I didn’t feel like writing so I took this video. It was actually filmed yesterday, on the 24th. I’ll get around to writing a detailed blog with pictures on the conversion, the FrSky system in general, and the current quad progress in the near future.
In the last post about my quad construction, I built the basic part of the frame, attaching the arms to the plywood plate that makes up the body of the quad. This post continues from there, as I add the motor mounts to the frame.
For the motor mounts, I went to the craft store where I picked up the wood used to make the frame, and picked up a small sheet of 1/4″ thick basswood. I cut out four small squares from the sheet with a miter saw, each a little bigger then the motor mounts. I then marked the center of each with a line in the middle, and did the same on the arms of the quad.
I used the lines to line up the wood motor mount plates, then centered the aluminum motor mounts using the lines and eyeballing. I then held it together with finger pressure while I drilled two holes down through the wood plate and the quad arm, using the metal mount as a guide.
After I drilled the two holes, I marked the arm and the plate with a number and an arrow, so they went back on in the same location, as slight variations while hand drilling can mean a mount drilled on one arm may not fit on another. The holes were then drilled out with a bigger drill bit, to allow an M3 bolt to fit through.
I then glued the wood plates onto the arms, using the metal motor mount, and two M3 nuts and bolts to clamp it in place for about 30 minutes, then removed the bolts so they didn’t get stuck, and let it dry overnight. In the morning, I put the metal bracket back in, and used it to drill out the other two holes, and a hole in the middle for the motor shaft.
At this point, I took my motors and used removable blue locktight to mount the mounting accessory kit to my motors. Well, three of them, anyway. I’m not sure where the fourth kit is, right now.
I know where the mount for the forth motor is, just not the propeller mount, washer, bolt, and the mounting screws.
The mounting plate is mainly held on by the glue, although the bolts do provide a little bit of backup, but the main purpose of the bolts is to hold the motor in place, and allow it to be removed. The nuts are not yet secure, when I balance the motors and props, I will use locktight on the nuts as well. A lose screw or nut could make for a very bad day!
So this is what it looks now. It’s coming along pretty good, I think. Still quite a lot left to do, though. I plan on having it done before school starts again, though.
I ran some tests using the 12V lead-acid battery I pulled out of my motorcycle for the winter, and I’m only able to charge at a disappointing 1.5 amps, at which point the power supply is down to 10.07V, just above the charger’s low voltage cut-off of 10V. So, I either did something wrong, or I missed something. I’m not sure what I’m going to do about it at this point. At least I can charge though, if just at a very slow rate.
This is part 2 of a three part post on turning a PC PSU into a high current, 12V power source for a hobby charger. This was work done on the morning of the 15th, but I did not have time to post about it at that time, so I’m doing it now.
To begin with, I used the following site article as a guide to the conversion. In the article, they put outputs for +5V and +12V, as well as -5V and -12V. However, I really have no need for the other outputs, as I am also building a lab-quality, adjustable, dual output, linear power supply for my miscellaneous projects. So, I simply cut all the other output wires, so that I could add them in the future, if I ever wanted too. Also, there wasn’t a whole lot of room, so I probably would have needed a bigger case if I wanted additional outputs anyway.
What I did in part 1 was cut all the output wires I didn’t need, and solder some banana jack output terminals to the +12V (red terminal) and 0V (black terminal) wires. I had a purple and gray wire, which I was going to use for a “plugged in” indicator and an “power on” indicator, but decided not too, at this time.
If you look, you can see a gold heatsink hidden in the back, this is a 5Ω resistor, which provides a load on the 5V necessary for proper operation of the power supply. I just tucked in it back there because there isn’t a lot of room anywhere else.
I used a drill and a grinder cut a spot for the terminals in the lid, and mounted them in place with some silicon caulk I had handy to help keep them in place, but mainly to keep the mounting nuts from loosening over time. I found a power switch in my junk box and ran a wire from ground (black) to the switch, then from the switch to the green wire. This turns on and off the outputs, but doesn’t shut off the mains power. I then used liquid electrical tape on everything, as there were a bunch of solder joints and lots of cut wires.
To be double sure, I put a coat of liquid electrical tape on the side of the case next to the wires, as well.
More modern supplies have voltage sense wires, which are connected at the motherboard connector, to monitor the voltage of the outputs. These are smaller wires of the same color as the wires they monitor, and must be connected together. Mine had them for 3.3V (orange), 5V (red), and I can’t remember now if it had it for 12V (yellow), but I doubt it, as 12V is not critical on a computer. This is the 5V voltage sense wire, connected.
I put it all together (quite a tight fit now), and measured the output. It looked pretty good, at 12.09V, according to my $5 multimeter.
Here’s what it looks like, completed.
Now, I didn’t get a chance to test it much, but the initial results seemed disappointing. I put it on a half amp charge on my three cell Lipo quad pack, and I heard the fan slow down as soon as the charge started. I used the charger’s menu to find out the input (PSU) voltage, and it was around 10.4 volts. Wow, I thought, that’s disappointing, to drop that much under that little of a load. I then tried to up the charge to 6A, which I figured it should be able to handle no sweat, and the charger stopped the charge because the input voltage dropped too much (it can function properly down to 10V). Since it’s rated at 18A, I was honestly very disappointed. I mean, I know the charger won’t be very efficient, as it has to have a buck/boost converter, but even at 50% efficiency, at 12V input it should not have drawn more then 12A input, and I doubt it’s only 50% efficient, I can see 75%, but not 50%. But even then, I should have 18A, right?
Well, I figured I would, but it appears I don’t. I’m not quite sure why. I did think it might be because power supplies sometimes have split rails, and I might have only been pulling from one rail, so I might only have had half the power available. All in all, I’m not quite sure why I don’t have the power I should. I’ll test it more tomorrow, and see just how much current I can charge at before my power supply lets me down.
I’m also going to keep my eye out on a high current, 13.8V power supply on eBay, the ones designed to power radios and other high power electronics that are designed to run off vehicle power. They are generally pretty pricey though. I might be able to make my own, as well. We’ll see.
Testing results will appear in part 3.
My hobby charger, like many of them, runs on 10-18V DC, which is rather handy, as it allows you to use crocodile clips to connect it to your 12V car battery when you’re out flying somewhere, which is the handiest power source around. But, when it comes to home charging, this means you need a high current DC power supply. These can be rather pricey…or are they?
Hmm, what’s this? I like hackable parts.
Enter the PC power supply unit, or PSU for short. These can readily be found anywhere for free, just watch for someone throwing out a desktop computer. Being a geek, I tend to get a few old computers, and when I saw this 450W power supply I knew I’d have a use for it someday. Well, I had done this once before, for my dad and me when I was younger, and I knew it wasn’t a hard job. The label from the above picture says I can get 12V at 18A, which is pretty dang good. That’s 216W, and I only have a 200W charger at this time, so I should be able to use the charger to its maximum capacity, something I’ve only been able to do with a car battery as a power source until now.
I have to go, so I’ll just leave you a picture, but I have the power supply in working condition. I get somewhere in the neighborhood of 12V, which is cool with me, but I didn’t do extensive testing yet as that’s not a smart thing to do with the current state of the power supply. Nothing is protected against shorts right now, so even just checking the voltage had a potential hazard. Not to me so much, but mainly to the power supply, as one slip could short the output and render the power supply useless.
It’s not nearly as dangerous as it looks, just don’t touch the fat traces on the printed circuit board…
Still to go is a power switch, two power status indicator LEDs, and lots of liquid electrical tape slathered on all the cut wires and soldering joints. This, as well as the process used to convert an ATX power supply to something useful outside a computer, will be covered in part two.
Finals finished yesterday, for me, so I now have about a month with a lot more free time on my hands then I’m used to having. This is a good thing, I needed a break. It also means that I can, and did, start construction on my quad, for which I received all the parts to build back in October.
Right now, I have assembled the frame, which was made out of a 6″x6″ piece of 1/4″ thick birch plywood. This is the “body” of the quad, the platform upon which everything will sit. On the bottom, I attached the four arms with wood glue. The arms are 1/2″ square basswood, each 13.5″ long.
Here, I am aligning the arms onto my workbench, and using tape to secure them so they don’t move until I can get them glued. Not shown, but I also taped the arms to each other in the center, for gluing.
I applied glue to the arms.
I applied pressure, and wiggled it back and forth slightly until it felt “attached”, then held pressure and used my PowerShot staple gun to sink in two brads per arm, to hold them in place while the glue dries. The strength comes from the glue, not the nails. The brads were flush sunk with a hammer, as the staple gun leaves them sticking up about a millimeter or two.
Yes, that board is 6″x6″, and yes, I have big hands.
That entire process went really quick. I didn’t show it, but the plywood came as a 12″x6″ sheet, and I simply used a miter saw to cut it in half for my quad. Nothing fancy there. Here is the quad as the glue dries.
Lots of cool stuff in this picture.
I have to go run some errands, but once I come back, I plan on starting some work on the quad’s electronics, so there may be another update today still. If not today, tomorrow for sure.
Writing a blog is work, plain and simple. It might not be for others, but it is for me. Someone may ask why, and that’s understandable, after all, all a blog owner has to do is put some words down on the screen on a semi-regular or regular basis, right? Well, sort of, but not quite. First off, you have to have something to write about. Secondly, you need to have the time to write something. Thirdly, you have to have the desire to spend a fairly sizable chunk of time writing your blog post. Finally, all three of the above things have to happen at the same time. You might not have something to write about, even if you have the time and desire, but more often then not for a type of blog that I have, talking about projects, I’m much more likely to have something to talk about then the time or desire to actually talk about it on my blog. Indeed, a lack of desire is why I haven’t posted since the middle of October.
My lack of desire stemmed from being fairly busy, after all, I work 40+ hours a week at night, go to school in the morning, and sleep in the afternoon. Even such, I still have plenty of time I waste mindlessly browsing the internet, where I could have instead brought up WordPress and started a draft, which I could write in increments, right? Well, right. But I didn’t, because when I didn’t need to work, sleep, do homework, or be in class, I would rather see my girlfriend, catch up on my motorcycle forum, or check up on the latest position of the New Horizons then to sit down and spend an hour wrestling with my jumbled thoughts until I spew something somewhat legible onto the page and hope someone finds it interesting or useful.
An artist’s rendition of New Horizons as it will appear during its flyby of Pluto and Pluto’s moons on July 14th, 2015.
The bottom line is, however, that the more free time I have, the more likely that my desire to update my blog happens at the same time as I have time to write the said update. And, lately, I just didn’t have much time. Today, I just took my last physics test of the year, yesterday, my last calculus test. I have no homework due for tomorrow, which is unusual, but a result of classes winding up. I have three more lecture hours left, in three different classes, two of which will only be review for the final, the third (statics) I’m not quite sure (but homework is due on Friday for statics). I have one final Monday, and two on Wednesday, and then I’m done for the semester, which I’m pretty excited for. You might think I should be studying for my finals, but one can only due so much, before a point is reach past which extra studying in no good, and that point was reached today. Not only did I get unusually short on sleep this week, but I had review for the final in calculus class this morning, followed by doing homework for statics, then statics class, then last minute review for my physics test and filling out my note sheet, then my physics test. After that, I was pretty sure extra studying wasn’t going to do me any good, so after talking to a couple of people at school, I came home and just chilled. During this time, I decided to update my blog.
This post itself is another reason I avoid writing these when I only have an hour or two of free time, and that’s because this post itself is quickly heading towards the one hour mark. I’m currently at about 50 minutes and just over 630 words in this post, as I write. When I start writing, I generally don’t write just a sentence or two, and I generally like to finish it instead of saving it, which is why this post will end up taking over an hour to write, all in one block. If I wasn’t writing this, though, I could have been causing chaos in Just Cause 2. Do you know how much stuff you can blow up in an hour in Just Cause 2? Quite a bit, in case you didn’t know.
Looks like someone’s having a bad day.
Not only do I tend to write a bit, and want to get it all done at one, but then you have the time it takes to find or take, edit, and upload images, get the link codes, then correct mistakes, edit, and preview the post, find another mistake, and so forth, until the publish button is hit, and the post is complete.
Before I leave, I would like to mention a couple of things, which will probably receive time in future blog posts. First, I bought myself a rubber ESD mat for electronics work, and I’ve built up a 0-30V, current limited power supply…well, the part on the protoboard, that is. Second, I’ve bought my first high power LED flashlight, 600 lumens. Yeah, that’s bright. Third, I have not forgotten my quad, by any means. I plan to start the construction next week, when finals are over. Expect more blog posts at that time, as well.
I told you it was bright, but you didn’t believe me now, did you?
jseyfert3 