Atmel AVR Pick-by-light

AVR timeline

Timeline for AVR projects.


AVR layout

Top, bottom and silk overlay,
22 May, 2002

AVR status LEDs

AVR8515 status LEDs for a “pick-by-light” prototype. This was a project that was resurrected whenever funding was available and between gaps in other projects. There were many attempts at the host controller—the so called “industrial terminal”. Probably half the hardware on this website documents the various industrial terminal evaluations. In later years the technology would be available (iPad, BeagleBoard), but the energy is no longer there.

Single-chip for 3 pairs of 7-segment displays

AVR8515 PCB board top

The first prototype AVR8515 board for driving three pairs of 7-segment displays. The two yellow wires were due to the power and ground not being picked up on the layout. The size of the board was to fit into plastic extrusions used for electrical cables (95×19mm). These would be attached to 810mm shelving in a warehouse racking store. The 2×5 pin connector was the programming port. It would have to go on mass produced boards; possibly using spring loaded probes. The RS-485 buffer is near the power connection. (On right next to the crystall can). The four pin connector to the outside world was ground, 5V and a pair for RS-485.

AVR8515 PCB board bottom

The underside of the AVR8515 prototype board. The board was four layers, but would have to be two layers for mass production. Note the two transistors on the lower middle part of the board for multiplexing the left and right digits of the displays. The 7-segments were driven directly on the processor outputs. The large decoupling capacitor on the underside prevented the board sliding into the extrusion.

Testing

AVR pick-by-light displays

The running prototype “pick-by-light” displays. The multidrop network (RS-485) was difficult to test on standard PC hardware, as the direction contol is non-standard for RS-232. The initial testing to display a value used a RS-232 and RS-485 chip “back-to-back” without direction control. The pushbuttons were to acknowledge a ‘pick’. The multiplexed displays were a lot brighter to the eye than in the photo, which was lightened. The intended location was a warehouse—normally darker than office lighting.

The display boards were tested on the original evaluation board, so each 7-segment pair board had current limiting resistors. The single sided display boards were cheaper and to keep the resistors off the processor board. Some shelves would have three pairs of displays, others could have five. These were for pharmaceutical warehouses where any number of items more than 99 would be bulk picked—a number that would change later!

The dates on the original assembler files for the STK200 were up to 30th November, 1999. The programming on the prototypes were dated from February to October, 2002. The dates for the display boards were around May, 2002. There was a previous attempt at a two sided board in Port Elizabeth, but there were no decent photo plotting facilities or through-hole plating line.

Housing

AVR pick-by-light tubes

Ten tubes of three pairs of displays were made to test out ten shelves. The processor card in the prototype was too big to also fit into the plastic extrusion, so it was unceremoniously “cable tied” onto the housing. Programming required access to the 10-pin header and jumpers. The ribbon cables for the three display cards were stuffed pretty tightly into the extrusion. A close-up view of the housing and cable ties can be seen here Atmel AVR Projects.

Identified Problems