Heated Digital Stirplates

[megabyte]

If you do go with an external probe, can it be on a little retractable wheel thing so it just pulls back into the body when not in use

Ahh.. Yob have you mixed up your stir plate with your vacuum cleaner again!? :lol: Seriously, it would be nice though.

Hey, have you done a starter where you measure the side of the flask compared to what that current prototype thermostat is set to? And tracked it throughout the fermentation?

There's no substitute for testing and it's been difficult to get meaningful results with the changing weather lately. I.e Unless ambient temperature stays relatively stable the heat capacity of the starter can introduce errors - if that makes sense? I plan to set up a steady environment in my fermenting fridge and do a proper side by side test to work out if the external probe is worth while. E.g. If I set the fridge to 10C, and the heated stir plates to 20C, I will compare the actual measured wort temperatures to see if the external probe is necessary.

If possible, could you add a port to plug in an external probe (like a Type K thermocouple), which would override the plate thermostat when plugged in? Then customers can do that as an extra, if they want to.

Great idea but in the past I've found that thermocouples are really expensive for me to implement. The K Type plugs are hard to source and the signal conditioning chips are pricey too. My costings always work out with a DS18B20 probe being cheaper and a lot less fuss for the accuracy but the downside is you have less options for aftermarket probes. There must be a way to do K-Type sensors for cheap though considering all the cheap thermometers on eBay, I just haven't found it yet.

 

[technobabble66]

There's no substitute for testing and it's been difficult to get meaningful results with the changing weather lately. I.e Unless ambient temperature stays relatively stable the heat capacity of the starter can introduce errors - if that makes sense? I plan to set up a steady environment in my fermenting fridge and do a proper side by side test to work out if the external probe is worth while. E.g. If I set the fridge to 10C, and the heated stir plates to 20C, I will compare the actual measured wort temperatures to see if the external probe is necessary.

OK. I think i understand what you're saying. However, what's the problem with testing under practical conditions (i.e.: with variable ambient temperatures); and subsequently, how bad are the "errors" it introduces?
What i was thinking is that many brewers may be using it under those variable (weather) conditions, so maybe it's worthwhile testing to see how it performs. At least such that when you test it under stable conditions, you'd have a reliable comparison of how necessary it would be to provide those stable conditions. Just a thought!

Great idea but in the past I've found that thermocouples are really expensive for me to implement. The K Type plugs are hard to source and the signal conditioning chips are pricey too. My costings always work out with a DS18B20 probe being cheaper and a lot less fuss for the accuracy but the downside is you have less options for aftermarket probes. There must be a way to do K-Type sensors for cheap though considering all the cheap thermometers on eBay, I just haven't found it yet.

Hmmm. I was thinking you could let the customer worry about the additional cost of the thermocouple. If the required chips are pricey also, then that probably precludes the Type K from being a viable solution - i only suggested that one as i'm more familiar with it. If the DS18B20 (whatever that one is) is better/cheaper, then that sounds the best candidate; and it only needs one or 2 options of the probe for it to be viable!

 

[takai]

If you are considering a K-type then have you looked at the MAX6674/6675 chips? Fairly cheap in bulk and happily digitise the microvolt range K-types.

 

[Bridgey23]

Fark...just got my V3 stirplate a week or so ago and have only used it once (and now want one of these).

Lol same here. [emoji30]

 

[Yob]

How do you think I feel, I've got a v2, v3, a heated prototype and I also want a final version..

 

[Mardoo]

Wrong thread Yob...

 

[megabyte]

what's the problem with testing under practical conditions (i.e.: with variable ambient temperatures); and subsequently, how bad are the "errors" it introduces?
What i was thinking is that many brewers may be using it under those variable (weather) conditions, so maybe it's worthwhile testing to see how it performs.

Oh of course! Testing under practical conditions is important too, the only trouble is the weather hasn't been getting cold enough lately I'm stuck with the external probe design at the moment because there is no spare code space in my chip so I can't fit in the program to talk to the sensor, new chips are on order. I can still test the current prototype on its own and I'm setting up an experiment today.

If you are considering a K-type then have you looked at the MAX6674/6675 chips? Fairly cheap in bulk and happily digitise the microvolt range K-types.

The MAX chips would be my favourite route but they are pretty pricey in my experience. E.g. At Qty of about 50-100 units, the MAX6675 is USD$9.47 for the chip, and the socket is AUD$7.80. At least the K type probe is cheap, they're about a buck from eBay.

 

[real_beer]

How do you think I feel, I've got a v2, v3, a heated prototype and I also want a final version..

I hear on the grapevine v4 is going to have a glycerol cooling tank fitted and a range of Erlenmeyer Flask cooling jackets to select from.

However you must upgrade to Windoze 10 to be compatible with version 1, 2, & 3.

V5 is being designed specifically to work for the orbiting Spacelab and wont be available to the general public (at this stage at least) and will only work under Linux anyway!

To date I've no goss on v6 other that it could possibly have a built in refractometer option.

Cheers

 

[megabyte]

...and V6 is so exclusive that the only way to get onto the pre-order list is to create a parallel universe in which you're already on the pre-order list?

Okay, so I set up an experiment to run over the next 24 hours or so. I'm measuring ambient room temperature and the wort temperature through the side of the flask. I wish I had an extra probe ready to dunk into the liquid at the same time, but you work with what you have. Here's a pic:



The stir plate is set to 29C and 1000RPM, I doubt the temperature in the room will drop below 20C tonight but I do expect the starter temperature to drop a few degrees below the plate temperature. Here's a live view of the data being collected right now:

https://thingspeak.com/channels/63131

EDIT: It will plot a new point every 2 minutes. The water is straight from the tap and hasn't acclimated (wow big word) to room temperature yet so it may take a couple of hours for the temperature to stabilise.

 

[technobabble66]

 

[megabyte]

Hi, the preliminary results are in. I left the experiment running for a few days, monitoring ambient and liquid temps with the plate set to 29C since the weather is so hot. You probably wouldn't want to run your starters at this temperature in real life:


Link to the actual data: https://thingspeak.com/channels/63131

You can see a marked improvement in the troughs of the starter temperature. E.g. When the air temperature fell to 20.5C at night, the starter was kept up at 23.5C, meanwhile the day time peaks were barely any higher than ambient since the plate would never rise above 29C. This has smoothed out the temperature swings a bit and if it were a real life starter in the middle of winter I'm sure the yeast would be thankful.

It's not perfect though and there is an obvious temperature fluctuation between day and night and I think this can be smoothed out further by using an external probe on the stir plate. As such I've soldered on a digital temperature probe, reprogrammed the stir plate and begun a new experiment. Temperature is again set to 29C and the speed is 1000 RPM.




You can track its progress here.

 

[Yob]

Mind you, that test is with water too, a starter will generate a bit of heat too won't it?

 

[megabyte]

Yup, another reason to measure the wort and not just the plate's surface I suppose. Hey I just checked back on that chart, it looks like it's going to stabilise at its set point of 29C this time. Fingers crossed because that firmware update to get the probe working was a pretty big hack job :unsure:

 

[blotto]

Yep that temp probe has it sitting at 29 steady as, it's only a few hours in but that's a very straight line. Nice work.

 

[Mardoo]

. You can track its progress here.

Nice work. It's good to be able to watch someone else's starter from the toilet, rather than standing in the kitchen watching mine for 20 minutes at a time

 

[Yob]

Impressive

 

[mr_wibble]

It needs a nice tea-cozy.

 

[Blind Dog]

Nice work. It's good to be able to watch someone else's starter from the toilet, rather than standing in the kitchen watching mine for 20 minutes at a time

you stand in your kitchen watching your toilet for 20 minutes at a time? that's a little odd

 

[Mardoo]

Yob does it too :blink:

 

[idzy]

Is there a waiting list for these?