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1/2 lb - Heat Gun Element - Tc4+ - Fluidbed Roaster
Hi All,

Ive roasted a few lbs on my modified popcorn machine and want to build a roaster.
Mods to the machine at the time are dimmer on the main heating coil.

I would like to build something like cdrake did over in his post. Currently I am working on compiling a component list (see below)

Basically using a heat gun element to generate heat. and stacking old server fans in series to generate the required pressure, a tc4+ to regulate things.

Piping and champer:
Can be readily had on Amazon if you know where to look:
I stumbled upon this sight chamber and was able to go from there. No welding is required with a high-quality, industrial look.

This is a 3" diameter model, although narrower ones are available. if you can find a taller piece of glass and the rods, you can make a huge camber this way.



Im hacking this part for now, will upgrade later if needed.

I was able to generate 20g on a kitchen scale with each fan. I then stacked them in series with some space in between and saw that this scales up nicely, 2 fans generate 40g, 3 fans 60g etc.

so I want to roast about 0.5 lbs in a 3" round chamber, that works out to about 0.5 lbs / 7 in" or about 0.07 psi required

the fan area is just under 40 mm (housing is 40mm ) so about 2.5in^2 , and 20g is 0.044lbs. so that means
each fan is 0.044 lbs / 2.5 in^2 = 0.02 generated psi

so 4 fans in the series should give me what I want plus some room, minus some losses.
Who knows, it's just because I have these around already and I really want a DC fan to avoid all this zero-crossing stuff with the TC4+.

I want to use this heating element since it looks wayyy beafier than the amazon ones.

Bill of Materials:

HELP ME Please!
- attaching the square fan array to the round pipe (see diagram) . Worst case I just use aluminum duct tape for this. ideas?

- how do I suspend the heating element in the vertical pipe?

- I chose a 3" sight glass since I figured a thinner layer of beans allows for better heat dispersion. and larger batches down the line

- how do I prevent the beans from falling onto the heater? mesh ? I'm also thinking amount some sort of mesh basket I can lift out to dump the beans

- can I cool the bean in machine by shutting off the heater?


Will update as I go.
Edited by AgressivStreetLamp on 11/24/2021 2:55 PM
So I realized I built the wrong TC4. I bought components to a 4.0 and need the tc4+. Will probably just order one at this point. hopefully it gets here before the holidays
They shouldn't be SO different... what are you missing from TC4+ ?

The DC fan driver can be added externally, anything else ?
That's mostly it.
Im working on another project right now so I haven't put much thought toward this.

Youve got a point though.
I'm thinking I can use an old ESC and a 3 phase blower motor. The Arduino can use PWM to control the ESC.
I just need a 3 phase blower. Anything BLDC with up to 60V should be doable. I have a 60V 35A server supply I can use, and an ESK8 ESC laying around as well
I would check the EV bike motors market, 48V is the one of the most used voltage, but speed is too low for a blower I'm afraid...

Hi speed BLDC are in the multicopter heavy duty drones) area, but sooo expensive...

Better go on the well known way, vacuum appliance motor and PAC control with OT2.


renatoa wrote:
PAC control with OT2.

Can you explain that?
The cost of a zcm and a ZC SSR (if that's what you're referring to) is more than just ordering the tc4+ and a nice bldc blower.
For PAC you need an instant fire SSR. ZC SSR is for heater control using slow PWM, but instant fire works as well.
Here instant fire SSR are in the $10 range, the 40 Amps units.
Cost of doing yourself a zero cross module is under $5. Or buy a RobotDyn dimmer.

What nice bldc blower you can buy with such amount ?
The PWM output by TC4 is not suitable to drive an ESC, the waveform logic is significantly different.
You need a couple of hundreds watts to lift 300 grams, as I remember being your target.
What is a PAC?

All the SSR I have found are in the $40 range.

My limit is the ~1500 W I can get out of a socket. and based on the reference model, a heat element of 1500W limits me more to 250g. which is for now. so something like 1500 W of heating + 200W of fan should be a good combo. I think anyway,
Phase Angle Control.
Robodyn Dimmer seems really nice and easy.
I can use this for the fan but Im guessing the heater draws too much power?

So I can do Robodyne with a vacuum fan. And an instant fire SSR for the heater?
Can you link an SSr that is as cost effective as you describe?

Removing the triac from the board and placing it on a serious heatsink make that board a very capable device.
The RobotDyn board has a dedicated thread, you can find there more experiments.
That board IS a SSR also ! combined with a ZCD, you can use it as you want, either way. Or as ZCD alone, if you blow the triac one day Grin

For SSR, no idea how useful would be a link to a shop in Eastern Europe... there are generic cheap SSR everywhere, many without any brand. Like this Grin https://www.spark...ucts/13015
Ahh thank you! so much more info! yes I think I will start by just buildind the TC4 I have then!

THank you!
Time for an update. So I went and hung a hard left. Decided I wanted to try to convert my popcorn machine to something automated. Generally it was producing very decent results. Decent enough that I believe my own operation was the limiting factor.

I also like taking baby steps.

Basically on advice from some members above I went for the Robotdyn dimmers. 16a for the heater and 8 amp for the motor. Should give me some headroom. I have an exhaust manifold thermocouple in the champer and an old probe one for external temps.
The whole thing will get an enclosure to cover all the bits that bite.
I was wondering if anyone knew how to add a plate of some sort to help with tumbling the beans when aloft? I have a single circle in the center that's pushing air into the chamber evenly. Now I'm trying to get better distribution

Also, TC4 works beautifully! Once I have an enclosure I will make a video
This is the first time I have logged in to HRO in a couple years. Built my version of 'Frankenpopper' and have been learning how to coax the best flavors out of my roasts. All that to say that my build was based upon one posted by ChicagoJohn. The best thing I learned from his build was to cut a SST funnel to fit into the bottom of my roasting chamber, with the bottom of the funnel cut to mate to the 'circle' where the hot air blows in, and the top of the funnel fits to the wall of the roasting chamber. This changes the bottom of the chamber so that it slopes in at a 60 degree angle and has provided excellent mixing. One thing I did (kluge, but it works) was put a thin layer of RTV on the lip of the funnel where it meets the circle where the hot air enters. It's just enough to create a proper seal at this interface and keep the mechanicals/ electrics clean. Not sexy, but this has worked perfectly to promote proper mixing. Perhaps this will give you an idea of how to do something similar for your build.
Here is very popular the funnel made from a cocktail shaker top lid/filter, that part with a perforated plate.
The outer diameter of such funnel is 82 mm, for the 750 ml model, and the perforated hot air exhaust circle is about 45 mm.
You can keep the perforated plate, adding more holes, else pressure drop can be experienced.
For seal the kapton tape is the most usual.
Thank You @Monarda and @renatoa,

Unfortunately, I managed to explode my current motor because I put a : instead of ; in Artisan scope.

Anyway, I found a Poppery I on FB marketplace for like $25 shipped. Bit dubious if it was goign to arrive, and while it is quite dirty, it arrived and works! I need to redo the wiring, and come up with a new mounting solution but otherwise I am back on my journey towards my goals. I still think a 225g Roaster is achievable with the usual mods of this guy.

Hi all,

I have successfully built a roaster with my little Poppery I. However,
After just a single roast, my robotdyn module burns out for the heater.

My robotdyn is rated for 24 amps which should be more than enough.

I was wondering about the zero crossing. right now I am in PAC 3 mode, with the heater on OT1. But the zc is comming from the robotdyn for the FAN. I looked at teh waveform coming from the FAN robotdyne and it appears to be phase gating as expecte (fan is the inductive load so that makes sense)
However. some of the documentation seems to indicate that the heater should be using a "zero crossing SSR?" whatever that is since arent all triacs zero crossing by nature? And SSRS are just triacs with a heatsink irrc?

I haven't messed with the firmware other than changing to pac. 3
Heater should use a ZC SSR for (slow) PWM mode, to improve the control accuracy.
With an instant fire SSR the precision of control in PWM mode and 1 second cycle is 2%, versus 1% when using ZC SSR.
However, if changing the pulse cycle to 2 seconds, the control precision became 1% even for instant fire ssr.

Yes, SSRs have triacs as the power control element, fitted with a simpler or more complex gate control circuitry.
According to the fire circuit complexity they can be instant fire, or zero cross fired.
And nope, triacs aren't zero cross by nature, conversely, a naked triac fire instantly when a right voltage is applied on the gate, in any moment !

Regarding your robotdyn burned, please check the dedicated thread, we have there some talks about its capabilities, and how heatsink should be improved.
Hm ok. First of all thank you for the help.

So which mode is that for my setup? It sounds like the slow heater mode is the first (slow_pwm) mode. But that uses a DC fan, which I don't. Is there a way to use slow pwm mode but keep my AC fan (pac3) ?

So my understanding is that triacs only turn off when the voltage across the gated terminals is close.to 0. This is the nature of the silicon. So a ZC SSR also only turn on with zero crossing?

I will read through the robotdyn thread. Thank you
So update after a long while. Some built-in closets later and yeah just a long time. I just roaster my first batch on what I consider a viable machine.

I moved all the electronics to their own 3d enclosure and added a handle to the poppery so the work flow is actually really dang good. Now I just need to learn how to roast lol

idk what im doing... send help


AgressivStreetLamp attached the following image:

Edited by renatoa on 09/28/2022 1:26 AM
I do have an open question. Can someone explain ET and BT to me and where I need probes for either.

RightNow I measure BT with a thermocouple just above the beans when they are their highest. ET is a probe near air intake (reads ambient). I'm sensing that ET should be hot air in right before the lofted beans and BT should be "bean tempt" but actually is air temp within the lofted beans?
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