Actually building something

OK, here is a short primer on how the good guys build things in a serious hobbyist setting.

The development is done in 2 main stages. Breadboarding, and PCB construction (with presensitized board).

The reason why the breadboarding phase is because the Inet is great, but you can’t believe everything you read on it. What you want to do is look on the WWW for ideas and then breadboard them out. Once you get them reliable and you undersand their operation, you can use the technique in your personal projects.

How you do this on a budget (as it is the Great Recesion) is you get cheap Chinese breadboards on ebay for $5 a piece free shipping. Like here,

The latest and greatest idea, the only downside is that it takes longer than a week to get your stuff in but the price is right. You can also get broken out sensors and the like for dirt cheap (basically mounted great stuff the big guys use in smart phones and tablets). $5 per component is typical if you know where to go.

What you do is peal the backs off them an mount them to a 2’ x 2’ piece of plywood you can get at Home Depot. And you are ready to rock. next step is to find inexpensive, reliable power. A cool thing I’ve been playing with is tablet bricks because they are reliable, ubiquitous and a lot of them deliver a strong 1.0 Amp or 5VDC. Take your soldering iron, figure out the GND and the +5VDC and you have comfortable power on the 1 amp range. As always, PC switching power supplies are great too (just get a $5 DMM from Harbour Freight and sacrifice its leads so you have a constant digital power monitor…solder it on and wrap with electrical tape).

What you do is you mount everything on your plywood. You take your Fiscar’s drill (with $2 high-speed steel Harbour Freight drill bits) and you get a nice selection of dollar-store machine screws (and nuts) that you’ve “tackle-box-ized”. Shop the 99 Cent Store for these cheap tackle boxes and pick up about a dozen of them to keep your stuff in (resisters, relays, diods and voltage regulators). The trick with this is: mouser, but listen…you can get premade kits for around $70 but they have less than $5 worth of parts in them. What you want to do is put them together yourself and when you get low on standard parts (like certain resistor values) you just restock. All it takes is time to build these part kits, you put together generic BOM (bill of materials) for your tackle box kits so you have a nice selection of standard caps, diodes, transistors, MOSFETS, tiny relays, optoisolators, MCU’s like PIC’s and of cource exotics like NEO6M’s, preprogrammed MCU’s, and MCU6050’s.

Modern hacking requires attention to ESD (electrostatic discharge) because a lot of your stuff has sensitive digital logic in it. The fix is basic. Take a piece of silver solder and stick it in your ground power rail so about an inch of its hanging out. Every time you get up to walk around (where you accumulate chip-killing static) when you sit back down, just run your finger unconsciously across the solder tail. You are now grounded. Formal ESC with a wrist strap is ok too. But don’t wire yourself to ground btw as this can lead to you doing an impression of a light-emitting resistor (an old joke but a good one); think about it electrically.

OK, you BBB (in my case my BBBW), what you want to do is mount everything to your plywood so when the wife says playtime is over, you can just put it up. Also, claiming a second “junk drawer” in your kitchen is a life-saver specifically for all your little tools and tackle boxes.What you do is you get


To make standoffs you get a length of small-dimater ridged plastic tube and you cut pieces off yourself (getting them from Home Hardware is expensive) One of my little secrets.

To attach your BBB to the plywood, mark the holes with a fine Sharpy, load your bit in your Fiscars (at a slightly smaller diameter than the screw you will use) and just sink a hole half-way through. Then take handful of screws, a few standoffs and mount your BBB in a majestic location on your plywood. Takes like 30 seconds and its secured for weeks of tinkering.

Cut lengths of SOLID CORE insulated wire and strip the ends with a solid professional grade wire stripper (they are cheap and so worth it). Now you have all the wire you will ever need. First step with it is to wire your breadboards power rails. Connect all the blue (or GND) rails with insulated wire and what I do is run 3.3V on the left rail and 5V on the right rail (because I’m working a lot of times with both BBB and TTL), but if just working with 3.3V parts you can wire all your rails 3.3V to cut down on confusion.

You can do strain-relief by just knotting the power cord or whatever through a hole in your plywood. Keeps you from jerking sensitive wires and cables loose when moving around.


OK, what you do is you experiment on your breadboards connecting everything with wire. We all know how to do this. Get a complete working version of the circuit(s) on your breadboard set up. This will become your master reference for the next step: DIY PCB construction.

OK, throw out everything you think you’ve learned about DIY PCB construction and I’ll tell you how to do it the right way. lol jk.

OK what you do is you stick with SINGLE-SIDED presensitized board that you can get from ebay or MG Chemicals. Bear with me on this one.

What you need is a florescent source, so you might want to get the light little unit with metal stands full price. You’ll need a sheet of lexan its called (home depot), some printable transparancy sheets (and remember that laser and inkjet use different types, so get the right type for your printer…use inexpensive version and you tend to go through it so get a small stack). Ferric chloride solution is HAZMAT so obtain it locally by driving down to pick it up (as it costs $14 JUST for the additional hazmat on shipping). Also pick up a bottle of “developer” (its basically bleach concentrate). While you are running around pick up a box of disposable rubber gloves and some dollar-store foam brushes.

Forget gerber and eagle for now. What I want you to do is download OpenOffice (its free) and use the vector drawing program on it. Set your grid to 0.1" and snap on. Build up circles and lines of the appropriate line width. Its parametric so you get your little connection circles just right. You might have to eyeball a little with stuff like DB9’s so turn off snap and get it as close as you can (remember to turn snap back on). Remember to group things intelligently so you can duplicate things like DIP patterns and move them around like a pro.

Don’t get the bubbler. Again bear with on this one. This is how the pros do it. Get 2 glass casserole dishes for this and a small pyrex sauce pan.

What you do is you manually transfer your master reference working circuit you have breadboarded out to OpenDraw (its virtually identical to Adobe Illustrator, but its free). if you do it this way, its a total shortcut. Instead of wasting weeks, months on learning stuff you’ll never use, you just transcribe from the physical circuit to vector drawing program. And it works like the dickens. When you are ready to go to PCB load your transparency sheet and print. Cut it out with a pair of scissors.

Wipe clean your lexan (maybe even wash it with your dishes so its nice and transparent). Set up your light source and get your presensitized board. OK now STOP! I’ll give you years of experience right here. The actual transferring process is very TIME DEPENDANT. Follow exactly (like with a stopwatch) the time recommended by the presensitized board manufacturer. The reason why you use the full-price light unit and legs is because its also distance-dependant and radiance-dependant. You don’t do it right you will have residual mask on the board that is unreparable (you just throw out the ruined board and get a new piece of presensitized) under-exposed, or because transparency film isn’t perfectly opaque, the light will work its way around and through the black traces over-exposed.

I have years of commercial prototyping experience and this is the distillation of what I have discovered. Its prohibitively expensive for the hobbyist to just go through supplies like I used to to find these things out. (Elance: Rosewoodind)

OK, take the mask off the presensitized board (you can make smaller boards or get a large sheet and cut it down with a regular chop saw - abrasive blade, or band/jig saw) and quickly put the transparency fragment on it (THE RIGHT SIDE UPPPP its possible to transfer backward so think it through first. Measure twice, cut once kind of thing) and then DROP the lexan onto it so it holds it in place. Registration isn’t critically important here. But do it quickly/carefully all directly under the light source (turned off). Click you stopwatch and turn on the light source. AGAIN, exact timing according to manufacturer’s instruction down to about seconds to tens of seconds.

Throw one disposable glove on your left-hand (keep you right hand normal).

When the timer expires, turn off the florescent (its the UV from it that actually transfers, not the visible light) so you can look at the finished transfer under regular incandescent for a bit. You’ll notice you can see if it transferred right as it is a slightly different color than the unexposed traces.

Premix the developer (and you can do this in a lit room, its not as sensitive as photography, just move with a purpose) directly to one of the casserole dishes. Just add water and mix well with a foam brush. Concentration isn’t super-critical but measure. Temperature doesn’t matter. Then drop the transferred board into the solution. Grab it with your gloved left hand and take a foam brush and wipe it periodically and gently, carrying away the dissolving exposed photomask to the rest of the solution. How you know you are done is you will have bright copper-clad everywhere except for your traces (this is normal) which will be a kind of green-blue color. Visually inspect.

On your stove heat up your FC solution to very warm (this is warmer than lukewarm). Just touch your gloved left finger in periodically…get it just a touch hotter than hot bath water. Pour it carefully into one of your casserole dishes. Contrary to public opinion FC isn’t corrosive, but when warmed up (and I’ll tell you how to do this) it cuts through copper like a hot knife through butter. With that said, don’t get any on you as it is a real irritant. Don’t touch your eyes accidently, its like hot peppers on steriods.

Just drop your developed board into the ferric chloride solution. Heat is the key here. If its room-temperature you can wait all day for it to “etch”. If its very warm it only takes 10 - 15 minutes. Get a clean foam brush and manually wipe it across the surface carrying away the dissolving copper. You will know its done when the only copped left on it is under the photomask. remember, ZERO copper left on the paper-phenolic substrate…not even flecks. They will conduct.

When you have fully etched take the board to your sink and neutralize with regular tap water, maybe even washing it a bit with soap. This stops the etching processes cold. You now have a perfectly etched DIY PCB. You are done for now.

OK, a lot of you have wondered why I advocate the use of single-sided PCB. Let me justify my opinion.

When you work with DIY PCB’s enough you realize kinesthetically that you can’t geometrically wire up a real board with just one side (the reason why motherboards even have more than 2 “sides”…they laminate several layers together giving more “sides”). Especially with multiline busses. However you’ll find you can usually circle them around in such a way that you only need a few jumps to get finicky ones hooked up (like from one side of the board to another, or to pass a single line across a bus of lines).

What you do in your drawing program is you make a connector pad circle and you put “J#” next to it in copper. Then you do the other jumper the same way with the same jumper number (so you know at assembly time exactly which pads you are jumping). Then you take a piece of insulated, end-stripped wire and you run your jumpers on the top side of the board, snaking it around the components.

The problem with double-sided presensitized is that its pretty advanced to get the two sides to line up with the level of registration you need every time. The funny part about this is that the problem is the little whiff of air that slightly shifts your transparancy mask just a fraction of a millimeter when you drop the lexan on it, during exposure. Can you do it? Yes, of course, But its another skill to learn. To do this you just put circles with crosses through them and you line them up like crosshairs.


How do I complete my DIY PCB Board? Here are the steps: board cutting, drilling holes, mounting components, soldering, and cutting your leads.

Board cutting

You will probably want you board a certain size different than the presensitized blank. You can also etch multiple boards and sub-boards on the same blank. So you can case it, etc. etc. My opinion: chop saw with abrasive circular blade. Why? You can band saw it but you can’t get it perfectly straight. A cut on a chop saw takes about 5 seconds to line it up perfectly and cut a perfectly straight cut at 90 degrees. Can I use a Dremel tool? Honey, this is America, you can do whatever you want :smiley:

This approach is appropriate for enthusiast/serious hobbyist. Etch single-side bottom, then jumper the finicky ones on the top side. Anything else just wouldn’t be civilized.

Drilling Holes

As far as I’m concerned THE way to do it is with a Fiscars drill and precision bits (Harbour Freight - $8 for a set). You just palm the drill, insert the bit and hand tighten. You will find that your copper connector pads accept the precision bit perfectly Drill ALL the holes in the board in one operation. Tape or clamp the board to a sacrificial piece of plywood or just wood. For larger mounting holes just use your regular bits in the Fiscars.

Mounting components

Break out your tackle box or mouser package and lay out everything you need. You will need a scrap of paper with the resistor band colors on them. The rest of the components have their values on them. Don’t cut the leads yet, it’ll look like a porcupine when you are done but just insert the part and bend the leads outward to keep them on the board. One operation.


Use a nice hot soldering iron (just be careful).make quick contact with point with both lead and copper-clad and touch the solder to the point where they all meet. You’ll be an expert in about 2 minutes. I use a desoldering hand pump (spring driven) for mistakes.

Lead cutting.

Use a pair of “dikes”. This is one of the tools you don’t want to skimp on…an actual set of dikes with a spring. $2 at Harbour freight about the same size as your hand (not wire cutters…you’ll find out why).

This IS a set of dikes. Small, precise and spring-loaded.

Cut all the leads in one operations. You are done. You now have a perfect DIY board.

Addendum: Casing

Get plastic case. Mount with screws and nuts (maybe with standoffs). Cut large holes, sharpy marked, with dremel cutting wheel (clean up with barrel sander bit). Circular holes Fiscars/Bit. Remember that switches, LED’s, wire, all fit perfectly through drill holes. Strain-relieve by just a knot on the inside of the case. Casing also drastically cuts down on ESD, a real concern with today’s hobbyist electrons. My BBB cost me landed $80…I can’t afford a bricked component this expensive even localized burn-outs on my p8/9 so I case ASAP.


OK these standoffs ain’t bad and they are only $0.06 per.

Just don’t spend megabucks at Home Hardware is my point. Get a big ole bag of these. Important for BBB projects IMO. :slight_smile:

Example of simple PCB done in 5 minutes with external wired switch in OpenDraw (vector-based illustrator program). Print to transparancy and etch, drill, populate and solder. Put switch on insulated wire, and case in radio shack small ABS plastic case. Drill hole, remove nut on switch, put through hole, screw nut back on to afix and tighten.

Externally power by repurposing old 5VDC cell phone wall transformer, thread through case (strain relieve by knotting on inside) soldered direct to board.

Total design and documentation time: 10 minutes.

The Importance of Datasheets

One of the things I really learned doing this kind of stuff was the importance of datasheets. As far as I’m concerned, if a part doesn’t have a datasheet, I don’t use it. And I would go so far as to even say a datasheet in PDF format. They are important to use, to download to a specific directory on your computer, and important to actually use.

Datasheets can give you the dimensions of the part (like how they should be laid out on a PCB) as well as critical information as to their voltage rating, current carrying capabilities, as well as their function. Good datasheets also include any discrete networks that are important to operating the component well (you shouldn’t have to go hunting for related circuit designs that are needed to successfully use the component…though this is basically accepted culturally that you must).

For me datasheets are a must in that there is always some piece of information I need but can’t find. Datasheets help you avoid that long waiting time that it takes to go find the missing information and getting back to designing.

Make a directory called datasheets, maybe even in your downloads directory so that when you see a component you like or already have, you have every possible piece of information on it. This is key to any kind of serious hobbyist work IMO.

OK wanted to say something **** IMPORTANT ****

I’m a BIG believer in the open-source movement so where you can, please patronize Adafruit, BB, R-Pi and all of the really, really special people that are part of it. That you can get stuff cheap various places is still not an excuse to pick up a break-out board at Adafruit or whatever somewhere.

Just worried about your pocketbooks is all.