Multiple dampers with one HM


 

Darren L

TVWBB Member
Is there any reason that 3 dampers cannot be wired in parallel to one HM? These would all be on the same smoker moving the same amount. What I'm considering is a damper only control of a WSM. If current is an issue I can let the HM control a solid state relay and source the power to the dampers straight from the supply. Using 3 RD3s without fans on the WSM would allow for a more natural control of the coals. The other option would be to have one RD3 connected to a hose that goes to three dog bowls. It seems in theory that the damper eliminates the need for the fan unless the fuel supply gets low. I usually have more of a need to restrict the oxygen than I do blow more in.

Thanks
 

Steve_M

TVWBB Guru
I don't see any technical limitations to this. The servos can consume a pretty good chunk of power, so a dedicated 5v power supply for just the servos would probably be a good idea, but you can share the servo signal wire across all 3 servers.
 

Bryan Mayland

TVWBB Hall of Fame
Generally the fan is there now to overcome the constriction we put in place with our mechanisms and the extra closing you need to do on the existing vents to prevent the fire from going hog wild through natural convection. There is no technical reason the servo pulses can't be sent out to multiple dampers in parallel, but as Steve has pointed out, they do pull a ton of power when then need to move so they should run on their own dedicated power supply (as motors don't care as much about brown outs as CPUs do).

EDIT: That is, don't use the +5V/GND from the heatermeter output, just use the servo pulse output and wire it to servos with their own 5V/GND supplies.
 
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RalphTrimble

TVWBB Diamond Member
The RD25 has a much bigger opening in the valve, you could use one of those rather than 3 RD3's. If you feel you need an even bigger opening let me know, I can blow it up larger for you. Shoot me an email and I'd be glad to help you out.
 

Darren L

TVWBB Member
Thanks for the replies. I'll mess around with isolating the servo after I get everything working correctly the way its meant to. I just want to try a damper only setup on the WSM because it doesn't look like its been tried before. At some point I'm going to try controlling a wood burning stove with a fresh air intake, but that may be too off topic for this forum. Will be a sweet project though:)
 

RalphTrimble

TVWBB Diamond Member
Have you tried damper only with just one damper? I missed that you were talking about a WSM, the bottleneck will end up to be your vent opening, hence the need to use all three vents...
I could make a damper half only from the RD3 for you (x3), though I am not sure if three servo's will move on the one HM signal, or if they did calibration might be tough because each servo is different.
 

Darren L

TVWBB Member
I haven't tried anything yet. Purely theoretical since you are printing my first order of RD3s as I type. I was interested in three dampers to get the same burn pattern of the coals as manual operation of the vents. I'm also not against cutting larger vent openings. If this works, a single HM could poll a smoker every five minutes, make any adjustments and move on to the next smoker. The polling function would probably be done on a separate device, like a virtual selector switch. I'm just brainstorming here, so take it for what it's worth. I play with data acquisition and process control for a living, so I'm like a kid in a candy store with the RD3 and HM.
 

Benjamin Thibault

TVWBB Member
I really don't see why you would need all 3 dampers to be controlled. While not quite as big as WSM I do just fine controlling my PBC with just a servo damper from the HeaterMeter. I use my custom designed FlatDamper which is a door opening a 40x40mm square. Port direct to the side of the PBC. This has worked very well for me with it maintaining sub 20% opening to keep the pit +- 3* for the majority of the cook. Obviously it opens more towards the end of the fuel.

If your single damper doesn't have enough flow without a fan You could just set your other 2 dampers to what they need to hold slightly below your normal set temperature with the 3rd one closed off all the way. This way when you add the controled damper from the HeaterMeter it's only needing to do what is required to maintain and go above that.
 

RalphTrimble

TVWBB Diamond Member
You make a good point Ben, you could crack open two vents to allow a little less flow than required and let the damper on the third control the last bit of air flow. That said, sometimes people thing out of the box and want to experiment, the idea of a damper on all three vents wouldn't be the wackiest thing I have read on TVWBB...
 

WBegg

TVWBB Pro
I'm printing a few more adapt-a-dampers now. Once I get 3 made up, I'll give your idea a try to 1) see how much power they will draw 2) see how in sync they are and 3) post a video to view. I like the idea. I will need to find a 3-1 splitter for the cable.

Also, I see your from East Tennessee. I lived in Knoxville 21 years, now living and working in Montana.
 
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Darren L

TVWBB Member
Small world. I live just West on Knoxville and work in Oak Ridge. Did you move to Montana to be a dental floss tycoon? (Old Frank Zappa song.) One of my goals with this experiment is to eliminate the need for the blower and the constant attention from the HM. The HM could check in periodically to make adjustments. This could lead to a battery powered HM. I'm thinking a battery pack that attaches to the back of the HM case. The battery case would be the same dimensions as the HM case. My other thought is controlling or monitoring a wood burning stove. Would be nice to check on the stove remotely just by logging in, or have the stove snuffed out in an over fire condition. Both the smoker and the stove are controlled by dampers, so it's not much of a stretch.
 

MHutchins

New member
If your end game is battery powered, a single servo setup will likely require fewer Amp-Hrs of current than three servos working in parallel.

Mike
 

 

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