Cbot - Plant Maintenance Robot 1

Preliminary Development Projects

Updated 6/6/15


Development of the reservoir refill system

There were a lot of challenges to getting this part of the system to work right. Circuit boards had to be designed and built, water pumps integrated and an IR modulation scheme to allow the robot to remotely turn on the receiver pump when it needed to. The ability for the robot to autonomously (all by itself) fill its own portable water tank when it gets low before heading out to water the plants without spilling a drop on the floor or making a mess is essential!

To accomplish this, the robots charging station was modified so that it not only has the spout at the top connected to the reservoir pump, but a IR receiver to generate the on/off signals to the water pump itself. The reservoir is a large square plastic bin, with an integrated lid which contains the tiny fountain pump at the bottom. Holes at the top allow the power cable to the pump and water outlet to pass through.

The system works quite well, right now the pump tends to fill the funnel on the robot a bit too fast and it can overflow if I dont back off on the flow with a valve or reduce the pump voltage a bit. For now to prove the concept I used a pinch valve on the rubber tubing from the pump to regulate the flow. It takes about 15 seconds to fill the tank from the half full position. More detail below!

Left: Front view, the current configuration. The filling funnel is seen on the right side, which has a yellow rubber hose leading into the top of the on board water tank, here which is at the full level. On the left is the pump outlet, which now is stiffened by a aluminum tube and puts out a 1/4" water stream pointing straight down, as to go into the plants filling funnels. The robot will not actually pour water directly on the plants - the robot will hit a funnel in the corner of each pot as to not risk damaging the delicate plants. The funnels on the pots will route the water right to the plants roots using small tubing. The dome protects the sensitive circuitry from dust, water and falling objects. (plant leaves can short the board out).

Left: Top view, showing the white fill funnel on the right and watering tube on the left.

Left: Here is what the water tank looks like when at the FULL level. its about half an inch from the top. There is an internal sensor to mark this location, as there also is one for overfilling it.

Left: The secret to making the robot have the ability to turn on the water pump in the big reservoir is here, the lower white LED is a 914nm infra red device of high power that transmits invisible digital data. The method I used modulates the 39khz carrier used in the IR remote sensor on the docking station with 1 khz. In other words - a unique signal that never occurs in nature or nearly any man made appliance. This and ONLY this signal can turn on the water pump on the reservoir to refill. Obviously with a 4 gallon capacity, we must be careful to not dump the water out unless the robots funnel is under the spout!

Left: The start of the demo sequence. First I hook some jumpers up to the robots own water pump to drain the tank to empty. Normally, the robot would do this when watering the plants when on its "mission".

Left: To see the water level, the 4 red lamps light in sequence. Left is empty, next is FILL, followed by FULL and OVERFULL. Here, the FILL and OVERFILL is out since the water has not reached them with the tank half full.The robot uses this digital data to know when to fill its tank and when it is full and to turn off the fill pump on the reservoir.

Left: Robot is turned on simulating the point it will be approaching the dock when it has finished watering the plants.

Left: Now within 2 feet, it slowly drives forward - correcting its path so it will exactly connect with the charging plates on the dock. The red lamp in between the two brass charging plates is its aim point. It is actually homing in on the IR lamps inside the small clear bubble on the dock at the top.

Left: Dock achieved. The funnel is exactly below the fill faucet. Numerous tests show that after docking many times, the faucet is always within half an inch of the center of the funnel. This means the funnel is large enough to capture the stream.

Left: The robot next turns on the modulated beam and the water pump starts filling the funnel. It is set to never turn the pump on over 30 seconds. Just in case the funnel is knocked off or something bad happens to its position.

Left: After the tank reports to the micro controller that it is full, the robot shuts off the tank pump.

Left: Full tank. The third LED is lit. The over fill LED is not...

Left: The display reads the tank is FULL and how many seconds it took to fill it. To do this, I simply kept track of how many cycles of modulated 39kc I sent. 14,000 cycles were 14 seconds. It takes 1 mS (one thousandth of a second) to send one cycle. This is all generated in the master micro controller. (robots brain).

Left: Full tank with tiny 12v fountain pump inside. Ready to water the plants again.

Left: The front of the robot has a circuit board with a green LED at the top to indicate contact with the charging plates, and under it is a clear LED which transmits infra red data. Note the top of the IR LED is flattened with a file to spread the beam out to about 45 degrees width. The lens on a standard LED is much narrower, only about 15 degrees for this model. Those copper colored "wires" that contact the charge plates? Those are Guitar strings....

Left: Robot on charger/fill station parked waiting for night time. In the final version, the robot will look for daylight then wake up and go water the plants. When done, it spends the rest of the day back on the charger, now looking for night. Then it looks for daylight again...

This process is a bit complex, since it must take in account what happens if someone turns on the lights inside the house at night.

Left: The top of the reservoir tank. Holes on the upper right are for pump wires and tubing. A make shift pinch valve slows the flow of water for now.

Left: Inside the reservoir is quite spartan - a tiny fountain pump, same one as in the robot, and about 2 gallons of water. Cat litter bins are great!

Left: Electrical connections to pump and 18v power from the docking station. By making it easy to disconnect, we can fill up the reservoir fast with a minimal of effort.

Left: This is the micro controller board inside the docking station for receiving the modulated 39kc and converting it to pump on/off signals. The micro has its own 5v regulator, and the pump its own 12v regulator from the 18 v supply inside the dock. Everything is programmed in C. :)

Left: Schematic for pump receiver. Click to enlarge.
Movie 1
Left: a small movie of the robot docking and filling up. Yeah its tiny 160 wide, but hey, you can hear the pumps turning on and off...

Interested in learning more on the development of this robot? Here are previous uploads - LATEST AT THE BOTTOM:

Previous Articles
1. Plant watering sensors
2. Cbot basic concepts and project definition
3.  Docking sensor, battery charging and FSM explained
4.  Development of the water tank, pump and feed mechanism