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1231  Using Arduino / Motors, Mechanics, and Power / Re: Controlling and dimming outlets for aquarium lights on: April 10, 2013, 10:05:09 pm
On your relay board, the second largest-sized chip on that board marked "M7" on it is the diode. The stripe next to the "M" indicates the cathode, FWIW.

With respect to your LED blinking problem I would bet that it is the driver itself (assuming it's an AC driver?) acting inappropriately. Can you provide more details on that driver?
1232  Using Arduino / Project Guidance / Re: Looking for a more inexpensive microcontroller for my project. on: April 10, 2013, 09:53:06 pm
Chagrin, yeah, I'm getting interested in trying out bare chips.  Since these projects are probably going to be battery operated, I probably won't need any voltage regulator so long as I don't go above the specified voltage, right?  But I will have to somehow indicate or shut off the system when the voltage has dropped below the spec.  Is there a circuit to redirect the power to stop powering the chip and just flash an LED or chirp a speaker?

If your battery is of appropriate voltage then no, you don't need a regulator.

The AVR chip itself can monitor its own battery voltage. You have to set the analogReference to INTERNAL (which is 1.1V) or use an external voltage reference such as a TL341 and then measure the battery voltage against that. Once your chip recognizes that the battery is low you can set it into a sleep mode, waking it periodically to blink your LED, etc. and that will be much simpler and more efficient than any external monitoring circuit.
1233  Using Arduino / LEDs and Multiplexing / Re: High Power (Brightness) RGB LED shield on: April 10, 2013, 05:58:42 pm
Are you using this driver in buck, boost, or buck/boost configuration?
1234  Using Arduino / Project Guidance / Re: Looking for a more inexpensive microcontroller for my project. on: April 10, 2013, 05:42:48 pm
I require 2 analog ins, 5-7 digital outs (4 for an H-bridge, the rest for LEDs).  I ran across the ATtinys but I'm not sure they have enough memory (haven't looked into it far enough and am having trouble figuring out the download procedure).

It's worth it to learn how to use a bare chip like the ATTinys. As far as enough memory goes you just have to look at the size of your compiled script to know what you need. But if you think you still need the full 32K you can just buy a bare ATMega328P-PU for under $3; programming it is the same as with the Micro.
1235  Using Arduino / Sensors / Re: hacked air pressure sesor on: April 09, 2013, 10:09:22 am
There are a number of test points on the circuit board. It would be worth your time to stick a meter on them and see if any output an amplified voltage that corresponds with the pressure applied.
1236  Using Arduino / Project Guidance / Re: Controlling the voltage into heating element on: April 07, 2013, 01:09:34 am
You'd need three items; the PID controller; the relay, and a temperature sensor. The temperature sensor would preferably be a K type thermocouple (-200C to 1250C) and you should be able to find nice ones with stainless steel probes for a few dollars.

But yes, unless you need to programmatically change the temperature setpoint on the fly then a controller like this one would be the most straightforward solution.
1237  Using Arduino / Motors, Mechanics, and Power / Re: Relay shield on: April 07, 2013, 12:59:40 am
The board you exploded should have worked fine for a 40W bulb driven with 120V AC. Either you made a connection mistake or you just got a faulty board.
1238  Using Arduino / Project Guidance / Re: Controlling the voltage into heating element on: April 06, 2013, 02:56:06 pm
For both the OP and the project in the reply above the PID library should be used. You really can't beat it; you'll write far less code using it compared to trying to write your own implementation.
1239  Using Arduino / Project Guidance / Re: Help!! I need more decimal places in float. on: April 06, 2013, 01:20:55 am
M_PI is defined in math.h. Good as anything, I suppose.

Code:
root@here:~# grep M_PI /usr/include/math.h
# define M_PI 3.14159265358979323846 /* pi */
# define M_PI_2 1.57079632679489661923 /* pi/2 */
# define M_PI_4 0.78539816339744830962 /* pi/4 */
# define M_PIl 3.1415926535897932384626433832795029L  /* pi */
# define M_PI_2l 1.5707963267948966192313216916397514L  /* pi/2 */
# define M_PI_4l 0.7853981633974483096156608458198757L  /* pi/4 */

1240  Community / Bar Sport / Re: Where did you lose your packages? Who's lost packages as buyer/seller? on: April 05, 2013, 03:46:54 pm
...kudzu in the SE of the USA, the cane toad in Australia...

But those were deliberately introduced. Also the multiflora rose (Rosa multiflora) or asian beetle (Harmonia axyridis). So sometimes it takes a whole government full of lugnuts.

1241  Using Arduino / Microcontrollers / Re: ATmega8 with external crystal on: April 05, 2013, 02:21:08 pm
Have you seen http://www.engbedded.com/fusecalc/?
1242  Using Arduino / Motors, Mechanics, and Power / Re: Max amp load on LiPo battery on: April 05, 2013, 10:42:50 am
You have done something wrong there,  because LiPo batteries have a huge current capacity.
Or might be a bad battery / bad battery protection circuit.
1243  Using Arduino / Project Guidance / Re: LASERs on: April 01, 2013, 12:00:06 pm
I'd suggest paying the extra dollar or two (or less?) and finding a module with a focusing lens. It doesn't appear that this one has one. Without the lens it's a bit of a luck that gives you a nice dot or a wide blob.

http://dx.com/p/2-5mw-focusable-dot-laser-module-4-pack-3v-46390
1244  Using Arduino / Project Guidance / Re: WindReader/balloon following device on: April 01, 2013, 11:54:59 am
OpenCV will work on the Pi; I saw one example where someone did face tracking at 5 frames/second which should be OK. It's pretty involved stuff but if you're just trying to identify a single-color balloon it shouldn't be that hard. There's also reacTIVision which is kinda plug and play.
1245  Community / Bar Sport / Re: What is the most challanging device that you have successfully soldered? on: March 31, 2013, 12:38:58 am
Mine was an LGA-14 (analog accelerometer). Bought them for fun because they were very cheap. Second try I managed to get it soldered on a home-etched board but it started smoking after about 10 minutes because of (I assume) some leftover flux under it.
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