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Figure 2 - When using perforated board, the shape of the LED will dictate placement
Figure 2 - When using perforated board, the shape of the LED will dictate placement

Small-to-medium sized LED arrays can be made by placing the leads into the holes and then soldering them on the underside using copper strips and wires to create the series parallel connections. Most infrared LEDs will be available as 5mm wide plastic through hole devices like the ones shown in this project, so they can be packed onto a perforated board at about 16 LEDs per square inch. Yes, I mixed up my units of measure, but that is a common thing to do in the electronics industry. If you plan on making your own circuit board, then your only limitations on number LEDs in a given area will be the width of the LED bodies. 16 LEDs per square inch is actually very good for most illuminators, as it gives a decent range and field of view.

If you really have a lot of spare time and own a Dremel tool or small bench top grinder, you could actually grind down one side of the LEDs slightly and then pack them down to a smaller area. Figure 2 shows the LEDs trying to fit into the perforated board without having an empty hole between them, but without a little grinding, they just won't live together happily. A little buzz with a grinder and the LED would have a flat side, allowing them to be packed more tightly, but this is probably not necessary in this project as the idea is to use more LEDs to cover a wider area.



Figure 3 - Using 5mm LEDs, you can make an array with 16 LEDs per square inch
Figure 3 - Using 5mm LEDs, you can make an array with 16 LEDs per square inch

Because the spacing on most prototyping boards is the same as the spacing on standard dual inline chip packages, you will be able to insert the 5mm LEDs to create arrays with 16 LEDs per square inch, skipping one hole between each LED. 3mm LEDs would allow insertion without skipping a hole, but this size of LED is almost impossible to find with an infrared output. Your array can also have any number of rows and columns, but usually a square is best for the most even field of view. Another idea is to base the size of the array on the wiring requirement, using the number of LEDs in series as the width or depth of the array. For instance, if you have 1.2 volt LEDs, and plan to run 10 of them in series to make an even 12 volt power supply, then you could make your array with 10 or 20 LEDs across and as many parallel rows as you have power for. A 10 by 10 array will be large enough to light up a small room for practically any video camera.

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