Protection of a hall sensor in automotive circuit-Help

Jun 13, 2005 2 Replies
M

Hi,



i have a problem with tha Honeywell Hall sensor SS443. I use this sensor for mesuring the RPM of the motor. The device has functioned well for 2 days...........then the sensor is died. I've connect the Pin's supply direcly on the + Battery,so i think that the sensor died because the 12 volt of batery,when the car is runnig,is more and more over 12 volt,because the sensor is rated for 24-30 VCC max. Now i've thinked this circuit for protect the sensor:



from the line's battery i put a UF4004 diode(against the reverse voltage),after a 150 OHM 5W resistence and then a Transil 1.5Kw 18 Volt monorirecional ref. to - Battery and here i connect the supply pin of honeywell


UF4004 Transil 1.5Kw 18V Monodirectional



+(Batt)---->|---Resistor of 150 OHM----->//--------|--=B0=B0 OUT | (- Battery)---


What do you think? Can protect the hall sensor ? Thanks for Any Help



Ciao, MAX



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P

Vehicle battery connections are known colloquially as 'The Power Supply from Hell'

Under load dump conditions, it's not unusual to see up to 60V or more on the battery terminal leads. (I am painfully aware of this, as I design automotive equipment in my current life).

I can't read the schematic above very clearly, but provided the cathode is on the positive side of the feed, you may be ok.

Ensure the transorb maximum voltage is below your max rated voltage for the sensor.

Cheers

Petes

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K

Did you neglect to use a bypass cap? which alone might have sufficed. And instead of using two diodes as in your diagram you could accomplish pretty much the same thing by putting a zener in parallel with the hall sensor.

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