texts: Can I use a modified freezer to cool the hot side of a peltier element to reach very low tempetatures (-30°C)?

texts:
I'm quite new to this, so forgive me if I ask anything stupid, but I need some help and I hope that some of you here might be able to help me.

For a school project, I'm building a cloud chamber. The bottom of these chambers have to be very cold (-30 degrees C or -25 degrees F) . I have taken the compressor from an OLA freezer  and upgraded it. The copper plate on top reaches on average -7 degrees Celsius. Is it in any way a good idea to use an aluminium plate to make sure that the temperature is evenly spread across, place peltiers on top and add another aluminium plate as a top plate (with proper isolation and thermal paste ofc).

The plate is 50cm by 30cm. It would be okay if the peltier cooled area  is smaller. Should I try this (since my first attempt failed), could this even work, what peltiers should I use and what kind of temperature could I expect (I'm hoping for -30°C). I know I'm asling a lot, but any help would be appreciated. Thank you for reading.


texts: How do I know where to put stitching vias?

texts:
I'm working on a PCB that allows me to attach a TSSOP IO expander to a breadboard more easily for experimenting.  I asked a question regarding the configuration of decoupling capacitors for an IC with 2 supply pins.

One of the recommendations was to add ground pours to the top and bottom layers of the PCB to create low impedance ground connections for the decoupling capacitors and to tie the top and bottom layers with several stitching vias.

How do I know how many stitching vias to place and how do I know where to place them?

Here is what the board looks like so far:

Edit:

Because I'm new to electrical engineering (I'm barely at hobbyist level), it really helps me to see solutions visually.  For folks finding this in the future, here's what my latest state is:


texts:
I'm trying to interface an intel edison board with a 5mp mipi camera (https://www.sparkfun.com/products/13249)
The camera uses an OV5640 imaging sensor, and is used with a pcduino v3. It interfaces with the pcduino via csi interface. I'm trying to have the intel edison interface with the camera. Is it possible to interface it with I2C with the sda and scl pins from the camera module? Or do I have to use csi?


texts: Understanding Dali2 D4i, 202 memory bank energy data

texts:
Below is a log from memory bank 202:
Bank [202] , Loc[0x04]: 255
Bank [202] , Loc[0x05]: 0
Bank [202] , Loc[0x06]: 0
Bank [202] , Loc[0x07]: 0
Bank [202] , Loc[0x08]: 1
Bank [202] , Loc[0x09]: 49
Bank [202] , Loc[0x0A]: 107
Bank [202] , Loc[0x0B]: 255
Bank [202] , Loc[0x0C]: 0
Bank [202] , Loc[0x0D]: 0
Bank [202] , Loc[0x0E]: 0
Bank [202] , Loc[0x0F]: 49
Above are the values that I am getting from memory bank 202. luminaire was running at 38.9 W AC. Can some one help me interpret active energy data.
Thanks & Regards,
Adharsh R.


texts:
I am trying to better understand how flip flops work. I am asked:

  Desing a three-bit up/down counter using T-ff. It should include a
  control input called Up(bar)/Down. If Up(bar)/down = 0, then the
  circuit should behave as an up-counter. If Up(bar)/down = 1, then he
  circuit should behave as a down-counter.

The solution to the problem is this:

My question is basically how they came to this conclusion. I know from a truth table the behavior of a t flip flop:

Q Q^+ | T

0 0 | 0

0 1 | 1

1 0 | 1

1 1 | 0

I don't understand how to make a T flipflop into a up counter or a down counter respectively.


texts: How does the plastic-tube inductor in this wireless transmitter work?

texts:
This single layer PCB (solder side shown here) is from an old fan remote:

The inductor in the plastic tube is not connected physically to any components; however, the two loops of wire surrounding it are soldered to the board. This raises some questions into the transmitter's operation:

The frequency of the OOK transmission was determined to be approximately 305 MHz.

.

The data output from the HT12E encoder is a kHz-frequency signal as defined by its internal oscillator. At the two wire loops surrounding the coil, the data output from the encoder is observed (my scope cannot do >20 MHz), which is identical minus some voltage drop.

It seems that an inductor should be required for operation of what would appear to be a high frequency oscillator circuit (MPSH10 RF NPN), which would modulate the encoder output to 305 MHz. In the above diagram, "Loop 1" and "Loop 2" represent physical connections to the wire loops, where #1 is closest to the BJT.

Is it correct that the wire loops should also act as antennas?

Since the inductor is not connected physically to anything in the circuit, what is the theory behind its operation here? Why use such an inductor instead of a standard piece?


texts: Heat transfer in an airtight enclosure (component -> internal ambient -> heat sink on case?)

texts:
Are the thermal resistance values of heat sinks/etc reasonably reversible? If I wanted to dissipate an internal ambient temperature rise, could I use an internal heat sink on the enclosure wall coupled to a heat sink on the outside to pull heat out of the box?

Can I use the same thermal resistances of the heat sinks in reverse to calculate how efficient this will be at extracting heat from the air? (Assuming additional resistances of sink #1 -> wall and wall -> sink #2)

I'm developing a product that must be in a sealed enclosure. I'm also trying to have the highest operational temperature range I can (targeting -40 to 85 °C) I'm sinking some heat sources (power bricks, power op amps) directly to the metal enclosure... however I am not currently able to sink the heat from the CPU itself (~1W) directly to the case. I -could- add a wide temperature range heat pipe, but I'd like to avoid it.

We're not talking about that much heat, but I just don't have much room near the top of my targeted ambient range (105 °C Tj and 85 °C Ta)... The CPU would require a heat sink even if it wasn't enclosed.

EDIT

Okay, to clarify I guess I'm asking if a heat sink's thermal resistance is simply a thermal conductance value that I can use both as a number of how much of a temperature rise a certain amount of power put into it will cause AND the exact opposite in how much power it will conduct given a specific temperature differential across it.  (So, a 10 °C/watt heat sink would for 1 watt be 10 degrees above ambient, and that if ambient was 10 °C ABOVE the sink it would pull 1 watt of heat out of ambient)

...

Say my CPU is putting out 1 watt of power. With a heat sink, the Tjs (die to sink) is 0.5 °C/watt, and the heat sink's Tsa (sink to amibent) is 9.5 °C/watt, for 10 °C/watt total. My CPU is then 10 °C above the immediately nearby internal ambient temperature.

My internal ambient is getting about 1 watt of power sunk into it, and that power needs to go somewhere.

There is about 3" between my CPU heat sink and the enclosure wall.  With a thermal conductivity of air at 0.025 W*(m^-1)/°C, there would be a rise of about 3 °C across those 3" to transfer 1 watt. (right? This seems too low to me. Also, it's ignoring any kind of internal convection effects) Call this 3 °C/watt = Tax (internal ambient transfer).

The path is then normally Tac (resistance internal ambient to case) plus TcA (case to external ambient).

If I put heat sinks on the inside and outside, I then have Tah (internal ambient to internal heat sink), Thc (internal heat sink to case), TcH (case to external heat sink), THA (external heat sink to external ambient).  (although really I also have Tac and TcA still, for the case surface area not covered by heat sinks))

Say Tah is 3 °C/watt, Thc is 0.25 °C/watt, TcH is 0.1 °C/watt, and THA is 1 °C/watt.

I have 1 watt of power for Tjs, Tsa, Tax, Tah, and Thc. I additionally have up to 5 watts of power sunk into the case from other sources directly attached to the case. So, I have 6 watts of power for TcH and THA.

Can I then say that my external ambient maximum is:

Tjs + Tsa + Tax + Tah + Thc + TcH + THA, or 0.5 + 9.5 + 3.0 + 3.0 + 0.25 + 0.6 + 6.0 = 22.85 °C/watt?

With Tj of 105, my maximum external ambient would be 82.15 °C?


texts: Op. amp. with integrator - enough values to start?

texts:
All the red-circled values (Uref, C2, R31 and R36) are missing. I'm supposed to calculate them, but I think there's at least one value missing. Shouldn't Uref be known to calculate the rest of the values?

The waveform was given beforehand.

The power supply voltages are +/-15V for both op. amps, where the green line is the output of the integrator and blue one is output of the Schmidtt trigger.


texts: What happens when reaching the max temperature on a temperature sensor?

texts:
I need to monitor the temperature of a hot plate so it stays at 210C

I am just using a Arduino and lcd to display the temp using a DS18S20 (I have it ready but not actually using it to measure the plate with this) but that's only rated to 100C so I am buying a  LM34CZ DKF503N5 / DKF103N5  which goes to 250C.

My question is what will happen if it goes above 250? will it de calibrate it? will it explode? or something else? It is possible that it could go higher than that but for short periods of time until I can get the correct temperature on the plate.

I did read a few datasheets and it does not say anything about exceeding the rated temperatures.. that is why I am asking you experienced guys..

EDIT

Sorry I was on a US site and never realised it was F i switched over to UK and got the correct ones.. completely different models though


texts: Looking for a Constant Voltage/ Constant Current power supply schematic

texts: I would like to create as an hobbistic project a power supply circuit allowing to switch between a Constant Voltage mode and a Costant Current one. When Voltage Mode is on, Current regulation should act as an upper limit as well as voltage regulator should act as a limit in costant current mode. I know how to create two separate circuit, but no idea on how to merge them in a smart way.


texts: Fuel sender - need something to convert ohms to volts?

texts:
I need to connect a cars fuel sender(ohms) to a analog input on a GPS tracker (volts)

Here's the catch, in our tests most fuel senders we worked with seem to send the data as ohms/resistance

However, the GPS trackers analog inputs require volts (Generally gps trackers take 0.5 to 5.5 volts as their analog input)

In rare cases, we found some fuel senders use volts, but most use resistance.
Therefore I need to find a gadget (ideally one that already exists I could buy off the shelf) that will take the input from the fuel sender, and convert it to volts, so I can connect it to the gps tracker.

I've looked into arduino stuff, but it's a bit overkill for what i need, so was hoping a micro controller already exists for such a task (if micro controller is the correct phase) - Ardunio coding is not an issue for me, and have done some C coding for a car tuning company previously, so am familiar with the basics, but the price/setup time is quite high for this application.

The only curve ball here is that each fuel sender might send wildly different min and max ohms values from the fuel sender due to each car manufacturers fuel sender being made for their own gauges
Once data is in the software we can manipulate the readings easily to show the fuel level of the vehicle (notably the massive variation in data on a bumpy road)

So my questions are

Are there other things I may have not considered with the above project?
Is there an off the shelf micro controller that might do this, if so what is its name (for help searching online).
Also, are there any website online that might sell such a device
if the above does not exist, can anyone suggest what I would need to do to create my own one.


texts: What determines output voltage in a feedforward DC/DC converter?

texts:
I am designing system that includes a solar power stage with an MPP tracker. The DC/DC converter in the MPPT is feedforward, i.e. it regulates the input voltage of the solar panel to the maximum power point. However, the output is then left unregulated. Note: it will not be connected to a battery directly like it is often done, it will be a separate "MPPT bus" from which various loads will draw.
In such a configuration, what would determine the output voltage of the converter? Is it the load, or do component values play a role as well? Or is the duty cycle still defining the input/output voltage relationship?
I am using a buck/boost converter, but you can assume any non-isolated topology, I am looking to understand the principle.


texts: Buffer Clipping Below Negative Supply Voltage

texts:
I'm trying to understand op-amp operation, starting with the buffer circuit.  I have simulated the voltage follower using an LM324 in Multisim Live. I was trying to simulate output saturation by changing the magnitude of the input voltage to the buffer to drive the op-amp beyond the power supply limits.   The image included at the end of the post is my Multisim Live schematic and simulation results.

2 issues confuse me:

How do I determine the min/max output voltages from the datasheet?  The info given is for single supply operation, however the op-amp is described as dual supply up to +-16V.  Not sure how to convert the VOH and VOL specs from single supply to dual supply.  The VOH spec is also state for V+ =30V, so not sure how to convert to +5V.

The simulation results show the op-amp in both positive and negative saturation.  However the negative saturation is below VEE for the simulation.  Regardless of how close the output can get to the rails, my simulation shows it clipping below the negative rail.  I can't make heads or tails of this.


texts: How to flash the TI CC2650STK using a XDS110?

texts:
I have a TI cc2650STK (a.k.a. Sensortag 2) and a corresponding Debug DevPack. I've been trying to follow the instructions on how to use both together (as proposed in this answer), but I have not been able to flash the Sensortag.
Every time I try to select the device on the left hand side of SmartRF Flash Programmer 2 (v1.7.1), an error dialog pops up saying "The selected device could not be identified."

As you can see in the screen shot, the Debug DevPack shows up as an XDS110, for which I installed the latest drivers (release 6.0.83.1). I also upgraded the Debug Devpack's firmware to v2.2.5.1, as suggested by Flash Progammer's "Help Document".

So far, the only resources I found about this are only vaguely related, and they seem to suggest that using Flash Programmer 2 v1.6 or above fixes the issue (2nd source). But in my case this doesn't seem to help.


texts: Saving a voltage with ONLY analog components. Best idea?

texts:
I am challenging myself to create an analog voltage storage device.
I came up with some ideas and I would like some inputs on what is bests and maybe new ones.
Ideally, I could store a voltage in a capacitor (electrolytic)  and that's it. However, nasty leak currents and parasitic effect will result in a slow but inexorable drop in capacitor voltage.
Let's try with the easy one first:

Connecting the capacitor to a 1 MΩ resistance to the power supply. It is a wild assumption that the leak current will be the same across the Capacitor voltage but it would at least reduce the discharge effect. PROS: Simple, effective. CONS: it will slowly charge/discharge the capacitor above/below a certain Voltage depending on the internal resistance.

Use an op-amp to read the cap voltage, compare it with a second capacitor and push current to both capacitor if there is a drop (recharging both caps with one current burst). PROS: will compensate the cap Leak across all voltages. CONS: complex and requires fine tuning to avoid positive feedback.
I want to store the voltage in the 1 μF capacitor.

Use of integrator: Kind of same as option 2. I want to store the voltage in the 1 μF capacitor.

Another idea is to use an op-amp as Leak Current detector and cause a proportional voltage response to recharge the cap for the exact same charge (need still to figure out the details.)

Any other suggestion?


texts:
To charge a 4 cell Li-Ion battery pack, microchip have developped a circuit (board) that I am trying to understand, (the link for the PDF is here:https://www.microchip.com/developmenttools/ProductDetails/MCP1630RD-DDBK3)

The charger is built using a microcontroller and MCP1630V as an SMPS Contol Unit (see page 16/30 and 17/30).

The MCU feeds MCP1630V with PWM signal of Fs=500kHz.
If we look closer to the circuit, we notice that FB and COMP pins of MCP1630V are short-circuited, which means that the internal error amplifier of MCP1630V is used as a buffer.

My questions are all about the circuits that are connected to Vref of MCP1630V.

We have an OPAMP referenced as U4:B used as a second order active low pass filter cascaded with a passive low pass filter composed of R32 and C21. The output of this third order low pass filter is connected to the inverting pin the OPAMP referenced as U4:A in the circuit.
The non-inverting pin of U4:A is connected to:

1.the current sensing circuit of the battery (composed of R4 and R5).

2.VCC through R24.

My first question is, if we consider U4:A as an error amplifier (As it appears), what is the purpose to connect the inverting input of this OPAMP to the output of the 3rd order low pass filter  and the non-inverting input to current sensing circuit of the battery?

Second, why have we connected THREE outputs (through R22, R19, R12) to Vref of MCP1630V? How does these outputs influence PWM output(Vext) of MCP1630V?


texts:
In the ARRL (2011) section 9.3.1 about LC oscillator circuits it says that "[t]he N-channel JFET source follower shown appears to be the most popular choice nowadays", but does not explain the advantages of JFETs over BJTs.

All I can think of is the fact that BJTs need extra components in order to be biased, and JFETs have a higher input impedance.

What would be the advantage of a JFET (e.g. J113) over a BJT (e.g. MMBTH11) for this application? And why the preference for an emitter follower topology?

EDIT: Here are the schematics from the ARRL (2011)

And my simulation which works well when tested on breadboard


texts: Can I convert audio signals from an iphone to electrical signals to control another device?

texts: I wish to design a mobile app that will allow me to touch parts of the screen, generate a music tone that will be converted to an electrical signal to move part of a toy.  By touching different parts of the screen, different music tones will be generated which will move different parts of the toy.  The toy will have hold batteries to move the parts.  Can it be done without a processor chip?  If not, can anyone recommend how I would go about manufacturing the chip?  Thank you for your help.


texts:
I am trying to make a simple motion detector for objects within a few feet in a very small footprint with minimal parts. I don't need to know much info about the motion just simply if there was motion and the rate of the motion. I do not need to know the absolute level of light.

So far I have had pretty good luck doing this using a basic photo-transistor circuit and a micro-controller ADC with integrated gain.

The issue arises when I change light levels from a dark room to light room to cloudy day, the photo-transistor can easily saturate depending on overall light level.

A way to avoid this would obviously be to use a variable resistor type circuit, like a digital potentiometer or a voltage controlled JFET. These circuits are a little more complicated then I was hoping and would require constant checking and adjusting of the resistance.

My question is, since I do not need to know the absolute light level, is there any circuit that can automatically control the photo-transistor so that It remains out of saturation in any light level?

(I'm not too experienced in electronics, but is there a way to provide feedback with some hysteresis to a jfet or other resistance like device that would keep the photo-transistor between VCC and GND while allowing some high frequency fluctuations? (movement)


texts: OpAmp as Differential Amplifier Equation

texts:
I am currently reading a (german) textbook about Operational Amplifiers. In the Chapter about the use as an differential amplifier, the authors derive the equation for the output voltage (for the case that two resistors are equal).
I understand how they derive the equation until the last step. They somehow condense the equation but I dont know how. Can someone explain it to me step by step?


texts:
I have simulated the circuit with the following values. VDD = 1.8V, Vin is a sine wave with fin = 450MHz, pin = -5dBm, L1 = 12.5nH, C1 = 10pF, RL=50 ohm. I also gave a biasing dc voltage at the gate of MOSFET as 1V.
I got the following graph after simulation.

The red graph is the input sine wave. The yellow graph is the current at the drain of MOSFET and the green one is the voltage at the drain of MOSFET. But I am not exactly getting what the graph means or how to interpret it? If I am using it as a power amplifier how can I improve the output values of voltage and currents?


texts: impedance matching between opamp and microcontroller (or Arduino)

texts:
Based on my learning, Maximum power transfer theorem and Impedance matching, the output impedance and the input impedance of the components should be the same.  So does the output impedance of an op-amp (say LM741 which creates output based on a gain from sensor input) and the input impedance of micro controller (or Arduino) should be the same? Should we take the impedance values for design?

Please help. Thanks.
(This is for my information only, not for any specific circuitry)


texts: Extracting footprint existing PCB in Altium

texts:
I'm in the process of designing a carrier for an existing PCB. The upper layer of the carrier should contain pads to connect to the holes on the side of the original board.

I can re-create the lay-out by hand, but this is an awful lot of work. Can I extract the lay-out of the pads as footprint to a new PCB? I've tried to make a library out of the current board with Design -> Make PCB Library, but this doesn't provide an end result.

Can I somehow use the IPC tool to create a package out of the current board including a footprint?


texts: I need 0.5 ohm resistor in my circuit. Unfortunately, I am unable to find it in my nearby market. Can I use a piece of wire (with specific length) instead?


texts: Use single-pole voltage detector to check for currentflow on a lamp

texts:
I am using a single-pole voltage detector to detect if there is a current-flow / potential on the clamps of my ceiling lamp (See device in first picture below).

When the ceiling-lamp is ON and glowing, and I measure with the single-pole voltage detector, the detectors indicator lamp starts glowing, when I measure on phase (L), telling me there is a potential. -like expected.

If I measure the neutral conductor (N), my detector is NOT glowing.
But since my ceiling lamp is turned on and glowing, there is also power on my neutral cable (N), so I would expect my detector lamp to start glowing as well.

My Question: Why can my my single-pole voltage detector not detect the current-flow on my neutral cable (N)?

My assumption is the following:
When I measure on the phase-clamp (L), my detector is parallel to the lamp and also to my source voltage. Means it gets 230 V (See second picture below "1 Measure parallel"), so it can detect the potential.

When I measure on the neutral-clamp, I measure in serial to the lamp, but parallel to a short-circuit. So my Lamp gets 230 V, but my single-pole voltage detector gets pretty much 0 V (See last picture below "2 Measure serial").

Is this assumption correct? If not, what is the reason that my detector does not detect the potential of my lamp, which is turned on and glowing?


texts: Suddenly cannot flash ATmega328P due to verification failure

texts:
For a couple of years I have been flashing some boards I designed that use an ATmega328P using a USBtinyISP and avrdude. I have three identical boards that have been programmed successfully dozens of times. Suddenly I cannot program ANY of them. In every case, avrdude gives me a verification error. For any given board, it's the same address, but each board fails at a different address (0x02df, 0x0a97, and 0x043f). After the failure, two of the boards appear to be working (LEDs react appropriately) but I would not trust them. Interestingly, a fourth board, used for development, occasionally (rarely) flashes successfully. FWIW, the boards are connected to the USBtinyISP via pogo pins. But this connector has been working for a couple of years. I can see in my scroll history multiple successful flashes just two days ago!

What could possibly be causing this complete failure? What can I try? I'm at my wits end.


texts: Overall Q of a fourth order LPF and higher order LPF cascaded

texts:
If I end up cascading low pass filters to derive higher order filters, how should i calculate the Q of the overall filter?
For example if i have the following transfer function
$$
H(s)=\frac{1}{(s^2 +s \frac{1}{Q1}+1)\cdot(s^2 +s \frac{1}{Q2}+1) }
$$
Then what should be the Q of the LPF filter?
I think the Q of the last stage should dominate the overall Q so should be Q2, am i correct?

In general if i was to cascade more stages then what should be the overall response?


texts: At what point should I start considering to split the analog and digital ground planes?

texts:
I am designing a PCB which reads analog signals via some ADC, my circuit looks like this:

There are four of those in a single board. My top copper is filled with a power plane (3V3) and bottom copper is filled with a ground plane. The components under the pad 1, 2, 4 of A1 or A2 are the plug detect components, and components near pads 3 and 5 are the filters.

I have learned that the ground of the analog components should be separated from the ground of the digital IC components.

My questions are:

If I make another plane for the analog ground how would I connect them to the digital digital ground? Should I use some ferrite? And what values?
How big should the distance be between the analog and digital ground?
Am I overthinking things? the frequency of the signal that will pass there is only max 70Hz.

I already have a prototype and it works great, but because there are some minor adjustments, the opportunity is there to improve the design. I would like to respect good design practices.


texts:
I have an existing circuit powered with a 3.7V LiPo battery. To indicate when the battery is under 3V, I wanted to add an LED which shows me to charge the battery.
The circuit has to be very small.
I searched for circuits on the internet but they mostly had rather complicated circuits and not suited for my system. I need it to show me only when the battery is under 3V. It doesn't need to be adjustable. What  would the circuit look like? I saw many circuits with ICs and transistors. I didn't get how to choose the right components for my task.


texts: How to get the minimum transconductance of a BJT ce amplifier?

texts: We are being asked to bias a ce ampilifier circuit above to a gain of 15. It is given that the DC supply voltage is 10 V and a Vce,sat = 0.3V. Assuming that ro >> Rl >> Rload (on Vout when its connected), what should be the minimum transconductance?


texts:
I am learning Fritzing, and looking to create my first pcb. The components are fairly simple: 10x DS18B20, 1x resistor, 1x Konekt Dash. I plan to have headers to connect the Dash so it can be easily removed. When it comes to connecting the 10x temp sensors, I do not know where to start with choosing a connector. The prototype that I have up and running uses a full size breadboard where I used 3.5mm screw terminal blocks for each of the 3 wires for the temp sensors. Lots of wasted space...

How do you go about choosing a connector to maximize space used but ensure it is a simple choice when it comes time to solder to the board and wire up the sensors?


texts:
I hope I can explain what I am asking.

We will connect a DC motor to a single phase rectifier. Motor will carry a load. And motor sould be able to spin right and left. And when it is changing its direction there will be a counter EMF that can burn the motor.
The question is how do I prevent that ? Can I absorb counter EMF ? How?

Thank you :)


texts: How to simulate P-E loop of a lossy capacitor?

texts:
I want to simulate the P-E loop for a lossy capacitor (figure 1c below). For this purpose it's enough to plot the charge Q across the capacitor vs. the voltage V across the capacitor because \$P \propto Q\$ (ref) and \$E \propto V\$.

I tried using a capacitor with ESR (see 2 schematics below) but I only get results that look like ideal capacitor (figure 1a below). What am I doing wrong?

(source)

Simplest circuit

In this setup \$C_s\$ has ESR of \$100 \Omega\$. \$I_{ref}\$ is found from \$V_{ref}/R_{ref}\$, and the charge \$Q\$ is found from integrating \$I_{ref}\$. However, the plot of \$Q\$ vs. \$V_s-V_{ref}\$ looks nothing like expected.

simulate this circuit – Schematic created using CircuitLab

Schering bridge-like

In this setup \$C_s\$ is the sample capacitor with \$100 \Omega \$ ERS, and \$C_2\$ is an order of magnitude larger capacitor. Here I expect that plotting VY vs VX would give a P-E loop, but the result looks nothing like expected.

simulate this circuit


texts: How to gauge resistance on parallel circuit with step down buck regulator

texts:
I'm trying to create a circuit with two loads in parallel ( essentially piggy backing one circuit on the power supply of the other ). Circuit 1, the main circuit requires ~900ma at 12v. Circuit 2, requires ~70ma at 5v. To step down I'm using a buck regulator that provides 300mA at 5v. The main supply is 12v DC rated for 900mA, but in reality is providing more like 1.3A.
If I connect the circuits in parallel without balancing with resistors, all the current flows through circuit 1 ( its load will consume all available current ).

Now, correct me of I'm wrong, but I think I should add a resistor to each of the two circuits to manage current. So circuit 1 should get 12v / 0.9a = ~13 ohm. For circuit 2 though, I'm umsure how a buck regulator functions in this context. Should I add a 70 ohm ( 5v / 0.07a ) resistor after the buck regulator, or a 170 ohm ( 12v / 0.07a ) before the regulator. Or would both have the same effect?

Or perhaps I have it all wrong, so any advice appreciated.
Pseudo circuit attached:

======= UPDATE 1 =======
Circuit 1 is a terminal for a scale unit. So logic board, power to a high capacity battery and a display, and excitation for the load cell itself. All encapsulated.

Circuit 2 is a rs232 converter and bluetooth chip. I took the 1.3A reading across Vin and Gnd with just the terminal and buck converter in parallel. I'm not sure how to resolve this difference, essentially the DC transformer supplied with the terminal is rated at 12V 900mA so that was my assumption on the load of the terminal. I thought 70mA was probably not going to go missing.

======= UPDATE 2 =======
Based on Peter and Photons advice, and the discovery that I had misused my multimeter and blown the circuit by connecting the two probes in parallel (across the circuit) and not in series, I have now managed to connect everything up correctly and it works fine (as per the diagram with no additional resistors).

I'm not sure what the actual load from Circuit 1 is until I replace the multimeter's fuse, but it is less than the 900mA the supply is rated for, so the addition of ~70mA on Circuit 2 is not a problem and works fine.


texts: Using my sensor values, what are relevant data analysis techniques?

texts:
I am currently trying to devise a system using gyroscope+accelerometers placed in on a hat/cap in certain areas of the head (Front-left, Front-right, Centre, Back-left, Back-right). I want to create a system that can determine if the hat is roughly worn incorrectly (ie misaligned, tilted to the side, backwards).

The experiment is to:

measure sensor values(angles) when the hat is correctly worn and not in
motion (rest)
measure sensor values(angles) when the hat is correctly worn and in motion
(nodding up and down, side-to-side)
measure sensor values(angles) when the hat is Incorrectly worn in both not in motion and in motion.

I am asking is theres a suitable data analysis algorithm/technique to use these sensor values and essentially give a rough estimate if the hat is worn correctly or not.


texts:
I am beginner enthusiast. I was trying to make lights under my bed by following this tutorial:

http://aruljohn.com/blog/raspberrypi-christmas-lights-rgb-led/

It worked for me with a 1 meter color RGB led strip. However, when I put a white LED 5 meter strip, it can not go bright enough and it seems to be at 30% brightness.

The only MOSFET I have at home is IRF520. Is this the reason for my dim light? If yes, what kind of MOSFET would fit? Is there a way I can learn to calculate it?


texts: Why do transmission line equations use current through inductor rather than capacitor?

texts:
I could not fit the title in I actually wanted which was this:
In the transmission line equations why is the current difference either side of the inductor used in the capacitative current drop instead of the current difference either side of the capacitor?

In many references, eg. equation 2 from here:

  The rate of change of voltage with x at a particular time is a function of the rate of change of current with time and the current itself.

  $$
I(x)-I(x+\delta X)
  = \frac{\partial V(x+\delta x)}{\partial t} C \delta x \\
-\frac{\partial I(x)}{\partial x} \delta x
  = \frac{\partial V(x)}{\partial t}C \delta x
  + \frac{\partial^2 V(x)}{\partial x \mathrm d t}\delta x C \delta x \\
\lim_{\delta x \to 0} \frac{\partial I}{\partial x}
  = -C \frac{\partial V}{\partial t}
$$

the current drop through the inductor and resistor is used in the equation that relates the current drop through a capacitor to the capacitance and rate-of-change of voltage across a capacitor.

Surely the capacitance tells you about the current either side of the capacitor, in which case the currents used should be at the top and bottom of the capacitor?

EDIT: I will try to make this clearer as people ask questions. Normally I am used to \$CdV/dt\$ being given by the current through the capacitor (represented by \$C\$). But in the equation I linked to, \$CdV/dt\$ is being given by the difference in the current either side of the resistor-inductor pair. Why?


texts: Failed to use a low pass filter in order to convert PWM input to digital output

texts:
I want to convert a servo control signal to a digital 5V or 0V output.
This is the format of my PWM signal:

The different thing is my input pulse width will be either 1ms (minimum) or 2ms (maximum.) There can be a slight noise but there are no values like 1.5 ms. Only 1 or 2.
I tried to create a circuit that does this:

When I measure Vout:

1 ms pulse width: 170 mV
2 ms pulse width: 295 mV

I really do not know why it did not work.
I was expecting this:

1 ms pulse width: 0V
2ms pulse width: 5V

Do you guys know why didn't it work and what I can do to improve it?


texts:
A 220V series motor that has a total resistance (field winding and armature winding) of 0.2 ohms and runs at 1000rpm and takes full load current of 200A. The speed of the motor at which it develops half of the full load torque is?
I was doing this problem but got stuck as I could not find the value of the back EMF developed at half of the full load torque.
Here is my go at it:
$$ V = 220\mathrm{V} \\
I_{full-load} = 200\mathrm{A}\\
R = 0.2\Omega\\
N_{full-load}=1000\mathrm{rpm}$$
$$$$
$$E_{b_{full-load}} = V - I_{full-load}\times R\\
E_{b_{full-load}} = 220-(200)(0.2)\\
E_{b_{full-load}} = 180\mathrm{V}$$
$$$$
In a DC series motor, $$\phi \propto I $$
$$$$
$$E_b = \frac{Zp}{60A}N\phi\\
E_b = k\cdot N\phi\\
E_b = k^{'}\cdot NI\\
T=E_b I\cdot (\frac{60}{2\pi N})\\
T=c\cdot \frac{E_b I}{N}$$
$$$$
$$\frac{T^{'}}{T}=\frac12=\frac{\frac{E_b^{'}I^{'}}{N^{'}}}{\frac{E_bI}{N}}$$
from, $$E_b = k^{'}\cdot NI$$
$$N^{'}=N\cdot\frac{E_b^{'}}{E_b}\cdot\sqrt{\frac{T^{'}}{T}}$$
Only value for back EMF at half of full load torque is required to obtain the speed.
The answer is 1518 rpm.


texts: Interpreting pinout and the transfer function for this sensor from its datasheet

texts:
I have this pressure sensor with the following details from the datasheet:

The diagram for connections is given as follows as Vsupply, GND and Vout:

But the chip has 6 legs and described as follows:

1-) What is V1, V2 and Vex?
2-) And how can I obtain the transfer function equation? Is it Vout = Vs* (.009*P-.095) ± Error ?


texts: Alternative to A4988 stepper motor driver?

texts:
The stepper motor driver based on the Allegro A4988 (also A4983) has a lot of problems with temperature. It is getting very hot and stops to work. And it is difficult to set up with the potentiometer. When the current is too high, driver gets hot and steps get lost. When current is too low, there might not be enough power and steps get lost as well. Are there any alternatives to this A4983?

Pololu A4988 Datasheet


texts: Should I discard my inventory of old electrolytic capacitors?

texts:
I have been doing hobby electronics for more than 10 years, and some of my electrolytic capacitors are easily that age. They seem to work just fine and do not show corrosion or other visible defects, but they are usually used in prototyping rather than production.

Knowing that these have a limited shelf life, I'm curious if I should just discard what I have and purchase new inventory, and rotate it.

How best can I tell that my old caps have failed, are out of spec, or perhaps are going to fail?


texts: Please explain,How a 180 phase shift occurs in "ce" Amplifier. Change in input voltage leads to change in output voltage is some how I know,  but this happen in "cb" Configuration too. When Vbe increases Vce  decrease(PNP transistor)


texts:
I'm trying to built a circuit that amplifies music from a phone to a headset, based om ambient noise level. So if you're surrounded by noise, your music volume will turn up and in silent surroundings it will turn down.

My problem is that I want to implement a maximum where it stops turning up the volume no matter how much ambient noise there is, to avoid damaging the ears of the user. I think the max volume output (where the graph flattens out) should be in the range of 1-2V. I have included a figure to illustrate what I'm trying to do. I have looked into voltage regulators and I can see that it is quite simple for DC circuits, but not so much for AC circuits. Also, it would be easier to come up with a digital solution, but the learning goals for this semester limits me to work only with analog circuits... Any suggestions?

tl;dr
I need an AC voltage regulator for an analog circuit

Thanks!


texts: Which is the simplest way to transform +9V and +5V into 3.3V CMOS acceptable digital levels?

texts:
I have a device providing a signal of either +9v or +5v (depending on some action on the device) plus a GND. I would like to convert the Vin signal into something readable as a digital 1 or 0 on CMOS 3.3v levels, so I can know from a microcontroller when the action is happening. Ideally, with common components available without needing to get out of home.
I've tried with a voltage divider (to convert 9v/5v to 4.5v/2.5v for example) and then a couple of diodes to reduce the divided voltage in 1.4v so I get 3.1v/1.1v, but after some tests I don't get what it's expected.
Thanks in advance


texts:
I'm designing a device to switch a heating device driven by mains power. I've done quite a lot of research and realize there's a lot of information out there but as i'm dealing with potentially deadly AC i'd like to validate my design before ordering PCBs. This is my first time working with mains so please assume i know nothing :)

Requirements:

Switch a heating device (= resistive) load, up to 1000W
Compatible with 110-240V, 50 & 60hz
Driven by 5v MCU (ATMega328)
No need to pass regulations etc but absolutely needs to be safe
edit: Switching rate approx once every 5sec

Here's the schematic:

Notes:

D8 is the MCU pin
The resistor between the optocoupler and triac is a 1/4W through hole resistor, the other ones 0603
5A quick blow fuse
The two 330 resistors in series are there to keep the BOM simpler
The triac switches mains neutral

Questions:

First of all: is there anything here that i've missed or overlooked?
The heatsink on the triac is a bit unclear for me. I've calculated a maximum value of 10C/W, is this fine? My calculation is: (max temp - room temp)/(max on stage voltage * (milli amps / voltage)) - junction to base themal resistance ((110-25)/(1.65*(1000/230))-1.5 = ~10.35). Does this mean the triac will be at 110c all the time, seems a bit high to me?.. Ideally i would have a smaller heatsink though so i hope this is wrong :)
The optocoupler is random phase. The phase is only important for fading lights etc, right? Does the phase matter for a heating device?
Is a snubber circuit required? From what i understand this is only necessary for inductive loads?
Most of this circuit is on the bottom of a 2 layer 1.6mm board with other components min 4mm away on the top. From what i understand the creepage distance should be min 6mm but is it the same with the board in between?

I need to order the parts anyway so if you have suggestions for swapping components that's totally fine.

Datasheets:

Optocoupler (MOC3023M): http://www.farnell.com/datasheets/94947.pdf
Triac (BT138-600): http://www.farnell.com/datasheets/1651175.pdf

Any other tips or tricks are highly appreciated too!

UPDATE

After the tips here i changed the fuse to live (seems obvious now..) and added the snubbers. Updated schematic:


texts:
Asked here because EE's are familiar with concepts of rotating vectors...
Have as input inside a microcontroller, two signed numbers which correspond to rectangular coordinates. These numbers are related as the two rectangular components: a real and imaginary similar to R + jI.

Intend to have as output a display on four similar LEDs which would be interpreted by eye to indicate a vector angle...similar to atan2(real,imaginary). Light intensity will be done via Pulse-width-modulation (PWM). For example an input of (140,0) would light up LED 00 fully, while the other three would be off. An input of (38,0) would display similar full brightness on LED 00, since the display is for  angle, not amplitude.
Symmetry reduces the full circle into eight similar segments. It is obvious that at 0, 90, 180 and 270 degrees, only one-of-four LEDs should be fully lit with 100% PWM. And at 45, 135,225,315 degrees, two adjacent LEDs should be partially lit an equal amount.
But lit how much? relative to full 100% PWM. Should it be 50%/50%? Should it be \$ \frac{100}{\sqrt{2}} \$%/\$\frac{100}{\sqrt{2}} \$%?
Probing into intensity perception of human eye presents a morass of scenarios, each of which has a different non-linear transfer function between input  and perceived brightness. It is unclear to me which scenario applies here.

Display update rates will be close to, or just past persistence-of-vision, in the 20-40 Hz area. Background would be darker than LEDs, and LEDs would be observed directly.Edit - added goals: I hope to discern whether a vector rotates clockwise vs counterclockwise - it will be rotating quite slowly (period of one second or far more), but in a potentially noisy environment (phase noise). At some point, a PLL will be applied, and the vector should settle near LED00. This PLL will have a l-o-n-g time constant. I would be happy to be able to tell if it is locked in the presence of noise.

At angles of 0,90,180,270 degrees, PWM would be 100% for one-of-four LEDs.

At angles 45,135,225,315, PWM for two-of-four adjacent LEDs should be ???, considering the crazy erratic intensity perception of human eyes? Once nailed, I can probably work out a sane transition for intermediate angles (0-45 degrees).


texts: How can I make this symmetric non-overlapping clock using digital Logic components?

texts:
How can I make a (dead-time) non overlapping symmetric clock like this with digital components such as inverters and NAND gates with 7 separate phases?
The first photo is doctored to show what I want with three phases.
Thank you in advance

This is as far as I was able to get while keeping it symmetric and non overlapping, with only two phases. I need 7


texts:
As we know, the voltage level of a solar cell is lower than what a rechargable battery needs, and thus a DC converter is placed in between.( With feedback control for optimum V-I curve)

This just confused me, so what the solar cell is delivering?? DC converter provides power from outlet not the cell. Wasn't the whole point of solar cell to provide power? We could just charge the battery from outlet without the solar cell.


texts: 4Wire 120/208 High leg delta - 320v to ground, 420v to C phase?

texts:
I have a 120/208 High leg delta service 4 Wire. 208v/120v/120v

The reason for the call is main breaker failed. I get there and the 1 bus bar is not being powered by the main but the other 2 are.

Remove the meter, mess with the main breaker... Its broken.
Notice accumulating rust on bus bars natural, etc. Go back to customer and sell the panel upgrade and the need for outdoor rated equipment in the said building.

I test everything before and after. After I put the meter back in the high leg is reading 320v to ground, 420v to phase C, 240 to B.

I go out side and investigate and its a Delta high leg, center grounded I believe.

I can see the transformers on the pole. Tts the cheap 3phase. Standard house can with another house can for high leg.. 200amp main service on 2/0 - residential NEC rules.

I start to think its a corner grounded delta - my ground & bonding in the main is good. Even if it is a corner grounded....

How could I even change the voltage downstream.... from the meter box?

MAYBE if it was a unground system but even on a corner grounded system the grounding is up the pole. The high leg to ground reference shouldn't be changed.

MAYBE the rust and corrosion in the meter box? I replaced the load center and we are scheduled to replace the weathered meter box. But its the first time I've had to leave a customer without power; not a big deal as its a farm out building. But how?? I don't understand.


texts: Question about Static charges & dissipation

texts:
I have been practicing ESD safety procedures in my workplace. We typically use grounded ESD Wrist Straps and ESD mats.  If I correctly understand the static charges stay put until they come in contact with other object with different potential. What I wish to know is how the grounded wrist strap would help if static is built on my left hand and I am wearing the grounded strap in my right. Are the static charges built along the entire human body surface?

Thanks.


texts:
Let's say we have the basic feedback system of the picture

We know that the closed loop transfer function is given by $$T(s)=\frac{G(s)}{1+G(s)H(s)}$$ Now, the diagram above is equivalent to an open loop diagram with this transfer function .

Here's my problem . In the first diagram it's clearly a feedback system while in the second there is no feedback . How is this possible if these are equivalent ? Can a system have feedback or not depending on the perspective? I'm confused .


texts:
If two filters are in cascade and each has a certain rejection at a certain frequency offset.

We know that a filter rejects frequencies  by mismatch so at this offset we do not have a 50 ohm match and filter2 would be a load to filter1 when the reference plane is the input of filter1

question : can one add the 2 rejections and consider that this would be the total combined rejection?


texts: Explaining capacitance formula of electrolytic capacitor

texts:
As stated in this article at page 5, capacitance of a capacitor is generally expressed with the following formula:

My question is about surface area S, where it is described as "On aluminum electrolytic capacitor, “S” is effective surface area of anode foil enlarged to 60 to 150 times of the projected area through etching process.". What is the etching process here? And how to understand "anode foil enlarged to 60 to 150 times of the projected area"?

Second question about constant 8.855. Is it widely accepted constant value, or changing at some conditions?


texts: Powering a solenoid valve with a relay and no external power source

texts: I have a solenoid valve (12VDC, 540mA) that I would like to control with a 12VDC relay (15A SPDT). Is it possible to power the solenoid without an external power source seperate from the one powering the relay board (12V, 0.41A)? In the image, I have a logic signal in the input screws and I know that the relay is working with that signal (switching on and off with sound and light). The solenoid though does not seem to be powered. Should the wall outlet (currently going in at the DC power port) be stripped and connected to the input power screw terminal about ground? Ground power screw terminal currently is connected to ground of solenoid, and the other end of solenoid is connected to NC. Thank you for your help!


texts: Accurate ADC sampling with in-accurate clock

texts:
Im building a datalogger with a LPC11xx as CPU. It needs to wakeup at 256hz to take ADC samples, but this CPU has very in-accurate timed wakeup from deep-sleep, causing jitter on the sampled data.

So is there a very cheap component that can toggle a GPIO very accurately at 256hz, that wakes up the CPU from deep-sleep (using external interrupt)?

Or maybe even better: do there exists ADC's that have their own build-in clock, so that I can stay in deep-sleep for a whole second, and then read out 256 samples via I2C and go to sleep again?


texts: Can anyone identify this component? Looks like an op-amp

texts:
I am trying to identify IC3 in this picture.
IC2 is a LM723 and this is (obviously) a power supply. IC3 looks like an op-amp but I don't recognize some extra pins there: VC and FC.
Does anyone have a guess?
Thanks for the help!


texts: Solar charge controller with input from a laptop charger efficiency

texts:
Instead of connecting a solar panel to my 12v 30a PWM solar charge controller, I want to connect a laptop charger to make a DIY UPS.

Will the solar charge controller constantly draw the maximum output of my laptop charger @ 19v 4.74 (90W) and waste the excess power when the battery is full and the connected devices use less power?


texts:
What characteristics do I need to look for in an LCD to ensure it is easily readable in the daytime

Adding more info:
Low power, smaller size < 4" diagonal, either monochrome or color. Bitmap , not character.


texts:
When i've to generate PDF files with printout layers, i must always add the missing layer i need. For example i  usually draw the board outline on keepout layer, so everytime i have to add the keepout layer on the printout set.
Is there any way to build a custom template with all the printout layer and load it at once?


texts:
I've soldered 14 pins on the back of my LCD and connected to an AVR Microcontroller. The LCD powers on correctly and contrast is set correctly but I'm having trouble sending software initialization to the LCD via AVR Studio.The 8 bit bus pins are correctly configured to the ATMega 32 and same for the RS,RW, and En pins. I believe the error might be improper soldering.

Q: Is there a way to identify which pin, of the remaining 11, might be shorted out?

Since the pins are close I made sure that the solder does not touch adjacent pins but it's still hard to diagnose.

The LCD was receiving initialization code for a brief period but after moving the LCD around it simply stopped receiving init code all together.


texts: Does foam have the ability to broaden the bandwidth of an antenna?

texts:
In some designs of aperture coupled patch antennas, a foam is used between the ground plane and the patch substrate.

What would be main logic using it there? The reason of using it may be that when feed line substrate and patch substrate are the same?

The design by side view like that;

Patch

Patch Substrate (Ep:3.55)

Foam

Ground plane(with aperture)

Feed line Substrate (Ep:3.55)

Feed line


texts: Find all the Kirchhoff's circuit equations in a multiple batteries circuit

texts: So I saw this exercise where it says to find all the currents that flow in the circuit and all the equations for the currents and voltages. Any help would be more than welcome]1


texts: Can I estimate remaining battery life by measuring its voltage with the same MCU that it powers?

texts:
I'd like to estimate the remaining battery life of a battery that powers a microcontroller. Could I accomplish this by simply leading the battery into the MCU's built-in ADC?

My idea is that I could plot the voltage over time to figure out how much battery life remains. But would the change in voltage be noticeable? And would it be a problem that the same battery powers the MCU (and ADC)?


texts:
For example I have a 10 bits ADC，which has a reference voltage of 2.5V.
In single-ended mode,the input range 0-2.5V according with conversion result 0-2*e10.
And what about the differential mode？
I have two question,in differential mode,is the votage range -2.5V-2.5V?
and -2.5V-2.5V according with conversion result 0-2*e10?
Any assistance is appreciated.


texts:
I would like to have a rough estimate of the capacitance per unit length of a system composed by N parallel identical straight wires.
I tried to sketch the capacitance network but I'm able to solve it only up to 4 wires... Any idea how to smplify the problem?


texts: Does not Reset Handler move along with NVIC vector table?

texts:
My board: STM32F407G-DISC1 (based on STM32F407VGT6 microcontroller)
See reference manual. (pages around 371 are related)
My understandings
Each interrupt service routine is located in a memory address, and this memory addresses are hold in NVIC vector table. Normally, we have weak declarations of those interrupt service routine(callback) functions in startup.s file. So, overwriting them in a .c file, in main.c for example, will be enough to use them. Those names are defined strictly, and one have to use same names, for example : EXTI0_IRQHandler()
However, we also have VTOR, Vector Table Offset Register, by which I can relocate vector table to another memory region, and can use my customly defined callback functions with different names by writing their memory addresses(function address) to the new memory location of the corresponding interrupt vector.
So far, everything is fine, I confirmed that when I relocated the vector table by VTOR, the old names are useless unless, i.e, just defining an ISR function named as EXTI0_IRQHandler() is not sufficient without further work(writing its address to new vector table location for EXTI0).

Question
At this point, one thing confused me, even I migrate/move the NVIC vector table, pressing the black button(reset button) on the board resets the microcontroller still. But I would expect reset not to work since the ISR pointer for Reset_Handler() is not defined/found in the new location of the vector table.
My guess: Reset_Handler() does not move with NVIC vector table, always located at 0x0000 0004, and its definition is in startup.s. So, it will be the same.
I assume I have some conceptual misunderstanding in this. Can you point what is wrong with my thinking?


texts:
I'm currently traveling and only have access to basic parts (soldering iron, an arduino nano and a breadboard!) but I'm able to buy parts from local suppliers. for a project I need to be able to create some waveforms and verify the output of the circuit (I tend to only do it for about 10 to 100Hz, so nothing high frequency!).

I think I can use an instrumentation amplifier followed with a summing amplifier to adjust DC offsets (add or remove) and another inverting amplifier to get the original signal, which is finally fed into the MCU ADC input and sampled as fast as possible, then displayed on the PC using a serial monitor program.

I'm having some doubts about the audio output of my PC however. I'm not sure if it's bipolar (i.e goes below ground as well) or if it's unipolar with a certain amount of DC offset? I did some googling but couldn't find anything and I'm not sure how I can verify that.

The signals will be created using this website:

https://www.szynalski.com/tone-generator/

which gives quite a lot of options for the output waveform except anything for DC offset!

obviously the ADC on the arduino works only in the 0-5 range and is unipolar.
I try to take a picture of my current schematic and upload it, in case that's relevant information.


texts: should I use high voltage or high current to burn carbon rods to dust

texts:
I want to burn carbon rods in a vacuum chamber to coat samples in carbon and need the carbon rods to be completely evaporated (worn out /eroded) through electrical power. I also need the +ve terminal to be fed slowly towards the -ve as its eroding

My questions are, which would be most efficient way of eroding carbon:

1) should I use High voltage low current (eg flyback transformer) or
2) low volt high current (eg welding machine) or
3) AC / DC or pulsed or
4) which combination of above?

any other info on how to feed the +ve towards the -ve (as it senses no current flow) would be appreciated..


texts:
Here is my PCB drawing that couldn't fix EMC problem. There are peaks at 120-130 MHz at radiated measurement. Are there anyone who have any opinion to fix this?

Note: My circuit behave as led driver which drives at 500 kHz and output current is nearly 210 mA. R14 and R13 set output currents, these two resistors have 100 mA voltage drop and we can set output current by changing these resistors.
At input stage I have EMC filter but there is still something I couldn't suppress.


texts: How does a time delay affect the Gain and Phase Margin?

texts:
How does a time delay affect the gain and phase margin. Answers using nyquist plots would be helpful

I know that a time delay of t corresponds to gain multiplying by 1 and phase subtracting omega*T . So as omega goes to infinity it will rotate around the origin  getting closer and closer.


texts: I have board with TP4056 which will be used to charge Li-ion battery. But I wanted to use battery as a back-up power. So it's possible to have power connected to TP4056 all the time? Or it can damage battery?


texts:
It's a power entry part of a DAQ card, the bottom right is a DC jack. The power flow maybe:

Power DC jack -> ferrite bead -> cap -> common mode inductor -> cap -> ?

I guess the bigger black one may be a common mode inductor too. But I've never saw such a bigger one in this kind of package, and it seems it's full shielded, can't see the coils from side.

May anyone give some clues?


texts: IC 7805 constantly giving 3V instead of 5V causing relay to fluctuate

texts:
I'm new to electronics. I'm working on a project on IOT.
I'm facing a issue right now.
I ordered a batch of 7805 voltage regulators.  I'm using one to power my ESP32 board that needs 5V. I've also used a 470 microfarad capacitor at the input and output of the IC.
I'm getting a constant 3V output instead of 5V. This is causing my 2 channel relay to fluctuate. If I connect just 1 channel it works fine. I tried various way of debugging but my meter always show 3V at the output.
Could it be a faulty batch of 7805 ICs, or is there something wrong with my meter?


texts: Conformal coating and micro SD card sockets

texts:
I have a embedded computer design which uses a low profile micro sd card socket as an extra option in addition to an on board solid state disk as storage/booting mediums. In manufacture the board is coated with conformal coating but i'm in a bit of a pickle regarding the SD card socket and the coating.

The SD card socket should be masked i assume before coating is applied, otherwise it may seep into the connector i suspect, but then i am creating a bit of a weakness against moisture. It seems this particular weakness is inherent to the SD card socket.

Has anyone found a good solution for this on a professional level, or are these two things simply incompatible (card sockets and coatings/materials). Have you operated exposed sd card sockets in moist environments with a long durability ?.

What i'm mostly afraid of is that if i have the pin connections protruding from the chassis coated, the coating will seep into the socket. Expecting workers to be careful while hand coating stuff like this is probably too much and asking for trouble later.


texts: How to calculate noise voltage after amplification?

texts:
I'm simulating the thermal noise experienced by some instrument, outputted as a voltage vs time plot. To calculate the "power" of this noise, I'm using:
P = 4kTB (k = Boltzmann's constant, T = temperature (Kelvins), and B = bandwidth (MHz))
And I then convert to voltage using:
V^2 / R = 4kTB (R = resistance (Ohms), of course)
I then produce a series of random values, distributed as a Gaussian around a mean given by this voltage, and an RMS given by:
sqrt(4kTBR)
Now I'd like to take into account an amplifier that is attached to the instrument. I know the amplifier provides 60dB of gain, and it has a Noise Figure of 5. How do I calculate the resulting change in power and/or voltage?


texts:
I am planning on running a new circuit from my current board to a new unit in the loft that I am turning into a mini studio.

I am trying to work out what Amp MCBs I would need, however am not sure I got the math right!

For the ones that I have an output and volts I did Output * Volts to give watts. However that seems loads over what I had for the other laptop that had 45 on the charger. Plus, I find it hard to believe the decks have a 690 draw without any box in the way, forgive my lack of knowledge here!

I am going to be doing this wiring then getting an electrician friend of mine to actually connect it to the main unit via the MCB but he is too busy to do the whole job, so I am doing what I can with the wiring and cables. I just need to know what to buy to make sure I can do it while being safe!

Laptop: MSI PX60
Decks: Pioneer SX2
PC: Corsair rm650x
Screen: SAMSUNG C24F396 x3
Speakers: Pioneer DM40 x2
Laptop: HP Probook

Now, I was originally going to run each plug off of it's own MCB, however looking at the draw I can calculate I think I could run it off of four?

Basically, are my calculations for the breaker sizes accurate?

If not, where did I go wrong and what do I need to find out?


texts: Can I DIY wire a 3.5mm 1-Female jack to 2-Females jacks?

texts: Not sure how to keep flow in a single direction. I know these cables exist and can be easily bought but I was just wondering how it was wired.


texts: Why have resistors in a circuit down-stepping 230VAC

texts:
I'm trying to build a unit which will convert mains voltage (230vac) to approx 80vac. I have a similar product which I know works for my propose - but it works in a way I don't quite understand. There is a resistor before the output/load and another one in parallel to it.

Here is a diagram of how it looks, with the switch and fuse removed. I've used a bulb to represent output/load. The transformer has a primary coil of 220V and two secondary coils of 24v.

Why has this been done? What advantage does it have over not having the resistors?

EDIT1: The two secondary coils are connected, presumably to make one large coil.

EDIT2: The circuit will be used to power an A4 sample of Smart Glass, which will need around 2W (defiantly no more than 5W). The circuit does have a switch, which I was surprised to find was placed in the 80V circuit. (ie after the transformer)


texts: how to assemble SI7021 I2C command sequence

texts:
I am using EFR32FG14 starter board.I want to read data from SI7021(Without any driver which does everything for me)
Stricktly by manual, The address of the device is 10000000 which is Hex 80.from the command table shown bellow.
I want to use Measure temperature so i think i should use E3(from mnual shown bellow).But i cant understand the meaning of hold mater mode
What is clock streching?
What is the full command i should send?
https://www.silabs.com/documents/public/data-sheets/Si7021-A20.pdf


texts:
I am trying to design a simple RF amplifier for a 1MHz AM signal (for low-power transmission). My modulator (JFET-based) outputs ~800mV peak-to-peak. My power supply is 9V, and I want near the largest possible amplification without distortion (class A operation) - my modulator outputs a reasonably-clean sine with next to 0 harmonic distortion, so I might avoid filtering.
This is what I came up with:

simulate this circuit – Schematic created using CircuitLab
Reasoning:
As I understand, voltage gain is Rc/Re which is 6.8 here. That should mean an output of Vout = 800mV*6.8 = 5.44V, reasonably big and there is still a big room for non-precise Q point setting. I picked those two resistor values based on what I have at hand.
I want to set the Q-point so the output is at 4-5V. That should be at 0.74-0.59 mA. To enable a more precise setting, the lower resistor (1.7k) is a 10k pot.
As I understand, the BC238 should be capable to this amplification at this frequency, the datasheet has a 85MHz transition frequency at 0.5mA, so it should still have a bandwidth of f' = f / 6.8 = 12.5 MHz.
I built up this circuit on a piece of copper board I cut lands into with miniature powertool with a diamond cutting bit. I used an old analog signal generator to provide the test signal, set it to ~800mV 1MHz (rather imprecise due to it's analog nature, sadly), and monitored the output with a scope. With a 100MHz 10x probe on the 1x setting I got ~700mV, and on the 10x I got ~300mV. I am not sure what is the real output voltage (700mV or 3V). (this is solved, see edit 3)
In any case, the resulting signal is smaller than the expected output. I understand that internal capacitances in the transistor start to attenuate the signal at higher frequencies, but this drastic effect was unexpected for me. I feel like I might have overlooked something simple.
PS:
I have already tried adding a small (6nF-1u, the later was an electrolyt cap) cap between ground and emitter. That kind-of fixed the gain problem (both on 1x and 10x probe settings) but distorted the signal highly, the output more resembled a sawtooth than a sine.
So questions:

what is / how to find my real output voltage?
how can I increase the maximum working frequency of this amplifier?
is there a simple but fatal design flaw in my circuit?

Edit 1
I measured output voltage at lower frequencies. This generator can only go down to .1MHz, so from there I collected 10 data points up to 1MHz. Measurements were rather inprecise (the voltage display on my scope changed rather quickly, possibly the generator also is not perfect), but should be accurate to +- 10mV. All measurements were done on the 10x setting.
| f  | mV  |
|----|-----|
| .1 | 500 |
| .2 | 500 |
| .3 | 490 |
| .4 | 460 |
| .5 | 450 |
| .6 | 410 |
| .7 | 380 |
| .8 | 370 |
| .9 | 350 |
| 1  | 310 |

(all those number were the measured voltages with a x10 probe, so the real ones should be those x10)
The downward going trend is still apparent from this dataset. At 100kHz, I measured a 4.2V signal with the 1x setting, which I still do not understand.
Edit2
Measured two more data points - f=10kHz I got 5.04V from 800mV input, and at f=1kHz I got 3V from 400mV input. Those numbers are all around what I have expected.
The measurement problem (difference with x1 and x10) might be because my probe loads the circuit differently, and I have a big (6.8k) output impedance, but I am not sure of that.
Edit3 - probing
I am pretty sure now that the measuring problem is due to the different loading on my circuit in the x1 vs x10 mode. I experimented with a 10k-10k voltage divider and a 10V signal (1MHz). With x10, I measure 500mV that equals 5V, which is around correct. With x1, I only get around 1.5V, so I should really only trust the x10 readings.
So the question remaining is that why is gain dropping so much in this circuit?


texts:
I am confused as to why current in series combination of resistors remains the same?I get that it is getting one path to flow but shouldnot the current decrease when it passes through resistor 1 since its offering opposition to flow of charges and ultimately less current(assuming that speed of charge flow has decreased because it has lost energy) reaching resistor 2 ?Even if the speed doesn't effect current directly ,the time would be less right?
I think if 10 charges per second were to pass through resistor 1 shouldn't the current change to 10 charges per 2 second (Since I assume charges will pass through no matter the resistance offered by resistor but will take longer time and thereby decreasing current?)when it leaves resistor 1?


texts: LTSpice: simulate transient voltage and current in RL-circuit

texts:
My goal is to calculate transient current and voltage in a following circuit:

Also, immediately after the switch is closed, initial current is 0 and then it exponentially increases until the value reaches the value defined by the steady state. Mesh analysis gives 5mA for the mesh which contains an inductor and 1.75 mA for the other mesh. LTSpice transient analysis confirms these values.
Next step is to define the voltage and the time constant. For the simple circuit (voltage source - resistance - inductance in series) the voltage (immediately after closing the switch) is equal to the source voltage. Since this is the complex circuit, the Thévenin equivalent must be found. Here is the resulting circuit:

Now the voltage across the inductor immediately after closing the switch is equal to 90 V. Time constant
tau = L/R = 0.36/18k (s).

However, LTSpice shows that the voltage across the inductor is something below 60 V:

What is wrong with my assumptions and calculations?


texts: easiest way to detect a switch change using an arduino

texts:
I have a pinball machine thats an old electro mechanical type.  I want to add LED's and do some fancy programming on an Arduino to animate the lights according to the score value of whatever target you hit playing the game.  I have the programming- the LED, and the PWM dimming circuity and control down.  I have never worked with input signals to Arduino or much circuit design at all.

The pinball machine has a relay that opens when it needs to move a score reel, e.g. the reel holding the "tens" position will accuate 5 times if you score 50... so that relay will pulse 5 times and open and close a circuit.  The circuit runs on 26 V AC.

Whats the dirt simple stupid way to simply track this as a state change (or edge detection).  I could not care less about the actual voltage, in fact if I could simply measure conductivity without worrying about input voltage etc I would.  I cannot modify the game but for adding a wire to each pole of that switch.  I cannot FRY the Arduino by putting 26 V AC (or for that matter DC) into it (grin).

Considering half waver smoothed rectifier but unsure about how to calculate reisitor and capacitor needed then unsure about voltage scaling, do it before or after rectifier?/?

Or... is there is truly simple method I don't know about (which would cover a very large area or knowledge).

If you can help me with suggestions and resources to help me figure out HOW to build a functional circuit that would be great.

Remember all I care about is state change, so if it ends up being an input voltage detection I could care less if it goes from 0 -> 5 V or 0 -> 2 V just so long as i can detect the switch above noise.

THANK you so much for your advice.


texts: I am starting to learn to use operational amplifier recently. I construct a simple circuit with an amplifier (http://www.ti.com/product/op07c) with is driven by 9V (on VCC and GND). I have the V+ and V- connected to a function generator providing a sinusoidal signal of 500mV and 100kHz (also tried 100Hz). I have the output (Vout) feedback to the V-. T Vout connect to the V- via an 200ohm resistor (as shown in the fig). But if I observe the output with scope, it is not really a sinusoidal wave (it more like the positive section of the sine is flat while the negative section of the sine is like sinusoidal. But if I connect the Vout to V+ with an 200ohm resistor, the output is pretty well sinusoidal but the amplitude is attenuated instead of magnified.


texts: What is the effect of pulsed discharge on watt hour (Wh) efficiency of lead-acid batteries?

texts:
When discharging a (lead-acid) battery you see a voltage increase (volts rise) as soon as the discharge is paused.

source: http://uu.diva-portal.org/smash/get/diva2:461718/FULLTEXT01

In the quest for optimizing watt hour [Wh] lead-acid battery charge/discharge cycle efficiency, an idea is to do pulsed/paused/interrupted discharging (at a slightly higher discharge rate then with a constant current discharge regime) and give the batteries some time to recover (voltage) in the pauses.

Is there any study or measurement report that has investigated the effects of pulsed discharge on the Wh-efficiency of (flooded) lead-acid batteries?


texts: How to reduce distortion in a TPA3110D2 amplifier?

texts: I bought these cheap amplifiers (2x15W TPA3110, the red ones with four caps and 4 inductors.) They sound good at normal volumes but then distort at high volumes.  When I increase the input voltage, it becomes a bit cleaner but still distorts at peak volume.  I am using 21V to power it, and I don't want to try anything more than that because the amplifier gets damaged easily.


texts: Need to create -5.5/+5.5 and 25.5VDC from 12VDC wall wart

texts:
I'm looking for a cost efficient way to create +/- 5.5v and 25.6v from a 12VDC wall wart supply. The product I'm working on will probably use a DC wall wart so I need a solution that will work with that.

I need these voltages to drive the GWTS80MNFG1E by Solomon goldentek display. The 5.5v is supplied for the display driver chip while the 25.6v is used to drive the backlight. There is also 3.3v and gnd to be connected but I already have those on the dev kit I'm using along with 12v and 5v.

According to the datasheet max current draw should be 80mA for the 5.5v supply and the backlight current should be around 75mA at 25.6v. Max current draw for the 3.3v supply is listed as 50mA.

Ideally I'd like to breadboard the solution so I can test the display before designing a board.

Thanks for helping!
B

EDIT: I decided on the TPS65132 by TI which I'll power using the 5V on my board. For the LED driver I'm going to try using FAN5333 (not sure yet if I will be able to drive the 3 strings of 8 LEDs each with each string wired in parallel to the other one...)


texts: Driving servos using microcontroller and current limiting

texts:
I am new to electronics and would like to design a PCB that uses an Atmel microcontroller, and powers three servos. I was thinking of designing the PCB with a single power supply.

The servos I have can draw up to 500mA of current each, when fully loaded. If I use a 5V 1.5A supply (VCC), and connect the servos and the microcontroller in parallel to VCC I understand all sources will get 5 volts. But will they each only draw the current they need?

The Atmel microcontroller datasheet says it should only take a max of 200mA, so would I need to place a current limiting resistor? Or do I need to create a current divider circuit to fix the current flows to each unit? But the motor current draws can change depending on the load and it seems like it might be wasteful (?) to have resistors burning power if its not always necessary.


texts: TO-3 Transistor replacement needed that does not protrude through the chassis

texts:
I have a linear power supply that uses two 2N3771G. They are TO-3 style, and are exposed outside the chassis, on the heatsink.

I need to move this power supply into a new chassis, for commercial reasons.

I'm hoping to find a replacement transistor that can mount inside the new chassis, but not stick out through it. The new chassis will have heatsinks exposed on the outside.

Here are the specs of the 2N3771G:

\$V_{CEO}\$ = 40V max
\$I_C\$ = 30A max
\$h_{FE}\$ = 15 min
\$h_{FE}\$ = 60 max

How can I find a substitute?


texts:
How would I produce a pulse like this image? This is to power and actuate a solenoid valve.

I'm using a 3D printer Arduino board to do this.
This is what I have so far. The if code_seen() passes a number to the main function to change the usecs of the pulse.

inline void gcode_M530() {
  pinMode(VALVE_1_PIN, OUTPUT);
  uint16_t pulse_usec = 200; //default to 200 usecs
  if (code_seen('S')){
    pulse_usec = code_value_int();
  }
  WRITE(FAN_1_PIN, HIGH);
  delayMicroseconds(pulse_usec);
  WRITE(FAN_1_PIN, LOW);
}

http://www.theleeco.com/electro-fluidic-systems/solenoid-valves/vhs/standard-port-inlet_small-port-outlet-psp.cfm


texts: In a multicore cable, what is the nylon "string"?

texts:
I am using 4 core shielded cable. However, there is a strand of what I assume is nylon running parallel to the conductors. A bit like this

(source)

What is it for?


texts: Why erasing my PIC with PICKit2v2 doesn't work?

texts:
Below you can see the output of PICKit2V2 after clicking the Erase button:

As you can see above, all the memory addresses (I scrolled also) are equal to 3FFF.

Now when I click on the Read button, this is the output:

Scrolling:

As you can see above, the erasing didn't work fine. Does this mean my PIC is dead or something?


texts:
Based on external sensor inputs, I want to vertically pulldown & release (in a controlled manner) a 7mm neodymium magnet enclosed inside a circular elastic diaphragm. I want to keep the size as minimal as possible (around 20 mm in diameter). For this, I want to make a PCB coil electro magnet. The elastic diaphragm would be placed about 7mm to 10mm  above this PCB coil.  I want to power this preferably with 3.5V or 5V.

Can you please tell if this would work ? and also can you please suggest how to design a circuit to drive the PCB electro magnet ? Any pointers would be very helpful.

Hope the above description makes sense.


texts:
As per title, I'm trying to send a simple 'READ' (0x03) command to the device and get the contents of the CANCTRL register (0x0F). I even moved past our project board and bought Microchip's development board for the MCP25625 to rule out any weird HW design issue. In both cases I've measured the CLKOUT pin using my oscilloscope and it's correctly reading 2.5MHz (20MHz crystal / 8 default prescaler). So assuming the chip is getting the correct clock signal in and should be started correctly.

The only odd thing about both my setups is that I'm powering VDD from 3V3 and Vdda from 5V.

SPI MISO is pulled high using a 10K resistor to 3V3. SPI is running in mode 0,0 with data valid on the clock's leading edge, as per the picture attached. I tried everything so far:
1. Disconnected the MISO line from the MCU. Tried both pulling it up and leaving it floating. Same result (0xFF when it's pulled up, 0x00 when it's left floating).
2. Tried all SPI modes.

I'm genuinely out of ideas, the SPI data looks correct, but the chip isn't replying at all.

LE: Have discovered that, as soon as SPI is enabled and configured on the processor (Kinetis MKW41Z), the high voltage of all SPI lines controlled by the peripheral drops to 1.9V. I'm using 10K 3V3 pull-ups on all SPI lines. Currently trying to figure out why that would happen.


texts: Determining an aproximate position through triangulation

texts:
Disclaimer: I'm relatively new to electronics (although not to programming) so please excuse my ignorance.

First of all I should state that I'm aware there are already multiple, well answered posts about this topic. This question is about how to build the devices themselves.

I have an outdoor area 100m*50m in size. The biggest obstacle is this area is a structure that can be described as a 10m*10m*6m cube; and there are also several trees, bushes, (wire) fences and low (0.5m) walls. I want to determine the 2D position of a device within this area with relatively good accuracy (a 0.5m approximation would be ideal). It can take up to several seconds (it's not going to be in a loop), but it has to work at any time of the day.

Therefore, I think my best chance is to use RF to triangulate the position of the device by having several beacons broadcast a key (which the device would answer to, therefore enabling the beacons to calculate the distance by measuring the time taken). If you have a better idea on how to achieve my goal, please post it.

Since I've never worked with RF before, I don't know how to build the devices. My budget is limited and the device must be as small as possible. I have at my disposal Arduinos, ATtiny's and a Raspberry Pi.

What approach should I take to build the devices? Adapted consumer modules? Custom electronics? Some Arduino shield bought of element14?

Thanks in advance.

Summary:

The system will operate in an outdoor area (100m*50m) with some obstacles.
The system has to be relatively cheap to build, because my budget is limited.
The device being tracked has to be as small as possible (smaller than a PC mouse, for comparison).
The system doesn't have to be too accurate (0.5m accuracy would be ideal).
The system doesn't have to be too fast (The process can take up to several seconds).
The system can use as many beacons as necessary, and it only has to determine the 2D position of the device being tracked (no height).


texts: Higher order effects of CTAT and PTAT when testing a BANDGAP

texts:
I want to use candence to simulate the real behavior of a voltage reference and so far I found circuits that are based on the ideal models.

What non linearities can I introduce in this ideal model of testing a part of the bandgap circuit?
On the pins vD and v2I have to connect an opamp.

Proposed solutions are resistors or transistors in stead of the ideal current mirror. Is this a good approach?

Thanks!


texts: How to evaluate equivalent 'samples per second' from Time base value?

texts:
The following is from Tek DSO manual about the Time base and sample rates.

When i turn the knob further, i am able to read values like M 100ms or M 250ms.
What woud these evaluate to in terms of 'Samples/second'?

I am looking for how this computation from scaling parameter to Samp/s is done.

Thanks


texts: I have questions about building a current sensing op-amp circuit

texts:
I want to build this circuit I found at eetimes.com:

The idea is to use this circuit as a current sensor which outputs a voltage Vo which I can read and process using a tool like NI myDAQ.

I've come up with a few questions as I began simulating the circuit in software:

How do I model the system load as a resistance? For example, if \$V_{bus}\$ is a battery for a car and everything that the battery powers is the load, how do I determine the equivalent resistance of all the car's electrical systems? Also, if the car only exists on paper, how would I calculate an equivalent resistance that way? very large system that you couldn't reasonably calculate its equivalent resistance. How would I go about determining the equivalent resistance? What if the system does not actually exist--what analytic methods could I use to determine equivalent resistance?
How do I decide what resistance values to choose for Rf and Rg? Do I want to choose them such that the value of Vo is equal to the value of \$I_{load}\$ or can I choose any arbitrary values for \$R_f\$ and \$R_g\$?
How small can I make \$R_{shunt}\$? Preferably, I'd like to make it as small as possible so that I lose as little power as possible from it as possible.
Can I use the same source Vbus to power both the system load and the op-amp (\$V_{OA}\$)?


texts:
I'm just wondering how to access more than 32Kb on a TERASIC DE0 nano. It is based on an Altera Cyclone IV FPGA.   https://www.ti.com/lit/ug/tidu737/tidu737.pdf

It has 32Mb DRAM but there are

12 address lines
2 bank select lines
16 data lines

This gives a total of 32Kb.  There is a program that is provided called NIOS II which seems to be able to access the memory but there aren't any details about how it works.

So the question is how is the rest of the memory accessed?


texts: Why are there so many connections to ground in some computer connectors?

texts:
I was surprised by the number of connections to ground some pc-related connections have. For example, the parallel port has 8:

Also, the ATX power supply connector has 9 ground connections:

Is there any reason for such a large number of ground connections?


texts:
I would like to monitor the ON and OFF time of my refrigerator and push this data to the server via an ESP8266.
Below are my thoughts on how to detect the state of the refrigerator:
Use a voltage sensor to detect 230VAC
Use an optoisolator
Use of a current sensor

Please, kindly advice which would be the best solution and if there exists another.
Thanks


texts:
One of the questions in my book goes like this...
'A shunt generator delivers 450 Amps at 230 volts...'. The resistance of the shunt field, armature and brush contacts are given.
I get that the 450 Amps is the current passing through the load. But how can the voltage(230 volts) be constant? Though we can make the current in a dc generator nearly constant and unidirectional, but the value of the voltage always remains alternating, isn't it?


texts: Integrated battery charger for simulation in proteus 8

texts:
I am looking for a library that has an integrated that has the battery charger functionality (MCP73831, MCP73833) to simulate it in proteus 8.
Supposedly there is a library for proteus of this integrated, but I have not found it to download, does anyone know where I could find it?

It doesn't necessarily have to be that integrated, do you know any other battery charger that I could use to simulate?


texts: Unexpected behaviour of implication operator in SVA

texts:
There is an issue I face while using an implication operator in one of my code examples. This code can be found at  https://www.edaplayground.com/x/4fVz

Code Summary

In my code, I have defined states corresponding to each count of a counter.
I have defined a sequence s2_7 which is a sequence starting at (count == 2) and ending at (count == 7).

sequence s2_7;
(state == 2) ##1 (state == 3) ##1 (state == 4) ##1 (state == 5) ##1 (state == 6) ##1 ((state == 7));
endsequence

I have defined a property directive with label 'test_3:' which asserts the sequence s2_7.

  test_3: assert property ( @(posedge clk)   (state==STATE2) |=>s2_7)
    $display("%0.0t, Property s2_7 is asserted.",$time());

My code prints below the line when the antecedent of the property is true.

  35, Start property sequence s2_7 , state = STATE3

My code prints below the line when the sequence s2_7 has started.

  45, Starting sequence s2_7 , state = STATE4

Below is the output from my code.

              0, state = STATE1
              25, state = STATE2
              35, Start property sequence s2_7 , state = STATE3
              35, state = STATE3
              45, Starting sequence s2_7 , state = STATE4
              45, state = STATE4
              55, state = STATE5
              65, state = STATE6

Issue

I have trouble understanding below the line of the output.

  45, Starting sequence s2_7 , state = STATE4

Can someone explain this.


texts: How to calculate the torque constant for a BLDC motor

texts: I am designing a 12lb hobby robot with a 1000Kv BLDC motor at 14.8V nominal voltage and stall torque of 30A. How do I solve for the torque constant. I have seen equations where Kt(torque constant) = 1/Kv. And also equations where Kt = 30/pi(Kv). Which is the most accurate equation? Thank you,


texts: Why are load resistor values in common-emitter amplifiers so large?

texts:
So I have seen a few circuits for common-emitter amplifiers, like this one here.

I get the function of most of the components and thir placements, but my question is, why is the load resistor at 1.2kohms? For example, I have a speaker that home that is rated on the back "8 ohms 10 watts". From that, I calculated that the speaker uses 10 volts and 1.25 amps. The 1.2kohm load resistor would only allow 0.01A through, so what am I doing wrong here? Do speakers not need that much amperage?

I do understand that the load resistor and the emitter resistor need to be large to create gain, but I don't understand how it can transmit enough power to use a large speaker.

Thanks in advance!


texts: I have this circuit and want to calculate the voltage at v2 when t>0. v1 has a 6 volt step at t=0. I tried to do nodal analysis and came to 2 equations for the 2 unknown nodes, but did not know what to do from there. In order to solve this could I simply use v+(v0-v)*e^(-t/RC), with R being the two resistors in series?


texts: Equations for voltage/current through a transistor

texts:
Given the following circuit:

I can figure out the current through the 'bottom wire' by doing:

V = IR
9 = I * (2690 + 1000)
9 = I * 3690
I = 9 / 3690
I = 0.002439 or 2.44mA

How would I find the current going through the top wire that goes through the transistor and diode?

Also, is there an equation that shows whether the transistor is 'on' or 'off'?

Transistor values:

LED values:


texts: How to drive 4000 LEDs using as few pins as possible?

texts:
I need to be able to control ~4000 LEDs with as few digital IO pins as possible. I can't really explain why as the project I'm  working on is confidential, but the plan is for this project to be driven by an arduino, or similar, microcomputer.

So far, the most efficient method that I've been able to find is charlieplexing which offers n^2-n number of controllable outputs for n pins. Even this doesn't look as though it's going to be feasible for this number of LEDs.

Is there an even more efficient method and, if not, would anyone have any suggestions of how I could proceed?

Unfortunately, I don't believe that utilising multiple "slave" controllers to add more IO ports will be possible due to the size constraints (it will have to be not much bigger than a large mechanical keyboard).

Some additional information asked for in the comments:

LED Power: I haven't determined the exact make of LED that I'll be using yet, but they'll be 1mm LEDs so shouldn't require much power at all.
Refresh rate < 1Hz would be sufficient.
Only On/Off LED control is necessary although being able to control the radiance of the entire array uniformly would be useful (with every LED being the same brightness).


texts: replacing diode array with discrete components

texts: I have a little proyect where I will be using a SIM908 GSM module. in the SIM908 Hardware Guide it states that a diode array should be used to protect the SIM lines, recomending an ESDA6V1W5 (datasheet) or SMF05C (datasheet). the problem is those have a very small SMD footprint; I will probably try to use one of them on the final board, but was thinking if I could replace it with discrete PTH diodes for the prototype? and if so, what kind of diodes should i look for?


texts: What happens when a computer is plugged into another computer by USB?

texts:
I am just curious about what happens when you have a USB 2.0 cable with two male ports, and plug both the ends in two different computers (not for data transfer reason, or any other reason, just curious)?
I have read this similar question on quora, where a writer says:

Answer

My actual concern
I purchased one 4 port USB hub and one input cable for the USB hub. I want to power my HDD + USB keyboard + mouse, and charge a phone from the USB hub.

I successfully plugged that into my laptop with the power bank, and nothing happened.
But when I write data to the HDD, the power drawn by the HDD from the power bank is significant, despite connected to the laptop as well:

So I have to keep the power bank plugged in, and maybe replace the power bank with a 5v 3 AMP phone charger. My concern is can it damage my laptop (and / or laptop's USB port) in a long run?


texts: Lithium-ion battery Internal resistance myth

texts:
I am making a battery tester, for lithium ion batteries in particular.
I want to measure the internal resistance, but after testing few cells, I am skeptical of my results. Most of them, new or old are around 500-800 mOhm, totally not close to 150 mOhm range as it should be.
The photo: For this instance, the open voltage is 4.18V and load voltage is 3.41V with 1525 mA discharging current; 4.18V-3.41V/1.525A= 0.504 ohm;
Is this the correct way to measure internal resistance? Since new and old cells all have similar result, is it safe to say that internal resistance is irrelevant to the health of a li-ion cell?


texts: The project I'm working on involves streaming video from an image sensor to an LCD, preferably as cheaply as possible. My question is: can I get an image processor/sensor SOC (a la https://www.aptina.com/products/soc/mt9v117d00stc/) and stream that data directly to an LCD, then only using the MCU to initialize those two components? Or do I need the MCU to act as a buffer between the two and feed the data from the image processor to the LCD? Unfortunately I don't have access to the datasheet for the image SOC just yet, so I understand if it's hard to say for those specific systems. But the general question still remains: do I need an intermediate MCU for video streaming between an image processor and an LCD for anything other than initializing communication?


texts: How does the basic RS Flip-Flop (also known as latch) works?

texts:
Ok this is a basic question but i am not able to figure out how does this work

1: This is the representation of the RS Flip-Flop with the truth table given in my
book

I am not able to connect the truth table to the representation as inn my knowledge every time the answer should be same, which i know that i am wrong so please help me.

2: what does Disallowed and no change stands for.

Thanks

Akash


texts: How is the switch current related to output current in a DC-DC converter?

texts:
I have designed and implemented a DC-DC converter with the following specs:

Input Voltage: 5V
Input Current (max): 3A
Output Voltage: 12V
Output Current (max): 1A
DC-DC Controller: MC34063
Inductor: 15uH/5A max
Schottkey diode, 550mV Vf 1A max
50KHz switching frequency

I have tied the Drive and Switch collector to form a darlington pair. The device outputs 12V, but the controller gets very hot (way beyond spec of 70C) even at 0.5A at the output.

The device says it has a maximum switch current of 1.5A, and I've incorrectly thought this is the maximum output current rating.

How do I figure out what the maximum output current will be, if I'm specified the maximum switching current?


texts:
simulate this circuit – Schematic created using CircuitLab

simulate this circuit

I would like to better understand the meaning of voltage source placement. To me, these two subcircuits seem the same, but I am not sure. Are they the same?


texts:
I'm a beginner in electronics repairing and I need help troubleshooting a tv which doesn't turt on, neither the power LED lights up.

The board is a cheap chinese (check the attached image). When I opened it and started troubleshooting I found out that the H. O. T was shorted, and the fuse was blown. I made some checking on a few other components and I couldn't find any other fault. So I replaced the defective components (fuse and h.o.t).

Then I powered it up through a 60W series bulb but it didn't turn on, so I measured some voltages, the readings are as follows:
Mains Filter - 315V, H.O.T Vce - 315V, R531 was open, I replaced it. I traced the voltage from R520 and it's dead (0) after R522 (check the attached image). And THERE'S NO VOLTAGE ON THE SECONDARY SIDE. Can someone help me by explaining what's going on AND/OR what to do?


texts: Minimum AND gates for 4 input-2 output functions

texts:
It seems that Karnaugh maps and Quine–McCluskey algorithm are used to minimize the general number of gates to represent some truth table (boolean function) with $n$ inputs (usually small $n$) and one output.

My problem is different from the problems the above techniques solve in two aspects:

Need to consider 2-output-bit rather than 1
Can use AND, NOT, XOR and need to minimize number of AND where the number of XOR and NOT gates do not matter.

The functions I'm working on have 4 input bits.
My question is whether there is a way to determine the minimum number of AND gates for realizing certain function.


texts: How does a washing machine intake solenoid valve control flow rate?

texts:
Our washing machine, an AEG L69480VFL ( seen here )  has a pair of solenoid valves on its water intake looking like this:

(One controls the flow to a tube running to a detergent compartment, the other to a conditioner compartment.)
Running the machine with the top off it's possible to observe the resulting flow through some clear plastic channels above the detergent/conditioner compartments.  And I was surprised to see that rather than just a straight on/off flow control by each valve, at certain parts of the washing cycle the flow seems to be deliberately more restricted and less "gushing"; apparently with the cleverly designed purpose of causing the flow to take a slightly different path bypassing those compartments.
Given that the valves seem to be controlled by AC mains voltages (it says 230V 50/60Hz on them in the above image) and that there's just a couple of wires to each, running from a controller unit... how would the different flow rates actually be selected?  It's obviously not controlled by polarity if it's AC.  Would it use a reduced voltage, or something more like PCM?
Exit side view from here


texts:
I am designing a board, which will have several SMA connectors.

I am mainly concerned about the minimum distance between SMA connectors on the board, since we need also account for the size of the mounting tool that we need to use in order to mount the cable on the connector. Is there any general recommended min distance?


texts:
I bought 4 12V Tech-12706 Peltier Kits
Room Temperature Average 30' C
How many Kits I have to install to cool a Insulated ACP Sheet Box Area of 3 Cubic Feet / 90 Litre ?
I tried Calculator but could not understand
To support which Voltage=Ampere Power Adapter I have to use ?
Temperature required inside is 15-20' C