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Kai Klaas
12/19/05 10:43
Read: 733 times
Germany


 
Msg Score: +1
 +1 Informative
#105539 - Electrolytic, really?
Responding to: Farshid Jafari Harandi's previous message
Farhsid said:
There is a condenser (a .25uf Capacitor) with it's lead connected to the transistor and GND.

If the interrupter, whether mechanical or electronical, is suddenly opening, without this capacitor an enormous inductive kick voltage would develop. This would be deadly to the mechanical interrupter, because it would totally burn-down. Here the capacitor is needed to keep it alive.
With the transistorized ignition system, this capacitor is also needed, although there exists an additonal zener protection: In order to achieve a stable ignition voltage (35kV), which is created by the principle of induction, the duration of collapse of magnetic field must be very well controlled. The capacitance and inductance of primary winding of ignition coil form a characteristic time constant in order to produce a stable and well formed spark.


Farshid said:
They said placing the cap helps to make better sparks due to the LC characteristics which it makes and it also suppresses generated noises.

Imagine, that no capacitor was connected across interrupter. Then, rise time of potential change on this cable (between interrupter output and ignition coil) would be very high. This would cause the emission of extreme interference.


Farshid said:
By opening some of these Axial Capacitors I find out that this a Electrolytic Capaitor.There is no Voltage rating on the ones I've seen.I could guess they should be atleast 25V(Back EMF?).

Hmm. I don't think that this capacitor should be an electrolytic one. Electrolytics are highly unstable, especially at the high temperatures, that typically exist near the motor! More, they show a huge change of performance when temperature changes.
Also, typical transistor of a transistorized ignition system is protected by a zener barrier of about 320V and can withstand a collector emitter voltage of about 400V. So, nominal voltage of this capacitor should also be at least 400V.
I would use a polypropylen foil capacitor rated at 630V for this task. By the way, my car doesn't have this capacitor. It's already built-in, in the ignition modul.

Kai

List of 73 messages in thread
TopicAuthorDate
What do you guess it could be ?      Farshid Jafari Harandi      12/16/05 14:14      
   Van Der Graaff generator?      Andy Neil      12/16/05 14:27      
      Whimshurst      Farshid Jafari Harandi      12/16/05 19:08      
   Gas light      Steve M. Taylor      12/16/05 15:58      
   Sparking plug?      Kai Klaas      12/16/05 18:11      
      That's it !      Farshid Jafari Harandi      12/17/05 08:33      
         Very well dangerous...      Kai Klaas      12/18/05 07:26      
            Condenser      Farshid Jafari Harandi      12/18/05 08:45      
               Electrolytic, really?        Kai Klaas      12/19/05 10:43      
                  RE : Electrolytic, really?      Farshid Jafari Harandi      12/19/05 15:36      
                  Could my modifications be harmful ?      Farshid Jafari Harandi      12/21/05 05:41      
                     Capacitors      Steve M. Taylor      12/21/05 05:49      
                        it's always in my sight ;)      Farshid Jafari Harandi      12/21/05 09:21      
                     DCCS      Farshid Jafari Harandi      12/21/05 09:25      
                        So      Steve M. Taylor      12/21/05 10:34      
                           Specifications      Farshid Jafari Harandi      12/21/05 14:10      
                              dash      Steve M. Taylor      12/21/05 14:55      
                                 Box and remote starting      Farshid Jafari Harandi      12/21/05 22:10      
                                 Vacuum forming      Farshid Jafari Harandi      12/22/05 14:44      
                              Plastic Boxes      Jon Ledbetter      12/21/05 15:52      
                                 potting boxes      Farshid Jafari Harandi      12/21/05 22:16      
                                 Potting Boxes?      Farshid Jafari Harandi      12/22/05 14:43      
                                    Vacuum Forming      Jon Ledbetter      12/22/05 15:18      
                                       Thanks for the link      Farshid Jafari Harandi      12/22/05 15:31      
                                          Still need a nice "front"      Steve M. Taylor      12/22/05 16:52      
                                             Casing...      Farshid Jafari Harandi      12/23/05 04:56      
                                                display      Steve M. Taylor      12/23/05 09:38      
                                                   Hidden until light up      Farshid Jafari Harandi      12/23/05 11:10      
                                                      Visiting Tehran      Steve M. Taylor      12/23/05 11:17      
                                                         mail ?      Farshid Jafari Harandi      12/23/05 11:29      
                                    Laptop      Steve M. Taylor      12/23/05 03:11      
                                       Hmm...      Farshid Jafari Harandi      12/23/05 05:17      
                        Dash      Jon Ledbetter      12/21/05 10:53      
                           ...nor      Steve M. Taylor      12/21/05 11:08      
                           Covering is hard      Farshid Jafari Harandi      12/21/05 14:02      
                     Battery seems to be disconnected!      Kai Klaas      12/21/05 09:45      
                        blocking      Steve M. Taylor      12/21/05 10:37      
                        Electrical sytem      Farshid Jafari Harandi      12/21/05 14:01      
                           As I suspected...      Kai Klaas      12/22/05 07:46      
                              How to connect the second battery      Farshid Jafari Harandi      12/22/05 09:50      
                                 Err      Steve M. Taylor      12/22/05 10:22      
                                    Dual battery      Farshid Jafari Harandi      12/22/05 13:06      
                                       OOOPS      Steve M. Taylor      12/22/05 13:17      
                                 You could try this      Kai Klaas      12/22/05 18:31      
                                    RE :You could try this      Farshid Jafari Harandi      12/23/05 05:19      
                        Electrical sytem      Farshid Jafari Harandi      12/21/05 14:03      
            Neat trick      Steve M. Taylor      12/19/05 12:30      
               arcing cables      Terry Lingle      12/19/05 12:57      
                  no way      Steve M. Taylor      12/19/05 14:18      
                  Wow !      Farshid Jafari Harandi      12/19/05 15:38      
                     50,000 volts        Terry Lingle      12/19/05 22:49      
                     Switching techniques      Andy Neil      12/22/05 20:45      
                        Per Plug ?      Steve M. Taylor      12/23/05 03:10      
                           Sort of      Andy Neil      12/23/05 18:38      
                        New techniques      Farshid Jafari Harandi      12/23/05 04:55      
                           Current techniques      Andy Neil      12/23/05 18:44      
                              DC/DC Converter not dedicated coils      Farshid Jafari Harandi      12/23/05 20:54      
                           Ferrari 348      Kai Klaas      12/23/05 19:13      
                              Distributor-less      Farshid Jafari Harandi      12/23/05 20:54      
                                 Not quite      Kai Klaas      12/24/05 06:00      
                                    Look here      Kai Klaas      12/24/05 06:16      
                                       Coils      Farshid Jafari Harandi      12/25/05 01:28      
                                 Distributor-less      Andy Neil      12/24/05 06:16      
                                    Wear and tear      Kai Klaas      12/24/05 06:41      
                                       Amazing      Steve M. Taylor      12/24/05 11:58      
                                    Distributor      Farshid Jafari Harandi      12/25/05 01:28      
                                       Electrical field strengths would be huge      Kai Klaas      12/25/05 06:05      
                                          Big 'uns.      Steve M. Taylor      12/25/05 14:22      
                                             Interesting      Farshid Jafari Harandi      12/25/05 20:57      
                                                Hate to think      Steve M. Taylor      12/26/05 06:10      
                  Porosity of cables      Kai Klaas      12/21/05 09:19      
                     corona      Steve M. Taylor      12/21/05 13:54      
                        Ah, that's the right word.      Kai Klaas      12/22/05 07:14      

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