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# Electrical components Answered

Is there any components that set the minimum energy to pass through? When the energy is lower than the fix amount , no energy will be passing through.

I'm trying to make a project. I'll put a dynamo on my bicycle, and it will be connected to 3 LEDs. When I cycle in low speed, only one LED will light up. When I increase my speed to certain level, 2 LEDs will light up and if it passes a certain speed all LED will light up. Any idea?

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## Discussions

All diodes have a forward voltage drop. Look at the operational current graphs -- they don't work until that voltage is reached. They then draw current at a rate that increases with voltage, until the max allowable is reached.

It's been suggested that your LEDs might be in series. That's one possible explanation -- although devices in series always draw the same amount of current, so it's more likely that differences (in manufacturing) create small variations in the forward voltage drop of each LED. Above a certain voltage (pedaling speed), they all light together. Below that voltage, only some light.

Those variations would be apparent for parallel LEDs as well, which sounds more likely for low-voltage optionation. For series wiring, the voltage drop would be cumulative -- the supply voltage would need to be greater than the sum of the voltage drop for all LEDs.

Another might be that your LEDs have different voltage drops (true of different types / colors).

If you're rectifying the incoming voltage to convert to DC, don't forget those diodes (the rectifier itself) also have a forward voltage drop, which "disappears" about 0.7V.

Always peddle fast! Sorry I couldn't resist. How are your LEDs wired. Sounds like you have them in series, power goes to first one, and then power from the first one goes to the second and so on... I'm assuming you have resistors before each LED so you're getting enough current to light the first LED, but not enough to pass through the second resistor and light the 2nd LED until you're speed is up. Wire each LEDs resistor directly to the current source and all 3 should light at the same time. Although they'll probably be dim until you pick up speed in which case you could reduce the value of the resistors. Hoping that helps a little.

Measure the output of your dynamo at the set speeds.
Adjust a LED voltage bar to work with these values.
Connect your additional LED's for those of the voltage bar.
Since I assume a great lack of knowledge about standard electronics I suggest to do some reading first.