Seeing lawn spinklers constantly running in the rain, John thought about how silly and wasteful they are. So he developed a device that monitors the moisture content of the soil and automatically triggers a sprinkler system when required. The sensor is a pair of electrodes (based on bicycle spokes), while the controller for the device is based on a fluid detector powered by the nominal 24V ac most sprinkler systems use.
Water minder parts list
Allied Part #
Relay, 24V dc
Switch, SPDT Toggle
Trim Pot, 50k
LED, Red, T1, ¾
Zener Diode, 24V dc
Cap, Elec, 220 mF/50V
Resistor, 270V, 1W
Additional parts required: Fluid detector, miscellaneous resistors and capacitors, and bicycle spokes
The LM1830 has a built-in oscillator, a comparator and output drive circuitry. When the sensed pin has a higher resistance (drier) than the reference, the output turns on. In this case the output cannot supply sufficient drive current for the signal LED and relay, so a transistor buffer is added. The dryness setpoint is set by the trimpot and a bypass switch is included for testing, etc. The relay specified can handle 10 amps – plenty for a water solenoid.
The sensor is a pair of electrodes that contact the soil at the desired level. They should be stainless steel to resist corrosion. Where’s the best (cheapest) place to get these – bicycle spokes! I potted 2 of them in a 35mm film canister and put heatshrink on all but the lowest 1” of the spokes.
Camera ready artwork for the pcb and chassis cover are available from:
Sunspot Svcs, 115 Greenbrier Dr Simpsonville, SC 29680 $2, check or money order plus S.A.S.E.
A quick look into the merger of two powerhouse 3D printing OEMs and the new leader in rapid prototyping solutions, Stratasys. The industrial revolution is now led by 3D printing and engineers are given the opportunity to fully maximize their design capabilities, reduce their time-to-market and functionally test prototypes cheaper, faster and easier. Bruce Bradshaw, Director of Marketing in North America, will explore the large product offering and variety of materials that will help CAD designers articulate their product design with actual, physical prototypes. This broadcast will dive deep into technical information including application specific stories from real world customers and their experiences with 3D printing. 3D Printing is