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46  Using Arduino / Sensors / Re: Ultrasonic sensor to determine water level? on: July 01, 2011, 01:21:06 pm
I didn't get around to installing it yet, but maybe you don't have to deal with the 30cm distance problem if you place your sensor cleverly, or use several sensors? For me it is mainly to detect if the water level is running low, so if the magnet is far away, it just means that everything is fine.

Anyway, I did get several quite strong magnets just to be on the safe side when building it.

The magnet I am planning to use is a ring magnet with 7.7kg strength. I hope it will do the job.
http://www.supermagnete.de/eng/R-19-09-06-N

I also got a couple of these
http://www.supermagnete.de/eng/W-12-N

and finally
http://www.supermagnete.de/eng/S-25-07-N

47  Using Arduino / Microcontrollers / Re: Freetronics Eleven vs Genuine Arduino on: July 01, 2011, 12:46:48 am
Hi,
I have no experience with the Freetronics Eleven, but I have tried other clones (Seeeduino and Freeduino) without problems. I would even hold the Seeeduino to be slightly better than the original.

If it says 100% compatible you can probably expect it to be.

Good luck!
48  Using Arduino / Microcontrollers / Re: Digital ports Seeeduino Film on: June 30, 2011, 08:02:34 am
I've no idea about the stars thing. I would just code away while waiting for the device and then try it out.

If it compiles in the Arduino IDE, there is a good chance it will run without a hitch when you get the device.

49  Using Arduino / Sensors / Re: Ultrasonic sensor to determine water level? on: June 30, 2011, 06:59:22 am
I have dealt with the exact same problem, but for a 20L tank and found several threads in the subject of water level measurement on this forum. Search around and you will find a lot of good input.

All-in-all, I have decided to go for a float with a neodymium magnet on it and measure the magnetic field strength using a Hall effect sensor. This has the added benefit that your electronics can be outside of the tank, provided it is plastic. IR will probably work as well I guess.

50  Using Arduino / Microcontrollers / Re: Digital ports Seeeduino Film on: June 30, 2011, 06:54:17 am
I believe the Seeduino Film is a completely Arduino compatible clone, i.e. all pins are the same and named the same. If it works on your regular Arduino, the same program should work unmodified on the Film. Haven't tested, but that's the theory at least.

51  Using Arduino / Microcontrollers / Re: "[...] please define PAGEL and BS2 signals" (ArduinoISP + ATiny85 problem) on: June 30, 2011, 06:16:57 am
Indeed I am!

This is all done using a first generation alu Macbook running Snow Leopard (MacOSX 10.6.7).



52  Using Arduino / Microcontrollers / Re: "[...] please define PAGEL and BS2 signals" (ArduinoISP + ATiny85 problem) on: June 30, 2011, 02:06:45 am
Thank you both!

@Coding Badly
I gave the thread a read and I will try out some of the tips. I think I came across that thread last week, but at that point I was still reading up and not trying out yet.

@Bobnova
Yes, that's what I will do near-term to continue learning about programming the thing. Going forward I would like to have a fully working configuration though, if possible.


/Anders

53  Using Arduino / Microcontrollers / "[...] please define PAGEL and BS2 signals" (ArduinoISP + ATiny85 problem) on: June 29, 2011, 03:17:56 pm
I'm having mixed success using the ArduinoISP sketch to program an ATiny85. It works, but with errors. The sketch transfers and is subsequently running on the Tiny, but I'm getting error messages from avrdude all the same. See below and attached screenshots for additional info.

I have searched the forum, but only found dated threads on this topic. Hoping that someone here might shed some fresh light on it. As most of my projects are quite limited, the prospect of moving to a cheaper and simpler microcontroller is very compelling.

The setup
I'm using the Arduino 022 IDE together with an Seeeduino with the standard ATmega 328.

The IDE has been upgraded with the Arduino Tiny cores from http://code.google.com/p/arduino-tiny/ and the installation seemed to work out just fine. I have also enabled the ATiny85 in the boards.txt file according to instruction.

To get the programmer going I have followed this guide mainly: http://provideyourown.com/2011/arduino-program-attiny/ together with http://arduino.cc/en/Tutorial/ArduinoISP, but added some tweaks I picked upp on the way from misc. threads in this forum and on the internet. Main resources used for tweaks:
- http://arduino.cc/forum/index.php/topic,65099.0.html
- http://laclefyoshi.blogspot.com/2011/01/note-of-caution-for-arduino-isp.html

Using only the two main guides did not yield any working configuration. In the end I have ended up with the following:

ATiny85 pin --> Arduino pin
1 --> Digital 10
4 --> GND
5 --> Digital 11
6 --> Digital 12
7 --> Digital 13
8 --> 5V

Additional connections
- To prevent the auto reset, I have a 120 Ohm resistor from 5V to RST on the Arduino.
- To test the Blink sketch on the Tiny, I have a 330 Ohm resistor and an LED on ATiny pin 5 (digital 0) to GND.


The problem
As mentioned above, the sketch transfers and starts executing (The LED on ATiny pin 5 starts blinking as expected), but I'm getting errors from avrdude saying:

Code:
Binary sketch size: 748 bytes (of a 8192 byte maximum)
avrdude: please define PAGEL and BS2 signals in the configuration file for part ATtiny85
avrdude: please define PAGEL and BS2 signals in the configuration file for part ATtiny85


The question
What have I done wrong? Any clues welcome.



Thanks!/Anders




54  Using Arduino / Project Guidance / Re: Which platform to use, question of voltage, current, plus SPI question... on: June 14, 2011, 10:47:27 am
For battery applications, you can seriously extend the battery lifetime by using the sleep modes in the AVR chip. Wakeup on internal watchdog or external pin interrupt.

See http://donalmorrissey.blogspot.com/2010/04/putting-arduino-diecimila-to-sleep-part.html
and http://interface.khm.de/index.php/lab/experiments/sleep_watchdog_battery/

55  Using Arduino / Project Guidance / Re: Bioelectrical Impedance on: June 13, 2011, 04:06:44 pm
Ok,
again, I am no expert, but I notice you use the term "impedance" instead of "resistance", so that to me would give a clue to the 4-connector, vs. 2-connector question you had.

2 terminals = resistance
4 terminals = impedance (real + imaginary part)


Impedance also suggests alternating current (AC) to me. Are you planning to tap your measurement reference signal directly from the grid? Although I agree it is probably accurate enough, it is not healthy to send that amount of voltage and current through your subjects. You need to drop it down to under 110V I guess, probably under 70V to be withstandable by the subjects.

I would also worry more about the algorithm. Once you have your reading, how do you tell fat content from muscle based on that?

56  Using Arduino / Project Guidance / Re: Bioelectrical Impedance on: June 13, 2011, 03:27:15 pm
Very interesting project! How would it be connected to the user (feet+hand, hand+hand, ...)? What algorithm had you intended to use for the calculation, once you've got your reading?

I'm no expert, but I would say that generally, the Arduino is not a small current, low voltage device. I would be bolder in voltage/current output to get more reliable readings. As long as it is not fatal, but only stinging/buzzing for an adult you should be fine. Just put a visible disclaimer on the device and make sure it does not look "professional" so that no one can claim they were fooled by the looks of it.

57  Using Arduino / Project Guidance / Re: Maglev baby cot? Feasibility question. on: June 07, 2011, 12:18:00 pm
Oh!,
I didn't realize that it would be loud! Definitely thought it would be silent. I have no experience at all from working with coils and magnets. Didn't realize they make any sound meanwhile.

I guess I'll just store away this idea for later reuse in some other shape or form.

Thanks for the feedback!/Anders
58  Using Arduino / Project Guidance / Re: Maglev baby cot? Feasibility question. on: June 07, 2011, 08:04:22 am
Indeed! :-)

It's hard to describe without a proper sketch, but it would allow for a rotational "rocking" movement by the way it is attached to the loops, but it would at the same time prevent the whole cot from just floating away and falling off the magnetic cushion.

59  Using Arduino / Project Guidance / Re: Maglev baby cot? Feasibility question. on: June 07, 2011, 07:57:45 am
Good points.

My wife is already a little bit of a suspicious towards my Arduino hobby. Adding our baby into the mix will indeed be a complicating factor. I was however thinking about introducing some kind of guide mechanism to make sure only up/down movement would be physically possible. Something like two poles at the short ends, with rope or wire loops around them to prevent lateral movement.

60  Using Arduino / Project Guidance / Maglev baby cot? Feasibility question. on: June 07, 2011, 07:35:30 am
Hi,
while shopping for some minor magnets the other day for my balcony windmill project I realized there are some quite powerful magnets that are not too expensive and the idea of a building an Arduino maglev baby cot for my newborn child came to mind.

There are several pages describing solutions based on a magnet, coil and an hall effect sensor. The most serious treatment I've found however states that whatever you build will be inherently unstable (http://mekonik.wordpress.com/2009/03/17/arduino-magnet-levitation/). I don't want my baby to be tipped over and thrown out of the cot in mid air. The idea is to have her floating comfortably of course, maybe with some gentle rocking to promote sleep.

I am also a little bit worried about exposing my baby to strong magnetic fields for extended periods of time on a regular daily basis.

So I have two questions I guess.

1 - Is it possible to build a stable solution?

2 - Can the magnetic fields involved pose any health hazard to small babies?


I was thinking about magnets like these:

56kg
http://www.supermagnete.de/eng/Q-60-30-15-N

100kg
http://www.supermagnete.de/eng/Q-51-51-25-N


Any thoughts and input appreciated of course!

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