texts: Use spray paint to make mask for pre-sensitised board?

texts:
I'm about to etch my first simple board for a project. I have a pre-sensitised board that (as I understand the process) you expose to UV light, then develop the board in a sodium hydroxide solution, then etch. The UV light will negatively affect the protective lacquer and developing it after exposing washes away the lacquer, making the board ready to etch.

I got the lye and I got sodium persulfate for the etching but I did not have any transparent paper as I thought I did! And it's impossible for me to get a hold of it in time (= this weekend, I live far from the city and it's a small one and I haven't found any place that stocks it so I have to order online and that's sometime next week I'd get it at the fastest).

So I am looking for an alternative solution. What I am considering is printing the design to regular paper, cut out a mask carefully from this paper and place it over the board and paint a mask on. Spray paint most likely, then in theory I would have a UV mask.

Anyone see any flaws in this plan?


texts: Mesh current analysis - with AC in s-domain

texts:
I have the following problem:

Consider the circuit below, with

\$v_1(t)=5\text{V} \ \sin(\omega_0t)\$

\$v_2(t)=1.2\text{V} \, \cos(\omega_0t)\$

\$V_3=9 \text{V}\$

\$i_s(t)=0.5\text{A} \, \cos(\omega_0t+50^\circ)\$

The bottom of the arrow indicates the \$+\$-pole of each voltage source.
At \$f_0 = 1.25 \text{MHz}\$ the circuit is in steady state.
What is \$ |\mathbf{I_{out}}(s)| \$ at \$ f_0\$?
What is the phase of \$ \mathbf{I_{out}}(s)\$ at \$f_0\$ referenced to \$ \mathbf{V_2}\$?

EDIT
I tried to simulate with LT spice and got the following result:

But I cannot confirm if what I'm getting is a correct result. That is why I would really like some help with this problem.


texts:
The figure above illustrates a circuit with VCVS and its Norton equivalent model as seen from Port B. Given that Vo=5V,A=2,R1=1Ω,R2=3Ω,R3=5Ω, determine the Norton current IN and Norton resistance RN

Attempts:
I calculated Vout=7.857 V; u=5.714 V. I don't know how to calculate the Norton resistance, since the dependent source 2u cannot be suppressed to calculate the resistance looking from the output.


texts: Video camera exposed to lightning in clouds

texts: Suppose you are sitting outside in the dark and the video camera in the mobile is ON. If the clouds are lightning again and again, will this damage the video camera? As our eyes can get damaged by light (not thunder but maybe very intense light), I thought maybe the mobile camera can get damaged too.


texts: Why does the clk not appear on the device under test?

texts:
The clk signal is not being provided to the device under test from the test bench. I am unable to find the issue. It simply outputs 'U'.
What could be the issue?

The current output
Testbench for counterEx
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity counterEx_tb is
end counterEx_tb;

architecture arch of counterEx_tb is
    constant M : integer := 10;
    constant N : integer := 4;
    constant T : time := 20 ns;

    signal clk, reset : std_logic;  -- input
begin

    unit : entity work.counterEx
        generic map (M => M, N => N)
        port map (clk=>clk, reset=>reset);

    -- continuous clock
    process
    begin
        clk <= '0';
        wait for T/2;
        clk <= '1';
        wait for T/2;
    end process;

    -- reset = 1 for first clock cycle and then 0
    reset <= '1', '0' after T/2;

end arch;

counterEx (device under test code)
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity counterEx is
generic(
    M : natural := 6;
    N : natural := 4 -- N bits are required for M
    );
port(
    clk, reset : in std_logic
);
end entity;

architecture arch of counterEx is
    type stateType_moore is (start_moore, count_moore);
    signal state_moore_reg, state_moore_next : stateType_moore;
    signal count_moore_reg, count_moore_next : unsigned(N-1 downto 0);
begin
    process(clk, reset)
    begin
        if reset = '1' then
            state_moore_reg <= start_moore;
            count_moore_reg <= (others => '0');
        elsif rising_edge(clk) then
            state_moore_reg <= state_moore_next;
            count_moore_reg <= count_moore_next;
        end if;
    end process;

    process(count_moore_reg, state_moore_reg)
    begin
        case state_moore_reg is
            when start_moore =>
                count_moore_next <= (others => '0');
                state_moore_next <= count_moore;
            when count_moore =>
                count_moore_next <= count_moore_reg  + 1;
                if (count_moore_reg  + 1) = M - 1 then
                    state_moore_next <= start_moore;
                else
                    state_moore_next <= count_moore;
                end if;
        end case;
    end process;

    --out_moore <= std_logic_vector(count_moore_reg);
end arch;


texts:
I have a pcb which gets power from a 12v adapter through a DC-jack like this one.

Now that everyhting is working fine, i would like to make a housing for the project.

The housing i have has a front and backplate. In the front i made openings for a lcd screen and some other stuff.

In the back i thought of drilling a hole and pass the connector like this one

through the hole and to the DC-jack. But that won't look that nice i think.
So I looked online for other ways of doing this, and found a panel mount DC power connector.

If i place that connector on the backplate, how could i connect the back side of this connector to the DC-jack on the pcb? Do i need another type of connector? could i use something like a multi plug power cable?

Thanks!


texts: Can a cell phone's IMEI be tracked even if it is switched off?

texts:
I'm doing some research for a project and I have a doubt.

In a cell phone, along with the clock, is a part of the cell radio also on when the phone is switched off? And can a cell phone be tracked via IMEI or network geolocation even if the cell phone is switched off?

Do note, I haven't lost my phone, it's research for a project. Do enlighten.


texts: Linking two 4511's to drive two independent seven digits displays

texts:
I kind of remember to had linked two seven digits displays. using a single 7 bits output with two 4511's linked together, but can't find nothing about that in Internet.

The only way I had found is multiplexing the signal, with 8bits for the leds, plus 1 more bit for each digit.

Another way could be multiplexing a 4511, that would be 4 bits plus 1 more bit for each digit.

¿Any ideas?

PD: The main point is to drive an arbitrary number of Seven digit displays, using the minimal posible outputs (i'm using an arduino behind so complex logic isn't a problem).


texts: How can one use the earth as a second wire?

texts:
I read recently that the earth can be used as a wire to save wiring costs. My understanding of how this works is that a power source, say a battery, separates charge, creating electrons on one side and the absence of electrons on the other, or negative and positive voltage. So a 3V battery would produce -1.5V and 1.5V. Then if we hooked either side of this battery to a ground which has 0V, electrons would flow from the -1.5V to the ground and from the ground to the 1.5V.

However if this were true it seems that if we put a resistor on either side of the battery it would only enjoy half the voltage, i.e 1.5V, that the battery an produce since that is the difference between either side of the battery terminal and ground.

Thus Single Wire Earth Return solutions sacrifice 50% voltage for saving 50% wire cost. However, I cannot find any information stating my analysis is true. Thus I suspect there's something wrong with my reasoning and understanding of electricity.

Thanks for the help!


texts:
I made a part in eagle with vias using a set diameter (smaller then auto), but when I use the part on a board, the vias go back to having a diameter of auto. any ideas?

The left window shows the board view of the vias and the right shows the library view of the same vias.

EDIT: ok I can change the via pad sizes by changing Restring Pad values in Design Rules, but it changes it for all components ignoring what I set up in the library. This causes all pads for all parts to become thin, instead of just for the ones I need.


texts:
Morning!
I have a sensor, output of which is change in Duty Cycle of current. Now, this sensor is to be used with a MCU.
My knowledge of sensors with change in duty cycle as output is limited. So,i have the following question:

Would the change in Duty Cycle of current translate into change in duty cycle of Voltage if a resistor is attached at the output of the sensor?
Given such a case, what's the deciding factor for Sinking output vs Sourcing output?

In this case, its a Wheel Speed Sensor, output of which is change in duty cycle.

Thanks for you consideration!!


texts:
From this App Note:

  Gain adjustment resistors are dimensioned such that each range has an
  amplification of about eight times the previous. The number of
  switches may well be increased and the gain difference decreased,
  however, it is not recommended to have a larger gain difference than
  eight between two subsequent ranges. This because gain differences of
  around ten, and higher, cause the signal to degrade below 1% accuracy
  before it can be further amplified.

I'm planing to have two gains: 1 and 33. However, the difference is larger than the recommended. Is this actually a problem? It says it may cause the signal to degrade. Do you agree?


texts: Balanced Audio Line Driver Off Single Supply

texts:
I am working on a device that needs a balanced audio line driver that can convert an unbalanced signal to balanced and drive a balanced cable run between devices. I am looking at schematics using devices like the THAT1646 and also op-amp circuits that can do this, but the all seem to run off a bipolar supply (+/-15V, +/-12V, +/-9V, +/-5V, etc), whereas my device needs to run off a single ended supply (+9V only).
Does anyone have a circuit they can share to do this on a single ended supply?
Update: Would prefer to avoid using audio transformers. Looking for an IC or op-amp based solution.
Update: Looking for output to be hot, cold, ground (3 wire). This is meant for balanced xlr audio connections.


texts: How do AC/DC Adapters (Wall Wart) prevent AC Noise Coupling to DC?

texts:
I am wondering if AC noise (EMI) gets coupled to the DC side of the AC/DC adapter, what are the design methods used to isolate AC noise getting coupled to DC output in an AC/DC adapter. What are the relevant AC/DC adapter (Wall Wart) specifications that can help identify the quality of AC/DC adapters?
Thanks in advance for your help!


texts:
I am developing a system wich includes a laser-pointer and a digital LDR module. I'd like to switch the lasers with the GPIO pins on the raspberry. But, since I'm used to working with Arduino's and was not aware that the Raspberry has an 3.3V GPIO output, I bought lasers that ideally work with 5V power supply. It is necessary to turn the lasers on and off so the regular 5V output is not an option. So I thought using a transistor as a switch would be the answer.

My question in short: I have been looking at datasheets of different transistors but I'm not able to figure out what the switching voltage is called.

Does anyone know about a transistor type that can switch 5V power with an 3.3V switching voltage?


texts:
Using IR receiver in open collector configuration as shown in the schematic, the maximum detection distance is about 15cm. How can I increase the maximum detection distance? Current IR setup:

Transmitter: IR204C-A-L (http://www.everlight.com/file/ProductFile/IR204C-A.pdf)
Receiver: PT204-6B (http://www.everlight.com/file/ProductFile/PT204-6B.pdf)
The transmitter is always on or off. (No pulse)


texts: Antenna Design in relation to RLC circuit

texts: I am having trouble understanding how antennas can be "represented" as an RLC circuit; how do these two concepts, antenna design and RLC circuits, relate to each other?


texts:
I am using a 2N7000 N Channel FET as a switch similar to the circuit below.  The load is a 12V LED lamp and is connected to 12V not the shown 5V below.
Most of the time the circuit works perfectly turning the lamp on and off as desired. Occasionally the FET becomes damaged and the LED is lit st low brightness all the time reading about 6V at the Drain. When the GPIO turns on the FET will still light at full brightness and when the GPIO turns off or is even disconnected the LED is lit partially.  Replacing the FET fixes the problem.  The Lamp unit is a 22.5mm Techna lamp.  http://www.techna.co.uk/components/com_jshopping/files/data/LEDtec_LED_Indicators_and_Bulbs_Datasheet.pdf

Any suggestions appreciated. I am not sure whats damaging the FET or what could be done to prevent damage.


texts: I need a phone splitter (RJ11) to split 1 signal into 4 or more outputs. That's no problem, those can be bought in any store. But I was wondering if I can use a RJ45 cat6 patch-panel?


texts:
Background
I took my RC quadrotor to a windy field this weekend to fly it around.  After the battery died, I retrieved it and while carrying it back home, I noticed that the wind was spinning the propellers like mad.
Each propeller is attached to little electrical motor which, of course, runs to a circuit board and then on to the lithium battery.  This made me think, "Hmm--it would be cool if I could mount my QR to a stake in the ground and let the wind charge it back up while I eat lunch".  But I wasn't sure if this would fry the battery or anything.
I am not an Electrical Engineer, but have some familiarity with how electricity and circuitry works.
Question
Given a source of mechanical input, can an RC motor charge it's own battery without extra cicuitry involved?
Thanks!


texts: Properly isolating I2C for powered off MCU

texts:
What is the proper way to isolate the I2C lines of two devices where one is powered on and the other can be powered down? I'm not 100% sure if isolation is even necessary, but I suspect it is.
Here is a simplified explanation of what I am doing: I have a MCU and an RTC connected to each other via I2C. The MCU can be powered down while the RTC continues to be powered (the same 5v supply). The MCU and the RTC remain connected via I2C. Here is a rough diagram:

The first thought that came to mind was that I could use a MOSFET on each I2C line so that when the power is cut to the MCU, it severs the connection on SCL/SDA. Then I googled a bit and discovered TCA4311 which looks like it is basically built for this purpose. TCA4311 looks pretty interesting. I think pulling the EN pin to ground on the TCA4311 is all that is needed to sever the I2C lines.
I was hoping to get some feedback since I am a newbie. Does the TCA4311 sound like a good strategy? Or am I way off? Thanks in advance!


texts: Measuring Forward Impedance of a pulsed drive circuit

texts:
Background:

I recently built a thyristor driving circuit to supply a set number of trigger pulses to my thytratron (tetrode configuration). The spec sheet for the thyratron requires that my driving circuit has a "forward impedance of 50-100 ohms."

Question:
While the circuit is supplying the trigger pulses to the thyratron, how can I measure the forward impedance of the thyristor driving circuit (the device that supplies the pulses)?


texts:
Hi guys can someone please help me with the following problem:

I have figured out the Rth by turning the current sources to open and voltage sources to closed loop and i got this to be 50ohm but not sure how to do the Vth.
Thanks


texts:
What is the cheapest, simplest component or device that once receives power will wait approx. 1 second before outputting that power, like a delay relay.
It can be any small DC voltage as it will power a another 240 solid state relay, I just need that one sec delay? Can any single component achieve this?


texts: What is the purpose of a diode and resistor at the gate of a FET in this LED driver circuit?

texts:
I am trying to design a LED driver based the LM3409HV IC.
I am using the reference design from TI as a starting point.
The schematic in the datasheet has a diode (D2) and a resistor (R5) at the gate of the FET that switches current to the LED.

In the BOM, D2 is listed as "no load" and R5 is listed as having a 0 Ohm value.  I have never seen this and can't understand what it means.

I have also seen other designs based on the same IC and the gate is connected straight to the IC, without any diode.

Can anyone explain to me why these components are included in the schematic, and if I can safely leave them out in my design ?


texts: Designing an amplifier to drive a speaker

texts:
I am a beginner in designing this circuit, can someone give me a tip on how can I achieve the following specs?

Variable gain and a maximum gain of 12 dB
Input impedance greater than 30 kΩ
Load impedance of 8-16Ω (buzzer will suffice)
Input signal range 0 – 1 V pk-pk

I will be designing this in TinkerCad.
The components that I  plan to use are:

Operational amplifier (LM 741)
Rotary potentiometer, 100k ohm
Battery 9V (DC power dupply)
Buzzer (to act as the speaker)
0.1μF monolithic capacitor
Resistors – 10 kΩ, 20 kΩ, 30 kΩ, 47 kΩ
Breadboard


texts: Difference between line scan sensor and line scan camera?

texts:
I'm looking to build a multitouch table using line sensor/camera technology. I was hoping someone had already tried such a thing and could recommend the best suited between line scan sensor or line scan camera.

Project sketch http://www.ledsmagazine.com/content/dam/leds/migrated/objects/features/10/9/9/1309ledsweb_design3.gif

Thanks for your help.


texts:
In the past I calibrated the frequency of the High Speed Internal oscillator (HSI) in an STM32F0 device adjusting the value of the register RCC_CR, field HSITRIM. In the ref. manual it says that the calibration step is 40khz, more or less.

Now I'm trying to do the same in an STM32F745, but the ref. manual doesn't say which is the calibration step. At least not in the description of RCC_CR register, and I can't find anywhere where it says this value.

Anybody knows this value?, or better, where is it documented?


texts: Solving Entries in a Four Port Transmission Matrix

texts:
The well-known transmission (ABCD) matrix for a two-port network has entries which can be solved by setting open or short boundary conditions on the opposite terminals.

Mathematically, the two-port network is expressed as

$$
\left|
\begin{array}{c}
V_1 \\
I_1 \\
\end{array}
\right|
 =
\left|
\begin{array}{cc}
A & B \\
C & D \\
\end{array}
\right|
\left|
\begin{array}{c}
V_2 \\
I_2 \\
\end{array}
\right|
$$

And the entries are solved as
$$
A = \left. \frac{V_1}{V_2}\right|_{I_2 = 0} \ \ \ \
B = \left. \frac{V_1}{I_2}\right|_{V_2 = 0} \ \ \ \ , etc.
$$

However, when we extend this concept to a four-port network, in which there is one input port and three output ports, such that

$$
\left|
\begin{array}{c}
V_1 \\
I_1 \\
\end{array}
\right|
 =
\left|
\begin{array}{ccc}
T_{11} & T_{12} & T_{13} & T_{14} & T_{14} & T_{15} \\
T_{21} & T_{22} & T_{23} & T_{24} & T_{24} & T_{25} \\
\end{array}
\right|
\left|
\begin{array}{c}
V_2 \\
I_2 \\
V_3 \\
I_3 \\
V_4 \\
I_4 \\
\end{array}
\right|
$$

It no longer becomes straight forward to solve for the entries, as we will require that pairs of voltages and currents are equal to zero simultaneously.

How can the transmission matrix of a four-port network be solved?


texts: Retriggering 3V PIR sensor with 555 timer circuit and LEDS

texts:
Hi y'all

I'm putting together a PIR sensor circuit that will trigger a 555 timer in monostable and run a set of LEDS for about 5 sec all on a 3v cr2032 button cell battery and than reset until next motion is detected.

The PIR module I have is a 8845 module from TI that is specifically built for low voltage applications down to 1.8 V.

The timer is the TI LMC555 good down to 1.8 V as well.

Im trying to do it all on one button cell but have run into a re triggering issue where the PIR module re fires continuously one 5 sec cycle after another. I can make out a brief glimmer in between each cycle.

The timer and pir module both act great when not connected to one another.

When PIR Module has its own supply(another 3v) with common ground and the 555 and LEDS have the other 3V supply the system works good.

When the PIR module and 555 share positive supply and the LEDs has its own supply it has the same triggering problem.

This makes me think I have a problem with the way my 555 timer is setup. I have experimented what seems like endlessly and just can't seem to get it to work and like I said things work great separately until the 555 and PIR share the same power supply.

Any solutions?

S1 = PIR Module

EDIT: When I run the circuit with two 3V in series I still get the same problem so don't think it is a low voltage problem.


texts: Light Sensitivity Indicator (using transistor, LEDs, LDR)

texts:
I have;

1) 9 V dc source

2) two LEDs (red and green)

3) LDR

4) few resistors (kilo ohm)

5) npn transistor

I need to build a circuit such that the red LED lights up only at night (0 light intensity) and the green LED lights up only during the day (maximum light intensity).

How can I do this? I found out how to achieve the results for only one LED. The follwing is a rough sketch for the task at hand.

thank you


texts: LM358P output saturation around 6.05V (root cause turned out to be related to Arduino protection diodes)

texts:
For a constant current drain using a PWM input I am using the following setup:

simulate this circuit – Schematic created using CircuitLab

For small currents it seems to work as expected - the op-amp producing a voltage to the MOSFET which causes the current flow over the battery be such that the voltage drop over the 3.3 Ohm sense resistor becomes exactly the configured voltage, as expected.

But there must be something I have missed, because the current I can get maxes out much earlier than expected. This happens around 150 mA corresponding to an input voltage to the op-amps positive input (via PWM) of around 0.45V. At this point, the output from the opamp to the MOSFET seems to saturate around 6.05V. The problem is that further increases in the op-amps positive input has no effect. The opamp keeps producing a 6.05V output even though there is a large difference between the positive and negative input. I can see the opamp is getting, say, 0.8V at the positive input and is only seeing 0.45V at the negative input, yet it refuses to output more than 6.05-6.1V.

The Vcc to the op-amp is 12V so there should be plenty of headroom for it to output higher voltages even though it isnt a rail-to-rail opamp. I have looked in the datasheet but I cant seem to find a limitation that would explain this behavior, so I hope someone can explain what I am missing.

Update! I am a bit closer to resolving the mystery. I had a wire (not on the drawing) going from the output of the op-amp and to an analog input on the Arduino. I thought the analog inputs were high impedance so it wouldnt affect anything. But with that wire there I am seeing the 6V saturation (as measured by a multimeter, the Arduino only measures to 5V), but if I disconnect it everything works. Is this some type of oscillation involving the Arduino? Or is the Arduino draining the voltage?

NOTE! The root cause of this problem turned out to be different. I had connected a measuring wire from the op-amp output to the Arduinos analog input. My thinking was that it was high impedance and hence wouldnt affect outcome. I had noticed the measurements topping out after 5V but thought that was simply due to it being unable to report more than value 1023 and that it wouldnt actually affect the behavior of the circuit. This assumption was wrong; due to a protection diode in the Arduino inputs, the extra voltage was drained (the LM358P has a short-circuit voltage of 40-50 mA) causing the drop in the measured voltage (even with a multimeter) at the op-amp output. But the real culprit was the protection diode in the Arduino. Removing this measurement wire resolved the problem. I am leaving the original problem description in place so other people can find this report in case they encounter similar issues.


texts: Could sawtooth waveform be optimal for transformer input?

texts:
All the transformer theory I have reviewed uses sinusoidal waveforms, and concludes that a true sinusoidal input is optimal.  But I'm wondering whether a sawtooth waveform would actually be optimal in practice?

Theory depends frequently on the differentiability of the waveform, so it's "convenient" to neglect sawtooths because they are not differentiable when voltage changes direction.  However, I assume that:

It would be relatively easy in practice to produce an input from a DC power source that is a clean sawtooth.
A transformer would not suffer from the "harmonic noise" that might be suggested by an abstract attempt to approximate a sawtooth as a sum of higher-frequency sine curves.

On the other hand, one reason I imagine the sawtooth might not be optimal is the magnetic hysteresis of transformer cores: If that's large enough then the slow reversal of a sine wave could in fact optimize the transmission of power.


texts: Limiting discharge current of super capacitor

texts:
I'm looking to use super capacitors to heat up a short length of NiChrome wire. My caps are capable of supplying far more current than needed to get the wire up to temperature (about 6 amps). What I need then is a constant current supply that'll operate over a wide input voltage so I can get as much power out of the capacitors as possible. Most solutions I've found, either implemented in discrete components or integrated as a feature in a load switch cut out near 1.5v or more.

This seems like a simple enough issue - am I missing a very obvious circuit?


texts:
I'm simulating a single microstrip half-wave resonator (1.8 GHz) in Sonnet and using ADS LineCalc tool for calculating the microstrip length but I'm getting a wrong number.

Substrate parameters (LineCalc):

Er = 10
Mur = 1
H = 0.4 mm
Hu = 3.9e+34 mm
T = 0.001 mm
Cond = 5.8e7
TanD = 0.002

With Z0 = 50 and E_Eff = 180º I get: W = 0.379400 mm , L = 32.239500 mm.

Substrate parameters (Sonnet)

Bottom dielectric layer

Thickness = 0.4 mm
Erel = 10
Dielectric Loss Tan = 0.002
Diel Cond = 0 S/m
Mrel = 1
Mag Loss Tan = 0

Conductor(copper)

Thickness = 0.001 mm
Conductivity 58000000.0 S/m
Current Ratio = 0.0

But I've found empirically that the length should be approximately 30.4 mm instead:

Why is this happening?


texts:
I'm using circuit in the picture as a replacement for a mechanical relay running a 40 watt 220 volt water pump.

The problem is the circuit seems to be correct, but it doesn't work and I'm getting a weird result on the multimeter.

When monitoring the AC output of the circuit with a multimeter, it shows 220 volts when the logic input of the moc3042m is low. Also, this voltage doesn't turn on the pump. When changing logic input to high (5 V), the output doesn't change.

The actual pump is connected to the J4 terminal.
The Pump label in the picture is for the logic input.

If you see any problem in the schematic, please explain it.


texts: How can firmware loaded into a PIC16F87XA detect if Program Memory Code Protection is enabled?

texts:
The PIC's (PIC16F87XA) firmware can be programmed by an external programmer and have the Flash Program Memory Code Protection bit set or cleared.

How can the firmware check that the protection is enabled?

The configuration word (address 2007h) has a Flash Program Memory Code Protection bit (bit 13).

CP: Flash Program Memory Code Protection bit
1 = Code protection off
0 = All program memory code-protected

The configuration word appears to be inaccessible for writing by the firmware per PIC16F87XA 14.1 Configuration Bits.

  It is important to note that address 2007h is beyond the
  user program memory space which can be accessed
  only during programming.

As there is no need for the firmware to write the configuration word, loss of write access is not important.

The configuration word also appears to not have read access per the same 14.1.

Is there any way for the firmware to read the Flash Program Memory Code Protection bit, a copy of it, checksum/parity the firmware including the configuration word, somehow assess  or test if the firmware is protected?

One can re-connect an external programmer and attempt to read the firmware and either succeed or fail as a test.  Yet that is not the firmware itself doing this assessment.

I suspect there is no published solution - I hope I am wrong.


texts: Modelling a temperature measurement system

texts:
The accuracy of a measurement system can be significantly reduced by loading effects in the system. A thermocouple is used together with an indicator to measure temperatures. The thermocouple has a sensitivity of 50µV/°C and an output resistance of 500Ω. The indicator gives a measured temperature of \$T_M = 20V_{Load} K\$ and has an input resistance of 10 kΩ.

How do you sketch this system using Thevenin equivalent circuits? (I'm thinking something like this, but I'm not sure.)

simulate this circuit – Schematic created using CircuitLab

How do you determine the accuracy of this measurement system? I'm thinking I need to calculate \${T_M}/T\$, but I don't know how to determine the voltage across the load (\$V_{Load}\$).


texts:
I am thinking how it is possible to build C-meter which would have show some 8-9 digits (absolute accuracy is not that strict, only relative accuracy matters), over 0.1-10s measurement period.

Capacitor would be somewhere in 5-100pF range.

I guess, charging it through some large resistor, and measuring voltage via 24-bit ADC would not cut it.

Is that possible to make LC-generator somewhere at 10-100Mhz range, and then directly count each oscilation => calculate capacitance?

Or probably there are some better ways for precise capacitance measurement?

Update: 9 digits means that I need to see difference between 50.000000 and 50.0000001 pF. Knowing absolute value (50.0000001 pF) is not important, I just need to see that capacitance increased or decreased by .0000001 pF (or .0000237 pF, etc)


texts: When is an analog input amplifier needed?

texts: I'm reading in values that are coming within the ADC's Vref range... 2.5V. Why do all of the datasheets recommend driver amplifiers and what is the purpose of this if the voltage is in range? Is this only applicable if the input signal is really small and needs to be amplified to the ADC range?


texts: Absolute encoder or Incremental encoder?

texts: I'm planning on making a robot whose exact location can be tracked, which would be appropriate to  use-- an absolute encoder or an incremental encoder and convert the number of rotations to distance traveled?


texts: I have 2 charged LiFePO4, which should be between 2.5v and 3.6v both reading 6v. I think my meter is broken, but I just want to check: Is that possible?


texts: Natural Response of Parallel RLC Circuit

texts:
In the circuit shown below, I need to calculate the current through the capacitor, which is initially charged. I'm thinking I have to calculate the natural response of the circuit, but am unsure of how to do so. I can calculate the impedance and find the pole, but then what?

simulate this circuit – Schematic created using CircuitLab


texts: How do bypass capacitors recharge in high-frequency if the PCB can't deliver high-frequency currents?

texts:
I understand the whole theory behind bypass capacitors, how they are necessary to deliver high-frequency currents to the IC, as the PCB in general has high-inductance, thus high-impedance in high-frequencies. This graph shows the PCB impedance on the frequency-domain, showing how only the bypass capacitors can deliver the MHz currents the IC needs.

I understand this all on the frequency-domain, but not so much on the time-domain.

If an IC has a high-frequency I/O operation, switching from 5V to 0V, this current will come from the bypass capacitor, but as soon as the bypass capacitor starts to deplete, the circuit will try to recharge it.

The problem is, since all other parts of the circuit (bulk capacitors, VRM, etc) can't respond to such a higher-frequency, then how will the capacitors recharge at all?

As soon as they start to recharge, the IC will try to deplete them again and again.

An analogy I can think of is as if the bypass capacitors are a bucket full of water, the IC is a drain pipe connected to the bucket and the rest of the circuit (bulk capacitors, VRM and etc.) are a dripping faucet, trying to fill the bucket.

The dripping faucet will never be able to keep the bucket filled, as it can't fill the bucket as fast as the drain pipe is pulling water from it.


texts: Can someone help me with this power amplifier problem?

texts:
Wire the circuit shown:

R1 = 68KΩ
R2 = 10KΩ
R3 = 10KΩ
R4 = 200Ω ( two 100Ω in series )
R5 = 2.2kΩ
C1 = 0.1 µF
C2 = 0.1 µF
Q1 = 2N3904

Set the sig. Gen to 50mv RMS.  With frequency equal to 10KHz.
Record vo for the frequencies listed and calculate Av for each frequency:

f:
10kHz,
25kHz,
50kHz,
100kHz,
500kHz,
1MHz,
2MHz,
3MHz

This is what I got when I attempted to do the problem. However, I don't think it is correct because frequency does not affect my answers. Can someone tell me if my answers should be different and if frequency affects voltage gain?

vo
3.34m
3.35m
3.37m
3.45m
5.39m
9.02m
16.52m
23.42m

f
10kHz
25kHz
50kHz
100kHz
500kHz
1MHz
2MHz
3MHz

Av
0.066
0.067
0.067
0.069
0.107
0.180
0.330
0.468

Okay, so I did my circuit all over again, but I am even more confused now because I feel like my wiring is okay. However, this time, the output voltage is not changing at all when I increase the frequency. It stays at a constant 6.72V. I don't know what I'm doing wrong :(


texts: What is the bold part on monitor and some charger cables

texts:
On many monitor or chargers, there is a bold part:

First of all, what is it called?

Then, what does it do?

Does a cable without this part have any advantages as we see nowadays many chargers don't have this part anymore?


texts: What is the correct transfer function of a feedback loop if the summing amplifier has different input resistors?

texts:
Suppose I have a circuit below:

simulate this circuit – Schematic created using CircuitLab

I know the the transfer function of a negative feedback loop is:

$$H(s)=\frac{H_1(s)}{1+H_1(s)H_2(s)}$$

But this applies only if all resistors are equal in the summing amplifier and the input voltage is inverted.  The equation for the summing amplifier is:

$$V_3(s) = \frac{-R_3}{R_1} V_{in}(s) + \frac{-R_3}{R_2} V_2(s)$$

Where \$V_3(s)\$ is the resulting voltage of the summing amplifier, based on its two inputs, \$V_{in}(s)\$ and \$V_2(s)\$.

My question is how to correctly put both formulas together to get the overall transfer function of the above circuit?


texts: how big are the FETs used to drive Tesla cars

texts: So I've been looking into bldc  and motor drivers lately (ESCs). Generally larger the BLDC motor the larger the FETs need to be in order to suppluly needed current. One can do this either by using a higher powered FET or stacking them up (quite literally). Tesla cars use motors that are quite large. How large do the FETs need to be to run them?


texts:
I'm trying to get a home made LED matrix to show a rainbow pattern coming from the bottom up but it's playing this bizarre, dancing pattern.  The matrix is in series, with 4X WS2811 addressable LED strips and is 600 LEDs total.  12 horizontal, 51 vertical.  The controller is a K1000C that comes with software called LED Edit.
Each strip is powered with a 12v/5A adapter with all grounds going back to the controller.  Black wire is ground, red is power and yellow is data.
I realize this deals with software and hardware, but to sum it up I have tried many different wiring setups in the program, but this happens no matter where the data input is unless the pattern is going from left to right.  So the rainbow pattern works left to right and vice versa.  I should also mention it plays solid colours as well.
My question is, regardless of software or controller issues, did I do something wrong with the wiring?  In case it's not easily visible from the photos, the data input is the bottom right corner and the matrix goes in a zig zag pattern following the arrows on the LED strips.
Thanks


texts: STM32 Bootloader config. and datasheet discrepency

texts:
I have 4 quick questions regarding the bootloader/programming the STM32L0 chip series.

Q1&2

I'm considering a STM32 project coming from ATMEGA chips. From my understanding, the chips come with a bootloader pre-loaded, and you can then either program them through the SWD/JTAG or UART/SPI interfaces etc, if enabled by the bootloader (Q1 - is this correct?).

If programming through SWD/JTAG, is it possible to change the bootloader to set pin functions, or is this only possible if programming through UART, etc? (Q2 - can you set bootloader settings through SWD?).

Q3

I considered the STM32L011E4 chip, and there seems to be a disparity between the USART1 pins as defined on the default bootloader configuration document, and in the datasheet where it defines the functions of the pins. It seems that the bootloader states that it comes with USART1 on pins PA9 and PA10, however pins PA9 and 10 on the datasheet only have USART2 functionality. It looks like they've got the pins for USART1 and USART2 mixed up on the devices bootloader. (Q3 - How am I reading this wrong, as I can't imagine there's a typo here?)

[

Q4

Regarding UART1 and UART2 for flash programming on this chip: from the following image, am I correct in thinking that only the USART2 port can be used to program the flash memory? The UART1 is a low power variant so that could explain this. (I don't know whether to read it as "there are 2 UARTs that can flash the chip" or "use UART2 to flash the chip"


texts: Can someone please tell me why I am getting E for an output?


texts: Which diode configuration do I need for this solid state relay?

texts:
I want to add snubber or supression protection diodes for a solid state relay. Here is the diagram without the diodes:

And this is the SSR I'm going to use:
http://uk.rs-online.com/web/p/solid-state-relays/0346895/

What kind of diodes I need and where to place them? The load is a speed controller together with a single phase inductive fan-motor and will not draw more than 1A in steady state.


texts: eeschema: prevent Value, Reference from moving relative to symbol library?

texts:
When I create a symbol in the symbol editor and then drop it into a schematic, many of the fields (Value, custom fields) are automatically moved outside the bounding box of graphical objects.

In the image above, I have an emergency off button. I've placed the value (EMO) and custom PN field (A02ESI...) inside the "mushroom" in the symbol editor. When I drop this part into a schematic, ALL of my fields are moved. ??? Excuse me? I went through all of the trouble to make a good looking part and then I have to go an manually move all of the fields. Is there any way to better control this behavior?


texts: Back EMF protection of a bi-directional inductive load

texts:
I have been researching this subject for some time now and I found three ways to deal with this issue but I can't make up my mind on which one is the best for my application.
I have a high torque 12V 5A DC motor that runs bi-directionally using an H-bridge.  After turning the motor off, it still moves for at least 3 seconds which results in inaccuracies (high accuracy and instant response are highly crucial to my project.) I was thinking of putting a mechanical break in my system to stop it from moving but that's not quite possible, so I want to use a back EMF suppression system that can help with this issue and also protect my component and circuits. The three possible solutions that I found online:

Ising MOV across motors leads (their life expectancy and reliability are questionable based on what I found online)

Using a bridge rectifier and connect motor leads to the AC input and the other two pins to the ground and 12V
Using two Zener diodes with their anodes connected to each other

While researching the second solution, I came across something about noise being transmitted into my power and ground rail which I know very little about but it does seem like something I need to avoid.
Any feedback or suggestion on which of the three I should use or any other solution would be highly appreciated.


texts: Can somebody please explain how can I convert from Moore FSM to Mealy FSM and vice versa?


texts: Is it safe to have common grounds in this circuit?

texts:
For the sake of simplicity, I draw the illustration above.
System A is a device which is fed by a power supply 110V AC, and has sinusoid output with varying amplitude from 1V to 7V peak to peak.

Sytem B will be comparator which will convert these sinusoids to pulses and it is fed by another 12V power supply.

My questions are the following:

Is it safe to make all grounds common?

Do I need a shunt resistor between the device output and the comprator? IF so, what should be the value of it? 100k is ok?

edit: GND of 110V AC is isolated from GND of DEVICE output.


texts:
I am trying to build a T flip-flop from a D flip-flop. The D flip-flop looks like this

and the simulated waveform shows that it works.(when there is a rising edge D will be passed to Q)

So I started building a T flip-flop by connecting Qnot to D (I am expecting every clock rising edge Q will be toggled because Qnot is passed to Q)

but the simulated waveform looks like this

Q will oscillate when CLK is low. One oscillation period is around couple ns.
I played with different Clear and Preset signals but it still happens.

If anyone can point out my errors.
Thanks.


texts:
I am looking at migrating from a MCU of 200MHz to one of a lower frequency/clock speed. Now, I want to justify my action or rather do a feasability study. To explain that my descision to migrate to a slower MCU is justified and thereby helping reduce price and also ,in all likelyhood reduce EMI emmision and power consumption.

How can I go about such a study. My initial MCU(200MHz) is the LPC4337 from NXP. It is a dual M0/M4 core which runs an FFT.
A straightforward method would be to migrate/write the same code for a lower speed MCU and then see/compare the executioon time for both controllers. But that seems very basic. Is there any other parameters on which I can base such a study on ?

The MCU I would like to migrate to is the RPC564A80 from ST Micro. probably it could be costly, but I am merely interested in the processing power. Ofcourse , on a straight foirward glance, the LPC can run at a higher speed. But probably for my code such a speed might be an overkill. What is the test pattern I should follow to justify(from a frequency point,power and other factors are secondary)


texts:
I am trying to design a simple RF signal buffer using a MPSH10 BJT transistor. This is to operate at ~90MHZ and simply buffer an input RF signal to lower the out impedance of my oscillator which feeds it.

I am using LT Spice to simulate this circuit.

I have the transistor in a common collector setup biased midrail to a an 10mA quiescent current. The emitter resistor is 500 ohms. I AC couple a 3V pk-pk 90MHZ signal in from a source impedance of ~ 20k ohms. What I would expect to see is that same voltage signal on the emitter. Instead I see the expected 5 volts DC but only a very small ~100mv signal imposed on the output. When I look at the base current it is huge compared to the emitter current. It looks like the signal is being shunted through the BE and BC parasitic capacitance instead of through the BE junction.

How do RF amplifiers deal with these parasitic capacitance as even at the low 1pf BE capacitance of this transistor a 100MHZ signal sees a 1600 ohm shunt to the emitter. Would this not always form a huge voltage divider when trying to amplifer signals coming from a high impedence>

I have been reading "Radio Frequency Design" by Wes Hayward but have not seen any references to these parasitic causing such huge dividers. MOSFET's always have this capacitance so I don't see how using them makes it better.

Any guidance would be appreciated as I must be missing something fundamental. I have not taken a solid state devices course yet so my understanding of active devices is only from what I have learned from books and the internet.

Thank you


texts: TinyMesh device power consumption too high while in sleep mode

texts: I have a TinyMesh RC device (RC1181) configured as an End-Device, connected to an STM8S MCU. The datasheet says that if the device is configured in End-Device mode it should only drain 0.5 uA while mine takes around 8.7 mA plus 0.5 mA which are from the MCU. The MCU is also set to sleep and only wake up once every 90 seconds. For the TinyMesh device I have tried turning off all cofigurations which might drain power and none help. If someone can tell me the solution or maybe just point me in the right direction to solving it i'll be grateful. Thanks!


texts: Differences between a FET multiplexer and regular digital multiplexer?

texts:
I need a MUX 8-1 with a very fast propagation delay; <10ns. I was searching Digikey and found a category of digital muxes called FET multiplexers, and their propagation delay is insanely fast < 0.25ns, which seems too good to be true.

What are the advantages and disadvantages between using a FET multiplexer such as the SN74CBT3251 and a regular digital one such as the CD74AC251 other than propagation delay time differences?

A FET multiplexer seems like an analog one, but it's listed under digital on Digikey...


texts:
I am building a motor controller board (Based on an STM32) driving a motor with a switching frequency of 70KHz.
That same board (master) communicates with a sensor (Slave) on another board with short 20cm wires at a frequency of 1.5MHz.
Everything looks pretty clean (and working) when the motor idles.
However when the motor is controlled, the switching noise from the mosfets are triggering weird patterns on the MOSI and CLK lines.
On the oscilloscopes, while the switching noise is there all on 4 lines, only CLK/MOSI are reacting weirdly. CS and MISO both have pull up/down (respectively) which probably explains why they're not affected. During the actual data transmission (CLK/MOSI doing their thing) neither seems affected by the issue that much. As a matter of fact I have decoded a bunch of frames ignoring everything before a clean clock signal and everything is correct on MOSI - MISO is obviously junk due to the sensor seeing garbage in.
I have never encountered a scenario where pull up/down on CLK/MOSI were implemented but I did try to set a pull down on both CLK and MOSI with no visible improvement.
I am driving the NCS line through a GPIO (not using a hardware NSS) and it takes a few microseconds after NCS is brought low and CLK starts the clock. During that time, the erratic behavior of CLK and MOSI is causing the sensor to try to interpret an incoming command and obviously fails.
I have tried to focus on cleaning the switching noise as much as possible, I can continue to try to improve this but I suspect it will never perfect. So I am trying if instead I should try to focus more on understanding what's going on CLK/MOSI.
Has anyone ever seen anything like this?
Thanks
edit: Hardware pull downs on CLK/MOSI helps getting those ripple down faster but it still doesn't prevent these jumps from triggering the sensor into trying to interpret the incoming data.
-1st screenshot is motor idle
-2nd screenshot is motor active


texts: TMS320F280049C: Unwanted pulse on GPIO during power on/off

texts:
I'm using the TI TMS320F280049C microcontroller.

While testing its GPIO behavior during power on/off, I found a high to low transition on GPIO pin, on every power on/off.

I'm checking the waveform on the GPIO pin of the microcontroller itself.

I have used the same code provided by TI for GPIO initialization (C2000 examples)

// Initialization code as follows
GpioCtrlRegs.GPAPUD.bit.GPIO3 = 0;   // Enable pull-up on GPIO3
GpioDataRegs.GPASET.bit.GPIO3 = 1;   // Load output Latch
GpioCtrlRegs.GPAMUX1.bit.GPIO3 = 0;  // GPIO3 = GPIO3
GpioCtrlRegs.GPADIR.bit.GPIO3 = 1;   // GPIO3 = output

Waveform during power on/off:


texts: Measuring voltage/current digitally on two separate power supply rails

texts:
I'm designing a dual-rail DC power supply, with the two rails completely separate (except for sharing a dual-secondary transformer). The main design should work as-is, only by adding a fuse + mains switch, but I want to add a voltmeter and ammeter to each output (and preferably a voltmeter before the voltage regulators, too).
The problem here is that the "meters" will be a microcontroller's ADC inputs (or external ADCs), and the microcontroller only shares ground with ONE of the two rails. I need some way to safely connect the µC to both rails, perhaps opto-isolation or somesuch, while keeping the rails separate.

Don't look too closely at the exact schematic (below), though, as it isn't 100% correct: I couldn't find a dual-secondary transformer in MultiSim; the LM317 package is incorrect and the µC will be AVR-based.
This is just to give the general picture.

Full size image

Now, the problem: I want to measure output voltage and output current for both rails, from the shared microcontroller, which is powered by one of the two rails.
It would also be great to have a voltage probe just before the LM317s as well; that way, I can both monitor the input voltage, and also calculate and display the approximate LM317 heat dissipation.

The voltage measurement would be easy, if it weren't for the floating rails... A voltage divider, perhaps followed by an opamp voltage follower to take care of any impedance troubles, connected to an analog input on the  µC.

As for current, I'm not quite sure. An opamp would surely be needed to amplify the tiny voltage across the 68 mOhm shunts (68 µV - 102 mV for 1 mA - 1.5 A), but I'm not sure how to wire it up, since neither side of the shunt is ground. There's also the issue of offset voltage, not to mention the galvanic isolation issue.

Priorities are simplicity and cost, though needless to say some accuracy is also needed. It would be great to have 10 mV / 1 mA resolution, though something like 25 mV / 5 mA might be OK too.

Any advice on how to solve this? I'm unsure about much of it. I've considered external ADCs (shunt -> opamp -> ADC -> optoisolator -> µC), or shunt -> opamp -> optoisolator -> µC, but that doesn't appear to be a good idea since the optoisolator might muck with the analog reading. Frankly, I don't quite know what I'm doing (though I do feel safe about my knowledge about the PSU in itself), but I'm certainly willing to read up a little to learn.

EDIT: related to a previous question "Dual polarity vs dual rail power supply"


texts: Are there any dumb USB-C to USB-C cables available? Simple 24 to 24 pin cable

texts:
I made the mistake of thinking that the cables were dumb by default and the "smart" electronics were on the boards the cables plugged into.

I designed non USB compliant boards that used USB-C connectors and now my project doesn't work because all cables I find already have some circuitry inside.

Do simple 24 to 24 pin USB connector cables exist and how do I search for them?


texts:
cables that connect the two computer system carry ca current signal or dc current signal?

when two computer communicating(sending and receiving) with each other through the twisted cable, then the current in the wire is ac or dc?


texts: i2cget works, but i2cdetect does not show the device


texts:
I have come across the following site: Passive Band Pass Filter - Electronics Tutorials.

It is a tutorial about band passive filter circuits. The following formular is given with:

$$ C=\frac{1}{2 \pi f_c R} $$

\$C\$ is the capacitor, \$R\$ the resistor and \$f\$ the frequency.

So if I want to calculate the needed value for my capacitor I just need to fill in. If \$f\$ is in the kHz range I get a value for my capacitor with at least \$10^{-9}F\$.
But what if I want to just allow e.g. 400MHz-450MHz, then I get an extremly small value for my capacitor, even with resistors of low resistance. Should the capacitor then just be leaved? Or is this the wrong way to get a band pass filter in the MHz band?


texts: How can I convert very high, fluctuating, AC voltage to 240VAC at 50Hz?

texts:
I'm about to finish a generator-alternator setup which will generate 9-phase AC electricity at (as yet unknown) very high voltage, most likely around 4800V. I'm not sure what the frequency will be, as I'm going by trial and error in areas, but I think much higher than the 50Hz required for UK mains electricity.

I need the final result to be a smooth-enough flow of AC electricity at 240V with a frequency of 50Hz. At the moment, I think the below would do it but I was wondering if there are any simpler and/or more energy-efficient ways of doing this:

The alternator produces (for example) 4800V at a frequency much higher than 50Hz (I'm estimating 400Hz based on the likely RPM of the alternator). It is very likely that both the voltage and the frequency will fluctuate significantly.
This is passed through a number of step-down iron-core transformers so that the voltage is now fluctuating around 240V AC.
A voltage regulator (most likely from a car's alternator) then smooths out the voltage to as close to 240V AC as possible.
A silicon-controlled rectifier (thyristor) converts the flow to DC, preferably at the same voltage.
A capacitor (or more than one if required) is connected to smooth out the DC signal.
A 6, 12 or 18-pulse inverter then converts the DC signal back to AC to be fed into the grid.
Another voltage regulator and/or transformer could be fitted just before the grid tie-in point, if the voltage were not yet stable enough at 240V.

I'm very much learning as I go and may have misunderstood a number of points, but from the research I've done, I'm left with the following questions:

I presume that by generating 9-phase AC electricity, I am still able to 'merge' the phases such that there will be 3 bigger phases? UK mains electricity is naturally 3-phase and, as such, that's what will need to be fed into the grid.
Is a voltage regulator (I've found a supplier of 250V ones) suited for what I'm intending to use it for?
How can I tell what the frequency of the AC current will be once it's inverted back from DC?
Are there any steps that could or should be altered to make the whole process more efficient?

Much thanks for any and all advice!

Cheers, Chris


texts: Is reactive power periodic in nature? What is the exact difference between active power, average power, and real power?

texts:
Consider an RC circuit which is supplied by a sine source
$$v(t)=V_m\cdot \sin(\omega t)$$
The current through the circuit will be
$$i(t)=I_m\cdot \sin(\omega t+\phi) \\
\phi=\arctan \left(\dfrac{1}{\omega RC} \right)$$
The instantaneous power equation is
$$p(t)=V_m\cdot I_m\cdot \sin(\omega t)\cdot\sin(\omega t+\phi)$$

Clearly from this image we can see that the power equation has some frequency component also.
The average of this instantaneous equation over one cycle will give us average power.
The real power is going to be the first term which, however, has a zero and a high frequency component in it and the reactive power however has a high frequency component only (by high frequency I mean the value of frequency is higher (i.e.) twice the supply frequency.)
Are real power, active power and average power the one and the same same?
If they are not, then we don't see text books mentioning this high frequency component in the real power/active power/reactive power.
They directly give the average value as zero frequency component. This reactive power that is mentioned here always has only a high frequency component here. In the case of power systems, if we are speaking about reactive power are we just speaking about the peak reactive load demands and quantifying it for load flows and in case of real power in power system will we be speaking only about average value of real power load demands and proceeding with the load flow?
I lose clarity here and I am sure that I am wrong at some basic point. I would be grateful if someone is able to clarify this.


texts: Is it safe to design board at fab houses minimum trace width?

texts:
I am working on my first board to have professionally fabricated. Right now I am planning on using seeed studio mainly because they are the cheapest I have found. 10 5cmx5cm boards for $10 is pretty awesome. Their site says they can handle 6 mil traces with 6 mil spacing. I have routed my board to those specifications, and it passes their drc file. I am still a bit worried that this could lead to errors in manufacturing, or will be easy for me to screw up when soldering. It is mostly surface mount components of pretty generous pitches. SOIC and 0805 parts mostly, with a few through hole headers.

Is there any danger to making smaller traces? Is there anything to be gained by making them thicker? I am not expecting current over 100mA or frequencies over 1MHz. I am also planning on paying for 100% etest, so I don't think I need to worry about the fab house delivering non-working boards.

Information:

Seeed Studios

Seeed's Fusion PCB Service

Seeed authorised user review and guide to using their Fusion service


texts: I was trying to measure the internal resistance of an LDO that will produce 2.85V. I used a Digital multimeter to do this, but I got a resistance of 810 Ohm and the LDO can support upto 450 mA. Will the internal resistance of the LDO can be that high?


texts:
I’m building a homemade small magnetic transmitting loop antenna that I want to ultimately operate at up to 1500 watts over the HF ham radio bands. One of the challenges with these antennas is the high voltages present at the variable tuning capacitor, which range from thousands of volts at 100W to tens of thousands (up to 20kV) at 2KW and vary based on frequency, which can range from 1 MHz to 30 MHz.

The prevailing designs use vacuum variable caps, which are expensive and air variable caps, which are quite large. I need a variable capacitor capable of 10 pF to around 650 pF that can handle 25 kV or more. It must be tunable via a stepper motor to quickly adjust the antenna to resonance.

My design consists of 5 copper plates of at least 16 sq in (4” x 4”) spaced 0.06” apart, using 24 gauge (0.025”) copper sheet with oversized, 0.03” thick plastic sheet (PET) as dielectric, producing variable capacitor with up to 669 pF capacitance at 22.5 kV dielectric strength.  The design assumes oversized plastic sheets are glued to each copper plate after plates are attached to copper plate base via brazing and solder.  The plastic sheets act as insulators and capacitor dielectric material between each copper plate electrode element.  PET should have dielectric constant between 2.8 and 3.4 from sources I have found.

The idea is to then use a 3D printer style stepper motor with a slide screw linear actuator or equivalent to adjust the capacitor plates in and out. The assumption is that the plastic (PET) insulated copper plates can rub closely against one another and should pose no real issue. I believe this design will be smaller and less expensive than the alternatives and provide a much higher voltage rating vs vacuum or air variable caps in the same or less space.

Will this design meet the requirements as expected? Am I on a good track here?


texts:
If someone could push me in a decent / reasonable direction it would be much appreciated! I do a HNC part time on electrical / electronic engineering and with how busy I have been at work I feel I have missed / forgot crucial parts of this!

In my working:
f0 = 50
V1 = 350
V3 = 70
03 = 30
R = 15
L = 250mH


texts: Charging li-ion cell using constant-voltage only

texts:
Introduction

Various resources [1] [2] state that the optimal method of charging a li-ion cell -- such as one found in a mobile phone -- is to charge at a constant current (usually <1C) until a certain voltage threshold is reached, then switch to charging at a constant voltage until the charging current drops to about 0.1C, at which point the battery is fully charged.

The exact target voltage differs slightly for different battery chemistries, but according to National Semiconductor (see figure 5) it's common to switch from CC to CV mode at 4.1V with the CC target voltage being 4.2V.

Many manufacturers sell inexpensive charge-controller ICs that take the guesswork out of charging li-ion cells, but they're not as widely available to hobbyists as, say, an LM317 voltage regulator. Additionally, they tend to be small, SMT devices that are not breadboard friendly.

Question

Although both constant-current and constant-voltage charger circuits can be built with an LM317, a current-limited, constant-voltage circuit is particularly simple to build.

Is there a downside to charging at a constant voltage (say 4.2V) so long as the maximum current is limited to a reasonable value for the cell (say 0.5C)?

(In this context, consider "downside" to be more along the lines of "cell doesn't fully charge with CV-only, is damaged, explodes, steals your lunch money, burns house down, etc." and less along the lines of "CV-only charging takes longer", though that is also useful information to know.)

Background

I ask because the internal charger circuit in my mobile phone died unexpectedly and, while waiting for a replacement phone, I constructed a CC-CV charger using an LM317 and successfully charged the battery. This was a bit messier than expected, and I was curious if a simple current-limited constant voltage circuit would also be suitable for occasional use.

Edits

Possible duplicate of this question, which was answered with "If you really want to charge battery from time to time - charging with resistor and constant voltage 4.2V or less will work and battery will not blow up if you choose proper resistor." and a caution to ensure it's OK for the cell to be charged at high current when empty.
Fortunately, charger ICs like the TP4056 as well as assembled PCBs with such a chip and the necessary connecting pins are available cheaply on eBay and other vendors. Since I needed to safely charge lithium batteries for other, unrelated, electronics projects I've purchased several of them and keep a few spares around just in case. They work very well.


texts: What is the difference between courtyard top and top overlay?

texts:
I am creating my first assembly drawing and have noticed that my ECAD tool generates a footprint with a top/bottom overlay and courtyard top/bottom.

Top Overlay is the silkscreen, but what is the courtyard top used for? (I tried looking it up but I did not find a good answer).

Is the courtyard top necessary or can I delete it and keep it simple with Top/bottom Overlay and Top/Bottom Assembly Drawing layer setup.

I mainly want to create a footprint format that is professional and follows good industry standards.

This is what I have right now.
No courtyard top/bottom with Top Overlay and Assembly Top line thickness of 0.2mm. The dark blue below pads is a 3D Top generated by ECAD tool.


texts: Heat Conduction from ceramic resistor to iron rod

texts:
I'm trying to conduct a thermal conductivity test.
I've set up an experiment where I take a rod of a given material (steel, for example), measure its cross section, length, extreme temperatures and heat conducted and thereby obtain its thermal conductivity.

My problem is that I've tried using a 33Ohm, 5W ceramic resistor to send heat through the test element, but the resistor will heat to about 60 or 70 °C, and the hot side sensor (and the test element) won't heat up to anywhere near that temperature.

Has anybody dealt with the problem of getting the heat from the resistor to be conducted in a specific direction, instead of dissipating on the air?

_I've been using a thermal grease film of around 1W/K to create contact between the test element and the resistor.

_I haven't applied presure between the resistor and the test element.

_I haven't used a vacuum pump yet (that's the plan going forward)


texts: li-On charger Reverse polarity protection

texts:
I have   built the attached Li-On Battery charger based on MCP 73831 chip and it works well. However I would like to add a reverse polarity protection to it since I've burned 2 chips while putting the battery to be charged the wrong way.
Is there a reliable way to do this and sorry for my poor english language.

Thanks.


texts: Help identifying component values, same codes different sizes

texts:
this is a ESP32 dev kit board, I'm confused about the tantalum capacitor, I can read 106C on both of them which are likely to be 10uF and 16V however their sizes are different. Are those actually the same capacity and voltage rating?

I've looked a few schematics and they all say 10uF on both sides
My best two guesses are

Different ESR o other parameter
These things are sometimes not highest quality, so they my be trying to fool somebody?


texts: Proper thickness of different copper items normally used in Electric switch and socket?

texts:
When i open the plastic casing of electric switch and socket normally used in household like (250 V AC 16 A Switch , 250 V AC 13 A Socket) then  i found different shaped copper bar. copper rod, copper sheet. Shape of these items are not uniform so area is different. So for a certain voltage and current how can i calculate the proper thickness as well as the copper grade. For a cable diameter is uniform and in web there are lots of information how to calculate the diameter of wire but for these copper items i did not found any good reference where i can study.

Thanks in advance and sorry for this stupid question


texts:
I have written the following function to calculate the current timestamp (since 00h Jan 1 1900). The output I get is:

Current Time & Date : 20:5:32 25/7/2014<\r>
2014 7 25 20 5 32<\r>
retval 1 3597523200<\r>
retval 2 3597523200<\r>
retval 3 3613161600<\r>
retval 4 3615235200<\r>
retval 5 3615241664<\r>
retval 6 3615241964<\r>
retval 7 3615241996<\r>
retval 8 3615241996<\r>
Current time timestamp 3615241996

Basically I am printing the retval (function return value) at every step to check and verify the calculations.

The calculation match up till retval 4 (when current day hours are converted to seconds). I think it might be due to arithmetic overflow but not sure.

The issue seems to be happening in this line:

retval += (d.hr * 60 * 60); printf("retval 5 %"PRIu32"\r", retval);

retval is uint32_t and d.hr is uint16_t

uint32_t DS1307_GET_CURRENT_TIMESTAMP()
{
    uint32_t retval = SECONDS_SINCE_1900_TO_2014;
    ds1307 d;
    DS1307_GET_DATETIME(&d);
    printf("%u %u %u %u %u %u\r", d.yy,d.mm,d.dd,d.hr, d.min, d.sec);
    printf("retval 1 %"PRIu32"\r", retval);
    //process complete years since 2014 to current year
    uint8_t i=0;
    for(i=0; i<(d.yy - 2014); i++)
    {
        if(DS1307_IS_LEAP_YEAR(2014+i)==0) retval += 31622400;
        else retval += 31536000;
    }
        printf("retval 2 %"PRIu32"\r", retval);

    //process complete months from beginning of current year to current date/time
    for(i=1; i<d.mm; i++)
    {
        if((i==1) || (i==3) || (i==5) || (i==7) || (i==8) || (i==10) || (i==12))
        {
            //31 days
            retval += (31 * 86400);
        }
        else if ((i==4) || (i==6) || (i==9) || (i==11))
        {
            //30 days
            retval += (30 * 86400);
        }
        else
        {
            //i==2==february. check if leap year
            if(DS1307_IS_LEAP_YEAR(d.yy)==0) retval += (29 * 86400);
            else retval += (28 * 86400);
        }
    }
        printf("retval 3 %"PRIu32"\r", retval);

    //process complete days from beginning of month till current date
    retval += ((d.dd-1) * 86400);
    printf("retval 4 %"PRIu32"\r", retval);

    //process hours, min and seconds - CALCULATION DEVIATES HERE.
    retval += (d.hr * 60 * 60); printf("retval 5 %"PRIu32"\r", retval);
    retval += (d.min * 60); printf("retval 6 %"PRIu32"\r", retval);
    retval += d.sec; printf("retval 7 %"PRIu32"\r", retval);

        printf("retval 8 %"PRIu32"\r", retval);

    return retval;
}


texts:
I recently decided to use the MB102 Bread Board Power Supply module to power my op-amp in my circuit with the 5V power supplies. The schematics for this board is located here (http://digsys.upc.es/rpi/comp/PS_Schematic.pdf).

I need a positive and negative power supply for this op-amp and so I have tried to configure the positive terminal from the first power supply to the negative terminal of the second power supply. Thus the negative terminal of power supply 1 should give me -5V and positive terminal of power supply 2 should give me +5V. This method is currently not working for me and actually caused smoke to come from my first module. I was wondering why this is and if i'm doing something wrong.

I have done this method correctly using a regulated DC power supply and a separate arduino UNO R3 +5V with the same connection and it successfully powered my op-amp with no problem.


texts:
I would like to cut a small square out of the middle of a large square PCB.

The tricky thing is, I don't want to cut all the way through the board, just about half way. This would create a 1mm-deep square pocket in a 2mm pcb board.

I could do this with my CNC machine easily, but I want to know if something like this could be achieved during circuit board manufacturing. I would hate to have to load hundreds of panels of boards onto a CNC machine; this would raise the cost of manufacturing significantly.

One idea I had was to use fancy programming of the drill that drills holes in the pcb to act like a CNC drill. It would, of course, require changing the drill bit to a special one for milling.

Can anyone who is familiar with these machines (already setup in most Chinese PCB fabrication facilities) foresee a (cheap) way to use them to cut pockets out of a PCB?


texts:
Who owned Toroidal Isolation Transformers like this:

http://www.hammondmfg.com/289T.htm

Do you have a gaussmeter (or any magnetic field meter like the following)?

How low did you measure the magnetic field of it compared to a normal transformer? Is it one half or 1/3 or even lower?

I need very low magnetic field for some applications. In my testing. When I put the above EM meter 16 inches away from a normal transformer. I was getting 100 milligauss. I need it to be 20 milligauss or lower.

This is for one without Mu-Metal shielding.. and what did you measure when you add Mu-metal shielding?


texts:
There are several shields on my PCB: shield on CAN-bus, on RS485, on Ethernet, on ENCODER motor signals.

How do I correctly connect all these shields? If I use the star topology, which filters should I use?


texts: ASIC timing constraints via SDC: How to correctly specify a ripple-divided clock?

texts:
Introduction

Having found multiple, sometimes conflicting or incomplete information on the internet and in some training classes about how to create timing constraints in SDC format correctly, I'd like to ask the EE community for help with some general clock generating structures I have encountered.

I know that there are differences on how one would implement a certain functionality on an ASIC or FPGA (I have worked with both), but I think there should be a general, correct way to constrain the timing of a given structure, independent of the underlying technology - please let me know if I'm wrong on that.

There are also some differences between different tools for implementation and timing analysis of different vendors (despite Synopsys offering a SDC parser source code), but I hope that they are mainly a syntax issue which can be looked up in the documentation.

Please also see the related question ASIC timing constraints via SDC: How to correctly specify a multiplexed clock?

Question

This is about the following ripple clock divider, which is part of the clkgen module which is a part of a larger design using the generating clocks:

The generation of clk0 seems to be relatively straight-forward:

create_clock [get_pins clkgen/clk0] -name baseclk -period 500

Though I am not so sure about the SDC commands for the generated, divided clocks clk2, clk4 and clk8: How should the source and target options be specified? My initial thought was that target is the output pin on the clock generating cell, source is as close to the target as possible:

create_generated_clock -name div2clk -source [get_pins clkgen/divA/clk] -divide_by 2 [get_pins clkgen/divA/q]

The source could also be the module's clock input pin:

create_generated_clock -name div2clk -source [get_pins clkgen/clk0] -divide_by 2 [get_pins clkgen/divA/q]

Or the previously defined source clock, as suggested here:

create_generated_clock -name div2clk -source [get_clocks baseclk] -divide_by 2 [get_pins clkgen/divA/q]

...which also raises the question if the source or the target options need to be something other than get_pins, such as get_nets, get_registers or get_ports.

To keep the example as general as possible, let's assume that the generated clocks clk2, clk4 and clk8 could be driving other, potentially interacting (clock domain crossing) registers (not shown in the schematic).

I think the constraints for clk4 and clk8 should be obvious once we know how the clk2 constraint is written.

The X1 instance (a simple buffer) in the schematic is just a place-holder to highlight the issue of where in the clock propagation network the source option of the create_generated_clock should be set, as automatic place&route tools are usually free to place buffers anywhere (such as between the divA1/q and divB1/clk pins).


texts:
In 74HC4046's datasheet, section "Recommended operating conditions", i find this

I wonder if this is only applied to pin 5 - INH, the VCO eanble/disable pin?
Does \$SIG_{IN}\$ pin have any similar input transition time limitation? In my opinion, CMOS devices such as 74HC/HCT series usually have input transition time limitation. Such as TI's HC/HCT series, when \$V_{CC}=4.5V\$, the maximum input transition time is 500ns.

Update:

In a very old chip - CD4046B's datasheet, i find this:

For SIGin pin, it gives two limitations:

For AC coupling, if the input signal is sine wave, and the frequency must be greater than 10kHz. And at 100kHz sine wave input, the minimum sensitivity is 360mV (max.).
It also gives the rising/falling time limitation for signal pin when using phase comp. II, i thought this is for DC coupled signal.

I want to know, in AC coupling signal, for sine wave, why it limits the frequency? Does it have any relation with transition time? And for 74HC4046, when it gives the AC coupled input sensitivity, it also gives the test condition: \$t_{r} = t_{f}\$, if my AC coupled signal has a different rising\falling time, then what's the minimum peak-peak value of my signal?


texts:
I try to run an accelerometer (Data sheet) with this library (link).
Bus: I2C and Microcontroller adafruit-feather-m0-adalogger (link) is used.
If I wire the accelerometer to the muhC, I just get zeros for the acceleration values, but reasonable values for temperature. So I think that pull up resitors are needed. Correct?
I checked the data sheet of the accelerometer (page 103) for more information. But I still don't know which resistors to use. Could you help me?
Thanks!


texts:
I am doing Symmetric Inverter Sizing Based on load capacitance and propagation delay that is given.

Also mobilities, threshold voltages are given.

Symmetry ratio is process dependent based on mobility.

So how do I "size"/design this inverter ?


texts: What Common Mode Choke choose for EMI filtering at 250v

texts:
I'm designing a PCB with a microcontroller that have to handle 3 Relays. The main power source is an AC Inlet socket 250v, the maximum current for all the circuit from this source is 15A (I included a fuse for that).
Given that I have 2 radio modules in the circuits and I don't want EMI perturbation from this source power I want to add a common mode choke.
What kind of Common Mode Inductor should I use (impedance value, inductance value) and how can I do calculation myself for next time.
Thanks in advance


texts: What is the difference between driving a MOSFET gate and an IGBT gate?

texts: Can I use an suitable IGBT gate driver for driving the MOSFET, and vice versa? Which parameters (threshold, plateau, and turn on voltage ratings, gate capacitance, etc) must be the same for this compatibility? What are the essential differences between driving these two different types of gates?


texts: Is it possible to use a AV-receiver output for an "active" speaker?

texts:
I have a 5.1 output and I'd like to use the center-chanel output for a soundbar. The soundbar is active (has optic, coaxial and 3.5 mm jack).
Is any way to convert the output of the center-channel from the AV-receiver to an output compatible with an active speaker?

(Coaxial/optic does not work when 5.1 audio is activated, and anyway it is not the desired effect, for I want only the center chanel in the soundbar).


texts: How to change the voltage polarity in an inverting amplifier?

texts:
I want to implement a simple circuit which can map -10V  +10V voltage range to 0V 5V voltage range. Thus I'm planning to use two op-Amps, one for the slope and the other for the offset.
So basically I'm planning to use an inverting amplifier and a summing amplifier consecutively.

But Inverting amplifiers multiplies the input voltage with a minus sign. I need a positive slope. How can I overcome this?
Also Could you gibe me any ideas for a cheap op-Amp models for this purpose?


texts: 12V DC to 12V AC (50 Hz) converter / inverter for low loads (< 1A)

texts:
I am building a mobile sound system powered by a car battery. I have a small mixing table that runs on 12V but it needs AC power (50Hz) and won't work with DC (I tried that, with very weird results.)
Currently I am using a 12V to 230V inverter and the provided power supply to convert it back to 12V alternating current. This seems wasteful and I do not want to introduce another voltage level into my design just to power the mixing board.
How could one build a simple circuit that does this? I have basic electronics skills (soldering, know about resistance, voltage, current) but never built a circuit board. I would prefer to avoid opening the device, except it is very easy to do the modifications.
The mixing board is a Renkforce MX260 USB DJ Mixer.  Th manual can be found here.


texts: how to wire up potentiometer to subwoofer

texts: I have a Audio-Taper Potentiometer that I bought from RadioShack and would like to hook it up in-line to my sub woofer so my 5.1 surround sound's bass is not so loud.  However, the connections from the sub to the main receiver are proprietary plug on the back of receiver so I can't tell which is positive or negative.  Does this matter for hooking up a Potentiometer?  Where can I find a wiring diagram?


texts:
My son and I have an experiment we are trying to achieve-measurement to a moving object.

The moving object will be a mouse, in a 1X1m area.  On the mouse, we want to place some kind of sensor or reader.  Then we have a sensor just outside of the cage which will be fixed.

We want to measure the distance to the mouse (who is wearing some kind of sensor), so it is effectively the distance between the two sensors.  Our goal is to be accurate to 1cm.

Does anyone know of a product we can use for this?  Hoping there is something that already exists.

No mice will be hurt, it is our pet!


texts: What is the value present at the first address of flash memory of stm32 for every firmware?

texts:
Every firmware of Stm32 microcontrollers, the first value is starting with 0x2XXXXXXX, while working with custom bootloaders, I found that this is an address on SRAM,

1)What is actually present at this address of SRAM?
2)In custom bootloaders What is the significance of setting the MSP to this address on SRAM, before calling the reset handler of the user-application?
uint32_t msp_value = *((volatile uint32_t *)FLASH_SECTOR2_BASE_ADDRESS);
__set_MSP(msp_value);
app_reset_handler();


texts:
I am designing a VSC converter for HVDC. How to select the right DC link capacitor?  Is there any formula for this?
VSC is voltage source converter


texts: Design the circuit such that the output voltage is 2.4V

texts: How would  I figure out the value of R? How would I analyse this circuit?


texts:
I wanted to check redundancy in eeprom and crosscheck the data for any errors occurred or not and I ended up reading CRC code. I found it useful but have some doubts that need clarity.

My objective is to check the memory address locations 0-15k of eeprom and store the checksum in memory and do the same for next 15k-30k address locations. The Both address locations store the same data and it is done so that eeprom memory is utilized.

Well When I began reading the docs. I ended up with a useful code:

unsigned int crc32(unsigned char *message) {
  int i, j;
  unsigned int byte, crc;
  i = 0;
  crc = 0xFFFFFFFF;
  while (message[i] != 0) {
    byte = message[i]; // Get next byte.
    byte = reverse(byte); // 32-bit reversal.
    for (j = 0; j <= 7; j++) { // Do eight times.
      if ((int)(crc ^ byte) < 0)
        crc = (crc << 1) ^ 0x04C11DB7;
      else crc = crc << 1;
      byte = byte << 1; // Ready next msg bit.
    }
    i = i + 1;
  }
  return reverse(~crc);
}

Here as far as my understanding the 'message' awaits bytes and continues CRC calculation until the character is not received. If I wanted to check the two blocks of eeprom memory as said before. How can I append the eeprom memory to the message variable.

Well my
another *doubt is whether eeprom read have any limit regarding reading reading address from 0-15k at a stretch rather like eeprom write *
I need your inputs to make  this attempt useful and rewarding
Regards


texts: Hello, i'm at a complete loss, have never came across that type of a ribbon cable, could anyone point me in the right direction as to the nature of the "bridge" between traces there. Cheers


texts: What are the methods to measure distribution transformer vibration in 0.5g range?

texts:
It may seem obvious to use widely available analog devices MEME accelerometer for measurement in range of 0.5g. I did thorough study on this and found out that MEMS sensors either doesn't work or become erratic in high EMF surrounding. Since I wanted to measure transformer vibration and corresponding frequency by attaching the sensor on surface of transformer, it would always be in vicinity of high EMF.

There are industrial piezoelectric sensor available for this purpose but it doesn't detect small vibration in 0.5g range. There are industrial sensor available from National Instrument but looks very costly. Is there any particular segment of sensors which is recommended for this particular application?


texts:
I have an application where popping some solderless tie points on a PCB is a thing to to.  I picked up some 1x4 tie points, https://www.elexp.com/ProductDetails.aspx?item_no=03TB-IVR&CatId=

The issue is mounting.  There is a flimsy single lead on the back, with a plastic post at each end-- a longer one near the lead, and a slightly shorter one at the other end.

I can't find any real data sheet for the part.  Are these heat-posts??  If so, the plan for my Very small run (maybe 50 boards) would be a soldering iron with a spade tip.  Any forseeable problems?


texts: Two functions in the high priority interrupt

texts:
I'm using the PIC18F46k22 mcu and I'm using two function in my high priority interrupt routine:

#pragma code
#pragma code My_HiPrio_Int=0x0008
#pragma code
#pragma interrupt chk_isr

#pragma code
void My_HiPrio_Int(void)
{
    _asm
        GOTO chk_isr
    _endasm
}

void chk_isr(void)      /*Serial Interrupt*/
{
    INTCONbits.GIE = 0;

    if(INTCONbits.TMR0IF==1)   //Timer routine
        Timer0_ISR();

    if(PIR1bits.RC1IF)     //RS485 receiver
        RC_ISR();

    INTCONbits.GIE = 1;

}

void Timer0_ISR(void)
{
    nTick0++;

    if(pSet == 0) nTickSetPress++;
    else nTickSetPress = 0;

    if(pPlus == 0) nTickPlusPress++;
    else nTickPlusPress = 0;

    if(pMinus == 0) nTickMinusPress++;
    else nTickMinusPress = 0;

    if(pShift == 0) nTickShfPress++;
    else nTickShfPress = 0;

    if(pCountPlus == 0) nTickCount++;
    else nTickCount = 0;

    if(pReset == 0) nTickResetPress++;
    else nTickResetPress = 0;

    if(bCdlyStart == 1) nCdlyCount++;
    if(nCdlyCount >= nTickCdly) bCdlyStart = 0;

    if(bDisplayTime == 1) nDisplayTimeCount++;

    if(bBlinkDigitFast == 1) nTickBlinkFast++;

    TMR0H = TMR0HValue;
    TMR0L = TMR0LValue;
    INTCONbits.TMR0IF = 0;
}

void RC_ISR(void)
{
    rxbuf485 = RCREG1;

    if (rxbuf485 == 0)
    {
        return;
    }

    if (rxbuf485 == TOKEN)
    {
        b485RxToken = 1;
        return;
    }

    if (b485RxComplete) return;

    if (!b485SOH)
    {
        if (rxbuf485 != SOH) return;
        b485SOH = 1;
        n485RxDataPos = 0;
        b485RxComplete = 0;
        memset (RS485RXDATA, 0, sizeof(RS485RXDATA));
        return;
    }
    else if (rxbuf485 == EOT)
    {
        b485SOH = 0;
        b485RxComplete = 1;
        return;
    }
    if (n485RxDataPos == 50)
        n485RxDataPos = 50;

    if (n485RxDataPos>=RS485RXSIZE)
        n485RxDataPos--;

    RS485RXDATA[n485RxDataPos++] = rxbuf485;
    return;

}

void Timer0Init(void)
{
    T0CON = 0x07;
    TMR0H = TMR0HValue;
    TMR0L = TMR0LValue;
    T0CONbits.TMR0ON = 1;
    INTCONbits.TMR0IE = 1;
    nTick0 = 0;
    nTickSetPress = 0;
    nTickResetPress = 0;
    nTickCdly = 0;
    nTickBlinkFast = 0;
}

void RS485Init(void)
{
    TRISCbits.TRISC7=1;     // RX
    TRISCbits.TRISC6=0;     // TX

    TXSTA1 = 0x00;
    RCSTA1 = 0x90;
    SPBRG1 = 30;
    BAUDCON1 = 0x00;
    PIE1bits.RC1IE = 1;
    TRISCbits.TRISC3 = 0;
    p485 = 0;

    memset (RS485RXDATA, 0, sizeof(RS485RXDATA));
}

Can two routine be done in a high priority interrupt? Will there be any problem in long term?
This is because I'm trying to find out why my device always hang after running a few days...


texts:
I am playing with an ATtiny13 and I thought it would be good to use it with an external 8Mhz ceramic oscillator instead of the 1.2 Mhz built-in one. (I want to do a soft-uart at 9600 bps, so I figured 1.2 Mhz was too slow)

To change to an external oscillator, I ran 'avrdude -c usbtiny -p attiny13 -U lfuse:w:0x70:m -U hfuse:w:0xff:m'

Unfortunately I can't access the device anymore now. The 'Blink the LED on PB0' program that was in there does not run anymore and the programmer can't connect to it.

Not sure what to do here. Can I throw away this chip or is there a way to rescue it?


texts: what are the specs of a transistor that can't be find on internet?

texts: It is part of a switching-mode power supply for a PC. There is a number: 1035 and a logo above this number, that seems to be a capital D. I am trying to find a replacement but it is not as easy as it should be. It is used in an arrangement of three transistors with a heatsink. Right next to a couple of big filter capacitors. The one i am looking for appears twice next to the third/first (dont know what should be the order), a SPS S18-0703 E3150 transistor (apparently, +5V stanby).


texts:
I'm building an electronic load and I need to protect the transistors from overvoltage. This is the over-simplified version of it:

simulate this circuit – Schematic created using CircuitLab
I can't use a relay, because what if voltage changes after the relay is connected? Aside from that, I couldn't find a relay with contact voltage rating higher than 30 VDC.
I can't use any transistors because it's a 200W load with maximum current of 10A, any transistor there would be fried without a proper heatsink that I don't have. (I only have a big heatsink with fan for the main transistors.)
Can varistors help or are they too slow? How do I protect the transistors from over voltage?
Electronic load spec: 50 V / 10 A / 200W
2N3055 datasheet.


texts: Why wouldn't windows load the WCID driver?

texts:
I'm developing an embedded device with a DFU compatible bootloader. Right now I can hold a button and enter the bootloader and download new binaries, but I thought I would make it more convenient for the user by employing the runtime features of the DFU spec.
My application configuration descriptor includes one extra interface(no endpoints) for the DFU Runtime, which responds to only one request DFU_DETACH by rebooting into the bootloader. This also works fine with non-windows platforms. On windows however, I need to make sure the WINUSB driver is loaded for this interface for this to work.
My Microsoft Compatible ID descriptor is setup as following.
USB_MicrosoftCompatibleDescriptor msft_compID =
{
    .dwLength =  sizeof(USB_MicrosoftCompatibleDescriptor) + (2 * sizeof(USB_MicrosoftCompatibleDescriptor_Interface)),

    .bcdVersion = 0x0100,
    .wIndex = 0x0004,
    .bCount = 2,
    .interfaces = {
      {
        .bFirstInterfaceNumber = 0, //CDC
        .compatibleID = {0, 0, 0, 0, 0, 0, 0, 0},
        .subCompatibleID = {0, 0, 0, 0, 0, 0, 0, 0}
      },
      {
        .bFirstInterfaceNumber = INTERFACE_DFU,
        .compatibleID = {0x57, 0x49, 0x4E, 0x55, 0x53, 0x42, 0x00, 0x00},
        .subCompatibleID = {0, 0, 0, 0, 0, 0, 0, 0}
      }
    }
};

Windows recognizes this as a WINUSB device as shown in the attached image, but for some reason libusb is loaded instead of winusb, and I have to change the driver through Zadig inorder to get the DFU runtime interface to work.

Specific question I'm asking here is, is there something else I should do to make sure windows loads the correct driver(WinUSB) without user intervention?


texts: ESP8266 ESP-01 only responds "Recv x bytes" after an HTTPS request

texts:
I'm using ESP8266 ESP-01 for wifi data transfer.

When I send the request for 80 server's port, the data is successfully returned.

REQ: GET / HTTP/1.1\r\nHost: server.com\r\n\r\n

But when I send this request over 443 server's port, the data received is "Recv 50 bytes...  ...SEND OK..."

It's possibly an ESP or an HTTPS Headers problem? What i mean is what is needed to transform the Headers from HTTP to HTTPS (I did'nt saw any diference in Postman, but in Postman works only changing the server's port)?

Sequence in HTTP:

AT+CIPSTART="TCP","myserver.com\",80"\r\n

AT+CIPSEND=PKG_SIZE\r\n

GET / HTTP/1.1\r\nHost: myserver.com\r\n

Works OK.

Sequence in HTTPS:

AT+CIPSTART="TCP","myserver.com\",443"\r\n

AT+CIPSEND=PKG_SIZE\r\n

GET / HTTP/1.1\r\nHost: myserver.com\r\n

Doesn't work.


texts: What kind of damage could a soldering iron do to a component?

texts: As a follow-up to this question, what kind of damage could a soldering iron do to an IC or other component if left on it for too long at too high a temperature?  ESD damage can be subtle, for instance.  Is overheating damage usually obvious/complete destruction?  I've desoldered/resoldered things by just globbing on a lot of solder and heating it all up, probably using more heat than is recommended, but I've never noticed any damage.


texts: Need help with identifying transformer ratio

texts: Does the transformer ratio 240:15 or 240:30? It's a bit confusing


texts: How to clean this volume control? Which deoxit cleaner should i use?

texts:
Of all the contact cleaners deoxit offers, i'm not sure if i should use D series or faderlube. (Note: This is NOT a volume control of the newer ones that just sends a signal to the software, this one actually controls the volume)

Thank you


texts:
I have been studying the Fourier Transform and the convolution theorem is not clear to me.

Sometimes, I see this:

But other times I see this:

Which one is correct? Where is this constant factor from?


texts: Best way of making a trip-wire type device?

texts:
I'm wanting to make a type of electronic "trip wire".

My basic idea is to have like a laser and basically when the laser is interrupted then it sends some signal to a microprocessor.

I'm not tied to a laser but it was the first thing that comes to mind. The attributes it needs to have is it needs to be only like a "wire"(as in, it doesn't detect motion anywhere but head on) and it needs to be low power(like run for a few days at least off of 2 AAs). Also, an actual wire is out of the question because it needs to be capable of being "reset" after a certain time out(of say 1 second or so) The range it needs to work with is only 5 or 10 feet though. Also, it's not possible to have two parts to this device like a typical laser-photodiode setup. This needs to be contained all in one (preferably small) package.

What is my best bet with this? I was thinking maybe super-sonic sound like this but I think there would probably be a better way.

So basically what I have in mind for the device is like when you first set it up, you "calibrate" it for a certain distance. So for instance if there is a wall five feet in front of it, then this device would work if there was anything that came head-on with it in 5 feet. And etc.


texts:
I'm new to electronics and I'm trying to understand pull-up resistors properly. I have a problem with the following schematic:

I've redrawn the schematic into my following schematic for better understanding:

In the redrawn schematic, R1 represents pull-up resistor.

If we connect the circuits using the button, according to explanations I've read, the current should flow not to the MCU, but to straightly to the ground, because on that branch there is lesser resistance.
Based on conservation of charge, the current that goes in the branches, must come out of the branches, so I = I1 + I2. From that we can deduce I = U (1 / R2 + 1 / R3). However, branch leading straightly to the ground has (imo) approximately 0 ohms resistance, because there is no resistor, so I goes to infinity = short-circuit.

How is possible there is no short-circuit?
Is my redrawn schematic identical to the original one?
Also based on my knowledge of physics, even if we press the button and connect the circuit, there should be identical voltage on both branches in this parallel circuit. How is it possible that we can read 0 on the pin? Do we actually measure current instead of the voltage?


texts:
Recently I took apart 2 identical transformers from 2 identical devices. Each one has 6 leads on the output (quad core I think it's called). Since circuit lab only has double transformers, I used 2 of them. Now, I want to use them to make a +/- 20V power supply. Firstly, I came up with this:

simulate this circuit – Schematic created using CircuitLab

Then, I thought why not use all the leads like this:

simulate this circuit

1) Will the second circuit give more amperes?

2) Is it okay if I connect in parallel 2 transformers with different voltages (in order to increase amperage)?

3) In a multi-core transformer, are all cores independent? For example, If I use one core to power a device, will this affect the amperage of the other core?


texts: I am modeling chip MC14538 in PSPICE by building its internal circuit from the datasheet. I, however, can't figure out what logic gate they are using. It seems like an OR gate with some sort of circle on one of its input terminals. Also, what is the component designated by A


texts: How to convert a boolean function into K-map

texts:
I would like to know how can I convert the following boolean function into a truth table and accordingly construct the k-map

$$F=A′B′C′+B′CD′+A′BCD′+AB′C′$$

thanks in advance :)


texts:
Is it reverse or forward bias?

in real life and theoretical

for example: Voltages in the pic are 10V

What if I placed a resistor in series with the source on the right?


texts: How do I measure ~16V battery voltage in an ultra low power system?

texts:
I am trying to estimate remaining battery life in a low power system.  The battery is very well characterized so that reading the battery voltage will be sufficient for my needs to estimate remaining battery life.

However, the problem is that the system is comprised of low voltage chips (3.3V - 1.2V) and the battery voltage varies from 16V to 7V (dead).  Any solution that I use to monitor the voltage must have negligible power overhead itself.

I am looking for

A chip that can provide the voltage to a digital interface (I2C, SPI, etc.)
A circuit solution that provides an ADC value that is accurate across the ~10V swing and can interface with a 1.8V microcontroller. (maybe resistor divider + zener + ADC)

Any ideas?


texts: How can I have an ECL logic input for a CMOS logic gate

texts: I'm working on a triggering system that uses a comparator to check if the signal is below a threshold value. I found a great comparator for the job, except its output is ECL logic. I wanted to use the output of the comparator as one of the inputs for the logic control circuitry that follows it, which uses CMOS logic family gates. How can make those work together? Is there a way of converting the signal? Would they work fine without any extra steps?


texts: How to hide/delete the symbol pin types (named as pas/sup) from the eagle schematics?

texts:
Hi there,

I was trying to do something and not sure what I did without knowingly those small green circles along with names has appeared on ever pin of all the components I had in the schematics.

Could you please let me know how to hide/delete them.


texts:
I am charging a 26 Ah battery with a solar charge controller. The battery's manufacturer recommends charging with 0.1C. Which charges the battery at 2.6A during bulk mode. That is what I was going to charge with initially but I realized that for solar applications that will take up too much time so now I will charge with 5.2A (0.2C) which is lees than the recommended maximum charging current limit.
SO the question is what effects in terms of the battery's life cycle/lifespan does charging with 0.2C have over charging with 0.1C. The datasheet of the battery is attached below.
 Lead Acid battery datasheet


texts: I'm trying to fix a burnt blender PCB(due to short circuiting). I have tried to trace copper traces on the PCB and wondering if i Should cut off the burnt area and redesign the affected PCB or use a jumper? (Affected area has a heat sink + transistor )