SSR heating control question

I want to use a Koyo Click and a solid state relay to rapidly turn a 4500(18.75 amps) watt heating element on and off. Can any one tell me if this will work with these parts?


On .9 off .1 seconds
on .8 off .2 seconds
on .7 off .3 seconds
on .6 off .4 seconds
on .5 off .5 seconds
on .4 off .6 seconds
on .3 off .7 seconds
on .2 off .8 seconds
on .1 off .9 seconds



SSR

AD-SSR640-AC-280A
SOLID ST RELAY 40A SPST VAC INPUT N.O. 24-280 VAC PANEL MOUNT


http://www.automationdirect.com/adc/Shopping/Catalog/Relays_-z-_Timers/Solid_State_Relays/Panel_Mount_Relays,_Hockey_Puck_Style,10A_-_75A_(AD-SSR6_Series)/AD-SSR640-AC-280A

Click output module

C0-08TA
8PT 17-240VAC OUTPUT MODULE 0.3AMPS PER POINT


http://www.automationdirect.com/adc...cro_Brick)/AC_I-z-O_-a-_Relay_Outputs/C0-08TA

The short answer is NO. You did not say WHICH of the SSR6 relays you have chosen, so it is impossible to know what output voltage range your Click Output module must have to match the "control voltage" of the SSR relay.

Then you list an output module, but give the specifications for an INPUT module, which will not control the SSR relay.

Click output module
C0-08NA, 8PT 100-120 VAC INPUT MODULE AC INPUT

Click to expand...

No, the C0-08NA is NOT an OUTPUT module. Go to the link below, and select an OUTPUT module that has the voltage range to control your selected SSR relay. In other words, your CLICK output module must have a voltage range that matches the selected SSR "control voltage". I think you will need a C0-08TA, or C0-04TRS, or C0-08TR module.

http://www.automationdirect.com/adc...kable_Micro_Brick)/AC_I-z-O_-a-_Relay_Outputs

For the AD Class 6 SSR relay, you have a basic control-voltage choice of 3-32 volts DC, or 90-280 volts AC. I think you plan to use an AC SSR, so I reccommend the AD-SSR640-AC-280A. This is the 40 Amp version. From experience with SSR relays, it is best to go about 1 step higher than your load current rating to prevent burn-outs.

Which Click PLC are you using? If you choose the correct Click base unit, you probably will not need another add-on module to allow use of a SSR relay.

Does the click plc have a pid instruction? I would not think that it does. You may be better off with a temperature controller and not a plc.

Lancie1 said:

The short answer is NO. You did not say WHICH of the SSR6 relays you have chosen, so it is impossible to know what output voltage range your Click Output module must have to match the "control voltage" of the SSR relay.

Then you list an output module, but give the specifications for an INPUT module, which will not control the SSR relay.

-

Click to expand...

Sorry about that. That was a bone head mistake with copy and paste. I'll Fix that right now.

My biggest question was, can a Click output module and SSR handle switching that fast? From what I understand in the specs they can.

The Plc Kid said:

Does the click plc have a pid instruction? I would not think that it does. You may be better off with a temperature controller and not a plc.

Click to expand...

What I'm trying to do is use a c-more panel to set the heating element at a level, 1-10. I made the program last night and it seems to work. But switching that fast seems likes it could cause problems.

I know a pid controller would work well in this application, but I'm doing it this way to learn. PLC's are still pretty new to me and i'm trying to start off small and simple.

My biggest question was, can a Click output module and SSR handle switching that fast? From what I understand in the specs they can.

Click to expand...

Yes, the SSR can switch ON in about 10 milliseconds and OFF in about 4 ms. Your chosen AC output module can also switch ON/OFF as fast as about 2 milliseconds.

Question: Do you really need an additional add-on output module? Could you not use one of the Click PLCs with built-in triac (AC Transistor) outputs to switch the SSR on and off?

TIP: You can do the same job if you multiply your 10 switching ranges by 5. Instead of "On .5 Off .5", change that to "On 2.5, Off 2.5" (and all others similarly). This will still give you good simulated analog control, but with much less stress and wear on the SSR and PLC outputs. Longer times will result in poorer control, but longer SSR life. As always in life, it is a trade of between the Desired and the Practical. It is the "Per cent ON time" that counts - in other words the amount of time that your heater is ON out of the total elapsed time. That can be done with short ON/OFF times as you showed, or much longer times to prevent stressing your equipment.

TIP 2: You have a method to set your heaters to 10 different heat outputs. That is a good method for a teaching and learning program. However, notice that with a PLC, it is possible to simply use two PLC timers - Heater ON time and Heater OFF time (or just one timer with comparison instructions) and have the C-More just send a selected ON time to the PLC. Then your PLC program moves that time to the Timer Preset value. This way, you can have an almost unlimited range of heating outputs (instead of only 10).

The Click PLC has triac outputs. You might have to add a burden resistor on the SSR's input terminals, if the PLC leakage causes a false ON. Something like a 10k, 2 watt.

Anything greater than a few amps switched, and you need to have a correct-sized heat sink for the SSR.

Don't know the Click. however if it has an accurate PWM [Pulse Width Modulation]that can be assigned to an Output [Usually a High Speed Output] then use this to control the heater SSR. We do this all the time with a Siemens PLC.

My 2 Cents

Looking at the Click User Manual, it does not appear to have PWM output capability, only Out, Set, and Reset. A search for "PWM" did not find anything in the manual.

Lancie1 said:

Yes, the SSR can switch ON in about 10 milliseconds and OFF in about 4 ms. Your chosen AC output module can also switch ON/OFF as fast as about 2 milliseconds.

Click to expand...

Lancie1 said:

TIP: You can do the same job if you multiply your 10 switching ranges by 5. Instead of "On .5 Off .5", change that to "On 2.5, Off 2.5" (and all others similarly). This will still give you good simulated analog control, but with much less stress and wear on the SSR and PLC outputs. Longer times will result in poorer control, but longer SSR life. As always in life, it is a trade of between the Desired and the Practical. It is the "Per cent ON time" that counts - in other words the amount of time that your heater is ON out of the total elapsed time. That can be done with short ON/OFF times as you showed, or much longer times to prevent stressing your equipment.

Click to expand...

Thanks a lot for putting that much time in an answer. This is really what I was wanting to know and more.

Lancie1 said:

Question: Do you really need an additional add-on output module? Could you not use one of the Click PLCs with built-in triac (AC Transistor) outputs to switch the SSR on and off?

Click to expand...

I already have the Click plc, and I’ve used the out puts for other things in the project.

Lancie1 said:

TIP 2: You have a method to set your heaters to 10 different heat outputs. That is a good method for a teaching and learning program. However, notice that with a PLC, it is possible to simply use two PLC timers - Heater ON time and Heater OFF time (or just one timer with comparison instructions) and have the C-More just send a selected ON time to the PLC. Then your PLC program moves that time to the Timer Preset value. This way, you can have an almost unlimited range of heating outputs (instead of only 10).

Click to expand...

I was using two timers, I hadn’t even realized I could do it with one. Thanks for the tip.

Lancie1 said:

Looking at the Click User Manual, it does not appear to have PWM output capability, only Out, Set, and Reset. A search for "PWM" did not find anything in the manual.

Click to expand...

I don't think it does. I was planning on using outs and timers. Will that not work? I'm not looking for precision, just in the ball park.

I don't think it does. I was planning on using outs and timers. Will that not work?

Click to expand...

Yes, it will work just dandy. There are probably two different ways you can set up your C-more, depending on if it allows data entry in a number format. If it does, then you can set up an operator line to "Enter Heater % ON time: ?" and then type in your desired Per Cent ON time. Then your PLC program takes that Per Cent and, out of a fixed time period, for example 5 seconds, calculates the ON-time value and enters that into a Timer Preset value. If you entered "80 %" as the Percent ON time, then your calculation would be "0.80 X 5 = 4 seconds". Then your program should MOVe "4" to your ON Timer Preset, and 5-1= 1 second to your OFF timer. So then your heaters would be ON for 4 Seconds, and OFF for 1 Second, producing an average of 80% ON time.

Or you can leave it the way you have now and simply select a number from 1 to 9.

Yes it will work, however use longer periods, as the PLC is not synchronized with the frequency, it can happen that even when ssr is on no power is available as the sinus is low.