2 layers70 × 45 mm
2 layers100 × 62 mm
Magic switchboard
RincewindWizzard/magic-switchboard18A magic schwitchboard is a little box with four switches and four lamps colored in red, green, blue and yellow. The switches have got hats in the same colors.
- Size
- 100 × 62 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 26
- Nets
- 20
- Pads
- 78
- Tracks, vias
- 135, 0
- Pours
- 4
- Routed
- Yes
- KiCad
- KiCad 5 (file 20171130)
- Created
- 29 Apr 2016
- Updated
- 11 Apr 2025
Overview
Magic switchboard is an open-source printed circuit board by RincewindWizzard, from the RincewindWizzard/magic-switchboard repository on GitHub, published under the GPL-3.0 licence. It is a 2-layer board of 100 × 62 mm with 26 parts on 20 nets, routed with 135 tracks and 0 vias.
It is built around the ATTINY2313A-PU and BC547. Its parts include 5 resistors, 4 diodes, 4 transistors, 4 switches and 2 connectors. It belongs with the AVR (ATmega, ATtiny) boards of this library.
Main components
2README
README.mdMagic Switchboard
A magic schwitchboard is a little box with four switches and four lamps colored in red, green, blue and yellow. The switches have got hats in the same colors. You can change the position of the lamps and the hats in any way you want. But the red switch always lights the red lamp, the blue the blue, the yellow the yellow and the green the green one. How does this work? The magician is the one operating the switchbox. He has to remember which switch was turned off last. He then hands off the box to the audience and asks them to rearrange the colors. When the audience returns his box he remembers the sequence in which the lights turn on and turns the switches with matching color. For the audience it seems like the colors are connected somehow.
Wiring
You can find wiring instructions in the Schematics. The Attiny4313A can be powered with up to 5V.
With the BC547 transistor you can safely drive a current up to 100 mA and voltage of 50V for your light bulbs. For bigger loads consider using TIP100.
The voltage source for the arduino nano can be seperate to the voltage source of the lights, but they have to have a common ground (GND) for the circuit to work. For driving 230VAC (common household plug) light bulbs you might want to use a galvanic separation (opto-isolator). If you don't know what that means, don't try it.
If all lamps are off, the ATtiny is switched into sleep mode, which draws significant less current. This circuit doesn't have a low power warning, so if there is strange behaviour (lamps dont turn on as expected) you might try change your batteries.
How it Works
The sequence in which the lamps turn on is determined by last lever turned off. After a longer sleep time (ca. 2.5sec) it resets to default = 0 lever.
| Lever (left to right) | Turn on Sequence |
|---|---|
| 0 | 0, 1, 2, 3 |
| 1 | 1, 0, 2, 3 |
| 2 | 2, 3, 1, 0 |
| 3 | 3, 2, 1, 0 |
In order to connect the correct colors from levers to lamps, you need to remember which lamp turns on next and flip the lever with the corresponding color.
You find the code here.
Parts List
- ON/OFF switch (MTS-102)
- color caps
- light bulb socket E10 with print pins
- LED light bulbs E10 in red, green, blue, yellow
- attiny4313A DIP-20
- 4x 10kOhms resistors
- 4x BC547 transistors TO-92
- capacitor 100uF
- Battery Clip for CR2477: https://www.digikey.de/product-detail/de/keystone-electronics/3039/36-3039-ND/3884009
Parts
26| Qty | Value | Footprint | References |
|---|---|---|---|
| 4 | 10k | switchboard:Resistor | R1, R2, R3, R4 |
| 4 | BC547 | switchboard:BC547 | Q1, Q2, Q3, Q4 |
| 4 | MTS-103 | switchboard:MTS-103 Switch | SW1, SW2, SW3, SW4 |
| 4 | Red | switchboard:E10 Edison Socket Print Pins | D1, D2, D3, D4 |
| 2 | LOGO | switchboard:Siegelstempel | G***, G*** |
| 2 | M4 | MountingHole:MountingHole_4.3mm_M4_DIN965_Pad | , |
| 1 | 100uF | switchboard:CP_Radial_D6.3mm_P2.50mm | C1 |
| 1 | 3V | switchboard:BatteryHolder_Keystone_3009_1x2450 | BT1 |
| 1 | 5V max | switchboard:ScrewTerminal1x2 | J2 |
| 1 | ATtiny2313A-PU | switchboard:ATtiny2313 | U1 |
| 1 | AVR-ISP-6 | switchboard:ISP6 | J1 |
| 1 | LED_brightness | switchboard:Resistor | R5 |
Questions
How big is the Magic switchboard PCB?
It measures 100 × 62 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Magic switchboard use?
26 parts, built around the ATTINY2313A-PU and BC547. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Magic switchboard KiCad files?
From the RincewindWizzard/magic-switchboard repository on GitHub, at the commit this page was made from: the board is kicad/magic-switchboard/magic-switchboard.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.
Can I use the Magic switchboard design in my own project?
Its repository publishes it under the GPL-3.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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