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1  Using Arduino / General Electronics / Re: 4066 or 4016 to control canon camera shutter release. on: February 20, 2014, 06:12:59 am
You don't need 60mA through the LED.  A 1k series resistor will work fine.

(4mA through the LED gives you up to 2mA through the phototransistor, and you need less than 100uA to trigger the camera.)
2  Using Arduino / General Electronics / Re: 4066 or 4016 to control canon camera shutter release. on: February 04, 2014, 08:23:03 am
I've used transistors with success: npns in the "open-collector" or nFETs in the "open-drain" configuration. But I prefer opto-isolators just because it's harder to damage the camera. I used a MOC8103x, but it's likey most common types will work. Tested with an EOS 40D.
3  Using Arduino / General Electronics / Re: USB oscilloscope on: January 28, 2014, 11:03:56 am
Sure, you won't be able to see the shape of waveforms at the nyquist limit: everything turns into a square wave.  But you could make the same criticism of analogue scopes: at the bandwidth limit everything turns into a sine wave.

What really got me interested was the responsiveness: they claim 10ms delay and 100-200fps.  If I get that on my Android phone I'll be very happy.
4  Using Arduino / General Electronics / USB oscilloscope on: January 28, 2014, 06:33:22 am
This Kickstarter project might be of interest to people here.  It's a 100MS/s 45MHz USB 2-channel oscilloscope.  That's plenty fast enough to inspect even the fastest 8-bit Arduino signals.  It's also a signal generator, and an 8-channel logic analyser.

They promise software running on Android and iOS as well as desktop platforms.  So you could carry a 45MHz oscilloscope in your pocket -- how cool is that?!


https://www.kickstarter.com/projects/751733865/smartscope-reinventing-the-oscilloscope

By the way I have no connection with the team behind this project; I'm just looking forward to upgrading my 250kHZ USB Instruments DS1M12.
5  Using Arduino / Microcontrollers / Re: Arduino mini, pro mini power consumption on: November 22, 2013, 11:34:42 am
The power LED on the Arduino Mini is driven via a 1k resistor, whereas the ProMini has a 10k resistor.  That probably accounts for the difference.  To get really low power consumption you'll need to disconnect the LED and regulator.
6  Using Arduino / Microcontrollers / Re: Using Arduino Uno TX and RX pins on: June 16, 2013, 05:19:38 pm
Quote
mr_johansen, is this the USB-to-Serial adapter you're using?
Well as he said it had a 9 pin serial connector then I don't think so.
That was ThomasJJ, who seems to have a different adapter.
7  Using Arduino / Microcontrollers / Re: Using Arduino Uno TX and RX pins on: June 16, 2013, 04:36:26 pm
mr_johansen, is this the USB-to-Serial adapter you're using?

If so I'm not sure it will work with an Uno.  The Rx pin on the Uno's processor has a 1k pull-up (via the on-board USB adapter), which any external adapter has to overcome.  And I don't think the Arduino USB2Serial "Light" will be able to, because it's Tx pin is connected via a 500 Ohm resistance meaning it won't be able to pull the Uno's Rx pin below the threshold for logic-zero.

8  Using Arduino / Microcontrollers / Re: ATMega 328 Breakout Board on: June 10, 2013, 05:51:08 am
I want to do some low power (long battery life) stuff so I need to have a minimal circuit (no LEDs, USB, etc) and I was looking for a board to build this on.

I have been using Sparkfun's Pro-Mini for exactly this purpose.  They're easy to get hold of, and quite cheap at $10.  To get below ~1mA you just need to cut one trace to disconnect the regulator and power LED.  With this small modification (and appropriate programming) you can get the current consumption below 3uA.  The modification can be undone be connecting the two VCC contacts together.


Sparkfun have revised the PCB layout since I made this picture, but the cut is still in approximately the same spot.  The Pro Micro can also be modified, although it's slightly harder to do.
9  Using Arduino / Microcontrollers / Re: Moving to something smaller on: May 13, 2013, 07:44:32 pm
Sparkfun make a "Mega Pro Mini" board. It's based on the same chip as the Mega2560, so you wouldn't need to alter your code. Potential disadvantages are that it runs at 8MHz and 3.3V instead of the usual 16MHz and 5V. It also uses unusual connectors, and needs an FTDI adapter to program.

A number of people have made Arduinos based on the ATmega1284 chip which might be ideal for your application, but I don't know how you'd obtain one of these boards. The 1284 chip is available in a DIL package, so you could make your own on stripboard.
10  Using Arduino / Microcontrollers / Re: Unable to run this code on arduino uno. on: May 12, 2013, 01:48:05 pm
Quote
Code:
#define MAX_CAPTURE 584  // Line number 1
uint32_t now, start, capture[MAX_CAPTURE];

584 * 4 = 2.3 k-bytes RAM.
11  Using Arduino / Microcontrollers / Re: Atmega328p Power Saving Techniques on: April 25, 2013, 12:01:39 pm
The "power_all_disable()" does that.

Are you sure?  The datasheet makes a point of saying that the ADC must be disabled (ADCSRA) before being shutdown (PRR).  You commented that disabling the ADC doesn't seem to do anything, but it should make a noticeable difference.
12  Using Arduino / Microcontrollers / Re: Atmega328p Power Saving Techniques on: April 25, 2013, 11:04:45 am
Are you sure the watchdog is being set correctly?  Normally you need to set WDCE before changing WDE or the prescaler bits.

BTW, after the watchdog interrupt WDIF is cleared automatically (so you don't need to do it in the ISR).  Meanwhile the WDT is still running, and may reset the processor before the 4s delay finishes (not that it matters much in this case).

I also noticed that you're not switching the ADC off after disabling it (power reduction register, PRR).
13  Using Arduino / Microcontrollers / Re: UNO upgrade to crystal oscillator on: April 25, 2013, 01:53:33 am
A little while ago I compared the clock accuracy of an Uno with a Freetronics Eleven (Uno clone with a crystal).  The crystal was 47x more accurate and 35x more stable.  That's still not really good enough for long term timekeeping, but for applications such as interval timing and event-rate measurement it's a lot better than a ceramic resonator.

http://arduino.cc/forum/index.php/topic,69316.15.html
14  Using Arduino / Microcontrollers / Re: ATmega328P targeted at low-power battery use: help needed with baby steps! on: April 17, 2013, 11:36:43 am
If you have the Arduino IDE running then you already have everything you need (I'm less sure about Macs, but I think this is true).  Just get the half-dozen-or-so files that make up the bootloader source code and put them in a directory in .../hardware/arduino/bootloaders/.
15  Using Arduino / Microcontrollers / Re: ATmega328P targeted at low-power battery use: help needed with baby steps! on: April 17, 2013, 08:51:05 am
Thanks for letting us know it worked.  Quite right about the fuses, I forgot they'd need alteration.  BTW Optiboot is maintained by WestfW at http://code.google.com/p/optiboot/, and he's made the code very easy to compile using the tools already included in the Arduino IDE.
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