Computing stuff tied to the physical world

Assembling the LED Node v2

In AVR, Hardware on Dec 28, 2012 at 00:01

After yesterday’s little mistake, here’s a walk-through of assembling the LED Node v2:


Note that the LED Node comes with pre-soldered SMD MOSFETs so you don’t have to fiddle with ’em.

The LED Node is really just a JeeNode with a different layout and 3 high-power MOSFET drivers, to control up to 72W of RGB LED strips through the ATmega’s hardware PWM. Since there’s an RFM12B wireless module on board, as well as two free JeePorts, you can do all sorts of funky things with it.

As usual, the build progresses from the flattest to the highest components, so that you can easily flip the PCB over and press it down while soldering each wire and pin.

Let’s get started! So we begin with 7 resistors and 1 diode (careful, the diode is polarised):


Be sure to get the values right: 3x 1 kΩ, 3x 1 MΩ, and 1x 10 kΩ (next to the ATmega).

(note: I used three 100 kΩ resistors i.s.o. of 1 MΩ, as that’s what I had lying around)

Next, add the 4x 0.1 µF capacitors and the IC socket – lots of soldering to do on that one:


Then the MCP1702 regulator and the electrolytic capacitor (both are polarised, so here too, make sure you put them in the right way around), as well as the male 6-pin FTDI header:


Soldering the RFM12B wireless radio module takes a bit of care. It’s easiest if you start off by adding a small solder dot and hold the radio while making the solder melt again:


Then solder the remaining pins (I tend to get lazy and skip those which aren’t used, hence not all of them have solder). I also added the 3-pin orange 16 MHz ceramic resonator, the antenna wire, the two port headers, and the big screw terminal for connecting power:


Celebration time – we’ve completed the assembly of the LED Node v2!

Here’s a side view, with the ATmega328 added – as you can see it’s much flatter than v1:


And here’s a top view of the completed LED Node v2, in all its glory:


You can now connect the FTDI header via a USB BUB, and you should see the greeting of the RF12demo sketch, which has been pre-loaded onto the ATmega328.

To get some really fancy effects, check out the Color-shifting LED Node post from a while back on this weblog. You can adjust it as needed and then upload it through FTDI.

Next step is to attach your RGB strip (it should match the 4-pin connector on the far left). Be sure to use fairly sturdy wires as there are up to 2 amps going through each color pin and a maximum of 6 amps total through the “+” connector pin!

Lastly, connect a 12V DC power supply (making absolutely sure to get the polarity right!) and you will have a remote-controllable LED strip. Enjoy!

  1. hmm. nice touch. I 3 simple white LED strips in my living room, could i use the same kit to controll 3 single color led strips (1.5A each)

  2. Jcw,

    Now how do i power these things? when uploading the sketch i only connect through usb and the ftdi header but do not connect it to the 12v adapter? Or can i power them just fine with bith power supplies (usb and 12v adapter) during sketch development? And when puting in production?



    • Good point. For programming, connect and power through FTDI – for actual use, you only need 12V. Both supplies may be connected at the same time during development, but the LED strip will only light up when 12V is applied.

  3. @Mike – the MOSFET outputs are independent, so connect what you wish to the nominal RGB pins. For long, single-colour strips, the outputs can even be wired safely in parallel.

    In all cases, just be careful of the total current in the common path; a limiting factor is the connector and/or direct solder used there to the oversized copper track.

Comments are closed.