Hall Ignition Problem

[bobden72]

Hi all I have completed a Hoglet fitted with single Hall sensor that is triggered by two magnets, and using the lost spark system. The Hogletl is as per the drawings and the gear to which the magnets are fitted is of brass. My problem is I can turn the engine over by hand to set the timing etc and all works fine. I have connected the two plugs to the ignition unit with the shell of the plugs joined together and earthed to the ignition system. Activating the Hall sensor I get a brilliant spark on both plugs as expected. When I then fit the plugs to the engine and bond the engine to the ignition system, I have checked the bonding with an Avo and all is correct. When I then use the starter motor to turn the engine over to start it, after about 10 seconds the ignition system stops working and I find that the Hall sensor has blown. Now the only way this can happen is for the HT voltage to somehow be destroying the sensor. But How as everything is Bonded !!!
Anyone have a answer.

 

[stevehuckss396]

Hard to say without a drawing of what you did. Can you post a Jpg of the circuit?

 

[gbritnell]

Mainly the only time I have ever blown Hall sensors is because I had a poor ground or my ground wire fell off the engine while running. That's not to say that I haven't had a few head scratchers along the way but generally it's the ground. I use both the Jerry Howell and S&S ignitions and with both of them you need the 3 wires from the Hall sensor, positive, negative and sensor. Along with these you need a separate ground wire. You can't rely on the negative wire from the sensor otherwise it will burn out the Hall.
As Steve mentioned I would help if we could see exactly what your hookup looks like.
gbritnell

 

[michael-au]

All the problems I had with hall sensors being the earth

 

[fourstroke]

I had exactly the same problems as you and the cause was the hall sensor itself
Not all sensors are capable of withstanding the conditions
Once I changed to OHO90U all my burnt out sensor problems dissapeared. These sensors are not available here in Scotland and have to be imported from the US
What sensor are you using?
Dougie

 

[bobden72]

Here is the circuit, I believe its a grounding problem but what. It works on my other engines.

 

[bobden72]

Yep all wired as you say plus the extra ground wire. See the diagram I have uploaded.

 

[bobden72]

Now thats a thought, have you contact detail for the replacement sensors you used. The ones I am using are 3144 441.

 

[fourstroke]

try farnell or mouser,
http://uk.mouser.com/ProductDetail/Optek-TT-Electronics/OH090U/?qs=MYMjFsmMg9Zxhz344sS0jg==
these sensors are very robust
Dougie

 

[bobden72]

Dougie, thanks for your input I am now using Hall sensors 451s ogl as supplied by Minimag in the Isle of Wight. The problem has now gone, phew had my head spinning for a moment.
Thanks again for your helpful input.
Regards Bob