SparkFun Forums

[Ross Robotics]

Some questions:
Why are 2 additional ground plane polygons needed if the board already has top and bottom layer ones over the whole board?

They are needed if you are going to thermally isolate the plane around a device (regulator in this case).

Why do the drawn polygons need to overlap the device's pins?

I explained this in the vid. Since the regulator's screw mount is grounded internally, the thermal plane should be grounded as well. The easiest way is to have the plane overlap the ground pin so Eagle will create a connection to the ground pin. You don't have to do it this way. You can always make a connection with a trace from one of the vias to the ground pin.

Should Thermals be removed from the vias?

Yes

[RossWaddell]

Looks like you deleted your video - will you be uploading a new one soon?

[Ross Robotics]

The post with the Youtube link is correct. Made a video edit error and had to re-upload a new vid.

https://youtu.be/ZH8TaJm-7tw

Will be making more once I do some research on what tutorials are actually needed. Let me know if you have any suggestions.

[RossWaddell]

Followed your tutorial and drew the top/bottom GND planes plus the tStop/bStop polygons around the regulator. Added a bunch of vias (if you copy/paste them individually then it looks like it keeps them named GND). But when I draw the tRestrict/bRestrict area using the wire tool, I get DRC errors:

Eagle_DRC_Errors.png

Looks like it's complaining about going over the regulator's pins. Is this another case where I need to hide the tRestrict/bRestrict layers after drawing the shape and then running DRC (as I did with the bStop/tStop polygons; without hiding the layers you get DRC errors).

[Ross Robotics]

It's ok just to approve them.

[RossWaddell]

It's ok just to approve them.

Thanks!

EDIT: Gerber files generated and sent out to PCB house. Should get the board back in 3-4 weeks for testing. Thanks everyone for your help!

[RossWaddell]

PCB back from China - how does it look?

IMG_3747.JPG

[Ross Robotics]

Except fort he silkscreen mishap on the lower right, looks good.

[RossWaddell]

Except fort he silkscreen mishap on the lower right, looks good.

Yeah, even though I used the Mirror to flip it to the bottom silkscreen, it somehow ended up on the top. Fixed that just now, along with the two diode outlines that are on bPlace instead of tPlace.

[RossWaddell]

I think I may have put the heat sink on the wrong voltage regulator ....

I was thinking the motors would draw enough current that at 6V the 7806T chip would need to dissipate a fair amount of heat with a 12V supply, but it doesn't even get warm to the touch. On the other hand, I have a 78L05 voltage reg to supply logic voltage to the PIC16F1825 as well as 20 LEDs that are connected externally (which is why they weren't on my prototyping board and I didn't even think about them until now that the whole thing is all assembled) which is getting blisteringly hot. I measured the current draw of the board and it's around 300mA, which is more than 3 times what the 78L05 is rated for. So, even if I replace it with a 500mA or 1A version I think I still need to worry about the heat generated by the 7V excess (2.1W?).

Thoughts? Should I redesign the board to have a 7805 TO-220 pkg chip use the heat sink instead?

EDIT: Actually, with the two motors running the 6V voltage reg gets up to around 110 deg F. Definitely hot to the touch.