i need to put a led in a electrical circuit and cant find out what size resistor to install
i have a 24 volt supply
1.85 volt led
please help
2007-01-30 02:53:07 · 4 answers · asked by plummy 1 in Consumer Electronics ➔ Other - Electronics
I like to keep the current in LED's a little on the low side. Most will take 20 mA, but I use 10 mA. It's very hard to see the difference in brightness. To have 10 mA at 24 volts, just divide the 24 by 0.01 which equals a 2400, or 2.4k ohm resistor. This should work fine. This is 0.24 watts, or very close to 1/4 watts. You could use a 1/4 watt resistor, but I would go for a 1/2 watt resistor. I like to have some "head room" for my components.
2007-01-30 06:26:12 · answer #1 · answered by Anonymous · 1⤊ 0⤋
The LEDs are arranged in twelve series strings of three. by way of your information, they'll drop 3 * 3 = 9 volts and require 12 * 24 = 288mA. With 288mA flowing by way of a 330 ohm resistor, there might could be ninety 5 volts for the time of it! And it would be dissipating 27 watts! i think of the resistor cost is faulty. it is going to be closer 3.3 ohms (orange, orange, gold). that could supply you 288mA, if the PSU is actual putting out 10V, and could dissipate 0.27 watts. (Are you valuable you probably did not mistake gold for brown?) What voltages are you seeing (a) around the resistor and (b) between the common + terminals and the common - terminals that hook up with the resistor ?
2016-12-13 04:27:17 · answer #2 · answered by Anonymous · 0⤊ 0⤋
I think it worth pointing out to you that l.e.ds are not voltage operated devices. They are current operated.
The 1.85V you quote isn't its operating voltage. It is the voltage which will be developed across it at a particular current, which the manufacturer will have quoted in the device's specifications.
This is often, but not always, the maximum allowable forward current.
And that is often, but not always, 20mA as "wires" states.
Given that your l.e.d's maximum is 20mA then the minumum resistance with a 24V source would be 1k2 (which is the preferred way of writing 1.2k)
Take a look at this http://www.davidbridgen.com/leds
2007-01-30 09:47:44 · answer #3 · answered by dmb06851 7 · 0⤊ 0⤋
need to know the output, DC Output 24v 300mah?
2007-01-30 05:49:53 · answer #4 · answered by Anonymous · 0⤊ 2⤋