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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94 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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1answer
128 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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44 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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4answers
2k views

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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1answer
61 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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187 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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64 views

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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1answer
499 views

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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1answer
118 views

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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53 views

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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0answers
32 views

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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156 views

SCR triggering in LT Spice

I have been trying to trigger a SCR in my circuits but an error shows up every time. Unknown subcircuit called in xu1 n002 n001 n003 scr This is a screenshot of ...
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33 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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1answer
42 views

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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123 views

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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3answers
214 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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1answer
143 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 ...
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1answer
51 views

Why on shutdown the SCR can be compared to a power diode?

I have this as a homework question and can't seem to find the answer in my notes, book or internet. I know they will behave similarly when there is a reverse polarity on both, but the way my professor ...
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238 views

Xenon Flash thyristor trigger

I'm building a xenon flash unit with a power of 50Ws (300V 1000uF capacitor). I need to trigger it from a microcontroller. For that I use a MOC3041 to opto isolate my µC from the HV circuit and ...
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2answers
424 views

What happens for the SCR if I connect gate with ground when it is turned on?

When I connected a silicon control rectifier by applying positive voltage in anode and negative voltage in cathode, after that I triggered the gate by pulse voltage and it connected, after that I want ...
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1answer
778 views

What distinguishes an ordinary thyristor from a GTO thyristor?

A thyristor, I know, is a four-layer PNPN structure, with an anode on the first P section, a gate on the second P section, and a cathode on the second N section. This simple structure suggests that ...
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254 views

Trouble with simulating an SCR

I was reading about SCRs and I'm trying to simulate 2N5060 SCR but having some issues when I plot the currents and voltages: First by looking at the datasheet, I set the R4 to keep the gate current a ...
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1answer
288 views

Confused with turn on time definition of an SCR

The following question I encountered is asking about the minimum time for applied voltage to the gate of an SCR to turn it ON: And below is the solution: I can understand the solution looking for ...
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3answers
609 views

Testing a thyristor

I have a very large high voltage device that a friend asked me to take a look at. It has a bunch of BIG thyristor packages (Semikron, SKKT 106/18 E, Dual Thyristor Module, 600A 1800V). I'm testing ...
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1answer
88 views

Switch operating at particular touch IC voltage [closed]

Is there any circuit to perform such task more efficiently? I am trying to control a small motor (like a smartphone vibration motor) with specific outputs from the touch IC, so that it can be turned ...
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3answers
153 views

“Active Low” SCR

Background: I'm working on a circuit that uses an ATmega 328 processor, and a hall effect sensor. We're creating a small wireless sensor, so what we're focusing on now is power consumption. We want ...
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1answer
868 views

Dimensioning SCR crowbar circuit

I need to dimension an SCR crowbar circuit to reach a certain level of protection against overvoltage, without increasing much the complexity of the circuit of my control card. The need is to protect ...
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98 views

What's the best way to detect zero crossing in this design?

The design that I am talking about: I want to be able to detect the zero point with an MCU of which pin can withstand only 3.3 V. I'll forgo optocoupler because A. I want everything to be as cheap as ...
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2answers
561 views

Thyristor/SCR \$i^2t\$ and \$i^2\sqrt{t}\$ Rating

I have commonly seen the \$i^2t\$ rating for fusing in a SCR datasheet. This is a helpful rating for assessing if pulses which exceed the surge current rating (Itsm) of the SCR will damage it. ...
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1answer
212 views

GTO Driver circuit

i am new to power electronics.I am working in project where input is pulsating dc and i have to control it, i try with scr but we can control only on of scr not off so in some case the cycle cut ...
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2answers
547 views

Ideal component to switch 84V DC?

I wanted to control a 84V LED strip using a ATtiny13a microcontroller with minimal power wasted. I just want to turn it on and off, don't need any PWM dimming. The strip uses 270mA current and is ...
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527 views

What is the purpose of the SCR in this circuit?

I am trying to repair an old SMPS. The first step is to reconstruct the schematic and work from there on. The schematic on the low voltage side is completed for the +12V and the +5V circuits. However ...
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116 views

Why Does The NTE5465 SCR In My Circuit Remain Closed, Even With No Current?

See attached circuit. Circuit is designed to have the bulb light, when a very low amperage momentary switch is pressed. In the final circuit, the bulb will draw 4 to 5 amps for a short period of ...
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299 views

SCR switching conducted emissions

I have a circuit that drives a 240Vac line to line power to a resistive load. I am testing for radiated and conducted emissions. Radiated emissions went fine but conducted emissions failed with "broad ...
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1answer
202 views

How to know if a SCR is still working?

I'm using a TIC116 to control the power over an electric grill. However, I didn't use a heatsink and it got very warm. On the data it says that its upper limit is 110 °C. I suspect that the gate is ...
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1answer
202 views

Problem with using SCR to control power for an electric grill

I'm doing a power controller for an electric grill, where through PWM I allow to pass x number of cycles from the 124V @ 60 Hz source of my lab. Here you have the diagram: simulate this circuit &...
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5answers
3k views

Why are bulky SCR power controllers used when the same can be achieved with a relay?

This is kinda noob question. I recently got an SCR Power controller (WATLOW DIN-a-mite DB20-24CO-0000 Style B). This is the first time I actually got to test an SCR controller for myself. The input ...
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2answers
586 views

Turn-off an scr by a transistor

Hello. I understand that one of the method to turn-off an scr is by connecting a transistor parallel to it in order to short it. I would like to turn on the transistor(BC547B)by touching the wires ...
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1answer
1k views

SCR triggering using DIAC

I've found this method of triggering of the SCR through DIAC and I'm trying to understand it. I was able to figure out the whole trigger circuit and how to compute the values of RC in order to have ...
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2answers
4k views

How to use SCR to control the power of a heater

I would like to point out that I am not an expert (as it is perceived by the question) in the use of scr, diac, and triac and that this question is more for academic purposes than use in real life. ...
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1answer
1k views

Formula of snubber capacitor capacitance for SCR dv/dt protection

I have a formula here for finding the suitable value of shunt capacitance to be put on an SCR snubber. \$C=\frac{1}{2L}(\frac{0.546V}{dv/dt})^2\$ where L is the snubber inductor, V is the DC supply ...
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3answers
1k views

Wiring for 10000W 220V SCR Voltage Regulator Speed Controller

I live in the US and have the Twist Lock Electrical Plug 4 Wire, 30 Amps, 125/250V, NEMA L14-30P. It has 2 hots, 1 ground, and 1 neutral wire. I saw the following scr controller on ebay and am ...
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1answer
592 views

DC bus inversion to 3 phase AC modified sine wave using IGBTs

I'm working with a variable voltage inverter. I have 3 phase AC voltage coming in at 480V RMS line to line. It hits a full wave SCR front end, has a DC bus link, and is inverted with IGBTs to created ...
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0answers
104 views

Why does this transformer have an additional winding on the side of the core?

This photograph is of a wire feed welder. This unit consists of a step-down transformer with a bunch of taps on the primary side. It is fed from 115 Volt 60 hz supply. The switch on the left allows ...
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383 views

Identify a Thyristor

Hello would anybody be able to find the spec's of this SCR Thyristor General Electric C50FX425 937 Thanks in advance.
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1answer
1k views

Is this a good inverse parallel SCR drive circuit?

I have a design for a dimmer circuit, but I am unsure of its correctness or if there are issues with it. It's meant to be controlled by a 50% duty cycle PWM signal - the dimming responds to the phase ...
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1answer
318 views

Does this capacitor discharge? SCR and capacitor doubts

I'm having some doubts about this circuit and about capacitors charge/discharge in general SCR CIRCUIT; Igt= 100MicroAmps;Vgt = 0.7V Ok I have like 5 questions 1) Is flowing current through R2 and ...
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1answer
519 views

How to automatically turn off an SCR after being latched for DC supply

How to automatically turn off an SCR after being latched for DC supply? Type of switches that turns on/off a circuit with a certain voltage But when i try it in multisim it doesnt work.
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1answer
2k views

How do I find the firing angle of SCR practically? [closed]

Our teacher told us to find out the time period and then multiply it by 18.Then 180-(∆t*18) gives firing angle.Why 18 as a multiplier?