Minimal PLC

[richanton]

I have an application where I would like to be able to monitor maybe 6 analog and 6 digital points. I'd like to be able to just buy a real small PLC in a box and then plugin to a laptop to view the point status, alarms, etc. I also need to be able to send the alarms to a remote building management system that talks Modbus. I'm looking for cheap and dirty because it's only temporary. Has anyone done anything like this?

 

[ScottyUK]

Not sure about Modbus capability, but something like an A-B Pico or Siemens Logo! controller would meet the requirement otherwise.


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If we learn from our mistakes I'm getting a great education!

 

[amptramp]

Look at the DL06 line of PLC's from Automation Direct (

http://www.automationdirect.com).

The DL06 supports analog i/o via expansion modules and has a built-in RS-485 port that supports modbus. The DL06 has an option for a bulit-in LCD that can display register info and i/o status. See

http://www.automationdirect.com/static/specs/dl0506select.pdf

The DL series of PLC's are made by Koyo. Koyo has been making PLC's for a long time. They manufactured the original Series One PLC for GE.

http://www.automationdirect.com/static/press/koyo.html

Automation Direct is typically a low cost source of automation suppliies.

 

[eeinpa]

I agree with the comments on the Koyo DL05 and 06. They are nice units and the support software is pretty good. Unfortunately you have to buy the full software, which will exceed the hardware cost for your one-off project. AutomationDirect has recently added a "Click" lower cost PLC with completely free software, but not sure what it can do.

You might also consider the Eaton/C-H ELC line, which starts at $99 and has RS485 for Modbus. Programming software is free. The documentation and software are not even REMOTELY close to the quality of the Koyo (massive boo to Eaton!), but if you are willing to work at it you can figure it out. And the product does appear to reliably do what it claims.

I am using the Eaton PV28 "high performance" controller, because that base PLC will accept TWO moderately fast quadrature encoders with NO added hardware, for only $299. Try that with a Koyo and you will rapidly run through dollars.

 

[RajeevCell]

I would recommend Teco SG2 "smart relay" line of products. Siemens Logo was based on Teco. But Logo will not have 6 Analog inputs or Modbus. The SG2 line would have both modules.

 

[itsmoked]

They are at factorymation.com.

I've used them several times with generally good results. The price is right. The manual is less than great.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[eeinpa]

I fooled around with the Teco SG2 software downloaded from factorymation.com and have to say I was very disappointed in its limited abilities. If all you want to do is some very basic logic or interface to i/o points, it might work ok, but it seemed pretty difficult to use for any significant control. I think the ELC line offers far more capacity at its lowest levels. The documentation for the ELC is perhaps a tad better, though both companies should be ashamed!

For example, Teco SG2 ($80+) has only 200 lines or 99 function blocks of program memory vs. 4.5k memory in Eaton ELC-PB14 ($99). Granted, the SG2 does have a unit with 8 analog input for much less than the ELC... just depends on your needs!

I think it's cool that there are so many options in low level devices these days. There are a lot of solutions to your problems. Has anyone ever used the EZAutomation.net products I stumbled upon the other day? American made? What's that?

 

[richanton]

Thanks for all the suggestions. This is very helpful.

 

[itsmoked]

Just a noted correction. All the same style "smart relays" like LOGO!, Teco, Square D's version, and several others, are based on the LOGO! not the Teco. Siemens designed the original.

And Yes TECO's manual is horrid but you can't beat the price.

Keith Cress
kcress -

http://www.flaminsystems.com