All Questions
15
questions
1
vote
3
answers
112
views
Simple TTL: Is there a way to "detect" a high-z state and easily use that to drive other logic?
I have two TTL style logic chips, call them A and B (*), where the outputs of A are the inputs to B (think: 8 data lines). A has tri-state outputs, so when they are turned off they float. B is an ...
- 2,131
2
votes
2
answers
243
views
Differential capacitance change measurement (sensing) with 74LS628
I'm researching the possibilities to accurately register the capacitance changes of a big metal plate (area 10 m2) to the ground (GND, yes - earth, soil). It varies around 100-200 pF.
For now I'm ...
- 73
3
votes
3
answers
363
views
Power supply for medium-scale 74HC TTL circuit
I've developed an 8-bit computer, in the same vein as Ben Eater's wonderful 8-bit computer series. It's based on a collection of 74HCxx-series ICs, and fits (in theory!) on a single PCB board. I'm ...
- 31
2
votes
4
answers
235
views
74xxx logic. Cheapest, most space saving way to invert 10 logic outputs
Please see this circuit.
I'm trying to design a circuit that allows you to use a single button to increment a counter from 0 to 9 (then it will loop). Diode logic will convert the 10 logic outputs to ...
- 309
2
votes
1
answer
401
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 ...
- 21
1
vote
2
answers
1k
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 ...
- 113
0
votes
1
answer
158
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 ...
- 31
2
votes
2
answers
1k
views
What's the difference between 74LS00 "gates" and 74LS37 "buffers"?
The TI 74LS00 is "quadruple 2-input positive-NAND gates" and the 74LS37 is "quadruple 2-input positive-NAND buffers."
The pinouts are identical. The LCCC package is documented exactly the same for ...
- 990
1
vote
1
answer
103
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 ...
- 13
0
votes
1
answer
2k
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 ...
- 907
0
votes
1
answer
1k
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 ...
- 39
8
votes
4
answers
9k
views
10k Resistor Pull Up/Down Standard for 74 series chips
I've been having some issues lately with the usage of 10k ohm resistors as pull down resistors for 74ls series chips. Most people seem to choose 10k resistors as their default pull up/down value but I'...
- 470
4
votes
1
answer
3k
views
7405 TTL Chip outputting nothing when given low input
I’m struggling learning how to use some of these components for a lab. One thing I noticed is that when giving the 7405 hex inverter a low input, the output when checked by my logic probe shows there’...
- 75
1
vote
2
answers
453
views
7400 chip register with common in/out pins
First of all, I don't know if this kind of question is allowed here, so sorry if it isn't.
I am looking for a 7400 series register which has common in and out pins (like for the RAM ou EEPROM: ) with ...
- 187
-1
votes
2
answers
366
views
What is the difference between a 74*374 and a 74*377
What is the exact difference between a 74*374 and a 74*377? The first is classified as an octal edge triggered d-type flipflop while the latter is an 8-bit register. I don't understand the difference ...
- 107