Question on power

[ScreamingSamuraiStudio]

So..I'm basically a monkey playing with fire for the first time.

I've had some mild trial and error with my half finished projects, so far. But I got my kit wired up with about five LEDs. And I thought I got a battery pack large enough to support the lights. And it worked great for about an hour, then two of my lights flickered out and just won't light up anymore.

My question is..does this sound like i don't have enough juice going to my lights that wears down the batteries?

 

[Junkie]

Sounds like you might have too much power and burnt out the LEDs. I'm no expert on this but the voltage of the LEDs and the power have to match. Can anyone explain this more better - I should talk to an electrician and do a special show on this.

 

[ScreamingSamuraiStudio]

Well, I'm about to smash it against the wall and start all over with the broken pieces and hope my buddy doesn't mind the "battle Damage".

And I noticed the two of my lights were dimmer than the others and then just blinked out..I'm still not sure if I have too much or not enough since the two lights in question just seemed to dim out and fade away.
But you know...it's a learning experience, and I'm willing to keep on going till my girlfriend either sees a flashing skeleton in the living room or she'll see a nifty cool star trek model to ruin her decor of the house.

 

[Backbreaker]

Did u have the + & -ve the right way round, or the - & the +ve the wrong way round :'(

 

[ScreamingSamuraiStudio]

I think i put the lime in the coconut and drank it all up...could be where it ALL went wrong.

 

[Shark]

yeah I'm no expert but my first thought was you have to much power and burned them out. Did you scrounge the LEDs from something else like say a toy from the dollar store, or are they new? If they are from a toy, they usually have a resistor in the circuit, and if you left it off, well there you go. If you have new LEDs do they say what voltage rating they are? For example if they are 1.5 volts and you have them hooked up to a nine volt battery, well they you are they burned out. Now because you have so many you are lighting, you have the whole, "are they wired in a series, or are they wired parallel, does either one make a difference in the size of resistor, etc." Those questions are beyond my limited scope. I only know enough to know it might make a difference.

 

[Chas]

I'm going to go check my lamp post setup and see what the specs are. I've had the power on for about 15 minutes total... nothing has gone wrong yet.

Will let you know tomorrow night,

Chas

 

[ScreamingSamuraiStudio]

Okay, i fiddled with my model again tonight and the LEDs are still on..they're just very very dim.

Like my wit.

So, I think I'm gonna just sit down and actually read what the little bag said about the volts and such and do some math and try to find a suitable power source.

 

[Shark]

What?! You are going to resort to reading the directions! What is the world coming to?

 

[ScreamingSamuraiStudio]

You know...it's almost Spock logic when you think of it, eh?

Well, I want to thank all of you guys who contributed to the brainstorming and troubleshooting session. Now..I'm starting to feel like the ape who first picked up the bone to go completely bonkers at the beginning of 2001: A Space Oddity.

I think I'm going to transfer all of my efforts into the build of this tiny 1/1000 Polar Lights NX-01. I had already prepared my buddy to get a pretty crappy looking model, but I think this may be back on track again.

I'll start posting pics in a WIP thread soon.

 

[Gary]

resistors are futile.

Sorry, couldn't resist... couldn't resistor? Oh stop me now!

Seriously, resistors are key. 2 to 3 led's per resistor is max. You can get charts and assorted blather off the web on how to sort out the right resistors however asking a real electronics store person, not a Radio Shack employee, will give you a result worth the trip. They can usually set you up very nicely indeed. The lighting of the Eggscaliber was a result of having a lengthy chat with a wonderful little old lady in a shop in the Burnside Ind Park in Dartmouth. 1 resistor for the 4 engines and one for the 2 leds in the body. It still works months later with the same 9 volt battery power source. I'm too lazy to turn it off. Actually trying to see how long it will last.

Cheers
Gary

 

[JMac]

Is this for your BoP build? If your interested I have a article in an old magazine specifically about lighting a BoP. I haven't read or looked at it in very much depth, but it looks like it includes parts lists, templates for circuit boards, and explanations. Let me know if you want a scan...

 

[ScreamingSamuraiStudio]

resistors are futile.

Sorry, couldn't resist... couldn't resistor? Oh stop me now!

Seriously, resistors are key. 2 to 3 led's per resistor is max. You can get charts and assorted blather off the web on how to sort out the right resistors however asking a real electronics store person, not a Radio Shack employee, will give you a result worth the trip. They can usually set you up very nicely indeed. The lighting of the Eggscaliber was a result of having a lengthy chat with a wonderful little old lady in a shop in the Burnside Ind Park in Dartmouth. 1 resistor for the 4 engines and one for the 2 leds in the body. It still works months later with the same 9 volt battery power source. I'm too lazy to turn it off. Actually trying to see how long it will last.

Cheers
Gary

I had not seen this post. Thanks for the info and I'll check that out.

And Jmac, Any help would be awesome, though I think I may almost be done with the lighting, I'm still interested in finding as much info as possible.

 

[JMac]

No problem, I'll PDF it tomorrow and e-mail you a copy...

JMac

 

[Kitty]

Actualy Leds are quite easy to work with.
Just remember that in case of parallel LEDs each led needs its own resitor, since electricity takes the shortest road and if both use the same resistor, one of them will work, the other won't.
In case of connecting them in series you have to make sure that they all use the same operating current.

If you have a led with an operating voltage of 3.8V and a current of 20mA (most of them are 20 mA these days) and your power supply is 5v, than the resistor has to lower the voltage by 1.2V. and the resistor should be 1.2/0.02 = 60 Ohm.
If the difference between the operating voltage is more than the reistor should be a higher value so if your power supply is 9V then the difference is 5.2 V and the resistor should be 5.2 (V)/0.02 (A)=260 Ohm to have the LED working under ideal circumstances.

If you have a 9V powersupply and your LEDS are of the 2.8V 20mA variety you can put 3 of them in series and you need 8.4 V to make them work, that is a 0.6V difference. In that case you need to put a reistor in series with the LEDs of 0.6/0.02=30 Ohm.

If you have a mixture of Leds with different operating voltage and the same current in series you just add up all the operating voltages.
for instance a 9V power supply, a green Led of 2.2v,/20mA, a red LED of 1.8 V/20mA and a yellow LED of 2.8v/20mA you can put one of each in serie and you would need 6.8 V to make them work optimal.
Thats a 2.2V difference thus the resitor in series should be 2.2/0.02 =110 Ohm, nearest is a 120 Ohm resitor.

Since you don't need to be precise , you can use the nearest resitor from the E24 table but it might be wise to take the nearest one that has the higher resitance so your LED will be working on lower than max voltage, it will be a bit dimmer, but not noticably and it will live longer.

So the rule is add the voltages for the LEDs if you put them in series , subtract that from the voltage of the powersupply and devide them by the current to determine the right resistor value.

If you multiply the voltage (V) that is dropped over the resistor by the current(A) you get the power that the resistor consumes W=V*A so you can choose a 1/8, 1/4 or 1/2 W resitor as needed

Ohm =V/A.
And that is all you need to know to figure out how to operate LEDs.

 

[Shark]

Thanks for that. I know I'm going to reference it in the future!

 

[ScreamingSamuraiStudio]

Wow,
That was a lot to absorb there, but you know. It HELPS.

I have to say, I really, REALLY appreciate all of the help from everyone on this forum. Since this post, I've had a few trial and error runs on the model I was working on.
I've got it working, but I'm still on a long road to actually understand what it is I'm actually doing.

 

[JMac]

Thanks for the info Kitty, I'm planning to light a model in the near future and that will come in really handy.

 

[Kitty]

Oh, another thing, do not operate them at higher voltage than the max, because they just break down.
Do it right and they can last 50,000 hours (27 years or so) if you go a little below their operating voltage they can last several lifetimes, hence the advice to choose the higher nearest resistor to the actual value calculated.

Also choose your powersupply clever, if you are going to use LEDS in series mainly you need higher voltages but lower amps to drive it all and amps is what can cause wiring to burn out, the higher the voltage you use the less amps go through your powerleads so you can use thinner wire (that's why Europe in general is safer, we have double the voltage that they use across the pond and therefor we can send double the wattage through a wall sockett before the wires burn out)
In some cases i use insulated wire of 0.25 mm diameter or less (including the insulation) to power a led, that's thinner than a strand of fibre from a 64 strand cable, and I never use more than 5V powersupply into a model and i avoid EL lights, CFL's etc.
that means that my power leads sometimes need to be quite thick because they have to carry 2 amps or more. It also means less heat because i also use parallel LEDs only and i have to drop less volts (a resistor turns electricity int heat, something you want to avoid inside a plastic model).

 

[FourForty]

Sounds like you might have too much power and burnt out the LEDs. I'm no expert on this but the voltage of the LEDs and the power have to match. Can anyone explain this more better - I should talk to an electrician and do a special show on this.

Scott if you did a show on how to rig up these lights, you would be my favorite person in the world. I have all the supplies needed, but have no idea on how to set it up. Thanks.