A glance with "HotBox" shows current temperatures at
various points in the system. Here seven probes are visible - a total of 64 is supported.
The probe graphics can be dragged to any position. Each probe is represented as a rectangle: a red frame - the sensor's getting hotter - blue colder.
Logs temperatures and displays current state. Creates c:\hotbox\temp.log. Use Excel or Display to inspect the log.
The background graphic is customisable - you may design a bitmap of any size. Name your custom backdrop file as c:\hotbox\bckgrnd.bmp.
Use the mouse to select the probe text on top of your bitmap image. When first start Hotbox, off they default to the top left of the window.
Drag them to where you want.
They're sticky! Next time you run Hotbox you find them where you left them.
The HotBox configuration file format is here.
The temperature log can be viewed using "Display". Features: Zoom out, selected zoom in, Time and Temperature read out, trace enable / disable, temperature gradient.
The above image shows three day's worth of logging. Lower traces - external probes. Other probes placed around gas central heating system. Spikes occur when hot water is being heated.
The above shows a spike zoomed in. It shows more detail. ( Boiler shutting down during demand due to poor coil coupling in cylinder, or just an over-rated boiler.)
See the Display User Manual for more details.
Application Display.exe. Displays the log file.
Service - tempsvc.exe Logs temperatures as a service. Use this on NT or 2000 if you don't want HotBox running as an application on the desktop. Just as with the "visible" app HotBox, the service creates c:\hotbox\temp.log. On Windows 98 services are not supported, so ignore tempsvc.exe.
The PIC Source - all raw bit twiddling stuff! (PIC16L84). This contains the full documented source.
With the Arbiter wired up to the PC, the serial data from each temperature sensor can be examined with a terminal emulation program such as HyperTerm.
The frame format is slightly different depending on which Dallas Thermometer device is being read. You may have a DS1820, or a DS18B20. I describe each frame format separately: I have placed the DS1820 description here, and the DS18B20 description here.
The Arbiter doesn't care what device is connected. In fact you could put other Dallas "one wire interface" parts, as well as a combination of DS1820 and DS18S20 thermometers. The Arbiter will issue the Laser code ID command followed by the scratchpad RAM command, and serialises the response data as asynchronous RS232.
I don't show a layout for the Veroboard prototype - there is nothing too critical. Keep the crystal and associated components leads and tracks short.
They have improved accuracy (12 bits instead of 9) and a tighter temperature specification (0.5°C).
See the datasheet...
Dallas will be making the DS1820 obsolete. It is to be replaced with the compatible DS18S20.
I can't obtain a 2.4576 MHz crystal. I can get a 4.0 MHz. Will this work?
Is there a forum where I can discuss logging? Maybe get help building the logger?
Yes: Visit the Forum
Is there a DOS version of HotBox?
OK - Do you have anything for Windows 3.1?
No! 16 bit segmentation! You've got to be joking! I've been there 15 years ago - I have no interest in doing conversions for machines that should have been recycled long ago.
Dare I ask about Linux?
Nothing planned as yet.
I'm using a long cable between PIC and PC- I want to run at 2400 baud. Ideas?
See the bit delay description here.
Why did you bother connecting RTS and CTS?
I could have ignored these connections, but when the Windows operating system loads the serial port is examined. Any data seen at this time can be misinterpreted as a new plug and play device.
With this connection the arbiter shuts up during load time. With RTS de-asserted the arbiter stops sending data. If data is sent to the PC during re-boot the OS thinks it has got a new "plug and play" device!
I was with Bill the other day. He whispered in my left ear:
There are several switches that can be used to modify how Windows NT boots up, and these switches can be applied in the c:\boot.ini file.
Placing /noserialmice:com1 after the path to the Windows NT installation will cause NT to skip polling the com port during the boot up process.
I had to fix this as some UPS's will switch to battery when this port is scanned during the boot process.
Sorry about that, I should have documented that years ago!
This page was last updated on the 11th September 2010.