Mechanical Plant Watering Machine W/ Apple HomeKit Shortcuts Automation

Using a single pump, PVC tubing, valves, and connectors to make an indoor watering system has worked for me for several years. It is tricky to get enough but not too much water to each plant.

I decided that I needed a way to water with more control so I built this mechanical Plant Watering Machine that individually controls the flow of 8 water lines. For me, this approach seemed more doable (and fun!) than using an Arduino computer with moisture sensors, solenoid valves, expense, and, for me, a steep learning curve. Also I already had several of the main components and parts on hand to build this Machine. The total cost for project was less than $50 including $33 for the latex tubing.

The Plant Watering Machine is controlled with an Apple Shortcuts Automation controlling a WEMO WI-FI smart plug. - --- Even though this project is controlled by Apple stuff, there is probably an equivalent somewhere in Android/Google Land.

Supplies

This is a list of the materials I used but yours WILL be different.
• Plywood scraps (Baltic Birch is best), Wooden rolling pin ( solid Maple, 1/4” steel shaft, ball bearings,

• Wooden spring Clothespins

• Electric Motor with gearbox (I used an automotive power window motor)

• 2 - Limit Switches

• Nylon screws, plexiglass scrap, glue, washers, 1/16" aluminum, plastic tubing spacers, spring steel, wire, crimp connectors, wire nuts, junction box, duplex outlet, rubber feet, etc.<

• Natural latex rubber tubing 1/8”ID x 3/16”OD

• DIG brand fittings: straights, T’s, elbows (these are 1/8"ID and are a perfect, easy fit for the latex tubing

• Wi-Fi smart plug, Apple HomeKit compatible (Wemo, etc.) or Google/Android whatever

• Submersible fountain pump, 5 gallon pail or multiples daisychained together

• 2 - 5v Transformers (I needed these for my 12v motor. Depending on the motor you choose, these may be optional)

• A bunch of hand tools

General Layout

This top view shows a base plate made of 19mm BB plywood. Glued to it are two support blocks for the Camshaft (rolling pin) axel. Additional pieces were added to support the motor and switches. The valves are mounted to a separate removable baseplate. I provided space to mount a modified junction box and outlet. I made sure to leave open space in front and behind the Camshaft for the plumbing.

Camshaft Drive Assembly

The Camshaft has 9 positions. Positions 1 through 8 open and close 8 water valves in sequence. Position 9 is a rest position where all valves are closed. I divided the circumference of the rolling pin camshaft by 9 and drove 1/16” brass pins into the driven end of the Camshaft near the motor. I mounted the Camshaft to the supports adding spacers at each end for clearance. The Motor is something I had around and features a worm gear drive giving it high torque. I attached a drive pin to the Motor driveshaft. It engages with the Camshaft pins when triggered by the software program (below). This causes the Camshaft to revolve one step. Each time the Machine is triggered, the Camshaft revolves step by step to nine positions operating the valves in turn and then coming to rest at position nine where all valves are closed.

Motor note: The 12v motor used here is being powered by 5v transformers. Reducing the voltage sent to the motor reduces shaft speed and the impact of the drive pin hitting the camshaft indexing pins.

The Spring and Pump Switch

I added a piece of spring steel to press against the Camshaft end to provide friction. This was needed to keep the Camshaft from spinning freely and also to actuate the Pump Switch. Again, the Camshaft wants a nice push that allows it to move into position gracefully to reduce the tendency to spin.
Not shown is a screw in the path of the spring that presses against the Pump Switch to open it and turn off the power to the water pump socket (below) when the camshaft is in the rest position.

The Motor Switch

The Motor has a splined shaft on the opposite side as the drive pin shaft. I was able to press fit a piece of plastic tubing (Bic pen) onto the splines. I put a small wood screw into this to actuate the motor limit switch. In the rest position (shown in the shot with the light bulb), the screw holds the switch in open position.

Operation: Software causes the Wi-Fi smart plug to provide a short 1 second electrical pulse. This triggers the Motor shaft to rotate enough to close the motor limit switch contacts and supply electricity to the motor. The Motor will complete one revolution and will stop when the limit switch is opened again.

The Junction Box

A shallow plastic junction box houses a standard household duplex outlet. The side with the 5v transformer is directly wired to the power cord and is always energized. The other outlet (shown with a light bulb) is where the fountain Pump is plugged in. This side of the outlet is switched on and off by the Pump Switch. The schematic drawings show the wiring for both a Motor using low voltage and for a Motor using line voltage.

Safety Note:

My low voltage setup allowed me to send a 5 volt trigger pulse to power the motor for that 1 second or so while at the same time, the 5 volt transformer is also powering the motor as it is temporarily connected to the trigger transformer in parallel. Be aware of this and keep polarities straight.

If you are using 110 volts you may need to put a relay in the system to allow the trigger pulse cause the relay to temporally override the Motor switch at startup.

The Valve

What valve? We simply squeeze a piece of latex tubing closed with a modified wooden Clothespin. The Clothespin provides a strong clamping action that totally stops water flow. It also has a built-in hinge and lever. I glued a thin piece of plexiglas to the Clothespin top to provide a smooth, hard surface for the Camshaft lobes (nylon screws) to slide along. I created a staple shaped guide to assure the jaws of the Clothespin stay aligned. Wooden Clothespins are not a precision product and misalignments are to be expected.

The tubing exits the Clothespin Valve and terminates into a DIG straight connector. The connectors are held in place with a strip of aluminum. The groove holds the connector from twisting when attaching supply tubing to the Machine outlets.

The Valve Body

This assembly consists of eight spring style Clothespins glued to a piece 13mm board. The Clothespins are disassembled and the bottom arm drilled (+3/16') at an angle in the "groove" and filed smooth. Cut +3/16” channels on the underside of the baseplate for the valve tubes. I made this a separate assembly as it took a fair amount of screwing around and taking the assembly in and out to get things right.

The supply ends of the 8 valve tubes terminate in a manifold built up from DIG "T" connectors and DIG PVC tubing.

Camshaft Lobes

Camshaft lobes rotate into position and press open the Clothespin Valves. I used screws to provide for opening adjustment. I started with Phillips head wood screws which worked great except their cross heads were tearing up the clothespin surfaces. I switched to the nylon screws but had to drill and tap an 8/32 hole for them.

Again, it took awhile to get this all to work right. I had problems with slippage when a given position wouldn’t hold. I found that I needed to reposition some camshaft lobes.

The Software

This is a screenshot of an Apple Shortcut Automation. I have a Wemo Wi-Fi Plug called PlantControl as a Homekit Accessory. The automation first turns on the WI-FI plug. It then waits 1 second. It then turns off the WI-FI plug. That's it! A pulse of electricity has triggered the Motor and nudged the driveshaft enough to close the motor switch. The motor runs and revolves the Camshaft one position.

Write this little procedure and test your system. If all is well, the trigger pulse will start the Motor. The transformer plugged into the junction box will then take over. The motor moves the camshaft, closes the pump switch and water pressure goes to to the supply manifold and valve #1 opens. Water pumps out. Awesome! When you reach the desired run time hit the automation again and the motor will rotate the camshaft one position turning valve #1 off and valve #2 on. And so on. And so on.

Programming

I wanted each of my plants to receive just enough water so that only a small amount flows into the saucer. I have these indoors in a room with a wood floor. Too little water: unhappy dead plant. Too much water: ruined floor. And I’m 1700 miles away for a month or so. Tricky.

I watered the plants by hand twice a week for the last couple of months to determine the correct amount for each plant. I the set up the watering system and ran it and measured the time it took for each water outlet to deliver the proper quantity to its plant. A plant that is higher up and/or has a longer piece of tubing will cause water to flow more slowly than a lower plant with at a shorter piece of tubing, for example.

After trying a few different programming routines I found that simple is best. This example shows a string of the same three step things as above but adds a clock that triggers the automation. The intervals between triggers are watering times. Unfortunately, these intervals are in minutes. I tried to get down to the second in the following example as well as taking a different course.

These automations run in the background unattended and provide timestamped Phone and Apple Watch notifications each step along the way.

Programming 2

I tried this first. It made sense to have a list of watering intervals and loop the triggering routine using the list items as the amount of seconds of watering time. It would also be easier to tweak timings by easily changing numbers on a list. I also had feedback messages sent.

This just wouldn’t run right. Either there were errors or the total run time varied a lot each time. I think the WAIT times may be too long?

For now I’m using the first example.

If anyone out there has more experience with using Shortcuts for this kind of control application....Help!

Operation

Here is finished setup. The Watering Machine sits sort of centrally. Next to it are water supply buckets. The three buckets are linked together by siphon tubes. The nearest bucket contains the Pump whose output is connected to the input manifold of the Machine. Tubing connected to the 8 outputs of the Machine go to each plant or plant group. I have 13 plants in this room for the winter. I was able to direct water 6 of the large ones but had to group water 7 smaller ones with 2 outputs using DIG in-line valves to balance water flow among plants.

Use the natural latex tubing as specified (that black PVC tubing is too stiff and curly and difficult to make changes). I terminated each tube with a DIG elbow, a piece PVC tubing, and a stake or two.

P.S.

This thing is a Stepper Relay. I used to have one of these that I got out of an old pinball machine. An Awesome Electro-Mechanical Device! These can sometimes be found on eBay for <$40. Sending an electrical pulse to one of the coils triggers the relay to advance 1 position and latch there. Each pulse moves the switch to the next position. Sending a pulse to the second coil resets the relay back to zero. Use Wi-Fi switches and the type of program above to send timed pulses. Wire up to 24 solenoid water valves or little fountain pumps to the relay and you have large system on the cheap and easy!