Nuts & Volts - May 2007

■ FIGURE 18

■ FIGURE 16

■ FIGURE 17

Carrier 1 board, as well. The board sits higher than the FireCracker so you will need two to three layers of the foam tape for the added height. Attach the four-cell battery holder next. You may also want to use some tape to hold the sensor pad wires in place. Make sure you don’t use metal tape for this.

Load up program DDishP3.txt and program it into the DiosPro. This program takes advantage of a few of the hardware features built into the

DiosPro. The DiosPro has the ability to be put to sleep and will draw only about 40 µS of power from the battery in this mode. To wake up the DiosPro, we use another feature called the watchdog timer. When turned on, it will wake up the DiosPro after it has been asleep for two seconds. If you look at the code, you will see that I make 130 calls to the sleep command. This causes the DiosPro to stay on a low power mode for five minutes. Once it wakes up, it does a dish test then turns the X10

device on or off depending on the reading. We are providing the power to the FireCracker, so just before we put the chip to sleep the power is removed so that the FireCracker itself does not drain the battery.

Another hardware feature of the DiosPro is the ability to self-monitor the supply battery. We make a call to this routine once each cycle and if the battery voltage drops below 4. 24

volts, it will toggle the device five times to warn us.

Final Thoughts

LINKS TO PARTS

AVAILABLE FROM KRONOS ROBOTICS com/xcart/customer/ product.php? AT www.kronosrobotics.com: productid=16288

■ DiosPro28 — www.kronosrobotics. com/xcart/customer/ product.php? productid=16169

AVAILABLE FROM www.X10.Com:

■ Dios Carrier 1 — www.kronosroboti cs.com/xcart/customer/product.php? productid=16170

■ FireCracker — (Note the FireCracker can be purchased cheaper from an eBay eStore.)

AVAILABLE FROM ALL ELECTRONICS AT www.allelectronics.com:

■ EZRS232 Driver — www.kronosrob otics.com/xcart/customer/product.php? productid=16167

■ Strobe Light — www.allelectronics. com/cgi-bin/category/605/Strobes. html

■ Four-cell Battery Holder — www. kronosrobotics.com/xcart/customer/ product.php?productid=16323

AVAILABLE FROM HOME CENTER:

■ Foil Tape — Standard HVAC metal tape.

■ 36-pin Female Header — www. kronosrobotics.com/xcart/customer/ product.php?productid=16291

■ Double Stick Foam Tape — Used to secure the Dios Carrier 1 and FireCracker to the inside of the bowl.

■ Nine-pin DSub Plug — www.kronos robotics.com/xcart/customer/product.ph p?productid=16254

■ Hookup Wire — I used wire removed from standard telephone cable (Cat 3).

■ 100K Resistors — www.kronosrobot ics.com/xcart/customer/product.php? productid=16195

AVAILABLE FROM PET STORE:

I have been using the dish now for a couple of months and it has worked without a failure. The alkaline batteries I have been using also show no signs of significant drain.

The complete schematic for the final assembly is shown in Schematic 2. Feel free to make modifications. There are several ports available for connecting things like LEDs, beepers, or other devices. You could also run a couple of additional sensor pads to test different water levels. For instance, use port 14 to run a second toggle pad. Just make an additional call to the Dish Test routine passing I/O port 14.

As for the water level warning indicator, just about any lamp will work. I use something a little different. I use one of those strobe flashers connected to an AC adapter as shown in Figure 18. I’m using the standard lamp module that came with the CM18 FireCracker kit. The strobe will flash whenever the dish needs more water.

The FireCracker — also known as the CM17A — is not an X10 device, nor does it communicate with the X10 protocol. It is a wireless transmitter that is designed to work with the TM751 transceiver module. While you can purchase the CM17A by itself, it won’t do you any good unless you already have a TM751. This is why they created the CM18 FireCracker Kit. This kit contains the following modules: