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Allegro Hall Effect sensor For electronic ignition.

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m5aky

New Member
Hi
I've been looking into experimenting with a pic based electronic ignition system.
One which has been mentioned on this forum (Gompy) uses the Allegro 3141 sensor.
Can anyone tell me if this is still available? I've searched but can't find anyone that sells it.
Possibly it's obsolete and there is a modern equivalent.
Also the IGBT SKP15N60 doesn't appear to be too common. Would anyone know of a substitute for that?
Regards
Don, m5aky
Bristol UK
 
Thanks for the replies.
I'll look into the availability of those items in the UK.
As you say any unipolar Hall effect device will work as an experiment but finding one for the particular environment is the concern.
Don m5aky
 
Hi. It's taken a while to get round to it but I am progressing with my experiment with electronic ignition.
Just built up the circuit here:
http://www.electronics.gompy.net/cdi/index.html
Just got it working.
For the moment I am driving it with a 555 timer circuit that can vary the frequency and duty cycle until I sort out the distributor and sensor arrangement.
Well it all appears to work and I can see pulses coming out of the output to drive an IGBT.
I've got an rs232 to ttl interface but so far can see no response from the monitoring program.
Gompy gives no contact details so I assume he is a busy person and unable to offer support.
Has anyone built this system or can give any tips at all?
Any help most appreciated.
Regards
Don m5aky
 
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Most of the CDI discussion on RC Universe has moved to this thread by Jake Stewart (jakestew):

**broken link removed**

That ignition used a PIC 12F683. Because of some problems in posting and in posting various file formats on RC Universe, a branch from that discussion was started on RC Groups. That version uses the PIC 12F1840.

https://www.rcgroups.com/forums/showthread.php?t=1781959

As usual, CDI threads get quite long, and those threads are no exception. Eventually, maybe quite soon, Jake will post a summary. He has already done that for the 12F683 and a link to it is in the first link given above.

John
 
Hi John.
Thanks for those links. Lots of more ideas there.
In the meantime a bit of checking revealed a couple of errors in the stripboard connections and all seems to be ok with the program now.
Can see the revcounter and angle indicating ok and can load the curves to the PIC.
Just have to sort out the sensor and the drive to the coil.
Should be able to get a spark soon if only on the bench.
Regards
Don, m5aky.
Bristol UK
 
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Hi
Made a bit more progress.
Using a islv9v3036s igbt I connected a coil and spark plug last night.
I get a few sparks and then it stops. Looks like a spike caused by the inductance of the coil is upsetting the PIC.
If I bypass the PIC and drive the IGBT direct from the 555 timer circuit I get a good spark.
Any advice would be most welcome.
Don
 
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Please post your circuit here.

You will note that many of the more developed circuits presented in the above links use optical isolation. It doesn't take much kick from a coil to kill a PIC.

John
 
There is a lot to read on the links. I haven't got very far yet but hope to get a bit more time to go through them.
This is the circuit I am using. This is a starting point for me.
**broken link removed**.
Regards
Don
 
Here is another Gompy design:

Schematic Timer B board.jpg

OC1 is the part of interest. You can see how it would just drop into the circuit you are using. It is in the RC Groups link given above. Please confirm you are using Q2 to fire the IGBT and not trying to do it directly with the PIC.

Finally, there can be lots of electrical noise in these ignitions. Be sure the PIC is adequately decoupled with capacitors. Do you have a scope to probe around with?

John
 
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Thanks for the reply.
I am using Q2 and do have a scope.
I was looking into the opto coupler and as you say should fit in with no problem.
Is there a link to more info on that version ot the timer board. Haven't come across it yet.
Don
 
A problem I have had in following the threads on this subject is the relative lack of rigor in documenting who is using what. Starting with Gompy's (aka BigBoat) thread years ago, I have followed each thread on and off, and I have made a few devices myself.

IMHO, Jake Stewart has done a great job in trying to instill some consistency. He started the RC Universe thread as a "summary," but it soon mushroomed. Still, that first post is a useful beginning. Because of problems in posting programming on RC Universe, he started a separate site. That site is well organized, periodically updated, and most important, there is only one version. However, it does not include much on the hardware. Here is the link:

**broken link removed**

As for the hardware, at this time, it seems there is still a lot of variability. The first few posts in this thread for the 12F1840 give good links, including the one from Gompy that I posted above.

http://www.rcgroups.com/forums/showthread.php?t=1781959

If you go to the end of the thread, you will find some impressive work by Gompy: 4 HP @ 14,000 rpm from 25.4 cc.

In sum, if you are using some sort of PIC control for timing, that has been well handled by Jake. Using the optocoupler may solve the problem with destroying PIC's. As for creating the high voltage (i.e., the 250 to 400 volts for the ignition coil), I would recommend one of the designs using a transistor oscillator. People have tried to use a PIC or 555 to drive a switching transistor(s) with limited success.

John
 
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