symbols, so it shows a capacitor and a variable capacitor.
Someone has told us it is switch contacts, yet it is not a ladder diagram, nor is it laid out like a ladder diagram, therefore they should not be using the symbols for ladder logic, UNLESS as someone else has already posted, they let the wrong people do the "artwork".
Metric or Imperial anyone?
John Rumm - many thanks (I will also use the links to better understand some PLC stuff I sometimes see at work)
To others - of course - they cannot be capacitors. It is a timer switch.
I agree it is confusing - but we have to keep an open mind. There was no way they could be capacitors.
OP
Since you are so keen on Wikipedia...try this one...symbols commonly used for PLC wiring diagrams....
In message , BigGirlsBlouse writes
But it isn't nor does it contain, a PLC, does it ?
Where did I make any claim as to being keen on Wikipedia?
You can blame british standards for the bolloxing of the logic symbols though! (and I agree - the ANSI style ones were much nicer that the square block versions).
Convention perhaps, although the varicap symbol was not right anyway. Context and logic would dictate that that interpretation was very unlikely to be right though.
Depends on your target audience I expect - if you regularly design combinatorial discrete control systems then perhaps the symbols used are more "Conventional"
Just helps keep real engineers in jobs - seeing through the layers of obfuscation and making it work anyway. ;-)
Indeed having worked on American, Japanese and European semiconductor equipment I am fairly good at Jinglish, and interpreting everyones idea of how to draw circuit diagrams etc, obviously it helps if you know what it is doing. Should see the look on the faces of some of the more mechanical minded engineers when you open up the wiring diagram books, made even more user friendly when they have been reduced from A3 or A2 to A4!
They told us in an Electrical Engineering lecture *Forty years ago* that condensers were parts of steam engines.
8-)Derek
I think that the symbols used for ladder logic on PLCs was taken directly from drawing practice for hardwired relay logic, so that Engineers and Technicians could move easily from one to the other.
SteveW
But in most other languages (according to Wikipedia page-URLs) the local term is based on condenser.
Owain
OK you did say Wiki doesn't ensure credibility... but I have used many a ladder diagram for progammable logic controllers, and the symbols used there are definitely switches...normally open and normally closed which show the very same symbols as on the OP piccie.... but getting back to to OP email...the circuit does not make sense if we assume they are capacitors...unless it makes the compressor motor rotate in opposite directions, and even then the value of variable caps is only available in Pf's picofarads not Mf's microfarads as would be the approximate value required for motor compressor phase control.
With a Diagonal Steam Trap fitted just after them.
Could be timing capacitors for the 8hrs or 20mins...
A very vague representation of the device IMHO. For instance are the switches independent or ganged (as in SPDT)?
In message , BigGirlsBlouse writes
No I didn't - where ?
But it's not, nor does it contain, a PLC
Your point of relevant interest being ... ?
Yes I was puzzled too by the timer inference.... the switches are ganged as in single pole double throw, commonly known as a changeover switch. Even tried to get on Supcos website to see what it is, but the site times out.
The symbols might look like capacitors but it wouldn't make much sense if they were.
From the OP
If anyone is still interested - I guess the diagram on the switch isn't really a circuit diagram - but a schematic of the inner workings.
Anyway - I have ordered a new switch - and have carefully noted the wiring to the existing Sankyo switch.
Old New
1 = 3 3= 1 4 = 4 2 = 2I don't understand the wiring to the compressor - I am going to assume the blue wire is a permanent neutral (perhaps for the light) and the brown neutral (4) is from the motor.
Yes, 1 and 3 are swapped between the Supco and the Sankyo diagrams.
The wiring for the Sankyo effectively shows the following:
Supply from stat is (switched) Live and Neutral.
Feed to Heater is Live and neutral. The Sankyo timer switches the heater on the neutral side. There will be no other connections to the heater.
Switched pair from the Compressor is two neutrals, one permanent (blue) and one switched (brown). The compressor will be picking up a permanent live from elsewhere. There will be a contactor on the compressor which will pull the motor in when the timer-switched-neutral pulls the contactor coil in.
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