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16  Using Arduino / Microcontrollers / Re: MEGA 2560 reset voltage on: September 11, 2014, 10:00:24 am
@ Raschemmel... The operative point is the the threshold is not an absolute value, It depends on the actual applied Vcc..
Thus Vhigh is .9 X Vcc and Vlow or reset is .2 X Vcc not .2V or .9V

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17  Using Arduino / Programming Questions / Re: Measuring amperage on: September 11, 2014, 09:44:51 am
Yes it should I didn't really read the whole article but my suggestion Re: the op-amp as to leave the math to the op-amp and it's feedback (gain set) so as to produce a voltage that is equal to the amperage and to offset the bi-polar output to a single ended solution.
Thus it becomes a reusable solution that requires less code to convert for example the
Quote
ACS712ELCTR-05B-T
Which has a sensitivity of 185 mV/A to a number that is easier to use.
Since the part # mentioned is a 5A sensor (ideal I think) converting the output voltage from 185 mV to 0 to 5 A can  certainly be done in code there is still the Output + mV/A still has a possible plus or minus output value and requires the use of floats extensively meaning larger code because first you must scale the output to the actual current first and then display that number... Which can be done with int's much easier when the ACS712 output is representative of the actual current...
Your requirements and what I read of your skills indicates to me that a small read about op-amp's would give you more options.
It will also make a re-usable device much easier to implement should you need one for another use or another project.
One op-amp 3 or 4 resistors and 2 pots makes an easy circuit to use..
I've taken the liberty of attaching data sheets on the three devices mentioned... The ASC712 device is relatively cheap from fleabay , in the 3 to $5 dollar range and has a minimal loss due to it's sensing resistance.. The TIL431 is also in the same class (Vref and adjustable too).
The LMC662 is  very easy to use and is relatively stable... The Dip part is under a dollar (or should be) so "Give it a play"...
There are example circuits on all the data sheets too.
If you get lost, I'll be watching this thread.. so after Mr Google post a question and I'll try to answer it as best as I can...
The 20A ASC712 device has a 100 mV/A output but it sort of is out of range for small (1 to 5A) due to the
ADC limitations and while it would work I feel that it is not the best choice.. I do hope this helps.. you and anyone else needing a solution such as yours..

Doc
18  Using Arduino / Programming Questions / Re: Measuring amperage on: September 11, 2014, 08:21:01 am
Perhaps this would better done as a search by the OP But an Allegro ACS712 series hall effect current sensor might be a 'somewhat' better choice than attempting to use a sensing resistor... It requires nearly the same additional Op-Amp as would OP's attempt. is missing... But far more accurate... A TIL431 and a resistor and a pot for calibration make an excellent Vref source, Even considering the stated accuracy of the SAR ADC used in the 328P series of uControllers (+/- 2 counts, Typ).
The output of an ACS712 is Vcc/2 and changes as the current flow shifts from zero. Discharge is typically Vcc/2 + Vout and charge is Vcc/2 - charge depending on the polarity of the sense inputs which go in series with the load... This device can be used to sense either the positive or negative power supply lead. An LMC662 (dual rail to rail op-amp) can be the gain block to rationalize the output shift and the second op-amp can be used as a level shifter to convert a bi-polar output to a zero referenced output voltage.. Easily...
I leave the details to OP's skill with Google.. As I Know there are reference examples for both freely available from Google..
BTW Did the OP make even a small effort to search the Arduino site first..
This is not the first time this or similar requests have been asked here... The Answers are typically found in the General Electronics section and the answers are relatively simple... Once you "Search For Them"... I am happy to answer specific questions on methods and circuitry... Only if the OP has done his part in researching the question... The OP would learn little If I did the relatively simple engineering required... I'm not participating in this forum for anything else but what I don't already know...
If I can be of help with advice.. Great... But I don't consult for free and I will not do design work for anyone but myself.
This is a trivial issue and the answers can all be found in the "Op-Amp Cookbook".. It just takes some initiative from the OP to do the basic work... I'll be happy to fix bad circuitry But...

Docedison
19  Using Arduino / Programming Questions / Re: byte level boolean, calibrate crystal, eeprom as flash on: September 11, 2014, 06:16:46 am
@ Coding Badly?...
Thank you for this reference to a most useful library... A year or so back I bought 3 "Clock modules" from Fleabay...
They have ATMEGA8-AU's as processors and for the most part work well however the code was written in another environment that  I don't yet understand well enough to use (I've tried) apparently it is the Atmel Studio IDE and I've been looking for something like this. The unfortunate part is that the month and day data is written in what looks like simplified Han...
Combined with the HT1632 library because it's the display controller, will allow me to make a relatively painless transition to the Arduino IDE and 3 functional clocks with virtually no change to the board...
While I realize that a DS3231 is a much better choice I'd rather not make extensive mods to the board... The board has the ISP connections broken out to a 6 pin header so all I need to do is write what I need and test it.. I do have a spare HT1632 board for testing and I can develop the code on a breadboard and test it with a single HT1632 and display...

Doc
20  Using Arduino / Programming Questions / Re: Mosquito Anti Loitering Device on: September 10, 2014, 06:40:31 am
 Most professional "Perimeter denial" devices use a combination of both doppler radar and IR sensors...
I've designed Perimeter Denial devices with a 500 meter range using a 75 KG body mass as the doppler range and the IR function was for Hot  bodies... like automobiles... or close body radiation
The Mosquito device looks like a short range device working under the assumption that radiated IR from a human sized "model" was close enough to exceed the normal ambient IR radiation of a hot day or night where the ambient radiation is greater than the ~ 86 deg average body radiation of a fully clothed body...

Doc
21  Using Arduino / Microcontrollers / Re: MEGA 2560 reset voltage on: September 10, 2014, 06:23:32 am
@ Raschemmel your information is not quite correct... Pull up  the reset pin above ~ 11V (read the data sheet...) and you will place the chip in HV programming mode.. Commonly used to fix accidently Bricked controllers.. and become more familiar with actual Low and High input pin levels both  regular and Schmitt  trigger type inputs...

Doc
22  Using Arduino / Microcontrollers / Re: Using radio library with ATTiny84? on: September 10, 2014, 05:02:41 am
IF you'd taken the time to search for pcrel here in the Forum or [Gasp] Google for it you would have solved half your errors and I really don't care to do it for you... but you might just read this instead of asking others to do the same lame S**t...
http://forum.arduino.cc/index.php/topic,116674.15.html..
Ps: this took about 4 seconds to do.. mainly because I'm not a fast typist..
BTW there were about 75.5 K google answers... in 0.35 seconds.

Docedison

Btw... I think your "handle" was well chosen...
23  Using Arduino / Programming Questions / Re: Mosquito Anti Loitering Device on: September 10, 2014, 04:18:51 am
How did you confirm the sensitivity to a single Mosquito they are not large enough to be much of an IR emitter and to the best of my limited knowledge exothermic in growth or digestion of food...
IMO your test conditions are questionable... Better, I think to detect the noise generated by their wings in flight...

Doc
24  Using Arduino / Programming Questions / Re: Time.h and arduino-mk on: September 10, 2014, 01:02:46 am
@ Minchinion...
+1 A good lesson for those of us that believe we know better...

Doc
25  Using Arduino / Programming Questions / Re: Time and TimeAlarms Libraries – Ask here for help or suggestions on: September 08, 2014, 09:16:33 pm
THis might be of use to you for your current issues but I wrote it for a Mega2560.. a year or so back

Doc
26  Using Arduino / Programming Questions / Re: Help changing time on RTC1307 with buttons on: September 07, 2014, 10:00:24 am
# JimboZA Good point, there are many different 32 KHZ "Crystals" They are all Piezo tuning forks.. Not resonators or crystals in the normal "sense" of the word. Simply slightly different structures differing only in dimension a different combinations of Piezoelectric materials or both.
It is these small difference that require different loading determined by the RTC internal capacitance of the oscillator... clearly the OP is using the wrong device.
The best method would be to [Gasp] read the data sheet and buy the one recommended for his RTC chip..
There are no one fits all device although the frequency marking are the same.
Doc
27  Using Arduino / Microcontrollers / Re: What battery is best for Arduino Pro mini with nRf24L01 on: September 04, 2014, 09:58:13 pm
a 9V battery is a most poor choice for an uno project as it is capable of perhaps 50mA for 1.5 hours as the battery capacity rarely exceeds 100 MAH max
A 2S 1000 MAH Li-Po is IMO the minimum that can be used for long term rechargeable use with an Arduino 5V linear regulator as it causes the least amount of regulator power dissipation or power lost. I buy 7.5V 2A wall warts for my projects that require AC power
For my own use I prefer a buck boost mode switcher to convert the 4.2V max of a single cell to 3.3 V output and use my project @ 3.3V. Although buck boost converters rarely exceed 85% efficiency they are Much better than a power supply derived from a linear regulator
AS has been mentioned the Arduino 3.3V source is only capable of perhaps 50 mA and has one (C13 or C14) 1 uF capacitor for the bypass capacitor for the LP2985 3.3V linear regulator depending on the board.
Once as a test I connected a GPS receiver to a Pro mini and viewed the time from TinyGPS++... No LCD just the serial Monitor...
It lasted for 2 hours before the GPS device failed and this was with a buck mode switcher to convert 9V to 3.3V..
About 35mA for the PRo-Mini and 30 mA for the GPS U-Blox NEO 6 receiver..
3 AA cells connected to the Vcc connection operated the thing for 3 days (probably used batteries too)..

Doc
28  Using Arduino / Programming Questions / Re: Multiple IR recevers using IRLibrary on: September 04, 2014, 05:27:40 pm
Great construction example, Shows an active mind aware of the capabilities of the IR detector..
My take would have to cut the "funnel" off of those crinkly water bottles and paint them with an opaque... Water based paint
for however many light shields were required.. If you retain the caps it's a simple matter to make a hole in the cap big enough to clear the lense or the IR detector, glue the detector to the top of the cap... and using masking tape to cover the last 10 mm of the sensor wires and paint the whole assembly again with a black and IR opaque paint..
Mounting them with hot glue and wiring the devices to  a sensor shield with the common 3 pin servo extension  cables would be trivial.
I'd also test the paints for both IR transmissivity and reflection.. For a few dollars more plain old ABS tubing and some reducers and end caps might look more professional and might be easier to gain the non reflective properties that the Play Dough has...
The drawback is the playdough is a flour and salt + water mixture that will dry out and possible crack..
The cardboard or 'printed light shield is still a necessity to help prevent crosstalk.. With some black cheese cloth and an outer housing it could look very professional for very little cost as leftover latex paint can usually be had for the asking and the black pigment might well be finely ground charcoal... I would estimate the total cost might be a quid or so... Though oi'm not a brit...
 I should think an Euro would  be the most for recycled materials...

Doc
29  Using Arduino / Programming Questions / Re: Does Arduino Uno hibernate by itself or why does my scetch seem to halt? on: September 04, 2014, 01:00:59 am
There are also a few of that are capable of speaking several languages.. I can read and speak some spanish, some italian, some German and a little french and I find your comment somewhat condescending as it is your issues that I want to try to solve.
This Forum is a big part of my education.. along with books on  both my Kindle Fire and my Nook book readers that are never more than two to four meters away from me.
Even with Google Translate, which I use frequently as it is a serious part of my education... As well,
Google is a source of possible solutions to or direction to the answers required.
I am a 68 year old retired engineer trying to learn a new and versatile, valuable programming language... 
I realize that Google is my friend and I frequently use it to find solutions for those that can't or won't make the effort to do so..
I use it to find answers to what I don't understand... Yet.

Docedison
30  Using Arduino / Microcontrollers / Re: Migrating from an ATmega328p to a larger uC on: September 03, 2014, 09:20:13 pm
Paul Stoffregen has a nice arduino 'mostly' compatible product... Even uses the same IDE with his software addition to the Ver 1.05 IDE it's an add on that doesn't incapacitate the basic Arduino IDE use.
It runs Arduino code too and is a lot more capable. A 32 Bit ARM processor board similar to the Pro Mini in size called the Teensy3.1
Although the Arduino paradigm is still my favorite by a long shot because, although I have 20+ years in hardware design my code skills are poor at best compared to PaulS or Awol or any of the other heavy hitters... So I get the best of both worlds.
Although the Teensy lacks really strong pin drive capacity, it's other features make it ideal when casting about for a bigger controller...
Perhaps it's real lack is the plethora of pins that a Mega or a Due has (34 for the Teensy 3.1) 256K of flash and 64 KB of Ram make it very attractive for fast (overclocking @ 96 MHz) projects.. I use smaller processors (Mega1284 Bobuino) for high pinout devices like large GLCD's or large keyboards... I have a project involving a scrolling display and a 5" GLCD with a 40 key tactile keyboard and for that I use a Mega for display(s) and keyboard control...

Doc
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