texts: Multiple laser diodes in series using a driver board

texts:
I couldn't find this in the search so I hope that I'm not repeating a question that's been asked already. I'm using a driver board that monitors the photodiode feedback in a laser diode to maintain constant power. This works fine with my single LD but I am wondering if it is possible to put more than one LD in series? These are 3 pin LDs (LD anode, LD cathode/PD anode, and PD cathode). Any thoughts on how to wire these? Can I simply put the LD pins in series?

Thanks!


texts: How to connect four 18650 batteries to double voltage and capacity

texts: Im trying to do a DIY RC car with uses two 6-12v motors as well as some LEDS, servos and Arduino components. I was planning on using four 3.7v 2600MAH 25A 18650 battery cells, two on series and two on parallel so as to end up with 7.4v 5200MAH. Im using this picture to use the batteries from this website. The thing is, would this work without problem 18650 cells? Do i need to add things between them or just simply add a 2S BMS (Battery Management System) to both the positive and negative? Thanks!


texts: Resistance measurement across reversed batteries using multimeter

texts:
If you take two similar capacity batteries and put them in contact in a reversed configuration (anode-anode or cathode-cathode) in series, the resistance measured by a digital multimeter across the batteries is ~100 ohms, but if you exchange the leads of the multimeter the reading shows 0 ohms. Why is there a polarity issue for resistance measurement by the multimeter ?

I confirmed this with two independent multimeters. Can someone please clarify ? Thanks.


texts:
I need a circuit to convert variable capacitance value to considerable variable DC voltage.

Capacitance value range = 0pF ~ 20pF
DC value range needed = 0V ~ 6V

Please explain in detail as i am newbie.
Thanks in advance.


texts: I want to change the shape of my board in eagle, e.g. I want to create a hexagon instead of the square. Unfortunately I only found the possibility to move the square-edges around and increasing or decreasing the size of the board, but I could not find a possibility to add or remove edges. Is it possible in eagle to reshape the board? And if yes, how can I do that?


texts: In LCD technology what is the “duty cycle” of each pixel

texts: I am trying to determine how much energy is transferred from an SLA printer pixel to the resin. One of the key things I am having trouble finding a good answer to is given a static image how long is any given pixel actually on during the display time? Basically what is the “Duty Cycle” of that pixel. I am inclined to think that the duty cycle of each pixel would be would be theoretically 1/(number of rows in the screen). In practice obviously the transistors driving the Row-Column matrixes dont turn off immediately so it would be a little longer. Obviously since the screens are made to display images and this not really there purpose Im having trouble finding much decent technical information on the subject. If anyone has information on the how much energy would be absorbed in LC before it got to the resin that would be bonus.


texts: How does usb c charge and power peripherals with only one vbus pin

texts:
I am curious, if i am reading the digram correctly, how usb - c can charge a laptop and then with the same port(different time) power a peripheral device(like hard drive.) looking at the pinout it has the data pins (all the tx, rx, and d+/-) and cc for "negotiating" what voltage/amperage to charge at. however it seems that there is only one power pin for both ways. does usb - c send power the device over the same pin(s) it charges on? does each port requires its own ic to control charge and direction? what is vconn?

all help is much appreciated,
vesper krate

pinout diagram:


texts: DC voltage stepping down but keeping current uchanged with no regulator

texts: Is there any way to divide DC voltage or stepping it down but keeping the current peak unchanged? But I can't use a voltage regulator. In fact, I want to make a regulator 5V output into 4.5 ~ 4.7 V but keeping the current peak same. Current is now 1.7 ~ 2A.


texts:
I am building an AC dimmer circuit to control from an Arduino using this schematic:

I need to make this dimmer so that it can be used as a three way switch as well.  How would I modify this circuit to work in place of a three way switch?


texts: detection of absence of 118V DC voltage using optocoupler

texts:
I want to use an phototransistor interfaced with microcontroller to detect absence of 118 dc voltage.The problem is how to calculate the right resistor value of the input(LED) circuit as well as output circuit(collector emmiter cct)
thanks.


texts: Single- vs double-sided PCB assembly costs

texts:
I'm working on a new design (still laying out the components) and I have a chance here to reduce the size of the PCB by roughly 40%-50% if I use the other side for a QFP-100 IC (so it's heavy and will probably need gluing) and a few passives.

The PCB is 4 layers so savings are worth it, but I was wondering, if I used both sides and made the PCB smaller, how much extra will I pay for assembly? 2x? Will I be actually saving anything with those extra assembly costs, or might I end up paying more?

PS. I'm not sure I can get a quote right now, because I haven't finished the PCB yet, and they might need more info before they give me a quote, so I'd appreciate it if anyone with similar experience would share their thoughts with me, thanks.


texts: I've not found the clear explanation for the WHY we use the bus analyzer except to capture and analyze data across the communication bus.  Yes, we observe message structure, such as command words, data words, and status words, yet when observing the data output from the bus analyzer it is in all hex nibbles.  Essentially, what are we trying to achieve when observing data flowing from across the bus?  Yes, error, but looking for more descriptions.


texts: Homemade capacitor - crafting and testing

texts:
I'm a laic when it comes to electronics, but I want to venture myself in creating things with my own hands.
Looking for that, I found a tutorial that teaches how to make a capacitor with foil sheets and wax paper.
I need to know the formulas and all the variables and how I can safely test it to learn it's capacities (no site that I visited showed any of this.)


texts: Can a planar transformer replace a laminated transformer for 50Hz AC conversion?

texts:
I have seen planar magnetics transformers even with isolation up to 20 kV. However those devices seem to be designed for DC/DC conversion in 100 kHz range.

I am wondering whether low frequency laminated transformers can be replaced by a planar transformer?

In other words are there planar transformers which are suitable to convert 230VAC 50Hz to 20VAC (as an example)?


texts: Pull away voltage (energy) from a DC motor driver board when it does regenerative braking

texts:
I have 200 BLDC motor (six-step) driver boards. They work fairly well but, when I tested them on a heavy load (2500 kg), I discovered that they struggle when braking the motor. The PID algorithm can be set to slow down gently (low deceleration), but sometimes (in case of emergency, for example), a bigger deceleration is desirable. When I try a more steep deceleration, the boards get broken.
Investigating the problem, I discovered that the culprit is the voltage raising, due to the regenerative braking of the H-bridge.
The nominal power supply for the board is 48V rectified: a diodes bridge is outside the board, and the rectified voltage is fed to the board, which has a bank of capacitors.
When the motor is rotating at high speed (say, 2500 RPM), and a deceleration is wanted, the PWM for the motor is decreased. This causes a rise in the power supply which, if it is not too high, is tolerated. But if the rate of PWM decreasing is too high (big deceleration), the power supply (Vbus) rises too much, and a few critical components on the board do not tolerate it (for example, the mosfet drivers, and other voltage regulators for +15V and so on).
The electronic engineer proposes to deploy a resistor to dissipate the overvoltage; this resistor would be inserted between Vbus and GND when needed (the CPU has some spare pin to control the resistor insertion, but also an automatic insertion can be done, based on on a threshold, for example Vbus > 50 volts).
I don't like the idea of the resistor, because it would heat onboard, and because I thought what follows: why add a resistor, when I have a 350VA transformer which can dissipate energy much better? If only I could short the rectifier bridge when needed, I could discharge the extra voltage into the transformer. The rectifier bridge has exactly the task of impeding a current return, but in this case, sometimes, it is desirable.
I think it could work: a mosfet or a transistor to short (bypass) the bridge, activated when Vbus trespasses a certain threshold. Normally Vbus stays at 48-49 volts - only when braking it raises: if it stays under 58-60 volts there is no problem; if it raises more, the board gets broken. I implemented a software check: the software monitors Vbus and, if it raises too much when braking, the deceleration is reduced accordingly. The result is that the board does not melt down anymore, but I would like some more braking.
The schematic, in principle, is the following:

simulate this circuit – Schematic created using CircuitLab
(Sorry for the crude schematic, I am not very expert and it took a lot of time...)


texts:
I am trying to connect a DB25 male cable to a DB26 male receptable.

Seems that there are no out of the box adapters available for this, so will have to solder my own.

Having trouble and a lot of confusion on how to make the correct connections, so that's why I'm basically looking for a correct wiring diagram. (seeing some weird diagrams with crossing cables etc on a google search).

Some additional context:

I am currently building the open source https://opensfx.com/ project

This means that I have no possiblity to change the plugs / receptables on both the arduino and the servo motors, they come as-is.

Normally, the servo controllers come with a DB25 connector and simply connecting with a DB25 male to DB25 male cable is enough. However, my servo controller currently has a DB26 connector, hence it is incompatible with what I would like to achieve. I have seen forum posts that people were able to connect the DB26 to their breakout board though, but they didn't specify how.

It should simply be a matter of adapting a DB25M to DB25M cable towards a DB25M to DB26 cable by attaching the correct pins.

Pinouts:

Pinout servo controller side (DB26 female):

I am using the Mige MG-DS100S-75 servo controller for the Mige 90ST-M02430 servo motor. (link to manual), however the most important part is the pinout in the following picture

Pinout Arduino breakout board (DB25 female):

Reference:
https://opensfx.com/build-process-controller-wiring/

note: I am not using the default breakout connectors in the pictures, I am using the open source breakout board created by Pyroneus, however this is just a PCB version of all the wiring displayed in the wiring diagram, therefore you can see this breakout board as a simplification


texts:
I'm planning to use Resetable fuse PTC for cable protection of a sensor's cable.
The sensor will not draw more than 40mA.
So considering that PTC is not accurate and its affected by temperature I  choose this

so in case the environment get to 80C it will have I-hold of 70mA (50%)

But the question comes to the trip resistance. as these PTCs have leakage current and trip resistance. I cant find it in datasheet .. I think its good to know it to have parallel fault led near it? and to have way to notify the controller that the fault occurred..


texts:
I saw some schematic that uses optocoupler to make isolation to the MCU digital input pin. Schematic below.

I was wondering why do they need R700 as a pulldown since the LED inside the optocoupler is current controlled (not voltage controlled) and hence isn't sensitive to outside interference?

Is there any scenario where this pulldown would actually have a purpose?


texts:
I have a Raspberry pi and an amp circuit which both have different batteries/ power sources. I was wondering if it is possible to use a single switch to connect the two unified grounds to each of the grounds of the battery?

simulate this circuit – Schematic created using CircuitLab


texts: Reason for Distortion in Amplifier for Speech Signals

texts:
I've been working on an at home project recently that requires the use of a speech amplifier. My ultimate goal is to perform signal processing via a dsPIC on speech signals to identify key words or at the very least, detect frequency of speech. I've taken a break on the signal processing to work on the speech amplifier, but I have run into some difficulties.

My experience in hardware is limited to classes and a few simple at home projects, so I am not very familiar will the non-idealities of circuitry. I'm wanting to make a single supply amplifier using a LM318. The circuit would ideally be powered by 5V (cutting it close to the LM318's supply range limits), and would output an amplified speech signal over the entire voltage range to an ADC. In the non-inverting amplifier, I'm also wanting to include a band pass filter to keep DC amplification at unity and to prevent aliasing at the dsPIC ADC. I've modeled the microphone with a 2.5V biased voltage source with an impedance of 2.2kohms (really it is a microphone sandwiched by 2.2kohm resistors at power and ground). Not included are decoupling capacitors (any bonus advice on how to choose values for those would be appreciated).

I'm using TINA as a simulator. The AC transfer function of the circuit is what I expected with a pass-band from roughly 10-5000 Hz and a gain of 10 (Stack Exchange will only let me post 2 images).

These transfer characteristics are what I was expecting from this circuit, but it is the transient analysis that gave unexpected results. I input a 500 Hz 0.1 V amplitude sine wave. What I expected out was a 500 Hz 1 V sine wave, but instead, the simulation returned the following.

I've tested the amplifier at other frequencies, and it looks like the less gain there is at a frequency, the less distortion there will be. I'm at a loss for what is causing this. Any ideas?

I'm also open for any feedback on any other improvements that could be made to this amplifier.

This is not my field of study in EE anymore, but I definitely want to keep working on projects and learning about hardware. Any recommendations for readings or books on topics like these (non-idealities of circuitry/amplifiers) would be much appreciated.


texts: Implementing protection circuitry for a single cell

texts:
I'm hoping to embed a protection circuit for a single 18650 in my device's circuit. No over-charge protection is needed since it won't allow charging - so only protection against over-discharge, reversed polarity and over-current/short-circuit.

I see that there're ICs like BQ29312A, but they're for 2-cell packs. Does anyone know of schematics that protect single 18650s with a working current 3-4A?

Thanks


texts: Why does current not increase when batteries are connected in parallel?

texts:
I built a simple circuit consisting of two battery holders each including x2 1.5 V batteries, a slide switch, a LED and a 100 ohm resistor.
The current I measured with a multimeter when the two battery holders were connected in series (and the switch ON) was 25.9 mA:

I then connected the battery holders in parallel by connecting the positive contacts of the battery holders with the red jumper cable and the negative contacts of the battery holders with the black jumper cable:

This time the measured current is 6.72 mA. Shouldn't it be greater than when the battery holders are connected in parallel?


texts:
Why is the reed switch sticking when the magnet is no longer nearby? Only when I tap the switch it releases, otherwise it just sticks for many minutes.
Are there any best practices (do's or don'ts) with reed switches?
Does it matter what magnet you use? Eg. regular versus rare earth.

simulate this circuit – Schematic created using CircuitLab

Did I manage to magnetize the contacts?
Is the current too large (approx 4mA)?

It is one of these and exact part number is unknown.


texts: Can a circuit that shows an error if a 4-bit number is higher than 9 be simplified to "(DC) + (DB)"?

texts:
I need to build a circuit that accepts a 4-bit number and turns on a LED (representing an error) if the given number is higher than 9.

As I understood, it should represent an "error display for a BCD counter". Since a BCD accepts a number of 4 bits (0-15) but it only counts from 0-9, I should turn on a LED that represents the presence of an error on the counter.

So, I followed the steps below:

Built the truth table;
Built the expression based on the truth table;
Built the Karnaugh Map;
Built the simplified expression from the Karnaugh Map;

1. Building the Truth Table

Note: the X column represents the output that shows an error (i.e. the LED)

2. Building the expression based on the Truth Table

So, based on the Truth Table, I got the following expressions:

Note: consider the (!X) as a NOT X

(D)(!C)(B)(!A) + (D)(!C)(B)(A) + (D)(C)(!B)(!A) + (D)(C)(!B)(A) + (D)(C)(B)(!A) + (D)(C)(B)(A)

3. Building the Karnaugh Map

So, as you guys can see, I found two quartets.

4. Building the simplified expression from the Karnaugh Map

As I found two quartets, this is the final expression I found:

(DC) + (DB)

The conclusion and the final question

So, after all these steps, I tried to apply the Truth Table values into my simplified expression (ignoring the A column, as the simplified expression doesn't contain it). It seems to be correct after all.

My question is:

Let's suppose someone get close to me and says:

"I've built a BCD counter. It should only count from 0 to 9. If a number higher than 9 is given, then there is an error. I need YOU to build ANOTHER circuit. I'll give you the 4-bit number that entered on my circuit and then you need to show an error in case this number is higher than 9."

Considering my final expression, (DC) + (DB), should I just ignore the port A, since there is no A in my final simplified expression? Does it mean I can just leave A without being connected to any wire?


texts: Why are MAX-, AD-, LT- parts (among others) so expensive?

texts:
I'm curious why some IC manufacturers like Maxim, Analog Devices, and Linear Tech's parts are so expensive? I know they are much higher quality (better electrical characteristics, etc), but for some parts it still doesn't make sense. For example:

SD Flash Media Controllers (not identical, but to do the same thing)
Maxim MAX14502: $21.69 Mouser
Microchip USB2244: $2.18 Mouser

RS-232 Transceiver (not pin-to-pin identical, but do the same thing)
Maxim MAX3232: $5.92
TI MAX3232: $1.91
ST ST3232: $1.06

Accelerometer. This might be an extreme example. They're a little different, but both are 3-axis, digital accelerometer with the same sensitivity.
Analog Devices ADXL362: $9.73 (!?)
Freescale MMA8653FC: $1.09

And there are tons of more examples.

I'll try to frame the questions so this doesn't become a discussion. As a design engineer why would you want to select a part that is 5 to 10 times more expensive? What could be some technical reasons?

Obviously there are markets that require very high quality components, but is the demand for pricey, quality components even that big? How can the expensive-chip manufacturers compete with others that can make it so much cheaper?


texts: How can I constrain an imported netlist in Vivado?

texts:
I have a pre-compiled netlist (created by Xilinx ISE 14.7), which is imported into Vivado 2015.4 and used in synthesis to assemble my complete design. Vivado reports unconstrained paths for the imported netlist.

According to the Vivado Constraint Guide, Vivado does not apply xdc constraints (Xilinx design constraints) to netlists. This feature will be implemented in the future.
Setting an xcf constraint file (XST constraint file), while synthesizing the netlist with XST does not help. The xcf is read and processed, but is seems that Vivado does not apply annotated/embedded constraints from ngc files.
Storing a ncf files (netlist constraint file) besides the ngc file does not help, because Vivado does not parse ucf style constraint files. (ISE reads ncf files and applies them to netlists, if the have the same name and location as the ngc files.)
I cannot synthesize the netlist with Vivido because there are bugs in Vivado, which prevent me from changing the tool chain.

How can I apply the required timing constrains?

Notes:

I can open the inner netlist in Vivado and see its hierarchy.
I can rerun XST synthesis to recreate the ngc netlist.


texts: Buck-Boost PFC Peak Current in Critical Conduction Mode

texts:
I am considering to use Buck-Boost topology for Power Factor Correction but I'm having trouble finding much literature on it. My appliance is an LED fixture so it will always have a (fairly) constant load (150mA @ 30V). Since the input voltage range is going to be between 100-240 VAC and the output is 30VDC, using a Boost Converter with PFC is a bit unfeasible. I would prefer if the solution is single-stage due to space and cost. I want to avoid using a Flyback topology because at 240VAC input it will place a huge peak    voltage stress on the power switch.

From looking at the waveform (page 10 and 11) of a Boost topology working in Critical Conduction Mode, the peak current is:
$$
I_{pk}=\frac{2\sqrt2 P_{in}}{V_{rms-min}}
$$

My question is, does this result hold for Buck-Boost as well? I feel that it should because it is based on the waveforms and not on the topology. Another way to look at this would be that during \$t_{on}\$, the Buck-Boost and the Boost topology's inductor both have \$V_{in}\$ applied across them.

I am actually not considering the above linked part. I am considering Richtek RT7302. Unfortunately, for this IC, most of the literature is for Flyback topology and not for Buck-Boost - including their Excel Design Tool.


texts:
I was studying negative feedback in voltage amplifiers. I found this on Wikipedia for calculating input resistance as shown below.

Following the similar method, I tried to calculate the output resistance with feedback \$Z_{of}\$.
Connected a voltage source \$V_o\$ which supplies a current \$I_o\$. Applying Kirchoff's voltage law to the output loop, we have
\$V_o = I_oZ_o + A_v.V_{in}\$
For negative feedback, \$V_{in} = V_x - V_f\$ and \$V_f = \beta V_o\$. Therefore
\$V_o = I_oZ_o + A_v.(V_x - \beta V_o)\$
\$V_o = I_oZ_o + A_v.V_x - A_v.\beta V_o\$
\$V_o + A_v.\beta V_o = I_oZ_o + A_v.V_x\$
\$V_o(1 + A_v.\beta) = I_oZ_o + A_v.V_x\$
Dividing both the sides by \$I_o\$, we get
\$Z_{of} = \frac{Z_o}{(1 + A_v.\beta)} + \frac{(A_v.V_x)}{(I_o)(1 + A_v.\beta)}\$
The above expression is what I am getting. But the answer is \$Z_{of} = \frac{Z_o}{(1 + A_v.\beta)}\$. I am getting an extra term \$\frac{(A_v.V_x)}{(I_o)(1 + A_v.\beta)}\$.
What is the mistake in my calculation? Please help.


texts: Differential probe input impedance 1Meg, but 50ohm oscilloscope mode recommended

texts:
I will be experimenting with the Keysight company's N2792A differential probe.
Looking at the datasheet of the probe, the input impedance is 1Meg, but it is said to be used with the 50ohm impedance mode of the scope.
As far as I know, the 50 ohm mode of the scope is used for impedance matching, but the input impedance of the probe is not 50 ohm, so I am curious about the reason for using this mode.


texts:
This may be a loaded question, but is there a general understanding of the performance increase per clock between ARM9 and ARM11? Say, for a math-heavy function (FFT)?

Thanks!


texts: How is this extremely high-resolution stepping achieved?

texts:
This question pertains to this video as well as this one by the same person demonstrating his results with a stepper motor (along with a really neat testing method involving a laser spot on a wall a few meters away!).

How did he achieve this kind of high-resolution stepping behavior of < 0.04° steps (with 1-second holding at each step) on a standard, gearless 1.8° stepper motor?

The person claims to use "sine wave patterns" with Arduino's analogWrite function.

I am familiar with microstepping, but:

how is this done within an Arduino sketch and without some hardware like DRV8825 or L6470?
and how is he able to hold the position so definitely and accurately, something that articles about microstepping usually warn isn't exactly guaranteed?

(Obviously, there is no clear way to measure precision and accuracy here with the videos' limited provided information. However, approximating the wall's flat surface as part of a circle centered on the stepper, we can see that there are very fine steps formed by the laser spot -- as well as a fairly small deviation between expected and observed angle for each step, especially in the 2nd video I linked.)


texts: Minimum distances between box case connectors and PCB surface conductors

texts:
I am working on a few kV PCB design with external voltage connectors (HIGH and GND levels). So user interface connectors are thought to be bananas jacks (they support until 7kV but has soldering terminals).

Now I am searching commercial boxes for packaging the PCB. Providers, that I have consulted, they have boxes with fixed sizes, and they are not much long. Unfortunately I will have exigent area requirements, due components arrays with substantial volumes. So I must face box size limitation and PCB area needs.

The fact or question is that I have found one case that seems to be a solution in terms of long and width. Since we would like to fit bananas on the chasis as you can see at the picture:

I wondered for the minimal distances d1, d2 and d3. Having into account:

Kapton instead solder mask
Conformal coating after soldering
6kV and 0V wires from PCB (from relays) to banana connectors must be soldered but we will use some suggested silicones for this kind of junction (solder).
I doesn't choose the kind of material of the case, but it seems to be available in aluminium or PVC.
Black banana has 0V and red one is i e 6kV (it can be smaller)

If banana will be into the case surface is the distance between:

banana - banana: d2,
banana - bare conductor: d3,
banana - coated connector (terminal block with screws): d1

considered as the same distances on PCB board? in. ex: if clearance between a copper pad at 6 kV and other one at 0V -with a concrete CTI and pollution degree- must be 32mm, could I apply this distance between banana at 6kV - PCB conductor at 0V or banana at 6kV - banana 0V?


texts:
and thanks for bothering with my problem.
I have a two signals A and B that I want to route using several alternative paths via jumpers on my board. In one of the occasions I need to use the same input pin of an IC. Rest assured, when signal A goes to the IC pin, signal B goes to a different place. Please see the image attached:

The trace between the jumper pad and the IC pin is about 24 mm long. My question is, do I need some kind of termination for these traces in order to prevent reflections from the end that is not used at the moment?
The signals are about 3 V in amplitude, with rise/fall time about 0.7 ns, and are between 5 and 15 ns long.
Thanks,
ps. image annotation added


texts:
I am currently working on a microcontroller based system, the issue i am facing is that my inputs pins 40 and 39 of atmega32 are somehow getting internally high, Pin40 shows 2.5 volts and Pin39 shows 5v on my voltmeter. As far as I understand the pins are getting high due to code but I have cross checked several times but still cant figure out the issue with my code.
I am including the circuit diagram and code as well. Can any one please point out how my input pins are showing voltages.

#ifndef F_CPU
#define F_CPU 16000000UL // 16 MHz clock speed
#endif

#define D0 eS_PORTD0
#define D1 eS_PORTD1
#define D2 eS_PORTD2
#define D3 eS_PORTD3
#define D4 eS_PORTD4
#define D5 eS_PORTD5
#define D6 eS_PORTD6
#define D7 eS_PORTD7
#define RS eS_PORTC6
#define EN eS_PORTC7

#include <avr/io.h>
#include <util/delay.h>
#include "lcd.h"

void Init_ADC(void)
{
ADMUX|=(1<<REFS0);
ADMUX&=~((1<<REFS1)|(1<<MUX0)|(1<<MUX1)|(1<<MUX2)|(1<<MUX3)|(1<<MUX4));
// SELECTING CHANNEL0
ADCSRA|=(1<<ADEN)|(1<<ADPS2)|(1<<ADPS0);
// NORMAL CONVERSION WITHOUT INTERRUPT
ADCSRA&=~((1<<ADSC)|(1<<ADATE)|(1<<ADIF)|(1<<ADIE)|(1<<ADPS1));
// CLOCK/32 SPEED
}
unsigned int Read_ADC(uint8_t ch)
{
ADMUX&=0b11111000;
ch=ch&0b00000111;
ADMUX|=ch;
//Start Single Conversion

ADCSRA|= (1<<ADSC);
// Wait for conversion to complete
while(ADCSRA & (1<<ADSC));

// Clear ADIF by writing one to it
//ADCSRA|=(1<<ADIF);

return(ADCW);
}

void Wait()
{
uint8_t i;
for(i=0;i<20;i++)
_delay_loop_2(0);
}

int main(void)
{
int v,v1,v2,vref;
vref = 409;
DDRD = 0xFF;
DDRB = 0xFF;
DDRC = 0xFF;

Init_ADC();
Lcd8_Init();

while(1)
{
    v2 = Read_ADC(1);
    if(v2>=900)
    {
        Lcd8_Set_Cursor(1,1);
        vref = Read_ADC(0);
        Lcd8_Write_String(" Ref. Set");
        _delay_ms(2000);
        Lcd8_Clear();

    }
    else
    {
        Lcd8_Set_Cursor(1,1);

        v1=Read_ADC(0);

        if(v1>=1.05*vref)
        {
            v=0x01;
            Lcd8_Write_String(" HIGH");
        }
        else if(v1<=0.95*vref)
        {
            v=0x01;
            Lcd8_Write_String(" LOW");
        }
        else
        {
            v=0x00;
            Lcd8_Write_String(" OK");
        }
        PORTB=v;
        //Wait();
        _delay_ms(2000);
        Lcd8_Clear();
    }
}

}

Thnks everyone in advance !!


texts: explanation of DC ceiling fan motor and hum and noise

texts:
I asked a while back why does a ~$150 120vac electric ceiling fan, above my bed at home, hum and agitate me.
Didn't come to a 100% solid reason but I believe it's due to that motor being a brushless single phase AC where the windings in the case that surround the rotating armature cause the metal motor case to vibrate as the winding(s) are on/off energized to create a rotating magnetic field.  That force creates a vibration in the thin metal motor case, more so on the slow motor speed setting, that can be heard.  Maybe if it were a thicker metal case and the windings were encased in epoxy it would prevent any audible vibration from happening... but i get it,  unrealistic to mass produce such a thing and sell for $100.
I see DC fan motors now for ceiling fans being advertised, although such a ceiling fan runs $300+.  Not asking what dc motor ceiling fan i should buy... sort of... but can someone elaborate on the physical and electrical vocabulary and operating principles of such a multi-speed DC motor?  I want to have a good understanding to see if I can understand why or why not a vibration may or not be likely with such a motor... expecting them to be mass produced also having a thin metal motor casing.  I believe it's the motor casing that's vibrating when the electric motor is running causing an audible hum, would like to figure out how likely that would be possible in the type of DC motors being used in some ceiling fans now.


texts:
I have a source of power in form of a single impulse (around 40V for a fraction of a second), I need to convert it to a constant 12v for a longer time (like a tenth of a second) to power a small IC. I've searched through the forum with little luck, I thought to use a 555 Monostable but it needs a Vcc that I don't have, what I'd ideally need is something to do both the trigger work and the Vcc. I know it's already been done, I just need to be pointed to the right direction.

Thanks!


texts: Here how can we find steady state error?

texts: Here in the plot shown in attached photo, how can we find steady state error because both blue and orange waves have different amount of error at different time


texts: W5100: get MAC address from devices in network?

texts:
I'm using a single Arduino Ethernet Shield with an Wiznet W5100 chip to scan a network for all devices. (Find the project source code on Github).

All devices are in the same Ethernet segment. They are connected to a standard consumer router. They all were assigned to IP addresses in a range of 10.0.1.0 - 10.0.1.20. The goal is to identify devices in the same network, even if the IP has changed and to protocol when a device is online.

I was researching on this problem for weeks and I have not found anything useful on the Internet. This is the only piece of code I have found so far: http://mbed.org/users/va009039/code/w5200NetIf/file/a8df39b4f3aa/MyNetUdpSocket.cpp, line 124 W5100.readSnDHAR(_socket, mac) but it does not work.

Is it even possible to get a MAC address for a found device (IP is known then) in the same network?


texts: Very quick Question to those familiar with analog multipliers, specifically AD633

texts:
Bit of a basic tech question, but having looked through all the datasheets and also having used AD633 for years now, I am not sure what its 'base unit' is?

What I mean is, I want to now multiply millivolts, not volts as before, should this still work? (I am assuming yes)

So will it treat 60mV*60mV as such thus = 3600mV, which by means of the transfer function is then divided by 10V = so chip output should be 360mV? (Assuming all other pins grounded, using X1 and Y1 as inputs)

Last thing I want is it performing (0.06V*0.06V)/10=0.00036V

If I had time I would build this but components are in transit and existing setup that is using my 633s is working and valuable, so I rather not disturb it.


texts: How do I create a timer interrupt with Arduino?

texts:
I am trying to create a time delay interrupt with Arduino. I would like to use the interrupts() function, because it is an internal interrupt.

Example: Let's say, I would like to make a light blink on and off, with only the timing of the interrupt.

There is sample code, but it uses external interrupts (attachInterrupt()). I would like to remain using the internal interrupts.


texts: Using 38 KHz IR receivers to measure distance

texts: Can I somehow use Vishay's TSOP series IR receivers and IR LEDs to measure the distance from an object? Has anyone done that before or has any idea how one could do it(clever programming or circuitry, maybe?)?


texts: Does the number of ticks change when prescaling a timer of an Arduino

texts:
I am using a 16-bit, 16Mhz ATmega328P microcontroller. I have set the output of the timer to toggle mode. Hence generating a square wave.

my question is, do I still get a maximum of (2^16-1) 65535 when the 16MHz clock has been prescaled by 8 (2MHz)?

I want to know so that I can work out the duty cycle, as the value of OC1A changes.

Thanks!


texts: I need somebody to explain properly how the ground loop works, especially if this happens when is only a DC circuit like a power supply for a motor and a coaxial cable which carries a PAL signal. Because at start I thought that my signal will be very affected but nothing really happend. To be more precise let's say that I have 200m of cable which contains 2 conductor with 1.8 \$ \Omega \$ resistance at 200m and a coaxial cable with inner and outer(shield) conductor. If I tie the shield of coaxial at both ends will my ground loop appears and influence my video signal.


texts: How far away can DDR3 memory be placed from the SoC?

texts:
I thought of an idea where i have a pcb with a soc on it, and a seperate one with the DDR3 memory that can snap into each other.
This way i can replace or debug specefic parts of the system and have e.g. a how swappable soc in my system.
So my question is:
What is the maximum distance i can place DDR3 chips away from the SoC(so it still works) when all traces are length matched between each other?(Using 2,4 and 6 layer boards?)

Thanks


texts: Why is my linear pot is causing a non-linear voltage at my ADC input?

texts:
So I have a socket that connects an expression pedal to a simple input circuit that feeds a voltage to an ADC chip that I then read from a Raspberry PI. I've checked the resistance on the expression pedal and it's definitely linear (as per spec). While I move the pedal back and forth the voltage the ADC reads stays very high for most of the travel and suddenly drops to zero.

This is the circuit at the TRS socket:

When plugged in the expression pedal forms a linear 100k potentiometer between A and D. When unplugged the 3V3 voltage passes from E to D and on to the ADC. This allows the software to know when there is no expression pedal plugged in (assuming values near 3V3 at the ADC). The 150ohm is because the plug is short circuited temporarily when plugged or unplugged and it limits the current (I blew up a Raspberry Pi before putting this in). I don't know if it's enough. But I'm not game to try unplugging in a powered up state yet.

The actually more serious issues is that the voltage the ADC sees is not linear. Despite the variable resistance part being linear. Previously when I've implemented this circuit it has worked as expected. The voltage is proportional with the variable resistance between the tip and ring connections. Do I need to match the 150ohm on the ground side as well?

Or something else?

Edit: I think what I've done wrong is swapped the tip and ring like this:

This is light of the "standard" expression pedal diagram:

I think it might work if I swap them. Will try tonight and update.

Note: Potentially there is another "hidden" resistor between R3 and R1's wiper. But that would be inside the expression pedal. And somewhat unimportant in the grand scheme of things.


texts: I am trying to Reverse Engineering A PCB but I have problem to identify some PCB components(Highlighted components). I don't know whether these are transistors or FETs. As without knowing their actual model number i will not be able to identify their pin configurations.


texts: Are floating point numbers denormalised before the processor performs arithmetic operations on them?

texts:
Does the processor denormalise the numbers in IEEE 754 notation and normalise the result after storing or are the arithmetic operations performed on the numbers as they are?
I'm asking because in case of multiplication, let's say the exponents (denorm.) are e1 and e2. the normalised exponents in, say, single precision would be e1+127 and e2+127, the addition of which will lead to e1+e2+254, whereas what we want the final notation to be is e1+e2+127.
TIA.


texts:
I am trying to decide on what H-bridge driver (for MOSFET) I should pick. I am completely new to this field so I might say something wrong.

So I decided to make a full H-bridge using 4 N-Channel MOSFETs, IRF1405. In order to do this I need an H-bridge driver to turn on the high side.

I found one full H bridge drive IRS2453(1)D(S) that can drive both sides and has internal bootstrap FET.

But I also saw IRS2001, but this is a half bridge driver (so I assume I need to get 2 of these for a full H-bridge driver) and it also requires bootstrap which I'm not sure how to pick which capacitor and diode to use.

So can someone help me choose, or if there is any other alternative I'll gladly hear your suggestion.


texts:
I disassembled some old telephone and mobile phone. Every keypad is different, and yet, all of them have those "spirals" (see the image below) under the button or something similar.

What I don't understand is how those "spirals" can put in contact two ends of a wire. Are they some kind of sensor?

The two ends of a spiral are not connected. My guess is that when the button is pressed, they are short-circuited; however, I don't see how it should happen.


texts: Do current limits apply just the same on lower voltage?

texts:
Do current limits also apply on lower voltage?
For example:
I have a wire/fuse that is rated for 2A. I usually runs it at 10VDC. Then, I use 5VDC with 3A load. Will the fuse blow?


texts:
The design requirement is to generate a +/-12V square wave from a 0-3.3V square wave at 1kHz.

Here is what I came up with:

PILOT_CTL is the 0-3.3V square wave and the end of R6 should be the +/-12V output.

I built the circuit, plugged it in and Q1 promptly blew up. I believe this is because I tied the drains of the NFET and PFET together. Looking at the DMG6601LVT datasheet I can see that the Turn-Off Delay Time for the NFET is 31.2ns while the Turn-On Delay Time for the PFET is only 1.7ns. I think this means I am shorting +12V to -12V for ~30ns through the FET which is enough to make it go up in smoke.

Any suggestions on how to improve the design to avoid this problem?

Followup

I implemented the suggestion of adding resistors to each drain individually like so:

Q1 no longer blows up and a reasonable square wave is produced:

Looking closer however the rise time is nearly 40us

As was mentioned previously, this is due to the gate charge having to dissipate through a 10k resistor. Obviously I could use smaller pullup/pulldown resistors but this will only improve by one order of magnitude before < 1k resistors start burning too much power. Any suggestions? Is a new circuit topology required?


texts:
I'm doing a schematic on OrCAD and when I did the Design Rules Check I got a warning that says:

Checking Electrical Rules
WARNING(ORCAP-1608): Net has no driving source N30274

I have a fairly large circuit that spans three pages, so is there any way that I could search for where the error happened? And what does this warning mean? I don't have any part called N30274.


texts: How can I convert a 2 prong connector to USB?

texts:
I'd like to convert this:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=060-640&utm_source=googleps

to a USB? An ideal solution for me because of cost would be to use an existing usb controller from a usb keyboard. I was hoping someone might help bridge the gap in steps. What is necessary to wire the connector to the usb controller? Any help whatsoever would be much appreciated.


texts: Raspberry Pi UPS circuit review request + improvements

texts:
Based on this question I created the following circuit:
Since I made some (component) changes, first I would like to have a validation of the circuit for long-term usage (and some improvements).

Used components (different from linked circuit):

1N5822 diode
AO3401 P-channel mosfet
3.7V 2600mAh 9.62Wh (protected) Li-Po battery (from another project)
Added a ceramic capacitor and a toggle switch (I hope to the right position)

I made this circuit as a battery backup solution, so 99.9% of the time it will be powered externally, but I don't want the Pi to shutdown when there is a power outage.

Here comes my question #1: do Li-Po or Li-Ion batteries serve long time if I connect them to a TP4056 charger constantly?

Currently I'm testing with a Pi 3b+, but I later want to upgrade to a Pi 4. The circuit works fine when there's external power, but I have issues when I switch to battery powered mode. During boot, the Pi shuts down. If I'm right, the battery protection in the charger module kicks in and saves the battery from over-discharge. When this happens I get no voltage from the out pins. So I made this modification:

So I connected the battery directly to the mosfet, because the battery itself has a protection circuit. With this modification I almost get to the desktop, but a little before that I get a reboot. If I turn off the external power when the Pi is in idle state, the circuit works until I open an app and it reboots.

I don't know the C rating of my battery unfortunately, got it from China. But I have a linear bench power supply. Question #2: Is it safe to connect it to the TP4056 as a battery replacement to test how much current does the boost converter needs in battery mode?

#3: I'm thinking about buying a reliable 18650 Li-Ion battery with a high current rate. Do you think it will solve my problem?

  As an alternative solution I just connected another charger module in parallel like this (with a second battery), but I got weird things happening like they randomly showed 'charging-done' state when they weren't full. After reconnecting the external power they started charging again. So I would stick with one charger/battery if I can.

My question #4: is there a dc-dc boost converter which has higher efficiency than the MT3608 when using batteries? Also I don't really need the adjustable output, and actually that potentiometer looks like a cheap component which is not reliable at all. Just need a stable 5V output.

Thank you for your help and answers!


texts:
A buddy of mine just told me that the set up (linked to the question on Circuit Lab) would be able to handle 500 volts DC, even though each capacitor is rated for 20 volts DC. It was to my understanding that voltage would only add in series. Is he correct, or could the set up only handle 100 volts DC?

simulate this circuit – Schematic created using CircuitLab


texts: Why does the Atmega328 USART get trapped in a loop?

texts:
I have an Atmega328 micrprocessor.
I connected its RX/TX pins to an SIM808 module and uploaded this code to the processor to communicate with it and send commands:
#include <util/delay.h>
#define F_CPU 12000000UL
#include<avr/io.h>

#define USART_BAUDRATE 1200
#define BAUD_PRESCALE (((F_CPU/(USART_BAUDRATE*16UL)))-1)

int main(void){

    // default settings
    char recieved_byte;

    UCSR0B |= (1<<RXEN0)  | (1<<TXEN0);
    UCSR0C |= (1<<UCSZ00) | (1<<UCSZ01);
    UBRR0H  = (BAUD_PRESCALE >> 8);
    UBRR0L  = BAUD_PRESCALE;

    for(;;){
    // wait until a byte is ready to read
    while( ( UCSR0A & ( 1 << RXC0 ) ) == 0 ){}

    // grab the byte from the serial port
    recieved_byte = UDR0;

    // wait until the port is ready to be written to
    while( ( UCSR0A & ( 1 << UDRE0 ) ) == 0 ){}

    // write the byte to the serial port
    UDR0 = recieved_byte;

    _delay_ms(100);
    }
    return 0;   /* never reached */
}

It gets trapped in a loop, for example after typing at in the serial terminal it prints this back and it continuous until restarted:
OK

atOK

OK

atOKatOKatOKatOKatOK

I've a feeling that the code must be changed, but I'm new to this and I couldn't find a simple example.
PS:
I test these:

I've used an Arduino instead of a bare processor.  It works fine sending and receiving commands, so the SIM module is fine.

I've disconnected the SIM module and the echo program works well.

I've removed the echo part (I think) UDR0 = recieved_byte; but no luck.

Update 1:
I realized that the SIM808 works fine with an Arduino and/or other USB to serial if one connects RX to RX and TX to TX, it must be crossed inside the module.  It doesn't help if I use this code and a bareare AVR MCU and it only echos back commands which the MCU gets, not the response from SIM module.


texts: Could a PC consume more power from the plug if it oparates in a colder enviroment?

texts:
I have a mining rig (computer using its processing power to calculate hashes in order to eventually be rewarded with cryptocurrency tokens.)
The program I use to mine tells me each time the power consumption of my hardware (basically only the graphics card power consumption) which is around 900 watt stable (it measures it every few seconds.)
I also have a meter which shows me the total power consumption drawing from the mains/plug.
I noted the following discrepancies (or at least I found them to be.)
While my hardware is under the same load (99% +-1%) constantly and my mining program displays the same power consumption (900 watts) independently of the outside temperature while the meter on the plug when it is a warm day shows around 980 watts consumption but at night when it is cold (I keep my rig in a shed thinking that cold would do good in terms of stability and maintaing low component temperatures while under load) the meter on the plug shows more than 1080 watt usage.
Is there something in the circuitry of the meter that could mess with measurements because of low room temperature or do electronics (be it my computer's powersupply or my graphics cards) consumer more energy while operating on low room temperatures?
Note that the mining program power draw measurements are relatively accurate because either in cold or in warm weather if I increase the power consumption of the cards it shows an increased value while the meter on the plug also shows a somewhat proportionally increased value.
EDIT: By cold weather I mean about -5 to 5 degrees C and by warm anything above 12ish degrees.


texts:
I was musing about electric motors after seeing one randomly on TV, and there's something I'm must be remembering incorrectly.

It's just a thought experiment, so I'm imagining some theoretical DC electric motor, with a constant RMS current/voltage feeding in, and some constant load on it causing it to spin at some constant rpm and produce some constant torque.

Since voltage x current = electrical power = motor's mechanical power, that's the cap on how much you can get out of the machine.

But I remember that the greater the difference in rotational speeds between the rotor and stator fields (slip?), the more force/torque will be exerted on the rotor.

So in the hypothetical, if the motor is doing its thing and is stable with the load, if you suddenly increased the frequency of the input voltage/current, that in my mind would result in suddenly increasing the difference in relative rotational speeds of the stator/rotor, meaning the stator would feel more force/torque on it, which would make it want to speed up and catch up to the stator field, speeding up the load.

But only frequency changed and not how much electrical energy is entering the device, so there's no way that's possible! So I MUST be wrong, I just don't see where the error in my thinking is...

What's wrong with my thinking, and what would actually happen if you increased the frequency like that?

(I'm not an electrical person by trade, so there's a limit to my knowledge of concepts/terminology.)

[EDIT: I failed to mention that by "frequency", I'm referring to how DC motors can be controlled with pulse width modulation, and those pulses go in at some frequency. Otherwise it wouldn't make sense to talk about "frequency" with direct motors]


texts: Driving mosfet in battery balancing circuit by an mcu

texts:
I'm trying to make a simple passive battery balancing circuit using logic level n-mosfet driven by MCU. However, I've got some issue on how to drive the mosfets by the digital output of the mcu, and also having isolation between mcu ground and the source legs of the mosfet. Otherwise, in the case of the following circuit, the 2nd battery would be short circuited.

Looking forward to hear your thoughts or maybe another alternative to drive the mosfet. I was thinking to use optocoupler, but then I need another isolated supply. Thanks


texts:
I'm trying to program my school learning board with PIC16F88 on Ubuntu. I installed sdcc and picpgm.

PIC16F88 already has bootloader so I intended to compile C code in to HEX with sdcc and then upload it with picpgm. We used microC's microBootloader tool in school.

So I tried to compile first and got to the first problem: when I call

$ sdcc -mpic16f88 lucke.c

I got:

at 1: error 131: cannot generate code for target 'pic16f88'

Did I think in the right direction at all? This is my first time with programming chips.


texts: How to recreate square waves over wireless in 'real time'

texts:
I currently work with a product that is designed to capture data from three simple digital sensors and perform some calculations based on the outputs.

The sensors produce square waves (with different mark-space ratios) with frequencies from 1Hz to 100KHz.

The first iteration of the product was easy, it was wired, so was a simple matter of feeding the signals to a micro-controller and triggering interrupts.

The second iteration was a wireless solution where each signal had its frequency averaged over a short period, then sent via an XBee module, before finally reconstituting the averaged frequency at the other end.
This solution works OK when the signal frequencies don't change, but understandably has accuracy issues when they do.

So my question is; how can I recreate my three digital signals over wireless as close to real time as possible?

I have a couple of initial thoughts of things that 'might' work, but some more expert knowledge/guidance would be appreciated.

Sending some sort of time synchronisation message, and transmitting only time stamp data at a high data rate.
Using a low precision (4-bit?), high speed ADC to capture the signal, and then streaming the data continuously over wireless, and then using a DAC to convert this back to a signal again at the other end.


texts: AVR Assembly - Operations with two 8-bit registers in 16-bit two complement negative values

texts:
I have this code in which I try to multiply the given number by 4. I have two variants and that is that it is negative and positive, but it doesn't work for negative values, you don't know why?
.org 0
start:
    ldi r16, -120
    ;(r21:r16)

    ;WORK WITH  -
    cpi r16,0
    brge zaporny
    ldi r21, 0xFF
    ;r16*4
    lsl r16
    ;kontrola overflow
    BRVC over
    dec r21
    over:
    lsl r21
    lsl r16
    BRVC over1
    dec r21
    over1:
    zaporny:


texts:
How do I find the second-order differential equation, in terms of \$i(t)\$?

At time \$t>0\$, the voltage source will be gone, and I will have a parallel \$RLC\$. I am having problems with finding the equation because I used nodal analysis, and now I have an equation in terms of \$v(t)\$ instead of \$i(t)\$. What would be the equation?
How do I get this equation?

Further, I just want to confirm. At \$t\$ is in \$\infty\$, and there is a circuit, the circuit will be in steady state, and the capacitor will be in open circuit, and the inductor will be short circuit. Is it?


texts: Why is PWM used to control DC motor speed instead of using a variable resistance?

texts: My question is at the end (to change the speed) we are controlling the input voltage of a DC motor in both PWM (pulse width modulation) and variable resistance cases. Is the only reason for choosing PWM to obtain a better precision or not consuming extra power? If it is the only reason it seems odd to use PWM equipment for simple demonstrations.


texts:
Recently I've been trying to understand how multiple signals can travel along a coax cable. Indeed, I have already read "How are multiple signals propagated in a coaxial cable?", but it doesn't seem to be exactly the same question, nor is it specific enough, so please don't mark this as a dupe.

So how exactly are multiple signals transmitted on different frequencies? For example, I'd like to send data between two devices using a 50-Ohm cable, and I have a 7MHz carrier and a 11MHz carrier. Do I simply couple the signals to the cable using 50-Ohm resistors? Or capacitors? Transformers? Or some kind of push-pull line driver?

In addition, what are the typical voltage levels for coax? I can only find maximum ratings. If I were to design a device

Finally, how are signals sent bidirectionally? I suppose I could implement an EIA RS-232 or RS-422 where I could simply send binary data as negative and positive signals. However, I'd imagine that it would only suffice for sending data in one direction. If the two devices is is trying to exchange data, and one device is trying to output +1V while the other device is trying to send -1V back, won't there be some sort of contention, so to speak? I could do an I2C and have the "master" device coordinate the whole thing to send signals both ways, but I really want to do it the right way and send RF signals.

Thanks for your help.


texts: Measuring AC and DC earth ground referenced signals

texts:
I'm working on a product that will have several STPM32 metering ICs measuring voltage/current/power/energy consumption of  several relay-controlled circuits.  I am designing such that the relay and analog front end of the measuring IC can control/measure either a 0-40 V DC or a 230 Vrms AC source.

The DC source is either a battery bank and the AC source is an inverter.  The measuring IC is configured to measure the differential voltage across a shunt resistor located on the PCB as well as the differential voltage between the DC + or AC "hot" wire and a yet-to-be-determined reference point.

I am trying to figure out how to implement a grounding scheme between the analog front ends of the measuring ICs, and the voltage sources to be controlled/dispatched.

I've taken a crack at drawing a couple of rough schematics of what I'm talking about.

simulate this circuit – Schematic created using CircuitLab

The 1st schematic shows two channels (hence 2 metering ICs).  The first channel I have drawn showing the inverter connected (230 Vrms source), with another 12 V source shown as an available alternative (by switching SW1 and SW2).  This is intended for illustration purposes only (to really knock home that it could be a DC source feeding channel 1 just as easily as an AC source).  There is also a 24 V DC source that is feeding the 2nd channel at the bottom of the schematic.  The problem with this topology is that the voltages on the input pins to the metering IC will go above the max of 0.3V.  Another problem with this setup is that if the neutral wire gets unplugged while the relay is closed, the metering IC will get 230 Vrms on its I+, I-, and V- pins.

simulate this circuit

This 2nd schematic shows my original idea.  I was originally just going to tie all the grounds of the channels together on the PCB.  This works in terms of keeping the voltages on the metering IC pins within spec, but then I realized that the GFCI of the inverter would trip due to some current returning to the inverter via ground instead of via its neutral conductor.  Other than that it seems to be a good design.

If I simply switch to an inverter without a GFCI on its output, can I proceed and just tie all the grounds together on the PCB as shown in the second schematic (i.e. tie neutral to earth ground on the PCB?).

I'm starting to think that the only viable option is to have each channel galvanically isolated from the other channels.  That way, I can "float" each measuring IC to the neutral/DC- voltage, ensure that none of the pins will go above 0.3V (if neutral gets unplugged while relay is closed, the local metering IC ground will simply float up to 230 Vrms), and all the while ensure that all the current from the AC source returns via the neutral line.


texts: What are those wire terminals that mate with standard header pins?

texts:
I have purchased "dupont" connectors on Ebay that crimp onto a wire. They look like this:

http://www.hansenhobbies.com/products/connectors/pt1inconnectors/pt1in_ft/

I'm tired of waiting weeks for these things to ship from China so I would like to purchase these from Mouser but I don't know what they're called or how to identify them on mouser's website. They are the standard rectangular wire terminal that is normally used to slip into a 2.54mm housing but I just use them without the housing because then slip snugly only standard header pins. Can someone tell me how to find these on Mouser?

EDIT

I just wanted to follow up on this because, as stated by The Photon, there are different varieties of contacts that are IMO quite significant.

(source: ioplex.com)

Regarding the above image:

On the left is a "dupont" connector from China via Ebay. Its contacts are slim and form a sleeve that holds header pin squarely. This limits wobble to one axis.

On the right is TE Connectivity 1-104480-2. Its contacts pinch the pin with two fingers. This allows wobble on both axis. And I can guess that the surface area of contact is less. It also has a spur that useless and potentially annoying when used without a housing.

So unfortunately I still have not successfully identified the correct part and as such I have reset this question as unanswered.


texts: varable speed on a 4.5v-12v dc hobby motor

texts:
How can I vary the speed of a 4.5v-12v dc hobby motor?

This motor will run a set of conveyors to simulate a steel mill operation. The motor has small gears to run the conveyor, but i need to be able to slow it down so the school kids so not go wild with it.

I would like a slider type of control as i am using hoppy syringes with colored water to move the slide, this will act like hydraulic cylinders and at the end of the 4 conveyors the little blocks on the conveyor will fall into a bin and raise a gate to let the oxobot out and travel around.

I am not very good with elec. circuits, very good in hydraulics and pneumatics. Any help in this matter would be greatly appreciated. Thanks


texts: Replace BSS138 with AO3400A in level shifter circuit

texts:
I have to use level shifter circuit to interface MAX31855 with Arduino running on 5V.

I found easy to build level shifter circuit at SparkFun website. It is using BSS138 (datasheet) which I don't have. I am thinking to build same circuit with AO3400A (datasheet), which I already ordered last week for a pack of 100, so I hope to receive it by next few days.

My question is whether it will be completely OK to replace BSS138 with AO3400A in this particular circuit?

As per both datasheet, I think AO3400A is much much better in terms of \$R_{DS(ON)}\$. \$V_{GS(th)}\$ is also good for AO3400A. \$Q_g\$ is just slightly higher on AO3400A. (These are the parameters I usually compare to choose MOSFETs).

I am asking this because I don't have yet AO3400A to test. If AO3400A is wrong here, then I can order BSS138 soon. However, I don't think I will find any other use for BSS138, particularly because of its large \$R_{DS(ON)}\$ (datasheet says it is extremely low \$R_{DS(ON)}\$ !!) and low drain current capability.


texts: Calculating battery time giving its capacity and load

texts:
I am referring to the airplane shown here.
The battery is said to have 640 Whr capacity (actually this is the discharge rate), the load being a 2700 W motor. Then the endurance is giving as 110 minutes. Neglecting any other effects and focusing on the battery-engine, how is the battery time calculated?
I guess one can't know without knowing the battery's capacity in Coulomb.


texts: "31WOC" on a boost converter, but what datasheet goes with it?

texts:
Long shot, I know...

I have this Boost convert 1-5V in out 5.1-5.2V and I hope to modify it for a different output voltage.

So I'm trying to identify and find the datasheet for the main chip.

I think the chip reads 31WOC, but I can't find a datasheet for that number. Anyone familiar what the type is of the chip?

There is no more datasheet than the following:

IN 1-5V
OUT 5.1-5.2
Current: Rated 600mA (single lithium input), the maximum 700mA (single lithium input)

€ 1,50


texts: How to move objects within given distance using DC motor precisely?

texts:
I would like to get an idea how to control DC motor precisely. (i.e. deliver an object in a 100% right position) and I am not writing for the mathematical equations)

I am planning to make printer head which rotates left-right using DC motor but when I designed it, the following issue arose in my head:

I have thought that

  after the calculation and moving head using DC motor,
     can I 100% guarantee the accuracy of the distance?
  (from 1) if it is not accurate, it would need side components to verify its distance. How things like printer verify the distance?

I tried to search relevant information to analyze the issue, but could not find much about it.


texts:
I know Collector current formulae ic=(vcc- vce)/ R.
In above circuit
vcc = 5v
vce= 0.25v(from datasheet).
how can i decide value of R(load).


texts: I have just prepared a new template for Altium Designer schematics. I included an image to template. My question is that if i prepare a project with this template, how can i embed this image when i need to send another person? Because after i sent a project with my new template, i realized that the template image could not be seen on an another computer (It wrote on template as "Cannot open file C:...) I have some examples which are embedded for these situations however i don't know how i can do. This photo shows when i sent to another computer:


texts:
I have an RF amplifier (GHz), 50W. Power source 28V. Please tell me how do they calculate output power? I know only 1 method: V^2/r.

So, if I try 28^2/50 I got 15W. But its 50W. Another words, if I have 50W and 50 Ohm load, I need amplitude about 50V. But the power source only 28V.
How is it possible?


texts:
let's consider this image (from AAC book, see here)

The author wanted to show that a transmission line propagates not only voltage and current waves, but also an electromagnetic wave in the space between its 2 conductors.

But I have a question: from the image I think that the magnetic field shown is that generated by the wire, but how is the electric field? From the image I do not see its direction, if it is rotational or not, and I do not understand if it is the electric field generated by the voltage applied to the transmission line (since voltage between two points = electric field) or the electric field generated by the variation in time of the magnetic field represented in green.


texts:
I live in a area with frequent power failures lasting up to 5 hours. During this time I would like to power my router so that I can still use the internet with my phone/PC.

I've looked at UPS solutions, but they are quite expensive and not very efficient. I've decided that I want to build my own battery backup solution that uses a 12V 7 AH AGM sealed lead acid battery to directly power the router when the power is off (my router requires 12V DC)

The question is how do I charge the battery while there is mains power and how do I then seamlessly switch to battery power when the mains power fail.

I'll first need a charging circuit. Can I create a simple charging circuit using a regulator such as the LM317 of L200C or should I go for something more advanced such as TI's UC2906? Or what's the recommend way a charging one of those batteries? I assume I'll also need a small transformer and rectifier circuit to power the charging circuit. I would also like to see the battery's remaining capacity and an indicator to show that it is fully charged. Not sure of any of these options will make it easier?

Next, how do I set it up so that the battery goes from charge mode to supply mode when the power goes out? Can I simply connect the battery to the router and that way the charger both charges the battery and powers the router? Then when the power goes off the battery powers the router. Or would I need a switching circuit that senses when the power is off and switches to battery power (through a relay or some other means)?

Lastly, does the output of the battery need to go through a regulator to ensure it is exactly 12V or can I connect it directly to the router?

I've found this product, but I think I can make it my own battery backup for under $30 (plus it's a lot more fun)


texts: How diodes protect H-bridge DC motor driver?

texts:
I don't really understand how these diodes in this circuit and similar circuits (like driving a relay circuit) protects the controller circuit from the energy stored by the inductance of the coil.
I really appreciate if someone could graphically explain it. ( I mean how the the diodes block the current and etc)

the second question about this circuit is the capacitor. what happens if it isn't there?


texts: Square Wave (w / Pulse Missing) Generation

texts:
this is probably a simple one for anyone with some electronics design experience (which I do not have). Can anyone tell me how to build a simple circuit which generates a square wave but has every nth pulse suppressed? So, to put some (example) numbers to it, the wave form could be described as such: Three 1 µs-wide positive pulses at 5 ms intervals (i.e. 200 Hz) every 20 ms. So, this example indicates that every 4th pulse should be suppressed.

Thanks much in advance!


texts: How can I make the Raspberry Pi and BeagleBone Black talk via serial?

texts:
The BeagleBone Black is great.  You plug in the USB cable to your computer and a DHCP connection is established, allowing you to ssh to the BeagleBone in seconds.  Unfortunately the Raspberry Pi takes a bit more, and I am in the process of setting it up.  I was able to download the raspbian.img to an SD card using my BeagleBone Black using the dd command through the terminal.

Now I have an SD card that should allow the Raspberry Pi to boot into linux, but I have no HDMI cable or monitor, or keyboard to do this.

As I understand it is possible to reach the Raspberry Pi's command line through serial communication.  See here.  Typically people are doing this using a USB cable with an FTDI USB-Serial chip embedded in it (sold by Adafruit and others).

Is it possible to connect from the BeagleBone Black to the Raspberry Pi's command line through serial communication (such that I can connect to my BeagleBone Black via ssh from my laptop, and then connect to the Raspberry Pi through serial from the BeagleBone Black)?

As I understand there are only 3 pins required - TxD, RxD, and GND.

Unfortunately I see that the Raspberry Pi uses 3.3V logic, and as I understand the BeagleBone Black uses 5V.   This means some sort of level shifter circuit should be used.

With the level shifter circuit in place, would it then be straightforward to establish a serial communication between these two boards?

Or should I go with ethernet to connect them and look into setting up DHCP for communication?


texts: How do I calculate the resistor value for a simple LED circuit?

texts:
I have a simple circuit:

The max rating (current) of the LED is 30mA.

How can I work out what the resistance of the resistor needs to be? By using ohm's law I found it to be \$3V/0.03A = 100 \Omega\$. However using software called Yenka, and trial and error I got the minimum possible resistance to be 36Ω. However, if I use a 35Ω resistor, then the LED breaks. Is the software wrong, or (more likely) am I doing something wrong?


texts: Safety considerations in Android Wear products using high resistance electrodes

texts:
I am wondering how wristlet devices can safely measure a person's heartbeat without risk of electric shock. It seems everywhere I read, the threat of static discharge would be far greater with an electronic wristband. Isn't the "shortest route to earth" always through a person's body in this situation? The wristband and its internal battery ultimately are only connected by a person's body to real earth ground.

In the event of static discharge, thousands of volts are likely applied over some resistance in the watch - what guarantees, extra safety checks, and calculations are done to make sure this resistance is correct i.e. there isn't a short that goes through a person? Am I correct that the short case would ultimately go through whatever skin-contact electrode (lower resistance than the packaging) was being used to pick up the heartbeat signal from the wrist? Would these risks be mitigated using a high-resistance/high-impedance recording electrode?

For example, if discharge voltage were 1000V and deadly current were 1mA, a design with a factor of safety of only 1 would use recording electrodes with a resistance of 1 MOhm to avert deadly discharge. Real life you'd probably use 100 MOhm for safety?


texts: How do battery chargers deal with variations between cells?

texts:
Some battery types, like lithium-ion are sensitive to over-voltage or over-charging. How do chargers deal the differences between cells?

For example, a lithium-ion cell is 4V, so a 12V battery I guess will have sets of 3 cells arranged in series. The problem arises what if two cells are charged but the third cell is lagging behind? If the charger is applying 12V and two cells are full, but the third is low, then it could lead to an overcharge situation developing. How does the charger detect and deal with this?


texts: Why in some Communication Protocols the Wires are twisted?

texts: I think in some Communication Protocols it is sometimes recommended to twist the signal wires. Why and in which Protocols or Applications?


texts:
I have understood how the envelope detector works, but I am unable to find the formula for R and C appropriate values. The closest I have found is this link:
Explain The Square Law Demodulation and Envelope Demodulation of AM Wave
Any help?


texts: How is this EEG circuit amplifying and filtering input correctly?

texts:
Several weeks ago I posted several|questions about a DIY EEG reader that I found on Instructables. To my surprise, it appears to actually be a fairly well-designed circuit.

The main stages of this circuit are as follows:

Instrumentation Amplifier
60 Hz Notch Filter #1
7 Hz High Pass Filter
31 Hz Low Pass Filter
1 Hz High Pass Filter
60 Hz Notch Filter #2

In addition, the members of this community added some additional recommendations, such as:

Use an ADC early on
Implement an Op Amp

I was planning on building this EEG reader, including the above suggestions from this community, until I stumbled across a most-awesome Kickstarter for an open source EEG reader called OpenBCI. And so I am now strongly considering doing all of my R&D/proof-of-concepting with OpenBCI instead of my own DIY EEG. However, I want to make sure OpenBCI is of the same quality (if not better) as the DIY EEG mentioned above (including the recommended tweaks from this community).

Here is the open source circuit design for the OpenBCI board:

On one hand, I believe I see:

Instrumentation Amplifier
High Pass Filters

But on the other hand, I am not seeing:

Notch Filters
Op Amps
An ADC

And so, all this to ask: Am I missing something here, or is the OpenBCI design not of the same level of quality of the DIY EEG that I found (plus the tweaks recommended by this community). Or, is the OpenBCI design taking a different approach that will still yield the same "quality" (accurate bioelectrical wave measurements, granularity, noise reduction, etc.) in the end?


texts: Can this RAM bypass be prevented by making the particular memory controller "not idle"?

texts:
AbsoluteƵERØ showed me that memory can be bypassed at the memory controller.  https://security.stackexchange.com/questions/36592/can-linux-be-made-to-detect-foreign-connections-to-the-ram-bus

by showing me this patent: http://www.google.com/patents/US6745308

In the Abstract of the article, it says

  If particular memory controller components are idle, a memory client
  is informed that a bypassing of memory controller components is
  possible.

Does that mean that there can't be a bypass if the particular memory controller components aren't idle?  (More quotes on "idleness" below)

If so, how can a memory controller be kept from an "idle" state?

Idleness Quotes

  Only components that are idle or have no other memory requests to process may be bypassed.

  The method as in claim 1, wherein the step of providing, to the client, the signal indicating the state of the memory controller
  includes providing a signal indicating a level of idleness associated
  with the memory controller pipeline.

  The method as in claim 5, wherein determining a level of idleness
  associated with the memory controller pipeline includes analyzing
  memory request queues of a first component and a second component are
  empty.

  A system comprising:providing the memory access request to a bypass
  module when the signal indicates the first component is idle;

  Only components that are idle or have no other memory requests to
  process may be bypassed.

  At least one embodiment of the present invention provides for a method
  of bypassing memory controller components. The method includes
  receiving a first memory request to read data from memory. In one
  embodiment, a bus interface unit receives the first memory request.
  The first memory request may be associated with a cache fetch request.
  The method includes determining if a first component and a second
  component of a memory controller are idle. The first component is a
  Northbridge client interface used to organize received memory
  requests. The second component is a Northbridge arbiter used to
  arbitrate, or select, requests from different clients, allowing
  received requests from all the clients to be processed. The result of
  determining if the first and second components are idle is provided as
  a signal to the host bus interface unit. The method also includes
  providing the first memory request to the first component, when the
  first component and the second component are busy. The method also
  includes determining, in the memory controller, if the first memory
  request is valid for access by bypassing the second component. In one
  embodiment the second component is used to generate commands to open
  closed pages of memory. If the memory request needs to access a closed
  page of memory, the memory request is considered invalid. The method
  also includes enabling the first memory request to be accessed by the
  second component, when the first memory request is considered invalid
  for bypass operations. The method further includes enabling the first
  memory request to be accessed by bypassing the first and second
  components, when the first memory request is considered valid.

with many more.


texts: Read and write values in Multidimensional arrays in verilog

texts:
How can we read and write values in a multidimensional array in verilog, i had read in this link regarding different operations that can be done on multidimensional array.
like if there is a part of code like this

input [15:0] me;

reg [15:0] p_array [7:0];
reg abc_pqr [2:0];

abc_pqr[0] <= me[0];
abc_pqr[1] <= me[1];
abc_pqr[2] <= me[1];
p_array[abc_pqr[0]] <= me[0];
p_array[abc_pqr[1]] <= me[1];
p_array[abc_pqr[2]] <= me[2];

so is this code will work and will not produce any error?

What is the difference between these two while assigning value

"<=" and "=", i had seen "<=" in most of the places during passing values.


texts: Designing a linear regulated dual-rail power supply

texts:
I'm building a dual-rail power supply and need to drop about 5-10 V from the rectification output. It's for powering an amp so I need low noise and about 2A therefore I opted for linear regulators. Most schematics online use a positive and negative regulator for each rail, but I was wondering if my circuit below would work using the same regulator, one on the positive rail and one on ground.

Simulating it shows the correct output voltages, but what are the drawbacks to this design vs using a negative voltage regulator for the negative rail? Does it have power or stability issues/ there must be a reason designs keep using negative regulators.

simulate this circuit – Schematic created using CircuitLab


texts: Theoretical rechargeable battery capacity question

texts:
I have very little energy usage/storage knowledge but my question will hopefully prove to be a simple one.

If I have a 120 volt appliance that uses roughly 0.50 kWh a day and 600 watts at peak draw, is there a reasonably sized rechargeable battery (think large laptop) that could, in theory, supply this for 18 hours and be adequately recharged nightly.

Thanks in advance for any insight....


texts:
With the amazing amount of devices available to anyone, each one usually comes with it's own power requirements!

Right at this moment, on my work table i have these adapters which I have at arms length for various things (and many more which I shall not list):

9v dc 500ma (Arduino)
12v dc 1a
5v dc 700ma
5v dc 2a

How can I simplify my DC power requirements? Does a device exist where it's a power supply and can output any combination of voltage and current? And also have flexible adapter plugs?


texts: Kicad - Module refernces are being rendered, but don't show up on gerber plots

texts:
I am working on an open source design. I can view all the layers in PCBNew. The module references show up on the screen. They are visible even when I deselect Front Silk Screen (F.SilkS) in the layers menu. Under the "Render" tab, I have to select all three: "Text Front", "Modules Front" and "References" to see these values.

However, when I plot the Silk Screen, the values do not show up in the Gerber files. I have selected "Plot module values on silkscreen", "Plot module references on silkscreen" and "Plot other module texts on silkscreen". Still, they don't show up on the SilkScreen Gerber Files. I am viewing the gerber files with GerbV.

How can I make the module references appear on the Silk Screen gerber output?

Update: The Kicad project is available here: https://github.com/bkkcoins/klondike/tree/master/kicad


texts: What is the function of this diode in arduino uno(between +5V and reset)

texts:
I am doing my own avr dev board using atmege32a and basically I am looking into Arduino uno board design and try to mimic the common parts for best practices
like for example power and other stuff

I have noticed that there is a diode between the +5V rail and the reset pin and also the 10K resistor.

The resistor is for the pull-up that is obvious, but I do not understand what this diode doing in this place ?

EDIT

I have added the whole schematic from arduino website

https://www.arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf


texts: How to have a load pull more current from a low voltage high current battery

texts:
I am designing a pair of heated pants and have run into an issue with having to use batteries (or any other portable power source) to power them.

What I have now is about 50ft of Teflon wire with 5Ω resistance. The wire is 30AWG PTFE W-16878 Stranded wire rated for 600 volts.

For the power source, I have two of these 1.2 V 3.1AH batteries As they were the best option for a high current battery that can also handle higher temperatures.

The issue is with the two batteries in series they only provide 2.73V so when I connect the wire to the batteries it only pulls 0.546 amps which is not even enough to produce a noticeable change in temperature. Ideally the power draw should probably be around 30 - 60 watts but is subject to change based on how much heat the wiring actually ends up producing.

My first thought was to use an op amp and create a current to voltage converter, but there is the issue of if the op amp can handle the current I put in, and if it can continue operating when the circuit gets heated as the pants are heated. To be safe, any circuit made for the pants will use the same teflon wiring so I can avoid any wires burning up.

However, there is likely another easier solution that I am missing which is why I am posting here. I have tried researching battery powered motors to see if they might use circuitry that may help solve this issue, but had no luck finding anything useful.

Also please keep in mind that any solutions need to be reasonably portable as these pants will be used all winter.

Edit: The specifications for the wire is MIL-W-16878/4 Type E Stranded Wire with a temperature rating of: -55°C to +200°C. I can't seem to find a specific current rating.

Also as stated here: "M16878/4 is used in high temperature electronic applications M16878/4 has excellent thermal aging, solder damage, flame, and moisture resistance." Which is why I choose this specific type of wire.


texts:
I've see a number of terms that make reference to the word "bias". I've read the wikipedia article but I'm after are more practical answer.

Some examples of what a forward or reverse biased device is would also be well received.


texts: How do I connect this microphone to an ADC?

texts:
I have this component http://docs-europe.electrocomponents.com/webdocs/0f2a/0900766b80f2a57c.pdf. It is not clear to me what type of circuit I need to use to amplify the signal from this microphone and then convert it using an ADC.

I have a few of them, I measured their resistance using my multimeter, they show a resistance of about 1k ohm. On the underside of the microphone there seems to be some sort of SMD component (either resistor or capacitor) that bridges the metal part of the two terminals of the microphone. What purpose could this serve?


texts: MOSFET Drain - Source overvoltage protection

texts:
I am developing project of MOSFET switch that is going to be used as power switch device in application with 12S li ion battery. To keep power wastes in the minimum level, I have to provide the lowest possible RDSon value. In that application, the maximum voltage of battery will be at the level of 50.4V, so I've decided to use 60V MOSFETs. I really dont want to use 80V ones, as we know, the higher VDS breakdown voltage is - the more RDSon the MOSFET will have. But I am not sure, if this MOSFET will sustain any unpredicted, induced peaks of voltage (there is also BLDC motor on that power rail).
My question: Am I able to protect this 60V MOSFETs from unpredicted, induced overvoltage breakdown peaks?
Edit: Okay, I will ask in another way - Am I able to specify the value of overvoltage peaks from BLDC motor when I am disconnecting circuit in, lets say, 200A of load? Is the BLDC motor driver protected from that kind of problem - disconnecting power in full load?
Edit: Pseude electrical schematic:


texts: Why aren't current CPUs designed for more powerful cooling systems?

texts:
Chips on the present can't get smaller, higher speeds and voltages increase heating, so why don't CPU manufacturers aim for more powerful cooling systems instead of looking for parallelization?
We are stuck with a heat sink and a fan since I can remember and yet we have water cooling, heat exchangers and all sort of stuff for cooling computers that are still on the only realm of gaming computers.
Moving this thought forward, if dew point is a problem for moisture why don't we move to anhydrous environments like immersion systems or anhydrous sealed enclousures and then go sub zero?


texts:
This is more of a C logic query, but since the underlying issue is hardware, I posted it here. The code snippet is from Mr.Jack Ganssle's page on debouncing.
I was reading this code snippet:

Suppose I embed the code in a 1ms timer ISR, what would be the debounce time? Is it a determinate value?


texts: .elf or .bin file to be download as application code in ARM cortex M4

texts:
I am using a MCU with ARM Cortex M4 processor.
I Have written a bootloader on it.
Using USB CDC ACM class, i am writting the application code in memory address 0x002000.
I have generated both .elf and .bin files of the application code which i want to run through this bootloader.
Which file is required to be write in memory from bootloader?.elf or .bin?
I have generated both .elf and .bin.


texts:
The full wave bridge rectifier shown provides a DC output voltage of +/- 15 volts on which 1V peak to peak ripple is allowed. The supply should be capable of providing 1A DC current to its load resistor R find:

The required rms voltage that must apear across the transformer
The required value of C and R
The average DC current
The peak DC current through the diode

I don't get what is the relation between the DC output voltage and Vs in another word how can I get benefit from +/- 15 volt to calculate Vs?

Also (Vpeak = Vo + Vr) according to this law can I consider the Vo as 15 and Vr as 1? Is the ripple voltage value in this law for peak to peak or I have to regard it as 0.5? And what about the current of 1A, is it the average DC current?


texts: RN-42 Bluetooth - Can't use data mode with Tera Term

texts:
I just got the RN-42, and I am using a simple set-up where I just power the chip, and short-circuit the UART Rx and Tx pins, hoping that whatever I send from my "Tera Term" terminal will be returned back to me. But no..

The thing is that I can enter 'Command Mode', so I am certain that I can connect to the module, but then, when I exit Command mode (and presumably enter Data mode), I type characters in and nothing gets returned.

Furthermore, I tried opening a second terminal window, for the other port created by the bluetooth connection, but still, no data going back or forth (even though I am certain that by short-circuiting the Tx and Rx Pins, data should be displayed on the first terminal).

Oh yeah, and I also tied together the CTS and RTS pins just in case, but still, no results.

Any ideas?

Thanks!

Here are the module's settings as retrieved using the D, E, and O commands:

***Settings***
BTA=000666639EDE
BTName=RNBT-9EDE
Baudrt(SW4)=115K
Mode  =Slav
Authen=1
PinCod=1234
Bonded=0
Rem=NONE SET
***ADVANCED Settings***
SrvName= SPP
SrvClass=0000
DevClass=1F00
InqWindw=0100
PagWindw=0100
CfgTimer=255
StatuStr=NULL
HidFlags=200
DTRtimer=8
KeySwapr=0
***OTHER Settings***
Profile= SPP
CfgChar= $
SniffEna=0
LowPower=0
TX Power=0
IOPorts= 0
IOValues=0
Sleeptmr=0
DebugMod=0
RoleSwch=0
Ver 6.15 04/26/2013
(c) Roving Networks


texts: How does this part of the schematic control the torque?

texts: This is a part of the schematic for a chinese built TB6600 stepper driver. The TQ pin (torque setting) can be either LOW when the torque is reduced to 30% or HIGH when its 100%. How does this part of the schematic work? STEP signal is the clock signal that turns the motor by a single step. No part numbers for the transistors were provided but I'm guessing they are something similar to a 2N3906(?).


texts:
Input signal (a) is AC.
Input signal (b) is varying DC.

As (b) has a frequency but does not change direction, does the capacitor's reactance have a different effect
than input signal (a)?


texts:
let's consider this circuital model for an LC oscillator in which the parasitic resistance R is affected by thermal noise (represented here with an equivalent noise current source, according to the Hajimiri model):

I put my questions in bold inside the text of my book:

  Being \$i^2_n\$ a white Gaussian noise, it can be interpreted as the sum
  of infinite mathematical impulses of uncorrelated current and
  area \$qδ(t)\$.

Why?? Why are they the product of a charge and a pulse?

  This means that at each instant t a charge q is provided by the power
  source. This charge will go on the terminals of the capacitor,
  determining an instantaneous voltage variation equal to \$q/C\$.

Why is that variation equal to q/C?


texts: Subtracting a larger binary number from a smaller binary number

texts: Is it possible to subtract a larger binary number from a smaller one column wise . For example subtracting 1000 from 0111 ? I always use the 2s complement but is it possible to do it column wise ?


texts: How do I connect a 0-10V analog input to MCU with high input impedance?

texts:
I'm trying to connect a 0-10V analog input value to my MCU which is running on 3.3V. I used the below circuit but when the input is floating I read about 0.3V on the analog input. I need to eliminate the bias current from the analog input.

simulate this circuit – Schematic created using CircuitLab
Can anyone give me a hint what is the best practice to connect a 0-10V signal to an MCU?


texts: Why do BLDC motor (1 kW) controllers have so many MOSFETs?

texts:
I have a 1 kW three-phase BLDC motor from China, and I was developing the controller myself. At 48 Vdc, the maximum current should be about 25 Amps and a peak current of 50 Amps for short durations.

However when I researched BLDC motor controllers, I came across 24-device MOSFET controllers which have four IRFB3607 MOSFETs per phase (4 x 6 = 24).

The IRFB3607 has an Id of 82 Amps at 25 °C and 56 Amps at 100 C. I can't figure out why controllers will be designed with four times the rated current. Keep in mind that these are cheap Chinese controllers.

Any ideas?

You can see the controllers here, if you need any part of the video translated, please let me know.

https://www.youtube.com/watch?v=UDOFXAwm8_w
https://www.youtube.com/watch?v=FuLFIM2Os0o
https://www.youtube.com/watch?v=ZeDIAwbQwoQ

Considering heat dissipation, these devices would be operating at 15kHz so about half of the loss would be switching loss.

Keep in mind that these are $25 chinese controllers and each mosfet would cost then about $0.25. I don't think these people care a lot about efficiency or quality. These controllers are warrantied for 6 months to 1 yr max.

BTW in the lay language of the users, Mosfets are called MOS-Tubes. Hence tubes.


texts: Ideas for troubleshooting a noise generator on a PCB

texts:
I am building an electronic "dice" that uses an ATTiny84 to sample avalanche noise from a 2N2222 in reverse-bias and generate random numbers, which are then displayed on 2 7-segment displays.
When I prototyped this on a breadboard, it worked just fine, so I decided to move to "production" and put it on a PCB.

Unfortunately, the noise generator on the PCB is running into some issues: It does not seem to be outputting (the "output" is the collector of the 2N3904) a noisy signal.

Now, as I am a student with limited means, I would usually go into the university lab and use one of their marvelous oscilloscopes to troubleshoot the signals themselves; however, they have locked all the labs for renovation or something and I can't use their equipment.

Therefore, I am asking for some suggestions as to how to troubleshoot with the tools I do have: soldering/desoldering equipment and a basic digital multimeter. I have already confirmed that all of my traces are intact and going where they should, and that steady voltages are what they should be. Every other component of the circuit works like a charm, except this generator. How can I glean some more information about it with what I have, and/or is there something I am overlooking that might explain the problem?

Thank you so much for your help.


texts: Dropped Bluetooth Connection While Charging through Solar

texts:
I am trying to charge a device (not of my own invention) with a solar panel. Sorry for the lack of name, but I’d like to keep my project my project. The panel is rated for 4.8v at 100 mA, and the device charges via micro usb: 5v at 500 mA (approx.). The device has to be turned on while charging. I am not necessarily trying to keep it at 100% charge, but to prevent it from dying for an extended period of time. The device connects to a smartphone or a tablet via bluetooth. The problem I’m having is during charging with the solar panel.The charge would be stable (at around 60%-90% or so) but the bluetooth connection would drop.

　　 In the control tests, with the device functioning regularly without a charger, the battery life was about 6 minutes and 15 seconds , but the connection here dropped at about 4 minutes and 15 seconds with what should have been a stable battery life. It is registering that the unit is charging with the panel.

　　I tried decreasing the distance from my light source to bring the voltage up to 5, but that didn’t change the effects.

　　Due to the fact that the unit emits a quiet buzzing sound while being charged with the solar, I believe there may be a switcher in the power regulation circuitry. When charging with the panel, the noise is like the Doctor’s sonic screwdriver, except at both a slightly high pitch, and a lot quieter. While charging via usb (from lightly used iPhone charger), there is no noise. I’m no expert, but I think the small spikes in current it produces may be interfering with sensitive bluetooth communication. Another high frequency in the device is the communication to an onboard motor, which may also be causing some interference due to the less precise (precise, not accurate) charging from the solar panel, as the device vibrates slightly uner the light. I’m really not sure. I will get an oscilliscope in a week or so, and I’ll hopefully be able to check any spikes. Due to the battery life and the size, I wouldn’t guess that it contains very high quality components, though the Bluetooth connection is rated for 180 feet.

　　To help smooth out the power coming from the panel, I put in two capacitors in parallel with both each other and the main circuit, though this didn’t help. One was 470 microfarads, and the other was 0.2.

　　Just out of curiosity, does this sort of thing (error while charging with solar) happen often? I couldn’t find anything on google.

　　Thanks for any help! :)


texts:
The place where I work has a fairly large UPS comprising of rows of sealed lead acid batteries (Haze HZS-7.5HR).   The batteries are now 6 years old and are not holding charge very well.

The service technician report states, among other things that ".. the batteries may go into thermal runaway and therefore become a danger to the site."

Is this statement fair, and if so, why would older batteries - which I assume have less energy then new batteries be more likely to suffer from thermal runaway?


texts: What does 'capacitor jumping up and down' mean and what work does it do?

texts:
While studying about capacitors, I came across with an explanation talking about "jumping up and down when a capacitor separating two stages".
I understood from several articles here that capacitors block DC when it is fully charged and that the idea of 'charging and discharging' of capacitor.
'This page' explains

If a capacitor has the negative lead connected to the 0v rail, it will charge and discharge
If a capacitor is NOT connected directly to the 0v rail, it will JUMP UP AND DOWN.

and with the following figure, says

the capacitor will 'fall'and the voltage on the negative lead can actually go below the 0V rail

where I totally lost my understanding.

(source: talkingelectronics.com)
(please refer to '4. A capacitor separates two stages' on 'the linked page.')
The pages explains that

By knowing how much a capacitor jumps-up-and-down, you can "see" a circuit working.
and here my questions came.

I can't understand the difference between 'charging/discharging' and 'jump up/down'. I thought even though it's not directly connected to 0V rail, still depending on its reference voltage, it can be charged and discharged. What is the difference in those two expression to comprehend their meaning?
What happens when capacitor jump up and down?
How can I calculate the amount of the 'jumps'?