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SMD NPN Relay Module Interface Board

$7.46

Connect your Raspberry Pi B+ (and newer) microcomputer to relay module boards from SainSmart and others. Uses SMD NPN transistor to drive “active-low” relay module inputs.

49 in stock (can be backordered)

SKU: SDR-RD-SMDNPN-015-2022-02 Categories: , Tags: , , , , ,

Description

Drives relay board inputs from microprocessor outputs. Intended for use with “active-low” relay boards such as the SainSmart 8-channel relay module. Uses SMD NPN transistor to convert a logic high value to a logic low value with sufficient current sinking ability to drive relay module inputs. Transistors help isolate and protect microprocessor I/O pins. Board edge input connector designed to mate straight with Raspberry Pi (B+) GPIO connector pins 3-21 (odd side). Output connector designed to mate straight with 8-channel relay modules having 10-pin GND/Input/PWR connectors. The board can be integrated with a wide variety of microprocessors, it’s just designed to connect directly to the Raspberry Pi with the standard 40-pin GPIO connector. Version 1.5 of the board uses the MMBT2222ALT1G transistor. When the board is used in conjunction with the Raspberry Pi and one of the SainSmart active-low relay modules, less than 1.5 mA is required to control a single relay.

A logic high signal on an input pin (J1) will drive the associated transistor to saturation, which will connect the relay module input pin (J2) to ground. Since the relay module is active-low, this turns on the associated relay. Check the datasheet for the installed transistor to make sure you are able to maintain a logic low signal level (GND) on the J1 input pins of this board – the saturation voltage level of some transistors in fairly low.

J1 connector is mapped to the Raspberry Pi B+ 40-pin GPIO connector, pins 3-21 so that a single row IDC-style plug can connect directly to the relay module interface board, which keeps cable runs simple and clean.

J2 connector is mapped to the primary input connector of relay module such as the 8-channel SainSmart board, which allows for a simple (flat) ribbon-cable connection between boards.

J3 connector provides +5VDC to power the relay module. The +5VDC power supply must be able to provide sufficient current to activate the maximum number of relays that you intend to use at the same time. The relays that have been used on the SainSmart boards in the past typically require ~70-72 mA per relay to energize the coils. So, to power all eight relays at the same time on an 8-channel board would require approximately 8*72 mA = 576 mA. Ground must be shared between the controlling microprocessor, the SMD NPN Relay Module Interface Board, and the relay module itself.

Note that when using SainSmart devices such as the 8-Channel 5V Relay Module, there is typically a 3-pin jumper block on the relay module board that can be used  in one of two configurations: 1) connecting VCC to JD-VCC through a jumper to route power from the VCC supply to the relays so that a single power source can drive the relay inputs and supply power to energize the relay coils, or 2) connecting a separate power supply to the JD-VCC and GND pins so that the control signals driving the relay inputs are fully isolated from the power supply used to energize the relay coils.

3D Model

     

Warning

This product involves the use of electrical power. Care must be taken to safeguard against personal injury (shock or electrocution) and the risk of fire. Make sure you are experienced with handling electrical power and know how to properly connect power cables, connectors, supplies, and interconnected equipment. Double-check the polarity of all power-related connectors before applying power.

Resources

3D Model

Schematic

SainSmart 8-Channel Relay Module Schematic

RoHS Compliant

Additional information

Weight 0.25 lbs
Dimensions 1.77 × 1.5 × 0.5 in
Manufacturing

Layers : 2, Finished Copper: 1 oz, Material: Normal FR-4 Board TG 170-180, Thickness: 1.6 mm, Surface Finish: Immersion gold, Via Process: Tenting Vias

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