Using Relay Boards to Control Linear Actuators

Written by: admin@makezilla

In this Instructable, we'll be learning how to use the relay boards to control linear actuators. All of the relays act the same, the only difference is how many are on the board.

Four relays can be combined with the MegaMoto control board to allow the board to control 2 actuators. The MegaMoto gives speed signals to the actuators, the relays choose the direction.

Two relays can also be used to create an H bridge to drive a motor, up to 30V, at 10A.

These relays use the input current to activate a electromagnet. The electromagnet pulls the switch from one position to the next, which allows the higher power currents on the other side of the relay to flow. In this way, a small powered circuit (Arduino control side) can control a large power circuit (actuator control).

For this project, you will need:

- 1x Arduino Uno

- 1x Relay board

- 1x MegaMoto motor controller

- M/F jumper wires

Step 1: Wiring the Board Basics

On the control side, the relays have a GND pin, followed by all the INx pins (1-8), and a Vcc pin. The relays take a fair bit of power to hold active, around 70 mA each, so it is best to use a dedicated 5v supply for this. The Arduino will struggle to provide enough power if all relays are active at once.

The amount of power the Arduino can deliver is dependent on how the Ardunio is being powered. A safe assumption is that it can provide a few hundred milliamps, which means its can power 2 relays easily, 4 relays maybe, but 8 relays definitely needs an external supply.

Control Side:

1) Connect the 5V supply to the Vcc and GND pins on the relay board.

2) Connect the INx pin to the Arduino pin that you want to use to activate the relay

- The 8 relay board have diodes beside the relays (D1, D2, D3...) that tell you which IN pin corresponds to which relay. The 2 relay board, the IN1 is the top relay, the IN2 is the bottom relay (top and bottom based on the GND, INx, and Vcc pins being on the left). The 4 relay board is clearly labeled.

3) The relays are activated when the corresponding INx pin is connected to GND

Relay Side:

1) The center screw terminal is the common (COM) connection. The top connection is the Normally Closed (NC) connection, and the bottom is the Normally Open (NO) connection.

2) If you have no connections to the INx pins, the relay will be connected between NC and COM. If you have 5V applied to the INx pin, the relay will be connected between NC and COM. Only if you connect the INx pin to GND, will the relay switch to connect NO and COM.

This step just covered basic wiring, we will go into more specific projects in other steps.