Limitation of usage

Thread Starter

Lightfire

Joined Oct 5, 2010
690
Hello,

I was wondered last night about that project.

Well, my project was about "limit".

For example, I will limit my light usage. After one hour of using the light, it will OFF automatically.

And this one, I want my devices will ONLY ON if the set time has begun.

For example, I set my light at 7:00 AM then it will on at exactly 7:00 AUTOMATICALLY.

I know this is a bit silly or so but please help me to have it true. :)

Can somebody help me???
 

Adjuster

Joined Dec 26, 2010
2,148
This is what time switches are for. The electromechanical ones using synchronous motors are OK if you have a reliable mains supply with a stable frequency.

If your mains supply is not reliable, a quartz-based timer could be better. That might cost you a bit more, and one down-side is that it might not be so tolerant to spikes on the mains - these timers often use solid-state switching.
 

marshallf3

Joined Jul 26, 2010
2,358
Yea, but he wants a timer that counts down from the on time.

It can be done but not easily, I'd use a photocell (or equiv) + circuitry to control a triac. When the light is on it triggers a timer that starts a countdown circuit.

Come to think of it a few solar cells would run a CMOS 555, someone take it from here please?
 
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Wendy

Joined Mar 24, 2008
23,415
Actually that is very easy. I have some experiments written for Volume 6 showing a 555 monostable that will come close. A 555 is a integrated circuit, a very common one.

If you are wanting to do this with your house wiring I strongly recommend against. If it is with a flashlight or LED circuit then let me know what you want.
 

Thread Starter

Lightfire

Joined Oct 5, 2010
690
If you are wanting to do this with your house wiring I strongly recommend against.
No. I don't want to die yet. :)

Am, I will just use it with a 12 v halogen lamp. :) and will be operated by a 12 volts battery at the same time. :D :D

Anyway, what I want is to open the halogen lamp automatically at the set time (for example 7:00 in the morning) and then it will close after one hour has been counted...

Anyway, what is the different between dry cells and voltaic cells? I've noticed that dry cells are weaker than voltaic cells. How true is this???
 

wayneh

Joined Sep 9, 2010
17,496
Am, I will just use it with a 12 v halogen lamp. :) and will be operated by a 12 volts battery at the same time.
Bill will want to know the wattage of your light
Anyway, what is the different between dry cells and voltaic cells? I've noticed that dry cells are weaker than voltaic cells. How true is this???
You really should start a new thread when an off-topic question comes up. And you should first read what Google can show you very quickly, for example:
http://en.wikipedia.org/wiki/Battery_(electricity)
http://www.ehow.com/about_5510631_wet-vs-dry-cell-battery.html
 

Wendy

Joined Mar 24, 2008
23,415
Actually it is really easy. Most MOSFETs turn on with really low ohmage and decent current specs. I don't know what kind of electronics stores or parts are available where Lightfire is though, so I'll assume a generic device.

Using a similar schematic to the 555 Monostable, here is how you would adapt it to a MOSFET and light.

 

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kubeek

Joined Sep 20, 2005
5,794
You're right; that'll work for any reasonable wattage the bulb might have. But it won't turn on at 7AM.
If you want that, you will need some small microcontroller, for example running at 32768Hz, and some computer to set the right time
 

Wendy

Joined Mar 24, 2008
23,415
Or one of several 4060 circuts that have been develops on this site. I didn't realize he wanted a alarm clock circuit. My bad, it was stated clearly.

An alarm clock could also be modified for it. The buzzer used to trip a simple circuit.
 
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