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A switch either opens or closes a circuit.
- Open = off
- Close = on
A push button switch is usually the normally open (NO) kind. You close it by pressing the button.
Single pole, double throw switches will either stay opened (off) or closed (on) once you set the position of the lever. Push button switches are probably open if you aren’t pressing the button (normally open), and close as long as you are pressing the button. I mostly focus on the pushbutton switch in my videos, because they tend to be able to be used on an electronic prototype breadboards. Although they tend to pop out of the board for a while.
Video:
- 3 – 5mm LEDs should typically have the current through them limited to no more than 20mA.
- Most resistors are rated for 1/4W. They should be kept below 1/8W to be safer.
- Using a 470Ω resistor to protect an LED from 9V will keep current below 0.02A (20mA) and will keep the wattage of the resistor below 0.125W (1/8W).
- 9V – 2V red LED drop = 7V across the current setting resistor.
- 7V/470Ω = 0.0149A (15mA) through the circuit (resistor, LED, battery, connectors).
- 7V x 0.015A = 0.105W resistor heat that must be dissipated.
Good pages to check out next:
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