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If you apply 6v to this coil. What's the primary current

Geo-TH,In

Geo-TH,In

Well-known Member

cvphoto142941.jpg


If you put a 1.5 ohm resistor in series with this new coil what is the primary current

cvphoto142942.jpg

And the voltages used by the new 1.5 ohm resistor and the new volt coil?

The meter on the left is ballast voltage. the meter in the middle is the primary current and the voltage on the right is the coil voltage.

This goes against everything in thought was supposed to happen.
 
(quoted from post at 15:39:57 12/15/22)
<img src=https://www.yesterdaystractors.com/cvphotos/cvphoto142941.jpg>

If you put a 1.5 ohm resistor in series with this new coil what is the primary current

<img src=https://www.yesterdaystractors.com/cvphotos/cvphoto142942.jpg>
And the voltages used by the new 1.5 ohm resistor and the new volt coil?

The meter on the left is ballast voltage. the meter in the middle is the primary current and the voltage on the right is the coil voltage.

This goes against everything in thought was supposed to happen.
Click to expand...
don't know what you expected, but I 'expect' that the resistor isn't 1.5 Ohms.
 

Forget about the 1.5 ohm resistor.
Using a different resistor, what is the primary current when 6v
is applied to the coil and 6v is applied to the ballast?
 
(quoted from post at 17:42:20 12/15/22)
Forget about the 1.5 ohm resistor.
Using a different resistor, what is the primary current when 6v
is applied to the coil and 6v is applied to the ballast?
Click to expand...
have no real idea of what you are trying to do, but I = V/R, whether the R is coil winding resistance or the resistive wire inside the resistor.
 
Jessie.
I simply want to know what is the primary current of a 6v coil
when 6v is measured across the coil.?
 
(quoted from post at 18:14:55 12/15/22) Jessie.
I simply want to know what is the primary current of a 6v coil
when 6v is measured across the coil.?
Click to expand...
ou can only know that by measuring the current or by knowing the coil primary resistance. Something keeps whispering in my ear that you already know that.
 
Im not good with electrical stuff and the math required would certainly give me a headache. Id be more interested in knowing why you would want to know that information.
 
George, I'm not sure exactly what or why your question ?????? you already know this and unless Ohms law has changed.........

QUESTION If you apply 6 volts to this coil what's the primary current (I define primary to be coil current)
ANSWER Per Ohms Law the current is 6 volts / the coils resistance: WELL DUH you already know that !!!!

QUESTION (as I understand it) If you add in series a 1.5 Ohm ballast resistor and place 6 volts across the series sum of the ballast PLUS coil,,,,, THE CURRENT IS 6 / 1.5 PLUS coils resistance WELL DUH Of course if you placed 12 volts across the series sum current = 12 / resistances WELL DUH

I just dont understand your question or what youre getting at I = V/R

Please explain your question and why Ohms Law may not apply ??? You may have too much time on your hands lol but hey like me you're retired and enjoy interesting questions WHICH I ENJOY AND GLAD TO HELP SO KEEP THEM COMING

John T Bushnell Florida
 
Something keeps whispering in my ear that you already know that

I agree JMOR X2 George has to know this surely

John T
 
John T
Forget the picture, Forget the ballast resistor.
One simple question, If I applied 6 volts to a 6 volt coil, what is the primary current?
 
It will be obvious once anyone answers the simple question.
What is the primary current when 6v is applied to a 6v coil??
 
JohnT
Why won't anyone answer the question, what is the current??
If you don't know, please say I don't know.
 
5 Amps. 6 Volts across THAT coil.

Sorry got disturbed, deleted most of my answer and posted without review. Back now and saw my error.
The primary resistance of THAT coil is 1.2Ω, which is in tolerance for a 1.5Ω coil. The resistance of THAT 1.5&Omega resistor is actually about 0.9Ω.

This post was edited by deanostoybox on 12/15/2022 at 04:15 pm.
 
Assuming the 6V coil has 1.5 ohm primary resistance, adding 1.5 ohm ballast, and feeding it your 11.99 volts, would yield about 3.99 amps if running straight to ground. Is that what you're after?

I detest the terms 6v and 12v coils when it comes to old school points coils, it's misleading. There are just coils with, and without, internal ballast.
 
I DONT KNOW GEORGE

I dont know the RESISTANCE of the coil. Tell me that and then I will use I = V/R

What dont you understand about Ohms law ??????

John T
 
You ask One simple question, If I applied 6 volts to a 6 volt coil, what is the primary current?

THE ANSWER IS I = V/R What dont you understand about ohms law ??????

Tell me the coil resistance and ONLY THEN can I give you the answer DUH
Have you been drinking tonight lol

Merry CHRISTmas George

John T
 
With respect, there is no modern coil with internal ballast or resistor. They are just designed to operate at 14.5 volts, or just over 7 volts, by increasing the number of turns in the primary. Just like a 12v or 6v fan motor. Jim
 
You ask

One simple question, If I applied 6 volts to a 6 volt coil, what is the primary current?

ANSWER CURENT IS VOLTS / RESISTANCE

John T
 
The correct answer, unless Ohms Law changed:

The Current is the Voltage / The Resistance

If you apply 6 volts across a coil, the current is 6 / coils resistance

If we know the resistance of the coil we can answer how much current will flow through it with 6 volts applied

Please tell us the coils resistance

CAN YOU BELIEVE THIS THREAD ?? A simple Ohms Law I = V/R can get so complicated lol Somebody getting into the egg nog maybe lol

Have fun with it yall God Bless and have a Merry CHRISTmas. A little humor is good for us this time of year..

John T
 
What is the primary current when 6v is applied to a 6v coil?

Current is 6 / Coils resistance

John T
 
Jim, Ive told em that for over 20 years on here, they just will never get it lol

Merry CHRISTmas

John T
 
I just can't resist!!! We have a nice 10 inches of white wet snow as I respond. a few broken bracches, but no grief. Peace on earth good will to men (Mankind) Jim
 
All I know if one thing , you GEORGE just have too much spare time. You need to come south and help me I can find several more productive projects for your skills. I did get the switch in the grinder I showed you and now it runs half speed from what it did before the bad switch. Hope you have a Merry Christmas
 
I have never seen a coil marked internal resistor, no external resistor required The poor wording stating no external resistor required should read For operation on 12v with no resistor. The easily misunderstood factor is that if no external resistor is required, there must be one inside. Unfortunately the wording's implication is bogus. Also unfortunate is the coil manufacturing industries near universal use of the printing. Jim
 
If the maker says its a 6 Volt coil, and you apply 6volts to it, the current could be zero if the coil is not in a complete circuit. Otherwise the current is unknown since we are not told the resistance or the ability of the device supplying the 6 Volts. I might have missed it, but are assuming DC supply?

Some way to observe the current (amperage) is to see if any smoke emanates or the coil gets warm or stays cold! That's if there is a complete circuit!
 
With the 1.5 ohm resistor in series with the coil, that means that its current will be the same as the current thru the coil. If you read 5.21 volts across 1.5 ohms, then current must be 3.47 amps. At least one of the meters cannot be correct, or the resistor is not really 1.5 ohms. Allowing for tolerances, it does appear that the resistor voltage and coil voltage add up to the applied voltage fairly closely.
 
George, I think you're assuming the resistance of the coil and ballast resistor are constant. I'm pretty sure they're not. Ballast resistors have a positive temperature coefficient so their resistance increases with with temperature. This allows hotter spark for starting while reducing current once the motor is running. If you check the resistor with an ohmmeter, the current is negligible. But when you have several amps going through the resistor its resistance rises and the voltage drop increases.
 
Congratulations to everyone, lots of fun n time on such a SIMPLE OBVIOUS question

The obvious answer is Current through the COIL is I = V/R but no one could give an answer UNLESS THE COILS RESISTANCE IS KNOWN !!!!

The Current at any given time is 6 Volts/Coils Resistance at that point in time. If the coils resistance changes with time or temperature so does the current WELL DUH

In some older car coils there were encased in the bottom of the can temperature compensating discrete stand alone resistors (thermistors). Later year standard external ignition ballast resistors (like on all the old farm tractors Ive seen) were more like simple standard resistors, carbon or wire wound, that dropped approximately 6 volts leaving 6 for a 6 volt coil another WELL DUH Im sure everyone here knows that

I DO NOT think the coil George pictured and asked about is one like old cars used as shown and explained in the pictures below, I DO NOT think it, his coil ALONE (His question asked about current when 6 volts was applied to the COIL) (NOT having one of the temp compensating resistors inside) operates the same as the old car coils with internal temp compensating resistors, although sure as temp increases even a modern coils regular wire windings resistance changes slightly NOT AS MUCH AS THE OLD CAR COIL BELOW WITH ITS TEMP COMPENSATION RESISTIOR INSIDE

REGARDLESS the CORRECT answer to what the current is with 6 volts applied to the COIL remains I = 6/R

Fun thread keep em coming neighbor George

I hope this helps explain things and answers the fun question !!!!!!!!!

Merry CHRISTmas

John T
cvphoto143042.jpg
 
> With respect, there is no modern coil with internal ballast or resistor. They are just designed to operate at 14.5 volts, or just over 7 volts, by increasing the number of turns in the primary. Just like a 12v or 6v fan motor. Jim

How do you know? Wouldn't increasing the number of turns change the coil's inductance?

I suspect they use smaller gauge wire in '12 volt' coils, but I've never cut one open to find out.
 
Mark,
The answer to my question is the current in a 6v coil can be anywhere from 3 to 6 amps. Which means the ballast resistance should match the coil's resistance if you want to have 6v applied to a 6v coil and 6v to the ballast. People guessing at the ballast resistor and not measuring the voltage and amps, will complain they don't make points like they used too.

The current in a coil will increase when the alternator kicks in. 12v can be over 14 volts. That will also be responsible for points burning out faster.

I would like to see an ohmmeter, a YT member owns, that can measure the exact resistance of a ballast and the resistance of a coil accurately to 1/100 of an ohm. I'll settle for 1/10 of an ohm accuracy. I don't have any such meter. I have to settle for measuring volts and amps.

BTW, I had to make 14g leads to accurately measure amps. The hair-like leads on my cheapie HF meters had enough resistance to mess with the current and voltage distribution.

The answer to my question is, there is no standard primary current.
 
> Which means the ballast resistance should match the coil's resistance if you want to have 6v applied to a 6v coil and 6v to the ballast.

Here's the deal, George: Coils don't operate on voltage, they operate on current. The energy stored in a coil is a function of the coil's inductance and current; voltage doesn't enter into the equation. Sure, if you know the resistance of the coil, you can calculate the steady-state current from the voltage, but the resistance probably isn't fixed and is likely to increase with temperature.
 
You should have let me get my meter out of the truck and do a little testing.

Running half speed is a head scratcher.

Only guessing, something inside the motor is causing excessive current and burned out the switch.

A motor has to come up to full speed to produce a reverse EMF or the motor will draw excessive current.

Only guessing, your start windings are not disconnecting which could be caused by the end switch welded shut.

If my small Cadillac has cargo space on my return trip from Fishing in Florida I may haul it back to Terre Haute and look at it.
It's not worth paying freight to have it shipped to me.

We'll have to come up with a way for me to look at it.

I wish we lived closer. It would be fun working on your round 2 it projects.

The cheapest penny pincher YTer I know wants me to put this motor back together. He couldn't figure out how to get the brushes out of the way.

cvphoto143064.jpg


Are you interested in another scout?

I saw one on my way to town. It's not for sale.
I could stop off and offer him a price he may not be able to refuse.
 
Mark,
You are absolutely right, coils need enough current to make a strong magnetic field.
However too much current will fry points and the coil.

If you recall a ballast resistor was used to limit current to the minimum current needed to make a spark at operation voltage, alternator voltage. A minimum of 13.6v and a max of 14+. not 12v.

The ballast was bypassed during cranking on my old cars that used points and condenser.

So the current, which is determined by the voltage applied to the coil, in the primary is not enough to start a tractor if the ballast is not bypassed when cranking.

Some people converting to 12v don't bypass the ballast. My jubilee has no place on the starter solenoid to bypass the ballast. I use a diode to bypass the ballast.

Some people give up on points and convert them to electronic ignition.
I feel it is all related to the wrong ballast, the wrong primary current.
 
> Some people converting to 12v don't bypass the ballast. My jubilee has no place on the starter solenoid to bypass the ballast. I use a diode to bypass the ballast.

Bypassing the ballast makes for a hotter spark, but most folks don't bother with the additional circuitry to do it.

> Some people give up on points and convert them to electronic ignition.
> I feel it is all related to the wrong ballast, the wrong primary current.

I feel the problem is poor quality ignition parts for old engines. Condensers that crap out in a matter of minutes, points that don't hold up. Switching my Ford over to Pertronix INSTANTLY solved my problems. I'll never switch back.
 
JohnT
Your answer is right and not realistic.

Who has an ohmmeter that can measure resistance precisely to 1/100 or an ohm or 1/10 or an ohm?

If you have a meter that is accurate to measure 1/100 of an ohm please let me know. I want one..
 
(quoted from post at 21:56:44 12/15/22) 315 Amps

John T
Click to expand...
t the instant you apply the voltage to the primary coil terminals, Geo, the current is ZERO! In the time following that instant, it rises exponentially until it reaches a steady state current limited by the coil primary winding resistance.
Like this, Geo:
3MebMGG.jpg


This post was edited by JMOR on 12/16/2022 at 06:44 am.
 
I'm cheap. I'm old school. I'm not converting.
I just want to make the old way work as it should.
Jubilee is retired. It's my boys when he moves out of a subdivision and can have a pole barn.
 
> If you have a meter that is accurate to measure 1/100 of an ohm please let me know. I want one..

Get out your wallet, George. 1 milliohm resolution, accuracy is 0.02 percent of full scale + 0.003 ohms.
Fluke 8808A
 
Your answer is right

THANKS George, Im glad I was able to help you and answered your question RIGHT

I WAS NOT ASKED NOR MADE ANY COMMENT ON REALITY OR PRATICAL LOL Post THAT question again and I will be glad to help !!!!!!!!

Merry CHRISTmas Good Neighbor

John T
 
I agree in EE school we referred to that time as T = 0+ at which time the current depends on if the load
was resistive or inductance or capacitance

Goerge did NOT ask nor get into that however, it was tricky enough as it was let alone if you add that in
the mix lol

Im sticking with the COIL current is I = V/R as correct

Take care Jessie, good info

John T
 
Who has an ohmmeter that can measure resistance precisely to 1/100 or an ohm or 1/10 or an ohm?

Unfortunately THAT WAS NOT PART OF YOUR ORIGINAL QUESTION lol You asked about current when 6 volts was applied to the COIL but did NOT give the coils resistance nor ask about ohm meter accuracy or anything else. Hey Im not blaming you its easy to leave out a part of a question were neither getting any younger neighbor lol

Take care George keep those fun questions coming just word them better next time may help IE ask what it is you want to know and give the resistance if you want to know the current..

Merry CHRISTmas good neighbor take care now best wishes

John T
 
Who has an ohmmeter that can measure resistance precisely to 1/100 or an ohm or 1/10 or an ohm?

Where I worked in the past (Navy) they were available

Hope this helps

John T
 
(quoted from post at 11:11:45 12/16/22) Who has an ohmmeter that can measure resistance precisely to 1/100 or an ohm or 1/10 or an ohm?

Where I worked in the past (Navy) they were available

Hope this helps

John T
Click to expand...
uch precision is not needed, most especially in any old machinery Geo has.
 
I just recently found on YouTube about voltage drop. I cant believe that I never knew this, could have used this a few times. Check motor age they explain about voltage drop.

Dennis
 
Mark,
Go back and see if I limited the meter one the average person my YT has
Using Ohm's law is worthless if you can't measure resistance with any degree of accuracy. It's better to calculate ohm. I think I'll make a simple electronic quiz to show people how to use the cheapie voltmeters and ammeters to calculate the resistance of a coil and ballast.

If I really get bored, I'll experiment to see what is the minimum coil current needed to make my Jubilee start and run properly. Remember the cranking voltage is less than 12v.
The running voltage is closer to 14v.

Just a brain fart. Can I use the meter people use to test the voltage of their electric fences to measure spark plug voltage?

My neighbor has an electric fence gismo..
 
George may just be on a suger high as he had a sweet roll type dinner at Cracker Barrel Wednesday. Good to see you again old freind. forgot to ask when you are leaving for Florida? You are going arent You? LOL
 
> Go back and see if I limited the meter one the average person my YT has

I don't think you did. But if you're serious about wanting an accurate multimeter, there are plenty of new and used lab multimeters available on eBay for a few hundred bucks; basically the price of a good new handheld DMM with true RMS capability. Here's one such multimeter: <a href=https://www.ebay.com/itm/165483740746>Refurbished Fluke 8840A</a>.

> Using Ohm's law is worthless if you can't measure resistance with any degree of accuracy. It's better to calculate ohm. I think I'll make a simple electronic quiz to show people how to use the cheapie voltmeters and ammeters to calculate the resistance of a coil and ballast.

The problem you're dealing with here is the resistance is not a fixed value. Measuring the resistance of either the coil or resistor with a multimeter will yield a different value than the resistance under full load.

> Just a brain fart. Can I use the meter people use to test the voltage of their electric fences to measure spark plug voltage?

I think the peak voltage of a typical electric fence is far less than the voltage of a typical ignition system. You can buy cheap spark testers at any auto parts store. Here's one: <a href=https://www.autozone.com/test-scan-and-specialty-tools/ignition-tester/p/oemtools-adjustable-ignition-spark-tester/10257_0_0>AutoZone spark tester</a>
 
January,
I have your motor assembled. Used toothpicks to hold the brushes in place. Had to solder on extension power wires. I used liquid rubber, instead of heat shrink.
I should know soon if the motor will work. You are still a penny pincher. Thanks for a good visit at cracker barrel.
 
(quoted from post at 08:22:01 12/17/22) &gt; Go back and see if I limited the meter one the average person my YT has

I don't think you did. But if you're serious about wanting an accurate multimeter, there are plenty of new and used lab multimeters available on eBay for a few hundred bucks; basically the price of a good new handheld DMM with true RMS capability. Here's one such multimeter: &lt;a href=https://www.ebay.com/itm/165483740746&gt;Refurbished Fluke 8840A&lt;/a&gt;.

&gt; Using Ohm's law is worthless if you can't measure resistance with any degree of accuracy. It's better to calculate ohm. I think I'll make a simple electronic quiz to show people how to use the cheapie voltmeters and ammeters to calculate the resistance of a coil and ballast.

The problem you're dealing with here is the resistance is not a fixed value. Measuring the resistance of either the coil or resistor with a multimeter will yield a different value than the resistance under full load.

&gt; Just a brain fart. Can I use the meter people use to test the voltage of their electric fences to measure spark plug voltage?

I think the peak voltage of a typical electric fence is far less than the voltage of a typical ignition system. You can buy cheap spark testers at any auto parts store. Here's one: &lt;a href=https://www.autozone.com/test-scan-and-specialty-tools/ignition-tester/p/oemtools-adjustable-ignition-spark-tester/10257_0_0&gt;AutoZone spark tester&lt;/a&gt;
Click to expand...
dditionally, the voltage for the duration of the spark is far less that the voltage it took to initiate the spark.
 
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