GPIO as VCC and GND

To connect a device directly to arduino, we can set the digital pins to HIGH and LOW, which will act as VCC and GND

Connecting DHT22 directly

PULL UP resistance connected from the data line can be done internally by arduino.

To do this, set the data pin to INPUT_PULLUP pin mode

Sktech

#include "DHT.h"

#define DHTPIN 4
#define GNDPIN 3
#define VCCPIN 5

#define DHTTYPE DHT22 

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  Serial.println(F("DHTxx test!"));

  pinMode(DHTPIN, INPUT_PULLUP);
  pinMode(GNDPIN, OUTPUT);
  pinMode(VCCPIN, OUTPUT);

  digitalWrite(GNDPIN, LOW);
  digitalWrite(VCCPIN, HIGH);

  // THIS DOES NOT WORK UNLESS VALUE is 255
  // TO make HIGH = 3.3V, usw PWM pin for VCC
  // value = (255/5)*3.3
  // analogWrite(VCCPIN, 170);

  dht.begin();
}

void loop() {

    // SAME AS BEFORE
}

Precautions!!

The GPIO pins are connected to the MC, unlike the actual VCC pin. Hence take the following precautions,

1) Make sure that your breakout can operate at 5V

2) The current flowing through the circuit should be less than 20mA. For this, check the device current rating, which tells how much current will be drawn maximum at the operating voltage(If you supply 5V to a device which can operate at 3.3V, it will draw more current)

3) Connect the circuit in the breadboard first to double check if the right current is flowing.

Accelerometer ADXL335

Accelerometer is used to measure the orientation of the device. It is an analog device with three analog pins for measuring x, y and z axis orientations

1) It is more common to use an accelerometer fixed on board to the device.

2) But ADXL335 works at 3.3V.

3) Make sure that the breakout you purchase has a voltage regulator in it

Adafruit version has a voltage regulator, but Sparkfun version does not

How does a voltage adapter look?

A voltage adapter will look like the small chip right next to barrel plug on arduino board