PID Controller For Double Burner Shotmaker Propane

[PrecisionAmmunition]

Hey everyone,

I wanted to start a thread to throw around some ideas for making a PID controller for my shot maker which runs two propane burners. Firstly my understanding is this would require two pid controllers to control both valves I plan to install.
http://www.ebay.com/itm/Methane-Gas-Fuel-Propane-2-Ways-NC-Solenoid-Valve-3-8-BSPP-Connection-110VAC-/251266479575?pt=LH_DefaultDomain_0&hash=item3a80a635d7

the valve in question will be run inline with a T fitting before it and a ball valve running off the extra part of the fitting. This will run a small amount of propane to the element acting as a pilot light.

for this to work I planned to drill and tap a second feed line into the bottom of my propane bunner and run a small piece of copper line.

I was also looking at this PID controller with the 4" k type probe.
http://www.ebay.com/itm/DIGITAL-PID-TEMP-CONTROLLER-F-C-25AMP-SSR-WITH-HEATSINK-AND-PT-100-PROBE-/261286976034?pt=LH_DefaultDomain_0&hash=item3cd5eada22

I have looked up the wiring diagrams and I just need to understand that if I run the valve as a on off switch similar to the LEE pots on a PID controller if everyone thinks it will work or not, I am just starting to collect parts so I am open to suggestions as I am new to the PID controller world.

Thanks
Jeff

[Faret]

I do not think you will need it with propane as you are puting out a constant form of heat that is regulated. Electric yes where the element is either on or off I would use one. Once my temp is set I do not have to touch mine.

[rsrocket1]

Look at how a gas stove works. That's the same principle. You can make it proportional and always on or you can start it and stop it like a stove (or gas house heater/hot water tank). I don't think you need 2 PID's. You can control the temp with just one thermocouple and one valve for both burners.

[PrecisionAmmunition]

So you think one larger valve could support both burners? I should mention I run a double burner and dual propane tanks, this machine now with 14 drippers pumps out the shot easily upwards of 200lbs a hour. I found with a single burner mounted in the center I was getting uneven heat across the entire machine and it would cause the outside edge drippers to drip slowly if at all. So I had a spare burner and I tossed it on and run both burners at about the lowest setting and it gives me nice even heat. But with adding lead ingots to the pot I notice sometimes I have to adjust the heat or as the machine starts to get lower on lead I have to adjust it again. I would really just like to add some control to it and make it so much more automated.

[Frozone]

So you think one larger valve could support both burners? I should mention I run a double burner and dual propane tanks, ......

or 2 valves, one for each burner.

Don't use 2 PIDs, they don't play well with others.

Because you are using a slow to respond design you could get away with a relay output PID.
Just slow down the control cycle to say 5 second.

This is why a proportional control is a better choice.
It's far easier to make a small change in the volume of gas flowing than it is to start, light, and stop a (relatively large) burner.

You might want to look into your burner design too.
It seems you're trying to fit 2 round pegs into a square hole. Look into getting a rectangular burner that goes all the way across the dripper.

[dragon813gt]

If you really want to control the temp properly you will need a modulating gas valve. Simply turning the gas on and off w/ a solenoid valve could lead to temp swings. It's also 100% output or nothing. Why put out 100% if you only need 25%. Especially w/ propane which isn't cheap. It makes sense to modulate the gas output.

[PrecisionAmmunition]

Ok so I am now looking for a modulating gas valve. At the time I built this machine entirely out of parts and pieces I had laying around thats why I went with the double round burner and not a square burner. Mind you I could build a square burner now out of some steel I have laying around. Frozone I was hoping you would reply as I was speaking to you about this before.

[Faret]

I would try and split the gas line and run both burners on one regulator and make one square burner tube. Trial and error will get you there!

[PrecisionAmmunition]

I have now decided to build a new burner this week. But I need help with selecting the proper valve that would work as proportional or modulating if anyone has a suggestion.

[kitsap]

Use your favorite search engine and put in home brew PID. The beer guys have been using PID's for some time with different types of heat sources including modulated valves.

DougF

[PrecisionAmmunition]

SO after researching I have come up with what the homebrew groups consider the safest and most effective valve that is intermintent.
90749

Tell me what you think, looks like a total cost around 300$

[Frozone]

Well, you can skip the Auber unit and save $15+ right off the bat.

[PrecisionAmmunition]

Frozone I need a relay output type PID controller, Everywhere I look I am only seeing SSR setups. Any suggestions?

Thanks

[Frozone]

I have one around here somewhere. I got samples of the various types from Mypin (and others) a couple years ago.
You can have it cheap if I can find it.

[PrecisionAmmunition]

http://img.tapatalk.com/d/13/12/24/qy9ynugy.jpg

[PrecisionAmmunition]

91873

getting there.

[Frozone]

looking nice. huh, I would have thought that shot needed to fall farther.

[PrecisionAmmunition]

I thought so as well but I guess it's been tried and it doesn't work. I could always only half full my coolant tank and try again.

[Frozone]

I believe you. I just seem to recall reading that the shot tower at a <major manufacturer> was over 100 ft tall.

[PrecisionAmmunition]

Yes your correct, I have a major manufacture close to me and the tower is huge but they are also sir cooling there shot rather then liquid cooling it. I have gone and watched them make Shot in a tower it's pretty neat. I would say tower shot is a little rounder but I haven't had my machine running perfect just yet, so we will see.

[PrecisionAmmunition]

So I now have all the parts to finish the build, roughly 500$ of parts to make this machine PID controlled and a recirculating coolant system. Give me two weeks I will have some test videos and such to share.

[taiden]

What about this? Just an idea

Take a line from the tank, bring it to a Y, one branch has your PID controlled solenoid, the other branch has a flow restrictor that is sized to only sustain the burn, collect it back into a single line via a Y, then distribute it to your burners with an effective manifold.

One solenoid, one PID controller, but extra tubing work. Figure out what the maximum switching frequency is of the solenoid. If it's below relay frequencies, then you can skip the solid state relay (although with the price of them, I'd run one anyway, two in parallel if you want component redundancy for machine reliability).