Yet another PCB design review... - Page 1
Forum section: electronics / projects

author: void_error
author_rank: Frequent Contributor
timestamp: March 08, 2015, 02:50:50 pm
content: Just asking for experts' opinion.There will be no soldermask/silkscreen - cheap home made board.U1 - PIC12F675 (smallest 3-bit up/down counter I could come up with)U2 - 78L05U3 - LM358U4 - UC3843No component values because I'm currently too lazy to double check everything, I have most of them figured out.If you're curious about the weird THT - SMD mix it's because that's what I currently have lying around.

author: nickm
author_rank: Regular Contributor
timestamp: March 08, 2015, 04:22:38 pm
content: Looks decent for a single layer design. I don't know if you mentioned it in a different thread, but whats the purpose of U3?

author: void_error
author_rank: Frequent Contributor
timestamp: March 08, 2015, 06:32:49 pm
content: Quote from: nickm on March 08, 2015, 04:22:38 pmU3.2 is a PGA, with gain set by R12-R15 which are binary weighted and handles the current feedback part. It's then OR'd with U3.2 which handles the voltage feedback - limits the output voltage when the load (10W LED) is removed.

author: PeterFW
author_rank: Frequent Contributor
timestamp: March 08, 2015, 08:39:05 pm
content: Quote from: void_error on March 08, 2015, 02:50:50 pmI am no expert but i will say somethiny annyway :-PDepending on your soldering skills i would increase the isolation slightly, without soldermask some of the joints would annoy me when i had to solder them.Most times i go for a bigger board if i etch them myself just to make it more convenient.But besides that, looks good.

author: tautech
author_rank: Super Contributor
timestamp: March 08, 2015, 08:55:28 pm
content: Quote from: PeterFW on March 08, 2015, 08:39:05 pm+1 on isolation and clearances especially for hand soldering. Also consider any possible rework in your layout.Consider making TH pads oval/rectangular for increased clearances/room for between pad routing.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 08, 2015, 08:58:13 pm
content: Hmm... given the process (single sided) and spec (basic old fashioned boost, low to moderate power), the power area isn't too bad. I think that'll work pretty well. I would still like to see some sort of shorting or jumper or loop across the ground pours, here, and here, and, maybe spanning kind of around here......ehh let me just draw this, alright?(red = jumper, white = solder, blue = cut)Also, the strip of ground going off around the right side doesn't do anything, it might as well be chopped off. Or if you can move the outline so there's ground going around the bottom, so it connects, that'd be good too.I don't like that the 3844 seems to have no bypass on it, which might be passable for the REF pin but VCC probably really does need it (somewhat contingent on what value gate resistor you've chosen). You could always tack on a leaded part between pins 6 and 8 to handle that, without needing it indicated on the layout.Tim

author: Ice-Tea
author_rank: Super Contributor
timestamp: March 08, 2015, 09:29:45 pm
content: I would probably keep components away from the bottom of the coil...

author: Lizerd
author_rank: Contributor
timestamp: March 09, 2015, 08:35:37 am
content: What about the component holes ?Are thy supposed to be that small because you only want to solder on one side ?seams to be 0.3mm , when it should be more like 0.9-0.8mmI do not know about the current L1 should be able to handle, but 0.3mm cant handle much

author: void_error
author_rank: Frequent Contributor
timestamp: March 09, 2015, 10:06:06 am
content: Quote from: Ice-Tea on March 08, 2015, 09:29:45 pmI'm not sure if I can route those somewhere else but I don't think the coil would affect that part - there are only digital signals there.Quote from: Lizerd on March 09, 2015, 08:35:37 amThe 0.3mm 'holes' are just drill bit guides, everything will be drilled by hand to 0.8mm first then enlarged where needed. L1 will carry 1A max.

author: Cside
author_rank: Regular Contributor
timestamp: March 09, 2015, 10:44:58 am
content: was this drawn in diptrace?

author: void_error
author_rank: Frequent Contributor
timestamp: March 09, 2015, 01:11:32 pm
content: Yes, that's DipTrace.Made some tweaks following Tim's suggestions, it should be better now.