I found some cool LED strips that run at 5 volts and require about 1.2 watts to run. I was hoping to hook one up to a digital output and just set the output to power the LEDs and certain points in the code to get a cool underglow effect. Would i be able to power these with a digital output or would they fail to provide enough power? I feel like it should be totally fine because they can output 5 volts no problem and i don’t really think they would be unable to provide the very low current needed to run the LEDs but i want to be sure before i purchase anything.
For reference this is the product i am talking about…
Watts = Volts * Amperes
Amperes = Watts/Volts
Amperes = 1.2/5 = 0.24 = 240 mA
That’s well below the nominal 1 A/port. But here’s the catch: I can’t find a spec on the Vex site as to how much current the DO pin can provide, as opposed to how much the power pin in the port can provide. (I poked about the chip’s datasheet:
and I believe the limit is stated on page 3 as 25mA/pin. The schematic Vex provides for the controller module does not indicate that there’s any enhancement of this.) You probably could run this from a DO port, if you used an external device that modulates the power from the power pin with a signal from the DO signal pin. (Technically, that’s not hard to do. Whether it would be “competition-legal”, though is a different matter.)
Hmmm. This complicates things a bit. So you are saying that the port as a whole can handle 1 amp but the individual pin can only handle 25mA?
It’s even worse than that. If you look at the specs page here: https://vexforum.com/wiki/index.php/VEX_Microcontroller_V0.5 you’ll see that they mention a 1K series resistor between the PIC and the external port (they used to have a schematic showing this too but I can’t find it right now). 5v/1000ohms = .005 amps = 5 milliamps. Note that in the specs on that page they only guarantee that an output can drive 1mA per pin.
The 1A refers to the total current that you can draw from all of the +5v pins together.
Ouch. I don’t think i will be powering any LED strips any time soon. At least not in a competition legal way.
Use a buffer and you should be fine.
LED strips for decoration are allowed. However, Adding additional electronics ONLY for decorations MIGHT fall in the rules. You should ask this question on the Official Questions forum.