Hard wiring AAA powered LEDs for 12V???

[getout]

I bought some LED puck lights from Costco that I like because they're remote controlled and they can be individually pushed on and off. The only problem, they're powered by 3 AAA batteries and I don't want to be changing batteries all the time. I'm trying to figure out how to wire them so they can run off the 12V system. If there are some Electrical Engineers out here, a little help would be greatly appreciated.

Or you can just tell me I'm crazy and this won't ever work. I thought I'd try though. Here's what I know:

The 3 AAA batteries in series produce 4.76 Volts and the current is 112.8 Mah when one light (set of five LEDs) is on.

I used some online calculator that told me to go from 12V to this system, I would need a 2W, 68 ohm resistor. I thought I could run that and a 12V linear regulator to make this work. I haven't tried it yet because the resistors are special order. Cheap, but I thought I'd ask if this all makes sense before I spend a week waiting for parts I won't use.

Here are some pictures:

Thank you all!

[Totem]

resistors. radio shack or chinese cheap ones.

[waiter]

Your math looks good

You want to drop 7 volts and the series current is about 0.112 amps. That comes up to about 62 Ohms, at 1 watt. Wire the resistor in series with the light.

Goto Radio Shack, get whatever they have thats close. . i.e. 51 ohms or wire two 120ohm in parallel (this would equal 60 ohms). Probably best to go with 2 watts. Get whats cheapest, don't worry about tolerance.

JOhn Mc

88 Dolphin 4 Auto

[waiter]

Just noticed something, these are dim-able, so all bets are off.

Goto Radio shack, Get a 7805 regulator, wire this in series with a 50 ohm 2 watt resistor. The 5 volts will stay 5 volts, regardless of current draw, up to about 1/2 amp.

JOhn Mc

88 Dolphin 4 Auto

[getout]

Just noticed something, these are dim-able, so all bets are off.

Goto Radio shack, Get a 7805 regulator, wire this in series with a 50 ohm 2 watt resistor. The 5 volts will stay 5 volts, regardless of current draw, up to about 1/2 amp.

JOhn Mc

88 Dolphin 4 Auto

Sweet. Thanks for the info. I'll give it a shot.

[waiter]

Are you comfortable wiring the 7805?? I don't think it will get hot, that's the purpose of the resistor, to make life easy for the 7805. the resistor will drop about 1/2 of what you need dropped, and the rest will be dropped by the 7805.

These come in different styles, I don't think you need the one that mounts on a heat sink. when you hook the stuff up, keep an eye on the heat to make sure your OK.

Google "7805 voltage regulator" and you'll get all kinds of help on hooking it up.

John Mc

88 Dolphin 4 Auto

[zero]

I bought some LED puck lights from Costco that I like because they're remote controlled and they can be individually pushed on and off. The only problem, they're powered by 3 AAA batteries and I don't want to be changing batteries all the time. I'm trying to figure out how to wire them so they can run off the 12V system. If there are some Electrical Engineers out here, a little help would be greatly appreciated.

A simple IC voltage regulator chip is all you need. Much better then a resistor since it regulates the voltage. A LM7805 chip costs less then $1. Shipping cost more then the chip itself unless you can pick one up locally. I've bought them as cheap as 20 cents. LM7805 on the input accepts 8-24 volts DC (or somehwere around there) and puts out a regulated 4.5 to 5 volts DC.

[zero]

Waiter - I didn't mean to be redundant. I didn't see your post until after I sent mine.

Back to the reg - if a person wants to be fancy an extra $1 worth of components can be added to the regulator chip if wanted. This is the LM7805 or the NTE960.

[getout]

I've seen pictures of the voltage regulators and have a decent idea of where they go in the system. I suck at soldering though so that might get interesting.

If I'm understanding correctly, I've got a few options:

• Use a LM7805 and a 50 ohm, 2W resistor
  
• Use just the LM7805
  
• Use just a NTE960

Price wise it looks like maybe only $1 a piece or so between the options though the NTE960 seems more expensive. I'll be doing about 18-24 lights.

What's best/difference?

[Alvin]

Your power loses won't be huge with an LM7805... or just a resistor, but why waste the power? You should get a high efficiency DC-DC converter... something like this:

http://www.amazon.com/Converter-Step-Power-Supply-Module/dp/B00A71CMDU

Use the google search "DC-DC converter 12V to 5V" and see what you come up with.

DC to DC converters modulate the DC voltage input, adjust the level, and use a high frequency modulated P-FET or N-FET to provide you with a well-regulated output at a given voltage level (in your case 5V). I design these systems all of the time in my job as an EE, but you can buy one cheaply and ready made for your application. You won't have the dropout power wasted as with the LDO solution suggested above (LM750x types). If you have any back-leakage on the EMI you can quiet it down with a ferrite but I doubt that will be a problem at all (unless you're trying to meet mil-std's with your RV. lol).

Your efficiency will be around 90% or better for the power conversion. I like 7805's, but not on vehicles where battery life should be conserved.

You can also pick up any 12V car cigarette lighter to USB charging adapter... and pull off the 5VDC and GND from 2 of the 4 wires. Maybe you already have one of these... so just get an old USB cord and do a little surgery. Type "Car USB charger" into amazon.com... you'll see what I mean. USB charging voltage is 5V and most new ones will do 2 or 3 amps. Old ones at least 1Amp.

[Maineah]

If they are all going to be on at the same time series wire them.

[getout]

Could you run all 18-24 lights off one converter as opposed to wiring voltage regulators into each light?

[getout]

Ok. I did some more research. Tell me if I'm thinking about this all correctly.

I want to run the lights in parallel because they'll be on and off individually and not all together. Doing that also means they need the same 5 volts delivered to each. As more of the lights are on, the amps will increase.

So, if each light draws .1128 amps, if all 24 were on at the same time it would draw just less than 2.8 amps. I should be able to get a 5amp, 12v to 5v converter like the one below and run all my lights from this one converter without regulators or resistors.

http://www.ledoes.com/product/203008-52388877-dc-converter-step-down-buck-module-12v-24v-5v-5a-25w-waterproof-car-led-display-power-supply-converters-wholesalers.html

My next question, how does the 30-60 feet of wire affect all this?

How am I doing? Am I getting this figured out?

[waiter]

If you want to run all the units off the same 5 volt supply, yes that little unit you linked to will work, at if its able to supply 5 amps, you should be in good shape. Wire size around #20 shouldn't be a problem.

John Mc

88 Dolphin 4 Auto

[Alvin]

getout, your wire resistance will be negligable. Look at this web site:

http://en.wikipedia.org/wiki/American_wire_gauge

Notice that 20-AWG wire, the resistance is about 33-ohms per kilometer... or about 33-milliohms per meter. So you would need about 30-meters of wire just to have one ohm of resistance. You're more than safe. I think your selection of a DC-DC converter that you linked to is great and that your plan to run several of these circuits in parallel is fine. You'll get alot of light for your 25W investment and taking into account the 90% efficiency, 27.5-Watts in, will produce 25-Watts out. This is a very good solution to your project.

Side note: You may want to consider tapping on plugs for any other 5VDC appliances or devices you have just for the sake of handiness; about 50% of all of those devices we use that have 120VAC wal-warts attached are really just supplying 5V to some small circuit. The trick is to make sure you connect the polarity right. I'm a huge snob when it comes to getting rid of walwarts. Walwarts are the scourge of the digital age. lol.

[stamar]

It was much cheaper for me to buy six 12 volt leds from ebay

You can also buy a 12 volt dimmer switch from ebay for 4$ shipped and put it in the lights circuit dimming all of them at once.

The lights I'm using are extremely much brighter than the pucks you bought, those are most usefull for putting inside the drawers

And as karin said having a non deep cell cycled power source for emergencies is good.

I can see the desire for remote controll operated lights, but if you put a dimmer switch by your head its similar function.

I realize you have the pucks now and want to have a use for them, and might even enjoy projects its just youre ending up with a dimly lit interior for a lot more money and hassle.

http://www.ebay.com/itm/12V-24V-8A-PIR-Sensor-LED-Switch-Dimmer-LED-Strip-light-Dimmer-Cotroller-/290736130969?pt=LH_DefaultDomain_0&hash=item43b1394b99

the pucks are better for what they are, throw a puck inside each cabinet, and then one overhead for a non house powered light source.

for that use the enclosed batteries should cover your lifetime several times over.

[waiter]

One other consideration on the remote LEDs, they never turn off, they will always draw a small amount of current, even when turned off, we call this "Phantom Loads". 1/2 amp doesn't sound lik e much, but in a week, your battery will be dead.

I have several Phantom loads in mine (LCD TV, AM/FM radio, GPS bluetooth receiver, etc) I added a power switch under one of the cabinets to supply all the phantom loads, this way I can turn off the power to these loads and they don't run the battery down when I'm parked for a couple weeks.

JOhn Mc

88 Dolphin 4 Auto

[stamar]

a remote switch to turn off your remote lights.....

Ive got a 21 foot motorhome and the most remote part from me while im lying down is about 10 feet.

Its very nice though to be able to turn the lights off when youre going to sleep.

But unfortunately the pucks you bought arent suitable to really light up the interior in the first place, they are made for a small space or just to light up an area so you can see it. like the bathroom.

your real interior lights are still incandescent lights that use tons of power.

as soon as someone installs that 12 v dimmer switch in a real led interior light that should really be the final solution. just put the switch near your head where you sleep, wired right to converter box fuse for the lights. that way you have dim and off.

you could even wire your puck peices in somewhere I guess.... but why would you? what you sort of have once you remove the battery is kind of something that needs a lot of soldering to become something no one really needs.

thats why its not for sale...

[stamar]

this reminds me off the clapper. I wonder if theres a 12 volt clapper fuse on ebay somewhere.

[Dolphinite no longer here]

Waiter,

I didn't know that LED's never really turn off. Is that all LED's or just those puck lights? Would LED tail lights drain my starting battery?

John

[Alvin]

If you have a switch on the front end of your power (the 12V side), it's off... no phantom load issue. So lets say you have a 12V to 5V dc to dc converter and you put the switch on the 5V side, you may have a tiny load because of the converter (not the LED loads on the converter). So, get out a micro-amp meter, put it in current measurement mode, then connect the meter to the circuit. If you measure 0.1-milliAmps or less, don't worry about it. Here's why:

The battery will lose capacity over time anyway even not connected, you need to charge it for 10 or 15 minutes every month or so to extend the life. uA loads (micro Amps) aren't typically enough to worry about compared to an amp or two for powering even a small light bulb. If you can run a small light bulb for 1 hour, then you can run a 100-microAmp load for 10,000 hours.... where the calculation breaks down anyway if you're not charging your battery periodically due to losing battery capacity naturally.

10,000 hours is more than a year.

[waiter]

John,

The little units that he bought are controlled with a small remote control transmitter, The "LED" turns off, but the remote control receiver inside the units is always on, and draws a small amount of current.

I'd be willing to bet the small 5 volt power supply will also draw a small amount of current, even if nothing is connected to it.

JOhn Mc

88 Dolphin 4 Auto

[Maineah]

I agree John most switching supplies have an idling current.

[getout]

It was much cheaper for me to buy six 12 volt leds from ebay

I'd really like 12 volt lights but they're not cheap. We don't have any fixtures anymore in our motorhome so we'd have to buy all new fixtures as well. Also, it would be nice to turn some lights on while keeping other lights off. I thought about doing the Ikea LED pucks but are they any brighter than what I've got? How can I do this without breaking the bank?

One other consideration on the remote LEDs, they never turn off, they will always draw a small amount of current, even when turned off, we call this "Phantom Loads".

I figured I'd run a switch through a relay before the voltage converter. Shut all the lights off in the whole unit. I'm going to put the switch close to the door though.

a remote switch to turn off your remote lights.....

But unfortunately the pucks you bought arent suitable to really light up the interior in the first place, they are made for a small space or just to light up an area so you can see it. like the bathroom.

The remote sounded like a nice luxury item. It's probably going to end up in it's little holder on the wall 95% of the time. Brighter lights would be nice, but I seem to have a hard time finding an affordable solution to that.

Going the Costco puck light route looks like it will cost me $30/pack x 4 packs for a total of 24 lights and $120. A $10-$15 voltage converter and I've got all my interior lights for around $140 or so. We're used to tent camping so any mounted/permanent lighting will be a plus. I'd be willing to dump the idea of the remote and ability to turn on individual lights for brighter ones if I could light the motorhome for about the same price. Any ideas?

[Alvin]

I've been buying 12V replacement lights and fixtures for my 89 Odyssey here:

http://www.amazon.com/gp/product/B000BRCL5E/ref=oh_details_o05_s00_i00

and here:

http://www.amazon.com/Progressive-Dynamics-PD781WSBCV-Single-Ceiling/dp/B000BRJVIY/ref=pd_bxgy_auto_img_y

There are 12V, cheap, and require no converters. I don't consider these expensive at all?

[waiter]

Alvin,

nice fixtures, and good price. Slap some of these LEDs in them and your now modernized...

LED Light Upgrade

John Mc

88 Dolphin 4 Auto

[Alvin]

I like the LED light mod suggestion. Thank you. I found that you can buy a bag of 100 of these for $80 here:

http://www.ledmarketing.com/p/36-1210-smd-led-car-light-panels-980-37399106.html

Should do about 10 Odyssey's.

Buy 300 or more and you can get the price down to 72-cents each. lol

[getout]

Do you not need to install a voltage regulator on those LEDs? Can they handle the extra voltage from the alternator?

[Derek up North]

Both of these can (reportedly) be direct wired to 12v:-

http://www.ikea.com/us/en/catalog/products/10192107/

http://www.ikea.com/ca/en/catalog/products/50192073/

Perhaps other, too.

[Alvin]

Do you not need to install a voltage regulator on those LEDs? Can they handle the extra voltage from the alternator?

No, and yes.

These LED's are wired for 12VDC and require no regulator.

To a point, LED's are resliient to voltage and power surge transients. They do have a built non-linear in-internal resistance (RDS) that limits the current some, and if you drop more voltage across them, thereby increasing the current a bit, for just a moment, the LED may brighten just a bit for a moment if it's not saturated optically, but will not fry.

[getout]

So you're all starting to convince me to go 12volt. My next question, could you use this in place of rear brake and turn signal bulbs?

http://www.ledmarketing.com/p/36-1210-smd-led-car-light-panels-980-37399106.html

[waiter]

IMPORTANT NOTE on Interior LEDs. Make sure you get "warm white". The "warm white" spectrum that these put out will be almost identical to a standard 1141 incandescent bulb. ALSO - The ones I used, the brightness is almost identical to the 1141 bulb. Although photos aren't good for judging light spectrum, you can see the obvious difference, look at the photos in this link: Bottom line, same color and brightness as 1141 bulb, but 1/5th the current draw.

LED Interior Light Upgrade


As for your tail lights, The ones you linked to will not work. For the rear, you need two levels of brightness.

Take a look here to give you some ideas:

LED Running Light upgrade

LED Tail light upgrade

My goal in converting to LEDs was to reduce the power consumption to a level where the OEM 55 amp alternator would have no problem keeping up with the loads, AND, I want the reliability of never needing to replace the light bulbs again. (This factor was driven by a constant issue with tail lights intermittent because of the bad sockets. I had similar problems with the interior lights, the switches and sockets were intermittent.

John Mc

88 Dolphin 4 Auto

[Vanman]

I got several LED's for home use to try in place of compact flourescent bulbs. The light temperature varies with different models, but one thing is a constant, the aluminum fins at the base get hot. I thought the 120VAC LED's were supposed to be energy savers, but this is just waste heat. The digital meter I have now doesn't measure current and these LED lamps use too little current to register on my old clamp-on amp probe. Is what I'm seing a byproduct of the electronics rectifing and voltage dropping inside the lamp??

Reading the old post on the LED's in a Toy one of the posters said his LED's got hot. With the current loads being reported I would think heat is not an issue. ???

[stamar]

some of the direct links in my signature to ebay auctiions are a little out of date, but you just follow thhe relisting.

it shows all the leds you would want for your toyota motorhome, most of the bulbs are 50 c or less.

ive got the interior tail and brake, and the marker lights done.

even an amazon reseller is just buying them from ebay and reselling them to you for more.

so we all bought 36 smd leds 12 volts for 4.50 apeice. you can get cheaper ones in fact I got blue 18 smds for 75 cents. but those are bright enough.

theyre also this years leds whereas something sold in a store in america is something made in china from years ago.

now as far as fixtures thats something ive never taken on. I would personally just yank them from a junkyard somewhere. but the fixtures are probably for sale cheap online.

[Maineah]

I got several LED's for home use to try in place of compact flourescent bulbs. The light temperature varies with different models, but one thing is a constant, the aluminum fins at the base get hot. I thought the 120VAC LED's were supposed to be energy savers, but this is just waste heat. The digital meter I have now doesn't measure current and these LED lamps use too little current to register on my old clamp-on amp probe. Is what I'm seing a byproduct of the electronics rectifing and voltage dropping inside the lamp??

Reading the old post on the LED's in a Toy one of the posters said his LED's got hot. With the current loads being reported I would think heat is not an issue. ???

Yes there is heat from conversion but the LED's with the cooling fins are driven very hard to get the high light output.