texts: Can MCPCBs be used for audio frequency and/or MCU clock frequency applications?

texts:
For purely aesthetic reasons1, not for heat dissipation, I am contemplating using MCPCBs for these two applications:

Audio frequency circuits, such as a Baby 8 sequencer, Atari Punk console,  synthesizer filters, audio effects, etc., and;
MCU circuits, such as so called "barebones" Arduino projects, where an ATmega328P-PU is employed, and a clock frequency of 8-20 MHz is used.

Would I encounter any adverse effects (capacitive or otherwise) due to the higher frequency ranges used (when compared to DC, or 50 Hz AC, high power LED applications)? I initially assumed that the metal substrate would act as a PCB wide ground plane, and therefore not cause any problems. However, after thinking about it a bit, I am not so sure.

I have seen MCPCB applications for audio amplifiers, so I assume that, for the former, there aren't any issues. For the MCU applications, would the several orders of magnitude higher frequency of the crystal/clock be an issue?

FWIW, the metal substrate would be of the thicker variety, 3.2 mm or higher, ideally 5 - 10 mm. MCPCB dimensions would be limited to a maximum of 120 x 500 mm, but typically 100 x 200 (or less) mm.

Here is an example of an MCPCB used for an LED:

1 For live performance of Chiptunes, ByteBeat, and the such like.


texts: ATtiny13A cannot be programmed anymore with Arduino as ISP at 500 Hz

texts:
My ATtiny13A fuses are set to use the internal 128 kHz clock without clock divided by 8.
I found online an ArduinoISP sketch that allows me to program it with that clock speed. But then I uploaded some code with those lines at the start of my main() to set the clock division factor to 256:

CLKPR = (1 << CLKPCE);
CLKPR = (1 << CLKPS3);

So my clock should normally now runs at 500 Hz. I guess it works, but I now cannot program my ATtiny13A anymore, it gives me unexpected signature error.

I found this ArduinoISP sketch online: https://github.com/lmpipaon/ArduinoISP_slow_SCK

Seems nice but it says it does not work with the 256 prescaler, which is what I need. When I try nevertheless to use the 256 prescaler with 600 baud rate in the ArduinoISP sketch, avrdude (avrdude -b600 -cstk500v1 -P /dev/cu.wchusbserialfa130 -pattiny13 -e -U flash:w:lowVoltage.hex) still gives me unexpected signature errors.

I also tried adding -B 8000 or -B 10000 with my upload command but apart from giving me different device signatures, it does not upload my code.


texts: What is the proper dB unit to use when expressing the amplitude of a sample in a digital audio recording?

texts:
I've seen 20*Log10(amplitude) as the proper way to calculate dB, where 0 < amplitude <= 1. (So, to get amplitude when signed integer data types are used to represent amplitudes, you use value/maxvalue for positive values and value/minvalue for negative values.)

I know this formula generates 0 for extreme values and negative numbers for everything else. I also know it's showing a relationship between the sample and an extreme sample value. Is this properly called dBu or dBv or something else? I've seen both, plus just "dB".

I didn't study electrical engineering, so as close as you can get to a layman's explanation of why a particular unit is correct would also be helpful.


texts:
I know there are tons of examples of music driven LED circuits out there, but they mainly control just one LED or one string of them. I want to make a circuit that will control quite a few LEDs, with each LED at a different range of frequencies.

To do this, I am planning on making an array of band pass filters. Each filter would drive a different LED (or string, or something else)... through a BJT perhaps? Here is a quick sketch of what I am thinking.

I might add in a high and low pass filter in the end, but I'll decide that later.

Anyway, would this work? I am wondering if you have advice for me, or maybe some different tricks that could reduce the complexity of this project. Are there certain things to watch out for, such as my source not being able to supply enough power to my filters, ect?

Thanks in advance! I really appreciate any help!


texts: Max voltage per thyristor in 3phase thyristor full bridge rectifier when Iout is DC

texts:
I was wondering: Suppose we have a circuit as the title states where $$\omega L >>R, (L\rightarrow \infty) $$ ). So the output current $$I_{out}$$,is considered a DC one.

My book says that the max, voltage that will a thyristor conduct is $$\sqrt6 V_i^{RMS}$$. Why?Isn't this the max output voltage? Doesn't a thyristor conducts at max, the max value of the input voltage $$\sqrt2 V_i^{RMS}$$???
Also, it has a graph with the waveforms of output voltage for different values of $a$ angle. And as I can see, the max output voltage may be less than $$\sqrt6 * V_i^{RMS}$$ for bigger values of a. So maybe it means that the max, value of a voltage thorugh a thyristor is $$\sqrt6 V_i^{RMS}$$ out of all - possible a values? But for a particular, a : for instance $$a=90^o$$ is the max, voltage though the thyristor less than $$\sqrt6 V_i^{RMS}$$?.
Is there a formula, for the max value that the thyristor conducts relatively to $$a$$?


texts: How to implent a LoRa class A by Arduino?

texts:
I'm trying to make communication between multi node and one gateway using Arduino Uno and LoRa(SX1278).
I read from "LoRaWAN® Specification v1.0.3" document that in class A, every endnode after uplink message it send, open two window and wait for downlink message.
The question is should I implement this in my code? (I visit lot of website but they don't write any code for that and write only code for communication between nodes)


texts: LTSPICE - Changing parameters of a pulsed voltage source

texts:
At the moment I'm simulating a basic buck converter circuit and would like to be able to vary the duty cycle given to the circuit by a microcontroller (switching a MOSFET).

I'm simulating the micro using a pulsed voltage source, and I want to vary the tOn parameter but am not sure how. I've tried placing {dutyCyc} in the tOn window, and adding
.param dutyCyc=value*time
to the circuit, which doesn't work.

I've seen suggestions on stepping through a list of values, but that performed multiple simulations as opposed to a single one with an increasing duty cycle over time.

What am I missing?


texts: Interference suppression coils for 9V DC adapter for audio equipment

texts:
I am about to add voltage regulation to an unregulated 230V AC to 9V 150mA DC adapter, by adding an L7809 voltage regulator and ceramic 0.33µF and 0.1µF capacitors.
I want to use this adapter to power a couple of (digital and analog) guitar effects pedals, but it was originally intended for use with a computer MIDI interface, not (directly) with audio equipment, so I was wondering whether I should take additional precautions against interference, especially in the audio spectrum.
I had a look at 9V adapters made specifically for use with audio equipment, and e.g. the ubiquitous Boss PSA-230S contains what is described as:

High-quality interference suppression coils in extra housing

What type of coils would these be, and how would I choose the right ones to add to my project? Also, how important is it that these are added near the end of the DC cable, and not to the adapter itself?

The unregulated adapter as it is now. (click images to enlarge)


texts: Can I stop the batteries in a device from draining by taking out just one?

texts: I bought a blood pressure monitor and at the moment I'm taking the batteries out after each use.  I'll probably end up buying rechargeable batteries and not worry about taking the batteries out, but I'm curious to know if I need to take out all of the batteries to keep them from draining or if I can just take out one.  My (basic) understanding of electronics leads me to think that as long as the batteries are in series, I should only need to take out one to break any kind of circuit that might be present.


texts:
I'd like to get familar with an implemebtaion of modern CPUs. Are there Amy processors with an open-source Hardware Decriprion Language? Perfectlt, I'd like to take a look at Intel/AMD implemebtaion, but Im not sure it is open.

So is there any CPU with an open source decription? I'm loooking for any architecture: x86, Arm, DEC-Aplha, etc...


texts: Difference between online PID and offline PID tuning?

texts: I've been reading about PID control on the internet lately (Wikipedia). I came across the words 'online' and 'offline' in PID tuning. I googled it but couldn't find anything. What does this mean in simple words?


texts: Lithium Battery Pack Cell Arrangement: Parallel First or. Series First (4P16S or 16S4P)?

texts: I am looking to arrange 64 individual LiFePo4 cells into a large 48V pack. So I can do 4P16S or 16S4P. All cells are new. I can add individual fuses to each cell if necessary. The capacity of each cell is 100Ah. What are the considerations and Pros and Cons of both arrangements. How can one decide which arrangement to go with? The cells will be balanced by an active BMS.


texts: EAGLE schematic capture and board layout problems

texts:
I’m about to start the manual and then auto routing process of my schematic see the following link for my schematic but before doing this I’ve read quite a lot on different bits of advice on completing the schematic properly before embarking on any routing.

With regards to the routing I’ve read up on main aspects such as the selection of the routing grid in relation to the trace width, avoiding dimension errors and avoiding clearance errors.

Regarding my schematic I’ve got two components with each having a pin that I do not need to connect to anything at all. I’ve followed different pieces of advice and realized there is no “not connected” library in Eagle hence I created mine as per the following link. I then connect this custom symbol to my IC pin but no connection takes place and when I run my ERC check I come across the following errors in relation to both pins:

“No SUPPLY for POWER pin U1 TAB”.
“Unconnected INPUT pin IC1 ADJ”.

Original image

In addition to the above problem, can anyone see any other issues with my schematic? Apart from the values of specific components which I intentionally deleted can anyone see any problem on my schematic that I might have not anticipated? Any help is appreciated.

Now moving on to the board routing (which BTW I undertook before realizing the above mentioned problem), I’ve come learn a lot in the recent days about the following things to watch out for when laying out components and subsequently undertaking the routing:

Selection of the routing grid (in relation to the trace width): I have a routing grid of10 mil and in the DRC sizes setting I have a minimum trace width of 10mil.
Selection of the trace width whilst watching out for current carrying traces.
Avoiding dimension errors.
Avoiding clearance errors.

The following link illustrates the placement of my components before I undertake manual routing and after but if need be auto routing. Just to mention in the image below I have already used the ratsnest tool

Original image

Can anyone please identify anything at all that would cause me a problem in any way? Again any help is appreciated as it would save me time and effort solving errors.


texts: Arduino Bluetooth Module not holding connection

texts:
I am using an HC_05 Bluetooth module and an Arduino Uno to try and set up a simple bluetooth connection with my Windows Phone (HTC 8X). I am following the online tutorial here.

When I go into settings, my phone sees the "HC_05" bluetooth signal. I click on it, and it  connects right away. It stays connected for 5-10 seconds, then suddenly disconnects.

I am thinking that my phone is not receiving any data from the bluetooth module, and thus deciding that the signal is worthless, and dropping it. But even if that, why? When I call btSerial.read() from the linked code, isn't that talking to the device?

I'm have tried directing RX/TX directly into 0/1 on the UNO, with a voltage divider, into ports 10/11, redirecting the power to 3.3V, all show the same problem of not holding a bluetooth connection with either my phone or computer.


texts: What makes a short-circuited circuit have little current?

texts:
I have an old 9 volt battery that I've measured at 7.2 volts. I've measured the resistance of the wires in the circuit I'm using, and it came out to 1.5 ohms. Therefore, according to Ohm's law I'd expect over 4 amps of current.

However, when I connect it up to a 0.2A fuse, it didn't blow. I tried connecting it in series with a multimeter, and it just read 0.35 mA. How come it's so low?


texts: Designing and simulating a common source amplifier circuit

texts:
This is the problem:

And this is my design for R1 and R2:

So, using B2 Spice simulator I made this circuit according to the design:

Vin_ and Vout_ are voltmeters.

But the problem is that when I run the simulation, I get this graph:

Vin_ shows correct result.

Vout_ should be amplified by Av(=10) but I don't know why it is not in this graph !!

Please show me where the mistake is.

Thanks.


texts: Power on reset circuit for microcontrollers

texts:
In this schematic, there is a reset circuit with two pushbuttons:

The button marked "warm reset" sends an active low signal to one microcontroller, while the button marked "cold reset" sends a signal to all the microcontrollers on the board. The signal to all of them is normally pulled up by the resistors. Can you help me design a power-up reset circuit for this board? I looked online but most schematics are for active-high signals. I was thinking the correct way to do this is to connect a 10uf capacitor instead of the ground symbol at the bottom of the reset circuit, with the negative side connected to ground. Is this right and if not, what is correct?


texts:
I was playing around with a circuit, and I am not understanding its behaviour, it appears to be wrong.
I am using this circuit.

If you close the switch, the current will flow through the inductor, since it will appear as a wire. But when you open the circuit with the inductor already charged, the current reverses itself which is impossible right? There is no instantaneous change in current in the inductor, right? So how may this be possible?

EDIT: Included circuit images:

open circuit

inductor charged

current reversed when the switch is open


texts: What will happen on regulator as battery gets depleted?

texts:
I want to make a 5V-power source with four 1.5V-AA batteries. I think it can be done easily with 7805 regulator.

What I am concerning is the case that batteries are getting depleted as time goes by. With my knowledge, voltage of AA batteries go down gradually (but not to 0 V).

In that case, will the 7805 still provide a stable voltage output until some point? Some point that the four batteries provide acceptable (but weak) input for the 7805?


texts: Is compliance with IEC60320 mandatory for Type A pluggable equipment?

texts:
I’m trying to work out if compliance with IEC60320 (appliance couplers for household and similar general purposes) is mandatory for type A equipment under IEC60950 (Safety of information technology equipment).

Our product is designed to go outside so instead of using a regular IEC power socket, we want to use a Bulgin PX0730/P and PX0731/P plug and socket for 240Vac input power on a Type A device so we can achieve an IP65 rating. http://www.bulgin.com/media/bulgin/data/Standard_power.pdf

According to IEC60950 2011, section 3.2.4 an appliance inlet shall meet all of the following.

Be so located or enclosed that parts at hazardous voltage are not
accessible during insertion or removal of the connector (appliance
inlets complying with IEC 60309 or IEC 60320 are considered to
comply with this requirement); and
Be so located that the connector can be inserted without difficulty;
and
Be so located that, after insertion of the connector, the equipment
is not supported by the connector for any position of normal use on
a flat surface.

So, to me the first part of section 3.2.4 implies that compliance with IEC60320 is not mandatory.

Checking the definition in IEC60950 2011, section 1.2.5.5 of a detachable power supply cord

Flexible cord for supply purposes, intended to be connected to the
equipment by means of a suitable appliance coupler.

Then, checking the definition in IEC60950 2011, section 1.2.5.1 connection to the supply for type A equipment.

Equipment that is intended for connection to a mains supply via a
non-industrial plug and socket-outlet or non-industrial appliance
coupler, or both.

So, I guess the only catch would be if the regulator considers the Bulgin PX0730/P connector an industrial or non-industrial connector. I couldn’t find any definition of what constitutes an industrial or non-industrial connector. I think the application environment would determine if a connector was industrial or non-industrial?

I realise that the easiest way to achieve the IP65 rating would be to make the power cord non-detachable and use a cable grommet to seal it’s entry to the enclosure. Unfortunately, due to requirements this is not an option (don’t ask….). Likewise with providing a sealed junction box housing terminals for a direct connection.

I’ve also considered using an external DC power plug pack which would avoid any potential IEC60950 issues, but the product requires up to 500 watts of power making this solution effectively unworkable.

My questions

Is compliance with IEC60320 mandatory for pluggable type A
equipment?
Would the bulgin PX0730/P be considered an industrial plug?

I’m not sure on the legality of linking to a pdf of IEC60950, so have not included a link to it. My apologies for any inconvenience this causes.

EDIT: I should also add that a IEC60309 connector is mechanically unsuitable (way too big) for our application.


texts: Active low pass filter giving constant output regardless of input

texts:
I have a sensor that gives me an output between 1 and 4V, and I wanted to filter out noise present on the output to give me a more stable and accurate reading.

I set up an active 2nd-order Butterworth filter using a Sallen-key topology to try to filter out any signals above ~42Hz with 0dB gain. I'm pretty sure I've constructed the circuit correctly since it's only 5 components, but the output is remaining at 2.7V regardless of input which I've been varying.
What might be an issue, is that the rail to rail voltage of the op-amp is 0-5V, the same supply used for the sensors.
The Op amp I'm using is an LT1013, which I've checked is a single supply op-amp.

It's been a while since I've done any analogue design, so I'm a little rusty... Any idea where my problem might lie here?

Component values
R1 = 0
R2 = 10k
C1 = 220nF
C2 = 470nF

Sensor datasheet. From what I can gather the output impedance it 10kOhms and 20nF.

The output from the filter will feed into an ADC (MCP3202).

EDIT:
I tried to take the output impedance into account, using it as my R1 value and adjusting the other component values accordingly. However the problem persists mostly, but I am now getting a very slight movement in the output, though no where near the magnitude of the input.


texts:
I have a relay which is rated for 30 VDC @ 10 A or 28 VDC @ 10 A (which appears on this relay module) and I am running 12 V @ 6 A through the relay and this solenoid.

After a short amount of time (hundreds of triggers) I still hear the relay clicking but there is no longer continuity across the contacts. I have read that I can possibly put a non-polarized capacitor across the switch contacts to prevent sparking. Is it fair to assume the relay is failing due to sparking (even though it does not appear to be welding) and if so, what size capacitor should I implement?

Update 2018-03-19

Here is the schematic of how I'm currently running the circuit:

simulate this circuit – Schematic created using CircuitLab

If I've understood answers correctly, here is what I should do to avoid sparking and damaging the relay:

simulate this circuit

I'm now considering using this diode.

Update 2018-03-22

I've placed a flyback diode as in the second schematic. When touching the connections in place of where the relay will be there is still some slight sparking but it significantly reduced. I may have to look for other ways to continue to reduce sparking.


texts: PIC32MZ, MPLAB Harmony with I2S hangs after adding extra function

texts:
I have referred http://microchipdeveloper.com/harmony:i2s-tutorial and am able to configure the I2S and read continuous data from a microphone.

I am facing issue with the microphone data, and have been already discussing it here PIC32MZ: MSB of I2S data from digital microphone is always high. However, that is another issue altogether.

I have configured the I2S on DMA, and am able to continuously read the digital microphone data in my buffer.

My problem is, whenever I add a function to calculate the mean, average or to filter the DC offset from the data, my PIC32MZ program gets stuck.

I get the DMA interrupt, and there-by the I2S digital data once, but after that I never reach the breakpoint where I read the data.

Following is my code for reading data at the DMA interrupt:-

void APP_VOICE_RECORD_LOOP_BufferEventHandler(DRV_I2S_BUFFER_EVENT event,
        DRV_I2S_BUFFER_HANDLE handle, uintptr_t context)
{
// The context handle was set to an application specific
// object. It is now retrievable easily in the event handler.
//MY_APP_OBJ myAppObj = (MY_APP_OBJ *) contextHandle;
uint32_t convertedBufferCount = 0;
uint32_t evenCount = 0;

switch(event)
{
    case DRV_I2S_BUFFER_EVENT_COMPLETE:

        // This means the data was transferred.
        appVoiceRecordLoopData.codecClient.rxbufferObject = (uint32_t *) micbuf2;
        DRV_I2S_BufferAddRead(appVoiceRecordLoopData.codecClient.handle,
                appVoiceRecordLoopData.codecClient.txbufferObject,
                appVoiceRecordLoopData.codecClient.rxbufferObject,
                appVoiceRecordLoopData.codecClient.bufferSize);

        uint32_t receivedBufferSize = appVoiceRecordLoopData.codecClient.bufferSize / sizeof(uint32_t);

        for(evenCount = 0; evenCount < receivedBufferSize; evenCount++)
        {
            if(evenCount%2 == 0 && micbuf2[evenCount] != 0)
            {
                ConvertedAudioData[convertedBufferCount++] = (micbuf2[evenCount] >> 14);
            }
        }
        //uint32_t average = CalculateAverage(ConvertedAudioData, convertedBufferCount);
        appVoiceRecordLoopData.state = APP_VOICE_RECORD_LOOP_STATES_CODEC_WAIT_FOR_BUFFER_COMPLETE;
        break;

    case DRV_I2S_BUFFER_EVENT_ERROR:

        // Error handling here.
        break;

    case DRV_I2S_BUFFER_EVENT_ABORT:

        // Error handling here.
        break;

    default:
        break;
}

}

Code works properly when I comment

//uint32_t average = CalculateAverage(ConvertedAudioData, convertedBufferCount);

However, when I uncomment this function, code never reaches here the second time.

Any suggestions what I might be doing wrongly here?

Thanks in advance


texts: What is the purpose of resistor at the input of the OpAmp?

texts: I have just seen this integrator circuit here. As seen from the picture, there is a resistor at the positive input of the OpAmp. Could you explain what is the purpose of this resistor?


texts:
How can I find the phase shift as a function of \$R_1\$? I found online that the equation is \$\phi = −2\arctan(R_1/X_c)\$, I just can't figure out why the 2 is there.

simulate this circuit – Schematic created using CircuitLab


texts:
I've got a question about coding an algorithm for a Texas Instruments TMS320C64xx DSP in MATLAB:

I've got a working sloppy implementation of my filter in MATLAB. My goal is to use MATLAB Embedded Coder to convert this algorithm to C which I can then import to Code Composer Studio and load onto the DSP.

To do this, I know there are certain things I need to do to my MATLAB code. For example, I need to pre-allocate space for matrices so it knows what size to make them (unless I want to fuss around with variable sized data). All that massaging of MATLAB code into C'ish code so that MATLAB coder can convert it I more or less understand. However, I have no idea how to make sure that my data types (for example the coefficients of my filter) are fixed point rather than floating point so that MATLAB Embedded Coder will convert my code to C which only involves fixed point data types.

So I guess my overall questions are:

Is there a way to ensure that MATLAB Embedded Coder does not create float data types?
Do I need to use the MATLAB Fixed Point Toolbox?


texts:
I'm using TLV71333P-Q1 to regulate the input voltage of 5 V to get the output of 3.3 V.

It says in the datasheet that in normal operation, "The input voltage is greater than the nominal output voltage added to the dropout voltage" and when I looked up in the Electrical characteristics table there's a field of dropout voltage (VDO).

5V - 3.3V = 1.7 V is clearly greater than all of the above values but VDOs are different as the different of IOUT.

The question is how can I determine the IOUT of this regulator. And if my input voltage is lower than 5 V (may be 4 V or 4,5 V), how can I determine the VDO.


texts: Two step up converters to build dual supply with a virtual ground

texts:
I would like to amplify a difference signal from two electret microphones.

I would like to use an instrumentation amplifier with dual supply (AD620 for testing, probably INA103 for the final product).

Using dual power supply close to the maximum rating e.g -15V and +15 V will allow higher gain, and higher gain will result in much higher CMRR. I need high CMRR because the common mode signal will be far more louder than the differential signal.

I'll use a factory calibrated instrumentation amplifier instead of a simple differential amplifier for the same reason.

In the environment where this will be used, there is only a (noisy) +12 V power supply. My idea is to use to DC/DC converters, create +15 V and +30 V, and use the middle point as a new ground.

Suppose that the whole circuit will be isolated from the common ground, what are the disadvantages of using 0, +15, +30 V  instead of -15, 0, 15 V?

(The DC/DC converters can do at least 1000 mA, much more than I need)

UPDATE: modified the requirements to +/-5V for making the design simpler. Would this circuit work, or should I use 7905 instead of 7805? I'm not sure.

simulate this circuit – Schematic created using CircuitLab


texts: Can a MOSFET h-bridge class-D amplifier be used as a digital-to-analog converter?

texts: They are used as de facto DACs for low power audio systems and in power inverters. But how common are they for high frequency D/A conversion(or broadband)?


texts:
We have designed a medical device that is battery-powered. In order to sell our product in the US, Ul-Certificate is mandatory.
now I am getting the battery packs in which only the individual cells are UL-Certified and not the whole battery pack. So can we go ahead or the entire battery pack needs to be UL-certified?
I am unable to find the pre-certified battery packs and the cost of certifying them is too high for us.


texts: What determines the continous ratings of electric motors?

texts:
I've seen variations of this torque-speed curve for brushless DC motor performance, and I'm curious what criteria determine the rated torque and speed of permanent magnet DC motors in general.

Does thermal dissipation of joule heating limit the max continuous torque? Do mechanical limitations (max bearing speed due to friction, mechanical stress, etc.) limit the max continuous speed? Are there any "rules of thumb" for predicting the max continuous torque and speed of electric motors?


texts:
I am planning on creating a RGB LED POV globe only physically larger then that one.

I am planning on using 64 RGB LEDs, requiring 3x pins per LED for a total of 192 outputs. Obviously I am going to need some shift registers. I have looked in to 74HC595 (8bit) and it would require 24 of these chips to handle all of these LEDs.

I am planning on putting these shift registers in series with 6 per channel from my micro-controller.

The 74HC595 has a switching frequency of 100 MHz.

I been told that I will need to spin the Globe at around 1500 RPM (25 per sec)

The plan is to use a Arduino for the micro controller but I am open to suggestions.

My questions are:

Is there a better suited chip then the 74HC595 for this project?
Besides the Arduino is there a better suited micro controller for this project?
I don't want to power the LEDs off of the micro-controller So I am going to need external power. How would I go about doing this?
With 6x 74HC595 in series, How fast could I switch all of the LEDs colors on this channel?
With 12x 74HC595 in series, How fast could I switch all of the LEDs colors on this channel?


texts: What do the specifications of this RF power meter mean?

texts:
I am looking for RF power meter to measure the output power of RF based PCB board which is estimated to give an output power of 45dBm at 868MHz.
While searching for meter I have come across specification "Dynamic Range" which is about 70dB and the power meter comes along with the power sensor which says that the  measurement range of power sensors I have seen is around -60 to +20 dBm. Can anyone help me whether these specifications are suitable for my application ?


texts: Drive a DC motor rated for higher than 5V

texts: How would I go about if wanted to drive a 10V DC motor with 5V logic, suuch as the one found by an Arduino, at different rotation speeds? Is there such thing as a motor driver that accepts an analog/digital value specifying motor speed?


texts:
I am reading Practical Electronics For Inventors 4th edition and on page 384 there is a figure that shows basic power supply with single diode,I think its called half bridge.

There is picture that shows transformer that steps down wall plug ac down to 10 volts.There is written "10 volt AC rms",then it shows single diode,a 1 milliFarad capacitor and its all finally connected to 100 ohm resistor that represents load.

Its kind of a thing where author of the book ask you to calculate and find average dc output. The author says the correct answer is 12.92 V,I absolutely dont understand why its so high.

I calculate voltage like this, average voltage of sine wave is the rms, a 10 V rms AC average voltage is same like 10 V dc average voltage. The picture clearly shows the bottom half of the sine wave completely blocked by diode, only positive peaks are there,now if the sinewave was 10 V rms before it got rectified,then after half of it is chopped away,it must be 5 V rms or 50%! Yet instead of decrease by half the author says its 12.92 or almost 13 V.

With 10 V rms AC, you completely block half of it and then you suddenly have 12.92 V dc?

My question is: Where does the extra voltage come from?


texts:
I am searching for a non-technical picture or diagram or explicit textual instructions explaining how to wire a GY-521 Accelerometer/Gyro to an Arduino Uno R3.

I am a software developer and need something that doesn't assume that I know how to do it already. Searching Google has only found diagrams that I can't read or textual instructions where the terms don't match up to the names on the pins on the Uno R3.

Arduino +5V to VCC on GY-521 and to Hv on the Logic Level Converter
Arduino +3.3V to Lv on the Logic Level Converter
Arduino GND to GND on Gy-521 and both GNDs on the Logic Level Converter
Arduino analog input pin A4 to ch1 Tx on Hv side and ch1 Tx on the Lv side to SDA on GY-521
Arduino analog input pin A5 to ch2 Tx on Hv side and ch2 Tx on the Lv side to SCL on GY-521

I don't know what they are talking about ch1 Tx and Logic Level Converter.

The version of the board I have is +5V compatible using the +5V from the Uno as it has a voltage regulator on it already.


texts: keep bathroom fan running for a few minutes after power off

texts: What is the best way to keep the bathroom fan running after cutting the power to it? I assume a capacitor can be used, but which one should I use and how do I connect it?


texts: What is this small circuit board used for in a 12v light?

texts:
Repairing a home-made disco light that was used in a nightclub during the 80's/90's and it consisted of 16 12v 50w lamps arranged on 8 legs.

I have discovered a small circuit board within each lamp which has an LED on the back. What was this small board used for and can it be removed?

The lights were powered in serial, so would this board of allowed for the rest of the lights to be powered if one light blew?


texts:
I have asked question in the past about this circuit, this is a new question based on some information provided in this answer here namely concerning the "throwing away" of the signal.

Op-amp supply rails:

ISL28210: -38V   +2V
AD8676:  -2V    +10V

I've tried to do a basic online circuit simulation and playing around with the resistors, it would seem that if I reduce R8, R9 and R10 by a factor of 2 then I will get the same output voltage.
It also means I wouldn't need the -38V supply rail which currently comes from a bulky charge pump configuration on another board and could use a smaller voltage (I currently have -10V I use elsewhere so could piggyback off of that I assume)

I have looked at other questions and answers concerning the size of the resistors used, this answer in particular. I don't think power dissipation will be a problem as the circuit i working in the uW range, so I can't understand the choice for the 2.2M resistor in the first stage

The circuit was originally designed by a colleague who has since left so I have nobody to consult on this

My questions are:

Would reducing the size of these resistors cause a problem?
In reference to this answer, how does reducing the amount of signal "thrown away" increase speed and reduce noise?

As an extra aside question from this:

Why would C15 and C19 be different values? I calculate it that the cutoff frequency in the first stage at ~72kHz and in the second stage at ~125kHz, does it make sense to have different cutoff frequencies for each stage?

I calculated the cutoff frequency using  which I hope is correct

Datasheets:

ISL28210
AD8676
Photodiode


texts: How to bypass step-up voltage converter?

texts:
I bought this great solar panel unit on amazon that has lithium batteries, 12v input and 12v output. I use it to power a 5v ESP8266 and I have a step down voltage converter from 12v to 5v on my end but the batteries on the unit are not lasting as long as I was expecting (~2 weeks) and the sun doesn't seem to charge the batteries fully.
I opened the unit, it has a 8v (2x18650 lithium batteries) battery pack and a bunch of step-up and step-down converters and other features on the circuit to display an LEDs scale for the charge amount.
Would anyone have any suggestions on what components I should look for to bypass the step-up voltage converter? Because of that converter, on my esp8266, I cannot check the battery status (voltage seems to step up whatever is left on the battery to 12v) and I suspect it consumes quite a bit batteries.
At the bottom of the picture is the output, but I'm a bit puzzled as to why there is a CR43-4R7 which is usually a step-down converter.


texts:
I am interested in almost duplicating the functionality of the new Mustangs. When the rear tail lights are activated (there are 3 in a row on each side), I'd like the first one, then the second one, then the third one to light up, and when the power on the whole system turns off, all three go out (at once or in the same order they turned on would work). I originally considered using capacitors for this job, then I realized that would not provide the correct look on the other side.

The bulbs would be taillight brake bulbs, not necessarily LEDs. I'd like to hack this together without buying some "kit".

The functionality can be described:

How would I make this work? What sorts of directions should I explore in circuit design?


texts: Requesting help to understand this audio amplifier circuit

texts:
I will be using the attached circuit diagram to build a Phono Cardio Gram (output of the attached circuit through a band pass filter and the microphone attached to a stethoscope). I need help understanding the functions of the various resistors and capacitors in the circuit. From reading this https://thephysicsportal.wordpress.com/2012/02/22/day-8-more-op-amp-circuits/
I believe that the opamp is used as a non inverting, integrating amplifier? I understand that the 1 M resistor is for nullifying the drifting D.C offset but is clueless about the resistors in series with the capacitor and the other capacitor -resistors combination at the non inverting input. Any help would be much appreciated.
AJ


texts: De Morgan's Theorem applied on the SR Flip Flop characteristic equation

texts:
How the second equation is resulting by applying only De Morgan's theorem on the first one?
How does the second one helps you build the SR flip-flop with only NAND gates?


texts:
Could you please give me your feedback on following circuit?

.

simulate this circuit – Schematic created using CircuitLab

Bigger image is available here

Explanation in brief:

Intention is to read a sensor value by a uC every 15 minutes and save as much energy as possible since it is going to be portable and battery powered. So I put uC in sleep mode when it's not reading. I also cut sensor power when uC is in sleep mode.

Procedure:

uController is sending a signal through D1 to N-ch MOSFET (IRL1540G) >> P-ch MOSFET (NDP6020P) to turn on Load.
Voltage is applied on Load (sensor) through buck converter
Load (sensor) output, which is in range of 0.5V-4.5V and scaled down to maximum 3.3V, is going to A1.

.

Notes:

uC current consumption is 0.24 mA (sleep mode) to ~12 mA (up). Operating voltage is 3.3V.
Load current consumption is ~7mA. Operating voltage is 5V.
Buck converters quiescent current is 1.5mA , datasheet. But measuring by MM showed even lower at around 0.9mA.
Batteries are 3x26650 6A in series.

uC is waking up every 15 minutes, for 5 seconds, to turn on sensor and read its value, and goes to sleep mode.
On A2 I'm reading battery pack voltage.
Based on my calculations it can run for around 13 months. Though I'm planning to use solar panels to prolong lifetime. That's why I'm feeding uC from 12V battery pack, and not AA batteries.

.

I would like to have your feedback and suggestions on followings:

Are C3 and C4 values appropriate? Is it OK to use Ceramic capacitors, and not tantalum or other types?
Do you have any suggestion on more-efficient buck converters with less quiescent current? or do you have any suggestion on reducing current consumption? Does it limit current consumption if I put a resistor after D1? or any suggestions in general?

.

Answering any of the questions is appreciated.

Thanks in advance


texts: Turning a high impedance output state to a concrete voltage value using a pull up resistor

texts:
I have this switch datasheet.

I also have a connector with default pins arriving to switch D point.
S points are connected to another circuit point.

Note: D side connector is an output connector and matches with another input connector that will connect D points with IN logic gate inputs.

When the set of switches is ON, S will be connected to D point. But I am interested in looking at D during the OFF state.

I'm assuming that D is high impedance state during off. I want to turn this high impedance state into a "high level state" signal, 12V, in order to be a logical gate input for the next stage.

I have two questions:

Could be said that D is really totally disconnected (high impedance) or I am missing something about the devices that can influence that they are not fully electrically isolated to say that they are in high Z?
Is it a correct way for turning high impedance into 12V?
How can I choose an appropriate value for this Resistance?


texts: Designing a differentiator op amp with a maximum voltage gain and gain limiting frequency

texts:
Hi I am required to design a differentiator for a project which requires a maximum voltage gain of 22 and a gain limiting frequency of 30kHz.
Heres my progress so far:

If im not mistaken (correct me if im wrong) Av=Rf/R1 which is already solved. However isnt a gain higher than 1 supposed to make the output signal larger than the input?
Also i am having trouble finding sources for the formula of gain limiting frequency.
Thank you in advance!


texts:
I found this device in my father's basement, but I can't figure out what this device is.
It has only 1 SCART connector, 1 power cable and only 1 button in front of it.
I think it may be some old video decoder, but I'm not sure.
These are the images of the device outside, and the circuit board.

Thanks in advance.


texts: What's the problem in designing a bright enough LED lamp?

texts:
So far the most powerful household LED lamp I've seen had consumption of 2.1 Watts and gave light equivalent to maybe 15-25 Watts incandescent lamp. That's maybe good for illuminating a Christmas tree, but totally unusable for using as usual lighting - too dim. The situation hasn't changed over the previous three years - I see more models on the market, but they are still very dim.

Is there some design problem in creating a more powerful LED lamp?


texts:
I have a problem with simulating a Schmitt-Trigger and analyze it with MATLAB. I can do this with MultiSim or Proteus but for more advanced analysis I need to do this in Simulink.

In Library Browser under SimScape, there is a Foundation Library and "Electrical" inside it. There is no problem until here.

But when i take an op-amp and couple of resistors, I can not create a simple Schmitt-Trigger circuit. I mean there is not any junctions for supplying opamp.

I'm really new at using Simulink and searched over google and here but can not find any solutions.
And another problem how can I measure the output voltage and plot it to see classical Schmitt-Trigger response?


texts:
I'm looking for a switching buck/boost regulator that works from a Li-Ion battery (e.g. rechargable 18650) with high efficiency and capable of providing high current pulses for GSM application.

While I was searching on the internet I came across on this Linear's design note (http://cds.linear.com/docs/en/design-note/dn307f.pdf) and I was wondering if there's a standar topology in switching power supplies for applications like this or I'll have to search for particular ICs like Linear's?


texts:
I bought a car reversing sensor system... I bench tested it with a simple 12 V PSU, and it works great. Integrating it into my car is another matter since finding out that most cars since 2008 have CAN bus wiring. So a simple piggy back into the reversing light  12 V + is fraught with problems (apparently, reading up on this and googling many pages)

There is a whole line of 'expensive' addons that get you into the CAN bus  network without upsetting the system, but they are more expensive than the reversing sensor kit!

I don't want to piggy back into the wiring then, but can I use some kind of voltage sensor taped to the reversing light's insulated wiring and get a signal to switch a relay to supply a 'direct from the battery' 12 V to the kit I bought?

I had thought of an optical circuit (when the reversing light comes on) to detect that, but would have to be sensitive to bright light only (the bulb) rather than false trigger by daylight.

Hmmm.. I am open to any ideas, the simpler the better.


texts: Wireless or wired solution for perimeter fence security?

texts:
We are currently working on a project where we would like to place around 350 vibration sensors on our university's perimeter fence for security. The field layout is almost 1km to 1km (square - 1km^2 - 4km of fence).

We had two solutions in our mind; wired and wireless.

For wired solution, we thought using a half duplux RS485 network where each node will be sending two types of messages:

Alive: Nodes will be sending an "alive" message periodically (every hour or etc.) where we would like to know each sensor is healthy.
Vibration: Nodes will be sending the vibration message when ever there is a vibration.

For wireless solution, rather than putting a 4km RS485 line around the campus, we thought using simple low cost wireless transmitter modules (example project) with antennas and a long distance wireless receiver in the middle of the campus (on a roof of a building).

Receivers will be working on batteries where we can replace/charge the batteries very 1-2 years.
Receivers will be in sleep mode unless they are sending a "I'm alive" and "there is a vibration" messages.

The buildings in the campus are no higher than 3 flats and terrain is flat but there is a high voltage line passing in a small area (at the back of the campus).

We are still researching and would like to get some recommendations.

What are the pros and cons using a wireless system over a wired system? Is it doable? (reliability, cost and etc.)
Which type of RF technology should we consider for a wireless network? (Wifi, XBee, a reguler 433Mhz RF transmitter/reveicer and etc.)
For a wired solution is a half duplex RS485 the right solution?


texts: ATTINY85 pin doesn't go fully LOW when in PWM

texts:
I have connected 3 LEDs to ATTINY85 (PWM mode). Each LED is connected with NPN3904 and 68 ohm resistor to the PB0, PB1 or PB5 port.

Everything works great, except for some reason when I set the OCR0A or OCR0B values to 0, nether will go fully LOW, but instead will continue to give out a weak signal, while setting OCR1B to 0 works as expected and PB5 goes fully LOW:

Code:

#define F_CPU 8000000

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

void main()
{
    DDRB   = 1 << DDB4   | 1 << DDB1   | 1 << DDB0;
    TCCR0A = 2 << COM0A0 | 2 << COM0B0 | 3 << WGM00;
    TCCR0B = 0 << WGM02  | 1 << CS00;
    TCCR1  = 0 << PWM1A  | 0 << COM1A0 | 1 << CS10;
    GTCCR  = 1 << PWM1B  | 2 << COM1B0;

    for (;;)
    {
        OCR0A = 0x00;
        OCR0B = 0x00;
        OCR1B = 0x00;

        _delay_ms( 1000 );

        OCR0A = 0xFF;
        OCR0B = 0xFF;
        OCR1B = 0xFF;

        _delay_ms( 1000 );
    }
}

I have rotated all the components and tested with VCC in the range from 2.7v to 3.5v but still the same result occurs. The issue seems to be tied to the PB0 and PB1 pins specifically. Any hints on what am I missing? Thanks!


texts: Accessing the STM32L412KB Serial Wire Debugger (SWD) Connections (Novice User)

texts:
I am attempting to program an STM32L412KB device using ST-Link/V2-1, a Raspberry Pi 3B+ and OpenOCD software.

To do this however, I require access to the SWDIO connection and the SWDCLK connection of the ST-Link on the STM32. From looking at this diagram of the connections, I am struggling to see a way of accessing these connections. Pins PA13 and PA14 are used on other boards but are inaccessible here. I am thinking the only way is through the micro USB port. If I then plug in a micro USB cable to the device, which pins on the larger end represent the SWDIO and SWCLK so I can then connect them to the complimentary pins on a Raspberry Pi.


texts: Why can a single resistor be used for many parallel LEDs?

texts:
One of the first things students are taught about LEDs is that each LED in a parallel circuit must have its own resistor. This question describes this perfectly and the accepted answer is great. However, often those cheap LED fairy lights use a single resistor at the battery box for the entire circuit, and that's it.
Why don't the theoretical properties described in this answer apply to LED string lights? How are they manufactured without a resistor for each LED in the circuit?


texts: Measurements of the volume and surface resistivities of electrical insulating materials

texts:
According to this article in table 1 there are values of volume resistivity measured with application of electrodes made of conducting rubber ρvr and evaporated silver ρvs.

Under table 1 is note:
"Results     of     resistivity     measurements     obtained     with     application  of  electrodes  made  of  conducting  rubber  are  always higher (few tents-few hundreds %) in comparison to that obtained for metallic electrodes"

My question is why resistivity   measurements of conducting  rubber electrodes are always higher than electrodes  made  of metallic electrodes?


texts: How to quickly understand circuits with BJT transistor?

texts:
I am aware this may be a silly question, but I am constantly told by everyone I met more experienced than me in engineering that the only silly questions are the one not asked, so here I am..

About a year ago I learnt at university the basics of how BJTs work, their I-V characteristics, some of their limits and praises. However, when encountering new circuits, I'm constantly struggling to understand at first sight what is actually happening in the circuit. That is, I cannot understand in a few looks what the circuit is doing.

As an example, take an RC or a CR filter, you can see it as building block filtering incoming signals and outputting filtered signals, that is very intuitive after having seen their transfer function and the physics behind it. Same for operational amplifiers, within limits, you can think of them as building blocks outputting a modified version of their input.

I can not do the same thing with transistor, I usually have to start with an hypothesis (ex. for an NPN, that the base is forward biased), check if it holds and then go on from there, as I have been taught in university. This is fine, but it takes time and may not be that easy for non trivial circuits. I wonder if practitioners and experts have more intuitive/quick methods to understand what a BJT is doing (or, more in general if you feel like it, what a non linear component is doing).

For a pratical comparison, take an astable multivibrator circuit. I can get my head around it reasonably quickly (also because I know what it should be doing), but when we step up to a circuit like the Royer oscillator you see here, it takes me some more time to work it out. How would a professional go to understand its workings?

As a final note, I would like to add: this question comes partly from the fact that I know I can plug the circuit in a simulator such as LTspice, but I want to know what is happening (or should be happening) in order to be able to tweak the circuit, and partly from the hope that practitioners may have some commonly accepted and used rules of thumb.


texts:
I have made a portable device charger with a 5 volt voltage regulator(7805-TO220 package),a 9 volt battery and a few capacitors.The problem is,when I connect the charger to a certain device(whose original charger outputs 5 volts and 2A) and the device starts charging, after a few minutes,the image starts flashing and then it shuts down,then the start-up screen appears,then the screen turns black and so on a few times,then it shuts down completely and remains in this state.I connected the circuit to another device whose original charger outputs 5,1 volts and 700 mA and all works just fine.

simulate this circuit – Schematic created using CircuitLab

Why does the first device behave this way?
I don'think it's about the voltage or current.
The 9 volt battery is a Varta High Energy model-6LP3146.
EDIT:I noticed that when charging the second device,its battery drops after a while,whether discharging on its own or being discharged by my charger(I added a diode between the output pin of the regulator and the positive terminal of the device,so it's unlikely).


texts: When are MIPS control signals generated?

texts:
Are the control signals for a given instruction generated within a single cycle
for the pipelined, the multicycle as well as the single-cycle implementations of the MIPS32 datapath?

I think they are for the single cycle implementation but not for the pipelined and multicycle implementation.


texts: How to connect multiple devices to UART bus?

texts:
I want to use a UART bus (RX-TX-GND) to communicate between one master and multiple slaves.

NUCLEO-F401RE board is the bus master. B-L072Z-LRWAN1 and ESP32 are the slaves.

Communication over UART works between master and one slave at a time. However, when I connect both slaves to the bus, communication stops working. Of course, I made sure that only one slave is sending at a time so I do not see where is the problem.

Can it be due to UART pullup resistor configuration? I have tried different configurations but nothing works for now.


texts: Unstable wheatstone bridge simulator circuit - help required

texts:
simulate this circuit – Schematic created using CircuitLab

I am looking to implement a wheatstone bridge circuit so I can accurately adjust the signal into a strain gauge amplifier circuit.

Is there a preferred method of doing this?

I currently have resistors soldered together with a pot in one leg, it works, however adjust-ability is very sensitive.

Bridge supply is 0-5V
Returning signal is -11 to +11 mV.

Ideally I just want 0-11mV returning, and nicely adjustable and stable.

Bridge supply is powered by 24V battery via an LTC3646 Buck.


texts: EMI filtering at end of a long copper wire transmitting high DC power

texts:
I have a long (20 - 50 m) copper wire for supplying DC power. One one end there is a AC-DC converter supplying 600W-1000W of power at 60V output. At the other end I have a switching type (100-140 kHz) DC-DC converter out-putting 24/12 Volts for a power requirement of 400W-800W.

I understand that there will be large line losses due to the DC transmission at such low voltages and high power. But I am more worried about the EMI effects of the long wire on the switching type DC-DC converters.

The wire will have significant inductance and resitance. How can I choose appropriate bypass or decoupling capacitors for the DC-DC converter in order to mitigate the EMI effects due to this lengthy wire?

As of now I have planned to use the following capacitors near the DC-DC converter:

1) 4.7 nF between all the input/output terminals and the baseplate/ground to eliminate high frequency common mode noise,

2) 0.2 uF between the input terminals to handle high frequency differential mode noise,

3) 100 uF between the input terminals to handle low frequency components and current droops on the power supply,

4) 0.01 uF between the output terminals to handle high frequency differential mode noise,

Are these capacitor values appropriate? Also I need some guidance on what can be done on the AC-DC converter end to improve the EMI filtering?


texts: Difference between incandescent/fluorescent/LED wattages?

texts:
If the numbers on the 'light output' table at the bottom of this page (here) is correct, and if I have a lamp (like this) that has a maximum wattage of 60 and takes incandescent bulbs:

Does that mean that I'm limited to 800 lumens?
Could I replace the 60-watt incandescent with an 6-8-watt and have the same brightness?
Could I replace the 60-watt incandescent with a 25-28-watt LED and have about 3 times the brightness?
Can a lamp take any bulb type? Why would a lamp specify that it takes incandescent?


texts: how to drive peltier cooler pad at home?

texts: I purchased an peltier cooler plate (90W maximum, but it could work at different power) like the model shown in this link http://pcbheaven.com/wikipages/The_Peltier_Thermo-Element/ . It has a wide working range on voltage and current. I use a AC-DC power supplier (12V, 0.5A), which was used to drive MP3 player, to drive the peltier. I also connected a fan (12V, 0.9W) in parallel to the peliter to the supplier. When I plug it to the home socket, it works for 10minutes, one side of the peliter is very cold and other side is so hot, and the fan is working (but spinning so slow). After 10 minutes, the power supplier becomes so hot. I thought the power of the fan is constant and the supplier provide 12V, so why the power supplier is getting that hot, it seems like it is drawing more and more current out of the wall.


texts: How do ALU flags communicate with the rest of the computer?

texts: How are ALU flags connected to various parts of a computer? I've just finished building an 8 bit computer in Logisim that can add subtract and compare... and am wondering how I can make it multiply (in software) using ALU flags.


texts: Finding the frequency of opamp to get a specific voltage gain

texts: In the following question, they ask for the frequency at which the gain would be 1.41 V/V. The dc or low frequency closed loop gain is 2V/V (6 dB). Is the solution of the following question done correctly? I think it is wrong as they get the answer for frequency to be 5MHz, while 5Mhz is the closed loop 3db frequency of the amplifier. The frequency resulting in 1.41 V/V gain aught to be larger than that. Please tell me if their solution is correct or not and if it is not then what is the correct one?


texts: Do UART RX interrupts require support from the transmitter?

texts:
I'm trying to understand why I am seeing RX interrupts when tying RX to TX of my SAMR34 but not when I connect it to the transmitting device.  The transmitting device notes the following restrictions:

Serial hardware flow controls (RTS/CTS and DTR/DSR) are not used and will be ignored.  In addition, the receiver must not use software flow control (XON/XOFF)

I do see data from the transmitter when I poll. Does interrupt driven UART require support from the transmitter?  Should I switch to DMA to resolve this issue?  Here is my setup


texts:
What is the fastest mains outage detector at <1ms?
Anything that uses a 12V DC adapter or a mechanical relay is not an option for me because it has a long delay.

Is there an AC driven static/solid state relay/switch?

Or maybe an AC-DC converter using a diode/resistor just to trigger a solid state relay around 3-32V DC? is this fast?

What I need is at least a sensor/switch that can act as fast as possible after the mains outage so that a microcontoller can switch the AC load to a different source like an inverter within <10ms. As I know, computer power supplies and some AC-DC adaptors have a hold-up time of 16ms.


texts: I2C: How to connect Raspberry Pi (power cut) to ATmega328p

texts:
I would like to interface a Raspberry Pi with an ATmega328p microcontroller using the I2C bus. These two parts act both as masters, but not at the same time. The Raspberry Pi is powered through the +5V pin on the GPIO header and power to the RPi is controlled by a p-channel MOSFET through the ATmega328p µC (see schematics). When the RPi is in power cut state, the I2C bus is pulled low disabling all I2C communication.

How do I disconnect the RPi from the I2C bus when power cut?

simulate this circuit – Schematic created using CircuitLab

In detail, there are the following two operation modes:

The Raspberry Pi is powered on (running) and acts as I2C master. The Raspberry Pi reads/sets the time from an PCF8583 RTC (I2C slave) and displays time and other information on a HD44780 compatible 16x2 LCD connected via an PCF8574 I2C expander IC. While the RPi is running, the ATmega µC I2C bus is sleeping and is not involved in any I2C communication.

This modus works as expected.

The Raspberry Pi power is cut via a p-channel MOSFET when shutdown. While +5V line is disconnected by the FET, the RPi is still connected to common GND pulling all GPIO pins on RPi low. Hence the I2C bus constantly pulled low and I2C communication is disabled.

My question is, how can I isolate the Raspberry PI I2C connection from the bus when it is in powered off state?

I tried the following solutions:

The RPi is powered through the normal micro USB plug and held in
reset state (P6 header) when powered off. The I2C lines are high
impedance and not interfering with the rest of the bus. This
solution works, but I would like to cut power to the RPi completely.
Adding simple diodes in SDA and SCL lines. This works for the SCL
line as the RPi I2C bus always acts as master and generates the
clock signal for the I2C slaves. However, the SDA line is
bi-directional and hence communication is not possible with a diode
inserted in between.

What is the easiest solution? I found suggestions here, but I do not understand how these circuits work and no explanation is given. Which of these schematics is best for this problem (if any)?

Any other (simpler?) solutions are welcome.

Thank you very much for your help.


texts: DC DC Boost Converter - Why that high Ampere?

texts:
I have a question for the electronic experts of you! I want to create an DC-DC boost converter circuit for a project to get from 5V to 12V.

Calculated with help of this site: https://learn.adafruit.com/diy-boost-calc/the-calculator

There is this result:

My question: Why there is an Ampere size of 5.76A!! oO I don't get it why this number explodes that much... Can you explain this to me (or if I can choose a lower Ampere tolerant Schottky diode?

Thank you! :)


texts:
For an assignment I was asked to evaluate the quality of a square wave I had generated with an op-amp. After spending quite a bit of time searching I have yet to be able to find a definition of the quality of a square wave.

I know of the slew rate and can make an argument for rise time / on time but have not found a formal expression for the quality of a square wave.
Is there a formal definition for the quality of a square wave?


texts: 64k x 8 RAM - what exactly does it mean?

texts:
I'm looking at this microcontroller because it has the protocols that I want and a really interesting price.
My doubt is related with this field: RAM Size   64K x 8.
What exactly does it mean? I know what it means RAM but 8 blocks. How it works?


texts:
I have the following circuit that I am using to implement an Arduino project. Now I tend to focus more on the coding side of things usually so I lack the electrical knowledge. Could someone please provide me an explanation of the workings of this circuit.

I am trying to understand how each of these components are used and fit together, and how their required values were found.
Much appreciated.


texts:
Have this ZOOM recorder and it came with 150V power adapter. It got accidently plugged to a 250V and went dead. I opened to see if it can be fixed and found this RAM IC EM638165TS in this condition:

Im just a amateur in this field can't understand if this picture looks normal. The other side there is also a TMS320 which is texas int. DSP but it look smooth surface.


texts: Flyback Diodes For Inductive Loads With Long Wire Runs

texts:
I have a project that uses several high power DC solenoids (50 VDC) that will have ~10 feet of wire between them and the driver board. This is for pinball machines. These solenoids typically come with flyback diodes pre-installed on their terminals which makes sense and is very common with any switching inductive load.

However, when I look at schematics for the old driver boards from their heyday in the 80's and 90's I see flyback diodes there too.

Is there a reason you would want flyback diodes at both ends of the wire run?

simulate this circuit – Schematic created using CircuitLab


texts: Signal routing to power amp LM1876 based on TS5A22362 SPDT

texts:
Has anyone ever used the TI's TS5A22362 CI to route audio? I though of implementing the circuit below on which I intend to use the same supply voltage to switch between normally closed and normally closed pins, from a ceramic cartridge preamp and a RIAA one, to a LM1876 power amp. Will it work? Any dos and don'ts abut my circuit? What I want is: COM1 and COM2 straight to LM1876, NC1 = COM1 and NO2 = COM2, upon applying a voltage to IN2 and then, NO1 = COM1 and NC2 = COM2 upon appolying a voltage to IN2, and in both case what is connected to the four inputs, NC1/2 and NO1/2 are audio signals from a RIAA pre amp and from a ceramic cartridge pre amp, as shown on the image.

https://www.ti.com/lit/ds/symlink/ts5a22362.pdf?ts=1611247159628&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTS5A22362


texts: How to measure 120 V, 60hz with an oscilloscope?

texts:
I wanted to measure the voltage of the electrical outlet. I wanted to see the signal with an oscilloscope, but I don't want to break it down. What is the best way to do that?

I have seen that some oscilloscope probes make the signal greater, they are x10 or x100 probes, but I am not sure if exists x0.1 or x0.01 probes. I was thinking also about using an operational amplifier to attenuate the signal. What would you recommend me. I want to do that because I am making a dimmer, and I want to see the signal.


texts: Why is there no shot noise in conducting wires?

texts: Why is there no shot noise in conducting wires, while it is present in junctions and barriers like PN junction? Is electron flow not quantized in wires? If it is, why do a resistor and perfectly conducting wire not produce shot noise? What is the fundamental difference in electron flow in barrier based devices like Bipolar transistor and wire?


texts: Audio: 2 Speakers * 200 Watt versus 1 Speaker * 400 Watt?

texts:
What is the difference between 1 speaker of 400 watt and 2 speakers of 200 watt? All the speakers are 12 inch.

Of course, I know the difference is mono/stereo. But I want to play in a little band including two guitars and an electrical drumset (which has to be monitored). For the guitars, we won't notice the difference. But I guess that the drumset will be bad monitored.

I own the speaker of 400 watt, and my opinion is that the 400 watt speaker is not enough and that I need an extra SubWoofer Speaker.

What would you advice? The 2 of 200 watt or the single of 400 watt?

Thanks in advance.


texts: Why is saturation region called so in BJT characteristics?

texts:
I understand base-collector (current) linear relationship is lost in saturation region and collector current will be lesser than  \$ \beta * Ib \$ . Hence,at max, we can call such a region as non-linear region.

Saturation literally means something remaining constant and  not increasing further (upon variation of another quantity). Which quantity is getting saturated in so called 'saturation region' of BJT ?


texts: sensing light and outputing voltage suitable for audio

texts:
I have an idea for a project where I use a pc fan to make an oscillator. The oscillation is created by the cycle of light/dark falling on a light sensor as the blades of the fan rotate.

My initial research points to the use of the photodiode in combination with a op-amp to provide a suitable line audio output. My question is: What are the critical parameters for the circuit?

Here is the datasheet for the photodiode i'm prototyping: http://www.jaycar.co.nz/products_uploaded/ZD1948.pdf

Rob


texts: In the following SMPS circuit I was wondering  what is the type of filter at the input (marked in red). It's neither  pi or t type as far as i can tell.


texts: One transistor square wave amplifier: why doesn't it work?

texts:
I want to amplify a square wave coming from my signal generator using a single transistor and a 100V DC power supply.
This is the circuit I created:

https://everycircuit.com/circuit/4628349765550080
(The orange component is a Volt meter)
I would expect the voltage across the 50 Ohm load to be 100V pulses, but instead the voltage is only 10.9V in the simulation when using a 12V square wave to the transistor base.
How do I amplify the 12V square wave from my signal generator to a 100V square wave using this setup?
Thanks in advance!!


texts: I imported a graphic into Eagle, and what it did was make a ton of little tiny lines to get the image.  I want to now delete all of that. I tried selecting the group, and then using the DELETE command. How can I delete this stuff?


texts: Constant Current Output driver connected to 2 COB LEDs - is the hookup valid?

texts:
I have a lamp with this hookup. Can someone confirm whether the electrical specs match up such that these can be connected in this way.
ld009d-cu03036-m9 - MagTech Constant Current 24-36v output driver
AC Input: 120Vac 0.15A 60Hz
DC Output: 300mA,24-36V (7% current tolerance)
Rated Max Power: 9W
-- Weird - seems like this power supply isn't sold anymore, and when I calculate 36*.300 I get 10.8W which makes me scratch my head. The others on the page calculate to about 9W as the series supposedly supports. Here's a page listing the others of the same style:
http://www.esop-power.com/products_detail/productId=196.html

These are the COB LEDs, two connected in parallel:
http://www.edison-opto.com/get.php?f=Edison+Opto_EdiPower®+V+2PHM03xWxxP32020_Eng_V1.pdf&s=Edison+Opto_EdiPower®+V+2PHM03xWxxP32020_Eng_V1.pdf&path=doc

I'm struggling to figure out whether the electrical hookup is causing the LEDs to blink sometimes at power on. I have two lamps that have the same issue - and one of them has now burnt out one of the COB LEDs.


texts:
I took apart a disposable camera and found the flash capacitor inside.

It says:

4 (2)
 0c

There are no other markings on it. What is this supposed to mean?


texts: Is a USB charging A-to-C Y-cable a really bad idea?

texts:
I know it's non-standard, just trying to figure out if it could work safely.

On one end is a standard USB-A plug that can be plugged into chargers or computers.
On the other end are two USB-C plugs that can be plugged into power sinks/Devices for charging both at once.
USB-C plugs would have CC pins connected through 56 kΩ to VBUS, as in the standard "USB Type-C to USB 2.0 Standard-A Cable Assembly"

CC devices won't turn on their own VBUS, since CC pins are pulled high, indicating that they are at the power sink end of the cable.  So that's fine.
It can't be damaged by USB PD over the CC pins, since those don't connect to the charger.  So that's fine.
However, older USB PD was transmitted using RF signals over the VBUS line?  So one branch could send those signals to a PD charger, VBUS could jump to 20 V, and the other device on the other branch could get fried?  Or is that not how USB PD works?
What about Qualcomm Quick Charge or other such proprietary things?
I guess the BC1.2 D+ and D- lines might be in conflict, too.  Each device would try to measure for the short circuit at the same time, confusing each other?


texts: Difference between RAM and internal storage chips in HTC Sensation

texts:
Just having a small discussion at work about my HTC Sensation phone. My question is: is there a difference (in chips) that are used for internal storage and RAM memory?

Must they be using other chips? Can't they be both the same flash chip with a partition? Is there a speed difference between the chips?


texts: Smart lead acid battery charger circuit - is this practical?

texts:
I have thought of making a smart lead acid battery charger using the following schematic. I am not sure if the circuit will work the way I expect it to, or not.
My expectations are:

The battery starts charging at constant current mode through UI, as the relay's NC connects input to U1.
When the closed circuit battery voltage crosses 14.1V (or a little more,) Zener breakdown happens in ZD1 and transistor TIP31 starts conducting. The relay turns on and now U2 starts getting input instead of U1.
Now the battery charges at constant float voltage of approximately 14.2V (considering forward voltage drop at D2, the R4 is set in such a way that the output of the voltage regulating part is little higher than 14.2V, e.g. 14.5V.)
I don't want to keep the charger always connected to the battery. So, when fully charged, I would disconnect the charger manually. This means I don't want the charger to make any extra effort to start or stop charging automatically.

The voltage values might slightly vary, I know. But, will the following circuit fulfill the expectation? Will this circuit fulfill these expectations? I am also in real doubt if I am going in the right direction to charge an SLA battery in 2 modes - first fixed current then fixed voltage. Please let me know if my expectation are right in order to make a working charger.

simulate this circuit – Schematic created using CircuitLab


texts:
Say your trying to find the Thevenin equivalent of a linear circuit with dependent and independent sources.

You would find \$V_{OC}\$ (voltage across the short circuit) and \$I_{SC}\$, the source current, and the Thevenin resistance would be \$R_{Th} = \frac{V_{OC}}{I_{SC}}\$.

But is it possibly for both the voltage across the short circuit and the source current to be zero, leaving the Thevenin resistance indeterminate? Why or why not? What about the source current being zero?

Please note I am specifically talking about a circuit containing dependent and independent sources.


texts: Call Serial.print in a separate tab/header file

texts:
I'm writing a program in Arduino 0022.

Calling Serial.println works fine in my main sketch code, but when I attempt to use it in my header file "Menu.h", which is in a separate tab, I get an error:

  In file included from AppController.cpp:2:
  Menu.h: In constructor 'Menu::Menu()':
  Menu.h:15: error: 'Serial' was not declared in this scope

How can I use Serial.println outside of sketch code?


texts:
I was wondering if a power MOSFET fails due to overheating, will it usually burn as an open-circuit or short-circuit?

Also, does over-temp damage usually cause the gate oxide to blow through as a low resistance ( < 100 Ohms)?


texts:
While winding a coil my wire snapped, I would like to complete winding of the coil and still have a functioning coil?

Will it have any effect on the performance of that coil?

It’s being wound around a ferromagnetic core (some alloy). I wound 200 turns and there are 400 more to go.

What’s the best way to splice the wire?


texts: Mplab X IDE insists I'm trying to change protected boot memory even though all CodeGuard options are disabled

texts:
I'm new to this whole thing, so forgive me if I'm missing something obvious, but the only relevant thing I could find is over 9 years old, using a different programmer and different PIC.
I'm using MPLAB X IDE v5.35, trying to program a dsPIC30F6015 using PICkit3, and I get the "You are trying to change protected boot memory" error. However, under Project Properties > XC16 > xc16-ld > CodeGuard all options are set to "no" ("no flash", "no_eeprom," etc.)
Under "Generated command line" I have:
--stack=16 --check-sections --data-init --pack-data --handles --isr --no-gc-sections --fill-upper=0 --stackguard=16 --library-path="." --no-force-link --smart-io -Map="${DISTDIR}/p6015.${IMAGE_TYPE}.map" --report-mem

I'm not familiar with the flags, but I assume they reflect the whole "no" settings.
The person who originally programmed the thing is using a PICkit2, and when he programs the device, it works properly. He says he doesn't need the "Boot, Secure and General Segments" option chosen, but for me it's either choosing that or getting an error.
I'm not sure he uses the MPLAB X IDE to program it. I imported the project he sent me as an MPLAB IDE V8 project, so he might be using an older version of the MPLAB IDE, but I can't find MPLAB IDE V8 on the microchip website, and I'm reluctant to download things from sites I'm not familiar with, especially since I'm working on this in a lab in a university.
Another problem I'm having is that when I program the PIC using the code I got, it just doesn't work. I can't imagine security settings interfering with the code serving its purpose, though I can imagine it happening when there's a bug in the code. (The size of an allocated array is too small, and data is written to/read from indices that are out of bounds. I guess I should've tried again after fixing it, which I will do when I'm back at the lab, which is why this "other problem" is more of an off-hand thing. I didn't want to modify his code because when he programs the PIC, it works).


texts: Beacon detector using microcontroller and BLE

texts:
I am looking for BLE device which can detect ibeacon or beacon module/tag.
I am interested to use microcontroller with BLE module instead of smartphone for beacon detector.

Can any one suggest where to start?
Does any BLE module with central role support beacon detection?
Can any one suggest BLE device name for beacon detection?

It would be really helpful, if you can provide hint for same.


texts:
To start off, I am aware that neither battery type should be “trickle charged”.

That being said, I have a product that really needs to randomly “trickle” charge a rechargeable battery. I have a device that will have sporadic and unreliable solar energy as the only source. While the device is low energy, it also contains some power hungry sensors that need to turn on once a day or once a week. The power required is above a reasonably priced super cap (would need ~500F at least). So my solution is to use some NiMH AAA batteries or a Lithium Cell. The reason I believe trickle charging could be ok is because I do not need anywhere close to the full capacity of the battery, so I would set a max charge voltage to below the nominal full cell voltage, and use a current control charge to limit it to a safe charge current, so the cell is charged in a safe manner until it reaches some voltage below the full cell voltage. I.e. for a NiMH that has a full cell voltage of ~1.5 I would charge to 1.35V.

I’m unable to find any information on this type of setup online, it seems all the typical trickle charge questions are about trickle charging to full capacity and beyond, which is a no-no for both the named chemistry above.

I’m also aware this is not an ideal situation and testing would need to be done to ensure the batteries hold up alright in this configuration. If anyone has any advice for alternative storage systems I’d be thrilled. I’m limited to ~1/4W of solar power and the device needs to operate for a few minutes at a time with a peak power of ~1-2W.

Edit:

So after reading some posts on Stack Exchange, and the comments below, it seems like partial charging of Li-ion is a good solution since at most I only need 50% capacity. The internet is full of stories about how dangerous Li-ion can be that I have mostly avoided it, but in this case, it seems to be a good solution other then the wide temperature range that I need to look into.


texts: Battery imbalance - two 12v lead-acid 100ah in series

texts:
I have just installed two brand new 12v lead-acid batteries in series to for my 24v “house system” on my boat. I connected them to my 24v charger to ensure they were charged to 100%, to synchronise my battery monitor. However, the voltages of the two batteries whilst on charge was markedly different: batt 1 15.1v, batt 2 13.8v.
This immediately triggered an imbalance alarm from the battery monitor (mid-point voltage difference). After about half an hour the charger entered its float stage, and the voltages were then: batt 1 14.1v, batt 2 13.4v.
Do I have a problem, or is this behaviour perfectly normal? And if this is normal, how much of an imbalance should I accept?


texts: Understanding RS Component's "Program Memory Size"

texts:
When looking at RS Components' website, for example this link

they indicate Program Memory Size as two figures for a microcontroller:

Why are there two figures?


texts:
Given an isolated DC/DC converter, such as Traco TMR4. The GND fill, and internal GND layer(s) would be referenced to the -Vout pin. The TMR4 has an application note showing a fairly typical EMI filter for this kind of components. (https://www.tracopower.com/sites/default/files/products/application_notes/tmr4_emc.pdf)
Should the section of the board that contains the EMI filter have a keepout for the GND fill (illustrated by option 1)? Or is is better to let the GND layer (and top layer fill - with appropriate clearance) cover the entire board (option 2)?
Blue layer is inner GND layer. (Illustration only, this is not the actual circuit)


texts:
I'm designing a fluorescent lamp dimmer circuit which will work with Arduino pro mini.
The mcu will detect zero cross from mains outlet and will give out offset for TRIAC.

I would just like to get sanity-check on this circuit, why it would or wouldn't work?

X_DETECT_IN - Zero cross detection for Arduino
OFFSET_PULSE - Offset pulse from Arduino

[Ignore 2 AC generators, didn't find AC+ and AC- in KiCad]


texts: Can I change the capacity in a camera flash light so it can support 14500 batteries?

texts:
I have a Sigma 530DG Super and usually I would use 4 AA batteries with it (1.2/1.5V x 4 = 4.8/6V). Last night I was adventurous (and stupid) and I put in 4 14500 batteries (similar to AA batteries but made in lithium and can produce a higher voltage at 3.7V, so 3.7V x 4 = 14.8V). I did this because I imagine it would give the flash light a higher "recharge" speed (the gap between each time I can fire). I was able to turn a regular AA battery powered toothbrush into a super sonic toothbrush by changing the battery into 14500 battery, so I was guess my trick would work on the Sigma 530DG as well. Unfortunately it didn't, and it burnt the capacitor in the flash light. See the picture below:

Now the capacitor says "100 10m" on top, so it's a 10V 100uF capacitor. My understanding (based on my vague memory from college) this means it can take as much as 10V and releases 100uF when fired. So my question being, if I simply change the capacitor to something like 20V 100uF, would it work the same but with the added support for 14500 batteries? - Meaning now it would work with both AA batteries and 14500 batteries.


texts: What is the typical error of a voltage follower opamp

texts:
I am trying to identify design elements that might have error from unit to unit.  In the design I am looking at, there is a voltage follower configuration for an opamp (in this case, an LM2014), which has an ideal gain of 1 (by definition).  Of course, in the real world nothing is ideal, everything has some amount of variability and error, and I would speculate that the gain of a unity gain opamp is no exception.

I was unable to find any rule of thumb on real world gain errors for this configuration, and I'm not good enough with discrete electronics and opamp specs to narrow the answer down for myself.

What should be considered a typical error in the gain of a unity gain opamp?  (e.g., is it safe to say 3, 4, or 5 decimal places?)  How should I go about figuring this out from the specs of a given opamp so I can do this myself next time?

simulate this circuit – Schematic created using CircuitLab


texts: Microcontroller Core Frequency vs Crystal Frequency

texts:
If I use an external 8MHz crystal connector to a microcontroller, but the core can run at a higher frequency. Like what factor decides that the core should run at a higher frequency ?
And whether increasing the crystal frequency value, say from 8MHz to 40MHz part, increases the load capacitance value that is connected to the crystal?


texts: Using microcontroller's ADC to measure the voltage between LiPo cells

texts:
What I want to do is to measure the balancer output of a 3 cell LiPo, and if any cell drops lower than 3V I want to put my uC in the shutdown mode. Gonna be using STM32F401RET6.

First question is: is it actually a good idea to do it this way, or should i do it externally (not in uC), using a couple of op-amps.

And secondly, what kind of socket do I need to plug the balance connector to my pcb. Dualsky is my Li-Po manufacturer.


texts: Datasheet or termal resistance for this heatsink

texts:
Can someone please help me find a datasheet or at least the thermal resistence for the following TO-220 heatsink?

My local supplier doesn't have more info about it. They just marked it with those numbers that I don't know what they mean: K6439 and 183001/15 (15 is the heatsink height in mm). It looks like it's made of aluminium.


texts:
I'm trying to understand the pattern used for page interleaving on word lines in MLC flash.  I've come across a number of resources that show how even-odd paging works in detail, but the few examples I've found of interleaving or "All bit line" (ABL) in the MSB or LSB of a wordline are less clear.

For example, in this textbook on page 267, we have the following diagram:

I don't understand how you decide which pages to place together in either organization, in terms of mapping a page number to a wordline number and its upper/lower bit.

From cross referencing other materials, I've gathered that the first and last wordline map together the page numbers (0,4) and (122,126) respectively.  It appears that all other wordlines map together pages as (N, N+6).  I'm having trouble finding any other pattern with the limited example numbers here.  For example, this journal article shows a flash memory with 128 pages, with what appear to be special cases in the first and last word lines:

Could anyone explain a closed-form expression for what wordline and bit each page will map to?  I can treat the first and final page as special cases, but I have no idea if that represents what is actually done.


texts:
How do I create a frequency detector that can detect low "hum" sound? (quite low frequency sound probably made by a air-con or similar type of machine)

Please feel free to ask me questions if my question is unclear.


texts: Will this PCB trace GSM antenna be affected by EMI?

texts:
I am designing a PCB in which there are 3 SIM800 GSM modules sharing a (commercial) external antenna. The external antenna is connected to the PCB via an antenna connector, and from that connector, the antenna signal is “shared” via PCB traces running to the GSM_ANT port of the GSM modules (please see photo)

The reason I prefer this design is that it is both cheap and convenient.
But without in-depth knowledge on antenna design and EMI, my question is Could this be a bad design? Or should there be scenarios that this design does not work reliably?

Just to provide more info, the PCB will be housed inside a steel enclosure, and its main PSU is an AC-DC adapter (good brand) which is already sealed for EMI. The adapter is also inside the steel enclosure. The steel enclosure will be deployed in a residential area where there are no large machineries around.

Thanks in advance!
Dave

UPDATES:

Following some of your answers, I update the question as follows:
Below is the old design, which uses 3 separate antenna connectors for the 3 GSM modules. However, these 3 antenna cables are combined (soldered) into one (with seal) outside the PCB and go to the external antenna.

The 3 GSM modules are supposed to be sending signal one at a time.

This old design has been tested and worked (though I suspect that signal strength are just around 8/10 of what it should be - good enough for the application though)


texts: KiCAD: Footprints for {Axial, Horizontal, Through Hole} Resistors

texts:
I have these two resistors in my schematic, that i want to find footprints for:

Body dimensions = 2.5 x 6.8mm AND Leads dimensions = 0.6 x 28mm (like this one: https://www.acdcshop.gr/resistormetalfilmtht2k06w121625x68mm50ppmc-p-28928.html 1)

Body dimensions = 1.9 x 3.7mm AND Leads dimensions = 0.45 x 28mm (like this one: https://www.acdcshop.gr/resistormetalfilmtht100komega04wplusmn1oslash19x37mm50ppmdeg-p-15162.html)

i understand that the (Body dimensions = 2.5 x 6.8mm) part is useless. The only info left is (Leads dimensions = 0.6 x 28mm).
I opened the datasheet but this info is not clear to me since i can bend the leads wherever i want.
Also, do i care about the diameter of the leads (0.6mm)?
There is no clear P value (in KiCAD's terms) in order to select one.
I opened up the footprint library and there were a ton of THT axial horizontal resistors, but each carried a different prefix like DIN0309, DIN0411 etc. What do these mean and how to select one?


texts: Calculating SPL from voltage output of a microphone with MAX4466 amplifier

texts:
I'm using Electret Microphone Amplifier - MAX4466 with Adjustable Gain and I'm getting the output voltage ranging from 1.5V to 3V (which, to my knowledge, is already amplified by MAX4466). I know that the sensitivity of the microphone is -44dB @ 1kHz. It is also stated on the mentioned product page that the gain can be adjusted from 25x to 125x by adjusting the trimmer pot on the back of the breakout as needed.

I'd like to know a way to figure out the op-amp gain and ultimately, calculate SPL dB (Sound Pressure Level) from the measured voltage. Any help is appreciated. Thanks.


texts: Replacement for no longer found sand block resistor in subwoofer amp?

texts:
My SVS PB13-Ultra subwoofer stopped working. It happened after a voltage sag, probably followed by some spike.

After inspection, the fuse and a power resistor were blown.

I am sending you pictures attached. This is the PCB of the 1000W power supply of the sub driver. The missing indicated component is a 7 Watt, 5 ohm resistor.

Along with the other same resistor, they are the very first thing (after a usual varistor) that the AC circuit sees. I assume both these resistors are part of the LC filter at the input stage, the resistors probably dampening the filter's response.

These sand blocks are old fashioned resistors. I tried to find a similar one in mouser and digi-key, but no luck at all. 2 questions:

1) Is there ANY difference in replacing it with an ordinary wirewound power resistor, eg:

http://www.mouser.com/ProductDetail/Welwyn-Components-TT-electronics/WHS7-10RJT07/?qs=sGAEpiMZZMtTURnxoZnJAET%2fHU6QB3QMhCsG69Ld%252bHU%3d

or a 10W one:

http://www.mouser.com/ProductDetail/Ohmite/TWW10J10RE/?qs=sGAEpiMZZMsPqMdJzcrNwsOTZqx7B%2f%2fzcWOTb0%252bMDhQ%3d

I didn't find any 5ohms, >= 7W, so I'd have to replace both resistors.

2) What is the story behind these sand blocks? Aren't they wirewound internally? Why did they stop being produced?

Funny thing is that the date signature in back of PCB is 2010. It is not that old!
tks!


texts:
I know from the title may sounds wired. But it makes sense to me at least for my restricted knowledge of high voltages. I'm always working with low or house voltage as well as this question may refer more to physics.

Let me try to explain: There is a threshold voltage (break down - described by a formula) to break through an air gap. Reach this voltage and electrons will start to flow.

Here my concerns start: after enough current has flown in the gap air get heated and become plasma that is something completely different and has high conductivity. The air gap has become a conductor. As any resistor some energy will be wasted in heat to compensate the cooling of the plasma and keep the "channel" open.

When current is too low, too little heat is produced and plasma resistance begins to increase. This will (at constant current driving) increase resistance and start heating again plasma -> this should (if current sufficient) balance the system at a constant amount of plasma.

When current is too high heat will start to increase expanding the plasma that will balance the system at a point where extra heat will be same as the heat that plasma exchanges with the air.

So if those considerations are right then, after the initial breakthrough, current may be used to modulate plasma "size".

From my guess this is partially confirmed as once a friend was showing me a "music modulated" spark in his garage (that was producing sound) and he was modulating current; whether the only phenomena that would be able to produce sound waves was plasma.

But if so, there can be found a minimum current to keep the plasma channel and therefore the lowest current point at which a spark can be maintained alive.

Is this description accurate?  If so, how can I determine the lowest current necessary to maintain a spark over an air gap?


texts: Named nets not connected in Eagle board design

texts:
I set up my schematic in Eagle and used named nets to make all of the connections.  If I highlight any of the connections in the schematic everything lights up properly.

When I switch to board design though most of the connections are missing.  I have GND and VCC nets, each with multiple connections which show up properly on the board.  But all of the point to point connections (connector to IC) are missing.

Any idea what I'm doing wrong?


texts:
I am working with TLP281-4 optoisolator, there is a board which used this IC in it. It connected like this:

Why can't I connect 5V to the collector and take the output directly from between emitter and GND? Output is read by microcontroller. Is there any advantage of using those transistors?


texts:
I made a board recently and just started checking it out yesterday. I used a typical lithium coin cell and a boost converter (Microchip MCP1640). With a battery plugged in I get no voltage out of the boost converter (i.e. 5V to GND measures 0V). Worse yet, I measure very nearly 0V from BATT_PWR to GND with the battery in circuit.

So I removed the battery and fed 3V from a benchtop power supply into the FTDI_PWR net and sure enough was able to measure 5V. The PSU indicated I was drawing about 50mA. I experimented with lowering the voltage, and the booster held 5V, but current draw increased as input voltage decreased (which I believe is expected).

So, is the peculiar battery behavior described above due to the battery current limiting? Is there likely to be some more insidious problem at work here - how might I determine that? If this is the wrong way to boost a coin cell to 5V, what's a better way?


texts: safe to use an unshielded jack for 10Mbps Ethernet?

texts:
I have a hardware device which includes Ethernet connectivity. I have a surface-mount Ethernet jack, with top entry (as opposed to right-angle). Part number is RIA Connect AJS03B8813, if that helps. No integrated magnetics, this is fine, I have a discrete part. All is well and good.

Except that I'm having trouble finding that part, so I need to find a replacement. However, it seems that no one makes a jack that has all of the following features:

top-entry (i.e., part sits flat on board and cable comes "down" into it, perpendicular to the board -- in other words, NOT right-angle),
surface-mount, and
shielded.

I can find shielded right-angles aplenty, and shielded top-mounts, but they're through-hole (not an option, the other side of the board is densely populated.) All I can find are unshielded parts, such as

Molex 0855135013
Molex 95503-6891 (yes I know this has support posts but that's OK, I have those holes on the board)

So, my question is: are there any potential problems using this unshielded jack in a 10Mbps Ethernet application? I can't see the shielding on the jack mattering that much, since most clients don't use shielded cat5 anyway.

Any input would be appreciated. Thanks!

EDIT: thanks for all the replies. I'll just go ahead with the unshielded part. I know that most cables aren't shielded, so I figured it was probably pointless, just wanted to get some other opinions.


texts: How to think about Power Factor when adding new devices to a generator

texts:
I've been tasked with checking to see if an existing backup generator will be powerful enough to handle a new building in addition to the buildings it is currently handling.

First, here is the details I got off the nameplate of the generator:

Name: Olympian
Model: GEH275
Rated Power - Prime:
    250.0    kVA
    200.0    kW
    0.80     COS θ
Rated Voltage: 415/240 V
Phase: 3
Rated Frequency: 50 Hz
Rated Current: 348 A
Maximum Ambient Temp: 27 *C (There is a note that it can go up to 50 *C but will affect outputs and that the manufacturer should be contacted)

The new building will have 33 AC units which will be the primary power consumers. Here is the details I found on the AC labels:

Phase: 1θ
Frequency: 50Hz
Voltage: 230V
Cooling Capacity: 6448 W
Normal Input: 2149W
Normal Current: 9.8A
Max Input: 3733 W
Max Current: 20.6A

I checked the generator panel at different times during the day, and this is the highest reading I ever got off of it:

AVG: 415 V L-L 100A 50.0 Hz
L-L: 413V/136A, 418V/72A, 415V/89A
L-N: 239V/136A, 240V/74A, 241V/89A

My understanding of the above is that I am current using:

239*136 + 240*74 + 241*89 = 71.713 kVA

This represents 71.713/250 = 28.7% of the total kVA possible

According to the AC labels they are normally operating at 9.8*230 = 2.254kVA and they peak at 20.6*230 = 4.738kVA. 33 of these units will be running at 67.62 kVA and peak at 142.15 kVA.

If the ACs all turn on at the same time, the generator will need to supply 142.15 + 71.713 = 213.82 kVA which works out to 85.5% total kVA. During normal AC operation the total should be 55.7% total kVA.

I am not sure what I should be doing with the power factor information. Should I be working in kW and using the total of 200.0 kW? I am also wondering how much the ambient temperature can affect things. The ambient temperature where we are operating this generator is regularly above 40*C


texts:
I'm experiencing failures on thick film resistors.
In a metering device which samples the mains voltage through a voltage divider formed by a series of 150K 1% 1206 SMD resistors, many of the resistors have increased in resistance value to 10M or more.

Has anybody experienced this failure mode?
What could be the cause of this problem?


texts: Can RF/switching PS noise travel backwards through a circuit through a power supply

texts:
In the schematic below there is a sensitive ADC and sensor with 4 MHz SPI lines from the ADC to a 3.3V MCU, along with a 1 MHz boost converter powering an LCD. Could switching noise generated from the boost converter travel backwards through its power supply to affect the analog and digital LDOs? And if so would placement of ferrite beads as shown be a good approach to isolate the LDOs from the noise? And could the analog LDO be affected in the same way from noise in the digital LDO if the ferrites were not in place?

The PCB is 2 layer and has an analog and digital side with a ground plane, I haven't tested it or made it yet, I'm just looking for help on design. Thanks.

ADC LDOs to be used: http://ww1.microchip.com/downloads/en/DeviceDoc/mic5305.pdf

Boost converter: https://www.torexsemi.com/file/xc9141/XC9141-XC9142.pdf

simulate this circuit – Schematic created using CircuitLab


texts: I need to design a band-pass passive filter with pass band 10kHz~150KHz. One of the needed inductor is 2.2mH. I find there are two choice: Axial type or Can type. But it seems they are designed mainly for EMI filter. May I use them in signal chain filter?


texts: How to use the LM3880DBV circuit in a multi rail power supply?

texts:
I'm struggling a little bit here with the LM3880DBV circuit usage in  a multi rail power supply circuit

So, here is my power supply circuit block schematic:

And this is how I sequenced my circuit:

My problem is I don't know where to put the sequencer circuit in my main power supply design schematic! As in the above schematic, it looks like the sequencer has to be connected to the end of the last output which is so confusing!!!! While in the LM3880DBV datasheet it seems to be placed before the generated outputs, as shown here:

The last output circuit: