Is there more to it?
Having used a few CAD packages, including DesignSpark PCB, I was curious to look around to see how people work on drawing schematics. I was not interested in the way they draw or the design itself, but was only looking at the importance they attribute to drawing and configuring their schematics. The general practice seemed to be – draw the circuit, translate to PCB and let’s work out things on the PCB side. I was wondering whether this approach was right.
The schematic is the closest in context to the design and layout provides the necessary connections physically. Whenever, we need to look into the design, our first action would be to refer to the schematic.
The most important aspect of a PCB layout, perhaps, is the width of the track. Tracks are drawn based on the properties of the Nets specified in the schematic. For example, when we connect two component pins through a net, we can change the width of the track according to the current carrying capacity needed. We do this by clicking on the net and pressing ‘S’. We get to change the width in mils or the units we have chosen.
For VDD and VSS, we may draw tracks with 60 to 80 mils whereas for a I2C signal such as SDA and SCL, we may go below 15 mil too, depending upon the size of the board.
As the schematic gives us a better idea about the current and voltages involved in a particular part in relation to the end design, specifying track widths would help us to pre-fix the track widths to the appropriate values.
Rachael
I am instaling the software now but I have not received the verify Code/Number yet.
How long do you have to wait before it is received.
Rachael
EVELWEEVIL
I am just contemplating trying DesignSpark, so am rooting around first. I had hoped to be able to make a comment without joining or installing the program, but not the case, so a couple of first off onservations if I may.
The install was a bit odd, I run multiple physical drives, and isolate all design work to one, so normally I click BROWSE->E: to select my work drive, and let the installer do the rest. in this case it dumped everything into the E: root directory. I can't think of another program I've installed in the last 10 years at least that didn't create it's own subdirectory.
On the idea of schematic vs PCb layout relative heirarchy I guess you'd call it. I do preliminary design in the Schematic, and many years ago looked at writing my own functions to relate schematic net to track width, but realised that I don't work that way. For me PCB layout is primarily about pin optimisation to minimise vias and track lengths, and it is often very difficult to do this at the schematic stage. i tend to design extremely small PCB's that are packed, so this is critical. I also hand do my PCB routing, since I have yet to find an autorouter that can cope. My typical currents are microamps, so wide tracks are rarely important from that perspective. Of couse I like to make power and ground as wide as is reasonable, but most signal tracks are 6-10mils wide. I tend to use wider tracks where a connector is involved, or where flex board is used, but that is more about being physically robust. It is tedious going back and reassigning pins/nets on the schematic, and a back annotation like utility for that would be nice, but for now manual is OK.
Finally I may be oddball, because my first point of reference when debugging is the PCB where signals are clearly visible, so I can see physically where to hook my probes to.
MikeBK
Hi EVELWEEVIL, thanks for your comments.
DSPCB does normally create its own directory upon installation, to be honest I have never tried to install it in any other location than the default. I will try to reproduce your problem when I get a chance to run through another installation (which should be later on this week).
DSPCB is equipped with a back annotation tool, sipmly select it from 'tools' menu when you edit your PCB file.
Humphrey
I am drawing a simple Flyback driver but when it is translated to pcb then many connections are lost showing just the component. Help.
daveegg
I forgot to mention,once you've set-up all your net classes for the type of boards you design you can save the Technology File, or range of Technology files, for different type of boards and call these up when you start a new design. Then, all you net classes with appropriate track widths are set-up ready to use. So you hit the ground running......!
eldonb46
I use DesignSpark only occasionally, and therefore I am very much a novice.
The example circuits appear to be very easy to work with and I have done so. But, when I Start a new circuit, I get lost adding the first circuit element. After deleting the example, How do you get started accessing the libraries?
Maybe there is a simple "Getting Started" tutorial, but I have not found it.
Can someone help make it obvious, for the new guy, to get started with his new design.
Note, this may have been discussed many times before and solutions provided, but for this Newbe getting started with DesignSpark is a challenge.
Thanks.
Regards,
Eldon Brown
zambardiluigi
i haven't see in the library LM3886 Why?
is it possible to convert or creat a library of this IC?
Thank you
daveegg
DesignSpark already handles this requirement perfectly under net classes; All you do is set-up a range of net classes in your Schematic Technology, then in PCB Layout Technology set-up the same net class names with all the varying track widths and the via sizes you want in the layout. After making a connection in Schematics click to select the connection, r/h mouse menu and select Properties. There you can select from the drop-down menu the particular net class for this connection, and if you wish you can even change the connection colour so you know what class of connection this is. Finish the Schematic, translate to PCB and all the correct track widths and vias are set-up corresponding to the net classes. Give it a try. DesignSpark makes this an easy process.