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 low price and ubiquity. The 556 timer is simply two 555 timers in a single package.

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Is the NE555 the IC I need, and if not, what do I replace it with?

I've noticed that whilst I have a well-known solution using an NE555, that IC doesn't fulfill my needs perfectly. Others have told me that the NE555 is very rarely an appropriate solution to one of ...
Marcus Müller's user avatar
6 votes
2 answers
25k views

555 timer, one shot trigger

I'm trying to create a circuit that will pass a 12V pulse on the rising edge of a push button (it can be triggered by the entire input pulse but rising edge preffered). I've had some experience with ...
Jordan Cartwright's user avatar
6 votes
2 answers
12k 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 ...
akhmed's user avatar
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3 votes
2 answers
1k views

How to turn a Latch circuit from Press-ON/Press-OFF to Press-ON/Hold-OFF circuit and how to make it auto-off when power is first connected?

I'm building a Latching circuit using 555 IC. The schematic is as follows: The Input voltage is 12V and is used to operate the 555 IC that switches a relay coil through a transistor. When the circuit ...
ElectroMechanical's user avatar
2 votes
1 answer
5k views

Why does this Edge Trigger Work on input of 555 monostable config?

I recently wired up a 555 timer in a mono stable configuration and found that when the trigger was held low for longer than the configured output pulse width, the output would stay high. After ...
Steven Lutz's user avatar
5 votes
2 answers
8k views

555 timer in astable mode: How can I achieve longer low output than high?

I'm attempting to make a simplistic solenoid driver circuit using a standard astable 555 timer configuration with a TIP122 NPN transistor. The problem with the current circuit is that the output is ...
JYelton's user avatar
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2 votes
3 answers
17k 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 ...
Zack Frost's user avatar
1 vote
2 answers
1k views

Astable 555 circuit always on, not oscillating

It has been quite a while since I've used a breadboard or looked at circuits (probably 20+ years since high school and college physics.) I'd like to think I know how they work, but something isn't ...
Mike Felts's user avatar
10 votes
3 answers
5k views

How do I pick a part that goes into a breadboard when I order it?

I have just bought some 555 timers and they are timers for microelectronic circuits...could anyone tell me what I need to search for in order to get larger ones which will fit a breadboard? Thanks
James Hatton's user avatar
5 votes
2 answers
36k views

555 to drive a MOSFET

I wish to drive a MOSFET using a 555. I dont have a driver handy, will it be fine to use a transistor instead? So the output of a 555, could activate a transistor(as swtich), which allows a source to ...
cheeky's user avatar
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2 votes
2 answers
11k 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 ...
roman's user avatar
  • 409
1 vote
1 answer
1k views

Generating a delayed pulse of 0,5sec with one 555 timer upon powering up the circuit

In the link below, this circuit I found is what I needed. Only the length of the pulse and the delay are not what I want. When I want just 0.5sec before pin 3 is up and the pulse duration I want is ...
Jorn's user avatar
  • 11
12 votes
4 answers
18k views

Square Wave input into Transformer

Can a square wave generated using an astable NE555 be used as input of a transformer instead of AC? Say, I generate a square wave of 60Hz using NE555 and a 24V at 6A supply and feed it into a ...
AvZ's user avatar
  • 317
11 votes
4 answers
15k views

555 timer: how to set values to take an hour

I'm new (and novice) in electronics. I came to seek your knowledge to see if someone can help me with a very basic circuit. It is a 555 chip, which should light a LED (for about 1/2 second) every ...
Xavi Gómez Canals's user avatar
7 votes
11 answers
41k views

Astable 555 timing circuit (0.5 Hz and 50% duty cycle)

I am trying to build a timing circuit to generate a 0.5 Hz 50% duty cycle signal. In other words 1 second on, 1 second off, and so on... I have searched a few places and found the following ...
user43916's user avatar
6 votes
2 answers
9k views

Is there a way to control the PWM duty cycle of a 555 timer without using a variable resistor?

I need to control the duty cycle of a Pulse Width Modulation (PWM) circuit from a DC voltage input. To do this, I've been looking into 555-timer circuits - but every circuit I've come across involves ...
Froot's user avatar
  • 157
5 votes
2 answers
10k views

What is signal ground

I encountered signal ground symbol while studying 555 IC Please explain why isn't a simple ground connection used and how does signal ground differ from normal ground. I am a first year undergraduate, ...
Kutsit's user avatar
  • 261
3 votes
1 answer
3k views

How do I reset NE555 output to LOW when powered on?

Here is a functional NE555 push-on push-off switch. But the problem with this is whenever the power source is connected, it starts in random On or Off position. How to modify it so that it always ...
Bimal Poudel's user avatar
3 votes
5 answers
3k 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 ...
lkrasner's user avatar
3 votes
1 answer
6k 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?
Klasik's user avatar
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3 votes
3 answers
4k views

555 timer with a 50% duty cycle

I'm trying to build a 555 timer with a 50% duty cycle. I followed the instructions given here (pg 12). I used a 470 μF capacitor, a 150 Ω resistor and a 1 kΩ resistor. The output voltage is always low....
Olshansky's user avatar
  • 135
2 votes
1 answer
685 views

Holding voltage high, for monostable 555 timer pulse

I want to know if there is a simple (and cheap) way to make a momentary button (for which we cannot control the time it holds when pressed!) press to virtually hold for about 1-2 seconds. More ...
nitzpo's user avatar
  • 123
2 votes
4 answers
533 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 ...
dwwilson66's user avatar
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2 votes
1 answer
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How do I extend the output (high) time of my circuit (retriggerable)?

I need help with the design of a timer delay circuit for the output of a sensor circuit which can keep the output HIGH for an adjustable time range (about 1 to 10 min), after the digital output of the ...
rocknroll's user avatar
1 vote
2 answers
1k views

Design review - RGB LED color mixer using PWM

I'm trying to make an RGB color mixer. LED strip runs on 0.5-2A. It has internal resistors. LED Strip needs 5v, has one pin for that, one for red, one for green, and one for blue. Each LED module that ...
EmeraldVolts's user avatar
1 vote
2 answers
724 views

Momentary switch to activate 555 timer

I am very new to circuits and I've tried everything online but nothing seems to be working. I am making this circuit for a class. I am trying to emulate this circuit diagram from this youtube video ...
try_hard's user avatar
0 votes
2 answers
3k views

Resistors and capacitors calculation for 555 timer circuit

I am new to electronics and I want to try an experiment. I want to use a 555 timer to create an automatic food dispenser for my aquarium (something like opening a small door when the timer has ...
Rakesh's user avatar
  • 3
0 votes
1 answer
495 views

Get ADC value to run external 555 Timer

I am working on Motor speed and position control. The requirements of the project are: 1. Set a speed to run the motor at a particular frequency. 2. Use a potentiometer to set the speed displayed on ...
David Norman's user avatar
  • 1,485
0 votes
1 answer
4k views

How to generate a 555 fixed time delay even if trigger button is held on? [closed]

Can any one help me how to make it when the switch is presed for long time but it will not affect the time delay
niladri pal's user avatar
-1 votes
1 answer
2k views

555 timer to drive IRFP460

I am trying to make a Slayer exciter using a MOSFET. From here. It uses these parts R1 = 2 Ω R2 >= 22 kΩ D2 = 1N4148, or 1N400x (x is a number) U1 = MIC4452 Q1 = 2SK2542 I don't have a MIC4452 ...
Huya Wachako's user avatar
-1 votes
3 answers
646 views

NE555 stable frequency vs duty cycle change

I am experimenting with NE555 trying to get it to output stable frequency as duty cycle is changed. Circuit is powered with a 9V DC supply. The schematic is attached. The R3 is here so that the charge ...
Jimmy Falcon's user avatar
27 votes
7 answers
5k views

Why are two 555 timers in separate sub-circuits cross-talking? (Poltergeist in the Breadboard)

As an introduction to electronics, I am following Charles Platt's Make: Electronics (2nd edition). Every circuit worked as expected, until Experiment 17: Set Your Tone. In circuit on ...
Ad N's user avatar
  • 391
22 votes
6 answers
6k views

Where do overtones in a 555 generated square wave come from?

I have built a 555 oscillator and connected it to a speaker. Using an oscilloscope I adjusted the 555 to generate a 2.5kHz square wave. I then held a microphone up to the speaker and fed the input ...
JShorthouse's user avatar
17 votes
4 answers
5k views

Why are 555 timers so prevalent? [closed]

I've noticed is that 555 ICs seem to be extremely common. Why is the 555 so prevalent, or ubiquitous; what about it so useful?
voices's user avatar
  • 1,069
13 votes
5 answers
14k views

Formula for Logarithmic (audio taper) pot

What I would like I am trying to determine the formula for an audio taper (logarithmic) pot. I would like a formula that takes R and P as inputs. R being the total resistance and P being the "...
Tim's user avatar
  • 243
11 votes
2 answers
6k views

NE555 Based Speed Controller circuit - Contradicting Pins in 2 Tutorials

I am a newbie of Electronics and learning it as a hobby. Over a course of time I realized that Electronic Blogs are not the best place to learn Electronics, unless you have a strong basics and can ...
sribasu's user avatar
  • 735
11 votes
4 answers
25k views

How do I use pin5 to control duty cycle of a 555 based PWM?

I have built a simple PWM using a 555 IC to drive a motor for an optical chopper and I want to be able to use the output of the chopper signal as a speed correction feedback for the PWM. I think I ...
Jonathan's user avatar
  • 111
10 votes
4 answers
36k views

555 timer boost converter doesn't meet spec

I've been messing around with nixie tubes lately which requires a high voltage source (~150V-200V) to turn on. I searched around for a simple high voltage generator and found this circuit which uses ...
tangrs's user avatar
  • 1,029
9 votes
3 answers
8k views

purpose of diode in this 555 timer application

I'm a newbie in electronics. I need to make a 555 timer base circuit(Refer to the schematic below) such that O/P pin of 555 is held LOW by default at power on, and the I/P pin is held initially at ...
jacks's user avatar
  • 363
8 votes
6 answers
5k views

6 Month Countdown Timer Circuit

I need to design a timing circuit. After a duration of 6 months a LED must come on. The LED can then be turned off at the press of a button and the 6 month count-down must begin again. Anyone have ...
user avatar
7 votes
2 answers
2k views

Help with 555PWM motor control

I'm making a laser spirograph for a school project. It requires speed control of three motors. I used a simple 555 astable circuit with a pot for control, then the output goes into the base of a power ...
Kevin Macklin's user avatar
7 votes
5 answers
10k views

Random time timer

I'm constructing a simple circuit that beeps a beeper on a given time interval, using a 555 timer. Is there any simple way to randomize the time on the 555 timer between two given intervals, say, any ...
Chris's user avatar
  • 617
6 votes
4 answers
3k views

Multiplexing a Circuit

Frankly, I'm overwhelmed with this circuit that I have to start building in lab tomorrow. Last week we built an octal decoder that takes a 3-bit binary input from 000 to 111 and displays a unique ...
JGill's user avatar
  • 75
5 votes
4 answers
9k views

How can I make a 15 minute egg timer circuit?

I want to make a 15 minute timer for a game. I would like it to count down 3 x 5 minute segments of time, and then ring a bell when the 15 minutes is up. To do this, I want to push a button to ...
Ben's user avatar
  • 299
5 votes
2 answers
11k views

Functional difference between various astable 555 circuits

Looking through some 555 square-wave-generator circuits (possibly with variable duty cycle for 4-wire PWM fan control) I've found three different circuits: From the Wikipedia 555 article, a "standard ...
Andrew's user avatar
  • 161
5 votes
3 answers
9k views

555 timer one-shot 30 second light LED strip, TOTALLY CONFUSED!

I'm working on a personal project and I am at my absolute whits end here. I have a configurable N.O. or N.C. switch (nteinc Magnetic Alarm Reed Switch) so I'm not too concerned with which way I use it....
xytheron's user avatar
5 votes
3 answers
2k views

What determines the transmit frequency in this 555-based transmitter?

I'm a general class ham, and am just starting to do my own homebrewing. I was planning on basing a QRP transmitter off of this instructables project, seeing as I have a veritable plethora of 555 ics ...
technowizard12's user avatar
5 votes
2 answers
6k views

What is the output voltage of this 555 timer high voltage circuit?

I'm trying to calculate the theoritical output voltage of the following 555 timer high voltage circuit. It claims to output up to ...
tigrou's user avatar
  • 1,883
4 votes
1 answer
504 views

What's wrong with giving a really long low pulse to a 555 timer?

A number > 0 of 555 timer tutorials warn against holding the trigger of a 555 timer in monostable configuration low for longer than the duration of the output pulse. Why not?
joeforker's user avatar
  • 5,636
4 votes
3 answers
484 views

MOSFET driver blows out in half-bridge DC motor PWM controller

EDIT: I've redone the MOSFET circuit diagram; it now represents what my actual layout is. I wanted to spare myself redrawing the circuit but ended up confusing everything, I hope it's clearer now! ...
Solmyr999's user avatar
  • 149