Heat Shrink and Heat Sinks (two questions)

[TheAeronut]

Okay folks, two questions...

First, why are almost all ESCs wrapped with a thermal insulator (heat shrink)? Wouldn't you get a slightly higher heat dissipation without it? Would it be OK to remove the heat shrink if you are right on the edge and running hot?

Another question. Certainly the BECs on almost any ESCs have limited heat dissipation capacity - thus limited load capacity depending upon the input voltage. Would it help (be worth the effort) to attach a small IC type heat sink to the BEC regulator chip? You could use a tiny dab of conductive epoxy, or even CA (yes, I know - it's a insulator, but should produce a very thind bond).

??

Thanks;
J.P.

[Fred Bronk]

I have cut the heatshrink away from the FET's for better heat disapation. Seems to work well.

Schulze does the same with a heatsink installed. But I would only use transfer paste or glue.

[KillerWatt]

I've also wondered about the "unique" shrink wrap arrangement seemingly exclusive in the "electronic power dissipation device world" to e-flite pack Esc-Bec's......... Any electronic device capable of generating operationing function limiting ammounts of expected wasted heat should certainly have a thermally uninhibited air-flow layout design, esp equipped with the add weight of a heat-sink...... The shrink wrap is certainly not helping the heat dissipating problem.......... kw

[jiri]

Question for Shawn:

If I cut a small piece of the shrinking tube on PH10 and place
some heat sink with the past on the FET,

do I lose the quarantee???

Would you recommend this when e.g using PH10 with
four micro servos on 3x Kokams????

Thanks,
Jiri

[Shawn Palmer]

Jiri - 4 servos and 3s is a ways out of specs - either with or without heat sinks.

I don't see why a heatsink addition would void the warranty - you'll be ok there if you want to try it.

Shawn

[Quacker]

Jiri: The linear regulator(s) used for the BEC are not only thermally limited but instantly current limited. This is the internal nature of the chip. Thus, even a very short demand for excessive current can overload the regulator and cause the output voltage to droop quite a bit. Micro servos have a large current surge when commanded to move. My HS-50 measured easily over an amp. With 4 servos starting to move at the same time, the current adds to a very high peak that can depress the voltage quite a bit. During the droop, the BES sees the current overload at increased internal voltage drop--meaning additional heating. If you keep slamming the servos back and forth, the additional heat could be excessive.

Best,
Q

[TheAeronut]

OK, I posted my questions here because most of the ESCs that I have are Castle Creations products - including my new Phoenix 25 and my very new (I just got a couple days ago) Phoenix 10m. I didn't think to mention that in my original post. Anyway...

What is Castle's OFFICIAL (OK, maybe UNofficial) position on removing the heat shrink cover? I still haven't seen any response as to why that heat shrink insulator is being used in the first place.

J.P.

[feathermerchant]

I have been flying 2 airplanes with 4 servos and PH controllers on 3S LiPo no probs but I make sure to have plenty of air flow.
Have wondered about heat sinking also. In school, many semiconductor devices could handle much more load if sinked.

[Quacker]

If I were Pat, I'd bite the dissipation bullet and put on heatshrink to insure that the circuit could not short out on anything. Naturally, this reduces the heat dissipation capability. The regulators and other hot parts dump heat dominantly through the leads. On the regulators, the center lead (which has a tab of metal under the part that can be seen exiting at the top edge as well) has the most heat conduction capability. Putting a heatsink on the plastic body helps a little, but not nearly as much as making thermal contact with the tab, which at present is dumping heat mostly to the circuit board. Good airflow (removing the heatshrink) is your best and easiest path to improvement. But Pat may not like the number of failed units he gets back from accidental shorting if he endorses removing the skin. Let's see what he says. Meanwhile, don't forget that even without heat considerations, the regulators have internal current limits and are only going to pass so much current before limiting occures.

Q

[jiri]

Originally posted by Shawn Palmer
Jiri - 4 servos and 3s is a ways out of specs - either with or without heat sinks.


Does this also hold for the new PH10? I have heart that
the additional FET was added mainly for Hornet CP users
which need to run four servos? Nevertheless, the manual
on your web-page does not say a word about the additional
FET?

So my question is: "is it also out of spec. to use the new PH10
on 3s for four HS-50 servos in Hornet helicopter?"

Thanks,
Jiri

[Dave Hederich]

I tend to think of the heat shrink covering on an ESC as a light protective covering to help prevent damage. I've often thought of taking a pin or needle and poking a bunch of small holes in the shrink wrap to help it breathe. Then again, I trust someone like Patrick to engineer his ESCs so that they do not require customization to function properly.

[Shawn Palmer]

The shrink is essentially short protection.

Also correctly surmised, is that the board itself, and the leads do the majority of the heat dissipation work.

Jiri - 3s and 4 HS50's is indeed out of spec, but widely and successfully used as a common set-up for the hornet. You would get into problems only if you experience binding in linkages, or experiment w/different brands of servos (none better than Hitec).

Shawn