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-   -   Scratch Built Ignition??? (https://www.rcuniverse.com/forum/engine-conversions-92/743937-scratch-built-ignition.html)

c_moore 06-05-2004 06:32 AM

RE: Scratch Built Ignition???
 
Yes. I got a lot of great info, from that site.Thanks for the onfo.

cu. in. 06-09-2004 10:18 PM

RE: Scratch Built Ignition???
 
Correct me if I'm wrong :), but it looks like the USA built ignition systems discussed here and the system from Norway all use the PIC chip for controlling spark timing.

There is another chip used for controlling spark ignition on the Czech Falkon ignition systems found on ZDZ engines. The technical data sheet that accompanies the Falkon ignition systems lists an Intel MCS 51 chip for controlling the spark timing. Here is the link:

http://www.intel.com/design/mcs51/index.htm

I'm not an EE, so I don't know the difference, but it looks like there is more than one way to skin the spark-timing cat.

Bruce

ZAGNUT 06-09-2004 11:57 PM

RE: Scratch Built Ignition???
 
what chip they use isn't that important, most microcontrollers can easily handle the simple timing operation needed on these engines. they simply count the RPM and vary the amount of delay.

the important part is the code that needs to be written to program the chip. without that it is a worthless piece of plastic with metal legs. for some people the needed code is super simple and for others (like me) it is totally incomprehensible. the most basic PIC project is making a LED blink and after failing at it too many times i simply gave up. i'm better with wrenches and machining....


dave

Marlowe 06-11-2004 04:58 PM

RE: Scratch Built Ignition???
 
Zag,

You are correct in your programming of the PIC comments. I have a PIC programmer board and a PIC C compiler/programmer.

I'm hoping to build a PIC controlled CDI ignition and I have thought a lot about how to advance/retard the ignition. On the test stand, I envision an optimization procedure that hand tunes the spark advance at various engine RPMs and logs the results. The optimal settings will be later burned into the operational PIC. One can go further and tie into the throttle servo input and log the setting. One can then construct a throttle demand function and modify the advance accordingly.

These are just thoughts for now. I just got my Ryobi 31 running with the stock magneto. The conversion went smoothly and quite fast and the engine runs and starts quite nicely. My next priority is to break it in and then put it into a large plane. The scratch built PIC controlled CDI ignition is a future project.

This has been a great thread with lots of very useful information.

Marlowe 06-11-2004 04:58 PM

RE: Scratch Built Ignition???
 
Zag,

You are correct in your programming of the PIC comments. I have a PIC programmer board and a PIC C compiler/programmer.

I'm hoping to build a PIC controlled CDI ignition and I have thought a lot about how to advance/retard the ignition. On the test stand, I envision an optimization procedure that hand tunes the spark advance at various engine RPMs and logs the results. The optimal settings will be later burned into the operational PIC. One can go further and tie into the throttle servo input and log the setting. One can then construct a throttle demand function and modify the advance accordingly.

These are just thoughts for now. I just got my Ryobi 31 running with the stock magneto. The conversion went smoothly and quite fast and the engine runs and starts quite nicely. My next priority is to break it in and then put it into a large plane. The scratch built PIC controlled CDI ignition is a future project.

This has been a great thread with lots of very useful information.

cu. in. 06-11-2004 05:35 PM

RE: Scratch Built Ignition???
 

This has been a great thread with lots of very useful information.
Ditto!

Bruce

W5RA 06-11-2004 09:05 PM

RE: Scratch Built Ignition???
 
I have been flying a Scratch built Ryan's Rebel for about 3 years now with a home converted Ryobi 31cc engine. It has always flown very well, turning about 7300 to 7500 on a Zinger 16 by 6-10 wood prop. About 4 months ago I built a Timm-6 ignition using one of Jerry Howells kits and coil. I cut the center out of an old Ryobi flywheel and ended up with about a 3/4 inch diameter piece. I drilled two holes as close together as I could and placed in each a 1/8" rare earth magnet both of which I got from Radio Shack. That provided enough Dwell time for the coil to charge between sparks. I put this system on My Ryobi on the Rebel after a number of bench runs. I have probably flown it 25 to 30 times since, and have been very pleased with it. It still turns the same RPM as before, but is now some lighter. I am using a 5 cell 1800 mah NIMH battery pack on the TIMM 6 and have not had to recharge it at the field. It holds up as good as does the 4 cell NIMH 1800mah flight pack battery.
I have also built one of the CDI units designed by Floyd E. Carter that was published in a 1980 RCM issue. I have only bench ran it on a Ryobi and it seems to work well, but I have not yet flown it. At the time I built it I could not find the specified toroid coil, so I wound the transformer on an old transistor radio antenna ferrite rod about 1 1/2 inches long and it worked fine. It may produce a little more RFI than would the toroid, but it does not appear to be a problem.
I do enjoy this hobby!

Willdo 06-11-2004 09:52 PM

RE: Scratch Built Ignition???
 
What type of coil did you use on the TIM 6 ?.
Good to see that you are having success with all your ignition systems, and that you are doing some lateral thinking with coils etc. on your CD ignitions!

W5RA 06-12-2004 06:59 AM

RE: Scratch Built Ignition???
 
I am using the Modelelectric PE coil on the Tim-6. I have several old antique model airplane ignition coils that I obtained at swap meets and have bench ran them on the Ryobi with the Tim 6 and they have operated fine, but haven't flown with them.

c_moore 07-04-2004 06:25 AM

RE: Scratch Built Ignition???
 
To anyone interested,I Have Transformers For the Cd ignition for sale.The price is 15+ shipping in the US.The Transformer is a Bobbin and E-core design.It is wound to produce around 400 volts.The dimensions are 9/16sq x 1/2. You can reply to me At [email protected]

Antique 07-04-2004 10:41 AM

RE: Scratch Built Ignition???
 
Hey TKG ! Competition ! :D

tkg 07-04-2004 05:10 PM

RE: Scratch Built Ignition???
 
[:-]

Marlowe 07-12-2004 12:14 AM

RE: Scratch Built Ignition???
 
Progress report:

I have my Ryobi 33 just about broken in now, a CDI ignition from c_moore, and a coil/spark lead from C&H. I have interfaced it to a PIC 16F84 chip, which I programmed to demonstrate that the PIC could control the spark. After I get my Ryobi back from my friend who is machining down the magneto/flywheel to give adequate prop adapter support I will be embarking on demonstrating a computer controlled spark advance. I've upgraded to a PIC 16F628 chip since the old 84 chip is being phased out. The 628 costs less, about $4.00 from Mouser Electronics, and has twice the programming capability. It also has analog input capability which could be used for future expansion such as for engine temp input.

To give him a plug, the stuff I've gotten from c_moore is great and it does the job. He has also been most helpful.

My first integrated test run should be within a week. I'll keep you all posted as to the results.

c_moore 08-25-2004 04:48 AM

RE: Scratch Built Ignition???
 
Hi everyone, I have 2 HV boards for sell 25$ plus shipping in US. contact me at [email protected]

Mitty 08-25-2004 06:16 AM

RE: Scratch Built Ignition???
 
Hello Everyone.

How's things with scratch built ignition advance?Any progress?

Marlowe 08-25-2004 10:29 AM

RE: Scratch Built Ignition???
 
OK, progress to date:

Had to machine down my Ryobi flywheel/magneto to accommodate the short shaft prop hub. I then mounted the two magnets on this short hub section. I'm using a latching Hall sensor that turns on with the passage of a North magnet and off with a South pole magnet. I have a PIC 16F628 chip reading the Hall and computing engine speed through the time the Hall is turned on. The software then goes into a table of Hall on time (really software count cycles) versus the spark delay. Higher speeds require a short delay time and a slow speed requires longer times for the proper spark advance.

My results so far are a process of trial and error. I discovered placing the CDI ignition module and PIC board in a grounded aluminum box enhanced reliability. I also isolated the +6 volt supply of the CDI from the PIC by using Zener diode as a voltage regulator. Also the distance from the magnets to the Hall is critical in maintaining the latching feature. I have to work on a better method of attaching the Hall to the Ryobi since I believe this the cause of the rough high speed running. FYI, I'm using 40 degrees between the two magnets and the last magnet turns off the Hall 32 degrees BTDC.

I'll be away from this project for about two weeks, but I'm anxious to get this completed and fly this puppy.

hblester 09-08-2004 07:05 PM

RE: Scratch Built Ignition???
 
Do not know how many times I have read this thread & the one about 33 homelite saws bought a new in the box homelite on ebay for 56 + shipping then two other fliers after listen me go on about the homeys they each bought one from Home Depot for 100 we have already got the motors out of the 2 from home depot and machined the flywheel down (Walbro better spark? and 28 walbro carb) looks almost it was made for models with the small crankcase. Now what I was really wanting to ask is about the home made ignition could you use a gm hei module or maybe a Ford tfi module as they us a hall effect switch ect. Know that I am not the first to thank of this just wondering.

c_moore 09-08-2004 07:56 PM

RE: Scratch Built Ignition???
 
I Don't believe the they will work.They don't have the circuit the boost the voltage.

Marlowe 01-19-2005 04:25 PM

RE: Scratch Built Ignition???
 
I don't know if this forum is still active but in the past Mitty asked if there was any progress. Anyway here it is:

After many months of neglect finally I returned and finished this project. The hardware is a 31cc short shaft, Ryobi taken out of a Harbor Freight weed eater and fitted with a Wacker Engines muffler, mount and prop adapter. A friend machined the flywheel/magneto down to seat the prop hub (that was a bear of a job). The spark coil and resistor lead is from C&H Electronics and the high voltage CDI module is from Charlie Moore. The automatic advance is via a PIC chip, a 16F628 that is programmable. The PIC reads a Hall switch which senses the passing of a rare earth magnet glued to the prop hub. The PIC then counts internal clock pulses to measure the period between each passing of the magnet. At each passing of the magnet, the PIC starts another countdown to send out a delayed, measured pulse to the CDI module, which in turn sends a pulse to the coil, and finally a spark occurs. The software has a programmed algorithm that computes how long a spark delay is needed for the revolution time period. In effect it relates a spark delay angle to RPM, which is the basis of the computation.

Ok, with that as a background here are the results. On the factory magneto the lowest reliable idle was about 2,800 RPM and full throttle about 6,400 RPM turning a 16x8 inch Master Airscrew prop. (My driveway sits at 5,500 ft. altitude and the 15% thinner air makes for lower power.) With the operational PIC/CDI combination the performance improved dramatically, with easy idling at 1,500 RPM and full throttle of 7,800 RPM. Another benefit is easy hand starting after the engine has warmed up, always on the first flip.

I had plans to do some engine hop-ups such as installing a large throat carb, opening up the read valve stop, increasing the compression ratio, etc but this puppy runs so well I have put all that on a back burner. On to mating this to an airframe and flying this puppy!!

Mitty 01-19-2005 08:41 PM

RE: Scratch Built Ignition???
 
Quite interesting,marlowe!
I was trying (and still do) to talk my friend in to writing a code for 16f processor to compute delayed signals however there was a problem with acuracy.The higher rpm the less acurate software calculates the delay however he ensured me that it still will work. Eventually i got the schematic and code written but i got too much on my hands now ,simply have no time to solder the board and burn the hex. Then i'll have to test.
Anyhow,keep us posted.Thats quite interesting topic!!At least to me!.
Take care and thanks.

Mitty

rcp2005 01-19-2005 08:46 PM

RE: Scratch Built Ignition???
 
I'm planning on installing an OS 120 with pump in a Balsa USA 1/4 scale Cub. Any comments or suggestions? Is this a good choice of engine? Thanks for any replys........

captinjohn 01-25-2005 11:24 PM

RE: Scratch Built Ignition???
 
I guess the question was about the OS 1.20 on a Cub. It should work good. If you have both already ...go for it!!! You may get more replys in another forum. For now I guess ....its back to Scratch built Ignitions. A very interesting subject! Best Regards Capt,n

Marlowe 03-08-2005 12:53 AM

RE: Scratch Built Ignition???
 
Mitty,

On your concern of accuracy, this is my take … If you use a PIC you are working with an eight bit device and the computations are restricted to 8 bit accuracy. Sure you can expand things to 16 bits via the software, my C compiler allows this. But the higher computational overhead associated with the more complex 16-bit math makes for cycle problems. I have just completed some test runs today that have gone from 1,400 RPM at idle to 8,200 at WOT. The 8-bit computations work just fine over that RPM range. My only worry is that very low RPM (under 1200) the 8-bit counter will overflow and the PIC then thinks that the RPM has suddenly jumped to very high RPM and will move the spark advance from -5 to 32 degrees BTDC. That would cause one heck of a backfire and probably throw the prop!! My code has a computational trick to mitigate this from happening, but I still worry this might happen. My testing so far has not produced this phenomenon.

Marlowe

Mitty 03-08-2005 09:51 AM

RE: Scratch Built Ignition???
 
Marlowe,howdy!
Good to hear about yout progress.
I have been having a family issues i was far from rc for a while.But everything seems to get on it's way so i am hoping in a next month or so i'll give a try to the software i have .I'll post the results.
Have a wonderful day and good luck .
Keep in touch.

Antique 03-08-2005 10:13 AM

RE: Scratch Built Ignition???
 
What's wrong with an old simple cheap fixed ignition that has been proven for 20 years ? TKG and I both offered circuits for about $35..Very few takers...
Why re invent yhe wheel ? Spark retard is only necessary for starting..My G26 conversions are fixed at 28 BTDC...NO complaints yet...No one has yet come up with a better system..:D


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