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CDI charging unit and OFF circuit?

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mos68x

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I have been working on a personal project for a while and have been swamped with ideas and don't really know electronics well enough to decidedly use one or another.

I got some free disposable cameras and reclaimed the photo flash capcitors out of them to use for boosting the ignition power in a project car (91 Camaro). My desire is to create a plasma arc across a spark gap of about .08in.

My original intent was to use a small inverter to power a step-up transformer to bring voltage up to 250-300V pulsed full wave dc, obviously using a rectifier. Then to use that voltage to directly charge a capacitor bank that would dump across the spark gap when the stock ignition would strike it's spark. I want to "size" the caps right so that they are quick to charge (within micro-seconds) and still discharge over a few degrees of rotation in the motor.

I wanted to use a magnetic inductive pickup coil (like a timing light's inductive pickup) to trigger an OFF switch so that the charging circuit would not be connected at the time the caps are discharging. I don't want to use a mechanical solution because anything mechanical I seriously doubt will endure operating 63 times per second (engine running 7500 RPM). That leaves .016 seconds firing TDC to firing TDC, which will have to include both discharge and recharge.

I want to use a toroid coil for the inductive pickup and was just thinking of using a "secondary winding" to continue the OFF position after the high voltage has passed and if the caps are still discharging.

I am not schooled in electronics design so please bare with me. I want to make a unit for each plug similar to a coil-on-plug type ignition, with the high voltage from the distributor going to one end. With everything inside the unit, from toroid to caps and exiting the other end and going to the spark plug. No grounds in the unit or grounded to the engine at all until it reaches the base of the plug. The only power in would be a 12v connector or a 250-300V connector and the spark from the distributor.

Anyone have any ideas to a better option? Or a circuit that I can use to shut off the charging circuit at the time the high voltage spike hits the plugs?

Thanks for the patience
Leon
 
CDI is better suited to 2 stroke applications, the spark duration is very short & doesnt ignite the mixture optimally especially in a large bore high compression 4 stroke engine unless it is a multispark design.

Ignition IGBT's are the latest in ignition coil switching.

tgau
 
You will find yourself hard pressed to find an ignition system now that is not CDI, commercially or race circuit, escpecially with waste spark systems in any vehicle from 96 and on. My question is not for the use of CDI, but for the use of a capacitor bank to be used in conjunction with the standard ignition of an older vehicle, ie 1991. Although HEI has advantages, I want to extend the spark/arc duration and increase it's power(J) across the plug, in short create a plasma arc. It can be done with 110V pulsed DC started with the high voltage spike from a distributor. What I want to do is have a predetermined value of energy @ 220V stored in a capacitor and then released across with the gap with ionized field from the high voltage spike. During the time of the HV spike I want to diconnect the charging circuit from the cap, since my last post a friend came up with a simple but effective circuit using a couple ideas of mine. Similar to a timing light, using an inductive pick-up coil, although toroid instead, with that signal sent to a transistor to shut off another power transistor that allows charging to the cap. Although doing it this way will create a fast, large, and loud discharge at the plug I would like to extend the discharge time if I can that will be closer to that of a plasma arc in the plasma cutters and still be variable in timing with the engine. Basically NOT computer controlled with all sorts of sensors to allow it to work. Charging time may be an issue but cap sizing and choice should reduce that considerably to where it will not be an issue.
 
Cdi

You could use a Hall Effect as your pickup sensor to toggle a on/off signal to an external coil and collect EMF, rectify it with FWBR and send it to caps.
The more magnets you add the quicker the caps would charge. I suppose you could also use a 555 timer with a switching transistor to create the on/off action for the coil.
Seems to me it would be diffcult to use a toroid as the pickup as you would have to pass thru the center of it. Some Hall transistors can also sence an oncoming magnet in the form of resistance as feedback for location, exact timing etc. just a few thoughts, take care
 
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