Edgar Perez

My Feedback: (13)

any experience with this one? Price is $199
[link=http://www.aircraftinternational.com/catalog/power_box/rrs_module/index.htm]Powerbox RSS[/link]

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Power Box RRS Module
Redundant Receiver System

The world's first redundant "standalone" redundant receiver system.
Selects the receiver with the best reception automatically
All modulation modes can be used, all PCM, PPM and PPM-IPD
All receivers can be used, JR Futaba, MPX, Graupner, Berg, Airtronics, Spektrum, etc.
All frequencies can be used, 35 Mhz, 40 Mhz, 72 Mhz, 2.4 Ghz
Compatible with all PowerBox systems
Servos can be connected directly, even without a PowerBox
no additional power supply is required
Ready for use without prior programming (in the case of the PCM, only the Fail-Save option need be programmed in the transmitter)
Weighs only 1.55 oz. / 44 grams

LCD display reads the following information:
receiver function
which receiver is active
how many receiver switch-overs were made during the previous flight
reception quality of both receivers in percent

Ehab

My Feedback: (44)

Looks like a good idea. It may make the spektrum Rx's even more solid...

smokin-gun

My Feedback: (18)

looks like it is lacking in channels though!

Edgar Perez

My Feedback: (13)

I wonder how the unit decides which is the best signal?? It's only connected to the receiver servo outputs...

dragonpilot

My Feedback: (38)

It appears that you connect each channel of each receiver with servo extensions to each side of the unit and then plug the servo leads into the bottom portion. I guess it decides the stronger signal pulse that the receiver is sending and then sends that thru to the servos.

Dave Wilshere

Guys

Because it's designed for the Powerbox units, it has seven input channels, the maximum any PB has-but these can drive 24 servos!
The unit will allow the Rx with the strongest signal to control the aeroplane.
I have one in my Composite ARF Pitts S12 driving 15 servos through a Champion PB.

Dave Wilshere

mr_matt

My Feedback: (10)

Nice looking unit, but others have similar products

Check out the Emcotec DPSI twin, it has powerbox functionality, still limited to switching 8 channels, however. You leave the other "scale" detail channels (canopy opening, missle firing, pilot flipping the bird) to "non redundant" channels.

This system (or the Emcotec), using a normal PCM and a 2.4 GHz as a back up on the trainer port might be very interesting.

Edgar Perez

My Feedback: (13)

Still I don't undertand how the unit determines the best signal?????

If I have one reciever with PCM go on failsave, the unit will send a valid pulse to the RRS. How the system knows to use the other reciever signal by only looking at the servo outputs in the receiver???

mr_matt

My Feedback: (10)

I can only speak for the DPSI Twin (but my guess is this Powerbox is similar).

One of the PRIMARY side RXs channels must be set as a failsafe channel. A failsafe event on the primary RX frequency will cause the failsafe channel on the primary RX to switch the units to the backup RX. This is not a great solution, IMHO. I am not sure how the Weatronics works, but the ACT is completely different. It compares the 2 RF sections received data continuously and selects the best data at that instant in time (BEFORE the data goes to the servos). This is done via RSSI and (I believe) other data analysis.

The DPSI Twin (and probably this PowerBoxunit) ONLY waits for a failsafe. In the PPM mode, the DPSI twin also has a criteria to sanity check the PPM servo signals before deciding to switch to the backup. This algorithm might be similar to the DSP checking done on Multiplex RXs, Berg and others, I honestly do not know.

I do know that ACT told me that after they had seen the real world results of PCM performance, they would exclusively move to PPM with onboard signal integrity checking (ala Multiplex, ACT, Berg, etc).

Edgar Perez

My Feedback: (13)

Thanks for the explanation... I guess I need more 'thinking time' to figure out how does this unit fits in the cost/benefit ratio versus the other options..

dragonpilot

My Feedback: (38)

Mr. Matt,
If you would, Could you explain that sentence in more detail, I am intrigued but not quite sure what it is saying as I don't know any history about ACT. Thanks

rc4flying

My Feedback: (21)

Here is a pic of my installation in a 40% Extra 260.

The unit is always looking for the strongest RX signal. and will switch from rcvr 1 to rcvr 2 seemleesly and back to alway use the strongest rcv'd signal. The display will give a signal strength of the Rcvrs and how many times it has swished, but this readout would need to be observed prior to powering off the plane, as the unit resets the readout when power is first applied again.
It is also setup with a FS channel settings that is hooked up to a spare channel . Pic was taken prior to fully understanding how to hook it up, and is shown as not hooked up. This channel is programed for O%- 100%. Then you set the FS for this channel to go to 100%. When the RX goes into a FS mode, this channel detects this and also switches to the second RX.

Edgar Perez

My Feedback: (13)

Hi Joe

I will say the 'mystery' is how the unit determines the strongest signal, if its only connected to the servo outputs of the receiver....

Of course, the failsafe setup will clearly indicate a lockout, but that is not the claimed receiver switching…

rc4flying

My Feedback: (21)

Edgar,

I understand what you mean, but I have seen the display change from 100% to something other and have the unit switch just with the TX during setup and the antenns not pulled out all the way up. I think the rx antenna orientation to the TX would see a weaker signal for a moment. Not totally lose it, but be weaker in signal strength.

So far, I have maybe 50 flights and sometimes After the flights, I notice it has switched from rx 1-2, so it is doing it's thing.

TommyWatson

My Feedback: (1)

Sounds like a low cost alternative to the Weatronic.

Regards

Edgar Perez

My Feedback: (13)

I though it could be that, but not really sure...

You still need two receivers (say $100 to $160 each = $200 to $320) + RRS ($199).

That's $400 to $520. You are almost to the weatronic, and missing a lot of features. Don't think the math holds, unless you use inexpensive receivers (but then will you do that with your jet?)

TommyWatson

My Feedback: (1)

Hi Edgar,

I agree, I would go straight to the Weatronic (I have two of them). The Weatronic is all integrated and works perfectly. You do need a PC to set it up but it can do wonderfull things. The GPS and Gyro are great.

Regards

taprackflip

My Feedback: (29)

I think the Weatronic is a lot less than you think. You can get into a 10-20 dual receiver for about $505.00. http://www.allspectrum.com/

Woketman

My Feedback: (6)

So how does this thing determine the strongest RX when in PPM mode?

mr_matt

My Feedback: (10)

Re: PCM switching, I can only speak of the Emcotec for sure, perhaps the PowerBox unit operates similarly.

Normal PCM transmitters encode the entire "frame" (the instantaneous pulse position of all of the servos at a single instant) and send that information to the receiver, which then decodes it and decides if it was valid. If the frame is not valid, most PCM receivers will go into a "hold" mode and wait for a good frame. After some number of bad frames in a row (the exact number depending on the brand) then the receiver can go into the failsafe mode, wherein the servos all travel to a preprogrammed position. The Emcotec and the Powerbox unit use this feature (failsafe channel causes the switching) when in PCM mode. You have a "primary" receiver and a "backup" receiver (that can be on the same or different frequencies, more on that later). When the failsafe channel of the primary receiver activates, the unit switches over to the backup receiver.

To Mark's question (on the PPM case), again I can only speak about how the Emcotec works (but my guess is that the Powerbox is similar). In the PPM case, the Emcotec analyzes the PPM data stream and checks it for validity, namely how long the pulses are, the gaps between pulses, etc (similar to Multiplex IPD and Berg). In this case you do not have to wait for a bunch of bad PCM frames, the unit switches as soon as it detects the corrupted PPM stream.

Now the ACT (and I think the Weatronics) are really completely different animals. I can talk more about the ACT as I have that set up (I think I have this right, it has been awhile). The ACT is not switching from a primary to a backup receiver, but rather combining the signals of both receivers continuously.

The ACT receivers look at the continuous stream of data coming in on both receivers and constantly send the best signal to the servos on a case by case basis. This has a big advantage over the Emcotec and Powerbox type switching solutions. This allows for the receivers to take advantage of the better signal you get by having diversity antennas (a fancy term for 2 or more antennas that are located apart and/or with different orientations). This diversity antenna feature is similar to what is used on the Spektrum and the Futaba FASST spread spectrum radios. It is a powerful design technique in the RF world.

Now back to the transmitted frequencies. The Emcotec, PowerBox and ACT allow you to transmit on 2 different frequencies (if you have a radio that will do this, I did it on the amateur frequencies and I think ACT is making a module in Europe that transmits on 2 frequencies).

This gives a measure of frequency diversity as well; again, Spektrum does this on 2.4GHz. The ACT has a way to exploit both antenna diversity and frequency diversity. I am not sure if the Weatronics does this or not, meaning I do not know if the 2 receivers can be on 2 different frequencies.

The Weatronics also uses a synthesized receiver that can adjust to the transmitter frequency very closely for better performance. I think this is unique to Weatronics.


Honestly, the work on spread spectrum has sucked a lot of the oxygen out of these solutions, although I am looking at an interim capability that would use a normal broadband (72 MHz type) primary with 16-20+ channels and a backup spread spectrum system for 8 primary flight control channels. This would be used primarily to avoid a shoot down case.

Woketman

My Feedback: (6)

"The ACT receivers look at the continuous stream of data coming in on both receivers and constantly send the best signal to the servos on a case by case basis."

What criteria is used to determine the "best" signal?

Thanks.

mr_matt

My Feedback: (10)

A combination of RSSI (received signal strength) and the PPM signal analysis. I think that is why ACT pushes PPM so much.

Woketman

My Feedback: (6)

But how does it get the RSSI info from a stock PPM RX?

Edgar Perez

My Feedback: (13)

I was able to ask about this in the Jetpower fair. For PCM it uses falsafe activation to switch to the other receiver. Of course, if both are in failsafe, then you are done. To be more effective you should position the antennas to protect all aircraft orientations. So for PCM, if you see a lot of switching, things must be bad[X(]
For PPM, its checking valid ranges for servo outputs.. Did not ask a lot about that, since I was only interested in PCM.

somethnextra

My Feedback: (22)

What's the advantage of the RSS when using it with 2.4 Ghz? Doesn't the 2.4 GHztechnology take care of the interference problem itself by hopping? How would you use two 2.4 GHz rx's with the same transmitter?