Questions tagged [detector]

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2 answers
142 views

Peak detector circuit for AC RMS value

The peak detector circuit based on a precision rectifier with buffer allows to obtain the peak value. The RMS value in an AC circuit is obtained from: RMS = V peak / sqrt (2) = V peak * 0.7071 AC ...
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1 answer
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What is the purpose of VD2 in this circuit?

This is a simple sonar device using piezoelectric mic and speaker. I understand, the C2-VD1-VD2-C3 is detector circuit that is intended to enable the sound generator based on CD4001 that produces ...
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2 answers
47 views

LNA and DC amplification

In a THz detector, it produces a DC output voltage proportional to the input signal intensity. I need high SNR. My doubts are: Can I use LNA as a preamplifier? Is DC amplification possible with LNA? ...
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1 answer
90 views

DC offset cancellation

I am working on THz detector and was going through research papers. In the receiver stage a preamplifier is used in the circuit shown below. Why can't we directly use the amplifier? How does the dummy ...
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1 answer
76 views

What am I doing wrong with metal detector coil?

I saw on the internet a lot of people making metal detectors so I was thinking of building my own. I took 35 turns of 0.5 mm wire over a 20 cm diameter air core, connected it to a function generator (-...
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1 answer
107 views

Building a metal detector to detect 3mm particles

I am trying to build metal detector to detect some stainless steel and copper and iron particles with size approximately 2~3 mm embedded on circular food product. Its diameter about 2 cm and width ...
4 votes
1 answer
329 views

Metal detector vs ground penetrating radar (GPR) frequencies

I was reading about metal detectors and at first got thinking they use lower frequencies because of ground/rock losses. Low frequencies will penetrate better, but seeing GPRs penetrating much deeper ...
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1 answer
82 views

Electromagnetic induction metal detection circuit

I am trying to develop a metal detector for use in a minesweeper competition. I aim to use a coil based metal detector because it has a long range and can detect underground metals. There was a ...
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1 answer
59 views

Photodiode arrays: how can different wavelengths be compared?

In DAD (diode array detector), aka PDA (photodiode array) detectors, the light is dispersed and different wavelengths fall onto different diodes. This allows finding out which wavelengths were present ...
1 vote
0 answers
112 views

Low intensity UV light detector

I wanted to build low light UV detector, I mean the measurement of light with wavelength 405 nm. I found two schemes: First circuit: And the second circuit: I wanted to use operational amplifier ...
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1 answer
31 views

Counting rotations of plastic and metal plate

I have a thin (~1-2mm) rotating plate, where one side is made of metal and one side is made of red plastic and I want to count the number of rotations it makes. The plastic and metal plate are housed ...
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1 vote
1 answer
21 views

Looking for a simple circuit to switch power to IR LED's at night (2A @ 12 volts)

I'm looking for a simple and cheap way to switch power to a few hi-current IR led's at night. So some sort of photo detector and a solid-state or traditional relay. Unless there's a single-component ...
0 votes
2 answers
130 views

Turn signal detector

I'm trying to figure out the simplest design possible. I want a video camera to activate on my truck when I activate either left or right turn signal. Each side mirror has its own camera. So basically ...
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2 answers
173 views

Peak/envelope detector circuit for 30 MHz sine pulses with a 10 kHz PRF

My goal is to input 30MHz sine pulses, with a pulse width of 10us and gap of 90us between the pulses. The circuit should convert this pulse train to a TTL signal that goes from 0 to 5 volts. To ...
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2 answers
88 views

Is this circuit measuring the electrical field?

I have found the following circuit on the web (https://electroclinica.org/2018/03/23/fabricacion-de-un-sencillo-medidor-de-campo-de-rf-diy/) which claims to be an "RF field" detector/meter/...
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0 answers
39 views

How to add more lights and sirens to motion detector

I have a motion detector size of a cigarette box that rings bell or simple song when activated using a small remote control. We turn it on after closing the business to go home. We've had many ...
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1 vote
2 answers
103 views

HF Peak detector

This is a peak detector taken from page 21 of the opamp ADA4610: I need it to capture peaks from 500KHz sine wave. I can't understand why when the sine starts it goes above the peak and then ...
0 votes
1 answer
99 views

Novice looking for help with a current sensor circuit

I'm an electronics novice trying to figure out how to detect when current is flowing to certain tools in my shop so I can add some automation to my dust collection system. I essentially want to build ...
-1 votes
2 answers
515 views

Gain of photodetectors

I found this in a lecture about "Optical Wireless Communications." It is slide 15. Does anyone have idea how gain was computed?
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2 answers
230 views

Antenna for contactless 50/60Hz AC detector

Many simple circuits can be found online for building an AC detector that look something like the circuit below. These are simple devices to e.g detect AC lines in your walls. They feature a short ...
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3 answers
430 views

Balance metal detector sensitivity for smaller pieces of metal

As suggested by Andy in these posts proximity sensor technology, range of 150mm, Metal detector "Head sensor" and How can I drive an LC tank circuit to get a nice and clean sine wave?, I ...
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2 answers
289 views

AC current detector / sensor without splitting wires

I saw this question about measuring AC current without splitting wires. I understand why this is difficult and inherently imprecise. Is it, however, easy to just detect whether an appliance is on or ...
-1 votes
1 answer
367 views

Simulate a double balanced coil for a metal detector on PROTEUS

I am trying to build a metal detector with double balanced coil, (the scheme source is the french magazine : L'ELECTRONIC POUR TOUS project: EN1465 Un détecteur de métaux très sensible, the magazine ...
10 votes
6 answers
1k views

A few questions on PIRs and other motion detectors

I grew up incorrectly believing that motion detectors (as part of burglar alarm systems) were designed to detect movement, when in actual fact it is the movement of a heated (like body heat) object ...
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1 answer
445 views

Circuit to detect only one zero crossing when a sine wave changes from negative to positive half cycle

In a Grid Tie Inverter design, I need a circuit which can detect only one zero crossing of the Grid signal, (when the signal will change from negative to positive half cycle). I have made a circuit, ...
1 vote
1 answer
83 views

Detecting a location of the needle inside a cavity having multiple IR emitters , using IR Detector at the tip of the needle

I am working on a project where I need to find the location of a needle that has the IR detector at the tip of the needle. These needles are medical suturing needles that would help us to detect the ...
0 votes
1 answer
79 views

Microwave detection circuit verification

I want to develop a circuit which can detect electromagnetic waves (radio wave, microwaves.) This circuit will just act as a tamper detect and not physically measure/compute the radiation. I have ...
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1 answer
449 views

Metal detector circuit description

I found a circuit for this metal detector and would like to make PCB. I can not find anything about this circuit. Maybe someone would know what this circuit is. What are the best component housings to ...
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2 answers
913 views

Why are alkalines "required" for metal detectors?

A handheld metal detector specifies only "Alkaline" batteries and not "heavy duty" or "rechargeable". Since there are li-ion 9v batteries available not at low cost I was ...
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1 answer
60 views

Designing a Light/Dark Sensor with LDR 555 alternator LED and Motor

I am working on a project which I need to turn on LED alternately as well as motor turned on while it is dark. I managed to create an Electric circuit which can turn on the LEDs together. However ...
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0 answers
29 views

Feed-through termination to vary bandwidth and signal power

I'm currently facing an interesting problem regarding RC low-pass filters. In my experimental setup, I have a reverse-biased photodetector (DET01CFC from Thorlabs). To amplify this signal, I make use ...
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1 answer
109 views

Is this a demodulated signal?

1st attempt I have a problem. I built the FM demodulator circuit, but i am not sure if this signal is demodulated. This was my first attempt which following an answer, resulted in a 2nd attempt ...
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1 vote
1 answer
227 views

How to balance antiphase Rx coil in metal detector?

In this question How can I drive an LC tank circuit to get a nice and clean sine wave? I learned to get clean oscillation waves of a tank circuit (Tx) and consequently its reception through antiphase ...
2 votes
3 answers
799 views

How can I drive an LC tank circuit to get a nice and clean sine wave?

As advised by Andy in this post, I constructed single loop transmit and receive coils: I use this circuit to transmit a powerful field: The Tx signal has a large spike that is reflected in the Rx ...
0 votes
1 answer
216 views

Linear regulator power consumption

I have this circuit linear regulator with UVLO so I would like to calculate the power consumption of this block any person can help me, please Vout = 1.5 V (Iss = 15.2 μA, Vout = 1.5 V, switching = 32....
1 vote
1 answer
817 views

Envelope detector RC values [closed]

I have understood how the envelope detector works, but I am unable to find the formula for R and C appropriate values. The closest I have found is this link: Explain The Square Law Demodulation and ...
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0 answers
28 views

Maximizing signal to noise ratio for very small radiation detector

I have a very small radiation detector that outputs signal of small amplitude. Requires preamplification before going to an actual amplifier. When constructing the system prior to the preamp, would I ...
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1 answer
75 views

How do I calculate the power consumption of the polarity detector circuit?

What method can I use to calculate the power consumption of this block? In the paper it's equal to 3 μW at 1.5 V. The datasheet of the piezo sensor. The datasheet of the MAX9119 comparator. Circuit:
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1 answer
189 views

How does this under voltage lockout (UVLO) work?

In my project, I need an under voltage lockout (UVLO) to connect the load electronics to the energy-storage element via a power-gating transistor when the voltage across the supercapacitor exceeds ...
2 votes
1 answer
860 views

Help choosing modern replacement for Hitachi 1SS86 Schottky diode

I’m trying to find a modern Schottky diode to use instead of the 1SS86 Schottky diode (Hitachi version, specifically). I want to use it along with a low current LED to build a lectenna that works for ...
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0 answers
62 views

Fisher Scientific T-30 Metal Detector - Circuit schematic

Looking for service manual for this old thing or a very similar detector it is from 1965 with germanium transistors .. I didn't think there was any real use for it until someone asked .. some photos ...
1 vote
2 answers
185 views

Infant cry detector

I want to use an electret microphone to detect infant cry. I came up with this design: According to those papers: Pitch Analysis of Infant Crying Frequential Characterization of Healthy and ...
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1 vote
1 answer
118 views

Amplitude detection

Why is second analog multiplier(marked with red color) used to detect the amplitude of the input signal in this circuit instead of diode? The point of this circuit is to maintain the output level of ...
1 vote
1 answer
298 views

Simulation of voltage sensitivity of ideal detector diode circuit

Application note 969 derives the voltage sensitivity at zero bias of a detector diode: \$ \gamma = \frac{V_o}{P_{\rm in}} = \frac{0.52}{I_s(1+\omega^2 C_{j0}^2 R_S R_V)} \cdot \frac{R_L}{R_V+R_L}, \$ ...
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1 vote
2 answers
101 views

Switch off power when 0v is sensed / Short to ground

I have already posted this question but I made a mess of the diagram so deleted it and am posting again, apologies to anyone to answered the original question. I'm fairly new to electronics and am ...
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2 answers
547 views

How would i go about detecting if a rs-485 cable is plugged in?

The basic problem were trying to solve is certain secondary device's cables gets left unplugged and we need a way to detect a cable that is plugged into my device,and check if that cable is actually ...
0 votes
0 answers
69 views

Transformer-insulated flame ionization detector. How to improve response? Triode, messure current safety, ignition fires

I am trying to do a isolate flame ionization detector with a transformer ignition. But, when I put it on the frame, nothing change.. (0.2VAC) I put a amplifier (10 teraohms impedance) to read the ...
3 votes
2 answers
103 views

Use of ceramic capacitors in HV system

When I opened the supply board to the detector (Geiger counter,) I got the above circuit. The detector uses a gas-filled tube with a central wire at high voltage to collect the ionization (charge) ...
0 votes
2 answers
134 views

Sequence Detector forced to wait a specific number of bits

So I have this little problem, where I am supposed to build a sequence detector which is forced to wait a specific number of bits before going into the reset state. It's kind of like pin codes work. ...
1 vote
3 answers
1k views

Most simple way to detect small voltage changes(~150mV)

I have one unit of museum cabinet detector that works on 18v. I want make simple security circuit with detector. I've figured out that two output ports on detector are normally contact(NC), but it'll ...
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