Introducing the next evolution in servo control : the opto flight !
there are many advantages to using fiber optics over conventional copper.
these include :
- 100% RFI proof
-complete electrical isolation between RX and servos (excessive current draw from servos will not cause battery voltage drop possibly leading to RX brown out and loss of control)
-no inductive feedback
- can use 5cell batt for RX while using 7.4v lipo unregulated with new high voltage servos .
-boards can tolerate up to 18volts dc
kit includes :
1x receiver board
8x servo boards
1x 10ft fiber optic cable
20x fiber optic cable terminal connectors
1x terminal polishing kit
learn more at www.evuas.com/index.php
18 units available for pre-order . shipping august 20th .
Comments
Still - while I can see benefits in an opitcal system, I question just how well it actually isolates hardware from interference. Accepted, it will remove the copper inter-connect to servo's which is a known major "pickup" for RFI, but copper interconnects are not the only "pickup" points for RFI. Most interference that can/is picked up by copper wire runs, is also interferance that can be picked up by servo electronics as well (i.e. the components contained inside the servo frames).
The 2 best ways to isolate servo's from RFI?
- shielding the frames
- a seperate star-grounded shield for the servo copper interconnect cable
- and last but not least (probably the most important consideration) - distance: meaning the distance of any potential pick-up point from the source of interference - you only have to move a GSM phone 2" - 3" further away from a computer MoBo, or speaker coil, or some other pick-up point connected to a computer to see ("hear") see effect that distance can play - and very small changes in distance at that.
Your last comment in reply to my earlier note, is where I think a lot more value lies in developing the project: the ability to accomodate so many different protocols on one system. Now, that has to have potential ....
Keep working on it
patrick
due to complaints about price i have considered a redesign and have found some components that will bring the cost down to ~ $15 for a single channel . I am looking at TOSlink devises, toshiba has recently put out a new line of optic TXs and RXs that will allow for a very dramatic price drop .
@ patrick
this system has nothing to do with a controller area network (CAN).fiber optics is a direct replacement for copper . in this case you can take a ttl level signal at baud rates ranging from 5mbs to dc send it down i fiber optic line and reconvert back to ttl . the specific protocol does not matter . this will work for any ttl signal whether it be RS-232 , can ,spi ,i2c, parallel ,pwm,pcm,ppm .
The problem with CAN/BUS is that one break in the network, of course depending where that break is, has the potential to shut down a whole bunch of servos, whereas one conventional servo control wire break with conventional setups will only ever effect one servo.
Although, admittedly I guess the question can be asked: just what are the chances in the first place of having a servo cable break - and truth is, so long as you've wired things up properly, then the chances are pretty small in the first place.
Still ........... accidents are just that - they happen because they are not anticipated.
The Beemer CAN/BUS blinker analogy?
Your Beemer will never fall out the sky if it has a CAN/BUS failure (worst case scenario: it will cruise to halt) - not so with your UAV!
servo companies are moving to this technology as in Futaba's SBUS and i am not trying to compete with the establishment on this . If I were to go down that road I would use open servo , i think the old servo drivers need to be replaced with this technology .
fiber optics would be neither synchronous nor asynchronous it just carries the signal . how ever it is purely one way.
Thanks for the heads up on the splitters . a quick google puts them around $6.00 US.
with economy of scale and moores law I hope eventually will make both of these technologys much more accesible to consumers . a good example of this in action is the fact that high end car manufacturs have been using fiber optics for tail blinkers . I figure if its good enough for you blinker on your beemer why not your servo on your Sukoi ?
Openservo I2C is a synchronous physical layer. A fibre is asynchrous. You will need another processor between openservo and the fibre.
To be popular you will also need to be compatible with standard servos. Not everybody wants to modify to openservo.
Any chance that you will use CANbus on the fibre? Get broadcasts, addressing, message filters, error checking, retries and hardware acceleration for not so much $.
audio toslink splitters are £3.80 in 50+ quantity. Maybe cheaper than your 7 extra fibre TRX ports.
@ ken
" uh, nothing is 100% " and i suppose you are 100% sure of this ?
I'm curious, did you try intermediate transmission systems before jumping to fiber? Did you try a differential signal over twisted pair to differential amplifier on the receiving end?
I think part of that is because you jumped in with "extreme" claims and offered to sell one part of something which is priced more than the entire system for the majority of people here. I think most people here are hands on folks who are put off by exaggerated marketing claims.
* world first fiber optic servo system
uh, maybe "first under $1,000 civilian fiber optic servo system" 'cause there's (cough) stuff we can't talk about.
* 100% RFI proof.
uh, nothing is 100%. Are the servo cases also shielded? Input power filtered?
Bottom line is that "always", "never", "100%" etc. bring bile to the mouths of engineers & technicians. Read Dilbert. Watch him face palm when the pointy haired boss makes product claims.
* complete electrical isolation between RX and servos (excessive current draw from servos will not cause battery voltage drop possibly leading to RX brown out and loss of control)
uh, if the servos are powered separately. But that isn't any kind of first.
I think if you had opened with something a little more modest you might have gotten a better reception. A rough draft might look like, for example, "For some time now I have been working on getting the RFI/EMI out of the servo lines and feedback into the receiver in a large UAV. Even optocoupler isolation wasn't enough in the environment we were facing because there were still long wire runs. The solution isn't inexpensive, but we were able to
1) use fiber optics between RX & servo to avoid long servo wire runs, thus limiting
a) picking up EMI and causing servo jitter
b) bringing EMI back in to the receiver
B) allow the use of a wide power supply voltage range and (optionally) an auxiliary battery to power servos reducing the risk of current draw induce brownouts of the receiver and other critical electronics.
This extreme solution isn't for everyone, but we hope to offer it for sale to those who need it before the end of this month."
Save the marketing hype for the glossy brochure. When us engineers, technicians, makers, and tinkerers gather in this place to hoist a cold one and chat we leave the salesman out in the car. Next round's on me. Whatcha havin'?
pls don't take it personally that some one is offended by this product. I am sure no one is offended or means to offend , We are diy community and therefore we try to do most of things ourself( if for nothing else but to just cut the costs or to do better than some one else most of the time to impress the community( I assume you are doing the same)) , and there starts every type of analysis and justification (for cost of any product on it usability value or technical value if that pleases you.) Cheers
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