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Building a liquid monitor box help Answered

Hello. I have little experience with these things so I am seeking help here.

I have a prototype design for a liquid drop monitor. There is a tube that drip liquid and be detected by a photodiode hooked up to an Arduino. My question is about how to build an enclosure for it subject to my requirements. If anyone has advice for any of my needs below, the help would be much appreciated. I am not very knowledgeable of these kind of things.

The circuit is in in two parts on two small breadboards, the detector on one side and an LED on the other. A tube will go through the box vertically from top to bottom. The box will be made out of acrylic because it's cheap, see-through, and I have access to a laser cutter.

First question, how can I mount these breadboards in the acrylic box in such a way that I can remove them when needed or later replace them with a PCB later.

Second, what sort of mechanical device can I use to adjust the distance between the LED and the detector? Essentially, I just need to be able to move the LED towards and away from the detector in one dimension.

Third, I will need to change out the tube often to adjust the thickness. How could I allow for adjustable sizes? If the tube hole is the same size then I will only be able to fit one. Alternately, I could move the detector and LED horizontally to select different tubes. Is there a mechanical device for this?

Fourth, I'm using acrylic because it's cheap and I have access to a laser cutter, but most designs for boxes I've seen are not made to be opened. I will need to be removing and rewiring things often. So is there a common or easy way of making/mounting a hinged acrylic door or a removable top?

I apologize for the simplicity of my questions, but I really could use the help. Thanks!

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Breadboard Mounting:
1. Epoxy magnets to the breadboard
2.Epoxy sheet  metal pieces to the box or duct
    tape metal to box
3. Magnets will attract to sheet metal and hold boards.

Distance Adjuster:
Telescoping radio antenna

Tubes:
 Acrylic rods with same outside diameter
 but bored with different sized inside diameter.

Hinge:
  Just use duct tape  along  the entire lenght
  of one door edge

Sweet. Very helpful. As for the telescoping radio antenna, it sounds cool but are there any things wider or just not as long? The box will be kind of awkward to hold/transport with an antenna sticking out. : |

You could use two pieces oh thin wood or plastic,
one on top of the other. Position them to your desired length and
hold them together with binder clips or rubber bands.

To mount a circuit you can use a simple tube and a long threaded nut and bolt or you can mount them like I did these circuit boards. The first one is like a bolt with a long hex head that is a screw on one end and a bolt on the other, the second is like a long nut you screw in both ends. 

https://www.instructables.com/id/Photo-Components-Testing/

https://www.instructables.com/id/Photo-Components-Testing/step6/Testing-In-the-Tester/

https://www.instructables.com/id/Pocket-256-Bit-Logic-Analyzer/

Now there are a number of ways to mount the LEDS and that depends on whether you want fine movement, gross movement, or both. It can be as simple as a screw slide or a mount with a variety of holes.

For the tube try a tapered hose connector.

Try a card box like this one.

https://www.instructables.com/id/Scanner-and-Photocopier-Light/

What kind of liquid are you monitoring? Does it have to be in a lightproof enclosure so that no outside light interferes with the reading? I'm sure you can base this design off of commercially produced lab/testing equipment out there. A box with a hinged door is a box with a hinged door.

Care to spare a link to this lab/testing equipment? It does not have to be lightproof. I'm not sure that the type of liquid matters but it's a mixture approximating spinal fluid.

I would think searching on flow rate testers would be a start. Medical intravenous drip pumps would have sensors to detect flow and blockage.

Thanks for the help. Although it would be nice to get direct answers to some of my questions as I would like to learn.

Sorry, but the consensus here is that we have no problem in guiding people toward the answers so that you can become a better maker by learning how to search or be more resourceful. We get too many questions from people expecting the answer to be given without any effort or thinking on the part of the asker. So, what similar devices have you found based on the previous suggestions that might work or not work for you? Why or why not and what needs to be changed? Upload a sketch of what your device is if you want other people to visualize what you want to develop and provide feedback. Design is a process where you try to think everything out.

My questions are all related to acrylic or mechanical fixtures that I am ignorant of. I don't know how to make my questions any more specific and I can't move along in the process until I have even a vague idea of what to do. I don't have enough money to waste on parts and materials that may be irrelevant. None of the search results for those devices have details I want since they are actual products and I want to build a prototype. Also, no drip detector is customization or moveable in the way I need my design to be. The questions I asked reflect a design I have conceived. I will try to upload a picture when I can get access to a scanner.

Enclosures and aesthetics can come later. You just need to knock together a cardboard prototype of your device. Your measuring tube can be held in place by a collar with three setscrews or flanges on each of the ends of the box which the tube passes through. This is what is used on ceiling lights to fasten a glass globe cover. You probably want a small platform or mount for the photo emitter or detector on a threaded rod which also has supporting side rails. That lets you adjust the placement in or out and can be calibrated if you know the thread size and need accurate settings with a lockscrew. If you look at how a bench vise works, the same screw mechanism is used to move the platform in and out. Yeah, everything can be made from acrylic and lasercutter but you may just need a wood frame or aluminum rail structure to house your device. I don't know how big it has to be so if you just look at pictures of 3D printers, you can get an idea of prototype housings.