BudDryer v2.0

[sunnycoaststoner]

nice post al b.

[Al B. Fuct]

Thanks JJ & SCS.

 

BDv2.0 works OK for the time being, but when I get the parts in, I'll finish the job and post some stuff about it.

 

If I'm feelin' motivated, I might even buy a new, better quality container and do it all up real pretty & professional, once the tech issues r/ temp control are sorted.

 

I'd like to get the design nailed down to the point where anyone can replicate it and have a complete parts shopping list, but there's some variables like the type and size of heatsink, variations in fan performance, whether one has use thermally conductive grease on the resistors and so on.

 

However, with 680 ohm resistors and a thermostat installed, most of those variations should be able to be compensated for by adjusting the tstat or tweaking the current with a dimmer. It should be able to put 252W max into the 4 resistors and thus into the heatsink- and be dialled downward from there. I am a tick hesitant to run 50W or more continuously through these 25W resistors, but when bolted to the fan-cooled heatsink, they should be OK. BDv1.0 ran for 7 years with 25W resistors being pushed to 50W.

 

BDv1.0 could put about 100W into the heatsink and maintained 29C OK even when intake air was 10C. I designed 2.0 with 4 resistors running at 26W each to get the usual operating current closer to the component's free-air rating to ensure longevity yet still put about 100W into the sink, but I didn't count on the new fan arrangement being able to remove heat from the heatsink so much more effectively. Need more wattses to keep up with the fanses.

[Al B. Fuct]

K, just put in an order for six of the 680 ohm 25W resistors. Figure I may as well have a couple extra if 4 doesn't warm it up enough. The limit is the 500W dimmer, which is now no longer optional in the revised ckt.

 

To drop no more than 500W across the dimmer, at 208V (the max V the dimmer seems to want to pass), it needs to look into a load no lower than 86 ohms. Four 680 ohm resistors in parallel is 170 ohms. Six in parallel is 113.33 ohms. Eight in parallel would be 85 ohms. We know that at 208V, each 680 will drop 63 watts, meaning eight of them could put 504W into the heatsink.

 

However, we're making a bud dryer, not a chicken roaster, so we'll see how we go with 6.

[Al B. Fuct]

The new schematic looks like this, with 6x 680 ohm resistors.

 

Edited July 2, 2007 by Al B. Fuct

[Al B. Fuct]

Resistors have come in (bless you RS Components).

 

Thermostat has come in from Jaycar. Tore it apart and located the thermistor; real easy to relocate it inside the bud drying chamber.

 

It's manicuring time so I can't screw with it any more at the mo, perhaps early next week.

[Anfo]

I am going to be starting a grow in a few weeks and I think i'll have to whip myself up one of these!

[Pam]

I swear you used to work for NASA, Al!

But I have to agree with the need for curing...I am old enough to remember the brick shit we used to get..(used to pack the trunk of my "63 Galaxie convertable with the crap and run it cross state) I agree that the leaf made the smoke harsh, but the shit wasn't cured at all unless you count the garbage bags I carried it in.

I once got like a half pound wet by accident and had to dry it out and THAT stuff tasted so much better, ppl were hanging outside my bedroom window for more! They didn't even realize that it was the same crappy mex dirt... {I remember one of my friends had a 5 gal fish tank half full of seeds from that crap we used to get! I made myself sick one night eating them...}

So I also have to believe that rewetting does do something.

Thanx for the memories!

[Al B. Fuct]

I swear you used to work for NASA, Al!

 

Wotchoo mean 'used to'?

 

Finally got around to refrobbing the heater unit. Now has 6x 680 ohm resistors being driven with a HD 500W light dimmer. Each resistor is rated 25W which means I should be able to run them at 130V (see Ohm's Law calc). However, at 130v, one of the resistors started smoking and 2 more were noticeably overheating! Not good! Backed it down to 100v which drops 14.7W across each R, but I can't understand why I can't drop 25W across an aluminum body resistor bolted (with thermal compound!) to a fan-cooled aluminum heatsink, without smoking it. Would like to have an oscilloscope to see what this light dimmer is doing to my waveform. Wonder if I have some bad resistors.

 

At 100V, 88.2W is being dropped into the heatsink, but that's not enough to bring the heater's air temp to 29C if the ambient intake air is below about 16.5C.

 

Seems that my fans are a little too good at cooling my apparently efficient heatsink... so... I'm going to add a motor speed controller which will handle both fans. Slowing the airflow should bring the air temp up to the 29C point for speediest drying without THC degradation; doesn't need anywhere near the amount of air these Sunon 120mm axials can move- and would be much quieter. Off to the hdwe store...

[Nameless]

Hi there, and thanks for the unreal design AI!

 

Just wondering, is there an update to your design since last post?

 

Did you get the problems that you had sorted out?

 

I would love to make one of these things, since smell and drying time is also an issue for me

[pszarwufl]

I have a question

 

could you just buy one of those heating, oscillating fans, connect it to a thermostat and tell it to heat until it reaches 29c inside your box ??