#41 A FAILED ATTINY85 EXAMPLE (GSM/GPRS)

My first attempt to build a small circuit which controls a relay to an alarm speaker was a failure. Contrary to popular belief failure in electronics projects is quite common and I would argue that it is of paramount need if you want to learn anything.

Surprisingly my failure was in using the ATTINY85 instead a Pro Mini, Uno or Mega. Some problems I had were:

• Not enough RAM to hold all my variables (I had to scrounge 😢)
• Very limited FLASH memory.
• GSM module interferes with the ATTINY’s 5v power source when connected using the same source with no filtering.

In a later project I created a reliably working solution with the Pro Mini as the brains.

My goal was to create a small circuit which uses the ATTINY85 as the brains. It uses the A6-GSM-Module to receive SMS’s, phone calls and sends TCP data. Finally it has a 5v relay which will switch on/off an alarm speaker. The theory is that when I’m on the farm in the fields and not near the house, I have the option of remotely starting an audio alarm at will. This should be a deterrent to potential criminals.

After making an easier to debug circuit I tried to get the ATTINY85 to work happily with the GSM module. This was going to be a bit complicated and I suspect I would have to isolate power between the ATTINY85 and the GSM module. This would require more components and the board is already looking cramped. A much easier solution is to use the Pro Mini instead of the ATTINY85.