Introduction: Arduino No DAC SINEWAVE
/* RESISTIVE LADDER DAC OUTPUT
THIS WILL PRODUCE A SINEWAVE Connect a 1 Meg resistor to each pin. Connect all the resistors together. At the common point you will measure a SINE WAVE. With an oscilloscope. To create a usefull output a high impedance amplifier is required. */
void setup() { pinMode(2,OUTPUT); pinMode(3,OUTPUT); pinMode(4,OUTPUT); pinMode(5,OUTPUT); pinMode(6,OUTPUT); pinMode(7,OUTPUT); pinMode(8,OUTPUT); pinMode(9,OUTPUT); pinMode(10,OUTPUT); }
void loop() { // Call the Max Frequency loop 10,000 times for ( unsigned int lt=0; lt <= 10000; lt++){ // lt = loop time MaxFrequency(); } delay(200); // Max frequency loop END //Call the LOWER FREQUENCY loop 10,000 times for ( unsigned int LFlt=0; LFlt <= 10000; LFlt++){ //LFlt = Lower Frequency loop time Frequency(10); // 10 delayMicroseconds } delay(200); //Call the LOWER FREQUENCY loop 10,000 times with a longer delay between steps for ( unsigned int LFlt=0; LFlt <= 10000; LFlt++){ //LFlt = Lower Frequency loop time Frequency(100); // 100 delayMicroseconds } delay(200); // Lower Frequency END /* Uncomment this block to enable sweep // Call the Frequency function 200 times the loop time is much longer so less loops for (unsigned int St=0; St <= 200; St ++) // ST = Sweep time { for (int F=1; F <= 30; F = F + 1) // F = Delay Longer delay = lower frequency { Frequency(F); // Pass F as TIME to Frequency function } for (int F=50; F >= 1; F = F - 1){ Frequency(F); } delay(200); } // Sweep Frequency LOOP END */ // Uncoment to enable sweep }
void MaxFrequency() { for (int UP=2; UP <= 10; UP++) // Count UP pins 2 - 10 Change or add pins here { digitalWrite(UP, HIGH); } for (int DOWN=10; DOWN >= 2; DOWN--) // Count Down pins 10 - 2 Change or add pins here { digitalWrite(DOWN, LOW); } }
void Frequency(int TIME) // TIME = Delay time { for (int UP=2; UP <= 10; UP++) // Count UP pins 2 - 10 Change or add pins here { digitalWrite(UP, HIGH); delayMicroseconds(TIME); } for (int DOWN=10; DOWN >= 2; DOWN--) // Count Down pins 10 - 2 Change or add pins here { digitalWrite(DOWN, LOW); delayMicroseconds(TIME);
} delayMicroseconds(10); // Twiddle this for oscilloscope sync }
Step 1: Read Me
Arduino-No-DAC-SINWAVE-
Output a sine wave with just resistors on your Arduino If you want a sine wave out you do not need a DAC . Just attach a resistive array to a set of pins . I used a bus terminator. Eight 1 meg ohm resistors tied together . Each pin provides additional current to the common point. By creating a loop of count up , count down nested loops you get 1-8 then 8-1 . Using an oscilloscope you will see a sine wave. This method will provide almost no current . A high impedance amplifier will be required to make the output usefull. At full speed the rise and fall time will smooth the output . As you add delay between each step you lower the frequency but see a more stepwise waveform. The included code will demonstrate full speed and then a lower speed. I have also included a swept wave that adds delay then subtracts delay. I will comment out the sweep to make testing easier. The max frequency will depend on the system clock. I know a faster method is possible but this is easy to understand.
