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Newbury And District Hackspace |
The display modules are made up of 8x8 LED displays and each module has 9 displays. The size of the LED displays varies between modules, however the various sizes of module all appear to use a similar drive circuit - this needs confirming.
LED displays used for the bulk of the modules are CSM 88121Y which are 'Super Bright Yellow' and have a luminosity of 25mcd. Data Sheet is here http://pdf.dzsc.com/autoupload/d5ac332c-aefb-4d72-8b88-2b85ac163fdb.pdf
Power Requirements:
The display modules are 5v, this is fed directly to the chips with no protection so don't get this wrong or you will fry everything!
Current drawn: Estimated at 1.8A for each module assuming all the LEDs are lit on one row. According to the data sheet each LED draws 25mA.
Circuit
The rows are driven one at a time by MOSFETs connected to a 74HCT138 (3 TO 8 LINE DECODER DEMULTIPLEXER). Data Sheet is here http://www.datasheet4u.com/datasheet-pdf/Diodes/74HCT138/pdf.php?id=931568 The address lines A0 to A2 are connected to the header on the display modules.
The columns are all driven by A5821 8-Bit Serial Input Latched Driver. Data Sheet is here http://pdf.datasheet.live/6e987f6f/vishay.com/UCN5821A.pdf See the data sheet for details of how to clock the data in for all of the columns. Once the serial data has been clocked in it is moved to the output by triggering the STROBE. There is also an OUTPUT ENABLE to blank the display. This arrangement allows one row of data to be displayed whilst the next row is being clocked in.
Data Connector
The displays have two 14 pin DIL Headers to allow daisy chaining of the control lines and also 2 power connectors to allow daisy chaining of the power.
14 Pin Connector - numbered such that all the grounds are the pins nearest the LED displays.
1 - Clock - Active HIGH
2 - Column Serial Input & Column Serial Output - Depends on the connector
3 - Row Address A0
4 - Row Address A1
5 - Row Address A2
6 - Strobe - latches serial data - Active HIGH
7 - Output Enable - Active LOW
8 - Gnd
9 - Gnd
10 - Gnd
11 - Gnd
12 - Gnd
13 - Gnd
14 - Gnd