sous vide thread


 
So, is anyone here doing sous vide without a crock pot? I have a fancy electronic crock pot, and don't really want to buy a new dumb one just for sous vide, so I'm thinking I will try to rig one up similar to the classic DIY Sous Vide Controller, only with the HeaterMeter controlling the coils, rather than a PID. I'll probably just buy a submersible pump, 3 heating coils (or a bucket heater like this), an SSR and some lamp cord and see what happens.
 
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It's be cheaper and easier to buy a cheapo crock pot, but not nearly as fun as what you have planned. I would like to put a pump in mine, as I can measure temperature differences in my crock pot. Not a good thing for sous vide.

Let me know what you find for the pump.

dave

Kyle Christensen said:
So, is anyone here doing sous vide without a crock pot? I have a fancy electronic crock pot, and don't really want to buy a new dumb one just for sous vide, so I'm thinking I will try to rig one up similar to the classic DIY Sous Vide Controller, only with the HeaterMeter controlling the coils, rather than a PID. I'll probably just buy a submersible pump, 3 heating coils (or a bucket heater like this), an SSR and some lamp cord and see what happens.
Click to expand...
 
For mine I used a 20L Burco Boiler. I've added a piece of copper pipe to 'hold' the probe without it sitting in the water and also have a small aquarim pump which circulates when heating. It works great!

I'll post photos when I get chance
 
Ok, so I decided just to hijack my gf's basic crockpot and go that route instead of a bucket heater. Being a noob to electrical stuff, I wanted to confirm what I understand the wiring to be before I go electrocuting myself based off of this post:

- Hot wire goes in to the SSR on 1 and out 2 to the outlet's hot side
- RCA plug (I'm wiring an RCA plug in vs hacking a cable in half) goes RCA center (+) to 3 on the SSR, and the sleeve goes to 4 (-) on the SSR
- Neutral and ground to outlet (top and bottom)

Tape everything up, toss it in a box and I'm good to go?
 
That is correct as long as:

1. 1 and 2 are on the "load" side of the ssr
2. 3 and 4 are on the "control" side of the ssr


dave

Kyle Christensen said:
Ok, so I decided just to hijack my gf's basic crockpot and go that route instead of a bucket heater. Being a noob to electrical stuff, I wanted to confirm what I understand the wiring to be before I go electrocuting myself based off of this post:

- Hot wire goes in to the SSR on 1 and out 2 to the outlet's hot side
- RCA plug (I'm wiring an RCA plug in vs hacking a cable in half) goes RCA center (+) to 3 on the SSR, and the sleeve goes to 4 (-) on the SSR
- Neutral and ground to outlet (top and bottom)

Tape everything up, toss it in a box and I'm good to go?
Click to expand...
 
Well, finally got some time to put my box together. Got it wired up, broke out the multimeter to make sure I wasn't going to electrocute myself, and realized that the IEC connector I got with fuse holder (from China on ebay) didn't actually have a fuse in it. Oh well, gotta go find one tomorrow.

It's certainly not code, but I don't think it will kill me:

 
So, my fuses came today and while I don't have the crockpot here, I plugged in a lamp and played around and it seems to work!

Evan MJ said:
Settings: MIN and MAX fan speed both set to 100% to force "Long PWM" or "SRTP" mode. PID gains started as stock, and I tuned them a bit to reduce oscillation and overshoot. The gains I ended up with are P=10, I=0.007, D=20. I have not tested those gains from a cold setup to see how much they overshoot, but steady state I got it easily within +/- 0.5 degree F, and even for a while within 0.1 degree of the setpoint. Most blips in the temp were due to me opening the lid to flip the pork around since I have no setup to mix the water up and the bubble in the bag made it float a bit.
Click to expand...

Are these PID settings what you are still running with Evan? Does anyone else have any suggestions? I plan on using preheated water in the crockpot to speed up the process, but I am not familiar with PID tuning, so I'm wondering if anyone else has any input.

Still on the prowl for an affordable submersible pump that will hold up to the temperature, the front runner is this 12v one from Ebay, but it's like $34 which is a little spendy for what it is.
 
Honestly I found the default settings worked very well for me. I need a circulation pump to make it better.

dave

Kyle Christensen said:
So, my fuses came today and while I don't have the crockpot here, I plugged in a lamp and
played around and it seems to work!



Are these PID settings what you are still running with Evan? Does anyone else have any suggestions? I plan on using preheated water in the crockpot to speed up the process, but I am not familiar with PID tuning, so I'm wondering if anyone else has any input.

Still on the prowl for an affordable submersible pump that will hold up to the temperature, the front runner is this 12v one from Ebay, but it's like $34 which is a little spendy for what it is.
Click to expand...
 
D Peart said:
what about this pump?

http://www.amazon.com/exec/obidos/ASIN/B004HHW0FU/tvwb-20
Click to expand...

That doesn't look like it is submersible to me, so you'd need in/out flows somehow (which could make using a lid tricky).

http://www.ebay.com/itm/250722722452?_trksid=p5197.c0.m619

That's the one I was referring to earlier, it's 12v so you'd need to hack a connector for a wall wart somehow, but it's submersible. It's only good to 80C though which is right around where you'd want to be cooking vegetables.
 
Yeah it does, those exposed wires on it threw me. The reviews are not so great however, apparently it is only the size of "8 quarters" and only moves 1L/min (vs 6L/min on the ebay link). Does not seem like very much to me, even with a relatively small volume of water like a crockpot.

I guess if I am going to spend money on a pump, I'd want something I could transition to use in a cooler with an immersion heater since from everything I have read is the next step up as far as capacity and stability are concerned.

I did quite a bit of searching on pumps and just can't seem to find anything that seems like it has any sort of longevity and has a suitable output for multiple gallons of water (that isn't full blown industrial and $$).
 
So, my experimentation so far has not been fantastic. Take today's chart for example:

7mmZL8J.png


The dip around 10:15 is when I put 3 (cold) eggs into the bath, and as you can see with the stock PID parameters, and the crockpot on high, it took nearly 40 minutes to rebound 5F! And then it overshot.

Now I guess it could be a number of things:

- Maybe I should be using room temperature eggs instead of cold eggs
- My volume of water (I didn't totally fill the crockpot) is not great enough to be thermally stable?
- This crockpot is anemic and doesn't have enough power
- I should try the alternate PID parameters suggested in this thread next time

Anyone else have any suggestions? I made sure I set the minimum fan speed to 100%, but other than that the settings are stock.
 
Yup I can see what's happening here, and this is a great example. Let's look at how your situation interacts with the PID algorithm.

P - This is your setpoint - actual temperature. When you put the eggs in, the temperature drops to roughly 10 degrees off the setpoint. The default P constant is 3, so 3 x 10 = 30% power. This is why you see roughly 30% power applied once the temperature reaches its low point.

I - This is the error sum. For every second, the difference between setpoint and actual is added up into a sum and multiplied by the I constant. The default is 0.005 so for every second, 0.005 x 10 = 0.05 % is added to the 30% from above. This is why you see the power output slowly creeping up roughly 1% every 20 seconds, and why once it passes the setpoint it keeps on going as the sum starts to decay just as slowly. The I is sort of the "learning" portion that adapts to needing more or less power to maintain the same temperature when something causes a change.

D - Because everything is changing so slowly, the D term doesn't do much for us here. It looks roughly 30 seconds back to determine a temperature trend then multiplies that by the D constant. Such a small change (let's say 0.1 degrees) times the default 5 constant doesn't even change the output by a whole percent.

So what can we do to fix it? It looks like if you increased your P term to maybe 5 or even up to 10 you'd get a tighter response as the temperature delta would take care of most of the tuning. I'd also consider upping the I term to provide a faster response to changing conditions such as food being added. Somewhere in the are of 0.01 to 0.05 maybe?
 
Wow, thanks for the explanation! Your suggested parameters are pretty close to what Evan suggested earlier (10/0.007/20). I'm going to put my foodsaver to work this week and give a steak a try with 10/0.01/5 and see how it turns out.
 
So, with PID values of P=10 I=0.05 D=20, it seems relatively stable although there is about 2 degrees of overshoot that I'm not sure I will be able to do much about.

9MIxgN7.png


The latest peak on the right hand side is with 10/0.05/20, the prior ones were with smaller values of I and D, and resulted in more overshoot and slightly slower responses. I am not sure at this point if increasing the I value above 0.05 will reduce the overshot any more, but it seems relatively stable.
 
I used the values posted by Evan earlier in the thread: P=10, I=0.007, D=20

It seemed to work fine with my setup... I ran for 24hrs over the weekend and the water temp very stable.
 
N Waring said:
I used the values posted by Evan earlier in the thread: P=10, I=0.007, D=20

It seemed to work fine with my setup... I ran for 24hrs over the weekend and the water temp very stable.
Click to expand...

I fired my sous vide setup up again for the first time in a while with your settings.. huge difference!

BvGbhE8.png
 
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