Output Devices¶
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measure the power consumption of an output device
Katies power consumption
Measure the power consumption of an output device
'For most non-portable "desktop" projects, a 5V DC switching power supply is ideal. This small 2 Amp supply is good for a a meter or so of NeoPixel strip.'
Adafruit Battery Power for LED Pixels and Strips Overview
'The recommended 5 Volts is a "nominal" rating... we actually have a little bit of wiggle room here. About 10% above or below this figure works fine. You can see this by measuring the output of a wall adapter with a voltmeter: due to manufacturing variance, the actual output could be anywhere in this range. So anything from about 4.5 to 5.5 Volts is safe for these LEDs and 6V is the 'rated absolute maximum'. Any higher and they'll burn out quickly. Any less and the colors will appear muddy and brown.'
What ada fruit suggest on their website:
'To estimate power supply needs, multiply the number of pixels by 20, then divide the result by 1,000 for the “rule of thumb” power supply rating in Amps. Or use 60 (instead of 20) if you want to guarantee an absolute margin of safety for all situations. For example:'
Calculations
I have 45 neo pixels:
45 (neo pixels) x 20 mA / 1,000 = 0.9 Amps minimum 45 (neo pixels) x 60 mA / 1,000 = 2.7 Amps minimum
Showing neopixels loosing colour due to not enough Power
I have been watching these videos online about neopixels and how they work with FastLED which is a way to make the patterns. The link to the videos are here and whne watching the guy shows us how when you light up a long string of neopixels with not enough power the last few loops go yellow when they should be bright white. This is because they are not recieving the correct amount of power when plugged in, to avoid this you can add more power every 1 meter he says in his video but best to double check
Here is the photo of the neopixels going from bright white to yellow.
Jonny's power consumption
We shall be using Ohm's Law which states that power is equal to voltage multiplied by current
P = V*I
My NEMA 17 stepper motors have a rated current of 1.7A. I'm powering them with 12V which means they have a rated power of 20.4 watts
I've used a multimeter to test how much current my NEMA 17 steppers are drawing while in operation. Although there is a rated current, the amount of current they're actually using will vary according to how much work they are required to do. Moving a small load would draw less current than a heavier load. Furthermore I have used the current limit switch to put a ceiling to how much current they can draw
I've set the stepper motor to move constantly using a typical speed for my project. Each motor is pulling approximately 210 milliamps. This gives a power of 2.52W.