The voltage at the cathode will be 0V, and the voltage at the Gate will be about 0.8V when the switch is pressed.
About 1us later the cathode will be at 11.2V and the gate at 12.6V.

Max voltage at thyristor gate is 1.5v
If it goes to 12.6v i think it will burn!

 

Max voltage at thyristor gate is 1.5v
If it goes to 12.6v i think it will burn!

No, you have confused it with the maximum voltage between the gate and the cathode.

 

This circuit marked in red has its own source which is 1.5v
So the voltage in this circuit from the gate to cathode can not go above 1.5v

While the other circuit marked in yellow has voltage 12v from anode to cathode and the whole circuit marked in yellow

 

The maximum Vgt of this thyristor is 1.5v

You seem didn't go to compare two circuits of the gates, what's the difference between two gates?

 

Why do you insist in trying everything except the the circuit you have been given?

I will try once again:

The cathode should be connected to both battery negatives.

The motor should be connected, through a switch, between the 12V battery plus and the anode of the scr.

 

View attachment 276340
This circuit marked in red has its own source which is 1.5v
So the voltage in this circuit from the gate to cathode can not go above 1.5v

While the other circuit marked in yellow has voltage 12v from anode to cathode and the whole circuit marked in yellow

It is conventional, when no other 0V point is specified, to Assume it the 0V reference is the negative of the main power supply, and measure all voltages from that point unless specified otherwise.

 

Why do you insist in trying everything except the the circuit you have been given?

I will try once again:

The cathode should be connected to both battery negatives.

The motor should be connected, through a switch, between the 12V battery plus and the anode of the scr.

You can see there is a switch between motor and the 12v

And you can see the two batteries negative connected to the cathode

!!!!

 

Why do you insist in trying everything except the the circuit you have been given?

I will try once again:

The cathode should be connected to both battery negatives.

The motor should be connected, through a switch, between the 12V battery plus and the anode of the scr.

What is the wrong with the circuit?

 

View attachment 276344
You can see there is a switch between motor and the 12v

And you can see the two batteries negative connected to the cathode.

!!!!

No, that is not what. see!

The twelve volt battery negative is connected to the cathode only through the motor/diode.

When I say connected, I mean directly connected, by a wire, not through other components.

 

No, that is not what. see!

The twelve volt battery negative is connected to the cathode only through the motor/diode.

When I say connected, I mean directly connected, by a wire, not through other components.

Like this?

 

No. Now you have both battery negatives connected to the thyristor gate instead of to the cathode.

 

No. Now you have both battery negatives connected to the thyristor gate instead of to the cathode.

I tried of this, how to connect it right?!

 

Your layout doesn't follow the schematic exactly as in post #50. The schematic is correct.

 

Using your posted schematic in Post #50, not the crayon drawing but the actual schematic in post #50.

Ron

 

@Momentory Circuit Lab is a free Schematic S/W

 

Where should the wire out from battery negative (1.5v) connect to?

 

Using your posted schematic in Post #50, not the crayon drawing but the actual schematic in post #50.

Ron

This wire in yellow is connected from negative 12v to cathode in the drawing and in the schematic
And wire in the green is connected from the 1.5v negative to the wire between 12v battery and the cathode in the drawing and in the schematic

What is the different between drawing and schematic?

 

Is this right?

The 1.5v negative directly connected to the cathode of the thyristor?

 

That looks correct. SCR cathode to both commons and both commons tied together. SCR anode to your load (motor) low side (neg) and motor high side (pos) to your motor supply positive. Pushing the button will latch the motor On and opening the switch will stop the motor.

Ron

 

The schematic in post #58 is correct but the drawing is wrong unless your SCR has a non standard pinout. Post the datasheet for YOUR SCR.

Les.