relays,contactors, PLC's etc

[freeradical]

You will need a DPDT not a single throw.

Remember, you are switching the ouput of the ballast, not the power to the ballast. Your cord to your lamps have two wires, maybe three with a ground? You need to switch both wires. Obviously the ground does not have to be switched.


SOMEONE JUMP IN AND CORRECT ME IF I AM WRONG

The two lamp commons can go to the same ballast common (relay common). But now after reading your post, I realized the extra functionality of a DPDT. You cannot use other devices on the same relay with an SPDT because you are flip flopping the ballast voltage and regulated current. With a DPDT, one pole will be dedicated to the ballast, and the other to 120v devices (or whatever your household voltage is). DPDT it is. Thanks yamaha.

 

[yamaha_1fan]

http://www.icmag.com/ic/showthread.php?t=35561&page=1&pp=15&highlight=flip


It may work your way but every discussion about building a flip-flop uses DPDT relays and they flip the hot and common to the lamp. There must be a reason but I dont know what it is.

 

[Azeotrope]

Be carefull!!! The starting pulse from the ballast can hit the 4kv to 5kv range and will blow out "relay" contact pads. You need 600v, 4 or 5kv rated contacts to do it right. A lot of the grow room stuff is just spun together without a lot of thought in regards to safety.

You should look for a contactor instead. I do not wish to rain on one's parade, this is an area in which I am an expert. There are many areas of this growing craft in which I am not an expert.

Safe Growing to all!!!

 

[badugi]

The contacts on the 5X847 are silver cadmium alloys, that will help with the inevitable arcing.

Regardless, good thing I'm using contactors.

 

[boolmag]

PLCs are cool
I only have a tiny cab for a couple plants at a time but I hooked up all devices to it for easy control, not that's there's much anyway...Note everything here was free as I got it all from a fire job I was on, plus I already had the software & cables etc...anyway

 

[yamaha_1fan]

I think for the moment I am going to skip the PLC. I will have much work on my hands on this new room and KISS will be key.

I will be running around 9k per room to start (two rooms) for a total of 18K. Future plans will probably have each room running 15-18K, basically doubling the lights.

I am pretty sure I will be running 600's 3-4 per table. So that is 12-16 lights per room. I can get the ballast kits for about a hundred bucks each

If I was going to flip the lights, would it be wise to stagger the startup? Maybe 2500W at a time, every 5 minutes?

I am thinking if i want to stagger the lights, I may be better off skipping the flip, and just using ballast for each room, some timers and contactors

 

[badugi]

Yes I think you should stagger the startup by banks of ballasts. Maybe one light at a table at a time, rather than lighting up sections of the room at a time.

 

[Azeotrope]

badugi -

Good call on the contactors. I replace many failed relays, contactors and such in my line of work and also use them in new design and service. I see them incorrectly applied and installed at times. I believe in trying to cycle the line side of ballast (primary) where possible.

 

[hoosierdaddy]

Nice set-up with that AB, boolmag!

 

[yamaha_1fan]

I was doing some thinking and I think a flipflop would be the best choice versus multiple ballasts.

To stagger startup times, I was just going to use multiple timers with different programs.

But now I am also considering hot starts. If the power goes out, can a PLC sense that and start the lights back after 15 minutes, then stagger the startup?

I found this site http://www.plcs.net/contents.shtml to help learn PLC logic. Anyone know it or can recommend another site?

What PLC would be good in this situation? What would I need to sense a power outage?

 

[Stay Puft]

I was doing some thinking and I think a flipflop would be the best choice versus multiple ballasts.

I do not feel it is a good idea to switch the ballast output unless you have carefully selected the PROPER relay. Azeotrope pointed out the exact reason for this.
I see lots of people here switching the ballast output (HV) with contacts that are not rated properly for the application. I do not subscribe to the "well it works" approach when it comes to these kinds of activities. You MUST consult the data-sheet for your switching devices and ensure you are operating them within the mfg. ratings. K?

But now I am also considering hot starts. If the power goes out, can a PLC sense that and start the lights back after 15 minutes, then stagger the startup?

One approach to consider: It may not be required for the PLC to actually "sense" a power outage. What if the programming in the PLC had a fifteen minute delay at the start of its program? (The program ladder starts from the beginning when power is removed/ applied) That would achieve the same results.

If you wanted to do this with relays, you would use a "retriggerable delay-on" relay.
Regards,
Puft

 

[yamaha_1fan]

Well is there a proper relay for this? There is one part # floating around here that everyone seems to be using. Is that the wrong relay?


Forgive me as I have never used a PLC, but lets say that we use a PLC with a clock. Lights come on at 3:00PM with a 15 minute delay, off at 3AM. Now lets say there is a brief power failure at 11:00PM. Will the logic say, hey its only 11:00, we need to turn the lights on and still keep the 15 minute delay or will it just turn back on? Same thing with the staggering, will it keep the staggering pattern

I guess we dont need a clock but just that it turns on and off every 12 hours. But if the PLC reboots after 8 hours of lights on, will it start another 12 hour cycle?

Hope I explained my concerns correctly.

 

[Stay Puft]

More good questions:
A PLCC with a real time clock keeps track of the current time without power. (actually a battery keeps the clock going-just like your PC)
We would only buy a PLCC with a Real Time Clock (RTC) for this application. This RTC enables the PLCC to keep time even when power is removed. (It knows "what time it is" all the time [once set] lol)

If your programming is good ..it will still have the delay and staggering.
You should not associate the 15minute delay (hot start prevention) with the timer function. This is not what you want. You would insert your 15 min before the timer, instead of behind it.
Almost all PLCCs I have used will place the relays in the "off" (de-enegized) position when power is removed and returned unless the software specifically tells it turn back on.
Ihope that makes sense sorta.
Salutes!
Puft

 

[Stay Puft]

For your PLCC software developmenterhaps you should try a flowchart to think this out....

Edit: I do not mean to dodge the relay question. My first choice would be to use a seperate ballast for each lamp and switch the AC Input to the ballasts. When you are talking ~10KW op, the added cost is not THAT great. (compared to risk of failure)
The problem with "certifying" a relay for this application is almost impossible to get "real numbers" plus it would most likely be cost prohibitive. It is very difficult to calculate what the exact max voltage for a HID system is.... especially during a lamp failure! (The D is for discharge--no path to discharge!!eeek)
Like Azetrope said it is at least in the 5K-6K V range for sure. Now... you also want it to carry how much current?
Most relays that fall into this class will be considered specialty items and cost plenty of extra$ !
You can buy 120V/240V relays (in almost any configuration/current rating) all day long for cheap.
These are the reasons why it is prudent to just buy the extra ballast and switch the mains instead.
As always..i could be wrong..
Let's face it..deep down- I am a F-ing Marshmellow!

 

[yamaha_1fan]

What kind of PLC would you suggest I get? I googled PLC and there are so many kinds, its mind boggling. I assume I want one with a display so I can program?