BitESC – Electronic Speedcontroller for bitcars

The BitESC is a small electronic speed controller for those little RC cars like the MicroSizer / BitChar-G. It can be used in a small RC plane to have some control over the speed of the motor. The speed of the motor ramps up or down, depending on which of the buttons on the transmitter you press. If no button is pressed, the ESC will ramp the throttle down to a stop after a few seconds. This safety net comes in handy when the plane flies out of transmitter reach.

How to use

The BitESC weighs in at 0.3 grams, without leads, and has a size of 9 mm x 12 mm. It uses an IRLM 2502 to drive the motor and can pull 1.5 A continuous. The microprocessor used is an Atmel AVR 2343 which runs at 1Mhz.

To be able to use the BitESC, you’ll first need to read about the different modifications required on either the transmitter and the reciever. You can read more about how to modify the receiver of a BitChar-G car at the following topics on rcgroups.com:

To get the best results, it is adviced to modify the receiver by adding a longer antenna. I use 1/8 of the wavelength, for 57MHz that gives an antenna length of approx. 63 cm. After extending the antenna, you should retune the receiver by adjusting the coil.

The best hack for the transmitter is to increase the power to the RF circuit and removing the cripple cap, if your TX has one.

This BitESC should cope easily with motor noise. I use a KP00 without a noise reduction capacitor on the Cootie and it works just fine. Although it is a very good idea to add a noise reduction cap to the motor.

The BitESC expects 5 leads to be soldered. The next schematic shows the wiring diagram. The negative of the motor is connected to the BitESC, the other lead goes to the plus lead of the battery (BAT+). The BitESC contains a small RC filter to filter out motor noise.

Example

Here’s a photo of my Cootie (Designed by Ralph Bradley), which I equipped with a BitChar-G receiver and my BitESC. The actuator is connected to the H-bridge on the receiver, which normally connects to the motor and provides forward and backwards motion. The BitESC is connected to the left and right channels. To be able to use the transmitter comfortably, you’ll need to switch the controls.

Schematic

Making a BitESC yourself

If you want to make the BitESC yourself, the next information should get you going. Here’s the link to the PCB layout, assembly code and hex file.

I can provide a programmed 2343 and/or a PCB and/or the components, for those who want to solder the BitESC, but so not want to make the PCB or program the MCU.

Here’s a printout of the assembly source.