Hot answers tagged

19

The reason for the long gap is so that the transmitter can send all of the other servo positions. In the days of clothes-pegs and crashed aircraft from frequency collisions, radio control was done with AM at 27 MHz. The transmitter would send a sync pulse, and then a series of 1-2 ms pulses, one for each servo. The earlier ones delayed the later ones, didn'...


16

The reason such a pulse is so destructive is because it has a broad frequency range, and can therefore affect things with a wide range of physical dimensions, and the large amplitude of the pulse. Every bit of conducting material acts like a antenna. In normal experience here on earth, ambient RF radiation is so low that the resulting currents and voltages ...


15

Those are small PCBs with a passive filter network in a single inline pin package potted with epoxy. The schematic on the far left within the dashed lines shows the components of a single board (notice, the pin-out for that part of the circuit is labeled 1-7), and it is not drawn for the others (presumably identical) to save space. You can replace them with ...


14

Any half-decent reputable resistor supplier will have pulse power dissipation limits such as this one from Vishay: - It tells you how much power can be delivered in a pulse to a resistor. For instance, an 0603 resistor can take pulses of power up to about 20 watts if the duration is only a micro second. For a milli second the power can be no more than 1 ...


14

In the video the circuit worked as if the negative pulses were nonexistent. Yes, that effect is due to the chip. Let's have a look at the SN74LS08's datasheet and look at the circuits on the chip: Notice the two Schottky diodes between the inputs A and B and GND. These diodes are needed to protect the sensitive transistors in the chip. Nearly all chips ...


12

You want something called a one shot. Basically, you ignore everything except rising edges of your input signal. You copy the rising edge to the output, but make up your own falling edge. A one shot is a timing component that does exactly that. You can set one up so that when a rising edge comes along, it starts a timed pulse. Since your pulses vary ...


12

To the inexperienced it sound like a "trivial" task to amplify the signal from 1 V to 7 V, right? The problem is the speed you need for this. Your signal is 2 ns on, 6 ns off so that's 8 ns total, corresponding to 1 / 8ns = 125 MHz. 125 MHz is getting close to "RF" (radio frequency) signals, this means you have to consider parasitic capacitances and ...


11

Yes, these are called latching relays as Ignacio Vazquez-Abrams noted in his comment. From Wikipedia: Relay/Latching Relay A latching relay (also called "impulse", "keep", or "stay" relays) maintains either contact position indefinitely without power applied to the coil. The advantage is that one coil consumes power only for an instant while the relay is ...


10

Two things make an EMP weapon destructive: the tremendous amount of energy released the very short duration of time over which it's released Another smaller, but similar example is lightning. A lightning strike might release 500 megajoules of energy in just a few milliseconds. For comparison, a 50 kW AM broadcast station releases the same amount of energy ...


10

The actual 555 timer frequency depends on the RC time constant, which is strongly affected by variations in the actual resistance and capacitance. The resistor has initial accuracy spec (like 1% or 0.1%) and also varies with temperature. The capacitor also has initial accuracy spec (often +20%/-80% or worse) and varies with applied voltage. A better way is ...


10

Let's do a bit of rough gathering of numbers: Fry is a pretty relative term. Damaging a sensitive device that is actually designed to receive energy from electromagnetic waves is certainly much easier than to damage e.g. a fridge. So, let's stick with *intentional receivers. That mostly means phones, but maybe also things like drones, gate openers, intercom ...


9

The main problem of current is that when it runs through a resistance it drops a voltage and hence generates heat, which causes a rise in temperature. A lot of things will break down at a certain temperature (think of light bulbs, fuses). When the spot where the heat is generated is thermally-connected to something that can quickly absorb a lot of heat and ...


9

You may implement this digital design for detecting rising edge. simulate this circuit – Schematic created using CircuitLab The output will go high as soon as a rising edge is detected on the D input. The output is cleared on the next rising clock edge.


9

Any jellybean NPN transistor (2N2222, 2N3904, etc.) should work fine in this circuit. The manual is quite detailed in describing exactly what each circuit does. As Zuofu said, the 7-legged orange squares contain the passive circuitry shown inside the dashed line in the schematic diagram excerpt you show. One of these and a pair of transistors constitute one ...


9

The characteristic impedance of any cable at high frequencies is determined by the inductance per unit length and the capacitance per unit length. It should not to be regarded as a conventional lossy resistor - characteristic impedance is simply the impedance that the cable should ideally be terminated with to prevent reflections. So, reflections happen ...


9

As others have said, a Schmitt trigger will clean it up. Reducing the 51k resistor to 10k or so may help as well. Also consider this waveform distortion is irrelevant for the typical intended electronic music function of the IC. A perfect 18kHz square wave is barely audible under good conditions. The harmonics of the imperfect square are way above audible ...


8

You can have one 555 timer be the enable for a second 555 timer. One in mono-stable mode and the other oscillating at whatever frequency your pulses need to be at. Then just make the first 555's single pulse long enough to contain how ever many pulses of the second you want. simulate this circuit – Schematic created using CircuitLab Note the pin ...


8

The simple and obvious answer that meets your specs is: This thresholds the input around the midpoint of what you say the high and low levels are. In practise a little hysteresis is probably wise: This will create about a 50 mV hystersis band. For example, when the input goes high so that the output goes high, the input has to go 50 mV lower before the ...


8

Pulse handling is a highly variable characteristic. You can often find this this information in manufacturers' handbooks, occasionally on the datasheet. Some resistors are specially designed for pulse handling capability and that will be well characterized. Things like the trimming method can affect the maximums- I would suggest not taking chances if ...


7

To make a pulse generator, use a resistor, a capacitor, an AND gate and an inverter: simulate this circuit – Schematic created using CircuitLab To make a dual-edge-triggered pulse generator, use a resistor, a capacitor, and an XOR gate: simulate this circuit EDIT by another user: An excellent answer with one caveat: As the signal into the gate is ...


7

Sampling and quantization are two entirely separate concepts that you seem to be somehow conflating. If you sample a continuous-time signal without quantizing it, you do indeed end up with a PAM signal. But it is not a digital signal. An ADC both samples its input signal and then converts the amplitude of each analog pulse to a digital word. The word is a ...


7

Of course it is generating an EMP. I'm sure it works fine. The spark you mention when flipping the switch, that would only occur if it worked. The coil you've wound is a type of electromagnet called a solenoid. If the coil form that it is wrapped around is hollow (which it might be, it looks like a container for something, not sure what), try placing ...


7

Would I hear a sine tone or the speaker popping as if it was being pushed back and forth? Usually, for audio, the PWM frequency is substantially above 20 kHz (and usually above 100 kHz) so the speaker (if directly connected to the PWM signal) would reconstruct the audio on the cone because it has mass and cannot move the cone at the PWM rate. In other ...


6

Incandescent bulbs fail because the filament wears out and gets too thin, and then breaks. DC filaments also suffer from uneven wear called "notching". Since the filament gets thin and brittle over time, it tends to fail when mechanically shocked ( for example at turn-on when the resistance is low). There is a distribution of lifetime that is an ...


6

The point there isn't really Duty Cycle. The 1ms to 2ms pulse is one that is easy enough to "decode" both in analogue and digital circuitry, so it is adopted as a standard. You need standards to be able to mix and match stuff, and in RC systems there's many different applications and sub-devices, so the standard is strictly adhered to, to keep the market ...


6

The nuclear bomb EMP pulses can affect such a large area because the bomb contains such a large amount of energy. Referring to https://en.wikipedia.org/wiki/Nuclear_electromagnetic_pulse#Starfish_Prime and https://en.wikipedia.org/wiki/TNT_equivalent, the high altitude "Starfish Prime" which caused electrical damage in Hawaii, about 1,445 kilometres (898 mi)...


6

We have to assume that "it's impossible" is not the right answer, so that means that we can assume that the CPU has enough power to poll the pin at a rate that's fast enough not to miss any pulses. I don't know why you think that "you need to hardcode the transition pattern". All you need to do is find the 0→1 and 1→0 transitions and count one or ...


6

You have two errors which impact your 20 kHz simulation. The first is your hold capacitor. At 1 uF, a 15 V/usec slew rate requires a charge current $$\frac{dV}{dt} = \frac {i}{C} $$ $$i = C\times \frac{dV}{dt} = 10^{-6}\times 15\times 10^6 = 15 \text{ amps} $$ and there is simply no way you'll get that out of an AD825. A 20kHz, 3.4 volt triangle wave ...


6

You could consider just using a fast comparator such as a LM1711/1712 They will operate with a 10V or even 12V supply. At currents of 1mA or less you'll get almost the whole supply swing at the output. Output rise and fall times are in the 2ns range with a 10pF load, and propagation delay is less than 5ns typically with 20mV overdrive. A more ...


6

Electrons generally speaking do not travel through a wire. They do, very slowly, for DC current. So slow you could walk next to them, talk to your neighbor, and easily catch up. It's called the drift speed. It's mostly unimportant for electrical circuits. It can be important for static electricity and electrochemical processes. What travels through a wire ...


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