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1  Using Arduino / Project Guidance / Re: Putting pressure/weight sensors in shoe insoles? Feasable on a budget? on: May 10, 2014, 05:00:37 pm
I think the wiring for me would likely be the easy part.  Trying to find out if there are sensors small enough to comfortably fit in a shoe is where I'm struggling.

I searched for some "load cells".  They seem rather large, and/or thick in general though.  Also had searched for various other terms like "pressure sensor", "weight sensor".  Didn't find much promising, maybe I'm searching wrong, or maybe a flat, low profile sensor doesn't really exist..
2  Using Arduino / Project Guidance / Putting pressure/weight sensors in shoe insoles? Feasable on a budget? on: May 09, 2014, 02:59:57 pm
I'm trying to figure out if it is feasible to put strategically placed pressure sensors in the insole of a shoe.

The idea is to monitor weight distribution on various parts of the foot, such as under the heel, ball of the foot, and outside edge, to make sure weight is distributed the way it should be, and to monitor throughout the day, as someone becomes fatigued, making sure they still are distributing weight correctly.

It seems simple, however I'm having trouble figuring out what types of sensors to use, and if they exist and are affordable.   Just hoping for some sort of pressure sensor that is flat, and can read up to perhaps 100lbs each, but won't break if the load is exceeded.  The idea is the load will be spread across multiple sensors so they don't need to read the full person's weight, however if the person inadvertently stomps or something, don't want them to break.  Does such a sensor exist for an affordable price?
3  Using Arduino / General Electronics / Re: Is there such a thing as micro crimp connectors? Or micro butt connectors? on: February 19, 2014, 12:07:38 am
I definetly like those Lineman's or Western Union splices, although I was hoping for some sort of small crimp connection to go over that in addition.  Basically something similar to the type of U shaped crimp that's on dupont connectors.   

I suppose I could just cut that part off of a dupont connector, and use just the crimp part, crimping it over the linemans splice. I just figured though there has got to be a standard solution designed small gauge inline wire splicing, but perhaps not?
4  Using Arduino / General Electronics / Is there such a thing as micro crimp connectors? Or micro butt connectors? on: February 18, 2014, 01:35:24 pm
I'm looking for alternative ways to join small wires together, when you don't want to solder.  Wires in the 20-30 gauge range.  And preferably a commonly used way

I know for larger gauge wires like 12-18, butt connectors are common.  And for small gauge wires, there are all sorts of nice crimp on "end" connectors, like dupont connectors, however I haven't been able to find anything designed to crimp together wire ends.

Ideally I'd like to be able to just slip some shrink tube over one wire, then take both wire ends and overlap them, likely twisting together as well, then crimp a connector over this overlap, then slide the shrink tube back over and shrink it up, joining them into one continuous wire, without soldering, and with minimal added bulk.  Is there a commonly used and readily available crimp type connector for this purpose?
5  Using Arduino / General Electronics / How can I drive this random speaker at max power, and various frequencies? on: December 23, 2013, 10:51:17 pm
I have a random speaker out of a cheapo subwoofer, and I want to make some "Cornstarch monsters", which require a low base tone.  But after much googling I can't quite figure out how to simply make it work. 

I know I have to feed it some ac voltage, at various frequencies, but I have no idea what voltage is required, how much current, and also if it needs to be a sine wave, or if a square wave can work.  All I know is when I measure resistance with a multimeter I get 7.3 ohms.

Can anyone help, and suggest the cheapest and easiest way to drive this speaker at up to its max potential, and preferrably variable frequency?  I don't really care if I end up blowing it out, its just a junk speaker.
6  Using Arduino / General Electronics / Trying to replace blown power capacitor on laptop motherboard. Having issues. on: November 24, 2013, 03:18:02 pm
I plugged this laptop in one day, and it made a pop and some smoke.  It was still working, but continued to make an obnoxious burning smell.  I took it all apart, and found one component which was was completely blown open.  Identified on the motherboard as PC153.  Guessing its a capacitor.  The nearby similar parts themselves labeled as 15 1E4N, but I couldn't figure anything useful from that number, and couldn't find that same part to order.

So I grabbed a capacitor of my own, really don't know much about them, but I took one that was 25V 47uf, figuring 25v is plenty (since the laptop supply puts out 19v), and figured based on its size, the 47uf is likely larger than the one its replacing.  I paid attention to polarity, and soldered it in with the positive side of the capacitor on the same side as the little white marking on the motherboard.

Put everything back together, and plugged it in, and the power supply just blinks, which is what they do when they detect a short.  I removed the cap, tried putting it opposite just to try, didn't work.  Tried removing it completely, no luck, tried shorting across the  2 terminals, everything gives the same result.  Which is strange because it still at least worked when the blown open piece was in there.

Is there something I'm doing wrong?  Is that perhaps not a capacitor at all but something different?  Think it can still be fixed, hopefully didn't do any damage by the experiments i did above? 

You can see the empty spot where it was near the upper center of the image attached.  It looked the same as the other 3 nearby components labeled 15   14EN

Thanks.
7  Using Arduino / General Electronics / How can I read mains voltage with this oscilloscope? on: November 21, 2013, 01:38:05 pm
I'm getting my first oscilloscope, just a budget USB scope, most likely the popular budget choice hantek 6022be.

One of the things I'm interested in doing is reading the 120V mains sine wave.  Not too concerned with getting any super accurate reading, just want to see how smooth it is, and how much ripple might be introduced when switching on various loads.

Its my understanding that this hantek only has a 5v range, which can be increased to 50v if you flip the little attenuation switch.  However the AC sine wave for 120 v RMS, is actually in the area of 340v from peak to peak.

Is there any cheap and simple way I can measure this?  I was thinking perhaps clip a couple of high value resistors to the leads, and stick the resistors in?  Thinking use ohms law to choose a couple resistors which will have enough voltage drop to put things well into the oscilloscopes safe range. I'm guessing that will drastically throw off the measured voltage, but that doesn't matter, I already know the voltage, just looking for ripple.  Would this be a good way, or is there a better way?

PS: I know the dangers of mains voltage, and will take all precautions.  I've worked with live mains voltage for a living, and use multimeters on it all the time. I just have zero oscilloscope experience.
8  Using Arduino / General Electronics / What happens when high voltage is breifly introduced into a low voltage circuit? on: November 21, 2013, 01:21:23 pm
I've searched everywhere, but can't figure this out.  In electrical theory, what exactly happens to the voltage and current of a lower voltage circuit, if a very brief high voltage low current is introduced to it (like a spark striking it).  I'm not going to do any of these things, I just am trying to understand it.

2 examples.
1. If there were a 12 volt DC circuit, and a million volt but almost no current arc from a van de graaf generator struck the positive wire.
2. On a 120v ac circuit, if a quarter million volt, but low current like the arc of a tesla coil struck the hot wire?

What exactly would happen to the current and voltage?  And how bad would it be for whatever loads are connected on either circuit?

On one hand I brainstorm that perhaps almost nothing will happen, since the current is so low.  For example, if the 120v load already is drawing multiple amps, say for example it has 5 coulombs of electrons flowing through it, then a few extra milliamps, is a very small amount of electrons added to the flow, far to few to do anything, but who knows?  Then what about the voltage?  I brainstorm that perhaps on one hand it may be such a brief spike, that perhaps it only raises the RMS or average value by a negligable amount.  But then I wonder, can that extra voltage from the spark, encourage other electrons already flowing in the wire to move through the circuit causing a massive over-current in the load?  I don't know, just brainstorming, can't really wrap my head around exactly what would happen.

So can anyone explain what will happen to the circuit voltage, circuit current, and likely what would happen to the load connected?
9  Using Arduino / General Electronics / Can anyone explain how current discharging into the air works? on: November 15, 2013, 03:06:27 pm
Tried googling this, but I must be using the wrong terms.  I'm just wondering if anyone can explain the electrical theory behind how current discharges into the air, and where it goes, since there isn't a complete circuit. 

The main example I'm thinking of is a tesla coil.  It builds up a high voltage and low current in that torrid, but then the sparks just shoot off into the air.  With no apparent completed circuit. 

I could understand if the sparks all struck ground, completing the circuit, and making a path for the current, but if it just shoots off into the air, then where do all those little electrons go?
10  Using Arduino / General Electronics / Where can I find transformers for a tesla coil or jacobs ladder? on: November 15, 2013, 02:03:03 am
I don't know if I'm just looking in the wrong places or what, but I am having a really hard time finding a transformer to use for a jacobs ladder or tesla coil.

I understand typically a neon sign transformer is used, roughly in the 15KVA range, and roughly 50-100ma range.  And supposedly it must be one without GFI protection, and supposedly most of the newer ones have this.

So does that leave the only option to somehow find or salvage old used ones?  Closest I've found is looking on ebay, and the selection is small, and the ones I do see are around $150-$250 for an old used transformer.  Is this my only option (besides the more complex solid state tesla coils), or is there some other good source or type of transformer I'm missing?

11  Using Arduino / General Electronics / Can you stack, or daisy chain many transformers for high voltage? on: November 10, 2013, 11:01:43 pm
Tried searching before posting, but didn't find much on this issue.  Just wondering if you can stack or daisy chain transformers to achieve high voltage?

I'm guessing there is some sort of limiting factor, because I don't see it done much.  And I often see people pay good money for transformers to use on jacobs ladders, or tesla coils, or other very high voltage applications.

Couldn't someone just buy 3 or 4 of the cheapest transformers they could find, and chain them, causing the voltage to exponentially increase each time, to deliver similar results?  Perhaps even chaining 10 or so to get up to multiple millions of volts?

And in the same sense, its my understanding that a tesla coil is basically 2 transformers, usually one in the base which steps the initial voltage up quite high for the primary coil, and then the primary and secondary coils are the second transformer.  Well, why not add another a 10:1 ratio transformer somewhere in the chain to make the tesla coil 10 times as strong?  I'm guessing there is some limiting factor, since I don't ever see small tesla coils making 10 foot sparks.
12  Using Arduino / Project Guidance / Re: Help reading values from a MPU6050 accelerometer? on: July 10, 2013, 11:40:00 am
The example is at the bottom of the page at http://playground.arduino.cc/Main/MPU-6050.  I tried to post it in this message but it exceeded the maximum allowed length of 9500 characters.

So huge I can't really understand it.  In the past when I had used an ADXL335 accelerometer, all I had to do was an analogRead, and would get a value.  With this MPU6050, the code is so long and complex, I don't really know what commands to use to simply read a particular value.
13  Using Arduino / Project Guidance / Help reading values from a MPU6050 accelerometer? on: July 09, 2013, 09:07:41 pm
I'm trying to simply be able to read a value from an mpu6050 accelerometer, one value at a time at certain intervals for a project.

I have the MPU6050 working, i have the example sketch loaded from the arduino playground, which reads all 3 accelerometer values, and all 3 gyro values.

The problem is that example sketch is many pages long, and way too complex.  I don't know how to simplify it for use in my own project.  I've spent hours cruising the web, with the same result, all example sketches are pages long and way too complex.

If I could just find out the minimum amount needed, and the proper command to simply sample the value of one axis.  For example the z axis of the gyro, or the Y axis of the accelerometer.  With another accelerometer I've used in the past (adxl335), all I had to do was an analog read.  For this MPU6050 I have no idea what command to do.

Can anyone help?
14  Using Arduino / Programming Questions / Re: I'm struggling with this simple motor balancer. Any help? on: July 09, 2013, 11:34:27 am
That's basically it, that's the whole loop section.

Heres the full code.
Code:
// these constants describe the pins. They won't change:
int led = 13;
const int groundpin = 18;             // analog input pin 4 -- ground
const int powerpin = 19;              // analog input pin 5 -- voltage
const int xpin = A3;                  // x-axis of the accelerometer
const int ypin = A2;                  // y-axis
const int zpin = A1;                  // z-axis
int zcurrent;
int zmax;
int zmin;
int zdifference;
int time;
long previousMillis = 0;
long previousMillis2 = 0;
int delayamount;
int zcurrent2;
int zlast = 0;
unsigned long currentMillis = millis();
void setup()
{
  // initialize the serial communications:
  Serial.begin(9600);
 
  // Provide ground and power by using the analog inputs as normal
  // digital pins.  This makes it possible to directly connect the
  // breakout board to the Arduino.  If you use the normal 5V and
  // GND pins on the Arduino, you can remove these lines.
  pinMode(groundpin, OUTPUT);
  pinMode(powerpin, OUTPUT);
  digitalWrite(groundpin, LOW);
  digitalWrite(powerpin, HIGH);
  delayamount = 50;
pinMode(led, OUTPUT);
}

void loop()
{
zcurrent = analogRead(zpin);
if (zcurrent > (zlast + 1)) {               //the plus 1 is to eliminate sporatic readings
  zlast = zcurrent;
}
if (zcurrent < (zlast - 2)) {
  zlast = 0;
  digitalWrite(led, HIGH);
  delay(1);
digitalWrite(led, LOW);
delay(1);}


}

Seems like each time the motor spins one rotation, and the heavy side makes the accelerometer pass its peak, the light should blink.  Seems like it should be consistent, but its not, the light strobes while the motor is in all positions.
15  Using Arduino / Programming Questions / I'm struggling with this simple motor balancer. Any help? on: July 08, 2013, 10:50:42 pm
I am pretty much a newbie.  I am trying to make an optical motor balancer to balance RC motors. 

I'm using an adxl335 accelerometer, which is attached to the rc motor mount, which is loose, and allows motor vibration.

The idea is to figure out which side of the motor is the heavy side, and strobe an led on it.

I've tried quite a number of things, but my current code looks like this.
Code:
zcurrent = analogRead(zpin);
if (zcurrent > (zlast + 1)) {               //the plus 1 is to eliminate sporatic readings
  zlast = zcurrent;
}
if (zcurrent < (zlast - 2)) {
  zlast = 0;
  digitalWrite(led, HIGH);
  delay(1);
digitalWrite(led, LOW);
delay(1);}

The idea is to keep taking accelerometer readings as long as they are increasing, and the moment they decrease (heavy side of the motor just passed), to blink the led for 1ms.  Seems like it should blink the led 1 time per motor revolution at just the right spot, however its just not working that way, seems to be strobing pretty much randomly.

Anyone know how I can improve or rework this?

PS: I just thought perhaps a gyro would be better suited for this task?  I do have a MPU6050 on hand, although no idea how to use it, could not find a good tutorial with both hookups and example sketch.
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