PDA

View Full Version : A Lux V question I haven't seen directly answered



Kamurah
11-13-2007, 02:42 PM
Did the due dilligence and searched the forums but I haven't seen this answered / asked before:...please forgive if this is a noob question :D

Would it be possible to run this setup->

A Lux V with a buckpuck AND a MR board (for sound) using a separate 1000mah buckpuck with a dpdt switch using a single 7.2 volt battery pack?

In other words, two buckpucks wired off of the same battery pack, but one (700 mah) going directly to the Lux V, and a SECOND one inline between the battery pack and the MR board (1000mah)....

Would it work, or is this not possible due to the voltage (vice current) requirements / limitations?

Thanks for any answer on this one.

xwingband
11-13-2007, 03:03 PM
What in the world would the second one be doing??? That doesn't even make sense.

Ghostbat
11-13-2007, 03:29 PM
I think I understand what you are trying to do setupwise, but it should be unnecessary. The puck is there to drive the luxeon, everything it is doing to the lux is irrelevant to the board.

You would want the batteries to go to the dptd, then to the puck and the soundboard. power then returns from each to a common ground. The LED then comes out of the puck and the speaker and clash sensor from the board.

Novastar
11-13-2007, 03:41 PM
X and Ghost are correct--you do not need any kind of puck to run the MR board.

However, yes... avoid giving an MR board 7.2v. At the maximum 6v--which might be pushing it.

Kamurah
11-13-2007, 04:06 PM
Guys, I know this sounds a bit crazy but bear with me...

I know you don't need a puck to run a MR board....HOWEVER...you cannot run a MR board off of 7.2 volts (= fried MR board).

BUT...you need that much voltage to run the LUX V.

So what I was thinking was that if ONE OF THE TWO Buckpucks ran the LED (@700mah), then the second one would limit the voltage to the MR board.

So they are run in parallel off a SINGLE battery pack, not serial.

This way, you have a Lux V for the LED, with a MR for the sound.


So now if that explanation makes sense.....will it work or no?....or do you need a different type of voltage regulator (which is what I thought a Buckpuck was.....a voltage regulator)?


Thanks for the info :)

DACOTA
11-13-2007, 04:29 PM
I would say you should use a resistor for the voltage drop to the mr board because a buckpuck is a luxeon driver not an adjustable voltage regulator. So calculate 5v for the mr board and just find out what resistor will drop 7.2 to 5 or 4.5 for the board then splice the batt pack wires over to the buckpuck for the led or however you do that part.

Kamurah
11-13-2007, 04:35 PM
Ya...ok...but if we recommend Buckpucks here on the board because they are more efficient (and predictable) regulators than resistors for LEDs.....why won't it work as a voltage regulator for the MR board?

I mean....isn't that all a "driver" is?...other than the ones that have additional features like clash, and fade in/ fade out....


Help me understand :shock: 8) :D

vortextwist
11-13-2007, 04:51 PM
I don't think the puck running to the mr board is goin to work the way you think/want it to. maybe a custom batt pack.

Ghostbat
11-13-2007, 05:48 PM
Hmmm... looking at the datasheet I can't see any reason it wouldn't work, but I'm not familiar enough with the tolerances involved to have any confidence and I am not convinced that you couldn't get the exact same benefits in a cheaper and smaller package by using resistors to peel off the required voltage.

But since it's your board and not mine I say give it a try and let us know how it works :)

Steeljack
11-13-2007, 06:12 PM
Guys, I know this sounds a bit crazy but bear with me...

I know you don't need a puck to run a MR board....HOWEVER...you cannot run a MR board off of 7.2 volts (= fried MR board).

BUT...you need that much voltage to run the LUX V.

True so far.


So what I was thinking was that if ONE OF THE TWO Buckpucks ran the LED (@700mah), then the second one would limit the voltage to the MR board.

So they are run in parallel off a SINGLE battery pack, not serial.

This way, you have a Lux V for the LED, with a MR for the sound.

Ah. Right idea, but slightly wrong approach.


So now if that explanation makes sense.....will it work or no?....or do you need a different type of voltage regulator (which is what I thought a Buckpuck was.....a voltage regulator)?

As far as driving LEDs goes, BuckPucks are current regulators, not voltage regulators. LEDs differ from a lot of other components in that they're tolerant of a wide range of voltages, but will cheerfully gorge themselves to death on current, given a chance.

That's the bad news. The good news is that the BuckPuck also happens to include a voltage regulator which outputs 5V. That's what the "REF" line is. (The original design goal, as far as I know, was to enable you to drive a microcontroller, but the MR board is, as far as I know, tolerant of voltages up to 5.5V and so should work just as well.)

Run a line from REF to the positive terminal of your MR board, one from the negative terminal of your MR board to the negative terminal of your BuckPuck, and you should be good to go.


Thanks for the info :)

I hope this helped.

Kamurah
11-13-2007, 06:43 PM
Outstanding....

Thanks for the help and info.

Cheers

Steeljack
11-13-2007, 06:56 PM
I would say you should use a resistor for the voltage drop to the mr board because a buckpuck is a luxeon driver not an adjustable voltage regulator. So calculate 5v for the mr board and just find out what resistor will drop 7.2 to 5 or 4.5 for the board then splice the batt pack wires over to the buckpuck for the led or however you do that part.

How exactly do you propose to make a resistor act as a voltage regulator?

If you attach one leg of a one-megaohm resistor to the positive lead of a 7.2-Volt power supply, you will still measure a voltage of 7.2 Volts on the other leg. (You'll be able to pull a vanishingly small current through it, but it'll still be at 7.2 Volts.)

You could try to create a voltage divider (http://en.wikipedia.org/wiki/Voltage_divider), but voltage dividers are really only good for sensing currents. The moment you put them under load, as the article notes their voltage tries to wriggle out from under you.

Eandori
11-13-2007, 06:59 PM
One problem I see is this...

The Buckpuck going to the MR board is not so much a soft limiter of 700mA but it will TRY to drive 700mA as hard as it can. If the MR board is for some reason taking less current then that, the buckpuck would respond by pushing the voltage input higher to attempt to maintain that 700mA.

So if your battery supply going into a buckpuck was 9.6v, and your MR board really only needed 100mA to drive the speaker, then a worst case scenario would be the BuckPuck pushing slightly less then 9.6v to the MR board in an attempt to reach the rated 700mA.

So I would not hook up a buckpuck like this unless the MR board was ok with BOTH restrictions....
MR board can handle up to 700mA
MR board can handle input voltage of 7.2v if it was using less then 700mA

My kneejerk reaction (without any data) would be to guess that just an MR board with a speaker would not use 700mA. I figured those speakers were closer to 1 watt with the board itself only dissipating like .1 watts. a 5v input on the MR board and 700mA is closer to 3.5watts of power being "shoved" into a device. Seems like too much.

One easy test would be this... Hook up a DMM in series with your MR board to a known safe battery voltage. Measure the min and max or at least average curren that board uses. Try not to exceed that.

pipster79
11-13-2007, 07:01 PM
my sugestion is to go to radio shack and get a 5v voltage reguator there very small, bout 7mm square or smethig like that i think, easy to wire up, 3 pins, 1 is ouput 5v, one is groun, and one is input max 32v i think it is, that will protect ur mr board, and there only around 5 bucks, mayb when i get back from dinner ill find a link so u can c it for uself.

only one thng about it, when the voltage drops below 4.5v input, it will stop putting out voltage. ie u will stop getting sound till u recharge the battery pack

Kamurah
11-13-2007, 07:20 PM
ok...so....

BOTH the 700mah and the 1000mah BuckPucks have a control voltage REF pin of 5v....

So....theoretically.....could I use just ONE 700mah Buckpuck - wiring the LUX V to the LED output pins and the REF pin to the MR Board with a 7.2v power supply?

I suppose I would still need to measure the current draw from the MR board to make sure the current flow wouldn't be too high right?

Steeljack
11-13-2007, 07:55 PM
ok...so....

BOTH the 700mah and the 1000mah BuckPucks have a control voltage REF pin of 5v....

So....theoretically.....could I use just ONE 700mah Buckpuck - wiring the LUX V to the LED output pins and the REF pin to the MR Board with a 7.2v power supply?

I suppose I would still need to measure the current draw from the MR board to make sure the current flow wouldn't be too high right?

Ergh. Probably not. I just did what I should have done before shooting my fool mouth off, and checked the datasheet (http://www.leddynamics.com/LuxDrive/datasheets/3021-BuckPuck.pdf) for the BuckPuck.

While the REF pin does indeed provide 5V, it's only guaranteed for up to 20 milliamps. While that's adequate to drive a microcontroller or other small component, it's not going to be anywhere near enough to provide you with sound.

That means that pipster79's got the right idea: you'll want a separate voltage regulator.

The good folks at Spark Fun have a couple of different regulator ICs you could use to this end. The LM7805 (http://www.sparkfun.com/commerce/product_info.php?products_id=107) seems like a good choice: 5 Volts, and more than enough amperage for your purposes.

The spec sheet suggests placing capacitors between the pins, but in any case it ought to be fairly simple to build into a circuit. (Feel free to PM me if you want to delve into the grotty details.)

pipster79
11-13-2007, 09:40 PM
use a regulator, u dont need to worry bout current going to the mr board only the voltage, so just go to radio shack and get a voltage regulator for 5 bucks, much easier then trying to figure out how to wire a buck puck to do the same thing

pipster79
11-13-2007, 09:43 PM
oh and if u must know the output of the 5v voltage regulator is 1a, but its totaly safe for the mr board, i have one in my anakin saber and it works fine

edit, steeljack thats the one i was talking about but rather then wait to order it from some place online u can just walk into your local radio shack (or "the source" as its called in canada) and pick one up

there nice and small but very easy to work with, and no need to worry about figuring anything out like amperage or what not, and u dont need capacitors between the pins, those diagrams were for different models and for different configuations, if using it just as the positive regulator that is its primary pourpose u only need wire the output + to the mr board and the input voltage and ground from your battery pack, u can run the groud from the battery pack straight to the mr board. or what migh b easier is wire the positive and negative from the mr board to the regulator and then the positve and negative from the battey to the regulator, either way works fine

neophyl
11-14-2007, 01:47 AM
You definately do NOT want to use a puck to drive the MR board. You do want a 5v regulator like Pip mentioned. They come in a variety of sizes and ratings, from 100ma, 200ma, 500ma (which will drive a MR fine) and the 1A and even 2A versions.
It shouldnt cost more than a couple of $ and for this application you wont need the smoothing caps really although if you want to add them then fine.

About the 5v from the puck, besides it being only 20ma of current output you couldnt use it to drive the mr board properly anyway even if there was enough current. See when you switch the puck off power will be lost to the MR board immediately which means no power down sounds.

Novastar
11-14-2007, 02:19 AM
Excellent comments everyone...

One last thing I can add is... you MIGHT want to add a small heatsink to the voltage regulator if it ends up shunting off quite a number of volts. It will get REALLY hot.

Corbin did this for one of the BOP I sabers, and as near as I could physically test and tell... it was certainly needed. I might be wrong but... 2.2+ volts seems like an awful lot of heat, and MAN did the voltage regulator get hot!

This may have been because he had to place the regulator RIGHT next to the FX board... and we didn't want to kill it with so much heat.

Kamurah
11-14-2007, 03:30 AM
Thanks everyone....great discussion. I appreciate all the input.

Eandori
11-14-2007, 10:23 AM
Yeah, I agree. Just use a simple 5v regulator and put a small heatsink on the fin or find a way to bolt it to the body of your saber for heat dissipation. I'm sure that would work fine, especially with a 5v regulator that can supply up to 1 amp.

pipster79
11-14-2007, 10:27 AM
may be a different model u have in yours novastar the one i have in my anakin saber has 6v going to it and only gets a touch warm

alpine
11-15-2007, 04:05 PM
ive read this entire thread, and now im confused! im so confused i might beat myself over the head with my saber.

Steeljack
11-15-2007, 04:38 PM
ive read this entire thread, and now im confused! im so confused i might beat myself over the head with my saber.

You could do that. Or you could post detailing what it is you're confused about, and we can try to help you. :-P

Kamurah
11-15-2007, 04:40 PM
ive read this entire thread, and now im confused! im so confused i might beat myself over the head with my saber.

it's perfectly simple:
If you're not getting your hair cut, you don't have to move
your brother's clothes down to the lower peg, you simply
collect his note before lunch after you've done your scripture
prep when you've written your letter home before rest, move
your own clothes on to the lower peg, greet the visitors, and
report to Mr Viney that you've had your chit signed.

Eandori
11-16-2007, 01:40 AM
it's perfectly simple:
If you're not getting your hair cut, you don't have to move
your brother's clothes down to the lower peg, you simply
collect his note before lunch after you've done your scripture
prep when you've written your letter home before rest, move
your own clothes on to the lower peg, greet the visitors, and
report to Mr Viney that you've had your chit signed. A Python fan, very nice :)

Don't use a puck for anything but driving LED's. Use either the proper voltage battery or a higher battery with a proper output voltage regulator for the driver board.

Think of it like this... all systmes that supply power either try to regulate voltage, or regulate current. A battery works as if it's regulating voltage, since current changes a lot and the voltage not much. A voltage regulator works like a battery. Varying current but solid voltage. A buckpuck is a "current regulator." Voltages will vary, but it tries to keep the current constant.

Clear as mud?

A sound driver board is made for a certain INPUT VOLTAGE, so you want to give it something that supplies a CONSTANT VOLTAGE. Which is either a battery or a voltage regulator.

LED's operate at varying brightness based on CURRENT. They have a forward voltage which is true... but what you really care about is the current. So... a buckpuck is a perfect driver.

Novastar
11-16-2007, 03:25 AM
may be a different model u have in yours novastar the one i have in my anakin saber has 6v going to it and only gets a touch warm6v might be a bit much for an FX board over a long period of time (both short-term usage such as 2 hours with no "offs"... AND long-term, such as will it work after 4 years)...

...but I say you're fine. And you're right--that means you are only "shunting" away 1.2v or so on a full charge... and as the pack is used a bit, the regulator will have to kill a lot less energy (more like 1v or even 0.8v)...

...so I imagine it would just get "warmish-hot" in the beginning and later become a non-issue.

Kamurah
11-16-2007, 03:35 AM
[quote]

Don't use a puck for anything but driving LED's. Use either the proper voltage battery or a higher battery with a proper output voltage regulator for the driver board.

Think of it like this... all systmes that supply power either try to regulate voltage, or regulate current. A battery works as if it's regulating voltage, since current changes a lot and the voltage not much. A voltage regulator works like a battery. Varying current but solid voltage. A buckpuck is a "current regulator." Voltages will vary, but it tries to keep the current constant.

Clear as mud?

A sound driver board is made for a certain INPUT VOLTAGE, so you want to give it something that supplies a CONSTANT VOLTAGE. Which is either a battery or a voltage regulator.

LED's operate at varying brightness based on CURRENT. They have a forward voltage which is true... but what you really care about is the current. So... a buckpuck is a perfect driver.


This is the best answer I have seen on this subject yet! Awesome. Yes, to Eandori we listen.

8)

Eandori
11-17-2007, 04:43 PM
Glad to be of help :)