Mode Zero

Elmic quick blip was a physical 'logic gate' via a contact on the rotor, if the rotor passed say 45° AND the button/relay was released, then its a quick-blip....

With the design I have here, the rotary wheel is kept centred by power from the 'centre' microswitch, which is powered by the Rx 'normally closed' pin. So the wheel will rotate:

1 - if the Tx is not energised with a signal (if energised, a left/right microswitch is powering the wheel)
2 - if the Centre microswitch is closed (which is the case with all positions except centre)

So a quick-blip is easy to define - it's when the wheel is in its first quarter, and being powered by the center microswitch. A simple slider on the first quarter connected to the centre microswitch will only be energised then, and can power a sequential switch.

Anyone know where old rotary telephone exchange switchgear is still available cheap?

There's a Strowger Uniselector up for sale on Ebay. Bid at time of posting, £20.

https://www.ebay.co.uk/itm/Uniselector- ... SwcPpepD~J

I think they usually run at about fifty volts and draw about an amp when moving. Pretty big heavy things so not much use in a model except perhaps a very large boat.

But would be a cool thing to set up on the bench to play with.

I don't know about the condition or type of the one up for sale.

Interesting trivia is that Strowger was an undertaker, and was motivated to invent the dial/switching system because a rival undertaker's wife worked as a telephone operator: in the early days of the telephone, all calls were connected by operators, and she was routing most of the calls requesting funeral services to her husband, so Strowger was losing business.

Those uniselectors aren't cheap. are they? Collectors seem to be interested in them...

The most attractive one which comes up if you search ebay for 'uniselector' isn't a telephone one, though - it's one from a junked MiG-29. Perhaps, if you can buy enough parts of ebay, you could make a complete...

Phil_G's point about the Elmic was vary useful. I think it would be easy to add a couple of contacts to my disk, and get a pulse out which would drive a selector switch, and give me a Quick Blip. A 3v stepper might power one? I enclose a diagram showing what I mean...

Hi Dodgy
Re the over-run & brake, try wiring all three microswitch 'make' contacts together and through a 47 or 100 ohm to neg. At each stop this will partially short the motor acting as a brake, whilst not presenting a short to the neutralising current:


(microswitch commons must be on the motor side)

It works! Shows you what experience can do, as opposed to my smattering of technical misunderstanding....

If it makes you happy.... here is the actuator running with a 100 resistor - you can see it on the wiring. The motor stops much more abruptly now...

Hmm...when I added the video it just said 'error parsing server response'. Ah, well, tomorrow is another day...