questions on internal resistance

[azazzera]

i have been reading up on ingnition systems and following the conversations on the hot coils. my question is wouldnt a high internal resistance produce heat in the coil. would it be more helpful to provide most if not all resistance external. how do you controle voltage to the coil other than resistance. i guess im still getting this all straight in my head. thanks. also ive seen coils with fins to disapate heat. would that help or is it all about limiting the build up of voltage in primary.

[ndutton]

Good question. Your reasoning would be correct if internal coil resistance was achieved by using the same type of resistor . . . . .

. . . . . but it isn't.

The external ballast resistor heats up by design taking advantage of the resistor's properties in relation to heat - - - serious heat in this case. What follows is not from me but paraphrased from an online source. Parenthetical notes are mine:

The ballast resistor (the type we've been recommending for external supplemental resistance) is a temperature sensitive, variable resistance unit. A ballast resistor is designed to heat up at low engine speed as more current attempts to flow through the coil (energy duration in terms of dwell and RPM related time). As it heats up its resistance value increases causing lower voltage to pass into the coil. As engine speed increases the duration of current flow lessens. This causes a lowering of temperature. As the temperature drops so does the resistance allowing the voltage to the coil to increase. At high speed when a hotter spark is needed the coil receives greater voltage input.

The ballast resistor is a coil of nickel-chrome or nichrome wire. The nichrome wire`s variable resistance properties tend to increase or decrease the voltage in direct proportion to the heat of the wire.

[romantic comedy]

Neil, that is what I had always thought. Hence the name ballast resister. It is a variable resister, that provides stability.

[hanleyclifford]

Neil, that is what I had always thought. Hence the name ballast resister. It is a variable resister, that provides stability.

I have mine running thru 3 paths on the resistor block so voltage variation is minimal.http://www.moyermarine.com/forums/at...8&d=1331592235

[romantic comedy]

Hanley, do you ever get to SW Florida? I gotta see this boat.

Are you adding the resistors in series?

[hanleyclifford]

Hanley, do you ever get to SW Florida? I gotta see this boat.

Are you adding the resistors in series?

The array has 3 parallel switched paths; each path has a 1 ohm block and a 10 watt light in series. I sure do want to get back to Florida. Right now I'm sorta living aboard in Wickford and the harbor is plumb froze. Edit:http://www.wickfordyc.org/

[azazzera]

I always appreciate the response to my questions. I however feel that its at times one step forward and two steps back in regards to my understanding of the physics of it all. my studies continue. I suppose i have to ask the proper questions to "the google" I have stumbled on to the "hot spark" site and at first glance they seem to be quite explicit about using the proper resistance in your coil. they explain very clearly that if not enough resistance is used with ei coils will be fried.. I would like to hear from people that have used there product.

anyway, thanks for the continuing education. until next question.

[ndutton]

and here's another coincidence

It turns out I decided to give the HotSpark EI a try on my spare engine coupled with a Moyer 4.3Ω coil and no supplemental resistor. I haven't run the engine enough since completing the rebuild to offer a useful report. All I can say right now is it starts easily without the 'R' terminal bypass and runs smoothly.

I know of one other forum member using the HotSpark. So far so good.

[HalcyonS]

News on Hotspark?

I came across this product in a reference by Neil, while researching points issues (as one does). Its been a longtime now - any updates on your test engine with Hotspark, Neil, or anyone else?

[hanleyclifford]

But the question remains

how does the coil achieve it's internal resistance?

[hanleyclifford]

Here's a little picture I found at Google (the sum of human knowledge). We know how we measure for ohms across the terminals. So the question again, how does the coil develop it's internal resistance?

[joe_db]

The wire in the coil has resistance. There is a LOT of wire in there and it is thin. You can measure it with an ohmmeter. Coils are usually sold with a stated resistance. You can buy 3 ohm coils, 4 ohm coils, 0.6 ohm coils, etc. etc.
When the coil resistance is less than desired, we add ballast resistors...or buy a lot of coils

Here's a little picture I found at Google (the sum of human knowledge). We know how we measure for ohms across the terminals. So the question again, how does the coil develop it's internal resistance?

[hanleyclifford]

The wire in the coil has resistance. There is a LOT of wire in there and it is thin. You can measure it with an ohmmeter. Coils are usually sold with a stated resistance. You can buy 3 ohm coils, 4 ohm coils, 0.6 ohm coils, etc. etc.
When the coil resistance is less than desired, we add ballast resistors...or buy a lot of coils

A lot of Truth there. But the question then becomes, how is the means of resistance inside the coil different from the means of the external resistor? Do not both generate heat?

[joe_db]

Yes they both do generate heat. The coils heat up when used from current flow as well as being bolted to a hot engine.

A lot of Truth there. But the question then becomes, how is the means of resistance inside the coil different from the means of the external resistor? Do not both generate heat?

[hanleyclifford]

Yes they both do generate heat. The coils heat up when used from current flow as well as being bolted to a hot engine.

That's what I thought.