Introduction: Church Lights
If you watch the video you can see how the colour of the foam church changes when I rotate the potentiometers.
I used a tricolour LED. However, you can use three bright LEDs of different colours.
You also can try normal LEDs instead of bright LEDs but they could be very dim. Also, there are colour changing bright LEDs sold on the internet nowadays. Their colour slowly changes with time. They are expensive and certain cheap bright LEDs could be smaller than expected when they come in the mail.
parts: 20 kohm or 10 kohm variable resistors, general-purpose NPN transistors - 10, bright LEDs of different colours - 4, wires or 1 mm metal wire, 3 V, 4.5 V, 6 V battery harness or 9 V battery harness, batteries, 2.2 kohm resistors - 5. 10 kohm or 4.7 kohm resistors - 5, 330 ohms resistors - 5, masking tape, piece of cardboard or matrix board, packaging foam or cardboard box.
tools: wires stripper, scissors, hole puncher or compass, pliers.
optional materials: solder, high power metal wire.
optional tools: multimeter, soldering iron, voltmeter.
Step 1: Design the Circuit
If you are using 10 kohm potentiometer than all Rvb resistors (Rvb1, Rvb2 and Rvb3) need to be 4.7 kohms or 5.6 kohms.
You need to calculate the maximum current across each of the three LEDs. The maximum currents will be about the same and will equal to:
ImaxLed = (Vs - Vbe - Vled) / Re1 = (6 V - 0.7 V - 2 V) / 330 ohms = 3.3 V / 330 ohms = 10 mA
You can do calcualtions for other voltage sources:
Vs = 3 V: ImaxLed = (3 V - 0.7 V - 2 V) / 33 ohms = 0.3 V / 33 ohms = 9.0909 mA
Vs = 4.5 V: ImaxLed = (4.5 V - 0.7 V - 2 V) / 180 ohms = 1.8 V / 180 ohms = 10 mA
Vs = 9 V: ImaxLed = (9 V - 0.7 V - 2 V) / 680 ohms = 6.3 V / 680 ohms = 9.2647 mA
Re1, Re2 and Re3 must be all of the same value or approximately the same value.
Step 2: Simulations
Simulations show that the maximum LED current is 10 mA. Thus my calculations are correct.
Step 3: Build the Circuit
You can see that I used a single multi-channel bright LED instead of three bright LEDs. The first channel is the negative terminal or ground. The other three channels are red, green and blue.
I twisted the wires together underneath the small piece of cardboard. I did not use a soldering iron.
However, I used a soldering iron to attach wires to potentiometers. This is not necessary if you attach the potentiometers to the packaging material with high-power wires as shown in the cover photo of this article.
Step 4: Build the Sculpture
I used high-power wires to attach the church piece to the ground piece of this sculpture.
Step 5: Testing
You can see in the video that the control of this sculpture is limited.
You can spin the potentiometer in the clockwise or anti-clockwise direction. The position of each of the two potentiometers can be classified into 3 main categories/settings:
- zero resistance setting,
- midpoint resistance setting,
- and maximum resistance setting.
Because there are two potentiometers there are 9 possibilities total, because each of the first potentiometer 3 settings/categories can have an additional 3 settings/categories for the second potentiometer.
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