We’re rewarding the question askers & reputations are being recalculated! Read more.

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.

Filter by
Sorted by
Tagged with
22
votes
4answers
2k views

Do engineers still design for volume using discrete through-hole bipolar transistors?

As a hobbyist who likes plugging BJTs and discrete components into solderless breadboard for entertainment and education, I recognise that people like me are an insufficient market to make it ...
22
votes
5answers
2k views

Astable 555 circuit not oscillating

I'm a complete beginner to electronics, but I'm trying to follow Ben Eaters video series "Building an 8-bit computer". I tried to do the first part of an astable 555 timer, but the LED does not ...
21
votes
6answers
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 ...
17
votes
4answers
4k views

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?
12
votes
3answers
4k views

Why 555 timer IC has three 5k resistances and not any other values?

Why does 555 timer IC has three 5k resistors and not other values, like 10k-10k-10k or something else?
10
votes
4answers
12k views

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 ...
9
votes
3answers
4k views

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
9
votes
4answers
2k views

Super Duper Vdd stiffening required on 555 timer, what is the best way?

I am using a 555 timer for a (16bit) frequency sensor/counter. It works by counting the number of pulses read in the 125ms sample time set by a 555 timer; resets & repeats... I am using the ...
9
votes
5answers
1k views

What to make with hundreds of 555 chips [closed]

This is a little bit different question than normal.. Aliexpress is ruing my life, sometimes i order things i don't even need because it seems cool. A few time ago I ordered 500x 555 chips for just a ...
9
votes
2answers
715 views

Why doesn't this radio transmitter correctly transmit some songs?

I made transmitter from this question with some minor modifications (100 K pot for resistor between 8 and 7 and 22K for resistor between 7 and 6. 22 pF for the capacitor). Here's the picture: When ...
9
votes
2answers
782 views

Why does my 555 stop oscillating under load?

I've got a 555-timer circuit. When I examine the output-pin on an oscilloscope, I get a nice square wave. I want to turn an LED on and off, so I've attached an LED and resistor to the output pin (...
8
votes
2answers
3k 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 ...
8
votes
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 ...
8
votes
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 ...
8
votes
1answer
3k views

Which is better for the 555, a smaller capacitor or a larger one?

As I understand it, there are many ways to combine two resistors and a capacitor to give the same time characteristics in a astable 555 setup. My question is which is better, a larger capacitor or a ...
8
votes
1answer
1k views

Simon Says without Microcontroller

I'd like to create the classic game of Simon Says utilising nothing but logic circuits, LEDs and ICs, no Microcontrollers like the Arduino. I would like to use 4 LEDs and 4 Tactile Switches for this ...
8
votes
1answer
478 views

Cassette Input From TRS-80 - Design Review

I'm working on getting an input from a cassette for a TRS-80 microcomputer (of 70's vintage). This is what I've worked up. It is a second order high pass active filter with rolloff frequency of 2kHz ...
7
votes
6answers
637 views

Why can't my 555-based DC-DC boost converter supply even 3 milliamps at 12V?

I hope someone can help me. I've been tearing my hair out for the past couple of weeks trying to make a simple DC-DC boost circuit. It puts out a nice 12-ish volts when not loaded, but as soon as I ...
7
votes
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 ...
7
votes
2answers
1k views

555 saw tooth generator diodes purpose?

I'm given this 555 timer based monostable saw-tooth generator. This is a known arrangement for this part. The difference from other circuits I've seen is that the bias network of the external ...
7
votes
3answers
3k views

Problems with Atari Punk Console circuit

I am trying to build an APC using the following schematic: And the output is having some issues. Sound only comes out when the rightmost potentiometer is at 0 resistance, and in that position the ...
7
votes
2answers
744 views

Trouble getting 555 timer IC circuit to work properly (Make Electronics Book Experiment 18)

I am currently reading a book titled “Make: Electronics”. This is an electronics book whose target audience is supposed to be complete beginners. One of the book exercises (Experiment 18) includes a ...
7
votes
3answers
820 views

Detecting sparks at the output of a high voltage flyback transformer

I was trying to generate plasma inside a cylinder for a hobby project, so I decided to use a flyback transformer from an old TV and drive it with a 555 timer as shown in the schematics. It solves my ...
7
votes
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 ...
6
votes
5answers
2k views

How do I mix two audio tones from two 555s to make a polyphonic chord?

I have set up two 555 chips in astable mode to produce a tone each through a speaker. However, I am not sure how to mix them together to produce a musical chord. If I directly combine the two ...
6
votes
5answers
7k views

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 ...
6
votes
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 "...
6
votes
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 ...
6
votes
9answers
28k views

Astable 555 timing circuit (0.5 Hz and 50% duty cycle)

I am trying to build a timing circuit to generate a 0.5 Hz 50% duty cycle signal. In other words 1 second on, 1 second off, and so on... I have searched a few places and found the following ...
6
votes
2answers
4k views

How can I prevent a 556 timer IC from becoming very hot?

I built the circuit described in a previous question/answer which I will repost here: It's been running quite well, actuating the solenoid at regular intervals as designed. The TIP122 transistor is ...
6
votes
4answers
2k views

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 ...
6
votes
1answer
1k views

LED driver circuit interfering with 555 timer?

Below is a circuit I put together that uses a 555 timer and an LED Driver: But the strange thing I see is that the timer does not follow the 1.1*R*C equation. The led remains lit for much longer. I ...
6
votes
2answers
2k views

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 ...
6
votes
1answer
3k views

Ramp generator using 555 timer

I want to use a 555 timer to generate a ramp to my soft starter. The problem is, I want it to be continuous after reaching it's value. Unlike this shown below, Instead of discharging I want it to ...
5
votes
4answers
2k views

Is there a small (6-pin) DIP I can use to generate multi-MHz squarewave clocks with an external crystal?

I'm building a circuit that I'd like to run at 8 MHz to begin with, but I want to be able to try it out at 10, 12, 16, 20, and, maybe, 25 MHz. I know that many microcontrollers have the ability to ...
5
votes
6answers
2k views

555 timer FM transmitter

So online, I found this 555 timer FM modulator circuit. But To make this a working FM transmitter, is all I have to do is attach an antenna to the output modulated signal? Or do I have to also have a ...
5
votes
3answers
10k views

What are the disadvantages of using a 555 timer as a resistance to frequency converter?

Since we know that a 555 timer configured as an astable multivibrator depends on the resistance the timing capacitor sees, what stops people from using a 555 as an ohmmeter? How does the accuracy ...
5
votes
3answers
2k views

Creating positive and negative voltages from a battery

I have a circuit that is usually powered by +9V and -9V (uses two 9 volt batteries), but I am trying to power this from a rechargeable 3.7 V battery. The circuit does not draw much power (can be ...
5
votes
1answer
3k views

How long can a 555 be run on a 9V battery?

Is there a way to figure how long can a 555 run on battery, when reset is grounded, to have no output?
5
votes
4answers
2k views

basic arduino question - do I need a 555 timer?

I have an Arduino (duemilanove) connected to a floppy disk drive and I can happily control the stepper motor using three pins on the ribbon cable to three digital pins of my Arduino (well 2 + the ...
5
votes
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 ...
5
votes
2answers
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 ...
5
votes
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 ...
5
votes
4answers
677 views

How can I generate a logic pulse from a broken IR beam?

I would like to trigger a [7]555 timer when a phototransistor stops receiving light from an IR led, more precisely when the (expected to be smallish) signal from the light-sensitive voltage divider, ...
5
votes
5answers
511 views

Can someone check over my schematic?

This is the first schematic I have made that was not a simple LED. I want to know if it seems good before I go and build it (and buy the parts). Here is the schematic: Here are a few of my concerns: ...
5
votes
1answer
5k views

Difference between NE555P and 555CN?

I'm working on a circuit that uses two 555 timers. At the electronics store, they gave me a handful of 555 chips, I only noticed the difference when I finished my circuit: the R1 value is shorted out, ...
5
votes
3answers
1k views

Using timer to power on/off a high current circuit

I'm working on a Arduino project that takes measurements from the environment and sends them to a remote server over WiFi. The circuit should be battery powered and I've measured that what I have at ...
5
votes
1answer
3k views

How to prevent 555 timer interference

I made a triple PWM motor controller with a 555 timer hooked up to 3 IRF621 MOSFETS to the motors. I am having interference troubles. When I turn one knob up, the other motor wants to change speed a ...
5
votes
1answer
397 views

555 trigger frequency signal

So, I'm remembering that back in school, I managed to make a 555 signal create a tone signal, and that another 555 could trigger the 555, such that I had a variable toned signal that could be pulsed. ...
5
votes
3answers
759 views

single-capacitor oscillator choice for digital theremin

Intro One of the pupils puzzled me with a question of building a theremin - a basic musical instrument which has a pitch manipulated by moving the hand around the vertical antenna. Due to specifics ...