texts: The Differential I2C Bus Extender is only working for 1 channel

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Currently I'm working on a project where I want to use multiple scales in a fridge. When something will be taking out of the fridge the scale detects the different weight and send an event to my server. I'm really a noob to I2C and at this moment I can't figure out why it's not working...
I'm using a Raspberry Pi 4 Modal B with a pHat attached to the GPIO pins. From there I use a Qwiic cable to connect the bus to a PCA9615. Then I use a 2m S/FTP cable to connect the other PCA9615. Then the signal goes to a TCA9548A to use the bus with 8 different channels. I need the 8 channels because the I2C address of the NAU7802 is 0x2A and is hardware defined. A multiplexer/Mux is required to communicate to multiple NAU7802 sensors on a single bus.
Now the problem that I'm facing is that everything is working correctly when I don't use the I2C Bus Extender. I see all of my channels and I can change the channel to retrieve the weight of the multiple scales. But when I connect the I2C Bus Extender there is only 1 channel working and the other channels are not available. Is there any solution how to fix this problem?
Products that I use:

SparkFun Qwiic pHAT v2.0 for Raspberry Pi
SparkFun QwiicBus - EndPoint
SparkFun Qwiic Mux Breakout - 8 Channel (TCA9548A)
SparkFun Qwiic Scale - NAU7802

Schematic
The red lines are indicating that the connection is not working. I only see 1 NAU7802 when I use the i2cdetect command. Now when I disconnect the red lines but connect the green line, everything is working correctly. But that's unfortunately not what I want to achieve.


texts: What is the relation between FFT length and frequency resolution?

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If I have sampled a signal using proper sampling methods (Nyquist, filtering, etc) how do I relate the length of my FFT to the resulting frequency resolution I can obtain?

Like if I have a 2,000 Hz and 1,999 Hz sine wave, how would I determine the length of FFT needed to accurately tell the difference between those two waves?


texts: Voltage induced in aircraft high-tension magneto ignition system

texts: Why is there no voltage induced into the secondary winding (in high-voltage step-up transformer) when the ignition switch is closed (OFF)? When the current flows in the primary winding of the coil a magnetic field is generated. This interacts with the flux from the magnet. Assuming that the ignition switch (stop switch) is closed, the flow of alternating current created by the interaction of the two magnetic fields will flow to ground. Will the flow of alternating current in the primary (while the ignition switch is closed, OFF position) induce a current in the secondary? If it does not, why not?


texts:
I am working with a robot that uses USB (not by choice lol) in a very static-prone environment, and I'm having problems with ESD locking up my USB hub. I found an "Industrial" USB hub that claims it can withstand a 15kV shock through air and an 8kV direct contact shock. I'm wondering what the effectiveness of that would be as compared to using USB Surge Protectors inline between a standard USB hub and the slave/master devices? What about using both at the same time? Would that actually help at all, or just introduce weird problems due to capacitance and whatnot?

Edit: I should mention that non-COTS PnP solutions are not an option unfortunately (for example I can't solder a special ESD protection chip to the data lines)


texts:
Is it possible to use IGBT to replace a relay? Previous I used EV-200 (1A relay) to switch DC 600V 500A like the picture below.
Now I want to use IGBT to replace, but I have no idea about how it be just switch for single stage voltage.
I'm gonna use FF400R07KE4 IGBT module.
Thanks for any advice and suggest first!


texts: Unexpected Highly Asymmetric Slew Rate on Op-Amp

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I recently set up a circuit with an ADA4870 op-amp for driving an ultrasonic Piezo element. I chose this specific op-amp because it was advertised as having a slew rate of up to 2500 V/us (symmetric on rise and fall) on a 10-40V power supply. To test it I set it up with +30V for positive power, GND for negative power, and two 2.4k resistors from out to V- and V- to GND (for a 2x gain with feedback). I then fed in an Arduino digital signal set to be high for 5us and then low for 10us. The measured input waveform is a sharp step function, but the output from the op-amp looks like this:

The rise is very sharp as expected, but the fall is extremely slow at roughly 1 V/us. Normally a slow rise/fall time would make me suspect parasitic capacitance somewhere, but I can't see why that would slow down the fall time but not the rise. Does anybody have an idea of why this might be showing up?


texts: What is the name of the electrical latch with one toggle input?

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For example pressing a momentary push button to toggle an led off and on through a Flip-Flop.
I’ve only seen the ones where there are two buttons and you press both to switch the states.
However I know one exists where you only have to push one momentary button to alternate between the states of the Flip-Flip.
Edited thread to be more contextual as suggested by @Jack Soldano, Thank you all!


texts: Balanced Charging of ZOP 2s lithium ion battery

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Good day everyone,

I recently purchased a “ZOP Power 7.4V 2200mAh 2S 35C Lipo Battery T Plug” for a project. I have designed a circuit to charge the battery, but now I am wondering if it is necessary to ensure the batteries are balanced when charging. I am using an 18V, 10W solar panel to charge my battery through a buck converter which controls the charging modes (CC/CV), the battery is connected to an RC car to extend running time. Through research, there are websites and forums with completely conflicting views, some say it is very important to balance charge batteries in a pack, whereas others state since there are only 2 cells present balanced charging can be ignored and the battery can be charged normally in series.

There doesnt seem to much information on these batteries, but this website contains some basic information on it:
https://www.banggood.com/ZOP-Power-7_4V-2200mAh-2S-35C-Lipo-Battery-T-Plug-p-992114.html?cur_warehouse=CN#jsReviewsWrap

I look forward to hearing peoples advice and opinions!


texts: How can computer replace PLC in industrial machines?

texts: I am having internship in a semiconductor manufacturing company and learning about machines in front-end section. Technicians say that the machines all use computers as they process multiple complex tasks such as image processing in stead of PLC. From what I have known, PLC is designed to be easily installed and operated in industrial environment. Is it possible for computers to fully replace PLCs?


texts: How do you convince people to use Arduino

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So I have this friend with a problem...I swear...it's not me! I like Arduino. I wasn't sold on the concept at first but I'm firmly in the "it's awesome" camp.

Anyway, what I'm really looking for is a pitch to some (tech) friends about the benefits of Arduino over going out and rolling a different solution from scratch (or ordering a eval kit from a uC vendor). I'm also trying to convince a school that Arduino is a great way to teach kids programming over other starter kits and such. They also want to do some robotics eventually, so I figured I could sell them on that.

I have some ideas on what to tell them, but I really want to hear what others have to say. And before anyone says it, I understand the best way would be to show them. But some things need to be explained before that and that's what I hope to hear from everyone. Thanks!


texts: I am not familiar with using fuses and working with such high amperage. Can someone help to see if my diagram is Ok especially where the fuses are placed and the amperage of the fuses used? Feel free to ask me any questions about the devices used. Thanks.


texts:
I have been trying to program my STM32L476RG micro-controller based breakout board using ST-LINK v2 as the programmer. I have hooked every VDD of breakout board to 3.3 V pin of programmer and connected VSS of breakout board to ground.

Also, I've connected SWCLK and SWDIO respectively. But every time I try to connect it in ST-LINK Utility it is initially giving me "Can not connect to target ST-LINK. After I reset it is giving "USB Communication Error" and same error thereafter.

I have tried using solutions presented in Patrick Hood-Daniel tutorial and also pulling up the BOOT0 pin but neither seem to work.

Any suggestions on this problem will be of much help.


texts: Solve differential equation for R-L circuit

texts:
Given that Ri+Ldi/dt=Vsin(wt).
The answer given here is
i= (V/Z)[sin(wt- Φ) + ke^(-t/τ)].
I could not solve this equation further.


texts: How can a three-phase motor have 20 Nm of torque at 1432 RPM and 1.8 kW?

texts:
I am trying to work out the maximum torque a motor puts out to do some stress analysis on a structure, and I have just been given the motor details from the manufacturer. They said it produces 20 Nm of torque, rotates at 1432 RPM and has a power output of 1.8 kW. I didn't pick up on this at first but later found some errors in my calcs, which pointed back to the motor specs not being in line with each other. From a mechanical standpoint, I've always gone with the Power[W] = Torque[Nm] X Angular Velocity[rad/s] to do any rotational calcs. In this case, if the power output and speed are correct, the torque would be 12 Nm not 20 Nm.

The manufacturer has come back and told me he confirmed the original figures he provided me and they are correct. I was wondering if anyone can tell me how this would work?


texts: Not getting an ac current output through my speaker in my amplifier circuit

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Will the dc current output affect the speaker, and prevent it from functioning properly? I have already tried different capacitors also change the input voltages and frequencies.

I would really appropriate any help with this problem.


texts:
SMA tee connector is something like this:

What does it do? Is it something like a power divider?


texts: How Backlit LCD Moniter Works, How it Looks Without a Backlight

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I'm thinking about repurposing an lcd backlit monitor's front panel as an 'overlay' type panel over something else without a backlight.
My understanding of the function of a backlit monitor that the front panel on an LCD monitor filters the backlight as specified by the input values telling what pixels to let light through on.

what I am wondering is this: if I were to remove the filtering panel and put in the image input for the inverse of a black circle as shown below, would the panel perform as a more-or-less transparent window with the circle portion visible?

Feel free to correct anything I misunderstand about the general ideas expressed above, I'm very new to the topic.


texts: P Channel MOSFET to do automatic switch between battery and power source

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I need an application to switch between power source and battery. When the power source is absent, then battery will act as the power source for the load.

I try out with the P Channel MOSFET to do the power switching.

The MOSFET I am using is as follow.
MOSFET datasheet link

simulate this circuit – Schematic created using CircuitLab

This circuit works where the MOSFET Turn off when V1 is on but when the V1 is switched off, then MOSFET is turned on. So RLoad will get the voltage source from battery when V1 is off.

However, i tried to measure the current flow from BAT1 to the circuit when the MOSFET is off and there is some current flow as well according to the RLoad.

As the RLoad higher then the current from the battery is going higher as well even the MOSFET also turn off.

I thought on the MOSFET turned off, then it would have no current flow through but there is still some current flow it from the battery source.

Is there anyway to prevent the battery current flow as this could reduce the battery voltage ?


texts: Do I need to use a resistor with a microswitch to limit current for an Arduino Uno?

texts:
I'm using an Arduino Uno to control a small robot and I'm starting to add micro-switches as bump-sensors. I know that when I'm creating a circuit with LEDs I need to use resistors to limit the current so I don't mess up the Arduino, but do I need to do the same with the micro-switches? If so, how do I calculate the necessary resistance?

If it makes a difference, my micro-switch is Pololu #1405, Snap-Action Switch with 15.6mm Bump Lever 3-pin, SPDT, 5A. The Arduino outputs 5V and has a maximum of 40mA.

EDIT: I've done some more research and I found a page that seems to describe exactly what I want to do (http://arduino.cc/en/tutorial/button), don't know how I missed it before. So if I'm understanding the situation correctly, the only resistor I need is the pull-up/down one between the switch and ground, but none between the switch and the pin that's reading the switch.


texts: Understanding electrical characteristics of comparators: input offset voltage and open collector output

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I have two questions regarding the electrical characteristics of comparators:

Is there a way to adjust the input offset voltage of a comparator to
fit a custom application?
Which comparator output type is the ideal choice for powering an LED circuit?

I am designing a circuit that will detect a failed LED (open or short circuit) by comparing two voltages and triggering a second LED, indicating a failure if the voltages ever differ. I am having trouble sourcing a comparator chip that will allow the correct amount of  voltage fluctuation at it's inputs. For example, if the voltage fluctuates by 100mV this should not trigger the second LED but, most comparators have a very small input offset voltage. I am curious if there is a way to externally adjust the input offset voltage of the comparator to fit my needs.

Additionally, I'm having trouble understanding the best comparator output option for powering an LED. I believe the term "Output Short Circuit Current" is used to describe the amount of current that the chip is able to provide at it's output. Is there a specific output type that is preferred when powering something like an LED?

Please consider the following circuit:

I plan on using a voltage reference (REF2933) rated at 3.3V as one input and the voltage across the LED as the second input. The TLV1701 will compare these two voltages and remain low until the voltage across the LED falls outside of a given range. If the voltage reference has a 2% accuracy (3.234 - 3.366V) and the voltage across the LED varies from 3.0 to 3.4V then it is possible for the comparator inputs to be 0.366V apart. I understand that the input offset voltage is used to determine when the comparator switches from high to low or low to high but, is there a way to change this value to allow more room for error?


texts: Help converting analog potentiometer to digital

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I have a 3 dial motor control assembly that is using 3 potentiometers to control 3 independent 110v motors speed.

The label on the pots read TO50K 1339 (first O has a "S" like shape inside). I have not been able to find any spec sheet on this specific pot but in readings with a multimeter I can the following data.

~50V depending on pot position
0.05A
~30K Ohms (at max, of course ranges based on pot position)
2.5 Watt (based on V*I)

So with all this in mind. Would it be possible to replace the analog pots with digital ICs? I have been trying to match the data with an IC but cannot find anything with the correct voltage or wattage that seems to be required. End of the day, I would want to control the 3 dials with an Arduino board so I can monitor and change motor speed over the internet.

So if anyone has a moment and can help map out a circuit for a single or for 3 pots I would really appreciate the help.

Thank you!


texts: How to control the driving frequency when working with high power ultrasonic transducers

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I would like to know the simplest solution to dynamically tune the driving frequency of an ultrasonic transducer to its resonance frequency.

My amplifier has a power meter that I can read an optimize via LabView but I would like to know if I can do the same using a multimeter and a controller that changes the frequency of the function generator. Can this idea be applied using a multimeter and a controller?

I have the following setup and in this question there is more information about the problem:


texts: How propagation delay of synchronous counter is less than asynchronous counter?

texts:
My question is very basic one, but thought of asking here to clarify.
In asynchronous counter the output of Flip Flop is given as input to other Flip Flop as clock, where as in synchronous counter the output of Flip Flop is given as direct input to other Flip Flop. So in both cases the next Flip Flop has to wait until previous output of Flip Flop is available.
Can someone explain how synchronous counter has less propagation delay than asynchronous?


texts: Improve the performance of Buck Converter Loop Stability

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The following are the specifications of my Buck Converter.

Input Voltage Range : 6V to 16V

Output Voltage : 5V

Switching Freq : 2.1MHz

Output Inductor : 22uH

Minimum Load Current : 200mA

Typical Load Current : 500mA

Maximum Load Current : 1A

I have output capacitors of 2 qty of 10uF (25V 1206 package) and one Feedforward capacitor of 10pF (0603 package).

Added feedforward capacitor to improve the loop stability performance based on the recommendations given by this AppNote

I'm using Omicron Bode 100 to perform and view the loop stability analysis.

Since my switching frequency is 2.1MHz, My crossover frequency should be atleast 1/10 or 1/20 of my switching frequency. Which happens to be around 105kHz. But from testing, I am observing the gain crossover frequency of less than 105kHz at the mentioned voltage ranges and minimum to maximum load currents.

Could you please provide the reasons why this is happening and provide me a solution to improve the crossover frequency to meet the criteria.


texts: Identifying components in a headphone amplifier circuit

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As part of furthering my understanding of opamps and audio electronics, I put this headphone amplifier together on a breadboard. Only one channel shown:

The circuit works like a charm, and is based on a number of schematics I scrounged on the web (swapping alternative parts in and out with whatever I had in my junk drawer).

I'd like some help to identify the purpose of some of the passive components, how their values are chosen and why they're necessary. The parts I understand (although correct me if I'm wrong!):

The 10uF (C2) and 22nF (C3) capacitors are the IC power decoupling (bypass) capacitors. The 10uF provides a small measure of voltage smoothing in case of voltage dips, while the 22nF filters out high frequency noise.
The 4Kohm and 1Kohm (R1 & R2) resistors form the negative feedback network, and set the gain of the amplifier - in this case, 5 [(4/1)+1].
The 22Kohm (R6) resistor on the audio input is a pull-down resistor, there to give an open circuit a path to ground if no audio source is connected (noise filtering).

Questions:

Typically, I've found recommended values of 10uF and 10nF for decoupling capacitors. I used 22nF capacitors for C3 because that was all I had, but it seems to work fine. How are these values determined, and what is ideal?
There is a ferrite bead on the input of each power rail (green on the schematic). I used 45ohm ferrites (again, all I had) although the source schematic called for "6.9ohm" ferrites. I understand that ferrite beads are used to block EMI interference... somehow... but again how these values selected?
What does C1 (150pF) parallel to the audio input do (and how was its value chosen)?
Ditto for R3 (1Kohm) on the audio input?
Ditto for R4 and R5 (10ohm) on the output of each opamp?
Lastly, the buffer (BUF634) itself. I understand that the first opamp (OPA2227) is amplifying the voltage, and that the buffer essentially does the same for current. Does this mean that if the load wants to draw more current, the buffer provides more current than the OPA2227 alone could supply?

Thanks in advance.


texts: How different is the performance of TVS vs Zener diode in flyback protection

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So far I know that it is possible to protect a Switch, MOSFET, Relay from flyback with different kind of diodes:

One diode: It is simple but it affects the speed of valve
One diode + a resistor: faster in closing but choosing a suitable resistor is hard and not optimal.
One Zener diode and one diode: So far it has been the best solution I have found. It is very fast. Only need to be several volt higher than Vcc and also Vcc + Vzener < V_ce_of_mosfet

I have seen that some people are more in favor of TVS diodes for such application!

How different is TVS diode in protecting against flyback in terms of performance?
How should I choose one that is able protect the MOSFET and is also optimal in response.
What type of TVS is suitable for this kind of applications? Bipolar?

Thank you.


texts: Measuring power consumption in Arduino and raspberry-pi system

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I have a system that consists of 1 Arduino, 1 Raspberry-pi, 2 power banks, and a set of different sensors. Each of the Arduino and Raspberry-pi is powered by a separate power bank. I need an accurate method to measure the total power consumed by the entire system.

I also need this power measurement as feedback input to the Arduino to control some sensors. Is it better to tap some power measurement circuit on each power bank or is there a better way to measure it by Arduino/Raspberry-pi.


texts: What affects a microcontroller IO's VOH_min and VOL_max?

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What affects VOH_min and VOL_max? Is it just the current being sourced/sunk by the pin? Or are there manufacturing variances or temperature effects etc that can swing the output voltage away from supply/ground even with no or very little current in the pin?
Edit: What affects VOH and VOL?  What are the major contributors causing VOH be lower than supply and VOL be higher than ground?


texts:
I want to make a case for a FPGA eval board and wanted to monitor the temperature inside to start a fan if the temperature exceeds a certain value.
What kind of sensor is best suited for this task in case of simplicity and accuracy of +-1 degree celsius?
Best regards


texts: Implementing boolean function using OR-NAND and NOR-OR

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This is the boolean function: F(A,B,C,D) = Σ (0,4,8,9,10,11,12,14) and so after using a K-map to minimize it, I came out with F(A,B,C,D) = C'D' + AB' + AD'. Now the other two parts of the problem were representing it with AND-NOR gates and NAND-AND gates which I knew how to do. How do I do it with OR-NAND gates and NOR-OR gates?

Do I simply look for 0's in the karnaugh map and write a minimized boolean expression for 0's and then negate it? I'm very much confused by how to do this with OR and NAND gates. Any help appreciated.


texts: What is this component on my dog's door opening collar?

texts:
I am having some frustration with my dog's pet door opener. This is an off-the-shelf system from a company called HighTechPet, and the collar unit uses a coin-cell battery with a special carrier glued onto it in such a way that you cannot simply replace the battery alone: you have to order replacements with the carriers pre-attached (at a considerable mark-up) from the company.

Now, this would not be so egregious, except the batteries only last 2-3 months.

While I had the unit open for the second time, I thought I'd take a look at the circuit and try to see if the three-month lifespan is really the best that can be done. (Call me cynical, but I am suspecting not.)

Below are two pictures of the open unit with the component side of the PCB exposed.

The component labelled MS4-C is presumably some kind of ultrasonic transmitter. Here is what the Web site has to say:

  Our VP of Engineering, Bob Schilken, one of the most accomplished analog electronic engineers in the world, contributed the extremely creative directional ultrasonic detection circuitry that performs rings around conventional infared, magnetic and RFID circuits.

How might I go about finding more information on this component?

EDIT: Here are some oscilloscope traces sampled from the positive lead of the presumed ultrasonic transducer.

One thing that immediately catches my eye is that the lead is held high, and pings are produced by pulsing the line low with a signal that lasts 2-3ms every 25ms. Wouldn't having the line be normally high like this waste a lot of the coin cell battery power?

This trace is a zoomed-in view of a single ping. It appears to oscillate at 40kHz, which would put it well out of audible range (as you'd expect). I don't know why it's shaped like that, though… Some deliberate signal or just an artifact of the way the circuit and/or component behaves?


texts: First-Order Transient Circuit with Capacitor

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Consider the following circuit, where the switch is in position A for a long time and moves to position B at time \$t = 0\$. For \$t \geq 0\$, \$v_C(t)\$ and then \$v(t)\$ need to be found.

I found \$v_C(t) = (10 - 6e^{-2.6t})\ \mathrm{V}\$, which is the given correct answer. However, I am not sure of the correct answer (not given) for \$v(t)\$. I am getting three different answers using three different approaches:

If I use \$v(t) = v(\infty) + [v(0^+) - v(\infty)]e^{-t/\tau}\$, I get \$v(t) = -2.31e^{-2.6t}\  \mathrm{V}\$.
If I use \$v(t) = 5i_C(t)\$, where \$i_c(t) = C\frac{dv_C(t)}{dt} = 3.12e^{-2.6t} \mathrm{A}\$ (differentiating the earlier expression for \$v_C(t)\$) is the current through the capacitor leaving the positive terminal, I get \$v(t) = 15.6e^{-2.6t}\ \mathrm{V}\$.
If I use KVL for \$t \geq 0\$, I get \$-v(t) - 10 - 8i_C(t) + v_C(t) = 0\$, which gives \$v(t) = -30.96e^{-2.6t}\ \mathrm{V}\$.

Which is the correct answer? The approaches make sense to me logically, but why are they giving different results?


texts: Is it possible to replicate the ENIAC using logic gates

texts: Can one rebuild a small scaled model of the original ENIAC computer using only logic gates?


texts: Is the input impedance of an infinitely long line equivalent to the characteristic impedance if the attenuation constant is 0?

texts:
My book says that the input impedance of an infinitely long line is equal to the characteristic impedance as long as the attenuation constant is not equal to 0.

Is this true? I think it may be an error in the book because the formula for wave impedance of a lossless line, expressed in terms of the distance, is equal to the characteristic impedance when d-> infinity


texts:
I've seen these two swollen caps in a symmetric +12, 0, -12V power supply.

The circuit (a theremin) seems to be working properly, but I don't know if that caps are going to cause damage in the whole circuit in the long term. Should I replace them?


texts:
Given the following posistions of resistors as a part of a bigger circuit, how can I simplify it? The wire between R1 and R2 is a short as I am using Thevenin's theorem. I've tried to make R1 and R2 and R3 parallel but the answer for the whole circuit doesn't match with the answer that comes on when i simulate it on circuit maker! HELP

simulate this circuit – Schematic created using CircuitLab


texts: Solar cell driven transistors - circuit explanation

texts:
Question: what is the purpose of resistor R23 with value 1Mohm?

Schematic of solar cell driven circuit is below.

Circuit works as follows:
When solar cell voltage is higher than 0.7V , LED is OFF
When solar voltage is lower than 0,7V, LED is shining with low intensity powered from battery.

Output voltage simulated with circuitlab:


texts:
In this circuit:

The diode is an ideal diode

The diode is on since V(anode) > V(cathode) and then we replace it by a short circuit.

Now, how to calculate Vo when two sources are existed?

I = (10 + 2) / (2k + 4.7k) = 1.79 mA.

I tried using KVL:

-10 + 2k (1.79 mA) + Vo - (-2) = 0

=> Vo = 4.42

Or:

Vo = 4700 * (1.79 mA) = 8.413

Which answer is correct? and why the other one is not correct?


texts: Inter Vehicle Communication System Project

texts:
I am doing the project with my friend.
So, in this project every vehicle has a transmitter & receiver. Considering a particular vehicle we need to locate how many number of vehicles are there in its surrounding ( In the transmitter range ) along with the angle ( direction ) with respect to the car from which we are looking..

My friend was speaking about using radar.. he wants it to be installed in the system so that we could get this task done..

What I want to know :
1. Is this a possible solution? If not what else we can do to get this job done.
2. How much approx is going to cost for a small range Radar?
3. Suppose, there are 2 different vehicles separated by a distance of 10-20 cm in a traffic Jam.. can the radar show them clearly on the display / it will over lap the points on the display..


texts: LTspice: behavioral modelling elements for propagation delay

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I'm trying to create a subcircuit in SPICE (currently using LTspice but want a pretty agnostic model) for an AND gate that delays an input by some amount TPD.
I'm currently just inputting 2 offest clock signals to the following subcircuit:
.SUBCKT AND_GATE_TEST A B OUT VCC VEE
    XOUTLOGIC A B OUT_LOGIC VCC VEE LOGIC_FUNCTION
    XOUTPD OUT_LOGIC OUT VCC VEE PD_FUNCTION
.ENDS

************************************************************

.SUBCKT LOGIC_FUNCTION  A B OUT VCC VEE

    GAND VEE N1 VALUE = {V(A,VEE)*V(B,VEE)}
    RN1 N1 VEE 1
    EOUT1 OUT VEE N1 VEE 1

.ENDS

************************************************************

.SUBCKT PD_FUNCTION IN OUT VCC VEE

    GDEL VEE N1 VALUE = {V(IN,VEE)}
    RN1 N1 VEE 1
    EDEL = OUT VEE DELAY N1 VEE TD=10ns

.ENDS

The first logic function works fine and outputs the expected AND logic given the inputs A and B but I get tripped up with the propagation delay function.
The error that LTspice outputs says Missing gain value but no matter how I use the E element (or any behavioral elements for that matter) as a delay function I can't get it to work properly.
I think I'm missing something fundamental on the syntax of the behavioral elements
Any help on how to best approach this would be greatly appreciated.


texts: constraint error and illegal load problem in Virtex-2

texts:
I am trying to test a very simple deskew circuit on a virtex-2pro FPGA (xc2vp30-fg676-5). I use xilinx ISE and the deskew IP (two DCMs with a DDR flop) provided by core generator. I also try to observe the related signals on GPIO pins. But I have got the following translate error in my design. The details of the error and the design is pasted below. Please give me some hints.

Resolving constraint associations...
Checking Constraint Associations...
ERROR:ConstraintSystem:59 - Constraint <INST "rex_clk"  LOC="N3" |>
   [xc2vp30.ucf(14)]: INST "rex_clk" not found.  Please verify that:
   1. The specified design element actually exists in the original design.
   2. The specified object is spelled correctly in the constraint source file.

ERROR:ConstraintSystem:59 - Constraint <IOSTANDARD="LVCMOS33" ;>
   [xc2vp30.ucf(14)]: INST "rex_clk" not found.  Please verify that:
   1. The specified design element actually exists in the original design.
   2. The specified object is spelled correctly in the constraint source file.

Done...
Checking Partitions ...

Checking expanded design ...
ERROR:NgdBuild:809 - output pad net 'clk_o' has an illegal load:
     pin C on block cnt_0 with type FDC

Verilog module

module xc2vp30(
    //probing
    output rex_clk,
    output rex_rst,
    output rex_cnt_i,
    output rex_cnt_o,

    input rst,
    input clk,
    output clk_o,
    output rst_o,

    input cnt_i,
    output cnt_o
);

wire clk_ddr;
reg cnt;

assign rex_clk = clk_ddr;
assign rex_rst = rst;
assign rex_cnt_o = cnt;
assign rex_cnt_i = cnt_i;

assign clk_o = clk_ddr;
assign rst_o = rst;
assign cnt_o = cnt;

always @(posedge clk_ddr or posedge rst) begin
    if(rst)
        cnt <= 1'b0;
    else
        cnt <= cnt + 1'b1;
end

////////////////////Deskew/////////////////////

deskew deskew_0(
    .U1_CE_IN(1'b0),
        .U1_CLKFB_IN(clk_ddr),
        .U1_CLKIN_IN(clk),
        .U1_CLR_IN(rst),    //high reset
        .U1_PRE_IN(1'b0),
        .U1_RST_IN(rst),    //high reset
        .U2_RST_IN(rst),
        .DDR_CLK0_OUT(clk_ddr),
        .U1_CLKIN_IBUFG_OUT(),
        .U1_CLK0_OUT(),
        .U1_CLK180_OUT(),
        .U1_LOCKED_OUT(),
        .U2_CLK0_OUT(),
        .U2_LOCKED_OUT()
);
endmodule

UCF file

NET "clk" PERIOD = 40 ns HIGH 50%;
NET "clk" TNM_NET = clk;
#================================================ Pin assignment
#------------------------------------------------ Clock, reset, LED, and SW.
INST "clk"          LOC="B13" | IOSTANDARD="LVCMOS33";           # Clock input (X2)
INST "rst"             LOC="E21" | IOSTANDARD="LVCMOS33";           # Reset input

INST "clk_o"       LOC="AE1" | IOSTANDARD="LVCMOS33";              # Clock output
INST "rst_o"          LOC="Y26" | IOSTANDARD="LVCMOS33";               # Reset output
INST "cnt_o"          LOC="U2" | IOSTANDARD="LVCMOS33" | DRIVE=6;  # data output
INST "cnt_i"          LOC="V5" | IOSTANDARD="LVCMOS33" | DRIVE=6;  # data input

INST "rex_clk"     LOC="N3" | IOSTANDARD="LVCMOS33" ;           #  observe clk output
INST "rex_rst"     LOC="M4" | IOSTANDARD="LVCMOS33"| DRIVE=6; # observe Reset output

INST "rex_cnt_i"     LOC="L3" | IOSTANDARD="LVCMOS33"| DRIVE=6; # observe
INST "rex_cnt_o"     LOC="K3" | IOSTANDARD="LVCMOS33"| DRIVE=6; # observe


texts: Why do optical interconnects require less power than electrical?

texts:
Why is it that optical interconnects require so much less power than electrical ones?
update from comments:
This question was prompted by this video.  The speaker shows a table at 50:43 that indicates that optical interconnects require much less power for the same port speed. He also mentions at other points in his talk that photonic integrated circuits require less power.

Description of the video:

Published on Dec 27, 2013
(Visit: http://www.uctv.tv/) Photonics has transformed our work and, indeed, our lives, by enabling the Internet through low-cost, high-capacity fiber optic transmission. In data centers, photonics is replacing electrical cables, thereby allowing for higher and more economical performance. In his talk, John Bowers, professor of electrical and computer engineering and materials, discusses the evolution of photonics and what the future holds for this technology. Recorded on 10/3/2013. Series: "Institute for Energy Efficiency" [12/2013] [Science] [Show ID: 25995]


texts: Using multiple ports to transfer data to single device

texts:
I have the datasheet of a camera which has various interfaces (computer buses) via which it can transfer data to other devices: I2C bus, CAN bus, RS-422 serial port. I know the camera can use different interfaces for different devices simultaneously.

My question is, can the camera use all the interfaces to transfer data to a single device, assuming this device also has a I2C bus, CAN bus, etc.? And if so, will the speed of data transfer be affected negatively (total speed not equal to sum of the maximum speeds of each bus?)

I guess the answer could be device-specific. If that is the case, could you please share the most common behavior of devices regarding using multiple ports?. Thanks in advance!

PD: Data sheet of camera Page 10 for info on Data Interface


texts: How does current equal \$i_o\$ in this op amp problem?

texts:
I took a guess at this multiple choice question and got it right, however I'm not sure how current through the 1 kOhm resistor is equal to \$i_o\$?

I understand that for the ideal op amp, the voltages at both input nodes are equal to each other. However, because each of the voltages are divided across varying resistances, I do not understand how the 2 current values are equal. Can someone please help me understand this?


texts:
While I use the internal clock for DCM clkin input I am getting clk0 as perfect frequency of output same as internal clock but not in remaining o/p  pins. I changed from previous coding like this and also schematic as below.

module dcm_clockverilog(clk,rst,clkdiv,clk0,clk2x,locked,clock);

input clk;
input rst;

output clkdiv;
output clk0;
output clk2x;
output locked;
output  clock;

wire clk0;
wire clk2x;
wire locked;
wire clkdiv;

reg [7:0] count=0;
reg clock=0;

dcmm instance_name (
    .CLKIN_IN(clock),
    .RST_IN(rst),
    .CLKDV_OUT(clkdiv),
    .CLK0_OUT(clk0),
    .CLK2X_OUT(clk2x),
    .LOCKED_OUT(locked)
    );

always @(posedge clk)
begin
   count <=count+1;

if(count<=9)
   clock<=0;
if(count>=10)
   clock<=1;
if(count>=19)
   count<=0;
end

endmodule

//---------------------------------------------plan ahead

# PlanAhead Generated physical constraints

NET "clk" LOC = P57;//-- (GCLK)
NET "clk0" LOC = P7;//--(I/O)
NET "clk2x" LOC = P8;//--(I/O)
NET "clkdiv" LOC = P10;//--(I/O)
NET "clock" LOC = P11;//--(THIS CLOCK I ASSIGN AS INPUT FOR DCM CLKIN) )
NET "locked" LOC = P12;//--(I/O)
NET "rst" LOC = P18;//--(INPUT SWITCH)


texts: Setup and hold time output when violated

texts:
Consider a positive edge triggered D flip flop with input signal X with a setup time of 20 ns and a hold time of 0 ns. What will be the output?

C is clock signal with a period of 40 ns.

During the 6th positive edge, we see that the data (or X) is not stable for 20 ns (setup time) before it as it goes from 1 to 0. So the output is not predictable, right?

When I asked this to my professor, he said that the output of the flip flop would be the value of the input (X) before 20 ns which is 1 here.

Is he correct?


texts: Why can we hear the full range of square waves from 1 Hz-20 kHz, but not sine waves of the same frequencies?

texts:
I connected the output (50Ω) of a function generator to a 35 watt 5Ω speaker.

When I sent square wave signals of 1 Hz-20 kHz to the speaker, my friends and I were able to hear them. But when I sent sine waves across the same range, no one was able to hear anything below 100 Hz.


texts: While studying the NMOS amplifiers in my book I came across operations with differential output voltages and this circuit specifically.I want to understand what are the drain voltages and what is the Vdd voltage in this case?


texts:
I'm working on the following problem:

I found the correct answer for part (i):
$$
Z = \left(\overline{(\overline{A + B})C}\right) (C\overline{D})
$$
How can I simplify this expression?


texts: Voltage converter (220V to 110V) with surge protector power strip—how much wattage do I need, and is it safe?

texts:
For the next 6 months, I'll be living in a country where the voltage is 220V. The risk of frying electronics is also much higher there, so I want to get a surge protector. I've been researching this for the past 5 hours, however, for some reason, finding a good power strip that accepts both 110V and 220V—and also has good surge protection—isn't easy.

So instead, I'm thinking of doing the following (*it seems USB plugs aren't surge protected on power strips—manufactures don't put this information up front):

  Voltage converter (220V to 110V) -> 110V power strip w/ 900J+ surge
  protection -> USB charging hub*

  Laptop plugged into the power strip and USB devices (iPhone, iPad, ereader, portable charger) charged on the USB charging hub

How much wattage would I need with the voltage converter?
Would this setup be safe? Would there be overheating?
Not all power strips/hubs/etc. are UL certified. How important is this?


texts:
I'm experimenting with early electrostatic devices, and I'm measuring spark gap length to determine voltages generated. How dangerous is it to observe these arcs with the naked eye? Should I wear something like welding goggles?
Does anyone have information about the relative dangers of different kinds of arc vs duration of observation and distance from the source? I imagine that something that would handle a welding arc wouldn't have a problem with a Leyden jar spark but I have no way to know how a high voltage low power spark compares.


texts: feedback resistor value for a crystal oscillator

texts: Does the feedback resistor for a crystal oscillator need to have a very accurate value? If a 16Mhz crystal requires 1Mohm, should one expect a problem when 200kohm or 2Mohm is used instead?


texts: Op Amp Unity gain gives an unexpected constant saturated output

texts:
I have this following circuit;
I use an Arduino DUE to send a 12-bit DAC output and I want to feed this in an Op Amp.

Every ground is tied to the same ground.
The Op Amp is ADA4000-2 from Analog device.

The USB power is used and DUE (SAM3 series MCU) outputs DAC output to the Op Amp input.

I created a DAC signal that goes up/down from 1.55V. As you see the yellow signal (channel 1), this 1.55V is like a DC-Offset.
The blue signal (channel 2) is the Vout pin, the output of the Op Amp.

If you take a close look at the part where the values are lower than 1.55V from channel 1,
I was expecting the same decreasing pattern from channel 2.
However, that part is constant to 4.1V and I think the output becomes saturated.

I cannot understand this reason.
What seems to be the reason for this constant output?
I wanted a unity gain, but I cannot find the reason for this.
Appreciate your help.


texts:
In the process of developing an RDM Compatible DMX receiver board (using a ATMEGA328) and I have been fortunate enough to come across kimliv's most informative answer concerning such a board;

DMX on Arduino with RS485

However I was wondering why (if) it is necessary to use a TTL Compatible isolator? In this case the 6N317 or if perhaps a more traditional repeater isolator style circuit could be implemented using a more common and cheaper isolator for example the H11A1 (which I just so happen to have in stock).

This all said it seems several DMX circuits I have come across utilise the 6N317 but so far as I am aware the transceiver (MAX481) could be used to drive other isolators.

Is there something obvious I am missing here? or anything in particular that makes the 6N317 quite so desirable for its use here?

thank you.


texts: LEDs not lighting up with reverse bulbs on my truck

texts:
Recently purchased the WSFS-NW180-BK LED Light strip from superbrightleds.com, but the LEDs are not lighting up in conjunction with my reverse bulbs. I spliced the LED positive wire with the Reverse bulb positive wire. The LED ground wire was bolted to the frame. The FIRST time I tried it, BOTH lights lit up. But the SECOND time I tried it, ONLY the Reverse bulbs worked and the LED's didn't.
Any Ideas???

My plan was to splice the LEDs in with the reverse bulbs so I had more light for backing up at night. One 10 inch section of the LEDs on each side of the truck.


texts: What Operating Systems are available for Arduino?

texts:
This question seems to suggest that people are developing Operating Systems for the Arduino platform.

What Arduino OS projects are you aware of?

Please list only one project or OS per answer, and give a short list of goals or features of that OS.

For the purposes of this question software frameworks, task handling utilities, and similar projects are considered Operating Systems.  While there are many AVR frameworks and OS projects that work on Arduino hardware, please only list those that work within the Arduino software development tools and platform without modification.


texts: Why use a Zener in a regulator as opposed to a regular diode?

texts:
If you had a regular diode with a turn-on voltage of 5V (hypothetically), and a Zener diode with a reverse-bias of 5V, would the Zener diode still be preferred in a voltage regulator?

I'm trying to understand why a Zener diode would be used instead of a regular diode if you could achieve the same regulation with both. Do Zener diodes have a more constant breakdown voltage over a wide range of currents compared to the turn-on voltage of regular diodes?


texts:
I want to build an interactive whiteboard which uses an infrared ped. I want to use a camera to track IR position on the projection screen.
I plan to keep the camera a little further away from the laptop. So what will be the best way (wifi/bluetooth/usb) to get the continous video input from camera? I am worried that if the video input is slow then processing (using openCV) the image to track the IR position will be slow. I want to track the IR pen in real time.

What would be the fastest way for to achieve this? Should I buy a IP camera or build one from raspberry pi? Or Usb webcam will be better?


texts: Could You Use Common cathode RGB LED without providing power to G and B

texts:
I know this kind of defeats the purpose of an (common cathode) RGB LED, but if you only wanted Red on a RGB LED would it be acceptable to use only the R pin and the Cathode pin to get just red?
Sorry in advance for my bad grammar.


texts: Designing a Buck Boost Regulator 12V Circuit

texts:
I have been trying to source a Buck/Boost IC to design a circuit for my needs but I'm having a little trouble understanding how I would do this.

I am currently designing a circuit that will provide a regulated 12V output (around 3A max) from either a 12V battery or 12V DC input.

My go-to would be an adjustable linear voltage regulator, but these can only step down to voltage levels that are less than the voltage input (dependant on the dropout voltage of the regulator). As battery voltages will decrease over time (approx 12.65V to 11.9V) the linear regulator would not suffice (Not to mention that 12.65V is within the voltage dropout range of the linear voltage regulator when it is set to output 12V).

I could decrease/increase the input voltage and combine that with a boost or buck/linear regulator to achieve a 12V output but I would prefer to keep the input as 12V.

I found this post (Stabilize 12V to 12V) which recommends a Buck-Boost Converter. This seems like it would work for my application.

I've had a look on RS components through some datasheets but the typical circuit applications either show the IC in Buck or Boost configuration and not as a Buck-Boost. (Example TI MC33063AP)

Therefore, I was just wondering if there were some pointers on how to construct a suitable circuit for this application. For example, some ICs seem to mention PWM control, I assume this would mean I need to include something like a 555 IC to control the buck/boost functionality?

There also seems to be a lot of terminology for Buck-boost (Buck boost switching regulators, Buck boost controllers, Synchronous buck boost etc..) is there a particular type that would be best suited to this application?


texts:
In Verilog, I am trying to store the input up to 4 previous values and then operate on them.The code is fine in simulation but on FPGA, it calculates output with the current input instead of previous ones. what are the registers not being synthesized to memory blocks where past input can be stored? the past input values are supposed to change only on change in the current input.
All the operations have to be performed with stored 4 values of x-> x0,x1,x2,x3
Works in simulation, fails in hardware (Spartan 3E)
Top module:

module main(input [7:0] x,input clk,reset, output [15:0] y,output reg[7:0] x0,x1,x2,x3
);
  //reg [7:0]pxe[0:3];
  reg [7:0] h0,h1,h2,h3;
  reg [7:0] addr;
  wire [7:0]m0,m3,m1,m2;
  wire [3:0]s2,s3,s1,s0;
  wire [15:0] mult0,mult1,mult2,mult3,out0;
  wire [15:0] sout0,sout1,sout2,sout3;
  wire [7:0] xconv0,xconv1,xconv2,xconv3;
  wire [7:0] sin0,sin1,sin2,sin3;
  wire [15:0] po0,po1,po2,po3;
  //reg [3:0] s0;
  assign out0=8'd0;

  check inst_1(h0,clk,reset,m0,s0);
  check inst_2(h1,clk,reset,m1,s1);
  check inst_3(h2,clk,reset,m2,s2);
  check inst_4(h3,clk,reset,m3,s3);

  cla3input int_1(mult0,sout0,out0,po0);
  cla3input int_2(mult1,sout1,po0,po1);
  cla3input int_3(mult2,sout2,po1,po2);
  cla3input int_4(mult3,sout3,po2,po3);

  xconv ist_1(x0,s0,xconv0);
  xconv ist_2(x1,s1,xconv1);
  xconv ist_3(x2,s2,xconv2);
  xconv ist_4(x3,s3,xconv3);

  shiftin it_1(h0,xconv0,sin0);
  shiftin it_2(h1,xconv1,sin1);
  shiftin it_3(h2,xconv2,sin2);
  shiftin it_4(h3,xconv3,sin3);

  shifter i_1(sin0,s0,sout0);
  shifter i_2(sin1,s1,sout1);
  shifter i_3(sin2,s2,sout2);
  shifter i_4(sin3,s3,sout3);

  booth_a is_1(mult0,x0,m0,h0);
  booth_a is_2(mult1,x1,m1,h1);
  booth_a is_3(mult2,x2,m2,h2);
  booth_a is_4(mult3,x3,m3,h3);

  assign y= po3;
    always@(posedge clk)
    begin
      h0<=5;
      h1<=-3;
      h2<=1;
      h3<=2;
      if (reset)
      begin
        x0<=0;
        x1<=0;
        x2<=0;
        x3<=0;
      end
      else
      begin
        x0<=x;
        x1<=x0;
        x2<=x1;
        x3<=x2;
      end
    end
endmodule


texts: Length of wire to calculate its power losses

texts: Let us say I have 12V DC battery and I am using 10m long wire to connect my load with it. Now if I want to calculate power losses in the wire then should I use wire length as 10m or 20m (since there are 2 wires + and - each of 10m in length)?


texts:
I am trying to design an RF circuit/ a PCB that has Bluetooth functions for transmitting data. I am looking at how to integrate this into a power source. I am quite new to this and not too sure how to get started. Are there any references or examples that can help me get started?

Thank you so much!


texts: DC Fault Characteristics of a Voltage Source Converter

texts:
According  to this paper, the three stages in the DC Fault characteristic of a VSC are

Capacitor-Discharge State (Natural Response)
Diode Freewheeling Stage (When source AC gets disconnected and \$V_C = 0\$; Natural Response)
Grid Side Current Feeding Stage (Forced Response)

The diode freewheeling stage comes into picture when the source of the AC power is disconnected and the capacitor is completely discharged. But then, the grid-side current feeding stage takes the source AC into consideration. How is this possible?

Also, the first and second stage is described as a natural response and the third stage is described as a forced response. What exactly is forced here?

The referenced content is in Section II, Subsection B under the title "VSC DC Fault Characteristics".


texts: How calculate three phase kilowatt hour from time sampled data of voltage and current of each phase

texts:
My problem is I want to calculate three phase kilo watt hour from time sampled data of current and voltages.

My doubts

1) How can I calculate the kilowatt hour from time sampled data? Is it any equations is available?

2) Is it need to take the phase shift ? ( How can I calculate the phase shift from sampled data of voltage and current? How I link this to calculating the three phase power.)

3) Please suggest me if some better platform is available for solving my doubt?

4) Is it true when I calculate the kilowatt hour of each phase separately and some up all?

I get the instantaneous sample value (Not continues).(I have some sensors that gives the current and voltage - I convert this to digital for processing). Around 50 samples are got from 1sec.(Is it to be zero when we some up all the power of three phase - due to phase shift of 120) . How can I calculate total three phase kilo watt hour from these sampled value. I am processed my data in arduino.


texts: Why am I not receiving a 60 MHz signal from CLKOUT in sync.FIFO mode on the FT2232H?

texts:
I tried to set sync.FIFO mode on FT2232H.

According to paragraph 4 (pg.10) of AN_130 (FT2232H Used in an FT245 Style Synchronous FIFO Mode) I expected a 60MHz signal at pin No.32 (CLKOUT) after set sync.FIFO mode. But there was no any signal.

I also tried to use MSSP mode to make sure the quality of the solder CLKOUT pin.

The solder quality is good.

What I am doing wrong?


texts: Wide range current conversion transimpedance amplifier

texts:
I am struggling trying to think out a solution to design a transimpedance amplifier (TIA) which can convert 100 nA to 10 mA. This is 5 decades. I want to be able to amplify these to 1.5V minimum. (3V max).

I want to do most of the amplification in the TIA due to lower total noise.

If I have a fixed value resistor in the TIA feedback loop it can maximum be 300 Ohm for achieving 3V amplitude for 10 mA. This means that to be able to amplify 100 nA to 3V I would need to have a gain of 100 000 which is too large and would give too much additional noise in cascaded amplification stages.

If I reduce my range to 1 uA to 1 mA (not wanted..) which is 3 decades. Now I can have a fixed resistor at 3000 Ohm. And need to have a gain of 1000 which is more doable.

My first solution was to use a digital potentiometer in the TIA feedback loop. This would solve most of my problems, but creates some new ones. The gain vs frequency vs. code plot shown in some data sheets AD5260/AD5262 (page 11 and 12) shows poor performance for frequencies above 100 kHz and I need 500 kHz minimum. So I could use this digital potentiometer and have a stable variable resistor with values as low as 200-800 Ohm (50k or 200k version of the digital potentiometer) and as high as 200 kOhm, but I would need to calibrate my system for this. Additional gain stages are needed in addition to this as well, but noise performance would be a lot better.

Other:

I also looked at the logarithmic transimpedance amplifiers (which can convert many more decades), but I want to investigate the possibility to use a linear transimpedance amplifier first.

Multiple feedback loops with different resistor values and analog switches have been considered and if shown is necessary can be accepted. This would eliminate question/problem 1 and 2 below, but introduce analog switch noise.

Questions:

Will the digital potentiometer add any additional noise?
Will I be able to use a fixed capacitor in the feedback loop to prevent oscillation/ ringing when the resistor has such wide range?
Is there a better/other way to achieve this?


texts: Does hole concentration fall below the intrinsic concentration, if Si is doped with pentavalent impurities?

texts:
If we increase N type doping in a pure Silicon then according to the equation
$$P_n=\frac{n_i^2}{N_D}\text.$$
Then mathematically, hole concentration is less than \$n_i\$, if \$N_D>n_i\$.

Why does \$P_n\$ even depend on \$N_D\$(doping)? It should only depend on temperature, right?
Then why can't we just take \$P_n=n_i\$ and  \$N_n=n_i + N_D\$?
What happens in the semiconductor physically?
(Explanation by Energy band theory helps greatly.)


texts: Male/female wire connectors - How to tell AWG/mm^2 rating?

texts:
So I have a project where I will be running 20 AWG wires. Now there will be one section where I will need to connect the wires with a male/female connector.

I'm having trouble identifying which connectors should do the job safely, as I prioritise safety first.

How does one figure this out? When I type in "male female 2 pin connector" on Aliexpress I get a lot of results, but it's never stated for which wire gauges the connectors are for!

I also keep hearing about "pitch", i.e. "SM2.54 Kits 25 sets Kit in box 2p 3p 4p 2.54mm Pitch Female and Male Header Connectors Adaptor". In the example here "2.54mm pitch", what does that mean?


texts: Is it safe to use a DC power adapter that isn't UL Listed or CSA certified?

texts:
I picked up a 9V switching DC adapter from SparkFun a while back, but I've been hesitant to use it because it doesn't have any of the usual "safety" approvals that you normally see on power adapters (UL listed, CSA approved, etc.)

Is this just unfounded paranoia?  Are there safety issues to think about when using a DC power adapter for a project that will run 24/7?


texts: DIY current-limited 40A+ power supply to emulate LiPo batteries

texts:
I want to do some experiments developing brushless DC motor control hardware, and maybe wiring my own motors for my own edification. LiPo batteries aren't convenient enough, and I want current-limiting protection against shorts or failure in my electronics or motors.

The intention is to use commercial 'Hobby' RC BLDC motors, and my own hardware to drive BLDC motors. (I will try to use commercial RC ESCs as well, for testing)

Almost all of the BLDC motors I am interested in are 3 LiPo, i.e. a nominal 11.1V, or less.

I would like a bench power supply which lets me set the current limit, in order to reduce the chance of damaging my electronics or motors. The aim is to emulate LiPo batteries, but with a user-defined current limit. For the sort of things I expect to do, 40A should be plenty.

Unfortunately, the sort of equipment sold by electronics distributors is unacceptably expensive. 40A Bench PSU's seem to start at 500GBP, which is too much cost for a 'hobby' project when motors and electronics are under 50GBP. e.g. Farnell

So I am looking for a cheaper solution which would provide over-curret tripping (like an electronic fuse).

There are lots of switch mode power supplies which claim 12V at 40A or more, for around 50GBP. 12V is close enough to 3LiPo's that it is an acceptable compromise.

A real bench power supply limits the current, and that would be ideal. However, I don't see a way to achieve that at sub-100GBP. Something which rapidly turns off power when it detects over-current, would be an acceptable compromise (unless I am missing something).

I could make an over-current sensor using an off-the-shelf current shunt measuring chip, and a microcontroller. I would 'dial in' my required current limit using a suitably tasteful human interface. It would measure the actual current, and signal an over current measurement, which needs to disable the power supply.

I am not sure how fast switch-off should be. I expect, say, 20ms (1 cycle of UK mains) would be good enough (500W for 50th second sounds survivable). I would like faster, but I am assuming I might need to switch the mains input power off. I would much prefer a solution which does not require me to control the mains input.

I am happy to put fuses in the line too, but I do not believe they are flexible enough, or convenient enough to be the primary current limit

I had imagined some switched power supplies would have an "enable" input, but I haven't found any so far.

Edit: Q1: is no longer relevant
The proposal is to 'disconnect' the PSU power from the BLDC driver after the PSU, using a suitable implementation of an electronic fuse.

Q1a. Will a rapid (couple of ms) disconnect of the PSU from the reactive load create a problem that might damage a switched PSU?

Q2: There is going to be a lot of quite high frequency modulation from the motor control PWM, as it switches power to the motors (I am guessing in 100's of kHz).  Is it likely that this will significantly effect a switched power supply, and maybe even make the whole idea unworkable? Might a simple fix, be several mF of capacitors, or is it more complex than that (i.e. it'd need a tuned circuit, Edit: or adjust motor PWM to work around the power supply)?

Edit Q3: was "I assume the current shunt should be on the high-side. Is that correct?"
Response:
Commercial RC ESC's don't care because they are designed to work off batteries.

However, using a high-side shunt should make experiments and test-rig measurement a bit easier, by maintaining a ground reference.


texts: Microcontroller pin out configuration upon power up

texts:
I have this S32K142 microcontroller, in the 64 pin package.
I have 2 SPI interfaces, 1 I2C interface, 2 UART interfaces, 6 ADC inputs, a few GPIO and PWM output requirements.
My question:

On initial power on condition, what should the state of the SPI interface pins, I2C and UART, ADC pins? Like, should it be pull-up or pull-down or floating?

How to configure those pins upon start up condition and where is this information provided?

From the reference manual, I see that each port has multiple functional peripherals.
Since I have 2 SPI interfaces, I am using LPSPI0 (PTB0, PTB1, PTB2, PTB3 ports for LPSPI0 module) and LPSPI1 (PTD0, PTD1, PTD2, PTD3 ports for LPSPI1 module) for the 2 interfaces. Am I correct?

In the reference manual, why are two peripheral chip select options given for the LPSPI0 module in case of PTB5 port? How to understand this?


texts:
I have a Solenoid Normally Open gas valve rated at 29VA. It can be operated using 220VAC or 12/24/48 VDC. When i power it with AC mains voltage, it draws only 3mA @ 220V and the valve closes. When i power it with 12VDC nothing happens. I've tried controlling it using an Arduino with TIP120 but still it only draws 15mA @ 12VDC with a TIP120. My calculations say that it should draw about 2.4A @ 12VDC whith the rated power 29VA. whats wrong? why isn't it working and is only drawing 15mA?
*I'm powering it with a lab power supply rated @ 30VDC 5A by the way, just in case you needed to know.


texts: Understanding "Current Draw" in terms of "Ohm's Law"

texts:
I'm having trouble understanding Current Draw as it relates to Ohm's Law (V = IR).

I have a power supply rated at 5V and 500mA.  I'm trying to power a string of LED lights.  According to my datasheets, each LED draws ~50mA of current.  If I have a string of 5 LEDs, that would draw 250mA. If I have a string of 10 LEDs, that will draw 500mA of current.

Here's my problem:

According to my understanding of Ohm's law, Current = Voltage / Resistance.  As I understand it, when I add additional LEDs to my circuit, each LED should contribute resistance to the circuit.  If this is the case, according to Ohm's Law, I would expect that current would DECREASE with each additional LED. In other words, as Resistance increases and as Voltage stays the same... when I divide V by an increasing R, this equation results in a lower I.

Instead, it is INCREASING!

Am I misunderstanding something here?

EDIT:

Yes, I was misunderstanding something there.  The LEDs on my LED strip are wired in parallel, not in series.  Resistances wired in parallel lower the total resistance through the circuit, so current would INCREASE coming from my power supply.

Additionally, LEDs don't function exactly like a regular resistors.  As Voltage increases, current increases non-linearly, so Ohm's Law cannot apply perfectly.


texts: KiCAD: Footprint for pushbutton (arduino)

texts:
In the last days i was trying to figure out how footprints for KiCAD work.
With help from people of this forum, i have achieved in completed all the footprints except one.
I have a pushbutton for an arduino shield.
This is the description of the button:
https://www.cableworks.gr/ilektronika/arduino-and-microcontrollers/components-and-ic/buttons/5pcs-momentary-tactile-push-button-switch-6x6x6mm-for-arduino/
As you can see there is no datasheet.
I have been trying to figure out how to find a footprint for many hours but i have not reached a conclusion yet.
KiCAD has "codes" to contain information in their footprint libraries, but i have not found documentation on what these codes are.
This is a Through Hole button, but i plan to use it as an SMD one.
I am looking at the Button_Switch_SMD library.
There are hundreds of footprints in there.
The dimensions of the button are 6mm X 6mm.
The distance between the two pins on each side is around 4mm.
I am sorry to ask what some people may consider basic, but i am very frustated and i am one step from designing the board and sending to the board house. Google didn't prove much useful in this case, just KiCAD forum links, 3 years ago, with different libraries.


texts:
I'm working with MircoBlaze_mcs core and implement simple GIO file from the tutorial but it gives  error ( "xiomodule.h" No such file or directory  )when I synthesize the project .

I find it in the API documentation in the SDK Project Explorer, under /BSP
Documentation/iomodule_v1_00_a .

this is the tested code :

#include <stdio.h>
#include "platform.h"
#include "xparameters.h" // add
#include "xiomodule.h" // add
void print(char *str);
int main()
{
    init_platform();
    u32 data;
    XIOModule gpi;
    XIOModule gpo;
    print("Reading switches and writing to LED port\n\r");
    data = XIOModule_Initialize(&gpi, XPAR_IOMODULE_0_DEVICE_ID);
    data = XIOModule_Start(&gpi);
    data = XIOModule_Initialize(&gpo, XPAR_IOMODULE_0_DEVICE_ID);
    data = XIOModule_Start(&gpo);
    while (1)
    {
        data = XIOModule_DiscreteRead(&gpi, 1); // read switches (channel 1)
        XIOModule_DiscreteWrite(&gpo, 1, data); // turn on LEDs (channel 1)
    }
    cleanup_platform();

    return 0;
}


texts: I'm trying to figure out how to control the color in the LED 5050 RGB strips--how are the 4 contact points usually mapped (my strip does not indicate). I'd also like to ratchet down the brightness--the strip currently runs on 12V/5 amps. To ratchet down the brightness, is that a reduction of voltage or amperage; how far can I ratchet down and still expect the LED strip to function; and how best to ratchet down?


texts: Does a Buck-Boost Converter/PWM controller significantly reduce the energy you can get from solar panels?

texts:
As a heads up, I edited this question to make more sense based on what I have learned. I think this is okay since no one has answered the previous question yet.

So I'm designing a solar system and was looking at the MPPT linked below:

https://www.amazon.com/TRACER-3215RN-Solar-Charge-Controller/dp/B008KWPGAE

I read one of the points of this MPPT was that it uses

"4- Stage charge with PWM output."

From that, I know this MPPT uses PWM to adjust the output voltage. I know this is necessary because you need to change your output voltage to fit the rest of your system (as an example system, think of a dc-to-dc step down from 36 input volts to 12 output volts or dc-to-dc step up from 36 input volts to 48 output volts). My concern is this: will this PWM significantly reduce the energy I can get from my solar panels? Let me explain why below:

I'm basically asking if I have PWM technology or a buck-boost converter that deems I need a duty cycle of 0.4 to reach the voltage I want (this means the switch is open on the buck-boost converter or PWM circuit 60% of the time), does that mean I don't generate power with my solar panels 60% of the time? For example, think of a natural gas generator that runs 8 hours a day but you only have a load plugged into it for 40% of those eight hours. That's a lot of natural gas wasted. Similarly, I'd lose 60% of my insolation on my solar panels, right? Since they only actually generate power 40% of the time since the switch is open the other 60% of the time on my PWM circuit or buck-boost converter.


texts: Why does input capacity of an opamp increase noise gain?

texts:
On the image below you can see an inverting amplifier with input capacity C1 and capacity C_F for general stability.

Now my book shows me following frequency plot:

A_n ... Noise-Gain

A_D ... open-loop gain

A_U ... V_out / V_in --> inverting amplifier gain

You can clearly see that C1 is increasing the noise gain at some point. And C_f is stabilizing A_n and A_U.

But why exactly does C1 increase the noise gain exactly?


texts: Capacitor selection for RC power filtering

texts:
I want to design an RC filter to create a constant current supply from a PWM current supply.
The background of where I got here is...
I'm using a constant current driver LDB-600L to provide constant 600mA of current to a power off brake (https://sepac.com/products/view/thin-spring-brake/). That is what is needed to get it to click over from engaged to disengaged. Once the brake is disengaged, the required hold current is about 1/2 that much. So I'm using the dim functionality of the LDB-600L to make reduce the current. But the output is then PWM, so I decided to use a capacitor to filter the output current and provide the brake with a constant current.
For the brake, R=38.7Ohm
PWM frequency is ~576Hz
I figure the output RC filter corner frequency 1/(2 * pi * R.brake * C) should be much lower than the PWM frequency. So, I chose 15uF for a corner frequency of 274Hz.
But now, how do I choose a capacitor (or array of capacitors) to best fit this application. I feel like low ESR will be important since we'll be seeing some real ripple current in the capacitor. Are there any suggestions on selecting this component like type, product line, or even alternative solutions to using an RC filter to drive the brake? Would higher capacitance lower the corner frequency and lower the ripple current? Would a parallel array of capacitors lower the ESR and heating? I'm a newbie, so anything will help!


texts: What type of 4-pin 1mm-pitch clippy connector is this?

texts:
I have recently bought a lidar sensor with a peculiar cable type. I cannot identify it, but it has some interesting characteristics. It has a pitch of 1mm, and each pin has at most a 0.5mm width. The cable itself is for UART, but I'm not sure if the connector was made for it.

Here is a close up of the male end.


texts: LTC3862-2 Step Up problem, output voltage drop

texts:
I'm designing a solenoid powering and control device which is centered around the LTC3862-2 Step Up controller (see datasheet). I have taken as a design start point the typical application shown in page 38 of the datasheet. I have only modified the resistor divider values in order to get a 40 V output (316 kOhm and 10kOhm) instead of the 80V shown in this typical application.

My requirements are:

Vin= from 6 to 8.4 Volts
Vout= 40 Volts
Iout= 2.5 Amps

Plus, the basic circuit schematic is shown below:

simulate this circuit – Schematic created using CircuitLab

The problem comes when I activate the solenoid. Instead of having the 40V/2.5A from the step up, there is a sudden decline from the moment M1 closes from 40V to 24V, plus the current is only about 1.5A. As a result, the solenoid is far from moving the mechanism it is meant to. When the load is not connected, the output is stable at 40V.

Additionally these are other measures from the experiment:

Battery voltage under load= 8.3V @ 5.5A (LiPo battery can deliver more than 30 A continuously).
M1 transistor source(GND) to gate voltage 4.8V (transistor datasheet)

Do you know what is happening or the reason of this behavior? Can you think of a solution to avoid this output voltage drop?

Any help is very much appreciated. Thank you in advance!

----Edit: Schematics----

Hi guys, sorry for not posting thee aactual schematics. Here I attaach the typpical application from the IC datasheet as well as the schematic from the board I have manufactured.

From this schematic, I have only made this minor modifications:

Changed output caps to 100uF 63V since output voltage for this application is 40V.
Input capacitors changed from 50 to 16V since input voltage range is 6-8.4V.
Resistor divider to FB pin in order to have 40V output (12.4 kOhm to 10 kOhm and 796 kOhm to 316 kOhm).

This results in this schematic:

Hope this sheds more light. Thank you very much!


texts: How to strongly fix N-type connector to thick RG cable?

texts:
Can someone tell me what kind of solder or conductive hardening paste is used here to fix the inner conductor of the cable to the pin. I tried soldering of the pin to such cables with tin, but this does not stay fixed when applying stronger tension to the RG cable and the rf-matching box is not able then to match impedance.
This solution (silver like glue from inner conductor to pin) looks professional und not soldered, but what is used here and is there a good tutorial?


texts: Register LED blink without reference to ground

texts:
I'm trying to trigger an Arduino pin based solely on the voltage across a blinking LED. I.e., when the LED blinks, I want to register the blink with the Arduino input pin. Unfortunately, I only have access to the leads of the LED, not to any other part of the circuit (I don't even have a reliable ground to connect to).

I know my multimeter can measure the voltage across the LED, so I know in principle that it is possible to capture the information, but I'm not sure how to build a circuit to do it.

A semi-working solution was to connect an optocoupler in parallel with the LED, but that (not surprisingly) caused the LED brightness to drop significantly, and additionally, the voltage difference wasn't sufficient to reliably switch the optocoupler.


texts: Set array of wires to integer value in Verilog test bench

texts:
I am writing a test bench for a module that takes an array of inputs that represents a number using the following code:

module ComparatorTest;
wire [3:0] a;
wire [3:0] b;
output aHigher, bHigher, equal;

Comparator c (a, b, aHigher, bHigher, equal);

initial begin
    $dumpfile("test.vcd");
    $dumpvars(0, ComparatorTest);

    # 0  a[3:0]=1111, b[3:0]=0000;
    # 20 a[3:0]=1111, b[3:0]=1111;
    # 40 a[3:0]=0000, b[3:0]=1111;
    # 60 $stop;
end
endmodule

I want to be able to set the arrays a and b either in base 10 or in binary like I would a number.  How do I go about doing this?  The code that I have gives me a syntax error (ComparatorTest.v:12: Syntax in assignment statement l-value.)


texts:
We need to drive a motor with around 40 Amps. The mosfet has an Rdson of about 7 mohms at 90 degrees Celsius. That is a whopping 11.2Watts of heat generated on the poor mosfet.

We are very space constrained so initially we thought we'd use a surface mount mosfet, such as D2PAK. Is it at all possible a surface mount mosfet to handle so much heat? We thought of mounting the mosfet on a large copper pad (that sort of diminishes why we chose the D2PAK in the first place though, since we can't use that board space anymore), and placing many thermal vias on that copper pad all the way to the backside of the board, and on the back, again on a large copper plane, mount an heatsink. Can we dissipate the heat in this fashion? Would the vias on the board be an effective thermal path?

Another option is to use TO220. But we can't figure out a good way to cool TO220's in our restricted space. There are individual heatsinks for TO220s on the market, but without forced airflow, most of them are capable of cooling the device down to about 80 degrees above ambient at 11.2W. That is a bit too much.

I would like to hear your experiences in cooling mosfet packages, any ideas would be appreciated.


texts:
I am not entirely sure this is the place for my question but it is the closes i found.
I am not an electrical/electronics engineer and this is my first attempt to what i am trying to do so please be patient and polite if my question is non-technical/specific or too broad.
I am trying to diagnose a motherboard which does not power up. No fans spinning, no PSU mains.
It an old one (ASUS p5k) with the P35 - ICH9 intel chipsets.
Trying to diagnose the issue i found out about the power-up sequence.
To my understanding the power-on pins on the board are high and when button is pressed they get low.
This signal (psin) goes to the SuperIO chip (winbond W83627DHG).
This chip sets low another output (psout) which goes to the southbridge.
It also sets the RSMRST signal to high (also going to the south bridge).
Then it receives the susb# signal from southbridge in order to set the PSON low and start the PSU main.
5/3.3 V standby is ok. PSU starts with ok voltages when manually triggered (PS-ON - ground connection).
Everything in the sequence seems to be ok to the point where i am supposed to receive the susb signal from the southbridge. No such signal is present.
I suspect a problem with the southbridge.
I have checked IDE,USB,SATA and pCI slots for shortings and they all seems to be ok.
What is the next step? in way that if someone who has more experice from me on repairs what would he suggest?
Thanks again.


texts: Calculating the size of a capacitor in a sample and hold circuit

texts:
Question: In sampling system the sample rate is 500 Ms/s with an input signal of range of 1 V peak−peak and a clock jitter of 1 ps rms . A performance of 60 dB is required for all signals the Nyquist baseband. Calculate its size of the capacitor.

My solution

First, I calculate the jitter power with an equation given in the book

Next, I calculate the signal power

Now, I know that SNR = Psignal/(Pjitter + PthermalNoise),

However, I seem to be getting a negative value for the thermal noise power?? My plan was to use this thermal noise power and equate it to kT/C to get my capacitor size. But the thermal power is negative?? What am I doing wrong?


texts:
I have a requirement to vary resistance according to time in finite number of steps. I have already come across a solution where we can time vary resistance value by creating a time varying voltage source with name say Vr and then assigning R = V(Vr) for resistance value but I want to achieve this using finite many values, i.e. Resistance is supposed to take only a number of values which will be varying with time and is periodic.
Any help is really appreciated.


texts:
Is there a resource that describes how CANopen frames are constructed down to the byte level?

I'm trying to decode a hex dump from a CAN bus, see the image below. The high-level CAN messages that created this data are:

# Parameter: Node Id
NodeId = 127                                                   # Node Id

#-----------------------------------------------------------------------------------------------------------------------
# Initialisation
mc.Can.SdoWr(NodeId, 0x3000, 1, 1)                             # Reset error register
mc.Can.SdoWr(NodeId, 0x3000, 1, 0x77)                          # Relative positioning 150 counts


texts: Do carbon film resistors have any effect on AC?

texts:
Carbon film resistors are basically an insulating (probably ceramic) rod covered in a carbon film that is twisted around it, as shown in the picture below:

However, this seems very similar with a coil. I know that on DC, there is no problem, but this shouldn't have some other effects on AC, like a coil? Are there any situations where this kind of resistors are avoided in AC applications?

P.S. I am sorry for using a vague terminology, but I haven't studied AC for a very long time, so I don't completely understand it and the exact effects various components have. But I know that a coil have a different effect on the current than a resistor, and I have some intuition about them.


texts:
I am planning to use this motor for a project but I am not sure if I can control the speed of this motor.

This is 100rpm motor and I would like to use a potentiometer to control speed.


texts: What does input/output resistance/impedance mean?

texts:
This keeps coming back in every single class, and I still don't have a clear idea of what it is. I keep seeing certain statements in other explanations such as "seen by X", "looking into Y" and so on. However, I don't quite get what that means?

Could you explain to me what they are intuitively, where we place them on the circuit, how we calculate them, and what would be a desired value for them?


texts: Negative part of Line level audio waveform clamped

texts:
Im trying to record output from an old synth chip (YM3812). The output waveform is centered around 2.5V with peaks at approx. 2.5 +- 1.5V. I can easily connect a pc speaker with a TSSR cable to hear the sound. I connected 2.5V to GND and the audio signal to either the left, the right or both audio channels.

My problem: If I try to record the signal with a PC line input, the signal is clamped at 2.5V. Every part of the waveform that is "negative" relative to GND is removed.

Do you know, why my speaker could handle the negative voltages, while the line input just clipped? Should I connect 0V to GND instead of 2.5V?

Edit: This is the relevant part of my circuit:

simulate this circuit – Schematic created using CircuitLab


texts: Bypassing a polarity protection diode with a part of a circuit. Dangerous?

texts:
I recently built a logic probe adapting a circuit from an old magazine. One of the modifications I introduced is adding a polarity protection diode (1N4007) in series with the positive power rail, because the probe is intended to be powered from the circuit under test and I want to avoid damaging the probe should I mistakenly connect the power rails to the wrong place.

This has led to a small error in the definition of the voltage levels the probe recognizes as HIGH and LOW. That's because the thresholds are defined by a 3-resistors divider placed across the rails, which in the original design sensed the actual supply voltage of the circuit under test, and which now suffers from a 0.7V drop due to the protection diode.

I didn't want to modify heavily the circuit, so I thought of connecting the upper leg of the divider directly to the power rail of the circuit under test, bypassing the protection diode. I simulated the circuit with LTspice and everything is fine.

Here are the schematics for the input stage and the power supply stage:

My question is: is this design decision risky in case of a polarity inversion in the rails?

In this case I reckon that the current that may flow along "wrong paths" will be heavily limited by the resistors of the divider, which are rather large. Moreover the divider is connected to the inputs of an LM358 opamp, which should be quite insensitive to reverse voltages spikes of modest energy content (it's a bipolar design, so no MOSFET gates that can be damaged by voltage spikes even if current-limited).

Am I missing something? Is my reasoning correct?

P.S.: I assume a max reverse voltage of 20V (worse scenarios are less likely, and I won't bother to design a foolproof protection scheme for those).


texts:
There have been several cases of mobile device explosion while charging and using to make call.
 There is also cases of power bank exploding  while using it to charge phone [but not plug to ac source].

Why is this happening, is there extra energy introduced in the system?


texts: In which of the LCR circuit the charge will decay faster?

texts:
Our instructor gave this problem.

  Cc << C. At time t = 0, the capacitor C has charge Q. In which circuit
  the charge Q will decay faster.

Its answer is Charge Q decays faster in (A).

I can understand the answer but I am not sure how to approach this problem if Cc << C is not given. So I what I am asking is what would be general strategy to solve such problems.


texts: Why is the switch drawn like this (NRST, STM32)?

texts:
The below part of a circuit is from the AN2586 Reference design for an STM32F1:

https://www.st.com/resource/en/application_note/cd00164185-getting-started-with-stm32f10xxx-hardware-development-stmicroelectronics.pdf

RESET goes to the NRST pin of an STM32, and the left clipped line towards a JTAG connector.

B1 is a button, but what is the advantage of having the lines near 3 and 4? What is the difference with a simple 2 pin button?


texts:
I have a schematic which uses a triac, for example a BT136. Please have a look at the attached schematic (this is a schematic for a soldering station)

What parameters from the datasheet we should take into consideration, when we are searching for a equivalent triac?

For example, if I used BT138 instead of BT136, will the soldering station work correctly?

I searched the datasheets for both BT136 and BT138, and I saw that the gate trigger current for BT138 is higher that the gate trigger current of BT136. Meanwhile, in the MOC3041 datasheet it does not mention the maximum current, only the surge current. So I can't find if the BT138 is compatible with MOC3041.

I am wondering if I can use BT138 as a substitute for BT136, in the uploaded schematic?

Datasheets

BT136-600
BT138-600.
MOC3041

Later Edit: I searched again for datasheet using the exact part number of the two components and it seems that the gate current is the same for both components. Please confirm if I am right.
I apologize.


texts: What's the best way to connect a 4-digit 7-Segment LED to Atmega168

texts:
I'm working on a device with a 4-digit 7-segment counter and wondering what is the best way to drive all the LEDs. Right now I have a custom PCB that's driving them all from an Atmega168, using most of the I/O pins. The problem is that some of the numbers appear brighter than others. For example, a "1" is brighter than an "8888".
Someone suggested that should be using an LED driver such as the TLC5940.

Is this necessary? Since it's for a wearable device, I'm trying to keep the size and power to a minimum.

The current prototype works well, but I want to make sure the digits are equally bright and as bright as they can safely be, to increase it's visibility.


texts: 8Khz vs 48Khz audio sampling and noise expectations

texts:
I'm messing around with this dac/dsp combo going into my picmx32.   Finally I have loopback stable and working cleanly at 48Khz sample rate.   This is a little too much data for me though so I want to bring the sample rate down to 8Khz.   When I do that audio still works but there are two things that bother me.

First the noise increases, or it seems to turn into a more of a hissing noise like background noise on an un-tuned radio or TV.   Maybe the noise is there but cleaner at 48Khz, I can't tell.

Second I get what sounds like a metallic tone that starts to show up when I record sound with the mic.

My question is, mainly about the noise, is this to be expected?   If this noise increase at lower sample rate is just a fundamental concept that I'm not familiar with then I'd like to learn about it.  If not I'll try to debug it more myself.   But no sense hunting it down if it's just a fact of lower sampling rates.


texts: Motor that allows threaded rod to pass through

texts: Is there a motor that can travel linearly up and down a threaded rod. I already know that you can attach a motor to the end of a threaded rod and make a nut travel along the threaded rod but this is not what I'm trying to do.  For example, if the magnets inside a stepper motor were threaded like a nut, then when the motor spins it will travel along the rod. Is there anything like this already made?


texts:
I am trying to connect a RFID reader chip to an W3113 antenna on PCB. As said in datasheets, the antenna pin of the reader chip has internal 50 ohm impedance and antenna W3113 also has 50 ohm impedance. I first use 50 ohm microstrip and a L-network matching circuit with capacitors but it does not read RFID tags.

Now I use a 50 ohm microstrip and 0 ohm resistor to connect them together. It works, but the performance of reading RFID tags is not so good. It can only read tags with really short distance. I guess this might still be the problem of impedance mismatching. I am thinking to add some capacitors to the matching circuit, but I do not know what values might be better, because both datasheets only say impedance is 50 ohm. Any advice for this? Thank you!


texts: Complete fiber optic transmitter and receiver with standard fiber optic connector and integrated power circuitry?

texts:
I am having a very difficult time trying to find a simple, completely self-contained module to convert digital signals (<2Mbps) to fiber optic, that uses a robust, standard fiber optic connector (for instance, LC).

Does anyone know if such modules even exist?

I have seen lots of modules that have internal power circuitry but have unnamed fiber connectors (e.g. this). There is a strong chance I just don't know what this is used for and how it is supposed to be attached to a standard cable.

On the other hand, I have seen modules with standard connectors but require external drive circuitry (e.g. this).

Are there none that have both standard connectors and internal drive/power circuitry??


texts: United Kingdom Split Phase Transformer / Centre Tapped Earthed (CTE) / 55V - 0V - 55V - How do you wire the connector?

texts:
I'm working on a weird project which involves making a custom cable for a British CTE Transformer. For those not in the know, these transformers are typically used at jobsites to provide 110V power. There is no neutral contact; instead, there is a -55V, a ground, and a +55V contact.
These type of transformers use IEC 60309 connectors for their outputs, with a key at the 4h (120 degree) position, like this.
My question is: Which pin is +55V, and which pin is -55V? I've been looking everywhere for this information. I'd call a company in the UK, but timezones get in the way for me.


texts:
I am on a project which nearly completed. But what remains is balancing. My project is making a quadcopter. All the programing and hardware stuff is completed. But when i fly it, it doesnt goes up, it goes to a side so i just take it down again. I tried different balancing tecniques, using mpu6050. The procedure for balancing i use is;
Find the accelerometer values from mpu6050.
If lets say ax is less than 0 then speed up one side motor and slow down other motor, and similarly other. But that doesnt work,
Please show me how can i balancing it, because that methods are not working for me. And if i am off topic please point me where to ask this question.


texts:
I built a circuit with a 5V power supply and a 300-ohm resistor. With a multimeter I did the measurements of resistance, voltage, and current across the resistor. The values were:

\$R = 298 \mathrm{\Omega} \$

\$E = 4.94 \mathrm{V}\$

\$I  = 16 \mathrm{mA}\$

So I made the calcs to obtain the power dissipated by the resistor:

\$P = EI = 4.94 \cdot 0.016 = 79 \mathrm{mW} \$

\$P = \dfrac{E^2}{R} = \dfrac{4.94^2}{298} = 81.9 \mathrm{mW} \$

\$P = I^2 \cdot R = 0.016^2 \cdot 298 = 76.3 \mathrm{mW}\$

My question is: Why there are differences between the power results? It's because of the lack of precision in measurements, the increase of resistor's resistance when powered or a combination of both?


texts: Multiplexer CD74HC4051, always giving a true out

texts:
I'm testing a multiplexer from Texas Instruments (CD74HC4051). Both +5V and Ground rails are connected to the Arduino Duemilanove board.

I've got a +5V signal in the channel A7 (pin4) and A0 (pin 13), moving my address selectors to different addresses than A0 and A7 still keeps the output active.

When dashing through all the 8 addresses, the output is basically always +5V.

How come?

The images below are: the CD74HC4051 pinout, my setup connections, and the 4051 truth table. The photos at the end of the post show three different address configurations.

CD74HC4051 Pinout:

Setup connections:

Photo 1 - Address False, False, False:

Photo 2 - Address True, False, False:

Photo 3 - Address True, True, True:

Below is the schematics with the pull down resistors. This solves the impedance issue of the IC pin internal resistance and possible noise and float signal to the pin.


texts: Headphone OUT to microphone IN for mobile phones

texts:
My AIM is to feed audio to mobile phones over MIC IN port. This audio would be coming from Laptop's headset out port. The way i am testing is making call from the test device which is connected to my laptop. What is want is to hear the audio which been played on system at the call termination mobile device.  I tested the these two circuits and here are my observation :

Circuit 1 : NO audio received at the terminating mobile. May be the resistor values are too high. I didn't tired with lower resistor values.

Circuit 2 : Audio was received at the terminating mobile device but was very low. I removed resistor and capacitor both and tested directly.Audio became loud enough but quality was poor. There was too much of 'air' like audio with some high peak audio loss too. i just connected capacitor and tested. Audio became little low but quality was still poor.

Please suggest how this conversion is possible, maintaining  high audio quality ? May be i am using too high capacitor and resistor?

Circuit 1:

Circuit 2:


texts: Different package size of the same component

texts:
I am trying to create different package of the same component(grid size), with same pins. Thought that package variant is what I need. However it looks like I can't have same package with different variant names. Those are referring to the same package. If I change size of one variant, another is also changed. Now I am confused about variant.

Update:

one more attempt to explain question. As far as I understood variant is applicable for each unique package. So I created two identical packages, then gave unique variants to each.

My expectation was that variant will make my package unique and I could have different size of part in each package variant. But it looks like variant is just label and package itself should be unique. In other words if I want to create two packages with little difference of the same device, then I have to create two different packages. I really don't see the use of variant, at least within my subject.


texts: Is there any risk when battery packs are connected in parallel?

texts:
I bought several battery packs each of which I intend to fill with 3 non-rechargeable alkaline metal-encased AA batteries and connecting all the packs in parallel.
All the batteries are of the same type, they also have the same nominal voltage, brand and product name.
I wonder, is there any risk that I should know of? I am mainly concerned about the possibility of one of the batteries failing — can we get a short circuit with the batteries possibly catching or causing fire?
Thank you.
EDIT: I use only new unused batteries.
I also used my voltmeter and verified that each battery pack individually provides ~4.5 V.


texts: How to prevent short circuit between output pins

texts:
I am trying to hack some signals coming from an old computer going to a Floppy drive using an ATtiny1614 microcontroller.
Normally the computer has full control of the signal lines but at some window in time, the computer is decoupled and MCU takes over.

The signal lines (I am using 4, but for simplicity I have drawn only one) are cut off using a CBT3257 FET 4x 2:1 (de)multiplexer as not to disrupt the original timings, since it's high speed.
Switching is controlled by the MCU pulling the output-enable (_OE) on the switch high which turns the switch output to high impedance, then making the SEL pin on the MCU an output.

Vcc is 5V TTL everywhere
No info on the current the computer can sink or source, or on the Floppy
ATtiny can sink/source 45mA max per pin
I cannot use the secondary input pins of the switch on 2 of the 4 ports since I am using those to switch 2 select lines around.

problem
If there is a bug in the MCU software it can occur that both the switch and MCU outputs are enabled, which then can short.
What can I do to protect the circuit in case I mess up the software?
Preferably using fairly inexpensive components, and not too many. I would like to avoid another IC.
what I've tried

I need about 122 Ohm to limit 5.5V TTL to limit the sink/source current of the ATtiny's pins to a a safe 45mA. This can be implemented by putting down two 68 Ohm resistors on the line. The Floppy, however, fails to respond properly using anything much above 22 Ohm (as per the picture).
Wether this is because the signal gets too weak, voltages out of spec or some timing issue maybe due to a capacitive effect I don't know.
replacing the CBT with a 74LS257, which has proper TTL output, to boost the output and enable me to maybe use a higher resistor on the line, but this resulted in timing errors.
AND-ing the lines from the switch and the MCU using diodes and pull-up resistor, but this also caused the computer-floppy communication to fail.

I have access to an 8 port logic analyser with digital (I assume CMOS level) inputs and an analog Scope (so no memory).
Any ideas? Thanks


texts: Help with producing a circuit that costs 17, then 9

texts:
I'm am completely stuck on this question:

We want to design a circuit that determines if a four-bit number is less than 10 and is also even.

a. (10 points) Write an expression of M such that M=1 if the four-bit number X (x3 x2 x1 x0) is less than 10
and is also even.

b. (20 points) Using only NOT gates, AND gates, and OR gates, show that the cost of the circuit you
produced in part a can be implemented with a cost of 17.

c. (15 points) After further inquiry, we have determined that it is not strictly necessary that M=1 in order
to determine if X matches our criteria. Write the expression for M̅, the complement of M.

d. (15 points) Draw the circuit which implements M̅, using only NOT, AND, and OR gates. Show that the
cost of the circuit produced in part c is 9.

Ok so I did part a and got this formula: f(X3,X2,X1,X0) = X3'X0' + X2'X1'X0'.

I had M = (0, 2, 4, 6, 8), which is where I got the above equation from.

My problem is that in part b, I keep getting a cost of 18, not 17. I even used a digital logic calculator to help figure it out, but no matter what, even adding the 10 or removing the 0 and such, I can never get a cost of 17.

I can't even get a cost of 9 for part d.

Is there a typo in this problem or something? How is a cost of 9 even possible? Did I do this problem incorrectly? I've spent so much time on it and tried every possible solution, but I cannot get a cost of 17 or 9.

EDIT: the cost is calculated as follows, example: a 2 input AND gate would have a cost of 3 (2 inputs, plus the gate itself). Not gates have a cost of 2 (one gate plus one input). So for part b, I keep getting a cost of 18 because of 4 NOT gates = 8, one AND gate with 3 inputs, and one AND gate with 2 inputs = 7, and one OR gate with 2 inputs = 3, therefore 8 + 7 + 3 = 18.


texts: Multiple LED's, one controller, diagram included

texts:
I want to make sure that my logic is correct and this would work.

I'm trying to control 5, 16.4' LED strips of 5050 RGB SMD's at 60 LEDs/m or 300/strip.  I want all of them to be ran off the single controller.

I believe my 360w power supply would be enough (extreme overkill?).  I came up with an idea to use terminal blocks to run the LEDs as opposed to direct connecting them to the signal amplifier.  The purpose of this was so that I can use ring terminals to connect two of the LED strips to the terminal block, then have one set of wires running to the amplifier.

I plan to run the output from the controller to another terminal block and connect the signal/power amplifiers to that.  The RF controller has the power to run a single 5050 strip on its own so I figure I would directly connect it to this terminal block.

In case you can't see it in the photo:

LED Specs are 60w max per strip, 8.64 watts/meter operating wattage or 43.2w/single strip.  My diagram shows this wrong.

RGB Controller is a 12-24v/12A output, 12v input

Power supply is a Regulated Switching, 3-channel, 360w power supply, 12v/30A output.

Extra large diagram link:  https://www.dropbox.com/s/q7kdv4amaaidg03/LED-Diagram.png?dl=0


texts:
I’m currently using a Hitec HS-645MG servo to swing a piece of thick piano wire approximately 2ft long in a 180 degree arc. Servo being controlled via Arduino.

It needs to swing back and forth quickly.

I was able to get it to do the motion but the servo makes quite a bit of noise.

Any way to make it quiet? Perhaps I’m using the wrong component? Maybe there’s something else than a servo that doesn’t make as much noise?