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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Floating charge pump for high side N-channel MOSFET bias

This question is derived from this one. I'd like to keep gate on for an indefinite period of time (100% Duty cycle) and for that I'd like to use charge pump since idea with relay is not attractive. ...
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2answers
228 views

Is this 12 volt LED circuit correct?

I found this "Plant Grow LED light" circuit on the Internet and I wanted to know if: (Please don't feel pressured to answer all my questions. You can just answer a few only if you like.) this is ...
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3answers
118 views

wiring 555 to disconnect itself from electricity

i had idea for a circuit with 555 and here is the IDEA: circuit is stationary somewhere, it is in "passive state" meaning its drawing no current from battery and pin 3 is set low, then someone comes ...
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81 views

Slightly weird astable oscillator in a 555, where does this capacitor discharge to?

In the 555 datasheet, the cap is usually connected to pin 7 (discharge), but in this circuit, it's not: When the capacitor voltage is >2/3Vcc, output will turn off and current will have no where to ...
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158 views

Modifications to 555 LED Fade Circuit

I was looking for a circuit to fade an LED on and off using no microcontrollers, and found this nice circuit: http://www.555-timer-circuits.com/up-down-fading-led.html it seems like exactly what I ...
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73 views

Boost converter simulation keeps getting fried

In my project I want to use a couple of old russian VFDs. To drive them, I need 28V from a 12V power supply. The plan is to use a DC-DC boost converter as calculated here and here. I've ported the ...
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1answer
59 views

NE555 Timer Problem

I need help using an NE555 timer to flash an LED. Here is my current set up: All resistors are 220 Ohms and LED is link The capacitor is 10uf and same result happens with 1uf. I am using a 9V ...
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195 views

555 timer one-shot 30 second light LED strip, TOTALLY CONFUSED!

I'm working on a personal project and I am at my absolute whits end here. I have a configurable N.O. or N.C. switch (nteinc Magnetic Alarm Reed Switch) so I'm not too concerned with which way I use ...
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1answer
60 views

I need help in starting this 7segment from 0

I am making a control system as my project. Here i have used 2 555 timers one in monostable and the other sin astable. The monostable outputs when process one button is pushed and this also triggers ...
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1answer
31 views

Running a 12VDC motor for adjustable interval

I want to set up a timer circuit that will run a high-torque, low RPM 12VDC motor (max 200mA) for an adjustable amount of time. This motor drives an auger in a home designed pet feeder and I need to ...
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2answers
87 views

555 timer ciruit errors

I have set up a 555 Timer circuit on my breadboard following this diagram. These are the values I use: R1: 1k R2: 1k C: 0.1uf Vcc: 9V The only problem is, on pin 5, I have a 0.001uf capacitor. ...
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4answers
103 views

Any reason I cannot just switch a transformer from a 555 to generate high voltages?

I had an idea to finally start using my nixie tubes and thought why not just switch a mosfet which switches a transformer to generate required high voltages for nixie tubes from a low voltage supply. ...
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76 views

How is 555 astable timing affected by a resistor on Vcc

I am trying to build a circuit that will plug in to a cell phone and let me read the value of a thermistor by generating a tone to the microphone, where the frequency is a function of the thermistor's ...
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2answers
56 views

Choosing resistor values for a 555 timer

I have to design a frequency counter using a 555 timer as a pulse generator. I included a schematic for part of the circuit, but this is my first time using a 555, so I also included the original ...
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2answers
72 views

Can you set up a monostable 555 timer so it reverses the output?

I would like to make an alarm that goes off about 1 minute after it has been triggered. To do this, I want to delay the circuit using a 555 timer in monostable, but I can't do this as they turn it on ...
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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?
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2answers
95 views

555 Timer Monostable Mode Self Triggering

I'm working on a simple project with 555 timer. I'm trying to generate a high-state output for 10s when Vcc is applied to the circuit(It is initially off). However, I have not managed to operate the ...
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1answer
91 views

using one 555 timer to control the pulse of another

tried making something like this Limit Number Of Pulses From 555 Or Similar but it doesn't work. I'm not sure what it needs. I'm trying to make the first timer put out voltage to the second one for ...
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1answer
94 views

Can I make a step up transformer using these components?

I have a step down transformer that converts from 220 volt to 15 volt. I want to connect the secondary coil of this transformer to the output of 555 IC that produces ( 5 volt / 100 KHz ). Is there ...
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1answer
98 views

Where does the current in a Dickson Charge Pump come from? Does the oscillator/PWM pin of a microcontroller also source current?

Well, I am making a small circuit which looks like this: When simulated, the load current gets up to about 200-280 mA no problem, so I want to implement this circuit in real life. My only problem ...
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0answers
69 views

555 timing formula when the diode forward voltage drop is not neglected

(Image Sources) In this modified astable multivibrator circuit the forward voltage drop of the diode D1 is always ignored, and the timing formulas are given as $$ t_1 = \ln(2)R_1C_1, \quad t_2 = ...
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0answers
52 views

monostable 555 current is bleeding, battery dies

This is likely an obvious question to an electrical expert, but I am only doing my best. My monostable 555 project is currently working: when triggered, an LED gets 5V and stays on for 5 minutes. ...
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79 views

I guarantee this one will be fun - Need help putting several circuits together into one

So I did my best to annotate the schematic with what I'm trying to do. Where I'm really running into trouble is past the output of the 555. This is basically a control circuit for a camera's ...
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4answers
1k 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 ...
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2answers
256 views

Why does this circuit keep killing my 555 timers?

I have a 555 timer set up in a standard monostable oscillator configuration. Nothing fancy, no modifications whatsoever. I'm driving it with about 12V. If I trigger the 555 with the ground directly, ...
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1answer
66 views

Analog PWM generator from 0%

I have to prepare easy analog PWM regulator which can operate from 0% (0V). I know that one 555 can't do that... Do you know any circuit that can handle that?
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1answer
197 views

Generate PWM signal based on 555 for Meanwell LDD driver

I am using a Meanwell Led Driver LDD-1000H. It has a single pin for PWM input for dimming. I have seen many sketches using the 555 to dim a LED but in these cases the LED was part of the circuit. How ...
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3answers
127 views

Need help with an LED flash circuit

I joined just because I'm having sort of a dilemma. I need to design a flash circuit for a tiny SMD based project, and I have a way of doing it, but I want to see if I can make it better and I haven't ...
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2answers
316 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 ...
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179 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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330 views

Use 555 for additional 40KHz PWM in Arduino

I need to transmit infra red signals using IR LED from my Arduino device. The IR signals consist of PWM 40 kHz periods and "silence" periods of various length (typical IR remote signals). I know ...
2
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1answer
115 views

Monostable and Astable 555 Timer

To begin with, I must say this is kind of a "homework" but I tried to do it on my own and I haven't succeed maybe someone can help me out with this matter. We're learning about digital systems, ...
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1answer
77 views

Count number of hours elapsed

It's been a long while since I played with circuits, I'd appreciate a sanity check of the following design; I'm trying to count the number of hours since the reset button was last pressed. Ideally ...
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1answer
133 views

555 timer as a humidity sensor

I want to use a 555 timer to measure humidity using a humidity dependent capacitor which goes from about 300-> 400 pF. This makes the frequency way to high for me to measure. Is there some similar ...
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2answers
272 views

555 as a Schmitt Trigger and an ON delay timer?

I've scoured the internet trying to find this out to no avail. I would like to use a 555 timer to produce a Schmitt trigger with an ON delay of 20-30 seconds. Is this possible? Or will I have to use ...
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1answer
147 views

555 timer flashing led circuit

I just have a question about this simple circuit or example: http://www.555-timer-circuits.com/flashing-led.html. I just don't get 1) why do they use 9V battery to power a single red LED light. 2) why ...
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4answers
332 views

I just fried a 555 timer IC and I'm trying to figure out how

I'm very new and just fried my first ic, trying to learn a lesson from it. Here's what I was building: (also here) on the 6v in I used 6 AA batteries that were reading about 7.5v on my meter, was ...
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4answers
347 views

Steering Diodes

What are the "steering diodes" next to the pot for? Source: http://www.youtube.com/watch?v=OXsu29K_Ap4
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3answers
456 views

How to make 7-segment display count up ?

I've connect 7447 decoder and 74193 counter as shown in the picture but I have not used 555 timer yet. Is there any way to test the circuit before using 555 ? I've connected the pins (up and down) ...
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1answer
116 views

How do I enable/disable a running 555 astable oscillator with a control signal?

I am going to control a fan using PWM signal. PWM is generated by a 555 IC. The duty cycle rate of the PWM is controlled by a PTC thermistor. And an NTC thermistor decides when to turn on and off the ...
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2answers
160 views

How can I turn pulsating DC (square wave) from a 555 IC timer into an ac square wave?

I am trying to create build a morse code transmitter. I know that morse code is sent at 500 KHZ so I set my 555 to spit out pulsating DC in a square wave with 9 volt peaks. But I am unsure wether ...
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1answer
118 views

Problem in creating one-shot impulse circuit

I am a student in university and I have a problem to be solved. I have to design a circuit that gives just one pulse (not periodic signal) when the 220V source is active. I will give 220V to the ...
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4answers
1k views

How to get more current from 555 timer?

My power supply is filtered regulated 5 volt 500 mA . I am using a 555 in monostable mode to switch the motor on for a certain amount of time after the 555 is trigerred. (The 555 is being trigerred by ...
4
votes
2answers
279 views

CD4029 does not initialize at 0

I am attempting to build a very simple 4 bit counting machine using a CD4029 ic and a 555 timer. I have built my circuit on a breadboard and everything seems to be working perfectly, however on the ...
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1answer
1k views

How to build a blinking 12V indicator LED light

I attempt to build a blinking circuit using 12V truck light ( like this one: http://www.princessauto.com/pal/en/Tail-Lights/4-in-LED-Stop-Turn-Tail-Light/8126047.p). I have try to build a single LED ...
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0answers
105 views

How to combine a 555 timer and an MC34063

So, I've been at a project for a couple of weeks now, far too long in my opinion. I'm coming down to the final push and my last obstacle is to connect two circuits together to make a Piezo transducer ...
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2answers
68 views

555 delayed after threshold goes above control voltage

I am messing around with some 555s I bought a while back (NE555N from STMicroelectronics) and I'm getting some unexpected behavior. I have a capacitor hooked up to both the trigger and threshold pins ...
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1answer
60 views

555 servo controller “modulation input”?

Exactly as the question says. On the TI 555 Rev. C data sheet, what is the modulation input for the PWM circuit? Also, can I round the resistor and cap. to 10k and .022uf, respectively?
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2answers
1k views

Simple methods for switching a boost converter, to get a stable output voltage?

I've made a boost converter circuit, with a MOSFET as a switch, and a (7)555 timer operating as an astable oscillator, and it's output goes directly to the MOSFETs gate pin. The problem is that the ...
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2answers
205 views

How long will this low duty 555 LED blinker last on batteries?

I know there are many questions about LED blinkers, but I haven't yet found a clear answer for this. I have a 555 circuit blinking a blue led (or three in parallel). I has a low duty cycle (using a ...