texts: How does voltage/current limits work in switches?

texts:
I want to get a rotary switch, it says that it can handle 600 V and 40 A. I will use it to turn ON two DC brushed motors of 12 V 20 A. So, the voltage is way too high but the current is just right.

If the current goes above 40 A will the switch work? The voltage is just 12V.

Rotary switch


texts: Controlling multiple RGB leds with PWM from a Atmega328P using one transistor per color

texts:
I want to be able to control 9 RGB leds, each color from a potentiometer.
Each color needs 20mA, so when all the colors are present the leds will need 540mA (9*3=27, 27*20mA=540mA).

My RGBs leds are common cathode so between the micro controller and the anode for every color y will put a transistor(TIP31C), with this configuration:

Do you think it will work? or I will need another voltage source? since I am giving just 5v to the micro controller.

Thanks for any advice in this project.


texts: PLD, FPGA or microcontroller for PWM decode?

texts:
I need to handle PWM output from a single channel of an R/C receiver. I want to count the width of the pulse roughly in 4ms increments, and based on different widths take action by switching LEDs (20-40 mA) on and off.

I know how to do this using an Arduino but would like to know if it is possible to do the same thing using a simpler (and cheaper) programmable device such as a CPLD or small-scale FPGA. Basically I need to time the pulse edges and manage the on-off states of outputs. If the outputs can sink the LED current so I don't need to add transistors, that would be a plus. Ideally I'd like to be able to handle steady state as well as flashing.

There seem to be a lot of parts that can generate PWM (i.e. motor drivers) but not as many examples of PWM decode, apart from Arduino examples. Which device(s) would you use to solve this problem?


texts: 3v output to switch on transistor for 5v fan

texts:
Im having trouble selecting resistors for my circuit. I have a 5v supply and my wemos board has a digital pin output of 3v.

I want to use the wemos output pin to switch a transistor (BC547) on to power my 5v fan. Without resistors im only getting 2.5 which is odd as i definitely have 5v at the transistor collector.


texts: Should I connect 4 solar panels (3.6v 900/1A) in parallel, in series or independently to the PCB to gain better power outcome?

texts:
Good morning,
I have 4 solar panels with 3.6v 900/1A each, ~3.4W.
I would like to connect them using a PCB to be able to charge an internal lipo battery, a smartphone or other devices.
My question is: should I connect them in series, in parallel or independently to the PCB to gain better power outcome?
Please bare in mind:

The panels will be displayed all at the same time or just one and the rest kept in the dark.
If connected independently, the wires will be respectively 9cm, 23cm, 36cm, 50cm, in the parallel or serial cases only less than 1cm each, except the first that will still be 9cm).
The possibility to connect all of them in series, bring the benefit to increase the voltage, a downside of these panels, but consider will bring the voltage input in a range of 2/14.4v, as when only a single panel is displayed the initial voltage when it could start to produce energy is ~2v.

The benefit I see in using an independent connection is a more efficient energy harvesting when only one panel is displayed (9cm wires) and the rest of the panels are kept in the dark.
In my understanding in this case the rest of the panel acts as a resistance.
The downside I see of this solution is the excessive wiring could cause the same problem when all panels are displayed as such long wires could increase the resistance as well.
Also it will span the range of incomming Amperage between few mA and 4A.
Thanks in advance for your advice
Andrea


texts:
What is the maximum temperature you would recommend for an isolated trace on the surface of FR-4? (I.e.: not an inner-layer track.) Is there an IPC recommendation? Does it really matter if it is past the glass transition temperature? (What is this value for FR-4? Wikipedia says "above 120C".) I mean, even if it's soft, will the track still stick with high reliability? 'Suppose what I'm looking for is a MTTF vs. temperature (vs. trace area) set of curves, but experienced guesses are encouraged.

This is useful when calculating trace widths vs. temperature rise. I've always limited traces to the lower of about 100C or whatever the connected parts can manage.

[For the Mech-E, Chem-E, and Mat-E: I guess the question can be boiled down to the intersection of shear stress between copper and FR-4 caused by differences in thermal expansion, which would be related to track width, and the decrease in shear modulus as temperature rises.]


texts:
I was reading the following tutorial from Analog Devices:

https://www.analog.com/media/en/training-seminars/tutorials/MT-040.pdf

They include the following image and state:

  In most op amp circuits, the inverting input impedance is reduced to a very low value by negative feedback, and only Zcm+ and Zdiff are of importance

I don't understand this point. How is Zcm- swamped by negative feedback and how can it possibly be reduced to a low value? Then the output of a follower would have to supply large current into the inverting input terminal, which is obviously not the case. To me it would make more sense to say that Zdiff is bootstapped by negative feedback and Zcm+ and Zcm- are therefore the only impedances that are significant.

What does Analog Devices mean by this quote?


texts: Use of output inductor for high-voltage supply circuit

texts:
I am in the early stages of designing an adjustable high-voltage DC/DC converter (similar to the EMCO C80 module) and one of the goals is to be able to closely monitor & respond to the output current (e.g. if we sense arcing in the application we want to reduce the output voltage). As a result, I am wondering if instead of using capacitors to filter/buffer the output I might be able to use inductors for this (help maintain stable current).

Is this feasible? Should I be concerned about the withstanding voltage? Despite being used in a high-voltage supply, there shouldn't be much voltage across the inductor. What are some things I should be keeping in mind?

Update:
This supply is used to generate a corona, which will result in some small current (~50uA?). If the current suddenly rises to a higher level that indicates a fault (i.e. arcing or short). My current design uses a full-wave Greinacher/Cockcroft–Walton multiplier. There is a capacitor at the HV output to reduce the ripple, but I am wondering if this possibly also reduces its ability to limit current (capacitor could supply a burst) or if I should care. Are there simpler ways to limit output current than monitoring it (e.g. via shunt + op-amp) and using that as feedback?


texts: How can brushless DC motor has constant torque?

texts:
Have read somewhere, that brushless DC motors have constant torque.

How can this be true?

Regard motor on the picture:

If constant current flows as red arrows indicate, the magnetic field appears as blue arrows indicate. The permanent magnet (not shown) tends to put it's N and S poles appropriate.

All this time, the current remains constant.

Then how the torque can be constant, as the magnet approaches it's final position? Isn't torque decreasing as this happening?

Wouldn't it be more constant torque, if I power the winding coils with three phase sinusoidal current, having phase ahead by some value relative to rotor?


texts: How many (m)W should 120 ohm CAN bus terminators have?

texts:
When I started with Arduino I bought a set of 600 resistors (30 times 20 values). However, I found out 120 ohm needed for CAN bus is not among them.

So I need to buy 120 ohm resistors (I don't want to combine multiple). However, I was wondering how many watts they should handle.

I want to connect two or later maybe three devices, all running on USB power (5V). But I cannot find how many (m)A CAN is using.

My calculations:

V = I * R <=> 5 = I * 120 <=> I = 5 / 120 = 41,7 mA

P = I * V = 0,041666 * 5 = 0.208W

or:

P = I^2 * R = 0.041666 0.208W

So I would be safe with default (0.25W) 120 ohm resistors?


texts: How to use an Arduino to turn a supply voltage to another device on and off?

texts:
The Question:
With what kind of extra components if needed, can I use to output a signal out of one of the Arduino pins to turn the voltage on and off to a device. The goal is to output a HIGH or LOW on a certain OUTPUT PIN to turn this device on and off.

The Limitations:
I can't power this device with a pin from Arduino directly(I think..). Trying to find a simple solution, I don't have access to too many intricate parts, other than a NAND gate and a bunch of resistors and capacitors.

The Solutions??:
I can get my hands on some additional components such as relays or if there is some sort of a voltage control switch with a transistor I can be setting up here to turn a 5 Volt supply on an off, if the max current I can deliver from my arduino pin is 40 mA, how would I go about setting up that circuit if thats a possible solution? Help much appreciated!

extra details:
https://www.walmart.ca/en/ip/laser-x-2-player-blasters/6000196696362
The device I am trying to turn on and off, if a certain OUTPUT pin on my Arduino is set to LOW.


texts:
simulate this circuit – Schematic created using CircuitLab

How to solve this circuit for Thevenin and Norton circuit given RL in the circuit.
My guess is to remove RL (open circuit). But I'm unsure where the Voc will be measured.


texts: Modifying LM334 reference schematic to 100uA/500mV

texts:
I'm trying to understand how to modify the circuit below to provide a 100uA constant current drain and 500mV Vds for an ISFET.

Based on the help so far, this is the schematic I've come up with:


texts: Using Raspberry Pi to write to an EEPROM

texts:
I've been trying to use a Raspberry Pi as an EEPROM programmer, and I haven't had much luck. The EEPROM in question is the AT28C64B, and I have yet to be able to write anything to it even manually. I've given it 5V in Vcc and tried to disable write protection, but nothing seems to work. I can read from it just fine, but I can't seem to be able to write to it. the code of the write operation is in python.

    self.ce.on()
    self.oe.on()
    self.ce.off()
    self.address.value = address
    self.we.off()
    sleep(50e-9)
    self.data.value = data
    sleep(150e-9)
    self.we.on()
    self.ce.on()


texts: I need help with hairpin filter design. Can anyone help me with the design steps and equations?

texts: I have the coupled line design. But don't know how to convert it to a hairpin structure.


texts: Extremely Simple reliable way to switch logic level signals

texts:
I am designing a failsafe system for an Unmanned Aerial Vehicle, and it needs to be able to switch 6 PWM outputs from one source to another. My initial thought was to use a series of logic level relays but they cannot fulfill all the requirements that I have listed below, what are some alternative methods I can use?

Survive intense vibration (~.3G at 300-600Hz)
Fail safe, in the event of a total loss of power the signals will flow without impediment
Listed MTBF or MCBF (hoping for around 1,000,000 Hours or 100,000 Cycles per channel)


texts: Are there PCB connectors capable of suporting more than 3.5kV of working voltage?

texts:
I was thinking of a design for bringing VCC+ and GND to a board through a PCB connector. VCC = 6 kV. It comes from external source towards a banana jack within a metal case. The first idea was to fit the PCB design into this case.

I don't find any PCB connector with 6 kV capable to support the 6 kV voltage difference from other connector with 0 V at the same PCB side. I have found some of them, Wurth, with 3.5 kV dielectric strength. This is the maximum I have found.

In this situation I thought that the material offered by my manufacturer could be a good insulator with 1.6mm --> 40 kV > 6 kV. So, if I put VCC on top side and GND on bottom side (I think of doing it this way) the connector dielectric will never fail.

But now my problem is that someone asks for me to put all the connectors at the TOP of the PCB: VCC+ and GND, in order to access both them by the same side. The connectors have only 3.5 kV of dielectric strength.

Is it possible to place the 2 connectors at top side of a PCB with these features: 6 kV between VCC+ connector and GND connector, being two connectors having a maximum voltage = 3.5kV according the manufacturer datasheet?

I need PCB connectors for supporting this 6 kV between them. I can't find any. I have looked for connectors at typical and non-typical distributors, without success. Is there a way to do this? How can I put connectors with this voltage difference between one connector and the other?

Clearance calculation does not take into account connector dielectric. I don't think it could be solved applying clearance or creepage calculations without taking into account the 3.5 kV connector dielectric strength.


texts: Short circuit vs lossless transmission line

texts: A transmission line is made of 2 conductors and a dielectric between them. Does the dielectric make these conductors different from a short circuit? Voltage drop across a short is 0, but it's the same for a lossless transmission line. Doesn't that mean that voltage and current in a short is maintained? I'm guessing that short circuits don't have characteristic impedance as a transmission line does, as characteristic impedance isn't the same as resistance. In a diagram, one can see that there is a difference between characteristic impedance of the line and impedance of the load, but I'm trying to understand why EM waves will reflect off a short after going through a transmission line if both shorts and transmission lines are wire, though transmission lines are 2 strips of wire, but with some dielectric between them.


texts: High potential between ground and neutral wires in wall outlet

texts:
I would like to test if ground connection works properly in my wall outlet. To do so, I have tried to measure voltage across ground and neutral wires. And here comes the interesting part:
U(Live, Neutral) = 198V (220 +/- 10% V AC, fine)
U(Neutral, Ground) = 89 V (What?)
U(Live, Ground) = 108 V (what?)
Yes, I know it's not correct way to test it, but at least this method should give general idea if ground works or not. In reality, resistance should also be measured.
But how can it happen that I observe such voltage ratings?


texts: How large should PCB traces be to control a solenoid?

texts:
I'm working on an electronics project that'll regulate and offboard solenoid. The leads controlling the solenoid will need to sustain fairly high levels of current. This is the solenoid I'm working with:

This is the schematic I currently have set up, with the solenoid in the top-right connecting via a screw connector. I've set the trace at 48mil.

Is this a large enough trace or will it burn up?


texts: Mid-band magnitude gain of a Cascode Amplifier

texts:
Looking to do some theoretical analysis on a Cascode Amplifier and compare it to a simulated model. Please see the circuit schematic below followed by the bode plot developed in the simulation software:

I am looking to try and obtain the Mid-band frequency gain of the amplifier (From the bode plot it can be seen to be approximately 20 dB). Any help in trying to figure this out would be greatly appreciated - so far compared Quiescent Levels which appear to match theoretical values.


texts:
I am trying to use a LA6500 to increase the current output from my MCP4725 that I am controlling with a raspberry pi. I have Pin1 attached to the output of my DAC pins 2&3 are connected to my pi's gnd, pin 4 it connected to a small fan and pin 5 is connected to a 5v pin on my pi. With this setup I was expecting the OP-Amp to output the same voltage but with more current availble but it only outputs a steady 5 v output. What am I doing wrong?

simulate this circuit – Schematic created using CircuitLab
EDIT 1
I've changed the wiring to be a follow voltage but now I can't get it to go to zero, it will go to ta high point and a midpoint but not to a zero point. Any help is appreciated sorry if this is too basic.
EDIT 2
Just wanted to say Thank You to everyone for helping me. It has been several years since I have last had to work with any OPAMPS and I am trying to reteach myself some of the stuff I have forgotten since college. This has been an informative experience.


texts: Switchmode converter for bench power supply

texts:
I want to build a bench power supply. My basic reqirements are:

0 - ~30V adjustable output voltage
0 - ~2A adjustable output current limit
input from mains

I found this design by EEVblog guy loosely fitting my requirements, except for point 3. So my idea was to insert isolated switchmode converter beetwen the mains and said circuit like this:

Swithing converter would output voltage needed at the output + linear regulator's dropout voltage. The converter would: convert 230V to lower voltage without the need of bulky transformer, isolate output from mains and reduce power dissipated on linear regulator - without converter in the worst case scenario power on the regulator could be as high as 60W in my case, while with converter outputing voltage 2V higher then output voltage maximal power on regulator equals 4W.

So I started looking for the switching converter IC that satisfies these conditions:

Isolated
Mains input voltage
0-30V adjustable output voltage
2A output current

I searched mouser, digikey and tme and didnt find single IC that satisfies both 2 and 3. Am i expecting too much from a single IC, or am i just bad at searching?

If such ICs really aren't available, would you advise me to achieve my goals in 2 separate converters (one isolated non-adjustable converter lowering voltage to <50V and second adjusting the voltage to the needed value), or rather to design my own DC-DC converter control circuit(my knowledge about switchmode power supplies is very limitted)? Or maybe the whole idea is ill-formed and the best way is to use a 50Hz transformer, large heatsink and fans?


texts: Flywheel current doesn't change direction

texts:
The motors are permanent magnet DC motors.

First I power the motor with a flywheel and a motor with no substantial load. (same kind of motor).

simulate this circuit – Schematic created using CircuitLab

I then disconnect the voltage source and the amperage dips negative for a moment and then returns to being positive. (The voltage stays positive throughout) Since the motor with the flywheel is being used as a generator shouldn't the current be always negative?

simulate this circuit


texts: How is a transconductance amplifier used to measure current?

texts:
In this post Design for a Precision LCR Meter the author says:

  Current is measured via a transconductance amplifier (again with programmable gain) which produces a voltage proportional to the current through it, but without the ‘burden voltage’ associated with a simple resistor as used in most current measurement.

How is this achieved? All the information I have found regarding the use of OTAs shows them using an input voltage to control an output current, rather than the other way around as described above.

It should be possible to measure current using a current amplifier or integrator as shown below (the integrator circuit would be the same as below except with a cap in place of R1) however both those options still require the use of a burden resistor or capacitor.

simulate this circuit – Schematic created using CircuitLab

The way the quote is worded suggests the author had a different approach in mind.

Is is possible to measure current using an OTA without the use of a burden component?
Are there any other ways to precisely measure small currents without introducing burden components?


texts: Accidentaly shorted Arduino Leonardo VIN pin to GROUND. Is my board fried for ever?

texts:
I accidentaly shorted the Vin pin to the Leonardo's GND pin and the ON led flashed. After the flash, the L led turned on with the ON led and stayed that way. Then the AtMega32u4 started to heat up fairly quickly, so of course I unplugged it. My power source at the time was DC 9.6V 600mA.
I tried pressing the reset button countless times and it doesnt do anything, and I've also tried uploading new, empty code, but the Leonardo doesnt even open the port. I guess since the AtMega is heating up, it is because something somewhere is fried. but, is that something replaceable?


texts:
I have an old Keithley 175A multimeter that has been suffering from a bit of drift lately.  Internally it uses a 6.35V zener and a couple of resistors to create a -2V reference, but the zener is obsolete and no longer available.  So I was thinking about replacing the reference circuit with something more modern but I can't seem to find a -2V reference...most of them are +2.048V.  Looking for suggestions to construct a highly accurate -2V reference.

( Scan from http://www.utwente.nl/tnw/onderwijs/practica_tnw/doc/apparatuur/multimeters/keithley175.pdf )


texts: Linear actuator power supply and remote or switch

texts:
This will be my first DIY project involving electricity so I want to make sure I buy the correct components. I'm purchasing a used telescoping column (aluminum and steel, 4000n) that has two actuators hidden within, with two cords coming out the black and red wires within each cord.

Each requires a 24V 3.5A power supply, so I assume I would need a 24V 7+ amp power supply... but then when I Google around, all I get are these crazy looking power supplies with 10-15 different connectors on one side. When I look at the 12V power supplies it's simple... they look like battery chargers, cut off the end and strip the wires, make sure it's the right amperage before I do that obviously, and bam you're done.

Can someone help me figure out what a good beginner-friendly store or brand would be? I am not asking for shopping brand advice, but for safety advice. I don't want to buy something that's going to blow up in my face or electrocute me.

I would prefer something super simple, or a link to a great guide about power supplies (all I could find was some really old information).


texts:
In the following application I want to control a DC motor powered in 24 V and about 50 W. For that I use a microcontroller of the STM32 range which will be able to provide me a PWM signal of 200 kHz. To filter this signal I would like to use a LC filter, except that I do not really know at what frequency I must filter and also what value of my L and C would be the most appropriate. Would you be able to provide me some help on this subject?
Here is the schematic of my H-bridge.
Thanks in advance.


texts: Simple blinking Led with control over both the pause rate and flash time?

texts: I was hoping someone could help me understand a very simple approach to creating a flashing led. While many simple examples exist, I cant quite find one that allows me to control both the pause rate and display duration times.. for example: led on (emitting) "10ms" led off "30ms" (repeat forever). Or perhaps I swap out a capacitor to creat "led on 500ms" led off "2ms" (repeat forever). Anyhow, I have capacitors to work with, 555 times, resistors, diodes. I'm a real beginner obviously, and do not know how to design around the 555 - but if someone has a very easy suggestion I can attempt I'd appreciate it. I'm attempting to study the effect of "charging" a glow in the dark object with a 3.3v UV Led and thought it would be neat to see the minimal amount of strobing required to energize the glow. Thanks!


texts: Why we can't use AHB in the Cortex M0 MCU?

texts:
I found coretex M0 MCU module's bus interface has not HBUSREQ and HGRANT, and HRESP when i trying to implement with AHB Bus.

Is there any way to use AHB not AHB_lite. I can't use multi-layer interconnect system. only I can use AHB.


texts: Why does Ethernet on UTP have much greater range than other modern protocols?

texts:
OCuLink, SATA, USB 3, and Displayport all provide on the order of a few Gbps per signaling pair, and are limited to a cable length of just a couple meters. Ethernet via comparable cabling provides comparable speed, but 50 times the length! For example, 10GBaseT over cat6a can do 100m. What accounts for that extreme difference?

I'm asking in electronics rather than networking since this is a physical link issue, not a networking issue.

EDIT: although latency doesn't appear to be the explanation, people have brought it up, which gave me an idea: why don't all high-speed wired protocols incorporate a latency measurement upon connection (with an upper limit of 200ms for all practical purposes), and add some fixed number of clock cycles to that measurement to establish the retry timeout value for the duration of the connection? Then the timeout is never set higher than necessary, yet all connections ranging from one meter to thousands of kilometers can be accommodated without being limited just by latency. Noise measurement and cancellation, adaptive rate, etc to achieve high speed at long range are more complex, and unnecessary for protocols designed for a few meters or maybe a few tens of meters, but just latency measurement seems very simple and worthwhile, and would avoid arbitrary latency limits like in USB 2 yet without requiring standardizing on an excessively high timeout limit. It just requires a ping, then count the clock cycles until a reply is heard. (To avoid silly misunderstandings: I don't mean ICMP ping; I mean a PHY-to-PHY ping.)


texts: What is meant by "input/output impedence" of a transistor stage in amplifiers?

texts:
I am studying BJTs (bipolar junction transistors)(npn), different types of amplifiers built with these transistors and their small signal equivalents (hybrid \$ \pi \$ - model without capacitances)  but I don't understand some of the phrases I encounter.

Example:
I am studying ASCE-stage (anti-series common emitter configuration) (also known as differential stage) at this moment and its small signal equivalent.

I have not mastered the biasing of transistors yet, hence minimalistic amplifier stage:

ASCE-stage:

Small signal equvalent:

According to the book, ASCE-stage has "high input impedance". Like, I don't understand where that impedance is being "measured". Do you just "measure" it across the input terminal of the small signal equivalent? What is its impedance then?

I have been trying to understand that for a while now and I would appreciate any advice I receive.


texts: Why is there a lower limit on amplification for this filter design method?

texts:
I'm designing an active low-pass filter for a differential input. The input is on a ±100V scale and needs to be scaled down to the standard ±10V scale.

I found this application note which describes how to design a 2nd order multiple feedback filter and convert it to differential inputs:

http://www.cirrus.com/en/pubs/appNote/AN048Rev2.pdf

However, they state in their first step that the magnitude of the amplification factor H0 needs to be at least one, without giving a reason (in our case H_0 = -0.1).

I don't see a reason for such a restriction, so I ignored it and designed such a filter (Bessel, with about 9kHz corner frequency) and it seems to work as expected, both when simulated with LT-Spice and in hardware.

Does anybody know where this condition originates?  Is it a real restriction, or is it just arbitrary, maybe copied from somewhere without understanding the math behind it? Is it maybe because you would tend to use a different topology for gain less than one, though there is nothing really wrong in using multiple feedback?

Curiously, TI's Filter Pro also didn't let me enter anything less than 1 for the amplification.


texts: Why is vo = 0 when VI(gate voltage) = 0. Also why is are both mosfets operating in the saturation region . Could someone explain why this is so?

texts:
According to the book Vo =0 when VI(gate-voltage) = 0. Why is that so?

Why does the book also assume that both mosfets are operating in the saturation region? when VI = 0.
I appreciate the help. Thanks alot


texts: Error Analysis due to Voltmeter Constraints

texts:
I got a situation: at the moment I am unable to access both channels for Keithley 2182A nanovoltmeter using LabVIEW. However, for some odd reason, while I cannot access the channels at once, LabVIEW does give me the ability to access channel 1 and the ratio between the two channels - from which I use those points to find channel 2.

However, again, because of my hardware, it appears I would need a minimum of two measurements (the minimum size of my buffer is of two), so I am wondering if the following decisions are sound with experimental good practices:

Given that I get two measurements for channel 1 (V1), I cannot just pick one of them (either at random or deliberately) so I calculate the mean of the two measurements and keep the mean measurement of V1.
Likewise, given two measurements of the Ratio of channels 1 and 2 (V1/V2), I too calculate the mean and keep the mean measurement of V1/V2.
And finally, I calculate the ratio between these two measurements to yield the mean of channel 2 (V2).

Right now this is just a draft, proof-of-concept so I can do some measurements to teach myself basic lab techniques. However, I also know, from experience, that what I just described sounds like really bad in terms of error propagation. For instance, I think I can able to stand by steps 1 and 2 in terms of error propagation, but the third step, the ratio, I am wondering: how bad is this ratio measurement in terms of error propagation?

Also, any books, papers, etc about experimental techniques in electronics would be greatly appreciated!


texts: How to place components automatically according to a script in eagle cad?

texts: I am using eagle cad to design a clock with smd leds .There are 60 leds and i'll place those leds on a circle pattern which like an analog clock is there any way i can do this easily like a script or can i export components coordinates and angle data to a file then i can change them with a vim macro then import again ?


texts:
I'm trying to power a microcontroller (ESP8266) from a solar cell and a supercapacitor. It might or might not make sense, but it's a hobby project.
The thing is - ESP8266 doesn't boot if the voltage is brought up from 0 gradually. Either the main microcontroller or the flash memory fail to get in an operational state when the solar cell is slowly charging the supercap.
I've tried using a supervisor to toggle its EN pin, but apparently that doesn't work either, and even if it did work, I'm fairly confident the narrow hysteresis of the supervisor would make it unusable.
The MCU in question draws upwards of 70 mA when in normal operation (let's say 100 mA to be safe). I don't really need it to run "forever", and its nominal operational range is from 3.6V down to 2.5V. I'm perfectly fine, for what I want to do with it, if it turns on at 3.6V and then depletes the supercap (or not, depending on sunlight and my 150 mA nominal solar cell) until it reaches 2.5V.
I've searched around for a supervisor with such a range but can't find anything simple-ish and through-hole. Is there a simple way, with through-hole components, to make a supervisor-like circuit with a large hysteresis, which would power the MCU?


texts: How can I identify what is the maximum frequency for iron core power inductors?

texts:
I have a couple of yellow-white inductors like this:

I can't find any datasheet and I don't know what is the maximum frequency where I can use these.

How can I measure it?


texts: What did I do wrong - recharging sealed lead-acid battery with recycled computer PSU

texts:
Today I took an old computer power supply, stripped the yellow +12v and the black ground, and twisted half of them together each into 4 separate pairs. I then took a lead acid battery, which seemed to have no fluid left, and tested it to have 0V. I then filled it with diluted* battery acid and tested it immediately above 12V. I connected the red+ terminal of the battery to my unplugged +12V PSU and the black- terminal to the ground of the same, still unplugged, psu. It began to spin the fans of the PSU and I could tell it was being powered. I reversed the direction to place the black- to the +12v PSU and the red+ to the black ground of the psu, still unplugged. I saw a small whiff of smoke come from the PSU and removed the connection as quickly as I could.
Neither of these results is what I expected, my anticipation was that I should be connecting red+ to the +12V and the black- to the ground in order to charge the battery, but it did reach 12V immediately after being filled. My question is - what happened here? Was there an excess of latent electrical charge on the plates and the battery acid was enough to reinvigorate them without any further charging? Was there such an excess of electricity that it was flowing "against stream" in a way since there was no current flowing when I connected the terminals? Do I just not know anything about how electricity flows?
I appreciate any elaboration you can provide this novice, thank you.
Edit: I should note that I also twisted together the green and ground on the computer PSU in order to indicate an "on" status for it. It was unplugged from electrical supply the entire experiment though.
*Diluted battery acid using distilled water and sulfuric acid. It arrived this way already. The packaging is uncertain but reviews indicate ~30-35% sulfuric acid by volume so mostly just distilled water.


texts:
I've recently made a test in our laboratory at the University.

We have a 3 phase synchronous generator connected to a synchronous motor.

The generator has its exciter coil connected to an external power supply.

Our professor says that in this case, when there is no load connected at the output of the generator, the mechanical power consumed \$P\$ is:

$$P = P_\text{loss, mechanic} + I_0^2 R_0 + P_\text{loss, iron}$$

I understand that the generator has losses due the friction.

I also understand that the generator has some losses due the magnetization of the stator.

The problem is that I cannot understand why the losses in the exciter coil affects the mechanical power drained from the motor.

I think, this power loss affects the external power supply connected to the exciter coil.

Is that right?

If not, can somebody explain me this effect?


texts: Is there any reason as to why the schematic symbol of comparators is almost equivalent to that of op amps?

texts: They do similar tasks, but they are almost completely different because comparators output digital signals. In that case, I am confused as to why their schematic symbol is almost entirely the same. Is it implying something else that I am not realizing?


texts: Implementing logic expression and the truth table of logic function

texts:
(a) Expression for \$Z\$

\$Z=(B+\overline{C})A+B(C+\overline{D})+BD\$

\$Z=AB+A\overline{C}+BC+B\overline{D}+BD\$

\$Z=AB+\overline{A}C+B\$

\$Z=B+A\overline{C}\$

(b) Truth table

A B C || Z
==========
0 0 0 || 0
0 0 1 || 0
0 1 0 || 1
0 1 1 || 1
1 0 0 || 1
1 0 1 || 0
1 1 0 || 1
1 1 1 || 1

(c) Karnaugh Map

       | BC  00  01 11 10
 ------------------------
 A  0  |     0  1  1  1

    1  |     1  0  1  1

I was sure about what the last two questions (d) and (e) were asking me. Can anyone provide some guidance on how to solve these last two questions? Thank you in advance.


texts: Circuit for controlling AC signal polarity in real-time

texts:
I'm going to start a project on a controlling speaker array and I need to control the signal's polarity fed into each speaker. I want to make a 'router' or 'controller' to make it easy, so I don't have to change all the wiring when I want to change the polarity distribution.

I googled some keywords and found H-bridge IC. But I'm not sure if that is compatible with AC signal. Besides, I'm afraid of controller size, because I need the controller for speaker ARRAY including many speakers, at least 9.

So, anyone who has an idea how can I solve the problem would be appreciated, very much. Now I'm thinking about kind of multi-channel connector that I can assign the signal to each port. (e.g., (+) signal to 1,3 port and (-) signal to 2,4 port)

Thanks for reading, I'm waiting for the advice. Have a nice day!


texts: Importing Drawings ( DXF,DWG ) in Altium

texts:
I'm having trouble importing DXF / DWG into Altium.

I followed File-->Import-->selected my dxf,dwg-->config-->Information show Done!!-->and nothing shows up on my mechanical layer.

I'm using Altium Version 15.1

Any tips or workarounds ?  THK


texts: Reduce number of switches for amplifier with two power sources

texts:
I am building a bluetooth speaker with two power sources: AC power supply and LiPo battery with a charging module (BMS PCM).  As you can see from the diagram I have three switches.  The goal is to allow for several states:
1. Speaker working on Battery module
2. Speaker working on Power Supply
3. Speaker off, but Power Supply is charging the battery
I don't like the fact that there are three switches for this and the operator has to know different sequences for s1, s2, s3 positions in order to operate the bluetooth speaker.  Is there a smarter way to manage this using different logic?


texts:
I have the ADS4249 differential ADC from Texas Instruments here is the datasheet.
On page 55 it says:

For a full-scale differential input, each input pin (INP and INM) must swing symmetrically between
VCM + 0.5 V and VCM – 0.5 V, resulting in a 2-VPP differential input swing

So I have a single ended signal that is converted to a differential one with an opamp (lets assume a gain of 1) and biased to VCM and fed into the INP and INM ports of the ADC.
To get the full scale differential input my single ended signal has to swing between VCM-0.5V and VCM+0.5V. But my single ended signal never becomes negative. It swings from 0V to 0.5V.
How can it be done that I stil get the full-scale differential input on INP and INM?
If it swings from 0V to 1V will I get the full scale differential input?
Here is the schematic:


texts: STM32 - Problem debugging using openocd and st-link

texts:
I am trying to follow this guide "Installing a toolchain for Cortex-M3/STM32 on GNU/Linux" (available: https://www.olimex.com/Products/ARM/ST/STM32-H103/) with the STM32-H103 development board from Olimex. Everything works as expected up till the point where I need to copy my compiled program into flash using openocd.

Following the instructions I start the openocd server ('openocd -f openocd.cfg') and then telnet ('telnet localhost 4444'). Initially starting the openocd server fails to start giving the output:

Info : This adapter doesn't support configurable speed
Info : STLINK v2 JTAG v23 API v2 SWIM v4 VID 0x0483 PID 0x3748
Info : Target voltage: 2.038896
Error: init mode failed
in procedure 'transport'
in procedure 'init'

trying again however seems to work... However 0 breakpoints and watchpoints seems suspicious.

Info : This adapter doesn't support configurable speed
Info : STLINK v2 JTAG v23 API v2 SWIM v4 VID 0x0483 PID 0x3748
Info : Target voltage: 2.054665
Info : stm32f1x.cpu: hardware has 0 breakpoints, 0 watchpoints

In this state I can't halt or probe the device.

> reset halt

in procedure 'reset'
> flash probe 0
Cannot identify target as a stm32x
auto_probe failed
in procedure 'flash'

I then found this article on the NuttX website (http://nuttx.org/doku.php?id=wiki:howtos:jtag-debugging) which seems to help me slightly (I am not using the NuttX RTOS however, just bare metal). By following the article and holding the reset button until the 'reset halt' command times out I can successfully probe the device. Also note there are now 6 breakpoints and 4 watchpoints.

Info : This adapter doesn't support configurable speed
Info : STLINK v2 JTAG v23 API v2 SWIM v4 VID 0x0483 PID 0x3748
Info : Target voltage: 2.047244
Info : stm32f1x.cpu: hardware has 6 breakpoints, 4 watchpoints

> reset halt
timed out while waiting for target halted
TARGET: stm32f1x.cpu - Not halted

in procedure 'reset'
target state: halted
target halted due to debug-request, current mode: Thread
xPSR: 0x01000000 pc: 0x08000250 msp: 0x20005000
> flash probe 0
device id = 0x20036410
flash size = 128kbytes
device id = 0x20036410
flash size = 128kbytes
flash 'stm32f1x' found at 0x08000000

However then when I program and run the device I get the following error output..

> stm32f1x mass_erase 0
stm32x mass erase complete
> flash write_bank 0 main.bin 0
wrote 9704 bytes from file main.bin to flash bank 0 at offset 0x00000000 in 0.719990s (13.162 KiB/s)
> reset run

in procedure 'reset'
jtag status contains invalid mode value - communication failure
Polling target stm32f1x.cpu failed, GDB will be halted. Polling again in 100ms
jtag status contains invalid mode value - communication failure
Polling target stm32f1x.cpu failed, GDB will be halted. Polling again in 300ms
jtag status contains invalid mode value - communication failure
Polling target stm32f1x.cpu failed, GDB will be halted. Polling again in 700ms
jtag status contains invalid mode value - communication failure
Polling target stm32f1x.cpu failed, GDB will be halted. Polling again in 1500ms
jtag status contains invalid mode value - communication failure
Polling target stm32f1x.cpu failed, GDB will be halted. Polling again in 3100ms

At this stage I can't see the LED flashing on the board like the guide suggests will happen. Does anyone have any idea what is going wrong?

[EDIT] I have found flashing the main.elf file (instead of main.bin) does not cause the errors above to be output after 'reset run', however I still do not see the LED blinking.

Then using gdb with the command 'arm-none-eabi-gdb -tui --eval-command="target remote localhost:3333" main.elf'.

If I input 'c' for continue I get

(gdb) c
Continuing.

Program received signal SIGINT, Interrupt.
0x00010100 in ?? ()

And if I input 's' for step through I get

(gdb) s
Cannot find bounds of current function


texts: How to choose resistors(RD & RL) for optocoupler circuit

texts:
I am working on a project in which I am driving 6 ultrasonic sensor 4  of them are NPN (NC) and 2 of them are NPN  (NO) ,for safety of the MCU I am using optocoupler EL817 for isolation between sensors and MCU but I am going through very unreliable behaviour of the circuit ,my all sensors work initially but after some time 2 of them does not give proper output voltage I am using pull-up circuitry as mentioned in the <img src="https://i.stack.imgur.com/wcT9K.jpg" alt="figure
" />, technically when there is input from sensor the output pin of optocoupler give voltage reading LOW and when there is no input from sensor output voltage at the optocoupler output pin will be 3.3V (Vcc) but optocoupler circuit for 2 sensors initially show correct voltage but after some time even there is input from sensor output voltage at optocoupler output pin show (2.9) V but it should show (0.70V) and if I put sensors in LOW voltage from 2.9V change to 3.3V
So I think this voltage swing is due to improper calculations of resistors in the optocoupler circuitry
Suggest me if is there any other factor . Please suggest me how I can calculate Ic , If , RL and RD for the optocoupler circuit

NPN (NO) sensor operating voltage 10-30 V I am operating at 24V
NPN (NC) sensor operating voltage 10-30 V I am operating at 24V
3.Output current of both sensor <200mA
4.MCU GPIO pin current 8mA
VCC is 3.3 V
In my case input from sensor is 24V and Rd=2.6K and RL=4.7K


texts: Schematic review: STM32 Bluetooth antenna

texts:
I am working on a device based on the STM32WB55xx line of microcontrollers.
In the latest revision of the PCB, I altered the antenna filter and chip antenna components to better match the device documentation. However, the device is now failing to connect to a phone over Bluetooth, while the previous version connects just fine. I'm looking for feedback on the schematic design, so we can try to determine whether our bug is in hardware or in firmware.
Here is the original Bluetooth antenna schematic:

And here is my new antenna schematic:

Here's the microcontroller datasheet guidance on the RF subsystem:

Finally, here is an excerpt from the ST AN5165 reference document, which specifies the antenna filter specific to the 100-ball BGA package type we're using:

Is there anything I'm missing at the schematic level? I think I have implemented ST's guidance correctly. If the schematic looks okay, I intend to post a follow-up question focused on layout.
On page 40 of AN5165, the document reads:

"As a conclusion, the IPD reference MLPF-WB55-01E3 can replace the RF output network of
the STM32WB for the QFN packages (an antenna filter is still needed) for a 2-layer PCB."

Does this imply that the output filter from the microcontroller and the input filter to the antenna are two separate filters? I assumed that there should be one filter between the microcontroller and the chip antenna, but now that it's not working, I'm revisiting my assumptions. I'm noticing that the original schematic has the Murata bandpass filter chip, and then an additional pi filter before the antenna.
Do I need to add an additional filter stage between the ST IPD chip and the antenna? Or does my schematic look okay as is?


texts:
I have a PCB that is exposed to a sharp inductive-voltage collapse, around 100V/100nsec. The voltage collapse happens when the current through a transorb reaches zero. When this happens, the board and everything connected to it rings. At this point the board is turned off, nothing is happening, all activity stopped many usec ago, and the ringing is not large enough to turn anything on: it barely touches the power circuits on the board. The fast signal is directly connected to a bunch of power FETS (all well off) and not much else.

It creates a lot of conducted emission, and enough radiated emmission to cause a problem on a comms line routed around the edge of the board.

What should I be measuring, what should I be asking, how do I describe the problem, what do I have to know to ask a sensible question?


texts:
How much time does the nrf24l01+ take to switch frequency through RF_CH?
Can this switching time be parallel to switch between Tx/Rx/Standby modes?


texts: Impedance matching an amplifier near 1 dB compression point

texts:
I am using a RF amplifier (model: Minicircuits LZY-22+) to drive 6.5 MHz oscillation in a coil. I am using an antenna tuner (model: MFJ-969) to impedance-match the output of the amplifier to the coil. Up to some power (~40 dBm), I can get pretty good matching with almost no reflection (SWR < 1.1). But as I try to increase power beyond 40 dBm, SWR goes up and it's hard to keep it below the value of 2 while I try to optimize the matching again. I noticed that this transition seems to be close to the 1dB compression point of the amplifier.

Q1: Does the nonlinearity of the amplifier near 1 dB point actually mean that the impedance is changing, and hence I have to re-optimize?

Q2: Why would the SWR show an increasing lower bound near the 1 dB point, even after trying to re-optimize the tuner?


texts: how to determine the small signal parameters of nMOSFET from Datasheet?

texts:
as I want to calculate the transfer function of circuit that is meant to generate source current using an Op amp as control loop, I need the gm and r0 of the mosfet(to determine the transfer function of the Op amp current source with nMOSFET)
here is the picture of MOSFET with showed parameters

and here are the link for the datasheet

https://docs.rs-online.com/c5c9/0900766b80dcb3d2.pdf


texts: What kind of failure would I see in moisture sensitive parts?

texts: I am reflowing a design using an electric skillet. When the uC and LEDs arrived they were in moisture sensitive packaging. They were in sealed bags with moisture indicator cards. After I opened them I put them in sealable sandwich bags. Now one of my products is failing and I am wondering if moisture damage during reflow could be a culprit. Any ideas what kind of failure would result from a part taking on too much moisture?


texts: How should I organize this star grounding network?

texts:
I am trying to lay out a PCB for a SEPIC switching regulator. However, I cannot be sure how to layout the ground tracks. My area and budget are limited and my components are big. A picture says more than my words, so here are the schematic, my questions and some more details:

I only included some of the components for the sake of simplicity, if the whole schematic needed, I can upload.

Grounds of CU2, U2 and U1 are tied together (may be daisy chained), then gathered in one point which is "AGND".

Grounds of C1 (which supplies the additional current to the push-pull driver since 78L12 can only supply 100mA), Q2 and Q3 are star tied together at one point that is "PGND".

Then, PGND and AGND are star tied to the ground point of C6, which I've chosen to be the reference point.

If my star network is connected wrong or can be problematic, how should I organize it?
Is the ground side of C6 a good place for the reference point for the star ground network?
Will daisy-chaining AGND nodes lead to problems?
Should I star-connect 12V rails, if so, how? (U1 has a 100nF bypass cap which is not shown here)

Here is the datasheet for Q3 which is a IXTP44N10T. BC817 and BC807 are 500mA transistors. Here is the internals of 78LXX.

If it will help, here is my current board layout for the mentioned part:

Top, Bottom, Bottom Inverted


texts: Coating a soldered connection on a small circuit board

texts:
I have a small PCB, about the size of a quarter and having a Bluetooth chip on it. I have 4 wires soldered to the board. 2 of which are for a 3.7 Volt battery connection and 2 are to connect a small loudspeaker.

All of my components (PCB, battery, loudspeaker) are going to be encased in a cloth band and worn on a persons ankle. I am worried that through repetitive movement, my soldered connections will get disconnected.

Is there a recommendation for further protecting the soldered connections. I feel like wrapping it in electric tape won't be enough. Is there some kind of latex coating I can use to either coat the soldered connections or even the entire board?

I've heard of conformal coating. Is that my solution? If so which type for my case?


texts: using one 555 timer to control the pulse of another

texts: tried making something like this Limit Number Of Pulses From 555 Or Similar but it doesn't work. I'm not sure what it needs. I'm trying to make the first timer put out voltage to the second one for about 6 sec then have the second one on for about 1 sec then off for .5 sec till the 6 sec runs out. thanks for any help.


texts: Does anyone know what this step between the two lines mean?


texts: Connector Identification: Flex Ribbon E-Paper Connector (Kindle 3G)

texts:
This connector can be found on a Kindle 3G's display (which itself is sold as Part Number ED060SC7), but I'd like to interface with it, so i need the matching socket.

Dimensions:

plastic body is about 8,5mm (0.335") wide (long side)
all contacts combined are about 7mm (0,276") wide
there are 34 pins (perhaps 36 if the ones at the ends count?).
which would give them a distance pin-to-pin of about 0,4mm (~0.016")
length is about 1,5mm (0.06")
height (above flex-board-surface) is ~1mm (~0.04")

I would like to know the name of the part and who manufactures these. Extra points if somebody knows of a breakout to something tinker-friendly!


texts:
I’m building a simple garage door circuit that have two solenoid locks. Each solenoid lock is rated at 12V/3Amps and is only supposed to be activated during 3 seconds each time the “open door” button is pressed.

I'd like to use a power supply that can feed 12V/4.5Amps, so it will not be able to provide the required current for both solenoids.

I was wondering if I could add a (big) capacitor to the Power supply output that could supply the extra energy during these 3 seconds, so I wouldn’t need to buy a new power supply. Basically this capacitor would have to provide (rough figures) 12V*1.5A=18W in 3 seconds. I could easily implement a protection delay in the button so that the solenoids are not activated before the capacitor re-charges.

Would this be possible?
How could I calculate the value of the capacitor?

Thanks

EDIT

Thanks for all the comments.
This was question was a mix of real need and a theoretical exercise.
I could understand its theoretically/technically possible, but not really feasible/economical due to the high value of the capacitor, afecting its price.

From a CAPEX (investment) point of view, I could understand that investing in a 12V/10A power supply could be the cheaper option. However, from a OPEX (operating expenditure) perspective would that still be the case?

My point here is that having such a powerfull power supply turned on, standing-by, 24/7 just to activate a pair of solenoids a couple of times per week would have a small but continuous electricity cost that could change the business case on the long-run. Even though the 10A aren't being drawn, the residual consumption would be bigger than a smaller PSU, right?

What I'm evaluating now is to use the original circuit to activate a relay instead of the solenoids, and that relay will turn on a bigger power supply that is directly connected to the solenoids. This way, the PSU is turned off most of the time. This seems a good approach, but I'm concerned because the PSU will "boot" everytime with a huge load - not sure if it wouldn't hurt it.


texts: Low voltage audio amplifier clips on 8 ohm loads

texts:
Exposition time:
One could call me a freshman in electronics and I just designed my first little audio amplifier for headphones. (Pocket design, I want to be able to drive 4 headphone pairs from a single source)
Here's the schematic, so you guys know what I'm talking about:
(Without power supply (9V bat) and single channel)

Ofc, 4 headphones draw a lot of current, which is why I need a proper output stage. Up to 200mA to be precise.
The current design I made uses 2N5551 and 2N5401 transistors but their DC current gain is horrible (<10) which causes the OPA to overdrive. I don't want to much load on the OPA as well (max 20mA). A higher input voltage is out of question.
Therefor I need better output transistors (Q3 & Q4) which provide a higher current gain but also are capable of switching fast enough for audio signals. They should be cheap and small. I don't know that much components and the market out there is just a jungle of different parts.

The question:
Is it possible to compensate for the clipping with different output transistors? The circuit behaves great on 32 ohm but a lower load impedance wrecks it.
I'm also open for darlington array solutions.

*EDIT: I can't use SMD parts. I need through hole packages.

**EDIT: Juuuust figured! This OPA is not even able to supply 20mA, because R9 & R17 are to large. In that case, a darlington setup with the current transistors could work, I just have to lower those resistors. Will keep you guys updated. ;)

Solution:
There's more than one solution to this problem:

Use a different OP amp which can drive the transistors rail to rail (see accepted answer). This only works if the 2N5551 and 2N5401 output transistors are configured in a darlington setup. However, the OPA used in this circuit almost drives rail to rail, already. (+-4V on the output)
Other output transistors with a better gain. 8550 (PNP) and 8050 (NPN) behave greatly for this application, they still need a darlington setup, though. (Special thanks to Spehro Pefhany)
Increase the supply voltage. This works like a treat, IF you're actually able to do so. Sadly, I am not in my setup.
Replace the output stage with a "diamond buffer circuit". It performs well in the simulation, did not test it on the bread board, yet. But it's nature of a voltage follower driving the push/pull transistors decreases the total swing of the op-amp, which results in better slew rates and therefor also frequency response of the circuit. Thanks to  ioplex for adding this in.

My Solution:
I kept the OPA and used a darlington setup on the output. On my previous tests I forgot to modify the voltage divider to adjust the offset voltage between both transistors. I fixed that and now the circuit works. No clipping even on the worst input signals, that's what I wanted. Tests with my bench supply show that it actually operates down to +-3V which is great if you consider the voltage drop on the battery as it decharges over time. This is just the first design, I will change some things in the future. It is pretty clear that this is not the best setup and that I'm not using the best components for it. Design goals, however, were low component costs and supply voltage. And these are met with a decent performance of the circuit. It does sound gorgeous, feel free to try it yourself! :)

Thanks to everyone for the help I learned a lot through this project.
Here is the new schematic (2N5550 is a 2N5551):

PS: What's no in this schematic is the compensation cap on the COMP - COMP/BAL pins of this particular op-amp. It's 47pF but LT-Spice has no proper symbol for the NE5534P.


texts:
I'm designing a MIDI project using these SDS-50J connectors.  The datasheet provides a suggested footprint diagram and labels the pins 1 through 5:

It does not, however, label the bottom-most two pins circled in red.  Should I assume that these pins are for mounting only and should be left unconnected, or are they shield pins to be grounded on one end?

EDIT:  You can see this pins on the photo, too:

Also, this table on page 2 of the datasheet may provide a clue:


texts: Homemade GPS Receiver: Cascading LNAs and Band-Pass Filters?

texts:
Over the last couple of months, I developed a software-defined GPS receiver. Unfortunately, it's not very sensitive, and can only detect very strong satellite signals. For the RF front-end, I am using a cheap active GPS antenna and an AirSpy SDR, as in Figure 1.
After doing some research, I tried inserting a second LNA between the active antenna and the SDR, as in Figure 2. However, it did not make much of a difference. If anything, it just reduced the sensitivity even further. This is not entirely surprising since, with the first approach, the signal was already pretty large after being digitized (i.e. its span was close to -1...1).
Finally, I am considering adding a second band-pass filter after the external LNA, as in Figure 3; I've seen this approach in commercial GPS front-ends, but I don't really understand why it helps -- after the first filter, the signal should contain very little power outside of the band-pass frequency. I'm sure I'm missing something -- what is the purpose of the second filter? I'd appreciate some example calculation on how/why it helps increase SNR.
A few extra notes:

I am confident the Active GPS Antenna is not the problem because, when connected to my off-the-shelf GPS receiver, it's able to receive very weak signals.

I am also confident that my GPS software is not the problem. In fact, I am only running the acquisition part of the receiver, which only detects GPS signals but does not attempt to track them. I've verified that it works correctly with these sample RF signals. In addition, I tried running my own signals through their acquisition pipeline, which barely detected anything.

These are the components used:

Generic GPS Antenna
For the first approach (Figure 1), I just connected the active antenna to the AirSpy, using the built-in bias-tee.
For the second approach (Figure 2), I used a wide-band noelec LNA (powered by the AirSpy's bias-tee) and an extra external generic bias-tee to power the active GPS antenna.
For the third approach (Figure 3), I used a single pre-filtered LNA, externally powered, which also supplies the bias power to the GPS antenna.

Thank you!

Also, I measured the power over 1525-1650MHz, with various settings for the SDR gain. You can clearly see that LNA noise over the noise floor of the SDR.


texts: Pipelined designs with outputs in differentes delay clocks

texts:
I have a pipelined design that ends in 13 clock cycles when the input value is not close to zero, but when the input is close to zero, the design only needs about 4 clock cycles, because of all the intermediate calculus is not needed. Therefore, my question is: Is it possible make a pipelined design where the output is delayed two differents number of clock cycle?
Actually I think this question has not sense because I have never seen a similar question or design with this specs.


texts: What do the numbers on computer power supply transformers mean? Where can I get datasheets for these types of transformers?

texts:
What do the numbers on computer power supply transformers mean?
Where I can get datasheets for these types of transformers?


texts:
I'm trying to understand the circuit in figure 1 of this document which describes CCD interfacing (http://www.analog.com/library/analogdialogue/archives/32-1/signal_pro.html). Shown below:

(source: analog.com)
My questions are, as follows:
Does this represent the circuit in the output stage of the CCD? Typically CS and the 2 MOSFETs would be internal to the CCD?
If I need to add these parts what value would I typically use for CS, which MOSFETs.


texts:
I cannot find the name of those power/charger connectors they have on the electric scooters and "hoverboards".

It seems to be some 3-pin XLR-like plug.

Can anyone help?


texts: How to control RMS output of an DC-AC inverter?

texts:
Is it possible to design an inverter, with 270V DC input and RMS output of 115V. I don’t want to use a chopper or a transformer. Is it possible to meet this requirement by using PWM only? Or chopper/trafo is a must for this case?
I am using SPWM and I have already applied a modulation factor of 0.5, still not getting 115Vrms

Edit: My inverter is working. But the RMS value at the output is higher than my desired value. How do I reduce the voltage RMS value of the inverter?


texts: What's the purpose of this voltage noise test circuit?

texts:
Ran in to this circuit from parts.io tweet.

This is my analysis of it thus far:

It is using TI's MC33078 OP-AMP. It is a dual OP-AMP, but in the example only half of it is used.

The name of the circuit is Voltage Noise Test Circuit. It suggests that it tests for noise between 0.1 Hz to 10 Hz. Checking some cut-off frequency of the filters, I see 2 low pass filters, and 1 high pass.

The low pass filters (4.3kohm/2.2uF and 2.0kohm/4.7uF) have cut-off at 16.8Hz. And the high pass (22uF/110kOhm) is at 0.1 Hz. I have used this online calculator for these values.

These number do not exactly match with the description of the circuit (0.1Hz - 10 Hz), but perhaps it's close enough.

Also, the negative feedback on MC33078 has about 5 gain factor (1+ 100K/24.3K). It is amplifying the output of DUT by that amount.

So far so good.

Now I look at DUT. I had to look it up to see what it means. DUT apparently means "Device Under Test". So this is the device I am testing the voltage noise for.

However, I am not sure why the positive feedback is there. Both inputs of the DUT are grounded. There shouldn't be any current flowing through the 10ohm resistor and the 100Kohm resistor, as there is no voltage source.

So in short, I am confused as to what the circuit is testing. Is it testing for the supply rails of DUT?


texts:
I have a 5 volts DC motor and want to make H-bridge.
This is my schematic:

I doubt whether the transistors I used are correct.
IRF9630 on top and IRF630 on bottom.
Could I use BJT instead of MOSFET?

I'm also not sure of the overall circuit. Is it correct or not?
I'm using STM32F103C8T6.


texts: Why is the voltage positive while the current is decreasing?

texts:
The question is:

The solution is:

The formula used is:

So, based on the formula it should be like this:
$$v_L(i)= L\frac{di_L}{dt}$$
$$v_L(i)= +0.4\frac{0.1-0.5}{0.01}$$
$$v_L(i)=-16V$$
Why did he change the formula?
The question and answer are from:
FE Exam Review: Electrical and Computer Engineering 1st Edition
by Myron E. Sveum
Publisher : Professional Publications, Inc.
ISBN-10 : 1591260698
ISBN-13 : 978-1591260691
The formula is taken from:
FE Reference Handbook 10.0.1
By NCEES
ISBN 978-1-947801-11-0


texts: How to test an optical sensor board from printer

texts:
I have salvaged an optical sensor board from a HP printer just as the one shown c9101-80190-A to use it other hobby projects.

The problem is, I cannot be sure whether it's working or not, as I get always the same voltages (with and without séparation between the diode and the receiver) as shown in the following schematic.

simulate this circuit – Schematic created using CircuitLab

How can I find out if a photogate is working or not?


texts:
I'm using this gate driver IC. My question is, do I have to externally pull up the /RST pin? Because it can't be left floating, but I don't get the part that says "pulled down internally".
In the datasheet this is mentioned,

So is this correct to be connected like this?


texts: AVR TIMER0 treating with prescaler and without to blink a led

texts:
I am playing with ATMEGA168A's TIMER0. CPU is running at 20MHz and there are two treatments.

a) Blink a LED at 20ms frequency by using a 1024 prescaler. In that case i count the the times that an overflow occurs for the frequency that prescaler of 1024 'gives' me. And according to the formula,  to achieve 20ms delay with 1024 prescaler, timer should overflow 1 time and in the second loop to count 145 'ticks' more. With that method LED is blinking but offcourse we cannot see it. Here is the code:

#define F_CPU 20000000UL

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>

volatile uint8_t total_overflow;

void timer0_init(void)
{
    // Setting the 1024 prescaler
    TCCR0B |= (1 << CS00) | (1 << CS02);

    // Initialize Timer0
    TCNT0 = 0;

    // Initialize the overflow interrupt for TIMER0
    TIMSK0 |= (1 << TOIE0);

    // Enable global interrupts
    sei();

    // Initialize total_overflow variable
    total_overflow =0;
}

// Interrupt service routine
ISR(TIMER0_OVF_vect)
{
    total_overflow++;
}

int main(void){

    DDRB  = 0b00000001; // SET PB0 pin as output

    timer0_init();

    while(1)
    {
        if(total_overflow >= 1)
        {

            if(TCNT0 >= 145){

                PORTB ^= (1 << 0);
                TCNT0 = 0;
                total_overflow = 0;
            }
        }
    }
}

b) Blink a LED at 20ms frequency but without using any prescaler. CPU and this time runs at 20MHz. Here occurs that to achieve a time delay of 20ms, TIMER0 needs to overflow 1568 times and in the 1569th time to count 160 more 'ticks'. In that case the LED doesn't light. Here is the code:

#define F_CPU 20000000UL
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>

volatile uint8_t total_overflow;

void timer0_init(void)
{
    // Setting the no prescaler
    TCCR0B |= (1 << CS00);

    // Initialize Timer0
    TCNT0 = 0;

    // Initialize the overflow interrupt for TIMER0
    TIMSK0 |= (1 << TOIE0);

    // Enable global interrupts
    sei();

    // Initialize total_overflow variable
    total_overflow =0;
}

// Interrupt service routine
ISR(TIMER0_OVF_vect)
{
    total_overflow++;
}

int main(void){

    DDRB  = 0b00000001; // SET PB0 pin as output

    timer0_init();

    while(1)
    {
        if(total_overflow >= 1568)
        {

            if(TCNT0 >= 160){

                PORTB ^= (1 << 0);
                TCNT0 = 0;
                total_overflow = 0;
            }
        }
    }
}

Any idea why this happening ? Am i doing something wrong or there is a limitation on how many times a timer can be overflowed (<-- that seems silly idea).

Thank you.


texts: I'm new to this forum, so apologies if I am posting this in the wrong place. I am looking to start a DIY project, and this entails electricity and water; I know, two things that  shouldn't ever  be near each other! However, I want a device that is plugged into an outlet, can spin water around (almost like a dishwasher arm). I made a basic checklist for the electrical components: I need a motor, a few fans, wires, and an AC to DC converter. I did some preliminary research and found that a BLDC motor would suit me best (little to no maintenance). I chose DC because I need multiple devices (the motor and the fans) to run on either 120V-240V AC current (plugged into the wall). What is your take on this. I by no means have a degree in mechanical/electrical engineering (I'm still in HS). Would it just be better to simply use separate lithium-ion batteries (Duracell, for example) per device (one battery for each fan, and motor), or is what I'm suggesting feasible? Thanks in advance!


texts: Can I measure inductor current by adding a secondary winding?

texts:
I have a buck converter and I want to add a current loop to it. I don't want to use a hall-effect sensor or something expensive like that. I think it is not practical to use a sensing resistor since the output current is very high.

I want to know if there is a way of sensing the current adding a secondary winding to the inductor as seen in the schematic below. I know I can turn this inductor into a current transformer by making the secondary turns count at least 100 times the primary turns, but this is just a hobby project and I don't think I can wind that many turns by hand.

The inductor voltage will be high when the high side MOSFET is on. It will be negative when the low side MOSFET is on. And it will be near zero both when the output current is high (at the final moments of large duty cycles - am I correct?) and when there is a light load. How do I make it differ high current and no load cases? I know that the method I used below is incorrect, and I'm looking for a way to correct it.

Note: My PWM controller is TL598 which exactly same as TL494 except that it gives totem pole outputs.


texts:
I have made this circuit:

Now I am trying to use this circuit in my bike. My bike has a 12V 9amp battery and while charging (bike running), the voltage fluctuates from 12V to 20V. To power this circuit with no fluctuation, I have made a voltage regulator circuit with LM7812 and capacitors (0.33uf, 0.1uf) as given in its datasheet.

I checked with multimeter, the output is good (around 11.9V to 12.1V), the problem is that the 7812 heats up (so much that I can't touch it) within 20 secs after switching on the supply. I believe that as the output current of 7812 is 1amp, it needs to reduce much current, causing so much heat. Do I need to change caps or is there something else I should try?


texts: Sync Buck - how to estimate switching loss?

texts:
Here is the problem I am working on, from pg105-106 of Fundamentals of Power Electronics 2nd edition.

As stated in this book, "The ability of the MOSFET channel to conduct current in the reverse direction makes it possible to employ a MOSFET where a diode would otherwise be required". So I believe two MOSFETs' conducting resistance are source of conducting loss, and should be calculated with \$(D+D')I_L^2*R_{on}=I_L^2*R_{on}\$ where \$I_L\$ equals inductor or load current.

But I have no idea on how to solve switching loss. In question (a) and (b), I am not sure what is the source of switching loss. Though I have seen example on how to calculate diode switching loss in the book, but it is the case that diode are conducting current. Now the only thing open and close to conduct current is the MOSFET channel. So I totally do not know how to make use of parameters of body/external diodes and how to calculate switching loss.

What makes me most confused is (c), as the question gave me the feeling that on some range of frequency an external diode will worsen the efficiency!

So how to do the math correctly? Thanks.


texts: How does DPSK work? What are the advantages compared to BPSK?

texts:
I have two questions that I would appreciate some help with.
Comparing BPSK and DPSK I noticed that BPSK has lower BER.  Why is this?
Are there other advantages of using one over the other?
In what specific applications would DPSK be more useful compared to BPSK?
BPSK = Binary Phase Shift Keying
DPSK = Differential Phase Shift Keying
BER = bit error rate


texts: Would running a heater for 10 seconds on then 10 seconds off be the same as alternating on and off every 1 second for 20 seconds?

texts: Just as the title implies... I'm curious whether given a heater is on for exactly 1/2 of a period of time does the frequency of the heater turning on and off impact the  net result of heat created? For instance if it was on for 10 seconds and off for 10 would that have the same net effect as turning it on every 1 second then off the next repeatedly over the same length of time?


texts:
I am trying to calculate the power rating of a schottky diode. The diode in question is the 1N5822U from ST Micro (a rad hard schottky diode). The datasheet is - Diode datasheet

Now, I am using in a circut that has about 2Amps. Now, the power dissipated throgh this diode is given by the equation below
. It is given in the page 2 of the datasheet.

Now, i am assuming If(av) = 2Amps. What would If(rms) be ? This is a dc system so the RMS can be assumed to be just a dc level current ?

Also, now from this value I get the power dissipated by my circuit and not the max rated power of this diode. For, this I am making use of the Thermal resistance value = 7degree Celcius/Watt.
The max operating or junction temp possible is 150degrees celcius. So, taking this into pic the difference from normal operating room temp and the max (150-25 = 125). So, the max is 125degrees celcius rise. This means that 125/7 = 17W. Approx 17W is the max power rating of trhis schottky. Is my assuption correct ?


texts: Probes with protection against slipping?

texts:
There have been a number of times when troubleshooting something where I have caused more damage than was originally there when my probe would slip off a test point and short some things together.  So my little brain started churning.  What about test leads with a clear sheath that is spring loaded that covers the whole probe tip. This is always extended over the point. You press down on a test point and the plastic sheath pushes back until the metal probe tip comes in contact with the node.  If you slip the plastic shoots back out to cover the tip and hopefully avoid a short. I am not sure how effective this would be but it might help. I did a search because I am sure someone thought of this and they have to out there somewhere but I haven't found anything just yet.  I was going to try and make this but I don't really have the tooling.  Has anyone seen something like this? If so can you point me to them, or am I missing the obvious design flaw?
Thanks for the help,
Russ


texts: STM32 USB CDC: How to stop device transmitting via USB when not connected

texts:
After over 3 weeks of testing and debugging, I have finally got my STM32 transmitting data reliably over USB. The problem is it NEEDS an application on the other side of the USB to consume the data. When connected to my PC, and a program displaying the data is active (Realterm, Python script etc...) it will function indefinitely.

If for any reason the program on PC closes, or is never opened, the µC will function for half a minute then freeze. Here is the code for my transmission, I have tried to get the µC to test if there is activity on the bus before sending data but that apparently doesn't work. The µC freezes on the while(pCDC->TxState) condition. After failing to send data, the flag is never reset.

uint8_t CDC_Transmit_FS(uint8_t* Buf, uint16_t Len){

uint8_t result = USBD_OK;
volatile uint8_t bDeviceState = (volatile uint8_t) hUsbDevice_0->dev_state

// If no activity on the bus for past 3 seconds fail
if(bDeviceState == USBD_STATE_SUSPENDED)   // <----- This doesn't seem to work
       return USBD_FAIL;

// wait for previous transfer to complete
USBD_CDC_HandleTypeDef *pCDC = (USBD_CDC_HandleTypeDef * hUsbDevice_0->pClassData;
while (pCDC->TxState) { }

USBD_CDC_SetTxBuffer(hUsbDevice_0, Buf, Len);
result = USBD_CDC_TransmitPacket(hUsbDevice_0);

// wait until transfer is done
while (pCDC->TxState) { }
return result;
}

My question is how do I let the application on the µC know that it's not connected and continue functioning? ie. if there is no host application receiving data, just return from the CDC_Transmit_FS function. If I remove the while, the speed at which I am sending data ends up overwriting data in the buffer. If I put it, the µC blocks when not connected to a host.


texts: After dismantling an old PC power supply I recovered what seemed to be the primary transformer, after following the traces etc its purpose became less clear as it has two terminals and a ground connection , it receives ≈ 250VAC on one terminal and outputs an unknown voltage on the other terminal, which feeds into a bridge rectifier which feeds into 2 200v filter caps. This leads me to believe that it is used as a step down transformer but if so I don't understand its operation, could someone please clarify or explain the funtion, thank you.


texts: From a state transition table, how do I determine if I'm dealing with a Mealy or Moore machine?

texts: From the state transition table below, how do I know if I'm constructing circuits for a Mealy or a Moore machine? Could someone explain the difference and what I should be looking for?


texts: Recursion in VHDL, performance? what is the difference with a conventional programming language?

texts:
I've seen in the Ashenden book that recursion in VHDL is possible... however i was wandering how should i look at recursion in terms of performance? In conventional progrmaming language the recursion imply stack memory using, which as example could go in overflow in extreme cases...

Be careful that the recursion i mean that we could have a design with a generic parameter n and with such parameter we could know at compilation time the deep of the recursion (so it isn't in real time actually, like in conventional programming language i mean).

Pro and cons of vhdl recursion?


texts: Single miniature part with zener diodes in series

texts:
(source)
Is there any single part/assembly with zener diodes in SOT-23 package (or comparable with 3 pins)?
I can use BAT54S for diodes, but can not find similar for zeners. The goal is a minimal footprint, limiting audio signal to ±5 V.


texts: Simple short range object proximity identification using capacitive sensing

texts:
I'm designign a device capable to sense proximity with other identintical devices and communicate that to a central node via bluetooth. The problem I'm trying to solve is showed in figure.

So far I identified two strategies:

IrDA: cheap but there must be free line of sight between devices
NFC:
expensive, need 4 NFC chips and design antennas

Instead I'm wondering if I could use capacitive sensing, as implemented by ICs like the MPR121, to implement the above scenario. Could metallic pads on each side of the device be configured to provide a unique capacitance value when in proximity of another device pads?

Thanks!


texts: How to calculate flux density between perfect parallel-plate capacitor?

texts:
How to calculate flux density, using Gauss' Law, between the plates of a perfect parallel-plate capacitor with +7C and -7C on the top and bottom plates, and a plate area of 1m^2, with a separation of 1m.

The answer is -7C/m^2, but i cannot understand why or how.


texts: Ability to push and pull objects (theory)

texts:
So, I do not know much about electricty but it has always been interesting to me. (Especially solar cells) but negative is attracted to postive, etc.

So couldn't you theoretically have an "object" in your hand with postive energy and a "object 2" with negative energy like 1+ feet away from you that attact each other so the "object 2" would be pulled closer. (I assume the stronger the differnce in postive/negative energy the stronger the positive attraction)

I also assume I am not the only one who thought of this so is it hard to lose/gain electrons without touching the object? Just was an interesting thought I had. (As said I don't know much about this stuff, I've just learned about how electrons flow and free electrons" so I was curious.


texts: Injecting power into circuit to find a short to ground

texts:
I'm trying to find a short to ground on a Nintendo Switch of which there are no schematics.

The short is present on the 3v3 line.

What I would like to do is inject power into this line from my bench top power supply to see if the short presents its self with heat.

What I'm asking is the point of injection into this line important or can it be anywhere on the line as long as it is the 3v3 rail obviously.


texts: How can I make a simple analog to digital converter?

texts:
I'm trying to hook up a sip-puff air pressure sensor (datasheet) which outputs 0v to 5v depending if the pressure is -ve (sipping) or +ve (puffing). I want to use it to drive a Bluetooth keyboard controller (info) to help a disabled person use an iPad. When pins on the Bluetooth controller are driven low, they send a key press - the idea being when you sip it sends key 'a' and when you puff it sends 'b'.

I need some help coming up with a simple circuit to interface the two, thus:

When the sensor output is 0v - V1 then drive pin 1 'a' low (sip)
When the sensor output is V1 - V2 then do nothing (dwell / dead zone)
When the sensor output is V2 - 5v then drive pin 2 'b' low (puff)

I'd also like a couple of trimming pots in the circuit to set V1 and V2. I have transistors and resistors to hand so it would be helpful if I can build using those, otherwise it's no problem to get other components if needed.

Thanks in advance for any pointers!


texts:
Suppose I have a coil antenna that receives an ideal 100kHz ~200uVpp signal which I would like to measure.  Can this signal be amplified to 2Vpp (10,000x gain) with 1% error for moderate cost (< $10)?

What specs/variables should I be considering in order to determine the feasibility of this?  Also, would using a resonant capacitor help amplify the received signal, or does it only serve as a filter to remove other signals?

If this is not possible, what is a ballpark combination of frequency, gain, and percent error that could be comfortably achieved for $5-10?


texts:
I'm looking for an affordable op-amp to be used as a low-frequency (<100Hz) low-output-power (5V 1mA) rail-to-rail voltage follower that can run on -0/+5Vdc. So far my best bet looks like the MCP6002 which approaches the rails within 25mV. The common-mode input and output swing are way better than LM* devices in the same price range. However, the output swing specification is curious:

What does overdrive mean in this context?
The input is expected to frequently visit either 0V or Vdd=5.0V, which - if I read the spec correctly - this device can tolerate. The loss of 25mV on both ends is acceptable.


texts: Band Pass Filter for musical note separation

texts:
I have a school project that i need to separate musical notes with filters at least i thought that i can do it with band pass filter, here are the results

These are the resistor and capacitor values that i calculated for note frequencies

These are first two band pass filters

And this is my problem these are Vout values and they are so close to each other. I want to connect a LED for to every output that will be on at max vout value, i need your suggestions what should i do about these values.


texts: So today I was working on a DIY project, that involves me heating up a nichrome wire, and for some reason the nichrome wire is not heating up. I am using a 38 gauge wire, I calculated that I would only need 0.33 AMPS to heat up the wire, using 10inch of nichrome, 12V voltage source, as well as I have read 0.4 amp in my circuit. My circuit consists of the same nichrome wire, measured to be 31 ohms, and a 330 ohm resistor in series; so using current divider, I calculated 0.36 current should be going through the nichrome, but instead the resistor heats up and the nichrome is cold,any idea were I missed up. I can provide photo of my circuit if needed.


texts: What are the effects of single ended signals on twisted pair conductors?

texts:
I'm currently using a cable that has multiple twisted pair conductors. I'm attempting to send a several single ended signals down some of these conductors at a frequency of 12.5MHz. Essentially, I'm only using one conductor of each twisted pair.

Will this pose any issue? The fact that there is an unused/unterminated conductor twisted around one of my conductors, will this have any transformer like effects? I have been unable to find any resources online.

Thanks,


texts: What are some good representative transistors for a beginner's electronics class?

texts:
Context:  assembling coursework for a beginning electronics class.

There are various kinds of transistors commonly used in electronics circuits.  What kinds of transistors would be useful to include in a class for beginners?

The educational objective is to demonstrate:

common uses of transistors
what all transistors have in common
how the various types of transistors differ

This is not a shopping question, but if you have a concrete model number that might be useful.


texts: What is the simplest and cheapest way to convert 11.1VDC battery pack to regulated 9VDC?

texts: I have a portable multitrack digital recorder which I'd like to use where there's no power available for longer periods of time than regular alkaline dry cells allow. I'd like to use this 11.1 volts 4400 mAh battery pack salvaged from an old laptop. The current draw of the recorder is 200 mA.


texts: Choosing a damping factor in a RLC Low-pass filter

texts:
I have some basic understanding of what the damping factor from control theory. However, I don't know how I should choose it.

We have 24VDC which goes through a input power filter (RLC low-pass filter) and to a buck converter which converts to 5VDC.

I suppose to tune it as close to 1 without causing too much effect in the resistor is one way to go.


texts:
I'm struggling to wrap my mind behind the concept of RS flip-flop. For me, the diagram seems very non-intuitive.
Whenever I accept, for example, that Q is HIGH and follow signal route (is it even correct to say so?) I come to a logical contradiction (say, NOT Q being also HIGH).
Could you please share some knowledge and enlighten me?


texts: Can a USB Oscilloscope be used reliably and accurately for RF projects?

texts:
Are USB based oscilloscopes "sensitive" or able to be used with RF circuits?  In particular, are they able to see the waveforms, carrier wave, etc. of something like a crystal set?

I saw something like these (I picked these a random, first ones I saw),

DigiTech QC-1929 (Hantek 6022BE) USB Oscilloscope

Hantek 100MHz PC Based USB Oscilloscope

The first is much cheaper, but the second is $200 (where I saw it), and that is getting close to a new or used scope.

For context, this is for hobby/enthusiast.  It is also mostly for RF based projects like a Crystal Radio and seeing AM, Shortwave, and the like.

For example, I want to see the carrier wave and the AM modulation and what ends up getting sent to the earpiece, the "information."  That may not be the right terminology.  Hopefully you understand what I want to see.


texts: Error when simulating spice model in OrCAD PSpice

texts:
I am trying to simulate a circuit based on TS522 op-amp using OrCAD PSpice 16.5. The manufacturer's website did not have a model for this op-amp, and I had to look for it elsewhere. I was able to find one and import it into my OrCAD project, however, the PSpice simulator throws en error, every time I am trying to simulate the netlist. The error says:

ERROR(ORPSIM-16371): Extra text on line

The model file is located here.

Could anyone help me with this error? I am not very familiar with detailed of Spice syntax, just have the overall idea what netlists are.

Thanks.


texts: What possible issues with running a fan inside a freezer?

texts:
I need to turn on a fan inside an ice cream display cabinet when the lid is closed, and turn the fan off as soon as the lid is opened.

I'm looking for a way to have as little temperature derivation as possible throughout the whole display cabinet.
The ice cream pans (actually it's gelato) sit at the very top of the inside of the display cabinet and it is opened and closed frequently during operation, which causes a certain amount of ambient temperature air inside everytime it is opened.

I figured by positioning an appropriately sized fan at the bottom of the freezer that turns on when the lid is closed, that will move the colder air up and even out the temperature difference as much as possible.

I'm wondering if there are any issues with running a fan inside a freezer at -12 degrees celsius, or what type of fan would be more appropriate for this task.

Will the fan freeze? Maybe this is crazy..

Any thoughts?


texts: How important is saturation current for an inductor?

texts:
I have a 15µH 1.6A inductor, this one.

The operating current is 1.3A, but the saturation current is 1.6A.

What is the difference between these?
Will the inductor work properly at less than 1.3A or less than 1.6A?


texts:
While designing an LM2586 SMPS circuit using the TI Workbench, the software recommended the following transformer:

This is apparently the 749196510.

The TI workbench states that this is a 89.1uH part. However, the datasheet states that the inductance base is 9.9uH. Even if I were to connect all 3 primary windings in series, surely that would only result in 29.7uH? Is there a mistake somewhere?


texts: Memory management problems with ATTiny85

texts:
The setup is as follows:
I have a little program to drive single color 8x8 led matrix using 595 shift registers that are supplied with data by ATTiny85 through USI as SPI Master. I upload program to ATTiny85 using Arduino Uno. Program is compiled and uploaded using Visualmicro plugin for VS2010 or Arduino IDE (both with the same results). Compiled program is 2970 bytes long (36.3% of chip's memory)

The issues are:

The Array Problem: I cannot declare array that is longer then 296 bytes.
I have array that holds binary representation of a font to display characters on LED matrices. The desired size for this array is 760 bytes. It is declared as follows:

byte font[] =
{
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Char 032 ( )
    0x30, 0x78, 0x78, 0x30, 0x30, 0x00, 0x30, 0x00, // Char 033 (!)
    ...
    0xE0, 0x30, 0x30, 0x1C, 0x30, 0x30, 0xE0, 0x00, // Char 125 (})
    0x76, 0xDC, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  // Char 126 (~)
}// 760 bytes total

If I refer to first element of the array in the code, I receive 648th element [first byte of fonts character 113 (q)]. Whole array is messed up. Blocks of 8 bytes or more (n*8bytes) of the arrays content are mixed up with each other and with completely unrelated areas of memory.
If I try to display any text on on the matrices I see completely different characters or some mess (I think what I actually see is the very program running in the memory - it's cool but useless). If I cut the array down to 296 bytes everything works fine.
The Pointer Problem- to work around problem #1 I split the array into 3 smaller arrays(296 bytes max). I declared pointer to point to proper font array depending on character to "render". I cannot point this pointer to any array inside the "if" block

char c1='a';  //character to display
byte font1[]={...};  //binary font representation split in to 3 arrays
byte font2[]={...};
byte font3[]={...};
byte  ascii_offset1= 32,ascii_offset2= 69,ascii_offset3= 106;  //offset for each array
byte * font_ptr1=font1; //This works fine.
font_ptr1=font3;        //This also worked fine in tests.

if(c1>=ascii_offset3)
{
    font_ptr1=font3;  //This DOESN'T work at all
    c1-=ascii_offset3
}
else ...

In fact I think that line, commented as not working, is actually hanging up the ATTiny. I see nothing on matrices, except for few LEDs constantly lighten up.

In case of issue #1 I suspect that compiler or linker messes something up. But #2 is total mystery to me. I thought that maybe it's stack overflow, but according to documentation stack size is limited only by SRAM size, witch is plenty and additionally I don't allocate any memory dynamically.


texts: How to move an object through 30 degree rotation?

texts:
I want to make an electronic bird feeder in which the feeder floor tips 30 degree down to exhaust the used seeds. I know how to work with PIC micro controllers to do the timing and enabling an output, my problem is: How to make the bird feeder floor or cup floor (made from plastic) move 30 degree down and then up?

I have researched and I found that to make the thing move I should use an motor but I could not find an appropriate one. Is here an appropriate technique that I should use?


texts: SPI internals _ missing MISO clock during read operation

texts:
I am currently writing C++ code to utilize SPI protocol.
I am using popular library as a guide.
Run into few questionable areas and after some discussion on the library board forum I have been told "it is an internal problem " ( of the hardware ).
To be specific - using MOSI "port"  I can "write" to hardware and monitor the outcome via software. Neither MOSI or CLK ports are connected to any SPI slave device. I have no issues there.
When I "read" MISO port,again not connected to slave device ,  I do expect no valid data  - no actual MISO signal. That is fine.

However

The master DOES NOT send CLK at all!
The master / device empties buffer(s) which are filled DURING the "write" cycles DURING "read" from slave operation.

My actual general question I would like to get answered is

Does SPI master require physical connection to slave to send CLK to slave during slave read operations ?

Per SPI documentation - master sends CLK during "write" to slave  and sends CLK during "read" from salve. Master SPI is the CLK source.
Only the SPI "write" part works as expected.


texts: Why does this comparator not output a square wave?

texts:
I have a 4.43MHz sinusoidal output from an IC that I want to convert to a TTL square wave to use as a clock. The signal has a DC offset of around 2.5V and has an amplitude of about 0.5V peak to peak.

I attempted to convert this to a 0-5V square wave using a TLV3501 high speed comparator with this circuit.

The comparator appears to work as expected: with RV1 at one extreme the output at SQ_OUT is 0V, at the other it is 5V, at a point roughly in the middle I see a waveform. However it has a DC offset and doesn't look much like a square wave.

(Above is 0.5V / div and has a DC offset of nearly 2V).

The datasheet shows a square wave generated from a 50MHz signal so obviously I am doing something wrong. I am using a breadboard but the IC is on an adapter with C1 and C2 soldered to the pins. I also tried disconnecting SQ_OUT from the breadboard and measuring the output at the pin, but saw the same result.
How can I get a 0-5V square wave?

Edit

Following the suggestions here I fed the comparator with signals ranging from 500hz to 20000hz and offset by 2.5VDC. I mostly observed the same result: with RV1 at one extreme, a 5V flatline, at the other, 0V, and in between a waveform of about .5Vp/p and offset at around 2.5V (the offset varied depending on RV1).

The closest I ever got to expected output had flat peaks at 5V but still not swinging between 0 and 5V.

This would seem to rule out scope issues, so it must be either the electrical environment (I'm using a breadboard) or else I've wired it wrong (which I doubt, but I will certainly be triple and quadruple checking). Or possibly a dud chip, which also seems unlikely.

I'm wondering if these issues could be a factor:

I'm using a breadboard (SQ_OUT is not connected to the breadboard though).
There is no load connected, except for the scope probe. Previously when I was feeding 4.43MHz there was a load connected (clock input on an AD724).
Could RV1 which is a 20K voltage divider be too much resistance?

Edit 2

I believe my problems were caused by a noisy power supply (5V unfiltered USB), and exacerbated by stray capacitance from the breadboard.
With the USB supply the comparator seemed to have 3 states: flatlining at 0V, flatlining at 5V, or the voltage at the input. This was the case even without any signal, just 2.5VDC. I'm guessing the "middle state" was high frequency oscillation.
I managed to get the expected output by powering the circuit from a battery and got best results when I removed it completely from the breadboard. Only then did I get only 0V or 5V flat lines with no "middle state".
On the breadboard and supplying a 1000hz signal, I see a 0-5V square wave with some zigs and zags around 2.5V, showing that the output is not a clean. I guess if I want to continue with this device I'll have to put it on its own board and filter the power supply. Thanks to everyone who contributed.


texts: How to plot root loci of loop gain G(z)= k/(z-0.5)(z-0.5)(z-0.5) in z plane?


texts: Interconnected ground planes on signal/component-layer

texts:
From what I understand, RF- and microwave-circuits needs separate ground planes to avoid coupling between signal and DC/digital currents. I'm currently involved in an RF-project where we're going to use a SPDT-switch to control the path of the signal. The switch is Mini-Circuits SWMA-2-50DR+.

What confuses me is the suggested PCB layout, which includes signal-ground and TTL-ground terminals on a shared plane that's grounded through a lot of vias. I can't see how the currents can be uncoupled with this geometry, and where the vias are supposed to go if I have two ground planes. I know that separate ground planes need interconnection to tame unwanted modes, but I find it strange that it happens on the signal/component-layer.

I'm sure the layout is sensible, but I just don't have the experience to understand it yet. Enlightenment would be very much appreciated.

Best regards
-paw


texts: Using an analog demultiplexer as a digital demultiplexer

texts:
If I want to use an analog de/multiplexer as a digital demultiplexer, do I have to use pull-up / pull-down resistors?

For example when driving a CMOS IC like the 4015 with the CMOS analog 4051, do I have to use pull-down resistors?