Automatic Electronic Plant Waterer

Hello, welcome to my instructable on how to make an automatic electronic plant waterer. This project was intended to make a machine that would automatically water my plants so they don't turn dry. This goal was somewhat reached, more about that later.

This project is intended for beginners, minor electronic knowledge and basic soldering skill is required!

Note: some of the pictures were taken outside but this is intended to be an inside project!

Firstly you must gather all the materials to make the waterer, all of the listed materials can be bought on eBay or from the local supermarket/hardware store. I also added a list of tools I used.

Materials:
- Plant humidity sensor "stake" style. I bought mine for a few dollars off of eBay. Be sure that your sensor has a analog readout and not a digital one.
- 12V solenoid valve
- 1/8 Bsp male - 8MM straight push in fitting
- 30 cm of speaker wire (or any other type of thin double channel wire)
- Coca-cola bottle
- Super glue
- Stick/stake (I used an aluminium extrusion) about 2 feet
- Rubber tubing (8mm outer diameter to fit into the fitting, and an inner diameter according to your solenoid valve (mine was 5mm)
- Duct tape
- M3x10 bolt with 2 washers and 1 nut
- Battery or power supply with matching wires/plugs/connectors accordingly (12v)

Tools: - Knife - Soldering Iron - Wire stripping tools - Drill

Once you have collected everything you can start building your automatic waterer!

Firstly, take a look at the back of your sensor. If it is assembled without screws (like mine) it will be easy to open, just pry a knife between the casing to open it. If there are any screws be sure to take those out first. Once you have opened it up repeat the same step for the analog sensor (mine only has some tape holding it together).

Once the needle is exposed take a close look at it. If it is covered in enamel you will want to scratch that off because the enamel coating acts like a insulator. Next you want to determine where you want you "cutoff" to be, the cutoff being the level at which you want the waterer to kick in. I decided that once the needle hits the red zone (not enough water) it turns the waterer on. Mark that spot with a line and align your drill so that you drill right past the line (to the left). The hole needs to fit the M3 bolt.

Next, stip the speaker wire to about an inch length on one of the channels, the other channel just needs to be soldered so it does not need to be stripped as much. put a washer on the m3 bolt and wrap the largely stripped channel of the wire around the bolt. Then cover it with another washer "sandwiching" the wire. Put the bolt though the back of the display making sure the needle is on the correct side. Then secure it but placing the nut on the front.

The other wire needs to be soldered to the metal framework that connects to the needle, mine has a little prong but yours may be different. Finally drill a hole in the back and put the wire through, while at the same time putting the back of the case back on.

Now you have essentially created a switch that closed when the waterlevel drops below a certain point!

In order to make water flow from the bottle to the valve there need to be a waterproof connection via the tube. Firstly, drill a hole in the coca cola bottle cap that fits the fitting. Then, screw the fitting in the hole and waterproof it with the glue.

If you bought the right tube it will fit right into the push in fitting and also on the valve. You will need to see what configuration is easiest for you, you don't have to make it exactly like I did if you have a better way. If you do choose my way, tape the valve to the push fitting and connect them with a piece of tube (be careful not to pinch the tube in the corners!)

Finally, drill a hole in the bottom of the bottle to let air out, be sure that it's a hole that you can cover with your finger so you can fill the bottle. Attach the bottle to your stake with the tape, fill the bottle and screw the cap on the bottle

Now you must connect the wires. Depending on what type of power source you chose you must connect the positive wire of the plug/battery to the valve, and the negative wire to one of the wires leading to the sensor. Attach the other wire from the sensor to the other terminal of the valve.

Congratulations! your automatic plant waterer is done now! Place the sensor and the stake of the bottle in soil and connect it to the power. Be sure the hose from the valve leads the water into the plant.

As a final note I would like to add some information and suggestions that might be helpful
- If you cut the bottom off the bottle (top when upside down) you can refill it
- Be sure you can twist the cap with the solenoid off (be sure it doesn't hit the stake)
- Cover the wires and terminals in tape or shrink wrap so they don't short circuit
- Make the stake think, the bottle will weigh a lot and eventually fall over

Feel free to add suggestions in the comments!

Also, I would appreciate your vote in the contests that this instructable is entered into!