Tuesday, October 30, 2012

Peter Visick's Farmboy (and ignition problem)

I got the following e-mail from Peter on Oct 30, 2012:


Hi Allen

Finally, except for the inlet v/v spring, for which I forgot to order some wire, the Farm Boy is complete; photos attached.

However I have a problem. The ignition light stays on permanently and I am not getting a spark. Possible reasons; the Hall sensor gives me a  circuit between 2 and one of the other leads. Is that correct or have I damaged the Hall sensor?

They say we are two countries divided by a common language. Having dropped the magnet and having to sort out which side was north and which south, I wonder if we speak the same way about magnets. Does your south attract or repel the north on a compass?

Finaly could it be my coil wiring. The coil I had was produced by Mini Mag in the UK. It has one lead (yellow0 which they say should go to the pos on the battery; I put it to coil + on your pcb; the black lead, the neg to the coil - on the pcb, with the HT to the plug. Is that correct?
If the Hall is damaged could you give me its ref no or technical details as it probably makes more sense to  get one over here.

All in all good fun to build. You dimension things differently to us, even from when we worked in imperial, so everything had to be converted to metric and rounded up or down with threads to the nearest metric or BA. In any future models I would stick with BA, much smaller changes in dimension.

Look forward to hearing from you and I am sorry about the J class yachts in the photos.




Hello Peter,

Thanks for the e-mail and the pics!  I will get these posted on our User Forum in the Farmboy section sometime today or tomorrow.  Looks great!

Regarding all technical questions, please see the following link:


With that being said, I will try to answer some of your questions.  If the red LED stays on, then there is a problem with the hall sensor or one of the other transistors on the board.  Start by replacing the hall sensor.  The one you have should have the identifying numbers on it if you want to try to get it locally, otherwise, we sell them for $2.50 each.  Many builders purchase add'l sensors, as they will burn out easily if you do not have everything solidly grounded while testing and operating.

Regarding the polarity of the magnet provided, I use a small bar magnet that is labeled N and S on each respective end.  I have checked it's polarity with some of Dad's original kits to make sure it is polarized properly. It is, HOWEVER, I do sometimes make mistakes and still tape them on the instructions in the wrong direction (seldom, but it happens).  Buy a good quality bar magnet at a local toy or hobby store to check the ignition magnet polarity, or simply reverse it when you test if it doesn't trigger the LED on the ignition module.

If the ignition LED has been staying on, then I doubt the problem is with your coil, however, the coil could have been damaged if it ever got too hot, as it seems the ignition module may have kept it energized if the LED never went out.

Sorry about the unit of measure differences, but us Yankees simply adapted what the homeland has been using for hundreds of years (English Units).  You guys changed - not us!    ;)



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