Kiwi's XPS test results are up.

[Black Sheep]

	Quote: Originally Posted by youngflyer
	so your saying that absolutely every 2.4 failure is due to incorrect powering of the system, thats a long stretch, dont you think?

He didn't say that at all. Re-read the bloody post.
You are the one blowing stuff out of proportion and saying stuff he DIDN'T say !!

[Black Sheep]

	Quote: Originally Posted by KrisW
	Jim. . has it ever occured to you that we do not CARE about your excuses???? You are NOT going to sell anything to US. . . . .Really, you won't. We aren't that gullible. Please go peach to your choir.. . not here.

You guys it seems, are on a frigg'n witch hunt
You ask him to explain stuff and when he tries you give him this crap.

I don't claim to be a radio techie by any stretch of the immagination and if this is the sort of crap that it leads to, I have no intention of being one either!
All I know is I have seen many, many XPS systems in use for a long time now without any failures but I have witnessed a couple of the others go in.
I'm not saying who has the better system but from what I've personally witnessed, I'd have to say some of the failures (any brand) were/are user created. (incorrect programming/incorrect power sources etc).

But, it seems that you guys WILL NOT accept these facts

[dirtybird]

	Quote: Originally Posted by Julez
	I beg to differ. Analog servos work like this: They recieve the pulse from the RX with the length "a". The internal poti makes a circuit create a pulse with the lenght "b". Should "a" and "b" not be equal, the electric motor will be given a current pulse with a lenght "c", that will depend on the difference of "a" and "b". Logically, the current pulse will always start at the same time, after the RX pulse has been recieved. Thus, when the RX puts out the pulses synchronously, the current pulses of the connected servos will also appear synchronously, which leads to load spikes. When it comes to digital servos, the continous current draw is not so important, as the PWM does not depend on the RX pulses. What counts here, is the current surge that every electric motor has when it accelerated from a standstill. These surges are synchronized, when the RX signals are. They sure have. But in case of any problems, my telemetry will warn me.

Well I beg to differ with you. Those current spikes are very short and do not create a current surge. A current surge takes many of those current spikes to create it. In fact it takes a large difference between pulse A and pulse B over a number of frames to create a current surge. By definition the difference between pulse A and pulse B cannot exceed 1MS every 20MS.
In the digital servo an A/D conversion with a sample an hold circuit creates a large number of spikes in a short time period. Even so, a servo motor takes considerably more time than 20MS to accelerate to the point where back EMF nullifys the current surge.

[Woketman]

Nah, you are misleading folks. It's simply what you do!

I have been flying for almost 37 years now. Flying XPS and then FASST 2.4 for almost three years. NEVER had an insufficient power issue. NEVER!

At least two of the turbine guys that I know that had issues with crappy 1st gen XPS (lost planes) had more than adequate power supplies that you continually tried to blame as the culprit. They did not buy your excuses and I don't either.

Stay away from lousy R/C gear guys, stay VERY far away!!!

	Quote: Originally Posted by JimDrew
	I am not misleading anyone. I am pointing out the facts and trying to educate people. The AMA has us do a seminar every year at the AMA expo on powering radio systems because we can demostrate all of these various failures to modelers right there in front of them... no smoke and mirrors. The reality is that people have been flying with improper power systems for decades. Now that we have much more strict power requirements due to using computer based receivers, the problem is becoming more obvious (all radio brands). It's hard to convince people that their super-duper $$$ regulator system is junk, but we see reports every single day of regulators, power expanders, power boxes, battery sharing devices, and switches failing. Even the cheap non-A123 batteries will work fine if you don't use all of the junk to interface them to the receiver. Plug the battery straight into the receiver and call it a day. Inconvenient? How inconvenient is shoveling what is left of your $$$ plane into a bag? Seriously, anyone reading this go and do a search on RCU for "2.4GHz lockout" and then go and see what the root cause is nearly every single time - bad power.

[JimDrew]

I am not offering any excuses, I am pointing out the simple fact that no matter what brand radio system you use, and no matter what frequency it might be using, improper power will lead to a crash.

FASST receivers reboot below 2.7v. Spektrum receivers reboot below 3.5v. Hitec states that their 2.4GHz receivers reboot below 3.7v. Our original receivers reboot below 3.2v, and receivers we manufactured in the last year reboot below 3.0v. Our 7 new receivers being shown next week at the AMA expo reboot below 1.8v. However, the reboot voltage is not everything. Once you reboot, you have to have a quick reconnection. We have the fastest reconnect, and we always have. But, since TTL voltages are required for the proper operation of servos (per manufacturer specifications), you should never really see receiver input votlages below 4.8v. If you do, you have a problem, pure a simple. Accept it, fix it, and continue to fly safely. Our new TattleTale device is already opening people's eyes that their expernsive power systems do not work as advertised.

[Cherokee Jim]

The drive to our servos is a PWM ( Pulse Width Modulated Signal ) that can be 0% for no change to 100% for a stalled servo this means in the case of my 4132s 1 amp. For varying servo loads the servo can easily be on long enough to overlap the on time of another channel so if my three servos driving my swashplate are under heavy enough load to over lap each other at any given time then my power system will see a 3 amp load plus what ever the rest of my electronics is pulling ( gyros, receiver, throttle gov., etc. If you have a digital servo which can draw 5 amps thenyou are looking at 15 amp plus the rest! In the servos that I have measured the current, I am writing a servo test article for an electronics magazine and one heli mag, JR4131, 8131, 8311, 8714 and a multiplex servo, the servo current as measured with a current sense amp and a 0.01 ohm current sense resistor in series with the V+ supply lead of the servo - the amplitude of the servo current is the max for the servo type - the percent of time the servo amplifier is on is what changes, 0 to 100% on time.

I have measured many components, connectors, switches, etc using a Linear Technology developed milliohm meter circuit and at times had some surprising results - some of my older switches had more than 1 ohm of contact resistance and at 1 amp thats a 1 volt drop, if your receiver was expecting a 4.8V supply it would only get 3.8V.

Another example a little less extreme, 3 servos pulling 5A under heavy load ( servo drive times overlap ) 15A and switch and connector resistance of 0.1ohm = a 1.5V drop. Now of course is the voltage drops 1.5V then the servo current will also drop - you can end up with an oscillation as the servo pulls more then less then more current. Power systems are never so simple as we would like.

Today we have very reliable radio systems, the worst system for sale today is more reliable than the early reed, analog propo and digital propo systems - But underlying this reliability is complexity even though it looks all so simple. Enough contact resistance and wire inductance can and will ruin your day.

For you Giant scale folks there is no way you should consider running your servos and and receiver off the same battery pack, "WILL I HAVE BEEN DOING JUST THAT FOR YEARS WITH NO PROBLEM!" some will say - will just keep flying and you will likely find out the hard way.

We have become a Plug and Play generation but RC Helicopters, Large Aircraft, and RC in general are complex systems that must be respected and kept up to par. Anyone not willing to put in the time, and sometimes money ( just spending money won't keep your equipment in top shape, that takes planing and putting in the time to check and do things right ) should find a new hobby, I know that sounds like a mean thing to say but if we ever have a bad accident because of carelessness it can negatively affect our hobby.

In the next few days I will go into work and take some oscilloscope photos of servo current measurements to post for all to see.

Happy Flying,
Cherokee Jim Mahoney

Now for all this the biggest cause of crashes is not equipment! its Pilot error. Who Wants to Admit to Pilot Error?

[Woketman]

	Quote: Originally Posted by JimDrew
	I am not offering any excuses, I am pointing out the simple fact that no matter what brand radio system you use, and no matter what frequency it might be using, improper power will lead to a crash.

I absolutely agree. However, will you also agree that another simple fact is that using a crappy single antenna 2.4 GHz system that won't hop with an adequate power supply has already lead to many crashes?

[Woketman]

Oh no, I should not have posted that slightly negative post.... I just sold two million more systems for Jim!!!!!

[Cherokee Jim]

	Quote:
	I just sold two million more systems for Jim!!!!!

Look on the bright side! If true you should receive a commission from XPS!!!

Happy Flying,
Cherokee Jim

[Woketman]

That would be sweet. But I think we all know that JD is full of crap when he says the "you talk bad about XPS and we sell more!!!"

In general, if his lips are moving, he's talkin' baloney!!!

[Josh Price]

	Quote: Originally Posted by Cherokee Jim
	Today we have very reliable radio systems, the worst system for sale today is more reliable than the early reed, analog propo and digital propo systems - But underlying this reliability is complexity even though it looks all so simple. Enough contact resistance and wire inductance can and will ruin your day. For you Giant scale folks there is no way you should consider running your servos and and receiver off the same battery pack, "WILL I HAVE BEEN DOING JUST THAT FOR YEARS WITH NO PROBLEM!" some will say - will just keep flying and you will likely find out the hard way. We have become a Plug and Play generation but RC Helicopters, Large Aircraft, and RC in general are complex systems that must be respected and kept up to par. Anyone not willing to put in the time, and sometimes money ( just spending money won't keep your equipment in top shape, that takes planing and putting in the time to check and do things right ) should find a new hobby, I know that sounds like a mean thing to say but if we ever have a bad accident because of carelessness it can negatively affect our hobby. In the next few days I will go into work and take some oscilloscope photos of servo current measurements to post for all to see. Happy Flying, Cherokee Jim Mahoney Now for all this the biggest cause of crashes is not equipment! its Pilot error. Who Wants to Admit to Pilot Error?

I agree to a entent,
WILL I HAVE BEEN DOING JUST THAT FOR YEARS WITH NO PROBLEM is exactly right and I am one of those guys.
it WILL bite you in the butt if you do not make sure your equipement is in working order. I have x number of flights before I recharge and follow that religiously. I check voltage before every flight and load test all the batteries before every flight. I also have a double redundant system. I have switches designed to fail closed, and in the event a bat dope off it will power the entire plane off one bat. then it hits the regs (one for each bat) the go to a power expander that gues what does the same as the switch always draws from the hottest battery and will provide power to the entire plane in the event one bat was to drop off. on the planes I dont have the expander I run dual rx. not that the bat is a great way to do things b/c on the giant electrics it is a must it is just in the gas when you have 4 batteries and all the other stuff adding another batt so you feel safer is almost pointless after all the other safety devises you have in place.

guys it is SIMPLE. use a system you trust and believe in. that is for all your equipement. from servo extrensions to switches to radio gear use good stuff. you will save money in the long run and always come out ahead.
you know the most usefull information anyone ever gave me in this hobby is DO NOT LISTEN TO THE SALESMAN, look at the PRO's.. all the names out there that you see every single day on the net like Noll, Jeskey, Donhakl, lesburg, McMurty, Shulman(s), Gritter, Chitty, maxwell, and on and on and on use equipement that works. they dont use it b/c they believed the salesman they use it is what they trust. I still go look in people's plane when they they are putting it together or taking apart b/c of amny reasons. one you see what they use, you find new stuff that either has not hit the market or you have not seen, and you have the oppertunity to ask a questions.

I think XPS has the potential to make great stuff, dont buy some of their stuff they are selling (in product or by mouth) just b/c I cant trust it.

and yes your right it is two easy to scream I lost it when you did lose it but not b/c the radio was not working. I have seen many many many times someone fight a airplane all the way in and then say they lost it.

[JimDrew]

	Quote: Originally Posted by Cherokee Jim
	In the next few days I will go into work and take some oscilloscope photos of servo current measurements to post for all to see.

Jim, I think you might be surprised at some of your findings. People have this belief that servos draw the most amount of current when stalled - that is not true. We have found in testing using digital storage scopes w/current analyzers (like what you are about to do and show) that a servo instructed to change directions mid-transit will draw 2-5 times more current than when stalled. Albeit the duration of the current draw is short, but it can be long enough to cause a reboot when the power system is insufficient.

Some other things to consider:

Servo pins - manufacturers of the servo pins we use state the max current draw is 3A sustained, 5A peak. If you are using a single power input (common with R/C systems), then you are supplying ALL of the servos with single power/ground pins only capable of supplying 10A peak. As you pointed out, 15A draw is certainly possible (and is actually very common, especially with numerous and/or large servos). When the current can not be supplied, something has to give, and that "something" is voltage. A drop in voltage can cause a reboot. We outgrew our servo pins at least 10 years ago.

Resonant vibrations in switch contacts - something often overlooked. As you pointed out, switches can (and do) have some serious resistance. What about those gas or glow setups where a certain throttle position causes a resonant vibration that causes the metal plates in the switch to vibrate and make intermittent connection. Sound far fetched? It's not. We have seen it happen ourselves.

Battery construction - we had a customer have problems with his 1/8th scale glow R/C car. Everytime he would land at the bototm of a jump, his receiver would reboot. It turned out that one of the spot welds on his 4 cell Nimh pack was broken and only being held in place by the shrink wrap. Twisting the pack actually turned off the receiver. We have had numerous reports of this same problem in aircraft, where no problems existed until the engine was started. This made it look like some type of interference due to the ignition system when in fact it was vibration rubbing the broken spot welds on the battery.

Battery charging - you can't charge a 5 cell Nimh pack with a 4 cell wall charger and expect it to be charged! Likewise, you can't charge your dead 2700mAh 4 cell Nimh using your 4 cell wall charger in 8 hours and expect it to be charged! These are EXTREMELY common problems in R/C.

We have gotten away with a lot with 72MHz systems for decades. Why? 72MHz receivers use shift registers. These are CMOS devices that can run litterally just on fractions of a volt. When the voltage got too low, we saw uncommanded movement (a "glitch") on the surfaces. This was due to the shift register being out of phase for a frame... so the channels were shifted by some amount (i.e. channel 1 output was now occuring on channel 3, channel 2 on 4, etc.) Servos also became "spongy" in low power conditions. A good example of this is watching someone doing a knife edge where the tail "waggles". The waggling is not caused by the pilot, it is caused by the load on the rudder servo causing and inadequate power system to dip, which provides less voltage to the rudder servo so the holding torque become less. Less holding force allows the air to push the rudder downward, causing the nose to drop. Now, once the nose drops, the voltage comes back up and now the rudder moves back to where it should be and the nose rises... of course putting more load on the servo and dropping the power. The cycle repeats over and over again causing the waggle.

Switches are serious source of problems. We don't use them. We use a Deans Ultra connector pair as our "switch". Plug the two together (which will handle 60A continuous) and there are no worries of vibration or thin metal plates arcing. Yes, this method is inconvenient, but everything from our 40% SX to our turbine jets use the same setup.

We have well over 100,000 customers so we have a great deal of experience with what the public uses for powering their radio systems. Our customer base is particularly tough because we upgrade radio systems that are typically 10+ years old (or more). Many of these people are really trying to use the original 600mAh Nicad pack that came with their system - the one that takes all night to charge and still only shows 4.5 volts without a load!

[Woketman]

Yeah, keep trying to misdirect everyone with power systems. Oops, his lips were moving.... You all know what THAT means!!!!

JD, will you also agree that another simple fact is that using a crappy single antenna 2.4 GHz system that won't hop with an adequate power supply has already lead to many crashes? Answer the question Jim!

[Cherokee Jim]

Jim, if you remember back to the days of Bonner Servos some folks hardwired their servos onto a servo carrying PCB --- No Connectors on servos. Connectors were a problem then and the connectors had 5 to 7 pins, not 3 as we use today.

In steady state, not changing directions the max current will be dictated by the resistance of the motor winding. The Kick that you are seeing comes from the motors' inductance, for a very short time the Back EMF due to the inductance becomes Forward EMF and a little extra voltage is applied to the motor.

You are dead right about our connectors being out of date, I am conservitive, I just count the steady state rating - 2A and this rating goes down hill the more times you connect and unconnect a connector Pin and Socket - they are usually rated for as few as 200 mating-unmating cycles!

Cannon makes some connectors which are spring loaded and have at least 7 points of contact - many would be surprised by how small the actual contact area of our standard Futaba/JR/Airtronics connectors.Cannon or the Hypertronics pins and sockets would be a goo way to go, also having 6 pin 2 pins parelled in sets of three would help, but that still won't be good for 15 amps for some Digital servos.

Power systems, power distribution and power sequencing --- Yes these are Big Issues, just ask our buddies over in the Aero Space and Military Electronics field! Many a missile had problems with connectors - connectors a simple component one would would think, switches too, but its all in the details --- How many Atlas Missiles Blew up on the Launch Pad due to a failoed ten cent switch --- More than one at maybe $70 million dollars a pop - some Bean Counter really saved some money buying that 10 cent switch!!!

The reliability of our RC Systems depend on every link in the system, an underrated connector will have as much chance of causing a failure as any other item in the link.

Connectors, Batteries, How we take care of our batteries, wiring, yes all these simple things will bite your xss when you get careless and don't give them there proper respect!

Now for the folks who say that they are using the same sloppy techneques for the last 20 years - will I am willing to bet they are the same people who had similar problems then as now.

Just remember the Brainless Statements given out after Challenger

" We saw the problem but it had not caused a Failure Yet! " Great Management Decisions!

You Giant Scale and Jet Folks have much more critical requirements and a lot more money is involved than for the power link in standard RC, 30 - 60 size helicopters and aircraft, all the more care is needed - proper care is of course needed at all levels.

Happy Flying,
Cherokee Jim Mahoney

[Woketman]

While I agree that our present connectors are likely not adequate for giant scale birds and the huge aerobatic types, they are fine for what I fly. I am talking of moderately sized jets limited to 200 mph or less. Been flying them for ten years (more than half of that time with fancy-shmancy digi servos) without a single power issue (batteries, voltage, connectors, etc...) that I did not bring upon myself (and even that issue was non-fatal to the airframe). Inescapeable conclusion: standard JR/Futaba type connectors are fine for what I fly or smaller planes. If you go bigger, watch out!

Now, back to the real question (not the popular mis-direction via the power issue discussions): JD, will you also agree that another simple fact is that using a crappy single antenna 2.4 GHz system that won't hop with an adequate power supply has already lead to many crashes? Answer the question Jim!

The truth is yes: It HAS lead to several crashes of high dollar jets. Jim, please concur.....