Ignition Coil Interrupter

most ignitions use IGBT transistors now, usually with a build in ~400 volt clamp

google for "ignition IGBT" and you'll find plenty

-Lasse

--
Frayed knot...

Just think:  to get the energy into the coil of a conventional
(Kettering) ignition system  you've got to turn a switch ON to send
current through the few primary turns, and then to get the HV spark out
you've got to open the connection to the primary and let the many turns
of the secondary cut the rapidly decaying magnetic field.

Using an SCR for the switch, that way, how are you going to turn it off?

There's another way, though...

http://en.wikipedia.org/wiki/Capacitor_discharge_ignition

JF

Yes

SCR Turn off with a reverse bias.

I'll look into it.

Thanks, Chris Maness

What can you used for a ~400V clamp? Gas discharge?

Thanks, Chris Maness

I used to charge a few uF of oil caps to, say, 600 volts and dump that into an ignition coil through a thyratron tube. I used the old metal-can coils with the big black bakelite insulator on top. The spark would crawl out from inside the insulator and hit one of the primary terminals. It would laugh at any insulation I could find. What worked was to run a wire up the middle, tape a plastic tube to the outside of the insulator, and fill it with motor oil. I could get 4" sparks.

As I recall, the classic coils running at 12 volts, with a "condenser" in place, would fly back to 120 or maybe 200 volts. So a 400 volt power mosfet should work as a switch. Maybe include a series power diode to keep the fet substrate diode from conducting.

An SCR would work too. Charge a 1 uF cap to 400 volts and dump that into the coil. The classic "CD ignition" circuit:

+400--------R------+----------C---------+ | | | | | L A scr L coil primary trig ------GK L | | | | gnd gnd

Fairly long gate drive pulses make fatter sparks. A diode across the SCR may help, too.

John

--
OK, how?

JF

It'll ring once, then turn-off... short spark, residual charge left on capacitor.

See my website for a _working_ CDI. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
      The only thing bipartisan in this country is hypocrisy

I suspect some one is getting confused with a capacitor discharge system.

They do make GTO's how ever. Maybe that is what is confusing the issue ?

If you want a circuit diagram just go to 4HV.ORG

Shaun

I just made a circuit diagram!

John

John Fields wrote in news: snipped-for-privacy@4ax.com:

Here's some ignition coil humor for you; when I was a kid,I wanted to make a Jacob's ladder using an auto ignition coil,so I mounted one on a board,made two wire antennas for the spark to climb,then wired the coil primary to a 120VAC power cord.

Sunday morning at the kitchen table,mom across from me reading the paper...I plug the coil into an extension cord,and KAPOW! BIG flash and spark,kitchen lights go out,mom jumps a mile in the air,starts screaming at me....

I didn't know the 12v primary was like a dead short to 120VAC.

--
Jim Yanik
jyanik
at
localnet
dot com

"Chris" wrote in message news: snipped-for-privacy@h4g2000pre.googlegroups.com...

Go to digikey and type in "igbt ignition" here's one:

I've made plenty of points-bypass modules. Used them on my own vehicles (bikes) and sold a few of them to other bikers. So you can take my word that igbt's work for driving coils. Coil-driver igbt's are designed and manufactured specifically for use with automotive ignition coils. Check out the datasheets, you will probably see built-in clamping consisting of a zener from drain to gate that will cause the igbt to conduct in case of excessive drain voltage. But you can get coil driver igbt's over 400 volts, so they will only clamp if a plug cable falls off or something unusual like that. A dwell circuit is a lot easier to build than capacitive discharge. There are two ways to do it. Control the igbt from the gate, or use a cascode circuit. In the cascode, instead of turning the igbt on and off at the gate, you interrupt the current at the source terminal using some other device. That's how I do it when using them on an actual vehicle. Hardwire a 1k resistor from the gate to +12 volts from the ignition switch, and wire the source terminal to the points. When the points open, the igbt blocks the voltage flyyback from the coil primary. That way you don't need a condenser and it doesn't even matter if your points are in bad condition. The igbt does all the work, handles the voltage spike. As long as the points can conduct the full coil current, the igntion will function properly. So the whole circuit just consists of one igbt, a resistor, and the points. The igbt itself contains the rest of the components for clamping and gate protection. You could build yourself a cascode circuit using the same scheme. Have a low-voltage bjt or mosfet switch and wire it in cascode with an igntion coil driver igbt. Drive the switch however you like, with a 555 or whatever. Simple and easy.

12v | +--------, | | | | | coil | | | _| '--1k--|_ igbt | | switch | gnd

pdf

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Thanks, that looks like the perfect solution. Nice way to have a solid state relay do the job instead of burning up relays. It is such a noisy mess too. Now I just have to go dig out my old ignition coil and start having some fun. ;o)

Also, in that data sheet there was a component refered to as ICE in the test circuit schematic. What is that?

Regards, Chris Maness

=A0 =A0|

=A0 =A0|

=A0 =A0L

=A0 L coil primary

=A0 =A0|

=A0 =A0|

=A0gnd

most systems now it just switch the coil ground with an IGBT, some coils have the IGBT and a pull down resistor build in so the ECU just outputs a

0-5v signal at ~20mA.

coil primary is ~1 Ohm and dwell time is in a few milli second to get ~10A

the clamps is just there to prevent the transistor and/or the coil from killing itself if the plug or cable fails.

-Lasse

That's fine for a vehicle ignition, but if you want serious fireworks you can't use the coil in magnetic-energy-storage flyback mode... you have to dump a charged cap into it.

John

Thanks, that looks like the perfect solution. Nice way to have a solid state relay do the job instead of burning up relays. It is such a noisy mess too. Now I just have to go dig out my old ignition coil and start having some fun. ;o)

Also, in that data sheet there was a component refered to as ICE in the test circuit schematic. What is that?

Regards, Chris Maness

Maybe it refers to collector-emitter current (Ice) That could be a sense resistor in the emitter.

John Larkin was suggesting capacitive discharge. Here's a cute CDI circuit from Jim Thompson. Don't know if this link will work. CD-Ignition-Basic.pdf

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The link did not work.

Chris

For the real deal...

...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
      The only thing bipartisan in this country is hypocrisy

a

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t t "

=A0 =A0 =A0|

=A0 =A0 =A0|

=A0 =A0 =A0L

=A0 =A0 L coil primary

=A0 =A0 =A0|

=A0 =A0 =A0|

=A0 =A0gnd

=A0 =A0 ...Jim Thompson

=A0 =A0| =A0 =A0mens =A0 =A0 |

=A0 | =A0 =A0 et =A0 =A0 =A0|

=A0|

=A0 =A0 =A0 |

The real fun would be to line a plastic trash can with tin foil inside and out -- ground the outside of the can. Charge it from the tower of the ignition coil through high voltage rectifier. I had a teacher friend that would charge one of these with static, and it sounded like a gun when discharged.

Regards, Chris Maness