Questions tagged [555]

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation and oscillator applications. The part is still in widespread use, thanks to its ease of use, low price and good stability. The 556 timer is simply two 555 timers in a single package.

Filter by
Sorted by
Tagged with
3
votes
1answer
378 views

555 timer monostable time constants

When making an monostable circuit with a 555 timber, the time that pin 3 is on is calculated using this: time on = 1.1 x R1 x C1 My question is why is 1.1 included.
3
votes
4answers
3k views

Resistance to Digital converter

I am trying to make a digital ohmmeter on a parallel port interface that can measure resistance with at least 95% accuracy. I have tried a 555 timer monostable assembly which generates a pulse with ...
3
votes
3answers
10k views

Determine suitable resistor for the base of transistor as switch (NPN)

I have designed a program to count the frequency and time period of the pulse generated by a 555 timer IC using PC Parallel port. I’ve connected a base of BC547 (NPN) transistor to the output pin (no. ...
3
votes
2answers
635 views

Original 555 timer transistor output implementation

I am a beginner casual electronics hobbyist trying to learn about how chips work internally. In order to accomplish, this I went out and got a 555 timer soldering kit and started experimenting with it....
3
votes
1answer
2k views

555 timer as Dual Direction H-bridge driver

I am trying to design an analog direction driver circuit for an H-bridge configuration on a small DC motor. I have a pretty tight space constraint, and a simple requirement for my design, hence why I ...
3
votes
1answer
416 views

555 IC - Transistor Tester

Why are Pins 7 and 5 floating for this 555 IC and how does an NPN and PNP transistor when connected to E B C act a switch? Without the use of Pin 7 surely the capacitor cannot discharge which would ...
3
votes
1answer
4k views

Control duty time and frequency with different potentiometers using one 555 timer

How can I regulate duty time and frequency of 555 timer output with 2 potentiometers?
3
votes
2answers
1k views

How to mathematically determine the frequency of a tone based on components being used

My REAL question is how to choose the right components if you want a specific frequency spit out from a 555. In my particular case I want a potentiometer to control an output frequency from 16Hz to ...
3
votes
2answers
697 views

Turning on and off car ignition - created two pulses?

I'm building a car DVR using a GoPro. The GoPro can be turned on by shorting out two pins on the gopro bus and then turned off by shorting out the same two pins. So when the car's ignition is turned ...
3
votes
2answers
2k views

NE555 above 100kHz frequency problem

At first I searched this problem and could not find anything with this specific. I am using NE555 to generate frequencies. I'm using the calculations of this website. I am using 10nf as it says. My ...
3
votes
3answers
3k views

Output frequency unstable in 555 oscillator

I'm trying to make a simple astable NE555. The output frequency increasing alone. For example it start from for example 4.2 kHz and immediately change to 4.3 kHz, 4.6 kHz, 5kHz, then play around 4.5 ...
3
votes
2answers
3k views

DC-DC boost converter not working as it should

I have been experimenting with DC-DC boost converter design. After I made some calculations in order to obtain a certain output based on certain parameters, I tested the SMPS and saw that it's not ...
3
votes
2answers
333 views

Best way to sync LED's to light NES figures on a wall clock?

Advice & Ideas needed... Working on a project - a custom wall clock with perler bead NES sprites in the place of the numbers. The figures are mounted to a wood board with cutouts underneath, and ...
3
votes
2answers
112 views

Why would you loop 'Out' back to 'Vcc'?

I do not understand the NE556 circuit depicted in this data sheet: https://cdn-reichelt.de/documents/datenblatt/A200/NE-SA-SE556-TI.pdf on page 6 in figure 1. More specifically I do not understand ...
3
votes
2answers
269 views

What is incorrect with my 555 LED flasher circuit?

I have built a circuit to flash an LED using a 555 timer IC, but it doesn't flash... the LED just stays on steadily. -- I carefully followed the instructions on a common tutorial, which is: http://...
3
votes
1answer
505 views

Astable 555 Timer creates longer pulse when just turned on

I have a question regarding the behavior of a 555 timer circuit that I have made. It is depicted below. Now, here is some interesting behavior, I wrote a program on arduino that measures the lengths ...
3
votes
2answers
1k views

Can you use a 555 to modulate a laser

Will I be able to modulate a 1mW laser using a 555 timer LED circuit by replacing the LED with the laser diode?
3
votes
2answers
7k views

How to make a LED flash twice every second?

I know that I can make a LED flash using a 555 timer. How may I make it flash twice every second? What I am trying to do is to make the LED flashes two times, then wait a second, and then flashes ...
3
votes
1answer
458 views

555 timer monostable operation not so stable

I'm experimenting with a bunch of Texas Instruments NE555P IC's that I bought recently from Amazon, I made a basic monostable operation circuit on a breadboard with the following schematics simulate ...
3
votes
1answer
1k views

Kaustic Machine's Atari Punk Console: Line Output or Log Pot?

I'm planning to make a atari punk console for an electronics project, but i have a question, the original circuit published here: http://compiler.kaustic.net/machines/apc.html has a "line outout". Is ...
3
votes
1answer
257 views

Alternative to TPST Shift Registers?

So I'm building a musical sequencer that uses a shift register to close relays and pass the discharge pins of three 555 timers through a manual switch and potentiometer (acting as a variable resistor) ...
3
votes
1answer
6k views

555 Temperature Controlled PWM

I am trying to build a temperature controlled 555 circuit to drive a cpu fan (used for cooling my entertainment center) I built this using slightly different diodes and MOSFET, and it works great (...
3
votes
3answers
3k views

How to keep led in “ON” state using 555 IC?

I have made dark detector using this following circuit diagram: Whenever the LDR is closed with finger,the LED would glow. Now all I want is to keep that LED in ON state for a while or alternatively ...
3
votes
1answer
6k views

How to find electrical conductivity from frequency in my PLC project

I am using a 555 timer which is supposed to measure the electrical conductivity of milk. Here's a circuit for a conductivity sensor: It provides the needed isolation, uses AC measurement, and the ...
3
votes
4answers
4k views

555 Schmitt Trigger works well with CMOS LMC but not NE555?

I have an NE555 (the non-CMOS version) running in astable mode at 118Khz. I have the output pin3 connected to input for a second 555 running as a Schmitt Trigger to invert the signal. What I found is ...
3
votes
1answer
2k views

Losses in NE555 oscillator and Sallen-Key filter

I use a Sallen-Key bandpass filter in a project at university to isolate the 1kHz sinusoidal part of a square signal produced by a NE555 oscillator. Here is my circuit: When I simulate it on PSpice, ...
3
votes
1answer
523 views

can pins 3 and 11 on the 556 timer use the same capacitor to ground?

can the control voltage pins 3 and 11 on the 556 timer use the same capacitor to ground? I assume that I can double the capacity of the 0.01\$\mu\$ capacitor to 0.02\$\mu\$ and share the capacitor ...
3
votes
1answer
115 views

555 timer that does not output low when reset

I'm trying to design a circuit with the following goals: When not active, output can be either Vcc or floating When triggered by pressing a button, output pulses several times to GND at some ...
3
votes
1answer
677 views

555 timer delay circuit + light sensor?

I am quite new to electronics and I would like to combine these 2 circuits together so that during complete darkness on the LDR, the LED would turn on instantly and when light falls on the LDR there ...
3
votes
2answers
179 views

voltage traces across pwm driven dc-motor: is that ok?

I'm driving a dc-motor with a BJT turned on and off with a 555 generated PWM signal. Here's the circuit (V1, Rl and L1 simulate the motor): There actual circuit - same parts - is on a breadboard and ...
3
votes
2answers
521 views

How does this circuit work to fade an LED in and out?

I'm new to electronics. I'm trying to figure out how this circuit works to fade the LED light in and out: This is how I think it works (of course, I'm wrong): When you initially connect the circuit, ...
3
votes
1answer
273 views

12V variable-speed fan as a function of temperature using 555 timer

I would like to turn the car fan into a variable-speed fan using a the analog temperature sensor of the car, and a 555 timer. While temperature decreases, resistance (of the sensor) increases. Can I ...
3
votes
1answer
529 views

General circuit debugging techniques, and my 555 timer in particular

I am looking for help in two ways: learning general techniques for debugging circuits that do not work figuring out why this circuit in particular is not working The circuit is a timer that runs for ...
3
votes
2answers
8k views

Generating a delayed pulse with one 555 timer upon powering up the circuit

This is a very beginner's question - I apologize if this is some trivial extension of a known practice. Can I use one 555 timer without any extra transistors/IC to generate a delayed pulse as shown ...
3
votes
1answer
2k views

Generating PWM from rectified sine wave using 555

I want to generate a PWM signal from a rectified sinus wave similar to the image below using 555 timer IC. I have designed the circuit below for this. I want to get a duty cycle of 80% at the peak ...
3
votes
1answer
234 views

How can I create the characteristic warp core sound?

I'm trying to build a miniature warp core (purely decorative, not functional) with the main element being an LED chaser circuit with 10 LEDs. I'm planning on using a 555 timer and a 4017 decade ...
3
votes
1answer
106 views

LM555CN chip acting weird

I'm in high school computer engineering, and I'm experimenting with the 555 Timer chip on my own. I'm using the Electronic Experimenter Box. Pin 8 is connected to +5V Pin 1 connected to ground LED1 ...
3
votes
2answers
4k views

independent control of frequency and duty cycle in 555 timer (formulas)

I want to control frequency and duty cycle of output pulse of 555 timer. I searched and find this schematic in a post in SOV but I don't know how calculate frequency and duty cycle in the circuit. ...
2
votes
3answers
14k views

What is the equation for the 555 timer control voltage?

I was just wondering what the equation is to find the 555's output frequency is, when a control voltage is applied to pin 5. That would be very useful for me to know! [Edit By OP] So based on what ...
2
votes
5answers
2k views

Limit Number Of Pulses From 555 Or Similar

I need as small a circuit as possible that can produce 2 pulses (say maybe 200 milliseconds long and apart) when I press a button. My thought was to use a 555 timer and set it up for my desired pulse ...
2
votes
4answers
544 views

Any reason I cannot just switch a transformer from a 555 to generate high voltages?

I had an idea to finally start using my nixie tubes and thought why not just switch a mosfet which switches a transformer to generate required high voltages for nixie tubes from a low voltage supply. ...
2
votes
4answers
424 views

A question on specifying RC combinations in analog timer circuits

When making analog op-amp or 555 timers, many times RC time constant is employed. Lets say we want 1 sec time constant: We could chose for instance the combination R=100k and C=10uF. Or we could ...
2
votes
2answers
9k views

What is the job of the capacitor in a 555 circuit?

Let's say you've got a standard astable multivibrator (AMV) 555 circuit that includes all the wiring, two resistors (R1, R2) and a capacitor (C1). I wonder what is the purpose of the capacitor and how ...
2
votes
2answers
286 views

Using high resistance resistor greater than 10M possibly does not work with 555 Timer

I am trying to create a 20 minute timer for 20-20-20 Rule with some bunch of resistors and capacitors available with me. I am using a 10M reistor here in place of R1 and some 10K/20K in place of R2. ...
2
votes
3answers
4k views

Modifications to 555 LED Fade Circuit

I was looking for a circuit to fade an LED on and off using no microcontrollers, and found this nice circuit: http://www.555-timer-circuits.com/up-down-fading-led.html it seems like exactly what I ...
2
votes
2answers
12k views

What do Capacitors do in a System with a Speaker?

I made a circuit based on a diagram from my physics teacher. The circuit has a 555 chip connected to seven wires that make up a circuit. The circuit includes a photocell resistor that acts as a ...
2
votes
2answers
12k views

NE555 timer not working - how to identify the element at fault?

background Im a beginner in the field of electonics, and I have been trying to put together a IR remote control / laser tag system using Arduino Nano. I am using a TSOP4840 receiver and a TSAL6100 as ...
2
votes
4answers
466 views

I need help designing a very simple timer

I'm designing a very simple led light timer based on the Pomodoro time management technique. For those of you unfamiliar, you work for a set amount of time, take a short break, and repeat. My end ...
2
votes
5answers
4k views

Simple Mosfet driver

I need to switch 8 IRF9540 (P-Channel Mosfets) with about 32kHz (so 1 MOSFET about 4kHz) so that only one is On at one time. I thought about using the decade counter 4017 for this, and the 555 Timer ...
2
votes
3answers
2k views

Obtaining a triangle wave from a square wave using a LM324N op-amp

I am generating a square wave with a 555 timer chip and I am trying to obtain a triangle wave from the 555's output by using an op-amp (LM324N) as an integrator. The op-amp is in single power supply ...

1 2
3
4 5
16