Peter Kaltenbach
Believe it or not the Arduino is about to turn 20 years old and Pump Studios is nearly 18. An entire generation of young engineers, including many at Pump, grew up with the tools to prototype control circuits regardless of specialization. At the same time we got low cost microcontrollers, there was an explosion of 3D printing and a vast increase in the accessibility of what were once expensive and exclusive prototyping tools. This transformed how we work, giving us tools to prototype and iterate faster and with higher fidelity. We’ve written about our mechanical prototyping process, and the tools/supplies we can’t live without. Let’s dive into what we do to integrate electronics into our early proof of concept prototypes and test fixtures.
First, let me say that none of this allows us to bypass proper electrical design. If anything, being more familiar with electronics gives us a better appreciation for our electrical engineers, and helps us collaborate more effectively.
(Testing hall effect switches and cycle testing a hinge for a current project.)
Building Basic Mockups
Using an LED to illuminate a light pipe or wiring a switch or a button into a prototype represent the most basic level of electrical integration, and it’s only a little more work to add a microcontroller and build more interactive mockups.
(Hinge cycle testing and the final design with custom hinge incorporated. – Trimble XR10)
(CW from top-left – Initial breadboard, first functional prototype, final PCB, and integrated design. – iFetch)
Over the years we’ve built many initial prototypes, proof-of-concept models, and test fixtures with a few special tools and components. Testing lightpipe performance and repeatedly cycling a hinge to evaluate long term durability, or in the case of both the iFetch and GO! Big cutter, building a fully functional first prototype. With a quick refresher on Ohms Law (V=IR), Kirchhoff’s Current Law, and the Power formula (P=IV), you can be up and running in no time. Some engineers, who grew up with Arduino and 3D printing, can come up with the wiring and sketch for an arduino completely on their own. For the rest of us, there is a wealth of example circuits and arduino code to build off of. Instructables, Hackaday, Sparkfun Tutorials, or Adafruit, and others, almost always have something close enough to get us started. Here are some of the critical tools and parts you need to get up and running with your own interactive prototypes.
Tools: (some of our favorite versions are linked below)
- A decent soldering iron – It should have the ability to regulate temperature and interchangeable tips. We use the Weller WE1010. The interchangeable standard tips allow us to also use the iron to install threaded inserts in plastic parts.
- Tweezers / Pliers – There are bound to be small parts to handle while soldering, crimping, etc. A range of holding tools is essential.
- Wire cutters, strippers, crimpers – At a minimum, buy a combo stripper, cutter, crimper. We prefer a dedicated tool for each. (I personally love self adjusting wire strippers).
- Power Sources – We use our benchtop power supply all the time (here’s a comparable one to what we use), but having a box of power bricks handy allows you to wire up a more portable prototype. We save these from old projects and products.
- A good Digital Multi-Meter (DMM) – You will need a DMM to measure voltage and current, check continuity, or measure a resistance, among other things. After years working with cheap knock-offs that didn’t work for us, we purchased a Fluke 87V Multimeter. We trust the measurements, it’s a true RMS meter (for measuring alternating signals), and our EE friends don’t make as much fun of us anymore.
- A magnifier or microscope – To work with small parts, old eyes like mine require help. We use a basic lighted magnifier with clips to help hold our work.
- Solder sucker – Undoing solder work can be as important as soldering parts together; Learn to love this tool!
(Soldering Iron – tips for plastic inserts – Solder sucker)
(Some of our go-to tools in the shop)
Parts: (some of our favorite versions are linked below)
- Wire – Various colors, sizes, gauges; stranded and unstranded; little jumper wires terminated with pins and sockets. You really can’t have too many different types.
- A resistor kit – These are the components you will use most often and need in the largest variety. Resistors allow you to properly power LEDs off of fixed power sources, and adjust the voltage within your circuit. If you can’t remember the color codes, we’ve built a handy calculator to help you keep track of them. https://pumpstudios.github.io/#/resistor
- Breadboard – A super quick way to test a circuit is to connect all the parts together with pieces of wire. This can quickly turn into a rats nest, but working with a breadboard helps tame the mess. Fritzing is a great tool to plan and test out your breadboard before you make any connections.
- WAGO Connectors – These lever lock connectors make terminating larger wires quick and easy. They are more reliable than twisting and taping wires, faster and less permanent than wire nuts and solder, and come in a range of configurations.
- LEDs – Old school, bulb type LEDs are the easiest to prototype with, but we also keep an assortment of LED strips (most are cuttable to length), Chip-on-Board components that we can connect with wires, and a range of surface mount connections for going small.
- Switches, Buttons and other inputs – A range of switches, buttons, potentiometers, power plugs and jacks will come in handy time and time again.
- Perfboard – Perfboard can bridge the gap between the breadboard and a custom PCB. With a perfboard, you can build a custom circuit on a somewhat standard footprint and solder appropriate length wires and components in place, providing a more robust, appropriately sized mockup.
- Arduino and compatible boards – Whether we are building a test fixture and want to measure and monitor outputs, drive a motor, or we simply want to simulate a basic user interface, we can generally accomplish what we need with an Arduino or Raspberry Pi. The standard form factors, wide range of shields available, and generally simple integrated development environments, make wiring and programming these devices accessible to your average mechanical engineer.
(CW from top left – Arduinos and shields, resistor kit, wire assortment, WAGO connectors)
Where to find parts
Two of our favorite go-to sources for hobby electronics and parts are Sparkfun and Adafruit. Both have tons of cool parts, development kits, shields, breakout boards, cables, etc. Both sites also have a wealth of knowledge, including tutorials, documentation, and an active community forum. Some of the products specifically made by both Sparkfun and Adafruit are also available on electronics specific sites like Mouser and Digikey, and we go to these outlets as well when we need a wider variety or higher quantities.
Going Deeper
If you get truly ambitious and want to make custom PCBs, stay tuned. We will cover custom PCBs in another installment.
