Electric smoker


 
R

RJ Riememsnider

TVWBB Pro
After having a bad time and having the food come out hours late I have decided to replace the cheap mechanical temp control in my electric smoker with HM.

Bryan, the PWM output that drive the blower will in my case drive an SSR. I looked to see if i could find some info on this as I vaguely remember a thread a year or 2 ago but isn't there some code in HM specific to this? I remember a conversation about how many power steps but I can't remember the context. Also, I'd like to get some opinions about sensor placement. This is a smokin-it #3 and is 15"w x 20"h x 22"d on the inside with 4 racks and a u shaped heater element that runs from back to front. I'm thinking placing the sensor about 3/4 the way up in the center of the back wall.
 
I don't have any useful details at the moment, but I am currently running my electric smokers with a HM. I know I tweaked a few settings in HM config, definitely no hardware changes except for the SSR in lieu of a fan.
 
You can drive an SSR directly from the blower output. I've got an electrical outlet in a wall box that I added an RCA jack and an SSR that works just fine with the HeaterMeter code. It tries to switch ~500 times a second but the SSR will only switch up to 120 times per second. It seems to work but you can also switch it so it just runs X% of every 10 second period by setting the min/max fan speeds to 100%. If you do that the resolution of the output is only 10% intervals (0%, 10%, 20% etc).

You can't run two pit probes with one HeaterMeter. The code is designed to have one input and one output and everything is based around that. If you tried to rewrite it to support two you'd have a decent amount of work on your hands. If you tried to rewrite it to support "multiple" (i.e. a variable number) you'd almost certainly run out of program space on the device. Two pits, two HeaterMeters.
 
Thanks Bryan, what i was suggesting is not 2 actual inputs but 2 probes in parallel on one input with different parameters to compensate for the difference in resistance. It was just an idea spawned by trying to find a decent place to mount the pit probe in this electric and get a half way accurate number.
 
Or, I could do 4, 2 in parallel in series with 2 more in parallel, that should get a more even sampling. Anyone have thoughts as to why this would not work?
 
Yeah if you want to use the same coefficients, you'd just wire two runs of two thermistors in series in parallel, which would average the temperature across the 4. You also could do just two in series or parallel but you'd have to recalculate the coefficients (which is easy because you can just math the resistance from a table).
 
Stan, I got everything pit all together and think I understand why I was having some issues. I now have a much better temperature range but am having overshoot issues. Do you mind sharing what PID values you are using?
 
Bryan Mayland said:
You can drive an SSR directly from the blower output. I've got an electrical outlet in a wall box that I added an RCA jack and an SSR that works just fine with the HeaterMeter code. It tries to switch ~500 times a second but the SSR will only switch up to 120 times per second. It seems to work but you can also switch it so it just runs X% of every 10 second period by setting the min/max fan speeds to 100%. If you do that the resolution of the output is only 10% intervals (0%, 10%, 20% etc).

You can't run two pit probes with one HeaterMeter. The code is designed to have one input and one output and everything is based around that. If you tried to rewrite it to support two you'd have a decent amount of work on your hands. If you tried to rewrite it to support "multiple" (i.e. a variable number) you'd almost certainly run out of program space on the device. Two pits, two HeaterMeters.
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I have this working but getting a stable temp has proven illusive. I'm thinking it just takes so long for the heat to affect the internal temp and by the time HM shuts off the element, there's already too much heat generated. The blower output looks like a really sharp sawtooth oscillating between 0 and about 75% instead of being consistent. Is there a way to limit the min and max while using an SSR?
 
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Thanks Matt, good idea, I'm sure it would help but I think the bigger issue is with the 10% steps and the time it takes to make heat. Say we're at 31% and there is a temp drop, HM says ok, lets start to increase so I'll go to 32 then 33, then 34, then 35, etc. By the time it gets to 40 where more heat will be added, the system is already adding % to the blower pwm value faster and by the time the element starts to have an affect on the IAT, it's already at 80-90% so with an insulated smoker it will almost certainly lead to an overshoot. I did finally get some PID values where the amplitude eventually drops a lot but I still think the 10% stepping is a big contributor. On a side note, I need to talk to you about a custom case I can mount to my smoker. I'll get you some pics and we can discuss.
 
I also have an electric smoker that I use for making sausage, I built a controller from another forum using a Arduino Uno with a SSR. The code allows me to change the target pit temp every hour. I was wondering if the HM has that capability or if anyone has tried to incorporate that feature. I'm currently waiting for a board to arrive so I can start building my first HM :)
 
You can use alarms to do that.

dave

Tim Guenther said:
I also have an electric smoker that I use for making sausage, I built a controller from another forum using a Arduino Uno with a SSR. The code allows me to change the target pit temp every hour. I was wondering if the HM has that capability or if anyone has tried to incorporate that feature. I'm currently waiting for a board to arrive so I can start building my first HM :)
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D Peart said:
You can use alarms to do that.

dave
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Dave, I was asking, about the control automatically ramping up the setpoint every hour. When I do sausage it starts at 110 deg and ramps up to 180 over time, but i might want it at 110 for 2 hours then 120 for 2 hours etc... i realize i can set a timer and bump up the setpoint manually... but i'm always looking for the easier way :) :)
 
Yep, I understand. Take a look at ramp down and time delays on the wiki. It isn't automated, but the capability is there. I know that alarms were revamped recently so I don't know if it is easier to do now.

https://github.com/CapnBry/HeaterMeter/wiki/Alarm-Script-Recipes

dave

Tim Guenther said:
Dave, I was asking, about the control automatically ramping up the setpoint every hour. When I do sausage it starts at 110 deg and ramps up to 180 over time, but i might want it at 110 for 2 hours then 120 for 2 hours etc... i realize i can set a timer and bump up the setpoint manually... but i'm always looking for the easier way :) :)
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Yeah I haven't really been able to figure out how to make time-based stuff work and make it configurable. The simple answer is of course "well you make a profile and then it does it" but the details behind that are somewhat overwhelming. That and it isn't something I'd use so there's not a lot of motivation, but time-based triggers are on my todo list once I figure out what the config would look like.
 
I'm just glad someone else is interested in them, now there are two of us :) I find that I watch the HM so much anyway that I just change my temp settings manually when I need to. So I've never looked into trying to automate it either.

dave

Bryan Mayland said:
Yeah I haven't really been able to figure out how to make time-based stuff work and make it configurable. The simple answer is of course "well you make a profile and then it does it" but the details behind that are somewhat overwhelming. That and it isn't something I'd use so there's not a lot of motivation, but time-based triggers are on my todo list once I figure out what the config would look like.
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Update. I've got my electric working much better by relocating the pit probe farther away from the element. Where is still a temperature delta between that probe and the other 3 which I have placed in various locations for testing. Right now I'm using an offset to correct this but it's a patch until I find a better mount solution.
 
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