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3 votes
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When do we need 1500 mA current to drive LEDs?

I googled and found the higher resolution images from Amazon. If you look closely, all 10 LEDs are directly in parallel, and then those 10 are in series with the next ten: This design maximizes the ...
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5 votes

When do we need 1500 mA current to drive LEDs?

It would be better if you could find a source that provides better technical details than amazon, as I would be very hesitant to trust that. But, there is a way that you could design the led circuit ...
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3 votes

When do we need 1500 mA current to drive LEDs?

It's very likely to be a series/parallel array of LEDs. It works because all the LEDs come from the same batch and so will be reasonably closely matched. It won't be exact, but an array that size ...
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3 votes

Why is ESP32 GPIO pin 14 HIGH at start up?

Some pins are initialized to something when the ESP32 boots. The GPIO 14 is in the list of such pins. At boot, it seems to be a JTAG port TMS input signal, so it likely is physically configured as ...
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0 votes

LEDs lighting up sequentially

Here's one approach, using CD4049 CMOS inverter gates. Starting with just 4 LEDs. I omitted current limit resistors since the gates have inherent output current limiting. simulate this circuit –...
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1 vote

LEDs lighting up sequentially

The LM3914 (with some kind of analog ramp input) is probably your best bet within the given constraints. Another option that doesn't involve oddball ICs would be something like 3x LM324 and 20 or so ...
2 votes

LEDs lighting up sequentially

8 to 10 Leds one at a time, battery operated? A cd4017 decade counter, with a 555 timer to trigger the stepping, would do this with no coding. It's called an led chaser. See https://electrosome.com/...
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1 vote

LEDs lighting up sequentially

If you want to use Arduino, you could use a pull-down type shift register with it, such as STPIC6D595. Arduino-specific instructions: https://docs.arduino.cc/tutorials/communication/guide-to-shift-out ...
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1 vote

Why is this an example of actuator?

The LED has two signals that could be considered a controlled variable (output signal): 1) the colour, and 2) the intensity. The colour is fixed by the band-gap energy as is the voltage drop across ...
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1 vote
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Converting my PC's On/Off Status LED to a Fading LED

There are unanticipated results with such an approach. First, be aware that LED current is proportional to what we see, not LED voltage... Upon turn-on, C1 starts charging from zero volts, ...
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2 votes

Why is this an example of actuator?

I suspect this was not a statement that it is an actuator, but it was a question how it could be an actuator. "to actuate" from the Cambridge dictionary to make a machine work or be the ...
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4 votes

Why is this an example of actuator?

Actuator is one of those poorly defined words. In a narrow dictionary definition, I think you would be right. But I can understand where your teacher is coming from. He has generalised an actuator to ...
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1 vote

Nodal analysis with LEDs

It depends at which level of accuracy you want to carry out your analysis. If by "nodal analysis" you mean "linear nodal analysis", the thing they usually teach at undergraduate EE ...
0 votes
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8 LEDs in parallel each having a switch with a constant voltage supply of 12 V

LEDs are current operated. Operating voltages given are typical at a specified current. Connection of a 2V typical device at 12V will cause it to die so fast it probably will not even emit any ...
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How can I detect the level to which an LED is dimmed?

0-10V dimming is probably the easiest way. this is probably a do-over. unless you can find a 0-10V sender that works with your existing dimmer.
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3 votes

Two 3.3 V low signals to light bicolor LED

Find a common-anode LED - two LEDs in one package with the anodes tied together. Connect the anode to 3.3V. Connect each cathode to a separate resistor and then one of the pins. Green cathode -> ...
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What is the best way (using solid state) to power off lights when another light circuit powers on?

A solid-state switch is one way to power off lights when another light circuit is powered on. To use a solid-state switch, first identify the outlets in both rooms where the lights are being used and ...
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Circuit to light up LED only once

Here is another circuit, it consumes about 100 fa current when not used Push the button to turn on the circuit, you can adjust the on time by tuning the potentiometer or changing the value of the ...
2 votes

Circuit to light up LED only once

I am not sure this will work. I didn't simulate it. But some variation should work. simulate this circuit – Schematic created using CircuitLab
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3 votes

Circuit to light up LED only once

The 74C14 (unbuffered) hex schmitt inverter has a static whole package (6 inverters) current of typically 50 nA at 15V supply and maximum 15 uA across the temperature range. At 25C it will usually be ...
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7 votes

Circuit to light up LED only once

simulate this circuit – Schematic created using CircuitLab Dare I suggest something as crude as the circuit above? The only quiescent current is the leakage through the capacitor. D2 is there ...
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0 votes

Circuit to light up LED only once

A reset / power monitor device can do this, and consume very little power in the process. 0.1uA may be difficult to attain however. This one’s less than 2uA: https://www.maximintegrated.com/en/...
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0 votes

Circuit to light up LED only once

Here's the circuit I mentioned in my comment last night. In my case, the output fed an I/O to a microprocessor. You won't be able to light an LED directly with this, instead you'd probably sent '...
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0 votes

Circuit to light up LED only once

Check out this circuit below The circuit above is done by 555 timer. When the circuit is in off state it consumes about 353ua current. When the circuit is in off state the capacitor charges through ...
3 votes

LED 12 V, 30 A power supply blinking and 0 V output

I found the PSU's schematic but I'm not going to share it here. The converter is a TL494-based half-bridge converter having CV and CC control. This means that as long as the output current is below ...
1 vote

What is the theoretical limit of lumen/watt for lighting systems?

1 cd = 1/683 W/sr = 4π/683 W/sphere = 4π lm ⇒ 1 W = 683 lm then the maximal, theoretic efficiency is 683 lm/W. D. I.
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Grayscale using LED

Using different brightnesses certainly works, and "greyscale" LED walls have been used to great effect in a number of places; perhaps the biggest is the BMW Museum in Munich, which (from ...
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3 votes

Grayscale using LED

The brightness of LEDs is most often controlled with pulse-width modulation (PWM) because it is quite complex to build the efficient voltage or current regulator. If it is just a ballast resistor, it ...
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3 votes

Grayscale using LED

I've played with this a bit (mainly with a red LED) as a single status indicator with multiple states. It's worth giving it a try with an Arduino, because that gives you PWM very easily and it can ...
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11 votes
Accepted

Grayscale using LED

Is there a grayscale LED If you have a clear LED and put a black background behind it it will look black when off and in-between when partly lit. If you have a diffuse LED and paint the base and ...
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3 votes

Grayscale using LED

LEDs have linear luminance with current, so you can control them with analog voltage. Or PWM but depending on what frequency it might just look flickering. Also note that human eyes are non-linear ...
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14 votes

Grayscale using LED

Grey is white at a lower brightness, so all white LEDs produce grey when put next to a brighter white LED. The most common way to produce different shades from LEDs is to use PWM. Nearly all ...
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0 votes

How to connect multiple star PCB LEDs?

Should each of these PCBs have a separate heat sink? Wouldn't be necessary as long as you don't need the heatsinks to be isolated from one another. Whatever heatsink you use, make sure that it is ...
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3 votes
Accepted

Driving different number of LEDs in series with a constant current driver

Here I'm lost. Why does the datasheet talk about adapting the current with the number of LEDs if the number of LEDs doesn't change the current in the string? The idea behind average current ...
2 votes

Driving different number of LEDs in series with a constant current driver

Many applications indeed use parallel LEDs. Since the voltage at the output pins must not exceed VCC, it might be a good idea for your circuit to not use LEDs in series.
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2 votes

Blinking 3 W, 12 V LED not bright

If you measure 11 VDC with an 11.1 V battery, the bulb is as bright as it can be. It may be a lot brighter when connected to an automotive battery which will be at least 12.5 V and usually about 13.2 ...
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0 votes

Blinking 3 W, 12 V LED not bright

In the schematic, it looks like the diode is connected backwards. If the output on the buck converter is isolated from the input, then the output signal from the Arduino will not have any potential vs ...
0 votes

Need help scaling 3 W LED fade circuit with 555

I was unable to get this working properly... so I moved on to an arduino nano approach.
3 votes

The LED bulb in my room has written 9 kWh/1000h on the box; what does that mean?

It means it uses 9kWh for 1000 hours of use. Energy efficiency is often written in kWh because that's the unit on the electricity bill. So your calculation is correct: 1000 hours will cost 9 x £0.52 = ...
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0 votes

Efficient way to drop AC voltage in LED constant-current driver

The circuit is essentially a Switched Mode power supply (SMPS), using the resistor Rs to sample the current circulating. LC5200 switches fully On or Off depending of some parameters, for instance to ...
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3 votes
Accepted

Efficient way to drop AC voltage in LED constant-current driver

Short answer: you don't need to do anything, the 5202 takes care of that for you. You limit the voltage to LEDs to limit their current, the 5202 limits the current directly. The power dissipation ...
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Doesn't using resistors serial to LEDs all the time waste a lot of energy?

Yes, if you have an LED that requires 1.5 V and you're powering it with a 9 V battery; then the resistor would actually use 5 times the power the LED is using. The only thing you could do to increase ...
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Sanity checking an LM2596-ADJ constant current supply design for driving LEDs

Since asking this question I've had some great input from the fine folks on Twitter and Mastodon, plus on another question here. I've also done a bunch of additional analysis myself. I'm going to ...
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Why do LEDs require a constant current source and not a constant voltage source as power supplies?

Also for multiple LEDs, it’s easier to drive them in series than in parallel. Rather than try to determine what voltage to use based on the LED count and voltage drop, it’s easier to get a constant ...
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4 votes
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Controlling LEDs with I2C

What you want is an I2C GPIO expander IC. If you're driving LEDs from one, make sure you check the maximum current allowed per pin, as well as the total maximum current for the device. If you need ...
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4 votes

COB LED unwanted blinking

This sounds like your load is tripping the overcurrent protection on the power supply, which is constant voltage. You need some way to limit the amount of current going into the diode. Whether that'...
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1 vote

How to toggle two LEDs with a minimum of components?

No, it's not possible. Other answers make various suggestions, but not meet the narrow specifications of the challenge. I think Spehro's answer is closest to guessing why the well-meaning guide made ...
4 votes

How to toggle two LEDs with a minimum of components?

That would be very easy if you had a resistor included: since red LEDs generally need a lower voltage (1.5-1.9V) to run compared to the green LEDs (1.9-2.4V), all you need to do is turn one of them so ...
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1 vote

How to toggle two LEDs with a minimum of components?

I can do it with the motor added. Otherwise, I don't think it is possible. In the below R2 represents the motor. simulate this circuit – Schematic created using CircuitLab

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