How to Prototype Without Using Printed Circuit Boards

Intro: How to Prototype Without Using Printed Circuit Boards

When I learned how to build ‘one-off’ projects thirty years ago, I used the "wire wrapping" technique. Back then, I had access to an electronics shop with a $100 wire wrapping gun, kynar wire and a supply of wire wrap IC sockets. At home, however, with limited resources and no wire wrap gun, I had to make do, so I developed a technique that uses perfboard, kynar wire and solder that results in a neat, quick to assemble and very dependable electronic board.

Assuming you've developed your design on a breadboard and made a schematic, the steps to build your circuit board are:

1.  Place your components on the circuit board
2.  Plan the wiring on the board using a Perfboard Layout Planning Sheet
3.  Connect the components using Kynar wire

STEP 1: What You'll Need

In addition to the perfboard and a soldering iron, you'll need some fairly common tools and supplies:

Kynar wire: This is an insulated 30-gauge single strand wire. It's a rather thin wire which is useful for low current and low voltage digital circuit connections. I use three colors: Blue for Ground, Red for +, and Orange or Yellow for all the other connections. This wire is also "pre-tinned" so it takes solder very easily.

Wire Cutter, Wire Stripper and Needlenose Pliers: I have a special stripper that is permanently set to strip the Kynar wire. It may take a few tries getting the correct setting, since you don't want the stripper so tight as to nick the wire itself, or so loose that it just slides off of the insulation. A good pair of needlenose pliers are required to hold short lengths of wire when stripping off an end.

0.8mm Rosin Core Solder and Solder Paste: The paste (you can use a rosin pen as an alternative) is useful if you want to flow solder over and join a socket pin, a wire and copper pad quickly and without too much heat.

Tweezers: I have a surgeon's tweezer (the kind you got in biology class in school when you had to dissect that frog) that I use for looping wire ends and a sharper, more precise steel electronics tweezer for holding wire during soldering.

“Helping Hands”: This inexpensive reconfigurable alligator-clip holding device is an indispensable tool when using this prototyping technique.

Reading Glasses / Magnifying Glass / Manual Dexterity: Depending on your age, reading glasses may be of assistance. If you don't have steady hands, you may have difficulty managing some of the smaller, more finicky aspects of this technique. If that's the case, printed circuit boards are probably a better choice.

STEP 2: Place Your Components on the Circuit Board

In this example, I'm using a 7 x 9 cm perforated circuit board from Seeed Studio; this board has numbers and letters on the top side indicating the columns and rows, and round copper solder pads around each hole on the back side. The letters and numbers come in handy when planning the wiring (Step Two), but any perfboard can be used as long as it has copper pads for soldering. I have also used stripboard with this technique, but it requires that you to cut the copper strips and letting the kynar wire carry the signals, defeating the purpose of the strips.

You should place your components to minimize the length of wire required. This will reduce the possibility of stray capacitance wreaking havoc with your circuit. To further deter parasitic voltages, place one .01 uf capacitor across the + and Ground beside each integrated circuit that you use in your design.

To hold the components in place, you can bend the pins outward slightly on the back side, or you can use a dab of quick setting glue on the front of the board. If you use glue, don't use it on the wire pins or you may not be able to achieve a secure and dependable electrical connection. Eventually you will be soldering each component onto the board, you so don't need a lot of glue, just enough to keep the component from falling off of the board during assembly.

Note: Use IC sockets whenever possible. Try to avoid soldering integrated circuits onto your board, and if you use sockets, make sure they are empty during assembly. Some ICs use CMOS technology that are very sensitive to static electricity charges.

STEP 3: Make Your Wiring Plan

This stage is crucial. The time and care you take in this step may be the difference between a circuit that works and one that doesn't.

I've developed a wiring planning sheet (attached) that is a modification of the Meccano stripboard planning sheet. Feel free to share it with your friends.

The planning sheet will represent the back of the perfboard, where you will do all your wiring. Because it shows the back side, it is a backwards mirror-image of the front of the board. This is where the numbers and letters are helpful on the front of the board, to help you navigate this mirror-image world of the circuit back side.

Correspondingly, there are numbers and letters on the planning sheet, arranged inverse to the order on the front of the perfboard. Use the following steps to create an error-free wiring plan:

1.  Use a pencil to fill in the holes for socket pins and component wires. Check and re-check the placement. I find that once I have reliably established one component on the board, I can count across or down a certain number of holes to locate the next component.

2.  For IC sockets, name the IC and number the pins. Remember that pin numbering on the back side needs to be done in a mirror-image compared to front side pin order.

3.  Refer to your circuit schematic: Draw lines to connect the + and Ground rails to the components. On my perfboard, there are large pads along the right and left sides, and I use these for + and Ground.

4.  Refer to your circuit schematic: Draw wires for all the other connections. Try to avoid having more than two wires connect to a pin or a component; there is a limited amount of space on a pin for wire connections.

STEP 4: Connect the Components Using Kynar Wire...

This step is actually repeated for as many times as you have wires to connect. The process is straightforward:

1.  Strip the end of the wire about 2mm
2.  Measure the length of wire required
3.  Strip the other end
4.  Loop the bare wire ends
5.  Place the loops around the pins or component wires
6.  Crimp them so that they provide a temporary hold
7.  Solder the connections to make them permanent

It's time to turn on your soldering iron and clear your workbench.

Affix your circuit board, back side up, to the helping hands tool.

In the next steps we will deal with each step in detail.

STEP 5: Measure and Cut the Wire

Use the planning sheet to determine what connection to make.

Before cutting the wire, strip 2mm of insulation from the end.

Line up the wire on the perfboard so that it extends from one connection contact to the other to get a sense of how much wire you'll need.

Add about 5mm extra length, cut the wire and strip off 2mm of insulation.

You now have a wire with 2mm stripped off both ends.

STEP 6: Make Loops Around the Wire Ends

Using the end of a pair of tweezers, make loops over the bare ends of the wire and fit them over the pins or component wires. If you have other wires already soldered in place, you may find it helpful to feed the wires underneath the existing wires; this method will help you hold the new wires in place before you solder them.

STEP 7: Crimp the Loops Over the Pins, Then Solder Them

Use tweezers to crimp the loops tightly around the pins. The connection only needs to last as long as it takes to apply the solder.

If more than one wire is to be connected to a pin, you have a choice:

a) Do the same as above, crimping a second loop to the same pin and then solder both wires to the pin.

b) Solder the first wire to the pin. For the second wire, don't loop it, keep it straight. To connect it to the already soldered pin, dip the end of this wire in some rosin paste (to clean it and encourage the solder to bind to it). Re-heat the solder on the pin and push the wire onto the molten solder.

If you use soldering paste, avoid using too much. The paste residue can carry current which, unless removed, can wreak havoc on your circuit. You can use a toothbrush with isopropyl alcohol to remove excess flux.

STEP 8: Testing Your Work

Repeat steps 5 - 7 until all your connections are made. As you proceed, you may find it useful to complete one component (such as an integrated circuit) and then start on another. This enables you to test each component as you build it.

My blog has examples of other projects that use this technique.

Comments

[Phil Young]

Thanks Michael. This is very helpful.

[a9189000]

hi
can i help me how to drew this circuit in PCB ??

[xepherys]

Ah wire wrapping! I actually found this page because I'm using perfboard for probably the first time ever. Lots of experience with ordering small batch custom PCBs for projects, but I was considering what the best way to wire a circuit on perfboard would be. This makes absolute sense, I've just never done it. But I recall quite a bit of this the first time I dissected my Atari 800.

[xepherys]

Also, good call regarding the side pads for power and ground. I had considered that myself, and feel better knowing someone with more experience on perfboard does this as well. Makes a lot of sense.

[Kike_GL]

I do not understand why abandoning the old technique of winding wires is faster and easier circuit to build or modify. The connections are safer and the components can be rejected when they are removed.

The wire-wrapping tool is still available in electronics stores or Amazon and now the wires have silicone linings.

Greetings from an old electronic man.

[firesign]

Thanks for your comment. My technique isn't any faster or easier, and you're correct that the wire wrap technique has many advantages over mine. This instructable came out of my wire-wrapping experience (in the mid-80's) where I was building stuff in a shop that had a nice wire wrapping 'gun', and we built boards to plug into racks that had lots of space between boards. My technique evolved because I didn't have a wire wrap gun, nor was I willing to pay the premium for wire wrap sockets, and I wanted my circuits to fit in a much smaller space. Thanks for the link to the wire wrap tool on Amazon. Can you also elaborate on wires with silicone linings? How are these wires different from the Kynar ones?

[xepherys]

The silicon jacket wire is both a blessing and a curse, though I use it almost exclusively myself. The initial benefit is flexibility, which PVDF also offers, but the silicone is incredibly flexible. I started using it for wiring on 3D printers due to the constant and sometimes rapid movement of the carriage and a desire to minimize physical resistance and maximize lifespan of the wiring harnesses. It is also flame resistant (like PVDF), but has a higher max temp rating (180C vs 120C). Of course most project boards don't need that level of flexibility or heat resistance, but if you only have room/desire/money for one type of wire, silicon jacket is incredibly usable in almost any situation.

The one down side is that the extreme flexibility of the jacket can also lead to kinks where the wire core bends and the jacket is slightly "pulled" in toward the center for very short (jumper) wires. I find that the best resolution is to just lay the jumper down on the flat work surface and roll it back and forth a few times under your finger.

[dronekop]

Hi thanks in advance If I know where the wires go on a small andriou board which I messed up while learning Can I simply just resolDer the wires on a new replacement board or must it be programmed again Forgive my ignorance I'm a pensioner trying to learn

[dronekop]

Really appreciate your advise and lessons as a pensioner I find it very useful

[SRPFHELL]

What would cause a empty circuit board hole be smoking?

[throbscottle]

Really good instructable. Very nice construction.

I actually found this because I was looking to see if there's a "standard" way to use perf-board.

Couple of things spring to mind.

I've been using wire taken out of solid core cat5 cable for this. It's an incredibly bad idea, the insulation shrinks back when soldered and melts through when the wire gets hot! So if anyone was thinking of using it, don't!

I've used Vero-wire for this in the past, which works really well. Much easier than having to strip individual wires. You get a special wiring pen which you thread the wire through.

I think the Vero wire is the same as solderable magnet wire, and I'm about to try building a prototype on perf-board using some from an old signal tranformer. Wish me luck!

[jezbo]

Thanks for the printouts big help.

[NunoL1]

Broken link http://nscadesign.ca/mleblanc/

[firesign]

Thank you very much for letting me know... I've repaired the link.

[robobot3112]

Cool, Needed a way of making my own boards without any etching, Thanks for the

ible!

[rusty0101]

Wanted to say thanks. I've been working on and off with perf boards for some time, as well as boards that are analogs for breadboards, and the perfboards (similar to those described here) have been giving me headaches, as I'm "sure" there is a better way to build with them than what I've been doing. This looks like it. I'll have to start looking for the wire, and I may use forceps rather than tweezers, but I have pretty much everything else already, so it's worth a go I think. So, Thank you.

[firesign]

You're welcome. You can buy the wire at dx.com or ebay.

[MaxF1]

Useful stuff, thanks. Your list states 8mm solder, should read 0.8mm!

[firesign]

oops!

[kgwolf]

Great writeup! I'm just getting started with building circuits, and I found this very helpful. However, the planning sheet is a bit confusing. The numbers and letters on the sheet correspond to the letters and numbers on the front of the board, so rather than just being able to fill in the holes that correspond to your setup, you have to count backward from opposite end on the sheet. It would be more helpful if the numbers were inverted on the sheet, so you could just look at where your parts are plugged in, and fill in the corresponding inverted holes. Your description was very clear and useful though.