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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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486 views

Logic-level switching 12v

I implemented the following schematic trying to follow Jon Watte's reply to this question. There are two things I don't understand: Why is the probe Q14 showing 4.34 volts? Why is it not closer to ...
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1answer
2k views

What's wrong with my simulation for Bi-directional logic level converter?

I am trying to make a simulation by using Multisum 14 for i bi-directional channel for Logic level circuit from SparkFun which use Philips AN97055 IC as a Bi-directional level shifter... The ...
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1answer
285 views

Comparator with latch as trigger

I was hoping to use a Linear Comparator with a latch such as LT1016 as a trigger for the Register output clock for a 74HC590. The 74HC590 is going to be cascaded with it's RCO going to several more ...
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1answer
365 views

Do I need a level shifter with an open drain output

I'm currently doing a schematic that has an IC that operates at 3.3V (HDC1000 for those curious), and the rest of my digital operates at 1.8V. I have a level shifter for the I2C lines, but there is an ...
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2answers
332 views

-5/0 volt to 0/5 volt logic levels?

Does anyone know a good way to convert -5/0 volt logic to 0/5 volt? I'm using a chip as seen in the diagram below, but I'm not sure what to do about the inverted logic levels. Basically, I need to add ...
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2answers
314 views

Set multiplexer inputs to a logic 1 state

How can I set, in Orcad, all the entries of multiplexer(in the picture) (except: 1, 13), to logic state '1' (for example, I understand that if I place 'ground' to some entry, then it will be ...
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1answer
629 views

How to PWM-drive a N-channel non-logic level power MOSFET with a 3.3V signal?

Follow-up of Using IR21531 as a simple 1 channel gate driver After doing the above question (I'm very sorry, beacuse my question seems a XY one), I'll try to explain better what I believe that I want ...
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1answer
219 views

Using IR21531 as a simple 1 channel gate driver

I've bought the only gate driver I've found on the local hardware store (IR21531). I want to use it only to drive a IRF630 with a PWM 3.3V signal. How should I do the wiring? As you can see on the ...
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1answer
662 views

Power Path Controlling with GPIO and MOSFET

I'm not particularly well acquainted with MOSFET logic design and need some verification on a few things to make sure I've got them correct, and to see if there's any better ways of doing it. I need ...
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2answers
465 views

Where is the ground/earth used in the Sparkfun Logic Level Converter

I am studying the Sparkfun Logic Level converter and the basic aim of this is to understand how these BSS138 transistors are used in logic level conversion. I have used transistors before in driving ...
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3answers
893 views

Switch (Relatively) High Voltage from Logic Level

The Situation: Basically, I would like to switch a load that requires 30v using a switch that cannot have more than 5v across it. More descriptively, I am trying to drive the anode of a VFD segment ...
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1answer
215 views

uni directional logic level conversion with active drive current

I'm trying to connect an EM4095 to a cortex m0. The EM4095 requires an active high drive voltage of min 4V and has an internal pull down of 50K. Additionally it must be low during boot, otherwise it ...
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2answers
114 views

Why is Vtyp less than Vmin on a CMOS chip

Regarding the chip 74HC08 On the table describing Static Characteristics (Section 9). Why is the typical VIH lower than the minimum value. And vice versa for VIL
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1answer
116 views

Rotary Switches - 4 Positions, Two Outputs - How to determine the selected “mode”?

My apologies for not such a great description.. so I will clarify here. I have a rotary switch from an old aircraft panel that has 4 positions and two outputs. Using my voltmeter's resistance mode I ...
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2answers
557 views

Noisy Logic Level Converter for SD Card

I have designed a Arduino shield that is designed to be placed in the field and log data from a sensor which it then saves to an SD card. In order to log this data, I must convert 5v SPI to 3v3 of ...
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1answer
72 views

Low voltage PWM to logic level PWM

I have a sensor which constantly outputs serial data at very low voltages (in the milli-volt range), however I need to read this serial data using a PIC micro controller. How can i convert this data ...
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1answer
79 views

Do any flip-flops use separate clock levels for “sample” and “propagate” events

Many kinds of sequential logic require that the output of one register be fed into the input of another register which is strobed by the same clock. In such logic, it's necessary to ensure that a ...
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1answer
184 views

How does a bipolar transistor work on logical level?

When does a BJT conduct electricity and from where to where does it flow? I thought a BJT is off when the base is low and ...
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1answer
1k views

Driving MOSFET gate using PIC

I would like to drive a MOSFET gate using 12V (in order to reduce the drain-source resistance). Using the answer from a few post i've read I have come up with the following circuit. Will this circuit ...
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2answers
694 views

MOSFET driving MOSFET for reduced reduced Rds [duplicate]

I am using a PIC to drive the gate of a logic level MOSFET. Although the 5V logic output of the pic is sufficient to exceed the threshold voltage I would like to drive the gate using 12V to reduce the ...
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2answers
369 views

How does this logic level converter on the Adafruit HUZZAH work

I am busy with a project where I am connecting a 5V(Amtel ATMega328) MCU to an 3V(ESP8266) via the serial port. Obviously I need some logic levels converted. I looked at the schematics of several open-...
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3answers
111 views

CMOS Logic system

When I was practicing logic circuit design using PMOS and NMOS , It's said that we have to use all PMOS for Pull Up Network (PUN ) and NMOS for Pull Down Network (PDN). But we know that for input ...
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3answers
821 views

Ignore Pulses Less than a Given Width in a Pulse Train

Let's say I have a 5V pulse train that varies between 0 and 75000 pulses per second. Pulse width, let's say, is 5 microseconds. How could I calculate or determine the best way to filter out all pulses ...
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2answers
625 views

Is noise a problem when using a logic level shifter?

Good morning everyone, I'm building a device that uses several bidirectional logic level translators to interface 3.3V microcontroller to 5V, 2.5V and 1.8V sensors (via I2C lines). But I wonder if ...
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2answers
115 views

Measuring Switch State using PIC

What is the best way to measure the state of a latching switch using a micro controller? Keeping in mind the voltage level of the input to the switch is higher then the maximum voltage input to a MCU ...
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1answer
111 views

Where do voltage level limitations of logic level translators come from?

When browsing through available bidirectional level translator ICs, I always see the condition that reference voltage on one side of the translator must be strictly less than voltage on the other side....
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2answers
154 views

Overcoming the logic level translator limitations

Good morning everyone, I have a STM32F407 microcontroller running on 3.3V logic level, and I have a plethora of peripherals that I want to connect to it. The problem is that these peripherals run at ...
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2answers
257 views

Unexplained voltage drop in input clamping & buffering circuit

I'm designing a circuit consisting mainly of 74LS series logic. I am clamping and buffering several input signals using a zener diode and a 74HC7014 Schmitt trigger buffer. A relevant excerpt of the ...
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4answers
400 views

Can I use a line multiplexer as a level shifter as well?

I have 40 x 5V inputs that I want to read using 3V GPIO pins on the beaglebone black. I am planning on using 5 multiplexers (such as the 74HC151 or 74HC251) that will be sharing the 3 select lines. I'...
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2answers
320 views

For production boards, is a buffer IC best to translate single unidirectional 3.3v to 5v logic without inversion?

I've read plenty of advice on how to deal with 5v <-> 3v logic translation and there seems to be a ton of methods, some of which I'm clear on and some I'm not. Most of the material is geared ...
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2answers
3k views

Design Priority Encoder using only NAND and NOR Gates

I'm trying to build an 8-to-3 priority encoder using only nand and nor gates. Below is a 4-2 priority encoder, however it is using only ands, ors, and nots. If I have specific activation levels (some ...
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2answers
136 views

Why we don't see adjustable “High” and “Low” Voltages for discrete logic gates

For single, discrete logic gate chips, why is it that we don't have adjustable types? The closest we have are those that vary along with voltage supply. I suppose it uses a voltage reference in the ...
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2answers
1k views

Logic Level Converter only works reliably when multimeter attached

I have this logic level converter that only lets data flow when my multimeter is set to measure milliamps and the leads are placed across the high and low signal pins. On the low side I have an ...
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1answer
786 views

interfacing a Stratologger altimeter with an Arduino Uno

The Issue I am trying to interface a stratologger altimeter to my arduino uno and I'm unable to successfully read data being output by the altimeter. The Setup I have a stratologger altimeter, an ...
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2answers
3k views

Logic level conversion for servos

I'm trying to spy on the state of servo communications with a RC receiver and optionally change the output. Unfortunately my controller is 3.3v while the servo logic is ~5v. I'm trying to figure out ...
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1answer
575 views

Z80 control pins not reading a defined logic level

I'm having trouble getting my simple Z80 based project to work. I asked for help here last week, and received an excellent response on troubleshooting the Z80; here is the relevant part: There ...
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1answer
2k views

FTDI ft232rl 3.3V logic interfacing PIC microcontroller

I want to interface a ft232 with PIC16F73. I am using the circuit below: VCCIO is connected with VCC which is 5V. Then I think all logics from TXD,RXD will be 5V, isn't it? If I connect VCCIO with ...
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1answer
115 views

Measuring if a transistor can work for SPI/UART when doing logic level conversion

I need to convert 3v3 to 5V and 5V to 3v3 for SPI/UART. I found many options. But I'm still confuse whats good for me. Because Transistors and few other components has rise and fall time. I want to ...
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1answer
115 views

Enable connected to unpowered regulator on another board

I have an ARM board which uses a VIO of 1.8V and requires that no i/o line be driven before it is fully powered up. It signals this readiness by asserting its "SYSEN" line. My design has SYSEN from ...
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3answers
2k views

how to increase the voltage of a digital signal?

I'd like my Raspberry Pi GPIO port to communicate with a digital circuit that works at 2x the GPIO voltage. The communication will be at a relatively high frequency (up to 500kHz). The main question ...
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1answer
939 views

Combining CMOS and TTL logic

I have a bunch of 74LS383 (TTL octal transparent latch with three-state outputs) and MM74C83N (CMOS 4-bit binary full adder) that I would like to connect together. I need to connect the output of the ...
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1answer
2k views

Voltage shift from 3.3V to 12V

I'd like to use MX-FS-03V 433MHz transmitter together with a Raspberry Pi (RPi). The Raspberry Pi's outputs have 3.3V, but the MX-FS-03V operates on 3.5-12V (the higher the voltage the higher the ...
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3answers
190 views

Bi-directional logic level conversion

I'm trying to design an accelerated CPU (65816) for the Apple IIGS by using a high speed ARM processor combined with a software emulator + software emulated cache. The CPU I'm using is the LPC4300 ...
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1answer
3k views

Convert 5V to 3.3V without logic level converter

I've got a 2.2 SPI monitor (QVGA TFT monitor & SD Card), but I am using Arduino UNO board. All pins are 5V. How can I use a resistor to communicate between TFT, SD and UNO? I have lots of ...
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3answers
1k views

Logic level shifting from 5v to 2.8v and vice versa

I need to use a logic level shifter in my circuit which translates 2.8V logic level into 5V and the other way round. I found this document. The device itself is presented on the page 10. It is very ...
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2answers
445 views

why emitter is connected to high level and collector to low level?

generally, in all switching circuit, emitter is connected to ground and collector is connected to high level. i am not getting why is it so? is there any special purpose?
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1answer
627 views

LSM9DS0's Accelerometer not reading correctly

I have a LSM9DS0 Gyroscope/Accelerometer/Magnetometer breakout board. I am using an Arduino Uno which operates on 5V. The LSM9DS0 is communicating to the Uno using I2C through a Logic Level Converter. ...
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1answer
209 views

Why is the MISO not level shifted in this circuit?

I am looking at SparkFun's CC3000 breakout board schematic. CC3300 is TI's wireless module. The CC3000 operates on 3v3. And because the breakout board is intended to be used with an Arduino (which has ...
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2answers
1k views

What is the usage of this resistor?

I'm thinking about this part of this board : As you can see, there is a resistor in the red rectangle (R26). my question is what is the usage of this resistor? Well being a resistor for D14(CANRX) ...
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4answers
5k views

High Frequency Logic Level Conversion

I am using Arduino DUE for my project which gives a 3.3 volt output signal. I have to convert it to 5 volts to use it with another device. The problem is that my signal frequency is 1 MHz. I have ...