We are conducting a research on a lake and we are trying to take into account of all nutrients entering the lake from tributaries, runnoff, groundwater and wet and dry deposition.
We are mostly good for everything but we have a problem with the wet and dry deposition auto sampler that cost a lot of money to buy.
The design of such a sampler is actually quite simple mechanically. The rainfall sample is collected in a bucket that is closed with a lid mounted on an arm that tilts back when it rain allowing rainwater to be collected. Once the rain is over, the lid tilts back and closes the bucket.
How do I build the electronic portion of this contraption? I was thinking about using a water sensor used in irrigation and maybe a one that controls a solenoid valve. A DC stepped motor would control the movt of the arms moving the lid, but how do I stop the motor when the lid is removed and how do I let it go back to its original position?
I know how to solder on a board once I know what the circuit board controller look like but I am incapable of designing such a thing. In other words, I can follow a recipe but I cannot make the recipe.
Google search the term(s) “Arduino sensing rain,” “arduino moving a stepper.” I really thing a stepper would be overkill. Look into actuators. Or even simpler, a regular DC motor with an opening mechanism.
Once you have found projects like this, just copy theirs and get yours working. Like just detecting when it rains… Then get the opening mech working by its self. Once you have them working, you will have learned enough to combine the code and mechanical aspects with ease.
Your project wouldn’t be hard, but if someone does it for you, they would need to have their hands on it to design and build the mech for the door…
Is it just the control electronics you are having trouble with or also the actuator mechanism? The electronics is simple: it can be done completely with relays. [Here is a schematic of a door opener/closer I designed that uses a couple relays and limit switches to control a chicken coop door.
The drive mechanism could probably be done with a gearmotor (sf has a few that may be suitable depending on how much force it takes to move the door) and a drive belt. However, as mentioned before, it is much easier for someone to build this if they have access to it.
OTOH, if you can drive it with simple RC servo (how much travel do you need?), then the complex way might be simpler. An Arduino can control an R/C servomotor quite easily and you wouldn’t need travel sensors.
Now, if I were to ignore those photos you linked, I’d ask if there is something special about that cover mechanism? Could you use a simple sliding cover or a hinged one? Might be mechanically easier.
Our focus is the atmospheric dry and wet nutrients.
the bucket # 1 collect the dry atmospheric deposition when it does not rain. The bucket is thus opened during non rainy events. When it rains, the lid of bucket #2 open and closes the bucket #1 so that bucket #2 collect rainfall while bucket #1 remains closed.
The opening and closing can be various designs so if Lyndon has an easy way to do this I will take it.
Thank you all for you additional inputs. I am sending this to my grad student so that he can look at your tips.
I don’t suppose it has anything to do with fish with big teeth, then
OK, your grad student can post here to get more help. If email is easier, he can PM me for an email address. I have a lot of experience controlling physical mechanisms so we may come up with some new ideas to do this.
After googling some of the search terms provided and looking over the various mechanisms proposed, using an actuator to slide a lid back and forth, controlled by an Arduino Uno and a rain drop sensor seems most appealing to me. Does this sound feasible? Looking at prices online, it seems this setup could be purchased for ~$100 and I think it would be a cinch to implement into the overall design. I have no experience with coding, but I found a thread on the Arduino site requesting a code similar to what we need (http://forum.arduino.cc/index.php?topic=227714.0) so I am pretty sure it can be done.
We do have some money to work with, so it doesn’t have to be super cheap. We need something that will hold up to high heat and moisture as well. We are not electrical or mechanical engineers (ecologists) so we will certainly trust your experience with this over our own.
So, I’m guessing you will be building everything here. Is that correct? The first thing I’d be concerned with is the environment. Since by definition, this assembly will be rained on, it will either need to be rust-resistant, or non-rusting.
A linear sliding assembly is easy to do, but now as I take a second look at those photos, it occurs to me that one advantage of the 4-bar linkage they are using is that it makes it pretty easy to remove/replace the buckets. A slide riding above the buckets will make taking a full bucket out a bit harder since you’d have to slide it sideways instead of simply picking it straight up.
Since the electronics are pretty simple, I’d focus on building the mechanical hardware. It looks like you will need approximately 46 cm of travel to move the cover back and forth. An aluminum sheet cover riding on small rubber/elastomer wheels in a C-channel track would make a good sliding mechanism and not be expensive. On the flip side, if you kept the mechanism in the photographs, those pivots could probably be made easy with off the shelf hinges.
Question: how many manufacturers of these things are there and do they all use the linkage shown? There may be a reason for that if they do.
Depending on the type of actuator, that may be all, or you may need a motor driver. Waterproofing should not be a big problem: there are thousands of electronics enclosures rated for outdoor use.
http://kodu.ut.ee/~olli/eutr/LiseFig8.jpg
