3-Way Input Selector - Looking for Feedback on Design - diyAudio
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Old 26th November 2014, 02:22 AM   #1
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Default 3-Way Input Selector - Looking for Feedback on Design

I'm not sure if I'm posting this in the right forum - if there's a more suitable one, mods please move this thread there.

I've been working on a rather crude relay-based input selector design. There is no logic, no digital stuff and no microcontrollers involved here - the device used to route power to the correct relays is a simple (break-first, of course) selector switch. I've given designing a PCB a try, and I'd be very grateful if someone more experienced could give me some feedback on whether there's still stuff I could improve - this is my first "serious" (well, not all that serious I guess) PCB that I'm planning on having produced by OSHPark.

In the attachments, I have included the schematic, the eagle project files and the preview renders from OSHpark. I haven't been able to find any mistakes, but it's very possible that there are still some problems. Any feedback is very appreciated - I'm especially wondering whether separating the ground planes as I have done, with both ground planes on the lower part of the board (the input side) being tied to the 12V ground and the upper ground planes both being used as signal ground and whether combining all output signal grounds together could lead to any problems - the relays are DPDT (but I'm using them as DPST), so the signal grounds are switched too and I'm under the impression that should prevent any problems. I also tried my best to closely couple the ground planes with lots of vias - not sure if it helps in any way, but I'm sure it can't hurt.

And finally, the relays I had in mind were Panasonic DS2Y - if there's something noticeably better at a reasonable price (not gonna shell out $15 a pop for NOS SPST mercury wetted relays), I'd love to hear about it.
Attached Images
File Type: png board_bottom.png (78.1 KB, 232 views)
File Type: png board_top.png (103.1 KB, 231 views)
File Type: png copper_layer_bottom.png (90.9 KB, 229 views)
File Type: png copper_layer_top.png (69.6 KB, 228 views)
File Type: png drills.png (21.2 KB, 225 views)
File Type: png silk_screen.png (43.8 KB, 33 views)
File Type: png solder_mask_bottom.png (41.0 KB, 31 views)
File Type: png solder_mask_top.png (41.0 KB, 22 views)
Attached Files
File Type: zip relay input selector eagle files.zip (166.8 KB, 9 views)
File Type: pdf schematic.pdf (30.0 KB, 45 views)

Last edited by butizzle; 26th November 2014 at 02:58 PM.
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Old 26th November 2014, 10:03 AM   #2
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For the same purpose I have made that :

Click the image to open in full size.

Click the image to open in full size.

Fully mecanic.

One input > six outputs or six inputs > one output.
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Old 26th November 2014, 03:01 PM   #3
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Well, that thing looks pretty amazing! I have to admit though, I cannot imagine how it works... For starters, where are the inputs/outputs?
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Old 26th November 2014, 04:01 PM   #4
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Click the image to open in full size.

G for left.

Blue for cold wire, red for hot wire.
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Old 26th November 2014, 04:13 PM   #5
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I like the cams and switches. Is that a gear motor in the middle?
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Old 26th November 2014, 04:29 PM   #6
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Yes, to motorize the device, an there is a clutch.

Double Over Head Camshaft.
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Old 26th November 2014, 11:02 PM   #7
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Well, I still don't quite understand how that thing works - how is the contact between the selected input and the output established? What are those things that are driven by the gears?


Also, does anyone have any suggestions for my PCB? I made some more changes to make it a bit more compact and streamlined the routing of the traces, I'm attaching the new design to this post. The schematic hasn't changed so I'm not uploading it again.
Attached Images
File Type: png board_top.png (105.5 KB, 15 views)
File Type: png board_bottom.png (75.6 KB, 14 views)
File Type: png copper_layer_top.png (64.5 KB, 11 views)
File Type: png copper_layer_bottom.png (83.7 KB, 8 views)
File Type: png silk_screen.png (48.1 KB, 10 views)
File Type: png solder_mask_top.png (40.4 KB, 10 views)
File Type: png solder_mask_bottom.png (40.4 KB, 9 views)
Attached Files
File Type: zip relay input selector.zip (213.1 KB, 3 views)
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Old 27th November 2014, 05:55 AM   #8
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Sorry, you are right, it is not an answer at your specific question.
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Old 27th November 2014, 08:16 PM   #9
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No problem, your design is very interesting and I don't mind you sharing it here at all - it would be nice to have some more detailed information on how exactly it works, it looks very intriguing!

About my selector PCB, after having another look at the price OSHPark would charge for the design as posted above ($45 for 3 boards), I've decided I'd rather sacrifice aesthetics in favor of a lower price and move all the relays closer together. I'm also going to arrange the diodes differently, maybe even make them SMD and/or place them on the back side so I can reduce the height of the board as well. I'll post the results once I'm done with the redesign.

I think I'm only going to order 3 boards of this design because I've already got my 18 DS2Y relays and then I'll do another design using SMD relays mounted on both sides with each channel getting one side of the board. That, together with those tiny Omron G6K SMD relays, should bring the board size right down and if there's any interest I might even host a group buy for the boards.

On another note, diyaudio member Calvin mentioned that running signal traces below the relay past the coil (as I'm doing now) leads to very strong crosstalk between the coil supply and the signal when using subminiature relays like the G6K (Best sounding signal level relay? ) - could this also make trouble with the DS2Y relays I'm using? I'm going to "feed" them with 12V from my "The Wire" PSU which is very low noise, but I'd still prefer to avoid any opportunity for crosstalk.
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Old 27th November 2014, 11:21 PM   #10
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Well, I managed to make the whole thing more compact, reducing the price of 3 boards to $30, which is more than fair for a double-sided board with silkscreen on both sides IMO. I'm leaving out the soldermask picture because it's pretty useless anyway - you can see everything on the board pictures. I decided to change the diodes to SMB package ones - I prefer SMD anyway and they're smaller.

I think I'm gonna place an order for 3 of these boards if no one alerts me to any issues in my design. I'm especially worried about the coil supply crosstalk - does anyone have any experience with this using relays of a similar size in a similar layout to mine?
Attached Images
File Type: png board_bottom.png (66.0 KB, 10 views)
File Type: png board_top.png (104.0 KB, 12 views)
File Type: png copper_layer_bottom.png (82.2 KB, 12 views)
File Type: png copper_layer_top.png (66.3 KB, 9 views)
File Type: png silk_screen.png (53.7 KB, 9 views)
Attached Files
File Type: zip relay input selector eagle files.zip (224.0 KB, 0 views)

Last edited by butizzle; 27th November 2014 at 11:30 PM.
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