Building Simple Things

One thing that continues to shock me when I try to build simple things is just how complicated they actually are. Even basic devices simply don't work most of the time I build them and only after a whole lot of tinkering and reading how other people did it can I make it work.

Well, this guy took that to an extreme that even I wouldn't consider. He tried to make a toaster out of rocks.

Raspberry Pi Crossing the Atlantic

I have considered buying a Raspberry Pi quite a few times in the last few months. At $25-$35 it makes for an ultra-cheap computer with which to do silly things. So far I have been held back from buying one because I just haven't seen a lot of projects which are the caliber of what I see on the Arduino. That, and unlike the Arduino the hardware is not open source which will ultimately limit the ability of people to tinker with it.

Still, if anything makes me change my mind it is that this guy is planning an attempt at crossing the Atlantic ocean with a home-made solar powered boat twenty inch long boat. The boat will be fully autonomous crossing the ocean without major input from anyone. Now, I join with many in thinking that this will fail. It doesn't look like his boat is robust enough to make the trip and this is still in the thought process phase. Still, I feel like I could actually have a shot at doing this for under $1000 and a few hundred hours of tinkering.

None of the technology is all that difficult, GPS autopilots are widely available and open source. Solar power modules that can survive a year at sea shouldn't be a real challenge, a motor which can survive the trip might take some real thought for selection but I don't imagine that there is any shortage of motors which can survive a year or so at sea.

The hardest part would probably be tracking it. It would need to send regular signals reporting where it is. Then you have to manage to be in the right place at the right time to pick it up. You would also depend on good weather when it is near shore or it will wash up on shore somewhere. I suspect the route will need to stay five miles or more from shore until the last rush into a calm port.

As for the Raspberry Pi, if I was to take on a similar project I feel like an Arduino Mega might be sufficient. After all it is pretty easy to buy GPS shields for them and the autopilots are freely available. I suppose the ability to take and store photos would be the only real area where the Raspberry Pi might come out ahead.

What this will do to drug traffic should be interesting. I would think one could be made to look like a floating log or piece of trash quite easily.

Three Phase 6 Pulse Inverter

One of the primary things i wanted to do with my Arduino was turn my generators into motors. My simple generators were not simple to turn into motors but this proved to be particularly tricky with my three phase generator. Doing this requires me to create a three phase inverter. The first time I looked at a circuit for this, I thought it would be dead simple. All I need is a few transistors and a few diodes then I can hook them up like this:

and it would work. This turned out to be untrue. That diagram really leaves out a whole lot of details which had me scratching my head for weeks. In particular the transistors connected to the high side just will not work without additional circuitry.

After about four or five failed attempts I got one to work. Here are three almost identical videos of the finished product:







Here is a wiring diagram showing how it is hooked up(click on it for a larger version:

Components consisted of:

1- Arduino Uno r3

3- NTE 2980 Logic Level N Channel MOSFETs

3- SPP15P10PL H Logic Level P Channel MOSFETs

6- 200 ohm resistors (actually I ran out of these and used 100 ohm and 4000 ohm resistors from the output of the MOSFETs to the Arduino Uno, but 200 ohm are probably a better choice)

1- 100 ohm resistor

3- 100,000 ohm resistors

3- 1,000,000 ohm resistors

3- TC4432 MOSFET driver chip. Be really careful with these, not sure if it was static on my part or poor quality control from the supplier but half of these didn't work. If you want a inverter above 30V this component will need to be replaced with a different MOSFET driver. Another alternative might be a charge pump circuit.

1- 7805A R1424 Voltage regulator. This powers the Arduino from the battery pack. The onboard voltage regulator on the arduino could probably substitute for this.

1- capacitor. Unfortunately this didn't have a legible label on it so I am not quite sure what I used beyond that it was not an electrolytic capacitor so it was probably fairly low capacitance. This was just to lower any ripple which occurred on the DC side of the inverter.

1- battery pack with six rechargeable 1.25 volt batteries. I also ran this circuit using a 20V DC supply but if you do this pin 3 on the TC4432s must be disconnected from ground and the voltage regulator must be replaced with a separate DC source to power the Arduino or the voltage regulator will overheat. Above 30 Volts the circuit will need to be redesigned.

6- NTE in4007 Diodes, These are to prevent any voltage spikes during switching from damaging the MOSFETs.

1- Potentiometer. This isn't really necessary unless you want speed control of the motor. 

The code used to run this circuit is the following:



int PhaseA1 =  5;      // the number of the pin controlling the High side of Phase 1
int PhaseA2 =  6;      // the number of the pin controlling the Low side of Phase 1
int PhaseB1 =  7;      // the number of the pin controlling the High side of Phase 2
int PhaseB2 =  8;      // the number of the pin controlling the Low side of Phase 2
int PhaseC1 =  9;      // the number of the pin controlling the High side of Phase 3
int PhaseC2 =  10;     // the number of the pin controlling the Low side of Phase 3

int ledStateA1 = LOW;             // ledState used to set whether that MOSFET is on or off
int ledStateA2 = LOW;             // LOW side MOSFETS are on with a HIGH
int ledStateB1 = HIGH;            // HIGH side MOSFETS are on with a LOW
int ledStateB2 = HIGH;            // At any given time 3 MOSFETS should be ON, 4 OFF
int ledStateC1 = LOW;             // Each Phase should have one MOSFET which is on
int ledStateC2 = LOW;

int sensorPin = A0;             // Pin which reads output from the Potentiometer
int sensorValue = 0;            // Initial sensor value

// the follow variables is a long because the time, measured in miliseconds,
// will quickly become a bigger number than can be stored in an int.
long previousMillis = 0;        // will store last time a cycle finished was updated
long wavelength = 500;           // wavelength of the output, the read from the potentiometer changes this setting
;

void setup() {
  // set the digital pin as output:
  pinMode(PhaseA1, OUTPUT);
  pinMode(PhaseA2, OUTPUT);
  pinMode(PhaseB1, OUTPUT);
  pinMode(PhaseB2, OUTPUT);
  pinMode(PhaseC1, OUTPUT);
  pinMode(PhaseC2, OUTPUT);
}

void loop()
{
unsigned long currentMillis = millis();      // Records the time at the start of the program
sensorValue = analogRead(sensorPin);         // Takes a read of the output from the potentiometer
if(sensorValue>900){
  PhaseA1 =  5;     // will switch the phases depending on the value read from the potentiometer
  PhaseA2 =  6;     // wswitching the phases will change the direction of rotation of the motor
  PhaseB1 =  7;
  PhaseB2 =  8;
}
else{
  PhaseA1 =  7;      // will switch the phases depending on the value read from the potentiometer
  PhaseA2 =  8;      // wswitching the phases will change the direction of rotation of the motor
  PhaseB1 =  5;
  PhaseB2 =  6;
}

if(sensorValue>900){
  wavelength = 10500-10*sensorValue;  // will change the wavelength depending on the output of the potentiometer
}                                     // changing the wavelength speeds or slows the motor
else{
  wavelength=500+100*sensorValue;    // will change the wavelength depending on the output of the potentiometer,
}                                    // changing the wavelength speeds or slows the motor

if(currentMillis - previousMillis < wavelength/2-wavelength/12 && currentMillis - previousMillis > wavelength/12) {
  ledStateA1=LOW;          // Sets the state for the A phase MOSFETs so the output from the inverter follows the correct waveform
  ledStateA2=LOW;          // Does this by turning on and off the correct MOSFET at the correct time
  digitalWrite(PhaseA1, ledStateA1);
  digitalWrite(PhaseA2, ledStateA2);
}
  else {
  if(currentMillis - previousMillis > wavelength/2+wavelength/12 && currentMillis - previousMillis < wavelength - wavelength/12){
  ledStateA1=HIGH;
  ledStateA2=HIGH;
  digitalWrite(PhaseA1, ledStateA1);
  digitalWrite(PhaseA2, ledStateA2);
  }
else{
  ledStateA1=HIGH;
  ledStateA2=LOW;
  digitalWrite(PhaseA1, ledStateA1);
  digitalWrite(PhaseA2, ledStateA2);
}
  }
if(currentMillis - previousMillis > wavelength/3+wavelength/12 && currentMillis - previousMillis < 5*wavelength/6-wavelength/12  ) {
  ledStateB1=LOW;  // Sets the state for the B phase MOSFETs so the output from the inverter follows the correct waveform
  ledStateB2=LOW;  // Does this by turning on and off the correct MOSFET at the correct time
  digitalWrite(PhaseB1, ledStateB1);
  digitalWrite(PhaseB2, ledStateB2);
}
else{
  if(currentMillis - previousMillis < wavelength/3-wavelength/12 ){
  ledStateB1=HIGH; 
  ledStateB2=HIGH;
  digitalWrite(PhaseB1, ledStateB1);
  digitalWrite(PhaseB2, ledStateB2);
  }
 else{
  if(currentMillis - previousMillis > 5*wavelength/6+wavelength/12){
  ledStateB1=HIGH; 
  ledStateB2=HIGH;
  digitalWrite(PhaseB1, ledStateB1);
  digitalWrite(PhaseB2, ledStateB2);
  }

else{
  ledStateB1=HIGH;
  ledStateB2=LOW;
  digitalWrite(PhaseB1, ledStateB1);
  digitalWrite(PhaseB2, ledStateB2);
}
}
}

if(currentMillis - previousMillis > wavelength/6 + wavelength/12 && currentMillis - previousMillis < 2*wavelength/3-wavelength/12  ) {
  ledStateC1=HIGH;  // Sets the state for the C phase MOSFETs so the output from the inverter follows the correct waveform
  ledStateC2=HIGH;  // Does this by turning on and off the correct MOSFET at the correct time
  digitalWrite(PhaseC1, ledStateC1);
  digitalWrite(PhaseC2, ledStateC2);
}
else{
  if( currentMillis - previousMillis > 2*wavelength/3+wavelength/12) {
  ledStateC1=LOW; 
  ledStateC2=LOW;
  digitalWrite(PhaseC1, ledStateC1);
  digitalWrite(PhaseC2, ledStateC2);
  }
  else{
  if( currentMillis - previousMillis < wavelength/6 - wavelength/12) {
  ledStateC1=LOW; 
  ledStateC2=LOW;
  digitalWrite(PhaseC1, ledStateC1);
  digitalWrite(PhaseC2, ledStateC2);
}
else{
  ledStateC1=HIGH;
  ledStateC2=LOW;
  digitalWrite(PhaseC1, ledStateC1);
  digitalWrite(PhaseC2, ledStateC2);
}
  }
}
if(currentMillis - previousMillis > wavelength){
  previousMillis=currentMillis;  // resets the stored in CurrentMillis before restarting the program
}

}

I Am A

I am really starting to like reddit Ask Me Anything threads. One problem with news is always that it is so second hand. Finally, you have a way to find out information from so many topics directly from the source.

Nobel Prize Winner in Economics.
Guy who visited North Korea.
Russian Mail Order Bride.
Guy with magnets implanted in his fingers.
Time traveler. OK, sometimes this site does have a credibility problem...

DIY Drones

I just ran into the ArduCopter and AeroQuad projects. It really is remarkable just how easy it currently is to construct drones. Sure, these aren't up to the standard of military equipment, but some of these are getting amazingly close. Another few years and the open source movement will have some readily available plans for drones every bit as capable of photographing things at a distance. It would be almost trivial for any nation to hire some decent engineers to piggy back on that to make a true army of them.

Here is an example, a pre-programmed 19km flight of a DIY drone:






I also refuse to believe any UFO story at all now that these things are flying around at night: