Which arduino board would you recommend?

Short explanation:

battery powered very simple low power programmable input output device: reading of a sensor, 0 or 1 output varying in time (e.g. on each input I, give a zero output for 3 minutes)

Any recommendations? thanks!

Long explanation:

Problem setting

Water sensor – programmable input/output device – motor output

This problem may sound a bit weird, well, that’s not because there are no other or better solutions that are easier in the technical sense. Let’s just say that this particular option is the only one left because some greedy humans don’t give shit about the law, and to make them give shit, it would come at a higher cost than fixing it myself. Here it comes:

Two tubes of 13 centimeter diameter are connected in a T – junction at 90 degrees just under ground level. The vertical tube is about 80 cm long. There is a very slight airflow in the horizontal tube that needs to be limited or stopped at the uphill side. This is now done by manually pressing a foam ball in the T-junction. However, (sewer) water can flow from the uphill side of the horizontal tube. When water flows in the horizontal tube (uphill side only), it needs to pass the T-junction. This opening or closing of the T-junction at one side should be automated. Extra difficulty: this is a no AC power environment; batteries will have to be used (AA or 1/2/3s lipo’s). Another difficulty: the whole automatic system should be lightweight, so it can be mounted inside the vertical tube without drilling, or without damaging it (e.g. some strong double sided tape, pu foam or the like, or it can be hung inside the tube be putting an extendable bar under tension in the tube).

So I was thinking: some kind of cover that fits the tube, with a water sensor attached to it, some kind of super low power Arduino device, and some kind of low power motor. However, as a psychologist/economist, I have no experience whatsoever with any of these three devices (I like to experiment though

I think generally a trap is used for this purpose: https://en.wikipedia.org/wiki/Trap_(plumbing)

Very funny, I'm not stupid. I can't install a trap there. As mentioned, this involves a very weird situation where the normal solutions are blocked by an ass**** landlord. So please just help with the problem as stated/given.

I wasn't trying to be funny. You said you're a psychologist/economist. How would I know how knowledgeable about plumbing you are? As much as I love microcontrollers, it's always worth considering the more simple alternatives first.

So what's the problem with the foam ball? Or any cap that closes the vertical tube? What's the purpose of the vertical tube? I feel there are things that are obvious for yourself, but not for us.

When you say "super low power" how long do you want the device to operate from a single battery charge?

My guess is that the amount of energy used by any motor that can do what you need, even if running for a brief amount of time, will be 1 or 2 orders of magnitude greater than the energy needed by the microprocessor so I doubt if being super-abstemious with the MCU is important.

Have a look at Nick Gammon's low-power tutorial.

Really, you need to hook up a suitable motor and measure the energy it uses while doing the job you require. Then you can figure out the appropriate size of battery.

If you are thinking of using a lead-acid battery you should be aware that they do not like being left partially discharged for more than a few days. Maybe you could use a solar panel to keep the battery topped up.

If the application just requires something to open and close then maybe a servo would be convenient as it has the motor and the control electronics in a convenient package. If necessary you can get your Arduino to shut off power to the servo when it does not need to move.


@pert ok sorry, I though you were just making fun of me

@others I'm well aware the motor might require more energy than the control device

Therefore, some extra information:

The motor would only have to work like once per hour approximately. I will add some pictures for clarity. The horizontal tube is obviously a sewer output connection, the only place we can access it without breaking out walls is the vertical tube as shown on the picture. The landlord won't fix it (he should but ... you know how it goes), and we are not allowed to break down walls to try to fix it, nor do we want to start breaking down walls. Also we are a bit on a budget, because we are students.

So that's how we arrive at this problem with these very odd constraints.

The problem with the current solution is that I now have to manually lift the foam ball with the stick and run some water through the tubes by e.g. flushing the toilet. A few times a day. As the vertical tube is located outside, this is not sustainable to do in winter or in the long run. I tried to fix it indoors, but there are too many penetrations all around the house that let the sewer smell in.

I came here to get some advice on the microcontroller. But if you have advice on sensors of motors, or mounting solutions, also welcome.

I'm an rc hobbyist (drones) so I have a lot of 650 mah 3s lipo's and the charging devices. Also, I can program in MATLAB and a bit of C++.

picture of access pipe
everything should be mounted inside the pipe
nothing can stick out, no solar panel, etc etc

the longer the battery lasts, the better, I mean, I have some 4500 mah 3s packs, they can keep a 1 kg quad in the air for 20 minutes, so I guess maybe power is not the most difficult problem (although the lighter the better, these batteries are 300 grams, the heavier the more difficult to mount without damaging the pipe, althoug minor damage is allowed)

designing the arms that will close and open the valve will, any ideas on which fora people might help out with these designs?

If you want the lowest power device, then use a naked ATTiny85, and run it from 3 volts or so at 1MHz. It will only need microamps to run 'every now and then', while sleeping most of the time..

As Robin2 suggested, you need to decide what motor you will use. The servos from your drones will work, but servos are power-hungry. Perhaps you could run the microcontroller from one circuit, where the battery would last for a year or more, but power the motor separately (which is recommended anyway.) If you have a multimeter, hook it up as an ammeter, and measure the current needed to start, and to sustain the motor. Then calculate how long they will last on a single battery charge. Perhaps consider adding a battery charging circuit, either plug-in, or solar if you are off the grid.

ps, Robin, "super-abstemious"... You sir, are a vocabulary god!

schematic in attach

Wow! Look at the corrosion/sludge in there. You'll need to protect your circuitry from exposure (potted?) but also provide for movable parts. I'm thinking a low power motor, attached to a long screw. Everything can be inside a protective capsule, with only a small, o-ring sealed opening for the screw. Attach your foam ball to the screw, so it moves up and down, depending on which way the motor turns. I'd start with your biggest LiPo for power.

nice picture. Another thought, how about an inflatable balloon/air bladder. This would minimize external moving parts.

Image from Reply #9 so we don’t have to download it. See this Simple Image Guide


And from Reply #7




I also thought of that. But then I need pressed air... . I think that will run out fast. Also no idea how to program a valve for a pressed air canister... .

There are also these motors that have 2 positions: they work with a magnetic field that switches the position of the motor when put on. Does anyone know their name? The flip very very fast, like in 20 ms.

thx for the tip of separate power circuits

I wonder how I can program a servo to turn like, 5 times and than stop? My drone motors run on betaflight, so no programming needed :).

babipsylon: everything should be mounted inside the pipe

I understand why you say that but I suspect that requirement will be a deal-breaker. As well as the limited volume the whole space will be very humid - just what you don't want where there are electric currents.

Even though the motor will only run a few minutes per hour (or even 1 minute per hour) it will consume a lot of energy relative to the capacity of any batteries that would fit into the pipe.

Have you measured how much force is needed to lift the sponge? That needs to be a very early part of the plan. Without knowing that choosing a motor and figuring out what size battery is appropriate will be just trial and error.

Another important issue IMHO is "equipment" to verify that the system is working. When you attend to it personally you subconsciously check that all is well and do things to ensure that it is.

I guess one way to ensure the system works is to make it significantly over powered so that it can't not work. But that has implications for battery life.

I must say I like @ChrisTenone's idea for something inflatable. Maybe you could run a small bore plastic tube from a pump inside the house out to the pipe. That would require only very little to be outside the pipe.


So, maybe I reformulate my question: what's the easiest board to:

program easy instructions have output to the motor have option to power off the motor via the board

what accessories do I need to connect the arduino to my computer in order to program it?



Well, I would have to redesign the mechanics: now the foam ball is kept into place by pressure. That means a motor would have difficulty lifting it while the foam is pressed inside the tube.

So I would have to design a cover lid, like in the schematic I uploaded, that is held by an arm or the like. That's why is was thinking about 2 position switch motors (forgot the name), as they only consume energy when flipping. The lid would be held in place by the motor, because it has only 2 positions it is held firmly into place without energy.

Sadly no connection from the house can be made to the T-junction. Found this, but like I sais, can't break up the pavement sadly: https://www.youtube.com/watch?v=F0UJVdq_6d4

Ach, actually this is interesting, don't know it's possible to fit in though: https://www.youtube.com/watch?v=CdHOW41mMxg

babipsylon: So, maybe I reformulate my question: what's the easiest board to:

program easy instructions have output to the motor have option to power off the motor via the board

Any Arduino board will do that.

But you cannot connect a high-power device like a motor directly to an Arduino. You need a h-bridge or motor-driver-board in between the Arduino and the motor.

what accessories do I need to connect the arduino to my computer in order to program it?

A USB cable - and the Arduino IDE (programming software)