texts: Is there a solution for converting printed schematics to spice netlists?

texts: I would like to be able to scan circuit diagrams into a circuit simulator. While I am aware that symbols are not entirely standardized, is there any software that will do an approximation of this?


texts:
Based on my previous question about IC UC3845 I want to ask about feedback in these schematic:

Pin 2 on schematic above is VFB, Pin 1 is COMP, Pin3 is CURRENT SENSE.

I can't define negative feedback of Error Amplifier. As I presume it is P1+R10 and R8+C12. But why is C12 if it is DC. How it will works?
As I understand voltage drop on R11 is 2.5V at steady-state because of Op-Amp features.
And will voltage on out of Error Amp(COMP pin) be negative because current flows through P1+R10, C12+R8 and voltage on pin2 is 2.5V.

And this remaining part of schematic for full understanding:


texts: Best way to produce 50 VDC, 20 mA from 5 V

texts:
Ok, so I need to generate 50 V from 5 V, with a load of 0 to 20 mA, for a mass-produced device.  There are simple boost converter circuits like this LT3467 example:

but it seems these are limited by the maximum voltage on SW (in this case 42 V).  Are there any that can go directly to 50 V?

If not, there seem to be several possibilities:

external FET with higher voltage rating
charge pump after the boost converter
autotransformer instead of inductor

1: Is adding an external FET sufficient to get up this high?  It seems like it, though I don't know how much current this can supply:

(from here)

2: Can also use a charge pump / voltage doubler after the boost converter, without an external FET, something like this (with the FET built into the boost converter IC):

(from here)

Then the SW voltage can be half (or less) of the output voltage.  One advantage of this is that it produces intermediate voltages, which might be useful.  In this case, should the feedback be before or after the voltage doubler?

3: Other examples show an autotransformer replacing the inductor, and no external FET:

(from here)

(more here)

So, uh, what's the simplest/cheapest/best way to do this?  What are the advantages and disadvantages of each solution?  Which external components cost the most?  Which solution can supply the highest current?  Which has the best output regulation?


texts: Nano Electric Receiver Switch - Circuit Components

texts:
I want to recreate the circuit board below, but I am having a hard time figuring out what components I need. I have been trying to look them up on mouser but I haven't got any results.

It is called the NERS V2, the board uses a PWM signal from a remote control (RC) receiver to open or close a circuit. 1-2ms pulses at 50hz, where pulses > 1.5ms turns it on, and <1.5ms turns it off

Does anyone know what these parts could be?

Heres the board, all components are on one side.


texts: external power treatment in the powered board

texts:
I'm working with an audio board (company project) that is powered by a external 9V power supply. Actually an ordinary AC adapter, like this one: http://www.sweetwater.com/store/detail/MAud9v500. The power supply project of our board seems to me kind of an overkill. I say that because of this lot of capacitors, also I not sure about the inductors. Are they really doing any work there? Since the external power supply is - supposed to be - linear, I guess all those capacitors are necessary.

Apart that, those caps are taking extra money and extra space in PCB board.

What do you think?


texts: Simple power line communication circuit PLC design?

texts:
I need simple PLC power line communication design which I could transmit /receive a packet of data through two points ?
Any block diagram with little details will be great for me  .

Update :
Data speed doesn't matter , distance of transmission will be large (several kilometers ) , Data will be packets in 4 bytes +- 2 bytes, security is very important ,what's the available off-the-shelf products .


texts: How to fix a specific design problem and turn led on and off with shift register output signal

texts:
I've made a design mistake in one of my prototype boards and I need help to fix it.

The circuit is a common-anode 7-segment display driver based on a 74HC595 shift register and an Atmega328 uC. The problem circuit is shown below.

I wanted to control the led (the display decimal point) with the QA signal (output pin 15 on the 595), but the problem is that the LED is always on, regardless whether QA is HIGH (5V) or LOW (0V). I made the mistake because I though I was driving a common-cathode display, so I thought that the +12V source was actually GND.

How can I fix it, easily, with the least amount of through-hole parts and taking the least space on the board?

My only guess would be to add a 7V zener (reverse biased) between R1 and LED1 like in the figure below. Assuming a voltage drop of 2V on the LED, it would be OFF when QA is HIGH, because the voltage on the zener would be around 5V (12-2-5=5V), less than required for the zener to conduct, while it would be ON when QA is LOW, because the zener would then be submitted to around 10V (12-2=10), which is a higher voltage than required for it to conduct.

Would adding the zener work? Or I just don't know how zener diodes work at all?


texts: What is deciding the current of an AC to DC circuit

texts:
I'm a beginner, trying to build a power supply based on the sketch below to convert 230V AC to 5V DC. My final aim is to supply precision voltage for Arduino, which I think is 5V 700mA.

Here is the circuit diagram:

So what are the parameters here to decide the current, or how can I get a sharp 5V 700mA DC output? Also do I need to add any more components here to make it more precise for this purpose?

Also one more request: The Voltage regulator specified is LM7805. Is that OK or are there better options? Kindly advice any serious changes needed on the circuit.
(Reference I'm using here is this video)


texts: How to drive a high side MOSFET with an optocoupler correctly?

texts:
I am trying to create an absolutely minimal motor driver, to create a <5$ low power odrive. But since I am only a software developer, I do not have a 100% understanding of analog components, and need some help for calculating the right values.
I am following this web page, which describes the calculations:
https://learnabout-electronics.org/Semiconductors/opto_52.php
I have also read this answer on this site: How to drive a MOSFET with an optocoupler?
My schematics looks like this:

For simplicity, I am using only OnSemi components.
The goal is to drive a 24V around 2A BLDC motor at around 30kHz PWM.
ECH8660 is a dual complementary MOSFET, 30V, 4.5A, 59mohm, -30V, -4.5A, 59mohm. Since KiCAD did not have the necessary symbol, I had to create one by copying parts from other symbols.
My first question: The P Channel MOSFET is mirrored, so the Source looks up, and both MOSFETS have their body diode pointing upwards. Is this symbol correct?
FOD817A is an optocoupler with Continuous Collector Current 50mA max. It has the following CTR:

My second question: If the MCU's datasheet lists max 20mA output per output pin, then is driving by 10mA an acceptable choice, or should I go lower if it is possible?
My third question: The FOD817A datasheet lists information for other versions, and actually I wanted to use FOD817C: CTR 200–400% (instead of FOD817A: CTR 80–160% which I guess is on the graph), but I cannot find the CTR graph for that. How can I deduce that information?
Using the above linked Stack Exchange question, I have both a pull-up and pull-down resistor (R2 and R3), which should pull down the MOSFET gate to +12V (it has an absolute maximum Gate-to-Source Voltage of +-20V).
Fourth question: Is -12V a conservative drive voltage, or should I use different resistors? (Having identical R2 and R3 would make the BOM simpler.)
The above linked tutorial web page has two examples, both driving a PC817 at 5V/4mA. In the first example, the output power supply is 5V, and it calculates 4.6mA output (at 115% CTR). But in the second example, the output power supply is 12V and it says that:

As the CTR of the PC817 is around 115% the phototransistor can supply about 9mA as the supply to the phototransistor output is now taken from the 12V motor supply.

Fifth question: Should I follow this advice and calculate with 10mA * 125% * (24V / 5V) = 60mA instead? Or should I use 12V only in the calculation, because the two resistors halve the voltage at the optocoupler? (Obviously I want to charge/discharge the gate the fastest possible.)
Sixth question: How to calculate what kind of D1/D2 I need for handling the back EMF?
Seventh, final question: Is it possible to eliminate D1/D2 and just use the body diode? (I know that it is only a parasitic crap diode.)
I ask this, because I see the following prices (for 1K+ units at OnSemi site):

ECH8660: $0.2071 @ 3K (seems to be cheaper than two separate N and P channel MOSFETs)
FOD817A: $0.092 @ 2K
MBR130T1G: $0.0648 @ 3K (1.0 A, 30 V, Schottky Power Rectifier)

So two diodes + dual MOSFET costs 0.3367$ while a ECH8690-TL-H costs only $0.2913 @ 3K. (It is 60V, 4.7A, 55mOhm, -60V, -3.5A, 94mOhm, protection diode built in.)
Thanks, any help is greatly appreciated!


texts:
I want to set some rules for certain components. These rules are in the minimum solder mask sliver however I'm stuck on the query.

So far I've written IsDesignator = U7 but nothing seems to change and I'm still getting error for rule violation.

I'm not sure if my syntax is correct but regardless, using designator to set the rule is inefficient. I want to include the component type instead.


texts: How to determine electrical energy consumed by knowing the current of motor?

texts:
I have an AC motor. It is running for 1 hours and I read the current every one minute and it reads 2A.

So how to know how much the energy my motor already consumed? In this case, voltage is steady at 220V and not knowing the power factor(or make an assumptions that it is constant).


texts: Fast detection of transient temperature change.. RTD? Thermistors? Thermocouples? or something else?

texts:
If I want to detect temperature changes on the order of 10ms, what is the best technology to use (besides IR)?

I know Thermocouples and RTDs are pretty slow.. not sure about Thermistors.


texts: 3 State Shift Register with 2-to-1 multiplexers

texts:
For a homework assignment I need to

  Redesign the right-shift register circuit of Figure 12-10 using four D
  flip-flops with clock enable, four 2-to-1 MUXes, and a single OR gate.

The figure mentioned has three states, No change, Load, and Right shift. The loads are each from different inputs. I have been able to figure out how to do any two of these states without the OR gate, but I can't seem to figure out how to get all three to work. I suspect that I need to somehow stop the clock when I want to achieve the "No change" state.


texts:
I have a doubt on the relationship between phase and frequency. We know that the definition of angular frequency is:

ω(t) = d(\$phi\$(t) / dt, where \$phi\$(t) is the istantaneous phase of our signal.

In this case ω(t) is a function of t. We can write:

If we pass to Laplace domain, we get:

Is it correct to say that, if we want to pass to Fourier Transform, s = jω, and so writing

\$phi\$(jω) = ω (jω) / jω

?

It seems quite strange to me (I think that s = jω represents the angular frequency of the signal "angular frequency" ω(t), and so not equal to jω), but somewhere I read this statement.

For instance, I saw this statement for proving that the Spectrum (power spectral density) of Phase noise is bounded to that of Angular frequency through the relationship:


texts:
I have found a turbocharger from a motorola device which has 5V, 9V and 12V outputs.
I want to use this charger to run raspberry pi 4.
I need to know how tutbocharger changes the voltage?
I am scared of the fact that it can supply 12 volt too. Which will burn the board.


texts: VDC booster effect on LiFePo battery run time?

texts:
Looking for info to devise a solution for a mobile video rig.  I work in the film industry and it would be VERY beneficial to run my video cart from battery power, as opposed to always having to plug into AC mains.  I would love to use off-the-shelf components to distribute DC power for my various video devices, so in case of failure I'm minimizing my need to break out tools and a soldering iron, and can just replace parts.  I would utilize 12-14v batteries common to film sets for this.

I use 2 large production OLED monitors than can be powered via AC or DC, and DC can range from 12-24v.  However the consumption of the monitors is about 50w each, which is just over 4 amps per monitor at 12v, which exceeds the per-port capacity ratings for the off-the-shelf DC power distribution components I'm considering - using 4-pin XLR connectors.

My idea is to put a small voltage step-up regulator on the back of each monitor to boost the nominal 12-14vdc to roughly 24v, which would bring the amperage draw for each monitor down to just over 2A for each monitor, if I understand correctly.  My question is, am I correct in my assumption here that this would NOT overload the XLR circuits for the monitors in the power distribution equipment by adding these regulators?  I know I'll have some energy loss due to the conversion, and how would this potentially effect other 12v equipment on on the same power network, all pulling from a single 30Ah LifePo battery?  Would it be better to put the dedicated circuits for these step-up converters directly from the battery on their own lines separate from the rest of the distro?

Thanks in advance.


texts:
I want to make a fan with led. I have a motor and led which are from old toys and torchlight. I not sure about their "specs" but this are their operating voltage and method:
Motor:
using two AAA batteries, 3V
Led:
using three 1.5V button cells, 4.5V, not sure about the amperages,
How can I circuit it with 5V USB with 1A? Just need some help on resistor. Parallel or series circuit work? If I have any wrong please tell me.
p/s:sorry for my grammar, I'm not a native speaker of english


texts: I found some sensors in online shops titled VDO sensors (Click on this link to check an example). I checked on google but nothing much came related to VDO. Can anyone kindly explain the meaning?


texts:
Please take a look at this waveform of a 3 phase, BLDC motor:

Check out that rising and THEN falling slope...Pretty nice.

Now, take a look at what I'm getting on my motors sensorless resistor divider(s):

Not bad, but the BEMF is backwards...It rises when it falls, and it falls when it should rise.

I've tried manually commutating this thing from hundreds of mS all the way down to uS, where it freezes...Nothing seems to get this thing to turn around.

I've taken the advice from here, but nothing seemed to straighten this out.

I've inverted the PWM/GNDing phases for each of the 6 commutations steps, and that didn't change anything.  I've tried physically swapping the phases on the output terminals...nothing there (not that I would have expected it to....I would have just expected the motor to run backwards).

What causes this?

EDIT

Here are some schematics of what I have going on here:

And here's a logic trace of the noninverted outputs from the micro to the gate driver.  Keep in mind that each of these has a complimentary output as well, to let the gate driver pull the phase high or low, but that signal isn't shown here... But, trust me, it's there.


texts: How do I find the resistance between A and B in this circuit?

texts:
Find the resistance between A and B in the following circuit:

My Thoughts:

It is not the typical circuit that I see, but I'll give it my shot. Now part of mind is saying that the resistance should be 30 Ohms, because that is what it is between A and B. But then that would make this whole question too easy, and too good to be true.

But, lets suppose we find the Resistance of the two parallel resistors 30 Ohms, and 30 Ohms. We have:

I apologise in advance for drawing this by hand because I don't know how to draw computer version of circuits.

But still the Resistance between A and B is 30 Ohms. The answer at the back of the book is 10 Ohms, and my book shows no method whatsoever.

Why is the resistance between A and B equal to 10 Ohms?


texts: How to realise bidirectional ports in FSMC function of STM32?

texts:
I am using FSMC(Flexible static memory controller) function of STM32:reference manual.On page 494 of referencec manual, the data bus should be bidirectional. It is reasonable but i have no idea how to realise it in STM32 because it has only two modes: input and output mode(on page 166). After refering to examples from ST, i know that the data port should be considered as ouput push-pull mode as shown below,

/*data line configuration*/
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_8 | GPIO_Pin_9 |
                            GPIO_Pin_10 | GPIO_Pin_14 | GPIO_Pin_15;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOD, &GPIO_InitStructure);

So,can anyboy tell me how can STM32 realise bidirectional port using output push-pull mode?


texts: Warming PCB in cold environment using SMD components only

texts:
I made a sensor board that needs to operate at about -55 degrees Celcius. Unfortunately, its key component often malfunctions when the circuit is cooled for days at the temperature and then powered up. The sensor starts to operate normally after it runs (improperly) for several minutes since the power-up time. Thus I want to warm the board up and then power up the sensor.

There are environmental conditions that make it very difficult to use a simple solution. An external heater cannot be used, because I have no more space than the space for the PCB itself(3cm x 3cm x 5mm). It seems the only feasible approach is to heat the board by adding several SMD components to the PCB circuit, for example, a linear voltage regulator and resistors. The max. power supply is limited to 0.5W, but the sensor IC already consumes up to 0.3W. Thus the sensor and the heater cannot run at the same time. I might have to heat the PCB first and power up the sensor. The allowed time for the heating is up to 30s.

Could you please suggest efficient solutions to the problem? I wonder if there is a better solution than to place a linear regulator with a heat-sink and 2 to 4 0603(1608)-size resistors around the sensor IC. By the way, the board has 4 layers(top/power/GND/bottom) and the copper content is 1oz.


texts: LTSpice - simulation doesn't match predicted (Chebyshev filter)

texts:
I'm a newbie who's trying to simulate a Chebyshev filter for which I used the calculator at https://www-users.cs.york.ac.uk/~fisher/lcfilter in LTSpice. The behavior I'm seeing in LTSpice (XVII if that makes a difference) doesn't match what's predicted by the calculator.

Here's the circuit:

Here's what's predicted:

Here's what I built in LTSpice - definitely not a 171 MHz highpass filter based on the graph.

What am I doing wrong?

Arsenal pointed out in the comments that my range was obscuring things. I adjusted the range to show more reasonable values:


texts: How can I control the connection/disconnection of 8 bi-directional logic level lines, one 5V-50mA power, and a ground line with one SPST switch?

texts:
Using a single SPST switch, is there an IC (or other device) that can act as a relay for 10 individual circuits?  8 Logic level bi-directional lines, one 5V-50mA power, and one ground.

I considered using 10 transistors, but I don't believe the bi-directional logic data would work over this.


texts:
Power supply for headphone tube amp gives me 10-12V lower voltage comparing to the schematic (my measurements are in red for amp under load). Current under load is about 70 mA.

Using simple formula : 150V * 1.414 - 2V = 210V also gives approx voltage shown in the schematic.
I even tried to do simple simulation by using www.partsim.com, and it also gives about 170V for B+ and about 210V on the first filter capacitor.

I don't know what is wrong. I've triple checked all diodes, capacitors and resistors. They are all fine, and are connected correctly. I am still missing 10-12V.
Edit : transformer data


texts: Choosing bypass capacitors for successive linear regulators

texts:
Background:

I am reviewing my prototype PCB to iron out previous issues. The PCB is a Bluetooth data capture unit for liquid levels and flow. I am a software programmer by trade and I have some formal digital electronics training, the rest I learn as I go along, I would really appreciate it if some of the buffs over here could point me in the right direction.

Circuit breakdown:

Supply

10 - 15Vdc -> Buck/Boost -> 12VDC -> 5VDC -> 3.3VDC

Load: +-500mA

two 5V MCUs
5V RDM6300 RFID reader.
3.3V HC-06 Bluetooth module.
two 12V 4-20ma sensors
four 5V LEDs
two transistors

Problem:

Reliability. Currently I drive a LD1117V33 3.3V regulator from a 7805, which I drive from the 12v DC/DC converter. As you might guess the 7805 gets hot even with a heat sink. I love the boards and would like them to last a long time out in the hot field. So due to the affordability and seeming simplicity of regulators as opposed to DC/DC regulators and the fallout of cascading ripples on my analog circuits, not to mention the questions about shared grounds and isolated grounds etc, I want to add an additional 7809. So that I have 12v -> 9V -> 5V -> 3.3V to share the thermal dissipation load.

My problem is how do I go about calculating the input and output capacitors for each of these regulators? Particularly, how to address that the output capacitor of one regulator is the input capacitor of the next regulator? The current 7805 -> LD1117V33 seems to work fine with 1uF input and 100nF output on both.


texts:
I am looking at the product specs for an IR light and see that it has:

Beam Angle: 50 deg

Viewing Angle: 25 deg

What is the difference between viewing and beam angle?

What is the difference between the two?


texts:
I would like to be able to reset an XBee with an Arduino by connecting the reset pin on the XBee to a General I/O pin on the Arduino. I'm wondering if any additional components (transistors, resistors etc.) are necessary between those pins.

I found this tutorial on ladyada, but it shows how to reset the Arduino with the XBee which is the opposite of what I'm looking for.
Schematic from the tutorial:


texts: Simulation issues with a simple 3-phase rectifier circuit

texts:
I'm trying to do a ngspice simulation of the currents flowing through a diode bridge and smoothing capacitor from a 3-phase permanent magnet generator. I'm consistently riddled with convergence issues (Timestep too small; ... trouble with node "l13"). The circuit seems simple enough and I can't figure out what's wrong with it. The only odd thing about it is the large amount of power, around 200 kW.
Other system parameters:

the rectified voltage is about 500Vdc (each phase amplitude ~308V)
the average rectified current about 400A
the three ideal voltage sources I'm simulating below are, of course, offset by 120°

Here's what I'm simulating (if I haven't messed up anything in the code):

simulate this circuit – Schematic created using CircuitLab
The code is:
.title 3-ph smoothing cap simulation
.include DIODE2.lib
VV2 0 L11 DC 0V AC 1V SIN(0V 308.641975308642V 500.0Hz -0.0s 0Hz)
Rsrc1 L11 L12 0.004
LESL1 L12 L13 2.6e-05
DD4 L13 up DSEI6006A
DD1 down L13 DSEI6006A
VV3 0 L21 DC 0V AC 1V SIN(0V 308.641975308642V 500.0Hz -0.0006666666666666666s 0Hz)
Rsrc2 L21 L22 0.004
LESL2 L22 L23 2.6e-05
DD5 L23 up DSEI6006A
DD2 down L23 DSEI6006A
VV4 0 L31 DC 0V AC 1V SIN(0V 308.641975308642V 500.0Hz -0.0013333333333333333s 0Hz)
Rsrc3 L31 L32 0.004
LESL3 L32 L33 2.6e-05
DD6 L33 up DSEI6006A
DD3 down L33 DSEI6006A
RESR_C up cap_up 0.048
CC1 cap_up down 0.0027
Rload up down 1.25
.options TEMP = 25C
.options TNOM = 25C
.options ABSTOL = 1e-14
.ic V(down)=-250.0 V(up)=250.0
.tran 6.944444444444445e-07s 0.006s 0s
.end

The model for the diode is:
.MODEL DSEI6006A D( IS=148.21E-6 N=1.8882 RS=3.0622E-3 IKF=811.78E-9 CJO=1.0000E-12 M=.3333 VJ=.75 ISR=406.73E-9 NR=4.9950 BV=600.05 IBV=1.2932E-3 TT=26.602E-9 Vpk=600 Iave=60A Vpk=600.0V Iave=60.0A)
I've looked into "Overcoming SPICE Convergence Issues" but it does not seem to help.
Besides the large power, the other thing I think might be the issue is the rectifier diodes. I've tried different models, and the ones in the code (DSEI6006A) are grossly inadequate for the power, but were the most powerful I had models for (the real application will use a proper diode bridge module rated for ~500A).
Question
What's wrong with my ngspice code, why it causes trouble? I'm new to SPICE so I don't know what the pitfalls are.


texts: Connecting multiple HC-06 bluetooth modules to multiple smartphones at the same time

texts:
So I'm having a "robotics" workshop for kids and we are going to control 6 robots with bluetooth modules. They run on Arduino. I tested the code before class and it worked as expected. I also changed the names of all six modules to random numbers/letters. Now here comes the problem.
When the children connected the modules and powered them on, there should be 6 bluetooth devices listed in the smartphone bluetooth list, right? Well as it turns out, only one was seen. From 6. If we powered only 2 on, there would still be only one detected bt device on smartphone. When one was disconnected, the other one showed. I don't even know where to start searching for help, so I thought maybe somebody here could give me the correct answer.
Thank you!


texts: High power three phase ac motor controller

texts:
I have come across this question a lot in the design of a special 3 phase motor controller I plan to build this summer and I think I need to ask it directly to solve it.

I need to be able to modulate 3 phase ac with mosfets with a 12 to 24 volt dc supply voltage.
I have this figured out for the most part I want to use only n type mosfets for phase symmetry. Driving them with a high power source relative to the main supply they are switching. I will use optical coupling to the MCU.

However I need to drive between 8 and 200 amps, the driver boards can be made separately in different capability ranges. But I don't think I can get around wiring mosfets in parallel this device also has to conserve space and weight.

What is the best way to create the driver circuit preferably out of surface mount parts?


texts: How is this figure supposed to be interpreted in the datasheet for the LM4766 audio amplifier, and determining the needed power requirements?

texts:
First off, I really have no experience when it comes to audio electronics, so forgive me if these are naive questions.

In any case, let me explain what I'm doing/trying to do. I have two speakers that can hand 25 watts (RMS) with a 50 watt max. The impedance of each is 8 Ohms.

Ohm's law gives us the simple equation P = V^2/R, so V = 20V when we're at our 50W max. Also, the speakers would draw 2.5A each.

I obviously need to amplify my audio source, and to this, I plan on using the LM4766 from Texas Instruments (Datasheet). According to the datasheet on page three, the supply voltage is defined to be |Vcc| + |Vee|, where Vcc is the positive supply voltage and Vee is the negative supply voltage. The max supply voltage is 60V.

Now here's my question. In figure 18 on page 10, pictured below, Output Power vs Supply Voltage

is plotted. I find this plot somewhat ambiguous. Is it saying, for example, that if Supply Voltage = 25V (Vcc = 12.5V and Vee = -12.5V), then the output power is roughly 27W? Or is it saying that if Vcc = 25V and Vee = -25V, then the output power is roughly 27W?

Any input would be appreciated.


texts: High-side switch 24V 6mA control by Arduino

texts:
I would like to ask for best solution for my issue.
I need high side switch for 24VDC 6mA (it is enable signal for a device).
This device I want to control by Arduino (input 5 V 20mA).

What is the best solutions for this low current?

I tried to use Sziklai pair, but PNP transistor is still open. I don't know how to calculate resistors between NPN and PNP :-(. Do I have to use a sziklai pair or is there something else?

simulate this circuit – Schematic created using CircuitLab

Thank you so much

Lukas


texts: How does a powerbank detect a connected USB device?

texts:
I got a powerbank powering a raspberry pi over the micro usb port of the raspi. The usb cable I use, has only to lines, Vcc and GND. When the powerbank is off due inactivity and I connect the raspberry pi, the powerbank does not turn on by itself, only if it is turned on by its hardware button.
But when I connect my smartphone to the powerbank, it turns on automatically.
So my question is, how does the powerbank detect when an USB device gets connected and how can I make it to automatically detect my raspberry pi on connection?

Thanks for all help.


texts: What is the difference between SPI,SCI and SDI?

texts:
Hi I'm trying to interface an audio codec chip VS1053B  with my STM32L476 Microcontroller. But in the microcontroler there is SPI interface and in the VS1053B  chip it is SCI interface with few extra pins as,
XCS  - Send Command (Active Low)  ,
XDCS - Send Data (Active Low),
XRST - Reset (Active Low),
DREQ - Data Request.

What is the purpose of these pins? is it possible to interface this IC using SPI? What are the major differences between the interfaces, SPI,SCI and SDI??


texts:
Question:

I had solved easier circuits problem using nodal analysis but this one it has supernodes on nodes 2 and 3 which I find it difficult solving. thus I need help as I am trying my very best to solve.

i think we had two supernode and applying kCL see below.


texts: pic16f628a internal oscillator setup error undefined symbol "INTOSC"

texts:
I want to set internal oscillator for pic16f628a, according to datasheet page 96, I have to set FOSC_INTOSC, but I get this error main.c:11: error: undefined symbol "FOSC_INTOSC"

if I set the other option FOSC_HS or FOSC_LP or FOSC_XT it works fine (no error)

but it's not working with FOSC_RC and FOSC_INTOSC .it's not because  for FOSC_RC and FOSC_INTOSC, there is two possible value for both of them (page 96 datasheet)?????

code :

#include<htc.h>
#include <pic.h>
#include <pic16f628a.h>
// Config word
__CONFIG(FOSC_INTOSC & WDTE_OFF & PWRTE_ON & CP_OFF);

// Define LED pin
#define LED  RA0

// Define CPU Frequency
// This must be defined, if __delay_ms() or
// __delay_us() functions are used in the code
#define OSC 4
// Main function
void main()
{
        TRISA0 = 1;                // Make RA0 pin output
        TRISB = 1;
        LED    = 0;                // Make RA0 low
    while(1)
    {
        LED = 0;               // LED off
        LED = 1;               // LED on
    }
}


texts: I would like to remove the n27 sockets from household light fixtures and replace them with LED lights used in the automotive industry. I would like to put a reasonable amount of LEDs in the fixture to provide commensurate light of say, a 100 watt bulb. I would like to have a light in every room (7) and run them off of a 12v battery charged by PV.  Obviously wired seperate from the AC system which will be abandoned. My question is do I have to regulate amperage.  If how or what do I do that with, do I need it for each light fixture?  If not you're my new favorite.


texts: Wiring for Logic Level Converter to 1.8V SPI Flash with a 3.3V programmer

texts:
I have a 3.3V SPI flash programmer that I would like to use to flash a 1.8V SPI flash chip.
I have read that I could use a logic level converter to do this but I can't find wiring diagrams.

There is a good article here "How do I write to SPI flash memory?" on how to flash SPI but I can't seem to find any good article on how to wire a Logic Level Converter like "https://www.sparkfun.com/products/12009" to convert 3.3V to 1.8V to flash a 1.8V SPI chip with a 3.3V programmer.


texts: problem in defining parameters in CST Suite Studio

texts:
I want to define the thickness of a material as a parameter in CST Suite Studio. When I give the integer value to the parameter, the model is designed correctly and has a thickness, but when the value of the parameter is decimal, the material is drawn without thickness and does not accept the value of the parameter.
Thank you for guiding me if you have any ideas.


texts: Okay to have both negative and positive grounded equipment at same site(location)?

texts:
We have a radio comms site with multiple equipment. Originally the site was set up with a positive ground at the rectifiers. We have some new equipment that is powered from the rectifier shelf, that will not work well with a positive ground. We were thinking of changing one of the rectifiers to a negative ground. My question is would this cause a problem?

In my mind, having a positive ground and negative ground connected to the same main site ground just seems wrong, but is it? Would there really be a conflict here or not?

All voltage is DC, with exception of input power to rectifier shelves (120AC).


texts:
I am trying to design a SMPS for a project (I have to make a custom one for integration purpose).

This SMPS have universal input (85-265V AC at 50 or 60 Hz) and an output of ideally 53V (but it can be between 51 and 55V, it does not really matter much).

I am not really familiar with SMPS design, so I used the WEBENCH TI tool to get a quick design that I can integrate in the project (it does not have to be perfect yet, it is just for a prototype).

My question is: how do I select and off the shelf transformer (from mouser, digikey or else) to meet the design requirement (again nothing as to be perfect) because I do not want to other custom design transformer for something that will likely change in a couple of weeks (and I do not know one thing about winding one).

Here are the parameters from TI calculation tool:

PS: I want to precise thatI tried several time to do it by myself, but I think that I do not understand the system weel enough to make a proper selection.
For example, I do not know how the inductance affect the output voltage and current.


texts: Which of these approaches for a watchdog timer?

texts:
I recently learned about watchdog timers, and am trying to implement one for my circuit for the purpose of resetting my (AVR) microcontroller if it hangs (i.e., doesn't respond to the watchdog).

Based on some research, it appears to me that there are around four options:

Connect my microcontroller with an external dedicated watchdog-timer-specific IC.
Connect my microcontroller with an additional microcontroller (some very basic, inexpensive one), the latter coded for the sole dedicated purpose of watchdog-timing.
Lay out my own 555-timer-based watchdog circuit and connect it to my microcontroller.
Use the internal watchdog timer capability on my microcontroller.

.

Which of the above approaches would you rank higher and why?

I would like to set a watchdog time of around 6 seconds, based on certain criteria for the way I'm making the rest of my design and code (the device will be a battery-powered, periodic temperature logger).

A little note: My preference would be Option 1, for simplicity, however, based on the couple I have found, these parts either appear to be expensive (I'd like a solution under 1.25 USD at most), or only allow only less than 2 seconds for the watchdog timing period.


texts: Over-volting an hard disk voice coil actuator

texts:
I have disassembled an old hard disk and I making the voice coil move by applying a voltage between the terminals of the coil.
I plan to use this to raise or lower a flag attached to the actuator arm.

The problem is that if I use a voltage of 5V the actuator can't generate enough torque to lift the flag. If I give it 12V, then it works.
The current across the coil is around 600mA.

However at 12V when the actuator is powered the coil will start to heat very quickly, enough to be painful to touch.
I have tried to keep it powered up for around half an hour and I didn't see any damage, just a lot of energy being converted into heat.

However I am worried that on the long run the heat might damage the coil. In my application the coil might remain powered for around 3 to 5 hours, in an environment that can get to 40°C ambient temperature.

Am I being paranoid or is there actually a risk of melting the the coils or otherwise damaging them ?

To clarify, after reading some of the answers below: I appreciate the fact that I am using the device well beyond its designed operation parameters for a function it was never intended for. What I would like to know is if this can cause enough stress to destroy it, or if there are no other likely side effects beyond the extra heat that is generated.
For example I know that a DC motor that is operated at a too high RPM can destroy itself in a various ways. But I have no idea about a voice coil actuator.


texts: What is the valid capacity ranges of Lithium Ion 18650 batteries?

texts:
I'm seeing wildly varying capacities that are seemingly fake on 18650 cells, such as these "9,800 mAh" ones on eBay, but are ~$1 / cell.

However, 'genuine' cells from Panasonic and similar name brands seem to top out around 3,500 mAh or so, but cost more like $8 / cell.

How can I tell true capacity apart from the lies?


texts: How to connect to tiny pogo pins in test fixture?

texts:
I'd need to build a test fixture with very small pogo pins (1.27 mm spacing between the closest pins).  I've seen fixtures before that use very long, very thin pogo pins almost exactly like this one in the drawing - 0.5mm diameter:

Now the question: how the heck does one attach anything to the base of this?  The base is just a round pin, no solder cup or anything, there is really nothing that a wire can attach to, and I don't think soldering to a PCB through hole is the usual approach either.

I've seen an array of these stuck through a piece of drilled fiberglass (I think just press-fit through) but I never saw what the electrical connections looked like underneath.

What's the usual approach to building test fixtures using these types of very small pins?  How to connect electrically and how to hold them in place?


texts: Need some help to calculate the resistance in a transistor circuit

texts:
I need some help with my transistor circuit. I have this circuit and I'm supposed to find the value for RD and RS, all other values are known. I think I managed to simplify the circuit on the second figure. However, when I try and calculate the resistance for RD and RS I get negative values. I'm not quite sure if my equations are set up correctly or if I'm missing something here.
I_DQ = -6mA
E = 12V
Vgs = 1.025V
Idss = -12mA
R3 = 400k ohm
R4 = 200k ohm
RL = 400 ohm
Thanks


texts:
You need 4 channels to determine your position (including elevation), and I can understand that a few extra channels increase accuracy. However, there are maximum 12 satellites in view at any time, so why have receivers with more channels? I've seen receivers with 50 or even 66 channels, that's more than the number of satellites up.
I don't see any advantages in this explosion of number of channels, while I presume that it does increase the receiver's power consumption.
So, why do I need 66 channels?


texts: Do the MCP23S17 GPIO pins need protection against latch up ESD within this circuit?

texts:
I wrote about this system before. I will focus my questions now on "ESD protection" direction.
I have an SPI based system in which a Raspberry talks with a GPIO expender device using SPI communication. The chip reads and/or writes '0'/'1' and send it to the Raspberry by bus.
The expander GPIOs circuit is a very simple circuit, but somedays a dangerous overconsumption/overheating (it almost burns) is triggered randomly after hours of correct operation. This stops when I reset the device. After this, the device has normal behaviour and normal consumption. Nowadays system is being connected and tested on a protoboard. So, wiring or lab material may be affecting a little or a lot.
Some people suggest that this behaviour seems to be a "latch up" caused by ESD. Otherwise it could be caused by voltage spikes, positives spikes or negatives GND ones. So, they told me that my GPIOs need to be protected with resistors, diodes and capacitors. But I don't see any example with diodes, Cs and Rs protecting inputs/outputs in other microcontroller or microprocessor based projects. The most I have seen are series resistors at some of the GPIO pins.
My circuit is too much simpler than those I have seen:

8 expander pins will be inputs. The rest will be outputs.

Expander outputs will be writing '0', never '1'.

Expander inputs has an internal Rpull up that put input at 3.3V when not connected.

I put a wire at every output and this wire could be connected directly to the inputs or not. So when read  the 8 input pins, those who are connected to the inputs will read '0', and the rest, will read '1'.

An input would read these 3 scenarios:

'1' (when not connected),
'0' output writing (if they are connected)
'0' = GND (if a GND point makes direct contact with an input).

A particular characteristic of this system is that GPIOs will not be configured as inputs or output for the rest of the times. So during one execution a pin can be configured as an input during initialization, but at the next execution the same pin could be configured to be an output.
This overheating phenomena doesn't happens more than once or twice per day. But I'm afraid that once would be enough to destroy the system.
At final PCB design GPIOs pins will be traced through the board achieving a 64-pin connector. Input and output will be connected through a wire that will connect -or not- two of the 64-pin connector pins by human connection during execution. This way, a circuit  between one input and one output could be closed. But there could also be open circuits between the rest of inputs and outputs.
I have added 10K Rs at every device GPIO and I'm using a 100nF between VDD and GND. It seems not to happen anymore two days ago, but I would like to ensure my GPIOs if the circuit really needs.
Does this circuit need GPIO protection? Are these resistor enough?


texts: 9V powering to the safest maximum brightness of 4 IR LEDs in series

texts:
I have created a circuit which powers 4 infrared LEDs (datasheet as shown below).

I wanted to know if I am very close to getting the maximum brightness out of my LEDs. Here is my schematic:

9V DC-22 ohms resistor-4 IR LEDs (in series)-GROUND


texts: I am using MAX1484 chip for communicating thru RS485. It is a two way communications with Receiver and Driver built in. If I am to use only the receiver part and I want to disable the driver part, I need to pull low the DE (driver enable) pin. And also the DI pin. What I want to know is whether this pin can be directly shorted to ground or pull to ground via a resistor like 1k or 10k.


texts: Can I use multiple MOSFETs with one 555 timer?

texts:
I would like to use a 555 timer to operate a 12V heater which draws about 13 amperes.
Would using two MOSFETs in parallel connected to the 555 output be a good solution to improve output power compared to one MOSFET? I have a couple of 2SK1941 spare with a rating of 16A.
I was looking at this earlier.

Would simply using one resistor from each MOSFET to the 555 with maximum 200mA output be ok?
Should I have the 555 output trigger a transistor with a higher power rating to drive 2 MOSFETs?
Is it going to be very complicated to split the load evenly between the MOSFETs?


texts: How to multiplex one clock among multiple selectable outputs?

texts:
I'd like to route a single clock signal to one of several possible destinations by means of a few (2 or 3) address select lines.

Background: I'm driving 595 shift registers from a microcontroller (Arduino for now, possibly ESP8266 later).  I want to have multiple (probably 4, possibly 5 or 6) separate chains of SRs that can be driven separately, so that I can (for example) drive 14 segment displays on each chain, and scroll (shift) each separately.  My original design had all of the SR chains sharing \$\text{SER}\$,  \$\text{RCLK}\$, and  \$\text{SRCLK}\$ lines from the microcontroller, and using a 3-8 decoder to drive the \$\overline{\text{SRCLR}}\$ as a sort of "Chain select".  However, I realized that \$\overline{\text{SRCLR}}\$ also clears the input registers, which would ruin the ability to scroll the outputs... I'd need to "refill" each SR chain after its \$\overline{\text{SRCLR}}\$ was low.

My next idea was to use a separate \$\text{SRCLK}\$ for each SR Chain.  Option B of this ESE answer suggests the same approach.  As long as \$\text{SRCLK}\$ doesn't change, any signals on \$\text{SER}\$ won't change the input registers and any change on \$\text{RCLK}\$ will re-latch the same data to output.  However, I don't want to have multiple physical pins for the multiple clocks because (a) pin count constraints, and (b) I'll probably use the Hardware SPI port to send data to the SR chains.

Which leads me to the question.  Assuming I have a single clock pin (output) from the microcontroller, how can I send that signal to only 1 of several possible destinations?  Assume 3 address lines driving a 3-8 decoder, giving me 8 "SR Chain Select" signals.  I'm considering using an AND gate for each SR Chain, with the clock as an input to each, and the 8 Chain Select signals as the other input to each (ignoring for now that most 3-8 decoders output 7 highs and 1 low, so I'll likely need an inverter on each decoder output line).  See schematic below (only 4 AND gates shown for reduced size). Is this the best solution, or is there a better approach?

simulate this circuit – Schematic created using CircuitLab


texts: Wardrobe Under Shelf LED lighting that can be moved about freely

texts:
Hi I have seen a design for some LED strip lighting that is very simple to understand but am really looking for the various components so that I can replicate it. It seems that I don't know the right keywords for a successful google search so if you could translate it into the right components I would be grateful.

The wardrobe shelving is cantilevered off the wall. The system comprises of metal wall profiles and metal shelf brackets that hang off this and attach to the shelves.

Now here's the cool bit.
The wall profile has an electrical dual contact strip running the entire length of the profile - about 2meters - this is connected to a 12V transformer to drop the mains voltage - this is no more than 1-2mm thick and 8mm wide:

The shelf bracket then has what looks like a strip of flexible circuit board with adhesive backing and a pair of electrical contacts at both ends. The far end contacts look like they are sprung prouder  - almost small ball switches on an LED strip - so that when you insert the bracket into the wall profile, they get a good connection:

There is a similar connection on the side of the shelf itself so when it is attached to the bracket you get a good connection as well:

The LED's are then wired normally by coring through the shelf and routing a channel for the LED profile:

This design means that if you need to change the configuration of the shelf you don;t need to do any re-wiring.

So the components I'm looking for is:

The long contact strip - possibly some sort of dual silver alloy strip?
The slim pair of contact terminals
The ball switch connectors for the shelving.

I hope this make sense.

Thank you


texts: Troubling understanding simple diode circuit

texts:
Assuming that the diode is OFF, the following affirmations come:

I can't understand the affirmation that Vd can't be positive... Where does that come from?


texts: If voltage is the potential, is current always within the potential?

texts:
I hear plenty of people saying that voltage is just the potential for current to flow through, ergo, not actual flow.

However, if the potential is higher, the current CAN be higher.

So my question is, if the voltage is, say, 120v, does that mean current can't be more than 120 amps(falling within a potential)? If no, please elaborate on what "potential" exactly means within a circuit.

Saying "the difference between two points" doesn't really form a good understanding in my brain.

Voltage = current / resistance. If a circuit has no resistors, does that imply that the current is equivalent to the voltage(no resistance)?

If I'm right, please explain how. If I'm wrong, fill us all in here with what exactly "potential" means, and how it affects current, is related to power/energy, etc.

EXTRA: What I can't seem to understand is how this all works together. Someone tells me voltage is current divided by resistance, but if there's no resistance the current can be enormously powerful with almost no voltage? What?! No one seems to make sense of this.


texts: New to microcontrollers...options for getting up and going cheaply

texts:
I've never designed a microcontroller circuit before, but have programmed them on dev boards. I've Googled around for a while, but haven't found a definitive answer. Maybe I'm missing something.

I would like to use a microprocessor to buffer the output of an ADC, and get the results back to my Raspberry Pi via SPI. However when it comes to programming the actual micro controller I don't really want to spend a lot of money on a programmer.

Surely there must be open source tools which i can use for this? If so, which chip manufacturer has the best open source support on the web?


texts: What is meant by the term "baseline noise" in this context?

texts:
I came across this article about oscilloscopes. Under the figures and scope screenshots there is a term called "baseline noise".

I googled but it turned out this baseline noise is used at different disciplines for different things.

Does "baseline noise" regarding a scope mean that the noise floor measured when the probe inputs are shorted? Or?

(English is not my mother tongue)


texts: Read from BRAM and write into 2D array in VHDL

texts:
I have initialized a single port BRAM (clk,din,dout,addr,we) 8X10 with .coe file. I want to read from BRAM and write into the 2D array of dimension 10X8. As the dout of BRAM is 8 bit but the width of array is 10 basically, I want to do transpose. Kindly suggest me some solution. Please zoom the image below for better details.
entity dummy_handle is
    Port ( clk : in  STD_LOGIC;
                --test : out STD_LOGIC_VECTOR(7 DOWNTO 0);

           rst : in  STD_LOGIC);
end dummy_handle;

architecture Behavioral of dummy_handle is

type array2D is array (0 to 7,0 to 9) of  STD_LOGIC;
signal M: array2D;
signal addr_array : STD_LOGIC_VECTOR(2 DOWNTO 0) := "000";

signal we_A: STD_LOGIC_VECTOR(0 DOWNTO 0) := "0";
signal addr : STD_LOGIC_VECTOR(3 DOWNTO 0) := "0000";
signal din : STD_LOGIC_VECTOR(7 DOWNTO 0);
signal test : STD_LOGIC_VECTOR(7 DOWNTO 0);
signal dout : STD_LOGIC_VECTOR(7 DOWNTO 0);
signal i : integer:= 0;
signal j : integer:= 0;

COMPONENT array_print
  PORT (
    clka : IN STD_LOGIC;
    wea : IN STD_LOGIC_VECTOR(0 DOWNTO 0);
    addra : IN STD_LOGIC_VECTOR(3 DOWNTO 0);
    dina : IN STD_LOGIC_VECTOR(7 DOWNTO 0);
    douta : OUT STD_LOGIC_VECTOR(7 DOWNTO 0)
  );
END COMPONENT;

begin

    test <= dout;

print_array : array_print
  PORT MAP (
    clka => clk,
    wea => we_A,
    addra => addr,
    dina => din,
    douta => dout
  );

dat_process: process(clk,addr,i,j,test)
begin
        if rising_edge(clk) then

                if j = 9 and addr = "1001" then
                    addr <= "0000";
                    j <= 0;
                    i <= 0;

                else

                    M(to_integer(unsigned(addr_array)),j) <= test(i);
                    addr_array <= addr_array + 1;
                    i <= i + 1;

                    if addr_array = "111" then
                        j <= j + 1;
                        addr <= addr + 1;
                        addr_array <= "000";
                    end if;

                end if;

        end if;

    end process dat_process;
end Behavioral;

This is my code,it works ok for 0th column of array , but rest of the column upto 9 is showing undefined. It is not updating j.
This is the test bench.
ENTITY dummy_handle_test IS
END dummy_handle_test;

ARCHITECTURE behavior OF dummy_handle_test IS

    -- Component Declaration for the Unit Under Test (UUT)

    COMPONENT dummy_handle
    PORT(
         clk : IN  std_logic;
         rst : IN  std_logic
        );
    END COMPONENT;

   --Inputs
   signal clk : std_logic := '0';
   signal rst : std_logic := '0';

   -- Clock period definitions
   constant clk_period : time := 20 ns;

BEGIN

    -- Instantiate the Unit Under Test (UUT)
   uut: dummy_handle PORT MAP (
          clk => clk,
          rst => rst
        );

   -- Clock process definitions
   clk_process :process
   begin
        clk <= '0';
        wait for clk_period/2;
        clk <= '1';
        wait for clk_period/2;
   end process;

   -- Stimulus process
   stim_proc: process
   begin
      -- hold reset state for 100 ns.
      wait for 100 ns;

      wait for clk_period*10;

      -- insert stimulus here

      wait;
   end process;

END;

dout is the out of BRAM, and it is of 8 bit ,how can we make it as a 10 bit and also I am not able to understand the long and short vector point, it will corrupt the original data ,i think.Pls help me in that.
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use ieee.std_logic_unsigned.all;
use IEEE.NUMERIC_STD.ALL;


texts: Deciding capacitor value to use in my circuit

texts:
I have a power source which supplies 1A at 5V. I am using a switching regulator which supplies 1.3A at 3.3V. The load requires a burst of 2A without reducing the voltage across it than 3.2 V for 477 usec after every 5 minutes. The normal operating point is 500 mA at 3.3 V.
I want to use a capacitor to provide that extra current for the required duration without reducing the voltage.
How to choose proper capacitor value with low ESR?


texts: What is symmetrical output voltage swing?

texts:
what does it mean by symmetrical output voltage swing (Amplifier)? Vcc = 10V.

It is a basic, but i can't find any reasonable answer for this question. I am almost a beginner in electronics.


texts: Measured continuity between live and neutral

texts:
I was trying to get rid of the humming noise coming from my speakers in my hi-fi system. It is an old piece of equipment from back when the UK appliances did not come with the mains plug and you had to add it yourself.

I noticed that the amplifier was not grounded so I added a cable from the chasis to the ground pin in the plug and violá: no more humming.
I did test the continuity between the 3 pins in the plug using a multimeter, and also tested between live and the chasis of the amp and everything was nice and dandy.

I then connected (via rca) my CD player and I got hum again... so effectively, after checking the plug I found no ground in this one either, so I repeated the same procedure.

When testing, I found that between live and neutral in the plug, there was a little bit of continuity! So I checked my work, as I assumed, I messed up and accidentally made a contact between live and neutral somewhere... however, this contact was nowhere to be found.

Maybe there is something wrong with the cable I used for ground? I thought. So I unplugged it and put the device back to how it was earlier. But this small continuity was still present.

When measured in terms of resistance, it gave me a value of around 22 KOhm.

Is this normal at all? I am afraid of plugging the device to mains now!

I’m new to electronics and electrical theory, I just know very little from high school and I just finished my first semester of electrical engineering at university.


texts:
Could you be so kind to provide me with type of connector from this picture ? It's for PMS5003 particle sensor.

Connector has 8 pins
Distance between pins is roughly 1mm (sorry, don't have caliper)
Width is 11 mm
Thickness is 2 mm

Better pictures:


texts: Using a Line Decoder (Multiplexer) to set multiple outputs high

texts:
When using a 3-to-8 Line Decoder / Multiplexer such as the 74HC238, can I set multiple outputs (1-8) as high at the same time?

As opposed to only one output high at any given time, and the rest are low.


texts:
\$ R_1=1.2 k\Omega\$, \$R_2=2k\Omega\$, \$R_3=8.2k\Omega\$, \$V_R=15V\$

Exercise:

For which value of \$V_i\$ the diode is conducting?
Find \$V_o\$ as a function of \$V_i\$.

Attempt solution:

First I suppose the diode is not conducting and I find: \$ \frac{V_i-V_A}{R_1}=\frac{V_A+15V}{R_3}\$, from this I get \$ V_A=\frac{R_3V_i-15VR_1}{R_1+R_3} \$, but since 2 is at \$ 0 V \$ the diode to conduct must be \$ V_A > 0\$, and I find \$ V_i>15VR_1/R_3\approx 2.2 V \$. This should give me the first answer.

Then I suppose the diode is conducting, and we have \$ V_A=0V\$, then \$ \frac{V_i}{R_1}=\frac{15V}{R_3}-\frac{V_o}{R_2} \$ this gives me : \$ V_0=-V_iR_2/R_1+15VR_2/R_3 \$.

So the second answer should be :

$$ \begin {cases}0 & \text{if}\ V_i<2.2V \\-V_iR_2/R_1+15VR_2/R_3\  \text{if} \ V_i>2.2V
\end{cases}
 $$


texts: Why is this digital potentiometer working?

texts:
I've been working on a circuit to dim a Shop Light that according the manufacturer is 0-10V dimmable.

Built into the light is an LED power supply that provides two wires, a purple DIM+ and grey DIM-.  The power supply appears to source a constant 0.1mA current on these wires, and the measured the voltage between them is 10V.

When the wires are unconnected or connected with a resistor >= 100KΩ, the light runs at maximum brightness. Shorting them or connecting them with a resistor <= 270Ω causes the light to run at minimum brightness.

I want to control this light with an ESP32 microcontroller, so I looked at  digital potentiometers.  The idea was to make a rheostat to control the resistance between DIM+ and DIM-.

When I was looking at digital potentiometers a unifying theme for almost all of them is that the maximum voltage on the rheostat pins tends to be right around Vdd, which in my case is 3.3V.

Since I need the rheostat to be able to handle 10V, I purchased a Microchip Dual Rail Digital Potentiometer.  This chip has dual supplies, so the IC itself can be driven with 3.3V, and the rheostat can be driven with a separately supplied voltage.  Here's the circuit I came up with (using a separate 12V supply for the pot's V+):

After hooking this up and writing the ESP32 software everything is working.  The light dims.  But here's the problem:

When I completely disconnect the 12V external supply from V+/V- (pin 14 and pin 10 are NC/floating), it still works.  The rheostat measures the correct resistance depending on the value I store in the wiper register and no smoke is observed.

My question then is - why is this working?  The follow up is do I really need a dual-supply potentiometer or could I get something cheaper?

For what it's worth, I can see connecting something like 20-30 of these lights together, so current could go up to 2-3mA.


texts:
I'm currently trying to make a system where sending a message to my Raspberry Pi from my phone will send a signal to my apartment's buzzer to open the front door, however I've been having problems choosing an appropriate optocoupler for the job.

The rough schematic that I had planned to use is as follows:

simulate this circuit – Schematic created using CircuitLab

I'm a total rookie in this field, so you'll have to forgive me if my drawing doesn't make much sense.

The door buzzer that I have is this model, where on the second image the top right metal switch is the one that I'm hoping to force to connect by using the optocoupler connected to the raspberry pi. I tried using this optocoupler, however it seems that while my circuit design seemed okay, there wasn't enough flow through the optocoupler to get the door's buzzer to activate. I tried replacing the buzzer with a simple LED, and while it was activated when I sent the message, it was extremely dim.

As such, I'm convinced that the problem is likely down to the optocoupler not carrying enough voltage/current (not sure which) to activate the buzzer.

I welcome any and all criticism and suggestions, as I'm just doing this project to help learn about some basics of electronics.

Thanks in advance.


texts: What do LM78XX type regulators do with low input voltage?

texts:
If one gives less than the proper voltage to an LM78XX type linear regulator, what do they do? I'm well aware that there are no guarantees once you violate the specs given in the data sheet, but I'm analyzing something that someone else did, and I want to make sure of what it's doing before I risk boards on it.

The specific circuit in question normally has 22 volts feeding the input of an LM7815 (the data sheet lists the minimum Vin for this part at 17.5 volts). If I were to feed it 12, what would be the probable behavior? Obviously it's not going to make 15 volts out of that, but (assuming a stable +12) will it make a reasonably stable voltage? Or is it going to do some oddball oscillating behavior?

The application is the PCB from an old Atari Centipede, which includes an LM7815 and LM7915 to make + and - 15 from + and - 22. I'm planning to use an adapter I bought, which substitutes +12 and -12 for the original cabinet's +22 and -22. I'd like to understand why that might work, before I go plugging things up.


texts: Minimal circuit for a current limiter for small dc voltages and low power

texts:
I remember to be able to build a current limiter for small dc voltages around ttl levels using a zenner diode, transistor and resistor and some math. I couldn't find one when browsing, how do I build one?

Suppose I have a 5v, 5W capable power supply, feeding a led lamp that takes 5V and 0.5A, and I want to limit the current as a small safety If I connect a different one that I have, that is 5V and 1.5A.


texts:
I have issues with getting ESP8266 to work for me. The current state is that when I connect power I get this output on 74880 bitrate:

  ets Jan  8 2013,rst cause:2, boot mode:(2,6)

  Fatal exception (0):  epc1=0x4010006a, epc2=0x00000000,
  epc3=0x00000000, excvaddr=0x00000000, depc=0x00000000

I tried esptool.py with nodemcu firmware, I tried ESP Flash Download Tool according to instruction from here: https://www.allaboutcircuits.com/projects/update-the-firmware-in-your-esp8266-wi-fi-module/ - still the effect is the same.

One thing to note is that I also have issues with getting the upload to work, but once it starts it always succeeds. Later, however, it does not seems to have any effect.

I saw many people having similar issue, but reflashing for me does not help. Any further ideas? What do these numbers mean?

UPDATE:
I have just noticed that when restarting the module multiple times from time to time I get this output:

 ets Jan  8 2013,rst cause:1, boot mode:(3,0)

load 0x40100000, len 816, room 16
tail 0
chksum 0x8d
load 0x3ffe8000, len 788, room 8
tail 12
chksum 0xcf
ho 0 tail 12 room 4
load 0x3ffe8314, len 288, room 12
tail 4
chksum 0xcf
csum 0xcf

2nd boot version : 1.2
  SPI Speed      : 26.7MHz
  SPI Mode       : DIO
  SPI Flash Size : 8Mbit
jump to run user1

Any idea what might cause different behaviour from time to time? Note that I would expect +OK next, but it never happens.


texts:
I am working on a project with HDMI.
I use an HDMI in and HDMI connector where i connected thru the data lines, but i want to ground the shields (TMDS shield 0, 1, 2).
Will i need a decoupling capacitors ? And how do i calculate them.

Thank you


texts:
let's consider AD8318, a chip which contains a logarithmic amplifier, often used for power measurements.

I have read its datasheet and there is a thing that I do not understand: no maximum input RF voltage is declared. We may see from page 6 that only maximum input power is declared (12 dBm). Why? How can I know which is the maximum input RF voltage?


texts:
With the aim to combine some good properties of two different opamp types we can make use of the composite amplifier principle (see the figure). For example, we could combine good (small) input offset parameters (amplifier OP1) with good (large) slew rate properties (amplifier OP2). As another advantage, the resulting combination will also exhibit an increased small-signal bandwidth (GBW). In the presented example, the closed-loop gain will be $$A_{\text{cl}}=1+R_2/R_1$$

However, we have to watch the stability properties of the circuit. For this purpose, it is common practice to investigate the loop gain (determination of stability margins). To generalize the problem, we further should discuss the corresponding block representation (\$G_1,G_2,H_1,H_2\$) as shown under the circuit diagram.

In this context, the following problem exists:
We can identify three different feedback loops in accordance with three different openings:

at output \$H_1\$ (\$G_2-H_2\$ closed),
at output \$H_2\$ (\$G_1G_2-H_1\$ closed), or
at output \$G_2\$ (all open).

And now the following questions arise:

From the beginning, is it possible to decide which of the three loops must be analyzed to find the relevant loop gain (resp. the relevant stability margin)?
With other words: Is there a dominant loop that mostly determines the closed-loop behaviour?
If the answer is "yes" - which loop, and why? (An answer to this question is important because we like to know where to introduce compensating elements, if necessary).

According to my knowledge, this question has not yet been answered in the literature.

EDIT/UPDATE: Because input/output nodes are not relevant for the loop gain(s) I have redrawn the system without these terminals. Now, we cannot discriminate between "inner" and "outer loops.

UPDATE (Okt. 2018):

Finally, I have a simple answer to the problem:

A system with two or more feedback loops has no "stability margin". Such a margin can be assigned to a each of the feedback loops only;
Hence, if we can define three different loops within the system, we can find three different loop gains and, therefore, three different stability margins (phase or gain margin);
The phase (gain) margin is a measure for the (unwanted) additional phase shift (or gain) that must be introduced into the loop to reach the stability limit.
Therefore, we cannot say, in general, that a loop with a phase margin of PM=30 deg is more critical that another loop in the same system having PM=45 deg. because the probability is important with which such a disturbance within a loop can occur. (Example: Time delay within a loop can produce severe phase lags).


texts: Problem understanding some BSRR assignment operations

texts:
I'm learning about the STM32F405/415 in my course and having some trouble understanding some applications of the BSRR. Specifically how it's used in this function:

void HAL_GPIO_WritePin(GPIO_TypeDef* GPIOx, uint16_t GPIO_Pin, GPIO_PinState PinState)
{
  if(PinState != GPIO_PIN_RESET)
  {
    GPIOx->BSRR = GPIO_Pin;
  }
  else
  {
    GPIOx->BSRR = (uint32_t)GPIO_Pin << 16U;
  }
}

The function is part of the HAL driver. It's called by this code in particular:

while (1)
{
  JoyState = HAL_GPIO_ReadPin (JOY_C_GPIO_Port, JOY_C_Pin);
  HAL_GPIO_WritePin (LD6_GPIO_Port, LD6_Pin, JoyState);
}

The effect of the code is that the LED toggles on and off with the press of the left direction on the onboard joystick (JOY_C_GPIO_Port and Joy_C_Pin) but I can't really tell why it works.

My understanding of the code is that this section below is assigning the location of the pin to its own port and that this is somehow turning it off:

if(PinState != GPIO_PIN_RESET)
  {
    GPIOx->BSRR = GPIO_Pin;
  }

And my understanding of this part below is that the pin location is being assigned to "16U" of the port that the pin belongs to, and if the pin is not set it now will be. But I don't know what 16U is (16th register? documentation says 1-15? "U"?)

Can anyone explain this?


texts: Calculate required toroidal core size(Cross section area) for transformer

texts: How to calculate required toroidal core size(Cross section area) for 200VA transformer.is that any formula or method to select core.I mean to say suppose I won't make 200VA toroidal transformer so how to select required core size OD, ID, Height of toroidal core.


texts: Design help for my 1A variable power supply

texts: In a 1A Variable Power Supply circuit given below is it possible to use a 2A transformer and 1A bridge diodes.


texts:
I have an HVAC unit and I know the phase 1 current, phase 2 current and phase 3 current. I know the voltage of the unit, from this, how can I calculate the power used by the entire unit?

Further information, does the HVAC unit have 3 separate voltages for 3 phase? I know  for example, the one on my roof is 230 volts and it is 3 phase. Does that mean that I can use a voltage of 230 for calculating the power of each of the phases?


texts: What is the minimum required voltage for charging a 3.7 V Li-ion battery?

texts:
I have a cell phone battery that has the following written on one side:

3.7 V 1000mAh
Limited charge voltage: 4.2 volts

I understand that the first line means, that the battery will always give 3.7V (at least in theory) at its output terminal. Also the battery will last for 1 hour if the mobile circuitry draw 1000mA.

The second line means that under no circumstances I should increase the input charging voltage beyond 4.2V, else it might damage the battery.

Is my understanding correct?   If I am correct I would like to know for this battery what is the minimum required voltage for charging?


texts:
The question maybe a bit basic, but I was not able to understand it.
When we are biasing a transistor, why don't we add the AC signal source in series with the bias voltage provider? At the output, if we use a capacitor, it should delete the magnified DC (bias voltage) part of the aggregate (AC+DC) signal. Then why do they use a coupling capacitor in series with the AC signal source instead?


texts: making an automotive "dizzy" switch with using a latching relay

texts:
My engine builder wants me to be able to turn my car over without it starting to pre-oil the motor due to a remote oil filter. The car needs to be wired so that the coil will not have juice until I push a momentary switch which will activate the latching relay/coil until the ignition is turned off. It will also act as an anti theft device. I bought a latching relay (Hella latching/bistable relay, 30A, 12V part # 74994) and a momentary switch to accomplish this but the latching relay didn't come with instructions as to which terminal does what. Can somebody help me with a schematic so I can wire this up? I plan to use the battery/hot wire to the HEI ignition coil as the entry point for the system. Also included would be the ignition from the key and the momentary switch.

Thank you in advance!


texts:
I'm want to use I2C communication isolated but it's error. I don't know why. My circuit:

MCU: STM32F103RDT
ISOLATION IC: Si8600 I2C

Chanel 0: SENSOR_SCL
Chanel 1: SENSOR_SDA
Chanel 2: SCL_ISOLATED
Chanel 3: SDA_ISOLATED

I2C Setting: standard mode - 100kHz
I want to know why waveform I2C Isolation doesn't same as
My English is verry poor.
Thanks all.


texts: What is the difference between a crest reading volt meter and a peak reading volt meter?

texts:
We are measuring pulse DC voltage up to 35K on Tinker & Rasor high voltage holiday meters for checking the thickness of coating applications.

I would like to check our units each time they go out between calibration cycles. We need a peak reading volt meter but have a crest reading volt meter. how do they differ and will the crest reading volt meter give me a correct reading?

Thanks Gene

The Tinker & Rasor Model APS High Voltage Holiday Detector supplies 800V to 35 kV in one instrument with two ranges: high range of 3,500V to 35,000V, an low range of 800V to 8,000V. Typical applications are checking coatings on pipelines and other coated structures, tanks, concrete, sewers, and manholes.

Also here.


texts: Translating mic sensitivity dBV to dBSPL

texts:
In mic datasheets, mic sensitivity is usually expressed in dBV that equates to 94 dB SPL (@1kHz).

So if my mic sensitivity -46 dBV equates to 94 dB SPL, does that mean that if I double the signal by 2 (+6dB), a -40 dBV measurement will equate to 100 dBSPL for that mic?

I made a dBV to dBSPL calculator and based from this assumption (sens: -46dBV):
-46 dBV = 5mV (94dBSPL)
-40 dBV = 10mV (100dBSPL)

Are these correct? So the two dB units are just linear offsets?


texts: Diode oring for solar charger with dual battery isolator?

texts:
I want to charge a deep cycle battery with a solar charge controller and dual battery isolator powered by the car alternator. The dual battery isolator will provide the most charging power when driving and the solar will help to keep the battery topped up when camping.

As I am feeding two power sources into one battery do I need diode oring to avoid damaging the two different chargers?

Below is a the wiring diagram of a 12V system. The Dual Battery Isolator will provide up to 120A and solar up to 10A. So I thought I put strong Schottky diodes in protect each charger.


texts: FET Default on, Turn off with Optocoupler

texts:
I am relatively new to electronics and having trouble designing a circuit for a redundant power supply, which I would like to switch to battery if the voltage regulator turns off. This will be approximately 40V, and high current (60A). I

I have an idea that the FET will be pulled up using the battery source which will default on. Then, I would like to use an optocoupler to turn it off. I have designed a voltage regulator which has 9V auxiliary power out under normal conditions, which I would like to transmit via the optocoupler.

The trouble I am having is how to use the the optocoupler signal to override its pull up voltage.

Do you have any ideas on how to do this?


texts:
I recently came across a term “current fed converters”, but was unable to find any good reference online.

What are they and how are they different from voltage fed converters? And when are they more useful that their counterpart? And can you use a normal voltage fed IC for a current fed converter?


texts: Why enc28j60 is not responding to another enc28j60?

texts:
I interfaced enc28j60 with atmega328p. Then I connected the enc28j60 board1 using ethernet cable to my laptop. I have checked the transmission and reception over the ethernet and it worked. I can sent packet and receive packet to/from the laptop. I actually need to communicate with two enc28j60. I have another board which is same as that of first one. I checked the second board for transmission and reception by connecting it to my laptop.

After that I connected frst enc28j60 with second one through a ethernet cable. Both the boards are working individually when i connected it to laptop but not working when connect first board to second board. Already, I verified the ip address and mac address configuration on both boards. But it didn't work.

Whether there is any part that I am missing while doing enc28j60 to enc28j60 communication?

I am using tuxgraphics TCP/IP stack and it working perfectly with my laptop. But the same code is not working to the boards. Both the board have same configuration of all registers only the difference is in the mac address, IP address and port number.


texts: I made a temperature controller - the PID works but the heater still doesn't work

texts:
The setpoint doesn't affect the output voltage to heater.
How can I fix my circuit so current goes through to the heater?


texts: I have designed RF-PA and to test the circuit, I want to design an oscillator which can give me a 2.45 GHz continuous wave. What are the simplest ways to design such a circuit? What are the requirement or the design procedure?


texts: I'm designing a robot and I'm looking to use mainly I2C to control different sensors and stuff. I'm now looking into motors, specifically this motor. However all of the ESCs I have seen use a PWM interface. I'm wondering if there are any ESCs which use I2C, or if anyone knows of an easy way I could implement one myself? I've already seen a couple of application notes which provide reference implementations of an ESC on an AVR (AVR444 and AVR493) but they are old and use IAR so id rather not re-impliment them. I'm wondering if anyone has an already functional implementation?


texts:
I have a boost converter.
Vin=10-16V
Vout =23V
Iload=250mA.
Fsw=125kHz

  NCV3063

I have a Boost converter App note from TI. Boost Converter TI App note

I tried to design my boost converter circuit using the formulas provided from the app note as I was not able to understand the formulas provided in my NCV3063 Boost Converter datasheet.

Can I use the App note formulas to design my boost converter inductor?

Why are there different formulas for the same boost converter topology?

Thanks.


texts:
I have a nordic radio module http://www.olimex.com/dev/mod-nrf24L.html which I am attempting to create a c# driver for (the device is a Fez Rhino). I've been able to initilize the device and been able to send it data however I'm not sure if the device is receiving the information on the SPI bus. Whenever I send a command down the bus I get back hexadecimal "E". I have been reading the chip specification (NRF24L01) trying to determine if the hexadecimal E response is normal, an error or is an invalid response for this device. All the example code that I've found doesn't seem to care about the response from the device so I don't even know if to expect a response.

My question is: Does the device respond when commands are sent to it, and if so can you point me in the direction of that literature?


texts: Can someone explain this microcontroller ADC interface (for reading solar panel voltage)?

texts:
I am trying to understand the functionality of a circuit found in TIDA-00121 (you can download the design file from here)

I assume that this has to do with the fact that the PV is not directly tied to ground (reverse current mosfet may be turned off when the solar panel voltage is too low to prevent any reverse current from flowing into the panel)

As for the transfer function (from source code), the voltage at the microcontroller side equals to:

V=0.086045Pv-0.14718475V (PV is the panel voltage).

this was extracted from the fact that Vref=2.39,10 bits ADC and the source code equation:

  Panel Voltage = 36.83 * PV - 63

to verify my assumptions, from the source code:

  Battery Voltage = BV * 52.44

which yields to voltage at microcontroller side of the battery voltage divider:

V=0.122BV which is the voltage divider ration (14K/100K network)

The question is:

What is the role of the pnp transistor network?
How to calculate the transfer function of the voltage at the microcontroller side?

Thank you very much.


texts: Why does PWM create lots of EMI and signal ground noise?

texts:
TI had a note to create DAC signals using PWM.
http://www.ti.com/lit/ug/tidu027/tidu027.pdf

Whereas I also found an article that says

http://www.mosaic-industries.com/embedded-systems/instrumentation/pulse-width-modulation-pwm-controller-driver-actuator/noise-reduction

"High current, high frequency PWM signals are notorious for creating and radiating electromagnetic interference (EMI and RFI).

Consequently, if you use PWM currents for controlling power devices, you should make your connections in a way that minimizes or limits the radiated noise.

In general, single point grounding and using shielded twisted pair cable are essential to prevent EMI or mitigate PWM noise."

Why does high current / high frequency PWM signals can create EMIs and signal ground noise? It looks like this is related to electromagnetics, but I cannot clearly explain the reason.
Does this also mean that PWM based buck converter, like the LM3671/-Q1 2-MHz, 600-mA Step-Down DC-DC Converter, can create EMI to nearby circuits? It makes me feel like I have to populate the Bluetooth/Wi-Fi microcontroller far away from this buck converter.

In the LM3671 datasheet, it says

http://www.ti.com/lit/ds/symlink/lm3671.pdf

2-MHz PWM Fixed Switching Frequency (Typical)
Automatic PFM-PWM Mode Switching


texts: Simple IR pulse detector with IR phototransistor

texts:
I understand the basic circuits used with phototransistors:

I believe that this is essentially a voltage divider, commonly used for all sorts of analog sensors. In the left circuit, in the dark, the phototransistor is very high impedance, making Vout close to Vcc, and dropping as more light is detected. In the right circuit, Vout is close to GND, going up as more light is detected.

I would like to use an IR phototransistor to detect IR pulses (low frequency, of unknown duration), and I'm not sure how to choose a value for the resistor. Ideally, I would like to avoid using an ADC, and just detect a logic high/low with a microcontroller. If I need to use an ADC and detect voltage at a certain threshold, then that is possible, as well.

How do I choose an appropriate resistor given datasheet values for the phototransistor? I know that dark current is 100nA (Vce = 15V) and light current is 20mA (Vce = 5 V, H = 20 mW/cm), and collector current is 25mA, but I'm not sure how to turn those values into a suitable resistor. An application note I found says that "the load resistor (RL)
should be set in relation with the collector current (IC) as Vcc < RL × IC." That gives me a resistor of 132 ohms or less using 3.3V, however, and that seems pretty small, given what I've found recommended elsewhere (up into the tens of kOhms).

How do I chose this resistor value appropriately?


texts: Price and process of rewiring a bus to run from solar power?

texts:
I want to rewire an omnibus from running off of gasoline to running off of solar panels. Not my field.

What are some things that would have to be done? Specifically, what would it entail to completely change how a bus runs? And just rough estimate pricing as a side. Also, if you know any good sources for me to go to to find out about this, that would be helpful. I don't know where to even begin....


texts: Is it possible to use an RFID tag inside a stainless steel enclosure? I am looking for a way to uniquely and easily identify a sensor. An alternative possibility is a laser engraved bar code.


texts: Adding a resistor to reduce crossover distortion in an LM324/LM358

texts:
I was watching a video of the legendary Bob Pease, in which he says that the regular LM324/LM358 is not a low distortion amplifier, however, if you add a 10K resistor from the output of the opamp to the negative supply rail, then, distortion is greatly reduced.

It appears that in the video they are using bipolar power supplies, so my question is: if im using an LM324/LM358 with a single supply, say 9V and ground, will adding a resistor from the output to ground also lower the distortion? I must add that im adding a 4.5V bias to the input of the opamp so the output is idle at 4.5V. The following schematic displays what I'm doing

simulate this circuit – Schematic created using CircuitLab

The video link is the following: Whats All This Distortion Stuff, Anyhow?


texts:
I just wanted to ask, which platform is the best suitable for a small commercial car system. It will comunicate with our server via 3G/EDGE (upload and download database with points of interest). It should have small camera, GPS module and be connected with a laser jammer.
What plarform and components do you recommend? I have experience with Arduino and AVR and I study a Bachelor's degree (HW engineering) and this project could also be my thesis.


texts: ATMEGA1284p and RFM95 sleep current around 35µA: can it be reduced further?

texts:
In my project, I am using an ATMEGA1284p processor in the TQFP-44_10.0x10.0x0.8P package as well as a RFM95 LoRa module.
For the low-power mode, I'm using the rocket scream low-power library: https://github.com/rocketscream/Low-Power
The bootloader comes from maniacbug: https://github.com/maniacbug/mighty-1284p
I've measured a sleep current of around 35µA (300mAh LiPo connected).
The RF95 module is configured to sleep, where it should consume less than 1.5µA.
As clock, I use a 16MHz external one: Yangxing Tech X322516MLB4SI
VDD and GND from the LiPo are delivered to the ATMEGA1284p and the RF95 module continuously, there is no power circuit.
Where should I look at to further reduce the sleep current?
Resources:

ATMEGA1284p datasheet
RF95 LoRra datasheet
LoRa LMIC library

EDIT: I have eventually found the source for the current consumption, just two voltage dividers, one connected to 'a potential sensor source' and one to VCC. The one connected to VCC should draw around 13µA (320kOhm, 3.9-4V LiPo supply when fully charged).
I'll try the following steps:

remove the voltage divider connected to the LiPo battery
Configure the input pin for the generic sensor input as output
remove also the second voltage divider


texts: Does anyone know the name of this specific part?

texts:
I bought these 10K linear faders some time ago and would like to use them in a current project.
The only problem is that I don't know what they are so I can't order more / find the datasheet!

My suspicion is that they are bourns parts but I do not know the part number and the datasheets I found do not have any reference to the code on the bottom.

anyone able to fill me in?


texts: Tracking Down Compiled Binary Output Differences

texts: I have a program compiled using AVR-GCC. I'm getting a small difference in the HEX files generated on two different computers that are ostensibly set up with the same environments. I also have an ELF file for one of them. So reading the HEX file I know the precise addresses where the differences occur. How do I figure out what is causing this difference? Can you describe a process that can identify what data or function these addresses are associated with in terms of the C/C++ source code? I've ASCII-ified the HEX files to see if they are somehow simple differences in readable string data, but that is not the case. I assume this can be done using something like avr-binutils...


texts: Why is this logic vector assignment delayed?

texts:
I'm a beginner in FPGAs programming, and I've came across this issue recently:

In  a synchronous process, what is the logical explanation for a signal not being able to be read right after its assignation? (I have an idea of the answer but I want to hear your take on this)

On the following snippet of VHDL code:

if byteCnt = 0 then                -- On the 1st clock cycle, I assign the first byte of data to block_count's MSByte
    block_count(15 downto 8) <= rx_data;
    byteCnt := byteCnt+1;
elsif byteCnt = 1 then             -- On the 2nd, the LSByte is assigned
    block_count(7 downto 0) <= rx_data;
    cmd_internal <= block_count;   -- Here cmd_internal = 10101010UUUUUUUU, why?
end if;

A quick workaround would be cmd_internal <= block_count(15 downto 8) & rx_data; but that's not the point of my question :)


texts: I am converting my project from Arduino uno to a PCB to reduce the size and wanted to know if the i2c channel will still be accessible?

texts:
I read this answer and used the same circuit as shown : https://electronics.stackexchange.com/a/67114/149281

but i am not sure that if i use this circuit, i will still be able to use the i2c bus to communicate with an lcd as i ran out of pins on uno.
Any help will be highly appreciated.


texts: NodeMCU to control MOSFET, not enough voltage

texts:
I'm trying to make a HomeKit device that will turn a component on and off. The component's power supply is 12v at 2amps. I figured I'd put the NodeMCU inline with the power (the component's power adapter into the NodeMCU, then the NodeMCU switches the rest of the power on/off to the device). I'm using a L7805CV 5v voltage regulator to give the NodeMCU 5v off that power. So far so good.

Next I'm using an IRF740 MOSFET to switch the power on/off to the component.

The problem is the NodeMCU pin only provides 3.3v, which is not enough power to trigger the MOSFET for the voltage/amps the component needs. If I jump the gate pin to the 5v, the MOSFET works.

So, I need to somehow have the 3.3v pin from the NodeMCU trigger 5v into the gate of the MOSFET.

Is there an easy way to do this without using a logic level shifter? I'm trying to keep this as simple as possible with as few components as possible. Can I somehow use another IRF740 to trigger the 5v? I'm not sure how to do that, as the MOSFETs are switching on the grounded side of the circuit (12v into component, component's ground into MOSFET).


texts: Controlling multiple LEDs down to 0.25mA

texts:
I need to drive 50 (standard 5mm) LEDs, controlling the brightness of each LED individually, down to only 0.25mA and up to 25mA.

I started using TI's TLC5947 to drive these LEDs.
This chip, as many of these CC LED drivers, use an external resistor for current reference.
Using the built-in grayscale PWM, you can get a good brightness range.
To extend even more this range, I change the current reference between the max and min on the datasheet.
However, this chip can only go down to 2mA (practically 1mA) before the outputs get unstable. I need to go down to 0.25mA on each LED.

For a single LED it would not be a big problem, probably I just would implement a constant current sink using an op-amp. But when you have multiple LEDs, the problem is the number of control lines required, the cost of the circuit, and the complexity to keep to a minimum the difference between each "channel" of the circuit.

I need a way to implement this without having to replicate 50x an op-amp based circuit, to keep the complexity and cost realistic.


texts:
I am a bit confused with this circuit.I uploaded the circuit as you can see I already removed the resistance where I need to calculate the thevenin resistance. I know how to find the Thevenin voltage. Our mission is to find the
Thevenin equivalent circuit at R1 resistance.

simulate this circuit – Schematic created using CircuitLab

I know how to find the Thevenin voltage but if I don't understand how to find the Thevenin resistance.
Let is remove the voltage sources:

simulate this circuit

As you can see I already removed the R1 resistance and named the nodes A and B.
I know that the R7 and R3 in series connection.But I don't understand what to do with R6 R4 and R2 they are in star connection.
My quenstion it is useful to use star-delta transformation ? If yes how to do it properly?

Edit: I want this circuit to be reduced to this:

simulate this circuit

As I mentioned above I know how to find voltage I need the Rth and star-delta transformation is little confusing.


texts: Is there a difference in heat produced on a conductor between AC and DC at the same amperage and voltage?

texts:
Is there a difference in amount of heat produced on a conductor between AC and DC at the same amperage and voltage?

For example if you ran 50A at 480V through a conductor would the heat produced be the same for AC (60hz) and DC?


texts: Laplace Transform (Voltage Transformation)

texts:
So I was solving some circuits with the use of Voltage Transformation and Laplace Transform and I came up with this circuit. I'm not sure how to solve for
IL and IC.

R3 and V1 are the voltage transformation of a 2H inductor while R4 and V2 are
the voltage transformation of a 1/2 F capacitor.

By observation, I think it would be easier to choose nodal analysis.
However, I'm not sure how to properly arrange the components to limit the number
of nodes/equations needed.

simulate this circuit – Schematic created using CircuitLab


texts: Managing I2C address conflicts with multiple MCP23017 on the same bus

texts:
I'm using a Raspberry Pi with the I2C master and I successfully wired 8 different MCP23017 chips, each with their respective addresses by setting the last 3 bits of their 7 bit addresses. They are all working flawlessly.

My problem is that the basic addressing of the chips are permanently set to 0x20 to 0x27, which seems odd. After using i2cdetect I see so many other potential addresses.

My first question is:
If the chips are locked on the 0x20s will there be any conflict IF any another I2C device uses the same device address?

Secondly:
Is there a way to modify the basic addressing scheme (0x3*, 0x4*, 0x5*) to maximize all these potential addresses or are they permanently set for each device?


texts: Considerations when using Opamp as comparator

texts:
For cost reasons, I want to use an opamp as a comparator. So far in terms of making sure the opamp is suitable, I have:

Making sure the output can slew fast enough
Making sure it can handle large differential inputs
Making sure it can go rail to rail
Ensuring that the current draw at maximum swing is acceptable

Are there any other crucial points?


texts: Constant power discharge of a non-ideal capacitor

texts:
My employer sells boost converters to hold up motor drives during power loss. These boost converters are fed from capacitor banks. In order to size these banks correctly, we need to take their voltage, capacitance, and ESR into account, to ensure that there is enough available energy from the capacitors to hold up the drives for a spec'd time at a spec'd power. Right now we do this with an approximation method, but it would be nice to have a more exact equation.

We're assuming ESR, capacitance, and load power are constant.

$$
I \text{: current}\\
P \text{: power}\\
R_{C} \text{: ESR}\\
C \text{: capacitance}\\
t \text{: time}\\
V \text{: capacitor voltage}\\
\text{Standard capacitor equation:}\\I(t)=CV'(t)\\
\text{Power out of the cap equals power into the ESR plus power into the load:}\\
V(t)I(t) = P + R_{C}I^{2}(t)\\
\text{Substitute:}\\
CV(t)V'(t) = P + R_{C}C^{2}(V'(t))^{2}\\
$$

If I'm right, this gives me a non-linear differential equation, which puts me well past my mathematical comfort zone. If I understand correctly, solving a new non-linear differential equation would qualify as a significant contribution to the field of mathematical knowledge. Given that, I'm unlikely to solve this on my own.

Does anyone know any good approaches for solving for V(t)? Does anyone know if this equation has already been solved? Am I possibly misunderstanding the problem? Or should I move this to the math Stack Exchange?


texts: 4-bit Self-correcting Johnson Counter on D flip-flops

texts:
I had a task assigned by my teacher to implement self correcting Johnson Counter. The task goes this way:

  Design a self-adjusted 4 bit Johnson counter. Counter must be implemented on d flip flops and perform self adjusting only on 1st bit. Design should preferably be made with use of Johnson's code.

Frankly, I have no idea how to tackle this task. I made all but this one, I read the other questions/answers here but I'm still not sure.

Could you please at least give me a hint how to do this task?


texts: One SIM card shared between two devices - IC?

texts:
i have a GSM breakout board and a 4g dongle. I'm curious whether it is possible to share one SIM card between both of them? Does anyone know if there is any IC available to do this?

edit: Only one device would use the sim at a time. Ex. first the gsm module for 30 min then the 4g for 1 hour.


texts: Significance of Linearity in RF Power Amplifiers

texts:
I have started studying the topic of "RF" Power Amplifier (PA) operation, and so far I have come across description like, if PAs are non-linear, it does not form a straight line and rather it has a curved line (more so in the higher region). And non-linear region of PAs can cause distortion. This is very vague to me still, specifically in understanding, why do specifically RF Power Amplifier have to be Linear? What happens when they are linear? And then what happens in the non-linear region (or what does it mean by distortion here?)?

Thanks.


texts: PCB labelling bare part number vs assembled part number

texts:
1st time posting question here.
I'd like feedback on best practice for labelling PCBs with the board (bare PCB) Part Number (PN) and/or assembled (PCBA) part number. We give bare PCBs a PN, then the assembled PCBA gets different PN, however within the company there's a lot of division over what should be printed on the silkscreen. Bare PCB number only, PCB + PCBA numbers or PCBA only. PCBA makes it easier for production staff to identify but makes design changes difficult since even a component replacement requires silkscreen update, not to mention I want to introduce variants, so we have same PCB used in multiple PCBAs. This is complicated by us being medical device designers/manufacturers so there is lot of concern around traceability. In summary what's best practice;

only bare PCB part number on silkscreen (or copper)
bare PCB part number & assembled PCB part number printed on board
only assembled PCBA part number printed on board
bare PCB part num printed on board, label PCB assembly part number with adhesive label
other?

Note we do include versions but I've left out of discussion to keep it simple
Andrew


texts: High output current hex inverter in SMD capsule

texts:
I am trying to find a hex inverter which has as high output current as 74AC04E (50mA) but surface mounted.

I haven't had any luck so far...


texts: Why did my homemade PCB turn out like this?

texts:
I did a first experiment with the UV-lamp + Transparency + Presensitized-Board method.

Using a randomly drawn pattern, this was my (promising but unsatisfactory) result:

What could typically be the culprit behind such speckles, i.e., the patchy-nature of the copper rectangles/lines?

For the record, this is my method:

Print pattern on transparency
Print pattern again on same transparency (double toner = double mask darkness)
Place transparency on presentisized board (positive photoresist), and hold down flat using plexiglass
UV exposure (with 13-watt CFL bulb) for 8-9 minutes
Develop in NaOH + Water for about a minute (at end, there was clear contrast between the pattern and the rest of the board)
Etch in FeCl with periodic agitation by hand


texts:
I want to use MSP430 launchpad to control a switch working between 1.65V and 2.75V.
So, I wanted to force Vcc value to 2V instead of 3,3V while it is connected to my PC. I connected Vcc and GND pins to a power supply delivering 2V. But, now, I have a real problem. Even after taking off connection cables, Power led blinks and Vcc varies between 0V and 3,3V. I think that my kit doesn't work anymore. Could you tell me if it is the case.

Fortunately, I have another kit, I decided to work with it. But I don't know to force my Vcc to 2V to control my switch while the launchpad is connected to my PC.

Thank you very much !
Alice