Design Low cost Weighing Scale

Hi Natesh,

can you show a schematic?

Kai

Hello Natesh,

TI's series of ADS123x devices are designed for resistive bridge sensors and weigh scales.  The ADS1235 is the most recent device and has a lot of great information on designing with bridge circuits in the applications section of the datasheet (9.2) .  The ADS1231REF and ADS1232REF evaluation / reference design boards will likely also be helpful.

Hi kai

i follow this schematic and i get analog output depending upon the load but it's not stable.

Hi collin Wells
i want to make low cost Weighing Scale like a less than 2000/INR(indian rupee) (including controller, load cell, setup for weighing scale)
that is the reason to ask help to find low cost instrumentation amplifier
regards
Natesh kannan
IOT Developer

Hi Natesh,

this can have to do with the LM741. It needs a minimum supply voltage of 10V. So, it will not work here.

Another issue is the offset voltage of bridge. This was discussed here:

electronics.stackexchange.com/.../ad620-in-amp-reference-pin

Kai

hi kai
thanks for your reply
i will check and update soon
i think it will be most help to make low cost load cell

regards
kannan natesh

hi friends

i can't get exact output from ad620 so i change to design with ads1230 so please help to complete my weigh scale project.

can you please say about this ADS1230 IC, 

my need

1.i get exact weight value depend upon the load

2. my device doesn't tare the weight when power is On

3.that is must shows exact value because some ic's (HX711) is work with tare option. but i don't need that.

thank you

Hi Bob B

Thanks for your reply
1.this is my first project with Ti
2. I have cc3220 Evaluation Board I don't know how to Program this and how to connect with ADS1230. Before that i was work with some MC like a PIC16F877A, Arduino...
3. I never work with SPI Communication at all.
4.that is the reason for i ask that questions before i start with TI
5.So please guide to develop my Low cost weigh Scale start to End.

Hi Kai

i get output 10mv for 1kg. my ad620 give some volage in null position like 1.88v but this voltage is not stable some time this voltage is increased in mv or decreased like a 1.92 or 1.70, or 1.52,

how can i fix this voltage level in null load

can you please help to find the solution for this problem

thanks in advance

with regards

kannan natesh

Hi Natesh,

this can have to do with the load cell itself caused by offset temperature drift or hysteresis. Many times the load cell overheats and needs some current limiting.

Can you show a schematic and a link to datasheet of load cell?

Kai

 Hi Kai

thanks for reply

I follow this Schematic but Load cell buy from a local seller so i don't have a data sheet for Loadcell.

it is a 80kg loadcell

So Now what can i do

with regards

kannannatesh

Hi Natesh,

The circuit you have shown amplifies the load cell signal and shifts the output to the proper input range of the ADC.  This circuit would be necessary if you are using the ADC in a micro for example.

The TI devices mentioned have an integrated PGA, so there is no need for an external amplifier to add noise and drift.  In fact, the input referred noise will actually lower with the PGA gain of our ADCs.  This reduces the parts count and BOM cost.  So for the ADS1230, for example, you would use 5V for excitation of the load cell and use the same 5V for the AVDD and reference input of the ADS1230.  You would then connect the +/-SIG from the load cell to the AINP/AINN inputs of the ADS1230.  You would also need to set the remaining pins of the ADS1230 to the appropriate positions for the gain, speed, etc., followed by the SPI connections to the micro and read the new data when it becomes available.

I'm attaching a design guide that is more specific to the ADS1232, but the information would still apply to the other TI devices mentioned.

3286.Weigh Scale_Design.doc

Best regards,

Bob B

Dear Bob,

thanks for your reply, i will choose ADS1230 with CC3220 for my Weigh Scale design, i request to Sample for this but i don't get any response from TI. What can i do. 

can you please tell me how to get sample.

thank you 

Hi Natesh,

You will need to use your myTI account to order. From the ADS1230 product page, you would select the tab "Order now". From there you see a button labeled "Request Sample" for the various orderable devices. By pressing the Request Samples, you should see a new page with the desired part listed and a new button labeled "Add to Cart". Click the Add to cart button, and then a new pop-up box will show to either "Checkout" or "Continue shopping" for other devices. Click on the Checkout button. You should now see your cart with similar options as to what was just shown in the pop-up. Select "Checkout". Fill out the checkout form with all the required sections. This will include the Shipping Address, Shipping Method, Regulations, Regulations Compliance, and Final Review.

When all sections are completed, and you have successfully checked out, you should receive an email stating the sample request has been made. It may take a few days before the device ships.

Best regards,
Bob B

Dear bob ,

there is shows three types ADS1230 like a

ADS1230IPW

ADS1230IPWG4

ADS1230IPWR

which can i choose for my weigh scale project

thank you 

with regards 

Kannannatesh

Hi Kannannatesh,

There is actually no differences in the device for any of the 3 part numbers you mentioned.  The numbers relate to orderable part numbers.  Any TI device ending with G4 means it is a lead-free package, however all of our devices are now using lead-free packaging.  So this part number is a carry over from when we still had lead device packages.

The other difference is between the PW and PWR versions.  These are orderable part numbers as they relate to whether the devices are packed and delivered in tubes (PW) or are in much larger tape and reel (PWR).  No matter which sample request, the device will actually be the same.  This information is listed at the end of the ADS1230 datasheet.

Best regards,

Bob B

Hi Bob B,

thanks for your clarification and i request to sample ads1230 and 1130,

after getting this i will connect with CC3220 evaluation board. so can you please update any example for my project (weigh scale) .

i am newbie for TI that is the reason for i ask example so if you can help me to learn and develop projects with TI.

thank you.

with regards

KannanNatesh