Show Posts
Pages: [1] 2 3 ... 58
1  Using Arduino / Project Guidance / Re: Should I outsource my counting to something external? Micros is too slow. on: June 19, 2013, 08:58:00 pm
Yeah, that's not going to work too well if you really care about repeatability and accuracy.  You can achieve better than 1uS resolution if you need with great accuracy and repeatability if you use the Input Capture Facility feature of Timer1.  I have posted a previous example that would capture the time between two rising edges for the full cycle time, but it could be easily modified to just capture the time between a rising then falling edge by changing the edge detected in the interrupt handler.  

The ICF is the only truly accurate way to measure pulse timings since it's all done in hardware.  This means that you won't get variations caused by interrupt handlers running or other things that might be going on.

If you're interested, I could post a modified version to time between each edge instead of the total pulse length.

EDIT:  I see you want to watch three different pins now, that makes things a little tougher.  An external MUX might solve the problem easy enough though.
2  Using Arduino / Microcontrollers / Re: learning the ARM CORTEX M3 on: June 18, 2013, 03:53:52 pm
Above in my post there is double vs double comparison. Interesting are the @1MHz results.
The best compiler is the microchip's C32, imho..

That PIC32 is really fast.
3  Using Arduino / General Electronics / Re: Peltier based aquarium cooler/heater? on: June 10, 2013, 02:59:48 pm
With the BTS7960 rated at 43A I guess up to 4 peltiers (10A each) can be connected. 

I was looking at power supply units for such a project and it seems a DIY AC->DC will be needed.  I had no problem finding bridge rectifiers rated for 50A, but where does one find 50A transformers (240v AC to 12v DC)? 

They're available but cost a pretty penny.  Here is a 120V to 12V@600W(50A):
http://www.amazon.com/Tiella-Lighting-800AT600T-Remote-Transformer/dp/B007JY3U66
4  Using Arduino / General Electronics / Re: Why did I burn my TIP120? on: June 08, 2013, 12:50:05 pm
I hope you aren't applying 12V to that power connector in your schematic and then feeding that to the +5V pin of the arduino board as that will likely destroy your board.  Connect the 12V to Vin instead. 

Since your pump is rated at 35-45W@12C that means it will be drawing about 3-4A of current.  Assuming a 1V drop thru the TIP120 (It's probably higher than that), that means the TIP120 needs to dissipate 4A * 1V = 4W minimum.  Without a heatsink it will roast the transistor.
5  Using Arduino / General Electronics / Re: Arduino starts blinking fast 3 times and not working on: June 07, 2013, 01:02:40 pm
I have compiled and installed optiboot successfully.  I do believe it will time out like I described.  What version of the IDE are you running?  You should find a folder named "bootloaders" in the installation tree.  Inside that you should find various folders containing different bootloaders.

In a nutshell, you just go into the optiboot folder and adjust the Makefile to build a bootloader containing the fuses you want, the number of blinks and the baud rate it communicates at.  You then point to the output from the "boards.txt" file and then you can burn the bootloader into a second board/chip by loading the first one with ArduinoISP.
6  Using Arduino / General Electronics / Re: Arduino starts blinking fast 3 times and not working on: June 07, 2013, 11:55:05 am
Three blinks definitely sounds like a bootloader.  It probably thinks it received a byte and then hangs forever waiting for more instructions.  Make sure you don't have the RX line floating or shorted to ground.  A possible solution is to change the bootloader to a more modern one that will "time out" and then continue booting the loaded sketch.
7  Using Arduino / Installation & Troubleshooting / Re: Uno r3 multiple com ports on: June 04, 2013, 07:35:41 am
This is what is supposed to happen, at least with the port enumeration anyway.  Even though the devices have identical VID and PID values, they still have a unique number inside that windos pays attention to. 

No idea why you are getting the error unless you've got the wrong baud rate to talk to the bootloader or something else is wrong with it.  Did you do any tinkering with ArduinoISP?
8  Using Arduino / Project Guidance / Re: ATMEGA Chip consuming more current than the datasheet states on: June 03, 2013, 03:21:53 pm
i tried running with power_all_disable() and the current is still higher than what it should be.

Is that what I should of used?

I don't think that's enough.  Read this thread about the very subject:
http://forum.arduino.cc/index.php?topic=53821.0

9  Using Arduino / Project Guidance / Re: ATMEGA Chip consuming more current than the datasheet states on: June 03, 2013, 02:33:55 pm
Look at the first page of chapter 29, those currents are with all peripherals disabled.

Quote
All Active- and Idle current consumption measurements are done with all bits in the PRR register
set and thus, the corresponding I/O modules are turned off. Also the Analog Comparator is disabled
during these measurements. The ”ATmega88PA: Supply Current of IO Modules” on page
356 and page 380 shows the additional current consumption compared to ICC Active and ICC Idle
for every I/O module controlled by the Power Reduction Register. See ”Power Reduction Register”
on page 42 for details.
10  Using Arduino / Project Guidance / Re: High resolution, high accuracy temperature sensor on: June 02, 2013, 10:12:59 am
Quote
I need 0.05 deg resolution and 0.5 accuracy.
This makes no sense. A sensor that reports a temperature like 78.95 degrees when it is really 78.5 is useless. The accuracy has to be close to the resolution in order for the data to be useful.

Not if you care about relative measurements.  Even though the overall accuracy is only .5 deg, the relative measurements between steps will be much more accurate and may be entirely useful depending upon the application.
11  Using Arduino / Microcontrollers / Re: Upload hex to a PIC16F628 on: June 01, 2013, 04:51:23 pm
You should be able to block that .6V with a silicon diode in series.
12  Using Arduino / Microcontrollers / Re: Arduino duemilanove Pin 13 releasing from default signaling on: June 01, 2013, 03:10:26 pm
It's most likely coming from the bootloader.  You can compile a new bootloader (optiboot) and specify how many blinks you want, or you could just overwrite the bootloader by using a regular programmer or ArduinoISP.
13  Using Arduino / General Electronics / Re: Low cost decent oscilloscope recommendations? on: May 30, 2013, 05:35:18 pm
You can buy a Rigol 100MHz DSO for $399.
14  Using Arduino / Programming Questions / Re: one arduino 2 programs on: May 28, 2013, 04:01:08 pm
Maybe have setup() call your setup1() and setup2() routines.  Then have loop() do the same by calling loop1() followed by loop2().  This has its obvious limitations, but is simple to implement.  You have to be "smart" about your loopx() routines and not tie up a bunch of time doing nothing, such as calling delay() or any other delay loops for that matter.  
15  Using Arduino / General Electronics / Re: Real time clock for keeping accurate timing between two arduinos on: May 28, 2013, 01:41:24 pm
This would work:
http://www.ebay.com/itm/10-MHz-sinewave-FE-5680A-Rubidium-Oscillator-Std-50ohm-/180518264100
Might want to massage the output into a larger amplitude square-wave by using a comparator.
Pages: [1] 2 3 ... 58