glass and electronic

[inse]

Don’t overcharge an electronics novice, it should be a readily available solution, I would suggest.
The electronics needs to be close to the sensor array, so it probably wouldn’t get smaller than something like in the eBay link.

[Analog Kid]

Good advice. Let's wait for the most easily implemented solution to appear here.

[inse]

Good advice. Let's wait for the most easily implemented solution to appear here.

Switch

[Andy Chee]

Let's not forget the second major design requirement by the OP, a timer of some sort.

My plan is to create a vessel that has rings around the outside that when I place a test tube into the ring it sets off a trigger and a water pump goes off on a timer.

Normally a 555 would be able to do this job.  But if the OP's requirement demands for a particular combination timing sequence of test tubes, then an Arduino may be better suited.

[Analog Kid]

Since the OP wrote

when I place a test tube into the ring it sets off a trigger and a water pump goes off on a timer

I think that means just one test tube triggering the event, and a timer that (I'm assuming here) turns the water pump off after a certain interval. So no need for a microcontroller, I don't think.

[Andy Chee]

I think that means just one test tube triggering the event, and a timer that (I'm assuming here) turns the water pump off after a certain interval. So no need for a microcontroller, I don't think.

So what happens when a second (or third) test tube is inserted before the timer runs down?  What happens to the timer when a test tube is removed?

It is this timing behaviour which the OP needs to describe.

[Analog Kid]

Well, sure, that's their job.
In the meantime, our job is to come up with a workable scheme for triggering a circuit by placing a test tube in a ring.

Seems like the foil-conductors-as-switch might be the easiest way to go here.

[inse]

Hannah, without basic electronic equipment like soldering iron, wires, side cutter, a multimeter and basic understanding of electronic components it will be hard to finish this project.
Are you familiar with Arduino programming already?
No one there to support you locally?
I mean if it’s part of your education, how could they throw all stuff at you which is far from your discipline and expect a result?

[Andy Chee]

Well, sure, that's their job.

And until the OP describes their proposed trigger-timer relationship, we cannot know whether a 555 or an Arduino is the simpler solution.

[nali]

I think a better approach woild be just to put a load cell in a base, and use the Arduino to continually check for the added weight of test tube(s). Google "Arduino weight sensor" for some ideas.

[Analog Kid]

So OP, @Hannah: Could you tell us how you intend this thing to work? Meaning what happens when, in what sequence, when test tubes are placed or removed. You don't need to use any technical terms, just explain the sequence of operation of the installation. That way we can figure out what's needed electronically to make it go.

Be as complete in your description as you can.

[Hannah]

hi, hope these pictures help to understand. the rings are hot attached and would like it to function by a snesor picking up on the test tube being put into the rings which then sets off the pump to let water through into the large vessel. hope this helps

[CatalinaWOW]

Even small microswitches are relatively large.  Opto-interrupters tend to be smaller and could be made to work in a variety of ways include having hinged flag that is pushed into the path by the test tube or using a transmitter-receiver pair and having a patch of paint on the test tube.

Hall devices can be tiny indeed, and adding a magnet to the test tube (or having the magnet on the ring with a ferrous pole piece on the test tube) would be very compact and reliable.

Ultrasound is another option which could be discrete.  The approach would be to sense the change in damping that occurs when the test tube is inserted.

Other questions come to mind.  Do you want any single test tube to start the action, or must all the rings be filled?  Do they have to be filled in a particular order, or does the order of filling change the rate or other character of the filling.   Does which ring is filled control how much fluid goes into the vessel?

Some of those operations would lend them selves to having an optical fiber between rings with the coupling path going through the test tubes (and thus changing the coupling). 

Other possibilities would include the use of polarized light in the sensor and quarter wave plates in the test tubes so that coupling was poor until the tubes are inserted.

A lot of this will depend on your artistic vision.  Maybe those on this forum can help once you have picked an approach that is consistent with your vision.

[Analog Kid]

hi, hope these pictures help to understand. the rings are hot attached and would like it to function by a snesor picking up on the test tube being put into the rings which then sets off the pump to let water through into the large vessel. hope this helps

Thanks. Don't want to bug you, but you didn't really answer the question. Since we can't read your mind, what exactly is the sequence of events you want to happen? Is it just the one test tube being picked up that you want to start the pump? And does the pump then go off after a certain interval?

If you could give us a complete description of the action, including everything that can happen to the device (like what if the test tube gets replaced before the pump goes off? things like that), it would really help people here to figure out how to implement this electronically. If the sequence is really simple, then the electronics should also be simple.

[Hannah]

sorry my bad. so i would like every test tube to be able to trigger of the water pump by putting it into the ring. yes so the pump will have to be coded through the arduino to only go off for a maybe 3 to 5 second interval then back off. ill just reexplain the whole thing i guess. what i want to happen is that any test tube being put in a ring will set off the water pump to let water out for a few seconds. i would like it to work that if there is no test tube in the ring the circuit will not be complete therfore the pump and valve are not activated so if the test tube gets taken out like you sugest to get replaced it willl just stop and start. so sequence should be test tube into ring pushes switch which completes circuit and sets the pump off and opens the valve for a few seconds then back off. hope this helps

[inse]

No need for Arduino, then - a simple timer circuit can do that.
If you don’t want to get into electronics, time relays are readily available as well.

[Hannah]

Hi everyone, Thank you so much for all of your help, I have got very far in this project and have learnt so much. I have gone with the reed switch option, thank you for the suggestion! so the left side of my breadboard is the 12V and the right is 5V, the arduino is coded so that when it recives input pin 11 on high (5v) which will be from the reed switch making contact to give the output on pin 8 for a few seconds. (i have got them in the wrong way in the picture i forgot to check the code properly). My question is with the reed switches, after soldering them to the wires, where do i put them in the breadboard to make it into a parallel circuit, i will have 4 to 5 reed swiches. thanks in advance 

[Andy Chee]

The way I understand your test tube behaviour, is that you want each individual tube to independently trigger the pump?

If that's the case, connecting the reed switches in parallel will not give the desired effect.  What would happen is that after one tube is inserted, subsequent tubes will have no effect.

Given that you've decided to go with an Arduino, I would give every reed switch its own separate input pin on the Arduino.  This also has the advantage of flexible timing changes by simply rewriting some code.

[Hannah]

that is a very good point, i hadn't thought of that. thank you!!

[daqq]

The simplest solution is indeed a microswitch of some sort - this is electrically trivial. They come in small forms and it might be possible to hide them in a way that does not distract from the art too much.

If you can use custom test tubes, it might be possible to embed a single loop of wire and sense that with a single turn inductor? That could be discrete enough.

There's probably a bunch of more exotic techniques that do not require visible wiring on the sculpture itself, like tuned mechanical glass resonators that get de-tuned when a tube is inserted, visual inspection (a camera and image processing), possibly some fiber optics with invisible light doing the actual detection, or even these fellows: https://www.rvmagnetics.com/ , but these would require a lot of skill to implement. Like 95% of the time of the whole project 

Good luck with your project!

[Kasper]

Congratulations, I think you have made it through the hardest steps.

Here are some limit switches you could use:
https://www.digikey.ca/en/products/filter/limit-switches/198

I would mount to the underside of the ring so it presses against the side of the test tube.

If you want to reduce the number of wires, there are other options but that will likely complicate it.

[Hannah]

Hi, me again!
i have sorted all the electronics out and there seems to be a problem somewhere, starting off with the code i am just checjing through everything. is there anyone on here that could check this code for me. thank you. i want the script to do the following : switch pin 8 high for 5 seconds when any of the pins 9, 10, 11 and 12 are high. (high being 5 volts from the reed switch). thank you
// Define the pins
const int pin9 = 9;
const int pin10 = 10;
const int pin11 = 11;
const int pin12 = 12;
const int outputPin = 8;

// State variables
bool isOutputHigh = false;
unsigned long outputStartTime = 0; // To track how long pin 8 is HIGH

void setup() {
  // Set input pins
  pinMode(pin9, INPUT);
  pinMode(pin10, INPUT);
  pinMode(pin11, INPUT);
  pinMode(pin12, INPUT);

  // Set output pin
  pinMode(outputPin, OUTPUT);

  // Ensure the output starts LOW
  digitalWrite(outputPin, LOW);
}

void loop() {
  // Check if any of the input pins is HIGH
  if (digitalRead(pin9) == HIGH || digitalRead(pin10) == HIGH ||
      digitalRead(pin11) == HIGH || digitalRead(pin12) == HIGH) {

    // If pin 8 is not already HIGH, activate it and record the time
    if (!isOutputHigh) {
      digitalWrite(outputPin, HIGH);
      isOutputHigh = true;
      outputStartTime = millis(); // Record the time pin 8 was set HIGH
    }
  }

  // Check if pin 8 has been HIGH for 5 seconds
  if (isOutputHigh && millis() - outputStartTime >= 5000) {
    digitalWrite(outputPin, LOW); // Turn off pin 8 after 5 seconds
    isOutputHigh = false;         // Reset the state
  }
}