Hey Guys, I was in maplin the other day and got some InfraRed LEDs* plus an LDR** in the hope that I could add some night-vision to my webcam. Maplin codes: [despite the fact that the codes on the receipt relate to different versions of the same] * 8x cy88v (3mm) + 2x cy85g (5mm) (Not certain about these codes.) **- 1x N55AY or N56AY (not sure, but the guy seemed to think it was the right one.) My plan was to get power from the USB. Is this going to work? And if so, how?! TIA, j
I know what IR leds are, but whats an LDR? IR leds you could probably hook in paralell with the 5v using resistors
Just leave the LEDs on all the time. You don't need to bother with the ldr, or any associated required circutry.
You can use the LDR in a comparator switch circuit to turn the lights on below a certain light level, or use a 555 as here. (There's a slightly better IMHO 555 circuit here from a few days ago using a thermistor, swap for LDR. OTOH, his uses less parts. ) Will work without the relay & 1N4001, using a transistor current-boost switch as shown, TIP31C will switch 3A or a 2N2222A will switch 600mA. Change R1 (his VR1) to suit your LDR.
You can switch with just the LDR, a resistor, and a transistor, but it may be a bit erratic on the actual light-level it switches at, and will go through a partly-on stage as daylight fades. Extra bits just make it more accurate and sharper on/off. Needs a very-high-gain transistor, like a TIP110 (2A) or TIP120 (5A) for several leds.
Excellent, thanks. just outta interest: Could it just be a straight circuit in theory (no transistor)? (Power > LDR > LEDs > Ground) or would that burn out the LDR?
No. the resistance of a typical LDR is high enough ( >10k ) that the LEDs would not light at all. Unless you're still planning on using a battery, just ditch the whole affair, and run the LEDs all the time.
since the guy in the shop used the wrong code (i.e. on the receipt) I don't know if he gave me the 1.8k-4.5k or the 12k-35k. He did say that I should be able to use it as I'd explained, so perhaps it is the former.
Well I made it, and it appears to be useless. I popped one of the LEDs and a couple of the others don't work, but it seems that the IR light simply doesn't get far. I even made a reflector to try avoid wasted light. Just thought I'd let you know. Don't know what's wrong with mine - perhaps I was expecting too much from it. I think I may have to get a commercial one.
You must be doing something wrong as this was taken in total darkness using same type of emitter. jazzle-just tried twelve of these together to light the room and it didn't work too well,they seem only to give good illumination up to 600mm.The beam from a tv remote shows up a lot better than these.Going to try a different type which should be a lot brighter.
sorry to sound so new but how does this work, u just get some IR Leds put em on, point them at ure face, turn ure webcam on in the dark and .. thats it?
That's exactly my problem unfortunately - I was trying to illuminate the pavement outside and downstairs, so that's a good ~11 feet away.
Hmm, I have seen mention of removing an IR filter in webcams elsewhere on the web, and guess I need to do the same. Not 100% happy about taking the cam apart though... edit: Have opened it up, but there was nothing I could do to the lense.
Yeah you do need to remove the IR filter to enhance the performance of that... otherwise its the same as wearing sunglasses at night.
Are you just using it for pictures, or general illumination? If the former, you can use them like a flash, because most dont mind ~.5A for a few milliseconds. Otherwise, just get the maximum current you can through them, as high as they safely say you can.
