How do I wire an LED to AC current?
I’m trying to make an LED nightlite in a small size I have basic electronic understanding but am looking for some insight and possibly formulas describing how to make my circuit the LEDs I want to use need 4V and have a 350MA draw I plan on using 6 of these LEDs. presumably I need some sort of device (diode?) that would convert the current from AC to DC and then a resistor/s right?
So if I Use 2 LEDs back to back I would have to have them in parallel wouldn't I with one reversed from the other? or else the circuit would remain closed wouldn't it? An LED/Diode acts as a one way valve from what I understand, so with 2 LEDs in series if the ac switches direction they would either both be closed or both be open wouldn't they?
Tagged with: ac to dc • acts • diode • insight • leds • nightlite • resistor
Filed under: Electronic Circuit Diodes
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This is actually very easy. You can connect the LED directly to AC with a series resistor to limit the current. But when the voltage reverses the diode will blow. So put two LEDs back to back with the same series resistor and one will conduct when the AC is one direction, and the other will conduct when it switches. Easy!
to convert AC to DC, you can start with a Bridge rectifier, which is a formation of diodes. However, you will also need to bring down the current and voltage using a transformer.
Luckily, there is an easy way to get the whole package. Many devices like cell phone chargers, and anything else that plugs into a wall with a chunky black plug and ends with a cylindrical silver jack, will get you where you need. Just look at the Input and output to see what it starts at, and what you end up with.
yes. Assuming you want to operate from 120 VAC, put the 6 LEDs in series with a rectifier rated at 400 volts, and a power resistor. The resistor would be calculated as follows:
Half wave rectified AC has an average DC value of about 60 volts. You will drop 4*6 = 24 volts in the LEDs, leaving about 35 volts across a resistor. At 350 ma (which seems high) this comes to 100 ohms, 20 watts. Note that you will be dissipating 4*.35 = 1.5 watts in each LED, so they will get hot.
You seem to have some high power and high voltages here, so be careful. I's start out with a 2000 ohm 2 watt resistor first, it may give you enough light. When it is all working OK, then move to a 1000 ohm, then a 300 ohm, finally the 100 ohm resistor.
This will be a very bright night light!!
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First of all, you can use AC (lowered in voltage) current to run an LED. The LED itself is a diode, so it will rectify the AC current all by itself, no need for an additional diode or rectifier.
You say the LED you are using draws 350mA. That seems like a lot. Most led’s operate with a few mA to maybe 20 mA.
Double check the current value of the LED’s.