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10561  Using Arduino / Programming Questions / Re: Continuous Rotation Servo + PIR Sensor Help! on: May 16, 2011, 03:28:35 pm
Quote
On the library i can only find rotation codes for non continuous servos (e.g codes that rotate the servo a fixed amount of degrees either to the left or right) and so forth, could someone direct me to a library concerning continuous rotation servos?

Same library is used, same signal to the servo. However while a normal servo rotates and stops given a signal from 0 (degrees) to 180 ( degrees). The same commands going to a modified servo would result in  0 = full speed in one direction, 180 = full speed on the opposite direction, and 90 = stop. Values sent between 0-89 or 91-180 would result in continous rotatation at a specific speed. Note that the 90 degrees = stop may have to be tweeked to find the specific stop condition for your specific servo due to calibration variation between servos.

Lefty
10562  General Category / General Discussion / Re: What Board to Buy? on: May 16, 2011, 02:01:42 pm
Actually the arduno boards a pretty affordable so don't think that your first arduino purchase will be your last and therefore buy the biggest first. The standard ardunio 2009 or Uno is probably the best starting point.

 You didn't state if you are new to hardware electronics, but if you are your first purchase should be a decent digital multimeter as you will be responsible for proper wiring of components and checking for proper voltages, etc. Those darn electrons are invisible and you need to the meter to tell you where they are hiding and how many are ready to launch into creating problems for you.

Lefty

10563  Using Arduino / General Electronics / Re: Amplifying a signal using an Op-Amp on: May 16, 2011, 01:44:31 pm
From your link, it looks like with 6V this give me about 1/3 Watt, and with 9V I can do about 1/2 Watt.  So together with the 1/2 W speaker from SFE (above), would that get me the volume level I'm looking for?

Most likely, however speaker efficiency and proper speaker baffling/mounting enter the picture for actual SPL sound level output Vs audio electrical power consumed.

Also, If I go with the 9V version, can I just feed it directly from a 9V wall wart, or would I need a regulated power supply for it?

Yes you can power it directly from the a 9vdc wall wart. However you may have to add additional filtering caps if there is too much 60/120hz ripple voltage coming from the wall wart. I've used LM386 chip in some projects in the past and they do work well, however hum and other low level noise can be a problem if circuit layout, signal routing and power quality are not up to snuff. It's all about learning to solve the problems as you come across them if you want to learn and build this kind of stuff yourself. Otherwise buy pre made solutions.

Lefty

10564  Using Arduino / General Electronics / Re: Amplifying a signal using an Op-Amp on: May 16, 2011, 01:43:52 pm
From your link, it looks like with 6V this give me about 1/3 Watt, and with 9V I can do about 1/2 Watt.  So together with the 1/2 W speaker from SFE (above), would that get me the volume level I'm looking for?

Most likely, however speaker efficiency and proper speaker baffling/mounting enter the picture for actual SPL sound level output Vs audio electrical power consumed.

Also, If I go with the 9V version, can I just feed it directly from a 9V wall wart, or would I need a regulated power supply for it?

Yes you can power it directly from the a 9vdc wall wart. However you may have to add additional filtering caps if there is too much 60hz ripple voltage coming from the wall wart. I've used LM386 chip in some projects in the past and they do work well, however hum and other low level noise can be a problem if circuit layout, signal routing and power quality are not up to snuff. It's all about learning to solve the problems as you come across them if you want to learn and build this kind of stuff yourself. Otherwise buy pre made solutions.

Lefty
10565  Community / Bar Sport / Re: My electric blanket doesn't work ... on: May 16, 2011, 01:35:55 pm
When it comes down to features Vs reliability, put me down for reliability first. However it's not always easy to determine that when purchasing stuff like electric blankets in stores and higher price doesn't always mean more reliable either.

I recently bought a new refrigerator from a Sears store. The salesman commented unsolicited that they don't make the appliances as reliable as they use to. Of course he was using that as a hook to try and get me to purchase the 'extended warranty'.  smiley-roll-blue

Lefty
10566  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 16, 2011, 01:24:09 pm
Quote
Would moving the auto-voltage switch to a daughter / companion board be a good idea?  That would free some space and reduce the component count for people who intend to run the board from a 5 volt source.

Not as useful as just s@#t canning the whole concept of auto-voltage selection. It's such a lame function that uses way too many components and space for what it brings to the table. Real people should use real switches or jumper clips for things like voltage source or voltage level selection, auto-reset enable/disable, and any other useful user hardware selection feature required or desired. Auto-voltage selection was an idea that might have had the best of intentions for beginners, but if just limits flexibility and has some questionable design points.

OK, I'm done with my arduino rant for the time being.  smiley-wink

Lefty

 
10567  Using Arduino / General Electronics / Re: Amplifying a signal using an Op-Amp on: May 16, 2011, 12:36:38 pm
Most op-amps are mainly voltage amplifiers and make poor POWER amplifiers by themselves. Op-amps are just not normally designed to drive standard 8 ohm speaker loads.

There are many audio amplifier chips that contain both internal op-amp and power stages to offer a more complete solution for driving speakers. Things you have to know or define before selecting components is the impedance of the speaker, power rating of the speaker, efficiency of the speaker, actual SPL sound level you require, source voltage and current capacity avalible for your application.

An op amp by itself is quite capable of generating a audio line level output that is suitable for plugging into standard computer speakers that contain the audio amplification needed to drive their internal speaker(s) to useful levels. Computer amp/speakers can be found quite cheap or even used in thrift stores for a couple of bucks.

Lefty
10568  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 16, 2011, 12:13:33 pm
You guys make it sound like I need to get the prototypes ordered yesterday!

No, but you have seemed to have created an itch in a lot of us. I'm still not convinced that all the software hurdles have been leaped over yet, clock @ standard 16Mhz, bootloader compiled to run at 16Mhz, etc. Pin mapping should be the same as 644p however.

 I'm glad you are still considering the manual Vs auto-voltage switching function. Can live with either but still think the board space could be used for more useful purposes.

Lefty

10569  Using Arduino / General Electronics / Re: help finding a particular 2 pos. rotary switch on: May 15, 2011, 10:52:06 pm
Must it be rotary? Here is a spring loaded rocker switch for cheap:

http://www.allelectronics.com/make-a-store/item/RS-146/SPDT-CENTER-OFF-ROUND-ROCKER-SWITCH//1.html

Lefty
10570  Using Arduino / Microcontrollers / Re: Looking for the right document(s) on: May 15, 2011, 08:34:27 pm
The pin mapping that the Arduino team used to abstract the port/pin names to pin numbers is unique to the arduino project and will not show up in any Atmel document or datasheet or general C/C++ manual. Here is a spreadsheet someone put together to help, call it the arduino rosetta stone.  smiley-wink

https://spreadsheets.google.com/pub?key=rtHw_R6eVL140KS9_G8GPkA&gid=0

I use the arduino reference section as a starting point for usage info and move on from if needed.

http://arduino.cc/en/Reference/HomePage

Lefty
10571  Topics / Home Automation and Networked Objects / Re: Arduino Power? on: May 15, 2011, 07:43:48 pm
Yes it will run as long as you continue to pay your electric bill each month.

Lefty
10572  Using Arduino / LEDs and Multiplexing / Re: cheapest place to get 500 or so LED's on: May 15, 2011, 07:37:28 pm
Led cubes look much better when using diffused leds so that their light is evenly spread over a wide viewing angle. I think you will be disappointed if you happen to go with clear or 'high brightness' leds.

Lefty
10573  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 15, 2011, 11:47:56 am
If it was my design I would throw out all the auto-voltage switching components and instead use a simple 3 pin SIP and a jumper clip. This would save on component costs and board space avalible for more useful stuff. I never liked the Arduino auto-voltage circuit, looks like a solution looking for a problem.

Lefty

10574  Community / Bar Sport / Re: Your latest purchase on: May 14, 2011, 10:32:03 pm
Here's a cool gadget I got recently:



It's a dummy load. So you might have a 5V plug-pack that claims to put out 750 mA. But does it? Well you plug it into the load side, dial up 750 mA and see what the voltage does. The labels were added by me.

Only $19 too (plus delivery, which thankfully was not $600).

You can buy the LCD screens separately, as you can see they 6 lines x 14 characters, so pretty useful for this sort of thing. Only $6.80 each.

Cool, got a link?
10575  Development / Other Hardware Development / Re: ATMEL Mega1284P evaluation board avalible on: May 14, 2011, 09:15:57 pm
Wow, this is like watching a baby being born, only not as wet.  smiley-wink

Lefty
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