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151  Forum 2005-2010 (read only) / Development / Re: Anyone done any small scale production runs? on: December 13, 2010, 05:44:32 am
I guess for 20 pieces, it's never going to be cheap to send for assembly outside (whether it's local or offshore). Try settling on using whatever tools and methods that could help in assembling them more efficiently (use home made reflow oven and stencil). 150 components is quite a lot and tiring for hand solder. smiley
152  Forum 2005-2010 (read only) / Development / Re: swarm , find position of robots on: November 08, 2010, 06:45:05 am

I'm not sure whether there's any off the rack solution available.
But, long long time ago (it seems long for me), TI was talking so much on the location engine on their CC2431 Zigbee chip. The software stack that time was so unstable when we were testing them back in ~2006/2007. But, I'm not sure what is the current status on the CC2431. If there's any company that develop modules (Zigbee) that is based on the CC2431, the location engine feature might be included. But, if I recall correctly, you need 2 (at least) stationery nodes (robots) in this case as reference location. If the module is available, then making an Arduino Shield should be feasible.
153  Forum 2005-2010 (read only) / Development / Re: zigbee network on: October 18, 2010, 09:34:57 am
There are series 1 modules that are for point to point use
Series 1 can also do point to multipoint but not mesh. So, if the 10 transmitters are able to reach the receiver using direct connection, Series 1 is adequate.

I am using Maxstream Xbee module.
Check what series you are using 1st.
154  Forum 2005-2010 (read only) / Development / Re: Low Power Arduino on: September 10, 2010, 10:54:49 am
How did you solder those?

I usually use hot air for those IC without legs. Sometimes I used hot plate and toaster oven too. Anything that has pins, I would use a solder iron with very sharp tip. smiley
155  Forum 2005-2010 (read only) / Development / Re: Low Power Arduino on: September 09, 2010, 12:15:42 pm
If you go for lower load you will get more pullability and thus less precision / stability.

Yes, you are correct as the pullability is proportionally to the inverse of load capacitance square. I was also thinking of removing the 2 capacitors (that's why I was saying about 6pF crystal, smiley), but obviously it will increase the ppm value too.
156  Forum 2005-2010 (read only) / Development / Re: Low Power Arduino on: September 08, 2010, 09:38:07 pm
Higher load capacitance implies less pullability. Thus in doubt better precision.

Thank you for pointing that out. I will try to find a crystal with lower load capacitance, probably 6pF.
157  Forum 2005-2010 (read only) / Development / Re: Low Power Arduino on: September 07, 2010, 10:04:00 pm
If you decide to try your hand at calibrating I would certainly like to hear how you get on.

I will definitely post it here if I manage to get it work. smiley

Hmm, the processor has a 32kHz crystal, so it should be able to automatically calibrate. I think there exists an application note that describes this process but I seem to be able to find it with Google right now.

I think the application note is AVR053 but it doesn't need a 32kHz crystal for this calibration process. The programmer (AVRISP/JTAG/STK500) will supply a 32.768kHz clock to the MCU for calibration. I found that we can write the OSCCAL register directly in AVR Studio but we have to point where the value is in EEPROM or flash using one of the programmer. So, in this case we don't have to load this value in the sketch.

It includes interchangeable power shields for various sources (solar/battery, piezo, peltier, RF), but nothing explicitly for charging LiIon yet.

I made something similar for my company usage where we have different power shields, RF shields, and sensor interface shields that fits into different applications. But, we were using ATmega128 as our board was based on Crossbow's Micaz at that time. It provides flexibility but it gets annoying when your stacking goes higher and higher although we were using low profile board to board connector (1.00mm pitch).

Did you get a chance to measure the sleep current on this design?
I have yet to measure yet because I went straight to the 2nd revision as I changed the buck-boost converter (LTC3530) to TPS63001 instead as it uses so much less external components and cheaper too! But if I recall correctly, using ATmega128 and similar setup, it was around 40 uA. I didn't go for very low LDO design like MCP1700 as I think some other shields might need more than the 250 mA for the 3.3 V rail. For example an XBee Pro module. Once, I get the 2nd revision up running, I will post the current during power save mode here. smiley

Do you need the 22pF caps on the watch xtal, or is that in case you can't find a 6pF xtal.
The crystal load capacitance is 12.5pF. I estimate the stray to be around 5pF and using C=2CL-CS it comes out to 20pF actually. But I have a reel of 22pF lying around, so I think might as well give it a try.
158  Forum 2005-2010 (read only) / Development / Re: Low Power Arduino on: September 06, 2010, 10:14:36 pm
Where could we see the schematics? Preferably in Eagle format.
And where can we buy this?

I just uploaded the schematic. I did the design in Diptrace because it's easier for me. I'm not sure whether I would sell this but it depends on whether people are interested. smiley


I'm crazy about low power stuff as it is so important in my 9-5 job.
The external 7.5 V to 36 V input was meant for solar panel but needs a Li-Ion/Li-Pol on top of that. smiley Thanks for the links.

I'm looking into that but it might need to load the calibration values into the OSCCAL register during power up from any storage like the EEPROM or flash in the sketch itself. But we tested the serial communication up to 1M, it works fine but haven't test against temperature variation yet. I'm quite sure it needs calibration as LilyPad itself change from Internal RC to the external resonator probably due to this same reason.

159  Forum 2005-2010 (read only) / Development / Low Power Arduino on: September 05, 2010, 11:07:34 pm

This is our attempt to make a low power Arduino variation board. Some feature of the board:
  • It uses the "breadboard" (ATmega328 on a breadboard (8 MHz internal clock)) as the board option in Arduino IDE 0018.
  • Utilizes full SMD components to reduce the cost of assembly.
  • Ultra can be powered by either the USB, external DC source, Li-Ion/Polymer or all of them at the same time.
  • Runs on 3.3 V rail as most low power interface runs on 3.3 V rail or lower.
  • A low power 32.768 kHz is present to allow the board use it as a asynchronous timing source during power safe mode. This removes the need of an external dedicated RTC IC.
  • Microcontroller - ATmega328P-AU
  • Clock - Internal RC 8 MHz oscillator
  • External DC source range - 7.5 - 36 V, 2 A
  • Battery - Lithium Ion or Lithium Polymer with temperature monitor for charging
  • Battery charging - Maximum 500 mA charge current
  • Buck-boost converter stage for usage of input voltage lower than 3.3 V
  • On board temperature sensor - MCP9700 connected to ADC7
  • Battery voltage monitoring - Connected to ADC6
  • USB port protection - 500 mA resettable fuse
  • Analog reference voltage with LC filter
  • Indicator LED connected to digital pin 13
  • Has Arduino standard breakout pins at the bottom side using SMD 2.54 mm headers
  • Dimension - 55.88 mm x 68.58 mm

We tested the 1st PCB attempt in terms of functionality and found out that we forgot to supply the MCP9700 sensors with supply,  :o. Have yet to measure the current consumption especially during power save mode but we hope it goes near the design specifications.

Schematic Revision 1.00
160  Forum 2005-2010 (read only) / Development / Re: real name for stacking headers? on: August 17, 2010, 03:01:34 am
Bulk is like a reel (sometimes 1K, 2K, etc). If you notice, Sparkfun uses quite a lot of their connectors based on the datasheet they attached. smiley
161  Forum 2005-2010 (read only) / Development / Re: real name for stacking headers? on: August 17, 2010, 12:06:33 am
You can get them from 4uconnector. They allow sample buys up to 10 pieces. It's USD0.0582 per piece for the 6 pins version. You can also buy in bulk with them. I usually buy from them in samples quantity but have to wait 2-3 weeks to see any big buyer buying in huge quantity, so they can squeeze in your small order.  And also use cheap registered mail to save $$$.
162  Forum 2005-2010 (read only) / Interfacing / Re: ic or component that stores energy on: January 08, 2011, 10:30:11 pm
Are you looking for some energy harvester IC?
163  Forum 2005-2010 (read only) / Interfacing / Re: XBee and bluetooth on: November 12, 2010, 07:41:04 am
X-CTU is a software provided by Digi to be used together with their XBee module.

For the Bluetooth Bee, you need to send strings of command to the Bluetooth Bee as shown in the manual.

They both have same footprint, but that doesn't make them capable of using the same configuration software.
164  Forum 2005-2010 (read only) / Interfacing / Re: Xbee sending junk on: November 19, 2010, 09:18:16 am
Check your baud rate.
165  Forum 2005-2010 (read only) / Exhibition / Re: Remote controlled antenna switch on: October 11, 2010, 11:12:19 pm
That's very cool. It's something like what they have on those GSM base station where they can control the antenna direction, frequency, and other parameters from a web interface.  smiley
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