Author Topic: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED  (Read 4513 times)

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Online Ian.M

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #25 on: November 29, 2017, 04:21:57 am »
The '3V' LEDs at the URL the O.P. posted, don't have any series resistor.  They are relying on the internal resistance of a 3V coin cell to limit the current enough for them to survive.  If you connect them direct to a larger battery, they'll probably blow as there wont be enough internal resistance to limit the current sufficently.  If you connect two in series, direct to a 6V lantern battery they'll also probably blow.   Using a higher voltage and a properly calculated series resistor or other current limiting circuit is the easiest one of the very few way to run them reliably from a large battery.
 
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Offline John B

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #26 on: November 29, 2017, 04:37:07 am »
Those cheap chinese LM2596 modules also come in adjustable constant current varieties too....just saying.
 
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Offline IanB

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #27 on: November 29, 2017, 04:48:41 am »
The '3V' LEDs at the URL the O.P. posted, don't have any series resistor.

It's true they don't look like they have a series resistor. However the text claims that they do. I have been trying to work it out.

If I had them in my hands I would examine them closely, measure them and then calculate a series resistor accordingly if needed.

With all of this technicality it doesn't seem like a "plug and play" solution for someone who doesn't have the knowledge.
I'm not an EE--what am I doing here?
 
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Online Ian.M

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #28 on: November 29, 2017, 04:58:57 am »
Those cheap chinese LM2596 modules also come in adjustable constant current varieties too....just saying.
That's a lousy idea as directly paralleling LEDs typically results in current hogging.  The one that has more current gets hotter, its Vf goes down so it grabs even more current till it blows (thermal runaway).  Then it depends on if there is enough current to blow it open circuit.  If so the current through the other LEDs goes up by a factor of N/(N-1) and the thermal runaway process starts again with another LED.  If not, it shorts them all out and the whole lot go off.

The '3V' LEDs at the URL the O.P. posted, don't have any series resistor.

It's true they don't look like they have a series resistor. However the text claims that they do. I have been trying to work it out.

If I had them in my hands I would examine them closely, measure them and then calculate a series resistor accordingly if needed.

With all of this technicality it doesn't seem like a "plug and play" solution for someone who doesn't have the knowledge.

The illustrated 3V LED doesn't have a resistor, and that would be consistent with  white or blue LEDs with 3V Vf,  but it seems they do other colours for 3V and one would not expect 3V Vf for some of those colours, so those probably do have resistors.

@O.P: Please post a close-up photo of one of your LEDs with the full lead length visible in the photo.


 
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Offline rstofer

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #29 on: November 29, 2017, 05:46:24 am »
The vendor also sells a dual AA battery holder for these LED strings so the internal resistance of the coin cell isn't the only method of current limiting.
 
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Offline withwings

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #30 on: November 29, 2017, 05:46:50 am »
The event is 100 miles away. No electricity available because of cords. I can't stay for ten days and too far to keep driving there  :scared:
 

Offline IanB

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #31 on: November 29, 2017, 05:52:37 am »
Does it need to be illuminated 24 hours a day? Can someone switch it on and off at appropriate times?

There is unfortunately no way around it. Having something lit up 24 hours for 10 days is 240 hours in total. Even with the most economical lights that will require a very big battery.
I'm not an EE--what am I doing here?
 
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Online Ian.M

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #32 on: November 29, 2017, 05:58:47 am »
Battery powered programmable digital time switch?
 
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Offline John B

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #33 on: November 29, 2017, 07:52:20 am »
Those cheap chinese LM2596 modules also come in adjustable constant current varieties too....just saying.
That's a lousy idea as directly paralleling LEDs typically results in current hogging.  The one that has more current gets hotter, its Vf goes down so it grabs even more current till it blows (thermal runaway).  Then it depends on if there is enough current to blow it open circuit.  If so the current through the other LEDs goes up by a factor of N/(N-1) and the thermal runaway process starts again with another LED.  If not, it shorts them all out and the whole lot go off.

Constant voltage it is! I guess I am wondering whether its worth "complicating" things past a plug and play module. Without some active circuitry the lights are just going to dim as the source voltage decays.
 
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Offline soubitos

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #34 on: November 29, 2017, 08:24:12 am »
You might find this useful.
https://easyeda.com/catech75/TP4056FLEXADV_V3_00-9fe9350f414a4cacb9a8683de565d007

It is made so that it charges the LiIon battery/ies from virtually any power source you might have in hand and uses a joule thief circuit to power a common 12V LED string (can be found around 1$/m these days).
I just got the pcbs for this two days ago together with most of the parts for the board, others i need to wait to arrive from China via snail mail.

If you find low power led string (2,4W/m are the smaller i can find locally) this will power it for many hours on a single 18650 cell easily.
You will need more cells in parallel and certainly you cannot expect it to keep the leds on for 10 days straight on a single battery anyway and unless you use A LOT of cells, this will make sure you will recharge the cells safely and also has all the protection you need from overcharging and overdischarging.
 
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Offline withwings

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #35 on: November 29, 2017, 05:06:35 pm »
no not really
 

Offline rstofer

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #36 on: November 29, 2017, 05:40:12 pm »
I wonder if a solar garden light (or equivalent) can be hacked.  I don't know whether solar cells work from indoor lighting but they might.

Does the lighting really need to work ALL night long or just work for a few hours after dark?

If the lighting needs to work during daylight hours, this might not be a good approach.

Still, why wouldn't a doll house have solar energy?


 

Offline kalel

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #37 on: November 29, 2017, 05:48:24 pm »
Solar cells (at least on cheap ones) are very poor indoors. Perhaps if the room has tons of light, but I have tried a unit and it only gets a few seconds of light (with 2 LEDs), after a few days. The current supplied is limited too, usually set by an inductor, I'm not sure it could run 24 LEDs (at least effectively).
 

Offline soubitos

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #38 on: November 29, 2017, 05:48:39 pm »
garden solar lights are not a viable option hacked or not... lots of them are designed around an YX8018 joule thief chip which charges a NiCd/NiMh battery during daytime and discharges it to light a single LED.. there are other YX8xxx chips to light 2-3 leds but unfortunately, i cannot see the YX8128 (i think) anywhere which is charging a li-ion battery and can go up to 1W in LED power....
 

Online Ian.M

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #39 on: November 29, 2017, 06:03:09 pm »
Lets do the math to see what minimum battery capacity you actually need.  If you can get away with less current (and brightness), the battery capacity required will reduce proportionately.  Also we are going to work in WH (Watt hours) rather than the more common AH (Ampere hours), as we need to know the total energy.  All calculations rounded to three significant figures.

Assume the website is accurate and the LEDs each draw 20mA at 3.0V.

  10 days * 24 H = 240 H (hours)
  20 mA * 3.0 V = 60 mW
  60 mW * 240 H * 25 LEDs = 360 WH

At 3V, that's:
  360 WH / 3 V = 120 AH

For comparison:
An Energiser E95 Alkaline D cell is good for about 2000mAH.  Over its usable life the voltage will drop from 1.5V to 0.8V averaging about 1.2V, so it can deliver 2 AH * 1.2V = 2.4 WH.   That's 0.67% of the energy you need and I'm not even going to bother calculating how many D cells that is.

Another comparison:
A premium 18650  Li-Ion cell , the Panasonic NCR18650B is rated at 3400 mAH.   Its average voltage over its entire usable discharge voltage range will be about 3.7V so it actually stores 3.4 AH * 3.7 V = 12.6 WH.  That's 3.49% of the energy you need, so the absolute minimum will be 29 18650 cells.


Unfortunately a LED driver that runs from a bank of Lithium cells, wont be 100% efficient - 85% isn't unrealistic for a good one, and generic 18650 cells wont have the high capacity of the Panasonic one.  Good quality ones are typically in the range 2000mAH to 2600mAH.  Fakes may be much lower.   Assuming 2200mAH cells and 85% ( 0.85 ) efficiency in the LED driver, each gives you 2.2 AH * 3.7 V =8.14 WH, result * 0.85 = 6.92  WH effective energy.  That's 1.92% of the energy requires so you'll need 52 cells.

A further fly in the ointment is Lithium cells behaviour at end of discharge - if you discharge them below 3.0V you will damage them and they may be unrecoverable + attempting to recharge deeply discharged Lithium cells can be hazerdous, so if you use to simple a controller that doesn't have over-discharge protection, any delay getting to them at the end of the event and you'll probably have to scrap them.

That scrapyard 100AH car battery I suggested earlier probably has about 60AH capacity left (make sure it load tests OK before purchase).  If you don't want to kill it stone dead, you cant use more than 40AH of that.  The average voltage over the full discharge range of a Lead Acid battery is approximately 12.3V.
40AH * 12.3V =492 WH, result * 0.85 = 418 WH effective energy, which is 137% of the energy you need, so there's margin to spare.

Even if you decide that a measly 2mA is bright enough, you'll need six 18650 cells to be reasonably certain they'll run the LEDs long enough.

For brightness testing, you could do a lot worse than putting a 100 Ohm resistor and a 1Kiloohm potentiometer (aka 'pot', wired as a rheostat), in series with ONE LED and powering the resulting assembly from 5V.  You can use a USB charger wall wart for the 5V if you don't have a variable lab grade power supply.  If the wall wart output is over 5.2V, add a Silicon diode in series to drop the voltage a bit.

Turn the pot to maximum resistance and the LED will get slightly under 2mA.  Turn it to minimum and it will get about 20mA.   To measure the LED current, measure the voltage across the 100 ohm resistor.   1V is 10mA, so simply multiply the reading in volts by 10. (If its under a volt and the reading is in mV, divide the number by 100).
Its also a good idea to measure the voltage across the LED when you are happy with the brightness.   

Please also measure the voltage across the LED as close as you can get to 2mA (200mV across the 100 Ohm resistor) and 20ma (2V across the 100 ohm resistor),  If you cant get all the way up to 20mA, and you added a diode earlier, turn back the pot, remove the diode and try again, taking care not to go over 20mA.   

Post the final readings here and we can help you find a cost-effective battery system that will do the job.  The 2mA and 20mA LED voltage measurements are to help us design or recommend a suitable driver circuit.
 
« Last Edit: November 29, 2017, 08:27:56 pm by Ian.M »
 
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Offline withwings

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #40 on: November 29, 2017, 06:42:26 pm »
I am really impressed with ALL your willingness to assist me! I have been reading through all the replies and trying to find a solution. I have never made a doll house before,yet  I was familiar with the old way to light a doll house and found that they have not yet moved with tecnollagy to LED lighting. So I went looking and found that train moldels had. Now some of you have mentioned a "STRING" of led's instead of my indevidual lights. Well this would work if I was dong track lighting lol in every room. But to make a doll house LOOK realistic it needs to have lighting in many places. Now I was planning on using up to 5 lights possible in each room. Like a lamp on a table and four strung together to make a chandelier. Now they do have like four already strung together on just two wires that would work for a Chandelier.  :-DD  https://www.modeltrainsoftware.com/4-led-smd.html
they also have instructions for installation after reading some of your comments now I am ever afraid of their instructions !    https://www.modeltrainsoftware.com/installing-leds.html

my plan was to use maybe five single lights in each room run all the wires up behind the walls to the ceiling. wire each room together and then conect all rooms together and tract to power source. Now I can run each room seprate and and have many power sources becasue I have a huge hiding space as part of my structure. Timers or dimmers or any thing I can add to make it work is fine I did buy a remote that will dim the lights as pointing it at each rooms sensor   https://www.modeltr/Users/REDADRONE/Desktop/24201296_1944587892225561_1237606415_o.jpgainsoftware.com/led-remote-control.html The doll house is on display 10 days 9 to 9 and I will not be able to switch anything on it once its set.  I really do appreciate  all of you and your understanding of my ignorance of electroics ! Like I said I am an artist and sculpture  https://www.facebook.com/paula.nerhus.9
« Last Edit: November 29, 2017, 07:11:35 pm by withwings »
 

Offline withwings

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #41 on: November 29, 2017, 07:12:46 pm »
wow you have out done yourself  :popcorn:
 

Online Ian.M

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #42 on: November 29, 2017, 07:42:30 pm »
Thanks for the photo, that really does look like its a bare SMD LED brought out to user friendly wire ends.

The dimmer link was badly borked: https://www.modeltrainsoftware.com/led-remote-control.html
Odds are its a simple PWM controller.   Its input voltage needs to match the LEDs you are using.   It will help with extending the battery life, but a digital timeswitch programmed for 12 1/2 hours each day (so it comes on 15 minutes before opening and goes off 15 minutes after closing) will immediately reduce the daily consumption by 48% without compromising on brightness.   If you are going to use the dimmer, you need to know if it remembers its settings if disconnected over-night, and comes back on when reconnected.  If not, you cant use it with a timeswitch.

The next thing we need to know is how urgent is this project?  If its got to be ready in the next few days, you are S.O.L. as we wont be able to resolve the problems quickly enough.   If you've got a couple of weeks or more so you've got time to get parts the prospect's very good.  In-between its more iffy - it all depends on how much time you can put in, how quickly you can get parts and how easily you learn and understand new concepts.   If you're not comfortable with wiring circuits from a schematic, and you've got a teenage kid around with good marks in Physics, rope them in to help!
« Last Edit: November 29, 2017, 07:45:50 pm by Ian.M »
 

Offline ez24

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #43 on: November 29, 2017, 08:02:07 pm »
Next are LEDs in the eyes

https://www.etsy.com/shop/paulanerhus

Nice dolls.  Will they be in the doll house?

Seriously, since the doll house is to be seen, is there anyway someone could replace batteries every couple of days?  Could you use a car battery?

Have you heard of the Arduino?
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Offline withwings

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #44 on: November 29, 2017, 10:20:26 pm »
 THANK YOU! no my dolls will not be in this house. I am making a mouse house lol  :-DD I could use a car battery if it is possible
 

Offline ez24

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #45 on: November 29, 2017, 11:20:52 pm »
It is rare that a newbie sticks with us - thanks  Usually they get too confused by all the answers  :-DD

Do you have or access to a multimeter?  Do you order from Aliexpress, Ebay, or Amazon?  If yes, then maybe a cheap voltage regulator and a car battery might work.

I am thinking of something like this

https://smile.amazon.com/SMAKN%C2%AE-Converter-Power-Supply-Module/dp/B00ODL140M/ref=sr_1_3?ie=UTF8&qid=1511994327&sr=8-3&keywords=12v+to+3v+converter

But other members probably will have a better solution.   Also I would contact the company and tell them you have 25 LEDs and you want the current use of them.  Ask them for the datasheet for the LEDs, everyone would like to see this.
It is the current that is driving us nuts.

Can you solder the connections?  If not maybe something like this
https://smile.amazon.com/HTTX-Alligator-Clips-10-Pack-5-Pair/dp/B06XNVB66F/ref=sr_1_9?s=electronics&ie=UTF8&qid=1511994539&sr=1-9&keywords=alligator+leads

You would need something like this for the car battery
https://smile.amazon.com/Alligator-Booster-Battery-Charging-Charger/dp/B06XSHQLFZ/ref=sr_1_46?s=electronics&ie=UTF8&qid=1511995196&sr=1-46&keywords=automobile+battery+clamp

It would be a very good idea to have a fuse, here is one option
https://smile.amazon.com/Replacement-Connector-Emergency-Universal-Chargers/dp/B01857INDU/ref=sr_1_6?s=electronics&ie=UTF8&qid=1511995316&sr=1-6&keywords=automobile+battery+clamp

But 200a fuse ?  Too much I think.  Ten days unattended I think should require a fuse (but much less than 200a).  I do not think I have even seen a 200a fuse.

Here is another fuse
https://smile.amazon.com/2-pack-Gauge-Fuse-Holders-FUSES/dp/B01NBD7PU9/ref=sr_1_4?s=electronics&ie=UTF8&qid=1511996515&sr=1-4&keywords=fuse+holder

Someone mentioned a buck which is another 12 to 3v convertor and this would be good (maybe the best) if you know how to use a multimeter to adjust it (to 3v and x amps)

So I think I (I have a multimeter) would use a buck like this
https://smile.amazon.com/GEREE-Converter-Transformer-Synchronous-Adjustable/dp/B00TANQW96/ref=sr_1_8?s=electronics&ie=UTF8&qid=1511996987&sr=1-8&keywords=buck+converter+dc+to+dc

But you need to adjust it to your needs, 3v and the required current.

So in summary here is what I would use:

- car battery
- jumpers
- car battery jumpers
- fuse holder
- buck convertor


Again thanks for sticking with us  :-+  and look forward to pictures




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Online Brumby

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #46 on: November 30, 2017, 12:25:37 am »
Here is a suggestion that is crude - but simple - using a 12V car battery.

It relies on the fact that LEDs will work at slightly lower voltages than specified - but at the cost of reduced brightness.

Take 5 of your LEDs and connect them in series - that is, make your own string of 5.  They will need to be connected with the + of one connected to the - of the next, just like batteries.  Connect the free ends of this string to the car battery and see how brightly the LEDs shine.

If that isn't great, then extend the string to 9 LEDs and use two 12V (borrowed?  ;D ) car batteries connected in series, giving 24V.

As with all things simple, there are tradeoffs - and in this case, there is one which might be a deal breaker... As the battery/batteries discharge the voltage will drop, affecting the brightness - with the concern that, before the end of the exhibition, the brightness will have dropped below acceptable levels.  Unfortunately, without at least a multimeter, testing of this will take ... ... 10 days per test.
 

Offline Gregg

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #47 on: November 30, 2017, 12:42:39 am »
To save power, perhaps you could incorporate some passive IR sensors that would turn on the lights only when someone came near the dollhouse.  Search for "PIR sensor" "PIR switch" "Passive infrared" etc. for some pictures and ideas.
 

Online Ian.M

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #48 on: November 30, 2017, 01:19:31 am »
5 nominally 3V LEDs in series off a battery which when fully charged and rested will be at about 12.6V, certainly under 13V? :-DD  |O

That's between 2.6V and 2.5V per LED to start with, dropping to maybe 2.4V to 2.3V as the battery discharges.   If you want to get an idea of how dim that will be, take the 3V 2xAA battery holder that came with the dimmer kit, and with fresh batteries (or at least ones new enough to give the full 3V at its output), put a single Silicon diode* in series with the anode lead connected to the red lead of the battery holder, then connect a single LED, black leads from the holder and LED together, red lead to the cathode lead of the diode.   The diode will drop enough voltage to put the LED voltage in the 2.4V to 2.5V balllpark and you'll see just how feeble the glow from those LEDs will be without having to wire them all up first.

The car battery itself is a great idea - we've just got to be smarter what we put between the battery and the LEDs.   e.g. an EBAY (or Amazon which will be quicker) LM2596 buck module adjusted down to 3.5V a 47 ohm resistor in series with each individual LED would be a good start.  the black leads of all the LEDs go together, the red lead of each goes to its OWN resistor and the other leads of all the resistors go together.   You would need to set the output voltage of the LM2596 module to 3.50V *BEFORE* connecting any LEDs as over-voltage could easily blow them.  Check its still 3.50V powering a torch bulb, then you are OK to hook it up.
You can carefully trim the brightness with the voltage adjustment - *DON'T* go over 3.95V - you may want to practice with the LEDs disconnected.

This would be compatible with using a timeswitch - just put the timeswitch between the LM2596 module and the battery.   Remember, car batteries can supply dangerously large amounts of current so always put an inline fuse in the positive lead next to the battery terminal.   1A should be suitable for this application.   Reverse connection would kill the LM2596 module so either be very careful or put a silicon diode* in series with the battery positive lead as well, cathode away from the battery.

* The diode should be a nominally 1A 1N400x series, or 3A 1N540x series (where x is 1 to 7) , or similar.  The end with the stripe round the body is the cathode, the other end is the anode.
 

Online Brumby

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Re: LOL I AM THE BEGINNER ! using lipo battery to light doll house with LED
« Reply #49 on: November 30, 2017, 01:51:41 am »
5 nominally 3V LEDs in series off a battery which when fully charged and rested will be at about 12.6V, certainly under 13V? :-DD  |O

That's why I added the 24V (nominal) alternative.  Having 2 batteries also doubles the available energy capacity.  Want to try 3 batteries and a string of 13 LEDs?

All these ideas are well and good - for people like you and me - but for someone who has been quite open and honest about their abilities, I just wanted to offer some alternatives that they could manage.

The result may not be any good, but it is an easy experiment - and WE do not know what level of brightness would be acceptable.
« Last Edit: November 30, 2017, 01:54:51 am by Brumby »
 


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