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Read more about the article Stripe Authorization In Open Event API Server

Stripe Authorization In Open Event API Server

The Open Event System supports payments through stripe. Stripe is a suite of APIs that powers commerce for businesses of all sizes. This blogpost covers testing of Stripe Authorization Schema and endpoints in the API Server.

The Stripe Authorization class provides the following endpoints:

'/stripe-authorization'
'/stripe-authorization/<int:id>'
'/events/<int:event_id>/stripe-authorization'
'/events/<event_identifier>/stripe-authorization'


In the pull request made for adding documentation and tests, these two endpoints were removed:

'stripe_authorization_list',
'/events/<int:event_id>/stripe-authorization',
'/events/<event_identifier>/stripe-authorization'

This is because each event can have only one stripe authorization, so there can not exist a list of stripe authorization objects related to an event.

The ‘stripe_authorization_list’ endpoint is made POST only. This is because Open Event does not allow individual resources’ list to be accessible. Since, there is no endpoint which returns a list of Stripe Authorizations the StripeAuthorizationList(ResourceList) is removed.

The ResourceDetail class was modified to add a query to support  results from ‘/events/<int:event_id>/stripe-authorization’ endpoint.  suThe view_kwargs for the detail endpoint has to contain the resource id, so event_id from view_kwags is used to get the id for stripe authorization.

stripe_authorization = self.session.query(StripeAuthorization).filter_by(event_id=view_kwargs['event_id']).one()
view_kwargs['id'] = stripe_authorization.id

Writing Test for Documentation

(Tests for the /events/1/stripe-authorization  is described here, for others please refer to links in additional references.)

To test the  /events/1/stripe-authorization endpoint for GET, we first insert a Stripe Authorization object into the database which will then be retrieved by the GET request and then compared with the expected response body from the documentation file.

Since stripe-auth has a required relationship with event class, an event must also exist for strie auth object to be created. The event is also required because the endpoint ‘events/’ expects an event object to exist. The StripeAuthorizationFactory takes care of this with event as a RelatedFactory. So when a StripeAuthorization object is inserted, an event is created first and passed as the required relationship to stripe_list_post endpoint.

The event is related to the stripe object by setting event_id = 1 in the factory.

Adding the pre-test hook for GET:

@hooks.before("StripeAuthorization > Stripe Authorization for an Event > Get Stripe Authorization Details of an Event")
def event_stripe_authorization_get_detail(transaction):
   """
   GET /events/1/stripe-authorization
   :param transaction:
   :return:
   """
   with stash['app'].app_context():
       stripe = StripeAuthorizationFactory()
       db.session.add(stripe)
       db.session.commit()


The expected response for this request can be found here.

Additional References:

Continue ReadingStripe Authorization In Open Event API Server
Read more about the article Handling Errors While Parsing the yaml File in Yaydoc

Handling Errors While Parsing the yaml File in Yaydoc

Yaydoc, our automatic documentation generator uses a yaml file to read a user’s configuration. The internal configuration parser basically converts the yaml file to a python dictionary. Then, it serializes the values of that dictionary using a custom serialization format. From there it associates those values with environment variables which are then passed to bash scripts for various tasks such as deployment, generation, etc.. Some of those environment variables are again passed to another python layer which interacts with sphinx where they are deserialized before use. This whole system works pretty well for our use cases.

Now let’s assume a user adds a yaml file where they have a malformed section in the file. For example, to specify a theme, one needs to add the following to the yaml file.

build:
  theme:
    name: sphinx_fossasia_theme

But our user has the following in their yaml file.

build:
  theme: sphinx_fossasia_theme

Now this will raise an error as we expect a dictionary as a value for the key ‘theme’ but we got a string. Now how do we handle such cases without ignoring the entire file as that would be too much of a penalty for such a small mistake? One approach would have been to wrap each call to connect with a bunch of try-catch but that would render the code unreadable as the initial motivation for implementing the connect method was to abstract the internal implementation so that other contributors who may not be well versed with python can also easily add config options without needing to learn a bunch of python constructs.

So, what we did was that, while merging the dictionary containing default options and the dictionary containing the user preferences, we check whether the default has the same data type as that of the incoming value. If they are, It’s deemed safe to merge. There are certain relaxations though, like if the current type is a list, then the incoming value can be of any time as that can always be converted to a list of a single element. This is required to support the following syntax.

key:
  - value

key: value

The above two blocks are equivalent due to the above-mentioned approach although the type is different.

Now, after this pre-validation step is over we can ensure that the if the assumed type for a key is let’s say a dictionary, then it would be a dictionary. Hence no type errors would be raised like trying to access a dict method for another object, say a string which happened with the earlier implementation. After this, an extra parameter was added to the connect method to which we can now pass a validation function which if returns false, those values would be ignored. Usage of this feature has been implemented to a small level where we validate the links to subprojects and if they look like a valid github repo only then will they be included. Note that their existence is not checked. Only a regex based validation is performed.

It was also important to notify the user about these events when we detect that a specific section is invalid and provide informative and helpful error messages without failing the build. Hence proper error messages were also added which were informative so that the user knows exactly which section is to blame. This is similar to compilers where the error message is crucial to debug a certain piece of code.

Resources

Continue ReadingHandling Errors While Parsing the yaml File in Yaydoc
Read more about the article Uploaded Images History in Phimpme Android

Uploaded Images History in Phimpme Android

In Phimpme Android one core feature is of sharing images to many different platforms. After sharing we usually wants to look in the our past records, where we uploaded what pictures? Which image we uploaded? What time it was? So I added a feature to view the upload history of images. User can go to the Upload history tab, present in the navigation drawer of the app. From there he can browse the repository.

How I added history feature in Phimpme

  • Store the data when User initiate an upload

To get which data uploading is in progress. I am storing its name, date, time and image path. When user approve to upload image from Sharing Activity.

Created a database model

public class UploadHistoryRealmModel extends RealmObject{

   String name;
   String pathname;
   String datetime;

   public String getName() {
       return name;
   }

   public void setName(String name) {
       this.name = name;
   }

   public String getPathname() {
       return pathname;
   }

   public void setPathname(String pathname) {
       this.pathname = pathname;
   }

   public String getDatetime() {
       return datetime;
   }

   public void setDatetime(String datetime) {
       this.datetime = datetime;
   }
}

This is the realm model for storing the name, date, time and image path.

Saving in database

UploadHistoryRealmModel uploadHistory;
uploadHistory = realm.createObject(UploadHistoryRealmModel.class);
uploadHistory.setName(sharableAccountsList.get(position).toString());
uploadHistory.setPathname(saveFilePath);
uploadHistory.setDatetime(new SimpleDateFormat("dd/MM/yyyy HH:mm:ss").format(new Date()));
realm.commitTransaction();

Creating realm object and setting the details in begin and commit Transaction block

  • Added upload history entry in Navigation Drawer

    <LinearLayout
   xmlns:android="http://schemas.android.com/apk/res/android"
   android:id="@+id/ll_drawer_uploadhistory"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   android:background="@drawable/ripple"
   android:clickable="true"
   android:orientation="horizontal">

   <com.mikepenz.iconics.view.IconicsImageView
       android:id="@+id/Drawer_Upload_Icon"
       android:layout_width="@dimen/icon_width_height"
       android:layout_height="@dimen/icon_width_height"
       app:iiv_icon="gmd-file-upload"/>

   <TextView
       android:id="@+id/Drawer_Upload_Item"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="@string/upload_history"
       android:textColor="@color/md_dark_background"
       android:textSize="16sp"/>
</LinearLayout>

It consist of an ImageView and TextView in a horizontal oriented Linear Layout

  • Showing history in Upload History Activity

Added recyclerview in layout.

<android.support.v7.widget.RecyclerView
   android:id="@+id/upload_history_recycler_view"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:layout_below="@id/toolbar">
</android.support.v7.widget.RecyclerView>

Query the database and updated the adapter of Upload History

uploadResults = realm.where(UploadHistoryRealmModel.class);
RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(this);
uploadHistoryRecyclerView.setLayoutManager(layoutManager);
uploadHistoryRecyclerView.setAdapter(uploadHistoryAdapter);

Added the adapter for recycler view and created an Item using Constraint layout.

Resources

Continue ReadingUploaded Images History in Phimpme Android
Read more about the article Implementing the tickets API at the ‘tickets/add-order’ route

Implementing the tickets API at the ‘tickets/add-order’ route

In Open Event Frontend, we have the ‘tickets/add-order’ route for a specific event which facilitates us to add the order based on the tickets that we create at the time of creation of event. The tickets are listed at the ‘tickets/add-order’ route where we can select the tickets required for example, ‘free’, ‘paid’, the payment type and proceed to the ticket buyer’s info page.

This is how we achieved implementing the API:
We use table to show the data to the user, the columns of which are Ticket Type, Price, Quantity, Item Total something like:

So, the workflow to achieve this is as follows:

  • Query the tickets for current event.
  • Have a controller to calculate the ‘Grand Total’ of the individual tickets that the user wants to buy.
  • Show the tickets in our table.

Querying the tickets: Since we are using ember data, we query tickets by the following query in our model method of route.

  model() {
    return this.modelFor('events.view').query('tickets', {});
  }

Thus, the above query shows that we get the current event by actually querying the model for route ‘events.view’ which returns the current event and then query the tickets model so that we get the tickets associated with the current event.

Since there is no UI table support for ember data, we are using a custom table for all the tables in Open Event Frontend and pass the data to it. To render the data in tables, we follow the following approach.
In our controller, we have a columns property as:

columns: [
    {
      propertyName : 'name',
      title        : 'Ticket Type'
    },
    {
      propertyName   : 'price',
      title          : 'Price(US$)',
      disableSorting : true
    },
    {
      propertyName : '',
      title        : 'Quantity',
      template     : 'components/ui-table/cell/cell-input-number'
    },
    {
      propertyName : 'itemTotal',
      title        : 'Item Total'
    }
  ]

The propertyName maps the property of the objects returned from the server i.e in our case, the ‘tickets’. Thus, we pass this skeleton of columns and data from the model to our component so as to render the table in view.

  {{events/events-table columns=columns data=model
    useNumericPagination=true
    showGlobalFilter=true
    showPageSize=true
  }

Also, as seen from the image shown earlier in this blog post, we can see that we also need to calculate the ‘Grand Total’ of the total purchase. Thus, we have a computed property in controller to do this:

  total: computed('model.@each.itemTotal', function() {
    let sum = 0.0;
    this.get('model').forEach(ticket => {
      sum += ticket.get('itemTotal');
    });
    return sum;
  }),

We iterate over the each ‘itemTotal’ in the model and keep on adding it so that the total purchase gets added accordingly. Lastly we show the Grand Total to the user as seen in the image shown earlier in the blog.
Thus, the user can select the tickets and proceed towards the checkout.

Resources:
Ember data official guide
Blog on ember data by Andy Crum

Continue ReadingImplementing the tickets API at the ‘tickets/add-order’ route
Read more about the article Shortcuts in the Phimpme Android Application

Shortcuts in the Phimpme Android Application

The Phimpme Android application comes with a great functionality of capturing moments, editing them, and sharing it with the world using various social media or cloud platforms integrated into the application. Sometimes, the user may want to directly go to a particular section of the application without having to go to the home activity all the time. We have solved this issue using the App shortcuts option which is provided on Android versions greater than 7.0 Nougat. When the user long clicks on the icon of the application, it provides us with multiple options to choose which activity or section we would like to go to as depicted in the screenshot below.

In this post, I will be explaining how we have achieved this functionality in the Phimpme Android application.

Step 1

In the Phimpme app, we have three main sections named Camera, Gallery and Accounts and we have added these three options in the app shortcut menu. To do this, first of all, we need to add a meta data to the main activity in the AndroidManifest.xml file. To do this, search for the activity which contains “android.intent.action.MAIN” and add the following line of code in the activity tag.

<meta-data android:name="android.app.shortcuts"
  android:resource="@xml/shortcuts" />

Step 2

Now after we have configured the manifest file, we need to create shortcuts.xml file in the resources folder which will contain the information about our app shortcuts along with the intent action to go to a particular activity.

After creating the xml file, add the following line of code.

<shortcuts xmlns:tools="http://schemas.android.com/tools"
  xmlns:android="http://schemas.android.com/apk/res/android">

Now after this we have to create a shortcut tag and define the id of our shortcut and should add the icon to it which will be displayed to the user along with the shortcut text as depicted in the screenshot above. This can be done using the following line of code.

android:shortcutId="camera"
android:enabled="true"
android:icon="@drawable/ic_camera_alt_black_24dp"
android:shortcutShortLabel="@string/camera_short"
android:shortcutLongLabel="@string/camera_long"
android:shortcutDisabledMessage="@string/camera_short"

Now after this, we have to define the action which we want to perform when the user clicks on a particular app shortcut. To do this, create an intent tag and add the following lines of code in it.

<intent
  android:action="android.media.action.IMAGE_CAPTURE_SECURE"
  android:targetPackage="org.fossasia.phimpme"
  android:targetClass="org.fossasia.phimpme.opencamera.Camera.CameraActivity" />
<categories android:name="android.intent.category.DEFAULT" />

The above code sets the action type as Image capture and defines the package name of the application. The above code is used to open the Camera activity of the Phimpme Application from the shortcut menu. In the similar fashion as described above, we have implemented the option to open up the Gallery and Accounts section of our application by just modifying the action name of the shortcut.

This is how we have implemented the App shortcut functionality in the Phimpme app. To get the full source code of the Shortcuts.xml file, please refer to the Phimpme Android repository.

Resources

  1. Android Developer’s Guide – App shortcuts – https://developer.android.com/guide/topics/ui/shortcuts.html
  2. GitHub – Google Sample Project to depict the usage of app shortcuts – https://github.com/googlesamples/android-AppShortcuts
  3. Blog – Using app shortcuts in Android 7.0 – http://www.brevitysoftware.com/blog/how-to-use-app-shortcuts-in-android-7-1-nougat/
  4. GitHub – Phimpme Android repository – https://github.com/fossasia/phimpme-android/
Continue ReadingShortcuts in the Phimpme Android Application
Read more about the article Showing Pull Request Build Status in Yaydoc

Showing Pull Request Build Status in Yaydoc

Yaydoc is integrated to various open source projects in FOSSASIA.  We have to make sure that the contributors PR should not break the build. So, I decided to check whether the PR is breaking the build or not. Then, I would notify the status of the build using GitHub status API.

exports.registerHook = function (data, accessToken) {
  return new Promise(function(resolve, reject) {
    var hookurl = 'http://' + process.env.HOSTNAME + '/ci/webhook';
    if (data.sub === true) {
      hookurl += `?sub=true`;
    }
    request({
      url: `https://api.github.com/repos/${data.name}/hooks`,
      headers: {
        'User-Agent': 'Yaydoc',
        'Authorization': 'token ' + crypter.decrypt(accessToken)
      },
      method: 'POST',
      json: {
        name: "web",
        active: true,
        events: [
          "push",
          "pull_request"
        ],
        config: {
          url: hookurl,
          content_type: "json"
        }
      }
    }, function(error, response, body) {
      if (response.statusCode !== 201) {
        console.log(response.statusCode + ': ' + response.statusMessage);
        resolve({status: false, body:body});
      } else {
        resolve({status: true, body: body});
      }
    });
  });
};

I’ll register the webhook, when user registers the repository to yaydoc for push and pull request event. Push event will be for building documentation and hosting the documentation to the GitHub pages. Pull_request event would be for checking the build of the pull request.

github.createStatus(commitId, req.body.repository.full_name, "pending", "Yaydoc is checking your build", repositoryData.accessToken, function(error, data) {
                    if (!error) {
                      var user = req.body.pull_request.head.label.split(":")[0];
                      var targetBranch = req.body.pull_request.head.label.split(":")[1];
                      var gitURL = `https://github.com/${user}/${req.body.repository.name}.git`;
                      var data = {
                        email: "admin@fossasia.org",
                        gitUrl: gitURL,
                        docTheme: "",
                        debug: true,
                        docPath: "",
                        buildStatus: true,
                        targetBranch: targetBranch
                      };
                      generator.executeScript({}, data, function(error, generatedData) {
                        var status, description;
                        if(error) {
                          status = "failure";
                          description = error.message;
                        } else {
                          status = "success";
                          description = generatedData.message;
                        }
                        github.createStatus(commitId, req.body.repository.full_name, status, description, repositoryData.accessToken, function(error, data) {
                          if (error) {
                            console.log(error);
                          } else {
                            console.log(data);
                          }
                       });
                 });
              }
        });

When anyone opens a new PR, GitHub will send  a request to yaydoc webhook. Then, I’ll send the status to GitHub saying that “Yaydoc is checking your build” with status `pending`. After, that I’ll documentation will be generated.Then, I’ll check the exit code. If the exit code is zero,  I’ll send the status `success` otherwise I’ll send `error` status.
Resources:

Continue ReadingShowing Pull Request Build Status in Yaydoc
Read more about the article Using RecyclerView Instead Of ViewPager For Gallery

Using RecyclerView Instead Of ViewPager For Gallery

Phimpme is an Image app that provide camera, editing ,sharing options and a gallery section. The Gallery section allows us to view large number of images that are locally available in the users device. Generally developers used viewpager to swipe the horizontal images although we are also using viewPager but the problem is it is taking more time to load large size images and that disturb the user smooth experience. After so much research I came to new solution. So in this post, I will be explaining how to use recyclerview to view gallery images instead of viewPager.

Let’s get started

Make sure you have Recyclerview support in your dependencies in build.gradle. As recyclerView required an adapter and viewHolder to set data in recyclerView. So I will be explaining about adapter.

ViewHolder for RecyclerView

public static class ViewHolder extends RecyclerView.ViewHolder {
  ImageView imageView;
  LinearLayout linearLayout;

  public ViewHolder(View itemView) {
      super(itemView);
      imageView = new ImageView(context);
      linearLayout = (LinearLayout) itemView.findViewById(R.id.layout);
      WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
      Display display = wm.getDefaultDisplay();
      Point size = new Point();
      display.getSize(size);
      int width = size.x;
      int height = size.y;
      LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
              width, height);
      imageView.setLayoutParams(params);
      imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
      linearLayout.addView(imageView);
  }
}

Right now the imageView is adjusting according to device screen size so that it will be compatible with all devices.

I am passing the width and height in LayoutParams to parent of imageview i.e in our case linearlayout is parentView.

Adapter for RecyclerView

public ImageAdapter(ArrayList<Media> media) {
  this.media = media;
}

@Override
public ImageAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
  View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.unit_image_pager, null, false);

  return new ViewHolder(view);
}

@Override
public void onBindViewHolder(ViewHolder holder, int position) {
  Glide.with(getContext())
          .load(media.get(position).getUri())
          .diskCacheStrategy(DiskCacheStrategy.SOURCE)
          .thumbnail(0.5f)
          .into(holder.imageView);
  holder.imageView.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
          basicCallBack.callBack(0,null);
      }
  });
}

MediaList is an arrray of media that contains the list of images with URI that will help to load images. I am using Glide to load images you can use any library to load images. Adapter helps to load data in recyclerView.

Now set viewPager where you require to scroll images horizontally

@Nullable @BindView(R.id.photos_pager)
RecyclerView mRecylerPager;
mRecylerPager.setLayoutManager(linearLayoutManager);
mRecylerPager.setHasFixedSize(true);
mRecylerPager.setLongClickable(true);

Our recycler view is ready now the most important part is to set things onPageChangeListner. For example : In Phimpme we are getting path of current position image to show in image description so to update the value we are writing that codde in onPageChangeListner and to update the toolbar.

mViewPager.setOnPageChangeListener(new PagerRecyclerView.OnPageChangeListener() {
  @Override
  public void onPageChanged(int oldPosition, int position) {
      getAlbum().setCurrentPhotoIndex(position);
      toolbar.setTitle((position + 1) + " " + getString(R.string.of) + " " + size_all);
      invalidateOptionsMenu();
      pathForDescription = getAlbum().getMedia().get(position).getPath();
  }
});

To scroll to the given position we require to set the position to recyclerView and it can be done by the following code

mViewPager.scrollToPosition(getCurrentPsotion());

This is how I implemented the recyclerView instead of ViewPager to load gallery images faster as compare to ViewPager.

RecyclerView in Phimpme to load gallery Images

Resources:     

 

Continue ReadingUsing RecyclerView Instead Of ViewPager For Gallery
Read more about the article Creation of Icon Pack for Meilix

Creation of Icon Pack for Meilix

An icon theme is a set of icons that have common looks and feel. The user can select the icon theme that they want to use, and all apps use icons from the theme if a particular icon is not available in theme the fallback theme is used .

An icons theme is only a mapping. Given an arrangement of indexes to search for icons in and a theme name it maps from icon name and icon size to an icon filename.

Icon in Meilix are stored in /usr/share/icons/meilix.

We need to create a index.theme file which tells the LXQT desktop where the icons for a particular application or mime type are located

[Icon Theme]
Name=Meilix
DisplayDepth=32
DesktopDefault=48
DesktopSizes=16,22,32,48,64,128,256
ToolbarDefault=22
ToolbarSizes=16,22,32,48
MainToolbarDefault=22
MainToolbarSizes=16,22,32,48
SmallDefault=16
SmallSizes=16,22,32,48
PanelDefault=32
PanelSizes=16,22,32,48,64,128,256
DialogDefault=32
DialogSizes=16,22,32,48,64,128,256

#################################
#   Fallback icon theme to use  #
#################################
Inherits=oxygen

 

After defining the icon theme name and sizes we next define the fallback icon theme to use icons from in case of missing icons so we have chosen Oxygen icon theme which is very similar to Meilix icon theme to have a consistent looks and feel.

We further define the different types of icons with their locations , resolution and type.

Meilix icon theme use four different sizes 16 , 22 , 24 ,32 ,64 and two types scalable for svg icons and fixed for png icons.

[actions/32]
Size=32
Context=Actions
Type=Fixed

[actions/48]
Size=48
Context=Actions
Type=Fixed

#  Apps

[apps/16]
Size=16
Context=Applications
Type=Fixed

[apps/22]
Size=22
Context=Applications
Type=Fixed

 

Meilix Icon pack directory structure

Adding more icons to theme

To append a custom icon to Meilix icon theme xdg-icon-resource can be used. This will resize and copy the icon to /share/icons/meilix. With this method, custom emblems can also be added. Examples:

$ xdg-icon-resource install --size 64 --context --theme meilix emblems meilix-example.png --mode system # add as emblem
$ xdg-icon-resource install --size 64 --theme meilix meilix-example.png --mode system # add as normal icon

Mime type icons

file managers get definitions from /usr/share/mime/ . Calling an icon according to the definition found there and copying it to /share/icons/meilix will cause the file manager to display the custom mime type icon.

Creating a custom icon for text files (*.txt)

# grep txt /usr/share/mime/globs | egrep -o '.+\/[^:]+' | tr '/' '-'
application-x-kate ;# rename your icon according to this output
xdg-icon-resource install --size 64 --context mimetypes --theme meilix application-x-kate.png --mode system

Resources

Continue ReadingCreation of Icon Pack for Meilix
Read more about the article Electrical Experiments with PSLab

Electrical Experiments with PSLab

PSLab has the capability to perform a variety of experiments. The PSLab Android App and the PSLab Desktop App have built-in support for over 70 experiments which are commonly performed by students. In addition to that, it can be used in other experiments conveniently. This blog post is in continuation with the previous two posts regarding performing experiments (links in the reference) and this blog deals with another category of experiments that can be performed using PSLab.

The blog lists experiments which mainly involve the basic circuit elements like resistors, capacitors and inductors. These experiments involve the study of R-C, L-R, L-C and L-C-R circuits. These circuits have properties which make them important in real life applications and this blog attempts to give a rough picture of their importance.

Ohm’s Law, Capacitive Reactance and Inductive Reactance

These experiments involve the study of each of the basic circuit element individually. The current and voltage characteristics of each of the elements is studied.

The definitions of the above are:

Ohm’s Law – This is a law familiar to most. It relates the voltage and current of a purely resistive circuit stating that the voltage and current are proportional to each other and their ratio is a constant called the resistance. In this case, the current and voltage are in the same phase.

Capacitive Reactance – Across a capacitor in an AC circuit, the current and voltage are not in the same phase and the current leads the voltage. For a purely capacitive circuit, this difference is 90o.

Inductive Reactance –  Across an inductor in an AC circuit, the current and voltage are not in the same phase and the current lags behind the voltage. For a purely inductive circuit, this difference is 90o.

The reactance is given for capacitor and inductor is given by 1/wC and wL respectively, where C & L are the values of capacitance and inductance respectively and w is the frequency of the AC signal.

The circuit for the setup is shown below. We need to observe the plot of the input waveform and the plot of the voltage across individual elements to observe the phase shift.

  1. Connect CH1 & GND across the input terminals and CH2 & GND across the terminals of any of the elements.
  2. An external signal can be used or can be generated using the PSLab. Use the PSLab to generate a sinusoidal signal of frequency 1000 Hz. by connecting the ends of PV1 in the circuit.
  3. Observe the waveforms. In case of the resistor, there should be no observable phase lag between the two. In case of the capacitor and inductor, there will be an observable phase difference of 90o.
  4. For the capacitive and inductive circuits, just replace the resistor in the above circuit with capacitor/inductor.

RC Circuits

Drawing their names from their respective calculus functions, the integrator produces a voltage output proportional to the product (multiplication) of the input voltage and time; and the differentiator (not to be confused with differential) produces a voltage output proportional to the input voltage’s rate of change.

RC Integrator circuit

For constructing the RC integrator circuit, connect the circuit as shown in the diagram.

  • Construction of the integrator circuit is fairly simple once the differentiator circuit is done.
  • Interchange the positions of the capacitor and resistor in the above circuit and the circuit for the integrator is complete.
  • Observe the output waveform. Plot both the CH1 and CH2 data simultaneously to compare the waveforms.

RC Differentiator circuit

For constructing the RC differentiator circuit, connect the circuit as shown in the diagram.

  • The values of resistance and capacitance used here are 10k ohm and 0.01uF.
  • Connect the CH1 and GND pins of the board with the input side marked as Vi. Ensure that GND is connected to the GND of the circuit.
  • Similarly, connect CH2 and GND with the corresponding ends of the output side marked as Vo.
  • PSLab can also be used for supplying the input to the circuit. Connect the ends of W1 and GND across Vi. W1 can be used to generate a square wave of 10V peak to peak voltage with a frequency of 500 Hz.
  • Observe the output waveform. Plot both the CH1 and CH2 data simultaneously to compare the waveforms.

RL Circuits

RL Integrator Circuit.

For constructing the RL integrator circuit, connect the circuit as shown in the diagram.

  • Construction of the integrator circuit is fairly simple once the differentiator circuit is done.
  • Interchange the positions of the inductor and resistor in the above circuit and the circuit for the integrator is complete.
  • Observe the output waveform. Plot both the CH1 and CH2 data simultaneously to compare the waveforms.

RL Differentiator Circuit

For constructing the RL differentiator circuit, connect the circuit as shown in the diagram.

  • The values of resistance and inductance used here are 470 ohm and 10mH.
  • Connect the CH1 and GND pins of the board with the input side marked as Vi. Ensure that GND is connected to the GND of the circuit.
  • Similarly, connect CH2 and GND with the corresponding ends of the output side marked as Vo.
  • PSLab can also be used for supplying the input to the circuit. Connect the ends of W1 and GND across Vi. W1 can be used to generate a square wave of 2V peak to peak voltage with a frequency of 5000 Hz.
  • Observe the output waveform. Plot both the CH1 and CH2 data simultaneously to compare the waveforms.

Frequency Response

Frequency Response of an electric or electronics circuit allows us to see exactly how the output gain (known as the magnitude response) and the phase (known as the phase response) changes at a particular single frequency, or over a whole range of different frequencies from 0Hz, (d.c.) to many thousands of megahertz, (MHz) depending upon the design characteristics of the circuit.

Frequency response of a circuit can be studied using different tools like Bode plots, phase plots etc. However, this blog would limit to using simple RC and RL circuits as they can be easily visualised using an oscilloscope.

RC Circuits

  • For observing the frequency response of RC circuits, the circuit can be constructed as shown below.
  • The values of resistance and capacitance used here are 10k ohm and 0.01uF.
  • Connect the CH1 and GND pins of the board with the input side marked as Vi. Ensure that GND is connected to the GND of the circuit.
  • Similarly, connect CH2 and GND with the corresponding ends of the output side marked as Vo.
  • PSLab can also be used for supplying the input to the circuit. Connect the ends of W1 and GND across Vi. W1 can be used to generate a square wave of 10V peak to peak voltage with a frequencies ranging from 100 Hz to 5000 Hz.
  • Switch to the X-Y mode of the oscilloscope and observe the waveform formed.

RL Circuits

  • For observing the frequency response of RL circuits, the circuit can be constructed as shown below.
  • The values of resistance and inductance used here are 470 ohm and 10mH.
  • Connect the CH1 and GND pins of the board with the input side marked as Vi. Ensure that GND is connected to the GND of the circuit.
  • Similarly, connect CH2 and GND with the corresponding ends of the output side marked as Vo.
  • Note: PSLab in this case cannot be used as an AC source as the maximum frequency of waveforms produced by PSLab is limited to 5kHz. However, this experiment would also need frequencies much higher than 5 Hz i.e upto 50 kHz. So, a dedicated function generator is needed. However, the oscilloscope would work just fine.
  • Switch to the X-Y mode of the oscilloscope and observe the waveform formed.

References:

  1. The previous blog on experiments using PSLab focusing in electronics https://blog.fossasia.org/electronics-experiments-with-pslab/
  2. The previous blog on experiments using PSLab involving some general experiments https://blog.fossasia.org/fascinating-experiments-with-pslab/
  3. Read more about differentiators and integrators and their uses https://www.allaboutcircuits.com/textbook/semiconductors/chpt-8/differentiator-integrator-circuits/
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