USB Tester OLED Backpack: Surprise Feature 3 (Not Needed Anymore)

wpsuperadmin friedcircuits, USB Tester Leave a Comment

This post was about a feature I was going to add, but after prototyping I realized that it isn’t needed. The microcontroller can be connected to both power sources and before the sense resistor without any affect on measurements. The maximum power you can use is still affected as mentioned at the end of the post.

If no host computer is connected for the microcontroller, it will draw power from the same source as the device you are measuring. This can make it convenient for checking a device without needing to be near a computer or 2nd power source. This will be great for testing on the spot. In the future it might be possible to do some light data logging to the microcontroller via a firmware update or if someone wants to add it. It would be possible to design another addon to add a SD card or flash memory for logging.

I thinking that instead of the switch I could have a solder jumper so that you can still discount the power from the measuring device and or add a button for future use.

Post your thoughts below of what you would like to see.

Here is the original post:
In December we released the USB Tester for measuring voltage and current of your USB project and devices. This tool made it easier to connect your digital multi-meter for measurement. You can read the full product description here: This month we are working on releasing an OLED Adapter backpack. This will allow you to view the voltage and current without the need for a DMM.

Previously I announced two features:

Today I wanted to announce the final feature that the OLED Backpack will have.

The final feature will be a power source selector switch. This allows you to power the OLED display and microcontroller from the same source as the project you are measuring. This will be great when you are measuring a device away from a computer such as a phone charging, Raspberry Pi, or something that is greater than 500mA. Once you are back at a computer and want to data log, you can flip the switch to the off position. The switch is also connected to a pin on the microcontroller so it would know the power source.

Remember that it will slightly reduce the maximum power your measuring device can use depending on your power source. For example, if you are measuring an XBee from a 500mA power supply with the switch on, the maximum the XBee could use is 460mA, since the backpack with the OLED display is about 40mA. So for the most part it shouldn’t be enough to affect most devices.

This will be a great feature for measuring devices on the go. I can’t wait to finish development and get this in your hands to help your project developments!

Thanks for the support. Look for the upcoming fundraiser on

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