Central Heating control with display and PWN output

This example shows how to measure and filter the temperature, compare it with the setpoint and output a Pulse Width Modulator.


The scheme kept is simple by using sub scheme's. The sub scheme (filter.sch digit.sch display.sch) contains its own scheme and is connected to the main schematic with in and out.

Learn more about sub schemes.

Filter.sch

The sub scheme filter contains:


The scheme is executed once a second. It is a moving avarage filter.

Digit.sch

The sub scheme filter contains:


This scheme is executed on input change. The value is divided by100 for the first digit. The rest value divided by 10 for the 2th digit and te rest value for the 3th digit. The value 0..9 is converted to a 7 segment table.

Display.sch

The sub scheme filter contains:



This is how 3 7-segment display's are multiplexed. With execution on timer interrupt the scan frequency is 1000Hz.

Download

DIGIT.zip

Prepared for devices: ST72311 other devices can be used by reconnecting I/O pins.