• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 51 subscribers
  • Views 1091 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

is cc2540 suitable for a single chip ble weigh scale using load cell

ke fan
Expert 1890 points
Other Parts Discussed in Thread: CC2540, ADS1231, ADS1131, AFE4300

Hi,

is cc2540 suitable for a single chip ble weigh scale using load cell?

the load cell output rating is 2mv/v at maximum weight of 2kg,

use the 2v-3.6v power supply of cc2540 as excitation votage and VREF, the full-scale output of the load cell is about 4mv-7.3mv.

use the opamp with gain of 500 to amplify the output rating from 2mv/v to 1v/v, so that the full-scale output of the opamp is about the same as cc2540 power supply.

 send the output of the opamp to the ADC with 12bit ENOB.

if needed make an average of many conversion results to reduce noise.

is it possible to get a display resolution of 1g ( or 1 count in 2000 ) and displays the results on a LCD by SPI interface?

Please help.

Thanks.

  • 0
    Prodigy 20 points

    Hi ,

    i'm also working on a wireless scale using a CC2540 , please could you tell me if you found a suitable strain gauge

    and wich AOP do you use for the analog front end.

    Thans

    Azdine

  • 0 in reply to BAHOU Azdine1
    Expert 1890 points

    the planned ble weigh scale is to be a simple single chip device.  choose any load cell with sensitivity of 2mv/V, analog front end just use the on-chip opamp and ADC, with opamp set to work with gain of 500(so that the signal to Vref ratio will be 1:1) and the amplified differencial signal sent to the on-chip ADC with 12bit output. 

    if you want a precision weigh scale, ADS1131 or ADS1231 will be best AFE choice from ti. but it need a minimum 3v supply voltage and thus a 3v dc-dc converter is needed.  the ADS1131 has a Serial interface, ADS1231 has a specific SPI, and it seems the SPI API of BLE stack will not work directly with these 2 chips( this is not confirm by ti).

    AFE4300 is another good choide for weigh scale, it has single-shot mode and continuous mode.

    Signal Conditioning Wheatstone Resistive Bridge Sensors