Servo either doesn't move or runs continuously

B Frame

New member
I have a 4.3 HM with the Macro Damper using an SG90C servo. With the default settings of 1000us - 2000us, the servo runs continuously. I have tried various different settings in the Servo Pulse Duration with varying results. In all cases where there is any movement of the servo, it runs continuously, sometimes slower sometimes faster. Currently it is set at 1500us - 1800us. In Manual Mode this has the servo not moving until the fan % reaches 65% (% going up) and stops moving when it get to 45% going down. I just tried 1200us - 1800us. At the low percentages, it goes one direction, faster at 0% slowing down as the % increases, stopping completely at 30%. Then at the top end it starts in the opposite direct at about 85% and speeding up until it reaches 100%.

In manual mode the fan is responding correctly to the changes in %.

I am using an SG90 servo from Mouser: DFRobot Accessories TowerPro SG90C 360 Degree Micro Servo ; Mouser # 426-SER0043. This is the only SG90 servo I find in Mouser. Is this the wrong one? DFRobot's website says the neutral position is 1500us as the Wiki says in the Servo Mode.

Any suggestions would be appreciated?
 

B Frame

New member
I have tried that several times. Unfortunately, the servo either does not move at all or spins continuously in one direction or the other. In the paragraph above the Setting the Servo Endpoints topic discusses the servo jumping all over the place and suggests it "can be solved by adding a capacitor as close to the servo as possible. A 10uF-100uF/10V capacitor usually works well" This sounds like what I need, unfortunately I am an absolute newbie in electronics, so I am not sure what to order and exactly how to install it. I believe I saw something someplace that indicates that it connects to the power lead and the ground lead of the servo. If so, does it matter which side (+ or -) goes where? And some guidance on exactly what type of capacitor to order would be appreciated. Unfortunately, Mouser has many different types of capacitors, and I have no idea exactly what I am looking for. Thanks
 

Gary V

TVWBB Member
should have read your post a little closer. The capacitor does help eliminate the hunting that occurs with the servo. Not sure how you have wired the micro damper up, but on mine i do not use the connector, i hardwired everything. I did use the recommended cap and soldered it to the servo 5+ wire and ground. The other posibility is you got a bad servo. I have been using Vorpal servo`s and like the quality and they are very stabile. Go to Vorpal website and order their servo. Last thing is inside the micro damper space is very limited for making connections even when using the connector. Take your time and make sure you do not have connections shorting to each other and make sure fan blade in not being hung up with wires. When attaching the moving part of the damper to the servo, do not over tighten screw. Tighten enough to hold moving part to body. Make sure the moving part and body do not have any burrs which could cause drag. Also did you build the correct micro damper for the servo you bought. If servo does not fit properly in body, this can cause movement issues..
That`s all i got.
 

B Frame

New member
OK, so I am obviously not well versed in electronics. I purchased a servo that is designed to rotate 360 degrees, not 180 degrees. Once I replace it with the correct type of servo (9G SG90) everything worked just fine. Sorry for any confusion. It is great to have the whole thing working correctly now.

Next step is to get it mounted to my smoke followed immediately by a test run of the smoker to see how well the HM/MacroDamper works on my homemade offset smoker.
 

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