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1  Using Arduino / General Electronics / Re: Powering Arduino Uno using AA batteries on: July 30, 2014, 04:53:01 pm
The Atmel chip will take a wide range of voltages, but you have to consider what else is connected and how tight those voltage tolerances are, too.

I built a little robot, I just powered it from four NiMH cells, as Paul suggests. About 4.5 to 5V, no problem running the Arduino and servos.
2  Using Arduino / Sensors / Re: Building a laser "electric eye" sensor on: July 30, 2014, 02:17:51 pm
This is why most systems like this don't use a Laser, but instead just use a focused LED.

You can also put the LED and phototransistor in two tubes parallel to each other, and put a retroreflector on the other side. A bicycle taillight or a piece of license plate or reflective strip off of a safety jacket works as a retroreflector.
3  Using Arduino / Installation & Troubleshooting / Re: Nano V3.0 connection with Win 8.1 needs older FTDI drivers on: July 30, 2014, 02:09:43 pm
I had the exact same problem, from the same source, with the same solution.

4  Using Arduino / General Electronics / Re: Powering Arduino Uno using AA batteries on: July 30, 2014, 02:04:08 pm
You'll need a very low dropout regulator, but you'll still lose a lot of battery capacity. Or you can run an Arduino on less than 5V, although you may need to run it at a slower clock speed.

A buck-boost switching regulator could take the 4 to 6V coming from the batteries and regulate it to 5V, or either a buck switching regulator or a low dropout linear regulator could regulate the 4 to 6V down to 3.3V.

Yes, PoE can supply power and send data at the same time.

5  Using Arduino / General Electronics / Re: homemade pulse sensor for detecting hartbeat? on: July 30, 2014, 11:07:34 am
You may also try placing them closer together, by putting them head to head. But with an opaque something between them. I suspect they are simply too far apart for the phototransistor to pick up much of the IR from the LED.

The clear case on the phototransistor may be a problem, as it will then also respond to visible light.

The signal you are seeing may be AC hum. What frequency is it?
6  Using Arduino / General Electronics / Re: homemade pulse sensor for detecting hartbeat? on: July 29, 2014, 02:04:29 pm
I need a picture. Those are side looking IR phototransistors and LEDs, but you need them to both point up, not at each other. As AnalysIR says, there should be something blocking between them to prevent IR from passing over directly.

Yes, the IR is supposed to diffuse into your fingertip. Then some bounces back to the phototransistor. The amount of blood in your flesh affects how much bounces back, so your heartbeat can be seen in the current flowing through the phototransistor.
7  Using Arduino / General Electronics / Re: Foward and reverse op amp motor control.... on: July 27, 2014, 07:38:13 pm
Rotate, crop, and resize. I can see the quantum vacuum foam in your image.
8  General Category / General Discussion / Re: Generating Square Wave with with modulated carrier frequency on: July 27, 2014, 07:36:50 pm
And....

But - what kind of resolution do you need and how accurate must that 18kHz be?
9  General Category / General Discussion / Re: Arduino Commercial Application on: July 27, 2014, 12:24:45 pm
Well, the Atmel AVR chips are available from Atmel, you don't have to buy it on an Arduino board. I certainly would not want to release a commercial product with a bunch of shields plugged in to it.

Or there are more cheaply available products like the Arduino Mini, Nano, and the Teensy boards. The  Teensy 3.1 especially allows you to use a QFN high pin count 48/96MHz Arm Cortex M4 chip without having to solder that monster chip. Or maybe that is not a problem if you have the setup and experience to solder them yourself, or are having them manufactured.
10  General Category / General Discussion / Re: Generating Square Wave with with modulated carrier frequency on: July 27, 2014, 12:19:37 pm
You could gate an external oscillator using two PWM outputs. Both at 50% when A0 is at 0%. Then as A0 increases, one reduces PWM, the other increases PWM. An external XOR logic is used to gate an external 5MHz clock.

But - what kind of resolution do you need and how accurate must that 18kHz be? You can set a higher PWM frequency from the Arduino, but it isn't infinitely variable, and the resolution (bit depth) is reduced at higher frequencies.

I come from a hardware background. So I picture doing this with a crystal oscillator divided down to 5MHz and 18kHz, using a ramp to generate the PWM signals, XOR to gate the 5MHz signal, and use the Arduino to control the ramp/PWM generator.

I'm sure someone here can help with doing nearly all (or all) in software. Perhaps with something faster like a Due or Teensy 3.1.
11  General Category / General Discussion / Re: Generating Square Wave with with modulated carrier frequency on: July 27, 2014, 10:49:15 am
This should have been the first thing you gave us.
12  Using Arduino / General Electronics / Re: IR Led and Phototransistor connection give always 0 value on: July 26, 2014, 06:15:50 pm
Don't use delay() at all. Read up on "Blink Without Delay".
13  Using Arduino / General Electronics / Re: Switching High Current Loads on: July 24, 2014, 02:07:05 pm
No. Most MOSFETs are rated for a maximum gate to source voltage of 20V.

In addition, you said it was a 60V MOSFET, yet you are supplying 112Vdc.

The 10k resistor is going to mean a very long turn on time, resulting in a lot of heating in the MOSFET.

Is this just a typo and you meant 12Vdc?
14  Using Arduino / Motors, Mechanics, and Power / Re: arduino micro + peltier module + h bridge + LM35 on: July 24, 2014, 09:35:56 am
Peltier junction devices are very sensitive to voltage and won't operate very efficiently outside a relatively narrow range. Have you confirmed that yours will operate on 9V?

What kind of power source is this? Peltier junction devices draw on the order of 5 to 15A.
15  Using Arduino / General Electronics / Re: What's this peice called? on: July 23, 2014, 09:05:20 pm
That is a capacitor. It looks like, by placement, it may be a bypass capacitor on the 3.3V regulator. Your best bet is to ask Adafruit.

See page 44 of the PDF, it has a schematic of the board. Perhaps you can trace some of the PCB traces back and figure out which capacitor this is.

https://learn.adafruit.com/downloads/pdf/adafruit-cc3000-wifi.pdf

Wow, that is freakishly faded.

Bottom left corner of this PCB pattern, it does appear to be one of the bypass capacitors. One end to ground, the other end to the tab on the regulator.
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