Infrared L.E.Ds Help! - Electronic Circuits Projects Diagrams Free

liddley · 30th November 2008, 08:12 PM

Hello there!
Was wondering if any one had an experience with infrared L.e.ds
I am new to electronics and thought I would be an interesting project to build an IR lamp that would assist a CCTV camera I have fitted in my garden to see in the dark. I have chosen to use a standard 150w halogen flood light housing for the project.
I stripped all the internals out of the flood lamp and fabricated an acrylic plastic face plate that has 20 5mm equally spaced holes in, which fits snuggly behind the glass front of the flood lamp housing. This face plate holds 20 infra red l.e.d`s I bought from Maplins.
This was the easy part now all I need to know is the best way to run them.
Any circuit ideas would be much appreciated, how to work out the mA/Amp`s of the transformer required ect ect. I was also hoping to incorporate a photocell in the circuit so the leds only operate at night.

Boncuk · 30th November 2008, 08:36 PM

Hi liddley,

IR-LEDs normally have a forward voltage of 1.2 to 1.3V. Assuming a forward current of 20mA each you might connect 10 LEDs in a chain (series) and one current limiting resistor using a 15V stabilized power supply.

Use two chains to have 20 LEDs supplied.

The current limiting resistor is calculated: RL=+Vin(V)-(10X1.3V)/0.02A(IF), RL=100Ω. The power it dissipates is calculated: P(W)=VL(V)*IF(A); P=2V*0.02A, P=0.04W (40mW). A standard resistor has a power rating of 250mW. It will suffice.

Boncuk

Hero999 · 30th November 2008, 10:23 PM

Use a 15V wall brick power supply and a resistor, you might need to measure the voltage because it's likely to put out much more than 15V when lightly loaded.

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30th November 2008, 08:12 PM	#1
liddley	Infrared L.E.Ds Help! Hello there! Was wondering if any one had an experience with infrared L.e.ds I am new to electronics and thought I would be an interesting project to build an IR lamp that would assist a CCTV camera I have fitted in my garden to see in the dark. I have chosen to use a standard 150w halogen flood light housing for the project. I stripped all the internals out of the flood lamp and fabricated an acrylic plastic face plate that has 20 5mm equally spaced holes in, which fits snuggly behind the glass front of the flood lamp housing. This face plate holds 20 infra red l.e.d`s I bought from Maplins. This was the easy part now all I need to know is the best way to run them. Any circuit ideas would be much appreciated, how to work out the mA/Amp`s of the transformer required ect ect. I was also hoping to incorporate a photocell in the circuit so the leds only operate at night.

30th November 2008, 08:36 PM	#2
Boncuk	Hi liddley, IR-LEDs normally have a forward voltage of 1.2 to 1.3V. Assuming a forward current of 20mA each you might connect 10 LEDs in a chain (series) and one current limiting resistor using a 15V stabilized power supply. Use two chains to have 20 LEDs supplied. The current limiting resistor is calculated: RL=+Vin(V)-(10X1.3V)/0.02A(IF), RL=100Ω. The power it dissipates is calculated: P(W)=VL(V)IF(A); P=2V0.02A, P=0.04W (40mW). A standard resistor has a power rating of 250mW. It will suffice. Boncuk __________________ Proper Planning Prevents Piss Poor Performance

30th November 2008, 10:23 PM	#3
Hero999	Use a 15V wall brick power supply and a resistor, you might need to measure the voltage because it's likely to put out much more than 15V when lightly loaded. __________________ I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong. Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.