What does OPTO mean? - RC Groups
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Mar 21, 2011, 07:47 PM
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335driver's Avatar
Question

What does OPTO mean?


I was looking at an Exceed RC 80A ESC and it said 80A OPTO
(without BEC) I know that means you need a separate BEC unit wired in to provide power to rcvr & servos. Is that all OPTO means? Or is it something else. I have several Exceed RC ESC's and they seem to work for me. Anyone else use these or am I swimming against the flow?

Thanks
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Mar 21, 2011, 08:36 PM
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Bruce Abbott's Avatar
OPTO is supposed to mean 'opto-coupled', where the throttle signal is coupled into the ESC via a light beam. The idea is that there is no direct electrical connection between the receiver and the business end of the ESC, therefore stopping electrical inteference from travelling down the wiring into the receiver.

However there quite a few cheap 'OPTO' ESC's available that don't have an opto-coupler, and should really just be called 'No-BEC'. For most applications these work fine. If you have a 2.4GHz radio then interference won't be a problem, and if you connect an external UBEC to the motor battery then it bypasses the opto-coupler anyway.
Mar 21, 2011, 09:48 PM
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335driver's Avatar
Thanks for the explanation, Bruce. I really had no idea what it meant?
Mar 22, 2011, 04:25 AM
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If it's a real opto ESC, you always need to use all three wires to the receiver. Don't cut the red one, like you normally do with a regular ESC, when using a separate receiver power supply.
Mar 24, 2011, 08:35 PM
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Hi Guys .. I have a Jeti JES 40 - 3P OPTO ( 6 - 10 NC ) that I used with a nicad
powered plane. My question is ... can I use it with a 3S lipo battery ? Any information
will be appreciated.

Rosie
Mar 28, 2011, 08:15 PM
Registered User
So how do you determine if you should cut the red wire on the esc.
Mar 28, 2011, 08:48 PM
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Bruce Abbott's Avatar
Try powering the receiver directly from the ESC (no receiver battery or external UBEC). If this works then the ESC has an internal BEC, so you should cut the red wire when using an external receiver power source.

If the receiver dosn't work directly off the ESC then it does not have an internal BEC, so you should not cut the red wire (this applies to all 'OPTO" ESC's).
Mar 28, 2011, 09:20 PM
Registered User
Opto isolator.
Mar 28, 2011, 09:26 PM
Dude, I do fly all day long!
rcalldaylong's Avatar
Quote:
Originally Posted by Bruce Abbott
Try powering the receiver directly from the ESC (no receiver battery or external UBEC). If this works then the ESC has an internal BEC, so you should cut the red wire when using an external receiver power source.

If the receiver dosn't work directly off the ESC then it does not have an internal BEC, so you should not cut the red wire (this applies to all 'OPTO" ESC's).
I've been cutting all the red wires or at least not plug them in...(even opto ones)

if you don't cut the red wire off and it plugs into the receiver, I take it this would share the same place (plug) with the power wire from the external BEC. Is that the recommended setup???
Mar 28, 2011, 09:52 PM
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Bruce Abbott's Avatar
A true opto-isolated ESC will not work if you cut the red wire. It needs 5V from the receiver to power the input side of the optocoupler.

You can wire an external BEC into the ESC's servo cable, and you can even use the red wire to feed battery voltage into it (but you will have to re-route the wire to battery +ve at the ESC end). You also need to splice into the negative (black/brown) wire. Doing it this way eliminates extra wiring, and frees up an extra channel on receivers that don't have a dedicated battery port. However it may be a bit tricky to impliment.

Alternatively you can just use a Y cable, but this is bulkier and may reduce reliability (one extra connector for the power to go through). It's best to wire the UBEC directly onto one leg of the Y cable.
Dec 11, 2016, 10:20 PM
Embedded system developer
RandallM's Avatar
Quote:
Originally Posted by Bruce Abbott
OPTO is supposed to mean 'opto-coupled', where the throttle signal is coupled into the ESC via a light beam. The idea is that there is no direct electrical connection between the receiver and the business end of the ESC, therefore stopping electrical inteference from travelling down the wiring into the receiver.

However there quite a few cheap 'OPTO' ESC's available that don't have an opto-coupler, and should really just be called 'No-BEC'. For most applications these work fine. If you have a 2.4GHz radio then interference won't be a problem, and if you connect an external UBEC to the motor battery then it bypasses the opto-coupler anyway.
Bruce,

If it means optical (via a light beam) - and I'm not doubting you, then why don't any of the Escs I find out there including supposedly high end devices recommended on this forum, have a fiberoptic cable? The three servo wires are just that - copper wires. Copper does not carry photons. I'm confused.

I realize the post I"m responding to is almost 7 years old... but maybe somebody can answer this.
Dec 11, 2016, 11:32 PM
Registered User
Quote:
Originally Posted by RandallM
Bruce,

If it means optical (via a light beam) - and I'm not doubting you, then why don't any of the Escs I find out there including supposedly high end devices recommended on this forum, have a fiberoptic cable? The three servo wires are just that - copper wires. Copper does not carry photons. I'm confused.

I realize the post I"m responding to is almost 7 years old... but maybe somebody can answer this.
https://jaenal91.files.wordpress.com/2009/02/bb.jpg

Just because an asphalt road leads to both naval ports, doesn't mean that there is also a road in between both naval ports.

The gap in copper takes place inside the opto-coupler chip onboard the ESC. Much smaller, cheaper, and more energy efficient than fiber optic cables. Keep in mind that fiber optic is used to provide high-speed, long distance NOT noise immunity, but their inherent noise immunity provides much benefit for long distance transmission. But if all you're looking for is noise immunity, there are other cheaper, more effective solutions.

There are other types of chip-based galvanic isolators that exist too, capacitive, microscopic transformers , and RF transmission that happens over chip-scale distances.
Last edited by DKNguyen; Dec 12, 2016 at 12:12 AM.
Aug 08, 2017, 09:07 PM
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aerografixs's Avatar
Quote:
Originally Posted by DKNguyen
https://jaenal91.files.wordpress.com/2009/02/bb.jpg

Just because an asphalt road leads to both naval ports, doesn't mean that there is also a road in between both naval ports.

The gap in copper takes place inside the opto-coupler chip onboard the ESC. Much smaller, cheaper, and more energy efficient than fiber optic cables. Keep in mind that fiber optic is used to provide high-speed, long distance NOT noise immunity, but their inherent noise immunity provides much benefit for long distance transmission. But if all you're looking for is noise immunity, there are other cheaper, more effective solutions.

There are other types of chip-based galvanic isolators that exist too, capacitive, microscopic transformers , and RF transmission that happens over chip-scale distances.
I will be setting up a video shortly . but for now, here are a few other facts. Some years ago people started using two receivers to equalize the amperage load on large airplanes with multiple servos . Not for redundancy.
But there is a better , never plug the servos , any servos directly into the receiver. Let the servos have there own larger battery and the receiver can operate on a smaller lighter battery. How you may ask, well a few ways, one is to connect the negative of both batteries together and the positive of the smaller battery for the receiver, and the positive of the larger battery for the servos. Simple but there is a slight problem with this setup, the servos and receiver still has an electrical connection in common , the negative wire. You might ask "so what?" Here is why, if for any reason at any time, a servo goes bust, caput, it can and usually will feed back to the receiver , and guess what that does, you got it, fail safe with no chance of recovery, "crash" not good.

You need to isolate and I mean totally isolate the two batteries optically so if that servo goes bad, it might start draining the servo battery but the receiver is intact and continues working perfectly.
Another reason to optically isolate the receiver from the servos, is there is never any current spikes and receiver works at its optimum, yes better, much better, no more brown outs, no more current spikes , just clean signal.

There other reasons, for instance I am presently using a radio system with 8 channel receiver but I can get the full 16 channel by using Sbus system, yes other then Futaba has this possibility. but the problem with SBus on my 50% Dalotel or 55% Pitts special is you have 4 channels for each decoders, add another 3 decoders for the full 16 channels, all coming from a single output on the receiver with a 22 gauge wire which can support an grand maximum of 7 amps, not a good prospect. and yes I am using the full 16 channels this way on the Dalotel, Ok here is how I do it . instead of plugging servos on the Sbus decoders, I plug in the Fiber Optic encoder, draws less then 20 ma each so now you have 16 times 20 ma and you have 320 ma plus what the receiver draws lets say another 30 ma for a grand total of 350 ma. you can see why lets say 1000 ma lipo would work very well , then on the other end of the fiber optic cable, you have the decoder which draws less then 15 ma each, so you have a total of 240 ma,
Now each decoder supports a servo or many servos , I prefer to use one servo each so each servo has its own channel.
Now we come to the servo battery/batteries, this battery powers all the decoders plus all the servos used
Another tidbit , the reason most radios today are not very good at handling more then two servos on one output is simple, the signal output voltage is a bit more then 3 volts, so you can see where this would be a problem, now with Fiber Optic extensions, the decoder produces the same signal voltage you use from the servo battery, in my case 7.4 lipo,
Once I have a decent video, which I'm not very good at making I will post it here. stay tuned
Aug 09, 2017, 12:36 AM
I am a nice guy! Really!
@Aerografix: You have taken an old thread discussing an Opto coulpled servo signal to an ESC and started a completely different topic about isolating servos from the receiver battery. It would probably be better if you started a new thread in the Radios section instead of doing in this thread.
Aug 09, 2017, 06:18 AM
Registered User
aerografixs's Avatar
Quote:
Originally Posted by Mike Dubovsky
@Aerografix: You have taken an old thread discussing an Opto coulpled servo signal to an ESC and started a completely different topic about isolating servos from the receiver battery. It would probably be better if you started a new thread in the Radios section instead of doing in this thread.
actually the post just before mine was more or less replying to his about fiber optic


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