Automation - Is PLC Best Option?

[uptickk]

Hello,

I am new to the forum (not a engineer) and trying to get some advice from those that are more experienced.

I am trying to automate a process on a limited budget. I have a wheel that has 8 molds attached (equally spaced) with a lead pot above that pours lead into the molds when they pass under the pot. The wheel rotation is motorize by an indexing arm so I have a fixed amount of time to pour the lead into each mold before the arm indexes. I would like to purchase a trigger sensor that acknowledges when a mold is under the pot. At that point it would activate a timer to wait approximately 0.5 seconds (needs to be adjustable) before allowing an electric solenoid to pour for 2 seconds (needs to be adjustable). Once the arm indexes the trigger sensor would release restarting the cycle. The idea is that the pot would not be able to pour lead into a mold unless a mold is present.

Now to the question. Since this is such a simple cycle does it make sense to purchase a PLC or is there an easier/less expensive way to automate the process? I like to tinker but do not even know where to begin with which PLC to purchase if that is correct route or what type of timers, senors, solenoid I would need.

Any help would be greatly appreciated.

 

[IRstuff]

Depends on what you mean by PLC. There are industrial PLCs, intended for controlling industrial processes and machines, and monitoring industrial sensors. There are small microcomputers that can do most of what a PLC can do, like the Arduino:

http://www.aliexpress.com/item/Mega...able-Free-shipping-Best-prices/689721585.html

or

http://www.aliexpress.com/item/Best...le-Free-Shipping-Dropshipping/1140229347.html

They have A/D, D/A, digital inputs/output, etc. Obviously, much more DIY than a commercial PLC. This kit:

http://www.aliexpress.com/item/-/937711496.html

shows pretty much what can be attached to and used by an Arduino.

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[tygerdawg]

A small industrial PLC is a very good fit for this. The advantage of PLCs is that they are build for industrial use, can survive quite a lot of abuse and generally very robust. They are programmed in ladder logic, which is a very easy graphical programming environment. Pro's and con's of various small PLCs have been discussed in detail here. The brand that seems to bo on everyone's list is AutomationDirect. There are others.

You make no mention of how much cost is too much, and the magnitude of cost is always relative to one's perception. But it seems to me this could be a very simple, inexpensive solution.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[jraef]

http://ab.rockwellautomation.com/Programmable-Controllers/Micro810

This is an example of what's often referred to as a "Smart Relay" or a nano-PLC, something like this would be a good candidate for your application. PC programming software is free from the various vendors and if you later want to expand the capabilities, the program is exportable into more capable versions (at least in this version). Plus typically now the software also programs a set of small HMIs that can be added later if you want to make changes to time values without the software. These things typically start at around $100 each, depending on I/O configuration and voltage.

"Will work for (the memory of) salami"

 

[uptickk]

Thank you for all your suggestions! I have been looking into each and think I might be over engineering this. I think I might be able to use a simple solid state timer,

http://www.mscdirect.com/product/54051123?fromRR=Y.

In addition to the timer I can use a trigger switch to acknowledge when a mold is in place and a pour solenoid to pour the lead. The timer isn't cheap but I think I can pick one up used to cut down on costs.

Thanks again all and I will let you know how it goes once I get all the parts.

Still would like to play with a PLC but will wait until the need arises I guess.

 

[xyzz]

Uptickk, you are doing a typical mistake of a novice in automation: you imagine more or less clear the normal operation of a system, but do not think of malfunctions.
Here is an example: what if the sensor signal disappears instantaneously when the pouring is in process?
If all the logic (hardware or software) is two cascade timers driven by the sensor, timing will restart, and the entire pouring will be redone and added to the terminated one.
And here comes the advantage of a programmable controller:
you can add, delete, or modify the logic, in order to correct own mistakes and omissions.
The mentioned timer costs comparable with entry-level PLC, not to mention programmable relays (smart relays).
I would strongly suggest using a programmable controller.

 

[xyzz]

Forgot to mention: look for a controller with integrated display, to allow the necessary adjustments.

 

[waross]

I like the smart relay suggested by jraef. A smart rely was my first thought when I read your original post.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

Lol, you are going to pay nearly twice as much for that timer as you would for a smart relay that will do everything that timer will do, yet the timer does less...

Oh well, to each his or her own I guess.

"Will work for (the memory of) salami"

 

[waross]

You missed a small point Jeff. The OP wants a time of .5 sec (adjustable) and a time of 2 sec (adjustable), so that makes two timers for about 4 times the cost of a Micro810. LOL with you.

Bill
--------------------
"Why not the best?"
Jimmy Carter