Pellet Grill Control


 
J

Jonathan Hulsman

New member
I am getting ready to get a pellet grill and was thinking that if the there was a way to make the servo pin on/off control, the heater meter would work well for a pellet grill.

I am not good at software, but the heatermeter could be used to drive SSRs for the fan and auger.

Basically the servo be set to 100% when greater than 0, and this drive the fan, and the auger is driven by the fan using the 100% min option. PIDs would obviously have to be adjusted but I was wondering how difficult that modification to the code would be, and if there are other people interested.
 
The servo output isn't an on/off sort of thing. It is a pulse that's roughly 0.1ms-2.5ms long with a 20ms period. Running 100% at the largest setting is only going to get you roughly 10% duty cycle on the output. To do what you want you'd throw out all the servo code completely and make it on/off control or something.

You could always attach a servo to a manual switch that turns on and off something or use the blower output to drive some other sort of circuit. I thought pellet grills already had temp controllers though?
 
Pellet Grills to have temp controllers, but most are not wifi, and don't give you the logging that the heatermeter does.

How difficult would it be to make a selection box in the UI for servo or on/off, I am going to look into it tonight, but I like the idea of using this pin because it is already wired out.
 
There's servo full open/close only but that's not going to do what you want because it is still going to be a 50hz signal that only occupies 10% of the time period.
 
Brian, i downloaded the code and looking at how to modify it, I found where it is set to 50hz. I am not a programmer, but wondering if the refresh rate being set in the UI is something that you have considered. I am not sure how difficult that is or if there would be a benefit for anyone but me with what I am wanting to do.
 
What sort of refresh rate do you want? I am still a little in the dark about how you intend to convert a servo signal to anything besides a servo signal. You can the refresh interval in code but there's a pretty somewhat range where it works (the code expects it to fall inside the right multiplier range I think).
 
I don't know if it is possible but I would like it to be an on off control. I know the heatermeter isn't design for what I am trying to do but I am wanting to experiment with it controller a pellet grill because of all the monitoring capabilities
 
Doesn't the pellet grill have it's own controls to hold the temp? Why not just add the HM on the side to add the monitoring capability but let the built in pellet controls run the pit?
Or maybe if you want to try and control the pit from the HM get yourself a servo damper, leave your blower on all the time and let the servo damper clamp down the air flow, then use the fan output from the HM to flip a 12v relay that would power the auger... You would have to play with the fan settings, setting a min and max of 100% would make the fan output be pulses of 12V that might be able to drive your auger?
 
The grills do have temp controllers but the steps are quite large in settings. It is a good idea about a servo damper for the fan. I am planning on using a ssr for the augur and would with the fan if it could be an on off control
 
Jonathan I wanted the same but gave in and bought the updated wireless controller for my Greenmountain Daniel Boone pellet grill. I still use the HM to check (4) probes and the GM wireless to control the grill.
 
I have a Traeger, I have seen those before and it would not be hard to adapt the controller I don't think. I wasn't sure how hard it would be to make the servo pin to an on/off control selectable from ON/OFF and servo.
 
If you don't mind editing the code, you could just go to grillpid.cpp void GrillPid::commitServoOutput(void) and change it:
Code: 
  // ADD THIS
  digitalWriteFast(PIN_SERVO, output ? HIGH : LOW);
  return;
  // EXISTING CODE vvv
  output = mappct(output, _minServoPos, _maxServoPos);
 
I'm very interested in this!

Now I know you can use a Rock's stoker to controller the Savannah Stoker PID on the traeger, so there has to be a way to do the same for the traeger. If we could make some code and adapter boards for the traegers, I think this would take off like crazy!
 
A thought just came to mind, forgive me if I am way off base 'cause I don't have experience with pellet smokers.... From what I gather there is a fan that is used to regulate the pit temp but there is also an auger that feeds the pellets to the fire. If there is any way to make the auger motor have a speed control (rather than just on/off) you could use the HM servo to adjust the speed control for the auger and calibrate the range needed with the SPD setting for the servo on the HM. This would let the HM manage the pit temp with air flow regulation and you could scale the auger output to whatever proportion would be needed to maintain the fire. It would allow you to adjust the amount of pellets the auger serves up in relation to how much the fan needs to blow to achieve your pit temp, and you could adjust how much pellets get fed by setting the low and high end limits on the servo (SPD settings), which would be moving the auger speed control....
 
Last edited:
I don't know how you control proportion if you just use on and off for the auger? You could use the blower output and set min/max to 100%/100% and that would pulse the blower output which could control the auger drive, but then you don't have a blower to regulate the pit temp (cause it's driving the auger). So my idea was to use the HM blower control to drive a blower and use the servo to physically control a speed control for the auger. That would allow the HM to control the pit temp as normal (with forced air) and allow some fine adjustment to how much the auger feeds (by varying the SPD settings on the servo and thus adjusting how much it turns the auger speed control).

I guess that concept could be used the other way around too, using the blower set to 100%/100% which would give you an on/off 12v output that could flip a relay and turn the auger on/off, then use the servo to rotate an external blower speed control to control the air flow....
 
The combustion fan on a pellet muncher should be 100% all the time (except when lighting?). The auger could have a variable duration "on" cycle or be pulsed to turn slowly, like 1-2 RPM (not exactly sure of the specs, but you could time it and see).

I would suggest the use of a repeat cycle timer (like one by Futurekit) to set the "on" and "off" duration for a feed cycle on the auger, and Ralphs servo suggestion for manipulation of one of the knobs on the cycle timer to change the temperature via increasing or decreasing the feed rate by [on/off] cycle timetime for the auger.

You could also adjust the temp by turning the knobs manually rather than have the HM servo cocontrol do it.
 
I am very interested in this concept. I have a Green Mountain Pellet grill that I love. It produces great BBQ with minimal effort. I know that it upsets some BBQ purists, but I enjoy being social instead of tending to the smoker all the time.

With this in mind, I got all the parts to a HM with the intent of applying it to the smoker. Recently I have had more and more trouble with the built in control system. All the components work, but I think the design can be improved. The smoker I use is the larger model and as a result some of the meat can be 2 or 3 feet from the temperature sensor. To start, I plan to have the HM verify what the built in controls are reading, then hopefully use the HM software to control the combustion fan as well as the auger.

If anyone has any tips going into this project I would appreciate it. I do enjoy tinkering around with electronics, but I am far from an expert.
 
You must log in or register to reply here.

 

Back
Top