correct. Over time I have become something like a RC expert, and I noticed this:
There are only 2 channels normally used. Backward AND forward is one channel, and left and right is ONE channel. It is just the motor moving the other direction, but on the same channel.

So it has 3 channels, one unused, and not 5.

Brian Henderson (author)Elmardus2012-04-16

An important distinction! Thank you for the information. This is why I love Instructables. Looking again at the datasheet I found, it does indeed only say the following:

"The RX2D has five control keys for controlling the motions (i.e.
forward, backward, leftward, rightward and the turbo function) of the
remote controlled car. It can be used together with TX2B."

Note that it says that the chip has "five control keys", NOT five channels. I've seen the TX2/RX2 referenced as a five channel chip set in various places around the web, but perhaps that's a misconception on others' part.

bowlofnoodle (author)2012-04-15

Thank you for the tutorial. Really appreciate!

aertemis (author)2012-04-15

thats sooo CUTE...

darthbean18 (author)2012-04-13

Thanks for the 'ible! I'm trying to work through it with a very similar car, and I'm wondering how you hooked up the 'fire' button?

No problem - I whipped up another drawing that I'll add to the Instructable. Paper for iPad is quickly becoming my new MS Paint for diagrams :)

It's a simple circuit - just put a switch or button between pin 6 of the TX-2 chip and ground. If you don't know where to find ground, just use the negative battery terminal of your remote control. Pretty safe bet.

You might want to add something in your instructable about SMD chips. I took apart a fairly large car a while back with this chip, but to save money the companies who make them will often use the SMD version of the chip (at least in the car). It was tricky with my dull,cheapo radioshack soldering iron I had at the time, but I managed to solder a small wire to the turbo pin. A lot of people will probably get the smd version, especially on the tiny cars (which could make some pretty cool projects themselves).

Dominion-Network (author)2012-04-13

Damn you, I was going to do an instructable on this as well, but I take my hat off to you sir! a very nice instructable

Aaah! Same here! I had a bunch of these lying around and so I took them apart and looked up the datasheet. I noticed the turbo pin and hooked things up to it and added a button on my remote, but I guess it never made it past the prototyping and tinkering level. Never thought to make an instructable on this. Great job!

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Bio: I'm entirely self taught in electronics, although I do have a chemistry degree which I currently don't use at all in my day ... More »
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