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LED lamp project

Adkarako

May 9, 2011
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May 9, 2011
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Hey all!

I have chosen this site because it looks great with these small icons. English is not my mother tongue so sorry for the mistakes.

So my project is building an LED lamp (nothing special so far,huh?). I would like to use narrow angle LEDs (spot) and wide angles. I'm going to combine them to build a room lighting.
The second part is I'd like to switch them!I mean sometimes only the spots are lighting sometimes only the wide angles and sometimes both. It's because we don't need always the spots, only if we are reading sg.

I built this circuit http://www.reuk.co.uk/LED-Dimmer-Circuit.htm It worked perfectly!

One more important thing is the supply should be 19V or 20V because I'm going to use a laptop charger to convert 230V to 20V.

My question is I don't know what kind of timer,IC,transistor do I need.
If you have any idea feel free to leave a comment. :)
 

Adkarako

May 9, 2011
4
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May 9, 2011
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Hi again!

No one answered,maybe I was not clear. I have a new question.

So I have this LED Lamp with wide and spot LEDs. I would like to build a controller which can control the lamp in 3 state: 1. Off 2. Wide+Spot 3. Half light-intensity (ambient light).
The 3. state can be a kind of design lighting,it can be useful during the night when you go to the kitchen to drink something.

My idea is to use a potentiometer to control the light.
Any idea?Feel free to post.
 

poor mystic

Apr 8, 2011
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Hi Adkarako :-D
what knowledge of electronics do you have? Do you have any test equipment?
 

Adkarako

May 9, 2011
4
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May 9, 2011
Messages
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Hi!

I'm student and doing my final project. So I don't have 10 or 25 years experience in this profession but I'd like to learn a lot.

I do not have test board but I've already built the board with 2x5 wide angle LEDs. So there are two rows of wide angles and there will be one more row with spot LEDs.
I tested the wide angles and they are working on 30mA @ 20V (30mA on both rows).

I tried to find circuit about controlling lamp but I did not find anything.Do you have any idea?
 

poor mystic

Apr 8, 2011
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Hi Adkarako
it sounds like you can run your wide-angle led's from your laptop power supply.

If that is so, the led's can be dimmed by using a pulse-generating multivibrator to control a power transistor, switching timed pulses of current to the led array at regular intervals. The best transistor for the job would probably be a FET, because junction transistors waste valuable voltage in the base-emitter junction.

When the pulses are short, the light seems dim, and when the pulses are long the led's are "on" most of the time so the light seems brighter.

Can you design your free-running multivibrator? This might help:https://secure.wikimedia.org/wikibooks/en/wiki/Practical_Electronics/Astables/555

Let us know how you get on!
 

Adkarako

May 9, 2011
4
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May 9, 2011
Messages
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Hi poor mystic!

I was very happy about you wrote some suggestion.

My plan is to supply my circuit from a laptop charger but when I tested my LEDs the supply was from a normal voltage generator,so I set 20V and 60mA.

I worked with 555 timer if you check my first post I linked a site about a circuit what I also built and I worked with 555. So yes, I can use that circuit (555) but not with BJT but FET and of course the number of LEDs are more.

My other plan is to control this lamp. As I wrote there would be a 3 state: Off,LEDs on,half light intensity and the custumer can choose what he/she wants.
I'm searching on the internet but I could not find anything yet.
I think it can be simple,so I should use a potentiometer: at off state the current is too low to light the LEDs, on state the current is normal and half state the potentiometer is between the on and off state. Am I right?
 

poor mystic

Apr 8, 2011
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Hi Adkarako :)
If you mean that you will use the potentiometer to change the mark:space ratio of the pulses from the 555, the answer to your question is "yes".

The 555 produces pulses that can be made to provide power when "high" and not provide power when the pulse returns to zero voltage. When the 555 is working like this the name given to the periods when o/p is "high" is a "mark", and when the o/p is "low" we call that a "space". You need to be able to vary the relative amounts of time the 555 spends in its high and low states, while keeping the frequency of the pulses fairly stable.
Make up a circuit to run the 555 at a few hundred pulses per second, and vary the mark:space ratio using your potentiometer in a suitable circuit. When the pulses are "on" about half the time you'll see that the lights appear dimmer.

Trying to dim the lamp by partly blocking the flow of current will not work as well - things will get hot and the results will not be as repeatable.
 
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