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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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8
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1answer
479 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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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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4answers
6k views

RC time constant in astable multivibrators

I'm having trouble figuring out why exactly \$T=0.693 R C\$ is used for astable multivibrators (and why \$T=1.1 R C\$ for monostable). At first I assumed this was only used for 555 timers but the ...
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3answers
379 views

Example circuit of fading tone?

I'm looking for a simple circuit, preferably based on the 555 in order to get continuous configurable fading tones (chimes), just like a "door open warning". It will fade in and fade out, not very ...
8
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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 ...
2
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2answers
3k views

Reset and Trigger connected in 555 timer circuit

What is the effect of connecting Reset and Trigger together in a 555 monostable circuit? I am modifying someone else's circuit and don't see why they say a need to connect Reset to Trigger instead ...
0
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1answer
880 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?
5
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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. ...
4
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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 ...
3
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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 ...
2
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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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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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2answers
2k views

Why does 555 timer output change based on load?

I have a 555 timer setup in astable mode, with a frequency of about 1Hz which I measured and verified without load. Out of curiosity, I connected an 8 ohm speaker, expecting not to hear anything. ...
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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
5
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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, ...
3
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1answer
2k views

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, ...
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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 ...
3
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1answer
103 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 ...
4
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2answers
8k views

Functional difference between various astable 555 circuits

Looking through some 555 square-wave-generator circuits (possibly with variable duty cycle for 4-wire PWM fan control) I've found three different circuits: From the Wikipedia 555 article, a "standard ...
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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 ...
3
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2answers
636 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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1answer
809 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
16k views

How to produce digital pulses using 555 timer IC for stepper motor? [closed]

I need to run bipolar stepper motor with 555 timer IC. Is there any simple circuit to produce the pulses to rotate the stepper motor clockwise, anti-clockwise with the desired speed? If there are ...
4
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1answer
1k views

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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4answers
627 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 ...
4
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4answers
8k views

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
6k views

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 ...
3
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3answers
9k views

Determine suitable resistor for the base of transistor as switch (NPN)

I have designed a program to count the frequency and time period of the pulse generated by a 555 timer IC using PC Parallel port. I’ve connected a base of BC547 (NPN) transistor to the output pin (no. ...
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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 ...
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2answers
2k views

Parallel Port - Voltage / Current required for input pin

I am developing a program to send and receive sigal to my circuit and pc. Actually I have to count the pulses or (frequency of high pulse) generated from a 555 timer IC in my circuit. When I connect a ...
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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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1answer
515 views

can pins 3 and 11 on the 556 timer use the same capacitor to ground?

can the control voltage pins 3 and 11 on the 556 timer use the same capacitor to ground? I assume that I can double the capacity of the 0.01\$\mu\$ capacitor to 0.02\$\mu\$ and share the capacitor ...
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2answers
8k views

What is the job of the capacitor in a 555 circuit?

Let's say you've got a standard astable multivibrator (AMV) 555 circuit that includes all the wiring, two resistors (R1, R2) and a capacitor (C1). I wonder what is the purpose of the capacitor and how ...
4
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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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2answers
8k views

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, ...
9
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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 ...
5
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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 ...
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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 ...
5
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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 ...
2
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2answers
589 views

Power cycling circuit

I am designing a circuit which may fail to start up. It has a power good output which is high when the supply is working. When the power good output goes low, the circuit has failed to start ...
3
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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 ...
8
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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 ...
4
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1answer
431 views

What's wrong with giving a really long low pulse to a 555 timer?

A number > 0 of 555 timer tutorials warn against holding the trigger of a 555 timer in monostable configuration low for longer than the duration of the output pulse. Why not?
5
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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, ...