I’m a musician trying to rationalise my effects pedal power system. I’m checking each device’s power draw with a multimeter. Two devices state their draw in the documentation as 300mA. My measurement on both devices read 150mA. Have you any idea why this discrepancy occurs? Might I be doing something wrong? The devices in question are Zoom GFX707 multi fx units.
While I’m at it, would my measurement on your lovely WAV Trigger be 80mA, rising to 100mA when outputting audio? Would this be ok to power from a laptop USB port?
Hi davesteb,
While we cannot assist you with troubleshooting non-SparkFun products I have a couple of tips for measuring current with your Zoom GFX707’s. The 300mA listed in the documentation could be the peak current draw of the devices and there is another rating (probably close to 150mA) for operating/nominal current. You might also only be measuring a portion of the entire current draw depending on where and how you are testing it. Are you making sure to measure the current in series with the power circuit as we demonstrate in our [How to Use a Multimeter Tutorial?
Now, for your question about the [WAV Trigger. You are correct, the WAV Trigger draws ~80mA while idle and ~110mA when playing a track but the current can spike up to 200mA if you are using the on-board audio amplifier and driving a speaker at high volume.
You can absolutely power the WAV Trigger with the 5V out from a USB port but there is no USB connector on the board so you will need to break out the 5V and Ground lines from your USB port. You can use a breakout like [this to split out the power and ground pins (Vcc and GND) on your USB connection and then run those to 5V and GND pins on the 2x4 header on the side of the board. The silkscreen is a bit confusing on this header so just to avoid confusion, the “top” row of silk (labeled MC, DI, BC and LR) is the inner row of pins and the “bottom” row of silk (labeled GND, PLO, 3.3V and 5V) are the outer pins on that header.
Alternatively, you can connect a [5V FTDI Basic Breakout to the FTDI port to power the WAV Trigger. Just note you need to close the jumper labeled 5V above the 2x4 I2S header and if that jumper is closed, make sure to not provide power from the barrel jack connector while the FTDI is connected. This and much more about the WAV Trigger is covered in [robertsonics’ User Guide and our [Hookup Guide.](WAV Trigger Hookup Guide V11 - SparkFun Learn)](http://robertsonics.com/wav-trigger-online-user-guide/)](https://www.sparkfun.com/products/9716)](SparkFun microB USB Breakout - BOB-12035 - SparkFun Electronics)](https://www.sparkfun.com/products/13660)](How to Use a Multimeter - SparkFun Learn)