Computing Projects
Environmental Monitor
Designed by Mark Little
Source and Doc. Files
The unit was marketed in the early 2000s by Dick Smith Electronics Australia as the "Hot Chip". Although this unit does not provide the power of modern single board microcontrollers like the Raspberry Pi, it can still be used as an effective monitoring tool - and that beats leaving them in the junk box, gathering dust.

Programs for this chip are  written using the MikroElectronika mikroBasic PRO for AVR Version 7.0.1. Using the registered version of the compiler allows programs to use the full program memory capability, unlike the free version that restricts the amount of program memory that can be used by a program.

The AT90S8535 provide eight (8) input analogue channel that are multiplexed to a 10-bit A/D converter. The primary function of this environmental monitor program is to sample those inputs, scale them as defined (can be modified during run-time) and send the scaled reading out on a serial port.

The Environmental Monitor communicates with a host computer using the serial port at 19.2k Baud. The commands and data are transferred using ASCII text strings to allow for easy debugging. The relatively slow speed of the serial port means that this program is only suitable for slow speed data gathering.

Typical applications for which it is suitable is the measurement of things like the sunshine levels or ground temperature where reading are taken at intervals greater than a few seconds. The image blow shows a recording of uncalibrated sky brightness levels measured using a Light Dependent Resistor (LDR).

The readings were read by a Hot Chip microprocessor and fed, via a serial port to a Linux computer than stored the readings in a database. Another program was used to extract the information from the database and plot it as a graph. Where the levels are shown as a large smooth curve, it indicates that the sky was clear and the level was only determined by the angle of the sun during the day. The jagged curves show where the sky intensity was altered by cloud coverage, perhaps being even brighter than a clear day when there is sunlight reflected from clouds and direct sunlight.
The Environment Monitor is designed to run on an Atmel AT90S8535 or similar microprocessor running at 8MHz, although specifically it runs on an "ABC Mini"  which is an AT90S8535 on a board providing the same pin layout as a 40-pin DIL IC.