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Pulling apart a RC car to re-use... What might I do wrong?

Former Member

Ok, I just spent a fair amount of money on a decent but broken RC buggy... Everything about the buggy is fine EXCEPT the control board.. which is great because I don't want it anyway (I want to make my own).. So I've now started my journey of trying to figure it all out.. First issue I've ran into... my DC motor has a weird yellow thing attached in parralel (see picture) I believe it might be a resistor, but I'm not certain.. Next is that my 7.4v lithium batery (which came with the RC car) is actually measuring 8.27v :S... My thoughts might be that the pcb that it was originally connected to took the higher volts and regulated them down to 7.4, that way as the batery drained there was a constant power supply coming from the battery... thats just a guess though.

 

Also... I have baught a L293D IC to control the motor and then controlling the server direct from the pi.. Is there anything I should know? like is there anway to improve THIS project to add stability to voltage or to make it more reliable etc etc.

 

http://img706.imageshack.us/img706/8112/photoadn.jpg

 

 

Finally... My servo that is inside of the RC car unfortunatly has 5 wires coming out of it, meaning that it needs some ic's to allow pwm control to the motor which I guess are on the old (broken) pcb... I might be able to salvage some parts off of the pcb, though I don't know if I will be able to.. These are my options:
1. find a new servo which fits in the same slot/has enough power to move rc car (1/14th) whilest it operates

2. rewire the servo I currently haves IC (its a micro servo (as seen here in this kit) to be used for the bigger servo (see below.. you will see what I mean by, ones small the others massive)

3. buy some IC's that will allow me to convert my 5 wire servo to a 3 wire (pwr, gnd, pwm) maybe the ones here or here2 or here3? (looking at the manual this looks hard... is there a kit??)

4. your suggestion that wasn't like any of these..

 

Thanks for all the time and help guys..

 

http://img838.imageshack.us/img838/2775/photo4qp.jpg

  • That little yellow guy on the Servo is just a mylar capacitor with a value of .1 uF.

  • You may also want to use an L298 motor driver instead of the L293D as it is only rated for up to 600mA output, and that motor could take more amps than that. If it is under 600mA, then it's fine though, but the L298 can handle up to 2.0A. You may also be able to hack the original control board and use the original motor driver/H-bridge/transistors for the motor control.

     

    Also you may want to use a separate battery just for motor supply power, and one for the Raspberry Pi, because most of the time the motors will draw too much power and then cause the Pi or other control board to become unreliable becasue of reduced power (the Raspberry Pi is very sensetive to this, needs at least 700mA or 1.0A ideally if model B, less if model A which is at least 500mA) On my first Arduino robot I used a RC car for the chassis, and soon realized the problems with one battery for both control and motors. I have made sure to separate the power on my Pi based robot (also using the same RC car) with the car's built in battery pack powering the motors, and a USB charging battery pack 1.0A/2.1A for the Pi, USB wifi, Arduino, and webcam (soon).

  • in reply to Former Member

    that what im trying to do but go bigger using a Radline RC the board is 2 parts the blue board Digital 49mhz antena the green is Motor Control the Digital Antena has a RXD pin i want an Arduino to read the Signal it receives command from the controller then once i get the data i needed set up another Arduino to receive command off the Blue PCB RXD the Arduino is gonna control Solid State Releys on a GoKart

     

     

     

     

    http://www.element14.com/community/thread/22747