Before The Plunge...

[Science_Guy]

Hi Guys,

I'm happy to admit that I'm a complete novice in the world of computing and the Pi!

I was looking for a very simple answer to what I'm sure is a very simple question for people well versed with Pi:

I have a "system" in a laboratory which is required to "speak" to a light - essentially to turn it on and off when requested. The system is capable of digital and analog output/input with 1V pings, which I'm hoping could be interpreted by the Pi and converted into the on/off commands of the light at specific times. The light source will be 12V.

Is this something that the Pi is capable of doing?

Any help would be massively appreciated as the work going into this (if it is indeed possible) will be for a large research charity in the UK.

Best Wishes,

SG.

[karrika]

What is a 1V ping that works on digital and analog inputs/outputs?

[Science_Guy]

What is a 1V ping that works on digital and analog inputs/outputs?

Hi karrika,

Thanks for the reply.

I'll PM you the I/O box I would be using.

[B.Goode]

It's up to @karrika how he deals with this, but my preference would be to continue the discussion on these forums so that the whole community can benefit.

[Science_Guy]

It's up to @karrika how he deals with this, but my preference would be to continue the discussion on these forums so that the whole community can benefit.

Hi B.Goode - I'm more than happy to post it here too:

https://www.gelifesciences.com/gehcls_i ... 210201.pdf

This is the I/O box and equipment that would be used during this study.

Again, any help confirming whether this is plausible or not would be greatly appreciated.

[B.Goode]

After a quick first look...

My reading would be that the I/O box you have is designed to be connected, using some closed and proprietary communications protocol, to a larger system that contains an AKTA controller, using the built-in "Uninet-9" connection.

That's not to say that some 'hack' ie. use of the kit in an unexpected way might not be possible. But using the kit outside its design spec might invalidate the readings you get and thus the integrity of your research.

Some research only succeeds because of a refusal to accept that something is not possible. I don't think there is enough detail in the linked document to help you interface it to an RPi, either electrically or in terms of the data that will be generated.

[Science_Guy]

Thanks for taking the time to look B.Goode

For clarification of the set-up; the I/O box would be connected to the AKTA system using a Uninet-9 connection, but it would also be connected (via any of the other available ports) to the RPi which would in-turn receive a signal from the AKTA via the IO, and convert to on/off signal for a lamp.

AKTA -> I/O Box -> RPi -> Lamp

There's no feedback required from the light or RPi, all that is required is to literally just turn it a light on and turn it off at specific times during the study (without someone having to run in and out of the lab to physically flick the switch!). Most of this work would be carried out overnight currently, meaning some sacrificial member of staff would be waiting for the "big switch".

Would the RPi be able to receive input information from this kind of connection at the I/O box

[B.Goode]

So looking at the tables on pages 5 and 6 of the document, you have 4 digital outputs that are simply open/closed circuits.

On the face of it, that should be trivial to interface to the gpio pins on the header of an RPi.

You might like to look at the programming examples for gpiozero to see how easy it is to get the RPi to react to changes on a gpio input. https://gpiozero.readthedocs.io/en/v1.3.1/

[drgeoff]

If you only want a 1 volt = on, 0 volt = off signal to switch a lamp on and off, a RPi would be totally unnecessary. A RPi is incapable of directly switching enough power for any lamp other than an indicator LED. It sounds like you will need a relay and there are easier and cheaper ways to interface that to a steady state control signal than using a RPi.

[B.Goode]

You will need external circuitry to allow the 3.3v and tiny current capability of the RPi gpio output pin to control the 12v and significant current light source. (And unless you need anything 'smart' doing with the signal, the suggestion that the RPi is redundant is worth considering!)

[Science_Guy]

Thanks very much both of you for your input.

I'm looking to do exactly what @drgeoff has just described. Nothing fancy, I'm just looking to save dedicating an entire human-being to light-switch duty during the night!

Would you be able to point me in the correct direction for assembling a relay/steady state control signal device? Is this more basic electronics than computing?

[drgeoff]

Yes, nothing to do with computing. Just basic electricity and perhaps some electronics. The GE document does not contain sufficiently detailed information about the digital outputs to advise you further other than to say you should consult a local qualified electrical technician who can physically examine both the I/O box and the lamp you propose to control.

It is possible that the I/O box contains 'volt free' contacts which could directly switch the 12 volts supply to the lamp. But is is also possible that the output cannot handle the lamp current and/or that although you say the lamp is 12 volts, that figure refers only to the bulb but the complete item is mains powered. Using the I/O box to switch mains electricity would be extremely dangerous and against all safety regulations.