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 Water Valve Controller
This Project was submitted to Parallax by Jamie Callin.
After hearing stories of people coming home from work only to find their basements flooded because of a water heater leak, I decided to develop a system to turn the water pressure off to the house when I left for work in the morning. Initially I purchased a 12 volt dc normally closed solenoid controlled valve with a switch near the entrance door to shut off the power to the valve when I left the house. This solenoid valve was expensive (around $100) but did work fine for a number of years. The system also had a 12 volt battery backup in case the power failed. Unfortunately, the solenoid valve was expensive to maintain and the power supply to keep the valve open when I was home slowly consumed ac power, the cost of which became significant as power rates increased.
So I decided there must be a system that only consumed power during opening and closing. I found at a local surplus store a high torque, slow speed cordless drill motor for under $10.00. Now the problem was to control this motor. Since I had used Parallax Basic Stamp 1 and 2’s for some time, the Basic Stamp was a natural fit for this application. Programming was easy and quick and most importantly, I wanted a system that didn’t consume much power. Since the program was not large and only a few inputs and outputs were needed, I choose a Basic Stamp 1.
I also purchased a low-cost standard water valve. After some work in the shop with a cut-off saw, a drill press, a Dremel tool and a lathe, I made a motor mount and a shaft system to determine the position of the water valve.
 Then I made a small interface board with transistors in the switching mode to act as an interface between the Basic Stamp 1 and the motor. The final step was to write the software for the Basic Stamp 1. The software was fairly basic but did become reasonably extensive due to the number of failsafe mechanisms required. Some of the features of the system are:
- An entrance switch to open and close the water valve
- A means to adjust the valve closing torque (using software)
- A means to halt the motor if the shaft between the motor and the valve fails to move or becomes jammed (using software)
- A sonalert to provide an audible means of indicating successful opening and closing of the valve and also a jammed shaft (using software)
- A means of reducing the current drain to a low a value as possible (using software)
- A two piece spring loaded shaft between the valve and the motor (using hardware)
- A final failsafe mechanism to prevent excessive current drain by the motor (using a fuse between the motor and the interface board)
 The power supply for the entire system is 6 D cell batteries or 9 volts. The Basic Stamp has an on-board 5 volt regulator for the Stamp circuitry while the motor uses the 9 volts directly. The motor turns at a rate of 4.9 rpm at 9volts and even at that low voltage still has enough torque to damage parts if it were not for the two piece spring loaded shaft and more importantly, the fail safe mechanisms built into the Basic Stamp 1 software. The Basic Stamp has been programmed to operate in the sleep mode for about 95% of the time so consumes very little power. For about 4.9% of the time it is in normal operating mode checking for status of the control switch. Even in this mode, it consumes less than 2 ma. About 0.1% of the time, it is either opening or closing the valve. In this mode, the system draws about 114 ma. At these rates, the D cells should last a very long time.
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Click on Image for a close-up | I have been using the system for a number of months now and it works well and only requires an occasionally oiling of the shaft mechanism.
Contact: Jamie Callin |
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