Digital output from sensor

[coolchip]

I have a hall sensor which sends pulses with max and min as 1v and 0v.
How can I translate it into logic outputs ?

Thank you!

 

[VVV]

Use an LM393 (or LM339) comparator, with a 0.5V reference. At the output, use a pullup resistor connected to +5V. That will give you the logic output. Make sure you have some hysteresis added to the comparator, say 10-50mV.

 

[coolchip]

Use an LM393 (or LM339) comparator, with a 0.5V reference. At the output, use a pullup resistor connected to +5V. That will give you the logic output. Make sure you have some hysteresis added to the comparator, say 10-50mV.

Pardon my ignorance - How do you add hysteresis to the comparator?

Thanks for help!

 

[skydiverc]

hysteresis can be accomplished by using a feedback resistor to adjust the threshold up or down depending on the output.

Example: Power comparator with 5V
with .5V set to - input and the sensor to the + input pin.
When sensor excedes .5 V output goes high ~5V.
Then using a large value resistor feedback the output signal to the + input.
This feedback will move the voltage at the + input slightly higher.
With this higher input in order to go below the .5V threshold the sensor must go down lower than .5V to switch the output due to the voltage fed back from the output.
This is so that if you have a little noise on the sensor output the comparator wont go chattering as the sensor voltage deviates above and below the .5V trip point.

With most comparators you only need a 3-5mv difference to switch the output.
ie if + pin is 3-5mv above - pin output is Positive, if pin + is 3-5mv below - pin output is low. ( single ended 5V supply )
So hysteresis is used to prevent noise from causing spurrious changes in the comparator output.

However in you circuit I doubt hysteresis is really necessary as you already have a significant differential from 0V to 1V and yours is a digital circuit.
Hysteresis is more commonly used in analog signals where there may be only a small change in voltage that must be detected like 50 to 100mv or less.

 

[VVV]

Here is a schematic. For explanations, see skydiverc's post.
Note that the output is inverted, but you can always swap the input with the reference. The hysteresis should be around 20mV with the values shown.
I always recommend hysteresis be added to comparators, since it helps eliminate multiple output pulses, which could be created by noise. It only costs a couple more resistors, but they usually pay off later.

R1 can be eliminated (shorted out) if the 0.5V reference is obtained with a resistive divider (as it usually is). But you will generally need it if you swap the input and reference.

 

[smxx]

I think u can use PAM (Puls Amplitude Madulation& Demadulation ) technics.