A simple to build, 3D-Print based set of circuit building blocks you can make for beginners.

Nearly everyone in electronics, as a hobby or trade, started their journey with some form of educational kit. From boards full of holes with spring terminals where components are held together, to consoles with fixed components and movable wires, to snap-together circuits using plastic mouldings and press studs, they are myriad and varied. However, few are home-made, yet many makers will know an emerging maker and have the skills to help.

We saw an interesting concept on social media a while ago. Circuit Tiles by J. C. Barros are a set of wooden blocks with nails in them. J.C. has used wire crimps (ferrules) to connect different components to the nails, and drawn on the wooden block for a label and connections. They are a great concept, and very home-made. We really liked the design, enough that we wanted to make our own. However, we always view these things in multiple situations. If you need something that can survive, say, being handled by a class full of kids over and over, then you might need something more enclosed. That, and the fact that we have the means to do so and like the overall outcome for its own sake.

Having wires on the surface exposes them to being caught on things and damaged. That would be especially true when the tiles are packed away in a box. Additionally, having the wiring underneath helps keep sharp solder points or component connections away from fingers and hands. That is not to say the original tiles are not good: In fact, they're quite tidy, very well thought out, and we liked them a lot. We just wanted something more rugged, that had labelling built in rather than hand-drawn (some of the office handwriting and hand drawing skills are so bad it's an oxymoron), and that is a bit more durable than wood which gets dirty quickly but is hard to clean.

If everything on the surface of a piece of wood with nails for connections is ok for your situation, such as building a set for your own kids, then the original design is great. Regardless of what you need, we encourage you to check out the link at the end to see the original creator's work and give them some views.

OUR IDEAS

Our project based on J.C. Barros' original utilises 3D printing because such a large percentage of makers now own one. You could still build some of these designs in wood if you prefer and have the skills, and we will describe how at the end. We have three versions of each set that we will demonstrate. The first uses binding posts for the connections and can be connected by bare-ended wire, banana plug leads, or crocodile clip leads. The second uses banana sockets and can be connected with banana plug leads only. The third uses M3 nuts and bolts in a configuration that allows connections with crocodile clip leads. There are advantages and disadvantages to all three.

The binding posts are the most versatile but the most expensive. They also have the binding posts sticking up which make them look more cluttered and obscure the view of the component and label to a degree. The banana sockets are the cleanest and least likely to snag on anything, but can only be used with banana plug leads. The nut and bolt version is the cheapest to make but can only be used with crocodile clip leads. So, how you use them may determine which one is best for you.

The next logical step after figuring out how we wanted to make connections was to make a list of what we wanted. The biggest challenge is resistors and capacitors: How many values do we use? Given that most learning circuits are very general, it made sense for us to simply choose the 10x values, and a few in between. That's 10Ω, 100Ω, 1kΩ, etc, and a few in the middle. For capacitors, it was much the same. However, we realised that it was better to make the platform generalised, with a space for a printed label. If we made this the right size, it would work with 12mm label machine tape, or 65up (65 to a sheet) 38 x 21mm labels cut in half horizontally and vertically. These are about the smallest address label size available from most label manufacturers like Avery.

Then we needed a few different sorts of switches, some common semiconductors like diodes and transistors, and a few basic ICs, too. Of course, we had to have some variable resistors, but we decided to add some instruments, too. A voltmeter and ammeter were logical, and we went with the same moving coil analog concept that the original Circuit Tiles used, because they are passive and do not need external power. Speaking of power, we need that too, and some LEDs, light globes, motors, pushbuttons, and relays to go with it. We wrote all of this down on paper, thought about it a while, and added and subtracted until we were happy. Then, we set about designing the 3D prints.

THE PARTS WE USED

While things like resistors and capacitors are pretty standard, and we have a range of hole spacings for those anyway, the situation is not quite the same with other components like switches. In some cases, like the toggle switches, there is something of an industry standard for them. However, you might not have the same ones that we used to set the sizing. For this reason, we have included blank plates in the file download. You can either import these into a 3D modelling program and add holes of your required diameter, or print them as-is and drill holes. This would not be as neat and would lack the surrounding walls around the perimeter of the holes, but it is achievable if you have never 3D modelled before.

However, to help things along, here is a list of the parts we used from Jaycar, and the equivalents from Altronics if we can find them and are certain they're the same. The reason we generally use Jaycar parts even though Jaycar and Altronics are both advertisers with and supporters of DIYODE, is purely logistical: there is a Jaycar store fifteen minutes away from the office and three minutes from one staff member's house, while the nearest Altronics store is in Sydney, over an hour's drive away door to door. That's just the nature of where we are. If we were near neither store and were instead ordering online rather than shopping in store, we would use both suppliers regularly.

The table does not include any resistors, diodes, transistors, ICs, or potentiometers, because these are standard sizes. The resistor, capacitor, and diode plates will take different sizes of component, while the potentiometers used are 16mm types.

Parts Required:	Jaycar
4AA Battery Box	PH9200
Red Binding Posts	PT0453
Black Binding Posts	PT0454
Green Binding Posts	PT0455
Red Banana Sockets	PS0406
Black Banana Sockets	PS0408
Green Banana Sockets	-
Red Banana Plugs, Standard	PP0400
Black Banana Plugs, Standard	PP0402
Green Banana Plugs, Standard	-
Red Banana Plugs, Piggyback	PP0390
Black Banana Plugs, Piggyback	PP0391
Green Banana Plugs, Piggyback	PP0381
Red Hookup Wire	WH3010
Black Hookup Wire	WH3011
Green Hookup Wire	WH3015
M3 Nuts	HP0426
M3 Bolts	HP1350
Solder Tag Eyelets	ST0335
Toggle Switch	SP0710
Pushbutton Switch	SY4058
6V Relay	SL2650
6.3V Lilliput Edison Screw (LES) Globes	SL2622
Green LES Bezel	SL2620
Red LES Bezel	RD3485
Light Dependent Resistor	-
Negative Temperature Coefficient Resistor	-

THE 3D PRINTS

All 3D prints share the same feature: They are a box to contain and protect the wiring, and a lid which contains the labels, symbols, and holes for the components and attachments. The lids are printed upside down, both to eliminate the need for supports for the lid recess, and to ensure a smoother facing surface. Holes for the connections are on the same centres for the two- and three-most versions, although things like ICs and the relay are a different story. The space for the label is surrounded by an indented border, but is not itself recessed - this would be too big a gap for most printers to bridge.

The vast majority of these models are printed face-down. This ensures a clean, smooth surface for the face, but only if your 3D printer is adjusted appropriately. If the bed is too close to the nozzle on the first layer, the filament over-extrudes and thus the fine detail is lost, as in this one we printed as a test run.

The ideal nozzle spacing is only just close enough to maintain adhesion. The challenge is that most printers are set up to be a bit closer. This might normally only result in minor elephant's footing, barely a problem in formal prints, but that is a problem in this case. You could print face-up, too, but that needs support for the edge in the binding post and banana socket versions, and almost the whole lid in the M3 versions. Also, some printers are not as neat on the top layer as they are on the bottom layer, like this one:

FIXED RESISTORS AND CAPACITORS

We designed our base plate so that when these are made, the value can be chosen and the label added adhesively. Only the circuit symbol is part of the 3D print, as well as a recess for the label. The holes for the legs of both the resistors and the capacitors are a line of many more holes than needed, so that any component lead spacing can be used. To keep things neat, the centre is marked.

VARIABLE RESISTORS

Variable resistors constitute anything that is not fixed, and many people forget that this includes light-dependent resistors and temperature-dependent resistors. So, we have a baseplate for each of a potentiometer wired as a variable resistor, a potentiometer with all three terminals accessible, an LDR, and a Negative Temperature Coefficient resistor, with symbols to match. The potentiometer-based plates have a hole for the shaft of a 16mm potentiometer, while the LDR and NTC plates have two inline rows of holes for the most common lead spacing in each case.

VOLTAGE DIVIDER

We also decided to include a pre-built voltage divider in the collection. This can be made as you wish, with equal or different valued resistors. Each resistor has a symbol included and space for a label. It has five resistors in series.

MOTOR

The motor is a bit harder, because nearly every motor on the market is a different size. We have designed ours for the 5V DC geared motors commonly used with Arduino, because these are more standardised and also safer for kids to use if something is attached. The slower speed helps make glueing or Blu-Tacking onto the shaft a more realistic prospect than on a faster motor. The motor sits in the bracket and will need glueing in.

SWITCHES

We have baseplates for SPST and SPDT toggles, and SPST pushbuttons. The SPST and SPDT are the same switch, just wired accordingly. The main difference, really, is the symbol, and the ease of use if the unused terminal is not included on the SPST version.

POWER

We have chosen 6V to run the circuit, and so four AA batteries will work well. The plate has space for a 4AA side-by-side battery pack, and two binding posts. However, because different brands of pack have different screw sizes and spacings, and some have none, we rely on glue to hold this on. You could also use a switched battery box if you want the extra safety of being able to isolate power and not have a situation where the binding posts may have wires attached and be dangling around unconnected at the other end.

LIGHTS

We have two options for lights: LEDs, and lilliput globes in bezels. The LED version has the resistor included in its symbol, because soldering it into the circuit prevents destroying the LED by mistake or forgetfulness, and eliminates the need for the beginner to figure out which resistor is needed. That is particularly important if you chose limited resistor values which may not include the right one for the LEDs. The light globes are 6.3V as-is, so they are fine on the four AA batteries.

RELAY

There are few 6V relays on the retail market, so we went with the most accessible one. You may need to file the case or modify the model yourself for a different one. It is glued into the case.

SEMICONDUCTORS

Diodes and transistors follow a similar pattern to the resistors and capacitors: Multiple holes are included to cope with different component spacing. We anticipate using 1N4004s and 1N4148/1N914s for the diodes, and BC337s and BC327s for the NPN and PNP transistors. These transistors cope with at least 500mA continuous current, which is good for the motor or multiple light globes. You could use other transistors as well, as long as they are in the TO92 package. You could possibly drill out the holes a little to use the TO126 package for, say, a BD139 and BD140.

We also have an 8-pin IC version. We realise this is getting ambitious for a beginner circuit, but an LM311comparator would function with the LDR, potentiometer, and transistor output driving a globe. Likewise, the NE555 is not completely out of reach, either.

ASSEMBLY - BINDING POST

The binding posts assemble with their own nut, followed by a solder tab eyelet and another nut. That means all can be fitted and secured before any soldering is done. Then, the components can be added as relevant, either with legs through the panel or by mounting in the case of switches and potentiometers. Finally, hookup wire can be used to connect the relevant items.

ASSEMBLY - BANANA SOCKET

The banana sockets are similar to the binding posts, except that they are more flush. They also have a plastic retainer underneath that the nut seats against, with the solder tab eyelet in between without its own retaining nut. Because of the metal-on-plastic interface, it is better to mount the components and solder the wiring first, so the tab cools before it goes anywhere near plastic.

ASSEMBLY - NUT AND BOLT

The nut and bolt version is the hardest to assemble. This involves heat-setting a nut in the case first, followed by the application of the bolt, a solder tab eyelet, and another nut. The recess on the underside of the nut and bolt version lids features a post with a hexagonal recess in it that is slightly smaller than an M3 nut. Use a soldering iron to heat and inset these.

Then, add an M3 x 20mm bolt from the upper side. Spin it until there is enough through for the eyelet and second nut.

Then, add the eyelet and a second nut. To tighten this, it is advisable to use a screwdriver to hold the bolt from rotating, and tighten the nut against the heat-set one with the eyelet between them. Then, the wiring can proceed as long as the dwell time on the solder tab is not high.

WIRING

There are several choices for wiring in this project. Pre-made crocodile clip leads are suitable for the M3 and sometimes the binding post version. You can clip them into the top if the jaws open wide enough, or around the threaded post if the top screws up far enough.

The binding posts will also take banana plugs, and the banana socket version will take these only: there is no way to use crocodile clips on them, unless you happen to find a different design to the usual. You have the option of using single plugs, or piggyback plugs so that more complex circuits can be designed.

The M3 version uses crocodile clips only, but you may also like to twist bare wires around the screws. This is ok for short-term home use, but the ends of the wires will not

take too long to become tangled, messy, and broken, not to mention corroded. On that note, bare wires can be used for the binding posts, too. You can pass them through the hole in the post and screw the top back down, or use forked terminals crimped onto wires. You could solder the ends of the wires for longevity if using binding posts, and go down that road.

MAKING WIRES

There is a variety of banana plugs on the market, as well as some premade options. Premades are more expensive but convenient. Packs of crocodile clip leads or banana plug leads are easy enough to buy and work well. However, if you want to make your own, you can save money and also increase suitability.

We prefer to have red and black wires for power and polarised connections, and another colour for non-polarised and intermediate connections. For the cheapest banana plugs, however, there is only the choice of red or black. Thankfully, that's nothing a coat of automotive plastic primer and a coat of green spray paint cannot fix! If you do use piggyback plugs, these are more expensive but generally are available in a range of colours.

It's harder for crocodile clips. The soft vinyl covers do not take paint, even with primer. For these, we are limited to red and black. For other colours, they will need to either be sourced online, or used without the covers. They still work well without covers but this has a minor risk of surface lacerations to the fingers. If you do go down this road, it's a lot cheaper than buying the pre-made leads.

As mentioned, using forked terminals with the binding posts is an option. We removed the PVC bits at the end, because these are always red for this smaller wire size. Heat shrink does the job of keeping fingers safe from stray wire ends, and glue-lined heat shrink would make a very secure connection, too.

If you really want to keep costs down, bare wires are ok too. However, unless twisting them around the M3 version, we suggest twisting the ends and soldering them to make sure they can go through the binding post holes again and again.

Finally, the size of wire you choose is also somewhat optional. We found that for many suppliers, there are some relatively thick choices, and some thick choices, and not much in the middle. Altronics has a good range of sizes here. However, what we wanted but could not find was silicone wire. If you can source some in a good size, it is much more durable and handleable than PVC coated wire. In all cases, be aware that sometimes, a wire looks to be a good size but actually has very little copper inside, instead having a thick plastic sheath.

BUILDING AND USING A SET

Having read this far, you will have a pretty good idea of how everything goes together. What needs to be decided is what connection system and wiring type suits you, your end, use, and your budget. Then, you need to decide what components to use and what values for things like resistors and capacitors.

Once that is done you can download the files required and bring them into your chosen slicer. Remember to print them face down for the lids.

There are two sizes of boxes to print. The resistors, capacitors, lights, switches, relay, diodes, and transistors are all based on a 50 x 50mm square. One box file suits all of them. The remainder, being the battery, IC block, and panel metres, take a 100 x 100mm box.

So, once you have decided how many of each face plate you are making, fit as many as possible on your printer. We found it easier to print faces in one print, and boxes in another. If you want very basic circuits, like battery-light-switch, this will not take long.

If you want to have the whole E24 resistor series and every value of capacitor, you'll be printing for a while!

Once printed, all you need to do is mount the attachments as outlined above, fit your components, and solder using any hookup wire - nothing will be seen from outside anyway.

How you employ these blocks is up to you. You could find simple circuits online or even create your own structured learning series for your kids or for a class. However, we have a few basic circuits that you can download as well, ranging from a simple battery, light, and switch, to an NE555-based light-activated switch.