HARDLY, SCARCELY, BARELY, NO SOONER

We use as soon as to show that something happens immediately, i.e. ‘at the very moment another action is completed’, or ‘shortly after another action is completed’.

• I’ll call you as soon as I arrive.
  [= ‘I will arrive and then I’ll call you immediately.’]
• As soon as I have the information, I’ll tell you.
  [= ‘I’ll get the information and then I’ll tell you immediately.’]

As soon as I will . . .

We do not use will with as soon as when speaking about the future:

• I’m going to have a shower as soon as I will get home. 
• He will be back tomorrow; I’ll give him the message as soon as I will see him. 

Position of as soon as in a sentence

As soon as comes at the beginning of a subordinate clause. We can begin our sentence with either the subordinate clause or the main clause – the meaning is the same. Look at this example:

• As soon as we got out the car, it started raining.
  [subordinate clause]                  [main clause]

• It started raining as soon as we got out the car.[main clause]         [subordinate clause]

Which tenses do we use with as soon as?

Tenses used with as soon as

We use the present simple with as soon as when we speak about repeated actions. As soon as he wakes up, he checks his phone for messages.

We use the present simple with as soon as when we speak about the future. We do not use will. I'll go to the shops as soon as it stops raining. as soon as it will stop

We can also use the present perfect with as soon as when we speak about the future. The meaning is the same. I'll go to the shops as soon as it has stopped / as soon as it stops raining.

We use the past simple with as soon as when we speak about the past. We can also use the past perfect. The meaning is the same. They restarted the tennis match as soon as the rain stopped. They restarted the tennis match as soon as the rain had stopped.

http://speakspeak.com/resources/english-grammar-rules/conjunctions/as-soon-as

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No sooner … than, Hardly…when

AUGUST 20, 2013 - 

If the second event occurs immediately after the first, we can express that idea using the structure no sooner … than.

Note that in this structure no sooner introduces the event that occurred first.

• No sooner had I arrived at the station than the train came. (= I came first and the train arrived right after me.)
• No sooner had we heard the noise than we rushed to the spot.
• No sooner had she finished one project than she started working on the next.
• No sooner had I closed my eyes than I fell asleep.

Note that did is also possible in this structure.

• No sooner did I arrive at the station than the train came.
• No sooner did we hear the noise than we rushed to the spot.

Notes

When we begin a sentence with a negative word, we put the auxiliary verb before the subject.

• No sooner had she read the letter than she started crying. (NOT No sooner she read the letter than she started crying.)

Note that when and before are not possible in this structure.

Hardly and scarcely

It is possible to express the same idea using hardly/scarcely…when.

• Hardly had I reached the station when the train came.
• Scarcely had I reached the station when the train arrived.

As soon as

This structure is also used with the same meaning.

• As soon as I arrived at the station, the train came.
• As soon as she finished one project, she started working on the next.

http://www.englishgrammar.org/sooner-hardlywhen/

http://www.grammaring.com/hardly-scarcely-barely-no-sooner