1-Wire Energy Management Projects

Home Telemetry and Control Systems to Monitor and Reduce Energy Costs

 Control Box in Attic 

Updated: 08.13.2013 (prior page version is here)

The attic control box is 2' x 2' and stores the:

  • DSU421 board (1) for USB Micro-controller U421
  • DS2450 board (1)
  • DS2408 boards (2)
  • DS1000 power supply
  • 24V AC power supply for the sprinkler valves
  • Mechanical 24V AC relays that monitor the HVAC Systems to know when they turn on and off (more about that below)

My current box supports 22 IO ports but can support many more. If you compare this picture to the original design four years ago (bottom of the page), I've been able to eliminate all the control wiring like Ground, 5VDC and data line since all my boards can inter-connect with each other and have a connector board that supports the "U" shape configuration.

Also notice I now have the ability to add power supply to up the amperage. The USB Microcontroller only supplies 1/2 amp. Adding the power supply adds another amp and it's run off the 24VAC already present on the board for the sprinkler system control.

The power supply plugs right into the DS2408 or DS2450 boards and takes up two IO slots. The two IO slots cannot be used in this configuration but the addition of the power supply can support up to 64 IO slots. Need more power, add another power supply module!

Above is a picture of my control box. Not cheap. I purchased the box from AutomationDirect.com (see Links on this web site for more information about them).  This is a high-quality, heavy gauge steel box and costs about $250.

Below is the first generation control boards of mine (2009). Notice all the control wiring in the middle of both boards.

The silver looking screw terminal running down the middle is the "common" line of the 24V AC. This was a prototype design. In the production version (if and when) this will be eliminated since the 24V AC will be carried by inter-connect on the DIN Rail.


This is one of the three different Output boards used to switch the 24 V AC (control voltage of the sprinkler system). This board can plug into the DS2408 board or the DS2450 board and measures 1in x 1.5in (not including the laminated labeling)

The white box on the board is the mechanical relay.  The red LED lights up when the replay is closed. Like most all mechanical relays, it supports Normally Open (NO) and Normally Closed (NC) connections.

This is also a Output relay board but instead of being mechanical like above, it's Solid State. While there are advantages and disadvantages to Solid State relays, it mostly depends on the application.

This relay above (the black chip) is a Panasonic AQH3223 which can handle 600V AC @ 1.2A. Well above the requirement for the sprinkler system valves that switch on 24V AC @ .2A (or 200mA). These chips are very affordable too at $2 each. (the mechanical relay above was $1.75)

The disadvantages are:  

  1. There is no Normally Closed (NC) capability
  2. More sensitive device electrically (while the mechanical relay is very robust electrically) I burned up 2 or 3 of these chips during testing because of applying the wrong voltage.

The advantage is lower part count, 5 for Solid State versus 7 for the mechanical relay above.

This is an Input board using a 4N27 Optically Coupled Isolator Phototransistor (or OptoCoupler). Very standard item that costs about 35 cents each. This board is used to monitor when my Air Conditioning/Heating Systems are on or off and when the Rain Sensor turns on.

As the other boards, this board plugs into the DS2408 and DS2450 boards. As you can see, I can mix and match boards all day long depending on the application.

And finally, this was the "test" board I setup that allowed me to test all the different applications of this one board. Because the cost to produce these boards can be expensive I made one board design support three different chips. I had 50 of these little boards made for about $200 or $4 a board.

If I had made a board for each chip, it would have costs about $15 a board at quantity 10 each or about $450.

What you have to understand is one (1) board is going to cost about $125. Ten boards will costs about $135. Twenty-five boards will cost about $150. Keep in mind also there are other factors that can affect board pricing, like turn-around time.

I have recently added a fourth chip to this board for isolated digital output and also fuses to prevent over-amping the Solid State relay. none of these boards have been made.

Below is the design for the 4-IO board to be produced next year. This one board will support either:

  • AQV201 SSR - 40V AC/DC @ 500mA
  • AQH3223 SSR - 600V AC only @ 1200mA
  • 4N25 through 4N28 for isolated input
  • 4N25 through 4N28 for isolated digital output


Wire Length

The other advantage of these devices is the distance you can run the wires (phone cord) from the controller.

Sources on the internet claim 1-Wire devices support distances of thousands of feet. I've not tested that but so far my shorter distance tests have been successful.

In my project I plan on running about a dozen temperature sensors with wire lengths of about 300 total feet. (This is not as easy as it sounds but we'll discuss that in my "Timeline" articles)