Proximity Mask Head (A2045) Manual

The A2045 uses the same circuit as the A2052. Instead of mounting with three snap-top standoffs, as does the larger A2052 board, the more compact A2045 mounts by gluing it onto a rectangular flange that fits around the bottom side of the board. When glued into an enclosure, the A2045 over-heats if left on for more than a few seconds. Twenty-four
Proximity Mask Head (A2045) Manual - schematic

hours of continuous operation is likely to damage the circuit, as described below. This over-heating is the result of miscalculations in our design, and would be corrected on any A2045 by changing power-dissipation resistor R3 from 47 © to 100 ©. The A2045 is complies with the LWDAQ Specification. It is LWDAQ Device type 1 for the purpose of device-dependent jobs. The LED driver is element number 0 or 1. Command bit allocation is as follows. The A2045 ignores DC8, which is normally the WAKE bit for LWDAQ devices. But the A2045 has only two states: off or on. The off state is equivalent to the usual sleep state. Look here for the Operation section of the A2052 manual, which applies also to the A2045. The figure below is a picture of a Proximity Mask being viewed by a Proximity Camera. The Blue Proximity Mask uses the A2045R. The Black Proximity Mask uses the A2045L. We intended the the A2045 (and also the A2052 ) to pass 80 mA through its nine LEDs. The HSDL-4400 LED`s maximum continuous forward current is 100 mA. We wanted to operate below the maximum, in order to extend the life of the diodes. With the R5 equal to 22 © as shown in the schematic, the circuit does pass 80 mA through the LEDs. But the 1400 A2045s and 1200 A2052s we made for ATLAS had R5 equal to 15 ©, and so passed 110 mA through the LEDs. This higher current will, no doubt, reduce the operating lifetime of the LEDs. Not only did the ATLAS circuits pass too...

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