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Old 02-04-2011, 07:42 PM   #21
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Man, I don't know why you chose to ignore kladue. If your PID has a 0-20mA output a 500 ohm resistor would have been perfect. I work for a company that specializes in data acquisition equipment and kladue's suggestion is perfectly valid.

The reason they have products like that is because they usually offer isolation as well. Isolation would be good if the signal is coming from an electrically noisy environment and you want to keep that noise out of your panel. Or they are used to repeat the signal if their is too much of a burden on the current analog loop.

Dont chase the bid on that thing too hard, you really dont need it.
I don't think I really ignored kladue, although I was not diligent in immediately looking at the actuator he mentioned. After that post I looked at the wiring diagram he pointed out (the Belimo LR24) and saw what he was talking about. Right in the instructions it showed, just like he said, a wiring diagram on how to convert from 0-20 mA to 0-10V. Obviously you guys have a LOT more knowledge than I do on this stuff (as does ANYONE who has done anything like this before-- I am a total noob to this kind of stuff), and I do put great value on what you all say. I plan to wire it exactly as Kladue showed.

As for the PID-- it is true that I don't need something as complicated as the UDC3300- it will be more difficult to program and understand than the lesser units, I think, but it is a screaming deal at 36 bucks, when the next option that would work is 69. At the price I got it it is less than the auber PIDs that I have , and still is by far the cheapest option I have seen for a PID with analogue output of any kind, especially with dial loop current control. I would rather have a 1/16 DIN unit and the UDC 3300 is a 1/4 DIN, but for the price I couldn't turn it down.

Thanks everyone for the help. I will try to write it up once everything arrives.

Klaus
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Old 02-04-2011, 08:03 PM   #22
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Klaus, my apologies. I thought the auction was for a voltage to current loop converter.

I am interested to see as to how it integrates together, a valves change in surface area in relation to it's position is anything but linear. Well, unless it is a V profile needle valve. So the tunning on the PID is going to be interesting. I definitely think it would work and bet a bunch of HERMs brewers are waiting with baited breath for the results.

One last thing, you will want to set the valve to a 2-10V input if the output of the pid is 4-20ma.

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Old 02-04-2011, 08:14 PM   #23
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whoops... just noticed something that may cause an issue... the valve I have (a honeywell M7410F) has input voltage as 24 volt AC... ALTERNATING current, but the control voltage is listed as 0-10v DC.... Can't really put a resistor between these two (alternating and direct), can you? Some valves seem to work on DC as well as AC, but I don't see this anywhere in the product manual. Output of the UDC3300 appears to be 4-20mA DC.

Klaus

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Old 02-04-2011, 08:28 PM   #24
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HI CodeRage-- no problems! Ultimately I am planning in the distant future to switch to HERMS and a three vessel system, but not until I can move to a bigger house which is several years out. At the moment this is sort of a project looking for a reason to exist. I am using it as a learning tool mainly, but it is just going to control the rate of the wort outflow through my chiller so the wort heads to the fermentor at exactly the right temperature.

It actually is an interesting problem, I think. I will not be able to set the PID to cool, I don't think, and will have to have it control HEATING. If it was on a cool cycle, when it thinks the wort is too hot it will power the actuator, which will open the valve MORE, thus increasing the rate at which wort flows through the chiller, warming it up. This is the opposite of what the PID would expect and I think it would make it not work at all. If it works through the heating cycle, on the other hand everything should work well, I am just not sure how the thing will respond to overshoots... if it completely closes the valve at any time, then that will kind of defeat the purpose. At the moment I am thinkning of running a very small guage bypass tubing from before the valve to just past the valve. THis would allow a trickle of wort past the valve even if it is closed. Since the rate would be slow if the main valve is closed, it would be very cold wort and would actuate the valve again. The UDC controller also has a variable dead band setting, but I don't really understand this, but if it means I can make he valve NEVER completely close, then I can avoid a bypass.

I'll do some experimenting when it arrives.

Klaus

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Old 02-04-2011, 08:29 PM   #25
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nah, you're fine. The 24VAC is the power the actuator needs to function, the control signal will still be DC. Find a doorbell transformer that puts out 24VAC with a 110VAC input and is capable of at least 1.4VA.

Edit.
The deadband is the space around the process variable (temp) +/- x degrees that the controller sees as good enough. Ie dont tweak the valve if you're only 0.1 degrees off and at a steady state.

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Old 02-04-2011, 08:38 PM   #26
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Looking at the UDC3000 manual it should do anything you need. Its quite a capable controller to be honest. For $36 you might as well have stole it .

Page 9 states the control signal can be set to direct or reverse action. So if the valve behaves in the opposite fashion you desire set it to reverse and the valve should work in 'cooling mode' if you will.

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Old 02-04-2011, 09:39 PM   #27
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subscribed.

i have been pondering something like this to control the flow through my tankless heater. i would be able to just hit 'go' and get 170 degree water out and let it alter the flow rate for me, rather than having to tinker with a valve all of the time to get the temp right.

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Old 02-04-2011, 11:25 PM   #28
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The ramp function is going to be an important part of the tuning as the time lag between control change and temperature change on start up can cause big temperature and control output swings as the controller settles.

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Old 02-05-2011, 05:22 AM   #29
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Thanks for pointing out the reverse function from the manual. Perhaps I can have it on a cooling cycle after all and just reverse the action. That would seem to make more intuitive sense, as it is in fact controlling the flow of wort through a chiller. The manual is such a massive beast that I have to say I can't understand about 90% of it. That's the downside of getting such a complex controller. The price was right, though!

I didn't even consider that i might have to futz around with the ramping when it starts. I am used to using PIDs with heaters (I wired a PID for fermentation control to control a few brewbelts based on a thermowell RTD sensor for winter use) and don't have any experience controlling valves. The way plan to use it is with heating control, so when the temp gets too cold, the PID sends a signal to open the valve a bit more and heat it up. I think I figured out a way around the bypass valve that I had planned, too. I just need to turn on the cooling source for a while during recirculating (I clean by recirculating boiling wort for 15 minutes), and not turn power onto the valve until the wort is already running cool. The valve takes some time to open (not sure how long), and I presumed that, since the PID can send signals quite frequently of how much to open the valve, it should stabilize rapidly. Guess not though, huh. So would you set a ramp to start at like 55 degrees (approx groundwater temp in early summer) and then over 1 minute ramp it up to 68 or whatever the recipe calls for?

And if anyone knows, I assume that reversing the action on the PID controller would allow me to put it in cooling mode, as it would basically turn the valve into a "normally open" type. Is there an advantage one way or the other. Seems to me with a proportional valve it should be able to do the same thing whether set to heating mode or cooling mode because it is trying to hit whatever value you set. Am I wrong?

Attached is the flow diagram I plan to use, or something like it, at least. I will have to modify the 3 way T valves to turn 360 degrees around so I can use them as a stopcock- off to the direction the handle points. This setup lets me do a lot of things with the system (RIMS recirc, recirc boiling wort to sterilize equipment, either chill the whole wort volume or use hopback and chill only when going to fermentor).

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Old 02-05-2011, 11:36 AM   #30
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Thanks for pointing out the reverse function from the manual. Perhaps I can have it on a cooling cycle after all and just reverse the action. That would seem to make more intuitive sense, as it is in fact controlling the flow of wort through a chiller. The manual is such a massive beast that I have to say I can't understand about 90% of it. That's the downside of getting such a complex controller. The price was right, though!

I didn't even consider that i might have to futz around with the ramping when it starts. I am used to using PIDs with heaters (I wired a PID for fermentation control to control a few brewbelts based on a thermowell RTD sensor for winter use) and don't have any experience controlling valves. The way plan to use it is with heating control, so when the temp gets too cold, the PID sends a signal to open the valve a bit more and heat it up. I think I figured out a way around the bypass valve that I had planned, too. I just need to turn on the cooling source for a while during recirculating (I clean by recirculating boiling wort for 15 minutes), and not turn power onto the valve until the wort is already running cool. The valve takes some time to open (not sure how long), and I presumed that, since the PID can send signals quite frequently of how much to open the valve, it should stabilize rapidly. Guess not though, huh. So would you set a ramp to start at like 55 degrees (approx groundwater temp in early summer) and then over 1 minute ramp it up to 68 or whatever the recipe calls for?

And if anyone knows, I assume that reversing the action on the PID controller would allow me to put it in cooling mode, as it would basically turn the valve into a "normally open" type. Is there an advantage one way or the other. Seems to me with a proportional valve it should be able to do the same thing whether set to heating mode or cooling mode because it is trying to hit whatever value you set. Am I wrong?

Attached is the flow diagram I plan to use, or something like it, at least. I will have to modify the 3 way T valves to turn 360 degrees around so I can use them as a stopcock- off to the direction the handle points. This setup lets me do a lot of things with the system (RIMS recirc, recirc boiling wort to sterilize equipment, either chill the whole wort volume or use hopback and chill only when going to fermentor).
That is a great looking setup

Regarding your question on how long the valve will take to open will depend on what the settings for proportional gain and integral are. Integral really determines often it makes a valve adjustment to reduce the error between the measured and the setpoint.

Not sure if that controller has a auto tune or not but you may want to run a few tests with water and let the auto tune do its thing. PID gains may also change depending on flow rates. Its possible to get middle of the road gains that will cover a large range of flows.

You may want to auto tune at multiple flows to see how it responds. Good luck. It sounds like you'll end up with a really trick setup

edit: Yes, if the controller has both actions then you could heat and cool with the same controller. It complicates things a tad and may require slightly different gains however very doable.
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