RE: Scratch Built Ignition???
 

Hey, there is nothing wrong with the fixed ignition if the performance suits your needs. A magneto system has a fixed spark timing and but I found it lacking in achieving low RPM at idle and it was lacking at the high end too. I understand that the factory magneto is "tuned" for weed cutting gardeners, so it has its limitations for aircraft use (not to mention the weight issue of the magneto).

With that said, my experience is that a computer controlled CDI has the advantage of getting reliable idle from 1,200 to 1,400 RPM @ -3 deg ATDC and full throttle of over 8,300 RPM @ 30 deg BTDC. Do I need this improved RPM range? I don't know yet, I'm putting my Ryobi into a plane now and I have yet to fly it. It was a great learning experience for me to develop the software for the PIC controller.

RE: Scratch Built Ignition???
 

Like I said, it's the challenge that makes it worthwhile...
Idle speed is more a function of prop weight than timing...A CD ignition will fire at 1 rpm, so if there's enough inertia the engine will idle as slowly as you want it to...Mine will idle at 1400 all day long with a heavy prop, timed at 28....And you're doing better than I am if you can tell any difference between 28 and 30 for top rpm.....
Hey, if I knew anything about electronics I would be doing it too...
I buy the boards and components, and if I solder all the little pieces in the right place it works..
Very well, I might add :D

RE: Scratch Built Ignition???
 

OK, then think of value added. I have added a $3.00 PIC chip with almost no other components (no Xtal, no extra switches, only one diode) programmed it with some simple software and tied it to a CDI. This, in my opinion, is a cost effective solution to make a gas engine more versatile. If you are happy with fixed ignition timing and it's doing your job, that's fine too.

RE: Scratch Built Ignition???
 

Hi,

I am looking information about the chainsaw ignitions that have automatic advance. The manufacturers websites give little in the way of details, ie;

How many degrees of advance are provided?

At what RPM the total advance is attained?

Is the curve linear?

How heavy is the system, less flywheel? I'm comparing it to a CDI with a battery capable of storing enough energy to operate the system for up to 4 hours.

Is the whole thing built into one unit or are there seperate parts?

I would very much appreciate someone directing me to where I can find out the answers to these questions. My local chainsaw repair shops haven't encountered a reason to work on or replace these units and so have no experience with them. From what I can tell, all the brands are covered with lifetime warrentees.

Thanks very much,
Dan Clarke

RE: Scratch Built Ignition???
 

testing

RE: Scratch Built Ignition???
 

Hi! I have found in here [link]http://www.sportdevices.com/ignition/ignition.htm[/link] this.
http://www.sportdevices.com/ignition/ignition.gif http://www.sportdevices.com/ignition/ignition_TCI.gif
Will this works that you think about?
It will be work on Hall sensor?

RE: Scratch Built Ignition???
 

The first schematic has a high voltage alternator, which produces 200-300 volts. This makes it a bit easier to generate enough high voltage from the spark coil. The second circuit acts on pulsing 12 volts through the spark coil. I'm not sure that it would work, but maybe it does with the right coil. The way the input to the PIC is shown will work with a PIC.

RE: Scratch Built Ignition???
 

Hi Dan,
I just bought a ECHO CS-4400 off of ebay. It has slope advance ignition. I thought that it would include a bunch of additional electronics, when I took the saw apart I found a flywheel and coil simular to other saws. The big difference is that it has three magnets instead of two. The flywheel is 3 15/16" and the coil is mounted on the saw frame. The engine is the one used for the BME 44cc power house, so I am looking forward to testing it with a prop. I ran it in the saw just to confirm the it was a good motor. It had easy starting even with a fouled plug and good transition. It will be interesting to see any difference with the slope advance system. The G-38 and some Redmax saws use three magnets in thr flywheel. I am going to make a bracket to mount the coil. I would like to install a CDI ignition later.

Regards, Dave

RE: Scratch Built Ignition???
 

Hi there. I want to build my own electronic ignition system with variable timing advance for a homelite 45cc or poulan 46cc engine. I'm currently researching to find all the components needed.
I think an easy way to to vary the timing is with a pic chip. I found some interresting magnets at http://www.leevalley.com/hardware/pa...363,42348&ap=1

I'm looking for timing advance values or curves for these engines. I would also like some schematics for ignition systems similar to CH ignition or ZDZ ignitions. Thanks in advance

RE: Scratch Built Ignition???
 

Thanks for the info Dave,

If you are able to run the unit with an automotive timing light, I would appreciate knowing about the advance slope and the total range of the electronic advance in degrees.

Thanks again,
Dan

RE: Scratch Built Ignition???
 

Sigh...
A while ago i was hot about electronic ignition.Well,now with gas cost $2.20(and keep on going up) and methanol cost $2.99(as 6 months ago) i think i will convert everything i got to glow.
For the extra 70 cents a gallon i'll be flying methanol.Yeah i know engine uses about twice as much methanol but saving of weight and ignition cost is obviouse.
Thats my point about scratch built ignition.
Mitty

RE: Scratch Built Ignition???
 

Where do you get methanol for that price?
what about nitro ?

RE: Scratch Built Ignition???
 

I buy methanol in local race shop.Mix 5 gal of methanol($15) with 1 liter of KL100($8) get almost 5.5 gal of 5% oil and 0% nitro.
It's about $4.60 a gal. As few experts out her informed me 5% for the ball bearing engine is safe and healthy so look for yourself.
If you really cheap (like i am :) ) mix 32:1 or 40:1 just like you mix your weedeater fuel.In that case it's even cheaper to fly.
I got cought up with few very important things at work that keep me from flying nowdays but soon i'll be back on trac.Then all my weedeaters will turn in to a methanol engines.
Oh yeah, on one of the weedeaters i used a coupling from hardware store to replace the prop hub.After all thats what it is all about -cheap ,right?:)

RE: Scratch Built Ignition???
 

Yeah I was thinking about going to a gasser because it just killed me everytime I had to spend $15+ per gallon.

With your info I found a place were they sell me 99.9% methanol (these guys even sell to pharmaceutical companies).
With oil, it will cost me about 1/4 of the price.....and at that price I'm getting a nice super tiger.90.
They are really cheap at ecmc.com 150 cnd
Thanks

RE: Scratch Built Ignition???
 

I’m trying to build the (Floyd Carter) capacitive discharge circuit, found in the 80’s RC Modeler magazine .Im wondering if I can use an e-core instead of the toroid core, for faster winding time.
Does any one know if this can be done? I'm trying to save money. Just got married!!!! BROKE.. I have salvaged some e-cores from a TV and VCR’s. No luck on finding any toroids yet. Any help would be greatly appreciated.

RE: Scratch Built Ignition???
 

Yes e-core will work even tho less efficient .But in cdi it won't matter.The size of ecore will be bigger i think.
Ask Marlowe,he outta know for sure.

Mitty

RE: Scratch Built Ignition???
 

alex_scratch_built
Just remember you will use methanol at twice the rate that you will use gas, so even if you can get the same quantity for the same price a 10min flight will still be twice the price but i suppose if you use a smaller engine it wont be so bad.

RE: Scratch Built Ignition???
 

I built one a while back and wound the transformer on a piece of an old ferrite rod that was originally an antenna in a small transistor radio. The e-core should work fine.
W5RA

RE: Scratch Built Ignition???
 

anyone have a scanned copy or pdf of this article? My bride "cleaned" the garage (it's typical of European-bred women) and out went my 30+ year collections of RC magazines.... :(

[:-]

RE: Scratch Built Ignition???
 

I'd like to get a copy too if possible...Please.Or i can scan paper and convrt in PDF if needed.
Mitty

RE: Scratch Built Ignition???
 

I have the article somewhere. If I can find it I'll scan and send if I have the e-mail address.

RE: Scratch Built Ignition???
 

If you go back and look at the first page of this thread, the 5th post down, ANEAT gave the info to look at the article in the RCM archives. I don't know if you can look at it if you are not a subscriber. I do subscribe to RCM. I clicked on the address that he showed, and it came up without asking for any member ID. I do also have a copy of the original magazine, and could possibly scan it, if I can find it.
W5RA

RE: Scratch Built Ignition???
 

You can also find a schematic which is very similar to the one in RCM by looking at the 10th posting of the 9th page of this thread.
W5RA

RE: Scratch Built Ignition???
 

thanks W5RA... got 'em....

I guess you're pretty much up on this stuff :D

[:-]

RE: Scratch Built Ignition???
 

Thanks for the help. How many wraps and and size wire should I use with the E-core, and does it use a socondary,primary,and feedback like the toroid?What size e-core should be used?The plan I have for winding the toroid does not show the size of the core to be used.The secondary 450 turns #34 (29feet)primary#24 15 turns feedback#30 6 turns.The plan gives a old part # for core to a company that is no longer in buisness (fuji-max usa, 2747 n. Giddings, visalia, Ca. 93291.By the way I think Ive found a core in a old computer how do I know if it is the right kind.and does size matter?