pic to detect voltage change

[max_imum2000]

hello
i am trying to make a pic detect a small voltage change 0.2v to 0.6 volt
not measure it , just detect its change
i have to use 16f628, anything else is not an option
any suggestions ?

 

[Marks256]

Analog to Digital converter, maybe?

 

[Pommie]

Check out the comparator and voltage reference sections of the data sheet. You can set Vref to 5/24 * 2 = 0.4V and use a comparator to detect if the other input is above or below it.

Mike.

 

[akg]

as already suggested use the internal comparators

 

[kamdy]

I think it is better to amplify the voltage 10 times using low noise operational amplifier such as TLO71 to get greater ampltude and and then use a window comparator to detect the change of the voltage

 

[Nigel Goodwin]

I think it is better to amplify the voltage 10 times using low noise operational amplifier such as TLO71 to get greater ampltude and and then use a window comparator to detect the change of the voltage

Regardless of amplifying it or not, it makes obvious sense to use the internal comparators in the PIC - there's also no requirement for a window comparator, as he's not looking to detect a 'window', just above or below a certain value.

 

[max_imum2000]

thanks all
i know about using an opamp
but actually i am trying to minmize the use of components

so is it possible to just connect the source to the input pins of the comparator and set the Vref. and thats it
with no amplification or whatever ?

 

[kamdy]

what is the maximum voltage of ths source you are using

 

[Nigel Goodwin]

thanks all
i know about using an opamp
but actually i am trying to minmize the use of components

so is it possible to just connect the source to the input pins of the comparator and set the Vref. and thats it
with no amplification or whatever ?

Read the datasheet about it!, there are low and high ranges for Vref, the low range covers from 0.2V to about 3V in 0.2V increments.

 

[Pommie]

thanks all
i know about using an opamp
but actually i am trying to minmize the use of components

so is it possible to just connect the source to the input pins of the comparator and set the Vref. and thats it
with no amplification or whatever ?

just do as I said earlier.

Mike.