DIY smoking rig

[HowardLi]

I've done some research and it looks like the factors to control are dry-bulb temp, wet-bulb temp, and RH (or any two of the three). The amount of smoke seems to be fairly easy to control, e.g. lots of it is fine.

So far, the system is as such:

- There is a smoking chamber constructed from some material safe and robust enough for the intended application

- The smoking chamber has some mechanism(s) adjustable such that heat loss is a controlled factor (damper vents, etc)

- The dry-bulb and wet-bulb thermometers are Pt100 RTDs.

- Both thermometers are at approximately the same height as the food.

- There are two PID controllers controlling one solid-state relay each

- PID #1 reads the temperature of the dry-bulb thermometer inside the smoking chamber.

- PID #2 reads the temperature of the wet-bulb thermometer inside the smoking chamber.

- There is a pot of hot water inside the smoking chamber, resting atop an electric hot plate.

- External to the smoking chamber is a smoke generating system, consisting of:

-- A modified charcoal chimney of sorts, to contain the smoke-generating fuel and facilitate ash collection

-- An air conduit between the charcoal chimney and the smoking chamber; its intake is underneath the wood pile of the charcoal chimney and its discharge is to the smoking chamber

-- An AC motor-powered fan inside the air conduit between the charcoal chimney and the smoking chamber; this fan sucks air towards the smoking chamber

- PID #1 powers the electric hot plate through its relay when the dry-bulb temperature drops below a certain point; when this happens, the pot of water heats up and eventually raises the relative humidity

- PID #2 powers the fan through its relay when the wet-bulb temperature drops below a certain point; when this happens, oxygen is pulled through the wood pile and both heat and smoke enter the smoking chamber

Any thoughts?

[HowardLi]

Would such a system ever reach stability with the two interacting sources of heat? Could adequate ventilation (heat loss) ensure that both kick-on when needed?

[Smithy]

Have you allowed for upper limits on each of the PID controllers?

[radtek]

I found this website to be of immense help. Here is a link to "smokehouse plans"... http://www.wedlinydomowe.com/smokehouse-plans My recommendation is to read everything under the smoke-houses link for starters. IIRC they discuss humidity in several areas and it led me to believe it was more important when smoking for extended time-periods and that fluctuations weren't critical.

[HowardLi]

Have you allowed for upper limits on each of the PID controllers?

What do you mean exactly?

The other option I was thinking of was instead of using a hot plate as a source of humidity, I could duct in a small external humidifier and run the smoke all the time as a constant source of heat.

[Martin Fisher]

The other option I was thinking of was instead of using a hot plate as a source of humidity, I could duct in a small external humidifier and run the smoke all the time as a constant source of heat.

I think that's a much better idea.

I would also pipe in the smoke with an A-Maze-N smoke generator (piped in only because I think that high humidity may interfere)

The A-Maze-N smokers are great. I highly recommend them.

http://www.amazenproducts.com/

~Martin

[Smithy]

Have you allowed for upper limits on each of the PID controllers?

What do you mean exactly?

I mean that you described at what point you'd have the PID controllers call for "on" but you didn't state when they'd call for "off". Without setting the "off" parameters you'd have an overheat. It might have been an oversight in your description instead of in your plan, of course!

[HowardLi]

Have you allowed for upper limits on each of the PID controllers?

What do you mean exactly?

I mean that you described at what point you'd have the PID controllers call for "on" but you didn't state when they'd call for "off". Without setting the "off" parameters you'd have an overheat. It might have been an oversight in your description instead of in your plan, of course!

Yes, certainly.

[HowardLi]

How does one typically increase the longevity of wood fuel for smoke production without increasing creosote content?