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Part 5: More Parts On The Way.

ElectroMaster — Wed, 26 Aug 2009 23:20:43 GMT

I�ve ordered a few more parts which are needed for phase 1.

EDF Ducted Fan Unit 2.56 inch 6 Blade

Code:

Blade Diameter: 66mm / 2.56inch
Outer Case Diameter: 70mm
Wall Thickness: 1.9mm
EDF Length: 61mm
Front Shroud Diameter: 81mm
Motor Mount Holes: (Adjustable, from 25~26mm)
Blade Type: 6
Shaft Size: 3mm

Recommended Motor: 380 / 28-47 9 Turn
ESC: 36A
Rpm: 4,000kv
Power: 750~950g Thrust

This is a fantastic EDF unit, the look, size and specifications are perfect! One problem I see is the motor that I ordered has a shaft of 2.26mm which could pose a problem. But hey, we�ll resolve that problem when we need to.

Hitec HS-55 Micro Servo Motor

Code:

Speed (sec/60o): 0.14
Torque (Kg-cm/Oz-in): 1.3/18
Size (mm): 23 x 12 x 24
Weight (g/oz): 8/0.28

Servos will tilt the EDF units, 2 have been ordered. Another component that may cause an issue, this is due to the torque being rather low. But again we will have to do this by trial and error.

SFE Single Axis �300�/s Gyro Breakout Board - LISY300AL

Code:

Complete rate gyroscope on a single chip
Single Axis 300 degree per second maximum range
Low power single axis gyro 
Comes fully populated and tested
Dimensions: 0.8" x 0.8"

The gyro will allow the Axon micro controller to determine the angle of the HK which will keep the craft stable while hovering � which is actually more a phase two feature but it will be important to start work on this early..

Next testing, then construction� We�re well committed now!

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Part 4: Specifications For the Motors, ESCs, And Battery

ElectroMaster — Sun, 23 Aug 2009 15:14:19 GMT

Since I've never made anything like this before, choosing these parts was rather hard. I have done as much homework as possible but there is no way to know how well a part is going to work with another until you try it. So here are some details..

Motors: Mystery 5000 Rpm/V Outrunner Brushless Motor D2825-5000

Code:

Model: D2825-5000 
Rpm(Kv): 5000Rpm/V 
Max Currect: 25A 
Max Eff: 96% 
Weight: 35g ( Motor Net Weight ) 
Total Length: 40.1mm (Motor and Shaft) 
Motor Body Diameter: 27.8mm 
Shaft Diameter: 2.26mm(Front) 
Shaft Length: 13.9mm 
Recommended Input Voltage: 6 - 18 Volt

I was rather impressed with the weight a lot lighter than expected and the max current is perfect to allow more air time than orignally thought.

Electronic speed controllers: Mystery 30a ESC

Code:

Constant Current: 30A 
Input Voltage: 5.6V - 16.8V 
Max Current: 40A 
Low Voltage Cutoff: Shut Off / Power Reduce / Ignore 
Inside Impedance: 0.0044 
Reversion: Yes 
Size: 57mm X 25mm X 8mm 
Weight: 18g (Net Weight) 
PWM Frequency : 8KHZ/16KHZ

Since I ordered the Axon microcontroller a few days ago I've been reading about frequencies and timing. The PWM (Pulse Modulation Width) 8KHZ doesn't give us enough speed variations, so 16KHZ is perfect!

Battery: Mystery 25C 11.1V 2200 mAh Lipo Li-Po Battery

Code:

Capacity: 2200mAh 
Burst Rate : 30C (2200 X 30 = 66000mah = 66amps) 
Continuous discharge rate: 25C (2200 X 25 = 55000 = 55amps) 
Voltage: 11.1V 
Cells : 3 
Size :105mm x 33mm x 22mm 
Weight: 170g 
T / Deans Connector

This is a relatively light battery for the capacity and was a major factor in deciding on this battery. It will definitely have enough grunt to run two motors (25 amps each) Depending on the overall weight of the HK we might put two of these in or replace with a heaver more powerful version.

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Part 3: Choosing A Micro Controller

ElectroMaster — Fri, 21 Aug 2009 01:36:56 GMT

After a few solid weeks of being tied up with work, I've managed to get a few hours free, and am going to try and use that time to decide on a Micro Controller.

So since we know most of the requirements it shouldn't be too hard. For the HK to work we need a minimum control over 2 servos, 2 speed controllers, 2 gyros, and about 4 proximity sensors. Other peripherals would be GPS, Bluetooth, and maybe Wi-Fi. We also require the Micro Controller it to be as light as possible. I found a few that meet the listed requirements, there is some really neat stuff out there for this kind of thing.

Qwerk
Features: 340 grams, 32+ IO, 200 MHz ARM9 RISC processor
Pros: Very powerful processor, has Wi-Fi built in.
Cons: Weight and size are an issue.

VEX
Features: 127 grams, 16 IO, PIC18F8520 Processor
Pros: Robust, very powerful processor.
Cons: Weight and size are an issue.

Axon Micro Controller (small and light)
Features: 34 grams, 55+ IO, Atmega640 Processor.
Pros: Lots of headers, small and light, powerful processor and lots of memory.
Cons: Not much built onto the main board requiring lots of peripherals.

Arduino MEGA ()
Features: ~60 grams, 70 IO, ATmega168 Processor
Pros: Lots of IOs
Cons: Peripherals can be bulky.

Arduino Bluetooth
Features: ~60 grams, 8+ IO, ATmega168 Processor
Pros: Low power requirements, has built in Bluetooth
Cons: Peripherals can be bulky.

Droids SAS MuIn
Features: ~50 grams, 13 IO, PIC18 Processor
Pros: Supports Xbee for Wi-Fi, Free GUI
Cons: Peripherals can be bulky.

I think most of these would be ideal for the HK, the only two that don't really fit are the Qwerk and the VEX as they are just too heavy. The Axon on the other hand is a mere 34 grams, has all the features needed and was the final choice. Over the next day or so I'll order an Axon and within a week or so I should have it to play with!!

Oshonsoft 16Fxxx Ext Module 74LS164

ericgibbs — Sun, 16 Aug 2009 12:27:47 GMT

External module for a 8 bit Shit Register, for use with the Oshonsoft Simulator.

Unzip the zip file to the hard drive.
Run the 74LS164a.exe file, a simple asm/hex demo file is included in the zip.

Running the *.exe will start Oshonsoft.

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SRzipped1.zip (43.6 KB, 67 views)

Marvin the Martian awards

unclejed613 — Sun, 09 Aug 2009 20:40:36 GMT

"I'm going to blow up the earth, it obstructs my view of Venus......"

quite often there are posts i see, that remind me of this classic cartoon line. common subjects are EMP generators, lasers (in the Megawatt or Gigawatt range), and other devices in the "infernal machines" class. usually the interest in these devices is from some type of annoyance factor ("my neighbor plays his stereo too loud", etc...)... in fact i've been known to dabble in the "infernal machine" category myself from time to time (once built a Tesla coil that blanketed the 4-story apartment building i lived in with wall-to wall RFI, and burned out every CMOS chip within 50 feet). my interest was just plain curiosity, i wanted to build one just to see it work. while i have no problem with experimenters trying stuff out to see it work, i do have a problem with annoyance driven projects whose purpose is to intimidate or exact retribution. grow up, and tell your neighbor his stereo is too loud.

fortunately, for the rest of us as well as the tinkering megalomaniac, the laws of physics imposes severe limitations on the ability for the average tinkerer to create anything that will have much of an effect for more than a few feet. EMP devices are a commonly attempted construction project, but considering the number of watts one can tap from their typical home AC supply, and the physical limitations of the components available to the experimenter, i highly doubt anyone could build something that could do much more than erasing one's computer hard drive from 5 feet away. one of the limiting factors here is the Inverse Square Law. the intensity of an electromagnetic field decreases by a factor of the inverse square of the distance. when it comes to homebrew lasers of any significant wattage, the limitations on the tinkerer are very severe. many of the materials used in making lasers are somewhat pricey. you can't just go down to the hardware store and ask for a ruby or sapphire rod. to make gas lasers is less expensive in terms of materials, but the expertise required in glassblowing, as well as the tolerences in the mirror alignment (two optically flat 1/4" diameter mirrors a foot or so apart, aligned to within a 1/4 wavelength parallelism) still place these out of the abilities of the average tinkerer.

so, when i see "i'd like to build an EMP device to shut down my neighbor's stereo" or "i want to build a huge laser to burn my neighbor's dog when it barks all night long" don't expect any helpful comments from me. i WILL however, award you a Marvin-the-Martian award, because you need to grow up and learn to deal with your neighbors face to face.

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Simulate to verify Not to design

Mikebits — Sun, 09 Aug 2009 08:11:49 GMT

Back in my early days of design, we would work out designs on paper, put them to a schematic, and head for the cad department. As time grew a certain newly appointed project engineer gave the whole design team a speech. �Simulate, simulate, simulate� he said, as he emphasized the importance of simulating ones design prior to production release.

This was very good advice and I followed it as I learned the sim tools of Mentor logic. From this project managers advice I have become a disciple of simulation in the practice of engineering.

With that said, I find far too many now rely on sim tools as a design tool rather than a check tool of ones design. Instead of working out a problem, many rely on the simulation tool to do the work for them. This is not what the sim tool is for. You must first design your circuit, have a reasonable understanding of how it should work, once the design is made, then a simulation should be run. Do not use the sim tool as a crutch for understanding how your design should actually work.

I fear, far too many now use the shotgun approach to design work and merely tweak values on a simulator until the proper output is achieved. Perhaps the shotgun approach may bring you to achieving your goal, but you will never grasp why, and the why is essential in your growth as a designer.

My point, design first, simulate after, do not design by simulation.

Part 2: Size and Weight

ElectroMaster — Mon, 27 Jul 2009 12:12:32 GMT

A big part in this project is choosing the size to build the HK, and also the weight. To figure this out I have been trawling the internet looking for potential motors and batteries that will be suitable. By knowing the thrust of a motor it will allow us to determine the maximum weight that can be supported and then will give us an approximation on how big to built the HK. Also knowing the battery will give us some insight into how long it will be able to sustain flight.

So in my search, I actually came across some great info. It was quite a big learning curve as I never even knew about brushless motors. I was somewhat blown away by their power and efficiency! They are smaller, quieter and more efficient that a normal bushed motor. Excellent! I found one motor which weights 76 grams and can output 1000-1500 grams of thrust. Having two of these would support anything from 2000, to 3000 grams in weight (theoretically). Batteries have also come a long way since I last checked in. Last time I remember, there was just one common type of battery (that was affordable), and that was a typical Ni-Cad 7.2 volt. However, once again it seems like there have been improvements and I have my eyes on a Li-Po battery which is about half the weight of the old Ni-Cad battery type weighting only 180 grams and has the same, if not more power.

It seems we can reasonably get about 2000-3000 grams of thrust from two brushless motors powered by a li-po battery (or two?). However, it's important to note that 2000-3000 grams would be a measurement based on the maximum load of each motor. If the HK weighed this much it would more than likely only able to hover, and would have very little agility or acceleration, if any. In conclusion and after careful thought, I believe the best weight for the HK would be around a total of 1kg. This should allow enough power and thrust for it to quickly change course if needed or rebalance itself if hit or affected by its surroundings. At 1kg I would expect the HK to be around 50cm long.

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wouldn't an AC ohmmeter be handy?

unclejed613 — Fri, 24 Jul 2009 03:49:00 GMT

it would be nice to be able to measure impedance of an AC circuit as easily as measuring DC resistance, wouldn't it? there are many times in the audio business, when i would like to find out what the impedance of something is at a particular frequency, and i usually have to resort to some indirect method. an impedance bridge is a piece of test equipment that measures impedance, but such a beast is expensive, and is an indirect method, and a bit more complicated than putting a pair of test leads across a device and reading a number. i would like to be able to put a pair of test leads across a device and know it's impedance as a direct measurement. of course there would be one added step, dialing in the frequency i want to measure at, but i can live with that one extra step. so how to go about it?

a DC DMM ohmmeter circuit is a simple device. you have a digital voltmeter across a pair of probes, and a DC current source set to a known current. if the current were for instance 1mA, then the voltmeter would directly read 1V/kΩ, so a reading of 0.6V would be a measurement of 600Ω. simple.... i like simple, so how to do it for AC? could it be that simple? i think so. i have a function generator with a sine wave output, and a true RMS voltmeter, so how do i get a known AC current, when my FG has a voltage output? a series resistor introduces error, especially once the impedance being measured is more than a few percent of the resistor's value, so a series resistor is not the answer here.

it pays to browse the Application Notes of IC manufacturers like Analog Devices, TI, and National Semiconductor. i've learned a huge amount over the years from app notes, more in fact than one could learn in school. if you have a creative mind, you can see something almost insignificant in an app note and solve a huge problem with it (like using LEDs as opto sensors. somebody saw a little blurb about it in one of TI's app notes back in the 70's, did some experiments with it, and now it's common practice). so, while thinking about how to make an AC current source, i remembered seeing a "bipolar" current source. of course, this current source was shown with a DC input, because nobody in their right mind would ever need an AC "constant current" source (AC constant current source IS a bit of an oxymoron, isn't it?). so i did a search and found a whole app note by NS, about the Howland current source. it turned out to be EXACTLY what i was looking for, but from the text, not hardly a mention of using it for AC. so i loaded up LTSpice, drew the schematic and ran the sim using an AC source instead of DC. perfect, with 1V AC going in and a 1kΩ scaling resistor i got 1mA out, no matter what the load resistance was. stage 2 was actually building it expecting some unexpected error that would disqualify the circuit as unusable. no such error ocurred, it worked exactly like the sim (which if you have any experience building what you have run on a sim, is the exception rather than the rule). so now i have a working current source, and the scale factor is easy to set. with 1Vrms in, and a 1k scaling resistor i get 1mA out. with a 100Ω resistor i get 10mA out. i can literally take a DVM and my device, dial in a frequency, and do a direct measurement of impedance. so, shown below is an excerpt from NatSemi's AN-1515, and the circuit i used for my current source. i used a TI TL2072 op amp instead, and replaced the input voltage source with my function generator (the -2072 is a vastly improved -072).

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Part 1: The Beginnings...

ElectroMaster — Wed, 22 Jul 2009 14:24:48 GMT

I have an idea, a big one. It's going to consume many hours - and annoy the heck out of my girlfriend, but it's going to be awesome! I plan to build an autonomous model air craft based off the Terminator movies, it's call a Hunter Killer, H.K. for short..

Since this is a rather large project I plan on breaking it down into three phases. The first phase will be building the craft (my initial thoughts are to make it approx 50cm long) which will have many hard to accomplish mechanical feats. The first one that comes to mind is solving the power to weight ratio. This will require choosing the correct materials for the hull and also deciding what types of motors, batteries, etc to use which will have enough thrust to lift it off the ground. This first phase is all about building the craft so that it has the engineering to fly.

Phase two, we have the challenge of getting the HK to hover and balancing itself (autonomously). Now, if you search YouTube for "model vtol", you will see that many of them are radio controlled and are very unstable, hard to fly, etc. This is because they have no auto balancing. For the HK to balance itself and eventually navigate it needs have some automatic system to detect its balance. It also needs to be able to correct itself when affected by the surrounding such as nearby wind, rain, etc.

The third phase we will focus on the brains of the HK and to challenge it. The first goal will be to control the HK manually in all directions, up, down, forward, back, left and right. Once we have full control the challenge will be to get the HK to navigate from point A to point B (using GPS) avoiding objects.

At the moment this is a simple outline of objectives that I want the HK to be able to accomplish, it's just the start. Over the coming weeks and months I will keep updating this blog with notes, test results, and any construction. Until next time!

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Rtfm

unclejed613 — Wed, 22 Jul 2009 02:06:41 GMT

everybody should know what this means...... if not here's a linux page with a description of this command and it's usage.........
http://www.wlug.org.nz/rtfm(1)
:D

ok, if after you read that, and you're still not sure, it means Read The Fine Manual, Read the Fun Manual, or another version not suitable for polite conversation.

working for a large service center, i see a lot of equipment that comes in for repair which, frankly, wouldn't have to if people pulled out that mysterious book that comes with your shiny new home theater system, sat down and read it cover to cover just once. and those who should read the manual are not only the consumer, but the sales staffers who guide the consumer in their purchasing decisions. two examples of this are from actual pieces of equipment that came in for repair recently one of them is from a consumer, one is from a home theater sales "tech". the first one (from a consumer adding an additional feature to their home theater setup, i.e. a second TV monitor) is the complaint on a Blu-Ray player. the customer, already having an HDMI TV monitor connected, was adding a secondary monitor to the setup, by attaching the second monitor to the component jacks (red, green and blue plugs). his complaint? no audio through the second TV monitor...... no it doesn't work like HDMI, it also needs a pair of audio cables, which is shown on page 6 of the owner's manual.
the second came from a sales floor "tech". complaint? multichannel surround receiver only has 2 channels of audio out to the speakers. the "fix" for this one was a single push of the Surround Mode button on the front panel, which switched from 2CH Stereo to 5CH Surround...... BTW, that one was on pg 12.
the sales "techs" and consumers aren't completely at fault here. engineers and marketing execs have their place in this mess too... a recent editorial in an engineering magazine was talking about the consumer electronic industry's fixation on "Feature-itis". Feature-itis has always been part of the consumer electronics industry, but for a long time, there was a very real, physical limitation on how many features could be implemented in a piece of equipment, it's called FRONT PANEL SPACE. mechanical switches and controls were limited on how close together you could put them in a piece of sheet metal, and you could see where every single one was set. there were also circuit board real estate and power dissipation issues. the more features, the more PC board real estate required, and the more packed the PC board, the more heat had to be vented somehow (and packing PC boards closer together made this difficult).with modern technology, however, there is literally no limit to the amount of features that can be installed (actually programmed is a more accurate term) into a piece of equipment. all that's needed on the front panel is a very few small buttons, and a few square inches for a fluorescent or LCD display and a window for a remote sensor. inside the unit you have a power supply, an amplifier section (i'm using a receiver as an example), and input-output boards for the signals and speaker outputs. these all take up a generally standard amount of real eatate inside the chassis.

what is new is the electronic "magic" to a) control all of the systems, interpret user input, perform signal and power switching, b)take all of the input signals and manipulate the signals, even adding effects and filtering, and c) monitoring the system for fault conditions such as shorted speaker wires, all of this continuously.

and all of this "magic" resides in an epoxy square, about 1" (2.54cm) on a side and 0.1" (2.5mm) thick. it all resides in DSP code, there can be thousands of features and settings coded into this small device, menu upon submenu upon feature settings. so many submenus and choices it's easy to get lost and forget what you just changed. you can no longer see the whole "front panel" at a glance and say "oh, i forgot to switch this back to 'tape 2'". all of your settings are hidden behind the front panel, where you can't see or remember them, and any one of them can dig you in deeper when you try to correct a mistake that suddenly cuts the sound out or makes it sound terrible. don't get me wrong, modern technology is very useful, and DSP solves a lot of difficulties that audio designers have been wrestling with for years (yes, now there IS such thing as a "brick wall" filter, and it works!!!!), but having too many features, many of them hidden in layers of submenus, is a perfect breeding ground for Murphy's Law, "If there is an option that causes a malfunction, the option will be set." Fortunately there is (and this is usually in the owner's manual near the back) always the Master Reset, which is great for getting a piece of equipment working again, but then the consumer has to start all over (but this time hopefully he Reads The Fine Manual.....).....

M41T00 Clock PCB

3v0 — Mon, 06 Jul 2009 18:17:17 GMT

I needed a clock module students could use on their BBs. I tried a few designs and came up with this right angle concept. I am sure it has been used by others.

The PCB is in two parts. The battery, clock chip and associated parts are on the main board. The I2C pullup resistors are on the upright PCB. More importantly the upright board provides a nice way to label the I2C and power signals.

The header pins come through the main PCB and soldered surface mount style to the upright.

The PCB did not come out well but it works, It was an experiment.
3v0

zip file

bryan1 — Sat, 04 Jul 2009 11:34:21 GMT

File for be80be

be80be board.zip

i void warranties.....

unclejed613 — Tue, 23 Jun 2009 03:56:48 GMT

actually, not me, since i work for a warranty service center, but i saw the t-shirt and had to post a picture of it. it says "I void warranties" and has a picture of many common screwdriver bits used in consumer electronics. if it's broke and it's still under warranty, get it fixed for free, don't open it to poke around. if it's out of warranty, and you don't have a service plan you paid for, go ahead, poke around all you like, it's already broken and you will a) find something simple like a bad solder connection, b) figure out what component has failed, c) take it to get fixed COD (take my word for it, the repair will cost less if everything is back where it belongs), or d) give up on it and toss it and buy a new one.

there may be no such thing as a free lunch, but a free repair on a warrantied item (or maybe the manufacturer can't figure it out and gives you a new one anyway) is a pretty good deal if you can resist the urge to see what made the thing tick before it broke.

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1kW inverters for free!!!!!!!!

unclejed613 — Sun, 21 Jun 2009 19:29:54 GMT

i see (and answer) a lot of posts both here and elsewhere about 1kW inverters. my immediate answer is usually something along the lines of "there's no such thing as a free lunch". first of all do the math. 1000W/12V=83A. assuming about 15% in losses, that's pretty close to 100A. not only are we talking "heavy iron" here for a transformer, we're talking heavy copper too, since the wire used in the primary circuit needs to have negligible copper losses at 100A. you also need about 20 MOSFETs per side (of a split winding on the transformer) assuming 10A devices, and a safety factor of 2:1. that also makes for a very large heat sink. so basically we're looking for a "welding" transformer with a 12Vct @100A winding, 00ga wire (or at the very very least 2ga kept very very short) 40 MOSFETs, and a very big heat sink.

like i said above, there are 1000W inverters that can be had for free, but it takes a bit of looking to find one that works from 12V. these would be computer UPS supplies. 90% of these run from 24 or 48V batteries, but once in a while you will see a 12V one. 99% of all UPS supplies get scrapped because of sulphated batteries, and the fact it's usually cheaper to buy a new one than pay somebody to replace the old batteries. these are a good "starter" for a 1kW inverter, since the heavy iron, wire, transistors, heatsink and driver board are already there, plus it's already in a chassis with AC outlets. however once you replace the batteries, you will soon find that you can't get it to run on demand. the reason for this is that the control logic wants to see the device pluggedin to line voltage when idle. you will usually want to find this with a schematic, but there is an AC detector circuit that wants AC present, then see the AC go away before it triggers the inverter into operation. the best thing to do here is find the actual logic line that starts the inverter and put a switch there, bypassing the AC detector. every UPS is different, so this is only a generality. you WILL need a schematic to find this, unless the signal is marked on the board somewhere (try looking for a signal marked something like START/STOP, or ACDET).

3 amp constant Current Schematic

bryan1 — Wed, 10 Jun 2009 09:03:10 GMT

Screendump of the schematic done in Splan5

The PCB artwork in Jpg format

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