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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Digital output protection against accidental contact with 230V AC

I plan to build a "Wire Tracer" device to identify mystery wires around the house. I found this schematic, which uses a NE556 based tone generator and a contact-less receiver. Hopefully it ...
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Capacitance via 555 timer & resonance. Sources and possible cure?

I apologise in advance if this topic has already been discussed here. I am no EE and have have no choice but to ask experts to move my project forward. I am developing a capacitive sensor via a ...
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555 PWM circuit set frequency shifting after 2 months

Please refer to post PWM generator circuit review for initial simulation and bugs on the circuit. In general, the circuit works very well and I can control a 12V fan with the PWM output of the 555 ...
RWeiser's user avatar
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Strange behavior of 555 timer

Having problems with the 555 timer, I have decided to configure it in the simplest way possible to test its behavior, by controlling only the inputs to the trigger ...
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Multisim : Wrong Output for 1 way traffic light using 555 timers

I made a curcuit using the given diagram in Multisim but my output is of the order Green->Yellow->Green->(Yellow and Red) . Pls tell what should I do to get the output of the order Green->...
Krishanu Kashyap's user avatar
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How does this timer 555 and transistor circuit work?

Is this the way this circuit works ? If vref = 5v on the pin #5, then Vthreshold = 5v, and Vtrigger = 2.5v With Vthreshold = 5v, if voltage on pin #6 Vp6 > 5v, then Vp3 is Vo = 0 With Vtrigger = ...
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Will my 555 timer circuit work the way I want it to?

Essentially, I am trying to implement a safety system for another project of mine. I am running a very high current through a rather large solenoid and want to ensure that a failure in its control ...
Pizzashape23's user avatar
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How to protect my 555 timer against DC motor noise?

I have this circuit: (Sorry for such a bad schematic.) As you can see, there is a DC motor that gets power from 12V source, using a NPN transistor controlled by a 0-5V signal. Please note that ...
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Cascade of 555 timer with Control Voltage not triggering

Hi I'm currently working on a cascade 555 circuit, both operating in the monostable mode. I also want to be able to control the pulse width with a voltage so am using applying 0-5v to the ctrl pin (...
Martin's user avatar
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Triggering a signal on the falling edge of an input, and not re-triggering when it stays low

I have a 555 in monostable mode that will generate a signal from the transition to low from one of it's inputs (as they do). The issue I have is that the trigger will out last the signal by an order ...
QueueHammer's user avatar
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Alterning LED's in breadboard with timer 555, 2 circuits doing the same but i don't understand one of them

I am working on an alternating LED circuit. Initially, I implemented it following the circuit shown below. From this circuit, I understand that the capacitor discharges from R2 to the discharge pin (...
Aleat's user avatar
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How to simulate a button press on DFPlayer Mini?

I have a DFPlayer Mini with an SD card with one song on it. I want to make a circuit to power it on, and after a couple seconds, simulate a button press through a 33k resistor on pin 12 to trigger the ...
Marvil's user avatar
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MOSFET H-bridge

But I'm trying to build robust controller to reverse a motor in a harsh environment. The motor has built-in limit switches, which stop it from running-on at the end of it's stroke, which is fine for ...
Madaxe's user avatar
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Want to add a timer circuit to shut down battery powered toy

Would like to have: Operates down to 3V, Open drain/collector output, Programmable with resistor/capacitor/other, Integrated clock divider would be nice. Was thinking of using a 555 chip to shut off ...
Jean's user avatar
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Capacitor on control voltage for 555 timer

I was trying to tinker around with a 555 timer, but I don't have any 100 nF capacitors for pin 5 the control voltage. Can I use a 68 nF capacitor? I also thought about stacking two capacitors in ...
LordOfChimichangas's user avatar
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Motorcycle indicator flasher module

I have built an electronic indicator flasher module based on 555 timers to replace a broken module for my motorcycle. I guess I could have just bought a replacement, but they are a little more ...
Grant Lee's user avatar
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I am making a theremin-like circuit using a 555 timer and an LM386 amplifier chip. It’s currently not outputting any sound. Why is it not working?

This is the 555 timer circuit that I am using: This is the LM386 circuit I am using: I have connected the output of the 555 timer to the 10k potentiometer. If I connect the 555 timer part of the ...
Tara's user avatar
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555 timer monostable → simulation is not working

I would like to build a simple circuit with a 555 timer, in monostable mode (monoflop). I looked at these two diagrams for this purpose. http://www.learningaboutelectronics.com/Articles/555-timer-...
Daniel's user avatar
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PWM generator circuit review

I've designed the following circuit in order to control a 12V fan with PWM. The circuit is meant to stay at a fixed frequency of around 25kHz but a variable duty cycle controlled by a potentiometer. ...
RWeiser's user avatar
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How does the 555-timer AM radio work?

The 555-timer is used here as a demodulator. I don't understand how the 555-timer generates the desired signal. Shouldn't the output have the same frequency as the carrier signal? Can someone please ...
Amor's user avatar
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IR receiver somewhow being triggered by cell phone screen?

First time asking a question here. I am curious why the TSOP4838 ir sensor is acting erratically when my Google Pixel 2's screen is facing it. As you can see from the schematic, I have a 555 arranged ...
Craftyjam's user avatar
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1 answer
52 views

555 timer output equation

I've read that that the output voltage available at the Vout pin is approximately equal to the Vcc applied to pin 8 minus 1.7V. This is for an input voltage of +15V. I wanted to know if there is an ...
rohitt's user avatar
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Using an NMOS as a switch for a 10V DC source in a 555 timer circuit

I used NI multisim and created a circuit with a 555 timer that will allow a diode to flash at a frequency of about 4HZ. This is the circuit: As you can see in the above image, the oscilloscope graph ...
mstar42's user avatar
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Reset and trigger 555 timer with one push button

I want to turn on a LED with a single push button. When the button is pressed, the LED has to be turned on for an X amount of time. But what I also want, is to turn of the LED with the same push ...
leon bouman's user avatar
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482 views

Calculate Ra and Rb on a 555 Timer

I have all the units and calculations I need but I'm not sure which formula to use, and how to go about it. Please help. Frequency - 10.53 Hz Duty Cycle - 52.63% C2 - 100 uF (e12 value) Time High - ...
Jaedon Glover's user avatar
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Delayed Switching Between USB Peripherals

I have two USB sensor pads that cannot be connected simultaneously to the computer. Currently I am using a USB hub with individual on/off switches for each port. To change pads the user MUST turn off ...
Roger Anderson's user avatar
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217 views

555 timer unstable pulses

I'm using a 555 timer to drive the clock of my circuit. However, even with capacitors from VCC to GND, and from Pin 5 to ground, I'm still getting this "bump" when the timer transitions from ...
DuckMonster's user avatar
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1 answer
619 views

LED bar pattern shift (right to left) using 555 timer resistors and LEDs and SIPO shift register

I've build the 555 timer and got my resistors and LEDs ready. What I don't know or understand is how to shift a pattern using the serial in parallel out shift register (SN74LS164N). I want to shift ...
Lilly A's user avatar
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Blinking an LED once when a slide pot is pulled to ~zero ohms

I am developing a little circuit to control a servo linear actuator that is used to control fine injection onto a microscopy set-up. I am using a 555 circuit (see below) to generate the PPM signal ...
Priegel's user avatar
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555 timed power at high to low edge in battery powered circuit

I have a lovely Atmel touch sensor whose output is high only as long as it's touched. I want both off-on and on-off edges of its output to initiate two 3 sec pulses (and the time between edges is > 3 ...
user1621287's user avatar
1 vote
2 answers
123 views

Getting trigger signal for 555 timer from elevator button

I want to turn a load like light on for a certain time when one of elevator buttons pressed say button 1 and while the button pressed the load should be on. In the figure below circuit 1 describe how ...
lolo's user avatar
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LMC555 Fading led problem

I'am developing a simple badge with a fading led. My idea was a LMC555 timer powered by a cr1025 battery, these batteries have a nominal voltage of 3v. I chose the LMC555 for its low operating voltage....
Lux's user avatar
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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. ...
Craig Ringer's user avatar
1 vote
1 answer
169 views

Mono and Astable multivibrators not working when connected together

I have made a monostable multivibrator and an astable multivibrator using 555 timers using a popular circuit design found on the web. The monostable (out via pin 3) is used to control the astable (...
Richard's user avatar
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1 vote
1 answer
115 views

PNP Transistor - Use IC 555's internal resistance as pulldown?

I have a circuit that uses a PNP transistor to enable or not the current to flow and turn on a LED. The point is, is it a good engineering practice to conect the base of the transistor to the Vcc of ...
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556 circuit not working

I just got my 556 timers and I wired it up just like the 555 but now: it flashes one HighTime and stays off then... I used this calculator and basic diagram: http://www.ohmslawcalculator.com/555-...
dessi's user avatar
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Retriggering 3V PIR sensor with 555 timer circuit and LEDS

Hi y'all I'm putting together a PIR sensor circuit that will trigger a 555 timer in monostable and run a set of LEDS for about 5 sec all on a 3v cr2032 button cell battery and than reset until next ...
Brendan's user avatar
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Transistor for 38kHz IR pulse amplification

I am trying to build a timer circuit in which I will send a modulated 38kHz (almost) signal to an IR Receiver (TSOP38238 in Arduino Nano) and I want to amplify the square wave to the IR Led to ...
vamoirid's user avatar
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162 views

Can I control the charge of a Cell-Phone with a 555 Timer and a Transistor?

I want to charge my phone in a controllable manner, using a 555 and a Mosfet transistor. The 555 is a countdown timer that gives an output (pin 3) of 5V for 1 minute, and then remains at 0V until an ...
MellowRiki's user avatar
1 vote
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289 views

How to vary the range of a potentiometer...is this even possible?

I am a total noob so apologize if this doesn't belong here but I haven't had any luck finding an answer to this... I have a simple circuit with two 555 timers...similar to an Atari Punk Console. I ...
Ell's user avatar
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Dark detector with 555 timer and output pin has a LED

I am a complete novice and I had done it in a hurry with my kiddo around. I have redrawn it, with the values I used. The circuit works. Also between pins 6 and 7, if I use a 100 K/10 K it works. ...
electronicsdummy's user avatar
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clarification on a particular 555 implementation for 4017 johnson counters

I'm trying to build a 13 count johnson ring counter (which flashes LEDs sequentially 1 thru 13 and then repeats), and I found this circuit which looks perfect: I assembled it with an extra LED on the ...
G Math's user avatar
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674 views

555 to debounce comparator output for PIR circuit

I'm trying to create a circuit that takes an input from a PIR and outputs a high signal when movement is detected. My circuit currently looks like the schematic below (VCC is 5V). The circuit works ...
Joseph Roberts's user avatar
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4k views

How to calculate the Ra and Rb values for the desired frequency and duty cycle?

I am designing a DC-DC boost converter for Vin = 5V to Vout = 15V. To generate gate pulses, I will be using a NE555P Timer by TI - http://pdf1.alldatasheet.com/datasheet-pdf/view/161277/TI/NE555P.html....
PsychedGuy's user avatar
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555 timer blink circuit not working

I received my 555 timers in the mail today, and I wanted to make a simple blinking circuit, but no matter what I do, the LED just stays on, it does not flash. Even stranger is that this exact circuit ...
benji bon's user avatar
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0 answers
121 views

Designing a DC motor speed control circuit using PWM

I am designing a DC motor speed control circuit. I am using a centre-tapped transformer to get a dual voltage of 12v. The problem is both the 555 timer and the motor need a positive supply and ...
Tolu's user avatar
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NE555 pulse extender for PIN photodiode radiation detector is it fast enough? And more

I've designed a circuit using a PIN photodiode for a radiation detector aimed at identifying radium in an old watch. However, I'm uncertain about its effectiveness, particularly regarding the speed of ...
Doobalo's user avatar
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2 answers
94 views

Combining two RC time delay circuits to generate both LOW and HIGH pulses with two push buttons

I have come up with the following circuit that can be used to momentarily generate either a LOW or HIGH pulse based on what push button is pressed. Can you please tell me if there is any issues with ...
David Refoua's user avatar
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0 answers
100 views

Clock logic for 8-bit computer

I have been in the process of remaking Ben Eater's 8-bit-computer, and have a few questions. I got to the part where the clock, which consists of 3x 555 timer, is connected with logic gates. However, ...
lukasm06's user avatar
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1 answer
148 views

Alternatively blinking two LEDs with 555 Timer

I tried to make a simple 555 timer circuit which turns on one LED when its output is HIGH and turns on another LED when its output is LOW. I tried connecting two LEDs with single 1k ohm resistor (...
Muhammad Nowfer's user avatar