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Koffee Kosmo
OfflineAdmin
· 08/12/2020 5:37 PM
And I thought it was just me that couldn't access the site All good now - coffee kept me company

JackH
OfflineAdmin
· 08/10/2020 8:46 PM
Had to make myself another cup of coffee to get through it.

snwcmpr
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· 08/10/2020 7:33 PM
I went into withdrawal for a bit. Now .. all is good. roar

mtbizzle
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· 08/10/2020 7:26 PM
Yeah Jack I think so, I couldn't access for a bit

JackH
OfflineAdmin
· 08/10/2020 6:51 PM
Did we lose the site for a while?

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TC4+ Arduino coffee roaster shield (TC4-compatible)
ROSTARN
Oh Man! I found that one wire to one thermocouple was a little loose so i tighten it. And voila the instability is gone. I confirmed it by removing and inserting the wire again while it was on and the arduino froze up again like before with the same error message in artisan as in previous post. I did capture it in serial monitor but nothing really useful to see.
I post it anyways if someone is interested:

982 21:08:07.008 ArduinoTC4: COM4,115200,8,N,1,1.0 || Tx = READ || Rx = ['']|| Ts= -1.00, -1.00, 0.00, 0.00, 0.00, 0.00

981 21:08:03.497 ArduinoTC4: COM4,115200,8,N,1,1.0 || Tx = READ || Rx = ['']|| Ts= -1.00, -1.00, 0.00, 0.00, 0.00, 0.00

980 21:08:01.989 ArduinoTC4: COM4,115200,8,N,1,1.0 || Tx = READ || Rx = ['27.4', '78.1', '48.8', '32.1', '35.2', '0', '0', '0']|| Ts= 78.10, 48.80, 27.40, 35.20, 0.00, 0.00

979 21:08:00.483 ArduinoTC4: COM4,115200,8,N,1,1.0 || Tx = READ || Rx = ['27.4', '78.1', '48.8', '32.1', '34.7', '0', '0', '0']|| Ts= 78.10, 48.80, 27.40, 34.70, 0.00, 0.00

There is no issue now running both power sources. I didnt remove anything from the board yet so its all stock tc4+. DC in and out are also connected.

What I did before was connecting an external mosfet circuit through the io3 pins, as I did on the TC4 setup. No power connected to DC IN, bypassing the onboard mosfet and voltage regulator. It seemed like it fixed the problem but in reality I was probably just touching the thermocouple wire a little so it made contact for a while and later vibrations loosened it again. Makes sense now.
Hopefully I dont speak too soon and the problems come back. (has happened many times before)

Just a thought: if its that sensitive why not having caps in series and parallel on the thermocouples channels as the tc4 does? I did notice the temperature was swinging more than on the tc4, although not noticeable when increasing the post filtering by 10%. Most people (myself included) cant choose a suiting cap or know where to buy one. You have the solder pads ready and it would become a better product.

Thanks a lot for the help guys, feels good knowing there is support here Grin
 
mg512
Oh, happy to hear you solved it. Still a little odd, a loose TC wire shouldn't trip up the Arduino as a whole. Is it possible the wire (or its metal shielding) was touching elsewhere and creating a short?

I don't think the original TC4 had those capacitors as standard, at least as far as I know. I intentionally don't solder any by default so that users have the most flexibility - as you observe software filtering can achieve the same effect, but then you can turn it off. On my own setup I prefer little or no filtering, for instance. I could populate them in the next batch though if people would prefer that.
 
https://www.tindie.com/products/15798/
JackH
I am glad it is working! Thanks to mg512 for helping with this!

I believe JimG left the capacitors optional on later TC4 designs. Pads were there to add them I think.


One of the troubleshooting/testing procedures I did when building the older TC4 was to temporarily jumper the TC inputs (+ to -). This would allow me to test all inputs (the temperature read should be about ambient).
JackH attached the following image:
tc_inserted.jpg

---Jack

KKTO Roaster.
 
renatoa

Quote

mg512 wrote:

...Still a little odd, a loose TC wire shouldn't trip up the Arduino as a whole.
Is it possible the wire (or its metal shielding) was touching elsewhere and creating a short?

...


It's possible, the ADC is the culprit, any channel that is not used must be grounded, or inputs shorted, else will hit the MCU, even ESP. Sounds odd, but the inputs of an unused channel, if left floating, can influence readings of other channel, or even reset the whole board !
 
ROSTARN
Thats interesting, I will from now on short my unused channels and maybe something to put in your guide for TC4+?
The TC4 I have is from member Will2 and that had caps everywhere on the channels.
If I had the knowledge of which caps and where to buy them, I would.
Can anyone recomend, preferbly within EU?
 
greencardigan
I use 10000PF 50V X7R caps on the TC4 boards I build. The TC4 uses a mix of 0603 and 0402 sizes but Matthias could confirm what size has been allowed for on the TC4+ boards.

Here are links to the actual caps I've been using at Digikey.

CAP CER 10000PF 50V X7R 0603

CAP CER 10000PF 50V X7R 0402
 
renatoa
You have attached a typical TC amp input filtering that kills any noise, even at 0.012 C resolution !
Consider there is a BT dongle at 5 cm from TC amp/ADC boards Grin
renatoa attached the following image:
tc_amp_schematic.jpg

Edited by renatoa on 12/13/2019 7:28 AM
 
mg512
Odd, I have always left my inputs floating, and have never had any issues with that. I'll have a look at this for future revisions though and do some testing. The BT module shouldn't create any interference in my experience, much too high frequency.

The capacitor pads on the TC4+ are all 0603-size, if anyone wants to add caps. The ones that greencardigan linked should work. You'd need 12 of the 0603 ones (get a few extra, you will drop one on the floor and never find it again... ;))
 
https://www.tindie.com/products/15798/
ROSTARN
Update
I ran the machine for almost three hours yesterday and got two freeze ups after maybe an hour each time during warmup and idling, same as before.
Fortunatly I managed to do two roasts during this time with no problem, except I had to raise the fan speed on ot2 by 5-7% to get the same speed as on tc4 setup.

I did shorten the unused thermocouples channels but that didnt help in my case.

As my setup is electric drum roaster with dc drum motor on io3 I need it to run stable for hours. As a next move I will solder caps kindly provided by greencardigan on the solderpads and hope it will solve this problem, otherwise Im out of ideas.
 
JackH
Could there be some electrical interference somewhere? TC4 too close to motor, etc..
---Jack

KKTO Roaster.
 
renatoa
Why drum motor need to be controlled by software ? Are you changing speed in mid roast ?
Why not power it completely separate, using a DC PWM box, like this:
https://www.ebay.com/itm/PWM-6-60V-DC...3288261278

If you know your power grid is problematic, with frequent brownouts, setup should be designed accordingly, with electronics powered on batteries, and having quick backup solution in place in case of a laptop or board reboot.
 
mg512
The freezes you have now, are they the same issue you had before with the onboard voltage regulator? Or is it the issue where Artisan says something about a serial exception?

And is this now with the external MOSFET circuit you mentioned a few posts above, or with the on-board MOSFET?
 
https://www.tindie.com/products/15798/
ROSTARN

Quote

JackH wrote:

Could there be some electrical interference somewhere? TC4 too close to motor, etc..


Physically its approx. two feet away and the motor has a flyback diode.


Quote

renatoa wrote:

Why drum motor need to be controlled by software ? Are you changing speed in mid roast ?
Why not power it completely separate, using a DC PWM box, like this:
https://www.ebay.com/itm/PWM-6-60V-DC...3288261278

If you know your power grid is problematic, with frequent brownouts, setup should be designed accordingly, with electronics powered on batteries, and having quick backup solution in place in case of a laptop or board reboot.


Yes I'm changing speed as roast progresses. My first controller (pre TC4) was analog and I had a similair circuit you linked. Hard to get consistent results if its not software controlled. I used roastlogger to read the thermocouples.

But I say again, I've used the very same setup with a tc4 (not tc4+) and it was super stable for over a year until I shortened it by accident.
My grid is very stable and almost never black outs.


Quote

mg512 wrote:

The freezes you have now, are they the same issue you had before with the onboard voltage regulator? Or is it the issue where Artisan says something about a serial exception?

And is this now with the external MOSFET circuit you mentioned a few posts above, or with the on-board MOSFET?


Yes its the same freezes, arduino stops responding, clock on display stops counting and from Artisan I get this serial error message, its always been these symptoms combined.

Right now Im using the onboard mosfet.

Earlier I did manage to provoke the freeze by disconnecting and connecting thermocouples while running, so I'm guessing the ADC is quite sensitive and could cause the freezes. Hopefully the caps will help.
Im giving another update when Ive soldered and tested them. It will take a while since it ships from Australia to Sweden
 
mg512
I have to admit, I don't know what's going on here. In general, the ADC is indeed the least robust component in the system. Of the handful of hardware failures I've seen with the TC4+, it's almost always been the ADC. BUT, I've never seen it fail like this. It always broke permanently, not intermittently, and it never took down the Arduino with it.

Anyway, I am very curious to hear if the capacitors make any difference. I am also happy to send you another TC4+, if you want to try if that makes a difference. I suppose it's possible the ADC on yours is defective in an unusual way, trying a new shield would test for that. Email me your address if you'd like that.

Just to check, I assume you tried a different Arduino, right?
With disconnecting and connecting thermocouples, were you able to reproduce the error repeatedly, or did you try just once?
Is there any correlation with how long the system has been running? You said a few posts up it happened a couple of times when it was running for an hour, is it always running that long when the problem happened?
 
https://www.tindie.com/products/15798/
shortyjacobs
Hey - can I get a sanity check quick? I'm diving deep into this, and while I have plenty of experience with household wiring, and a decent amount of experience with line voltage controls wiring (espresso machine and electric brewery), this is a whole new ball of wax.

I need to control a 240V 2KW heater and a 120V universal vacuum cleaner motor. I plan on using an Arduino Uno and a TC4+.

I have plenty of experience with the cheapo FOTEK SSR units, and plan on using one for the heater. If I understand right, as a zero crossing SSR, it can only switch at 0V, so 120 times per second max. That means on at one crossing, and off at the next, right? For a heater, if I want ~1% control granularity, I need to then run it at a 1 second duty cycle, right? that gives me 120 zero crossings, 120 peaks or valleys of AC current, to turn on and off. It would give me 120 setpoints from 0-100%, or about 0.83% control granularity. If I wanted less granularity, but smoother heat, I'd run it at a 0.5 second duty cycle, giving me 60 setpoints from 0-100%, or about 1.7% control granularity. I see I can set duty cycle in the Arduino sketch for the TC4+ - what duty cycles do people normally run?? I'm thinking 0.5 sec (2 hz) is pretty good. I can use OT1 on the TC4 for this, with a 2 hz pwm frequency, and it should work, right???

OK, next, the motor. I can't use a zero crossing SSR because a 1 or 0.5sec duty cycle would lead to a lot of pulsation in my motor. So I want to be using phase angle control, for which I need a ZCD and a randomfire SSR (which can turn on/off at any time in the AC cycle). For that I'll buy or make a ZCD circuit, connect the output to IO3, and use that to trigger the SSR firing off of OT2 on the TC4+. This will allow me to run at either 60 or 120 hz, (I'm not quite clear on that), which is fast enough for the motor to run smoothly.Did I get that right?

What's a good random-fire SSR to purchase?

If I'm doing one Random Fire SSR for the motor, why not just run the ZCD signal for both motor and heater and run random-fires on both so I get smoother heat output too??

Thanks folks, still learning...
-Keith
 
greencardigan
I'd recommend a Crydom D2425-10 for the random fire SSR.

When the TC4 sketches are in phase angle control mode for the motor, it also does integral cycle control (ICC) for the heater. Not quite as smooth as phase angle control, but you won't know it with the heater. ICC also doesn't require the more expensive random fire SSR.
 
shortyjacobs
Awesome, thanks greencardigan!
-Keith
 
mg512
I think the standard people use for the heater is 1s / 1Hz duty cycle. 0.5s / 2Hz should also work though. You're correct about how many steps of effective output resolution that gives you.

For the motor with phase-angle-control, indeed 60Hz mains frequency will effectively give you 120Hz "PWM frequency" so to speak. A portion of each half-sine is "chopped off" to vary the motor speed.

As an alternative to a ZCD & random-fire SSR you could also consider a PWM AC dimmer module such as this one: https://www.tindie.com/products/bugro...50hz-60hz/ With this, you basically leave the Arduino in PWM configuration, and the dimmer board translates the PWM signal into a dimmed AC waveform. IMHO that's a little easier to set up, though there are benefits and drawbacks to either approach and it's ultimately down to personal preference.
 
https://www.tindie.com/products/15798/
renatoa
If you are using a low inertia machine, like a FB or TO, i.e. not a drum, then 1% control resolution is at the limit of not enough.
The ultimate gain of such machine is somewhere near 5 (C degrees per % of heat). You can find this value during autotune. Or simply experiment: set the heater % to a value, let stabilize, note the temperature, then push 1% and check the new stabilised temperature. Or, more useful, find the % of heater values needed for two reference temperatures of hot air, 200 and 270C, you will need these values as red lines in your roast. 200 is the maximum temperature for charge and 270 the maximum overall. Having heater % values for these temperature make easy to find the machine gain, as degrees per percent of heater control.

A 5 C degrees jump in ET would make your BT RoR look awful, with an appearance of oscillating as a drunk fly. Following a profile with such control is a frustrating experience.
The best approach to roast with such granularity of control is let the natural machine curve do its magic. Increase slowly the power to reach the peak of RoR at minute 3, about 15-20 C/min, then push another some %s during all the rest of dry, then Maillard phases, and decrease 2-3% before FC and during development.
For example, the Eth Guji Ambela roasted yesterday, on my TO machine, the values of the process described above were: 40% during charge until TP, then ramp to 64% by minute 3, then +1% every minute up to 69% at minute 8, when started to lower, reaching 66% during development at minutes 10-11.
Don't use as reference the gas value changes you see in the profiles done on drum machines, or use them, but with other units... the dynamics in hot air is completely different. 10% change in gas is 1% change in power on a hot air machine. Grin
Edited by renatoa on 01/05/2020 6:32 AM
 
shortyjacobs

Quote

mg512 wrote:

As an alternative to a ZCD & random-fire SSR you could also consider a PWM AC dimmer module such as this one: https://www.tindie.com/products/bugro...50hz-60hz/ With this, you basically leave the Arduino in PWM configuration, and the dimmer board translates the PWM signal into a dimmed AC waveform. IMHO that's a little easier to set up, though there are benefits and drawbacks to either approach and it's ultimately down to personal preference.


Thanks! I did look at that module, and it's way cheaper than the ZCD/RF SSR, but the 5A limit scared me. I've read vaguely that the limit can be raised with a larger heat sink, and I've also read vaguely that while that's true, the traces in the PCB are also a 5 amp limiting factor. I have no idea how much my motor draws, but it came off a vacuum with "12 amps of POWER" written on the front, (a big Hoover).

Renatoa - thanks, that's really really helpful info.
-Keith
 
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