The Engineering Projects

Control Stepper Motor with Raspberry Pi 4 using Python

Hello friends, I hope you all are having fun. Welcome to the 10th tutorial of our Raspberry Pi programming course. In the last chapter, PWM was utilized to regulate the DC motor's speed and direction with a motor driver L293D. In this chapter, we'll advance our skills with PWM and use it to control a stepper motor using the same motor driver L293D.

Here's the video demonstration of this project:

Let's get started:

Components Required

Here's the list of components, which we will use to control the speed and direction of Raspberry Pi 4:

• Raspberry Pi 4.
  
• Stepper Motor.
• Motor Driver IC(L293D).
• Jumper wires.
• 9V Battery.
• Breadboard.

The Raspberry Pi with desktop is required for this project. An SSH connection can be made, or the RPi can be shown on an LCD screen with a keyboard, and mouse. (We discussed this in previous chapters)

What is Stepper Motor?

• A stepper motor(step motor or stepping motor) is an asynchronous, brushless DC motor having electromagnets(stator) to rotate the rotor in a number of equal steps.

• The Stepper motor gives precise movement and its precision increases with the increase in electromagnets used.
• The Stepper motor has normally 4 or 6 wires to control the motion.
• The electromagnets are turned ON and OFF in a sequence in order to make the rotor rotate.
• Stepper motors are used in applications where high torque at low speed is required.
• Because of its precise & accurate movement, its normally used in open-loop projects.
  

Stepper Motor Working Principle

• The below image shows the internal structure of a simple stepper motor, I have designed it for explaining the stepper working.
  

• As you can see in the above figure, it has a rotor in the center surrounded by 4 pairs of stator coils(electromagnets).
• When current passes through this stator coil, a magnetic field is generated around it.
• This magnetic field attracts the rotor towards it.
• In the first figure of the below image, pair A stator coil got energized and aligned the rotor.

• In the second figure, the coil A pair got de-energized, while the coil B pair got energized and the rotor aligned itself with pair B by taking a rotation of 60 degrees.
• In the third figure, the coil B pair got de-energized, while the coil C pair got energized and the rotor now aligned with coil C and thus covered another 60 degrees.
• That's how the rotor completes its rotations in the stepper motor.
  
• This switching of coils is carried out in nanoseconds.
  

L293D Motor Driver IC

We will use an L293D motor driver to control the direction and speed of the stepper motor. In our last lecture, we controlled the DC motor with the same driver i.e. L293D and I explained it's working & why we use it? in detail there. So, please check that tutorial out, if you are new to this motor driver.

• L293D Pinout is shown in the below figure:
  

• In the last lecture, we discussed that 2 DC motors can be controlled by a single L293D chip at the same time because a normal DC motor has 2 pins in total.
• But Stepper motors have either 4 or 6 pins to control their rotation.
• So, we can control only 1 Stepper Motor from a single chip of L293D.
• Four controlling pins of stepper motors are connected to the Output pins of L293D.
  

Stepper Motor with RPi4 Circuit Diagram

The below figure shows the circuit diagram of Stepper motor interfacing with Raspberry Pi4:

• As you can see in the above figure, we have used all 4 input pins of L293D to control a single stepper motor.
• The rest of the circuit is the same as that of the DC Motor Control i.e. Vss is provided with 3.3V, Vs is connected to the +9V from the battery, GND of battery & Rpi4 is connected to the GND of L293D motor driver.
• Moreover, both the Enable Pins of L293D are connected to Rpi4 GPIOs.
  

.

The wire mappings from my Raspberry Pi 4 to a stepper motor driver are shown in the below diagrams:

 

Python Code for Stepper Control with RPi4

Open Thonny text editor. Importing the GPIO and time modules is the first step. Make sure you type the GPIO module's name exactly, case-sensitively, on the first line.

• Set the mode of GPIO pins to the board:

• Set up the control pins, which are going to connect to the Input pins of L293D:
  

• Use a for loop to set all the pins as output:

• Create a sequence list, 1 being high and 0 being low.
• As you can see in the below code, this sequence is turning ON the consecutive coils.
  

• Take user input for the number of rotations:
  

• Substitute the input value for the rotation and place a for loop to move the stepper motor in steps using this code.

• Finally, clean up the pins after the code execution is complete:

Conclusion

Congratulations! You have made it to the end of this tutorial. We have seen how PWM is used with a motor driver IC to control a stepper motor. We have also seen different stepper motor control techniques, how to set up our circuit diagram, and how to write a Python program that controls the steps for our motor. In the next tutorial, we will have a look at how to control a Servo Motor with Raspberry Pi 4 using Python. Till then, take care and have fun !!!

How to Protect Your Servers from Natural Disasters?

According to NASA, areas in the north of the U.S will experience higher rainfall, increasingly extreme hurricanes, and sea levels will rise by about eight feet by 2100. With climate change, extreme weather events have become much more frequent, and their magnitude has increased globally. This scenario presents a significant risk to server rooms and data centers by increasing the likelihood of water and fire damage.

Can Your Data Center and Business Recover After a Natural Disaster?

Data loss or inaccessibility after a natural disaster is a significant concern. After Hurricane Sandy in 2012, data centers in Manhattan had to extract water from the generator rooms and restore switchgear to become operational. In the U.K., flooding in Leeds caused immense water damage to a Vodafone facility that it had to close for several days.

According to the Insurance Information Institute, over 25% of businesses never reopen after an extreme weather event. Fortunately, preventing disaster-related downtime is possible through proper monitoring systems and a disaster recovery plan.

Tips To Protect Your Servers From Natural Disasters

Knowing which natural disasters to expect based on your server room and data center location can make the difference. Here’s how to protect your facility from the most common natural disasters.

1. Fire

Whether you wish to set up a new server room or bolster an existing one, here are several tips to fireproof the area and prevent data loss.

Include fire-resistant materials during construction

Three levels of fire protection exist.

• Building level. Your data center should install systems that will safeguard the entire structure. These include extinguishers, fire sprinklers, and secondary protection like firewalls and floor assemblies, which ought to slow down the fire and prevent it from spreading.
• Room level. If your data center is in the U.S., you are probably aware of National Fire Protection Association (NFPA) standards 75 and 76 which help safeguard tech equipment and telecommunication facilities.
• Rack level. This protection level focuses on the server room and equipment inside.

Install suppression systems

Your country will have specific fire suppression system standards. Typically, data centers choose between two sprinkler systems, wet pipes or pre-engineered. The former will have water in its pipes which automatically flow once you trigger the fire alarm. The only con is that wet pipe sprinklers can suffer leakage, damaging the servers.

On the other hand, pre-engineered sprinklers require two-point activation to disperse water. It’s also the preferred choice for many businesses. Depending on the model, some pre-action sprinklers operate on a quadrant level. Therefore, they will only disperse water in that specific area once activated. Like the wet piping, this system poses a risk of water damage, so you should consider installing a gaseous system instead.

Gaseous systems employ a clean agent or inert gas. The latter uses nitrogen and argon to reduce the oxygen in the server room, thereby putting out the fire. Note that you will need to install sound muffling equipment to prevent damage to hard drives.

Clean agent systems like FM-200 are a better option. They eliminate the fire through absorption. Also, they have low emissions and are non-conductive and non-corrosive, making them environmentally friendly.

Schedule regular inspections

Regular inspections ensure you stay compliant. Typically, the expert will confirm that the suppression systems and fire alarm is in good condition. More importantly, they’ll inspect whether the fire protection interface meets the sensitivity prerequisites.

2. Flooding

Flooding can cause grave consequences from short circuits to corrosion. Besides rainfall-related flooding of a server room, several water sources can threaten the data security of your server room. These include:

• Air conditioning units leakage
• Condensation resulting from increased humidity
• Groundwater leakage

Before taking action, you’ll need to perform a risk assessment to determine areas that require water leakage detection.

Install leakage monitoring systems

Monitoring systems are the simplest way to detect water leakage to prevent water damage. Various systems are available in the market. Typically, businesses choose between zone leak and distance-read leak monitoring systems. Zone leak detection is the ideal choice for small server rooms. In comparison, distance-read monitoring systems are suitable for large server rooms precisely because they can pinpoint the exact location

Which system should you choose? We recommend a centralized one that detects water leakage and humidity, motion, plus ambient temperature. A vital aspect of this system is a distribution list for fire alerts. Emails, SNMP, and SMS are excellent circulation, monitoring, and reporting channels.

Set up cable runs

Different leak detection cable runs range between two and fifty meters. These cables can go under power cables. And if any water starts leaking from the air conditioning systems or backup drains, these cables can detect with pinpoint precision and let you know the exact floor tile.

In case of leakage, swift action is paramount to save equipment and other items in the server room. An experienced water damage remediation company will perform immediate water extraction and contents restoration.

3. Earthquakes

Earthquakes impact the most damage to server rooms and data centers than any other natural disaster. Approximately 500,000 incidents occur globally. The double aftermath of IT equipment damage and downtime can result in business closure. And although the world is yet to come up with tech that would predict the exact time and location of an earthquake, there are seismic planning activities you can do to protect your servers.

Rigid bolting

Rigid bolting is the most common server protection approach. Doing so secures equipment racks to the floor. And as a result, it prevents the server racks from vibrating during an earthquake. While you may want to perform cabinet bolting instead, this method only protects the employees, and servers can only escape damage if it’s a mild earthquake.

Base isolation technology

Base isolation technology is a more effective earthquake protection method. It works by significantly decreasing the path through which vibrations pass. As a consequence, it channels the seismic motions away from your servers. If your data center is located in an earthquake-prone area, base isolation systems ensure your business achieves tier 4 classification, i.e., zero disruption to the critical load.

4. Hurricanes

Preventing power outages in your server room is perhaps the primary focus when preparing for hurricanes.

Here’s what you can do.

• Install uninterrupted power supply(UPS). As a preventive measure, raise the UPS to prevent contact with water (limits the risk of sparking).
• Have a dedicated support team available 24/7 to ensure you receive alerts in real-time.
• Have standby generators. UPS is only ideal for a short-term outage. Generators might come in handy if the blackout is a longer-term occurrence. Ensure you enclose the structure with steel to offer added protection from the weather elements.
• Implement the 3-2-1 rule. The 3-2-1 is a backup strategy that entails having three data copies and transferring two to 2 storage media, e.g., cloud and disk, to a remote location. Ensure to schedule test backup regularly.

Natural disasters have proven to be a significant threat to data centers. For some businesses, the equipment damage is beyond repair, and for others, the downtime results in loss of customer trust. Having robust monitoring and report systems can mitigate disaster-related damage, thereby ensuring business continuity. Preparedness always pays off. Ultimately, leaving your servers unprotected with such high stakes would be a miscalculation.