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| Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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19th Mar 2024, 4:37 pm
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#1 |
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Dekatron
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 3,767
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L.E.D. voltage
I have a load of L.E.D'S is there a way to determine the working voltage .Mick.
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19th Mar 2024, 5:03 pm
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#2 |
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Octode
Join Date: Feb 2018
Location: Southampton, Hampshire, UK.
Posts: 1,063
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Re: L.E.D. voltage
I'm currently working on some small star LED and other projects. I refer to kitronik.co.uk or this website for information: https://www.ledsupply.com/blog/what-...ow-about-leds/
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19th Mar 2024, 5:08 pm
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#3 |
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Octode
Join Date: Feb 2018
Location: Southampton, Hampshire, UK.
Posts: 1,063
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Re: L.E.D. voltage
I also find this online LED resistor and current calculator very useful:
https://ohmslawcalculator.com/led-resistor-calculator |
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19th Mar 2024, 6:53 pm
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#4 |
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Hexode
Join Date: Nov 2009
Location: Cambridge, Cambridgeshire, UK.
Posts: 495
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Re: L.E.D. voltage
When I last went through some leds with the same objective, I started with 5ma drive current and increased it 5ma at a time. Then monitored the brightness. When it looked correct I noted the voltage and current.
Most of the time I just test them individually in the application I'm using them for and pick a resistor for the voltage supply. Edit: just noticed my little tester thing has an led forward voltage function, I may have a look... |
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19th Mar 2024, 9:55 pm
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#5 |
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Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,208
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Re: L.E.D. voltage
As a rule of thumb, small or normal LEDs can be driven up to 20mA. Starting at 5mA seems sensible. The voltage across the LED should be reasonably stable between 5mA and 20mA. Just to reiterate the obvious: the LED itself determines the voltage drop. They should always be driven with a limited current, i.e. with a resistor or constant current source from a higher voltage.
(white) LEDs intended for lighting can often be driven up to 300mA or 600mA but will be in a casing that will enable them to dissipate the power. |
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19th Mar 2024, 9:57 pm
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#6 |
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Nonode
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 2,130
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Re: L.E.D. voltage
The forward voltage of "classic" LEDs is largely determined by colour.
Red= about 2.5 volts Orange and yellow slightly higher than red, but only slightly. Older green types, the dull yellowish green ones just under 3 volts. Newer bright emerald green about 3.5 to 4 volts Blue, a little higher than green. However some newer types of red, orange and yellow LEDs are in fact deep blue LED chips with a phosphor These have a forward voltage of about 4 volts, as do white LEDs which are blue with the addition of yellow phosphor. |
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22nd Mar 2024, 3:22 am
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#7 |
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Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,208
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Re: L.E.D. voltage
It all depends on the exact chemistry. Red can be anything between 1,6 and 2,5V. I think there's also some more variants of the green and yellow ones.
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8th Apr 2024, 2:48 pm
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#8 |
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Octode
Join Date: Nov 2010
Location: Cullompton, Devon, UK.
Posts: 1,435
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Re: L.E.D. voltage
I purchased a backlight tester HWL300 which is a brilliant bit of kit it will test any led and give its voltage, ideal for finding the dud leds in a string. that reminds me I loaned it out must get it back.
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10th Apr 2024, 4:58 pm
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#9 |
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Hexode
Join Date: Apr 2007
Location: W Yorks, UK.
Posts: 407
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Re: L.E.D. voltage
Useful?
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10th Apr 2024, 5:53 pm
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#10 |
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Heptode
Join Date: Sep 2009
Location: Tonbridge, Kent, UK.
Posts: 689
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Re: L.E.D. voltage
Very!
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