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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2answers
191 views

What is incorrect with my 555 LED flasher circuit?

I have built a circuit to flash an LED using a 555 timer IC, but it doesn't flash... the LED just stays on steadily. -- I carefully followed the instructions on a common tutorial, which is: http://...
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9answers
4k views

How do I produce a 1Hz clock output using a 555 timer IC? Are there better ways other than a 555 timer IC?

I've been messing up with timer ICs, looked up on how they work and now I want to design a simple digital clock using a 1Hz pulse generator. Is a 555 timer IC sufficient enough to make accurate 1Hz ...
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2answers
5k views

Is there a way to control the PWM duty cycle of a 555 timer without using a variable resistor?

I need to control the duty cycle of a Pulse Width Modulation (PWM) circuit from a DC voltage input. To do this, I've been looking into 555-timer circuits - but every circuit I've come across involves ...
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1answer
115 views

Is there anything wrong with this particular timer circuit utilizing 555?

I created following simple timer circuit for one shot operation. My expectation is it to give 5v as output (for D RELAY and SP RELAY) for certain number of seconds/minutes soon as it got powered-on. ...
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2answers
594 views

555 timer circuit with d type flip-flop

Found this circuit for a 555 timer. I can't understand the use of the d-type flip-flop. Please explain.. And is the variable resistor used to adjust the frequency?
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1answer
89 views

Replace button by a component/circuit in 555 diagram

I need your help im crazy with this, i already tried many ways to do it, i need to replace the push button in this circuit by a component or circuit to be activated for a signal of 5 v such as a ...
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2answers
749 views

Replacing push button by transistor in 555 circuit

TL;DR: I need to replace the button S1 by a circuit/component that could close the circuit which the button is closing by applying a 5V signal (with 0.5s duration) in the new circuit/component. Well, ...
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1answer
207 views

What is the diode for in the astable IC 555

I am trying to get my head into electronics, so my teacher challenged me to find out what this diode does. I have done a ton of experiments and i just cant put my finger on it... Everything from ...
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1answer
248 views

12V variable-speed fan as a function of temperature using 555 timer

I would like to turn the car fan into a variable-speed fan using a the analog temperature sensor of the car, and a 555 timer. While temperature decreases, resistance (of the sensor) increases. Can I ...
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4answers
3k views

Resistance to Digital converter

I am trying to make a digital ohmmeter on a parallel port interface that can measure resistance with at least 95% accuracy. I have tried a 555 timer monostable assembly which generates a pulse with ...
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2answers
708 views

555 timing capacitor discharge via threshold input

The circuit below is the timing logic for the SC280 UV exposure unit. Based on my judgement the design of the circuit is poor - and I'm planning to replace it -, I'm posting my question only to learn ...
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7answers
4k views

Using microcontroller as oscillator for high voltage power suppy?

MightyOhm has designed a geiger counter which is here. I am not very clear but I think he is using the 555 timer as an oscillator in the high voltage power supply section. I've attached his schematic ...
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3answers
3k views

556 dual timer circuit not clear to me

I have the following question about a cascade 555 timer circuit. The thing what I do not understand in this schematic how the second input trigger (2) is triggered for low condition. I know that the ...
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1answer
447 views

7805 Voltage Regulator powering astable 555 Timer yields LOW voltage as input to timer circuit

Hello stack exchange, So, I have two batteries powering a circuit and I want to only use one. 12.7V comes from a lead acid battery, and the smaller one is a stack of 4xAA that yield around 6.4V. The ~...
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1answer
176 views

how can i add more leds to police light circuit?

This project uses a 555 timer and a 4017 decade to produce the flash police lights. This circuit has only 4 leds , 2 blue and 2 red. I want to connect in 16 leds ( 8 blue and 8 red ) is that ...
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1answer
261 views

Please critique my high-current voltage regulator [closed]

A project I'm working on requires a source of power which need to be both regulated (5.00V) and high current (~4A). An external power source may be any from 6V to 12V but it can be assumed that it can ...
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0answers
73 views

minimalistic digital 2-speed oscillator with 555

I'm trying to figure out how I can turn a schematic of a one-speed simple 555 astable multivibrator that's available everywhere on the internet to a digitally controlled astable multivibrator in which ...
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1answer
257 views

will this voltage tripler circuit work?

I need power supply for my opamp as i only have 5 volt supply. I need at least 14 volt power supply so that i can power my opamp. I recently got this circuit of voltage tripler using 555 IC. Will it ...
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1answer
717 views

Does the Low State in NE555 go to GND?

Here is the first schematic that I created : . The Vcc is at 5.1V and I a self made using the LM317, Works Fine. When I checked the Output with the Multi-meter I use., I was getting a high state of ...
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1answer
84 views

Discharge of capacitor bellow 0.5V

I have a conundrum that I am trying to solve and am afraid I am stuck. Could anyone share some insight please? My circuit is displayed on image above. 5V (5Vsw) and 3.3V (3V3sw) are used as supply ...
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3answers
121 views

Is the rise time of the output of a logic IC or optocoupler independent of the rise time of the input?

Is the rise time of the output of a logic IC (e.g. flip-flop or inverter) or optocoupler independent or dependent on the rise time of the input? If the answer is dependent, are there any other ...
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3answers
505 views

Installed 555 timer socket backwards - can I reverse the chip in the socket?

I installed the socket for a NE555 timer ic backwards on a PCB. Can I just reverse the chip in the socket to cure the mistake?
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1answer
498 views

General circuit debugging techniques, and my 555 timer in particular

I am looking for help in two ways: learning general techniques for debugging circuits that do not work figuring out why this circuit in particular is not working The circuit is a timer that runs for ...
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2answers
483 views

How does this circuit work to fade an LED in and out?

I'm new to electronics. I'm trying to figure out how this circuit works to fade the LED light in and out: This is how I think it works (of course, I'm wrong): When you initially connect the circuit, ...
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3answers
1k views

On— off— on— off timer circuit

I want to make a circuit to do something that is relatively simple but I need to find the optimal way to do it in order to take as little current as possible. Here is what I want to do: When a ...
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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 ...
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4answers
4k views

555 Schmitt Trigger works well with CMOS LMC but not NE555?

I have an NE555 (the non-CMOS version) running in astable mode at 118Khz. I have the output pin3 connected to input for a second 555 running as a Schmitt Trigger to invert the signal. What I found is ...
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1answer
629 views

Very Basic 555 Timer oscillator not working

I've been trying to make an LED blink. My first approaches were without the 555 timer, and they were unsuccessful. I decided to make an Astable multivibrator circuit. I'm using an NE555, and I'm using ...
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2answers
194 views

Low power delayed off circuit

I am running into problems creating a circuit that once a button is pressed ( clicked ) will latch and run for a few seconds and then turn it self off. This would be trivial with a MCU but now I am ...
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3answers
411 views

How to check for quick oscillations without an oscilloscope

I'm working on a 555 timer oscillator circuit, and I'm trying to get an LED to blink. The LED turns on, but I'm not sure if it's blinking. I do not own an oscilloscope I've tried a few things, such as ...
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2answers
320 views

With a 555 + 4017, how do I light 7 LEDs, then 6, then 5… then 1 then 0?

I'm in the process of turning a Raspberry Pi project into a simpler circuit board powered with 555 and 4017 chips. I want to be able to start by showing 7 LEDs, then go to 6 then to 5 and so on until ...
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1answer
395 views

How to drive a 555 timer with pwm input?

I'd like to create a square wave generator with variable frequency that is determined by the presence of a 0-5 volt input signal. I have a very sketchy understanding of electronics - but I know what ...
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1answer
179 views

555 - HIGH then long delay [duplicate]

I trying to create a circuit with only one 555 to send HIGH on output(3) for very short time, like 200ms, then set LOW for something like 20~30 seconds. Then I'm just need turn on circuit, then: a) ...
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3answers
1k views

Simple analogue=>pwm circuit with inverting and noninverting outputs

I was interested in making an analogue to pwm circuit. I want to feed the output to a differential amplifier that will then drive the gates of transistors. The differential amplifier==>isolation ...
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0answers
197 views

Transistor for 38kHz IR pulse amplification

I am trying to build a timer circuit in which I will send a modulated 38kHz (almost) signal to an IR Receiver (TSOP38238 in Arduino Nano) and I want to amplify the square wave to the IR Led to ...
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1answer
456 views

Creating stepper motor driver using only TTL ICs [closed]

I am trying to drive a 5-wire unipolar stepper motor WITHOUT a microcontroller or driver ic, just using logic gates and JK flip flops (74LS107N's). The motor shaft needs to rotate a certain number of ...
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1answer
44 views

Timer with fixed input [duplicate]

I'm using a lm555 IC in monostable mode. When my input varies from 5v to 0v the output goes from 0v to 5v. But this only happens perfectly if it happens just a pulse at the entrance, in case my input ...
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1answer
462 views

How do I drive pin 2 on my 555 IC low so the one-shot timer will fire, using an IR sensor in place of my pushbutton switch?

I have a basic one-shot timer circuit (shown below in schematic). If I press the button, it brings pin 2 low and triggers the timer one time for a period which with my cap is about 5 seconds. Use IR ...
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1answer
127 views

Relay sending too many signals.

I have a 555 timer clk output going to the coil of a relay. 5volts going throw the contact. The 5volts is then going to the clock bit of a CD4026 then to a 7 segment display, Seems the relay is ...
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1answer
87 views

Keeping a PIR on all the time

I've just moved to a student accommodation,and they are using sensors to keep the lights in the room on(I'm almost sure that they are PIR). The problem is that they turn off way too quickly and it's ...
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2answers
655 views

What is the simplest possible monostable 555 timer circuit?

Say for instance, the goal is to light an incandescent bulb for x amount of seconds (let's say 20). What is the simplest configuration possible? Of course, simple timer circuits aren't rare, and can ...
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2answers
444 views

How to fade LEDs switched by a 555 timer when supply is cut

Based on the well-known Inventable.eu article, I combined their CMOS timer PWM with adjustable duty cycle with logic that switches the supply to the timer circuit. Only when the gate conditions (AND; ...
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2answers
699 views

How to stop a 555 timer [closed]

I have a 555 timer set up so each cycle it will count up a 7 segment display. clock output of 555 goes to a CD4026B clock input , this feeds the 7 seg display. I would like when the 7-segment ...
2
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1answer
416 views

PWM of Diaphragm pump

I'm pretty new in this area so sorry if this question seems foolish. I have a 12V 20Lpm Diaphragm pump that draws around 18 Amps. I'm using it on a home built herbicide spray system to help deal ...
2
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1answer
336 views

Power & Reset in momentary switch in analog circuit

So I am designing a circuit and wanted to implement both power and reset in one momentary switch. What I mean is, if the switch is pressed, it sends a reset signal (4.5v), but if it is held for x ...
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0answers
136 views

Can I control the charge of a Cell-Phone with a 555 Timer and a Transistor?

I want to charge my phone in a controllable manner, using a 555 and a Mosfet transistor. The 555 is a countdown timer that gives an output (pin 3) of 5V for 1 minute, and then remains at 0V until an ...
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1answer
318 views

Q: Can I use the LM3914 voltage indicator IC as a low-voltage cutoff device?

I came across these two circuits, and tried them out successfully: LM3914 Battery Monitor, drives 10 LEDs in a linear relation to the input voltage. NE555 Low-Voltage Cutoff, uses a 555 timer to ...
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1answer
639 views

Building a 555 timer's SR Flip Flop using Op Amps

How can I build a SR flip flop using op amps? (for a hand made 555 timer) Transistors may be used. I was thinking of using a hysteric op-amp and putting a schmitt trigger on the input of comparator 2. ...
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2answers
240 views

Using a lower pot value for motor bidirectional controller

I'm looking to make a bidirectional motor controller. I would like to use the following diagram. What values should the resistors be in order to use pot(S) of smaller value than 100k and the circuit ...
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2answers
202 views

IR Barrier with a 555 [closed]

I'm trying to build an IR Barrier with an 555, a sfh4547 and a tssp58038. Here are the datasheets: http://www.ti.com/lit/ds/symlink/ne555.pdf https://www.osram-os.com/Graphics/XPic0/00209793_0.pdf/...