texts:
I need my 5v 10 amp power supply to power both my LED strip and arduino.
I will have the LED strip directly wired to the power supply, then for the arduino I have two ideas - either cut a USB cable and connect its power/ground wires to the power supply, or wire the 5v/ground pins of the arduino to the power supply.
My question is would 10 amps be too much to give an arduino through either of these two ways? Using the 5v pin to power the arduino is unregulated, but I'm not sure if this is relevant to amps or just volts? My understanding is that the arduino and components plugged into the arduino will only draw as much amps as they need. I know the strip can handle the amps, but can the arduino? It will only be connected to a basic LCD display and joystick to control the colors.


texts: Connect HC-05 and esp8266 with MQTT protocol

texts:
I trying to use Bluetooth HC-05 with esp8266 to connect with Mqtt broker (Raspberry Pi), I already know how to connect by Wi-Fi, because there are a lot of example code for it. But not for Bluetooth.
Can it possible to use Bluetooth to connect with Mqtt with Adafruit library, does anyone know any reference code about that matter. or any way to do it. The hardware I using is HC-05 and arduino iDE.


texts:
It's been many years since I looked at hardware.  I want to build a circuit; a 16 pin GPIO that switches a 5V Coil, 6A relay to switch a 6A, 15V Peltier.  So working from the Peltier, I found a relay that can switch it on, I hopefully (power supplied using PC Power supply) - If not, then I'll need to fix this before going on.

Now my question is, can the GPIO chip switch the relay?

What I could find in the datasheet is that the GPIO output current on a pin is 25mA (Page 27 of 16 pin GPIO) and the relay requires 1A? (Page 1 of 5V Coil, 6A relay) - or is it 6A?


texts: Kirchhoff Voltage Law in a two port network

texts:
In a tutorial about h parameters of a two port network, I find the below snippet in the image unable to grasp. According to KVL, the total voltage in a loop is the algebraic sum of the individual voltages. But why in this tutorial ( equation 1 in below image ) it's given so. It should be something like V1 = h11 I1 + V2 according to KVL. What is this h12 V2 mean?

The whole tutorial is here.
https://www.electrical4u.com/hybrid-parameters-or-h-parameters/


texts:
In The Art of Electronics 2nd Ed. it is said that:

The Ebers-Moll equation is $$I \approx I_s(T) e^{\frac{V}{25 \, mV}}$$ and the change of voltage with temperature at constant current is

$$\left. \frac{d V}{d T} \right|_I = -2.1 \frac{mV}{K}$$

The way the authors calculate relative changes in the current is

$$\frac{\Delta I}{I} = e^{\frac{- \left. \frac{d V}{d T} \right|_I \Delta T}{25 \, mV}}$$

which indeed they use to state that a for \$\Delta T = 30 \, K\$ you get a factor of \$\approx 10\$ increase in the current.

Is there a valid reason for this or just a mistake in the book?

At first this does not make sense to me, since they are using a coefficient that was found assuming constant current in order to calculate the change in current!

EDIT:

In short, from the definition of \$\left. \frac{d V}{d T} \right|_I\$ I think the right calculation is

$$ \frac{I_s(T + \Delta T)}{I_s(
T)} e^{\frac{\left. \frac{d V}{d T} \right|_I \Delta T}{25 \, mV}} - 1 = \frac{\Delta I}{I} =  0$$

This would mean that they are actually calculating the change in saturation current:

$$ \frac{I_s(T + \Delta T)}{I_s(
T)} = e^{\frac{- \left. \frac{d V}{d T} \right|_I \Delta T}{25 \, mV}} $$

Right?


texts: How to design a contactless mechanical shaker

texts:
I am trying to design a circuit to make an inductor oscillate with high-current (around 50A) at a low frequency. The inductor will act as a high-powered electromagnet.

Most designs I've worked/messed with for oscillators were used for higher frequencies, in MHz or KHz, like the Hartley or Colpitts oscillators. But I only want the inductor to resonate at 80Hz.

Edit: To be more specific, what would be the "best" (simplest, cheapest, more efficient, any combination of thereof) way to drive an inductor (1-10mH, this is the kind of coil I work out to obtain the electromagnetic forces required for my application) with a 80 Hz periodic signal (doesn't have to be sine, square would be better) and high current.

Mechanical shakers are what we have used in the past for this. However, here I need to shake an object inside a closed vessel without moving the vessel itself, only the "shaker" therein, which would be a permanent magnet. The vessel has to be non-moving so that it can be connected to rigid fittings, so fluids can be pumped in and out of it. And the fluid system can have no penetration to the outside, because no contamination must occur (biomedical application). Thus, the force must be applied at a distance with no direct contact, which is why I am looking at electromagnetism.


texts: What is this component? 1970s electronics

texts:
I broke it while trying to repair a nearby component on a 1970s board. It has two wires at one end that look like they are going to a coil and two axial wires. One of the axial wires came out with some pieces of glass.
The only markings are "P/F" which mostly likely means Philco/Ford.
The "silkscreen" was marked with "S1" and nothing else.
The end with the two coil wires is angled at 45 degrees I presume to indicate polarity.
I also need a way of working out what value it is so I can get a modern replacement.
Thanks!


texts:
I recently soldered a number of white LEDs to a PCB using a Weller "standard" soldering station. I noticed some LEDs were glowing slightly during soldering. The PCB was placed on an ESD mat, but I doubt that this had an influence. Is that a thermal or electrical effect?

I suspect the former, because I am quite sure the metal iron tip is grounded.


texts:
We have started to incorporate the IPC7351B standard in our design. We use mils for our layouts.
For Example consider part RC0603JR-070RL.

As per IPC7351B,

In mm

RESC1607X60N

and in mils

RESC62992799X23622N

Am I doing it right?

Should we transit from mils to mm?


texts: What is the capacitor charging time when charged with a pnp current mirror circuit?

texts:
I want to use a 555 in monostable mode to make a ramp signal generator. The capacitor would be charged using a current mirror circuit.

Given a input voltage, what would be the charging time of capacitor?

My understanding is: \$ \dfrac{V}{V-V_{EB}} \cdot R \cdot C \$

where \$ V_{EB} \$ is 0.545V and constant.

I am using a circuit from here:


texts: What will be the value of saturation current in this series NMOS/PMOS circuit?

texts:
It's only a theoretical question; no particular circuit needed.

Some backstory: Suppose there are, say, two NMOS transistors with different W/L ratios in series. Further, suppose that both of them have their gate voltages equal, and their corresponding drain and source voltages. Neglect body and channel length modulation effects. Assume both are in saturation voltages.

The current in first NMOS: Id1= (W1/L1)* kn' *(Vgs - Vt)^2

The current in second NMOS: Id2= (W2/L2)* kn' * (Vgs - Vt)^2

All the terms in both the equations are equal except the W/L ratios.

My Question: When individually calculated, the drain currents of both the transistors are different. More specifically, the drain current is higher in the transistor with higher W/L ratio, and smaller in the other one. But, when both of them are in series, what would be the actual/total drain current in the circuit? Will the current be equal to Id1 or Id2 or something else?

I'm still posting a link of a random figure(ignore the PMOS circuit) for a better idea:
http://ece-research.unm.edu/jimp/vlsi/misc/IMG00002.GIF


texts: Historical Addressing Modes/Conditions that Complicate Page Fault Handling

texts:
I was reading this linked question and the following paragraphs stood out to me:

  For example x86 and 68000 had instructions which access memory two or more times. Each memory access could cause a page fault. Hence the CPU must either roll-back the incomplete instruction and save enough state to re-run the instruction from the start, or save enough state to pick up and continue the incomplete instruction. In either case, that might be millions or even billions of instructions later, with other instructions in between also suffering page faults.

  ...So 'incomplete instruction exceptions' save different state on the stack, and hence have to be handled differently for normal interrupts.

Today, CPU architectures except for x86 by and large don't permit multiple memory accesses per instruction. That said, I am wondering historically what addressing modes, and CPU state (such as a page fault in the middle of an instruction) would require special state to be saved to restore processor state? Additionally, what CPU state would conceptually need to be saved?

For the remainder of this question, assume I have a CPU that restarts an instruction on page fault (x86), and one that stops in the middle of an instruction on page fault (68k).

Also assume these CPUs are is a in-order CISC-like; they allow both src and dst to be memory operands for MOVing data and arithmetic operations can access memory directly. This creates an ISA where insns can have multiple memory accesses. Additionally, ignore complications caused by pipelining. I'll ask about x86's edge cases, as alluded to, as a separate question.

I can think of only two badly-behaved historical addressing modes offhand- pre decrement and post-increment. Additionally, an instruction that spans a page boundary can cause issues.

Pre-decrement/Post-increment

On a "restart on page fault" CPU, state for a faulting pre-decrement would need to be able to revert the dec/incremented register, regardless of why the instruction faulted (span page boundary or page fault on access); decrement would occur before any memory access, but increment will occur between memory access on MOV.

Instruction spans pages

On "restart on page fault" CPU, an instruction may have started already while
waiting for the remaining instruction bytes. So the instruction boundary needs
to be known to refetch (as well as state to revert side effects of the insn's addressing
mode) after the page fault handler runs.

AFAICT, the only state that needs to be saved on a CPU that "stops in the middle of an insn on a fault" is "how far the instruction proceeded" before the fault, and continue from that point, regardless of fault reason. Registers need need not be reverted, and I don't even think the "fault reason" needs to be saved.

Is my explanation/understanding accurate? Are there any other CPU state and addressing modes (plus their combinations) that I should consider?


texts: need for decoupling capacitor in a Fender Bassman

texts:
why is there no need for a decoupling capacitor in the second preamp stage (highlighted section)?
I would imagine a 0.02-400V capacitor just before the grid of the second half of the valve to block high DC voltage from reaching the grid


texts:
When t<0
Components in circuit are Jt = 3 A, R1 = R2 = 2 Ω, R3 = 4 Ω ja L = 10 H

At t=0 switch K will be closed and i need to figure out what iL(t) is when t=4

So i tried to figure out iL(t) with  differential equation.
First i combined R1 and R2 to get R12=1Ω
Then i transformed power supply from current to voltage Et=Jt*R12=3A*1Ω =3V
Then i combined R12 and R3 to get Rz=5Ω
Now i can create equation which is
$$E_t=L*\frac{di_L(t)}{dt}+R_ti(t)          $$
After adding constant i can start solving equation
$$10*\frac{di_L(t)}{dt}+5i_L(t)=3          $$
$$           u(t)=e^{\int5dt}=e^{5t}    $$
$$           e^{5t}* \frac{di_L(t)}{dt}+ e^{5t}*i_L(t)=e^{5t}*3 $$
$$           \frac{di}{dt}(e^{5t}*i_L(t))=3e^{5t} $$
Then for integral in both sides
$$           u=5t $$
$$           \frac{du}{5}=dt $$
$$           e^{5t}*i_L(t)=\frac{3}{5}e^{5t} +C$$
Then divide in both sides
$$           i_L(t)=\frac{3}{5}+ C*e^{-5t}$$
Now i need to figure out what is iL(0) so that i can get C, but i don't know how.


texts: Using PID relay to drive multiple contactors

texts:
I am a physicist by training but have been tasked with designing a heating controller box for a custom application that will be used in an industrial setting. I would like to make sure that I am following best practices before I follow through on assembling the control panel.

I want to simultaneously drive up to 4x 3 phase - 480v - 3kW heaters (configured as a 3-Wire delta) using an on-off cycle rather than actual PID to save switching lifetime and complexity. Based on my calculations the per phase load of each heater should be about 3.7A. I was planning to use contactors to switch each phase and I wanted to make sure that it would be kosher to drive all 4 contactor relays in parallel from the AC Relay output of my selected temperature controller.

The controller SL4848-RR is rated for 5A AC (240v) output and the contactors WDP25-3L-230 have a typical input power of 10VA@230V and inrush of ~50VA. This would put the peak power draw at <250 VA Peak to run the controller and and contactors off of my control transformer PH350MQMJ which is rated for 350VA at 240V. If I place the coils of the contactors in parallel I expect the total resistance to drop by a factor of 4 and the current to be shared equally across the coils of each contactor at the  peak current of 200VA and running current of 40VA. Is this naive to assume? Should I explore a different configuration? I also assumed I don't need a flyback diode because the coils are AC driven, but this may also need to be revised.

For extra context:

I have selected 20A FAZ-B20-3 input breakers for each phase input and I will be placing  supplementary breakers FAZ-B6-3 on the high side of each contactor with a per phase rating of 6A (3.7A/80% for thermal overhead and derating for worst case T of 50C). All breakers were selected with B type curves as these loads are 100% resistive. The control transformer will be powered on two of the input lines.

TIA and don't hesitate to ask for more information.


texts:
I have some basic LEDs and recently purchased some 4MHz Quartz Oscillators and since they haven't arrived yet, I was wondering what would happen if I hooked up the crystals straight to an LED in DC?

My guess is it may explode from being continuously pulsed 4 million times a second but then hooking it straight into the power is infinitely faster as there is no delay and they don't explode.

If it does explode, is there any kind of key or calculation you can perform as to obtain how many oscillations are required to fry specific components?


texts: How to test a power adapter (wall wart) safely?

texts:
I need to evaluate the build quality of 3rd party 120V AC -> DC 5v 1a wall wart type switch mode power supply/adapter. The supply is supposed to have over current and short circuit protections as well.

My question is how do I safely test all the specs are working as advertised?

I'm self taught w.r.t electrical engineering so I guess I'm looking for a sanity check on my approach.

My first test will be to hook the supply up to an adjustable current load so that I may check the voltage ripple (if any) with my oscilloscope. Nerve level on this test: 0 out of 10
Second, I will up the current load and see what happens approaching and above 1a. I will monitor the temperature of the supply while I do this. Nerve level on this test: 3 out of 10
Third, I want to test the short circuit protection, but just shorting the supply output to ground sets off warning flags in my brain. Nerve level 10 out of 10

Is there a safe way to test short circuit protection without damaging my equipment? Or, should I just plan for it to either a) work or b) fail catastrophically?

Thanks,


texts: What actually happens when we set direction on GPIOs in controllers ?

texts:
Generally, while working on GPIO pins of any controller/device, we set the directions for the GPIO pins. Let's say in LPC2148(ARM7 core) controller, we have IODIR to configure the direction of Pin. We set the IODIR for output and clear for input.

IODIR0 |= (1 << 26); //output
IODIR0&= ~(1 << 10); //input

How setting/clearing the pin makes it as output/input. I think it is due to pull-up and pull-down transistors but I couldn't conclude a specific reason.

And another question, Is configuration of the direction of IO varies depending on the architecture/CPU we use?


texts: Consequences of misalignment connection that grounded power supplies

texts:
Having the following mezzanine expansion connector

and the related +VSYS_IN part of the schematic

What would be the consequences of a misaligned connection that shorted both +5V and +VSYS_IN to GND in case the diode D18 was not mounted? And if it is mounted ?

Note: I'm trying to understand the implications of the situation described in the following post. The diode was placed in the following revision of the board but it is not clear to me what was the intent and how it can solve the misalignment problem.


texts: FTDI disappears when powering circuit with it.

texts: I'm trying to us the ESP8266 wifi board and when I power it over the 3.3v out on the FTDI the entire usb disappears from ubuntu. as soon as I take the power away it shows back up again. What could cause the /dev/ttyUSB to disappear when using the power from the FTDI?


texts:
Hello and thanks for taking your time to help.

On the picture below you can see the 40244 that I have issues with.
While it is clear to me what most symbols mean, I am confused about the "20".Some insight on it would be great. (hopefully it is not just number of pins...)

EDIT: looking more at it, it looks more like an "O" than a "0"

EDIT2: So far it seems to me, that its meaning is that 2 Pins/Inputs are responsible for each Output (2 O(utput))

Final EDIT: Thanks for @Finbarr ´s Answer, makes the most sense to me.


texts:
I'm having issues calculating the power losses associated with the operation of a bidirectional isolated Dual Active Bridge DC/DC converter. The converter is controlled using Phase Shift Modulation (PSM). The converter is shown below. There are 4 "switches" on each bridge (switch here meaning a parallel combination of MOSFET, anti-parallel diode and capacitor).

The switching cycle can be broken into 4 main intervals, not accounting for transitions between these intervals. During each of these 4 intervals, two MOSFET on each of the bridges conduct. During the transitions between intervals, certain capacitors and diodes also conduct. In order to illustrate the logic behind this, the following diagrams and tables are provided. N.B. The circuit diagrams are incomplete, however, the remaining circuits which have been omitted follow the same trend indicated by the diagrams given.

Switching Cycle Circuit Diagrams:

Current and Voltage During Intervals:

Okay, so my goal is to calculate the power losses in the converter during a switching cycle. I am aiming for my total losses figure to include core losses, conduction losses of diodes and MOSFET and switching losses. In relation to switching, Zero Voltage Switching can occur under certain conditions, in which case the switching losses for the switching question will be given as zero.

Now for my question:

The plot of current and voltages above only shows periods where the MOSFET are conducting. In this ideal case, I understand that conduction loss would simply be the square of the RMS current by the resistance of the MOSFET in question. However, my issue relates to the period of time for which the diodes and capacitors conduct during the transition period between intervals. In order to calculate the conduction losses in the diodes, I will need to identify this time period.

Can somebody explain how to calculate the losses in the devices during these transient periods?


texts: Is it possible to de-cap a ceramic capacitor

texts: Would it be possible to remove the case from a ceramic capacitor ? Like the ones surrounding the IC in this picture?


texts: Smoothing capacitor for scooter regulator - High constant current drawn

texts:
I've researched the forum before posting, but it seems my question is a bit specific and not answered before. Please excuse me if I'm wrong.

So what we have here is a chinese scooter alternator, which gives 70W max. The alternator is a half wave stator, half of the power is converted to DC through a regulator to charge the battery, the other half is also regulated by an extra regulator I put there and drives a 45W LED headlight. So far so good. But the problem is LED flickering due to the nature of the regulator/rectifier.

So I'm trying to decide what smoothing capacitor to add after the regulator. I noticed by trial and error that the flickering stops completely after I put a 10000uF electrolytic cap in there. I also after that, calculated that a minimum 4700uF cap is needed for an approximately 5% ripple voltage, for the current drawn (2V ripple at around 14VDC).

But the main problem, which I think everyone misses (or I am wrong and I'm trying to figure which of the two stands here) is the CONSTANT current draw (Irms) for the smoothing capacitor, in order to maintain a smooth output.

I've run a simulation with a full bridge rectifier and it seems a 10000uF, if inrush current is left out, it draws a constant current Irms of around 9A!!!!

So, unless I'm missing something here, the alternator which can only give 70W max (so 5.8A at 12V), will be constantly overloaded and eventually will burn out.

Of course half wave stator will give half of the power and the available power will be half of 70W, but I have no problem with that, I can fix it to run full wave by removing the center tap. My problem is the constant current drawn from the smoothing cap.

Could anyone please help me on that and tell me if my calculations/simulation are wrong or if indeed that is the case here? And if it is so, what could I do in that case?

Thank you all very much in advance!


texts: how to select an LDO regulator to get 3.3 v 200 mA of output from 5v and 250 mA of Input?

texts:
I would like to power my stm32 microcontroller the supply voltage is 3.3v and 160 mA of current. So i would like to regulate my buck controller output of 5v to 3.3v to power my microcontroller.

My input to LDO regulator:

input voltage : 5v

input current : 250 mA

Expected output:

output voltage : 3.3v

output current : 200 mA ( to power my STM32 microcontroller)

Iam planning to use Texas instrument TPS730 LDO regulator to get 3.3 v as output.

TPS730 power consuption:

(Vin-Vout) *Iout = (5v-3.3v)*200 mA = 0.34 W

In datasheet Maximum junction temperature is given as 150 degree C and Rthja as 225.1 degree C/W

so 225.1 *0.34 = 76.54 (degree C) + 25 (room temperature) = 101.54 degree C

so i think it is safe to use based on Power consuption. if iam wrong correct me whether it is safe or not.

My doubts:

i need an out put voltage of 3.3v and 200 mA of current but in datasheet it is given like

What does this means . only if my output voltage is 5v then only i can able to get 200 mA as output current.If it is like this i cannot use this regulator because the maximum output voltage i need is 3.3 v so can i able to get 200 mA of output current with 3.3 v of output voltage if my understanding is wrong please correct me.
or can i able to get 200 mA of current by having 3.3 v as output voltgae

and What does this means i am confused.Is it telling like only if my input voltage is 5.5 v then only i can able to get 200 mA. if it is like this i cant use this regulator because my input voltage is 5v .Is it like that or can i use this regulator with 5v of input to get 200 mA of output

Iam really confused after a large number of search i am asking this question in stack. Can i able to use this regulator by having 5v as input and i need 3.3 v output voltage and 200 mA of output current.

Please find the Datasheet of Texas instruments TPS730 enter link description here

In the above datasheet in Page 13 it has given the adjustable output voltage .

Basically can I use this regulator based on my specifications ,If no is there any regulator based on my specs with decent power consuption.


texts: Why does water short out PCBs? (i.e. Why doesn't electricity follow the path of least resistance?)

texts:
If copper is more conductive than water (at any reasonable PH), submerging copper electronic circuits in should have no effect, as the electricity should continue to follow the path of least resistance (the highly conductive copper PCB paths, for example) rather than shorting into the mildly conductive water.  However, dumping water on electronics clearly shorts them out, even though copper is the superior conductor.

Why does this occur when the path of least resistance should be the copper rather than the water?


texts: Does a BJT controlled relay need protection diodes?

texts:
I am fairly new to electronics, so please pardon my mistakes.

I am attempting to build a Wi-Fi controlled relay. The problem, however, is that the relay runs on 5 V, but my ESP-12E can only supply 3.3 V. I figured to connect the (+) end of the relay to the VCC (5 V input) and then the GND end to a transistor which also connects to ground. The base of the transistor is connected to my ESP-12E's 3.3 V GPIO output. Here is what my circuit looks like:


texts: Which one is more damaging? overvoltage or undervoltage?

texts:
It is not easy to get the exact supply voltage required by loads. The supply is usually either a little bit higher or lower than desired.

It is known that both over & under voltage can potentially damage the device. I was working on supplying 120 V 15 LED fixtures. I had the voltage drop calculations and here I was thinking what if for any reason the voltage drops below 120, or if the voltage gets higher than 120 V, then I thought that the design should be based on avoiding the worst case scenario. If one of them was the worst, then I should add/subtract marginally in the calculations.

So, which one can be more damaging than the other? overvoltage or undervoltage?

Note that the question is applicable to be general although my intention is to ask on long-term design need basis but not on what could happen outside the circuit on short-term (for example, spikes or transients in voltage supply).


texts:
I found several related answers to my question but none of them seem to clarify my case. I followed this answer and this one, but still getting warnings and when synth/impl. Here's the conceptual block design:

here's what I put in the .sdc file:

create_clock -name {external_100mhz} -period 10.000000 -waveform {0.000000 5.000000} CLK_100MHZ
create_clock -name {external_12mhz} -period 83.333333 -waveform {0.000000 41.666666} CLK_12MHZ

create_generated_clock -name the_100 -divide_by 1 -source [get_pins {BLOCK.CLKA}] [get_pins {BLOCK.ClockGen.GLA}]
create_generated_clock -name the_20  -divide_by 5 -source [get_pins {BLOCK.CLKA}] [get_pins {BLOCK.ClockGen.GLB}]

and here are the warnings:

@W: MT530 |Found inferred clock ClockGen|GLB_inferred_clock which controls 169 sequential elements including BLOCK.Module.REG_DATAo[7:0]. This clock has no specified timing constraint which may adversely impact design performance.
@W: MT420 |Found inferred clock ClockGen|GLB_inferred_clock with period 10.00ns. Please declare a user-defined clock on object "n:BLOCK.ClockGen_0.GLB"
@W: MT548 |Source for clock the_100 not found in netlist. Run the constraint checker to verify if constraints are applied correctly.
@W: MT548 |Source for clock the_20 not found in netlist. Run the constraint checker to verify if constraints are applied correctly.

I feel like I am close to get the syntax correct. Please, help clarifying it.
I see [get pins] and [get ports] - when should be used which?
Also the answers mentioned above use / and | when specifying source. Which one should be used when?
In this answer they also put constraints on the synchronous/asynchronous aspects. In my case the external input clocks (100MHz and 12MHz) come from different oscillators, also, the GLA and GLB signal clocks are derived from the ClockGen CCC, so they are probably synchronous. Should I include the following constrains as well? Although, the external_100mhz and the_100 may be the same clock?

set_clock_groups -asynchronous -group external_100mhz -group external_12mhz -group {the_100 the_20}


texts: High resistance between control ground and power ground of a gate driver IC in high-side configuration

texts:
I am working with a circuit configuration where a gate driver IC (ISO5852S) is used as a high-side gate driver and the bias supplies of this IC is coming from three isolated DC-DC converters. I intend to use this gate driver for high voltage (close to 10 kV). However, the gate driver IC is rated for maximum 5.7 kV. Hence, isolated DC-DC converters for bias supplies and optical fiber for PWM signal isolation are being used.
That said, whenever voltage level of the DC supply reaches close to 5.5 -6 kV, the gate driver becomes faulty. I am suspecting that the control/input side ground of the gate driver IC being in a floating state is causing the problem.
Any suggestion to solve this problem will be highly appreciated.
Is it practical to use a large valued resistor in between the control and power ground of the gate driver IC and another same valued resistor between the control ground and the input ground of the DC-DC converter so that the control ground has a specific reference voltage?
Thanks in advance.


texts:
simulate this circuit – Schematic created using CircuitLab
Hello,
I would drive a machine to pilot its ON/OFF status.
So in idea it should be OK but is it?
What requires attention or this is an error in concept?
Regards


texts:
Good morning

Could somebody please explain the operation of the attached diagram to me?

The circuit was proposed here and here as a low voltage cut-off circuit, which switches off the MOSFET when the voltage drops below the reference voltage set by the voltage divider.

What I don't understand is how the TL431 keeps the MOSFET on when the input voltage is above the reference voltage? And also how the MOSFET is switched off when the voltage drops below the preset voltage? Also, will the value of the set cut-off voltage influence the working of the circuit (e.g. can the reference voltage be set too low to be able to switch off the MOSFET)?

I read through the datasheet, but it didn't help me understand this phenomenon. It did help me to choose my resistor values, though.


texts: Understanding connector footprint on PCB

texts:
I wish to make a footprint for Amphenol GSB343K33HR connector that I am using on my PCB. I am however having difficulty in understanding the PCB layout that has been mentioned by the manufacturer in his drawing. The drawing is present at the following location: http://media.digikey.com/pdf/Data%20Sheets/Amphenol%20PDFs/GSB343K33HR_dwg.pdf

The rest seems fine to me but I am unable to understand what the oblong parts on the layout edges are. Are they through-hole or SMD pads? Also what would be the X- and Y- widths of the oblong parts. The '2-0.50' is not clear to me.


texts: What operating systems have been ported to Cortex-M3?

texts:
I am working with an ARM Cortex M3 (specifically STM32F217IGH6).

Are there any OS that have been ported to it?


texts: How to choose UART maximum output speed?

texts:
When I open up a project in STM32CubeMX and configure a UART, there's a Maximum output speed configuration (under GPIO Settings) that defaults to Very High. The options are:

Low
Medium
High
Very High

In STM32CubeMX User Manual it says the following about Maximum output speed:

  GPIO maximum output speed (for communication peripherals only)
  It is set to Low by default for power consumption optimization and can be changed to a higher frequency to fit application requirements.

But it's actually set to "Low" only for regular Output GPIOs. For UART TX/RX pins it's actually set to Very High.

I have a few questions regarding this:

What "application requirements" would require a higher setting?
Why does this settings default to Very High in UART, and Low in Output GPIO?
Most importantly, can 2 UARTs with different Maximum Output Speeds talk (communicate), or should they be configured the same? What implications would occur if the UART of each side was configured differently regarding this setting?


texts:
I am used to work with PICs, but I want to start using AVRs as well. One thing I like in the PICs is the EPWM (enhanced PWM) peripheral, in which you just set a couple of registers, and the PIC will generate all the control signals for a H-Bridge, or Half-Bridge control, including dead-time and push-pull signals.

I want to know if there is something like this in the Atmel MCUs, and it's name, so I might find it on the datasheet and select the proper MCU for my projects.


texts: How to choose an Electronic Speed controller?

texts: I'm having a go at making my self a quad-copter and was wondering how one would go about choosing an ESC?. I've chosen this motor and this ESC, Is the ESC suitable for that motor?


texts: Atmega Standalone, Running without crystal oscillator

texts:
I plan to run the atmega328p without external oscillator like in this tutorial:

http://www.instructables.com/id/Atmega-Standalone-Running-without-crystal-oscillat/?ALLSTEPS

Some guy here saying:

"The internal oscillator does lead to inaccuracies but I2C is one of those protocols that does not require a synchronized clock with the device it's interfacing with, so no I2C will not be adversely effected by the internal oscillator. The protocol that does require a higher level of accuracy is UART or 'Serial'. Without getting into too much details the faster your baudrate of your UART the more likely there is to be errors. So if you are going to use a UART with the internal oscillator just try out a baudrate like 115200 and see if there is garbage outputting to the Serial Monitor if so reduce the baudrate to 57600. I've personally seen garbage come out on 115200 but that was not consistent. It's probably because the oscillator is temperature dependant."

Could using the internal oscillator cause a problem with wireless communication with 433MHZ RF transmitter using the VirtualWire library?

Thanks


texts: crystalline structure of single crystal wafers used for MEMS fabrication

texts: When they say that we have a {1 0 0} single crystal wafer, I know that the surface normal to the wafer is oriented in the <1 0 0> family direction, but if I draw a line on the wafer, parallel to my primary flat, does it indicate a crystallographic direction family too? Like <1 0 0> or <1 0 1>. I mean it's obvious that it cannot be <1 1 1> due to the FCC lattice of Si(I am making the assumption that the thin plane of the primary flat is at exact right angles to the wafer surface, if that angle is allowed to be 54 degrees, it can also be a <1 1 1> ), but it can surely be directed at none of the crystallographic directions at all, so the question is, if I draw a line on the wafer surface parallel to the primary flat, will it be directed towards the <1 0 0> or the <1 0 1> family, or does the manufacturing process just slice an arbitrary flat out of the Si ingot before slicing it into wafers?


texts: Impedance Matching and Large Trace Widths

texts:
I am currently working on a design in which one of my ICs specifies the use of a 50 ohm trace. The answer to this question, Characteristic impedance of a trace, shows that a 120 mil trace is required to get this impedance.

The IC only has room for 18.8 mil traces, and that is assuming no space between traces. So, how can I actually design with that trace impedance kept in mind? Obviously I can decrease the board thickness or increase the copper height, but only to some extent and I would like this to be fabricated for somewhat cheap. How is this usually dealt with?

The IC that I am using is the MAX9382 which can operate up to 450 MHz, I will probably be using it around 400-450 MHz. The data that is being used is initially analog, but has to be hard limited to become digital in order to be used with that IC.


texts: Can I connect a capacitor in parallels to power supply of a router

texts:
In the building where I live, because of older wiring, the mains voltage frequently drops for a fraction of a second and this restarts my wifi router. I am planning to solder a capacitor in parallel to either input or output of the 9V power supply.

Would this work, and would it cause any problems?


texts:
I am working on triggering LEDs from a camera for a unique exposure process.  Each exposure is roughly 15ms. Essentially, I get a high signal from the camera for the duration of the exposure, and during this time I need to have the LED on to light the target.  The confusing part for me is that I need to turn on 4 different LEDs in succession.  Let's call them A,B,C, and D.  My initial thought was to use a decade counter (4017) and just have four outputs correspond to LEDs A,B,C, and D.  The problem with that is the exposure signal goes high for each exposure, rather than one for the duration of all four LEDs.  I then thought to use the exposure signal as an enable for the 4017, but I figured it would also be problematic.

I made a crude diagram of how it works.

I am leaning towards using an Arduino to handle the switching, but is there a circuit that can switch outputs given my situation?


texts: What is a good power electronics textbook?

texts:
I really want to learn as much as I can about power electronics, switching mode power supplies, and overall analog design.  Unfortunately my universities computer engineering program is still relatively new and does not have these specific courses.

I have looked over the ones on amazon but I really just feel like I can't trust the review there.

If I may pull from the large amount of experience here, what would be a good power supply text book to learn these fundamentals?


texts: Intuitive explanation for this hysteresis circuit?

texts:
simulate this circuit – Schematic created using CircuitLab

I am trying to get an intuitive understanding of this small circuit.
I have both breadboarded it to look at behavior on a scope and simulated
it on LTSPice, and it does display a clear hysteresis (see LTSpice
generated V-I curve below).

What is less clear is why. I have a very hard time understanding this
circuit intuitively.

First question : when the voltage at the emitter of Q1 rises, it reaches
a level around 1.02Volt where everything seems to abruptly open wide. But
then, as voltage rises, the intensity rises with it, in an almost linear
fashion. I was expecting the whole thing to behave more like a diode and
open very wide very abruptly, but its behavior once open resembles more
that of a resistor.

Not sure why. I suspect R1 is some sort of feedback loop, but an explanation
on the resistor-like behavior would be very welcome.

Second question: where does the hysteresis really come from ? As voltage
generated by the triangle voltage source goes back down, why doesn't the whole
thing turn off again exactly where it turned on ? What is is that is asymmetric
in these two BJTs (I assume the "seed" of the asymmetricity is not in R1) that
makes this thing finally turn off at a much lower voltage that it turned on at ?

Thanks in advance for pointers to help me understand !


texts: Periodic timer (64Hz) with ARM processor and (embedded) Linux

texts:
I want to call a function 64 times per second with a ARM processor which is running linux.
(ex: Rasberry Pi or Freescale i.mx6).

Ideally, I don't want too much jitter. I want to perform a task periodically... (ie: scanning a device)

If possible, I would like a hardware interrupt called 64 times per second.

With "standard PC hardware (x86)", it was possible to use IRQ8 from the RTC (clock) to achieve that behavior.

What is the equivalent with ARM processor architecture?

Reference 1, See section "Old "RTC Class" Drivers"

Reference 2


texts:
I am designing the JTAG for a Altera Cyclone 3 (EP3C5E144C8N). I was only aiming at normal JTAG, and do not need Active Serial. I have attached the schematic and board in the *.zip file (http://www.mediafire.com/?0gt55eyperbm385)

Or just a snapshot here:

Would you please having a look for me?

I have some doubts:

Should I connect  nCE of JTAG directly in to nCE of the FPGA, or nCE from FPGA is connected to ground?
About the clock: I see that there are 16 clocks (clk0 t clk15). To which clock I should connect the output from oscillator to?
In my board, I only use 3.3V (the label VCC means 3.3V). Is that ok?
By the way, would you please showing me how to add a flashing LED to indicate the JTAG is working?


texts: Matching solar panel to charging controller

texts:
I hope its not a silly question but ill ask any way :)
I would like to connect a 9v solar panel to charging controller. The input range according to it's data sheet is 7.5v to 28v.
The output of the solar panel can vary and its value can get to lower than 7.5.
I noticed that most of the charging controllers has input range so the minimum value is not that small (I saw also 4.5).
I guess that on voltage under 7.5 it will stop charging, isn't it inefficient? I mean I can be sure that the output voltage of the solar panel will drop under 7.5v during the day...
Am I right or am I missing something?
Thanks
EDIT:
This is the 9v\460mA solar panel I though about
This is the controller was suggested here by @Marko Buršič (input range- 5v to 28v)


texts: Why does this RL circuit gives out wrong results when a square wave generator is applied across it?

texts:
The circuit below is an RL circuit with a square wave generator created in falstad website.

http://www.falstad.com/circuit/circuitjs.html?cct=$+1+0.000005+14.235633750745258+47+5+50%0Av+176+256+176+80+0+2+50+10+0+0+0.5%0Ar+176+80+336+80+0+180%0Aw+176+256+336+256+0%0Al+336+80+336+256+0+2+0.02086883215129382%0Ao+1+64+0+4099+10+0.05+0+2+1+3%0Ao+3+64+0+4099+20+0.05+1+2+3+3%0A

I am using a 50Hz, 240V square wave generator , a resistor of 180 Ohms, an inductor with 2H

1) Why the voltage across the resistor is sawtooth shaped ?, it must be a square wave since the voltage across a resistor can change instantaneously.

2) I am not surprised to see a square wave shaped voltage across the inductor, but why is it not flat all the way? Why is it decreasing as the current rises?


texts: 60Hz to 50Hz frequency transformer/inverter?

texts:
I need to transform the frequency from 60Hz (220V) to 50Hz (220 or 230V). Alternatively I can use 110V 60Hz for the required output. I'm looking to find cost and space effective solution, it is for build-in coffee machine and build-in microwave appliances bought in Europe (max. 1kW each, can be always used separately). What would do this do the job?

I've seen normal transformers just change the current 110/220V and vice versa, but leave the frequency the same. Since I already have 220V power supply I just need to change the frequency, what appears to be not that easy. I also thought if there would be anything in the appliances inside that would be cheaper to change, but probably that's not the case since these models would not have their US counterparts, although both are Whirlpool.
(the biggest problem is the micro, since the coffee machine works, but is a bit 'slower' than it should...)

Can please anyone help?


texts:
I have heatgeneration rate in W/m3 and I wanted to know how much temperature it can generate. The heatgeneration element is Platinum resistor for MEMS project. I want to know numerical relation?

Thank you in advance.


texts:
i have a read out ic of optical front end which gives out digital pulse(0-3.3V) of width 10ns to 150ns repeating at a rate of 1Hz-70KHz

i have to measure the pulse width, but it needed a high end setup(high end  FPGA like Arria from Altera costing 700$ ) which increases the cost a lot, so in order to go for low end pulse width measurement set up i.e. in my context a very low end FPGA(a cyclone-IV or V from altera costing 70$) which can run maximum at 100-200MHz clock , so i thought of expanding the pulse by a factor of 10

so my 10ns-150ns pulse would become 100ns-1.5us pulse, which makes me easy to measure the pulse width, by using a low end setup

but now my confusion is how to expand the pulse by a factor of 10 only ??? while i have in my previous project tried a comparator latches, which have a RC time to be programmed, but here the pulse width should not be made constant but should be replicated by a multiplication factor


texts: What is the usable area (for connectors) of a PCI Express card bracket?

texts:
I have a number of awkwardly shaped connectors that I need to cram into a single PCI Express slot metal bracket without any of them colliding with the host PC case's metalwork.  The connectors are a mixture of proprietary and standard.

My connectors will obviously need to be arranged so that they do not interfere with the PC case's metalwork so this means they they must fit within some sub-set area of the metal bracket (the red box).

Where can I find the official dimensions of the red box? (specifically the maximal area that I'm allowed to use while still being "compliant" with the physical spec of PCIe).

The specs that I have seen give details on the spatial relationship between the metal bracket and the add-in card PCB, but they do not seem to give details of the space that may be used for connectors to pass through.

PC cases vary so much from one brand to another (high-end versus low-end particularly) that I'm worried that if I don't get this right early on in the design then I'll have to re-spin all my PCBs and metalwork later on when someone finds a case that this device won't fit into.


texts: Transformerless stabilized power supply for isolation amp

texts:
I'm building a circuit similar to this: https://courses.cit.cornell.edu/ee476/FinalProjects/s2008/cj72_xg37/cj72_xg37/
(voltage and current sensing of a 230V line)

I'm using two HCPL-7520 isolation amps to separate the line voltage side from the low voltage side. The low voltage side will be powered from USB or an external wall-wart regulated down using a 7805, as this side will need considerable current (Arduino, etc.)

But, on the HV side, I only need a power supply to power the HV sides of the HCPL-7520's, each taking a maximum of 19 mA. So, I'm wondering, whether I can use a transformerless power supply to drive the HV side? Since the HV side also needs stable voltage, I'd use another 7805 on this side.

So, I need a transformerless power supply, stabilized with a 7805, and capable of outputting 40 mA.

What are the design considerations for such a power supply? What type circuit would you recommend? Does the 7805 consumes a significant power, which would mean that the transformerless supply would have to output more that 40 mA? The HV side of the circuit will be completely isolated from users, so there's no problem with the whole power supply circuit being considered live, as it is the case with all transformerless designs.

I'd also like to implement the circuit in a way, that the input connector could be connected either way (e.g. switching line and neutral on the input doesn't matter)


texts:
Can someone explain to me what means figure of merit in terms of an oscillator?

There is no explanation online related to this.


texts: Why can you simply short a line-level output to ground?

texts:
I've read that one of the ways to sum two line-level outputs into mono is to simply ignore the right channel and connect the left channel to the mono input.
In doing so, it has been said that you can (and should?) simply short the other right channel to ground.
Why does this not cause interference / heating effects? Is it really safe to do this? (of course there are probably better ways but this seems like a simple "quick and easy" way)


texts:
As a way to power-on/-off a circuit load, a MCU is used to drive a relay through two MOSFETs. The problem is, when the MCU GPIO output is measured 0-volt, the relay could stay connected.

Can anybody demonstrate how this could have possibly happened?

More details that may or may not be relevant to the problem:

This happens very rarely. We have not got enough chance to troubleshoot the issue.

Usually the process to operate the circuit is: MCU set GPIO 0; human switch the input off; the load circuit is changed; human switch the the input on; MCU set GPIO 1. When the input switch is turned off, the voltage will drain slowly as the schematic can show there are big decoupling capacitors.

We suspected that the relay is bad. Changing to another piece of relay only marginally changed the chance of running into the problem. Multiple boards are showing the same problem, thus it seems to rule out a damaged relay or MOSFET or any other single component.


texts: I have AC signal that varies from 50mV (pk-pk) to 420mV (pk-pk). I am trying to use a PGA (programmable gain amplifier) to amplifiy the signal so that it can be sent to the ADC in an ATmega328P. The signal sent to the ADC needs to be within 0-3.3V. I can't add a DC shift centred around 1.65V before passing it through the PGA, as this will also amplify the DC shift, which puts the signal outside the ADC range. How can I go about shifting the signal and amplifiying it using a PGA which is supplied from a single supply?


texts:
This is supposed to be a simple NAND gate.
I understand how the output is 1 if one of the inputs is zero
but if both inputs are 1 then the base of Q1 is supposed to be zero. This is what I don't understand. I know that Q2 and Q3 will be in cut off so the base of Q1 is floating. If that is true, how is it zero then?When A and B are open does current flow through Q2  Q3 via R1 to turn on Q1?


texts: Using the GPIOs of an STM32 Discovery board

texts:
I would like to start learning how to program an STM32, because of this I bought the STM32L152C Discovery board.

It's a very nice board, full of goodies, but I would like to use just part of them: for instance I don't want to use the LCD which uses a lot of GPIOs, but I want to use the integrated 32.768 kHz quartz to perform RTC funcionalities.

Is it possible to use the GPIOs without interfering with the internal goodies? I mean, if I use a GPIO pin which is also used by the LCD, can it be a problem?(for example draining to much current)

Greetings!


texts:
I am new to dsp and I want to try making my own effects for electric guitar. I ordered a Line6 Tonecore developper kit but I won't have it before summer. Since I also want to try other embedded devices, I found the Rasberry Pi and there is a sound card available for it. But I am wondering, is the "normal" input on sound cards, like the Rasberry Pi and PC ones, are ok for a guitar signal? I got an impedance converter for guitar but is that enough? I know that the tonecore pedal has a built in low pass filter, but it could probably be programmed manually if I don't have one on my device.

Is there anything special that makes a guitar input different from a standard input?


texts: Connecting Altera de2 to a sensor via UART

texts:
Is Nios II required when implementing UART core using the SOPC? (or a default Nios is included) I tried writing my own module for the uart connection but it didn't work out. I need a method to  connect a sensor to the de2, any method is fine. If you guys could give a clear method about how can this be implemented

This link gives an idea what could be done but its not that clear

I need a idea on how to go about it. With so many manuals and softwares available for the Altera..


texts: High Voltage Transformer - effect of increasing frequency

texts:
I have a 110 V to 15 kV transformer (60 Hz) which I'm using for high voltage experiments.

I need to increase the frequency of the input / output power to be in the kHz or MHz range. Can you tell me what would the effect be on the transformer? Would it burn out quickly or blow up?

Cheers


texts: Why does the power company provide a neutral line?

texts:
I understand that power is often transmitted in 3 phases (with no neutral). Then, when we get to a certain substation, the power company basically gives house 1, L1, house 2, L2, house 3 L3, and connects them all to a common neutral line. That is, each house gets one phase of power and a neutral shared between all 3 lines. Then, that neutral is grounded to earth at the substation.

It is also my understanding that in the main panel in my home the neutral is tied to ground. It seems to me, if we are going to do this, why do we need the neutral wire at all. In fact, in any system, if the power company actually grounds the neutral wire at the substation, why can't each individual house simply provide its own neutral (i.e. each house has a single phase and a metal pole or two out in the back in the ground that serves as a neutral (current carrying earth ground) and a ground (for safety)). It seems to me this would save the electric company from having to provide a neutral wire. My point is is that the neutral wire is earth grounded at the substation and in each home, so why is it even necessary to provide it?

In my setup, current would flow from the 1 wire coming into the home from the pole (single phase) and current would flow to an earth ground provided at each home. There is no reason for the power company to provide the neutral.

Can you fix my misconceptions please? I have read many posts and I get conflicting or contradictory information about this.


texts: Running 100 24v 1 amp solenoids with low amperage power supply

texts:
I am trying to run around 100 24v solenoids with a low amperage power supply. I originally thought when I began trying to run the solenoids I would go with a 100 amp power supply as each solenoid is about an amp. High 24v Power supplies are not only hard to come by but also usually very expensive and big.

Each solenoid is on frequently, never are they on at the same time, however I would like it to be possible to turn all on at the same time, in case me or anyone who is trying control my solenoids has full control over what they are doing and are not limited. I would say most of the time 70 of the solenoids are on. My question is, how low amperage power supply could I use? Thank you


texts: What cable do I need to connect rows of male header pins together

texts:
I have a Jaguar motor controller that has a set of 5 inset male header pins to connect an encoder. The encoder has only loose wires coming out.

What type of connector should I be buying to solder/crimp onto the end of these?

Also, there're a couple of sensor boards with a similar arrangement of 0.1" male headers. The control board also has male headers. However, every compatible cable I can find is male to female.

Do servo cables with sockets at both ends exist?

This is what the controller looks like. Encoder slot is on the front, as the freehand-circling below shows


texts:
I'm trying to control 24V solenoids using logic level inputs at 5V. The following circuit works when replacing both power loops with a single 9V battery, except that the voltage across the gate and source is not 0 as expected when the switch is closed.
When attached to the actual components with the correct voltages, the MOSFET always powers the drain, regardless of whether the switch is closed.
Can anyone tell me why the circuit works differently than in the simulation? How can I improve it?

https://www.circuitlab.com/circuit/p6ahpvb2fx5s/24v-output/
Edit: The load (solenoid) is represented by R8 in this schematic


texts: Connecting 12V fan and 3V LED to 9V batteries and drawing more power

texts: I tried to connect a 12V fan and a 3V LED to a 9V battery. But I did not get the required power for the fan. So I connected 2 batteries in series. When I connect the fan alone, it draws the required power. But when I connect the LED along with it, the fan turns slower than before. However, I would like to maintain the speed of the fan. This is for a project to make a unit that looks like fake flames. So I need the fan to maintain some good RPM so that the cloth that I will attach later flutters well and looks like a flame. I am new to this. Please help.


texts:
I can't get the same answer as they are getting..
Here is what I'm getting:

$$ Acc = \frac{V_{oc}}{v_{ic}} = \frac{-R\beta i_b}{v_{ic}} $$
$$ i_b = \frac{v_{ic}}{r_{\pi+2R_0}}   $$

=> $$ A_{cc} = \frac{-R\beta}{r_{\pi+2R_0}} $$


texts:
As far as I understood ATTINY85 doesn't support serial communication. I'm trying to understand how to do this via code.

Is is possible to specify BAUD rate or set some kind of communication speed rate and use a register like this to send a value?

 PINB0 = 0x63;

If not, then as far as I understood I have to use the low level approach, but I'm a bit confused how this really works.

As far as I understood, based on my ATTINY85 CPU speed and target BAUD rate, I need to calculate expected 'intervals' between each 'high' and 'low' I'm going to send out to simulate serial communication for the other device to understand. Correct?

[start identifier?] 0 [5ms] 1 [5ms] 1 [5ms] 0 [5ms] 0 [5ms] 0 [5ms] 0 [5ms] 1 [20ms]

Where can I find out more about the correct intervals and logic behind this? Thanks!


texts:
I realize a very similar question has been asked here, but I'm slightly confused about the derivation, specifically the quantities Lq and Rq which refer to the armature inductance and resistance. I'm using this transfer function to get the total loop gain of my BLDC closed-loop speed control system, so that I can model it and settle on some approximate PI coefficients using root-locus. The system uses trapezoidal control and gets speed measurements from hall sensors, feeding that speed measurement into a PI controller which updates a PWM duty cycle. So I need a gain that relates angular velocity to applied voltage:

Using this reference the transfer function is derived as follows:

$$V_{ab} = 2Ri + 2(L-M)\frac{di}{dt}+ (e_{a}-e_{b}) $$
since \$e_{a}=-e_{b}\$
$$ V_{ab} = 2Ri + 2(L-M)\frac{di}{dt}+ 2e_{a} $$
$$ V_{ab} = R_{a}i + L_{a}\frac{di}{dt}+ K_{e}w(s) $$

where \$K_{e}=\frac{2e_{a}}{w(s)}\$ is the line back EMF constant, \$R_{a}=2R \$ is the line resistance and \$L_{a}=2(L-M)\$ is the line inductance.

With \$i = \frac{T_{e}}{K_{t}}=\frac{\omega(s)B + J\omega(s)s}{K_{t}}\$
then the equation becomes: $$ V_{ab} = (R_{a} + sL_{a})\frac{\omega(s)B + J\omega(s)s}{K_{t}}+ K_{e}w(s) $$ and we get:
$$\frac{\omega (s)}{V(s)} = \frac{K_{t}}{JL_{a}s^2 + (BL_{a} + JR_{a})s + (BR_{a} + K_{e}K_{t})}
$$

My question is:

If the transfer equation derived above is correct, is \$L_{q}\$ in the post I mentioned above equivalent to the \$L_{a}\$ (the line inductance) in my equation? I'm not exactly sure what \$L_{q}\$ or \$R_{q}\$ are, though I do have them identified for my motor. I did read somewhere that line inductance changes as the rotor moves, which would seem to make this model totally useless for my purposes. Again, not trying to do FOC, just need trapezoidal speed control. Which inductance value do I use?

Thank you.


texts:
I have a 90's handheld CB that I'm powering using 10x1.2V NiMH cells all in series. Because these cells are rather old (at least 8 years), when I got a low voltage warning, I decided to measure all the cells one by one. Originally they were charged together, now some of them are still at around 1.2-1.25V, some are down to 0.9-1.0V, but a couple are measured by my voltmeter to be about 0.02-0.07V.
My first guess is that they are old and damaged and belong to the dumpster (the appropriate one of course), but I'm not sure. So I would like to know what happens in the cell to reach this stage and if they sustained permanent damage or they can be safely recharged.


texts: Is my wiring for this 5m 2812B Led Strip correct?

texts:
I'm building one of those infinity mirror cubes:
and I have some questions regarding the wiring.
This is what I came up with:
Green is data, black is ground and red is 5v power. Every strip has 18 (not 25 like in the picture) LED's and will cover 1 edge of the cube. There are 216 LED's in total. Sp105e is a led controller, I might switch it with an arduino later. The power supply is 5v 20A (15A should suffice, but 20A is much easier to find).
Are there any mistakes?
Additional Questions:

From what I read the wires should be 14AWG or even 12AWG for 5v 20A, but can it be smaller since it's pulling alot less most of the time and is split over 4 strips? How thick should the data wire be since it's going
all the way around, but I'm not sure how much current is going through it.

Would an off switch between the wall and power supply work or would something break when I turn it off that way often? What about turning the led's off over the controller and then switching the power off?

I'm a bit worried about heat inside the cube, it has 216 LED's inside a 30cm cube with infrared reflecting mirrors on all sides (There are some airholes at the top). Does anyone know how hot it might get inside? I'm mostly worried about the glue that holds the mirrors on the frame.

Thank you and sorry if I worded something wrong, english isn't my first language. If you need any more information, please ask.


texts: Circuit to switch off circuit "B" for 2-3 seconds when circuit "A" is switched off

texts:
Am really a noob in this regards, therefore, need help to build an easy 12V circuit which when circuit "A" is powered off enables "B" circuit to switch off for 2-3 seconds and then turns on. Hopw I have clarified myself, I have searched it but not found the answer. Would really appreciate the help.

Thanks so much everyone for the prompt suggestions, will get the material and build both the circuits tomorrow and will let you know the results.
It is a required for cluster of my vehicle and circuit 'B' is basically always open circuit as it supplies power to retain clock/date memory in the cluster. Here I will add that if this circuit 'B' is disconnected for longer duration the memory of clock/date is reset.
As far as circuit 'A' is concerned it is basically the ignition switch and when it is ON nothng is required to be done to circuit 'B', however, when 'A' is switched OFF then 'B' has to be disconnected for 2-3 seconds and then connected again to overcome a problem of the dials illumination (i.e the power remains ON in the cluster when the vehicle is switched OFF if not cutoff). Hope I have clarified myself :)


texts: When is it OK for connectors to be SMT instead of TH?

texts:
A lot of boards with predominantly SMT components have TH connectors on them for things like headers and power connectors. Take a standard barrel power jack for example:

TH:

SMT:

When designing a board, how do you decide whether a connector can be SMT or not?


texts: Is a TXB0108 apt for level-shifting in SPI programming?

texts:
I plan to use a TXB0108 to level-shift between the cheap CH341A programmer voltage and the Winbond W25Q64FW from 3.3V to 1.8V

On the silicon I can read:

25Q64FWS1G
1429


texts: Are there op amps or comparators that run on >100V?

texts:
I was using two op amps with inputs crossed as seen here:

to make inverters for stepping up voltage with high efficiency. The design works well, but op amps seem to be only built for low voltages. I am looking to make a royer converter similar to the one shown here:

Are there op amps or comparators that can run off 120 or 240 volts? If not, why?


texts: Impedance mismatch as internal signal layers cross multiple power planes

texts:
I'm worried that I might have some impedance mismatch issues in my design.

I have an 8 layer PCB arranged as Sig-Gnd-Sig-Pwr-Pwr-Sig-Gnd-Sig except that the internal power planes have splits that run across the internal signal layers. So from an IO pad, a signal trace might cover 5mm over one power plane and 5mm over another before reaching a point where it can have ground planes on both sides, this is the worst case and many internal signals have shorter trips and/or only cross one plane.

Every signal trace has a continuous unbroken ground plane on one side but the internal layers have broken power planes on the other side. It's for a large BGA FPGA (a Stratix V) and the IO power pads are right in the middle of the IO signal pads so I'm a bit stuck in that regard. The tracks are all 0.125mm (~5mil) and every dielectric layer is 0.2mm (~8mil).

With clock rates be hitting 600-800MHz, am I likely to have any major signal integrity/impedance mismatch issues where the tracks cross the power planes?

This is for a hobby project so I can't afford to add more layers (the price goes up nearly 6x) or change track widths (not enough room). In order to route out all the IOs I need, each track is already at the minimum width the fab allows (with an impedance already a bit on the high side). Once out from under the chip the tracks transition to the correct width and will have unbroken ground planes everywhere. It's just the first 10mm under the chip where the tracks cross power planes I'm worried about.

EDIT: To everyone who suggested I change the stackup and or trace width/space, I'm not doing this as part of a commercial product, Euro circuits was the only fab (that I'm aware of) that would make an 8 layer board at a price I could afford (170 Euro for a 75x75mm panel), making the trace width/spacing thinner or changing the stack up would both push the price to nearly 1400 Euro for the same panel which is far more than I can afford to throw at this project.


texts: Hello I have a question regarding resistance. I have a 5v supply and I want it to be brought down to 1v at a certain part in the circuit. How do I Know how much resistance I need to go from 5v to 1v? Thanks - Jack.


texts: Inductance and Coil Diameter for High Frequency Transformer?

texts:
I am working on a project using Raspberry Pi and several components to operate high voltage equipment and read analog input from sensors for one of my clients.

I'm more a high level web developer but I have worked on these kind of projects in the past. So my situation right now is: I need to measure phase voltage (I'll be reading 100v~250v) and I contacted a company that makes this high frequency transformer that I need to achieve that. But they are asking for very specific data such as:

Inductance
Coil Diameter
Winding Number

And they won't recommend this data to me (maybe to protect themselves). Can you guys recommend which specification to give to each one of these requirements?


texts:
I recently bought a few types of resettable fuses, but now I'm a little bit confused using them.

I have bought:

30-UF200 (Hold: 2A, Trip: 4A)
RUEF300  (Hold: 3A, Trip: 6A)
R30400   (Hold: 4A, Trip: 8A)
RUEF600  (Hold: 6A, Trip: 12A)

Now, if I understand it right, they will cut off at trip value.

My question is:

If I have in this case the 30-UF200 (Hold: 2A, Trip: 4A), what will happen between those two values Hold and Trip?


texts: 3v3 Microcontroller controlling a MOSFET that needs 5V

texts:
I'm designing a heater controller that has a primary input voltage between 12 and 24V. Everything except the heater runs on 3V3, including microcontroller, LED's, potentiometers and the MOSFET.

The problem is the MOSFET wont be operating at it's full potential,  http://www.onsemi.com/pub_link/Collateral/NTD5406N-D.PDF Figure 2 shows that 3V3 limits the current to about 5-6 Amps. I need to switch up to 8 Amps.

As a work around I've considered the following:

Using a 5V Regulator with a Shutdown Pin (LP2951) not ideal for PWM.
Using a 5V Regulator a level shifter.

I'm planning to manufacture 1,000's so my goal is low parts count and reliable, cost is always a consideration but at around $0.50 (either of the above solutions) isn't too expensive.

Since I don't need much current (<1mA) and I only need a little more voltage (<4V total) on the MOSFET could I safely use a Zener diode or a voltage reference? What would that circuit look like? The couple of attempts I made at simulating these types of circuits didn't work.

Edit:

I created a simulation of what I think is Alex's answer could somebody verify my understanding?
Simulation of Alex's Circuit
If this would work in the "real world" I like it. Simple and doesn't require another Voltage Regulator. FYI: The Zener pictured is 5V1 and the Input ("L") is 3V3.


texts: Transformer with diode to provide a battery backup

texts:
I have a small solar setup running with a low capacity battery plus a 100w solar pannel and i have 3 raspberry pi's getting juice from it. The thing is that sometimes with a cloudy day i can have my batteries runing low on voltage.
Can i have a transformer hooked up to my load with a diode to prevent the eletricity to go to the transformer when the voltage is higher, and let the power flow from the transformer to the load as the battery voltage goes below?
Or should i put relays to switch the power source? (batteries / transformer)
What can go wrong if i take the simpler aprouch? can the transformer be back feeded when the sun is shining even with the diode properly placed?
The system is 12v rated the transformer too, near the load i have at minimum 10.5v and when the sun is shining its near 14v.
Thanks!
Edit:
-The transformer its just a 12v power supply from a old WiFi router;
-I'm doing this just to learn / have fun, i know that i can toss the pannel and the battery away and plug everything to the wall;
-I can reduce power, but i cannot power off all the RPI's its a web server (or a cluster :P)


texts:
I'm using an MCU to drive a set of SSRs, and whenever I reboot the MCU, the outputs that I have attached to the SSRs go high temporarily. I know that a pullup/pulldown resistor can keep a CMOS input from "floating", but can I do the same for an output? I tried putting a 47k resistor between the output and ground, but that did not change the behavior I'm seeing. What else can I try?

I've asked the vendor, and he suggests a 1k pulldown instead of the 47k pulldown, as shorted.neuron suggests. That seems like a lot of current, however, given that I'm going to have at least 16 of these outputs. It may be true that something in between there might also work, but a more elegant solution must be possible?


texts: Determining the correct amount of bulk decoupling capacitance for a PWM LED driver

texts:
I have a number of LED strips (the simple versions: 3 LED + resistor per "section")  that I want to modulate with a PWM driver at ~ 1kHz.  The design looks like:

simulate this circuit – Schematic created using CircuitLab

My expectation is that the capacitance C is going to be related to the output impedance of the 12V power supply, however I'm not sure how to determine the output impedance of the power supply.

If I could narrow down the impedance at 1kHz of the power supply, I could use that for a low pass filter.  However I'm not sure if there is a simpler way to figure out the correct bulk capacitance.


texts:
I am using the FT801 (datasheet) to drive a Newhaven 4.3" TFT display (datasheet). The TFT datasheet specifies the normal timing parameters (hsync/vsync peroid, front porch, back porch) on page 6. However, the FT801 video driver datasheet (pg 37-42) defines timing registers that are named very differently (HSYNC0, HSYNC1, HOFFSET).I am not clear on the relationship between these two different sets of timing parameters. Could someone please clarify this?

FT801 Registers

  VSYNC1: The value of these bits specifies how many lines for signal
  VSYNC takes at the start of new frame

  VSYNC0: The value of these bits specifies how many lines for the high
  state of signal VSYNC takes at the start of new frame.

  VOFFSET: The value of these bits specifies how many lines takes after
  the start of new frame.

  VCYCLE: The value of these bits specifies how many lines in one frame.

  HSYNC1: The value of these bits specifies how many PCLK cycles for
  HSYNC during start of line.

  HSYNC0: The value of these bits specifies how many PCLK cycles of
  HSYNC high state during start of line.

  HOFFSET:  These bits are the number of total PCLK cycles per
  horizontal line scan.

  HCYCLE: The value of these bits specifies how many lines in one frame.


texts:
I should design an inductor which has these features:

3F3 magnetic ferrite material
Temperature is between 35-70 celcius
Copper filling factor, kc = 0.5
Max 10A DC or 10A AC 50kHz
U type inductor
12 microhenry

I should find these:

flux density
current density
turn number
gap space (if there is)
turn area

I considered using this resource, page 300.
Am I on right way? Do you have any trick point for me? Like advising, resources, etc.


texts: Resettable Fuse: Do they have a "Reset" limit?

texts:
Sorry for the confusing question, but for PTC's or Resettable Fuses such as something like this:
http://www.sparkfun.com/products/8357

Is there a "limit" on how many......I guess "resets" it can handle? Im assuming it becomes more and more inefficient each time it "resets" after cooling back down? Is there some sort of limit someone should give these fuses? or are do they pretty much have an indefinite lifespan?

Thanks


texts: Controlling a relay with a MCU output pin and trying to drive a solenoid using the same power source

texts:
I've used a known circuit design to successfully (wait for it!) control a 12V relay using a 3.3V MCU pin, from the pictures you can check that I am using the same 12V power source for both (relay and MCU) but the MCU is being supplied by the output from a L78L voltage regulator that converts 12 to 3.3V.
The problem appears when I use this relay to drive a solenoid (1A current and using the same 12V power source for it), after the NO switch is closed all current goes to the solenoid and none is reaching my MCU (consequently turning it off), only after 1 second the current flow is established again in the MCU and it is reset.

My question: Is there any other way apart from inserting big capacitors (>100uF) on the L78L output to try to keep my MCU powered on when the relay is active (thus making a 1A current flows to the solenoid) ?

EDIT: The issue here is that both my circuit (MCU+Relay driver) and the solenoid are connected in the same power source (12V) and the solenoid is draining all the power source current for about 1 sec.
Summary:

12V -> Solenoid and circuit

12V_Protect -> Relay Driver and L78L

TP_3.3 -> MCU

If I use a different power source for the solenoid the circuit works fine.


texts: Do decoupling capacitors offer electrostatic discharge (ESD) protection?

texts:
I'm currently trying to ESD protect a design I'm working on by using TVS diodes. I'm placing these diodes on user interface components (pushbuttons, switches, exposed pins, etc.).

In the process of doing this, I had placed a TVS diode parallel to an IC's power pin, where I had also previously placed a decoupling capacitor. Because the voltage across a capactior can't change instantaneously, I'm curious if any ESD would just be filtered by the cap.

Question: Do decoupling capacitors offer ESD protection?


texts: Can I use IS42SM16160K DRAM instead of IS42S16400 DRAM?

texts:
I have designed a custom board based on the STM32F4 controller and IS42S16400 DRAM. For some reason, I want to use IS42SM16160K mobile DRAM instead.

Should there be a change in programming and software packages?


texts: I'm going to order the NE555 chip from Texas Instruments (Link) to build a circuit, but they only have NE555P, NE555DR etc. Can I use the NE555xx instead of NE555? What is the difference between them?


texts: What is the noise level as read on my oscilloscope?

texts:
The above is what I'm seeing on my oscilloscope.  It's zener diode noise.  Scope's set for 0.5V/div vertically, and 1ms/div horizontally.  The oscilloscope has a 20MHz bandwidth, but the noise doesn't really change much at higher speeds.  You certainly can't see individual waves at 20MHz.

The trace is about 5 divisions high (this may be difficult to make out on my image).  5 divisions = 2.5V from top bit of green to bottom bit of green as judged by eye.  The longer you watch it, the higher some of the peaks can be seen to go.  That's the stochastic nature of white noise.

What does this 2.5V represent?  It can't be RMS as it's only some bit of green that I can see.  It's a kinda peak to peak but one that changes depending on how long you watch it.  Is there a rule of thumb to determine a X volts/sqrt(hz) value?  Datasheets give noise values for op amps.  They must be able to measure it somehow.


texts: STM32F4 SPI Program hangs at TXE non empty

texts:
I have been taking a udemy course on STM32F4. The course uses a different board than the one I have but from same family STM32F4. I couldn't make the SPI driver developed in the course to work in my board, so I tried t0 first test it using HAL.
I am using this video as a reference to communicate to L3GD20 Gyro in the development board. What I'm doing this is writing 0X11 to the CTRL_REG1(0x20) of the Gyroscope and then reading this register to check whether the value is written successfully or not. I could do that in HAL code

// ***** Spi Transmit ***** //
    // 1. Bring slave select low
    HAL_GPIO_WritePin(GPIOC, GPIO_PIN_1, GPIO_PIN_RESET);
    // 2. Transmit register + data
    spiTxBuf[0] = 0x20;
    spiTxBuf[1] = 0X11;
    HAL_SPI_Transmit(&hspi5, spiTxBuf, 2, 50);
    HAL_GPIO_WritePin(GPIOC, GPIO_PIN_1, GPIO_PIN_SET);

    // ***** Spi Receive ***** //
    // 1. Bring slave select low
    HAL_GPIO_WritePin(GPIOC, GPIO_PIN_1, GPIO_PIN_RESET);
    // 2. Transmit register + data
    spiTxBuf[0] = 0x20 | 0x80;
    HAL_SPI_Transmit(&hspi5, spiTxBuf, 1, 50);
    // 3. Receive data
    HAL_SPI_Receive(&hspi5, spiRxBuf, 1, 50);
    // 4. Bring slave select high
    HAL_GPIO_WritePin(GPIOC, GPIO_PIN_1, GPIO_PIN_SET);

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {

}

Above code works

But to learn the register level code I tried to create a write function

void SPI5_write(unsigned char data) {
    while (!(SPI5->SR & 2)) {}      /* wait until Transfer buffer Empty */
    SPI5->DR = data;                /* write data */
    while (SPI5->SR & 0x80) {}      /* wait for transmission done */
}

and used that to send data (reference)

// ***** Spi Transmit ***** //
    // 1. Bring slave select low
    HAL_GPIO_WritePin(GPIOC, GPIO_PIN_1, GPIO_PIN_RESET);
    // 2. Transmit register + data
    spiTxBuf[0] = 0x20;
    spiTxBuf[1] = 0X11;
    //HAL_SPI_Transmit(&hspi5, spiTxBuf, 2, 50);

    SPI5_write(spiTxBuf[0]);
    SPI5_write(spiTxBuf[1]);
    HAL_GPIO_WritePin(GPIOC, GPIO_PIN_1, GPIO_PIN_SET);

    // ***** Spi Receive ***** //
    // 1. Bring slave select low
    HAL_GPIO_WritePin(GPIOC, GPIO_PIN_1, GPIO_PIN_RESET);
    // 2. Transmit register + data
    spiTxBuf[0] = 0x20 | 0x80;
    HAL_SPI_Transmit(&hspi5, spiTxBuf, 1, 50);
    // 3. Receive data
    HAL_SPI_Receive(&hspi5, spiRxBuf, 1, 50);
    // 4. Bring slave select high
    HAL_GPIO_WritePin(GPIOC, GPIO_PIN_1, GPIO_PIN_SET);

  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {

    }

But it's not working.
I checked using debugger. What I understand is that, it sends first byte and when SPI5_write called second time, it hangs at first while loop==> TXE buffer not empty

What causing this?

EDIT: Complete code
IDE : KEIL MDK 5


texts:
I am solving the following problem:

Consider a GaAs emitter. Calculate the transmittance for the interface GaAs/glass/air. Assume near
normal incidence. GaAs: n= 3.4; glass: n=1.5. Answer: 81.6%

My attempt:
I know that the reflectance and transmittance are given by:
\begin{align}
R&=\left\lvert\frac{n_1-n_2}{n_1+n_2}\right\rvert\\
T&=1-R
\end{align}
Then I calculated for both interfaces GaAs/glass and glass/air
\begin{align}
R_1&=0.387755102\\
T_1&=0.612244898\\
R_2&=0.2\\
T_2&=0.8
\end{align}
I don't know to relate both transmittances to obtain the global one.


texts: Eliminate reflections on pulse signal transformer

texts:
I am trying to isolate an RLC ringdown signal via an RF signal transformer but I'm having trouble maintaining the signal integrity through the transformer. Below is the simple schematic describing my system:

The ringdown is coming from a capacitor discharge which drives the current \$I_p\$ through the shunt resistor \$R1\$. The current is on the order of a few kA so the ringdown signal typically has an amplitude of about 10V and a frequency of 1.25 MHz. Here is an LTSpice simulation of what it looks like:

All I really care about is the first two cycles since I am using compactors to extract the needed data such as the rise time, amplitude and frequency. I ordered some samples of the ADTT1-6+ RF signal transformer and made a makeshift simple prototype board using copper clad pcb and an exacto knife. Here is the layout:

Here you can see that my \$50 \Omega\$ termination resistor \$R2\$ is actually split into two resistors summing to \$51 \Omega\$, this is because I also want to scale the voltage down eventually, however I have tried this with a single \$50 \Omega\$ resistor directly across the transformer output with similar results. Additionally, I tried probing the output with a a scope probe, as well as sending it back into a coaxial cable to go directly to the scope (I tried it in 1M and 50 Ohm mode). I first tested this prototype with a function generator producing a 1.25 MHz sine wave and I got a perfect sine wave out(I also tried at 100kHz and up to 25Mhz with the same fidelity):

Unfortunately, when I tried to measure an actual ringdown signal, this was the best I could get:

It seems that there are reflections on the coaxial cable causing the artifacts on the first quarter cycle. It does make sense to me that the actual ringdown contains many more (higher) frequency components than a simple sine wave from a function generator which, is probably why I am seeing these reflections only in the ringdown. However, I am surprised to see such bad reflections! The artifacts are minimized if I use a 1ft coaxial cable between the source and the transformer vs a 6ft or 10ft cable. However in the application the cable will need to be much longer. Probing with a scope probe resulted in massive ringing from the probe capacitance(I assume). The best signal (as seen above) was through a coaxial cable going to the scope in 50 Ohm mode.

My assumption is that if I had a perfect match at the transformer I would not see any reflections (or if the source was perfectly back matched, which it is not) therefore my simple \$50 \Omega\$ resistor is not properly matching the coaxial cable to my transformer for all the frequencies that it sees. I would like to get a second eye to confirm that I am on the right track, and hopefully someone has the experience to know how to better match the signal. I have already tried terminating the signal with a \$50 \Omega\$ resistor immediately on the board(placing it in parallel across the input of the transformer) to get the best match possible and then terminating the transformer with a ~1k resistor so that it does not present a significant load across the \$50 \Omega\$ resistor, but rather just "listens". This did not show significant improvement.

How can I best terminate this signal to minimize reflections?


texts: What is the importance of dc-dc booster efficiency?

texts:
I am going through Texas instrument web bench design suit and get 40% efficiency for some booster circuits

if booster can handle the load (Vout and Iout) according to design given by TI
what is the disadvantage of having 40% efficiency over 70% or 85% efficiency design?

is the booster unstable?

will bolster fail at some time (within calculated load range can there be a voltage drop after some time?)

will booster waste energy as heat?

Energy loss and heating is OK for my application.


texts:
I want to implement Interrupt Request via GPIO on Intel NUC d34010wkb.

Are there any accessible GPIOs on board and how to access them?

If there aren't any accessible GPIOs then what could be a possible solution?

By switching GPIO I want to run a shell script.


texts: I wanted to make a modification to the clap clap switch with a schematic diagram below but instead of a LED lighting I want to make it turn on a small fan..


texts: Best approach to share/switch UART between multiple interfaces?

texts:
I'm building a board where I want to support multiple types of interfaces like RS422/RS485, CAN Bus, RS232 and connect these to my MCU using UART. If I only have one free UART on the MCU, what is the best way I can switch between those different options?
For example I might have a MAX3488AE IC to connect UART for Rs422/RS485 and also maybe an ST202CDR for RS232 communication and also a CAN Transceiver (MAX 14878 maybe). Is there a good/standard way to wire all of these to a single UART RX/TX pair? Then either via firmware using GPIOs to activate some switch IC to switch between those or even a physical switch to let the user do it manually (since likely they won't need all of those). Would it be acceptable for example to just control which of those interface ICs gets VCC and is therefore on, or do I need to switch all the Rx/Tx lines?
The goal is not to use any of these simultaneously but just to allow choice (preferably via firmware by setting GPIO to some switcher) as to which is active.


texts:
I have a transistor for which no datasheet is available

the transistor is supposed to be NPN (which implies BJT).

(BD247C-Transistor-NPN, 100V 25A, 120W in TO220)

how can I find out easily if it's a MOS or if it's a BJT?

I have a Digital multi meter and a +5,+12V power supply.


texts: is there any way to get current from vibration?

texts: I was wondering if you have something that vibrates , is there any way that you can make some power out of it?


texts:
What is the advantage of using transistors on the power rails of an opamp over more typical boost circuits?

I have seen a circuit topology called the "Widlar Boost" made famous by Bob Widlar.

The power rails on the opamp have series resistors and the bases of the boost transistors are attached between the resistor and the opamp.  Like this:

There are other variants where the power to the opamp's rails go through the transistors emitter/collector or drain/source.  Like this:

What would these circuits do better than what a more common approach could (like transistor(s) on the output of the opamp to boost current capability)?

Edit:
I am pretty certain I understand how these circuits boost the output:  voltage drop across the series resistors (which is directly related to output current) affects the transistors in such a way that they provide the bulk of the current to the load.

My question is why would we want to do it this way?  I am having trouble understanding how this could be better than hanging one or more transistors off the output of the opamp.

It seems to me that causing the voltage at the opamp's rails to fluctuate like this would only serve to make noise or distortion worse.

The second circuit I posted is the more mysterious one to me, even though it shows the entire circuit.  It strikes me as needlessly complicated for what it is trying to accomplish, so I would like to learn what makes this a good solution (i.e. what problem is it trying to solve that a more basic circuit doesn't?).


texts:
I have to "fix" some 50 micron tungsten wire to copper/brass.

Has anyone soldered this material?
If so, what solder was used and what advice can you give?

Note that this is on a scale that is too small for a mechanical connection to be used (screws, clamps, etc.)


texts:
I have been working on a project and one of the ideas was to control power supply of LCD 16x2 module and IR sensor via I/O pin of microcontroller, basically to have them on/off when i need them to be. I know that that can be done using MOSFET and BJT transistors (aka. High/Low Side Switches). I am using pic18f4550 for this project.

In worst case those two modules consume around 30mA on 5V. I have done the math and made circuit that provides me output of 33.3mA on 5V.. Here is what i have done so far:

simulate this circuit – Schematic created using CircuitLab

I have googled for high/low side switches but so far i haven't been satisfied with answers I found. Is this going to work or do i need something else to make this work? Thanks in advance.


texts: I'm interested in generating reasonably high amounts of current (50-100 amps), and I was wondering how to go about making that much current without insane amounts of voltage. I've read about current transformers, but am unsure about their operation


texts: Freq. measurement using pin change interrupt + 4024 counter?

texts:
I have an oscillator which I need to measure using an AVR MCU running on an 8MHz Xtal. The output from the oscillator is driving the clock input of a 4024 counter. The freq. range on Q6 (input signal divided down by 128) is between 900 Hz and 140 KHz. My goal is to measure the freq. with the best precision I can using this simple hardware.

My plan is to enable the output from the counter (disable master reset) and measure the time it takes between that and until I detect a falling edge on Q6 which would mean counter overflow.

After I disable the master reset pin on the counter I start a counter running at 8MHz, when the falling edge on Q6 is detected the timer is stopped and the counter value is read. From these numbers I can calculate the input freq.

I'm wondering if this would be accurate enough?


texts:
I have a load-cell setup with some noise that I would like to filter out. I have a vague understanding of low-pass RC filters.

I have a strain gauge with 350 ohms of resistance (no load). How can I create an RC circuit to attempt to filter out some higher frequency signals? Is it as simple as using capacitor to match the resistance of the load cell for a given cut off frequency? Or will I need external resistors?

If external resistors are required, will this not change the output voltage (and thus the signal I'm intent on measuring?)


texts: When trying to find the voltage between two points on a schematic I get the opposite answer

texts:
I have the following schematic:

simulate this circuit – Schematic created using CircuitLab

I need to calculate \$V_{AC}\$. I figure \$V_A = 12V\$ relative to ground and \$V_C = 0V\$ relative to ground meaning my answer should be:
$$
V_{AC} = V_C - V_A = 0V-12V = -12V
$$
But, the textbook I am following says it should be \$+12V\$. Why am I wrong?


texts:
I need to change the DMA content(the values of the memory) for my application(doing animation on ws2812b strips).

DMA circular mode
DMA with PWM generation

To further clarify, here's code for a single frame:
static uint8_t LEDbuffer[LED_FRAMES * LED_BUFFER_SIZE];

static void MX_TIM3_Init(void)
{
  htim3.Instance = TIM3;
  htim3.Init.Prescaler = (uint32_t)((SystemCoreClock / TIMER_CLOCK_FREQ) - 1);
  htim3.Init.RepetitionCounter = LED_BUFFER_SIZE + 1;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = TIMER_PERIOD - 1;
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  HAL_TIM_PWM_Init(&htim3);

  sConfigOC.OCMode = TIM_OCMODE_PWM1;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;

  HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_1);
  HAL_TIM_PWM_Start_DMA(&htim3, TIM_CHANNEL_1, (uint32_t *) LEDbuffer,
            LED_BUFFER_SIZE);
}

What I wish to do is change LEDbuffer on the go.

I've tried reconfiguring PWM and restarting DMA, but didn't work:
    HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_1);
    HAL_TIM_PWM_Start_DMA(&htim3, TIM_CHANNEL_1, (uint32_t *) LEDbuffer,
            LED_BUFFER_SIZE);


texts: Do Pick and Place machines check their work?

texts:
For example, if a Pick and Place machine accidentally drops a component, will it realize this and grab an identical replacement?

The only reason I can think of as to why it wouldn't do this is to save time.


texts:
As an amateur to breadboarding I'd been learning about transimpedance amps and photodiodes earlier this year for a project. Eventually I picked up a phototransistor (3DU5C) at a hobby shop, mistaking for a PD, so I learned a bit about them and found this circuit on physics portal after failing to get any readable voltage from a common-collector circuit:

simulate this circuit – Schematic created using CircuitLab

The first time I tried the circuit using Arduino as a voltmeter I'd forgotten to hook up the Vcc- pin on the op-amp to GND, but the transistor responded to light (4.18V at ambient light and ~4.75V with a phone flashlight. When I noticed it, I completed the power supply to the OA and it started reading 5.00V consistently. Hooking up one power pin to different ports produced other various ranges, the highest being the Vcc port to GND (1.35-4.07). The transistor also seems to work with no power supply to the OA at all. Additionally, all cases seem to be switch mode. Any idea why this is, and how could I change this circuit to active mode?


texts: I need to draw this pinwheel antenna pattern in altium designer. But I have no idea how to do it (drawing spirals) with altium equipments. Do you have any suggestion?


texts:
Possible Duplicate:
  Powering a breadboard with USB

I was wondering if it is possible to cut open a usb cable, and use its "sub" wires to get its 5v power and gnd.

I am currently doing a digital circuit school project, and would like to power my bread board (protoboard) using the vcc and gnd of the usb. Is this possible?

I have read that the usb cable has atleast 4 wires, red for +5v and brown for gnd.


texts: Why is propagation delay a function of supply voltage?

texts:
In the context of FPGAs, it was brought to my attention today that propagation delay varies with supply voltage. When I asked why this was so, one of the FPGA designers stated that a logic gate is essentially an amplifier (which I do agree with) and that more supply voltage means more gain (which I'm not so sure about) and more gain means faster propagation.

I didn't really buy this argument. All else being equal, simply increasing the supply voltage should not increase the small-signal gain, which is out of scope anyways since the 'amplifier' is being over-driven with digital signals.

The only thing I can think of is that a larger supply voltage suggests a higher absolute output voltage slew rate and since the FET threshold voltages don't change (I think), the thresholds are hit more quickly, leading to less delay.

Is my reasoning correct, or is there something else going on here?


texts: I have this connector that connects 2 50 pin cables together.  The opposite side is also male.  The pin spacing is 0.1".  From my research it appears to be a IDC50 SCSI connector, but I have been unable to locate any types of these connectors or cables that are male to male.  If I am correct, what are some additional search terms that I could use?  I already tried to use the term coupler or male to male, but neither returned any results.


texts: Solving circuit with source transformation

texts:
Using the following circuit:

How do you find the current i, using source transformation? What is the principle of it, and how to use it?

All I know about it, is that you must simplify the circuit, but I'm not sure how.

This was my attempt, this was the one thing in class I really struggled with:


texts: How to use 18650 batteries and increase voltage from 3.7v to 12v

texts:
Im trying to do a DIY RC car with uses two 12v motors as well as some LEDS servos and Arduino components. I was planning on using two 3.7v 2600MAH 25A 18650 battery cells on parallel to have a bigger capacity while keeping the same voltage. Considering this, would I be able with a boost converter increase the voltage to 12v to power the motors and then charge the batteries with a TP4056? Would there be any problems with trying to do this or should I try something different?
I was also think on maybe trying to use four batteries to double the voltage and capacity (or maybe 6 batteries to have triple voltage and capacity), in this case I should use a 2S or 3S BMS right?
Im pretty new to this and I know very little about batteries so sorry if my logic is wrong. Thanks!


texts: Wire sizing when connecting multiple motors

texts: I'm connecting two electric motors and an electric heater in parallel together in a circuit, all three phase. Electric motor 1 has a rated current of 20A, motor 2 is rated 2.5A, and the heater is rated 25A. Branch circuit conductor sizing per the NEC is as follows: 125% of highest rated motor full load current (FLC) + 100% of each other motor FLC + 125% of non-motor noncontinuous load FLC. This totals to an FLC of about 59 amps. A conductor carrying 59A should be about 6 AWG THHM wire. My question is this, do I need to be running 6 gauge wire throughout my circuit (contactors, circuit breakers, etc)? This seems to be what the NEC recommends, but shouldn't the small motor receive 2.5A at most, why does it require such a thick wire?


texts: Is there any circuit like "Burglar alarm " or "Proximity dector" with a range of 100 meters

texts:
I am in search of a circuit which works with
IR or RF wave with a range of 100 meter to detect proximity or burglar.

I need this to detect the presence of human or animals
One thing important is i can only use the circuit in this way.

0metere ------------------------------------------------------- 100 Meter

Signaler (IR)  ...................................................................>|(obstacle)

Receiver (IR or RF) <---------------<---------------------<<<<|(reflected from obstracle)

That is I cant place the receiver at the end of 100th meter, but it much work with
reflection...

  I have found the same circuit but it has a small range of less than a
  0.5 meter

  The circuit I have found is  "Circuit download...."


texts: I2C line dropping voltage before making call to slave

texts:
I have been coding an stm32f3discovery to talk to the arduino nano as part of my project for building a drone. I have had it working before but have since made my own pcb for it all to link into and now the two won't talk to each other. After linking it up to an oscilliscope I can see that the voltage seems to drop off before then making the call to the slave (arduino) if I unplug the board it works fine and the signal looks as it should. It also does the same thing when talking to the accelerometer built into the stm32f3discovery.
In this call it is trying to call the number 30 (001_1110)
DATA LINE
This is what it looks like:

And this is what it looks when it is zoomed in. The fact that you can see the clock lines in the signal line is something I have often come accross with arduino and it hasn't caused an issue before

CLOCK LINE

To me this feels like a wiring issue but I am very new to all of this so may be completely off. This is also the link to the pcb. I have now linked both up to the one power source
https://1drv.ms/u/s!AvQFsm9Fi805gacTSmSaViNqiqsV6A?e=6cz4R1