Cbot - Plant Maintainence Robot 1

Preliminary Development Projects

Updated 5/9/15


Development of the water tank, pump and feed mechanism
For a mobile robot to water plants at various locations around the home, it must carry and maintain a tank of water which is fills, travels with to the plants and then dispenses. And when it is low, it must refill as needed. Here we are going to show you this weekends progress on this facet of CBOT, and some testing of the water pump in action!

Left: Here is the water tank (Tupperware) on the bench to show its internal sensor. This consists of a flat plate with electrical contacts at various levels in the tub, which mark four different levels. As the water touches each set of contacts, the circuitry detects the change in resistance and indicates the water depth with a LED lamp, and sends a TTL level to the micro controller so it knows where the water level is at all times. Now it doesn't have to know EVERY water level there is, just when we are at four key positions. A huge cup of water is waiting on the left to be dumped in. The tub is 8 inches across and 4 inches deep.

Left: Schematic of the water sensor. CMOS logic gates are used to detect the change in conductivity and put out a 0 - 5v level for each step.


Water at several steps as I fill the tub, showing the LED lamps lighting as the water level gets higher. There are four levels indicated - Too Low where the pump water intake occurs, Fill is the low point normally, Full is the maximum when full, and Over full is way too high and will make a mess.

Left: Now mounted on the side of the tub, the circuit board is ready for action. Wires send the signals to the micro controller on the top deck.

Left: The latest view shows the water tubing coming out of the pump, through the lid and on to the post mount on the right side. A quarter inch mast will run the tube up to the top.

Left: Well, this is the basic concept on how I plan to have the robot water the plants. There will be 2 - 4 planting trays exactly like the one here, with funnels mounted in two or three places on each. The robot stops at each funnel and turns on the pump. The funnels connect to a tubing distribution system for each plant that carries the water right to the base of the plant. This way the robot does not have to be dangerously close to the delicate plant. Now the cool part - each funnel will contain watering instructions as to how long to run the pump so each plant gets the exact amount of moisture daily. I will determine this for the week and place a color chip at the funnel. A small camera with a color sensor will read each color at the funnels and send the amount of water I have indicated. So like red is pump for say 1 second, and blue for three, etc. (wait till you see the color sensor, its totally cool!)

The end of the tube will be attached to a curved piece, which I dont have here yet!

Left: Setup to see how much water will squirt out when I fire up the pump! Here Im manually filling the tank. The plan will be the docking station will do this automatically each time the robot docks for the night.

Left: And - Blastoff! with 12 volts on the pump motor in the tub, we get a very nice stream.

The next steps are to now automatically fill the water tank. The robot will actually do this by monitoring its water levels and running the fill pump on the dock by itself. Now that will be a trick...

Interested in learning more on the development of this robot? Here are previous uploads:

Previous Articles
1. Plant watering sensors
2. Cbot basic concepts and project definition
3.  Docking sensor, battery charging and FSM explained