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241  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.

242  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.

243  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?
244  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.
245  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.
246  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?
247  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.
248  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.
249  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.
250  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".
251  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?
252  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.
253  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.
254  Using Arduino / General Electronics / Re: Spent 2 days trying to get TIP 120 fan control to work on: July 23, 2014, 06:41:58 pm
Do you really need 0rpm? The airflow is going to be indistinguishable from random air movements even at a few hundred RPM.
255  Using Arduino / General Electronics / Re: Linking audio amp problem. on: July 23, 2014, 06:40:25 pm
An audio amp is essentially an Op Amp but with the negative feedback internal, the input ground referenced, and the output designed to drive a low impedance.

There are some potential problems with using an audio amp as a small signal amplifier. One is noise. The amount of noise voltage on the output that is inaudible in an 8 ohm speaker may be intolerable when used as a small signal amplifier, especially when followed by another amplifier. The outputs may be a bit unstable when run with no or a high impedance load. The frequency compensation is suited to an audio amp, and may result in decreased gain above 20kHz.

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