Web Site: www.parallax.com Office: (916) 624-8333 Forums: forums.parallax.com Fax: (916) 624-8003 Sales: sales parallax.com Sales: (888) 512-1024 Technical: support parallax.com Tech Support: (888) 997-8267 Single Relay Board ( 27115) The Single Relay Board can be used to turn lights, fans and other devices on/off while keeping them isolated from your microcontroller. The Single Relay Board allows you to control high-power devices (up to 10 A) via the on-board relay. Control of the relay is provided via a 1x3 header friendly to servo cables and convenient connection to many development boards, such as the Board of Education, Propeller Board of Education, Professional Development Board and Propeller Professional Development Board. Features Control high-power devices up to 10 A Provides isolation between microcontroller and device being controlled Screw terminals for relay connections 3-pin servo-style header for power/signal interface LED indicator Specifications Power Requirements: 5 VDC ~85 mA (Relay Power), 3.3-5 VDC (input signal) Communication Interface: Logic High/Low (3.3-5 VDC) Operating temperature: -13 to +158 F (-25 to +70 C) Dimensions: 1.57 x 1.06 x 0.71 in (4.0 x 2.7 x 1.8 cm) Application Ideas 120 VAC brushless fan/lighting control 12 VDC automotive applications Copyright Parallax Inc. Single Relay Board ( 27115) v1.0 5/1/2013 Page 1 of 4 Precautions As with any device capable of switching high voltage, precautions should always be taken to avoid damage and/or injury. The following precautions are recommended in addition to any precautions by the manufacturer of any equipment connected to this device. Always disconnect main power when connecting circuits to the Single Relay Board. When using high-power circuits, mount the Single Relay Board inside a suitable enclosure or electrical panel using standoffs. The board should not be able to move. Secure all electrical connections to the board so they cannot move provide strain relief for any wires extending outside the enclosure. Fuse any incoming voltage rails that are to be switched by the relay, prior to entering the Single Relay Board terminal block. Always be sure any incoming voltage rails are powered off prior to connecting them to the Single Relay Board. Observe Max Switching Current 10 A 250 VAC / 30 VDC. While mechanical relays provide electrical isolation from control circuits, it is possible for EMF generated by high-power devices to affect the control circuits. This is especially true if the control wires and/or power leads are longer than 6 inches (~15 cm). Always try to keep wires as short as possible and avoid running high-power leads near or across control lines. Quick-Start Circuit The Single Relay Board has an on-board transistor that switches the relay coil on/off. Diode protection of back-EMF is provided via an on-board diode. Essentially youre providing a common ground, relay supply voltage of 5 VDC and a signal input to activate the relay via the transistor. Figure 1: Connection Example In the example in Figure 1 the relay is switching a 120 VAC load, such as a lamp or brushless fan. Notice the fuse in the example is 5 A, not 10 A. The fuse should be chosen according to the load, not the max current of the relay. You want the fuse to blow when the device draws more current than it is supposed to. Notice on the input that the S input connects to P0 of a BASIC Stamp Module, Propeller chip or any I/O pin from any 3.3 V or 5 V microcontroller. The order of the 3-pin header makes it compatible with the servo header connections on many Parallax development boards. You could also use pluggable wires to makes these connections. Copyright Parallax Inc. Single Relay Board ( 27115) v1.0 5/1/2013 Page 2 of 4