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Old Jun 02, 2007, 01:40 PM
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Futaba Gy401/9254 combo - Do I need a Voltage Regulator?

My Trex 600 comes with a 5.1 v regulator designed to use between my digital servo & gyro (for most setups) I bought the 401/9254 combo boxed together and it does not mention any voltage regulator required per the Trex instructions. Is it needed with this combo or can the 9254 handle the straight 5.8 volts?
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Old Jun 02, 2007, 02:19 PM
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Anybody??
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Old Jun 02, 2007, 02:28 PM
Foam's Law
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Yes, use the reg.
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Old Jun 02, 2007, 02:39 PM
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My only question is why is it not mentioned anywhere in the manual. It even had a drawing of the 401 connected directly to the 9254. Since nearly every receiver puts out the same voltage, one would assume that a drop down is not necessary - at least with this specific combination.

Is it possible that when the 401 dip switch is moved to 'DS' that the voltage is stepped down internally?
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Old Jun 02, 2007, 03:27 PM
A man with too many toys
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Quote:
Originally Posted by QuietRiot

Is it possible that when the 401 dip switch is moved to 'DS' that the voltage is stepped down internally?
NO




If you look at Futaba’s specs for the S9254 servo it says 4.8v and no higher. 5.8v is way over the limit and will dramatically shorten the servo life.

Most helicopter flyers use a separate 5.0v regulator (UBEC) for everything.

http://www.gpmd.com/cgi-bin/wgpinf100p?&I=FUTM0224



RC
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Old Jun 02, 2007, 04:00 PM
Foam's Law
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It is all down to the spec of the servo connected to the gyro, for instance the 9650 digital that a lot use for a 450 tail is 6V compatible. The 925* series of servos however do all state 4.8V max.

Kev
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Old Jun 02, 2007, 04:17 PM
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If the 9254 is a 4.8 volt servo, how much can it actually take before shortening it's life?
I did a voltage check with and without the Align regulator and there is surprising little difference:
Without the regulator, my voltage shows 5.87 right from the receiver
With the regulator, it reads 5.58
Is this enough to even make a difference? And why does it read so high when Align specs it at 5.1 volts?
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Old Jun 02, 2007, 05:32 PM
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Mine too... maybe Align has sent out several defective regulators. I'm thinking of making my own - any thoughts out there on doing this?
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Old Jun 02, 2007, 06:10 PM
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no you dont need it -- 5.1 volts is fine more that 5.4

use the stepdown for safety
http://www.readyheli.com/K10333A_5_1..._p/k10333a.htm
or the duralite version

or get a

arizona from fromeco -- Duralite- MPI -- linear regulator





this image might help


http://www.runryder.com/fastphoto/31...x_1en-9972.jpg





for all the DIY


DIY 6v -> 5.3V TR Stepdown

Goto ratshack and get a pack of 3a silicon diodes. Either of these part #'s will work:




276-1141 <-- I used this one
276-1144
276-1143
247-1661

The actual diode part number is 1n540x series diodes, encase you wanted to order from digikey or mouser.com. But it's cheaper to get it from ratshack because of additional shipping costs.

Get a short servo extension, and cut the red wire in the middle. Then solder and heatshrink the diode inline with the red wire. With diodes voltage flows only one direction, from the anode to the cathode (white stripe on diode). So be sure to align it correctly, or you won't get any juice flowing to the servo.



Because of the way a diode works they induce a voltage drop across the line under load, and it's about 0.7v. Under no-load you will generally see no voltage drop, or a quite small one < 0.2v. This is what steps down the 6v to ~5.35v which is safe for the 9253/4 TR servos.

You have two options for placement of the stepdown, between the rx and the gyro, or between the gyro and the TR servo. I chose to put the stepdown between the gyro and TR because I wanted a consistent voltage to the gyro. In theory the other way might cause cause calibration problems. Also the 401 is fine with a regulated 6v, which was another reason I chose to do it this way.
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Old Jun 02, 2007, 06:11 PM
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Need what?
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Old Jun 02, 2007, 07:27 PM
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I haven't seen anyone come right out and say - you need it because the Align BEC outputs a voltage that is too high for the Futaba 9254. the graphics in adres.c's post indicates it though.

It's an Align setup item that's why your Futaba directions don't comment on it. If it's reading high - that may be because you don't have a load on it. I'd put a servo on it and turn on the radio to see what kind of voltage under load it produces.
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Old Jun 03, 2007, 12:31 AM
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Hmmm, what about using a 5.1 volt Zener Diode rather than a Rectifier Diode. Zeners act as more of an actual regulator by design...though I noticed Align uses a 2amp 50v Rectifier Diode. Very simple circuit btw.

Not sure why folks even buy the $15 in-line regulators anyway when you can make your own with a $1.50 part. Besides the cost, too many plugs/harnesses is never a good thing anyway. Even if you have an Align (or other) regulator, it's best to desolder the diode and place inline into the existing servo or gyro wiring...just my two bits. -QR
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Old Jun 03, 2007, 02:42 PM
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Sounds like a great idea - like you said, the fewer the plugs the better - esp. on the critical tail servo (one less connection to work itself loose). Radio Shack only had the 3amp 50v Rectifier Diode, so I'm going with that one....
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Old Jun 04, 2007, 12:40 AM
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here's my .02...i bought one of these and wondered about the 5.6v output to the cyclic servos (fut9252 in my case)...
http://www.advantagehobby.com/produc...5&cat=0&page=1
so i researched a futaba forum, and found the following:

Hi Serafim,

The maximum regulated voltage should not exceed around 5.5 to 5.7Volts. The amount of torque and speed will increase approximately 10% at the peak of the batteries voltage.

I hope you find this information helpful. You can also reach our Futaba support team at 217-398-8970 opt 2, or via fax at 217-398-7721.

Sincerely,
Krysta Hunt
Product Development & Support Specialist
Futaba Service Center USA
quote:

ORIGINAL: SERAFIM

Hello from Greece

My question is the following. What is the maximum regulated voltage that I should use for Futaba digital servos that are rated for 4.8V only? I assume that it is higher than 4.8V, since a fully charged 4.8V pack has a higher voltage, but how high can it be? Also, should I expect more torgue-speed with this higher than 4.8 regulated voltage than the numbers stated on the servo specifications?

My servos are S9151, S9252 and S9650

Thank you in advance

Serafim
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Old Jun 04, 2007, 12:52 AM
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Quote:
Originally Posted by QuietRiot
Hmmm, what about using a 5.1 volt Zener Diode rather than a Rectifier Diode. Zeners act as more of an actual regulator by design...though I noticed Align uses a 2amp 50v Rectifier Diode. Very simple circuit btw.

Not sure why folks even buy the $15 in-line regulators anyway when you can make your own with a $1.50 part. Besides the cost, too many plugs/harnesses is never a good thing anyway. Even if you have an Align (or other) regulator, it's best to desolder the diode and place inline into the existing servo or gyro wiring...just my two bits. -QR
That does sound like a good idea. Something to think about if building such a circuit is how much current the zener will add to the mix. That may change the number of servos that the BEC will handle. Limit the current to the zener with a properly sized resistor.

For further engineering data, you can start here: Zener Regulators
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