Arduino interfacing with a load cell w/code - PRIZE: 3Month Pro membership

I'm looking for a good example of how to interface some load cells I have with an arduino.   I haven't found a whole lot in that area here on instructables.

I recently received a code for a 3 month Pro membership for having a featured instructible I made, and I will pass the membership on to the person I think submits the best, most complete write-up.  Deadline is May 31st, 2014, or until I find a good one :)

Success criteria:
--------------------------------------------
*Relatively cheap parts (under $20 USD)
*Includes a schematic that can be built on perf-board with a plain-old soldering iron (no tiny surface mount parts, please)
*Includes some basic code to run on the arduino for proof-of-concept that reads weight from the load cell.

Here's some info on the load cells I have:
--------------------------------------------
Rated Load: 5Kg
Rated Output: 2.0mV/V±0.2mV/V
Creep: 0.014%F.S./30min
Input End: Red+(Excitation), Black-(Excitation)
Output End: Green+(signal), White-(signal)
Recommended operating voltage: 5 ~ 12 VDC
Input Impedance: 1060±15%Ω
Output Impedance: 1000±5%Ω
Protection class: IP65
Accuracy class: OIML R60 C3


Thanks & good luck!

switch623 years ago

Have a look at http://airtripper.com/1626/arduino-load-cell-circu... . The load cell amplifier circuit is standard. I think they are using a 1.0mV/V load cell, so you will need to change the gain resistor. Using VREF5 you will need around 120R to get 5V at 5kg. Use a 150R or 200R 10 turn trimpot. If you use VREF10 then you need to double the trimpot 300R or 400R, to get 244R for the gain resistor.

Refer to the INA125PA datasheet. http://www.farnell.com/datasheets/676080.pdf

They also have a calibration procedure for the load cell/amplifier combination. Leads from the amplifier to the load cell should be soldered and never changed. Once calibrated the load cell, cable, and amplifier should be kept as a set.

The INA125PA is around $6 USD. You may need to ask the guys at airtripper if you can use their code.

OH, I don't need the 3 month Pro membership. Glad to help.

Keep your pro membership and do a simple Google search. The first result i get is an instructable for using a load cell on an arduino.