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Powering 3.5v Led With 3v?


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#1 m.browning

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Posted 06 May 2012 - 09:01 AM

I am new to led modding, and i do not understand how you can power a 3.5V led (such as a white one) when there is only 3V coming from the 2AA pack. Can someone please explain to me how this is possible? blink.gif
I don't understand how people can have so many LED's on a wireless controller when it only puts out 3V.

#2 psphackr

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Posted 06 May 2012 - 04:18 PM

When it comes to electronics you don't have to always be exact as far as the voltage goes.

For instance, I do some electrical work on cars. I put a new radio in mine a few months back. Since the radio is meant for a car's electrical system, it's of course rated for 12 volts DC. However when I put a volt meter on my car battery it usually only reads out at about 11 or 11.50 volts.

Just make sure you don't put a ton of lights in it or you'll put too much amperage on it and ruin your controller. Idk what the amperage rating is for the controllers but it's probably not that much.

Edited by psphackr, 06 May 2012 - 04:21 PM.


#3 RDC

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Posted 06 May 2012 - 05:12 PM

QUOTE(m.browning @ May 6 2012, 02:01 AM) View Post
I am new to led modding, and i do not understand how you can power a 3.5V led (such as a white one) when there is only 3V coming from the 2AA pack. Can someone please explain to me how this is possible? blink.gif
I don't understand how people can have so many LED's on a wireless controller when it only puts out 3V.

2 x AA batteries don't output 3v, it's closer to 3.4v or so when they're both new, but that drops to 2.2v over the useful life of the battery, as far as the controller is concerned. That's only considering Alkaline batteries also as the PnC pack is around 2.7v and drops to around 2.2v or so.

A lot of LEDs will work on a little bit lower voltage than what they are rated at, and not all White LEDs need 3.5v to work.

It also depends on who's controller it is. They could have added in a DC-DC Boost regulator or LED driver to step up the voltage and drive them, or they could simply just be working on the lower voltage the controller outputs.



QUOTE(psphackr @ May 6 2012, 09:18 AM) View Post
When it comes to electronics you don't have to always be exact as far as the voltage goes.

Yes, you do.

QUOTE

For instance, I do some electrical work on cars. I put a new radio in mine a few months back. Since the radio is meant for a car's electrical system, it's of course rated for 12 volts DC. However when I put a volt meter on my car battery it usually only reads out at about 11 or 11.50 volts.

Either your battery is going bad, or the one in your meter is, because that's not correct for a good 12v car battery, and if you found that voltage difference odd, start the car up and check it again. wink.gif

Electronics made to work in vehicles use Regulators to step the voltage down and keep it at 12v or lower, depending on what the electronics need to work, and even those parts of a car stereo that say 12v will still run off a volt or less with no really noticeable difference as that higher voltage is used for the Amplifier section in the head unit, whereas the main bits of it will run off of 5v or less, but it's there.

Likewise, larger outboard Amplifiers use PWM and DC-DC to step up voltages for driving larger speakers.

LEDs on the other hand are current driven devices, and if there isn't enough voltage to 'turn the LED on', there isn't going to be enough current for it to work at all, and that margin for working/not working is much smaller than the head unit for a vehicle.

QUOTE

Just make sure you don't put a ton of lights in it or you'll put too much amperage on it and ruin your controller. Idk what the amperage rating is for the controllers but it's probably not that much.

Pulling too much current form the controller will just cause the batteries to heat up and possible melt or catch something on fire, the same as with any battery, but you have to pretty much dead short it for that to happen. The 'average' LEDs aren't going to cause ay issue like that as they typically pull around 20mA or less each, so you'd need to have more than a few of them in there to even tank the charge in the battery quickly.

Edited by RDC, 06 May 2012 - 05:24 PM.


#4 m.browning

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Posted 07 May 2012 - 07:15 PM

Well the LEDs that I am looking at say 3.2-4 volts. Would I be able to run them in a standard wireless controller?

#5 Bandit5317

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Posted 08 May 2012 - 03:20 PM

QUOTE(m.browning @ May 7 2012, 02:15 PM) View Post

Well the LEDs that I am looking at say 3.2-4 volts. Would I be able to run them in a standard wireless controller?

The short answer: no. They'll work for a little while using fresh Alkaline batteries, then they'll start dimming. On a side note, the old matrix-style wireless controllers seemed to have better voltage regulating circuits for the RoL LEDs. Last time I tried to install 3.6v 0603 LEDs in one of the newer controllers, they ended up getting much dimmer soon after new batteries were installed. These same LEDs worked great in the original matrix wireless controllers. This may not be the case in all of the newer controllers, as there are many revisions which I haven't worked with. RDC may be more familiar with this phenomenon, given his experience with all of the controller revisions.

#6 RDC

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Posted 08 May 2012 - 07:21 PM

@ m.browning - Where are you wanting to install these LEDs at? and how many?

If you're going to replace the player LEDs and have a Matrix version controller you'll be alright to use them, but if it's a CG version then, as Bandit5317 also pointed out, I wouldn't recommend it.

If you're just installing them around the controller wherever, and are dead set on using those, then you should look into some Charge Pump, DC-DC Boost regulator or LED driver type of circuit to power them then.


@ Bandit5317 - The older Matrix controllers, as well as the new Matrix2 version, use PWM to drive the player LEDs, whereas the CL and CG versions are linear.




#7 m.browning

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Posted 08 May 2012 - 10:52 PM

I was going to place one in the dome, and two in the back that are rumble activated. I was also going to replace the RoL lights to. Are the charge pumps or DC-DC's complicated to install or hard to understand? I have basic electronic knowledge.

#8 RDC

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Posted 09 May 2012 - 12:10 AM

Not especially, they're not really more than a handful of parts that get put together, but the selection of some of them needs to be done correctly. Most DC-DC or LED drivers use an Inductor, which is one of the parts that needs to be picked carefully, then some might need an external FET. You should find enough versions that are thru hole and easier to solder up, but then it's going to get kind of big quick. So depending on how much room you want to sacrifice, you might want to make the whole deal SMT on a board, which means more time and money, and a lot smaller parts to work with. It needs to be able to handle the current you plan to draw from it as well.

Having the Rumble activated LEDs adds another layer of work with those LEDs also, unless they light up enough for you wired straight up, you'll have to test that and see, which is easy enough and can be done with no soldering. The simple way to wire them so they also use the DC-DC or whatever source, would be to use Transistors as switches, so the Rumble lines turned them on, then they turned the LEDs on.


#9 m.browning

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Posted 10 May 2012 - 07:40 PM

Is there a good tutorial around for any of theise?

#10 RDC

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Posted 10 May 2012 - 10:16 PM

For installing them in a controller? not that I know of, but you can Google the different types of circuits up all day long and learn more than you'll ever need to know about them.

A good example with descriptions of one, used for other purposes though, is the Minty Boost made by Ladyada.

Edited by RDC, 10 May 2012 - 10:17 PM.


#11 m.browning

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Posted 11 May 2012 - 05:31 AM

I got some LEDs today. When I tested them out they all worked just fine. Fully lit-up no resistor needed. Only problem is the purple one I have to light my dome comes through as yellow. Is there a way to fix this or it just going to be that way? If so I will just move purple to the back and blue to the dome.

#12 RDC

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Posted 11 May 2012 - 11:52 AM

Any LED you put in there is going to have to shine thru the greenish color of the plastic of the button, and that's going to mix with the color of the LED, so none of them are really going to look that great, unless that's the color you're going for. About all you can do there is to get a replacement button set, or make your own, so it's clear or more of the color that you're wanting.


#13 m.browning

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Posted 11 May 2012 - 05:11 PM

I have noticed that when I put the purple LEDs to the rumble post that it does not light up as much. I guessing this is because they have a lower voltage than the other connection point. Would I be able to use the main connection point( positive battery post ) and the negative post of the rumble to get a brighter led, but still only come on when it rumbles or would they be on all the time?

#14 RDC

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Posted 11 May 2012 - 05:30 PM

It doesn't light up as much because the Rumble isn't on as long, and the motor is taking up some of that current as well.

I don't know what version of controller you're using so, I couldn't say which way might work better or not, but wiring it up that way will most likely have the LED on all the time, then go out when it Rumbles. Using a Transistor would be the best way to go about solving all of that. So again, the Rumble turns the Transistor on, then the Transistor turns the LED on and you'll get the most voltage for the LED you can that way also.


#15 m.browning

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Posted 11 May 2012 - 07:40 PM

I am using a CG2 I think. From everything I have read that seems to be the one I have. If I was to use a transistor, would the base leg go to the negitive rumble post, emmiter to the negitive leg of the led, where does the collector go?




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