www.robowars.org

RoboWars Australia Forum Index -> The Marketplace

Opto Isolation
Goto page Previous  1, 2

Post new topic   Reply to topic

How Many Channels do you want
1
0%
 0%  [ 0 ]
2
0%
 0%  [ 0 ]
3
100%
 100%  [ 5 ]
Total Votes : 5

  Author    Thread
Nexus
Experienced Roboteer


Joined: 17 Jun 2004
Posts: 903


 Reply with quote  

Well put me down for one for the IBC.

Glad I prompted you about this little black box.

I think 2 channels will do me as the third channel is going to be used as an invert switch so unless it is recommended for this channel as well then 2 will do. cheers.

On a similar subject has anyone tried shielding their reciever.
Documents I have found suggest Caps, twisting wires, running them through braid placing reciever in metal box and isolaton.

What could yu use to shied the reciever, alumium foil, lead box or something in between.
A more dirrect question is does shielding work if you just use a plate or a wall between the components or does it have to be encased in something in a full metal jacket.
Oh yeah last lame question is do all metals shield
_________________
Bots that do not destroy you, only make you stronger.

Post Thu Oct 14, 2004 9:19 pm 
 View user's profile Send private message
Timothy Forde
Experienced Roboteer


Joined: 16 Jun 2004
Posts: 247
Location: Vic ,Belgrave South


 Reply with quote  

well I think minimower has foil over there resiver? but you need to talk to gary about that I guess on it's effect
_________________
Team KO

Post Thu Oct 14, 2004 9:25 pm 
 View user's profile Send private message Send e-mail MSN Messenger
Glen
Experienced Roboteer


Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect


 Reply with quote  

i shielded the reciever in a steel box which i grounded to the chassis once and didnt the other time.

both setups gave me worse range. thats just my experience.

but george i *think* youll have to have one on every channel you use as the reciever will then be powered of the BEC and a reciever battery. not sure if the rx will like that.. jake?
_________________
www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

Post Thu Oct 14, 2004 9:42 pm 
 View user's profile Send private message Send e-mail Visit poster's website MSN Messenger
kkeerroo
Experienced Roboteer


Joined: 17 Jun 2004
Posts: 1459
Location: Brisbane


 Reply with quote  

A great way to shield your receiver and other related gear is to buy one of those Aluminium project boxes from Jaycar or Dick Smiths. And if you have the know-how grounding the box to the receiver by conecting a wire from the negative terminal of whatever is supplying power to the receiver directly to the metal box helps muchly. I use this shielding method when testing partially assembled electronic gizmos at work and it has doubled my pass rate Wink .

Or you could just wrap the receiver in al-foil.
_________________
Get Some!!!

Secretary of the Queensland Robotics Sports Club inc.

Post Fri Oct 22, 2004 6:02 pm 
 View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
Valen
Experienced Roboteer


Joined: 07 Jul 2004
Posts: 4436
Location: Sydney


 Reply with quote  

we found that foil only had a marginal improvement.
i think its probbly because of the magnetiv fields causing problems possibly
_________________
Mechanical engineers build weapons, civil engineers build targets

Post Fri Oct 22, 2004 7:11 pm 
 View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger ICQ Number
Nick
Experienced Roboteer


Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW


 Reply with quote  

I have to agree with Jake. Receiver shielding did almost nothing for me with the IBC. In our particular situation with the IBC, Jake has proven its noise carried or induced in the receiver leads. Sheilding never hurts but the opto isolation is the best bet.
_________________
Australian 2015 Featherweight champion
UK 2016 Gladiator champion

Post Fri Oct 22, 2004 10:43 pm 
 View user's profile Send private message
Knightrous
Site Admin


Joined: 15 Jun 2004
Posts: 8511
Location: NSW


 Reply with quote  

We removed our radio problems by actually setting the aerial system up better. We can easily get 10m with the aerial retracted and a good 30+m with the aerial extended. The UK guys even found buy using tuned aerials, instantly the IBC worked like a charm.

It's like giving a deaf man glasses when he cannot hear.....
_________________
https://www.halfdonethings.com/

Post Sat Oct 23, 2004 12:00 am 
 View user's profile Send private message
Valen
Experienced Roboteer


Joined: 07 Jul 2004
Posts: 4436
Location: Sydney


 Reply with quote  

more akin to giving a man with perfect hearing a hearing-aid whilst you talk to him from 5 meters away with a megaphone.
problem is you are in the middle of a rock concert.

the opto isolation moves the rock concert next door.

look at RC cars and aeroplanes, they regularly get ranges well in excess of 1km. with the signal strengths involved we should be able to run with any old ball of wire as an antenna and get 30-50 meters. With a vertical quater wave antenna a ground vehicle should get at least 250 meters and more like 500.
_________________
Mechanical engineers build weapons, civil engineers build targets

Post Sat Oct 23, 2004 1:05 am 
 View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger ICQ Number
kkeerroo
Experienced Roboteer


Joined: 17 Jun 2004
Posts: 1459
Location: Brisbane


 Reply with quote  

My home made speed controllers (used in Hellbringer 1 and The Aggressor) hade optocouplers between the receiver and the speedos and we had no radio range problems AT ALL despite the use of the old 2ch AM radios with the antennas coild up inside the robot.
Also sheilding around the receiver (including al-foil) will be greatly improved if the shielding is grounded (as I said above).
_________________
Get Some!!!

Secretary of the Queensland Robotics Sports Club inc.

Post Sat Oct 23, 2004 12:17 pm 
 View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
Nexus
Experienced Roboteer


Joined: 17 Jun 2004
Posts: 903


 Reply with quote  

Was looking at a website for BioHazard and found a mention of the use of Magnesium as a bulkhead material.
Doing something similar in that am trying to put up walls to seperate components but am considering options for materials.

Things can be grounded fair enough but what about magentic fields.
Question is does anyone know the qualities of Magnesium that would make it suitable for this application.
Would rather put up a wall instead of Al Foil particularly if this wall has other screening purposes.

And one more question, what sort of interference can your batteries cause if you had your reciever an inch away from them.
Do batteries create more interference when they are using more current and get hot and is this magnetic interference or is it something else.
_________________
Bots that do not destroy you, only make you stronger.

Post Sat Oct 23, 2004 3:33 pm 
 View user's profile Send private message
Glen
Experienced Roboteer


Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect


 Reply with quote  

i wouldnt think batteries would cause rfi, more likely the wires from the batteries would induce the interference. in this case you can just twist the wires.
_________________
www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

Post Sat Oct 23, 2004 4:13 pm 
 View user's profile Send private message Send e-mail Visit poster's website MSN Messenger
kkeerroo
Experienced Roboteer


Joined: 17 Jun 2004
Posts: 1459
Location: Brisbane


 Reply with quote  

Magnetic interference is not much of a problem, it is the radio frequency interference (rfi) you need to look out for. Rfi is an electrical signal that can be generated by the brushes of a motor, the switching on and off of a motor or switch mode power supply or even by any metal parts rubbing together (lots of things can cause rfi, it is very hard to trace). This rf electrical signal affects every part of the circuit and is why opto isolation is effective as it is a way of seperating circuits (for those who don't know opto isolaters pass a signal as beam of light, there is no electrical path through the device). The rfi noise may be transmited to other devices by turning the entire circuit into a transmiting antenna where it is picked up by the circuits nearby (example: overhead flourecent lights). This is what shielding is for as radio waves will not pass through the GROUNDED sheilding and into the delicatly tuned receiver.
Yes, twisting wires together helps but there is lots of theory to explain why so I wont explain.
It is also important to seperate power and signal wires as much as posible so placing the receiver away from batteries and not running battery and servo lines together is something to keep in mind (this is because of the rfi transmiting as above).
_________________
Get Some!!!

Secretary of the Queensland Robotics Sports Club inc.

Post Sat Oct 23, 2004 5:21 pm 
 View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
kkeerroo
Experienced Roboteer


Joined: 17 Jun 2004
Posts: 1459
Location: Brisbane


 Reply with quote  

Just thought about it some more.
I good way to explain rfi transmision is to think of a bell being struck. The bell being an electric circuit.

The object striking the bell is what is causing the vibrations (RFI) in the bell.
These vibrations will spread throughout the bell causing the whole bell to ring.
The vibrations can be dampend by, say, putting cloth over the bell (filtering caps on motors) but will not completly stop the ringing.
The vibrations will be transmited as sound causing nearby bells to vibrate.
But placing sound dampeners between the bells will stop the vibrations being transmited (GROUNDED shielding).

Hope that hekps the hard of thinking.
Also, magnesium was used in Biohasard because it is a very light weight metal, not for any particular shielding properties.
I also enphasise the term GROUNDED beacause I don't like people saying that shielding does not work when thier shielding is not correctly GROUNDED!
_________________
Get Some!!!

Secretary of the Queensland Robotics Sports Club inc.

Post Sat Oct 23, 2004 6:11 pm 
 View user's profile Send private message Send e-mail Yahoo Messenger MSN Messenger
  Display posts from previous:      

Forum Jump:
Jump to:  

Post new topic   Reply to topic
Page 2 of 2

Goto page Previous  1, 2

Forum Rules:
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

 

Last Thread | Next Thread  >
Powered by phpBB: © 2001 phpBB Group
millenniumFalcon Template By Vereor.