How about this Sunpentown for SC/To setup?

[mp]

Instead of buying a new Sunpentown, I bought a very old (but like new) 1470 watt Galloping Gourmet Convection off ebay for about $50 (lucked into a local pickup).  I rewired to have separate cords for the heater (which gets controlled via my Arduino and an SSR) and for the fan.  I've never done a side-by-side comparison between a Sunpentown and a GG, but the GG is very heavy duty and, I believe, higher power.

-Phil

You say it is 1470 GG vs 1300 for the Sunpentown, so yes it is more powerful than the Sunpentown.

How much did the Arduino and SSR set you back? So your Arduino both sets and displays the current running temperature of your GG oven?

 

[Tex]

Instead of buying a new Sunpentown, I bought a very old (but like new) 1470 watt Galloping Gourmet Convection off ebay for about $50 (lucked into a local pickup).  I rewired to have separate cords for the heater (which gets controlled via my Arduino and an SSR) and for the fan.  I've never done a side-by-side comparison between a Sunpentown and a GG, but the GG is very heavy duty and, I believe, higher power.

-Phil

I have two GG myself - great elements & fans. I too split the fan & heat circuits - fan runs at 100% always and I control the heat with a router speed control. Although I seldom use the SC/TO anymore I break it out when I have a bean the Sono doesn't do well.

[mp]

Instead of buying a new Sunpentown, I bought a very old (but like new) 1470 watt Galloping Gourmet Convection off ebay for about $50 (lucked into a local pickup).  I rewired to have separate cords for the heater (which gets controlled via my Arduino and an SSR) and for the fan.  I've never done a side-by-side comparison between a Sunpentown and a GG, but the GG is very heavy duty and, I believe, higher power.

-Phil

I have two GG myself - great elements & fans. I too split the fan & heat circuits - fan runs at 100% always and I control the heat with a router speed control. Although I seldom use the SC/TO anymore I break it out when I have a bean the Sono doesn't do well.

May I ask how you do that Robert?

 

[Tex]

Instead of buying a new Sunpentown, I bought a very old (but like new) 1470 watt Galloping Gourmet Convection off ebay for about $50 (lucked into a local pickup).  I rewired to have separate cords for the heater (which gets controlled via my Arduino and an SSR) and for the fan.  I've never done a side-by-side comparison between a Sunpentown and a GG, but the GG is very heavy duty and, I believe, higher power.

-Phil

I have two GG myself - great elements & fans. I too split the fan & heat circuits - fan runs at 100% always and I control the heat with a router speed control. Although I seldom use the SC/TO anymore I break it out when I have a bean the Sono doesn't do well.

May I ask how you do that Robert?

 

One of these controls the voltage of the element;

I use a digital thermometer to monitor bean mass temps, and vary the voltage up & down as needed. No switches, no other control is needed. I did put a Kill-A-Watt between the RSC and the element so I could read the voltage being sent to the element.

edited: There are simpler ways to do it, but they require someone with Peters experience to know instinctively when to cut the power and when to cut it back in. I prefer a more complex, but measurable way of doing things.

[mp]

Instead of buying a new Sunpentown, I bought a very old (but like new) 1470 watt Galloping Gourmet Convection off ebay for about $50 (lucked into a local pickup).  I rewired to have separate cords for the heater (which gets controlled via my Arduino and an SSR) and for the fan.  I've never done a side-by-side comparison between a Sunpentown and a GG, but the GG is very heavy duty and, I believe, higher power.

-Phil

I have two GG myself - great elements & fans. I too split the fan & heat circuits - fan runs at 100% always and I control the heat with a router speed control. Although I seldom use the SC/TO anymore I break it out when I have a bean the Sono doesn't do well.

May I ask how you do that Robert?

 

One of these controls the voltage of the element;

I use a digital thermometer to monitor bean mass temps, and vary the voltage up & down as needed. No switches, no other control is needed. I did put a Kill-A-Watt between the RSC and the element so I could read the voltage being sent to the element.

edited: There are simpler ways to do it, but they require someone with Peters experience to know instinctively when to cut the power and when to cut it back in. I prefer a more complex, but measurable way of doing things.

That device looks interesting.

Is that like a mini variac?

How much does one of those cost and where did you get it?

Does it work like a variac?

 

[peter]

edited: There are simpler ways to do it, but they require someone with Peters experience to know instinctively when to cut the power and when to cut it back in. I prefer a more complex, but measurable way of doing things.

Be one with the bean, and it will tell you when it is happy.



I thought you knew by now Tex, that answering Mikey's questions is like feeding a stray cat; once it all it takes and you'll never be able to stop.   

[mp]

edited: There are simpler ways to do it, but they require someone with Peters experience to know instinctively when to cut the power and when to cut it back in. I prefer a more complex, but measurable way of doing things.

Be one with the bean, and it will tell you when it is happy.



I thought you knew by now Tex, that answering Mikey's questions is like feeding a stray cat; once it all it takes and you'll never be able to stop.   

Sorry Peter ... I've never seen one of those guys that Robert pointed out. I am very curious as to how they work.

I even managed to find a link to where he bought it:
http://www.harborfreight.com/router-speed-control-43060.html

I still don't understand quite how it works however.

 

[Aromajunkie]

Speed controls like the one shown use Pulse Width Modulation (google it :-). Different from a variac, which actually changes the voltage of the output. PWM is a cheaper solution.

[mp]

Speed controls like the one shown use Pulse Width Modulation (google it :-). Different from a variac, which actually changes the voltage of the output. PWM is a cheaper solution.

Thank Aromajunkie.

This guy explains it pretty well IMHO:

Circuit Skills: PWM (Pulse Width Modulation)

The way I understand it, it seems to make the motor better able to accept and utilize the current to make it run more efficiently.

Am I understanding this correctly?

 

[pwest]

Instead of buying a new Sunpentown, I bought a very old (but like new) 1470 watt Galloping Gourmet Convection off ebay for about $50 (lucked into a local pickup).  I rewired to have separate cords for the heater (which gets controlled via my Arduino and an SSR) and for the fan.  I've never done a side-by-side comparison between a Sunpentown and a GG, but the GG is very heavy duty and, I believe, higher power.

-Phil

You say it is 1470 GG vs 1300 for the Sunpentown, so yes it is more powerful than the Sunpentown.

How much did the Arduino and SSR set you back? So your Arduino both sets and displays the current running temperature of your GG oven?

 

I actually had a bag of high power SSR's sitting around, so I didn't have to pay for that (surplussed units (what mine are) can be gotten cheaply on ebay).  Arduino's can be gotten cheaply, too (I recently ordered a 'Chinduino' from China off ebay for $13.  On my system, I have a digital thermocouple shield (see prototype picture below) that interfaces to two TC's (Bean Temp and Env. Temp).  The Arduino reads those temps and sends them over wifi (another arduino shield) to my laptop.  My laptop logs the data, makes some calculations and sends the PWM value back to the arduino which drives the SSR.  Arduino code is C and the PC code is Python.  The whole roaster assembly is mounted in an aluminum 80/20 chassis.  Note that instead of using a popcorn stirrer for a roast chamber, I made one out of a couple of cake pans, a drive shaft, and a variable speed DC motor.  I've attached a few pics.

[peter]

Yowee!  What a nice rig that is!  How does the bottom portion release from the motor/shaft for dumping?

[pwest]

Speed controls like the one shown use Pulse Width Modulation (google it :-). Different from a variac, which actually changes the voltage of the output. PWM is a cheaper solution.

Thank Aromajunkie.

This guy explains it pretty well IMHO:

Circuit Skills: PWM (Pulse Width Modulation)

The way I understand it, it seems to make the motor better able to accept and utilize the current to make it run more efficiently.

Am I understanding this correctly?

 

There are several related topics going on here.  PWM, as described in the video is exactly what I use on my system to control the speed of the DC motor.  I also use PWM (or Duty Cycle Modulation) to control my heater, but instead of turning on and off a DC signal, I actually turn the AC power on and off.  On my system the duty cycle modulation period is 1.667 seconds. The SSR only turns on or off at AC zero crossings, so to ensure that you get adequate control/precision you need to have the period be sufficiently long so that many cycle pass--in this case 1.6667x60 = 100, giving me 1% resolution on my power control.   The harbor freight speed control (I'm pretty sure) uses a triac or quadrac to turn on/off during some part of each AC cycle, according to some 'phase' setting and works the same way modern light dimmers work (see, e.g. http://home.howstuffworks.com/dimmer-switch.htm).  I used one of these for heat control on my GG before I got the Arduino setup working--now I use it to control the fan on my cooler.  Finally,  a variac is actually just a transformer that can reduce or increase the voltage.  All different approaches to doing similar things. 

-Phil

[pwest]

Yowee!  What a nice rig that is!  How does the bottom portion release from the motor/shaft for dumping?

After I start hearing 2C, I:
 - Turn off the stirrer
 - Lift up the GG handle (which turns off its fan and heater)
 - Lift the GG off the cake pan and set it on that round rack you can see over on the left in the photo
 - Lift up the roast chamber by the little black handles that you can see (they don't get hot)
 - Dump the beans in the cooler.

The axle shaft that goes through the cake pans is actually just a 1/4-20 bolt, and the drive shaft that connects the motor to the bottom of the axle is just 1/4" square steel stock with a socket on each end--one that fits the axle and one that fits the motor output  (You can see some of this in the rear view).  Simple.

I didn't mention it in the earlier post, but I have separated the GG heater and fan circuit so that I can modulate heat and leave the fan running full speed. 

[farmroast]

Phil, nice.
Hadn't seen a pic of your most recent set up.
Yes, find a nice used GG top on ebay. There were several models over the years. The earlier were 1440 or 1470watts a newer was only 1200. The wattage is listed on a sticker on the back of the GG top so if not listed you can question the seller to check. I've got close to 2000 roasts on mine.
I use the TC-4 arduino setup on mine.

[mp]

Looks like you guys have rigged your SC/TO setup to have software similar to a professional coffee roaster.

Do you setup up custom roast profiles too with the Arduino?