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Old August 24th, 2009, 04:38 PM   #1
juanmdx
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Home Automation - Dim Lights with PLC

Hello,

Can anyone tell me how can I dim the lights with a PLC (maybe external relays, but which ones?), I'm doing some home automation and this is the last thing I need to control.

I really don't care much about which PLC brand I'm going to use, I'm pretty familiar with Siemens, AB and Beckhoff, so I'll just go with the cheapest one I can get here.

Right now I'm quoting the project, but I've had a difficult time figuring out how to dim the lights.

Hope someone can help me.

BR

Juan
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Old August 24th, 2009, 06:19 PM   #2
LadderLogic
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Beckhoff may be the answer because they have this: http://www.beckhoff.com/images/bus_t...L2761__web.jpg
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Last edited by LadderLogic; August 24th, 2009 at 06:42 PM.
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Old August 24th, 2009, 09:45 PM   #3
leitmotif
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Quote:
Originally Posted by LadderLogic View Post
Beckhoff may be the answer because they have this: http://www.beckhoff.com/images/bus_t...L2761__web.jpg
With respect to link
I did not get any inkling of how that will control lighting - there was no spec's or description.

relays are basically nothing but a switch - the controlled load is either on or off.

A bit more information about what kind and location of lighting you want to control would sure help.

you may want to go see a lighting distributor and see what they have for this idea or for other options.

What kinds of control are you trying to do with PLC that you cannot do with "standard" lighting control?

Intensity with respect to outside ambient light, occupancy, or,,

Dan Bentler
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Old August 24th, 2009, 10:03 PM   #4
LadderLogic
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Quote:
Originally Posted by leitmotif View Post
With respect to link
I did not get any inkling of how that will control lighting - there was no spec's or description.
My bad, Dan: I gave link to a picture, not the page. Here is the correct link: http://www.beckhoff.com/english.asp?...nal/kl2751.htm

KL2761 has higher output power rating but apparently exists only in 220VAC version; KL2751 supports 120 VAC as well. There are links to documentation files on the sidebar.

My guess is this is an SCR bridge with variable phase control.
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Old August 24th, 2009, 10:13 PM   #5
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If you are trying to control intensity of the light based on ambient light.
Then use LDR for input to sense the ambient/reference light and scale the block in the PLC and trigger an analog output and connect this output to a input of SSR and load side to the lamp.
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Old August 24th, 2009, 10:26 PM   #6
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Quote:
Originally Posted by LadderLogic View Post
My bad, Dan: I gave link to a picture, not the page. Here is the correct link: http://www.beckhoff.com/english.asp?...nal/kl2751.htm

KL2761 has higher output power rating but apparently exists only in 220VAC version; KL2751 supports 120 VAC as well. There are links to documentation files on the sidebar.

My guess is this is an SCR bridge with variable phase control.
Looks like a neat setup - maybe a little too professional or industrial for home use?

Phase control is a new term to me in controlling lighting. I think like you say SCR voltage control using PWM.

Dimming fluorescants was quite expensive about five years ago not sure if price has dropped that much. Think made by Lithonia or maybe Lutron??

Experience Music Project in Seattle - 1998? - had all kinds of fancy lighting and controls. All variable light units were incandescant type. As best I recall fluorescant was not dimmable.

Dan Bentler
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Old August 25th, 2009, 06:59 AM   #7
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I'm thinking it will be prohibitively expensive to do what you want with a PLC. If you insist on PLC control of lighting, I would go with one of the many available lighting controllers that allow RS232 control and have the PLC serially manipulate the lighting controller.

Lutron, UPB, Z-Wave all have controllers w/ dimmers that are RS232 controllable.
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Old August 25th, 2009, 08:02 AM   #8
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This is somewhat like using a PLC to drain your swimming pool. Yea, it can be done. Does it make real good sense? Not in my opinion. Too much custom-made hardware out there makes lighting control simple.

Now, using the PLC to control curtains, theater screen, yard irrigation, hey, I'm all with ya.

Just my 2 worth.

Bill
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Old August 25th, 2009, 09:33 AM   #9
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I just got the image in my head of a servo motor controlling a dimmer switch and it made me laugh....just thought I'd share...
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Old August 25th, 2009, 10:54 AM   #10
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Quote:
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I just got the image in my head of a servo motor controlling a dimmer switch and it made me laugh....just thought I'd share...
Its not that wild just a variation of a method used in the past.
Church I know of had a large motor driven variac to dim lights.

Dan Bentler
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Old August 25th, 2009, 11:32 AM   #11
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Seriously, for home automation, use something designed for it. ZWave products are becoming very inexpensive, and are incredibly more robust then the old X-10 system.

Some info:
http://www.zwaveworld.com/
http://www.leviton.com/OA_HTML/ibeCZ...4&respid=22372

ZWave products include everything from lighting/outlet control, to thermostat control, door locks and security monitors.. even multi-speed fan control.
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Old August 25th, 2009, 12:50 PM   #12
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Here is a past thread on the subject:

http://www.plctalk.net/qanda/showthread.php?t=15812
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Old August 26th, 2009, 12:38 PM   #13
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Does anyone know which Function Blocks are related to the KL2751 (or KL2761), I downloaded the building FB's on http://www.wagotoplon.com/html/eng/p...plications.htm
but I wanted to know if there are any specific FB's for this KL's.

Thanks

Juan
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Old August 26th, 2009, 12:46 PM   #14
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Quote:
Originally Posted by juanmdx View Post
Does anyone know which Function Blocks are related to the KL2751 (or KL2761)
It's been a while since I used the KL2751, but I think you only need to send a value (0-65535) to it and the brightest of the light follows. What were you actually wanting a FB to do?
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Old August 26th, 2009, 12:51 PM   #15
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Well I know I can gradually dim the lights like from 25% to 65%, but I was looking for an FB that could do that, to avoid the fors or whiles I might use.
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