Hall Sensors dying on Holt 75

[michelko]

Hi,
i tried an old self made Transistor ignitiion with the same effect, so its sure the problem is not located in the ignition itself.

But i think i found a solution.

i moved the triggerwheel 0,4 mm away from the sensor and also used some heatglue to isolate the sensor. Donīt realy know why but that worked so far.
Ran the engine a couple of times for several minutes without frying the sensor.

Michael

[petertha]

Hi Michael. I've been following this thread. Glad you are making progress. Can you show some pictures or sketch of your trigger wheel & hall sensor proximity?
I'm curious about this stuff as I'm nearly ready to make a distributer based on design ideas from others once some more materials arrive. I want to try both a shutter wheel & magnet wheel on the bench first.

[michelko]

Hi Peter, of course. After my Ski Trip i will Post the Information

[michelko]

Here is a cut view of the Ignition system
You can see the triggerwheel with the small windows. The magnet is glued into the dizzy body

[petertha]

Thank for sketch to help me understand. Hopefully your issue is becoming resolved. I cannot offer anything constructive or useful as I'm just about to start on a bench test distributer myself. Both a magnet wheel style & shutter wheel style just for personal interest. In both cases, heavily leveraging on the work & help of others who graciously shared some details. I have a method to hold the hall effect sensor in what will probably be a plastic part, maybe 3DP. But that has more to do with it being a fiddly little thing to make in metal. I'm not really certain if plastic vs metal is better from electric/magnetic perspective. I did evaluate the V8 distributer dimensions provided by George Britnell in another post, hopefully he doesn't mind me including attached CAD renditions of his 2D PDF & of course he would be the expert to consult on that design. (Assuming I drew it right) this is his shutter window relative to magnet size. And I think I measured about 1.2mm between magnet & hall effect faces. His shutter wheel is very thin. A lot of 'stuff' packaged into that ~26mm OD distributer body to fire 8 cylinders.

Anyway, I didn't want to drift off your troubleshooting topic which is maybe completely unrelated to 'design', especially since you mention it has already been running. Thanks again! PT

[michelko]

After the small adjustments it is running fine. no more fried sensors so far.
Here are some pics from the trigger setup.

[petertha]

Thanks for the pictures. I've been working on a spreadsheet that calculates some ignition related parameters. I think I understand your shutter type disc/wheel configuration. I have a few questions:

- what is the shutter open window size & magnet diameter it is exposing. Just as an example, 4mm wide window exposing 3mm diameter magnet, 22mm wheel/disc diameter....
- do you have an estimate of your typical idle rpm & max rpm range?
- presumably the trigger wheel is made of steel? What is plate thickness?
- you mentioned you moved the trigger wheel to 0.4mm from sensor, what is the distance between magnet to sensor face?
- when you had difficulties before, do you recall if the engine was at sustained low speed? And now you are basically repeating the run & no further issues?
- does either the Chinese or the MBI module instructions/documents mention anything about a minimum or maximum dwell time?

I don't want to speculate on anything because I am complete novice to this ignition stuff, but just wondering about some things...

[michelko]

Hi Peter,
i attached a drawing of the trigger wheel made of mild steel
Idle rpm is about 900rpm, max not measured yet. I believe it would be around 4-5000 rpm.
Distance between Magnet and sensor is aprox 2,2mm, the magnet is a 3mm dia neodym.
No dokumentaion with the chinese ignition.  But they are firing at opening of the window while the transistor ignition is firing at closing.
Just like a kettering Ignition with points and capacitor

Greetings