texts: Why do ceramic insulators have a stacked disc structure?

texts:
I've seen these stacked-disc structures on high voltage power lines everywhere. I could not find any information regarding this particular shape, though.

From what I've noticed, high voltage ceramic insulators only insulate conductors end-to-end (not inside to outside, like traditional plastic insulators). I can only assume the shape makes it difficult for an electric arc to travel along the ceramic material, as opposed to, say, along a solid cylindrical piece.

Why exactly are ceramic insulators shaped like that? Is it to reduce cost? Thermal concerns (from possible electric arcs)?


texts: What is the least expensive way to build a three-bit shift register?

texts:
I'd like to build a queue of three internal bits as inexpensively as possible. Externally, the queue has two input bits and one output bit. The inputs are (dataIn) and (shift), and the output is (dataOut). The internal bits are arranged from the left to the right, and can be implemented in any way imaginable, as long as it's as inexpensive as possible. In my mind's eye I'm thinking of something like a DRAM, where there's just one transistor/capacitor pair per each bit, but I don't know if that's possible.

The output (dataOut) always has the value of the internal bit on the right. While (shift) is low, all three internal bits just retain their current value. When (shift) goes high, the internal bit on the left takes the value of (dataIn), the internal bit in the middle takes the former value of the bit on the left, and the internal bit on the right takes the former value of the bit in the middle.

In particular, I'm interested in whether or not this can occur with just three internal bits, or whether instead each bit has to have a master (set on one edge of changing (shift)) and a slave (set from the value of the master on the other edge).

Also, a size of three is just a fairly simple example of what I want to have; ultimately my design is going to need much larger groups of internal bits.


texts: Altium Designer 21 Duplicate Net Name Error

texts:
I have a design that is erroring at compilation time with (among other errors) a bunch of duplicate net name errors. I have searched around including reading up on the top result for this problem (changing the net identifier scope doesn't solve the issue and causes many more errors).
The error makes no sense in context. I have three power rails in this design (12V 5V and 3V3). The project is setup in a hierarchy (top level showing connections between all other sheets). Power from the power supply to loads is done using Ports. Each schematic uses Net Labels internally to connect the Input Port to various components.
The error occurs on all schematics that use Net Labels which I guess makes sense but the nets are supposed to have the same name since they are connected (but visually it would be messy to draw a wire between the two points).
How do I inform Altium that the duplicates are intended?
P.S. I apologize for what may be terrible grammer it is currently 2:23AM as I write this.


texts: USB fail to pass ESD test even with TVS diode protection

texts:
I have read some articles about USB ESD protection and followed the suggestion to add TVS Diode Array USB6B1 in my design. However, my design is still failed to pass the ESD test and I don't know where the problem is.

This is the testing procedure and result:

Inject electrostatics on the product's metal surface, which is connected as the GND of the PCB.

-- The USB transceiver reboot and USB connection break.
Inject electrostatics on the USB port's shield.

-- Same result as step1.

This is the circuit about USB protection. The power source of the board isn't from the USB, so the VBUS output pin is floating.

Can someone tell me where my problem is? Thank you~


texts:
I am a beginner at digital electronics and I am supposed to create a circuit on a breadboard using some kind of a flip-flop. I designed the circuit and decided to use a D- Flip flop since I only have two inputs. However I don't know what to connect to the CLK input part of the flip flop on the breadboard. Is there something that works a clock that I can simple connect or should I build a clock input? I saw some examples using a cyrstal, will that work as the CLK input.

The answer may be straightforward but thank you in advance for your consideration.


texts: How does an induction motor start when it has no capacitor or inductor?

texts:
The photo below shows a bench grinder.  If you look carefully, there are only two wires for the main winding.  There's no capacitor or inductor.  I also verified this using the parts diagram.

I was under the impression that a single phase induction motor cannot start on its own without a capacitor or inductor connected to a secondary winding.

My only guess is that this motor is a shaded pole motor, but I was under the impression that they are too under powered for this application.


texts:
I have problem with my nixie clock. There are ghosts when changing numbers on the lamps.

I'm using multiplexing with TLP627 opto-coupler to control anodes and NPN MMBTA42 bipolar transistors to control cathodes. Transistors switch at 0.283 ms, TLP627 at approximate time. Extending the switching time did not help. I tried to solve the problem by extending the switching time of the lamps, but it had to be really long was almost 0.2 seconds, but was still ghosting. IN-14 lamp is powered by 180V, the current does not exceed 0.9mA on it. I'm running out of ideas ;(


texts:
I'm considering re-implementing my thermistor measurement circuit to be isolated, since it's destined for an industrial environment. The thermistor is a simple passive sensor and is not grounded on the far end.

U1 is a 5V/5V regulator rated for 3kV isolation. The line out to the thermistor is connected to protection shottkys, a TVS zener, and caps that set the time constant at (I think) ~1s.

U3 is a "linearized" optoisolator rated to 3.75kV isolation.

Back-of-the-envelope calculations for the following nominal values:

the input and output of U2 at 2.5V,
the LED current at 8.7mA,
Irm1 = Irm2 = 90uA,
line time constant = 853ms

simulate this circuit – Schematic created using CircuitLab

Questions:

Have I made any mistakes in how the circuit is connected or the passives are chosen?
Is it even necessary for this isolation to be done, given that the far end does not have its own ground?
Are there any rules I should follow with regard to PCB layout (especially shuffling around the diodes and caps, etc.)


texts:
I need help solving this task, if anyone had a similiar problem it would help me.
The task is:
Determine the power dependence for an electrical circuit
current through the receiver Rp in relation to all generators in the circuit. What is the contribution
current through the receiver of each of the generators separately?

I tried this:

$$Re_1=\frac{R_p\cdot R_4}{R_p+R_4}$$

$$Re_2=Re_1+R_3$$

$$Re_3=\frac{Re_2\cdot R_2}{Re_2+R_2}$$

$$ U_{AB}=\frac{E_1}{R_1+Re_3}\cdot Re_3$$
$$I_{11}=\frac{U_{AB}}{R_p}$$
Is this right for I11?
Thanks in advance !


texts: Is there such as thing as an ideal Zener diode?

texts:
I was trying to clamp voltage down across a 2.7 V supercapacitor and by measuring what is going on was reminded that Zener diodes have both a very soft "knee" region and a leakage current I can't ignore (several mA for the ones I've used). Is there a type of Zener diode which would have a sharper knee and next-to-no leakage current?

Alternatively, what else could be used instead of a Zener diode? What leakage could be expected from an LDO regulator?

Well... garbage in, garbage out :) I was using the name "ideal diode" in the sense of such circuits (made from FETs) I've seen described, but after reading more about them, they are probably not what I can use here.

I'd value more something which would have next to no leakage current (single-digit µA range) than a sharp knee (where I basically need to clamp a power source which could in theory spike up to 5 V down to the 2.7 V the supercapacitors can handle).


texts: I recently built a device which needs to be charged using a standard 12v adapter and a certain number of amperes. I was told the adapter needed to be at least 3A to charge the device. So my question is can I use any number of amperes as long as it's greater than 3A, for instance a 12v 5A adapter? I just need to know if using more amperes than the needed amount is fine, or if it can be harmful at all. Thank you


texts:
My wife said her office had an old UPS that was being scraped because it wasn't working.  I picked it up and plugged it in and nothing happened.  No lights, no warnings, nothing.

It's a small guy.[EDIT: APC Smart-UPS 700]  Holds two 12V 7.2Ah batteries in series.  I checked the batteries with a volt meter and each of them are sitting at 2.7-3Volts each.  Okay, really dead batteries.  I hooked the battery connectors to my DMM and plugged it in again to check for voltage.  I got a quick spike up to around 8 volts when I first plugged it in but then the voltage just bled away...assuming a cap discharging (?).

I guess my question is this.  If there are no batteries connected to a typical UPS (it's like an APS brand UPS) will it just sit there and act dead?  What is the usual way a UPS goes about doing its job of providing power while collecting some for a rainy day?

I don't really want to go out and buy new batteries for this unit if I haven't confirmed it works.

What can I check before I start ripping the thing apart for connectors and inductors?


texts: Circuit only works while touching the ground

texts:
so I am doing a small ESP8266 relay module. The relay is used as a SPDT switch so you can turn on the light with a normal switch on the wall but the module can shut them off after no motion is detected and vice versa. With this approach I need to know whether the light are already on or off so I don't turn on light that are already off.
To do this efficiently I used the flowing circuit:

The PCB is 4 layer stackup (top - GND - 3.3V - bottom). As an antenna I made a small 5-turn wire loop around the common pin on the relay contacts on the second layer (GND). I don't have a ground pour under the relay and AC supply. After I assembled the PCB I noticed some weird behaviour, but removing the LED and replacing it with a 1k resisitor and adding a 47uF electrolytic capacitor to the existing one I can get it to work but only if I physically touch the ground with my finger, if I don't it either doesn't change state or just pulses (50 Hz). I can't really scope the circuit  because when I connect the scope ground it works normally. This seems to be some grounding issue but I can't figure out how to fix this so if annyone has some input on it I would be thankful.


texts: Pressure switch and wattage temperature control of water heater

texts:
I need this last data to help decide what to do with it. Note for Multipoint heaters located not inside shower area, one doesnt usually turn if off, so this safety is bypassed. Anyway this photo shows another brand with thermostat control from low to high like in a radio button or volume

 It can even get warm with very little water. Does electronic control of temperature give another layer of safety? Like it cant suddenly go to maximum? Because i may buy another just like in the picture if electronic control of temperature add another safety layer and give away the old heater or take it apart as an electronic collection.
Previous post
The instant tankless water heater has 3 switches: low, medium and high. The spec mentions when at low, 2.5kw is used, medium at 3.5kw and high at 6kw. Does it use full wattage is used or can it adjust at say low temp switch to say just 1kw. Here is the power diagram.

In the original i was contemplating about replacing the pressure switch with a flow switch so it can turn on at lower water pressure:
Any illustration what is inside the pressure switch water pusher (the white round thing encircled in green label) of this instant tankless multipoint water heater?  When there is certain pressure, it pushes the switch on the left of the round white part
Also why don't they just use a flow switch instead of a pressure switch?


texts: Connecting an electret microphone to an ESP32 via MCP3424

texts:
I have a need to use an electret microphone to sense noise level spikes for impact detection.
My circuit consists of an ESP32 communicating with an MCP3424 via I2C. The electret micropgone is a CUI CMEJ-9745-37-P (datasheet).  The microphone is connected to MIC_1 (+) and MIC_1- (-).  I2C_SCL and I2C_SDA are tied high via 10k pullup resistors as the datasheet recommends. I am using the MCP342X library.
In my program, each loop I'm doing a simple one shot conversion request and I can only ever get values 1-9 if I tap my finger on the microphone with a lot of force. Even then, it might just be interference that I'm picking up.  The connection test to the ADC chip in the setup() method seems to pass as I get the successful connection printout.
Any ideas why I'm not able to get a solid input with this type of setup?  If not, any recommended setups for interfacing an electret with an ESP32?  I'm trying to opt for minimal component count and the 3424 with its 4 channels and I2C interface looked like a good option at the time. I've tried all the different gain settings (1X, 2X, 4X, 8X).
The schematic is below:

Code:
#include <Arduino.h>
#include <Wire.h>
#include <soc/sens_reg.h>
#include <soc/sens_struct.h>
#include <esp_adc_cal.h>
#include "ESP32TimerInterrupt.h"
#include "MCP342X.h"
MCP342X adc1 = MCP342X(0x68);

void setup() {
    Serial.begin(115200);
    adc1.configure( MCP342X_MODE_ONESHOT |
                   MCP342X_CHANNEL_1 |
                   MCP342X_SIZE_12BIT |
                   MCP342X_GAIN_2X
                 );
    Serial.println(adc1.testConnection() ? "ADC1 MCP342X connection successful" : "ADC1 MCP342X connection failed");
}
void loop() {
    int16_t result = 0;
    adc1.startConversion();
    adc1.getResult(&result);
    if (result > 0)
        Serial.println(result, HEX);
}

EDIT: Applied voltage and appropriate cap/resistor combo per Mattman944's suggestions resulting in the following schematic:


texts: A question on limits of resistor vaules in an op-amp input

texts:
Here below is a non inverting adder where the resistors R1 and R2 are preventing the loading of V1 and V2. But when determining their size there is a limit as far as I read.

When reading a comment on sizing resistors for the above circuit, it was mentioned that 10-100 kΩ will be good value for most cases. It is mentioned that if we make R1 or R2 too high, the node on pin 3 will too easily pick up stray noise. What is meant by stray noise here and why the high R1 or R2 had a bad effect? Is there a way to explain this in a simple model?


texts:
A Joule Thief is a simple step-up converter with which you can drive a 3.6V LED with a 1.5V battery even if it is spending the last drops of its life. It merely consists of a transistor, a transformer and a resistor.

The circuit is very forgiving especially concerning the number of coils of the transformer. But I was wondering if there is a way to precicely calculate the voltage produced. It would be nice to use an old 1.5V battery to power a microcontroller. I read people reporting that zeners would interfere with the oscillating behaviour of the circuit.

Does anyone have deeper knowledge of these kind of circuits? And would it be possible to create a stable 5 volts to power a microcontroller?

update
The discussion here is the closest I could find and the request is very similar to mine.


texts: what i did here is take current over the 4.7 kilo ohm and since there are no other voltage input other than the one then shouldn't the Vout be 0.2127 volts? thats not possible for a non-inverting amplifier right? do i just assume Vin = Vout in this case then?


texts: How deep does the depletion region in power diode penetrate the lightly doped n- layer under no bias?

texts: I could find references for describing the depletion layer in a power diode under reverse bias and the consequent classification of Non-punch through and Punch-through diodes.  But I couldn't find a satisfactory explanation of how the depletion layer looks like under no bias. How far does the depletion layer extend into the n- layer? My guess is that the depletion layer width is small in the heavily dopes p+ region and large in the lightly doped n- region (but less width than in reverse bias condition).


texts: How to detect whether a solenoid is actually attached to a MOSFET?

texts:
An injector is usually switched to ground to turn it on using a an N channel Mosfet. But how does the MCU knows when this is disconnected?

I'm trying to drive a solenoid, but if the solenoid is disconnected, I'd like my MCU to know that.


texts: (Reasonably) accurate 1Hz clock generator

texts:
I would like your advice on components before I purchase anything.

I am going to make a digital 24hr clock using probably JK flip flops/multiplexors with 7 segment displays. But it must be battery-operated.

Is using a 32kHz quartz crystal, a good way of producing a 1Hz clock signal for my FF's? I know I will have to do some frequency division (2^15) with FF's.

If so, is there an IC I can buy that produces a 1Hz output signal? If anyone knows any part numbers off the top of your head, it would be good if you could share them.

Does the quartz crystal require any other circuitry to operate?

I haven't used the mentioned component before, sorry if the questions are silly.

Thanks


texts: How many turns do I need for the primary coil of a transformer?

texts:
I need to know the number of turns that should be connected to 220 volts AC.
I can measure resistance only, I don't have a device that measures inductance.

If I need the primary coil to be 220V / 1A (For example). Can I omit the inductance and turn (wound) the coil so that it has 220 ohm of resistance only? Does that make a major difference in the current?
If I can not do that, How can I know the number of turns without knowing the inductance?

Thank you very much,


texts: What stages do PCB mass-assembly techniques come in?

texts:
There's a spectrum of how you get PCBs assembled.

1) Have a human pick out all the parts, solder them all on by hand, and check them all by eye. Low cost of entry. Good for low-volume high-mix work. Surface mount is difficult/impossible, depending on the package.

N) A pick-and-place machine, wave soldering, and automated optical verification. Very expensive equipment. Only cost-effective at high volumes, 100+ at least. Through-hole is difficult/impossible for some pick-and-place machines.

What's in between? Reflow ovens? Automated solder paste dispensers? Some sort of automated part dispensing system that's between a wall full of bins and a pick-and-place machine? Stuff I haven't imagined?

The bigger question is this: what steps can be taken to increase the efficiency of an entirely hand-solder operation? In what stages can such an operation make the transition from all hand-soldered to fully automated production? And what is the cost range on the equipment involved?


texts:
I had to find the resistance of this circuit between A and B. My teacher said that since the blank wires have zero resistance, the potential difference across the ends of the blank wire is zero(according to v = ir) and thus 1,4 are equipotent and 2,5 are equipotent and the circuit is thus simplified.The equivalent resistance comes out to be 2r/5.

MY QUESTION:If the points 1,4 and 2,5 are equi-potent how can current flow through the circuit.

MY REASONING: The potential difference across each branch of a parallel circuit is same and in this case it is 0 and hence no current can flow through the circuit.


texts:
I'm working on a project for which custom ICs are being designed by another person on the project. The process being used is a mixed voltage CMOS process which uses a \$1.8\mathrm{V}/5\mathrm{V}\$ logic level along with a \$60\mathrm{V}\$ high voltage capability. Essentially the circuits being designed involve high voltage output drivers which must be driven from the low voltage logic. Naturally this requires level shifting.

The high voltage transistors in the process are designed for \$60\mathrm{V}\$, but as with most transistors, this is only the \$V_{ds}\$ rating. The \$V_{gs}\$ rating is naturally much lower - in this case only \$5\mathrm{V}\$.

The restricted gate voltage clearly makes level shifting difficult - somehow a \$5\mathrm{V}\$ control signal for the low side needs to be shifted up by \$55\mathrm{V}\$ in order to control the high side transistor of a half-bridge. However this is not a simple task as the gate voltages are limited.

The IC guys who are working on this basically have two solutions. Firstly, use a resistor for the high side rather than a PMOS which as you can imagine would consume an awful lot of power as the resistance needs to be low enough to achieve fast rise times (\$20\mathrm{ns}\$) into a fairly large (\$10\mathrm{pF}\$) capacitive load. Secondly, use a resistive divider driven by a low side NMOS to produce the \$60\mathrm{V}/55\mathrm{V}\$ logic level for a high side PMOS - but again this would use a lot of power as the gate of the PMOS is a ~\$2\mathrm{pF}\$.

Not being an IC designer myself, I'm leaving them to do their job, but I suppose it's just been bugging me. I can't help pondering over the problem and thinking there must be a better way, but I can't think of one.

I'm curious as to whether there are typical ways of achieving this sort of level shifting with limited components?

Effectively the only components are the PMOS/NMOS above, resistors, diodes, and I think 5.5V Zener diodes too. There are capacitors in the process to but as I recall they are low voltage, so couldn't be used in structures I've seen that can level shift pulses over a large voltage using capacitors for isolation.

I suppose what is bugging me the most is it seems odd that IC fabs offer high voltage processes with seemingly no 'nice' way of linking the PMOS and NMOS transistor together to form push-pull drivers.


texts: Controller area network arbitration with same message id

texts:
I am learning Controller area network. The arbitration for bus access is done with a message identifier(as given in CAN specifications). So if two nodes tries to transmit data on the bus with same message Identifier, then who will win the arbitration or what condition will arise under this situation?
Maybe this is a silly question to ask at initial stage of my learning but if this condition arises how will the CAN bus behave.


texts: Why do resistors in parallel with each diode in a diode string prevent high voltage damage?

texts:
The book said that we can increase the reverse blocking capability, and when we connect a resistor in parallel with each diode it can protect the diodes from high voltage damage.

Why?

Parallel connected resistors can't divide the voltage, but the series connected can.

I mean if the the voltage in the  \$A\$ point,\$V_a\$, is \$100V\$, then the voltage in the \$B\$ point, \$V_b\$, should be \$100V\$, too,\$R_2\$ can't decrease \$V_a\$.

So why do lots of books or websites say to connect a resistor in parallel with each diode to protect the diodes from high voltage damage?


texts: How does this RPM sensor work? – Induction in an open circut

texts:
I'm looking for explanation of some basic induction concepts.

It's common to see an RPM sensor for small two and four stroke engines where an open-ended wire is coiled around the spark plug's ignition coil wire at one end, and the other end of the wire is simply routed to pass in front of a conductive plate connected to some circuitry which then apparently does the pulse counting. Hooow exactly does this work?

1) From what I understand, the ignition coil's pulsing current produces a pulsing magnetic field, which is now aligned with the "sensor wire's" coil around it, thus inducing a voltage potential in the sensor wire? In a closed circuit where there's actually a current flow, I can understand that induced current, but I actually don't remember anything from my uni EE courses about induced voltage.

2) On the other end of the open-ended sensor wire, where it simply passes closely in front of a conductive plate, how exactly does that plusing voltage potential in the wire affect the conductive plate such that it can be measured? Obviously there must be inductance happening here as well, but that's still not clear to me when there's no current.

I've definitely done a lot of video watching and reading, but I've been unable to connect these dots.


texts: Using LEDs as light sensor - how to level shift 0.2 V logic up to 3.3V threshold

texts:
I have a reel of punched paper tape (https://commons.wikimedia.org/wiki/File:PaperTapes-5and8Hole.jpg) and I would like to design a simple optical circuit that can read the binary values from it using a microcontroller.
The punched holes are on a 0.1" pitch, so I was hoping to use a pair of "10 Segment LED Bar Graph" displays, one as a simple illuminator and one as a light sensor.  Imagine the tape sandwiched between them with the light being able to pass through the holes.
The voltage emitted by the sensor when the LED shines directly on it is 0.2 V, and naturally 0 V when the light is blocked by the paper.  The microcontroller I want to use is a 3.3 V unit so naturally I need to level shift this potentially noisy 0.2 V pulse train up to as close to 0-3.3 V as possible.
I'm not particularly well versed in the finer points of NPN transistors as voltage amplifiers but I managed to come up with this so far (Voltage source V4 is pretending to be the LED light sensor outputting a digital pulse sequence, and the OUTPUT on the right goes off to the microcontroller's input pin)...

Now LTSpice seems to indicate that it would work quite well, because the amplified signal transitions through the microcontroller's threshold region (~1 to ~2 V) rapidly and sweeps the majority of the 3.3 V supply.
Is this naive design likely to have any downsides?  Can it be done using fewer parts?  I'm going to have to solder all this together dead-bug style and cram it carefully into a tight space so reducing the part count would be handy.
Additional info:
I'll be pulling the paper tape through very slowly by hand so I'm only aiming for perhaps a top speed of 10 bits per second through this circuit.


texts:
There is something I'm struggling to understand about passive RC filters: When considering a simple low pass RC loop, what exactly is the gain/output at DC and low frequencies? I've been assuming two possible events:

The input charges the capacitor, setting the output equal to input as soon as the capacitor is charged;
Due the high reactance of the capacitor at DC and low frequencies, the current, the capacitor can be ignored, and thus there is a small drop across the resistor, which will depend on the load resistance and current.

However, both seem to contradict each other, particularly as to whether or not there is an actual voltage drop across the resistor.


texts: I understand that the Radio Frequency Choke at the collector of a Common emitter is suppose to block the radio frequency from reaching the transistor and therefore interacting with the output. So by adding a resistor Rc in parallel to the RFC don’t we essentially nullify the RFC?


texts: About ground when dealing with batteries

texts:
my question is how I decide my ground reference in a circuit when only using batteries.
Let's say I'm using a battery pack with slots for up to 2 AA 1.5V batteries, creating 3V. In this case, I will use 3 of these batteries packs in this circuit. Two of them will be connected in series, creating 6V and one will be standalone.
Using this picture to describe my scenario.
If my V1 has 6V (Two battery packs in series), and my V2 has 3V (Only one battery pack)
Where will my ground be (do I decide it?), is it under V1 (negative pole) or can it be in the same terminal as the negative pole of V2?
If I wanted to measure the voltage at any point of the circuit, what will I use as a reference?

This is what a battery pack is


texts: Digital circuit to toggle on rising edge of two signals

texts:
I need to design a circuit to toggle on the rising edge of two signals A and B. A is a square wave @10Hz, 50% duty cycle. B is a pulse that gets generated approx 20-30us after the rising edge of A.
I came up with a circuit to achieve it, but it uses monoshots which I wish to avoid. The monoshot is triggered by the pulse and it's Q' as well as signal A are the inputs to an AND gate to generate the required output Y=A.B'
Can you suggest a better way which uses digital circuits only? Thanks.


texts:
I am using an ADC MCP3424.

After breaking one of the ADC inputs, I was saw this thread:
ADC input protection?

I also read Microchip app note TB3013. Figure 3 in particular:

The ADC's analog inputs need to be clamped at ± 0.3V of the supply rails.

The Vf of a schottky like BAT85 depends on the current flowing through it. So for a Vf < 0.3V, we would need a series resistance of 10k, to keep the current less than 1mA (assuming the Opamp Supply is +15V/-5V). Now the problem is wouldn't the 10k resistance slow down the charging time of the sampling capacitor and reduce my 18-bit accuracy? I am measuring slow moving DC voltages.

Is there any solution for the problem ?


texts: Reducing electrical noise induced from a small DC electrical fan

texts:
What's a canonical method for reducing / eliminating electrical noise induced in ADC from a small brushless DC fan? For reference below, I'm also using this wall-wart and this 5V linear regulator.

My baseline system looks like this:

I have some options in my head and I'm wondering what the best one might be.

My first idea is this [OPTION A]:

My second idea is this [OPTION B]:

My third idea is this [OPTION C]:

There are probably other options that I haven't thought of, as well as permutations and combinations of these options. What are the merits and drawbacks of these options? What option would you choose and why?


texts: Output of XOR gate with high-impedance input

texts:
One of the exercises in university was to output a truth table for the gate, which takes an input

t, and returns

t ^ t, where ^ is a xor gate.

Now if t = 1 or t = 0, the output is always 0.
Furthermore, even if the input is
t = X (don't know), the output is still 0.

What I am not sure is the answer in case an input is Z (high impedance).

My guess would be that the output is also Z, because the output wire is not driven by anything. Could anyone confirm / deny this?

Also, any other examples using other gates (such as AND / OR) and Z values would be appreciated.


texts: VHDL: Are if-else and case statements supposed to synthesize the same hardware?

texts:
The if-else and case statements are equivalent. The later maybe easier to read when we have a lot of possibilities being checked.

A conditional is supposed to infer mux in hardware. However, there is different between having a chain of 2-to-1 mux and a big n-to-1 mux doing the same thing in terms of propagation delay.

Is the if-else statement and case statement supposed to infer the same hardware? Or is there some difference in how they would be synthesized?


texts: 2 terminal SMD resistor marking code with Omega+F

texts:
What kind of code are the markings on the resistors in the picture?
I think they write out the Omega symbol, just because there is enough space on the component and looks nice, but I was not able to find any matching result online about the meaning of the letter 'F' and 'J'.
What kind of marking system is it?


texts: How to find the power absorbed by independent voltage source if there is an independent current source

texts:
I have a circuit as shown in the figure below:

I want to find the power absorbed by the voltage source (which I think should be negative, considering voltage sources deliver power not absorb them). Let's say I do not know what the value of V1 is. I have connected an ammeter in series with the resistor. Let's say it gives the following values:
a. 2A
b. -2A
c. 9A
How would I find the power absorbed?


texts:
I have a SN75176 chip. The datasheet shows it with a semicircle at one end for orientation however my chip looks like this:

Is it safe to assume the pin by the circle is pin 1?

Why would the datasheet show a semicircle and then a circle at the other end?


texts: Dirac Delta Impulse Response of series RC circuit (Voltage across the capacitor)

texts:
I have evaluated the transfer function of an \$RC\$ circuit, getting the following transfer function:

$$H(s)= \frac{1}{1+sCR}$$

the impulse response (i.e. output response to a Dirac's Delta) would thus be the inverse laplace of the same expression and that would be a decaying exponential function with a peak value of \$1/(CR)\$.

How can we explain the sudden rise of capacitor voltage to \$1/(CR)\$ (remember, a capacitor needs a finite interval of time before completely charging)?

Moreover, is this the maximum limit of voltage across the capacitor in this circuit ? (considering that we have applied an impulse at the input and thus applied a very high value of voltage at the input)?


texts: Is it possible for an LED to blink at 10GHz? Context VLC aka LiFi Experiment

texts:
According to this article: http://eandt.theiet.org/news/2014/jul/li-fi-sisoft.cfm originally found while reading the Wikipedia page on LiFi, Sisoft has been able to produce 10Gbps (10Gigabits per second) throughput using a single LED.

In my experience, a simple Light Emitting Diode cannot "blink" more than say at 5MHz. So 10GHz sounds nearly impossible and therefore I'm questioning the feasibility of their experiment simply based on the physical limitations of a diode. Can an LED be bread-boarded to blink at 10GHz? It raises the question of whether or not this "experiment" could have possibly transmitted 10Gbps, perhaps with modulation and more than one diode...


texts: Automotive tachometer signal interpretation

texts:
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 is related to the ignition coils, and after a little digging around on the Internet I realized how to convert the frequency of this signal into a real RPM value.

Let me show you what I'm talking about:

Each cycle begins with a gradual increase from 0 to ~ 0.7V. Then for a few milliseconds it stays at that level. After that we can see sharp falling edge. This part is completely understandable to me and does not create any difficulties. Problems begin further: after this pulse there can be a surge up to 1V for a few microseconds. But also these surges can sometimes not be observed. But the worst part is that some of the main pulses can be interrupted by other bursts with a length of about 100 microseconds.

This is an example of a typical burst after main pulse.

And here is what this surge looks like at a closer look.

Here is an example of how a useful signal being interrupted.

And here we can observe something like a double rise.

Measurements has been done with Saleae Logic 8 at 10MHz resolution (without any scaling probes).

What I'm know for sure is that somehow, tachometer in the car can cope with signal well. Unfortunately, my ideas do not go beyond using an RC circuit with an op amp. However, this will not solve the entire problem. Please tell me how best to filter/convert this signal so that it can be used as an interrupt for the microcontroller. I would also be very interested to know the nature of this signal, why it is exactly the way we observe it, and why these bursts and other artifacts appear.

Thank you in advance!


texts: Using KVL for a mesh with a switch and inductor in parallel with capactior

texts:
I'm currently studying for second order circuits, and I'm stuck understanding this example in my book pictured at the bottom.

I got the same KCL equation, but I don't understand why the KVL equation on the right-hand mesh isn't
$$v = \frac{1}{C}\int i(t)dt +6i+{L}\frac{di}{dt}$$
The book just has: $$v = 6i+{L}\frac{di}{dt}$$ and I don't understand why you don't account for the voltage across the capacitor. Even if it doesn't initially have voltage across it, it would still be changing, right? Because I think that we're concerned about the rate of change, not just the initial value or the infinity value.
I am also a little confused why you cannot just take the derivative of the KCL equation like this:
$$\frac{v}{4}+i_{L}+i_{C}= \frac{v_{s}}{4}$$
$$\frac{d}{dt}(\frac{v}{4}+\frac{1}{L}\int v(t)dt +C\frac{dv}{dt}=\frac{v_{s}}{4})$$

$$\frac{d^{2}v}{dt^{2}}+\frac{dv}{dt}+4 = \frac{dv_{s}}{dt}$$
which leads to the characteristic equation for the problem $$\lambda ^{2}+\lambda +4 =0$$
Thank you in advance for any help!


texts: Understanding negative feedback in an inverting op-amp

texts:
Below is a basic inverting op amp. I'm having trouble seeing the negative feedback operation.

simulate this circuit – Schematic created using CircuitLab

If I understand the "golden rules" of op amps correctly, the voltage at the negative terminal should be at ground (at least in equilibrium). Let's say for some reason that the negative terminal is held at a small positive voltage then because of the differential amplifier, vout should be a large positive number. How does this generate negative feedback (aka, how does this force the negative terminal to go down)? I'm also having trouble seeing the same situation but if the negative terminal is slightly below ground.

Hopefully there is a "intuitive" reasoning behind this. Thanks!


texts: How to increase max output voltage on CCP pin using PWM on PIC16F882?

texts:
I am trying to replicate a circuit containing PIC16F882 that I found in an electronic appliance. I wrote code in MikroC that perfectly follows that logic, but the peak voltage of the CCP pin that I'm using for PWM barely crosses 3V. I checked the same using Proteus simulator first, and I got similar values of voltage.
However, the output voltage from the CCP pin is 5V in the circuit I have, which does not contain any amplifier. Is there any way to increase the output voltage of the CCP pin upon using PWM? I find that other digital output pins do have about 5V output, except the CCP pin.
I have read in other forums and asked around, and FYI I did put ANSEL = ANSELH = 0 in the beginning of the code.

Edit:: As requested by many, following is the circuit schematic, as made in proteus. Ignore the components disconnected.High res image updated.


texts: Where to send voltage peaks while ESD-protecting a subcircuit? To a subcircuit Vcc or to a global circuit Vcc?

texts:
I am going to use ST DALC112S1 (http://www.st.com/web/en/resource/technical/document/datasheet/CD00001317.pdf) to protect the SIM card connection between uBlox Leon G100 and the SIM card holder (VSIM, VRST, SIM_IO, SIM_CLK lines) against ESD.

This DALC112S1 has REF1 connected to the anodes and REF2 to the cathodes and it is clear that REF1 shall be a GND in this case (I have one GND for the whole circuit) but I don’t know if I should connect the REF2 to VSIM or better to a circuit Vcc (VSIM < Vcc(3.8V)).

Connecting it to VSIM is hazardous to Leon as there are no capacitors to absorb the voltage peak if it occurs. The circuit Vcc has lots of them but on the other hand there is a small risk that the whole circuit gets damaged with the ESD on the SIM.
So, what is the usual way to do it?


texts:
anyone knows if it's possible to use a led strip with 3 pins without a controller? I got this 1,5 meter strip without controller, I don't know if I should've bought it or not...

please see attached images, there's a (+), (-) and (+3.6v) pin
how can I use it without a controller, just a battery?


texts: Can I use a standard latching relay to switch AC for a power socket?

texts:
I'd like to remotely control a power socket.

I'd like to create a circuit that opens and closes a relay, effectively turning the socket on and off. I can handle the logic and the DC, but I'm less comfortable dealing with AC.

I prefer a latching relay, as I only want to apply power to activate / deactivate the socket: I don't want the logic circuit to be leeching power just to keep the socket enabled.

I've found a relay I think I'd like to use.

  OMRON G5RL-U1A-E-DC5

It is rated at 16A and is through-hole, but it's small and I worry it can't carry the current. If it's rated at 16A, does that mean it can handle 16A continuous? I'm not seeing any thermal properties in the datasheet.

I'd like to put a fuse in-line, but I've only found surface-mount fuses. I'd like a resettable fuse, if possible. If not, does this look like it would work? Any suggestions on overcurrent protection?

  Schurter 3403.0286.23

I plan on using a 2oz copper PCB. According to this calculator online, I would need a trace width of 271 mils on the top or bottom layer (20C Ambient +10C rise). Am I reading that correctly? If so, could I use the top and bottom layers simultaneously? 8A on one layer is only 104 mils, which seems a lot more manageable.

Lastly, I'm thinking quickconnect terminals might be preferred over the standard terminal blocks with screws. I can't seem to find any I think would survive being jammed back into a gang box, and the quick connect terminals seem like they'd work fine AND be cheap to boot.

I know I need to keep any DC logic 6mm from any AC power planes. Anything else I might be missing?


texts: range switching problem in auto range multimeter using PIC microcontroller

texts: I am designing a auto range multimeter with PIC microcontroller and added extra circuitry for attenuating the signal uu to 3.3V for ADC of PIC controller. The problem I am having is in the auto range switching. I have designed the system to give me 0-2048 for positive range and 2048-4095 for the negative range. The problem occurs at the transition 2048 where it keeps switching between different ranges randomly instead of staying in the correct range. I am not asking specific solution. But if somebody can provide me the correct way to switch range in the auto range multimeter.


texts:
I recently bought a few electromagnetic coils wrapped around ferrites. I was intending to use them to induce a voltage from surrounding magnetic fields. When I went to wire them however, they seemed to have four leads instead of two. Cannot find an answer anywhere. Possibly I am searching the wrong thing? The leads are black and red (+ and -) and then green and a colourless wire. Could this be for AC? As I mentioned, I am a beginner.

Product: FERRITE W/COIL AM RADIO


texts: Why do we need to use transistors when building an OR gate? Wouldn't we be able to achieve the same result without transistors at all, just by joining the two inputs and reading the output?


texts: What is a good choice for an ARM to interface with external memory?

texts:
I just completed a project using the LPC2132 chip, but ran into problems with using up the whole 64kb of RAM.

For my next project, I'd like to use something that can reference an external, much larger memory chip. What sort of ARM can do this and what do I need to do to get the two devices talking?


texts: Reading corresponding pins from a circuit diagram

texts:
I am completely new to Arduino tinkering and am trying to make sense on how to wire a 8x8 LED matrix using the following diagram:

This chart is supposed to correspond to this 8x8 LED, 12x12pin LED matrix:

Now, the question:

The physical led matrix has 12 pins on top, 12 pins on the bottom.
The diagram shows 16 pins on top, 8 pins on the left.

How am I supposed to make sense of this? I highly appreciate an actual answer as opposed to someone pointing to arbitrary articles because reading articles on this is all I've done the past two evenings.

Side-notes:

Yes, this is homework, but we have no book for the course and we haven't learned to read diagrams like this yet.
The components used are: Arduino Uno + MAX7219 + 1588ABEG 8x8 LED Matrix


texts:
I have a signal for which I want to cutoff signal till around 3 MHz. Here is my circuit diagram.

The calculated cut-off frequency is 3.4 MHz. But when I use it, is just does not work, it seems to pass all frequencies. I am not using any load, I am just using the probe to measure the voltage across the inductor. Vin is the output from a Colpits oscillator.

Here is a frequency domain snapshot from my oscilloscope. Yellow is the input and green is the output. The reddish vertical line is where frequency is 3.17 MHz, and green vertical line is 0MHz.

I have tried lot of stuff to work it out. But nothing seems to work. In low pass mode things work fine, but in high pass mode nothing seems to work. Your guidance will be greatly appreciated.

Capacitor datasheet (Class II): http://www.mouser.com/ds/2/212/F3101_Aximax-461059.pdf

Inductor: http://www.digikey.com/product-detail/en/api-delevan-inc/1025-04J/1025-04J-ND/4183026


texts: Chaining transistors. why does first led not light?

texts:
I am trying to understand transistors by experimenting. Having a pushbutton drive a single transistor to switch on an LED works, but trying to drive the second transistor from the first has me confused. Even though the second transistor turns on and drives its own LED, the LED of the first transistor doesn't switch "on" any more.
Can someone explain the theory why the first LED doesn't turn on?
This question is similar to my previous question 2 but I specifically want to know why this circuit behaves that way.


texts:
I had been using Visio to create my schematics for years but am now launching a product for which I will need PCBs manufactured.  I hate having to learn a (for me) completely new software program, but I digress.

I downloaded the free version of Eagle.  Played with it for an hour or two and decided this wouldn't be too bad to pick up.  Since the larges board I plan on producing will be 7.5" x 2.75" (which calculates to about 133 Sq CM), I bought a 3 year subscription of the Pro version, which states that it supports producing boards up to 160 Sq CM.  So far so good.  Then I spent a couple days creating the schematic as I learned the program.  All is well at this point.

The frustration came when I found that even with the MARK adjustments I could not place parts on a board 7" long even if it was only 1" wide.  I went back and looked at the Autodesk website again and it says nothing about maximum dimensions, only a maximum board size of 160 Sq CM.  I spent quite awhile messing with it before I came looking for answers.

Does anyone have any workarounds, or am I just stuck?

Sorry, the versions available for a fee are "Standard" and "Premium", not Pro.  I bought the Standard version for the reasons stated in my original post.  On their site where you buy the subscription the option listed for Standard only states 160 Sq CM as the maximum board size, with no reference to specific dimension restrictions.

After buying it and then realizing the unstated restriction I went ahead and bought the Premium edition too, so I could continue working to complete the project.  That did take care of the issue in a very expensive manner.  I am hoping they will reverse the charges for the initial Standard edition purchase.

Had I not already invested such a large amount of time in working on this with Eagle, I would have looked for other options.  The jump from $300 for a 3 year subscription to $500 for a 1 year subscription is a pretty steep jump to get what I needed to make it work, and in my view to address something that was falsely advertised.

Oh well, here I am.  Sorry for my whining.  I appreciate the responses.


texts:
Below I am presented with the following circuit and asked to solve for the current through R1:

EDIT: in the diagram below I made a mistake, V2 is shown as 8V, it is supposed to be 40 V.

I apply a source transformation (ST) on R5 and V2 to get:

Then I combine R11 and R12 to get:

Then I apply another ST on R16 and I2 to get:

Finally, I add R20 and R21 to get :

Then I continue to solve by trying an ST on the I4 and R25 to get a DC voltage and the 30 ohm in series with the rest of the components. Then I write a KVL to solve for the overall loop current but I get the wrong value. Where have I gone wrong in my procedure?

Second Edit:*
Here I have tried some of the suggestions (which I had already previously attempted) that I am showing:

I will now call this point A:

Going from A to B thru an ST:

Going from B to C by combining the 20 and 30 ohm:

Then I write the KVL:
-6 +4i + 12i + 32 = 0

Solving for i = -1.65 A. However, when I run a sim on the original circuit I started with, I am showing 825 mA as shown below:


texts: 3 band audio equalizer circuit transfer function

texts:
I am trying to find the transfer function of part of a 3 band audio equalizer circuit that amplifies low frequencies but I am confused about the topology. Here is the topology:

I was under the impression that the circuit could be reduced down to your normal inverting amplifier where the transfer function would be -(Z_f)/(Z_S) but it looks like part of "Z_s" is also a part of "Z_f" in the picture above and this is confusing me.
Update:
I used the node between c1 and c2 and the node between the negative terminal of the op amp and RF to find the transfer function. I got the following:

from my understanding, this is a typical form for a transfer function for a bandpass filter. How can you use this transfer function to create a bandpass filter of a particular center frequency? no information is given about bandwidth or cutoff frequencies. However, for the particular equalizer I am making I want a center frequency of 500 Hz and all component values are given in the above diagram. using those component values I should be able to come up with a particular bandwidth and reuse that bandwidth but shift the center frequency to 500Hz.


texts: Compensating for voltage drop across current-sensing resistor in a TL494-based SMPS

texts:
I'm trying to wrap my head around this reference design from this TI document.

This is a 5V power supply that is rated at 10A. I see they are using one error amp to limit current and another to stabilize voltage. At 10A voltage drop across R13 would be exactly 1V which is applied to pad 16 and compared with 1/5 of Vref which is 1V. And they stabilize voltage by measuring Vo relative to GND and comparing it to Vref. So Vo relative to GND is kept at constant 5V. But the load is not connected between Vo and GND, it's connected between Vo and R13!

So at 10A the voltage across the load would be 4V, right?

Is there any way to stabilize Vo relative to the shunt resistor R13, not GND, so that output voltage is truly kept constant?

UPDATE:
So far there are several ideas, but I don't know if they are any good:

Reduce R13 to a much smaller value to the point where its voltage drop is negligible, and then amplify that value (suggested by Andy).
Use a current transformer to measure current and neglect the voltage drop in its primary winding.
Use an external amplifier circuit to subtract voltage drop across R13 from Vo and then compare this result to some reference.


texts: PCB, pads with holes but with different nets on top and bottom sides

texts:
I need pads with holes in by PCB, but the top and bottom side of the pads need to have different nets i.e. the top and bottom sides must be isolated. Here is the picture
Is this possible to fabricate for the PCB manufacturers? If yes, how do I design this in Altium?


texts:
I have two DLM 60-10 Sorenson bench power suppllies (10A limit) that I am wanting to stack in parallel so that I can provide between 1 and 20 A, at a consistent 12 V. I'm not particularly an electrically-savvy person so I am wondering the best way to go about this. It seems to me that the each power supply won't know that the other unit exists -- so since they will always be operating at the same power settings, is it as simple as splicing the outputs...? I'm guessing not.
I'd appreciate some help in trying not to electrocute myself.

EDIT: Turns out that the particular DLM 60-10 power supplies we have do not have a master/slave mode built in

Austin


texts: Heat sink via holes under voltage regulator LM2596

texts:
I am designing a board with LM2596 voltage regulator (12V/5V 3A)

I want to make heat-removing holes under the microcircuit. For this, I decided to use via holes. The board has two layers.
The question is, is this the right solution? Or do they do the heat sink differently?

UPD.


texts: I'm busy working on a uni practical in which we are required to construct a chopper modulator and I'm busy creating a schematic in orCad to run some simulations. I'll be using a Texas Instruments CD4066b CMOS quad bilateral switch and was hoping to find a spice model on the TI site but unfortunately there isn't one. My question is what could I use as an alternative in orCad?


texts:
After many years, I'm getting back into some simple wiring.  I'm trying to make a self-sustained wifi tracker.  This tracker will have a 3.3v Button cell lipo battery as a battery backup and I want to be able to charge this battery backup any time it's plugged into the main battery.  The main battery can be up to 42v, and needs to be stepped down to 3.3v to charge the button cell without damage and also to run the ESP8266 wifi module.

In the diagram below, I'd like to be able to shutdown the pololu step-down converter when the button cell lipo is charged, but I don't know what this is supposed to look like.  Possibly an N-channel mosfet?

Here's the diagram:

I'm hoping this circuit isn't completely wrong in the first place, but if it's not - how do I use the SHDN (shutdown) pin on the Pololu to not allow any more voltage to come through?  I feel like I need a switch behind the button cell to turn off when the button cell is 3.3v or more?

Edit: The reason I want the button cell in there is incase the main battery falls off or is disconnected in any way.  Also, this will be "always on", so when it IS hooked to a battery, it will charge the 3.3v button and "turn back on" if it has previously died.


texts:
I am looking to hook up a radio with an ATtiny861A microcontroller. The radio that I will be using is the CC2520 from Texas Instruments. The RESETn pin(on the CC2520) will allow me to put my circuit into a sleep mode and this requires me to have the reset pin attached to the MCU(The datasheet says that I could reset it through SPI but I want to know if I can use one of the pins that I have left over). The RESETn Pin says it is a TBOUTH/SVSOUT. Leftover on my 861A MCU I have pin 4 which is OC1B/PCint11, pin 17 which is AREF/PCINT3, and pin 9 which is ADC9/INT0/T0/PCINT14. Am I able to connect any of these pins to the RESETn from the CC2520 radio?
Thanks


texts: Can a battery powered circuit experience input voltage overshoot on turn-on?

texts:
I'm trying to track down why my SMPS stopped working. One thing that caught my attention is this paragraph in the datasheet for the regulator:

I'm using a 2700mAh 3S LiPo (rated at 35C, 70C peak) connected through about 18" of speaker wire to the circuit, and turning it on/off with a SPST switch spliced into the V+ line.

I'll be the first to admit that I don't entirely understand the process described in this paragraph, but it does appear that I have the ingredients for what they describe, and don't have the tantalum cap across VIN.

So - can the fact that I'm using long-ish leads to a battery cause the ringing / overshoot described?

Circuit for reference:

SMPS for reference:
http://www.ti.com/lit/ds/symlink/tps62125.pdf


texts:
I am not familiar with electronics at all, but as I was strolling through the stack exchange network I've noticed how it is dangerous to electrocute oneself by touching a wire with one hand and another with the other, which creates an electrical path throught the heart which is very sensitive.
I wonder if this specific danger could be alleviated by wearing (extra long) handcuffs? Which would short circuit the hand-to-hand path?


texts: Use battery pack instead of wall charger for musical gear?

texts:
I have a Moog analog synth module (musical instrument) that takes a uses a AC plug that coverts it to 12V DC and consumes 7 watts according to the manual specs.

Would it be possible to safely create a portable battery pack for it using just standing AA rechargeable batteries in a series? I would image the battery pack I make wouldn't have a super long life between charges but I'm more concerned about messing up the electronics of my synth module. It seems like this post goes into some detail about how that might be done but I want to make sure its safe to do so first.

Would there be other batteries better to use than AA? C's for the duration? Remote Control Car battery packs?


texts:
OK, before I start I know that there is significant difference and that the Arduino Uno is not designed to run off button cell batteries especially to run both the board AND its load but what if the load is on a different power source?

I need to run 2 micro servos to operate a type of elevator styled door system. One Uno sketch I came across mentions that the 2 opposite running bi-directional motors need to be on a separate power source than the Uno itself. My goal is to run my apparatus with as few batteries (must be batteries preferably 1 9V and 2 CR2032) as possible to maintain design.

Now, since the servos obviously would kill the button cells in no time I was thinking i might be able to power the microcontrollers off the BCs and the servos off the 9V. This is not a continuous action device as I stated the doors close and the system stops until the same button or a separate one is pressed then they reopen and stay.

Anybody feel that this might be possible or should I resort to a 6V camera battery. A key factor is that this is a sort of prototype for a toy and thus I am trying to make it as practical as I can.

Even the servos and Uno are a far step to me but with the limited space I am working with I am having trouble finding simpler mechanical options with significant power.


texts: Finding the voltage gain at low frequencies

texts:
can anyone explain how the second expression for the gain is obtained?
they multiplied or divided the first equation and came up with second one.


texts: How does a 8 bit register bank hold 8 regsiters of 8 bits each?

texts:
In 8051, there are 128 bytes of RAM. Of which, 32 are set aside for registers in the form of banks, 8 registers to each bank. Each bank is addressed from say 00 to 07, 08 to 0F, etc, that is, occupying 8  bits each, with each but corresponding to a register, thus 8 registers in each bank.

How can this be possible, when the registers themselves occupy 8 bits? Won't each bank occupy 8*8 = 64 bits instead of 8?


texts: what is the difference between logic,reg and wire in system verilog?? explaination with an example would be helpful

texts:
explanation with an example would be helpful.i tried:- input logic [9:0] data1 as the input of the counter and loaded this value into the count1 (logic [9:0] count;)
and then assigned count1<=data1; at the time when load was 1. but it shows some error.


texts: Calculating the average power dissipated in an AC circuit

texts:
This is the question from a very important assignment I am working on: "A load is being driven by an AC source. At a particular time, the voltage across the load is 120cos(wt+50) and the current through the load is 20sin(wt-10). Calculate the average power in Watts dissipated by the load."

My working:
I first convert the current into cosine to give 20cos(wt-100)

Then I use the formula \$\ P=|Vrms||Irms|cos(\theta v -\theta i)\$
which gives me -1039.2 W

I assumed that the question asked for real power since it is the power dissipated in the resistor and thats the only equation the literature gave.
 An online calculator gave me a complex number with the real part twice the value that I found. Is this correct? Negative power in a resistor? Where did I go wrong?


texts: Problem of resistance of a sphere with a cylinder in exactly one point

texts:
I am modeling nerve cords that have fibers (yellow - blue stick) and a cell body (blue ball) :

This is most often modeled using electrical circuits. Now each segment has its specific resistance \$R_i\$ and so of course the blue sphere - but now I wonder:
Actually, this sphere is connected to the neighboring segment at exactly one tiny point, and following Ohm's law, the current strength would then be quasi infinitely large, because the resistance at a single point is incredibly small.
How do you describe the current flow in such a case?


texts: Design of a low cost/low power Isolated AC/DC SMPS

texts:
I am looking to replace a classic 50Hz transformer/rectifier circuit with an SMPS.
The input is to be 230VAC (EU) compliant and the output should be 5V/0.2A minimum while 5V/0.5A is a nice to have.  An external adapter is not accepted (the apparatus also has a 230VAC output for pump control).

The cost of the current circuit is less than 2€ (50Hz transformer (1.05€), rectifier, regulator).

I've started by looking in to the lowest cost SMPS controller to find that the total BOM is quickly exceeding the origincal circuit's cost (100kHz transformer 1.1€, controller 0.2€, rectifier, optocoupler).

So the bigger transformer costs less than the smaller 100kHz transformer.

Should I be looking for an SMPS controller with higher switching frequency (does that exists) to get a smaller (cheaper) transformer or is it currently hopeless to design an SMPS that is cheaper that the classic 50Hz transformer centered design?

What is the best approach. Example: find the transformer first and then the controller?

Where's the state of the art of Isolated AC/DC SMPS at today ?

Edits:

looking at pricings for volumes of 2k to 10k/annum.
The current power solution parts cost $2.5 (50Hz 220V/1.5VA transformer, bridge, caps and LDO).
Must I conclude that the best AC/DC SMPS solutions are using around 100kHz, 15x15x15mm transformers, and that smaller (/cheaper) solutions using 1MHz for instance, a smaller transformer do not exist/are not available?

My conclusion after consulting several sources:
 - For a custom design the cost of an isolated SMPS is higher than simply rectifying and regulating the transformer output.

Thanks to all contributers for your feedbacks!


texts:
I have been told that the fastest logic gate family is ECL.

My first question: Is this true?

In this or another family (Depending on the answer to the above question),
Is there any particular gate who's internal structure is:

simpler, faster, requires less energy, creates less electrical noise e.t.c. ?


texts: Converting 7-Segment Display output to binary

texts:
I know this is very unusual but I need it. A PLC has outputs to drive 7-segment display. However, I have a new device that works only with Gray Code or Binary. This new display and the old 7-Segment will be working together. To do this, I need a circuit converting 7-Segment output to Binary or Gray Code.

Is there any such thing? Or how can I do this?


texts: Looking for a Wall Wart Power Supply with an Earth Ground Connection on the Output

texts:
I am looking for an AC or DC output wall wart power supply
that provides an isolated output and brings out the earth
ground connection to the output.

Specs --

Either single output or bipolar output
Any voltage 7V to 18V (preferable 7V)
100mA of current
Must be new and in production (no surplus)
Must have UL/CSA/TUV approval
Must be encapsulated or closed (no open frame designs)
Earth ground can be a separate connection or tied to
the power supply return.

I haven't seen these made in a long while. All of the
wall-wart type supplies that seem to be made are isolated
and there is no earth ground.

Thanks for your help.


texts: Help identify black cylindrical component with two blue rings

texts:
Can someone help identify the component with the two blue lines?  I was testing the board for broken diodes and all of them checked out, but the VD prefix followed the labeling for the other diodes so that led me to believe it might be one as well.

It would a plus if you could help me figure out enough to get a replacement.


texts: Three phase short circuit and line to ground short circuit

texts: Why is three phase short circuit calculated current higher than line to ground or (phase to ground) short circuit calculated current in most cases?


texts:
Hi I am trying to identify what I think is a varistor. The problem I am having is the markings, other than the voltage don't seem to corrolate with anything. So I'm not sure if it is a varistor or if it just has obscure markings.
The markings are :
05
K385
1146
I know the k385 is the voltage from what I can find, but have no idea what the current is or what part number it matches up with. It's currently part of the 12v input on an electric fence energiser.


texts:
I've just analysed a Wilson current mirror (part (ii)) and was wondering if someone could check that I've done it correctly. The input current should be mirrored to the load current right? Isn't that the whole point of a current MIRROR? It's just I saw another example where the load current was 10 times more than the input current...

Would I instead need to calculate I(C) of Q2?

Also any ideas for part (i)? Not sure what a load plot line is and couldnt seem to find one anywhere.

Thanks]1


texts: What Protective Eyeware Should I Use for Protection From Soldering Fumes?

texts:
I would like to know what kind of mask is better for protection against soldering fumes and dust. And since I have glasses I think it would be troublesome to find appropriate protective goggles.

Are there goggles that are designed for people with glasses?


texts: Using voltage divider with appropriate resistor calculations to give +/-1V signal a 1.65V level shift

texts:
simulate this circuit – Schematic created using CircuitLab
I am trying to use this circuit to level shift V2 which is +/-1v to 0.65 to 2.65V, pretty much adding a 1.65v offset, and I have V1 a 3.3V source to work with. I know my calculations to set resistor values are wrong but I am not sure how to fix them.
I chose an arbitrary value of 10k for R1, and then I thought that R2||R3 should be equal to R1 because if I were to replace R2 and R3 with a single equivalent resistor Rx it would be in parallel with R1 for a voltage divider based on a Thevenin equivalent. Since I am only going from 2vpp to 2vpp, or a ratio of 1/1 I thought then R2||R3 = 10k = R1. So I again chose a value of 10k for R2 to solve for R3 but I got -9k for R3 which doesn't work.
Simulating the circuit At 0V input my output is only 1.06V when it should be 1.65V.


texts: Principles of DC/DC converter w/ jumper-selectable outputs?

texts:
I have an application where the load is a user-selectable component (an electric door strike) that comes in many flavors, with each flavor requiring a specific DC voltage, most commonly either 12V or 24V. I would prefer not to have separate parts for the different voltages, and so I would like to have a jumper-selectable 12V or 24V DC/DC converter on my board.

I have played around with TI's WBENCH Designer and it seems like getting an efficient DC/DC converter for a single voltage is a piece of cake, but how do I go about adapting one to produce different outputs depending on the jumper configuration?

My first thought was simply to use WBENCH Designer to produce two different designs based on the same TI chip and then "meld" them into a single circuit with some creative hackery. I'm reasonably confident this could be made to work, but I'm also pretty sure there would be some redundant components from going this route (particularly the large and relatively expensive inductors) and naturally I'd prefer to avoid that.

Oh and obviously I'm ignoring the possibility of using a voltage divider or simple dissipating regulator because I'd prefer not to waste power, but should I be? Is there a way to use one that isn't wasteful?


texts: How to get a low clocking rate by ARTY 7?

texts:
I need to use 8 kHz as a clock signal for my LFSR IP core in my block design. But this low rate can not be implemented in ARTY 7 , as shown in the attached picture !

What are the other choices I have in order to achieve the output of LFSR at the low rate that I want ?

I read about delays in FPGA , but I found delays are not synthesized in FPGA !

Looking for your help,

Thanks

Edit :
I added enable signal (i_en) , which is controlled by a counter. As shown in my code below:

    -- Library's
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.numeric_std.all;

-- Uncomment the following library declaration if using
-- arithmetic functions with Signed or Unsigned values
--use IEEE.NUMERIC_STD.ALL;

-- Uncomment the following library declaration if instantiating
-- any Xilinx leaf cells in this code.
--library UNISIM;
--use UNISIM.VComponents.all;

entity LFSR3 is
   Port (
      i_clk           : in  std_logic;
      o_lsfr          : out std_logic_vector (2 downto 0)
     -- i_en            : in  std_logic
    );
end LFSR3;

architecture Behavioral of LFSR3 is

signal i_en    : std_logic := '1';
signal r_lfsr   : std_logic_vector(2 downto 0) := "100";
constant maxcount  : integer := 625;
signal counter :  unsigned(9 downto 0) := to_unsigned(0, 10);

begin

  o_lsfr <= r_lfsr;

  LFSR_proc: process(i_clk)
   begin
    counter <= (others => '0');
    i_en <= not i_en;
    if (i_en = '1') then
       if(rising_edge(i_clk)) then

          r_lfsr(2) <= r_lfsr(0) xor r_lfsr(1);
          r_lfsr(1) <= r_lfsr(2);
          r_lfsr(0) <= r_lfsr(1);
       end if;

    else
    -- line 75 (the error)
      freq_8kHz: while (counter <= maxcount) loop
          counter <= counter + 1;
       end loop freq_8kHz;
   end if;
  end process LFSR_proc;

end Behavioral;

And , when I run synthesized an error appeared :

"[Synth 8-3380] loop condition does not converge after 2000 iterations ["d:/Users/dell/Vivado_projects/LFSR2/LFSR2.srcs/sources_1/bd/LFSR/ipshared/4f95/src/LFSR3.vhd:75]"

I have pointed to the error location in my code (line 75) . So plz , could you tell me why my loop seems to be infinite (does not converge) !?

Thanks.


texts: arduino UNO light LEDs right-to-left and then reversed

texts:
I have 8 LEDs lined up on a breadboard, and I am trying to make them run from one end to the other and back, sorta like the lights on KITT (from night rider - hope that clarifies). the LEDs are all set up and correct and work.

I have set up my code like so:

int ledPins[]={2,3,4,5,6,7,8,9};

void setup()
{
  for (int i =0; i <8; i++)
  {
    pinMode(ledPins[i],OUTPUT);
  }
}

void loop()
{
  for(int i =0; i<8; i++)
  {
    digitalWrite(ledPins[i],HIGH);
    delay(100);
    digitalWrite(ledPins[i],LOW);
  }

  for(int i =7; i<1; i--)
  {
    digitalWrite(ledPins[i],HIGH);
    delay(100);
    digitalWrite(ledPins[i],LOW);
  }
}

but it doesn't cycle the LEDs from right to left and then back like I was aiming for.

EDIT: What it does do - is light the LEDs from right to left, but doesn't light them the opposite way (left to right). It just keeps going from right to left, right to left

I am using an Arduino UNO, and basing my circuit off the experimentation kit for Arudino CIRC-02

EDIT #2: So I have changed the for-loops to while loops:

int ledPins[]={2,3,4,5,6,7,8,9};

void setup()
{
  for (int i =0; i <8; i++)
  {
    pinMode(ledPins[i],OUTPUT);
  }
}

void loop()
{
  int i = 0;
  while (i<7)
  {
    {
      digitalWrite(ledPins[i],HIGH);
      delay(100);
      digitalWrite(ledPins[i],LOW);
      i++;
    }
  }

  i = 7;
  while (i >0)
  {
    digitalWrite(ledPins[i],HIGH);
    delay(100);
    digitalWrite(ledPins[i],LOW);
    i--;
  }
}

and it works as intended!
However, I am still interested in where my for-loop went wrong, if anybody has any ideas


texts:
simulate this circuit – Schematic created using CircuitLab

EDIT:  I have boiled the problem down to it's simplest component. I need to use the Emitter of a PNP (2N3906) to be the base of a NPN (2N2222) to light an LED.

I have a circuit I'm trying to get to work.  Here is the relevant part.

The battery is actually an at 11.1v (DC power supply).  I know in this image the PNP is kind of pointless, but it's necessary for the overall project. If this isn't enough info I'll draw up the whole circuit, but I think this is the relevant part.

So when I push the button I need an LED to go light up from receiving the hot end of 5v.  I need the same button to send a ground signal to a sound trigger (represented here by a Red LED).  The blue light poriton of this works great, but for some reason the NPN is ALWAYS completing the circuit to the Red LED.  I'm hoping to have it only complete the circuit to the LED when the button is engaged.
What am I doing wrong?
The NPN is a 2222
The PNP is a 3906

simulate this circuit

Figure 3. OP's circuit redrawn in conventional manner reading from left to right with current flow from top to bottom.


texts: How to calculate the values of capacitors for 5V DC power supply

texts:
I am trying to make a power supply of 5 V; as we all know it uses a bridge circuit, then capacitors and LM7805.

But I want to know how the value of capacitance is calculated. What is the formula for it?

If the formula is \$C = I_t / V\$

Then what will be the value of \$I\$ and \$V\$? What is \$t\$?

I have 220V, 60Hz main supply. What are the calculations?


texts:
I want to synchronize multiple Behringer U-Phoria UM2  (that are at different locations) via GPS clock. These interfaces are used by musicians to make music together in "real-time" over the internet (as far as real-time is possible here).

The idea is to "extend" the interfaces with a word clock input for a sampling rate of 48kHz (which is also going to be the GPS clock frequency). Furthermore, the user can chose (e.g. via a switch) whether the interface is clocked from the wordclock input or clocked internally (so the interface does not become completely useless in case of the absence of the external clock source).

The Behringer interfaces are build with a Cool Audio V2902 codec Datasheet here which is clocked by a single 12MHz crystal. In order to clock the codec from the word clock input I need to multiply the incoming word clock frequency (48kHz) with the factor 250.

I tried to find some solutions online but it seems that this is a rather unusual case. The Texas Instruments Webench tool suggested the CDCM6208V1 for this task. ( Datasheet here ).
While I have no doubt that this solution would work I was wondering wether there is an easier solution. An other approach could be the design of my own Phase Locked Loop (PLL) circuit.

Is designing my own PLL for this a feasible solution or will this result in a ton of work without a functioning circuit and in the end switching to the CDCM6208V1? Are there any other solutions that I am not aware of?

I will use an uBlox EVK-M8T  for the GPS Clocking.


texts:
I'm working with a circuit that should control the intensity of several LEDs using the CTL and REF pins on a buckpuck driver part number 3021-D-E-1000. I'm using an AD5204 digipot configured as a rheostat between the CTL and REF pins on the buckpuck to modulate the current seen at the CTL terminal, which in turn modulates the current the buckpuck sends to the LED (the higher the current seen at CTL, the lower the LED output). I'm using an Arduino to control the AD5204. The complete circuit I'm investigating is pictured below:

I believe the pertinent part of the circuit is:

I can't get the LEDs to turn on. The switches (SW-SPDT) and the BJTs (Q1-3) are both used as on/off for the LEDs, while the digipot is supposed to control the intensity of the LED output.

My initial thought was that I wasn't communicating properly with the digipot, but I've confirmed with a logic analyzer that I am sending the correct SPI commands to the AD5204. This is the code I'm using (the Arduino 7,8, and 9 pins are written high to put the BJTs in cutoff, and the mechanical switches are connected to the Arduino pin, not to GND, so theoretically the current at CTL should be dictating the LED output):

#include <SPI.h>

int cs = 10;
int address = 1;
int potval = 10;

void setup() {
  pinMode(7,OUTPUT); digitalWrite(7,HIGH);
  pinMode(8,OUTPUT); digitalWrite(8,HIGH);
  pinMode(9,OUTPUT); digitalWrite(9,HIGH);
  pinMode(cs,OUTPUT); digitalWrite(cs,HIGH);
  SPI.begin();
}

void loop() {
  digitalWrite(cs,LOW);
  SPI.transfer(address);
  SPI.transfer(potval);
  digitalWrite(cs,HIGH);
  delay(10);
}

So I'm beginning to doubt that communication with the AD5204 is the problem, but that leaves me pretty lost. I'm not sure why the LEDs aren't turning on, especially since even if I weren't communicating with the AD5204, by default all pot values should be set to midrange (5kOhm).

At that point the LEDs should be on, as far as I understand. Is there something I'm overlooking in the rest of the circuit?

I've tried to be thorough with the information I've provided, but sorry in advance if I've left things out, and I'll try to add information as soon as possible if I have.

EDIT

Okay, so a couple things I've found:

(1) I don't seem to be changing the wiper value on the digipot--it remains at the default value of 5kOhm no matter what value I try to write to it. So that's one problem I need to figure out.

(2) At the same time, when the rheometer has a value of 5kOhm, the LED should be on. I've confirmed this on a breadboard with the same buckpuck I'm using on the PCB and a mechanical rotary pot--at 5kOhm the voltage at the CTL terminal is ~1.23 V, and the LED is at its brightest.

(3) On the PCB with the full circuit as pictured previously, I'm getting 4.3V at the CTL terminal for each RDAC on the 5204, which doesn't accord with (2).


texts:
I'm trying to turn on a laser (3.3v - 4.5v, 100mw) using a 9v battery and LF33CV as voltage regulator(TO220 package, 3.3v output). After 20 seconds the voltage regulator is getting so much hot. I was wondering if it's natural and how can it be fixed?

update1: Here is the test circuit in LF33CV datasheet, is it possible because of not using, capacitors?

update2: Laser draws 0.1 ampere when connected to a DC power.

update3: Original circuit (below picture) was changed with an equivalent circuit.

update4: Thermal data:


texts: How to properly shield a < 5v Circuit from EMI from a 220v motor?

texts:
I've designed the following circuit:

It may be trivial to most people but I did not know that the EMI generated by the motor and coil would interfere with my circuit. After some research I stumbled uppon the concept of Snubbers. So I upgraded the circuit as such:

I've upgraded the code aswell, coded a small logic to check if the button was really pressed 50ms after the initial trigger.

Things improved a bit, but sometimes if I turn the motor on and off many times in a row (like 10 times), it may get the circuit to a corrupt state, not responding to button presses, but still working, updating the LCD, etc.

Any ideias on how to improve the design and get rid of that EMI (I'm assuming it's EMI) ?


texts:
I am interested in putting together a tennis ball launcher.

It's accuracy/precision are not important.  Even varying distance by ~50% or more per shot doesn't matter (it's for my dogs).

What type of solenoid can I use to drive this in a hollow tube, like the picture?

If this is impractical please give an actual reason.

I would also like to be able to drive this with a reasonably sized battery (12-24V; I could use a car battery but hopefully that is not required).

A tennis ball weighs (58.5g).  Lets say that it needs to launch the tennis ball upwards ~6m

$$
H = v^2/(2g) = 6m
$$
$$
v=\sqrt{(12*g)}=10.8 \frac ms
$$
$$
E_k = (m*v^2)/2 = \frac{58.5*117.6}2 = 3.43 J
$$

Likewise the energy stored in a capacitor is:
$$
E_c = \frac{C*V^2}{2}
$$
If I discharge from a capacitor to achieve this energy quickly, (lets say 24V)
$$
C = \frac{E_c}{2V^2} = 3mF
$$

Rough sketch:

Any inputs are appreciated


texts:
let's consider a MCU (for instance ATMEGA328) with a crystal.

I know that the electrical model of a crystal is this one:

My question is: which is the circuit that makes it oscillate? I do not see it because it is connected to two pins of the MCU. What is there between them? Power supply, a logic gate etc


texts: What is the perfect definition of time constant?

texts:
Is it the time when the current throught the inductor is 0.63 times of the maximum possible current through the inductor?
Or is it the time when the current is 0.63 times of the maximum possible current?
The difference between 1st's maximum current and 2nd's maximum current is... if inductor is present in parallel with source then the current will not be same... I mean current through the L and current from the source.


texts: Are the connections for reading a temperature sensor using CCS( constant current source) really like in my picture? The analog and the current source seem to be shorted.


texts: How to find wires of a given width in Eagle

texts:
I have almost finished a somewhat dense layout, and I have found out on the statistics menu that there are two wires of a smaller width that I don't really want to be using any more. The thing is that I am unable to spot these wires by just looking at the layout.

Is there a way to search for and highlight wires of a given width in Eagle?


texts:
I am looking at implementing a non-trivial finite state machine (specified as a UML hierarchical statechart) on a 32-bit MCU with gcc.

Are there any rules of thumb what works better and what works less well? My gut says that a switch-based (or even computed goto) implementation should be slightly more performant while a function-pointer based transition table is generally reputed to be more maintainable.

Also: has anybody evaluated Boost MSM for embedded applications? I know that Boost MSM is generally lauded as being very efficient, but for embedded applications efficiency might be measured differently than in the world of PC programming.

Does anybody know what the compiled state machine engine of MSM looks like? More like a switch jumptable or more like a function pointer transition table? Does it use dynamic memory allocation or can it used statically?


texts: What is the difference between Hall Effect and Magnetoresistance?

texts: I was learning about sensors. I was confused about the Hall Sensors and Magnetoresistive Sensors. They both seem to be same.


texts:
I'm currently looking at SRR1240-8R2M. On the datasheet, it shows us the inductance of the inductor at 100KHz is 8.2uH. But I'm trying to run my circuit at 2.2MHz.
How do I determine the inductance when I'm running at 2.2MHz? The SRF is 7.96MHz.
Thanks.
Edit: Sorry, I made a mistake. The SRF is 32MHz, not 7.96Mhz. 7.96MHz is the test frequency.


texts: How to verify the reliability of torque rating of DC motors given on online sites?

texts:
I have to decide the motors to be used for my robotics project, but while searching for the DC motors I have found out a rather unusual fact that I can find several motors who provide the same torque while there is a significant difference in weights. I am curious to know why?

For eg. I can find 12 kg cm torque motor weighing just 125 gm whereas I can also find 17.5 kg cm torque motor weighing 600 gm. I really don't understand where does the difference lie? And is it reliable to use the lower torque motors.


texts: low-cost transmitter and receiver, no MCU involved hopefully

texts:
a newbie on electronics here.
I would like to create a simple RF kit. on transmitter side, only 1 button. on receiver side, if a valid code is received, a relay activates to provide 12VDC to a load.
i would like the transmitter to send out a unique code so that it doesn't activate another receiver kit.
any suggestion on how to send out a unique code without MCU? i would like the solution to be low cost, off the shelf, and can fit inside a typical car key fob case.
thanks in advance!


texts:
I have just started to program some code at the lower levels.

I have been told to change any signed integers into unsigned integers and store these in the HW registers.  I have done this OK but I am wondering why I need to do that?  What if I would have a 32bit signed integer, How would I handle that?

The values are going to be used by the HW itself sometimes, but also by SW.  When SW uses them I convert them back.

All of the HW registers are 32bit in size.


texts: Can I leave bootstrap pins floating? (Internal pull-up)

texts:
I have a microcontroller that uses 4 GPIO pins as "bootstrap pins". The state of these pins (high/low) at boot time will determine important features of the microcontroller, such as output voltage to the flash chip.

It is therefore very important that these bootstrap pins have the correct state at boot.

They are defined to have internal pull-up / pull-down by default. The pull-up / pull-down has a strength of 75uA.

Can I safety leave these pins floating and rely on the pull-up / pull-down to set the state at boot? The datasheet seems to suggest that I can.
However, I'm worried that stray noise or a finger (or a near by device), might overpower this 75uA drive strength.

Is this a realistic worry? I would like to save the space used by these 4 pointless external pull-up / pull-down resistors that I'm using if possible.


texts: My sequence detector for 1100 shows the correct output for all input 1100 sequences except one in the beginning. How should I debug the code?

texts:
The code I am using is the following. I am using five states as this is a Moore model and non overlapping sequence is assumed. The state logic is correct as far as I can tell. However when I run it there is one test case that it does not pass. The fact that I have trouble understanding is that it passes all cases after that with 1100 as the input and leaves out just one. I don't have the test bench for this and only the test cases are used to determine the validity of design.

module sequence_detector_fsm(
        input Clk,
        input X,
        output Y
);

parameter A = 0,B=1,C=2,D=3,E=4;
reg[2:0] PS,NS;

always @(posedge Clk)
begin
PS<=NS;
end
always @(PS,NS,X)
case(PS)
A : NS = X ? B : A;
B : NS = X ? C : A;
C : NS = X ? C : D;
D : NS = X ? B : E;
E : NS = X ? B : A ;
default : NS = A;
endcase
assign Y = (PS==E) ;
endmodule


texts: Cheap load cell and ADS1232 strange oscillation

texts:
I'm using four of these load cells wired in parallel and connected to an ADS1232. Overall the device (scale) is working well, but I am seeing a strange signal over a period of a few minutes after I turn the scale on. I have the ADS1232 hooked as in this schematic:

I have the ADS1232 wired to output 10 sps which go to a MCU that does a moving average over 32 samples (3.2 s window). When I start the scale and record the output from this filter I see the following signal (purple line):

I have seen the same signal a few times now. It seems to go away after appearing once on startup.

Does anyone have any ideas as to what could be causing this signal?

Edit: Here is the code for the moving average filter (N = 32 in this case). The Input method is passed a new sample every 0.1 s.

**

template<size_t N>
class MovingAverageFilter {

    double samples_[N];

    size_t write_;

    double sum_;

    double average_;

public:

    /*initialize a filter with the necessary parameters*/
    MovingAverageFilter(double init = 0)
        : samples_{0}, write_(0), sum_(init * N), average_(init) {
        Reset(init);
    }

    /*clear buffers*/
    void Reset(double init = 0) {
        for (auto &i : samples_) {
            i = init;
        }
        sum_ = init * N;
        average_ = init;
    }

    /*input a new value*/
    double Input(double input) {
        auto oldest = samples_[write_];
        sum_ -= oldest;
        sum_ += input;
        samples_[write_] = input;
        write_++;
        write_ %= N;
        average_ = sum_ / N;
        return average_;
    }

    /*get the last output*/
    double LastOutput() const {
        return average_;
    }

    /*get the last input*/
    double LastInput() const {
        auto index = (write_ - 1) % N;
        return samples_[index];
    }
};

**


texts: Gadgeteer voltage sensor that can measure up to 8000 volts?

texts:
I am a software engineer by day and a pig farmer the rest of the time.  I am looking at automating many of the mundane tasks around the farm by deploying IoT all around my farm.  One of the first tasks is to gather the current voltage of my many hot lines scattered about the farm.  The most powerful shock might be in the 8k volt range.

Is anyone aware of a ready made voltage sensor that could be wired into a Gadgeteer solution?

If not, how might I accomplish monitoring voltage this high in a manner that I could wire into a Gadgeteer solution?

Update

What is Gadgeteer:

This is a set of modules that can easily be plugged together to create something interesting.  You can then deploy C# code to it via USB and quickly get a working thing up and running.  In the case where a readily available module is not available you can use a bread board and wire in any other readily available circuit/sensor that is on the market.  This tool set allows software developers to dabble in the hardware world.

What is a Hotline:

In this case I run a pig farm (among other animals to be managed).  I keep the pigs in a paddock by surrounding it with a set of steel wires that is not directly grounded to anything.  A pulse is fired from a (solar in this case) electric charge box every X seconds.  The pulse without any interference for up to 30 miles worth of wire tops out at 8000 volts.  When the animal touches the wire...and the ground...they get a good zap to teach them to step back.  I have touched it a few times as have my kids...and it is a GOOD ZAP.  I have basically this model charger: http://www.tractorsupply.com/en/store/zarebareg%3B-30-mile-solar-low-impedance-fence-charger

Do I need to measure for the exact voltage?

No - not really.  I need to mostly establish a baseline.  So if the 8k voltage was some other numeric value that I could establish as a baseline to be measured every hour or so that would be good enough.  I need mostly to be able to collect data and then reason over it.  If a fence was down I could pretty quickly get a notification for being way below allowable tolerances.  But in the case that weeds grow up all around the fence the number of plant contacts over time would slowly but significantly impact the effectiveness of the fence.  So baseline plus semi-accurate deviation would be good enough.


texts: How does AVRDUDE communicate with the programmer?

texts:
I'm trying to understand exactly how AVRDUDE communicate with the AVR Programmer, for example USBtiny or Arduino itself as a programmer, to send the firmware to the microcontroller.

As a motivation to my question, suppose that I want to build an USB In-System Programmer for an AVR microcontroller from scratch. So, using another microcontroller, I build an ISP that can load code to the AVR.

Now, what if I want to use AVRDUDE to send to my ISP some code to load into my microcontroller? What kind of protocol will AVRDUDE use to send the code via USB, so I could read it correctly and generate the correct SPI to program the AVR? How the people who created USBtiny, for example, knew (or specified) the protocol avrdude would use to send the data to USBtiny, so they could interpret it correctly?

Any help is appreciated!

Thanks!


texts: Unbalanced three phase system with unbalanced phase to phase voltages

texts:
I've got quite a problem here trying to solve this 3 phase system (2nd U12 should be U31) and hope you can help me:

I'm trying to calculate the single phase voltages and currents for the drawn case with the connected neutral and once for the disconnected neutral.

However, the first problem for me already arises with the fact, that the sum of the phase to phase voltages is not zero, as indicated by the phasor diagram below:

After hours of research on the internet or in literature I couldn't find a single problem, calculation or simulation where this case was treated and if I think about it, it just doesn't make sense that the sum of phase to phase voltages isn't zero.

Therefore, the underlying question: Is this system even possible?

Thanks for reading and hoping for your answers!


texts: Why does my circuit short when powering through the same board as compared to an external power?

texts:
I have designed a board which follows this schematic:

What I’m trying to achieve is using a N-Channel MOSFET to make the SDOOR inputs connected. The SDOOR inputs are from another controller (STM20) which when connected will open a sliding door.

The issue I’m facing is when I’m powering the board through the STM20 controller, the controller gets shorted when the mosfet is activated (it gives an error message saying 24V overloaded.)

However when I power the board with an external power, there is no issue at all.

I have read that N-Channel MOSFET requires an additional voltage rail while a P-Channel MOSFET does not. Not too sure what an "additional voltage rail means" but could the issue be solved if I switch to a P-Channel MOSFET?

I’m not sure what is the cause here. Could it be because of the ground plane that I have on my custom board? Or is my schematic wrong? Hope someone can point me to a correct direction!

*Edit: I added a simple drawing to show a simplified connection of the circuit.


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I'm new to the world of Digital Systems :D I want to know whether the output of the Ultrasonic range finder sensor is analog or digital, so I can connect it to Altera DE2 GPIO directly or I need an ADC?
Thanks in advance :)


texts: Why increasing block sizes in caches leads to decreased miss rate?

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My book about computer organization said that:

If size of a block is 1 word (4 bytes), it will encounter 10 misses when accessing 10 consecutive integers in an array.

If we set the size of a block to 2 words, we can achieve a reduction from 10 misses to maximum 6 misses when probing those 10 consecutive integers. (Assume an integer takes 4 bytes).

I don't get why it is 6 misses, I thought it would be more reasonable to be 5.


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I have an M35SP-11NK stepper motor that I would like to be able to drive with an L293D driver chip. The circuit below is how I've got it wired up so far. I've derived this from numerous sources on the internet and referring to the datasheets linked to above. Do I have this wired up correctly?

In all of the schematics that I've seen, nobody seems to use any current limiting resistors? This seems a bit odd to me, but I'm not that great at electronics so maybe there's something I'm missing?

I know the stepper motor coils have a 25Ω internal resistance, but if I'm providing them with 12V (through pin 8 of the L293D), doesn't that mean they'd be able to draw up to 480mA of current (applying Ohms law 12v/25Ω = 0.48A, assuming no internal resistance in the L293D), do I need to stick another 15Ω resistor in series with the 12V supply to limit it to 300mA, or won't the phases in the stepper motor ever draw that much?

Also, do I need any resistors between my 5V supply from the Raspberry Pi and the L293D, again, I've not seen anyone put anything there, but it seems odd not to? I'm struggling with the myriad of values on the datasheet and finding which ones are relevant for my purpose.

Just wanted confirmation that I've got this right before I inadvertently destroy my Pi.. thanks :)

simulate this circuit – Schematic created using CircuitLab


texts: Why is the time constant of RL series circuit be \$\frac{L}{R}\$?

texts: We all know that the time constant \$\tau_L\$ of RL series circuit is \$\frac{L}{R}\$,and i think there should be an explanation,except the result of circuit simulation, to explain why  the  time constant of RL series circuit is \$\frac{L}{R}\$,why isn't \$\tau_L=RL\$,just like \$\tau_C=RC\$.


texts: Why do we use a CMOS for inverting a circuit when the PMOS already achieves that?

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The output in a PMOS is as follows:

I/P    O/P
 0      1
 1      0

Why can't I just use this instead of using a CMOS for inverting logic?
(Please explain in simple terms as I am a beginner in this topic and subject)


texts: Why some microcontrollers have so high price/performance ratio?

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PIC16F877A is $6.72 / 1 pc,     $4.68 / 100 pcs from Digi-Key.

ATMEGA328P is $4.98 / 1 pc,     $2.77 / 100 pcs from Digi-Key.

LPC1113FBD48 is $2.24 / 1pc,    $1.64 / 100 pcs from Digi-Key

I know that my compare is not fair in the case of manufacturer, packaging.. However, by the means of functions and capability, isn't $4.68 too much for PIC16F877A, or $2.77 for ATMEGA328?

Why are these parts so expensive? Do you think that they are going to be  cheaper?

Pardon me if it is a silly and/or off-topic question.


texts: What does ClockDivision do, as opposed to the Prescaler for STM32 timers?

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I am using an STM32 board (F7 series), and am looking through the HAL API documentation.  When I initialize a timer, I see two values, Prescaler and ClockDivision.  Now I understand that the Prescaler is used to divide the frequency of the clock.  However, what is the ClockDivision supposed to do?  I see it has three possible values, DIV1, DIV2, and DIV4.

My auto-generated code says the following.


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I have to measure a DC voltage and an AC voltage around 100V.
I found the circuit with an AD629 and one OP177.

I simulated everything in Spice and it works fine, at least in the simulation. In reality the power supply (V_IN) is isolated. It doesn't share a ground with the rest of the measurement circuit. V_OUT should be converted by an ADC which doesn't share a ground with V_IN.

Is it still possible to use this circuit because of the high input impedance? If so should pin 1 (Ref-) of the AD629 connect to the V_IN ground or to the shared analog ground with the rest of the circuit?

And do you think there are problems when measuring DC voltages instead of AC voltages? In the simulation it doesn't matter.


texts: I made this FM transmitter from this video (https://youtu.be/joFourugXvs) but it has a very short range (30 cm). Where's my mistake?


texts: Are there hand tools for applying electrically conductive adhesive and stringing wire for manual wire bonding?

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It would be handy to be able to place small jumpers on PCB without soldering.

Are there specialty hand tools for applying electrically conductive adhesive and stringing fine wire, sort of like a manual wire bonding technique?