====== Building up a Soil Moisture Meter ======

===== Needed Parts and PCB =====

You need a **PCB**. You may use the layout from [[https://github.com/breaker27/smarthomatic/tree/develop/hardware/soil_moisture_meter|Github]] and etch it yourself or [[https://www.smarthomatic.org/shop/|order]] the PCB.

==== Partlist (in buildup order) ====

^  Amount  ^               Part                      ^  Placing   ^             Picture                    ^
|    1     | PCB Soil Moisture Meter                 |            |  {{ parts:pcb_soil_moisture_meter.jpg }}     |
|    1     | Battery holder CR2032                   | BAT        |  {{ parts:battery_holder_cr2032.jpg }}       |
|    1     | Capacitor 1µF                           | C1         |  {{ parts:capacitor_smd_603.jpg }}           |
|    1     | IC ATMega328 TQFP                       | IC1        |  {{ parts:atmega_smd.jpg }}                  |
|    1     | Transceiver PCB RFM12B                  | IC2        |  {{ parts:ic_rfm12b.jpg }}                   |
|    1     | IC 74HC14D                              | IC3        |  {{ parts:ic_smd_74hc14d.jpg }}              |
|    1     | Connector AVR Mini ISP 6pin             | JP1        |  {{ parts:connector_mini_isp.jpg }}               |
|    1     | Connector pin header (for serial TX debugging etc.)  | JP3   |  {{ parts:connector_pinheader.jpg }}  |
|    1     | Antenna (82,2mm wire)                   | ANT        |  {{ parts:antenna.jpg }}                     |
|    1     | LED 2mA                                 | LED1       |  {{ parts:led_yellow.jpg }}                  |
|    1     | Resistor 560R                           | R1         |  {{ parts:resistor_smd_603.jpg }}            |
|    1     | Resistor 1M                             | R2         |  {{ parts:resistor_smd_603.jpg }}            |
|    1     | Resistor 100k                           | R3         |  {{ parts:resistor_smd_603.jpg }}            |
|    1     | Button                                  | S1         |  {{ parts:button.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.

  - 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.
  - Measure with a continuity checker if there are any short circuits and remove them carefully. Especially check the pins of the ATMega.
  - Solder the LED and ISP connector.
  - Flash the device.
  - Now connect a multimeter to **check the power consumption**. Press the button when the device starts up. The device will blink some seconds very fast and then go to power down mode. **The device should draw only ~0.1µA.** If the current is much higher, you may have a short circuit somewhere.
  - Solder the debug TX pin, the RFM12B module and antenna with a soldering iron as usual.
  - Switch on the device and check power consumption again. With connected RFM12, it should now be ~1.7µA.

{{https://raw.github.com/breaker27/smarthomatic/develop/hardware/soil_moisture_meter/placing.png?500}}

//(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, [[http://www.smarthomatic.org/builds/builds.html|download a prebuilt binary package]] or [[build your own firmware|build your own firmware]]. If you bought a hardware kit, the ATMega should already be flashed.

===== Integrate it into a housing =====

describe it...