Monday, June 29, 2009

433MHz RF remote control system for RC Cars

After the 2 weeks of continues development we finally design suitable RC remote control system for cars. This RC system has,

  • Battery eliminator circuit (BEC)
  • Control System
  • 433MHz transmitter and receiver module
  • Motor driver and servo controller

In this design both transmitter and receiver modules are based on seeed studio’s 433MHz RF link kit and control systems are based on microchip’s PIC16F84A MCU.

At the design time we test this circuit with Futaba, Airtronics, JR-Radios, HiTec and "Mystery" (available in eBay) micro-servo units. This circuit may support standard electric motors (brushed DC motors) and during the testing stages we drive RC helicopter motors and RC airplane motors successfully with this system. To drive this circuit we use 7.2V 500mAh Li-Po batter pack.

During the circuit assembling and testing, make sure to take necessary actions (e.g: shielding) to prevent/minimize the EM interferences which was generated by the motors. Most of the time these EM noises may reduce the performances of the 433MHz receiver module.

To get the maximum performance use 830mm (or higher) telescopic antenna with the transmitter and 20cm antenna with the receiver.

We design this system for RC cars but it can also use with RC airplanes, helicopters and boats with some minor modifications to the receiver module.

All the circuit diagrams and MCU source codes are available to download at here.

Monday, June 1, 2009

Finding electronic parts and instruments in Sri Lanka

Most of the times finding the electronic parts in Sri Lanka is (extremely) difficult process. Lots of electronic part suppliers have fast-moving electronic parts only. (such as general resistors, capacitors, semiconductor devices related to the Hi-Fis, TVs and general consumer electronic products, etc.) For my electronic experiments I'm getting most of these “uncommon” electronic parts from following suppliers,

Farnell : Farnell is my "number one" choice for most of the “uncommon” electronic parts and instruments, specially semiconductor devices and test instruments. Compared with other suppliers there prices are bit high but also had a nice service and higher reliability. Most (all ?) of there parts are coming from reliable and popular vendors. Most interesting thing is “There are no minimum order quantity levels in there orders”, which means I can order 1 unit of electronic part from them.

Orel Corporation (Pvt.) Ltd.

Bay: 12-13.Trace Expert City,
Tripoli Square, Maradana Road,
Colombo 10.


Tel: (941) 0114 792 103
Fax: (941) 0115 376 678
Web: http://export.farnell.com

Silvertones Ltd : Silvertones is one the oldest electronic part supplier in Sri Lanka and they also have good collection of electronic parts. Most of the Silvertones parts are coming from branded electronic part manufactures, due to this reason some of there parts are bit expensive than standard once.

Silvertones Ltd

132 Vauxhall Street
Colombo 2
Sri Lanka.

Tel: +112 436141, 2 335634
E-mail: silvertones@eureka.lk
Web: http://www.silvertonesonline.com

DigiKey : Digikey is one of the world's largest electronic component supplier and unfortunately there are no any local agents for DigiKey. I brought some hard to find electronic parts from them via online and there service is also excellent. Only problem in DigiKey is it's higher shipping and handling charges.

Web: http://www.digikey.com

Other than these local/international suppliers eBay have several electronic part suppliers. Most of them sell lot of rare semiconductors and other electronic components. Most of these eBay suppliers ship parts with free of charge and they are not much expensive as DigiKey or Farnell.