Questions tagged [astable]

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34 views

555 timer Theremin - capacitor choice, and question about mixing signals

I'm trying to create 555-timer based Theremin, but I have a few questions that I don't quite understand. For now, I'm building it on a breadboard (yes, I know it's not the best option), but I don't ...
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2answers
43 views

NE555 - astable flashing alternative LED circuit

NE 555 help - astable alternate flashing LED circuit "In the circuit, the LED1 lights when the output pin has a HIGH state and LED2 lights when the output is in a LOW state." - I couldn't ...
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1answer
42 views

What would be the main advantages of constructing an astable multivibrator with two CMOS inverters?

What would be the main advantages of constructing an astable multivibrator with two CMOS inverters? Can these semiconductor devices be declared to introduce small parasitic capacitances to the circuit?...
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0answers
36 views

Circuit question for LM358 and NE555

I have made an IR proximity sensor which works fine when an LED is connected. Figure 1: This is the IR receiver and emitter part of the circuit. The white LED is connected to ground via a 270 ohm ...
3
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1answer
272 views

Astable multivibrator: what starts the first cycle

I think I understand how the astable multivibrator works once the LEDs are blinking (cf. below), but I don't understand how the first cycle begins. I can see that at first, the 2 LEDs are on (based ...
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0answers
45 views

555 Timer Astable Mode

Just to clear things up. This is NOT a homework question, but it is lecture notes used as a practice exam. I am trying to understand the 555 timer in oscillation (Astable) mode particularly the ...
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0answers
14 views

A light dependent current astable multivibrator

i have basic knowledge about multivibrators and how a photodiode is operated but i'm having trouble trying to combine them into one circuit. Suppose if i am to operate the photodiode on the circuit as ...
1
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1answer
60 views

I'd like to know whether my attempt to increase duty cycle will work

I've been looking for a solution to make an astable multivibrator give me a 90% duty cycle or a duty cycle above 50%. This is what I came up with. I have very limited resources and means of testing, ...
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0answers
72 views

I've built dead bug (on steroids) boost converter

I know it looks sloppy but this is my very own homemade boost converter! It outputs 6watts of power from a 3.7v battery(phone battery)... It's switched by an astable multivibrator, and the switch is ...
2
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2answers
547 views

Bypass capacitor in 555ic

What will happen if we don't bypass capacitor at pin 5 of 555 ic as an astable multivibrator.Will voltage/current changes in line affect on pulse width?will capacitor at pin 1 discharge late?
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0answers
43 views

How does a boost converter power the oscillating circuit and load at the same time?

so I've put together a boost converter circuit of my own and I have a problem, I want my boost converter to output reasonably high current but whenever I connect a high current load - the astable ...
9
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4answers
7k views

How does this astable multivibrator circuit with FETs work?

I am having trouble understanding this schematic. I do understand that it is pretty simple, but I just can't seem to get my head around part of it. The schematic is a more complicated version of an ...
0
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1answer
48 views

CMOS astable circuit

I have made the following astable circuit in Multisim: However, it didn't work (oscilloscope reads 0V as an output.) I think the problem is because of VDD and GND pins which are hidden in Multisim. ...
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1answer
67 views

Feedback on astable 555 timer circuit to control MAC valve for turbo control

I have some questions and wanted to get feedback on this circuit I have put together. Basically to see if there is something I missed or obvious that I should change or should have designed ...
0
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1answer
125 views

Two questions about astable multivibrators and transformers

Here's something that confuses me: The output on an astable multivibrator will be shown on a multimeter as half the input voltage (for example we have 9V-0V-9V-0V...and the multimeter averages it out ...
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2answers
158 views

Gating an astable 555 output signal in a way that oscilation always starts with a Low to High transition

simply, the circuit is a 38KHz signal generator for an IR remote project. the output signal should be gated by an MCU according to IR timing intervals recorded earlier. the design with the 4148 diode ...
22
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5answers
2k views

Astable 555 circuit not oscillating

I'm a complete beginner to electronics, but I'm trying to follow Ben Eaters video series "Building an 8-bit computer". I tried to do the first part of an astable 555 timer, but the LED does not ...
3
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1answer
174 views

555 timer that does not output low when reset

I'm trying to design a circuit with the following goals: When not active, output can be either Vcc or floating When triggered by pressing a button, output pulses several times to GND at some ...
1
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2answers
155 views

Astable multivibrator not working

I was wondering if you can help me to know why my circuit is not working. I have tried with different pre-existing circuit values to make sure the circuit was working properly before I put my ...
1
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0answers
76 views

Astable multivibrator inverter

I'm new to electronics and trying to make an astable multivibrator oscillator. The PSpice simulation doesn't work (it says netlist error when I place a mosfet or a diode) and I get a really low ...
1
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2answers
45 views

Explain how this astable chain(?) circuit works

The circuit below fades on and off a cascading series of leds in an alternating fashion. I tried reproducing it on a breadboard with 5 leds to try to understand it how it works, and got all sorts of ...
2
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2answers
461 views

BJT astable multivibrator generate triangle wave

In this circuit there is a bjt astable multivibrator. It generates a square wave. And according to the description, at the output of the opamp it generates a triangle wave from this square wave. I've ...
1
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1answer
70 views

Op-Amp Astable Multivibrator - Effect of bypass Switch

For your consideration, I have this Astable-multivibrator via a classic Op-Amp Schmitt Trigger delivering a square signal (here 1.82Hz). I am fine with the circuit with SW1 open as C2 is basically in ...
0
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1answer
59 views

Electric astable circuit not working

For school I have to build a astable circuit that stays on for 5 seconds and then turns off for 1 second. However my circuit isn't working I am do not know why here is my circuit on a bread board. The ...
7
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3answers
916 views

Adding Diodes to Transistor Astable Multivibrator; 1N5818 Schottky diodes work but 1N4148 diodes don't; can't figure out why

I am an avid electronics hobbyist, not an electronics engineer. I built a transistor-based astable multivibrator circuit and then fed its output to an op amp buffer amplifier which then drove an 8 ...
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1answer
736 views

What is the purpose of higher-resistance resistors in Astable Multivibrator circuit?

The astable multivibrator circuit has two higher-resistance resistors (47k on the pic). What are they there for? Wouldn't it work without? And what is exactly their function? I spent a lot of time ...
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1answer
83 views

Why does the first pulse have a different duration than the other pulses?

Why does the triggered astable in the next figure have the duration of the logical component "0" of the first pulse lasting 2 times the logical component "0" duration of the next pulses (see the ...
0
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1answer
172 views

555 Timer Giving Unexpected Output (Astable Multivibrator)

I am using this design with the only exception that C2 is 150nF to change timing slightly. When I plug in the circuit and attach an LED across GND and pin 3 output the LED is static on. However, on ...
2
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1answer
881 views

Astable 555 timer circuit that resets on a heartbeat

I'm trying to design a circuit that will reset my ESP8266 when it crashes/hangs. It does this by sending a heartbeat to a 555 timer every minute which resets the 555 timer. The 555 timer is configured ...
5
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2answers
227 views

555 Astable Timer produces incorrect period/frequency

I am building a 555 astable timer circuit for a course which must match the BPM of a song. The song has a BPM of 104, which requires a timer frequency of roughly 1.733 Hz. The circuit looks as ...
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0answers
64 views

Variable frequency of an astable

I have to make the frequency variable of an square waveform generator built with the help of an astable. I modified a circuit a found on the internet and everything seems good with only one exception: ...
-3
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1answer
445 views

Astable 555 not oscillating [closed]

I've been struggling with building a 555 timer for a project. I get the expected voltage at pin 3 (output), but the problem is that it's not oscillating. The Vout is constantly 8.4V, while I expected ...
2
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3answers
347 views

CMOS frequency of oscillation

How to find the frequency of oscillations in this circuit CMOS circuit: simulate this circuit – Schematic created using CircuitLab Assuming the ideal CMOS gate with the threshold at 0.5Vdd. ...
2
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2answers
197 views

How does this TLC556 work?

I'm having trouble understanding what the upper part of an electronic metronome depicted in the below schematic does. I already asked about the lower op-amp part in another topic, but I also can't ...
1
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1answer
346 views

555 stepper motor controller

I need to make a square wave generator to control a stepper motor driver. It needs to be controlled with a potentiometer and get an output range from 40 Hz to 4 kHz. I don't know a heck of a lot ...
1
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2answers
416 views

nand gate astable vibrator do not work at 400kHz

I want to build a 400kHz square wave oscillator with NAND GATE using the CD4011BE circuit. Unfortunately, it does not work as expected when I use R2 and C values according this schematic: ...
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2answers
208 views

555 astable - frequency not linear with discharge resistor for smaller resistor values

I'm trying to use a 555 timer to create a variable frequency from a resistance, the output frequency should be about 1 kHz up to 300 kHz. I'm using a TS555CN CMOS version, which can oscillate up to 2....
-2
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1answer
236 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 ...
4
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2answers
267 views

Naive VCXO design - runs at 3rd harmonic, I need the base freq

Consider this a hobby question. (How do you call a hobby project on the fringe of your nominal work? A skunkworks job?) I mean to say that I'm not an EE design pro. I'd appreciate your opinion about ...
1
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1answer
95 views

BJT Bitonal Astable Multivibrator, can someone explain me how this circuit works?

I've been analyzing this circuit and so far I think it divides in two separate oscillators, but I still don't have a clear idea on how this two work together. I'm leaving a picture of the circuit, ...
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0answers
384 views

How to design a low voltage astable multivirator

I am currently trying to design a solar powered energy harvester. It requires a DC to DC boost converter to increase the output voltage and keep it regulated. I found that this can be achieved using ...
0
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1answer
178 views

PWM signal is affected when motor is connected

I am working on a fun side project where I am creating a PWM waveform using the LM324 and a small solar panel. I am using the LM324 for the astable multivibrator, integrator, and comparator. The ...
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2answers
981 views

Alternate design for an astable 555 circuit

I was looking at how to get a sign wave from a 555 chip and found this article. It seems to say it's using an astable 555 circuit outputting to an LC resonant circuit. However, the circuit diagram ...
0
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1answer
187 views

Astable timer: Halve frequency while maintaining the same “up” pulse width?

Disclaimer: I am not an electrical engineer, but an environmental science student. I'm trying my best here. I have a basic astable 555 timing circuit with the following components: \$R_1 = 10k\...
1
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1answer
982 views

A stable negative supply for an op-amp (using 555)

I need a differential amplifier circuit for my design and I am using the LM358 op-amp. The problem is of negative supply. I need to give negative power voltage to my op-amp(-Vcc). and I only have a 9v ...
4
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1answer
1k views

astable multivibrator: capacitor polarization

Looking at this circuit, I'm wondering if the capacitor polarization "+" is correctly draw. Assuming T2 is in cut, T1 is on, left capacitor will have a 0.7v in its right side (connected to T1 emitter) ...
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2answers
512 views

Astable 555 timer [closed]

The circuit diagram is above R1,4,6,7:1K R2,5:10K R3:100 ohms C1: 0.047 uF C2,3 :100uF C4:69uF C5:0.1uF And we finished building the circuit and connected the battery onto it. But the LEDs stayed on ...
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2answers
172 views

555 Astable Timer: Why do these two circuits simulate differently?

I've modeled up the following two circuits in LTSpice: simulate this circuit – Schematic created using CircuitLab and... simulate this circuit (I've left out the other connections for ...
2
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2answers
8k views

Why is a common LED failure mode to flicker astably or oscillate? [closed]

There are many cases of LED lights failing by beginning to flicker intermittently. I am not talking about the intentional duty-cycle modulation utilized in many driver circuits. I am referring to ...
1
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5answers
2k views

Does a 555 astable dissipate more power at higher frequencies?

I'm planning on running a circuit on a 9V battery and it uses a 555 in the astable mode to generate pulses. I want this circuit to be as efficient as possible, and not have to replace the battery ...