Temperature Controller SSR Output...

[KenLockett]

Recently bought one of those temperature controllers off of Amazon that I have read other forum members have used. The unit I have has one relay alarm contact (AL1) and one SSR output (OUT). The manual was translated it appears from Chinese and the wiring diagram simply shows a '+' and '-' terminal configuration. My assumption was that this was a solid state relay output and thus would read zero ohms (short) across the terminals when the output is energized (in heating mode of course) and infinite ohms (open) when the output is de-energized. Well, in my case the the resistance across the terminals is always zero ohms irrespective of the output state and checking across the opposite polarity yields zero ohms and the multimeter display begins to fade. Also, in either output state, I read 24VDC across the terminals. Either I simply don't understand how the SSR output on this device works or I have a defective unit. Can anyone provide any insight that has used these units. The alarm relay contact is working perfectly fine. I was ultimately trying to wire the SSR output into an digital input channel on a PLC while wetting through the 24VDC positive bus of my system.

 

[ewdudley]

Can anyone provide any insight that has used these units. The alarm relay contact is working perfectly fine. I was ultimately trying to wire the SSR output into an digital input channel on a PLC while wetting through the 24VDC positive bus of my system.

The 'SSR output' is a DC output signal (typically 8-32VDC when active depending on the controller) that is connected to an external SSR as its activation input. You may need a small pull-down resistor across the the two terminals to simulate the presence of an SSR in order to see two different states because solid state leakage can cause the voltage to read high even when the output is in its inactive state. Also it is normally possible to configure the unit to disable the 'SSR output' and send the PID output to the relay output, in which case the 'SSR output' might float to the 24VDC you're seeing.

To use as an input to a PLC you would need to configure the PLC input as a current sinking input and you might need a voltage divider to bring the 'SSR output' voltage down to be compatible with the PLC input requirements.

What controller is it?

 

[KenLockett]

The 'SSR output' is typically an 8-32VDC signal that is connected to an external SSR as its activation input. You may need a small pull-down resistor across the the two terminals to simulate the presence of an SSR in order to see two different states. Also it is normally possible to configure the unit to disable the 'SSR output' and send the PID output to the relay output, in which case the 'SSR output' might float to the 24VDC you're seeing.

To use as an input to a PLC you would need to configure the PLC input as a current sinking input and you might need a voltage divider to bring the 'SSR output' voltage down to be compatible with the PLC input requirements.

What controller is it?

It is the TA4-SNR. I have a better understanding of the output now in that it it similar to the solid state outputs I deal with with PLC output modules. Since I am using the alarm relay output as a DI input to the PLC card and I believe I am wiring the KOYO controller inputs as 'sinking' type inputs in that all channels share the common return from my 24VDC power supply through terminal 'C1' on the controller and each individual input terminal 'X1, X2, etc.' is wired through the device (i.e. relay alarm contact, PB, then to the hot side of the 24VDC power supply.

My question would be since the SSR output is not 'dry', would I simply wire from the positive terminal SSR output to the input terminal of the KOYO (i.e. X2). Do I leave the negative terminal of the SSR output floating or do I tie it back to the 24VDC negative of the power supply. Is the pulldown resistor necessary in this manner? Would appear that the SSR output negative terminal is now floating and there is a relative voltage difference between the SSR negative output and the 24VDC negative of less than 0.2 VDC.

I suppose another option, and probably the same thing the SSR would do, is to add a small general interposing relay at the SSR output, then wet the dry contacts of the interposing relay as I am the pushbutton and wire that in as the input. Don't want to go this route as all wiring is now dressed.

Thanks again for your feedback.

 

[KenLockett]

It is the TA4-SNR. I have a better understanding of the output now in that it it similar to the solid state outputs I deal with with PLC output modules. Since I am using the alarm relay output as a DI input to the PLC card and I believe I am wiring the KOYO controller inputs as 'sinking' type inputs in that all channels share the common return from my 24VDC power supply through terminal 'C1' on the controller and each individual input terminal 'X1, X2, etc.' is wired through the device (i.e. relay alarm contact, PB, then to the hot side of the 24VDC power supply.

My question would be since the SSR output is not 'dry', would I simply wire from the positive terminal SSR output to the input terminal of the KOYO (i.e. X2). Do I leave the negative terminal of the SSR output floating or do I tie it back to the 24VDC of the PLC. Is the pulldown resistor necessary in this manner? Would appear that the SSR output negative terminal is now floating and there is a relative voltage difference between the SSR negative output and the 24VDC negative of less than 0.2 VDC.

I suppose another option, and probably the same thing the SSR would do, is to add a small general interposing relay at the SSR output, then wet the dry contacts of the interposing relay as I am the pushbutton and wire that in as the input. Don't want to go this route as all wiring is now dressed.

Thanks again for your feedback.

What size pull down resistor would you suggest? I assume roughly the same size as the impedance I would see through the coil of a typical SSR? 100 Ohms or less? Want to try simply putting the pull down resistor in only across the terminals to see if I can get a voltage drop change across the terminals on change of state of the output. Also noticed that the 24VDC polarity relative to terminals 3 and 4 according to the so called instruction manual appears reversed.

 

[KenLockett]

What size pull down resistor would you suggest? I assume roughly the same size as the impedance I would see through the coil of a typical SSR? 100 Ohms or less? Want to try simply putting the pull down resistor in only across the terminals to see if I can get a voltage drop change across the terminals on change of state of the output. Also noticed that the 24VDC polarity relative to terminals 3 and 4 according to the so called instruction manual appears reversed.

The alarm output configured for low alarm is working beautifully. I have programmed it with time delay and Tx alarm setpoint approximately where I need to reload boiler via buzzer (very loud at 100DB at 10cm ! great alert). For those of us who don't have storage this works well as a reminder to reload. Few variables that make it a non-exact science but overall works nice so far. Controller has real time clock so I can also time stamp my idle cycles, which by the way is why I need the SSR output as unit only came with one alarm contact.

 

[ewdudley]

My question would be since the SSR output is not 'dry', would I simply wire from the positive terminal SSR output to the input terminal of the KOYO (i.e. X2). Do I leave the negative terminal of the SSR output floating or do I tie it back to the 24VDC negative of the power supply. Is the pulldown resistor necessary in this manner? Would appear that the SSR output negative terminal is now floating and there is a relative voltage difference between the SSR negative output and the 24VDC negative of less than 0.2 VDC.

I suppose another option, and probably the same thing the SSR would do, is to add a small general interposing relay at the SSR output, then wet the dry contacts of the interposing relay as I am the pushbutton and wire that in as the input. Don't want to go this route as all wiring is now dressed.

It looks like the 'SSR output' from the TA4-SNR is 4VDC inactive, 24VDC active. In order to save on terminal count, the inputs on your PLC appear to be arranged in banks that share a common. Internally they have opto-isolators compatible with current flowing either direction. It sounds like the rest of your inputs switch 24VDC and present positive voltage to the current sinking input pins.

But the TA4-SNR generates its own output voltage on its pins 3 & 4 from its own internal power supply. I believe this means you will have to consume an entire separate bank of inputs on the PLC because you can't share the common (minus, pin 4) of the TA4 with the common of your other 24VDC source.

Or as you say, use the TA4 output to activate a relay that switches your 24VDC to an input pin on the PLC.

 

[ewdudley]

What size pull down resistor would you suggest? I assume roughly the same size as the impedance I would see through the coil of a typical SSR? 100 Ohms or less? Want to try simply putting the pull down resistor in only across the terminals to see if I can get a voltage drop change across the terminals on change of state of the output. Also noticed that the 24VDC polarity relative to terminals 3 and 4 according to the so called instruction manual appears reversed.

Needing the pull-down I mentioned was based on speculation that the TA4 output was floating high, but according to the spec sheet it is supposed to be 4VDC when inactive. I think this means that when you saw 24VDC 'in either output state' maybe you didn't actually have the output in any state other than active. There's an LED on the front that should indicate whether the SSR output is active or not. In any event it wouldn't hurt to connect a 1K-4K across to make sure lack of load is not the problem. If you end up connecting it directly to the PLC on a separate bank of inputs you won't need a resistor because the PLC has one internally. I don't think you'd need a resistor if you used the SSR output to activate a relay, either.

I'm seeing pin 4 as negative in the documentation I'm looking at, does the voltmeter disagree?

 

[KenLockett]

Needing the pull-down I mentioned was based on speculation that the TA4 output was floating high, but according to the spec sheet it is supposed to be 4VDC when inactive. I think this means that when you saw 24VDC 'in either output state' maybe you didn't actually have the output in any state other than active. There's an LED on the front that should indicate whether the SSR output is active or not. In any event it wouldn't hurt to connect a 1K-4K across to make sure lack of load is not the problem. If you end up connecting it directly to the PLC on a separate bank of inputs you won't need a resistor because the PLC has one internally. I don't think you'd need a resistor if you used the SSR output to activate a relay, either.

I'm seeing pin 4 as negative in the documentation I'm looking at, does the voltmeter disagree?

Yes, it disagrees. pin 4 shows as positive. I think the board is defective. I picked up a small 24VDC general purpose relay yesterday, and wired the coil side of the relay into the 3 and 4 terminals (with disagreeing polarity mentioned above) and the relay stays energized (LED on relay) all the time irrespective of the state of the SSR output on the Tx Controller (OUT status LED is turning On and Off). Anyway, I ordered a TA4-RNR model with a relay output that should be here Tuesday. Guess I will return the other unit as defective.

Thanks for the help.

 

[KenLockett]

Yes, it disagrees. pin 4 shows as positive. I think the board is defective. I picked up a small 24VDC general purpose relay yesterday, and wired the coil side of the relay into the 3 and 4 terminals (with disagreeing polarity mentioned above) and the relay stays energized (LED on relay) all the time irrespective of the state of the SSR output on the Tx Controller (OUT status LED is turning On and Off). Anyway, I ordered a TA4-RNR model with a relay output that should be here Tuesday. Guess I will return the other unit as defective.

Thanks for the help.

'EW', did you find a copy of the spec sheet on the web? If so anyway you could forward it to me. I don't see anything in my 'instruction sheet' that indicated output state active/inactive is 24VDC/4VDC. Only states that output is 24VDC +- 2V / 30mA which I assume is active state. Thanks.