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soil_moisture_meter

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Building up a Soil Moisture Meter

Needed Parts and PCB

You need a PCB. You may use the layout from Github and etch it yourself or order the PCB.

Partlist (in buildup order)

Amount Part Placing Picture
1 PCB Soil Moisture Meter pcb_soil_moisture_meter.jpg
1 Battery holder CR2032 BAT battery_holder_cr2032.jpg
1 Capacitor 1µF C1 capacitor_smd_603.jpg
1 IC ATMega328 TQFP IC1 atmega_smd.jpg
1 Transceiver PCB RFM12B IC2 ic_rfm12b.jpg
1 IC 74HC14D IC3 ic_smd_74hc14d.jpg
1 Connector AVR Mini ISP 6pin JP1 connector_isp.jpg
1 Connector pin header (for serial TX debugging etc.) JP3 connector_pinheader.jpg
1 Antenna (82,2mm wire) ANT antenna.jpg
1 LED 2mA LED1 led_yellow.jpg
1 Resistor 220R R1, R6 resistor_smd_603.jpg
1 Resistor 1M R4 resistor_smd_603.jpg
1 Resistor 100k R5 resistor_smd_603.jpg
1 Switch S1 switch.jpg

Buildup of PCB

Since this is a SMD PCB, you usually don't solder the parts with a soldering iron manually. Instead, you apply soldering paste to the PCB, place the parts on it and heat everything in a special oven. Please search in the internet on how to do that. You could also help writing a short “best practice” howto in this wiki.

  1. The first step is to solder (with soldering paste) all the SMD components, which is everything except the RFM12B module, the two pin connectors, LED and antenna.
  2. Measure with a continuity checker if there are any short circuits and remove them carefully. Especially check the pins of the ATMega.
  3. Solder the ISP connector and debug TX pin.
  4. You should flash the device now and see if everything works.
  5. Measuring of the idle power consumption is helpful to make sure there are no high impedance short circuits somewhere. (Note: Firmware has to be changed to allow that without connected RFM module.)
  6. Solder the RFM12B, LED and antenna with a soldering iron as usual.

(Image directly loaded from external GitHub source. If it doesn't work, fix link in wiki!)

Flashing the firmware

If you have a new ATMega where nothing is flashed onto, download a prebuilt binary package or build your own firmware. If you bought a hardware kit, the ATMega should already be flashed.

Integrate it into a housing

describe it…

soil_moisture_meter.1415285515.txt.gz · Last modified: 2014/11/06 15:51 by breaker27