load cell

nina · Joined: 20 Apr 2007 Posts: 111

I have a load cell as sensor (range output 0 to 2 mV/V).
I want develop a project using PIC to mesure weight and show over LCD or display. Does anybody here can help me?
I have some knowledge about PIC, electronic, a programming.

Thanks a lot

libor · Joined: 14 Dec 2004 Posts: 288 Location: Hungary

You'll have to use a precision op-amp, or a hi-res ADC, or both (the PICs built-in ADCs have not enough resolution for this)
Look for AN1030 on the Microchip website for some clues here

Guest · Posted: Sat Apr 21, 2007 1:41 pm

thank you for explanation...but how I will read an external ADC like AN1030?

yours

libor · Joined: 14 Dec 2004 Posts: 288 Location: Hungary

Do you want to make a real working calibratable digital weigh scale ? What range/precision is required ? Or is this just a hobby example project you are thinking of to put together ?

I am asking this because the precise and repeatable measurement in the mV resolution (a load cell output) is not only a difficult task from the programming point of view (filtering algorythm, calibration, etc.) but also requires experince with analog signal conditioning circuitry like low-noise op-amps, high resolution ADC, etc.

The external A/D converter mentioned in that application note has an SPI bus interface.

Guest · Posted: Sat Apr 21, 2007 2:05 pm

thanks again with your explanation...

first I would like just build a project like...
sensor (load cell).....external ADC....PIC...display or LCD..

After this work...I will try improve it to be better but first of all...I just want put in practice.

Thanks again

Guest · Posted: Sun Apr 22, 2007 7:13 am

Does anyone here have an example about a project using any kind of external ADC?

Thanks a lot

Ttelmah · Guest

Hint. Look in the files that come with the compiler...
EX_AD12.c, reads values using the supplied driver for two 12bit ADC's.
There is also a driver for the AD7715 16bit ADC, designed for exactly your sort of application.

Best Wishes