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Old 6th Sep 2019, 1:46 pm   #1
Chris55000
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Default Depicting Rotary Switches in the simplest way on diagrams?

Hi!

Have any Members got any suggestions for depicting Rotary Switch Wafers on Circuit Diagrams?

I know virtually electronics primer or reference book that shows electronic circuit symbols will draw something like a 3P 4W rotary switch as a pole in one of four positions, but a lot of the wafers on T & M like oscilloscopes, signal generators, valve–testers, etc., etc., are a good deal more complex than this, with special shorting and non–shorting functions that open/close simultaneously in various positions, etc.

Tek use SPST symbols referenced to a table showing which contacts are made in each position but I don't think this works for wafer switches!

This problem's often made more difficult by there being no indication as to which position the diagram was drawn in, Levell, cough, cough!!

Ideas/Suggestions?

Chris Williams
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Old 6th Sep 2019, 1:59 pm   #2
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Default Re: Depicting Rotary Switches in the simplest way on diagrams?

Can't speak for 'scopes etc but for radio receivers the Trader sheet method is one I always found easy to understand and follow, it gives a switch table showing what's open and what's closed for the function selected, the columns running left to right for fully anti-clockwise through to fully clockwise, and wafer diagrams showing what tags are what and where viewed from.

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Old 7th Sep 2019, 11:35 am   #3
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Default Re: Depicting Rotary Switches in the simplest way on diagrams?

I totally agree with Lawrence on this.
Quite a few maker's diagrams get awfully complicated where many wafers and contacts are part of one switch assembly, and thus difficult to follow. This is exacerbated when viewing second generation photocopies or poor photographs of the diagram.
Being able to refer to a table of functions of the contacts is far easier.
The main proviso then, is simply that the contact identification letters/numbers are clearly visible on the diagram. Tony.
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Old 7th Sep 2019, 12:19 pm   #4
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Default Re: Depicting Rotary Switches in the simplest way on diagrams?

yes I prefer a table too, makes fault finding easier as it allows you to include or discount particular circuit routes when tracing what's happening. I dislike the 70's habit of some circuit draughtsmen who depict a rotary switch as a ganged sliding switch stuck in one position with ambiguous symbols to show which bit moves and which bit doesn't.
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Old 7th Sep 2019, 2:40 pm   #5
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Default Re: Depicting Rotary Switches in the simplest way on diagrams?

Quote:
Originally Posted by McMurdo View Post
<snip>I dislike the 70's habit of some circuit draughtsmen who depict a rotary switch as a ganged sliding switch stuck in one position with ambiguous symbols to show which bit moves and which bit doesn't.
Hear, hear.
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Old 8th Sep 2019, 1:01 pm   #6
Chris55000
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Default Re: Depicting Rotary Switches in the simplest way on diagrams?

Hi!

In the light of Member's replies to the question I posted to begin this thread, I think that a separate Circuit Diagram sheet showing each contact function separately on an extract of the main diagram, with a table showing which contacts are made/not made in each position of the switch, is the way to go forward!

I have found it IS possible to draw rotary–switch wafers schematically on my S Plan circuit–diagram software, but it's not a quick or easy job – it does need a lot of patience!

Also, of course, you do need an example of the actual equipment in order to compile a switch contact table, as you need to verify which contact segments close/open in each position with a meter, unless you can mentally "draw" each switch wafer position from a maker's diagram which I can't!

I might add I don't think any UK maker that draws rotary wafers on diagrams has ever bothered to compile a contact function table, Gould, Farnell, Scopex, Dynamco, etc., all don't!

Chris Williams
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Old 21st Apr 2020, 1:07 pm   #7
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Default Re: Depicting Rotary Switches in the simplest way on diagrams?

Thread reopened at OP's request.
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Old 28th Apr 2020, 12:26 pm   #8
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Default Re: Depicting Rotary Switches in the simplest way on diagrams?

I dont have anything to add but never found a good way of showing switches. I do struggle with many a schematic. good question.
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Old 28th Apr 2020, 8:14 pm   #9
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Default Re: Depicting Rotary Switches in the simplest way on diagrams?

Hi!!

I eventually came to a conclusion from the Solartron CD1740 Service Manual and ERT Service Sheets combined!

I found it I draw each pair of contacts as a SPST contact nearest to the switched components, then placed a table next to the contacts showing which closes for each function, that depicts the switching arrangements, then place a drawing of the physical wafer below the switch contact symbols in the position annotated on the Maker's bookwork, that then 'keys' the wafer to the switching arrangements a bit more clearly than just drawing a wafer on the circuit diagrams alone!

Once you've drawn or (photographed the wafer if actually have the piece of gear!) copied the wafer, you can draw a P.W. style wiring diagram showing the wiring connected to the wafer switch tags!

Chris Williams

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