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Ah, the bliss of populating THT circuits on manufactured PCBs… just follow the silk-screen and you’ll be fine. in contrast, the fun-factor of soldering perfboard is way lower. your eyes move from your plan (if you happen to have one) to the board and back, your brain is trying to mirror the layout while you flip the board back and forth all the time. while this might be OK for a single board, what if you have to assemble two? or three? or even more?

for my latest project, i have to populate 10 identical boards. why not have a PCB manufactured, you may ask. well for different reasons: first, it’s too expensive, because the boards are rather large. secondly, i have to get rid of a larger amount of perfboard. third, the layout is not complicated enough to justify a manufactured board.

anyway, in a former similar project, i used a CNC mill to plot the traces onto the board:

plotted pcbs

this was extremely helpful, but setting up the files and the mill took some time. now in the recent project, i experimented with toner transfer to not only put the layout on a perfboard but also a silkscreen on the top. the result is a board that is as easy and flawlessly to assemble as your first beginners electronics kit back in the day and it is neither complicated nor time comsuming:

bothsides

although this is supposed to be some kind of tutorial, i’m not going into details about the toner transfer process, because this is described in other tutorials.
the base of the process is to have a board layout. i normally create layouts even for my perfboard circuits in Cadsoft Eagle. if you set the grid to 0.1 inch and stick to 90 degree angles, you’ll be fine. after that, you usually print out the layout and use it as a template while soldering.
but soldering is still pain in the rear. so why not spend a few minutes with a laser printer, an iron and a sip of water to create a professional perfboard™?

first, i CNC’ed out the boards, because they have a rather odd shape.

milling

if you have no access to a CNC, just use a hacksaw, jigsaw, scroll saw, chainsaw, dynamite, whatever. if you cut your boards manually, you maybe want to cut it after the silkscreening to have an outline for cutting.

for the toner transfer, laserprint the layout onto a piece of catalog or anything else that does not absorb the toner. you may want to stick to one of the toner transfer tutorials i linked earlier for details.
now it gets a little counter-intuitive: keep in mind that during ironing, the layout gets mirrored. that’s why you should only mirror the TOP layer before printing, not the bottom layer. it’s a good idea to print out of Eagle directly. printing into a PDF first is likely to result in unwanted scaling of the layout.

bottom

top

printed_layout

this is a little tricky: you have to carefully align the perfboard grid to the layout grid. i made good experiences with aligning towards a window or a ceiling light, then holding both layout and board with two fingers, carefully putting it on a table upside down and carefully taping it into place. did it mention that you should be very careful? before ironing, check the alignment again.

alignment

putdown

taped

ironing

after ironing, let the board cool down and put in into a bowl of water. peeling/rubbing off the paper is easy if done underwater (only the board and your hands need to be under water). if you decided to do layout AND silkscreen, just repeat the whole process, but be sure not to iron the second layer too long, because you will re-liquify the toner on the other side and the board will stick to the surface.
satisfied? then go solder your professional perfboard™.

heap

stack

detailtop

summary of things to keep in mind:

* print directly out of Eagle/yourLayoutSoftware
* mirror the top layer, print bottom layer normal
* carefully align layout and perfboard grid
* check alignment before ironing
* iron second layer only half a minute or so

if you have any questions or ideas to improve the process, please do comment!

UPDATE: here’s timelapse of soldering the board. it took about one hour and the video is speed up 10x:

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About a year ago, i joined a group of hackers to take part in the Nokia Push Challenge, which was basically a hacking contest brought up to advertise the N900 smartphone that was released at the end of 2009. The teams were asked to come up with creative ideas to use the phone.
The Solderin’ Skaters wanted to equip a skateboard with motion sensors in order to use it as a real life gamecontroller for a skating game running on the smartphone. the skateboard sends 6-DOF IMU-data to the phone via Bluetooth. a software on the phone uses datamining in order to detect the tricks the skater performed and award those with points in the game.

skateboard complete

i was one of the two hardware people that build the skateboard. the electronics were designed by the other guy and my main task was to mount them to the skateboard, sp o in this post, i will only focus on this aspect of the project.
what sounds simple at first is in fact fairly difficult. besides the strong vibrations while riding the skateboard, huge g-forces are applied to the electronics when you land a trick. another problem is that almost every part of the skateboard is exposed to kicks, scratches and impacts, which has to be kept in mind when searching for a spot to mount the electronics. additional constraints are Bluetooth connectivity and the sensitive LiPoly battery that powers the system.

spacer closeup

we decided to put everything between the deck and the trucks of the skateboard. therefor i designed a special mounting consisting of four important parts. first a frame that holds the electronics in place and protects them from impacts. second a set of transparent covers that allow to observe the status LEDs on the PCB. another important component is a custom foam rubber cushion that surrounds the PCB in order to damp vibrations and impacts. finally a thin piece of PVC separates the LiPoly battery from the PCB and keeps it safe inside the truck.

spacer montage

all parts were designed in a CAD software and CNC milled afterwards. after some try and error in the design, the results were pretty satisfying. the skateboard has been in sporadic use for about a year now and it still works fine.

besides the Push Challenge, we presented our work at the ACE 2010, the 7th International Conference on Advances in Computer Entertainment Technology in Taiwan.

demo of the application:

links:
solderinskaters.net, infos about the project
Solderin Skaters @ Flickr
Nokia Push Challenge

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