texts:
I want to make a DTMF decoder and use it on an internal DC phone line. I made a decoder with PIC microprocessor (Black DTMF decoder) that works with signals around 0V. My internal phone line consists of a 9V battery, a 330 ohm resister and a phone, all in a series circuit and the DTMF signal is read from resistor ends. My problem is that the signal is always above 0V (around 3.5V that changes if I use another phone) and I need to shift it around 0V but I don't know how?

Edited: This is my circuits diagram.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm planning to start with uclinux with my ARM cortex M-3 based MCU .

Uclinux's requirements include ~4MB of RAM (SRAM - DRAM - .. whatever) and flash (SD card - NAND Flash - ... whatever).

My MCU memory controller supports external SRAM (in different modes).

I have couple of thoughts and need some one to clarify them for me:

Let say I want to add 4MB external SRAM (despite how internally organized) this will take for example 8 pins for data and 22 pin for address, So most of pins will used only for external memory. This is not acceptable for embedded devices where the number of pins is limited.
As the below image describes, instruction could be executed from internal flash (I-bus), internal RAM or External Bus Interface (D-bus), doesn't this make a bottle neck? (data and instruction will be fetched from the same lines as ARM is a Von Neumann architecture).
A general question (it maybe not make sense) but could I used instead a SRAM chips with SPI interface ? could I fetch instruction from SRAM in this way?, also what about speed issue when using SPI instead of parallel bus lines .


texts: What is the pole frequency of a three-phase LC filter?

texts:
Suppose I have this configuration:

Assume L1=L2=L3 and C1=C2=C3. What is the pole frequency of this filter?

Edit: As mcmiln says, this is not identical to the question here:
Cut Off Frequency in three phase LC filter

I want the closed form (and preferably derrivation) of the filter pole.


texts:
So I'm working on the PCB layout to assign testpoints to pads.
I've created vias to connect to the pads as testpoints, double clicked on the via, checked the 'Assembly Top/Bottom'
I then went to Tools from the toolbar, Testpoint manager, and clicked on 'Assembly testpoints' however it failed to assign testpoints I don't know why.

I'm following this procedure from this link: http://techdocs.altium.com/display/ADOH/Testpoint+System

I'm not sure what I'm missing.


texts: Physically sharing 5v and ground between multiple sensors

texts: I'm using the Adafruit Trinket with two sensors that both need to be connected to power/ground pins (Trinket has one 5v output power and one ground). The final size of a whole thing matters so I cannot use stripboards (at least as a whole). What is the physically smallest way to share the 5v and ground between the sensors? Can I just solder multiple wires into one hole?


texts: Registration issues with OSH park 4 layer boards?

texts:
I just got back a 4 layer board from oshpark and have a few shorts on the board (no components stuffed).  In particular I have two .050" pitch connectors with 4 pins each.  It appears as though all the pads of the connectors are shorted together.  The design passes DRC without issue and there are no overlaps anywhere.  One of the connectors has two pins that each have a single short trace on the top layer only.  Somehow these pins are shorted together (and to the surrounding pins).  My best guess is that there's a registration error with the internal layers such that somehow the connector is being shorted on one (or both) of them.  Has anyone had a similar issue with either oshpark or another fab shop?  I've looked carefully at the tow inner layers in eagle and cannot find anything obviously wrong (more importantly neither does the DRC).  Can you think of any other reasons why these pins are shorted?

Screen shots of the inner layer in Eagle for the area in question:


texts: What is the meaning of this line? "Memory-mapped, cached view of external QSPI flash. The cache is specified as 32 KB with 4-way associativity."

texts:
Memory-mapped, cached view of external QSPI flash. The cache is specified as 32 KB with
  4-way associativity.

Does it mean that my external QSPI Flash is only 32Kb or it has been memory mapped onto 32Kb?

Does cached view mean that repeated read will get the data cached within the processor and not actually access the memory?


texts: Need a switching circuit that is closed when Vgs is negative and open when Vgs positive, any ideas please?

texts:
I need a circuit that will be closed when Vgs is negative and open when Vgs positive. Basically the inverse of Enhancement mode MOSFETs or JFETs.

I appreciate your help with this.

Thank you!


texts:
This morning I woke up wanting to drink a cup of coffee and, as usual, it annoys me that I have to turn on the machine only to wait a minute before I can begin brewing.

I want to be able to turn on my coffee machine from my mobile phone.

Now I have the knowledge to make an app and to get the wireless->mobile part to work, but I don't know how to go about the actual hacking of the Nespresso Lattisima that I own.

Does anyone have any schematics or pointers as to what I should be doing?

I own an aurdino mega, and have both atmega and attiny chips that I can use for the project.

Where do I go for electronics information on the Lattisima?

The sequence of actions I have to perform to get coffee:

Turn on Machine
Press coffee button (4 different types of button).
Turn off machine


texts:
I am using below scheme for generating different voltages using transformer.

T1 transformer generates 15V and 48V ac and then rectified by AC-DC converter to generate different DC voltages (12V_Op amp Supply, -12V_Op amp supply, 16V_Logic, 38V_Constant Current Source) for my circuitry. But transformer is generating noise which is hampering ADC circuit and variation observed in ADC.

What techniques I can ensure to eliminate noise from transformer, please someone guide.

Thanks in advance.


texts:
I’m currently working on a solar powered boat with a modest sized team of people. For our competition we are only allowed to have 3 12v batteries on board but we are allowed to have up to 52v at any point in our setup. We are hoping to kick up the speed of our outboard motor for the sprint portion of the completion and are looking into using a boost converter for this.

After doing a little research I’m a bit confused about how they fundamentally work. From what I can tell they take in a voltage and current and put out a higher voltage with a lower current with some level of efficiency. But it seems to be independent from the load( in this case the motor) which doesn’t make much sense to me because I thought the current would be determined by whatever my load is. How do loads actually interact with boost converters?( The simpler the better.)

For reference we are using the Saietta 119r motor system and I’m considering using the MPS MPQ3425 boost converter.


texts:
I just designed this MPPT solar charge controller which outputs 4.2 V regulated via MPPT, it uses the SPV1040 IC. This will be used on a satellite with 4 side panels, each with 8 solar cells in parallel outputting 2.6 V at approximately 122 Ma. Each panel will have this exact circuit and all the outputs will be connected in parallel to a 3.7 V lithium ion camera battery.  When active only 1 solar panel will be active and the other MPPT circuits will be offline or providing a very low amount of current. How should I connect the 4.2v to the battery, just directly or using some sort of controller to stop charging at 4.2v? Keep in mind the battery will always have a load and it will charge for around 50m in a 90m cycle due to being eclipsed. I would obviously like the battery to last as long as possible so I am not sure what are the implications of constantly having a battery connected to 4.2 V during 50m. Thanks.

The schematic was made based off a simulation made using the ST Edesignsuite directly from the provider.

Excuse my previous question about this, wasn't properly worded.


texts: What would happen if 2.4 Volts is applied, instead of 1.25 Volts, to an FPGA?

texts:
We have a production batch of PCBs with faulty regulators that produce 2.4 Volts instead of 1.25 Volts. The only load on the 1.25 Volt node is the VccInt input on a Xilinx Spartan 3E FPGA. The max limit is 1.32 Volts according to the datasheet. Oddly, nothing has blown up. We see random odd behavior from the FPGAs where they seem to partially lose their configuration but recover after a reboot. They run a little warm too.

Would an overvoltage on the 1.25 Volt input cause what appears to be partially corrupt configuration at random times?

Why do you suppose the overvoltage didn't smoke the FPGAs? Is there built-in overvoltage protection?

Edit:
BTW, the 'bad' regulators turned out to be counterfeit parts.
Everybody seems to think that an over-voltage would smoke the FPGA but we ran the voltage up to 4.8 Volts and it still didn't smoke - it would stop running occasionally but would spontaneously re-start after an apparent cool-down. The only reason we stopped at 4.8 Volts was because we melted a test lead.


texts: Resistive and inductive load on same transformer?

texts: Is it ok/safe to put both a resistive load (heating elements) and inductive loads (servo motor) on the same leg of a 240VAC transformer? I have some electrical knowledge but it has been a while since I've dealt with servos, and heaters.  I sort of recall some caution about mixing both resistive and inductive loads.  My heaters will be be controlled by zero crossing SSRs and temperature controller. The servos will be controlled by by a servo controller.


texts: Series vs Parallel termination load for transmission lines

texts:
I have a source with 5V 10Mhz Squarewave output, then I have an OR logic gate then 20m coaxial cable and then I have another OR logic gate. I guess I will need a matched load (now it is 100Ohm (random resistance)) for this system. Should I add the termination load in series or using voltage divider?

I must note -  I do not need any numbers, I am just curious about pros and cons in the two following systems.

Here is the updated picture.
Coaxial cable: 20m, 50Ohm
Voltage Source: 5V, 10Mhz, Square Wave


texts: Moment calculation for DC serial generator question

texts:
DC serial generator tag information : 9.25kW, 185V, 1500rpm .
this is the table

I have two solutions, which one might be right


texts: Projection clock: how to make a custom display?

texts: I have a projection clock which projects a red image of the current time on the ceiling. I want to know if it's possible to find/build a similar display that would be computer-controlled (project arbitrary ascii content specified by a computer). What's different than a normal projector is that this thing doesn't need a very bright projector bulb or a fan - it's silent and on 24*7 and doesn't need expensive bulbs changed often (as a projector would). I want to use the same technology to project different text (I don't need images or high-res, just to control the text). What technology is it using - my web searches haven't turned up the right thing.


texts:
I have a 1 kHz sine-wave signal with an amplitude of 5V (peak-to-peak), and a +2.5V offset.

I want to rectify the signal so that I only get the portion of the signal above 2.5V.

If the signal wasn't offset, this would be easy. I would just use a half-wave rectifier. But what do I do when my signal is offset above 0V?

I have a number of op-amps in my current project, so adding more wouldn't be a problem if that is what the solution requires.

Edit:

I have drawn a quick diagram of what I'm looking to do


texts:
I'm trying to analyze the below circuit. It's a textbook problem (Malvino's Electronic Principles) and the answer is given in the back (8966), but I am unable to reach that answer or approximation.

The goal is to figure out what is the total voltage amplification of the below circuit:

The Op-Amp part is pretty easy, since it's simply a non-inverting amplifier with a feedback configuration, so the amplification is (47k/1k + 1 = 48).

For the transistor, I'm having a difficult time. Particularly, the 1k resistor is throwing me off. I think it's in series with the voltage divider biased circuit, so I am approaching the analysis like this:

\$I_E = (15(10/33)-0.7)(1/5600) = 36.4 mV\$ (assuming 1k, 22k, 10k resistors form a voltage divider)

\$r'_e = 25 mV/I_E = 36.4 ohm \$

\$r_c = 6800\$ assuming the input impedance of the 741c is very high

\$A = r_c / r'_e = 186.8 \$

Total Amplification = 186.8 * 48 = 8967 which gets me pretty close to the textbook's answer.

I don't know if my analysis is correct though. I tried to simulate the circuit in LTSpice, but I got a larger voltage drop across the 1k resistor than my analysis would suggest so I just wanted to see if anyone would approach differently.

Thanks


texts: 2 Crossovers in parallel: how are frequencies distributed?

texts:
So, the other day I connected on parallel a dual-voice subwoofer-system (a Pyle XSUB1-150-4-12d crossover —  like this one ... link might be unavailable after Aug 28, 2019 ... — and 2 individual subwoofers) with a 3-way-speaker-system (Weconic) and they sound good together! As far as I can hear with the help of a 7-band-equalizer (100Hz, 200Hz, 400Hz, 800Hz, 1.6kHz, 3.2kHz, 6.4kHz) there is no frequency not being reproduced and the 3-way-speaker seems to receive less of the waves with frequencies below — and arround — 100Hz than the "dual-voice-subwoofer". This is the "roll off point" of the XSUB1 crossover.

I wonder how the distribution happens... and have some doubts...
++ UPDATED ++ (based on the first 4 comments)

Does the XSUB1 crossover "pull" the frequencies below-and-around 100Hz? Or does it "block" the others >100Hz?
Or does the XSUB crossover-elememts absorb the frequencies I don't hear through the subwoofers? Are these transformed to heat or magnetic fields in the capacitor or coil? respectively?
Should I know more about what a crossover's "roll off point" does to the frequencies?

Sorry if my questions are pointing in different or vague directions and thanks for helping me know what happens to the information travelling!

++ EDIT ++

Here are the wiring instructions of the XSUB1:

I've been unable to find any information on the XSAT3-150-12d.

Here is a handmade schematic of the complete system:

with some of the data/measurements.

I have used components from several items:

two identical subwoofers
100Hz stereo crossover
Yamaha NS-G7's 3-way-crossover
Weconic 3-way-drivers.

It turns out the tweeter of these drivers is dead... so I can't give an Ohm value...


texts:
I wanted to build a simple amplifier for a square wave generator with the following configuration:

The presence of the amplifier is crucial since with my 12Ω load the output peak current may be near to 2A.
My main problem with this configuration is that my square wave generator is (and must be, for my project) adjustable. So, I can choose its amplitude value and set it from 0 to 20V, while the voltage supply is 24V.
Since the voltage supply is 24V, there will be a huge voltage drop between collector and emitter terminals, which will become heat.
Do you have an alternative configuration which avoids this problem?
It's exactly the same problem of a general linear voltage regulator. In such a case it's solved by choosing a PWM switched mode regulator. But that's true for a DC voltage regulator. Is there a similar configuration for a square wave voltage regulator?


texts: What would be the difference in the voltage transfer curves of this two circuits, assuming the op-amps are not ideal?

texts: How does the resistor connecting the non-inverting terminal to ground affect the transfer curve?


texts:
I have recently started working (no previous experience of working with BLE) on BLE2 click module (RN4020), I could successfully connect TTL-USB cable to my laptop and could communicate with the module via the MLDP mobile application.

However, now I would like to use it in UART mode and as per the link: http://microchip.wikidot.com/ble:rn4020-operating-modes , I should be working in MLDP mode, i.e. CMD/MLDP pin should be connected to Vcc, is my understanding correct?

Also, I would like to clarify on this point which is mentioned on the same webpage: "To enter Command mode, set the WAKE_SW pin high." Is it WAKE_SW pin that should be held high or CMD/MLDP pin should be held low?

Also, can anybody provide information regarding the set-up required to interface the module with MSP430 mcu, can i directly connect the module to MSP430 after performing the following steps using TTL-USB interface:

+                // echo on
SF,2             // perform complete factory reset
SS,C0000000     // enable support of the Device Information and Battery services
SR,00000000     // set the RN4020 module as a peripheral
R,1             // reboot to apply settings


texts:
I'm relatively new using PIC microcontrollers and MPLAB XC8 compiler.

I want to communicate two PIC16F887 using I2C. I did use this tutorial (https://
  electrosome  .com  /i2c- pic-microcontroller-mplab-xc8/) as my introduction to this protocol, but although my code compiles, my proteus simulation doesn't do anything. The objective is only send the count from 0 to 3 through I2C from the master to one Slave, and the slave should show that number on 2 led on PORTB.

I debugg the program on the master side and the program seems to get stuck inside my I2C_Master_Wait() function, I really try to understand whats happening inside this function, but i dont get any result since too many days ago.

void I2C_Master_Wait(){
    while ((SSPSTAT & 0x04) || (SSPCON2 & 0x1F));
}

Hope someone could help me with a better tutorial or some explanation about whats going on in that function and maybe other way to do it. I attach here the folder with the code of master and slave and the proteus simulation.

Thanks!


texts: Determining suitable wire gauge for LED-strips (voltage drop)

texts:
I am software engineer by trade and a novice in this field, please point out any mistakes in my assumptions and vocabulary regarding this topic.

I am designing a lighting plan based around commonly available RGBW LED-strips. These strips contain the so-called 4-in-1 5050 SMD LED modules that combine a red, green, blue, and (warm) white LED in a single form factor. The strips are powered via a shared positive 12V DC lead, and each of the four 'colour channels' has its own return lead. To control the brightness and the effective combined colour output, a PWM chip controlled by a Raspberry Pi switches a MOSFET on each return channel at a suitable frequency with the desired interval.

Each lighting unit consists of three 45cm strips of this type of LED-strip, connected to the incoming leads in parallel (so voltage drop across the length of the strip within each lighting unit is probably minimal). These strips consume 19.2W per metre; roughly 4.8W/m per colour channel.

In this diagram I have drawn three of these units, relatively close to each other. The distance between the power source and the PWM controller too is presumably negligible for the purposes of this question. The distance between them and the lighting units is five metres. The power source provides 12V DC, and I can tweak it to increase or decrease the output voltage by about 10% both ways.

From what I understand, these LEDs function best if they receive power that is fairly close to 12V DC. Using the knowledge found on this Stack Exchange and other sources, I think I know how to compute the voltage drop. If I simplify my scenario to just a power source, 14 AWG leads, and something drawing 6.5A of current at a distance of five metres from it:

14 AWG copper wire resistance: 8.286mΩ/m
Roundtrip distance: 2 × 5m = 10m
Voltage in: 12V DC
Load current: 6.5A

Total resistance: 10m × 8.286mΩ/m = 82.86mΩ
Voltage drop (V=IR): 6.5A × 82.86mΩ = 539mV = 0.54V

Correct?

Does this mean that the LEDs get 11.46V of voltage or 11.72V (minus half of 0.54V, because they are halfway on the circuit)?
I am assuming that a voltage drop of at most 0.54V is acceptable for these type of LEDs. Is that correct?

Now in my scenario there are not one, but essentially four circuits, all sharing a single positive lead, but each with its own return lead, and each drawing at most roughly 1.6A of current.

If I use, say, 14 AWG for the combined positive lead, and a smaller gauge for the return leads (one that has a four times higher resistance, say 20 AWG) then does the voltage drop calculation above still hold true? That is, because the current in the return leads is a fourth of the combined current, does the same voltage drop occur with a wire gauge with a resistance fourfold that of the incoming lead?
Is this a suitable method of determining the (minimum) wire gauge for such a project?


texts: Correct Term for Radiation Pattern of Target

texts:
I am hoping that this is the right forum for questions related to radar systems.

The radiation pattern for an antenna is (a plot of) the relative strength of an emitted antennas signal as a function of the direction out from the antenna.

However a radar "target" will also have its own radiation pattern in response to an incident wave. The relative strength of the reflected waves will depend on the direction from which they are viewed, as well as the direction of the incident wave. I have come across the term Radar Cross-section, but I am not sure if this is the correct term for what I need to describe(Particularly since I'm not ultimately describing a radar system).

So does anyone know a term for the "radiation profile" of a wave reflecting object as a function of both incident and reflected wave direction?


texts: I have these switches in my home which you push once, they don't flip over just go back to the initial position. We have like 4 of those and I really want to know how they work. Can someone explain please?


texts: Calculation of capacitance parallel to Bidirectional TVS diode

texts: How to find the value of suitable capacitor, parallel across the Bidirectional TVS diode? Is there any formula to calculate?


texts: Why do buck converters end up in steady state?

texts:
I'm studying buck converters such as the one in the following simulation:

I have learned that for buck converters that are in continuous conduction mode and at steady state, the following equation holds, and I find its derivation convincing:
\$D_{\text{uty cycle}}=\frac{V_{out (avgerage)}}{V_{in}}\$
However, it's never explained why the buck converter has to end in a steady state.
I have simulated the circuit and played around with components and their values and the circuit always seems to end up in steady state eventually.

How can I tell if the buck converter will or will not operate in steady state?
What are the conditions required to assume the circuit will reach and stay at a steady state eventually?
Can I actually design a buck converter that will not reach steady state?

For clarity, this is for a buck converter with no feedback control that operates at some fixed frecuency and duty cycle.
EDIT: The original question proposed "Why doesn't the current in the inductor gradually increase in each cycle until it reaches infinity? (assuming ideal components)". This has been adressed in the answers. I'm removing it because it was not the main question but it seems to have particularly captured the atention of most since it was the most obviously wrong statement. Thanks for the clarification.


texts: How to output sounds over a headphone wire?

texts: I soldered some headers to a headphone line and was wondering how to make sounds come out of an audio device connected to that. I don't mean music, or anything advanced. Just two tones for RTTY. I'm using an arduino and know it has a sound library. Would that help at all?


texts:
I have an application where it would be useful to provide some external data to a program via the USB mouse or keyboard.

The Teensy USB Development Board would be ideal, since it's small and has direct USB support.  Unfortunately, it would require a USB drive, and I would prefer a direct plug-in, like a thumb drive.

Given that the Teensy has the USB support built in, how difficult would it be to modify the board so that there's an edge card connection (terminology?) such that the unit can be directly attached to a computer's USB port?

Can standard layout tools and board fab services make such a board?  Are there any routing specs available that can be dropped in to an existing board design?

Alternatively, are there any existing designs that might already include the USB edge connection?


texts: Single ended ADC negative voltage protection

texts: How to protect ADC input against the negative voltage?


texts: Best way to deal with surge in current from DC motors

texts:
I have a Li-po battery 12V 9800mAh (typical current 2.4A) which powers a 4WD drone using 4 DC motors (which I have not yet characterized).

Driving the motors from still to max speed without transients will cause a spike in current consumption that goes beyond what the battery can supply.

I can (and most likely have to) use the SW to make the transition gradual, so that the peak current is somehow manageable.

However so far I only performed empirical attempts and I think most likely they will be sub-optimal, depending on the level of charge of the battery.

After googling, I still couldn't find an ultimate answer to how to address this problem.

Some advice says to put a large capacitor in parallel to the battery, but is it all? I can use a power supply to replace the battery and measure the actual peak current and its duration, but what to do after that?

I am not sure using an RC circuit is a good idea and I wouldn't know if there is some active circuit that could handle the peak current.

Is there some standardized way to solve this problem?


texts: Requirements for closed, open, and short circuits

texts:
In terms of understanding paths in a circuit, let's take a few example circuits:

(1) Would the following circuit be considered closed or open (or something else) since it doesn't have a voltage source?

What are the requirements for a circuit to be closed? Is it that there needs to be both a voltage source and ground with a connection between the two, or something else?

(2) For short-circuits, for example:

When is a circuit considered shorted vs not? For example, what if it is a voltage_source+capacitor? what if it is a voltage_source+led? Do all components (minus a direct wire connection) added between a voltage source and ground make it a non-short circuit? Or, what are the requirements for a short circuit? (The concept I have in my head is a closed circuit with a too-high current.)


texts:
I recently saw an article with a LED cube 8x8x8. I saw that it relies on an optical phenomenon called persistence of vision (POV).

So I wanted to create a simple circuit with 4 lines each one with one LED, that will light up with a frequency that will give the illusion that they light up all the time. (I know how to light up 4 LEDs but I want it simple now to catch the point)

Can someone help me and tell me what parts should I need to create this?
I have an Atmega 16L microcontroller. Can I complete this without any other chip?
Can I achieve this also with 555 and flip flops?

EDIT:

Sorry if I cant be understandable.

I want a simple circuit like the one in the below picture that will light up each strip for a certain time.This time must be sort enough to see a constant lighting.

The black box is whatever parts it will need because I dont know them.


texts: buck regulator MOSFET turning off for a short duratiopn

texts:
I am designing a regulator system using a buck regulalator. The datasheet is - datasheet.

Now, the regulator can be configured to switch at 100-500kHz, and this is done using a resistor connected to the Fset pin. The schematic is as shown in the datasheet and is placed below as well -

.

I have configured my regulator to give 3.3V from an input of 10V at 300kHz.
Now, there is a weird behaviour happening. I am probing the TG pin of the IC, which basically controls the control mosfet or the higher MOSFET.

The scope data is as shown below -

Now, the MOSFET is working fine or rather there is gate signal for a significant amount of time with the required frequency of 300kHz. But, then the gate goes low which disables the MOSFET.

I am unable to understand the reason why this is happening. Now, the Vc pi (error voltage) is a wave with voltage going from approx 0.75 to 1.23V. Is that notmal ?


texts: Diagram symbol for an inductance with a neodymium magnet as a core

texts:
I want to know if there is such a symbol (i.e. an electrical diagram symbol for an inductance with a magnet as a core).  If such is the case how is it specified the orientation of the poles of the magnet?
Thanks in advance


texts:
I was attempting to get familiar with the  Texas Instruments CDCE62002.
While checking the datasheet of the evaluation module, I came across the following indicator in the schematic. I'm curious about the dashed line which is visible. For a full view of the schematic please check page 11 of the EVM datasheet

Reasons I could think of why they did this:

I am overthinking a random scribbly line
They want these ground points to be as close together as possible? (if this is the case, why would you place such information inside a schematic instead of a pcb layout/guidelines section)

TL;DR: Why is there a dashed line connecting grounds in this schematic?


texts: My team and I are testing our Peltier Thermo-Electric Cooler Module+Heatsink Assembly - 12V 5A from Adafruit. We are using an external power source and sensors to get readings for the current, voltage, and temperature. The problem we are facing is that the sensors are reading the fan RPM and not the frequency for the power. We cannot disconnect it as this causes a huge temperature difference in the module. Any advice? This may be sensor or code related.


texts: Adding a small protoboard-like area to a PCB

texts:
I'm currently laying out a PCB in eagle for a circuit that will form the basis for some experimentation. Instead of adding a row of headers so that I can plug it into a breadboard, I figured I would try and layout a small protoboard directly onto the PCB itself. I have room to spare on the board and the resulting creations will be somewhat more resilient. This PCB is a good example of what I'm shooting for.

I have considered using vias, but I seem to recall they are usually sealed off with a chemical to prevent solder from bonding. This is obviously not what I'm going for. Adding hundreds of single-pad components to my schematic does not seem very appealing either.

What is the best way of achieving this using Eagle?

EDIT: Thanks for your help everyone. Here's the design and here's the finished product.


texts: How should I power my 5V 5mA components while developing?

texts:
I'm doing a hobby project at home involving an atmega128 at 5V. It's going to run from battery, but during development, I'll need some other power supply. What is the cheapest and most simple solution?

Is there a way to pull 5V from USB? What is a component that converts the mains to 5V called? I'll need around 5 mA.


texts:
I have just inherited a piece of equipment that is powered by a 12V DC permanent magnet motor. My hope is to drive it using an Arduino PWM and a H-Bridge to manage the current requirements (7.3A continuous load, peaks at around 10A on start up). That is all fine and good and working, my only concern is that there are three wires coming from the motor, a red and black which I've taken as the DC input. Plus another wire, green and yellow striped like a mains earth.

My question is, is this just an earthing cable for the metal case? and where should this be attached I'm presuming it shouldn't go to the DC ground.


texts: VHDL error: multiple constant drivers for net

texts:
I can't find how to deal with the error: "multiple constant drives" which occures when I try to read and set the same net in a single process.

I need to set the "output" for some clock cycles on the rising edge of "enable" input and then reset the "output". My code:

library ieee;
use ieee.std_logic_1164.all;

entity trigger_slave is
    generic (
        OUT_ON_PERIOD   : integer := 10 - 1
    );
    port (
        enable          : in std_logic;
        clk_1MHz        : in std_logic;
        OUTPUT          : buffer std_logic
    );
end trigger_slave;

architecture behavior of trigger_slave is

begin
    process (enable)
    begin
        if (rising_edge(enable)) then
            OUTPUT <= '1';
        end if;
    end process;

    process (clk_1MHz)
        variable counter        : integer range 0 to OUT_ON_PERIOD := 0;
    begin
        if (rising_edge(clk_1MHz) and OUTPUT = '1') then        -- here is the problem!
            if (counter = OUT_ON_PERIOD) then
                counter := 0;
                OUTPUT <= '0';
            else
                counter := counter + 1;
                OUTPUT <= '1';
            end if;
        end if;
    end process;

end behavior;

Please, help me with this code. Thank you very much.


texts: How to do high frequency simulations in simulation softwares (proteus, multisim, etc)

texts: So i am trying to build a buck converter which requires switching at high frequencies. Before making the whole circuit however, i decided to use a circuit simulation software so that i can experiment with the values of the components and trying to see if a concept works or not. However, the problem comes when simulating the circuit. the simulation time will come down to a snail's pace that it would take a long time to get proper results. I've tried using multiple simulators such as proteus and multisim. Both of them perform poorly when working on high frequencies. Is there any way to lighten the workload for simulating these sorts of circuits?


texts: Overvoltage protection with zener - How do you get a sharp knee clamp for analog input?

texts:
I'm working with an MCU that sees a 0-5V input range. I have a possibility where they may accidentally see 12V (user error).

My problem is this analog input using a 5V Zener has a knee that isn't as sharp as I'd want and can load the sensor reading giving a bad measurement.

How can I get a sharper knee for around 5-5.5V or so?


texts:
I'm (again) looking at high-side load-switching. The load shall be switched on with a controlled rise-time (=limited inrush current) and be switched-off quickly when a controller (not shown) detects an error condition.

My problem with the typical slew-rate control circuit is the dependence of output-slew rate to supply voltage level. Also turn-off is slow since the gate is pulled up only by R2.

simulate this circuit – Schematic created using CircuitLab

What I came up with in response is the following schematic:

simulate this circuit

Q2 is there for fast turn-off. Addition of Q3 seems to solve the problem of supply dependent rise-rate - at least in LTSpice. However, frankly don't know why.

Apparently I'm using Q3 not as a switch, but in it's linear region to "regulate" the current through R2, but the component values are made up by trial and error and I would like understand the matter. Could someone also comment on temperature influence?


texts: Can current flow ever oppose a current source?

texts:
I am currently learning about voltage controlled current sources and small signal models. Current sources in general have always been a source of confusion for me (no pun intended).

I drew a circuit diagram below to illustrate my problem. In this circuit, what happens to resistor Re? I thought that since there are current sources on both sides of it the current would come in from both ends and cancel eachother out. Ultimately, no net current would flow through it, making it "open".

If VCCS1 is greater than VCCS2, would that make current flow from left to right in Re? is it possible for the current coming from VCCS1 to "override" and oppose the current coming from VCCS2 and make current travel up as opposed to down that right branch?

simulate this circuit – Schematic created using CircuitLab


texts:
This is a full wave bridge rectifier

I have read that if you put a capacitor parallel to the load resistor instead of DC pulsed signal we get a more smooth DC signal.

However I am unable to understand the working principle and I have read many websites and couldn't figure it out.
Any help? I know that this has to do with discharging and charging of the capacitor.
Any help?


texts: Control one mosfet with 2 PWM signal sources

texts:
Currently I'm facing small issue and I can't find the answer. I've bought one of these Chinese RGB controllers which are using 2.4GHz touch remote control. Surprisingly for me this device is working fine for now but I want to add it to my Home Automation hub using ESP8266. Please check following pictures of the main board:

As you can see there are 2 chips - one is the main MCU the other is about the 2.4GHz communication, after that are the 3 mosfets for the LED strip.

My goal is to preserve the current functionality and "just" to add one ESP8266 module for further "improvements". Is it possible? How this can be achieved? I will appreciate any advice/comment. Thanks!


texts: Rise and fall timings of a pulse generator

texts:
In a digital programmable or static device, does the rise and fall timings and waveforms of a square pulse obey the reimann sum when observed at much higher resolutions?

If sampling rate of this device or some other DAC, a higher sampling rate scope or observer measures the signal at better precision then the output device can generate. I just want to know the experts' opinion on this because my favourite scope is in the office now and I can not measure it. Is it reimann sum or something like an exponential behavioral ?


texts: Building a dual-rail, regulated DC power supply: 1 diode bridge & center-tapped secondaries, or 2 diode bridges and separate secondaries?

texts:
I'm looking to build a dual-rail, regulated, 18VDC power supply based on the 78xx and 79xx regulators. The circuit is inspired by AMB Audio's sigma25 (amb.org/audio/sigma25/) and sigma26 (amb.org/audio/sigma26/) regulated power supplies. I have also Googled around and came across these:

eleccircuit.com/wp-content/uploads/2008/10/dual-variable-regulator-power-supply-5-25v-by-lm7805lm7905.jpg
eidusa.com/Interface_Boards_PN15_PS.htm

However, I am torn between using a 2x9V transformer and connecting the secondaries as such, using only 1 bridge rectifier to supply both regulators:

...and using a 2x18V transformer, each secondary feeding its own bridge and regulator, as such:

What are the pros and cons between the two, apart from (slightly) more parts count in the latter schematic?

Many thanks for any enlightenment given.


texts: Why is power of a signal equal to square of that signal?

texts:
Is there any logic as to why the power of a signal \$\mathrm{x(t)}\$ is taken as \$\mathrm{x^2(t)}\$?
I searched everywhere and there's no clue. My professor told: "It's a standard result so shut up!"


texts: General LiPo and Li-ion question regarding NTC

texts: Is it only me or are most of the smallish (1500mAh) LiPo rechargeable batteries don't have the NTC pin (only POS and GND)?


texts: Getting the numerical value of a capacitor's impedance

texts:
I understand that the impedance of a capacitor is \$\frac{1}{j\omega C}\$. For the circuit above, I have

\$\frac{1}{Z_V} = \frac{1}{Z_{V1}} + \frac{1}{Z_{V2}} + j\omega C_V\$

and

\$V_V = \frac{Z_V}{Z_V + \frac{1}{j\omega C_{CV}}}V_C\$

Are my equations correct?

Also, since the impedance of a capacitor has an imaginary component, how do I get a numerical value for \$Z_V\$, i.e. without the \$j\$?


texts: Linear dropout voltage transfer function

texts:
I am reading this application note from Texas instrument : http://www.ti.com/lit/an/slyt187/slyt187.pdf?ts=1591543592096&ref_url=https://www.google.fr/. The application note give us the transfer function Vout/Iout of an LDO built with a PMOS. Here is the model :

Here is the transfer function :

where R12 is equal to :

I have actually some troubles to understand why Rds is in parallel with the capacitor Cb. The voltage across Rds is equal to (Vin - Vout) and the voltage across Cb is equal to Vout ? So why Rds is in parallel with Cb ?
Thank you very much and have a nice day :D (I know that I have some troubles with AC model)


texts: Will multiplexing impedance measurements from the AD5933 act as a series resisitance?

texts:
Image of block diagram of the AD5933 at: https://www.researchgate.net/profile/Douglas_Dutra/publication/292976112/figure/fig1/AS:520210098917376@1501039160818/AD5933-Functional-Block-Diagram-10.png

I am going to attempt to multiplex the chips vout and vin so that the system can measure more than one impedance. Other than ON resistance will there be any other issues? as I can compensate for the series reisitance in software. I was intending on using a CD4051BEE4 multiplexer. Any  advice would be greatly appreciated.


texts: step response data extraction from response data of a model(simulink)?

texts:
I want to design a PID controller with the step response method, so I needed to save the step response of my model in simulink in workspace (Vout) with saved format :structure wih time, I exctracted the time value by using
the command

t=Vout.time

and signal value as:

y=Vout.signals

then run the command to exctract the data to matlab:

load StepInfoData t y

so I can analyse it by calling the function plot(t,y) and S1 = stepinfo(y,t,0.4)
but it shows the error following

Warning: Variable 'y' not found.

Warning: Variable 't' not found.

and the same for plot function. actually, I am not sure if the workspace is the correct method to save the data.
link:https://se.mathworks.com/help/control/ref/stepinfo.html#mw_cab22a5a-b8ef-49fd-b071-3e7888430c00
the model looks like:
thanks


texts: Should I attach a current limiter to my jerry-rigged power supply?

texts:
So, I have an old transformer style power supply rated for: "16V AC nominal 1A" and I basically just shoved in a full bridge rectifier and a cheap ebay DC-DC switching buck converter so I could use it for electronics projects.

What I would like to know is that, if I attach something that uses a lot of current (e.g. a Peltier device) is there a risk of overheating and shorting out the wires in the transformer if it uses more than the 1A listed on the transformer? If it does, should I add a current limiter or does AC amperage and DC amperage mean different values like how it does with voltage?

Thank you for your time and apologies if this has been asked before.


texts: Does electrical field intensity force equation apply to non-circular objects?

texts:
I read that Couloumb's law, which replaces the force  in order to measure electrical intensity at any point in space around unit charge only applies to circular objects.

Does that mean that if I have some rectangular piece of metal positively charged, I wont be able to measure what is the intensity of its field at some random point in space? If so, how can I change the equation to solve such an occurrence? I suppose it might be somehow related to finding center of the gravity for the charge inside that rectangular piece of metal?

Thanks in advance.


texts: When you connect two batteries in series, why doesn't the middle short? The connection between the positive terminal on one battery and the negative terminal on the other battery has no load, so shouldn't it be shorted? But I don't notice heat or explosions or anything like that when I connect batteries in series.


texts: Common mode problem with floating sensor

texts:
So I'm trying to measure the signal from a potentiometric sensor, that has a working and reference electrode. Electrically it can be summarized with the picture below. Note that my circuit is intended to be mounted on a PCB and powered by a battery.

Now my problem is that the sensor is left floating. I initially thought that's not a problem with a differential input, but I realized that if it "floats away" it will saturate my internal nodes and kill operation. I know that its not going to drift millions of volts away due to leakage currents, but I am still concerned that it will move too close to one of the rails and distort. I not sure how to estimate how far it will float away other than by physically building it and seeing what happens, hence why I'm looking for a solution beforehand.

I was thinking of the following solutions:

I can't use a high pass filter because I want to read what is essentially a constant voltage.
I thought of grounding the reference electrode to my PCB ground, but I'm fairly sure that this defeats the purpose of a differential input. Am I right to assume that the common mode noise would then be transmitted to my signal via ground?
Do the same thing as above, but via a pull-up/-down resistor. Does adding a resistor change anything? I don't understand why.
Add a 3rd electrode and connect it to my circuit via a buffer.

I'm getting really confused with this problem and would appreciate any suggestions or pointing me to potential solutions.

Thank you.


texts: How to design for a component that says "Electrical Design: DC PNP" in the datasheet?

texts:
I'm not a guy from electrical engineering and I'm having a little trouble with a small garage project that I'm working on.

I want to use a photoelectric sensor to measure distances. I'll probably stick my sensor - an O1D105 - in a little board with a microcontroller to do some early processing and communication with a server. I'm used to dealing with components that already provide me some pre-processing of the data and communicates through SPI or serial RS232, but this is my first project with something of such a low level.

I don't know how to project a circuit to this DC PNP output that the datasheet is talking about. Also, I can't understand the pin diagram that was shown to me: what is L+ and L-? VCC and GND? And where is the output? Could it be pin 2, where the guy placed an amperemeter? It looks from the datasheet that I should measure the current to get an analog output for this device, but I could be wrong. And how do I connect this output to a microcontroller? Is it the usual workflow to find information about my microcontroller's input ports so that I can make sure that the output is in an acceptable range (I haven't chosen a microcontroller yet)?

Also, what should I start studying to figure this stuff out for myself? It looks to me that this is something really obvious to someone that works with the standards referenced by this component, but that I don't have a clue about.

UPDATE

About the distance between the controller and the sensor: there might me some meters of distance between them (probably no more than 5 meters) and it could be attached to a lamppost, so I guess I'll follow the tips to avoid noise.

Thanks for all the really detailed answers. I'm gonna try to work this out so that I can decide which answer was the most helpful, but I guess all of them could be the right answer. Thanks again!


texts: ADC signal close to D+/D- signals layout suggestion

texts:
My circuit is laid out in way so that the analog front end is on a different pcb than the MCU board.

The two PCBs are connected with a vertical connector of which 4 pins are used to transfer two low frequency (<50 Hz) ADC signals and their return current.

My question is whether you think the D+ and D- signals from the USB connector going to the FTDI chip will affect the ADC signals in terms of crosstalk/noise.

My estimate is that, even though the actual signals are relatively seperated, the  high frequency return paths of the USB signals will be spreading quite a lot affecting the ADC lines.

The alternatives I have in mind are either leaving the layout as it is or placing the GND pins for the ADC signal somewhere on the left side of the connector, further apart from D+,D-.

Note that I cannot change the position of the ADC1,ADC2 signals.
But I can rearrange some things up north to push USB connector further up slightly.

Any suggestion is appreciated.

EDIT:

Ok, after the suggestions in the comments and th answer I've updated the layout to increase the distance even more between the signals in question and not use the connector's pads as a path for the data lines.
Also, I added a small cut-out in the top ground layer on the left but I doubt it makes a huge difference.

The question that arises now is should I place a bigger cutout in the bottom ground plane, right there between ADC and Data lines?


texts: Detecting Specific PWM Signal Without Programming (Only Electronics Components)

texts:
I want to detect a specific PWM signal by electronic circuit components i.e. transistors, opamps, capacitors.
update:
I want to build simple ID system. I want to detect specific PWM signal for example 65% with 5% resolution at 1kHz. If 65% PWM signal comes as an input I want to make output circuit on. Other than 65% with 5% accuracy, I want to make output circuit off(low).


texts:
In a simple PARALLEL RC circuit with two components of Resistor 150 Ohms and Capacitor 0.000000075F (75nF). AC supply 10V at 20,000Hz.

Impedance has a phase angle of -54.7 degrees if my calculations are correct.

What is it lagging -54.7 degrees behind? I suspect the answer is "Voltage supply" at 0 degrees but am unsure.

EDIT. Ill try to rephrase.

Can anybody complete this sentence:
"......" is lagging "......" by 54.7 degrees

This should enable me to understand what is at what angle

*EDIT 2:
For reference my understanding of phase angle has now improved and I will attempt to explain the answer I was looking for.

In the above described circuit the phase angle is 54.7 degrees. This angle represets the phase difference in degrees between:

Resistance and Impedance.

Conductance and Admittance.

True power and Apparent power.

And most importantly, Current (which is in phase with Resistor voltage) and Supply voltage.


texts: In an n-channel JFET, why isn't the formation of depletion layer symmetrical?

texts:
When a reverse bias voltage is applied between the gate and the source, depletion layer is formed between the p-type and n-type materials in the JFET. My question is why isn't it symmetrical? Why does it move more towards the drain than towards the source?

Also, my text book tells that this happens because there is more voltage drop near the drain than near the source. Please explain this statement also.


texts:
I'm not sure how to calculate the following. I want to SMD solder either 3 LEDs or 6 LEDs to an aluminium core PCB. The LEDs in question are PK2N (datasheet) and, according to the datasheet, the Thermal resistance of Junction to Slug is 8 deg C / W.

So, if I want to run these at around 2.2W (600mA * 3.6V typical), does that mean that they generate approx 18 deg C each? So, if I place 3 of them, do they raise the temperature by 54 deg C? For 6 of them, 108 deg C? Also, the resistors will dissipate approx 2W or 4W (if I use 3 or 6 leds).

The total area of the AL PCB will be approx 9.1 cm2 (17 mm radius, 34 mm diameter) and 1mm thick. It is 35um Copper (1oz) but I don't have the datasheet for thermal conductivity figures.

How would you go about trying to work this problem out? Do I need extra fins on the PCB? Or should I limit myself to just 3 LEDs?


texts: Calculate temperature of kanthal wire per electric Watt

texts:
I'm trying to get an estimation of the temperature that a Kanthal (A1) wire would get, when applied an amount of electrical power.

The wire is 30cm long. The diameter is 0.3mm (or there about).
The electrical resistance from the specifications sheet says "1.45 Ω mm2/m" (I'm not sure how to read this). I'll actually leave you the spec sheet link:
https://www.kanthal.com/en/products/material-datasheets/wire/resistance-heating-wire-and-resistance-wire/kanthal-a-1

In the specifications sheet they provide a temperature table, from which I kind of understood that the temperature is not going to be a linear function, but a rough linear estimation would be just fine.
My ultimate goal is to calculate the minimum and maximum electrical power that I need to supply to the wire, in order to control it between 50°C and 100°C 100°C and 200°C.

Edit, as requested by @Transistor

I am unsure where to find a more appropriate spec sheet, in that page you can expand the sections to reveal the data. Anyway, I have also found these 2 pages:

https://temcocontent.com/attachments/kanthal_wire_data_sheet.pdf

https://www.hi-tempproducts.com/pdf/the-kanthal-furnace-mini-handbook.pdf

Maybe they provide more useful information.

The "element" will be used for a foam wire cutter (thus, not really an element, just a bare wire). As far as I could find, foam can be cut at 200°C, but that may be too aggressive so I'd like to keep it a good amount below that temperature. I am going to make tests later, but right now I only need to "convert" W to T(°C) in order to calibrate an initial electrical circuit...


texts: How to measure small capacitance with high parallel resistance

texts:
I have a sensor that can be modeled as a capacitor and resistor in parallel. The problem with this sensor is the resistance is on the order of 10's MOhm and the capacitance (we believe) is single pFs.

I have tried using a resonant circuit to find the capacitance, but the results end up super noisy and with an extremely low q factor. Does anybody have any ideas of how to determine the capacitance?


texts: Can you create a circularly polarized signal with dipoles that are perpendicular but not crossed?

texts:
All of the circularly polarized phased arrays that I can find use elements that are themselves circularly polarized, that is, two perpendicular dipoles that are crossed at their midpoints (the picture on the left). Would something like the pattern on the right work, where the antennas are still perpendicular but offset? If so, would the horizontal and vertical elements still be fed 90 degrees out of phase, or would it get more complicated? I can imagine that this would make them easier to pack, but it's very possible that I've missed something obvious.

Thank you so much!


texts: Flyback diodes for motors wired in parallel

texts: When driving two DC motors wired in parallel, do they each require their own flyback diode or can they share a single diode?


texts: Controlling speed of PSC induction motor (Questions about operating at high slip)

texts:
Induction motors typically run synchronous speed since most motor types (CS/CSCR/Permanent Split Phase) have high low-end torques. A PSC motor on the other hand doesn't have much low-end torque.

FAN applications don't require much starting torque, this means you can operate at a significant slip away from synchronous speed (speed reduction) by lowering the toque created by the the coils without fear of stalling the motor.

(The synchronous speed of the motor will remain the SAME at ANY supplied voltage but the resulting operational speed can be significantly different when using lower power coil-torque configurations. At low coil power the motor will settle at a higher slip operational point on the performance curve.) Coil-torque can be controlled by varying the voltage supplied to the coils.

Here is a Motor Torque vs Fan Load at different operational voltages.

After much research, common (under 1HP) 3-speed PSC motors have speed control implemented by using extra windings on 2 of the 4 poles of the MAIN WINDING.

Here is the motor schematic:

Motor Wiring (Red = Main Winding, Black = Auxilary Winding, Blue = extra speed control windings)

I have a few questions

1) It seems the voltage reduction present, feeding the main+auxilary windings, is only due to the resistance present from the two additional coils (blue). Is there anything significant about inductance present from these windings? (Would a resistor voltage divider have the same performance and efficiency loss?

2) If bypassing the extra windings, can you instead connect a transformer OR dimmer (triac) to the HIGH line input and achieve the same speed control but with greater efficiency?

3) How much slip can be achieved? If adding a transformer or a dimmer onto the line input, can speeds lower than what is built into the motor via the low speed wire be achieved?

4) What happens to motor efficiency at high slip?

I've searched for hours on google, but still couldn't find the answers.


texts: How to use shielded audio cable with micro-fit molex connector?

texts:
This is typical shielded audio cable which I’m supposed to use with micro-fit molex connector. The problem with that cable is that the ground cable/the shield is not insulated and I found it very difficult and messy to crimp it and use it with the micro-fit molex connector. Any ideas how this should be done properly?

By the way, maybe there is a different type of cable which would have 8 wires and would be suitable for everything the power, audio analog and digital signals and would be suitable for use with micro-fit molex connectors, so I don't have to use different types of cables?

Connector:
https://www.molex.com/molex/products/datasheet.jsp?part=active/0430251010_CRIMP_HOUSINGS.xml

Audio cable:
http://www.tasker.it/en/p/1625/c121?f=18


texts: Flooded LAN RJ-45 connector may damage connected router?

texts:
I had an accident in the house and one of the LAN (cat. 6) cables including RJ-45 connector has been flooded. This "flooded" cable, along with other (dry) ones, was connected into a working gigabit router with WiFi but it was the only one that was not connected to the PC.
After a few minutes, I took out the plug from the water and dried up with a paper towel. Currently, I do not see an anomaly in the operation of the router, but its operation is very important to me. I do not know if there is a risk of a short circuit in gigabit LAN/RJ45 (568B) technology.

I have a question if could the water (with a large amount of dish liquid) cause a short circuit and damage/harm the router to which the cable was connected?


texts: How can module TB trap $fatal from module A

texts:
I have an RTL simulation where module TB is the testbench for module A.

Module A generates $fatal when it meets some condition it doesnt like.
Module TB generates/collects transactions to/from A. Is there a way I can trap $fatal or $error statements in module TB ?

I am looking to add a few lines in TB like

always @*
begin
  if (FATAL_CONDITION_SEEN) begin
     log("there was a problem");
  end
end

Ideas ?


texts:
I've got an LED controller that uses SPI control for 5050 LEDs and similar. The maximum current is 12CH@5A, so 60A. At 24V that's 1,440W. On the box there is a second port pair for V-. You can see it in the attached image. Wiring schematics suggest connecting V+ to both V+ inputs and the V- to all four V-. Why might that be? Especially the doubles V-. I imagine pairing the connections is to cope with the potentially high current draw?

I haven't looked inside yet, but would you not say it looks a bit puny to be doing 60A @ 24V?


texts: What DC Power Supply Do I Need To Get For This Device?

texts:
I recently bought a small 3 to 1 HDMI Amplifier Switcher. It can work without power adapter only if the 3 HDMI inputs are connected and supplying current. I want to operate it with only 2 input which is impossible without DC. On specifications it says that it needs a 5V p-p(TTL) signal while it has a maximum power consumption of 5W. What kind of power adapter should I ask from a store for this product ?

EDIT 1 : After request, I post the specifications of the device.

EDIT 2 : The DC Input of the device.


texts:
I've been playing with a frequency counter (Racal 2202R) that has a built-in rubidium standard.

It has two outputs, "Rb OUT 1" and "Rb OUT 2". I could not find any documentation at all, but the waveforms look like this:

They're clearly both 10 MHz, and "Rb OUT 1" looks like a sine wave.

What might be the other output, any why does it have this peculiar shape?


texts: Basic design of low-wattage 5V battery charger (is this realistic?)

texts:
I'm trying to come up with a solution for keeping a very small GPS tracker mounted someplace where it will stay indefinitely without an external power source. Since my main interest will be using such a thing on my vehicles in case of theft, one possible way it could be self-powered would be through kinetic energy.

I'm thinking I might be able to make a 'shake flashlight' style dynamo - a rod on a shaft which moves past copper coils as it bounces up and down. I know it'll work to generate electricity, I'm just not sure how much will be enough to realistically charge a ~3-5v lithium battery. All I know is my 18650 battery charger says it supplies them with 4.2V DC at 750mA.

As for a GPS receiver chipset with GSM rx/tx, it requires very little power when set to connect only a few times per day and send its location. Even the smallest GPS trackers you see on eBay claim about 2 weeks battery life with just their built-in 400 mAh battery. So, if I can make this work, I believe that on a bicycle, motorcycle, etc., as long as it's being ridden it should be able to keep enough of a charge. Forever. In theory.

So, please, tell me why nobody else has done this.. Would it just be too much trouble to convert a trickle of microwatts into ~3 watts, over time?


texts: Designing a BJT amplifier for a specific voltage gain

texts:
Our teacher gave us a homework assignment to design a common-emitter amplifier.
My task is design an amplifier which has 12 voltage gain rate.
Firstly, I drew its small signal model, nd determined its voltage gain formula.
Then, I assumed some values. For instance RE, RS, RC, RL, \$\beta\$(beta) and tried to calculate R1 and R2 according to 12, voltage gain.
Unfortunately, when I calculate R1 and R2, the rate was negative. I said that is not possible because resistances are always positive. Unfortuntaley I couldn't make my homework but I want to learn what my problem is and what I did wrong.
My solution and question:


texts: First Order Filter - Voltage Follower Attenuation

texts:
I have a first order filter. It is supposed to have unity gain at frequencies below the 3dB frequency of 50Hz. I have simulated two of these first order RC filters. One where the signal is fed into a universal op-amp acting as a voltage follower and another as a simple RC network. I have attached images of both the schematic and the response.

When conducting an AC sweep of the circuit the signal given into the op-amp voltage follower there is a constant -2dB attenuation. Universal opamp 2 has been chosen from the LTSpice component list. For the RC network not fed into a voltage follower there is 0dB gain below the cut off frequency which is what is desired.

Why is there -2dB gain for the voltage follower and how can this be corrected?


texts:
The rechargeable battery info: 1900 mAH (1 battery)

A device that have input of 3V DC and output of 5 V / 500mA

If one rechargeable battery is inserted into the device,
I can expect that it can provide me (1900 mAH / 500 mA of 3.8 hours) of output. (or it can last me for 3.8 hours)

So, if two rechargeable batteries are inserted in parallel,
I can expect 3.8 hours * 2 = 7.6 hours of output

So, if the device only provide me 1 hour of output with 2 batteries inserted,
can I say that the circuit is faulty?
Suggestive that the device provide 3800 mA of output in 1 hour?

Also, a side note - the device becomes hot (temperature around 40 to 45 degree Celsius)

The 2 battery is insert into the following device:


texts: Reverse engineering random camera module from mobile devices

texts: I have A camera module I believe either from a tablet or a cell phone and I want to know where to find information on the serial pin out or on how to read the ribbon of the camera


texts: Qucs How to add 10uF Polarised Capacitor

texts: I'm new to this site. I have a small experiment. I did trying to make a circuit from a schema that needs 10uF Polarised Capacitor in the schema. I use Qucs (Quite Universal Circuit Simulator) qucs.sourceforge.net as the tool. But I couldn't find the Polarised Capacitor there. Does anyone know where is it ?, xD. Hehe sorry I barely learn about E-Engineering. Thanks before


texts: What is the effect on power grid when utilization goes down some threshold?

texts:
Today (April 5th, 2020) at 9:00 PM IST, people across India are expected to switch off lights for 9 minutes.

This has apparently raised concerns that there would be problems to the power-grid, due to under-utilization of power.

Can any one explain this (in layman's terms)?

a)
Specifically, will the generator be overloaded and stall because the power lines will eventually be saturated and achieve the same potential as that of the generator (given that energy flows from a source of higher potential to that of a lower potential)?

b)
If it is the case, is there no control to simply reduce the amount of power generated to match the consumption?

c)
Or is it the sudden decrease in power consumption that is the cause for concern?

PS: There is a similar question here -
Why does the frequency of power generation change when there is a change of load on the power grid?

But I'm looking for an explanation that can be understood by a layman.


texts: How I can interface my inductive proximity switch with an MCU?

texts:
I want to use an inductive proximity switch (Leuze 50129985) with my MCU (Texas Instruments CC1350). For isolation, I want to use an optocoupler (Sharp PC817). [Links to datasheets.]
How can I interface the switch through the optocoupler to the MCU?
Inductive switch specifications:
Supply voltage: 10-30VDC
Switching current max: 200mA
Voltage drop: <=2V
Switching elements: Transistor, PNP
Switching principle: Normally Open
Switching frequency: 500Hz


texts:
Please look at the schematic below. This is a very simple resistive adder that works fine with any standard ! (TTL,CMOS,...) or any arbitrary voltage that is fed into it. On the other hand as there is no active component in it, it is extremely fast. It is just made of a few resistors , so it is very cheap. On the other hand there is no limitation for number of input bits ( it can be easily expanded to 32, 64 or hundreds of bits ).

So, Why should we need DAC ICs? I am looking for a 32-bit high frequency DAC. Such devices are not found easily and also if found, they are rather expensive. I mean What is the advantage that I should pay for to find such devices?  I think there must be some advantage that they worth to be bought. The only thing that I can think about is their inherent amplification ( for example TTL -> 10V or so), but this goal is simply achievable with any kind of amplification.


texts: welling yxb-250-4 induction motor spin start direction is inconsistent

texts:
This motor is also often referenced as W11283592. The best pictures of it are in http://www.gmcc-welling.com/Homeen/Product/detail/id/187.html and https://partsdr.com/part/w11283592-drive-motor.
The most informative site I found is
https://partsdr.com/part/w11283592-drive-motor
 There I found a sentence: "The motor should measure between 3.5 to 6 ohms through both the clockwise and counterclockwise windings."

My connector has 4 wires:

Earth ground - green.
Black
Yellow
Red

Black to Yellow -> resistance is 5 Ohm
Black to Red -> resistance is 5 Ohm
Yellow to Red -> resistance is 10.1 Ohm

No connection from Green to other wires.

When I connect 120V AC to Black and Yellow the motor can spin in CW or CCW direction.
When I connect 120V AC to Black and Red the motor can spin also in CW or CCW direction.

From the statement on the Sears site I expected direction of the spin to be stable and consistent based on the wire that is energized.

Am I wrong or is there something wrong with the motor? 3rd option?
Confused...
And frustrated, since I can not find a Service manual for any of the washing machines that use it. Chinese motor in an american product... Tech support is minimal.

Update 1: I've ordered and received a 50 uF running cap. Here is the spec: http://www.farnell.com/datasheets/1796777.pdf
I've connected it in series with the red wire, and now the motor starts CW every time. So far I've not tried to disconnect the cap once the motor is running. So far so good, but no load yet either.

It looks like Sears web page mislead me (or I misunderstood) - I thought it implied that the 2nd winding was only for the CCW operation.


texts: Why do some mobile devices require a minimum battery charge level before they can be powered up?

texts:
I've noticed the battery level must reach a minimum level before it can be powered up on some mobile computing devices. This requires waiting several minutes with the device plugged in. I often wonder if the battery is being used for a secondary purpose such as providing some kind of filtering or power regulation regulation.

Is the battery doing more than just providing current? If not, why can't the circuit draw current from the wall wart while charging the battery at the same time?


texts: How do I stop coiled (telephone) wire blocking signal?

texts:
This circuit is working just fine if the output signal uses a straight wire, even if it is a very long wire with say a 1K resitor added to the end of it.

However, the signal does not get through when I use coiled (telephone handset) wire.

The only noticable result is that LED3 does not fully turn off (as it does with a straight output signal wire). Increasing the collector voltage and current to better push the output (by changing R1, R2, Rc & Re) only makes it glow a bit brighter.

The telephone wire carries 9V from a mains powerpack and GND via the main proccesing unit to this sub-circuit and returns the output signal back to the main processing unit.

I am perplexed as I have four other trigger circuits that work just fine through the coiled wire, including a very low signal PIR that needed the same "invert and amplify transistor block" to push it's signal through.

Presumably I have an issue with inductance or AC or something introduced by the 433Mhz radio link, but I don't want to give up on the convenience of coiled wire - so what do I need to change to get this working?

Probably the only thing I still have left to try is to replace this "invert and amplify block" with a Hex inverter.

Thanks in advance for any suggestions, component values or other help.


texts: What components do I need to build a motor controller from the L298?

texts:
I'm thinking of buying a pair of L298Ns, to control a pair of 1.6A motors. I'd like to control each motor with a signal PWM wire and a direction wire. However, I've hit a couple of problems.

It is unclear whether the chip includes internal diodes or not. Some sources say yes, some say no. There also seems to be general confusion between the 298 and the 293.
Looks like I need to invert the direction line so that the two inputs are opposite. However, if that messed up, current could flow through the chip.

Would pulling the PWM "enable" line low while switching the direction signal solve this?
Would a MOSFET be suitable to negate the signal?

Or would I do better just to buy this complete motor driver?


texts: What is the effect of heavy loads on the electrical grid?

texts:
When our neighbors turns on a motor, a bulb in our home turns off for a very very short time and then it turns on again. It is something like a quick flash but a man eye can notice it.  Would you tell me why that happens, please? What could be the reasons? Is that because of the coils inside the motor? or the motor needs much power to start?

At larger scale, If a factory turns on a lot of large motors at the morning, Does that affect the nearest city or district?


texts: How can I calculate transfer function of Boost converter considering all resistances?

texts:
From the title It may seems like I need someone just do me the transfer function, but it is not.I'm looking for some directions.

I'm trying to calculate transfer function of \$ \frac{v_t}{d}|_{v_g=0} \$ of boost converter considering all resistances like inductor resistance , switch 's resistance , diode resistance and capacitor resistance (\$R_L,R_S,R_D,R_C \$) in CCM mode. This is my small signal model of the Boost converter:

simulate this circuit – Schematic created using CircuitLab

where $$X_L=sL/D'^{2}$$
$$X_C=1/sC$$
$$R_e=\frac{R+DR_S+D'R_D}{D'^2}$$
$$V_e=\frac{V_{out}-I(R_D-R_S)}{D'}$$

Here \$D=\frac{T_{ON}}{T_{ON}+T_{OFF}}\$ and \$D'=1-D\$ ,\$V_{out}\$ is  output & \$V_{in}\$ input in DC and \$v_t\$ is small signal output

Now to find the transfer function of the ratio of output voltage and duty cycle,
$$\frac{v_t}{R||X_C}+dI+\frac{v_t-V_e}{X_L+R_e}=0|_{v_g=0}$$  which leads to
$$\frac{v_t}{d}|_{v_g=0}=\frac{R}{D'^3}.\frac{D'V_{out}-I(sL+R+R_D)}{RD'^2+(1+sCR)(sL+R+DR_S+D'R_D)}$$
This do not seems right as there should be at least two zero, but I can't find where did I do wrong. Again I thought if I replace value of \$V_{out}\$ and \$I\$ in terms of \$V_{in}\$ then it may give some good value. But as they are DC value and do not introduce any pole or zero, it did not help much.

My request is,  if any one of you derive this transfer function considering all resistances, can you point me out where I may done some wrong calculation. Or any link where detail explanation for this derivation is explained. Most of the link I found use approximate transfer function and do not derive them . Some references  derive transfer function using state variable, but considering all this factors , deriving from state variable very very tough for me as those references  use values instead of symbols like \$R_L,R_S,R_D\$ .

FYI:

I don't give total calculation here cause it's nearly 2 page calculation and clumsy But if you need it, ask in comment . I'll add them. I go through them couple of times, hope there is no mistake.

My small signal model seems current to me as when I neglect \$R_L,R_D,R_S\$ it become the  Boost converter small signal model given in  Book(Fundamental of Power Electronics by Erickson & Maksimovic).


texts: How to modify the power low to 5V and fit this circuit?

texts:
This circuit able convert PWM input signal to 0-10 DC output.
But I only have +5V power supply and I just only need 0-4.5V DC output.
How to amend more suitable ?


texts: Explanation of transistor amplifying action

texts:
I am reading "Electronic Devices and Circuit Theory" by Louis Nashelsky, Robert L. Boylestad.
I am not able to grasp article 3.5: Transistor Amplifying Action. I've mention some particular points on which I am having questions. In general I want to understand this article. I want to understand what the authors are saying here.
At the last of the  article the authors say that "because the source current is transferred from a low- to a high-resistance circuit, that's why we call this device as transfer+resister \$\rightarrow\$transister." But I don't understand the way they reached this statement.
I've bought this book and I don't want to waste my money; I do not want to put this book aside and buy some other book. Please help me understand it.
The circuit schematic is as shown:

Input resistance \$R_i= 20Ω\$,
Output resistance \$R_o = 100KΩ\$.
Input voltage \$V_i = 200mV\$
The emitter current \$I_i= V_i/R_i = 10mA\$

Since \$α_{ac}≈1\$, so \$I_c≈I_e\$
Output voltage \$V_L=I_LR=(10mA)(5KΩ)=50V\$.
Voltage amplification is \$A_v=V_L/V_i=50V/200mV=250\$.
What I don't understand is:

What is \$200mV\$, is it the instantaneous voltage, rms voltage or peak voltage? What are \$I_L ,\ I_i,\ R_o\$ and \$R_i\$ etc's?

Why the input resistance doesn't get affected by the load resistance. In fact, what determines the input resistance? Are the \$n\$ region and load resistance acting as a set of two parallel resisters for \$V_{in}\$?

Since there is no DC biasing i.e \$Vcc\$ is \$0\$, how is this high output voltage supplied?

How can we apply KVL to the loop BCB? The power dissipated across \$R\$ is \$I_LV_L=0.5W\$. What is the source of this high power, is it the minute reverse bias collector junction (which is quite impossible because a P-N junction cannot provide energy)?

This circuit acts like a current source. \$I_L\$ is completely independent of the load resistance. How can we use this (common base) circuit as an amplifier for low resistance load? Or suppose we want to apply the \$V_L\$ to some resistor of order 10 ohms, the output will reduce to \$10 \Omega \times 10mA = 100mV \$ so the output voltage is reduced than the input voltage(200mV).
If the biasings are suppressed please explain this circuit. That is with proper biasing at the same parameters and how much \$V_{EE}\$ and \$V_{CC}\$ should have been applied? what are the actual input and output waveforms?


texts: Counter that counts in a loop of multiples

texts: I need to design a counter that counts in a loop of 5 mult: 0-5-10.. My attempt is down below but I`m not sure how to form the kmap for every D ff as I have 5 current states and we never worked with a 5 var kmap so im assuming it has to be done some other way.It s first year digital logic so a simple counter is requested.


texts: How to view the optimized combinational function after HDL synthesis?

texts:
I am using Xilinx ISE v8.1, and VHDL language. I have a simple design implemented using behavioral approach, which gives me a set of combinatorial functions.

I can see the schematic of the outcome after synthesis by going to "Synthesize - XST" - "View RTL schematic". But what I am looking for is the Boolean algebra equations. Do we have an option in there to extract the equations? That will help me to feed the equations into another tool and do some other processes on them.

I just can not find the option that shows the generated function equations.


texts:
I've got some common Dutch "huishoudsnoer" (household-cable? Mainly used for powering lamps. Not solid core, 2*0.75mm² cable) laying around, that's rated for 1380 watts. Our wall sockets provide 230V at 50 hertz, so 1380 watts is 6 amps.

I've got a 3d printer, on which I want to change the power supply. The current one is 21 amps at 12V DC, or 252 watts. Way less than 1380 watts.

Am I safe using the cable I've got laying around, or is there some magic involving DC and AC? If so, how do I calculate how much DC power a cable can carry, given a certain AC capacity?


texts: Capacitive moisture sensor not quite working

texts:
I have spent the past few days trying to reverse engineer a capacitive moisture sensor I ordered from eBay a while ago. The particular one I received looks like this:

What fascinated me about this sensor was that I could put it in a plastic bag and it would still be able to give accurate moisture readings. In air, the output voltage of the sensor is about 2.3V; in water, I am getting around 0.7V when submerged directly and 1.6V when submerged in a plastic bag. After analysing the circuit, I came up with this schematic (Note: I have left out the voltage regulator and the four corresponding caps, because I am feeding in 3.3V DC from my bench supply directly):

I then built a prototype on a breadboard, which gave me this result:

Unfortunately, my sensor does not work as well as the one I bought, because the voltage drops seem to be a lot smaller.
The output voltage in the air is the same. But when submerging it directly in water, I am getting 1.6V (as opposed to 0.7v for the bought one). When submerging it in a plastic bag, I can only see a voltage drop of 10mv to about 2.29V.
I have already re-measured the component values several times and also buzzed out all the traces again to make sure I got the connections right, but I obviously must be missing something.
One thing I have noticed while testing is that decreasing the value of C1 from 23nF to something like 470pF causes larger voltage drops, which makes my custom built sensor behave more like the bought one. But I'm still far from what I would like to see.
I'm an electronics beginner and this is one of my first reverse engineering projects, so any advice/tip would be greatly appreciated. I suspect that there is something wrong with my 555 timer circuit, but since I don't have access to an oscilloscope, I could not really confirm that idea so far.
SOLUTION: I finally managed to get my custom sensor to work like the bought one. To make it work, I did the following:

Replace all electrolytic capacitors with ceramic ones
Added a 100nF ceramic capacitor between VCC and GND
Change the value of C3 from 40nF to 10nF
Change the value of C1 from 23nF to 470pF

Also, the 555 chip used makes a huge difference. When using a TI NE555DR, I doesn't work as well as when using the original NE555 of the bought sensor.


texts: i want to duplicate a signal generator output

texts:
I want to duplicate signal generator output to dual. since i want to use same  signal to two different place. Is this possible without amplifying and inverting the signals. Let me share some circuit.

i just tried using two OP-AMP 741 and failed.

I have only basic knowledge in electronics.

Finally found working using below circuit...


texts: How to narrow down choice of diode given max voltage and max current drawn

texts:
I'm working on a project that uses this board I made and the Arduino Mega 2560, where the board will need to be powered by the Mega's +5V pin at certain times.  A connector will be used to bridge the bus on the Mega (containing the +5V pin) with the board.

When the board is being powered by a DC supply (+12V regulated to +5V), and not the Arduino, I want to make sure that the Arduino +5V pin is protected from reverse voltage (seeing as the +5V pin is not an input.)

Questions:

Would a Schottky diode be the most ideal solution to make this work?
I do not want to draw more than 500 mA of current, what part of the diode spec sheet would this apply to?
+12V will be the largest voltage input for the project, so what range should I consider for the reverse voltage breakdown?
Is it considered good practice to add a capacitor to ground on the cathode side of the diode?  Or is that a specific design consideration (e.g. AC to DC rectified situation.)

Thanks.


texts: Does a boost converter affect the life span of the source battery?

texts: Will using a 3 to 5V booster IC affect the power capacity of the battery I use in my circuit? as in, will it consume more power?


texts: Please review design for a wifi controllable led driver

texts:
I'm trying to dabble a bit in circuit design. As a starting project, I've taken it upon myself to create little wifi controllable led drivers for a couple of (very cheap) light strings I own. The idea is simple: have a power source (usb charger), hook it up with a DC jack to the circuit, power an ESP-01, have the ESP-01 control a mosfet which allows a current through the leds. I've mapped this circuit out in Kicad. I've built a variation of it in real life, and that currently works well enough, but I'd like some pointers about what I designed, so I can learn from it :)

Update:

I've switched the mosfet out for a BS170, and added an output capacitor as specified in the datasheet.


texts: What circuit would I use to automatically charge a capacitor?

texts:
I'm new at this, so I'm just trying to get certain basics right now for specific mini projects.
I'm trying to design a circuit that would automatically charge a capacitor by having a transistor turn on when the capacitor voltage reaches at or near 0 volts, then turn off only when the capacitor is fully charged and at the same voltage as the power supply.
So is there a way for a transistor to turn on when the voltage gets below a certain point, but only turn off, not just when it gets above the first point, but at a higher specific voltage?


texts:
I have found a smt component that I'd like to test.
It has all the terminals underneath the casing. For my test I'd like to connect it to a breadboard.
The dimensions of the components are shown below (datasheet):

What is the approach to take to be able to attach these to the breadboard? Is it possible to avoid building custom stencils and PCBs just for testing the component?


texts: Can I connect a Solar Panel to augment my computer's power supply directly to a 12V line?

texts:
I use my computer to mine Bitcoins with a HD 7970 GHz Edition GPU. It currently draws a steady 465W.

I would like to offset the draw, if possible, with a reasonably priced solar panel (~240-500W). This will likely not ever power the entire computer (I live in Minneapolis, MN).

What are my options for connecting this? I'd rather not buy an inverter to make it AC and then reconvert back to DC and suffer the associated losses.

Can I regulate the output to a clean 12V1 line and connect it right to the output of the power  supply, with perhaps some diodes to not have any backfeeding? Will the PSU just 'see' less draw? I'm not really concerned with the 5V or 3V3 lines, as the majority of draw is the GPU which is pulling from four 12V1 lines.

I also have this connected to a UPS on the floor, with a battery and likely it's own inverter. Can I just hook the solar panel (again with some regulation) to the battery of the UPS? What are my options here?

(also, recommendation on solar panel specifications or models would be helpful. I.E. ideal voltage output, wattage, or brand)


texts: Why does antenna tuner in crystal radio use capacitor and an inductor?

texts: I know that antennas can be capacitive or inductive depending on the relation of antenna length to the \$\lambda\$. I know that crystal radios use both antenna and capacitor for tuning and I don't understand why because for me it would seem the antenna should only be capacitive and you should only need inductor for tuning. Why is there a capacitor in crystal radios and why is it used for tuning?


texts: Flyback Converter Capacitor Value selection with given ripple voltage limit

texts:
I need to design a flyback converter for my project. In my design the output voltage is 15 V. I calculated all the parameters including inductance values, diodes selection etc.

However there is a design requirement which states the following:

  Find the value of the output capacitor from the allowed ripple value
  at the output. Note that the capacitor supplies the output current
  during (1-Δ1) of the cycle.

The allowed maximum ripple voltage is said to be 20 mV. Can anyone help me to calculate the output capacitor value using these values?


texts:
Recently for no reason at all some Altium shortcuts have stopped working, although not in all modes.
For example, while placing anything in the schematic mode, pressing TAB no longer jumps to the properties panel but in PCB mode it still works.
Another example, when moving a component, pressing X or Y no longer flips the component as it used to (only in the schematic mode, in PCB mode it still works fine). Instead X popups up the menu in the attached image, while Y does nothing.

I tried restoring the settings from Tools -> Preferences -> Set to default (all) with no success.
Tested on Altium 20 and recently I upgrade to 21 with the problem persisting.
Any ideas?
Thanks


texts: Evaluate and enhance my Super Capacitor Power Bank

texts:
I am not an Electrical Engineer, but know some basics from reading and practicing on this topic. Please evaluate my circuit for a Super Capacitor Power Bank to charge my phone, and clarify my points below.

If the input is fixed at 2.5V, do I need any protection board for a 2.7V Super Capacitor (3000F)
I plan to power the circuit using USB, so I need to step down 5V to 2.5V. One option is to buy a step down module, but is there any other simple technique I can use? Diodes?

Basically, the USB input charges up the capacitor and the LED lights up. The top left switch is not required, but it simulates the Power Bank being charged or not. When the switch on the top right is on, the capacitor discharges into a Step-Up Booster USB Charge Module, like this...

http://www.ebay.com/itm/5PCS-PFM-Control-DC-DC-USB-0-9V-5V-to-5V-dc-Boost-Step-up-Power-Supply-Module-/201542969731

Perhaps, it may be better to use two capacitors in series. Would I need a protection board, if I keep the input voltage at 2.5V max?

Anything else I am missing?


texts: Analog controlled H-Bridge to digitally controlled?

texts:
I am using this circuit to control a motor.

Initially I was using 12V PWM generated from a 555 astable circuit. I am now trying to make the circuit controllable via an 8051 Microcontroller

The problem seems to arise when I apply a digital PWM. The motor does opperate, but at a low torque/speed. The digital PWM is of course only 5V. Upon playing around with my circuit, I noticed that if I disconnect the 12V that's powering my H-Bridge, the motor will still run just fine. Thus, I've discovered that the H-Bridge is being completely powered by my PWM voltage.

Is there a way I can amp up the voltage of my PWM? I've tried Op Amps, but that limits the current being delivered and doesn't allow my motor to start. Or is there a way to make my H-Bridge use the voltage I power it with and only control speed/direction based on my PWM signals?


texts:
I got a Kit for AM radio transmitter , and i understand the function for most  of the circuit except two capacitor i wonder about their functionality  is ?. See the picture below

I understand the AM transmitter contain 3 main parts 1th the mic circuit then amplifier then LC circuit , but what i don't understand the function of C3 and C5.

When i tried to simulate the circuit all current except small amount  [ from the sours ]  used to flow from mic through C2 then C3 to ground .

also C5 I would like to know what its function ?.

i lost simulation, but if needed i will re-do it again upon request

Thank you a lot in advance


texts: SN74LS393N Integrated Circuit is confusing me

texts:
Today, I was playing around with digital devices I had lying in my circuit supply box, and I picked one of my ICs, looked up it's part number, and found out that it was an SN74LS393N, a type of IC for 4 bit binary counting, it seems. I was interested to get it working, because its functionality sounded interesting, but I haven't always shined in circuitry (The datasheets and schematics tend to overwhelm me, sadly). I accessed this part's datasheet, made a circuit that I thought would work, but it does nothing, I tried changing the IC into a different one of the same model, but to no avail, so the problem is my circuit, not the chip. The datasheet only gives me data on what to provide the IC, but I just can't figure out a working circuit for it.

This is the datasheet I used:
Dual 4-Bit Decade And Binary Counters, Texas Instruments

Here is an accurate schematic I made to represent the circuit I created for use with this chip.
Thank you very much for your time, I really appreciate it.


texts: Building a prototype rig with naked boards and wires (running 24V, 3.6 A): how to be safe?

texts:
I am building a prototype rig. It includes:
1) A "naked" 24/48 V motion control evaluation board.
2) A I=3.6 A stepper motor.
3) A power supply.

I wired up the motor to the board with four wires (A-, A+, B-, B+). I wired the board to the power supply: source (24 V) and ground wires.

The power supply allows to set both voltage and current. I am planning to set the power supply voltage to 24 V, not sure about current. By default it's at I=0.1 A, but I guess I might need at least 1 A to activate the stepper.

Now, a pessimistic assessment of the skin resistance is 500 Ohms (Wikipedia article on electric shocks). At 24 V, this would give a through current of 48 mA, causing heart fibrillation, breathing difficulties and inability to let go of the wire -- not cool.

How do I play it safe?


texts:
I got around to fixing an ATOM headlamp, and upon opening it up realized it was only an LED that had apparently burned up (brown coloring around LED and wires from battery). I suspect that the absence of a resistor led to more current than the LED could handle. While the lamp still turned on, it was not as bright as before. The lamp is powered by 3 AAA batteries in series.

Now, I replaced the LED (from what I could tell online it's an SMD LED) with an LED of the solar light variety, but was not sure if a resistor was necessary. Do you think adding a resistor would be worthwhile since it wasn't included in the circuit in the first place?


texts: Why do spectrum analyzers use envelope detectors?

texts:
Spectrum analyzers can usually be represented by the following block diagram:

Before entering the video filter, the signal passes through an envelope detector. What I don't understand is why this is done.

As far as I understand, the envelope detector presents at its output just the envelope, and not the carrier. So, wouldn't this filter out the carrier signal? I believe this is undesired because one would like to see on the display the frequency content of both the carrier and the envelope. How does this actually work and why?


texts: Electric motors high volts low amps vs low volts high amps

texts:
I have a little electric motor that im trying to use to spin a turn dial. I tryed useing a 5volt 1.55 amp power supply but it just dont have enought power to spin it. I can hook it up to my portable battery charger which is 5volts 2100 milliamps and it will start to spin it better. But im trying to find out how to give it power to spin it but not turn speed. What would be better High volts and low amps or low volts High amps?

I asked the question wrong the info i was looking for is which volts and amps will give the motor the most torque without realy changing the rpms.

The motor is hooked up to a pully That is made to spin a Rod that sticking out of it the motor doesnt have enought torque to spin the pully.i need enought torque to spin the pully but not have the pully spin to fast


texts:
I can think of some reasons why modern LED streetlights would likely be pulsed;

Efficient voltage conversion starting from line voltage would likely include an AC or switching step higher than 60 Hz.
Highest efficiency operation of LEDs often occurs at a current greater than can be sustained continuously due to heating issues.
Conversion back to steady DC (edit: at line frequency 50/60Hz) would require additional components that could fail, and would have no benefit that would offset the reduced efficiency operation.

There is a short section in Wikipedia about pulsed LED operation but it just introduces the concept without addressing how widespread pulsed operation is in the field.

As long as the frequency were sufficiently high that there were no chance of flicker perception, it seems to me that LED streetlights would be pulsed - or at least the blue LEDs used to excite the phosphor. The phosphor could have a long enough half-life to make most of the spectrum of the resulting emitted light steady even if the LEDs were pulsed.

Because some white light LEDs rely much more on LED's primary blue light than others, I'm going to ask my question primarily about the LEDs themselves, rather than the emitted light.

Are LEDs in modern streetlights usually pulsed? If so, roughly what frequency? 100 Hz, 1 kHz, 10 kHz? While there could be substantial variation in some regions, I'd expect in regions where cities are implementing widespread conversion from gas (mercury, sodium) to LED, there must be some commonalities or general trends/convergence in design.


texts: How do I route many FPGAs in JTAG chain?

texts:
I'm designing a chain of Xilinx FPGAs. There are many (e.g 32 or more) devices with short distance (about 10~15 cm) that I want to connect them together in a chain.
I'm not sure about TMS and TCK signals integrity. Each device has buffers in JTAG I/Os, should I use other buffers for TMS and TCK in the middle of path because of long distance between near and far devices?


texts: Why does four Apple Model Numbers (A1457, A1518, A1528 & A1530) have two FCC IDs (BCG‑E2643A & BCG‑E2643B)

texts:
These are model Numbers of iPhone 5S.
I want to know why two Model numbers of iPhones have the same FCC ID?
I am assuming that as they are two models, they are NOT the same for Apple yet they have the same FCC ID .
What constitutes a change of FCC ID and when does it take place?

Another example would be of iPhone 5 where Models A1428, A1429 and A1442 have the same FCC ID BCG‑E2599A.

Why so?