Re: Hall Effect Sensors

Michael wrote:

Hi,

I'd like to interface Hall Effect sensor to a uC and have picked out the A1301EUA-T (data***: http://www.allegromicro.com/en/Products/Part_Numbers/1301/1301.pdf ) with no particular reason - just seems easy to get hold off.

Now based on the graph at the bottom left on page 5, am I right in thinking:

Output from HES fed through a non-inverting amp. with gain of 250 would produce a voltage of 625mV at 1G when the supply voltage is 5.0V? It just seems a bit too easy (I'm guessing changes in temperature etc are going to have a significant effect but right now just trying to get hold of the basics.)

If I told you the application was going to be a motor tachometer - is it 'better' to feed the (amplified) voltage through a comparator and so convert the analog signal into digital signal (when above a theshold go high, below or at theshold go low type setup) or feed it into a ADC pin and work out the digital signal using software? I'm worried that if I tied that to a ADC pin then it could go over the pin's max voltage (5V) so would I need something along the lines of a zener diode to dump any 'extra' voltage over say 4.5V to be on the safe side?

I've only just started learning electronics so don't know if the circuit's above are 'suitable' and so would appreciate any help. ( It's not a homework assignment :-) )

Apologies if that's a few too many questions.

Thanks in advance,

Michael



I wouldn't worry to much about going over the voltage of the ADC pin how every, I would be concerned about the response time of the ADC when using it as a tech (HI speed input)..
you would be better to use a simple Op-amp with hysteresis, or I think the input's of the PIC already have some hysteresis in them, so you might be just fine.
I would look into assigning an input to one of the counters in the micro. (High Speed COunter).


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