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Intelligent Fan Timer

Using the MSP430 low-power processor

Intelligent Fan Timer
This processor-driven automatic fan controller does not just run in parallel with the toilet light, but instead allows the user to adjust the running time of the fan using a single-button system. The selected time can be read from a single-digit display. The fan can also be stopped early using the same button.Most toilet fans are switched on and off along with the toilet light, and some continue to run for a certain amount of time after the light is switched off. Since the need for fresh air is closely related to the particular reason for visiting the toilet, the author of this article wanted to have a bit more influence over how long the fan continued to run. The nicest solution would be to have a fan whose running time could be entirely chosen by the user. Naturally, switching the fan off early should also be possible, and it would be a useful extra feature to have the operating time of the fan shown on a display.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Resistors:
R1 = 8k?2
R2,R5,R7,R8,R10 = 10k?
R3,R4 = 47k?
R6 = 1k?
R9 = 270k?
Capacitors:
C1 = 47nF 400V, Class X2
C2 = 220µF 16V radial
C3-C6 = 100nF
Semiconductors:
D1,D4-D11,D14 = 1N4007
D2 = zener 3 V/500 mW
D3,D13 = BYV10
D12 = 1N4148
T1 = BC327
THY1 = TIC106D
LD1 = HD1105-O
IC1 = MSP430F1121, programmed, order code 020170-41
Miscellaneous:
K1,K2 = 2-way PCB terminal block, lead pitch 7.5mm
F1 = fuse, 500 mAT (time lag), with PCB mount holder
S1 = pushbutton, 1 make contact, Class 2 (for test purposes only)
S2 = pushbutton, 1 make contact, Class 2, e.g., Omron type A3DT-7111 with cap A3DT-500R (Farnell)
Tr1 = approx. 20 turns, bifilar, on Philips core TN14/9/5 (material: 3C85)
Enclosure: e.g., Hammond type 1591B (red)
Disk, project software, order code 020170-11 or Free Download
PCB available from The PCBShop
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