plane addicts

My Feedback: (271)

MY understanding is that the casing is the biggest change in the kill switch. Some of the companys that have newer shipments of the RCexel kill switches have this style now.

MTK

Dan, I admit that your writing made me stop and take note (not the usual stuff one reads on these pages)....I did think there was value there.

True enough, there are no perfect filters. But the designer has done his homework on this device. I know first hand since I helped test the prototype units. I don't mean just simple bench testing, although Ed the designer did do considerable O-scope work before it was acceptable enough to test in a 2.4 gig real set-up, mine. Continuous development then led to the unit shown today that has been extensively tested with many different radio brands, modulation types and frequencies, as well as radio age (at least 15 year old equipment).

At the end of the day it's a matter of risk. In my experience, the Tech Aero unit is about as low risk device as we have on our planes, but it may not be able to overcome bad set-up of the CDI and associated wiring (lots of metal to metal, loose plug cap, etc).

I can't speak for any competitive product since I don't use any of them. I do know a few guys who fly Pattern and IMAC competitively that have been converted to the Tech Aero unit from whatever they were flying before.

I also believe its just a matter of time before this goodie really gets discovered. I am only bringing the word to try and help guys in making a bit more informed decisions.

All Day Dan

My Feedback: (5)

Hi Matt, thanks for the reply. Dan.

karolh

Not trying to hijack this thread but since we are on the subject kill switches I would appreciated your thoughts on the RCATS electronic kill switch. I currently use one in my gas powered Extra on 72Mhz and so far it has worked flawlessly, but I would really like to know if I am possibly courting danger by using it.

Karol

All Day Dan

My Feedback: (5)

Karol, it should work perfectly. That's the way they should all be designed. You get the isolation you need through that optic fiber line. That is just what the other units don't provide. I hope that's the one you're using. They may have more than one type. Dan.

karolh

Thanks for your response Dan. Unfortunately I am using the earlier RC-100 version switch which does not have the optic fiber line. I plan on switching my Futaba 8UAF Tx from 72 Mhz to 2.4Ghz via a module change quite soon, do you think going this route this will lessen the risk of interference causing a problem. I sent RCATS an e-mail on this issue and am awaiting their response.

Karol

J-3

I too have the RCATS RC-100FO electronic switch that has 24 inches of fiber optic cable, but I have not flown with it yet and have been looking at all the other options. I hope to fly someday soon.....Brian

All Day Dan

My Feedback: (5)

Karol, there is absolutely no scientific reason to believe that the spread spectrum band is any more or less suseptible to radio frequency interference than any other band. The best thing to do is to protect youself against RFI and we have the tools to do it so use the kill switch that provides the most isolation. That is the one with the optic fiber line. The one with the signal line going straight to the receiver from the switch has the real capability of bringing that interference right in to the receiver. Dan.

Brian, you're using the right one. I have three of the Smart-Fly units that are similar in my planes. I'll attach an image I've posted on other threads about this subject. The optic fiber line is the heavy black wire running by the retract switch. Dan.

bcchi

Now that is to neat.Good Job.
BCCHI

MTK

I don't totally agree regarding 2.4 Gig freqs. Although this is true in general radiofrequency terms, the fact is that the 2.4 Gig frequency requires an interferring signal with the right wavelengths. In fact, that kind of interfering wavelength is just not generated in adequate power to cause interference in our models when 2.4 gig freq is doing the control. (For other, lower bands such as 900 MHz or 72 MHz, your mileage may vary)

I'll give you an example:
I have a large RC truck powered by a 26cc Magneto Ignition gasoline engine (the absolute noisiest ignition there is). It came with a 72 Meg off brand radio installed. Once the engine fired up, the only way I had any control was to actually touch the antennas. Switched the radio to a 2.4 gig land type (Fut Fasst) and I regained 100% control. There was nothing else done other than change radio frequency. The ignition is within 3" of the RX is this case and the battery maybe 4" away.

I understand the theory better than most having worked in the arena for 20 years, and now I am a believer in the practice. 2.4 Gig is a better arrangement of control for models powered by gasoline/ignition type engines.

If any one specific installation is just badly done, fiberoptic connections can and will be overcome even in 2.4 Gig installations. But if good practices are involved in installation of the typical 72 Meg system, FO will give extra protection

Rocketman_

karolh,
I use the RCATS RC-100 ignition kill switch and have no problems on 72MHz. The tiny relay inside that little enclosure apparently helps to isolate the receiver from the ignition wiring. It also shuts off the ignition if receiver power is lost.

Rick.

Aw rats!!!!!

I bought the RCExcel opto kill switch believing that in the event of either RX or TX failure the switch would not be held 'on' and the sparks would stop!  seems i was a bit mistaken then

I use a Spektrum 2.4 Module in the back of my trusty Futaba 9c - so only the throttle channel shuts down if the tx signal is lost - and if the receiver failed (ie, no power to the servos) it looks like the kill switch would remain 'on' thus ensuring my plane went in under power - great - NOT

If this is the case I'm very unhappy with the way the RCExcel product is marketed because equipment failure, and the inability to kill a gas engine if the servos, for any reason, can't operate, is the main need for this kind of safety device.  I mean - if the radio is working fine then throttle close is sufficient to stop the engine and a kill switch is not needed - it is in the event of a radio failure that an automatic kill is required, and if the RCExcel unit can't do that without it being programmed as a channel failsafe setting (which as i've said, i can't - other than by throttle servo), then its really no use at all is it?????

Total waste of 15 quid (20 odd bucks).........................Rick ' the gullible'

Howard

My Feedback: (55)

I am scratching my head trying to understand why you have an issue with the RCExcel opto kill switch I think I am trying to say how would the opto switch know if your TX was turned off unless your radio is capable of generating a failsafe position for the channel you are using to turn the opto switch on or off. It seems to me that the dissapointment would be better directed at the radio rather than the the opto switch. Of course it is very likely that I am misunderstanding something about how these work and if so please steer me in the right direction.

Howard

AA5BY

I'm in agreement with Howard... I don't understand why it can't be done with your radio. If the throttle is the only one with fail safe, use a Y harness on the throttle.

karolh

As I mentioned in my initial post, my RC-100 switch has worked flawlessly since it's install which was several years ago, but this thread just got me to wondering that's all.

Karol

a1pcfixer

My Feedback: (7)

I'll assume you set the ign kill up on ch 5. Have you tried setting it up as if it had 'failsafe' ability, and set 'failsafe' to a big negative value?

If you can't do that, then it's that Spektrum (JR) module holding you back.

I just yesterday, went trough all my glow & gas models, checking and setting 'failsafe' on all. Found I'd missed setting 2. One was on ppm(fm) not pcm, and normally you can't set failsafe on a Futaba Super 9CAP if it's not pcm. Well, I set it up in the tx as if it were pcm and had failsafe ability, then reset to ppm, turned off the tx & ....tada...it worked. It was a glow and all it did was pull the throttle back to kill the engine, after the tx was switched off.

Various Futaba TX's on 72 mHz don't even show you the 'F/S' feature unless it's set to PCM.
My futaba 10CAP w/2.4 gHz module DOES show 'F/S'.

Probably got to be something bad about that, but what?
Shoot, it worked!

Rick.

thanks a1pcfixer i'll try that as my tx is set to ppm as required by the Spektrum module.

Howard - well the bottom line is that its irrelevant wether the tx has failed or the rx has failed or the battery has failed or wether failsafe can be set or not - what matters is that if the servos cease to function the loss of signal to the kill switch should imo cause it to sever the ign battery to cdi link. If the Rx failed in flight it may well inhibit the ability of any failsafe to kick in by chopping all servo power!

If the kill switch doesn't click over when the Rx dies then one faces the prospect of a plane with servos set to cruise positions, circling and maybe climbing whilst drifting off down wind for the 45 minute tank run.  Its quite conceivable that by the time the tank ran dry the plane could be 30 miles away at 8000 feet.

aa5by - ummmm - if you fit a Y lead from the throttle to the kill switch signal line, then wouldn't the switch kill the sparks as soon as you throttled back to idle?? and of couse my above comments apply too, cos if the Rx is unpowered, then no failsafe servo position signal can be sent.

w8ye

My Feedback: (16)

The kill switch needs to be normally open upon no signal?

a1pcfixer

My Feedback: (7)

I'm pretty sure the TX setup for ign kill switch(es) require a -/negative value to function in failsafe mode.

Futaba PCM receivers get their F/S settings updated by the TX every so many seconds/minutes(?), which is stored in the PCM receiver. No power=no signal=ign kill should be off....yes/no????

Mluvara

My Feedback: (10)

Karol/All,

One of the posts above mentioned good advice about installation,etc. RCATS makes two types of electronic switches. One is RC-100 and RC-100 fiberoptic version. The difference between the two is that the fiberoptic "optically" isolates the switch portion from the command portion and places distance between the electronics. To be honest, I sell 200:1 of the non fiberoptic to the fiberoptic version. There is no fool-proof way to install radio equipment, and any time one has wires in an airplane, they can have potential issues with RF interference. 2.4GHz has eliminated much of the problems that many used to see on 72MHz since most ignitions,engine electronics, installations,etc do not put out any noise in that high of an RF band. There are many misconceptions that the RC-100 directly connects the ignition to the receiver. This is false. RF interference can happen in any environment and since all installations are different, there is no way to say what is perfect. In my personal opinion, going to 2.4GHz does lessen the general sense of interference. Most RF noise generated in these aircraft are low frequencies that are near 72MHz. One of the biggest issues in this area is wire length, as it was common to have extensions acting as antennas in aircraft, because 72MHz is a much larger wavelength. Also 72MHz equipment was very primitive in its noise rejection, which made interference very apparent. 2.4GHz is much superior in dealing with noise rejection in many respects.

Bottom line: if you see any issues using the RC-100, you have a very electrically noisy environment.

I have played with a lot of complex installations in UAV's,etc. There are issues in all types of installation. One just has to look at the known noise sources and deal with it.

Regards,
Michael Luvara
RCATS

bcchi

If you used a Y harness into the throttle channel,everytime you pulled throttle back would stop the engine,not good. I use the RCEXL engine kill on several airplanes,but I can set fail safe on the engine ignition kill channel.
BCCHI

All Day Dan

My Feedback: (5)

Thank you Michael for your input. Do you have any spectrum plots or any analysis to back up these two statements.

"Most RF noise generated in these aircraft are low frequencies that are near 72MHz."
"2.4GHz is much superior in dealing with noise rejection in many respects."

Thanks, Dan.

Mluvara

My Feedback: (10)

I do not have any stored plots of such, but can tell you that if one looks at the interior circuitry and such of ignitions, there's very little reason to think that it could produce 2.4GHz signals. Besides, the RPM that one is running in a frequency is very low when translated to cycles and potential RF output.

One thing to understand: 72MHz technology had very little inherent noise rejection for bad data as compared to 2.4GHz which is a totally digital system and is spread across a wide band. It can filter out glitches,etc whereas some 72MHz would pass them right through to the servo outputs. PCM did a lot to mask the bad data. It was still there, but filtered out.

There are two types of interference-

1. Radiated (emitted as a radio frequency to air)
2. Conducted (sent down a transmission line)

Most of the issues 72MHz has seen are because of a signal that ends up on the same as that of the model's rf link or something that affected the internal IF circuitry,etc. 2.4GHz, while having varied types of transmission (DSSS, FHSS,etc) are a totally different system altogether. 72MHz is a very narrow signal and a very primitive transmission scheme, by comparison to the amount of bandwidth that a more complex 2.4GHz system uses, which reduces the probability of interference. If 72MHz was a frequency hopping/dsss scheme like 2.4GHz, it could be different. Think about it this way - 72MHz is less than 1MHz of available total channels and we only use one narrow channel (20kHz if memory serves correctly). 2.4GHz uses approximately 80 MHz of available channels to pick from, whether it is a hopping or Direct Sequence system (which typically spread the code over a 1Mhz or similar channel, or narrow, saw 20kHz if FHSS).

As for 2.4GHz, it is possible that lower frequencies can get into the system and affect its operation. But, one would likely not see local interference stepping on the transmission frequency. Think of it as a crowded room with discussion. The more people you have, the more the noise floor goes up. This is why separating things helps. Signal falls of with the inverse of the square of distance. The lower the noise floor, the better the hearing is. Your RF transmitter is shouting, but is further away than the noisy atmosphere near the receiver. The general rule of thumb is "he who shouts loudest wins".

Thus, without going into great detail, I stand by my statement that 2.4GHz is far superior in inherent noise rejection methodology.

Michael

a1pcfixer

My Feedback: (7)

No, it needs to see a -/negative value to shut off in F/S mode. Throttled back, it's still +/positive.

Possibly true for many of us with same brand TX & TX modules, his is NOT that way.
Perhaps you missed it, but he has a Spektrum (aka JR) module in his Futaba TX. It
requires PPM (FM) mode be set in the TX.

If he had stayed with a Futaba 2.4 gHz module, he wouldn't be here with his current
problem, but he is.

karolh

Michael,

Thanks for your comments on noise induced radio interference as it relates to our 72Mhz and 2.4Ghz systems, and for also allaying my concerns about the use of the RC-100 switch in my model.

Karol