Simple Trick for Determining 2.1mm or 2.5mm Barrel Jacks
Here’s a tip I got recently from Donald Bell’s Maker Update. It’s from an old DigiKey “Teaching Moment.”
Many barrel jacks have a consistent 5.5mm outside diameter. But the inside diameter can vary, usually either 2.1mm or 2.5mm.
If you don’t have your digital calipers handy, you can determine this inside diameter with common objects: a toothpick, a ball point pen, or a test probe.
The brass housing on a ball point pen is 2.2mm. If it doesn’t fit inside the barrel of your jack, then the jack is 2.1mm. If the pen easily fits inside, the jack is 2.5mm.
A standard toothpick is 2.1mm. If it fits snugly in the jack, it’s a 2.1mm jack. Also a common multimeter probe needle with fit closely inside of a 2.1mm jack and be very sloppy inside of a 2.5mm jack.
Eink, E-paper, Think Ink – Collin shares six segments pondering the unusual low-power display technology that somehow still seems a bit sci-fi – http://adafruit.com/thinkink
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.