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Old Mar 21, 2011, 06:47 PM
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335driver's Avatar
USA, TX, Round Rock
Joined Dec 2006
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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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Old Mar 21, 2011, 07:36 PM
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Bruce Abbott's Avatar
Hastings, New Zealand
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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.
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Old Mar 21, 2011, 08:48 PM
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Thanks for the explanation, Bruce. I really had no idea what it meant?
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Old Mar 22, 2011, 03:25 AM
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Letchworth, Great Britain (UK)
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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.
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Old Mar 24, 2011, 07:35 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
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Old Mar 28, 2011, 07:15 PM
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So how do you determine if you should cut the red wire on the esc.
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Old Mar 28, 2011, 07:48 PM
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Bruce Abbott's Avatar
Hastings, New Zealand
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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).
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Old Mar 28, 2011, 08:20 PM
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United States, FL, Melbourne
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Opto isolator.
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Old Mar 28, 2011, 08:26 PM
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San Jose, California
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Quote:
Originally Posted by Bruce Abbott View Post
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???
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Old Mar 28, 2011, 08:52 PM
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Bruce Abbott's Avatar
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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.
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