[Kizo] repurposed a flatbed scanner to use as an exposure box for making printed circuit boards. Exposure time is controlled by an AVR ATtiny2313 microcontroller. The device is connected to a separate display board to control four 7-segment displays using one shift register for each. Time is set in ten second increments and once started, switches on the lights with a relay. Once the right exposure time has been reached, the lights are switched off and a piezo speaker is buzzed. There’s no mention of they type of bulbs he’s using but they look like compact fluorescent with tin foil beneath as a reflector.
We’ve covered homebrew PCBfabricationtechniques about a billiontimesbefore. What sets this tutorial apart is that it collects many bits of knowledge otherwise scattered all about the web, and then depicts the entire process on video, from initial printing to cut PCB…because reading about it versus seeing it done are two different things entirely. They give a number of immensely useful tips throughout: choice of materials and where to get them, tools and techniques, and dispelling several myths about these methods (for example, they’re adamant about notusing acetone to clean toner from the PCB). Well worth the 30 minutes to watch. If that’s too much and you’ve been stuck on just one part of the process, the tutorial is in three segments.
Trimming finished boards on a paper cutter? Who would’ve guessed?
[Viacheslav] built a plotter that is fast and accurate. He wanted to take it one step further and added a laser in place of the pen. The 300 mW unit does a nice job of wood-burning any pattern sent to it, but isn’t strong enough to serve as a laser cutter for anything other than thin-film. We wonder if it can be used to cut solder paste stencils for surface mount PCB production.
In the video after the break you can see some plotting that uses a pen. In addition to writing on paper, [Viacheslav] has tested this as a method of applying etch resist to a copper clad board for PCB production. He’s able to achieve 0.8 mm pitch but the production process is limited by the resist pen’s tendency to wear out quickly and to only prevent etching for a short period of time (compared to toner transfer resist).
Just like with his touch sensitive keypad project, he’s taken the time to thoroughly document his work. Build notes, pictures, CAD files, and source code are all available for your perusal and hackage.
Above is a video detailing one method for populating a two sided surface mount PCB. We covered using a stencil to apply solder paste for a PCB a few weeks ago. In the comments there was a debate about the virtue of using stencils as well as a question about how two sided boards are populated. This was a good question because reflowing a board twice can cause components on the underside to fall off.
[Wim L's] comment mentions that there are a couple of methods for two sided population. In the video you will see that a stencil is not being used, but instead, paste is applied by a pedal actuated syringe. The paste is applied to the underside of the board first, then a teeny dot of epoxy is added to hold the component in place. Each part is then positioned normally and baked in a reflow oven. This process both reflows the solder, and cures the epoxy. When the board is reflowed a second time, the epoxy holds the bottom components in place as the top solder reaches its melting point.
This method of applying solder paste is slower than using a stencil. But if done correctly, every component can get the amount of solder needed.
[Zibri] found a very simple method for using brain waves as a controller via a DB9 serial port. He’s using Uncle Milton’s Force Trainer which we saw yesterday in the brain controlled Arduino. In that project the Arduino tapped into the LEDs and interfaced those signals with a computer via USB. This time the connection was made using an RS-232 transceiver to pass data from the programming header inside of the toy’s base unit to a computer over the serial port. Tapping into the programming header has a lot more potential and should be more reliable than sniffing logic out of LED connections. [Zibri] has written an application to display the received data but it doesn’t look like he’s made the code available for download.
Apparently he tipped us off about a week ago. We recall seeing this submission but as you can tell it’s a little bit light on the detail. So if you want your tips to be at the front of the line, make sure you do what you can to fill us in on all the details of your project. At our request [Zibri] provided a picture of the PCB from the Force Trainer’s base unit. See it after the break. Read the rest of this entry »
[Oleg] is the creator of the USB Isolator and therefore has a need to frequently populate the same board. He’s using an acrylic frame that fits the PCB perfectly to hold it in place so that paste and be applied right up to the edges of the board. He ordered a laser cut Kapton stencil for applying the solder. The paste is squeegeed into the stencil holes, the stencil is removed, and parts are placed with tweezers and a steady hand. For the final step, the boards go into an old toaster oven for reflow.
[Oleg] uses temperature marker on his boards to monitor the progress of the reflow. This marker is basically a crayon that begins to melt at a specific temperature. When the board has cooled, the melted mark can be scraped away or removed with alcohol.
Of course this is only really useful if you have a bunch of high-quality boards to populate. But with the relatively low cost of getting professionally made boards we think the need for this type of assembly process is on the rise.
We’ve seen severalcreativeprojects from [Sprite_tm] and this one sets a new bar. He got his hands on some paint that changes color with temperature. By covering a circuit board with the paint then heating the circuits he’s created a heat actuated 7-segment display (his post is in Dutch). Three seconds at about 1 amp is enough to turn the black paint white. When the segment has been disconnected for about one minute the paint fades back to black. Now that we’ve seen his concept, leave a comment and tell us how you’d use it.
It started with a simple need: keep tabs on SparkFun Electronics’ in-house kegerator so the beer won’t run out at inopportune times. But of course SparkFun and “simple need” make strange bedfellows…throw beer in the mix, and you know this can’t end well. The result, as you might imagine, reads like a who’s-who of electronics hackery buzzwords.
They’ve assembled a nice build tutorial on how this all went together, including code, example circuits, an explanation of some of the sensors used, and links to other tutorials for such things as Twittering and persistent storage in EEPROM using Arduino. Not to mention the eye candy: a custom Arduino shield (solder mask and all), custom acrylic tap handle, custom SparkFun pint glasses. They never do anything halfway, do they?
Full Spectrum Engineering has offered up a tutorial for their inkjet direct PCB kits that repurpose direct-to-CD capable inkjet printers (such as the Epson R280) to print etch-resistant ink straight onto copper clad board. This is easier and less error prone than some iron-on methods, especially for two-sided boards. Just print (no need to reverse the design), dry on a hot plate or in a toaster oven for a couple minutes, and your board’s ready for etching!
Homebrew methods exist for all of this, but for those who would rather move ahead with their design than spend time scrounging for the required bits, the kits offer a pretty good value. They can also meet you halfway…say if you’re only lacking access to a laser cutter and just want the CD stencil…all of the parts are available individually or as a complete set: the resist ink cartridge, the stainless steel board-holding stencil, and a supply of double-sided copper clad boards precisely sized for the stencil (3.5 by 2.5 inches). The small board size is well within the limits of the freeware Eagle Light Edition software.
Concerned about gunking up your nice inkjet with non-OEM ink? You can dedicate hardware to the job without breaking the bank. Many of the compatible printers are of the “free printer after rebate” bundle variety that can now be found inexpensively on Craigslist or eBay.
Fritzing is an open source project designed to help you move from a prototype to a finished project. Aimed at those basing their projects around Arduino, you start by building your physical prototype, then recreate it with Fritzing software’s graphical editor. From there you can generate a schematic, PCB artwork, and PCB production files.
