PLC help

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RichB

RichB

Senior Member
Location
Tacoma, Wa
Occupation
Electrician/Electrical Inspector
Hi Everyone,

Need some PLC help here. Looked thru the forum and did a google search, but I have been out of the design and operastion of systems far too long, so I could use some suggestions on what we need here..

I have a test bench we built as proof of concept and it went over great---except for the constant clicking of the timers (Omron type) and the ice cube relays. So we are now looking at a small inexpensive PLC or PC based controller to run 9 ice cube relays (11 pin) and 4 timers.

My experiance has all been with the large AB and Mitsubishi types.

I have drawings and photos of the bench -- to big to post here so if you would like to see them please email or PM me and I'll send them on.

Thanks all!!

Rich
 
Awesome folks!! That's the kind of things I was looking for!!

Thanks!!
 
Thanks folks--One other question I forgot to add in the OP

I am NOT switching a load--I just need to momentarily close contacts on a coil of 14AWG to change the inductance seen on another coil--Do these need to switch a load (current or voltage) like a triac or scr
Thanks again
 
RichB said:
Thanks folks--One other question I forgot to add in the OP

I am NOT switching a load--I just need to momentarily close contacts on a coil of 14AWG to change the inductance seen on another coil--Do these need to switch a load (current or voltage) like a triac or scr
Thanks again
Click to expand...
You can get versions that have true relay outputs, just ask to be sure.

The AB Pico is being replaced by the Micro 810, go that route if it is going to be built in the future. The Picos are still going to be sold for retrofit purposes for a while, but the 810 is the future. They will start raising the price of the Picos in a little while to encourage the changeover.
 
Awesome again!1

Thanks guys. I love the info, knowledge and expertise available here--I always learn something!!

Oh and what happened to the smileys?? I can't see them or add them?

OK, now that larnin' has tooken place--kin I git home wit' pay now??

Thanks all

Rich
 
Jraef said:
You can get versions that have true relay outputs, just ask to be sure.

The AB Pico is being replaced by the Micro 810, go that route if it is going to be built in the future. The Picos are still going to be sold for retrofit purposes for a while, but the 810 is the future. They will start raising the price of the Picos in a little while to encourage the changeover.
Click to expand...

I quit using the PICO because they so limited and very pricey considering what I could get a CLICK for. AB rep was pushing me to try the 810, I may have to break down.
 
Jraef said:
You can get versions that have true relay outputs, just ask to be sure.

The AB Pico is being replaced by the Micro 810, go that route if it is going to be built in the future. The Picos are still going to be sold for retrofit purposes for a while, but the 810 is the future. They will start raising the price of the Picos in a little while to encourage the changeover.
Click to expand...

Thanks for the heads-up on the discontinuation of the Pico's, I guess I should have anticipated that since they have been around a long time. I was just getting ready to order a Pico for a small panel I am building but I took a look at the Micro 800 series. They sure have a lot more bells and whistles then the Pico's so I was a little fearful of what the price would be. I got a quote on the appropriate Pico and a Micro 830 (I need more then 4 relay outputs) and the 830 is about $100 less then the Pico, It would appear that Rockwell has already started hiking the prices on the Pico's.
 
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RichB said:
Awesome again!1

Thanks guys. I love the info, knowledge and expertise available here--I always learn something!!

Oh and what happened to the smileys?? I can't see them or add them?

OK, now that larnin' has tooken place--kin I git home wit' pay now??

Thanks all

Rich
Click to expand...
Smileys still work for me...
:):slaphead:
 
eric9822 said:
These guys also have some inexpensive micro controllers but I have never personally used them.
http://www.automationdirect.com
Click to expand...

+1 on the Click. Free programming software, expandable, and cheap. AD's tech support is fantastic, and free too; very helpful when learning a new platform. They come with relay outputs if you need them, though if this is a test rig that will see lots of cycles, consider using a transistor output version to switch external relays. It's much easier to replace an ice cube relay than an internal-to-the-PLC relay when they wear out.



SceneryDriver
 
SceneryDriver said:
+1 on the Click. Free programming software, expandable, and cheap. AD's tech support is fantastic, and free too; very helpful when learning a new platform. They come with relay outputs if you need them, though if this is a test rig that will see lots of cycles, consider using a transistor output version to switch external relays. It's much easier to replace an ice cube relay than an internal-to-the-PLC relay when they wear out.



I am leaning toward the Click--Thanks Guys--SceneryDriver--That's qwhat we are trying to get away from--currently using ice cubes but some people in the shop are complaining about the constant clicking
Click to expand...
 
130829-1209 EDT

RichB:

I have not read all the posts closely, but I believe you indicated a need to switch different inductors in a circuit to show how inductance affected the circuit. This seems to imply a bidirectional low impedance switch. Further you have indicated a noise problem. I don't believe there was any current or voltage information specified.

I suggest looking at reed switches. Searching for --- AB power reed switches --- I came across http://www.meder.com/power-reed-switches.html?&tx_jppageteaser_pi1[backId]=339 . One of these is rated at 1000 VDC and 1 A. I believe AB used to have a 5 A power reed switch.

.
 
gar said:
130829-1209 EDT

RichB:

I have not read all the posts closely, but I believe you indicated a need to switch different inductors in a circuit to show how inductance affected the circuit. This seems to imply a bidirectional low impedance switch. Further you have indicated a noise problem. I don't believe there was any current or voltage information specified.

I suggest looking at reed switches. Searching for --- AB power reed switches --- I came across http://www.meder.com/power-reed-switches.html?&tx_jppageteaser_pi1[backId]=339 . One of these is rated at 1000 VDC and 1 A. I believe AB used to have a 5 A power reed switch.

.
Click to expand...

gar, I think I follow--but here's the situation in a nut shell--I am attempting to just close a switch to complete a coil--from one side of the contacts it goes out to a coil that is wrapped inside another coil and back to the switch--by closing this switch it simulates a car passing over a loop in the roadway by causing an increase in the inductance of the coil wrapped around the one I am completing, which is connected to an amp and then to the controller which sees this spike and counts as a vehicle passing that loop. I only need to close the contact for a split second to cause the increase in the "main" loop.

I am not switching any voltage or current just need to make a complete circuit. The noise I referred to comes from the ice cube relays we are currently using--clickety-clack, clickety-clack--some of our techs don't like to hear that in the shop for several days at a time.

I can PM you a copy of the cabinet prints etc when I get back next week if you would like to see it. Just trying to upgrade from relay logic and get with the modern era!
 
RichB said:
gar, I think I follow--but here's the situation in a nut shell--I am attempting to just close a switch to complete a coil--from one side of the contacts it goes out to a coil that is wrapped inside another coil and back to the switch--by closing this switch it simulates a car passing over a loop in the roadway by causing an increase in the inductance of the coil wrapped around the one I am completing, which is connected to an amp and then to the controller which sees this spike and counts as a vehicle passing that loop. I only need to close the contact for a split second to cause the increase in the "main" loop.
Click to expand...
For those who are interested, a loop detector can either work by sensing the increase of inductance that occurs when a ferromagnetic lump of metal moves over the loop, or by sensing the increased losses (lowered Q) of the inductor caused by any conductive mass of metal moving over the loop.
The latter kind can better detect bicycles or other vehicles which have more aluminum, magnesium, etc. than steel in their construction.
To test one of these detectors, you can short out an inductor which is inside the loop, causing increased losses.
 
130829-1853 EDT

RichB:

Then use a smaller reed switch. I expect you are unfamiliar with reed switches or relays. These make very little acoustic noise, switch rapidly, have low resistance and are environmentally protected (no low voltage contact resistance problems). Also low power. Can be used to connect a calibration resistor in a straingage transducer circuit.

I have switched these at 60 Hz and had less than a millisecond jitter.

.

.
 
GoldDigger--Thanks for that--I hadn't thouoght of explaining what and how traffic loops worked:ashamed1:

gar--yup I am familiar with them--just never even entered my mind!! Thanks!!
 
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