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Old 10th February 2019, 06:57 PM   #11
nigelwright7557 is offline nigelwright7557  United Kingdom
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Originally Posted by rsavas View Post
When I do pcb outlines, I try to use mm as it is easier for me to work with unless it is a round imperial number.
I got caught out with imperial/ metric a while back.
I used metric to step and repeat some TQFP SMD pads.
It turned out that metric is converted to nearest imperial thou of an inch.
This accumulated errors until the 16th pad was half a pad out !!!!
Had to bin the pcb's when they came as useless.
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Old 10th February 2019, 07:45 PM   #12
rsavas is offline rsavas  Canada
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I see these rounding errors when I build a part in mm and do the layout in imperial.
Funny how I always used KK100, KK156 connectors (Tyco call them MTA100,156), I recently find out, Molex re-named them to KK254 & KK396 Some doc's show the old number, some show the new number. Molex or the new breed are even messing with my mind = Idiots, like the Humbel did not teach them anything.
I always design in mil, I am old school, brain works that way and libraries are built in what ever the spec shows. Usually in mm. Pads are std drill increments of 5 mil. Placement outline is usually 25 mil, not 0.635mm
Quote:
It turned out that metric is converted to nearest imperial thou of an inch.
No where near enough resolution for a conversion.
I think with orcad it is something like 0.01 mil rounding error, even the resolution they show in some menus round to 0.1 so you do not see it until you look further, using a different menu.
Most my stuff is 100x100mm, so I do the board outline, switch to mm and back, they show 99.99, I just edit it in the fab drawing layer
When in question, I always do measurements in layout and gerber viewer to make extra sure I or the tool did not mess up. You know check, check and check again or you could be screwed, even then **** happens, Murphy wins again Cheers mate.

Back to this thread, if someone wants me to duplicate this Hafler pcb, send a sample of it to me (PM me), so I can do it. I will get some pcb's made up, send some of them & your sample back to you.
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Old 10th February 2019, 07:54 PM   #13
rsavas is offline rsavas  Canada
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Somone already did it, no soldermask, no silkscreen, it's a copy alright.
NOS HAFLER PC-19C (PC-19) Bare/Blank Driver Board (DH500, DH-500, DH220, DH-220) | eBay
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Old 10th February 2019, 09:06 PM   #14
jackinnj is offline jackinnj  United States
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PCB copies
Get the freeware PCBExpress. Make a 1:1 PNG image of the board and download it 100% to Paint. Paint will give you the XY coordinates in pixels when you mouseover, PCBExpress will give you inches when you mouseover.

If you have paint in one window and PCBExpres in the other you can quickly convert an image to a PCBExpress board. They are quick and not too expensive.
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Old 10th February 2019, 09:13 PM   #15
Monte McGuire is offline Monte McGuire
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PCB copies
Some PCB software, such as Eagle, lets you work in either metric or Imperial with no improper rounding nonsense. Just switch the grid and you can work in whichever unit you like. Regardless, the results will be rounded to the final output Gerber resolution anyway, but as long as the internal resolution is higher than the output resolution and there are no accumulated errors, there should be no reason to have roundoff issues from accumulated roundoff errors.

Many SMD packages are defined with metric units now, but most PCB houses use Gerber files with Imperial units, rounded to some number of digits. So, the conversion has to happen somewhere, and as long as the dimensions are properly rounded at the final output, nothing bad happens. The PCB manufacturing process has tolerances and errors anyway, but as long as they do not accumulate, you can still get work done despite finite resolution.

The odd thing about metric vs. Imperial is that there's actually an exact conversion between the two. But, again, there are always tolerances on every dimension and every manufacturing process. So, there's no reason to be forced to use one unit system over another - you need to use both in practice.
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Old 10th February 2019, 10:13 PM   #16
rsavas is offline rsavas  Canada
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Quote:
Get the freeware PCBExpress. Make a 1:1 PNG image of the board and download it 100% to Paint. Paint will give you the XY coordinates in pixels when you mouseover, PCBExpress will give you inches when you mouseover.

If you have paint in one window and PCBExpres in the other you can quickly convert an image to a PCBExpress board. They are quick and not too expensive.
It might work for this pcb, but in general, I would never trust this method for accuracy.
I can not even trust printing a layout out on the laser, as a way of checking, it is off by some small amount.
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Old 11th February 2019, 02:17 AM   #17
stocktrader200 is offline stocktrader200  Canada
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I had to measure and remeasure from ExpressPCB to the main pcb in sx-780 to get it right. I am about to drop in a daughter board on top of 780 amp section with a much better amp.
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Old 11th February 2019, 04:03 AM   #18
PB2 is offline PB2  United States
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Why don't you scan it to a .png to scale before you populate the board?
Then you'll have a reference in case you want to make more of them.
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Old 11th February 2019, 07:57 AM   #19
schillg11 is offline schillg11  Germany
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Hi,


i still have 2 PC-19C equipped by my own and untested and no more Hafler DH-220. Maybe it is interesting for somebody!

BR
GŁnni
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Old 11th February 2019, 02:39 PM   #20
prasi is offline prasi  India
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PCB copies
An option and an easy one.
place the PCB on a glass with a light behind it. take a photograph from above . all the traces will appear dark. From same position, switch off the light and take another photo, all the silk will be visible clearly. Do not disturb the camera position in-between.

Import the pictures in sprint layout and adjust the scale of the image to match PCB size.

Start drawing and use standard packages and adjust trace widths approximately (make them slightly bigger if you like). Run DRC to check for clearances based on supply voltage.

Once you are satisfied , take print of sprint image/pdf to scale and compare with actual PCB against light.

Generate gerbers and send for manufacturing protos.

regards
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Last edited by prasi; 11th February 2019 at 02:43 PM.
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