RE: New CDI - opensource project JMJ and Bigboat
 

Hi Brett,

that board is a Ardunio development board. the micro controller on board is a AVR by Atmel. There microchips competition. The way that board works is there is a bootloader programmed into the chip. Then with the avr compiler you write code and then do what they call boatload the hex into the chip. Pics have the same capability. With the bootloader you don't need a programmer,just a pc with a serial port.

RE: New CDI - opensource project JMJ and Bigboat
 

So Rob,

Any thoughts on my questions?

RE: New CDI - opensource project JMJ and Bigboat
 

http://www.picbasic.com/
http://www.picbasic.org/
http://www.picbasic.nl/indexes_uk.htm

RE: New CDI - opensource project JMJ and Bigboat
 

Hi Rob,

I am aware of those products.

RE: New CDI - opensource project JMJ and Bigboat
 

Rob,

Are you determined to go with the 12F pic or what is the big plan?

RE: New CDI - opensource project JMJ and Bigboat
 

Everthing is possible, I'm waiting wat the programmer(s) will do.
If it's possible to program a 12F for the CDI/TCI why will we take a 16F ?
I'm not the expert for programming.

RE: New CDI - opensource project JMJ and Bigboat
 

OK thanks.Keep us posted.

RE: New CDI - opensource project JMJ and Bigboat
 

I programmed a alarm with PicBasic.(it's Dutch, but pics can say more then words)
http://www.kreidler.gompy.net/Alarm/index.htm

RE: New CDI - opensource project JMJ and Bigboat
 

Thats cool. How is everyone doing?;)

RE: New CDI - opensource project JMJ and Bigboat
 

I feel like an orphan.. no software for my old timer board...:(

RE: New CDI - opensource project JMJ and Bigboat
 

I've ask if they will use the old timerboard for the new software so people can upgrade there board.
The new board have less problems with the ocsilator.

RE: New CDI - opensource project JMJ and Bigboat
 

Rob, is the 12f chip compatible pin for pin with the 16f chip for the existing timer board? or do we have to build a new timer board to accept the 12f chip?
I have 12 of the newer timer boards sitting here waiting for chips..Should I order new 12f chips for them?

John

RE: New CDI - opensource project JMJ and Bigboat
 

<span id="result_box" class="short_text"><span style="background-color: rgb(255, 255, 255);" title="Eln&eacute;z&eacute;st"> </span></span><span class="short_text" id="result_box"><span title="tipus" style="background-color: rgb(255, 255, 255);">Type:UC3845 (error circuit). Regards nyemi.
</span></span>

RE: New CDI - opensource project JMJ and Bigboat
 

John

The 16F series is an 18 pin DIP, the 12F series is an 8 pin DIP. Not only that, but the architecture is totally different.

AlZ

RE: New CDI - opensource project JMJ and Bigboat
 

[:-]

John,

You should have some.

RE: New CDI - opensource project JMJ and Bigboat
 

So I still have to redesign the timer boards..wow..I thought we had kind of a final design with the newest ones I built and were just waiting for a software update..
Thinking about all this, I guess I'll stick with CH Synchro spark..easier to hookup. That way I can use any of my new CDI power boards with them only changing one resistor location... I can't keep making new boards everytime something changes. I must have 12 boards sitting here unuseable..
There is one consolation in all this, I bought stocks in Radio Shack solder.. ;)

John

RE: New CDI - opensource project JMJ and Bigboat
 

John,

Don't throw away your boards just yet. Once the software is released its easy to adapt the code to a 18 pin pic. That way you will still be able to use your boards. Once I build my ignition simulator where I can see the curve change I will start to play with the software too.I want to see what Rob comes up with.

RE: New CDI - opensource project JMJ and Bigboat
 

I'm afraid we will have to etch new boards. The pin out configuration is totally different. We can't change Vdd and Vss with software.

This is truly disappointing since I was about to etch a board and build one of these. Now I'm not sure if the existing software will even work.

Spring is just around the corner and I want to fly airplanes, not tinker in the shop. It looks like my Edge540 is going to get the Xcel ignition.

AlZ

RE: New CDI - opensource project JMJ and Bigboat
 

Hello everyone,

Allow me to introduce myself. I am the programmer Bigboat was referring to. While I don't have a particular interest in RC models, I do in (old) motorcycles, and have build replacement CDI units for old bikes before. I am an embedded systems engineer, with a fair amount of experience in microcontroller programming and hardware design.

I usually use AVR microcontrollers for hobby projects, but since I write everything in C, the code is quite portable to other similar microcontrollers, like PICs.

So far, I haven't written a lot of code for this project yet, but I have written some design notes.

I haven't really have had any time to read the whole topic, but I intent to read it soon. When the requirements are clear to me, I'll post a rough design.


I do have a couple of questions for you:

Do you prefer an inductive or capacitive ignition system?Why?

What kind of power supply do you have available? DC, AC, if AC, low or high voltage? How important is energy efficiency?

What type of crankshaft sensors do you use? Just hall sensors, or also other sensors, like pickup coils, possibly with a missing tooth sprocket?

Is it possible to position the sensor so that one of the edges occures at the correct position for ignition at starting speed? If not, it will probably be necessary to measure the speed before igniting for the first time, to prevent igniting at the wrong time. So, are you free to position the sensor or the notch or magnet it detects, or not?

Do you only need support for 1 cilinder, or also for multiple cilinders?

Do you want a rev limiting option? If yes, do you prefer spark suppression or retardation?

It is necessary to support older board designs? If yes, which design(s)? The designs I've seen so far aren't quite ideal, mostly because of the way the inputs and outputs are connected to the microcontroller. I'd prefer to use available input capture and output compare I/Ofor timing, or external interrupts for the inputs, but the designs I've seen don't take this into account.


The initial design is intented to support all of the options, but it would be helpful to known what Ishould concentrate on first.


@azalner:it may be possible to use the same board, either with a small patch for the power lines, or by abusing the protection diodes in the controller, although this is a huge hack. Basically, it is possible to supply the power to a microcontroller trought the I/O pins, if the current is very small. Otherwise, you could lift the power supply pins from the socket (if you use a socket), or break the tracks on the PCBand patch it there.

Iassume an SMD version (in the future)would be interesting for space and weight reasons?

RE: New CDI - opensource project JMJ and Bigboat
 

Hi SparkyGSX,

Glad to meet you and welcome to the forum. I can't speak for all here but I think the majority here are using this on a single cylinder engine. If its feasible I think sticking to the old 18 pin pic design would please most here. I my self use a hall sensor for crank input. I don't think it matters to the end user how you capture the input as long as the output is a low going pulse. a rev limiter is not necessary.I think the big thing here is to be able to change the spark curve as easy as possible and have rpm down to a low as possible. One thing is some here set up the engine with a initial timing of 30 degrees. At that much advance the engine will kick.So a retard of 23 degrees is needed for startup to eliminate the kick. I think any other options are up to Rob and the rest here.Thanks for introducing your self.


You asked about the voltage input. I thin most here use a 4.8 volt dc battery. If it is used for airplane use.

RE: New CDI - opensource project JMJ and Bigboat
 

In response to most of the things that take place with these systems, all types of uses are apparent. Some require RPM limitations, some use crankshaft position sensors like the hall effect sensors...while others are using these systems for existing flywheel ignition triggers. There will have to be alot of options built into the software or different versions for each application.

If the code is easily ported to a different chip for support, that would be a great thing. Mostly, the original design was intended for R/C model use. Software limitations in the chip were our stumbling block. If this can be dealt with, everything else should fall into place..
Just my views of course as an R/C pilot..

John

RE: New CDI - opensource project JMJ and Bigboat
 

As I allready say, the programmer have the last word(s).
The new schematic is better I think, no flybacktranformer any more.
There is one problem....it's a hole new designe with new components.
For now I think we have to use the old boards because a lot of people use this board allready.
With new software we can tackel the problems with the timerboard, we can make self the flyback better and better.

I start with picbasic (again) and hope to make the software by myself for the new designe (hope get some help).
For now I use a normal NE555 for the transformer to see wat Voltage I get to load/unload the C.
Positive is the transformer can't saturate, so the transistor(s) aren't hot or burnout anymore with this schematic.

Ton welcom and thx to joy the topic.

RE: New CDI - opensource project JMJ and Bigboat
 

Rob,

I played around using a pic to drive the transformer for the high voltage. I think you are better off sticking with the feedback circuit. The problem I into is I wasn't sure how to get the duty cycle right as not to over load the transistor. measured the duty cycle with the feedback circuit and its about 25%. Plus I think the parts are cheaper with the feedback circuit. a resistor and cap vrsus a pic.If you want I am more than willing to work with you on this. I use PDS so your code will be similar to mine.

RE: New CDI - opensource project JMJ and Bigboat
 

Hi Sparky GSX, Welcome to the Forum

Speaking from the standpoint of an RC flyer, I think CDI is the preferable system for two reasons. One is that they can be configured in smaller packages, an important consideration in model airplanes. The other reason is that we use 2-cycle engines that burn a gas/oil mixture which can cause fouling of the spark plug gap. The higher initial discharge of a CDI system may be able to “burn” off these deposits better than a comparable inductive system. This last is my opinion and subject to debate.

Power supplies for RC ignition systems are 4/5 cell NiCd or NiMH. Lately some of the fellows have been using 7.2 volt LiPo’s with a 5 volt regulator. Most commercial CDI systems are very sensitive to overvoltage. e.g. a 5 cell NiCd freshly charged can deliver 6.8 volts.

I’m not sure about your question regarding sensor positioning. We have some flexibility in where the sensor is positioned, but there it stays in that position all the time.
By far the overwhelming majority of our engines are single cylinder, so in my opinion that is where the initial focus should be. Having said that, the fellows flying 35% and up use 100cc and larger engines. These are typically two cylinder.

We do not require rev limiting. Normal speed range is: 300 RPM for starting, 1600 RPM idle, 9000 RPM max

I just purchased all the components to build a CDI using Rob’s timer board and John’s power board. (John was kind enough to provide a transformer). My concern is if we have the correct software for the timer board. If not when will it be ready. Rob’s new circuit looks interesting and will probably be an improvement, but time is running short and I will have to fit my plane with a commercially available CDI ignition. These are not cheap, thus my and others interest in this CDI design.

If we were building commercial units, SMD would be the way to go. All of the commercial units I have looked at are encapsulated in epoxy so it is hard to tell what they are doing. I think DIP is the way to go for the processor because most of the guys I fly with don’t do programming and don’t have the gear to burn a processor. With DIP we can prevail on one of our gurus to burn the chips and away we go.

Again, welcome to the forum. Good questions! Some photos of a “homemade” CDI on a RC plane are attached.

AlZ

RE: New CDI - opensource project JMJ and Bigboat
 

You need a *death-time* when you change the direction of the *wave*

ll ll high
=l l=l l=l l= death-time
ll low

The death-time can be short, ~5% of complete wave, but must be there.
If you don't do this, the *flashback* from wind 1 will go into wind 2 right on the moment you open transistor 2.
The transformer will be flybacktransformer at this time and put a lot of Voltage back into transistor 2.
The death-time have to kill this so you don't get overload transistors.