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1  Using Arduino / LEDs and Multiplexing / Re: Using pots to control rgb values of an rgb strip? on: Today at 01:25:55 pm
You can use 'm with an arduino + transistors, but using an RGB-strip and 3 10k pots only..., probably won't work. Pots often can't handle much current and dimming won't be smooth.
2  Using Arduino / LEDs and Multiplexing / Re: Reading LEDR-L-7113ID-12V datasheet on: September 15, 2014, 05:25:37 am
Your LED apparently isn't a standard LED, a standard LED doesn't have an internal resistor. (page 1). Maximum forward voltage of a normal single LED is also about 4 volts and far less (~ 2.4 v) for a red one.

On page 2 of the sheet it says 8.5 - 11.5 mA forward current and 14v max forward voltage.
My best guess is that you don't need an external resistor to limit current, unless you want to feed it more as 14 volts.

As long as the voltage applied is higher as the forward voltage (~2.4 volt for a red led), the LED will probably give light. But since yours is already limited to 12-14 volt, current will indeed be much lower when applying 5 volts only. Adding another resistor at 5v will only result in even lower current/less light.

Most leds will indeed need current to be limited to 20-25 mA max as explained in the book. Your calculations are not exactly right though.

You need to subtract the forward voltage of the led from the supply-voltage first, before dividing.

A red led at 5 volt and 20mA  will result in the next calculation,  (5v-2.4v)/0.02A = 130 Ohms

A blue led (~3.4v forward voltage) connected to a 5v supply will need an (5v-3.4v)/0,02A = 80 ohm resistor to limit current to 20mA.

It's not always possible to find the right resistor when calculating btw, if you can't find a 130 Ohm resistor, it's better to use a 150 Ohm one instead of a 100 Ohm resistor. You're always safe when current is lower as the maximum your led can handle.
3  Using Arduino / Project Guidance / Re: USB power to Nano, only DC power connections No data Wires on: September 12, 2014, 04:44:34 am
You can indeed use the nano and disregard the usb-datalines. Keep in mind though that the USB-chip, which provides 3.3volts, is still connected to pins 0 and 1 if you do. It's best to avoid using those pins in your project.
4  Using Arduino / Project Guidance / Re: Need ideas for a College Project with Arduino Boards on: September 11, 2014, 03:05:21 pm
5  Using Arduino / Project Guidance / Re: Using an optical mouse to retrieve coordinates on: September 06, 2014, 09:24:29 am
Not without an rather expensive USB-hostshield and probably a lot of programming.
I guess you'll have more luck finding an SPI-sensor in an PS2-mouse.

Question, do you actually need to read the optical sensor itself ?

If you use a PS-2 mouse, 2 arduino pins and the  PS2-mouse library, you can read position and get 3 inputs+scrollwheel for free.
6  Using Arduino / LEDs and Multiplexing / Re: 3x seven segment w/ shift register code on: September 05, 2014, 06:36:06 am
The compiling error is a result of the next 2 lines
First example :
#define data 2
#define clock 3

Second :
#define data 2;
#define clock 3;

Next problem, you want to use an array in your second example, but you don't name it.
I haven't tested it, here's an example of how it could work.

#define data 2
#define clock 3

byte number[10] = {B00000001, B11000111, B00100010, B10000010, B11000100, B10001000, B00001000, B11000011, B00000000, B10000000 };

void setup() {
  pinMode(clock, OUTPUT); // make the clock pin an output
  pinMode(data , OUTPUT); // make the data pin an output3

void loop(){
  for(int mE = 0; mE<10; mE++) {
     shiftOut(data, clock, LSBFIRST, number[mE]);
7  Using Arduino / Project Guidance / Re: need help for project work. on: September 04, 2014, 04:51:47 am
Looking at the original board I notice a 12 MHz crystal.
You may have to replace that since most arduinos run at 16 MHZ.

It's not clear to me what you would like to do with an pro mini btw.
It has a different size and pins probably aren't located on the same place as the original controller. You could, in theory, remove socket and wire all pins between pro mini and controller board, but replacing the DIP-chip with an DIP 328-chip will probably be a lot easier though.

Unfortunately a picture isn't the best info to check what's possible, a schematic would tell much more. Do you have a link to more info ?
8  Using Arduino / Project Guidance / Re: Chair prank on: August 31, 2014, 07:06:17 am
Seems possible to me.

You'll need 2 arduino's and 2 bluetooth boards. You could also use cheaper nrf24l01  or other wireless modules as well though.

Instead of using a pressure sensor it may be possible to detect someone using  Capacitive sensing, requiring just a piece of metal and 2 resistors.

With an transistor+ relay you could operate the button.

I'd do my best to hide 'evil' intentions by the way. When the doorbell starts ringing at the moment people sit down, they'll soon know there's a relation between both.

If the bell starts ringing after a random period of sitting and occasionally 10-20 secs just after they left the chair though it will be much harder to detect what's happening.
9  Using Arduino / Project Guidance / Re: related to pwm on: August 30, 2014, 04:14:03 am
Unfortunately you can't choose every frequency, but you can set pwm pins to higher frequencies.
10  Using Arduino / LEDs and Multiplexing / Re: 8x32 Sure Electronics Dot Matrix Display causes the Arduino to lose power?! on: August 21, 2014, 04:26:07 am
It's hard to see how you connected boards, but it still might be a power issue.
The voltage regulator on an arduino can't handle much current. If your led-module asks too much, there will be a voltage drop, which shuts down your arduino.

You could solve that connecting grounds of both arduino and led module and using a separate 5 volt supply (1 amp or preferably more) for your Led-matrix.

There's no voltage regulator on my 16x32 sure display, so be sure not to feed it more as 5v.
11  Using Arduino / Project Guidance / Re: How to feed data to an arduino leonardo on: August 14, 2014, 02:25:33 pm
Yes, that's possible.
When you connect your arduino, it will show as a com: port on your PC.
Since your PC may have different serial ports, your PC programm needs to address the right one.
Speed settings in both PC-program and your sketch should also match.

When it comes to handling datapackets, you may want to check how it's done best.
Crunching huge amounts of data is for example best done by the PC itself. It probably operates a few hundred times faster as an arduino and may have a million times more ram available.

In your sketch you can simply use Serialbegin() serialRead() and other Serial-commands to communicate with the program on PC.
On your PC it doesn't really matter what language/IDE you use, as long as it can handle the serial port.
12  Using Arduino / LEDs and Multiplexing / Re: Klingon Proton Collector on: August 12, 2014, 06:09:10 am
It's hard to tell how much space you've got, about two 9v batteries would be nice.
Looking at the pictures it seems... enough for at least a few coincells, 6 leds, 6 resistors and a Mini, Pro Mini, Micro or Nano.

The first two boards are the smallest, but need an external USB-breakout board to program them.
Unfortunately the product pages of these boards don't specify size, each pin on a connector is placed 0.1 inch from the next though.

Next part, how would you like to control/configure your leech ?
You could for example use a power switch to start the (standard programmed) routine, which requires access to a pc when you want to change settings. Looking at the original leech, you may also be able to include some switches/potentiometers to adjust settings without the need of a PC.

Most of the functions needed are described in the first two sections of the built-in tutorial of Arduinos IDE by the way, it shouldn't be too difficult to get a working proto(n)-type ;-)
13  Using Arduino / Project Guidance / Re: Nano stops running and flashes the power LED rapidly... on: August 11, 2014, 04:22:04 am
The powerled flashing is strange. If the nano is built like the original design, the led (+resistor) should be connected to +5v and GND only. Even if you would use too much RAM  it shouldn't effect the powerled.

Blinking rapidly could indicate a problem with your power-supply. It would also explain the blanked display, since not only the led, but the controller of your Nano is turned off/on every time the led blinks.

Could you post your complete code (using the #-button) and a schematic of your project ?
14  Using Arduino / LEDs and Multiplexing / Re: Novice Question re shift registers on: August 08, 2014, 04:27:23 am
A far as I understand the most significant bit, bit 7, is set to zero in your example. It wouldn't blink a light if a led was attached to outputpin 7 when using MSBFIRST-mode.
Personally I would simply connect 8 leds to experiment / see what happens though.

A dice could be treated as a 4 segment object btw. With the 8 outputpins of a shiftregister it is possible to throw 2 dices if you use 6 pins to each light 2 leds and 2 pins to each drive 1 led..


(*= no led used)

15  Using Arduino / Project Guidance / Re: What´s the best Arduino for my project? on: August 07, 2014, 04:26:47 am
Must say I haven't tested this technique yet, maybe Capacative sensing could be a solution to check whether the bench is occupied or not.

Using just 1 resistor and a piece of metal plate/foil/wire mesh you can detect the presence of a person with it  from a small distance. You can connect several of these sensors to one arduino to check each seat.

You'll probably do need to experiment with the value of the resistors and size of the metal plate.

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