MIKROE-3319 Opto 3 Click Mikroe MIKROE-3319 Opto 3 Click is a relay Click board™ equipped with two pairs of optically isolated Solid-State Relays (SSR). One pair of SSRs provides reinforced galvanic isolation for the external signals that drive the microcontroller (MCU) pins. The second pair allows the host MCU to drive some external equipment. Thanks to a very low on resistance, this allows up to 40V between the SSR contacts in the OFF state and currents up to 2A while in the ON state. The Mikroe Opto 3 click can be used in applications that require reinforced galvanic isolation for both their input and output stages.