texts: How to decide on the values of a set of resistors for a circuit?

texts:
Say i have a PN2222 transistor that i want to integrate into a circuit to amplify a signal with a gain of 100 or so.

From the datasheet of the transistor i can determine that

Vce = 10V and Ic = 150mA for a min gain of 100.

So i need to derive a circuit to satisfy at least those conditions. (Lets say i have a 12 volt power supply as the source.)

How do i come to a decision about the values of the resistors? Is it just a matter of picking them arbitrarily at this point? Is there some algebraic way to solve for the best possible values i could use? Maybe plotting all the different possible values for the resistors or something?

I'm very lost as to how to proceed, and google only seems to return very basic 'intro to circuits' stuff.

Thanks in advance for anyone who replies.


texts: 802.15.4 - how are the baseband and RF signals related?

texts:
The 802.15.4 standard says:

"In the 2450 MHz, 915 MHz, and 868 MHz bands, the half-sine pulse shape is used to represent each baseband chip and is given by:

$$ p(t) = sin ( π \frac{t}{2T_c}) \quad{for}\ \  0 ≤ t ≤ 2 Tc $$

According to the figures in that document, \$T_c\$ is the duration of a chip, which is 0.5 microseconds for the 2.4 GHz frequency band; that is, there are 2 million chips per second.

To my understanding, that gives 2 MHz sine wave as the value of \$p(t)\$. How exactly is this sine wave related to the 2.4 GHz RF signal?

That is, how does one, given the 2 MHz signal, produce the 2.4 GHz signal and vice versa? (I'm looking at various RF transceiver schematics, but my questions is more about "what is the mathematical relation?", not "which components to use?".)


texts: Output impedance of circuit with ideal op amp

texts:
I have the following circuit which I'm asked to calculate the output impedance Zout, assuming the op-amp is ideal.

I use the following equivalent circuit:

simulate this circuit – Schematic created using CircuitLab

I get:
$$i_1 = \frac{V_x}{R_{i}+R_1}$$
$$V_i = -\frac{V_x R_{i}}{R_{i} + R_1}$$
$$i_2 = \frac{V_x - A_{vo} V_i}{R_2 + R_o} = \frac{V_x}{R_2 + R_o} + \frac{A_{vo} V_x R_{i}}{(R_{i} + R_1)(R_2 + R_o)}$$
$$I_x = I_1 + I_2$$
$$Z_{out} = V_x/I_x = \left( \frac{1}{R_{i} + R_1} + \frac{1}{R_2 + R_o} + \frac{A_{vo} R_{i}}{(R_{i} + R_1)(R_2 + R_o)} \right)^{-1} \approx \frac{R_2}{1 + A_{vo}} \approx 0$$
$$\implies Z_{out} = 0$$

Using the fact \$A_{vo} = \infty\$, \$R_{i} = \infty\$ and \$R_o = 0\$ for an ideal op-amp.

The solution says \$Z_{out} = R_2\$. My question is : what's wrong in my approach?

Thanks


texts: Reopen zener diode after reverse bias breakdown

texts:
I've been learning about using zener diodes to generate a reference voltage for a small comparator circuit, the intention is to detect when a motorcycle battery is charging (i.e more than 13v), and use that to activate an Arduino circuit with a relatively high draw of 2A)

I've been fortunate enough to be given an example I can work from here on SX. However, something occured to me whilst learning about Zener diodes.

Once they are electrically closed, the input voltage has to be removed, before the open again. (speaking in terms of electrical continuity). To put that another way, once more than 12v (for a 12v 5A Zener) is seen, and the reverse bias breaks down, I (apparently) have to completely remove the input voltage in order to sever the connection.

Is that accurate, and is this expected, normal behaviour? I need to be able to power down my device when the voltage at the battery drops back down below 12v.


texts: Hand Warmer Heater circuit . Need tips for element

texts: So I have this simple project I'm working on to make a rechargeable hand warmer, but I can't figure out what type of resistor I should be using for the element. Does anyone have any ideas? I'm trying to get this to heat up to 45 degrees Celsius. Any tips for me?


texts: Why do LDO regulators have so big a voltage drop?

texts:
Why do LDO linear regulators not use MOSFETs as the main component to be able to have minimal dropout=0 (well, depending on current, must be still a few mV)?

Or can one expect to build a 0-dropout regulator based on a MOSFET and an opamp?


texts: Is there a latch / flip-flop with this behaviour?

texts:
I've looked at the most popular flip-flop types, and none of them seem to have this desired behaviour:

It would have two inputs: A set signal, S, and a data signal, D.

If the set signal is true, it would save whatever is in the data input. However, if the set signal is false, nothing would change.

Let Q be the current saved bit.

This would be the truth table:

S   D   Q(next)

0    0    Q

0    1    Q

1    0    0

1    1    1

I've managed to reproduce this behaviour using a JK-flip-flop, two AND-gates and one OR-gate. Wouldn't this be particularly useful in computers? If so, why is there no such flip-flop (I may be wrong here)?


texts: How do you independently program a GSM/GPRS IC

texts:
I see these GSM/GPRS modules that you can use with a microcontroller but all of them use the microcontroller to control the module using AT commands.

After a bit of googling i saw this GSM/GPRS IC 'SIM808'. Looking at it's datasheet i see that it has GPIO pins, UART, Bluetooth, GPS, I2c communication and an ADC!!!!.

As you can see this ic is really powerful but i have no idea how to program it. (i'm quite okay at programming AVRs using C)

My question is how do you do this?

How do you write programs and upload them to this ic?
(it would be really good if it was C++ or even C)

The Datasheet

https://cdn-shop.adafruit.com/datasheets/SIM808_Hardware+Design_V1.00.pdf

The IC


texts: TDO unable to capture MSB of Shifted data in JTAG

texts:
With reference to my previously asked question What stage is used to shift out TDO in JTAG?
I have another querry.
The JTAG document says that the last bit of data/instruction should be shifted out the same time as Exit1 State is activated. However it also states that TDO is tri-stated in all the states except Shift-IR and Shift-DR states i.e just when Exit1 state is activated, in the following negetive edge of clock, TDO is tri-stated. That means the last bit information sampled on TDI in Exit1 state is lost! How to deal with this situation? I have simulated the RTl for JTAG and sharing the simulation results (waveform snapshot). Please guide.

As seen in waveform, thr IDCODE register is shifted out with value 0xc3631093 and last 2 bits i.e 1 and 1 is shifted out on IDCODE_shift_out at 48.50 us and next 49.50 us respectively.
However TDO only captures the first 1 at 49.0 us and the next 1 is not captured as TDO becomes Z. The test sequence is such that I am shifting out IDCODE on TDO through the state Shift DR -- Exit 1 DR -- Update DR -- Run Test Idle and so on.
Just for reference, these are the different states coded
parameter TEST_LOGIC_RESET=0,
                RUN_TEST_IDLE=1,
                SELECT_DR=2,
                SELECT_IR=3,
                CAPTURE_IR=4,
                SHIFT_IR=5,
                EXIT1_IR=6,
                PAUSE_IR=7,
                EXIT2_IR=8,
                UPDATE_IR=9,
                CAPTURE_DR=10,
                SHIFT_DR=11,
                EXIT1_DR=12,
                PAUSE_DR=13,
                EXIT2_DR=14,
                UPDATE_DR=15;

Edit: Also adding the screenshots for IR selection and IDCODE Shift sequence. Please note, there is no Shift for IR, the sequence for IR is Capture-Exit1 IR-Update IR i.e Just write.

The first screenshot is for IR selection with timestamps
@12.5 us: Sel_IR is high in TAP controller
@13.5 us: Load_IR is high, IR value 0x001001 is pre-loaded
@14.5 us: Load IR register gets IR value (one cycle delay to capture). Meanwhile, Exit_IR state in TAP Controller.
@15.5 us: Update_IR is high, actual IR register updated(commited) with 0x001001
@16.5 us: Instruction sent to Decoder, decoder outputs 10 resulting in selection of IDCODE register. Sel_DR is high.
@18.5 us: Shift-DR is asserted, and IDCODE data is read into Shift register (Shift_idcode_q).
@19.0 us: Negedge of TCK, TDO gets LSB of shift data
@19.5 us: Data starts right shifting out from Shift register
Coming to waveform 2 screenshot
@49.5 us: MSB of IDCODE is shifted out. State is Exit-1 DR. Shift_DR is de-asserted.
@50.0 us: TDO is again tri-stated.


texts: Pros and cons of using resistor networks over individual resistors?

texts:
I've been looking over some board designs and have been trying to identify the reasons behind using resistor networks over individual resistors. Some guesses I can think of are a reduced part-count and complexity. Does it also follow that a design using a resistor network is cheaper than one that uses individual resistors? Because of this, I would think one would try to maximize use of networks, but many of the designs use several individual resistors instead and I can't figure out why.

And a separate but relevant question: are capacitor networks in the same boat?


texts: Why does this resistor get ignored in the calculation of voltage across the capacitor

texts:
I am trying to follow this example problem:

I understand the current calculation. What I dont understand is why the 5 kOhm resistors voltage drop does not need to be taken into account when finding v2. The book says v2 is the same as the voltage across the 4 kOhm resistor. Why do you not need to take into account the voltage drop across the 5 kOhm resistor?


texts: Help interpreting car window wiring diagram

texts:
I would be grateful if anyone can help interpret the attached wiring diagram for my 2003 Toyota Camry power windows.
The switch for my driver side window is busted so it is currently stuck at down.
I want to attempt to jump the connectors to get the window up again.
Can anyone point out the main pin connections for the power, ground and up and down positions (i.e front right window)?


texts: Simplest display for homemade 8080 based computer-what to use?

texts:
I'm designing a 8080 processor based computer and I want it to be able to at least output something visually.

I have thought about using SMD LED matrix made by myself, but even with the 160 x 120 px it would cost about $65 for the LEDs themselves, and I'm trying to be as cheap as possible here, plus that requires a ton of soldering, so that's not the best idea.

The second one of my ideas would be to use a soviet CRT oscilloscope tube 6ŁO1I, but that requires generating X and Y signals and synchronising them together with the modulation of brightness, and that is also pretty complicated, at least for me.

I want the display to be serviced by a DMA controller accessing the part of RAM that is not entirely free to use because its addresses would correspond to EPROM adresses (writing to them would cause the data to be written into the RAM and reading would read from EPROM, unless an addressable D-latch is triggered, so the RAM can be read form the "EPROM region". And finally, I heard about Intel's 8275 CRT controller and that it's possible to use it as a composite video output, however I lack the knowledge about TV signals and i am afraid i wouldn't be able to make it work properly.

Can anyone help me with that? I know it's an ambitious project and I'm working on certain parts of it individually, but I need to think about everything at once too so I don't forget about implementing something crucial for the operation of the machine it might become.

Thank you for any answer.


texts: Is the excess of current the only problem in a motor overvoltage?

texts:
I'm designing a Full Bridge for a Brushed DC motor control. My circuit will have a current measurement, so I'll can control the output current, sinked by the motor.

Whit this current control, I think that I could safely overvoltage my motor, using a battery with a higher voltage that the specified to the motor, since I'll never allow the current to overcome the max. current of the motor. With this, I could achieve bigger velocities.

My doubt is if you see another problens, rather the overcurrent, when I do a overvoltage? I could see the insulation of the motor and also the mechanical problems, like the gear, shafts, bearing and etc, these could be overstressed too.

But, eletrically speaking, the limiting factor, since I can limit the current, is the motor insulation, right?

Someone can see other problems?


texts: Xilinx ISim Post-Route Simulation produces unexpected result

texts:
I am trying to observe the propagation delay difference between a 4-bit carry ripple adder versus a 4-bit carry look-ahead adder.

The carry ripple adder VHDL architecture is:

entity adder4 is
    Port ( Cin : in  STD_LOGIC;
           x : in  STD_LOGIC_VECTOR (3 downto 0);
           y : in  STD_LOGIC_VECTOR (3 downto 0);
           s : out  STD_LOGIC_VECTOR (3 downto 0);
           Cout : out  STD_LOGIC);
end adder4;

architecture Behavioral of adder4 is
    component fullAdder
        Port ( Cin : in  STD_LOGIC;
           x : in  STD_LOGIC;
           y : in  STD_LOGIC;
           s : out  STD_LOGIC;
           Cout : out  STD_LOGIC);
  end component;
  SIGNAL C : STD_LOGIC_VECTOR(1 TO 3) ;
begin
    stage0: fullAdder PORT MAP (Cin, X(0), Y(0), S(0), C(1));
    stage1: fullAdder PORT MAP (C(1), X(1), Y(1), S(1), C(2));
    stage2: fullAdder PORT MAP (C(2), X(2), Y(2), S(2), C(3));
    stage3: fullAdder PORT MAP (C(3), X(3), Y(3), S(3), Cout);
end Behavioral;

And the carry look-ahead adder architecture is:

entity adder4LookAHead is
    Port ( Cin : in  STD_LOGIC;
           X : in  STD_LOGIC_VECTOR (3 downto 0);
           Y : in  STD_LOGIC_VECTOR (3 downto 0);
           S : out  STD_LOGIC_VECTOR (3 downto 0);
           Cout : out  STD_LOGIC);
end adder4LookAHead;

architecture Behavioral of adder4LookAHead is
    signal c : STD_LOGIC_VECTOR (3 downto 1);
    signal g : STD_LOGIC_VECTOR (3 downto 0);
    signal p : STD_LOGIC_VECTOR (3 downto 0);

begin
    g(0) <= x(0) and y(0);
    p(0) <= x(0) or y(0);
    c(1) <= g(0) or (p(0) and Cin);

    g(1) <= x(1) and y(1);
    p(1) <= x(1) or y(1);
    c(2) <= g(1) or (p(1) and g(0)) or (p(1) and p(0) and Cin);

    g(2) <= x(2) and y(2);
    p(2) <= x(2) or y(2);
    c(3) <= g(2) or (p(2) and g(1)) or (p(2) and p(1) and g(0)) or
        (p(2) and p(1) and p(0) and Cin);

    g(3) <= x(3) and y(3);
    p(3) <= x(3) or y(3);
    Cout <= g(3) or (p(3) and g(2)) or (p(3) and p(2) and g(1)) or
        (p(3) and p(2) and p(1) and g(0)) or
        (p(3) and p(2) and p(1) and p(0) and Cin);

    S(0) <= (x(0) xor y(0)) xor Cin;
    S(1) <= (x(1) xor y(1)) xor c(1);
    S(2) <= (x(2) xor y(2)) xor c(2);
    S(3) <= (x(3) xor y(3)) xor c(3);

end Behavioral;

Both of the adders produce right output in behavioral simulation. The only strange thing is that for Post-Route Simulation the outputs have exactly same propagation delay! while I expect to see different propagation delay.

What am I missing here?


texts: Equivalent series resistance vs. parallel leakage conductance

texts:
I am studying a book called RF Circuit Design by Reinhold Ludwig and Gene Bogdanov (2nd Edition).
In the first chapter on capacitors, they introduce the loss tangent and equivalent series resistance, with \$ESR=\frac{tan\Delta}{\omega C}\$.
This seems to make sense to me, with the loss angle \$\Delta\$ being the angle between the real and complex components of the impedance of a capacitor in series with a resistance.
However, just before that, they also define the loss tangent relative to the leakage conductance \$G_e=\omega Ctan\Delta\$. This leads to an interesting connection between series resistance and parallel conductance: \$ESR=\frac{G_e}{\omega^2 C^2}\$.
After thinking about this quite a bit, I suspect what they've done is calculate the impedance of the capacitor and leakage conductance in parallel, and make an approximation for very small conductance:
$$Z=\frac{1}{G_e+j\omega C} \approx \frac{G_e}{\omega^2 C^2}-\frac{j}{\omega C}$$
with the assumption \$\omega C >> G_e\$.
Firstly, am I understanding this correctly? If so, what this tells me is that parallel resistance can be modelled as an equivalent series resistance. Is this a standard way of calculating ESR? All other references I have seen on equivalent circuits for capacitors include two separate resistors, one in series and one in parallel, equating ESR with the resistor in series. Is it normal to lump the parallel resistance in with the ESR like this book seems to be doing?


texts: What is the deal with resonant frequency?

texts:
During the last day or so, I have studied the topic of resonant frequency over a few circuits.
Now, I could easily see that every time my circuit operated upon that resonant frequency something special happened.
I'm aware that the deal with resonant frequency has to do something with oscillation but I couldn't figure out exactly what.

In a regular RLC circuit in series with an AC voltage source operating in resonant frequency I get that the impedance equals to the impedance of the resistor alone. So?? What does oscillation  has to do with it?
In the different example where we deal with RLC parallel circuit we get that for AC voltage source operating in resonant frequency I ended up with a pure imaginary resistance, what does it mean?
In LC parallel circuit with an AC current source I ended up with infinite impedance, what is that have to do with anything?

So, in general I'm a bit confused with the whole resonant frequency making weird stuff on any different circuit, can someone please help me clarify this a bit..?


texts:
Find the full scale output of a 4-bit DAC produces an output of 0.1v for a digital input 0001
I am trying to learn digital circuits. While trying to do so I got stuck in this question.
Edit: Thanks @mhaselup, I got it now- 0001 is 1 in decimal. Since the DAC is 4-bit it can get a maximum value of 1111 which is 15 in decimal. So for 1 it produces an output of 0.1v, so for 15 it would produce an output of 0.1*15=1.5. So the full scale output is 1.5v.


texts: Rogowski coil response factor frequency dependence

texts:
I am creating a high current (kA) pulse (<1 ms) by discharging a supercapacitor into a low resistance (<1mOhm) circuit. The switching is done by paralleled power-MOSFETs.

To measure the current I use a rogowski coil (RCT16-50000 from Accuenergy, no data sheet provided). According to Wikipedia, the output from the coil is:

This output is integrated by the math function of my PicoScope's software to deliver a function proportional to the measured current. This function must be multiplied with a (coil dependent) response factor to get the current.
According to Accuenergy, my coil's response factor is 2.0 mV/kA @ 50 Hz and 2.4 mV/kA @ 60 Hz. They don't provide the full specs (A, N and l) of the coil (companies support is not responding).

I don't understand why the response factor is frequency depended, even though frequency is not a factor in the equation above.

Also, I don't know the frequency of my current pulse. Any ideas how to calculate the proper response factor of my coil for my pulse?


texts:
What can I use to recognize if a surface in touched or not?
What kind of sensor I need to do this?

I want to detect if an object is on the table or the object touch and go out.

I'm using Arduino board.

Any idea?

Edit: My object is a ball and my surface is a 4 person kitchen wood table.


texts: Converting "wet" contact closure to "dry" contact closure

texts:
I have a "wet" contact closure circuit that is outputting 3V DC. I need to eliminate that voltage to create a "dry" contact closure.

How is this accomplished ? Please answer in very basic language, as I am not an electronics expert - just a tinkerer.


texts:
I'm trying to develop a switchable 5v/3.3v power supply. I've got a switching 5V regulator that will drive my 3.3v rail. I've looked into using an LDO, and I think I'm going to go that route after investigating this option, but I thought I'd see if my concept is completely impractical, or I've missed something fundamental. I'm kind of expecting both.

So the idea for my 3.3v regulator is to switch my zener (2.4v@5mA) from the low side with a resistor in series with the anode such that it drops the remaining voltage from the desired rail voltage.

The zener resistance is 100 ohm, +80(r1) = 180 ohm. Rds is a few hundred milliohms, which I'm ignoring for now.

Zener drop:3.3v - 2.4v = .9v

Resistor drop: 5mA * 180 = .9v

The circuit: 5v switch on the high side, and 3.3v diode regulator circuit on the low side.

As you can see, I'm hoping to draw 1A out of this to power basically anything; dev boards, sensors, maybe DC motors. What would it take to make this work? Is the premise completely wrong?


texts: Can this portable power generator charge this battery?

texts:
I am considering purchasing an e-bike but I have no outlets at my parking space and it's a non-removable battery. The e-bike looks like a motorcycle.

I am considering getting one of those portable power generators so I can recharge it at home and bring it down to charge the bike overnight.

I am completely ignorant when it comes to electricity. I just googled for a couple of hours trying to understand the different things (Amps, Volts, Watts, Watt-hour).

The bike specs are:

Motor:   500W
Battery: 72V/20Ah GEL SLA
Charger: AC100-120V, Smart Charger (Battery maintained while charging)

The battery I am looking at is titled: AIMTOM Portable Solar Generator, 42000mAh 155Wh Power Station, Emergency Backup Power Supply W/ Flashlights, for Camping, Home, CPAP, Travel, Outdoor (110V/ 100W AC Outlet, 3x 12V DC, 3x USB Output)

This is where I get confused. Looking at the 42Ah it looks like this could fully charge the bike twice.

Since I am not sure what I am doing, I also am looking at the 155Wh. From what google told me, the bike battery would be 1440Wh.
So this power generator would not even tickle the battery.

I am not sure what to think here. Can someone clarify?


texts: How can I time-switch a few loads very precisely?

texts:
Let's say there are 5 different loads, and I need a circuit to switch them on/off based on a pre-tunable delay. (E.g. first one immediately, second one exactly 2.78 seconds after the first one, third one 5.33 seconds after the second, the 4th load 0.24 seconds after the third, and the last one 1.05 seconds after the 4th). 0.01 seconds precision is enough.
The time delay between each one needs to be adjustable (not during the circuit operation, but using variable resistors ,manually, before turning on the main circuit).
Can this be done without oscillators or pulse counting stuff?
I can measure the circuit results precisely using other methods (to test if I've tuned the delays close enough to desired times.)
I'll repeat the run-measure-tune cycle enough times to reach the 0.01s precision.


texts: Understanding Op-Amp gain bandwidth product

texts:
Below is the schmatics and AC transfer function for transimpedance amplifier from this design.

According to the datasheet, OpAmp has the gain bandwidth product of 20MHz.
But, here the gain is 94.58 dB = 54954 V/V and the bandwidth is 1.464 MHz.

So, Gain * BW = 54954 * 1.464 MHz = 80452 MHz, which is a lot than the value specified in datasheet. Can anyone help me understand how such high GBP is possible here?


texts: How to choose a 3A power supply for a project involving a micro controller?

texts:
I am designing a project where a ATMega 328p chip triggers a 3V step up transformer to produce a 7kV spark gap.

I have found some 3A transistors which I can use as obviously the 238p cannot supply a high current to the boost module.

However I want the project to have one wall socket so it directly plugs into the wall.

What is the best way to power this. I know one can buy 5V 3A wall warts. However my concern is that they will not be sufficiently regulated to provide a stable 5V to the 328P chip.

Would it be better to get a higher voltage wall wart and then use a L7805 before the 328p and then a higher current regulator before the 3A device?

Or is there a better option all together?


texts: Multiple controllers for a single RGBW circuit

texts:
I currently have an installation that consists of (1) wall mounted touch screen LED controller which controls a circuit of (4) RGBW LED strips.  What i'd like to do is add another WiFi based controller to the circuit.  Both controllers are PWM output.  I've considered the option of terminating all the wires together and using diodes on each leg to prevent back-flow into the other controller, but i want to make sure that is on the right track.  Thanks for any insight.

simulate this circuit – Schematic created using CircuitLab


texts: Interface Submersible water pump with microcontroller using Contactor Relay

texts: I am making a automatic water level controller for my home,I am new to Electrical Engineering and learning things. I am using a MCU to turn ON/OFF submersible water pumps using some float switch to detect water level in overhead tank. This pump has Start Switch(Normally Open), and stop switch(Normally Closed), connected with some contactor. For my project I want to replace these mechanical switches with Relay(Electromechanical Relay)- 5V 10A, which is controlled using MCU. But I am stuck with how to interface contactor (ON/OFF) mechanism with Relay (NO and NC) contacts. I am planning to use general purpose relay, something like this but of 10A capacity: General purpose capacitor. Here is an block diagram for it. .Submersible pump here is of 2HP, 230V,Single phase. Can anyone suggest me how to do it or direct me read any such article that helps? Thanks in Advance!


texts:
I need to control a compression driver with an arduino and send it triangle waves of variable frequency (from ~100 Hz to ~1500 Hz) and variable amplitudes. I have tried to research what I need but I can't find exactly what I'm looking for. However, I'll try to list what I know and what I get wrong can be corrected.

First I need to generate the triangle wave. How can I do this and control it from the arduino? I think this can be done with some sort of dac, but I don't know how exactly.

Next I need to amplify the signal. I think there are chips that do this or I can make my own with simpler components. What is the best way of doing this?

Then finally I can connect the output to the compression driver.

Is there anything else I need in the circuit? I heard that I might also need a capacitor to protect the compression driver, is there anything else I need like that?

EDIT:

The compression driver will probably be have a power rating of 100W and impedance 16 Ohms.

A compression driver is a type of speaker. See here for more information.
As far as variable amplitudes it needs to go from 0 to whatever is good for the speaker. I believe the max voltage for the numbers I gave is \$V = \sqrt{PR} = \sqrt{100*16} = 40V\$ (this would be RMS voltage, right?).


texts: Arduino Nano and water pump (2n2222a switch)

texts:
Hi there, I've created the circuit following this thread. The arduino D9 pin get 5v and I measured with the tester a VBE of 0,82v, which is right for the transistor saturation. Unfortunately the pump doesn't start!
I've tried attaching the pump directly to the 8.3v battery pack (2x18650 batteries in series) and works fine, consuming 150mA.
To calculate the 200ohm resistance for the driving current of the base I've followed this guide. The arduino port when HIGH provides 4.7v, so 4.7-0.80=3.9v drop. The resistance should be 3.9V/0.02A=195ohm, i've just rounded to 200.

The pump is connected with the + to the + of the battery.

Any suggestions on how to make it working?


texts:
I had a little confusing regarding the address of GPIO_PortA
As mentioned in datasheet:

Based address of GPIO PortA:0x40004000
and GIOP_DATA has Offset : 0x000
which mean the address of GPIO_PortA = 0x40004000;

Problem starts from here:

why this code is not working as expected: (Using datasheet addresses)

#define porta_data (*(volatile unsigned long*)0x40004000)
...
while(1)
{
 porta_data=~porta_data
}

and why this code is working with wrong address (saw during edX online lec)

#define porta_data (*(volatile unsigned long*)0x400043fc)
...
while(1)
{
 porta_data=~porta_data
}

there is another problem.
when I use bit binding method and use the formula.

bit_word_addr = bit_band_base + (byte_offset * 32) + (bit_number * 4)

As:

#define bit_word_addr (0x40004000+(0x0000*32)+(1*4+4))
#define porta_pin0 (*(volatile unsigned long*)bit_word_addr)

using the base address and offset as mentioned in datasheet
I could toggle the individual bit as expected.
But using the same address I couldn't toggle the whole port (GPIO_PORTA).


texts: How is interaction with CDC device with no interface endpoints working?

texts:
I'm working on uploading to Digispark board. It uses micronucleus bootloader and i can see uploader code. I've modified it a bit to see interfaces and endpoints count:

    nucleus->device = usb_open(dev);

    // added by me - start
    int interfaces, endpoints, j;
    struct usb_interface_descriptor *interface = NULL;

    interfaces = dev->config->bNumInterfaces;
    fprintf(stderr, "Found interfaces: %i\n", interfaces);

    interface = &(dev->config->interface[0].altsetting[0]);
    fprintf(stderr, "Endpoints: %i\n", interface->bNumEndpoints);
    // added by me - end

    // get nucleus info
    unsigned char buffer[4];
    int res = usb_control_msg(nucleus->device, USB_ENDPOINT_IN| USB_TYPE_VENDOR | USB_RECIP_DEVICE, 0, 0, 0, (char *)buffer, 4, MICRONUCLEUS_USB_TIMEOUT);

I wonder how it's working because interface #0 has no endpoints:

$./micronucleus --type intel-hex /tmp/Start.ino.hex
> Please plug in the device ...
> Press CTRL+C to terminate the program.
Found interfaces: 1
Endpoints: 0
> Device is found!
connecting: 40% complete
> Device has firmware version 1.6
> Available space for user applications: 6012 bytes
> Suggested sleep time between sending pages: 8ms
> Whole page count: 94  page size: 64
> Erase function sleep duration: 752ms
parsing: 60% complete
> Erasing the memory ...
erasing: 80% complete
> Starting to upload ...
writing: 100% complete
>> Micronucleus done. Thank you!

Usually i expect interface to have 2 endpoints (in & out from usb.h):

#define USB_ENDPOINT_IN         0x80
#define USB_ENDPOINT_OUT        0x00

Can anyone explain me how usb_control_msg(nucleus->device, USB_ENDPOINT_IN| USB_TYPE_VENDOR | USB_RECIP_DEVICE, 0, 0, 0, (char *)buffer, 4, MICRONUCLEUS_USB_TIMEOUT); is working without endpoint?


texts: STM32F4 doesn't boot after reset and enables read out protection

texts:
Sometimes my STM32F4 board doesn't boot after a power-off, power-on reset. All voltages are fine, but the code does not execute. What is interesting, when I connect to the board with ST-link utility, it shows me that there is read out protection enabled (although I didn't enable it). BOOT0 pin is connected to the ground via 10k resistor, decoupling seems OK.

What can be causing this issue? From what I have read in reference manual page 92, to change option bytes, first one should write two specific key values to two different registers. That seems to be very unlikely to happen by accident even once, and my issue appears once every several dozens of resets.


texts: How to read/write in M25PE80 using PIC18F67k22 controller?

texts:
I have a PIC18F67K22 controller. I am a making data logging system using an M25PE80 external flash memory for storing data. I have interfaced this flash to the controller using SPI.

My question is when we write or read from flash, are the addresses automatically incremented or must we do it manually?

(If anyone has some demo code, it will be helpful.)


texts: getting an 'include map' from a project file?

texts:
I am trying to understand a program in a Keil project. It has several source and header files for its functions but they are not directly included in main file. Instead header files include other header files to finally get included in main. This makes it difficult for me to understand how each module integrates in the final project.
Is it somehow possible to get information on how these files are included in the main file? I am using cubeMX IDE and I want to make something like a block diagram for the program to better understand it.
How can I get a graphical diagram or block diagram for a C project?


texts: Direction of N-channel mosfet when replacing the diode in the buck convertor

texts:
In a buck-converter with a diode, in the first and second phases (on and of states) current is supposed to flow like the following circuits:

I am looking for a way to replace the diode with a MOSFET and after a few search I came by the following design:

My question is this:
considering the polarity of the N-channel MOSFET, Shouldn't the direction of the MOSFET be like the following circuit instead?


texts: Auto need a power source ONLY on when car is off. So when car is on this source of 12V power would be OFF

texts:
Yes, the opposite of what is usually asked for.
I need to charge a device ONLY when the car is stationary and the ignition off. This is needed because the device doesn't work while its charging.
I am looking to power a 12 V to 5 V, 2000 mA charger. Basically a cell phone car charger.
The device to be charged will not operate while it's being charged.
The goal is to keep it charged so that while the car ignition is on, car is moving the device is charged.
So far all I can think of is 12 V timer operated switch that I can set to charge device a few hours every night while car is stationary.
Thanks for any suggestions.


texts: How can I locate items from a phone? RFID?

texts: I'd like to be able to put something small on items (eg glasses, car keys, etc) and have an Android or iPhone app that will tell me the direction or proximity of a certain item. Current phones usually just communicate via cell, wifi, and bluetooth, but for these the other end of the communication has to be powered, which increases the size of what I attach to my items. Is passive RFID what I'm looking for? (In which case I'd have to wait for phones to come out with better RFID readers.) If yes, what size passive tags have what ranges? For range I'd like to be able to find a device a couple floors away, but even just within a room would be useful. For size, the smaller the better, with maybe a quarter the size of a dime as the minimum practical/usable size. Do you think that the RFID readers in phones will be able to take advantage of those maximum ranges? (Currently the ones I've looked at, eg Nexus S, have to be inches away.) And finally, where do you recommend I buy such tags?


texts:
I am hoping some of you may help, I am currently answering an assignment question for uni and as such I have to write a code for an egg counter/ sorting using VHDL.

there are 4 sizes of eggs that depending on the size depends which counter counts etc.

I have generated the following code firstly (for the first size of egg) and then attempting to use the TB to try and start seeing it working, however the clock I have generate (egg_available signa/input) on TB stays static at either 1 or 0.

any ideas??

here is the egg sorter code so far :

-- Library Decleration
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;
use IEEE.std_logic_unsigned.all;

--entity decleration
entity egg_sorter is
    port (  Reset       : in std_logic;
        Egg_Size    : in std_logic_vector(2 downto 0);
        Egg_Available   : in std_logic;
        A_Count     : out integer range 0 to 12;
        A_Full      : out std_logic);

end entity;

-- architecture
architecture behavioral of egg_sorter is

-- signal declerations due to being outputs and VHDL not being able to read outputs
signal A_Count_Value : integer range 0 to 12;
signal a_full_S : std_logic;

begin
    -- this is the count process for size A eggs
    A : Process (Reset, Egg_Size, Egg_Available)
    Begin

        if ((rising_edge (egg_available)) and (egg_size <= "001"))  then

            if a_count_value < 12 then
                A_Count_value <= A_Count_value + 1;

            elsif a_count_value <= 12 then
                a_full_s <= '1';

            end if;

        case a_full_s is
        when '1' => a_count_value <= 0;
        when others => a_count_value <= a_count_value;
        end case;

        end if;

    A_Count <= A_Count_Value; -- this puts my signal value to my output

    end process A;

here is my TB code

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;
use IEEE.std_logic_unsigned.all;

entity Egg_Sorter_TB is
end Egg_Sorter_TB;

Architecture sim of Egg_Sorter_TB is

component Egg_sorter is

Port (      Reset       : in std_logic;
        Egg_Size    : in std_logic_vector(2 downto 0);
        Egg_Available   : in std_logic;
        A_Count     : out integer range 0 to 12;
        a_full : out std_logic);

end component;

signal      Reset       : std_logic;
signal      Egg_Size    : std_logic_vector(2 downto 0);
signal      Egg_Available : std_logic;
signal      A_Count : integer range 0 to 12;
signal      a_full : std_logic;

constant period:time:= 10 ms;

Begin

E1 : Egg_sorter port map (
                reset => reset,
                egg_size => egg_size,
                Egg_Available => Egg_Available,
                a_count => a_count,
                a_full => a_full);

 -- egg_available process
process
Begin
Egg_Available <= '1' ; wait for period/2;
Egg_Available <= '0' ; wait for period/2;

end process;

process (reset, egg_size)
begin
egg_size <= "001" ;
reset <= '0' ;
end process;


texts: Is it possible to read calculator LCD values?

texts:
Hi all,

I'm thinking about a project, but I have no idea if it's even possible...
So the general idea would be to have a calculator that can display letters and other characters. I have a very basic calculator (Sharp Elsi Mate EL-376S) with a 7-segment LCD. Is it possible to read the values from the calculator's chip and write them to another LCD? (both read and write with an arduino or any micro controller) The "old" display would be detached.
Letter/Character mode could be changeable by pressing a key on the calculator.

Calculator PCB:

(Solar cell power on the left(wires detached), battery power on the right)

Please share any thoughts, tutorials, concepts I should read/know! Thanks, in advance!


texts: Protecting Electronics From Sustained Overvoltage (36-60V)

texts:
I have a problem I need to solve.

I have a power filter circuit that looks like this:

The input voltage is 18V to 32V and I need my circuit to be protected during overvoltage situations. I have TVS diodes to protect from transient surges, but I also need to protect my circuit from 5 minutes of 60VDC.

How can I accomplish this? The 60VDC blows away most, if not all, TVS diodes that are in the proper specification range.

I was thinking of using some sort of high side switch that shuts off if my voltage exceeds a certain level, but how would I approach that?

To make things worse, this circuit needs to work up to 125C.

Any insight or ideas would be greatly appreciated! Thank you.

edit: 200mA of current is the current draw of the circuit.


texts:
I have two switching power supplies:
a step-down that generates 5V from 12-24V, using a TS30042 (see datasheet), and a step-up  that generates 5V from a 3.7V battery, using a MIC2876.

The two power supply are enabled alternatively but there is an overlap period of about 1 second in which they are enabled at the same time.

The MIC2876 datasheet states that the output is completly disconnected when the chip is not enabled.

The TS30042 datasheet states that the switching pin tolerates 42V even if the chip is not powered.

My question is: is it safe to connect the two outputs together?
I tried and everything seems to work fine but I am concerned about the reliability.

Many thanks for every comment.

Marco


texts: Using a 220ohm resistor in a mains circuit?

texts:
I work in a charity shop where our display cabinet with a rotating glass shelf has stopped working.  The electrics are clearly visible, and the fault is that a 220 ohm resistor between the live lead and the motor has broken.  This is a 'normal' small resistor with no markings other than the resistance.

Can I replace the broken item with a standard 220 ohm resistor?


texts: Stochastic optimal control different in finance and engineering

texts:
What is the different between stochastic optimal control approach in finance and engineering?
Why methodes used in finance approach like Ito calculus are not used in engineering?


texts:
I am looking for a circuit to drive a speaker to make a fairly loud simple tone - a square wave driven from a microcontroller (Arduino/ATMega).

There are obviously a billion chips and amplifiers out there that talk about "gain" and stuff, but I want to do something much simpler. I currently have a darlington pair transistor stack which will dump a couple of amps from a 12 volt source through the (4 or 8 ohm) speaker, from the uC's digital output pin.

For a "Standard 4 ohm speaker" - I am not sure how to drive this. Is it okay to just dump a "12 volt / 3 Amp" square wave into the speaker - or should I step up/down the voltage/signal with a transformer?

If the speaker was purely resistive (which it is not) one would argue that I need to only provide adequate current so that with the 4 ohm load I am not exceding the maximum wattage of the speaker, per (W=IIR) (Where I is controlled by the transistor, R by the speaker, and W is the maximum wattage).

Is it as simple as this, or am I missing something?


texts:
I am working with the Altera Quartus II compiler for my Cyclone IV. I am not happy with what is considered Info, Warning, Error, etc.

For example, inferred latches are Info, but I want them as Warning. Parallel compilation disabled is a Warning, but I want it as an Info.

Is there a way to customise the compiler messages in Quartus II?


texts: Calculated crystal capacitance is out of range

texts:
I know, another question about crystal capacitor values.

I would like to use
this crystal in the 20 MHz version to clock an ATmega1284.

According to the crystal's datasheet, it has a load capacitance of 20 pF.

Using the formula \$C = 2(C_L - C_S)\$ and assuming a stray capacitance of 2 pF or 5 pF, I get a value for each capacitor of 36 pF or 30 pF, respectively.

However, this is outside the recommended range for the capacitors of 12-22 pF according to page 46 of the ATmega1284 datasheet.

So, can I even use this crystal, and if so, with what capacitors?


texts: Using internal pullup, pulldown resistors to find floating IOs

texts:
I want to find at runtime if a GPIO is floating (nothing connected to it).

I assumed I'd find tons of answers on Google, but maybe I'm searching wrong.

My approach has been to:

enable the internal pullup resistor and read the IO
disable the pullup, enable the pulldown and read the IO again

If it reads high first and low second, the input is floating.

Since I've not seen a lot f discussion on this online, I'm wondering if I'm doing something unusual, or if there's a better way, or if this approach doesn't work in the general case and I simply lucked out in my application.

If this does work in the general case, I'm curious what happens with GPIOs that don't exist in a package. Presumably, if a particular IO line doesn't come out to a pin, there are no pullup or pulldown resistors for this line either. I'm curious particularly about what STM32 does in this case.


texts: How is the short term frequency stability of a crystal oscillator?

texts:
I have a circuit board with two identical crystal oscillators. Can I assume that one is always faster than the other?

Say that I count the number of oscillations from each and reset the counters every second. Will one counter always show a higher value than the other, or will it typically vary from second to second which counter shows the higher value?

The oscillator accuracy is obviously limited by the PPM value in the datasheet, the question is whether this PPM value is constant over short times given constant age, temperature, etc.


texts:
My question perhaps belongs to general ability test or something like that. It is not directly related to Embedded devices.

I have been given a variable resister which can rotate infinitely and is of 10kΩ. ADC is set for value range 0 to 1023 sampling. By which I've to control light luminosity/intensity.

The ADC value range is divided into 32 steps for 1024/32 levels of brightness. The issue is the pot has to be rotated 16 times to get to extremities. Which is very harassing. Now its time when I can't change the pot hardware but the firmware.

I thought of doing as follows, please help me from here:

I'll choose a range window within the [0 1023], say of 32 steps. Lets ignore the ADC noise for now.

Then we have 32 steps in that 32 step windows.

If I start from 0, the intensity will be increasing till 32. The 32 is max intensity possible. Then if I rotate more, the intensity should remain maximum at 32 all the way till 1023.

And as soon as it is started to decrease from 1023, I will have decrease in intensity till ( 1023-32 ) and will remain at 0 intensity all the way till 0.

if I rotate back from any place it should follow the above explained moving window rule.
How to start with it?

I did as follows:

 void processADC_data()
 {
        ushort adc0 = (ushort)ADC_DATA;
        adc0_Avg = adc0;

        // If Noise
        /*
        ushort adc0_L = (ushort)(adc0 - 40);
        ushort adc0_H = (ushort)(adc0 + 40);

        adc0 = (ushort)read_ADC( adc0_L,adc0_H );

        adc0_Avg = adc0 * 20 + adc0_Avg * 80;
        adc0_Avg /= 100;
        */

        IsInceasing = (adc0_last - adc0_Avg) < 0 ;
        adc0_last = adc0_Avg;

        if (IsInceasing)
        {

            // Extrimity has to be handled
            if (!HasPerformedIncreased)
            {
                adc0_center = (ushort)(adc0_Avg - window);
                HasPerformedIncreased = true;
                HasPerformedDecrease = false;
            }
            else if (HasPerformedIncreased)
            {
                IsCrossingLimit = ( (adc0_Avg - adc0_center) > window );
                if(IsCrossingLimit)
                {
                    adc0_Avg = LIGHT_SENS_MAX;
                    IsCrossingLimit = false;
                }
                else
                {
                    adc0_Avg = (ushort)(adc0_Avg / LIGHT_SENS_MAX);
                }
            }

            //judge_brightness(adc0_Avg);
        }
        else
        {
            // Extrimity has to be handled
            if (!HasPerformedDecrease)
            {
                adc0_center = (ushort)(adc0_Avg + window);
                HasPerformedDecrease = true;
                HasPerformedIncreased = false;
            }
            else if (HasPerformedDecrease)
            {
                IsCrossingLimit = ( (adc0_center - adc0_Avg) > window );
                if(IsCrossingLimit)
                {
                    adc0_Avg = LIGHT_SENS_MIN;
                    IsCrossingLimit = false;
                }
                else
                {
                    adc0_Avg = (ushort)(adc0_Avg / LIGHT_SENS_MAX);
                }
            }

        }

            brightness(adc0_Avg);

    }

Thanks


texts: Which boot mode does the STM32F0 discovery kit use?

texts:
I am using the STM32F0 discovery kit which looks like this;

In the MCU datasheet, it mentioned about 3 boot modes;

boot from User Flash memory
boot from System Memory
boot from embedded SRAM

Which mode does the STM32F0 discovery kit use by default? How can one change which mode to use?


texts: Why are PCB-mount AC DC converters so expensive?

texts: In a thrown-together prototype, I used a few wall warts to get the various voltages I needed. Now, I'm trying to build a cleaner version with a single plug and put it all on a PCB to eliminate my rats nest. The board mount versions are way more expensive though. I can get a 2A 12V wall wart for $6.22 but a 2A 12V board mount converter is $27. Why the huge difference? Am I missing some more reasonably priced version of the board mount version?


texts: Does the feed line contribute to the function of a PCB patch antenna?

texts:
First let's make sure I've got my terminology right. The following are both 2.4GHz antenna:

The first is a simple coaxial antenna that's just cut to the appropriate length for the relevant wavelength (or some fraction of the wavelength).

The second is what I understand is called a PCB patch antenna - the antenna is laid out on the rectangular PCB and allows for a more compact antenna design. The wire that has a u.FL connector at one end and connects to the the PCB at the other is, I believe, called a feed line.

From googling around it seems the choices about the feed line are an important part of the antenna design, i.e. it's not simply just "a piece of wire".

But my question is does the feed line contribute to the antenna's ability to receive signal?

I.e. the feed line in the picture above is quite long - if I snip it in half (and then solder down the exposed wire as I've lost the u.FL connector by doing this) will I affect the function of the antenna?

These kind of antenna are used in pairs for small RC receivers and there are a lot of "facts" asserted about them without any obvious evidence to back them up.

You see competing mount styles like the following - compact, one arm and two arms:

The one thing people seem to agree on is that the antenna should be mounted at 90 degrees to each other and that one PCB should be rotated 90 degrees around its central axis relative to the other.

The mounts with long arms that stretch out the feed lines to their maximum seem to rather negate the whole idea of the PCB antenna and its more compact layout.

Some people - especially those who mount the feed lines, not just the PCBs, at 90 degrees to each other - claim the feed line is essentially part of the antenna, i.e. the feed lines placement affects
the ability to receive signal.

Other people - such as those using the design where the two feed lines are run along the same arm - probably just feel they want a mount that lifts the antenna free of the surrounding body.

Such a setup doesn't seem to have gained anything in compactness over the classic setup with long coaxial wires but perhaps it gets better reception for the same amount of space?

In the compact mount design the feed lines are just treated as wires that can be coiled up without affecting the overall function or the behavior. From the googling I've done treating the feed lines like this is perfectly acceptable but perhaps I've misunderstood?

I hope people won't move to close this on the basis that it seems more about solving a hobby RC problem than addressing an understanding of the underlying physics or electronics. In the RC forums there's so much made up information - and I'm genuinely interested in what's going on here at a technical level and really appreciate and find interesting the information related to
this in existing questions here, e.g. how does a coaxial aerial cable work?


texts: Polling interrupting my codec reads and USB writes?

texts:
Another USB question here... same as last time; USB Audio on an ARM microcontroller. I have both endpoints (input and output) as isochronous/asynchronous transfers. In addition I have Timer Counter (TC) interrupts to poll for UI processes on my board.

To summarize, when I have a clean bypass (no USB involved), I get no interruptions; clean signal. Great!!! No weird out of sync issues with the I2S bus/codec; no weird blips, nothing. However, when USB Audio is enabled, things get weird. In my previous question on stackexchange, I didn't have any other UI processes going on (checking for button presses) so the USB audio was pretty clean.

How I read from codec to USB:

(1) USB Input enabled, start USB writes
(2) Write an empty buffer to USB endpoint
(3) Send USB data buffer
(4) Wait for USB write callback
(5) Completed USB write; do the following:
    (a) read next buffer from codec (I2S-DMA) and load that into USB buffers
    (b) Send next available USB buffer to endpoint
    (c) Repeat Step 4-5

Ways I have tried to poll for UI processes (button presses):

(1) USB start of frame interrupts
(2) Timer Counter interrupts
(3) Main while loop polling

All of these cause glitches in my USB Audio writes/codec reads. I can only guess that when an interrupt happens, my codec read gets interrupted and the mcu drops some samples. However, I'm not sure why just regular polling is causing a glitch issue. In terms of interrupt priorities, my I2S-DMA and USB interrupts are highest priority whereas my TC interrupts are very very low (like the lower number).

The question (if you haven't already guessed) is: How do I get my mcu to happily read/write continuous audio from my codec to USB while polling for these other UI processes? I can only imagine I will need to do more than button presses in the future so I'm thinking this could be applicable to other mcu peripheral applications.

Sorry in advance this is an easy question or the answer is really obvious; I'm still relatively "new" to microcontrollers and USB. I can easily figure out things in the software domain now but when it comes to hardware AND software... it's a whole different story for me. Any articles I can read without bothering anyone would also be appreciated. Thanks!

EDIT - Answer:
So I know there was code here before but through posting it... I realized my mistake. In my button processing code, I had reads/writes being done to mcu's flash as well. When I removed those parts of the code, I didn't hear glitches anymore. Ugh! Sorry for bothering everyone, such a user error on my end. The reads/writes to flash were just there to save certain settings in case the user was to accidentally disconnect power.


texts: In a DC circuit, are there any reasons for wiring overcurrent protection such as fuse or pptc PHYSICALLY near the load?

texts:
In a DC circuit, are there any reasons for wiring overcurrent protection such as fuse, pptc, etc.... PHYSICALLY near the load(or inside it)? By wiring "physically near", I mean in the power wire going to the load, but near the end of the wire physically closest to the load.

As to an example of what prompted the question: Any wires exiting body controller of Tesla's model 3 are left exposed and vulnerable along the length of their run to the load and might need protection near the load as opposed to near the power source. Many such wires exit the body controller, in the form of wiring harnesses, and the body controller can selectively protect(from its end) any loads/branches by switching off the mosfet for that load. However, these mosfets are located INSIDE the body controller which leaves the load and remaining length of wire to the load vulnerable and unprotected. Consider what would happen if some other power source were to make contact along that length AFTER the mosfet switch and between the switch and the load; bypassing the protective mosfet switch. By protecting near the load as initially postulated this problem might be addressed.

So in a DC circuit are there any realistic scenarios where protecting physically near the load is worth the trouble/cost? How common are these problems? Doesn't have to be automotive related.


texts: Are there official roadmaps or release dates for future Bluetooth versions?

texts:
I am currently researching about certain Bluetooth versions. 5.0 and 5.1 were released in 2016 and 2019, but I haven't been able to find a official statement of the SIG about the release of planned future versions (i.e. 5.2).

Are there any official roadmaps or release dates by the SIG?


texts: Overcoming cogging/ripple torque in gimbal motor

texts:
So I'm trying to figure out how to spin a camera on a brushless gimbal motor. I am feeding each of the terminals a sinusoidal pwm signal from a via 3 half bridges on the SN754410. Each of the pwm signals is 120 degrees apart in phase.

When this signal is fed into the motor I get a kind of cogging (almost like a clock) and not smooth motion. see this https://www.youtube.com/watch?v=tDNnhxuPoEQ

I am wondering how normal gimbal drivers (for quadcopters and stuff) accomplish smooth motion. From what I understand, you can create acceleration maps with a magnetic position sensor and then do compensation (inverse and apply) to get smooth motion

 but it seems like those gimbal motor drivers don't use magnetic postion sensors.

How do those gimbal drivers work?


texts: Which one must be used matched output voltage or open circuit voltage?

texts:
I designed a circuit for my graduation project in automotive engineering department, that circuit will measure the heat energy from exhaust system and turn it into electrical energy by using thermoelectric generators (TEG). In the final stage I found two voltage values on TEG which is the matched output voltage and open circuit voltage .

Is the matched output voltage is the actual voltage after load?
And which value I must depend on (open voltage or matched voltage) to design circuit to charge a 12v battery by using these TEGs?


texts: convert self-powered speakers to passive

texts:
Is it possible to convert a self-powered speaker into a passive one?
(and if yes, how?)

My scenario:
I have an old pair of PC speakers i'd like to use with my portable MP3 player even if there is no power outlet nearby...


texts: Can a classical Toffoli gate be built from irreversible gates?

texts:
The Toffoli gate is a reversible gate with three inputs (A, B, C) and three outputs (S1, S2, S3) generated as

S1 = A
S2 = B
S3 = AB ^ C

It can be implemented in a classic way using the following circuit:

simulate this circuit – Schematic created using CircuitLab

However, the AND gate and the XOR gate are not reversible. Hence, is this implementation of the Toffoli gate actually reversible?. More generic in a mathematical way, given a homomorphism, can it be implemented using irreversible gates?.


texts: Does thickness or density of material between a wireless charging transmitter and receiver affect the power?

texts:
I'm planning to build a small enclosure out of wood for a wireless charger and have been testing various thicknesses of wood to ensure my phone still detects and receives a charge, however, I'm only checking that the phone detects power transmission, not the rate of charge, which would require running lots of time consuming anecdotal tests.
Assuming conductivity properties of a separating material are equally non-conductive (i.e., no metal or wet wood), does the density or thickness of the material affect the rate of power delivery of a wireless charger?
For example: would 3mm thick walnut cause a reduction in power resulting in a slower charge than 1.5mm walnut?
Alternately, would 3mm thick walnut (680kg/m^3) cause a reduction in power resulting in a slower charge than 3mm thick butternut (370kg/m^3)


texts: What is the meaning of Technology, Package and Variant with regards to an electronic component?

texts:
I am currently designing a PCB in EAGLE and while creating a footprint/package of a logic IC (http://www.ti.com/lit/ds/sdls029c/sdls029c.pdf) I came across the terms technology, package, and variant.

P.S.: I know what package means and that the IC might be available in EAGLE as a device. I have just mentioned it as an example.


texts: What is the difference between PDIP and MDIP?

texts:
What is the difference between these opamps?

MDIP: http://dk.rs-online.com/web/p/komparatorer/5338186/

PDIP: http://dk.rs-online.com/web/p/komparatorer/0428458/

PDIP: http://dk.rs-online.com/web/p/komparatorer/7140789/

I need an LM311 which I can use on bread board as a comparator with fast switching. Some has MDIP some PDIP. What is the difference? ?Are all these the same except their switching times and voltage ranges? Will they be treated the same way?


texts: I have a failure with a PNP Transistor (B772) and i want to replace it with another one, but my supplier does not have it , so what are the PNP transistors that i can use ???


texts: Why should collector voltage need to be higher than emitter voltage?

texts:
I'm reading up on npn (and by extension pnp) transistors, and I got tripped up on a note from my book (Practical Electronics for Inventors, 3rd edition, p. 433)

"For an npn transistor, the voltage at the collector must be greater than the  voltage at the emitter by at least a few tenths of a volt; otherwise, current will not flow through the collector-emitter junction..."

As far as I'm aware, an npn transistor is symmetrical in construction, so it shouldn't matter that the emitter voltage is higher. What is the physical distinction between collector and emitter?

Thanks


texts: LED Corn Lights Faulty On/Off or flickering, Mains 230VAC/50HZ

texts:
I wonder if someone could help, I have these cheap Chinese corn LED globes that either go ON/OFF randomly after a while or they dim to about 1/3 brilliance or less with faint flicker. they're also not hot to touch, grab or remove.

From new for a couple of hundred hours or so, all was good, then they start to play up. When you first switch them on they may run good for upto half an hour or so.

In the pic there is a diagram of what seems to be the cct for the light. Difference being the capacitor size and voltage. Under the capacitor their are 3 resistors unlike the diagram that only has two. In the light shown I have also re-soldered all the connections as best as I could but the result remains the same.

Any ideas what could be causing them to fail.

Update. I think I figured out what is the cause. Bad Design/Designed to fail/Incompetant design/ Take your pick.

I placed a meter on it and it draws 54ma and the chip runs at around 56 degrees. In the extract from a datasheet I found there are two diagrams 12W and 24W. In their wisdom I would say, O' 12W close enough no need to add another chip. So the chip eventually fails. To add insult to injury thinking they are smart they replaced R1 and R2 with two 68 ohm resistors. O' well nothing can be done about it 3 identical globes 3 failures, 10 bucks down the drain.

I bought the globes from here


texts: Altium AutoRouter problems with mixing power signals

texts:
I'm using Altium for my board layouts, and for the most part, I hand rout the boards. I'm currently working on a particularly dense board, so I decided to use the autorouter after hand routing about 40% of the board. I had already routed all the power and ground connections, and after setting up the rules and running the autorouter, I found MANY places where the autorouter connected my power and ground plans! How is this possible? It placed(see picture) a power via over a ground via and connected them, after I had already routed power and ground to their own respective vias! Any ideas? I know autorouters are somewhat unreliable, but this is ridiculous..

https://drive.google.com/open?id=0Bws5pmYyaBJSTUhIeUxSR3JoS1U

Thanks all!


texts:
I'm trying to create a power supply for biasing a Langmuir probe. It needs to run some sort of predictable wave (I need to compute an I-V curve for a plasma, so I need to vary the voltage in a predictable way) at about 1000 Hz. It needs to be +/- 60 V. I don't really have time to order any new major parts so I've been wondering if there's a purely-analog solution to this problem. A friend recommended using a capacitor circuit to generate a triangle wave but this presents the problems of:

Having a 120 VDC supply (perhaps daisychaining 9 V batteries), and
Biasing such a wave -60VDC (it should run at +/- 60 V, not 0-120 V).

Anyone have any ideas?


texts: What are the building blocks of digital circuit design in ICs?

texts:
I think that the building blocks of digital circuit design can be described as:

Counters
Finite State Machines
Memory blocks (use address to access data with read/write signals) and simple registers (use clock to store 1 bit)
Arithmetic and Logic operation blocks
Multiplexers/Demultiplexers

I think that all digital circuits can be broken down into these "functional" blocks. Ultimately Finite State Machines are made up of arithmetic & logic operations also and registers. Counters contain them as well. However, I think that is sufficiently low level of abstraction to describe complex digital circuits. Therefore, when a person starts learning digital circuit design and has grasped the concept of boolean algebra, logic gates, flip-flops and registers and they have to do their digital design, they should think it terms of this.
Another important aspect in hierarchical designs is, communication between different blocks. This could take form of simple handshake using read/valid signal or more complex interaction that is based on well defined data buses like Avalon, AMBA e.t.c.
I think that things like shift register and FIFO should be there in the list but am a bit confused.
Am I missing something here or got something wrong? Is there an agreed way to write down the list as a flat list or as a hierarchy? I think such a list can be help for new learners.


texts: 4 input CMOS NOR gate simulation showing metastability

texts:
I'm simulating a 4 input NOR gate in LTSPICE but with different inputs, i.e., the inputs going into the Pull-up network are different from the inputs going into the Pull-down network. The inputs are square waves arranged to form a Gray Code counter (so only one input changes at any given time). I expected the NOR gate to respond with either a 0 or 1 but it goes metastable most times.

Here's my NOR gate:

Here are the square pulse inputs in the schematic file I'm using in Gray Code format:

The inputs look like so:

Finally, this is my output for the 4 input NOR:

As you can see, the output is showing some metastability instead of landing on 0 or 1.

I'm not using any MOSFET models. Just the ideal NMOS4 and PMOS4 models. For now, both NMOS4 and PMOS4 have aspect ratio 1.8u/0.6u.

What could be causing this metastability?


texts: I am trying to make system where I want lights to turn off automatically. It should work like that if someone kept lights on by mistake then it should turn off automatically without any human intervention (like in IoT we can turn off with our phone ). For this I have tried thinking about putting camera in room which will detect the presence of human in room and if no human is detected then lights should turn off. But I am having difficulty to figure out how to turn off lights automatically? I mean what can be used ?


texts: Why would DC motors be preferred over brushless AC induction motors for cable cars propulsion?

texts:
According to this article San Francisco cable cars system uses a set of traction cables driven at constant speed and each car can connect to the cable when its operator want the car to move and disconnect from the cable when the car needs to stop.

The article further says the cable drums are being driven by 510HP (380 kW) DC electric motors that were installed during restoration in 1982. So this is not a case of just continuing to run some well built old motors.

Now why would DC motors be preferred?

An AC induction motor with a squirrel cage rotor has no brushes and runs continuously just fine. Speed variation which is hard for AC motors is not needed for this system, so that's not a problem. 1982 is long after the War of Currents ended and AC became preferable for distribution. Driving a DC motor requires a powerful inverter and DC motor brushes will need servicing and there're no obvious benefits.

So it looks like an AC induction motor would be preferable for this application.

Why would DC motors be preferred?


texts:
I'm at my wit's end trying to get a 32.768 kHz tuning fork crystal to work and I don't know what I'm doing wrong.

First, some background: I'm using a 16MHz crystal in conjunction with an Atmega 328P-PU microcontroller and that's working fine and I'm trying to run an RTC chip off a 32.768 kHz crystal which is where I'm hopelessly stuck. I'm using 10-20 pF ceramic load capacitors and of course I'm using an oscilloscope to verify everything.

I'm trying to run this RTC chip with this inexpensive crystal. However I cannot get it to work whatsoever, either on my PCB or a solderless breadboard. I've used several different load cap values and my crystal is wired up as the RTC datasheet specifies. I've replaced the chips, the caps, and the crystals, and that didn't fix anything.

I even tried connecting the tuning fork crystal to the Atmega chip XTAL pins instead of the 16MHz crystal and that didn't help either.

Do tuning fork crystals need a special circuit to work, or did am I inadvertently damaging every single one I touch...? I even tried different crystals of a similar design from different manufacturers.

Help is greatly appreciated.

EDIT: I solved my problem by switching to a non-tuning fork crystal and getting new capacitors. I think the root cause was the use of low-quality ceramic capacitors that I had bought in a assortment kit online.


texts: How do you fix the glitches in the following Karnaugh maps?

texts:
The following circuit is supposed to output 1 if the input is greater or equal than 1010 (decimal 10). The truth table is given and we are supposed to convert that to POS and SOP using Karnaugh maps. Here's the truth table with the minterms and the Maxterms:

Here's the Karnaugh map I did for the SOP (Sum of Products)

Same for POS (Product of Sums)

I remember my professor saying that when you make groups on the Karnaugh map if there's adjacent groups there will be a glitch.

I have three questions:

Is it possible to fix the glitch without the Karnaugh map? If yes how?
How do you fix the glitches on the Karnaugh map?
How do you fix the glitches on the resulting circuits (I have to make one for the POS and one for the SOP).


texts: Why do utility companies supply at a frequency of either 50/60 Hz?

texts:
It just struck me that Utility Companies world-wide supply domestic users at either 50/60Hz. It could have been selected to be 10 Hz, or 100 Hz ... whatever

Was 50/60 chosen at random? Is there some rationale involved (efficiency, easier to construct/control etc) in restricting domestic supply to either 50/60 Hz?

In other words, if I were designing a power system, why would I pick 50/60 Hz instead of some other frequency?


texts: Clarification on LED strip specifications

texts:
I am curious on doing a DIY LED light ring as seen in this video.

https://www.youtube.com/watch?v=xsd5b9p19nM

I appears that I know where to get all of the parts specified in the video. While I could not find a 10W LED strip, I have a 4.8W LED strip available for me, as seen in the link below.

http://www.cdrking.com/index.php?mod=products&type=view&sid=17321&main=30#.VRkJAXqUdGt

I am not sure if its a warm light, but that's not the point I'm trying to make. I just want to get some clarifications out to better understand the LED strip specs given in the link. I will just paste them here for everybody's convenience.

Non-waterproof
Light Source: LED
Type: Flex LED Strips
Lamp Luminous Flux: 780-900 Lumens/Meter
Lamp Body Materials: Adhesive
Item Type: Light Strips
Input Voltage: Dc 12V – 3A
Working Temperature: -20 to 40 degree
Length: 5M per roll
Emitting Color: White
Lamp power: 12V 4.8 Watts
Working Lifetime(Hour): 50000
LED Quantity: 60 LED's/meter
Net Weight: 48g
Packaging size: 230mm x 65mm x 250mm (L x W x H)
Gross Weight: 308g

What I only care are numbers 7 and 11. From what I understand 12v 3A means that that is the entire power consumption per meter of the LED strip (or is it saying the entire 5 meters?) If I break the strip, since I am going to try make a Light ring for DSLR, does each LED has a voltage capacity of 12v? Given that the LEDs are presumed to be laid in parallel? Then in the Amps, should I divide the 3Amps to get each Amps per LED bulb?

on 11, does the 4.8W means that it is the entire brightness of the LED strip, or is it per LED?

Bonus, question: If you watched the video, the author used 6 AA batteries. I'm thinking of using two 9v batteries in series to get 18v and just step it down using resistors. Would that be safe?


texts:
I tried to run this simple circuit for DC operating point. The transistor is in saturation with Vth = 800mV.

What makes me confused is about gmbs.
It is not zero but also very large compared to gm.

Why gmbs is not zero when B and S are tied together?

Thank you.


texts:
How to bias a photo-transistor (the resistance in the collector)
given that:

Vcc = 5v
Vce(sat) = 0.4v
Ic(on):
   min: 0.2 - 1.6
   max: 0.6 - 2.4

I'm using LTR-301 photo-transistor.
I want to use it in the Active mode, to get the heart pulses
and what about Vce, if it's low, (it's supposed to saturate the photo-transistor, I don't want that to happen)
I need the range of values of Vce to calculate the thresholed in the Comparator (to convert the signal into a pulse train)

Do I need amplification if Vce is big enough?


texts: Can I improve the directivity of an X-band radar module with integrated plane-patch antenna?

texts:
Lots of detail provided in case it's needed.

I'm continuing to tinker with remote proximity sensors driven by an Arduino (and eventually just an ATMEGA* chip and its safety buddies) and have a pretty good prototype so far. It picks up motion just like the PIR module and signals the same, which the Arduino turns into a mechanical knocking via 5V solenoid. The PIR module does not work behind insulated glass (predictably) and making it an outside unit requires more work (and power management for batteries) than I'm willing to invest at the moment.

To simplify things, I decided to try an x-band radar module so I can keep the units indoors and avoid weatherproofing. The allure of pointing a microwave device out through a brick wall to detect motion was quite powerful. :-) I'm using this Parallax module (data sheet).

The problem is the unit is picking up movement behind it in addition to anything antenna-side, even with the sensitivity pot set all the way down. Looking at the data sheet (and seeing the graphics representing its field - don't know the terminology), it does seem to be expected behavior. HOWEVER, I want to focus it into a forward-facing beam (relative to the device) so I can aim it outside.

I know enough to figure I need some kind of waveguide but every attempt at blocking its back with metal (aluminum foil, a cut Coke can, and a conical piece of 1950s pendant lamp I replaced with a ceiling fan) has failed. The module keeps picking up movement behind it. I even encased the whole thing in an aluminum project enclosure just to verify that I can in fact blind it. It seems somehow to go straight through the enclosure and pick up movement anyway. This was unexpected. I suspected interference but the detection ONLY coincides with actual movement.

So: what makes a good waveguide? How would you guys approach the problem of focusing a pulse doppler radar into a reasonably narrow beam for motion detection? Thanks for any insight you can offer. I'm happy to get more specific or clarify any of the above.

Note: I'm sure the subject could probably be more specific but this is my first electronics project and I'd rather be vague than confusingly incorrect. :-}

Interference Addendum:

I'm still not convinced there isn't some sort of interference occurring. As I have no oscilloscope (yet), I'm not sure how to test this theory.
This thread seems to suggest my approach is flawed: apparently the module's state should be read from an analog pin with noise and time thresholds. I've been reading it on a digital pin HIGH/LOW.


texts: Why does my diode log amplifier in LTspice not match theory?

texts:
I am trying to learn about analog multipliers, and I'm trying to implement one using a log-antilog design.  I am currently having some difficulties with the log part because simulating an ideal amplifier gives results that are consistently about 0.4 V lower than what the formula from  Wikipedia says.  I am running a voltage sweep 0-100V and the same problem occurs throughout the range.
For my "what the theory says" graph I took the saturation current from the SPICE model for the 1N4148, and 300 K for temperature.


texts: Circuit analysis with a dependent current source

texts:
I have been working through Boylestad and I am having trouble with this folling question.

simulate this circuit – Schematic created using CircuitLab
h = 50.
this one i'm finding difficult because the current source depends on another part of this network.
I tried applying Kirchhoff's law around the both loops to get loop currents \$I_1\$ and \$I_2\$.
$$hI = I_1 - I_2$$
So \$I = I_1\$
Then I got $$hI_1 = I_1 - I_2$$
$$0 = I_1(1-h) - I_2$$
And I used kirchhoff's around the outer loop to get the second equations.
$$20 = I_1(2000) + I_2(2000)$$
So I used these two equations using determinants but I didn't get the result in the book which was \$19.62\angle 53^\circ\$
Am I on the right path here or is there a better way to try and get the correct answer?
Now correctly completed with the help of @TimWescott and @relayman357 with the correct equations:
$$I_1(1+h)-I_2=0$$
$$I_1(2000) + I_2(2000) = 20\angle 53^\circ$$
Then using determinant to determine \$I_2\$ to then find \$VR2\$.


texts:
Background:

I'm planning on making a hard tube modulated pulsed power supply. This will use a thyratron set to trigger at a frequency of 6 Hz, a 60 nF capacitor bank, and a 0.625 mH inductor.

The capacitor bank has a rise time (dV/dt) of 2,879 V/uS and is charged with 10 kV DC.

Question 1: What will the peak current be?

Question 2: Will the energy of each pulse be around 3 J? This assumes that 0.5CV^2 can be used to predict the approximate energy of each pulse.


texts: How to analyse such circuit with op amps?

texts:
V(вх) is input voltage, I need to find output voltage(in the center). Yeah, it must be amplifier, of course. Just, I know and understand how to calculate simple non-inverting, inverting circuits with negative feedback. Can you, please, give me good examples (or links, books where to read) of, maybe, circuit with two op amps, how to calculate them?

P.S. It is Russian circuit, so rectangles are resistors here ;)


texts: My project Super OSD fits on a PCB with dimensions of approximately 40mm x 70mm. It's very space constrained and I can't expand the PCB too much. How should I approach this problem? I realise it's not strictly electronics, but it is a problem many have presumably solved before. I first considered screws but I didn't find any ones small enough - I need to go as small, or smaller than 4mm diameter. I was thinking of using heatshrink to keep the module secure if screws were not an option. Any opinions?


texts:
I have this big immersion heater which my friend gave this to me. He said that this is originally design to be a 230V 9kW 3ph immersion heater (star).
I am planning to convert this to single phase.
Question is, how will the conversion affect the heating capacity of the heating element? Will it generate the same heat?


texts: Help with LDM instructions on ARM Cortex-M3 processors

texts:
Consider the instruction LDM R4!, {R0-R3}.
Does the instruction LDM R4!, {R0-R3} load the MEMORY ADDRESS pointed to by R4 to R0 and 4 plus the MEMORY ADDRESS pointed to by R4 to R1 etc, or will the instruction loads THE VALUE LOCATED AT THE MEMORY ADDRESS contained in R4 to R0 and THE VALUE LOCATED AT THE MEMORY ADDRESS 4 bytes above the memory address contained in R4 to R1 etc.? In other words, after the instruction, will R0=&R4 and R1=(&R4)+4 or R0= *(unsigned int)R4 and R1= *(unsigned int)(R4+4)?


texts:
Why are Pins 7 and 5 floating for this 555 IC and how does an NPN and PNP transistor when connected to E B C act a switch?
Without the use of Pin 7 surely the capacitor cannot discharge which would render it useless?


texts: Coil switching for resonance with an arduino controlled TRIAC

texts:
I have a capacitive system which I need to power via resonnance using a coil. Resonance occurs at several frequencies, therefore I need a different coil for each frequency. So far I've manually switched the coil whenever I needed to use the other resonance frequency. However I feel like this process can be automated, so I've designed a shield for my arduino that allows me to do just that, to switch coils using a button or later an automated command coming from the computer to the arduino's serial. (The arduino here is an UNO).

Since it's using alternative current, I needed to use a TRIAC. The design I've come up with so far looks like this

It works this way : The Signal + connector at the top goes into a function generator with an amplifier which outpus an AC voltage which can range from 5V to 20V in higher voltage uses. The Signal - connector at the bottom goes to my capacitive circuit, which itself is connected to a shunt resistor and eventually back to the function generator.

On the shield, as can be seen is a small 2 poles connector onto which the coil is plugged. There's another coil-switcher right next to this one as I'll be using 2 coils on this system but that I haven't shown as it's exactly the same as the first one. There's a small  opto-TRIAC (the MOC3031M) to separate the arduino from the rest and to trigger the actual TRIAC. I drive the opto-TRIAC using a simple MOS from the arduino.

My question now is the following : Is that a good way to control such a system?

What I really only want to do is to be able to select between one coil or the other without having to physically change the component.


texts:
I have read that watchdog timer pushes microprocessor/controller into reset state whenever it experiences any software anomaly like executing in infinite loop.
and after some time a very senior prof told us that after reset the processor resumes operation from the next instruction to the erroneous one.

when watchdog timer resets the processor, from where does the processor start its next execution?

I just wanted to know what is correct or if some other concept is employed?


texts: STM32F030R8 Nucleo-64 Board ADC Voltage Reference

texts:
I want to decrease the reference voltage of the ADC to have a better resolution, by now I do not want to try other options.

Could someone explain me how can I do this?
I am using the Nucleo-64 board STM32F030R8 and CubeMX to generate the code.
Do I have to configure something in the programming code or I just need to provide the correspondent voltage to the right pin of the board?


texts: What is actually transformed in quarter wave transformer?

texts:
I'm reviewing some stuff on quarter wave transformer for a transmission line but since I have not had any experienced in handling these type of stuff, I am struggling to understand this concept intuitively

http://www.ittc.ku.edu/~jstiles/723/handouts/The%20Quarter%20Wave%20Transformer.pdf

What I don't get is that all the calculation involved in this "quarter wavelength transformer" is to calculate the input impedance Zin at a quarter wave length away from the load. What is the point of that?

What is actually done in the field to change the transmission line network into a matched network using quarter length transformer?


texts: This picture is from top252 ic of smps. Out of million questions, why is a capacitor[C6] is connected across transformer.


texts: Trying to identify this rocker switch in a KRK speaker

texts:
I am trying to replace a broken (the rocker arm was pushed in) rocker switch on a KRK V4 speaker, and am looking for a suitable part number. I don't see a number on the switch and don't want to take it off until I get a good part since the speaker still sort of works and I need to use them every day.

Can anyone identify this switch, or possible give me some keywords to search for, for example on digikey.com? I'm not sure what language to use for the form factor, poles, conductors, etc. As far as I can tell it is an on-off-on surface mount with the voltage in the pictures, and there are 6 conductors exposed. See images below, thanks!

UPDATE: Added fourth photo with board layout


texts: Should I re-apply conformal coating after hot air soldering?

texts:
I'm working on a PCB of a drone. It had some failed MOSFETs that I've replaced using hot air soldering.

It works fine again, but parts of the PCB were covered in a glue-like substance which I think is conformal coating. I figured the coating would probably interfere with the hot-air soldering, so prior to applying the hot air, I removed parts of it using paint thinner. Now I have a few questions:

What is the purpose of this coating?

I suspect it's to prevent malfunction of the PCB when it gets moist. Maybe when the drone would fly in moist air or fog. The drone really isn't made to fly in the rain. I'm confused about it because it's only partial - only at the places where components are. I'd expect a coating like that to be applied over the whole surface of the PCB. Or are traces and vias not prone to getting moist because of the solder mask? Could there be another reason for a coating like this?

Is conformal coating ever used to prevent service to a board? Like when a manufacturer would rather sell new boards or new devices than having a technician service a broken PCB? Removing the coating before service is a lot of work and might discourage the technician.
I've taken off the coating at the place I needed to do the rework. But it takes quite some scrubbing with paint thinner because the surface is very uneven (mounted SMD parts.)  The coating becomes very sticky when in contact with the thinner, but needs scrubbing to come off. So where the coating is not completely removed, there is now a mix of re-hardened coating and fibers from the cloth that I was using. (When the thinner evaporates, the coating becomes hard again.) The fibers are very small, and best seen with a magnification glass (hence no photo), but are also in-between the legs of the ICs (see picture 2.)

Is it likely that this will lead to problems? E.g. if moisture would be trapped in those fibers?

Is it advisable to re-apply the coating? If so: Are there any household products I could use for that? I was thinking about hairspray. Or is that a really bad idea?

Picture 1: Partially applied coating. It has a blue-ish/transparent color to it.

Picture 2: Closeup of the part I did rework on, prior to the rework. The coating on the bottom of the PCB (picture 1) was clearly applied nicer than the top (this picture). On the top, there is quite a thick layer at some places. I removed the coating near the MOSFETs, but also around the two high pin count ICs (MOSFET driver and microcontroller).


texts: Residual-current device: Would a big coil trigger it because it stores electrons?

texts:
Imagine a residual-current device at your home - basically it counts influx of electrons vs outflux of electrons. If there is a missmatch (e.g. I=30mA over t=30ms), it triggers and disables the circuit.

What if I connect a big coil? Because of the inductance it would store a certain amount of charge which is released later on when it is disconnected from the voltage source.

Would the missing amount of charge be able to trigger a RCD? Because the RCD would see only some charge flowing into the coil but not coming out again right after connecting the coil?

What would happen if I connected a big capacitance?


texts: How were Power Bank limits decided by airlines?

texts: Why is a 160Wh power bank considered safe to carry on board, but not 170Wh, for example? What defines this maximum safety limit, how was it determined? Obviously airlines across the globe have agreed that this limit is sufficient, but what make it sufficient (or if they are not sufficient in your opinion, why are they not sufficient)?


texts: op-amp pin is sitting at high voltage (active low-pass filter)

texts:
I am looking at using the OP1177 to act as an active low pass filter. I need to smooth out a 20kHz signal burst with a minimum of 50 cycles to reach a voltage on the output to interrupt an microcontroller.

I have tuned my circuit succesfully first with the passive RC and obtained the required rise time.

However when I use the op-amp I get a very big offset voltage at the input. I have a gain of ten but I get a minimum input voltage of ~160mV. The input offset voltage of the op-amp is 60uV maximum so it can't be that. Does anyone have any idea what parameter or method of analysis I should be looking out to defeat this problem?
I am going to change to a LT1001 op-amp which runs without this problem in simulations but any ideas would be greatly appreciated!

Regards,


texts: Arduino 3.3 V to 5 V to controll Stepper Driver MA860H

texts:
I'm currently working on a project with an Arduino Due and Stepper Driver MA860H. The issue I'm running into is translating a step Direction and Pulse from the Arduino Due to the MA860H. The Due has 3.3 V output and the MA860H needs a 5 V signal.

MA860H Stepper Driver

In the beginning of the project I had done some research and figured all I would need is a voltage translation from 3.3 V input to 5 V output. I went ahead and purchased Spark Fun Voltage Level translator. I got all the parts together and soldered the appropriate wires together and I'm unable to get the right voltage through the Level translator. In the past I have worked with this driver before, but with an Arduino Uno. This seemed to work just fine. So I know its possible with an uno at 5 V. My only other option is to use the Due for TFT, hall effect sensor data, and then running the test. Then I would have a Uno that would run the motor once the due told it through digital write. In the end this might be the easier route to go, instead of trying to get the due to do 4 things at once.


texts: So I've come across a case where an input from a little 5v I/O system will trigger the coil of a reed switch but not it's direct equivalent that has a built in flyback diode and changing the resistors that are in series with the input doesn't seem to work. Far as I can tell it's a CV supply though. Thoughts on getting it to work?


texts: How can I make a model of a single wire CAN bus cable?

texts:
I'm currently working on a project of analyzing the latency of a CAN bus network with transceivers and without transceivers. The latency parameter here will be analyzed with the effect of bus line length variations (2 m, 5 m, 8 m, 10 m, and so on). I'm trying to figure out the maximum bus length that a "non-transceiver" CAN bus network can work with.

The "non-transceiver" CAN bus network requires a single wire bus line. I'm using this application note as my reference to build the "non-transceiver" network, the figure of a CAN bus without a transceiver will describe what I meant by "single wire". mikrocontroller.net/attachment/28831/siemens_AP2921.pdf

As you can see from the document, it is stated that the "non-transceiver" CAN bus can only work for only << 1 m bus length, but I've found someone has used this "non transceiver" network for a 4 m bus line, and it worked. So there's no scientific proof of the statement of "it is only usable for << 1 m". My goal here is to find the maximum bus length for the "non-transceiver" bus length.

(I've tried the "non-transceiver" network and it worked. The CAN nodes can communicate to each other.)

I'm having a problem with making the equivalent circuit (model) of single wire bus for a certain bus length (let's say 10 m for an example). What is the resistance and the inductance for the model? How do I make the calculations? Can somebody help me with this?


texts: constant character darkness on lcd even in low battery

texts: At this time I have an lcd where I hook up a 1k resistor between contrast and ground. As the battery voltage drops, the text on the screen also fades. I could make a manual switch and switch between resistor values to compensate but I want something more automatic. My lcd is a stanndard 5v hd44780 display. Could I get away with a zener in which cathode connects to 5v and anode to contrast pin with resistor in parallel? If so, what values should I use for the resistors and diode connected to lcd contrast pin for optimal display output?


texts:
I am designing a board with an stm32f722 MCU (64 pin version) and I can't afford to waste / not use any GPIO.

My question is following:
Is there an option to only use the Rx-pin of a uart / usart so that the Tx-pin can be used for something else (in my case SPI_SCK)?

If I enable a uart / usart in STM32CubeMx and go to the "Configuration" tab I can change "Data Direction" to "Receive only". But this doesn't disable the Tx-pin.

Another way may be using half-duplex mode but then the Tx-pin would be used anyways and I couldn't use it for SPI.

Note: I am still planning my own board and don't have any hardware to test.


texts: How can I trickle charge NiMH batteries as part of an IOT controller?

texts:
I have built an IOT motor controller board that's powered by 4 AA NiMH batteries in series. I want to use a solar panel to trickle charge the batteries, but the voltage slowly decreases even when the ESP12F WiFi module is sleeping and there's full sunlight on a 5v 200mA or 6v 150mA panel.

Why am I never seeing an increase in voltage?


texts: Amplitude of antenna-voltages induced by microwaves

texts:
I’m rather new to electronics and I encourage you to prepare yourself both mentally and physically for some very stupid questions – and some assumptions of my own (possibly very wrong) – about fundamental RF and antenna theory.

Starting from the beginning:

If I hold up a piece of metal in the air, AC voltages of various frequencies are induced in the metal and co-exist in the material.

Another piece of metal may also possess some geometric qualities causing it to resonate at a particular frequency.

Using the swing analogy – in the same way that a parent pushes their child on a swing in phase with the swing’s already existing pendular momentum, the intrinsic resonant frequency of the piece of metal constructively interferes the frequency of interest causing a small gain in the signal.

I assume the voltages induced by waves in, say, the UHF band, are of very low amplitude. What I would like to know is; which order of magnitude are we talking about here? Is it mV, tenths of mV? What would be considered an average peak-to-peak voltage induced by ambient radio waves at some particular frequencies? How much does resonance work to amplify the signal? How does RF-power output come into the picture (dBm) ?

Could someone point me to a source (book, article) that will help me understand this intuitively?

As an aside:

When I was browsing for some schematics of wideband transistor RF-amplifiers, many of the comments were phrased as if a 20dB gain was a great achievement – is it a great achievement? Or is it assumed that it will have to be cascaded to be useful under most conditions?

It would help to hear some empirical examples (unless I’m completely barking up the wrong tree) of what other people have done, be it Bluetooth, SDR or HAM – rather than just the mathematical realities (also appreciated, of course).


texts: Powering a 30 watt computer in the middle of the desert

texts:
I'd like to power a small, headless, linux box in the desert for 10+ hours a day. It draws the lower end of 30-40 watts. I'd like to not use a generator and go the battery + solar route. Can you tell me the best setup I should use in terms of battery size vs solar panel output?

EDIT: Adding additional info:
The desert where this unit will be for a week will have about 5 hours of useable sunlight each day (Black Rock Desert, early September). The computer is a standard shuttle (mini-pc) with SSD and wifi (more details in the comments). I know I can get lower than 30-watts PC but for the application and user load I expect, I'd like to stick with what I have now for the initial version (though hardware suggestions are always welcome).

I will be charging the battery up fully before the week long stay, which would allot me a little time with no sun / solar panel setup. Thanks.

Update! I took some advice below and got an old NSLU2 off of Craigslist for $45. Now I'm running a Debian web server at 2.5 watts! (6.4 watts with two usb hard drives and while transferring files.) I may be able to run the whole setup off a battery all week without the need for a charge.


texts: Resistance changes when keeping two ends of a metal bar constant but increasing the thickness of the middle?

texts:
In this imaginary scenario I am taking a metal block and measuring the resistance. If I were to add a piece of metal in the middle of the metal block (i.e. the metal now has a bulging middle but the two ends of the block are still the same dimensions), would this change the resistance?
From the resistivity equation, I don't think it will but I was wondering if anybody could verify this.
Many thanks.


texts: Switch inductive load: relay instead of switch

texts:
I have a transformer based AC fan regulator with five output steps. The regulator has a manual rotary switch (5 steps) which selects different windings on the secondary coil to give different output voltage (240-120V). I would like to replace the switch with something I can interface from a microcontroller.

Can I assume the regulator already contains circuitry to handle the inductive load discharges while breaking current, so it should be safe to simply put in a relay (one relay for each output step) instead of a switch? Or is a relay more sensitive to voltage spikes than a manual switch, so I would need some extra protection?


texts:
I have a few n-channel MOSFETs (the irlb8721's) and I was able to use it as a switch to control an led with the gate at 5 volts.

I would like to change the source/drain voltage to 11.1v from 5v and current will be 20a with still having the gate at 5v (so I can control it with a microcontroller). Would this be possible? Or do I need to add additional transistors/resistors?

simulate this circuit – Schematic created using CircuitLab


texts: Tesla Coil/Slayer Exciter : Aluminium or Copper wire?

texts:
I was making a slayer exciter recently and I ran out of copper while winding the secondary up, with a goal of 1300 turns..
I ran out of Cu wire, but I do have a lot of aluminium(37 AWG) wire(enamelled) laying around...
Can I use that instead?
My guess is it should work, although aluminium is a bit less conductive, but I need some help from experts or anyone who has better knowledge about all this stuff
I do have a 18 AWG copper coil for the primary ready
(4 windings).

P.S I'm powering the exciter with a 40V DC input, using a MJE3055T power transistor/TIP41C.. the circuit is pretty basic..