24 replies to this topic

[HowardLi]

Parts list:

Sestos D1S-VR PID controller
Panel-mount M8 3-pin female connector
eBay Pt100 probe spliced into a M8 3-pin right-angle male plug /w cable
Corcom AC input filter /w integrated switch and double fuseholder (currently using 10A fast blow fuses)
Omron G3NA-240B DC5-24 solid state relay attached to an old CPU heat sink (with Thermalright Chill Factor III thermal paste)
NEMA 5-15R receptacle
NEMA 5-15R receptacle (GFCI-protected)
Various terminal blocks
Various crimp connectors
Various screws and bolts
Proctor-Silex 1000W electric burner
Electra 1150W immersion heater

What isn't shown is a 3" round by 3/4" thick piece of cork that the probe sticks into so that it floats on top of the water. I have used both the electric burner and the immersion heater with good success.

AC wiring is brown - live, blue - neutral, green - ground per current European standards. Well, the ground wiring is supposed to be striped green/yellow, but I didn't have any handy. The receptacles are wired in such a way that the GFCI receptacle also protects the regular receptacle from earth leakage current. The GFCI unit is always on and can be used for pumps, fans, etc. while the regular unit is the one powered through the relay.

Any questions?

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Edited by HowardLi, 06 June 2011 - 06:25 PM.

[Big Mike]

I like the cut of your jib, sir.

[dcarch]

Very nice work. Very professional.

Questions:

Should the heat sink for the solid state relay be truned around for better sir circulation?

Should the heat sink be somewhat further away from the controller electronics?

dcarch

[HowardLi]

Looks like I can no longer edit the OP, so here's a pic of the panel after cutting.

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[HowardLi]

Very nice work. Very professional.

Questions:

Should the heat sink for the solid state relay be truned around for better sir circulation?

Should the heat sink be somewhat further away from the controller electronics?

dcarch

1) The heat sink is not optimally positioned, no, but the relay can handle a lot of heat before de-rating its current handling. Moreover, even if the current handling was de-rated due to temperature, the relay starts off at 40A (forty!), which is 4 times what I need.

If you flipped the heat sink around, it would be better, but the relay would then be much more difficult to maintain. I suppose I could have stood the heat sink on its end, but it really wouldn't have made a big difference, and the heat sink is now permanently affixed; I used 2-part epoxy to glue it to the inside of the panel.

2) No. The heat sink only gets warm (the relay has a very low cycle time at steady-state anyway). If anything, the internal wiring between the probe connector and PID is too close to the AC wiring, which may be inducing voltage (error) into the circuit, but since the probe has a good steady-state reading, I'm not worried about it.

Edited by HowardLi, 06 June 2011 - 08:00 PM.

[dcarch]

I noticed the probe cables are very close to the power lines.

You can do this if you feel like it to improve. If you twist the cables one way and then counter twist the other way same number of turns, the induced noise will tend to cancel itself out.

dcarch

[davidkeay]

Very interesting to see! I just built my first last week, and it a bit of a mess of wires since I opted not to try to fit it all together in a frame. I'm not happy with how well it works, so I'm going to look into upgrading soon!

[HowardLi]

Very interesting to see! I just built my first last week, and it a bit of a mess of wires since I opted not to try to fit it all together in a frame. I'm not happy with how well it works, so I'm going to look into upgrading soon!

What's wrong with it? These are fairly simple beasts - in fact the worst part is probably getting the sensor to read accurate temps, IMO.

[HowardLi]

Just realized I didn't tag the OP properly.

I wonder if this will work

sous vide SV cooker system controller temperature probe sensor PID calibrate submersible immersion heater relay pulse width modulation pwm resistance accuracy precision tune tuning auto automatic plastic bag ziploc zip-loc vacuum zip-lock ziplock npt fitting offset

lol

[HowardLi]

I think the next thing I need to do is to set up a smoking rig. Apparently a cardboard box loses enough heat such that a 1000W burner cannot achieve temps of over ~200F - I'll have to see what I can scrounge up to make a reliable smoker.

[dougal]

Howard, it looks good.
Some points though.



The enclosure. Its a difficult choice. And constrained by availibilty! There's no need for a weatherproof box, if you are using indoor-type power connection sockets. Also a well waterproofed box has no ventilation for the heat sink! A plastic box is easier for cutting the various holes, but a metal box (earthed of course) can better conduct away the heat from the heat sink.
I wanted to adopt the same simplifying approach of attaching everything to the box lid, but given the size of UK power outlets and plugs, that wasn't possible for me. I couldn't find a small box with a big enough lid!
I chose to put the power distribution and SSR in a different box to the controller, thinking I might use it on other projects. At $10 delivered (eBay) for the SSR, the simplicity of putting everything in one box and minimising flying-lead clutter is something I'd now strongly recommend. The heat from the SSR being less than I'd feared also supports the all-in-one approach.
The weight and tension of mains electrical leads are significant in the stability of the box(es), so choosing the best place for all external mains cable connectors is the first layout consideration.
My power box has a non-controlled (manually switched) outlet used for the controller box, but also catering for a constantly running pump or fan. Without it everything could have been smaller! The power box also has an isolation switch with a power-indicating neon. Again, I'm not sure I'd bother in future. With an all-in-one-enclosure design, the PID display shows its on!
My power box has its control input in association with the controlled output. It shows which outlet is which. With an all-in-one, I'd similarly choose to have the probe input signposting the controlled power outlet.
The other design consideration is keeping all the external cables away from the PID and its control buttons.

The SSR. I have the 25 amp version of your SSR, on a large (antique Mac 71/8100?) cpu heatsink (which barely gets at all warm), stood-off from the walls but within a vented plastic box. On UK 240v mains, my 1800 watt heater pulls less than 8 amps. So my SSR is rated at over 3x my highest current. Is there any advantage to using an even higher rated SSR (40 amp would be 5x standard load) - like less heat for the same current?
Worth noting is that as a 'zero-crossing-switching' SSR, it produces no mains or radio interference from switching. But it does 'quantise' the power control. On a 50Hz mains, with a 2 sec PID cycle, the SSR restricts the output to 200 steps - adequate resolution, I think.

Your probe (and its float). Could you give some more detail? I'm using a (not really cheap) "fully immersible" Pt100 from Auber, which I have mounted to the rack in the bottom of my tank. I have been thinking that having the probe mounted in a consistent position was important to the measurement being a consistent indication of the tank temperature - surely if it can float about in the tank, it might sometimes be measuring near the centre and sometimes near the edge (which would be cooler)?

The probe connections. For a Pt100 ptobe, its nice that we can easily have a connector giving us a break-point -- for a K-type (for example) you need to take account of the connector. Noting your smoker intent, I've seen an Auber gas temp K-type probe but not a Pt100 gas probe. Any ideas there? (I've been wondering about a homebrew hot air chocolate tempering control...)

Any comments about your choice of PID?
I have an N2006P via eBay. One thing it lacks is a manual over-ride, but one (undocumented) feature that it has is the ability to display the output power demand. Stable at 56C, my tank needs about 8% heater on-time.
The N2006P auto-tune isn't perfect, but its good enough (I generally reduce twitchiness by reducing the D term).
Especially if you are going to use different containers and heaters, auto-tune should be a must-have feature when choosing your PID. (The P I & D factors need to be set differently for each combination of tank and heater - even changing the water level in the tank changes the response and needs a different tuning.)
My PID has two 'alarm' outputs, which I don't use.
I do have a completely independent thermal safety cutout, in the form of the mechanical thermostat on my tank. I don't turn it all the way to maximum - instead I set it above my working temp, but below boiling, so that if my homebrew control kit 'failed on', the mechanical thermostat would prevent boiling, and particularly any possibility of 'boiled dry' dramas.

And Howard, your workmanship is much neater than mine!

[HowardLi]

The SSR. I have the 25 amp version of your SSR, on a large (antique Mac 71/8100?) cpu heatsink (which barely gets at all warm), stood-off from the walls but within a vented plastic box. On UK 240v mains, my 1800 watt heater pulls less than 8 amps. So my SSR is rated at over 3x my highest current. Is there any advantage to using an even higher rated SSR (40 amp would be 5x standard load) - like less heat for the same current?
Worth noting is that as a 'zero-crossing-switching' SSR, it produces no mains or radio interference from switching. But it does 'quantise' the power control. On a 50Hz mains, with a 2 sec PID cycle, the SSR restricts the output to 200 steps - adequate resolution, I think.

Your probe (and its float). Could you give some more detail? I'm using a (not really cheap) "fully immersible" Pt100 from Auber, which I have mounted to the rack in the bottom of my tank. I have been thinking that having the probe mounted in a consistent position was important to the measurement being a consistent indication of the tank temperature - surely if it can float about in the tank, it might sometimes be measuring near the centre and sometimes near the edge (which would be cooler)?

The probe connections. For a Pt100 ptobe, its nice that we can easily have a connector giving us a break-point -- for a K-type (for example) you need to take account of the connector. Noting your smoker intent, I've seen an Auber gas temp K-type probe but not a Pt100 gas probe. Any ideas there? (I've been wondering about a homebrew hot air chocolate tempering control...)

Any comments about your choice of PID?

And Howard, your workmanship is much neater than mine!

I have a 40A relay because that's what was in stock at my local electrical supply store. If I had my druthers I'd be using a 25A unit from eBay for 1/3 the cost. Those too are zero-switching. I don't know that it makes a big difference, though, unless it plays funny with the GFCI - a resistive heating element certainly doesn't care.

The probe is a through-tank style, with a ~4" cylindrical probe body welded to a 1/4" NPT fitting, with a coiled wire bend relief for the cable. Exactly the same as this one:

http://cgi.ebay.ca/Thermocouple-Temperature-Control-Sensor-Probe-PT100-1m-/360370037493?pt=LH_DefaultDomain_0&hash=item53e7ba62f5

For hot air control, at steady-state I should think the Pt100 would do well, but I'll admit there is a lot of thermal mass for the air to heat up. I'll have to give it a shot as is, and if the response is too sluggish (and ends up causing oscillation) I would have to go with a smaller element meant for air.

As I said before, the float is simply a disc of cork that the probe is inserted into. I can let it float around or I can secure it in place. As long as it isn't too far away from the food, it'll give a good reading.

The PID is fine. It's easy to use and has a great auto-tune. Build quality is unquestionable.

[dcarch]

HowardLi, for heating of your "smoker", you can consider this:

Use high-wattage halogen light bulbs hooked up in series, or in series with a diode (to cut out half of the AC current).

A halogen bulb operating at reduced voltage will last forever. It is a great source of infrared (100% efficient). In a reflective smoker environment, the heat will be distributed very evenly.

An insulated smoker (1" thick rigid foam) may be OK with less than 300 watts of heating to maintain operating temperature. Can be less than 50 Watts if no air leaks.

dcarch

[HowardLi]

HowardLi, for heating of your "smoker", you can consider this:

Use high-wattage halogen light bulbs hooked up in series, or in series with a diode (to cut out half of the AC current).

A halogen bulb operating at reduced voltage will last forever. It is a great source of infrared (100% efficient). In a reflective smoker environment, the heat will be distributed very evenly.

An insulated smoker (1" thick rigid foam) may be OK with less than 300 watts of heating to maintain operating temperature. Can be less than 50 Watts if no air leaks.

dcarch

Halogen lights would certainly work as a heat source. Even a bunch of incandescent ones would work. Longevity is questionable due to carbon buildup on the outside of the bulb (and potential hot-spotting).

However, the advantage to using an electric burner is that you can easily smoke using wood chips.

[dcarch]

"----Halogen lights would certainly work as a heat source. Even a bunch of incandescent ones would work. Longevity is questionable due to carbon buildup on the outside of the bulb (and potential hot-spotting).

However, the advantage to using an electric burner is that you can easily smoke using wood chips."

Once you step down the voltage, the temperature on the quartz jacket becomes significantly lower and carbon hot spots will not be a problem. I have used halogen bulbs that way for a bread proofing set up for many years. Never had to replace a bulb yet.

True the bulbs are not meant to generate smoke. they are only used to maintain temperature.

BTW, another option to cool the relay is to use surplus heat pipe heat sinks for laptops. They are very cheap. You may know, heat pipe can conduct a lot of BTUs.

dcarch

[HowardLi]

Some action shots

I have to apologize for the size of the one that shows me with a beer, it seems the aspect ratios are not all done uniformly lol

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Edited by HowardLi, 08 June 2011 - 09:28 PM.

[HowardLi]

It says 62.5 because that's what I had set it to before I double-checked my F to C calculations.

[dougal]

Howard, a couple of questions regarding this picture -

Its kinda hard to see, but is your meat completely submerged? (Seems like you aren't using any ballast.)


And how much temperature difference are you measuring with the bath like that?

Being congested, with the heater and control probe separated by quite a long, relatively shallow (and congested) space, I'd be expecting there to be an easily measurable difference between the vicinity of the heater and the probe.

Its in exactly such a situation that actively boosting the circulation, with either a pump or bubbler, should show the greatest benefit.



Something that I do habitually is to occasionally give my bath a vigorous manual stir (for vertical as well as horizontal mixing) with a big spoon (to mix and thus average out the bath temperature) and watch to see how much this average temperature differs from the pre-stir indicated temperature. (Remember that my probe is in a standardised position within the tank.)
Because (apart from shortly after adding 'cold' bags to the tank) the "stirring variation" rarely shows as more that 0.1C, I decided not to bother with forced circulation. But, even though its a big 'deep' tank, I do make a point of stirring the tank a few times during the first half hour after adding new bags, or when cooking fish (a 'quick' process).

[dcarch]

HowardLi, based on the pictures, it is unlikely that you can get even temperature throughout the bath even with the auto-ranging PID controler.

A small aquarium submergeable pump ($10.00) with a long vinyl tubing plugged at the end and perforations along the tubing will give you pretty good circulation in you ultra-high density cooking style.

dcarch

[HowardLi]

I did not measure the temperature variation throughout the cooler; I had other pressing issues to deal with. It certainly wasn't the worst case for temperature uniformity, though, since the meat was at the top and the heater at the bottom.

I did have a pump but decided for some reason not to use it.

Yes, everything was submerged.

[Simon Lewinson]

Hi Howard, I too am building sous vide gear and have a couple of questions for you

What are the programming parameters that you have in the D1S?
How much overshoot do you get?

I have a REX-C100 controller (only 1 degree resolution) and can get less than 2 degrees C overshoot, but using the Sestos I get huge overshoot - almost 10 degrees! I am quite familiar with tuning PID controllers but cannot make much sense of the D1S parameters.

I will be posting an article on my build once it is finalised.

Thanks
Simon

[HowardLi]

Hi Howard, I too am building sous vide gear and have a couple of questions for you

What are the programming parameters that you have in the D1S?
How much overshoot do you get?

I have a REX-C100 controller (only 1 degree resolution) and can get less than 2 degrees C overshoot, but using the Sestos I get huge overshoot - almost 10 degrees! I am quite familiar with tuning PID controllers but cannot make much sense of the D1S parameters.

I will be posting an article on my build once it is finalised.

Thanks
Simon

I always leave it in auto-tune mode. I'll measure the overshoot I get next time but I don't think it's much.

[HowardLi]

OK - before the summer is over I will be trying to get a smoke job done on some pork with this unit. I've happened on a kind-of-but-not-really-reasonably-priced film RTD at McMaster-Carr, PN 6568T46. 3-wire 100 ohm; most likely European standard tempco. I'll attach it to something thin and put it inside a cardboard box, with a wood chip-filled cast iron pan on the hot plate doing the heating.

[HowardLi]

I got the probe thermometer. It's got a ring terminal for mounting so I'm going to attach it to some aluminum square tubing for mechanical and temperature stability.

I also waterproofed my RTD by slipping in some silicone tubing up to the hex nut and crimping it. It's not a perfect solution, but now water won't get inside. I had it going right into the water before and it caused the RTD to intermittently fail, which was (obviously) bothering me.

Pics to come soon.

[HowardLi]

RTD in standard configuration with coil relief



Relief removed



Silicone tubing slipped over and clamped