Should my STC 1000 temperature reading change all the time?

[DuncB]

I use an STC 1000 for my ferment fridge control ( now on number 3 ), the probe is stuck to the side of the fermenter with blu tack and then strapped over this some insulation as well.

The temperature never stays fixed always wavering up and down by up to half a degree, I have calibrated it and have another electronic probe sensor mounted similarly that keeps a steady temp reading.

The ispindel is also steady, I am awaiting some parts to make a brewpiless monitor and controller for the future.

Is my STC 1000 behaving normally ( the others have behaved the same as well)?

 

[day_trippr]

Jiggling between 10ths is one thing, but if the STC-1000 is literally jumping a half degree up and down there's something amiss - or at least that's definitely not normal behavior...

 

[homebeerbrewer]

I agree, both of mine are pretty stable. Occasionally, they'll jiggle a 10th of a degree, but not very often.

I wonder if it's a faulty unit. How old is it?

 

[day_trippr]

fwiw, if the sensor/probe is routinely immersed in a liquid that'd be where I'd start....

Cheers!

 

[homebeerbrewer]

Well, I've read that the probes that come with it aren't waterproof. But, the OP did say that it's on the outside of the fermenter, so I don't think that would be the issue.

 

[MaxStout]

When you say "wavering up and down a half degree," how fast is that wavering? The STC-1000 has a temp range function that allows min/max swing. That temp range can be set by the user. If it's wavering 0.5 degrees rapidly, something's wrong with it. But if it's fluctuating 0.5 degrees over a normal span of time (i.e., several minutes), that's just the actual temp responding to the programmed temp swing.

 

[DuncB]

@day_trippr , @homebeerbrewer , @MaxStout

Have just done a short real time video of the fluctuations. Also showing my other one which does the same, a bit older and broken so it is just a temperature display for keg fridge. The probe for this one is in a thermowell in some liquid so a stable environment away from fan and chill plate.

Had this first video of STC about a year, keg fridge one about 6 months older. Probes never been in liquid or even condensate.

 

[MaxStout]

OK, def not normal temp swings. Maybe the probe is wonky? You could replace the probe and see if that fixes it. However, you can get a whole new unit for about $15.

I did find this thread on HBT where someone else experienced changing temp readings.

 

[DuncB]

@MaxStout Thank you
I have got some spare sensors so I will try those.

Surprisingly this variance doesn't seem to affect the stability as the ispindel is showing only a temp change of about 0.08 celsius with hourly readings.

I'll try a new sensor and see what happens.

 

[Beer666]

I have 6 of them and none behave like that.

 

[RufusBrewer]

Those up/down readings look like what a meter does when it hooked up to an open wire or a capacitive circuit.

Check you connections. Remove and inspect all connectors. Look for rust, oxidation, and discoloration.

Every screw terminal loosen the screw remove and visually inspect the wire and screw terminals and then return the wire to the connection. Make sure the screw is good and tight, A little extra twist after it Is finger tight.

Inspect all solder joints. Give each wire a little jiggle look for a cracks where solder meets connector.

Definitely try a new probe. If the old one proves bad, break and throw it away. Order a replacement before you need it.

Consider giving each solder joint a refresher flow of solder to the joint. This might be too advanced if you are not familiar with solder techniques.

 

[DuncB]

@RufusBrewer
I haven't tinned the wires where they are plugged in just twisted and screwed them down. I will have a go at that later 0100 here at present with a solder to them all and a re screwing in.
I have changed the temp probe and it's behaving the same, brand new probe straight out of wrapper.
When you say inspect all solder joints do you mean inside the SCT? looking for failed solders I assume?

I have made three ispindels so my soldering is genuinely basic. But having said that they all worked so there is potential and am ready to do a flat solder joint when my 2.69 boards arrive for the next ispindels.

The first stc had a total probe failure, I then had a complete failure on the relays and couldn't control heating or cooling.
Got a replacement that failed very rapidly within a few days which I returned for a refund. Then got sent a further STC which has behaved as video from day 1, but worked.

Is it possible that the fridge has damaged the STC in all these cases, they have quite a high load on them when turning on.
I notice that the use of a further relay such as this
https://www.aliexpress.com/item/4000349016103.html?spm=a2g0o.cart.0.0.740d3c005IIBbm&mp=1was recommended for a brewpiless ( which I'm planning to build ) the other component looks similar to an STC
https://www.aliexpress.com/item/32995903972.html?spm=a2g0o.cart.0.0.740d3c005IIBbm&mp=1

 

[Climb]

Check to see if your STC-1000s use the Microchip microcontroller. If they do, reprogram them using the STC-1000+ software. It is rock solid and enables creating 6 different fermentation profiles. Do a search on HBT for 1000+ and if am sure you will find the thread.

 

[DuncB]

@Climb
I'll look for those tests, get a diagnosis and hopeful treatment. Thank you.

 

[RufusBrewer]

@RufusBrewer
I haven't tinned the wires where they are plugged in just twisted and screwed them down. I will have a go at that later 0100 here at present with a solder to them all and a re screwing in.
I have changed the temp probe and it's behaving the same, brand new probe straight out of wrapper.
When you say inspect all solder joints do you mean inside the SCT? looking for failed solders I assume?

I have made three ispindels so my soldering is genuinely basic. But having said that they all worked so there is potential and am ready to do a flat solder joint when my 2.69 boards arrive for the next ispindels.

The first stc had a total probe failure, I then had a complete failure on the relays and couldn't control heating or cooling.
Got a replacement that failed very rapidly within a few days which I returned for a refund. Then got sent a further STC which has behaved as video from day 1, but worked.

Is it possible that the fridge has damaged the STC in all these cases, they have quite a high load on them when turning on.
I notice that the use of a further relay such as this
https://www.aliexpress.com/item/4000349016103.html?spm=a2g0o.cart.0.0.740d3c005IIBbm&mp=1was recommended for a brewpiless ( which I'm planning to build ) the other component looks similar to an STC
https://www.aliexpress.com/item/32995903972.html?spm=a2g0o.cart.0.0.740d3c005IIBbm&mp=1

Running leads is not important. In fact I would suggest bare copper wire is better because they can compress and get you more contact area than tinned cable.

I was suggesting brush if you had existing soldered terminals, like XLR connectors, to reflow the connection is not the worse thing you do.

I do not think board level repair is worth doing on such an inexpensive device as that. Cheaper, easier and more reliable to get a brand new unit.

 

[DuncB]

@RufusBrewer
I am on bare twisted flex into the STC not tinned and not solid cable. Have decided not to have a good look in it as it's busy looking after current ferment and is very stable with fluctuation of 0.04 celsius which is pretty good I think.
Might be easiest to just put a bit of masking tape on the .x part and then I won't see it changing all the time!!
Then await parts and build a brewpiless,once confident with that go to BrewPi remix.