Linked Questions

-1 votes
2 answers
85 views

Can a gpio pin be read as an input without voltage going through? [duplicate]

I have pi 3 and I want to use one of the pin as an input. It will be connected to tapped off wires from a switch that has 2 volts going through it when it is closed. So I want to feed this 2 volts as ...
83 votes
2 answers
123k views

Raspberry Pi Power Limitations

There are very many, often contradictory, claims about the power requirements and limitations of the Pi. What are the exact requirements?
1 vote
2 answers
719 views

Lots of LEDs in a chain

I need to control about 90 LEDs with a Raspberry Pi. I am thinking of doing with with 3 chains of 30 LEDs, so I can control each set of 30 LEDs independently (turn 30 on and off at a time) and change ...
3 votes
3 answers
2k views

GPIO input and output levels

I have some basic questions, sorry, I have'nt found this. What are output levels of GPIO (Raspberry Pi) I mean the voltage ranges of low and high for input/output What is the maximum current that ...
3 votes
2 answers
1k views

Do I need a base resistor for a transistor? [closed]

All I plan to drive a 51 ohm LED using the pi's 5v pin using a 2n2222 transistor connected to the GPIO. Do I need a resistor on the base pin of the transistor or can I connect it directly to a GPIO ...
2 votes
2 answers
366 views

Multi-Joystick (Joystick, rotary Encoder, push Button) to GPIOs

I'm trying to connect a Joystick/Encoder/Button (Copal Electronics CJ25) to a Raspberry PI. Using gpiotest I managed to get it up and running pretty well - using 3.3V input (though the data sheet ...
1 vote
1 answer
741 views

RPi 3 3.3v GPIO normal current [duplicate]

so I've read around forums that the max current from a RPi 3.3v GPIO pin is 50 mA, but since it is the max I don't know if I should take a resistor for 50 mA or for a lower current.
2 votes
1 answer
2k views

GPIO Voltage tolerance for input

I have not been able to find the input tolerance on I/O pins, especially on the Input pins. If I apply a voltage 3.6v (3.3v +0.3) on an input will it be dangerous or is it ok ? Does somebody have a ...
0 votes
1 answer
209 views

GPIO only reaches 2,4v when high

TLDR; Under little load the GPIO 22 reaches 3,5v whereas under more load it only reaches ~2,4V, which is not enough to trigger the reset-line on an ATMEGA328P. UART GPIO Pins still reach 3,3V in both ...
4 votes
1 answer
1k views

RS232 to Raspberry Pi Zero W

I know this may be a dumb question but can you connect a RS232 Tx, Rx, and Ground from a device directly to the Rx, Tx and Ground on a Raspberry Pi Zero without having to get a Max3232 or something ...
2 votes
2 answers
387 views

Short pulse detection about 35ms, is it possible

I got somewhat short pulse 35ms, I written script in python using RPi.GPIO, using event and callback. Is it possible to detect so short pulses? On related question how close to 3V3 I need to get? I ...
0 votes
5 answers
346 views

Connecting 5V / 2A DC adapter positive line to GPIO

I have a working DIY UPS for my Raspberry PI 3B board. My requirement is that whenever the main power goes off the PI, the software should be able to detect it and immediately trigger a graceful ...
1 vote
1 answer
2k views

Precision of Raspberry Pi GPIO outputs voltages [closed]

Raspberry Pi has several output voltages, GPIO outputs theoretically giving exactly 0V for False and exactly 3.3V for True, 3.3V line and 5V line. However, how precise are these outputs? Can the ...
4 votes
4 answers
8k views

Raspberry Pi GPIO input voltage Limit

I am doing a project in which I have a component that outputs a 5 Volt signal. Since the Pi is only able to handle 3.3 V I connected the signal to a voltage divider. I used a 4.7 kiloOhm and a 2.2 ...
0 votes
3 answers
373 views

How to choose appropriate transistor and resistor values for the 4 digit display?

I bought this 4 digit led display I'm looking at this tutorial and I don't understand why he used such big resistor for his circuit. Excerpt: Please note that the pinouts of LED displays vary ...

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