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556  Using Arduino / Project Guidance / Re: Building custom Led tail lights. Total noob here. on: February 25, 2013, 08:12:04 pm
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My idea is to have brake/running lights so I need to have it run at 50% and then go up to 100%. Then for the turn signals I wanted a sweeping effect.
I assume you'll need high-power LEDs... probably 1W?    But, if you can get-by with standard (~20mA) "super bright" LEDs, that will simplify things a lot.   Have you experimented with LEDs yet to check the brightness?

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I have an arduino, but am now learning I may need a different micro controller for LED matrices...
A matrix is one way to do it...  The Arduino can drive a matrix, depending on the size of yoru matrix and which Arduino you are using.

How many LEDs are you going to use?   My current project is a music driven lighting effect that has 48 individually-addressable "super bright" LEDs driven by six MAX6968 LED driver chips.   These chips are driven serially, and can be daisy-chained serially, so you only need 3 microcontroller output lines to control many LEDs.  I have a "stereo" set-up, so I'm actually using 4 control lines (separate left & right data lines) from an Arduino Uno to control two banks of 24 LEDs.   

There are many different LED driver chips...  This particular one can use PWM dimming to dim all of the LEDs as a group.  (You can turn on & off the LEDs individually, but all of the on-LEDs have to be dimmed together).   I'm not using that feature, but it would work for you in your applicatication.

If you use high-power LEDs, you are probably going to need a separate dimmable constant-current driver circuit for each LED.  You can buy or build constant-current LED power supplies.  You could control these serially (using shift registers) or with a separate microcontroller-output for each LED.    Depending on the number of LEDs, these "high power" LED drivers could get expensive.

Basically, the hardware design & wiring are the hardest part.  Not really that big of a deal, but it could be a lot of wiring...   It felt like it took me "forever" to solder wires to 48 LEDs, and also solder the wires on the driver-end. 

The microcontroller programming is simple... Assuming you've done some programming before. 

P.S.
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so I need to have it run at 50% and then go up to 100%.
That's easy to experiment with, but I think 50% is not enough contrast/difference...   I was guessing 25 or 33%...   I looked-up a dual filament bulb and it was 6W & 21W.    Both filaments are on in the bright blinker/brake state, so that would be 6W when dim and 27W when bright, or about 22% when dim.



557  Using Arduino / Project Guidance / Re: Positive and Negative Voltages (Can I do this circuit?) on: February 20, 2013, 05:07:12 pm
Your basic idea looks like it would work, with a couple of limitations...

What kind of source do you have?   What's it's impedance or current capability?

Diodes are nonlinear.   You need to have 0.5 - 0.7V across them before they turn-on.  That means you are not going to read any positive voltages below around 0.5V, and you'll need to add the diode-voltage drop to any readings you get.   (You can do the compensation is software.)    The biasing resistors on the negative input will turn-on the "negative" diode, so you will be able to read small negative voltages, but again you'll have to compensate for the diode-voltage drop.

Also, you WILL need that voltage divider for +10V, because connecting more than 5V to an input pin can damage the Arduino.
558  Using Arduino / Project Guidance / Re: Which board to use for recording guitar and bass? on: February 15, 2013, 06:08:31 pm
Yeah...   An Arduino or other microcontroller isn't going to add anything other than possibly making the thing more portable than a computer.    And compared to programming a computer, the whole project is more difficult because you have to design the hardware as well as the software.

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Then again, I'm not familiar with a lot of the behringer products. Thanks for telling me that, I'll check that out and see how well it works.
The Behringer gizmo is probably the most economical way to plug a guitar into a computer, but there are all kinds of audio interfaces with instrument inputs, mic inputs, or line-level inputs. (With these, you are not using your computer's soundcard unless you are using it to play-back or monitor the recording.)

For acoustic guitar, another simple solution is a "studio style" USB microphone.   These things can give you nearly pro studio results if you have a good acoustic space or studio, and if you are recording mono.  (You can generally only record with one USB mic at a time).   You can get these starting around $100 USD, and again you are bypassing your soundcard.   I do not recommend a cheap "computer microphone".   


A regular soundcard is pretty much worthless for good-quality recording because the mic input is designed for a computer mic and it's the wrong interface for any performance/studio mic (low-impedance balanced with an XLR connector, or a guitar (very high impedance).

Your software development will be a lot easier if you start-out analyzing recordings.     If you can get that working, it shouldn't be too hard to make your application work in real time.  And the hardware interface requirements will be the same either way.

Once you have the hardware set-up, recording is easy!   Most interfaces will come with software.  Or, any "audio editor" application can record.   Audacity is FREE.   I've used GoldWave for many years ($50 USD with free upgrades).

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...and one of the options I'm adding is the ability to grade what you play.
Now the  bad news...   That might be difficult or impossible.  smiley-sad  There are programs for converting single-note sounds into

MIDI
.  But from what I understand, there is nothing that works very well with chords or multiple instruments playing at the same time. 

But, the place to start is with FFT.    I'm sure you can find an FFT library for C#.   FFT will give the frequency content of any signal at any point(s) in time.   From that, it's fairly easy to determine the root frequency and convert that to a root note.  It's analyzing the harmonics & overtones that becomes tricky.


559  Using Arduino / Project Guidance / Re: I want to make driver circuit for a small but loud siren on: February 14, 2013, 08:06:19 pm
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3 volts@ 1.3amps.
Have you tried 3V into an 8-Ohm speaker (with a MOSFET to boost the current)?    At a high-pitch, it might be loud enough.   


BTW - You won't get 1.3A through an 8 or 4 Ohm speaker at 3V.  (Ohm's Law).  And,  you won't get 375mA out of the Arduino (rated 40mA max), so you need a MOSFET (or something) to boost the current capability.

With an H-bridge circuit you can get double the voltage-swing +3V to -3V across the speaker, which will result in twice the current and 4 times the power, and 6dB more loudness.    And, going from 8 to 4 Ohms will double the current for twice the power or another 3dB.     So, with those two "tricks" you can get an additional 9dB.
560  Using Arduino / Project Guidance / Re: Sinusoidal linear motion using a DC motor on: February 14, 2013, 07:42:40 pm
I agree that without continuous position feedback (similar to a servo motor*) you are not going to get true sinusoidal motion, but you might be able to get some sort of speed-ramping.   DC motors just don't respond that linearly to drive voltage/current.   I think it's just going to take some experimentation. 

The motion is also going to depend on load (mass & friction).   You can "map" the torque/voltage curve for aDC motor, but a speed/voltage curve is a lot trickier, especially at slow speed.   If you have a "nice" constant load (like lifting a weigh on a pully) you could convert torque to speed, but I suspect you don't have such a nice load.

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If more feedback sensors were added, say a total of 5, could the system be more reliable? two near each end and one in the middle?
I'm thinking 4 sensors...   An additional sensor for "almost open" and "almost closed".

And, I'm just thinking maybe a non-linear, non-smooth voltage curve might work best...   Something like run at full speed (or accelerate) at the start of the motion.   Then when you hit "almost open" or "almost closed", drop the voltage quickly.  Then, ramp-up the voltage to make sure the drawer closes.   That's how a mechanical door-closer works.   It closes quickly at 1st, then it hits a point near-closed and it suddenly slows-down.




* A regular servo motor only rotates about 180 degrees, so it probably won't work...     I suspect you'll need to gear-down and use several revolutions.

P.S
An alternative is a stepper motor.   With a stepper motor, you can precisely control position & speed, and you can run slow (or "hold") at full-power.    You'd still generally want 2 sensors to confirm your end-points.
561  Using Arduino / Motors, Mechanics, and Power / Re: SSR question on: February 07, 2013, 03:39:00 pm
It should work fine without any additonal circuitry.   

Motors are inductive, so I'd kind-of like to see if it's rated for inductive loads...   But, at 75W you'll be using less than one amp so you have quite a bit of safety margin.

The price is lower than usual, so it's probably surplus or removed from equipment (used).
562  Using Arduino / Installation & Troubleshooting / Re: Accidental capacitor discharge on Arduino on: February 07, 2013, 02:03:17 pm
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And when I have this other arduino board is the burning of the bootloader done by the areduino software?
Here are the instructions for using the Arduino as a programmer.  (I have not tried it.)
563  Using Arduino / General Electronics / Re: How do you finish a project on: February 06, 2013, 08:11:08 pm
So the LEDs are separate from the controller, right?   Do you want to mount the LEDs in little boxes, or in the stroller?

For mounting LEDs, I've used hundreds of these over the years.

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2. How should I handle to cabling, (is it better to solder everything or use sockets)
It's your project, so that's up to you.  For stuff that's external to your main contoller box, I'd use connectors.    Everything inside the box can be soldered.

Look at how a computer or a piece of stereo equipment is made...  Everything plugs-into the main unit, except sometimes the AC power cord is permanently attached.  A mouse or keyboard has a cable permanently attached, but usually a printer does not.   (If you look inside your computer or stereo, you will see lots of connectors, but for a simple home-built project this usually isn't necessary unless you have multiple circuit boards.)

If you are not using a pre-built Arduino board, I'd put the Arduino chip in an IC socket.  In fact if there are any other ICs, sockets are nice if you have a problem...  You don't always know if you've got a bad/blown chip or something else, and having a socket makes troubleshooting/repair a lot easier!

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3. I don't want to use my Mega to run it, so I bought two arduino kits (quarts, chip, ceramic resistor, etc)
How's that going?  Did that kit come with an Uno board, or just an Arduino chip?
564  Using Arduino / Project Guidance / Re: IC w/ individual PWM for RGB high current application on: February 06, 2013, 04:30:46 pm
I did a quick search and the 1st thing I found was the LM3406.   For RGB you'd need 3 of them, and they are surface mount so you'd have to make a board or otherwise deal with that.

If you want DMX, you'd have to program that into your Arduino (and build the interface circuit).

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I'm looking for the most efficient(least amperage) and cost effective way to power several 3w RGBs (300-350ma...

... Using LM317s per channel might be the most cost effective, but, certainly not most efficient with 3v dropout per module.
Any switching regulator will approximate 100% efficiency (if properly designed).    That means you can get more current-out than goes in (at less voltage-out than goes in), and almost no power is dissipated by the regulator itself.  The switching circuit is going to require an inductor, which adds a bit to the complexity & cost.

The power loss (and associated heat) with any linear device (like the LM317 or a resistor) depends on the current and voltage drop across the device (P = V x I).   It's not unusual for the regulator (or limiting resistor) to waste more power than goes to the LED. 

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certainly not most efficient with 3v dropout per module.
The voltage drop is the difference between your power supply voltage and the LED voltage.    You'll have more than a 3V drop ONLY if your power supply is 3V higher than the rated LED voltage.
565  Using Arduino / Audio / Re: Mems microphone lavalier style ( tie/shirt clip microphones ) on: February 06, 2013, 02:27:54 pm
Yeah...   Nothing about that is easy...

I wouldn't recommend building an RF transmitter/receiver yourself.  RF is a specialty area and doing it right would require an oscilloscope, a frequency counter, and probably an RF spectrum analyzer and a signal generator.    Just renting that kind of equipment would cost more than a good wireless mic set-up.

As far as digital signal processing, that's going to take a fairly high-power processor (assuming you want good audio quality) or a special-purpose DSP chip.   If you've done some DSP before, that might not be a big deal.   But if you haven't, you are probably looking at a few months of study.   And, you might have to invest in a software/hardware development kit once you choose a processor.

Other than the mic preamp, building an ADC & DAC are probably the easiest part.  But, I wouldn't say "easy"...     So, you might look into that first.    If you think you can handle that, you might look into the RF & DSP aspects.
566  Using Arduino / Project Guidance / Re: Automotive Flasher Relay on: February 06, 2013, 01:48:56 pm
I'm not going to attempt to write your sketch for you...

It looks like you just need some if statements and/or some if-else statments to control what your program is doing.    Conditional execution (if statements, etc.) and loops (doing stuff over-and-over) are the two most important concepts in programming.   They are the things taht make programming worthwhile.

I think you just need to read-through the Programming Language Reference and take a look at a few more examples, and then just start experimenting and learning!     Add a couple more lines of code to your sketch at a time to add features/functions.   

Do NOT try to write the whole program before trying it out!   Add a few lines of code at a time.   That way if there is an error or a bug, you'll know where to look instead of trying to find 100 errors at a time.  smiley-wink

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Hazard warning lights switched on off on within 2 seconds, indicator strobe effect (recovery vehicle etc)...
  That sounds like an if-statement that changes the delay time.

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Finally load sensing so when a trailer is attached it flashes the trailer indicator reminder light on the dash ( optional but already does it on the standard relay).
I don't know how that's wired-up, but the Button Example reads the state of an input pin and with an if-statement, turns an LED on/off.  That should get you started.   ...Don't connect 12V directly to an Arduino input.  Use a voltage divider (2 resistors).
567  Using Arduino / Project Guidance / Re: Looking for enclosure with a slot for dip switches? on: February 06, 2013, 01:17:33 pm
I'd look for a local "Precision Machine Shop" or a "Precision Sheet Metal Shop".   Then, you can bring your box in and talk to them about approximate prices, and if it seems resonable you can get a formal quote.

If you are in the U.S., the set-up time (for each run/batch) is probably going to run a couple hundred dollars.    So, the per-unit cost will depend on quantity.   If you are making 10 or 20 units and you need to keep the cost down, doing it yourself with a hand-nibbler and a file might be the best option.

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If I did decide to go with the custom case route, have them cut it then I might as well go all the way and have my company logo printed/painted on too.
A full-custom (sheet metal) box will probably become economical at around 100 units.      Silkscreening & painting should be the same for a modified box or a fully-custom box.   Again, the set-up costs for silkscreening & painting will be a significant consideration if quantities are low.

Where I work, we use a small simi-custom box.  The box-bottom is sent out for machining (probably in quantities of 100) to add a couple of countersunk holes.   The aluminum front & rear panels are custom made by a sheet metal shop.    These might be made in smaller quantities because the same basic box is used in several different products.   The rear panel is brushed-& silkscreened.   There is a custom adhesive plastic front-panel overlay with printing, a cutout for a switch, and windows for LEDs.   The cost of all this stuff adds-up to about $35 USD per unit.
568  Using Arduino / Programming Questions / Re: How to do exact time blinking for a Led on: February 05, 2013, 02:08:58 pm
The crystal-clock in your camera is probably MORE accurate than the Arduino resonator-clock. smiley-wink

But nothing is perfect, and if you shoot with multiple cameras they will drift apart after several minutes (or maybe an hour) of continuous shooting.  And if the audio is recorded separately, you can start to see "lip-sync" problems after a period of time.

With professional audio/video they use a very-accurate master clock linked to all of the equipment to keep multiple cameras and multiple audio recorders in sync. 

And of course, the playback system is equally important...  If you have two copies of a DVD and two DVD players, and if there were a way to start both players at exactly the same time, but the end of the movie, they would probably be out-of-sync by at least a couple of frames.
569  Using Arduino / Audio / Re: Audio input via computers built-in microphone? minim for arduino? on: February 05, 2013, 01:48:21 pm
P.S.
If your goal is to have fun with Arduino and learn about it, a VU meter could be a good project.  But, if your goal is to build a VU meter, there are easier ways to build one without programming a microcontroller, such as this kit.

...I have a VU meter lighting effect that's built with an Arduino, but it it's programmed to do lots of random things, like reverse, invert, dot-mode, and other sequences/ options that are not VU meter related.

P.P.S.
I didn't read carefully...  Of course you don't have a "Windows" mixer, and GoldWave does not run on a Mac either (but Audacity does).
570  Using Arduino / Audio / Re: Audio input via computers built-in microphone? minim for arduino? on: February 05, 2013, 01:19:25 pm
You know...   most recording/audio editor programs (Audacity, GoldWave, etc.) have a meter display on the computer screen (with no additional hardware).

If you are going to use the Arduino and buld some circuitry, I'd recommend NOT using a computer. But, if you want to use the computer as an amplified microphone, you can simply turn-on the mic in the Windows 'Playback' Mixer and turn it up volume.   Then, the amplified line-level signal should come out of the headphone jack...  You can run the headphone-output into the Arduino (with the proper signal conditioning to block negative voltage swing, which can kill the Arduino).

I normally use a Peak Detector Circuit to condition the audio input.   But, you can also use a pair of  resistors and a capacitor to simply bias the signal at 2.5V.

Here is a little pre-assembled PC board with a microphone and an amplfier.   You can connect it directly to the Arduino and you won't need a computer.  (of course, you will need a computer during the design & construction process to to develop your code and to program the Arduino.)

Before you start making a VU meter, this simple Analog Input Example blinks an LED depending on the analog signal.   You might want to experiment with replacin the pot with an audio input.

Here is a VU Meter Example Projcet
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