Was waveform F captured with the scope ground lead still connected to the DC GND?

ak

 

The spike has infinite slope. So if you differentiate IT the result is also a spike of infinite slope. There's little difference in infinities

so how did it turn into a sine wave in the circuit here

thanks for ur help everyone but i'm actually stuk with this circuit
View attachment 185254 View attachment 185255 what i can't understand is how did waveform E turn into waveform F ? how could a spike wave like E turn into a sine wave like F ?

 

Here is a typical case of 101 Q & A that is nothing but a red herring.

Now that we know the real context, you can all ignore the first 20 replies.

The spike is a trigger that turns on the SCR.
The signal that is noted as F is not a spike turning into a sine wave signal.
F is the fullwave rectified AC line frequency when the SCR is turned on.

 

F is the fullwave rectified AC line frequency when the SCR is turned on.

but how ? it is not coming out of the mains it is com8ng form the pulse transformer ? the waveform passing through the scr is supposed to be a sine wave that's right but how is this changed to be a sine wave too ?
and i wasn't asking for this circuit only . i realy wanted to know if a pulse can turn int a sine wave

 

but how ? it is not coming out of the mains it is com8ng form the pulse transformer ? the waveform passing through the scr is supposed to be a sine wave that's right but how is this changed to be a sine wave too ?
and i wasn't asking for this circuit only . i realy wanted to know if a pulse can turn int a sine wave

Ok, understood.

The SCR is fed a fullwave rectified signal from the AC mains supply.
The secondary winding of the transformer is fed from the cathode of the SCR. It sees the same fullwave rectified signal after the SCR has been triggered.

 

Back to the transformation of a pulse into a sine wave:

An infinitely narrow pulse is called a delta function. The frequency spectrum of a delta function shows infinite frequencies, that is, it contains all frequencies from 0Hz to infinity.

In theory, you can extra any frequency you desire from an infinite spectrum. In practice, what you have is a finely tuned resonant circuit. Any energy input into the circuit will cause it to "ring" or oscillate at the resonant frequency. A simple analogy is a bell or tuning fork. Strike a bell with a hammer and it will ring at its resonant frequency.

 

Ok, understood.

The SCR is fed a fullwave rectified signal from the AC mains supply.
The secondary winding of the transformer is fed from the cathode of the SCR. It sees the same fullwave rectified signal after the SCR has been triggered.

so the wave F will appear AFTER the scr is triggered
i understand now thank u

 

Waveform "E" leads to waveform "F" because the SCR device is triggered into conduction, and after that the waveform is the result of the voltage drop across R4, the load resistor, arriving through the connections back to where the monitoring point is located.
If this circuit had been presented at the start the answer could have been available much sooner.
The SCR is a very non-linear device and so the input and output signals do not represent any convenient math relationship other than repetition rate.

 

Yes. Synchronize sine generator with spike series.

i can't understand is how did waveform E turn into waveform F ? how could a spike wave like E turn into a sine wave like F ?

Spikes are synchronized with beginning of every AC half wave A.
So, spike turns ON SCR, which conducts half wave A.
When voltage of half wave A becomes zero, SCR automatically turns OFF.
With next spike process repeats.
One spike - one half wave.

 

Here is a typical case of 101 Q & A that is nothing but a red herring.

Now that we know the real context, you can all ignore the first 20 replies.

The spike is a trigger that turns on the SCR.
The signal that is noted as F is not a spike turning into a sine wave signal.
F is the fullwave rectified AC line frequency when the SCR is turned on.

I am wondering why they placed the SCR at the top of the load and not the bottom so no transformer is then needed.

 

I am wondering why they placed the SCR at the top of the load and not the bottom so no transformer is then needed.

Seems transformer Tr2 and optocoupler are for isolation 5V DC from 12V AC.

 

Seems transformer Tr2 and optocoupler are for isolation 5V DC from 12V AC.

Oh yes i did not see that 5v input because i assumed the circuit would run completely off of the already present 12v (or so) DC supply.

Now i have to ask what this circuit will be used for because it looks too complicated.

 

Now i have to ask what this circuit will be used for because it looks too complicated.

It is DIY educational circuit, published here: http://www.learnabout-electronics.org/Semiconductors/thyristors_62.php

 

Oh yes i did not see that 5v input because i assumed the circuit would run completely off of the already present 12v (or so) DC supply.

Now i have to ask what this circuit will be used for because it looks too complicated.

The lamp is below the SCR for a number of reasons, the first one being that it allows one connection of the lamp to be ground, which is important if folks are intending to use an oscilloscope to look at the wave form. And also, the circuit is not really "too complicated" considering what it is doing. It is using a zero crossing detector and a ramp, instead of the very cheap simple phase shift scheme. Do not presume that everything that you don't understand is "too complicated", OK.

 

The lamp is below the SCR for a number of reasons, the first one being that it allows one connection of the lamp to be ground, which is important if folks are intending to use an oscilloscope to look at the wave form. And also, the circuit is not really "too complicated" considering what it is doing. It is using a zero crossing detector and a ramp, instead of the very cheap simple phase shift scheme. Do not presume that everything that you don't understand is "too complicated", OK.

He he, thanks for the reply.

But when isay too complicated, i mean too complicated. But OK i wont go into detail i'll just ask another question.

Why is there an external 5v power supply?
Why is there a ramp?

I also dont know anyone who designs circuits so that it makes using an oscilloscope easier to use