Questions tagged [3.3v]

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3
votes
2answers
1k views

3V power rail from 5V

I've mistakenly ordered some 3V PIC18 L F14K22 instead of the 5V 18F14K22. 3V output is fine for the designed circuit but I need to make a 3V power rail from the available 5V rail. Since only a ...
7
votes
3answers
12k views

Bidirectional level swiching 5V <-> 3.3V

I am looking to interface a 3.3V device with a 5V one. This will require the shifting of the logic levels between the two devices. Doing this in one direction is a trivial matter, but I need to do ...
1
vote
2answers
171 views

Recharging a lipo battery while using it

Right now I am designing a circuit that will charge a lipo battery via usb, using the mcp73831 (at 100mA). The battery voltage(nominal 3.7v) will be regulated to 3.3v to power a microcontroller like ...
8
votes
3answers
17k views

MOSFET and 3 V power supply

I want to control an N-channel MOSFET from a 3 V power source. The thing is, I have difficulties understanding how to know the minimum Vgs value is to be applied for the MOSFET to be saturated. ...
13
votes
1answer
4k views

How is this circuit for level converting (5V<>3.3V) working?

Does anybody know, how is this circuit exactly working? It is level converter between 5V and 3.3V logic and it is bi-directional. I have some theory, but I am not sure with it (I never worked with ...
7
votes
1answer
6k views

Voltage Level Shifting

I know there are similar questions on the site, but I wanted to ask it from a somewhat different perspective. I've got a 5V device (Device A) that can operate at 3.3V. I've got a 3.3V device (...
4
votes
3answers
28k views

Resistor requirement for 3.3v

I have a quick questions: can I safely power a LED with 3.3v without a resistor? I have some LEDs that I typically power with 5v and a 220Ω resistor, but I can only supply 3.3v at the moment. ...
2
votes
2answers
1k views

Driving a 24V isolated load from a 3.3V MCU

I am looking to drive a 12-24V purely resistive load from a 3.3V MCU. I would like to use an opto-isolator to separate the circuits electrically. I've drawn up the following circuit, but I'm not ...
1
vote
2answers
1k views

How to drive multiple LEDs from a Li-ion battery (with varying voltage)?

I want to supply constant voltage to my LED's but the supply varies from 3.7V to 4.2V (Li-ion battery). I cannot use 3.3V voltage regulator as it will need at least 4.3V voltage at the input but my ...
14
votes
4answers
36k views

For 3.3V microprocessors, what's the best way to power the gate of a MOSFET?

The new processors are all 3.3V and dropping. So while I am used to 5V arduinos being able to power the gate of a MOSFET, at least most of the way, this is not going to be true any more. And for an ...
2
votes
4answers
5k views

How can I turn off a 3.3V circuit with a 3.3V microcontroller

I'm working with ATTiny85 that has low current (40 mA) GPIO. In the other side I have a power supply (battery with ~5V) connected to a LM317 and an ESP8266 that demands high current (more than the ...
11
votes
4answers
9k views

Is it possible to drive TTL inputs from 3.3v microcontroller

I need a quick heads up on a problem I am trying to solve at work. I'm trying to connect to a parallel data port on an interface module we use to access smart cards. The port has an 8bit input and an ...
7
votes
1answer
13k views

MOSFET choice for 12v LED Strip and 3.3v Logic

I'm currently planning a project on a low-cost WiFi-enabled RGB LED controller and could use some help in looking over my parts list and general concept. What I'm wanting to do is a build a ...
3
votes
2answers
13k views

Changing a 3.3V signal to a 5V signal using a BJT transistor

I saw someone asking this EE.SE question in a thread over 2 years old and could not really understand some things about the answer. He had a 3.3V input signal that he wanted to change into 5V signal. ...
1
vote
1answer
917 views

HC vs LVC for 3.3V Logic

I am designing a circuit in which Vdd=3.3V. I have checked datasheets of hex inverters 74HC04 and 74LVC04 and both of these can work good at 3.3V logic circuits. If I have to select one of them then ...
1
vote
1answer
1k views

Wide voltage range input regulation (24V - 3.3V)

TL; DR: I need a circuit capable of handling input voltages from 24V to 3.3V (with a 10mA/5mA maximum current) and delivering 3.3V to the microcontroller (ESP32) input. Recently, I've been working ...
6
votes
4answers
14k views

Options for getting 3.3v @ 220mA from small batteries

I have a system running at 3.3v requiring 70mA at most times and 220mA at peaks (roughly 20% of the time). I'd like to find a way to power this from coin cell batteries or other small portable source. ...
2
votes
3answers
12k views

Safely pull 5V to GND on 3.3V GPIO

I want to control an 5V relay board with an ESP8266 (which operates on 3.3V). Schematic of the board: IN2 is normally on 5V and must be pulled to 0V for enabling the relay. I saw people using an NPN ...
2
votes
3answers
1k views

LM1117 3.3 output gives 4.2

I used this circuit and formula as a reference for 5V to 3.3V It's from the LM1117 datasheet but output gives 4.2V. Here is my circuit: I changed resistors with different values but output give ...
1
vote
2answers
1k views

Solid state relay (or equivalent/alternative) to drive 6V DC from a 3.3V micro

I have to open/close two wire from a closed device. I cannot open due to it's under warranty, and the only part that I can open and modify is an external button that connects the two wires. Firstly I ...
2
votes
5answers
4k views

3V LED Pulse Circuit

I am trying to make a very compact and lightweight circuit that will cause an IR LED to blink on and off at a constant rate, preferably at least once per second but the flashes can be more spaced out. ...
1
vote
2answers
269 views

how to choose level shifters for serial / UART

I have so far been using some MAX3323EEPE chips for shifting between 3.3V and 5V logics on serial / UART communications. This is quite some stuff to solder on a PCB, and the chip is a bit expansive. I ...
0
votes
5answers
2k views

3.3v to 5v conversion with non-5v tolerant part. (single npn transistor?)

I was wondering if I can convert 3.3v to 5v when the 3.3v part isn't 5v tolerant. I was thinking of using this layout: However I'm not sure if the gpio pin will get 5v "for a second" or if this is ...
-2
votes
2answers
4k views

3.3V from 5V Voltage regulator

I wish to build and get 3.3V from LM7805 voltage regulator with some extra parts like resistor and maybe a zener diode. How can I achieve that, is it even possible to do that?