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3091  Forum 2005-2010 (read only) / Development / Re: Interest in micropower / energyharvesting Arduino? on: July 07, 2010, 12:15:21 pm
With regard to the displays: this is incredible. It implies that I might be able to add a display to my batterie less timer. This would be way cool smiley
Since I do not have a lot of processing power at such lower currents I would be satisfied with a low power equivalent of a LED. Do you know any cheap micropower 1 pixel displays?

3092  Forum 2005-2010 (read only) / Development / Re: Interest in micropower / energyharvesting Arduino? on: July 07, 2010, 11:46:52 am
Now this is really good advice. My voltage source is a basically a 3V INPUT with something of maybe 30k pullup and a switch level around 2V. Mileage may vary. So what I am trying to do is to power a controller through the pullup of some other controller. That is something like found here: http://www.dslr-forum.de/showthread.php?t=419146.

However I want to have a crystal oscillator connected in order to get more precision. It follows that I need more power and thus a bigger cap and thus have slower voltage rise. This in turn locks the processor with to much current drain at startup.

I have the impression that the voltage detector approach may require less parts (thus less soldering). So I think I will try this first. Can you recommend any 1.5-2V voltage detector? Maybe a part that stays below 2uA? With some short search at Digikey I found only 6uA parts and this drains a lot from my limited power budget. I will search more but if you already know one I would be happy to learn about such a part.
3093  Forum 2005-2010 (read only) / Development / Re: Interest in micropower / energyharvesting Arduino? on: July 04, 2010, 08:18:03 am
The datasheet say in section
"26.2.13 Current Consumption in Reset and Reset Pulsewidth" that it will draw >50uA on POR @1Mhz.
In section
"8. System Control and Reset"
It seems that POR will always trigger before BOD.
--> I will most probably need an external circuit smiley-sad

Udo

3094  Forum 2005-2010 (read only) / Development / Re: Interest in micropower / energyharvesting Arduino? on: July 04, 2010, 06:40:14 am
Yes, I read about the TIs. The AVRs have the significant advantage that my software is already completly tested, the toolchain is already working well and I already know all the registers and the assembly language. Otherwise I would be less reluctant to try the TIs. As soon as I can spare some time (which is currently dedicated to my first "big" project) I will try this out and report the results.

Udo
3095  Forum 2005-2010 (read only) / Development / Re: Interest in micropower / energyharvesting Arduino? on: July 04, 2010, 04:07:42 am
Now I found this here
http://www.atmel.com/products/avr/picopower_sleep.asp?family_id=607

Since my controller will be sleeping most of the time it seems that enabling the BOD is exactly what I need. Obviously I will have to try and figure out in hardware. The question that is stated nowhere is: how much current will it draw if POR triggers below the BOD level? If this is >15uA then I will be screwed and have to go for an external ciruit. If it stays below, great smiley

Udo
3096  Forum 2005-2010 (read only) / Development / Re: Interest in micropower / energyharvesting Arduino? on: July 04, 2010, 03:32:15 am
I double checked with the datasheet. Unfortunately BOD current is >15uA. This would be OK before startup. However it is not OK anymore while running. So I will have to search for some different solution.

I think you hint got me on the right track though. Now I found AVR 180.
http://www.atmel.com/dyn/resources/prod_documents/doc1051.pdf
Let's see what I can learn from it.

Udo
3097  Forum 2005-2010 (read only) / Development / Re: Interest in micropower / energyharvesting Arduino? on: July 04, 2010, 02:59:24 am
Very good point. I will try this.

Thanks a lot, Udo
3098  Forum 2005-2010 (read only) / Development / Re: Interest in micropower / energyharvesting Arduino? on: July 03, 2010, 03:15:07 am
The macros already exist. Arduino is based on AVR-LIBC and this contains power macros.
Code:
http://www.nongnu.org/avr-libc/user-manual/group__avr__power.html

Drmn4ea: I already experimented with some low power setups. My biggest issue was not getting down to <5uA. My biggest issues was getting "over the hump". That is: at startup the reset circuit draws to much power. Since my power source had >30k impendance I never got the device to startup on low power. Once running I was always <5uA average.

Since you probably have way more experience in this area: how do you solve this sepcific problem? Of course I can charge a capacitor for the startup. But how do I detect that I am "over the hump" and how do I then connect power to the processor? Preferably with parts available to an amateur.

My (equivalent) setup is:
3V source with 30-50k say 47k impedance, some yet to be conceived device, an Atmel 328P (aka "Arduino") (running at 1Mhz while awake but sleeping most of the time). The old thread is here:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1273507808

Any hints would be very much appreciated.

Udo
3099  Forum 2005-2010 (read only) / Development / Re: Interest in micropower / energyharvesting Arduino? on: July 03, 2010, 02:59:29 am
The LTC3108 looks like an incredible toy. I need to get hold of one smiley

Udo
3100  Forum 2005-2010 (read only) / Development / Re: stand alone chip on: September 12, 2010, 09:01:19 am
I was talking about external components. My point was that disabling the reset pin will get rid of the requirement for an external pullup.

@deSilva: what exactly do you mean by "very precise"? How precise? I do not get how "very precise" and "temperature dependent" fit together.

Udo
3101  Forum 2005-2010 (read only) / Development / Re: stand alone chip on: September 11, 2010, 11:32:48 am
If you know what you are doing the bare chip will suffice.

If you do not need precise timing the 8MHz RC Oscillator is good enough.

If you have a HV programmer you do not need to pullup reset - you can completely disable it by proper fuse settings. But do so at your own risk. This is a way to lock you out of the chip.

If you have 4.5V-5.5V supply (or slightly lower if you are running @8MHz) you can get rid of the regulator as well.

It all depends on what you are doing. If you do not fully understand what is going on you can not get rid of the caps though.

Udo
3102  Forum 2005-2010 (read only) / Development / Re: Low Power Arduino on: September 10, 2010, 09:48:48 am
OK, got it.

I looked up your schematics. The power path controller and the regulator come in very small packages. How did you solder those?

Udo
3103  Forum 2005-2010 (read only) / Development / Re: Low Power Arduino on: September 09, 2010, 11:53:00 am
I don't get your point. If you go for lower load you will get more pullability and thus less precision / stability. Is this what you are aiming for?

Udo
3104  Forum 2005-2010 (read only) / Development / Re: Low Power Arduino on: September 08, 2010, 11:04:45 am
Higher load capacitance implies less pullability. Thus in doubt better precision.

With regard to the callibration: I thought the RC oscillator is much more affected by temperature. Hence a recallibration at startup might be reasonable to improve precision.

Udo
3105  Forum 2005-2010 (read only) / Development / Re: Low Power Arduino on: September 07, 2010, 01:57:48 pm
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.

Udo
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