67 lines
2.7 KiB
Markdown
67 lines
2.7 KiB
Markdown
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design choice
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=============
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v2
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--
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- LEDs have the same brightness
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v1
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--
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- production friendly design (not through hole devices, or double sided load)
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- each LED/status should have a unique color
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v0
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--
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- the connectors need to have through hole mounting tabs to ensure they don't break from the board, particularly the micro-B receptacle.
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- to power the LEDs I used small batteries I had around: CR2032. They are plenty sufficient to power LEDs, especially because I provide them with less than 0.5 mA. Thus the battery should last testing cables for years, unless you leave them plugged in.
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- to keep the board small, I decided to put the battery holder on the back of the board. This requires you to solder it last, else it would cover the hole for the USB-A receptacle.
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- I did not specify the colors of the LEDs, or the value of the resistors, in the schematic, since I wanted to try out alternatives while assembling them.
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changelog
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=========
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sometimes there is a battery connection issue.
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this is because the CR2012 hole is small, and the HASL is thinner as the silk screen.
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this has been fixed by making the pad larger, and adding the solder paste (not sure if this is a good idea for such a large pad though).
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v2
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--
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in v1 I mixed the LEDs for OTG and B-CHRG.
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I used the opportunity to improve on other aspects:
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- the USB A is shifted to the left to cover mouse bites
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- the USB micro-B can be shifted a bit to the bottom to allow for large plug assemblies
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- the white OTG LED was too bright
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- the green LED was too bright
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- the blue LED was too dim
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- the QR code is white solder mask on green silk screen can't be read by all readers because it's inverted
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v1
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--
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v0 needed dual side hand assembly, though hole soldering, and lead cutting.
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v1 is an assembly friendly redesign.
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it now uses only parts which can be SMD soldered.
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all parts are on the top side of the board.
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because the coin cell holder is also on top, I used a CR1220 holder instead of a CR2032 holder, so the board remains small.
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for quick and infrequent cable tests, a 35 mAh CR1220 is sufficient.
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since the battery can be side loaded, instead of top loaded, the holder is even smaller.
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I also used different color LEDs for each test.
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v0
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--
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first prototype, used as proof of concept.
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I used parts I already had in my inventory.
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parts need to be solders on both sides of the PCB.
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first, solder the LEDs and resistors on the top side.
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then solder both USB connectors on the top side.
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the tabs of the USB connectors need to the soldered on the bottom side, and provide rigidity.
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cut the leads of the USB connectors so the bottom side is flat again.
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finally, place the battery holder on the bottom side, and solder the leads on the top side.
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