Using Fibre Optic to Switch a Voltage?

[sjohnr]

I have a slightly bizarre control problem.

We have a solenoid operated hydraulic control valve at a remote location. The solenoid is operated by a 24 Vdc supply. There is a plentiful supply of 24 Vdc at the remote location but the only link to the remote location is by optical fiber, of which there are plenty of spare ways that could be used.

In the interests of keeping the cost down, and keeping the system simple, is there a product available that would act as a relay, switching the 24 Vdc in and out depending on the presence of light at the end of the fibre?

 

[jacekd]

Hi,
If you have some skills in electronics you could built it by yourself useing any optotransistor.
Other solution (almost off the shelf) which came to my mind:
take two identical fibreoptics photocells (for separate transmitter/receiver fibres),
use one as a light source - wire it in such a way so you could switch it on/off;
second use as receiver only and to the output wire relay suitable to switch you valve solenoid.

Regards,

Jacek

Do it right or don't do it at all.

 

[nbucska]

<

http://www.keyence.com>

has what you need.

<nbucska@pcperipherals.com>

 

[sjohnr]

Gents,

Thanks to both of you for your good suggestions.

Since the "communictaion" is one way, I am thinking of using an emitter and detector module at each end of the fibre. Although these seem to be designed for comms systems they are cheap. I just need to get hold of a data sheet and work out if it's feasible and how to do it.

Any other thoughts would be appreciated.

Thanks again.

 

[electricuwe]

Keep in mind that there are lots of different kind of optical fibres (diameter, material,..), each requiring special kind of receivers and transmitters.

 

[nbucska]

If you want more, we need the switched 24V current, the
distance.

Why only optical fiber? The requirement as you told could be satisfied with a piece of string...

Is it explosion danger or HF noise insulation?



<nbucska@pcperipherals.com>

 

[sjohnr]

I can't imagine any control systems engineer reading my question and believing that a piece of string would do the job. I've already stated the objective, low cost and high reliability, which we intended to achieve by keeping the system simple. Why only optical fiber? As I've said in the question, because that's all we've got linking the center to the remote location.

The distance is 10.6 km. The current to be switched is about 80 mA.

I am not asking anybody to design it for us, I was asking for suggestions on how it could be done.

 

[nbucska]

The originel requirements were:
Switching 24V from remote location, simply, using fiber optics.

The word "remote" may mean from 1 mm to 100 lightyears.

Any engineer can solve a problem only if the necessary
data are specified.

You still haven't told us everything: e.g. there is a
10.6 km fiber cable -- is it/intended_to_be used for
something else, too, or only for this switch.

In the first case we must know the other system if
the switch is supposed to coexist with it.

What is the swithing rate, required switching spead, reliability ? MTBF? error rate? Is the switched load
inductive ? is yes, its data ?


<nbucska@pcperipherals.com>

 

[sjohnr]

For a control systems engineer the word remote does not mean 1 mm.

Again, I am not asking anybody to design the system. We are doing that ourselves right now.

 

[nbucska]

The solution may be trivially simple, difficult or impossible depending on data. Nobody can help with any confidence of correctness without knowing a lot
more than you have told us.

Do you need expert advice or wild &*^% guesses?

Forgive me for being inpatient but it is frustrating to
spend usually more time on extracting necessary data
from the inquirers than on solving the actual problem.

Why don't you just neglect it and answer the questions?


<nbucska@pcperipherals.com>

 

[sjohnr]

nbucska,

I really appreciate your concern over this but the information provided by others (and you) at the start of the thread was actually all I needed to start the design of the system. I think you should put your energy in to some other thread.

Thanks anyway.