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OpenSprinkler v1.2u Build Instructions

(Note: all images below are ‘clickable’, in order for you to see the full-resolution details. )

To Begin: Parts Check
If you haven’t done so already, check your kit against the parts list. The picture on the left shows the PCB, bags of components, and the project case with screws. Bag 1 contains ICs and sockets; bag 2 contains diodes, resistors, capacitors, pushbuttons, pin headers, inductors, crystals; bag 3 contains triacs, screw terminals, Ethernet connector, USB connector, case screws, and 16×2 LCD.
Additionally, you need a sprinkler valve transformer (rated at 24VAC) and one or more sprinkler valves (24VAC as well). These are not included in the kit, hence you need to purchase them separately. If you have set up a watering or irrigation system in your garden, you should have these parts already; if not, you can purchase them in a variety of brands (Orbit, Hunter, Rainbird…) at a variety of places (Lowes, Home Depot, Amazon…). Check the F.A.Q. page for some suggestions.
To give you a heads up, here are two high resolution images of the assembled board (front and back). Click the images to see them in full resolution.

Part 1: Power Supply
To begin, place the PCB onto a a vise, and turn on the soldering iron. (Optional: use a fume extractor to help remove solder fumes).

Remember: all images on this page are ‘clickable’, in case you want to check full-resolution details.



Insert and solder all IC sockets (from the IC bag). Be careful when inserting the IC sockets: make sure all legs go into the PCB holes correctly. You can tape them to the PCB to avoid them falling out during soldering.

Every socket has a small notch (see the picture on the left) to help identify its orientation. This notch must match up with the silkscreen on the PCB.

Now we will build the power supply section, the components of which are all located at the left side of the PCB.

First solder D1, a 1N4001 diode. It looks similar to D2, so be sure to read the label on the diode. Use pliers to gently bend the two legs to 90 degrees. Note that diodes have polarity, allowing current to flow only in one direction. Before inserting it to the PCB, identify the end with a white stripe (the negative leg). This stripe should match the silkscreen on the PCB. Again, when in doubt, click on the images to get a full-resolution view.

On the back of the PCB, bend the legs to the side, so that you can flip the PCB and the diode will stay in place. Solder both legs.

To make sure the component lies tightly on the PCB, you can solder one leg first, then keep the soldering iron on the joint while pushing or pulling the component towards the PCB. Once it’s in place, proceed to solder the other joint.

Next, use a diagonal cutter to clip leads just above the end of the solder joints.
Follow the same method to solder D2 — a 1N5819 Schottky diode, as well as D3 and D4 — 1N4148 diode. Again, be careful with the polarity of diodes.

Now solder the green LED. LED is a diode, so it also has polarity. The longer leg of the LED is positive, and should go into the PCB hole marked with + as shown in the photo on the left.

Next, solder RLED, a 1.5K resistor. In the package you will find a strip of two 1.5K resistors. The colored rings on the resistors should read Brown-Green-Red. Resistors are non-polar, so you can insert them either way.

The other 1.5K resistor goes to R7, located above diode D4. This is a pullup resistor for the USB programmer.

Now solder the PTC fuse. I’s a yellow, disc-shaped component used for current protection. Use plier to straighten the legs a little bit, so it can go into the PCB holes easily.

If you don’t want current protection, you can instead solder a wire across the fuse to disable it.

Moving on, now solder RSC, a 0.47 ohm resistor located next to the PTC fuse. The colored rings should read Yellow-Purple-Silver. This resistor needs to be positioned upright, so bend one leg 180 degrees down, insert to the PCB holes, and solder it.

Heads up: during operation, the switching regulator will generate slight audible noise. This is normal. If for some reason the noise is unacceptable, you can replace RSC with a 1 ohm resistor, to limit the output current.

Next, solder CT, a 220pf capacitor. It is a timing capacitor for the switching regulator. This is a small yellow ceramic capacitor, and it comes by itself (i.e. not on a strip). The label should read 221. It is non-polar, so you can insert it any way.
Moving on, now solder C1, a 100uF/50V electrolytic capacitor. It’s a relatively large component. Electrolytic capacitors are polarized, so make sure the longer (positive) leg goes into the hole marked with +. To double check, there is a white stripe on capacitor body which points to the negative leg.

Similarly, solder C2 and C3, two identical 220uF electrolytic capacitors. Again, watch out the polarity and maker longer leg corresponds to + hole.

Now solder IC2, an MCP1700-33 linear regulator (from the IC bag). It has 3 pins and is shaped like a half cylinder, similar to transistor. Note: be careful not to confuse it with MAC97, which are triacs from the screw terminal bag.

Align it such that the semi-circle matches the PCB silkscreen. Then solder the three legs at the back of the PCB.
Next, solder RT, a 30K resistor. This looks very similar with the 10K resistors, so be careful. The ring colors should read Orange-Black-Orange (in contrast, the 10K resistors have Brown-Black-Orange colors and come in a strip of three).

The three 10K resistors should go into RRST, RB (close to the switching regolator), and R1 (located right above the 74HC595 shift register. So solder them as well.

Next, solder L1, a 220uH inductor. The label should read 221.
Note: more recent packages are shipped with a 270uH inductor, the label of which is 271.
Now you can solder RLCD, RD+ and RD-. These are three 47 ohm resistors that come in a strip of three. The color rings should read Yellow-Purple-Brown.

After you are done with this step, check your PCB against the image on the left. Click the image to get a high resolution view.

Now solder the Slide Switch, the USB connector, and the power supply Screw Terminal on the left edge of the PCB. Check the image on the left.

The slide switch and USB connector will touch with each other. This OK, no worry about it.

We are almost done with this part. Insert IC1 into its socket. This is a MC34063 switching regulator, which is used to step the input voltage down to +5VDC. Make sure that its notch matches the notch on the socket. Refer to the picture on the left.

Double check that you have inserted MC34063, not the other two ICs (24LC128 and ATtiny45) which are also in 8-pin package.


Now it’s time to test the power supply section. First, slide up the power switch to turn it off. Then, insert the two wires on your 24VAC sprinkler transformer to the screw terminal on the left. After you have tightened the screws, slide down the power switch, and you should see the green LED lit.

Important: (although this is unlikely) 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.

During operation you will hear a slight audible noise due to the switching frequency of the regulator. This is normal. If the noise is unacceptable replace the 0.47 ohm resistor with a 1 ohm resistor, but keep in mind that this will limit the output current.


Voltage check: use a multimeter, measure the voltage between GND and VIN (located at the upper-left corner of the PCB). It should read about +5V. This is the voltage supplied to the LCD.

Next, measure the voltage between GND and VCC, it should be around +3.3V. This is the voltage supplied to the rest of the circuit.

Important: It’s crucial to check and ensure these voltage readings are correct, otherwise your controller may not function properly.

After testing the voltages, disconnect the power.

Part 2: MCU and Ethernet Controller

 This part includes all components relevant to the microcontroller and Ethernet controller. Start with X1, a blue 8 MHz resonator. It has 3 pins and is symmetric, so doesn’t matter which direction you insert it. It is located right below ATMEGA328. Note that it is ‘double parked’ with two small holes above it. The two small holes are reserved for future use.

Next, insert C4, C5, two 0.1uF ceramic capacitors. These capacitors are on a strip of four, and the label should read 104. The other two 0.1uf capacitors should go into C7 and C8, located on the right side of Ethernet controller.

Tip: while you can solder each component one by one, you may consider improving productivity by soldering multiple components at once. To do so, you can use tape to fix multiple components to the PCB, so that they remain in place when you flip the board. This allows you to solder many of them in one pass.
Insert X2, a 25 MHz crystal. It has 2 pins and no polarity.
Insert CX1, CX2 — two 18pF ceramic capacitors. They looks very similar to 0.1uF but are on a strip of two and the label reads 18J. These are located next to the 25MHz crystal.
Also insert C6, a 10uF electrolytic capacitor.
Next, insert R2, R3, R4, R5, four 49.9 ohm resistors. They come on a strip of four so it’s easy to identify.
Also insert R6, a 2.32K resistor. The color rings should read Red-Orange-Red.
Next is RN1, a 680 ohm resistor network. It has 8 pins and consists of 4 isolated resistors. The label should read ‘681’. This component is symmetric so you can insert it either direction.
Now solder L2, a ferrite bead. It’s a dark, cylindrical element, and has no polarity.
The last step in this section is to solder B1, B2, B3, three right-angle pushbuttons, as well as the RJ45 Ethernet jack. Once this is done, the PCB should look similar to the photo on the left.

Part 3: LCD and Valve Driver
This section deals with the rest of the circuit. First, take out the LCD, the 1×16 male header and 1×16 female header. Solder the male header to the LCD. Note that the header should be roughly perpendicular to the LCD surface. The easiest way to achieve this is by making use of a breadboard to hold the LCD still during soldering.
Next, solder the female header to the PCB.
Now insert all ICs to their sockets: IC3 (24LC128) is a 16KB EEPROM, IC4 (ATmega328) is the MCU, IC5 (74HC595) is a shift register, IC6 (ENC28J60) is the Ethernet controller, and IC7 (ATtiny45) is a pre-programmed USBtiny ISP.

For each IC, bend its pins slightly inward on a hard flat surface. While inserting, carefully check to make sure no pins are left out or twisted. Finally, check your PCB with the photo on the left to make sure all ICs are inserted to the correct socket.

The next step is to solder RN2, RN3, two 330ohm x 4 resistor networks. The label should read ‘331’.
Then proceed to solder the eight triacs (MAC97) T1-T8. Use your hand or pliers to bend the middle pin slighted backward, so that you can easily insert it to the PCB holes.

Finally, solder the COM screw terminal, the 8-port station terminal S1-S8, and the Rain Sensor terminal. Now you are all set with the soldering part! Result is shown on the left.

Part 4: Project Case
Now you can assemble the project case. First, check the case, including the top, bottom, four case screws (long, #4 3/8″) and four PCB screws (short, #4-40 3/16″).
Fix the PCB to the case bottom using the four short screws. You will need to pull out the LCD momentarily to work on the screws.

Put the LCD back in. Now you can install the plastic cover. Slide the cover from the right-hand side, because the holes on the right-hand side have to go through the pushbuttons and the Ethernet jack. Then press the cover down and make sure it is in good contact with the bottom.

Use a screw driver to carefully insert the case screws from the bottom of the case.
That’s it! Now you have installed the controller to the case. Note that the back panel of the case is wall mountable.

Some notes about usage:

  • Every time you insert wires to terminal blocks, you need to take off the plastic front cover first. If you are making frequent changes to the wiring, just use a small piece of tape to fix the cover to the back panel. This way you can easily take off the front cover without messing with the screws.
  • Important: the case is not waterproof. While it can protect the circuit from accidental water splashes, it is by no means meant for outdoor use. DO NOT leave it outside unprotected. It should be placed in a garage or shelter that won’t catch rain or flood. If you must place it outdoors, enclose the circuit completely inside a waterproof box. It’s your own responsibility to protect it properly!

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