Hi guys,
I have decided to make a plant watering system for my yr 12 major project, it will be using sensors in the soil to give readings which will activate a pump (this bit I have done before) however the challenging bit is that I have added a "moving" shower over the top that will use a 10rpm motor along a fixed rack to move its way along. My question is how do I get it to run from external power? and how do I set parameters? (e.g. not going off the end of the rack).
I have attached some photos of my first prototype from Fusion 360.
Cheers in advance
To run a dc motor off external power (by which I assume you mean, not from the Arduino 5V) you need some kind of driver module like one of these, chosen to suit the motor's voltage and current requirements.
A dc motor's probably not going to be controllable reliably by "parameters", where you might eg run it 10 seconds each way. So you might want to put encoders on, so you can count how many revs it did, or opt for a stepper motor.
Or you can rig limit switches at the ends of the travel, so when the motor nudges the switch, or maybe do it optically or magnetically, Arduino senses that the motor has arrived and reverses direction.
I would add an encoder, so you not only know how far you moved, but also whether you're moving at all (or that there's an obstruction along the path).
Limit switches are a must, at least on one side, so you can know where you are when the module starts up (if not triggered already, move slowly one way until you trigger the limit switch).
You may consider a stepper motor for this for better control (no need for an encoder in that case).
I notice you have solar panels in the diagram. I have a very small solar powered plant watering system that has a rechargeable battery. Initially I assumed the panel would keep the battery topped up, but that is not how it works. Instead the amount of sun determines how much charge is put in the battery and that in turn determines how much water is pumped i.e. rather than being fully charged most of the time the battery is flat most of the time.
Anyway I know this is deviating from your question but as well as using sensors in the soil to measure moisture you might want to also measure the amount of sunlight. That would give a cross check on the soil sensors which might give patchy readings. Also you might want to avoid evaporation loss by not watering when the sun is strong.
Is there any reason you are going for a moving gantry rather than surface or sub-surface pipes?
you must have end switches. you can have a stop on one end, and when the amps jump, you know your motor jammed and is not moving.
at the home end, you hit the stop, back, up. hit it slooowly and when it changes state, you are 'home' all measurements from there.
the rack is a poor mechanical choice as anything can fall into it and it will collect debris and water. works fine for the theoretical. chain drive on the overhead, the chain lays on the rail so that it does not move. fixed at both ends.
are you going to shower the entire time and move at some speed ?
or, are you going to point A and run the sprinklers for a set time ?
there is a lot of stuff on motors. determine your max speed (return home at 4x to 10x normal speed) since you can go back, and forth over an area, you really could use only a few speeds.
one pass = 1 liter and you just make X passes. there and back.....
two sets of solenoids and 1 on = 1 liter,
lots of options.
ardly:
Is there any reason you are going for a moving gantry rather than surface or sub-surface pipes?
my local greenhouse has a huge area on concrete with overhead gantry.
they grow seedlings in one area, replant to get bigger
then pot for shipping. they store them on the floor of the greenhouse with the gantry.
they can plot X and Y area and only water where the pots are until they are loaded and shipped.
Thanks for the advice, I will be doing a lot of research and keep you all updated on how it's going.
Another question I have is, can you put different sections in the code i.e. only water section 1 of plantation area?
Thanks again
Yeah, I see what you mean about the external power. I would try to make the motor stationary and use a screw or a some other way to move the gantry. It complicates things having to take care of the cables keeping them out of the way, dry etc...
Of course you can. You will have to come up with some coordinates or way of describing the sections which the Arduino can use.
Your water pipe won't work as drawn. That doesn't let the gantry move. Managing the length of pipe is going to be a big part of getting the project to work in the real world. I used to work on machines with tracks that were kilometers long and the segment of the machine which managed the electrical cables was the most expensive part. Even short hoses and cables don't always work the way you expect without some effort managing them.
lots and lots of options.
you can have a bar code at the start of each plant type, read the code, set the pressure (volume) and speed and water away.
you can use a grey scale encoder and know where you sprayers are. google encoder strip.
think stripes on the highway. linear encoders are easy to make with simple 'car follower' type optics that see black and white.
as for the motor at the end, you can run a simple cable, think old-old fashioned clothes line pulley.
larger pulleys = more surface area= less slip.
one drive shaft that has two pulleys, one on each side. and then your motor has a small belt with a larger driven belt on the shaft.
as for hose control, a looped garden hose that has a hook at the top of each loop, that hook rides on a rail or on a wire.
as you extend, the loops stretch out, as you retract, they get longer. distance is the question. how long is your proposed gantry? each loop connection slides along a rail or pipe
Nice image - but how is that sprinkler bar suspended? I can vaguely make up a single wire - which is not enough for proper control - and not at all the water supply.
wvmarle:
Nice image - but how is that sprinkler bar suspended? I can vaguely make up a single wire - which is not enough for proper control - and not at all the water supply.
I would have to modify it to work, however, do you think it will be better than the rack and pinion idea by having a single or 2 axis system?
So I have found a video on youtube of what I basically want to achieve, I will be modifying the design of the structure but it has the basics of what I need. Let me know of what you think of it and any improvements you think it should have.
