texts: Change in Base-Emitter Voltage due to Emitter Degeneration

texts:
I am stuck on this circuit from The Art of Electronics, page 117 figure 2.85A.
I have been working on how to derive the equation for the change in Vbe.

My calculations have been assuming that:
$$ \ i_c \approx i_e $$
Then
$$ \Delta V_c = -i_cR_c = \Delta V_{out} $$
$$ i_c = - \frac{\Delta V_{out} }{Rc}$$
Therefore, for a small change in the base voltage $$\Delta V_{in} = \Delta V_{be} + \Delta V_e $$
$$ \Delta V_{be} = \Delta V_{in} - \Delta V_e $$
$$ \Delta V_{be} = \Delta V_{in} - (\frac{-\Delta V_{out}}{Rc}\times Re) $$
$$ \Delta V_{be} = \Delta V_{in} + \frac{R_e}{R_c} \Delta V_{out}$$
So I've ended up with the addition of the feedback, which doesn't seem quite right. I've looked around at similar websites and found this, which seems to have a similar calculation as I do for the change in Vbe.
What am I doing wrong? Is it because the arrow on Vout in the figure is in the opposing direction to Vin?


texts: Finding common mode level and max output swing in two stage op-amp

texts: I just want a hint on how to even start attempting this question. I wasn't able to link any equation to the given values in the question. Felt like too much was unknown.


texts:
I have a few circumstances which invlove someone being shocked with 20 watts of electricity and whether it would be deadly. So here they are:

Would 1000 volts at 20 miliamperes of AC (2MHz frequency) be dangerous or deadly?
Would 1000 volts at 20 miliamperes of DC be dangerous or deadly?
Would 10 Kilo volts at 2 miliamperes of AC (2MHz frequency) be dangerous or deadly?
and
Would 10 Kilo volts at 2 miliamperes of DC be dangerous or deadly?

Thanks for everyones help.


texts: Now that most vendors offer a diverse variety of ARM Cortex-M chips, why would one pick a Renesas or Freescale product? I understand that there are reasons for somebody to go with a PIC32 as they are familiar with tools etc, there also reasons to use a 16 or 8 bit MCU from TI or Atmel as they might think it's somewhat more suitable for their design, but why would one want to use a Renesas RX or Freescale ColdFire?


texts:
A transformer of primary voltage 220 V and turns ratio of 11:1. The secondary of the transformer is connected to a 30 Ω inductive reluctance in series with a load resistance (R). If the current flowing in (R) must not be below 0.4 A. Then the value of (R) is:

The answer on my book is at most 40 Ω , but I found the answer to be at most 20 Ω

What is did is that , secondary voltage , which can be easily found by the turn ratio, is 20 V

Then, to find the current at the  secondary side we divide the secondary voltage = 20 V over the total resistance = 30 + R Ω

after doing the math R should be at most 20Ω for the current at the secondary side not to drop below .4 A

I don't know where is my mistake , Could someone explain to my what I have done wrong on this problem


texts:
I'm designing a 3 stage amplifier, being the first stage a common source MOSFET amplifier (using a 2N7000 MOSFET). I have made some basic calculations to calculate the resistor values. It must have a 1.25M Ohm input resistance, and a maximum drain current of 10 mA

I have calculated some values and simulated the common source amplifier. The gain seems to be fine but the output waveform seems more like a square wave rather than a sine wave.

Does anyone have an idea on what might be happening? How can I solve this?

I used the characteristics of the MOSFET that I obtained through a DCA Pro:

V(GS(on))=2.390 V at i_D=5 mA at i_G=5 μA

V(GS(off))=1.678 V at i_D=4.7 μA

gm=27.7 mAV at i_D=3 mA  to 5 mA


texts: Altium plated mounting hole, Un-Routed net constraint

texts:
I am trying to resolve a problem I am having with Altium, maybe I am just missing something obvious but i'd like your insight.

I have a 8 layer board, build out of signal layers, and internal planes.
I recently tried to ground my mounting holes so I plated the pads I use as mounting holes. However after assigning the GND net to my mounting holes and running the DRC, I get an Un-Routed Net Constraints for all my mounting holes.

When I use the 3D viewer everything seems as expected, the internal GND layers seem connected to the mounting hole, and power planes are not connected.
Where do these Un-Routed Net Constraints come from while everything looks the way I want it too?

  The Error I am getting

  Class Document    Source  Message Time    Date    No. [Un-Routed Net Constraint
  Violation]    mypcb.pcbdoc    Advanced PCB    Un-Routed Net Constraint:
  Net GND Between Pad Free-(162mm,-32mm) on Multi-Layer And Pad
  Free-(162mm,-32mm) on Multi-Layer     13:53:43    17/01/2019  19


texts: Help understanding secondary cells discharge curve

texts:
This is what I've understood about the process of discharging of a secondary cell. If I have a rechargeable cell, full charged, and I make it discharge at a certain constant current, let's say 1A, I will notice that its tension will go down since the EOL (end of life) tension. If I measure how much time the discharge process takes, let's say 1 hour, and if I multiply this value for the constant current, I get the capacity of the battery at that specific discharge rate (in this case the capacity is 1Ah). If I repeat the same experiment using higher currents I will obtain shorter time, but also lower capacity according to Peukert law, or some more realistic law. For example at 10 A I could get a capacity of only 600mAh. Often the constant current is written as function of the nominal capacity, so a discharge rate of 2C for a nominal capacity of 1Ah, means a discharge current of 2A. But what I really don't understand graphs Tension-Capacity, like this one:

Following my previous argument, given a certain discharge current the capacity is uniquely determined while tension stays inside a certain range. I wuold draw something like this:

Any help is very welcome.


texts: Total output resistance (Rout) is calculated when Early voltage is completely unspecified and neglected. How?

texts:
Here, the total output resistance is calculated when the Early voltage is completely unspecified and neglected (I suppose it's zero). How has this been done? The formula for terminal output resistance (Ro) for BJT Amplifiers is (Va + Vce)/Ic where Va is the Early voltage, Vce and the collector-emitter voltage and Ic is the collector current. Vce and Ic are calculated via the Q-point. Rout is then calculated by taking Rc and adding in parallel with the calculated Ro. However, my calculation gives me 29.6k Ohms, not 39k Ohms as said in the solution. (Vce/Ic)||Rc gives me 29.6k Ohms. Please let me know where I went wrong. Here are the relevant images:
Solution
Question

What are Av, Ai , Rin, Rout, and the maximum amplitude of the signal source for the amplifier in
Fig. P14.1(g) if RI = 500 , RE = 110 k,
RB = 1 M, R3 = 500 k, RC = 42 k,
VCC = 15 V, −VEE = −15 V? Use βF = 100.


texts: How to calculate the resonance frequency of this oscillator?

texts:
I created the following square wave oscillator in LTspice, which works fine. But I'm not sure how to choose the values of the components. I manually adjusted the values of C1, C2 and L1 until I got a frequency of approx. 1MHz.

Is it possible to calculate the resonance frequency similar to this?
$$f_0=\frac{1}{2\cdot \pi \cdot \sqrt{L\cdot C}}$$


texts: Relationship between heat coefficient and conductance

texts:
I'm involved in a project and part of it involves heat coefficient and heat conductance. What's the relationship between the two, given that the SI unit for heat coefficient is \$W/mK\$ and the SI unit for heat conductance is \$W/m^2K\$?

\$W\$ - Heat Energy (Watts/Joules per second)
\$m\$ - Length
\$m^2\$ - Area
\$K\$ - Difference in Temperature (Kelvin)

Does anyone know the above parameters for steel? Especially heat conductance.

Thank you.


texts:
I received this little two tube preamp
http://www.gikfun.com/electronic-diy-kits-c-7/6j1-tube-preamplifier-board-20-stereo-multiple-diy-kit-p-730.html
It comes with 9 470uF caps. The symbol on the board for them is a circle, with white strips across one of the legs. Does anyone know if that indicates the positive leg of the capacitor?
Also, I don't read Chinese characters. Which set of RCA plugs are the input?
No word back from GikFun to these questions yet.
There is no schematic posted to work out the details myself.
Thanks
Updated - added a picture of the labels
Updated - added a picture showing two of capacitor pins that both connect to the RCA plugs common plane - and to the common pins of the AC input jack.
Ah ha! Found an e-bay listing that confirms  Tony Stewart Sunnyskyguy's answer.  Thank you!


texts: Which resistor watt rating to use for this circuit and Arduino 5V?

texts:
http://www.skillbank.co.uk/arduino/measure.htm

I am looking to build the circuit this guy recommends for making a better analog reference source. I found the voltage reference diode, and now I am looking for the proper resistor. I found a few 560Ω resistors with 1% rating. Now I am wondering what wattage they should be set at.

I think, the amperage for the 5V output of the Arduino is 500mA or so. Can anyone comment on that? Is there a best resistor watt rating you would choose for this circuit?

Are using watt ratings too far above necessary - bad? Or is that ok? Or stupid? Why?


texts:
I am confused regarding the voltages of NMOS and PMOS. For a NMOS, let us say it is in cut-off, thus making Id = 0. Then does that mean Vds = 0? I was initially under the assumption that Vds can be anything, doesn't matter since it is in cut off. I ask this because in the following circuit,

the statement given in the solutions is "For N1, if N1 is on, then Vx= Vout =Vdd because the current through N1 is zero. Then Vgs = Vdd - Vdd = 0 for N1, and N1 must be offÆ contradiction. So N1 is off." But with regards to the first sentence, I am not sure why that is true. Because Vd can very well be a different voltage. Can someone please clarify this?

Also, my reasoning for which transistors are on is, only P2 "can" be on. Since Vin is set to Vdd, P1 is off. Making the current id = 0 for P1, N1, and N2. Is my reasoning valid here? I did not use the round about way of assuming N1 is on and disproving it.


texts: Why is this 5V voltage regulator not outputting 5V?

texts:
I purchased a bunch of LM330T voltage regulators and in my testing, it's outputting about 5.9V when I feed it 6.5V.  It's listed as a 5V regulator at Digikey:

LM330T-5.0/NOPB

Here's the data sheet: LM330

I must not be understanding something very fundamental here.  Can anyone explain?


texts: Question based on rotary potentiometer and resolution

texts:
Can anyone help me how to come up with this question's solution?
Question:

A rotary potentiometer consists of a fine wire wound on a circular former, whose inner diameter is 2.5 cm. The resolution in degrees is 0.176. Calculate the maximum number of turns that can be wound on the former per cm.

Answer: 260

My solution:


texts: How to Estimate Rotational Velocity of a Beakman's Motor?

texts:
What is the equation to determine the rotations per second of a Beakman's Motor (a.k.a. half-motor or single pole pulse motor, composed of a power source and a single coil with 1/2 exposed coil leads that connect to the axle-stands/terminals)?

I'm also interested in an equation in which you could feed in the coil length, coil type, gauge of magnet/copper wire in coil, distance between coils, diameter of the coil, distance from axis to magnet, size of magnet (or flux, but I'm not sure that flux would be helpful to someone trying to buy an appropriate magnet, so would need that info), voltage, and amperage of the DC terminals. The reason I ask is that my daughter and I put together a half-motor this evening and noticed that with greater voltage and amperage, it didn't go faster, but we could tap the terminal (on/off) to reduce the power and it went faster. So, I imagine there may be a practical way to determine this. If you need constraints, we are using 24 gauge magnet wire and about 2/3 inch diameter coil of maybe 25 loops with almost no distance in-between each coil, and roughly 1 1/4 inch from the axis to the 2 in x 7/8 " by 3/8 in ceramic magnet. It seems to be designed for a D battery.


texts:
I own a Kettler Ergorace indoor bike. It's possible to create exercises using the USB interface. When plugged into a PC, it is shown as a virtual com port (SiLabs CP2102)

I would like to control it from my Android tablet (over Bluetooth, Wi-Fi or any RF)

My project is to build a simple (and cheap) wireless bridge from this USB port to my tablet. First idea would be to use a Raspberry Pi + Wi-Fi dongle + some kind of pass through program. Is there a cheaper solution ?


texts: Using Android Accesory mode to access a USB serial device, use a VNC2?

texts:
In a current project we use an Android application that talks to a USB Serial device (which speaks the Prolific USB serial protocol). This works fine with Android devices that support USB Host Mode, but there aren't too many of those.

So, I would like to use this device with a device that only supports Android Accessory mode, by putting a bridge device in between: this device speaks the Android Accessory protocol on one side, and the Prolific USB Serial protocol on the other. So,

+---------+       +--------+           +----------+
|         |       |        |           | Prolific |
| Android | ----> | Bridge | --------> | USB-     |
| Device  | <---- | Device | <-------- | serial   |
|         |  ADK  |        |  Profilic |          |
+---------+       +--------+  USB      +----------+
                              Protocol

In which the incoming data stream from the serial device is forwarded to the inputsream of the ADK device, and vice versa.

I plan to base this device on an FTDI VNC2 (with the V2DIP2, there's a development board that has all the hardware I need for this).

Is this chip indeed the best choice for this kind of bridge? Is there something else on the market that perhaps does this bridging out of the box?


texts: Voltage Noise Simulation with white noise variation issue

texts:
I am trying to simulate the behaviour differential AOP, with its input common mode and differential mode filters, which is placed at the 2 outputs of the sensor, whose one  is noisy.

Of course, the average value of the output of the sensors can have differents values: for the example, 2.5V and then 5V, which i want to simulate with the same noise.

Here is the schematic:

When I simulate with V3 = 2,5V, i got an rms noise value of 24mV of Vsensor_output1_with_noise (after removing dc value)
When I simulate with V3 = 5 V, i got an rms noise value of 20mV of Vsensor_output1_with_noise (after removing dc value)

So I can't simulate the behaviour of that stage for different dc input values but with the same level of noise.
Do you have any idea to have a total independant noise source ?

Note: i can't put a high voltage source resistance value because it would take part in the filters..

Thank you,


texts:
I want to measure a voltage of a battery (14 to 25 V) with an ATtiny85. The plan is to simply use two reistors. My ATtiny will get a VCC of 5V, so I need to reduce the voltage to 0 to 5 V for the ADC. Based on my calculations, 15k and 3.3k gives the approximate desired range.

USV is a valid ADC Pin on the ATtiny85.
Is it really this simple?


texts: LPC-Link2 Not Working as CMSIS-DAP with OpenOCD

texts:
I'm working on a project with the NXP LPC824 using VisualGDB and OpenOCD. Using the LPCXpresso824-MAX dev board I had no trouble programming and debugging using OpenOCD. I am using the version of OpenOCD that comes with VisualGDB (0.10.0). I have recently built my first prototype PCB for this project and purchased an LPC-Link2 to use as a CMSIS-DAP debugger with it. However, I am unable to get the LPC-Link2 to work with OpenOCD. I keep getting a "CMSIS-DAP command CMD_INFO failed" error.

I have flashed the CMSIS-DAP firmware to the LPC-Link2, reinstalled the drivers, and followed any other troubleshooting tips I could find, but with no success. The LPC-Link2 works when flashed with the Segger J-Link firmware and also with the CMSIS-DAP firmware when debugging through MCUXpresso, so it does not appear to be a problem with the probe or the firmware but rather something specific to OpenOCD. There is nothing wrong with the target board because, as a workaround, I have removed the target MCU from the LPCXpresso824-MAX and am using its external debug header to debug the target MCU on my PCB.

Here is the output of my version of OpenOCD with the LPC-Link2 with debug turned on.

openocd.exe -f interface/cmsis-dap.cfg -c "debug_level 4"
Open On-Chip Debugger 0.10.0 (2019-08-28) [https://github.com/sysprogs/openocd]
Licensed under GNU GPL v2
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
User : 14 6 options.c:60 configuration_output_handler(): debug_level: 4
User : 15 9 options.c:60 configuration_output_handler():
Info : 16 13 server.c:311 add_service(): Listening on port 6666 for tcl connections
Info : 17 16 server.c:311 add_service(): Listening on port 4444 for telnet connections
Debug: 18 19 command.c:143 script_debug(): command - init init
Debug: 20 21 command.c:143 script_debug(): command - target target init
Debug: 22 23 command.c:143 script_debug(): command - target target names
Debug: 23 26 target.c:1431 handle_target_init_command(): Initializing targets...
Debug: 24 59 cmsis_dap_usb.c:251 cmsis_dap_usb_open(): Cannot read product string of device 0x46d:0xc232
Debug: 25 65 cmsis_dap_usb.c:251 cmsis_dap_usb_open(): Cannot read product string of device 0x46d:0xc231
Debug: 26 1075 cmsis_dap_usb.c:409 cmsis_dap_usb_xfer(): error reading data: (null)
Error: 27 1081 cmsis_dap_usb.c:503 cmsis_dap_cmd_DAP_Info(): CMSIS-DAP command CMD_INFO failed.
Debug: 28 1088 command.c:630 run_command(): Command 'init' failed with error code -107
User : 29 1103 command.c:695 command_run_line():

Does anyone have any ideas as to what is going wrong? Is this a bug with OpenOCD? I have a workaround in place now so this is not holding up development, but it would be nice to get it working.


texts: I am modifying a mini cooler/heater and there is one component whose role I don't understand. The Peltier cell is attached to a heat sink on one side and is in contact with a metallic block on the other side. On top of this metallic block there is a black plastic cylinder with two incoming wires. The two wires are set at 0 V both when cooling and when heating. What does this unknown component do? Thank you.


texts: I would like to run a 6V dc motor using a 9v battery supply. The motor specification states that current is 150mA at 6V which I calculate to be a resistance of 40 ohms (when I measure the resistance of the motor at rest it is only 6 ohms). Is it okay to just put the motor in series with a 20 ohm resistance to get the required voltage drop ? Is the resistance of the motor likely to change much under different mechanical loads ?


texts: Gain of an active filter without calculating the transfer function with two OP-AMPs

texts: I need to calculate the gain of the filter without explicitly calculating the transfer function, ie I have to replace the capacitors with an open circuit. The problem is that I've been trying to solve the problem but I do not know how to start. Thanks.


texts: How to activate a solenoid using TSOP4838 IR receiver

texts:
I have a TSOP4838 whose output is 5v normally and 2.5v when I press a button on my DVD remote. I wish to activate a solenoid when the DVD remote button is pressed. The circuit is is powered by a 9v battery going through a voltage regulator.

I have both NPN and PNP transistors but these TSOP4838 are the only IR components I have at this time.


texts: Does a LC filter filters the voltage or the current or both?

texts:
The above image shows a simple low pass LC filter with an AC input source. Imagine that a resistor is being connected at the output as the load.

Does it filter the

1)  high frequency voltages

2)  high frequency currents

3) or both of them?


texts: measure the voltage of electronics component connected on breadboard using own software

texts:
I wanted to ask something related to breadboard designing.
Is this possible that we can design own breadboard such that when it interact with software, then if you put the leads between the nodes of any electronic component then it can measure the voltage and show that voltage on software(just like when you put multimeter leads in between any component then it can measure the voltage of that component). I want to replace the multimeter with my software.
Please suggest me.


texts: Precision 0.5 degree Stepper needed for Turntable

texts:
Basically our project brief is to design a turn table, an object weighing around 10kg which will be placed off centre (but allowing around 20kg in case) to rotate in 0.5 degree increments, pausing for a few seconds to have a photo taken and continue through to 180 degrees. We're currently using Arduino.

We thought of having the turn table on a lazy Susan bearing to distribute weight.
From research we've figured we want a stepper motor with high torque and possibly a worm shaft to prevent the table from continuing motion on the bearing once stopped. Our concern is the specific increments of movement as most stepper motors move in 1.8 degree steps. We've looked at micro-stepper motors but we haven't found one which can carry the load desired/ hasn't got enough torque. We're not super experienced in this but we'd like to play around with a prototype given reasonable suggestions.

Could anyone provide any advice about how we could set our system up for precision and efficiency?


texts: Unexpected behavior of the Sallen-Key second order filter

texts:
I met an unexpected behavior when I simulated under Multisim (National Instruments) the Sallen-Key circuit given on the image below.

The circuit is designed to receive a 1.8kHz modulated sin wave as input.
The equations are :

\$ H(j\omega) = \frac{k}{-\left(\frac{\omega}{\omega_0}\right)^2+j\frac{1}{Q}\frac{\omega}{\omega_0}+1}\$
\$k = 1+\frac{R_b}{R_a}\$
\$f_0 = \frac{1}{2\pi\sqrt{mn}R_1C_1} \$
\$Q= \frac{\sqrt{mn}}{m+1+mn(1-K)}\$

Values that are imposed to me are :

\$ n = 1 \$
\$ C_1 = 100 nF\$
\$ R_a = 1 k\Omega \$

For my situation, I choose and/or calculate the following values :

\$R_b = R_1 = R_a = 1k\Omega \$
\$mR_1 = 470\Omega\$
\$C_1 = nC_1 = 100 nF \$
\$ f_0 = 2300 Hz \$
\$ Q = \frac{\sqrt{2}}{2} \$

So, the circuit schematic is the following

And the Bode plot simulation gives :

And I just do not know how it's possible to rise after \$ f_0 \$

If someone see the where is the problem.

Thank you in advance to any one who may be able to give me some ideas.

Here is the schematic netlist (I changed some values but behavior is nearly the same)

** PasseBasOrdre2 **
*
* NI Multisim to SPICE Netlist Export
* Generated by: Dim
* Mon, Nov 18, 2013 20:46:37
*

*## Multisim Component U1 ##*

xU1 1 3 VPOS VNEG BasculeSeuil 5T_VirtualU1 params: Vos=0.001 Ibias=8e-008 Ioffset=2e-008

Av=200000 BW=100000000 SR=1000000 CMRR=100 Iomax=0.025 Rin=10000000 Rout=10

.subckt 5T_VirtualU1  In_p In_n Vpos Vneg Out params: Av=200k BW=20Meg CMRR=100

+SR=1Meg Rout=75 Iomax=25m Rin=100meg Vos=0.1m Ibias=1n Ioffset=1p

.param Rp1=1e6

.param Rs1=1e6

.param K_Is2a=sqrt(Av)/Rs1

.param K_Is2b=sqrt(Av)/Rp1

.param Cp1={Av/(2*pi*BW*Rp1)}

.param CMRR_lin=10**(CMRR/20)

Rin In_p In_n {Rin}

Bcm 4 3 V = { V(cm)/CMRR_lin}

Voff In_p 4 {Vos}

Ibias1 In_p 0 {Ibias}

Ibias2 In_n 0 {Ibias}

Ioffset In_p In_n {Ioffset/2}

Rcm1 In_p cm 10meg

Rcm2 In_n cm 10meg

BIs1a vref vs2a I = { K_Is2a*(V(3)-V(In_n)) }

Rs1 vs2a vref {Rs1}

BIs2b vref vs2b I = { K_Is2b*(V(vs2a)-v(vref)) }

Rp1 vs2b vref {Rp1}

VCp1sense vs2b vs2b_ 0

Cp1 vs2b_ vref {Cp1}

D3 vs2b_ 8 Limit_Diode

D4 8 vpos Limit_Diode

B_SRp 8 vpos I={I(VCp1sense)- (Cp1*SR)}

D5 10 vs2b_ Limit_Diode

D6 Vneg 10 Limit_Diode

B_SRn Vneg 10 I={-1*I(VCp1sense)-(Cp1*SR)}

DVpclip vs2b_ Vpos V_limit

DVnclip Vneg vs2b_ V_limit

Bout vref out_ I={(V(vs2b)-v(vref))/Rout}

Rout vref out_ {Rout}

Voutsense out_ out 0

D9 out 15 Limit_Diode

D10 15 vpos Limit_Diode

B_outp 15 vpos I={I(Voutsense)- Iomax}

D11 16 out Limit_Diode

D12 vneg 16 Limit_Diode

B_outn vneg 16 I={-1*I(Voutsense)-Iomax}

R5 Vpos mid 1000000

R6 mid Vneg 1000000

Eref vref 0 mid 0 1

.MODEL Limit_Diode  D (IS= 1.0e-12)

.MODEL V_limit D(n=0.1)

.ends

*## Multisim Component R3 ##*

rR3 1 2 1000 vresR3

.model vresR3 r(  )

*## Multisim Component V3 ##*

vV3 0 VNEG dc 5 ac 0 0
+           distof1 0 0
+           distof2 0 0

*## Multisim Component V2 ##*

vV2 VPOS 0 dc 5 ac 0 0
+           distof1 0 0
+           distof2 0 0

*## Multisim Component V1 ##*

vV1 4 0 dc 0 ac 1 0
+      distof1 0 0
+      distof2 0 0
+      sin(0 {1*1.414213562} 1800 0 0 0)

*## Multisim Component R4 ##*

rR4 2 4 390 vresR4

.model vresR4 r(  )

*## Multisim Component R1 ##*

rR1 3 0 68000 vresR1

.model vresR1 r(  )

*## Multisim Component R2 ##*

rR2 BasculeSeuil 3 33000 vresR2

.model vresR2 r(  )

*## Multisim Component C2 ##*

cC2 1 0 1e-007

*## Multisim Component C1 ##*

cC1 BasculeSeuil 2 1e-007


texts:
I have a Nokia BH-503 bluetooth headset with 4 buttons on the PCB.

From the buttons side of the PCB, I only see 4 pieces of metal.

From the other side I see 4 resistor (I think that are resistors).

I want to wire those buttons to replace it for some push buttons.

Is that possible? How can I do that?
I want to prevent (much as possible) solder wires on resistor if that is the solution.

The same for the leds (buttons side of the pcb)

I'm making a frankenstein of headsets and I want to crop little as possible from the new headset


texts:
Four 240v, 50Hz, 16kW motors are installed in a factory. Each has a power factor of 0.86 lagging and efficiency of 78.2% while running. Determine the shunt capacitance required to deliver unity power factor...

I'm not sure if I'm going about this question the right way. Any help would be much appreciated.


texts: Octave bode plot looks like a decade plot in LTSpice

texts:
When I do a bode plot on a load over a simple LRC filter then compare graphing the frequency in OCT and DEC, I would expect their plot shapes would look different given OCT plots the x-axis in 1Hz,2Hz,4Hz,8Hz,16Hz,32Hz... and DEC plots in a log scale (1Hz,10Hz,100Hz,1kHz,10kHz,100kHz,1MHz,10MHz,100MHz)

But when I generate the simulation, they had the same shape with 10Mhz and 100Hz align on the x-axis.


texts: Calculation of the slew rate of an inverter with active load

texts:
I'm studying the inverter with active load, whose scheme is the following:

Now, the author of my book says:

"We have to ensure a proper large-signal driving of the output node. The load of the inverter is always a capacitance (otherwise, a finite resistance would dissolve the voltage gain) but during transients, the circuit must provide a drain or sink current to charge or discharge that capacitive load. When the current is provided by the input transistor we have no limitations. In contrast, when the current is furnished by the active load, we have an upper limit. It is given by the current generated by the active load itself. This, in turn, sets the slew rate limit

where Cload is the total output capacitance"

I would appreciate if someone can give me some hints on how to calculate the slew rate. Suppose I give a large swing at the input voltage, then what kind of reasoning should I do in order to calculate the slew rate for this circuit? Why do we have that "When the current is provided by the input transistor we have no limitations. In contrast, when the current is furnished by the active load, we have an upper limit"?

Thank you


texts: I am trying to design a USBL acoustic pinger location system for a school project. I am struggling to determine if the frequency of the acoustic beacon ping places a constraint on the distances between hydrophones in the array. I have found in one source online that the hydrophones must be less than one half a wavelength apart to be able to implement the phase-comparison method for angle of arrival calculations. Is this the case?


texts: Amplification of sinusoidal signal from filter circuit

texts:
Intention of the project is to obtain sinusoidal signal generator of frequency range 10Hz to 100Hz and 5v signal from microcontroller i.e arduino uno,

using pwm from arduino uno I got the square waves of 4.3v - 5v, the signal was fed into the RC low pass filter of four stages and cut-off frequency of 50Hz, the output after simulation was found to be a sinusoidal signal of 50Hz but with low volts of about 400mv, I tried to amplify the signal using OPamp amplifier with LM324 IC but the output was found to decrease to almost zero volts, But after swapping between filter and amplifier, now the I'm amplifying the square wave before filtering the signal voltage raised to almost 900mv. Intention is obtain sinusoidal signal with 5v and frequency between 10Hz and 100Hz. Please any best way to accomplish this.


texts: Problem with conditional signal assignment

texts:
I'm really desperate right now.
I have written a VHDL code that gets an input of type std_logic_vector(0 downto 0) [in__con1_dio4_rs485_rs] which it should collect in 8-bit blocks. For this I use an 8 bit vector [tmp], whereupon I perform a left-shift.

My problem here is that I only need every 8th result of tmp for the output, i.e. always when the vector has been completely rewritten with the inputs.
Therefore I wrote a simple if-statement, which passes the tmp-value to the output [Whole-Frame] using the signal cntclk, which counts the passes of the overlying if-statement.

Unfortunately, it does not work if I check the cntclk for 7 (8 bits), because then the value is passed correctly at the beginning, but not anymore. But if I set cntclk to other values, like in the attached pictures, to 7 bits or 9 bits, it works fine.

I'm sorry if it should be a trivial question, but I've been looking for a solution since last week and can't find the right way.

Here the code:

LIBRARY IEEE;
USE IEEE.std_logic_1164.ALL;
USE IEEE.NUMERIC_STD.ALL;
USE IEEE.MATH_REAL.ALL;

ENTITY User IS
PORT (
Whole_Frame_ch5 : out std_logic_vector(7 downto 0) := (others => '0');
in_con1_dio3           : IN std_logic_vector(0 DOWNTO 0); -- SCLK
in_con1_dio4_rs485_rx  : IN std_logic_vector(0 DOWNTO 0); --MOSI
in_con1_dio6           : IN std_logic_vector(0 DOWNTO 0); --CS
    );
END;

ARCHITECTURE rtl OF User IS
signal clkT :   std_logic := '0';   --clock
signal tmp: std_logic_vector(7 downto 0);
signal cntclk : integer := 0;
BEGIN

clkT <= in_con1_dio3(0);

PROCESS(clkT)

BEGIN

if falling_edge(clkT) and in_con1_dio6(0) = '0' then

--left shift 8 bit vector

tmp(0) <= in_con1_dio4_rs485_rx(0);
for i in 1 to 7 loop
    tmp(i) <= tmp(i - 1);
end loop;

cntclk <= cntclk + 1;

if cntclk = 8 then    --only changed this value for screenshots
  whole_Frame_ch5 <= tmp;
  cntclk <= 0;
end if;

end if;

END PROCESS;

END ARCHITECTURE rtl;  -- of  User

Screenshots:
the output is the second last wave, cntclk the last wave

Screenshot: cntclk = 6 --> passes tmp to output after 7 shifts
Screenshot: cntclk = 7 --> passes tmp to output after 8 shifts --does not work
Screenshot: cntclk = 8 --> passes tmp to output after 9 shifts

The only thing I have changed between these screenshots of the simulation was the value for the if-statement that checks the cntclk.

Thank you in advance..

Mik


texts: Can multimeter measure 3200µF if capacitance measuring range:10p...40n/400n/4µ/40µ/200µF?

texts:
A multimeter that has this specifications:

Capacitance measuring range:10p...40n/400n/4µ/40µ/200µF

will not be able to measure a 300µF or 3200µF capacitor?
That's how it sounds, but I want to make sure since a range up to 200µF sounds pretty useless ...
And it's not an extremely cheap multimeter (though not expensive): https://axiomet.eu/gb/en/product/axiomet/digital-multimeter/ax-594/


texts:
I am trying to find a solution to create a 4MBit NVRAM module (FRAM or SRAM, doesn't matter) with a standard PC with Windows.

I want to store up to 1MB of data in less than 1 second with 50-100 write commands.

Unfortunately, the USB has a high latency and so I need up to 3-4ms for each write access.

So my question is: is there a faster way to send the data to a NVRAM module than USB? I was thinking with a PCIe interface, but probably I need some signed drivers to do it over PCIe. I can't find any modules with NVRAM on the web.


texts:
if we connect a capacitor with charge = 5 volts , with buffer (op-amp) , will the capacitor will discharge it's voltage ? or because of high impedance will keep it's charge ?

simulate this circuit – Schematic created using CircuitLab


texts: Do you need initialization when sending raw RGB data to a ILI9341 based LCD?

texts: The title pretty much says it all. Can I just send RGB data according to the protocol or I need some init before that to make it work?


texts: Running a brushless DC motor on low rpm using servo tester

texts:
Background

I'm working on a gift for the wife for Christmas - an electric bobbin winder (a winding machine/spooling machine) - which will work in the same way as this machine:

It winds yarn on spools, and you control the rotational speed using a pedal. My idea for the motor and control setup is as follows:

Brushless motor for durability and low noise
Brushless motor is connected to an ESC (electronic speed controller)
Electronic speed controller is connected to power supply AND an analog servo tester
I utilize the potentiometer on the servo tester, for speed control of the brushless motor.

The motor will have to run smoothly on low RPMs ( < 15 rpm) as well as high RPMs (~5000 rpm).

Questions:

What should be the specs on the motor - will more poles be better? (i.e. 24n22p is better than 14n12p?) Should it be sensored?
Will a setup as described, using a servo tester, be able to run the motor on low RPMs ( <15 rpm)? Or do low-RPM running of motor require different type of controller unit? (i.e. arduino, raspberry pi, ...)


texts:
In our current design, we have two devices which communicate with each other using I2C. But their I2C logic levels are different, so we need to use a level translation?
Can I use a simple level translator for this?
I have chosen this part MAX13003
http://datasheets.maximintegrated.com/en/ds/MAX13000E-MAX13005E.pdf


texts: Avoiding copyright violations when writing header files

texts:
Many manufacturers apply licenses to the header files they publish for their products.  These files usually consist of a long list of #defines which are a correlation between the names and adjacent numbers in the datasheets.

If I want to produce a driver or other software solution which is free of these license restrictions, will using the same names in my header file be valid?  Am I allowed to copy the #defines straight out of the license file?  Does it matter whether I type it out by hand from the datasheet or programmatically access the .pdf file or other data structure containing this information?  (the datasheet isn't covered by the license.)

I'll assume that I need to leave licensed macros, functions, comments, and all other information outside of the #defines behind, but do I need to do more, like use a common prefix for these names (which I might do anyways to avoid namespace conflicts) or come up with my own acronyms/abbreviations?  Do I have to reverse-engineer the registers without looking at the datasheet?  Or is it completely impossible to produce a copyleft header file?


texts: Parallel external supply to CR2450 coin battery

texts:
I have a temperature data logger which should be used within the time period of 1 year as according to the supplier the battery would be drained by this time.

The logger has a program stored inside a chip which I am unaware if volatile or non volatile and the supplier is not interested in providing more details.

I want to enhance battery life by providing an external power supply to the already present(and soldered) CR 2450. My idea is to stop the battery drain further as at current position battery is at 3.23 Volts which I believe is very good.

I cannot simply replace battery because battery is soldered to board which mean If I try to remove than it might lose the program stored probably.

My question is
Is it good idea to provide external supply of 3.3 Volts through a voltage regulator? Could it damage battery? If I do provide an external supply, what voltage and what amperage?

EDIT:
Processor in circuit is 432G2533
There is another chip 564Rk-K540, I google it and could not find purpose of it.


texts:
I'm designing an interface board to connect a MIPI DSI LCD screen to an RPi. The screen is a KWH070KQ40-C08 (link to pdf), but the datasheet isn't quite clear and I don't get an answer from the company. I tried googling, but found no topic talking about interfacing MIPI DSI screens.

These are the pins with their recommended voltages. The datasheet only talks about current draw on the LED+/LED- pin (which is around 180mA).

LED+: 10V (Anode LED blacklight)
LED-: 0V (Kathode LED blacklight)
LCD_VGH: 18V (Gate ON Voltage)
LCD_VGL: -6V (Gate OFF Voltage)
AVDD: 9.6V (9.4V - 9.8V) (Power for analog circuit)
VDD: 3.3V (Power for digital circuit (1.8V))
VCOM: 3.15V (2.85V - 3.45V) (Common Voltage)

The board will be powered by a 5V USB connection and has a 3.3V voltage regulator. (not on schematic)

For making the 10V (LED+), I plan on using a DC-DC switching converter (MIC2288), which may or may not be an overkill. Can I connect LED- with the ground or do I use a 0R resister inbetween?

For VCOM and AVDD I was thinking on using respectively +3.3V and +10V and drop the voltage with a Schottky diode or voltage divider with buffer. But since I don't know the current draw I'm not sure what to choose.

Same goes for LCD_VGH and LCD_VGL, I could use a second MIC2288, make 24V and shift it down somehow by 6V. Or use 2 voltage converters for making -6V and +18V.

Besides the power pins, we have the 4 datapairs and clockpair. These I will connect directly. (not on schematic)

Lastly, the 4 signal lines.  UPDN, SHLR, STBYB and LRSTB, as there is no further information about these pins, I made room for a pullup and pulldown resistor so I test which one it is. (not on schematic)


texts: Do I need a blocking diode for bulk capacitors connected to solar panels?

texts:
I have two 100 uF bulk capacitors connected directly to a solar panel which connects to a BQ24298 charge controller on a Particle ESeries microcontroller.

I have them left unpopulated because I don't know whether the reverse current could damage the solar panel (5.5 watt 6 volt).

Would it be bad to connect these capacitors without a blocking diode? How about the smaller bypass capacitors?


texts: Why it is recommended to not to add copper planes and to avoid routing of signals under the common mode chokes?


texts: How to drive up to millions of ws2812 or APA104 LEDs?

texts:
I've driven more than 2k of APA102 from a computer using a USB to SPI interface for an interactive project.
Since then I've been curious how I could made the same setup for even a large pixel area, up to a million or more pixels from a computer.

Definitely it wouldn't be with USB-something interface and it would probably require output from a Ethernet connection (similar to the sending and receiving card of a display screen matrix).

What drivers exist on the market to accomplish this kind of setup?
Maybe it would require a fpga to parallelize the output data.

I'm looking for a commercial ready solution mostly.

Edit
Looks like Pixblasters can do exactly what I'm asking for, but is not yet available.


texts:
1- How does a typical street lighting circuit look like? (for 230V/50Hz, with details)

2- Without having the network plans or knowing anything about the topology of the circuit, is it possible to map out the circuit by a series of measurements at the junction box of each post?

My idea is to:

adding a known load to each post
turning ON and OFF the load
measuring the current and voltage at that point
then calculating the voltage drop
finding the topology, etc. with a series of calculation

Can I find the topology by measuring voltages, phases, ect?


texts: Problem with update to Keil uVision 5 with STM32F4 discovery

texts: My dev system doesnt work in Keil with STM32F4 discovery (STM32F407VG). I am using uVision 5. All my drivers are up to date. The code gets compiled without any errors, however, I cant get the Logic Analyzer to show any data. With the board, the core clock is 16 MHz. I have all combinations of core Clocks in the Trace Tab. The weird part is that the same settings and code seems to work with uVision 4 with 16 MHz as the core clock in Trace Tab. Can anyone tell me what am i doing wrong in uVision 5?


texts: Does decrease in voltage decreases the speed of electrons in a series circuit?

texts: Let's say we have a 5V battery and a ohmic conductor that consumes energy connected in a series circuit with constant resistance. When we increase the voltage, the number of electrons flow through a point per second increases as well. But when the component consumes the energy and creates a potential difference of 5V, the energy per unit of charge decreases, therefore, will the current in a series circuit always changes after the component? Or is it that the change in rate is too insignifant and we ignore it. Of course, current in a series circuit is the same everywhere, if not, there would be a 'traffic jam' of electrons in the wire which is weird. So can I know why?


texts:
I'd like to find a simple way to control the lights in our local theater. We have panels and everything, but I'd to experiment with the way I can control the colors of the lights. I'm a web developer and interface designer by profession, so I'd like to 'design' a Web-like interface for this.

Now I wonder: could it be possible to use the audio-out of my computer and/or telephone to send a DMX512 signal?

Every 'command' could be a 'pre-recorded' sound, stored in a WAV. "Dimmer Number 5 To 256!" could then be, conceptually, an iTunes song.

I'm not worried yet about how to couple the devices. I believe it must be doable using op-amps or optical coupling.

I am worried about the 'frequency'. Could I indeed create 250 kHz signal that would make it all the way to the audio-out? Would the signal 'survive'? (250 kHz signal is based on the 4 micro second width of a bit in the DMX512 signal).


texts: Mobile headset audio OUT to MIC of another mobile using adapters

texts:
I want give sound output of one android mobile to MIC of another android mobile using adapters only ( I can not build circuit).
One person suggested some work around using adapters , Please find below the handmade diagram based on suggestion. Can anyone please confirm whether it will work ? Because as per my understanding we can not feed sound output directly to MIC of another mobile due to level of sound.
Please guide on the same or please suggest some sample or something better whatever is in your mind or YouTube video to achieve the same.
Below adapters are used in this diagram as of now -
male TRRS to two female TRRS cable, male TRRS to Microphone and headset splitter, 3.5 mm mono to stereo adapter, 3.5 mm male to male TRS cable.

My target is to transcribe ( speech to text ) the voice of the caller on mobile1 to mobile2 using some speech to text software installed on mobile2. So If I will get call on my mobile1 then whatever caller will speak will be translated to text on mobile2( using some app installed on mobile2).


texts:
I had a recent design flagged from the PCB house because of a via that almost didn't connect to the power plane it should have, due to its placement on a split line (see below).

I want to add a design rule to catch this type of potential problem in the future, but I can't figure out how to do that. I've tried using the "Incomplete connections" and "MinimumAnnularRing" rules, but neither one is flagging this.

Is there a design rule in Altium that will catch when most of a via's copper is masked off due to a split line?


texts: Inability to forward bias diode in a simple circuit

texts:
I am struggling with forward biasing a diode in the circuit in the attached.

All the wires are attached properly, as there is continuity. The diode drops only 0.400V with a 9 V battery connected, the resistor being 330 ohms. I cannot understand why the diode would not drop the amount required to forward bias itself and as a result allow current through the LED. At the moment most of the voltage is being dropped across the resistor and LED. Am I making some fundamental mistake I cannot see? Of course I tried connecting both the diode and LED in reversed polarity with no change.
Apologies for not posting more pictures. I have RSI and need to limit how much I use the computer.


texts: Op Amp Input Offset Voltage vs Common Mode Voltage

texts:
I would like to use an op amp AD8618 for a design, and need the input offset voltage to be low. For this op amp it seems fine with maximum of 65uV, but looking at the charts on page 6 etc, it seems to indicate that the input offset voltage in fact changes depending on the common mode voltage (at the inputs?) to much higher than that. (https://www.analog.com/media/en/technical-documentation/data-sheets/AD8615_8616_8618.pdf)

I intend to bias the amp at 2.5V, which could mean very poor results!? Is this a characteristic of all op amps, could someone explain to me or provide me a resource on this phenomenon?


texts: 100 mA current sink with LM317 does not work above 25V

texts:
I needed a current sink for something and I arranged one with LM317T:

simulate this circuit – Schematic created using CircuitLab

It has a switch to select whether I want to sink 100mA or 500mA of current. I've plotted the whole thing for completeness, the actual problematic part is only the 100 mA side, through the 12 ohm resistor. Both the SPDT and the resistors are beefy enough to handle the current.

After assembling it and putting a heatsink on the LM317, I measured what's the max power that can be dissipated. I used a bench power supply connected across my device (no other load besides the circuit above). At 12V in, and configured to sink 500 mA, it stayed within the SOA indefinitely, and the current was stable, so 6W were okay to dissipate with the heatsink I chose (it could handle more, briefly). Figuring that at 30V / 100 mA, the dissipation would be only 3W , I also tried it, but I noticed that while the current started at 100 mA, it quickly backed down, as if some kind of protection was triggering inside the IC. The problem starts at around 25V in, below that I get the expected 100 mA indefinitely.

What kind of non-ideal behaviour am I hitting here? The datasheet doesn't mention anything other than the resistor being needed, and also the circuit is within the design limits (indeed, at 20V/100 mA the heatsink is much cooler than at 12V/500 mA). I'm almost sure that heat/power isn't the culprit here.

EDIT:

As suggested in the comments, the oscilloscope traces revealed the issue, it was oscillating, at around 3 MHz:

Top trace is Vout-Vadj (i.e., Vout-Gnd), 1V/div. Bottom is Vin-Vadj, 5V/div. The oscillation appears at Vin > 15V, and only becomes worse at higher voltages. No oscillation for Iout=500mA, even at Vin=30V.

So I guess I should put some 10µF across IN-ADJ, right?


texts: How do I know if there is internal resistance in an LED?

texts:
So I have a circuit that seems to defy all that I know about LEDs.

I cut apart 2 flashlights that run on one 1.5v battery each with a variable resistor (0 to 50 ohm) to change brightness. I am now running them off of a 12V battery with leads connected to their battery terminals. In testing they both come on if I connect them in series with 1.5v and no resistor and draw 25mA which is strange because I thought you needed to double the voltage if you double the LEDs.

Since there was no resistor and they didn't burn up that implies that 1.5/2 is the voltage drop of the diode but then why didn't they burn up with 1.5v and no resistor across just one of them? What is going on with these?


texts: Are travel adapters safe to use permanently?

texts:
I got a phone from Malaysia and it comes with a UK charger(I think? see pictures).

I live in EU and would need to use an adapter permanently to charge it using the fast charger it came with.

Is it completely safe? (no fire risk or damage to the phone or the house)


texts:
I am developing a dolly-pan-tilt system, where an Arduino is connected via I2C to three independent rotary encoders for positioning. Having read a few posts on this site and elsewhere, I am aware that I2C has a limitation regarding distance of the cables for correct signal transmission. My issues/questions are the following:

SDA and SCL wires ought to be twisted, although some think they don't need to?
I am thinking of using a twisted SDA/SCL for each function, dolly, pan and tilt movement, which sit very close to each other on a 24pole flat ribbon cable.
So, twisting is probably adequate as well as an I2C repeater, as the distance between the Arduino controller for the dolly encoder is around 2.20m, the distance for the panning encoder is about 1.80m and the tilt encoder is closer with 0.60-0.70cm.

However, I have seen mention of I2C repeaters as well as extenders: which one is better suited as they seem to both be doing the same?

I2C extender: P82B715

I2C repeater: CPC5902G by Clare

What is truly the difference and advantages between the two ICs?
Also, I read somewhere, that the overall distance between the master and his I2C slaves ought to be considered, in my case: adding up the above mentioned distances 2.20m+1.80m+0.70m for all three movements, and not consider them independently towards the microcontroller; —is this valid?

As unfortunately all three I2C cable pairs are right next to each other (distance between each line is 1.26mm) on the ribbon cable followed by the GND line, it can still get noisy as thereafter are the cables driving the DC motors +/-  @ 12V and up to 2A.
I did my calculations regarding wire capacitance concerning the ribbon cable AWG (28), based on this website and ended up with 38.51pF for 2.5m of cable.

The datasheet of my encoders demands though to remain below 10pF, in order to ensure correct operation!


texts:
sorry for spamming about questions today, but I am riddled here.

SOMEHOW there's 2.2V at the output is that even possible?!

LM833N Datasheet

simulate this circuit – Schematic created using CircuitLab


texts: 18V/5W solar panel to trickle charge a 12V car battery?

texts:
I'm running a small Arduino project out of an old 12V car battery (that was on my car since 2008 till 2015).
I also have a 18V/5W solar panel.

Can I connect them together so the solar panel charges the car battery? The Arduino project is really really low on consumption so even a trickle charge will be enough to keep it running "forever" with the help of 1-2h of sun per day.

Thanks!


texts:
My charge pump circuit is giving increased Vload in simulator, about 22v.

but when I breadboard and test, with Vsupply from a 12V power supply, multimeter shows Vload about 11v.

I've tested changing parts of same model but still getting same voltage so I think my parts is working.

what might be reason?

Is there anything I should know about choosing my parts? power level of resistor, etc.

So I tested and C7 not charging, C13 charges though, what is causing error

oops, I missed resistor 1.5k. Now I can get 20 volt


texts: I am having problem with a few millivolts of ground loop in my single channel amplifier circuit when I ground the input (pin 1 on socket, - input of op amp). I am using INA121 instrumentation amplifier with LT1012 voltage follower to create virtual ground from power supply. Should the reference channel of the INA121 be isolated from the virtual ground, or could the cause be something else?


texts: Light Activated Switch Circuit with delay

texts: In reference to this circuit: Photoresistor snap-on/off switch. If I wanted to add a small delay so that the circuit doesn't immediately turn then and off if the ambient light temporarily dips below the "on" threshold, could I add a capacitor like so at the base of the NPN? Or should the capacitor be placed elsewhere?


texts:
I have a problem that I need to measure an RPM of a rotating axle with a single element (circuit) attached to it - i.e. I can't use a hall effect sensor, because I can't use a separate magnet - I can only use what's mounter on the axle. The axle will rotate only on one axis - but that could be X, Y or Z. So the solution should be modular in that regard. I'm looking to measure up to 150 RPM most, and I'm using an Arduino for the readings.

I was thinking of using an accelerometer, a gyro or a compass. Compass feels like it would fill the bill best, but I'm not sure it would work properly on every axis, not just Z?

What would be the best component and implementation strategy for a solution to such a problem?

Thanks for the "-1"s, here are the clarifications:

A single element as in one part product - for hall effect we'll need two parts - the sensor and the magnet. So the whole end product should be a single element.
An axle can rotate only on one axis, but it could be initially placed on different angles - so the same circuit should work for any kind of setup (any axis).
The speed information will be collected on the rotating part.


texts: Working of a Comparator based Oscillator Circuit

texts:
I was trying to understand the working of this circuit, but couldn't figure out, how does it generate a square wave.

Here is what I figured out by looking at this.
The Op-Amp behaves as a comparator. Assuming output to be +3V initially, the capacitor will charge. Once it charges the output will be -3V.

The bottom circuit, looks like a divider giving -1.5V at the non-inverting input.

What happens next?


texts: Noise performance at cryogenic temperature

texts:
I want to know what kind of improvemend electronic circuits get at cryogenic temperatures.I looked at online noise calculator and it shows that if I go from room temperature to 1 kelvin the noise drops by 3db,that is lot less that I expected.

So if I have galium arsenide transistor at room temperature and then I cool it with liquid helium to some very low number like 5 kelvin,is 3db really all i get? Does the noise drop proportionaly across the whole spectrum from DC to the maximum freqency of the transistor,or does the noise drop more in specific part of spectrum,for example if the temperature have more effect on 1/f noise in the lower freqencies.

It seems to me the mild drop in noise doesnt justify the added expense of using cryogenic electronic circuits,can you name me the benefits of running amplifiers at low temperatures?


texts: The electronic analog tachometer on my small boat diesel has recently started to overread on startup of the engine (e.g. it reads 2000 rpm on idle).  After about 5 - 10 minutes it drops back quite suddenly to more realistic figures (about 750 rpm on idle, and about 2250 at cruising speed, both of which are probably not far off the truth). I don't have a fitted voltmeter, but do have a portable multimeter, though accessing the batteries whilst the engine is running is difficult. System is 12 VDC, and for the engine electrics, common negative via the engine block. Grateful for any advice - e.g. instrument failing or alternator failing etc.


texts:
Is it possible to do an LLC resonant converter with an air core transformer (wireless power transfer)? I've read basics about it but I've all read that they use some type of ferrite cores. I think that it should be possible at first but I am having second thoughts based on what I've read but I just want to know from more experienced ones.

I was thinking for an air-core based, the inductances (and coupling factor k) simply change depending on the 'state' of the two coils (primary and secondary). By state, I mean it depends on how far are the two coils (distance) and how axially oriented are they. I believe it goes like this:
1.) Lm (magnetizing inductance) represents how much flux is coupled from the primary to secondary. Thus, if the two coils are further, less flux is coupled from primary to secondary coil, and this changes Lm.
2.) Lk (leakage inductance) represents how much flux is "wasted", meaning how much flux isn't coupled from the primary to secondary coil. So in a air-core one, since permeability of air is not high, Lk would be high compared to ones with core. Moreover, Lk also changes when distance between two coils are varied since as distance becomes larger, more flux is "wasted".

For an LLC resonant converter, the tank consists of Lm (magnetizing inductance), Lres (resonant inductor, external?), and Cres (resonant capacitor, external). I do know that resonant controller ICs use variable frequency control to regulate the output instead of PWM. So I was thinking, in an air-core transformer, distance can change which means Lm (part of resonant tank) changes. This also changes the resonant frequencies. And I believe in the design part I've read, resonant frequencies are part of the design so with changing resonant frequency in an air-core, is implementing LLC actually possible?

Thanks


texts: On interpreting this set of curves (Transistor in Saturation mode and decrease of \$h_{FE}\$)

texts:
The following figure was excerpted from Horowitz's The Art of Electronics, Appendix  G: Transistor Saturation (page 1089 for the 2nd edition),

It represents the current gain \$\beta\$ of an npn transistor ( or \$h_{FE}\$) as function of the collector to emitter voltage in the saturation mode of operation.

If I understand the curves correctly, for a fixed collector current value, for example 10mA, the current gain \$ \beta\$ decreases as \$V_{CE}\$ diminishes. What I don't understand is how can \$I_{c}\$ remain constant while \$ \beta \$ decreases?

We know that \$ I_{C} = \beta I_{B} \$, thus, if we reduce \$ \beta \$ by decreasing \$ V_{CE} \$, then so must \$I_{C}\$, i.e., it should become less and less smaller than 10mA as \$V_{CE}\$ is reduced. Or am I misinterpreting the curves  ?


texts: 10GHz Regime Differential to Single Ended Conversion

texts:
I'm looking for a board mount (IC) solution that will take the differential output of something like ONET1191 @10GHz and convert it to 50 or even 75 Ohm single ended.

I've looked through various suppliers for:

Baluns (and other transformer solutions)
Differential Amplifiers
Receivers/Transceivers

However, I can not seem to find any modules with a pass band around 10GHz. I see tons and tons of ~6GHz modules (makes sense because 1080p60).

Alternatively, I could simply pass it out through 100 Ohm twinax and into a discrete RF amp that takes differential input (those do exist, but they are expensive!!!). I am hoping to avoid this, due to cost reasons.

Just throwing this out into the wind to catch some useful suggestions, thanks!


texts: Ceramic capacitors in series to increase AC voltage rating

texts:
If I put 4 of 1uFx100V cercaps in series I will virtually have one .25uFx400V capacitor.

As I know I should use balancing resistors for even distributinon of the voltage across the capacitors. However if I skip them in the simulation I did not find any diviance in the voltage - no matter which ESR or parallel resistance deviance I put into model.

So my conclusion is that in case of AC (no DC) there is no need for balancing resistors. Is that correct?


texts: How are LEDs timed? (How is the pulse latency measured?)

texts: Please excuse the awkward phrasing of the question; it seems that LEDs have pulse latencies of nanosecond and sub-nanosecond durations. The question is, how was it possible to measure such precise increments of time? Is there ultra-high frame rate footage of this?


texts:
Anyone know if the footprint wizard in Altium can be used to generate SOT669 package footprints?

It appears to me that its only capable of 3 lead MOSFETs. I searched the web and couldn't find anything, I don't mind making footprints by hand but its a standard form factor and I'm a little confused why its not an included option.

Someone feel free to correct me if I am missing something entirely within the options on Altium.


texts: How to receive a startup hex string during a debug session?

texts:
This is my setup:
I have a 'smart display' connected to the serial interface of a PCB with a PIC microcontroller. The PIC powers the smart display.
This smart display uses a boot mechanism.
When the power is on, the display start bootup. This process takes a few seconds.
At bootup, the  display sends a hex string to the serial interface.
I want to debug this serial interface using MPLAB X: I want to see the values of the received hex data.
However, during a debug session, it always hangs in an infinite while loop of an EUSART routine, waiting for data to receive.
I can't find a way to 'catch' this hex string during a debug session. Is there a way to receive hex string somehow?


texts:
I was reading and found that there are different ways to calculate "link budget" and I want to know which one is correct because they are confusing to me.
For example, some sources state that link budget is equal to the received power at the receiver (accounted for gains and loses).
Other sources state that link budget is calculated by subtracting the receiver sensitivity from the received power. This is something other sources denote as "link margin".
And then there is "max link budget" which is the difference between transmitter power and receiver sensitivity.
Can someone please help clarifying this.


texts: Understanding short circuits (in Arduino) and identifying electronic devices

texts:
I'm a programmer and I recently purchased an Arduino Uno and I've very scared to short circuit it.  I've been playing with http://www.falstad.com/circuit/ and have been able to create a few LED sketches and a piezo buzzer circuit.

So far, I've stuck everything behind a 470Ohm resistor.  I have two problems.

First, how far can I reduce my resistor but maintain board integrity?  Bonus, what should I look for in Falstad's circuit app? Possibly current over a certain threshold?
Second, what are some good ways to identify scavenged supplies so I can build safer circuits?  Such as unmarked piezo buzzers, LEDs, and motors.

I've been doing research these past two days and discovered resistance lowers current not voltage.  In order to lower voltage I can use a voltage divider


texts:
This is the schematic for the project. I'm using an IRF520 transistor (http://www.futurlec.com/Transistors/IRF520.shtml) which goes from left to right Gate->Drain->Source. So the problem is that when gate is connected to a pin on the arduino the transistor will always be open regardless of what that pins state is but if I pull it out the transistor closes. Any help would be appreciated.
imgur.com/a/dYliz
EDIT:
Added Schematic link


texts:
Will there be any current in the given circuit? If current exists then why do they exist and what will be the forward and reverse current and voltage(across the diode)?
As a student of Physics I will love to have an intuitive explanation on the context of electron flow as the reason of current!


texts: Will the measured powers & energies of two 120V circuits == that of the 240V circuit?

texts:
I'd like to design a circuit using the STPM34 (2 channel power meter) that can measure either the power and energy delivered on two separate 120V circuits (one circuit Red Wire, other circuit Black Wire), or the power and energy delivered on the 240V circuit (Red Wire + Black Wire).
The STPM34 reports complex power, and accumulates energy measurements over time. Fundamentally, is it the same to calculate these values by measuring the voltage between Red and Black (and current through Red/Black) as it is to calculate them both for Red-to-Neutral and Black-to-Neutral, then sum them?


texts: Multiple Power Supplies Powering Long LED Strip - Proper Way to Ground

texts:
Please refer to the above diagram.

The 2 power supplies are each placed in the opposite end of the led strip.

I will be connecting the signal ground and the power ground just before it connects to the led strip to reduce noise.

But do I need to tie the grounds of the 2 power supplies? I searched around and it seems I do indeed need to until I came across this thread:

Can identical DC power supplies with common ground produce varying voltage on same circuit?

RoyC said, "The better one has the horizontal ground line just below the supplies removed and the ground from each extra supply connected directly to the strip it is driving as well as the ground from the driver board".

I may have mistaken the meaning of his statement but does that mean I have to connect the grounds of the 2 power supplies right before the load and not right after the power source as seen by the orange line drawn in the diagram?

But the length between the start and the end of the strip is around 13M and the distance between each strip is different (strip 1 and strip 2 distance is around 11M while strip 2 to strip 3 is 1M). Does that change anything?


texts: Can a fixed output buck have too much output capacitance?

texts:
I'm working on a design with this buck regulator:
tps62130
I'm using the 5V fixed output voltage version. I'd like to have significant capacitance on the 5V output because the device can be powered through another source (separate from the buck entirely) also feeding the 5V line. I'd like to throw on something around the order of 220uF tantalum. I've read plenty of warnings about causing loop instability with too much output capacitance on buck regulators, in the datasheet and in other questions like this:
can-there-be-too-much-capacitance-on-a-buck-regulator-output
My question is since I'm using the fixed output voltage version that doesn't use the feedback pin, is it still susceptible to loop instability due to the output capacitance? The datasheet is pretty clear about recommended output inductor/capacitor selection, but the document covers all versions of the buck - including the adjustable output ones that use the feedback pin and I'm sure require the specifically tuned output caps. It's not clear if that applies to all versions of the regulator.
And if the capacitance would cause a problem, my follow-up question would be how do you deal with that situation? Is there a recommended way to isolate the two power sources so capacitance on the other source doesn't affect the buck, or any other way people have dealt with it?
Thanks for any any insight!


texts:
I have a project which involves building a 64 x 48 (3072) LED matrix driven by a Raspberry PI computer. I am a first-year computer engineering student so I am still inexperienced with shift registers and multiplexers. I'm wondering what would be the most efficient way to go about multiplexing these LEDs. Some of my options include the MAX7219 multiplexers, or 74HC595 shift registers. In particular, I'm interested in knowing how much of each chip would be required to multiplex this matrix, and which would be the better way to go?

Also, in terms of power, I was thinking of using a power supply like this one to power all of these LEDs. Would that work or would I be faced with brightness issues and power draining driving all of these LEDs at once?

I'm also interested in hearing any tips or thoughts from someone with experience in a similar project in terms of things that could go wrong in a project this big with so many LEDs, and how I can prevent them.

The LEDs are 3mm super-bright red (5 Candela) rated at 1.9-2.1 DC Voltage and 20mA forward current.


texts:
For a robotic application, we bought Adafruit boards of the very popular BNO055 IMU. We can still buy plenty of these modules, but it seems the BNO055 chip itself is unavailable. It even disappeared from the Bosch website without any information.
Why is this chip unavailable and what could be a good alternative that includes sensor fusion?
Ultimately, I would plan to use it with ROS.


texts: Odd hundreds of amps when switching on braking after adding braking resistor to H-bridge

texts:
I am trying to deal with current being rejected by a H-bridge when doing dynamic braking of a motor: to control the amount of braking, the PWM duty cycle adjusts the time the motor spends coasting (all transistors off) vs being short-circuited (both high transistors on).

When coasting, the braking current still flowing goes through the H-bridge's body diodes and tries to make its way to the supply, but it is unidirectional. So I've added 3 Zeners in series to take care of transients, but I would like to redirect the bulk of the power dissipation to a power resistor, so I've added one. Without associated chopper, I don't mind the inefficiency.

After adding in the resistor, very regularly within 10ms for example, I have hundreds of amps flowing from the supply (dark blue) - and 10A through the Zeners (green). These spikes always occur when the high transistors are switched on.

Where do these spikes come from and how to remove them (a diagram would be nice if relevant)?

P.S: DC brushed Motor parameters: R=10 Ohm, L=50mH, backEMF=40V, motor current (outU to outV)=1A decreasing down to -2A in 10ms. PWM duty cycle is 50%.

Edit: This spike goes through all transistors AND diodes of the lower half to ground! What's happening?

Edit 2: Adding a 10uF capacitor in parallel of the H bridge solved it - but I am still curious about why this happened.


texts:
I'm building a new gaming computer, my first one, and I've been reading a lot online about grounding and ESD, but can't seem to get enough understanding on how it works and how I can prevent damage. For context, I live in a small apartment on an upper floor, and every floor is covered in wall-to-wall rug, except the tiny kitchen and tiny bathroom. I have radiators and obviously wall sockets, but I do not have any tools laying around besides the very basic toolkit (screwdriver, hammer etc). I did purchase a set of anti static gloves but now I've read that it may not be enough for ESD protection.
My last part will arrive today, so I was hoping to build it tonight, but if I need to buy an antistatic mat to prevent damage I can do that. Any help would be great. Thanks
Edit: The motherboard comes in an antistatic bag and I think (?) that would be the only other antistatic related thing I have.


texts:
I first did a simulation of a simple circuit with the IC SN74HC74D and it outputs 5V, please see attached image.
I made a circuit and ordered a PCB. When soldered it only outputs 2.5V(Pin ~Q_2). I cannot figure out the reason.. Is the simulation faulty?


texts: Can I use the output of mobile charger as a DC source for my circuit?

texts:
The title explains it all. Can I use the voltage and ground pins from the mobile charger and use it in my breadboard circuit? Is it safe?
If it isn't, what is the thing I need to buy so as to convert 230V AC to 5V DC? I don't know the name of that thing..


texts: Where to find pre-made wires for plugging into headers?

texts:
Headers like these:

http://uk.farnell.com/harwin/m20-8760342/header-smt-vertical-2x3way/dp/1517388

I'm looking for cables that connect to these, with female headers on either end. Any length more than ~5cm is ideal. But I can't seem to find any results on my favourite websites. I'd rather not spend time crimping them myself as I have to produce a lot of them.

For this application I need 4 way connections, but it would be nice if many different way counts were available, so I know what to buy in future.


texts:
Here is the circuit I am trying to understand:

It comes from the following application note from LT:

https://www.analog.com/media/en/technical-documentation/technical-articles/D61_EN-Convert.pdf

I am wondering how the Nmos will ever be triggered. Now from my point of view, the op-amp's negative input should track the voltage on the positive input, setting transistor M2's source voltage to Vin. Now since the op-amp is in the voltage follower configuration, the voltage at M2's gate would also be Vin.

Now that seems to me like Vgs would always be 0V and the FET would never turn on.

I am absolutely certain that my analysis is wrong, I am just not seeing where.

Thank you in advance for all advice.


texts: How can a synchronous motor have RPM other than 3000/3600?

texts:
It is said, that synchronous motor is rotating at the same speed as magnetic field rotates. But three-phase made magnetic field rotates as the frequency of current, i.e. 50 or 60 times per second, which means 3000 or 3600 RPM.

How can synchronous machines on Aliexpress have other RPMs, like below?

There multiple of these, no any mistake expected. Many of them has 3 explicit inputs.

UPDATE

Sorry I agree that in slow RPMs reduction gears are most probable inside.

But can I be sure, that if motor is "synchronous", then magnetic field is rotating at 50/60 Hz and inner rotor is rotating at the same speed?


texts: DC Motor pwm control and flyback diode question

texts:
Suppose we are controlling a dc motor via pwm. he motor has a flyback diode across it.

Question : During pwm off period, the motor current freewheels through diode. Won't the motor experience a braking torque then. Is it desirable for efficiently controlling the motor?


texts: Voltage Controlled Current Source - help needed

texts:
I am designing a voltage controlled current generator for the currents in a range from 0 - 2.5mA. The load resistance is within the range of 0 - 5k Ohms.

I decided to go with difference amplifier approach, similar like this:

Here is the part of the board that I designed and manufactured for testing purposes:

I used SPI-controlled DAC module (AD5620) to generate reference voltage for the voltage controlled current source. Generated current can be expressed by the following formula:

Iload = VREF/R1 = VREF/1KOhm

Consequently, if my DAC gives 1V to the current generator, the load current should be 1mA.

You can also see that I am using low-side current monitoring. 10 Ohm reference resistor together with LTC2054 opamp whose gain is equal to 100 helps me generate the voltage proportional to the load current, that can be expressed with the following formula:

Vi_monitor = 10 x Iload x 100

So, if my load current is 1mA, the voltage proportional to the load current will be 1V.

In addition to that, I am also monitoring the voltage on the load resistance by the help of voltage divider circuit made of resistors R2 and R4.

Before making a PCB, I simulated the above circuit in LTSpice and noticed it behaves as expected.

I finally manufactured the PCB and did some on-board testing. I used digital voltmeter/ammeter to measure the current through the load resistor. Here is what I got:

For the loads whose resistance is up to 2.5k Ohms (more or less), everything behaves as expected. Measured load current is proportional to the reference voltage generated by DAC module. However, when I increase the load resistance to the limit of 5k Ohms, the measured load current is saturated (less than theoretical value).

What is confusing me is the fact that even though I detect the saturation of the load current (on my ammeter display), the voltage proportional to the load current (Vi_monitor) still behaves as theoretically expected which implies that I have desired current passing through 10 Ohm reference resistor (the same current should be passing through my load resistor!?).

Do you have any idea what is going on here? Why do I measure current saturation with the ammeter, but my current monitor tells me I have desired current through the load?

I supply the differential amplifier with 18V which should be enough, given the fact that the voltage across 5k Ohm load for the load currents of 2.5mA (worst case) would be 12.5V.

To give you a complete picture of my circuit, I would like to mention that I am using an MCU-controlled SPDT dual switch (TS3A24159DGSR) that helps me change the orientation of the load resistor and, consequently, the direction of the current passing through the resistor:


texts: Short circuit current of 3-phase open delta transformer

texts:
For a 3 phase open delta transformers:

When you are computing the short circuit current between the 208v high leg (point B) and neutral. Do you only use one 75kVA or do you add the other transformer to produce 75kVAx1.5 (or other value) = 112.5kVA?

Im thinking if you need to add because between point B and neutral, there are more than 1 winding (or 1 transformer) involved. What do you think?

The following is the nameplate of the transformers and the lever was set to 2nd:


texts: Calculating resistance for integrated circuit with logical gates, so that the circuit works properly

texts:
I have found this task with its solution:

For the circuit shown below calculate \$R\$ so that the circuit works
properly. All gates belong to the \$TTL\$ series.

Solution:
$$\begin{align*}R_{max} &= \frac{V_{CC} -
 U_{OH_{MIN}}}{\color{red}{N_O} \cdot I_{OH_{MAX}} +
 \color{blue}{N_{I}} \cdot I_{IH_{MAX}}} = \frac{5 -
 2.4[V]}{\color{red}{4} \cdot 250 + \color{blue}{3} \cdot 40 [\mu A]} = 2321 \Omega \\ R_{min}&= \frac{V_{CC} - U_{OL_{MAX}}}{I_{OL_{MAX}} -
 \color{blue}{N_{I}} \cdot I_{IL_{MAX}}} = \frac{5 - 0.4 [V]}{16 -
 \color{blue}{3} \cdot 1.6 [mA]} = 410  \Omega \end{align*}$$

Please ignore the actual current/voltage values, they come from the \$TTL\$ specification.
My questions are:

how can I determine what's input and what's output?

To my 'sense', \$ABCD\$ are inputs while \$XYZ\$ are outputs.

Why \$\color{red}{N_{O} = 4}\;\$ (number of outputs) and \$\color{blue}{N_{I} = 3}\;\$ (number of inputs)?

This is the part I am struggling with.
How can I determine what's input, what's output and how many of them are in the circuit diagram?


texts: I am doing single phase inverter,and the inverter will cause double line frequency, and it will affect the input port, and I would like to use active filter like buck-boost type to reduce the double line frequency ripple, but I don't know how to design the Lb and Cb and how to control the switch in the figure below, can someone give some advise?


texts: Voltage of a sine wave given max wattage rating

texts:
I would like to test a speaker by giving a sine wave of 200 Hz. On the technical datasheet following are mentioned

Sine Wave : 30W

Maximum music load : 60 W

Frequency Range : 40 to 2000 Hz

Impedance : 8Ω

What should be my voltage and current of the sine wave ? Ensuring safe operation.


texts: Difference between h-bridge, dual half bridge and quad half bridge

texts:
Note: I am beginner.
I'm looking at motor drivers on this website
Various motor drivers have different specification for output configuration, i.e. :h-bridge, half bridge, quad half bridge and PWM. I know an h-bridge is used to reverse polarity to the motor, but what is different about a quad half bridge, dual half bridge or half-bridge.
I want to use 2 of these motors


texts: What happens if the primary and secondary side of a transformer are short circuited mistakenly?

texts: I have described the condition in the transformer picture I have attached. Will the transformer still function in this condition?


texts: On a PCB, can an antenna for 433MHz RF be "far" from the transceiver?

texts:
When I design PCBs I always try to keep antenna as close as possible to the transceiver.
Now due to the design I need the transceiver schematic on the left side but the antenna on the right side of the PCB. Can I connect the antenna "far" from the transceiver(of course the wire of the antenna's connection will be on the ground plane so the wire doesn't work as "antenna").
Would it be a problem if the antenna's wire(trace) goes under/over components and other wires(traces)?


texts:
I am trying to use the GPDMA which is present in LPC43XX parts.

The UM10503 data sheet constantly warns about memory boundaries (datasheet section 21): basically it says that you don't want to try a burst across a memory boundary otherwise "the transfer will be split into two AHB transactions".

The problem is that I don't understand what these memory boundaries are.

Here's some information (datasheet section 3):

RAM sections:

Memory Map

Are the memory boundaries those solid lines? If so, they seem to be too wide for me.

Any hint?


texts: How do star- (wye) plus delta-connected windings provide a phase change every 30°?

texts:
From the twelve-pulse bridge subsection of the Wikipedia article on High Voltage DC converters:

  The phase displacement between the two AC supplies is usually 30° and is realised by using converter transformers with two different secondary windings (or valve windings). Usually one of the valve windings is star (wye)-connected and the other is delta-connected. With twelve valves connecting each of the two sets of three phases to the two DC rails, there is a phase change every 30°, and harmonics are considerably reduced. For this reason the twelve-pulse system has become standard on almost all line-commutated converter HVDC systems, although HVDC systems built with mercury arc valves usually allowed for temporary operation with one of the two six-pulse groups bypassed.

I've looked at this and this answer, but I'm not familliar with the terminology or notation of phasor diagrams and their use in transformer winding connections.

Is there a simple way to explain how a star (wye)-connected and delta-connected set of windings can provide a phase change every 30°? How does this produce twelve equally-spaced pulses per cycle?

Image: "12 pulse bridge with thyristor valves" from here.


texts: What is difference between MOSIS and dedicate MPW services of foundries?

texts:
Most foundries, such as TSMC, SMICS, and Samsung have MPW and IC prototyping services.
What is the difference between these services and MOSIS or Europractice?
Question is:
Why use MOSIS services instead of direct use of foundries IC prototyping services?


texts: Strange behavior from a 4017 Johnson counter

texts:
I'm using a HEF4017BP connected to LEDs and a pusbutton to control some LEDs.

Here's the schematic:

So I'm using the pushbutton to drive the clock, the capacitor is there to help with debouncing and since the actual light level of the LEDs isn't important for me, I'm using one resistor for all on them. Not shown on the schematic is the decoupling capacitor, also 100 nF.

I'm expecting the counter to go through the LEDs as described in this diagram from the datasheet:

Instead of that happening, Q2 is always on, except when it should be on. In those cases, it's off. The other outputs are behaving normally.

So am I missing something or is the part damaged?
It came in stuck to a conductive "sponge" in an antistatic bag and I took the time to touch a grounded object before actually doing anything with it, so it shouldn't be damaged by ESD.


texts: Transistor with two voltage levels, Vb ≠ Vcc

texts:
Why is my transistor only driving 5V instead of 6V?  How can I fix it?

I have a 6V, 25mA circuit running some LEDs.  I can control them by connecting and disconnecting the positive terminal of the battery pack.

I want to control them with an Arduino.  So I added an NPN bipolar junction transistor with the base attached to the arduino's digital output pin and the collector-emitter acting like a wire from the positive terminal of the battery to the LED circuit.  I also connected the Arduino's ground to the battery's negative terminal, but the Arduino is powered off a separate power supply.

          o---------o
 #####    |         |
 #   #  |/         /+\
 # A #--|         (   )
 # R #  |>         \-/
 # D #    | ####### |
 # U #    | #     # |
 # I #    o-# LED #-o
 # N #      #     # |
 # O #      ####### |
 #   #              |
 #####--------------o

The problem is that the LED circuit really needs 6V to run, while the Arduino's digital pins only output 5V.  I don't quite understand why, but even though the collector is attached to 6V, the emitter is not really driving 6V, even when the base is on at 5V.

It's a little hard for me to debug, since the circuit is all diode-y, so if it doesn't get enough voltage that part just turns off in a non-ohmic way.  Part of the circuit only needs 5V to function, and it works, but the longer series of LEDs only works when I connect the base to a 6V source.

  What is going wrong, and just as importantly, how do I fix it?


texts: Electrical noise on guitar pickups from computer. Due to radio interference, or inductive coupling?

texts:
When I point my guitar pickups towards my desktop computer from several feet (2 1/2 - 3) away, I can hear a lot of buzzing/clicking, depending on what the computer is doing (idling vs, say, playing video). Are the pickups picking up radio interference from the computer which is being demodulated by the amplifier, or are they inductively coupled to the computer, despite the lack of coils & distance?

I have trouble believing that it's radio interference that they're detecting (I've never gotten an AM signal through my amp, for example), but given the distance, I also have trouble believing that inductance is generating the noise. Can anyone shed some light on this?

Thanks

EDIT: To clarify, I'm talking about a single coil pickup, not a humbucker. I'm not really interested in reducing noise, it's not an issue for me. I'm just curious about what mechanism is involved.


texts:
I have an RFID tag and I would like to know the manufacturer. According to RFID journal, the E0 format uses an 8-bit manufacturer ID. I've got this code. Is there some table where I can look up the manufacturer?

Please note, I'm not looking for the table of E2 manufacturers


texts: Is moving fast will effect WiFi transceiving beavior?

texts:
Let's say I'm driving a 2010 Bugatti Veyron 16.4 Super Sport, with speed of
431 km/h = 268 m/h = 119 m/s

Now I have a WiFi signal receiver installed on the top of the car and a WiFi transmitter in a fixed base station.
[An access point in a fixed station that covers area of 4km , and a WiFi receiver with high power]

Will moving this fast effects receiving the signal ?
What are the parameters to calculate the possible drop in signal
receiving ?
Will any packets get dropped when moving this fast ?
Is it the same situation for transmitting from the car to the station
?

What I found till now that Doppler effect may effect , but I don't know how.

Update#1:
Wi-Fi in high-speed transport communications


texts:
I want to design a paintball counter. I have a metallic or plastic tube through which a paint ball passes.

How can I detect that the ball passed? What kind of sensors do I need?

I cannot see the ball from both ends of the tube, thus I need a sort of non mettalic detector.  I dont want holes, and not microphone because of the tube will shake. And no obstacles in the tube.


texts: Why do accelerometers have holes etched in their masses?

texts:
I have been studying MEMS for a while now and I noticed that in almost every accelerometer design there are holes etched in the mass that is attached to the hinge. Why is that?

A thing I thought of is that the masses are so tight to the packaging that pressure on one side could affect the mass if it was moved or shaken with. But that would be easily solvable by putting it in a low vacuum.

I attached a schematic drawing of an accelerometer that we used.


texts: What header file replaced  in the Atmel ARM processors?

texts: I am not interested in using ASF. Is there a header file that is used to set register bits as you do with AVR besides using asf.h?


texts: Trouble connecting to temperature controller using MODBUS,RS485 and MATLAB

texts:
I am trying to communicate with a temperaturature controller ATR-401 using MATLAB but i am having trouble just connecting to it and reading temperature data.I have set baud rate, data bits, parity and stop bits based on the user manual but it still does not recognize the device. The image below shows my code:

The image below shows my device manager :


texts: How to reduce LED flash rate (frequency)

texts: I have purchased an LED flasher circuit from Ebay (see jpg) for use on a model plane, but the flash rate on the circuit is much too fast, about 4 flashes a second. I am trying to achieve 1 or 2 flashes a second. What component would I need to change to reduce the flash rate? I have listed the components in the PDF and have drawn out the circuit, so I hope that helps. Many thanks


texts: How to determine bipolar stepper motor wiring (came from a 3.5 inch floppy drive)?

texts:
I have extracted a small stepper motor from a 3.5 inch floppy drive, that I intend to use with an Arduino or Raspberry Pi. The problem is: initially a thin ribbon cable was attached to it, with no labels.

I couldn't use them, so I soldered wires to it. how can I determine which cable is what? I don't have a multimeter at hand, are there any other ways?


texts: Different screw and their material purpose for computers

texts:
At our computer store, I had a luck to get to screw sorting (uh, how I like that) and got to question: is there any guide/rules, where should each of them be used. There are different color/material, like: silver/light-blue, quicksilver, orange/gold, black (coated?), yellow/greenish, and maybe some more. What are material properties of each? Does black coating gives anything more than look? Does black coating with gray end mean something?

There are different head caps, like: round with flat washer, round with jagged washer, round with philips, truss with philips, flanged-hex/Phillips-head combined, pan with Slot/Philips combined, flat with philips, and many more (currently counted about 70 types).

There are tapered shanks or a non-tapered shanks, and at least three different shank sizes: fine, normal and large (for FAN/Cooler mountings etc).

Most of them I have usd learning from experience, seeing "what others do". BUT, is there any good-style where each of one should be used? Maybe, there are some with better electrical conductance, good for motherboard grouding/chassis points, others are good for vibrations with breaking head base, maybe others have high durability, others are good for plastic parts, others are non rusting. I don't know, please, guide me.

Some pictures from another store:

Cross round head with washer bolt, Steel, nickel plated, M3*.5, 5mm
#6, 1/4" long, 6.3mm, Philips hex head, 6/32 large thread screws. nickel plating.


texts: Unable to upload anything to Arduino Uno

texts:
Any time I try up upload a sketch to my Arduino, I get the following error message:

That "1 of 10" then repeats all 10 times, and ultimately fails. I know that this board works, as I am able to upload to it and the serial monitor loop-back test work fine on another computer.
I am using an Arduino Uno, plugged in via USB, and COM1 selected in the Arduino IDE. COM1 in my Windows device manager claims to be running fine:
I am running Windows 10, and I am using this board I am out of ideas. Can anyone help me get uploads working?
Edit: OK, now I'm getting a new device on my device manager, but Windows can't install any drivers for it:
I went to the Arduino help page for installing drivers, and found this: https://www.arduino.cc/en/Guide/ArduinoUno#install-the-board-drivers
I found the "arduino.inf" file exactly where that page said it would be, but if I try to pick a driver manually, I get this error from device manager when selecting the "drivers" folder containing "arduino.inf":

Edit 2: OK, had a breakthrough. Using Windows device manager, I right-clicked on my unknown USB serial device and was able to select "update drivers", "browse my computer for drivers", "let me pick from a list of available drivers on my computer", "Ports (COM & LPT)" and select the Arduino Uno.
Now COM3 shows up when I plug in the Arduino and disappears when I unplug it, and I get a different error message when uploading now:


texts:
I know what thermal voltage is and what it does to the semiconductor, ie. it's the agitated electrons producing electric fields proportional to the absolute temperature.
But, like the "r'e", the emitter resistance, its equation is thermal voltage over collector current. But doesn't it add when AC voltage is applied? If I'm applying 20 mV, shouldn't it be 20 mV + 26 mV? (maybe it's a vectorial sum)
If it's taught 26mV/Ic, it should be it, I just need to understand why this is the only voltage considered, even with AC signal.
Thanks in advance.


texts: I'm creating a power supply circuit to regulate the power from a 12V power source to sap flow sensors that will be installed in a tree. I have a protocol and circuit diagram I am following but am confused about how to set the voltage using the trimpot. Through the calculations I was given, using the resistances of the sensors attached to the circuit, I know that I need to regulate the voltage to 4.94 V; however I cannot figure out how to do that using the 1K trimpot. This may be dumb, but do I need to hook up the 12V power source before I am able to set the voltage on the trimpot? Also, I believe I set the voltage of the trimpot using a multimeter...does it matter which terminal end of the trimpot I touch the multimeter lead to? I have both terminal ends hooked up to the circuit (per the diagram I am following), so I'm not sure which end to touch the lead to for the reading or if it matters.


texts: How to use a Linker File with Keil uVision5 ARM?

texts:
I am trying to follow a tutorial implementing a custom bootloader on a STM32F072 (ARM M0 Core), which requires remapping memory areas when compiling for both the 'bootload' application and the 'main-application', which is then programmed to the section after the 'bootload' space in FLASH.

The tutorial has a bootload.ld file that already does this for me, but I cannot find how to tell Keil to use this bootload.ld file when linking.

I can only upload a "Scatter File" but that does not seem to be the same thing, after some reading on the Keil forums.

How can I import this linker script or what do I have to do?

These are the only options under Linker:


texts: Emitter follower regulator with sziklai pair, transistor heating up!

texts:
I have a wireless chip esp8266 that requires input voltage of 3.3V and can draw current up to 500mA.

Unfontunately at the moment I don't have any 3.3v regulator IC's or buck converters or any 3.3v voltage source, so as a temporary measure (until my ordered stuff arrive from China) I made the following design using voltage divider to limit output voltage and sziklai pair to boost the current output:

simulate this circuit – Schematic created using CircuitLab

Now I'm using a bunch of LED's in parallel with 100ohm resistors as the testing load, and by drawing only 40mA the PNP transistor started to heat up considerably and I'm worried it would blow up if i draw more than a 100, also I'm concerned that the increased temperature might change the output voltage considerably due to decrease VBE according to Ebers-Moll module.

The 2N3906 datasheet says that the max Ic current is -200mA, so why is it heating up at 40? and also I need more than the double of that to drive the wifi chip.

What can I do to fix these problems and make a stable voltage source with 0.5A output?


texts: Are there downsides in using cat5 / cat5e cable for USB 3.0 connection?

texts:
It's been pointed out many times that USB 2.0 can (more or less) safely be used with cat5/5e cables and connectors, at least as long as these requirements are met:

Data pins are on its own twisted pair
Power pins are on the separate twisted pair
To keep it in safest way possible, the two pairs used are the "spare" pairs of 100M line, so on RJ45 pins 4, 5, 7 and 8
You don't plan to mix any connection with POE ports/fed cables!!!!!
You avoid plugging such cable from USB host to the network devices, since some (seen on 100M hubs) might have pair pins merged together, resulting in bridging your USB power lines.
You really really have a good reason to use this in the first place

Now, with keeping all that in mind, I do have a good reason. However, I'm interested in knowing whether the same twisted pair topology is ok (mostly performance-wise) to be used with USB 3.0.

As USB 3.0 includes additional two natively twisted paired connections, I was thinking of using the first two pairs (normally used for ethernet) as new USB 3 StdA_SSRX−, StdA_SSRX+, StdA_SSTX− and StdA_SSTX+ pins, with old Data + and - pins used on third pair and power on fourth.

Could this decrease performance of the USB 3.0 (when used in non-excessive lengths)?
What damage can be made in case of such use and plugging the host-side of the cable into Gigabit network port of the PC?

The reason I'm interested in this is, that I need to have USB 3.0 connection between two boxes, that can be disconnected and connected easily on-the-go, cable length would be between 10 to 15cm, the reason for this connector is that both boxes already have RJ45 on them and changing them for USB would mean a few troubles here and there.
Please, don't start to "why not this why not that", I'm interested in an actual answer, for informative purposes rather than suggestions on how to handle my case specifically. :)

Thanks!


texts:
I'm working on a design which must read temperature using RTD pt100 with at least 0.5 degree Celsius accuracy in the range -10 to 50 degrees . I want to use AD7705 ADC. my design looks like this.

I want my design to be independent of the changes in current source. that's why I used a reference resistor (R1) and fed it's voltage to ADC's reference pins. what I want to know is, shouldn't the reference pins be constant? will this configuration work? I appreciate any additional suggestions but I want the whole thing to cost less than 18$.


texts: How to hook up a fan to this switching circuit

texts:
I am trying to build a controlable fan with a raspberry pi and I have found the below circuit for a switching circuit to allow the 12V power to go to the fan

My question is how do I then hook the fan up to this for it to recieve the 12V power. Am I missing something?

The current and everything i have checked, i just need help with physically wiring up the fan.


texts: It's a scheme for microphone adapter, from XLR to mini-jack, with the conversion of 48V phantom power to plug-in power 6.2V. Could you describe how the circuit works?