microbit
The BBC microbit came out in 2016 and people took notice. It costs around $16, can be programmed from a browser using blocks javascript, micropython or scratch (they say even more than those). In addition to USB connection to a computer (download program, drag & drop onto microbit in the drives), programming can be done with a mobile via bluetooth. It has 2 input buttons, a 5x5 array of LED's for display, compass, accelerometer, temperature sensor, the 25 LED's can act as a light sensor, it can communicate with other microbits via radio, is powered by 3V (ONLY 3V, don't overpower), and has 25 connection pins. 3 of the general purpose input output pins (0, 1 & 2) and 3V & ground are easily accessible via alligator clips. The others are smaller and really need the microbit to be plugged in to and external "breakout" board.
This has created a whole new industry of general and specialized breakout boards. I call something a "general" board if it wants to get access to all the pins for multiple functions, like motors AND servos AND LEDs... as opposed to a breakout board that just wants to run 2 motors and nothing else. Sparkfun and Adafruit are places from which I have bought accessories (Amazon also and there are many more). Makerbit, bit:booster, and CRICKIT are general boards that I have worked with.
There is a good amount of curriculum and technical support. There are examples and tutorials all over the Internet (microbit teach , lessons ; hackster , Adafruit , Sparkfun ). There is a community magazine micro:mag that wants people to contribute projects and articles. you can download pdf's of issues (3 as of Feb 2019)
If you dont' have some microbits for your school or coding/robotics club (or for yourself)... what are you waiting for??
There are 25 pins, 3 for voltage and 3 for ground, which leaves 19 for inputs/outputs. You can run servo's and motors and LED's and neopixels and LCD displays... get inputs from switches and buttons and microphones... When you start using the microbit for several inputs/outputs at once, you have to pay attention to what pins you are using because there might be conflicts. For example, you would not want to use pin 3 as an input or output IF you also want the 5x5 LED array to work correctly - that pin is part of the array. Refer to the pinout diagram from micro:bit (image). You can shut of the array with a line of code (in blocks it is "LED enable false"). Also some pins (0-4) are analog, meaning they want values that range from 0-1023 (think dimmer switch) and others are digital, meaning they work with values that are 0 or 1 (think light switch, on or off).
If you dont' have some microbits for your school or coding/robotics club (or for yourself)... what are you waiting for??
There are 25 pins, 3 for voltage and 3 for ground, which leaves 19 for inputs/outputs. You can run servo's and motors and LED's and neopixels and LCD displays... get inputs from switches and buttons and microphones... When you start using the microbit for several inputs/outputs at once, you have to pay attention to what pins you are using because there might be conflicts. For example, you would not want to use pin 3 as an input or output IF you also want the 5x5 LED array to work correctly - that pin is part of the array. Refer to the pinout diagram from micro:bit (image). You can shut of the array with a line of code (in blocks it is "LED enable false"). Also some pins (0-4) are analog, meaning they want values that range from 0-1023 (think dimmer switch) and others are digital, meaning they work with values that are 0 or 1 (think light switch, on or off).