Condenser/ Capacitor

[Brownie450]

GEO's question about the pressure switch contacts
is a good one. Pressure switches usually switch
alternating current [AC]. On AC, the voltage falls to
zero 60 times per second. With DC the voltage doesn't.
Thus not as much arcing on AC.
Jim

 

[Jim.ME]

Jim.
I enlarged your diagram. My eyesight is a little fuzzy. I think you just proved the condenser is in parallel with the noise suppressor. They are connected with the black wire

There is no noise suppressor in the wiring diagram I posted. It shows the ignition condenser hooked to the negative coil terminal the same as the points.

 

[Geo-TH,In]

GEO's question about the pressure switch contacts
is a good one. Pressure switches usually switch
alternating current [AC]. On AC, the voltage falls to
zero 60 times per second. With DC the voltage doesn't.
Thus not as much arcing on AC.
Jim

What you say is true, zero voltage 120 times a second and 60 times a second + 155 peak volts and another 60 times a second -155 peak volts and the current is many times more on a pump vs 4 amps on a coil.

I know what happens without a condenser. In 5 miles the points on my motorcycle were toast.
I wonder how many people think they can't buy good points anymore when perhaps the condenser isn't good or too small?

 

[Geo-TH,In]

There is no noise suppressor in the wiring diagram I posted. It shows the ignition condenser hooked to the negative coil terminal the same as the points.

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.

 

[Jim.ME]

This diagram does show noise suppressor is on the +12v.
I have seen some people add the noise suppressors to the + of the coil.

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.

There is no noise suppressor in the drawing of the Kohler ignition I posted in post # 38, replying to you posting (#35) the condenser of your Cub Cadet was hooked to the + side of the coil. The condenser for points on those Kohler engines was located outside of the points cover and was wired to the same coil terminal as the points.

You are now posting a link to an article to tell me, what I told you back in post #8.

 

[Geo-TH,In]

There is no noise suppressor in the drawing of the Kohler ignition I posted in post # 38, replying to you posting (#35) the condenser of your Cub Cadet was hooked to the + side of the coil. The condenser for points on those Kohler engines was located outside of the points cover and was wired to the same coil terminal as the points.

You are now posting a link to an article to tell me, what I told you back in post #8.

Jim
I did edit my last post the same time you were replying to mine/
"Jim you are right. I'm suffering from Old timers. Brain Fog."
I got my wires crossed.
Sorry

 

[John T]

"Illustrated parts Guides" put out by various parts manufacturers such as Standard, Echlin, etc. list the values of SOME (but not all) condensers by part number.

Note that this diagram is for a (+) ground system, reverse the legends for a (-) ground system.

(From John Deere FOS-20.)

As always great info Good Post. I use that same picture when I gave seminars at tractor shows even if most have no clue lol
John T

 

[Texasmark]

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

Well its a matter of V=Ldi/dt. The cap just sucks up that V (energy) slowing the rate of rise below the arc point while the secondary rises to the arc over voltage of the plug, completing the circuit for dissipating the energy stored in the coil.

 

[olddavid]

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.

And in some cases, in industry there were RC snubbers across the contacts. RC snubbers are series resistor and capacitor networks designed to reduce arcing across the contacts of AC switches and relays.

 

[wore out]

Simplified circuit. Now... given what you're saying about a condenser wired to "+" inside of the coil... I don't know... the position of the points and condenser could be switched relative to the coil primary. But either way, the noise suppressor (C_Noise) would go across the whole shebang.

There are some true aficionados of old school ignition that may be able to point out some details I'm missing here... but it's the general gist of things.

The "Coil" would be L_Primary and L_Secondary... in the diagram...

For "positive ground" systems, you could just switch power and ground in the diagram on the primary side.

will, that diagram would be WRONG for most common Kettering ignition systems, as it shows the "low" end of the secondary winding GROUNDED vs. being connected to the coil primary.

What was the source of that (incorrect) diagram, please?

 

[MarkB_MI]

will, that diagram would be WRONG for most common Kettering ignition systems, as it shows the "low" end of the secondary winding GROUNDED vs. being connected to the coil primary.

What was the source of that (incorrect) diagram, please?

will, that diagram would be WRONG for most common Kettering ignition systems, as it shows the "low" end of the secondary winding GROUNDED vs. being connected to the coil primary.

Whether or not the secondary winding is connected directly to ground isn't that important. The primary resistance and inductance are so low compared to the secondary that the primary winding pretty much looks like ground.

 

[olddavid]

Whether or not the secondary winding is connected directly to ground isn't that important. The primary resistance and inductance are so low compared to the secondary that the primary winding pretty much looks like ground.

I agree, but technically it is an auto transformer unlike the picture shows. I'm not saying a separated primary/secondary coil wouldn't work and maybe has in some cases but I am not aware of any.

 

[wore out]

Whether or not the secondary winding is connected directly to ground isn't that important. The primary resistance and inductance are so low compared to the secondary that the primary winding pretty much looks like ground.

Whether or not it's "important", WHY not use a diagram that pertains to the vast majority of systems being discussed here?

 

[da.bees]

No conversation would be complete without mentioning ac motor capacitors zapping unsuspecting repairmen and pranksters charging condensers then placing them where victims pick them up and receive a surprise.

Then there were repairmen who paid no mind to getting oil on their skin and clothes from exploded capacitors before dangers of PCBs were understood.

 

[Janicholson]

will, that diagram would be WRONG for most common Kettering ignition systems, as it shows the "low" end of the secondary winding GROUNDED vs. being connected to the coil primary.

What was the source of that (incorrect) diagram, please?

Agree, the secondary winding is connected (as an autotransformer would be) to the primary providing a circuit to ground through the cap/rotor/wires/plugs, and a path to the battery and points the other way. the secondary is grounded intermittently by the points and rings into the condenser and finds positiveness in the battery. Jim

 

[will-max dairy]

will, that diagram would be WRONG for most common Kettering ignition systems, as it shows the "low" end of the secondary winding GROUNDED vs. being connected to the coil primary.

What was the source of that (incorrect) diagram, please?

I just drew it. I drew it like a flyback; which is more familiar to me.

As has been mentioned, rigorously many ignitions are an "auto transformer" with a connection from the primary to secondary, as you state.

The voltage from this point to ground is, as also has been mentioned, so low compared to the secondary, that, for modeling purposes (which... my schematic is a model, not necessarily a connection diagram) it's essentially ground.

Here is a new diagram as an autotransformer for comparison.

Feel free to critique, it could be made better.

 

[will-max dairy]

And in some cases, in industry there were RC snubbers across the contacts. RC snubbers are series resistor and capacitor networks designed to reduce arcing across the contacts of AC switches and relays.

It would be interesting to look inside of a solid state replacement ignition that (probably) uses a transistor, as opposed to points. They may have a snubber-type circuit across the transistor, as opposed to a simple condenser (capacitor). Snubber design for transistor switches can be complicated.

 

[teddy52food]

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

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!

 

[olddavid]

Here is a new diagram as an autotransformer for comparison.

Feel free to critique, it could be made better.

Keep trying. Break the connection of the lower secondary wire and move it up to the top of the primary coil and I think you will have it. The junction of the two coils receives the ignition voltage with the other primary wire going to ground through the points. It is a bit confusing.

 

[will-max dairy]

Keep trying. Break the connection of the lower secondary wire and move it up to the top of the primary coil and I think you will have it. The junction of the two coils receives the ignition voltage with the other primary wire going to ground through the points. It is a bit confusing.

interesting...

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:

Ignition coil polarity

But... it's easy enough to draw what you're describing.

At this point, this isn't a matter of me being "confused"... it's just a matter of... there are many flavors of ignition and coil I've drawn a few possible forms... I'm sure that there are many others.

I should add... in none of the forms, that I know of, would the noise suppressor cap be across the points and condenser. It would be "further out" in the circuit, with broader coverage, usually encompassing the entire primary side.

Noise suppression on the spark plug side is usually done by putting some form of resistance in the spark plugs to "dampen" ringing and such. Or, the plug wire design can be modified to try to contain more of the energy, as opposed to radiating it.

I've done quite a bit of design work in electrical and switching noise suppression...zero in ignition itself, other than fixing ignitions on old tractors and cars.