Wayne Parham wrote:I'm not sure the forward voltage is all that relevant. I even have blue LEDs in one of my builds - which require much higher forward voltage - and they look great. I think more an issue is the lumens per mA and the diffusion. And one more important factor: the lead length. Some LEDs have long leads but some barely make it.
All that said, in my opinion, the "good old" generic T1-3/4 (5mm) LEDs we were all familiar with in the 1970s are what you want. They are diffused and have a color and brightness that work well in the Altair. You definitely don't want a non-diffused LED but other than that, most of 'em will work.
BillO wrote:Also, the LEDs today are many times brighter than they were in the 70s. Unless you want to light up a room with them you might want test them first and choose your resistors for reasonable light output.
AltairClone wrote:Mouser has over 500 in stock: https://www.mouser.com/ProductDetail/Br ... QPkg%3D%3D
Mike
TheoAU wrote:Wayne - what resistors did you use with the HLMP-D101 LEDs?
Wayne Parham wrote:TheoAU wrote:Wayne - what resistors did you use with the HLMP-D101 LEDs?
I used the 2KΩ resistors Mike calls for in his schematic and BOM. I used that value for both my "red" and "blue" builds. They both have what I would consider to be the "proper intensity" and they look great.
As an aside, I find that LEDs illuminate pretty brightly with very low current. Light perception must be like sound perception, on a logarithmic scale.
For example, I have a little audio preamp controller that I developed for tube amp manufacturers. It controls RDACs to provide remote-controlled volume and balance. And it also includes an input switcher to control what source is active. The audio controller is based on an Atmel AT2313 (or AT4313), which monitors (front panel) push-button inputs and senses pulses from an IR receiver that reads the remote. It is also connected to the RDACs and to a bunch of LEDs that show power (on/off), input selected and volume.
I initially chose LED current-limiting resistors, the "normal" way, calculating the value based on voltage across the resistor and the desired current, basically 10mA or 20mA. Kinda standard. Works great for giving a nice safe resistor value that turns the LEDs on all the way without smoking them.
But man, the LEDs I chose for the prototype would put your eyes out. And they're not even the super bright LEDs that need heatsinks. They're just little-bitty things. But they'll still put your eye out.
So I started dialing back the current with higher and higher resistance levels. Ended up with a crazy high resistance of 12KΩ, and even that seems too bright.
All that to say the days of running a 220Ω or 330Ω series resistor to an LED with a 5v source are gone for me. They're
just too dang bright!
Users browsing this forum: No registered users and 1 guest