Computing stuff tied to the physical world

Meet the LED Node v2

In Hardware on Dec 14, 2012 at 00:01

The LED Node has been around for a while, but I wasn’t 100% happy with it. In principle, the LED Node v1 is a JeeNode plus 1.5 MOSFET Plugs plus an optional Room Board.

There is a small but significant difference with regular JeeNodes (apart from their very different shape), in that all three MOSFETs are tied to pins with hardware PWM support. This is important to get flicker-free dimming, i.e. if you want to have clean and calm color effects. Software PWM doesn’t give you that (unless you turn all other interrupt sources off), and even with hardware PWM it requires a small tweak of the standard Arduino library code to work well.

The neat thing about the LED Node is the wireless capability, so you can control the unit in all sorts of funky ways.

But I didn’t like the very sharp pulses this board generates, which can cause problems with color shifts over long strips and also can produce a lot of RF interference, due to the LED driving current ringing. The other thing which didn’t turn out to be as useful as I thought was the room board part.

So here’s the new LED Node v2:


The big copper areas on the left are extra-wide traces and cooling pads, dimensioned to support at least 2 Amps for each of the RGB colors, for a total of 6 A, i.e. 72 W LED strips @ 12 V. But despite the higher specs, this board will actually be lower profile, because it uses a different type of MOSFETs. They are surface mounted and come pre-soldered so you don’t have to fiddle with them (soldering such small components on relatively large copper surfaces requires a good soldering iron and some expertise).

This new revision has the extra resistors to reduce ringing, and replaces the room board interface with two standard 6-pin port headers: one at the very end, and one on the side. These are ports 1 and 4, respectively, matching a standard JeeNode and any plugs you like. If you want, you could still hook up a Room Board, but this is now no longer the only way to use the LED Node.

Wanna add an accelerometer or compass to make your LED strips orientation aware? Well… now you can! And then place them inside your bike wheels? Could be fun :)

Details to be posted on the Café wiki soon, as well as in the Shop.

  1. Could this v2 be adapted to drive an RGBW ledstrip?

    • One way I can think of is to add a MOSFET Plug to it. It will probably have to use software PWM, though. All the easy pins with PWM support have been used up, I think.

    • Sounds to me like the perfect upgrade for the lednode v3! Another addition would be to make the footprint of the lednode ports the same as they are on the jeenode so you can just stick on a roomboard the regular way.

    • A variant with the dimmer plug onboard, and the 3/4 FET’s on a separate board (same width as LedNode) would also be nice.

      Then one could go either way…

      And with 16 outputs, I could drive 4 RGBW ledstrips using just one LedNode!!!


  2. Instead of doing PWM over long high-current lines, you could use a stripe with those new “digital” RGB LEDs that have a builtin PWM controller and allow individual control over 100s of LEDs from a single µC pin.

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