Upgrade MR Saber with Makoto's led design

**Jedi-Diah** · 09-30-2008, 02:04 PM

Thanks. That's the one I saw recently over on FX-Sabers from your post last year that got me interested. I'll watch it again though. I love the active EQ effect on the blade.

You mentioned making the MR blade brighter. I haven't messed with the led strips from a MR blade before. What do you recommend we can do with the stock MR blade that would make it brighter while we wait for better alternatives (including making our own led strip blades). I think you mentioned "shunting" the resistors (to ground). Would this be like bypassing them or replacing them with wire? I have a stock Anakin that I'm willing to experiment with.

Thanks for your help and expert advice (seriously).

Originally Posted by erv

you can have a good "apetizer" or "starter" with the youtube video link above, despite it's one year old !

**erv** · 09-30-2008, 10:19 PM

MR blades are composed of 6 segments and 64 leds total, each one having its current limitation resistor. It's calculated so that the LED takes more or less 20 mA leading to a total of 1280 mA when the blade is fully lit.
The MR electronic is very basic for the LED driving section : there's no current or voltage regulation. The resistors are calculated so that it's bright with fresh batteries then when voltage goes down, current goes down too, it's the Ohm Law
Voltage = Resistance x Current
or V = R x I (don't remeber if you guys use U or V for voltage, we use U)

you can write it also :
I = U / R
the resistors are fixed, so when the voltage U is going down, current is going down, brightness is dimming out.
To light up a segment of the blade the MR electronics sends a logical level (a '1') to a bipolar NPN transistor located close to the blade connector. It acts as a gate a lets the current flow, like a remote controlled switch. Voltage is then applied to the segment.
All LEDs of a segment are wired in paralled, meaning that the total current is the sum of the current of each LED : MR couldn't do otherwise since the voltage applied is only 4.5V (3 AA of 1.5v) and LEDs, are like 2.1 or 3.6 V, depending on forward voltage (which depends on the colors, and therefore on the semiconductor used, InGaN or GaAlInP). Those values are average, you have rare blue led going down to 3.0V and red going up to 2.5V.
With a voltage as low as 4.5V, you can power 2 leds in serie, well it would work for red but not for blue / green.

Reducing the overall current could have been done by changing the ladder structure, wiring PAIRS of LEDs so that you have only pairs in parallel, which divides the current by 2, but this requires to increase the power supply voltage, which is quite easy with 2 li-ion cells leading to 7.4V (don't do that on your MR, you'll probably fry the sound board, I'm not sure but...).

Now, knowing that :
- you can replace each resistor of the MR strip by another SMD one to increase the current in the LEDs
- or if you build the ladder structure, you replace all the resistors by a single one, and makotosai proposed a resistor calculator chart.

during my tests, I didn't use any resistors, that's why I remove them and shunted the pads on the MR strips : the voltage applied to the segments is setup using PWM from the board (I suspect that's what the Hyperblade electronics does too, I don't think he has resistors on his pcb neither).

But remember, the time you'll spend to change the resistors on the MR strip will the more or less the same for building a new ladder with HB leds so... you'd better directly go to the improvement
PERIOD, OR
you can remove the LEDs AND the resistors, shunt the pads, keep the MR strip and solder the HB LEDs on it
HOWEVER,
despite the PCBs is white, it has obstacles in front of the LEDs which reduces brightness and even aspect of the blade

I think it's time to think "ladder" wise

Erv'

**Jedi-Diah** · 09-30-2008, 11:06 PM

Ok. So, best to make a new led ladder than to "fix" the MR strip since it has too many problems anyway. Now, I guess the question is where to find the "best" HB leds?

Thanks for taking the time to answer these questions Erv. Now, I'll let you get back to focusing those crystals or whatever you call it...

**erv** · 10-01-2008, 12:12 AM

I'm on the way to buy and test 2 sort of LEDs I've selected, if they work well,
I'll see if I can compare the specs with makotosai.
He probably wants to keep his local source, which I understand, but he might either sell the LEDs or the ladder, or at least post some detailed specs.

Makotosai, for the rest of us, if you could post :
- the current at which the LED is supposed to be used (aka nominal current)
- diffusion angle (read somewhere it's 45°, is that it, or is it more like 30 or 60)
- brightness ratings. Just what the manufacturer says, that what they all use for spec sheets even the number itself does not mean much since it's just on the paper. Name the color for each millicandela value.
I'm guessing it's about 2500-3000 mcd for blue, and probably up to 12000 mcd for green.

this will help to source something equivalent to what you have and make the process of prototyping quicker, so that a CF led strip version board can be made soon.

Thanks !
Erv'

**erv** · 10-01-2008, 05:06 AM

LEDs ordered,
and I've sourced some nice wire that will probably allow the scrolling effect wiring without the hassle of the shadows as eastern showed on his prototype.

I'm going to test 3 things in total :
- custom ladder I'll make, with scrolling effect
- modified MR PCB strip with HB Leds and other mods
- comparison with the HBlades

being in the manufacturing of the CF new batch (at home, in my personnal lab, by hand), I'll have the time next month, this will give me some time for the LEDs to arrive to my door.

Erv'

**Jedi-Diah** · 10-01-2008, 08:31 AM

I wouldn't want you to neglect your "current lab project"

for the sake of a new one. But I'm glad you are interested in the "new project" as well.

Thanks!

Originally Posted by erv

LEDs ordered,
and I've sourced some nice wire that will probably allow the scrolling effect wiring without the hassle of the shadows as eastern showed on his prototype.

I'm going to test 3 things in total :
- custom ladder I'll make, with scrolling effect
- modified MR PCB strip with HB Leds and other mods
- comparison with the HBlades

being in the manufacturing of the CF new batch (at home, in my personnal lab, by hand), I'll have the time next month, this will give me some time for the LEDs to arrive to my door.

Erv'

**Jonitus** · 10-01-2008, 09:03 AM

Oh yes, I shall watch this project with MUCH interest. As soon as I saw the Mako style blades, I knew it was going to be something I wanted for a display saber.

Looks as though I had better set aside some monies after the sale of my next couple of sabers to buy some LEDs and get a ladder built in preparation of getting one of Erv's new CF that support this style of blade.

**Jangotat** · 05-21-2011, 05:49 AM

Hey can you use "flashing LED's 5mm) the seem to be easier to find and cheaper. Will they work alright for solid on?

**Azmaria Dei** · 05-21-2011, 06:47 AM

Originally Posted by Jangotat

Hey can you use "flashing LED's 5mm) the seem to be easier to find and cheaper. Will they work alright for solid on?

holy necroposting batman! this topic is like 3 years old! and the CF still doesn't support string blades... as for blinking LEDs, with all your LEDs blinking randomly you would get a lot of uneven blank spots and the effect would be really bad... even the yellow candle flicker ones wouldn't be very visually appealing.