Questions tagged [detector]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
10
votes
1answer
419 views

How to design a 1-500MHz sine wave level detector to -90dBm?

I want to build a sine wave level detector that works for a single 1-500MHz sine wave in the range of -40dBm to -90dBm. This is a hobby project - so cost is not a big obstacle :-), but I want to stay ...
9
votes
6answers
746 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 ...
6
votes
2answers
4k views

Why does this CO detector forbid the use of lithium batteries?

I have several Kidde KN-COB-LP2 CO detectors installed in my house. They look like this: They operate on standard AA-size alkaline batteries, and typically last several years on such batteries. The ...
5
votes
3answers
10k views

Conversion from dBm to Volt/ meter

I have no experience with electronics but I have a question. Actually I'm using a circuit for a project that is able to measure RF power at its input in dBm; the circuit provides the integration of a ...
5
votes
1answer
945 views

Any simple short range metal detector?

I'm looking for a simple short range metal detector. I've looked everywhere and I can find only complex metal detectors circuits to find metal at several cms of distance, most over 60cm, they are an ...
4
votes
5answers
2k views

Tri-State Detection

Some of you may have read my answer here to detect when two digital signals are either high or low, i.e. not both tri-state. One method uses window comparators the other opto-couplers to detect when ...
4
votes
2answers
99 views

Reducing the range of a D flip-flop frequency detector

I'm designing a frequency tracking circuit and I came up with a circuit that tracks frequencies from Fclk to Fclk/2: However, it would be very nice if the bandwidth was a bit narrower, from Fclk to ...
3
votes
5answers
8k views

convert falling / rising edge to pulses with minimal components

I have a signal that changes from high state to low every few minutes, after changing state it will remain constant, all level changes are clean. I'm looking for the smallest possible circuit that ...
3
votes
5answers
806 views

Measuring relative rf signal strength [closed]

I'm trying to measure the relative signal strength received by a dipole antenna for orientation purposes. I'd like to do so using an ordinary multi-meter. I don't know much about RF circuits, but ...
3
votes
2answers
92 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) ...
3
votes
2answers
6k views

Parameters of a metal detector coil

I built metal detector called MiniPulse Plus (it is a kit. comes with calibration instructions but says nothing about the coil, except that it should be between 300-500uH). A circuit sends a pulse ...
3
votes
1answer
183 views

Triangulation with Single Tone FM TX and Three RX using Phase Detection [closed]

I'm looking for some IC and frequency suggestions to accomplish the following task. Modulate a tone onto a carrier and continuously broadcast this signal toward an array of three receiving antennas(...
3
votes
2answers
924 views

Identify discriminator circuit?

The Dynaco FM-3 tuner uses what appears to be a Foster-Seeley discriminator with one diode reversed, or, if you prefer, a ratio detector without the third coil and stabilizing capacitor. The Dynaco ...
3
votes
1answer
67 views

Noise in crystal detectors (historical)

I'm reading over the history of British WWII radar systems, and one thing that really struck me was the improvement in crystal detectors. The were a vital component of microwave radars, and while the ...
2
votes
1answer
2k views

Light intensity and photodiode current

Recently i am using a LED as a photo detector . Follow by this instruction : http://makezine.com/projects/make-36-boards/how-to-use-leds-to-detect-light/ An opamp is used to convert the photocurrent ...
2
votes
2answers
4k views

How exactly do I null my metal detector coils?

I've finally started work on my metal detector project and after a fair start, I'm a bit stuck. The circuit is based almost entirely on the buccaneer VLF circuit to be found here. I've made some ...
2
votes
1answer
381 views

High voltage led detector

I need a circuit to indicate if the DC voltage across two points is exceeded a certain High value (350 V) by using LED as an indicator. For example if the voltage is 355 V then the LED will light,but ...
2
votes
2answers
154 views

Is there a simple way to detect which connector is powered?

I have a circuit with two power connectors, J1 and J2. I would like to be able to detect which one the power is coming from. The trick is that the connectors need to provide power to each other. ...
2
votes
2answers
4k views

Falling and Rasing Edge Detector

I will use a motor adapter in my design.This motor adapter doesn't have a spice model. Therofore I will design inside structure of this adapter. In this motor adapter has a delay and xor gate part.I ...
2
votes
2answers
121 views

Is it possible to convert the audio signal from a smartphone's headphone jack into radiowaves? [closed]

I was watching a video of someone using his smartphone and a custom designed coil to make a metal detector. The smartphone was connected to the coil via headphone jack. I couldn't understand how he ...
2
votes
2answers
2k views

Bandpass Filter: Single supply op amp design

I have taken on a hobby project and I am trying to make a circuit which would be able to identify an acoustic signal with a frequency of 40kHz. Here is the circuit of a band pass filter for this: ...
2
votes
1answer
610 views

Detection of the 3G network

Is it possible to detect a 3G mobile network without having the orthogonal code or the spreading code used in 3G? By detect I mean pick up the radiated radio frequency from the mobile phone then see ...
2
votes
3answers
193 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 ...
2
votes
1answer
251 views

Building an inverted peak voltage detector

So I am trying to build a detector that will find the lowest voltage dip of a DC source. So for example, if I attach a load I can see what the voltage drops to. I have built this peak detector in ...
2
votes
3answers
647 views

Violin bow position tracking with SMD LEDs and photoresistors

Objective: Marking labels indicating the positions of the violin bow on an acoustic signal, for example, a single musical note played by a full-length bow. The following video shows the example I am ...
2
votes
1answer
784 views

High Power RF Detector Circuit [closed]

I was tasked to work on an 'RF Detector Circuit' for work. The circuit has an input RF power of 72 Watts at a 7.5GHz frequency through an 8mm wire. It's supposes to reduce that power and voltage, and ...
1
vote
2answers
2k views

Does a simple bug detector detect electric field or magnetic field?

Hi. This is a very cheap and simple bug detector that is supposed to make sound when it detect RF signals between 100Mhz-2600Mhz. I found out that it doesn't do what it supposed to do,since its ...
1
vote
4answers
3k views

High Frequency (16 Mhz-48 MHz) Peak Hold/Envelope Detector Circuit?

I'm trying to make a peak hold circuit for a very high frequency bandpass filter that needs to be able to operate at 16 Mhz, 40 Mhz, and 48 Mhz. I've singled out the peak hold part of my overall ...
1
vote
1answer
67 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
2answers
221 views

Flatness vs Frequency parameter in RF zero bias detectors

I require the measurement of RF power from a port, and I am considering using a zero-bias RF detector in order the measure the power being delivered through the port. These devices give a voltage ...
1
vote
2answers
128 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 ...
1
vote
1answer
130 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}, \$ ...
1
vote
2answers
88 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 ...
1
vote
1answer
101 views

Why do some TSOP1738 have a metal cross over their window?

Why do some TSOP1738 have a metal cross over their optical window while some do not have this cover? Does not it obscure the view and shorten the range of the sensor? Does it have some positive ...
1
vote
2answers
1k views

Envelope detector

I would like to have the envelope from a signal using a simple circuit composed of a diode and a low pass filter. I know : *Tam > t >> Tcarrier *The diode must be a germanium diode because of the ...
1
vote
1answer
704 views

RFID chessboard

I want to make a electronic chessboard that detects the position of every piece on the chessboard. So I did some research, and one way would be to put RFID tags under every chess piece. Each tag ...
1
vote
2answers
114 views

Automotive tachometer signal interpretation

I'm trying to build a custom dashboard for a car (Daewoo Lanos 1998 with Delco ECU). Tachometer signal, that comes to dashboard with a separate wire looks a bit strange to me. It seems that the signal ...
1
vote
2answers
477 views

Comparator as a current detector

I'm looking for a simple circuit that uses only a comparator (or an opamp) to detect the presence of a small current through a high-side current resistor. The idea is for a microcontroller input to go ...
1
vote
1answer
220 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 ...
1
vote
3answers
573 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 ...
1
vote
1answer
261 views

How to calculate noise power (dBm) of a photodiode?

I want to check the thermal noise spectrum of a photodiode (PD) at different frequency response but I do not know how to calculate it. Below graph is an example which shows noise power (dBm) as a ...
1
vote
1answer
461 views

Metal detecting using a small inductance

I have a coil with approximate indutance of 15uH used to detect metal through changes in inductance. I want to use an op amp or 555 to oscillate with frequency based on the inductance. However this ...
1
vote
1answer
670 views

Induction loop detector

I am trying to create an induction loop detector by following this http://www.allaboutcircuits.com/projects/metal-detector-with-arduino/ but apparently something is wrong on my side or I missed ...
1
vote
1answer
198 views

Mobile Phone Signal Flash Light 3-12V - not working. Circuit viable?

Another ebay-heist that does not work as adverstised. I build it, and tested with some normal g3 cellphones, but no dice. My antenna at J2 is an 8cm long wire (not really lambda/4 of anything, but i ...
1
vote
1answer
94 views

About the combination of two signals with capacitors

Here is a link of an article I've been reading. http://www.analoguehaven.com/moog/thereminblack/hotrod.pdf In page 4 there is a circuit schematic. Notice there is a part called variable pitch ...
1
vote
1answer
80 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 ...
1
vote
1answer
64 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 ...
1
vote
1answer
238 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 ...
1
vote
0answers
3k views

Metal Detector using IC 555 Timer project

I want to build some project about metal detector using integrated circuit 555 timer. I already made a schematic in proteus 8 application. I made some change with the original schematic i found on ...
1
vote
2answers
714 views

Non contact (contactless) AC or DC detection?

I'd like to detect AC or DC current (not the current level just nothing or something => ON/OFF) in a wire with a (DIY) sensor just in contact (glued) with the wire plastic insulator. At the end the ...