Questions tagged [scr]

A Silicon Controlled Rectifier - A PNPN or NPNP semiconductor device that once triggered stays in permanently conductive state until the current is removed. USed in protective circuits and chopper style light dimmer switches. Also know as a thyristor.

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20 views

Scr threshold voltage

recently I was going through a thyristor's data sheet, I saw one unfamiliar parameter called "threshold voltage " , can somebody explain what it is?
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Pure sine inverter + SCR voltage regulator = ❤?

A SCR voltage regulator should work with no issues downstream a pure sine inverter by partially chopping the wave. What worries me is the possibility that the inverter is backfired by some kind of ...
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37 views

reversed-functioned scr

Like in a scr say in thyristors or triacs we know we can turn the scr "on" after a certain anode-cathode break-over voltage depending on the current present at the gate.But I want to know ...
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How can I calculate the RMS and Medium Voltage in a Controlled Three-phase Full-Wave Rectifier?

I want to calculate Vrms and Vmedium for the angles of 30º, 90º and 150º on the circuit above with and current source and a resistor load. I found a variety of formulas on the internet, but them all ...
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Triac phase control

It's a triac phase control circuit, my book says. I know the conduction angle or the firing angle can be adjusted by adjusting the gate current in both cycles. but the question is what is the purpose ...
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53 views

Scr gate resistor

as we know in transistors, current controls current, in JFET voltage controls current, but how about SCR? I have learnt that the gate can be triggered using both voltage and current (called gate ...
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783 views

Why does diode keep conducting even after voltage across it is negative

consider single phase two pulse semiconverter asymmetric configuration. simulate this circuit – Schematic created using CircuitLab Note the high value of inductance L1. Let ...
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32 views

Holding Current and Latching Current dilemma

I have gone through lots of resources looking up for holding current and latching current. All I can get is: Latching current is the minimum current that is required to maintain the "on" ...
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58 views

If you have a MOSFET in series with a thyristor, can turning the MOSFET off cause the thyristor to turn off?

This is a purely theoretical question. The values in the circuit below do not matter, and I understand the circuit is completely useless. Consider if SCR1 and M1 are both turned on so that current is ...
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34 views

control ac motor with SCR

I want to repair the circuit of a Mixer that used the TS820 thyristor. The other components were healthy except the thyristor so I replaced the TS820 with the BT151 but the circuit did not work. Now I ...
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126 views

Powering LEDs in a container farm

Container farms take a lot of light. Powering it is not cheap. And I have spent a lot of time pondering the different possibilities. I've developed a PCB to control 4 x 300watt PWM amplifiers. This ...
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32 views

Common Ground across SCR and Diode Bridge

I am trying to use a common ground to enable a regulated output across the circuit, however as you can see the SCRs and Bridge use the common earth to relay the positive channel in the bus.. Is this ...
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163 views

How does a capacitor and resistor affect an SCR's firing angle?

Greetings! High schooler here studying SCRs. I've been looking at sites and books on the concept of increasing an SCR's firing angle, and what I've noticed with these references is that they show you ...
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A question on thyristors and phase control

High schooler here reading on thyristors. Videos online and books say they can be used as light dimmers. I assume that's because we can control the amount of current that can enter a load. But what ...
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92 views

Controlling underdamped LC circuit with thyristor

I am trying to design a circuit that gives me an underdamped sine wave. I am controlling the SCR from an external transformer by microcontroller. When I simulate this circuit, V3 has no effect on the ...
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44 views

Non-insulated control of inverse parallel SCRs

I'm converting an inverse parallel (a.k.a. anti-parallel, back-to-back) SCR load switch from insulated control to non-insulated control. Here is the original circuit using an optotriac to turn on the ...
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Gallium Nitride SCR/Thyristor?

I have an application that requires switching on a load very fast (1ns or so). There are N-channel / low side GaN MOSFETS. I would really like to switch a load on the high side, which causes problems ...
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What type of vintage semiconductor device is this? Is it an SCR?

I found this circuit board from an 1980s old humidity controlled chamber. This definitely looks like a temperature regulator of some sort. It has a M logo which means made by Motorola. It has the ...
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Why would a “power switch” be designed this way?

This unit is an ARINC 429 bus analyzer, manufacturer "AIT" (Aircraft Interface Technologies), model "429A". Yes, it's confusing. Rated 115VAC/3A/60-440Hz. It has a 250W SMPS inside ...
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Thyristor SCR gate trigger

I'll work for the first time with a Hockey Puck type SCR with a high di/dt application. So far I've mounted it properly, with the proper clamp and heatsinks. Now I'm concerned with the gate drive, ...
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54 views

Why are thyristors used in xenon trigger coil circuits?

Looking at the datasheet for the ZS1031-11(H) trigger coil, the test setup activates the trigger coil with a thyristor: In the datasheets for other trigger coils, and in other circuit diagrams online,...
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Datasheet/pinout for S116T (1A 400V SCR)

In my inventory, I found a component labeled S116T. I bought it a long time ago from a shop which describes it as "THYR 1A 400V". So the device is an SCR, but I can't find any datasheet for ...
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78 views

Problem with SCR latching circuit

I put this circuit together to demonstrate latching properties of SCRs but I'm finding that the SCR doesn't behave as I expected it to from the datasheet values. Specifically, I found that in the ...
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Simple security Alarm incorrect schematic diagram

I am a student and my Applied Physics teacher gave an assignment to create a schematic diagram of a security alarm. The main Components are, Switch (Simple on/off) SCR C106B (Silicon Controlled ...
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38 views

Is there a one trigger latch for AC?

SCR is good for latching DC source, one trigger will turn on the source indefinitely. But how about AC source? Latching mechanical relays is good but it is too big for me. Triac is designed for AC ...
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Is there a protection needed in the mcu connected to SCR?

When an SCR is connected to high voltages (220Vrms) while it's gate is being controlled by pulses using a microcontroller powered by only 3V, is there a protection needed in the microcontroller? My ...
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SCR surge voltage rating

A question on SCR/thyristor voltage rating: For SCR rated at 100A 400V. i.e. It seems common the rated current can take 10x more surge current so 1000A surge for 100A SCR without damage. Can also ...
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High power heating element control

How to control high power (~5kW) heating element using MCU? I need a very simple application that shuts down the element, when it reaches set temperature. Maybe I can do it using SCR? F.e. Т161-160 (...
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87 views

Snubber circuit to protect SCR/Diode

In my circuit I need to discharge a capacitor into an inductive load using SCR. In order to make the circuit oscillate there'll be a diode antiparallel with the SCR, as you can see in the picture. My ...
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interfacing MOC3021 with high current back to back scr

I want to drive two back to back thyristor with moc3021 for soft starter.Here is the circuit: This circuit works for medium power SCR such as BT152,But I want to drive a couple of disk thyristor that ...
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back to back SCR firing circuit

I am trying to design a 3-phase soft start circuit.Are these two circuits different? My PCB design and RC snubber between anode & cathode is based on the second one.I want to make sure my circuit ...
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202 views

Triacs are getting damaged BTA41 BTA24

guys, I tried to make an SSR for my window Air conditioner 2 Tonnes "2.5kW" the problem the Triacs get damaged instantly I tried 4 Triacs so far 2 BTA41 and 2 BTA24 I tried different circuits, I'm ...
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Why crowbar is needed?

I know it is to protect sensitive load, but doesn't the zener diode in the power supply already do that? zener diode inside the power supply already limits the voltage to its breakdown voltage. Why do ...
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Can I use any digital component to avoid 7805 killing my microcontroller directly when its ground is disconnected (hence 12v goes to uC directly)?

My idea is to have an intermediate cheap component that will blow-up before my uC if the voltage goes above 5v from 7805 (or even some fuse, but I am not sure if a fuse will blow-up with over-voltage ...
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228 views

TL431 crowbar simulation problem

I'm trying to simulate crowbar circuits, which is mentioned on page 8 of ON SEMI TL431 datasheet (https://www.onsemi.com/pub/Collateral/TL431-D.PDF). I'm using TINA TI for this. There are two circuits,...
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62 views

What happens when we discharge a capacitor through a SCR which we leave open?

I am wondering what would happen when we discharge a capacitor, by using a SCR, through a coil and we leave a current applied to the gate of the SCR. The coil should generate a ‘reverse’ current right?...
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Open load detection using SCR

I have a load I control via back to back SCR during zero crossing circuit. The load is powered via 208Vac and pulls about 15A. I have an EMI filter using safety caps at the output. I need to detect ...
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Why in the world would the tab on a TO-220 package have a connection to anything (but GND, if applicable)?

I know this is in some way a different version of the prior question In i.e. a TO-220 package, why is mounting the (pin connected) tab to case safe? But I am not looking for ideas what to do to mount ...
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228 views

Debugging a battery charger circuit

I have built a circuit of a battery charger here. Here is the circuit in the original project: However, it doesn't seem to work. The output I measure at the battery charging clips is only 1.2 V or so ...
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383 views

How DIAC works?

I edited my whole post for more refreshed information I learned about DIAC. Let's consider the following circuit and how it works. First of all the Vs must be higher than break voltage of diac, so ...
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SCR for load bank switching?

I'm building a load bank for testing high power lead acid batteries, and expect to pass up to 800 amps at 12 VDC. I could do it with contactors but would like to use an SCR with a pot and allow the ...
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How to install a scr model in ltspice

I have downloaded an scr model file from this website and pasted it in the same folder as that of my .asc file. But ltspice still shows unknown subcircuit called for the scr present. What am I doing ...
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Arduino died when grounds got disconnected

Alright bear with me since English is not my first language and it's my first time posting here. So I was using my Arduino Nano (not genuine) to drive a single phase full bridge rectifier. The ...
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Turn on Mosfet by SCR

can the Mosfet be turned on as shown on picture? My desire is voltage on M1 fire the SCR stay on forever. V2 is ramp voltage.
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Is zero loss turn-off possible for thyristors?

Consider this very basic circuit: simulate this circuit – Schematic created using CircuitLab Don't mind the values - they don't matter, as this question is conceptual. Imagine that Vcomm is ...
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35 views

SCR reverse current during switch off

In the figure below is shown the dynamic behavior of an SCR in terms of its current during switch off. I'm interested in calculating the maximum reverse current (iR in the plot). The parameters that ...
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Question regarding the trigger circuit for an SCR-based coilgun

I'm an EE student, trying to design a coilgun project. I have had luck with a basic prototype similar in construction to the one on this site, however with smaller flash capacitors in parallel (total ...
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How to reduce spike in Power Supply and GND (SCR + Ignition Coil)

My circuit: Signal coupled in power supply (3.3V) of STM32F103 during spark: Is there any benefit to using this diode (circled in red) or not (without this diode the snubber circuit will start ...
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318 views

Crowbar Circuit Resistor

I have a crowbar circuit which uses an SCR with 100mA gate current shown below. In order to use this resistor value at 100mA it would need to be rated for 60W. Obviously here the resistor will pop. ...
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246 views

What can I use to turn on a circuit at 5V?

I'd like to power an Arduino using a supercapacitor. I already have that part of the circuit figured out. But I want to charge the supercapacitor using an external power source, without the ...