resistance as analog input?

[meera83]

i m using PIC16F877..
the input for PIC is from another temperature sensor that send output as resistor value..

is it i can directly port the resistor value to PIC Ana input?
or i need to convert the resistance value to voltage?then what kind of chip i can use to convert it?

thanks..

 

[Nigel Goodwin]

Use the resistance as part of a potential divider, this will give you a voltage for the PIC to measure.

Or you could use it to charge a capacitor, and measure the time it takes - check my joystick tutorial which does this (as do your PC joystick inputs).

 

[bananasiong]

The output of the sensor is resistance? I haven't seen this kind of sensor, and I don't know much about sensors.
Use voltage devider, add a resister to form voltage devider.

One of my senior used wheat stone bridge with a LDR to make a color sensor with temperature compensation.

 

[simrantogether]

simple question...

i m using PIC16F877..
the input for PIC is from another temperature sensor that send output as resistor value..

The question you've asked is very simple... here's the answer...

the output is from other temperature sensor... It sends output in resistor value means.. the graph between voltage and current for that sensor is linear in nature...

is it i can directly port the resistor value to PIC Ana input?
or i need to convert the resistance value to voltage?then what kind of chip i can use to convert it?

thanks..

if the pic has the inbuilt Analog to digital sensor then input that analog input from sensor.. hey.. this resistance.. is not in ohms - but this is the property of sensor that it is just like the resistor.. you directly input that...


I would be happy if once again you confirm from Nigel .. what i said.. i think i am right...

Regards,

Simran..

 

[ericgibbs]

i m using PIC16F877..
the input for PIC is from another temperature sensor that send output as resistor value..

is it i can directly port the resistor value to PIC Ana input?
or i need to convert the resistance value to voltage?then what kind of chip i can use to convert it?

thanks..

hi,
What is the resistance range output of the sensor, over its temperature range?
Also for reference, is it a linear resistance change wrt temperature?

Eric

 

[mramos1]

If you have an A to D input, that is a fast way to do it via a voltage divider.

If you want to use a digital input, I have used Nigel's joystick version with a thermistor before and it works well. Also done it with LDRs.

It is a good learning project using the digital input.

 

[dknguyen]

The output of the sensor is resistance? I haven't seen this kind of sensor, and I don't know much about sensors.
Use voltage devider, add a resister to form voltage devider.

One of my senior used wheat stone bridge with a LDR to make a color sensor with temperature compensation.

There are RTD, by definition a resistor that varies with temperature, the gold standard of temperature sensors! There's also the much crummier thermistor which is probably what s/he is using.

 

[DavidT]

The resistor divider/ADC approach is simple but since the current through the device varies as resistance changes it can convert a linear characteristic to non-linear. If you need to maintain linearity, then Excel can generate a formula for 'straightening' it again, either in the PIC or outside. Alternatively you need to maintain a constant current through the sensor using either a voltage regulator (in a current limiting configuration) or with a current regulating diode.
David.

 

[HafizH]

as far as i understand from tutorial 4 in Nigel Goodwin's site , the capacitors have been used to read input from joystick, the time measured to charge the capasitors. but i dont understand how we interpret that time? Particularly the HiX LoX part!! how do we use these bytes to locate the position of potentiometers???

please, if anyone could explain i would be thankful !!
Hafiz

 

[be80be]

Use the resistance as part of a potential divider, this will give you a voltage for the PIC to measure.

Or you could use it to charge a capacitor, and measure the time it takes - check my joystick tutorial which does this (as do your PC joystick inputs).

What more would you need this covers all the bases

 

[HafizH]

Thank you,
now i got that!