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Futaba PS-01 RS 5.0v Regulator

Chris Mulcahy tests the new Futaba PS-01 RS 5.0v regulator.



Main Application:4.8v Rudder Servos
Input Voltage:6.0-8.5v
Output Voltage:5.0v
Rated Output Current:1.0A (momentary max. 5.0A)
Distributed by:Great Planes

With high voltage servos and power systems becoming the norm on today's modern high performance helis, extra care is needed for most rudder servos as they are designed to operate on 4.8v. We therefore are required to run a step down regulator in line between the tail servo and the gyro/receiver. There are a few step down regulators available on the market already, and I actually have been using the Align 5.1 reg, so I decided it was time to actually put it to the test along with the new Futaba PS-01 RS 5.0v regulator.

There really isn't that much to getting the PS-01 installed and running, but through some testing I did find out some interesting information!


This is it! Very simple packaging, and really that is all that is required. You get the regulator, a warranty card, and an instruction page. The single page instructions consist mostly of the standard warnings about attaching to the aircraft, and not operating continuously with a locked up servo. It also states that you cannot use the PS-01 with a y-harness. Another important note is that it is designed for 2.4GHz systems only.


Follow closely, this is the technical part!... Unplug rudder servo from gyro/receiver, plug servo into regulator, plug regulator into gyro/receiver, done! I installed it in my Titan X50, which I'm running off of a LifeSource 6.6v 2100mah 2 cell battery. My rudder servo is the Futaba BLS251 brushless servo, which is rated for 4.8v.

Here's a photo of it installed...


Remember the interesting stuff I mentioned earlier? This is it! My flying buddy and heli cohort Bob also runs his own car repair business, and he has a very cool diagnostic tool in his arsenal. It's made by Snap-On, and is called the Verus diagnostic and information system. It is basically a portable computer that has a lot of cool diagnostic tools attached to it with some great software to diagnose all kinds of electrical problems (amongst other things). We were able to hook up a couple of probes to the regulator to read voltage output, and loop a low amps probe around the wire to get the amps read out. This data was then displayed real time in a graph, which is the two images below! Now, I am not an electronics expert, but was able to read the data pretty clearly, and here is what we found.

We started with the Align 5.1v step down regulator, the regulator that I had already been using for a while. We powered up the helicopter and found that in a neutral state, without any load, the Align regulator sat at 5.9v! I then moved the rudder servo to it's left and right extremes several times (that's the squiggly line in the middle) and found that the voltage peaked at 7.11v max while the amps peaked at 4.4. Needless to say that I was quite surprised at how high the voltage was on this regulator.

We then hooked up the Futaba PS 01-RS in the same fashion. We performed the same tests and discovered that at neutral with no load the regulator sat at 4.95v - perfect! Under load, as before by moving the rudder servo left and right several times, the volts peaked at 5.76v, the amps at 4.0.

In the graphs below, the top yellow line represents the volts, the straight line at the beginning is at neutral, and where it gets all squiggly (did I mention I'm not an electronics expert?..) is where I was moving the servo back and forth. The green line below represents amps.


Will you notice a difference in your flying? Nope. However your rudder servos will last longer! I was surprised to find that my 6.6v system was only being regulated to 5.9v with my old regulator, conversely I was very happy to find that the Futaba regulator does exactly what it's supposed to do. I am sold, and will be using this regulator exclusively going forward.

It does exactly what it says it will do
It's compact and easy to install

Haven't found any yet!

Last edited by Angela H; Dec 01, 2011 at 12:03 PM..
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Dec 01, 2011, 01:47 PM
NiCd + Mabuchi 550 was da bomb
The Align "regulator" is nothing more than a diode with a forward voltage drop of 0.7V.

This is why your 6.6V system with a 0.7V voltage drop sits at 5.9V. The Align regulator is intended for use with 6.0V onboard power sources.

Do us a favor and slice the shrink wrap on your Futaba regulator open so we can see what goodies it has inside.
Dec 01, 2011, 02:13 PM
Team Futaba
CSpaced's Avatar
That is true, which is why I like the Futaba reg so much. It doesn't matter what the input voltage it, it regulates to 5v. I found the "5.1v" label on the Align regulator a little misleading.

I think I'll just use the regulator for a while before cutting it up!
Dec 01, 2011, 04:37 PM
Ignint McNugget
Rumple's Avatar
I can't make sense of this:

Originally Posted by CSpaced
Another important note is that it is designed for 2.4GHz systems only.
How does the regulator know, and why would it care, what frequency is used to communicate between the Tx and Rx?

On another note, FWIW - "4.8V" servos or gyros stem from old 4s NiCd packs, which can be as high as ~5.8V when fully charged - so I certainly wouldn't be scared to run at this voltage.
Dec 01, 2011, 04:44 PM
Team Futaba
CSpaced's Avatar
Originally Posted by Rumple View Post
I can't make sense of this:

How does the regulator know, and why would it care, what frequency is used to communicate between the Tx and Rx?
This is the official word from Futaba about the 2.4 question:

The Futaba regulators are switching regulators. Any switching type of regulator can emit spurious RF noise from the switching operation which could interfere with a 72 MHz system. However the noise is at too low a frequency to bother systems operating on 2.4 GHz.
Dec 02, 2011, 11:16 AM
Registered User
Originally Posted by Rumple View Post
On another note, FWIW - "4.8V" servos or gyros stem from old 4s NiCd packs, which can be as high as ~5.8V when fully charged - so I certainly wouldn't be scared to run at this voltage.
This is a bogus assumption. Although 5.8 volts might not instantaneously blow out the servo, operating it continuously at this voltage may overheat and burn it out. 60 seconds into the first flight you are not operating at 5.8 volts.
Dec 02, 2011, 01:09 PM
Ignint McNugget
Rumple's Avatar
Good point - the voltage under load of a 4s NiCd pack would be below 5.8V.
Dec 11, 2011, 10:27 PM
Prop buster extrordinaire
MrBreeze's Avatar
Another quality Futaba product. Thank you for your review.
Jan 06, 2012, 08:45 AM
Registered User

Lasting longer

For any skeptics in the audience, I ran a couple of my servos directly on a 7.2v pack last week, and it took about 3 minutes before one burned out... Oops.
Jan 06, 2012, 11:25 AM
Registered User
The increased voltage 7.11 and 5.76 is due to the back EMF from the motor in the servo.
(I had this problem once with a triac switch turning off when the servo moved/stopped)
With the Align the return voltage is blocked by the diode and you see it all, with the Futaba its probably sinking into some output smoothing caps and hence the reduced value.
The increased current 4.4 is due to the fact the servo is running faster (higher voltage) with this sett up.

Hope thats helps a bit and isnt too wrong ;-)

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