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March 21, 2012
31, electrical engineering degree - finally trying to put it to some good use :)
about 2 years ago
The LED will also light at 5V. I measured the built in current limiting resistor at 464 ohms. Current at 5.7V was 6mA, indicating the forward voltage of the LED was 2.9V. It even lit dimly at 4V, drawing 2.8ma, meaning 2.7V forward across the LED.
My particular 5V Arduino can source or sink 40mA per pin (200mA total), so conveniently these work directly connected to my Arduino’s pins.
about 2 years ago
[I ordered the green button, but I’m adding it here as well]. I’d like to add that the LED will also light at 5V. I measured the built in current limiting resistor at 464 Ohms matching what others said below. Current at 5.7V was 6mA, indicating the forward voltage of the LED was 2.9V. It even lit dimly at 4V, drawing 2.8ma, meaning 2.7V forward across the LED.
about 3 years ago
Hey, I’m sorry I didn’t see your messages earlier. Congrats on getting it to work! Hopefully you inferred that my setup and solution is specific to the 12V Sparkfun inverter with a common power source for Arduino and Inverter.
I just got a nice email from Sparkfun. It has me optimistic the next version of this product will be a lot easier.
As long as your two wall warts' DC sides do NOT have a common ground connection, I can see why this works as well. You’re activating the TRIAC using the opposite “Quadrant” – see here: http://en.wikipedia.org/wiki/TRIAC.
I might add a slight warning to others that doing this particular jumper (Inverter GND to “Raw voltage +”) with a common power source for Arduino and Inverter. I believe you’ll be short circuiting your power source.
Hi Greg -
I think I understand why I didn’t have to connect that jumper; it has to do with my particular setup vs. what is shown in the tutorial. First, we should point out that the bildr tutorial is for the Sequencer, which is different from this product, the Escudo.
In the tutorial, they show a separate battery-powered inverter, and it’s ambiguous as to whether that inverter is being powered by the same battery that they power the onboard Arduino with via BATT.
I find their description of the purpose to be a little misleading: “To make this work, a wire needs to be soldered between the “power” and the “output” of the EL Driver section”. I think it’s clearer to say, “The purpose of that jumper is to connect HVGND to GND”. It allows the current from the Arduino’s output pins to actually flow relative to the HVGND - and this is something necessary for the TRIACs to activate.
In my setup, I have a single 12V power source powering the Arduino Uno and my 12V inverter. As I mention above, the inverter has a common ground between it’s 12V side and it’s high voltage side (the barrel’s outer conductor and the black wire on the HV JST). With one battery powering both, I effectively have the same jumper.
Hope this helps!
I also [finally] got my El Escudo, 12V inverter, and Uno working today. For my first experience with Sparkfun, it seems like they never update their product description, and that blows.
I’m powering everything off a single 12V source. In this configuration, the jumper shown by PhysicsGuy would effectively short the inverter (that’s bad). The inverter’s 12V side and high voltage side share a common ground (you can disassemble it and see, or measure the resistance). This is why they use a red/black JST connector, even though it’s AC.
Here’s what’s working for me:
+12V from my power supply connected to Vin on the Arduino Uno, and the center pin of the barrel power connector on the inverter.
Cut (disconnect) the jumper between the Escudo shield Vin and the Arduino Uno’s Vin. If you look at the diagram, the Escudo’s Vin is only connected via capacitors to ground (AC filtering). Following Member #132179’s excellent points above, I also jumpered the 3.3V on the Escudo (carried up from the regulator on the Uno) to the Escudo’s Vin, but I doubt that’s really necessary in this setup.
Ground from my power supply connected to the Uno’s ground, as well as the inverter’s 12V barrel connector’s outer conductor.
I found this configuration to drive all 8 Escudo outputs at once with ease (each has a 1 meter wire connected), and I believe the code comments in Ryan’s reference implementation about “up to 2 strings can be turned on at once” must refer to when using the 3V inverter (COM-10201).
Code wise, I’m using the Arduino 1.0 IDE, so I had to do the wiring.h => Arduino.h, as well as rename the F constant as per http://arduino.cc/forum/index.php/topic,93451.0.html
I also had to take the pins HIGH in the definition of on(). This makes more sense because the Escudo uses TRIACs. TRIACs activate when the gate has current flowing from a voltage relative to HVGND. As mentioned before, the 12V inverter has a common ground, so HVGND is GND – thus, pin HIGH means TRIAC is on.
Less obvious to me (but hey, it works) is that I also had to modify off()’s definition to take them LOW before turning them back into the high-Z INPUT mode. Otherwise they would float and commonly stay high, resulting in intermittent and unpredictable results.
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