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Electronics => Beginners => Topic started by: Houseman on May 07, 2021, 06:22:37 am

Title: Transfer 10mA square wave through glass
Post by: Houseman on May 07, 2021, 06:22:37 am
Hi forum.
Sounds strange but I need to transfer a 10mA square wave (period 3ms duty cycle 20%) (-15V +15V) signal through a dividing glass I cannot drill with wires.
I have a generator that outputs with two wires: signal wire + ground (return) wire to the transducer but the problem is that the transducer needs to be inside a glass and completely sealed. No leakage is allowed so no wires has to cross the sealing.
First question is: is such a device possible?
I was thinking of an inductive transfer but the problem is if I can transmit square waves.
Do I need to code them?
Could you please point me to some direction?
Thank You so much
Steve
Title: Re: Transfer 10mA square wave through glass
Post by: Robert Smith Eco Warrior on May 07, 2021, 06:48:40 am
Glass is a good insulator so I don't know how you would directly conduct a signal. Could you have an infrared led one side and reciever the other side to pass the signal through the glass?
Title: Re: Transfer 10mA square wave through glass
Post by: TopGun on May 07, 2021, 06:57:42 am
Maybe some kind of optical isolating transfer? You can square it up with an opamp later...
Title: Re: Transfer 10mA square wave through glass
Post by: Twoflower on May 07, 2021, 07:31:21 am
The question I have is: Do you want to transfer the information, the energy or both?

If it‘s just the information you could amplify a weak signal after detecting it at the receiving end of the fiber. Think of it like a really long opto insulator.

Transfer energy is much harder to archeive. But there are solutions to get energy to the receiving end (reasonably powerful laser and photovoltaic cells at the receiving end). But that has losses. If you can‘t amplify the signal you can‘t use that.
Title: Re: Transfer 10mA square wave through glass
Post by: nfmax on May 07, 2021, 07:41:45 am
I don't know the details of your glasswork, but hermetic glass-to-metal seals are a well known technology (think thermionic valves). You may be able to use one with a low temperature glass frit seal to your glasswork?
Title: Re: Transfer 10mA square wave through glass
Post by: Houseman on May 07, 2021, 07:42:38 am
Thank You all.
In reality I need to transfer both (energy + information).
The glass is not such thick (think about a lab becher). The fact is that the glass can be further replaced with non light-transparent material.
So as far as I understand, it is better to transfer energy and then let al the circuitry inside right?
Regards 
Title: Re: Transfer 10mA square wave through glass
Post by: Brumby on May 07, 2021, 10:41:07 am
It would be a whole lot easier to offer useful suggestions if you can be more specific about what you are actually trying to do, rather than get us to blindly present ideas to a narrow view of the problem.

When the full scenario is outlined, other options become apparent - and better solutions can often be found.
Title: Re: Transfer 10mA square wave through glass
Post by: MasterTech on May 07, 2021, 11:02:17 am
Your problem needs to be split in two:
1) Powering the circuit inside the glass/plastic or whatever non-conductive material you need. For this you need a transformer primary outside and a secondary inside
2) Transmitting the signal, via optical means in case of translucent material or transformer for opaque materials.
Title: Re: Transfer 10mA square wave through glass
Post by: Zero999 on May 07, 2021, 12:43:12 pm
Again this sounds like an X Y problem. Can we please see the bigger picture?

The power is 150mW, so a transformer is the only sane way to do this. It can be used to transmit both power and data. Don't transmit the actual signal. Use a much higher frequency and signal between high and low levels,  by changing the frequency slightly; a technique known as frequency shift keying.
Title: Re: Transfer 10mA square wave through glass
Post by: Robert Smith Eco Warrior on May 07, 2021, 01:00:30 pm
Your problem needs to be split in two:
1) Powering the circuit inside the glass/plastic or whatever non-conductive material you need. For this you need a transformer primary outside and a secondary inside
2) Transmitting the signal, via optical means in case of translucent material or transformer for opaque materials.
good idea about the split transformer.  :-+
Title: Re: Transfer 10mA square wave through glass
Post by: David Hess on May 07, 2021, 10:39:55 pm
With some cleverness, the same split transformer can be used for power and information transfer.
Title: Re: Transfer 10mA square wave through glass
Post by: wizard69 on May 07, 2021, 10:58:41 pm
I don't know the details of your glasswork, but hermetic glass-to-metal seals are a well known technology (think thermionic valves). You may be able to use one with a low temperature glass frit seal to your glasswork?

I'd look into this, that is glass to metal sealing, as the best way forward.   Old tubes easily accommodated 8 pins and many more for certain types of tubes.   You apparently have electronics inside the glass already so adding wires shouldn't be a problem.   

Of course doing this isn't easy if you are not familiar with glass work.   You may be able to get help from a local glass blower or even somebody working with neon lights.    Glass blowers often have been called upon for custom laboratory glass, so it might help to check with a local university or research center.   

Of course going this route pretty much makes for a permanent container so that might be an issue.   There are other ways to go if you have a two part container, that is a container with a plug or lid.
Title: Re: Transfer 10mA square wave through glass
Post by: Marco on May 08, 2021, 12:09:48 am
Since this is in the beginners forum ... solve the power transfer with modules : https://www.adafruit.com/category/331 (https://www.adafruit.com/category/331)

What's left is sending a square wave with a LED and receiving it with a phototransistor and creating the the 30v peak to peak signal inside the glass.
Title: Re: Transfer 10mA square wave through glass
Post by: MIS42N on May 08, 2021, 09:34:31 am
A quick read says common inductive power transfer works above 100kHz. Could you modulate that to transfer your information? Swap between two frequencies and detect that to recreate the square wave. It would not be instantaneous, the receiver would have a delay. Alternately inject a small amount of RF (garage door opener frequency) for on, pick that up in a suitable receiver.
Title: Re: Transfer 10mA square wave through glass
Post by: radiolistener on May 08, 2021, 04:50:30 pm
It looks like RFID technology, so you can use it.
Title: Re: Transfer 10mA square wave through glass
Post by: geggi1 on May 08, 2021, 05:34:00 pm
You should loock in to inductive transfer.
Possible if you need to power a circuit and  use inductive power transfer almost like a inductive charger for a mobile phone. The signal in return could be som kind of optical transfer possible your signal modulated on top of a led source with a photo diode as detector.