Gaui ESC built in SBEC

[g-bru]

Quick question fellas, what voltage are you running your Gaui ESC BEC?

I was running at 5.25V when I had Align DS610's on my flybar setup. Since my crash I have replaced them with Turnigy BLS950's and as I am now FBL want to go up to 6V for maximum torque. The BEC is rated at 6V so I imagine it can deliver?

G




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[terrabit]

The 610's should deliver planty of torque at either voltage however, they will pull less amps at 6v than 5.25v. My inclination is that the BEC would run more efficiently at 6v based solely on the fact that 6v is closer to the pack voltage than 5.25v. My only rationale for keeping 5.25 is the tail servo. I've run BLS251's at 6v for more than a year but that is not within Futaba's recommended spec. Also, I know nothing of the Gaui's ESC. I would like to be certain that it maintains a constant voltage before I push my $130 tail servo to it's threshold.

[g-bru]

Thanks dude!

Running a Align DS650 on the tail which is 6V capable. Had a fly today no drama's except a vibe which is going to be posted in another thread.

G.

[Al Austria]

Originally Posted by terrabit

The 610's should deliver planty of torque at either voltage however, they will pull less amps at 6v than 5.25v

The servos will be pulling MORE amps on 6V than 5.25V. At higher voltages, servo speed and torque will increase thus, the onset load will also increase accordingly. It is not like an HV power system where you can regulate the load by gearing for a particular RPM.

[terrabit]

Correct me if I'm wrong but, I believe that is only true if your flying demands more torque - in effect, if you load the servos up more. If the same amount of "work" is done, less amps will be required at 6v than 5.25v. It takes one watt to move one kg one meter in one second. Amps * Volts = Watts. Thoretically, the same load at a higher voltage would require less amps. At any rate, we aren't talking about much. The difference should be quite minimal.

[Al Austria]

Originally Posted by terrabit

If the same amount of "work" is done, less amps will be required at 6v than 5.25v. It takes one watt to move one kg one meter in one second. Amps * Volts = Watts. Thoretically, the same load at a higher voltage would require less amps.

The amount of work is essentially the same, however, the amount of power derived is not. The thing you must consider is that when you increase a servo's speed and torque(which additionally increases servo speed under load), you are decreasing the amount of TIME it takes the servo to execute a command. Now in physics, power is defined as work over time.

To decrease the amount of time it takes for a servo to displace its respective control surface say, X degrees, the servo's power output must INCREASE. Naturally, in order to increase a servo's power output, you need to increase its power input(more watts/voltage AND amperage).

Now if you're just hovering the difference could be deemed as negligible, but all bets are off if you are doing any kind of 3D aerobatics.

[torana74]

100% with Allan on this. Will strain the bec more on 6v for the exact reasons mentioned.
The DS610's are known to be hungry and get even thirstier on higher voltages.
G, the 950's combined with your 650 SHOULD be well under the 3amp mark.

There are others running the built in bec with 451's,251 with FBL and i haven't heard of any blackouts etc. Did hear of dropouts with FBL and 610's though.
I personally am running a 850mah Life receiver pack so really can't comment from personal experience

Hope that helps some

Vas

[terrabit]

I follow the logic but I'd need to see some inflight data to support it. I'm not saying you're wrong. I'm just not ready to say you're right either. I just took a physics class, we covered these exact priciples. I'm certain there's a formula by which the difference can be calculated. Let's see, the difference in torque should only come into play after the stall force at the lower voltage is exceeded.

Let's just say it's a 3A load.

5.25V * 3A = 15.75W
6V * 3A = 18W

18W/15.25W = increase of 14.28% output without increasing amperage. The difference in speed by my calculation should be about .0125 seconds to 60 degrees. .08/.0925 = 13.51% decrease in time to 60 degrees. 14.28% - 13.51% = .77% net lower consumption. I know that's over simplified. We could collect some data, make some charts, calculate a margin of error and see whether enough of the data falls within two standard deviations to prove convincingly one way or the other. Na, I don't care enough about it to try that hard.

Whatever, it's all good!

[Al Austria]

Interesting calculations. Don't forget that our servos do not operate at 100% efficiency.

Here is a simple comparison. Say you want to decrease the amount of time it takes for an electric powered helicopter to complete 2000 revolutions at the head, or in other words, increase its headspeed. You could do this by either increasing the throttle pulse-width input and thereby increasing the duty cycle of the ESC, or by getting a larger pinion. In either case, your amperage(load) will go up, period. This is no different for our servos. That said, it is IMPOSSIBLE for the load to remain consistent, assuming you allow the servos to operate at the higher speed afforded with the increased voltage.

Theory aside, it doesn't take a highly controlled testing environment to see this. Empirical experience will show that increasing servo voltage will increase your average mAh consumption per flight 99.9% of the time. The other .1%, like I said, would only occur if you were hovering with the precision of an F3C pilot.

[terrabit]

mAh consumption can increase at the same bec amperage. I am not an engineer and it's pretty clear to me that you aren't either. The initial question was whether it would be harder on the esc to run the bec at 5.25 or 6v. I'll concede that the extra .75v could make the esc's life harder. I'd still like to see some real numbers. I'm funny like that.

[g-bru]

Vas, thanks bud, running at 6V with no issues.

Terra & Al thanks guys, I am no rocket scientist either, lets just agree that 6V is fine, simples.

[Al Austria]

Originally Posted by terrabit

mAh consumption can increase at the same bec amperage. I am not an engineer and it's pretty clear to me that you aren't either. The initial question was whether it would be harder on the esc to run the bec at 5.25 or 6v. I'll concede that the extra .75v could make the esc's life harder. I'd still like to see some real numbers. I'm funny like that.

You're right, I'm not a certified engineer, but I am an ME student. That said, these concepts are not beyond a high school level math or physics class. My whole query is that your statement "The 610's should deliver planty of torque at either voltage however, they will pull less amps at 6v than 5.25v" is not only incorrect, but misleading.

[terrabit]

Well then, thank you for correcting me. It is my intention to help others here, not mislead them.

By the way, I'm a third year business student at UW currently but I have taken some college level physics and I just completed the calculus series.

[marcosp]

Uuhh, everyone throwing shiny badges at each other. Cool down! Has anyone either a young impetuous student or an older serene mister, it doesn't really matter, get an amp meter and measure this? Someone with a friend of a friend employed in some servo manufacturer's lab? Empirical evidence is so practical sometimes...

[terrabit]

Yeah, my ego may have gotten the best of me. You know, it's funny. I bet if Al and I ever met on the field or elsewhere we'd get along famously. I tend to like strong willed, opinionated people, and I get the sense that he is.

I do have an amp meter. But I think I'm too lazy to do any testing. I'd rather just ask someone. I occasionally fly with a guy who has a double masters from MIT (an actual rocket scientist). Maybe he'd know, maybe not. I don't suppose it matters all that much. I haven't read any posts that state bec voltage settings as a reason for loss of control. Though, to be fair, I may not be looking in the right places for that either.

[Al Austria]

Originally Posted by marcosp

Empirical evidence is so practical sometimes...

I base EVERYTHING I advise on my own empirical experience, and I use theory as a means to help understand that experience. If anyone is offended by this, I apologize.

[marcosp]

I doubt anyone was offended. I was just trying to find if someone had done any tests or had some analysis done already. I heard too that HV servos end drawing more amps even though they work at higher voltage. Quite the opposite to motors and LiPos. I believe it is more related to holding power than to speed. Under extreme load the higher voltage implies stronger torque and therefore higher amp peaks to keep position. Besides this, the math you were analyzing holds its logic. Regular calculations apply until you stall the servo. Now this IS pure speculation!!!! hahaha.