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Re: Ignition circuit issue.

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Den tirsdag den 28. marts 2017 kl. 01.25.23 UTC+2 skrev Jim Thompson:
> On Sun, 26 Mar 2017 15:36:06 +1100, Sylvia Else
> <sylvia@not.at.this.address> wrote:
> 
> >I'm using this circuit to provide 250V pulses to an ignition coil.
> >
> >https://www.dropbox.com/s/1w33uss3eedem05/ignition2.pdf?dl=0
> >
> >The IC is a Linear Technology LT1243.
> >
> >12V is provided on G$1 to the left. G$2 accepts a trigger pulse, and G$3 
> >is ground.
> >
> >LTSpice says that this works, and indeed the real implementation does. 
> >Mostly.
> >
> >The difference is that after the circuit has been triggered once, it 
> >won't charge the capacitor again (above about 25 volts) for a varying 
> >period that can be up to half a minute. It's as if the wrong level is 
> >being used internally to compare with the feedback pin. In that regard, 
> >I'll mention that Q3 is used to pull FB up so that the circuit stops 
> >driving the FET, since otherwise the SCR never turns off. I've checked, 
> >and the problem is not that Q3 remains on, nor is it that the SCR fails 
> >to turn off. In any case, the 1.5uF capacitor C1 does get charged 
> >somewhat, as I mentioned above.
> >
> >When the issue resolves, it does so rapidly, within a fraction of a second.
> >
> >Connecting an oscilloscope probe to the RT/CT pin of the IC restores 
> >function, but only if the scope is set to DC coupling - not AC coupling 
> >- and functioning continues only as long as the probe remains connected 
> >- until the aforesaid varying period has elapsed. Touching the pin with 
> >a finger has a similar effect.
> >
> >That is, connect probe; works. Disconnect; stops working. Reconnect; 
> >works, etc. until eventually it starts working continuously.
> >
> >This cannot be capacitive loading - there's already a significant 
> >capacitance between RT/CT and ground.
> >
> >The fact that the coupling has to be DC made me think that some small 
> >current was flowing to ground through the scope, so I bridged C4 with a 
> >100K resistor. It didn't make any difference.
> >
> >I tried changing the IC (a pain, given that it's surface mounted), but 
> >again it made no difference.
> >
> >Any other ideas about what might be happening here.
> >
> >Sylvia.
> 
> Using a PIC when you should have gone analog >:-}
> 
> <http://www.analog-innovations.com/SED/CD-Ignition-Basic.pdf>
> 
> <http://www.analog-innovations.com/SED/CDI_Inductor.jpg>

why even bother with CDI? most car do fine with regular coils, many coils even have the driver igbt buildin all you need is a 5V driver for a few ms of 
dwell time  

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Thread

Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-26 15:36 +1100
  Re: Ignition circuit issue. John Larkin <jjlarkin@highlandtechnology.com> - 2017-03-25 22:33 -0700
    Re: Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-26 17:33 +1100
      Re: Ignition circuit issue. Larry Sheldon <lfsheldon@gmail.com> - 2017-03-27 00:54 -0500
        Re: Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-27 19:34 +1100
      Re: Ignition circuit issue. dagmargoodboat@yahoo.com - 2017-03-27 07:16 -0700
        Re: Ignition circuit issue. makolber@yahoo.com - 2017-03-27 09:18 -0700
        Re: Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-28 11:13 +1100
  Re: Ignition circuit issue. Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-03-27 16:25 -0700
    Re: Ignition circuit issue. Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-03-27 16:31 -0700
      Re: Ignition circuit issue. Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-03-27 16:36 -0700
      Re: Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-28 15:19 +1100
        Re: Ignition circuit issue. Neon John <no@never.com> - 2017-03-31 14:41 -0400
          Re: Ignition circuit issue. Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-03-31 11:55 -0700
    Re: Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-28 12:03 +1100
      Re: Ignition circuit issue. piglet <erichpwagner@hotmail.com> - 2017-03-28 08:39 +0100
        Re: Ignition circuit issue. Sylvia Else <sylvia@not.at.this.address> - 2017-03-28 20:54 +1100

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