I'm trying to automate my methanol recovery still using an Omega C9000A PID Controller. I got some help with wiring the system (thanks Graham)...and it seemed to work well when I connected it to a light to test it.

I adjusted the set point to 75 or so, which made it so I could get the thermocouple up to the set point by holding it in my hand. The controller seemed to operate correctly (it shut off a little below the set point so it didn't overshoot)...and turned back on when the temp dropped back down.

Now that I have it hooked up to the still (with the set point at 152 in the head space), it's not keeping the heat turned on....

Is there something I'm missing? Is there a reason the controller would not apply heat when it's not up to set point yet?

Hi Dan

You should be using the relay out terminals 9 & 10.

SP1 indicator should be lit when you are below the desired temperature.

Try these settings inititally for SP1...

Set the Integral and Derivative times to 0 seconds
Set Proportional Band to 1%
Set Proportional cycle time to 15 seconds
Set Heating output limit to 100%

Make sure output 1 is set as reverse acting (Heating mode)


Hope that helps,

regards,

Graham

if i understand correctly, you are suggesting turning a PID controller into a simple two-point controller (on an off). the good thing about PID controllers is that they can keep the temperature just where you want it with minimal fluctuations. why throw that away?

Hi Harry

I agree, but we're just trying to diagnose the problem first.

If we can eliminate all the fancy stuff, get it working as an on/off controller (which for 99% of biodiesel processing is plenty good enough anyway) we can then introduce the other features.

Trying to walk first, then run.

Hey, Graham, I see your common sense showing again.

Seriously, I always follow your post with great interest. Your common sense coupled with a great imagination makes for very interesting, and thought provoking, reading.

Keep up the good work.

Now it's working...thanks so much for your help!

How would you change the parameters to make it work better...or does it matter for this type of application? I don't want to run before I should.

Hi Dan

Good news!

OK, so now we can get the controller to 'AutoTune' and it will set itself to suit your processor.

First, change the Proportional cycle time up to 30 seconds.

Next got to page 49 in the manual and set the controller for AutoTune.

You must start with a tank of cold oil, with the pump running, and the AutoTune will monitor how the temperature changes as the heater is switched on and off.

It will then choose the best settings, taking into account what it sees as your heater's 'heating speed' and your insulation's 'heat-loss speed'

Then you should be all set.

Sounds good. I'll completely insulate the tank and hook up both heating elements before I let it learn. I won't be able to do that for a couple weeks...I'll let you know how it goes when I do it.

Thanks again for your help. Dan.

This thing is working great! I've got it all insulated and hooked it up to a countdown timer that automatically shuts it down after 8 hours.

I've been producing 95% pure methanol...is there any benefit to changing the settings on the PID controller by using the autotune feature? It's working so well, I don't want to mess it up....

Sharpdan,
How bout a pic of your setup? Are you recovering methanol from BD or the glycerine byproduct?