Roll Your Own CDI

[Ratchetbirds]

Hey,

I remember seeing that pic you posted (thanks) of the original internals. The coil looked a little mashed up but I did see that it was pretty tiny.

$10 for what you got on e-bay - just can't go wrong. The the plug wire and all.

Some background - I'm a chronic DIYer with just about everything. I've got 2 mb 2stroke kits on the go as well as a 4 stroke non kit in development and a pocket bike engine aching to be installed on something. All of my CDIs are currently functioning just fine - but I want to know that I can do it and have one ready replacement. I've got a couple of bins of salvaged electronic parts for other DIY projects so I'm looking forward to seeing what can be cobbled together.

Also, I just remembered that in one of my electronics parts bins I've got a camera flash that has some big caps and I think a transformer in it - that circuit may be almost exactly made to become a CDI - if it is I'll post it.

thanks for all your input in this thread!

I can sure understand being a chronic DIY'er <G>. If you decide to do a coil I am in hopes you will make a new thread called "roll your own ignition coil" with pictures and drawings and all that cool stuff. I would love to follow that one.

 

[impression]

got a blown resistor today in my CDI. SO i upped the Ohms value by 50% let's see how that goes

 

[rohmell]

got a blown resistor today in my CDI. SO i upped the Ohms value by 50% let's see how that goes

Which resistor blew?
Did you up the Ohms value or the Wattage of the replacement resistor?

 

[KCvale]

One note about any CDI enhancements...
Don't skimp on the re-wire.

I remove the motors wires right at the magneto and replace them with nice flexible 16 gauge outdoor speaker wire from Fry's Electronics, but any good 'power cord' wire will work better than the crappy thin kit wires.

And if you are not using the unregulated white motor wire to power something cut the darn thing off at coil, your kill switch works just as well across the blue and black wires.

I am just putting a keylock on the stock CDI's for now, but I take the black and blue from the CDI up to the throttle kill button and connect it directly to the throttles kill button connections as well.

Just getting the garbage quick connections out of the circuit by directly soldering each end of all wires alone adds a reliability factor so why not right?
Besides, it sure pretties up the look ;-}

 

[rohmell]

Another place to get replacement wire is an old computer-type power cord.

Some types will have green, white and black wires, others will have blue, brown, and greenish yellow.

If you are lucky, you will have some of both types to get the black, white and blue wires to match the factory color configuration.

 

[decoherence]

i used connectors that are used for trailers.
the wires & connectors are both made to be weather resistant.
i am using a few 2 & 3 wire pieces.

 

[impression]

Which resistor blew?
Did you up the Ohms value or the Wattage of the replacement resistor?

the 18 Ohms resistor blew.

I put a 15 and 11 Ohm resister in series

Same wattage though. Otherwise i would've put one with double the capacity but didn't have any in my kit

 

[impression]

thought it was a bad idea using resistors in series, but hey when the electronic store is so far away :/

The schematic is solid, but i had to use bare minimum parts
SO replacing them and we'll go from there

I'm off to the electronic store buy some new gear and make one Solid CDI


If no signs of wear for 2 weeks of solid riding i'll offer to make one for other people


I'm also going to pickup some wire for my magneto/stator and rewind that

 

[impression]

No more interest in this thread ?

Oh well Here's hoping this liven's it up a little bit

AN early Mockup

board getting there and test fitting inside the case

Attaching wires

Attaching the external blue and black wire connections

attaching the positive out

 

[impression]

part 2 of previous post


All together view 1

all together view 2

Enclosed view.... Looks like an airport scanner view

 

[Ratchetbirds]

No more interest in this thread ?

Oh well Here's hoping this liven's it up a little bit

Nice heatsink ! Gonna try to roll my magneto today. Waiting on some pc boards I bought before building my next CDI. Should be here soon. Got a project box big enough to put the coil inside it also. Pics coming soon.

 

[impression]

yeah i got some 33 gauge wire to wind my next stator now. although it's 1am and i should sleep :/

ah screww it i'm off to wind my stator by hand

3199 winds to go...

 

[impression]

Got a project box big enough to put the coil inside it also. Pics coming soon.

Oh Nice. I'm using a car's ignition coil... so not really practical to put inside a plastic box :/

 

[rohmell]

Nice usage of the binding posts for connecting up to the external world.

 

[Ratchetbirds]

Oh Nice. I'm using a car's ignition coil... so not really practical to put inside a plastic box :/

Yeah, but it's a Benz coil and looks really cool. If I were to use a car coil it would have to be a bosch from a Jaguar It's just how I roll <G>. This all in one box thingie is for use with a pitbike coil. And since it isn't a Jaguar coil, I will hide it in the box. Also my box is quite a bit larger than the box you are using. I still love that heatsink. Gotta run for a bit but when I get home I am going to post some pics over in the Magneto thread from my winding experience today. Hey Rohmell, if I can wind that dinky wire, anyone can <g>. I still smile when I think of you with a snotted wad of thin wire all jammed-up around your fingers, LOL.

 

[impression]

well i don't know what's up with my cdi at the moment

using the same design all i did was change to 5W instead of 0.5W resistors and i get stuttering when i ride feels like the bike is trying to stop or it's pre-firing way to early i don't know

could it be because i changed Diodes too ??

i went from the following parts

18 Ohms 0.5W resistor
82 Ohms 0.5W resistor
1n4004 400v diode x3
630v 1uF capacitor ( metallic) x2

to

18 Ohms 5.0W resistor
82 Ohms 5.0W resistor
1n4007 1000V Diode x3
No change in capacitor

Using the same design circuit and switch...

i don't know what's up all i do know is that the 82Ohm resistors get really hot in my circuit and that's why they use to blow and i upgraded to better rated components

 

[rohmell]

If the upgraded resistors are wirewound, then the inductance could be affecting it at higher speeds(frequencies).

 

[impression]

ah, thankyou I never thought of that.

looks like i'll have to find some carbon or metal film resistors that are about the 5 Watt range

 

[rohmell]

Hey Rohmell for all the work you have done and are still doing, I did some work for you today. Opened my original Grubee GT-5 CDI box and here are some pics. Someone with your savvy and test equipment should be able to trace things out and get values for most components. Can't read the components because of the epoxy but it sure looks familiar to me from following this sticky. The covering on the cap came off with the epoxy. You can see half of the cap covering stuck to the coil. On the PCB I can see the scr, a diode, and a resistor and can easily guess which way the other components go. The PC board didn't have any epoxy stick to the bottom and I have tried a few combinations of the numbers in internet searches but no luck yet. If you would like to see this stuff for yourself feel free to PM me with your mailing address and I will shoot it off to you. My equipment for electronics stops at my DVOM and my soldering irons hehehe. Anywho, hope this helps.

Do you still have this PCB? Trying to do a reconstruction of the circuitry.

 

[Ratchetbirds]

Yes I do. Let me know whatcha need.