Servo Testing


 
1000-2000 should be safe, though the servo's are all calibrated different so what I would do is set those numbers and plug in the servo and send it to one extreme, then unplug the servo right away and make sure it has some room left to move in that direction. Then do the same for the other direction. This way you know you are not pegging the servo on one side or the other. With the roto damper you should have a little bit of travel left at both 0% and 100% after it is calibrated.
 
The alignment still confuses me, and frustrates me because of the high potential for damage.

This is what seems easier and safer to me...

TowerPro MG90S range specs (I have two variations from two different sources):

Spec A (this confirms the default)
Close : 1000 µs
Middle: 1500 µs
Open : 2000 µs

Spec B (I will use this as open/close limits)
Close : 400 µs
Middle: 1500 µs
Open : 2400 µs

Find middle:
1) With the server disconnected from the arm and fan housing, power the servo with Spec A.
2) Set fan at 50% power. This will be the servo's middle.
3) Connect the servo to the arm and fan housing with the air duct open at 50%.

Find Closed:
1) Fan power at 0%.
2) Fan duct opening should be closed.
3) If fan duct not closed, decrease the closed pulse duration from 1000 µs, but no less than 400 µs.

Find Open:
1) Fan power at 100%.
2) Fan duct opening should be open.
3) If fan duct not open, increase the open pulse duration from 2000 µs, but no more than 2400 µs.
 
I noticed the Servo Configuration wiki has enabled "Invert Output".
This would mean that 950 is the max, and 1750 is the min? This seems wrong.

servo-config.png
 
You should use the setting open at max only. It will be easier to see the mid max numbers. Every servo I have had has a setting of around 900 to about 2250 or so, to allow the air inlet to go from closed to open.

Set the blower to manual mode and set the upper limit to about 2200-2300 and turn the blower on. The servo should turn to the number given. If the air inlet in not open, unscrew the servo a bit and turn it by hand until its open and retighten. Turn the blower off, and turn it back on and readjust if needed, until its at maximum opening. After you get the upper number, start at 1000 or so on the smaller number and with the blower off, adjust the setting until the servo closes the air inlet completely, that will be your low number.
 
Yah, it flips the max and min as you describe. So for instance, 900 will be going more toward open and 1800 would be going more toward closed.
 
UPDATE:
Received servo replacements. The nice thing about having multiple parts is the opportunity to do comparisons and troubleshooting. I noticed two things between the first and the replacement: 1) Difference in opacity. 2) There appears to be a small fracture in the plastic around the shaft. Difficult to discern without comparing side-by-side.

Notes:
a) The servo wiring sheath needed to be stripped. Punching down the wiring into the jack won't make a good contact.
b) I keep the servo barrel attached to the duct loose so there's less friction/work for the servo, and so the servo doesn't make a small buzzing noise.
b) The servo was acting like a dying bug and jumping around a lot. The ethernet cable might be to blame; I replaced the cable and the problem went away, but I was doing a lot of other troubleshooting that may have resolved the problem.

For the configuration and alignment, this is what I did:

1) Set servo pulse duration 1000 - 2000, inverted.
2) With fan at 0%, attach the servo to the arm/fan housing so the housing duct is closed.
3) When you adjust the fan to 5%, you may notice the duct is not open. Adjust the pulse duration.
4) When you adjust the fan to 0%, you may notice the duct is not closed. Adjust the pulse duration.

At this point you'll have the pulse duration properly set and aligned for the closed position.

5) Adjust the fan to 100%.
6) You may notice the duct is not completely open, or too open. Adjust the pulse duration.
 
JakeBrown said:
Notes:
a) The servo wiring sheath needed to be stripped. Punching down the wiring into the jack won't make a good contact.
Click to expand...

Yeah, using a wired cat5 jack, can be a pain sometimes, I would take a box knife blade and push the wires down and wiggle the knife blade a bit until the servo or blower would turn on. Or if you have a newer Rotodamper you can get an adapter board and all the connections will be through a wire header.
 
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