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Questions tagged [ttl]

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

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17 views

MAX232 Replacement

I have a circuit where a 12V square wave signal (a Profile Ignition Pickup signal from a Ford EDIS ignition module) was fed to an MCU via a MAX232 chip. My understanding of the MAX232 is that the ...
3
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1answer
58 views

Switch between USB and Bluetooth module TTL

In my project I have an MCU that I want to communicate with via 5V TTL serial. I have two methods of doing this in my circuit, USB via an FT232R (5V) and Bluetooth via an HC-05 module and level ...
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1answer
29 views

Pull down for 74HCTXX series logic ICs

I am building an adder with standard 74HC/HCT series logic ICs. I see the result when input pins are left floating are erroneous. Shall I have to connect some pull down resistors. Thank you.
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2answers
59 views

What specs does the “gros condo” (big capacitor) needs to have?

I have a pair of Dynaudio Air 20 at home. Unfortunately, the cable that used to control the speakers via RS232 died. I opened the cable, and saw that it was a customized RS-232 to TTL adapter, but ...
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0answers
42 views

Setting measurement points of the 74HC86 delay time

simulate this circuit – Schematic created using CircuitLab I'm measuring a propagation delay and transition delay of a 74HC86 chip. I setted somewhat high frequency square-wave signal(100kHz) ...
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2answers
68 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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1answer
40 views

Unpowered 74ls chips vs Powered Nano?

I have a power-hungry 74ls digital logic project that I want to connect a USB-connected Arduino Nano to, but I'm not sure how design the interface between them safely. The project has an external 5V ...
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2answers
101 views

Converting a variable frequency to TTL HIGH and LOW levels, based on a fixed (possible non-fixed?) frequency

I have a square output from an LM324 op-amp (0 and 5 volts) which has a frequency between 1 to 500 Hz (yes, low frequencies). I would like to find a simple way to have HIGH TTL signal when it is over ...
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1answer
69 views

Supplying TTL Signal via USB

I have two pieces of hardware I'd like to interface with via USB. The first are 2002 Series Actuated Valves and the second is a Mass-Flo Controller for regulating gas exchange. To my (admittedly ...
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4answers
101 views

TTL Logic for displaying large 7-segment values [closed]

For fun, I was trying to imagine how I might implement large values in 74 series logic (or any commonly available discrete logic from the 1970s). An example might be displaying prime numbers up to ...
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3answers
55 views

TTL square wave inverter adjustable duty cycle

I am an amateur and I don't have experience with logic circuits so please forgive me if this is very simple. I have a 5V TTL crystal oscillator (4-pin). I need to create a second square wave from it ...
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1answer
68 views

STM32F407 CMOS or TTL or HC

I wonder which logic technology is STM32F407 MCU based on.. CMOS or TTL or HC or LVT etc? Although its mentioned in the datasheet that the GPIO's are CMOS and TTL compliant. I am concerned about this ...
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3answers
146 views

Interfacing GPIO 3.3V to 74HC04 5V

Will it be safe if I connect STM32F407 GPIO outputs (Vdd=3.3V) to 74HC04 hex Inverter inputs (Vdd=5V)? What is the best recommended method to add an inverter at the output of STM32F407 MCU? edit: ...
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1answer
69 views

PL-2303TA TTL UART data corruption

For a lot of projects, I use a fairly common USB to serial dongle called "Prolific USB to Serial" which uses a PL-2303 TA chip to allow USB to 3V TTL serial (i.e. this kind on Alibaba). I actually ...
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5answers
102 views

Will this 555 circuit prevent a car from disconnecting power to the radio when starting?

To start with I'm a little rusty with electronics, I haven't done much in 20 years and it was only a hobby back then. In my car I have a head unit with a touch screen which relies on software to run ...
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2answers
91 views

Can a TTL LS device (low-power Schottky) serve as an input to a basic TTL device?

A 74121 (One-shot) worked well as a reset to a counter device. There is an enable line using a 7400 NAND gate to allow or disallow the trigger to pass. While duplicating the circuit, I found that all ...
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2answers
139 views

What is the point of 2 inverters in series? [duplicate]

In the datasheet for the Nexperia HEF4543B, in the logic diagram, there are 2 inverters in series: What is the point of these inverters in series?
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1answer
165 views

Can't type on Virtual Terminal Proteus

I've connected my SIM900a module with PC via a USB to TTL converter. I'm using Proteus Virtual Terminal for check the AT commands. The problem is I can't type anything on the Virtual Terminal. Copy ...
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0answers
64 views

Why can't I get the output of a 74LS221 to idle at 5 VDC?

I have an industrial machine with an encoder feeding a Measurement Computing USB-CTR08 counter board. In order for the board to count the pulses the counter's gate ...
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3answers
84 views

TTL IC logic high output doesn't reach high enough voltage

I've been having a problem trying to build a breadboard circuit. The problem being, that some IC high outputs doesn't reach a high enough voltage, staying around ~2V. That is not sufficient for a ...
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1answer
31 views

Initial noise prior to square pulse

I have a high voltage system (~5kV) to generate pulsed spark. I was able to detect the spark ignition. It has been shown in the images by the yellow line. This signal will be used to generate another ...
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2answers
84 views

Are there still programmable clock synthesizers with single ended TTL output leves (in 2019)?

I'm looking for a clock synthesizer IC that can drive my vintage 5V NMOS CPU in the range of 5 - 50MHz. The granularity would preferably be in the range of 100kHz or less. All I can find when ...
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1answer
36 views

Optical receiver output voltage higher than power supply

The part is a optical receiver from Broadcom. It has TTL output, but specified with a maximum output-high voltage higher than the power supply. I wonder what's special structure internal may make it ...
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1answer
78 views

Questions about RS422 driver

I am using a GPS receiver board which transmits a PPS signal into a TTL <-> RS422 board I need to design. The receiving end (of the RS422 signal) is 15-20 meters away. Here is my design: My ...
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0answers
52 views

Serial communication between raspberry and laptop not giving right values

I want to communicate between a Raspberry Pi 3 model B and a laptop using a USB to RS-232 cable and this RS-232 to 3.3V TTL converter via the serial module in Python: GND is connected to board pin #6 ...
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1answer
108 views

Change serial converter voltage from 5 V to 3.3 V using resistor

I have a USD-TTL converter which uses 5 V. Can I change the output voltage from 5 V to 3.3 V using a resistor? Product: https://www.amazon.com/Breakout-USB-TTL-Module-Lilypad-ATmega328/dp/B01LQYO1AI/...
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0answers
28 views

UART Current in PIC18F46K22 & 7404 Input Current

I am currently making a decision to invert the UART signal from my PIC18F46K22 and have 2 choices to either use 74LS04 and 74HC04 but there is a difference between the LS and HC that the LS can output ...
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5answers
126 views

RS485 IC Termination Resistor Configuration

I've made a mistake on a design, that went into production... It was built like the drawing on the left, with R702 to 5V and R703 to GND, it should have been backwards... like the drawing on the ...
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2answers
119 views

Power issues on TTL circuit

I am building a homebrew 8-bit computer on breadoards and PCBs with TTL logic IC's (LS, HCT and ALS families). This is a small portion of the circuit (3 modules): I'm using an ordinary phone charger ...
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1answer
69 views

TTL gate characteristics

In case of BJT for example, the input characteristics can be described with \$I_B=f(V_{BE})\$ and output characteristics with \$I_C=f(V_{CE})\$. How can the input and output characteristics be ...
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2answers
78 views

74AS TTL to CMOS pull up resistor and maximum speed (or lowest delay)

Hello I have to pilot a CMOS input 5V chip device with a 7474 flip flop with the lowest possible delay to minimize clock jitter. Signal is about 11.3 Mhz I have two options: 1) 74HC74 (CMOS ...
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1answer
202 views

Clock signal generator using 7400

I have an old PCB that uses this clock generator (means I'm absolutely sticking to the schema). The IC is standard 7400, resistors are the same, but the capacitors I'm using have 470 uF (500's are ...
1
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1answer
98 views

What is the purpose of the Load transistor in a TTL Logic NOT gate?

My professor presented the NOT gate in the Transistor-Transistor logic as the following: Where V is always 5Volts. The two symbols are MOSFETs N-type transistors. The first transistor (which is ...
-1
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1answer
660 views

Why do some Arduino-compatible boards provide a crystal for the CH340? [closed]

I have an uno-shaped Arduino compatible which uses the CH340(G) serial to ttl converter chip and it is connected to an external crystal. I also have nano shaped compatible which uses the CH340(C) ...
2
votes
1answer
286 views

What was the use-case for the 74hc590?

The 74hc590 http://www.ti.com/lit/ds/symlink/sn74hc590a.pdf is a binary counter followed by a register with a tri-state output. I thought about using it an a (homebrew cpu) design, as it's wider than ...
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1answer
112 views

Replacing CMOS SRAM with equivalent TTL SRAM

I want to replace an IS62WV51216BLL-55 (http://www.issi.com/WW/pdf/62WV51216ALL.pdf) with an AS7C4098A-12 (https://au.mouser.com/datasheet/2/12/as7c4098a_v1.2-1288279.pdf), as the latter has much ...
1
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3answers
353 views

True 5V CPLD other than PIC/Altera ATF150*?

Are there any True 5V CPLD's families still in manufacturing other than PIC/Atmel ATF150*? I am talking not just "5V tolerant IO", but rather ones with 5V VCCIO, able to drive 5V loads without ...
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0answers
124 views

Are pull-up resistors mandatory for inputs on modern parallel ports?

Here I go again testing more circuits on two computers with each reporting completely different data yet I feed the same data in. Now this time, the data coming back is all logic highs on my laptop ...
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1answer
161 views

TTL NAND logic circuit

how can find the maximum fan-out of the TTL-NAND gate using LTSpice ? i tried to solve problem by hand, but the problem how to find fan-out using ltspice
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3answers
557 views

How to find out whether serial standard is RS232 or TTL when stated as “serial(RS232/TTL)”

I am recently moving from C programming into automation engineering. I have learned about RS232 and TTL standards, and I understand that they are based on the same concept of serial communication, ...
7
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2answers
1k views

How to manufacture chip on board?

I am a developer of a cheap product and i have no experience in mass production. Device is fully functional and represents a single sided PCB, a microcontroller, a bunch of diodes and a few passive ...
1
vote
1answer
585 views

Can I covert a 3.3v/5v USB TTL Serial device to 1.8v using a LM1117 1.8v regulator?

I have a HDD which has serial access but needs 1.8v TTL serial. I only have 3.3/5v serial devices. The standard PL2303, A UART Usbbee, and a generic serial adapter. The PL2303 & generic have 3v/...
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2answers
1k views

What is difference between USB and TTL? [closed]

I have one question about USB and TTL. Both USB and TTL works on the same voltage range (0 to +5 V), both are serial protocols. From my point of view, they are the same. Why then we have USB to TTL ...
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1answer
93 views

5V to 3.3V Converter

I have a problem in connecting Raspberry PI to an MCP3202. I am using MCP3202 at 5V and knowing that raspberry pi works on 3.3v. I have found a solution to convert from 3.3V to 5V using 74HCT244. And ...
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0answers
26 views

CPT LCD display part number explanation

Does anyone know what the letters of Chunghwa Picture Tubes LCD mean in the part numbers for example 7" or 6.95" displays of a series all start with CLAA069LAXXX where XXX is a random assortment of ...
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1answer
199 views

What is the function of diode and capacitor in RS232 shifter circuit?

as shown in the picture, can anyone explain the capacitor and diode in detail? Thank you!
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1answer
142 views

Difference between MAX3430 and ADM483 for TTL-RS485 Converter

I want to use TTL-RS485 Circuit as in the attachment. The circuit is working when I use ADM483 Transceiver for U1. It can provide communication. However the circuit is not working when I use MAX3430 ...
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1answer
89 views

Using RXD to generate Audio signal and serial communication all connected to each other

I'm using RXD to transfer audio to an amplifier (1) and TTL communication with USB/TTL converter (2) for communication. Everything works but I can not get maximum output from the amplifier. When I ...
0
votes
2answers
124 views

HC-SR04 Distance Sensor Trigger Signal on 2.5V Voltage level gives no reading

I am using an Arduino on a breadboard setup with an ATMEGA328p MCU. The whole circuit is designed to work in a low-power state and is powered using a 3V (Nominal) voltage Coin Cell. The HC-SR04 is ...
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1answer
66 views

Driving a ThorLabs piezo controller with TTL external input

I am trying to drive a ThorLabs piezo controller (https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=2421&pn=KPZ101) with an external +3.3V TTL signal provided by a microcontroller (using ...