Stampede Interior temp

[dr16049]

New to smoking had this prob a year it’s been great. However I was noticing that I think the interior temp is not what is showing on the controller. I hung the meat probe next to it (calibrated) and it read 17 less. I saw another thread similar but am looking for feedback on what I should do or buy before I move forward. Thanks

 

[CajunSmoker]

You must use a temperature probe to measure against what the controller says. By saying temperature probe, I will say that means the probe is rounded at the end unlike meat probes that are pointed. I used a thermoworks smoke alarm to check mine. If it shows a big difference after using an internal temperature probe, then calibrate it. Look on you tube for RecTeq WiFi controller- Offset Calibration.

 

[dr16049]

You must use a temperature probe to measure against what the controller says. By saying temperature probe, I will say that means the probe is rounded at the end unlike meat probes that are pointed. I used a thermoworks smoke alarm to check mine. If it shows a big difference after using an internal temperature probe, then calibrate it. Look on you tube for RecTeq WiFi controller- Offset Calibration.

Perfect thank you. Now I know what to look for on YouTube. Couldn’t find it before. But gotta get the right gauge first

 

[dr16049]

Tons of those alarms, which one ?

 

[Wslayer]

Any of the thermometers will work. I have set even my meat ( calibrated probes) around inside smoker to find hot spots.

 

[NBK]

Thermoworks has a 25% sale going on. I saved $60 on a Signals™ BBQ Alarm Thermometer with Wi-Fi and Bluetooth® Wireless Technology. Should show up Monday. Curious to see what the Bull is accuracy wise. The temp probes are spot on according to my thermo-pen. Main reason for the purchase is for the temp alarms. Unfortunately the Recteq app alarms DO NOT work as advertised.

 

[SmokingHokie]

Except for a past minor hiccup, the RecTeq app alarms work fine. I ways back I bought the Thermoworks DOT and then later bought a temp probe to check the grill temps.

 

[kennethk]

I called RT about this once.
They said the PID controller looks at different things to calculate the temperature it displays.
Due to this it might not match a temp probe all the time.

 

[fullhouse32]

On a very serious note I would like to learn more how the PID system works.
If the PID a takes an average, an average from where just the temp probe in one location?
don’t you have to have more than 1 to have an average? Or is it over a time period?

Please don’t take this is me being a smartass.
I truly would like to understand how it works.

if there is a website/video that someone can recommend that I can nerd out on, I’m ready to learn.

Thank you in advance

 

[C. Keeper]

PID is Proportional, Integral, Derivative.

It means this is a closed loop. When the auger feeds pellets the RTD is expected to change, feedback.

The PID can be tuned and the math involved is beyond me. There is some averaging with the formulas based on time or loop response.

 

[Greg Jones]

On a very serious note I would like to learn more how the PID system works.
If the PID a takes an average, an average from where just the temp probe in one location?
don’t you have to have more than 1 to have an average? Or is it over a time period?

Please don’t take this is me being a smartass.
I truly would like to understand how it works.

if there is a website/video that someone can recommend that I can nerd out on, I’m ready to learn.

Thank you in advance

In a nutshell, what @Chris_G said. If you are still looking for a more in-depth understanding, search for ‘pid temperature controller’ instead of a search that includes anything to do with a grill. I found that to give me much better educational articles instead of links to grill manufacturer web sites.

 

[ol' stonebreaker]

AS I said in another thread put your remote temp probe in your oven and see the results.

 

[NBK]

I ran a pit temp test on my RT-700 today using a Thermotemp "signal" as the test unit. What I found out wasn't a surprise. The software on the Recteq is not granular regarding the graph or the temp scale. It's true fluctuation was up to 23° hotter than set temp. In the scheme of things, it's not too bad. Some of the other brands can move as much as 75°+. Below is the Recteq vs. the Thermotemp app.

 

[BoostLife]

On a very serious note I would like to learn more how the PID system works.
If the PID a takes an average, an average from where just the temp probe in one location?
don’t you have to have more than 1 to have an average? Or is it over a time period?

Please don’t take this is me being a smartass.
I truly would like to understand how it works.

if there is a website/video that someone can recommend that I can nerd out on, I’m ready to learn.

Thank you in advance

I also do Homebrewing and have a 50A 240V electric brewing system that I built which uses PID control.

From a high level here is an example of how a PID system differs from a non PID.

Think of something like a basic water heater. You have a thermostat set to lets say 160F. As it is heating water the burner has only two settings, going wide open or pilot. If the water is at 120F the burner is wide open which is fine. However if the water is at 159F the burner is still wide open. Once it hits 160F the burner cuts off and goes to pilot. Well the temp is still rising. Kind of like a car with the cruise control set when it is going up a hill. Once it crests the hill you might accelerate above your set point a bit. This is why they often overshoot. In the case of a water heater, it really doesn't matter that much if it over shoots to say 165F. Now this example was a gas water heater but an electric water heaters typically do the same thing.

In my homebrewing rig I use a couple 5500W electric heating elements from a water heater. They are wired into a solid state 40A relay. If you are not familiar with what a relay does, think of it as a light switch that gets turned on and off from an electric signal rather than your finger. You use these because a PID isn't capable of having 30A of 240V pass through it. The PID would have to be massive. Also doing this switching and carrying this load generates a ton of heat where we have to use massive heat sinks on them. We use solid state ones because they can be power cycled really fast. The relay looks for a signal on the coil side which is sent by a PID. So in this set up I have 240V 30A going through the SS Relay to power the 5500W heating element but only 12V DC coming from the PID to the coil side on the SS Relay. The PID also has a temp probe input. What happens in the kettle is if we are shooting for 160F temp, much like with the gas water heater example it is running wide open at 5500W when the temps are way below the set point. Lets say wide open at 120F. When I say wide open in the case of the relay it is a constant 12V from the PID to the relay. As the temp starts to get close to the set point what happens is it will start to pulse the signal. This is what we call Pulse Width Modulation (PWM). It is still getting 12V from the PID but it is pulsing the signal. This is why we use DC for this signal. So imagine turning the light switch on and off really fast. How long (time) those pulses on vs off are taking place. This is how some dimmers work on your lights. It is also how some motors are controlled like say a fan motor to go from low speed to high. The PID is controlling the on/off cycles and duration, watching the temp rise until it eases up to the set point. This then avoids over shooting it.

If you look at the temp graph (one is posted above) from one of the grills that is what they look like from my homebrewing rig. Well they are a little less jagged because water has a lot of thermal mass and I am heating with a very controllable energy source. However you will see a steep rise in temp but then as you near the temp the rate of rise trickles off. Going back to the water heater example this is why PID control really isn't wanted there. They don't care if they overshoot but they would rather get to that 160F set point as quick as possible. It is also more complexity than is needed. Relays fail, PWM is really hard on them and are simply not really needed. Also water has a lot of thermal mass so it takes a lot of energy to change 40 or 60 gallons of water 1F. However, if I am using the same heating element to heat 5 or 10 gallons of water it impacts the temp much quicker. I am also many times shooting way higher as I am boiling the water.

To do this, the PID is not only looking at the temp, but also at the rate of temp rise. The PID doesn't know what it is trying to heat, if it is heating a kettle of water or a grill, if the fuel source is electricity, gas or wood. It just knows to control the output based what the current temp is, what the set point is and how quickly it is getting there.

Now it is a bit tricky with these grills which is why these systems overshoot. I actually am kind of shocked that RT can get within the numbers they do with the PID. The problem is you can't pulse that burning of wood like you can electricity or to a point a gas burner. You can't have the pellets burning one split second and not the next. When I am talking PWM it is cycling the power on and off very quickly as in fractions of a second. They can control the speed of the fan which will in turn promote or limit the rate at which the wood is burning. Also there is of course the auger control. However, I suspect that they mostly control the temp via the fan. Since the fan is probably 12V it likely doesn't need a SS Relay like I am doing. Of course we are throwing variables at it such as different pellets at times that might have different BTU ratings. Outside temps also can differ. Not to mention every time we get impatient and open that lid there goes the heat. To be really honest, if they are staying in that say 20-30f range that is pretty darn good based on what they are dealing with.

 

[fullhouse32]

Thank you all for the info, I like to know how some things work. @BoostLife your explanation helped me understand it more. I did a lot of reading last night on PIDs.

 

[Maule Guy]

Great description "BoostLife" !!

I actually am pretty impressed with the PID control on my 590. It seems to "learn" the heating profile and slows down the heat up as it approaches the set temp. If mine overshoots, it is not be much.

I previously owned a Louisiana Grills LG 900 which would reliably overshoot the set temp on start up (let's say 225F) by150F-200F and the temp spread between left and right was easily 30F at a 225F set temp. That spread may not sound like much but it makes a huge difference if you have two pork butts cooking and one is cooking at 225F and the other is cooking at 255F-260F.

Once their unit got to "set temp" the temp at the thermometer could vary by huge amounts while the "actual" temp display stayed at the set temp display. I changed out the motherboard and then, at least, the actual temp did show something close to what was happening but the temp variation and swings were still excessive.

Bottom line is that ReqTeq seems to be doing a much better job. At the end of the day trying to regulate temperature of what is essentially a pellet stove in an uninsulated barrel has got to be a challenge.