Blue Sky Stepper Damper thread - Breakout from RaspberryPi + LinkMeter blue sky


 
Received my servos today. Bought 2 just in case I destroy one.

I went with the MG90S Metal Geared Micro Tower Pro.

First basic servo question - How will I be able to determine the centre position of the servo prior to putting on the control arm attachment? If it's connected to the HM, will the HM set it to centre/0 ?
 
You can attache the control arm, rotate it manually clockwise to the limit, then counter clockwise to the limit, and guess the middle.

dave
Steve_M said:
Received my servos today. Bought 2 just in case I destroy one.

I went with the MG90S Metal Geared Micro Tower Pro.

First basic servo question - How will I be able to determine the centre position of the servo prior to putting on the control arm attachment? If it's connected to the HM, will the HM set it to centre/0 ?
Click to expand...
 
If you plug it in without a pit probe, HeaterMeter will set the servo to the 0 position. It is helpful to have the configuration page open at this point to be able to adjust the zero position if the default is too low. At that point I use the menus on the device to go to manual mode, jack it up to 100%, and adjust that value from the configuration page.

I did this with the arm not attached but the servo mounted, then attached the arm to set the damper in the right position. Finally I tweaked the servo delays from the configuration to get it just right.
 
Bryan, Do I recall you saying you changed something with the servo wiring so that it has a regular ground now to reduce the total number of wires to operate the servo and fan? I am wiring in a CAT5 jack to my HM case so I can run the servo and fan from one wire, since the CAT5 plug will take a phone cable as well I want to choose very carefully what wires I put where on the connector, so I can use a phone cable for fan only operation if I want....
 
I am testing the concept with the lmremote boards I ordered. I just got the parts today but the footprint that was in eagle is (no surprise) totally wrong on every dimension. I can't tell you which pins are going to be which until the part fits and the concept works.

It is actually the fan that is being changed, which currently is 12v and not-ground, it may be ground and not-12v on future versions.
 
What kind of servo arm to damper arm ratios are you guys using? With the servo being able to move 180 degrees but the damper only needing to move 90 degrees to be wide open, is there a "sweet spot" ratio? Is 100 degrees ideal to match up with the 0-100% blower output? Is 135 degrees better, giving a 1.5:1 ratio? I would assume that the further we can move the servo to achieve the 90 degrees on the damper, the better resolution and control we'll have.
 
I have the range of my servo damper set to go from closed to almost 90 degrees, probably about 85. I don't push it all the way open cause it could possibly close the other direction (travel 180 degrees) rather than return to the "home" position. In the HM config my numbers are 500 - 1500 for fully open to fully closed (500), so I am running it at 500 - 1450 to make sure the damper always returns to the "home" position. I didn't arrive at this by a very scientific method, I just looked up the Pulse Width Range for my stepper and experimented with numbers from there....
 
Right, but by moving the linkage arm on the servo horn to a position closer to the servo gear and leaving the linkage in the same position on the damper, you can move the servo at a much greater range while the damper still moves more than 85-90 degrees.
 
I think the sweet spot is probably the 1:1 mapping simply because of the complexity. Having 100 different vent positions is a lot and the system is going to be constantly moving around by at least a few percent anyway. The more likely issue isn't the resolution of the damper but the quality of the computed output value. If you can get it nailed down to the point it is bouncing between 2 different output percents, like 15%-16%, then your temperature is changing probably less than 0.3F which is the resolution of the probes at 225F. Can't get any better than that.
 
I know it's kind of specific to a limited number of smokers, but has anyone tried using the servo to open/close the sliding door of a BGE? I know normally it takes a lot of force to slide this door, but if something similar could be accomplished, it might be the easier solution to construct for us guys that don't have 3d printers.
 
I've played with the idea and even gone so far as to try to rig up a CDROM's eject stepper motor to the slidey panel. Like you say, the panel takes quite a bit of force to move so the motor wasn't able to move it. A larger servo might have a chance of moving it but the range of travel would be pretty low unless you had a large servo arm. The torque to drive that would be even greater.

I also had a hard time imagining how to affix it in a removable manner. I thought something could grab the handle bit and then somehow clip onto the nest to push off of. I'm not very mechanically inclined though so you may have better success than I did.
 
Has anyone thought of making a square valve? Rather than changing the square opening on the fan round to fit the pvc pipe. Why not keep it square, and use 2" square tubing. The opening on my fan fits nicely into 2" square tubing with some wiggle room, and would be alot easier to install on my pit as opposed round pvc. Not to mention a higher melting point.

D Peart said:
Would a 2" piece of PVC work better?

It is easy to draw one up. You take the inner diameter of whatever PVC pipe you want to use, make a disc 1/8" thick with that diameter. Put a hole through it, I put two, then trim it with a sphere to get rounded edges.

I can draw up a 2" one if there is interest.

On my UDS I get to 325F with the 1.5" all the way open, which was hot enough. I run 20-30% open for 225.

dave
Click to expand...
 
Just to show how much having the blower in affects the airflow, my damper has a removable fan so I set the fan to "Only at Max" and the average output was about 65%. Once I removed the blower (leaving just the damper), the output drops to about 25%.
 
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