Rate my mods? Fluid bed Phidgets rebuild

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Mr_Flauschig
Posts: 18
Joined: 2 years ago

#1: Post by Mr_Flauschig »

I'm just getting into roasting and bought a used fluid bed roaster. The hardware is good, but the software implementation sucks, so I'm going Artisan.

The machine is 1400w and rated for 60-120g. It uses a single thermocouple for BT. I'm going to add two more for inlet temperature and environment temperature, and use three RTD probes connected to three TMP1200_1 modules. They then connect to a VINT hub, HUB0002_0.

For outgoing commands, I'm doing PWM using OUT1100. These PWM commands go to two optoisolator triac drivers MOC3023, which then control the fan and heater, separately. The optoisolators and triacs are built into the roaster, so for controlling the roaster all I have to do is provide the PWM signals (hopefully).

Just because I can, I'm also going to add a load cell (via DAQ1500) to monitor the weight loss real time.

I've created a basic schematic of what I'm going to do. I've been searching the various roasting forums, to see how other people did similar projects, so I think I'm on the right track? If anyone has thoughts or recommendations, they would be appreciated.


georgemvg
Posts: 29
Joined: 6 years ago

#2: Post by georgemvg »

Hi! I think i saw it again at Sweet Μaria, to roast with a scale. Maybe I am missing something, but how will the scale work if the beans are flying in the air?

randytsuch
Posts: 502
Joined: 15 years ago

#3: Post by randytsuch »

I looked at the out1100, it shows a min pwm frequency of 100 Hz.
Pretty sure that is too high. FWIW, when I was putting my roaster together, I landed at 5 Hz, and it seems to work fine in my SCTO.
I see my heater turn on and off when I adjust power levels during the roast.

Randy

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MaKoMo
Posts: 850
Joined: 16 years ago

#4: Post by MaKoMo »

Mr_Flauschig wrote:..and use three RTD probes connected to three TMP1200_1 modules. They then connect to a VINT hub, HUB0002_0.
You should use TMP1200_0 modules. The newer TMP1200_1 modules are way noisier thus cheaper.

Mr_Flauschig (original poster)
Posts: 18
Joined: 2 years ago

#5: Post by Mr_Flauschig (original poster) »

Thanks for the advice. I see some people have had trouble implementing PWM, so I hope not too. I think the duty cycle on the stock machine is around 140Hz, but I'm not sure, my scope is broken :( I'd really like to look at the signal, but I can't without starting a whole other project. I will look for other PWM units that have a lower minimum rate.

Mr_Flauschig (original poster)
Posts: 18
Joined: 2 years ago

#6: Post by Mr_Flauschig (original poster) »

Thank you!

randytsuch
Posts: 502
Joined: 15 years ago

#7: Post by randytsuch »

In my roaster, I use a a zero turn on SSR to control heater power, a Crydom D2450.
So the SSR will only turn on at the zero voltage crossing, and at 60 Hz, you get 120 zero crossings per sec.

So in my case, a duty cycle of 100 hz or more doesn't make any sense. The PWM output might turn on and off, but my SSR would stay off.

I use a zero turn on SSR for heater power so there is no current surge when the SSR turns on. Since it only turns on at 0V, there is no current at turn on.

For heater power, I don't see any reason to use a PWM in the 100's of Hz. My 5Hz pwm is fine.
A long time ago, I had a arduino based program that I think used an even slower rate, might have been 1Hz.

Randy

Cranked
Posts: 92
Joined: 1 year ago

#8: Post by Cranked »

I am considering a similar build. I was going to use a TC4+ and Arduino to connect to Artisan, based on this:

http://www.jasonwolley.com/images/qm3_tc4_20.jpg

With Artisan run through the laptop, the 10k potentiometers are not necessary, neither is the LCD. Maybe one wants them as backup to run the roaster without the laptop.

I was also going to use a PWM to control the fan (eliminating the D2425-10 and ZCD).

This is not my field of expertise. Comments welcome, and perhaps it contributes to the current discussion.

Mr_Flauschig (original poster)
Posts: 18
Joined: 2 years ago

#9: Post by Mr_Flauschig (original poster) »

I've read about such issues with SSRs and PWM. My roaster uses triacs, which run a bit differently, and I believe/hope work fine with higher switching rates. Unfortunately, Phidget doesn't offer any other PWM units, besides the VINT itself (and they don't give a minimum switching rate for the VINT). So if 100Hz is too high, I'd have to go to a completely different control system, which would be fairly annoying. Once again, I really wish I had my scope to look at how the control signal is currently working.

Mr_Flauschig (original poster)
Posts: 18
Joined: 2 years ago

#10: Post by Mr_Flauschig (original poster) »

I've heard of the TC4+/Arduino but don't know much about it. I wanted to go with Phidgets to minimize any programming I might have to do, it is an area I just don't want to have to deal with. I also want to use RTD probes, which Phidget supports, but I'm guessing the TC4+ can't. Good luck with your build, keep us updated!