greencardigan wrote on Mar 14^th, 2008, 10:50am:


No, it won't. There are 2 heating coils. The larger, outer one, is the main heating element. That one is not in series with the fan, and is the only one you need to use. The smaller, inner one is the one used to drop voltage to the fan.

You might mave some fun getting the Crazy Popper dismantled. I pulled one apart for parts and it was a nightmare! You can't access the screws as the circuit board is mounted over them. So it seems that you need to un-solder the circuit board from the fan motor before you can access the other mounting screws. My B&D popper was much easier to work on as it didn't have this problem.


regards,
Bill

In my opinion it won't work for another reason.

Crazy Poppers tend to run hot.
So to increase roast times you need to get more cool air into them.
Merely splitting the fan from the heater won't do anything because you aren't going to increase fan speed too much before you'll probably overwork it to death.
And slowing it down is not what you want to do at all.
So perceived control over the fan in reality is in my opinion worthless.

Also, increased fan speed would blow the beans out of the popper.
Mine has a custom fitted exhaust pipe and it lost the occasional bean with the standard fan.

Back to what you need to control.
As I said, you need more cool air OR you need to be able to adjust the heat DOWN.

I managed to get 15 minute roasts by increasing airflow.

If you look closely under the Crazy Popper you'll see that half of the air vents are baffled, thereby restricting the airflow.

To get my 15 minute roast I ended up taking the airflow idea to it's extreme.

I removed the bottom vent altogether as additional holes wasn't enough.
I recommend adding back some plastic fly screen mesh to keep any stray chaff out.

The big difference in the end though came from removing the top half of the popper's body.
You'll see some screw hole plugs around the edge at the top of the popper.
Prise or drill these out to access the screws.
By removing the top half you are introducing thermal inefficiency and letting a lot of heat escape that previously was trapped inside the popper.
When popping corn I'm sure it's a good thing.
When trying to slow down a bean roast it's not.

When you've gone this far you can then measure your chimney because the roasting chamber is larger in diameter than the hole in the top of the popper.

If you want to keep it looking prettier then you could try what I didn't get around to and cut out large sections of the top half of the body.
This will let out the heat and you can screw the top back on.
Mesh again could keep out stray chaff and give the popper a more finished look.
I'd recommend metal mesh here though.

The above works without having to play with 240v.

Mal wrote on Mar 14^th, 2008, 6:15pm:


That's not exactly how the wiring was connected in the 2 poppers I've pulled apart. The 2 heating elements were wired in parallel, not in series. There are 3 wires coming from the heating elements. 1 wire is connected to a common end of both elements, and the other 2 wires connect to the other ends of each heating element. The popper puts out plenty of heat with only the main element connected. You don't need to use the smaller, middle one at all. ie. You only need to use 2 of the 3 wires that come from the heating elements - the one that is common to both, and the one that connects to the other end of the main element. It'd be easier to explain if I could draw the circuit diagram on here....


Mal wrote on Mar 14^th, 2008, 6:15pm:


Yep, just make sure you use a ceiling fan speed controller, NOT a light dimmer. A light dimmer doesn't work when wired through a transformer, but a ceiling fan speed controller does. They may look the same, but they obviously arn't, as I can verify as I have tried both.

For even more control you can also wire a high power light dimmer (NOT a domestic light dimmer, as it can't handle the power - you need something that can handle 1200W) to the heating element, which is what I have done.


regards,
Bill

Horses for courses.
I outgrew the popper.
A corretto will do 280g in one batch and therby save you time and effort.

A 50% improvement already.

Do you have a fan? The extra airflow keeps the chaff away and helps both with the cool air entering from underneath and driving the heat withinin the body away.

The cooler evening air will also help.

2min to first crack is VERY Crazy.

Thundergod wrote on Mar 15^th, 2008, 5:32pm:


No, no fan. May try that when it's still, but it's a rare day here when there isn't a stiff breeze outside.

Yes, it is crazy. There are two problems, I think. First, when I got my popper, I hadn't done any background reading, so I deliberately chose the one with the highest wattage rating, thinking more was better. In hindsight that wasn't very smart, and I know $35 isn't much of a sunk cost, but still... Second, I think there is some random variation in manufacturing, and in local voltage, and between those two things I have way too much grunt in the popper department.

Anyway, I just tried again, with a wider tin for a chimney - the outside temp is now around 17C - and first crack didn't come on until four minutes, and I took it until nearly 8 minutes. I think I could do better too, because this roast was 100g of beans, and probably fewer beans would go more slowly. And it's a warm day, as the winter comes on no doubt roasting times will lengthen.

It's a conundrum. I got a popper after a workmate persuaded me it was a good idea. I am almost tempted to move on and up to a heatgun-based setup - but I feel I want to see what I can do with the popper first. Get my $35 out of it...

Mal wrote on Mar 15^th, 2008, 7:24pm:


I bought one from a UK online electronics place. I got the 2000W one from here: http://www.quasarelectronics.com/ci0013.htm - £16.98 + £9.95 shipping
It works great. I work to a spreadsheet which shows my target temp profile for every 15sec interval. With practice I know approximately how much heat I need to apply at each stage of the roast to follow my target profile, however if the thermocouple reading shows it deviating slightly off the expected path I can just nudge the dimmer control up or down slightly to compensate. I've done roasts up to 17mins duration so far, but I could go much longer if I really wanted to. It really gives me virtually unlimited control - well I could add a PID as well for more hands free control, and this is something I may consider in the future, but it's working well for me as is for the moment.

Batches are relatively small, however this can actually be an advantage in some situations, like when experimenting with various roast profiles. You can roast a number of small batches to different profiles to see which works best, without wasting a lot of coffee in the process.

Later on I may want to move on to something that can roast larger batches though, and I quite like the idea of building a fluid-bed roaster, but the popper suits my needs for the time being.


regards,
Bill

Part Two. I have purposely split the post as the two parts really address different issues.
My Crazy Popper has been modified as described by TG to allow better air flow. ie. all the vents in the base were removed and the large hole left in the base plate was covered by insect mesh, siliconed in place and larger feet added to raise the popper off the bench. The top moulding was also removed to expose the roasting chamber to help dissipate the heat and a chimney added with a purpose made, long temperature probe mounted down the middle of it.
I tried a couple of roasts with these modifications and found that first crack was around 9mins, with the first snaps of second crack at around the 14min mark.
Prior to this first crack was around 4/5mins and I usually stopped the roasts between 8 & 9mins depending on the colour of the beans.
After I split the fan motor supply from the popper supply, I tried running the fan on a 13.8 v DC power supply I already had, but found that the fan was not putting through enough air to move 100g of green beans.
I rigged up an experimental power supply that I could adjust, but not while roasting and found that the motor ran happily at voltages from 22v down to 16v and had no trouble moving 100g of beans.
So I tried a roast at 18v and found that it stalled before first crack.
Then tried a roast at 16v and while it got to the first snaps of first crack, it stalled there and didn't get to rolling first crack.
This is in Brisbane in the middle of summer so the ambient air temperature wasn't exactly low.
Any way the moral of the story is that the quantity of air flow through the popper has a big bearing on the roasting temperature.
If you are going to go this route, then some form of variable control is required over the fan speed so that you can up the voltage to get everything moving then back it off as the beans lose moisture to allow the temp to keep rising. ie. a solid state ceiling fan controller as suggested by others should do the job although I have not tried one myself.
Or you could go to a 'Corretto' BM/HG setup as I have done, and you get all the control you want, irrespective of the ambient temperature.
My standard roast is 200g, as I don't need large amounts, and I get nice even roasts, so this is not much up from what most try to put through a popper.
If you only want small roasts, make sure you get one of the smaller bin BM's. The Breville BB250 is ideal in this respect.

Cheers,

Alan.

grimsby wrote on Mar 16^th, 2008, 5:03am:


Excellent couple of posts there Alan, top stuff.....

Mal.

I forgot to add my roast notes for my unmodified crazy popper.  This was my first roast in this popper and I think I left it too long.

It ended up very dark, but tasted great.

0:00 - 120g into pre-warmed popper
2:20 - Getting darkish
2:40 - Heard 1st bean crack
3:20 - Lots of loud cracks
4:20 - Still cracking
5:00 - No cracking
6:50 - start of second crack
8:20 - Still cracking
10:00 - Still cracking
10:30 - Dumped beans, still cracking.

Hi gc,

A simple way to separate the fan motor from the 240v AC circuit without having to play with any 240 v wiring is to cut the PC board tracks just before the motor contacts. Then carefully drill holes through the PC board on the other side of the motor contacts and solder in your new DC wiring. While you are at it you can remove the 3 ceramic caps at the ends of the tracks as they no longer serve any useful purpose. Keep your new DC wiring well away from any 240v wires and lead out through a new hole drilled in the popper body.
All this can be done without dismantling any part of the popper once you have removed the base. It's really quite simple and safe as long as you have the popper unplugged from the 240v supply.
All the best with it.

Alan

Will these transformers be ok to power the seperated fan?

The first one is 2A at 30.  I'm guessing it will handle more current on the lower voltage taps??

Can I use the multiple taps to vary the fan speed instead of a ceiling fan controller?

http://www.dse.com.au/cgi-bin/dse.storefront/47eb06e8073934cc2741c0a87f9c06b7/Pr...

This one is the same price but 24V 3A.

http://www.dse.com.au/cgi-bin/dse.storefront/47eb06e8073934cc2741c0a87f9c06b7/Pr...

Hi gc,

If you want to run the standard CP fan motor at 24v then the current draw will be 2.25amps (approx). I calculated this in theory and checked it in practice.
If you run the AC secondary voltage through a rectifier then you drop 0.6v per diode before you feed the resulting DC to your fan motor.
If you want to be able to run your fan motor up to 24v then you will need a 30v transformer at a minimum 3amps rating. The DSE offerings won't do this for you.
Suggest you look at Jaycar. They have some that suit but you won't get the same multitap range as the DSE M1991 to vary the voltage that way.
As I indicated in a previous post, you may need to investigate the solid state ceiling fan controllers to achieve easy control of your motor voltage.
Maybe others can help you in this area.
All the best with it.

Alan

G'day gc,

I didn't actually use a store-bought fan controller mate, just knocked one up out of parts from my odds'n'ends bin. The "Standard" 300VA unit would be plenty big enough but maybe even too big . Some of these devices require a "Minimum Load" in order to keep functioning properly so trying to find a controller rated at 90-100VA would be more likely to work satisfactorily on a fan that you're running from maybe 15VA up to 30VA.

Just have a read of the info on the side of the product's box if possible, to see if it states that it must run at a specific minimum load and what that figure might be. If there's nothing stated then it might be quite OK to use on such a small load.

All the best mate ,
Mal.

P.S.
If you know a qualified person, another option is to use a "variable speed controller" from an old 240V AC Power Tool that could be removed and installed in a suitable Jiffy Box. You might be able to convert a local Sparky to CS by offering a bag'o'beans for the job..... It's been done before

Bill wrote on Apr 2^nd, 2008, 1:22am:

Good one Bill and handy to know.....

Cheers,
Mal.

greencardigan wrote on Apr 2^nd, 2008, 8:47am:


Should be ok, I'd think, although Mal may be the better person to answer this. I'd imagaine that part would be pretty expensive though. How much is it?

greencardigan wrote on Apr 2^nd, 2008, 8:47am:

G'day again gc,

Yep, these controllers would handle a popper element without much problem. In reality, they shouldn't be all that expensive but who knows in this day and age of 1000% mark-ups. Since they need to handle larger load currents, they will almost certainly have some kind of Heatsink(s) attached to the power device(s). Not a problem in itself but would imagine they will require more room to fit and an allowance for air circulation across the Heatsink(s).

See if Bunnings can get one in for you to have a look at, and then work out if it's going to be a practical device to use. All the best mate ,

Mal.

Cool. So what are you planning to use for the heater control? I can highly recommend the 2000W dimmer I got online from Quasar Electronics in the UK, which I mentioned earlier in this thread. It says it's a 'kit', but it actually comes as a fully assembled circuit board - no soldering required. Just needs to be mounted in a project box of some sort.