Neomorph
Posts: 4
Joined: Sat Nov 17, 2018 3:50 pm

Reading old weight scale

Sat Nov 17, 2018 4:03 pm

Hello Everybody,

I have an old digital weight scale sitting on my desk. The LCD broke off but other than that it's functional. I was wondering if there is a way to simply read out the information from the scale and print it to the terminal?
I'm new to all of this and hope you could provide some information since I don't even know where to start.
I searched on google and found someone using an HX711 weight sensor, so I thought it should somehow work with the original weighing sensor aswell.

https://imgur.com/a/USOn9LU
https://imgur.com/a/Caj3hqA

Thank you very much.
Marv

User avatar
tlfong01
Posts: 1312
Joined: Sat Jun 02, 2018 1:43 pm
Location: Hong Kong

Re: Reading old weight scale

Mon Nov 19, 2018 12:58 am

Neomorph wrote:
Sat Nov 17, 2018 4:03 pm
Hello Everybody,

I have an old digital weight scale sitting on my desk. The LCD broke off but other than that it's functional. I was wondering if there is a way to simply read out the information from the scale and print it to the terminal?
I'm new to all of this and hope you could provide some information since I don't even know where to start.
I searched on google and found someone using an HX711 weight sensor, so I thought it should somehow work with the original weighing sensor aswell.

https://imgur.com/a/USOn9LU
https://imgur.com/a/Caj3hqA

Thank you very much.
Marv

Digital Weight Sensor - Where to Start

I usually buy cheap from AliExpress, learn free from SparkFun, and steal code from Arduino. :lol:

Appendix - HX711 Digital Load Cell Weight Sensor

Sparkfun Load Cell Amplifier HX711 Breakout Hookup Guide US$10
https://learn.sparkfun.com/tutorials/lo ... okup-guide

The HX711 load cell amplifier is used to get measurable data out from a load cell and strain gauge. This Hookup Guide will show you how to get started with this amplifier using some of the various load cells we carry at SparkFun.

AliExpress 5KG Digital Load Cell Weight Sensor + HX711 Weighing Sensors Ad Module for Arduino US$3
https://www.aliexpress.com/item/5KG-Dig ... 485d51bd4c

AliExpress HX711 Weighing Sensor Dual-Channel 24 Bit Precision A/D Module Pressure Sensor - US$0.6
https://www.aliexpress.com/item/HX711-W ... 85d51bd4c

Spec
Brand Name: EC Buying
Material: Mixture
Model Number:Digital Load Cell Weight Sensor
Output:Analog Sensor
Usage:Pressure
Sensoris_customized:Yes
Type:Acceleration Sensor
Theory:Digital Load Cell Weight Sensor


Package
1 pc 5kg weight sensor
1 pc HX711 AD module


Connection Guide
Wiring Method: red: Power +
Black: Power -
Green: Output signal +
White: Output signal -


Avia Semiconductor HX711 Weighing Sensor Datasheet
https://cdn.sparkfun.com/datasheets/Sen ... nglish.pdf

24-Bit Analog-to-Digital Converter (ADC) for Weigh Scales

Power Supply - 5V

Input - Bridge Sensor - differential input channel to interface directly with a bridge sensor’s differential output.

Programm - No programming needed for internal registers. All controls are through the pins.

Serial Interface - Pin PD_SCK and DOUT are used for data retrieval, input selection, gain selection and power
down controls.

Example C Driver Program (less than 20 statements!)

Code: Select all

//--
sbit ADDO = P1^5;
sbit ADSK = P0^0;
unsigned long ReadCount(void){
 unsigned long Count;
 unsigned char i;
 ADDO=1;
 ADSK=0;
 Count=0;
 while(ADDO);
 for (i=0;i<24;i++){
 ADSK=1;
 Count=Count<<1;
 ADSK=0;
 if(ADDO) Count++;
 }
 ADSK=1;
 Count=Count^0x800000;
 ADSK=0;
 return(Count);
}
...
AliExpress 4pcs 50KG Human Scale Body Load Cell Resistance Half-bridge Strain Weight Sensor + 1pcs HX711 AD Weighing Module - US$8
https://www.aliexpress.com/item/4pcs-50 ... 82503.html

Product Description
4pcs 50KG Human Scale Body Load Cell Resistance Half-bridge Strain Weight Sensor + 1pcs HX711 AD Weighing Module

50kg Load Cell
This load sensor, sometimes called a strain gauge, is the same one found in digital bathroom scales (you know, the ones you use in January for your New Year’s resolutions, and then forget about a month later).

The sensor is a group of half-bridge strain gauge, there are 3 ways to use it :

1. Use one sensor with an external resistor to form a full-bridge measurement, the range of a sensor range: 50kg. External resistance on the higher requirements.

2.Use two sensors to form a full-bridge measurement, measuring range for the sum of the two sensors: 50kgx2 = 100kg

3.Use four sensors to form a full-bridge measurement, measuring range for the sum of four sensors: 50kgx4 = 200kg

HX711 AD Module:
This module uses 24 high precision A/D converter chip hx711. It is a specially designed for the high precision electronic scale designwith two analog input channelthe internal integration of 128 times the programmable gain amplifier. The input circuit can be configured to provide a bridge type pressure bridge (such as pressure weighing sensor mode) is of high precisionlow cost is an ideal sampling front-end module.

Arduino Load Cell / HX711 References
https://github.com/aguegu/ardulibs/tree/master/hx711
https://www.youtube.com/watch?v=nGUpzwEa4vg

Rpi Tutorial - Build a digital Raspberry Pi Scale with Weight Sensor HX711
https://tutorials-raspberrypi.com/digit ... sor-hx711/

RPi Forum - Load Cell and HX711 - Seregone 2017-May-15
viewtopic.php?t=183710#p1162825

HX711 interface without bit banging - arctic_white 2018-Jul-03
viewtopic.php?t=217261#p1336040

HX711 x 5 -sonarscope 2018-Apr-05
viewtopic.php?t=210126

Rpi3 and HX711 - elter1ster 2016-Apr-12
viewtopic.php?t=144153

Build a digital Raspberry Pi Scale (with Weight Sensor HX711)
https://tutorials-raspberrypi.com/digit ... sor-hx711/

RPi Forum - LOAD CELL AND HX711 - Seregone 2017-May-15
viewtopic.php?t=183710#p1162825

Pigpio HX711.py hangs - qtfp 2018-Feb-19
viewtopic.php?t=205873

HX711 Python Class
https://github.com/gandalf15/HX711

HX711 Pigpio Class
http://abyz.me.uk/rpi/pigpio/code/HX711_py.zip
...
Attachments
sparkfun_load_cell_amp_2018nov1801.jpg
sparkfun_load_cell_amp_2018nov1801.jpg (185 KiB) Viewed 5570 times
I am an electronics and smart home hobbyist.

User avatar
tlfong01
Posts: 1312
Joined: Sat Jun 02, 2018 1:43 pm
Location: Hong Kong

Re: Reading old weight scale

Mon Nov 19, 2018 6:11 am

tlfong01 wrote:
Mon Nov 19, 2018 12:58 am
Sparkfun Load Cell Amplifier HX711 Breakout Hookup Guide US$10
https://learn.sparkfun.com/tutorials/lo ... okup-guide

AliExpress 5KG Digital Load Cell Weight Sensor + HX711 Weighing Sensors Ad Module for Arduino US$3
https://www.aliexpress.com/item/5KG-Dig ... 485d51bd4c

Avia Semiconductor HX711 Weighing Sensor Datasheet
https://cdn.sparkfun.com/datasheets/Sen ... nglish.pdf

AliExpress 4pcs 50KG Human Scale Body Load Cell Resistance Half-bridge Strain Weight Sensor + 1pcs HX711 AD Weighing Module - US$8
https://www.aliexpress.com/item/4pcs-50 ... 82503.html

Product Description
4pcs 50KG Human Scale Body Load Cell Resistance Half-bridge Strain Weight Sensor + 1pcs HX711 AD Weighing Module

50kg Load Cell
The sensor is a group of half-bridge strain gauge, there are 3 ways to use it :

1. Use one sensor with an external resistor to form a full-bridge measurement, the range of a sensor range: 50kg. External resistance on the higher requirements.

2.Use two sensors to form a full-bridge measurement, measuring range for the sum of the two sensors: 50kgx2 = 100kg

3.Use four sensors to form a full-bridge measurement, measuring range for the sum of four sensors: 50kgx4 = 200kg


HX711 Summary Notes

Analog Inputs

Channel A differential input is designed to interface directly with a bridge sensor’s differential output. It can be programmed with a gain of 128 or 64. The large gains are needed to accommodate the small output signal from the sensor.

When 5V supply is used at the AVDD pin, these gains correspond to a full-scale differential input voltage of ±20mV or ±40mV respectively.

Channel B differential input has a fixed gain of 32. The full-scale input voltage range is ±80mV, when 5V supply is used at the AVDD pin.

Output Data Rate and Format

When using the on-chip oscillator, output data rate is typically 10 (RATE=0) or 80SPS (RATE=1).

The output 24 bits of data is in 2’s complement format.

When input differential signal goes out of the 24 bit range, the output data will be saturated at 800000h (MIN) or 7FFFFFh (MAX), until the input signal comes back to the input range.

Serial Interface

Pin PD_SCK and DOUT are used for data retrieval, input selection, gain selection and power down controls.

When output data is not ready for retrieval, digital output pin DOUT is high. Serial clock input PD_SCK should be low.

When DOUT goes to low, it indicates data is ready for retrieval.

PD_SCK high min = 0.2uS, max 50uS (1/50uS = 20kHz) (typ 1uS)
PD_SCK low min = 0.2uS (typ 1uS, 1MHz)

By applying 25~27 positive clock pulses at the PD_SCK pin, data is shifted out from the DOUT output pin.

Each PD_SCK pulse shifts out one bit, starting with the MSB bit first, until all 24 bits are shifted out.

The 25th pulse at PD_SCK input will pull DOUT pin back to high.

Input and gain selection is controlled by the number of the input PD_SCK pulses.

PD_SCK clock pulses should not be less than 25 or more than 27 within one conversion period, to avoid causing serial communication error.

PD_SCK Pulses / Input channel Gain

25 clock pulses - select A channel with gain = 128
26 clock pulses - select B channel with gain = 32
27 clock pulses - select A channel with gain = 64



/to continue, ...
...
Attachments
hx711_summary_2018nov1803.jpg
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tlfong01
Posts: 1312
Joined: Sat Jun 02, 2018 1:43 pm
Location: Hong Kong

Re: Reading old weight scale

Mon Nov 19, 2018 7:25 am

tlfong01 wrote:
Mon Nov 19, 2018 6:11 am
AliExpress 5KG Digital Load Cell Weight Sensor + HX711 Weighing Sensors Ad Module for Arduino US$3
https://www.aliexpress.com/item/5KG-Dig ... 485d51bd4c

Avia Semiconductor HX711 Weighing Sensor Datasheet
https://cdn.sparkfun.com/datasheets/Sen ... nglish.pdf

AliExpress 4pcs 50KG Human Scale Body Load Cell Resistance Half-bridge Strain Weight Sensor + 1pcs HX711 AD Weighing Module - US$8
https://www.aliexpress.com/item/4pcs-50 ... 82503.html

My cheapy 50kg 1k Ohm load cell
...

Appendices - Wheatstone Bridge and Strain Measurement

The Wheatstone Bridge Circuit basics and theory of operation
https://www.hbm.com/en/7163/wheatstone-bridge-circuit/

Comet strain measurement method
http://www.tml.jp/e/product/strain_gaug ... comet.html
http://www.tml.jp/e/product/strain_gaug ... /comet.pdf
Attachments
weight_sensor_50kg_1k_ohm_2018nov1802.jpg
weight_sensor_50kg_1k_ohm_2018nov1802.jpg (182.25 KiB) Viewed 5538 times
I am an electronics and smart home hobbyist.

btidey
Posts: 1616
Joined: Sun Feb 17, 2013 6:51 pm

Re: Reading old weight scale

Mon Nov 19, 2018 8:26 am

If you are trying to re-use most of the original scale then one approach would be to read the signals that drove the LCD display.

This would need a bit of research to work out what they are and how to input them into the GPIO of the Pi.

You don't show the LCD display in the pictures but it is likely to be a 7 segment LCD with some extra elements for say decimal points and lb/kg units. It is also quite likely to be multiplexed so that each digit is selected and driven in turn. This would mean approximately 4 or 5 digit selector signals plus 7 for the segment signals plus a few more for the extra display elements.

You would need to find out the signal levels being used to drive these so that an interface into the GPIO could be worked out.

Then the software would need to sample the GPIO (faster than the multiplex), work out which digit is being driven and translate the 7 segment signals back into the decimal equivalent.

Not 'simple' but quite do-able.

User avatar
tlfong01
Posts: 1312
Joined: Sat Jun 02, 2018 1:43 pm
Location: Hong Kong

Re: Reading old weight scale

Tue Nov 20, 2018 2:37 am

tlfong01 wrote:
Mon Nov 19, 2018 7:25 am
AliExpress 5KG Digital Load Cell Weight Sensor + HX711 Weighing Sensors Ad Module for Arduino US$3
https://www.aliexpress.com/item/5KG-Dig ... 485d51bd4c
AliExpress 4pcs 50KG Human Scale Body Load Cell Resistance Half-bridge Strain Weight Sensor + 1pcs HX711 AD Weighing Module - US$8
https://www.aliexpress.com/item/4pcs-50 ... 82503.html
My cheapy 50kg 1k Ohm load cell

50kg Load Cell Board Assembly Notes
Attachments
load_cell_2018nov2003.jpg
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tlfong01
Posts: 1312
Joined: Sat Jun 02, 2018 1:43 pm
Location: Hong Kong

Re: Reading old weight scale

Tue Nov 20, 2018 3:43 am

tlfong01 wrote:
Tue Nov 20, 2018 2:37 am
tlfong01 wrote:
Mon Nov 19, 2018 7:25 am
AliExpress 5KG Digital Load Cell Weight Sensor + HX711 Weighing Sensors Ad Module for Arduino US$3
https://www.aliexpress.com/item/5KG-Dig ... 485d51bd4c
AliExpress 4pcs 50KG Human Scale Body Load Cell Resistance Half-bridge Strain Weight Sensor + 1pcs HX711 AD Weighing Module - US$8
https://www.aliexpress.com/item/4pcs-50 ... 82503.html
My cheapy 50kg 1k Ohm load cell
50kg Load Cell Board Assembly Notes

HX711 Testing Notes - Part 1 - Flashing Wemos D1 Mini
...
Attachments
hx711_test_2018nov2001.jpg
hx711_test_2018nov2001.jpg (202.42 KiB) Viewed 5473 times
Last edited by tlfong01 on Tue Nov 20, 2018 9:22 am, edited 1 time in total.
I am an electronics and smart home hobbyist.

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tlfong01
Posts: 1312
Joined: Sat Jun 02, 2018 1:43 pm
Location: Hong Kong

Re: Reading old weight scale

Tue Nov 20, 2018 5:34 am

tlfong01 wrote:
Tue Nov 20, 2018 3:43 am
50kg Load Cell Board Assembly Notes
HX711 Testing Notes - Part 1

HX711 Testing Notes - Part 2 - Rpi 3B+ & Wemos D1 Mini
...
Attachments
wemos_d1_mini_2018nov2101.jpg
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Last edited by tlfong01 on Tue Nov 20, 2018 9:24 am, edited 2 times in total.
I am an electronics and smart home hobbyist.

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tlfong01
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Joined: Sat Jun 02, 2018 1:43 pm
Location: Hong Kong

Re: Reading old weight scale

Tue Nov 20, 2018 9:17 am

tlfong01 wrote:
Tue Nov 20, 2018 5:34 am
50kg Load Cell Board Assembly Notes
HX711 Testing Notes - Part 1

HX711 Testing Notes - Part 2 - Wemos D1 Mini setup

HX711 Testing Notes - Part 3 - Rpi PSU, USB hub setup
...
Attachments
hx711_test_setup_2018nov2001.jpg
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I am an electronics and smart home hobbyist.

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tlfong01
Posts: 1312
Joined: Sat Jun 02, 2018 1:43 pm
Location: Hong Kong

Re: Reading old weight scale

Tue Nov 20, 2018 3:05 pm

tlfong01 wrote:
Tue Nov 20, 2018 9:17 am
50kg Load Cell Board Assembly Notes
HX711 Testing Notes - Part 1

HX711 Testing Notes - Part 2 - Wemos D1 Mini setup

HX711 Testing Notes - Part 3 - Rpi PSU, USB hub setup

HX711 Testing Notes Part 4 ESP8266 HX711 Routing Board Assembly Notes
...
Attachments
esp8266_hx711_route_2018nov2002.jpg
esp8266_hx711_route_2018nov2002.jpg (169.97 KiB) Viewed 5312 times
Last edited by tlfong01 on Wed Nov 21, 2018 9:31 am, edited 1 time in total.
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tlfong01
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Location: Hong Kong

Re: Reading old weight scale

Wed Nov 21, 2018 6:32 am

tlfong01 wrote:
Tue Nov 20, 2018 2:37 am
AliExpress 5KG Digital Load Cell Weight Sensor + HX711 Weighing Sensors Ad Module for Arduino US$3
https://www.aliexpress.com/item/5KG-Dig ... 485d51bd4c
AliExpress 4pcs 50KG Human Scale Body Load Cell Resistance Half-bridge Strain Weight Sensor + 1pcs HX711 AD Weighing Module - US$8
https://www.aliexpress.com/item/4pcs-50 ... 82503.html
My cheapy 50kg 1k Ohm load cell
50kg Load Cell Board Assembly Notes

HX711 Testing Notes - JIT DIY

The other day when I was trying to fix the 50kg Wheatstone thing on an aluminium plate, I found a problem - there are no screw holes, and Google could not give me any hints. There is another problem - I could not find standard weights as heavy as 50kg to do the testing and calibration. One more thing is that the cheap thing is only half bridge, and I don't know and too lazy to find out how of connect.

So I gave up and decided to get a standard full bridge bar, for 10 yuans.

TMall Cell Load Load Cell 1kg = ¥8, 5kg, 10kg, 20kg = ¥10


I ordered the evening before yesterday, paid yesterday morning, and this afternoon the toys are already on their day from ShenZhen, and should arrive Hong Kong any time, Just In Time for me to start playing.

In the mean time, I am doing some preparation work to welcome the new toys, such as finding out who invented the Wheatstone toy, and how to set up the bridge thing etc.

Wheatstone Bridge - Wikipedia
https://en.wikipedia.org/wiki/Wheatstone_bridge

Express Delivery Track and Trace
...

Code: Select all

2018-11-19 Mon 20:51:31 placed order
2018-11-20 Tue 09:36:45 paid by aliPay
2018-11-20 Tue 12:03:46 SF Express collected
2018-11-20 Tue 12:03:59 goods dispatched
2018-11-20 Tue 17:52:00 SF EXpressed collected
2018-11-20 Tue 23:14:00 ShenZhen FukTin
2018-11-20 Tue 23:46:00 ShenZhen ChoiTin
2018-11-21 Wed 00:03:00 ShenZhen ChoiTin to ShenZhen Main Centre
2018-11-21 Wed 02:03:00 ShenZhen Centre arrived
2018-11-21 Wed 03:04:00 ShenZhen Centre to Hongkong TsingYi
Attachments
christie_&_wheatstone_2018nov2101.jpg
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Neomorph
Posts: 4
Joined: Sat Nov 17, 2018 3:50 pm

Re: Reading old weight scale

Wed Nov 21, 2018 11:06 pm

btidey wrote:
Mon Nov 19, 2018 8:26 am
If you are trying to re-use most of the original scale then one approach would be to read the signals that drove the LCD display.

This would need a bit of research to work out what they are and how to input them into the GPIO of the Pi.

You don't show the LCD display in the pictures but it is likely to be a 7 segment LCD with some extra elements for say decimal points and lb/kg units. It is also quite likely to be multiplexed so that each digit is selected and driven in turn. This would mean approximately 4 or 5 digit selector signals plus 7 for the segment signals plus a few more for the extra display elements.

You would need to find out the signal levels being used to drive these so that an interface into the GPIO could be worked out.

Then the software would need to sample the GPIO (faster than the multiplex), work out which digit is being driven and translate the 7 segment signals back into the decimal equivalent.

Not 'simple' but quite do-able.
Thank you very much all the information. That's exactly what I had in mind indeed. My first thought was to use the 16 LCD connections as source for the wanted data and reading it with the GPIO. Which initially sounded easier than it actually is. It all sounds quite difficult to me right now, but I like researching, solving problems and learning from it.

I just uploaded a picture of the LCD. The black part in the middle was connected to the 16 connection points. You can still see the rough spots where the display was connected to the board. The range of the scale was 0.01 to 200 g and it had five buttons with on/off in the middle, tare - right upper corner, light - right lower corner, PCS - left upper corner and units - lower left corner.

https://m.imgur.com/a/JUIOb4y

I'll start gathering more information about what you mentioned. But I most certainly will have to ask you some things because I don't even know how a simple LCD works and how data is displayed. I guess I'll start there.

Thank you again.

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tlfong01
Posts: 1312
Joined: Sat Jun 02, 2018 1:43 pm
Location: Hong Kong

Re: Reading old weight scale

Thu Nov 22, 2018 3:51 am

tlfong01 wrote:
Wed Nov 21, 2018 6:32 am
HX711 Testing Notes - JIT DIY

Wheatstone Bridge Load Cell Come Lately

The new toy I only met just a couple of days ago may have come lately. So this morning I could do nothing more than look at the specs.

I googled a while and summarized the following spec:

Fake ¥10 5kg Loal Cell Spec
5kg, Excitation 5~10V , Sensitivity 1.0mV ( +- 0.15 mV), full load = 5mV)
Alloy steel, I/O 1066R
Input Red +, Blk -, Output Grn +, Wht -
Safety Load 120%, Absolute max 150%
Dimension 80mm x 12.7mm x 12.7mm
Mounting holes, M5, 5mm, 15mm from edge


HX711 spec says that the selectable gain is 64/128 for 40mV/20mV. So the resolution for my fake load cell should be 22 bit, good enough for my toy projects.

20mV = 24 bits resolution
5mV = 22 bits resolution
20mV = 1111, 1111, 1111, 1111, 1111, 1111, 1111, 1111
5mV = 0011, 1111, 1111, 1111, 1111, 1111, 1111, 1111


I vaguely remember that the HX711 module had a jumper to select resolution. I looked at the module again and found that I was wrong, the jumper is to select output rate of 10 or 80 samples per second.

The resolution or gain factor is selected by the serial clock number. This is too clever for the newbie like me. I have never thought of that! :o

Load Cell References
https://detail.tmall.com/item.htm?id=57 ... 3ad45aKuxJ
https://www.tecsis.com/
https://www.tecsis.com/force/load-cells.html
https://www.tecsis.com/force/load-cells ... -3-kg.html
https://www.tecsis.com/force/load-cells ... 50-kg.html
https://www.vetek.com/loadcells/pm?gcli ... 44QAvD_BwE
https://www.vetek.com/01-30kg/pm
https://www.vetek.com/load-cell-1-kg-si ... l-/article

Ginny Come Lately
https://www.youtube.com/watch?v=QD-ZB8csvKI
Attachments
hx711_rate_2018nov2201.jpg
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tlfong01
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Re: Reading old weight scale

Thu Nov 22, 2018 6:19 am

tlfong01 wrote:
Thu Nov 22, 2018 3:51 am
HX711 Testing Notes - JITDIY
Wheatstone Bridge Load Cell Come Lately
5kg, Excitation 5~10V , Sensitivity 1.0mV ( +- 0.15 mV), full load =
Alloy steel, I/O 1066R
Input Red +, Blk -, Output Grn +, Wht -
Safety Load 120%, Absolute max 150%
Dimension 80mm x 12.7mm x 12.7mm
Mounting holes, M5, 5mm, 15mm from edge


Load Cell Bar Mounting Plate Making Notes

Dimension 80mm x 12.7mm x 12.7mm
Mounting holes, M5, 5mm, 15mm 20mm from edge


Errata - 2018nov22hkt2045

I made a careless mistake. The two holes are 5mm, and 20mm from edge. In other words, centre to centre is 15mm.
Attachments
load_cell_mount_plate_2018nov2201.jpg
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Last edited by tlfong01 on Thu Nov 22, 2018 12:49 pm, edited 1 time in total.
I am an electronics and smart home hobbyist.

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tlfong01
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Location: Hong Kong

Re: Reading old weight scale

Thu Nov 22, 2018 8:01 am

tlfong01 wrote:
Thu Nov 22, 2018 6:19 am
HX711 Testing Notes - JIT DIY
Wheatstone Bridge Load Cell Come Lately
5kg, Excitation 5~10V , Sensitivity 1.0mV ( +- 0.15 mV), full load = 5mV

HX711 ESP8266 Evaluation Kit assembly notes

Now I have assembled something to evaluate the HX711. There is an adjustable voltage reference of 0mV ~ 7mV to test HX711 Channel B's 32x gain.
Attachments
hx711_esp8266_eval_kit_2018nov2203.jpg
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I am an electronics and smart home hobbyist.

Neomorph
Posts: 4
Joined: Sat Nov 17, 2018 3:50 pm

Re: Reading old weight scale

Thu Nov 22, 2018 8:29 am

tlfong01 wrote:
Thu Nov 22, 2018 8:01 am
tlfong01 wrote:
Thu Nov 22, 2018 6:19 am
HX711 Testing Notes - JIT DIY
Wheatstone Bridge Load Cell Come Lately
5kg, Excitation 5~10V , Sensitivity 1.0mV ( +- 0.15 mV), full load = 5mV

HX711 ESP8266 Evaluation Kit assembly notes

Now I have assembled something to evaluate the HX711. There is an adjustable voltage reference of 0mV ~ 7mV to test HX711 Channel B's 32x gain.
Thanks tlfong01 for all these topics and links. I'll try to look into all the stuff and extract what I can use for my project. Since my scale goes from 0.01 to 200 g and is using an unknown sensor I most probably just have to try.
First off I'll have to find out how the LCD worked with these 16 connenctions and how the data is displayed.

By the way, I found an instruction for this topic which may very well address exactly what I'm searching.

https://www.instructables.com/id/Direct ... urpose-IO/
Last edited by Neomorph on Thu Nov 22, 2018 1:48 pm, edited 1 time in total.

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tlfong01
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Location: Hong Kong

Re: Reading old weight scale

Thu Nov 22, 2018 11:53 am

Neomorph wrote:
Thu Nov 22, 2018 8:29 am
1. Thanks tlfong01 for all these topics and links. I'll try to look into all the stuff and extract what I can use for my project.
2. Since my scale goes from 0.01 to 200 g and is using an unknown sensor I most probably just have to try.
3. First off I'll have to find out how the LCD worked with these 16 connenctions and how the data is displayed.

Digital Scale LCD 0~200g

1. You are welcome. Actually I have never played with any weight scale thing, so I googled and found the topic interesting. SparkFun has a very good tutorial, so I started learning, hoping I can get some knowledge for everybody's project.

2. If your digital scale has no model number, you may like to google images with keywords such as "amazon 200g digital scale lcd" and let us know which model looks like yours.

https://www.google.com.hk/search?q=amaz ... 01&bih=920

3. I once played with two portable digital scales. The one I like most is the following.

https://www.amazon.com/Whitelotous-Elec ... B06XYB8TWV

4. LCD of 16 characters x 1 line is very common and usually have 16 pins connector. You can control with Arduino or Rpi GPIO. But the easiest way is to use I2C. Perhaps later I can show you which AliExpress cheap things you can start with.
...
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tlfong01
Posts: 1312
Joined: Sat Jun 02, 2018 1:43 pm
Location: Hong Kong

Re: Reading old weight scale

Thu Nov 22, 2018 2:51 pm

[quote=tlfong01 post_id=1395193 time=1542867592 user_id=269
[color=#0040FF wrote:Load Cell Spec
5kg, Excitation 5~10V , Sensitivity 1.0mV ( +- 0.15 mV), full load = 5mV
Input Red +, Blk -, Output Grn +, Wht -
Safety Load 120%, Absolute max 150%
[/color]

Load Cell Test Setup Notes

The load cells finally arrived this afternoon. Now I am setting up for testing.

My test plan is as follows.

1. Test 1kg load cell stand alone with 5V input at Red and Black, and measure output Green and White. No Rpi or ESP8266 will be used.

2. Test load cell with Rpi GPIO, MCP23017 GPIO, or ESP8266 GPIO.
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Neomorph
Posts: 4
Joined: Sat Nov 17, 2018 3:50 pm

Re: Reading old weight scale

Thu Nov 22, 2018 4:30 pm

tlfong01 wrote:
Thu Nov 22, 2018 11:53 am
Neomorph wrote:
Thu Nov 22, 2018 8:29 am
1. Thanks tlfong01 for all these topics and links. I'll try to look into all the stuff and extract what I can use for my project.
2. Since my scale goes from 0.01 to 200 g and is using an unknown sensor I most probably just have to try.
3. First off I'll have to find out how the LCD worked with these 16 connenctions and how the data is displayed.

Digital Scale LCD 0~200g

1. You are welcome. Actually I have never played with any weight scale thing, so I googled and found the topic interesting. SparkFun has a very good tutorial, so I started learning, hoping I can get some knowledge for everybody's project.

2. If your digital scale has no model number, you may like to google images with keywords such as "amazon 200g digital scale lcd" and let us know which model looks like yours.

https://www.google.com.hk/search?q=amaz ... 01&bih=920

3. I once played with two portable digital scales. The one I like most is the following.

https://www.amazon.com/Whitelotous-Elec ... B06XYB8TWV

4. LCD of 16 characters x 1 line is very common and usually have 16 pins connector. You can control with Arduino or Rpi GPIO. But the easiest way is to use I2C. Perhaps later I can show you which AliExpress cheap things you can start with.
...
1. That's wonderful. I didn't even know where to start searching. I'm a medicinal chemist and I'm able to compute molecular binding to any protein but when it comes to digital stuff like robotics or the simplest things like LCDs, I'm totally clueless.

2. + 3. You are dead on my friend. It was indeed the model you attached as a picture, only with a green LCD instead of a blue one. But that's not of any importance I believe.

4. I have an Odroid C2 and a Rpi 3B+ so I guess one of both or even both should be capable of performing the task.

I'm also playing with the thought of building an automated weighing device where I can enter a mass and it will add substrate until it reaches the entered amount. But that's something to consider when I'm done with the first step of attaching the scale to a Rpi or odroid.

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tlfong01
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Location: Hong Kong

Re: Reading old weight scale

Fri Nov 23, 2018 4:11 am

tlfong01 wrote:
Thu Nov 22, 2018 11:53 am
4. LCD of 16 characters x 1 line is very common and usually have 16 pins connector. You can control with Arduino or Rpi GPIO. But the easiest way is to use I2C. Perhaps later I can show you which AliExpress cheap things you can start with.

I2C HD44780 LCD 16 x 2 Module for Newbies

For newbies, I would suggest the following cheap thing to test the water:

AliExpress 1602 16x2 HD44780 Character LCD /w IIC/I2C Serial Interface Adapter Module US$2
https://www.aliexpress.com/item/1602-16 ... c30a07bf-7
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tlfong01
Posts: 1312
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Location: Hong Kong

Re: Reading old weight scale

Fri Nov 23, 2018 4:44 am

tlfong01 wrote:
Fri Nov 23, 2018 4:11 am
tlfong01 wrote:
Thu Nov 22, 2018 11:53 am
LCD of 16 characters x 1 line is very common and usually have 16 pins connector. You can control with Arduino or Rpi GPIO. But the easiest way is to use I2C. Perhaps later I can show you which AliExpress cheap things you can start
I2C HD44780 LCD 16 x 2 Module for Newbies
For newbies, I would suggest the following cheap thing to test the water:
AliExpress 1602 16x2 HD44780 Character LCD /w IIC/I2C Serial Interface Adapter Module US$2
https://www.aliexpress.com/item/1602-16 ... c30a07bf-7

MAX7219 8 digit 7 segment LED Display Modules for Newbies

I have also played with 8 digit LED Display a year ago, and I will be using it in my HX711 project.

This module is very cheap, only USD1.2, because of economy of scale, in turn because of mass production, in turn because of popularity, in turn because it is efficient and effective, easy to use, etc, etc. In other words, I like it not because it is cheap - I would still like it even it is ten times more expensive.


AliExpress 8-Digit 7 Segment MAX7219 LED Display for Arduino US$1.20
https://www.aliexpress.com/item/FreeShi ... 97c610a-6
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tlfong01
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Location: Hong Kong

Re: Reading old weight scale

Fri Nov 23, 2018 6:31 am

tlfong01 wrote:
Thu Nov 22, 2018 2:51 pm
Load Cell Spec
5kg, Excitation 5~10V , Sensitivity 1.0mV ( +- 0.15 mV), full load = 5mV
Input Red +, Blk -, Output Grn +, Wht -
Safety Load 120%, Absolute max 150%
Load Cell Test Setup Notes
The load cells finally arrived this afternoon. Now I am setting up for testing.
My test plan is as follows.
1. Test 1kg load cell stand alone with 5V input at Red and Black, and measure output Green and White. No Rpi or ESP8266 will be used

1kg Load Cell Testing Notes

The time has come check out if this fake thing works!
:mrgreen:
...
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tlfong01
Posts: 1312
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Location: Hong Kong

Re: Reading old weight scale

Fri Nov 23, 2018 6:41 am

tlfong01 wrote:
Fri Nov 23, 2018 6:31 am
Load Cell Spec
5kg, Excitation 5~10V , Sensitivity 1.0mV ( +- 0.15 mV), full load = 5mV
Input Red +, Blk -, Output Grn +, Wht -
Safety Load 120%, Absolute max 150%
Load Cell Test Setup Notes
The load cells finally arrived this afternoon. Now I am setting up for testing.
My test plan is as follows.
1. Test 1kg load cell stand alone with 5V input at Red and Black, and measure output Green and White. No Rpi or ESP8266 will be used
1kg Load Cell Testing Notes
The time has come check out if this fake thing works!

0.5kg load ready
...
Attachments
half_kg_load_2018nov2303.jpg
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tlfong01
Posts: 1312
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Location: Hong Kong

Re: Reading old weight scale

Fri Nov 23, 2018 7:45 am

tlfong01 wrote:
Fri Nov 23, 2018 6:41 am
Load Cell Spec 1kg, Excitation 5V , Sensitivity 1.0mV, full load = 5mV
Input Red +, Blk -, Output Grn +, Wht -
Safety Load 120%, Absolute max 150%
Test Plan
Test 1kg load cell stand alone with 5V input at Red and Black, and measure output Green and White. No Rpi or ESP8266 will be used

1kg Load Cell Test Results

Load / Output

500g / -1.9V

500g + 110ml Avengers milk / -2.2V

PS - Just in case the London Bridge is falling down, I have moved all the circuit boards on plastic trays, ...


London Bridge is Falling Down - 120,128,393 views
https://www.youtube.com/watch?v=pUu0FWlMpgk
...
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tlfong01
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Location: Hong Kong

Re: Reading old weight scale

Fri Nov 23, 2018 8:11 am

tlfong01 wrote:
Fri Nov 23, 2018 7:45 am
1kg Load Cell Test Results
Load / Output

500ml water = -1.9V

500ml water + 110 ml milk = -2.2V



Sensitivity Calculation
...
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