(FOR THE SAKE OF PEACE,  I GOT RID OF THE CANNON TITLE - I wonder if the number of viewers will reduce drastically :)
(Credits for picture and video - katjahommel.com)
This is a laser mounted on a cannon-like structure made for a single purpose: Point to the sky and trace the position of a satellite. It gets data form a small program via Serial port and shoots to the infinity. It's not easy if you haven't done anything with electronics, but if you learn a couple of things, it's pretty basic. The design has two major drawbacks, that could be improved later:

• The code works but the movement is Jaggy when tracking in realtime. Converting angles expressed in doubles (A decimal point number with a lot of digits like 225.365844E) to the limited steps of a motor is just impossible. Possible gearing and fine-tuning to make movement smoother on slow tracking situations are still lacking

• The cabling is still cumbersome and  it won't allow fluid 360° movement in the Base (Azimuth) axis. So when passing from 359.9° to 0° the motor will have to go a whole revolution back in order to keep the track.

Being warned, we can start:

Step 1: Find the components

1 Arduino, (The bluetooth version would spare the need for a BT module, but wireless control is optional)

1 Adafruit Motorshield,  You can look on the site to get a distributor and will need to assemble the thing yourself (DIY from the very beginning). Making it is good for your self esteem.

1 Green Laser pointer, Depending on your country this may get hard to get on a store, but you can always trust in Ebay where they are cheap and easy to find.

1 Stepper Motor Recommended to buy a standard Stepper like the linked one from Sparkfun. I chose this for the base (azimuth) that needs to fully rotate 360°, because it has a decent step "resolution" and it's also a lot easier to control than a 360° servo.

1 Servo Motor  Standard servomotors are the easiest motors to control and they are light to mount in different orientations. They also have an absolute 0° position so you know it will always go back to the same position after you reset. For the elevation rotor this is ideal and their 180° range is more than enough.

1 Pan/Tilt Bracket This is useful to mount the laser on the Servo.

1 Lithium Battery or external power source. Depending on your stepper motor, this should give you between 7.4V and 12V with 600mAh - 1000mAh. The link shows the battery I used, but it discharged quite quickly and chargers aren't cheap. My household tip is to use your Video camera battery. That saved me in one presentation and the battery didn't even noticed it. Warning: A standard 9V Battery you'd use for prototyping will not offer you enough current to move the Motor flawlessly, so don't try too much with it else the stepper will behave erratically.

1 Bluetooth modem (Optional) If you work with a non BT Arduino and want to incorporate wireless communication, then let's try this.

1 Accelerometer compass (Optional and experimental) This gives you the chance to tell your cannon where the north is located, so it is more precise. But there are some issues to it and you're not really trying to shoot the sat down, so it's all up to you wether you want precision or not.

Prototyping wires (Jumper) A bag of 30cm-long and one of 15cm-long capped wires will be ok. These help keep things in place and some order. Yo'd like to have also a couple of wire rolls, just to patch something else or build the circuit for the laser.

1 Mounting hub for stepper Motor and some L Servo Brackets to assemble them motors...

1 Custom laser holder. This was self made and printed in a hacklab in Berlin, You might want to find a solution with some other holder or download the .stl find a 3D printer near you

4 acrylic plates of approx. 10x10 cm or bigger for the case

Bolts and nuts + steel angles + a driller and a screwdriver (See pictures in step 4 if this is not clear)

A silicon gun or a cold-silicon tube.
<p>hmm lithium ion 7.2 to 12 volt . I think with a regulator a lead acid battery (car battery) would give a huge runtime.</p><p>also it there any chance it could hit a plane and piss off the piolet </p>
<p>Could you modify this to track a star? As in, input the azi/alt or RA/Dec of a star, and the mount slews the pointer to point there? That would be awesome!</p>
you would have to study the movement of that star from a reference point, then build your machine on that point. its not tracking the star, it just pointing the laser were it is. that would mean you don't need blue tooth<br>
Great ible! As far as all the people complaining about pointing this at planes, please remember that it is pointing and tracking at an object very far away, thus barely moving. An aircraft is far closer to the source and will pass through the beam in a split second. In the very rare chance that the actual cockpit was in line with one if these, it would pass through before the pilot had a chance to realize it had. Again, great ible! Kudos
There are a lot of heated emotions and unhelpful wild speculation here. Many of these laws are posted online. Cornell was kind enough to post the primary U.S. Federal law on this subject here: http://www.law.cornell.edu/uscode/text/18/39A <br> <br>Many states have their own laws. And surely other countries are likely to have similar laws. <br> <br>It doesn't do anyone any good to speculate. And let's try to help each other, not get angry about it. <br> <br>And in many places, if you don't like the law, there is a process for changing it! <br> <br>Hey, have fun, and let's try not to hurt each other. :)
I really love Instructables; I think there's a lot of creativity and innovation that is expressed here, even if that includes spud guns or catapults that might inflict some minor local damage which might be mitigated by personal liability insurance. Or laser-printed fingernail tats ,,, <br> <br>And I understand that some authors believe they are protected by their liability disclaimers. <br> <br>But makers who discount the hazards of their expressions by saying, essentially, &quot;Well, maybe your laws would punish this to protect human life, but this might be legal somewhere ... maybe ...&quot;, gotta say: &quot;Get Real!&quot; &quot; <br> <br>Would Instructables publish a post about &quot;How to enliven a party by piercing a propane tank with an incindiary 30.06 round?&quot; <br> <br>No more blinding Instructable posts, please
A 5mW laser isn't going to blind any pilots, and it certainly won't disable any satellites. Everyone who is posting otherwise needs to do the math on diffraction-limited laser divergence; last equation on this page:<br> <br> <a href="http://en.wikipedia.org/wiki/Beam_divergence" rel="nofollow">http://en.wikipedia.org/wiki/Beam_divergence</a><br> <br> Even a PERFECTLY focused laser pointer beam will be spread over a spot several meters wide at airliner heights. To do the math yourself: green light wavelength is about 500E-9 m, and a laser pointer aperture is less than 1E-3 meters diameter, and planes fly at 10000 meters.<br> <br> This yields at least a 1.5m radius spot, and probably much more given that laser pointers have far from perfect optics. Moonlight is around 1mW per square meter, so the illuminated spot is guaranteed to be dimmer than moonlight, which makes blinding rather unlikely. Not to mention that the chance of just randomly hitting a plane is approximately zero. The only true danger from laser pointers distracting pilots is during takeoff/landing at an airport.<br> <br> No more uninformed criticism of projects, please.
Lets take your math as a starting point: 1.5 m radius at 10,000 m altitude, so 0.015m radius at 1 kilometer, right? And 100 times the intensity, your own math would indicate. Right? One tenth the diameter, one-hundred times the intensity? Because Pie are square? Ouch! That's gonna sting! And a jet traveling at pre-landing approach speed ain't' cruisin' at 17 kph! And is at a much vulenerable point in flight than when at stratospheric altitude. How about creating an instructable that interfaces a GPS with one of those computer-aimed telescopes to provide the same result with less dazzling impact?
Military pilots have reported routinely carrying their &quot;death ray&quot; shields... a pair of sunglasses. <br> <br>Engineers know the most common keychain pointers of 1mw and less are NOT ILLEGAL and NOT DAMAGING. Lasers come in Class 1, 2, 3, etc. A check of the laws (and the math) makes it obvious when a laser is a problem, and, when it's just silly to scream like Chicken Little. Hysteria is for those without a factual knowledge of science. (Some people are afraid of pure DiHydrogenMonOxide!)
DiHydrogenMonoxide is a commonly used industrial solvent which forms a large part of acid rain, can induce severe burns in its gaseous state and has been found in malignant tumors. and yet, it is still used in practically all food production. Only some companys are invested in reducing the concentrations in their produce. there are probably several sites on the evils of this particular chemical, and several petitions to have it banned. Everyone should conduct extensive research into this deadly chemical, then inform their senator/political representative/mayor/... to gauge their true intrest in public health ;)
Excellent description of H2O, can I quote your words? It's so hype-notizing! ;)
You can get more facts on DHMO at dhmo.org. For example, high levels of DHMO have been detected in many rivers and streams in the U.S.
Thanks for reminding me about that site, that's where I got my facts, but I couldn't remember the name
No, it's not gonna sting. Again, please don't post wild guesses about safety. 5mW / pi*.15^2 = .07 W/m, which is less than 1/10000th the intensity of sunlight and will not cause pain. And again, my numbers were conservative so it will probably be far less. As I said, it's enough to be visible and could be a distraction during landing, but we can probably assume that people are not doing stargazing at the end of a runway, so the chance of accidentally distracting a landing pilot is less than from just turning on an outside light, for example.<br><br>A computer-aimed telescope is much more expensive than this project, it can't point out satellites to a crowd of people, and it already comes with tracking software. Lasers are a very commonly-used tool of astronomy.
Also, even if you did somehow manage to hit the cockpit of a plane, planes aren't stationary. Typical cruising speed of a 727 is about 600mph. Traveling 1.5m takes a little less than 6 <strong>milliseconds</strong>. That's barely long enough to be noticeable, even if the apparent brightness were much greater than moonlight. I realize the length of the cross section of the beam will vary depending on the angle between the beam and the path of the plane, but this gives some idea of the order of magnitude we're talking about.<br> <br> On the off chance that a plane travels right through the center of your laser (<strong>highly</strong> unlikely) upside down (even more unlikely) they'll only notices a flicker of moonlight-intensity green light. Given that they're upside down, they probably have more important things to worry about.
Haha, good point.
Plus, wouldn't they have to be flying upside down for these calculations to matter? At the angle required to actually hit the pilot, they would be many times further away.
If swinging around almost 360 degrees at the zenith is a problem and you are truly using this as a sattelite tracking device you wont really be using it near the horizon. Therfore you could use an equitorial mount and point the equitorial axis at the north horizon. Then this problem would only occur at the south and north horizons but you probably cant track a sattelite much below 5 degrees from the horizon.
OK, so you have a gimbal lock at vertical---you could avoid that by having that axis pointing horizontally; the hemisphere would then be parametrized by both motors running between 0 and 180 degrees. On one hand, this loses half of the resolution, unless you gear the motor down 2:1 or more.. On the other hand, now you could use servos.
I agree. let's don't panic, this is not a weapon. Perhaps a symbolic one. I'd be eager to see moods and alternate versions of enthusiasts with more knowledge. If anyone gets to it, please share!
Deals Extreme (DX.com) has stated that PayPal is refusing to process orders on laser devices 5mw and higher. Not sure of veracity. Just a heads up for folks.
DX got a troll comment in a user reviews area on their site a long time ago. The person claimed to represent an agency of the US government and told them to stop selling lasers to the US. It was proven to be a fake troll comment, but DX never changed their policy. Maybe they did not have a person who knew english well enough to find out if it were true or not?
Great going on your laser ,remember yours and others safety depends on your safe positive input. 30 years ago I solved your stepper motor problems, by oscillating the fields and changing the band widths a 1,000 degree movement can be acheived. this was in answere to the event of a solar flare wiping-out those satelites you are looking at. this provided a portable means of triangulation.Navigation.The company was able to beak the code after 6 months and this was later sold BY Paravet . (Note)-All chinese computers use Paravet designed keyboards.
That idea of oscillation for better stepper accuracy, was that related to stochastic resonance? I remember George Carlson worked on that in the 1980's.
The problem with aircraft and lasers has to do with divergence. A laser pointer up to about 50ft looks like a small well point, but the further your &quot;target&quot; the larger the point will get. So on a nice clear night, you can effectively light up the entire cockpit of a airliner making it very hard to see for the pilots. <br> <br>However, on the legal issues (at least here in the USA) I am pretty sure as long as you don't intentionally &quot;paint&quot; aircraft with it you should be fine and lasers are legal for use in astronomy, but laws vary by place to place even in the USA so check your local laws first. Even if you happen to accidentally target an aircraft, since your laser is tracking a satellite its pretty much stationary and an aircraft will only get a blip of light from it before it passes. I doubt that is considered menacing aircraft, you would need to do it repeatedly. Obviously in high air traffic areas such as airports, large cities etc its just flat out illegal, but anyone out in the country or in small towns are probably fine.
All probably true and accurate. but very legalistic ... basically WHY would anyone want to project likely harmful interference that could blind, even for a moment, the guiding factors of aerial vehicles carrying potentially hundreds of fellow human souls? How selfish/solipstic is that? There are many devices and applications that can orient people to celestial events that don't involve the immediate jeopardization of fellow beings; just say &quot;no&quot; to pointing lasar beams randomly into the Universe ... (trying to be nice about saying &quot;Heck No!&quot; to random death ...) <br>
As stated in the very ible, its more about learning electronics then anything. Personally I feel even my comment was a bit over dramatic, and yours even more so. You have to remember, there has been a total of zero (0) deaths caused by laser pointers menacing aircraft. Yet yearly hundreds are fined, and caught for doing so and none result in death.<br><br>The fact you seem to think a simple laser pointer, pointed at an aircraft is putting hundreds of people in immediate danger of death is well, over dramatic and a bit silly. There is no &quot;random death&quot; here when used responsibly or even irresponsibly, only the very slight potential. You getting in your car and driving puts more innocent people at risk then all the laser pointer &quot;attacks&quot; on aircraft combined. Not trying to be argumentative, nor do I support menecing aircraft with laser pointers, but lets be realistic here.
Because it is &quot;coherent&quot; light, unless aircraft windows are going to be filtered/tinted against the specific frequency-range of these pointers, the risk of blinding a pilot or passenger remains very real. The comparison to driving are car come in a little too far from left field, as their is a necessity/grandfather-clause factor involved in the motor vehicle. Deliberately pointing a laser at aircraft is unnecessary and achieves little--all risk, no useful result.<br> <br> Here, in Australia, people <strong>actively</strong> menacing aircraft with high-power laser pointers resulted in their being banned. To own one you must be a registered member of a recognised Astronomy group and, it is common practice for the two clubs of which I am aware to advise CASA (Australia's <em>Civil Aviation Safety Authority</em>) of times and locations that such pointers are likely to be used. Even now, we still have too many instances of such <strong>deliberate</strong> menacing. While I'm not allowed to go out and buy a hand-held pointer, I can still purchase a high-power laser inside a DJ-rig and there is nothing stopping taking that outside and taking exactly the same risks.<br> <br> Australia, culturally, likes to point out the stupidity of Americans as a source of humor yet, we have our share of idiots too.<br> <br> If this is being used domestically, I would suggest a simple safety-modification: Create two laser modes, one for locating--where the laser remains &quot;on&quot; until the target is acquired and, the second for viewing--where the laser pulses &quot;on&quot; for 5 sec, &quot;off&quot; for 15 sec. Adjust the pulse widths to optimise the photographic opportunities of your viewing audience.<br> <br> A friend of mine has a tracking telescope. From the sound, and speed of movement, I think it takes a whole rotation of the relevant stepper motor to move the objective head by one degree. That's very low gearing indeed, although it's moving far more mass than your project.<br> <br> <strong>I like your project </strong>but I'm disappointed that other people's idiotic behavior raises such a high level of safety discussion in the first place.
&quot;Blinding&quot; pilots? Come on, we couldn't hold a beam on target long enough even with the STARWARS PROJECTS in America to do damage unless we spent BILLIONS of dollars on the equipment! <br> <br>This 'ible is not focusing a strong beam, the math does not hold up. <br> <br>Annoyance maybe, dangerous? No. <br> <br>This project has plenty of caveats and disclaimers, everybody calm down.
The discussion has <strong>exceeded </strong>the boundaries of this i'ble, and now targets <strong>idiots </strong>who actually want to do damage or injury.<br> <br> If I personally wanted to menace an aircraft from my own back yard, the only such craft available would be military, and they fly so fast and so low to the ground that they have been and gone before one even hears them. Despite living near a very good quality airport, we have no local civilian air traffic.<br> <br> I know the whole safety thing has been blown out of proportion and is getting off topic but, to paraphrase Einstein, &quot;There are two tings in life that are infinite--the Universe, and human stupidity but, I'm not so sure about the Universe.&quot;<br> <br> Average laser pointers are <strong>restricted</strong> in power such that a person has a chance to close his eyes before any permanent damage is done. Astronomical lasers in airspace are a <strong>potential</strong> hazard. High powered devices in the hands of idiots? I leave the potential outcome(s) to your imagination.<br> <br> Of course, the SDI platform didn't work. There is a huge difference in distance between <strong>air</strong>-space and <strong>space</strong>-space, and at this point in time one can generate far higher power laser beams on the ground than in orbit.<br> <br> If you can lift multiple tons of fissionable material into orbit without blowing Cape Canaveral off the map, and without it impersonating SkyLab, please publish it as an i'ble. NASA would be very interested and you'ld be offered excellent employment opportunities.
At the rate that a laser spreads and degrades, &quot;Universal&quot; distances would be quite safe. Even the strongest lasers available to &quot;domestic&quot; people would not be powerful enough to observe the reflection mirrors that NASA left on Luna.
Very true, you CAN get high enough powered once as a civilian in the USA that could potentially cause harm from such distances, but they are VERY expensive, rare to see for sale, and are not &quot;pointers&quot; they are table mounted lab equipment. Nor are they of any spectrum visible to the eye (IR).
<strong>Can</strong> or <strong>Could</strong>? As the main concern of all this discussion is menacing aircraft, I don't see that your average backyard idiot would derive any pleasure from painting an aircraft in IR. As a direct result of this discussion I am currently in conversation with Australia's CASA regarding filtering out the green laser frequencies on all Civilian aircraft, and it may well be that it becomes an International Standard on construction of all new aircraft because I do eventually see that rescue beacons will be aiming a laser directly into the sky to make them easier to locate.
WOW - I would be VERY careful about this one. First off, the feds ARE cracking down on any kind of HP laser operations anywhere near any big city and/or airport. As there are plans on other sites to specifically make rifle stock style &quot;laser cannons&quot; with HP devices just for &quot;painting&quot; aircraft cockpits your going to be very hard pressed to explain to that FBI or Homeland Security types just why this gadget is any different (&quot;oh, it's for blinding Satellites, not airplanes&quot; - right!). Having worked on optical sat ground systems I can tell you this little gig would probably not harm that 2 billion weather sat that's bucking down 10 terabytes of needed data per day but I would not entirely bet on it. But say it did it the jackpot and blind a surveillance sat (as in some enterprising DIY type put a 1000mw or bigger IR pumped laser on the platform) you can bet your last bippy you WILL be getting a call from the feds under possible &quot;terrorist&quot; charges (wanna bet the FBI and/or HLS follows Indestructibles even as we blog here?). This is a real gray area and you could be uncovering your assets doing this big time. <br> <br>BTW - I love 'sructables and the whole DIY concept but don't think for a minute you have a cart blanch to do possible harm to aircraft or 7 and 8 figure sat systems that millions depend on. I use a 5mw green laser to aim my 12 inch DOB reflector and I am very careful to ONLY use it way out at a dark-site and only momentarily to find a target.
Very cool instructable, but given the times we are living in I would absolutely agree with JTomM and NOT advertise this as a satellite aiming device. Anything to do with aiming a laser at planes, vehicles, satellites, etc is a very bad idea.
Holding a piece of paper up as a temporary sighting screen will accomplish the task easily. Stand beside the line of sight where the beam will point (not in the direct path of the beam), hold up the paper and *momentarily* flash the laser onto the paper and you'll see where the satellite orbital track is. Paper blocks the beam from entering the atmosphere and even the FCC does not complain about &quot;propagating an unrestricted beam of coherent radiation out of the atmosphere.&quot;
I disagree regarding satellites. If a ground-based domestic laser pointer can damage a satellite, it could only be optically and, that would mean that the satellite was viewing something it shouldn't be. A visit from the &quot;feds&quot; would be an admission of this. <br> <br>Yes, a bigger, more powerful unit could upset a weather viewing satellite, but highly unlikely. When it comes to interfering with communications (usually microwaves), please explain how &quot;light&quot; could upset it and, yes, you are allowed to treat me as ignorant on this aspect.
I was bitterly disappointed to find that this was not in fact, a moon blasting death ray.
Greetings: as a pilot, astronomer and owning several lasers myself, I understanding the concerns being expressed and they are to a small degree legitimate, I have to say first of all using a 5 mw laser on a sat. is of no concern in regards to how it affects the Sat. because it doesn't . The the beam will be so diffused by the time it gets there if any of the light arrives at all it would be virtually undetectable.. although there is one hand held green laser that is capable of painting a sat ( has a much greater output than 5 mw) ...and they are quite expensive... I have owned green lasers with output power up to 400 mw. and they are not capable of being a problem for orbital craft although they will easily burn things around the house .. In regards to aircraft, unless you live close to an airport the odds of you striking an aircraft by accident are almost non-existent . I have used the a fore mentioned lasers on my 16 inch reflector for years and will continue to do so. I have yet to paint an aircraft with one...It is literally the best way to aim that beast before you can begin to use the robotic tracking... I think your project is fascinating and you are right about some sats being very faint and this would make it easy to point out their path as well as to find them in the first place.. You have obviously stated your intent for the use of the device and mentioned the necessary disclaimers.. and as I stated it would be hard to hit an airplane in the windscreen with this device under normal flight circumstances if you wanted to.. In the event of an aircraft passing by and by some slim chance happens across your track you can always switch the beam off.. I think its a great project! Lastly in order for a laser to be effective in blinding the crew it would almost have to be targeted to do so and be at a time when the aircraft was on approach or possibly on departure although the window for the latter would be small as the nose points up climbing out. During cruise the best a laser could do would be to strike the plane on the bottom having virtually no effect on the crews visibility.. An aircraft would be most vulnerable on approach as the nose would be level or pointed down as they came in... In this scenario the laser on the ground could be at a very good angle to illuminate the cockpit but would almost still have to be intentionally aimed at the cockpit...But we live in a society that seems to think the answer to everything is to ban the device. I have no problem with arresting anyone who purposely shines a laser in to an aircraft , car or any other people mover and intended to do so.. but legitimate use of them should be available to everyone.. I understand every ones concerns ( and some are a little dramatic) but to cause flash blindness in the cockpit of an aircraft with a low power laser pointer you have to be very close and at an angle conducive to strike the windscreen of the aircraft in other words .. You have to be trying to do it...
Awesome project but unless if you are from outside of the US I was told that it is illegal to point a laser into the sky.
I'd hope that instead of focusing on arresting or prompting the arrest of a few jokesters pointing lasers skyward, those in relevant positions would work to harden technology that can so easily be foiled. If a laser is such a threat to an airplane or satellite, then enhance the technology to be immune to it. This could be as simple as adding filters or intelligent shutters. Heck, maybe we should write an Instructable or two for Boeing, Airbus and others to use as a starting point :-) <br>Relying on kids (and some curious adults) to stop playing around with lasers pointed skywards, is silly. The people who really are intent on destruction aren't going to be deterred. As someone else pointed out, they'd be using IR lasers among other tactics. The best deterrence here is hardening the target. <br>I've always found it funny when they ask people to turn off electronics during a flight. If this is such a real threat, then how do they know that some crazy person isn't sitting in the front rows with a carry-on full of safe-looking but modded electronics that he's not only not turning off, but he's also got directional antennas pointed directly at the cockpit?
I absolutely agree. Hell, I always ignore those silly requests to &quot;turn off electronics&quot; every time I'm on a plane...which is often. To this day, I've never seen a wing fall off or any other adverse reactions. Oh wait, I think I saw someone throw up once. Oops sorry, I guess I was wrong.
The &quot;cannon&quot; is actually what attracted me to it. No offense but count me as one of the people being lost.
Hello, i read that you have trouble with 360 rotation? <br>This is an idea why not have a stepping motor instead of a servo? <br>Second thing cable routing can always be time consuming why not mount the motor upside down and have the rest of your laser bolted to the motor and your sharf connected to a thick steel. <br> <br>third option will be hard but it would look cool make three ring tracks, use thin bits of copper or even cut a folk to use as a brush, with some crazy glue and some plastic bits you could have 360 rotation but i am sure you would still need that stepper motor. <br> <br>where to buy stepping motor?. <br>Don't. <br>Many can be found in broken printers and scanners.&quot;most printers and scanners have good stepping motors in them plus there FREEE&quot; <br> <br>nice work i shall duplicate sometime, as i not played with my arduino in sometime :(.
Protonumerique:<br> <br> An excellent project. I'm interested in the satellite-tracking aspect because I'm an amateur radio operator and there are a few &quot;birds&quot; launched by &quot;hams&quot; for their use. If you're interested, Google AMSAT. Anyway, the VHF and UHF antennas we use (often handheld) have narrow beams and they must track the course of the satellite. Usually this is done by hand, getting the Keplerian data on the satellite path to swing the antenna to follow it, often using the compass headings of landmarks as visual guides.<br> <br> This is made more tricky by the fact that there's a doppler shift as the satellite approaches (goes up in frequency a little) and as it heads away (frequency goes down). What the operator has to do is to manage both the tracking and the frequency shifts, all while making contacts (QSOs) over the satellite. A flyover (from horizon to horizon) lasts only 20 minutes. Here's a great demonstration video of a live session:<br> <br> <a href="http://youtu.be/1HfvmU_utI8" rel="nofollow">http://youtu.be/1HfvmU_utI8</a><br> <br> I'd like to automate at least the tracking aspect, and your project looks like a good start to me. After I get that working, I'd like to automate managing the doppler shifts. Thanks for your project. I'll let you know how my application works out!<br> <br> Todd Carney&nbsp;<br> K7TFC[at]arrl[dot]net
For step 2 i got my equation wrong. The correct way to get the exact step you want is to. This includes some pseudocode for motion vector. <br> <br>//Globals <br>int MotionVector; <br>int LastStep; <br> <br>//Step and LastStep must end up as the (int) type to avoid float precision issues. <br>//ANGLE is the input angle from the satellite data, float <br>//STEPS is the number of steps in your stepper, float <br>int Step=Round(ANGLE*(360.0/STEPS)); <br>NewMotionVector=Step-LastStep; <br>if((MotionVector &gt; 0 &amp;&amp; NewMotionVector &gt; 0) || <br>(MotionVector &lt; 0 &amp;&amp; NewMotionVector &lt; 0) || <br>(MotionVector == 0 &amp;&amp; MotionVector != NewMotionVector) <br>{ <br> SetMotorStep(Step); <br>} <br>MotionVector=NewMotionVector; <br>LastStep=Step <br> <br>As far as using the motion vector goes, this will just ensure that your step doesnt accidentally move in reverse in the case of the input angle not being perfect causing flipflopping between &lt; and &gt;= x.5 causing the motor to flipflop between 2 steps. Thats what i thought you meant about jitters. <br> <br>In regards to another command mentioning that you should gear it down to fix the jitters: this will also greatly increase precision as you can gear it so that moving 1 step will move your laser .25degree or less.
Is calculating the correct step to reduce jitters so hard? <br> <br>1.) store the calculated motion vector of the angle for the stepper. <br> <br>2.) step=angle/400.0 rounded to the nearest whole number <br> <br>3.) If the outcome of step 2 follows a similar motion vector as the stored one and is not the same step as the current, update the stepper. Either way, Update the last calculated motion vector with the new one. <br> <br>I think that would reduce a lot of the jitter which i assume is caused by your calculated angle not having a perfectly consistent motion vector. <br> <br>Correct me if im wrong.
Hi, thanks for getting into this, sounds like it might improve something. I map the current angle to the motor resolution like: (angle * motor steps) / 360, and I round this result to the closest whole number. Then I check if the step is different than the last one and update the stepper accordingly. What you mean is that the introduction of motion vectors would smooth the pass through steps?. The jitter I consider a thing to improve is that it sometimes takes long to actually get to the next step and when it does, the construction vibrates a bit, which is normal for the size and weight, and that there's no gearing at all.
i haven't read the whole page, but just from your comment alone... <br>maybe you could make it so the smallest step up is large enough to not have any jitters, but the smallest step down is regular. that way, if it needed to go up a tiny bit, it would instead go past that spot and then be able to slowly descend.
It is common in CnC equipment for a &quot;reverse&quot; action to overshoot deliberately and then step forward again to get the correct position. Extremely modern equipment actually includes gear-backlash measurements into the movement calculation.

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