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.

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2answers
18k 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 ...
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2answers
7k 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 ...
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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 ...
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3answers
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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
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8k 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 ...
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25k 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 ...
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1answer
2k 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
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4answers
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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 ...
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3answers
13k 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 ...
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2answers
5k 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 ...
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1answer
557 views

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 ...
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1answer
503 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 ...
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2answers
2k 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 microfarad capacitor, 150 ohm resistor and a kohm resistor. The output voltage is ...
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4answers
444 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 ...
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1answer
266 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 ...
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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 ...
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1answer
388 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 ...
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0answers
58 views

Delay timer for car bar light to stop mode cycling

I just brought a bar light for my vehicle. My problem is the light has 4 modes (white, white flashing , yellow, yellow flashing) and the modes are triggered by turning the light off then on in less ...
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4answers
5k 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 "...
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4answers
29k 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 ...
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3answers
18k 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 ...
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4answers
10k 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 ...
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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 (...
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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?
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3answers
6k 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 ...
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5answers
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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 ...
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3answers
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 ...
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2answers
8k 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 ...
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9answers
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How do I produce a 1Hz clock output using a 555 timer IC? Are there better ways other than a 555 timer IC?

I've been messing up with timer ICs, looked up on how they work and now I want to design a simple digital clock using a 1Hz pulse generator. Is a 555 timer IC sufficient enough to make accurate 1Hz ...
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4answers
8k 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 ...
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3answers
7k 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....
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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?
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1answer
4k views

Flyback transformer

Recently, I posted a question about a flyback transformer schematic I was having. (source: eleccircuit.com) If you didn't check the link, I was having problems with the frequency of the 555 timer ...
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3answers
3k views

555 AM transmitter

I looked on instructables and I found an interesting(at least for me) AM transmitter made with a 555 timer which acts as the oscillator:http://www.instructables.com/id/555-AM-Transmitter/ Is this ...
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3answers
2k views

how to calculate time for timer relay

In the below circuit of Timer Relay, how I can calculate the time for C1 to be fully charged? please don't use regulator, transistor or any other device I just want to use Resistance and want to ...
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6answers
3k 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 ...
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4answers
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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 ...
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2answers
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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 ...
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2answers
5k 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 ...
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1answer
431 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?
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2answers
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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 ...
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2answers
2k views

Flyback transformer - ambiguous schematics and other issues

I'm currently using this schematic for a flyback transformer: (source: eleccircuit.com) As you can see, there's a big problem - neither the schematic, nor the website describing it, give the value ...
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2answers
318 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 ...
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1answer
4k views

Ultrasonic signal generation

I am busy with a robotic arduino project. I have a 40kHz ultrasonic transducer and receiver. What would be the best way to generate the 40kHz signal to drive the transducer. I have found two ways to ...
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1answer
1k views

555 Monostable Timer delay

I have built numerous 555 circuits over the years. I recently had to built a Monostable 555 cct. as per this site : http://www.allaboutcircuits.com/vol_6/chpt_8/4.html The cct. is used in a motor ...
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1answer
2k views

Why is the output from this astable 555 the reverse of it's simulation?

The simulator in LTSpice looked OK ... so I moved to the breadboard with an LED (eventually replaced the LED with a buzzer) at pin 3. One more difference in the assembled circuit is the condenser at ...
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2answers
8k views

How do I drive a stepper motor using an LM555 timer?

I'm trying to drive a stepper motor's driver (QuadStepper) with an LM555 timer circuit, however the logic levels are known to be 5v compatible. While the driver has both 3.3 and 5 volt compatibility, ...
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0answers
51 views

CircuitLab simulation of 555 timer - OUT HIGH always delivering 5V irrespective of Vcc?

I've scratched together a design for a 555 timer based driver for an IR540 MOSFET. But in CircuitLab the simulator shows the 555's OUT voltage is always 5V when high, for Vcc ranges 3.3V through 24V. ...
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1answer
387 views

Why are MOSFETs switching at a different speed than the one they are being driven at?

I used a 555 oscillator to drive a MOSFET array for my entry-level tesla coil setup. When I measure the frequency at the driver output (Location #2) everything seems normal. When I measure it at the ...
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1answer
2k views

LED flashlight project: Need transistor ideas

This question is continuation of this question. I did some research on previous question and made a circuit as a starting point. Here's a picture: Now my problem is that TS555 device I plan to use ...