Comments for Small Golden Sceptre http://mythopoeic.org Technology, Rambling and Dragons Fri, 30 Mar 2012 14:58:43 +0000 hourly 1 http://wordpress.org/?v=3.3.2 Comment on Sous-vide Cooking by dhenke http://mythopoeic.org/sous-vide-cooking/comment-page-1/#comment-47556 dhenke Fri, 30 Mar 2012 14:58:43 +0000 http://mythopoeic.org/?p=873#comment-47556 Tom @#30: <em>I still don’t get the auto-tuning.. Why can’t it be as simple as simple “turn on when X degrees before the set value, and turn off on the set value..</em> There are lots of thermostats that work exactly as you describe (like probably the one on your home HVAC system). The problem with using one in this application is that they generally exhibit several degrees "bounce". With sous-vide cooking, temperature control within a few tenths of a degree (or better) is important. That's why I resorted to a PID controller. (PID stands for proportional-integral-derivative. Basically, it tries to build a mathematical model of the impulse response of the system, and uses that to figure out a duty cycle for the heater that'll bring the system asymptotically -- but still rapidly -- to the target temperature. The "PID Controller" link in the original post goes to a Wikipedia article with lots more detail.) > <em>I am 1000% sure I have the wiring correct, but weird stuff is happening.. Now, I’ve tried auto-tuning, many times and ways.. but sometimes my SSR will activate the heating element, even without the red light lighting up on the SSR!</em> That can't be good. My guesses, in order, would be: noise coupled in to the wiring somehow, or a flaky SSR. You might try disconnecting the PID controller from the control inputs to the SSR, shorting the SSR input terminals together, and seeing if it still activates the heater. If so, your SSR isn't working right. Another useful debugging technique is to connect an incandescent light bulb to the SSR instead of the heater. The PID controller "out" light, the light on the SSR and the SSR output should always turn on and off in unison. Finally, the only 0089 settings I ever changed are intY (sensor type) and CorF (temperature display style). The 0001 settings are only useful if you're using the alarm outputs for something. The 0036 settings are what auto-tune should be setting up for you. Tom @#30: I still don’t get the auto-tuning.. Why can’t it be as simple as simple “turn on when X degrees before the set value, and turn off on the set value..

There are lots of thermostats that work exactly as you describe (like probably the one on your home HVAC system). The problem with using one in this application is that they generally exhibit several degrees “bounce”. With sous-vide cooking, temperature control within a few tenths of a degree (or better) is important. That’s why I resorted to a PID controller.

(PID stands for proportional-integral-derivative. Basically, it tries to build a mathematical model of the impulse response of the system, and uses that to figure out a duty cycle for the heater that’ll bring the system asymptotically — but still rapidly — to the target temperature. The “PID Controller” link in the original post goes to a Wikipedia article with lots more detail.)

> I am 1000% sure I have the wiring correct, but weird stuff is happening.. Now, I’ve tried auto-tuning, many times and ways.. but sometimes my SSR will activate the heating element, even without the red light lighting up on the SSR!

That can’t be good. My guesses, in order, would be: noise coupled in to the wiring somehow, or a flaky SSR. You might try disconnecting the PID controller from the control inputs to the SSR, shorting the SSR input terminals together, and seeing if it still activates the heater. If so, your SSR isn’t working right.

Another useful debugging technique is to connect an incandescent light bulb to the SSR instead of the heater. The PID controller “out” light, the light on the SSR and the SSR output should always turn on and off in unison.

Finally, the only 0089 settings I ever changed are intY (sensor type) and CorF (temperature display style). The 0001 settings are only useful if you’re using the alarm outputs for something. The 0036 settings are what auto-tune should be setting up for you.

]]> Comment on Sous-vide Cooking by Tom http://mythopoeic.org/sous-vide-cooking/comment-page-1/#comment-47455 Tom Thu, 29 Mar 2012 22:31:52 +0000 http://mythopoeic.org/?p=873#comment-47455 Also to add, my settings are (those that are different than the defaults): ot = 60 (control period) filt = 2 (filter) rd = 0 (heating mode) CorF = 1 (F) temp sensor is P10.0 I've never changed the 0001 settings, and I can't imagine I need to change those values each time I use a diff temp. Also to add, my settings are (those that are different than the defaults):
ot = 60 (control period)
filt = 2 (filter)
rd = 0 (heating mode)
CorF = 1 (F)
temp sensor is P10.0
I’ve never changed the 0001 settings, and I can’t imagine I need to change those values each time I use a diff temp.

]]> Comment on Sous-vide Cooking by Tom http://mythopoeic.org/sous-vide-cooking/comment-page-1/#comment-47452 Tom Thu, 29 Mar 2012 22:22:53 +0000 http://mythopoeic.org/?p=873#comment-47452 I still don't get the auto-tuning.. Why can't it be as simple as simple "turn on when X degrees before the set value, and turn off on the set value.. I am 1000% sure I have the wiring correct, but weird stuff is happening.. Now, I've tried auto-tuning, many times and ways.. but sometimes my SSR will activate the heating element, even without the red light lighting up on the SSR! I have my filter value set to 2, and my temp fluctuates by .2 degrees (F); though at a filter value of 0, it fluctuates by a lot more.. But regardless of that, sometimes it will continue to heat even when it's several degrees PAST the set temperature. I still don’t get the auto-tuning.. Why can’t it be as simple as simple “turn on when X degrees before the set value, and turn off on the set value..

I am 1000% sure I have the wiring correct, but weird stuff is happening.. Now, I’ve tried auto-tuning, many times and ways.. but sometimes my SSR will activate the heating element, even without the red light lighting up on the SSR!

I have my filter value set to 2, and my temp fluctuates by .2 degrees (F); though at a filter value of 0, it fluctuates by a lot more.. But regardless of that, sometimes it will continue to heat even when it’s several degrees PAST the set temperature.

]]> Comment on Sous-vide Cooking by dhenke http://mythopoeic.org/sous-vide-cooking/comment-page-1/#comment-47248 dhenke Wed, 28 Mar 2012 16:21:38 +0000 http://mythopoeic.org/?p=873#comment-47248 Tom @#30: When you do the auto-tune, you are pressing and holding the ">" button and not one of the other buttons, right? (Sorry if that's a dumb question -- I ask only because I made that mistake myself and saw the same symptoms.) It should not matter what the starting temp of the water is. (Within reason. If your environment is very cold, your heater very small and your containment vessel very poorly insulated, it'll never be able to warm it up. If your environment and water are already over the set point, it won't be able to tune.) Normally, when you tune, the controller will fire up the heater, fiddle around a bit, overshoot the set point by quite a bit, then settle down in a nice steady state. The settings are based on a whole lot more than the probe type! They depend on the impulse response of the entire system. In other words, if I have the exact same heater and probe as you, but I use a different container and/or a different amount of water, my settings will be different. (It's probably overkill, but I re-tune each time just so I don't have to be careful about measuring the water.) Tom @#30: When you do the auto-tune, you are pressing and holding the “>” button and not one of the other buttons, right? (Sorry if that’s a dumb question — I ask only because I made that mistake myself and saw the same symptoms.)

It should not matter what the starting temp of the water is. (Within reason. If your environment is very cold, your heater very small and your containment vessel very poorly insulated, it’ll never be able to warm it up. If your environment and water are already over the set point, it won’t be able to tune.)

Normally, when you tune, the controller will fire up the heater, fiddle around a bit, overshoot the set point by quite a bit, then settle down in a nice steady state.

The settings are based on a whole lot more than the probe type! They depend on the impulse response of the entire system. In other words, if I have the exact same heater and probe as you, but I use a different container and/or a different amount of water, my settings will be different. (It’s probably overkill, but I re-tune each time just so I don’t have to be careful about measuring the water.)

]]> Comment on Sous-vide Cooking by Tom http://mythopoeic.org/sous-vide-cooking/comment-page-1/#comment-47238 Tom Wed, 28 Mar 2012 14:45:42 +0000 http://mythopoeic.org/?p=873#comment-47238 I am doing the auto-tune, but the light will just stay blinking blinking blinking. When you auto-tune the PID, does it matter what current temp is? No way can I keep water the same temp for an hour or so (if I could, I wouldn't need to build a unit like this). From my understanding, the settings (from the auto-tune) are based on the probe type - I'm using the 3 wire pt100, someone maybe want to just post their settings so I can bypass the auto-tune? I am doing the auto-tune, but the light will just stay blinking blinking blinking.
When you auto-tune the PID, does it matter what current temp is? No way can I keep water the same temp for an hour or so (if I could, I wouldn’t need to build a unit like this).
From my understanding, the settings (from the auto-tune) are based on the probe type – I’m using the 3 wire pt100, someone maybe want to just post their settings so I can bypass the auto-tune?

]]> Comment on Ponyspotting by Gary Barnes http://mythopoeic.org/ponyspotting/comment-page-1/#comment-43214 Gary Barnes Fri, 24 Feb 2012 21:21:54 +0000 http://mythopoeic.org/?p=1215#comment-43214 You are weird. You are weird.

]]> Comment on Sous-vide Cooking by grant7bar7 http://mythopoeic.org/sous-vide-cooking/comment-page-1/#comment-42359 grant7bar7 Sun, 12 Feb 2012 16:42:21 +0000 http://mythopoeic.org/?p=873#comment-42359 The tip about the alligator clip solved my latent, rapidly fluctuating temperature readings too. Thanks! The tip about the alligator clip solved my latent, rapidly fluctuating temperature readings too. Thanks!

]]> Comment on Sous-vide Cooking by dhenke http://mythopoeic.org/sous-vide-cooking/comment-page-1/#comment-37852 dhenke Sun, 01 Jan 2012 20:09:35 +0000 http://mythopoeic.org/?p=873#comment-37852 Philip @#24: I have added some pictures of the jumper wire. Hopefully that will help make it clear. Aside: I built a second version of the cooker for a friend. I plan to do another whole post about it, but one of the improvements was to use the waterproof Pt100 probe from LightObject. It did not exhibit the "bouncy temperature" problem, and did not require a jumper. Philip @#24: I have added some pictures of the jumper wire. Hopefully that will help make it clear.

Aside: I built a second version of the cooker for a friend. I plan to do another whole post about it, but one of the improvements was to use the waterproof Pt100 probe from LightObject. It did not exhibit the “bouncy temperature” problem, and did not require a jumper.

]]> Comment on Sous-vide Cooking by dhenke http://mythopoeic.org/sous-vide-cooking/comment-page-1/#comment-37495 dhenke Thu, 29 Dec 2011 21:56:29 +0000 http://mythopoeic.org/?p=873#comment-37495 It doesn't matter which of those two terminals on the SSR you connect to the supply vs. the load. Think of the SSR as analogous to a switch; when it's closed, there's continuity between those two terminals, and when it's open, there's no continuity. (To answer the question you actually asked: they swap which one is "in" and which is "out" 60 times a second -- it's *alternating* current.) Note that the control side of the SSR is DC, and polarity very much does matter there. It's clearly marked, though. It doesn’t matter which of those two terminals on the SSR you connect to the supply vs. the load. Think of the SSR as analogous to a switch; when it’s closed, there’s continuity between those two terminals, and when it’s open, there’s no continuity. (To answer the question you actually asked: they swap which one is “in” and which is “out” 60 times a second — it’s *alternating* current.)

Note that the control side of the SSR is DC, and polarity very much does matter there. It’s clearly marked, though.

]]> Comment on Sous-vide Cooking by morris http://mythopoeic.org/sous-vide-cooking/comment-page-1/#comment-37492 morris Thu, 29 Dec 2011 20:22:18 +0000 http://mythopoeic.org/?p=873#comment-37492 I have the same SSR as you, but I'm not able to tell whether pin 1 or 2 is the AC out or AC in. Could you enlighten me? Thanks! I have the same SSR as you, but I’m not able to tell whether pin 1 or 2 is the AC out or AC in. Could you enlighten me?

Thanks!

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