Identifying a really cheap embedded solution that is ideal for schools

As I said in my previous post, a few dads and I are going to help out with a Maker's elective at school.  The three topics we will be covering include plumbing, woodworking, and electronics.  Of the three, I'm probably most skilled in electronics, so that's what I am going to attempt to "teach".

My goal is not going to be to make the kids experts in electronics.  Heck, I'm not an expert and just kind of hack my way through projects.  I just want them to be comfortable enough with the basics that they will be able to work on their own projects after the course is over.  In addition, I would like them to have fun and excite their curiosity so that they will WANT to pursue projects.

The basics include an explanation of voltage and current, Ohm's law, and Kirchoff's Laws.  I will need to come up with analogies to make the concepts easier to understand, as well as piece together simple demonstrations to show how the laws apply.  I would also like to give an overview of basic components, like resistors, capacitors, diodes, potentiometers, switches, and LEDs.

Blinking an LED when you press a button is nice for a "hello world" kind of electronics project, but to really capture their interest, I'm thinking that demonstrating fun things is the right way to go.  For example, I might be able to hack together demos like the following:

• wiimote with accelerometer
• spinning a stepper motor to drive a car
• rotating a servo to move a Nerf cannon
• lighting up LEDs in series to emulate a Force FX light saber
• sound recording / playing (maybe to add to above light saber demo)

The list goes on and on... but then the question remains -- how in the world do you enable kids to create these projects?  When you think about schools and limited budgets in general, cost is a huge concern.  You also have to consider the programming hurdle for the kids, as well as what kinds of computers are available.  Are the programming tools free?  Do they work on Windows and Mac?  Can you program the board easily?

I created a matrix of products that had to be cheaper than $20, but the magic price I wanted to hit was $5.  That's a tall order, but I think I have reached a decision...

Dev Board	Cost	Extra Costs / Time	Solderable?	Free Programming S/W	Free Dev Env	Windows?	OSX?	iOS?	Experience?	Comments	Sources
MSP430 Launchpad	$10	No	N	Y	Y	Y	Y	N	Some	Bringup takes time	TI
EZ430	$10/$24	No	N	Y	Y	Y	Y	N	Some	Not sure if alibaba pricing is legit	Alibaba.com
Cypress PSoC	$4	Headers	N	Y	Y	Y	N	N	No		Cyproess
Freescale FRDM-KL25Z	$15	Headers	N	Y	Y	Y	Y	N	Yes	Bringup takes time, but really powerful tools	Digikey
Arduino variants	$15-20	USB cable	N	Y	Y	Y	Y	N	Some	I don't like Arduino	Adafruit, Sparkfun
PICaxe custom	$3	PCB, Headers, USB-RS232	Y	Y	Y	Y	Y	Y	No	Coding is easy	Sparkfun, Aliexpress
PIC custom	?	PCB, Headers, USB-RS232	Y	?	Y	Y	Y	N	Some	Not sure about cheap programming options	Digikey, Aliexpress
C.H.I.P.	$8	Linux	N	Y	Y	N	N	N	No	Delivery date? We are also not teaching them about programming computers	getchip.com
Raspberry Pi Zero	$5	Linux	N	Y	Y	N	N	N	Little	Impossible to get at the moment. We aren't interested in teaching Linux here	Element14
Onion Omega	$19	Mini dock	N	Y	Y	Y	Y	N	No	I have one, and the available libraries are quite limited right now	onion.io

This matrix aims to evaluate each available platform in terms of cost, ease of use, my ability to help the kids out with them, as well as accessibility to programming tools and development environments.

I have decided to go with a custom solution, and am currently designing a simple PICAXE-based PCB that includes everything a kid would need on a stick that plugs into a USB board.  It wouldn't need a voltage regulator because I would just rely on the 5V, 500mA USB port present on all computers.  The USB-RS232 converter and PICAXE are both 5V compatible.  I am currently going to go with the 14M2, which I believe will give them a reasonable amount of I/O to play with.  The PCB will include all required components, as well as female stackable headers so that the board can be plugged into a standard breadboard for prototyping.

The other nice thing here (if it works!) is that this gives the kids an opportunity to learn soldering and assemble a mixture of through-hole and surface mount components.  I am going to go with the largest surface mount packages available for each component so that it's easier for them.

If this works out, this board could be a really useful platform for future classes at our school, or at our engineering fairs.  I'll open source everything so other schools can use it as well, not that there's really anything I'm doing here except assembling the BOM and designing a PCB...

If you have any suggestions about useful electronics topics for kids, or anything else at all, please post them!