The circuitry

To develop the hardware, I used a Stellaris Launch Pad as unit control of my CDI. The CDI properly, I build a circuit that uses discrete components using the boosterpack concept (board to connect a Stellaris and realize a specific function, as a apendice of my main unit).

First video with the system working properly

You can watch my videos in:

Part 1

https://www.youtube.com/watch?v=ut-lboZrBrc

Part 2

https://www.youtube.com/watch?v=mDhRHL8ZJA0

After many tries, many software and hardware versions, finally the system is working as I wish!

I found many difficulties with this project because was very hard identify correctly the root cause of many faults. For a long time I did not understood why sometimes the system read a wrong engine speed value, the external interrupt looks like did not worked well...

But after many analisys and conjectures, I made sure that software worked properly and was possible identify a noise caused for EMI and RFI (during the spark ignition), that I could not eliminate, but I could filter for software.  

During the video, you can identify some spikes in engine speed signal and advance signal, I had no time to research the cause, but in fact, occurs between bluetooth comunication or in software treatment of mobile phone, because these spike can not found in my acquisition through the serial terminal (file *.txt).

Requirements of my profect

Requirements:

Tunning of the advance curve, with engine speed,  load and engine temperature compensation

Calibration on-the-fly (instantaneous), keeping it in memory

Use your own mobile phone as a calibration and monitoring tool, to analyse the engine functionality (engine speed, advance applied and etc), failure diagnosis, data recorder…

AC CDI (Use the energy generated by engine to do the spark ignition)

Speed Engine Limiter
Low cost
Easy to install and configure

Software description:

The software concept is create a general plataform (RTOS), basicly a temporal function scheduller with independent comunication (using buffers for inputs and outputs), and a dedicated routine to handle the priority ativities (specially ignition timing and comunication). Due

your modularised concept, it is possible to implement new features on demand, the system are drive to interrupt.

I´m not use FreeRTOS or other operational system, in my case, I developed my own OS (elementary) for this application, very simple but powerfull and easy to maintain.

In my concept, I choosed to calculate in runtime the scenario to applie the spark ignition (I use the n-1 data to predict n), different of the most Microcontrolled CDI systems, that use table values to minimize the microcontroller proccessing, the ARM Cortex M4 it is very powerfull for that...

There an specific order to treat all the information data and event management, and priorize each one, that’s the secret to implement succesfully this kind of system, I have a little experience for this.

Hardware

This is my Achilles' heel, I created a simple prototype electronic board and I had many problems  with EMI and RFI, wich I can not eliminate.

For my luck, this kind of interference, it can be filtered by my software strategy, even using opto-couplers, I could not eliminate all existing noise.

The biggest challenger, it was to build all the electronic structure: change HV coil, install sensors, create a wire harness, build circuits...

Start the project

The initial project is building a AC-CDI using some parts that exists in newest Walk Machine (CDI version).
Bellow  I will show you how was old assembly and how the new part was it changed:






This picture above I found on internet, its not my engine, but is similar!

The new part:












High Voltage Coil, Its a ignition coil for Yamaha DT200

I created my own instrumentation system, Its very complex install sensors in this engine because it is very small, totally compact and optimazed...



Two hall sensor (I did not have two equal, I used one DN6851 as 20BTDC and one SS41 as 60BTDC, for hold in position a used cotton and super glue.

JD37 - The powerfull 37cc

My biggest challenge to start this project, was gathering of information about this engine and its peculiarities…

There is not a lot information on the internet about him, it was produced to Brazilian factory called Hatsuta Industrial S.A and his model is JD37.

It has a 37cc displacement and 1hp at 7500rpm, it’s a elementary two stroke engine (similar a used in a grass cutting machine) and its used in a vehicle called Walk Machine (a success vehicle in the 1980s was created to transport and to amuse children and adults, it is a small and funny vehicle similar a small motorcycle).

The JD37 has a original ignition system using a contact breaker (first version of this engine, but the newest version use a Capacitor Discharger Ignition System, it does have ignition timing compensation (engine speed only), I have a conjecture that this ignition timing curve is not opymized for this engine, because in Brazil this CDI is applied in other engines that have totally diferent characteristcs, biggest displacement, other geometria, certainly his never works optimized…

The main characteristic I desired improve with the advent of my new project was a possibility to map the ignition timing angle, because in its the best way to get better combustion efficiency and optimize for all engine speed, engine temperature, load that works (facility to crank, more stable in Idle and fast response when desired), other important consequence is increase the rpm, this way increase the top speed.

PS: My engine has a exhaustion system and air filter different the first figure, it is like the picture above (old version)!

Blog´s objective

My objective to publicate this personal research is discuss about Ignition System design, building and calibration to improve engine performance. I would like to encourage students and electronic enthusiasts to try developed this kind of project, it is possible to develop with few resources, low cost and there are many ways to do this... This theme is very complex and there are lot of things to be considered to succeed in applying, adequate circuits and a ignition management software.
I will updating the blog as the project evolves.
If you have any doubt, curiosity or suggestion please send me a message (fabio_jerena@yahoo.com.br) or leave a message here in my blog, this is a channel for discussion about this theme, feel free to leave your opnion or sugestion!