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31  Using Arduino / General Electronics / Re: Uno's analog pins and short circuits on: April 14, 2014, 06:00:41 am
When pins are set as INPUT they have a very high resistance (megaohms).
32  Using Arduino / General Electronics / Re: Powering Ardunio UNO from 9 Volt battery and connecting it to USB on: April 14, 2014, 05:24:21 am
How did you connect the Arduino to the Raspberry Pi?

A battery will work, but I think it should work from the Pi if you have an external supply for the motor.




33  Using Arduino / General Electronics / Re: Powering Ardunio UNO from 9 Volt battery and connecting it to USB on: April 14, 2014, 04:37:51 am
How did you connect it? Did you connect all the GND lines of everything together?
34  Using Arduino / General Electronics / Re: potentiometer problem on: April 14, 2014, 04:35:49 am
hey guys i have some 10k potentiometer which i used for a dc circuit. I was wondering whether i could use the same pots for ac application of 220v 50 hz

This one is simple: No.
35  Using Arduino / General Electronics / Re: is there a difference between dc capacitor and ac capacitor? on: April 14, 2014, 04:34:40 am
DC capacitors can explode if you connect them to AC

https://www.youtube.com/watch?v=63c3NDwk2TU

Quote
ac-220v ,50 hz

a) Never, ever, EVER connect a capacitor to AC 220V unless it has a "Y" rating. They're usually blue and definitely don't have any polarity markings.

b) If you don't know if a capacitor has a Y rating then don't connect it to mains electricity.

There are NO exceptions to rules (a) and (b).

36  Using Arduino / Microcontrollers / Re: ATtiny84 with internal pull-ups on: April 13, 2014, 03:48:13 pm
And the current from each io pin to ground is 2.89mA, so I am not overloading the io pins

If the pin is OUTPUT_HIGH you normally see about 75mA when you short it to GND.

If the pin is INPUT_PULLUP you should see about 0.1mA.

37  Using Arduino / Microcontrollers / Re: ATtiny84 with internal pull-ups on: April 13, 2014, 03:44:31 pm
It makes no sense that adjacent pins should change.

38  Using Arduino / Microcontrollers / Re: ATtiny84 with internal pull-ups on: April 13, 2014, 03:12:31 pm
If an adjacent pin changes that suggests the pins are OUTPUT_HIGH and short-circuiting them.

I think you have bigger problems somewhere. Maybe you've damaged the chip.


39  Using Arduino / Microcontrollers / Re: ATtiny84 with internal pull-ups on: April 13, 2014, 02:37:38 pm
By connecting GND to each of the pins in turn and probing adjacent pins with multimeter, and going through and measuring the voltage at each pin.

?? How does that tell you if it's working/not?


I'd start with something like this:

Code:
if (!(PINA & (1<<PA4))) {
     turnOnMyLED();
}
else {
     turnOffMyLED();
}
40  Using Arduino / Microcontrollers / Re: ATtiny84 with internal pull-ups on: April 13, 2014, 02:26:22 pm
So how do you know if it's working or not?

41  Using Arduino / Microcontrollers / Re: ATtiny84 with internal pull-ups on: April 13, 2014, 02:13:03 pm
Maybe you need to post more complete code....
42  Using Arduino / Microcontrollers / Re: ATtiny84 with internal pull-ups on: April 13, 2014, 01:29:44 pm
Hi,
In my current project I have come across a rather weird situation. I am using an ATtiny84 programmed using the Arduino IDE and the core from: https://code.google.com/p/arduino-tiny/
I have 6 inputs connected to PB0, PB1, PA1, PA2, PA3 and PA4. I have activated internal pull-ups and set the pins as inputs using:
Code:
DDRA |= (0<<DDA4)|(0<<DDA3)|(0<<DDA2)|(0<<DDA1); // Define directions for port pins
DDRB |= (0<<DDB1)|(0<<DDB0);


Nope.

You just ORed a port with 0  - that code will have no effect. None!

Maybe you meant:

Code:
DDRA &= ~((1<<DDA4)|(1<<DDA3)|(1<<DDA2)|(1<<DDA1)); // Define directions for port pins
43  Community / Exhibition / Gallery / Re: The dsp-G0 Analog modeling synth on: April 13, 2014, 07:57:09 am
This is just a single voice on the dsp-G0.
This one uses 3 DCOs.

I'm twisting all the oscillator knobs and the filter but the waveform is Saw in the entire clip.

Cool.

With only one filter and one ADSR this is really just a monophonic synth. The other waveforms just provide harmonics.

Maybe you could try it with the filter cutoff in the middle of the range of notes being pressed.
44  Using Arduino / General Electronics / Re: Is capacitive sensing possible with batteries? on: April 13, 2014, 07:51:12 am
The "touch lamps" operate by sensing capacitance against the mains - 110 or 240V.  The "ground" side of the detector is actually the full mains voltage so that the capacitance of a person touching it provides a capacitive coupling to the actual ground.  I do not think he wishes to connect his bottle to the mains.   smiley-grin

This is what happened to me. I developed the code on an Arduino Uno, tested it on a Tiny85 with ISP programmer...it all worked perfectly.

Then as soon as I switched to battery power it stopped working. It took me a while to figure out why, ie. until then I'd always had a USB cable connected to the device and my PC was forming part of the system.

The difference in capacitance was easy to measure when it's on USB - it can actually detect a hand from a few inches away. Without the USB cable the difference drops to almost nothing. I had to go from 1MHz to 8Mhz clock to be able to measure it.
45  Using Arduino / General Electronics / Re: Level shifting advice on: April 13, 2014, 07:46:30 am
Of course the horrible Arduino libraries don't let you do that, they turn on the internal pullups which sends the bus to 5V.

Which is of course, precisely what you want them to for 5V logic.

It should really be optional, it breaks the I2C specification.

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