I wanted a board that shows the state of all I/O pins on LEDs with all of these properties….
- Works for Digital Input, Output, and Input Pullup
- Pushbutton to drive the pin high, very weak pulldown (much weaker than on-chip pullup)
- Works for analog pins (thumbwheel pot), but also works when the same pin is used for digital
- LED shows actual analog level – LED current should be linear to actual voltage
- LED current does not interfere with analog voltage
- LED does not interfere with weak signals, or input pullup or pulldown
- Inexpensive – under $0.50 per pin – many parts are ok, as long as they’re cheap!
I realize this is probably excessive design for most people, but when you’re making a development board and testing nearly every major Arduino library, it’s amazing how handy tools like this can be. So I thought I’d document this little circuit, and especially the 150K feedback resistor trick that makes it work so well with these higher impedances and the chip LMV358 opamp.
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.
Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7pm ET! To join, head over to YouTube and check out the show’s live chat – we’ll post the link there.
Join us every Wednesday night at 8pm ET for Ask an Engineer!
Maker Business — Peloton to break ground at a new manufacturing campus in Ohio
Wearables — Tear it all apart
Electronics — Disable unused channels!
Python for Microcontrollers — Python on Microcontrollers Newsletter: CircuitPython tops Tom’s Hardware Best RP2040 Boards 2021 and more #Python #Adafruit #CircuitPython @micropython @ThePSF
Adafruit IoT Monthly — Toddler Clock, Predictive Weather Station, and more!
Microsoft MakeCode — Arcade Beginner Skillmap
EYE on NPI — Maxim’s Himalaya uSLIC Step-Down Power Module #EyeOnNPI @maximintegrated @digikey
New Products – Adafruit Industries – Makers, hackers, artists, designers and engineers! — New Products 6/16/2021 Featuring Adafruit Etched R4 Keycap for MX Compatible Switches! (Video)
Sorry, the comment form is closed at this time.