Advice on minore iv pid operation

[rrm]

Hi,

I've recently upgraded from a BDB to a new Minore IV. The operation of the temperature indication of the pid brew temperature controller is quite different to what I expected.

I would appreciate some feedback on how other Minores behave.

The machine has warmed for 30 minute minimum , sometimes 45 minutes. The set temperature is 94c.

The display seems to hover between 93 and 94 and stays at 93 for up to 30 seconds.

On a few occasions, at the start of the shot is temp 94c and during express drops to 93c.

After the shot with the temperature at 93, the temperature will then overshoot to 95 and eventually settles to back to 94.

At the moment the quality of the brew seems fine. However all the fuss that is made of pid control seems to inconsistent with the practical operation.

What are fellow members finding ?

Can the pid response time be adjusted ?

Or is this normal operation?

[fdesa]

Hi

I have had my machine for 3 or so years. It takes approx 20 min to warm up. I do see minor flickers in temp (1 degree down and then back up). I have not noticed it hanging at the other temp for more than a couple of secs. Will pay more attention and post results.

[rrm]

Hi

I have had my machine for 3 or so years. It takes approx 20 min to warm up. I do see minor flickers in temp (1 degree down and then back up). I have not noticed it hanging at the other temp for more than a couple of secs. Will pay more attention and post results.

Thanks for the feedback. I seems to be behaving more like a temperature controller this morning. It is possible the controller is "self learning" and will settle down.

Meanwhile, I will try to find programming info.

[TC]

It is possible the controller is "self learning" and will settle down.

Doubt it. The Gicar PID used is pretty rudimentary and definitely doesn't have an autotune mode. I don't think it's smart enough to learn anything much at all.

[fdesa]

Update

Thanks for the feedback. I seems to be behaving more like a temperature controller this morning. It is possible the controller is "self learning" and will settle down.

Meanwhile, I will try to find programming info.

I watched more carefully this morning. Was stable on 94 during pour. Watched for while and it did momentarily drop/flicker on 93 and back to 94. Then did go to 95 for about 15 or so secs and then settle back on 94.

Still made a great coffee. Enjoy your new machine!

[rrm]

I watched more carefully this morning. Was stable on 94 during pour. Watched for while and it did momentarily drop/flicker on 93 and back to 94. Then did go to 95 for about 15 or so secs and then settle back on 94.

Still made a great coffee. Enjoy your new machine!

Thanks,

That's exactly what mine does/ did this morning.

However, I'm thinking PID control is a selling feature, rather a than key item in making excellent coffee.

And a basic electronic thermostat would do the same job.

[rrm]

Doubt it. The Gicar PID used is pretty rudimentary and definitely doesn't have an autotune mode. I don't think it's smart enough to learn anything much at all.

It should be "tunable" ? Does the manufacturer supply service data I wonder?

[artman]

The Alex Duetto PID can be tuned, if yours is the same you could use that as a guide?

Cheers

[rrm]

Thanks artman,

I've turned up a Youtube Video by Whole Latte Love which details the adjustment procedure, however the settings are for F degrees.

I'm reluctant to mess around because, PIDs being a closed loop system, with amplification, erroneous settings can cause system instability and in worst case oscillation.

The machine is under warranty so I have to tread carefully.

I already have a design for an automatic shot timer, soon to be bench tested and installed when out of warranty..

So rather than trial and error adjustments I'd really like see some factory doco if possible.

Is the Alex Duetto pid controller made by Gicar? Obviously AD will have different set points due different thermal characteristics

I'd still be interested to have the AD doco if a member could post/ or pm.

Cheers


Rob

[artman]

I can't recall the brand. I don't have to the information handy but if you google you will find a few results. The AD thread here has info on settings for the PID also. The AD uses the steam boiler as a preheater for the brew water and the steam boiler is switchable so some settings are better than others depending if the steam boiler is in use or not.

If you contact the supplier they should be able to provide the basic settings as a start.

Cheers

[artman]

Forgot to add, I wouldn't be too stressed by the display varying by a degree, especially if the brew tasted great.

Cheers

[TC]

Forgot to add, I wouldn't be too stressed by the display varying by a degree, especially if the brew tasted great.

Cheers

Agreed Artman. What's happening at the boiler is not reflected at the group for quite some time. 4+ kg of e-61 group does not change temperature rapidly. Minor fluctuations at the PID represent precisely nothing!

[rrm]

Agreed Artman. What's happening at the boiler is not reflected at the group for quite some time. 4+ kg of e-61 group does not change temperature rapidly. Minor fluctuations at the PID represent precisely nothing!

Maybe so,

but surely the temperature displayed IS the temperature of the water that is being "pushed" through the coffee, minus the heat losses/ gains through the internal plumbing, which ideally is already hot due to the thermo siphon action.

So the group temperature and indeed the thermal inertia of the group only serves to make sure the infusion water maintains it temperature.

I can't see that the group will change the temperature of the flow water too much, since the water isn't in group for very long.

But I hear what you say about minor temperature variations and the effect on the coffee. This is exactly what I've noted.

But having said this, from an electrical engineering perspective, it shouldn't be too hard to maintain the temperature within a close range to the set point , which after all is sole benefit of PID over a basic bimetallic thermostat.

EDIT: And I should say thanks to Chris and artman for their advice

cheers
Rob

[TC]

....but surely the temperature displayed IS the temperature of the water that is being "pushed" through the coffee

Erm- not really Rob. It's brew boiler actual temp less whatever temp offset is set at the PID.

As an example, an Alex Duetto will require an offset of approx 10 deg C at an 18 deg ambient. If you were using one in today's Melb temps in a home without aircon, the offset would be more like 6 deg.

Cheers

Chris

[rrm]

Erm- not really Rob. It's brew boiler actual temp less whatever temp offset is set at the PID.

As an example, an Alex Duetto will require an offset of approx 10 deg C at an 18 deg ambient. If you were using one in today's Melb temps in a home without aircon, the offset would be more like 6 deg.

Cheers

Chris

Yes, I was forgetting the offset of the pid, which For the Minore iv is set to 10C.

Out of interest I might stick a probe in the coffee flow, I'm getting curious now!