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Air pressure fan regulation. [project suggestion]
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Ttelmah



Joined: 11 Mar 2010
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PostPosted: Sun Jun 21, 2020 12:52 pm     Reply with quote

Quote:

The SSR is ZCD.


No it isn't. The part number he quotes is not a ZCD part.
temtronic



Joined: 01 Jul 2010
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Location: Greensville,Ontario

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PostPosted: Sun Jun 21, 2020 1:48 pm     Reply with quote

Just throwing this out for thinking....
AC motor control is 'challenging' at the best of times and I'm wondering if there's an inherent problem with using both a ZCD sensor and a ZC SSR. Depending on the program there could be a signifigant time delay between the sensor seeing the ZC and the actuation of the ZC SSR.
Say the ZC sensor trips at the leading edge of the +ve going phase.....then some 'math'...THEN the ZC SSR won't fire until the -ve going edge of the sinewave.

Hopefully someone well versed in this can shed some light on whether I'm right or wrong or if it really matters .....

Jay
bkamen



Joined: 07 Jan 2004
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PostPosted: Sun Jun 21, 2020 5:57 pm     Reply with quote

Ttelmah wrote:
Quote:

The SSR is ZCD.


No it isn't. The part number he quotes is not a ZCD part.


I was saying from my project. (poorly worded)

I'll go back and word it better...
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bkamen



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PostPosted: Sun Jun 21, 2020 9:17 pm     Reply with quote

temtronic wrote:
Just throwing this out for thinking....
AC motor control is 'challenging' at the best of times and I'm wondering if there's an inherent problem with using both a ZCD sensor and a ZC SSR. Depending on the program there could be a signifigant time delay between the sensor seeing the ZC and the actuation of the ZC SSR.
Say the ZC sensor trips at the leading edge of the +ve going phase.....then some 'math'...THEN the ZC SSR won't fire until the -ve going edge of the sinewave.

Hopefully someone well versed in this can shed some light on whether I'm right or wrong or if it really matters .....


That's a valid question -- and I remember thinking/wondering about it too.

I designed that gizmo almost 10yrs ago. I'd have to go back and look at the details.

-Ben
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Ttelmah



Joined: 11 Mar 2010
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PostPosted: Sun Jun 21, 2020 11:21 pm     Reply with quote

Thanks Bkamen. It read as if you were saying his circuit was using
a ZCD SSD. Smile

Fortunately, the inertia of motors 'helps' here.
You can switch off for three or four half cycles, and then on for just
one, and the motor merrily keeps swinging, but at a much reduced
speed. The big question is how quickly the motors slow, since this
affects how easy they are to genuinely speed control reasonably.
I've done controllers in the past allowing this type of motor to be
linearly controlled, but for this I synthesised the AC waveform using
MOSFET choppers, and could give a genuinely frequency controlled AC.
Unnecessarily complex for this application.
bkamen



Joined: 07 Jan 2004
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PostPosted: Mon Jun 22, 2020 9:48 pm     Reply with quote

Ttelmah wrote:
Thanks Bkamen. It read as if you were saying his circuit was using
a ZCD SSD. Smile



No problem.

And I need to go back and ultimately look at what I used --- as Jay mentions,

I may have originally opted for a ZCD SSR -- but not ended up needing/using one because of sync delay issues.

I'd have to go look -- but we've talked about it so the OP is aware.
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Dazed and confused? I don't think so. Just "plain lost" will do. :D
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