Difference between revisions of "Interface the HX711 to Pi"
(→Temperature Compensation) |
|||
| Line 1: | Line 1: | ||
| − | + | ==Installation== | |
| + | |||
| + | ===Method 1: Connect HX711 to P1/J8=== | ||
| + | [[File:Hx711 pi1.jpg|thumb|600px|HX711 with screw terminals and metal shield installed connected to P1/J8 on the Pi.]] | ||
| + | |||
| + | [[File:Hx711 pi2.jpg|thumb|600px|P1/J8 close up]] | ||
| + | |||
| + | Pins 2, 16, 18, 20 on P1 (Model A and B) or J8 (Model A+ and B+)are used: | ||
| + | |||
| + | {|class="wikitable" | ||
| + | !P1/J8 | ||
| + | !Pi | ||
| + | !HX711 | ||
| + | !Color | ||
| + | |- | ||
| + | |Pin 2 | ||
| + | | +5 | ||
| + | | Vcc | ||
| + | | Red | ||
| + | |- | ||
| + | |Pin 16 | ||
| + | |GPIO28 | ||
| + | |DO/RX | ||
| + | |White | ||
| + | |- | ||
| + | |Pin 18 | ||
| + | |GPIO30 | ||
| + | |CK/TX | ||
| + | |Green | ||
| + | |- | ||
| + | |Pin 20 | ||
| + | |Ground | ||
| + | |GND | ||
| + | |Black | ||
| + | |} | ||
| + | |||
| + | #define CLOCK_PIN 30 | ||
| + | #define DATA_PIN 28 | ||
| + | |||
| + | <br clear=all> | ||
| + | |||
| + | ===Method 2: Connect HX711 to P5=== | ||
[[File:Hx711b.jpg|thumb|right|600px|Two DCT Electronic HX711 boards with metal shield.]] | [[File:Hx711b.jpg|thumb|right|600px|Two DCT Electronic HX711 boards with metal shield.]] | ||
[[File:Hx711a.jpg|thumb|right|600px|DCT Electronic HX711 board plugged into P5]] | [[File:Hx711a.jpg|thumb|right|600px|DCT Electronic HX711 board plugged into P5]] | ||
Revision as of 16:57, 28 December 2014
Contents
Installation
Method 1: Connect HX711 to P1/J8
Pins 2, 16, 18, 20 on P1 (Model A and B) or J8 (Model A+ and B+)are used:
| P1/J8 | Pi | HX711 | Color |
|---|---|---|---|
| Pin 2 | +5 | Vcc | Red |
| Pin 16 | GPIO28 | DO/RX | White |
| Pin 18 | GPIO30 | CK/TX | Green |
| Pin 20 | Ground | GND | Black |
#define CLOCK_PIN 30 #define DATA_PIN 28
Method 2: Connect HX711 to P5
Building a Raspberry based electronic scale using the DCT Electronic HX711 board is as easy as Pi!
The DCT board comes with two sets of male headers, straight and right angle, and a metal shield.
You will need a 1x4 female header (2.54mm Pitch Straight Single Row PCB Female Pin Headers) and load cells.
- Order the board for $6.99 on Ebay
This one for $2.17 should work, too. - Download the software from gitHub
git clone https://github.com/ggurov/hx711 - Solder a 1x4 straight female header in P5 on Pi (bottom side of board) and a 1x4 male header on the DCT board
- Solder the load cells to the DCT board.
- Plug the DTC board into the Pi.
- Change the GPIO pins in hx711.c from 30 and 31 to 28 and 30. This way they are all on one side of P5:
#define CLOCK_PIN 30 #define DATA_PIN 28
| P5 | Pi | HX711 |
|---|---|---|
| P5-1 | +5 | Vcc |
| P5-3 | GPIO28 | DO/RX |
| P5-5 | GPIO30 | CK/TX |
| P5-7 | Ground | GND |
Calibration
Temperature Compensation
Temperature Sensitivity
From the CZL635 Spec Sheet link below:
Temperature Effect on Span 2.5 g/°C
Temperature Effect on Zero 5 g/°C
From the CZL602X Spec Sheet link below:
Temperature Effect on Span 0.02%F.S/10℃
Temperature Effect on Zero 0.03%F.S/10℃
Full Scale = 50 kg
.02% F.S/10℃
.0002 * 50 kg = .01 kg / 10℃
= .001 kg / 1℃
= 1 g/ 1℃
So the CZL602X are 2.5 times more stable than the CZL635
HX711 Spec Sheets
http://hivetool.org/w/images/d/d2/Hx711_english.pdf
