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4921  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: first-time possible user- what is the best fit? on: March 29, 2010, 02:23:22 pm
Look at this thread:

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267027090
4922  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: ROV on: March 27, 2010, 04:33:04 pm
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I'm building a small rov (3motors). to control it im planing to use arduino board to connect joystick with pots (only for movement left right forward and reverse) , and one sliding pot for up n down. Now, problem is im not that good in C. Please help me with the code or if u know when can i get samples

If I were going to build such an ROV (I am still assuming an underwater craft here; you haven't said otherwise) , I would actually use two Arduinos; the one on the ROV for decoding commands, and another on the surface sending the commands via the tether.

Based on your description, you are looking at building a tether for at least 3 potentiometers, and power. That will need a minimum of five wires in the tether. As you add peripherals (lights, video, etc) you are likely going to need more wires in your tether. The more wires, the heavier the tether, needing more powerful motors, etc.

Nip that idea in the bud immediately; go with a simple tether consisting of as few lines as possible. The easiest would be to use Cat5e with stranded core wires (not solid core); if you can find it with a silicone outer jacket, that would be even better (though more pricey). If you are working in a swimming pool environment or the like, then a standard jacket will be OK; but you will still want stranded core wires, because of the flexing as you reel it in/out.

Cat5 makes a pretty good tether, from what I can gather; its lightweight, flexible, fairly waterproof (provided the end points are sealed), and is designed for remote, long range electronic communications. The difficult part is reeling it in/out - I remember finding one guy's solution was to build a reel for his tether, and the reel had sliding contacts of brass loops and springs, so that he could reel in/out the tether as needed, but that communications wouldn't be interrupted, plus there wouldn't be tangling (as involved with just a manual coil of cat5).

With such a tether, you have 8 wires; you could continue with your plan of using those wire connected to potentiometers, switches, etc - but what would be better would be to wire two Arduinos together in a serial communications system, so that one (the topside controller) interprets the joystick/potentiometers values, then sends those down to the controller in the ROV, which uses those commands to activate the thrusters as needed (and/or switch lights on/off, command a gripper arm, send back telemetry data on heading/attitude/water temperature/etc).

Such a system would only need two wires of the eight available for transmit and receive; You would want to either have an on-board battery on the ROV for power, or send it down via two of the pairs on the tether (so, four wires - 2 for power, 2 for ground - because of likely current requirements, plus redundancy). If you send the power via the tether, that leaves two wires left; use those for an on-board video camera on the ROV (some of the telemetry info could also be sent up via video if you use one of those video overlay boards that exist out there).

If you need some ideas (and possibly some code direction), check out this guy's site:

http://aquaticus.info/

He uses an AVR platform, so some of the coding ideas may translate over to the Arduino. Other example code for what you would need (serial communications, PWM control of motors, reading potentiometers, etc) can all be found in the playground as well as in the examples that come with the Arduino IDE. The rest can be found on this forum.

Also note that there are a ton of sites out there geared toward people developing their own ROVs (and UAVs, but curiously, very few for developing UGVs - not sure why, though).

 smiley
4923  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: ROV on: March 26, 2010, 04:17:43 pm
zoomkat:, what I have found is that in the commercial and industrial sectors, the term "ROV" is universally used only to describe underwater remote operated vehicles. This seems to be a quirk of historical usage more than anything else.

The only time it is used otherwise, is typically in marketing literature, or by those who don't know the proper terms. I found this out in my own research, because I had originally termed the UGV I am building an "ROV", and I referred to such devices in that manner. As I was researching things using google, to see what others had done (using the terms ROV and "remote operated vehicle") I kept coming across underwater vehicles probably close to 99 percent of the time.

I continued to perform my research, and eventually found the definition "UGV" to describe my vehicle; searching on that yielded a ton more articles and information on ground-based remote operated machines. Further research at local libraries confirmed this difference in terminology.

Technically, I agree that it isn't right; in fact, I think there actually is a better term for underwater remote operated vehicles, but no one in the industry seems to use it to any great extent (from my research, it was in more common usage in the 1960s and 70s, then tapered off in usage to almost nothing afterward).

We are stuck with the terms as they are used, unfortunately...
4924  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: ROV on: March 26, 2010, 03:14:41 pm
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Don't forget waldo.

No, I suppose I shouldn't.

Terms like "waldo", "telechir", and "mobot" hold a special place in my heart; from a time period when science and technology was seen as potential savior of mankind from the ills of existence, when anything and everything seemed possible, and when the greats of hard science fiction writing were in their prime.

I wasn't alive then, but the period was certainly a facinating one in history...
4925  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: ROV on: March 26, 2010, 02:32:36 pm
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If the ROV (remotely operated vehicle) is not for use in water, the described sealing issues are not much of an issue.

zoomkat, here is the interesting thing, something that both you and possibly MichalPL, may or may not be aware of:

The term "ROV" is generally only applied to underwater, remotely operated vehicles.

The term "UAV" is applied only to remotely operated aircraft, eg "Unmanned Aerial (or Air) Vehicle".

The term "UGV" is applied only to remotely operated ground vehicles, eg "Unmanned Ground Vehicle".

In all of these cases, what typically separates them from a simple remote controlled vehicle (of any type or operating medium) is the addition of feedback (in the form of telemetry), in addition to the remote control aspect; sometimes the feedback may only be video, but in most cases it also consists of data about the operating environment, status of on-board systems, and other information like heading and speed.

These terms are well established in the industry; one would think that the term "ROV" could mean to refer to just about any "remote operated vehicle", but in the commercial sector (and military sector, I believe), the term is used specifically for remote underwater vehicles only. If another operating environment is intended, one of the other terms is utilized, or an explicit modifier term or phrase is used in addition to the term "ROV" (sometimes, you even see "Underwater ROV" - talk about confusing!).

Historically, such vehicles have also been termed as "telechirs" (the roots of which are greek, I believe; teleos, and chiro - I think - meaning something like "remote hand"), as well as "mobot" (which was actually a Hughes Aircraft trade name in the 1950s and 60s for remote manipulators used for remote manipulation of radioactive and other hazardous materials and/or environments).

 smiley
4926  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: ROV on: March 26, 2010, 11:24:45 am
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Now, problem is im not that good in C.

But I take it that you do have mechanical engineering experience? Because if you don't, you are about to get a good education.

One of the most difficult things to do in building an ROV is keeping the electronics (and depending on the design, the motors) dry at depth. This is mainly because of the electrical connections (at least, until you start going beyond about 20 feet or so in depth) leading in and out of the various pressure vessels. They make connectors for such usage, but they tend to be very pricey (and overkill for most hobbyist ROV designs). So, you have to design your own.

Good luck with your design, but the coding end is only the beginning of your education, so to speak!

 smiley
4927  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: ohm's law eludes me on: March 26, 2010, 01:55:04 am
Is this an LED or an incandescent bulb? While you can use a resistor with the latter, I don't think I've seen this done much.

Are you sure it isn't a 4.5 volt bulb (if incandescent)? Have you tried using a much lower voltage and ramping it up (once again, if incandescent).

Or - alternatively, have you tried a really large resistor (or maybe a potentiometer acting as a rheostat), and adjusted down the resistance until the bulb glowed as bright as needed - then read the resistance used?

My ohm's law is fairly rusty from underusage; though I have a feeling not enough information is being supplied...

 :-?
4928  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Arduino on pneumatics on: March 26, 2010, 02:37:51 pm
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A "managable" rocket fuel might be alcohol and concentrated hydrogen peroxide.

All rocket fuel is pretty nasty/bad/interesting stuff to handle, but in the concentrations required for the H2O2 - I am not sure about the "managable" part.

I suppose it beats some other combinations I have heard about (particularly some of the stuff the Nazis used for various rocket propelled machines in World War 2)...

 smiley-grin
4929  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Arduino on pneumatics on: March 25, 2010, 11:33:50 am
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But once you would allow for strings, why not provide the propellant from outside?

I thought about that myself (when he was talking 2 ounces, instead of 2 lbs), and it wouldn't scale; I am not sure it would scale for 2 pounds, either. You now are not only lifting the "lander" but the weight of the hoses as well.

The bigger issue though would be stability (because the hoses are going to give you a lateral force as they droop - but maybe you could add an automatic takeup reel system for the hose?), as well as whether you could get hosing that small (less than 1/2 inch diameter, I would imagine) which would still be very flexible.

Finally, I am not sure if the OP wanted to be able to navigate in 3DOF or 6DOF (degrees-of-freedom); the original real lander was a 6DOF machine (being weightless), although once it got to the surface, it became more of a 3DOF system (though attitude stability of yaw/pitch/roll was still important). You probably couldn't do a 6DOF system on earth at any scale, at least in free-flight in the air (not even the actual NASA trainers they used were 6DOF; they were designed for final landing approach and touchdown, a mainly 3DOF operation).

Once again, the only way I can envision doing that at the smaller scale we are talking about is within a tank of water or some other clear fluid; even there, it would be a tricky endeavour to get such a system to work - but it would likely be more realistic if you could, because the scale of the lander working against the fluid (which would have more resistance than air) could better simulate the lower gravity and effects on the moon, as well as provide the full 6DOF simulation (if things were carefully made nearly neutrally bouyant). It would be an expensive setup; you would need what would essentially be a large scale thick glass or acrylic aquarium made, which wouldn't be cheap.
4930  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Arduino on pneumatics on: March 24, 2010, 04:24:58 pm
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As "cr0sh" rightly observed, there are so many RC model components that most things are already resolved.

I didn't "observe" that, another poster did; but thanks for the attribution!

 smiley-wink

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It is unusual that nobody in US hadn't picked this one up before? It should be a question of national pride.

In a country divided up over a health care bill because it might -gasp- somehow fund abortions? Are you joking?

The vast majority of my fellow countrymen, notwithstanding the few on here and elsewhere, are tards who would rather scream about doing something, instead of doing it.

Then, when they do "do it", it gets offshored.

 smiley-razz
4931  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Arduino on pneumatics on: March 24, 2010, 12:15:15 pm
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anyway, while we are gathering ideas and knowledge in this thread, if anybody wants to try it,there is my favorite lunar lender game. It had been done by some Flash programmers here in UK. They are quite into Arduino themselves.

That was a pretty fun version of that game - although I think my all time favorite would be the text-only version (a version can be found in one of David Ahl's BASIC Games books; to truely appreciate it I am told it needs to be played over a 300 baud teletype, I never got that chance as I was too young).

As far as your simulator is concerned, I really don't think you are going to be able to do it - whether its 2lbs or 2 ounces; simply because you are fighting the earth's gravity. You are trying to stuff 10 pounds of potatoes in a 2 pound bag.

These are what they used to train the Apollo astronauts, I believe:

http://www.astronautix.com/craft/apoollrv.htm

Notice how big they were compared to the single test dummy pilot...

 ;D

Most of that space was for engines and fuel, just to counteract the earth's gravity for the simulation and training. It won't scale down, unfortunately (if it could, we would have all sorts of cool toys available by now).

If you are insistent upon a non-tethered vehicle, then I would suggest thinking about how to do it in another medium in which you can make the vehicle neutrally bouyant for the size you are looking at; a large clear acrylic tank (not cheap) filled with water or mineral oil could work. Electric motor thrusters could be used as the "rockets".
4932  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Arduino on pneumatics on: March 23, 2010, 09:49:01 pm
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just a table-top one. moon landing, real one in 60's, was my favorite techie adventure

DROBNJAK, I think you need to describe your idea better; here's what I think you may be going after (and if not, it would still make for a cool Arduino project):

You essentially want to create a physical "lunar lander" game of some sort; table-top size (perhaps a 1-2 meters on a side?) - so there is a base, with craters, landing areas, etc; and you are given so much "fuel" plus everything else to (hopefully) simulate a landing (and/or takeoffs).

As others have mentioned, you are not likely to get all of that (co2 and such for propulsion) inside the space and weight limits you have given yourself. Plus, you have to deal with regular gravity, instead of 1/3 gravity.

I want to propose an alternate (if somewhat less realistic) solution:

Use thin kevlar string (or thin fishing line) and electric motors. Place four of these motors, one each at the corners of the base table, and extend vertically a "tower"; set up a small winch reel on the shaft of each motor, around which the string is wrapped. These four lines would then lead up the tower, over a small steel loop, and down to a "point" - which is connected to the top of your "lander". Your lander would also contain its own microcontroller and such, with a simple wireless communication system - to allow communications from the master control microcontroller.

Essentially, the master microcontroller, thru h-bridges, would reel in and out the lines to allow you to place the lander nearly anywhere within the boundary of a cube described by the height of the towers and the area of the table-top board (practically, it will be smaller than this, but not by much). You could control the speed of the motors to simulate different gravity parameters (programmable, of course! Want to land on mars? no problemo!); there would also need to be feedback encoders on the motors, and there will be some interesting 3D math to solve to convert coordinates to reel/string/line lengths, but nothing impossible.

Using the wireless system to the microcontroller in the lander (powered by a battery), you could set things up to have it light LEDs for the "engines", make sounds, vibrate, whatever! If you can find a small enough 2-way communications system (maybe bluetooth?), you could have it feedback to the main controller its "orientation" status, or its "impact" on landing; or you could tell it to "explode" or whatever.

Put a black backdrop behind the rear-most towers, and the strings would be nearly invisible. Something like this would be the high-tech equivalent to the old-school "chopper rescue" spinny thing (can't remember what it was called) that were toys a long time ago (at one time as a kid, I had one that used a fan to act as the Starship Enterprise from TOS - if I hadn't broke it, then scavenged the motor - the thing would probably be worth a few bucks today).

 smiley
4933  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: multiplexers, the myth... on: March 24, 2010, 04:17:50 pm
Don't do the debouncing in software - use schmitt trigger (hardware) for debounce.
4934  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Ribbon Cable on: March 25, 2010, 11:39:58 am
Also, if you can find it, get some multi-color or "rainbow" ribbon cable; the different colors can help with counting and function separation as you design things.
4935  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Commercial Arduino based rollout on: March 25, 2010, 05:00:56 pm
Something of note: right now, it seems you can only source ATMegas out of China (though I have only checked thru-hole DIPs) - here in the USA, for example, Digikey and Mouser won't have any DIP ATMegas available until sometime in April or May (if I am reading their backorder stuff correctly) - but if you go on Ebay, you can find everyone and his brother selling them out of China (also check ic2ic.com - same thing; tons in China).

I would seriously consider going with an embedded ATMega instead of a full Arduino - you are likely going to have the boards etched, stuffed, and shipped from China anyhow (from a cost standpoint), so an ATMega with programming headers (to use an FTDI cable, for instance - you may also want to include pads or headers for an ISP programmer, too - in case a new bootloader is needed). It will probably be easier sourcing a big supply of ATMegas (well, at least from China) than a big supply of the Arduinos.
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