A brief characterization of the VAWT generator and estimation of tip speed ratio (TSR) with some clips of it spinning in the wind. I don't have power production data. Our wind resource is quite poor, and we might not have enough wind to collect power data for some time. The TSR is in the neighborhood of 1.2 to 1.4; a bit low for a VAWT, but not unexpected for a small turbine with relatively large wing chord.
A small 3D printed generator for a VAWT. This spins freely as opposed to the DC motor I used in a previous video. I did not put a lot of turns on the stator so the output voltage was quite small. I incorrectly estimated the power output at 1200 RPM in the video, it should be half that value (dividing Vrms squared by twice the stator resistance to account for a load), or about 0.8 Watts. That could be improved with an increase in the amount of copper in the windings.
An evaluation of a small BLDC quadcopter motor for use as a generator. This is a small generic three phase PM motor that costs less than $4. It is capable of producing around 1.5 watts at 3400 RPM. The cogging torque (torque required to get the shaft spinning) is approximately .001 Nm.
A design idea for a compass for use on a whiteboard. The pivot is a 5/8 inch ID flanged bearing from a tractor supply store. The arm is a length of 3/8" diameter dowel. The other parts are 3D printed. The files can be found on Thingiverse, but I tweaked them for my printer and the dimensions might vary with another printer.
An idea for a computer speaker for modular office furniture. The sound quality for this prototype was not great, but it is convenient and clears the desk of other speakers. Please note that the 4 ohm speakers might lead to the amplifier getting quite warm. I'd recommend either a lower voltage or 8 ohm speakers.
Just a few experimental rotors; one with double the magnets, one with narrower but thicker magnets, and one Halbach array. Doubling the amount of magnetic material nearly doubled the voltage output. Since the power output goes with the square of the voltage, the output power was nearly four times as great.
The maximum power output for the three phase generator at 1000 RPM was determined to be 0.84 Watts. I was hoping to boost that toward 1 Watt by moving the magnets closer to the coils. A new rotor was printed, and the magnets from the previous rotor were epoxied into place. Results from the modification are presented.
I wanted to see how much power a small 3D printed generator could produce. This design uses eight 1" x 1/2" x 1/8" neodymium magnets on a rotor and a single phase stator with 40 turns of 24 AWG wire. At 1000 rpm, it should be capable of delivering about 1/4 Watt to a load.
Two more phase winding were added to the generator in the previous video. When wired in a "Wye" configuration, the output voltage was very close to the theoretical voltage. The theoretical maximum power delivered to a load is just three times that of a single phase, or 0.84 Watts at 1000 RPM in this case.
installing quick release pins on the straps from the crane for lifting rafters- saves having to climb up 30 feet to release the straps. The pins can easily be pulled out from the ground via a long string. Blog: https://loghomejourney.wordpress.com/
A 2-Way transmission line speaker to be used with the Linkwitz-Riley active crossover and amplifier circuits shown in previous videos. For the design, I used results from an on-line transmission line speaker calculator and folded it a bit to fit in a shorter box and have the opening facing forward. I don't think the bass comes through in the video. It actually sounds pretty good.
A closer look at the active crossover circuit. This board is available at OSH Park as a shared project (search: Active Crossover). The intent is for a common interface board between a signal source and powered 2-way speakers. This is not a heavily engineered circuit. It is just what I used in a project and I wanted to share it. I apologize for the poor audio quality.
An overview and test of the Linkwitz-Riley crossover for the pair of speakers I'm working on. The actual crossover frequency appears to be just under 2400 Hz, or about 6% higher than the design frequency of 2250 Hz.
A look at a few different types of active crossover circuits for an upcoming speaker project. A first order RC filter with 6 dB/octave, a Sallen-Key second order filter with 12 dB/octave, a cascaded Sallen-Key and a Linkwitz-Riley fourth order filters with 24 dB/octave roll off are simulated using LTSpice.
We hired a guy with a nice pretty crane to help install our Ridge Pole (RP) because the cost of buying stronger chains and heavier equipment was the same as paying him to do it, and he could do in a day what would take us a month. With winter coming on, we want to get this thing dried in ASAP. The plan was to install rafters and RP at the same time, but when he released pressure on the RP, the RP decided it didn't like its position and rolled to about "1 o'clock". Crane guy got scared, and pulled off the job. Told me to call him when I got the RP stabilized. Fast forward 10 days- after a week of rain, and making a new pair of rafters, stabilizing the RP with a chain hoist, shims and more rebar, we are now ready for the crane again. Didn't turn out like we thought, but it will turn out alright in the end.
A circuit for "remotely" controlling a pair of powered speakers. The control box allows one to turn on power and adjust the volume of each speaker from a centralized location instead of doing the same at each speaker. Power is controlled using a p-channel mosfet and one pin of an XLR3 cable.
This is an MP3 player made from components I got off eBay. A panel mount MP3 player sends the audio signal to a 2x10W amplifier based on a PAM8610 chip. The speakers are HiWave BMR12 full range drivers.
My son also wanted an MP3 player. I couldn't distinguish stereo sound on my daughter's MP3 player because the speakers were somewhat close together. So this time I made a mono speaker with an active crossover, a 4" woofer and 1" tweeter. This video is mainly for documentation; a few audio clips and an overview of the circuit and speaker components.
A small addition to an audio amplifier to reduce pop when turning on the power. I'm using a TPA3118D2 based amplifier that I bought on eBay. I ended up using a 10uF capacitor and an SB130 diode because that is what I had in my spare parts box
I decided to borrow most of the components from the bi-amped active crossover speakers and use a tweeter instead of a full range driver. The crossover itself is a board that was made for an MP3 player for my son. I got three from OSH Park, so one for the MP3 player and two for these speakers. Overall, I am quite happy with these, but the bass is a bit strong. It may be good to stuff the box and dampen things out.
I had a couple of Peerless 5-1/4" subwoofers and decided to make some two-way speakers. The subwoofers were paired with Tang Band 3" full range drivers that had a similar sensitivity rating. Each speaker is powered by a 20 watt stereo class D amplifier from Adafruit (10 watts per channel with a 12 volt supply and an 8 ohm load). The left channel is used for the full range driver and the right for the subwoofer. The crossover consists of LM833 audio op-amps in Sallen-Key high pass and low pass filter topologies. The filtered signals are then sent to the appropriate driver amplifiers. Note: in the crossover simulations I used 15k ohm resistors, but in the actual circuit I used 16.2k ohm resistors. I like how the speakers sound; although, they don't sound as good in the video. I don't have a microphone (yet) to measure their true performance. Volume can be set for each speaker using a potentiometer on class D amplifiers. But it would be good for the source to have its own master volume control. Some sample music is provided at the end to show how it sounds with different music styles.
I added a simple bass boost circuit to the shelf speakers I made earlier. It is based on an LM833 audio op-amp. The intent was to increase the gain on frequencies below 100 Hz where the output of the speaker rolls off in hopes of extending the range a bit.
A speaker designed around the Tang Band W3-881SJF 3" full range driver. I plan on playing classical music with these speakers in my office. So the emphasis was on small size without a ton of bass. I am very pleased with the way these speakers turned out.
This is a powered speaker that is intended to look a bit utilitarian. It is powered by a 9 volt wall wart and accepts an audio signal through a stereo 3.5mm jack. The stereo signal is converted to a mono signal through a resistor network before being fed into an audio opamp and finally a small power amplifier. There is both gain adjustment and volume adjustment. The speaker is a HiWave BMR12 full range square speaker. The stereo to mono is just two 4.7k resistors (one for each channel) feeding a 47k resistor. If you Google "line in stereo to mono circuit" the image will probably show up near the top.
A guitar amplifier with more of a flat format. This uses a small class D amplifier along with a Dayton Audio exciter to turn a 1/4 inch thick White Birch plywood panel into a speaker. I like this amplifier because it is light, folds up for easy storage and transport, does not have a paper cone that needs protection, and has a warm tone. On the down side, it is not as loud as a typical speaker of the same wattage I think this would be best used with an acoustic guitar.
A small 5 Watt amplifier based on an LM4950 chip amp. The speaker is a GF1004 from DigiKey, the op-amp is an LM833 and the MOSFET is a 2N7000. Some details of the box construction are given. Overall, I'm pleased with the way it turned out. There is a slight crackling noise which I haven't tracked down the cause of yet. It produces enough sound for a small room. The circuit board and parts list can be found at OSH Park.
This is the completed line array speaker with 12 full range drivers. Each driver has a 1-Watt amplifier mounted on the back of the speaker. Details of the enclosure construction are presented. The electronics are described in a previous video. The input circuitry will be cleaned up a bit and mounted one the back as well after a bit of testing.
I'm working on a diy line array speaker. The plan is to have a dozen 1-1/2" diameter full range speakers spaced about 2-7/8" apart in a line. Each speaker will have its own 1-Watt amplifier. The inputs to the amplifiers will be driven by circuitry described in this video. Note: this is my first attempt at a line array speaker and I am not an electrical engineer. So take what is presented here with a grain of salt so to speak.
A circuit intended as an assignment for a class on EagleCAD. It is a one watt audio amplifier based on the STM TS4871 chip. It is powered by a USB cable, and the signal comes in through a 3.5mm jack. The speaker used to demonstrate the circuit is built around a Dayton Audio CE40P-8 speaker. This is a 1-1/2" speaker that is rated for 2 watts.
A circuit for protecting supercapacitors that are wired in series. This circuit is similar to those that can be purchased online except it uses a low power LM4041 for a voltage reference and a single NPN transistor. Shunt current is limited to about 300 mA, so it should only be used in low wattage application.
A buck converter circuit is used as an interface between a small solar panel and a super-capacitor. The input voltage from the solar panel is regulated to keep it operating near its maximum power point. The output voltage is controlled in the usual way to prevent the capacitor from overcharging. An LED driver uses the stored energy to provide light when the sun goes down. This project was inspired by Mad Electron Engineering's Infinity Sun Jar. I was trying to do something similar using "jelly bean" components.
A followup video about the VAWT035 project. This is a look at how the various components have fared after a couple years of use. I'm quite happy with how it held up. The tops of two of the blades were eroded; possibly due to woodpeckers. However, I took down the windmill because I use a solar panel now to keep a battery topped off and the pole is now gone because I got tired of mowing around it. Our location is not very suitable for wind power and I am not planning on pursuing the project any further.
In an effort to improve its performance, the wings of the Foam VAWT were made stiffer by adding some glass fiber packing tape along with a coating of clear packing tape. It did better than the foam wings by themselves.
We finally had enough wind to test the LM2596 controller. I wanted to highlight two improvements over the MC34063 controller. This controller limits the current on a cycle-by-cycle basis so I believe the current reading on the Watts-Up meter is closer to reality. The previous controller used a low frequency PWM signal to turn it full-on and full-off. So when it was on, the controller was hitting its current limits while the capacitors discharged. The Watts-Up meter would pick up on the current peaks and display a false peak current. The second improvement is in the software. As the input voltage nears the point where it will trip the SCR, the controller starts calling for higher levels of current (a more aggressive current vs. RPM curve) in order to slow the turbine and delay shutting it down with the SCR. This video is the last in my series on the 0.35 m^2 vertical axis wind turbine. My hope was to be able to produce them for a reasonable price. But I don't think it would be worthwhile to make and sell them for less than $800, and there did not appear to be a market. I gave this one away and have since moved on to other projects and turbines. (9/16/18)
We had a fairly windy day, so it was a good time to test the over-voltage circuitry. A 36 volt zener diode connects to the gate of an SCR. This is just a demonstration of the circuit function, and some data after the wind storm.
My previous controller was based on an MC34063 which is rated at 1.5 Amps which is too low and the controller failed. This controller uses an LM2596 buck converter controller which is rated at 3 Amps which should be adequate for my small wind turbine. The previous controller also operated in a burst mode; that is the controller was turned on and off at a relatively low frequency and a duty cycle that was adjusted based on the average input current. The problem with this type of control is that the MC34063 was always running up to its peak current capabilities while it was on. I believe that sort of harsh treatment led to its failure. This controller limits the current to a low level on a cycle-by-cycle basis so the switch is not so heavily stressed. Other benefits to this circuit are input over-voltage/turbine over-speed protection that does not depend on the micro-controller, battery over-voltage protection, and a MOSFET switch on the output to the battery to prevent drainage when there is no wind.
A quick look at the latest control board for the VAWT. It is basically a buck type converter with a micro-controller that cycles the converter to achieve an average current draw from the wind turbine. The buck converter is based on an MC34063 and an ATTiny85 is used for the micro-controller. (8/31/14)
One VAWT spent around a year on top of a 20 foot post and exposed to the elements including more wind than I get at my location. It had some electronics to govern its speed, but it would spin up to a good RPM. The goal was to see how it would hold up over time. A few weeks ago it met its demise when the mounting bolts failed in a storm. This video takes a brief look at the VAWT after its time in the field. Overall, it fared quite well. The bearings turned smoothly without slop or noise. The wings that did not take the brunt of the fall looked to be in good shape. Although, some of the foam on the ends of the blades did not get good epoxy coverage and the foam was eroding a bit. While the LED failed, I believe the PMA and SCR/zener governor is working since it has been able to regulate its speed. (This video was originally posted July 26, 2014)
An update on progress with the VAWT 035 wind turbine. We had some wind today and for the first time there is evidence that the turbine could produce at least 20 Watts under reasonable wind conditions. I'm using a new controller based on an MC34063 buck converter and an ATTiny85 micro-controller. The micro-controller sends a PWM signal based on turbine RPM and current sensing to the feedback pin of the converter to control current. Although, it appears that the MC34063 is operating near its maximum current capacity. I think I might try the same approach using an LM2596.
This is a small bass amplifier I built to have something portable but still capable of hitting low notes. The speaker is a Tang Band 6-1/2" Woofer and the amp is based on a TPA3125D2 Class D amplifier chip.
A test to see if the speed data available on a web page matches the actual speed of the turbine. It seems to be fairly close, but there is a lot of variability in the wind and filtering/lag in the web page presentation so the results are inconclusive. Please note that this web site is not up anymore since I took down the wind turbine.
One criteria for determining the maximum tip speed ratio (TSR) is radial acceleration. Small vertical axis wind turbines must spin at a high rate to avoid aerodynamic stall. But that speed comes with high accelerations that put a load on the blades.
Just a quick look at the wind turbine set-up on March 23. I put it back up with a new battery and changes to the controller software. The controller now turns the MOSFET off for 4 ms out of every 200 ms just to make sure the MOSFET stays active. It is a work-around until I finish the new circuit.
A project to provide wind speed data to the internet. An Arduino is used to measure the wind speed. It communicates via USB cable with a Raspberry Pi to provide the current data on demand. The Raspberry Pi inserts the data into a web page. This may not be the most elegant solution, but for the moment it is what I could get working. The Raspberry Pi is running Apache to serve the web pages which are written in HTML and Php. Python is used to communicate with the Arduino. The web page can be seen at winddata.noip.me provided it is up and running. It is still a work in progress. My hope is to interface the Arduino with a current controller for the VAWT 035 wind turbine to provide data on its performance as well. Note: this video is from April of 2014. The web server is no longer in use.
We had a wind storm run through during the night. I left the wind turbine hooked up to see how it would react. I believe there is still a problem with the controller, or something was neglected in the software and the MOSFET turned off. That unloaded the turbine and it began to spin very fast leading to failure in the blades.
All the parts for the 0.35 m^2 vertical axis wind turbine together for the first time. The first VAWT 035 was put on life test. This is a second one that charges a battery through an input current controller board. We got a little wind, and it appears that all the components are working. It produced a peak of 10.6 Watts in a modest wind.
A way to measure RPM by simulating an LM2907 is demonstrated using an Arduino and Adafruit 16x2 LCD display. This technique uses one digital pin and one timer. The timer generates an interrupt every 4 ms. The interrupt routine checks for a change on the input pin. If there is a change, a constant value is added to an accumulator or "bucket." In either case, pin change or not, the accumulator is multiplied by a value less than one. The value in the accumulator represents the RPM of the rotor generating the signals. The advantages of this technique include: regularly spaced interrupts, no division operations that could result in a divide by zero error, no timing problems with RPMs near zero, provides a cap on the maximum RPM, and no subtraction operation that could result in a negative value. It appears to be a robust way to measure RPM. It is best to use signals with approximately 50% duty cycle. Variations in the duty cycle might cause problems if used to measure frequencies near the theoretical maximum.
Documentation of a couple modifications made to the PCB board. The modifications include an improved circuit for turning on the 12 volt regulator and replacement of the frequency to voltage converter with a more conventional transistor circuit. All the diodes have been installed, modifications have been made to the software, and a test run was made with a VAWT PMA.
This video describes a work-around solution for a start-up issue I am having with the MOSFET driver. Under certain conditions, the driver will fail to turn on the MOSFET even though the TL494 is sending a signal to turn on. However, if that input signal is removed momentarily and then reapplied, the driver operates as intended. This work-around uses a 2N3904 npn transistor in parallel with the TL494 output transistors that is controlled by the ATTiny85 micro-controller to remove the input signal during start-up conditions.
This is a PCB version of the input current controller. It is a buck converter using Average Current Mode Control to control the current being drawn from the turbine (output current from the turbine / input current to the controller). The idea is to measure the RPM of the turbine using one leg of the PMA just before the rectifier and then program the controller to draw a current that is proportional to the square of the RPM. This is not Maximum Power Point Tracking, but it should load the wind turbine in a way that keeps it near its peak power production. This is an implementation of Lloyd Dixon's paper on Average Current Mode Control. The pulse width modulation is generated using a TL494 running at approx. 100 kHz. Calculations are made using an ATTiny85. The turbine speed is sensed using an LM2907 frequency to voltage converter. The n-channel MOSFET is driven using a high side driver, and the current is sensed using a 0.01 ohm series resistor and a high side current monitor with a gain of 20.
Some details regarding the input current controller circuit and design calculations. This is my interpretation of a paper entitled "Average Current Mode Control" by Lloyd Dixon. The intent is to be able to control the current drawn from a wind turbine in order to optimize its operation. If too much current is drawn, a VAWT will stall, and if too little is drawn, power will be wasted in aerodynamic drag.
A quick video of a circuit I'm using as an input to the prototype current control. It is simply an ATTiny85 that is reading a potentiometer, scaling the ADC reading and sending that value as a PWM signal out one of the pins. The PWM signal is then filtered by an RC circuit. This video looks at the characteristics of the analog output. The analogWrite function creates a PWM signal of 500Hz. The final filter uses a 4.7uF capacitor with a 13kOhm resistor. It has a corner frequency of about 2.6Hz and a ripple voltage of about 40mV. With a little bit of code, the PWM frequency could be upped to say 5kHz and the ripple would drop considerably.
I'm working on a circuit to control the current coming from a wind turbine to help it run at its optimum speed. One task for this controller is to measure input current. It could be done with a series resistor and a high side current monitor or a hall effect device, but I wanted to try it with a current transformer since I hadn't used one before and I wanted to see how it worked. This video shows the signal coming from a current transformer and some modifications to the basic circuit to get the desired waveform. Please note that according to the literature I read if your current is always positive as in this case the current must periodically go to zero to let the core "reset." (the term the author of the paper I referenced used) I added a diode that was not present in the literature because it seemed to be a good addition for circuit protection. (Note: I am not experienced in working with these transformers)
I'm working on a circuit to control the current being drawn from a VAWT to help the wind turbine run at a near optimal speed. This buck circuit uses a TL494 to implement an Average Current Mode Control scheme where the current to the switch (input current) is monitored and controlled. An ATTiny85 is used to generate a PWM signal to set the desired current. In the final design, the ATTiny85 (or similar ucontroller) would measure the wind turbine RPM and set the desired current that the turbine should be producing at that speed. If too little current is drawn, the turbine would lose energy to drag by spinning too fast. If too much current is drawn, the turbine would stall and produce little energy. This is different from my earlier controller in that the input current is being controlled directly as opposed to guessing what the input current is based on the output current setting and knowing the input and output voltages. (Note: this was one of my earlier prototypes (Nov 2013) but I'm posting this because I thought the TL494 circuit was interesting)
A quick demonstration of the prototype input current controller. This is a buck type SMPS which uses a TL494 controller. The purpose of the circuit is to control the current coming into the SMPS in order to regulate the power being taken from a vertical axis wind turbine. If too much power is extracted, the turbine will stall, and if too little power is taken, power will be lost to drag. This video just shows the controller going through its paces using a stepped reference input. I am quite happy with the results and will be making a PCB soon. An ATTiny85 is used to generate the stepped reference signal and to provide a PWM signal to a charge pump used to bootstrap the MOSFET driver. A video detailing the design of the TL494 compensation circuit is in the works.
A detailed look at an RPM sensor for a wind turbine using an LM2907 and one of the phases from the alternator. The output is a voltage that when sampled by a 10 bit A/D converter will yield 1 ADC count per RPM. The frequency response is low (about 1/2 second time constant), but the turbine RPM should not be changing too rapidly anyway. Calculations are shown at the end of the video.
Dramamask Evolution update video for September 2018. Just a short video showing some clips of recent projects and upcoming projects, including concrete casting, resin casting, silicone molding, latex molding and more...
If you enjoyed this video, please like and share. :)
The 0.35 m^2 vertical axis wind turbine was placed on top of a pole in a windier location for life testing to see how it holds up in the weather. There is no battery attached to it; just the lighting circuit. I was installed in early May, 2013.
We've been concentrating on the "tactical" aspects of citizen soldiery lately, but remember you're going to be eating way more than your going to be shooting. Start getting ready for it now. Here is one cheap and easy option for preparing food off the grid.
Repurposing the controller board for a lighting application. The 0.35 m^2 vertical axis wind turbine is being prepped for a life test. And rather than charge a battery, the power will be used immediately by a light bulb.
A test to see if the overspeed protection part of the controller can stop the 0.35 m^2 vertical axis wind turbine. The wind was not quite strong enough to test the trigger for the SCR, so it was triggered manually.
An early load controller for the 0.35 m^2 vertical axis wind turbine. This one measures the input voltage, estimates the current that should be coming from the turbine for optimal power, and adjusts current to the buck controller feedback circuit to either call for more or less current. This is not maximum power point tracking; in controls parlance, it is a feedforward approach.