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An LED is a light-emitting diode. Lighting an LED is considered the "Hello world" of a circuit design, and it can be as simple as putting a series resistor or can get more complicated, involving PWM and multiplexing.

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header unconnected; the "global" activity LED works normally. My idea at this point was to simply connect all the anodes to the supply from the "global" LED; this works to some extent, but when the "global" LED lights up, all the others turn off. Any idea what might be causing this? …
asked Oct 4 '11 by Simon Richter
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external boards are connected via cables that may be accidentally disconnected or shorted, I'd like to verify that there is indeed a LED connected on the other side. The signals are generated from an … FPGA, so I have a bit of flexibility in the implementation. Idea 1: Constant-Current 16-Output LED Driver IC with Fault Detection This integrates everything in a single package, but it seems all of …
asked Feb 16 '17 by Simon Richter
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Sure, whenever the diode is conducting. With greater \$V_d\$ the current across the diode increases exponentially, and if it exceeds the maximum the diode can handle, the diode is destroyed. When th …
answered Jun 24 '15 by Simon Richter
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I'd use a 5k potentiometer: simulate this circuit – Schematic created using CircuitLab Adjust brightness as desired by turning the knob. If you want to be fancy, mount the potentiometer so tha …
answered Mar 1 '18 by Simon Richter
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You could use dedicated LED controllers that combine current regulation and multiple channels, for example the TI TLC59281, which provides 16 channels, enough to drive two digits. …
answered Sep 6 '16 by Simon Richter
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I have a similar project, using a high current LED driver IC and a separate PWM generator. At these currents, linear regulators are too wasteful and would run too hot (a LDO with just 0.4V overhead …
answered Apr 16 '16 by Simon Richter
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Using a lower voltage for the LED is mostly fine. You will waste less power in the resistor, but you trade this for less tolerance in matching the resistor and LED. The edge case is obviously where … the resistor has to be 0 Ohms, and the forward voltage of the LED is 3.3V -- at this point, the U-I curve becomes fairly steep, so manufacturing tolerances will heavily affect light output. Whether a …
answered Apr 12 '16 by Simon Richter
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rearranged if needed. My board will need some adjustments as I supply the IC from the LED supply and I have a weird connector because of space constraints in my application. …
answered Sep 25 '18 by Simon Richter
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The LED driver regulates current, so it adjusts the voltage until the current is 20mA. If you put two LEDs in series, the LED driver will still regulate to 20mA, but the voltage required for that … will be the sum of the LED forward voltages. The downside is that you need a high enough supply voltage, and any channel that has only a single LED will need to drop the voltage in the driver. If it's a buck converter, fine, but a linear regulator will heat up quite a bit. …
answered Nov 1 '18 by Simon Richter
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If designing for simplicity, I'd probably use a current regulator, such as the NSI45060JDT4G, which will act like a variable resistor with exactly the right value, regardless of input voltage. Since …
answered Apr 15 '16 by Simon Richter
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Another thing that could work for you is to attach the the CEC bus on a free HDMI port somewhere. Switching the active source is announced on the bus, and it is always possible to ask the other device …
answered Sep 4 '15 by Simon Richter
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There are a number of constant-current LED driver ICs with PWM control for dimming. You can easily generate a PWM signal from an Arduino, although the IC only has four PWM controllers (so a single … using off-the-shelf components on the 230V side. Current carrying capacity on the DC side is an issue though. I've built a small board for four LEDs once, with up to 1A per LED, adjustable through a …
answered Mar 28 '17 by Simon Richter