AAA – Experimental Engineering

Posted on August 6, 2016August 1, 2016 by The Engineer — Leave a comment

Motorola Cordless DECT Phone Teardown

Another random teardown from the junk box time!
Here’s an old Motorola DECT landline phone, no use to me as I’ve not used a landline for many years.

Not much on the back, other than the battery compartment for a pair of AAA rechargables. The base unit contains the charger.

Here’s the main PCB removed from it’s casing. There’s not really much going on, one of the main ICs, which is probably a microcontroller, is a COB device, so no part numbers from there. There’s a row of pads for programming the device at the factory. The RF section is on a dedicated IC, a DE19RF19ZCNC from DSP Group. I couldn’t find much on this part, but it’s one of a range of DECT/VoIP DSP devices.

Inside the base unit is a similar board, just without the keypad. Main microcontroller is again a COB device, the RF IC is under the shield.

Removing the shield reveals the same IC as in the handset, only this PCB has a pair of antennas.

Posted on August 3, 2016August 1, 2016 by The Engineer — Leave a comment

ETI Thermamite Catering Thermometer

Here’s another bit of commercial gear, a catering thermometer. These are used to check the internal temperature of foods such as meat, to ensure they’re cooked through.

This was given to me with some damage, the battery cover is missing & the plastic casing itself is cracked.

Power is provided by 3 AAA cells, for 4.5v

There’s not much to these units, the large LCD at the top is driven by the IC in the centre. A programming header is also present on the board near the edge.

The core logic is taken care of with a Texas Instruments M430F4250 MSP430 Mixed-Signal Microcontroller. This MCU has onboard 16-bit Sigma-Delta A/D converter, 16-bit D/A converter & LCD driver. Clock is provided by a 32.768kHz crystal.
The probe itself is just a simple thermistor bonded into a stainless steel rod.

Posted on June 14, 2016 by The Engineer — Leave a comment

Digital Angle Gauge

Here’s a useful tool for the kit, a digital angle gauge/protractor. These use a silicon sensor to show the number of degrees the unit is out of level.

Magnets are provided in the base, so the tool can attach to any ferrous surface.

Power is provided by a single AAA cell.

Removing the rear cover reveals the brains of the unit, and there’s not much to it at all. The main microcontroller is a CoB-type device, so no part numbers available from that one.

The IC to the left of the main microcontroller is the sensing element. There’s no markings on this inclinometer IC so I’m not sure of the specs, but it will be a 3D-MEMS device of some sort.

The other side of the PCB has the power supply for the logic, and a serial EEPROM, probably storing calibration data.