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Old 11-11-2019, 07:57 PM
mattlydon is offline
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Powersafes, Backfed voltage spikes, P.A.D, Booma pour smooth

I just read up on a number of threads regarding promodeller failures caused by the diodes in powersafe receivers with their brushless servos. Hitec includes a PAD device with THEIR brushless servos (although I only see them sold separately in Europe for some reason).

Hitec has a video showing surface ‘backwash’, for lack of a better term, in which the surface overshoots center, then returns. Plug in a PAD, and that issue goes away - impressive video.

I noted last night that the 5955’s driven by a powersafe on my Yak do the backwash dance - it hasnt hurt my servos, but it’s definitely there. I run life’s, so the voltage isn’t as high, but then the servos aren’t hv rated either

So this backfeeding ‘issue’ may be more prevalent than just on PM servos (and I understand they’ve been updated to handle the spikes better)

So my thoughts (questions just go like this...

Using a spike absorbing device or two seems like cheap insurance, as I DON’T want to give up powersafe functionality to run right off of battery.

Are PADs some complicated device, or a basic capacitor like the Booma Power Smooth?

I can see a cap supplying reserve current in a voltage sag situation, but will they absorb spikes?

Am I reading too much into it...shut up and fly?

I welcome your thoughts,

Matt
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Old 11-11-2019, 08:23 PM
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The spikes from a brushless motor stopping and reversing can be huge. The datalogger on my racing quad shows huge spikes- like 100v+ when you hammer the throttle closed quickly. Looks to me that this one of those areas you may not want to be on the cutting edge of servo technology until they get the bugs worked out and you dont need an external band aid to prevent releasing the smoke from the weak link part.
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Old 11-12-2019, 10:07 AM
Xpress.. is offline
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Quote:
Originally Posted by mattlydon View Post
I just read up on a number of threads regarding promodeller failures caused by the diodes in powersafe receivers with their brushless servos. Hitec includes a PAD device with THEIR brushless servos (although I only see them sold separately in Europe for some reason).

Hitec has a video showing surface ‘backwash’, for lack of a better term, in which the surface overshoots center, then returns. Plug in a PAD, and that issue goes away - impressive video.
This is only on systems that can't accept the backflow, for example a lot of rc car racers don't need it because their systems don't have battery sharing tech, or regulators.

Quote:
I noted last night that the 5955’s driven by a powersafe on my Yak do the backwash dance - it hasnt hurt my servos, but it’s definitely there. I run life’s, so the voltage isn’t as high, but then the servos aren’t hv rated either
That is another issues entirely, digital coreless servos do not exhibit the same characteristics.

Quote:
Are PADs some complicated device, or a basic capacitor like the Booma Power Smooth?
The Hitec PAD is an intelligent device that reads current/voltage spikes and filters them out. It is not a simple capacitor.

Quote:
Am I reading too much into it...shut up and fly?
YES!!!

Quote:
Originally Posted by 2walla View Post
The spikes from a brushless motor stopping and reversing can be huge. The datalogger on my racing quad shows huge spikes- like 100v+ when you hammer the throttle closed quickly. Looks to me that this one of those areas you may not want to be on the cutting edge of servo technology until they get the bugs worked out and you dont need an external band aid to prevent releasing the smoke from the weak link part.
Your racing quad is a totally different ordeal than a hobby grade brushless servo. There is no bugs with the Hitec brushless servos, nor is utilizing the PAD a "bandaid fix". By the way, there has never been a reported instance of a Hitec brushless servo smoking any component it is connected to because of the backfed current. I personally tested this on 2 airplanes full of Hitec 9381's, on a system that needed the PAD's to work correctly, for well over half an hour, and not once did any component smoke when not using the PAD's.
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Old 11-12-2019, 06:34 PM
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[QUOTE=mattlydon;2912579]I just read up on a number of threads regarding promodeller failures caused by Crappy servo design with their brushless servos. ...............................

Fixed it for you
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Old 11-13-2019, 10:12 AM
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[QUOTE=terryscustom;2912907]
Quote:
Originally Posted by mattlydon View Post
I just read up on a number of threads regarding promodeller failures caused by Crappy servo design with their brushless servos. ...............................

Fixed it for you
Not a fan of PM servos?
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Old 11-13-2019, 10:44 AM
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running promodeler servos in several airplane the 420 brushless, 470 brushless in my beast, decathlon, 110" yak, and my Futura... all with power safe RX's and they are flawless.. great servos and the issue has been resolved.
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Old 11-13-2019, 12:03 PM
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Don't want to spread rumors but 2 people I know personally have had brand new PM's go nuts on a ESC setup in the last month. I saw one of these setups in person.

Futaba, Savox and JR servos all worked fine on the same power system.

.... So still looks like they need to do work to be compatible with regulated power setups. I hope they sort it out because their offerings are a fantastic bargain otherwise.
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Old 11-13-2019, 06:08 PM
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I was looking at the brushless 345’s and 470’s for an upcoming project.
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