texts:
Lets say I have a sine frequency sweeping circuit (1kHz-10MHz) that goes down in magnitude, from say 3V to 1.5V when it reaches its maximum frequency. I've tried buffering it (and even terminating with 50 ohms before, its impedance), however the voltage still varies, and much so more when the frequency gets higher.

What I desire for example.. A small AC will have the specific gain to reach 5V peak, or a larger AC (unlikely) attenuate to reach 5V peak, so I get a flat frequency response.

How would I amplify it to specifically go from 0V to 5V with its centre point at 2.5V for example? Will I have to employ some sort of buck/boost converter, or can it be done with some form of feedback with an emitter amplifier? An op amp might have something, but those destabilise at 1MHz, however if that is all I can do I can upgrade them.

Additional info. for Jippie: - about this "sweep device". It is simply a function generator (Hantek 3x25) and it tends to vary its voltage lower at higher frequencies, even with terminated output due to the quality of the device or whatnot (even though the sine wave is perfectly suitable that comes out.) It could be anything however, an XR function generator, just some variables sweep of some kind (a VCO in the future?). My scope and its probes are 40x the highest bandwidth my gen can put out, so not to worry for that :P


texts: Calculate transfer function given 3dB point?

texts: I'm not sure the relationship between transfer function from the 3dB point. The transfer function should give the gain, and I suppose when we put in the frequency at the 3dB point, the transfer function should be equal to a certain fraction?


texts:
I want to create an external accessory for a DC welder which would create square wave ac. This would be in the ball park of 20V 130A 60hz. My idea is to use solid state relays to flip the polarity of electrode and ground, this flipping signal could be altered to modify the positive/negative delay and the frequency.

My question is whether this is fundamentally flawed. Are solid state relays able to cope with most of their load capacity whilst being switched rapidly? Would there likely be a delay between swapping polarity which could be long enough for the arc to be extinguished?

If this is possible then perhaps this would be a way to weld aluminium occasionally without spending the not inconsiderable price-tag of a true AC welder.

Hope this isn't too vague, simple or silly.


texts:
I'm in the process of finding a suitable relay for switching the elements in a mini oven I want to use for solder reflow.

I've found what I think will be a good candidate, however I'm a bit confused by the maximum power ratings.

Here's the relay in question: http://www.rapidonline.com/Electronic-Components/Mi-ss-106l-6v-10a-Spdt-Relay-60-4598

Das Datasheet: http://www.rapidonline.com/pdf/60-4598.pdf

The ratings state a max load of 2500VA / 300W. The 2500VA seems to be an AC rating @ 250V and the 300W is for DC, but even taking that into consideration, the disparity between 2500VA and 300W seems huge?! I know that the RMS voltage of 250VAC is considerably less (circa 160V) but @ 10 amps that should still be around 1600W?!

What's going on here, can someone explain this rating disparity in greater detail?


texts: Installation of an AC Drive on a Mixer - Help

texts:
We have a 30hp 1440rpm AC motor installed on a mixer.
Motor Pulley: 6"
Machine Pulley: 20"
According to my calculations, the mixer runs at 432rpm.

Operating Procedure:
The mixer is loaded with approximately 200kg of raw material feed, along with water and several mixing compounds. The motor is then started by a "Star Delta" Starter.

Due to the high load in the mixer, the motor is unable to move in the "Star" Phase. The connected ammeter's needle touches the roof, so the current consumption is higher than 80amps (the max that the ammeter can measure).

When the Starter puts the motor in "Delta", it starts with a jerk and the ammeter reads about 60amps. After the initial 2-3 minutes, the mixer settles down and the motor's current consumption hovers between 30 and 40amps.

Considering that we install an AC Drive for the above motor, I have the following questions:

Would an AC Drive be able to maintain the necessary torque at extremely low motor RPMs?
I intend to have the AC drive slowly accelerate the mixer to the desired rpm, thereby giving the mixture enough time to settle down and reduce the need for high current consumption.
Would a V/F control type AC Drive suffice for the above application?
I am specifically looking at Siemens Sinamics V20.
What kind of energy savings would an AC Drive bring for the above application?

Other Details about Connected Power Supply:
V: 440V
F: 50Hz

I would greatly appreciate any and all assistance.
Please excuse me if any assumptions are wrong, I'm not well versed with this field.
Thank You.


texts: Why is non-inverting op-amp input resistance on a tee to ground?

texts: In many of the explanations I've read of non-inverting op-amps, the non-inverting input is given a resistance to meet the specs of the op-amp. I'm confused by how the resistance is applied. Since the resistor is just acting to control the input current, I expected it to be inline with the input voltage. However, the resistor is usually attached as a tee from the input going to ground. Why is the input resistor on a tee and not just inline with the non-inverting input?


texts: How do I turn off this constant current load circuit with a Arduino gpio?

texts: I need to turn off this constant current circuit with a gpio pin when an event is True. I'm using 6 of these circuits with 3 lm358 op-amps, so turning off the whole chip is not an option. Any ideas?


texts: How to convert 0-3 V (PWM range) to 0-24 V (device voltage requirement)

texts:
I have an Arduino with some PWM pins, output range is 0 to about 3 V and I need 0 to 24 V range.

I need to active a solenoid -  a hydraulic proportional solenoid

A 12V and 5V source is also available but, the final output (0 to 24V) must be controlled by the Arduino output (0-3V) .... for example, Arduino: 1V => output: 8V


texts: Which STM32 is best for logging a CAN network?

texts:
I would like to build a project based on STM32 that interfaces with a CAN network. The CAN network has a 250 kbit/s baud rate.

On this network I have to:

Log messages from 127 nodes with IDs between 0x381 and 0x3FF (each node transmits one message per second).
Transmit messages to nodes with ID between 0x581 and 0x5FF.
Receive responses to these messages that will have IDs between 0x601 and 0x67F.

I was thinking of using an STM32 with two CAN channels. My intention is to set up two different filters on IDs and limit interruptions. Is that a good choice? Can it be done with only one CAN?

I have doubts about the kind and the speed of processor to use. Can an STM32F1 be sufficient? Or do I need an F4?


texts: Effect of op-amp's input offset voltage on stability of constant current load

texts:
I'm designing a simple circuit to have a constant current load with good short term stability. The exact current value is not important, as long as it's stable short-term (10 seconds). R1 is the load - a nichrome heating element. The stability that I'm aiming at is around 2A of current stable to within +/- 0.5 mA.

I'm simulating it in LTSPICE. The voltage sources are all batteries so I'm expecting the voltages to stable short-term.
I've added resistance variation to the load to simulate the current variations that are happening in real life. I've also added resistance variation to the reference voltage divider resistors and the current source to simulate TCR (planning to use low TCR 25ppm resistors, simulating 2C short term variation).

My understanding is that the built-in op-amp model that I'm using doesn't account for the input offset voltage so I've added a 1mV voltage source (V4) in series with IN+ of the opamp.

I was expecting the offset voltage to result in a constant error in the current regulation but it worsened my precision 20 fold. So I'm wondering why this happened with the introduction of the constant input offset voltage.

I can use an ultra-low input offset voltage op-amp like LMP2021 and the offset voltage won't be an issue but just out of curiosity I'm wondering why this precision degradation is happening.

LTSpice model download

LTSPICE model:

Current without the offset voltage

Current with the 1mV offset voltage:

Edit: The voltage difference between IN+ and IN- looks is as follows:


texts: Measuring load resistance/inductance in an electric motor

texts:
How do I go about finding the load resistance and load inductance of a brushed DC electric motor? I would guess that:

Load resistance = Operating voltage / Load current

These values you can find in the datasheet. To find motor inductance, you operate the motor with a "nominal load" so that it uses an average current with the same value as the "load current" from the datasheet. You then need to take a scope plot of the PWM control signal and motor current from the current sensor (isense). Because inductance is defined by:

V = L di/dt

where V = the rising voltage of the PWM signal
di = the change in isense
dt = the change in time where the PWM signal is High

Then solve for L which would be load inductance. Is this method correct?


texts:
I've just started studying op amps recently and I am having trouble with the following problem from my textbook:
Design the difference amplifier circuit to realize a differential gain of 1000, a differential input resistance of \$ 2 kΩ \$ , and a minimum CMRR of 88 dB. Assume the op amp to be ideal. Specify both the resistor values and their required tolerance (e.g., better than x%).

Attempted solution:
Solving for differential output:
\$ V_{id} = V_{i2} \cdot (1 + {{R_{2}}\over{R_{1}}}) \cdot {{R_{4}}\over{R_{3}+R_{4}}} - V_{i1} \cdot {{R_{2}} \over {R_{1}}} \$
Since the differential gain of 1000 is needed, pick \${{R_{2}}\over{R_{1}}} = {{R_{4}}\over{R_{3}}}\$.
The differential gain becomes:
\$A_{d} = {{R_{2}}\over{R_{1}}}\$
(I hope I can use this approximation; otherwise everything becomes even more complicated).
Next, solving for common node gain:
\$ A_{cm} =  {{R_{4}}\over{R_{3}+R_{4}}} \cdot (1 - {{R_{2}}\over{R_{1}}}{{R_{3}}\over{R_{4}}})\$
Since, \$CMRR = 20 log {|A_{o}| \over |A_{cm}|} \$ and a minimum CMRR of 88dB is required, this is the expression that I have that takes this constraint in consideration:
\$ {|A_{d}| \over |A_{cm}|} = {|{{R_{2}}\over{R_{1}}}| \over |{{R_{4}}\over{R_{3}+R_{4}}} \cdot (1 - {{R_{2}}\over{R_{1}}}{{R_{3}}\over{R_{4}}})|} = 10^{{88} \over {20}}\$
Another constraint is \$ R_{id} = 2kΩ\$, which means that \$R_{1} + R_{3} = 2kΩ\$
I don't really know how to proceed from here. Of course, I can try plugging different resistor values and testing them assuming different tolerances (keeping the constraints in mind), but that doesn't seem like an efficient way to solve this problem. How would you approach a problem like this?


texts: How does a triode amplifier work? I mean, how does the different components help in amplifying the source wave?


texts: Raising ground level of Wemos ADC from Multiplexer

texts:
The Setup
I'm using a 74HC4051N multiplexer to interface with several analog sensors. I'm using a Wemos D1 Mini to read Z (output from the mux) using the Wemos ADC.

I've only illustrated one (of 4) TMP36 temperature sensors. I'm also monitoring the 12 V line from the battery. I use a 1.6 M ohm resistor to bring the 12 V down to 3.3 V at A0 in conjunction with the internal potential divider of the Wemos.

The Problem
If I disconnect all sensors (y0-y7) and iterate through all mux addresses, reading off values I get something like the following:

Address 0: Val 12
Address 1: Val 8
Address 2: Val 9
Address 3: Val 13
Address 4: Val 12
Address 5: Val 15
Address 6: Val 10
Address 7: Val 8

The low values are expected, the Wemos ADC is a bit noisy.

If I now connect the 12 V sense line only to say y1, the readings look like this:

Address 0: Val 476
Address 1: Val 802
Address 2: Val 436
Address 3: Val 410
Address 4: Val 469
Address 5: Val 398
Address 6: Val 401
Address 7: Val 451

The 12 V reading (value of 802) on address 1 looks to be correct. The Mux chip appears to be fine as using the TMP36 sensors on their own I see the expected output:

Address 0: Val 240
Address 1: Val 920
Address 2: Val 786
Address 3: Val 870
Address 4: Val 12
Address 5: Val 15
Address 6: Val 10
Address 7: Val 8

What am I missing? Why does it appear to raise the ground level of the ADC?


texts:
simulate this circuit – Schematic created using CircuitLab

Having some confusion this gate driver. It can be found in Design and Application Guide For High Speed MOSFET Gate Drive Circuits.
http://www.radio-sensors.se/download/gate-driver2.pdf

If Vin = 12V for example, when OUT is low, Qinv will be off, and Vg ≈ 11.3V (after the gate has been charged, accounting for VBE of Q1).

When OUT from the PWM Controller is high, Qinv will be turned on, Q1 will be off, and Q2 will conduct until the gate discharges to a certain voltage (voltage based on the values of R1 and R2).

Where I am confused is VCE of Q2 when it is conducting. Since Vg ≈ 11.3V, would VCE of Q2 not be 11.3V initially? If Ic = 0.2A peak, then power loss would be very high for a small amount of time which is what I'm worried about. Intuitively I don't think all the gate charge would dissipate in Q2?


texts: Single buffer line from 74ABT244 to 16 inputs for 74AHC245?

texts:
I am designing a circuit which will buffer 3.3V input from Raspberry pi using 74ABT244D,623 and there will be 4 output chains on the PCB. Each chain will be connected through FRC to a second PCB with an immediate buffer of 74AHC245. But one data line will be shorted into 4 to get 4 outputs.
So from 1 single output of 74ABT244D,623, can it drive 4 inputs to 4 74AHC245 each (16 total) ?
Reference image :-


texts: Can an isoSPI interface work without isolation?

texts:
Ive got a LTC6820 that I will be communicating with a LTC6811 and they both use isoSPI but all the example diagrams show the connections going through a transformers and twisted wire like this:

But in that example the wire between was 100m long, but I'm only going 8m tops and it will be in a shielded cable in a low noise environment, so I can't help but wonder if it would work to just have them wired like this:

simulate this circuit – Schematic created using CircuitLab


texts: I often end up charging my phone several times a day for 5-10 minutes each time. Is this more harmful to the (lithium-ion) battery than a single longer charge?


texts: Why does a thermocouple have two outputs (V+ and V-)?

texts:
Does that mean that there is two different voltages?

The potential is used to determine the temperature. (?)

I understand it's the seebeck effect  dictates how the thermocouple works.

Apologies if I'm missing a simple concept.

I have had no experience with thermcouples prior to my current thermopile project.

Thanks!


texts:
and sorry for this question, but it's been on my mind lately.

I'll start by telling you that I have never worked with a calibrator in my life. But I THINK I know how it should work.

I know that (at least in my country) to calibrate an instrument you need to use a calibrator 10x more precise than your instrument's precision (if you have a voltage/current meter with +-1%, you need a calibrator with +-0,1%). The instrument is adjusted according to the calibrator's output.

If this is how a calibrator works, then what's the difference between a calibrator and a precision PSU? Is the difference that the calibrator has a wider output range and/or formats? Is there anywhere that I can find the block diagram specification of a calibrator (like this that you can find on TI's page)?

Are there any other functionalities that I'm missing?

PS: I don't have a calibrator that I can crack open and buying an old/cheap calibrator from ebay is not an option (ebay doesn't send to my country and even if they did the taxes on it would bankrupt me.)


texts: What are "pick-up", "dropout" and "rated" voltages in a Relay datasheet?

texts:
Given the picture below, what are these voltages? Okay, for the rated one, I "think" I know what it is in the practical sense but if someone would ask me: "what is it?" I would spend significant time to word it out. Thus, I am not sure what it really is.

For the dropout, and pick-up voltages, I do not have any idea what they are. Lastly, you see the "min" and the "max" notations. I just did not understand what they refer to.

Note: Source of image or the datasheet is datasheet


texts: Isolation transformer = floating ac inverter

texts:
Its said that, in AC power system at power station neutral and ground connected together because of this reason we get electrical shock, as neutral and standing ground are same.
Assume, if I power a inverter 24 volt DC to 120/ 230 volt AC, without earthing its output AC terminals, keep floating ouput terminals, do someone get electrical shock (line tester shows dangerous voltage) when touching one of the floating ouput terminals, as its not tied to buiding earth.
How this circuit is completed (electrical shock), in floating AC inverter system placed on insulator board?
Is this floating AC inverter equals to isolation transformer?
If from floating ac supply, we will get shock, how isolation transformer (1:1) protect, somebody touches on one terminal.
How this earthing done in isolated floating AC supply?


texts: Measure Coil Resistance of a Large Transformer

texts:
I have a large transformer and I want to measure its coil resistance to find the primary and secondary. I set my multimeter in the 2000 ohm setting and measure. At first, it reads 500 something, and then the resistance slowly dies off to 0. What am I doing wrong? Why can't I make a steady measurement?
My multimeter: Craftsman 82141
My transformer: TKP0278-E142Z


texts: PID controller - should terms be completely independant?

texts:
I was under the impression that the P, I and D terms of a PID controller should be calculated independently of each other. That is, they would all use the same error information, but none of the three terms would be affected by either of the other 2.

But I'm looking at the microcontroller code for a turbocharger boost control system, and it appears to take the derivative term into account when calculating the integral term. If the d term is above a certain threshold, then the integral term is set to its full negative value. To me it seems to defeat the purpose of calculating 3 separate terms. This is from a real, working system so I know it functions correctly.

Is that kind of thing typical in PID controllers?


texts: Changing parameter values from a value list file in SPICE

texts:
In my circuit, there is a current generator. This generator generates vaules dependent on a parameter, we called N. But I want to use parameter as a variable. If values change linear, I will use .step function. But my values are gaussian distributed and 10k different value. Thus .step function does not suitable for me.

My question is, could I change N parameter value from an out .txt file continuously as .step function ?

Now, I'm using LTSpice. Tell me if any useful SPICE application you know.
I know PWL() function changes current generator values with a file. But there is a mathmetical formula in I2() and N parameter using in that.


texts:
I'm using an Charge Pump Inverter,MAX899R in free run mode with switching frequency of 500kHz like in the circuit attached. The problem is that I'm seeing a lot of switching  noise in the output, much more than i expected as it is visible in the figure attached. Moreover the noise has a frequency of 1MHz, and not 500 KHz, is this normal ?  How could i fix the problem ?

Update
After a suggestion of AndyAka, I checked the ground and it has the noise I'm seeing in the output, I read it would improve to use a ferrite bead after GND and after VCC but no improvements. I'm adding 3 more pictures with the noise at the ground(fig1), noise in the VCC with osciloscoppe earth probe closer to C11(fig2) and the noise in VCC with earth probe closer to C20.

Ground Signal

VCC with with osciloscope earth probe closer to C20

VCC with with osciloscope earth probe closer to C11


texts:
I'm trying to design a simple circuit that has the ability to charge a single cell Li-Po battery and can be used as +5v power source. I chose the circuit from here.

It seems that when VUSB is active, the +5V pin would select the VUSB instead of the step-up regulator because of two Schottky diodes, and the charger chip would charge the battery at the same time. When the VUSB pin disconnected, the charger would go off obviously and it seems that the EN pin of step-up would go high (Why?) and enables the regulator, then the +5v pin selects the output of the step-up regulator. My first question is what is happening to FET switch?

My second question is, does this circuit protect the LiPo battery from under-voltage discharge? For example, when VBAT goes below 3.2V. I'm using a different step-up regulator (AP3031) and I think I should calculate a different value for R15.

EDIT: here is the second schematic to make sure step-up regulator become active only when VUSB is off.


texts: Why use both packet detection and symbol time estimation in the receiver of WLAN(WIFI) in 802.11

texts:
n IEEE 802.11 Wlan, at the receiver side, we first use packets detection algorithm to detect the start of the packets, and then uses fine symbol timing estimation algorithm to find the start of the data symbol. However, if we can detect the start of the packets, we should be able to find the start of the data symbol since the length of the preamble is known at the receiver, so why would we use still employ the symbol timing estimation algorithm to find the start of the data symbol. The packet structure: Packet structure of 802.11

I guess it because the multipath fading or symbol time offset, but I can't figure out why, could any body explain this? I will really appreciate that, thanks in advance.


texts: How can this problem be solved with partial fractions? (Zero order holder with g(s) block function)

texts:
im trying to figure out how to solve this problems for values a=2; actually im stuck, professor told me how to work it, but i cant figure out what to do exactly, we are using partial fractions inverse z transform to solve and this is the problem:

it is asking for the transient response in unit step

I upload a example he sent to us with a=1, but i dont know how to work it properly to be true.


texts: I wonder what is the description of the first IC made by Kilby. The famous picture is shown in many websites, but I want to know what it is?!


texts: What is the name of the connector which hakko soldering irons have

texts:
I would like to build a soldering station for a Hakko 907 soldering iron, but I don't know the name of the connector what I'm going to need.

Here is a link for the soldering iron that I have ordered:
http://www.ebay.com/itm/311188226034

Can someone tell me what is the name of the female connector what I'm going to need?
Is it possible to mount this connector onto the front panel of my case?

I saw similar connectors but all of them were made for cables, not for cases. Probably I saw completely different connectors.


texts: How to calculate voltage and current of a circuit with input / output MCU pins

texts:
I would like to know the method to calculate both voltage and current in a circuit that use MCU input / output pins

In this example, how can we find the V / A of all resistances and Capacitors..

Also how to determine the voltage / Current in our input pin.. or EN pin...


texts: Large negative current spike in N-Channel MOSFET source when turn-off

texts:
I am working on repairing a power supply board of a LCD TV (200W power), more specifically, the PFC section (active power factor correction). See schematic (adapted from here):

I've replaced some defective components and now the power supply seems to be working OK (the voltages at their output seem OK, and some waveforms measured on the oscilloscope look good).

I still have no confidence to connect the power supply with its output connected to the TV, so at the moment I'm doing bench tests. The PFC has 2 MOSFETS in parallel (see diagram), but I'm currently testing the power supply (no load at the output) with only one MOSFET on the board.

I am analyzing some waveforms triggered at the moment the PFC is turned on (it charges the capacitors CP815/816 from 300V to the target 380V, so it have some work to do).

What's bothering me is the current spikes in the SOURCE terminal of the QP801S MOSFET (measured through the voltage on the RP820 (0.08 ohm) with the oscilloscope, using a very short lead).

See the detail of a negative current spike (the greater that occurs):

My question: Is this negative current peak (shortly after MOSFET turn off) normal? Note that it reaches -67A (-5.36V over 0.08 ohm) with a duration of ~50ns. [EDIT 2: figure and paragraph edited to show the greater negative spike that occurs].

Note that the positive portion of the current (while MOSFET is ON) is a normal ramp, charging the inductor with up to 4.75 A (0.38V over 0.08 ohm)).

EDIT 1: probe setup used to get the measurements, with short wire connected to probe GND (Agilent N2862B, 1:10 passive probe):

EDIT 2: See the figure below for a longer time capture (the scope was set into Acquire=Peak Detect mode, to ensure that the peaks are captured. The scope's A/D converter works at the maximum rate in this way).

It is possible to observe that the amplitude of the negative peaks follow the waveform of the input voltage of the PFC (60 Hz mains rectified with full bridge => 120 Hz half wave, T = 8.3 ms). May be this provides some hint about these spikes.


texts: Different PCB color (is it a different material?)

texts:
I have acquired this PCB.

The right side of the PCB handles high voltage AC power (250 V maximum,) while the left side handles low DC voltages (24 V maximum.)

They are separated, not only by board cuts, but also with this yellowish line in the middle. Is it just coloring to differentiate between the areas or is it some sort of protection material?

If it is some sort of protection material, how do I include it in my future designs?


texts: Would a small pressure sensor be orientation dependent?

texts:
I'm implementing the BME280 (datasheet here) into one of our systems. My coworker swears that pressure sensors are orientation dependent. I've found from online documentation that this is true for large flow-rate pressure sensors, but I haven't found any mention (searching for the terms 'orientation','offset' and reading the qualitative descriptions of the pressure component) of this particular sensor needing to be in a specific orientation.

Has any one found that the BME280 or similar sensors are orientation dependent, such that it causes a >1% difference in measurements between two extremes?


texts: Getting closer to figuring out my battery requirements

texts:
I have been doing research for at least a week and am still a bit confused, but think I am getting to the point where I am close.

I need to power 5V 3-5A.  Some days this power source will hook up to my Beaglebone (3A), others to my Arndale Octa Board (5A) (I believe I can supply 5A to the Beaglebone without issues).  I need a very light battery, that will last quite awhile hopefully.

So after reading a lot about batteries I think I need either a 2S or 3S LiPo battery.  I need to know if a UBEC (Ultimate Battery Elimination Circuit) can be more than a voltage regulator, instead work as a buck converter.  I think if its just a voltage regulator I need to stay at the 2S, but if I can use a buck converter the 3S should have longer battery life?

So here's my question, and you can put links or part #'s or just the specs I need to keep an eye out for.  What LiPo battery, items I need to safely charge it, and then what buck/ubec I need for my power requirements (5V 3-5A).


texts: How to measure mains AC voltage with an ADC from a microcontroller?

texts:
I want to measure the Mains voltage (230V/50Hz) using an ADC channel from a microcontroller.

This is my current approach ...

Below I have two schematics that add two voltages (one direct, one alternating).

Added to that, the both the AC and DC signals are going through voltage divider, but that isn't important.

I'm guessing that the output voltage on the second schematic is lower because of the impedance of the capacitor?


texts:
I'm trying to create sound detector to use with ESP12F you can see schematic below. I've made this on breadboard, but can't make it work stable. So i want to know how should I choose R1 and R2 values or should I use another design?

UPD. "Can't make work stable" means device either too senstive or not detecting sounds at all
I'm using HMO1003A so i can't find suitable datasheet :(

P.S. I'm not native english speaker so sorry for my english.


texts: What will happen if I connect a solar panel and batteries in parallel?

texts:
What would happen if I connect a 9 V solar panel in parallel with a battery consisting of 6 x AA 2300 mAh NiMH at 7.2 V in series?

Panel:

Voc - 11.25 V
Vmp - 9 V
Isc - 0.41 A
Imp - 0.38 A
Wmp - 3.5 W

Battery:

6 x 2300- mAh NiMH cells

There will be a Schottky diode, of course.

It is said if you want to connect two power source of different voltages in parallel, both should be CC/CV? I'm not quite sure if the solar panel provides CC/CV. Please clarify.

Does it need any regulation?

My purpose is to provide for a 5V, 2A load using a buck converter.

Thank you.


texts: Would spacing the magnets in a DC motor farther away from the armature increase RPM of the motor?

texts:
Regarding:  How to improve torque and RPM of a DC motor?

Based on the accepted response to the question…  in section #1, speed of the motor related to magnet strength, would this would work?

Since RPM varies based on magnet strength, what if the magnets were in an open frame, with each magnet hinged to one side with a spreader screw at the opposite side.  If the motor were running off a power supply set to X volts, it seems the RPM would increase if you turned the spreader screw to causing the magnets to open away from the armature like a clam shell (reducing their strength due to distance relative to the armature).   I’m not sure this has any practical application, but sounds like it would be cool to see in action.


texts: Is the op-amp inverting or non-inverting?

texts:
I am studying the function and characteristic of an op-amp to build a line-following robot with the schematics below. However, in many tutorials, the way to differentiate an inverting and non-inverting op-amp is by looking at the connection to ground via the inverting or non-inverting terminal.

However, in the schematics, the op-amp is considered to have connections to ground, thus in this case, how do I differentiate it then?

I may have understood the whole concept wrongly. Pls help!

EDIT: Please ignore the switch as it may have been drawn wrongly by the supplier.


texts: why will my transistor (TIP122) NOT switch?

texts:
My goal is to make a car turn signal flasher.
I used a 555 chip as the timer with the output driving a TIP122 transistor at BASE and a 100 ohm resistor between the BASE and the 555 output pin 3. The Emitter is connected to ground. The Collector is connected to one side of the the relay coil (90 ohms) and the other side of the coil to ground. Simply will not cycle. Tried different base resistors 100 to 2000 ohm.
Transistor NOT switching.

BTW the flasher circuit works fine when driving an LED only. (no transistor, relay etc).

Any ideas?


texts: Ethernet Switch used for CCA to CCA comm without FPGA/Proc for MAC

texts: I'd like to connect Ethernet between devices through magnetics without the FPGA or processor involved. For example, I have several off board (PWB) Ethernet signals coming onto my board and then onto other boards in the system (stack). If the Ethernet addresses are known (source-destination path), do I need to have some sort of processor or FPGA (MAC) in the path at all? In other words, can I truly have a point to point connection? I need to have both the purple and the black paths shown in the picture. Both CCA 2 and CCA3 have Ethernet with magnetics. What do I need to do to ensure that the black path is designed correctly such that it does not require the FPGA/Processor? Thanks - I hope this is clear enough.


texts:
How can I simulate the dc resistance/R_dc of a spiral inductor?
Here's the circuit I have:

I simulate the inductor with a dc source and get the series current from a I_probe.
Then calculated the dc resistance with R_dc=Vdc/I. Am I doing the right thing here?

(P.S. I didn't run a s-parameter sweep here because it gives me effective resistance = R_ac+R_dc, right?)

Edited: I am simulating with ADS.


texts: Why 802.11g has a maximum throughput of 54mbps?

texts:
Can anyone explain why the maximum throughput of the IEEE 802.11g standard has a maximum throughput of 54mbps I can not find that. I would like to know how do you get this 54 taking into account the bandwidth (22 MHz) and the modulation scheme used.

I guess that from the answer I will be able to understand how the get the data rates from 802.11n and 802.11ac. However, in this new standards something called MIMO (multiple streams) enters into the game.

Thanks in advance,
Edgar


texts: When to use a 1/4 Watt resistor vs 1/2 Watt resistor

texts:
I have never understood the difference between 1/4 & 1/2 watt resistors, and in all of my EE lab courses I have always just used 1/4 Watt resistors. When does one use 1/2 Watt resistors and what is the difference between 1/4 & 1/2 Watt resistors?

Would using 2- 20 ohm 1/4 watt resistors in parallel, be the same as using 1 - 10 ohm 1/2 watt resistor?


texts: I am trying to make an electromagnet, i would like to know what kind of core would work best, from what i have read a soft iron core would work best BUT i know some metals are known by number and i would like a number just to be more specific (if possible). i also need to keep the core from rusting and i was thinking of copper plating the core, would the magnet still work after doing so why or why not? (i know what wire i need to use i only need to know these last few things i asked)


texts: How to check if Neutral is grounded properly?

texts:
I was thinking of buying a Residual current device but I don't know if the power supply to my home is grounded properly or not. For initial testing I used my multimeter to check the voltage coming to my home. It was 220 V.
Then I checked each terminal from the power switch and compared it with the ground ( Had a metal rod dug very deep in the ground).
It was 217 V with respect to the hot wire and 3 V with respect to the Neutral Wire.
I was expecting to be a 0 V difference with respect to the Neutral wire. But it was constantly showing 3 V. I checked it many times.
Now, my question is,

Am I measuring it correctly? Is there any flaw?
Will the RCD trip in current situation?
Should I go ahead and buy one? If not then is there any way to fix the situation or any other device like RCD for the current situation?

PS, I even used the multimeter to check the continuity of the Neutral wire with the metal rod. It did not beep.


texts:
I am developing an I2C driver for an accelerometer.

My objectives (actually it's the restriction I have as per the project guidelines given in my institute):

use Linux flavour of operating systems - (software)
use ARM core based ISA (ARM CORTEX- A or M series) - (hardware)

Any help in this regard would be great.

One of the solution offered to me was to go for FreeRTOS on NXP's LPC1769 which is ARM cortex-M3 based SoC. (using LPCXpresso developmental board)

But my question is: Why go for RTOS when my requirement is driver implementation?  Why can't I take up normal vanilla flavour of Linux kernel or so?

And also any help regarding the developmental boards supporting the above configuration?

Any suggestions or thought process on this?


texts: Ways to accurately heat up SMD component(s) on a PCB to a specific temperature?h

texts:
I need to calibrate temperature sensors (ADT7481). My DMM can measure temperature with a thermocouple. And I expect it to be reasonably accurate (within ~1.0 Celsius degree).

Question at large however is the heating method. I can blow my temperature sensor on the PCB with my digitally controlled rework station, but I am afraid that this method will damage other components on the board. Also it won't be very accurate as the air will cool down when it reaches the surface of my sensor.

I have looked around a little bit, and found this product called Briskheat which uses silicone rubber tape to directly heat up the component [1]. I believe such method will be very accurate. Unfortunately it has a lead time of more than a month.

Are there any other ways to control the temperature accurately and safely with readily available tools (ie. alternate to Briskheat)?

[1] http://www.briskheat.com/p-401-silicone-rubber-heating-tape-bs0-with-sdc-digital-temperature-controller-special-bundle-price.aspx


texts: What is the gain of this n-MOS transistor?

texts:
I am wondering how to compute the AC gain of this transistor. So far, I know I have to apply the small signal mode, but I am not sure what \$V_{gs}(AC)\$ is. If someone could just clear that up from me, I would greatly appreciate it.

This is not homework, just self-study.


texts: I need a sinusoidal varying capacitor to test a differential capacitance circuit. I will use the circuit to test MEMS gyroscope/accelerometer capacitance change. But right now I do not have the gyroscope/accelerometer prototype. Is there any available chip or method by which capacitance can be change by varying the input voltage by function generator.


texts: Why is this GE rated for 6V 200mA and 5W?

texts:
I have a genuine GE 5-1075A AC/DC power brick that says that it can provide 200mA at 6V (1.8W).
My use case is that I want to power some old cassette players which I believe these are compatible with. The cassette players only list "6V" and no amp rating.
Why is this power brick listed as 5W if it also states voltage and amps nowhere near that value?


texts: Tesla coil help - Spark gap not arcing despite having 12 kV

texts:
(I've searched these forums and the web and can't find anything that helps, so I apologize if I've missed something.)

I'm working on my first Tesla coil and am at a loss.  This is what I've got going on.  See the annotations in the diagram for descriptions of what I've found so far.

simulate this circuit – Schematic created using CircuitLab

My first guess is that I've got a problem with the current being too low, but then again, it could be something totally different.

(Also, I started with an NST, but it had GFCI and I can't find a non-GFCI anywhere.)

Thanks in advance!

Updates:
 - People had questions about the switch. I was using the switch to require two stages of activation, so that someone doesn't accidentally bump one switch and set the thing off.  Switch has been removed.
 - All grounds have been removed.
 - Spark goes a bit over 1cm.
 - A photo of the layout (below).  Note: This is NOT where I use it.  I had to put it away and just pulled it out long enough to lay things out for you to see how it looks.

Once I get it functional, I'm going to lay everything out very neatly and solder all connections.


texts: Charging a 3.7v lipoly battery at less then 4.2v?

texts:
I'm trying to experiment with supplementing battery power using microbial fuel cells. MFCs are batteries that produce their charge from decaying matter, but they often only get up to 0.9v (unless youre an electrical wizard, in which they can go to 6v). I have an Arduino, while it is off Id like to switch to charging the battery with this MFC. The issue is its going to be low amp (I havent measure it yet) and around 0.9v. Will charging it this low even do anything? Assuming the battery charge will be higher than the MFC.

I additionally thought maybe 3 or 4 in series could solve the problem, but one is the ideal scenario. If its not possible would anyone recommend using a supercap to relay the MFC charge instead?


texts: Can you safely use a higher voltage than intended for a short duration?

texts: I have heard that for some electronics, it is safe to use a higher voltage than is intended if it is just for a short burst. I want to program my arduino to light up some 3v LEDs for just 1ms, like a camera flash, but at as high voltage as possible to get maximum brightness. Is this possible, or will it just burn out my lights? If it is, roughly how much higher can the voltage go?


texts: What are the parameters of choosing of right PWM frequency for a system?

texts:
In various articles I read that we can control a system using a PWM wave. In these articles it was noted that we can control the system by controlling the duty cycle of the wave. But I can't find anything to guide me in choosing the right frequency for a system (for example, a DC motor). I'd like to know what the parameters are for selecting a good PWM frequency for a motor or other typical system.

edit:  Thank you @SunnyBoy for your good regard. But I need a more precise answer. I have this motor as you can see in follow:

can you tell me what should be my PWM frequency to best control of motor?


texts:
I'm trying to use the Deep Sleep feature of the ESP8266 with an inexpensive ESP-01 module. These need to be modified to bridge GPIO16 to RST, in order to wake up from deep sleep.
Also, I have removed the power LED.

I'm using the Arduino implementation. The device enters deep sleep for the specified amount, and wakes up.
The problem is: most specs state in this mode, current draw should be in the "sub-100uA" range. I'm seeing about 3mA.

I have lifted all pins, even the FLASH chip VDD, but I simply can't seem to reduce the current draw. I have measured with two different instruments and the current reads the same, about 3mA.

There is no regulator in the circuit as it's all running from a lab supply for now.


texts: How do you measure the actual package temperature of PCB components?

texts:
We have an IR thermometer at work, but sometimes I feel like the results aren't completely accurate due to the beam width (especially on small components) or material emissivity.

Another way I've tried is to use a thermocouple temperature sensor from my DMM, but unless I put thermal paste, it wasn't accurate and. Using thermal paste was super messy, and it was hard to keep the thermocouple in place.

Are there any other methods or tricks for accurately and easily measuring temperature of individual components on PCBs?


texts: Failed to plot junction capacitance versus reverse voltage in LTspice

texts:
The 1N4001 diode's junction capacitance versus reverse voltage plot is given as follows:

I guess to measure this capacitance they applied 1MHz 50mV pk-pk sine wave signal as reverse biased and varied the DC reverse bias from 100mV to 100V(?).

I tried the following:

But I obtain the following:

For the capacitance I used 1/(6.28*1000000*(V(n002)/I(R1))) which comes from

Xd = |Vd|/|Id| diode capacitive reactance

C = 1/(2×pi×f×(|Vd|/|Id|))

So C = 1/(2× pi × f × Xd)

Obviously something is terribly wrong.

How can we obtain a similar plot by using LTspice? Is it even possible?


texts:
TLDR: Why do so many PCB-designers use non-metric units?

Sorry for asking this closed question again: what is the advantage of non-metric units

But I do not understand, and there is also no other answer for the linked question, why non-metric units used in so many places in electronic designs, for example for PCB and track sizes in mils, AWG for cables or copper thickness in oz/ft² (which is often written oz). And not mm, mm² or µm.

I see several disadvantages with imperial units or advantages of metric units:

The SI-units use only Factors of 10^N, the imperial "system" have a lot of weird factors (like 12 for foot (for cable length) and inch (for track length))
All complex Units exist only in the metric system like Volt: V = W/A = J/(s * A) = N * m/(s * A) = kg * m²/(s³ * A). And i think it would make sense to only use a single unit system. (so you don't end up with conversion errors or with a unit like H/ft = kg * m²/(A² * s² * ft) = 127/5000 kg * m/(A² * s²) ).
Every one should know the metric system, but not everyone should know the imperial system. The Most imperial units are defined with metric units (example: 1 inch is defined with 25.4mm, so you must understand the meter before you can understand the unit inch).
Every length written in inch or mils with a finite number of decimal digits can also be written exactly with a finite number of digits in a metric length, but not the other way around: (20 mils are exactly 508µm, 300µm are about 11.811023622 mils) (which can be a Problem when your PCB-tools use a internal inch-based grid).
Copper thickness: in imperial units, the copper thickness is often written in oz, which is very confusing: oz are a units of mass (or one of many volume units). And you can not give a thickness in a unit of mass. There should write oz/ft². Which is still not very useful when you not know the density of copper. A thickness in µm is much more useful (for example, to calculate the resistance of a track).
Some units in the Imperial System (like Ounce) still have significant different definitions and sometimes used for different physical quantity. For every metric units, the definitions did never change significant.

For the unit AWG, i see even more disadvantages to mm²:

The unit only works with Natural number, when the wire is too big, the number do not go from 0 to -1, which would make sense, it go from 0 to 00. Which is unnecessary complicated, for example to handle it in a database (it is not a number, it is a string, and need a extra sorting algorithm (00>0>1>2)). If you use mm², You can just specify any real number and sort it correctly.
The units have a wierd complicated formula of 127µm * 92^(36-n)/39 or 5mil * 92^(36-n)/39, with more or less random factors (92,36 and 39) (only works as long as n is positive), to get the thickness of a cable.
With mm², the DC resistance is directly proportional to 1/A (A is the cross sectional area), and the maximum DC current can you estimate with about 6-9A/mm².

The people who start designing PCBs were engineers, so the did know all this things, why did they still choose to use imperial units? (It was even worse at this time, with more different definitions of imperial units).

Why i think this question is relevant for electrical engineering:

The most common PCB-design tools, like Altium use a non-metric internal grid (which can lead to rounding errors).
Shops labels there cables often in foot and AWG
PCBs manufacturers often write there rules (for example minimum track size and minimum clearance) in mils or copper thickness in oz (when there really mean oz/ft²).


texts: What is the speed of I2C for AVR communication?

texts: I'm doing a project where I'll have a lot of slave ATtiny's and one master controller (either an Arduino/ATMega or an mbed). I assume the ATtiny with it's low clock speed of 10MHz will be my bottleneck(using builtin oscillator). I'm needing to establish how feasible a design is by how fast I2C can go on an ATtiny. So, assuming everything is perfect, how fast can an ATtiny transfer data by I2C in kilobytes per second? Also, what kind of clock speeds would we be talking about in Hz?


texts: Does the increasing of supply voltage, for a asynchronous motor, increases its speed?

texts:
I bought an asynchronous ac motor with 2 choices of windings connection, the first (220V~240V) is a parallel delta connection and the second (440V~480V) is a series delta connection like the figure 3DM03.

First thing I did , I putted an ac inverter driver (Delta) before the motor to protect it and I putted a 3 phase 380V from the wall outlet. And the result is a low speed ( not very good for my application).

Second step, I decided to step up the voltage to 470V -with a 3 phase transformer- to have more speed as the torque is fixed, but the suprise was no more speed with the increasing of voltage.

My question is where is the wrong thing in my project?
Please let me know.


texts:
Can somebody help me in deriving the expression for rise-time for second order RC filter.

simulate this circuit – Schematic created using CircuitLab


texts: Is there a Formula to Predict Delta Temperature based on previous trend?

texts:
I need a way to predict delta temperature curve based on previous trend. I do a lot of heat rise testing on electrical conductors and I would like to be able to atleast get an approximation of the curve before it is done.

For example if I already have the data points in this curve before the line. I want to me able to predict the rest after the line. It doesn't have to be that accurate. If I am within 10% that would be fine.

ETA:
I'd like to ahead some more light on this question. I think part of the problem with exponential decay not fitting to my graph is that the ambient rose over time. See below I added ambient to my graph and created another that is only rise over ambient. Disregard the large dip in rise over ambient after it stabilized. This data comes from a test that was done outside, so wind and or sun/shade could account for that.

Sample and Ambient Temperatures

Rise over Ambient


texts: Why is that Kirchhoff's voltage and current law always give answer? I mean if we apply node method at the end we can write the equations in form of matrix. The matrix could be singular, but it always gives an answer; why is that?


texts:
I have a PWM load which draws its current from a regulated DC supply. The supply and load will be separated by some distance, and I'm worried that the rapid changes in current through the current carrying wire between the supply and load will create excessive EMI.

The first idea was to have this:

simulate this circuit – Schematic created using CircuitLab

But the problem is on start-up the current drawn through R2 and C1 would be too great. Ideally the peak current drawn from the power supply would never be greater than 3A.

I'm looking for a simple circuit that just uses no more active components than a couple of BJTs to reduce rapid current changes and the initial current surge, while ideally not reducing the voltage to the load by more than about 2V. Any advice would be very helpful.

Thanks


texts: simulating a photo diode response- how to make use of pulsating current sources

texts:
Currently my photo diode is exposed to pulsed laser with

Pulse width           : 10ns < tw  < 150ns

Pulse repetition rate : 1Hz  < PRF < 70Khz

Expected peak current : 50mA

so when i try to design my circuits usually i use a current source for photo diode and a parallel capacitance and a shunt resistance, but how to simulate this kind of waveforms where the current will be present for 10ns and then off its like a switching current source but with different time and repetition rate

has any one tried to simulate a response like this, this kind of response may also be seen in photo diodes which are exposed to RC-5 signals from a IR LED of a TV remote

EDIT:
when i see different simulators all have a similar pulsating current sources,

TINA Current Generator:

NI Current Generator

ADISimPE Current Generator

but what exactly is the voltage source doing here ? , why are they introducing voltage source into current source ?, if suppose i want to use it for my purpose how should i play with it ?, i was not able to properly see my TIA behavior because of this confusion when i reduce the AC voltage of a current source i see my TIA properly functioning , any way this is just a try but i clearly dont know, how to use these pulsating sources as photo diode response


texts: Analyzing a non linear circuit with two sources

texts:
I want to analyze this circuit. V1 is a) +15V b) +10V c) -5V

I need V2, V3, I1, I2, I3

Uz=6,8V
UF=0,7V

And I hate to say this, but I'm absolutely lacking any approach. I don't know how to manage V1.

simulate this circuit – Schematic created using CircuitLab


texts: Why does a circuit with only reactive components have infinite Q factor?

texts: So I came across the statement in my textbook. So I have been trying to understand why this is the case, however I just have not been able to understand


texts:
I'm trying to build my first two-layer PCB layout using this example schema:

I'm using SMD elements, which I would place on the top layer. Also I would create a ratsnet area as GND on the top layer.

I would create some ratsnet area for the SW pin, the output inductor pins and the boost capacitor pins. In that areas I would put some vias and connect them with a ratsnet on the bottom layer.

I'm not quite sure if this is correct so far or if I misunderstood the example. Because then I do not understand the 'additional vias on the GND' of the capacitors.

If the GND area should be on the bottom layer, what about the trace from the SW-pin?


texts: Switching tone on and off at 120 bpm not working

texts:
I am trying to make a design that toggles a sound at a rate of 120 BPM (once every .5 seconds), and I am using a 50 MHz clock. Here's the tone module:

module tone(
input clk,
input enable,
output reg speaker);

parameter clkdivider = 25000000/440/2;

reg [14:0] counter;
always @(posedge clk) if(counter==0) counter <= clkdivider-1; else counter <= counter-1;

always @(posedge clk) if(counter==0) speaker <= enable ? ~speaker : 0;
endmodule

and here's the toggling module:

module lockstep_main(input clk, output speaker);

reg enable;

tone(.clk(clk), .enable(enable), .speaker(speaker));

parameter beat = 50000000/2;
reg [14:0] counter;
always @(posedge clk) if(counter==0) counter <= beat-1; else counter <= counter-1;

always @(posedge clk) if(counter==0) enable <= ~enable;

endmodule

As it is, the design doesn't work properly, just causing the speaker to emit garbled tones. Also, if I try setting the enable register to 1 initially and not changing it, I still get no sound. What could be the issue here?


texts:
I am working with the AD8222 dual package instrumentation amplifier from Analog Devices. I want to build a compact EMG system so I am trying to use this chip since there are not a lot of dual IAs on the market. I need 4 channels eventually.

I have the chip working on a dual supply, and I tested it with a sine wave and the amplitude increases based on the resistor. I tried building the system using a VS- as GND, VS+ as the supply voltage and a voltage divider for the reference voltage. I tested two values of gain resistor (499ohm = 100 gain and 4k which is about 10) and two values for the voltage divider (1k and 10k) to see if the impedance was changing anything.

The output of the amplifier is always the voltage divider value. If I change VS+ to 5V the output jumps to 2.5V. I have tested an input signal of 100 and 200mV with both negative and positive offsets and nothing changes.

The data sheet says the device should work in single supply mode so I am not sure what I am doing wrong. Does anybody have any suggestions of how to change the circuit, or a difference dual package IA that I could test. I really need the single supply since I want to run this system off a battery for a small embedded device.

EDIT: Fixed schematic to reflect the part better.

simulate this circuit – Schematic created using CircuitLab


texts: Can anyone identify this 6 pin SMD integrated circuit, or what it does?

texts: Can anyone please identify this 6 pin SMD integrated circuit or what it does? I could not find it by the code written on it. Can anyone find a datasheet for it?


texts: Relating DC motor with the Fleming right hand rule

texts:
I am studying DC motors and I know that what the direction of the rotation will be given by the left hand rule.

If I compare the right and left hand rule, if I point the thumb and the first finger to the same directions with both hands, only my second fingers will be in opposite directions (the current).

So I am wondering if I suddenly cut the current of the motor, then it will still be in motion due to inertia, then the right hand rule apply and a current will be induced in the opposite direction of the current that I was supplying.
Does this mean that I need to protect my circuit against reverse current? Or am I getting everything wrong?

Why this adafruit circuit doesn't protect against reverse current? It does the opposite, it protects against inducted current in the same direction:


texts:
I'm building a simple temp PID controller for turning an SSR on and off (yes, I know I can buy them fairly cheap, but its a learning project) and I need DC to power my RBBB arduino and mains AC for the SSR.  I'd like to do the AC to DC transformation in my project and I'm really  clear on how to do it.   Ideally, I have a small box that I'd like the project to fit in and the transformers of the circuits I keep seeing are way too big.  Obviously you can do it very small - the Blackberry travel charger* is the size of a large gumball and does 5v @ 750mA.

Is there different technology used in such a small device or am I simply not sourcing a small transformer correctly?

*Worst case, these are like 5 dollars and I'll crack one open.  It should be a sufficient current for me.


texts:
I wanted some opinion on my set up here, just to make sure I got the basics right.

I have a Li-ion battery charging circuit based on the MCP73113. This is designed to be a single-cell battery charger.

The battery itself (3.7V, 650mAh) comes with its own PCB with Schottky diode and current regulators as protection.
EDIT: Not a Schottky diode. Current limiter and a Protection IC.

By design, they work together just fine.

I have more batteries from the same manufacturer and wanted to make higher capacity packs by putting two cells in parallel. The two cells come with their own PCB, but I only kept one of them, as I soldered their leads together. It seems to work and they are charged and discharged just like regular batteries (3.7V, now 1300 mAh).

However, not all the packs I made work smoothly and I get a failure rate of 2 in every 10 packs. They all start out normally, but occasionally when the batteries are not charged for some time, or are used up, they tend to not work anymore. So far, in only 1 pack I found the voltage to be different (both now below 2V, aka dead).

I assume my method is not the right approach to ensure 100% success rate, so I was wondering how can this be solved. All the controllers I looked into was designed for multiple cells in series, not parallel. Am I fundamentally missing something here?


texts: Can't find suitable Bistable/Latching 12V DPDT Relay

texts:
I have a 12V actuator that is controlled by a 12V programmable timer. So my pulse is either power or no power. I am using a regular 12V DPDT relay which works fine.
However, I would like to use a Bistable relay so that I can turn off the power entirely (except for the timer of course) after the actuator is done extending/retracting.
My understanding of a Bistable relay is that it stays in it's last energized position even if it does not receive any power.
Based on that I bought several "Bistable/self-locking/latching" relays on ebay (Made in China) that claim to be "bistable/latching/self-locking".
These relays need a short trigger (like a momentary switch) to switch and stay in this position until triggered again.
BUT when power is removed entirely the relay switches back (reset). This is not how a bistable relay is suppose to work or am I wrong ????
Can someone tell me where I can get a relay like that (as cheap as possible of course)?
I found GE RR7 relays that are suppose to work like that but the ones I find are mostly remote controlled relays which I don't need. I am really having a hard time finding a 12V DPDT latching relay that stays in its last energized position even if power is removed entirely.
Thank you very much for your help !


texts:
I came across a "IGBT Bi-directional Switch" on the web while looking for a solution to my problem of protecting a TRIAC/SSR from a short-circuit.

Since TRIAC/SSR turn-off is not in my control, I'm quite interested in the IGBT solution. However, being relatively unfamiliar with them I wanted to ask here in case I was not fully understanding the circuit.

next to this circuit, I've also seen the following circuit which, at least, mentally I can follow and do think should work.

I have the following questions about this circuit:

Can this switch be viably used to switch mains 220V?
Since they are IGBTs, if I sense the current in the mains and if it exceeds a certain threshold, can I switch these devices off immediately?
Can other forms of transistors be used here? If not, why so?


texts:
I am trying to design a device that is used for capturing rotation. I think I will be using an IMU from Invensense, as I have a few of them to play with.

A big problem gyroscopes seems to be drift, particularly yaw drift, as the drift on pitch and roll axes can be (mostly) removed by using a accelerometer to monitor gravity.

Is there a reason not to mount the device "on it's corner/edge", assuming that most of the time the up axis will stay the same, so no axis will have to be aligned with the gravity field for long. I have tried googling for this, but haven't really found anything. I'm assuming there must be something wrong with my idea, as I didn't find it being commonly used.

In my case the computational power needed to rotate the "local" rotations to "world" locations is not an issue, as it can be either done on a 32-bit microcontroller or a pc that is connected to the uC.


texts: PIC24F debugger halts and resets upon I2C read of slave

texts:
I've been trying to debug my I2C communication between the PIC24FJ32GA002 and the PCA9546APWR bus switch for a couple of days now. I just want to test that I could enable a channel of the bus switch, so what I've done is write to the bus switch to enable a channel, and then read from the bus switch to confirm if the selected channel is enabled. I've had no problems writing to the bus switch using the debugger; however the debugger halts and resets all the time upon a read from the bus switch afterwards, although no breakpoint is set.

I've been trying a couple of ways to find out what is causing the halt, I've implemented exception handlers provided by Microchip: http://www.embeddedcodesource.com/codesnippet/address-error-trap  to see if hard traps such as address errors etc are causing this issue, but none of those handlers are entered when the debugger halts. The RCON and INTCON1 registers are zero as well.

So now I'm looking at the scope to trace the SDA signal line, somehow I couldn't capture the SCL line properly on the scope, but I assume it should be working if I see changes in the SDA line?

Here are a few pictures of the write sequence to the bus switch:

I think the sequence is right, from using the cursors, if each bit is 40us long, I get the correct write sequences and ACK from the slave. The switch address is 0xE0 for a write, and I'm enabling channel 2 of the switch. This is from pg 13 of the datasheet: http://www.ti.com/lit/ds/symlink/pca9546a.pdf

Now, here is the picture of the read from the slave:

From where my time cursor is placed(ignoring the ACK period from slave), I can see that I'm getting the correct results from the slave which is 0x02, but somehow the debugger halts here all the time. I'm a little concerned about the SDA line not going high after the ACK from the slave though. Could that be the issue?

Here is my code for the bus read as well:

char I2C_bus_read(void){

char status;

I2C2CONbits.SEN = 1;
while(!IFS3bits.MI2C2IF);
IFS3bits.MI2C2IF = 0;
I2C2TRN = BUS_SWITCH_READ;
while(!IFS3bits.MI2C2IF);
IFS3bits.MI2C2IF= 0;
I2C2CONbits.RCEN = 1;
while(!I2C2STATbits.RBF);
status = I2C2RCV;
I2C2CONbits.ACKDT = 1;
I2C2CONbits.ACKEN = 1;
while(!IFS3bits.MI2C2IF);
IFS3bits.MI2C2IF = 0;
I2C2CONbits.PEN = 1;
while(!IFS3bits.MI2C2IF);
IFS3bits.MI2C2IF = 0;
return status;}

EDIT: Following the comment below, my #pragma configuration bits have turned off the watchdog timer previously, and I'm running on the default 8 MHz clock. I2C is run at the standard 100 kHz.

I checked the RCON registers again, and I must have been confused prior, for RCON isn't zero as claimed, but the bits for power on reset (POR), brown out reset (BOR) and master clear reset(nMCLR) is set. What interests me the most is the (nMCLR) pin. Why is that pulled low? Could it be my hardware setup that is wrong? Attached now is my schematic for the I2C setup.


texts:
There's a bunch of posts about this, but they're all for very specific scenarios.  I'm a newbit, and some components, like op amps, require both a positive, and negative voltage.
But how do you get negative voltage?
I'm about to buy what I think are my last "essential" components, an assortment of voltage regulators, and an assortment of logic gates.  Aside from a collection of those, I have most breadboard components.

I've read you could use transistors kind of like a charge pump,
I imagine you could use wind a transformer 1:1 and hook on the "wrong" sides of the secondary?
Could you use a NOT gate, or does that give 0 V?

Like from a day to day, really basic stuff, just giving -5 V to an op-amp, how do you get negative voltage?
I haven't played with the op-amp either, but they're everywhere, and I never see how they manage to give it the negative voltage the schematics seem to say it wants/needs...
I'm just putting my kit together, and preparing to embark on projects, so I don't have to order parts, and wait, and it's the wrong part, etc...
I just figure there's an easy way to to it, or there's a part, or collection of similar parts I need to be able to get negative voltage when I need it...
Some parts want +5V and -5V and ground, so I can't just flip +5V and GND, either... can you even do that?
Anyone can help me understand?


texts: Adjusting duty cycle without affecting frequency of a VCO

texts:
I've looked around the internet for a simple voltage controlled oscillator that is able to produce various waveforms in phase with one another. I asked about it in this site and was directed to a dual opamp integrator/comparator setup, of which  a voltage-controlled version can be found in this schematic (from breadboardadventures.com)

I constructed this (except for the n-MOSFET switch, which I've replaced by a NPN due to lack of parts) and it seems to work as intended. However, I'm interested in controlling the duty cycle of the generator. I ran it in a simulator, and as expected, changing the ratios \$R_1/R_4\$ and \$R_2/R_3\$ (within reasonable limits as to not invert the integrator polarity) gives me different duty cycles, as well as different asymmetries for the triangle waves. Placing a pot in that position would do what I wanted, right? Well, no. Since it directly changes the slope of the integrator curves, it alters the oscillation frequency of the entire system. That is something which would be a hassle to adjust accordingly in the control voltage.

How could I adapt this circuit to adjust duty cycle and other parameters simultaneously using a single external control, in order to keep the oscillation frequency constant?


texts: Is there a IC to decode Johnson code to BCD 8421 or 7-segment?

texts: I'm studying Johnson counter and want to display the counting on a 7-segment display. Is there an IC to decode Johnson code to BCD 8421 or directly to a 7-segment displays?


texts:
What I have learned: In a ideal transformer, the power in the primary circuit will equal the power out in the secondary circuit.

Impedance matching: if I take the turns ratio of the transformer in such a way as to allow....

$$Z_{primary}= a^2 Z_{secndary}$$

then maximum power is transferred to the load at the secondary circuit.

My question: if all the power going in is transferred to the secondary circuit, why is the impedance matching required in the first place?


texts: Looking for confirmation on power supply project

texts:
First time poster - this site's been really helpful for me, so thanks to all of you.
I'm working on my first electronics project not from a kit, and am attempting to make a variable power supply.  I'm using this schematic as a reference: http://www.ladyada.net/library/equipt/diypsupp.html  However, I've modded it a bit:

I will be using a wall wart to power, and am planning on using a 19V power supply, with the option to use smaller adapters if necessary.  I'm not certain if I got the symbols right, but the V and A represent a digital voltmeter/ammeter.  My most pressing questions (in order of importance):

What connection do I make with the ground that is located below R2?
I'm interested in having a light-up switch for power. What would be the best way to draw the 12V it requires for the bulb?
I can certainly test this one out, but I'm wondering if I have the voltmeter and ammeter connected properly.
How might it affect my circuit if I increase C3 to be a 2.2uF cap?  This may be what's available to me, and it seems like it won't impact the circuit negatively, but I want to be sure.

Thank you for any thoughts or suggestions!


texts: Why a series diode for the mosfets in this circuit?

texts:
Whats the reason for the diodes on those two mosfets in the inverter?

Link: http://inductionheatertutorial.com/inductionheater/inductionschematic.gif


texts: How to combine wall outlets for higher amperage?

texts:
I have a large single phase AC motor that draws 30 amps at 125v. I only have access to NEMA 5-15R outlets (which are rated for 15 amps). However, several outlets are on different lines (different fuses) i.e. I can draw 15 amps from multiple outlets at the same time.
Is there a way to spread the load of this motor across 2 (or more) outlets so that each outlet supplies less than 15 amps while the motor receives all 30 amps it needs?


texts: Do I really need diodes to receive MIDI?

texts:
All the schematics above use a diode before the receiving pin on the optocouplers. The problem was, I never able to find the exact same diode as the schematics.

Before, I'm using H11L1, but it never worked. Now I have plan to move to 6N138, but I'm afraid I'll meet another problem with this.

The end goal was receiving MIDI with either Arduino or ESP8266. Or is there any easier way?


texts: Ripple current in synchronous buck converter

texts:
I am designing a synchronous buck converter and I am at the bread board stage in my design. I wanted to check the current waveform through the inductor, but I do not have a current probe available. I have a differential probe so I decided to add a 1 Ohm resistor in series with my inductor and measure the differential voltage across it, which should be the same as the current. Below is my waveform, I am wondering why the current waveform is not as triangular as I usually see for a switch mode power supply. Is it because I added the 1ohm resistor in series for an inductor (6.8uH) that only has only around 0.020 Ohms of DCR?

EDIT:

I switched to a ferrite core that should have substantially less core loss and I tried a few different FETs and it didn't seem to make much difference. Below is another waveform, this time CH2 is at the switching node. One thing I forgot to mention is that I am using a half bridge driver that adds a small amount of dead time to keep the two FETs from having any shoot through. Although I can't imagine that being the reason, it's probably worth mentioning. Also, I now have the scope triggering properly and the time scale is now correct.

I also put the diff probe across the inductor, and below is the waveform. I've never noticed the slope, is that due to the series resistance? Or potentially the Vds of the FETs changing because the current ripple is large?


texts: Measuring Resistance of a Wire With an ADC

texts:
I'm trying to design a circuit which can measure small resistances down to 0.1 Ohm and a max. of 10 Ohms. I won't be measuring actual resistors but rather large coil of wires, upto 500 m (as you can imagine, these wires are quite thick).

Here's the circuit I came up with:

The circuit works by maintaining a constant current through the device under test, R2. With a current of 100 mA, R2 would develop a voltage between 10 mV to 50 mV.

I think in an ideal world this would work but in practice I may have a hard time measuring 0.1 Ohms with this - mainly due to the ADC. Let's assume the ADC is 10-bit with VREF of 5V. This translates to 5mV per step. If R2 = 0.1 and Iout = 100 mA, then the voltage present at the ADC would be 50 mV - but I'm not sure how buried under noise this would be.

My question is, should I increase the gain to, say, 50. If the gain is 50, then the voltage present at the ADC would be 500 mV - but the max. measurable resistance would be 1 Ohms. To measure 10 Ohms, I would need to lower the current to 10 mA instead of 100 mA. A way to do that would be use an FET to switch out R1 and connect a 20 Ohm resistor at Iout.

I don't need the circuit to measure the resistance precisely - a tolerance of +/- 10% is fine.


texts:
I think this might be a bit of a stupid question, but I've got a bit of mental block on it.

I'm trying to power a CA3140 op-amp. I have a 12V source, and an AMD660 inverter to provide the negative voltage.

simulate this circuit – Schematic created using CircuitLab

However, when I connect the negative supply pin of the op amp to the pin to the output pin of the ADM660 inverter, the voltage reading on the ADM660 output goes to a few hundred (positive) mV instead of -6V(ish) it should be. Obviously the output of the op-amp does not descend into the negative region.

I've tried placing various resistors in series with the output of the ADM660 to reduce the current as it was fairly high, but this just results in a voltage drop across the resistor, and still leaves a positive voltage on the op-amp pin. What should I be doing? I feel like I'm missing something easy here, sorry if it's really obvious, I'm fairly new to electronics.

Thanks.


texts: Flyback Transformer - Grounding the Ferrite Core

texts:
Today I dismantled (I hope this is the correct verb) a flyback transformer. The thing that I've never seen is that one end of one of the windings is "glued" to the ferrite core (Before you ask; yes, the glued end is coated with solder).

Here's the schematic of the transformer (neglecting the dots):

simulate this circuit – Schematic created using CircuitLab

EDIT:

Some details:

Core: EE16 with center air gap
Bobbin: EE16 horizontal 2x5pin

Winding structure (from inner to outer):

1) 56 Turns - half of primary (Np1)

2) 35 Turns - Ng

3) 11 Turns - Secondary (Ns)

4) 13 Turns - Auxilliary (Na)

5) 50 Turns - Remaining half of primary (Np2)

One end of the Ng winding is GND and the other end is glued directly to the ferrite core. Ng is in phase with Na wrt GND.

So, I have a few questions:

1- What is the purpose of Ng winding? For better EMI performance?

2- Related to Q-1, is there any difference between direct ground connection and connection through a winding? Also, what if there was an external inductor (e.g. I-Core) instead of the Ng winding?

I know that iron-core power transformers are grounded for safety. But I think that this is different.


texts:
I got a NEMA11 bipolar stepper motor rated at 3.8V @ 0.67A, 5.6Ohm and 4.2mH. I thought to run it with the D1 mini powered via USB and using its 5Vout for the SN754410 H bridge and motor power:

However, when I tested it with my D1 Mini, it just wiggles and has zero torque. I started with the basic stepper lib code:
#include <Stepper.h>

const int stepsPerRevolution = 200;  // change this to fit the number of steps per revolution
                                     // for your motor

// initialize the stepper library on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, 1,2,3,4);

void setup() {
  // set the speed at 60 rpm:
  myStepper.setSpeed(60);
  // initialize the serial port:
  Serial.begin(9600);
}

void loop() {
  // step one revolution  in one direction:
   Serial.println("clockwise");
  myStepper.step(stepsPerRevolution);
  delay(500);

   // step one revolution in the other direction:
  Serial.println("counterclockwise");
  myStepper.step(-stepsPerRevolution);
  delay(500);
}

I ran another stepper a couple years ago with a similar setup (just using a Android Nano instead of the D1 Mini) and it worked great. Back then I used Accelstepper:
#include <AccelStepper.h>

#define HALF4WIRE 8

// Motor pin definitions
#define motorPin1  1     // A1
#define motorPin2  2     // A2
#define motorPin3  3     // B1
#define motorPin4  4     // B2

// Initialize with pin sequence IN1-IN3-IN2-IN4 for using the AccelStepper with 28BYJ-48
//AccelStepper stepper; // Defaults to AccelStepper::FULL4WIRE (4 pins) on 2, 3, 4, 5

AccelStepper stepper1 (HALF4WIRE, motorPin1, motorPin2, motorPin3, motorPin4, true);

void setup() {
  stepper1.setMaxSpeed(1200.0);
  stepper1.setAcceleration(100.0);
  stepper1.setSpeed(100);
  stepper1.moveTo(2000); //250 full rotations @ 48 steps each = 12,000 steps

}//--(end setup )---

void loop() {

  //Change direction when the stepper reaches the target position
  if (stepper1.distanceToGo() == 0) {
    stepper1.moveTo(-stepper1.currentPosition());
    delay(500);
  }
  stepper1.run();
}

However, I dug out the old motor, and even that one is just vibrating. It changes in tune with the Accelstepper speed, so I assume something is working as it should, but never moves out of the same position. I tried even an external power source but with no difference. Any tips what could be off? Broken chip, wiring, power?


texts: Voltage Drop Across Wire With Fixed Load Wattage

texts:
I am looking for an equation to calculate DC voltage drop across wires that run a distance, with a switching regulator and fixed load at the end (a known wattage).

Here are the specifics:

The power source is 19.5v (going into the length of wire).

The regulator is at the end of the wire, with an estimated 95% efficiency.

The regulator output voltage is 5v, and there will be a 0.8A load. 5V * 0.8A = 4W, and at 95% efficiency that is a load of about 4.2 watts (4W / 0.95 = about 4.2W) being drawn through and used by the regulator.

The total wire resistance is estimated to be 10.18 ohms (23 gauge, 250 feet each way, or 500 feet total).

And that is as far as I have gotten. I'm looking for an equation to calculate the voltage drop across the wire, given the above values.

At first I thought I could just make the following calculations: 4.2W / 19.5V = about 0.22A, then 10.18 ohms * 0.22A = about 2.24V, then 19.5V - 2.24V = 17.26V at the regulator's input. However, that fails to account for the power being "wasted" as heat, due to the wire's resistance. I would take that 0.22A * 2.24V and assume the wire uses about 0.5W, but due to the voltage drop of the wire, the current is actually higher in order for the regulator to still pull 4.2W.

So, how can I calculate the voltage drop, knowing the source voltage (19.5V), the wire resistance (10.18ohms), and the load wattage (4.2W)?


texts: Use magnetic field to estimate distance - best sensor type

texts:
I want to measure the position of something that movies along a single axis over a range of 150mm at a frequency of roughly 1kHz.  You can imagine that it is the piston on a shock absorber. I could attach a small magnet to the moving element.  I think it should be possible to position a magnetic sensor at one end of the range of motion and then capture the magnetic field as the item moves back and forth. The problem is that most magnetic sensor that I can find are hall-effect sensors that are designed to switch from 0 to 1 over a very short distance. What I need is a gradual change in voltage output over the range of motion so that I can estimated the piston position based on the sensor voltage over the 150mm of travel.

TMR sensors seem to be inherently better suited as they have  a more linear response to magnetic field, but I can't seem to find a simple sensor.  They are all configured as angle sensors (would these work for my application?) or proximity sensors.

If I can just get the raw response voltage and capture that with an adc on a microcontroller I think this would be fine.

Any ideas?


texts: Dielectric constant (relative permittivity)

texts:
I recently learned that the dielectric constant (or relative permitivity) is not actually a constant, but it depends on wavelength or frequency (dielectric function). If that is the case, why are we taught in an introductory EM class that the dielectric constant is constant? When we say that the dielectric constant is 11.68 for silicon, which wavelength are we referring to?

When we perform a calculation that requires a knowledge of dielectric constant, which value (corresponding to which wavelength) do we use? For example, calculation of the width of space charge region requires us to know a dielectric constant of material.

\${\displaystyle w\approx \left[{\frac {2\epsilon _{r}\epsilon _{0}}{q}}\left({\frac {N_{A}+N_{D}}{N_{A}N_{D}}}\right)\left(V_{bi}-V\right)\right]^{\frac {1}{2}}}\$

I am very confused. Please help!


texts: Controller for greenhouse control system

texts:
I'm working in a project where we are developing a greenhouse control system, to take care of temperature, humidity...

For the first step where we only log the parameters to an SD we have been using an Arduino board, but now we want to improve the system and add fans, humidifier, light sensing and control algorithms to maintain the greenhouse at a constant state.

Because of the grow of the system we can't use the Arduino anymore, we are looking for a SBC or Microcontroller board, powerful enough to do the job but we don't want a painful migration, we are looking for a easy to use board with RTOS or ever better embedded Linux. And if it is possible it shouldn't be so expensive.

Do you know some product that fits our needs? or Could you recommend me another solution?

Thanks you all :)


texts:
I am planning to use IMU for joint angle measurement of hand(shoulder ,elbow and wrist joint), I am confused about reference frames of accelerometer and gyroscope. According to my understanding accelerometer will measure angle between global reference frame and reference frame fixed on IMU , How to fix the global reference frame? I can only think of one axis along the direction in which gravitational force acts (vertically downwards), other two axis can have any direction in a plane perpendicular to gravitational force.
Also my understanding about gyroscope is it will measure orientation with respect to its previous position using reference frame fixed on imu. To fuse it with accelerometer the angle value has to be calculated with respect to global reference frame. How can it be done?


texts: Transfer Function for a Non-Inverting Op-Amp with Feedback

texts:
In the following problems, ideal op-amps are assumed.  This op-amp circuit appears in Dorf's Modern Control Systems, 12th Edition (pg. 136):

With \$v_{in}\$ on the left and \$v_{o}\$ on the right.  Dorf's answer key gives

$$
\frac{v_{o}}{v_{in}} = 1 + \frac{R_{2}}{R_{1}}.
$$

How?  A different problem gives a similar answer:

Where the answer is derived as follows:

$$
v_{o} = A(v_{+} - v_{-})
$$
$$
v_{o} = A(v_{in} - v_{o}\frac{R_2}{R_2 + R_1})
$$
$$
v_{o} = \frac{Av_{in}}{1 + A\frac{R_2}{R_2 + R_1}}
$$
$$
\frac{v_{o}}{v_{in}} = \frac{R_2+R_1}{R_2}
$$
$$
\frac{v_{o}}{v_{in}} = 1+\frac{R_1}{R_2}
$$

because \$A>>1\$.

I don't see how the first circuit yields an answer so similar to the second when its configuration is apparently different.

I'm not even sure how to go about solving circuit one; normally I'd use KCL on the \$v_o\$ node but there's no current through \$R_2\$.


texts: I want to design a VCO with a range between 1Khz - 100Khz. I am following the design from another forum Low frequency in this VCO design. I ended up changing c1 to 7pf which changes the range form 33.9Khz to 99Khz with a 1V-12V input. The upper limit is alright but I am having trouble changing the lower one to 1Khz. I also want to know what kind circuit this is so I can find some theory related to it. Finally if I want to get a sinusoidal output would I just integrate the signals coming out of the square or triangle waves? And how would I know what values of resistors and capacitors to use? Thanks a lot in advance. I have attached a picture of my design below.


texts: When to use step up and step down transformer

texts: Well I once saw a video in which a guy made a spot welder using a step down transformer and in another video I saw someone make arcer using a step up transformer. Why using a step up to jump arcs and step down to cause heat in transmission metal


texts:
I am trying to make a discharge system that use 2R2 resistors and relay to engage the system, until here everything is fine, I can trigger the system and discharge the battery.

I thought, that I could add a voltage monitor on the BATT trace and monitor the voltage but apparently I messed up something which I cant understand.
If I dont solder the 2R2 resistors ( R1 and R29 ) , I can sense the voltage and detect when it is dropping.

Once I have the 2R2 resistors soldered, I am not able to read it due to the voltage dropping almost to 0 on the reading circuit.

I am using an ATTiny and using the analog input to read the voltage with the following schematic


texts: Playing a sound when turning off a circuit

texts:
For my project, I am looking to have this (mock-up) circuit play a sound, e.g. the Windows XP shutdown sound, the moment it is powered off.
I have looked at capacitors, relays, opto-couplers, and a bunch of tutorials but they all only can delay the moment the circuit is powered off or act as a timer as to how long the circuit will run, which is not what I want and I can't find anything about this anywhere.
Am I missing something fundamental or is this just not possible?

simulate this circuit – Schematic created using CircuitLab
(Intentionally left out the speaker and potentially needed SD card module)


texts: How to draw a timing diagram for CSE 120 class

texts: I've never done a timing diagram before. So I basically have no idea what I'm doing or what the question is asking. I would appreciate any help! Thank you.


texts: How to prevent crosstalk between a twisted pair in a SCSI cable?

texts:
I am using a SCSI-2 Half-Pitch DB50 connector as an I/O expansion connector, due to size constraints.  However, it seems as if pretty much all cables manufactured in recent years are differential twisted-pair cables.  This creates a lot of problems for me, because the twisted pairs will crosstalk with each other in a pretty nasty way.

I have searched the typical vendors (digikey, l-com, mouser, newark) but I cannot find a single-ended SCSI cable.  They can sometimes be found on ebay, etc, but I am not comfortable using those for production units.

My question is, assuming I can't find a reliable source of single-ended SCSI cables, is there some method that I can use to prevent crosstalk between the twisted pairs of a SCSI cable?

EDIT:

Digital and analog signals are run in the cable.  The digital signals are 5V inputs and outputs.  Data rate is max of maybe 10 MHz, typically less than 1 MHz.

There are no differential signals.  The decision to use the SCSI connector was made before it was known that single-ended SCSI cables are a legacy product that are difficult to find.  I know that twisted-pair is designed to couple the wires; it's unfortunate that I discovered late in development that modern SCSI cables are twisted-pair.  I am considering potential solutions, but I wanted to see if there wouldn't be some "easy" way to decouple the wires before investigating other solutions (e.g. SCSI connectors that attach to ribbon cables)


texts:
A few days ago I had the brilliant idea of replacing the ugly antenna of a 40MHz car remote control with an extendable one. Now the range decreased from 50 meters to 3-4m.

I don't know exactly what I broke so I have some questions, maybe I can fix it:

How long exactly the antenna has to be? I broke the original antenna so I cannot measure it exactly, but it was about 37.4cm long (+/-2cm). The problem is that if I divide 7.5m to 1/4 or 1/8 I don't get near the original antenna length?  So, which is the closest 'round' number to 37cm?
The wire from the PCB to the new antenna behaves as an antenna and i has to be taken into account. Right?
How exact the length should be? Do I loose lot of power if my antenna is 2%-3% longer than it should be?
Maybe the problem is not the antenna but something else. For example: the new antenna is longer and goes very close to the PCB (to the quartz crystal). About 1.5-2cm close. Could it influence the correct functioning of the PCB?

Update:
I put the antenna back. Still doesn't work. I think accidentally touch and deformed some coils in the receiver.


texts: Inputs for flipflops sequential circruits

texts:
Not very sure if these inputs are correct before i draw my truth table.
Too many lines and i am confused.

JA = QB = KA = B
KA = B
DB = D'
TC = 0


texts:
In a course of digital electronics, our Professor wanted to give us just an introduction to charge pumps.
Here the basic topology:

Then he says that the circuit behaves like a bucket brigade chain: a charge packet is transferred by Vdd to CP1 (when CK' is high), then from CP1 to CP2 (when CK is high), and so on and, finally, from CPN to CS. At each transfer step, the voltage of the charge packet is increased. At each clock cycle, Vout is increased until the steady state is reached.

From a conceptual point of view it is clear to me up to now. But then he calculates the dc voltage gain as follows:

Question: why does he say that "each capacitor CPi is charged to the voltage across the preceding capacitor plus Vck"?


texts: Are these two schematics the same? (Amp circuit)

texts: Are these two schematics the same? The lower one is the original diagram. Can I rewire it to look like the top one? The chip is LA4597, if you might ask.


texts:
I read that the surge current for an Indction motor is higher than that of other motors. Therefore when one wants to power a 3phase IM the inverter rating should be much higher than that of a BLDC  (when the supply is DC ). Is it true?

Link to this: http://www.diygokarts.com/vb/showthread.php?t=9700

I am gonna start designing an electric go kart(for an event). I wanted to use an induction motor because of the following reasons:

Better overall or avg efficiency.
lower weight

This is from where I was like convinced to use an IM against BLDC: https://www.tesla.com/blog/induction-versus-dc-brushless-motors?_ga=2.70427863.694368311.1506343498-425824400.1494234243

Specs of the motor and batteries that I'm allowed to use [some extra info if it's needed ]:
- Motor rating <= 3kW
- Battery voltage = 48 V
- 20 Ah <= Battery capacity <= 50 Ah
- Max rpm = 3600
- Max torque = 10 Nm

Any advice is welcome.


texts: RS485 Pull-up, Pull-down and EOL resistors

texts:
I am going to connect several micro-controllers together using half-duplex RS485, but there is no absolute master or slave, each micro must be able to communicate others and this will cause problems if both of them want to send data at the same time (one makes A high and B low and the other makes A Low and B high, that will cause short circuit) so I am thinking of adding pull-up and pull-down resistors to the lines and send data by changing state of TxEn pin instead of TxDt pin of RS485 ICs.Here is my problem:

Pull-up, pull-down and EOL resistors form a voltage divider on the
RS485 data lines, does it make data communication problems?
What happens if I ignore EOL resistors and just apply pull-ups and
pull-downs at both ends?
Is there any relation between maximum cable length and resistors value?
Does using higher data voltage increases the data transmission reliability? If yes, is there any 12V RS485 ICs? (12V is the absolute maximum ratings of MAX485 and LTC1685, what about safety factor?)

BTW, if I have two 100ohm EOL resistors and 5V data voltage it means that communication consumes 100mA, that is too high for a device that consumes only 5mA, and it makes the devices to have a big voltage regulator and capacitors in comparison with other components!

^^^ A diagram I found in LTC1685 datasheet ^^^


texts: Relationship between band gap and built in potential for PN Junction Diode in equilibrium?

texts:
I wanted to know the relationship between the band gap (Eg) of the p/n regions in a diode and the built in potential in equilibrium.

My intuition says that Eg = e*Vo. I did a small calculation for silicon at T=300K. I got the relation to be approximately correct.

Looking at the band gap diagram, the valence band of the p side seems to coincide with the conduction band of the n side in equilibrium.

Is my intuition correct? What is the actual relationship?


texts: Total Cable/Splitter loss calculation for Gain value compensation

texts:
If there is an 8 port splitter attached to cables feeding an array, is the total Cable/Splitter loss = S21 measurement for each port (with terminations on others) OR I have to add the S21 value of each port?

This is confusing me.
So I expect -9dB for an 8-way.
I get -10.5 in my S21 measurements. (For each port, with slight variations from one port to the other)

So is the total loss for all 8 ports feeding array is the difference between 10.5 and 9dB (i.e. 1.5 dB to be added to Gain) or I'm completely wrong?

Another Q: If I only use 2 ports of the 8 way splitter... does the expected value become -3dB? Or it always remains -9dB regardless of port terminations?

Your explanations would be greatly appreciated.


texts:
I have Arduino which output 3 pwm signals into the gate of a irf731 FET transistors.
Their source is grounded, and their drain is going to the R/G/B of a led strip.
The led strip also gets 12v , so it has 4 pins, 12v,R,G,B(rgb from the drains) .

When i set an RGB value for red , i get the first gate on 3.3v, and the others on 0 .

Problem is , the led strip is ON but very low, and show wrong colours ( trust me, i have checked multiple times that my colours are connected ok to the FETS and Arduino)

It seems that maybe the FETS are not working properly with the 3.3v on their gate, could that be the problem? if so, how would you chose another FET or correct this one ?


texts: Implementing a simple counter using VHDL

texts:
Hi I'm trying to implement a counter with external control. I'm kinda new to VHDL and I keep getting syntax error for the following code. Can someone help me understand why there's an error here?

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity lab5 is
    Port ( Abbreviate : in  STD_LOGIC;
           Halt : in  STD_LOGIC;
           clk : in  STD_LOGIC;
              LED_left : out STD_LOGIC_VECTOR(7 downto 0);
              LED_right : out STD_LOGIC_VECTOR(7 downto 0));
end lab5;

architecture Behavioral of lab5 is
type State_type is (two, three, one, six, zero, seven);
signal state : State_type;
signal state_right : State_type;
signal first_time : integer := 1;
state <= two;
state_right <= six;
begin
process(clk)
        begin
        if (rising_edge(Abbreviate)) then
        first_time <= '1';
        end if;
        if(rising_edge(clk)) then
        case state is
        when two =>

        if (Halt = '1') then
        state <= two;
        LED_left <= "1111001";
        else
        state <= three;
        LED_left <= "1101101";
        end if;
        when three =>

        if (Halt = '1') then
        state <= three;
        LED_left <= "1101101";
        else
        state <= one;
        LED_left <= "0100100";
        end if;
        when one =>

        if (Halt = '1') then
        state <= one;
        LED_left <= "0100100";
        else
        state <= six;
        LED_left <= "1011111";
        end if;

        when six =>

        if (Halt = '1') then
        state <= six;
        LED_left <= "1011111";
        else
        state <= zero;
        LED_left <= "1111110";
        end if;

        when zero =>

        if (Halt = '1') then
        state <= zero;
        LED_left <= "1111110";
        else
        state <= two;
        LED_left <= "1111001";
        end if;
        end case
        end if;

        case state_right is
        when six
        if (Abbreviate = '1') then
        if (first_time = '1') then
        if (state = two) then
        state_right <= six;
        LED_right <='1011111';
        first_time <= '0';
        end if;
        else
        state_right <= seven;
        LED_right <='1100100';
        end if;
        else
        state_right <= six;
        LED_right <= '1011111';
        end if

        when seven
        state_right <= six
        LED_right <= '1011111';
        end if
        end process

end Behavioral;

The errors are at line 45 and it says syntax error near "state" and line 103 which says syntax error near "end"

Thank you in advance for helping out.


texts: How to calculate value of each component in an audio amplifier

texts:
Tda 2030a is a 19W audio amplifier. I have connected a 25W 4ohm subwoofer to it. I have done the soldering and the circuit is working successfully  but I want  to understand the working and the calculation behind each component. The diagram is from the datasheet of the respective opamp of the company. The link is attached below.

I want to know why there is a potential divider at the start (fig 1) and the gain of the opamp consist of resistor in series with capacitor (fig 2) and the fig 3 doesn't make any sense to me to all.

I also want to know the calculations behind all of this. I know for sure that all of this has been done to reduce noise and improve gain but I do not understand how exactly everything is working.Can anyone help me ?!! Thank you so much for your contribution!!

Datasheet link:
Tda2030a


texts:
I need to discharge a power rail from 3.8V to 0V within 200ms.  The control signal is active low (i.e. start discharging when control becomes low).  I think the easiest implementation probably is to use NFET and invert the control signal to feed the gate.  That means I need an inverter + NFET.  Any single IC that can achieve this function?

In detail, the control signal comes from a watchdog timer, which is powered by a different power supply.   The signal will hold low ~200ms and disable 3.8V regulator meanwhile, and then go back high and enable the regulator again.   I plan to use this signal to discharge the 3.8V rail at the same time.  I can't use PFET because it will stop discharge (~0.7V) when Vgs<-Vt.  My concern is if I don't discharge the rail to GND, I am not sure if the logic circuits can power up to the right states every time the power is cycled.  Can these residue voltages inside the ICs cause, say, latch up or other unintentional shorts?
Thanks.