I'm relatively new to this entire community and the arduino chip in general. I'm working on a project at school that requires the use of a microcontroller, and through the help of some friends, found out about the Arduino platform.
I was wondering if you guys could point me in the right direction for using the arduino. Simply put, I would like it to be:
-portably powered (not sure about voltage yet)
-take in a start/stop user input (from a button),
-a speed control (user defined, probably from a potentiometer or something),
-a timer (user defined, from 5 seconds to one minute, approximately).
-take in signals from an ultrasound
Also, I want it to interface with two dc motors and an electric control valve that will be connected between a hose and a sprinkler. The DC motors should be powerful enough to move a hefty sized object over a standard lawn.
My questions are:
-What arduino should I use? from a preliminary search, I was thinking about the simpler UNO
-How should I power this arduino, taking into account the motors and the valve?
-How do I control the motors? I heard about the Eagle motor control shield, but it's kinda vague on the details, so some clarification about its use would be nice!
-Where can I find some motors that will do the job for me?
I apologize if it seems like I am asking for too much. Helpful links to tutorials, reference websites, and other places would be appreciated, but personal experience would be the best.
Thank you in advance!
Thank you for you quick reply, Korman. I will be doing more research into powering and controlling DC motors today, and hopefully I'll be able to work something out with the Motor shield or the H-bridge circuit.
Anyone with motor experience want to help me out?
Thank you for your suggestion. Do you know if the shield can power high torque motors, capable of moving a pretty hefty object on grass? I don't know how much torque exactly that is, but I can imagine the motors are gonna be pretty powerful and demanding.
You can also do your research in reverse: What kind of motors can you afford and then check what kind of power they have and if you can live with that. I guess, that will tell you a lot quicker what options you have.
It might be worth building a separate motor power circuit, controllable by an h-bridge.
You might want to take a look at this project - while it may be larger than what you need, the principles are the same:
Thank you Crosh, that is a very interesting and helpful project that my partner and I will go over later.
On a second note, does anyone know how an electric control valve works? Something that can open/close a valve when given a specific signal from the microcontroller:
Thank you for your help concerning my project. One last question though:
How does one read the specs of a motor? I see stuff like:
yet I do not know what it means, in practical terms, to have 0.37 A.
Is that the current necessary to run it? If so, how much torque will this motor (as an example) give me?
Ahh... this is so confusing for a beginner!
Thank you for your patience!
Well, torque is usually expressed as an ability to move a weight a certain distance. In Imperial units, that's foot/pounds, metric it's Newtons (kg/m, yes?). You are basically going to have to determine about how much force you will need.. and the movement above assumes that you are working against gravity, vertically.. so if you need to move two pounds, you don't necessarily need two foot/pounds of force. You just need enough to overcome friction and inertia. Also, speed works into this... a geared motor might produce a lot of torque, but turn to slowly to be useful for example.
You are going to need to browse some physics texts to get it exact.. otherwise, I'd suggest looking for motors that are being marketed for robotics use, for roughly the same use, and taking a look at those specs.. RPM, Torque, and Current draw. RPM is how fast, and current draw is how much power it's going to use doing it. Find roughly the specs you need, then try to get as close to those as you can afford.
Typically, a good resource might be a good R/C car and plane hobby shop- they frequently can help a lot in these kinds of things...
kg = kilogram, a unit of mass.
A single kilogram, multiplied by the gravity coefficient (generally 9.8) gives the amount of newtons of force it produces on the surface (so.. 9.8N in this case).
Torque, as far as I know (which excludes american notations) is either:
kg/cm (yess, not a true torque unit, but it is used)
a Example to tell about torque
if the torque is 10kg/cm it means that the motor can lift 10 kg weight aconnected a cm apart like below
(motor)-- 1 cm --(10KG)
or 5 kg at 2 cm distance between motor and point where the weight is acting
but in case of tyres this all differs only in the start you will need more torque after wards you will need less torque ( thats why we have gears in motos cycle's )
well the previous post might be a little confusing
http://en.wikipedia.org/wiki/Torque (this is about torque )
and this about friction i.e the thing which make's movement hard at the first
Thank you for your replies. It's quite interesting how little practical information there exists about this kind of stuff.
One last question: with powering the Arduino Uno, the two motors, and the torque, what kind of battery do you think I'll need to make it work? Suppose the robot is about 20-25 pounds.
hi superego it looks like you didnt read into the topics related to torque and everything else the motor has a torque 0f 30 odd grams per cm and cannot handle the weight you want !! you will need stronger ones ! i.e higher torque
Thank you for pointing that out, Newbie, I completely forgot.
These motors are cheap and seem to have a good amount of torque 250 N/cm, http://www.virtualvillage.com/new-12v-dc-15-rpm-high-torque-gear-box-electric-motor-001480-114.html?utm_source=googlebase&utm_medium=shcomp. Will this work, you think?
1 pound force = 4.44822162 newtons
You want to move about 20 to 25 pounds !
Now do the calculations and find out if they will work or no
Newbie, thank you very much for your insight. I have narrowed my range down to a couple of motors.
Battery related questions:
Can one Motorcycle battery (http://www.acehardwareoutlet.com/productdetails.aspx?sku=8292211&source=GoogleBase) of 12VDC volts and 4Ah current output be enough to power two of these 12VDC motors (http://www.virtualvillage.com/powerful-high-torque-gear-box-motor-12v-dc-60rpm-001480-163.html?utm_source=googlebase&utm_medium=shcomp)?
Or does that mean I need a 24V battery?
Also, since I only require my robot to go in one direction, can I just scrap the entire line of h-bridges and motor shields and just use a transistor circuit like this: http://itp.nyu.edu/physcomp/Tutorials/HighCurrentLoads ?
Thank you! These are probably the most important two questions I need to answer to continue with my project!
Just bumping my latest questions. I promise those are the last ones I'll ask for a while!