Alternative popper mod suggestions

[Dimal]

Re: Alternative popper mod suggestions

Very cool indeed mate.... 8-)

That controller looks a bit stranded sitting up on top like that

Mal.

[emckissock]

Re: Alternative popper mod suggestions

Second picture of the special box o tricks.
It is a repurposed customised metal casing (originally contained shortbread).

Well spotted mal

[Dimal]

Re: Alternative popper mod suggestions

Is that a Biscuit Tin Who? :P

Mal.

[emckissock]

Re: Alternative popper mod suggestions

ITS ALIVE!!

Finslly got it all working last night. Cutting off he fan circuit was easy with the dremel. Wired up so the popper is separate to the control box. Popper now has power lead for heater and seprate fly lead for fan ac.
Control box has a standard ac power out for heater and spade connector for ac low voltage to fan. Control is by two triac power controllers from dead vacuum cleaners. Transformer from an old stereo amp. All components scavenged. Only cost was for a potentiometer to replace one that died.

First roast 160g malawi nyika, 16 min 30sec to first crack. Pulled at 22min just before 2nd crack. Will take a couple of roasts to learn how best to control, but first test is encouraging and the fan speed control certainly helps with larger batch size.

[emckissock]

Re: Alternative popper mod suggestions

Another short break and more progress.

This definitely comes under the category of dont try this at home..
The only power cable I could find was a two core, so it was rubber gloves, safety goggles and switch on from a safe distance, but I now have variable ac power of 0 to 28v available for the fan, once I scavenge a three core power cable and earth up the metal casing.

Next step is to hook up to the motor. Looks like cutting the tracks on the pcb will work (see marked lines on photo) to separate the rectifier from the internal ac supply.

Before I do that though, Ill run one quick roast with no mods as a baseline, and because Im almost out of beans.

[emckissock]

Re: Alternative popper mod suggestions

I do have a couple of spare bta triacs, just that I have a handy circuit board ready to go with a btb16 already in place (riveted onto the heat sink). Why mica insulation? Would that just be for heat? If so, hopefully not an issue - was going to mount the circuit board on rubber pads.

Interestingly  this board has only two pins on the triac connected, middle pin has been clipped off. Given that it came out of a 1200 watt vacuum and worked fine for controlling the popper before,  Ive not bothered checking how it works, though I probably should for my own education.
Edit: I think I may understand how it works with two pins only.
Probably using the live heatsink as part of the circuit.
Will have a look later

[Dimal]

Re: Alternative popper mod suggestions

Pity you couldnt grab two BTA16 Triacs.... You wouldnt have to worry about the (mica) insulation requirement of the BTB16 then.....

Should work really well in this application though

http://tinyurl.com/6avfmms

Mal.

[emckissock]

Re: Alternative popper mod suggestions

For now it will be 28v with option of going 33v if necessary.

Thanks to a client cancellation, I got an hour tonight to start on this. Have a suitable box for the transformer and controllers. I currently plan on triac power control for both transformer and heat with fan on all the time and heater switchable. One of the triac controllers is bta16 and will use the metal case as heatsink, the other its btb16 and will be isolated fom case and fingers.
Hopefully I got that the right way round, but will double check everything in due course.

Im not sure how much power the triacs actually dissipate and whether I should fan cool the casing, or if small heatsinks are sufficient.

[Dimal]

Re: Alternative popper mod suggestions

I agree...

Most of the motors Ive looked at over the years have been rated at 24V-- and given the losses youll get through the bridge, it should work out fine. Talk about a Frankenpopper, eh... ;D

Mal.

[Bill]

Re: Alternative popper mod suggestions

any thoughts on what voltage to use? I have a choice of 16.5V, 18V, 28V, 33V or 56V.  Im thinking of going 28V and avoid running full blast.

Yep, Id run 28V. 18V will run the fan much slower than standard. I used 30V in a couple of different ones with no problems (thats 30V AC connected to the rectifier on the fan - the DC voltage that actually gets to the fan is somewhat lower than that).

[emckissock]

Re: Alternative popper mod suggestions

Well my lightly modded popper died last week

Took it apart today and tested without the triac power control - the popper was still fine, which is a good thing. Closer investigation showed that one of the solder pads on the pot mounting had come away from the PCB track. So now I need to source a new 220K Ohm pot.

Since everything is apart anyway, it is time to install fan speed control as I recently picked up an old stereo amp which had a 135W multi tap transformer that ought to provide enough power for the fan - any thoughts on what voltage to use? I have a choice of 16.5V, 18V, 28V, 33V or 56V. Im thinking of going 28V and avoid running full blast.

As a comparison Ill take a sound recording of the fan running normally before the mod so I can tell when it is going beyond that level. I also know it can only successfully agitate up to 100g green beans which should be a handy data point.

Will update here when mods done.

[emckissock]

Re: Alternative popper mod suggestions

Sounds like you may already know how to overcome this incorrect supply issue but just in case you end up keeping this controller, there is a simple mod to allow it to drive the SSR. You need to ensure that the Input requirements for the SSR are met and not exceeded of course....

Hadnt even thought about that, but yes it is obvious now you mention it. I had considered a much simpler fix - use the internal relay to drive a small DC plug pack that then drives an SSR, not at all elegant, but dead simple and would save opening up a PID that might still be requested back (though it has been months now so it is highly unlikely).

[Dimal]

Re: Alternative popper mod suggestions

I clearly specified one that handles an SSR, but they still sent me the wrong one with an internal relay - fixed the problem quickly though and I still have the incorrect relay even though I tried to get them to take it back.
Another issue with the mechanical relay PIDs is that they are often only rated up to 3A (or 720W at 240V).

Sounds like you may already know how to overcome this incorrect supply issue but just in case you end up keeping this controller, there is a simple mod to allow it to drive the SSR. You need to ensure that the Input requirements for the SSR are met and not exceeded of course....

Remove the cover from the controller and locate the +ve feed to the existing Output Relay Coil. Being very careful and with an appropriate DMM, measure the supply voltage to this relay when it is operated. Knowing this information, you can now scale the output voltage to suit the SSR via the use of a Voltage Divider that can be accommodated within the controller case. If you want to ensure absolute isolation of the Output Voltage, very cheap Opto-Couplers are easily acquired and could be inserted between the Relay +ve and Ground. The Output from the Opto-Coupler can then be used to drive the SSR.

Most likely though, the Relay supply is already isolated in this way and the need for an Opto-Coupler is unnecessary. Never hurts to have more than one iron in the fire, as they say...

Cheers mate,
Mal.

[emckissock]

Re: Alternative popper mod suggestions

Since the weather has improved somewhat here in Melbourne and I finished work early, that gave me the chance to sneak into the garage and play with my big knob (see above for picture).

I did a small roast of 95g of Gambella Sundried full power to first crack at 3:40 (unusually fast for my popper), then down to 800W for a couple mins, back to 900W until 8min 30, then 1050W until I think I heard a snap of second crack at 9min 30 and pulled the roast - very pale CS6/7 so may have misheard. Unfortunately my spare thermocouple was in use for another task so dont know about temps

I have to say Im pleasantly surprised as I was worried that lower fan speed would mean the beans were in contact with the hot metal more than they should be and it might not provide the control I wanted.
Definitely warrants further testing with a temp sensor installed to keep a gradual ramp up of bean mass temp 1st to 2nd crack.

[emckissock]

Re: Alternative popper mod suggestions

Who me?, I like your power control setup. A big knob like that would give you plenty of room to mark preferred power levels.

Actually, I hadnt thought of that but yes that is a good idea.
I just thought that since I have one, it would be a shame not to put it to good use.