texts: Can anybody identifies type of this socket on MSI GForce Super video-cards?

texts:
I need to identify these two connectors on videocard's PCB to by them.
They are for backlight system and alike JST SH04 or Molex Picoblade, but i am not sure about it.


texts:
How do I check the polarity on a loudspeaker?

I have an 8 ohm 2 inch speaker with no wires soldered into it and the terminals have no markings.

How do I know which of the two terminals is positive and which is negative?

Thank you


texts: Grounded coplanar waveguide differential gap

texts:
I'm driving an ADL5802 RF mixer with a 5400BL15B050E RF balun. The balun turns a single ended signal into a differential signal on balanced lines for the mixer. In my attempt to match the balun datasheet land pattern, the balanced lines for a short distance are not right next to one another (though they do have the same length). However, I understand that differential signals should generally be placed immediately adjacent. Here's the current PCB layout, showing the mixer (left), blocking caps (middle) and baluns (right). The white squares can be ignored as they are just component courtyards

And here's the land pattern from the balun datasheet (same pin orientation as my pcb layout):

Am I better off ignoring the balanced line exit angles from the balun and keeping the lines next to one another, or respecting the exit angle and having some temporary separation between them? I could, of course, also move the miters closer together to minimize the separation a little.

Although its not shown since I haven't done the copper pour yet (or the via fence), these tx lines are grounded coplanar waveguides with width 0.34mm and gap 0.1524mm (I've used this for the differential spacing after the caps as well). The height to the next layer ground plane is 0.1702mm. The substrate is FR408 Oshpark 4-layer with a dielectric of about 3.64 at 6GHz, which is my max signal frequency. I've simulated the GCPW (grounded coplanar waveguide) with OpenEMS as well as the miters and blocking cap ground cutouts for a single ended line. I haven't actually simulated the effect of the second line on Z0, but I think it should be the same since each gcpw just sees a conductor 0.1524mm away.

Edit

I contacted the manufacturer who indicated tightly coupling the lines right out of the pads is fine (shown in the blue circle in the image below). So, that's what I'll use.


texts: Where can I find diodes by forward voltage?

texts:
I'm looking for a diode with a specific forward voltage (about 1V) when current is around 150mA (though the max current should be around 250mA or higher).

The closest I've come so far is the 1N270 (1V forward voltage around 200mA), and 1N4001 (about 0.7V forward voltage around 150mA). Does anyone know of anything closer to what I want, or know of a way to look them up? DigiKey is overwhelming when I just need something similar to the 1N270.

Thanks for the help!

EDIT

Apologies for the lack of background. I'm essentially looking for a component that can take a 3.7V nominal LiPo (4.2V when full, 3V when "empty") down to about 2.8-3.6V. I'm trying to power a device that typically runs on 2 AAs in series (3V). It has a bit of tolerance on the voltage. The device has a warning light that comes on at about 2.4V. The device operates at about 150mA on average (though it may range from about 100mA - 250mA).

I would like to avoid the warning light coming on too close to the LiPo's cutoff voltage (3V). I can use a 1N4001, which gives about 0.7V drop on average for my current. I'd like to have slightly more drop (closer to 1V) to give more time for the warning light to show before the battery cuts out (maybe at 3.2V - 3.3V on the LiPo). I know the discharge curves of LiPos get pretty steep towards the end, and I also don't want to push the LiPo too hard by having the user run it down all the way.

To sum up:

Source (LiPo) is 3.7V nominal, 4.2V when "full", 3.0V when "empty"
Device runs nominally at 150mA
Device warning light at about 2.4V (at device)
Would like 2.4V on device to map to about 3.2V-3.3V on LiPo
This leads to about 0.8V-0.9V desired voltage drop from LiPo to device

I understand that I can use a resistor, though I wanted something that gave a slightly less current-dependent voltage drop, and the forward voltage curve of the 1N270 and 1N4001 fit the bill fairly closely.

I also understand I can use a 3V regulator, and I've found a good one with low quiescent current. Though that reduces the effectiveness of the device's warning light.

I hope that explanation helps illuminate the purpose.

Big question: There's got to be a better way. What component(s) can I use instead to give a more predictable/consistent voltage drop?

EDIT 2

I was originally going to use the 3V MCP1700 LDO regulator(it's got a nice low quiescent current), with 0.18V typical dropout. The problem is that the LiPo will cut off at 3.0V, far above the 2.4V warning voltage... Using the MCP1700 would provide unregulated voltage only for about the 3.0V - 3.18V range. Any ideas?


texts: I'm thinking about using this circuit to update an old Hafler amplifier. But, I'm curious about the purpose and configuration of the zener clamps in the circuit. I added the red box in the circuit diagram. Can someone enlighten me? Thank you.


texts:
I have a project in mind that involves lights from a small LED (SMD would be nice) and i've come across this big problem but apparently there's no solution for it on Internet. I need that LED to be omnidirectional without using a reflector.

Ideally it should be only one (Maybe 2 as suggested) because its power source will be very tiny (A capacitor constantly being charged by electrostatic induction), it should light an led for a brief moment.

My main idea is to remove the mold from one (Leaving only the chip and connections for it), but that seems very complicated and i don't know if is even possible with chemicals.

Is there a simple way of doing this?, maybe i'm thinking in the wrong way and there are options to buy on the market (Although i already searched).
Thanks.


texts: PCB trace caps (a.k.a. finger / interdigital caps) formula

texts:
I am trying to calculate a two-fingered, both on the same layer, capacitor. I have run into a few papers on it but they are taking a ground plane on the other side of the PCB into consideration and they seem to be showing a meandered capacitor like this one

which is not exactly what I was looking for. I am after a simpler design:

I know that the capacitance formula is
where A = t * L;
t being the thickness of the copper pour and L being the length on which the two traces juxtapose, thus forming the plates of our capacitor.
Should I apply it as such (no ground plane beneath) ? Am I also right to be using these values ?

epsilon_r = 1 for air
t = 35 microns for 1 oz copper


texts: Will the short circuit damage electronic components or just the supply?

texts: This I have thought about. We know that shorting the supply creates zero resistance path between the vdd and gnd. We also know that current will pass through the least resistance path and since there is a zero resistance path, all current will pass through that path based on Ohm's Law. It follows then (if I am not mistaken), all connections to the supply will be considered as open circuit since no current will flow through them (because all current flows through the zero resistance path) and only the supply should be harmed?


texts: Help analysing a discrete voltage regulator circuit

texts:
I need a -140V reg which doesn't exist, so I'm trying to learn how to build simple discrete regulators (starting with positive regs). As I only need a few tens of milliamps with a fairly constant load, I feel this shouldn't be too onerous a task. I've spent some time reading and simulating, but as I often find with transistor circuits I start to get lost about what is controlling what. In this case, I have been looking at the circuit below:

The explanation of this circuit says:

  When the output voltage drops, T4
  pulls the emitter of T3 lower. This drives T2 harder, which causes the
  output voltage to rise again. R4 restricts the base current of T2. C1
  and C2 have been added to improve the stability of the circuit.

Now, I can see that the idea is you're providing feedback to give the regulator better stability and that they're saying that's coming from R6/R7 back to the pass transistor via T4 and T3.

I'm not understanding how the emitter of the T4 can be pulled low by the R6/R7 potential divider. When I looked at it I thought that T3's base must be at 78V (because of the two Zeners), therefore T4's base must be two Vbe drops below at roughly 76.8V and so that would be the voltage at the R6/R7 junction.

What am I missing here? Why does the voltage at T4's base go up and down and why T3's base voltage not override this due to the Zener voltage which I would have thought is constant and quite "stiff". I assume what must be happening is that as the output drops, T4's base drops and T3's base is dropping, however, how that works when the Zeners would to my limited knowledge be keeping T3's base at 78V I do not understand.


texts: Class A power amplifier: voltage and current

texts:
I am always having problems knowing the difference between providing a load with a voltage and providing the load with power.

So we have a Class A common emitter amplifier with a load resistor connected to the connector. As long as the transistor is in the linear region, there's voltage across it and current through it meaning it's getting power.

Now, we have another class A amplifier, only that its Q point is centered on the load line, but called a power amplifier. The question is why? Then, what is amplifier that I first described called? If there a line that can be drawn where an amplifier is a power amplifier, a current amplifier or a voltage amplifier?

I am familiar with Ohms law!


texts: Questions about modelling a typical crystal radio and simulating in LTspice

texts:
This might look like an awkward question but I'm trying to model and simulate an early typical simple crystal radio in LTspice. The first reason doing this was to add a variable resistor in series to the typical crystal circuit to adjust the Q-factor for different resonance frequencies.

Here I will try to explain what I was trying to do step by step to make my questions clearer.

One can tune an R series LC tank circuit to a particular resonance frequency to select a specific bandwidth. But the Q-factor hence the sharpness of the band-pass frequency response is directly related to the resistor value R. I will try to expound on this by using the below circuit and its values:

Here are some MATLAB plot for such circuit response in different resonance frequencies (plots are Vout versus frequency plots where Vin=1V sinusoid):

Below shows the results when the tuning capacitor is set to 500pF (R=27k):

And here below plot shows the results when the tuning capacitor is set to 200pF (R=27k):

As you can see on the above plots, when the capacitor is set to 500p for 503kHz station the bandwidth becomes 12kHz which is quite good for an AM radio signals since AM needs between 5kHz to 10kHz bandwidth. But in the second plot when the capacitor is set to 200p for 796kHz station the bandwidth now becomes 30kHz which is too large for an AM band. And I thought as a remedy a variable series resistor could be used to adjust the Q-factor hence the bandwidth. And I set the resistor to 66k for again 200p capacitor and 796kHz station. Here is the result:

As you see the bandwidth issue improved. But of course this could cause some power loss if the crystal earphone is 20k and I add a series resistor to it.

So my motivation was to implement a typical crystal radio by using a variable series resistor as shown in the above diagram.
But the first thing I noticed that the crystal radio circuits I found were not like in my first figure besides the diode of course. Here are some typical circuit diagrams for the crystal radio from some google search:

As you see these circuits do not look like R series LC circuit but they are just RLC parallel circuits. So I simulated parallel RLC circuit with a diode to model a crystal radio in LTspice not my first circuit. The impedance of a crystal earphone is about 20 kohm so I modelled is as a 20k resistor. For the sake of simplicity I chosed an ordinary diode in LTspice and the modelled the antenna as an AC voltage source with 5V amplitude.

But as you might guess since this is a parallel RLC circuit the voltage across R will always be the same with the voltage source. And below is the frequency response in LTspice:

My questions are:

1-) What is wrong here? Crystal radio circuits are RLC paralel circuits? I modelled the antenna as a "voltage source" and this doesn't look like a tuning circuit in LTspice. Was that the problem?

2-) Does my "adding a variable resistor in series to adjust Q-factor" to the first circuit to improve its selectivity make sense?


texts: LED Driver with minimum input current and large LED current(peak)

texts:
I am designing a LED driver.

Power source - 18V-42V (I can draw max of 6mA-7mA from source)
LED string - 4 series LEDs of 6 strings in parallel ( total 24 LEDs)

I need min of 200mA of peak/instantaneous current through LEDs with 20ms or 30ms ON every 1sec duration.

I am thinking to design like current sink method which will charge a big capacitor and I can draw current from it to drive LEDs.

Please let me know if anyone is having any different idea.


texts: How to design a passive filter from poles and zero of a transfer function?

texts:
I am using octave/matlab to get the coefficient of numerator and denominator of a filter with filter command such as butter or cheby1.

I just want to learn how do you convert this coeffecient to the value of passive components of Inductors and Capacitors?

For example, a second order butterworth filter with cutoff frequency 1000 Hz sample at 3000 Hz with the following command gives the following b and a coefficients of numerator and denominator respectively,

[b,a]=butter(2,0.667);
b=0.46554, 0.93108, 0.46554
a=1, 0.62147, 0.24069

How can we transform this into the value of passive inductors and capacitors?


texts: Lines with Circular Terminators and Symbols with Overlines

texts:
I'm a newbie to breadboards and Arduinos. I'm playing around with the 74HC595 shift register in order to power a basic segment display to show some numbers. I was looking at the data sheet for the 74HC595 and was curious about the conventions used in the functional diagram. I've included a screenshot of this diagram for your convenience. In particular, I notice that the MR and OE lines both terminate in a circle and have overlines in their symbols while the other lines do not.
What does this mean? What's the convention here? In the "PINNING" section of the data sheet, I see that these lines are active LOW. Is that the meaning of the circle and the overline? Or does it mean something else? Thank you in advance.


texts:
How does one efficiently implement a windowed counter, counting ones on a input line in the last say e.g. 10000 clk cycles (in VHDL for use on an FPGA)?

My idea: take a shift register (to delay the input line by 10000) and a special counter, incrementing when the input is high and decrementing if the shift register output is high.

For large windows (e.g. 2**20), this seems rather inefficient to me. Any suggestions on how to do this in a smarter way? I am not asking for a full implementation, just a pointer to some resources or an idea!


texts: How can I prove that for any control system root locus plot starts from poles of OLTF and ends at zeroes of OLTF?

texts:
simulate this circuit – Schematic created using CircuitLab

G(s)H(s)=N/D

T(s)=KN/(D+KN)

Proof:
]
But

For K=0 T=0

For K=infinity T=infinity

then how can K=0 {condition where forward path gain becomes zero} be considered as condition where the poles of T(s) will be equal to poles of G(s)H(s) when the transfer function has become equal to zero how can any value of s make the transfer function peak to infinity { condition of poles } and how can characteristic equation be defined for case  when T(s)=0


texts: I have designed a symetrical PSU using LM317, LM337 plus power BJTs. The desired output range is at least 24V-2V @ 6A max. Altough not shown in the schematic, i plan to add power resistors and a rotary switch to provide current limiting. What do you think about it? Is there some better way of limiting current, without high power pots, JFETs and resistors?


texts:
i wanted to ask what the different power/watt indictors for a soldering station actually mean in terms of the performance of the station or whether the number is just some marketing term.

Some soldering stations have low power itself, but the heater has a higher power. See for example the Ersa i-Con1, wich is a "80 Watt station" with a "150W heater", according to their homepage.
Some stations have high power, but the heater has lower power. See for example the JBC - CD-2BE. The homepage says, its transformer has 130 Watts, but the heater only 50 Watts. On some shops the same station is marketted as "75 Watt station", see e.g. here.
Some stations are marketted at 80 Watts, although their power specification lists only 68 Watts, see the Ersa I-Con Nano. The german website says literally: "This is an 80 Watt station with 68 Watts", both numbers appear on the same page without refering to different parts of the unit.

For me, 1. makes no sense. The iron is capable of 150Watt but can only be supplied with 80 Watts. Also 2. makes no sense, where is the power wasted? And 3. makes no sense either ...

Can someone clarify my confusion?


texts: Controlling 4x4 LED matrix with Huzzah Feather and 20-pin shift register

texts:
I have a Huzzah Feather and a 20-pin shift register TPIC6B595N.  I am trying to control a multiplexed 4x4 LED matrix which I have soldered appropriately.

I am trying to figure out the proper way to wire everything up so that I don't blow an LED because soldering it was a pain in the butt.

The Huzzah is powered by a microUSB to my laptop.

My first question is how do I wire up the Huzzah and shift register properly to ground?  So far, I am just connecting their respective ground pins to the negative row on my breadboard.  Normally, with a power supply, I would have a positive end and a negative end but since its powered by microUSB, I'm not sure what to do here.

Second, I've connected the USB power output pin on my Huzzah to the input voltage pin on my shift register.

Third, I've connected four resistors to the outputs of the shift register and then to the positive inputs on the LED matrix.

Fourth, I've connected the negative inputs on the LED matrix to ground, the same row as described in the first step above.

Now here is where I get a little bit lost.  My shift register needs a clock, data, and latch.  I believe I've located where they are but can't seem to figure out what they correspond to on the Huzzah.

The Huzzah data sheet makes no mention to either of those terms.

If anyone can help me answer my questions, that'd be great.  Thank you.

simulate this circuit – Schematic created using CircuitLab

Edit: I added the schematic of my 4x4 LED matrix as well as the resistor on the side but I couldn't figure out how to add a shift register or Huzzah Feather.  Also, can someone address my question about ground?  Do I just connect it to the negative row on my breadboard?


texts: Can I use pre-regulated PoE power safely/within specifications?

texts:
I'm attempting to design a PoE PD for fairly high-power applications; chiefly, powering/driving stepper motors. Currently, both motors and drivers run at 24V and will consume about 30W per PD. At that kind of power, regulation gets a little expensive, particularly when wanting isolated regulation.

My question is: if I do something like the below (which is heavily simplified), replacing the motor drivers (I think the motors can handle the higher voltage already) with higher-powered versions and tapping off the unregulated PoE voltage, will I be violating any important standard, safety or otherwise, that would present a hazard or cause problems if I wanted to get the device certified for commercial sale? Note the Tx/Rx pairs are device-side and already isolated, everything network-side is just the one line on the left.


texts: Identifying 4-pin plug in laser cutting machine

texts:
I'm searching for a splitter for a plug that I have in my laser cutting machine.
It's a Chinese model and the plug is responsible for a stepper motor (Y axis).
It's a 4 pin connection.

Does anybody know the name of this plug? And also, is it splitable?

The purpose of all this is so that I can switch to a round axis (lathe) from my Y axis, without the need to dig into the power box where the plug is now located.


texts: How do I calculate limit frequency of the attenuator circuit?

texts:
Calculate the limit frequency \$fg\$ of the attenuation \$v_u =\frac{ u_a} { u_e}\$ at the current source I (for the value given in example), so that for \$f>> fg\$ exist ideal behavior.
Note: First consider each capacitor individually by setting the impedance 0 and consider which of the resulting frequencies is relevant.

My problem:

I solved first part of example for \$C_2 \mapsto \infty\$, but I am having problem with another part.

\$C_1 \mapsto \infty\$

\$v_u =\frac{ u_a} { u_e}= \frac{r_D || (\frac{1}{i \omega C_2} +R_L)}{r_D || (\frac{1}{i \omega C_2} +R_L) +R} =\frac{r_D(1+iR_L\omega C_2)}{i\omega C_2(r_DR_L+r_DR+RR_L)+r_D+R}=\frac{r_D}{r_D+R}\frac{X}{1+iY}\$

So I dont know how to get the last step, how to write it in that form, because \$ Y=\frac{1}{\omega_g}\$ and after that I can find \$f_g\$ easy.


texts: What are the various files types in Actel (Microsemi) Libero?

texts:
While researching What files/directories are needed to recreate a Actel/Microsemi Igloo2 project?, I found about various files types. But not all are defined in the Libero SoC or Design Constraints, both v11.2 User's Guides. Specifically what are the files with the suffixes

bfm, cfg, cxf, dat,     def,     gen,     ipd,     loc,     log,     map,    pro,    rpt,    sdb,    xml?

This question is the same as List of Xilinx file suffixes (for ISE), but for Actel. I'm not worrying about SmartFusion2 parts, just Igloo2 for now.


texts: Confusion regarding considering a transmission line as lumped or distributed

texts:
I am just elaborating my question.

I have came across different formula's to say whether a Transmission line is lumped or distributed.

in one of the books i read
" Effective length of a electrical feature like rise time is = \$tr(rise\space time\space  in\space  ps)\over D(time\space delay\space in\space {ps\over in})\$.
If the trace length is > \${Effective\space length\over 6}\$ ==> then Trace is distributed in nature.

from basics what i remember,
"when any trace length is comparable to wavelength (\${\lambda\over 4}\$ or sometimes \${\lambda \over 5}\$ or \${\lambda\over (\sqrt{2\pi})}\$" ===> Considered as distributed line.

if i take rise time = 1ns and freespace  velocity = \$3*10^8{m\over s}\$.==> delay as \$85{ps\over inch}\$ \${10^{12}\over 3*10^8*39.37}\$

first reference will give
effective length= \${1000ps\over 85 {ps\over in}} = 11.765 in.\$
\${effective\space length\over 6} = 1.96 in\$
So, any transmission line which exceeds length of 2 in will be considered as distributed.

As per 2nd refernce which i mentioned.
for rise time tr = 1ns
Maximum freq \$(fknee) = {0.5\over tr} = {0.5\over 1ns} = 500Mhz\$
So, wavelength of this feature \$= {3*10^8 \over 500Mhz} = 0.1meters ==>~ 3.94inches\$(approx)

So, now

\${\lambda\over 6} = 0.6562in.\$

\${\lambda\over 5} = 0.787 in.\$

one of the value is almost double to the other method ( because of factor 0.5 used  in calculating knee frequency)

in some references i have seen knee freq was mentioned as \${1\over \pi*tr}\$ where \$\pi=3.14\$

in some references i have seen if the round time delay of the signal is comparable to the rise time then it is considered as distributed line.

if i am wrong please correct me.
Why these many variations.
I clearly don't know are there any different conditions under which each formula will be valid.


texts: I want to build a Frequency Modulation circuit

texts: Does anyone have a simple circuit design that can implement Frequency Modulation or even Amplitude Modulation?


texts: Why I could not change this eagle NFC class6 antenna footprint?

texts:
I am designing a NFC board prototype that uses NT3H1101 chip. For this, I use NXP AN11276 antenna design guide. This document contains sample file download links for class 6 antennas.

I downloaded this file. I can associate this footpirint to a symbol and use it in eagle. There's no problem with that. I want to change the widths or lengths of roads of this ready antenna design. But the design is like a mold. I can't change anything. As if it was locked. Anyone have any idea about this topic?

NT3H1101 datasheet: https://www.mouser.com/datasheet/2/30/NT3H1101_1201-1127167.pdf

AN11706 design guide: https://www.nxp.com/docs/en/application-note/AN11706.pdf

(The links in pdf are dead. I found the file here.)
https://www.nxp.com/products/rfid-nfc/nfc-hf/ntag/nfc-tags-for-electronics/ntag-ic-iplus-i-nfc-forum-type-2-tag-with-ic-interface:NTAG_I2C?&fpsp=1&tab=Documentation_Tab#nogo

(Also I uploaded it for you. This includes all the files mentioned in pdf.)
https://www.dosya.tc/server25/b4mb6d/AN11276_1_.zip.html


texts: Half Bridge with PWM- gate signal problem

texts:
After making a half bridge inverter using a square wave (I asked a question on this website about it previously) I have now decided to use PWM signal in order to obtain a sine wave output and have come across some new issues.

Here is the circuit on LTSpice:

The load is an 100u inductor and the PWM is created and input into a gate drive before it is used to drive the MOSFETs.

When I run the simulation, the high side mosfet signal (HO)- linked to the behaviour of Vs- follows the shape of the current in the inductor L1 and does not reach 0V and turn off as it should for much of the time causing the circuit to not work.

If I increase the inductor value and therefore decreased the current in the circuit the problem is fixed. However I am not sure I understand why a high current would cause the voltage to not reach zero.

If I replace the inductor with a resistor as the load then the problem also is fixed suggesting it is due to the behaviour of the current due to the inductive load?

Here are the waveforms from the simulation- the second set is the same but zoomed in to better show what is happening.

Can anyone explain what is causing this or what I need to change in order to fix this circuit?


texts:
Say I amt transmitting an RF signal from an antenna through a non-freespace medium (e.g. sand, water, cement) how can I go about calculating the absorption losses up to a certain depth level? I feel like this should be a fairly common and well-known equation, but I cannot seem to find it.
Thanks all.

EDIT: For simplicity's sake I am assuming the wave is only traveling through a single medium, meaning reflection is not a concern.


texts: How to find the required capacitor rating for a circuit?

texts:
I am planning a 220V AC to 9V DC rectifier circuit.

In order to provide a stable DC output, I've decided to put a capacitor. But how do I find the rating of the capacitor I should use?

In my circuit, the current flowing will be a maximum of 5mA, and the power will not be greater than 50mW.

Keeping these in mind, can anyone suggest what capacitor I should use?


texts: Why do many uC have more then one I2C interfaces?

texts: On I2C buses you can hock up 112 devices. So why do so many microcontrollers have up to four I2C ports, when you could just operate enough devices for most applications on one I2C interface?


texts: How to correctly connect a MicroSD card to an FPGA device

texts:
I want to ask how to correctly connect a MicroSD card to an FPGA device(not spi version), consider all FPGA pins will be floating for an amount of time before FPGA is configured. I've found a lot of different configurations with MCU, like SPI version, all pin with pull up, some pins with pull down, resistors on some lines ecc.. many are for SD and not MicroSD(I don't know if this matter).

Can someone tell me a working wiring that is compatible with all MicroSD?(Possibily tested)


texts: I'm a beginner in electronics and I am trying to do a "connected switch" with a relay and a wifi module ESP8266, but the thing is that to power the wifi module I need a second power supply and I find that pretty disappointing. I wondered if that was possible to integrate a 230v AC to 5v DC converter in the circuit to just take the power on the same cable. Sorry if my question is not very smart and thanks in advance for the answer.


texts: Can someone tell me (or link me) the response curve of an LDR. I don't mean the frequency response, just the intensity response; is it linear, or logarithmic?


texts: USB port controller, divider mode and BC compliancy

texts:
There're many 'universal' chargers out there on the market which claim to support maximum charging for a range of devices from iPhones, iPads to Samsung Galaxy S5, S6, etc. There're USB charging port controllers like TPS2543 that seem to do such things.

The DS states that it supports 3 charging schemes:

* USB Battery Charging Specification 1.2;
* Chinese Telecom Standard YD/T 1591-2009;
* Divider Mode, Compliant with Apple iPod, iPhone (1A), and iPad (2A) Mobile Digital Devices.

However, (at least) Samsung seems to be using its own signature where the voltage divider provides 1.2V to D+ and D- for the S4 (http://www.obddiag.net/usb-power.html). That said, another plug for the very same phone provides 2.5V to D+ and D- (http://forum.xda-developers.com/showthread.php?t=2274321). Are these BC1.2 compliant?

These signatures are not part of those 3 schemes, right? If not, how do port controllers handle these signatures and convince the load that's it's alright to pull as much current as it wants?


texts: If I solder outside do I need a fume extractor

texts: I've been looking into soldering and read up on the health risks and I noticed you need a fume extractor. I was thinking about using a fan but I don't think that safe. If I solder outside will I need to purchase a fume extractor or is the natural ventilation enough, also can I do it in a garage with the garage door open?


texts: Total Harmonic Distortion fundamental frequency clarification

texts:
I have a voltage controlled amplifier that I would like to calculate the THD of using the power dissipated at the (resistive) load.
My question is: if the input voltage frequency is 100Hz, would I use 100Hz as the fundamental frequency, or would I use 200Hz, since the power waveform would be P = IV = sin(100t)*sin(100t) = sin(100t)^2, which has a frequency of 200Hz.
Thanks for any help.


texts:
I need help solving this problem. I believe the current in the left side of the circuit equals the current in the right side. Therefore, $$K(V_{gs1} - V_t)^2 = 4K(V_{gs2} - V_t)^2$$

I also know \$V_{gs1} = V_{d1}\$, the voltage from the drain of M1 to the bottom rail
$$V_{gs2} = V_{d1} - V_r$$ where \$V_r = I_{d}R\$

$$g_m = 2\sqrt{I_{d}K}$$

but there seems to be no way of solving the equation.
Any help would be greatly appreciated.


texts: I read in a textbook that "Commutation Time is more in Current Commutation compared to Voltage Commutation".Kindly Elaborate.


texts: How do I prevent new pairings on an RN42 bluetooth module?

texts:
I'm working with an RN42 bluetooth module and trying to change the settings so that it doesn't accept any new device pairings. According to the command sheet, the command SX,1 should enable bonding which the user guide describe as telling the device to only accept connections from already paired devices.

I've tried the following command sequence in order to try to get this to work.

Factory reset (SF,1)
Reboot (R,1)
Clear all remote addresses (SR,Z)
Set bonding to enabled (SX,1)
Reboot (R,1)
Verify settings (D)

At this point, I am still able to pair devices with the module even though there shouldn't be any remote addresses stored and bonding is enabled. I've read through all of the commands and notes and can't seem to figure this out. My assumption is that I'm misunderstanding the bonding functionality. My end goal is to be able to pair a few devices with the module and then prevent connections from devices that weren't previously paired. Answers, ideas, or suggestions? Thanks in advance.


texts: Active transient voltage suppression clamp parts/design

texts:
I am revising a design that was originally specified with a SMBJ54CA [2] bi-directional TVS protection diode in front of an LM76202-Q1 [3]; this is in conformance with the design example in section 9.2.2.5.1 of the LM76202-Q1 datasheet in the positive direction. (Application requirements for reverse voltage are different, hence the use of a bi-directional TVS instead of an assymetric reverse TVS.)

The SMBJ54CA has a breakdown voltage range of 60.0 V - 66.3 V at 25°C, which is already a bit marginal -- the LM76202-Q1 has an absolute maximum rating of 65V. Unfortunately, concerns have been raised over the temperature variation of the TVS, which is about 0.1%/°C. Because the working voltage of the application is up to nearly 60V, going to a lower-breakdown-voltage TVS (to keep the maximum breakdown voltage <= 65V at maximum temperature of 85°C) is not an option.

TI has an article [4] on high-temperature TVS usage where they (of course) recommend their own alternative, the "flat-clamp" part family [5], which basically uses active control of a MOSFET to simulate a TVS:

From their material, this has a cost in terms of response time, but has significant advantages in terms of breakdown accuracy (at 25°C) and stability over temperature.

Unfortunately, they don't have a 60 V part for this, and while using a 27 V part and a 33 V part in series is a possibility, that wouldn't be my first choice.

So, questions:

Is anyone aware of equivalent parts (TVS-diode-style across-the-rails voltage clamps) that may fit the requirements here?
Does anyone have experience doing this with discrete parts (and in particular achieving the desired fast response)?
Am I asking the right questions?

[2] https://www.littelfuse.com/~/media/electronics/datasheets/tvs_diodes/littelfuse_tvs_diode_smbj_datasheet.pdf.pdf

[3] http://www.ti.com/lit/ds/symlink/lm76202-q1.pdf

[4] http://www.ti.com/lit/an/slva930/slva930.pdf

[5] http://www.ti.com/lit/wp/slyy127/slyy127.pdf


texts: Writing to Flash memory with Arduino Mega

texts:
I have just bought a 4Mbit flash memory chip.

But I cannot figure out how to use it with the Arduino Uno or Mega.

Can someone show me how to hook it up and use it.


texts: Fruit juicer motor generates very low voltage

texts:
I'm planning on connecting an elliptical trainer to an AC motor in order to charge some batteries and use the energy later. So I found an old 300 W juicer which I disassembled. Then I connected the bars to a multimeter and a drilling machine to the shaft.

So when I measure the voltage with the drilling machine on (at maximum power), I get maximum 1.8 V (see picture).

This is a very disappointing value for me, as I expected more...How much more? I don't know, but definitely not such a low, useless value.

The voltage of the drilling machine battery is 14.4V and the energy is 21.6Wh. Not sure if this has any relevance.

Can anyone help me to understand why do I get such a low voltage from a 300W motor? And if it is normal, why is it so low and what to do to increase it, considering that I want to connect it to the elliptical trainer.

Edit: Please see the picture with the specifications of the juicer.


texts: Can I safely use a MOSFET switch at the input of a MC33063 boost regulator?

texts:
I have a predominantly 3.3V system which occasionally needs to power on a 12V component. Most of the time the component will be off, so in order to preserve power I'd like to avoid idle voltage boosting.

The first thing which comes to mind is using a MOSFET switch in series with the boost converter's V_in rail, and opening with 3.3V applied to it's gate. As far as I remember, one needs to take into account whether the load driven through the MOSFET is inductive or capacitive, but I'm not sure what kind of load should I consider the boosting circuit to be...

The boost regulator circuit I'd use is one based on the example design in the MC33063 datasheet:

Is there any precautions I should take when I use the MOSFET as a switch in this situation? If this is the wrong way to do it, how can I best enable/disable the boosting circuit with a 3.3V control signal?


texts: Practicality of this LM317T PWM Voltage and Current control circuit

texts:
Ive been trying to design a LM317T power supply with a PWM (Arduino MCU etc) adjustable voltage and current limit. After various circuits, videos and tutorials i have designed the following circuit in LTspice.

I am a complete beginner in electronics, so can someone point out any practical considerations or something even more obvious that i've missed; before i commit this circuit in hardware.

I've run a few basic simulations and both the current and voltage limit seem to work without considerable oscillations.

Ive attached the LTSpice schematic below:

V3 sets the voltage

V2 sets the maximum current

R2 Represents the Load

Please note PWM filtering has not yet been implemented


texts: Can an electrostatic loudspeaker be considered as a capacitor?

texts: A basic capacitor works as two parallel plates carrying opposite charges and have an electrostatic force holding the charges in place (without making any contact); can't an electrostatic loudspeaker be considered a capacitor since it works by having a charged diaphragm between two plates of opposite charge?


texts: SCPI OUTput:COUPling command parameters AC|DC

texts:
In the SCPI-99 standard command reference the command 'output:coupling' is specified as taking the parameters 'AC' or 'DC'. However, this is the first time such a data type is mentioned! Should these be translated to boolean values as 'ON' and 'OFF' are? I don't see them fitting into any other parameter data type...

(I cross-posted this from http://stackoverflow.com/q/23713557/1292918 as it wasn't getting much interest there, but Im not sure of the rules on X-posting across SO sites?)


texts: Not able to read impedance from AD5933 Eval board using Arduino

texts:
I am trying to read impedance information from the AD5933 evaluation board using an Arduino Nano BLE 33. According to the information provided here (https://ez.analog.com/dds/f/q-a/29168/how-to-measure-the-impedance-charactersistics-of-a-unknown-valued-resistor-or-capacitor-using-ad5933-please-help-friends) by an official employee at Analog, I connected the SCL and SDA lines of the Arduino to R15 and R16 on the board respectively. I established a common GND between the board and the Arduino.
My first step was to try and get the Arduino to recognize the slave through I2C. I used the I2C slave scanner mentioned here (https://create.arduino.cc/projecthub/abdularbi17/how-to-scan-i2c-address-in-arduino-eaadda) but the slave was not recognized. I think all my wired connections are correct.
Does anyone know why the communication could be failing?


texts: Understanding PCB layer stack-up shorthand notation [2:(1(2+345*67)*16):7]

texts:
I was given a PCB layer stackup specification like this:

[2:(1(2+345*67)*16):7]

For an 8 layer blind via setup.

Could someone provide a reference to decode this shorthand notation?
What is the proper name of this shorthand notation?
How widely used is this notation?

Update: apparently it's from Eagle CAD's DRC (design rule check) dialog.


texts:
In researching whether or not it's common practice to run traces/place vias underneath electrolytic capacitors (specifically SMD electrolytics, didn't seem like it would be an issue to me), I came across this document which makes some statements about electrolytic capacitors that conflict with with other information I've found.

First: "For  circuits  where the polarity is occasionally reversed, use a bi-polar type of aluminum electrolytic capacitor. However, note that even bi-polar type capacitors must not be used for AC circuits."

I thought one purpose of using bipolar electrolytics is where high capacitances are required in AC circuits.

Then: "Do not print any copper trace under the seal (terminal) side of
a capacitor. Copper traces should be 1 mm (preferably 2mm
or more) spaced apart from the side of the capacitor body.

·  In  designing  a  double-sided  PC  board,  do  not  locate  any
through-hole via or unnecessary hole underneath a capacitor.

·  In  designing  a  double-sided  PC  board,  do  not  print  any
circuit pattern underneath a capacitor."

On every board I've seen with leaked electrolytic capacitors, the electrolyte leaked much further out than just 1mm from the capacitor body. I get that maybe in the ideal case it would be best not to route traces under caps in case they fail and leak, but is this practice commonly adhered to? Is it really a bad idea to route traces/via under caps?

What is your take on the above statements?


texts: How can you measure voltage differences less than thermal voltage (~26mV at room temp)?

texts: If thermal voltage is the average voltage of any given electron relative to the voltage at ground state, and this presumably fluctuates, how can you make any measurement on a circuit more accurate than 26mV?


texts: How do I get 15V from a 34V power supply?

texts: I have an audio amplifier with a regulated power supply putting out around 34V DC. I would like to add a preamp which requires on 15V. How would I draw 15V from the main power supply?


texts: Wearable transceiver safety considerations

texts: I am implementing a wearable band that will likely be fitted with a Zigbee or Bluetooth transceiver and worn on the wrist. However, I have seen many articles and datasheets specifying a distance of at least 20 cm between the transceiver and the body. For example, see this article: Wireless Products Safety Concerns. However, this device will be worn in close proximity to the body. Are there alternatives? What are possible ways around this?


texts: FPGA dsp-slices highest sampling rate possible

texts:
DSP slices (following Xilinx’s terminology) have certain speed grades (extracted from the switching characteristics of the device) that span up to some hundreds of MHz.

Those DSP slices are heavily used to produce digital filters. That digital filters would require to work after some ADC sampling. The rate of that ADC now could span up to several GHz.

I am getting confused on how those devices could be operated on such high clock/sampling rates?

Are those frequencies provided by the manufacturer the higher threshold such that down-sampling before reaching the slices becomes necessary?

Are there any techniques that would allow processing in even higher rates?


texts: Mosfet Temperature Rise: IRF4110 with 10% Duty Cycle Square Wave

texts:
So I have this MOSFET: IRF4110

I am switching on for 2ms and off for 18ms (Making it a 50Hz 10% Duty Cycle) and current in on time is 100A at 10V.

So the datasheet says 4.5mohm and thus I calculate the power dissipation as:
P = (100*10%)^2 * 4.5mohm
P = 0.45W

Thus the power derating says 2.5 W/C and from the looks it says that the temperature rise will be 0.45/2.5 = 0.18 C ?

I find my answer highly wrong and would appreciate if someone can give a nudge in the right direction.

Edit: Assume ambient temperature as 30 Degree Celsius


texts:
I am planning to use a Diodes AP5100 switching regulator to go from ~22V to 12V in my circuit, which will have a max current draw of about 1A.  This is my first attempt at laying out a switching power supply and I tried to follow the recommendations (double quoted below) in the datasheet as closely as possible.

"The input capacitor needs to be as close as possible to the IN and GND pins."

I put C1 close to IN pin 5. Should I try to get C1 closer to the ground pin 2?

"The external feedback resistors should be placed next to the FB pin."

R1 & R2 feedback resistors are near FB pin 3. I could move it closer if needed.

"These interconnecting impedances should be minimized by using wide, short printed circuit
traces."

I believe that was accomplished.

I am not sure if it's a good idea to route R2's ground connection under the IC to ground pin 2?  Maybe using a via directly to the ground plane is better?

Also, I am not sure if the ground island for minimizing ground bounce is laid out correctly or is even is necessary. It actually might be makings things worse in terms of EMI.

I think the inductor that I am planning to use might be too small.  It's current rating is only 1.6A.

Please offer any advice on how to improve the layout or anything else.

Revision #2

Thanks to everybody for all of the suggestions and I made the following changes:

removed the ground island
moved L1 closer to pin 6
feedback measured directly off C2 now
added double vias to the ground plane for C1, D1 and C2
added a second GND connection

Questions:

should pin2's ground connection be made with a double via also?


texts: Controlling max voltage (power supply) when Vin varies?

texts:
Is there a way to regulate max DC voltage on a circuit when the input voltage CAN exceed the desired voltage?

I'm trying to figure out power supply/regulation for a fan where the datasheet specs for 10.8v to 13.2v input at up to 4.6A.  I have bench tested the fan up to 14.1v and it didn't fail, so there is some margin of error above 13.2v.

However, my input voltage can vary from ~11.5v to 15.2v.  Normal operating range is ~12-14v.  Total draw for the fans is ~9.2 amps (2 fans).

I have looked at the following:

1) LDO regulators - generally can't supply enough power (even if divided into two circuits, one for each fan), plus I'd have to set for a low voltage to begin with (~11v) which would wind up wasting a fair amount of power most of the time.

2) Avalanche diodes - This could sink significant amounts of current, which would be bad..  not just for the PCB but also because of the battery chemistry it is drawing from as it would pose a fire risk.

3) Switch mode regulators - generally speaking you need some margin above your target output voltage, which isn't always the case here..

4) Using a power diode in series to drop the voltage some arbitrary amount and just heat sink away the wasted power.  Inefficient but may work.  The problem is I would need it to sink ~1v at the top end of the voltage range and less than that at the bottom (preferably closer to 0.5v) which doesn't really seem possible in the datasheets I've been looking at.

So far #4 looks like the best of the "not good" options..   But are there any options I'm missing here?


texts: What happens when primary and secondary coil of an isolating(1:1) transformer are connected together(in parallel)?

texts:
I am considering the case of an isolating transformer because both the coils are identical. If we connect both of these in parallel, they will act as mutually linked inductors if they are connected in phase. But what if they are connected out of phase(positive of one coil to the negative of the other), such that the magnetic field generated by one coil is cancelled out by the other?

According to the equations, if there is no magnetic field, there will be no current passing through the part. Which means to an AC signal this arrangement will offer infinite resistance, but for a DC signal it will act as a simple resistor.

Perhaps it can also be thought of as a transformer. A signal is applied to the primary, the same signal appears at the secondary. This signal is then superimposed on to the primary with a phase difference of pi, hence cancelling it out.

My questions are:

Does this really happen?
If so, has it been put to any use? This could be used as an AC filter


texts: Drawing Signal Flow Graph from Bridged-T Network

texts: I am confused about where to place R1. Is it a feed-forward or feedback term? Y1 and Y2 are admittances representing the capacitors.


texts: Why can this 7-segment LED show 2 colors?

texts:
I have a 3-digit, 7-segment+decimal display I bought from an ebay store.  I believe it is a hi-eff red one, and the seller provided this link to the data sheet.  A search found this data sheet which is more complete and seems to describe the part better, though bottom line - I don't know exactly which part I have.  The part has "C403E (1) T0831 RoHS" printed on one edge.

I checked each segment as I wired them on a breadboard, and when I inadvertently powered one without its resistor, surprise! It glowed green - not overly bright, and didn't burn out.  I repeated this with, and without its resistor; with a resistor it's red, without one, it's green.

Anyone know why / how this could happen? Every bi-color, common cathode part I've been able to find has two anodes per segment.  This one has only one.


texts:
I'm looking for ideas on cabling a sensor that is undergoing cyclic motion in a way that will avoid fatigue failures in the cable.

The sensor is an accelerometer mounted on a shaft that rotates through ~375 degrees and back at about 15-60 RPM.  The shaft is around 100mm diameter.  It might go through ~250,000 cycles in the sensor life.  It's okay for the cable to fail if it goes through more than 375 degrees.  What's the best type of cable to use so that the repetitive winding and unwinding won't cause failures?

Bonus points if the solution is (a) cheap, and (b) avoids lots of slack cable flapping around.

Alternatively, anyone with good ideas on how to accurately measure the motion of a church bellis welcome to put them forward.  By "accurate" I mean better resolution than 0.5 degrees in the motion of the bell, bonus points for measuring angular acceleration directly.


texts: Reserve Capacity Testing On Lead-Acid Car Battery

texts:
All car batteries have Reserve Capacity ratings instead of Ah ratings for deep-cycle batteries. Using this data to test the health of the car battery a good way to estimate life left?

Let say I have a car battery with an RC of 80 minutes with a constant current load of 25A I could, in theory, see if how long it takes until it reaches 10.5v. Based on the real data vs label calculate the loss of capacity in a used car battery (State of Health)?

That could be a very easy way to test. Just curious I had a thought about this.

Thanks!


texts: Using conventional notation in the diagram below, I understand that the circuit is not complete because the diode is in reverse bias. But knowing that the electrons actually flow from the negative to the positive terminal(direction of the arrows), wouldn't the electrons take a path from the negative terminal of the battery, go through the lamp and stop at the diode(the red path in the picture). If they would, then why doesn't the lamp light up with the first electrons that are able to flow through it before the voltage in the wire is built up and the current stops.


texts: Is there a limit at the voltage you can apply to a transformer primary?

texts: I have a 9v transformer but all it says is that, there is not info on the primary. The voltage supplied to my house is 120v. So, the transformer will just lower the voltage by a 0.075 factor, independently of the voltage I supply to the primary? is there a voltage limit to the voltage I can supply to the primary? what would happen if I were to used it in Europe for example, where they have double the voltage at home?


texts:
# of gates in a 32 bit ripple carry adder?

I know the answer to this question is (4X32=128). But could someone please explain to me why this is the case? I don't understand how they got the 4?

FYI: the full adder implementation is the one without the use of XOR gate in the C-OUT.


texts: Long distance Arduino sensor network - 1Wire protocol or RS422?

texts:
I have some sensors from each of which I need to
- read a voltage
- be able to switch them on. (They are powered by AC 220V power supply).

Distance to be covered is some 40 meters.

I don't want to use to many wires in order to achieve this.

Solutions I have been considering are as follows:
- 1-wire protocol - it's quite simple but some people have reported quite a few problems;

rs422, works well over long distances, but it might be a pricy solution.

In case I chose 1-wire protocol, how would I get my sensors connected to a 1-wire interface?

If rs422 is not too complicated and expansive I would go with this option as I might consider extending the network over some 200-250 metres in the future.

How would I connect my sensors to an rs422 interface? How would I get my Arduino talking with RS22?Have you tested any RS422 chips? I have seen quite a few of them online, but I am not sure which to choose.

Would it be too complicated to make an RS22 cable myself? I have looked on ebay and found only wires not long enough and too expansive.


texts: What would make me choose Verilog or VHDL over schematic design on CPLDs or FPGAs?

texts:
I have absolutely no background in programmable logic, I use mostly microcontrollers in my projects but recently I needed to work with video and the microcontroller is just too slow for what I needed so I started playing with CPLDs.

I was able to get good results with the CPLD only using schematic design but when searching for info on CPLDs I came across many examples using VHDL and Verilog. I am curious about what could make me want to define my device in one of these languages. What can they do that schematic design cannot? Are they used mostly for functions?

Until now I have only used CPLDs, do FPGAs designs benefit more than CPLDs from using these languages?


texts: 10 Lights (Lx), 10 Switches (Sx). S1 powers L1, S2 powers L1, L2, S10 powers L1. . .L10

texts:
simulate this circuit – Schematic created using CircuitLab
I'm trying to wire an educational toy for a child. If switch 1 (S1) is on, light 1 (L1) is illuminated. If switch 2 (S2) is on, light 1 (L1) and light 2 (L2) are illuminated, if switch 10 is on, lights 1, 2, . . .10 are illuminated.
I'm using 20 5v 60mA Solar Panels as the power source. 10 panels wired in parallel X 2 and those two resulting panel assemblies connected in serial. I believe that configuration should provide maximum values of 10v and 600mA.
A simple two light prototype using PCB Board showed me that I need something. With a simple wire bridge between the two circuits both lights illuminate when either switch is turned on.

Can I use a diode to between each circuit to ensure the current flow is in only one direction? I.E so that S1 on doesn't illuminate L2?
If so which diode will be needed?
Thanks for everyones interest so far. As suggested, I inserted a schematic of my initial design. I soon realized that once the current hits the PCB Boards as designed, everything lights.  Not what I want.
If I remove the PCB board and connect SW1 to D1, SW2 to D2, SWx to Dx I light the individual lights, but I want a design where if any single switch to a light is energized all the previous lights will illuminate.
Example: If SW2 state is changed, D1 and D2 will illuminate not D3.
Thanks again for your thoughts!


texts: How do I power a Twin Industries TW-E41-102B?

texts: I just bought a Twin Industries TW-E41-102B, and I'm new to physical logic gate stuff, how do I power the breadboard? Please help!


texts: Open a picture and read its Pixel Values

texts:
I want to calculate the Histogram of an Image is grayscale color mode

I have designed a memory and a Calculator of Histogram value, now I want to get Pixel values and put them in Calculator as Input

I have a picture (for example a Bitmap), I should Open it and scan it's pixels but I don't have any idea how do that

Is there a function in ModelSim to Open a picture ? (Like File_Open for text files)

How I should read its Pixel values ?


texts:
How do I move the schematic / page in ltspice. I meant if I have a schematic, and I want to move (move in the page). Like the "keep right press the right click and move" in Altium.

If I want to move, I should zoom.

Thank you


texts: Please explain this High-Gain Yagi UHF antenna design

texts:
A while ago I upgraded my TV antenna in preparation for Digital Switch-Over here in the UK. It's a high-gain "Triple Boom" design. The other day I started thinking what is the benefit of the 'triple-boom' design and how does it work? The booms are clearly angled, how does this effect things?

It also appears the elements are evenly spaced, in contrast to single-boom antennas, so I infer from this that the angling, and thus vertical distance between elements, leads to sensitivity at different frequencies. But why doesn't the horizontal spacing matter too (as in single boom designs) or does it? And why do higher-gain antennas with more elements just keep extending outwards but at the same angle? So a longer 'boom' means the furthest most elements are even further apart than normal. Doesn't this just mean they are resonant at even lower frequencies?

Comparing the performance of this antenna with traditional single-boom design shows it has a higher gain but also a wider acceptance angle. I can see how a triple boom array would increase gain, but why/how does it broaden the angle?


texts: Should series connected battery cells have similar internal resistance and to what degree?

texts:
I have some Toshiba SCiB cells that I wish to string in 4s configuration. These are Lithium Titanate (LTO) cells. They have a 20Ah capacity and operate safely between 1.5 V and 2.7 V. The cells were obtained after some light use. I was told they still have good capacity and should still have a solid amount of cycles left.

I have 14 cells and I want to know how to determine which four cells will perform the best when strung together. I could just grab four cells and place them in series ( with appropriate cell managing of course). Would it be worth it to measure the internal resistance of each cell and place in series the four cells with the most similar internal resistance?


texts: Current Sensing with ACS712 on Beaglebone Black

texts:
I am planning to use my BBB to perform some current sensing and was wanting to use the ACS712 chip. The chip operates off of 5V, but the analog inputs of the BBB have a max of 1.8V. How can I wire this up to make sure I don't fry my BBB?

Can I use a voltage divider? If so, how do I calculate the resistor values to get the correct scaling?

Thanks!


texts:
I have been scrolling like a zombie through Digikey, Farnell and Molex websites to identify the reference of this fairly common looking 5 pin connector of a board I am reverse engineering, but couldn't find it yet.

I would greatly appreciate if someone could shorten my sufferings.

Best regards


texts:
I am building a USB project and I want to use a Ferrite Bead in the USB 5V rail.
I am looking for 1206 Ferrite Beads. How to select them properly? Which impedance at 100MHz is a good one?


texts: How close are we to fabricating a Germanium IC?

texts: I am not actually talking here about SiGe(Silicon-Germanium hybrids) but an integrated circuit that uses entirely Germanium(doped of course in certain areas)? It is my understanding that even though Germanium was used to make the first discrete transistors, there are many problems with using it as a substrate for IC fabrication. Such as the fact that Germanium Dioxide is water soluble.


texts: bandwidth of digital control design in conventional dc-dc converter

texts:
I designed conventional single inductor two output dc-dc boost converter in psim.  This means inductor energy is stored and thrown to 1 output at one cycle and charged and discharged to the 2nd output at next cycle.  The two outputs are sensed by using voltage dividers and time multiplexed using analog mux at the speed of half of the switching freq to be processed in the digital control stage. My digital stage is very simple pid with z transfer func. After that pwm controls the switches on/off time.
 The design works well.

vin 2V
 vo1 4V
 vo2 6V
 fs =1M
 L=4uH
 c=50uF
 etc...

so my question is in above scenario, does the bandwidth in the control should be greater than switching frequency or less than switching frequency?
 thanks


texts: Confusing timing diagram for QCIF format in OV7670 datasheet

texts:
Any reply is greatly appreciated.
I  wanted to confirm about the QCIF timing diagram from datasheet (shown below). The ON time of the HREF for both vga and QCIF is shown as 640tp (tp=2tpclk). So does that mean each line of QCIF (174x2 bytes) take 640tp seconds? So in that case, bytes of a QCIF line arrive at the rate of 6.66Mhz (when HREF is high and for pclk frequency of 24Mhz) and not at 24Mhz?Hence if i were to sample bytes(of QCIF format), belonging to a line(when HREF is high),i must not sample at every PCLK rising edge?


texts:
There is a component in LabVIEW called as "Inverse Modulus".
It is used to eliminate the discontinuous jump that would occur when the DAC encoder of the hardware reaches the limits of this range.
Thereby making the signal a straight line.

How do I implement this block in Simulink?


texts:
I am trying to fix a rotary tool's AC powered DC motor controller, there is a resistor that has been burned out, I want to replace it for a new one, my question is how do I find the value of the resistor since I can't see clearly the color coding anymore and I don't have the schematic.
Thank you in advance for your help.
(please see the pictures)


texts: I need an amp meter that requires no splitting of the wires

texts:
I need to measure the amperes of the current flowing through a cable; the power is consumed by an electric motor.

For that purpose, I am looking for an amperemeter that requires no splitting of the cables. (As I understand that cables generally transport both types of currents together, I need to be able to measure the amps of the system without actually disarming the cable).

Where can I find such device?

Any type of feedback is appreciated. Thanks.


texts: Suggestions about proper usage of vk-200 choke

texts:
I have an old custom-built non-switching 5V power supply (usual 220V-12V transformer + bridge + 7805 regulator + various capacitors) that I'm using to power a HF upconverter and a HF LNA.

I'm currently fighting RFI/EMI and trying to place ferrites in all possible places to reduce/eliminate the disturbance I'm getting.
If I correctly remember, it should be good to use VK-200 chokes in series on the 5V power line.

Does anyone have a schematic / text or suggestions about the proper placement? I still have at least 20 of those VK-200 and I would be happy to use them.

The chokes are of this kind (axial 2.5 turns):

Adding the power supply schematic:


texts: Is there a workaround for a Hall effect encoder out of alignment with its sensors on a small motor?

texts:
I'm working with two budget SmartArduino 9V 25mm motors on a radio control tank project.
Motor-A has a problem in that the encoder wheel is situated laterally above the Hall sensors. Motor-A does not produce pulses on the hall sensors without intervention.
Motor-B's encoder has a very small overlap with the hall sensors. Motor-B does produce pulses on the hall sensors as the motor is manually rotated.
There is lengthwise play in the shaft on which Motor-A's encoder wheel is fixed. If I press down on the encoder wheel while manually rotating the motor, then the Motor-A does produce pulses on the hall sensors.
Q1: Is there an optimal position for the placement of the encoder wheel in relation to the hall sensors? I had assumed that they would have been more overlapping with the face of the encoder wheel.
Q2: Are you able to suggest a workaround or repair to correct the situation?


texts: Maximum range of 27 MHz ISM band NLOS radio broadcast

texts:
What is the maximum range of a 27 MHz ISM band when transmitting at full power? I am interested in general situation for US and EU but that will go back to the power limits allowed. My country (CZ in EU) allows 100 mW on "26.995; 27.045; 27.095; 27.145; 27.195 MHz" with a "channel width" (or spacing?) of 10 kHz.

The system should transmit only in one direction - it should broadcast GPS RTK corrections from base station to rover. Throughput needed is only 1 kB/s (= say 9600 bps). Desired range is 10-20 km but I am afraid I won't get that much - few kms is still very good though.

Will antenna size (not power) influence the range? I consider a case with the transmitter being a permanent base station (can have bigger antenna, but not huge) and the receiver being a mobile rover (small 10" rubber duck antenna). Both antennas will be omnidirectional.

I was considering using ham radio but that is most likely not legal ("broadcasting" for "general public").


texts:
I was discussing with a co-worker about a led driver for our project, something that is really simple and it could be irrelevant, but it now has a major relevance from my point of view for: for a huge increase in the price for multiple unnecessaries components. I believe he wants to show a "slow" fading (which is not necessary) led if he wants that. so drive the led to just turn on/off it could be easy to do with the design (2) (mine) instead of (1) with 4 extra components or 5 if I remove all the caps.

note: the pulse is coming from un microcontroller, not from a push button


texts:
OK, obviously I'm misunderstanding something.

I have a RedPitaya, which is an oscope+generator. Its output impedance is 50\$\Omega\$.

If I send a signal from its output to its input (which is 1M\$\Omega\$) and use a BNC T with a 50\$\Omega\$ terminator (to match impedance), I expect a signal drop of about half, since this is a voltage divider: 50\$\Omega\$ out, in series with 50\$\Omega\$ in, with the 1M\$\Omega\$ in parallel not affecting the signal much.

However, I do not see this on the trace. With the terminator, a 1Vpp (nominal) signal is almost exactly 1Vpp (1.003Vpp). Without it, it is about 1.05Vpp.

This makes no sense to me. The only thing I could think of is perhaps the RP "knows" when the terminator is connected and is doubling the voltage trace? Or, perhaps I don't understand how terminators work.


texts:
I am building an aluminium capacitor for fun and it got me thinking. Is it better for the plates on a capacitor to be rough or smooth?

My thinking is that it is better for the surface to be rough as it increases the surface area? I think that is why the carbon nano-tube super-capacitors are so good?

Or is there a trade off for roughness? i.e. increases one property while decreasing another property.

Apologies if this is simple. I am new to electronics.

Thanks.


texts: Doubts regarding constructing an emergency light

texts: I have made an emergency light using 12v LED strip (3 LED's on the strip) with a 9v battery, its run time was 10hrs plus. My doubt is if I can use the same setup with a 12v 200 Ah battery, what will I encounter? Is this even possible?


texts: Defining reference signal for PID controller

texts:
I am developing a PID controller to use in a buck converter (13V->5V). The problem is how to physically implement the signal which acts as the reference voltage and generate the error signal. I don't have a 5V DC voltage source to use as the reference (otherwise the buck converter would be useless because I would be able to simply use this 5V source).

I've heard something about using a DAC to implement this, but I am not sure how it should work.

Thank you


texts: Determining potentiometer sensor output resistance with parallel resistor

texts:
The data

I'm trying to understand a sensor circuit I've come across, which I've simplified to the following:

simulate this circuit – Schematic created using CircuitLab

In short, it's a potentiometer segment in parallel with a a resistor of lower value. The output voltage at Vwiper is fed into an automotive ECU. I can't measure the potentiometer resistance without modifying the circuit, but for the sake of the example, I've given Rpot a value of 1K.

I understand that the parallel resistor (Rpar) will limit the potentiometer's resistance range to the value of the parallel resistor.
I've also read that the curve of resistance seen at Vwiper vs. potentiometer wiper position should be non-linear.

Update: after the feedback in answers, I've further simplified the circuit and modelled the potentiometer as two resistors the value of which depends on the wiper position:

The voltage increases linearly with position in the simulation results, which seems to be confirmed by my measurements on the physical circuit.

I have also measured Rwiper vs position on the real circuit, which does not seem to be linear. It's a tiny potentiometer strip, so measurement is not exactly accurate:

Notice how the output resistance starts at about 65 Ω, peaks to ca. 250 Ω and ends up decreasing to the Rpar value (30 Ω). I assume it starts at 65 Ω because the wiper rest position does not go all the way down to 0 Ω.

For more background (skip if not needed), the sensor has a continuous resistor track, divided in 7 segments. Each segment of the track has a parallel resistor as the one shown, each with a decreasing value in logarithmic progression. I've lumped together the rest of the stacked segments into R4 for simplicity.

The output, taken between Vwiper and GND, is a logarithmic curve. I believe the purpose of the segments and the parallel resistors is to do piecewise approximation to obtain this voltage curve.

The question

I can measure, and plot the output voltage, but I somehow cannot grasp how the resistor network actually works.

In other words, given this simplified circuit, I would like to understand and if possible, plot, how the output resistance between Vwiper and Vinit varies as a function of the wiper travel.

It's been many years since I've done any circuit analysis, so any pointers would be helpful on the question:

What is the equation that determines the output resistance seen from Vwiper?


texts: Soldering the thermal pad of an SMD onto a PCB by heating the bottom with a solder gun

texts:
I am trying to build a dimmable LED circuit that consists of 4 SMD LED lights (datasheet: https://download.luminus.com/datasheets/Luminus_SST-10-UV_Datasheet.pdf). I am new to working with PCBs and came across a video of someone soldering some similarly small components onto a PCB using a solder gun by applying heat directly from the bottom (link: https://www.youtube.com/watch?v=ADrIWwEWF44 , start at 2:20) which looks incredibly convenient and efficient compared to most tutorials I've read/watched which either involves tools I do not have (I only have a solder gun, no oven or a hot air gun) or adding a via in the middle of the pad. I am uncertain what exactly he did to the PCB from watching the video, and have some questions pertaining to how his technique can work for a 2-layer PCB where only the top layer needs to be electrically conductive (have to get 2 layers instead of 1 as it is the manufacturer's default):

It appears as though he removed the solder mask and added a paste mask to the bottom layer. From what I understand, there is a thick layer of substrate that typically is made of FR4 which results in low heat conductivity between the top and bottom layers. Assuming his substrate is FR4, Is it possible to heat the paste mask of the top layer through the FR4? Or did he do something else to the layers?

The thermal pad of the LED is supposed to be connected to a relatively large pad on the top layer. Is that so that the copper can conduct the heat away from the LED? From my understanding, the copper sits atop the substrate - how does the heat escape if the substrate has low thermal conductivity?

If I added a via in the middle of the mask, and there is nothing in the bottom layer which connects to the via, is there a chance of shorting the circuit? I imagine that since the copper plate in the bottom layer is surrounded by insulators, the resistance will be very high and no current will flow, is that right?

Thank you in advance for helping me understand how PCB/electronics works.


texts: What should I do to control the impedance in piezoelectric energy harvester

texts:
I am trying to design an piezoelectric energy harvester circuit and using voltage multiplier rectifier to build it now.
I am using a piezo film, LDT4-028k as a source and it has 11nF cap inside the film. Based on the datasheet, what should I do if I need to make the input impedance as 10Meg ohm?
What is the reason that my circuit it so inefficient and just can charge a few microvolts at a time?
What should I change to enlarge the charge rate and how to determine the actual value of the components I need to use?


texts: Forwarding in RiscV multi cycle Pipeline

texts:
Any idea could be helpful
I have been trying for days to understand forwarding mechanism in RiscV but unfountly I keep failing, so I though about asking basic question to make sure I am building on correct knowledge.
In general there are 3 types of forwarding:
Write_Back -> Decode/Execute
Memory -> Execute

Can you help me know which type of data is being forwarded in each stage, for example:
Memory -> Execute

What are we moving here? the data or the location to where the data is saved?
Here's an image:

From it I can see a red lines from Memory (Addr) to the execute stage but that doesn't make sense... shouldn't we send the data instead?


texts: Increase dynamo output by increasing voltage?

texts:
I am trying to build a device that converts the output of a standard 3W AC bicycle hub dynamo to a 5V DC USB port. My goal is to maximise the power output, efficiency is secondary.

A lot of information about this topic online suggests that a bicycle dynamo behaves more or less as a constant current source. This means that when the resistance of the attached device is high, the dynamo outputs a high voltage, while the current is almost the same as with a low-resistance device. This means that the power output is higher with a high-resistance device, and some articles suggest that they have managed to get as much as 11 W out of a simple 3 W dynamo (in this case by putting several LEDs in a row).

My question is first of all, is this true? And if so, how can I make use of this fact to produce a high-current 5 V output?

As far as I understand, I basically need a voltage converter that makes the dynamo create a high voltage (by having a high internal resistance) and then converts this into a high-current 5 V output. So far I have been experimenting with regulating the voltage using a simple DC/DC converter, a Zener diode, and a buck converter. With the first two, I don’t think anything can be done about their internal resistance. About buck converters I don’t have a lot of knowledge about how they work. Are there differences between buck converters regarding their internal resistance, and how can I find one with a high one?


texts:
I am trying to figure out the role of each of the lettered components in this line filter circuit. The line filter is connected to a rectifier, which is connected to a high frequency power inverter, which is connected to a step down transformer.

Not sure if the above will display so here is the link https://ibb.co/ci0CmJ

What I think so far (which may be wrong!):
K1 is the common mode line choke which filters out common mode signals and lets differential signals pass.

C1 helps remove some of the high frequency noise coming from the mains and ensures any is not transmitted back into the mains.

C3 and C4 ground high frequency signals, but I am not sure how. They look like they are voltage dividers there.

I am not sure about C2 and R1.

Why do capacitors in parallel act as low pass filters, and is this what C2 and R1 are doing, and if so, how?

Also, from what I have read, for capacitors to act as voltage reservoirs to produce a steady voltage from an ac source, they have to be bigger than what is used in this circuit - is that correct?


texts:
I have 2 questions:
Is it possible to generate -35V from LM337 regulator with -12V in input??
The voltage output from LM337 is supposed to follow this equation, -Vout=-1.25(1+R2/R1)+Iadj.R2 but in ISIS simulation the output value is always the same as the input, I don't understand why, for example in the picture above output value is supposed to be -32V according to the resistances values but it is -39V because the input is -40V, the same for any other voltage.


texts: differential to single ended output problem

texts: I have a differential input of 2-V and it apply to TLV-2221 op-amp with unity gain of one, but the output shows the zero voltage waveform,can anyone explain why it happens? here i am attaching the screenshots of my simulation.


texts:
I want to establish a communcation between my ATmega32A and PC but there's a line that I don't understand.
The datasheet says that:"When data comes in,the RXC0 bit in UCSR0A will be set,and you can read the incoming data out of UDR0

The function to receive byte looks like this:

unsigned char USART_receive(void)
{
   while(!(UCSRA & (1<<RXC)));
   return UDR;
}

What I understand from this:We wait until all the bits are inside of the UDR register and when the RXC turns to 0 we gonna return UDR register.
Can someone clarify me if I'm right or not?


texts:
I'm using an open collector comparator LM339, and I want to isolate V2 from the circuit by a 4N25 optoisolator. I want V(out) to change its state from at least around 1V or less up to 10V. But I get the following result in LTspice IV where Vout swings between 8.5V to 10V:

I cannot change R8, and I want LED to blink for every pulse. I might be using the coupler wrong way. I also noticed R7 also have big effect on the coupler; if I set it to 10k it doesn't work at all.

How can I modify this circuit so that Vout can swing more(from around 1V to 10V) and LED blinks?

Edit:

Suggestion from a comment:

EDIT 2:


texts: Error when compiling "Does not name a type"

texts:
I want to inherit my own class from LiquidCrystal that creates some custom characters during initialization. Here's the code I've written so far:

MyProject.ino

#include <LiquidCrystal.h>
#include "MyLiquidCrystal.h"

MyLiquidCrystal lcd(8, 9, 4, 5, 6, 7);

void setup()
{
 lcd.begin(16, 2);
 lcd.setCursor(0,0);
 lcd.print("Welcome");
}

void loop()
{
}

MyLiquidCrystal.h

#include <LiquidCrystal.h>
#include <Arduino.h>

namespace MyProject
{
    class MyLiquidCrystal: public LiquidCrystal
    {
        private:
            void createCustomChars()
            {
                byte smiley[8] = { B00000, B10001, B00000, B00000, B10001, B01110, B00000 };
                this.createChar(0, smiley);
            }

        public:
            MyLiquidCrystal(uint8_t rs,  uint8_t enable, uint8_t d0, uint8_t d1, uint8_t d2, uint8_t d3)
                : LiquidCrystal(rs, enable, d0, d1, d2, d3)
            {
                createCustomChars();
            }
    };
};

I'm getting the following error at line MyLiquidCrystal lcd(8, 9, 4, 5, 6, 7);:

MyProject:5: error: 'MyLiquidCrystal' does not name a type

I've been googling for a while now but couldn't figure out what's going on.
Any help would be appreciated!


texts:
I've developed an automotive H-Bridge circuit using the DRV8702-Q1. It's pretty close to the reference schematic in the datasheet but it doesn't work. I've been racking my brain for ideas as to what has gone wrong, but I can't find anything obvious. The host controller is a Raspberry Pi CM3, using 3.3V logic levels to the DRV8702-Q1, with VIN at 12V. The mode pin is pulled to ground to configure it as a full H-Bridge.

The nFault pin indicates that the H-Bridge driver is not in a fault state (constant at 3.3V), the SO pin hovers between 5.4V and 5.48V. VCP is the 9.87V, which matches the high voltage I see on the MOSFET gates.

The MOSFETs I'm using are FDD8447L-F085.

I think the layout appears similar to the datasheet as well, though not identical

This is a scope of the low side gates (GL1, GL2) when EN is on. Changing the phase simply alternates which gate exhibits the waveform shown below. Looks nothing like what I'd expect. The high side gates seem to be stuck at the 9.87V (matching VCP) regardless of what signals are sent on PH/EN.  The behavior seems wacky to me, maybe the DRV8702 was failed by ESD.


texts: What does 'integration density' in the context of integrated circuits and electronics mean? I've seen the term tossed around a lot, but I've never found a satisfactory definition.


texts: Bistable circuts based on non-linear effects (like breakdown)?

texts:
Is there any known bistable circuits, which utilize parts in non-conventional mode, so that circuit is somewhat simpler than Bistable Multivibrator?

Something like non-destructive breakdown of PN junction comes to my mind....


texts: Differential probe design ground copper pour

texts:
What is the reason of no copper pour at the differential input side of the board. What would happen if i pour ground copper at that area as well.
The source of the design


texts: Ziegler Nichols for second order transfer function

texts:
I have a second order overdamped transfer function as follows -
$$
\frac{1}{(70s+1)(50s+1)}
$$
and now I want to use a PID controller and tune it using Ziegler-Nichols. I have worked with Ziegler Nichols only for higher order systems so used to think it's not feasible for second order systems. But recently I read somewhere it's possible if the system is overdamped which my system is (damping coefficient came out to be 1.69). But while making Routh array, I am getting just one condition which is K > -1. I am not able to get any K (= Kcr) to have sustained oscillations.
P.S. I have used L-T method and found the answer but want to know what's missing in the above method.


texts:
I am unsure whether I should edit on my previous question or create a new one. Please give me your feedback on the proper way of doing it here.Back to the question, I have struggled for the past few days in creating a 2 output flyback converter. Ideally, the Vo1 and Vo2 should be 12V and 8V respectively. The ideal current flow was 5A for both windings(Desired Pout = 100W) but I can't seem to get the desired result. Images are found below. As I am not allowed to post more than 2 links, the voltages that I obtained was Vo1 = 18V, Vo2 = 12V. I have based on my calculations as provided by the kind hearted people around here. I have based my calculations based on AN4137 and some design calculations by micro rohm.
In actual fact I would like to use the UC3844 as my controller IC but Im still negotiating with the people from PSIM to grant me access to it. Hence I base my switching device with a pre design available in PSIM. Some information that I think is needed,
Transformer core based on EER40, Ae = 149mm^2, AL = 5200, Lm = 2.9mH, Leakage based on 10%, Vin range: 220 - 240V. Np min = 58.38. Fsw = 100kHz
Sorry for the long post. I hope someone can guide me along. Thank you.

PS thanks for the upvote, I have uploaded the voltage output
PS I have adjusted the flyback design

.


texts: Buck converter based switching power supply?

texts:
simulate this circuit – Schematic created using CircuitLab

I have designed this circuit based on a buck converter. I'm just having trouble finding out which values to plug in. I.E. C1, L1, and the frequency for the output of MCU.

Also, as this will be my first PSU, I wanted to get some circuit analysis before I plug this into the main.

Note that I realize the output of the buck converter will have to be turned back into AC, and run through a transformer to isolate the circuit, then turned back into DC.

Un-Specified Components:

This is a theoretical circuit, thus I have I have not committed the values and specificity of the components. My question is whether this circuit could theoretically work, and how to select components for certain voltage values on the output.

Intended Operation:

BR1: This bridge rectifier turns the main's AC into DC.

Voltage Divider R1-R2: The resistance values are undefined because I have not selected a microcontroller for MCU. The voltage here will be dependent on the needs of the micro-controller I eventually select as MCU.

MCU: A microcontroller which will turn the NPN 1 on and off to form the cycles for the buck converter. MCU's VCC is connected to a transistor (PNP 1).  The function of PNP 1 can be defined as: IF there is no current coming from the buck converter, then the MCU is powered by the voltage divider R1-R2. This is because I would rather use the more stable buck converter's voltage to power the MCU than the unstable voltage through the voltage divider. The MCU will only be powered through the voltage divider until the first cycle begins.

NPN 1, L1, C1, D1, Load: This circuit constitutes a straight forward, run of the mill, buck circuit, with NPN 1 being used as the switch, fired by MCU.

Application of This Power Supply:

I'm building a 3-in-1 laser engraver, 3D printer, and CNC machine. I've built a prototype with a working area of 35mm x 35mm x 35mm. However, the prototype runs off of a Raspberry Pi, 3 dual-h-bridge modules , and a laser driver circuit. The end goal is to apply the code I wrote for the prototype to a completely scratch-built printer. The printer will require 9V at varying current loads. (I.E. the device driver needs more current to power a high torque CNC router than the 3D plastic extruder.)


texts:
I have an assignment in my electronics 1 class:
http://prntscr.com/jcdz1m

My idea was to find a Thevenin equivalent, convert it to Norton then i would get Io and calculate the graph for I1 and I2 for(0->100μs).

What can I do to calculate I1 and I2 for(-10μs->0μs)? I cannot perform circuit analysis since I cannot convert my inductor to a resistor.


texts: Connecting 12V fan to LM317 DIY PSU circuit

texts:
I am working on a simple adjustable DIY power supply using an LM317 voltage regulator. J1 in the image below represents the transformer rated at 18VA, which rectified produces about 25V DC. The output range should reach roughly 12V, 1A.

Interestingly, I've found a 12V DC fan/heatsink ripped out of an old Nvidia 9400GT to cool down the LM317. I am considering one of two ways of connecting it to my circuit.

The first option is to connect it across the last large filter cap C2, with J2 and J3 representing V+ and GND connections of the fan respectively.

1) Am I correct in saying that the first option would be essentially placing it in parallel with filter cap and the voltage regulator and therefore would place it permanently at 25V, whereas the second option would drop my voltage input to the regulator by 12V, and the fan would only be at 12V?

2) What are the advantages to choosing the second option over the first?

Edit: Based on the suggestions of @AndyAka and @DoxyLover it seems that placing the fan in parallel with the filter caps is truly undesirable given the input voltage to the fan, whilst the placing it in series also causes more problems.

3) Would it then be advisable to use an additional 317 to regulate the voltage input to the fan in such a configuration?


texts: PWM only works after touched with oscillicope probe

texts:
I am using two PWM outputs from a Netduino 2 to control two servos. One of the PWM pins works perfectly fine but the other doesn't work until I have touched it with an oscope probe. The probe doesn't need to remain connected or even grounded. Just a small tap gets it running.

I removed the pin headers so I could directly solder the wires to the PCB so perhaps I damaged something? It's strange because everything works fine after I tap the connection with the probe. Both servos are powered and grounded from the same rails.

Any ideas/solutions?


texts: Shifting Complex Baseband Signal with Pilot Tone

texts:
I am trying to shift a complex baseband signal. To do that, I am multiplying by \$e^{(j \times 2 \times \pi \times f_c \times t)}\$, where \$f_c\$ represents the shift amount. The baseband signal has a pilot tone component at DC (0 frequency), and I expected the pilot tone component to be shifted along with the rest of the signal. The pilot tone is prominent, and its power is higher than the average power of the rest of the signal. When I observe the PSD of the unshifted complex signal, I can see the pilot tone at DC.

However, the actual shifted result shows the pilot tone has disappeared. If I shift using \$cos(2 \times \pi \times f_c \times t)\$, I also get a missing pilot tone in the shifted signal.

Has anyone experienced this before? How do I fix this? I have attached a scan of some diagrams of what I am trying to accomplish and what is actually happening.

Thank you in advance.


texts: Can I use Arduino to alert by sound or LED when it detects a certain voltage

texts:
Can I use a Arduino board to alert me when voltage reaches 2.4v to 2.5v DC?

Can I use a Arduino board to alert me when voltage reaches 0.7 mV sine or co-sine Ac?

Or will I need sensors?


texts: Hardware implementations for a low-cost ADC array project

texts: I wonder what would be the best hardware platform or architecture for implementing and building a lowish-cost system to sample audio capture over a large array of microphones or sensors? say, 300 or 500 audio channels simultaneously, and be able to transmit the information either via USB or Ethernet


texts: Can anyone help me how I can find the NEF(noise efficient factor) from a low noise -low power amplifier in ADS (Advance Design System) software design? I have searched a lot but I can't find how I can measure it through the software.


texts: Finding Transformer Leakage Impedance from S/C, O/C and Winding resistance tests

texts:
I've recently done an experiment on a 415/100 V transformer. Performing the S/C test on the HV side and the Open Circuit test on the LV side and finding winding resistance from applied DC voltage and current.

Therefore I now have results from the experiment and have solved Magnetizing reactance, core loss Resistance, Copper/winding resistance and Leakage reactance equivalent values, depending on which side I transfer the equivalent values to according to my turns ratio (a).

The issue I'm having is that I cannot find a way to split the equivalent leakage reactance into its 2 components (LV winding and HV winding).

Equivalent winding resistances are split into their 2 values from the measured applied DC voltage and current Test.

I was beginning to think that if I had measured the voltage across the S/C side in the S/C test (although it would be small, it would still exist) I would have had enough unknowns to solve for Xl LV side; but because I did not measure that voltage assuming 0 volts, I cannot.

Any ideas? I'm stumped.


texts:
I want to drive a 650V 21A SiC mosfet at 100kHZ. Would this  mosfet driver be able to drive the mosfet?

How can I find Gate charge of the mentioned mosfet gate driver?

The mosfet I am planning to use is SCT3120ALHR.
Please suggest if this driver will be able to drive the mosfet.

If not, then please do suggest what other driver and mosfet can I use in place of these.

I will do simulations of the components.


texts: Why is the MISO not level shifted in this circuit?

texts:
I am looking at SparkFun's CC3000 breakout board schematic. CC3300 is TI's wireless module. The CC3000 operates on 3v3. And because the breakout board is intended to be used with an Arduino (which has a logic voltage of 5v), there is a 5v to 3v3 level shifter in this schematic. What I do not understand is why or how the MISO is untranslated and is used at 3v3. Does Arduino (Uno) work with 3v3 logic input level, while its logic output level is 5v?
If so, is this the reason why SparkFun did not use a bidirectional level shifter to cut cost?


texts: ALU once compiled giving errors of missing source signal?

texts:
This is ALU, not sure whether if it is all properly connected but all blocks are the correct ones. This has 3 4 bit latch registers, 5 2:1 ultiplexers, 4 4 bit adders. Can anyone help me?
The problems shown are: he OP's picture shows these error messages: Port "D" of type DFF of instance "inst6" is missing source signal Port "Cin" of type Everything on instance "inst14" is missing source signal.


texts:
Very basic question I'm sure

I am trying to buy components for a project I am doing, but I cant get the name of a component right yet.
But it has to exist somewhere.

I want a resistor array but instead of the resistors in parallel I want them in series with a point to take a measurement off after each resistor.

I have inserted a circuit if I have not been clear enough.

simulate this circuit – Schematic created using CircuitLab

.

Basically my idea is to have Vcc and GND on the end two pins and the take a voltage off after each resistor.
I'm using this to get an analog signal of the different voltage to select different settings in my micro processor.

I don't mind using just a bunch of resistors, but I would like it in a one package device for a neater board and a bit of space saving.

Any ideas of the name of the component ?


texts: How to connect absolute encoder on the rotating shaft. Please see the three options?

texts:
Hi,
Here I have added 2 options for connecting encoder on shaft.
Motor, gearhead and shaft is connected using coupling. But where will be best place for encoder (To avoid backlash from coupling and gearhead).
whether through hollow encoder is available? (see option 1).
I dont know which one will be best for this kind of system.
Which one is widely using arrangements?

Options 3 is Encoder will be placed before the motor.


texts: How do I detect user proxmity to lock PC.?

texts:
I can use one of the many open source usb keyboard projects that will run on an atmel avr to send Win+L to the computer when the user leaves. The question is: What sort of technique can I use to detect proxmity?

Some sort of pair of wireless transceivers like this product: http://www.vupointsolutions.com/browse.php?cat=security&page=SK-MT01-VP
Could I use an RFID? I think there exist the kind that allow for ~4ft detection?

I would prefer option 2 if thats possible.

I'm mostly look for a starting point. What sort of ICs can I use to do this? and/or if there is any example software/library that might interface with one of these IC? I'm a software developer not an EE, but I've dabbled in atmel avr and analog electronics.

(Side note: the reason I don't just use the a pre-made product is because our company will not let us install our own software. Any device that acts has a usb keyboard would be necessary. If there is an affordable premade solution for this, I'd be happy to use it.)


texts: AWG gauge for 10W cob leds and common ground

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Two questions:

How can I calculate the appropriate AWG for a 10W cob led (~12V DC at 900mA)?
Suppose the appropriate AWG is 22, and I want to use a common ground for them (for the purpose of this example, let's assume I have three equal leds). How can I calculate the appropriate AWG for the common ground?


texts: How do I shop for an efficient low-current buck-boost converter?

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I'm working on a low-power battery-powered application running at 3.3V; it needs a DC-DC converter to efficiently draw power from a range of possible battery combinations connected by the end user.
In short, here are my top priorities:

wide supply range (around 2-16 V)
ability to output at least 50 mA
high`efficiency at 10 mA
price under $10

I'm currently achieving those top priorities using the LT3129-1, and am now trying to achieve some secondary priorities:

low parts count (ideally monolithic)
low ripple in output signal
won't be damaged by reverse voltage or moderate overvoltage on supply

However, I'm having trouble searching for better options because it seems like nearly everything I see is inefficient at such low currents, and there are too many options among DC-DC converters (e.g. at Digikey) to find the needles in the haystack.
Can anyone recommend either a search term for my needs, or a specific product? Thanks in advance.


texts:
I was curious and looking at the datasheet of the buck converter IC LM2576, looking at the inductor selection guide it feels counter intuitive to me.

Why is the inductor value needed reducing as we increase the peak current?
Also what are the consequences of choosing a different inductor?

thanks for your help.


texts: Do I need a BMS for Li-ion batteries connected only in parallel?

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I have a device that runs on a single cell Li-ion / LiPo. The physical case for that device allows me to put in one to three 18650 cells. Unfortunately given the disposition of the cells, I can't buy a 2 or 3 pack already assembled.

The device already has a charging circuit. The maximum load will be 300 mA and the maximum charge current will be 500 mA.

Given the above, if I connect 3 cells in parallel (1S3P), do I need a BMS (Battery Management System) or any additional protection circuit?

I'll take care to have them at the same voltage level before connecting them together to avoid current flow between the cells.

TL;DR; Does a 1S3P Li-ion 18650 pack need a BMS?


texts: Surprising Inrush Current on a MOSFET Switch?

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I have the following P-ch MOSFET switch used to supply a 12V, 6-20A load:

When I enabled the switch, I measured the following voltage drops across +12VDC & +12VDC_GR. The yellow line is +12VDC (my source voltage) and the blue line is +12V_GR (my 0.5ohm load). As you can see, the +12VC has a sudden drop followed by a ripple.

I assumed this was caused by inrush current on my load, but when I removed the load and tried it again, I got an almost identical result:

I'm hoping someone in the community can give me some insight into what is going on/fix the issue:

Is this actually inrush current causing the issue or something else to do with the MOSFET?
Would adding a soft start between P-Channel gate and drain do anything to mitigate this? I'd like to understand the actual issues going on here.

Thanks!


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If I use a transformer to step the voltage down from 220V to around ~30V and I expect the 30V end to draw up to ~30A, what kind of current magnitude will I have to plan for or expect to see on the 220V side?

I am very noob. Please feel free to help make this question better/clearer or give suggestions.


texts: Audio being fed back into the circuit, beeping

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I am developing an audio amplifier with microphone, I have a problem that I tried in many ways to solve I could not, so I am here to ask you a second opinion.

My problem is that this circuit is generating a lot of feedback is I can not eliminate this whistle, I tried to put the electret microphone in polarization with a resistor, I also tested capacitors of various values in parallel is not resolved (the sound does not come out or distorted ).

I have already tried to lower the value of c17 to decrease the op amp gain from + -702 and the sound comes out noisy.
what do I do.

supply voltage: 12V.

The sound captures the return from afar +- 1 meter