Stepper Motor with Screw Drive for Horizontal Sliding Damper...Possible?


 
S

SCotton

New member
Excited to be starting my first build!

I was wondering if anyone has worked with a flat sliding damper before? My horizontal offset smoker has a very wide slide damper on the firebox, and I was hoping to use it in a way where I did not have to add another air intake, as it is in the only good position for the air intake (driving heat/smoke across the body). By covering it with a food service stainless steel tray, I can get away with just a few easily seal-able bolt holes and mate the blower into the food tray.

To control the damper, Im hoping to approach this with a stepper motor and a screw drive/sled like those you see on 3d printers. The damper has a perfect attachment point to link up to the sled already, so again, less modification of the actual smoker. I believe those motors are 4 wire that control two phases to turn the motor forward and reverse. So, based on what I have read up on with the HM servo control having a single value controlling the position of the servo, I would probably have to build out an intermediary circuit to interpret that single value into signals to the two phases of the stepper motor. If it comes down to it, Im sure I can take a long rod and do it with a servo, just wanted to explore this option as well and see if anyone had done it already or if it was just an idea that was incompatible with the way the software is currently set up.

Thanks all!
 
Check out this Primo Pure Servo control thread.

Stepper motors require the ability to calibrate a zero position before use, unlike a servo. There are screw drive and linear actuator servos, but they are quite pricey and would probably require you to power them separately.
 
It's a wide body dyna-glo horizontal offset smoker. Ive had great success with it so far manually (outside of the thin metal and battling some of the colder days we have here), and the damper is already pretty good, opening up a good amount of air-flow right below the coal bed, so I dont really want to use another location.

Thanks for the link Steve_M, that's my backup plan, to just use a servo to drag it one way and the other. Just thought the screw drive would be a bit more solid of a connection. I picked up a Nema-17 and a screw with matching supports/sled/motor adaptor. Im not too worried about having to build out a secondary circuit, but I was just wondering if anyone had done something like this previously. I am a web developer by day, so re-use and recycle is in my blood!

If I was having to power it separately, as well as having to adapt for the 4 wire interface, It shouldn't be too hard to at that point add a button onto the new board to allow a zero to be set when I bring the system up before use. All inputs captured from the HM connection could be made relative from that point. Or maybe there is a way to test resistance and do a self-set of a zero point on startup
 
I'm not familiar with your exact smoker, but if I read what you are saying correctly it has flat damper that opens in a linear fashion, from a small slit to a rectangle? If that is the case I would just fashion a rectangle metal insert, lift the grill damper wide open then seat it down on your insert. Then put a pipe of some sort into your insert and connect whatever kind of damper/fan rig you prefer....
...the only reason I would go through the trouble to actually move your grills damper would be if I wanted to run the rig with the damper only, it doesn't seem to make sense to put a dog dish/food tray over your damper and motorise your damper too... If you're capping off your grills damper with a food tray might as well just mount whatever damper/fan you prefer to the food tray and leave your grills damper wide open underneath it... Personally I would prob go with the metal insert plate, as it would look neater and be easier to put in/out... unless it will be too close to the fire and transmit too much heat to the plastic damper, if that's the case the food tray would help alleviate that.
 
Some pics to help

Here are some pics to help you visualize what I am trying to do. As you can see, the slide mechanism takes up the majority of the bottom of the fire box, so I think I need to pursue utilizing that as the software controlled damper. I would like to not have to go the 3d printed route with the damper on the blower if at all possible. Are there benefits to that route that I am not aware of?

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OK, thanks for the pics, make things much more clear. I guess the first question would be how easily does that damper move? If it moves very easily you may be able to swing the automation, if it is stiff it may be more trouble than it's worth. With all those individual openings you really have no choice but to cover over them with a pan or something similar.
The advantage of the 3D printed damper route is there are many tested and reliable options to choose from, any of which will mount to your pan very easily. They are all designed to work with a servo which the HM has native support for, so no custom engineering, endstops etc required.
 
Me personally I would just cut a 1 inch hole and close the your vent and use the hole to connect a RD25 damper(a bigger version the rotordamper).
 
Yeah, I was thinking about using the same servo so nothing much changes there, we would just be pulling/pushing the rod connected to the existing damper. It moves pretty freely, and weve already tested out backing out those screws a fraction to loosen it up even more, so Im not too concerned about that. If I continue down this path, am I going to have issues with the larger openings? I see most of the damper/blower solutions people go with rely on a smaller PVC tubing, but isn't 5-10 CFM the same regardless of how focused it is?

Thanks again for all your input guys, really appreciate it!
 
I assume your grill vent has larger openings because it needs a fair amount of air flow, so it shouldn't be a problem. In theory 6.7CFM is 6.7CFM, but if it is concentrated it can blow in a stream in the right or wrong direction, I would think you are good to spread out your air flow across that vent the way the grill is designed. Whether you leave it wide open and use an external damper or actually move the vent would be a matter of debate and preference, I'm kinda with John, I would go with an external damper.
Do you have any idea how much air flow you need? I think you noted a problem holding temps on cold days? Are you sure 6.7CFM is enough?
If you already have the stock HM blower what I would do is rig the blower to your pan and forget about the servo for now, then run a cook and see how well you achieve your temp. If the blower runs in the high range the whole cook you may need a larger blower, and may not need servo control at all if the blower opening restricts air flow enough to tamp down the temperature. This would at least give you an idea where you need to be for air flow to achieve your temp and how much restriction you need to tamp down overshoot before you go too far in one direction or the other.
 
You can get servos that are rather strong. I think most people here are just used to what is currently being used on dampers. If you check out HobbyKing you can get some servos that have pretty good torque ratings for not so expensive. Shoot me an email (at microdamper@gmail.com), I think we easily brainstorm something together seems like a fun little project.
 
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A servo uses a standard DC motor that turns a bunch of gears that turn a potentiameter. If you disconnect the pot, the servo will turn forever in what ever direction the voltage tells it to turn in. I made a small "direct drive' tank out of two servos by doing that. Perhaps you could remove the connection to the pot in a larger servo and then use the servo to drive a pinion and have a rack and pinion setup? Just thinking out loud.
 
SCotton said:
Excited to be starting my first build!

I was wondering if anyone has worked with a flat sliding damper before? My horizontal offset smoker has a very wide slide damper on the firebox, and I was hoping to use it in a way where I did not have to add another air intake, as it is in the only good position for the air intake (driving heat/smoke across the body). By covering it with a food service stainless steel tray, I can get away with just a few easily seal-able bolt holes and mate the blower into the food tray.

To control the damper, Im hoping to approach this with a stepper motor and a screw drive/sled like those you see on 3d printers. The damper has a perfect attachment point to link up to the sled already, so again, less modification of the actual smoker. I believe those motors are 4 wire that control two phases to turn the motor forward and reverse. So, based on what I have read up on with the HM servo control having a single value controlling the position of the servo, I would probably have to build out an intermediary circuit to interpret that single value into signals to the two phases of the stepper motor. If it comes down to it, Im sure I can take a long rod and do it with a servo, just wanted to explore this option as well and see if anyone had done it already or if it was just an idea that was incompatible with the way the software is currently set up.

Thanks all!
Click to expand...

Hey all, long time no see. SCotton, this is something I'm very interested in working on. Over the last year I built a 250 gallon reverse flow offset and am missing my automated control. I've had crappy results using fans and can't replicate the tight control I have on it just by sitting next to it and manually adjusting the large steel sliding door that I have. I want to have the HM do this for me but I think I'm going to need a motor with a decent amount of torque to drive an attached lead screw. I have a stepper that would fit the bill. The problem is that I my circuits knowledge is extremely limited so I have to piece things together using the few tricks I have. My initial thought was to use an arduino based solution to read the HM fan output and then covert that into a command to pass onto a stepper driver. I know it's crude but I think it will work. Any other suggestions?
 
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