Sunday, 11 October 2015

Teardown: Avery Berkel D104 Post Office Scales

This is a short teardown of an Avery Berkel D104 Post Office Scales, as used in post offices throughout the UK.

The case is constructed of cast aluminium with a large aluminium bed, large 2x20 high contrast LCD display. The unit is intended to be bolted to a work surface.

Three data connections are located on the base.

Inside the unit the is the load cell, small mains transformer, and three significant PCBs, one has a selection of voltage regulators and analog circuitry for the load cell, the other two are what appears to be the digital processing board and then the display board.

Inside the unit, with the LCD & Display board removed from the front. The dataports are located on the far right. The digital controller board at the front, load cell in the centre and finally the analog board at the back. As shown in the picture below.

Below is the reverse of the display controller, the LCD module is mounted on the other side, with a IDC cable connecting on the right. It contains 64kbytes EPROM, Intel 8032AH Microcontroller, SRAM, Intel n825306 Serial Communications Controller and two MAX232 RS232 drivers. There is a small power supply section at the top left as this board runs from a separate transformer tap so is isolated from the other boards.

Below is the analog board, power supply regulation on the left with discrete diode bridge rectifier and linear regulators for the voltages needed for the analog side. The analog front end for the load cell is located in the area to the right where i have removed the shielding can.

The digital board below takes a IDC cable from the analog board, located at that connector is a custom ASIC and an 32kbyte EPROM. Also on this board is another Intel 8032AH microcontroller, MAX232 RS232 driver and four opto isolators. I would guess these are for the three external ports and the internal display board which uses RS232 between the two boards.

The load cell below is a 6kg rated device, no manufacturers name can be found on it, given Avery Berkel's size this could be of their own design.