Incrementally move servo
#1
Thread Starter
Tech Rookie
Joined: Nov 2021
Posts: 6
- I am trying to use rc transmitter and receiver to remotely adjust the vent on my bbq smoker as I monitor the temperature from afar.
I have the AX-7s system tx/rec pistol grip. I have the SPT servo model SPT5435LV-180. 6v power converter arrives today.
I need to adjust the vent/servo frequently to open or close the vent on the smoker (2” travel) and have the vent/servo stay as adjusted! I’m using a lawnmower throttle cable from vent to servo!
How can I best accomplish my goal?
Obvious novice seeks advice!!
#2
your going to need a servo Id go with something that has a limited arc as in under 20 degrees of swing... build a housing to hold the servo pick a aluminum arm and connect a micro U bolt to hold lawnmower cable..maybe a lead end so you can dremel a slot to hold u bolt.you can use a high amount servo sweep but will have to make a swing arm to take up the extra amount of throw
#3
Tech Master
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Joined: Dec 2015
Posts: 1,418
From: San Jose CA
In the spirit of DIY, I will avoid the obvious question of - don't they make stuff for this? I get it, you have a cheap radio, and you want to try stuff 
Most transmitters are spring loaded and each function is designed to return to center when released. The exception would be a throttle channel on a airplane or helicopter radio. My approach to using what you have would be to use the steering wheel, disable the centering spring, and set the servo so that full left steering is vent closed, and full right is vent full open. Before you disable the spring, mark the top of the wheel, so you get a visual representation of the vent position.
Another possible option is to use the trim function, although I suspect you won't get enough throw.
Make sure the vent moves freely by hand in order to minimize load on the servo.
Good luck

Most transmitters are spring loaded and each function is designed to return to center when released. The exception would be a throttle channel on a airplane or helicopter radio. My approach to using what you have would be to use the steering wheel, disable the centering spring, and set the servo so that full left steering is vent closed, and full right is vent full open. Before you disable the spring, mark the top of the wheel, so you get a visual representation of the vent position.
Another possible option is to use the trim function, although I suspect you won't get enough throw.
Make sure the vent moves freely by hand in order to minimize load on the servo.
Good luck
#5
Joined: Mar 2011
Posts: 6,410
From: Austin,TX
I believe the 3rd channel on your radio is a flip switch and you would need a variable dial instead, something like this radio system here would let you use the 3rd channel incrementally adjust the air flow:
#7
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The transmitter is going to need to be powered on any time you want control of the servo on your smoker. If you plan on smoking for several hours you are going to burn through lots of AA batteries. I'd get another power supply/converter of the correct voltage and get rid of the batteries for the transmitter. You might also look into a servo
as you could eliminate the need for a transmitter or receiver, and all of the associated complications of getting everything to work together. You could probably mount the servo tester inside and extend the servo lead to connect it to your smoker. A fuze on both ends of the positive wire is probably a good idea if you go this route.


#8
Joined: Mar 2011
Posts: 6,410
From: Austin,TX
The transmitter is going to need to be powered on any time you want control of the servo on your smoker. If you plan on smoking for several hours you are going to burn through lots of AA batteries. I'd get another power supply/converter of the correct voltage and get rid of the batteries for the transmitter. You might also look into a servo tester as you could eliminate the need for a transmitter or receiver, and all of the associated complications of getting everything to work together. You could probably mount the servo tester inside and extend the servo lead to connect it to your smoker. A fuze on both ends of the positive wire is probably a good idea if you go this route.
#9
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#10
Thread Starter
Tech Rookie
Joined: Nov 2021
Posts: 6
If I understand the suggestions on using a servo tester…..I will have servo tester inside my house….run power from house to servo! Operate servo directly!
I currently monitor temperatures from the comfort of my sunroom. The smoker is 20 feet away. Won’t be a problem!
I hope I have this right!
thanks for the input from everyone!
I currently monitor temperatures from the comfort of my sunroom. The smoker is 20 feet away. Won’t be a problem!
I hope I have this right!
thanks for the input from everyone!
#11
Thread Starter
Tech Rookie
Joined: Nov 2021
Posts: 6
Thanks to all who posted suggestions! I believe the servo tester wired directly to the servo is my best solution! I had the “wireless” idea in my head and never considered this simple, and easily doable, solution! I’ll post when all is working! Thanks again
#13
Thread Starter
Tech Rookie
Joined: Nov 2021
Posts: 6
I’ve read that fusing the 33’ of servo extenders That I’m using to reach my smoker should be done! Videos I saw shows the fuse inserted in the ground wire and not the red wire! Which is correct or does it matter?
#14
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Last edited by waitwhat; 11-24-2021 at 07:30 PM.
#15
Tech Master
Joined: Jul 2018
Posts: 1,011
From: Florida
if you get a stepper motor its incremental by default. so then the question is how do you make it move? well i assume you are trying to control temperature. if you get an allen bradley micro810 you can pulse the stepper motor with the outputs. this will get the motor turning. then you get a thermistor to measure temperature and plug it into an analog input. write a few lines of code and you can have automatic temperature control.



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