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Author Topic: Available shields and shield ideas  (Read 6621 times)
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I see the Arduino Mega has a 3.3v pin, reading the specs it says it's coming from the FTDI chip. Is that only under power when the USB is connected?

Again, I'm just a computer scientist, so I'm just guessing here smiley-wink
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In my experience, boards can be produced for about $5 for arduino sized board. (much less for a second run from ourpcb - but that's another topic completely). Deal with board pricing when you get there in my experience.

Are you including somone populating the board or are you thinking that you would solder them yourself?

The components end everything obviously depend on how cheap you can get them. I would have thought that with that wireless module and a microSD slot, EEPROM, headers, resistors and all that other stuff, you could easily build the board for less than $20 if you are making 100. I would have thought that you could do about 25 for less than $20 per board also...

Mowcius
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I see the Arduino Mega has a 3.3v pin, reading the specs it says it's coming from the FTDI chip. Is that only under power when the USB is connected?

Again, I'm just a computer scientist, so I'm just guessing here

As far as I understand it, it is just a 3.3v power pin, not a 3.3v data pin. For those wireless chips you need 3.3v digital data rather than the 5v digital data that the arduino gives out. So you then need a logic level converter...

Mowcius
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I would like to have the boards populated in the factory, and I'm still talking about having the CC2500 on the shield itself, so i'm supposing you'd need a machine to do that?

$20 usd is fine, that's roughly 12 pounds uk or 13.5 euro. At that price point you could have a operational sensor node for 45+20 usd, or ~44 euro.

edit:

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As far as I understand it, it is just a 3.3v power pin, not a 3.3v data pin. For those wireless chips you need 3.3v digital data rather than the 5v digital data that the arduino gives out. So you then need a logic level converter...

makes sense, thanks.
« Last Edit: September 23, 2009, 07:40:53 am by niels.brouwers » Logged

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I would like to have the boards populated in the factory, and I'm still talking about having the CC2500 on the shield itself, so i'm supposing you'd need a machine to do that?
If you have a company in mind then they would normally do eveything, surface mount and all. You don't necessarily need a machine to do it...

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$20 usd is fine, that's roughly 12 pounds uk or 13.5 euro. At that price point you could have a operational sensor node for 45+20 usd, or ~44 euro.

If you are interested in getting the cheapest sensor node you can then you could add the atmega1280 chip to the board and have it all in one...
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Assembly is obviously much more expensive than just getting the boards made...

If you have the board design and parts list then you can contact ourpcb to get a quote. I have no experience of their assembly service but their production service and quality is pretty good...

You may have difficulties getting a board made and assembled for less than $20 but i'm not sure. If you did an all in one board then you could do it cheaper than $65...

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If you are interested in getting the cheapest sensor node you can then you could add the atmega1280 chip to the board and have it all in one...

That's always an option, but I would like to still be able to use all the shields available for the arduino platform. It's really nice to be able to walk around with a node and have a little screen with debugging information about the routing tables in the neighbourhood for instance.

I'll have a talk with a couple of my EE buddies and see what they think. I'd probably be interested in an initial run of 25 boards. If they solder all the components for me all I have to do is send them a BOM and eagle drawing? Or should I source the CC2500 chips myself and have it shipped to them? What other steps besides designing the pcb would I need to take to get the final product sitting on my desk?
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That's always an option, but I would like to still be able to use all the shields available for the arduino platform. It's really nice to be able to walk around with a node and have a little screen with debugging information about the routing tables in the neighbourhood for instance.

Ok, I see your point, but overall it will probably cost more...

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I'll have a talk with a couple of my EE buddies and see what they think. I'd probably be interested in an initial run of 25 boards. If they solder all the components for me all I have to do is send them a BOM and eagle drawing? Or should I source the CC2500 chips myself and have it shipped to them? What other steps besides designing the pcb would I need to take to get the final product sitting on my desk?

You send them gerber files, from eagle and they will send you a quote, it is less for not having lead-free etc. I'm not sure about components and everything. They have a stock of parts and I think that they would buy the CC2500 chips and other components and include it in the final cost...

If you are not sure as to how to get the gerber files then just search it in google. I'm afraid that I will not be able to reply again for about another hour, then I could help...

If you can tell me what components and everything you want then I can probably do a board design for you...

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Thanks for all the information! I'll go have a think about what the best option would be.
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I am planning on making a wireless + AVR arduino-compatible combination.  See
http://effluviaofascatteredmind.blogspot.com/2009/07/arduino-cpld-reconfigurable-hardware.html.

Actually, I did the complete eagle files for a shield but did not actually send it off because I wanted to integrate the wireless.  

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That's a very nice looking project indeed  vxir, I would be interested in a unit like that without doubt.
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Nice idea. Any chance you have a price in mind? What kind of wireless chip will it have?

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WRT price, as cheap as possible since customers will need to buy a few!  But its always a tradeoff between price and performance.  Should I use the 328 at $3.00 a chip or the 640 or 1280 at 10 or 15 dollars?

I'm open to suggestions for the wireless chip.  I have experience doing SMT and QFN parts so that is not an issue.  It looks like all the chips have the same tricky antenna requirements.

I want the board to be usable in sensor networks within a home/office setting and for small cooperative robotics.  So I want a range > 10 feet! :-)  Otherwise I am pretty open to suggestions.  It would be nice to offload as much processing as possible from the AVR, so that it can be used for the job at hand.  Lets go over the options and discuss pros/cons.  Please feel free to add to this list:

1.  Nordic Semi: nRF24LU1+
PROS:
Has an onboard 8051 and RAM buffer so basically there would be 0 load on the AVR
Has a pin/algorithm compatible versions that use different frequencies.

CONS:
Can't find a source or a price

2. TI CC2500
PROS:
In common use
Arduino library exists

CONS:
older?

price (100): 2.38

3. Atmel AT86RF230
PROS:
Single manufacturer solution, provides software and demo boards
Zigbee

CONS:
Specs on the antenna seem pretty scary compared to other chips;  it seems to be a lot more sensitive to interference (or maybe the spec is just being honest :-))

4. Cypress CYRF7936
2.4 ghz Has been used in a RC airplane environment so has good range
Comes with software (but for the Cypress PSOC)

costs: $3.33

CONS:
not Zigbee

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vxir, sounds like a nice idea. I'd probably prefer an atmega128l because I want to run a JVM which takes up ~40k progflash, so 128k would be preferable. You could also go for one of the newer MSP430s although compiler support is still shaky.

As for the radio I'd say go with a 2.4ghz packet radio. You want a small tx/rx buffer but a full 8051 on chip isn't really needed imho. I don't care about zigbee because I develop my own routing protocols anyway. If you want range you might want to take a look at the nRF905 which I've worked with before. I know people who had >2km range on them although this was a deployment on a lake and the reception was on a hill overlooking said lake. Still pretty impressive. I recommend the CC2500 because it's cheap and easily found.

Let me know if you go ahead with this, I'd be willing to purchase a few of these nodes if they're not too pricey. The CPLD chip sounds like it could be useful for distributed model checking :3
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Yes the CPLD will be useful first off simply as a voltage level converter.  But also for a lot of small logic like stepper motor control and PWM.  Yes, I know that the full 8051 is not NEEDED :-) but it would be cool if the price is low enough!

What were you thinking of in terms of board price?  Earlier in this thread you were talking $20.  But a ATMEGA1280 costs $15 itself so that price is impossible for that chip!  With the CPLD at $4-10 and the wireless chip around $5, the 1280 will cost as much as the other components combined.  On the other hand the 328 is only $2.70 USD ($2.56 lowest price, I'm sourcing some now for another project).  So the 1280 could double the cost of the board.  On the other hand, it gives you a LOT more functionality...

WRT MSP430, I want to stay within the Arduino family so we don't have to do a lot of portability software.  For this reason the 328 is also the better choice because it is directly register compatible with the Arduino, whereas the 1280 would be compatible with the Arduino mega...

Is your routing work in C or Java?

Best,
Andrew
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