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. As of 2003, it is estimated that 1 billion units are manufactured every year. - ...
-5
votes
2answers
69 views
How does the 555 timer IC circuit work?
As a beginner to electronics I'm having a tough time understanding circuits that have a combination of different components, including the following timer circuit. Its based around a LM555 timer IC. I ...
1
vote
1answer
43 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 ...
2
votes
3answers
64 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 ...
1
vote
2answers
91 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 ...
3
votes
2answers
72 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 ...
0
votes
0answers
74 views
lm555 circuit doesn't work
Why doesn't this simple circuit work?
\$R_1 = 15k\Omega\$
\$R_2= 15k\Omega\$
\$C_1= 1000\mu F ; 6.3V\$
\$v= 9V\$
It should have a cycle time of 30 seconds.
I placed a volt meter on a LED that was ...
1
vote
1answer
93 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 ...
16
votes
4answers
685 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 ...
0
votes
3answers
119 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 ...
2
votes
1answer
78 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.
2
votes
1answer
67 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.
3
votes
2answers
118 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 ...
2
votes
2answers
112 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 ...
8
votes
2answers
111 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 ...
2
votes
2answers
188 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 ...
-3
votes
1answer
96 views
having problem in creating 555 oscillator in breadboard [closed]
i am quite new in electronics department and so have a very little knowledge about it...ok so i am going to set up a 555 oscillator.....i have the 555 timer chip, a solderless breadboard and resistors ...
3
votes
1answer
233 views
How to make a LED flash twice every second?
I know that I can make a LED flash using a 555 timer. How may I make it flash twice every second?
What I am trying to do is to make the LED flashes two times, then wait a second, and then flashes ...
2
votes
4answers
171 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 ...
4
votes
1answer
170 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.
...
-3
votes
2answers
299 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 ...
0
votes
1answer
190 views
why will my transistor (TIP122) NOT switch?
My goal is to make a car turn signal flasher.
I used a 555 chip as the timer with the output driving a TIP122 transistor at BASE and a 100 ohm resistor between the BASE and the 555 output pin 3. The ...
3
votes
1answer
153 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 ...
3
votes
2answers
154 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 ...
0
votes
3answers
183 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 ...
6
votes
1answer
249 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 ...
3
votes
2answers
339 views
555 timer in astable mode: How can I achieve longer low output than high?
I'm attempting to make a simplistic solenoid driver circuit using a standard astable 555 timer configuration with a TIP122 NPN transistor. The problem with the current circuit is that the output is ...
6
votes
2answers
421 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 ...
1
vote
1answer
79 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 ...
4
votes
3answers
188 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 ...
3
votes
1answer
401 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 ...
8
votes
1answer
223 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 ...
2
votes
1answer
210 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 ...
0
votes
4answers
389 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 1.1*R*C is used for monostable).
At first I assumed this was only used for 555 timers but the same ...
7
votes
1answer
191 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 ...
1
vote
0answers
184 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
votes
1answer
233 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?
2
votes
1answer
142 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. ...
3
votes
1answer
548 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
votes
2answers
276 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 ...
0
votes
0answers
255 views
Atmel microcontroller LED circuit build [closed]
so now I'm building
this is a follow on from my previous posts. If this is first time reading.
I am trying to do-
press switch for activation first light comes on pre programmed in 1.5secs then ...
2
votes
2answers
494 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 ...
3
votes
3answers
1k 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 ...
3
votes
1answer
376 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. ...
6
votes
3answers
459 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
4
votes
1answer
466 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, ...
2
votes
1answer
363 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, ...
4
votes
5answers
963 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
votes
1answer
74 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 ...
2
votes
1answer
499 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 ...
1
vote
2answers
258 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 ...
