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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82 views

Power Latching Relay off/on in response to 12V ignition and 1 second ground pulse

I have the following sample schematic of a 12 volt automotive circuit to trigger about 60 seconds of power output to a latching relay on output pin 3 of the 555 Timer chip. The schematic below is a ...
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65 views

Using a 555 timer and 14-stage binary divider for 2 hour timing circuit

I am researching how to design a timing circuit that will activate a relay with a push button and deactivate the relay after two hours. My understanding is that I can feed the output of a 555 timer to ...
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54 views

how to design a low pass filter for square waveform

I have square wave signal of 100KHz with few high frequency ringing from 555 timer.when i tried to use a 100KHz first order rc low pass filter,i got a sawtooth waveform because the 100KHz square will ...
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How to Limit 12V Power to an NPN transistor to only 200ms

The following schematic is a 12 volt automotive circuit to trigger a latching relay on for about 60 seconds and then turn it off. The schematic below is a just a sample and not the final circuit. ...
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2answers
104 views

Can I add two LEDs to this circuit?

I am working on a diorama. I found this circuit online and it's what I want. (I'm NOT making a railroad diorama.) I want to add two more LEDs to this circuit to have 4 flashing LEDs. Like this: ...
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141 views

555 delay timer not working, it does not delay at all

My 555 timer is not working like normal. I don't really know what happened. I did this on a breadboard and it worked perfectly with a 5s delay at the deck. But now I am building a full circuit were I ...
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51 views

555 NOISE BUTTON/ OP AMP

I have this circuit from the image below that I am designing myself. part of this circuit is cut so 2 78xx is present. This circuit is being designed and tested in parts. This part of the circuit has ...
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2answers
78 views

Wake up circuit - keep the circuit off when not in use

Goal: As the power supply is a battery, I want to shut down the circuit when it is not in use. Circuit description: Basic 555 timer circuit. By pressing the switch, the light turns on. What I have ...
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4answers
123 views

What type of capacitor is most stable for use in 555 timer circuit?

I am building a 555 timer circuit with a frequency of 15, 30 and 60 Hertz. I will most likely use a 1µF capacitor but I was wondering what kind of capacitor would be best for keeping a stable value ...
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2k views

555 timer frequency is way off

I'm currently designing a 555 timer to provide a 38kHz square wave to drive an IR LED as part of a beam interrupt detection system. This beam interrupt is a part of an embedded product where we ...
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2answers
227 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. ...
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8k views

How to reset a 4026 counter IC when it reaches 6 for electronic dice

I'm trying to build a circuit to simulate a dice roll using a 555 in astable as it's heart. The output pulses are counted by a 4026 and then fed into a 4511 BCD to 7 segment decoder. It works ...
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528 views

power on power off pulses to two seperate controllers

I would like to request a circuit where a 500 ms pulse is sent to one rail when 12 volt power is supplied and another 500 ms pulse is sent to a different rail when power is turned off. 555 is the way ...
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139 views

Can I use a current divider to protect my IC?

I designed an oscillator circuit using a TLC555 timer IC to create a 2 second pulse, which is used to drive a 12V 6W solenoid via a relay. Both the IC and the solenoid are run off of 12V, but every ...
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61 views

Monostable and astable on breadboard

I am trying to fit all three modes on of 555 timer on a breadboard. But no matter what I do I am not able to get it to work on a single breadboard. When I move the circuits on different breadboards ...
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79 views

7555 monostable timer not resetting

I'm using a 7555 timer in monostable configuration to control a load of about 1A. If I disconnect the 1A load or use a bench supply it works fine, but the drop in voltage from the batteries seems to ...
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74 views

555 Timer Output Always V+ or Ground?

If the output of the 555 timer is not trigger to high, is it ground? Or is the output left floating?
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122 views

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

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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2answers
3k 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. ...
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2answers
57 views

Small ripple in 555 timer output when connected with a 2nd 555 timer chip

I have two 555 timer chips. The 1st is used to create a transition every .1 seconds while the 2nd is used in a monostable configuration to debounce a button. When using my DLA to look at the output ...
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1answer
82 views

Using the same potentiometer for two 555 timers

simulate this circuit – Schematic created using CircuitLab I have two 555 timers hooked up and I want them their duty cycle to be controlled by the same potentiometer. The second one has twice ...
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3answers
113 views

Why won't this 555 timer flashing circuit work?

The circuit which I made shows the following behavior, when power is given to the circuit: Sometimes it lights up, sometimes it doesn't. When it does light up, it flashes properly for a few seconds ...
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297 views

How can I use the component CD4538 or a 555 timer on Multisim?

How can I use the component CD4538 or a 555 timer on Multisim for a delay of 1 second ? I want both of the nor gates to be 1 for roughly 1 second when the output of the op-amps is either 01 or 10.
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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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1k views

How to build a circuit that generates a sine wave?

How can I build a circuit to generate sine waves? What I am working on is building a 555-timer circuit that gives 50% duty cycle square wave, then using a low-pass or band-pass filter tuned to the ...
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54 views

PWM with 555 timer IC

I am trying to build a PWM signal with 555 timer. I am following this website to build my circuit. simulate this circuit – Schematic created using CircuitLab I have placed my components in my ...
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1answer
150 views

Low cost PWM sweep

I have this project where I need to try and get a PWM duty sweep starting at around 30% up to 100%. The issue I have is that we don't have anything left in the design (BOM Cost). I would normally use ...
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2answers
108 views

Boost converter based on 555 timer not working

I tried to make a simple boost converter circuit for driving an LED using 555 timer IC, but somehow the output voltage is not increased at all. I suppose that the problem is the inductor I used, since ...
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1answer
184 views

555 pump controller not triggering

I built this 555 pump controller and it works correctly if I short the wires, however, when trying to use the electrodes in water it doesn't do anything. I am using a 12V 1A power supply so I don't ...
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1answer
89 views

Simulated 555 timer not working

https://www.tinkercad.com/things/2CN1eOTbmTe I am a beginner in electronics. I've been trying to make an astable 555 Timer in TinkerCAD as an oscillator for my own project of making a clock, without ...
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1answer
111 views

Designing a circuit with a “short-lived” switch with 555 IC

i am very new to electrical engineering and designing circuits and there is a particular project that i am working on that involves using a switch and a 555IC timer. So basically my desired output ...
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29 views

Total Power Cutoff circuit

I'm designing a battery controlled circuit using a 555 timer to control a mosfet to provide power to a load. The problem I'm trying to solve is to reduce the current draw while the circuit is not ...
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46 views

Wireless power transfer circuit to attain ~5W of power on the receiving end

I am designing a WPT system to run a ws1812 based pixel chain. The ws2812 pixel chain runs on 5v and consumes 500-800ma of power, means 2.5w-4w. The system I made is not able to transfer adequate ...
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53 views

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 ...
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49 views

Backup PWM signal for DC fans

Currently, I have a board that powers 4 DC fans. A PWM signal is received from an external microcontroller to control the fan speeds. Unfortunately, the microcontroller sometimes fails to send the PWM ...
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1answer
49 views

Simulation behaves differently in Proteus vs Icircuit

I'm an electrical engineer student and I'm trying to make an LED Flasher circuit using a 555 Timer. When I simulated the circuit in Proteus simulator, it's not working! But in Icircuit simulator it ...
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128 views

LM555 timers for control of a secure door

I will explain existing hardware followed by my desired operation thereof. I have a security door the controller of which has failed. The door has four electronic deadbolts. -- A) Two open ...
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3answers
260 views

555 timer not switching at threshold voltage

This is a 555 timer circuit which is supposed to generate two short pulses, back to back, at a regular frequency. The top 555 is configured as astable to control the frequency. It feeds the first 555 ...
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49 views

Comparing the results of two electronic dice

I made two electronic circuits each consisting of a 555 Timer, a CD4017 and 7 leds in the shape of what you'd find on a dice. They work great and all, but I want to "compare" the results of both and ...
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112 views

555 timer to drive transistors with low load resistance

Recently, I have a project that needs to heat up a metal filament with a single pulse voltage. I built a circuit with 555 timer and transistors to heat up the metal filament(0.2 ohm). The circuit ...
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103 views

Capacitor charging voltage showing ripples on scope. Origin?

I have an RC circuit delivering a square signal via a standard 555 timer set in monostable. I am powering the 555 with 4.88V DC directly from the Arduino, which itself is taking its power from the ...
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181 views

Latching switch to single pulse circuit? (monostable multivibrator with 555?)

I am looking at using a latching switch (SPDT) to momentarily connect two pins. This is for a power button for a raspberry pi, so to power the machine from a hold state you have to momentarily short ...
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113 views

555 as slow PWM driver

I would like a slow PWM output, driving a relay turning an AC heating element on and off. I desire a period time of around 10s. What is a realistic upper period time limit for a PWM circuit like the ...
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1answer
31 views

Time step Error In Multisim Using 555 timer

I am trying to simulate a circuit in multisim and I keep running into the following error. (new to multisim) I attached a picture of the circuit and error. Any advice on how to fix this? The purpose ...
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59 views

Back EMF protection

I made an ignition coil driver circuit which is nothing special - they are everywhere on the internet. What's really bothering me is the back EMF that would fry the 555IC. If I put a rectifying ...
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5k 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 ...
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4k views

Maximum Current Input for 555

I was looking over a datasheet for the NE555 Timer and I was wondering if the max supply current given under the electrical characteristics page is the max current you can supply to the 555 without ...
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123 views

Core rope rom not working

I am trying to make my own core rope rom, according to the link. I have 15mm ferrite cores, which I wound about 30 times with 1mm magnet wire. I thread the primary ( also 1mm wire) through one of ...
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59 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 ...
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120 views

555 square wave generation with frequency feedback

Knowing that 555's behaviour varies according to temperature, I wondered: In an astable configuration, is there some way to measure output frequency, compare it with some desired value, and use this ...