Jacdac - First Impressions

Jacdac is a modular prototyping/educational electronics system and protocol. This isn't Microsoft's first foray into this world. Some of you will I'm sure remember the .Net Gadgeteer system. 

In Jacdac, Microsoft have clearly learnt from their experiences of .Net Gadgeteer and produced an easy to use and more child friendly system, that can make use of the micro:bit, as well as other 'brains' using a selection of adaptors.

The Kit I was kindly given to play with is the Jacdac Starter Kit A, which is available from Amazon.com and elsewhere.

What's in the box?

The kit includes: 

• push buttons, 
• a rotary encoder, 
• a slider (pot), 
• a Neopixel (multicolor LED), 
• a bundle of Jacdac leads,
• a Jacdac micro:bit interface board,
• a Jacdac expander (if you need more connections)

Each module (even a key-switch) has a tiny microcontroller to handle communication, as well as indicator LEDs that show connection and communication is working. 

Getting Started

To get started, I followed this tutorial. Note that this kit only works with version 2 of the micro:bit (the one with the bumpy edge connector).

Follow each step carefully. I hadn't noticed that the slide switch on the micro:but adapter was in the wrong position, This needs to be set to the position labelled Jacdac.

Follow the tutorial, but in overview the steps are:

• Create a new Makecode project
• Install the Jacdac extension
• Download the new Makecode program onto your micro:bit
• Start plugging stuff in

Connectors

The Jacdac connectors are reversible (like USB-c) and great for kids -- at least compared to wrangling open the jaws of alligator clip leads. The kit helpfully supplies a selection of lengths of lead.

The leads can be connected to any of the ports on the micro:bit adapter and can be daisy-chained together, making the wiring simple and un-cluttered.

If everything is setup correctly, then when you connect one of the modules to the adaptor, the module will appear in the left-hand side of the Makecode editor window.

Here you can see that Makecode has become aware of the Slider and LED ring devices.

You don't yet have any blocks you can use, but if you click on the ADD BLOCKS button, blocks for using the devices connected will appear in the Modules category of blocks in Makecode.

The screen capture above show a program that sets the brightness of the LED ring depending on the position of the slider.

Conclusion

Overall, I really liked using this hardware. The quality is excellent and leverages the already popular micro:bit and Makecode nicely.

Pros

• Easy to use and child friendly
• High quality

Cons

• There is no concept of a circuit. It's modules plugged together. In extremis, you could just leave everything in the kit plugged together all the time. You are really just choosing which modules to use and which to exclude.
• A little on the pricey-side. But, looking at the design, I can see why it has to cost what it does. 

Who's it For

I think, that as an educational tool, this is an excellent system. Kids and educators will have a lot of fun with this.

It may also have some use during product design, as a way of producing a functional prototype very quickly, allowing usability to be assessed.

Who isn't it for

I don't see this being used by electronics hobbyists and makers. It's too expensive to be used in permanent installation of projects. Arduino and clones coupled with solderless breadboard migrated onto soldered prototyping board are a more realistic prospect.

Even though it's good for making prototypes from a user interface perspective, it of no real value in prototyping an electronic design. No electronic engineer is going to couple a microcontroller with every LED or push-button in an embedded system.  

New Book on ESP32 and MicroPython

I've had several requests, over the years, from readers of my books for me to write a book on the ESP32. Yes, there is lots of information out there on the Internet, but it's nice to have everything in one place, and also tried and tested on a variety of ESP32 boards. So, somewhat late to the party, I've finally written one.

I've based the book on MicroPython using Thonny. Thonny helps a lot with the ESP32. Not only is it a nice simple Python editor for those new to coding, but it also integrates with the esptools software, making it easy to flash your ESP32 board with the MicroPython firmware, without having to use the command line.

One of the biggest challenges in writing a book about ESP32 is the shear number of different ESP32 boards available.

This book is two-thirds Python programming, which applies to and ESP32 board and one third electronics using solderless breadboard. When it comes the electronics side of things, I provide breadboard layouts for two of the most popular ESP32 boards, the ESP32 Lite and the DevKit 1.

The paperback version of the book is printed in monochrome to keep the costs down, but a color ebook version is also available.

The book is available on Amazon.com.

In the future it will also be available from some of MonkMakes resellers and you can find details, here:

https://monkmakes.com/book_prog_esp32

All the example code is available on github here. https://github.com/simonmonk/prog_esp32

The books webpage is here: https://simonmonk.org/esp32

Review and use of: Katsu ZD-8915 Desoldering Station

Desoldering through-hole components with two or three legs, is pretty straightforward. Apply heat and some fresh solder to the underside and pull them out from the top. But when it comes to chips and modules with more pins, this approach doesn't work. 

Some people manage to master the use of the small pen-shaped 'solder-suckers'. The idea is that you melt the solder with an iron, and as soon as the solder is molten, place the solder-sucker over the joint and release the spring to suck up the solder. I've tried and failed to learn that skill.

Enter stage left, the desoldering station.

These use a hollow tip soldering iron and a vacuum pump, so that solder removal is a LOT easier than trying to use a pen-style solder-sucker.

I bought the model shown (Katsu ZD-8915 Desoldering Station) from Amazon, but they are also available on eBay and I'm sure elsewhere too. 

What you get

The package included:

• the control unit, that shows both the actual and set temperatures (up to 480C)
• de-soldering gun
• two spare tips of different hole sizes, giving you three tips in total (1.0, 1.2 and 1.5mm)
• a good solid stand for the desoldering gun
• spare wadding pads 
• three sizes of cleaning tools to poke out the solder from the hollow nozzle
• a factually correct but not very informative instruction book

Everything fitted together very well and actually felt like it was pretty good quality. The solder chamber containing the spring-loaded piston has to be occasionally emptied of solder and at first time is a bit confusing, as the wadding and metal disk just sit against the spring and fall out when you open up the chamber. Putting it back in, it took me a while to realise that the wadding pad goes in first, followed by the metal disk. After using the gun for a while I realised why there were spares of the wadding, as it gets spattered with solder.

Usage

I gave up on the instructions, which don't really explain how to use the gun and just watched a few YouTube videos.

Here's what I found to work for me, desoldering some DIL 7-segment LED modules for practice.

1. Push the back of the piston down to prime the spring
2. Apply heat to the solder joint until the solder melts (applying a bit of fresh solder and adjusting the temperature as required)
3. Pull the trigger to turn on the suction pump
4. Adjust the angle of the nozzle to get as good a fit over the solder joint as possible. I found that if you listened to the vacuum pump you could hear it work harder when you get a better seal.
5. Release the piston to make the final suck and you should see a splodge of solder fly up the see-through piston and embed itself in the cotton. Thats the fun bit!
6. Inspect the joint and repeat if necessary.
7. Get a flat-bladed screwdriver under the thing you are desoldering and gently lever it out - desoldering some more if it won't move.

Feeling very pleased with my new purchase, I turned it off and went and had some lunch. When I came to start again, it didn't seem to be sucking.

If I had read the instructions properly, I would have noticed the section warning me to ALWAYS ROD OUT THE NOZZLE BEFORE YOU TURN OFF THE HEAT!

I had bunged up the nozzle, just where it meets the cylinder. It then took about an hour of poking, changing the temperature, running in more solder and even pouring in liquid flux. Eventually I unblocked it by taking the front off the gun and poking the solder out by rodding it from the other side.

Obviously this was entirely my fault and I'd like to say I have learned my lesson, but its quite possible that I'll forget again. 

Verdict

Admittedly, this is the only desoldering tool that I've ever owned, so I don't have anything except the solder-sucking pens to compare it with, but I have to say I was very impressed.

This has already more than paid for itself because I had some expensive modules that I really needed to reclaim. Overall, the quality is pretty good and I didn't expect it to be as easy to use as it was.

If like me you have some high value components, or a PCB that can't easily be replaced then I can recommend this tool. It really does work. 

Just remember to clean it out before you turn it off.

How to Get Started in Electronics

I sometimes get asked how to get started in electronics and so at Maker Faire New York 2017 I gave a short talk on this topic. In particular I looked at how hobby electronics now almost inevitably starts with the use of a microcontroller board like the micro:bit or an Arduino or a single board computer like the Raspberry Pi. The question then arises, which do you pick?

Here are the slides from this presentation. You can also find a video of it here (although there was a lot of noise).

http://simonmonk.org

Conductive Paint Experiments

I have been experimenting with some Bare Conductive Paint that I bought from CPC after seeing it being used in screen printing at Lancaster's Highwire Lab. The paint is made by Bare Conductive in the UK.

The thirst thing I wanted to know was just how conductive is this stuff. So I cut myself a stencil with tracks of 1mm (40 mils) and 3mm (120 mils) and daubed paint onto the paper below.

It leaked a bit. I am really no good at art. However, the final tracks are good enough for a rough test.

Being somewhat impatient, I first tried measuring the resistance before the tracks were properly dry. The resistance was actually several hundred kΩ but falling as I watched. There is clearly a very high resistance until the paint is properly dry, which took perhaps 30 mins.

I left it for another hour to be sure and these are the results:

The 1mm (40 mils) track had a resistance of 780Ω / cm (2kΩ / inch)
The 3mm (120 mils) track had a resistance of 340Ω / cm (850Ω / inch)

So, its not quite like painting with wire at all, but that's not necessarily a bad thing as it means that you could very easily paint yourself some resistors. If you are using LEDs then just the tracks are going to provide more than enough current limiting resistance.

My next experiment was to see how well a surface mount 1206 LED would stick to the paint. So, I painted the arrangement shown below and popped the surface mount LED onto the wet paint with a pair of tweezers.

It actually sticks really well and shows no sign of falling off even when the paper is shaken vigorously and even curled up.

So the next step is to make an Origami frog and put a pair of SMT LEDs in series on its head to make it look demonic. The connections are made by painting back towards the frog's legs, where croc clips connected to a battery could be attached.

Conclusion.

This paint is an excellent product and very easy to paint with.

I will be trying out some proper stencilling with PCB layout's from EAGLE. It will be fun planning things out to account for the high resistance of the wire.

I also think there is probably some fun to be had with pre-painted Origami.