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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Need help building simple burglar alarm circuit

I'm trying to build a simple burglar alarm circuit and I've found one online that uses a knife switch, 9 V power source and an SCR. I'm trying to change it over to a PIR motion sensor but am unsure ...
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48 views

How to control voltage using PID when driving SCR?

I am designing a scr based digital battery charger for the first time and have successfully driven scr to provide 110V-DC from a 140V singe-phase transformer. 2 SCR-diode combination forms full bridge ...
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64 views

Use SCR and resistor as an inrush current limiter

I try to design an inrush current limiter using an SCR S2800F (https://datasheetspdf.com/pdf-file/1129612/Motorola/S2800F/1) and a resistor, as shown in the below diagram. A 600 VDC power supply ...
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224 views

Turning on SCR without latching it

The picture shows a typical SCR circuit. I have already simulated this circuit in multisim. Since multisim assumes this to be an ideal SCR (zero voltage drop for example,) the characteristics may not ...
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53 views

SCR latching current and holding current equivalent definition

understanding the definitions of Latching and holding current. suppose a particular value of the gate current I_g is given. Now that we increase the voltage across the SCR from 0V and onwards. Forward ...
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113 views

What circuit is used in industry for SCR firing?

I am a hardware developer. I have a requirement for designing a firing card for SCR. I am not very used to using thyristors and it has been a long time since I used one. I see on the internet there ...
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42 views

SCR bridge control circuit

I want to design a single phase 400V 1A power supply using mains (230VAC,50Hz). For which I plan to use a step up transformer which will step up to 400V and then an SCR Bridge rectifier to convert it ...
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66 views

Industrial SCR rectifier/battery charger circuit: best place for blocking diode, reverse diode, and dropper diodes?

I am working on a three phase 110 VDC & 100 A SCR rectifier/battery charger. I'm not sure which one of the circuits in the image is better for filter and diodes. Please help me with these ...
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120 views

How to build a DC motor speed controller with DC source and SCR?

So after asking a question from the book "Practical electronics for inventors" and getting recommendations to burn the book, I'm going to start this thread with the premise that I'm not ...
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169 views

Replacing Darlington with MOSFET for capacitive discharge circuit into a solenoid?

I have the following circuit and criteria and am wondering if it makes sense to replace the Darlington transistor with a MOSFET, and if so how would that change the circuit? This circuit turns on T1 ...
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90 views

How does this Snap Circuits SCR circuit work?

I came across some custom Snap Circuits projects. One of them was a homemade SCR out of non polarized capacitors, two bipolar (NPN) and (PNP) transistors, some resistors, and an L.E.D. I am very ...
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48 views

3 phase controlled soft starter and motor vibration

I want to make a soft starter for 3 phase induction motors. TRs are SCR pairs and ZCs are the zero-cross timing respect to line voltages (400V), not phase voltages (230V). I control the firing angle ...
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122 views

Can a Triac be driven using only positive voltage due to the laws of Q1 and Q4 quadrants?

I have a BTA12-600B Triac and an Arduino. Is it possible I can trigger both positive and negative amplitudes of an AC cycle by suppling only a positive voltage from the Arduino digital pin to the ...
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350 views

How does this regulator/rectifier circuit work?

I am working with the following circuit from a motorcycle. It provides 13.8V DC out from a 15V-100V AC generator input. I understand how the bridge rectifier (BR1) and smoothing capacitors (C1, C2) ...
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53 views

SCR vs diode VI characteristics

We know in an SCR when in conduction mode, triggered by some gate voltage, the lower three junctions will essentially turn into a single N junction and so the SCR essentially becomes a PN junction ...
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93 views

Confusion in minimum gate triggering current of SCR

I was reading an article about working and properties of SCR from eleccircuit.com and in a section How to pick a SCR -it is written that we should check its rating and one of the mentioned rating in ...
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77 views

SCR crowbar circuit gate voltage?

I'm designing a simple overvoltage / reverse voltage protection circuit for a 24 V battery system, with plans to upgrade to a 48 V lithium setup in the future. I selected the parts to trigger on a ...
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323 views

Is this component in falstad a tl431

I'm self studying electronics, I am now familiarizing myself with the tl431, which is pretty much a "variable zener" aparently. I was shown the following symbol. I would like to simulate ...
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66 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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46 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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163 views

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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85 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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792 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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86 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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71 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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64 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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128 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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42 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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729 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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52 views

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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155 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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67 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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109 views

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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241 views

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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97 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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202 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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164 views

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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44 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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29 views

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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82 views

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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57 views

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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131 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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280 views

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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512 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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103 views

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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127 views

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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369 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,...