using 120v power for LED lighting...

[smallhagrid]

Hi.
I have been called a nutcase because of my fascination with low power
consumption lighting and whenever I see a cheap item which is built
around LEDs I usually get 1 and disect it...
(Adding to my curiosity were some 120V lights I bought a year or 2 ago
that worked nicely - but not for long !)

I got a nightlight of the sort which plugs in, has just 1 white LED and
drives it with a small circuit seemingly composed of an electrolytic cap,
2 resistors, and one chip with a diode symbol only labeled 'd1ja'.

Being the adventurous sort I made a tester of 6 more 20,000 MCD white
LEDs and connected it with clipleads - and it lights just fine and stays
lit.

My question:
Does anyone here know what a d1ja is or have a similarly simple/cheap
circuit to make LED power from 120v AC so I can combine super low
cost white LEDs with it and make my own interior lights ?

And BTW: I also say STAY AWAY from any product by Lights of America.
Anything I ever got from that name was junk and they do not honor any
warranty statements they make.

Thanks !

mark

 

[DM51]

Welcome to CPF, smallhagrid.

This falls into the category of fixed (domestic) lighting, so I'll move it to the section we have for that.

 

[SafetyBob]

Welcome to CPF also.

Take a few minutes to look around on this forum which should run into hours. There are a small number of us "nut jobs" with you that have moddified or even built from scratch led lights just for interior purposes.

Electronics. Most of us are not electrical engineers. We just play one when we play with leds!! Take a look through here and see how most of us have done it. First, I will give you a hint. Transformer..... Advance and other manufacturer's have already done the hard EE stuff and have made some really nice, solid, light weight, and bulletproof led transformers. Ledsupply and theledlight come to mind as good websites to check out prices. If you have access to europe, you have significantly better choices as there are some kick *** choices being produced in Germany that haven't made it over here to the states yet.

Willing to go really deep into leds..... create at low voltage system for your house. You would then easily be able to tap off that say 12 or 16VDC and use simple BuckPucks or MicroPucks to control current to your leds. Think automation.

My first recommendation is: stop thinking about using a whole bunch of yesterday's 5mm leds. Those cheap, old leds are cheap for a reason. After not so many hours they will start to loose their intensity. They start dying is the best way to describe it. My one Seoul Semiconductor P4 that I buy from mouser (for about 6 dollars) and maybe an optic will kick butt over many, many of those little leds and do it for many, many hours and NEVER loose any noticable capacity. If you have a boat load already of those little leds and need to use them up, OK. If you don't have alot, look at the Seoul and Cree high powered leds to start, then step up with the multiple emitter options like P7 and MC-E (I think).

There will be alot of links to the manufacturers in this forum, so your research time should be shorter than it took alot of us to figure this crap out. You will find alot of reasoning also behind those choices.

Good Luck and welcome to the forum again.

Ops, forgot the most important rule of this forum (actually all of them) PICTURES!! We love pictures of what you are doing and HOW you do it. So show us what you have done so far so we can get an idea of your skill level and expertise with a soldering iron!!

Bob E.

 

[smallhagrid]

Thanks for the hearty welcome folks !
(Sorry I put that in the wrong spot too...)

Welcome to CPF, smallhagrid.
This falls into the category of fixed (domestic) lighting, so I'll move it to the section we have for that.

Welcome to CPF also.

Hi Bob.
I noticed that a few minutes could turn into hours so I tried searching instead and found little specifically about this - so I asked.

Very glad to hear that I am not the only nut job tinkering with this stuff here !!!

I am definitely NOT an electrical engineer - but I am a career tech and I do very much enjoy playing with leds.

The transformers by Advance and such sound nice but cost $$$ and I already have some goodies and tend to play for CHEAP as I can...

Truly I happen to LIKE the 5mm leds. They may be cheap old things but they are good enough for me - and I haven't noticed any that lost their intensity...yet.

As for pictures - I'll need to bring my camera inside and usually forget to; I keep it in my car because that's how it gets the most use - but I'll tell you right now I am not a neat solderer as I lack fine manual dexterity for it; so I may not be big on the pics after all.


Thanks for the replies and Best Wishes,

mark

 

[jason 77]

I got a nightlight of the sort which plugs in, has just 1 white LED and
drives it with a small circuit seemingly composed of an electrolytic cap,
2 resistors, and one chip with a diode symbol only labeled 'd1ja'.

That is most likely a rectifier IC, I have taken apart some cheap Chinese 5 millimeter light bulbs and they seem to use a small rectifier IC with some smoothing caps.

 

[RODALCO]

That d1ja item is most likely a rectifier of some sort.
Either a full bridge or just a diode.

I share your thoughts too and like the 5 mm LED's for most of my projects.

For 120 Volts I use 2 x 6800 ohms 1 Watt in series and a forward biassed 1N4007 diode to reduce heating in the R's.
The LED's run at 10 mA's which is more than adequate for me.

You can also use a capacitor to limit the current to between 10 and 20 mA's, and a series 470 or 1 k Ohm resistor is a good idea to limit the inrush current to the LED.
An antiparrallel diode is required to protect the LED against reverse voltages.

 

[Steve K]

Electronics. Most of us are not electrical engineers. We just play one when we play with leds!! Take a look through here and see how most of us have done it. First, I will give you a hint. Transformer..... Advance and other manufacturer's have already done the hard EE stuff and have made some really nice, solid, light weight, and bulletproof led transformers. Ledsupply and theledlight come to mind as good websites to check out prices. If you have access to europe, you have significantly better choices as there are some kick *** choices being produced in Germany that haven't made it over here to the states yet.

....<snip>.....
Bob E.

I was having thoughts about replacing some incandescents myself, and stumbled across this thread. The suggestion to look at power supplies from LedSupply and theledlight were helpful. $35 to get a 18W power supply for 700ma LEDs is not a bad price.

Still.... as a EE with just enough knowledge of switching power supplies to be dangerous, I'm still intrigued by the idea of building or designing a converter of my own. It would be a basic buck converter, current regulated, and probably of a hysteretic design (no complicated feedback stability issues to deal with). I've done a lot of analysis on an old voltage-feedback hysteretic design many years ago, so there's a natural attraction there.

Anyone have any suggestions, words of wisdom, or precautionary tales?? I've got a few projects in the queue ahead of this one, so I'm at the phase where I just sketch out circuit ideas when I have some spare time.

thanks,
Steve K.
(usually found over in the bike lighting area)

 

[jason 77]

I bought one of these guys off of ebay, I am hoping I can make it work the way it discribes..

http://cgi.ebay.com/High-voltage-co...34.c0.m14.l1262&_trkparms=|301:1|293:1|294:30

 

[markus_i]

That chip is probably a diode or a rectifier, depending on the number of leads. Diode would work, but result in more flicker (due to a 50% PWM). But since they're also using resistors, it's probably a rectifier (you can do it without the resistors, so if the designer allocated the money for the resistors, they probably also used the more expensive option of donating a full rectifier). The capacitor is (probably) the current limiter (remember, we're talking AC here, or at least pulsating DC).

Problem with this kind of approach is that it's not safe, i.e. if any component in the circuit fails to 'open' mode, there's the full mains voltage on that component's connections. In addition, any part of that circuit will have the full mains voltage to ground. About as safe as an old-fashioned electric toaster. Tolerable inside a secure housing, not really advisable as DIY if you don't know how to deal with electricity.

But since you're apparently still alive...

Anyway, safest bet to get power for a LED system is to buy a switch-mode DC power supply. Wall wart for smaller lamps (below maybe 10 Watts), something larger (maybe a surplus computer supply) for larger lamps.

Bye
Markus

 

[Steve K]

I just found out about a new controller IC from National Semiconductor. It's designed to power a string of LEDs when using a triac dimmer powered from 120vac (maybe 220vac too?).

http://www.national.com/pf/LM/LM3445.html

"The LM3445 is an adaptive constant off-time AC/DC buck (step-down) constant current controller designed to be compatible with triac dimmers. The LM3445 provides a constant current for illuminating high power LEDs and includes a triac dim decoder. The dim decoder allows wide range LED dimming using standard triac dimmers. The high frequency capable architecture allows the use of small external passive components. "

I'm not sure about the phrase "small external passive components", as it does require a number of diodes, a couple of transistors, some caps and an inductor. It might be physically small, though.

For applications where you are currently using incandescents with a dimmer, this seems like an excellent replacement.

regards,
Steve K.

 

[LukeA]

I just found out about a new controller IC from National Semiconductor. It's designed to power a string of LEDs when using a triac dimmer powered from 120vac (maybe 220vac too?).

http://www.national.com/pf/LM/LM3445.html

"The LM3445 is an adaptive constant off-time AC/DC buck (step-down) constant current controller designed to be compatible with triac dimmers. The LM3445 provides a constant current for illuminating high power LEDs and includes a triac dim decoder. The dim decoder allows wide range LED dimming using standard triac dimmers. The high frequency capable architecture allows the use of small external passive components. "

I'm not sure about the phrase "small external passive components", as it does require a number of diodes, a couple of transistors, some caps and an inductor. It might be physically small, though.

For applications where you are currently using incandescents with a dimmer, this seems like an excellent replacement.

regards,
Steve K.

This is something a lot of designers have been waiting for. Too bad about all of the external components, but I think a useful application of the IC will still be pretty small.