Capacitor for pulse application

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Post Reply
Ken1
Posts: 121
Joined: Sat Dec 31, 2005 1:01 am
Location: Sandy Lake, Manitoba
Contact:

Capacitor for pulse application

Post by Ken1 » Sat Sep 15, 2012 7:08 pm

Hi, I would like a recommendation for the best type of capacitor to use in an application with low frequency pulses around 200v. The capacitor parallels a coil. Capacitance needed is 0.22uf.

Robert Reed
Posts: 2276
Joined: Wed Nov 24, 2004 1:01 am
Location: ASHTABULA,OHIO
Contact:

Re: Capacitor for pulse application

Post by Robert Reed » Sat Sep 15, 2012 8:27 pm

Oscillator , amplifier or filter? Is stability important? Is rise, fall time of pulse critical?

Ken1
Posts: 121
Joined: Sat Dec 31, 2005 1:01 am
Location: Sandy Lake, Manitoba
Contact:

Re: Capacitor for pulse application

Post by Ken1 » Sun Sep 16, 2012 11:19 am

The application is for an old magneto ignition on a tractor. The condenser is defective and I thought a cheaper and easier alternative would be a suitable capacitor instead of going to the auto parts store and asking for 1 each of all the condensers that they have in stock and testing them with my capacitor tester until I find one of the same capacitance. Also auto parts supply stores don't keep much inventory on hand for points and condenser ignitions anymore; they can order it for you but then you are stuck with it if it's not what you want.

Robert Reed
Posts: 2276
Joined: Wed Nov 24, 2004 1:01 am
Location: ASHTABULA,OHIO
Contact:

Re: Capacitor for pulse application

Post by Robert Reed » Sun Sep 16, 2012 5:27 pm

Doesn't look like you would need any special specs here. One thing of concern may be the temperature rating of the cap since it would be internal to the engine block ( at least all the mags I am familiar with). Maybe try standard power line filter type caps such as the "X" and "Y" type rated at 250 ac volts.If memory serves me, I think the old point ignitions used paper type caps.

User avatar
haklesup
Posts: 3040
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: Capacitor for pulse application

Post by haklesup » Thu Sep 20, 2012 6:13 pm

Don't use plain wet electrolytic types. I think mylar or polyester film types might be a good choice being more temperature resistant. Low ESR is not important, you want something high relibility with heat and vibration and tolerance is probably not critical.

http://en.wikipedia.org/wiki/Types_of_capacitor
Wiki does a decent job summarizing major properties. Use the digikey catalog online and the search tool to further refine the search based on price and specs.

User avatar
dacflyer
Posts: 4549
Joined: Fri Feb 08, 2002 1:01 am
Location: USA / North Carolina / Fayetteville
Contact:

Re: Capacitor for pulse application

Post by dacflyer » Sat Sep 22, 2012 6:04 pm

i have substituted condensers in ignition systems many times. i have not seen any critical differences.
usually they all work.. their main job is to keep the points from burning up so fast.
you can really see a difference with the spark at the points as they open up.. with and with out the condenser.
if you really want a capacitor make sure it is able to take the heat. and i believe they may be non-polarized type

User avatar
Janitor Tzap
Posts: 1510
Joined: Sat Aug 12, 2006 5:17 pm
Contact:

Re: Capacitor for pulse application

Post by Janitor Tzap » Sun Sep 23, 2012 7:59 pm

I hate to throw a wrench into the works......
But have you checked on a Sold state ignition system?

I've seen kits for old cars, that either replaced the old distributor for the new one with the sensing unit built in to it.
Or on some, the only thing you did was pull out the old points and condenser,
and put in the sensor pickup for the new electronic ignition system.

Are you planning on holding on too this tractor for a while?
Yes?
Then consider upgrading it to a electronic ignition system.

Just my 2 cents...


Signed: Janitor Tzap

Ken1
Posts: 121
Joined: Sat Dec 31, 2005 1:01 am
Location: Sandy Lake, Manitoba
Contact:

Re: Capacitor for pulse application

Post by Ken1 » Tue Sep 25, 2012 6:14 pm

Hi, Thanks for all of your replies! I was not aware that it was possible to put in a solid state ignition; I will keep that in mind. As for now I will keep it points and condenser. I replaced the condenser with a capacitor and will leave it that way unless the capacitor fails, then I will probably go with another automotive condenser. I do intend to keep the tractor for a long time. I needed another condenser as the tractor stalled and would not run or start up; now it works great.

Post Reply

Who is online

Users browsing this forum: Google [Bot] and 37 guests