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LEDs and Structure Lighting
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To clarify this I am a design engineer for MPLX ELECTRONICS SYSTEMS. I work with LEDs on just about every project I handle. Here is what you need to know: <br />1. LEDs are directional in terms of polarity. The cathode is connected to ground and the anode is connected to V+. The cathode can be distunguished by a flat mark on side (T1 and T1 1/2 cases). For SMD LEDs, there is a similar approach. LEDs work fine on AC. The alternating current that most modlers come across is 60Hz. or DCC which is in the low KHz. If you are apt, take a LM555 IC and configure an oscillator with a pot. Adjust that pot. You will get a variety of frequencies. Observe the LED and you can see that if at a low frequency (somewhere around 30 Hz.), you will be able to see the flicker in the LED and if you adjust it low enough, you will see the individual pulses. At a minimum frequency of 60Hz., which is what the average moder sees, your eyes cannot see the rapid turning on and off. This is how you can get by with the appearance of continous light. THis applies to ALL lights working on AC. <br /> <br />2. Current limiting resistors are a MUST above appx. 2 V. Here is the formula : V+ minus VLED divided by IF where V+ is your power supply voltage, VLED is the rated operating voltage and IF is the rated operating current. <br /> <br />3. LEDs have a mcd rating. This is millicandellas which is a measure of luminous intensity. The higher, the brighter. However, LEDs such as this are NOT always rated ~ 2V 0.2mA and often a higher IF. <br /> <br />4. LEDs to have a small degree of emmision. I suggest getting one with a large viewing angle or using paper or foil to spread light as you desire.
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