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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137 views

Reset circuit loops forever on-off

I've designed the following circuit: This is a "self-reset" circuit, VCC_IN es 12V from source, VCC_OUT powers the entire board, including a PIC microcontroller. The idea behind this is whenever the ...
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96 views

How to change frequency range of this circuit

I need to design a frequency to voltage converter and I found this circuit on internet: I removed the resistor R6 and the capacitor C5 because what I need is the PWM output it gives on the 555 timer. ...
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1answer
218 views

NE555 and LDR circuit diagram

I have modified a schematic for my project with the following image: Instead of a 20K potentiometer, I use 100K for more precise adjustment. Do I need to add a disk capacitor of 10nf or 100nf to Pin ...
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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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142 views

Hall Effect pulse multiplier circuit

I would like to use a Phase Locked Loop (PLL) to multiply a 4x signal to be an 8x signal, and modify the same 4x signal to be a 64x signal so that all three signals are available as a 5v clean low - ...
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1answer
57 views

One time blink then turn off circuit

is it possible to change Circuit Diagram for the following example: http://www.redcircuits.com/Page146.htm or https://www.youtube.com/watch?v=mrxdiO1b29A Original: 4 short flashes stay on light ...
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1answer
59 views

SIMPLE digital control over 555 timer frequency and PWM?

I'm looking to create a sound generator with only simple ICs and components. I believe the 555 timer IC is a good candidate to be at the core of it, but I cannot for the life of me find out how best ...
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1answer
27 views

touch switch time problem

I was looking for a way to make a touch touch switch and i found this circuit on the internet but the problem is , it goes off automatically after few seconds is there any way that i can control it ...
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1answer
43 views

monostable 555 timer - buzzer motor and pulsing

I need this circuit to pulse an LED while running a buzzer motor for an adjustable period RV1 and C1 should give me 1 - 5s of pulse, while RV2 and C2 should adjust the LED ramp times The LED will be ...
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1answer
64 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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3answers
4k views

Simple Ray gun sound - buzzer

I am trying to put together a ray gun wrist gauntlet for my son's Buzz Lightyear Halloween costume. I think am going to do a little circuit with a big red LED and a 555 timer to make it flash (maybe a ...
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3answers
205 views

Eliminate AC noise from DC supply?

I have built an automatic water tank using the circuit given below: But this circuit was working well for 2 days. But after that, it triggers falsely. When a fan in another room is switched on, this ...
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406 views

555 timer digital clock

How would you go about connecting a 555 timer to a circuit with a 16x2 LCD display, which is already connected, to create a digital clock that counts the time? Do you have a sample of how this code ...
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1answer
47 views

driving a medium power darlington transistor with the output of a 555 timer

Question: What is the limitation on the output of the 555 timer with respect to the requirements of the input of the BDW42G? Can the 555 provide enough current at 5 volts to trigger (sufficiently) ...
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1answer
206 views

12V PWM controller for 12V fan that gets faster with the COLD

I need a controller for a 12 V - 1A fan, blowing on the cold side of a Peltier element to keep it at constant temperature. I have the hot side under control. I have seen multiple cheap PWM ready-to-...
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3answers
108 views

How to convert 8-bit information containing MIDI note, to square wave signal using basic chips and components? [closed]

Using basic electronic components (capacitors, transistors, etc) and/or chips (555, 74 series, etc) how do I convert from: Input: 8-bits containing the binary representation of a MIDI number "...
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109 views

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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2k views

Is the 555 timer accurate and uniform enough for a metronome?

I would like to create a simple metronome using the ICM7555 CMOS RC timer (datasheet), but I am not sure if the pulses will be "uniform enough". The datasheet states "astable timing accuracy" of 2% /...
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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, ...
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152 views

555 Astable Timer produces incorrect period/frequency

I am building a 555 astable timer circuit for a course which must match the BPM of a song. The song has a BPM of 104, which requires a timer frequency of roughly 1.733 Hz. The circuit looks as ...
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124 views

555 Timer PWM generator

I have the following circuit for a 555 Timer PWM generator: With 1: GND, 2: TRIGGER, 3: OUTPUT, 4: RESET, 5: CONT, 6: THRESHOLD, 7: DISCHARGE, 8: VCC I dont quite understand the use of R1. Is it ...
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0answers
43 views

Choosing Common Logic Level HF Buffer

I need help in choosing a common logic level buffer for a 555 timer output that will vary in frequency. I'd like to use n-channel/p-channel MOSFETs though I'm also open to cheap IC buffers. ...
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2answers
242 views

Why isn't my 555 cascading timer working?

I've made a 555 cascading timer. First stage is approx 90 seconds, second is 30 seconds. The first two led's light up in sequence as expected, but the 3rd doesn't light. I've checked all connections. ...
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117 views

Where to connect unused 555 timer ICs pins?

simulate this circuit – Schematic created using CircuitLab This question might not have a close answer since I think it heavily depends on the considered pin and IC. However, consider, for the ...
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0answers
266 views

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 ...
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1answer
11k views

Need help with 90vdc PM motor speed control circuit

I recently found a Permanent Magnet 90vdc motor, 2.5hp, 18Amps. It has simply two wires for voltage (red/black) and two for thermal breaker circuit i believe (blue/blue). It came out of an old ...
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166 views

3 simultaneous led chaser using only 555 and 4017

I've to design a circuit which consists of 30 LEDs in a row (RED, BLUE and GREEN) followed by a led matrix which spells out IN. Conditions which I've to follow: When the circuit is powered, ...
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1answer
2k views

Delay turn ON circuit using 555

I want to set a delay of around 5s between power supply turning ON and my circuit getting power. Here is the circuit I have come up with: Datasheet of mosfet I am using a 555 timer to set the ...
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5answers
112 views

Will this 555 circuit prevent a car from disconnecting power to the radio when starting?

To start with I'm a little rusty with electronics, I haven't done much in 20 years and it was only a hobby back then. In my car I have a head unit with a touch screen which relies on software to run ...
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1answer
32 views

Time triggered switch off

I'm trying to figure a circuit design that when it is powered it outputs high. Then, when it get a pulse as input (low or high, I don't mind) it wait some time and then put the output to low. The ...
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3answers
53 views

Using the same components for two 555 timers

I am building a circuit to operate a Linear Actuator to open and close a lid. The open and close times are the same. The standard monostable circuit works. There is one switch to tell if the lid is ...
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2answers
148 views

Hold Pushbutton for soft latch after X seconds

What I'm trying to achieve is have a momentary push button that must be held for say 5 seconds before latching on permanently. But the button must be held for entire duration or else timer will reset....
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4k views

555N vs. 555P? One works, the other does not!

I've implemented a water level indicator using a 555 timer. It works fine when I use 555N, but the output is always high when I replace it with 555P. I don't understand. I have tried four 555Ps to ...
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56 views

Nautical map model navigation lights

I would like to create navigation light sequences on old admiralty map of my local area. There are lighthouses and channel markers in area with mix of flashing and times. The single flashes I can use ...
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2answers
79 views

How can I dampen current spikes when using NPNs to drive an LED

Hi I have the following circuit, its purpose is to flash an LED once per second. I'm using a pair of transistors as a constant current source but I observe current spikes of 20% or so when it is ...
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2answers
66 views

555 timer circuitry

I have a 555 pulse generator controlling a relay going a little faster than 1hz. It is hooked up to start up when it receives positive voltage from the switched accessory circuit of a vehicle. That ...
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2answers
2k views

Parallel Port - Voltage / Current required for input pin

I am developing a program to send and receive sigal to my circuit and pc. Actually I have to count the pulses or (frequency of high pulse) generated from a 555 timer IC in my circuit. When I connect a ...
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3answers
559 views

555 Clock Circuit - how to choose resistor value? [closed]

I need to design a 555 clock circuit to output a clock pulse of a specific frequency. The circuit I'm using is this one (from here): I've used this circuit before and it works fine but the website ...
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1answer
73 views

Addition of limit switch for power supply stops circuit from working. Circuit works fine without the switch?

I am having an issue with a limit switch to turn on and off a circuit. I am using a L7805 5V regulator with a regular 9V battery as the power supply for my circuit. When I plug in the 9V battery ...
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1answer
295 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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50 views

Cannot share power source between audio module and 555 circuit

In this post, I outlined a circuit I was building to activate a solenoid with voice using a small Arduino sound detection module (this one). The output pulses from that module are too short to drive ...
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56 views

What's wrong with my boost converter circuit?

When I first created my circuit, everything worked fine. I didn't use a logic level mosfet at the time but I managed to acquire over 10V at the output (DC motor) and the next morning it stopped ...
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1answer
192 views

Can Pulsed DC be used in a radio transmitter?

I'm building a small radio transmitter based on a 555 timer. In my circuit a 555 timer in astable mode is used as an oscillator. kind off like : http://www.instructables.com/id/555-AM-Transmitter/ ...
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1answer
67 views

High and Low times for 555 oscilator are inverted

I’m new to electrical engineering and this is my first time working with an oscillator. I'm trying to setup a 555 timer ic as an oscillator with a low time of 1s and a high time of 0.5s. I've been ...
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345 views

Can I use a mosfet as a switch to power arduino?

I have a project in which I intend to use a NE555 timer to turn the arduino on/off on specific intervals. I don't want to use the ne555 output directly because of the current limitations of the chip. ...
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1answer
76 views

IC 555 as monostable multivibrator

How is the output of a monostable multivibrator affected if the trigger pin is kept at a negative voltage (0V)? The upper voltage reference comparator will change its output to logic 1, while the ...
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1answer
61 views

How can I turn off automatically, say after a fixed number of cycles, a 555 in astable mode?

I looked at the answer to "How to turn a 555 in astable mode into a decaying square wave" but this is really for an input to a speaker. I want the input to go into a counter to count the number of ...
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10k views

How does the 555 timer IC circuit work?

As a beginner to electronics I'm having a tough time understanding circuits that have a combination of different components, including the following timer circuit. Its based around a LM555 timer IC. I ...
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4answers
488 views

555 monostable/astable on one chip

Is there any way to use a single 555 chip which could be switched with a two-state switch between monostable mode (one-shot pulse of a certain width) and astable (continuous pulses of a certain width)?...
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50 views

Can I use the oscillation frequency equation for this circuit?

I'm not really sure if this is a question that can be answered so I'm sorry in advance if it isn't. I've just started doing electronics on a breadboard and I'm making a "Mini Strobe Light" from Jaycar'...