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4921  Forum 2005-2010 (read only) / Development / Re: 30 Amps per Channel, Four channel current-sink on: November 06, 2009, 03:36:55 am
Is this practical?  I thought most modern MOSFETs were designed for switching, and dissipated totally impractical amounts of power in their linear regions?
4922  Forum 2005-2010 (read only) / Development / Re: Custom arduino mega? Who could do this for me? on: October 26, 2009, 03:45:35 am
I'd sort of expect a "for commercial use" custom PCB design to cost upwards from $1000 to have someone do it for you (not including the actual boards)  That sort of consulting tends to run $100/hour and up, and starting from an existing design like the Arduino MEGA doesn't make it take THAT much less time.  10 hours disappears really quickly when you have negotiations of requirements, schematic entry, PCB design, interfacing with a PCB vendor, and carrying the little bits around.   You might reach some "deal" with someone (and be on less shaky moral grounds) if the design is made general purpose enough to appeal to the community, and released as open-source ("Arduino Mega Serial level translator shield" ?)  Or you might get someone with a less developed skillset to do them for less money as a sort of training exercise, though that's not a particularly low-risk route.
And some of the PCB vendors do layout as well, which might let you combine charges, especially if you're going to be building enough boards that the design-time becomes more negotiable.

But in general, "industry standard consulting fees" are ... expensive.
4923  Forum 2005-2010 (read only) / Development / Re: arduino with at90s8515 on: October 15, 2009, 10:16:56 am
Yes, that should work for programming a 90s8515.

In THEORY, it should be possible to slightly modify the arduino environment so that it can download to other chips via an external programmer (anything supported by the AVRdude utility, I guess, by modifying hardware/boards.txt, plus the core libraries.)  In reality, if you can do that then you don't have much need for the arduino environment in the first place...

4924  Forum 2005-2010 (read only) / Development / Re: arduino with at90s8515 on: October 14, 2009, 07:42:22 pm
what is device programmer
A piece of hardware that goes between your computer and a micrcontroller chip or board that allows programs to be loaded into the chip.  Typically these will support many different microcontroller chips, each with many options, and they're aimed at EE and CS engineers.  They'll consequently be much more complicated to use than an Arduino.
Examples include The Atmel STK-500 and the Adafruit USBtinyISP
4925  Forum 2005-2010 (read only) / Development / Re: arduino with at90s8515 on: October 12, 2009, 01:07:59 pm
The AT90S8515 is an "old-style" (one of the very first) AVR microcontrollers, and it does not have the SPM instruction or the ability to self-program its own flash memory, which is necessary for a bootloader-based environment like Arduino to operate properly.  Basically, you can't use an 90S8515 without a specific "device programmer" module, and one of those is comparable in price to a full Arduino (even the cheaper versions will likely cost as much as an Arduino clone.)

There is a newer AVR that is similar to the 90s8515 (ATmega8515), but except for pins it has less capabilities than even the older Arduino chips (like the ATmega8)  Arduino variants like Sanguino ( that use a 40-pin chip seem to have settled on the ATmega644.
4926  Forum 2005-2010 (read only) / Development / Re: Typical distributor markup? on: October 14, 2009, 07:31:06 pm
The typical number thrown around is about 40% at each level of distribution.   So your $30 arduino should be costing about $11 to manufacture (which sounds "about right.")  The other number I see a lot is that retail prices is about 5x the "parts cost" (where "parts cost" is something like "major chips + pcb" rather than a detailed summation.)

There was a Panel at Maker Fair (featuring Limor and others), and it was pretty good.  All panelists were pretty big on "DON'T set your price too low" (and the mark-up IS bigger than you'd like.)

You can probably go lower than 40% if your whole distribution network is "open source aware" and wants to discourage people from just going off and making their own.  You probably need to go higher if  you want your product to show up at Radio Shack or Fry's.  (I've seen some interesting articles on sales strategies at such stores - you don't push sales of the "expensive" items, you push sales of items where the retail markup is large...)
4927  Forum 2005-2010 (read only) / Development / Re: atmega328 setup help on: October 16, 2009, 01:25:42 am
I drew this 'modularized' version of the Arduino schematic, which will eventually get some accompanying text and be a "definitive" answer to this sort of question.  Until such text is written, perhaps just the schematic will be useful to someone.  The idea is that each "boxed" section can be included or omitted in a "reduced" implementation...

The "core CPU" box is the minimum requirement (but it will required using an 8MHz build environment.)
4928  Forum 2005-2010 (read only) / Development / Re: Max 232 And arduino/ sanguino schematics on: October 11, 2009, 05:22:01 pm
Much nicer!
Convention is that positive voltage symbols point "up" and Gnd and negative voltages point down.
You might want to add a bare pad on the max232 signal you're not using.  That might permit you to connect it with a jumper wire later if you find a use for it...
4929  Forum 2005-2010 (read only) / Development / Re: Max 232 And arduino/ sanguino schematics on: October 03, 2009, 03:55:34 pm
why a connection from VCC to ground is needed. It's for noise suppression.
Note that this is not a "connection" from VCC to GND; it's a CAPACITOR between VCC and GND.
4930  Forum 2005-2010 (read only) / Development / Re: Max 232 And arduino/ sanguino schematics on: October 03, 2009, 03:52:41 pm
There are standard eagle libraries "supply1.lbr" and "supply2.lbr" that contain assorted symbols and signal names.  (the actual "arrow" components I used.)  When you attached them to a net, it names the net to the appropriate signal name, and all nets with the same signal name are connected whether there is a  wire drawn between them or not.  (this also means you can draw a short net connected to a pin and use the "name" command to connect that piece of wire to the net with the same name.)
4931  Forum 2005-2010 (read only) / Development / Re: Max 232 And arduino/ sanguino schematics on: October 02, 2009, 10:58:34 pm
[quoteexplain to me what the arrowing at the end of V+ pin mean[/quote]
In order to avoid cluttering schematics with wires to the power supplies, it is common to use a common symbol to indicate "this is connected to the common gnd", or "this is connected to the common +5V", or whatever.  All of these are "invisibly" connected (or treated as the same connection, because they enforce the same "net" name.)  The arrows you see are a somewhat common symbol designed to show this connection.  You might also note that the max232 symbol I used (which is from one of the standard eagle libs) doesn't have power supply pins shown on the schematic.  These are also "invisible" and automatically connected to the like-named net.

In (large) professional schematics, it's pretty common to reserve an entire page for nothing but the bypass caps.
Actually, in large professional schematics it's pretty common for each signal to come off a pin to some sort of named arrow, with no actual drawing to show where its connected to, which can be pretty annoying (but I don't know how else you handled 100+ pin chips without making a mess...)
4932  Forum 2005-2010 (read only) / Development / Re: Max 232 And arduino/ sanguino schematics on: October 02, 2009, 08:36:58 pm
My eyes hurt.  A schematics is not supposed to look like a maze!
Here's my drawing of a similar circuit (but it hasn't been tested either.)
4933  Forum 2005-2010 (read only) / Development / Re: How to break or block internal arduino process? on: September 30, 2009, 06:54:31 pm
For all practical purposes, there is NO "background process" in arduino.
However, the level of abstraction provided by an arduino function call like digitalWrite(pin, val) makes it MUCH slower than something like "sbi PORTB,4"   About 20x slower.
There has been a fair amount of discussion on this in other threads.
4934  Forum 2005-2010 (read only) / Development / Re: Network audio player on: September 23, 2009, 07:35:36 pm
more a matter of sound quality
I wouldn't count on it.  The audio business is full of snake-oil and reverse frugality...
4935  Forum 2005-2010 (read only) / Development / Re: Network audio player on: September 23, 2009, 05:30:21 pm
I don't think that an arduino is particularly suitable for this task.
1) It doesn't have the CPU power to uncompress compressed audio.
2) (less certain) or to accept uncompressed audio-rate data over its network connection
3) no low-cost wifi
4) not enough memory to buffer audio streams in the face of network latency.

You might get it to work eventually.  Separate mp3 processor, bunch of add-ons.
Something like a BeagleBoard would be a more appropriate starting point.

However, this is the sort of "consumer" device that it is getting really difficult to build for less money than you can buy it for.   The £100 price tag buys an awful lot of electronics these days.  Have you considered looking for a cheaper commercial product?  "squeezebox" is a sort of brand-name "premium" product.  How about
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