20
votes
Circuit for flashing LEDs for airplane model wing, tail and beacon lights using 555
The granularity of the light sequence suggests a 555 oscillator period of 0.1 seconds (10 Hz). From there, it is a matter of counting and decoding:
simulate this circuit – Schematic created ...
- 27k
17
votes
Circuit for flashing LEDs for airplane model wing, tail and beacon lights using 555
The obvious answer here is to not even try to do this with evil 666 555 timers. You want three signals that need to be kept in phase, and one of them is a double pulse. While this could eventually ...
- 314k
12
votes
Accepted
How does this astable multivibrator circuit with FETs work?
If you understand how an astable multivibrator works, you can get to see how this one works, except that instead of going back and forth it actually goes "in a circle".
First of all, there should be a ...
- 5,536
10
votes
Accepted
555 Astable : Separate charge and discharge resistors?
Is there something wrong with putting one resistor for the charging
path, and one for the discharging path?
There's nothing wrong with it other than at some point, the resistor in the discharge pin ...
- 467k
9
votes
Accepted
astable multivibrator: capacitor polarization
Good question.
First off, the polarity of the capacitors in your picture is the wrong way around. The + terminal should not be connected to the base of the transistors.
Why the circuit works (when ...
- 5,157
8
votes
Accepted
Does a 555 astable dissipate more power at higher frequencies?
Yes it does.
Reducing the oscillation frequency \$f_{osc}\$ will have an impact on your circuit power consumption, because you'll be charging and discharging the capacitor less frequently, thus ...
- 5,811
8
votes
How does this astable multivibrator circuit with FETs work?
This is essentially three inverters connected in a ring fashion to make an oscillator. More about ring oscillators here: https://wiki.analog.com/university/courses/alm1k/alm-lab-ring-osc
But the lack ...
- 56k
8
votes
Astable multivibrator: what starts the first cycle
First, at some point the power must be turned from on to off.
Second, in the real circuit the capacitors won't be exactly 10.000 uF (or exactly equal to each other) and the collector resistors won't ...
- 132k
8
votes
Accepted
BJT astable multivibrator frequency increasing with voltage
The reason is that during switching cycles, the base of each NPN is pumped below ground. Most NPN base-emitter junctions will break down and degrade with 6-9 V reverse bias.
LTSpice and other ...
- 19.7k
7
votes
CMOS frequency of oscillation
Because the delay around the loop must be 360 degrees (why? Because the output at the junction of R3/C3 is identical to the input of the first inverter), it's clear that the phase shift of each ...
- 60.8k
7
votes
Astable 555 circuit not oscillating
As has been mentioned, Pin 4 should be connected to +V and also pin 5 decoupled to ground by about 10nF.
The 555 should not get hot at all! This is the big clue. I've played with this circuit and I ...
- 2,482
7
votes
Accepted
precise 50 Hz oscillator
Exact is not possible. How precise does your oscillator need to be and how much jitter can you withstand? What is your budget? Since you're mentioning a 555 timer, I'm assuming that spending over €...
- 10.5k
7
votes
BJT astable multivibrator frequency increasing with voltage
You are likely running afoul of too much reverse voltage from BASE-to-emitter: (from ON semiconductor data sheet
The base-emitter junction looks like a zener diode when you reverse-bias it. You ...
- 27k
7
votes
Regulating output of 555 astable oscillator
Build the circuit the other way around i.e. First 12V to 5V with 317, then drive the oscillator with 5V.
Alternatively, you can drive 555 with 12V directly and use a divider (or a resistor+Zener) at ...
- 38.1k
6
votes
Accepted
Astable multivibrator using op amps - why does it start?
The uncharged cap should not create any change in the difference of voltage between inverting and non inverting inputs that the op-amp could amplify, so I would expect that in a perfect simulation ...
- 178k
6
votes
Astable multivibrator using op amps - why does it start?
If you give the op-amp even a tiny bit of offset voltage when you connect the uncharged capacitor the output will slam to one rail or the other and oscillation begins.
Similarly, even if perfectly ...
6
votes
Accepted
Astable multivibrator not producing a square output wave, using two BJTs
There are mistakes: -
With no DC bias on the bases you will not get an oscillator.
This is how it should be done: -
However, it's not a great or stable circuit.
Try also this circuit (courtesy of ...
- 467k
5
votes
555 timer oscillator circuit
Try this: -
R1 dictates charge time of C1 and R2 dictates the discharge time.
Or this: -
Taken from here
Alternatively put a d type flip-flop on the output to divide the frequency by two and ...
- 467k
5
votes
Accepted
CMOS frequency of oscillation
I'll just throw this in here. Given ideal inverters, ie. they work like ideal comparators, with infinite gain and low output impedance. Note that this is not the case judging from your simulated ...
- 5,237
5
votes
Accepted
I'd like to know whether my attempt to increase duty cycle will work
This is easier if you don't stick to the original schematic. One capacitor is ten times the other.
- 2,461
5
votes
Would using the output of a 555 timer to charge/discharge its capacitor work?
Back in the 70's, so many people independently discovered/developed this circuit that when National Semiconductor introduced their CMOS version of the 555, they put the circuit in the datasheet.
Page ...
- 22k
5
votes
Accepted
Why does the output of my astable multivibrator using an op-amp turn into a triangular wave?
LM741 has 0.5V/µs slew rate.
30kHz half period is 16µs, so in this half period the output of LM741 can slew up or down 8V, so the maximum triangle wave amplitude it can output would be +/-4V.
So at ...
- 80.3k
5
votes
Low amplitude output in Opamp square wave generator
There's an important line in the datasheet:
- Wide Bandwidth (Unity Gain): 1 MHz (which is not actually very "wide" for your purposes)
In other words the ...
- 552
5
votes
Low amplitude output in Opamp square wave generator
Let's assume we want 200kHz rate.
Your circuit puts a lot of load on the output of the LM358. That op-amp is designed for combined load resistance above 2kOhm, ideally above 10kOhm. So we can rescale ...
5
votes
Accepted
555 astable resistor location
Imagine what happens when Discharge is pulled low by the internal transistor, R5 and R6 will form a voltage divider with Trigger and Threshold connected to the center of the divider. With it like that ...
- 26k
5
votes
Accepted
Unable to get my astable multi-vibrator working in LTspice
Here is one problem: The output of the op-amp is connected to GND.
There may be other problems.
- 5,670
4
votes
Accepted
Making a Triangle wave on LTSpice using LM741 opamp
There a few problems with your circuit:
1) The second stage will generate an exponential rather than a triangle.
2) The resistor values for feedback on the second stage are much too low - the ...
- 33.8k
4
votes
Accepted
triangular and square wave generator
The right hand op-amp looks like a comparator (with an open collector output). The emitter I suspect is pin 1 and this is tied to -15 V. Open collector outputs require a pull-up resistor hence the ...
- 467k
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