@jancumps : i do that all the time. no problem , but both legs are under the table
so no problem there.
Right some clarifications and addendums :
- PDF file : ain't donna happen for obvious reasons. Elektor is pondering e-book formats like iBooks or Nook or Kindle but the formats are very restrictive, especially for graphics heavy books like these are....
- I am working on an 'interactive chapter' for iPad. Sort of an assembly manual but with interactive bits. all the books have a unique code printed in the inside flap. use that code to register at the labworx website and you can download all sourcecode and other stuff like bill of materials, enlarged parts placements pdf's and layout PDF. ( Sorry no gerbers .. for obvious reasons ). the interactive chapter will be there for free as well.
- the UV exposure box : i just finished building the prototype gen II of that thing. one of the projects is a controller to make your own UV exposure unit. i built a plywood box and an acrylic box. version 1 had too many parts and was too iffy to assemble so i reworked it , reduced the number of parts by 15 and now have it ironed out.
The finished box in acrylic : all imagery on the box is engraved using the Laser ( i use an Epilog 60 watt Helix) . black acrylic turns almost white when fired at with the right power setting and pulse rate
front panel : ( the right panel is installed in the picture below but the handles and hinges are missing
The inside of the exposure chamber :
and when powered up :
i am using 420nM UV LED's that can be bough in adhesive strips off of ebay and other sources. Works liek a charm. the chamber gives a uniform light pool and you can exposu an 8 1/2 by 11 PCB without problems. The entire things is cut from two pieces of black 1/4 inch thick acrylic measuring 24 by 18 inches. The 24x18 inch acryilic size is chosen becasue 18x24 is a common bed size for lasercutters. The design will be made available as AI files for lasercutters. I haven't talked to the publisher about it yet but we may do a 'kit' of the plastic parts. you just go buy acrylic glue and you're set. Or you could download the AI (Adobe Illustrator CS5 format, readable by both AI and Coreldraw , which are the popular programs to drive lasercutters like the Helix and Zing ) files and cut your own.
Two acrylic sheets will set you back about 40$ , add a piece of transparent material for the exposure plate , another 10$ ( you need cast , so called museum quality, and not extruded acrylic for that ... ) . the UV led's can be had on ebay for about 40$ and the controller board is whatever elektor charges for it. the controller board is the one descirbed in the book. it uses the same atmel cpu as an arduino and you can actually load the arduino bootloader in it if you install the FTDI chip and USB connector so you could write your own control timer.
the timer as it is now allows you to run exposure an test as well as be an exposure timer. the sourcecode for the timer is downloadable form the website as well. nothing special. written in MikroE Basic for AVR and compilable with the Free version of the compiler.
here is the laser at work:
and the roll of led's from ebay:
- the same goes for the ringlight. i needed a PIC because that micrel chip uses a one wire control line that needs a pulse train to control the intensity. the code is again written in microbasic for PIC , can be downloaded from the website and is compilable with the free version of the compiler.
- the toaster oven is coming to a conclusion as well. i am late with the firmware for that thing. it uses the same PCB as the uv timer but you simply install the extra two thermocouple interface chips as well as the FTDI so you can monitor the profile on the PC. The controller is made for a CONVECTION oven and will NOT behave with an IR style oven. I deliberately chose a different approach than all the pizza oven soldering systems out there. IR is a very temepramentfull process and very hard to get right. you overcook the chips while white or very reflective parts don't flow. IR is a perfect process for localized rework like swapping a bga or tqfp on a board. it is NOT good to run whole boards. All the reflow machines in the industry are convection. they may be IR heated convection but the IR does NOT hit the board thye use it to heat an intermediate plate and create hot air using that plate. with IR hitting the board you can get massive gradients across the board, cooking one part while leaving another cold. Convection does not have that problem. if the air in the chamber is 310 degrees then no spot on the board can get hotter than that. with IR ... all bets are off how hot a part can really get ... i use a 59$ hot air tabletop oven made by Conair the controller drives the fan and the heating elements. two thermocouples monitor the process. one is measuring the air in the oven the other is obtional and can be used to track what your board is doing. the PC will display graphs of both ( it's a simple visual basic programm plotting temperature versus time. the whole interface between PC and controller is ASCII driven so you can roll your own if you want. the controller holds 10 recipies as well as a pre-heat recipe ) you simply program the endpoints of the tempearutre step and a dwell time inbetween. i use a simple bang-bang- control algorithm ( the relay can be 100% , 80% or 60% or 40% duty cycle. 100% being 10 seconds , 80 being 8 seconds etc. This is similar to what a normal kitchen oven does No need for PWM using SCR's under control of PID as the thermal masses are so large it makes no sense.
- so that is why the board dave showed says PANEL 2? Panel 1 is actually the control board that can be used for the UV box or the pizza toaster. ( if you want to make both the uv and toaster you will need to order two of the boards. it is the compnent stuffing that determines the function.)
- why this approach ? the projects in the book , while useful on their own, are actually intended to teach you the soldering techniques.... one project is full hand soldered , one is stencil soldered , another combines thru-hole and SMD and each project brings its own tips and tricks. you can deviate form the shown assembly process in the book without problems , but it is worth reading the explanations.
- why the elaboration on capacitors and resistors and components in the book ? as the scale of components decreases some physics comes into play. both the physics of soldering but also the material physics... capacitors for example start behaving very strangely... becoming microphones ... or acting a s speakers .... the materials used for such small form factor capacitros are also different from your normal thru-hole cap. you won't find barium titanate 22uF in thru-hole , while all SMD's are BaTi based... and this stuff exhibits specific behaviours not known to people dealing with thru-hole stuff. a 10uf 10 volt x7r in 0805 will , at 6v3 voltage, have about 7uF of effective capacitance. Take the same identical part but in 0603 ( so they need more layers internally and thinner layers to fullfill the mechanical constraint ) and at the same 6v3 working voltage you have 5uF left... so i need to sidetrack in the book and explain the problems encountered with certain components that are virtually inexistent in their thru-hole counterparts. same goes for resisotrs. the way they are cut , thin film vs thick film , and other aspects need to be explained.
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