Hardware: PCB Assembly

Dev Kit PCB installed on a Pi 2.

Parts

Parts List

Mechanical Drawing for RJ connectors.

Board Layout

Version 0.2

21 of these boards were released.

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  Connectors.

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  Console and 12 V power supply option 1.

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  Spare GPIO, I2C and I2S headers.

Version 0.3

43 of these boards were released. The rain gauge was moved to a different GPIO pin. The 1-Wire bus was brought out to spare pins on the DHT22 and rain gauge connectors. The DHT22 and rain gauge connector were moved. The order of the signals on H6, the I2S connector, was changed.

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  1-Wire connections added

Assembly

40 pin header

1. Insert the 2x20 female header from the bottom side of the board, tack two pins, and check that the header is all the way down on the board and is straight.

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  1.1 Insert the header from the bottom.

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  1.2 Solder one pin on each end.

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  1.3 Check the connector for alignment.

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  1.4 Melt solder and straighten.

2. After checking and adjusting alignment, solder the rest of the header pins on the top (component, silk screen) side of the board.

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  2.1 Solder the rest of the pins.

Resistors

Insert the resistors in the board. If you do not plan to monitor a 12 volt supply, you may not need R2-R5. If you do not plan to use a rain gauge, you may not need R6. R1 controls the brightness of the LED. The larger the value, the less current and the dimmer the LED.

Number	Value (Ohms)	Color Code	Purpose
R1	330 470	orange orange brown yellow violet brown	Controls brightness of LED
R2	200K	red black yellow red black black orange (1%)	12 V monitoring voltage divider
R3	1K	brown black red	12 V monitoring voltage divider
R4	2.2K	red red red	12 V monitoring Reference voltage divider
R5	2.2K	red red red	12 V monitoring Reference voltage divider
R6	1K	brown black red	Rain gauge input filter

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  2.1 Insert the resistors.

Male headers

Required

1. H8 1x4 and H9 1x6 for the HX711 board.

Optional

1. H4 1x4 for console serial port
2. H2 1x5 for I2C
3. H6 1x5 for spare GPIO
4. H7 1x7 for I2s
5. 4 1x2 for 12 V power supply option 1.

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  1.2

Capacitors

Number	Value (Ohms)	Purpose
C1	4.7 mfd. Electrolytic	Power supply filter.
C3	0.1 mfd Tantalum	Rain gauge filter.

1. Install C3 .1 mfd. for rain gauge filter. Observe polarity if tantalum.
2. Install C1 4.7 mfd. Observe polarity.

RJ1 and RJ2

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  Align latch pins with holes.

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  Check alignment before snapping in place.

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  Check all 16 pins stick through the holes before soldering.

1. Orient the 4 port RJ jack to match the parts legend on the top of the board.
2. Gently hold the 4 port RJ jack on the top of the board, carefully aligning the longer latch pins on each side with the holes. When the latching pins go into the holes, the connector will "seat" and move slightly towards the board.
3. While gently holding the RJ jack on the board, turn the board over and inspect the 16 leads. Make sure that each one is lined up with a hole.
4. If all the pins are lined up, firmly press the connector in by squeezing between thumb and fingers on each end and snap it in place.

Be very careful to check that all the leads are in the holes before you snap it in and solder it.

If a pin won't line up with a hole, it must be manipulated with a needle nose pliers until it will.

Solder shield on the HX711 board

Solder shield on HX711 board.

Solder shield on HX711 board.

1. Place the shield over the components making sure all 5 tabs go into the holes.
2. Turn board over and solder all 5 tabs.

Install the HX711 board

1. Insert the 1x4 and 1x6 female headers on the make headers.
2. Place the HX711 board on top of the 1x4 and 1x6 female headers.
3. Solder the 10 connections on the two headers.

LED

1. Install LED D1. Observe polarity.

12 VDC power supply if used.

Power Supply Option 1: D-SUN

WARNING: If you use the D-SUN 12 volt power supply it must be adjusted before you plug in the HX711 board or plug the board into the Pi! Failure to set the output of the 12 v supply to 5 volt will fry the HX711, Pi, SD card, USB peripherals.

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  Place the 4 1x2 female headers on the male headers.

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  Place the D-Sun power supply board on the 4 1x2 female headers and solder.

1. Solder four 1x2 male headers.
2. Solder blue screw terminal block. Make sure openings for wire face out.
3. Install four 1x2 female headers on the four 1x2 male headers.
4. Solder the Power Supply board on the four 1x2 female headers.

Power Supply Option 2: Fulree

1. Install Fulree voltage regulator
2. Install green spring terminal block.

Testing

If using Power Supply Option 1, the voltage must be adjusted to 5.0 to 5.1 volts before connecting to the Pi or HX711 board.