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After fumbling for some time with double-clutch heel-toe juggling, I decided I could help myself with a microcontroller. It starts with an IR sensor in the speedometer.
If you don’t know how an old speedometer works – a metal drum spins around a permanent magnet (could be more than one) spring loaded and connected to the speed needle. The induced magnetic field (current, actually – Lenz’s law) in the drum has polarity that opposes that of the magnet and subsequently, as the drum spins, it also applies a force on the magnet displacing the speed needle. The faster the drum spins, the greater the field disparity, the greater the force, and subsequently the deflection of the needle. Some energy is lost to the eddy currents, but overall it’s a clever system. Anyway – it’s the spinning drum which is moved by a cable connected to the differential of the car that is useful in this case. As it spins, the purple nail-polish stripes block (an then unblock) the reflection from and IR LED. A photodiode, then picks up this timing.
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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.
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Python for Microcontrollers – Adafruit Daily — Python on Microcontrollers Newsletter: CircuitPython 2025 Wraps, Focus on Using Python, Open Source and More! #CircuitPython #Python #micropython @ThePSF @Raspberry_Pi
EYE on NPI – Adafruit Daily — EYE on NPI Maxim’s Himalaya uSLIC Step-Down Power Module #EyeOnNPI @maximintegrated @digikey
