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Code Lock with One Button

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Code Lock with One Button
Code Lock with One Button
The unusual feature of this code lock is that it can be operated with just one pushbutton. In situations where a tamper-proof solution is required this circuit has a great financial advantage: only one robust pushbutton needs to be bought. The disadvantage of this solution is that it takes a little longer to enter the code.
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Materials

Gerber file

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PCB

Extra info / Update

The circuit diagram should be modified to show a common-cathode (CC) display in position LD1. A suggested type is the LITE-ON LSHD-5503. Supply decoupling capacitor C1 is not shown on the component overlay and may be fitted at the underside of the board.

Component list

Resistors:
R1-R8, R11 = 1k
R9 = 100
R10 = 6k8
Capacitors:
C1 = 100nF
Semiconductors:
D1 = LED, green, low-current
D2 = 1N4148
IC1 = PIC16F84 (programmed, order code 040481-41*)
LD1 = 7-segment display, red, common-anode (e.g., Kingbright Sc56-11SRWA)
T1 = BC547B
Miscellaneous:
JP1 = 3-way SIL pinheader with jumper
K1 = 3-way PCB terminal block, lead pitch 5mm
Re1 = relay, 5V coil, (e.g., Omron G6A-234P-ST-US-DC5)
S1 = switch, 1 make contact, tamper proof (see text)
X1 = 4MHz ceramic resonator
PCB, ref. 040481-1
source and hex code, ref. 040481-11

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