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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458 views

555 timer confusion [closed]

On the 555 we have pin 6,2,3 with opamps but no feedback other than ground so I wonder how this can be connected at work OK because I see on Wikipedia it has 25 transistors but only 8 pins so maybe ...
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General PSpice and 555 timer question regarding precision

I have been experimenting with values recorded using a multimeter versus the voltages (RMS) simulated using capture. I simultaneously setup a circuit using a breadboard and drew exactly the same ...
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1answer
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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 ...
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1answer
221 views

Using a soundswitch to activate a relay

I'd like as an end state of my project for sound to activate a relay and then either a) the relay to stay on for a limited amount of time (~15 seconds) or b) ideally - the relay to be triggered off ...
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1answer
2k views

Why is the output from this astable 555 the reverse of it's simulation?

The simulator in LTSpice looked OK ... so I moved to the breadboard with an LED (eventually replaced the LED with a buzzer) at pin 3. One more difference in the assembled circuit is the condenser at ...
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3answers
359 views

Trigger Monostable 555 When Capacitor Raises above 0.5 Volts

So I want to trigger a monostable 555 to fire when a capacitor raises above 0.5 volts. My plan was to use a Zener diode to bias an NPN transistor that would trigger the 555. But I discovered the ...
4
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2answers
286 views

How to use the same switch to control LED and vary resistance?

I am struck with a simple board design problem. The requirements are : I have a 4 position slide switch according to the position of the slide switch, I should turn on different colored LEDs and also ...
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1answer
4k views

Invert a 555 Astable Output Signal

I can't believe how much trouble I've had figuring out how to do such a simple thing. I have a variable frequency, variably duty cycle 555 configuration in astable mode. I'm using a set of pots to ...
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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 ...
2
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1answer
1k views

555 Monostable Timer delay

I have built numerous 555 circuits over the years. I recently had to built a Monostable 555 cct. as per this site : http://www.allaboutcircuits.com/vol_6/chpt_8/4.html The cct. is used in a motor ...
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1answer
355 views

555 timer monostable time constants

When making an monostable circuit with a 555 timber, the time that pin 3 is on is calculated using this: time on = 1.1 x R1 x C1 My question is why is 1.1 included.
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3answers
656 views

Inexpensive programmable RGB LED driver/IC/solution?

My desire is to have a simple setup with a dial device (ideal would be a 3 click dial with 3 distinct settings but an analog dial would also be appropriate) whereby position 1 would display a color (...
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1answer
2k views

555 timer astable time constants

When making an astable circuit with a 555 timber, the frequency of pin 3s pulse is calculated using this: f = 1.44 / (R1 + 2R2) x C My question is why is 1.44 included.
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2answers
398 views

Need second set of eyes on 555 50% duty cycle soldered protoboard

I'm a hobbyist trying to learn the basics of the 555 timer, and am working off of the 50% duty cycle circuit from the National Semiconductor data sheet for the 555 (PDF pg. 10 Fig. 14) and have ...
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2answers
5k views

What is the output voltage of this 555 timer high voltage circuit?

I'm trying to calculate the theoritical output voltage of the following 555 timer high voltage circuit. It claims to output up to ...
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784 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 (...
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2answers
4k views

Getting more amperage from a 555 output

I am working on making a drink mixer inspired by BAR2D2, I am using a gravity fed pump that is capable of running on a 9v battery. I am using a circuit with a 555 timer to control how long the pump ...
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2answers
3k views

NE555 load resistor?

I'm using 555 timer in astable mode. I've used Multisim to generate it ant this is what I've got: I'm little confised by the 100 ohms Rl resistor. Do I need it there ? If I do, why ? I've tried with ...
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4answers
444 views

I need help designing a very simple timer

I'm designing a very simple led light timer based on the Pomodoro time management technique. For those of you unfamiliar, you work for a set amount of time, take a short break, and repeat. My end ...
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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 ...
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2answers
692 views

what is 555 Timer? [closed]

what is timer 555 ?? can any one give me some links which talk about this topic ? or some references ? or texts ? how can we use this kind of timer ? how to create it ? any information will be ...
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1answer
424 views

Should I expect my power line to be this noisy?

I'm building a circuit that contains a 555 timer wired to operate in monostable mode. In the final project, the trigger to the monostable will be driven at around 60Hz, with the output driving some ...
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3answers
710 views

Revolutions (pulse) per minute counter circuit?

Does anyone know how to set up a circuit by using counters, decoders, 7 segment displays and a 555 timer to show the revolutions (pulses) per minute from a photo-transistor? I'm doing this as part of ...
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2answers
941 views

How to mathematically determine the frequency of a tone based on components being used

My REAL question is how to choose the right components if you want a specific frequency spit out from a 555. In my particular case I want a potentiometer to control an output frequency from 16Hz to ...
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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 ...
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1answer
480 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 ...
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2answers
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How to convert voltage into digital signals?

How do I convert voltage into digital signals or pulses? For some reason I have to get voltage readings of the battery connected to the UPS of the computer systems. For that purpose I am designing a ...
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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 ...
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4answers
678 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, ...
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1answer
881 views

Replacing MOSFET with tube

I am working on making a flyback driver with a 555 timer. The only part I need is a MOSFET power transistor. I am wondering is it possible to substitute a triode vaccum tube (14GT8) for the MOSFET?
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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 ...
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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. ...
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1answer
6k views

Using a 555 instead of 7555

Im creating this circuit and it requires a 7555 timer. A 7555 timer is like the next generation 555 since it is CMOS. Now there are no 7555s or CMOS 555 in my area and was wondering what will happen ...
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2answers
691 views

Turning on and off car ignition - created two pulses?

I'm building a car DVR using a GoPro. The GoPro can be turned on by shorting out two pins on the gopro bus and then turned off by shorting out the same two pins. So when the car's ignition is turned ...
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1answer
811 views

“ATML U942”, is it a 555 clone?

Was looking for 555's in my parts box, and while I did find one NE555, I found a dozen of these, in the same pouch. Wondering if the seller pushed me some slugs, because I can't find datasheet for ...
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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 ...
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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
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1answer
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Losses in NE555 oscillator and Sallen-Key filter

I use a Sallen-Key bandpass filter in a project at university to isolate the 1kHz sinusoidal part of a square signal produced by a NE555 oscillator. Here is my circuit: When I simulate it on PSpice, ...
3
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1answer
104 views

LM555CN chip acting weird

I'm in high school computer engineering, and I'm experimenting with the 555 Timer chip on my own. I'm using the Electronic Experimenter Box. Pin 8 is connected to +5V Pin 1 connected to ground LED1 ...
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2answers
637 views

Where is the oscilator in the 555 chip provided here?

I have tried a while to understand how the 555 chip is built, I opened the datasheet of TI available here : http://www.ti.com/lit/ds/symlink/lm555.pdf anyway this is the scematic from the datasheet ...
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3answers
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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 ...
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4answers
628 views

Buzzer alarm problem

I've got an assignment to make some kind of alarm. When user presses the push button, 1kHz sound should be generated and outputted on some kind of speaker (I'll use buzzer). That part I know how to ...
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1answer
4k views

Ultrasonic signal generation

I am busy with a robotic arduino project. I have a 40kHz ultrasonic transducer and receiver. What would be the best way to generate the 40kHz signal to drive the transducer. I have found two ways to ...
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4answers
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How can I make a 15 minute egg timer circuit?

I want to make a 15 minute timer for a game. I would like it to count down 3 x 5 minute segments of time, and then ring a bell when the 15 minutes is up. To do this, I want to push a button to ...
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2answers
3k views

Why are 555 IC pin diagrams so random?

I was going to start learning how to use a 555 timer as an oscillator, however am greatly confused in the pin configurations example schematics provide me. To show visually what I mean, A random ...
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6answers
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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 ...
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2answers
716 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 ...
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2answers
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How do I drive a stepper motor using an LM555 timer?

I'm trying to drive a stepper motor's driver (QuadStepper) with an LM555 timer circuit, however the logic levels are known to be 5v compatible. While the driver has both 3.3 and 5 volt compatibility, ...
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1answer
2k views

555 timer as Dual Direction H-bridge driver

I am trying to design an analog direction driver circuit for an H-bridge configuration on a small DC motor. I have a pretty tight space constraint, and a simple requirement for my design, hence why I ...
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1answer
2k views

LED flashlight project: Need transistor ideas

This question is continuation of this question. I did some research on previous question and made a circuit as a starting point. Here's a picture: Now my problem is that TS555 device I plan to use ...