Power Supply Unit
Power supply unit
SOHO scanners don’t consume too much power, so you can’t find powerful elements in their power supply units. The internal power unit of the device we examine today outputs 24V/0.69A, 12V/0.15A and 5V/1A. The light source – the cold-cathode lamp – needs high voltage of several thousand volts and it is power-supplied by another unit I have already discussed earlier.
There are numerous additional devices you can use with your flatbed scanner (they are usually purchased separately) like automatic document feeders and slide-adapters.
A scanner with an automatic document feeder is quite a bulky construction
A document feeder may be of invaluable help when you have to scan a ream of standard-size papers. To make sure your scanner supports feeders, take a look at its back panel and look for a connector marked as ADF (Automatic Document Feeder). An important note: auto-feeders are always “linked” with a specific scanner model or a series of models. There is no such thing as a “universal document feeder”! The reason for that lies in the fact that the feeder is controlled by the interface card of the scanner. Of course, it’s impossible for the feeder to work without a connection to the scanner, so be careful when shopping and make sure your scanner supports the feeder you want to buy.
This is the transparent window of the document feeder
from the other side of the glass
The feeder works like this: having completed the auto-calibration and status check, the scanner positions the head in front of the feeder’s transparent window. Then, original sheets are taken from the input tray one by one to be digitized as they pass through the transparent window.
The slide-adapter is an extra device for digitizing transparent originals (film, slides, negatives). There are two types of these adapters: passive ones use the scanner lamp and active ones shine through the original with their own lamp.