ckn,
I failed to note this earlier, but welcome to RCU. I think it's one of the best RC sites. Lot's of information and we all try to be cordial to one an other even when we disagree.

It is my dream to visit Australia. The Internet shortens the world but doesn't have the same sense of wonder as when I first heard the BBC. It was on that one tube regenerative shotwave set with earphones strapped to my head. The antenna was some #28 enameled wire tossed out my window to the nearest tree. I had to replace it every couple of days - I was trying to hide it feom my Mother. The "A" batteries worn down pretty quickly, but the 45 volt "B" battery lasted a long time. Good thing too as I had to mow lawns to save up for it.
Later,
John

Ahh, Such a simple subject made oh so murky
The application of simple Ohm's law has limitations here. Since we are dealing with a pulsed, DC fed, iron core inductor there are other factors to consider (reactance,core saturation, ringing etc.) . Add a slow, linear IC regulator etc..etc..etc.
A correction for other "power factors".

For the layperson (modeler/consumer) seeking a relative measure of actual power consumption it isn't really time to dig out a pile of theory . A simple measurement of the current differences with the different supply voltages should suffice. The current will be averaged by the meter and the measurements should help predict the battery running time as closely as needed. For the most part, in this case an increase in voltage will indeed find a fairly linear increase in current flow. Although the current increase with large changes in conditions will not be as linear as Ohm's law may have predicted. That is because OHM's law is looking for a constant resistance (impedance). Not the case in our ignition circuit.

Then again we could stir up some more murk. Perhaps to camoflage a few mis-statements ?

BTW: I miss the CW exam . It helped keep the CBers on 11 meters . Eliminated a ton of the SSB splatter we now have on HF. Too many of those CBers brought their home-brew amplifiers and "transmitters" along with their bad habits onto the HF bands.

DAHDAHDAH DAHDIDAH
DAHDAHDIDIDAHDAH
DAHDIT DAHDAHDAH DAH
DIDIDIDIT DIDAH DIDAHDIT DAHDIDIT
DIDAH DAH
DIDAH DIDAHDIDIT DIDAHDIDIT
DIDAHDIDAHDIDAH [8D]

Ex radio operators are everywhere . One of the most important lessons learned in school is that teachers are often dead wrong.

Yup it has limitations. But it is necessary to learn the basics. And even with ignitions put more voltage into it and the current will raise perhaps not to the exact value predicted by Ohms law that uses purely resistive circuits but close enough. Ever tried to teach a layman how to use current meters verses voltage meters? Now try it over the Internet . Way more energy required than I was willing to put into teaching basics. I thought simple math was easier. Turned out I was wrong but whose to say. At least with digital meters you don't blow the darn thing s up!

Nice to hear from you Ladyflyer - been a long time since I've read your posts.
John

Hello again,

Sometimes it is easier to just take the measurements . You may then seek out the theories to explain the figures.
Nothing special about inserting an ammeter in series with the power supply . Probably a lot easier than the 5 pages of writing

So after 100+ posts did anyone take the time to get any hard data, excuse me, fuel for the fire?


Of course the above post popped up while I was contemplating posting.

Just sitting here , staring into the embers. Hoping hubby brought the down filled bags. Could be in for a cold night.

Actually the numbers were post in the original thread about a poor running EVO 58, by BCCHI.
Just to re-post here, @ 8000 rpm.
4.8v = 400ma
6v = 500ma
7.4v = 600ma
As you can its linear
I think these numbers are very close to the "theorical math OHM's law numbers" that JNorton posted[:-]

Well said TKG, now may this thread now RIP.... AMEN.

Karol

For sure. That is why the empirical data is what really mattered for the subject at hand. That was my point, A SIMPLE SUBJECT MADE needlessly MURKY. Within this narrow range Ohm's law partially explains the results. The measurements show what you really needed to know, the relative differences in current draw.
Within the range of voltages presented , the load was fairly constant. Expand the voltage range and you will find the ohm's law calculations do not track. Nor will the simple R=E/I with the numbers presented generate the DC resistance of the ignition coil.

I was pretty much reinforcing your "JUST GET OUT THE METER" comment as well as John's similar opinion.

The original thread may have been about a bad running engine but much of the thread was bantering over Ohm's law. The tug of war over Ohm's law, three phase motors etc , information and disinformation makes tough copy for the layperson.

My point being the numbers, just show the actual measured numbers.
Beyond that the secondary point is :
The load being essentially the same, an increase in supply voltage will have a corresponding increase in current flow.


With battery/coil ignition circuits there are many elements outside the simple DC resistance of the coil that will affect the actual operating load. Those factors, like the Ohm's law debate are probably beyond the scope of this topic. Perhaps we could start a new thread ?

"Current Draw in Pulsed Coils At The Point of Magnetic Saturation" Anyone ?
We could discuss how voltage engine speed ,crankshaft dwell angle etc affect the saturation point as well.

I'm with Karol. This thread has run its course for me.
John

Maybe we could also expand the thread to discuss the relative merits of regenerative, super regenerative and superhetrodyne receivers[:-]
Johns reference to building a single tube regenerative receiver brought back fond memories of my first radio build, an AC powered, super regenerative model (3 tubes), with no AC isolation and no polarized plugs in those days. I'm lucky to have lived so long
Pete

It would be a heck of a lot more fun. Built my first transistor radio using a CK722 as a class A amplfier. It used a 1N34 germanium diode for signal detection.
John

Seriously probably time to close the thread.
John