PID Temperature Controller Help

[WMT]

Hello, I have been lurking for quite some time now and decided to join. I have been looking for a smoker to smoke my homemade sausage and pepperoni but can't find one with the specs I want so I decided to build one. I have aquired all the parts I need and built a PDI temperature controller with the Mypin TA4 PID controller to control the electric element of the smoker. I followed the in depth instructions in the "Johnny's reloading bench" videos which is the same as the diagram below and got it built. My configuration of the thermocouple is a bit different than the picture below. I just used terminal 7 & 8. As far as the controller goes it is doing what it is supposed to do. It senses temperature with the thermocouple, energizes and de-energizes the SSR (SSR-25 DA) as it is supposed to. The problem I believe I am having is, for some reason I seem to be blowing the SSR. According to my research a faulty SSR will keep the the power energized through it even with the control wires disconnected. That is exactly what is happening. The controller still works as it is supposed to, sensing temperature and energizing the SSR, but when it is supposed to shut off the power to the element, the element stays energized. I have gone through two SSR's already. Yesterday when I installed the new one and turned the power on to the unit I heard a pop and the above issue happened again, same as last time. Is there something obvious that I am doing wrong that I am just not seeing. Any help would be greatly appreciated.

 

[DIYerDave]

I would suggest using a higher amperage ssr. Also using an extension cord to power anything with a heating element is a big no-no unless you have a heavy enough gauge wire.

 

[Steve H]

Are you operating/testing your set up with the SSR not having a load? SSR's will not operate properly without a load on it.

 

[WMT]

Good to know about the no load thing. I am actually just using my electrical tester to test the voltage on the plug that the SSR is feeding. But with no control voltage going to the SSR shouldn't the contacts on the high voltage side be open giving me a 0 volt reading at the plug. Are SSR's a normally closed relay? It doesn't matter if I have control voltage from the pid or not, even with the control wires to the SSR disconnected there is still voltage across the high side to the plug. The pop I heard when I powered up the system brings me to believe that the SSR is faulty now. I will try to operate it tonight with some sort of a load on it and see if it makes a difference.

 

[Steve H]

Good to know about the no load thing. I am actually just using my electrical tester to test the voltage on the plug that the SSR is feeding. But with no control voltage going to the SSR shouldn't the contacts on the high voltage side be open giving me a 0 volt reading at the plug. Are SSR's a normally closed relay? It doesn't matter if I have control voltage from the pid or not, even with the control wires to the SSR disconnected there is still voltage across the high side to the plug. The pop I heard when I powered up the system brings me to believe that the SSR is faulty now. I will try to operate it tonight with some sort of a load on it and see if it makes a difference.

No, with no load the ssr with do this. Show power on the load side. Not sure about the "pop" you heard. But go ahead and plug something in the outlet you intend to use for the grill. A lamp, radio that is turned on, etc.

 

[Steve H]

Oh, if a ssr fails it remains "closed' One drawback of a ssr. test the ssr with no power on it. Both control and load side. Test across the load side using the Ohm setting on your meter. If it is open. You should be fine. If it shows resistance. Then chances are it is bad.

 

[Steve H]

 

[WMT]

I will do some testing tonight. Thanks for the info.

 

[Steve H]

Glad to help.

 

[WMT]

I have actually seen that video and have done the test but only with my volt meter in the plug and not an actual load. I will try with a load tonight

 

[Steve H]

But with no control voltage going to the SSR shouldn't the contacts on the high voltage side be open giving me a 0 volt reading at the plug.

No, you will see 110vac. A meter does not produce enough load to make the ssr to switch state.

 

[Steve H]

I have actually seen that video and have done the test but only with my volt meter in the plug and not an actual load. I will try with a load tonight

Hopefully you'll see that it is ok. If you did the wiring using the diagram you posted. Then I don't see a problem. Once you start using a PID. You'll wonder why you waited.

 

[Steve H]

Here is one of the ones I made. Real pleased with how well it works.
https://www.smokingmeatforums.com/t...fraid-of-sous-vide.287568/page-2#post-1963850

 

[JC in GB]

Hello, I have been lurking for quite some time now and decided to join. I have been looking for a smoker to smoke my homemade sausage and pepperoni but can't find one with the specs I want so I decided to build one. I have aquired all the parts I need and built a PDI temperature controller with the Mypin TA4 PID controller to control the electric element of the smoker. I followed the in depth instructions in the "Johnny's reloading bench" videos which is the same as the diagram below and got it built. My configuration of the thermocouple is a bit different than the picture below. I just used terminal 7 & 8. As far as the controller goes it is doing what it is supposed to do. It senses temperature with the thermocouple, energizes and de-energizes the SSR (SSR-25 DA) as it is supposed to. The problem I believe I am having is, for some reason I seem to be blowing the SSR. According to my research a faulty SSR will keep the the power energized through it even with the control wires disconnected. That is exactly what is happening. The controller still works as it is supposed to, sensing temperature and energizing the SSR, but when it is supposed to shut off the power to the element, the element stays energized. I have gone through two SSR's already. Yesterday when I installed the new one and turned the power on to the unit I heard a pop and the above issue happened again, same as last time. Is there something obvious that I am doing wrong that I am just not seeing. Any help would be greatly appreciated.

EDIT: Sorry my mistake.. The wiring diagram isn't the issue as I first thought.

What is the resistance in ohms of the heating element?

Do you have the SSR mounted on a heat sink?

Does it go poof immediately or does it work for a while then go poof?



JC

 

[Steve H]

EDIT: Sorry my mistake.. The wiring diagram isn't the issue as I first thought.

What is the resistance in ohms of the heating element?

Do you have the SSR mounted on a heat sink?

Does it go poof immediately or does it work for a while then go poof?



JC

He hasn't hooked the smoker to the PID yet. Hence part of the problem he is having. Running a ssr without a load will cause some of the things he is describing. I'm not sure about the "poof" either.

 

[JC in GB]

He hasn't hooked the smoker to the PID yet. Hence part of the problem he is having. Running a ssr without a load will cause some of the things he is describing. I'm not sure about the "poof" either.

You must have a load on an SSR or the thyristor device inside it will not achieve latching and holding current.

If it won't latch, it won't stay turned on. Use an incandescent light bulb as a test load.

You may also want to put a small capacitor across the SSR input leads. This will help make sure noise doesn't trigger your SSR.

Also, SSR trigger wires should be twisted to cancel out common mode noise which could also cause false triggering.

 

[WMT]

Steve is correct, I haven't hooked it to anything yet. I have only been testing the plug with my meter.
Ohms- not sure but if my calculations are right it should be 8 ohms. Here's a link to the element
yes it's installed with a heat sink
It gave a little pop the first time I energized it with power and has not done it since

 

[Steve H]

You must have a load on an SSR or the thyristor device inside it will not achieve latching and holding current.

If it won't latch, it won't stay turned on. Use an incandescent light bulb as a test load.

You may also want to put a small capacitor across the SSR input leads. This will help make sure noise doesn't trigger your SSR.

Also, SSR trigger wires should be twisted to cancel out common mode noise which could also cause false triggering.

Yup, already informed him of that. He is going to try that later. I don't usually worry about twisting the leads for that short of a distance. But, it doesn't hurt either.

 

[WMT]

What do you mean twisting the leads. Just twisting the strands of wires together after I strip them and before I hook them up. If so I have done that

 

[WMT]

Made it home from work and plugged a light into the control box and it worked as it is supposed to. Just like you guys said, all I had to do is hook a load to it. Looks like I’m in business thanks to you fine knowledgeable gentleman. Thanks a bunch guys