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Experiments with SMD devices in VeeCAD (Read 58 times)
FrankB
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Experiments with SMD devices in VeeCAD
Apr 19th, 2020 at 2:21pm
 
I have been experimenting with SMD devices in VeeCAD for some recent projects and have had some measure of success. I thought sharing my observations might provoke discussion or be helpful.

I find the 0805 size is fiddly but achievable with practise for LEDs, ceramic capacitors and LEDs. The 0805 size is near perfect for use with donut boards, on stripboard (such as Vero) or tripad boards. Smaller sizes such as 0603 I find are too small and fiddly to handle easily and larger sizes such as 1206 are too big to fit nicely into a 0.1 inch pitch grid and still be solderable.

I mostly use 0805 resistors, ceramic capacitors and LEDs on double-sided donut boards and find they can save a lot of space. I also use short lengths of wire-wrapping wire to make the connections even though it's rather fiddly and delicate.

Devices of the SOT-23 style (eg transistors) can be used if you're prepared to slightly rotate the device. A similar rotation heps with programmable LEDs such as the WS2812 and also little trimpots.

Tactile switches can also be used without too much difficulty. I have three kinds that sit nicely on a 0.1 inch grid.

But there are problems with some devices...

SOIC and other such shrunken devices with lots of pins clearly can't be used on a 0.1 inch grid so cheap Chinese "carrier" boards can be used to adapt them - not pretty but works.

Looking underneath a device is important because the conductors may span across tracks or pads, a problem I encounter with some electrolytic capacitors. The resolve is to cut away copper tracks or pads that would cause a short circuit.

In terms of use within VeeCAD, it obvious that a library of outlines will be needed. I attach my experimental FB_SMD.per file. I added ".txt" to the name to be able to attach it. Put it in the VeeCAD Library folder!

Be aware that the SMD devices appear on the top of the board  layout in VeeCAD even though you may be wanting to solder them on the underside.

Enjoy experimenting!
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FB_SMD_per.txt (38 KB | 11 )
 
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Roger Lascelles
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Re: Experiments with SMD devices in VeeCAD
Reply #1 - Apr 20th, 2020 at 7:20am
 
Thanks Frank.

Frank's library contains SMD shapes fitted onto standard pitch pins. You can place these in VeeCAD just like any through hole component. Great for introducing SMDs into your layout.

Frank's SMD_0805XXX is different - it is a true SMD component - hold down shift and you can drag it off grid. True SMD outlines are special - they connect to SMD pads that you create in the Track Editor by drawing pieces of Segment rather than Track. To see how, inspect one of the Atarado SMD board patterns in the track editor.

VeeCAD does not have an SMD outline editor. I will have to document the .per format so at least people can create SMD parts by hand.
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Roger
 
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