Timer Definition and 124 Threads

Hello experts! I have given 2 question in exams. 1)Explain why duty cycle of Astable circuit's output is always greater than 50%? 2)In monostable multivibrator, how low does the triggering voltage have to go in order to initiate the output pulse and why duty cycle must be greater than...

I would like to use a timer to turn on and off a 220 Volt appliance. With a "mechanical" plug-in timer you have 20 minute granularity. But I would like to have a 1 minute resolution. For example - 1 minute off and 1 minute on. I bought a cheap 10 euro digital timer. I was mislead by the...

I want to know the function of the two power amplifier ?

Just another monostable 555 timer question :D I have a 555 monostable circuit with a relay attached to + and pin 3. I tried attaching it to pin 3 and - but it didn't work. Anyway, its very temperamental and keeps going that when you push the button it will stay on for about 2 seconds or less...

Since I don't have a function generator, for some experiments at home with digital ICs I've used a 555 timer with 5V Vcc as the clock, and I noticed something problematic. It behaves rather erratically. I've mostly been using it to trigger a 74LS90 asynchronous 4-bit counter. Sometime it works...

Hello, I am not even a novice at electrical engineering. I am a web designer and a programmer (Actionscript 3.0 and PHP - also MySQL for my websites' databases-). Anyway, I am attempting to create a series of circuits that count items moving on a conveyor belt with an IR sensor, and runs a...

I found the following circuit http://www.555-timer-circuits.com/bi-polar-led-driver.html that suits the task I am trying to achieve. My only issue is I don't know what the frequency would be or how to change it. Is the frequency determined by the cpacitor and the 33K resistor or is it more...

I have been trying to make this circuit work for a few weeks now and it is slowly driving me crazy. I have on a veroboard a circuit. When i redo the circuit on Yenka (Crocodile clips) It works perfectly. The circuit is a 555 astable circuit with two LEDs, when i turn it on only one LED...

Hey guys, I'm trying to build a circuit where I can put in an analog signal (my voice) and have it output the same signal with a much lower pitch (speech synthesizer). Is there any way I could do this with primarily a 555 timer? I'm able to pulse width modulate the analog signal, but I...

I'm conducting an experiment to determine the brachistochrone. The setup is going to involve an inverted cycloid shaped track about 5 or 6 feet long. I need a way to measure the time it takes for a marble to roll down the track and I need a more accurate method than manually operating a...

Homework Statement Hi, I am trying to make a PWM circuit that calls for a LM555 timer but I only have easy access to NE555 timers (In Australia) and am wondering if it will suffice?? Thanks for any help, circuit found here...

Hi, I'm not sure if this is the right place to post this, so sorry in advance. I'm doing a project on water. One of my ideas (I need to have a few initial ideas) is a shower timer, which stops people wasting water in the shower (like it will shut off/reduce pressure after a certain number of...

I am trying to figure a way to hook up a timer to my pellet stove. The control board of the stove has an "on" button and a separate "off" button. The on button is a push button switch. My question is: is there a programmable timer that closes a circuit for a second and releases the switch like...

I am getting a bit older, and I have a Aluminum Communications Tower, and used to angle it up by myself from the back of the house to the side. Now I would like to lift the tower to its vertical position on the side of the house using the existing aluminum angled bracket plasma welded to a...

Hi, I am designing a board-level circuit to measure pulse width, in which I need a high-precision timer. I want to use a high-speed counter to implement the timer. Since the timer requires an accuracy of 500ps, this implies that the clock to the counter has to run at a frequency of 2GHz...

Im trying to make a countdown timer for my MATLAB class using the tic and toc functions. so far this is what I have: function lab4program1 disp('Welcome to the countdown timer program'); done = false; tic(); while ~done time = input('Enter a time (seconds) or negative number to...

Basically what I'm trying to do is have two LDRs connected to a differential op-amp. The configuration has it high when LDR1 is low and LDR 2 is high with the rest of the combinations outputting low. Theres two op amps connected so that there are two distinct output channels so i have two high...

I conducted an experiment involving a 555IC timer circuit and the hypothesis investigated the frequency and period of the LED connected. Using the formula for frequency; 1.44/(Ra + 2Rb)C where R1= 1000R R2= 10000R C = 10uF the frequency equals 6.857 (rounded value) now using data...

I've been looking at 555 timers and other stuff but don't have the ability to control this stuff. I want to trigger a circuit close with a relay, with accurate adjustments to a dial. I want to be able to accurately control the trigger of the timer between 0.3 seconds to 1 minute. So...

Homework Statement 3 3 6.21x10 kg/m converted to slugs/gal Homework Equations The Attempt at a Solution I don't know where to begin to attempt this. I am having a lot of trouble with conversions. Please help. I have never taken physics before. Thank you

Hi, I have a circuit that I am working on that I adapted from the 6v version here http://electronician.blogspot.com/2009/09/555-timer-project-15v-led-flasher.html I have a 12v supply with a total of 48 leds 24 on each bank. I have gotten previous version to work with single leds but now that I...

Homework Statement An accelerometer measures the acceleration of an object every 0.050s. The initial velocity is 0 m/s. The initial distance is 0 m/s. The accelerations at the times (in m/s^2): a(0.000) = 5 a(0.050) = 7 a(0.100) = 10 a(0.150) = 15 a(0.200) = 15 a(0.250) = 15...

Hey all. I am using a 555 timer chip to power an IR LED, which switches something on or off. My question is, now my timer chip is sending out 38 kHz IR light. My IR receiver is made to pick up 38 kHz IR light, but only the first 14 (I think) pulses, then ignores all pulses without a pause...

Hi, I was wondering if anyone could help me, I am studying industrial design at Loughborough and as part of my coursework I am re-designing a stopwatch. Along with this coursework I need to submit a simulation of the electronics that would be involved. We have all ben given a basic circuit...

Homework Statement It's simple, I need a simple timer, that when powered on, will count down from a variable amount of seconds that are preferably shown on several 7 segmant displays, when the timer hits "0" the output goes high, simple as. I figured I'd build it in 2 stages, the 555 timer...

i recently bought my 555 timer and i simply can't get it to pulse. I flick on the switch and i get my buzzer to work that is connected to the output but i don't hear it turn off and on. I set my configuration as astable 6.5 Hz. i checked all my connections and everything seems right. However...

Dear Mechanical Engineering experts, I would like to know how small a mechanical timer you have ever used or seen. Sincerely Ramone

Please help me quick everyone, thank you in advance. Homework Statement http://imgkk.com/i/EasJ1d.jpg a/We have two photogates placed as in the figure. We drop a marble through these at a negligble distance above the upper gate. The upper starts a timer as the ball passes through its beam and...

Here's the drawn circuit: http://imgur.com/DGo9M.png R1 is 10k Ohm resistor Pot is a 100k Ohm potentiometer C is 1.0uF Electrolytic Capacitor My question is, what happens when the potentiometer is turned down to 0 resistance? Would the circuit fry? thanks

How Could I do This? Motor to open and close doors on a timer?? Hey Guys, First post here, and I am picking my brain on how I could accomplish this. Here's what I have. http://img20.imageshack.us/img20/2835/doora.jpg Wow...Sucky computer drawing. That is a 8' x 3' piece of plywood and...

hi everyone, i am trying to build a very high current dc to ac inverter and i can't use a 555 timer IC because they can't source or sink but a maximum of 200mA, but i have found an internal schematic of the 555 timer IC online and have been studying it to see if i can build a very high current...

I am an electrical engineer student at SIU and I'm working on an personal project where I am trying to use the following items to supply current between 450-600 mA: 555 timer 2N2222 transistor 4 AA batteries in series for 6V Resistors and capacitors on 555 timer while just resistors on...

1. For a school project we're building an emergency braking system. In addition, we also want to trigger an audio-visual alarm system to alert a third party to the operation of the system. For the alarm system we are using a 555 timer to generate a squarewave output to alternate a buzzer between...

Homework Statement Plot a displacement-time, velocity-time, and acceleration-time graph for a wheeled cart that rolls down an inclined plane. Already finished the displacement-time graph, but am questioning the correctness of the v-t and a-t graphs. What should they look like? (Like d-t...

I want to first thank all of you for your help with my first 555 timer question. With that help and some more reading on the net I have it working perfectly. My next task on this timer project was to include an LED display. My intention was to have a display that would give me a numerical...

I have been having a great amount of difficulty with the 555 timer (Texas Instruments NE555P). I am going through a book published by McGraw Hill titled Understanding Electricity and Electronics. While I was waiting for the parts to finish my power supply, I started to work with the 555 timer...

Hey Everybody! I have been using this page as a guideline to learning how to use a 555 timer: http://www.kpsec.freeuk.com/555timer.htm I have been trying to make an LED flasher by using a 555 Timer for the first time, but after 2 days, I have been unable to see my problem. I am using...

Hello. I am currently trying to evaluate just how much power the external RC circuitry of a 555 timer uses over 1 cycle. Whilst the capacitor is charging the current falls exponentially. Naturally the voltage also falls through the resistors but this is couteracted by the rise in voltage of the...

Hello, Please could you help me with this problem; I need to design a timer whereby I briefly trigger it (using a push to make/push to break switch connected to a 6 v supply), there is a pause of 30 seconds and then it triggers with an output, say an LED - this stayes on for about 10...

Hey everyone, First off, hopefully I am in the right topic. Now i just had a lab last week, where we had to calculate acceleration and talk about motion using data we got from a ticker timer. One of the requirements of the report is to find and talk about uncertainty of the ticker timer...

I am having trouble with a mono-stable 555 timer circuit. When I connect this to a power supply (right now it is a 120VAC to 12VDC converter), the timer turns on and then off, like it would have if it was activated by the trigger. After this, when the trigger is used, everything works...

Can you tell me what is wrong with my timer. I want it to make a relay open and shut periodically. For some reason it's not working.

Hi I am currently using LCM555 timer for generating variable frequency based on relative Humidity (RH) of surrounding. The LCM555 is configured as astable multivibrator and centered at 20KHz. RA = 24K, RB = 200K and C is capacitive sensor having value of 160pF at 30C, 0%RH. The C is given by...

Homework Statement If I have two exact pendulum timers (like the one in the picture below) and I place a weighted object at the end of the one stick, and towards the bottom (near the base) on the other, which one will swing faster...

Hi guys I want to learn how to program a 555 timer. I searched google and there doesn't seem to be any sort of tutorials or good info for a beginner to get started I don't even know what equipment I would need to do it. I want to program a 555 timer for 15 pulses per second so I can make...

I am new to interrupts, so i have made a simple program using a timer interrupt to cause a delay of about 1 sec in displaying the binary numbers. However I have failed to achieve this. Anyone knows the problem with my program? any assitance will be highly appreciated. #include...

I want to build a digital timer that will switch my geyser on and off at a preset time in order to save power. I don’t know much about PICs so I would rather try using only logic ICs. It has to have at least 3 preset ‘on-times’ and 3 ‘off-times’. Can anyone help me to get started?

Guys, I need a simple timer that will count down from 1-20 seconds and then have a continuous output of high to run a electric motor. And time can easily be adjusted (potentiometer?) Ive been playing with 555 timers and timer circuits from diagrams of "555 timer" through google, but...

Im trying to do just that, that is build a timer that countsdown accurately to the minute. Ideally this device should have a range of about 5 second countdowns to 36 hour countdown. I'd like to add a 7-segment LED display wired to count as well but I am not sure I think i can do that with a 555...

I need to build a timer(using a 555) with a frequency of about 1KHz and a duty cycle of about 25% to provide my clock signal. So the 555 is obliviously in astable mode. From my engineering data sheet: D=\frac{R_B}{R_A+2R_B} f=\frac{1.44}{\left(R_A+2R_B\right)C} where C is my capacitance value...