Sunday, 29 March 2015

Making low-power version of MMR-70

I use modded version of Sony Ericsoon MMR-70 for different projects. It is cheap - less than a euro delivered and in addition to quite capable AVR controller Atmega 32L it has FM radio transmitter with RDS support, 32kHz crystal used together with FM radio and orange LED.

For remote  temperature sensor powered by CR2032 battery I've stripped down all unused components - FM radio transmitter, 2.8V regulator, I2C pull-up resistor, transistors connected to UART pins... So in Sleep mode MMR-70 board with RFM12BS transceiver and BMP180 as temperature sensor takes less than 8uA.
Pic. 1. MMR-70 with FM radio chip and I2C pull-up resistors removed. UART, I2C bus and some Digital/Analogue pins exposed to round header sockets. 32kHz crystal patched to Atmega32 for real-time clock support.

MMR70-mod code on Github.

Making Sony Ericsson MMR-70 breadboard friendly

I continue to play with Sony Ericsson MMR-70 board. So far I've done a few iterations on making it breadboard friendly using round header strips. I've started with round pins, but then switched to round sockets - sockets are easier to manage and it produces lower profile. Much more useful than the very first attempt :)
Pic1. On the left - version with round strip pins, on the right - sockets. Board on the right also is very low-power version - all components which are not needed unsoldered to save power when MC is in Sleep mode.

Pic.2 Round sockets (bottom) profile is lower than pins (top).