1-Wire Energy Management Projects

Home Telemetry and Control Systems to Monitor and Reduce Energy Costs

  Controller Chips

In order to manage the 1-Wire devices, there must be a master controller. Most all of the 1-Wire devices used are slaves.

This one effort trying to determine what controller(s) to use, how the software would work, how many Windows Services would be required and such occupied lots of time during the early months of this project.

USB Micro U401 and U421 Controller

Searching the internet under "1-Wire Controller" I came across the USB Micro U401. This is a micro-controller that talks to the 1-Wire devices and has most all of the "base" commands already programmed in VB6, VB.NET, C# and other languages. Since my experience was in VB6 and VB.NET programming it seemed to be the right choice and I was right!

Above is a very simple circuit connecting a few 1-Wire DS18S20 temperature sensors to the USB Micro controller (top of picture). Along with some example programs on the USB Micro web site, I had this working in less than a hour using Microsoft VB6. Later I was able to get a Microsoft .NET program working with little effort.

The U401 and U421 connect via USB to a Windows computer which is really doing all the controlling. This is not a stand-alone microcontroller. The Windows computer must be connected at all times and this was part of my design plans (but it would be a dedicated computer running Windows 2003 .NET Server).

In all original plans for my system ,this controller remained the leader. But after many months trying to program my own routine to scan the network for devices (an important feature working with the temperature sensor chips) I decided to only use this controller for the DS2408 and DS2450 boards.

Home Made DS9097 Controller for Serial Port

Lots of schematics on the internet for this controller.  A number of diodes and resistors assembled correctly will create a controller the Maxim 1-Wire drivers for Windows recognizes and it works well!

Pictured above is the (home made) DS9097 serial port interface for 1-Wire devices. Maxim no longer offers this design.

The problem with this controller is it's limited to controlling a small number of devices (like 6 to 8) and over a short distance of wiring (maybe 50 to 75 ft). The devices operate on "parasitic" power also.

For this reason, it's a GREAT bench test controller.

DS9490 1-Wire USB Adapter (Controller)

Most computers today no longer support Serial Ports. This controller from Maxim uses USB and it works GREAT!

Above is the DS9490 USB controller for the 1-Wire network made by Maxim. This device uses a standard RJ11 jack (phone jack, not Ethernet). 

I decided to use this device for temperature monitoring (so also meant a stand-alone Windows Service). Turned out to be the right decision simply for that fact that if you are building a complex Control System, it's best to break up the different systems as much as possible. This is because systems will fail!

If you design one software system to do it all, and one part of the system fails, the entire system fails. I decided to have two software systems, one for temperature monitoring and one to control the DS2450 and DS2408s which control my sprinklers and attic fans. Soon to control more around the house.

When I added insulation to my attic in July 2010, it shut down my temperature monitoring system due to static electricity. In other words, blowing insulation through a 100ft plastic hose generated static electricity. That insulation surrounded my temperature sensors, shorting out the network.

It took hours to get the temperature network working again but once the static electricity dissipated I've not a problem since.

My sprinkler and attic fan system never missed a beat! So it paid to keep the systems separate (If you are wondering, data is shared between systems via a Microsoft 2003 Access database.)

  1-Wire Chips

So far I've focused on three primary 1-Wire chips in my control system design, the DS18S20, the DS2408 and the DS2450. Each chip services a specific purpose, with some overlap a two of them. Below is a quick explanation of each chip and what they are used for.

DS18S20

This chip is a 7 or 12 bit resolution temperature sensor with settable trip points for monitoring a above or below expected readings. The resolution range translates into either a 1F (low resolution) mode and a .1F (high resolution mode). I use the high resolution mode in my project.

The chip can operate in two modes. Either a powered mode (where 5vdc is applied to Vdd or as a parasite mode where powered is stolen from the data line (DQ). Of course, the ground line (GND) is not option (required).

While it sounds great, parasite mode has complicated data signal requirements so all my uses have Vdd powered.

Another consideration you have to understand is these devices return degrees C, not F. So a simple calculation has to be performed to do the temperature conversion.

For more information on this device, download the datasheet.

DS2408

This chip is the workhouse of my control system. An 8 port addressable switch. My current systems uses two of these with plans to add more. Using two gives me 16 input or output ports, or a combination of both.

 

 

 

 

  Discrete Components

A number of discrete components make up the end board I/O switches. This part of the page is still in work.

Panasonic AQH32234

This is a Solid State Relay capable of controlling 600V AC @ 1.2 amps.

 

 

 

 

1-Wire Chips

All 1-Wire chips have a unique 64-bit serial number encoded at the time of manufacturer.

This is important since, this serial number becomes the key needed to access a particular chip. No two serial numbers are the same and will never be repeated.

So if you have 10 different temperature sensors located around the house, you can specifically request the temperature for a single device based on the serial number you provide in code.

Data Line is High or "On" by Default

One of the more peculiar features of the 1-Wire chip is the default state of the data line is High or On.

While it does not overly complicate working with the device it does take some altered thinking.