Mrechanical Uniselector Nixie clock

3 years 7 months ago #9557 by RedeyePete
Regarding the mechanical clock on your main page,
These use uniselectors from old Step type telephone exchanges and PBXs.
The ones I use to work on had 24 or 25 contacts (memory is a bit fuzzy) and worked off 50V.
If you know any old telephone techs they may be able to help.
There are some on ebay too.
The following user(s) said Thank You: Ian

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3 years 7 months ago #9559 by Ian
Hi Pete, thanks for that! Do you use them a frequently? I'd like to put together a clock based on these to go "full retro", but you know.... time....

How close did I get with my suppositions? Do you have anything that you'd like to add/correct about the article?

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3 years 7 months ago #9569 by RedeyePete
Hello Ian,
That line should have said “The ones I used to work on”
The D went missing somewhere
It was over 30 years ago when I started in Telecommunications and back then they were on their way out.
So I got to do maintenance on them but not installs. Mostly Eriksson.

This type has 22 sets of contacts. So you double them up. Nixi 0 – 9 would be Contacts 0 – 9 as well as 10 – 19.
For 1- 6 you could even repeat twice.
Once the uniselector reaches 20 it needs to return quickly to 0 in time for the next clock pulse.
That’s the “Bzzzt” you hear in the video.
50V would be applied to one of the wipers and you would common pins 20 – 22 to step the uniselector until it reaches 0. There are no contacts on the relay itself so either the advancement is done by feeding a square wave. Perhaps there is another relay in the customer’s relay box with a suitable cycle time to suit the uniselector drive. It could also be possible that the contacts are break before make and this is sufficient for the advancement.

There are a number of strips of contacts so you can use one for Nixi, One to advance the wipers to the start, and one to operate the advancement of the next digit uniselector.
BTW. Power applied to the magnet advances the pawl but the selector is advanced when the power is removed.
There are 2 sets of wipers opposite each other, so that there is no break advancing from 22 to 0.
I saw a similar clock on line but the timing wheel has 1 hole and rotates once a second.

There are some on Ebay but there not cheap.

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