Performance CDI layout and schematic diagrams

[Huffydavidson]

KC you'll dig this chit , today I took my Genuine Jaguar apart and you'll never believe what I found inside ????
Right there before my very own eyes , Jaguars bread cutting board .LMAO Straight up a proto board . Ahu could not believe it . As far as jumper headers vibing off that's highly unlikely even with the cheap ones they installed on the Jaguar its upside down when it runs it hasn't happened in two years yet . Okay we're back to the same argument no switches and now no Turnpots. Vibration is not our freind. Unless you roll a DAX,CRMACHINE,JAKE, ARROW, or a RSE Engine you got margarita shaker . Sorry that just the way it is.

 

[KCvale]

"should" the trimpot's wiper loose contact, the resistance value would go to 19 + ohms

No it wouldn't, I always tie the wiper to one end of the pot resistor so if the wiper fails it's still a 10 ohm resistor not an open ;-}

I am ordering parts and supplies this morning as I will need parts here to test the circuit board parts placement before etching any boards.
This is actually pretty easy, I can just print the circuit on paper and plug the parts in and if if a pad is not where it needs to be I just change the design.

 

[ivan H]

Hi, its unlikely that a jumper ever come off or the trimpots wiper loose contact, I was just thinking of covering as many bases as possible. Really, so long as u stay within the parameters that KC made sure of b4, either way of doing it is fine & people could easily juggle resistance values to do it their own preffered way if they wanted, without a problem. Same with Prototype board. I've read of people having trouble with early Jag CDI's suffering broken connections but imagine improper or inadequate soldering being the cause. I havent read of this problem for a fair while now. So long as its well soldered, prototype board is fine. I have guitar effects pedal made using prototype boars that are years old & still fine, & being stompboxes have been well & truely mistreated. Its a matter of personal choice whether to use resistor's & jumpers or resistor's & trimpot,,,, prototype or vero board or a dedicated circuit. ****, u could use tag strip if u wanted, it'll all work. I am looking forward to KCVale's circuit board design, & yes KC,,, it's a whole different skill where parts placement can need a whole lotta thought. Something like this CDI doesnt present too many obstacles but when u get into like, low level high gain audio or digital ir logic circuits where unintended coupling (capacitive, inductive etc) between not only components, but also the copper foil traces can wreak havoc, meaning a vast amount of knowledge in the field, as well as thought is needed to properly design circuit boards. Its deffinitely not a skill I posess. We're lucky to have KCVale offer to do this for us. Thanks again KC. Cheers

 

[KCvale]

Okay we're back to the same argument no switches and now no Turnpots. Vibration is not our freind.

I guess we'll see as I dropped a little over $300 today for enough parts to make 10 boards with a pot and a dual DIP switch for the caps.

That includes $56 for an etching kit with enough photo etching PCB and chemicals to make 20+ boards, plus 25 of those PC 'Keyboard Lock' key switches like HUffyD used, and 5 of these CR80 coils.
http://www.ebay.com/itm/290952219619

I have seen other coils and don't care for that design so I just got 5 and imagine the coil choice will change.

When it comes to trying something I help design I don't dick around, I jump in with my wallet to see if it works without questioning parts (they can't all be bad for example)

I still have a very challenging build on deck (79cc pred w/torque converter) but this pesky chopper is done.

You can't see it in the pic but it has a stealth black panel mount rocker ignition switch on the CDI cover for extra security as I didn't have any keylock switches left, speaking of which, I got those 25 keylocks at $2.29 each.

The keylocks will get used regardless.

 

[Huffydavidson]

My CDI has and does power a twin coil coil pack that come from a
YAMAHA BANSHEE 350 witch inturn fires the dual sparkplugs in
CRMACHINE'S DUAL SPARKPLUG HEAD .
The cdi has a name and a logo.
"HD's LIGHTENING"
Who says lightening doesn't strike twice.

 

[KCvale]

The cdi has a name and a logo.
"HD's LIGHTENING"
Who says lightening doesn't strike twice.

I like it ;-}

I went the easy way re-stocking for making PCB's and bought this $56 kit with my parts order.
http://www.mgchemicals.com/products...epair/prototyping/photofabrication-kit-416-k/

I should be able to run a couple complete boards in 10 days or so to see how they perform and I'll have 5 new 2013 66cc Skyhawk 2-stroke engine kits @ $134.21 delivered to test them on.

 

[KCvale]

Slow but sure progress on a timing adjustable CDI PCB layout, I pretty much only have the cap timing cap circuit to add now.

I am designing it to fit in the little 1.25 x 1.5 x 2" black plastic boxes I use and so far so good.

It will also have have a connection for the handlebar kill button along with the ignition keyswitch which will be optional.

Also note that much of the unused board space will be ground copper when I fill it in so it takes much less chemicals to develop and etch the boards beside the fact the lots of ground around circuit connections is a good thing.

I could have made it much more compact if I stood the resistors and diodes up but I don't need the room and the circuit is much easier to follow in 2 dimensions.

 

[KCvale]

I have the circuit done, just waiting on the DigiKey parts order to tweak it.

There is another wrinkle in the design now as the magneto in the new Skyhawk 'parts in a box' kits has changed, the white wire is gone and it looks like all the windings are for the primary now.

I can't see it effecting the circuit but something to consider.

 

[ivan H]

Looks good KCVale, well done. As u say, I cant see the stator coil not having the 6V/0.3A white wire winding making any difference to the ignition other than preventing the possibility of it being dragged down by people trying to pull too much current from it, which is a good thing. Cheers

 

[KCvale]

I sure like these cute little DIP switches I got for the cap circuit, they are basically just slide jumpers in about the same footprint with the same rating as most any hard jumper.

The rest of the parts should be here today so I can play with a paper PCB layout and get down to business next week.

 

[SKY120]

Finally got all my 1% metal film resistors on order. Fingers crossed!!

 

[ivan H]

I'm pretty sure the switches will be fine KCVale. They do look neat. Sky120, have u got a CDI up running yet? It will work with carbon films, like the resistor type isn't wot is stopping it from running. Let us know how u go with. Cheers

 

[KCvale]

It's time for photo developing, etching and drilling ;-}

Here is the 1.5" x 2" transparency for photo developing, the box it will go in, and the big parts that will go on the board with a Bic lighter for size reference.

Note there will be much more black ground plane filling in most of the 'empty' space in the final master multi-circuit template because dissolving copper with Ferric Chloride is not cheap so the less copper you have to dissolve the better, besides at least a partial layer of grounded copper around timing circuits is a good thing.

I have a 3x5" copper board that would take 4 circuits.
A 4x6" board that would take 6 circuits.
And a 6x6" copper board I could fit 12 on.

I think I'll just cut out a 1.5x2" piece from the 3x5" for the first test board and go from there but given the right size coil a single tunable CDI unit close to the stock CDI size could be made and given the proper mounting ability exactly what I am working towards.

 

[ivan H]

Impressive KC. Looking forward to seeing the finished product. Cheers

 

[KCvale]

Those CR80 coils I ordered on the 3rd are still not here.

What do you think about this Honda CR 450 Elsinore coil?

http://www.ebay.com/itm/Emgo-Igniti...981-1982-/310759615664?_trksid=p2054897.l4275

It doesn't say if it is a trailing edge fire or the dimensions but it looks like my box would attach right to it and with that nifty tab on it, a bicycle reflector strap could hold the whole thing to the bike as one unit, heck with a slightly larger box it could be just a little larger but enclosed other than adjusters like a stock CDI.

 

[KCvale]

What the heck, I ordered 1 of the above coils and this one too.

http://www.ebay.com/itm/Eton-Igniti...&hash=item25836a0cb7&vxp=mtr#vi-desc-maincntr

Again no clue about windings or firing but a very useable size and both will be here by Friday in case the 5 CR80 coils I ordered are still not here.

 

[ivan H]

Hi KC, both those coils should be fine. Over the last couple of years I have tried a number of different coils including Yamaha YZ465, 500cc Honda, even a coil intended for use in a HHO (Brown's gas) igniter that was schematicly the same. The last one (obtained thru "information unlimited", tho physically a little smaller than a CR80 coil produced spark between 2 electrodes spaced up to 15mm apart. Some "stun gun" HT coils are also schematicly correct with the bottom of both the primary & secondry winding's tied together at ground potential. Any coil of this design should theoretically work. Cheers

 

[KCvale]

Hi KC, both those coils should be fine.
With the bottom of both the primary & secondary winding's tied together at ground potential. Any coil of this design should theoretically work.

Being able to adjust the spark at the CDI I tend to agree Ivan.
Just to triple check tuning logic...
Resistors and Capacitors work as pair for the timing advance and duration of spark but for the most part the resistors set timing (retard from mag degrees TDC firing) and caps duration of spark correct?

One coil may have twice the windings on each side or different ratios but any slight differences should be able to be easily compensated for with the adjustments on the CDI I would think.

Both my first two little single PCB board creations were a total failure, I forgot how time and light sensitive these boards are and one ended up no copper, and the other I didn't bother to etch in solvent as I when I put the board in the developer my layout appeared for a second or two and was gone before I could get it out and rinse it.

That's OK, I have lots of material to work with which is easy, it has a sticker like material over the copper side. so ambiant light is not an issue.

I think just 60 seconds under my sons big black light will do the trick and I'll keep an eye on the developer phase. When the board is copper all but a faint green for traces it can go in the FC and I'll try to get some pics for you guys that may want to try this.

 

[ivan H]

Hi KC, pretty much just resistances set the initial firing point & how much the spark advances as revs increase & with this, the voltage from the magneto also increases, thus the advance. The 33 ohm & 760 ohm form a voltage divider (the negative voltage develops across the whole). The 1k & 390 ohm create a potential difference between the gate & cathode. (reducing resistance here will also retard spark & vise versa). The resistance between the cathode & ground also creates a potential differences. As we know, varying this resistance will alter spark timing so u could think of this resistance biasing the SCR, kinda thing. The R/C network formed by the 760 ohm & tantalum cap is responsible for the retard at mid/,higher revs. U can use an R/C corner frequency calculator to calculate roughly where the retard curve will start to kick in. A 760 ohm & 4.7uf give a corner frequency of around 4456 hz (equates to rpm). Using 5.7uf brings the point where the retard kicks in to around 3674 rpm. It also steepens the retard curve. Using a 3.3uf moves the point at which the retard curve kicks in up to around 6,346 rpm & also flattens the retard curve, which is how it allows the motor to attain higher rpm(if port timing also allows). Hope this helps & am looking forward to seeing ur CDI's. Cheers

 

[KCvale]

U can use an R/C corner frequency calculator to calculate roughly where the retard curve will start to kick in.

I have no time to mess with designing a better CDI circuit, just a better layout and function of the parts for the common user with few if any mods, but capable of pleasing the high performance tweakers.

Hi KC, pretty much just resistances set the initial firing point & how much the spark advances as revs increase

And that makes the externally accessible resistor pot the magic part for most and the internal cap switches for those that go extreme.

I layout stuff for user ease of function, heck look at how I do handlebars and this no different other than the adjustments will seldom change.

It is a 25 turn pot for 10Ω, that is .45Ω change per full turn.

To avoid any new install adjustment fiasco's like when CNS carbs had an accessible idle air/fuel mix screw and nobody new where to start I'll just ohm out each circuit for how many turns it takes to be at 'stock' and put it on the box so anyone can get back to 'should run' settings and try again from there.

Does that make sense to you Ivan?