Questions tagged [ttl]

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

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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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0answers
37 views

Connectivity issue with USB to TTL [closed]

This USB to DDL converter sometimes can transfer a signal but sometimes can't. What's the possible issue here?
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1answer
53 views

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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0answers
48 views

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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1answer
37 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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1answer
37 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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0answers
28 views

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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0answers
46 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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1answer
66 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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2answers
42 views

Switching characteristics in terms of TTL flip flops

I am a complete novice when it comes to electrical things. Fine at digital logic, haven't done electricity since high school. I'm looking at flip flops and I've run into something called switching ...
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3answers
835 views

How can I avoid a clock glitch?

I have a clock with a 50% duty cycle, driving a 3-bit ripple counter. When Q2 is high, external lines such as address are stable. I want to generate a short read pulse between 50% and 75% of the Q2 ...
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1answer
63 views

Are TTL to USB converters bi-directional? [closed]

I'm trying to convert 5V TTL signals into USB signals that a PC can read. However, most converters that I'm able to find are defined as USB-TTL converters. Can I convert TTL signals to USB signals ...
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1answer
68 views

How to fix this uln2003 circuit?

I am trying to make understand to working of uln2003 but not able to run this circuit properly please anyone help me to understand why this is not working..
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0answers
61 views

TTL in an RF switch

I am hoping to find help on how to properly connect supply voltage to my switch assembly in order to actuate. My switch has input requirement of +15, -15, GND, and +5V. Also, the 5v logic inputs. ...
3
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2answers
86 views

How to prevent short circuit between output pins

I am trying to hack some signals coming from an old computer going to a Floppy drive using an ATtiny1614 microcontroller. Normally the computer has full control of the signal lines but at some window ...
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1answer
103 views

How to interface a thermal printer to an Arduino

I've a thermal printer which has TTL, RS232 & a four pin interface. I want to connect it to an Arduino and take printouts with it. It has the following pinouts: RS232 & TTL GND TXD RXD DSR ...
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2answers
47 views

Using USB-RS232 adaptor for USB-TTL connection? [closed]

Seems there are plenty of questions relating going in the opposite direction, but I couldn't find anything that really told me if I could do this.. I have one of these https://uk.rs-online.com/web/p/...
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1answer
74 views

BJT transistor max switching frequency vs FET in high frequency computer architecture

Why arent BJTs used with RISC architectures to produce very high speed relatively sparse CPUs? My understanding is that BJTs don't have the forward bias gate capacitance requirements of FETs which is ...
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1answer
49 views

Does the 74LS09 have an adequate internal input pullup?

I want to feed an output of the 74LS05 open collector inverter into one of the inputs of the 74LS09 AND gate. The internal schematics in the datasheet shows that there is an internal resistor and 2 ...
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0answers
25 views

Custom HDMI-to-( TFT or LVDS ) decoder/driver

I am working on a custom-made handheld PCB based around a PI Compute Module 3+ and one of the hardest steps I have found is how to include an HDMI-to-50pin-TTL driver on my PCB to run an LCD TFT 7&...
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1answer
119 views

TTL to 232 with no conversion?

I was reading a blog about someone's application to ingest a TTL signal to a device and got perplexed. The author connects what appears to be a 3.3V TTL signal directly to a RS232 port (and it ...
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3answers
242 views

Bi-colour LED resistor value

I am trying to calculate a suitable resistor to give about 2mA to the a bi-colour LED in the following configuration: simulate this circuit – Schematic created using CircuitLab The LED package ...
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1answer
72 views

Convert 24 V signal to 5 V with galvanic isolation

I need to make an acquisition card signal (24 V) conversion to TTL signals (5 V) usable by intelligent cards with galvanic isolation.
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2answers
119 views

Can Bruce Abbott's inverting TTL to +/- 12V level shifter be improved to better frequency response and better matched impedance?

I am working with Bruce Abbott's awesome level shifter here. Level transformation 0/+5 V TTL logic to +/-9V how to maximize gain and frequency range (DC to 4 MHz) simulate this circuit – ...
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1answer
50 views

TTL Gates Power Dissipation Values

I am not finding any datasheets that provide clear information about the power dissipation of some gates of the 74LS series: 08, 02, 04, 00, 32 and 86. Can someone help?
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3answers
47 views

How do I build an RC-base negative edge detector, that makes a low pulse on a falling edge?

I keep coming back here searching for an RC-based negative edge detector for TTL levels, that generates a negative pulse on a falling edge. The only place I find this solution is a certain spot in a ...
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1answer
90 views

Input impedance of TTL driver in a RF switch

I have a RF switch "ZYSW-2-50DR+" which has a built-in TTL driver. So far as I understand, the driver is like a buffer which amplifies the current while keeping the voltage same(unity gain). ...
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2answers
106 views

Hardware debouncing using 74LS14 - inverter input does not drop below 800 mV

I just recently started dabbling with electronics, so probably I just made some beginner's mistake. Here's my problem: I want to debounce a switch in hardware. During my internet research, I found ...
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1answer
80 views

Capture PPS timing signal into PC with minimal latency

I am looking for a 20 us wide TTL signal to be ingested into my device so that I can sync my OS to a PPS (pulse per second) with chrony. I'm currently looking at all the ways to have the signal enter ...
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2answers
291 views

Can I use a CP2102 USB to TTL IC for programming an ATmega 328p?

I am going to start working with microcontrollers. I will need to programm it. To programm it, I want to use a USB to serial port shield. There are several options. Should I use https://www....
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1answer
80 views

3.3V TTL to other formats and impedance matching [closed]

I am trying to convert a 3.3V 50 Ohm Impedance TTL Pulse-per-second into other formats (GPIB, USB, RS-232, etc.). I've found some format adapters/convertors like the MAX232, but I am either ...
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1answer
48 views

Can I power TTL chips with an USB-powered MB102 board?

I am adapting the digital electronics lab assignments I teach so they can be done at home with inexpensive supplies rather than with the equipment in the hardware lab. I have breadboards, TTL chips, ...
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2answers
38 views

Flip-flop with numbered inputs

On page 3 of the datasheet for the SN74LS597 IC, I have found the following diagram: Notice that the flip-flops have some numbered inputs (1D and C1, 2D and C2, C3 and 3S/3R) and some simple inputs (...
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0answers
315 views

LTspice - how to simulate real TTL gates?

I am trying to make simpler more general questions that might have more generally useful answers. If you build a mixed analog digital circuit then you need to have models of real TTL or CMOS gates ...
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0answers
95 views

LTspice and TTL logic gate parameters, my edge triggered ramp generator is current starved? How to correctly estimate TTL gate impedances?

Continuing with my edge triggered ramp generator and its simulation, thanks to all your help I have the LTspice simulation set up that I can see a theoretical circuit work that uses the rising edge of ...
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1answer
72 views

Is voltage selector on 5v or 3.3v?

I bought this USB to TTL converter and it came with the option to switch between 5v and 3.3v. I want to use it at 3.3v, but I'm not sure where the (grounder?) should be placed? Thanks, see image below....
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4answers
69 views

Collector current in a BJT transistor whose base and emitter are forward biased

I'm reading a book about electronics and I have a doubt about a NAND gate implemented with Transistor-Transistor Logic. The question I have is actually about BJT transistors specifically (not the gate ...
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1answer
87 views

How do I switch a PIN diode using a TTL control signal?

I'm designing a transmit/receive switch for an antenna using a PIN diode. The PIN diode I'm using is UM7512 make: Microsemi. I need to switch between -400V (off) to +5V (on). The switching time should ...
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1answer
136 views

Is it common for such basic TTL gate chips as 74LS32, '08, and '86 to be broken? [closed]

I have too many failures with very basic gate chips, while the more complex chips seem to keep working fine. And I find that very puzzling. These aren't even CMOS where I know that a static discharge ...
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1answer
48 views

Automatic switching to the changed set of TTL inputs

I have 2 sets of 4 logical inputs. All inputs are active-low 5V TTL level lines with 4k7 pull-up resistors, as they may be pulled to ground by a a user pressing a switch or flipping a transistor with ...
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2answers
117 views

I need diodes to build a R-2R ladder DAC from original TTL chips (not Arduino) don't I?

I am thinking through how I could turn my analog oscilloscope with X-Y mode and Z input in the back into a simple computer monitor. I am learning about generating a proper sawtooth with a constant ...
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2answers
822 views

History question - why are logic levels inverted between TTL and RS232?

I'm just looking for a historical answer as to why TTL and RS232 don't transition logically in the same directions. The signals are the same, but basically level-shifted and inverted. Was there a ...
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0answers
46 views

Issues using a 74LS245 with Attiny85

I have a Raspberry Pi, a 74LS245, and an ATTiny85. I connected the Pi to the Tiny through 1k resistors, and am able to use SPI to program it, no problem. I have added a 74LS245 inbetween, to ...
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1answer
68 views

What kind of serial cable do I need? (TTL vs RS232)

So I have a headless NAS that I'm trying to connect to via a serial console so I can install a different OS. It has a 3.5mm jack on the back I/O labeled COM1. I had ...
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0answers
28 views

Chip shorting to ground when connecting the grounds

I have a pcb that converts USB to RS232, it is using a CH340G and a MAX2323. The output when not connected works as expected. I try to connect it to a separate device that has its own power supply. ...
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1answer
145 views

50 Ohm TTL Drive Strength

I'm designing a device that will output TTL (0-5V) over a 50 Ohm coax to an NI PXie-6672 with programmable 50 Ohm termination. I'm wondering if I will truly need 100mA of drive strength from my output ...
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1answer
33 views

Need to step down votage to test a heart rate monitor

I'd like to create a test bed for heart rate monitor devices. The type of monitors I'd like to test use chest straps to detect the voltage fluctuations caused by the heart. I'm told this votage ...
0
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1answer
114 views

TTL high input, outcome? [closed]

My books states that when a TTL input is high, the emitter diode cuts off and the emitter current is approximately zero. This animation shows that when a transistor input is high, the emitter diode ...
3
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4answers
897 views

Tachometer IC that does not require zero-crossings?

I recently built the basic tachometer circuit in this LM2917/LM2907 Datasheet shown below using the 8-Pin version of the device. I realize this circuit requires a VR pickup sensor, and so the LM2907/...
0
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1answer
35 views

Safety considerations (for parts) for a beginner building with expensive parts

I'm building for the first time (for me) a circuit with an expensive part (a $80 DEC J11 CPU) and would like to know some "safety" tips so I don't inadvertently destroy the thing while playing with it....

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