How Can I Use A 555 Timer To Disconnect And Reconnect An RCA Video Connection?

From Other - Electronics Forum:

How can I use a 555 timer to disconnect and reconnect an RCA video connection? I have created a 555 timer circuit that activates for 60 seconds when the switch is activated and then turns off. It works fine for a V circuit. I am wondering how I could set this up to turn on an RCA video connection when the timer is activated? In other words, I plan to splice open an RCA cable and somehow get the video signal to only be on when the 555 is activated for that 60 seconds at a time.

Answer: the output of the 555 timer will have to go to a transistor. the transistor will provide enough current to actuate a V relay. the video signal will go through the output legs of the relay. there are several different types of relays you can use. the only problem I can think of is that noise may be introduced into the video signal.

Is It Possible To Trigger A 555 Timer With An Active High Signal?

From Engineering Forum:

Is it possible to trigger a 555 timer with an active high signal? I have a 555 timer and need to activate it with a CDC input. Can I trigger the 555 timer when that signal goes from CDC to 30vdc? If so, can you please explain how to connect it? All of the circuits I've seen in the past use an active low trigger, and that is not what I need now.

Answer: You could use a transistor with a V power supply, when the voltage swings from 0 to 30 volts it would turn on the transistor whose output would be applied to the input of a 7404 hex inverter. When the input of the hex inverter goes high, the output goes low and then triggers the 555 timer. Hopefully the 0 - 30 volts is either 0 volts or 30 volts and not somewhere in between, otherwise using a relay with a 30 volt coil could be used to switch 5 volts to the hex inverter input.

How Do I Hook Up A 555 Timer For Pulse Generation And/Or Time Delay Applications?

From Engineering Forum:

How do I hook up a 555 timer for pulse generation and/or time delay applications? I have a 555 timer ( a 556 to be exact, but it's just two 555s) and I need to know how to hook it up for pulse generation and/or time delay functions, or a wacky combination of the both. Any help is appreciated.

Answer: This is a long story, so please visit this site " Hobby projects.com". They have schematics about the chip 555, or 556 for you to do more than what you need here! ( all you need is to navigate to " timer and counter").

What Is The Frequency Of A Capacitor In A 555 As table Circuit?

From Other - Electronics Forum:

What is the frequency of a capacitor in a 555 as table circuit? I have a 555 timer as table circuit with a K and K resistor going to a UFO capacitor, what is the frequency of the capacitor and how do you work it out

Answer: There is a formula in the 555 data sheet but for lazy people like me I use a calculator such as http://www.csgnetwork.com/ne555timer2calc.html Note the capacitance is in Farads so you need to multiply by 10⁻⁶ to get μF or to save faffing around with multipliers there's http://freespace.virgin.net/matt.waite/resource/handy/pinouts/555/ which has the capacitance in μF.

How Do I Wire A 555 As table Output To A Speaker?

From Engineering Forum:

How do I wire a 555 as table output to a speaker? With a 555 configured as a Hz as table, it is possible to wire the output (pin 3) to a speaker, producing an audible sound. How would I wire this output to a speaker? Would a capacitor be necessary? What about a transistor? Or a protection diode across the speaker? and where applicable where would these go? Any help is much appreciated.

Answer: You will need to put a capacitor in series with the speaker, I suggest you try a 5 μF electrolytic. Wire the + side of the electrolytic to pin 3 of the 555 timer. Don't use an expensive speaker. No protective diode is needed as the 555 timer's internal transistors will clamp the output pin to + Cc and ground every 1 millisecond ( =1/(2* 480) )

Is Possible That 555 Timer Can Connect To ADC By Adding Any Others Circuit ?

From Engineering Forum:

Is possible that 555 timer can connect to ADC by adding any others circuit ? I need the output of the 555 timer so that can input to ADC. IS possible can do this.

Answer: I assume you want to control some aspect of the 555 operation with a digital control signal. Almost certainly there are many ways to do that. However, knowing it is probably possible does not take you very far in designing the needed circuit. A better place to go to have hand holding through that design process might be the Yahoo discussion group called Electronics's. -- Regards, John Popelish

What Is The Function Of The 555 Timer In The Clapper Circuit?

From Physics Forum:

What is the function of the 555 timer in the clapper circuit? Are the two claps received by the 555 timer which sends a signal to the flip flop to turn on or off. OR, does the 555 timer just set the delay time between claps and the flip flop receives the two signals and turns the transistor on or off? The circuit diagram can be found at: http://www.freeinfosociety.com/electronics/schemview.php?id=2027

Answer: I am being a bit lazy, but glancing at the values of the timing circuit on the 555, it looks too short to sense the delay between pulses from the two claps. It looks like it may simply be insuring that the impulse from the clap is long enough - that is it not just stray noise - and then sending on a pulse to the flip flop. In general, digital circuits are very fast, and human scale actions are much slower, and so you almost always need to provide some sort of screening to prevent high speed responses. When you throw a normal switch, for example, you commonly get, literally thousands of tiny on-off switching just as the contacts are closing or opening, and in digital circuits, one often uses a 555 to effect a delay on when the circuit is to consider the switch 'switched'.

How Does The Frequency Of A 555 As table Vary When The Voltage At CV Changes?

From Physics Forum:

How does the frequency of a 555 as table vary when the voltage at CV changes? I would like to know values/a graph of the frequency of a 555 when CV is at a certain voltage (varied using a potentiometer. The 555 would be used as an as table for generating sound. Voltage would obviously be measured at CV pin (pin 5)

Answer: The 'standard' name for pin 5 is 'CTRL' ... in a 'standard' 555 as table circuit design this pin is 'nc' (not connected - in practice it is typically connected to a small capacitor and thence to ground) SO - to answer you Q, FIRST you need to give us a link to your obviously non-standard circuit design .. (see my link for standard designs ..)

How To Make A Switch Pulse With 555 Timer?

From Engineering Forum:

How to make a switch pulse with 555 timer? Recently, I have been experimenting with my 555 timer. My objective here is to build a 555 with a switch that when I press the switch, a high pulse will flow in, then I press the switch again, a low pulse will flow in. I've tried to manipulate with the reset and Cc input to the trigger but didn't manage to get it correctly. It would be helpful if you give me some link for the circuit that I wanted to do. Thanks :)

Answer: add a toggle flip flop after the 555

How Do I Make A 555 As table Multivibrator?

From Engineering Forum:

How do I make a 555 as table multivibrator? I tried to make a 555 as table multivariate from the instructions at http://www.qrp.pops.net/LEDs.asp, the top one (connected to a 4017 decade counter). I only changed the value of the potentiometer to K from K. However, when I try to use it, it operates in "one-shot" mode (I turn it on and only get one flash). Any assistance would be appreciated.

Answer: On the 555 tie pins 4 and 8 to the positive voltage Cc. Pin 1 to ground. Pin 3 is the output. Connect resistor R from the positive voltage Cc to pin 7 of the 555 and tie resistor R from pin 7 to both the capacitor C and pins 2 and 6 of the 555. Pin 3 will be high for a time equal to 0.693x (R1+R2)x(C). It will be low for 0.693 Xerox C. When C is charging via R Andra the output will be high and when C is being discharged via pin 7 of the 555 the output from pin 3 is low. This is how you make a 555 into an as table multivariate.

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