# PID Design Questions



## Murray (Jan 2, 2021)

Sourcing out components for a PID build and have a few questions.

1)  Can’t seem to get my head around solid state relays.  Internet research suggests that a 40Amp is better than a 25 Amp relay although a 25 Amp will suffice for a 800Watt element drawing 6.7 Amps. Why would I consider a 40 Watt when 25 Amps is more than enough. House current is 15 Amps.

2)  If I install a small fan is the enclosure do I still need a heat sink? I’m kind of thinking not but cooler electronics will last longer and perform better.


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## Steve H (Jan 2, 2021)

1) A 40 amp SSR is just beefier and should hold up better from all the on/off cycles a smoker is going to produce. And for the few extra dollars. It makes sense.
2) Yes, you should still use a heat sink. And use heat sink compound between the ssr and the heat sink. And add the cooling fan if you wish to ensure a long life from the ssr.


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## Murray (Jan 3, 2021)

Thanks.


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## olaf (Jan 3, 2021)

These ssr's that you see for cheap online are not always what they claim. I had grand plans making a totally wifi controlled smoker all I need are parts and some borrowed code. The 15 amp ssr's six of them failed within 2 to 25 hours of use. Some only had 3 amp loads on them. I went back to my 25 year old digital temp controller with a built in (industrial)  10 amp ssr switching a 1500 watt heating element, it's been working for years.


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## JckDanls 07 (Jan 3, 2021)

I will suggest that the heat sink be outside of the enclosure..  but I'm sure you knew that ...


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## Jonok (Jan 3, 2021)

In my experience, SSRs aren’t as robust as electromechanical contactors.  I’ve used the internal ssr in $15 pids to power a $15 40a DPDT contactor and I haven’t had any failures.  They make noise, but they just seem to work.


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## Murray (Jan 3, 2021)

I


JckDanls 07 said:


> I will suggest that the heat sink be outside of the enclosure..  but I'm sure you knew that ...


I  thought of that, then the enclosure gets too “bulky”.  I’ve decided to forego the fan for now, I’ll be able to add a fan later if needed. Figure I can stuff a TP-08 probe inside the enclosure to monitor temperatures and evaluate the need for a fan.


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## Murray (Jan 3, 2021)

olaf said:


> These ssr's that you see for cheap online are not always what they claim. I had grand plans making a totally wifi controlled smoker all I need are parts and some borrowed code. The 15 amp ssr's six of them failed within 2 to 25 hours of use. Some only had 3 amp loads on them. I went back to my 25 year old digital temp controller with a built in (industrial)  10 amp ssr switching a 1500 watt heating element, it's been working for years.


I see quite a price difference, I’m going with an Inkbird PID and their 40A SSR.  They are in my price range and it’s a recognizable respected name.


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## JckDanls 07 (Jan 3, 2021)

If no fan then you would want the heatsink even more so outside of the controller box (enclosure) ...


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## Murray (Jan 3, 2021)

JckDanls 07 said:


> If no fan then you would want the heatsink even more so outside of the controller box (enclosure) ...


You figure there will be too much and a fan is a necessity?  Other commercial PID don’t have fans that I can see so I figured I might be able to get away without a fan. That being said I have no idea what electronics the commercial ones use and how they mitigate heat. Thanks for your input.


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## JckDanls 07 (Jan 3, 2021)

No...  a fan is not necessary as I don't have one in mine...  The heat sink gets really warm .. and heat and the PID controller aren't the best of friends...


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## olaf (Jan 3, 2021)

Murray said:


> I see quite a price difference, I’m going with an Inkbird PID and their 40A SSR.  They are in my price range and it’s a recognizable respected name.


I was looking at that one a month ago just not ready to do my major smoker rebuild. If you do have problems with ssr not handling the heat or current don't hesitate to go to an old school relay.


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## Murray (Jan 7, 2021)

Steve H said:


> 1) A 40 amp SSR is just beefier and should hold up better from all the on/off cycles a smoker is going to produce. And for the few extra dollars. It makes sense.
> 2) Yes, you should still use a heat sink. And use heat sink compound between the ssr and the heat sink. And add the cooling fan if you wish to ensure a long life from the ssr.


Would  dielectric grease work instead of thermal paste?


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## Steve H (Jan 8, 2021)

Murray said:


> Would  dielectric grease work instead of thermal paste?



Probably not as well. Though I don't know for sure.


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## Murray (Jan 8, 2021)

Steve H said:


> Probably not as well. Though I don't know for sure.


Thanks, I have lots of dielectric grease on hand but no thermal paste. It’s not expensive so I’ll get a tube.


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## JckDanls 07 (Jan 8, 2021)

The heat sink I bought came with the paste .. .


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## Murray (Jan 13, 2021)

All parts ordered the same time, so far only the Inkbird ITC-106VH has arrived so I set it up on the work bench to play with it.  This unit is for an older MES at our summer home but in the mean time I’ll use it here at our winter home after I rewire the winter MES. A couple of questions.

1)  No grounding terminal on the Inkbird or the SSR so I’m assuming I ground only the receptacle? If  I install a switch(Question 4) should it be grounded? Plastic project box so no ground there.

2)  Once the PID is tuned to say 225F for a hot smoke and I want to keep beer from freezing in sub freezing temperatures(cold smoke) will the PID parameters need changing since it was initially set at 225F and now I’m trying to keep the MES around 37F? I used keeping beer from freezing as an example since there is a big temperature difference from 225F to 37F?

3) I haven’t allowed for a fuse in the design. I probably should put a 15amp. fuse inline on the hot side?

4)  I haven’t allowed for an off/on switch, figured pulling the plug would work.  Do I need an off/on switch for safety or is a switch a nice to have?

Thanks for you time and suggestions.


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## olaf (Jan 13, 2021)

I'm reworking my smoker for an inkbird controller also got mine today.
1 grounding conductor any terminal that will accept this will require the connection to ground just assume its needed if there is a grounding terminal.
2 not sure but I wouldn't change anything
3 fuse may be a problem because there is no time delay if your drawing 16 amps it's gone whereas your circuit breaker won't trip for an hour.
4 I'm a fan of switches pulling a plug is sometimes fatal to electronics 
5 switch the black conductor this also applies to the ssr the neutral and grounding wires go right on through.
6 black on brass white on silver green/bare on green.


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## Murray (Jan 13, 2021)

Thanks for the reply. I was thinking a fuse to potentially help with those power surges that sometimes blows up electronics and there’s a chance(small) that it might be run off a generator.  The heating element is 800W and a small fan, less than 1 Watt so say 7Amps through the circuit.  Found a on/off switch in the tickle trunk so that’s covered. If the box would arrive I can start assembly...


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## olaf (Jan 14, 2021)

Sounds like you'll have things covered well. Mine is more involved not sure why I'm doing it but I ordered 150 bucks worth of electric gizmos to put into the smoker. Good luck to ya or good luck to me I'll need it.


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## Murray (Jan 18, 2021)

It’s built and running.  No fan yet and based on my limited experience I don’t think I need one.  Currently I have the PID thermocouple hanging above a lamp in the basement and a digital remote thermometer (Inkbird) probe between the cooling fins on the heatsink.  The heatsink temperature started at 68F and has climbed to 70F over a two hour period and has been holding steady at 70F.  
Questions:
I hit the “Set” button once and I get A  some spaces then  fluctuating numbers ranging from 0 to 100.  I’m guessing the A= Amps and the constantly changing numbers are a % of Amps  being drawn?

Zero heat buildup in the heatsink playing in my basement with a SV value of 70F. Once I rewire my MES and start upping the SV to say 225F will the heatsink temperatures start rising?

I have a lighted on/off  3 pole switch. Pole 1 and 2 are hot in and hot out, pole number 3 has nothing hooked up yet.  What should be hooked up to pole 3 to get the internal switch lamp to light? Neutral?

Thanks for your input.


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## olaf (Jan 18, 2021)

I'm not sure about the A then numbers I don't think it will give a reading on amps it just changes how it cycles on then off times as it gets closer to the set point. Connecting the neutral to that should turn on the lighted switch unless it's a 12VDC switch then it will toast the light.


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## Murray (Jan 18, 2021)

olaf said:


> I'm not sure about the A then numbers I don't think it will give a reading on amps it just changes how it cycles on then off times as it gets closer to the set point. Connecting the neutral to that should turn on the lighted switch unless it's a 12VDC switch then it will toast the light.


Thanks, 120AC.


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## Murray (Jan 20, 2021)

Does anyone know if the factory supplied Type K thermocouple ITC-106VH is waterproof enough to withstand a calibration in freezing and boiling water? No mention in the supplied documentation.

Found the information I was looking for. It is not waterproof.


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## dr k (Jan 20, 2021)

Inkbird



Murray said:


> Does anyone know if the factory supplied Type K thermocouple ITC-106VH is waterproof enough to withstand a calibration in freezing and boiling water? No mention in the supplied documentation.
> 
> Found the information I was looking for. It is not waterproof.


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## Murray (Jan 20, 2021)

Thanks Kurt.  Took every thermometer we own, laid them out side by side and took an average to calibrate the PID. Tossed two away that were off by 5F and 7F that had no means of calibration.


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## Murray (Jan 21, 2021)

Murray said:


> Thanks, 120AC.


From Inkbird, the A is for Automatic mode as opposed M for Manual mode. No details about the changing numbers from 0 to 100.  They also sent me a link to their ITC-100 model that has an explanation to the menu driven setting and a much more detailed explanation of the parameters and the interaction between them.

https://pmod79883-pic31.websiteonline.cn/upload/ITC-100_Manual_V1.pdf


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## Buddy55 (Feb 4, 2021)

Steve H said:


> Probably not as well. Though I don't know for sure.


Thermal paste is easy to find (??) I found mine at a PC repair store. I wished I had known that I would need some. I threw out my old batch two weeks before I decided to upgrade my smoker.


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