HotKeys keyboard (2)
construction, software and a few tips
Published in issue 288, May 2000
Last month we described the features and the operation of this handy extra keyboard. Now it’s time to look at the hardware and the construction of the circuit.The schematic diagram of the hotkeys circuit is shown in Figure 6. All pins of the connector for the PC keyboard (K1) are connected through to the connector for the PC (K4), with the qualification that there is a pair of analogue switches inserted in the clock and data lines. These allow the hotkeys keyboard to open these lines. Power for the circuit is taken from K4. In addition, you can see a connector for the RS-232 interface (K2). Resistor R5 and diodes D1 and D2 limit the incoming signal to levels of approximately 0 V and +5 V.
Resistors:
R1,R2,R4 = 1kΩ
R3 = 330Ω
R5,R6,R10,R14,R18 = 10kΩ
R7,R15 = 2kΩ2
R8,R16 = 3kΩ9
R9,R17 = 6kΩ8
R11,R19 = 15kΩ
R12,R20 = 27kΩ
R13,R21 = 47kΩ
Capacitors:
C1,C3 = 100nF
C2 = 10µF 16V radial
Semiconductors:
D1,D2 = BAT85
D3 = LED, red, high efficiency
D4 = LED, green, high efficiency
T1 = BC557
IC1 = MAX323CPA or MAX323EPA
IC2 = ST62T60 (programmed, order code 002006-41)
Miscellaneous:
K1,K4 = 5-way SIL pinheader
K2 = 9-way sub-D socket (female), PCB mount
K3,K5 = 4-way SIL pinheader
S1-S16 = pushbutton, e.g. Marquardt (Conrad Electronic o/n 70 68 92-55, with cap 70 08 60-55)
Bz1 = 5-V piezo-ceramic buzzer (passive)
X1 = 8 MHz ceramic resonator
5-way DIN plug, pins arranged at 180 degrees
5-way DIN socket, receptacles arranged at 180 degrees
10 cm 5-way flatcable
|
Click below to download a PDF copy of this article from Elektor magazine. Please note. In view of the complexity of international markets, Elektor cannot guarantee the availability of components for this project.
|
Informative articles
Password forgotten?
' ))
