[TriEmbed] Coffee roaster sanity check

Craig Cook cncook001 at yahoo.com
Sun Dec 29 18:34:21 CST 2019


>Is this the same project I vaguely remember having some e-mails about a 
while back?  IIRC, we were never sure about the voltage rating for the 
fan.  This is a hot-air popcorn popper conversion, right?  Am I 
remembering correctly that originally, the heater was in series with the 
fan motor, acting as a current limiter?

Yes, same project. I am working on it again now.

> Did you ever (very carefully) measure the voltage across the motor while the popper was powered?

Yes. 0.134 Amp AC
Hmm... as I type that, it seems it should be a DC reading...

> I don't know how you plan to prototype this, but a solderless breadboard is going to melt if you run your heater power through it.

Yes, I realized that. That's why I have connectors to the SSR 110v pins. They will stay inside the unit somehow.

> I'm assuming you're using the 2-pin headers (J1-J5) to represent connections to off-board components. 

Correct

>This will be bad if you decide to lay out a PCB.  Use pairs of 1-pin headers instead.  Better yet, plan ahead for the correct number of off-board connections so that you can use screw terminal blocks in your layout.

Had not considered that. First attempt is to get the diagram correct. I have everything on a solderless breadboard now. I want to move to a something like this thing next https://www.amazon.com/Electronics-Salon-Prototype-Arduino-Shield-CZH-LABS/dp/B01J1KM3RM/ref=asc_df_B01J1KM3RM/?tag=hyprod-20&linkCode=df0&hvadid=312112107588&hvpos=1o3&hvnetw=g&hvrand=9103550878023998432&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9009736&hvtargid=pla-570550293295&psc=1

>Ah, if the diodes you added are what are currently in the popper, then they make sense for the popper but not your circuit.

>They aren't snubbing in that configuration.  They're forming a full bridge rectifier to turn the AC from the wall into DC for the motor.

Yes, that makes sense.

> In your circuit, the incoming power is already DC, so a bridge rectifier is unnecessary.

Interesting. I was hoping to make as few changes as possible. Considering someone who is going to replicate my work, it's probably not too much to ask to remove the diodes from the fan motor.

I was also considering using the 20v+ AC line from the popcorn unit and ditch my external DC 20v power supply (one less thing for someone to supply). Would that cause any issues?

> Where is the actual +5V coming from?  That isn't represented in the schematic.

It's coming from the Arduino 5v port (unless I should use a dedicated external DC 5v supply)

> The arduino's ground is not connected to your global GND.  A1 pin 7 should connect to a GND component instead of the PWR_FLAG to which it is currently connected.

Updated now.

> It may be wise to have a series resistance between the Arduino and the SSR's control pin.  250 ohms would be a good value to use here as well.

Updated now.

>100 Ohms may be too small for R4.

Changed to 250.

> D1 should be removed completely. 

Gone.

>Keep us in the loop.  I for one think it's great to watch you work on your design and share helpful knowledge when needed.

I really appreciate everyone's help.

Files updated on google drive.

Thanks

Craig




More information about the TriEmbed mailing list