Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Ac 230v delayed "off" timer circuit

Status
Not open for further replies.

sssuneth

Newbie level 4
Joined
Oct 31, 2012
Messages
5
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,330
Hello there,

Can any one please share a schematic for a delayed OFF timer circuit.

My requirement is to have the Light(230V) stay ON (approx 15 sec.) from the moment it turned off from the wall switch. I currently have a CFL (23W) bulb, if its not appropriate I can replace it with a LED light.

Thanking you,
 

Hi,

you nedd an energy storage.
23W x 15 s = 345 Ws = 345 J = 0.1Wh

if you use a capacitor. Let´s say 24V then Q = 1/2 * C * U^2
...
C = sqrt ( 2 x Q / u^2) = sqrt( 690Ws / 576 V^2) = 1.1F which is to big value.
Maybe you need a battery..

****
decide to dim the light to 5% durig those 15s.

(all calculated with 100% efficiency --> not realistic)

Klaus
 

cap.jpg

May I use one of these across the bulb +and (-) terminals?

(it does not have to exact 15seconds..)
 

You can not store AC in a capacitor so no, even if you could find a 1.1F/450VAC rated one it wouldn't work. Just for reference, the one you show is 1.5uF, that is almost 700,000 times too small !

Is the AC voltage present all the time, even when he switch is turned off? If it is, the solution is an electronic switch with a built in delay before it turns off. You can buy them 'off the shelf', they are commonly used in entrace hallways so the light stays on for long enough for someone to find a door or climb stairs before automatically turn the light off to keep costs down. They work with any kind of light bulb.

Brian.
 

Hi,

i gave you the formula:

Q = 1/2 * C * U^2

you are free to use it with the help of your calculator.

(it does not have to exact 15seconds..)
...but are 7ms enough?

Klaus

added:
my calculation is for rectified 230V into the capacitor...just to show the discrepace of energy.
 

1.) Thank you betwixt.
If you know any product or if you have a link please pass it me.
What I ve found is SIEMENS 6ED1052-1FB00-0BA8 (I feel like this is too much for my job)

2.) Thank you KlausST,
Q = 1/2 * C * U^2 I am not too sure what these letters reprecent.
I guess C=Capacitance but Q and U am not too sure.
 

Hi,

Sorry, I mixed some things.

Correct: W = 0.5 × C × V^2

Klaus
 

you can make simple delayed timer by using CD4538 or 555 timer I.C, simple google it and you will find your require circuit

Fragrance
 

Hi,

I looked at wikipedia.
https://en.m.wikipedia.org/wiki/Capacitor
At "Energy of electric field"
Wikipedia says W is the symbol for "work" with unit in Ws, Joule..
P stands for power in Watts...

(To clarify my wrong use of "U" of post#2: here in germany we use the symbol "U" for voltage, but "V" as the unit of voltage)

Klaus
 

Hello there,

Can any one please share a schematic for a delayed OFF timer circuit.

My requirement is to have the Light(230V) stay ON (approx 15 sec.) from the moment it turned off from the wall switch. I currently have a CFL (23W) bulb, if its not appropriate I can replace it with a LED light.

Thanking you,

It is not possible unless you use DC with LEDs and a very big superCap, even then it is not feasible.

Try to design a circuit with PWM dimmer instead that ramls down slowly on push button input .
 

PWM. Supercaps, timers and counters.....

Sssuneth is just asking for a time-lag light switch! 230V AC ---> switch ---> light bulb.

Brian.
 

There are many circuits you can find in google and just select one you like. For modifications or change, you can always ask some of our experts here. The switch is a SPST type and when you press it once, power is applied to the load and also a transformer that supplies 12V for the electronics is also activated. A retriggerable one shot is generated and the time for this one shot is predetermined. Once this one shot is out, the load switches off via a small relay. You can also use a triac instead of a relay.

Look for time delay switch and you can also include relays that can help set a fixed delay time.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top