UK 70TPS12 Thyristor - Help!

[mangoelectrics]

Hello All,
I am new here and I don't know if I'm posting in the correct place but I need some help with wiring up my Thyristor.

I have added below a photo of my thyristor.

I don't know why, but I cannot get it to work as a switch.

I will be running the gate off around 1.4v DC and I need to be able to switch around 400v DC.

I am simply trying to use it to switch off and on a 400v DC supply.

Any answers would be much appreciated!

 

[mangoelectrics]

Also, if I test across pins 1 and 3, I get an ohms rating of 120 Ω. But across pins 2 and 3 or 1 and 2 there is nothing.

 

[James]

http://www.datasheet.hk/download.php?id=1843527&pdfid=5535644E9C5EC6C2EE5E0CCF73222D96&file=0423\70tps16_5025539.pdf

 

[mainline]

Hello All,
I am new here and I don't know if I'm posting in the correct place but I need some help with wiring up my Thyristor.

I have added below a photo of my thyristor.

I don't know why, but I cannot get it to work as a switch.

I will be running the gate off around 1.4v DC and I need to be able to switch around 400v DC.

I am simply trying to use it to switch off and on a 400v DC supply.

Any answers would be much appreciated!

Is the circuit switching at all ?
can you show the circuit your proposing ?

 

[mainline]

I suggest using a battery circuit before playing with the higher voltage.

 

[mangoelectrics]

I suggest using a battery circuit before playing with the higher voltage.

Yep, that's exactly what I have been trying all day!

Will try to send you a schematic of my mini battery test circuit soon.

Thanks!

 

[mangoelectrics]

@mainline Here is the schematic. What I want is when I press S1, it should then light up LED 1. That is, if I have connected everything correctly!!! Hope this helps, and thanks for your help so far!

 

[mangoelectrics]

@mainline This is what it looks like. I am using an Arduino to power it with 5V just for testing purposes.
Thanks!

 

[mainline]

@mainline Here is the schematic. What I want is when I press S1, it should then light up LED 1. That is, if I have connected everything correctly!!! Hope this helps, and thanks for your help so far!

Once the thyristor switches on its going to latch on.
looks like your led is the wrong way around.

Have a read of this.

https://www.electronics-tutorials.ws/power/thyristor-circuit.html

 

[mangoelectrics]

Still nothing. Tried reversing the LED and still no light.

When I try this schematic below, it immediately lights up when plugged in, then when I press S1 the light goes out and immediately comes back on when S1 is released.

Obviously the power to the LED (LOAD) is coming through the 1k ohm resistor going into the SCR Gate.
When I remove that resistor the LED goes out and does not come on when the switch is pressed. Also if I leave the resistor in and remove the Negative lead to pin K of SCR the LED still works without the S1 pressed.

Still can't find the issue!!!

 

[mainline]

Still nothing. Tried reversing the LED and still no light.

When I try this schematic below, it immediately lights up when plugged in, then when I press S1 the light goes out and immediately comes back on when S1 is released.

Obviously the power to the LED (LOAD) is coming through the 1k ohm resistor going into the SCR Gate.
When I remove that resistor the LED goes out and does not come on when the switch is pressed. Also if I leave the resistor in and remove the Negative lead to pin K of SCR the LED still works without the S1 pressed.

Still can't find the issue!!!

Have you tried a resistor from the Gate to -

 

[mangoelectrics]

Have you tried a resistor from the Gate to -

Yes, here is another photo.
It lights up VERY dim. Obviously the only negative input is from the resistor coming through the gate pin.

Sorry, very poor image!

 

[mainline]

Yes, here is another photo.
It lights up VERY dim. Obviously the only negative input is from the resistor coming through the gate pin.

Sorry, very poor image!

have you a lamp or something instead of an led to try.

 

[mangoelectrics]

Will try something and get back to you on Monday. But thanks very much for your help so far!

 

[mangoelectrics]

have you a lamp or something instead of an led to try.

Just connected up a dc motor and have the same results as with the LED.

 

[mainline]

Just connected up a dc motor and have the same results as with the LED.

try another thyristor

 

[mangoelectrics]

try another thyristor

No difference!!!

 

[mainline]

No difference!!!

What happens if you put the gate to - and then power the circuit



What do you actually want to do ?

 

[mangoelectrics]

What happens if you put the gate to - and then power the circuit



What do you actually want to do ?

Can you tell me which pin you think is the gate? 1, 2, or 3? From the photo I think it’s pin 3, but thought I would get a second opinion. Thanks!

 

[Moley]

Looking at some data sheets the gate should be the one you've got marked up as 3. Also the minimum gate current to turn on should be 100mA.

 

[mainline]

Can you tell me which pin you think is the gate? 1, 2, or 3? From the photo I think it’s pin 3, but thought I would get a second opinion. Thanks!

 

[mangoelectrics]

Looking at some data sheets the gate should be the one you've got marked up as 3. Also the minimum gate current to turn on should be 100mA.

Thanks both of you. That’s very helpful to know for sure which is which. If I put - to the gate then the led or motor immediately is powered continuously even without the negative lead going into pin 2.

Hope this helps.

 

[mainline]

use a lamp or a motor.

Connect one wire of the motor to - of the battery.
Connect the other side of the motor to the K of the Thyristor.
Connect the A of the thyristor to + of the battery.

Connect a 1k resistor to G of the thyristor and - of the battery.

Power the circuit the motor shouldnt run.

If you run a bit of wire from + of battery and just touch it on to the Gate of the thyristor the motor should run and continue to run.

 

[mangoelectrics]

use a lamp or a motor.

Connect one wire of the motor to - of the battery.
Connect the other side of the motor to the K of the Thyristor.
Connect the A of the thyristor to + of the battery.

Connect a 1k resistor to G of the thyristor and - of the battery.

Power the circuit the motor shouldnt run.

If you run a bit of wire from + of battery and just touch it on to the Gate of the thyristor the motor should run and continue to run.

Will try this in the morning, thanks for your help!

 

[mangoelectrics]

use a lamp or a motor.

Connect one wire of the motor to - of the battery.
Connect the other side of the motor to the K of the Thyristor.
Connect the A of the thyristor to + of the battery.

Connect a 1k resistor to G of the thyristor and - of the battery.

Power the circuit the motor shouldnt run.

If you run a bit of wire from + of battery and just touch it on to the Gate of the thyristor the motor should run and continue to run.

Just tried that now. It does work as you say it should although it takes the positive power in through the gate pin and does not seem to activate the thyristor. Do you know why this might be?

Thanks again!

 

[mangoelectrics]

Also, when I remove the 1k resistor from - to gate then power the gate with + 5v the motor immediately runs, but does not continue to run after I remove the power to the gate, it should continue to run as I have permanent power to the K and A of the thyristor.

Im beginning to think my thyristors are no good?

Thanks!

 

[mangoelectrics]

@Moley Do you have any suggestions?
Thanks!

 

[mainline]

Also, when I remove the 1k resistor from - to gate then power the gate with + 5v the motor immediately runs, but does not continue to run after I remove the power to the gate, it should continue to run as I have permanent power to the K and A of the thyristor.

Im beginning to think my thyristors are no good?

Thanks!

What test gear have you ? I think you should have a read up on how to test scrs.

There are lots of videos on basic electronics etc i think you need to learn a bit more, especially when dealing with mains supplies.


If you just want to switch a higher voltage with a lower one then just use a contactor.

View: https://www.youtube.com/watch?v=dCEt_oaFPMY

 

[mangoelectrics]

What test gear have you ? I think you should have a read up on how to test scrs.

There are lots of videos on basic electronics etc i think you need to learn a bit more, especially when dealing with mains supplies.


If you just want to switch a higher voltage with a lower one then just use a contactor.

View: https://www.youtube.com/watch?v=dCEt_oaFPMY

Thanks, let me explain a bit further.

According to the video, mine are no good. They have measurements of between
G and K: 138 Ω
K and A: 63M Ω and always rising
A and G: 76M Ω and always rising

I am building a coil accelerator and so am needing to use the thyristor to switch on the coil when I give the command. But obviously I am running a 1900uf 450V DC capacitor charged to 400V DC so when I fire it, it gives a HUGE amount of power instantly and this was burning out normal switches.

This is why I was trying to use a thyristor. But if you have another idea of what I could use I would be happy to try that.

Thanks again!

 

[mainline]

Thanks, let me explain a bit further.

According to the video, mine are no good. They have measurements of between
G and K: 138 Ω
K and A: 63M Ω and always rising
A and G: 76M Ω and always rising

I am building a coil accelerator and so am needing to use the thyristor to switch on the coil when I give the command. But obviously I am running a 1900uf 450V DC capacitor charged to 400V DC so when I fire it, it gives a HUGE amount of power instantly and this was burning out normal switches.

This is why I was trying to use a thyristor. But if you have another idea of what I could use I would be happy to try that.

Thanks again!

If you have used those scrs on a coil the back emf may have destroyed them you would need a diode to stop that.

 

[UKMeterman]

A number of points. It needs a continous current of 100mA to hold it on,.
2. A motor has a comuninator in it, so the current is lumpy and so can drop below 100ma
3. You need to arrange safe isolation between the 400V and your control circits.
4. 400V with that capacitor will kill you.
5. You need a current limiting element in that circuit or stuff will blow up.


If you need this kind of help I wouls suggest you need to consider if you are competent to be working with 400V dc.

 

[mangoelectrics]

THREAD CLOSED

This issue has now been resolved.

Here is the final working schematic:

 

[mainline]

A number of points. It needs a continous current of 100mA to hold it on,.

An scr will latch on once triggered and will stay in that state even with no gate current.

2. A motor has a comuninator in it, so the current is lumpy and so can drop below 100ma

The motor will continue to run until the positive voltage at the anode stops.

 

[mangoelectrics]

An scr will latch on once triggered and will stay in that state even with no gate current.


The motor will continue to run until the positive voltage at the anode stops.

THREAD CLOSED

 

[mainline]

THREAD CLOSED

Is it ?? you could have fooled me.

 

[mangoelectrics]

Is it ?? you could have fooled me.

It is now working! STOP arguing please!

THREAD CLOSED

 

[mainline]

It is now working! STOP arguing please!

THREAD CLOSED

Nobody is arguing.
Misinformation is better to be corrected than just left.

 

[mainline]

If your circuit shows a transformer you cant drive it with DC
Transformers work by the principle of electromagnetic induction. A changing current in the primary coil (the input) creates a changing magnetic field, which then induces a voltage in the secondary coil.