Circuits / Getting started
Slide switch picks an LED
A changeover (SPDT): its middle pin is joined to one end or the other, so one switch sends the current down one of two paths
Tap a part to see its voltages and currents. It is a model, not a measurement.
What do you need?
- Slide switch SS12D00G3Search on Amazon
- Resistor 330 Ω × 2Search on Amazon
- Red LEDSearch on Amazon
- Green LEDSearch on Amazon
- Jumper wires × 3Search on Amazon
- BreadboardSearch on Amazon
How does a slide switch choose between two LEDs?
A slide switch like the SS12D00G3 has three pins and one moving contact. In either position, the middle pin, the common, is joined to one of the two ends, and sliding the knob moves it from one to the other. That makes it a changeover, or SPDT: single pole, double throw. Here the common goes to the 5 V rail and each end feeds its own branch, a 330 Ω resistor and an LED. With the knob to one side, the red LED takes about 9.8 mA and the green one nothing. Slide it and the current moves to the green LED: about 8.9 mA. The currents differ because this green LED needs more voltage, about 2 V against 1.8 V, which leaves less for its resistor. Each branch has its own resistor, so each can be sized on its own. In each position only one path is closed, so only one LED is on, and the switch carries only one branch's current.
Values from the Protoboard ISO simulation: a model, not a bench measurement.
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