Light Activated Switch
The circuit comprises a simple application of light operated switch. This circuit senses the ambience light and depending on the presence/absense of sufficient ambience light, it turnes the bulb On/Off automatically. The bulb gets on when there is insufficient ambience light (e.g evening or night time) and switches off automatically when enough ambience light is present. (e.g In day time, when the sun light is present additional light may not be needed.)
This bulb can also be your street lamp that needs to be switched on every evening, and switched off every morning. The circuit does this job automatically without any manual interference.
This bulb can also be your street lamp that needs to be switched on every evening, and switched off every morning. The circuit does this job automatically without any manual interference.
Light Emitting Diode Circuit
If you ever took a computer programing class, one of the first programs you wrote displayed "Hello World" on the screen. Well this circuit is almost the same thing in electronics. Take a look at the circuit to the left. It's a simple series circuit with a battery, resistor and L.E.D. (light emitting diode) all in series. The ground wire or common makes the circuit complete.
Here are some typical values for the series current limiting resistor. If the input voltage is 9 to 14 volts, then use 1000 ohms. If it's 5 volts, use 470 ohms. If you want a brighter light, use a smaller value resistor, but be careful, if you go too low you will destroy the diode junction and the led will fail. Since led's consume such little power you can use a resistor with a very low power rating, 1/4 watt or less. This also keeps the physcal size of the resistor small.
If you placed a small switch in series with, let's say the 9 volt battery and the 1K resistor, you can control the light off or on. We will do that with the next circuit, only we will use a transistor and not a switch.
Here are some typical values for the series current limiting resistor. If the input voltage is 9 to 14 volts, then use 1000 ohms. If it's 5 volts, use 470 ohms. If you want a brighter light, use a smaller value resistor, but be careful, if you go too low you will destroy the diode junction and the led will fail. Since led's consume such little power you can use a resistor with a very low power rating, 1/4 watt or less. This also keeps the physcal size of the resistor small.
If you placed a small switch in series with, let's say the 9 volt battery and the 1K resistor, you can control the light off or on. We will do that with the next circuit, only we will use a transistor and not a switch.