Relay Switch Board

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Sam
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Joined: Sat Apr 28, 2018 6:49 pm

Relay Switch Board

Post by Sam » Wed Sep 29, 2010 12:44 am

The PCB buy I arranged recently is still pending, awaiting the final layout of the relay switching for forward/reverse and transmit/reflect. While the PCB itself, which includes several other boards, is of interest to only a few people at this point, I thought a larger audience might be interested in the development of the switch board.



The original design accomplished good isolation in some paths, but the required fencing became complex, and it was necessary to place capacitors here and there to get good isolation.



Lin has done considerable testing and has come up with some very good ideas for improvement. Putting the relays and large capacitors on the bottom of the board will allow them to be 100% shielded pretty easily. Originally, the relay coils were controlled by "low side" drivers, meaning the coils had permanent +5 at one end and were grounded on the other end to activate them. Changing that to "high side" drivers, where the coils have a permanent ground at one end and are driven by a pulse of +5 at the other end, simplified the layout and should improve the isolation.



On top of that, the new layout will have ferrites and capacitors in many strategic places along the control lines.



We should all appreciate the effort Lin has put into this, and if my brain can stand it I will shortly have the final schematic/layout, and we can get this thing built.



Sam W.

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