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46  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: newb transistor question on: May 30, 2008, 07:50:03 pm
since the load will be between the collector and the ground (Vcc), and the emitter will be connected to Power V+?
No Vcc is +V

Emitter is tied to ground.
Load between +V and collector.

When base is higher than emitter by ~0.7V that "diode" goes into conduction, current can flow thru transistor, collector goes to ground (OK, 0.7V?) Anywho, you've got the load connected between Vcc and "near ground" = "ON"

When base goes to ground, base-emitter "diode" no longer in conduction, transistor = "OFF", collector voltage rises up to Vcc.

For future reference, if you put the load between the emitter and ground, the output will follow the input, not the reverse of it. (And if I understand, you currently want the reverse.) But, assuming you are using a bigger power supply on the load than the Arduino, be careful that your transistor base doesn't rise to a voltage above the Arduino's Vcc (5V). Powering ICs via their output pins is not a situation known to increase silicon life span.  smiley-razz

Here's some pictures...
47  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: newb transistor question on: May 29, 2008, 07:42:42 pm
Transistor biasing. Haven't done that in a decade or two. Gotta go pull that out of the backup tape in the basement archives. NPN transistor will conduct when the base/emitter junction is forward biased, meaning the base is at a higher voltage than the emitter. You want it on when the connection is open? Put your load between Vcc and the collector. Then maybe you tie the base to Vcc through a couple 10K ohms. That will keep it on until you pull the base low to shut off. Would that work for you?

48  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: HANDS ON - Resources for learning electronics on: May 29, 2008, 08:02:28 pm
You will likely get as many replies as people on this board. Everyone learns a different way.

I might suggest "The Art of Electronics" by Paul Horowitz & Winfield Hill
and / or
"Student Manual for The Art of Electronics" by Thomas Hayes and Paul Horowitz

I'm sure that there have been a few revs since I got mine. In the old days, "The Art" could be a text book or a book for EE graduates who still wanted to really get into the goodies, covered MANY topics. "Student Manual" was less detailed, lab oriented, and covered transistors, Op Amps, and the then-new microprocessor and supporting digital parts but not too much else.

$35-$110 on Amazon depending on condition. If you live in "civilization" you might find one in a library. My local library has romance and scifi. Technical? Hahahaha....

49  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Accelerometer to estimate speed on: May 06, 2008, 06:00:20 pm
I've got to echo mem. Integrating acceleration to get velocity (and integrating velocity to get position) can be done but doing it with any real accuracy is very difficult (hence the 10s of $K of commercial units). OTOH a wheeled vehicle can simply count revolutions of the axle. IMUs are needed only on water- and air- craft where the vehicle motion thru its media is not the motion over the ground since the media may itself be moving.
50  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Mood Light on: May 03, 2008, 08:17:03 pm



And I guess I still need to worry about the voltage differences with the Red/Green/Blue LED's. Red = 2.6V, Green = 4V, Blue = 4V (MAXIMUM ratings). But I've applied 5V to them (with ~600ohm to red, 1K to Green, and 1K to blue), and they're fine; they aren't heating up or showing signs of damage. Help!

1) what changes do I need to make in the code to fix the 'reversed' effect
2) what about the different voltages for each color in  the RGB LED
BTW, I'm not seeing any oranges...

Thanks for your support.

This LED isn't "Weird." Multi-element LEDs (whether multi-color, 7-segment, etc.) come 2 ways. Either common anode or common cathode. With a common anode (what you seem to have) the anode (long pin) goes to positive. Each junction (LED) is lit when its associated cathode is brought low. With a common cathode device, the cathode is tied to ground and each junction is lit when its associated anode is brought high.

Although our beloved Arduinos have the same source and sink current, many devices don't. Typically the pull up is weak (or even non-existent ("Open collector output"), and a (relatively) powerful transistor pulls down to drive an output pin. By way of example, the old 74xx series ICs level 1 output current is 0.4mA, but the level 0 current is 16mA. The old 74LSxx series ICs level 1 output current is 0.4mA, level 0 current is 8mA. So, anyhow, many devices use a common anode so that they are turned on by pulling the cathode low. Because that is where the current is!

Yes, your colors are reversed. The code was designed to output HIGH (analog write value 255) for full on. You are wired so that full on is output LOW (analogWrite value 0) Simple fix: Change your code in each place from:

analogWrite(selPin, i);


analogWrite(selPin, 255 - i);

Or, change the logic similarly as needed in other places.

51  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: atmega168 8 or 10 bit? on: April 26, 2008, 08:16:42 pm

could you please explain me if the atmega168 used in Diecimila is 8 or 10 bit microcontroller?
I think I'm a bit confused cause the data sheet says

with 8K Bytes

Also, does anyone know could tell me what is the sampling rate of the AD conversion in Diecimila?


Eh? 8 bits is 8 bits. Are you somehow confusing addressing range with native data type size? Even the 1980's era 8-bit 6502 could address 64KB...

As for sampling rate, read this:
52  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Mass of Arduino Diecimila on: April 21, 2008, 07:28:55 pm
Does anyone know what the mass of this microcontroller is? I can't find it on this site or any other site. The best I can do is 0.2 lbs as a shipping weight. We need this number to calculate our center of gravity requirement for a senior design project.

My digital kitchen scale puts the Arduino board at 1.1 ounces bare, 1.2 in a static bag.

The scale hasn't been calibrated since it left the factory a few years ago but my recipes turn out fine.  smiley-wink
53  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: A sensor to measure depth underwater on: April 04, 2008, 01:02:56 pm
Jaguarjoe gave a pretty good answer, but to get more & better answers we need some clarification. Do you want to measure how far TO the bottom from your current position? Or.... Do you want to determine how deep you are under the surface? What max depth do you need to measure to, and how much resolution do you need?

If you don't want to cobble together your own (and probably low power=short range) ultrasonic depth finder, you should be able to wire up to a small boat depth / fishfinder transducer. They have a few hundred (or even low-thousands) Watt pulsed output to achieve multi-hundred foot ranges. Pulses are short, total average current draw isn't too bad.


54  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: A sensor to measure velocity underwater on: April 04, 2008, 01:08:24 pm
Low speed? Get a "paddlewheel" type speed transducer from a local or online boating / yachting supply store (chandlery) or make your own. Little paddle wheel sits half in, half out of a cup (which is embedded in hull of boat). As boat moves, paddlewheel turns. Affixed to the paddlewheel is a magnet which trips a reed switch or hall effect sensor each revolution sending you a pulse.

55  Forum 2005-2010 (read only) / Bar Sport / Re: Book Recommendation on: March 26, 2008, 07:05:36 pm
Thanks, everybody. Sounds like a few of you are on the fence like me. Wow, $103 for a book. Are we talking college textbook?

Actually I'm pretty familiar with electronics, having read a lot of Forrest Mims in the late 70's, and earning a living herding trons around in the 80's and 90's. But, I spent most of 2000-2005 or so here or there doing this or that directly or indirectly helping to feed, clothe, and educate some very rural, very poor co-inhabitants of this planet. So I'm somewhat out of touch with what is available today. Cleaning out a closet a few months ago I came across a big ol' box of parts and that element missing from my life came rushing back at me ... I'm just not content when I don't have a soldering iron and a pile of parts on a desk someplace to absorb my creative energy.

Love Pascal, I can get by with C, but C++ creeps me. (The old crashing before the first line of main() thing.  :-? ) More than once have I hooked up a 7805, a 2732, and an 8051. But the ability to buy a 20MHz RISC CPU that is forgiving of supply voltage, has multi-channel A/D, PWM outputs, 20mA drive, onboard RAM & ROM, a free multi-platform development environment, and costs $6 (or less) qty 1 blows my mind. {  :o +  smiley } Can't find the old UV PROM eraser, but looks like I don't need that anyway.

56  Forum 2005-2010 (read only) / Bar Sport / Book Recommendation on: March 24, 2008, 06:53:56 pm
Considering spending some $ on bound printed matter. Igoe seems to have 2 books oft recommended, "Making Things Talk" -- which may be more Arduino oriented, and "Physical Computing" -- which may be more Stamp oriented. Both have a fair number of positive reviews, and 1 real negative one.

What would y'all recommend? "Physical Computing" or "Making Things Talk" or both?

57  Forum 2005-2010 (read only) / Bar Sport / Favorite 3.3V regulator on: July 20, 2008, 05:26:11 pm
With more and more stuff to connect to Arduino at 3.3V, tapping off of the USB is getting less handy.

What is everyone's favorite, bullet proof, probably LDO, 3.3V regulator?

58  Forum 2005-2010 (read only) / Bar Sport / Re: Hamvention on: June 23, 2008, 06:55:30 pm
When I lived in Indy I made it over a few times. The hamfests down here in FL can't hold a candle to Dayton's Hamvention.
59  Forum 2005-2010 (read only) / Bar Sport / Re: great service from on: May 10, 2008, 06:50:13 pm
can't say i had the same experience...

the ordering was fast, and shipped the same day, but they have there their company in the very south of America. I live in New Jersey. Shipping took about 5-8 days if i remember correctly. But i can't blame them, they're on the other side of the country....

Dude, study your geography. Boulder, CO is not in the "very south" of "America" it is almost the same latitude as New Jersey, and slightly west of dead center of the US.
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