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Table of Contents:
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A device that allows a large number of temperature sensors to be daisy-chained along a main branch cable. We are using these sensors throughout the system for temperature measurements that do not require the precision/accuracy/expense of a Lakeshore controller.
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Relevant Devices
Description | Qty | Source | Part Number | Link |
|---|---|---|---|---|
Sensor Controller |
1 | iButtonLink | LinkHub-E 32K | |
Power Supplies |
2
1 | HubPwr5-NA | |||||||||
Splitters |
(Likely a couple dozen of them) | iButtonLink | T-Box - 1-Wire Splitter | https://www.ibuttonlink.com/products/t-box (however likely any generic RJ-45 splitter would work) | ||||||
Sensors |
(Likely a couple dozen of them) | Maxim Integrated | DALLAS 18B20 1441C4 +800AB (label on devices used on ICON) | https://www.maximintegrated.com/en/products/sensors/DS18B20.html |
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Relevant Functional Block Diagram
The sensors are semiconductor devices with three pins:
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The sensor cables connect to the base via a custom cable, with an RJ-45 (ethernet) connector on one end and the sensors on the other. The base unit allows four sensor cables to be attached to it (with multiple sensors on each cable, like the one shown here).
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For the cable shown here a Winchester connector was used to allow the sensor section to be easily separated from the ethernet cable section. We will likely employ the same scheme for KPF.
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Note how the sensors can branch off the ‘main line', and also branch off the ‘branches’.
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Relevant Functional Block Diagram update to remove second instance
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Software Actions
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Action
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Notes
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Read temperature values from all sensors
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Required Adjustable Settings
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Setting
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When Needed
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Notes
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Build
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Observing
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Maintenance
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Sensor location table(s)
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YES
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NO
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MAYBE
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Sensor Read Frequency
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YES
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NO
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MAYBE
Device Setup Parameters
The current device settings can be listed through a telnet connection (see instructions below for changing IP address).
The current list of settings is included in the file here. Note our device was used previously by another project, so while these are the current settings they may not be the default settings.
Note the listing is provided here for reference only; we do not need to query or set these parameters in software.
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Required Telemetry
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Parameter
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Report Frequency
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Purpose
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Notes
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Temperature of each thermal sensor
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connected onto short sections of ethernet cable with RJ-45 connectors. The sensors are daisy-chained together using regular ethernet cables and 1-wire RJ-45 splitters.
Connection scheme shown below to show the concept. This pattern is replicated for as many sensors as needed, with sections of regular ethernet cable used as needed to bridge sensor locations.
Note that while the cables are described here as ‘ethernet’, the communication protocol for these sensors is different than that used for computer networks.
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Cable Details
Cable | Qty | Details | Notes | ||||||
|---|---|---|---|---|---|---|---|---|---|
Ethernet (Computer) | 1 | Cat6 Copper Ethernet Cable M-M, 6 feet long | Entirely within Cal Rack. | ||||||
Ethernet (Sensors) |
| Cat6 Copper Ethernet Cable M-M, lengths as needed to span distances between sensors. | |||||||
Sensor Cable |
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(Set by Sensor Read Frequency value)
Monitor temperatures
Custom cable: short length of ethernet cable with sensor on one end and RJ-45 connector on the other. |
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Photos of Devices
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Sensor Name Look-up Tables
Each sensor has a unique ID that is used by the LinkHub-E base. The IDs are not easily remembered so we’ll want a look-up table to tie the sensor IDs to a KPF sensor location.
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KPF Long Name
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KPF Short Name
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Sensor ID
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Notes
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e.g. Exposure Meter Enclosure
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e.g. 2890F1DD06000089
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Required Alarms
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Parameter
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Threshold
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Notes
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Temperature too high
(one alarm per sensor)
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TBC
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Temperature too low (TBC)
(one alarm per sensor)
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Thermal Sensor Locations (Spectrometer and Hallway) contains the list of sensor locations.
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Relevant Datasheets & Manuals
Description | File | Source | |||||
|---|---|---|---|---|---|---|---|
| 1 | LinkHubE User Guide |
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| 2 | LINK Family Manual |
| https://cdn.shopify.com/s/files/1/0164/3524/files/The_LINK_Family_Manual_1.7.pdf?7145028656254187831 | ||||
| 3 | Command Reference |
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| 4 | Sensor Datasheet Sensor was originally developed by Dallas Semiconductor but they are now owned by Maxim Integrated |
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Relevant Software
Description
File
Source
LinkHub_E_python.py is the main program.
LinkHub_E_commands.py contains functions called by the main program.
This code finds all of the sensors connected to the LinkHub E, and then reads their values.
Note first reading might report all temperatures as ‘85’; this seems to be a consequence of the first read to find sensor IDs.
The sensor IDs and values are read into a list format.Note this software does not differentiate between the 4 possible cables connected to the base unit; all sensors from all cables are added together into the same list.
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Python code originally written by Y. Ishikawa (SSL).
Simplified by S. Gibson to remove sections not relevant to KPF.
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Installation Instructions
Description | File | ||||
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Instructions on how to change the device’s IP address over Telnet |
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Software Details
Note that we have separate cables, however the software interface does not differentiate by cable when it combines sensor IDs into a list.