RC5 Sleep Timer
Everything off!
Published in issue 288, May 2000
The well-known ‘sleep’ function in clock radios and television sets switches off the equipment after a preselected time. However, what good does it do to put the television into standby mode while the stereo set or DVD player that is connected to it remains unaffected? The sleep timer described here sends standby codes to several RC5-compatible devices at the same time.Function and operationThe circuit shown in Figure 1 allows you to select the equipment that will be switched on or off as well as the sleep time, which might better be called the delay time. The sleep timer is operated using four pushbutton switches. The current state of the timer is indicated by four LEDs, each of which corresponds to 30 minutes of time delay. In normal operation, these diodes are enabled for only one second out of every ten, in order to save energy.
Resistors:
R1 = 10Ω
R2-R6 = 1kΩ
R7 = 10kΩ
R8 = 3kΩ9
Capacitors:
C1 = 47µF 16V radial
C2 = 100nF
Semiconductors:
D1-D4 = low-current LED, red
D5 = low-current LED, green
D6 = LD271 or SFH485 with reflector
T1 = BC547
IC1 = PIC16F84-04/P, programmed, order code 000026-41
Miscellaneous:
X1 = 4MHz ceramic resonator (Conrad Electronic #50 31 69)
S1-S4 = miniature pushbutton, 1 make contact, 6⋅6 mm2 for board mounting (Conrad Electronic #70 04 60, Bourns #7906H-001-000, Farnell #535-916)
10-way pinheader, plus up to 5 jumpers
Toko handheld transmitter case (Conrad Electronics #52 43 44)
Battery holder for 2 ‘Micro’ batteries
PCB, order code 000026-1
Disk, order code 000026-11
Conrad Electronics are at http://www.conrad-electronic.com
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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.
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