Jens Nickel
About the article

RS-485 Switch Board

ElektorBus relay module

RS-485 Switch Board

Our ElektorBus series has shown how much interest there is in home automation applications. Here we describe a small circuit board that can switch two AC (115/230 VAC) loads. Also, two of the inputs to the on-board microcontroller are brought out to terminals so that the state of two switches can be read back. The board works with the ElektorBus and so is an ideal building-block for a home automation system controlled from a PC, tablet or smartphone.

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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD 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.

Download the BOM list
The BOM (Bill of Materials) is the technically exhaustive listing of parts and other hardware items used to produce the working and tested prototype of any Elektor Labs project. The BOM file contains deeper information than the Component List published for the same project in Elektor Magazine. If required the BOM gets updated directly by our lab engineers. As a reader, you can download the list here.
Want to learn more about our BOM list? Read the BOM list article for extra information.
Component list
SMD shape 0603
R1,R2,R3 = 10kOhm
R4 = 0Ohm
R5 = 120Ohm
R6 = 4.7kOhm
R7 = 1.5kOhm
R8 = 10Ohm
C1,C2 = 22pF NP0 (0603)
C3,C4,C5 = 100nF X5R (0603)
C6,C7,C8 = 4.7µF X5R 10V (0805)
C9 = 4.7µF X5R 25V (0805)
D1 = S1M (1000V / 1A)
LED1,LED2 = LED, green (0603)
IC1 = ATmega88A-AU, programmed
IC2 = AP78L05SG-13
IC4 = LT1785CS8#PBF
RE1,RE2 = 12V, SPST-NO (e.g. G5Q-1A-EU DC12)
JP1, JP2 = 2-pin pinheader, lead pitch 0.1 in. (2.54mm)
K1,K2 = 6-pin pinheader, lead pitch 0.1 in. (2.54mm)
K3 = 6-way screw terminal block, lead pitch 3.81mm
K4 = 3-way screw terminal block, lead pitch 7.62mm
K5 = 3-way screw terminal block, lead pitch 3.81mm
X1 = 16MHz quartz crustal, HC-49S case
S1,S2 = pushbutton, SPNO (e.g. B3S-1000)
PCB # 110727-1
Ready assembled and tested board # 110727-91

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