HV Supply using an Ignition Coil

Thread Starter

JulesP

Joined Dec 7, 2018
342
Hi all,

I'm constructing an HV supply based on a car ignition coil as per the attached circuit from (http://chemelec.com/Projects/Car-Coil/Car-Coil-1.png)

I wanted to get my ground and HV connections right as this will deliver 10-15kV which I am using in some plasmolysis experiments.

As one can see from the photo of the coil itself, there is the main HV+ coming from the centre connection (that would go to a spark plug) and the two connections for the primary winding but I'm just checking that the HV Negative, that I will connect to one side of my plasmolysis plates, should be connected to the coil's primary negative ('Dist' in the schematic)? I assume doing so will not damage the FET.

I have secured a screw to the bottom of the coil casing which will connect to my circuit ground as per the suggestion on the circuit.

Thanks

HV Ignition Coil Driver.jpeg

Ignition Coil.JPG
 
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Lo_volt

Joined Apr 3, 2014
149
If your ignition coil is from a negative ground vehicle (most but not all are) the negative terminal is the common terminal. You'll get your high voltage from the center connection with the negative terminal as the reference. The input will be to the positive terminal with the negative terminal as a reference.
1617027943210.png
 

Thread Starter

JulesP

Joined Dec 7, 2018
342
If your ignition coil is from a negative ground vehicle (most but not all are) the negative terminal is the common terminal. You'll get your high voltage from the center connection with the negative terminal as the reference. The input will be to the positive terminal with the negative terminal as a reference.
View attachment 233925
So one side of the output coil is connected to the negative on the primary.
 

Janis59

Joined Aug 21, 2017
1,297
1) With sth rather similar to the "plasmolysis" I have worked rather much - high voltage pulsed electrolysis at different salts water solution. Creates porous erosion, porous skin growth etc effects, including production of supercaps, teeth enamel making on implants etc. Voltage is ca 100-500 V but no more DC, currents are order of 0.1-2.0 A/cm2. Simply 10 kV is there overkilling smashing any efficiency. 2) if about high freq HHO torch feed, better read the newest sci publication of PhD phys.Janis Kleperis, LU-CFI Hydrogen Lab Head, this year (https://www.cfi.lu.lv/notikumi/konferences/gadskarteja-lu-cfi-konference/) on high frequency water electrolysis with rather similar circuitry, but sure approven results.
 
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DickCappels

Joined Aug 21, 2008
7,157
Sorry, but the discussion needs to stick to the circuit, not its uses.

A post was removed. It was made by a user who felt the need to educate us on the prohibited topic. He has been banned from this thread.
 
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Sensacell

Joined Jun 19, 2012
2,757
Looking at the coil driver circuit provided - Looks like a MOSFET destroying machine to me.

The energy stored in the coil primary will generate enormous voltages if the secondary is not shunting the energy away, like when the spark gap is too large.
The IRF640 is rated for 200 V, the diodes do nothing to protect it. The 1n4005 *might* breakdown at 600 V while the 1n5400 is a 50V, 3A rectifier- which is forward biased by the induced voltage does nothing.

That energy needs a place to go- or the MOSFET go poof.

What gives?
 

Thread Starter

JulesP

Joined Dec 7, 2018
342
The 1N4005 diode from the MOSFET drain to ground should be replaced with a Zener of about 150V to protect the MOSFET.
Thanks. Yes this was part of my original query that the FET might get damaged, not so much by the initial pulse in the primary but when it shuts off. So a Zener will bleed any back emf if it goes above 150V.
 

Janis59

Joined Aug 21, 2017
1,297
Sorry, but the discussion needs to stick to the circuit, not its uses.

A post was removed. It was made by a user who felt the need to educate us on the prohibited topic. He has been banned from this thread.
I just said the circuit voltage is plainly wrong for stated aim. So my comment was for the circuit not a use.

However any reason of fet burnout obviously is that spark as a happening takes a normally picosecond to femtosecond time-scale. Thus the 1N4XXX series diode is some 9 to 12 zeroes too slow for save the fet from decades of kV overvoltages. Surplus to that, some RC dampfer circuit would be highly needed there as well, but take a care about ESR and ESL for so drastic reactive loads on it.

RE:""Looking at the coil driver circuit provided - Looks like a MOSFET destroying machine to me"" Rather well formulated fact
 
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Thread Starter

JulesP

Joined Dec 7, 2018
342
Looking at the coil driver circuit provided - Looks like a MOSFET destroying machine to me.

The energy stored in the coil primary will generate enormous voltages if the secondary is not shunting the energy away, like when the spark gap is too large.
The IRF640 is rated for 200 V, the diodes do nothing to protect it. The 1n4005 *might* breakdown at 600 V while the 1n5400 is a 50V, 3A rectifier- which is forward biased by the induced voltage does nothing.

That energy needs a place to go- or the MOSFET go poof.

What gives?
I’ve actually put a IN54007 instead of the 5400 which is a higher rating. Would a diode be better than the proposed Zener if the Zener’s reaction time is so slow relative to any backemf pulses?
 
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