Thyristor as switch

Thread Starter

Momentory

Joined Sep 4, 2022
67
I have two connected circuit

  • 12v dc battery
  • 12v dc motor
  • Thyristor ( input current max gate current 0.05 ampere) - (1.3v max gate voltage)
  • Resistor 39 ohm
  • 1n4007 diode
  • 1.5v dc battery

Picsart_22-09-15_12-23-19-594.jpg
The thyristor will be the switch for this circuit

My question is very basic but i want to understand how it works

In the circuit that has the thyristor

What is the voltage of this circuit ( A ,B), Is it 1.5v or 12v since the circuit connected to both circuit?
 

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Last edited:

Ya’akov

Joined Jan 27, 2019
6,575
What do you mean by “voltage of this circuit”?

There is no special attribute of a circuit called “voltage”. Components are identified by ”voltage” to indicate nominal supply voltage, nominal output voltage, or nominal operating voltage.

I don’t know what your question means because a circuit doesn’t have a voltage, it has many voltages wich can be measured at different points. Could you clarify?
 

Thread Starter

Momentory

Joined Sep 4, 2022
67
What do you mean by “voltage of this circuit”?

There is no special attribute of a circuit called “voltage”. Components are identified by ”voltage” to indicate nominal supply voltage, nominal output voltage, or nominal operating voltage.

I don’t know what your question means because a circuit doesn’t have a voltage, it has many voltages wich can be measured at different points. Could you clarify?
Sorry for this
I edited the post

A is the gate of thyristor
B is connection point between both wires
 

Alec_t

Joined Sep 17, 2013
13,153
Have you checked with the datasheet that the cathode and anode connections are the right way round for your particular thyristor? The centre pin of a thyristor is usually the anode.
A is the gate of thyristor
That's confusing. 'A' conventionally denotes the anode.
No A or B in the pic?
 

Thread Starter

Momentory

Joined Sep 4, 2022
67
Have you checked with the datasheet that the cathode and anode connections are the right way round for your particular thyristor? The centre pin of a thyristor is usually the anode.

That's confusing. 'A' conventionally denotes the anode.
No A or B in the pic?
"A" is not referring to the anode of the thyristor

It is just a word to point the points i want to measure the voltage from

A and B are points not referring to thyristor anode or cathode or gate

Battery negative wire goes to andode (middle pin) and wire from cathode goes to the motor
 

BobTPH

Joined Jun 5, 2013
5,773
Your circuit is incorrect. The cathode (pin 1) should be connected to both battery negatives, and the motor negative should be connected to the anode(pin 2.)
 

Reloadron

Joined Jan 15, 2015
6,979
Below is a basic schematic of a SCR / Thyristor circuit.

Thyristor SCR Ckt.png

SW1 is a N/C push button switch, SW2 is a N/O pushbutton switch. Momentary press on SW2 will start the motor and momentary press on SW1 will stop the motor. The anode, gate and cathode of the SCR are labeled. The resistors form a voltage divider for the gate voltage. Now using this example what exactly do you want to know.

Ron
 

Thread Starter

Momentory

Joined Sep 4, 2022
67
Below is a basic schematic of a SCR / Thyristor circuit.

View attachment 276280

SW1 is a N/C push button switch, SW2 is a N/O pushbutton switch. Momentary press on SW2 will start the motor and momentary press on SW1 will stop the motor. The anode, gate and cathode of the SCR are labeled. The resistors form a voltage divider for the gate voltage. Now using this example what exactly do you want to know.

Ron
I need the thyristor to has its own battery, but i do not understand why my circuit is wrong
 

BobTPH

Joined Jun 5, 2013
5,773
Your circuit is wrong because the thyristor anode and cathode are reversed. Do you understand that it only conducts in one direction?
 

Reloadron

Joined Jan 15, 2015
6,979
OK your circuit reflects a TO220 case for your thyristor. Normally less a data sheet to look at it would look like this.
Thyristor SCR TO220 Pinout.png

Now just note the pinout for Cathode, Anode and Gate. This is what everyone is getting at. To gate it ON the gate needs to be positive with respect to the cathode. Yes, you can use a separate power source for the gate as long as they share the same common.

Ron
 
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