Temperature Monitor 1
This device monitors up to four temperature sensors. It is programmed to sample each every second and store the highest of each in memory every 30 seconds. This allows 32 recordings and 16 minutes recording time. The intervals can be adjusted easily. The LED is illuminated when any sensor exceeds a threshold (50'C) giving a visual indication of a high temperature situation.
PLEASE NOTE: THIS DESIGN IS PROVIDED WITHOUT WARRANTY AND FOR PERSONAL NON-COMMERCIAL USE ONLY.
I have used Microchip's 8 pin PIC12F683 chip. Many other PICs with ADCs should work too. I have used the tiny MCP9701 temperature sensors; again many other 5v sensors should be suitable. I've compiled the program with the BoostC compiler.
As mentioned, each sensor is measured every second. This time period and the number of times sampled in each 'cycle' is fully adjustable. The 'cycles' set up a period for writing to the builtin EEPROM memory. It can only store 256bytes and 2bytes are needed for each reading. The highest reading in each cycle is stored because I was interested in peak temperatures.
I used surface-mount sensors as they are very cheap and I wanted something small. They were a bit tricky to handle but I took a piece of PCB and cut tracks in it, tinned these with solder, positioned the sensor and then remelt the solder while you hold the sensor in place. A filter cap is needed for each and three leads. There are many larger sensors available.
The device was used to good effect with my black paint heat transfer test.
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