How do you make the BADASS more badass?

Simple.  Add lasers.

Video of Vectorized Laser PCB Fabrication

The next generation BADASS board was too big to fit through the card laminator, so I figured I’d try my hand at Tom’s laser etching method.  By using the trace program included with CorelDraw I was able to make a vectorized path for the board.  One pass takes about 5 min at 50% speed.

PCB with Lasered Paint Resist and Fast Sponge Etching

TomG shows how he etches PCB boards using paint, a 25W laser cutter, Muratic Acid, 30% H2O2 and a sponge. Much frothing ensues.

The technique is a neat one, given the presence of a laser cutter, because it can take you from copper clad to etched board in a pretty quick amount of time.

One note, the Muratic Acid is actually from a pool supply store, not Home Depot. It is, of course, dangerous. Wear safety goggles, use gloves, use in a well ventilated area. (The acid smells like a punch to the nose, don’t inhale it)

My neverending quest for quick turnaround prototype PCBs

For years I have dreamed of a fast way to prototype PCB for projects I am designing.

20 years ago I was using rub on drafting tape and stencils – slow and spotty results.

I tried to modify a plotter to plot resist directly to a PCB – no luck.

Magic markers – I’m no artist.

5 years ago I hacked a laminate router by tapping into the stepper controllers and adding a better Z axis – It can rout boards ok, but takes some tweaking.  It only does fairly wide traces.  But its great at drilling holes!

2 years ago I tried the inkjet printing systems – lots of smeared wet ink and poor registration, not very effective.

I opened up a laser printer and tried to get a board to go through it – almost worked, but the fuser was to narrow to take the board.

Although I haven’t found a fast system yet, I get by with the PNP Blue material and a good laminator.  Although I am regularly disappointed when dust, not quite clean boards, minor wrinkles and other issues leave gaps in traces that need touching up.

Which brings us to the latest attempt:

Now that the maker space has a small laser cutter I am trying to find something I can coat a board with and either burn away or melt onto the board to act as an etch resist.

Early attempts with paint had moderate results – our laser cutters on only 25W so it didn’t burn it cleanly.  I have heard that using flat black paint and a more powerful laser works.

Paste wax and markup fluid weren’t dark enough for the laser to vaporize (thinking of trying black crayons)

The latest attempt uses laser printer toner (just like the PNP only skipping the printing and iron on steps.)

The problem is how to get an even coat on a board without it blowing around.  Static electricity has potential (just like what they do inside a laser printer) but I don’t like the idea of a 5KV power supply exposed and handling powered toner is an automatic mess.

So for the first attempt I mixed the toner with rubbing alcohol (30% water).

Messy stuff!

I painted it on with the tongue depressor but it seemed to coat evenly and took only a few minutes to dry:

It mixes well and paints on fairly easily, here are some sample prints I did at various power and speed settings.  I cleaned the board fairly aggressively with paper towel and rubbing alcohol.

None are quite clean enough to become PCBs but they are getting close.

Although the toner paint looked dry, it may still have had some water in it.  I plan on trying a batch with denatured alcohol (100% – no water) and see if it works better.



Updated progress

I have been trying a number of materials and methods to make my fast turn circuit boards.

I’ve decided that last toner is too messy and there are too many variables to create a repeatable process.  So now I’m trying various other masking materials:


Black and white spray paint – it works ok, but the ash left behind by the laser resists the etchant and leaves you with a poor etch.

I also tried tape:  Painters tape, electrical tape, clear and brown box tape.  The masking tape worked ok until the etch was slow and the tape started to dissolve.

I held a few of the boards up to the light so you can see how it etched:







One of the other members of the space found someone who had made the black paint work.  The process is to do 2 passes with the laser – the first burns off the paint, the second burns off the ash!  Then you wipe the board down with rubbing alcohol to clean off any residue.   Here is a set of 3 projects I lasered and etched at once:

This board turned out rather well, I had some trouble with the etchant taking for ever so lost some of the detail on the lettering, but the boards came out nicely.  I should get even better results on the next project.

In an attempt to speed the entire process up I tried to drill holes with the laser cutter from the back of the board:

   Not very good results!  After about 6 passes it still didn’t cut through thin PCB material and stunk and smoked the whole time!







So instead, I used the laser to cut wholes in a small piece of acrylic to use as drill guide:




This gives you a pattern to follow using a Dremel and the holes wind up in the right places and nicely lined up.  I drilled 2 holes in opposite corners of the board and used the leads from resistor to line up the template and board and hold them together while drilling.




This image shows the template attached to the board and about half the holes drilled.  This worked very nicely!  The only problems was small disks of acrylic getting stuck to the drill bit (you can see little craters on the left side of the board where these came from)  I had to clean the drill bit twice to drill the whole thing.  Either bigger holes or a different plastic might fix this.


This is first of the 3 boards I put together and it works just fine.  It is a level translator for the encoder you see in the holder.  The encoder will be attached to the drive motor in my electric car and feed back motor position to the controller.  The encoder is 5V and the controller wants a 15V signal.  The test bed uses a 15V power supply and LEDs on the 4 quaderature outputs.

Encoder test video

RN-42 Carrier Board


I got that RN-42 carrier board populated and working! Its ready for the GyroSkirt driver board, once I get that built.

There are a few errors on the board. TX and RX are swapped somewhere. Either on this board or on my USB to TTL-Serial board or in the RN-42 documentation. Also it seems the LEDs were meant to go to Vcc rather than ground. As a result my LED indication for connection status and RF traffic is inverted.

I can live with the errors as the actual data transmission works like a champ. To test the tranmission I hooked the carrier board up to a PC via a USB to TTL serial converter configured to operate at 3.3V.  The venerable Hyperterminal program was used to open the virtual com port on the PC. Then I downloaded Sena’s Bluetooth terminal program to my Android phone and used it to form a Bluetooth serial connection between my phone and the modem. The result: keys pressed on my phone’s keyboard appeared inside the Hyperterminal running on the PC and keys pressed on the PC keyboard appear inside the Sena Bluetooth terminal running on my phone. Bi-directional data flow at 115,200 baud.

Now that I have proven my wireless link works, I need to update the GyroSkirt/GryoBelt firmware to allow me to adjust the gain and the deadband over the Arduino’s serial port.  (In addition to actually making a driver board that has a spot for the modem.)

iTead Boards


I got my first batch of iTead Studio boards in!  iTead Studio is a  pcb printing shop that offers absurdly cheap prototype boards. The new boards look great. I’ll definitely use them again. It only took 2 1/2 weeks to get here. For the price its an awesome service.

The particular board shown is a carrier board for the RN-42 Bluetooth modem, which is only $15 from Sparkfun if you buy it in its surface mount form. For another $15 I now have 10 12! carrier boards that allow me to adapt the surface mount device to through hole technology as well as control infrequently utilized device specific features such as factory reset, BT Master mode, force 9600 baud and more. The more you know the cheaper electronics gets.

The carrier, populated with the modem, etc., is destined for the GyroSkirt. The idea is that I’ll be able to adjust the gain and deadband processing on the gyro sensor reading wirelessly from a program on my Android phone via the Bluetooth radio in my phone and one of these boards affixed to the GyroSkirt driver. The GyroSkirt will again be driven by an Arduino,  so I hope to leverage the Amarino library to speed my development time.