Servo Tests

I thought I would check out Servo motor to make the mechanical cutoff valve for the laminar nozzle. I picked up the cheapest one I could find at a regular old hobby shop. The long and the short of it is I am very impressed with servo motors. They are very simple to use and need little to no extra components to run them. I was quickly able to get it to turn to the desired location.

Setup:

The setup is really quite simple. I have a PIC Microcontroller 16F690. In order to program the PIC I am using Proton Development Suite. The code is fed to the microcontroller via a programmer by Microchip, PICKIT(TM) 2. I have a board that came with the PICKIT 2 that contains the microcontroller and some LED's and other peripherals. The servo is hooked to GND, +V, and Pin 12 (RC2). The servo has a PUSH/PULL rod which enables the cutter lever (a drilled out CD) to open and close the nozzle. The cutter lever is attached to the nozzle.

Note: For those of you following along at home there is NO water in this test. The code is very simple due to the wonderful software that I am using.

Results: The servo performed exactly how it should. I was able to get it to move to several different positions. I recorded some of the results. Just so you know, it's really hard to record and talk at the same time. I can do calculus, but I can't talk in front of a camera!

Setting up the servo was really easy. All it required was to hook it up via the header pins (I think that's what they are called let me know if you know). It was simple to get it to the proper position all that was required was to send the proper pulse which the software took care of and the servo moved to the desired position.

The simulation could have been better. Holding the servo by hand was difficult and as a result the cutter lever was never positioned over the opening. Conclusions I don't know if the servo will be fast enough, but I think with some tweaking I'll be able to get it to work. I'd like to use servos because the additional electronics involved are minimal. However, servos are slower than solenoids.

A very special thanks to my wife for believing in me and helping me get started on this journey!

Understanding Transistors Demostration Video

So here it is in all it glory. The video is pretty boring and I don't do a good job of explaining everything or anything for that matter. Perhaps you can glean some information from it anyway.

So why do we even care about the transistor and the fact that it can turn the DC motor on and off? Well, the simple answer is...you don't care. The more involved answer is that the DC motor won't be in the application, but it is in place of the solenoid. The solenoid will actuate the cutter valve that is yet to be determined. I have a couple of ideas of how to make it work, but I will spare you the details....for now.

Other concerns:

Drainage: I don't know exactly how or where to drain the water. I need to either have a very robust drainage system or a water return system and pump. The water return system is better since there wouldn't be any flooding, but it is clearly a lot more complex.

Water pressure: Since I will essentially running 8 nozzles constantly I am worried about the ability to keep all the nozzles pressurized in order to make all of them work properly. I think that if I can figure out how many gallon/minute my sprinkler system puts out I can figure out what the water pressure will be as the flow rate and how high they will be able to jump.

Solenoid/Servo: I've been playing with a servo motors as well. **That will be my next post** I like servos because of their simplicity, but I'm not sure that they will be quick enough in order to give a proper cut. Solenoids have the tendency to burnout if run to long. The solenoid that I am working with will (from what I've read) can only be on 25% and has to be off 75% of the time otherwise it will "burnout. If I can water proof the solenoid then maybe I could have water cooling them off, and then I wouldn't have to worry about burnout.

Manufacturing: Seeing as I only have a drill press manufacturing these can be difficult. I have to find a company that will be willing to take on my small little project. If anybody is interesting in me making some of these nozzles for you let me know now because it will be cheaper for all of us!
There are going to be 2 parts that I can't manufacturer at my house. Those are the brass nozzles and the clear plastic (lexan) to hold it in place. In previous post where I show some of the results from the nozzle I was just using the plastic cap as my nozzle. I believe the reason that I was getting those, "veins" or "rifling" in my water is because of the slight (and I mean slight) inperfections in the orifice. The plastic can't hold a sharp enough edge in order to get that brilliantly clear stream. Since I am making a special brass nozzle I need something to hold the nozzle in its place. I will post some picture of the entire nozzle once I get a model made up.

Tasks:
1. Find the Flow rate!
2. Test solenoids (when they get here.)
3. Find a manufacturer for the brass nozzle, and lexan pieces.

Understanding Transistors

So what does electronics have to do with Laminar flow fountain nozzles? EVERYTHING! I think I have the nozzle design pretty much nailed down. There are still a few question that I need to answer but those will come in time. I have to wait on some manufacturers to give me some quotes on making my brass nozzle orfice before I can make more progress on the nozzle. So my attention has been turned to the cutter valve. I've been doing a lot of research on this and I've found out that they don't cut the water before the nozzle they cut it after it leaves the nozzle. Why? My suspisions are that they have to in order to make it look clean and cut. If you have a valve that shuts off the water before hand then it won't have a clean cut to it and most likely will slowly die down. Likewise, when you open the valve it would take a second for it to start back up again.

So I've been researching motors, solenoids, and servos (which I guess technically they fit under the motor category, but it sounds more impressive if I have more categories). I started with solenoids because solenoids are CHEAP. I found some on a website for $0.99. WOW! I never knew that, but I guess that makes sense. It's just a couple of windings around an iron core. I have 8 on their way, and I should have ordered more since they were so cheap.

So a solenoid is just a push/pull type of motor. Actually it just pushes or pulls but not both. There is a spring that helps the shaft return back to its orginal position. My microcontroller that I am going to use to open and close the cutter valves can only output 5V and 40mA. So I need a way to get the voltage and the current up so that I can actuate the solenoid.

That's were the Transistor comes in. I read about them in the past, but never understood them. This time had to be different. So I went to radio shack and picked up a couple of different transistor based on my research. Since I don't have my solenoids I subsituted a DC motor that operates at 12V. I put everything together like I read. And it WORKED, kind of.....it worked but slowly. This wasn't good enough because I knew that the solenoid would need to draw more current than was being supplied to the DC motor. So it was back to the drawing boards. I looked over and over again trying to figure out what was wrong. As it turns out I'm not exactly sure what I was doing wrong, but I must have been hooking it up wrong or something. What I ended up doing was ripping everything out of my breadboard and started hooking things back up. When I turned it on everything was working just fine! I don't get it. I SWEAR I was hooking it up properly before! Oh well, at least now I have a working example to work from. I made sure to document everything I did so I can reproduce it in the future.

I ended up still using the TIP31 or TIP31A (I can't remember which one). I hooked the 12V to the motor and then the motor to the collector. The emitter was hooked directly to ground. The uC was hooked to the base via a 2K resistor. I made sure that the ground used for the uC was connected to the 12V ground so that I had a common ground.