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If you are new to soldering, please take a look at the Preparation page. The most important tool is a good and hot soldering iron: it should provide high temperature to melt and reflow solder. Cold soldering iron is a major source of soldering failure.

Warning: electronic components are small and easy to lose. Before soldering, carefully place the components in a box or container. Small components may get stuck in the plastic bag. DO NOT throw away the plastic bag until you are done with soldering.

[Note: due to minor changes in different batches, some components on your board such as relay, RTC, battery holder may differ from the images below].

Remember: all images are ‘clickable’.

[Note: if your board comes with DS1307 RTC, you will find an additional crystal X2 (32.768kHz)– it’s cylindrical and very small (see picture on the right). Make sure to solder this crystal as well. If your board comes with DS3231 RTC, you won’t see X2 as it’s built-in to DS3231].

To solder, insert the components through the PCB holes. To increase productivity, I usually insert multiple components, and use painter’s tape to fix them in place (see image on the left). You can use as many pieces of tapes as you need. Then flip the PCB and solder all leads. This way you can solder multiple components at once.

Make sure your soldering iron is hot, and can easily melt and reflow solder. After soldering, use a diagonal cutter to clip the excessive leads.

Continue to solder C2 (100uF, same as C1), and C3 (220uF, smaller). Again, make sure the longer lead goes to the hole marked +.

Next, solder the two IC sockets (40-pin and 28-pin). Before inserting the IC sockets to the PCB, check to make sure all pins are straight. Every socket has a small notch (see the picture below) to help identify the orientation. This notch should match up with the silkscreen on the PCB. After insertion, double check and make sure no pin is left out or twisted. The solder joints should be clean and free of any solder bridge.

Also solder the 10 metal oxide varistors (MOVs). Each MOV is a blue, disc-shaped component. It’s non-polar, and its main purpose is to absorb transient high voltage and protect the circuit from power surge.

[Note: if your board has no MOV slot above the rain sensor terminal, you can solder the MOV directly onto the two pins of the rain sensor terminal. See picture on the right].

Next, solder the eight triacs T1-T8 (MAC97). Each triac is shaped like a half cylinder. Orient it such that the half cylinder matches the PCB silkscreen (i.e. the flat side should face the fuse and orange terminal block). Use your hand to bend the middle pin slightly backward, so that you can easily insert it to the PCB holes.

[Note: some kits may come with yellow-colored relays].

It’s important that the pin header is seated tight on the PCB. Try to avoid any gap between the pin header and the PCB, otherwise it will be difficult to put the cover on later.

After the battery holder is soldered on, take out the CR1220 battery, and snap it into the holder. The flat side (marked by +) should face up. The easiest way is to first insert the battery towards the side with a straight metal piece, then press the battery firmly to snap it in. If you ever need to take the battery out, push the straight metal piece as much as you can, until the battery pops out.

Voilà, you are all set with soldering! Carefully check your board with the image below. At this point, DO NOT pop in the two ICs yet (even though the image shows they are inserted).

First, measure the resistance between VIN (+5V) and GND as well as between VCC and GND. These pins can be located in the pinout area above the LCD headers. The resistance should be at least several kilo-ohms. If either resistance is below one kilo-ohm, there is probably a shorting or solder bridge somewhere.

Next, take out the orange terminal block, wire in 24VAC power, and insert it to the 24VAC port on the left side of the circuit board. Slide down the power switch to turn it on. Measure the voltage between VIN and GND — it should be around 5V; also measure the voltage between VCC and GND — it should be around 3.3V.

Important: if anything burns or smokes, immediately turn off power. Check to see if there is any component visibly damaged. If you can’t figure out the problem, post a message in the forum and we will help you.

That’s all. Now you have a functioning OpenSprinkler. Congratulations, and hope you enjoy using it!