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31  Using Arduino / General Electronics / Running high power led's without drivers. on: October 05, 2012, 01:18:13 pm
I have a couple of questions about these high power LED's, such as the cree xml-t6 and some of the others.

1. Are drivers really that important?  I googled this quite a bit before asking, and everyplace recommends a using a driver, saying led life will be shortened without one, and power won't be as steady, etc.  But for something simple like a flashlight, where brightness is more important than steady light, is it really that important? 

1A. Wouldn't it be somewhat of a benefit running it without a driver, but with a good heatsink, to make it even brighter, sort of like overclocking a computer? 

1B. Even if life is reduced a bit, is it as big of a deal as people say?  If the typical LED has about a 100,000 hour lifespan, or something huge like that, even if I reduced it to 1% of its lifespan, that's still 1000 hours, by that time whatever device I'm using it on will likely be obsolete anyways, or the LED would be obsolete, replaced by a better one. 

2. I bought some other 3w led's that say they are rated at 700ma.  I also bought a driver that is supposed to put out 2800ma.  I wired up the driver, and had 4 of these led's in parallel, and using a 18650 battery (3.7 volts, 4.2 on full charge). Should total 2800ma, which is what the driver is rated at.  However, at full power, it only seems to be drawing about 700ma for all 4 of them, and when I hooked up the 4 led's directly to the battery, they are only drawing about 1 amp, when the specs say they should be drawing 2.8 amps.  Can anyone help explain why these numbers aren't adding up?

32  Using Arduino / Project Guidance / Re: Trying to figure out how to make a motor balancer. on: August 06, 2012, 07:37:51 pm
If anyone thinks a piezo would work better than an accelerometer, I'd be open to hearing that idea.  My main criteria for this project is low price and simplicity.

Considering right now the only way I can attempt to balance motors is basically, see how much it vibrates, start taking random guesses as to where to add weight, and just keep using trial and error to try and make it feel like it vibrates less.  Not efficient at all, in fact I usually waste a bunch of time doing that and give up. 

Obviously I'd like this motor balancer to work as good as possible, but considering I am a bit of an arduino newbie, if I go trying to make something too overly complex, it will never get done.
33  Using Arduino / Project Guidance / Trying to figure out how to make a motor balancer. on: August 05, 2012, 10:02:50 pm
I'm trying to figure out a way to make a simple and low cost device to help balance RC brushless motors.

While I'd be open to other suggestions, this is the idea that I had in mind that seems the simplest.

I could attach the motor to a loosely mounted motor mount that has an accelerometer (or some other sensor) attached.  It could monitor the values of that sensor, and each time one particular axis is at its peak value, it could strobe an LED light.  Should work like a timing light, each time the heavy part of the motor comes around, the light strobes so it basically freezes motion, showing exactly where the heavy side is.  Allowing you to make adjustments until the motor is in balance.

My biggest holdback is trying to figure out what sort of accelerometer, or other low cost sensor will function quickly and accurately enough to work. 

Anyone have any suggestions what sensor to use, or some other general pieces of advice towards making this project?
34  Using Arduino / General Electronics / Re: Always hard for me to find 96/4 lead free solder. on: July 25, 2012, 07:38:55 pm
Perhaps I may need to switch to a different type of solder, such as some of those cheaper options others mentioned.

I've just always used 96/4 because I know it worked and considering how many solders either don't say what they are made of, or list extremely cryptic details (that I'm sure I could understand if I spent 4 hours on google researching them, but haven't done that).  I was always afraid to using some sort of incorrect solder.
35  Using Arduino / General Electronics / Always hard for me to find 96/4 lead free solder. on: July 21, 2012, 11:58:01 am
I've been using 96/4 lead free rosin core solder, 96% tin, 4% silver, in the .031 (or .032) size for many years now.

I used to get it from radio shack. Since that's the type they sold, thats what I started working with.  They started charging too much, so I found it for cheaper at harbor freight.  However it just comes in tiny tiny little tubes that I go through very rapidly.

I have searched many times on ebay and the web for larger quantities like 1/4 to 1/2 pound, but never seem to find it.  I find all sorts of other solders, or other formulas, like 99.3/.7, acid core, and many others, but never 96/4.  On a rare occasion I have found a 1lb spool for like $80 from some no-name place, but I don't trust buying that large of a quantity of an unknown brand.  I just want the same quality 96/4 I've been successfully using for many years, in 1/4 to 1/2 lb quantities, at an affordable price that's cheaper than buying tons of tiny tubes at a time, like maybe a 1/4 pound for $25.

Anyone know why its so hard to find?  Am I perhaps not using the best stuff, and other solder formulations may be better?

36  Using Arduino / General Electronics / Re: Anywhere to get short female jumper wires? around 10CM? on: July 15, 2012, 06:26:34 pm
That poulu seems like a good place for making your own, I'll probalby buy some.

Still looking for short ready made ones.  The links provided were for ones around 6" long, give or take a little, which is what I always find.

I really wish I could find some short ones around 1", 1.5", and 2" long.

So many times I end up hooking up components that are only an inch apart, but have to use long 6" jumpers, since thats what everywhere sells, and pretty soon its a wiring mess that could be avoided with 1" jumpers.
37  Using Arduino / General Electronics / Anywhere to get short female jumper wires? around 10CM? on: July 15, 2012, 04:59:33 pm
I've searched high and low, but all the female-female jumper wires I find are always 20 or 30 centimeters long.

Is there anyplace I can find short ones around 10CM, or even just a little longer and shorter?
Or any way to get the same type of ends and custom make your own lengths?

Hopefully somewhere cheap, and that won't charge a hefty shipping charge for some tiny wires.

Right now I've been having way too long and sloppy wiring, or chopping and soldering to make short ones, which is a pain.
38  Using Arduino / Programming Questions / Any way to delay certain parts of code, without delaying the whole thing? on: July 12, 2012, 06:05:12 pm
I know the delay milliseconds command is very common, but I'm wondering if there is any way to delay just certain parts of code, without delaying the entire thing, heres a couple examples.

You have 3 sensors (A, B and C), monitoring 3 trigger events (Trigger event A, B, and C), and performing an action upon said trigger event (Trigger event A, B, and C).  However once a said event is triggered, such as Event B, you want to completely quit using sensor B for a certain 10 minutes, however you want to keep using sensors A and C, as well as running other parts of the software.

Example 2.  You want to blink 2 led's based on a rate of speed adjustable with a potentiometer.  With one led it would be simple, write high, then delay for said amount based on potentiometer value, then write low, then delay again....... However how would you make this work with 2 led's and 2 potentiometers?  Since the delay command delays the entire set of code, you'd have to somehow give each one their own independent delay so they don't effect each other.

39  Using Arduino / General Electronics / Re: What type of amplifier do I need for this project? on: January 07, 2012, 12:22:57 pm
Anyone have any idea if this amplifier would work?

Seems user friendly, cheap, and seems to have an adjustable knob, so I'm guessing I could maybe gradually crank that knob up until the point the speaker starts making distortion or something.

I apologize for such a simple question, but I just don't know much when it comes to audio amplification.  I've spent a few hours reading about it on the web, but still couldn't find good info for determining for myself what amp would be compatible.
40  Using Arduino / General Electronics / What type of amplifier do I need for this project? on: January 04, 2012, 05:58:29 pm
I'm trying to make a custom PA system for my car, but I am confused about what type of amplifier I need, and if I am able to make one with a basic schematic and minimal parts, or buy one.

I'm wanting to take the main sound unit out of a "personal soundtrack shirt" like this
but remove the speaker from the shirt and replace it with a PA horn.

I already have a pa horn that came with a "coga pa system"

I actually have already hooked up the sound unit from the shirt, to the pa horn, just by simply cutting the audio output wires, and hooking them to the wires of the PA speaker, and it does work, and is louder than I would have expected, but I don't think its nearly as loud as its potential.  The sound unit is only running off 4 AAA batteries right now, thats only 6 volts, and I believe the pa speaker is probably 12 volts (at least the normal PA amp that normally goes to that pa speaker is a 12 volt device).  According to the specs the amp that normally outputs to that PA speaker is a 40watt RMS 50watt max.  Unsure if that is the max of the speaker or not, but I believe I need to find a way to increase the output of the sound unit from the shirt, from whatever it is, to 50 watts.

Can anyone help?  Thanks.
41  Using Arduino / Displays / Question about the different types of serial LCD's on: December 16, 2011, 11:40:46 am
I have a few questions I've been searching everywhere for in regards to the different serial LCD's.

1. I have a couple projects that are designed to use the "sparkfun" 3 wire serial LCD.  These however just seem way too expensive for what they are, about $32 shipped, compared to simply the regular LCD's for around $2.50 shipped.  Are there any other LCD's compatible with the sparkfun ones for cheaper, or that can be made cheaper?  I did find this one that says it uses UART, not sure if its compatible or not, and still expensive, but at least its only $25 shipped, any idea if it will work?

2. Do serial LCD's, (either the regular 4 wire, or the sparkfun), solve the issue of LCD artifacting, or do you still need to manually workaround it?  What I mean by this is, when I have used the regular 16x2 non-serial lcd's on projects before, say I have a variable on the screen, lets say the number 15 for example.  Well if that 2 digit variable goes down to 1 digit, say 9 for example, the first digit does not clear, so even though the number is 9, it will appear on the screen as 19, since that 1 is an artifact.  Only way I had found to solve is by adding extra code to monitor how many digits and clear the first ones if necessary, but its extra work, would be nice if you didn't have to.

3. Are there any advantages to one serial lcd over the other, besides just that the sparkfun one has one less wire?

42  Using Arduino / Project Guidance / Re: IR Remote controlled finger for camera shutter (completed with demo video) on: April 26, 2011, 04:04:27 pm
By the way, here is the code.

/* Note, first time run, with no values stored in EEPROM might be a bit buggy,
as soon as values are stored, will work fine */

#include <IRremote.h>
#include <Servo.h>
#include <EEPROM.h>
int RECV_PIN = 11;  //ir reciever hooked on pin 11 through 220ohm resistor
Servo myservo;   // create servo object to control a servo

int position1;   //servo position 1
int position2;   //servo position 2
int position3;   //servo position 3
int codeValue;   //the code from the remote
int current;     //keeps track of current servo position

IRrecv irrecv(RECV_PIN);

decode_results results;

void setup()
  position1 =;    //default servo positon 1
  position2 =;   //default servo position 2
  position3 =;  //default servo position 3
  irrecv.enableIRIn(); // Start the receiver
  myservo.attach(9);  // attaches the servo on pin 9
  myservo.write(position1);   //start the servo out at position 1
  current = position1;

void loop() {
  if (irrecv.decode(&results)) {
    codeValue = results.value;
    switch (codeValue) {
    case 16753245:   
      current = position1;
    case 16736925:   
      current = position2;
    case 16769565:   
      current = position3;
    case 16761405:
      ++current;                //moves servo 1 degrees
      if (current > 179) current = 179;  //this makes sure the current variable doesn't exceed the servo range
    case 16748655:
      if (current < 0) current = 0;  //makes sure variable doesn't drop below 0
    case 16712445:
      current += 10;  //moves servo 10 degrees
      if (current > 179) current = 179;
    case 16754775:
      current -= 10;
      if (current < 0) current = 0;
    case 16720605:   
      myservo.write(179);  //moves servo all the way to 179
      current = 179;
    case 16769055:   
      current = 0;
    case 16738455:   
      position1 = current;  //stores current position as servo position 1
      EEPROM.write(1, position1);  //writes position 1 to eeprom address 1
    case 16750695:   
      position2 = current;  //stores current position as servo position 2
      EEPROM.write(2, position2);  //writes position 2 to eeprom address 2
    case 16756815:   
      position3 = current;  //stores current position as servo position 3
      EEPROM.write(3, position3);  //writes position 3 to eeprom  address 3
    case 16724175:    //this is for the laser sensor
      int sensorValue = analogRead(A0);     //cds photocell hooked to analog 0, has 10k pulldown resistor to ground
      while (sensorValue > 950) {              //value can be adjusted, 950 very sensitive for my conditions
        digitalWrite(13, HIGH);        //status light, led on means laser is armed
        sensorValue = analogRead(A0);    //reads sensor value again for the loop
      current = position3;
      digitalWrite(13, LOW);             //turns led off to indicate status that servo was activated.
      delay(1000);                        //delay just for good measure, holds servo for a second
      myservo.write(position1);          //moves servo back to position 1
      current = position1;
irrecv.resume(); // Receive the next value
43  Using Arduino / General Electronics / Can anyone explain a ground loop, and when tieing grounds together is needed. on: April 03, 2011, 12:14:43 am
I've heard about the issues of ground loops many times.  There have been times I've heard it is necessary to tie the grounds of multiple devices together, and other times when it isn't.  However after much googling, I surprisingly have not found much info on this topic.

Can anyone explain in pretty basic terms what a ground loop is?  What bad effects it causes?  And how do you determine when it is necessary or not, to tie multiple grounds together?
44  Using Arduino / General Electronics / Re: Question about piezo element impact sensor. on: March 17, 2011, 09:34:07 am
So are you saying that straining or flexing the piezo in one direction produces positive current, and flexing it in the opposite direction produces negative current?  Meaning a strong impact, which would cause it to vibrate, or distort back and forth very fast would be producing both positive and negative current?  That seems to be what mine is doing, although that does not match up with everything I have read.
45  Using Arduino / General Electronics / Question about piezo element impact sensor. on: March 16, 2011, 10:20:23 pm
I've done the basic knock sensor before, and I'm planning on implementing it in my project which triggers a camera when an impact is detected above a certain threshold.  However when I grabbed the piezo element that I had laying around (ripped out of a $1 door chime), I was experiencing something unusual.  I hooked the piezo up to my multimeter to verify polarity, and according to my multimeter it seems to be producing both positive and negative voltage interchangeably.  Its hard to tell since the multimeter refresh rate isn't super fast, but It almost seems like if I flex the piezo, it produces a positive voltage, and when I let it unflex, it produces a negative one.  If I simply give it a strong impact, sometimes it shows up positive, sometimes negative.

All my research has always indicated that piezos only have one polarity, positive in the center, negative on the outside.  So why is this one not matching up, and is it safe to use with the arduino?

Also, are piezos safe to use with arduino for very strong impacts?  Or could a very strong impact potentially produce too high of voltage?  (I'd be using a 1MegaOhm resistor like in the tutorial)  I want to not only detect somewhat sensitive impacts like knocks, but also very strong impacts such as having the sensor on the handle of a baseball bat or hammer that hits stuff, or strapped to the side of rifles or pistol slides to instantly detect the strong recoil.

PS: Is there any other cheap zero delay impact sensor I might want to consider that could be better, or is a piezo the best bet?  Doesn't have to accurately measure the "strength" of the impact, only that the impact is present above a set (very low) threshold.
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