Hi, so I am working on a project that calculates your BMI using an ultrasonic sensor and a bathroom scale and displays it on a LCD. So far I have figured out how to display values that I have gotten from the ultrasonic sensor to my Arduino uno. I also did some research on Arduino arithmetic and I know how my formula will work and look. Only problem I have is the bathroom weighing scale. I'll have a attachment of the circuitry of the scale. I am trying to connect the weighing scale to the Arduino so I can extract the data that comes from the weighing scale so that I can use that to calculate the persons BMI. Help would be appreciated.
Can you get the number off that chip U2 on that board? The circuit's a load cell bridge plus microcontroller (the blob), and an LCD display).
It might be easiest to junk the existing board, use an HX711 with the existing load cells.
Ok so I could kind of read the bottom part of the chip. It was 08123B there was something above that but it is pretty difficult to read.
MarkT:
The circuit's a load cell bridge plus microcontroller (the blob), and an LCD display).
What do you mean by this?
I don't have an hx711 because of the whole lock down thing here in SA. That's why I am asking if there if there is maybe an alternative way I can do this.
I am intrigued.
You can ask a punter to step onto bathroom scales.
You can measure her height.
I doubt if she wants you to measure her fat covering with any external instrument.
As I understand it. BMI is the ratio between height and weight. It does not account for muscle, fat, water content, body shape.
I know my height. I know what my "recommended weight" should be.
My bathroom scales report that I am overweight.
David.
david_prentice:
My bathroom scales report that I am overweight.
No David, you are just a little under tall. It's when a "Speak your weight" machine says "One at a time please" that you have to worry!
All I wanted to really know is If I can do this without a hx711 and if so; how?
OK, so you have a "Blob" chip, otherwise known as a "COB". It is to this chip that the load cell bridge is connected so you will require the HX711 module to substitute.
The second chip is not connected to the load cells but to a pinout labelled "CAL" and since this device does not have a calibration potentiometer, I'm betting it is an EEPROM which contains the calibration for the scales from the factory. 
Noted the "ON" switch is a vibration sensor. Now I know why those things are sold on eBay as I could not otherwise think of a use for them! 
It has been previously discussed (in other threads) that decoding the LCD display drive is a completely futile exercise, so you will need to use the HX711 module and none of the present electronics - and then re-calibrate it. My accreditation service tells me they do not bother carrying test weights unless they really have to but just weigh themselves on their standard scales and see if the "test" scales match. 