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Author Topic: LED COB blade -- a new design?  (Read 7637 times)

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Offline thatguyer

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Re: LED COB blade -- a new design?
« Reply #15 on: March 29, 2017, 08:24:47 PM »
Maybe Jake was right after all to use a Attiny :) With the chipset PCA9685 even a very small 8-bit controller could be used to program it, no need for PWM channels.
William, the challange is the driver stages, i.e. the mosfets. The chipset is as far as I understood a good PWM controller, but can output only ~20mA, enough for 1 LED, but not for many. Therefore you need mosfets, up to 16. So many to integrate on one board is a mess and a very narrow market segment. So you end up having to use an auxiliary board to house all your mosfets with enough surface to shed the heat. I guess this answers why all current single board solutions only support 6 segments. Nevertheless the LED string maniac stirs again in me... :evil:

Indeed. Personally, I was interested in learning about designing and building PCBs (just to get edumacated on these things). Below, you can see a photo of my custom board. I ended up adding the inertial sensor there, too, since it was small and shared the I2C bus.



I'm happy to share the Eagle files with anyone. You can also order the boards from OSHPark, but you'll have to assemble them yourself. If you really, really want one and really, really don't want to make it yourself, I have a few extras lying around.  :grin:



Offline thatguyer

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Re: LED COB blade -- a new design?
« Reply #16 on: March 29, 2017, 08:28:15 PM »
I'm not sure if that image link worked. Here's a link to the OSHPark project:

OSH Park ~ LED Controller v5

Offline thatguyer

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Re: LED COB blade -- a new design?
« Reply #17 on: March 29, 2017, 08:35:36 PM »
I have only been into this hobby for about a year and even though I have seen the experiments (online) with neopixels, personally, my enthusiasm is really stuck on string blades. Using COB LEDs is interesting, but, I am still resisting any move away from string blades. What is very interesting is the LED controller. The standard in string blades is six segments, but I would really like to try out more. I use several strings with 3mm LEDs and I have never seen any wires behind the foam. I guess that the LED controller that you use could drive 14 segments of a string blade, or is there a “but” or “however” that I have not considered? (Maybe 14 segments would mean too many wires, but let’s say 10-12...).

I did build two sabers using strings of discrete LEDs controlled by the same board. I first soldered together the entire string, then cut the ground side in 14 places and ran a separate wire back to the board. They share a common power rail (which also helps keep the string from falling apart!)

As you point out, the real issue is the wires -- they have to go somewhere. I ended up finding some very thin 28 gauge wire that did not block the light too much. What you want is something called "kynar wire", either 28 or 30 AWG. It has very thin insulation.

Offline Obi_1

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Re: LED COB blade -- a new design?
« Reply #18 on: March 30, 2017, 12:50:46 AM »
I'm not sure if that image link worked. Here's a link to the OSHPark project:

OSH Park ~ LED Controller v5

Welcome in the merry group of saber board manufacturers    :afro:

Offline thatguyer

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Re: LED COB blade -- a new design?
« Reply #19 on: March 30, 2017, 08:06:21 AM »
I'm not sure if that image link worked. Here's a link to the OSHPark project:

OSH Park ~ LED Controller v5

Welcome in the merry group of saber board manufacturers    :afro:

So true. I discovered profezzorn's Teensy Saber board while perusing the shared projects on OSHPark. It's the Wild West out there. The good news is that the software is relatively portable across boards.

Offline jbkuma

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Re: LED COB blade -- a new design?
« Reply #20 on: March 30, 2017, 09:05:37 AM »
I've been looking around for what seems to be the most optimal solution to balance battery performance with the size and demand of the boards.

I have an ATmega1284 board here that I've not played with yet.  After looking around it seems like I could reasonably make an 8 segment blade with 120mmx8mm 12v 3w pieces running a modified version of LSOS.  They are cool white, but they'd fit in a thick wall dayblade.  I'm not sure if that's ideal for making a colored blade, but perhaps an interesting experiment.  These would only pull about 6a in parallel at full power, so this should be manageable for a 3x18650 setup.  It could even be made a 6 segment blade powered by a DIYino making the first two segments being two long and use the existing LSOS code (or even a CF-LS).  Since the battery pack will either be a short and fat LiPo or long and slender LiIon pack, There's plenty of room to put in 6 or 8 transistors without the need for extra PWMs.


Offline thatguyer

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Re: LED COB blade -- a new design?
« Reply #21 on: March 30, 2017, 11:29:41 AM »
OK, here is a link to a photo of the custom PCA9685 board...

IMG_5233.jpg - Google Drive

The grid of pins at the back are connected to the MOSFET drains. The ground of each segment is connected to one of these pins. All segments share a common power rail.

The MOSFETs are pretty big for SMD components, so you could conceivably solder them by hand on a protoboard. Otherwise, you'll have to use discrete power MOSFETS (like this: N-Channel MOSFET 60V 30A - COM-10213 - SparkFun Electronics)

Offline thatguyer

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Re: LED COB blade -- a new design?
« Reply #22 on: March 30, 2017, 05:23:24 PM »
Below is a link to the circuit diagram. Yes, I know, it's old school, but it was fast to make.

IMG_6036.JPG - Google Drive

In case it isn't obvious, I'm only showing one segment with its corresponding MOSFET. Also, the pin locations on the boards are just approximate.
« Last Edit: March 30, 2017, 05:25:13 PM by thatguyer »

Offline JakeSoft

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Re: LED COB blade -- a new design?
« Reply #23 on: March 30, 2017, 06:41:49 PM »
Below is a link to the circuit diagram. Yes, I know, it's old school, but it was fast to make.

IMG_6036.JPG - Google Drive

In case it isn't obvious, I'm only showing one segment with its corresponding MOSFET. Also, the pin locations on the boards are just approximate.

Don't apologize, that' diagram is great. It's well drawn and easy to understand. Thanks for sharing.

Offline Greebles

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Re: LED COB blade -- a new design?
« Reply #24 on: March 31, 2017, 05:27:27 AM »
Following this with great interest!

-Denzil

Offline DarthBrooks

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Re: LED COB blade -- a new design?
« Reply #25 on: June 03, 2017, 02:46:55 AM »
I'm interested in making a saber with this design.

Is it poosible to make a red saber with cob's using a conventional sound card? I'm not interested in the scrolling, just want a bright blade.

I really like this design, seems much more efficient to have leds that shine outwards.

There are red cobs same as these in 3v, 1 watt. That would result in a 48 watt 1m blade.

Maybe using a square aluminium pipe and 4 cobs per segment would dissipate heat better because you get more contact surface to the aluminium?

I'm new to this so no clue really but I'm interested in learning.

 

retrousse