Is there a simple DC CDI circuit out there, with a complete parts list and schematic? If yes, can someone please post it?

 

I'd be surprised if there's anything much simpler (while being reliable) than circuits already linked or posted here; but good hunting.
Why not just buy an off-the-shelf CDI module if you need it in a hurry? Probably a good bit cheaper than building one, unless you intend using parts you already have.

 

I'd be surprised if there's anything much simpler (while being reliable) than circuits already linked or posted here; but good hunting.
Why not just buy an off-the-shelf CDI module if you need it in a hurry? Probably a good bit cheaper than building one, unless you intend using parts you already have.

I was going to say much the same - building your own was a common project in many electronics magazines of the early to mid-70s when electronic ignition was the preserve of high-performance cars and a ready-made unit was several 100 £/$; indeed I built my own C1974 for my first car, a Triumph TR4A. Most of the design I'm seeing published here are historical and 20y+ old. Those posted by @debe use parts you probably can't buy now and would need updating.

Now an off-the-shelf unit is 25 £/$ its hardly worth building your own other than as an educational exercise...

 

I started off with what I thought was a working circuit that ran off of a wall wart power transformer that stepped up through that cheap Chinese circuit and made a pretty good spark. When when I changed over to battery the circuit fried.

I got it to go again when I interposed an inverter into the mix and plugged the wall wart into that.

Then I was on the hunt for something that worked like a current limiting source similar to my inverter and transformer mix but that got lost along the way.

I was really hoping that you guys would be able to help me. You’re both smart and have done this in the past - maybe it’s lost the thrill because you have done this in the 70’s and there are cooler things now a days.

to me, this should be a simple as looking up a recipe on the box of a cake mix. The devices are everywhere. I’ve seen videos that I can’t understand of Indian kids scalping parts from TV sets found in the trash and making function CDIs for their mopeds. AC and DC alike.

I want to do something like that. Why is this so hard?

 

to me, this should be a simple as looking up a recipe on the box of a cake mix.
[...]
I want to do something like that. Why is this so hard?

Because these devices are using a transformer backwards for a purpose and frequency it wasn't designed for. Not all transformers are created equal. So if I was building a CDI myself, I'd either wind my own or acquire a few to see which works best, imposes least stress on the driving transistors, and has good compliance with, and recovery from, short circuit. And that needs test equipment you don't have. So recommending off the cuff - no, at best suggesting - a transformer that might work, that won't burn-out the transistors or itself in a few weeks/months, and that isn't twice the price of a ready-made unit, is difficult.

 

Because these devices are using a transformer backwards for a purpose and frequency it wasn't designed for. Not all transformers are created equal. So if I was building a CDI myself, I'd either wind my own or acquire a few to see which works best, imposes least stress on the driving transistors, and has good compliance with, and recovery from, short circuit. And that needs test equipment you don't have. So recommending off the cuff - no, at best suggesting - a transformer that might work, that won't burn-out the transistors or itself in a few weeks/months, and that isn't twice the price of a ready-made unit, is difficult.

Fair enough

 

You already have a Kit posted 1975, pretty sure the parts are still obtainable. Also i posted a circuit using a small transformer 2 x 10 V center taped to 240V this was salvaged from an old philips K9 coloured tv set. You are unlikely to find a CDI Kit as there is only a limited market. As others have sugested theres plenty of CDIs avalable from Ebay quite cheaply.

 

I am go

You already have a Kit posted 1975, pretty sure the parts are still obtainable. Also i posted a circuit using a small transformer 2 x 10 V center taped to 240V this was salvaged from an old philips K9 coloured tv set. You are unlikely to find a CDI Kit as there is only a limited market. As others have sugested theres plenty of CDIs avalable from Ebay quite cheaply.

Inam to go back through this entire thread and see what I can find. maybe I’m lost. I thought everyone was contradicting each other in some places and that’s why I feel I don’t have a solid circuit to build. I’m probably at fault.

 

This is what i made up as a replacement CDI system for an engine.View attachment 275575View attachment 275576

Debe - I made this 300VDC power supply (12 in and 300+/- out). it works and is great. My problem is the other box you made with the two yellow caps. How do I build that or is that the Jaycar circuit?

 

I thought everyone was contradicting each other in some places

I don't see any contradictions in this entire thread. You've been offered several alternatives, together with suggestions for using your existing HV module (albeit requiring some experimenting on your part).

 

Which is where?

Akron, Ohio - USA

 

That was the Jaycar circuit. Ive built several of them & they work.

 

I've tried using the 555 to switch my HV source on and off - it does not work. I swapped out the output caps, I tried using a 1uF cap... the circuit does not turn off fast enough. so all I have is a nice square wave generator that can make either an inverted or normal square wave.

I cannot find a 300-400VDC switch that wont break the bank.

I cannot buy a Jaycar kit anymore.

I've managed to build the 12 - 300VDC transformer that debe posted (from spare parts out of power supplies) but that just gets me 300VDC similar to the power supply I already purchased (just with less parts than the one I purchased).

I've managed to get myself all muddled about whether any of the other circuits suggested will be able to shut off the SCR or not.

I purchased a munch of fast diodes and SCR's to build a circuit that I have since lost track of in all the themes and variations. I am not the proud owner of 10 of each: BT151, 1N5408, 1N4004, NTC1, TIP41C, TIP122 and LM339. No idea what to do with them at this point. I guess I can put them in little drawers along with my extensive collection of collected other diodes, resistors and capacitors.

and now I feel I should lull a bit off to the left and dribble on myself...


oh, and if anyone is interested in showing poor taste - this is what is driving around all of my town in the USA: Joy Riders Car Window Clings Queen 765468100197 765468100197 | eBay

 

Could one use a 240vac to 12vdc power supply that you readily have for most UK computers as the transformer? You could feed it 12vac from the 555 and put a rectifier on the output to get 240 VDC.

 

You have said you want this as a learning experience, what happens when ,if you get one working, it fails? Who other than you the builder will be able to repair it or get it running again?

The suggestion a few pages back to use a GM HEI module, something available at any car parts store, is the one I've been hinting at. Yous said they were potted, what does that have to do with anything? They work, and when they stop working(not very often) you buy another one and the well is producing again. KISS. If you don't like GM for what ever reason, Mopar and Ford had similar ignitions that can be used, although the HEI is the most documented one out there.

 

I shall purchase one today.
I shall purchase two - one to soak in MEK or some other solvent.

I'll make something that works but I want to continue this project until I master it.



The 4-pin DC CDI / HEI module requires a hall effect input to trigger it.

This 7 pin version looks like my magnet and trigger coil will work just fine.

Comments anyone?

 

Could one use a 240vac to 12vdc power supply that you readily have for most UK computers as the transformer? You could feed it 12vac from the 555 and put a rectifier on the output to get 240 VDC.View attachment 276089

Unlikely... that 240v AC to 12v DC is almost certainly a switching supply with no useful transformer inside...

Here's a thought though... The HV power supply you blew up - is the transformer undamaged?

 

Unlikely... that 240v AC to 12v DC is almost certainly a switching supply with no useful transformer inside...

Here's a thought though... The HV power supply you blew up - is the transformer undamaged?

Yes it is undamaged and I have two more to boot.

 

take a look at this HEI module - you can see the bones

Speedmaster HEI DISTRIBUTOR 4 PIN MAGNETIC PICKUP HIGH ENERGY IGNITION CONTROL MODULE

Speedmaster PCE383.1024: HEI DISTRIBUTOR 4 PIN MAGNETIC PICKUP HIGH ENERGY IGNITION CONTROL MODULE - JEGS High Performance