Questions tagged [logic-level]

Logic level refers to the output voltage levels of digital logic, which is often 3.3 V or 5 V.

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Usage of 74LVC1T45 in open-drain case

I want to do one 'universal' or 'multiprotocol'-capable IO block and currently thinking of using 74LVC1T45 level translator to do the communication between two different voltage leveled systems. I ...
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3.3v input in a 1.8v logic question

In a board design there's a mistake in the voltage level to control a reset pin (Signal RESETB). It should be 1.8v but it is driven by a 3.3v level. The datasheet shows the next info: It looks like ...
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9answers
11k views

Logic-level transistor not switching

I am trying to use a transistor to drive a lamp from a Raspberry Pi (3B+) and I went after one that can be switched by the 3.3V logic. I found the FQP50N06L to have a max Vgs threshold of 2.5V, so it ...
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39 views

~150 WS2812b LED's with Pi Zero and SN74AHCT125N

I'm planning to control about 150 WS2812b LEDs with my Pi Zero and a 5v 11a power source (PC molex connector). Following this guide: https://www.thegeekpub.com/15990/wiring-ws2812b-addressable-leds-to-...
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Capacitor to discharge upon switch open

Update Please evaluate this third attempt: This is my first electrical project, so please be gentle with me. I know very little about electronics. I'm building a machine that has a crank that users ...
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4answers
769 views

Driving a 74HC245 in one direction with 3.3V when Vcc is 5V

I have a 5V device that accepts parallel data in. That data is buffered by a 74HC245 IC (TI datasheet, NXP datasheet) where the Dir pin is hard wired to drive in ...
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35 views

Single chip level shifter from LVCMOS to 12 V

I'm working on a nixie clock based on a STM32L476RG microcontroller and HV5530 chips. The microcontroller uses 3.3 V logic while the HV5530 really needs 12 V logic, which is a pain to implement. There ...
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2answers
90 views

Raspberry Pi with 74HC14 connecting to LED strip (WS2812B)

This might be a stupid question, but I can't seem to figure out how to convert 3.3V to 5V with the 74HC14. I have a power source which can supply 5V (see the power adapter at the left), and use it to ...
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23 views

Output voltage of AT28C64B into HC CMOS IC

I am trying to load the output of a AT28C64B parallel EEPROM into a 74HC194 shift register. The datasheet for the AT28C64B states that the minimum high level output is 2.4V, which I believe is not ...
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59 views

Switching 12v pilot with 3.3v logic

I have an entry gate pilot operating on 12v. I would like to connect it to my esp8266 (3.3v) to control it over the WiFi. I would like to use 12v power line which I already have. The components which ...
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55 views

Stepping Down Logic Level of a Differential Signal

simulate this circuit – Schematic created using CircuitLab Suppose I have a unipolar, differential 24V signal, and I want to step it down for use with a 5V differential receiver (such as RS-422)...
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3answers
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N-Channel Mosfet or NPN transistor for Low Power PWM Application

simulate this circuit – Schematic created using CircuitLab LED: 2.05V @ 350mA 5-6 Ohm Resistor for current regulation Hi, currently designing a circuit that controls a LED using a PWM logic ...
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Significant noise observed on channels of TXB0108

We're working with a ADC chip test setup that uses the TXDB0108 to step up 1.8V data lines to 2.5V that are connected to Kintex7 FPGA. The pin-out is as follows: VCCA is 1.8V, while VCCB is on a 2....
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How to convert a +/-12 V digital signal to 0/+5 V?

What would be a simple way to convert RS-232 +/-12 V digital levels into +5/0 V respectively? I considered an optocouple, but I can't find one that can withstand -12 V reverse voltage. I considered ...
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62 views

P channel mosfet as a switch on logic level

I'm quite confused about the p channel mosfet as a switch. I saw designs with zener diodes, other mosfets or BJTs but these seem overcomplicated. I have many P channel mosfets from broken chargers (...
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51 views

Voltage controlled connection of two signals that are at higher voltage than the control voltage

Given are two signals A and B. I want to control the connection between them by a signal C. However, signal C is a logic signal with a voltage of 3.3V for high and 0V for low whereas signals A and B ...
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1answer
109 views

Logic level converter for NodeMCU (ESP8266): Input 24V/16V (Hi/Lo), 500 Baud

I want to use a digital input pin of a NodeMCU board (ESP8266) to read a digital signal. The signal line idles at 24V DC. The logic levels are 24V and 16V. The signal speed is 500 Baud (each signal ...
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81 views

TTL to NIM logic translation Logic Gate Issue

NIM is a standard used in nuclear physics. I'm facing an issue with a logic gate being used in my TTL to NIM translation circuit, and I'm not sure what is entirely wrong with it. For a little ...
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SR Latch internal conflicts

it is known that "11" are invalid inputs for a SR Latch. But I do not understand the reason of that. I cannot see the electrical conflict in this structure: If R = 1, its NOR gate will give 0, for ...
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1answer
109 views

Can a 74AHCT IC be a drop-in replacement for 74HCT IC

I have a circuit in which I interface a radio module running on 3.3V indirectly from a 5V supply. I use a regulator to provide the 3.3V module VCC and the data is exchanged between both circuits ...
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1answer
104 views

Will using a microSD card reader with STM32 produce logical errors? [closed]

I have a microSD card reader which needs \$5\,\mathrm{V}\$ to operate. I am interfacing it with STM32 MCU operating at \$3.3\,\mathrm{V}\$. Will it operate normally when I provide only \$3.3\,\mathrm{...
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78 views

PWM logic level issue

I am facing new problems everyday at embedded system. I have designed D-SMPS and put an stm32f103 to drive mosfets.I have tested micro controller and it works well while giving outputs as GPIO.It is ...
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1answer
73 views

Would this MOSFET be suitable for use with an Arduino?

I'm looking for a MOSFET which can be controlled by an Arduino at 5V, and which can switch power on/off to a Raspberry Pi and peripherals (also 5V) that will peak around 3A of current. It's a battery-...
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98 views

Logic Level MOSFET IRLZ44N - under Wemos mini

I used IRLZ44N with Arduino Nano in order to dimm a 12v LED strip. When tried to use it with Wemos Mini - I get only 7.6v max ( when controlling a 12v source ). Probing the output pin (...
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72 views

In logic levels, why are the driver and receiver depicted as inverters?

In Digital Design and Computer Architecture (Harris and Harris), the following schematic is given , in discussing logic levels. Why are the driver and receiver depicted as inverters?
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STM32F4 and SIM800L logic level

I am currently using an STM32F401RE that I have to interface with a SIM800L GSM module via UART. In a first "toy example" I used Arduino and found no problems, but passing to the STM MCU I am unable ...
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1answer
44 views

Voh value not provided

I have this EEPROM IC where I want to check the logic level compatibility with another IC. But here Voh value is not given. I have observed this in my other IC also. Why is the Voh value not provided?...
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42 views

SPI pins logic level issue [closed]

I have ESP32 and the popular dot matrix module MAX7219 8*8 module to interface. It is connected through SPI pins. After a sample word printing on the maxtix it shows garbage outputs. Is it happening ...
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1answer
62 views

What is the purpose of Vih and Vil in the comparator's datasheet?

Looking into the MAX999 datasheet I can not figure out how to utilize information given for the Vih and Vil ...
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1answer
161 views

Do high and low side labels on bidirectional logic level converters matter?

Logic level converters like this one from Sparkfun have high side and low side labels on them. Now i have an application where I think I need to shift logic levels but the high side and the low side ...
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1answer
97 views

CAN Rx Line between STM32 and MCP2561

I discover a problem on my design, with a STM32F042K6 MCU and a MCP2561 Can Transceiver. I can send some frames on the CAN Bus but i can't receive any frames. When i put my scope probe on the CAN Rx ...
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3answers
163 views

5V digital output to 24V

I need to come up with something to convert a 5V digital output signal from a USB-1608G DAQ device with DIO to 24V digital output signal to reset the timer on a watchdog. The watchdog timer will only ...
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117 views

PX4FLOW (Optical Flow sensor) - Powering with 5v. Does it work with OmniNXTF7 I2C SCL/SDA at 3.3v?

I want to use PX4FLOW with OmniNXTF7 flight controller. This flight controller has 3.3v I2C SCL/SDA and no PullUp-resistors. I use the PX4FLOW only with I2C port, with 5v at VCC (not 3.3v). Does ...
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1answer
42 views

How to passively shift logic levels to drive LEDs

I have an input signal that is either 2.7V (low) or 9.9V (high). Is there any way to use passive components (excluding op-amps) to turn an LED off when the signal is low and on when the signal is high?...
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80 views

Switch from 5v to 24v - 150kHz - 20mA

I'm looking for a way to amplify a signal from 5v -> 24v. This signal is a PWM with a frequency of 150kHz. Amplified signal will have a fixed load of 20mA to power a LED with a Vf of 1.25v. I've ...
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2answers
164 views

Using Mosfet with seperate Logic Converter and Arduino

I am trying to use an IRLB3034 with an Arduino even though it is not a logic level MOSFET. I am planning on using an LM2937 12v regulator like the schematic below: The connection going off the page ...
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1answer
62 views

The simplest “adaptive” downward level shift solution?

I want to build a level shifter circuit for the RX pin of my ESP-12S. The goal is to convert any level between 3.3V and 5V to 3.3V as I might use many USB to UART breakout boards with different output ...
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1answer
60 views

Serial Communication Between Android and Attiny85

I am planning to build a sensor module for smartphone using Attiny 85 as its microcontroller. The sensor module will have a USB type A and to connect to the smartphone, OTG is required. Serial ...
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25 views

Logic leves and protocol, interfacing HP39GS to arduino Wemos D1

Im trying to connect HP39GS scientific calculator to Wemos D1 arduino. It has TTL RS-232 serial port. Pinout is somewhat: Vcc, TX, RX, GND. Looks like HP39GS protocol for serial port is not pure RS-...
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2answers
64 views

Preventing overvoltage on serial pin

I am trying to send data through serial from a 3.3v Arduino to a 5v Arduino. I assume I can't just connect the 3.3v tx to the 5v rx because, when I program the 5v one I am assuming it will send 5v ...
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2answers
192 views

NPN: Not fully sinking to GND

I'm using an NPN to pull a 12v (5mA) signal low from an MCU (logic level). My problem is that when I pull the 12v line low, 7.4v are still present at the 12v side of the line using the circuit below: ...
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0answers
51 views

How do I wire a Rasberry Pi 3B+ to a WS2812b RGB strip?

I am working on a project where I need to use a WS2812b RGB strip. I am really worried because I have already burnt 2 Raspberry Pis with my wiring. I just want to show my schematics, and be assured as ...
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1answer
72 views

Driving 12v logic from an MCU

I'm looking to drive 12v logic signals (logic level shift) from a PIC24FJ MCU, which can do 3.3v and 5v logic. In one instance, I need to switch a 12v line to LOW, and in an other, I need to provide a ...
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118 views

Component recognition from marking code

I need help to recognize a dead component from a lab instrument control board. It is part of a TTL-serial interface, arguably a logic gate or some level shifter, in a TSSOP-14 package. You can see ...
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40 views

3v3 VLogic for DG212

I am curious if anyone knows if a Vishay DG212 works with VLogic being powered by 3v3? The only test conditions the datasheet speaks of are where VL is being powered by 5v. Here is the datasheet: ...
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2answers
57 views

High level present in a pin of a non-powered IC can damage it?

I'm using a TXS0108E to convert from 5V to 3.3V and vice versa. The schematic is below: In the datasheet, in section 6, I read the following: Voltage applied to any output in the high-impedance or ...
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1answer
120 views

How to explain and possibly avoid undervoltage on I2C bus?

I've been testing different sensors for the I²C bus with two host devices: Raspberry Pi 3B (3.3V), and Sitec S4 (5.0V). Since one of them, namely the Sensirion SCD30, had communication problems every ...
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2answers
108 views

Help needed in understanding MOSFET datasheet

I am trying to find a logic level MOSFET for 3.3V operation. In my case, I am trying to compare AOD510 & AO4402. AOD510: \$\mathrm{R_{DS(on)}}\$ @ 4.5 \$\mathrm{V_{GS}}\$ = 0.004 ohm but has no ...
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1answer
100 views

Logic level translations

Have you ever had any experience with an ADG3304 IC? I've prepared a circuit which allows to translate logic levels in SPI interface. I want my circuit to be compatible with both 1.8V and 3.3V logic ...
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115 views

Logic levels on tri-state buffer,

i am working on some CPLD-controlled SPI devices that will be daisy-chained together. I will be using 74VHCT126AFTTR tri-state buffers to disconnect the SPI and Slave Select lines on the device from ...

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