CDI Ignition

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RC CDI Ignition 

Link to forum on RC Universe

-As simple as possible
-Programmable advance control
-Use no exotic hard-to-find components
-Use a normal 4.8V RX battery
-Integrated spark test function, no signal generator is needed.
(makes 4 or 140 sparks/second without the need for a trigger input)
-Spark control can be separated from the voltage board
(to be used as a front end for a CDI without advance)
-Integrated strobe light
-May be extended with a failsafe/engine stop module. (not designed yet)


The CDI is made by 2 modules; the voltage converter and the timing circuit.
It is best to make the timing circuit first, to have access to the test function when making the voltage converter.

Voltage converter
Based on a free running oscillator, it has a very low part count, and make 200-200 volts available for the coil.
It uses an ferrite core from an old computer as base for the voltage converter.
A description of how to make the transformer is here.


Timing circuit
Based on a PIC16F84, running a code based on transmics source 4.3

Please check out Transmic's pages, a lot of useful information there.


A lot of different coils is tested, and it is even possible to make a homemade coil.
This page has a full description of how to make a coil.

And on this page, you can see how to modify the original magneto coil.


Activating the test mode
Ground pin 3 on the Servo input before power is connected, and the CDI will start to generate sparks at a rate of 4 or 140 pr. second.
The rate is controlled by grounding pin 3  on the trigger input.
The CDI will stay in test mode until power is disconnected.
Short video of the CDI running in test mode.


PIC16F84 ASM file for the PIC program
PIC16F84 HEX file for the PIC program
Excel file for making advance curves, see transmic's web
Schematics, voltage converter   NEW
Schematics, timing circuit          NEW
Component layout                    NEW

The schematics and PCB is made by Jorge M. Barrera.


Part list:
Timing circuit
1 PIC16F84
1 resistor 240 ohm
2 resistors 470 ohm
3 resistors 10 K
1 green LED
1 red LED
2 capasitors 15pF
1 Hall effect device, Honeywell SS443A

Voltage converter

1 Transistor  BD242B       -   Can be replaced with MJE2955 or BDW94C
1 Thyristor  2N6237        -    Can be replaced with BT148
1 diode bridge
1 diode 1N4004
1 Resistor  500 ohm
2 Capasitors 4,7uF/16V and 0,47uF/250V
1 homemade toroid coil
1 Coil, Modelectric or homemade

The CDI project is developed by Jorge M. Barrera and me.                Last update 02.18.2008 .

The old CDI pages is here.

october 5 2005    -New CDI page uploaded
october 7 2005    -New schematics, datasheets added, 'homemade coil' page updated, 'modifyed magneto page' added, some errors corrected