Instructables

Using RC car parts as remote control

I sourced a lot of micro RC cars at ebay to use them for DIY projects.
The cars are from Enertec. The call the product "MICRO FLASH CHARGER, Formula 1". The product box contains batteries for the transmitter and the charging box, the transmitter box, a charging box and the car. There are 27Mhz and 40Mhz versions of the product.
The control of the systems contains functions to drive forward, backward, left, right and to drive "turbo" forward. All these functions are not proportional.
The motor is mounted in a small gearbox and drives both back weals at once. For the changing of the driving direction there front weels can be pulled left ore right. this is done by small coils that pull a magnet to the left or to the right. The magnet is mounted on the guidance mechanic.

I was interrested in using the electronic for simple remote switching purposes. For this project I only need the two pcb's. The other parts, like the motors are kept for later projects.
 
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Step 1: Analyzing the circuit

The transmitter is the easy part.
The receiver is more complex. I need some switching outputs. The easy part are the two coils that change the driving direction. Fine copper wires are soldered to the pcb and lead to the coils. The two transistors that switch the coils carry the SMD code 1P. Searching around the internet I found out that these transistors are NPN of the type MMBT2222A. Thinking about standard switching circuits I assumed that the transistors are connected to GND with the emitter connections and that the coils are directly connected to VCC. Some measurement on the PCB confirmed that. Only thing to do ist connect some LED to the switching outputs.
Doing further reverse engineering I found out that the transistors marked 1AM are MMBT3904L. These transistors are connected via resistors to the receiver ic (BA97). The transistors are NPN types, but the emitter connections are not directly connected to GND. I decided to simply remove the rest of the transistors and use the 1AM as the switching outputs.
APSX11 days ago

Do you know if I can buy a semi-assembled RC car without the receiver and the transmitter. Or can I build from scratch from the base chassis? I just need the servo motors, the base and the tires. Any ideas?

SeanLynch915 months ago

Are you able to light up the forward, reverse, left, and right LED's at the same time if you press all four of the corresponding switches down? Great project! I'm working on a project very similar to this, thanks for all of the insight!

nanonano586 years ago
were do you buy that rc car ?
check out alibaba.com then look up r/c cars uill be able find plenty of makers of them
frickelkram (author)  nanonano586 years ago
I bought a bunch of them on an eBay auction ... but they don't sell them on regular basis :-(
Kaiven5 years ago
Is there a way to mod the circuit to use even more things (like leds?) on the receiver and transmitter? I want to add a third motor to my broken rc car, because I want to do a lot of modding. I don't know how to attach the third motor. All it has to do is spin.
frickelkram (author)  Kaiven5 years ago
Hi, these simple circuits have 5 outputs. You can use them to switch leds but also to turn on small motors, that's what they are made for. Inside the car every output is used somehow. I described that in the Instructable. You can turn the car left, right, drive forward, backward and use the turbo. That makes 5 remote controlled functions. If you don't need one of these you can use it for other things. The only thing, that I can think of is the turbo. It is rather difficult to drive the car while using the turbo. Most of the time I avoid using it. If you use the turbo to switch on an other motor, keep in mind that the forward function is switched off when using it. You can see that in the video. Basically, I would say, it is not impossible but you are limited to the simple functionality of the system ...
every car I take apart only has 4 outputs :(
frickelkram (author)  Kaiven5 years ago
Hi,
some cars don't use the fifth function, but the ones I know use chip sets that implement these functions. Tale the RX2C for example http://www.ausmicro.net/v3/thedump/00A9FF9700A9FF98.pdf . I found this in a non name rc car. In the old Super Rebound (Year 2000 edition, the 4-wheel drive) uses Yuniden Taiyo 97-1 chip set. This one also has a turbo function but it is not used in the super rebound. I can't remember the chipset of the small car I tore apart here, but I can try to find out. It uses a more modern chip set very similar to the popular RX2C chip set.
Try to identify the chip set and search for the datasheet on the internet. If you find it you are able to find out what functionality can be used ...
I think I might stick with buying a five/six function chip of the internet. Some guy on YouTube showed me where. I would just need to go find the link he gave me.
frickelkram (author)  Kaiven5 years ago
broken link
broken link
amando96 Kaiven5 years ago
yea but u can use combinations of outputs... like right, back one thing left, back another thing then u'll have like 16 possible actions...

i made one like this, but it moved a spy mini camera around it was neat but i took it apart coz i needed the bits.. :(
i think i have it on youtbe though...
Hey i was just wondering if you replace the crystal from one transmitter into anther. Will it change the frequency?
casey321b5 years ago
from the looks of the car controller i could make a joystick with usb for my comp
cotton6 years ago
so whats the point why not hoiork the car to a reley and have one button that trigers the relay to turn somethingon and keep it on then another button for a onother thing and then pres the button again so it turns off
stevoIution6 years ago
Good instructable. The first thing I do is put a drop of hot glue at the base of each wire so they don't snap off from handling.
you can just solder it on well. it works much better with much less chance of the cord ripping off.
good idea.
frickelkram (author)  stevoIution6 years ago
It's a good idea to do that. It often happens that wires break because auf too much bending during examination .... thank's for the comment!
CyberBill6 years ago
Are there any other oddities in the transmitter with button combinations, for example left + right, or forward+backwards? Whats the range on these little guys? I really liked this instructable, it gives me a lot of ideas! :D
frickelkram (author)  CyberBill6 years ago
Hi CyberBill, there are no other restrictions that I know of. Turbo mode is the only one. Driving backwards there is not turbo mode, and therefore no restrictions ... :-) The distance is not very high. Basically the 27Mhz version has a wider range than the 40Mhz. Even the 27Mhz version has maximum of about 5 meters. But if you look at the construcions you may notice that the antennas are far away from being ideal! Getting better antennas on the transmitter and on the receiver side could extend the range. Other thing for optimization is the frequency of transmitter and receiver. These parts are so very cheap built that I am sure that you can get much better results if you trim the rf components a little bit. I think that the Chinese manufacturers do not adjust the components exactly, that takes time, and costs money. What for ... these cars do not need to work on a distance of more than 5 meters. They are build to be used in buildings. But I believe there is more potential in them. I already thought about making some tests but did not have the time, so far. But as soon as I get noticeable better range I will simply post an Instructable about how to do it ... :-)
great instructable, and great idea! (+)
Ohm6 years ago
I have seen people take the guts out of these cars and use them to make micro rc airplanes.
frickelkram (author)  Ohm6 years ago
You may expect some similar doings from me ... ;-) I'll post some of them here when I'm finished ...
i really can't wait :P
dan6 years ago
thanks for posting this. i did the exact same thing a while back, the whole system is very convenient for a $10 remote-control unit which can easily control a wide variety of stuff. if i recall correctly, the motor output transistors are connected in a standard H-bridge configuration, that allows the motor to be driven either forward or reverse.
frickelkram (author)  dan6 years ago
Hi Dan, yes, the circuit seems to be an h-bridge. The motor can be driven forward and backward. I had trouble analyzing the h-bridge layout, the pcb is far to tiny for my old eyes ... ;-) but I'll try again sometime, because I am very interested in the exact schematics of the car ... Because I bought a bunch of cars on ebay you can expect more instructables using parts of the cars in the future .... stay tuned ... ;-)