INTRODUCING: the "Roto Damper"


 
RalphTrimble said:
I've been back and forth, had jitter, and zero jitter depending on the combination of the above. I had initially not been fond of the move and rest firmware because my MG90s would sometimes twitch and stick open and the HM would put the servo to rest in the open position letting my fire go out of control. Frustrated with this I changed to a Hextronik HXT900 servo which never jittered or twitched a bit, working great for a year (powered on 24/7). Recently I flashed the latest firmware which I think keeps the servo energized and my servo was dead a few days later. Coincidence? Probably... I ordered another HXT900 and am installing it tonight, guess we'll see if it takes another year to kill this one! BTw, the HXT servo doesn't fit the std RD, the shoulder is too shallow, needs a custom part.
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What settings do you have for the HXT900? I'm trying to calibrate mine but cant get anywhere. Its closed or 360 partially open. Can't dial it in yet :(
 
I think I'm having a similar issue as the most recent. I've had my RD3 for a while now and done more than a dozen cooks with it:

Here is a video of the problem:
https://youtu.be/kHkGqa8LVeo

Also links to my settings and most recent burn:
https://ibb.co/eMVTun
https://ibb.co/hLkuZn

So despite the jitter the thing is running rock solid. Although at the very end of that burn the screw came off of the servo and that whole piece fell off.

I did read the other threads and even Ralphs old servo booster mod.

I am running about 50ft of ethernet cable to the RD3 so not sure if that is an issue.

This behavior is new but I have been tweaking my start up and servo settings to hone in on good settings for my rig.

If the solution is capacitor (47uF 10V polarized) .. can someone point me to a link as I can handle the install but get lost when looking at the various parts when I search that.
 
I was wondering if there's a way to test a servo out. I just built mine over the past couple of days and ordered a 4 pack of "RioRand MG90S" from amazon. When it was all delivered, it had "Tower Pro" instead of "RioRand" on the sticker on the servo. I was pretty excited because people seem to say that TowerPro is the better of the servos. So I hooked them all up and my first one moved a blip and then never moved again. OK, onto the second. It moved forward but the reverse had some jitter. Tried the third one and same thing. Tried the last one and it actually worked both forward and reverse without jitter. It also doesn't sound as whiny as the other two servo's did.

I saw the capacitor addition and maybe that's part of the problem. I didn't have any extras laying around so I couldn't test it with a capacitor. I'm not sure if the first one is just dead or what.

I was wondering if there's a way to test a servo other than hooking it up to a heatermeter.
 
You can buy manual servo controllers, but using the heatermeter is going to be the easiest route. All of these micro servos are bulk chinese cheap servos, so don't expect too much from a 4 pack of servos that cost less than 1 real, legit servo :)

What you can do is try and see if the servo operates better within a certain range. The servo should have about 180 degrees of movement, but you only need about 90 degrees of movement for the damper to be fully open or closed. Operating the servo within a specific 90 degrees of the 180 degrees of movement might yield a "sweet spot".
 
Mike, what are your servo pulse duration settings in your HM config? As an example, my settings are 680 to 2200, though every servo is a bit different. Did you calibrate your servo? Sometimes when the servo is not calibrated it can try to push the servo beyond its limit, where it will just sit there and twitch and beg you for mercy! Here is a link that explains how to calibrate the servo if you have not done that.

https://tvwbb.com/showthread.php?46...p=697522&highlight=Calibrate+servo#post697522

Also, if the servo fits too tight in the RD3, if you have to force it in there, it can bind and fail to move. Try operating the servo on its own to eliminate binding as a potential cause of the issue. You can easily widen out the servo opening in the RD3 to eliminate binding if that is an issue.
 
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RalphTrimble said:
Mike, what are your servo pulse duration settings in your HM config? As an example, my settings are 680 to 2200, though every servo is a bit different. Did you calibrate your servo? Sometimes when the servo is not calibrated it can try to push the servo beyond its limit, where it will just sit there and twitch and beg you for mercy! Here is a link that explains how to calibrate the servo if you have not done that.

https://tvwbb.com/showthread.php?46...p=697522&highlight=Calibrate+servo#post697522

Also, if the servo fits too tight in the RD3, if you have to force it in there, it can bind and fail to move. Try operating the servo on its own to eliminate binding as a potential cause of the issue. You can easily widen out the servo opening in the RD3 to eliminate binding if that is an issue.
Click to expand...

Thanks for the information! I just installed heatermeter and printed out the RD3 so I really don't know what I'm doing just yet. I'll have to run through the calibration because all I did was slap it in to see what happened.

I'm well aware that the quality of the servo's are really just a guessing game and many people say order a bunch of them to find one that works. I don't have experience with servo's so I didn't know how to get them going. I thought there would be some sort of calibration process or something to set the limits. Referencing that post above will help me out tremendously as I can now make a few adjustments.

Thank you again for the information! I really think that if I run through the calibration and maybe add that one capacitor, I'll be good.
 
Yep, servo's can be a crap shoot, specially the Tower Pro MG90s'. I have been experimenting with the hextronik hxt900 servo lately have and been pretty happy with it, I have only tried two so far, but they both have worked well. They do NOT fit the standard RD3 body, but I made a special servo disc that the hextronik fits into.

I think you will probably find your SPD settings are wacked, after you calibrate I think things will fall in line. Don't over tighten the screw on the servo, that can pull the RD3 parts together too tight and make the servo bind. In fact, when you assemble and calibrate the RD3 just press fit and leave off the screw. After you're calibrated then install the screw, just snug, then make sure the valve still opens like it did before you installed the screw....
 
The other question I had was related to heat and the RD3. I printed the RD3 in black ABS plastic, which is supposed to have a higher melting point than PLA. I connected the RD3 to my WSM with a 1" EMT compression fitting. I then drilled a 1" hole in my WSM near one of the vent holes to attach everything, then, closed the vents up. Unfortunately, the ABS started melting and the RD3 almost fell off the WSM before I caught it. I ended up adding a few screws around it to hold it in place, but I'm thinking there's a better solution.

Should I add a little nipple to the EMT so that the RD3 doesn't sit as close as it does?
 
I think most people using WSM are going with the dog dish method, which gives you some offset. I would suggest using one of the longer connectors to set the plastic back a bit, the temp will drop off a lot with just a little offset. Also try to make your metal pipe extend into the fire bowl as little as possible to minimize the heat transfer.
 
RalphTrimble said:
I think most people using WSM are going with the dog dish method, which gives you some offset. I would suggest using one of the longer connectors to set the plastic back a bit, the temp will drop off a lot with just a little offset. Also try to make your metal pipe extend into the fire bowl as little as possible to minimize the heat transfer.
Click to expand...

I figured the dog dish wouldn't give a tight fit and maybe some of the air would leak out from the fan, which is why I decided to drill a hole and use a 1" EMT compression fitting. The part that extends into the smoker maybe sticks in a quarter inch or so...

I ended up going to home depot tonight and got a 1" coupling and a 90* elbow. I didn't feel like buying 10' of 1" EMT so I just went with the elbow. I may trim a small part of the elbow off and give that a try. As you said, I think that just a little bit sticking out will drop the temperature tremendously. We'll see what happens!!
 
Yah, a little offset should be enough to cool things down. I've found that the Home Depot usually carries a few versions of each size EMT connectors, some really short and others a couple inches long. If you went with the short one you could try the longer one instead, or the elbow should work too...
 
FWIW, on my leaky Oklahoma Joe clone, I started with a 12" vanity sink tailpiece, and tested it with an IR thermometer. I figured I could probably go all the way down to a 4" or so tailpiece connected to a dog bowl over the air inlet. The firebox itself was off the scale of the thermometer.
 
Hi is there a way to buy this set up? I understand the creator wants to keep it open source which is awesome but i don't have a 3d printer
 
I'm having trouble getting the servo working. I searched but didn't find any answers - though the thread is pretty long.

I'm running the servo off the heatermeter 4.2 - with a straight through ethernet cable connected to the RJ Jack.

Servo wires on the RJ jack: Brown on pin 4, Red on pin 3, Orange on pin 6. I set the Servo Pulse Duration to 70, 2100, fully open at 100% and the inverted box is NOT checked.

With fan control on manual, and adjusting the speed - the servo gets hot after a little while. If the servo moves, it shakes and moves in a haphazard manner. After a while, it seems to go back to a default position and stops moving and seems to be locked at one extreme.

What am I doing wrong?
 
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Thanks for that info Ralph. I guess I mis-read the instructions on post# 514 of this thread. I saw that as 70, not 700.

I changed it to 700-2100. It still shakes about and seems to "reset" back to a home point, however.

Here's a video of me going from 0 to 100% on the fan using manual fan control.

If I connect the Micro Damper, that servo moves smoothly, as it always has.


And a screenshot of my current settings:
servosettings.JPG
 
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Wait a second!!!
I tried a different Ethernet cable and it's working smoothly now.
Odd - both were store-bought cables.
Thanks for listening.
 
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