Progressive LED light - How to ?

[Kagliostro]

I want to have the way to light a LED from darkness till his max light turning a knob

which is the best way to do that ?

does someone has a schematic for a little PS to be used for this purpose ?

Thanks

Kagliostro

[roberto]

Hi Kagliostro, what do you think about a PWM control?
Pay attention to the duty sweep, because light is not proportional to % of duty.

[Kagliostro]

any circuit is fine for me, enough to have a schematic of safe operation

Kagliostro

[John_P_WI]

Why don't you try a pot wired as a variable resistor in series with the led bias resistor?

400 ohms bias resistor (or what ever) + pot variable resistance + led

The lower the starting voltage the lower the pot value.

Simple and should work.... You do know the bias current of the led, right?

Edit: When I asked my EE co worker he said that this would be simple with an NPN transistor and a pot to vary the current, followed by something like buy a damn book and learn it yourself Hmmmm, seems top be a lttle animosity towards us mechanical engineer types today....

[roberto]

[img:630:359]http://www.discovercircuits.com/DJ-Circuits/LEDPWM2.JPG[/img]

[NickC]

........ Edit: When I asked my EE co worker he said that this would be simple with an NPN transistor and a pot to vary the current, followed by something like buy a damn book and learn it yourself Hmmmm, seems top be a lttle animosity towards us mechanical engineer types today....

Maybe you should show him this:

https://tubeamparchive.com/viewtopic.php?t=17527

[Tillydog]

Brightness depends on current, rather than voltage - How about this?

The LED will be off for the first ~30 degrees of pot rotation. If that bothers you, put a forward biased silicon diode in the connection between the pot and ground.

Andy

[srubelva59]

I just got this new refrigerator that has these cool blue LEDs that start low when you open the door and get brighter after two or three seconds. Since the newness hasn't yet worn off if I need something quick out of the fridge I'll still keep the door open until the LEDS are maxed.

TBH I'm struggling here trying to imagine an application in a Tube amp.

What's the plan? Just curious...

[davent]

http://pcbheaven.com/circuitpages/LED_PWM_Dimmer/

[Kagliostro]

@ Srubelva59

I think this is what is happening in your refrigerator

http://www.youtube.com/watch?v=ZVILXxGdlD4

----------------

[img:250:350]http://www.freewebs.com/valvewizard/ACltp2.jpg[/img]

substitute the 820R resistor with an adequate LDR paired with a LED

use something to control the light emitted by the LED

and imagin the result

-----

looking around I've also find this

[IMG:225:225]http://s2.imagestime.com/out.php/i669949_LedPS.jpeg[/img]

so, looking to the ideas shown till now, what do you think will be the most practical circuit to be used ?

remember I've only one LED but want to have a reliable and stable circuit

Thanks to all

Kagliostro

[John_P_WI]

Tillydog,

Yep, that is what the EE scribbled on the white board right before his mumble....

[Jana]

How about a mechanical aperture with a fresnel lens on it. The aperture is strictly mechanical controlled by the knob connected to a gear mechanism. The led is on all the time, of course. Who needs an EE to solve this problem!

[VacuumVoodoo]

Use a PIC uC to control a current source feeding the LED in small steps. Map light intensity vs current into uC memory. This is used by uC to set correct duty cycle of the PWM output. Why make it simple when we can make it complicated beyond reason? The beauty is proportional to the complexity of solution to a simple problem.

[Kagliostro]

So you suggest I must stop to the attached image (?)

instead of use the services of the CSAO

(Complicating Simple Affairs Office)

we want to spend much more
http://www.youtube.com/watch?v=X8gMrTk08Lw

Ciao

Kagliostro

[roberto]

http://forum.allaboutcircuits.com/pictu ... tureid=322