Let's also remember that it takes the servo motor about 0.1 second to move through 30 degrees. When the program then determines that the input data has fallen back below this threshold (indicating the start of a non-R interval), it sends an instruction telling the servo motor to move the fan back. When the program determines that the input data has risen above this threshold, it will send a rotate instruction to the servo motor, causing the fan to move. In our program, we will set the constant R_HEIGHT equal to this threshold. We will consider that values at or above a certain threshold correspond to an R-interval. The sensor output feeds into the A/D converter in the GR-SAKURA's microcontroller. Let's call the peaks 'R intervals', and the troughs 'non-R intervals.'Īnd let's write the program so that the servo motor turns 30 degrees when an R interval occurs, and then returns when the subsequent non-R interval occurs.įigure 1: Heartbeat Data Normal (above) and Excited (below) In both cases, the sensor shows fairly long intervals (troughs) of low voltage, punctuated by briefer periods (peaks) of high voltage. The upper signal is from a normal heartbeat the lower signal is from a more excited heartbeat. Now let's see what our sensor's output looks like (Figure 1).

Note that the motor's specifications tell us that the motor takes 0.1 second to move through this distance.

To avoid overstressing our servo motor, we will use an angle of 30 degrees. We want the motor to drive the fan through one stroke for each heartbeat.įor each fan stroke, we want the fan to move to a preset angle (displacement) and then return.

Specifically, we need a program that detects the information coming from the heartbeat sensor, and drives the servo motor accordingly. In this final session, we will create a program to control this hardware. In our previous session, we completed our hardware assembly.

Free sakura preset banks