Light Dimmers

Discussion in 'General Electronics Chat' started by Mongrel_Shark, May 30, 2012.

  1. Mongrel_Shark

    Thread Starter New Member

    May 30, 2012
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    So it's possible to make a photo sensitive switch.

    It's also possible to make a dimmer that gets brighter as ambient light increases, but what about a dimmer that gets brighter as light decreases.

    I want to do this to control a joule thief, or self regulating oscillator. So the brightness of the LED stays at the point I set (with a pot on the base of transistor) As the battery charge goes down. Yes I realize this will flatten the battery faster...

    Sorry for bumping an old thread. Been googling for a couple of hours and all I can find are photo-sensitive switches, not dimmers.
     
  2. absf

    Senior Member

    Dec 29, 2010
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    And all that running on a 1.5V battery? Not sure if it's possible.

    Allen
     
  3. Mongrel_Shark

    Thread Starter New Member

    May 30, 2012
    22
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    What about with higher voltage? Not all Joule thief circuits run on 1.5v...

    Some of the ones on youtube go as high as 24v supply, with 240v+ output....

    Found another thread with a diagram, but it uses some complex parts that I don't understand well. http://forum.allaboutcircuits.com/showthread.php?t=10300

    Like the X9503 digital potenciometer. The whole thing seems unnecessarily complicated.

    I'd like to keep it simple though.

    What I really want to do is invert the function of an LDR as simply as possible. Maybe with a triac? My knowledge of semis is limited, but I learn fast. :)

    Any help would be very appreciated...
     
  4. Wendy

    Moderator

    Mar 24, 2008
    20,766
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    Welcome to AAC!

    A thread belongs to the OP (original poster). Trying to take over someone elses thread is called hijacking, which is not allowed at All About Circuits. I have therefore given you a thread of your very own.

    This was split from Dimmer, light sensitive, How to do?

    You will note this is a 7+ year old thread that has sat idle all that time. All the posters are long gone. You have also practiced the art of necromancy, the revival of a long dead thread.
     
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  5. Mongrel_Shark

    Thread Starter New Member

    May 30, 2012
    22
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    Anyone out there that can invert LDR function?


    Bump

    (i'll delete this post and rebump tomorrow if no answer...)
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Good luck with that, new members are restricted as to what they can do. Deletions are foremost part of that. We were getting abuse from the homework crowd, they would post, get their answers, then delete the questions to keep their fellow students and professors benefit from their posts, which is against everything this site stands for. It kept happening, and most of these guys would never return, so changes were made.

    I think it would be easy to do myself, though the 1.5VDC is a problem. Most op amps require more voltage than that to operate, though I know a lot that go down to 2VDC.

    How well do you do electronics in general. If you have some background I would suggest throwing something out there on the fly, which will give the other members something to polish.

    If it were for LEDs then I would suggest starting with the PWM section of my article, LEDs, 555s, Flashers, and Light Chasers, chapter 5.

    Inverting a LDR is quite easy.
     
    Last edited: May 31, 2012
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  7. Mongrel_Shark

    Thread Starter New Member

    May 30, 2012
    22
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    Thanks Bill. I was reading your Led guide last night before bed, got tired, stuff started going over my head. interesting read though. few things there I have wanted to do before.

    As far as my electronic knowledge, it's pretty limit. I tried getting into it at primary school (age 7-11) but my maths was not up to par back then, I have done most of the projects in the Short Circuts, Or funway books as a youngling. Made Am and fm radios from drawings, but never fully understood everything. A lot of it seems really simple now I have a stronger maths ability... Although ohms Law is messing with me a little atm, not because I cant use it (8/10 success rate) But because Volts is current or C, which I would normally associate with amps, and amps is now I for intensity... I bet i'm not the first to be mixed up by this... Can we pick some better letters? or is that too messy? Bear in mind. I couldn't drive to save myself before I rebiult an entire car.... then, very next day. new lap record...

    I get most thing's now (20years later) But am hitting a wall with Semis. I got the hang of NPN's a few weeks ago as I made my first Joule theif. I looked into PNP's at the same time. Enough to see they are mostly used in amps, and filled that for next time I want to mess with my bass or its amp..
    After PNP & NPN semis are a bit arcane to me. I'd like to remedy that though. Been looking for a source of good advice and I think I found it now... Some great minds around here...


    Electricity on the other hand. I know well. Lived in a 12v solar house for over 10 years. I can do watt's law when passed out drunk(I have witnesses) Disighned everything myself. Had to due to remoteness. Either you made stuff work, or you read by candle light at night and bucket water everywhere... I'm pretty good with Mechanics, not bad with basic chemistry... I can fix most household/auto thingamajigs, although sometimes I need to Google first.. Necesity is the mother of invention. your imagination is your only limit to genius.




    If anyone wants to see the circuit I want to apply this to. It's on YouTube. http://www.youtube.com/watch?v=RC3q4Qon0m0&feature=plcp (I hope linking to my channel of 1 video is ok? I can upload here if that would be preferred)

    What I want to control is the amp draw. The led will always use the same watts once the pot is set. Either up in the 1 watt range for mode 2 (Running around 60-80hz, but as low as 30hz for 1.2w draw) or 0.04w or less for mode 1 (dim mode). If you watch the video you will see me adjust this via a pot on the base of my 2n3904, and you can see some stuff on my meters and scopes...

    What I found is that there are peak efficiency points, but to stay in them you have to constantly twiddle the pot. I'd like to start by keeping this one at 80ma as the voltage drops. Problem is The led or pot? wants to keep the watts the same. So as the battery gets flat. The amps go up..... I though LDR yesterday morning and spent most of the day giving myself a headache over it.... Then just before I crashed out last night I was thinking about how the LDR looks a lot like a solar panel..... they are kind of opposite....

    Still cant work out how to automate a pot without going digital though. I'd almost rather turn a pot with a servo than go digital, except that would probably use to much power...

    Seems like it should be simple, real simple. it's on the tip of my brain but I can quite grasp the idea. I think my lack of understanding with Mofsets and triacs etc is my problem... I can make a light operated switch 20 different ways, but not a dimmer that dims in presence of light. :(

    There are a few of us on YouTube working on making cheap lighting for undeveloped country's. Self regulating oscillators seem to be advantageous because you can run a wide variety of lights from a low voltage, and low current if you don't mind it being dim....

    Everything I do I do with the intention of open sourcing it all. Same goes for anything I learn here. But you guy are already doing that so I think this could be the start of a beautiful friendship....


    Any chance someone could tell me how to invert my LDR now? I have a 3000w 240v inverter, but I doubt that will be helpful :D
     
  8. Mongrel_Shark

    Thread Starter New Member

    May 30, 2012
    22
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    P.s. I'm not keen on using a 555 or other IC. Partly because I don't know if I have one, (maybe if they are in crt tv's I will have a few in my tub of salvaged IC's, but no guarantee I can id it or that it's not cooked) And partly because I am a strong believer in the KISS principle. IC's are not simple. I'd almost rather make the same function the hard way. using a big pile of 3 pin semis...
     
  9. Mongrel_Shark

    Thread Starter New Member

    May 30, 2012
    22
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    Just found this Data sheet (http://www.jaycar.com.au/products_uploaded/ZL3556.pdf) for a 556 (double 555) from my local retailer.

    It seems to include a drawing for how to make a 556 using transistors (If I can't get the right ones I'll scale up for more power:D) etc.

    I figure once I have made a working one. I will know all about how to ramp (is that the right word) the current to my led, as well as a ton of other stuff.


    Although if someone can help speed up my learning curve. while simplifiying thing's, (I love to: Keep It Simple Stupid) That would still be really helpful.

    Either way. I think I'll stick around. This is a cool forum. I've been looking for a place like this for a while now.. Thanks to Bill and all the other clever people that make this happen.
     
  10. absf

    Senior Member

    Dec 29, 2010
    1,493
    372
    Not only you can get the schematics of the LM555. Most of the schematics of the internal of TTL gates, op-amps like 741, 358 and comparators like 393,339 are also available in the datasheets.

    If you want to make your own simple op-amp using transistors, you may also refer to the tutorials in this forum

    http://www.allaboutcircuits.com/vol_6/chpt_5/17.html

    There is a wealth of informations in the tutorial sections. And if you can spare some of your time to read them, a lot of your questions can be answered.:D

    Allen
     
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  11. Wendy

    Moderator

    Mar 24, 2008
    20,766
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    I am one of the local experts on the 555. I am not the only one here, but I am one of the more knowledgeable. I may not always respond quickly, but someone will. I will to, eventually.

    A 555 really is a simple chip, there is always other ways to do the same job. However, you want to do something of an electronic nature, you're going to have to use electronics, the only question is what kind.

    It is late, and I'll be going to bed in a bit, so I'll get back with you.

    This is a teaching site, so odds are we'll show you how to do various things. One suggestion, put your approximate location in your profile (as I have mine). This will let people know what parts you have access to, and allow for better recommendations.

    BTW, I literally wrote the section on 555s in Volume 6. :D
     
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  12. Mongrel_Shark

    Thread Starter New Member

    May 30, 2012
    22
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    This link answered my original question: http://www.kpsec.freeuk.com/vdivider.htm (I think, about to try it.) as simply as can be. I see why no one answered. I needed to find this the hard way..... SOOOO simple!! If I had of played with my LDR for another 10 min, before spending a day bouncing abound the internet, like a squirrel that ate too many bouncy balls. I probably would have worked it out on my own....

    I bet I would have found the same answer here if I had of slowed down and read stuff properly... I just did a quick search. Couldn't find anything as usefull on this page: http://www.allaboutcircuits.com/scr...719j5vhl8&cof=FORID:9&q=Voltage+divider&sa=Go Although I think the script crashed my firefox, had 27 tabs so maybe not that script... (facepalm)

    Although This Page looks like it will be helpful in applying the theory I just learned, to the application I have in mind:http://www.allaboutcircuits.com/vol_1/chpt_6/3.html


    Been reading for 20+ plus hours on this. Mostly down the wrong path (FacePalm.Org), still learnt stuff so not time wasted. Although a link a little while back would have been nice... Although I can see this was a bit of a test of my resolve and intelligence.. (Bows from hip)

    Like I said. I am enjoying this forum. I hope my answers to some of the other threads have been helpful. If someone could point me to the page where I add a quote to the bottom of my posts that would be cool. I need to add a disclaimer, because some of my suggestions can be a little dangerous... I assume people are intelligent and get let down regularly (especially by myself, hence all the Facepalms)...


    Cheers

    Joel aka Mongrel Shark


    Anyway. this thread is officially dead. Unless anyone has some (more) tips for a nOOb like me. Or is there already a thread for that? Last forum I was involved in it was bad manners to start a new thread if there was already one on the topic.... nOOb's starting threads at all was also discouraged....

    At the least could someone give me a link to the rules and etiquette that I said I read when I made my account? (I lied when I ticked the box, Sorry.)


    Thanks for making my brain hurt. It's always a pleasure...
     
  13. Mongrel_Shark

    Thread Starter New Member

    May 30, 2012
    22
    2
    I made a dark sensitive dimmer. I got it working on my joule thief. Still using the 50k pot (as part of the divider) to drive base.

    Issue 1. Is that it's not nearly sensitive enough. The full brightness of the LED, to full darkness, only makes 9ma change in draw, I need to add a degree of magnitude or two... at least ten time as sensitive would be needed...

    Issue 2. Is that the pot now has about a tenth of the range of adjustment. I used to be able to turn it about halfway (25k ish) befor LED went out. I now have about 3° of turning adjustment... Maybe a kΩ or 3 up and down... This is also affecting total brightness. I now get half the lux, almost exactly half... This leads me to:

    Issue 3. I think its draining the battery faster by dividing the voltage... Whatever charge passses through the LDR and into negitive is just plain wasted.... I saw this one coming, as soon as I say the diagram, but I wanted to play with it anyway. Just so I could have something work. Sort of.



    If anyone can tell me how to make it more light sensitive. I'd be keen to have a try.

    But I think this ones "Busted"... Time for a new thread tomorrow...

    It'll be called: "how to adjust current linearly as battery voltage drops."

    I have no ideas.... I'm off to get take away and have a ponder...

    I'll be back a little later...
     
  14. Mongrel_Shark

    Thread Starter New Member

    May 30, 2012
    22
    2
    I just F***ed up. No stress. I do that a lot. As long as I work out how. I'm learning. and it's useful.

    Problem 1. was using low amp oscillator. using 2 bifilar toroids gives more amplification. And... wait for it... Pink led's work crap on ldrs..... (Yes I can hear you loling from all the way here in australia)

    Problem 2. I accidentally grabbed a 100k pot......

    problem three. I made an assumption. I was wrong.


    So. like I said. I just f***ed up. only way to explain it....


    (I can still hear you loling. glad someone got something useful out of this thread...)
     
  15. Mongrel_Shark

    Thread Starter New Member

    May 30, 2012
    22
    2

    Yep. it is. I have a 2 videos showing it. (Well it works in part 2).

    If anyone here has a youtube account. I'd love any feedback, questions, comments, advice, whatever. On youtube. where more people will see and learn. Especially if anyone can explain harmonics I show on my scope... I know little about harmonics. I know whats going on with mode 3, it's just a feedback loop from LED to LDR. But why do some of the waveforms remind me of what I see when I put my Bass on the scope and pluck a note? Understanding the resonant frequency's is going to be the main factor in getting this as efficient as possible...

    I would love some likes and subscriptions too. If you like what I am doing..

    Otherwise feel free to comment here. Any feedback is good feedback right now.

    Part three will be up soon. Showing the results of an 8 hour overnight test.

    I had 4.6172w draw on my 1.2v (@3.880ma) battery at the start. Lights off all night while I was in bed. Got up to 3.4335w draw (1.09v@3.150ma). Bugger. I want it to keep W the same until the battery just can't supply the amps anymore...

    I think I need to bridge the legs of my LDR with a low value (trying 1k to start) resistor to make it more sensitive while lowing is overall resistance..


    Thanks for reading.
     
    Last edited: Jun 2, 2012
  16. #12

    Expert

    Nov 30, 2010
    16,343
    6,828
    About that amps and volts confusion with Ohm's Law, post#7 in this thread...look at the top of the Chat page for "Ohm's Law for n00bies". It makes things really simple.
     
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