Arduino Forum

Forum 2005-2010 (read only) => General => Bar Sport => Topic started by: halley on Jan 19, 2009, 10:49 pm

Title: two power supplies in EAGLE?
Post by: halley on Jan 19, 2009, 10:49 pm

How do you specify two separate power supplies in EAGLE?

I tried something like this schematic, but when I play with the board layout, I can't seem to make it recognize the arrows as two separate supplies (VDD for 5V and VMM for 12V motor supply).

(http://i315.photobucket.com/albums/ll450/HariEdo/inductive-mosfet.png)

I understand about naming nets, but the warning I get isn't about the net-- it's about two different nets connecting to the (common) supply.
Title: Re: two power supplies in EAGLE?
Post by: westfw on Jan 19, 2009, 11:40 pm
You have to use two DIFFERENT "Vdd" symbols, since the special "supply" components cause a net to be named after them.  That's why the "supply" libraries have so many components that pretty much look the same.

(I don't see a VMM, but there's a "+12V")
Title: Re: two power supplies in EAGLE?
Post by: halley on Jan 20, 2009, 04:52 am
Thanks, westfw.

I am sure I'm doing a bunch of things wrong, but so far the "Rules Check" features have been appeased.

(http://i315.photobucket.com/albums/ll450/HariEdo/i2c8d-schem.png)
(http://i315.photobucket.com/albums/ll450/HariEdo/i2c8d-board.png)

Up to 8 of these boards will be able to ride the same i2c bus.  (Up to 16 if you use the pcf8574a variant on half of them.)  This one doesn't do a separate latching step, but maybe a later design will.  Yes, I know I'm not putting in room for a real heat sink on each Q0-Q7 package, I don't need that much dissipation.  I may add a power jack alternative to the +12V pins of the cable header.  The M hookups are at the right pitch for a block of screw terminals, or they can be soldered directly.
Title: Re: two power supplies in EAGLE?
Post by: westfw on Jan 20, 2009, 05:45 pm
It looks pretty good to me, not that I have a lot of experience with motor drivers.   Since you have lots of room, I'd make the "power" traces to the motors thicker...

While you may not need heatsinking, you can get a little "for free" by using copper "pours" on the PCB:
(http://lh4.ggpht.com/_NOmmtpdLD5M/SXX_U-xjUeI/AAAAAAAACJo/tQS7-j68ga0/motordrive.png)
Title: Re: two power supplies in EAGLE?
Post by: halley on Jan 20, 2009, 06:13 pm
Yup, I was looking into the different options for pours and polygons for just this purpose.  Are solid pours are better than hatched ones for heat?  I should block the soldermask under the transistors as well, I imagine.  That will come back from the board maker all tinned up like all other vias and pads, won't it?

I just wanted to get all the traces routed first.  Sometimes it was hard to get EAGLE happy with new vias I had to introduce, such as those under the IC.  It refused to see them as part of the net I was linking for a while.