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4681  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Mechanical Prototyping on: September 19, 2010, 06:19:50 pm
I personally just "bodge" things together, since I haven't got an interest in going from "prototype" to "production", yet - my "prototypes" are the "finished model".

What other options are there?

Well, there is fischertechnik - an expensive option, certainly.

Other things to look into:

Gridbeam (you could scale it down):

MicroRAX (small t-slot):

Are there any good software-based solutions?

There probably are, but they probably aren't cheap (or easy/quick to learn). For instance, software like 3DStudo Max, Blender, and others could be used to create 3D models and such, but to build a complex virtual working example will be a lot of effort (heck, just creating a simple model isn't easy). Google Sketchup might be an option. Then there are expensive (and not so expensive - even free open source if you know where to look) CAD/CAM packages (AutoCAD and others on the top-end, of course). I would also imagine there are complete prototyping on-screen "lego like" packages out there, but I can't imagine them being too inexpensive...
4682  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: How to SEARCH this forum? on: September 21, 2010, 10:02:26 am
I would conclude that it has never been discussed here!

I tend to wonder if there is this weird, "parallel" Arduino world out there that never (rarely?) interacts with this forum, and is secretly building crazy and wild things we would have trouble understanding (circuit-bending Arduinos, perhaps?)...

4683  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Chicago Electronics Stores? on: September 17, 2010, 10:29:12 am
Something else to keep in mind: Electronics outlets (as in "discrete components") in the US are few and far between; most of those that do exist only have online storefronts. Even the surplus outlets.

Indeed, we have one surplus outlet here in Phoenix that is pretty large called "Electronic Goldmine" - even though I live here, you can only purchase from them online.

Fortunately, we have another that isn't (Apache Reclamation and Electronics); though if they were smart they would go online - I can easily see why online works better (when you stock as much as ARE does, the mess gets big fast).

New electronics are pretty much limited to online only, with the exception of the few NTE supplied components at some Frys electronics stores (which I imagine they are phasing out - the stock doesn't move quick enough for a store of their size, and takes up valuable floor space).

4684  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Chicago Electronics Stores? on: September 17, 2010, 10:23:49 am
This place might have the motors you need...

Not sure how close it is to you, though...
4685  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: textonics development kit on: September 15, 2010, 11:18:15 am
This appears to be the site:

R.Vignesh, the dev kit appears to only contain transmitters, no receivers - do you have a receiver?

I have no experience at all with the products, but they certainly look interesting to me from the standpoint of VR/AR applications (hmm - imagine a cloth-like waldo suit)...

4686  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Can Duemilanove give 200 ns delay? on: September 15, 2010, 01:01:17 pm
I am not sure, but I think maybe he was intending/wanting to attach an image file to a post to explain what he wanted to do (hint: you need to use an external service like photobucket and link it in the post)...

I think he means "pic" as in "picture" (by the way, spelling out such words in a forum like this makes for quicker understanding), not "Microchip PIC microcontroller".

Then again, maybe I am completely wrong...?

4687  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Availability of radiation hardened Arduino? on: September 13, 2010, 10:07:32 am
Interesting, but it appears to be non-op right now...?

4688  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Linear potentiometer on: September 11, 2010, 07:10:41 pm
I don't know what your budget is but in the industrial automation world there are devices called "string potentiometers".

Interesting, but they don't look like anything more than a retractable cord reel attached to a multi-turn potentiometer (perhaps with some extra-gearing on the long travel versions); you could probably homebrew one using a surplus multi-turn pot and a retractable keychain mechanism...

Perhaps mate one of these:

...with one of these:

4689  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Linear potentiometer on: September 11, 2010, 06:30:07 pm
1. You might have to "gear down" the linear motion output in some manner (perhaps using a compound lever mechanism) in order to use a regular linear potentiometer.

2. Another option would be to use a multi-turn potentiometer (again, possibly with a gear down).

3. If you have the room, a regular potentiometer could be hooked to the linear travel part via a long lever, so that the travel causes the lever to move in a small arc.

4. You could also possibly measure distance using something like a Sharp IR sensor, or something like a Ping (ultrasonic) sensor.

5. A complex method might be to use a long linear CCD (like in a scanner), and measure the position of a light or a slit as it travels along it (by clocking the data out from the CCD and finding which element in the CCD is sensing the light/slit).

6. You could attach a linear gradient pattern to the linear portion, progressing from light to dark (or clear to opaque); such a pattern could be printed on a laser printer onto transparency plastic, or onto paper like for PCB etching and transfered via heat. Use a photodetector and light source of some kind to sense the level of light being reflected/transmitted by the pattern.

7. Similarly, you could print a binary pattern in a linear fashion and do the same thing with an appropriate sensor; look up "shaft encoders" to understand the idea; except instead of a "round" encoder, your encoder would be printed linearly. Note that depending on the precision needed (steps between measurements), your encoder may need a lot of bits (past about 10 bits, it is difficult to homebrew such an encoder - 10 bits would give you about 0.006 inches per step, though, over 6 inches of travel).
4690  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Can I get out information from SD cards with this? on: September 08, 2010, 08:34:23 pm
although it is possible to load program code into an external i2c eeprom such as in the same manner as parallax basic stamps

AFAIK, a standard Arduino (168/328) doesn't support anything like this; I am not saying it isn't possible - maybe something with a custom bootloader, or something is out on avrfreaks or such that could enable this; we're all ears if you could enlighten us more!

4691  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Can I get out information from SD cards with this? on: September 08, 2010, 04:45:49 pm
I read that you can upgrade your arduino to include a SD chip.
This would do great for the memory capability, but can you
take out the memory from the SD card and use it in the arduino?

First off, you need to understand that the Arduino (actually, the ATMega168/328) is essentially "at heart" a Harvard Architecture device, not a Princeton (or Von Neumann) Architecture like you are used to on a PC (and technically, a PC isn't a strict PA/VNA arch...).

What that means is, on the Arduino/ATMega, the code space is completely separate from the data space - it is such a design that the space for variables, vs program storage is separate.

Finally, on the Arduino, there's also a bit of memory in an EEPROM area - separate from the first two.

On the ATMega328, the size of each is: Program=32k (2k taken up by standard bootloader leaving 30k), Variable (sram)=2k, EEPROM (1k or 512 bytes - I forget which off the top of my head).

So when you say "expand the memory" - we really need to know what you are talking about.

The short answer, for a standard Arduino - is "no"; you can add storage space (think of it like a disk drive) via SD cards (or other forms of memory, like SPI/I2C accessible EEPROMs and RAM) - but doing so won't allow you to increase the size of your programs, or the amount of variable space, etc. It will just give you a separate storage area.

You could use such storage for a variety of tasks; logging data (like a temperature sensor or such) is a common one. You could also store data in such memory for later recall, provided you allocate enough room for the working area on your variable memory (sram) to receive the data to work with it.

This is a tight, low resource environment you are working in; for a robot arm, I can conceive that you could record position information for joints, for later playback, for instance - to an SD card, and have several of these recordings, perhaps selectable by a menu on an LCD or something like that. In theory, you could even stream joint position data real-time to an SD card, then stream it back for playback, to allow a "teach-pendant" type of recording, up to the limits of the card.

While you could - in theory - remove the RAM from an SD card, there really isnt' a point to doing so; there are plenty of easy ways to interface to such flash memory, and plenty of breakout boards/connectors exist to make it fairly easy to do so.

The only way you can get around some of these limitations would be by building or installing a small OS on top of the Arduino; there are a few projects out there that aim to do just this. With an OS, you can then run a "program" or "script" (interpreted, generally) that can be read and run on the fly from an SD card (and variable space could be managed in a form of virtual memory kept on the SD card or other storage), as well as perform other tasks at the same time via simple forms of multi-tasking. You gain some flexibility, but you lose speed.

In short, the Arduino can't be thought of as a general purpose computing system (that's why it is called a microcontroller); if you are looking to build a complex robotic system, you should look at the Arduino as a small building block for a larger system. Use it to control stuff, and communicate back to a regular PC (and if your system is to be mobile, there are many manufacturers of embedded PCs), which would handle all of the heavy lifting, processing, and control aspects.

4692  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: measuring amps consumption on a motor on: September 09, 2010, 11:53:18 pm
Know what? I figured out my problem. I need to set my meter right inline with the circuit. I've not measured amps in so long I forget that it's different. I set it on the '10A' setting, plugged my read lead into the 'amps' socket, but then measured across the motor while it was already running. It's a cheap-o $5 "CEN-TECH" digital multimeter. But it's served me well for the last year and a half. Course, all I use it for is checking the occasional voltage. And don't need super-precision.

I'm surprised you didn't burn that cheapo meter out - I love centech meters myself, too - I have a few of them kicking around.

BTW - what did the current reading come out to (and what toy did you get the motor from)?

4693  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: What EXACTLY can an Arduino accomplish? on: September 02, 2010, 06:27:50 pm
It is a penny, isn't it?

That's probably pretty close to what it costs Atmel to manufacture an ATMega - but they gotta have some markup...

4694  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: What EXACTLY can an Arduino accomplish? on: September 02, 2010, 06:20:23 pm
For a gimps of what I did see

Ah - that was a fun trip down memory lane - a whole host of similar projects were done for the Color Computer back in the day (though I was really impressed with the 3D shutter viewer you made!).

The Color Computer didn't have an easy-to-use user port, though; only the "cartridge port" (which was basically the 6809's bus brought out to a edge connector - necessitating the use of address decode logic and such), and a "bit-bang" serial port of sorts (interestingly, I don't remember any projects that used this port via shift registers - that doesn't mean they didn't exist, just that I wasn't paying attention, or they weren't published in the magazine I was subscribed to during that time).

Unfortunately, at the time I was only a kid without much of a clue about electronics; the only interfacing I did with my Color Computer happened thru the joystick ports (which were analog) - I did manage to make my own "light gun" device with a target "game"; I also rigged up my CoCo to control my Tomy Verbot using tones instead of "voice commands" which worked fairly well.

I didn't learn much else about electronics until I got out of high school...

4695  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: What EXACTLY can an Arduino accomplish? on: September 02, 2010, 05:27:57 pm
From the historic point of view, microcontrollers are not downsized computers, but beefed up MSI chips.

From the times of the intel 4004/8008 on, they were used to simplify circuits, in case the speed of signals would allow this.

This is why the smaller and older AVRs or PICs have no RAM at all!

Good point...

If you start on a high algorithmic level you should by all means consider a sized down real computer.
Like this?

I've looked at the mbed before; while I like it for what it is, what I don't like is the "web based programming environment"; it would be a fine thing if you could host it yourself, but I don't see that as something that exists. What happens if the company behind mbed goes out of business, but you have clients or others to support? What do you do if you've built up a large codebase for some device, and there is no longer a way to compile it? These are main reasons that have turned me off of mbed...

However, there are plenty of other "real computer" platforms available for embedded development; in fact, there are a ton of embedded PC platforms available, many much smaller than a mini-ITX motherboard (which is a pretty nice and cheap embeddable PC form-factor on its own - depending on your needs and the size of the project, of course).

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