Router Table w/Logic Controlled Motorized Lift

[LCHIEN]

Very nice. I wonder if a Raspberry Pi or other small controller would work?. Are there sensors on the motor or external?

the PLC the OP used is a special purpose "computer" that has conditioned I/O for switches and digital inputs and digital outputs, often A/D and D/A too but it appears the OP did not use any. The PLC also has native O/S programming which is specialized to run control programs that respond to the I/O and control things according to special commands.

The Rspberry Pi is a relatively more general purpose single board computer. It can be used in the same way. Its I/O probably requires some conditioning (surge protection etc when used around machinery) and perhaps an external board. The device also comes with out a O/S but they can be added. Programs in general purpose languages like C can be written to repond to and control inputs and outputs to accomplish the same thing, but with a lot more programming.

THe PLC is probably more like a forklift. Specialized for a specific class of task. THe Raspberry Pi is probably more like a light duty pickup truck. It also can carry stuff but its more general purpose. Outwardly they're similar - have four wheels, can be moved under their own power and steered and can move stuff.

The raspberry is also a barenaked board. An industrial PLC is usually a complete system with power supply and industrial (heavier duty than office or home electronics) duty cabinet and complete I/O panels for professional installation. The Raspbery is probably under $50 and the PLC is probably many hundreds if not $1000 or more.

Denco (the OP) used the PLC because he 1) got it free since it had one damaged input he wasn't going to use and 2) he was already familiar with how to program it.

[Denco]

"the PLC the OP used is a special purpose "computer" that has conditioned I/O for switches and digital inputs and digital outputs, often A/D and D/A too but it appears the OP did not use any. The PLC also has native O/S programming which is specialized to run control programs that respond to the I/O and control things according to special commands."

In response to the "Non-OP" (just kidding, Loren), it wasn't necessary to use the analog features in the controller. Digital was all that was needed. It uses what we call "block" programming, which are just digital gates (AND, OR, NAND, NOR) etc. Ladder logic is commonly used in many PLC's.

This program just had to turn motors on and off and look for conditions such as upper limit and lower limit. No speed control or anything like that. For motor speed control, I just added an aftermarket control (it's the red box above the control panel). I put in counters such as total time used on the motor and the overall system, and a hidden function or two. No upper level programming languages in this unit. We utilize higher level program languages at work, but putting a PLC in the router table was overkill enough. No need to go further. It was just simple programming, nothing like I deal with at work......however, I did consider having the router table activate my coffee pot, but LOML didn't want to have to go out to the shop for a cup.

For those not familiar with PLC's, they are often used to control machinery in factories and will have custom programming. It's the norm. Out of the box, they aren't generally programmed. In my industry (wastewater), they control pumps at treatment plants or onsite systems, telemetry, alarms, variable frequency drives, and the like.

[Bruce Cohen]

That is really cool, now do you have any energy left to make something with it. We got to see the pictures.

Bruce

[Tom Slick]

Another difference between a Raspberry Pi and a PLC is the PLC can be programmed in "block" format (as Denco mentioned) which is a dragging and dropping icons for various functions and connecting them together to get the logic sequence you want. There is no code writing, just a visual diagram (flowchart) that you manipulate.

Denco, Does the Logo only have relay output?

[Denco]

Denco, Does the Logo only have relay output?[/QUOTE]


The LOGO I used is the 120V version. 8 Dig Inputs, 4 Dry Contact-type Outputs.