Dimming an LED without wiring changes

[Dave Plowman (News)]

Nothing new there - even when there were only red green and amber ones they'd look different when driven the same. It may even depend on the individual's eyes.

[newshound]

The problem on my Openreach modem is that the lights are surrounded by ventilation slots. The Plusnet router is better. Need to design a suitably ventilated box when I move them to their final location, perhaps with a chimney to encourage flow.

[Theo Markettos]

I wonder how much that sensitivity varies too: hearing loss causes the higher frequencies to go before the lower ones. I don't know how the optical response curve varies between individuals.

Yes when the primary purpose is lighting. When the primary purpose is 'did I forget to plug it in' or 'has my fuse blown', a PWM circuit is a little OTT.

Theo

[Bob Eager]

I have a slight cataract in the eye, which makes it a bit worse I think.

[Dave Plowman (News)]

Vastly.

If you create a lightbox which allows you to make any colour by mixing RBG, and set it to the closest match to say a printed colour. Then get someone else to do the same. The chances are they'll have different settings.

Then try it with a narrow spectrum light like low pressure sodium or some LEDs. The difference between two individuals will be even more marked.

Basically, we all 'see' colours differently. But learn to call them by the same names.

[whisky-dave]

Quite a bit also ambient light levels are important. Your life style can also affect sensitivity. Being partiallly or fully colour blind is another problem.

It's just not optical either show the same colour to two people and there;s a chance thy'll see a diffenc in shade. Women can disiquish more colours than men apparently or rather a finer deta il detwwen shades, that;'s why they moan about the curtains and scatter cus hions not matching and therefor new ones are needed ;-).

There's a number of colour test charts that can be used to check monitors b ut the best don't rely on a human eye, there's got to be a reason for that.

It's the best and standard way to dim LEDs other than sticking something ov er them. I set the LEDs on my virgin superhub 2 to low, doing that the conventional way would require a switch to be set to low meduim or high rather than soft ware.

It's not really OTT because leds aren't all the same even the same colours because of manufacturing differencies the voltage they 'run' at can be slig htly differrent which means a slightly differnt current will flow LEDs are very suceptable to heat and that changes their characteristics too.

and using resistors you have very little riggle room unless you spend a lot on high tolerance resistors.

[polygonum]

Not always - I have lost a chunk in the middle.

[polygonum]

There is a degree of irony that colour blind people are sometimes far more sensitive to colour mis-matches than those with "normal" colour vision. Classic being where they don't even have to do more than glance where others need to spend ages carefully scrutinising - and may still end up not seeing a difference.