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1-Wire Boards

Recent Additions

Serial Base/Hub.
USB Base/Hub.
Battery analyzer.
Environmental Monitor.
Thermocouple Monitor
Linksys router serial adaptor.



New for 2010 is a thermocouple monitor. A need arose for monitoring an environmental chamber at extended temperatures.

These boards use the Dallas/Maxim 1-wire ind iButton devices. This is a fun little project to take up some spare time. You can e-mail me with any questions. 1wire at n952 dot dyndns dot ws

There may be a USB base/hub and/or a Serial base/hub attached to this machine at any time. Searching through things will, of course, reveal what's attached at the moment.
1-wire bus on this machine
The owhttpd daemon may be diabled at time, particularly when performing battery analysis.

This all runs using OWFS by Paul H Alfille.

Base/Hub

The Base/Hub boards provide a connection to the PC, in either serial or USB formats. Both boards may be reconfigured for use as remote hubs (i.e. eliminating the PC connection) by skipping installation of the DS2480/DS2490(although they will function as a remote hub with the DS2480/DS2490 in place).

The remote hub may be powered through the base/hub using typical network cable through J30 on the remote hub. To power the remote hub locally, use single pair (rather than the 4-pair used with network cables) to connect to the base

Both base/hub boards provide switched LAN segments on J60 and J67, the left-hand connectors. Jumpers are provided to accomodate a TA8515 weather station on either of these ports. The nominal pinout for the ports is the 1WRJ45 standard documented at http://www.1wire.org/en-us/dept_27.html
The serial base/hub and USB base/hub differ in their implementation of J70/J77. The Serial base/hub has these two connectors configured as 1-wire LAN segments using the 1WRJ45 pinouts. The USB base/hub has these connectors configured as counter channels.

Circuit boards cost about $25 each in quantities of 1-5. Dallas devices may be obtained from several sources although I went directly to Dallas/Maxim in order to obtain all of them from one place. Prices were best from Dallas/Maxim but shipping can be a bit of a problem. The Housing was obtained from Mouser Electronics. All of the remaining components are available from Digikey. Power for the base.hub board is through a 5-pin DIN connector. Several inexpensive +5V/+12V supplies are available from Jameco Electronics. Jumpers on the base/hub board allow several of the +5/+12/-12 supplies to be used as well.

Parts Notes

Surface mount resistors case size is 0805.
Surface mount ceramic caps are case size 0805 and 1206.
Surface mount tantalum caps are case size CWR11B/CWR11C. These also may be listed as T494B/T494C or as 3528-21/6032-28.
USB:

USB Base/Hub

Combination of DS2490 USB-1wire interface and the DS2409 hub. This board allow connection of three 1-wire segments to a USB port. Power is obtained from an external supply to avoid problems with the current limits imposed by USB. 2 1-wire branches are provided on the base board. A 2nd. board may be piggybacked to the primary board if additional legs are required.

In addition to the interface and hub functions, several pad sets are provided to allow temperature or other 3-terminal 1-wire devices to be added to the board.
A 4 channel A/D convertor is provisioned, with 1 pin of each of the 4 RJ45 connectors routed to the A/D convertor.
2 connectors are routed to a DS2423 counter chip through optical isolators.

Surge supression is performed by a dual schottky diode connected between ground and VRAW(12V). This allows programming of device that require programming voltage (such as EEPROM).

Parts Notes

C5 and C6 will probably be too large at 33pF. I had problems with the oscilaltor in the DS2490 starting so I removed C5/C6 and the board started working. I suspect that a 10pF would be a better choice although I haven't tried them.

Hardware Image Working Board
Schematic Image Schematic
Circuit Board Image Circuit Board
Parts List

Revision 1

Two minor changes. The protection device on the DS2409 channels is reverted back to a DS9503 (as seen on the serial hub). Pullup resistors are added to the MAIN/AUX channels on the DS2409 to provide power to devices when the bus is not selected.
Schematic Image Schematic
Circuit Board Image Circuit Board
Parts List
Serial:

Serial Base/Hub

This board is similar to the USB base/hub with the DS2490 replaced by a DS2480. Power provisions are identical.
This base/hub has 2 DS2409 hubs and no DS2423 counter, so all 4 RJ45 connectors are 1-wire lans.
The boards are the same form-factor with matching internal connectors so either may be piggy-backed

Note the use of the DS9503 surge supressors on this board. This limits the board to devices that do not require VRAW(12V) for programming on the connectors with a single DS9503 performing surge supression. The circuit boards I have in hand have a single DS9503 on all 5 1-wire ports although the schematic and circuit layout shown have a dual DS9503 shown on J30.

Parts Notes

Note in the picture of the board that R31 is installed and R32 is not. This is important, the reason being left as an exercie for the reader.

Hardware Image Working Board
Schematic Image Schematic
Circuit Board Image Circuit Board
Parts List

6 Port Base/Hub Configuration

Both the Serial Base/Hub and the USB Base/Hub may be cleaved along the separation line on the circuit board to allow an additional set of hubs to be added. The 2 board stack just fitrs in the indicated enclosure. A simialt albeit shorter enclosure is avaialbe, in the same series, that is large enough for a single board.

The specific configuration shown here has the upper row of RJ45 connectors all configured as 1-wire LAN's. This daughterboard was cleaved from the Serial Base/Hub.
The lower row, being the USB Base/Hub, has 2 1-wire LAN's on the left pair of RJ45 connectors, and 2 counter channels, one each on the right pair of RJ45 connectors.

In addition to the LAN segments presented on the front panel of the housing, there is a local 1-wire segment presented on the back side (along with the USB and power connectors). This segment, as you can see on the schematic, is connected directly to the DS2490 device.
Hardware Image Additional pair of DS2409, piggyback
Hardware Image USB Base/Hub in enclosure, Front Side
Hardware Image USB Base/Hub in enclosure, Back Side
Battery:

Battery Analyzer

This board is intended to allow discharging and profiling of AA and AAA NiCd and NiMH batteries. Cells are individually discharged, so cell reversal is not possible.

This board has dual DS9503 surge supression devices to allow programming voltage to be applied to the DS2433.
J4/J5 allow splitting the board into a separate control board and battery holder. When split, the form-factor of the control board is identical to the base/hub boards so the housing noted on the schematic may be used.

This board is similar to the base/hub boards, comments about the source of materials applies equally here. One major problem I have encountered being the battery holders. Solder flux needs to be thouroughly removed from the contacts on the battery holder and the batteries need to have the ends thouroughly cleand as well to obtain meaningful results.
The cell clamp shown on the layout drawing keeps the row of cells in the holder. I haven't fabricated and tested the clamp yet, so I find it necessary to exercise due care when inserting the batteries in the holders.

The board requires only a small ammount of power so it obtains power through the 1-wire connector, J3. Only 5-volt power is ised by the board. The board also has 10 pin headers located in the same position as the base/hub board, so it is possible to piggy-back this board with others. You will notice that +5V, +12V, GND and 1-wire data signals are routed through the headers.

The DS2409 is used on the design to separate the 1-wire devices on the control board from those on the battery board. Software need only know the path to the DS2409 to correctly function. The DS2450, DS2408, and DS1820 on the control board are on the main branch of the DS2409 with no other devices. The aux branch is routed to the battery board where only parasitic powered devices are allowed. Both the aux and main branches have a pull-up resistor to provide power to parasitic devices when the branch is not selected.
Hardware Image Working Board
Schematic Image Schematic
Circuit Board Image Circuit Board
Parts List

These plots shows a test of the battery analyzer. The batteries are loaded using both the R32/R42/R52/R62 and the R33/R43/R53/R63 load resistors. The loads are applied until the last cell reaches 0.5 volts.
Since the cells are NOT in series, it is not possible for any of the cells to reverse, so no damage occurs to batteries 3, 1, and 2.
The first plot is the first full discharge of the batteries following several months of service in a digital camera. They were charged in a processor controlled charger.
The second plot is a discharge right after fully charging the batteries (in the same digital charger).
The horizontal scale is hours, and the vertical scale is volts. Direct measurements are time and voltage. Current and power are calculated and integrated to give the battery capacity.

Keeping in mind that the battery load consists of 8 resistors on the control board, you can see the power dissipation in the temperature plots, the DS1820 is located closest to the load for battery 1, and indicates a drop when battery 1 is exhausted.
The 2nd. plot appears to indicate the batteries were removed from the charger shortly before begining the 2nd discharge (i.e. the Bat Temp shows a slight drop at the begining of the plot).
Battery Test Plot First Run

Battery Test Plot Second Run

Enviro:

Environmental Monitor

The typical temperature and humidity monitoring board. The board was made to monitor conditions in an electronics parts storage area. Initial build and testing indicate the board is functional.
This board has the same footprint as the base/hub boards to allow use of the same series of housings.
The board is now in its third revision with minor additions to improve the control function.

Temperature

Using the DS1820 series temperature sensor or the temperature sensor in the DS2438.
This implementation will make use of the termperture sensor in the DS2438, eliminating the need for additional temperature sensors.

Humidity

Pads for several humidity sensors. A/D is provided by either a DS2438 or a DS2436.
This latest revision switched to using a Honeywekk HIH-4000 series sensor as the Humirel device is no longer available. The HIH-4000 datasheet indicates that the sensor is ratiometric and is, therefore, sensitive to power supply voltage.

Counter

DS2423 in not installed in this application.

PIO

DS2406 channel A connects directly to a sonalert and channel B drives a MOSFET (revision 3 boards)

Hall effect sensor

Located in the lower right hand corner of the board. Intended to provide a garage door monitor. Not installed in the application that these boards are being used in.

Infrared Detector

Located in the central are of the board. Will have to look out through a hole in the top cover of the enclosure. Not installed in the application that these boards are being used in.

Sonalert

Annoying annunciator.

Board Image Large board image

Finished circuit board. Many of the components are not installed on this board. The application of this particular board is as an environmental monitor, so only the DS2409 and DS2438 are required. Only the J30 connector is installed, as it is the only connection required for this particular application.
The board is installed in the same type of case as used fby the hubs.

Schematic Image Schematic
Configuration Notes
R11/R16 are normally not installed. They are provided to accomodate piggy-back configurations (i.e. additional board attached through J1/J2 in the same housing) and to allow additional sensors on the AUX channel without the need for the DS2409B.
J30/J31 provide a means to daisy-chain several devices if required, while J60 provides a connection through the AUX port of the DS2409B.
R14/R15 provide power to DS1820 and friends when the DS2409 delelects the MAIN/AUX bus.
VR1 may be used to provide regulated 5 volt from the +12V line in some cases. Obviously you would need to remove JP30 and connect to the base through J30 in this case.
Install a DS2433 to allow board configuration and calibration coefficients to be stored on the board.

Circuit Board Image Circuit Board (Top) Circuit Board Image Circuit Board (Bottom)

Parts List

Thermocouple:

Thermocouple Monitor

Using the same form factor as the environmental monitor, but configured with a pair of cold-junction compensation circuits.

Temperature

Using the DS2438 battery monitor to read the voltage from an AD594/AD595 thermocouple amplifier. 2 channels are provide for on the board. In support of the environmental monitoring system in Van Allen Hall, a 2nd. DS2433 is provisioned (at U246) to allow storage for the 2nd. DS2438 A/D channel.

Sonalert

Annunciator.

Board Image Large board image

Finished circuit board.
The board is installed in the same case as the hubs.

Schematic Image
Schematic Postscript

Configuration Notes


Trim R24 for a voltage of about 2.5V. This will place 0 Deg C. from the AD594/AD595 to the VCC1 voltage and allow the thermocouple to monitor +/- 100Deg C.
R1/R2/R3/R4 and R201/R202/R203/R204 are provided to allow the AD594/AD595 to be trimmed for other thermocouple types. For type J and K thermocouples the chips are factory calibrated.

A haywire from pin 1 to pin 4 of the AD595/AD594 is required (not shown as such on the schematic).

Also missing from the design, is a load resistor on the output of VR2. The LT1117 device requires a minimum load to maintain regulation. A 470 Ohm resistor needs to be added between VCC1 and ground for the regulator to operate correctly (worst case minium load current is 5mA). Place it between C6+ and J2-3.

Type K Thermocouple Notes

Install U1/U201 as AD595
Trim R24 to produce 2.500V at the VCC1 pad next to R24. The DS2438 should show 2.5V when the probe is immersed in an ice slurry.
Omega 5TC-TT-K-24-72
Yellow wire to pin 1 of J101/J201
Red wire to pin 2 of J101/J201

Circuit Board Image Circuit Board (Top)
Circuit Board Image Circuit Board (Bottom)

Parts List


Linksys:

WRT54G/WRT54GS/WRTSL54GS 1-wire paddle card

This is a serial card for the Linksys routers. It has both a RS232 level shifter and a DS2480B 1-wire controller. The input connector configuration allows a fair degree of flexibility in connecting to the router (i.e. you can configure boards to allow 2 serial connections, or 2 1-wire connections or one board to do both and attach to either serial port)
Although this board has a small footprint, it is large enough to allow the fumble-fingered to build it.
Schematic Image Schematic

The circuit board is laid out, but I'm having difficulty locating the shell script I use to build the board images here.
Board
Assembly notes
Several of the resistor pairs are laid out to allow changes in pinout without the need to cut traces. when the board layout appears you will note that resistors on the Tx/Rx data lines can be re-oriented and installed to swap the lines. The DE9 connector may installed and configured as either DTE or DCE (i.e. male or female with TxD on pin 2 or Pin 3), again by re-orienting R1/R2/R4.

Parts List

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