PCB Pictures with Scanner
An image scanner can make great pictures of circuit boards. Not only are the pictures clear, they are very high resolution and have nearly perfect scaling. Perfect scaling means that you can actual make measurements from the image. Try that with a digital camera!
I picked up the pictured Artec scanner for about $20 some time ago. It is close to useless and takes the worse scans I have seen. But even so, it can be used to make usable PCB images.
This image shows the bottom side of the graphics LCD I am giving away (details in this post). You can clearly read the IC part numbers and some of the other part values. The image shows a bare PCB.
If you grab the high res version (just click on picture) you can see more detail. The parts of the LCD PCB which were not against the glass do not look so good. Trust me this is due to the way this specific scanner works. If you have a good scanner the image will stay in good focus for about ¼ to ½ inch. With normal scanners the image is in focus for a good distance but detail is lost as things are further from the glass.
To make these scans all you have to do is place the PCB on the glass. You should put the cover down on the scanner to block outside light. You could also turn the lights out in the room. Some scanners do not work well without a background. To get really good scans you may need to block the light that could enter around the sides of the cover. It is also very important to keep the PCB level with respect to the glass.
To make measurements from the scans, you need to figure out what the pixels are per inch or what ever units you want to use. I like to use mils and this scanner at 300dpi has about 2.4 pixels per mil. You can find the scale by measuring a known distance on the PCB. The selection tool in most programs will tell you the pixel length of the selection box. You maybe able to set the resolution in your program so you can read your selection sizes directly.
Stumble it!
December 17th, 2006 at 6:11 pm
place a decent ruler on the edge of the pcb when you scan it.
December 17th, 2006 at 6:26 pm
Charlie,
That is a good idea. Also if the scanner is working correctly the mode, ie 300DPI, should defind the pixles per mil. 300DPI = 3 pixels per mil.
December 18th, 2006 at 9:42 am
Hi, good job. On the scanner, didn’t the PCBs damage the glass of the scanner? I’d be careful with assembled PCBs with ceramics on them
December 19th, 2006 at 12:23 am
Some ceramic parts on the PBC could scratch the scanner glass if you applied significant pressure. So far I have not seen this happen but it stands to reason that ceramic parts are probably hard enough to scratch glass.
December 23rd, 2006 at 12:43 pm
If you wory about scratches, just put a transparent plastic sheet under the PCB.
December 23rd, 2006 at 10:04 pm
That could be a good idea. I’m not worrying about scratches, have not seen any so far and scanners are cheap.
January 4th, 2007 at 4:40 pm
dfowler - correction to your first post - DPI stands for Dots Per Inch - not Millimetre.
January 4th, 2007 at 8:45 pm
Chris,
I could be wrong but Mils is not equal to millimeters. Mills is millionths of an inch so 300 Dots per Inch would be 3 pixels per mil.
I have been using this measurement successfully and will be posting another article where I use a better scanner to do some cool stuff with circuit boards
January 4th, 2007 at 9:12 pm
A Mil is 1/1000th of an inch, not a millionth. Nor does it have anything to do with a millimeter.
300 DPI will yield 300/1000 or .3 pixels per mil. How you came up with 3 pixels per mil on a millionth must be some amazing math indeed!!
http://www.google.com/search?hl=en&lr=&rls=com.microsoft%3Aen-us&q=1mil+to+inches&btnG=Search
The power of Google!!!
Great idea though….I have a 1600DPI (optical) scanner that I think I will just set to 1000DPI for a 1 to 1 scan. You might want to consider interpolation as well. Will make for more accurate measurements.
January 23rd, 2007 at 2:25 am
Yes Elbarfo, you are correct. I often get confused by the name of that unit. Why name it Mills I wonder. Just to make some of us look foolish.
Thanks for the correction.
January 25th, 2007 at 7:54 pm
Mills being from the Latin (and French) “mille” for 1,000.
January 25th, 2007 at 8:37 pm
To make good measurements all you need is a precision machinists scale, the kind our grandads got for free from the tool supply guy. Mine go down to hundredths of an inch. Makes measurements easy. Not all scanners are accurate in their DPI. I work at a newspaper and we run into that problem all the time from customer supplied artwork
January 26th, 2007 at 2:02 pm
A good vernier caliper can be bought for $30-$50. That’s probably more accurate and doesn’t require a computer or image-editing software…
Neat idea though. I do a similar thing sometimes to get complex object profiles into CAD.
January 26th, 2007 at 4:10 pm
May I offer my 2 cents? In Europe, England, and many other countries, 1 MIL = 1 Millimetre or 1/1000th of a metre (yes we spell it meter—they dont)…..which is where much of the confusion comes in, I believe. I lived and worked as an electrical engineer where i looked VERY foolish on MORE than one occasion (try to order #16 AWG wire in europe and see how far you get—-in our language it means 16 wires laid flat side by side will measure 1 inch, but that is greek to them) until I wrapped my brain around it….the American version of MIL was first applied by American blacksmiths in the 19th century and was later adopted by the Society of Automotive Engineers (S.A.E.) who used it to define the thousandth of an inch; as a result we call ANY machine which fabricates things (metal, wood, etc) with any precision a MILL (I.e. CNC mill, woodmill, etc…).
To aviod confusion in the future….always specify standard or metric MIL….for while we ARE discussing tiny fractions of measurements—-the DIFFERENCE between a standard MIL and a metric MIL is HUGE!!!
January 26th, 2007 at 5:26 pm
lol my old site’s theme was made of two scanned rams ! here it is : http://www.bash.ir/index.htm
I’ll re-scan this ram for my new blog’s template
)
January 26th, 2007 at 8:21 pm
@Dude Man: i am european, and i gotta correct you on some stuff: A: i spell it meters, not metres(i think its the british only who do that..or the french..most countries in europe** however dont) B: i have never seen the abreviation MIL in connection with the SI-unit meters.. its commonly and correctly abbreviated mm(millimeter), but i can see how one not familiar with the U.S. MILs may think its some sort of different word for millimeters.
i think the common way to define wire thickness in europe is be their diameter(millimeters or fractions of millimeters)
other than that: thanks for the definition of awg..i never understood that
**yeah..ehrm..i couldn stop laughing when i read this:
funny how ppl from overseas tend to think that..you guys should come over check it out sometime.. were not as lame as ppl assume! and it turns out SI units do come in handy every once in a while
“In Europe, England, and many other countries”
turns out: europe isnt a country per se…there’s lotsa countries in it.
January 27th, 2007 at 3:45 am
Great discussion.. I use calipers as well. I like the PCB scanning as documentation when the board or a full drawing may not be handy.
I am doing a project where I don’t have any drawings for the board but I need to hack out a quick enclosure. I plan to print the PCB scan to scale and use it as a template to cut the holes in the enclosure. I could do this with calipers but It might be easier to use the scaled PCB scan.
January 27th, 2007 at 3:13 pm
US: mil -> milli-inch -> 0.0254 mm
UK: mil -> millimeter -> 1mm
thou -> one-THOUsands of an inch -> 0.0254 mm
February 3rd, 2007 at 10:27 pm
“as a result we call ANY machine which fabricates things (metal, wood, etc) with any precision a MILL (I.e. CNC mill, woodmill, etc…)”
Happy April’s fool!
No, that’s not why they are called mills.
They are called mills because of the original mills that made flour. Because of those, anything else that was powered and rotated or that created something, possible by removing small bits at a time, were also called mills. Look it up.
A similar thing happened in some dialects of Danish. My dear 88-year-old grand mother insists on calling a ventilator “en mølle” because it is powered, goes round, and does something useful.
April 21st, 2007 at 1:46 am
Im going to have to give that a try next time
April 21st, 2007 at 3:27 pm
this is cool
April 22nd, 2007 at 5:11 pm
This will come in real handy.
May 16th, 2008 at 3:06 pm
Small Cnc Milling Machine
I found your site on technorati and read a few of your other posts. Keep up the good work. I just added your RSS feed to my Google News Reader. Looking forward to reading more from you.