Infared light for night time

[George]

Diagram here if anyone interested? it can be made up on veroboard if you are not bothered about a PCB one.

The more leds on the cicuit the better the night vision.

[George]

Whats the best infareds for this project,Blue or Clear? as I found this site out of a few to be a lot cheaper in price.

[mick]

Probably part number 720-530 on page 21. Those will give 80mW radiant power each, if you adjust the resistors to put 100mA through each string of LEDs. Using a 12v supply you could make R1-R8 15 ohms rather than 39 ohms. This is running them close to their maximum so perhaps a slightly higher value may be better... Note that your total load current would be

400mA, so this isn't really for battery operation.

[meow2222]

Why use LEDs when filament lamps radiate IR well when run at under half rated voltage. Producing IR is the filament lamp's forte, or weakness when you want visible.

NT

[George]

Hmmm! yes I can see my electricity bill now. ;-)

ps I don't want to resemble part of blackpool illuminations

[meow2222]

unclear how thats relevant here. Filament lamps are about as efficient as LEDs at IR.

NT

[George]

IR Leds will last cosiderably a lot longer than filament bulbs.

[mick]

I suspect that they will be much more efficient than filament bulbs as the energy produced is monofrequency and the beam width is quite narrow (40 degrees for the part number given). Filament bulbs waste a lot of power radiating well into the visible region (even at half voltage) and also radiate in all directions.

It would be interesting to test this.

[geoff]

In message , George writes

How much longer will a filament lamp last at 50% it's rated voltage ?

[<me9]

From experience of using two in series in a past life, I'd say for ever, unless they were 15w pigmy.

[geoff]

In message , [e-mail] writes

S'wot I was thinking

I used to use pigmys as loads for soak tests and found that even they lasted almost forever when run at lower voltages