Here’s a a couple of videos of me and my brothers Stephen and Michael mountain biking some trails in Lambert Park, Alpine, UT. Michael has the helmet cam doing the taping and Stephen is up front in the white shirt. I haven’t been on a mountain bike in about 6 months. Actually since the last time the 3 of us got together I think. And it was years before then. It was a fun ride, it definitely makes me want to get a new mountain bike. Anyone got a decent full-suspension bike they want to sell?
So it’s been a couple of months since I’ve flown any of my planes or driven any of my R/C cars. They’ve all been busted up in a broken pile of parts and clutter and I just haven’t had the time or energy to get them back up and running…until last weekend. The last time I flew my Mini Showtime 4D the rudder servo stuck mid-flight with the rudder swung all the way out to the right. It was one of the cheap E-Flite S75 servos, the kind that just about everyone blames at one point or another for the loss of their plane. Fortunately I was able to land it with only minimal damage to the fuselage from a less-than-stellar landing (which didn’t have so much to do with the cocked rudder but a big pipe sticking up out of the ground that I somehow didn’t see. Doh!)
I replaced the rudder servo with a new S75 (I know, lessons are hard-learned) but it’s only a $12 servo and it only weighs 7.5g and doesn’t tax the BEC in the ESC. I did replace the elevator servo with the much-better Hitec HS-65HB servo which although is heavier and draws more current, is a very robust servo for a park flyer like the Showtime. I figured if I lost the rudder again, I’d at least be able to land it, but if I lost the elevator, I knew I’d be dead, so I didn’t want to risk it. My old S75 that was on the elevator was on its last leg anyway. The HS-65HB draws more current and according to the specs on the E-Flite 40-Amp V2 ESC, they don’t really rate it for running 3 micro servos and 1 digital servo, but I figured it couldn’t be too much more. Besides I’ve got the ESC placed so plenty of air flows over it. Of course, the loss of the BEC in your ESC is probably the worst thing that could happen mid-flight. I think at that point the plane is a total loss, so it’s somewhat of a risky tradeoff. But the HS-65HB is a smooth servo, and it’s a drop-in fit in place of the S75.
My first flight with the plane all fixed up went without incident. Though I was nervous since I hadn’t flown for so long. People talk about having rusty thumbs, and boy do I know it. I didn’t try anything too crazy, just flew around doing loops and some inverted flight and I kept it nice and high in the air. It was a blast to fly again though. And the new elevator servo really has some great authority to move the plane up or down on command. I’d like to replace all those stinking S75 with them. But a new BEC would be a must at that point, and it’s an expensive upgrade. So until another S75 bites the dust (and hopefully I can recover the plane) I’ll be sticking with my current setup.
Of course R/C planes aren’t my only vice, I also recently broke out the ole’ Micro RS4. I think it was some 8 years ago that this little 1/18th scale R/C car took the radio control world by storm. I spent more time than most people should playing around with this sweet little R/C car, so much so that it took up almost 3 years worth of my time and life. (Check out www.aktionRC.com and you’ll see what I’m talking about). Now it’s been more than 3 years since I even opened the boxes that these cars lie dormant in and inside of one weekend I have almost 4 complete rollers ready for electronics and ready to race. Now that my kids are a little older and the HOA built a full-court basketball court up the street, I’ve got the perfect racing team and perfect track to race at. Once I get them up and running I’ll throw up some more pictures and specs of what they’re running. For now it looks like the kids’ 2 cars will run stock motors on full-upgraded 540 and 480 chassis’ converted back for stock setups and my car will be running a 180-sized 6200 Kv brushless on an 11.1V li-po. Should be lots of fun! More details to follow…
So a good friend of mine is close to winning this Willy Wonka contest by having the most downloads of his music. So in an effort to help him win this contest, I’m throwing up the video player here and asking that anyone who comes across my blog to please give his songs a listen. Cary writes some great music with clean beats and catchy melodies that is sure to keep you coming back for more.
Turn up your speakers, sit back and enjoy the tunes. (Move your mouse over the player to unmute it). To hear more music from Cary Judd or to pick up a copy of his latest album, visit www.caryjudd.com. You can also hear more great songs by clicking on the Music tab in the player below. So here you go Cary, hope this helps you win.
Okay, I admit it, I’m not the greatest blogger in the world. I thought it would be more fun to do, or I’d be more into it, but as time goes on, it just interests me less and less. I’m either a lazy bum or I have nothing to blog about, or a little of both. I’ve always been sort of at odds with the whole “let the world know everything about you” frame of mind. Part of me wants to let loose, and the other more sensible side, keeps me in check. That’s why I don’t blog on this site very often, or update my Facebook status or worse yet, actually attempt to even create a Twitter account. Must be my age showing through, because I know the kids just love this sort of stuff. This post in fact may never see the light of day, as do many of my incomplete drafts.
So what has Dan been up to these days? Well, I’ve been taking tons of pictures with my Nikon D40 that I bought a few months back. Hands down best investment I’ve ever made in terms of capturing priceless memories. That thing has paid for itself out of the great photos I’ve taken of my kids. Pictures that have captured moments in their lives that hopefully they will be able to look at one day and remember when they were young. Sure, the point-and-shoot cameras capture memories too, but there’s something unique about the way an SLR can capture so much more out of a facial expression, or a laugh, or a smile in one of my children. I absolutely love using it and can’t seem to take enough pictures. So much so that it’s brought me to an interesting topic of conversation regarding picture management and back-ups. I currently have just over 104GB of digital pictures that span the last 10 years of my life and lives of my wife and children. That makes up 40,173 pictures in 522 folders on my computer as of this writing. So I usually end up struggling with two things – how do you manage that many pictures? And how to you backup that many pictures to ensure they last…forever? But that’s a post for another day.
Other than that, we bought an Xbox 360 and Guitar Hero World Tour. Bought the Arcade edition from Target (and got a Jasper core). So the wife and I have been staying up late at night playing that instead of just watching TV. We’ve both pretty much mastered playing most of the songs on Bass on Expert, which is a bit easier than playing Guitar on Expert. I can play most of the songs on Hard, but Expert is still too much for me, depends on the song, but I’m getting better. The kids actually like playing it too. We just need to get some other games.
Though playing Guitar Hero has its fun, it hasn’t stopped me from playing the real guitar and writing my own music (okay, so it’s slowed it down a bit). I did manage to build a mini recording studio (a very modest one at that) in our den with some equipment I’ve been accumulating over the years. I built a super cheap Digital Audio Workstation (DAW) out of an old 2.0 GHz P4 computer. I installed the latest RC of Windows 7 and have been using that in addition to some free software (Audacity, Riffworks) to lay down some tracks of some songs I’ve been wanting to work on. It’s a lot of fun, but so far I haven’t turned out anything even remotely decent. But I’ve had some fun doing covers of other people’s songs and just figuring out how to play some new songs. I’ve added Coldplay’s The Scientist to my list of cool piano songs I can now play. I was intending on transcribing it, but so far haven’t got around to it. If you’d like it, drop me a comment and I’ll get my butt off the Guitar Hero and finish it up. It’s such a great song and fairly easy play. I’ve also been figuring out the tab for Hey There Delilah by Plain White T’s. That’s a great song, I end up with it stuck in my head all day long, but it never gets old. And it’s a great song to just sit down and play. My wife wants me to teach her how to play it. And she never plays the guitar (unless you count playing Guitar Hero).
In other news, I’ve been dying to build a new Core i7-based computer to replace my aging 3.2 GHz P4 but so far just haven’t been able to justify the need to spend the $1300 it’s going to cost to get me the system I want (i.e., 920 CPU, 6GB RAM, X58 Mobo, 1920×1200 LCD, 10k RPM HDD, 2x 1TB HDDs, 4670 graphics, etc.). So it just sits in my Wish List over on Newegg while I watch the prices of hard drives, CPUs, motherboards and RAM drop into the dirt. Though in all honesty, the new MacBook Pros have caught my eye. I’ve been looking at getting a netbook to replace this massive Dell (that’s really just a huge brick) and the 13″ MBP just looks so stinking awesome. Not because I want to “switch” and become a Mac guy, but just because Apple’s sweet-looking hardware and insane battery life is so much better than anything Dell, Asus, Acer or HP have to offer, in my opinion. First order of business though would be to install Boot Camp and get Windows 7 on that little beast. That would be very cool. I’m not buying anything until Windows 7 is officially released. I’ve been using the RC for a month now and it is awesome. But again, a post for another day.
And that’s about it. It’s no wonder though that I never blog, this post alone took more time to write than I care to admit. Though I’m going to try and get a few extra posts in here in the coming months of some of the things I’ve been working on or playing with, and I’m going to try and keep them short and sweet, if that’s even possible coming from me. If not, we’ll see you in 8-10 more months.
I’ve got an old XEQ-2 active crossover made by EV that I’ve been using for the crossover on my subwoofer for my home theater. The one thing I always disliked about this EQ was the 30-Hz built-in high pass filter. Worse than that, the options for adjusting this filter don’t offer any solutions. Each click of the switch adds +6 dB boost at varying frequencies from 29Hz to 60Hz. Definitely not optimized for HT and certainly not for a subwoofer that is, by design, flat to 20 Hz. What I really wanted was to do was adjust the filter for a predetermined cutoff frequency that corresponded exactly to the maximum excursion capability of my new Audiopulse vented subwoofer. And this is how I did it.
First off, why put a high pass filter on a subwoofer at all? Commonly referred to as a rumble filter or subsonic filter, the idea is to remove frequencies below that which you can’t hear or those frequencies below where your sub can adequately produce, in an effort to reduce driver excursion and reduce stresses put on your amplifier. Any vented subwoofer will essentially unload below tuning which can cause the driver to exceed its rated xmax (or even xmech) causing potential damage to the driver. However, the problem with most rumble/subsonic filters is the cutoff frequency is arbitrarily chosen and usually does not represent the ideal cutoff frequency for the subwoofer to which it is connected. It is either too high, in which case it negatively impacts the natural frequency response of the driver/enclosure, or it’s too low and still allows the driver to exceed its rated excursion capability. An ideal subsonic filter is achieved by setting the cutoff frequency to be low enough to have a negligible impact on the acoustic response of the driver/enclosure while still maintaining just the right amount of safety margin below tuning for the driver so that it does not exceed xmax.
The EV XEQ-2 is the perfect crossover for achieving this. The first thing I needed to find was the service manual for this unit. I found it in an unlikely place – someone’s eBay auction that had ended months ago. They had a link to both the manual and the service manual. The service manual has the schematic for the unit which is key into figuring out how to adjust the high pass circuitry. This is what I learned while looking over the schematic. The filter for the low pass section is made up of a single-chip dual op-amp. The one op-amp is for the 18 dB/octave low pass section and the other is for the high pass section. This is how the high pass filter and boost work according to the service manual:
“U2 (1) is an active high pass filter. S2, the LF EQ switch, controls the cutoff frequency. In the FLAT position, U2 (1) becomes a second order (12 dB/oct.) high pass filter [which is down -3dB at 30Hz]. At other positions, U2 (1) becomes an underdamped high pass filter. In an underdamped second order filter, a peak occurs in the frequency response just before the curve breaks away from a flat response. Once past the peak frequency, the curve falls at 12 dB/octave. The peak frequency is noted in the swtich markings on the front panel. The peak amplitude is approximately 6 dB.”
This is the basic function for many bass boost circuits found in a lot of plate amps. It’s just an underdamped, i.e., high-Q, high pass filter which creates a peak is the response at a calculated frequency. The calculation for determining the f3 (or -3dB point) of an active 12dB/octave filter such as this is represented by the formula: f3 = 1/((2*pi*(R1*R2*C1*C2)^0.5). Damping is represented by Q and is calculated by the formula: Q = 1/2*(R1/R2)^0.5 where C1=C2. Since am trying to achieve a maximally flat response, I will shoot for a Q = .707, which results in a very simple resistor calculation represented by R2=R1*2.
For my application I wanted to reduce the FLAT response so that the corner of the filter is somewhere below 20Hz, or the same frequency that corresponds to the point where by sub begins to reach xmax. To determine the best -3dB point for my rumble filter, I checked out the excursion plots from Unibox for my sub design. Excursion doesn’t become a problem at 500W input until we go below 18 Hz. So that is about the point that I need the corner of this filter to be set to.
Though the formulas are usually enough for determining the necessary values, I ran across a really cool simulation tool that let’s you build a simple schematic and then run an AC analysis to see just how your circuit will look in the real world. It’s called National Instruments Multisim Analog Devices Edition. I found this tool while checking out some op-amps from Analog’s Devices web site. I won’t go into a lot of detail on the capabilities of the free version of this software, other than I found it works very well for modeling and simulating active filters, among many other things. I drew up the schematic, following the schematic in the service manual, of just the low and high pass portion of the entire EQ. This version is limited to 25 components, so I was unable to add the input unity gain buffer circuitry since that pushed it over the 25 components. For the simulation though it doesn’t really need it since it assumes the AC voltage source is a already a low impedance source. If you were to want to build this circuit, I would recommend adding the input buffer so the high output impedance of various receivers does not inadvertently alter your low pass cutoff frequency. A full schematic is shown here as well. I set up the low pass for around 80Hz with resistor values that were calculated using the formulas as defined in the owner’s manual for the XEQ-2.
UPDATE: Now you can create simple circuit simulations using MultismLive. It’s a web-based interface that requires no downloads, has no part count limitation and works great for simulating a wide variety of active filters. Plus you can export raw .csv data of the response which can be imported into Unibox so you can model the combined driver and excursion responses with your filter. I’ve simulated this circuit here, so go check it out and while you’re there, go and create some cool circuits of your own!
Multisim Live: EV XEQ-2 Filter
I entered the values for FLAT which is a 36k and 75k ohm resistor and ran an AC simulation from 1Hz to 1kHz. The results show up in a graph in a new window. The simulation appeared very accurate as the -3dB point was exactly 30Hz, right where EV says it should be, and right where I’ve measured it before. Also, the 80Hz low pass modeled correctly as well. Satisfied that my schematic is correct, and the simulation is working properly, I began adjusting R23 and R29 according to the results I had calculate above shooting for a Q of .707 and recording where the actual f3 turned up. In most cases everything was dead on. The simulated response was pretty much right where the formula said it would be and had no hump or bump, hence critically damped, and perfect for my subsonic filter.
Now this is all fun and games, but how do I decide what cutoff is right for my sub to prevent overexcursion? And how will it affect the frequency response? This is where a great feature in Unibox 4.08 becomes extremely useful. There is the option to import an .frd file, which is summed with the box response giving you combined response of your enclosure and your active EQ. Using NI Multisim I was able to export each of the simulated FR plots and pull them into Unibox to see just how the different cutoff frequencies affect both the FR and the excursion. My first filter cutoff was set to 15Hz, and although it had very little impact on the FR of the sub, it still allowed the sub to be overdriven below 15Hz at 500W input power. So I adjusted the filter and imported a 19Hz cutoff point. Now the excursion is in check and never exceeds 22mm at 500W input power and the FR is minimally impacted. This is most likely the ideal spot, if I had just one cutoff point to choose, but the great thing about the XEQ-2, is that it offers six different cutoff points which are easily selected between with a switch on the front panel. This is where as massive DP6T (dual-pole-six-throw) switch comes in really handy. I can select resistors values in pairs for all 6 switch positions which correspond to 6 different cutoff frequencies and remove using any boost completely.
So the plan is to replace R23-R36 with resistor values which correspond to cutoffs of 12Hz, 14Hz, 16HZ, 18Hz, and 20Hz with no bass boost. Then the last switch setting of FLAT I will remove the resistors completely which basically removes the filter from the circuit and makes the response flat to 1 Hz. So when it says flat, it will truly mean flat.
UPDATE: So I finally followed through, check out this post here detailing the updates to this little crossover making it into a truly adjustable subsonic filter.
Download the Service Manual Here
For the last year or so I’ve been wanting to get a new digital camera. Up until now our current Canon SD400 has been solely responsible for taking thousands of pictures of the kids, vacations, projects, speakers, computers, R/C cars, planes and everything else over the course of its life. It’s actually been a really great camera, so good that there’s been very little drive to buy a new one – until last week. My daughter turned 4 on Wednesday and my wife was throwing her a birthday party in which she found herself taking care of about ten kids all by herself. As she was juggling playing games, face painting and taking pictures of everybody there came a knock at the door. She was out on the patio in the backyard and she had set the camera in her lap but when she stood up suddenly to get the door, the camera went crashing down to the hard patio ground with a thud. She thought momentarily, crap, I broke the camera, I bet Dan will be thrilled.
Upon powering it up the lens did not want to retract back into the camera body and just beeped and shut off. I spent an hour or so messing with it trying to get it working again, even went so far as to tear the whole thing apart. It’s pretty amazing the complexity of a something like a digital camera, so many tiny pieces and parts that work together in perfect unison to do something as ‘simple’ as take a picture. I got all the way to the lens mechanism when I concluded it was probably was shot. It no longer would freely rotate in and out though I couldn’t tell exactly what had broken. But even if I could fix it at this point, or buy a new lens somehow, I’d probably never get the camera back together. So I figured it was time to say goodbye to the trusty point-and-shoot and pick up something bigger, something better, something like a digital SLR. So I bought a Nikon D40 and after taking only 30 or shots tonight, I couldn’t be happier.
There’s a lot of great DSLRs on the market these days and you can spend anything from a few hundred dollars to several thousand dollars without looking too far and from what I’ve read, just about any SLR is better than most point-and-shoots. Now I don’t consider myself a photographer by any means, but I really wanted to take a shot at getting a decent camera to see if photography was something I could really get into but I didn’t want to spend an arm and a leg for a super-fancy camera either. Ultimately I decided on the D40 because of it’s affordable price, numerous features, and great customer reviews.
The D40 came out in December of 2006, almost 2 years ago, but it continues to compare extremely well with even the newest cameras that are coming out. In spite of its relatively low pixel count by today’s standards, it’s got all the necessary features one would need in an SLR. Features I don’t even understand as of this writing, but hope to soon figure out. I bought a book to go along with the camera, because like they say, a camera is only as good as the photographer. Without learning how to use this camera, it probably won’t do me much good, or at least I won’t be getting all that I can out of it without learning how to set some basic functions and what they all mean. It’s all been very exciting. So far I’ve just taken a few shots of my 2-month old son on Auto, at night, inside the house, with the flash and they have all turned out 10x better than anything that old SD400 was capable of doing. My favorite part is the shallow depth of field that this thing has. Close-up shots show great detail on the face but everything else, like the background, are soft and out of focus. They make the pictures look so much more realistic with much more depth, rather than being just a flat 2-dimensional image, even though that’s still what they are.
I obviously have nowhere near the experience with the camera to give a decent review at this time, but with the many reviews that already exist, there’s nothing more I could say about the camera that hasn’t been said by seasoned professionals. Here’s just a few of the reviews that convinced me that even though this camera is probably the least expensive DSLR available today, it’s definitely worth looking into for anyone delving into the SLR world for the first time.
Ken Rockwell Raves about the D40
Steve’s Digicams D40 Review
Digital Photography Review – The D40
The Nikon D40 from Amazon
I bought the camera from Amazon for $431 and got a free $17 neck strap. I also picked up this book, the Nikon D40/D40x Digital Field Guide by David B. Busch and so far have made it through just the first chapter. It’s the best-reviewed, highest-rated book on Amazon for this camera, so it seemed like a logical choice of books to get. It seems like all my decisions these days are based solely on logic. Not sure what’s wrong with me. But according to Amazon the D40 the ranked #2 only behind the Canon Rebel XSi which costs $215 more than the D40. That’s just enough to pick up a decent 55-200mm VR zoom lens. Additionally the D40 is the least-expensive, highest-reviewed DSLR you can buy and gets a ‘Highly Recommended’ by all the major review sites that I came across. When it came to replacing my old (and now broken) point-and-shoot, the option of buying a new point-and-shoot did cross my mind briefly, but with the cost of the D40 being so reasonable, and the performance being so much better, it just didn’t make much sense to pick up anything else. I’ll be posting some pictures in the next few weeks so stay tuned.
