Questions tagged [3.3v]

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29 questions with no upvoted or accepted answers
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Level shifting with BSS138 - weird values

I need to connect 5V and 3.3V devices via I2C as follows: I've connected 3.3V and 5V pull-ups and tried to measure the voltage. There is 5V on HV and TX_HV but 4,7V on LV / TX_LV. Putting TX to LOW ...
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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 ...
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37 views

CAN Transceiver circuit problem with TJA1042T/3

I am a novice designer who recently started designing circuits. Using the STM32f407VGT MCU operating at 3.3V, using the CAN1TX(PB9) CAN1RX(PB8) pins, the circuit was configured by referring to NXP's ...
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0answers
62 views

MOSFET for 3.3v MCU

I'm building a custom board with ESP32-WROOM-32E that can supply 3.3v trough the GPIO. I need to power a screen using 3.3v power. I'm looking for a way to power off the backlight using the GPIO pins ...
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1answer
59 views

Using the same ESP8266's GPIO for 3.3v and 5v

I am designing a pcb which should receive various types of sensors. The microcontroller is an ESP32 and the external input are RJ11 linked to I2C GPIOs of the uC. I have already planned a LevelShifter ...
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0answers
51 views

On/Off latching circuit with a raspberry GPIO 3.3v

I'm currently failing solving my problem. Of course if I would good better in electronic, I would not post my question here but that's life, and any help would be appreciate. Context: I have around 50 ...
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0answers
30 views

Send a 60Hz trig signal over a 9m cable

I want to send a trig signal over a 9m cable, the signal is around 60Hz (each 15ms it sends a 1ms pulse). In order to avoid electrical interference I convert the 3.3V original signal with the ...
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0answers
53 views

ADC IC I2C problem

I'm trying to run ads7924 using stm32f series. But i2c does not work so I check the i2c line. Between 0R, MCU side 3.3V but ads7924 side 0V. I set pull up setting of MCU internally . What is the ...
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0answers
132 views

NodeMCU - Are all GND connctions born equal?

I'm designing a PCB which is based on NodeMCU board in its core. On NodeMCU there are some GND pins, most of them are to serve digital outputs/inputs, or external sensors which operate on 3.3V. Vin ...
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0answers
159 views

Need a Negative to Positive Level Shifter

I did a simple differantial amplifer for 0-3.3V output. But, as you see I got -3.3V output because gain. I need a shifter circuitry for non-negative output. Can someone help me? Thanks a lot.
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262 views

Turn ON/OFF 5V 2-5A by Raspberry Pi GPIO

I need to control few 5V 2-5A devices by rpi GPIOs, which has the 3.3V logic level. I come up with a simple circuit, but I'll appreciate any ideas, corrections, suggestions. The LOAD is something like ...
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0answers
1k views

VGS(off) for JFET in AGC circuit

I want to use a well known AGC circuit (see below) with 3.3V instead of 5V. The description of the circuit can be found here, and state the following about the JFET: Other JFETs with VGS(OFF) of 5V ...
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0answers
280 views

RXD line problem

Hi below is my setup block diagram to understand Setup description: I have two board , board 1 and board 2. Board 2 is third party board we purchase. Board 1 has on board SMPS which convert 230VAC to ...
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0answers
1k views

RTC DS1307 3.3V I2C and Oscilloscope impedance

I'm working on a library for STM32 to learn I2C protocol (Software I2C, not hardware). I connect my DS1307 (Sparkfun BOB-12708) : (Here is the module schematic) : I remove welding on the SJ2 jumper ...
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1answer
63 views

Raspberry Pi Pico 3.3V_EN pin control voltage inquiry

I am trying to turn on or off a Raspberry Pi Pico using a Raspberry Pi Model 3. The Raspberry Pi Pico seems to have a 3.3V_EN ping which is basically the 3.3V regulator enable pin (3V3_EN) pulled up ...
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1answer
49 views

How to choose a resistor value for Wheatstone bridge such that it is a balanced circuit?

I have a 3V sine wave input and I want to measure resistor precisely from 1 ohm to 40ohm. I have tried using Arduino to measure the resistor using voltage divider but it became obvious that I will not ...
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1answer
38 views

How can i turn a DPST button in to a DPDT?

How can i turn a DPST button in to a DPDT? I've replaced all the stock rocker switches in UTV, got all 14 of them done except for one all to Push Buttons. The push buttons are SPDT, "on/on" ...
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1answer
24 views

May I connect 3.6v Li-pol accumulator to 3.3v dc supply?

I have an old Bosch electric owen which has clock and timer on-board. The problem is: on each electricity fail (even milliseconds) this clock resets to the time edit mode and zummer starts to make ...
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0answers
41 views

Calculation of the resistors values in a voltage divider

I'm working on a circuit where a 3.3v flash memory, which comunicate with SPI protocol, has to be interfaced to an 8-bit PIC microcontroller working at 5v. For the MISO signal there should not be any ...
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2answers
177 views

STM32F411 Discovery Has to connect to an external 3.3V to power up?

I have an stm32f411E Discovery board and I'm working with it well. After I use it to work with an UART module suddenly it can't not power up anymore. I have to connect its 3.3V pin directly to ...
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1answer
103 views

Using ESP8266 to read digital input pin to be notified when motion is detected from 24VDC source device

Software developer here, trying to mess around with hardware (VERY NOVICE) and implement neat things around the house using ESP8266s and Arduinos. I have a commercial wall plug that is activated when ...
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1answer
78 views

Would this switching power supply work?

I'm trying to design an integrated power supply to use in IoT projects that I'm working on, some including microcontrollers like the ESP8266 or ESP32. In previous projects I've made, power supply ...
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0answers
98 views

What is the most sane way to switch between 5v and 3.3v on a PCB on the same lines?

I apologize for the blasphemy I may spit during this question, I am a newbie in electronics. That said, I want to design a PCB that will house an ESP8266, the chip I selected provides both 5v and 3....
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1answer
184 views

Low current RPi GPIO inverter

What is the lowest current way of inverting the output from a GPIO pin? I have a solar board that has an add-on that can turn a USB port power off if a LiPO gets below 3.3v. The problem is, they ...
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3answers
69 views

Limiting the current into Raspberry Pi GPIO pin

I have a dc dc regulator which can output .35A Current at 3.3V. I just need to check that the voltage it is producing is 3.3V by connecting it's output into one of the GPIO pins of Pi. So i was ...
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1answer
42 views

Combating voltage drop on low voltage distance sensor

I have a distance measuring sensor unit that I am having some issues with, its a Sharp GP2Y0D815Z0F Digital Distance Sensor (Datasheet) that takes a 2.7-6.2v DC input. When plugged directly into my 3....
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3answers
424 views

OpAmp VS Voltage Divider VS Buck Converter (Current Sensor Output)

I'm working on part of a project and I need to build the circuit that reads the current through a phase of a motor using this IC from Allegro. Assuming there will be no more than 5A, and using a VCC=...
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1answer
385 views

Connect 240v PIR motion detector to Raspberry Pi

I want to connect a 240V PIR motion detector directly to my Raspberry Pi 3. Inside its plastic case I found 2 PCBs. One is the power supply board which has a 24VDC relay, a S9013 NPN transistor, ...
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2answers
208 views

PMOS reverse polarized - 12v light

I've this circuit: simulate this circuit – Schematic created using CircuitLab I have a doubt, when I press the SW1 the LAMP1 turns on, when I press the SW2 the light turns on but the P channel ...