Forced Draft - MORE POWER

Discussion about all kinds of Mechanical and Electronic Smoker Controls
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alleyrat58
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Forced Draft - MORE POWER

Post by alleyrat58 » June 6th, 2012, 10:06 pm

Problem: BBQ Guru CyberQ states that it will only support up to two of their fans, but you believe you believe that you need more power than two of their fans will provide.

My Solution: Build an extraneous power supply to run the fans using a relay to control them.

First my disclaimer - if you do this wrong you can fry your BBQ Guru, your house, or yourself. I make no claim of warranty. Always unplug electrical devices before attempting to work on them. :explode2: Just saying.

In my power supply I overcomplicated this a bit more than I should have. I purchased 4 12VDC squirrel-cage PC blowers. These blowers put out 25 CFM and require 2 amps each. The Guru is only capable of about 1 amp at 12V so powering these directly from the Guru simply will not work. The main challenge with using DC blowers is that you need a large transformer, or you have to carry a battery. I was not going to rely on a battery, so I re-purposed a couple of ATX power supplies (PSU) from some old computers I had laying around. These are cheap (free if you have an old computer) and can output 300+ watts, more than enough to run the fans.

First thing I did was separate the the wire that I needed from the ones I didn't. I only need the yellow (+12V) and black (ground) wires.
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All ATX PSUs contain a switch that prevents the PSU from working if it is not plugged into the motherboard. I bypassed this by connecting the green 'ON' switch to a black ground wire. It's now ready to start generating current!
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I built a box and loaded two PSUs into it. I did this in case one dies on me in the middle of a cook. I bent up a piece of stainless to create the top of the box.
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I wired up both power supplies to four jacks that each fan will plug into. The four red lighted switches allow me to turn off/on each fan individually. The two black switches in the middle allow me to configure if I want the Guru to control the fans or just run constantly off the PSU. The second black switch allows me to switch between the two PSUs if one fails.
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The magic in all of this is the relay. A relay is a mechanical switch that is toggled on or off by energizing a coil which is isolated from the power supply it is connected to. So when the Guru clicks on, it send a +12v pulse which energizes the relay and switches the fans on. You can see the little black relays here, tucked in on their sides behind the PSU. I have two relays for two reasons: 1. They came in a pack of 3 so why not? 2. if one relay or the supporting circuitry fails I have a backup.
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One VERY important note when working with relays. You ALWAYS need to include in your circuitry a diode across the coil between power and ground. This is done so that when the power is removed from the coil in the relay, current cannot flow backwards to your power supply. The diode causes a forward bias and sends any stray voltages to ground, where they belong. I cannot get a pic of this, but I can help if others have questions.

This is a pretty good tutorial on how to setup a relay and the supporting circuitry. This tutorial is meant for folks using a micro-controller, but the principles are the same. Just remember this tuorial and circuitry is for +5V not +12V - you will fry it if you apply +12V to it. I know. :oopssign:
http://www.sparkfun.com/tutorials/119

One last note - when building your box, allow plenty of room for air to flow and cool the electronics. I have not had to add a fan to the box yet, but it was a consideration when we were building it.

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Here she is hooked up and running:
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Up next we are working on programming our own micro-controller to operate similar to the guru with what I think will be a better more responsive algorithm. I believe the Guru overreacts to often and is then slow to get back in line. I also want WiFi - LOL. I see Guru just came out with WiFi. Results on that as soon as we have a working proto-type.

:-B :jocomp: :jocomp2: :help:

I am sure I left something off of this post - let me know what else you might want to see from this little project.


Nothing I like more than to kick back with a Zima and a Virgina Slim reading 50 Shades of Grey with DCman (The Czar).

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Re: Forced Draft - MORE POWER

Post by PvilleComp » June 6th, 2012, 10:13 pm

Very Sweet FrankenQ.

I just tossed a boatload of old Power Supplies. Now I'm going to have to re-stock.



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Re: Forced Draft - MORE POWER

Post by alleyrat58 » June 6th, 2012, 10:15 pm

They're a dime a dozen - till you're looking for one - LOL. Stay away from the Compaq PSUs - I found some that aren't ATX compatible so the wiring is all screwed up.


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Re: Forced Draft - MORE POWER

Post by Frank_Cox » June 6th, 2012, 10:39 pm

Great tutorial! this will help a lot of people!

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Re: Forced Draft - MORE POWER

Post by PvilleComp » June 7th, 2012, 7:08 am

alleyrat58 wrote:They're a dime a dozen - till you're looking for one - LOL. Stay away from the Compaq PSUs - I found some that aren't ATX compatible so the wiring is all screwed up.
LOL Indeed they are - e-recycle company came by yesterday and hauled off 4 pallets of crap. When I came back to the shop later in the day there were already 3 more machines in the recycle room! ;)



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Re: Forced Draft - MORE POWER

Post by The Czar » June 7th, 2012, 7:16 am

:wtf: ..... :exp: ......


If you can't fix it by sheer force or cursing......then it can't be fixed.....


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Re: Forced Draft - MORE POWER

Post by Smokeone » June 7th, 2012, 2:09 pm

My brain hurts, now! :P I remember if I need one of these call AR!

That is a great post! :kewl: :points: Thanks Alleyrat!

I smell sticky glue!


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Re: Forced Draft - MORE POWER

Post by SoloQue » June 7th, 2012, 2:54 pm

:huh: :wtf: :exp:

I pick things up I put them down ... :biggrillin:

I pick things up I put them down ... :biggrillin:


I'm worried about plugging in the guru correctly, Lord help me if I have to factor in relays or transformers


If it can't be smoked .... try frying it. It that don't work, it's probably best just left alone

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Re: Forced Draft - MORE POWER

Post by Gizmo » June 11th, 2012, 7:00 am

Well done Ben! :kewl:
I promise: - You keep typing and I'll keep reading!...
THANKS!
:D

Done any experiments on splitting the airflow off one of the fans?


And on the eighth day God created barbecue …. because he DOES love us and he wants us to be happy. :D
Current smokers: Egor (trailered RF) and Easybake (tabletop pellet drive)

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Re: Forced Draft - MORE POWER

Post by alleyrat58 » June 11th, 2012, 7:16 am

I haven't messed with it - yet. That said, when we build a new controller our plan is to buy a large blower, like a furnace draft blower, that is capable of 200+ cfm and build a manifold to spilt the air across the fire. That is probably a year or so from seeing a prototype.


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Re: Forced Draft - MORE POWER

Post by Gizmo » June 11th, 2012, 12:02 pm

200 cfm!?!?

That's not a smoker - that's a FORGE... :-o


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Re: Forced Draft - MORE POWER

Post by alleyrat58 » June 11th, 2012, 12:39 pm

Rick wrote:200 cfm!?!?

That's not a smoker - that's a FORGE... :-o
Indeed, but I would be looking for a variable speed so that it could handle more or less based on the temp in the smoker. One of the main problems I have with the Guru is that it is on or off. So you are either blowing full CFM or nothing. In my observations it seems almost like the natural draft in the cooker takes time to recover when the pressure is relieved from the forced draft - so you flood your chamber with hot air, then the fan stops spinning, hot air works its way out the top, and then another blast. The blasts of air cause the temp to rise, the Guru slows the blasts causing the temp to fall and we start all over again. :wtf:

With variable speed there wouldn't be as dramatic changes to the pressure in the firebox. As the smoker heats up, the CFM drops until we hit the sweet spot then a constant pressure could be maintained until refueling the smoker is required at which time the controller would need to adjust. That is kind of where I am stuck with my early prototypes right now. My current prototypes would work great on a system that has a controlled feeder like a Stumps or pellet-pooper, but not so great on a system where you are opening the firebox door while you have food on the cooker.

#-o


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Re: Forced Draft - MORE POWER

Post by Smokeone » June 11th, 2012, 6:17 pm

I am intrigued (SP) Alleyrat. I want to see this bad boy come to life.


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Re: Forced Draft - MORE POWER

Post by Gizmo » June 11th, 2012, 7:44 pm

Have you tried a minion maze for briquettes?
I like what you're doing Ben - keep it up - you'll figure it out...


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Re: Forced Draft - MORE POWER

Post by alleyrat58 » June 11th, 2012, 9:46 pm

smokeone wrote:I am intrigued (SP) Alleyrat. I want to see this bad boy come to life.
All in good time. Just gotta work the bugs out. I also have to work around one of my buddies right now who is studying for the MCAT (test for entrance to medical school). He got a degree in computer engineering then decided he should go to med school and design medical implements for a living - so he's tied up a bit - and he knows everything about the circuitry and micro controller programming. Slow progress, also expensive...
Rick wrote:Have you tried a minion maze for briquettes?
I like what you're doing Ben - keep it up - you'll figure it out...
The minion maze is an idea. I am trying to work out a switching system that could be attached to the door of the firebox and door of the smoke chamber to cause the controller to react differently when one is opened vs. the other. Door to the smoker open I would want the fan to slow until the door is closed, then speed up a bit and settle back in the sweet spot. The firebox I'm just not so sure about. Might just have to add lit charcoal all the time. That minimizes the problems anyway...

Guru has a 'door sensor' in at least some of their models (if not all) but it just detects a drop in temp and shuts off the fan. I have two problems with that...
1. in a cabinet style build like mine, the probe is slow to pick up the drop. In most cases by the time it reacts I've already closed the door. Then it sits there for a few minutes until the temp starts to rise again and the process starts over. By this time my fire has started dying a bit and it takes a while for the guru to figure it out.
2. When the Guru detects the door open it cuts air to the firebox, but you still want good clean air for good clean combustion when the door is open, there is just no need for it to overreact to the temp drop and flood the firebox with air.
/rant


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Re: Forced Draft - MORE POWER

Post by Gizmo » June 11th, 2012, 9:52 pm

a magnetic door switch to a "pause" control would be simple enough.
I would think that whatever intake air leaks past the gate is enough to sustain combustion for the short time the door is open...


And on the eighth day God created barbecue …. because he DOES love us and he wants us to be happy. :D
Current smokers: Egor (trailered RF) and Easybake (tabletop pellet drive)

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