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ISTAtrol

ISTAtrol v0.1 prototype in action. Does its basic duty, some planned features delayed for v0.2.

ISTAtrol v0.1 prototype in action. Does its basic duty, some planned features delayed for v0.2.

The ISTAtrol is a device for controlling temperature of a heating radiator depending on the temperature of the ISTA heating consumption counter and, in a next step, also depending on room temperature. It's easily DIY-able and code is Open Source, so it can be custom programmed without too much effort. It means to replace traditional mechanical thermostats.

It was designed because these ISTA counters measure heating consumption based on the temperature of the radiator, only, which leaves much room for optimisation.

Features

All the planned features. Basic operations work fine, some had to be postponed. See below and the [[#TODO]] section.

All the planned features. Basic operations work fine, some had to be postponed. See below and the TODO section.

Of the shown features currently works:

  • USB.
  • External and USB voltage source (one of both required).
  • 1 temperature sensor.
  • Radiator valve motor.
  • In System Programming (ISP)

All other features require some schematic and PCB layout changes as well as an upgrade to an ATtiny4313. One could operate LEDs or user buttons right now, but then one would have to drop temperature controlling code due to ATtiny2313's tight program memory (2 kB Flash).

Disappointed? Well, at least it's demonstrated that the design principle works and an 20-pin ATtiny is suited for the task. Good preconditions for the next prototype :-)

How To Get It

Firmware sources, schematics and layout can be found at ISTAtrol on Github.

In its current state you likely want to fix some of the issues found during development first. If you do so, don't hesitate to ask for a PCB or two, Traumflug usually makes them happily and for free.

Assembly

Assembly is straightforward, simply solder in all components in order of raising height. Before inserting the ATtiny it's a good idea to connect the device to USB, jumper USB as voltage source and measure all the ATtiny socket pins that none of them receives more than 3.3 volts.

Firmware Upload

Firmware should compile out of the box with a simple

make

For uploading the firmware one needs a programming device, e.g. Pololu's PGM03A. This PGM03A can deliver signals at 5 volts, only, the current ISTAtrol design has voltage dividers built in to deal with this.

Before the first firmware upload, ATtiny's fuses have to be programmed:

make fuses

Then one can upload the actual firmware:

make program

After any firmware change, e.g. a change in configuration, only the latter command has to be repeated.

istatrol.1458904324.txt.gz · Last modified: 2018/05/27 16:10 (external edit)