PCB printing

[keenan1]

hi ! i'm a complete newbie to making pedals and pcbs so please excuse anything stupid i'm about to say ! i'm trying to print a pcb layout I have found on the internet and I have no idea of the size or scale it should be, I've tried printing it how it is and it comes out enormous, I can make it smaller and it seems normal but i'm not sure if its the size it should be. I guess what I'm asking is does size matter? if so how can i make it the correct size? thanks !

[EBK]

If there is an integrated circuit in the layout, the pin centers will usually be spaced 0.1 in. apart along each row.

The short answer is, yes, size matters.

If it is a pdf file, try selecting "actual size" (without scaling) in the print dialog rather than fit to page.

[keenan1]

hi, thanks for the reply! would you be able to check out the layout please? its the one discussed in this post I'm still unsure what i am looking for ! it has some sort of scale on the side but i'm unsure what it means thanks again !




https://www.ultimate-guitar.com/forum/showthread.php?t=1044588

[EBK]

hi, thanks for the reply! would you be able to check out the layout please? its the one discussed in this post I'm still unsure what i am looking for ! it has some sort of scale on the side but i'm unsure what it means thanks again !




https://www.ultimate-guitar.com/forum/showthread.php?t=1044588

When the length of those double-ended arrows on your printout matches the numbers, you've printed it out at the right size.

[Mark Hammer]

I'm using Firefox.  When I see a layout I wish to print out, I select File->Print Preview->Page Setup, and adjust Scale, which allows me to select the percentage.  Usually, I will find it takes a couple of tries to identify the right scale, although some layouts come with helpful information.

I Keep a piece of perfboard handy, and look for it to line up with pads that are supposed to have the same spacing (1/10").

[PRR]

> it has some sort of scale on the side but i'm unsure what it means

It is size. In Inches. Worse: in 1/32 inches.

If you are in a land which does not use Inches, this is very awkward.

I have re-notated in good metric units.



As Eric says, "If there is an integrated circuit in the layout, the pin centers will ...be spaced 0.1 in. apart". (At least for all the fat-finger IC ships we use in traditional stomp pedals.) That is 0.254mm. You MUST hit these spacings or the chip will not go in the holes.

The row-to-row center on this type chip is 0.3 inches; and an 8-DIP (4 legs each side) has 3 pin-spacings so the end holes are all 0.3 inches or 7.62mm apart.

Get more than 7.5mm but less than 8mm, you can make it fit. (80-pin CPU chips were a lot fussier.)

[keenan1]

thanks everyone this information has helped me massively ! thanks for your time!

[ElectricDruid]

Why on earth did they give measurements in 32nds? Even when you work in inches, on a PCB everything is tenths or twentieths, not 16ths/32nds. It's a bit odd!

[EBK]

Why on earth did they give measurements in 32nds? Even when you work in inches, on a PCB everything is tenths or twentieths, not 16ths/32nds. It's a bit odd!

32nds are more precise, and rulers that measure 10ths and 20ths are not common (other than Mark H.'s handy perfboard ruler). Would be better to use mm, or at least round off to the nearest 16th, IMO.

We can at least agree, I hope, that whipping out some precision calipers to measure this sort of thing would be ridiculous.   

[greaser_au]

32nds are more precise

Fractionals are for old-time horse carriage builders where even a difference of 1/8" is of no import...   Semiconductor engineers (even in the US) recognised this and began using decimal divisions prior to the 1950's. 

However, of course, none of this matters, because by the time you're 50, even 1/8" is impossible to see

david

[EBK]

32nds are more precise

Fractionals are for old-time horse carriage builders where even a difference of 1/8" is of no import...   Semiconductor engineers (even in the US) recognised this and began using decimal divisions prior to the 1950's. 

However, of course, none of this matters, because by the time you're 50, even 1/8" is impossible to see

david

The wealthiest merchants could afford more precisely-built horse carriages.

[greaser_au]

EBK,
I see your well-used 32nds rule, and raise with my desk rule of of yet higher precision at 0.5mm (that I fail to see equally as well as the 32nds grads)...    That said, if I turn it over,  the inch side has 32nds & 64ths  (this part is just a grey patch to me without glasses)  as well as the more electronics-useful 10ths,  20ths,  and (equally invisible) 50ths.  A real PITA is the 0.07" pitch through-hole  standard;  now THAT's a hard-to-find ruler!   

Out here in the antipodes, we have meen metric for over 40 years. however if I walk into a hardware shop I am still confronted by metricated equivalents of traditional English units.  Bolts and nuts in this market are still inch-fractional whitworth sizes,  but recently metric is starting to appear.  I reckon the  biggest problem is mixed units. The GM-Holden Commodore (car) used the buick 3.8L V6 (configured longitudinally) through six models (with about 4 more mid series updates)  between 1991 and 2003;  in that time the body fasteners were all metric, but the engine went from fully SAE in the earliest ones, to SAE block/heads plus metric accessories to  metric heads on SAE bolts...  idiots... 

if I go to the .au sites of RS or Farnell, most things are shown with metric sizes,  fair enough for many things, but 2.54mm pitch DIP sockets??? 

david

[EBK]

Reminds me of the summer I worked as a construction inspector for  my state's department of transportation.  They were just switching over everything from feet/inches to meters.  One bridge design needed to have its parapets made higher to prevent SUVs from rolling over the sides.  The parapets became the only part of the plan in metric.
Also had many conversations like this:
Contractor: "We're used to marking our segments every 100 feet. How long is this new 30-meter standard in feet?"
Me: "About 100 feet."
Contractor: "Oh."