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Please review design and error of electronic ignition

Thread starter #23
Exactly - so the FET is turned ON all the time by the resistors to positive power, and only OFF when the sensor detects a magnet and shorts the gate to 0V.

That's why I said a few answers back that you need an extra transistor stage to invert the signal between the sensor and FET.

Remember that the sensor has an open-collector type output - it's not low/high logic, it's off (open circuit) or on (shorted to 0V)
Ok i have mounted the parts on breadboard now..and it works as you told. it gives output without magnet and tuned off when magnet is at front of hall sensor. now question is..why its not working with my pcb? perhaps any part is mounted before or after somewhere? please check my first post with a pcb design and schematic.
Also i want my circuit should not give any output but only when magnet at front of sensor. currently it is doing totally reverse manners.
 

alec_t

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Most Helpful Member
#24
Also i want my circuit should not give any output but only when magnet at front of sensor. currently it is doing totally reverse manners.
What do you mean by "output"?
It is behaving as expected. The coil should be energised when the magnet is absent. The magnet presence should cause the coil to de-energise. A spark will be generated when the coil switches OFF.
 

alec_t

Well-Known Member
Most Helpful Member
#26
That is a standard Kettering ignition circuit which gives a spark when the points OPEN, allowing the stored coil energy to generate a high voltage. When the points connect the coil to ground (dwell time), current builds up in the coil and the coil stores energy.
 
Thread starter #27
That is a standard Kettering ignition circuit which gives a spark when the points OPEN, allowing the stored coil energy to generate a high voltage. When the points connect the coil to ground (dwell time), current builds up in the coil and the coil stores energy.
right, thtats how i want this circuit to work.
 
Thread starter #28
original reply to someone in the christopher's thread( actual designer of this schematic):
Christopher
Hi, sorry for the delayed response, I’m knee-deep in midterm exams and that doesn’t leave a whole lot of time for other things. To answer your question, I don’t believe that such a Hall effect device would work without modifications to the design. Most Hall effect devices are either sensors or switches, and this design – without modification – requires a latch. This is a result of needing the coil to saturate during the ‘dwell’ period. You could certainly implement some clever logic with a non-latching hall device, but – if you’re looking to reuse e-waste components – an alternate method would be to use a photo interrupter (commonly found in all kinds of discarded electronics) and a notched disk. My first breadboarded prototype actually used this method quite successfully, but it was too large to fit in the location I had in mind. Good luck!

October 5, 2013 at 3:58 pm
what does that means? am i using wrong sensor? what is difference between latch and hall sensor.
 
Thread starter #31
using permanent magnet is difficult to use on board. i wanted to use a simple 3144 hall sensor to work with this circuit. if anyhow anyone can modify this design would be helpful. as PAMCO ignition do. i just used melexis geaartooth sensor by mistake. actual hall sensor was A1250 hal latch. but i did not find in here. if any other hall sensor i can use.
 

alec_t

Well-Known Member
Most Helpful Member
#32
The A1250 may not be what you want for this application, as it's a latching type which requires an alternating-polarity magnetic field to operate.
Here's a datasheet extract:
"The A1250 Hall-effect bipolar switch turns on in a south polarity magnetic field of sufficient strength and switches off in a north polarity magnetic field of sufficient strength."
 
Thread starter #33
The A1250 may not be what you want for this application, as it's a latching type which requires an alternating-polarity magnetic field to operate.
Here's a datasheet extract:
"The A1250 Hall-effect bipolar switch turns on in a south polarity magnetic field of sufficient strength and switches off in a north polarity magnetic field of sufficient strength."
yes right, i need a simple hall sensor to work with south pole only , which turns on with south pole and turned off w hen field unavailable without need of north pole.
 

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