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Poppery II not "dimming"
meitzner
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Posted on 12/27/2013 7:36 AM
Hi all, I need some help. I picked up a Poppery II from Goodwill and it seems to work fine. I did the mods from Hiro/Jim to separate the heating and motor, and added a dimmer...but I did it all with parts laying around the house and it mostly works. But what doesnt work is the motor variable speed from the dimmer. I made two changes from the "plans" - I used an old laptop AC adapter that runs at 19.4V and 3.34A instead of the recommended Radio Shack 25.2V/2.0A transformer, and I used a rotary-style dimmer knob instead of the slider. It was cheap - $4.99, so I dont know if one or both of these deviations is causing my problem. What happens is that when I start to turn the knob and it "clicks" on, nothing happens. When I get about 1/4 turn, the motor/fan kicks on high, and then turning the knob higher does nothing. Turning it down does nothing until I hit the 1/4 point when it shuts down completely. Please help me figure out what to try next.

Thanks
 
allenb
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Posted on 12/27/2013 9:43 AM
Matt, when you get a moment, please post a little about yourself in member introductions.

On your popper issues, we'll need some information. AC or DC from the computer power pack? Is the poppery II fan AC or DC?

Another help would be a sketch of your wiring.

Welcome to HRO!

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
JackH
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Posted on 12/27/2013 10:36 AM
Those laptop power packs are usually DC voltage output. The Poppery II motor needs AC voltage (about 25VAC). The 25V Radio Shack transformer is AC output and will work.
 
Lawnmowerman
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Posted on 12/27/2013 11:21 AM
The popperyII motor is dc with diode bridge so it will run on ac or dc. Provided the polarity is correct for dc. Transformet shouldnt be the issue either. Sounds like the wiring to the dimmer. I think it needs to be in series with the load. I would check @ the light dimmer store. Or just buy a new one.
Bad coffee prevails when good coffee roasters stand by and do nothing.
 
Lawnmowerman
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Posted on 12/27/2013 11:31 AM
Oh wait a minute. The dimmer works on ac. Your transformer does need to be ac. It it is dc it will need to have the diodes removed.
Bad coffee prevails when good coffee roasters stand by and do nothing.
 
meitzner
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Posted on 12/28/2013 2:13 PM
http://3.bp.blogs...aticv7.jpg

this is the schematic and wiring diagram that I followed, only I used the laptop AC adapter in place of the 25.2V transformer. So, I have line AC voltage going into the dimmer, and then in series the output of the dimmer goes to the AC adapter. I figured that the dimmer would cut down the voltage and the AC adapter would just convert the variable/dimmed output to DC, which would be fine for the motor since it says "20.8VDC 1.78 A MAX".

I tried another dimmer today and same story. Actually, there is a point on the dimmer slider where the motor kicks on and then it runs at a constant speed until the slider is turned all the way down (even past the point where it initially kicked on). Not sure what's going on still. If the dimmer is cutting the voltage down at all, I would think I'd see at least some variability in the speed of the motor...but no dice. I guess it's off to Radio Shack to suck it up and buy the transformer.

Any ideas?
Edited by JackH on 12/28/2013 3:09 PM
 
JimH
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Posted on 12/29/2013 12:17 AM
Take a close look at your laptop power supply. If it says it is 19.4 volts regulated, then varying its input voltage isn't going to vary the output. Regulated supplies give the listed voltage until the input voltage goes too low, then they stop.

Also, the fans are usually running at 24 volts. In my experience, they give up the magic blue smoke around 32 volts. At 19.4 you will be running it a bit slow, and not really getting much loft for the beans. Biting the bullet to get a proper transformer really is a better solution, but you might also want to check around for a 24 volt unregulated power supply.
 
Lawnmowerman
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Posted on 12/29/2013 1:22 AM
I just reread post number one . I see what the problem is. Your laptop supply uses a switching regulator Im guessing. If that is the case then its a totally different power source. A switching supply regulates its voltage by switching a peak voltage on and off at the right rate to suppy the needed power for a laptop. The motor sees the peak voltage. Not the average voltage. A switching supply is the only kind of supply used for a laptop, in fact. So I concur with the last postB). You cant even convert them to straighr ac by bypassing all the internal circuitry, so you will definitely be best off with the specified transformer. Unless you h othe
Bad coffee prevails when good coffee roasters stand by and do nothing.
 
Lawnmowerman
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Posted on 12/29/2013 2:41 AM
Hi Jim I'd like to toss a question at you. Reguarding motor usage do you have any idea how much max current would be drawn by one of these motors? Could one use a lm 317 linear regularor? These are 1,5 amp max. Thank you in advance.
Bad coffee prevails when good coffee roasters stand by and do nothing.
 
JimH
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Posted on 12/29/2013 2:20 PM
Sorry, I only measured the voltage as I was destroying fans, I never measured the amperage or wattage. I'd check now but I switched to a 2 amp 110v AC fan a while back and have never looked back. Just as an uneducated guess, I would estimate that Poppery IIs use something like a 50 watt fan, so roughly 2 amps at 24 volts.

If someone has a stock, working Poppery II it would be easy to find out. Just put a Kill a Watt in line with the connections to the smaller heating element and fan. The heating element draws 150 watts, so the fan would be the remainder.
 
Lawnmowerman
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Posted on 12/29/2013 2:42 PM
Ok so anlm317 may not work. Thanks for the tip, Jim.
Bad coffee prevails when good coffee roasters stand by and do nothing.
 
JackH
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Posted on 12/29/2013 3:32 PM

Quote

Lawnmowerman wrote:

you will definitely be best off with the specified transformer.


This is pretty much what I wrote in post #3.

I hope he did not get too confused with all the second guessing and conflicting information.
 
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