texts: Why do I have 44V AC between ground and the V(-) and V(+) of a switch mode power supply?

texts:
I have a system were we wish to place a USB charger outlet. The output is placed in a bench made of metal, so even if the output is isolated and low voltage, it would be a good idea to ground the common output (V-) in case of failures of the transformer isolation or the power supply shorting in a bad way. We plan to ground the metal surface of the bench, but in case of this failure, we still have the bonding of ground between the shield or casing of USB connectors (V-/shield). So a double layer of protection.
I can ground the V (-) just fine, and the device works perfectly.
If I attach the multimeter in AC mode between building GND (AC input GND) and the V(-), I read 44V AC.
This happened with my USB charger and a couple of 12V SMPSs that I have laying around from different manufacturers. It seems like this is normal behaviour for this type of devices in my installation.
What could be the reason of this?  Could this be caused by a problem with my grounding scheme? (I plan to test in other installations.)

The USB charger its the Leviton T5632-W, but also tested an Eaton one.
Also tested with a generic SMPS for an LED strip, two different models with 12V output.
My ground seems to be all right, I have 120V  between phasee and GND, and less than 1V between neutral and GND.
This a USA type installation, with a grounding rod near the main panel, bonded with neutral only there.

After some reading yesterday, I came to some ill informed conclusions.

The output of an SMPS its almost "isolated", and you can leave a floating circuit just OK. It might be safer in some cases. NEC doesn't require grounding <50V, and systems normally don't require it. Some people mention that it could be detrimental if your ground has a lot of noise or undesired voltages. But normally it is ok and it is good to have a decent 0v reference in your circuit.
In most USB chargers (that I tested) the V(-) and shield are bonded together.
USB chargers that I opened or tested don't have continuity between the AC input ground and the V (-) or V (+). They are effectively almost isolated (Did some reading about in reality the input / output of SMPS having a capacitive coupling,  but this is still out of my understanding).
Some people recommend attaching V(-) or reference voltage of an SMPS output to ground, some other people don't. NEC doesn't recommend anything here (I think,) so it seems like both options are ok.

PD1:
Just read this:

Did you measure using DC on the multimeter? You need to measure the AC voltage that might be present between output and ground. Then you could see several tens rising to over one hundred volts AC - this of course doesn't mean it's dangerous - it's just the EMI decoupling capacitors (if any) on the output.
For DC measurements your meter's input impedance will likely reduce the voltage to near zero.

So that's exactly the situation. Seems like my plan of grounding the DC output its fine and safe then.


texts:
The regulator supports both digital circuits and analog circuits, which is shown in the diagram below.

My question is: can I place the regulator at the analog part? The regulator supplies the digital circuits with a thick trace. Usually, I put the regulator at the middle between digital circuits and analog circuits.

I think this way could be fine, since the return currents of MCU shall be low-frequency ones and shall go to Power In directly without going through the regulator.

Am I correct?


texts: I'm trying to learn about gates.Why is a resistor connected parallel across the output?


texts:
i'm using a MSP430F6736A the eUSCI_B0 i2c peripheral on my chip in INTERRUPT mode to communicate with a FRAM chip.
I'm trying to figure out why i have to drop my i2c clock to 130KHz in order to communicate "reliably" with a Rohm FEDR44V100A fram 1Mb chip.
To clarify, when i set the i2c clock to 400KHz, the FRAM chip 'sometimes' seems to send back just 0s (best case, or random data worst case), yet when i set the i2c clock to 130KHz, everything works superbly.
I am assuming it is the FRAM chip that is sending bad data & not the i2c port receiving bad data as i cannot "consistently" reproduce the error so as to capture it on a logic analyser.
From the FRAM datasheet, the chip can operate at clock speeds up to 1MHz.
My MSP430 is operating at 16.77MHz
the rise time on SCL & SDA is less than 200nS.
the pullup resistors on the i2c bus are 2K
the setup for the i2c is:
UCB0CTLW0 |= UCMST | UCMODE_3 |  UCSSEL__SMCLK;
UCB0BRW_L = 128; .................this is for 130KHz
UCB0BRW_L = 40;....................this is for 400KHz
UCB0BRW_H = 0;
UCB0I2COA0 = 0;
UCB0I2CSA = theSalveAddress;

the interrupt bits of UCB0IE are set/cleared at the relevant times.
I might point out that i had no problems whatsover communicating to a Microchip 47L16 EERAM chip at 400KHz which would indicate the problem lies (100%) with the ROHM chip...but why?
Any pointers as to what i could do to try & improve the speed would be appreciated, as would any suggestions as to why the communication has to be at this low speed.
thanks in advance.
the circuit...

clock wave at 129KHz..

clock wave at 382KHz..


texts: Estimating costs for producing and implementing RFID systems

texts:
What type of RFID could I attempt to emulate myself easily for projects in a classroom. There are many technologies that are available and I am having a hard time selecting an RFID system that would both allow a demo of RFID and and best cost effective for a teachers budget.

RM: I understand the question to be as follows. Azin should comment or edit to suit.

The company that I work for want to know how much does it costs to produce RFID tags and readers, and the typical end user cost for implementing overall projects including the costs of tags, readers and related equipment.

It is possible that building tags and readers from components would be most cost effective due to our circumstances but this would depend on the cost of component parts and the volume costs of available finished readers and tags - so I need to be able to get a feel for actual component costs so useful comparisons can be made.

An example system which sounds similar to the sort that we would like to implement is the one installed at St Charles Sixth Form College in West London, England. I have been unable to find any costing data on such systems.

The St Charles College system is mentioned on a number of websites including here and here {Wikipedia} but does not seem to be mentioned on the school's website.

... St Charles Sixth Form College in West London, England, started September, 2008, is using an RFID card system to check in and out of the main gate, to both track attendance and prevent unauthorized entrance ... .


texts: Device to smooth out power consumption of a heat gun

texts:
When I turn on a 2KW hot air gun that is not set to full power it does on-off power control which makes bulbs in my home flicker which I understand that it happens because of small voltage dips because of the additional 10 amps of current.

There's probably no harm in this flicker but I'm just wondering if it is feasible to make a device to plug in between the hot air gun and the mains that would consume a more even current at the mains side so that the lights don't flicker.


texts:
On a PCB a GPS patch antenna should be placed. The antenna feed pin goes through the board and is soldered on the bottom side. On the PCB top layer is a ground plane.
My problem is now to define the radius of the area around the feed pin that has to be kept ground free to achieve the best signal transmission. See graphic of cross cut.

Can anyone help me with this problem?

Parameters: PCB material FR4, 0.8mm thick. Antenna impedance 50 Ohm, feed pin diameter 0.8mm.


texts: Calculating single phase load from 3 phase power measurements

texts:
I need to record kW & kWh for individual phases on a circuit that has a 3 phase power meter that outputs the following data:

Total for all three phases:

kW
kWh
kVA
kVAr
power factor
Frequency (we can assume that this is universal across all phases)

For each phase, L1, L2, L3 the following readings are also available to me:

Volts (L-N)
Line Current (Amperage)

Considering that the load distributed unequally, I'm wondering whether there is a way to calculate individual load in kW, using the data that is available to me.
It seems to me that it should be possible to use a ratio calculation to calculate how much of the total load belongs to each phase:

kWL1 = (kVAL1/kVAtot)*kWtot

Can someone confirm this hypothesis?


texts: How to convert variable frequency small AC signal to square wave

texts:
I have been given an RM Young wind monitor (Nice!) but there is no amplifier circuit with it (Yikes!) here's the model: http://www.youngusa.com/Manuals/05103-90(M).pdf
My problem is with the wind speed, I'm trying to measure this with an ESP-wroom-32 and can't get my head around a good all around simple circuit to convert the wind speed signal into pulses of varying frequencies. In a nutshell, the wind speed monitor is a fixed coil and three magnets are attached to the rotor so we get a 80mv peak to peak up to 8 volts peak to peak signal of varying frequency proportional to 3 times the RPM (up to 10000 rpm). I tried a schmitt trigger but I get either a lot of false positive pulses or nothing at all. Here's my circuit:

simulate this circuit – Schematic created using CircuitLab
Am I at least on good tracks? After searching for a while I found the schematic of the OEM amplifier circuit: https://s.campbellsci.com/documents/ca/manuals/05603c_man.pdf
I have a very old oscilloscope with a 3 inch viewport, I believe I noticed disturbances in the sine wave, I believe that could be caused by the diode?


texts: Calculating size of cap & inductor for buck convertor

texts:
What is the idea of choosing inductor & capacitor value for buck DCDC convertors (no specific part number, in general)?

I've tried random one with low resistance, and it kinda works, but want to know idea behind calculation of optimal value (based on freq, and max current).


texts: Prevent ISE from bitswapping the configuration file

texts:
For some reason unknown to me, ISE provides a bitswapped configuration image: each byte has its bits swapped.

Is there a way to disable this bitswapping? (Having to do it again in C code slows down the image loading.) I've had a look at the Bitgen options and was surprised to not see what I wanted there.


texts:
I'm trying to purchase SMD capacitors online, but I'm not sure how to identify the voltage rating of the SMD capacitor.

How can we calculate the voltage rating of an SMD ceramic capacitor?
Is it dependent on the package size or what are factors to be considered?


texts:
I've  converted an existing 18v DC battery pack (for a power tool) to use replaceable 18650 cells. My plan is to charge the cells in a "smart charger" and discard the OEM charger. I'm only getting about 1/2 of use from the tool before power cuts out. This is an original battery pack which failed in service and I suspect the board may be toast.

If I wire up the 5 cells (in series) directly to the load pins that connect to the tool, do I need to consider some sort of discharge or thermal protection inline as well?  Specifically, I'm looking at This one which is good for 40V. Thoughts?

(update: Considering the 5S 21v 18v BMS board here since it's a little smaller https://www.ebay.com/itm/272724717408)
Thanks


texts: Shorted 12V wire to GND in ATX power supply. Did I fry it?

texts:
I'm a total noob, please forgive me.

I have several components that require 12V DC, and I decided to use an old computer power supply to give me the juice.
I snipped and stripped a matching pair of yellow and black wires...
After marveling at the results of hotwiring the electronic lock, I decided to test out the EL wire I bought ages ago.
However, I could not resist touching the wires together to see what a 12V spark looks like and now the power supply's fan stopped.
I tested the outlet, and it's fine. Did I just fry my power supply? Or perhaps I blew a fuse in the thing?

Why did my PS stop working and how might I fix it?


texts: Hack for fitting 0.04" leads in to a 0.025" hole on PCB

texts:
This might be a ridiculous question to ask - but I have made a mistake in a new library I created in Eagle for a component. The drill diameter of the plated holes for the component leads should have been 0.04" but I missed the fact that the default diameter of pads inserted by Eagle is ~0.025". The PCB has come back and lo & behold, I cannot fit my component leads. What are my options (if I need to get a proto build done immediately)?

The only option I can think of is: to file away the component leads until they fit into the hole.

Is there a better way?


texts: Bulding a physical calculator from scratch

texts:
As you can probably tell I am relatively new to the electronics scene and I'm rather stuck on a project I'm doing for school.

I am on my second year of an Electrical engineering degree, tasked to do a project. I chose to make a calculator as it seemed like a fun and doable challenge, but I'm stuck at square one with not much of an idea of where to go from here.

A few questions I have are:

Which language should I use for such a project for someone with minimal experience?(mainly python)
How would I go about coding such a program that could be implemented into a physical build?
Where is a good place to purchase the necessary components for the build.

Any thing to help a gal out would be greatly appreciated <3


texts:
I'm wrapping my head around this layout, I'm trying to extract its schematics so I can determine the logic function.

For what I understand we have two PMOS and two NMOS transistor. I see one connection to VDD, then a common diffusion and a connection to the output (yz). So the PMOS transistors are in series. However the same seems to happen in the bottom NMOS transistors. How does this happen? Shouldn't the two top transistors be in series and the bottom in parallel and vice-versa. I also don't quite understand what are "s", "sz", "y", "yz". I suspect this might have something due to logic negated inputs/outputs but I don't quite understand how does that translate in a schematics. I suspect this translates a logic function that is not as simple as I might be thinking. Can someone help me?


texts: Measuring True-RMS voltage of different waveforms - error?

texts:
I'm trying to measure True-RMS voltage for these three types of AC waves:
(freq, amplitude - waveform):
1) \$ 200Hz\$, \$2V\$ - sine wave
2) \$ 150Hz\$, \$3V\$ - triangle wave
3) \$ 250Hz\$, \$2V\$ - square wave

I'm using a function generator and three different multimeters in parallel: a high precision digital multimeter - Agilent 34450A and two old analog multimeters (about 15-20 years old). The problem is I expected the analog multimeters to read the RMS values of triangle and square waves wrongly, because they shouldn't read the correct RMS value unless we're measuring a sine AC wave. But, their readings were quite close to what the digital multimeter read. I'm confused by this result. Any explanation of why it would be so?


texts: Can I charge a 16V 16.6F supercapacitor with an 18V solar panel?

texts: I'm working on my calculus project (I recently started college) and my topic is using solar panels and supercapacitors to help mitigate the lack of energy/electricity in the rural areas in my region. I am not exactly certain as to how I go about with it. I found a circuit online which I could use but am wondering if I need anything more or require alterations on the circuit.


texts: Why don't LiPo charger chips isolate the output during shutdown?

texts:
From what I've gathered, boost regulators from MCP1640 to TPS61090 disconnect the load during shutdown so that the battery is not drained during shutdown.

However, charger chips like BQ24295 don't seem to isolate the output during shutdown (at least I can't find it on the datasheet). If my reading is correct, why is the output not isolated? Don't charger chips face the same issue on this front as boost regulators do? It shouldn't be difficult to incorporate some shutdown logic.

Thanks


texts: Worst-Case propergation delay in a full adder

texts:
I'm finding difficulty in understanding how the propagtion delay of this full adder is calculated in this primitve manner. Please see the following attached:

1) Lecture slide explaining worst case delay
2) Past Exam Question to calculate delay
3) Past Solution to exam question

For exam question (d, part i), I am still unsure how the answer is still 3 gate delays. I know S3:0 has changed from 0101(5) to 0110(6), more particularly bit S0 has changed from 1 -> 0 and bit S1 has changed from 0 -> 1. Bits S3 and S2 have remained the same.

Could you please walk me through which path was taken to calculate it's worst case delay (i.e 3 gate delays in this case)?

Many Thanks


texts: How do piezoeletric accelerometer sensors generate output voltage?

texts:
How does piezoeletric accelerometer sensors work technically?
I know that piezoeletric accelerometer sensors have a piezoeletric crystal, a mass and a spring.

But where is the voltage at the ouput coming from?


texts: Transformers codes or How can i find a replacement(or sellers) to this faulty transformer?

texts:
My cousin ordered a food processor called cuisinart fp-14dc from the US that is working on 110VAC while the local voltage in my country is 220v.
She plugged it without using a transformer to reduce the AC voltage to 110v and thus it is malfunctioning.
Using some of my electronics knowledge, i checked and it appears that the inner transformer inside the appliance is mulfunctioning.
I need help understanding the codes on the transformer so i can know how to find and order a replacement transformer.
Thanks in advance.


texts: ESD protection devices - necessary for MCUs?

texts:
I'm working with two chips on a board, a dsPIC33F and a PIC24F as well as a serial EEPROM (24FC1025.)

I've seen these little ESD protection devices in 0603 packages:

http://uk.farnell.com/panasonic/ezaeg3a50av/esd-suppressor-0603-15v-0-1pf/dp/1292692RL

For MCUs like I'm using, is this necessary? The boards may be constantly handled and the external interfaces (I2C, UART) may be exposed to ESD.

Would the internal diodes protect the chip anyway and make these pointless?


texts: How do i go about powering 15m of LED strips

texts:
So i want to install RGB LED strips all around near the ceiling of my room, it will be almost 15m.

So i will buy 3 x 5m LED strips and connect them together, but i think only one power supply wont be enough.

Is it correct to divide the 15m in 2x(5m+2,5m) and power both strips in both ends. like this:

Is this how i do it?


texts: Do HF (13.56MHz) RFID readers need government approval?

texts:
If I were trying to design a product and added a RFID reader in it, would that RFID reader need government approval from the country I'm selling in?

I believe UHF RFID readers need approval from each country/region that they are sold in, but what approval would an HF device need? Specifically China if it makes a difference.


texts: How to automatically turn off a Fan after a fixed amount of time?

texts:
I have an exhaust fan in my bathroom (used for removing the steam generated by a hot bath).
Currently, it can be turned on and off by a regular switch.
My goal: Exhaust fan should automatically turn-off 5 minutes after it is turned on.


texts: To evaluate equivalent resistance of the circuit by star delta method

texts: How do I evaluate this circuit via star delta method?


texts: From what I could understand, the state of a flip flop is the current value it is holding on to, i.e., the value that was previously inputted and is now saved for future use. My question is, where does it actually save that state? and how does it know?


texts: IIP2 Second Order Intercept Rule of Thumb

texts:
I'm faced with the problem of explaining the harmonic production in a system where the second order intercept points of the cascaded components are unknown. As a way to bolster my explanation, I would like to provide some realistic sample calculations that might reasonably approximate what we observe the harmonic levels to be, but I don't have any IIP2 information except what I can get from the observations.

In other words, I would like to show that the observations agree (within some reasonable amount) with what we could expect from a cascade analysis based on the IIP2 and IIP3 values of the devices involved. (Or, alternatively, what we observe is inconsistent with what should be expected!)

I know from experience (IIRC) that for the devices we are using, a rule of thumb is that the IIP3 is generally about 15 to 16 dB above the 1 dB compression point.

However, I never needed such a rule of thumb for the IIP2 until now. Is there one? If someone can cite an authoritative reference in addition to providing the rule of thumb that would be even better. (I will have to be convincing with my analysis.)

The active devices involved are multi-octave class A RF amplifiers.

I understand how to do the cascade analysis and I am experienced in doing it for narrow bandwidth systems. The system at hand has a multi-octave bandwidth, so harmonic performance is an important issue. I am trying to characterize an individual stage. Generally, I know the 1 dB compression point and IIP3 for each stage.

(Could someone help with the tags on this questions?)


texts: Inrush current of high voltage power supply

texts:
I have seen some solutions for inrush current, but my case I think it's a little different.
The point is that I need to limit the inrush current of 1500 volts peak rectified. In my project I need to keep charging and discharging a 200uF capacitor with 1500V every 50ms. So I could use a transformer and a bridge rectifier to do that like the following picture:

The switches would disconnect for a few microseconds the capacitor from the source and connect it to the load, then disconnect it from the load and finally connect it again to charge the capacitor. This loop keeps in 20Hz (I'll probably use power SCR's as switches).

The point is that the voltage is too high and the 50ms is too little time to charge the capacitor.

If I use just a resistor of 30ohm to limit the current, the power peaks reaches 30kW, as you can see:

(The first time charging the capacitor followed by the switching period in the time 0.5s)

If I use 1H inductor, the current keeps about 10A, that's also too much for it (The max current I've found is 1A for 1H inductor).
I couldn't find NTCs thermistors that could handle such voltage, current and power. Also, the NTCs would probably keep always hot due to the high frequency of charge.
Active components also can't handle the power here usually.

Do you guys have any suggestion?


texts:
The board I created uses the WS2811 which outputs a 12V RGB signal, with the high signifying an inactive LED and the low being full brightness. The components connected to this receive a 12V power signal in addition to these three 12-0V signals.

The RGB LEDs I bought have the exact opposite. Their high signal makes the LED active and have a common ground instead of a 12V power. Therefore the current essentially goes the opposite direction.

I.e. for a white RGB LED with 25% brightness:

Spec    | Common (V) | R (V) | G (V) | B (V)
--------------------------------------------
WS2811  | 12         | 9     | 9     | 9
RGB LED | 0          | 3     | 3     | 3

So essentially I want to subtract every signal from 12V. I feel there should be a simple soltuion for this problem, but my knowledge doesn't seem to reach as far.

Thanks for any help!


texts: Why do we use one hot coding for the FSM Machine? why not binary coding to be used?

texts: I would like to know why it is best to use grey coding or one hot rather than just binary coding.althiugh we would require more number of flip flops for its implementation.


texts: Replacing smoothing capacitors in vintage guitar amplifier without datasheet

texts:
I'm in the process of servicing my Carlsbro stingray super combo amp and whilst disassembling I noticed that one of large caps (I assume smoothing) has started bulging and leaking.

Ive tried searching the brand and markings etc to get a datasheet with no success. The closest I can find is this ebay listing: ITT 4700uF Industrial Cap. This shows 10A ripple at 100Hz 85C

Ive found 3 new contenders for replacing my caps:

Option 1 - nichicon

Option 2 - TDK

Option 3 Vishay

All of these seem to have ripple current capabilities in the 1-2A range and it seems rare to find anything with the 10A capability of that other cap in new stock

Without the datasheet for the ITT Caps in my amp, how can I determine a suitable replacement aside from the usual voltage rating >= old cap rating and new capacitance = old capacitance?


texts:
We have designed a board that uses an ATMega2560 and wanted to have the option to do remote firmware updates (it has a Sim800C as well for getting the firmware files).

Therefore we've added an SST25VF016B memory module (to store the firmware) and coupled it with a Logic Level Converter (as Atmega is operating on 5V and the SST25VF016B at 3.3V).

Our schematic is the following:

The problem we are facing is that we cannot program the ATMega when the SST25VF016B is soldered on our board.
After searching for a bit, I've found this Note from Atmel:

  Shared Use of SPI Programming Lines
  If additional devices are connected to the ISP lines, the programmer must be protected from any device
  that may try to drive the lines, other than the AVR. This is important with the SPI bus, as it is similar to the
  ISP interface. Applying series resistors on the SPI lines, as depicted in Connecting the SPI Lines to the
  ISP Interface, is the easiest way to achieve this. Typically, the resistor value R can be of 330Ω. This enables to
  program all the devices through a minimal interface. However, if there are no special design
  considerations, then all the AVR devices will respond to the ISP instructions. The SPI clock lines should
  be separately provided (can be gated using jumpers or DIP switches) so that only one of the AVR devices
  receives SPI clock at a time. Other SPI lines (MOSI and MISO) can be shared. This method ensures that
  AVRs are separated from the programmer by the same protection resistors, since they are all held in
  RESET while the ISP reset line is activated. The ISP clock can be gated using jumpers or DIP switches.
  An alternate solution is to use multiple ISP interfaces, one for each device, all protected separately with
  series resistors.

Question is if anyone has done something similar and knows that it will work.
Also, how could I use multiple ISP interfaces one for each device that is mentioned at the end ?


texts:
I am trying to analyze this simple diode circuit by hand, but I can't seem to get too far.

simulate this circuit – Schematic created using CircuitLab

Using circuit lab, it is evident that current will flow through both diodes, which makes sense to me conceptually, however, trying to analyze using the Constant Voltage Drop model results in an unsolvable circuit.

simulate this circuit

I have tried to use superposition, nodal analysis, and just KVL, but I can't seem to figure out how to solve this circuit.
Help would be greatly appreciated!


texts: Consistency Concerns Between Series RGB LEDs in a String

texts:
My concern/question:  If one has a string of series RGB LEDs (w/ independent elements) and was to light green to 100% and red to approximately 75% -- in an effort to illuminate the Amber color -- how consistent will the color be from one LED to the next.  More specifically, is the human eye capable of perceiving any discrepancies?  Clearly this is heavily dependent on the type of LED chosen, so please allow me to clarify further.
What I’m looking to do is drive a sting of RGB LEDs (independent elements), where each string (Red / Green / Blue) is controlled via a switch-mode controller.  In essence, each string is controlled via a constant current source.  Thus, there will be three controllers: one for the red string; one for green string; and one for blue string.

Luminous intensity (i.e. the mcd output of the LED) is fairly linear with respect to current (I realize it's not perfect).  Therefore, for all intents and purposes, we’ll assume if we cut current in half, we cut the luminous intensity of the associated string in half.
LEDs are far from perfect.  This is to say that, when comparing one LED to the next, luminous intensity across the elements (for a given current) will be different.  Particularly, the LEDs I’m looking at (ASMB-TTB0-0A3A2) employ the following luminosity spectrum (@20mA).

To make this a bit simpler, let's assume we have only two LEDs.  Let's also assume that we have determined the normalized amount of current that needs to be pumped through the Red and Green elements in order to emit a perfect amber color.  The main question is, when considering the worst-case luminous variance between the two LEDs under test, can the difference in color be perceived?
I have the LEDs of interest on order, and the necessary components in the lab (to build constant current sources) to allow me to do some testing and perhaps collect some empirical data. Going back to our assumption that current linearly maps to the mcd output, one could vary current through elements to effectively mimic the luminous variance effect, no?  The issue with this, however, is that I do not know where I'm starting at on the luminous spectrum.  For example, let's assume I increase RED to 9.01 mA while decreasing GRN to 0.88mA to explore one of the worst-case scenarios.  If the LED was already at the upper end of the RED spectrum, and here I am further increasing RED's current (mcd output), I've misrepresented the worst-case, if that makes sense.

My questions:

Am I overly concerned here?
Does anyone have experience with a similar paradigm and could share some tribal knowledge?
How reasonable/unreasonable is my proposed lab experiment?

Sorry for rambling, as I'm new to this site (or posting to the site, anyway).  I thoroughly searched for my answer, and although I found answers related to matching intensity across elements, I did not discover topics related to color consistency.  I'm very appreciative of your time/effort in helping me answer this question.


texts:
While desoldering useful components off of old computer hardware, I found quite a large number of 14.31818 MHz crystals.

This seemed odd to me. Why use such an irregular frequency with a very nontrivial conversion to human time units?

At first I thought that it must be a multiple of another frequency with a certain dedicated use (such as 44.1 kHz commonly used as an audio sampling frequency), but my guessing only led to two numbers pretty close to it: 1/7*10⁸ Hz and π/22*10⁸ Hz, both to about 2‰, and I can't seem to deduce what any of these would be useful for.


texts: USB Connector Current Rating for Charging

texts:
I have heard it mentioned that the current rating for a USB charger is dependent on the current rating of the USB port itself; ie a Type A connector has to be rated for 2A on a charger that says it supports 2A.

How true is this statement?

Looking on DigiKey, I am having trouble finding USB Type A connectors with a current rating of over 1.5A.  There are some that list 1 to 1.5A; many have no current rating at all!

Where are these high current USB ports for charging and how can I find them?


texts: Simplest way to convert 78 VDC to 3.3 VDC?

texts:
I'm doing a ESP8266 implant on a LED light driver, which converts 220 VAC to 78 VDC. I need to power the ESP8266 with 3.3 VDC.

What is the smaller, cheaper, easier and efficient way (if any) to do the conversion?

Thanks in advance.


texts: Conceptual Question regarding necessity to do level shifting

texts: I have a circuit where a 3.3V MCU which is not 5V compatible needs to drive an MCP23017. The MCP23017 will drive and read inputs and outputs from various 74HCT components. I'm thinking that based on the datasheet for the MCP23017, I can power it at 3.3V so it's communication to the MCP is 3.3V compatible.  It would also put out logic HIGH at close to 3.3V but that is sufficient for the HCT parts to recognize as HIGH.  I would power the HCT parts at 5V. Their outputs would be 5V for HIGH which, I believe, can still be read by the MCP23017 safely even if only driven at 3.3V. No bi-directional level shifter needed on the I2C lines?


texts: How should I solder one board to another?

texts: I have a small power regulator/charger and a IOIO-OTG that I'm trying to solder onto my protoboard. My current idea is to use male/male headers. Is there another way? What is the best practice when doing these things?


texts: What does edge triggered and level triggered mean?

texts:
I am studying 8085 microprocessor architecture and the word edge triggered and level triggered confusing me really very much. Can anyone explain me it in layman's words ?

While studying the interrupts of 8085 named RST 7.5, RST 6.5, RST 5.5 and TRAP i came across these words and they confused me.
Here i have attached one document link from which i was reading and i have mentioned my confusion diagrams.

in the document
RST 7.5 -> Edge triggered
RST 5.5 -> Level triggered.
TRAP -> Edge triggered and Level triggered. (why ? does it make any difference?).

the document link


texts: Finding correct flyback transformer for ZVS mode

texts:
I'm trying to design an offline flyback smps based on a L6565 chip from ST with 5V@1A output. I've found a small transformer from Coilcraft with auxiliary winding and turn ratio 1:1:1.

If I understand everything correctly, it can't work in ZVS mode, cause turns ratio 1:1 won't produce reflected voltage higher than input voltage, but I can use it in quasi resonant mode?


texts:
In my design I am using RS232 with DB9 connector in my PCB. idea is to log the data in PC and for programming via serial. Which connector I need to use in my board , it is male DB9 or female DB9.

Q1) What connector I need to use in my board male or female
Q2) If I use male connector in my board then Pin TO1 will need to connect to pin 2 or pin 3.


texts: Zero-Crossing AC SSR not working for LED lightbulb

texts:
I have a microcontroller driving a solid-state relay to switch an LED lightbulb (the household type).

EDIT: added circuit (maybe it addresses Andy aka's comment?).  PB0 is the bit 0 of output port B of the microcontroller (AVR tiny25)

simulate this circuit – Schematic created using CircuitLab

ADDITIONAL EDIT ABOUT ADDED FIGURE ABOVE:

Related to winny's comment/solution --- since I can't (in general) connect a resistor in parallel to a lightbulb (it would require hacking into the lamp or fixture), I could take advantage of the fact that GND (household GND) and N (neutral) are connected, and place those two resistors (only one is necessary, but placing two makes the contacts of the SSR output interchangeable).  Does this work?

--- END OF EDIT ---

I thought zero-crossing was a good idea, so I'm using the IXYS CPC1965Y.  It's not working: when I switch it on, the lightbulb gives out a flash (like a photographic camera flash) every 3 or 3.5 seconds.

It's not the circuit --- I replace the LED lightbulb with an incandescent lightbulb and it works perfectly ok. Also, a curious detail is that I first had gotten the CPC1976Y (2A, instead of 1A) and tried with that one, and it was working ok.  (then, digikey ran out of stock, so I got the 1965Y assuming that functionality would be identical)

The manual (both the 1965Y and the 1976Y) talks about low power factor; specifically, it lists 0.25 as the PF required for guaranteed turn-on, and a footnote says: "snubber circuits may be required at low power factors".  However, it does not say anything about what the snubber circuit should look like.

I think the notion of PF would not apply to an LED lightbulb in the strict sense, since it is non-linear; but I guess the issue for the SSR is the same.

Will I really need to switch to a non-ZC SSR?  (they're more expensive, surprisingly enough  :-( )

Any suggestions on how to make it work with the ZC SSR?

Thanks!


texts: Trying to better understand voltage and current sources

texts:
I feel like I am going a little crazy here because the more and more I read about these things the less I understand them.
So I understand that an ideal voltage source has no output impedance, no extra resistance in series between itself and the load, ensuring that nothing else will drop the voltage along the way, meaning the load will get the exact voltage listed.
An ideal current source has infinite output impedance, infinite resistance in parallel between itself and the load, ensuring that the load will get every bit of current as listed (no current will get diverted elsewhere).
I understand that these "ideal" sources are ideal and don't exist in practice. In reality there is always some resistance. What I don't understand is why then are are able to switch between them, or how we can talk about insensitivity to load changes when Ohm's Law says V = IR, if I have a voltage source, is that not fixed? And then if I add a bigger resistor, doesn't that mean less current must flow in turn? Or for a current source, if I change the resistor, am I not then changing the voltage? And since I am able to change the other variable, why are we then able to swap between them? (by swap/switch I mean replacing voltage with current sources and vice versa)
None of it makes any sense to me because I rarely see examples with numbers to illustrate what's going on and how I am supposed to think about these things. Can anyone please give a few examples showing these "ideal" forms, why they are unrealistic, why we are somehow able to switch between them, and what a "real" example might look like?


texts:
What I want to do is make a low pass filter using a simple RC circuit (first order), or possibly an LC circuit (which would be second order). Right now, I am in the process of determining the values for the resistance of the resistor and capacitance of the capacitor (I'm currently going with the RC circuit idea). As the equation is f=1/(2*piRC), I understand that if I want a crossover frequency of 200Hz, I will have theoretically infinite choices or R and C. Which values are better to choose? I've heard I should choose C first, because capacitors are more difficult to find in the right denomination. Still I am left with a few hundred possibilities.

Also, is there a best choice of type of capacitor? (electrolytic, etc)

My application, if needed, is that I want to filter out high frequencies of sound from entering my car sub woofer (powered by a 70 W amp), so I'm going to put the low pass filter between the amp and sub woofer (I would put it upstream of the amp, but in this case, the amp and head unit are one in the same device).

Thoughts?


texts: Tektronics 453 - Saving a single shot waveform for later analysis

texts:
I recently purchased a used analog Tektronix 453 and I want to capture some single shot transients. I also want to "save" the waveform so I can more easily measure things like peak to peak voltage of the transient. I know you can review saved one-shots in modern oscilloscopes but do analog scopes also support this useful feature?
In the manual, I see that single-shot trigger allows for "photographs" of the triggered waveform. However, after my trigger is activated, the waveform disappears. Changing the time/div or horizontal display doesn't show that any waveform is "saved". I am not sure how you would be able to photograph any transients since your window for taking the photograph would only be as long as your one-shot duration.
I would imagine analog memory to be much more expensive than digital memory but I don't  understand the usefulness of one-shot captures without the possibility for later analysis.


texts: How to find the frequency of the AC source in RL circuit?

texts:
I' m asked to find the frequency of my source with the given data (RL-serial circuit):
$$(R_L=3 \Omega;L=0.04H), R=30\Omega, cos(\phi)=0,819 (ind), X_L>X_C$$
This looks easy but somehow I cannot get the result offered in the result section:

The only thing that I did is this:

$$R_L=\omega L=2\pi fL \Rightarrow f=\frac{R_L}{2\pi}\frac{1}{L}= 11.93 Hz$$
$$cos\phi=\frac{R}{Z}\Rightarrow Z=\frac{R}{cos\phi}= 36.63\Omega$$
I also don't understand how I get different results for impedance (Z) when I find it through the usual formula:
$$Z=\sqrt{R^2 + R_L^2}=30.14\Omega; Z\neq Z ?$$

Why isn't the frequency which I got from the first equation correct? What am I doing wrong?
I also referred here but could't find anything relevant: http://www.electronics-tutorials.ws/accircuits/series-resonance.html
Can I at least get a hint? I've been starring at this for 2 hours and can't find out the correct way to solve it.
Original question:
EDIT
I'm given $$R_L  \quad not\quad X_L  $$


texts: Using MLX90614 OR is I2C and SMBus compatible?

texts:
I am trying to use a Melexis MLX90614 with Atmega8. I have failed in all my attempts till now. I tried sending this sequence

slave address(as 0x00 and 0x5A) --> opcode to read SMBus address
     --> data byte high --> data byte low

I get a slave address NACK for both SMBus addresses. Is it because I am using an I2C library? I understand we have to give a PEC also, but as the Slave address is NACK'd I don't think the sensor is responding to my commands. I tried using the write opcode and got ACK's for that. So the communication is ok. Can anyone tell me what kind of problem may be here?

Also how would one generate a PEC for SMBus protocol?

I looked at this code and it just sends 0x00 and 0x07 over i2c to fetch two bytes of temperature. How can that be possible? In the datasheet it is specifically mentioned how to read one word and how to write one word. How can this be bypassed?


texts:
I want to put together a device that allows >= 128kbps audio to be streamed over a wireless (wifi?) mesh network.

I'm a professional software engineer but have 0 experience in hardware, and I need the greatness of your community to help me get a grib on this. I have done extensive independent research into bluetooth / XBee / Zigbee / arduino wifi boards but haven't hit on anything that seems like the right solution and need some expert advice.

To flesh this out: I would like a durable and compact unit that would have a 3.5mm jack output to an external amp / speaker and a power input (preferably 12v so as to allow the use of batteries). Each unit itself should expand the wireless mesh network, with a range of preferably greater than 10 meters. These boxes would not need to have any audio input - just a wireless repeater (transmit and receive) and an audio out (for speaker). I imagine there would be a slightly different "source" box that would take audio IN and wireless out.

I ruled out bluetooth (master/slave relationship) and Zigbee (lacking bandwidth). I really was interested in the miniSwarm Arduino board (more info: http://forum.arduino.cc/index.php?topic=159327.0 ) but they failed to reach their indigogo goal. What is the best option?

EDIT: I was looking at the DigiX, which supports WiFi mesh and has an onboard DAC for audio http://www.kickstarter.com/projects/digistump/digix-the-ultimate-arduino-compatible-board-with-w . Would its 2 channels, 12-bit DAC with 1 mega-sample conversion rate in single channel mode suffice for this? Just looking around at options at this point.


texts: Make Arduino and 89C52 talk to each other

texts:
I am trying to create a project in which I am required to make Arduino and Atmel 89C52 talk to each other.

I know this can be achieved via UART but the problem is my Arduino is already using its TX/RX ports. Is there a way to make them talk by any other means? Like I2C or SPI interface? Would soft UART suffice? The whole project depends on then talking to each other effectively.


texts: How to create a serial key (Registration key)

texts:
We're designing a PIC based system. We would like that users enter a serial key (registration key) like the one commonly found in desktop software. For our system, we will have the user's email address and/or his cellphone number. The system is a standalone device with a keyboard and display. The system will allow the user to pay by punching in a specific registration code that he purchased via SMS. The user will send a SMS to a server. The server would use the provided user's email or/and phone number and generate a unique registration key.
Does anyone has clues on how to get started?


texts: Convert an audio signal to 0-5V using single supply op amp

texts:
I'm trying to capture an audio signal using an analog input of an Arduino Uno. The Arduino's analog input must be between 0-5V. I'd like to use a single power supply via an 9V battery, so I'm using a voltage divider to offset the input signal and feeding that to an LM321 op amp. Here's my current circuit:

Updated Circuit: Added 100uF cap before voltage divider.

Note: The audio input can be a microphone, mixer output, headphone jack, electric guitar, etc.

Originally, I was using the 5V power supply from the Arduino but I found that the amplified signal was being clipped around 3.8V. I believe this is because the LM321 is not a rail to rail op amp, and is limited to V+ - 1.5V according to the Vcm (input common-mode voltage range)...though I really don't understand exactly what that spec means. Is this correct?

I switched to a 9V supply and changed the voltage divider resistors to the values above to get close to a 2.5V DC offset. The non-inverting op amp is setup for a 2X gain, which works. However, the issue now is that although I have successfully amplified the signal, it is no longer centered at 2.5V. Here's a screenshot from my scope, the original source signal is in yellow and the output from the op amp is in blue:

What is the simplest way to get the output signal "re-centered" around 2.5V? Or, is this just a bad approach to solving the problem?

Solution

Thanks to everyone for their help. Here's the schematic for my final working circuit:

simulate this circuit – Schematic created using CircuitLab

And the oscilloscopic proof:


texts:
I'm trying to simulate a 16MHz Pierce crystal oscillator with the following parameters (see attached picture.) It doesn't oscillate, but when I simulate with lower capacitor values it works well.
What could cause this problem?


texts: Need help searching for a correct switch

texts:
I designed a PCB which uses switches. Sadly, I screwed up with the switching direction.
I bought these switches: Klick here. The position corresponds to the connection table below:

The problem is that I need the connections the other way around. If the button is set to position 3, then pins 2 and 3 must connect. If the button is in position 1, then pins 1 and 2 should connect. The middle position does not matter / does not have to exist.
Does somebody know a switch with the same dimensions but opposite toggle? Any help would be appreciated.


texts:
How would I design an op amp with a gain of less than 1? Is this even possible? Also would it matter if I used a non inverting or an inverting op amp?

I've designed a non-inverting op amp with a gain of 2 like so. Can I modify it to have a gain of say 1/2?

  1 + R1/R2

simulate this circuit – Schematic created using CircuitLab

I'd appreciate some help here.


texts: Why do the brightness, luminous efficacy and power of this lightbulb not agree?

texts:
A particular LED lightbulb has luminous flux (brightness) \$\Phi_{\rm v}=820\ \rm lm\$, consumes electrical energy at a rate of \$P=9\ \rm W\$, and has a luminous efficacy of \$\eta=83\ \rm lm/W\$.

The mathematical implication is that the bulb dissipates $$\frac{\Phi_{\rm v}}\eta = \frac{820\ \rm lm}{83\ \rm lm/W} = 9.9\ \rm W$$ in illuminating the ambient environment; however, this is already greater than the power consumption, and the rate at which the bulb dissipates heat hasn’t even been considered yet.

What gives?

Addendum: It actually isn’t clear whether the luminous efficacy cited gives the ratio of luminous flux to total radiant flux or whether it gives the ratio of luminous flux to the radiant flux associated with just luminous radiation.


texts: chip identification in synchronous boost converter

texts:
Trying to use a car 12V to 20V (laptop charger) for my TS100 solder iron and trying to find out why it shuts off, i blew up some component(s).
In trying to recover from that, created a partly schematic, but key is a chip in between PWM of microprocessor and P-channel FET.

housing: SOT363 (guess)
label 46 :2(rotated) and some dots.
I guess this is a FET driver, or just a PNP/NPN transistor pair to drive the FET.

I've searched on internet and I could not find it.
does one know what this exactly is?

Based on my reverse engineered (partly) schema, it could be a NPN/PNP transistor pair with base and emittor connected, and Collector of NPN to +20V, and Collector of PNP connected to ground. but that's just a best guess, a full driver IC also would be an option.
An example datasheet which seems to mach pinout if it was a NPN/PNP IC:
https://assets.nexperia.com/documents/data-sheet/BC846BS.pdf

Any idea's?

Thanks in advance,


texts: How can I mount a shield on a breadboard?

texts:
The non-standard spacing of the headers on Arduino boards makes it so the shields will not fit on a breadboard

From what I have read, there is no good reason for the non-standard pin spacing on Arduino. Is there any way I can mount a shield on a breadboard without risking damage?


texts: Controlling electrical flow from generator

texts:
I'm working with a factory which has a backup generator which is used during grid instabilities or whenever the factory must disconnect from the grid for maintenance. In these cases, the generator is used instead to maintain operations.

However, I'm investigating whether there's another opportunity in using the generator's excess capacity to sell power on the grid.

I'll advance now that this question is not concerned with energy-market regulatory or financial viability issues for this idea (I've simplified the context here). The question is whether this is technically feasible.

The generator would then need to power two separate networks (the factory and the regional network), as seen below.

I had to create this with Powerpoint due to do the particular setup for the generator, which needs to feed into the two circuits without connecting them with each other (otherwise that'd just be the grid powering the factory, when this is precisely in the case when that's not possible or desirable).

So, this is the first part of the question: is this even possible? Can a source power two circuits while keeping them isolated from each other?

Assuming it is possible, we then get to the second part of the question. The generator's primary objective is powering the factory. Whatever is done on the grid is secondary. So the power must satisfy the factory and -- if there's excess capacity on the generator -- then feed into the grid.

Now, my thinking is that the factory has certain power needs (let's assume 1 MW). The generator (let's assume it can generate 1.5 MW) can run at 2/3 capacity and satisfy those needs. However, if the generator is also connected to the grid and is ramped up to generate it's maximum of 1.5 MW, where will those new electrons go? The resistance of the grid will be effectively infinite (when compared to the factory or the generator), so the natural route would seem to be factory. Which would mean the generator fries the factory's circuit and feeds almost nothing to the grid.

So, is it possible to design a circuit or device (including PIDs, microcontrollers, whatever) such that as much power as needed goes to one circuit, and the excess goes to another?


texts: Like in a scr say in thyristors or triacs we know we can turn the scr "on" after a certain anode-cathode break-over voltage depending on the current present at the gate.But I want to know whether there is device or circuit which remains off if the applied voltage is greater than the specified voltage value according to the device and it will turn "on" if the applied voltage goes below that of pre-specified voltage value. In other word its a reversed-functioned SCR. (I do not care whether it is unidirectional of bidirectional)


texts:
In the following schematic the two Vss pins where are supposed to be the grounding pins don't connect to anything. Does this mean that the circuit is self-grounding (if that's even a thing)?

I'm planning on attaching this to a breadboard but I'm not sure how to power it since I don't have a direct connection to the TSL1402 ship and have to go through the accessible pins.

Here is the schematic:


texts: LED voltage indicator - why don't these LEDs blow?

texts: I want to make a simple voltage indicator for my 75VDC power supply.  I was thinking one LED for ~12V, one for ~40V, and one for 70+V.  I found this simple instructable online, which, for 3V-30V, turns on different LEDs.  They just put the leds all in parallel with differently sized zener diodes, very simple.  However, what I don't get is, why do the lower voltage LEDs not blow/burn up/etc when the voltage becomes higher?  It seems like if you had a 2.2V LED with a 1V zener diode, then once the voltage got up to 30V, this 2.2V LED would have 29V going through it?


texts: Is anything besides rx and tx actually used in rs232 nowadays?

texts:
Whenever I come across a PIC or even a FPGA project that is communicating over the serial port with a PC; only Rx, Tx and power are connected on the 9 pin connector and the other pins/signals are apparently never used.

The RS232 has several more signals that cover all 9 pins. Are they even used at all nowadays? I don't see PIC microcontrollers having these other signals. Even the MAX232 does not have them.


texts: I2C issue with 3.3V MCU master and 5V powered IC slave

texts:
I am trying to describe the issue I have as clear as possible here:
I have two self built development boards around a Silicon Labs EFR32 MCU. The boards are identical, but I encounter two different behaviors when using the boards and I cannot figure out what seems to be wrong. The connection between my I2C pins and the breakout pins looks as follows:
The I2c pins are also 5V tolerant going into the MCU. Now I connected my development boards to an MCP23017 GPIO expander and wired it up as described in the datasheet. With the first development board, communication was not problem whether the MCP was powered by 5V or 3.3V. But with the second development board communication was only possible while the MCP was hooked up to 3.3V, hooked up to 5V I just could not communicate. So next I hooked the I2C lines to my oscilloscope and suddenly the communication was no problem even though the MCP was hooked up to 5V. In the end it seemed like the MCP was always communicating, hooked up to 5V, as long as some conductive material was touching the SCL line even if it only was a screwdriver or an unconnected jumper cable.... I verified that all the components were properly soldered on both boards and that they had the expected characteristics. I still cannot make any sense of why my second development board behaves so weird. Maybe someone had a similar issue or might have any idea what the problem might be.
Any comment is greatly appreciated!


texts: How can I get a line cord to stay in a broken modular jack?

texts:
I have quite a few telephones. One I bought supposedly broken but I fished the jack out of the phone and found part of the connector was missing. A line cord could still snap in.

Today, I was swapping cords from my PBX and the part of the plug that keeps the cord in broke off. The cord is fine obviously but the jack is not. The only way to keep the cord in is by pinching down on it with my fingers which is impractical.

I tried duct taping them together tightly to force the wires to touch but they would only work for a few seconds or minutes. I have since removed all the duct tape. A clothespin will not fit around them.

How can I get the line cord to stay, or otherwise modify the cord or the jack to stay? I am not sure about rewiring.

This phone is useless without the jack working.

I am handy with telephone operation but not fixing wiring issues. What I envision would be either:

Wrapping something really, really, really tight around the cord and connector.
Strip the line cord, cut the connector off and somehow fuse (aka scotch tape) the four wires together
?


texts: How do I debug or visualise my ARM USB HID project on Mac

texts:
I've been looking around to try and find an application for Mac OS X that I can use to visualise the inputs of an USB HID device, like for example a game controller, or my USB HID STM32F4 Discovery project.

I'm working on a USB HID project in my free time, and would like to see how the inputs are responding on my screen, using the visualisation application.

Simply put, I'm looking for a game controller calibration/visualisation app like found on Windows:

I've been looking around, and can't find anything. Must be using the wrong search terms in Google. Can anyone recommend something?


texts: Are linear Hall Effect sensors concidered "benign" components for EMC testing?

texts:
The EU's EMC Directive lists reasons a component/product can be considered "benign" and therefore is exempt compliance testing. One of these reasons follows:

Equipment   containing   only   resistive   loads   without   any automatic  switching  device;  e.g.  simple  domestic  heaters  with no controls, thermostat, or fan;

Would a simple circuit board with linear hall effect sensors (like the DRV5055) therefore be exempt (or for any of the other reasons mentioned in the document)?


texts: What is the gain bandwidth product of an amplifier?  (What does it mean?) How can I find the gain bandwidth product for an amplifier which has a gain of -100?


texts: I have a PM DC motor. I am controlling the motor speed using PWM. I wanted to know what is the relation between the torque vs dutycycle and speed vs dutycycle for the motor( given the fact that the peak amplitude of the PWM signal is Vm and frequency is  f) . Characteristics of the motor in the datasheet are only stated relative to armature current. How do you relate armature current with the PWM voltage signal?


texts: I need some advice. I'm in the process of building a DIY aquarium fixture for my daughter. The light will be provided by 10W warm/cool white chips. My problem is this: I have several drivers for big 100W chips, the drivers specs are: 100W input voltage 85-265V, output voltage 30-36V, 3000mA. Can I power 10x10W chips on this instead of one big 100W? The 10W chips run at 9-11V, 900mA, so is this possible to run 10x 10W instead of one straight 100W?


texts:
Hi I’m currently learning about P=V^2/R

I’ve been asked a question on how to use the dimensions of P and V to determine the dimensions of R.
I know that’s
\$P=ML^2T^{-3}  \$
\$V=L^{0.5}M^{0.5}T^{-1}  ~\$ where L only meant Unit of Length and M unit of mass and T=time.

Engineers in EU and other Internationals use U or U(t) for volts and mostly America uses V or V(t) yet on the right \$P=\dfrac{V^2}{R}\$

Why do they make this confusing? Is it inaccurate?


texts: Finding a suitable ADC driver (SE to DIFF VCM+-0.5V)

texts:
ADC:ADC3424

The input is specified to be differential with each input swinging symmetrically around +-0.5V (i.e. 2Vpp with 1V input and G=1). I can't seem to find a suitable ADC driver for this. TI customer service suggested to use the THS4541 as it is supposed to be able to obtain these signals. However, nowhere in the datasheet can I find these output specifications. Instead, I find the following:

Instead of VCM+-0.5V, the output high and low is respectively 4.8V and 0.2V. What does this mean? As I have not been able to get more help from TI, could anyone here please help me to understand the datasheet specs (in case this ADC driver is in fact suitable), OR, possibly help me find one that will work.

Thanks!

Edit: So the Output voltage high/low are just the max/min ratings. The gain controls the swing and the +-0.5V offset is always centered around Vocm. The remaining question is, how is this +-0.5V offset controlled?


texts:
I am trying to figure out "beta" value of an NPN transistor, but I am not allowed to measure current directly. (Although I do have access to lab equipment and other components such as multimeters, resistors, etc). I figure I must use either

beta = (I_c/I_b)

or

beta = (I_e/I_b)-1

but I'm not sure how to find and of the branch currents without knowing beta to begin with. As you can see I'm in a bit of a catch 22. Any guidance would be much appreciated.


texts: Circuit for Recharging Battery with a Device

texts:
I am working on a hardware design that is meant to run off of an internal 5V battery or via USB power, and also to have the battery be rechargeable via USB. I have been looking at battery recharge circuits like those found here: http://www.ti.com/lit/an/snva557/snva557.pdf

I was wondering how the design of the recharge circuit is affected by the battery being part of the device, and how I might go about powering the device and charging the battery simultaneously.

Right now I have the battery taken out of the circuit via a relay when external power is connected to prevent the device from receiving power from both sources, but this obviously needs to be modified for the battery to recharge.


texts: Would this battery/solar powered esp32 weather station work?

texts:
I am trying to design a circuit that runs an esp32 with a dh11 sensor but i am unsure if it would work.

On the top left is a mcp73831-5-OT li ion battery charging chip (the random wire on the left is 5v in from the solar panel)
On the top right is the AMS1117 3.3v variant regulator (picked it for the tiny package and availabilty)
On the bottom left is a esp32 module and its accompanying circuitry (im really suspicious abou that circuit though)
On the bottom right is a dht11 connected to power and data with its accompanying pull up

So,if i build this,would it work? If not,what should i change?


texts: load-resistor value limitation for current mirror

texts:
I am trying to understand simple wilson current mirror circuit for regulating LED current based on external input.

Below is my challenge:
based on the value of the R1 resistor the current through the load R2 is to be changed. Current i am planning to pass through the load is about 20 mA to 50 mA.

Case1::  R1 ranges from 300 to 550. R2 set to 100 ohms. Below are the simulation results.

Case2: R1 range is same as above. R2 is set to 400 ohms. Below are the results.

My basic questions:
 1. have i got the basic wilson circuit correct?
 2. are the R1 and R2 values relative. For csae2 above, i see that, the current mirror is not successful. Is this because R2 is already bigger than R1?
 3. Any guidance towards the relation between R1 and R2, and improvements if any are welcome.

Edit:
My goal: To control the flow of the current through R2 (between 20 to 50 mA). Finally, i will have a LED in place of R2 and a small protective resistor. i have to control the resistance R1, from which the LED current should get regulated. This exercise is to understand more about wilson current mirror too.

Edit2
Added LED TLCR51 info: http://www.farnell.com/datasheets/463614.pdf

Thanks in Advance.


texts: Need help grasping the routing of coils for stator and rotor

texts:
I can see it with just a 3 coil motor, whether it be in different configurations, but loads of different motors have some 72 or umpteen different stator slots and winding for the rotor.

It was my original understanding, whether true or false, that per each configuration whether it be an A/C configuration or delta the three coils repeat around the stator and rotor.

So for a stator with 72 slots there would be 24 sets of coils starter, north, and south.... All in succession. However when looking at some of the industrial motors online I'm having a hard time making out how exactly I'd route the windings if I were trying to sketch up a 120 slot motor as apposed to a 72 slot motor, and quite frankly I'm not sure I'd be able to replicate or rewind one if I were to simply reproduce it.

The litz wire all seems to blend together when I try to trace the windings through either the rotor or stator.

If I were trying to design a motor, power output and what not aside, how exactly would I wind one?
What would the routing look like for rotor and stator with say 3, 6,
9, or 12 sets of coils?
Does this configuration simply repeat for a stator with 72 stator slots?


texts:
This is a continuation of this question.

Note that some of the circles should be filled, but have connections instead.

PCB Color Legend:

Red: Top Copper
Blue: Bottom Copper
Purple: Inner Copper 1

Extra note: There will be a ground plane on top copper.

Component Reference:

GPS: RXM-GPS-R4
MC1: AC32UC3
REG1: LD1117 (3.3V 800mA)
Accelerometer

White ovals are crystals with 21pF ceramic caps

I have uploaded the schematic, viewable on the software maker's website here.

Recap Qs:

The manufacturer says a maximum of 1oz. Does this mean that I should make the ground plate smaller to compensate for that weight limit, or will I not hit the limit (board is 3"x5") ?
The GPS says no wires should go under the chip, will the ground plane be okay going under the GPS?
Does this design look alright to the eye?


texts: Best Guesstimate for Capacitor Replacement

texts:
I'm repairing an old (circa 1960) console hifi system for my parents.  I'm no expert but also not totally incompetent.  It originally came from Sears, I do not know the model number, nor the power output of the unit.  Attempts to find any schematics online have failed.

However, it's pretty clear to me the problem:

The audio amplifier just produces a very loud hum with the signal mixed in softly below it. Investigating, I find the last large capacitor on the amplifier board is literally blown apart.

Capacitor is about 1.5" tall and 1/4" in diameter.  It's made of rolled paper inside.  Very much looks like a firecracker that blew apart.

Sadly, the only remaining plastic I can read, I can make out "35v" and the final digit "9" (at the end of what was a longer number).  And, it reads open with a meter, so I have no clue what it's original spec was.

Just looking for some procedure for replacing it - best guess, process of elimination, most commonly used rating for radio amps of the era, or other advice.


texts: How do I determine what magnet to use for a reed switch?

texts: I'm looking to buy this reed switch but I don't know how to choose a proper magnet.  I would like the optimal distance to be ~1 inch.


texts:
This is Figure 9-3(b) from Motchenbacher - Low-Noise Electronic System Design, so I would expect it to work, but I don't understand it:

  The addition of a discrete common-source stage at the input can offer lower noise. Overall negative feedback to the source of a common-source input stage, as shown in Fig. 9-3b, raises the amplifier's input impedance.

It seems like positive feedback to me:

Decrease in Vin →
Decrease in Vgs →
Decrease in Id →
Increase in Vd → (like a common-source amplifier so far)
Increase in Vo →
Increase in Vs →
Decrease in Vgs →
Decrease in Id →
...

Am I missing something?

For comparison, here's another circuit that is similar, but looks like negative feedback, and has actually been built and works:

Edit:

So that picture is from the 1993 edition.  I got my paper 1973 edition off the shelf (no Ctrl+F!), and the equivalent figure is 7-3(b), but with a BJT and the op-amp pins reversed:

  Overall negative feedback to the emitter of a common-emitter input stage raises the amplifier input impedance.

This makes more sense to me.  If the collector voltage tries to rise, the op-amp drops the emitter voltage to pull it back down and keep the collector at 0 V.  So I'm thinking the first diagram is just a mistake.


texts:
I have an amplifier in a closed loop, the diagram looks as follows:

The DC gain is simple which \$ -Rf/R1 \$. If I make \$ -Rf=2\cdot R1 \$ the the DC gain is two. This is verified using AC analysis in Cadence.

However there seems to be a complex conjugate pole also, which leads to unstable behavior.

Hence I modify the gain equation as:
\$Av= \frac{-Rf}{R1} \cdot \frac{1}{(s+\sigma + j\omega)(s+\sigma - j\omega)} \$. The notation \$ + \sigma \$ is because the phase goes negative. I observed that if I put a capacitor across Rf as shown in this figure then I can get rid of the complex conjugate poles. The value of capacitor is 1pF.

So now the gain equation becomes:
\$ Av= \frac{-Rf}{R1 \cdot C} \cdot \frac{1}{(s+\sigma + j\omega)(s+\sigma - j\omega)(s+p1)} \$ where \$ p1= 1/Rf\cdot C \$ This equation checks out because at DC, the gain is \$ -Rf/R1 \$.
My question is, from this equation how is the pole being compensated? Is my analysis even correct?
To add more information the open loop gain of the amplifier is a single pole system as shown here:


texts: Potential project: Wireless Security Camera with the Arduino Yun

texts:
I have been following Arduino and Raspberry Pi projects closely for a while and I am pretty keen on giving one a go. I have no real electronics assembly experience but can program.

I have chosen the 'Wireless Security Camera with the Arduino Yun'  project on Adafruit (https://learn.adafruit.com/wireless-security-camera-arduino-yun/introduction). However, I have a couple of things I need clarification on before I give this a go.

Firstly, the setup for the project described in the link is wired to a PC. I am aiming for a portable solution and from my research I could probably use an Eye-fi SD card and send pictures to Dropbox and send video streams to the internet (as described in the link). Is this a sensible method i.e. draws the least amount of power from the batteries compared to other wifi methods?

Secondly, with the setup in the link I am not sure what the power source is (I am probably missing something). Regardless, I would like to use a battery source and from my research it seems that 6 AA batteries will be the right way to go. The problem is that the webcam and the Eye-fi card plus all the other ports on the Arduino Yun will probably take a lot of power thus rendering the battery method useless in the longer term. Other than programmatically turning off all unnecessary ports on the board + the LED light (not sure if this is possible) what else can I do to decrease battery power draw down, keeping in mind that I would like live streaming and the ability to capture pictures in real-time?

Finally, is this a good project i.e. portable wireless motion-detection camera for Arduino or would this project be more suited to Raspberry Pi?

Any help and tips will be very appreciated. Thanks.


texts: Can I use this Panasonic battery charger in extension?

texts:
In our home, the the sockets are marked 5A. I'm using a Philips extension from the same so it reaches near my desk for my laptop charging.
The extension has written: 6A 250V~ 1500W (Max). So I guess it can handle 1500W power.
Here's the product (battery charger). And when checked on behind, I saw:

As you can see on charger image above, if I have 220V supply in my home, the power generated would be 0.3A x 220V = 66W (because Input = 0.3A is written on charger)
Which is much much less than 1500W of extension. So it should be safe to use right or would blast like if you plug a big summer cooler on it? Or do I need only socket in wall (5A or greater)?
Secondly, if you would see on charger, it's written some maths for Input and Output. What's the purpose of Output text? Does charger has to do anything with it? Isn't it for batteries only since they output the power to devices?
Note: The purpose of this question is to understand how to evaluate what device/charger will work on the sockets installed on wall and what can also work on extensions. I often face this problem.


texts:
A few minutes ago I asked a question here about a project for my raspberry that I want to achieve. After the theory, practice. But I do not know how to do it. I have
test plates (with track) of this type:

but also the same test plates but without track.

After some experience on a test plates with track where I had to cut with a cutter the tracks so that the circuit is correct and my elements organized in a harmonious way I find this laborious and in addition the track is taken off very easily (problem of quality of test plates?)

What are the primary techniques for creating a small plug-in using a few components and test plates would you have recommendations?

What bothers me is that the same principle as for a breadboard (there is necessarily a shift in the placement of the components (visually I speak) .I am obliged to cut tracks which greatly weakens the test plates and build bridges.

Else, is there any software that can give me a representation for a trial work of test plates, who could give me the layouts and thus tell me for example the necessary bridges to achieve but also the necessary cuts?


texts: Altium 18 Place 3D bodyl dialog box missing

texts: I'm trying to import a .step model into my footprint. I just upgraded to Altium 18 last night, and for some reason when I either click the icon to place 3D Body or go to the Place->3D Body menu, it doesn't open the dialog box. Instead, my crosshairs turn green and it wants me to define some kind of region. How do I get the dialog box to appear? It's not opening in the background...


texts: How can I allow a smaller clearance value for differential pairs in Altium?

texts:
I have finished routing a PCB in Altium (v17) and am resolving design rules violations.

In short, everything checks out except differential pairs that are violating the Electrical > Clearance rule which has a minimum clearance of 0.152mm for all objects. My differential pairs have a minimum clearance of 0.127mm within the same pair.

I created a new Clearance rule named Clearance_Diff which requires the first and second objects to both match a custom query IsDifferentialPair, and specifies a clearance value of 0.127mm. Testing the query correctly selects the number of differential pairs I have on the PCB.

The violation occurs whether the new rule is prioritized above or below the previous clearance rule.

How do I set up design rules such that differential pairs won't violate the general clearance rule?


texts: Inrush current limiter circuit for filament bulb - comparison

texts:
Context:

A 12V power supply is switching on externally connected 12V filament bulbs. The power supply's load switch implements an electronic resetable fuse (13A/τ=15ms) in case of an external short. In normal operation the load (bulbs) draw approximately 7A. To limit the bulbs turn on current, which is approximately 10 times higher than in normal operation an inrush current limiter is needed.

Coarse requirements of the limiter:

current limit ~10A
current limit active for approximately 1s, after that the limit shall be disabled. Otherwise the power supply internal short circuit protection wont trigger in case of a short
The current limiter must be somewhat independant from ambient temperature and Input voltage (ambient temperature range: -40°C to +70°C, Input voltage range: +9V to +16V).
Limiter shall be as small as possible to get mounted inline with the bulbs power cabling.

Proposed Implementation:

Considering the above i came up with two circuits which both implement the needed functions. The favoured circuit at this time is the one with less components due to the size requirement.

My questions at the moment are: does the limiter which has the lower component count has any downsides compared to the other one? Are there any obvious weaknesses in any of the two circuits which i did not think of (except that the PMOS chosen for the simulation is not suitable)?


texts: PIC18F25K80 4 > 20 returns true. How is this possible?

texts:
I'm using such code on PIC18F25K80 compiled with xc8 compiler:

unsigned long kline_kw1281_byte_time = 0;

void sendKline(void) {
  klineWrite(0x9);
  while (klineBusy());
  kline_kw1281_byte_time = millis();
  while (!klineAvailable()) {
      if (kline_kw1281_byte_time_out()) {
          mStatus = DISCONNECTED;
          while(Busy1USART());
          Write1USART(0x00);
          return;
      }
  }
}

bit kline_kw1281_byte_time_out(void) {
    unsigned long time_out = millis() - kline_kw1281_byte_time;

    if (time_out > 20){
        while(Busy1USART());
        Write1USART(time_out);
        return 1;
    } else
        return 0;
}

and I have strange issue.  In kline_kw1281_byte_time_out() function I have true statement for time_out > 20 but Write1USART(time_out) prints me lower number than 20. This happens random. The function most of the time works correctly.

this is millis() code:

#include <p18cxxx.h>
#include "timer0.h"

volatile unsigned long runtime_millis;

void initialize_timer0() {
    T0CON = 0b11000011;
    INTCONbits.TMR0IE = 1;
    INTCON2bits.TMR0IP = 1; //set timer0 interrupt priority high
    INTCONbits.TMR0IF = 0; //reset timer0 interrupt flag
}

void timer0(void) {
    runtime_millis++;
    TMR0L = 8;
    INTCONbits.TMR0IF = 0;
}

unsigned long millis(void) {
    return runtime_millis;
}

void delay(unsigned long ms) {
    unsigned long cTime = runtime_millis;
    while (runtime_millis - cTime < ms);
}


texts: This op-amp buffer is oscillating and I can't figure out why

texts:
Currently, this is the only assembled part on the circuit board. This is a simple inverting buffer circuit that should be at the input. The op-amp (LTC6241HV) is powered +/-5V from a linear bench power supply. The power pins are bypassed with 0.1uF caps.

I'm inputting a 1KHz sine and on the output I get a ~405KHz sine superimposed on the 1KHz signal. I have tried to build a second PCB but the results are exactly the same.

If anyone knows what could be the cause for this I'll be happy to hear.

LTC6241HV Datasheet


texts: Why do some components have their through-hole pins flattened/pressed near the housing?

texts:
Some components as depicted in the below picture have different shape in their pins.

I wonder to know is it because the manufacturer wants to tell us from where should we assemble it in the board ?


texts: Differential pair biasing by current sources

texts:
I'm having a problem understanding of how can a current be injected into emitter and pulled into collector via base, using only current sources at emitters and collectors of differential pair and not applying and base voltage directly (like shown in the schematic below).

simulate this circuit – Schematic created using CircuitLab
\$ I_e \$ could be a BJT constant current source and \$ I_{c1} \$ could form a current mirror with \$ I_{c2} \$. Which doesn't really matter here. What does matter is, how can \$ V_{be} \$ on both \$ Q_1 \$ and \$ Q_2 \$ be "formed" and both transistor to conduct current, if there is no directly applied voltage on either of differential pair inputs?
Here is a quote regarding biasing of differential amplifier from Wikipedia:

In contrast with classic amplifying stages that are biased from the side of the base (and so they are highly β-dependent), the differential pair is directly biased from the side of the emitters by sinking/injecting the total quiescent current. The series negative feedback (the emitter degeneration) makes the transistors act as voltage stabilizers; it forces them to adjust their VBE voltages (base currents) to pass the quiescent current through their collector-emitter junctions. So, due to the negative feedback, the quiescent current depends only slightly on the transistor's β.

So, emitter current is forced into each of transistors by \$ I_e \$ somehow, and both of them also pass it through the base into collector. But how that happens? Isn't it true that BJT acts as very high impedance load, if there is no applied \$ V_{be} \$ (basically open circuit between collector and emitter)? Also, both bases are floating, so \$ V_{be} \$ could be anything since we don't know base potential.
I hope someone could explain this matter from mathematical aspect using nodal analysis. If not that way, than any other way possible.
P.S.* I tried this circuit in LTSpice and the both transistors conduct current from their emitters/collectors, but \$ V_{be} \$ look like some random spikes, which doesn't tell me anything useful.


texts: Photodiode in photovoltaic mode, overcoming saturation

texts:
can anyone explain to me why moving to configuration (b) overcame the problems I was having with the photodiode saturating?

Many thanks,

John


texts: Problems with efficiency and heat in a rectifier

texts:
I have too much heat in a rectifier so there is a considerable efficiency loss. I've been searching about it and I've found it could be because forward voltage or even because high frequency AC input.

The context:

There is a small 3-phase generator providing 30Vac, 60A (max) and 1700Hz. I use this rectifier: http://ixapps.ixys.com/DataSheet/VUO52-16NO1.pdf
I use a 2200uF Cap for the ripple in the outside. After this I connect a DC/DC converter to set the DC voltage.

My question is if 1700Hz could be responsible of considerable losses for this normal kind of rectifier.

I see that it will be too much current for this rectifier so I am using far from the full power in the generator and still heats too much. I want to find another rectifier or even buy 6 diodes, and I don't know if in my case I must search for fast diodes or directly for bridge rectifiers. If the most important will be lower forward voltage or if fast recovery is needed also.
This diode could be enough?: VS-150EBU02

Thanks in advance for any kind of help


texts: Is an attenuators power rating for average power or max power?

texts:
Context:
I have a transponder that is explicitly stated to output 250W peaks and has been frying some nearby components.  The transponder average output is not stated but the average input is 7W and 12W max.  I need to do some tests with an expensive spectrometer that has a max input of 20dBm (-10dB) so I can figure out safe ranges and shielding solutions.  I've got a proper antenna and have been looking at attenuators to add to the circuit to attenuate about 40dB.  Most market attenuators are around '2W' which is where I'm confused.
Questions: Is the 2W label on attenuators max or average power input?  How can I find max power input?  If I use an 8W attenuator, would this suffice assuming almost all input power of my transponder goes to signal (standby mode is <1W)?  How would I search for companies that provide these types of attenuators?
My next course of action is to take readings at a far distance from the transponder but it would be helpful to have some close up readings at around 1m.  Any help is greatly appreciated.


texts: What is the cheapest way to synthesize ASICs in small quantities? (5-10 chips). I'm asking for a specific company, not method.


texts: What characteristic on op-amp datasheets indicates performance near the supply voltage ("rails")?

texts:
From looking at datasheets for inexpensive Op-Amps like the TI TL082 or ST MC1458, how do I determine the performance near the supply rails?

Is it the "Maximum peak output voltage swing" minus the supply voltage?  For example, the specs indicate TL082 VOM = ±12 V, VCC = ±15 V, so the output won't get within 3 V of either rail (with an RL of 10 kΩ)?  TI dedicates 6 figures to characterizing that parameter (especially over supply voltage), so I assume so, but ST leaves me shortchanged (c'est la vie?).

They seem to suggest that it's "symmetric", or the same near each rail, which I wouldn't expect.  Is that just ignored for the sake of brevity and the worst-case (approaching the high rail) assumed for the low?


texts: Features to include on a new embedded Linux board to make development and debug easier?

texts:
At my work we're planning on developing a new ARM based embedded Linux board. I want to give the hardware guys some guidance on features they could add that would make the software development easier. My list so far is:

At least one dual/tri color LED controllable by GPO
A JTAG header
An extra serial port for debug log messages
Extra GPIOs taken out to a header for monitoring by logic analyzer etc.

Can anyone suggest any features they found they later needed that would have helped if present on an initial board?


texts: How to change/calculate frequency of this oscillator circuit?

texts:
I stumbled on this circuit (PDF, redrawn below), built it on a breadboard and bingo - works like a charm with a nice 1.0053kHz sine wave on the output. A little noisy given the breadboard, but satisfying.

Questions:

1. What is this type of oscillator/circuit called?

2. How does one go about selecting the output frequency? At the moment it is set to around 1kHz - how would I (for instance) change this to 10kHz?


texts: Embedded PS vs ATX PS, can they used in place of each other?

texts:
The embedded power supply in my machine has gotten damaged/weak, It is used for powering only the Embedded Computer/Controller on the Machine. The Embedded Power Supply looks something like this. http://i.stack.imgur.com/pLFQc.jpg

The Power Supply has outputs of 12v 8A 5V 4A -12V 1A and input of 220VAC, these are the same outputs/inputs that an ATX PSU gives, so can substitute an ATX PSU for it because they are normally much higher rated than the embedded ps and cheaper too.

I am thinking of making it start by shorting the green and black wire, and connecting it to the machine, by making appropriate connections.

Would something like this work or is there a Fundamental difference b/w the two types of power supplies?

Thanks


texts:
Repairing a Macbook 4.1 (2008 model), I found something odd - the cables are breaking:

The left side has a break in one cable's shielding (the wifi antenna most likely, as it's connected to a "broadcom" chip.

The right side has a worn shielding on the wire so bad that a wire was showing - Most likely the reason this unit gives ugly yellowish-flickering that only went away by adjusting the laptop screen's angle.

These were both breaking right where the hinge moves, so I was wondering, is this a common problem on all moving-wire electronics? One cable seems to have cloth-type covering over it, and I didn't see any damage to it - what is this covering called, and can I add some to the wearing cable to prevent further damage? Or would a spot of silicone plastic sealant work as well?

Update

At step 30 of iFixit manual he's holding this wire and saying it's microphone wire:

So most likely this isn't the real problem, unless microphone wire is interfering, something's probably breaking elsewhere.

Update: You can remove the small plastic piece with a half-circle hugging the hinge, but that doesn't seem to make much or any difference in my case.


texts:
After doing plenty of research on how to generate VGA signals and looking at a few code examples, I attempted to write my a simple VGA signal generator that just displays a single solid color on the screen.  When viewing the simulation, the timing appears to be correct.  When connected to a monitor, the monitor does not even acknowledge that a signal is being generated.  This has got me stumped, any help would be appreciated.

I am using timing information found here: http://tinyvga.com/vga-timing/640x480@60Hz

Sync pulse generator:

module VGASyncPulseGenerator(
    input clk, //50Mhz input clock
    input rst,
    output HS, VS, //Sync Pulses
    output active //High when active area is being drawn
);

localparam HS_START = 16; // hSync start (end of front porch)
localparam HS_END = 16 + 96; // hSync end (start of back porch)
localparam HA_START = 16 + 96 + 48; // end of back porch
localparam LINE = 800; // Length of entire line;

localparam VS_START = 480 + 10; // vSync start (end of front porch)
localparam VS_END = 6480 + 10 + 2; // vSync end (start of back porck)
localparam VA_START = 0;
localparam FRAME = 525; // Length of entire frame

reg [10:0] hPos = 0;
reg [10:0] vPos = 0;

reg pixelStrobe = 0;

assign HS = ~((hPos >= HS_START) & (hPos < HS_END));
assign VS = ~((vPos >= VS_START) & (vPos < VS_END));

assign active = (hPos >= HA_START) & (vPos >= VA_START);

always @(posedge clk) begin //generate pixel clock at 25MHz
    pixelStrobe = ~pixelStrobe;
end

always @(posedge clk) begin
    if (pixelStrobe) begin
        if (hPos == LINE) begin
            hPos <= 0;
            vPos <= vPos + 1;
        end else hPos <= hPos + 1;
        if (vPos == FRAME) vPos <= 0;
    end
end

endmodule

Top module:

module VGATest(
    input clk, rst,
    output HS, VS,
    output [4:0] B,
    output [5:0] R,
    output [4:0] G
);

wire active;

assign R = (active) ? 5'd1 : 5'b0;
assign G = (active) ? 4'd16 : 4'b0;
assign B = (active) ? 4'd1 : 4'b0;

VGASyncPulseGenerator pulseGen(clk, rst, HS, VS, active);

endmodule


texts: How to test a cmos sensor without breaking it?

texts:
A couple of weeks ago my dad gave me a Syma X5C H5C camera that he found.
I wanted a camera for my robot project and I tried to just take the camera but I found a problem with it.

The pcb is called 2202M and is manufactured by a company called Joyhonest. (My next step after this thread would be to mail and see if I could get any information but I don't know if that will be successful)

Here is an image of the pcb (The text on the FPC is JH15A)

Image of my traces where the connections go. It's not complete but it makes it easier for me to see.

There is some copper visible on the top of the pcb that is connected to the write parts of a micro sd slot. I could use them to get the raw data that's written to the micro sd but that would only be to test if the camera works and not my final solution.

I could also just buy another sensor. That would make this easier but I like when I can take stuff slow and try for a long time. I would like to only take the camera part and use that for my robot.

Is there a way to figure out how to connect to this camera without breaking it?


texts:
I am trying to switch the ranges of an I/V amplifier, such that I can measure from 100nA to ~1mA of current up to 100kHz (similar to this question). I make the switching using an TS5A3357 analog switch, however I seem to be limited in bandwidth somehow, no matter what op-amp I use. I'm guessing it has to do with the ON/OFF capacitances of the analog switch, but I don't know how to mitigate that. Is an analog switch even possible in such application or would I need to use another component (such as a relay)?

Why is this thing not working?

Also note that the low-frequency gain, even though it should be 0dB, is -3.8dB.


texts: How to choose AC/DC adapter - high voltage low current vs low voltage high current

texts:
I got an LED light kit, 2 lights, each takes 60W, at 12-30V.

I'm planning to use these lights separately, and need to choose between:

12V, 5A adapter
24V, 2.5A adapter

Both will give me 60W, but one at higher current, and the other at higher voltage.

Which one should i get and why?

Thank you!

link to the light kit: AMBOTHER LED Pods Light Bar 4-Inch 120-Watt (Amazon)


texts: Help with charging lithium ion batteries

texts: I want to make a lithium ion power bank. I have lots of lithium batteries but I don't have very many that are the same. So if I connect 20 different ones in a parallel circuit and they all have the same voltage ,do you have to charge it with the lowest voltage/current value of the lowest cell? Or would I be better off connecting them in sequence? If sequence is better could someone recommend a charger for me that will go up to 20-50v 1-10amp....just as a side question for charging, can I use a c2h( can't remember the name ) charger to charge lithium ion


texts: MCU based I2C master receiver mode includes transmitter mode or not?

texts:
If I am programming an MCU I2C peripheral as a master of I2C bus that will be receiving data from other slaves on the bus. So I will set its direction as 'I2C_Receiver.'

But since an I2C slave will only send its data to the master after the master sends it the command to do so, does it mean that to send the command to the slave I will have to configure the master direction as 'I2C_Transmitter' and send the command first to the slave? Then I change its direction to 'I2C_Receiver' to be able to receive the data from the slave?

Or do I only configure the master in 'I2C_Receiver' direction and that includes the transmitter by default?

Edit:
The MCU will be RM57L843.


texts: How to control the output voltage for the different types of the dc generator?

texts:
Generally DC generators are classified according to the ways of excitation of their fields. There are three methods of excitation.

Field coils excited by permanent magnets – Permanent magnet DC generators.
Field coils excited by some external source – Separately excited DC generators.
Field coils excited by the generator itself – Self excited DC generators.

How to control the output voltage for the different types of the dc generator and how to reverse the voltage polarity?


texts: I have a standard USB adapter of 5 volts / 1 Amp and I would like to instead of cutting off voltage with resistor, I need to limit the maximum output to 200mA. I'm confused about how to accomplish this, because as far as I understood, if I would use a 6.8ohm resistor, it would cut down the voltage to 3.7v and cut down some amount of current, but the maximum potential of the current that can flow into my circuit will be still more than 200mA, correct?


texts: Can two x-bit ALUs/FPUs be combined to create an equivalent a single 2x-bit ALU/FPU?

texts: I was wondering, can 2 16-bit ALUs/FPUs be combined to create a 32-bit ALUs/FPUs, or are 4 ALUs/FPUs required? I was wondering if lower precision ALUs/FPUs can be combined in any way to create a higher precision equivalent ALU/FPU, so I may be understanding this topic completely wrong.


texts: What if there's current INTO an output pin?

texts:
maybe my question is easy to answer and maybe I shouldn't have asked it, but I'm really not sure.

I would like to connect an XBee ZigBee module (3.3 V) to a microcontroller (PIC, 5V) using the USARTs.
(I need to use 5 V. Using 3.3 V for the PIC is not an option.)

I want to use a level converter using two diodes as mentioned in Microchip's Tips'n Tricks document (DS01146B), page 8-7.

simulate this circuit – Schematic created using CircuitLab

When building this circuit, I will happen that there's current flowing INTO the XBee's TX pin.
(This will be the case if the XBee wants to pull its Tx line to 0 V but there's some higher potential on the pin due to external parts.)

In the XBee's datasheet (document 90000866_A, page 8), there's some information on the maximum transmit current. It's 45 mA with Vcc = 3.3 V.
But "transmit current" suggests that it's outgoing current (or at least one could understand so).

Maybe the device is not capable of sinking current into the Tx pin as it's only designed to drive outgoing current?
Or maybe it accepts current into the chip, but not as much as outgoing current?

Can I be sure that the value for "Transmit current" refers to both current into and out from the device?


texts: I bought some TXS0102DCUR, and I am not 100% confident that the first pin is from the side of the stripe (left side, relative to the picture). Could anyone confirm, please? I scanned through the datasheet but could not find any reference.


texts: I'm new to electronics,  I was working on a surface mount board and I desoldered one of the eyelets a bit too much and burnt its trace as well. What steps should I take to repairing this? I'm not getting any continuity from the damaged vias. Thank you I Took pictures from both sides.


texts: Real world efficiency of a LM3150 Webench DC power supply design?

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When designing a DC/DC step down converter with TI Webench with these parameters:

Vin min: 11.4 V
Vin max: 12.6 V
Output :  5.0 V
Iout   :  8.0 A
Ambient temp: 30 ºC

Then turn the efficiency knob to the right two times (this is highest efficiency) and then selecting the LM3150 buck topology design.

The resulting theoretical efficiency for 12V DC input (Vin = 12.0) is:

96.774% at 0.8 A load
98.115% at 1.6 A load
98.524% at 2.4 A load
98.696% at 3.2 A load
98.772% at 4.0 A load
98.800% at 4.8 A load
98.799% at 5.6 A load
98.781% at 7.1 A load
98.712% at 7.9 A load

The paper Towards a 99% Efficient Three-Phase Buck-Type PFC mentions an "error of 0.16% in efficiency" at full load between calculated and the results of calorimetric measurements.

When using exactly the components as specified in the BOM, including the prototype PCB (PC Board, Part Number 551600142-002), what will be the real world efficiency at these loads at Vin = 12.0V (instead of this theoretical simulation)?


texts: Is this the right layout and can i reduce the number of bridges?

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I have this LED light flasher circuit and want to put make it on a veroboard

This is my first veroboard project and below is my plan for the layout. Will this work and do I need to reduce the number of bridges?

Thanks!


texts: Does a 1 watt 660nm LED put out more radiant flux than a 1 watt 630nm LED?

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Given two LED chips consuming same or very similar amounts of DC power,
One emitting light peaking at 630nm,
The other at 660nm,

In terms of output of (but light irrelevant to the sensitivity of human eye);

Which one would output more energy in form of light / photons?
Which one is more "efficient"?

Taking into consideration:

660nm means less energy per photon,
630nm means more energy per photon;

Which one outputs more number of photos?
Does larger wavelength of 660nm mean it takes longer between photon outputs?

Also:

If it takes longer to create a single photon of 660nm, which has less energy than 630nm;

Does the energy difference between 630nm and 660nm photon is turned into heat by LED?


texts: What is the phenomena behind this DC generator plot?

texts:
There is a DC generator to be calibrated with its plot below. On the X-axis there is the ratio between the power of the generator/ nominal power of the generator. On the Y-axis there is the efficiency of the generator.
Can someone please explain what phenomena is behind the behaviour of the plot?
Efficiency sharply increases as the ratio increases, then peaks, then plateaus and declines at higher ratios of power of the generator/ nominal power of the generator.
Why is that happening?


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i"m designing a long metal1 wire. The parasitic capacitors and resistors are callculated.
I want to have an ac voltage at the output end of the line ( 0 - 3.3 V ) at 1GHz.
How can i calculate the power i need to supply at the input of the line and the dissipated power?