Retro electronics: sleeping stimulator

Another interesting clipping from '70s magazine "Юный Техник". This article describes device that is supposed to help with sleeping by generating regular audible pulses (60...90 Hz). It might be actually early predecessor of SITA. According to this article desired pulse frequency might be related to heartbeat.

Solar battery made from transistors

This is little solar battery I've made from few power transistors about 20 years ago (that's why transistors are little rusty).

There is one piece of 2N3055 (third from the left), four HOTs (some of them were already damaged before cutting the case - I've got them as damaged from TV service, but they still worked with no problems as solar cells) and most interesting - KT801A, medium power transistor from USSR with enormously large when comparing to case silicon area (fifth).

The unusual thing is that it's die has irregular shape - I suppose this transistor was hand-assembled. Even with some remains of protecting paint on it this transistor worked better than others.

The idea is even older - I've spotted it first in magazines "Zrób to sam" ("DIY") from late '70s or early '80s and "Юный Техник" ("Young Technician").


"Zrób to sam" - solar powered AM radio receiver:

 

"Юный Техник" - solar (and wind) powered scarecrow. It's solar battery is actually made of diodes (40-60 pieces) with glass packages.

 

eZ430-Chronos promotion

This week eZ430-Chronos kit is offered at half the normal price at tideals.com. Kit includes waterproof MSP430-based watch and two USB dongles: programmer/debugger and RF access point. Free shipping.

STM32F4DISCOVERY - cheap STM32F4 board

Farnell is currently selling STM32F4DISCOVERY board at a very low price, $16 per piece. Let's compare this with individual cost of components on the board:

• STM32F407VGT6 (MCU): $9.29 (directly from STM, with 1000 pcs quantity),
• LIS302DL (accelerometer): $6.8 (Farnell, no price info on STM pages),
• MP45DT02 (MEMS microphone): $2.87 (Farnell, 500+ quantity),
• CS43L22 (DAC): $3.12 (Mouser, 100 pcs),
• STM32F103C8T6 (another MCU working as USB to SWD bridge, on-board ST-LINK/V2 debugger interface):  $3.1 (STM, 1000 pcs),
• ... and PCB and bunch of discrete parts.

It definitely looks that STM is not making money with this board but sells it as a promotional product to popularize STM32F4 series microcontrollers. If you are interested in this family in particular or if you need relatively high-performance platform for audio processing this would be great buy. On the other hand this is kind of "bait and switch" offer as STM32F407VGT6 in small quantities has similar price to the whole development board. Other drawback (comparing to older STM32F103 board) is that ST-LINK part can not be detached by splitting PCB into two pieces.

AVR DDS signal generator

AVR-only (with no specialized DDS chip and no DAC chip) DDS generator from scienceprog.com seems to be valuable addition to hobbyist workshop. Its output frequency range is limited to 65 kHz for DDS signals (sine, square, saw, rev saw, triangle, ECG, noise) but that seems sufficient for many needs and it allows to use cheap operational amplifier and R-2R digital to analog converter. Additional HS (high speed) digital output would be useful as a spare external clock source for microcontroller projects or restoring misconfigured AVR fusebits.

New project version with improved analog part and some additions to firmware is planned to be released this summer.