user1335: I'm wondering if using the Adafruit 16-Channel 12-bit PWM/Servo Shield is it possible to switch relays, such as use that shield as a multiplexer and use digital output without PWM.
Is it possible? example code?

user2881: That will work. Just make sure you are not using Servo part of the library, but only the PWM part, and set the duty cycle to 100%. The relay should still work, even if the duty cycle is slightly lower, as the magnetic field takes a bit of time to collapse. Just make sure you don't forget to add a (flyback) diode to the relay. 
Looking at the datasheet I think you need to use the following code
pwm.setPWMFreq(1000);//put this in setup()
...
// enable relay at channel 15
pwm.setPWM(15, 1, 0);
...
// disable relay at channel 15
pwm.setPWM(15, 1, 1);


1335: <p>I'm wondering if using the <a href="https://www.adafruit.com/products/1411" rel="nofollow">Adafruit 16-Channel 12-bit PWM/Servo Shield</a> is it possible to switch relays, such as use that shield as a multiplexer and use digital output without PWM.</p>

<p>Is it possible? example code?</p>
 2881: <p>That will work. Just make sure you are not using Servo part of the library, but only the PWM part, and set the duty cycle to 100%. The relay should still work, even if the duty cycle is slightly lower, as the magnetic field takes a bit of time to collapse. Just make sure you don't forget to add a (flyback) diode to the relay. </p>

<p>Looking at the datasheet I think you need to use the following code</p>

<pre><code>pwm.setPWMFreq(1000);//put this in setup()
...
// enable relay at channel 15
pwm.setPWM(15, 1, 0);
...
// disable relay at channel 15
pwm.setPWM(15, 1, 1);
</code></pre>
