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31  Forum 2005-2010 (read only) / Development / Re: Crystal uses (compared to ceramic resonators) on: July 05, 2008, 06:31:29 pm
Just to be a protagonist, what about the aesthetics? Yes I said it. Resonators are fugly - crystals are sexy. Does it always have to be about tolerances?


32  Forum 2005-2010 (read only) / Development / Re: Professional custom board creation? on: June 14, 2008, 09:22:01 pm
This guy ( posts a lot over at the Sparkfun forums and is in the process of creating a similar service to batchpcb for doing smt assembly in small batches. Doesnt look like he;s got all the bugs worked out as yet but its a promising service.

33  Forum 2005-2010 (read only) / Development / Re: Skinny from SparkFun on: June 02, 2008, 09:40:12 am
About the shield issue... if its a concern that 5v shields would be used with this board and the solution is to change the pin spacing of the headers to force a new 3v shield design then I just have to ask whats the point of sticking with the arduino footprint?

If you plan to change the headers then just go ahead and shrink the board size and introduce a couple new smaller shield designs. I do like the idea of the lipo friendly factor. I think in the interest of ultraportability then just go ahead and make it smaller!

I have had this issue with the lilypad and now this board, your programming header doesnt really stick with any sort of standard. If you had the 6pin ftdi compatible pinout (look at lemore's boarduino or paul's bare bones) then your customers would have more options for programming adapters and you could enable the auto reset function in your designs.

Finally since this seems to be about options, I would add 2 pins at .1" spacing for + and - at the power connector to allow for some male pin headers to be soldered by the user instead of a barrel connector. This could be under the barrel connector or to its side somehow. If done well, the large holes for the bigger connector could be used as strain relief if soldering in wires.

And which vreg did you use? If it is indeed only good for 40mA then that really needs to be noted.

Make it smaller!


34  Forum 2005-2010 (read only) / Development / Re: Minimalist Arduino on: May 18, 2008, 09:36:34 pm
Been meaning to do this for awhile anyway so I made a few changes, reformatted it, an added it to the playground:

35  Forum 2005-2010 (read only) / Development / Re: Minimalist Arduino on: May 18, 2008, 08:28:32 pm
The pullup resistor on reset is only neccy when connecting a reset switch (that is connected to ground) to prevent shorting that pin out.

The most minimal setup (w/out changing internal settings of the chip) really just needs a resonator or xtal & 2 caps. Even though Im sure Ive posted this elsewhere before,  this is something I wrote up for my class on wiring up a breadboard arduino (assuming that the chip is programmed in the arduino board first):

36  Forum 2005-2010 (read only) / Development / Re: playing audio w/arduino on: May 14, 2008, 12:10:57 am
That is impressively simple! Ill have to spend more time looking at your design but I already want to make a standalone board. What is that something like 9 io pins? Combine this with a t class chip amp and then you could rattle walls!  ;D

37  Forum 2005-2010 (read only) / Development / Re: minimal Arduino - ATMEGA168 & USB? on: May 08, 2008, 04:16:41 pm
Interesting timing.... go look here:

As I mention there I would like to make an even simpler lower part count version too mainly for those times when you have a processing app that needs to read sensor values or something from just 1 or 2 things. The 168 seems like a waste though so maybe it would be possible to get the bootloader on a smaller AVR....?


edit: w00t - 51st post and no longer a newbie. Only took 2 years!
38  Forum 2005-2010 (read only) / Development / Re: Freeduino and Shields on: April 10, 2008, 11:18:36 am
Replicant... yeah, definitely more Dickian....

And anyway, standards, schmandards -  smiley-razz

39  Forum 2005-2010 (read only) / Development / Re: Arduino Diecimila gridded ground plane + EMC on: March 24, 2008, 02:26:59 pm
Im not really understanding the question but Ill take a stab at it....

To create a power plane in eagle the easiest method is to use the text command "poly" followed by a space and the net name for the plane such as "gnd". This is the easiest way to attach a polygon to a power net because once named it will not let you rename the polygon to anything else. So if you wanted to create a power plane attached to vcc the command would be "poly vcc" and enter to evoke the command.

Once the command is evoked you have the option to define the layer (top or bottom), the width of the trace that will compose the plane, whether the pour is solid or hatched (the "gridded plane" in your question), and a few other options.

It is possible to use the change command to change the pour from solid to hatched. IIRC Eagle will by default make all polygons solid so unless this was defined by the designer a plane will show up as solid. Some of the arduino files have solid planes but I just assume that is a fluke or they are older files.

It is also possible to have a hatched plane that appears solid. This would be because the spacing has to be set to greater than the trace width in order for there to be space or gaps in between the traces. Once the poly is drawn all these options can be changed by the change command.

Personally I almost always use hatched power planes partly because as Mossimo said, I understand them to be better physically for the board but also because Im an artist I am simply more attracted to them aesthetically. I usually dedicate one plane to vcc and another to gnd just to make things easier. I also avoid traces or planes under oscillators as I understand this too helps with EMI. In the end though even at 16mhz this isnt rocket science nor is it that high speed of an application that it matters much to the actual user.

40  Forum 2005-2010 (read only) / Development / Re: Arduino + AC switch on: March 07, 2008, 05:20:39 pm
For the most part I agree that solid state relays are the safest and easiest relay to use. Assuming your 50watt heater is using 120v AC then thats only about 400mA or less than half an amp. For this a simple 1A 5v reed relay from radio shack p/n 275-232 would work. For this a transistor is not needed but a diode across the coil is.

      |               o
      _               |
diode^  120vACIN--o------/ /-----o--120vACOUT
      |               |

Something like that should do it if you can make sense of it. Basically a reed relay is a very simple normally open switch surrounded by a wire coil. Take the hot wire or the black wire from the ac cord and connect it to both sides of the switch part of the relay. Connect a digital pin to one side of the coil and connect the other side to ground. Also make sure you have a diode (1n4001 or similar) connected across the coil as well. Theres a better drawing of how the relay works on the back of the package. Because this relay is so simple theres really nothing wrong with running it straight from the arduino. While this will work with solid state relays this is not the case with other mechanical relays.  

Above all, make sure you work safely, that nothing is wired while plugged in, and make sure that any exposed part of the AC side is protected with black electrical tape or heat shrink tubing.

41  Forum 2005-2010 (read only) / Development / Re: Need Some help planning out an arduino variant on: March 04, 2008, 07:28:10 pm
Actually, if youre happy to program the chip in the arduino (or variant) and just want a carrier board of sorts the actual implementation of the arduino can be very stripped down. In my class, I showed my students how to wire this up on a perfboard but you can find the class's notes here:

I was going to follow this up with a proper tut in the playground but didnt have the time. I think itll give you an idea of whats involved.

42  Forum 2005-2010 (read only) / Development / Re: motor party! on: February 13, 2008, 10:49:41 pm
That is really bizarre. Not only have I used the 754410 but my students have as well and we have never used external diodes. The whole reason to use the ti chip is that extra 400ma and in some cases that I have advised with, the h-bridge was doubled up to get a total 2a output on some larger motors. (Both sets of inputs tied together and both outputs tied together.) Not only has this worked with the Arduino but also the PICAXE microcontrollers with long term viability.

Look, the 754410 is even in Tom Igoe's Physical Computing page 257 and 258 again with NO external diodes. (I had to go look it up to be sure.) Sure, in any case external diodes will undoubtedly 'work better' but I just cant seem to argue with the amount of people who have practical experience using the chip without them. And again Ive seen the chip used with some gnarly 2A surplus motors to no ill effect.

43  Forum 2005-2010 (read only) / Development / PCB Roadblock: Using Surface Mount 168? on: December 18, 2007, 06:12:13 pm

Im working on a large-ish project (exhibition) that is made up of smaller individual works. Each work has a single control board (with microntroller, mosfets, diodes, and a few resistors) that controls a single unipolar stepper motor. The PCB Im working on will use mostly all surface mount components and as a result will be about the size of the Arduino Mini. I am also pretty new to SMT although have produced similar through hole pcbs for my work in the past. Heres a photo of the new in-progress board:

I will be having somewhere in the ball park of 30-50 of these boards produced. This means having the pcbs fabricated and parts placed through various means. I plan on using an Arduino-fied ATmega168 at the core of each board in the MLF32 package.

The problem is I am trying to keep this board as small as possible and am hitting my head against the wall about how many connectors I need to have. At the barest minimum I need the following pins: +5v, Gnd, PWM Out, and another Gnd. Id also like Rx & Tx so I can program it. Thats already 6 pins that Ill need to be bring out using pin headers. Thats assuming I dont need ICSP... which I dont see a way around as thats the only way to get the bootloader on there.

Here are some random questions I have:
1. Is there anyway to purchase a lot of ATmega168s with the bootloader already burned?

2. I assume not so if I purchase from Mouser or Digi-Key how would bare MLF32 168s come shipped?
(The board fabricators will only take parts on cut tape, tube, or waffle tray. If the chips came in a tray I could burn bootloaders on the chips prior to sending to the fabricator.)

3. I guess the bigger question is how are the bootloaders on the Arduino Minis or LillyPad mass-produced?

Any other thoughts or suggestions? Am I just missing something?
44  Forum 2005-2010 (read only) / Development / The Bread Board (Free/Ar)duino Variant on: September 18, 2007, 11:57:47 pm
In the flurry of the Freeduino movt and the anticipation of my students writing their first code tomorrow I had this idea to combine the sparkfun breadboard shield with paul's bare bones board in the spirit of parallax's homework board for the bs2. Out of all that came what I call the "bread board". (Ingenious I know. 8-)) The big square there is a space for the mini-breadboard used on the shields and available from sparkfun or elsewhere. The female headers should line up with the pin rows on the bb and stay to the same tried and true arduino format but I took some liberties with the power configuration. I also have wanted the option on my arduino to use a 5v regulated external supply so I changed that on this board so there are now 3 power selection options. Finally Ive kept to all through-hole parts so that if someone other than me were so inclined they could offer it as a kit or build their own. (Oh and I know theres no 1N4001 on there because they annoy me and the LM2940 has reasonable flyback protection.) (Oh, oh its also Diecimila compatible too.) (Oh, oh, oh, I should also give dimensions: 3.25" wide by just under 2" tall (1.85").)

In the spirit of things I offer it up as CC Attribution Share Alike so use it and abuse it but most of all let me know what you think.


And Here are the eagle files:
45  Forum 2005-2010 (read only) / Development / Re: Stepper Motor Shield on: September 11, 2007, 11:12:06 pm
The Arduino system is a natural for this. I happen to be collaborating with my father on a little project of his to make something very similar to the reprap project. Im sure he will be publishing documentation on this when he is ready but the idea was to make a single board control unit for the cnc aspects of a reprap and have a second daughterboard once the heads and extruders are brought online. I have just completed the first revision of the main board. It runs on a hefty 30A 5V external power source, has 3 uln2003s for onboard control of 5v unipolar steppers, uses a screw terminal for a large heatsinked current limiting resistor, has usb via ftdi's mm232r module, can connect 3 limit switches/photo interrupts, and brings the remaining pins out to headers. Its all through hole so that a kit might one day be offered. This is all in very rough stage at the moment with more information when its available. The only image I have is of the cad file but Im sure my father will post later once he receives the board in the mail and has a chance to get things hooked up. Im already thinking about the second revision and opening it up to variable voltages, finding drivers more robust than the 2003s, having a better interface (switches, rx/tx leds, etc), finding a better implementation of usb and so forth.


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