Charged Capacitor to Light an LED

Posted on Feb 6, 2014

For this project, we are going to charge a capacitor with voltage and then have the capacitor act as a temporary power source for the circuit. After we charge the capacitor with the battery, we`re going to disconnect the battery from the circuit. The capacitor will then act as the power source, giving current to the LED so that the LED remains on,

Charged Capacitor to Light an LED
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though not being powered anymore by the battery. When the capacitor acts as the power source, it dumps its voltage much quicker than a battery does so the LED is on only for a short period of time. However, nonetheless, it still gives power to the LED so that it can remain on. This can have great real-life application in which there is a very brief shut-down in power, for instance, if the power goes out for a few seconds and then turns back on. While the power is off, the LED or whatever desired load needs to be kept on can remain on if there is a capacitor acting as a backup power source. When the button is pressed down, closing the circuit, the battery does two jobs: it charges the capacitor up with voltage and it gives power to the LED, lighting it. Once the battery is on for enough time for the capacitor to be fully charged up to 9 volts, the capacitor cannot retain any more charge. This happens in a matter of seconds. The battery, however, keeps powering the LED. Now remove your finger from the pushbutton so that the circuit is now open. Now the battery is disconnected from the circuit, and thus can no longer power the LED. However, the LED still remains on for an extended period of time after even though the battery is disconnected. This is because the capacitor now acts as the (temporary) power source for the circuit, giving power to the LED, so that it stays on for a short while. A capacitor does not act like a...

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