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4951  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Servo "Chirping" on: March 31, 2010, 12:58:44 am
In the Servo.h file, located in /libraries/Servo, there are a couple of parameters you can play with; stick with your "simple attach" example as you adjust the parameters, then try your regular code.

In this file, the parameters are:

#define DEFAULT_PULSE_WIDTH  1500     // default pulse width when servo is attached
#define REFRESH_INTERVAL    20000     // minumim time to refresh servos in microseconds

I would first try lowering the REFRESH_INTERVAL to something like 19500 or 19000; I am not sure how low you can go, but if you don't notice any changes by 15000, revert it back to 20000, and try changing the DEFAULT_PULSE_WIDTH - by making it a little wider (increase the value) or narrower (decrease the value). I have a feeling your "dead band" is a little smaller than what the library is set up for; I am not sure why you can't change this with the attach command, but it isn't set up that way (you can only change the minimum and maximum pulse widths)?

Make a backup of the file (just in case), then use a text editor to alter the file and re-save it, then re-upload/compile your sketch in the Arduino IDE.

Hope this helps!

4952  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Looking for some input for school related work on: March 26, 2010, 12:19:26 am
Simple desktop rover robot:

1. Arduino
2. Two continuous rotation servos
3. Two 4-cell AA battery holders (one for the Arduino, the other for the servos)
4. Ping Pong ball (caster "wheel" for body)
5. One or Two Sharp IR sensors
6. Foam Core board (for body, wheels, etc)
7. Double stick tape and/or Hot glue
8. Various hookup wire

I think you can see how this would be put together; it would make an interesting educational kit (cheap, too) for such a class. There would be a bit of mechanical engineering involved (building the robot itself, figuring out where to mount the sensors, etc), electronics (hooking everything up properly to the Arduino), plus tons of programming (simple moving, to "turtle graphics" by mounting a pen on it and drawing on butcher paper, to solving problems like a simple maze - and if you had enough of them built by a full class, you could try complex swarm-based systems and such).
4953  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Arduino assembly programming? on: March 27, 2010, 04:00:07 pm
You want to write assembly? You pervert!

The whole point of Arduino is to be able to rapidly develop stuff - if you want so much control, why not create your own AVR board?

You haven't really coded until you've left blood on the toggle switches...

4954  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: lettering/graphics on project box on: March 29, 2010, 04:05:39 pm
I like the idea of trying toner transfer on metal faceplates.  I may have to try that out some time.

It supposedly works pretty good for placement/parts artwork on PCBs, so it should work good for faceplates. Something you could do would be to print the holes and such for knobs, switches, then transfer, then use those areas as guidelines for drilling/nibbling/cutting.

I am still interested in a working method for white labels on dark surfaces; that one is the nut to crack (haven't found anything on the possibility of existence of white toner).

4955  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: lettering/graphics on project box on: March 29, 2010, 12:13:48 pm
I was thinking about this as I was laying in bed going to sleep, and I thought of some other interesting ideas:

Do the toner transfer process on both sides of a piece of copper sheet of the lettering and graphics, and etch through the copper to create a stencil (for direct use or screen printing).

Etch the lettering and graphics in mirror-image negative on a PCB; then apply ink/paint to the board, squeegee off the excess (leaving ink in the wells), then place on the faceplate, and apply some pressure (almost like an offset/litho process).

For light-colored faceplates (or metal plates), you could just do a toner-transfer (black or color), then apply spray-on clear laquer; alternatively, you could print onto a large clear-label sheet the size of the faceplate, stick it on, then trim to fit.

Something I was also thinking about was if there were a way, using the double-side toner transfer process for a negative image, onto a very thin sheet of copper or alluminum sheeting, to then "burn" away the remaining copper/alluminum using an arc or something (electro-machining), to create a stencil (once again, for direct use or screen-printing with).

All of these are very "pie in the sky", but they all seem like something an individual could play with at the hobbyist level (and perhaps someone will have success?)...

4956  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: lettering/graphics on project box on: March 29, 2010, 01:50:19 am
You know, this really is a step that seems left out in the process of conceiving an electronic design and fully realizing it in a quality final implementation or prototype.

For the most part, DIY electronic enthusiasts can go from idea to realized project, in a nice case, fairly easily and quickly; this can include some very intricate and sophisticated operations, depending on the skill of the builder.

Even so, the final step of creating professional looking labels on the project's surface has always been lacking; there are techniques that turn out good results, but most are beyond the abilities (or finances) of the majority of builders.

I hope this thread continues; I would like to see some radical ideas brought to fruition. I was thinking if there were a way to use a laser printer and toner; perhaps making a negative mask on transparency film, attaching it to the front of the panel, then exposing the plastic to intense UV - not sure what that would do, if anything, but it might make for an interesting experiment (if you use some of the old white plastic, you could get an ugly brown color printing, I suppose).

Does anyone else have ideas?

4957  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:
4958  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: ROV on: March 27, 2010, 04:33:04 pm
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:

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).

4959  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...
4960  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: ROV on: March 26, 2010, 03:14:41 pm
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...
4961  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: ROV on: March 26, 2010, 02:32:36 pm
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).

4962  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: ROV on: March 26, 2010, 11:24:45 am
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!

4963  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...

4964  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Arduino on pneumatics on: March 26, 2010, 02:37:51 pm
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)...

4965  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Arduino on pneumatics on: March 25, 2010, 11:33:50 am
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.
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