help! simple DC-CDI

[maxpain]

hi, i'm a new member here, hope someone could help me. any idea on DIY DC- CDI that is very reliable. I made some of the ignition circuits posted here, but i can not twist open my throttle of my bike. is there any other circuit diagrams i could make. pls.


thanks....

BTW..... my bike has only one cylinder (4stroke)

 

[jpanhalt]

I made some of the ignition circuits posted here, but i can not twist open my throttle of my bike.

Which circuits did you build? Is the problem with the ignition not firing or the throttle? Did you try to time it to the 4-stroke or fire on every cycle (as generally recommended for simplicity)?

John

 

[maxpain]

Which circuits did you build? Is the problem with the ignition not firing or the throttle? Did you try to time it to the 4-stroke or fire on every cycle (as generally recommended for simplicity)?

John

the one with single transistor feed on a transformer. I used to
build using 74hc14, it worked but the chip is hard to find here

 

[jpanhalt]

the one with single transistor feed on a transformer. I used to
build using 74hc14, it worked but the chip is hard to find here

Please post the sircuit you used. It is not clear where the 74HC14 comes into play. If it was used as the oscillator, instead of a power NPN transistor, I doubt you will get the current you need for an engine. That is, you may get enough to charge the capacitor slowly, but not enough to charge it at 60 HZ (3600 rpm) and definitely not enough at the rpm some motorcycle engines run.

For comparison, model airplane CDI use one or two (in parallel) power transistors with ratings of 3 A to 6 A each.

John

 

[maxpain]

transistor oscillation:
**broken link removed**

and the one that worked but only one is build:
**broken link removed**

i tried to buy 4 pieces of new chip from other province but it never worked again, all other parts where ok.

i am currently using an AC-CDI but i want to use a DC since i always carry a battery for my lights as well as taking the advantages of DC-CDI benefits.

 

[jpanhalt]

transistor oscillation:
**broken link removed**

and the one that worked but only one is build:
**broken link removed**

I am really unclear as to what your specific question is, but let me take a stab at it based on your most recent post.

The first link shows a schematic that uses the 74HC14. Note that two oscillators are made from it. One oscillator(the one illustrated on top) drives a 2N3904 that drives the SCR for the spark. The second oscillator drives the IRF510 mosfet that creates the AC needed for the transformer.
The circuit as shown does not include any way to synchronize its sparks to the engine rotation. I would not recommend it for that reason and because: 1) It is more complicated than necessary; and 2) Driving the oscillator with mosfets has not been as successful as simpler designs based on the Hartley oscillator. Thus, I do not think you need the 74HC14, for which you had a problem finding a source.

The second link is to an earlier DIY CDI system. I suggest that you follow the more recent version. This design is similar to most recent designs I have seen, except the authors used a PNP transistor instead of an NPN. They also use a full-bridge rectifier; whereas, most circuits used for model airplanes use a half-wave rectifier (single diode) or a voltage doubler (two diodes).

If foregoing does not address your question, please re-state it and give more detail.

John

 

[maxpain]

don't worry, it's now clear to me. i could never learn without this furom, i will try building other circuits. do you have any circuits that would fit to a 4 stroke single cylinder motorcycle?

 

[Master scientist]

hey MAXPAIN

hanggang dito pala abot ka ha!!!

its me master circuits

whats up with your project,

try transmic.net it might help you along the way, just make sure to program the microcontrollers

cheers

 

[maxpain]

hey MAXPAIN

hanggang dito pala abot ka ha!!!

its me master circuits

whats up with your project,

try transmic.net it might help you along the way, just make sure to program the microcontrollers

cheers

i've been there before since i was single. what i am worried about is that building a non complicated parts DC-CDI. which will be a very great upgrade for my 1980 bike as well as the other people here who wants to live free against stator re-rewinding. help me....

(syensya ka na, nilubos ko na ang ingles para maintindihan nila.....)

 

[jpanhalt]

do you have any circuits that would fit to a 4 stroke single cylinder motorcycle?

Almost any of the circuits posted on this forum and on the modelers' forum that you have used should work.

Remember, with a single cylinder 4-stroke engine, you DO NOT need to time the spark to one-half of the crank speed. It doesn't hurt if you do, but it is much simpler to fire on each rotation. The spark during the exhaust stroke is not a problem usually. John

 

[maxpain]

Almost any of the circuits posted on this forum and on the modelers' forum that you have used should work.

Remember, with a single cylinder 4-stroke engine, you DO NOT need to time the spark to one-half of the crank speed. It doesn't hurt if you do, but it is much simpler to fire on each rotation. The spark during the exhaust stroke is not a problem usually. John

yeh! they are all worked. But the question is, i think (i think) there is something more to do with it to be applicable with my purpose......

with that circuit, it runs at idle engine but goes dead at rpm higher than idle.

 

[jpanhalt]

with that circuit, it runs at idle engine but goes dead at rpm higher than idle.

How do you know the problem is in the ignition? An increase of a couple of hundred RPM should make absolutely no difference to the ignition. Are you sure the problem is not in the carburetor?

In order to have any idea on where the problem may be, you really have to give more information about what you actually built and how you built it. How are you timing it to the engine? What ignition coil (the one that connects directly to the spark plug) are you using? How did you make the transformer (the one that increases voltage from battery voltage to about 250 to 300 V)? What guage wire did you use? For example, most transformers from fluorescent lamps (CCFL) will not work in ignition systems because of low current capacity, but they may give a spark during testing. John

 

[maxpain]

i followed the transformer building instruction and built it. as for the carburetor, its fine coz engine rpm is normal when i use AC-CDI. timing, maybe centrifugal advancer is usable.

i suspected that the charging circuit couldn't come up before it sparks (i think)
please more info.....

 

[jpanhalt]

i followed the transformer building instruction and built it

One more time... That does not describe what you actually did. Which instructions did you follow? What guage wire? What number of turns? Etc. As I said in my earlier post, one possibility is that the transformer you are using cannot supply the current needed to charge the capacitor during the time available. In order to evaluate that possibility, you must provide more detail of exactly what you have constructed.

What is AC-CDI? The capacitor in CDI needs DC to charge.

How are you timing the spark to the engine? What advance are you using for starting? Do you run at the same advance? Small engines like you have can be run without changing the advance, but you must have the correct setting to do that. Otherwise, they may start, but not accelerate. John

 

[maxpain]

here it is
**broken link removed**

what i mean about the AC-CDI is actually magneto fed CDI. the type that runs directly from alternator, no battery needed.

do you have any other transformer that can be easily build?