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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How to make a parallel connection between two components when each has its own voltage?

I have a problem to determine whether or not it is safe to make a connection as picture below. Currently I have a H7EC counter connected to a switch and it has 2.7 V across terminal 1 & 2 on the ...
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48 views

Attiny13 affects USBtiny programmer logic voltage levels

I wanted to port a simple program from an Attiny85 to the cheaper Attiny13. To make sure everything would work properly I started trying to upload a simple blink program to the MCU but could not get ...
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48 views

Using a Non-Inverting Buffer for Level Shifting

I've got a project that involves a 5V Arduino and a Raspberry Pi Zero (3.3V) that need to communicate through a serial interface. The easy solution here would be to connect them through USB, but I'll ...
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Correct MOSFET for logic level switching

I'm looking to switch a 12 volt 0.5A and 2A load using the raspberry pi's 3.3v GPIO pins. From what I've read a MOSFET is the best fit for this application but I'd like to avoid wasting energy as heat ...
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77 views

Is there a component/method that can take any signal, then increase it to 5 volts no matter how small the signal is?

I was using a logic level MOSFET that should turn on when a voltage other than 0 volts between two points is detected. My problem is that the voltage is at times less than 5 volts and probably won't ...
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How to do serial communication between 3.3V and 5V devices using THT components?

I know that there are many questions dealing with logic level conversion/shifting between 3.3V and 5V devices, but my goal is to do do this with standard breadboard parts, so either discrete parts or ...
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32 views

Compatibility of devices with different voltage thresholds/noise margins/static disciplines

tl;dr included at the bottom. Suppose we have two logical buffers from different logic families, where buffer A drives buffer B. Buffer A has the following voltage thresholds: \$V_{OH}=8\ V\$, \$V_{...
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28 views

NPN BJT NOR gate to drive LED. Base resistance problem

Here's a circuit I'm trying to get working : I have two digital signals (B and C in the diagram) coming from a CD40174 flipflop. I use these to light up two LED's. I also use these as the input for ...
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16 views

Why a CPLD input pin behaves almost like an output pin?

I want my CPLD (a MAX II CPLD, EPM240, see datasheet) to accept an S/PDIF input using an optical receiver with TTL-compatible output. I tested the receiver alone: when giving proper power and optical ...
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2answers
44 views

What happens when both sides of a bi-directional MOSFET logic level shifter try to drive it and how to make sure terrible things don't happen?

I understand the principle of operation of a simple MOSFET logic level shifter like the one described in this question. However, the answer to that question only states what happens when we apply ...
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Would this circuit interface be a safe interface between full duplex and half-duplex UARTs of different logic levels? [duplicate]

I'm primarily a SW developer who dabbles with electronics. I needs to interface my SoC's HW full-duplex UART with an SDI-12 compliant sensor, without burning either of them and hopefully without ...
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Logic Level MOSFET Behaving Unexpectedly Driving PWM Signal to PSU

I am trying to control a MeanWell dimmable PSU with an Arduino. Since I do not want to exceed 60% of the output of the MeanWell, I want to use a 0 to 6V PWM signal. I figured a quick and dirty way to ...
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1answer
38 views

Connect to LIN bus with logic level shifter as transceiver

Is it good idea to connect my microcontroller to LIN bus with logic level shifter (5 <=> 12 V) instead of factory LIN transceiver (MCP2003, TJA1020, etc.)? As I understand, LIN transceiver just ...
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63 views

logic input that can handle a higher voltage but output a low voltage?

I think some logic IC input can handle a range of lower voltage levels but will output at supply voltage... What is the best way to achieve an input that can handle higher levels but output at a ...
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CPLD High-Z pin - safe to drive over the high logic level voltage?

I have a CPLD connected to a BUS and an EEPROM. The bus has 3v logic and is 5v tolerant. The CPLD is 3v only. If I configure the CPLD pin to be in the high-z state and the eeprom drives that pin to ...
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74 views

Logic Level Converter for Negative Voltages

Here is logic level converter mostly used for converting signals between 3.3V and 5V. (Other positive levels such as 1.8V are also possible). What if I want to convert from 3.3V to -5V logic (negative!...
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67 views

which kind of design of level shifter suitable for high frequency data transfeing in range of 1MHz? [closed]

A circuit needed to convert 3.3V and 5V logical voltage. However, the issue was that the circuit was supposed to handle very high data transfer at or above 1 MHz and up to 16MHz. I thought of ...
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66 views

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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52 views

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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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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81 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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52 views

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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927 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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37 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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234 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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1answer
25 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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1answer
102 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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61 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
234 views

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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46 views

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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44 views

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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1answer
123 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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2answers
55 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
181 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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1answer
110 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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2answers
52 views

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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184 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
111 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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1answer
83 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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77 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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195 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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76 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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48 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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46 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
76 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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208 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
139 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
192 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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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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