Questions tagged [ttl]

Transistor Transistor Logic. Logic circuits built from bipolar transistors and resistors.

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Peak/envelope detector circuit for 30 MHz sine pulses with a 10 kHz PRF

My goal is to input 30MHz sine pulses, with a pulse width of 10us and gap of 90us between the pulses. The circuit should convert this pulse train to a TTL signal that goes from 0 to 5 volts. To ...
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MAX3232: Switch between RS-232 and TTL levels

Sorry in advance, electronics noob here! I need to make a proof of concept to get some data out of third party system which handles both RS232 and TTL levels. The computer/raspberry/arduino shall - I ...
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74HC74D initial output value after power up

I use a touch sensor (Active Low) to light up a light bulb. here I've used a 74HC74D D flip flop to turn on an off the bulb with the sensor pulse (sensor output is active low which is then converted ...
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Can I repair CY62256 with UT62256

The CY62256-55PC(SRAM) in my old computer is broken and I need a replacement for it but I can't find the same chip. The only one similar enough in my local store is UT62256CPC-70LL, HM62256ALP-12 and ...
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Changing voltage level from an incremental encoder from 5V to 3.3V for my Raspberry PI Pico ADC pin

Edited I want to read data from my DC machine through a Sendix 5000 (encoder datasheet) incremental encoder with a Rasberry Pi Pico. Optical encoder with RS422 output and 5VDC supply. The HIGH ...
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6 answers
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Reduce 3.3 V-8.4 V signal to 3.3 V input

I have a digital input signal which can use anywhere between 3.3 V and 8.4 V to signal "1", and I need to make this safe for a 3.3 V input on a microcontroller (RP2040). I currently have a ...
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What is the shortest pulse a controller can count?

I want to count short LVTTL pulses (about 20-25 nanosecond.) Right now, I use an Arduino with four IN74AC161N binary counters, but this solution has some Arduino limitations. I count pulses, send the ...
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Equivalent of multiple emitter transistor using regular one emitter NPN BJT transistor

I want make a simple NAND gate using transistors with transistor-transistor-logic aka (TTL). I saw on tge Internet (Wikipedia) that it requires two emitters as inputs. Source: https://id.m.wikipedia....
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7 votes
3 answers
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Tying open-collector outputs to TTL inputs

I know that open collector outputs are effectively either 0 V or high-Z. I also know that TTL chips tend to read a disconnected output as high, but that really you should have something like a 1 kΩ ...
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Why does the TTL NAND gate use a 4 transistor design instead of 2?

Why does the TTL NAND gate use 4 BJTs to make the gate when it could be done using only 2? I assume that the design with the 4 transistors amplifies the current so multiple levels of gates can be ...
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Fan-Out Calculation on LTSpice

I need to find the fan-out of the circuit below. This is a Schmitt Trigger TTL NAND Gate. How can I exactly find the fan-out of the given circuit using LTSpice or calculate it theoretically?
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I'm designing a 4-bit GPU and I need some suggestion about the RAM for it [closed]

I'm working a 4-bit GPU, the GPU run on 1.023MHz (1023kHz) clock while CPU only run on 127kHz so I need a screen buffer for it when the CPU is working on some instruction. The display I use is a 24 x ...
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3 answers
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TTL voltage drop

I recently bought a lot of TTL components like 8-bit registers, bus transceivers, etc. to build an ALU and 2 registers. My issue is that when I build a register, the voltage drops to 4.2, sometimes ...
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How can I find reverse current of 74lsXX integrated circuit

I'm using 74lsXX ICs for my 4-bit computer. I noticed that 74XX ICs have reverse current at the input; I know that the output of the IC allow the reverse input current flow back to it. But I'm a bit ...
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1 answer
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Can MAX485 TTL-to-RS-485 module be used as UART-to-RS485 module?

I'm trying to make a bridge from Modbus til Home Assistant using an ESP8266 (as outlined here), which uses an UART-to-RS485 module. I have this MAX485 TTL to RS-485 Interface Module. I'm not competent ...
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I have a JK flip-flop circuit that works in simulation, but not with real components on a solderless breadboard

I'm building a control mechanism for a seat heater in my car. Eventually, it will drive power relays to control the current to the heating elements. It works in a simulation on simulator.io, but it ...
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3 answers
260 views

How do you make a three input NOR Gate function as two input NOR Gate?

Hi this is my first question! So I'm clearly a beginner in electronics and studied for months, now the topic I've studying is logic gates and boolean algebra also the TTL ic. I've been curious if how ...
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2 votes
2 answers
573 views

Logic level converter from 29V to 5V schematic

Does it looks a good schematic to do a proper 29 V to 5 V logic level conversion, any improvements or suggestions?
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3 answers
132 views

Connecting a GPS to computer: Jackson Lab LC_XO serial TTL to RS232 port on computer motherboard

I am trying to hook up my Jackson Labs' LC_XO GPS disciplined oscillator (GPSDO) to my computer motherboard COM/serial port so I can talk to it and for it to send back NMEA messages. Basically, I am ...
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1 answer
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How to connect RS232 level shifter?

I'm trying to use this: https://www.sparkfun.com/products/449 to connect my RPi to my computer via a USB to serial device. (And eventually connect the RPi to other legacy serial devices) My questions: ...
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SIM800L V2 not responding to AT Commands from Putty over USB-To-TTL PL2303

My SIM800L V2 RoHS (the blue one) although it connects to the network and registers just fine, it's not responding to AT commands sent over the PL2303 (USB-STC-ISP) USB-To-TTL Adapter through which it'...
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2 votes
1 answer
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Is there a problem with a resistor inline between two TTL gates?

I want to adapt the output of a board to drive additional logic instead of an LED. The driver board has a current limiting resistor before the signal is routed to the connector. Is there any problem ...
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5 votes
3 answers
911 views

Why am I seeing -5 V or lower on the output pins reading an Intel 1702A EPROM?

I am building a breadboard/Arduino reader to dump the data on a very old Intel 1702A EPROM chip. (data sheet) When doing some basic testing by tying all the address pins to ground, I am seeing ...
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Trigger TTL input signal with a micro switch

I used to have a machine where an action could be triggered on a pontential free contact with a simple micro switch (that worked pretty easy and well for me). That machine got replaced and the new ...
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2 answers
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Convert PWM to TTL signal via IC or circuit

I'm fairly new to TTL logic. I have a PWM output 0-3.3V that I need to convert to a TTL 5V logic as the sensor only accepts a TTL signal. Is there an IC that would do this or a circuit I can build?
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SN75176 with 3.3V

Can I connect the SN75176 RS485 transceiver with a 3.3V microcontroller? The datasheet says that it must be powered with 5V and all inputs / outputs are TTL, but I'm not sure since the minimum high ...
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1 vote
1 answer
121 views

Why does the 74LS32N behave like an AND gate?

First of all I am a beginner. I am practicing with the 74LS32N (OR Gate) IC , I noticed that it behaves like an AND gate instead of an OR Gate. Only when both the inputs are 1 , the output is 1 , (Led ...
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8-channel/octal equivalent of 74HC125

I have a 12v powered 16-channel relay board, that required 5v logic level signals to control the relays. However, I am using a Raspberry Pi to control this, which has 3.3v logic level outputs. I have ...
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115 views

74HC08N doesn't latch [closed]

I am using the 74HC08N chip. Why doesn't the first AND gate latch itself? I have connected the output of the first AND gate to its own input. I have used two resistors, the one on top is a pull-up and ...
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What is "level of saturation" for transistors?

This is a term I've never heard of, and it's presented on a work analysis of a ttl nor circuit. It basically says that the transistor that links the output with the ground should have a higher "...
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2 answers
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What is the function of the latch pin on my 74HC595 IC?

I am using this code with a 74HC595 IC to control a 4 digit 7-segment: ...
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1 vote
2 answers
557 views

How do I step down a 12V pulse width modulation signal to 5V?

I want to control my new laser module from my repurposed 3D printer. The laser module has a 12V pin for power, a ground pin and a 5V PWM pin. My board's fan-control port can generate a 12V PWM signal, ...
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3 votes
0 answers
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Fan out of TTL Circuit

In this image When calculating the fan out of the TTL circuit the current in the TTL drive output is 16mA and is divided into the emitters of the load each emitter has 1.6mA because the fan out is 10. ...
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1 vote
1 answer
87 views

Delay TTL signal from board power supply

To preface, I don't come from an EE background so I'm sorry if this question is extremely simplistic. I have a shutter controller board that allows me to open and close a shutter (optical iris) with a ...
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1 answer
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"TTL OUT" on PCB

I was wondering what this TTL OUT means and what type of cable it takes. I think it might take a display or a camera but unsure.
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1 vote
1 answer
345 views

What is the output logic levels of this STM32?

I am struggling getting my head around the input and output logic levels, mostly the output levels of this STM32 (STM32F446xC/E). This table shows the output logic levels as dependent on if it is a ...
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1 answer
71 views

Optical pulse sensor not producing a clean TTL pulse

I have two of these optical pulse sensors monitoring LEDs on my electric and solar meters - Optical Pulse Sensor - Github The first sensor outputs nice TTL pulses at 5V, the second sensor outputs ...
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4 votes
2 answers
163 views

TTL NOR Gate analysis

I'm looking at the design below. I am reading this webpage where the picture came from. What I'm aiming at is the wisdom behind the design. Looking at the two transistors facing downward, I assume ...
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74f269 counter getting very hot

Hi I'm a DIY enthusiast and I got stuck with the circuit that I designed. The counter is getting very hot from the moment It's powered up. In my setup the 330Ohm resistors at the outputs are ...
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Modbus acquisition timings

Part 1 What is the standard timing method for bits acquisition for a receiver using Modbus RTU? For example, for UART: "Communicating UARTs have no shared timing system apart from the ...
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1 answer
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Design a relay driver from TTL input with common parts

I would like to drive a pneumatic relay from a TTL GPIO source, the TTL may be 0-3.3v or 0-5v I would like supply and cut 12v to the relay to control the air. I have a concept of what i'm trying to do ...
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1 answer
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Is powering the Nuvoton N76E003 with just the UART0 pins legitimate?

I bought an 8 channel USB/UART controlled relay board from banggood.com: https://www.banggood.com/2-in-1-DC-5V-8Channel-USB-Serial-Port-Relay-Module-UART-RS232-TTL-Switch-Board-CH340-for-Windows-Linux-...
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6 votes
4 answers
2k views

What is the methodology behind 555 timer design?

Small circuits in TTL and RTL we could do intuitively, without any methodology. But what about a complex circuit like 555 timer? If it was designed using logic gates, it could be easily deduced by ...
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1 answer
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Combining CMOS and TTL with drivers and Leds with relay driver

I need some practical advice on how to combine different component types. I designed a circuit with at the heart an up/down counter (74f269) The outputs of the counter are connect to via 330 ohm ...
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DC>DC Isolated Converter (ADuM5401)

I'm in a bit of a quandary as to if I've approached something the right way or if there's an obvious solution I'm missing. (Sorry for lack of schematic, still WIP). Goal: Self-powered isolated USB >...
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1 answer
77 views

TTL to USB (CP2102)(Driving 5V USB)

I have a USB to TTL Adapter. The Adapter uses the CP2102. I noticed that the CP2102 seems to derive it's power from the USB V+. My problem is that I need to supply power to the USB. The reason is that ...
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1 answer
42 views

Is there an IC that works like the PL2303 for TTL TO USB? [closed]

Is there an IC that works like the PL2303 for TTL TO USB and can connect to android device with driver? I have search a lot but I did not find such a thing.
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1 vote
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74LS47/74LS247 BI/RBO-pin usage

I am currently playing around with a 74LS247 BCD to 7 segment decoder. The basic usage for decoding works perfectly fine. But I would like to test out everything this IC has to offer including the ...
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1 vote
0 answers
74 views

Connecting RS232 GPS Board to Raspberry Pi

I purchased a NEO-6M GPS board to connect to my Raspberry Pi, and when I bought it I didn't realize that it was meant for RS-232 communication instead of UART TTL (which I believe is what the ...
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1 answer
289 views

CMOS vs TTL power and impedance

I need to compare and contrast a CMOS IC with a TTL IC. I've chosen a quad 2 input NAND gate IC, 7400 for the ttl version and 4011 for the CMOS. I'm having a bit of trouble with 2 of the requirements. ...
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