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136  Using Arduino / Microcontrollers / Re: Arduino IDE with ATTINY2313, how? on: July 06, 2011, 12:54:42 am
The dot-hex files are bigger than 2 KB or the binary sketch size reported by the IDE is more than 2 KB?

I was talking about the .hex file the IDE saves in a temporary directory before uploading it to mcu.

The IDE reports a "Binary sketch size: 788 bytes".
137  Using Arduino / Microcontrollers / Arduino IDE with ATTINY2313, how? on: July 05, 2011, 02:42:00 pm
Well, I managed to use an Arduino UNO as an ISP programmer to get a Arduino bootloader into an ATmega328, so I guess I could use the very same setup for uploading code into an attiny2313.

Now, I installed the Arduino-tiny and the Alternate-Core core files in order to compile some code for the attiny but I always get .hex files bigger than 2KB (which is the maximum an attiny2313 could load).

What am I doing wrong? I tryed compiling the very basic Blink sketch. Is the IDE loading some unnended libraries that make the .hex file so big? What's going on in the background? I have no clue right now. Any hint/guide/suggestion would be very much appreciated.

Roberto
138  Using Arduino / General Electronics / Re: LM317T Driving me nuts on: July 05, 2011, 12:54:31 pm
so voltage is like the pressure in a tap, even with your finger onit the pressure is still there, even though no current flows

There's an even more intuitive analogy with water ... think of a waterfall, the voltage value being the height of the water (and the water itself being the positive charge carrier). Water flows from high to low (from a higher voltage level to a lower voltage level).

You set a reference voltage level (the GND) being the zero volt. Other nodes in the circuits may have a positive voltage value or a negative voltage level. It all depends if those points are "higher" or "lower" than GND. When two points in the circuit have different voltage levels, there you may have a current flow (from V+ to V-) (*). Just like water flows from a higher altitude to a lower level.

It's all about potentials. Here in Italy is difficult to misunderstand the point since we call it ddp="differenza di potenziale" (=potential difference). It couldn't be less clear :-)

As you may see, there's no voltage flowing across anything at all. That's the point.

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(*) actually electrons flow from V- to V+ ... but that's another story.
139  Using Arduino / General Electronics / Re: LM317T Driving me nuts on: July 05, 2011, 08:25:43 am
The resistors you have in parallel, the .6 Ohm ones, are not meant to use as the Adjust R1 and R2 to set your voltage on your Voltage Regulator.
...
Oh, and an LM317 cannot source 2 Amps, you need a different voltage regulator.

You missed something in the thread. SgtOneill finally considered using an LM338 which is capable of 5Amp and he's not using it as a voltage regulator but as a current limiter instead.
140  Using Arduino / General Electronics / Re: LM317T Driving me nuts on: July 05, 2011, 03:14:44 am
R= (1,2*1,2)/(1,2+1,2)    R=1.02ohm

Wrong calculation. R = (1.2 * 1.2) / (1.2 + 1.2) = 1.44 / 2.4 = 0.6ohm !!!

And you get I = 1.24/0.6 = 2.07 amp which I think it's even better.
141  Using Arduino / General Electronics / Re: LM317T Driving me nuts on: July 05, 2011, 01:49:02 am
Don't get too concerned about the exact value of the series resistor.  It's value was determined from the nominal value of the reference voltage which may or may not be 1.24 volts and a desired LED current that we pulled out of a hat.

Don

By that I think Don means you can use different R1 values if it comes handy, so long you stay in the reference values for LM338 and the LED.

E.g. using R1=0.5Ohm you get I = 1.24/R1 = 1.24/0.5 = 2.48Ampere which is totally acceptable to your LED (that uses to work nicely even at 2.8Ampere) and to the LM338 that can sustain 5Amps continuosly. Since I don't know if a 5W 0.5Ohm resistor even exists, I'd suggest you use two 5W 1Ohm resistors in parallel in order to get an equivalent R1 of 0.5Ohm.

Anyway, a quick note on you calculations. Pay attention to the LED's datasheet. It states each LED drops 3.6 volts with a forward current of 2800mA (not with 1400mA!). In case you limit the current to 1400mA, each LED will drop 3.3V only.
142  Using Arduino / General Electronics / Re: LM317T Driving me nuts on: July 04, 2011, 04:56:42 pm
Remember you can put resistors in series or parallel to get closer to the value you want.

And if you use two big resistors in parallel you will cut down the current flowing through each one; hence you may get away with much lower wattage on each resistor.
143  Using Arduino / General Electronics / Re: LM317T Driving me nuts on: July 04, 2011, 05:14:19 am
just a quick question, i dont recognize that component on R1, the arrow pointing at a resistor? How's that suppose to be implemented?

Well, that's a variable resistor, the arrow pointing on R1 represents the third connection of a variable resistor (they have three pins; ref. http://www.pictutorials.com/resistors.htm), the one that moves along the resistant material and makes it change its value.

This circuit is an example of a "variable" current regulator; R1 is the variable resistor (could be a slider, a trimmer or whatever); by changing its value you change the result of the formula Iout=Vref/R1 and you get various currents.

In your case, you need a specific current value, so you don't need a variable resistor; you have to calculate R1 in order to get the needed Iout and use that R1 in your circuit.
144  Using Arduino / General Electronics / Re: LM317T Driving me nuts on: July 04, 2011, 12:13:48 am
I was checking the lm338 and there were some examples.

Precision Current Limiter seems to be a good choice for the LM338 implementation.
Probably will limit the current to 1.4Amps and work from there.

This is the one you need! SImple and effective to your case.
If you limit the current to 1.4Amp you're good to go with your led (ref. datasheet). You can even connect both leds in series (always at 1.4Amp) if you provide enough voltage to the LM338. And then increase the current even more since the LM338 is capable of providing a maximum 5Amps total (with proper heatsink).
145  Using Arduino / General Electronics / Re: Which capacitor with LM317 driving a series of leds? on: July 02, 2011, 11:05:18 am
No matter how many external components you connect to the LM317 and no matter what their configuration is, the LM317 is still a voltage regulator.

:-) Of course it is.
Current regulation is still a side effect of a peculiar configuration where the voltage regulation forces a fixed current on the output.
146  Using Arduino / General Electronics / Re: Which capacitor with LM317 driving a series of leds? on: July 02, 2011, 08:53:47 am
At least read through Grumpy_Mikes epic tutorial: http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

Nice tutorial ... good job Grumpy_Mikes, thanks KE7GKP for the hint :-)
147  Using Arduino / General Electronics / Re: Which capacitor with LM317 driving a series of leds? on: July 02, 2011, 08:37:11 am
Quote
Normally, no capacitors are needed unless the device is situated more than 6 inches from the input filter capacitors in which case an input bypass is needed. An optional output capacitor can be added to improve transient response
I think, this is true only for Voltage regulator. In case Current regulator you don't need any external capacitors, especially if you drive leds with PWM or turn  on-off them rapidly.
What is your set-up?

Plain and simple LM317L (TO-92 package) in current control configuration (with a 60R resistor) feeding a series of six bright white 5mm leds (at 20mA). There's no IC to worry about at all.

As you see, not much to worry about ... but I know if tension goes weird, that can cause damage to those leds (the LM317 does a good job in protecting itself most of the times) and I want to make it failproof (as long it's not overcomplicated). Fact is I don't know if I really have to worry about those capacitors; my first guess: a simple input bypass capacitor (0.1uF disc as per datasheet) can be enough to cover noise coming from the power supply and making the lm317 work without issues (but again, is that even relevant in such a simple circuit?).
148  Using Arduino / General Electronics / Re: Which capacitor with LM317 driving a series of leds? on: July 02, 2011, 07:10:23 am
Ok, this is pretty much what I've already read on the datasheet, fact is I don't want to overengineer it and still I don't want to be too lazy ad miss an important detail.

From the datasheet (and so does CrossRoads suggest too) I read I can put an input capacitor to be used as a bypass and an output capacitor to improve transient response.

Since I still have only a vague idea of what a "bypass capacitor" does and what a "transient response" is, I will start by following CrossRoads' suggestion but will dig deeper into this bypass_capacitor/transient_response stuff ... I really don't like doing things only because I'm told too.

Anyway, my circuit is pretty simple, no need to worry about that too much. It's just my need to understand how it all works. Making up this simple circuits is already a way to deal with more controllable scenarios and give me the opportunity to face basic concepts one at a time.

Btw, I'm using this: http://cgi.ebay.it/24V-DC-2-1A-50W-Regulated-Switching-Power-Supply-/250672045980?pt=LH_DefaultDomain_0&hash=item3a5d37df9c to power the circuit. I wonder if knowing that can help choosing the right capacitor.

149  Using Arduino / General Electronics / Re: LM317T Driving me nuts on: July 01, 2011, 02:37:37 pm
It should be like this:  Voltage Reg. vOut ---> RESISTOR ---> LED1 ----> LED2 ----> GND

Just consider Led1 + Led2 as a single Led that needs tyq
150  Using Arduino / General Electronics / Which capacitor with LM317 driving a series of leds? on: July 01, 2011, 09:22:50 am
I'm driving 6 white led in series with a LM317 used as a current regulator out of a 24V DC power supply. I wonder if I should/could use a capacitor (on the input/output side of the LM317).

I'm open to suggestions since I'm relatively new to this stuff :-)
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