Springing Into Action with Spring Connectors

Hello there, and happy Thursday (or whatever day it is when you read this). Before we plunge into the fray with gusto and abandon (and aplomb, of course), let me start by noting that I’m a digital logic designer by trade. I find comfort in the certainty of logical 0 and 1 values. Contrariwise, I find the wibbly wobbly world of analog design to be somewhat disconcerting.

I’m happy enough with the interface between the analog realm and the digital domain in the form of analog-to-digital converters (ADCs) and their digital-to-analog converter (DAC) counterparts. It’s trying to wrap my brain around things like analog audio amplifier designs that make my eyes water and my noggin ache, which is why I try not to do it.

I’m reminded of the Welsh comedian and magician Tommy Cooper. One of his classic jokes was when he said, “I went to the doctor the other day. I told him that it hurts when I do this,” at which point he raised his right arm in the air, “and the doctor said, ‘Don’t do it then!’” I didn’t say it was a good joke, but the way Tommy told it, you had to laugh. However, we digress…

It's not uncommon for me to find myself teaching electronics to beginners, with ages ranging from 10 to 80+ years old. I typically start with a modern solderless breadboard, along with a light-emitting diode (LED), a current-limiting resistor, and a battery.

As an aside, some people say and write “a LED” while others say and write “an LED.” Which is the correct form? I’m sorry to have to tell you that both are correct. It all depends on how you say the word “LED” and how you hear it in your head (I didn’t intend for this sentence to rhyme, but I’ll take it).

If you say “LED” to rhyme with “bed," then “a LED” is the way to go. On the other hand, LED is an initialism, so it’s typically spoken as the individual letters in the form “L-E-D” (“ell-ee-dee”), in which case “an LED” is the way to do it. Most engineers, educators, and hobbyists spell it out, but it’s up to you. The main thing is to be consistent.

Now, although today’s solderless breadboards are great, they haven’t always been with us. Let’s perform a thought experiment. Suppose we were transported back in time to the 1950s, and we wanted to create a kit to teach electronics to young people. How would we set about doing this? More specifically, by what means would we connect the components together?

Ideally, we want to get the users up and running as quickly as possible. Also, given a choice, we don’t want to make them purchase a soldering iron and learn how to solder because that opens a whole other “can of worms.”

As we discussed in my Bodacious Wooden Breadboards column, one approach would be to use a piece of wood as a base. We could hammer copper nails into this platform, and then wrap our wires and component leads around these nails.

Could we perhaps come up with a slightly more sophisticated solution? The American inventor, athlete, magician, toy maker, and businessman Alfred Carlton Gilbert (1884–1961) certainly thought so. I think it’s fair to say that A.C. Gilbert was an all-rounder, if not an overachiever. For example, he financed his education by working as a magician while earning his degree in medicine, and he tied for gold in pole vaulting at the 1908 Summer Olympics in London.

In 1913, Alfred developed a construction toy called the Erector Set. Over time, the eponymous A.C. Gilbert Company added chemistry sets (with real chemicals), microscope sets, optics kits, physics kits, and atomic energy kits (with real radioactive materials).

In the 1950s, Alfred turned his attention to creating electronics kits, at which point he asked himself the same question we asked ourselves earlier — how best to connect the components. The requirement was for something that was cheap to manufacture and easy to use. His solution was innovative and ingenious.

Perforated hardboard (commonly known as pegboard) is hardboard that has been pre-drilled with evenly spaced holes. The pegboard is usually mounted on a wall, and its holes are typically used to accept pegs or hooks to support various items, like tools.

Alfred decided to use a piece of pegboard as the platform for his electronic kits. It’s hard to find pictures of this, but I tracked one down on Allan Jayne’s very interesting Cockamamie website, and Allan kindly gave me permission to reproduce it as shown below.

As we can see, each individual component — like resistors, capacitors, inductors (transformers), bulbs, and switches — was mounted on a small rectangular base with metal binding posts or terminals. These bases were made from hard, rigid, early plastic — phenol formaldehyde resin — often known by trade names like Bakelite or Paxolin.

The lower ends of the binding posts could be pushed into the holes in the pegboard. Now, this is the clever part because each kit came with a bunch of wires. There were “Jiffy Connectors” on the ends of the wires, so-named because they allowed kids to connect things “in a jiffy.” For the sake of interest, these connectors were patented by Arthur R. Jubenville in 1951. The illustration below is from his patent number 2,578,360.

A different form of connector using springs started to appear around the mid-1950s. Electronic kits using these spring terminals gained popularity in the late 1950s and early 1960s, especially with brands like Philips (Netherlands), Kosmos (Germany), and eventually in the U.S. with Science Fair kits sold by Radio Shack. These terminals became the de facto standard in educational electronics kits during the 1960s and 1970s, especially those with titles like "50-in-1," "150-in-1," etc.

I had one of these myself as a young lad. I wish I still had it now, but you know how these things go. Fortunately, my friend Joe Farr, who is based in the UK, collects this sort of thing. Joe kindly retrieved his Maxitronix Electronic Lab 130-in-1 from the depths of his workshop.

This is a classic educational electronics kit designed for beginners and young learners. Originally released around 1999, it’s now considered to be a vintage kit by many, often found on eBay for $30 to $80. Having said this, it’s still offered by educational suppliers in places like Australia/New Zealand (see the Teacher Superstore, for example).

The image below shows a close-up of a portion of the kit’s working surface. Observe the spring terminals. These provide a fast and easy way to make connections — just pull the top of the spring up and slip the end of the wire between two of the spring’s coils. Alternatively, as my friend Robin Hodson told me after reading this column: "I always bent the spring over to 'open its jaws'."

Also, observe the components like resistors (left) and capacitors (right). Unlike some kits, these are presented on top of the board so you can see what they look like. Their leads pass through the board and are attached to the bottom of the spring connectors under the board.

Just for giggles and grins, Joe offered to implement one of the projects and video the process to show what’s involved. The circuit we selected was a simple electronic siren. The page associated with this circuit in the project book accompanying the kit is shown below.

In addition to the circuit diagram (lower right) and the wiring diagram and sequence (upper right), there’s a description of the circuit (upper left), which includes some suggested modifications the user can make. I particularly like the fact that each project in the book has a “Notes” area for the user to capture their thoughts and comments for future use. The video below shows Joe implementing this circuit.

Unfortunately, as we see in the first video, the resulting buzzer sound was very faint (sad face). This wasn’t at all how we remembered these things from our youth. So, Joe created a second video, as seen below, in which he tracks down the problem and fixes it, resulting in a buzz we can all be proud of (happy face).

I love this stuff, but it’s not all about me (it should be, but it’s not). So, what do you think about all this? As always, I welcome your captivating comments, querulous questions, and sagacious suggestions, which you can present on Hackster's "Throwback Thursday" Discord channel. I look forward to seeing you there.