Please tell me what I need to buy

[malifluous]

I am new to PLC's so please explain in detail what I need and who to buy from. I grow microalage and need a PLC to control illumination based on the density of the microalgae
I will try to exlain.

I would like purchase a PLC that will communicate with an optical density probe. The optical density probe would send 4-20ma outputs to the PLC. The PLC would control 20 lights . Each of the 20 lights would be 200 watt flourescent lamps. For example, Dictaed increasing density I need increasing light intensity. Light #1 would be on all the time, light number 2,3,4,5,6 etc would turn on and stay on with increasing density. I have everything but not sure hwat/ where to buy the right PLC. Any info about this would be greatly appreciated.

 

[controlsdude]

depends on if your familar with siemens or AB or whoever.

If you a low IO count and you like AB PLCs, I would go with a Contrologix PLC that is the Compact Logix brand. This way you can easily expand it in the future.

I would get ahold of your local plc reps. They can snowball you but it would be an easy way to see the plc lines yourself, then see how the local support where your project is going. All things being equal, the local support is critical if your not familar with plcs.

 

[roydm]

malifluous,
Your need is fairly basic 1 analog in several digital out, free software.
Steer clear of the big ones like Allen Bradley, Siemens, Modicon
Try Direct Logic or Automation Direct, Opto22 as suggested in the "Home PLC" thread.
You need to be careful with the output module, make sure it's rated high enough for the flourescent fittings, I suggest use interposing relays.
4,000 Watts of light, I hope you have sun glasses!
Roy

 

[jraef]

Actually, you could do this task with a smart relay, like the Siemens LOGO! (the exclamation point is officially part of the name, not a commentary). It can take the analog input and decide on light sequencing based on your simple logic. People use them as lighting controllers all th time.

 

[malifluous]

Thanks form all the replies. What should I expect to pay for this. I spoke to someone about LOGO! They said the cost of the hardware and programming would be about $2000. Im still waiting on an official quote.

 

[Skogsgurra]

Aren't you getting rather narrow-minded wrt makes lately, Jeff? ;-

Anyhow, it is a feasible solution. But, you may need to do some not so obvious coding of the outputs to get all those 20 lights controlled by the typically four outputs available in a LOGO! (if you do not expand the I/O).

I think that it could be done with four outputs. But you may have to reduce the number of lights to 16 instead of 20. And arranging them in powers of two would definitely make a "four out" solution possible.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

How much? 2k is reasonable if you are having someone else do it all.

If you are going to do it all. I'd guess around $300-400 in hardware.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

USD 2000 is way too little if you want it done by a professional.

Even if the task is simple - there is work to be done.


Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ykee]

Why not use lighting controls? You could use some of the Wattstopper products, and these will even dim, if you have dimming ballasts in the fixtures. A lot of companies sell relays to control the lights based on a 4-20mA signal, they are often called "power-packs" or something similar to that. These will elimiate the need for programming.

http://www.wattstopper.com/products/productline_list.html?category=20&type=Commercial

http://www.wattstopper.com/products/productline_list.html?category=30&type=Commercial

 

[malifluous]

Ykee, Thanks for the tip. his seems like the simplest way to do it. I could not find anything with 4-20ma control on the website but I will contact the company tomorrow.

 

[roydm]

Malifluous,
I think you should write yourself a mini specification describing what you are trying to achieve.
What input you have
What outputs you want to control i.e. Volts, Amps
What sort of interface with the control system you would like e.g. hard wired switches, touch screen, PC
Any requirements to log data e.g. how many lights are on

Then pass it around some of the PLC vendors, That way you will find out what they have to offer.

I think your 200 Watt flourescents will be hard on contacts so you should specify 5 Amp contacts at least.
I took a look at Direct Logic DL-05, I have never used one but it looks as though it would do the job.
Regards
Roy

 

[roydm]

I just went on the Direct Logic website
For $950 you can get
DO-06AA Chassis with processor
D0-06LCD Optional LCD display
F0-04AD-1 4 input analog card
2 x D0-10DT1 10 output modules
Software for a PC
D2 DSCBL cable for programming with PLC
(Perhaps someone with experience in the DL PLCs can check over this list)
There is a free version of the software on the website, I suggest you download that to try.

The DL PLC does have an AC output module but the contacts are only rated for 2 amps and as they have 4 outputs you wouldn't have enough slots. Some of the other chassis have DC outputs which would save you one output module but if it were me I would use 2 the same.

You would still need a small relay of each light with 24 VDC coil
A 24 VDC power supply to power the relays and your transmitter 2 Amps should be enough.
Fuses perhaps 1 x 10 Amp for every 4 lights
Terminals - about 20
Din rail to mount the terminals and relays on
a few feet of wire duct 2 x 2 to keep your wires tidy
Panel wire, 2 sizes in several colours
An enclosure to put it all in NEMA 12 if it's dry, NEMA 4 if its outside or wet
24" x 24" x 6" should be large enough with a removable panel.
If you go to an electrical wholesaler and tell them what you are trying to do they will probably suggest appropriate hardware.
Another suggestion would be to let a panel shop supply and wire the hardware, that way you would get a nicely finished product.
Good Luck with your project
Roy


Terminals

 

[jraef]

Don't know all your specs, but $2000 seems really high for a "smart relay" (OK Gunnar, no brand mentioned!).

The base relay with 4 relay outputs would be about $150, tops
2 ea 8 point relay I/O expansion (for 20 outputs total), about another $90 each so $180,
1ea 2 channel analog input module, about $80
Programming software package, probably no more than $150

That comes to $560. Where is the other $1400 going to come from? Are you sure that wasn't a package price that included programming?

 

[danbarber]

We have had success with Panasonic PLCs & Toshiba PLCs. We mainly use them on VFD applications.

http://www.clrwtr.com/Panasonic-PLC.htm

http://www.ctiautomation.net/Toshiba-PLCs.htm

I believe IDEC manufactures a pretty good SmartRelay if you want to go that route.

 

[Skogsgurra]

I think that USD 2000 is quite cheap if you are getting a cabinet, a terminal strip, schematics, operation manual, a few push-buttons, power supply, output relays, fuses, a main switch, the PLC, the program and all that one assumes comes with a complete control system. Good luck if you got a quotation in that range!

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[jraef]

D'oh!
Missed the statement that the $2k was for hardware AND programming. I agree that is a reasonable cost if only for the reason that most programmers would be unlikely to take on a small simplistic project like that without having it be worth something to them. Sometimes the cost has more to do with what that person could be making doing something else...

 

[danbarber]

If price is the biggest concern you can always go with some chinese manufacturer.

 

[itsmoked]

Yep, then later your biggest concern will change...

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jmm0837]

malifluous (Agricultural),
Hey, Just for my 2 cents. I have worked with controlling christmas lights and it's hard to get PLC's to handle the current required to turn lights on and off.
Most PLC relay contacts are rated up to 3A, but the real problem is the Common amperage. Some PLC's contacts can handle the 2 amps per Point, but the Output commons are limited to 6A.
As with the Automation Direct D0-06AR series, it has 16 relay outputs which you need to control your lights, but it has only 4 commons, so that limits you to 3 lights per common instead for the supplied 4. So now you have to buy more Output modules.
I would still recommend going with the Automation Direct, but use Solid State Relays controlled by the DC Outputs of the PLC. That way you can buy the SSR at the amperage you need for each light.
Parts:
D0-05DD - $99.00 PLC (8 DC Inputs/6 DC Outputs)
D0-16TD2 - $54.00 (16 DC Output Card)
F0-04AD-1 - $79.00 (2 channel Analog Card)
PC-DS100 - $0 (Software)
D2-DSCBL - $30.00 (Download Cable)
16 - Solid state relays $17.75 (AD-70S2-04B)
16 - Relay Bases $3.50 (782-2C-SKT)
System cost $687.00

 

[swhitlock]

I suggest finding a couple local control system integrators in your area (even if they're small 1 to 10 person shops), invite them over to take a look at your requirements, and ask them for a fixed price quote. They'll generally quote the hardware they're most familiar with, which is good because then you'll have local support for your system (in case it has problems or you need changes later).

Remember the following costs:
- Power supply (didn't see that in the parts list above)
- Panel construction and electrical installation (you may be able to do this in-house, but it's still a cost)



Scott Whitlock
PLC Programming Articles:

http://contactandcoil.com/