Extruder

[SS ELEC]

Using PID in the SLC. Time proportional control works well with this.

Snordvikqplas
How do you prevent the heat and cool coming on at the same time, or very close? Anyway you could send me your logic?

 

[snordvikqplas]

Which solid state relays would you suggest?

Our zones have to be sized for 50 amps and six to eight zones per line.

I have used Avatar SCRs (very nice by the way for those interested) for some applications (presses) where I have the footprint (cabinet size) available. However on the extrusion lines space is limited and with 6 to 8 zones that would require a rather larger heater control cabinet due to the size of the SCRs and Heat sinks.

Also with our building being non climate controlled, in the summer temps get very high so I would want to oversize (overrate) the SCRs and heat sinks to compensate for the degradation of the allowable amps.

I am open to new products or suggestions that I do not know. The heaters are single phase 240V, thanks in advance for any input.

 

[snordvikqplas]

Both heat and cooling are used at the same time, look up the time proportional control and that will make some sense to you.

Basically you have an output (whether is is a relay or solid state) from the SLC going to a mercury relay (or solid state relay depending on money and size). THis output is controlled using the PID (time proportional)

Cooling is an analog output from a analog output card so this would be just be PID control.

I cannot send any logic due to it does not belong to me and I do not understand your exact process.

All I can tell you is that you can control relay outputs with PID in order to turn on and off an electric heater using Time Proportional control.

http://www.plctalk.net/qanda/showthread.php?t=27338

 

[iant]

http://www.greegoo.com/Product/solid-state-relay-ssr.html?gclid=CMzFpK-Trr4CFZIrvQodPpsAqQ

I don't know what suppliers you have

Remember your hot climate is not running at 40 degrees C during summer

Most of these SCRs are mounted directly to a large fan cooled heatsink. This is for the high current units. 50 Amps and above.

 

[allscott]

Firm on using a PLC because we have one we're not using and we want to add it to our network

So you are wanting to add this PLC to an existing DH+ network? If so that can be accomplished with CLX as well.

As was mentioned the SRTP instruction in CLX works very well for this, there isn't a comparable instruction for a SLC.

Again I would do this with either CLX, a temperature controller for each zone, or a BTM module. Remember the BTM was developed for a reason and that reason is that this isn't easy to do using a SLC's PID instruction.

Use SSR's for the heaters. They are cheap and easy to come by. They have all the advantages of mercury relays without the mercury.

 

[allscott]

http://www.greegoo.com/Product/solid-state-relay-ssr.html?gclid=CMzFpK-Trr4CFZIrvQodPpsAqQ

I don't know what suppliers you have

Remember your hot climate is not running at 40 degrees C during summer

Most of these SCRs are mounted directly to a large fan cooled heatsink. This is for the high current units. 50 Amps and above.

I think you meant to say SSR?

 

[SS ELEC]

We already have the plc, I'm sure it would be cheaper to buy the BTM card than a new plc.

 

[snordvikqplas]

Hey allscott

Just for my own knowledge sake, why would I want to use a BTM module over controlling with Time proportional using the PID instruction in a SLC?

We have no issues and have been making product with these systems for a while.

I am asking because every time I think that I got it down I learn something new especially in this field of work. Thanks in advance for your time.

Stu

 

[allscott]

Hey allscott

Just for my own knowledge sake, why would I want to use a BTM module over controlling with Time proportional using the PID instruction in a SLC?

We have no issues and have been making product with these systems for a while.

I am asking because every time I think that I got it down I learn something new especially in this field of work. Thanks in advance for your time.

Stu

If you are comfortable doing time proportional control for the process and it works then there is nothing wrong with doing it that way. The BTM is designed specifically to do this though so why not use it?

Personally if someone walked up to me with an extruder and a SLC5/04 and said control the heat on this thing I would purchase individual temperature controllers and a devicenet card for the SLC. I have extruders out here using temp controllers, one with a BTM module in a PLC 5, and one using SRTP control in a CLX. The ones with temperature controllers are the easiest to work on.

There are lots of ways to skin this cat. I tend to go for whatever is easiest and proven.

 

[snordvikqplas]

Cool thanks.

I just spent some time reading on the BTM module and will read up on the SRTP instruction. Extruders here use 5/03, micro 1400s and larger ones are on the compact logix.

I like to learn other ways to skin a cat so thanks for the information in this thread.

 

[SamTheLightMaster]

Can You share your .rss file so i can try this test at home, i cant seem to get it rite... if so thank you..

 

[lfe]

I would try to do it with a floating regulation with an output varying from +100 to -100.

Positive for heating, negative for cooling.

With double set of regulation parameters.

Heating regulated on-off via SSRs.

The cooling also on-off on a solenoid valve, opening the passage of water in pulses, with faster responses than a motorized valve.