Should the case on a MKS DS95i be connected to GND?

[kalleh]

Not really a Warp question but I know a lot of people run this servo on the Warp so...:

Had a surprise yesterday when my balance connector started smoking when resting against the frame of my Warp.

I was a little surprised since I didn't expect battery GND to be connected to the frame, but after some troubleshooting it turns out my DS95i case is connected to battery negative through the servo GND lead (I removed the servo cable from the frame, it's not worn through anywhere).

Is this expected? I'm not an expert in electrical engineering, but having the only chassis-connected ground be a servo that's connected through an FBL unit which is then connected to a BEC doesn't seem proper.

[Luigi_tuga]

Funny stuff!
Just came from checking and all my MKS servos are exactly the way you describe.

[RudeRebel]

Originally Posted by kalleh

Not really a Warp question but I know a lot of people run this servo on the Warp so...:

Had a surprise yesterday when my balance connector started smoking when resting against the frame of my Warp.

I was a little surprised since I didn't expect battery GND to be connected to the frame, but after some troubleshooting it turns out my DS95i case is connected to battery negative through the servo GND lead (I removed the servo cable from the frame, it's not worn through anywhere).

Is this expected? I'm not an expert in electrical engineering, but having the only chassis-connected ground be a servo that's connected through an FBL unit which is then connected to a BEC doesn't seem proper.

Metal bodies connected to GND is normal. Now if your servo body (or body of any other electronics on your heli) or frame is connected to positive, that's when you get worried.

By the way, if you haven't noticed, your FBL, BEC and Servos all connect to ech other via servo connector, and all your servo bodies are attached to the frame which is conductive. This puts all your components on a level GND field (which is a good thing), but also means current applied to any component body, or frame can affect everything. This is normal. I'd actually be more worried that your balance connector has the possibility to transfer current.

[kalleh]

Originally Posted by RudeRebel

Metal bodies connected to GND is normal. Now if your servo body (or body of any other electronics on your heli) or frame is connected to positive, that's when you get worried.

By the way, if you haven't noticed, your FBL, BEC and Servos all connect to ech other via servo connector, and all your servo bodies are attached to the frame which is conductive. This puts all your components on a level GND field (which is a good thing), but also means current applied to any component body, or frame can affect everything. This is normal. I'd actually be more worried that your balance connector has the possibility to transfer current.

The "problem" in this case is that my there servos are plastic bodied DS92A+, which means that the *only* ground point to the chassis is the tail servo, which from my limited knowledge creates a non-ideal ground loop.

Why are you surprised that my balance connector could transfer current? One of the positive contact points where resting on the canopy support.

[RudeRebel]

GND is a problem if it is floating, i.e. Something other than zero, or your system is generating static, which the belt system can generate. Yes, your tail servo typically takes the load. But you shouldn't be avoiding GND, but rather you could be avoiding shorts to GND including static.

This includes avoiding cutting servo wire coating on frame edges, ensuring balance connectors can't short to anything, GNDing your tail boom (some use silicone on the belt, but I prefer GNDing ), and general care/maintenance of the heli. Your motor is also grounded to the frame but it will handle current better than a tail servo, but even it can fry if the current is large enough. With the motor connected to ground, essentially the rest of the heli pod and electronics are connected to GND. This brings focus back to the tail which is on an island of its own, with a belt which is generating static and transferring the static back to the pod.

This is my long winded way of saying, avoid shorts and static, gravitate towards GND.

In any case, yes, it is normal for your DS95i to be connected to GND, and yes, it will suffer when you have current shorted to GND, and receivers start to brown out, with static carrying enough charge to cause a brown out.