Dimming an LED without wiring changes

We are probably going to switch to having a row of monitors, keyboards and mice because KVMs keep causing problems. Too much cabling, monitors not getting properly detected and set up during boot if not the selected computer, need to reboot KVM at random intervals.

Hopefully we will get wireless keyboards and mice so much reduced cabling.

Reply to
polygonum
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I changed to Aten because I was having problems like that! I particularly had problems with three KVMs, all of which were 2 way and had Win 7 on one side and FreeBSD on the other. All three use ancient Model M keyboards.

At least it's easy to upgrade the firmware!

Reply to
Bob Eager

My problem started with a Dell keyboard with integrated smartcard reader.

Mine's about 9 years old (CS1764 not even the A version), no firmware published on the website other than what it arrived with, I did contact them and they gave me a non-published link to a slightly newer version which didn't fix the issue, I've gone back to a Model M keyboard but at the moment it's plugged direct into the docking station.

Reply to
Andy Burns

Permanent ink pen (for writing on CDs etc.)

I toned down a blue LED by inking over with a red pen

Reply to
alan

If you have a sign maker nearby, and offcut of black perspex? Depending on thickness it will let some light through.

Reply to
Dave Plowman (News)

Masking tape?

Reply to
Adam Funk

Yes, SWMBO mentioned that just a few hours ago. Will give it a go although the Blu-Tack seems to work pretty well (but not pretty, actually).

Nail varnish was suggested too.

Reply to
Bob Eager

Bloomin' customers - always changing the specs. :-) You want pretty as well as functional? Put a Swarovski crytal onto the Blue Tack.

Reply to
polygonum

I'm wondering if I have a scrap around somewhere.

Reply to
Bob Eager

Why do makers have thse indicator LEDS so bright? On the little (two thumb size) wireless keyboard they are so bright it makes it hard to see the keys. Bought a NAS enclosure LED on that lit the room up at night, attacked it with snips and aditional series resistor. Don't know what value I ended up at but the current was 50 uA (micro amps) and it was still a bit bright. The thing would glow dimly if you just lighly touched the wires with dry fingers.

Reply to
Dave Liquorice

The LED makers have vastly improved the efficiency of LEDs with time but electronic engineers still give them about 10mA drive current!

I have a cute little demo circuit with an original 1970's era red and yellow LEDs in series with modern ones and the result is startling.

Reply to
Martin Brown

As I said, I like the idea that HP have on the switches I have...the LED brightness is variable. I have them on the lowest setting.

Reply to
Bob Eager

Cut a square from the sticky strip of a post-it note? Similar to masking tape, but if you don't have any to hand...

Reply to
Etaoin Shrdlu

Any kind of black marker pen. Even a dry marker pen if you don't rub it.

Reply to
Martin Brown

The blue LED indicator lamps are the worse for this excessive brightness issue. On older kit using different lamp colours, they seem to have decided on the same value of current limiting resistor for all three colours (red, green and blue) with the result that the blue is uncomfortably bright compared to the more muted red and green lamps.

I've found that if I pick a resistor value that uses orange instead of red as the third band on the originally fitted resistor, that seems to drop the brightness to a more comparable level. :-)

But not as startling for LEDs of a colour other than the blue LED ime.

Reply to
Johny B Good

In many cases involving a blue LED, even that isn't sufficient. :-(

Reply to
Johny B Good

This is a massive green LED. Just glad it isn't blue! :-)

Amazing how much advice such a trivial problem has generated. Thanks everyone.

Reply to
Bob Eager

I recently designed a PCB with a series of indicator LEDs for different power rails, and decided to use a rainbow colour scheme white/blue/green/yellow/orange/red All but the white came from the same Kingbright range.

Not only were they painfully bright, they were all different levels of intensity. I had to spend half a day tweaking the resistor values to match the intensity across the array. To make it more exciting, the power rails were different voltages. Some of the resistor values went up by a factor of

100.

Theo

Reply to
Theo Markettos

Should have bought from the Notso 'kingbright range. :-)

Reply to
polygonum

One problem is that our eyes have a differnt sensitivity to that of those devices that measure brightness. They can also have diffenrt angles of view which can be another annoyance.

You shouldn't use the voltage or current to change LEDs brightness you shoud use constant cuttent and PWM to adjust the intensity.

Reply to
whisky-dave

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