Lastly, connect a 12V DC power supply (making absolutely sure to get the polarity right!) and you will have a remote-controllable LED strip. 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! Next step is to attach your RGB strip (it should match the 4-pin connector on the far left). You can adjust it as needed and then upload it through FTDI. To get some really fancy effects, check out the Color-shifting LED Node post from a while back on this weblog. 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.
Here’s a side view, with the ATmega328 added – as you can see it’s much flatter than v1:Īnd here’s a top view of the completed LED Node v2, in all its glory: 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:Ĭelebration time – we’ve completed the assembly of the LED Node v2! Then solder the remaining pins (I tend to get lazy and skip those which aren’t used, hence not all of them have solder). It’s easiest if you start off by adding a small solder dot and hold the radio while making the solder melt again: Soldering the RFM12B wireless radio module takes a bit of care. 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: Next, add the 4x 0.1 ♟ capacitors and the IC socket – lots of soldering to do on that one: of 1 MΩ, as that’s what I had lying around)
(note: I used three 100 kΩ resistors i.s.o. Let’s get started! So we begin with 7 resistors and 1 diode (careful, the diode is polarised):īe sure to get the values right: 3x 1 kΩ, 3x 1 MΩ, and 1x 10 kΩ (next to the ATmega).
SCREENY WEENY 4.0 FREE
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.Īs 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. 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. Note that the LED Node comes with pre-soldered SMD MOSFETs so you don’t have to fiddle with ’em. This relatively high 0.65 mA current draw was the main reason for including a MOSFET in the new JeeNode Micro v2, BTW.Īfter yesterday’s little mistake, here’s a walk-through of assembling the LED Node v2: It’s a bit of a silly distraction to do things this way, but now I do have a better idea of how current consumption increases on startup. Keep in mind that the changes are occurring at 10 Hz, so there’s bound to be some residual charge in the on-board capacitors of the RFM12B module.Īnyway. But there’s an intriguing split in the curve – this is most likely caused by a different current consumption when VCC is rising vs when it is dropping. Because it really doesn’t matter how we vary VCC over time. Here’s what happens when the input signal is switched to a sine wave:Īs expected, the essence of the curve hasn’t changed one bit. It’s essentially the same picture as before, because the sawtooth is a straight line, and so voltage rise is the same thing as time in this case. This type of analysis can also be done using the X-Y mode on most oscilloscopes: Note that this power consumption can’t be reduced: we don’t have the ability to send any commands to the RFM12B until it has started up! As you can see, the current draw quickly rises between 1 and 2V, and then continues to increase sort of linearly. The magenta trace is the current consumption, which turns out to be 0.650 ♚. The yellow trace is VCC, the supply voltage – from 0.3V.
This will have a slight effect on measurement accuracy – but no more than 2%, so I’m ok with it. So the idea is to apply a sawtooth signal to the RFM12B, rising from 0 to 3V at the rate of say 10 Hz, and to measure the voltage drop across a 100 Ω resistor at the same time. Well, time for a test using the power booster described recently:
For quite some time, I’ve wanted to know just how much current the RFM12B module draws on power-up.
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