Condenser/ Capacitor

[Jim in LA]

In early "tube" or Fleming valve) Devices they were called condensers. I remember them as that name. Jim

I believe the early printing of The Electronics Communications Handbook used the term "capacitor and later printings used "capacitor which is the term I prefer for electronics troubleshooting and theory.

 

[Jim in LA]

JC Whitney - Auto Parts and Car Culture

Explore JC Whitney for premium auto parts & accessories, dive into car culture, & stay updated with the latest automotive events & tech trends

www.jcwhitney.com

I still have a couple of their motorcycle and ATV catalogs. I bought quite a few parts from them in the mid seventies. Chrome shorty motorcycle mufflers for $8.99 ea. Now they are like $50.00 ea.

 

[wore out]

Jim you are right. I'm suffering from Old timers. Brain Fog.

www.jalopyjournal.com › forum › threadsHot Rods Coil Condenser..???? what is it?? - The Jalopy Journal​

Oct 17, 2018 · Noise suppression (capacitors) for RFI are installed on the + side of the coil to ground.

To be more accurate they should have written "Noise suppression (capacitors) for RFI are installed on the side of the coil that receives power from the ignition switch, with the other side connected to ground.

That would take into account that some electrical systems of the points era were (+) ground and some were (-) ground

 

[Jim in LA]

As the coil magnetic saturation collapses, the magnetic force passes through both the primary windings, and the secondary (where the high voltage is produced). At the instant the points break open, the ~4 am circuit is shut off, but in reality the voltage still tries to cross the increasing gap. The condenser (at that moment is not charged at all, and the voltage pushes into that "reservoir" limiting the arcing at the points. the coil magnetism is still collapsing and produces much higher voltage in the form of high frequency ac of 350 volts Peak to peak. This is also absorbed and reflected by the condenser as the coil magnetism is spent across the spark plug and the resistance in the wires/components. This is called "ringing".
In an AC electric motor the purpose of the capacitors is to modify the AC input phase in the starting windings this causes far greater starting torque from stopped and is a short term issue designed to be taken out of that circuit with a governed switch. The phase change issue is something to look up rather than spend a page of writing. The running capacitors on some motors also modify phase relationships increasing the efficiency of the design. Those are intended to stay in the circuit without heating. Jim

I have a device for "ringing" flyback transformers that surprisingly was still available in 2001. It uses an LED scale, The use of oscilloscope and signal generator is more accurate. I remember EICO made a flyback ringer, don't know if Heathkit did. Those companies made it easier for "just out of school" techs to do their jobs. I always wante to buy Sencore test equipment but could never afford it and by the time I was making decent money, The personal computer age and digital tech were taking over and the TV/radio repair field was disappearing.

 

[will-max dairy]

To be more accurate they should have written "Noise suppression (capacitors) for RFI are installed on the side of the coil that receives power from the ignition switch, with the other side connected to ground.

That would take into account that some electrical systems of the points era were (+) ground and some were (-) ground

these 56 words are worth my three pictures that I attempted to sketch to explain this point... and might be easier to understand than the sketches... lol

 

[olddavid]

I mean... like I said... I'm no ignition aficionado... but I'm willing to take some pointers to make the model better...

But, it would seem that there are different flavors. Some with where the power source is common to the primary and secondary. Others where the points and condenser is the common node with primary and secondary, similar to the previous diagram... and as shown here:

I'm not an expert either but that's what my Ferguson TE-20 manual shows. Others may do it differently.

 

[wore out]

I have a device for "ringing" flyback transformers that surprisingly was still available in 2001. It uses an LED scale, The use of oscilloscope and signal generator is more accurate. I remember EICO made a flyback ringer, don't know if Heathkit did. Those companies made it easier for "just out of school" techs to do their jobs. I always wante to buy Sencore test equipment but could never afford it and by the time I was making decent money, The personal computer age and digital tech were taking over and the TV/radio repair field was disappearing.

If you have an ignition 'scope (I do) you can look over the waveform from when the points open, through the "burn time" during which the spark at the sparkplug lingers, and then observe the length of time that the the coil oscillations linger (ringing), a period of time that involves the coil and condenser.

GOOGLE will show you lots of info on ignition system waveforms, however, they differ between conventional and EI systems in the area where the points close and dwell time.

For detailed info and interpretation of points system waveforms one can find an old copy of a 'scope informational booklet from the points era.

 

[Texasmark]

Two of the first things we learned in DC Circuits 101 is that current through an inductor can't change instantly, nor can voltage across a capacitor change instantly. When the points open, the current through the coil primary wants to keep flowing through the open points, so it the coil will generate enough voltage to jump across the point gap, UNLESS the current has another path to take. The condensor provides that alternate path, reducing arcing and preventing the points from burning out. And, as you say, since the coil and condensor form an RLC circuit, you get an alternating current pulse, such that the spark at the plug is actually AC.

On the aircraft weapons systems I used to work on, every relay (and there were hundreds) had a diode wired across its coil to supress the coil's inductive kickback. The diode would be reverse-biased when the relay was energized, but would briefly become forward-biased when power to the coil was interrupted, protecting whatever device powered the relay.

The problem with a reverse diode is that the reverse voltage is clamped to the diode forward voltage drop, usuaally half a volt or slightly higher in high current circuits. For a given amount of energy to be dissipated, the lower the voltage in the clamp, the longer it takes to dissipate the energy. In high PRF radars, a voltage dependent resistor rather than a reverse diode, allowing for a higher clamp voltage reduces the time to dissipate the spike worked better.

 

[Texasmark]

You've used this part in an automotive ignition system?

I agree it's hard to find a reliable automotive condenser these days; substituting an industrial-grade capacitor seems like a good solution.

My most reliable capactors were mica, hard plastic encapulated. Problem with mica is that you don't roll up a lot of layers of plates so for a given value of capacitance, they were big.....but voltage ratings of 500 to 1kV were easy to come by and they were rugged and hard to destroy.....unlike paper/plastic..

 

[Texasmark]

I would expect it to continue to run ,a bad condenser mostly burns to open,not to short.

My experience with paper or plastic insulated, rolled up capacitors is unsuspecting spikes in the voltage the cap. is trying to shunt that punch through the insulation, leaving burned metallic/conductive residue and once that happens you have a shorted capacitor....size and ohmic value of punch through determines amount of degredation. Open circuits require a disconnect between the leads and the foils and there is a lot of surface area there for contact and that is not a common problem

 

[Texasmark]

Just wondering what is the MDF of mag or auto condenser?
Isn't the job of the condenser to provide an AC current path from one side of the coil to ground? The spark will be a few AC waves. It's not a DC spark
I can't get my head around how a condenser saves the points. There will always be a spark when the points open and turn off the 4-5 amp primary current off.
If a condenser saves the points, a switch, Would a condenser save the contacts on a water pump switch or air compressor switch?
Please keep your answer simple so a first grader like me can understand.

The capacitor and the inductor (coil) form a resonant circuit.....sim wt. The frequency of that oscillation is specified to be low enough to keep the break in coil current that would (attempt to occur...V=Ldi/dt) otherwise slow that the rate of rise of voltage across the points occurs at a lower frequency that that at which the points would experience a sharp rate of rise causing a spark.

If the C is too small it doesn't prevent the arc. If too large it limits the max RPM of the engine.

 

[Texasmark]

Generally (not perfect or exact) if an automotive condenser is weak, open, or too small in rating, you might still get a spark albeit weaker snd points burn sooner,,,, However if way too big you may not get a spark at all and if dead shorted no spark at all

An analog ohm meter can help indicate if a condenser is totally bad like open or shorted (old kick back test) however it can’t show if it’s good or it’s rating like a true capacitor tester

A friend that runs a mag shop told me over half new condensors he buys are bad ir out of spec

Some condensors were used to reduce radio interference had nothing to do with ignition.

John T

John, for a rolled up capacitor to get weak, the only thing I can think of is that it wasn't a sealed unit and something (moisture) leaked into the dielectric and reduced it's dielectric resistance. Possibly a small spike punch through could reduce the capacitance of an otherwise good cap. and allow it to still function.

Being a power co. guy you are probably familiar with oil soaked paper as a dielectric.

 

[Texasmark]

Just wondering what is the MDF of mag or auto condenser?
Isn't the job of the condenser to provide an AC current path from one side of the coil to ground? The spark will be a few AC waves. It's not a DC spark
I can't get my head around how a condenser saves the points. There will always be a spark when the points open and turn off the 4-5 amp primary current off.
If a condenser saves the points, a switch, Would a condenser save the contacts on a water pump switch or air compressor switch?
Please keep your answer simple so a first grader like me can understand.

Since you have a capacitance and an inductance you have an AC circuit.....sine wt based on the value of both components in series.

 

[Geo-TH,In]

Since you have a capacitance and an inductance you have an AC circuit.....sine wt based on the value of both components in series.

I recall in my college E&M class the frequency of an LC circuit can be calculate.
There is a formula for calculating the frequency of resonance in a tank circuit( series and parallel tank) have different formulas
That frequency is created by the L and C values inside the coil.
Sun equipment made an oscilloscope so you could look at the resonance frequency.
The condenser provides an AC path for the - of the tank circuit (the coil's -) to connects to the metal frame and the other end of the tank circuit connects to the spark plug.
The coil is a special coil. I forget the technique name of the coil.
I also forgot if the coil is a series or parallel LC tank circuit.
I think it was series tank.
It been a lifetime ago since I was in college

 

[Bobnall]

Mark,
It's been a lifetime ago we had cars with points and condensers. Some time in the Early 70's cars went with electronic ignition and electronics voltage regulators. I recall converting my old mechanical regulator, one with relays, to an electronic voltage regulator.
I may be wrong, but I recall some places sold large condensers that were too big to fit next to the points. You mounted them next to the coil.
Some claimed the larger than normal condenser shortened the life of the points. I replaced condensers annually when I replaced points. I don't recall having a bad condenser back in the day. I had a Cub cadet lawn mower and never replaced the condenser.
Again that was a lifetime ago. Of course my long term memory is better than my short term memory. I open the Refrigerator door and have to ask myself, "Why did I opened the refrigerator door?"
I bet no one has that problem!

The main job of the condenser is to squelch the spark at the points. It speeds up the field collapse in the coil and lengthens the life of the points!

 

[Janicholson]

Jim; I keep saying there is more coming out of a coil than you put into it. In a round about way, you said the same thing!

Nope. Jim

 

[John T]

Mark,
It's been a lifetime ago we had cars with points and condensers. Some time in the Early 70's cars went with electronic ignition and electronics voltage regulators. I recall converting my old mechanical regulator, one with relays, to an electronic voltage regulator.
I may be wrong, but I recall some places sold large condensers that were too big to fit next to the points. You mounted them next to the coil.
Some claimed the larger than normal condenser shortened the life of the points. I replaced condensers annually when I replaced points. I don't recall having a bad condenser back in the day. I had a Cub cadet lawn mower and never replaced the condenser.
Again that was a lifetime ago. Of course my long term memory is better than my short term memory. I open the Refrigerator door and have to ask myself, "Why did I opened the refrigerator door?"
I bet no one has that problem!

Mornin good neighbor as an fyi

If I best recall no warranty if the capacitor were too big (to many farads) ) the coil might not fire but if to small still get fire but points burn quick. Sometimes external condensors were rigged yo reduce radio interference not the same thing as ignition condensors. Ie. Too small of condensor shortens point life whike too big saves points but subject to size harms spark

A mag builder told me nearly half the new condensors he buys are out of spec

Kettering ignition can take a book to explain no way im going to try and explain it here for non sparkies I’m still not up to it in my condition grrrr

John T

 

[John T]

Hypothetically ,if the ignition condenser failed and a good condenser was connected at coil WITHOUT disconnecting old condenser, would ignition perform normal?

A total shorted condensor yields no spark. A total open still gives spark but points burn quickly

John T

 

[John T]

I would expect it to continue to run ,a bad condenser mostly burns to open,not to short.

In years of messing with them I saw many that still worked sort of but had less capacitance due to internal shorts causing points too burn sooner. Not as many I saw were total open but sure anything’s possible

John T

 

[John T]

Just wondering what is the MDF of mag or auto condenser?
Isn't the job of the condenser to provide an AC current path from one side of the coil to ground? The spark will be a few AC waves. It's not a DC spark
I can't get my head around how a condenser saves the points. There will always be a spark when the points open and turn off the 4-5 amp primary current off.
If a condenser saves the points, a switch, Would a condenser save the contacts on a water pump switch or air compressor switch?
Please keep your answer simple so a first grader like me can understand.

George. For sure the condensor extends point life but I don’t feel like trying to explain it but many other fine gents can I trust

John T. Still not up to par grrr