YAPS Part Five - Design - PCB

RE: YAPS Part Five - Design - PCB

Andrew J — Sun, 09 Jun 2019 17:59:22 GMT

Bad news! I found 3 problems on the Control Stage PCB all of my making. I'd ordered a NPN in wide TO-92 rather than standard; The LT3081s come pre-bent - 3 legs back, 4 legs forward and I'd got it the other way around on the board; And I ordered the wrong package for the current source - a TSSOP rather than SOT-223. All my fault, not taking enough care with ordering or reading the datasheet: I spent ages reading them as well, how I missed it I don't know. I can only put it down to the picture at the front of the datasheet showing flat legs and I assumed I would bend them to fit.

I can't fix these problems with a drill! So I've updated the boards and re-ordered them so there will be a delay in progress. Whilst I'm waiting I might as well work on the 4Duino interface. I've not updated the images above as the updates don't change things significantly.

Another lesson learned.

RE: YAPS Part Five - Design - PCB

Andrew J — Sat, 08 Jun 2019 23:30:57 GMT

My next bit of advice is: don’t trust the Kicad footprints in the library. The footprint for the bridge rectifier on the power stage board has 1mm drill holes but the part has a min 1.02 and max 1.27mm lead size. Add to that a 0.08mm tolerance plus plating and you’re doomed.

Maybe not. I have some fine drill bits for a hand tool so could ream the 4 drill holes out to 1.5mm - I couldn’t fit the part at a smaller diameter and I tried two pieces. A continuity check shows that there is still a path through the part so that’s good. Whether or not solder will still take to the pad I’ll find out tomorrow.

But now, before I do any soldering, I will check parts on the other board. I’ve updated the power stage board, and updated the Control board to replace the LM7805 with a Dc-Dc switching regulator so I’ll take the opportunity to make sure everything else is correct.

Lesson learned.

RE: YAPS Part Five - Design - PCB

Andrew J — Fri, 07 Jun 2019 11:46:14 GMT

PCBs arrived - took 6 days from placing the order to delivery in my hand. Look pretty good too.

[View:/resized-image/__size/620x735/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-88eab33c-8dc0-4a85-b092-2ac83ef97c41/0753.contentimage_5F00_190970.jpg:620:735]

RE: YAPS Part Five - Design - PCB

Andrew J — Fri, 31 May 2019 12:20:28 GMT

Always check the Gerbers! I found a few vias that were a little too close to the traces and intruded - not shown in PCBNew but clear as day in the Gerber. 5 each of the Power Stage and Power Control costs under £4.78 from JLCPCB; shipping ranges from £5.50 to £24 depending upon how long one is prepared to wait.

Pictures from Gerber view - front silkscreen:

[View:/resized-image/__size/620x466/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-88eab33c-8dc0-4a85-b092-2ac83ef97c41/5023.contentimage_5F00_190965.png:620:466]

Front copper and solder mask:

[View:/resized-image/__size/620x468/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-88eab33c-8dc0-4a85-b092-2ac83ef97c41/1541.contentimage_5F00_190966.png:620:468]

Back copper and solder mask:

[View:/resized-image/__size/620x469/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-88eab33c-8dc0-4a85-b092-2ac83ef97c41/2112.contentimage_5F00_190967.png:620:469]

Power Stage silkscreen:

[View:/resized-image/__size/620x368/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-88eab33c-8dc0-4a85-b092-2ac83ef97c41/3683.contentimage_5F00_190968.png:620:368]

Front Copper and solder mask:

[View:/resized-image/__size/620x365/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-88eab33c-8dc0-4a85-b092-2ac83ef97c41/1538.contentimage_5F00_190969.png:620:365]

Back's not so interesting so I haven't added an image.