$50 automated pit controller - DIY

urbangriller · Post by **urbangriller** » Fri Jul 25, 2014 4:58 pm

MrT wrote:Hey. I'm super keen to make something like this. I already have the bulk of this for a sous vide controller I made. All I need to make is a blower.

Any tips on connecting a blower to a WSM?

Chris

MrT · Post by **MrT** » Mon Jul 28, 2014 11:29 pm

Stainless steel mixing bowl screwed into the existing vent? Is the vent removed first?

StoneX · Post by **StoneX** » Tue Jul 29, 2014 9:36 am

No, vent is just opened fully.

You can use a screw thing like this (I don't know what it's called) to attached it temporarily.

This has some alright pictures to help: http://www.instructables.com/id/Smoker- ... ontroller/

rotten · Post by **rotten** » Fri Aug 01, 2014 12:21 pm

Can I just check something.

Once vents are set (UDS for example) you set the temp and parameters on the PID, and the fan comes on to maintain temp by increasing air flow?

If that's the case I wonder if it's possible to rig up a vent that will close on another relay on the pid for when the temp gets too high?

The only problem I can see that if I do this I won't have the excuse of checking the smoker and sneak in a beer from the keg fridge while I'm there

StoneX · Post by **StoneX** » Fri Aug 01, 2014 12:53 pm

I don't think there is any need to close a vent as the fan adapter restricts the air flow quite a bit.

Apparently, from what I've read the PID also learns when to shut the fan down to reduce the temperature overshooting your target temp. I'm not sure if this is 100% correct and would be happy for someone to explain it better.

MrT · Post by **MrT** » Mon Aug 04, 2014 12:18 am

StoneX wrote:I don't think there is any need to close a vent as the fan adapter restricts the air flow quite a bit.

Apparently, from what I've read the PID also learns when to shut the fan down to reduce the temperature overshooting your target temp. I'm not sure if this is 100% correct and would be happy for someone to explain it better.

Yep. PID devices are not simply thermal switches. They have an algorithm build into them which monitors the past error (how far away from the target temp you are), and then tries to minimise the predicted future error. The anticipate the delay in changes in temperature and factor that in.

beaver · Post by **beaver** » Mon Aug 04, 2014 11:52 am

i wrote this guide to PID controllers to help others understand

Draft Control Systems

Why Use a Draft Control System?

Draft control systems help keep your pit at a constant temperature without having to adjust your dampers and/or use water pans.

how do they work

Draft control systems measure the temperature via a probe within your pit. On the draft controller you set the temperature that you want the pit to be.
at a very simple level a fan is attached to the intake of the pit (replacing the pits ability to have air added through a draft door) and the fan runs untill the pit is to temperature

How they work - Nerd Version
Draft control systems in most cases arent just an on/off system where the fan turns off when temp is reached. instead these systems use a PID algorith to calculate the "error value" which is the difference between the desired and current temperature.
the PID algorithm then works towards closing the gap on the error value by pulsing the fan on/off untill it reaches the desired temp. These "pulses" vary based on the algorithm, simply put the pulses are longer and less regular as the error value becomes smaller.
(I can elaborate on how this works further if there is interest)

Pros
- less charcoal used due to less wasted heat
- you dont need to "tend" to your pit as often or add as much fuel
- extremly stable temps in most cases
-logging or remote monitoring in some cases

Cons
- not as clean a burn due to less airflow
- reliant on power/batteries

what i have notices with many of these units is that when used with a kamado cooker they can in some cases snuff the pit out.
This happens due to a number of factors.
1. the thermal mass of the unit buffers temperature changes its for this reason that temperature changes are delayed and thus a draft system isnt able to "catch" a fire that is going out.
2. the pit constantly runs on a very little ammount of lit charcoal so it easily goes out if not given enough oxygen.

Setting up your pit for a damper control system
There are a few "gotchas" when it comes to setting up a pit for a damper control system. I will try to talk about the kamado as this is one i have had the most experience with.

1. lighting your fire
when choosing to light your kamado under a draft system it is important to note that "temp runaways" can happen so helping a draft system get to its setpoint is important but just as importantly is helping it not overshoot.
What i have found after much trial and error is these points.
-USE dense charcoal that is slow burning like mallee root. fast burning charcoal is prone to going out. this is due to the slow temp swing characteristics of the kamado
-Light only about 4 brickets worth of charcoal. a smaller ammount of charcoal is suggested so that the draft unit isnt choking the fire to bring it back down to temp
-allow the pit to come up to about 150F if you are aiming at a 225F pit before activating the draft system. this way, once again not too much charcoal is lit.
- use the minion method, this method allows for the charcoal to gradualy burn down instead of lighting too much at once

2. Placement of probe
on a kamado or any other pit is is highly recommended that the probe is not placed directly over the fire. on the kamado a probe is bes tplaced above a heat shield so that ambient temp is read instead of the temp of just the fire. this will help with the stability of the pit.

3. using smoking wood
Baring in mind that a draft control system burns much less charcoal it is suggested that only small ammounts of woodchips are added (sprinkled) around the lit charcoal. a draft system will have the fire pit only smouldering and thus much larger ammounts of smoke will be produced. take this into consideration when choosing your wood/ammount.

4.Waterpans
what i have found with a waterpan on a kamado or other pit with a small volume is that it further dampens the temperature swing leading to an unstable pit.

WHICH UNIT TO BUY
this comes down to budget, preference and i cant make this decision for you.
here is a list of a few of the options.
I will elaborate on them at a later stage as well as find more options(features, price ect ect)

Robbo5252 · Post by **Robbo5252** » Mon Aug 04, 2014 2:24 pm

Hey All,

In the process of researching one of these & was wondering why the white fan over the black fans available?
The one below looks like it would be easier to attach to a UDS or Pit but dont want to get it if it wont do the job?

http://www.ebay.com.au/itm/QZO-Brushles ... 4897.l5678

Cheers

Robbo

beaver · Post by **beaver** » Mon Aug 04, 2014 3:40 pm

just be aware that 30cfm is a fair bit of air.
most go with 5-10cfm for a wsm or kamado.

http://www.ebay.com.au/itm/75mm-x-75mm- ... 860&_uhb=1
try this one

Robbo5252 · Post by **Robbo5252** » Mon Sep 22, 2014 10:23 pm

Thanks Beaver, have ordered the fan, do you have a link to the PID you used?

Time to get this project moving!

Cheers

Robbo

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