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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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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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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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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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375 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, ...
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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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35 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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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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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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36 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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94 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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29 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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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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83 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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53 views

voltage traces across pwm driven dc-motor: is that ok?

I'm driving a dc-motor with a BJT turned on and off with a 555 generated PWM signal. Here's the circuit (V1, Rl and L1 simulate the motor): There actual circuit - same parts - is on a breadboard and ...
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54 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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67 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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171 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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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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92 views

555 timer circuit switching automotive solenoid with PNP & NPN switching transistors

I am trying to design a 30 second timer circuit to switch an automotive solenoid that draws about 0.8 amps, and need some help please. StackExchange posts have been very very helpful so far, and by ...
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143 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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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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54 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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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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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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63 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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44 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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37 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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Confusion with 555 transistor relay driver

This is probably schoolboy stuff, but before I construct it ... A 555 will output almost the supply rail, or down to zero. A transistor attached to that, with a relay on collector can drive a 12v ...
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56 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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43 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'...
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40 views

Inverted 555 Monostable Timer With a Sustained Input

I am using a 555 Timer to control a motor for a science team project. I have to make a Rube Goldberg-like machine and I am not allowed to use Arduinos or Raspberry Pis. However I need to trigger the ...
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82 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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85 views

555 Timer Giving Unexpected Output (Astable Multivibrator)

I am using this design with the only exception that C2 is 150nF to change timing slightly. When I plug in the circuit and attach an LED across GND and pin 3 output the LED is static on. However, on ...
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88 views

Swapping two 500kohm pots with one MCP42010 10k ohm digital pot

What additional elements do I need in my circuit to compensate for changing a pair of manual 500k ohm pots to a pair of digital 10 ohms? I'm a beginner implementing an Atari Punk Console on Raspberry ...
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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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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-...
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135 views

555 Timer Stops working after a few seconds

I'm building a LED dimmer using a 555 timer (yeah, lame I know). I'm using it to produce photographic flat frames which require perfect illuminated fields even with shutter speeds as low as 1/1000 of ...
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76 views

Self cancelling indicator project. Help needed

I am embarking on a new project to design a circuit for an automatic vehicle signal actuator. Outline of the project is this: The problem: I have a car that has indicators operating on a standard ...
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72 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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118 views

Astable 555 timer circuit that resets on a heartbeat

I'm trying to design a circuit that will reset my ESP8266 when it crashes/hangs. It does this by sending a heartbeat to a 555 timer every minute which resets the 555 timer. The 555 timer is configured ...
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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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1answer
72 views

Pausing a clock signal generated by 555 timer

I am planning to make a simple integer adder/multiplier which needs a variable frequency, comparatively slow clock (around 1 to 200 Hz) for demonstration purposes. I used the following generic 555 ...
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85 views

What is the purpose of the resistor between the Vcc and discharge pins in the astable 555 timer?

In a standard astable configuration of the 555 timer, we have two resistors R1 and R2. The capacitor charges through both resistors but only discharges through R2, consequently, the high interval is ...
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63 views

IRFZ34N doesn´t switch on when a NE555 timer pulse is applied

simulate this circuit – Schematic created using CircuitLab I have the above circuit in my breadboard. The problem in a nutshell is that when the NE555 timer is switching at 50kHz in astable ...
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63 views

Shift register led display not working?

I am very new to circuitry and have attempted to make a circuit (only using IC's) which displays 0's and 1's from the shift register as LED's either on or off, and through the use of a 555 timer shift ...
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57 views

Bistable and astable 555 IC interfere with each other

I am currently toying around with electronics and read Make:Electronics which is a very fun book. In one experiment (19) I came to a deviation in behaviour of my circuit compared to the expected ...
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123 views

Driving LED with 555 timer and BC639 transistor

I am trying to produce an LED dimmer circuit using a 555 timer circuit and a BC639 NPN transistor. I know there are better transistors that would suit the task better, but the BC639 is what I have to ...
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49 views

Why is the potentiometer setup in this configuration in this 555 circuit

I just started learning about chips and signals using the book Make: Electronics, in one of the circuits, used to generate a pulse in Monostable mode a potentiometer is used to vary the pulse length....
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121 views

How can I use a voltage to control the pulse width of a 555?

I have a variable PWM signal at 13.2 kHz. I want to control a servo with this signal, but the servo needs a much lower frequency, at most 80 Hz. My first idea was to use two binary counters, a NOT ...
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73 views

How to turn off 555 Timer for a period of time after Vout signal passes through

I have a single-shot 555 Timer. After triggering, output goes high for a period of time. What I would like to do now: After Vout goes high and then low again, I want to disable the 555 timer for a ...