PCB with 271 relays

Is that your test system?

Yes, it's the test board. Any pin on any front-panel connector (D25, D37, SCSIs, D9s, HD15, some BNCs) can be routed through a matrix into a 4W DVM, SCOPE, SMU, counter, some resistors, and other instruments. Control is USB or Ethernet. It has some self-test capability.

Two of these will be rack-mounted so we can service lots of DUT connectors.

Do you ship a carton of contact spray with that like they did in the old telco days?

The relays are surface-mount, gold contacts, sealed.

We will run a BIST routine, once every morning or every week or something. We should catch most relay problems.

For a few years it should be ok. Eventually the gold will wear off. I have some radio equipment which I use for EMC work and there the encapsulated relays have become really iffy. If I had my druthers I'd replace them all with PIN diodes and muxes.

I'm switching all sorts of voltages, and I need low ON resistance and low leakage. Relays are really hard to beat. The Fujitsu relays seem to be reliable; some equivalent Omron parts weren't.

Are you switch them with FPGA/CPLD? We probably need something similar.

I expect mercury would be more reliable. But unobtanium now.

NT

Ga-In-Zn alloys stay liquid down below 0F IIRC. Gallium is much less toxic than mercury but costs about four times as much, so gallium-wetted relays are probably doable.

Mark L. Fergerson

There's an ARM processor that drives an SPI string of TPIC6595 relay drivers. The relays take about a millisecond to settle, so we have plenty of time.

Email me and I'll send you the schematic. You could have some of our PC boards maybe. We'll also be developing a Python library to abstract function calls, to make test programming easier, and of course a BIST routine. Python test programs will talk to the various test equipment, too.

Here's the approximate block diagram...

There are five internal busses, A B C D and E. Any pin of any of the DUT connectors on the left can be connected to any bus. Test gear can be connected to the busses too.

Pickering still seems to be selling Series 88 and 80 mercury wetted reed relay switches.

The mercury is contained in a hermetically sealed glass capsule, so it shouldn't be a health issue.

It is once it gets chucked out & broken, in the eyes of the law anyway. Over here there are apps you can use things like that for, but certainly not for run of the mill electronics. And IIRC they have to be disposed of as haz waste.

NT

Reed relays are big, expensive, power-hungry, and generally horrible. The dry types tend to be unreliable; I don't know about the wet ones.

Pickering makes relay-based programmable resistors, like for RTD simulation, with the obvious problems. They have some amusing patents.

Hey (silly question) Does anyone make a electronically driven rotary switch? A tiny little stepper motor, or something, turning the shaft.

George H.

I'm sure they did. Telephone exchanges for a start! :)

They do motorized pots too, those were quite cool. At my old employer we used to use dozens of them for a self-tuning process thing. 10 turn with digital dials. It was funny when customers did not realize what they worked and started accusing each other of fiddling with them! Turn your back and they had moved.

They sure did- it's a step relay. Just found a few I had too. Were used in phone switches and elevator controls.

Very fun to watch in operation.

Ledex used to make them, but I haven't tried to buy any for several years.

Maybe it really is a year old, but should the title block dates be 2016?

Also, this Who song is nominally related. (It's actually about gossip, I think.)

Matt Roberds

I think old pinball machines had some step relays in them.

Mikek