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61  Using Arduino / Project Guidance / Re: Measuring Arduino Power Consumption on: August 06, 2014, 07:51:42 am
Am I measuring the current draw incorrectly?  

I'd say so.

Quote
Any guidance would be appreciated

Show us how you are measuring the current. A diagram would be best even if just drawn by hand.

FYI, here are measurements I've done:
http://forum.arduino.cc/index.php?topic=164146.msg1232507#msg1232507
62  Using Arduino / Networking, Protocols, and Devices / Re: Trouble with both DS1307 and DS3231 RTCs and time slowing down on: August 06, 2014, 07:38:35 am
I need a proxy, it costs me money to reply due to my ip ban.

Ok so it's nothing to do with it's internal resistance. .. but I remember leaving it for a couple of weeks, the coin cell drifted while the nokia battery was perfect.. maybe my coin cell was really low on voltage?

Could be, I might have checked it with a meter. Was the RTC being powered only by the backup battery, or did this occur while the RTC was powered by VCC? If the latter, it shouldn't matter what the state of the battery was. The RTCs that I use say that if a backup battery is not used, the VBAT pin should be connected to ground. I've also seen it said that if a backup battery is used, then one has to be present, even if it's dead, for the RTC to operate properly on VCC. Haven't checked that myself, though.
63  Using Arduino / Networking, Protocols, and Devices / Re: Trouble with both DS1307 and DS3231 RTCs and time slowing down on: August 06, 2014, 12:03:49 am
Use a lithium phone battery as it's backup power source instead of a coin cell...

When I did that, I went from losing seconds a day to seconds a month!

And what do you attribute that to?

It's odd that I've never noticed any trouble with coin cells.


Purely observational... but it's a true story, kinda leads me to believe the battery's internal resistance plays a part.

It may be a true story, but that's not a conclusion that I could accept. It can't be internal resistance, something else must have been going on. These RTCs only draw nanoamps from the backup batteries, and then only when Vcc is not present. My Microchip RTCs use a 1000Ω resistor in series with the coin cell, and this drops less than a millivolt because the current is so low.

Coin cells work fine with RTCs and they last for years due to the low load.
64  Using Arduino / General Electronics / Re: Gauging Interest: Printed Circuits on Paper on: August 05, 2014, 10:07:01 pm
I'll be interested to hear how it goes.
65  Using Arduino / Networking, Protocols, and Devices / Re: Trouble with both DS1307 and DS3231 RTCs and time slowing down on: August 05, 2014, 10:06:22 pm
Use a lithium phone battery as it's backup power source instead of a coin cell...

When I did that, I went from losing seconds a day to seconds a month!

And what do you attribute that to?

It's odd that I've never noticed any trouble with coin cells.
66  Using Arduino / General Electronics / Re: Gauging Interest: Printed Circuits on Paper on: August 05, 2014, 06:52:04 pm
Maybe I missed where the original poster gave the conductivity of the ink?

The folks with the idea on Kickstarter say 0.2 Ohms/square.
67  Using Arduino / Networking, Protocols, and Devices / Re: Trouble with both DS1307 and DS3231 RTCs and time slowing down on: August 05, 2014, 06:45:23 pm
I agree that a simplified sketch that does pretty much nothing but display the time is the way to go to debug this. I work a lot with RTCs and I'm not sure I've ever seen the symptom described.

Just another alternative, I wrote this library and it is known to work well with DS3231 and DS3232. (It might even work with DS1307, but I can't swear to it, I haven't tried it.)

Anyway, download the library and just run one of the example sketches that come with it, either "SetSerial" or "TimeRTC".
68  Using Arduino / Networking, Protocols, and Devices / Re: xbee ZBRxResponse(rx) on: August 05, 2014, 06:27:58 pm
Are you using XBee ZB modules (fka Series 2) ? If so the ZigBee Receive Packet frame (type 0x90, see the product manual, page 113) has 14 bytes before the payload BUT if some characters are escaped it could be more (you are using AP=2, yes?).

This will return the first byte of the payload:

Code:
ZBRxResponse rx;
...
uint8_t foo = rx.getData(0);

Not sure how you're printing, but I don't think that

Code:
Serial.print( rx.getData() );

is a good idea because it will probably just print until it hits a zero byte, which is not necessarily the end of the frame.

These functions may be helpful

Code:
uint8_t  getDataLength ()     //Returns the length of the payload.
uint8_t  getDataOffset ()     //Returns the position in the frame data where the data begins.
69  Using Arduino / General Electronics / Re: Gauging Interest: Printed Circuits on Paper on: August 05, 2014, 04:03:33 pm
I've seen this concept around the web once or twice. It's a cute parlor trick but as a fairly serious hobbyist I wouldn't consider it. I assume you must be aware of how inexpensive real PCBs can be had these days.

I agree. I think getting a PCB is not expensive in terms of dollar value but the process is expensive. The design, error checking, and delivery is time consuming, which is inherently expensive. You could etch your own but working with harsh chemicals can be dangerous. Ive heard of people hacking inkjet printers to do the same thing which is totally cool but who still has a deskt-jet that their willing to re-purpose for this. What retail store can i walk into in the United States today and get one, or 100 of my circuit idea printed before i leave the store and would that be something you guys would pay for?

I don't see how the design and error checking can be any different; the process you suggest supposedly fills the same role as a PCB so the design process has to be pretty much similar. I've etched my own and I don't consider the chemicals particularly dangerous. But with the inexpensive options available, I can get much better boards made for me. The turnaround time is the tradeoff. But if time really matters, turnaround time can of course be bought at a price. And the more boards, the less expensive it is. I would not consider paper PCBs as good for prototyping/PoC as the electrical characteristics have to be different as are the mechanical characteristics. The vast majority of today's designs are SMT; can the paper process handle 100-pin SMT devices with 0.5mm lead pitch?

It'd be a real good idea to get some experience with existing PCB technology before investing a lot into this idea. I only see it as suitable for very low-tech, low parts-count, non-critical circuits. I'd have to ask if that's a niche I wanted to play in.

Cost hasn't been discussed, what is the estimated price range for this technology? As a hobbyist, I can get good quality double-sided boards for $0.25/in2. I do have to wait 2-3 weeks for them, but I'm a hobbyist so basically nothing is very urgent.

This is probably coming off badly, close-minded and negative. I don't mean it that way, but I am being blunt and candid. Perhaps you see this a some sort of breakthrough, but I think it's more a solution in search of a problem. As ever, I am willing to be convinced, but I'm not there yet.
70  Using Arduino / Microcontrollers / Re: inaccurate millis() or MCU? on: August 05, 2014, 01:23:11 pm
If the statement in the original post implies an expectation of 100% accuracy, then you are bound to be disappointed as this will never be the case. Coding issues aside, the accuracy of millis() is dependent on the accuracy of the system clock, which will generally be somewhere between 5000ppm (if the clock is controlled by a ceramic resonator) and 20ppm (if the clock is controlled by a decent crystal). If the internal RC oscillator is used, the datasheet says to expect ±10% accuracy.
71  Using Arduino / General Electronics / Re: Gauging Interest: Printed Circuits on Paper on: August 05, 2014, 01:18:26 pm
I've seen this concept around the web once or twice. It's a cute parlor trick but as a fairly serious hobbyist I wouldn't consider it. I assume you must be aware of how inexpensive real PCBs can be had these days.
72  Using Arduino / General Electronics / NI MultiSIM Component Evaluator – Mouser Edition on: August 05, 2014, 11:55:17 am
Mouser announced a free version of this tool, just wondering if anyone is familiar with it, especially for schematic capture and PCB design.

http://www.mouser.com/multisimblue/
73  Using Arduino / Microcontrollers / Re: Attiny85 multiple Interrupts on: August 04, 2014, 04:40:15 pm
Sorry about that, got the physical and logical pins confused. The pull-down resistor seems odd but hard to comment without seeing the schematic. I've used PC interrupts and they work fine. If you have a minimal sketch and schematic, post them and I'll have a look and will wire it up if necessary. Explain what the sketch is supposed to do and what it actually does.
74  Using Arduino / Audio / Re: Saving a short wav file to Attiny85 via the sketch/memory? on: August 04, 2014, 12:34:03 pm
Fair enough! smiley-grin
75  Using Arduino / Programming Questions / Re: Interrupts and delay() on: August 04, 2014, 12:27:47 pm
What does this do
Code:
PORTB ^= (1 << PORTB0);

I can never get my head around that notation. Can you express the RHS as a binary value?

I'm wondering if bits are mangled in PORTB that should not be mangled.

...R

Toggles bit zero in PORTB, i.e. PORTB = PORTB ^ 0x01;

Shouldn't mangle any other bits.

Common idiom, worth mastering.

PS: But it is not an atomic operation, so if not executed with interrupts inhibited (as it is here by virtue of being in an ISR), it could cause unintended results.
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