Re: 136 relays

On Fri, 20 Sep 2024 04:57:00 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

On a sunny day (Thu, 19 Sep 2024 14:15:48 -0700) it happened john larkin
<jl@650pot.com> wrote in <bm4pej9b6hlv4ceot3kr9f4h3v534nk1sl@4ax.com>:
>

>
Can't wait to see this one built. It's an 8-layer board  with 2 oz
copper on all the inner layers.
>
https://www.dropbox.com/scl/fi/x083h0w96p9ihlbvidemp/P948A_PCB_Top.jpg?rlkey=5plqemb1n1k7ioso7olioovnp&raw=1
>
https://www.dropbox.com/scl/fi/sq7ac00n2ysy4r7pjjr3e/P948A_PCB_Bot.jpg?rlkey=y1sjpga50q5dlawe4058fsqov&raw=1
>
The bottom side has surface-mount relay drivers, shift registers and
sot-23 fets, and the thru-hole relay pins are selective-soldered.
>
I hope that all works.

>
Is it easy to replace a defective relay?

No, which is why there are so many polyfuses, to protect the relays
and the PCB traces.

I just measured some trace resistances. I specified 2 oz copper on the
inner layers, and I know that PCB houses often cheat down on copper.
This one is good, conductivity about 8% better than 2 oz.

Why use relays?
Is that the inductor switching thing you were talking about long ago?

It's a FITS, a cable fault insertion unit. AKA guillotine box.

Imagine a system with two boxes connected by a cable. Now chop the
cable and insert this board in the middle. It can simulate any wire
open, any shorted to any other, any shorted to ground. It can measure
and snap waveforms of any voltage or current and can measure
resistances.

This board does 24 channels but boards can be connected for bigger
cables.

It plugs into our modular power system

https://highlandtechnology.com/Category/MPS

That all started when one of our customers, on a zoom call, said "we
hate power supplies!"

I think I'll design the 8-channel power supply board next. It could
have some interesting variations, torque motor drivers or something.