Power Pack/Light Dimmer Popper Modification.

Divey

After reading about shape_shifters modifications to her popper and reading about the many adjustments she can make to extend a roast, a friend and myself decided to give some poppers our variation of a popper modification.

As my mate already had a Kambrook popper, I purchased another so we could modify the two of them together, and, seeing as he is a bit of a tech head, we stripped the 1st popper down to see what was going on inside this little machine.
Pretty simple to tear these things apart as long as you have a torx screw driver for just one of the screws underneath the popper. The little plug that holds the power chord that enters the machine was removed with a pair of long nosed pliers and a little prying with a very small screw driver.
WARNING....IF YOU DON'T KNOW WHAT YOU ARE DOING WITH ELECTRICITY, DON'T ATTEMPT THIS AS IT MAY KILL YOU.
It did not take too long to discover that the fan is being supplied by 20 volts and the element is being fed by 240 volts.  We then decided to go to Jaycar and buy some goodies. A couple of black plastic boxes, a few sockets and also a few switches.

We separated the two systems so we could test the fan first without the element being turned on.

Our first thoughts were to buy a 24 volt/1.25amp DC power pack and try that for the fan, however, this idea quickly got knocked on the head as we discovered that the fan requires a tad more, in fact a lot more than 1.25 amps, as the fan was pulsating due to power loss. We then had to go to a little more expensive unit and buy a 115 watt, 24 volt (variable) 6amp general  laptop power supply from Jaycar. Once we tried one of these, we knew we were on a winner. Wow, once you give that little fan 24 volts, the increase of the fan speed was incredible. It worked out really well as we quickly discovered you can change the fan speed whilst the fan is still running.

We then bought a stove-top control to change the heating element. That was a complete failure as it required a thermostat and that was just not going to work. So we scratched our heads and came up with the idea of using a 1200watt/220-240volt light dimmer. We bought two of these off eBay. They were cheap as chips and as soon as we tried one we knew it is was an instant success. These dimmers were slightly modified by trimming a small amount of aluminium off their mounting brackets so they would fit into the plastic box and then they were super glued into place. The external section of the box was then  marked into 9 equal positions with a hand held drill bit and the small indentations were then filled in with white touch up car paint.

Having purchased the black plastic boxes prior to determining that the initial power supply was not up to scratch, we were forced to mount the newer and much larger fan power supply to the outside of the box and run some external wiring back into the box. Once again, this was done with super glue. Probably not as neat as we would have liked but still quite acceptable. Bugger!!

We have discovered that the heated air from the element is changed by the fan speed.  The extra air rushing past the element is cooling the element down so it is a balance between ambient temperature/fan speed and element control to achieve exactly what profile of roast is required.

With 110 grams of beans in the popper and only the fan switched on at 24 volts the fan has a tendency to throw the odd bean out of the chimney. This gives you some idea of the power of the fan at 24 volts.  This power will never be needed. However, it is an indication that the quantity of beans may well be increased  in future tests.

At the moment, 18 volts on the fan and the heating element set at 7 gives a nice extended roast time in excess of 13 minutes with an ambient temperature of 20 degrees.

At the present time, I am roasting with the aid of an Infrared Temperature gun which is NOT considered to be as reliable and consistent as using a probe direct into the bean mass.  This will be the next addition to the power pack/light dimmer popper.

I have to keep telling myself now, don't fiddle with the controls!!



This is the complete package. The green switch supplies power to the fan and the element. The element cannot be operated without the fan switched on. The red switch is the element and the knob is the element control varying from 1 to 9.



This is the top view of the unit showing the power light and the fan voltage control.



This is a closer view of the fan voltage control. You can see clearly that it is set at 18 volts. Each change is defined by a nice solid 'click'.



This is the rear view of the unit showing a USB port and power socket.

Koffee_Kosmo

I just love ingenuity when it comes to coffee roasting Its also neat  :thumb: KK

shape_shifter

Oh s**t Divey, I'm sorry I never got back to you, little hectic here, I'm glad you were able to figure some of it out, OH is very weird about all this stuff, I don't know why, it's not that he's adverse to sharing he just feels he doesn't want to contribute to someone getting hurt. Looks very neat  :thumb:

UNM

Your popper control is functionally identical to my old popper. Much neater though - there was a thread elsewhere on my somewhat bodgy mods. Thing with poppers is that a LOT of heat is wasted as it just blows straight through. My hottop runs at 650W and can roast 300g (just). My old popper was 1200W and could roast 160g (just). As you increase airflow, the heat transmission to the beans reduces, so it is a different sort of dance to the one you do with a drum roaster. I ran my popper at 60-70% heat initially and managed airflow to keep beans gently tumbling, then as they warmed up (and became lighter), I increased heat input to keep the Rate Of Rise (ROR) I wanted and reduced airflow to keep agitation constant - otherwise they tended to jump out the chimney. When they got close to first crack I would use a sieve over the top of the chimney and more airflow to prevent the roast running away. A thermocouple will help a lot to understand what is happening, but with any fluidised bed roaster, you can't measure bean mass temp as such - the airflow ALWAYS influences the thermocouple reading to some extent. I used a single thermocouple 1cm above the base of the roasting chamber and dead centre - as close as I could get to bean temp. A second one right in the inlet airflow would  probably help for getting useful data. Ultimately though, every roaster is different and you need to play around and get a feel for how best to control it to achieve the results you want. The controls you have will provide all the control you need until the popper fan or motor dies - then you can chuck it and get a new one using the same control box. <STD-DISCLAIMER> I am not qualified to offer advice  on this topic or many others. All I can say is it MAY be worth what you just paid for it. :-|

Divey

on 1325939484:

SS, I can fully understand and is why I get very guarded... A couple of nubs can advise and make all sorts of statements and if some one gets hurt it is their own fault. A qualified person advises, and even if the other party does it 110% wrong; then the Qualified person is accountable. The law is very strict on these points...  Yes you can wire up what ever you want, But before power is applied, it SHALL be inspected and tested and tagged before being connected to a power source of any sort. Thus as a qualified person, I am also not able to assume or expect that a DIY person will in fact comply with the said demands for testing by a qualified person; regardless of what they say. Outcome re good risk management and keeping the solicitors away from all ones earnings and potential earnings.... If your not qualified, I can only advise you to get a qualified person to assist !

A.M., what you have pointed out is the very reason why I did NOT take any photographs of modifications that were taking place inside the popper and also the wiring of the internals of the plastic box. As it stands and from what I posted, one can only assume. 

Divey

on 1325976293:

Divey... Must admit I like ya train of thought and the outcome looks more than OK.. Now could one quickly patch said controller into a TO, keeping in mind the fan is 240V  :question: I will leave you with it... AM

I'm not up to speed with the Turbo Ovens .....so, do you want to control the heat or fan. :question:

Divey

on 1325982447:

Both... I have my own thoughts and similar to what you have done... But the fan needs to behave more like a HT.. That is OFF / LOW speed at the outset, while the heat rises.. approx 1st Crack - fan speed up and temp down From then on its a matter of USER as to which way  :rofl: The nasty part for the general public;is that it would mean accessing the internals of the TO and that mean Qualified persons. A: I have a mod for the HT on a external board but lazy means I can't be bothered to fit as a fixture = Don't bother and just manage the HT as intended. B: Have tweaked my TO to have reduced fan power (mod of the blades) and a re calibration of the thermostat (a tad tricky) but again, part of the mod is not available to a unqualified person. AM

Cheap as chips...... http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=140303463013