9 replies to this topic

[bill.french]

After a long journey trying to get reliable temperature readings using thermistors, I was finally able to test out my Sous Vide project using actual food last night using a Dallas DS18B20 OneWire temperature sensor and a onewire controller.

The basic setup at this point uses a netduino+, the onewire controller, the DS18B20 for reading the temperature, a PowerSwitchTail controlling a cheapo walmart electric pot and an electric motor for agitating the water. What will be kind of a unique feature of my setup (besides network control and monitoring, which is in and of itself very cool) is that I can us this setup to manage up to 6 Sous Vide devices, so that there could be a meat, veggies, sides, dessert, and even the next days meat all going at once.

I still need to tune the PID algorithm, but looking at the graph, I am very close to a very stable temperature (it was set to 173F):


The goal was a (very) hardboiled egg, without any green on the yolk, and I was successful:


This is a picture of the setup, taken at Fubar Labs, my local hackerspace.


Next up: Chicken Breasts!

[Chris Walker]

Wow, Bill. Impressive. I'd love to drive out to your hackerspace in NJ sometime and see what you are building (both with Netduinos, and generally!) Are guests welcome? Chris

[bill.french]

Of course! Thursdays are the "open hack nights" so there's usually some folks there doing something interesting for guests. Let me know when you're coming, I'll netduino up some steaks and print you a netduino t-shirt on our silkscreen press! We'll use bottle openers printed on our makerbot to open some Fubrew.

[Omar (OZ)]

Wow! that looks pretty awesome, I couldn't wait that long to eat thought . So I found out that there are no hacker spaces near my sad little city/town , maybe I could start one up when I am older . Again, very nice project !

[Chris Walker]

Of course! Thursdays are the "open hack nights" so there's usually some folks there doing something interesting for guests. Let me know when you're coming, I'll netduino up some steaks and print you a netduino t-shirt on our silkscreen press! We'll use bottle openers printed on our makerbot to open some Fubrew.

You know how to throw a party

I'm definitely going to have to take you up on that.

Chris

[segu]

Congratulations Bill Very well done, I am happy to see posts like this. They are very encouraging. You clearly show very helpful things can be done with Netduino Thanks a lot

[Chris Seto]

Can you post your PID code? What form are you using? (Ideal, parallel, etc)

[bill.french]

Can you post your PID code? What form are you using? (Ideal, parallel, etc)

LOL WUT?**

I am basically using a variation of this:
http://www.codeproje...ecipes/PID.aspx

...with the variation being for the integral i only remember the last 20 readings. At this point only P and I are doing much of anything, since the heating process is pretty slow, D doesn't really come into play very much with how I have it tuned currently.

**If you could direct me to a web page that explains pids and whatever ideal and parallel is, I would love to read it. Everything I've found (and there's quite a bit of it out there) seems to use technical vocabulary that I am not comfortable with. I feel like I've figured the essence of PIDs out, but it was a tough journey to wrap my mind around it since everything I was reading was not very approachable in my opinion.

[JonnyBoats]

This looks like a very fun project. I went and looked at some of the Souis Vide cookers and they are not cheap ;-) It looks like yours comes in at 1/10 the price and works just as well, congratulations! I am curious about your electric motor to circulate the water. Is it necessary and how much does it help? Also are you considering a mod 2 version and what changes, if any, would you make?

[bill.french]

Water circulation is definitely necessary. I didn't believe it at first, but the temperature differential between top,bottom, and middle of the water can be significant, as much as 5 degrees I was noticing, which is a big deal apparently, with hots spots at the bottom from the element, and a hot spot up top where the hot water rises. Also, the pot will set up pretty solid water currents from the convection, which now makes hot and cold spots horizontally. I do need to do something with the motor. I keep forgetting about that part of the project. Right now it's just a motor with the wand part of a baby bottle stirrer stuck on the end. It's super effective, too effective, really - it keeps moving the food around and sucks it into a votex and into the blades. An air bubbler would be easier, i think. I'm not quite at "version 1" yet, it's more proof of concept. I am going to now work pretty steadily towards etching my own PCB and get it into a shield form factor so that it will actually be usable and not require and hour of setup. Also, a lcd and interface are needed. Right now, changing the target temperature requires visual studio. I definitely want it to be easily multi-channel, as that's about all that really differentiates it from a $35 pid controller. I also need to test and build in some kind of safety so it doesn't burn my house down. Ultimate end-goal would be a professional produced "shield" product. I've always wanted to make and sell a product -- if one person buys it, that would be awesome and a check on my bucket list. The key for that is going to be getting it arduino compatible, and probably also make it useful for other things, such as environmental controls. It is basically a sophisticated thermostat. Once the netduino supports onewire out of the box, the game changes quite a bit. Thanks for asking, by the way. My family camps up in Alfred, ME pretty much every year. I'll have to invite you over for sous vide steaks finished on a camp fire.