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Universal Parallel Input/Output for PCs

Here’s a simple project with Windows control software that allows you to control up to eight relays or other actuators, and read back an equal number of input lines, all by means of the parallel port on your PC.The UPIO software and hardware (a board attached to the PC’s parallel port) allows you control up to eight relay outputs using a Windows-style user interface designed for user-friendliness. UPIO also allows you read back logic states on input lines.Circuit descriptionThe circuit that belongs with the UPIO program is very simple and consists of a few low-cost and easy to find parts. The circuit diagram is given in Figure 1. A tristate buffer type 74HCT241(IC5) arranges all input contact reading. An 8-bit latch type 74HCT574 (IC3) is used to preserve the output state during instruction execution. The third essential component is a power driver type ULN2803 (IC1) which enables output relays Re1-Re8 to be actuated and de-actuated.
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Component list
R1-R8 = 22?
R9 = 820?
R10,R11 = SIL array 4 x 10k?
C1 = 470µF 25V radial
C2 = 100µF 25V radial
C3,C4,C5,C14,C15 = 100nF
C6-C13 = 22nF
D1-D8 = 1N4148
D9,D11 = 1N4001
D10 = LED
IC1 = ULN2803
IC2 = 78L05
IC3 = 74HCT574
IC4 = 74LS05
IC5 = 74HCT241
K1-K8 = 3 way PCB terminal block, raster 5mm
RE1-RE8 = PCB mount relay, 12V, e.g., Siemens V23040-A0002-B201
K9 = 2-way PCB terminal block, raster 5mm
K10 = 36-way Centronics connector, PCB mount
K11 = 3-way SIL pinheader with jumper
K12,K13 = 4-way SIL-header
PCB, order code 002011-1
Disk, contains all project software, order code 002011-11
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