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5

A collection from another thread, posted here for the middle schematic. Pin 6 would be the GPIO pin. For better brightness matching, swap the red and green LED positions.


0

Good challenge for other solutions! If one of the two LEDs will always 'on' I suggest another circuit: A) the two LEDs connected in parallel but in opposite polarity; B) two resistors (chose the value) connected in series between +V and GND; B) one side of the couple of LED is to be connected to the GPIO; C) the other side of the LED couple is to be ...


11

You mention an IO pin; this is how you could do it with one IO pin if you are using a microcontroller (assuming one that uses 5V logic): simulate this circuit – Schematic created using CircuitLab When the IO pin is 5V, D2 will light up; when the IO pin is 0V, D1 will light up. Note that you will have to calculate the actual resistor values; different ...


5

simulate this circuit – Schematic created using CircuitLab You could also try this. simulate this circuit This would also work. simulate this circuit


4

On editing your question, I see that what you really want to do is to switch the LEDs from a microprocessor output. The easiest way to do that is in your program. Use two GPIOs, and always switch one off when the other is on. If you can't change the program, then you could do something like this: simulate this circuit – Schematic created using ...


0

In what region should MOSFET operate in "on" state? Linear or saturation? For this I've assumed the load current is 30 mA because it matched with a graph of MOSFET characteristic I had close to hand. For your load of 90 mA the green line will cross near the Y axis at 90 mA if you can supply enough \$V_{GS}\$ voltage: - When "on" the ...


0

After some investigation I found out that I just needed a RS Latch which can be made with two NOR gates.


1

Look into the function of an SR latch. In an S-R latch, activation of the S input sets the circuit, while activation of the R input resets the circuit. In your case the <30% signal can be connected to the set and >80% signal can be connected to the reset inputs. Fortunately, both the above won't be high at the same time. SR latch can be made using ...


1

Well, I managed to solve this by using a higher voltage, apparently 3 V wasn't enough to open the 2n2222 all the way, but 6V seemed to work, then a 47 ohm resistor to drive down the voltage (at 77 mA current I calculated that the resistance of the LEDs was about 40 ohm) to a level the lights could handle. This seemed to work. Note that I have not hooked up a ...


0

Any BJT based device is going to have a Collector to Emitter voltage drop. Specifically for the 2N2222, it is not to bad, looking at the plots it should be less then 100mV, assuming you have a base current that is reasonable, try something along the lines of 1mA (a 1k Resistor from your Arduino pin to the base should work) If it is still dim even with the ...


0

You need either to use a 3V relay, or better - go with mosfet. Problem (as You observed) is that it creates voltage drop. Why? 3V is not enough to turn it fully on. You have to look for oiwer mosfets compatible with 3V3 systems. Or build simple charge pump circuit (eg. on 555 timer) to create higher voltage for mosfet gate (and use open collector to drive it)...


0

It's presumed that it's an 8-terminal push-button 'DPDT' latched switch, with 1 'NO' contact for a pilot light. Here's the schematic. Pushing the button once would latch the switch to energise the actuator and the pilot light. Pushing it again would unlatch it to de-energise the two.


1

I found my answer. It is called a Master-Slave socket outlet.


0

If you really need to switch that amount of power at that high of a frequency, you likely need to use GaN or SiC transistors. Be aware that this represents and extremely challenging engineering task, and that you could likely publish a paper on just the switching circuit alone. If you can afford to switch at a lower frequency (say, 10-100kHz range) a half ...


-2

take a look on those circuits. An image is worth a thousand words, interactive simulation even more. Instead of copying circuits, try to understand them! Stay curious. Remember not to draw more than 1 or 2 mA from Raspberry GPIO - its not much, and not even close to maximum given by the manufacturer, but the fewer mili Amps the better (you have bigger margin ...


-1

(PARTIAL SOLUTION SO FAR): I've learnt by other sources (documentation, some forums of electrical engineer's fame with users which reported similar doubts). Since this is for controlling AC, then it's somehow indifferent whether you interchange LIVE and NEUTRAL, or even whether you "insert" the load in the path to one mains wire or the other. BUT!! ...


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