texts:
I have a Gumstix expansion board and want to make it communicate with some 24V PLCs.

I've read these topics for reference:

1.8V to 5V, still not comfortable with transistors
Transistors: why are resistors needed?
Simple design to switch 24v from PIC

Now my concern is to protect the controller since it's operating voltage is 1.8V and 24V will destroy it.

I thought I would isolate the 24V part by using an optocoupler or solid state relay. But have some questions:

Are mosfets safe enough to isolate the two parts? Reference MOSFET : NUD3160 (It's an inductive load driver. Can it be used in this situation?)
Which solution would be cost efficient?
Is Russell's solution (using a simple BJT to switch an ssr) better than a typical buffer like the 7407? (7407 is not 1.8V compatible though. If you can suggest an alternative, I will appreciate it.)
Is it a good way to use a MOSFET relay like CPC1002N? How can I drive the LED of it using a 1.8V I/O?


texts: During the recovery time the voltage VF in a diode is positive but the current IF is in the opposite direction. I think it’s very confusing, since all the current are flowing from high potential to low potential. I am really grateful that you may solve my problem since I didn’t find any explanation online. Thank you so much!


texts: MIDI sequencer timing accuracy using the Arduino

texts:
I build these music sequencers.

Only it's not exactly a sequencer, it's a physical interface for a sequencer. The sequencer is an application that runs on a laptop that the sequencer connects to, this thing lets the user make drum loops on the fly. It's pretty fun, but it requires a laptop because the sequencer isn't 'on-board'.

What I would love is to do the sequencing on-board my device.

Now let's assume I know how to solve for class compliance for USB MIDI connectivity, and let's also assume I can figure out how to wire up an arduino to send MIDI notes from a 5 pin DIN port. What I'm most concerned about is tempo drift over time due to inconsistent timing in minute amounts over every run of the event loop.

Some things I know:

You should not rely on delay() to control the tempo loop. Delay stops all operation of the firmware, and that can't work because i need to poll the physical user interface for changes while the sequence is running.
Calculations based on millis() are better because the firmware can continue to operate and act when a certain count has elapsed.
Even though none of my physical controls are triggering interrupt routines, some operations can delay the main loop() from running. If I design a function that waits for user input, that can obviously cause a problem of missing a "deadline" to act if the millis() count is way over. I know this problem is of my own design...

Questions:

A. Is the AVR-based arduino an appropriate microcontroller to poll a user interface and run a mission critical timing loop? I know there's an ARM based Arduino now that's a lot faster.  Would a Teensy 3.0 be a better alternative?  Both of these are 3.3V boards, so that's another set of issues to work with... but I'll ignore that for now.

B. Should I split the task into two microprocessors? One to handle polling and updating the user interface and one for mission critical timing loop.

c. Something else?

My main goal is to not have to use a computer at all. I also want to calculate for swing, but in this case, swing don't mean a thing if I ain't got a locked and timing accurate tempo. Thanks for your advice!


texts: Single transistor buffer and low pass filter

texts:
I want to build an input buffer for audio purposes.
This buffer should do 3 things:

have high input / low output impedance.
divide the signal by 2.
low pass filter the signal (cut freq. = 15KHz).

How about the circuit below?? Any other suggestion? Please let me know if you have better ideas.

Would it be ok to use a MOSFET like the BS270 instead of the bjt?

simulate this circuit – Schematic created using CircuitLab


texts: Unbrick MAX32660 that is programmed to drive SWD pin?

texts:
I thought I was being clever by remapping my UART output to the SWD output pin. I'm not a fan of debuggers (they don't scale). I assumed I could just reprogram my MAX32660 by holding it in reset, such as one does with AVRs for example.
Well it turns out that neither OpenOCD nor PyOCD wants to talk to the MAX32660 while it's in reset. For example, PyOCD says "Device state is Reset". I can't even halt the device.
It's hard to believe that there is no way to get the SWD function back. But in this thread about another Arm that (similarly to the MAX32660) can reassign the SWD pins, they claim that the device can only be reprogrammed if there is sufficient delay between the start of reset vector code and the time that it reassigns the SWD pins.
I am using a MAX32660 EVSYS to program the part. Can this programmer (which only supports SWD) unbrick the part? Could a JTAG programmer unbrick the part?


texts:
I'm unable to understand which PLL type (1 or 2) is better suited for frequency tracking and why? Can anyone explain how that additional integrator in type 2 will affect tracking?

Thanks in advance!


texts: Using capacitor to supply temporary surge

texts:
I am learning electronics on my own and I have a feeling a capacitor can solve an issue I have.

The datasheet for a part, which is powered by three lines (+12V, 0V, -12V) says that it draws 40 mA continuusouly, but that it can also draw up to 250 mA temporarily, for 0.1 second.

Well, let's say I just cannot afford to put on my board a power supply capable of giving 250 mA (I can go up to 80 mA). Can I use a capacitor to help supply the temporary surge?

I have thought of :

Capacity required : 0.250 * 0.1 = 0.0250 A.s (Coulombs)
Let's say I decide to connect the capacity to the +12V and -12V (is it ok ? Should I have two or three capacitors ?), then, with a 50 V capacity, that makes :

0.0250 / 50 = 0.0005 F

So I would need a 500 µF capacity to do the job. Is that correct ?

But then, when the part draws 250 mA for 0.1 s, the capacity get discharged, and it temporarily draws more current on the power source to recharge. I can solve this using a resistor, but where to put it, and how to choose it?

I have thought of that :

simulate this circuit – Schematic created using CircuitLab

OR

simulate this circuit

What do you think ? Is it even a good solution ?


texts: feeding another circuit a start signal (initializer) with d-latch (1,0,0,0,0...)

texts:
One of our lecturers has shown us a system for hardware compilation that uses control pulses.

Anyway, I basically want to generate a starting control pulse of 1 to be fed into another circuit. However, once this has been generated, this 'initializer' should only feed in 0s.

So I just need a simple circuit that outputs with the global clock:

1,0,0,0,0...

In the notes we have the starter given as:

However I don't see how this would generate a sequence of 1,0,0,0,0... (as i understand it, it would produce 1,0,1,0,1,0...)

Have I misinterpreted the diagram? Can somebody help me figure this out? thanks!


texts: How can I possibly get a 9600Hz square wave, for a serial baud rate?

texts:
I'm trying to create parallel to RS-232 serial converter using standard logic (serial transmitter only, no serial receive functionality). To get the clock signal my idea was to get a 7.3728MHz oscillator and then keep dividing the frequency by 2 until I get the desired frequency. This works to get common baud rates such as 460800Hz, 115200Hz, and 57600Hz.

The issue comes when I try to get lower baud rates, such as the standard 9600Hz, because below 57600Hz the frequencies I get aren't standard baud rates. For example, \$57600\div2 = 28800\$. This is no good.

I also can't find any oscillators or crystals online which oscillate at a multiple of 9600Hz. So, how is this usually achieved?

Thanks!


texts: Programming/Debugging with ICD3 and PIC16F819-I/P

texts:
ICD3 passes internal test with MPLAB IDE using the Test Interface Module
PIC16F819-I/P supports ICSP and In-Circuit debugging source.
ICD3 pinout is as follows (source):

1) Vpp/!MCLR
2) Vdd
3) Vss
4) PGD
5) PGC
6) LVP

The relevant PIC16F819-I/P pinouts are as follows (source):

 4) RA5/!MCLR/Vpp
14) Vdd
 5) Vss
13) RB7/T1OSIPGD
12) RB6/T1OSO/T1CKI/PGC
 ?) LVP

The documentation for the PIC states that it can be debugged using RB6 and RB7 provided that the DEBUG bit in the Configuration Word is set to '0' (page 102).
Q1) How do I do this? Can it be done through MPLAB?).

Q2) Is programming and debugging as simple as connecting up Vpp, Vdd, Vss, PGD, and PGC  (ignoring LVP) from the ICD3 to the pins of the PIC? I have a small breadboard to do this, but I'm wondering if I need additional passive components, which leads me to Q3.
Q3) How should I set up my breadboard to program the PIC?
Q4) Given Q1-Q3 are all satisfied, is programming and debugging as simple (using MPLAB IDE) as writing the code, downloading it to the PIC, and debugging from there? I understand that this question may fall outside the scope of my original 'how do I get started' question. Feel free to ignore it if you feel that it does.

Thank you so much for any guidance on this. I sincerely want to do this correctly!

EDIT: The resolution to this specific issue was eventually found here.


texts:
this is my first question in the forum because i can't find a solution
on my own... i hope you can help me. Also english is not my first language so excuse my writing errors.
i design an arduino system to be installed in a foresty truck, it has a series of sensors and
microcontrollers and it has to be power on even if the truck is power off. For that reason i know
that a need a sort of UPS (uninterruptible power supply) so i get one of this UPS for 18650 li-ion batteries.
18650 UPS Link
Previously, i think that i can use a powerbank to work as ups, but i realise that i cant, the powerbanks can be charged or charge something, but not at the same time. For that reason i take the 4.2 lipo batteries from that powerbank and i connected to the 18650 ups like in this picture.

so, my system is the next one,

The idea is that when the 24V battery is connected, the buck converter converts 24V to 5V and powers the UPS,powers the arduino circuit and charges the lipo battery.
I test this system and it works, but the problem is that the arduino system consumes more current (around 350mA )that the given by the buck converter from the 24V truck battery (150mA), so the system works but
the lipo battery is been discharged, so i need a way to take more current from the 24V battery...
I study the 18650 ups module and it uses a tp4056 as lipo charge IC and it should charge up to a current
to 600mA... so i dont know why it charges with so low current.
For the buck converter i am using a L2596 module, it can get a maximum input voltage of 42V and deliver up to 3A, i test it with a 12V input and a 10 Ohm load and it gives a current of 500mA, so it can deliver more than 150mA...
I dont know what to do now, for now, i'm simulating the 24V battery with a 42V ebike charger with a buck converter but i dont think that is the problem...
I will be attentive to answer any questions.
I hope you can help me, thanks in advance.
Matias


texts:
My company recently sent a product to undergo EMC testing. The product had passed all the tests except EFT and ESD. Somehow my company ask me as a fresh grads to solve it. TT. I really don't know from where I need to start. Can any expert here help out?

The product is a medical product, consisting of a robotic needle calibrator, which consists of 3 motors, and a PC to control the robot. The product failed ESD air discharge of 15 kV. The symptom was that the whole robot stopped moving and the PC hung/blue-screened.

I searched all over the net: most of them said use TVS/proper grounding. I don't understand how to add TVS for the ESD test though, since the tester only used the simulator gun and put it near the monitor and the system stopped.

Meanwhile, for the EFT test, the operation stopped when they applied the 2 kV, 100 kHz AC to the system. However, the PC did not restart, we can still use the PC and close the application and restart the system again. Same solution that I found from the net: use TVS.

I understand how TVS works, but I don't really know where should I add it because first of all I don't know where the root of the problem is. Anyone undergo such EMC testing before?


texts:
I would like to install an RCCB at the electrical point that will power a few devices that are going to be in my fish pond. Documentation and general info online say that Type AC RCCB can work with resistive loads but will not detect DC leakage currents or is not advisable for DC loads. I'm not sure if the devices in my pond could cause DC leakage current back into the AC line. The devices that will be downstream from this RCCB are an AC powered submerged pond pump (85W), a 12v/16A LED controller with dimmer.
I would also appreciate it if someone could explain what DC leakage current means and in what scenario a type A RCCB will work while type AC won't. Would this be a correct example: if the part of the wiring/circuit that comes in contact with a person (i.e. trigger a leakage current scenario) is the AC (alternating current) carrying part, then both the RCCB types will trip/work and if the part of the wiring/circuit that comes in contact with people is DC, then a Type AC RCCB will not work?


texts:
I am trying to implement values for the resistors and capacitors values for a PID controller with the following transfer function:
\$ H(s)=2.9 + \large {3.5\over s} \normalsize + 0.64s\$

I do know that the formula for \$2.9 = \large {R _{f}\over R_{i}} + {C_{i} \over C_{f}}\$ and \$ 3.5 = \large{1 \over R_{i}C_{f}}\$ and \$ 0.64 = R_{f}C_{i}\$.
I've tried many values for the resistors and capacitors but with no success. Any help would be welcomed.


texts: Where do the positive charges come from in P-Type silicon?

texts:
Can you please help me understand P-Type silicon?  I would like to propose a scenario and then ask you a few questions about it.  Scenario: If I take a block of pure silicon and dope it with boron, I now have P-Type silicon.  In this block the silicon atoms all have the same number of electrons and protons, so the silicon atoms are electrically neutral.  There are no silicon ions.  In this block the boron atoms all have the same number of electrons and protons, so the boron atoms are electrically neutral.  There are no boron ions.  The whole block of doped silicon is electrically neutral since the aggregate numbers of electrons and protons are the same.  Suddenly positive charges appear in this block of P-Type silicon.  These positive charges are strong enough to attract free electrons if the block is joined to N-Type silicon.
Questions: (1) If the positive charges in a silicon lattice are created by protons, where did these additional positive charges come from, since no additional protons have been added to this block of P-Type silicon?  (2) Is this phenomenon of positive charges seemingly appearing from nowhere been observed in other chemical or electrical experiments?  Or are P-Type semiconductors the only scenario where this phenomenon occurs?  Thank you.


texts: How to avoid RF signal loss in a conductive cage acting like a Faraday shield?

texts:
I have a standard chip antenna mounted on a large ground PCB plane.

The product is unfortunately encapsulated inside a relatively open (carbon-fiber) conductive cage.
Unfortunately, I see an obvious loss in the RF signal due to the Faraday cage principle.
How can I avoid such loss?
It would be difficult to put the antenna outside the cage. But would it make sense to have a wire or some conductive tape from the ground antenna plane to the cage itself or to "outside"?


texts: Over current protection for a 1-cell battery

texts:
I have a one-cell battery which protection circuitry is based on a DW01-P (with dual mosfet 8205S).

The datasheet says on page 2 "Overcurrent detection voltage = 150mV". How do I translate this number into how much current (expressed in Ampere) that this one-cell lipo battery can discharge at maximum before it cuts off?


texts: How to add remote testpoints to non-multidrop RS422 without causing reflections?

texts:
I have a RS422 non-multidrop connection between two connectors on a PCB (CLK+/- and DATA+/-) clocked at 1MHz, and currently routed with adapted edge-coupled microstrips (120Ohm differential impedance).
I would like to add measurement stubs, for example with oscilloscope probe tip connectors - but without degrading the quality of the bridge I am measuring.
The existing connection is about 10cm long, but the measurement stub will have to be 20 to 30cm long to reach a maintenance panel.

Because of the way the PCB is designed, I cannot just add testpoints ON the existing RS422 connection.
I thought about designing microstrips with differential impedance much greater than the signal I want to measure and leave the testpoint not terminated, but it's impossible for me to go above 350 Ohm.
I also thought about making a 120Ohm stub terminated with a 240Ohm resistor (since the equipment is not multi-drop, I suspect it won't handle 2 stubs with 120Ohm termination each - more likely to handle 50% more load), which currently is my baseline but I'm worried about the reflections from the 120->240Ohm transition and potentially from equivalent 60 OHm to 120 Ohm (see below).

What is the best way to handle this in your opinion?
Don't two 120Ohm stubs look like a 60 Ohm path at the fork, from the perspective of a signal upstream of the fork - therefore causing reflections?


texts: Data source switch with simple logic level shift

texts:
I would like to hack a 3.3v UART controlled Self Balancing Scooter in away that it can keep old logic (control), but optionally it should be able to switch to external control data source.

The question is will the presented schema do the job if

3.3v Data IN - is the original source. I have no control on it.
Switch 5.0v - is the switch to disconnect original source.
5.0v Data IN - is come from an Arduino UNO board and need to be logic level shifted to 3.3v
3.3v Data OUT - is the UART signal connected to motor control board of the hoverboard

In practice

I cut the wires between the Motor Controller and the Gyro Board.

Unfortunately I have no information about the schematics of the current circuitry.


texts:
Is there any electric circuit that can help a 2000W Inverter to run a motor with 500W but actually want a big power resource at launch time such as refrigerator?

I think if we have a big Capacitor it will work, is this true and how to implement this in the real world?


texts:
I currently have a setup where I take serial output from Arduino 1 and push it through a transmitter to the receiver of Arduino 2 where it is fed back into the serial input and further processed. I want to ensure that there is as little error as possible and recover the data wherever possible.

I have come across the syndrome decoding technique which seems to be the ideal one for me, but I am confused as to how I would go about implementing it.

I know that the Arduino Serial transfers data byte by byte, each being 8 bits, but do not know how this data is sent over the serial connection (i.e. how the start & stop bits & parity is implemented).

I would assume that a solution to this could either involve modifying the data in the buffer or reading it from the buffer and then operating upon it. I could also use adjacent bytes of data for error correction, but this seems wasteful.

How should I proceed with this?


texts:
I want to control a lot of LEDs (like 128) in an area of about 1 m2.

Instead of using separate wires, could I use a 28 AWG flat cable, and split/cut it wherever needed? E.g. split it in two wire groups and cut it wherever I want to place a LED?

Btw, I'm intending to use two MAX7219 ICs to control them using multiplexing.

According to the AWG table, I can use 0.226 A for each wire, which is enough (the LEDs I used are simple 3 mm LEDs and not intending to give them more than 0.2 A of current).


texts: Has anyone ever seen this transmission line setup (double series terminated)?

texts:
I am designing a custom PCB interface to be used with some off-the-shelf devices. The relevant off-the-shelf interface they provide is cumbersome and doesn't fit my application, so I am designing my own.

I would like to control the impedance of the communication lines connecting my devices, but after some reverse engineering to try and find their termination scheme I find something I've never seen and can't find anywhere else: it's double series terminated. Don't even know what to call it really.

A1 and A2 are just signal buffers. A1 represents the source, R1 is part of the source. T1 represents the line I am trying to design. A2, R2, R4, C1 is one device's receiver. And A3, R3, R5, C2 is a different device's receiver. The application allows for multiple devices to connect to the same bus, essentially in parallel. Notice the two 50ohm resistors in series with the line. I don't know what to do with this.

Also as point of interest. One of the communication lines is different. In place of R1 there is a series inductor and series R=100. Everything else equal. My assumption is that is some sort of clock.

What do I control my TL's characteristic impedance to, if anything? Has anyone seen something like this before or have any suggestions?


texts: One could variate the luminosity of an LED by either using PWM or by controling the current. Assuming either are doable which one is more energy efficient and why?


texts: What is the difference between nodes and terminals?

texts:
So my textbook uses both of these terms but doesn't really give clear definition of each which is starting to lead to some minor confusion. I was reading a Wiki entry on ports which stated

  A port consists of two nodes (terminals) connected to an outside circuit...

But this sort of confuses me because to me that is saying that each terminal is its own node.

simulate this circuit – Schematic created using CircuitLab

In this random example (I've encountered this when shorting the circuit between terminal a and b in problems) wouldn't these two terminal share the same node? How could they be separate nodes? Any type of clarification would be greatly appreciated!


texts: Combining power input and USB data port for a Raspberry Pi Zero (W)

texts:
I am attempting to design some peripheral circuit around a Raspberry Pi Zero W for a portable project. It will be powered by a lithium battery. I want to bring out the USB port of the Pi; I also wanted to use the same port for charging the battery, so I don't have to have separate power jacks.

Essentially, I am piecing three things together: the Pi and other on board components as the main load, the battery management circuitry and the battery (henceforth referred to as BMC) as the main power supply, and a USB port.

simulate this circuit – Schematic created using CircuitLab

Here is a link to the actual, more comprehensive schematics draft for my particular project.

I can't just connect all the power rails together; the two ends of the BMC (VIN and 5V OUT) will be tied together: not good. I can't just force power in only; then I must have an externally powered hub for whatever USB device I might connect.

Now, the port can be either a power supply to the BMC (a charger or a battery pack), or a load drawing a wee bit of power (USB device). I figured that the device attached to the port is unlikely to switch between these roles. So if I can detect whether something connected to the port is a power source or a load, I can make the circuitry act accordingly: connect the power pin of the ext. port to 5V OUT of BMC if the port is a load or to VIN of BMC if the port is a power source; and maybe leave it hanging if the type can't be determined.

Question 1: Will simply checking voltage differences between the power pin of the USB be enough to differentiate loads from power sources? Say, will phones, self- or externally-powered storage devices, etc. have a voltage on their connections even if they do not meant to supply power? Will some USB device not be identified this way?

Question 1A: Is there a better way?

Question 2: If affirmative to 1, will my design below work?

simulate this circuit


texts:
I am an electrical engineering student, and I am looking at creating a small PCB with a flashed microchip and a Bluetooth 4 module, as well as a Hall effect sensor for a flow measurement device I want to build.
I have built it with an ESP32 chip, and I want to look at using a flashed microchip and a custom PCB. I can get custom PCBs relatively easily through my university. I am mostly wondering where I should start looking to know how to design this, as it is my first time designing something with a flashed microchip.
Thanks in advance for your help, I am mostly just looking for pointers on where to start, as my Google-fu isn't working for me. I can scroll through parts on Digikey, but I am not really sure what I should look for.


texts: Limit base current on emitter-follower BJT

texts:
I'm using a BJT in emitter-follower configuration to control the current flowing through a high voltage load (170 V DC). The base is connected directly to an analog output of a BH2221FV DAC.

During normal operation the current through the HV load is Ic = (Vb - 0.6) / R1 (Ic = 4.4 mA max - Vb = 5 V max) and the base current is a few microamps, but if the load fails and the collector is left unconnected the base current rises up to 2 mA, far beyond the maximum allowed by the DAC output (1 mA).
There is a way to limit the current in such a case without affecting the normal operation? Should i put a base resistor and, if yes, in which way must be calculated?
Thanks!


texts: What is the general range of the structure oscillation frequency in MEMS gyroscopes and/or accelerometers?

texts:
Is there a general range for the oscillation of the internal structure in common MEMS gyroscopes and accelerometers?

I'm considering the possibility of damaging MEMS sensors via externally introduced vibrations, ideally through external stimulation at the internal resonant frequency. However, I haven't been able to find much information about the actual internal structure's resonant frequencies.

I'd assume it's fairly high, considering the scale of the features, but I can only really guess.


texts: Practical ways to obtain Bode plots for an unknown circuit

texts:
I want to use a practical method/way where I can obtain roughly the Bode plot of a system especially a filter. This of course can be done by using complex math or implementing the circuit in a SPICE simulator. But these requires knowing the circuit diagram and exact parameters of each component.

But imagine we don't know the circuit diagram of a filter in a black box, and we don't have time or possibility to obtain the circuit model as well. Which means we have the filter and we only have access to its inputs and outputs.(I also exclude the idea of obtaining filter's transfer function by applying an impulse to its input, I guess this is impractical(?))

But if we have a two channel oscilloscope and a function generator, we can see the input and output of the filter for a particular sinusoidal input.

By using a function generator, we for example can set the input as a 1Hz sinusoidal with 10mV pk-pk or call it Vin. In this case we can have an output of V1 pk-pk with a phase shift ϕ1. We repeat the same thing by setting the input this time as a 10Hz sinusoidal with again Vin pk-pk. In this case we can have an output of V2 pk-pk with a phase shift ϕ2. So by keeping Vin same amplitude and increasing the frequency equally we can obtain some points as:

Vin f1 ---> V1, f1, ϕ1

Vin f2 ---> V2, f2, ϕ2

Vin f3 ---> V3, f3, ϕ3

...

Vin fn ---> Vn, fn, ϕn

This means we can plot Vn/Vin with respect to fn; and we can also plot ϕn with respect to fn. Thus we might obtain Bode plots roughly.

But this method has some weaknesses. First of all since it will be recorded with pen and paper I cannot increase fn with small intervals. This is too much time taking. Another most important problem here is reading the amplitudes and phase shifts accurately in the oscilloscope screen.

My question is: Assuming we also have a PC based data-acquisition system, is there a practical and faster way to obtain Bode plot points for both amplitude and phase shifts roughly?(Points can be obtained as amplitude and phase shifts or a single complex number as well)


texts:
I'm a complete newbie. I don't want to bother this fantastic resource with my ignorance, but I'm starting to have strange thoughts.

How do I go from a bitstream (say, the output of an USB port) to a RF signal (say, to a QPSK chip like the AD8346)? A computer GPIO connection would probably be too slow for a bandwidth of say, 20MHz.

Are there some specific chips usable in the process or is the standard solution to use a FPGA as a buffer in between, reading the USB data and driving the QPSK modulator? (or maybe including the QPSK modulator in the FPGA itself?)

Thank you. I find the topic fascinating.


texts: Replacing the fast tube fuse with polymer fuse

texts:
I have a simple digital multimeter in which a fast tube fuse, rated at 0.1A and 250V is soldered directly to the plate.

Now, recently this fuse blowed and I have to replace it.  Because I don't want to mess with soldering every time a fuse is blown (and there is no place for a fuse holder), I was thinking about replacing the tube fuse with the polymer fuse rated at 0.1A and 60V (RXEF010).  Is this reasonable?

There are two possible concerns:

Will a polymer fuse break the circuit as fast as a tube fuse?
Is there a large ohmic difference between two fuses?  Voltage and current ratings suggest that the polymer fuse has four times smaller resistance, which should be advantageous.

Anyone has any idea about these issues?


texts: What are the general guidelines to conduct a stress test for an assembled PCB to test reliability after fabrication?

texts:
I got a PCB fabricated from a board-house. The PCB contains:

DC-DC power circuit
protection diodes
Atmel ATtiny microcontroller
LED's
USB hub and interface to a RPi

I want to conduct a stress test to understand the limits of operation of my assembled PCB.

What are some general guidelines to conduct this systematically and what parameters should I keep track of?

I have access to equipment like DC power supply, oscillopscope, Soldering station, hot air gun and a hot plate.

I would appreciate any help.

Thanks


texts: VF PWM for varying frequency reference function

texts:
I am new with PWM methods and there is a subject that I cant find an answer to and decided to ask here.

For a varying frequency PWM (VF-PWM) I have found that by using the following spectral modultion:

I am able to use some wave form reference (here cos wave) with a carrier (here sawtooth) and obtain the PWM output as shown below:

However, it all works fine if I know what shape my reference is and what is the frequency of it.

If for example I have a control system which outputs the following signal and I would like to insert it into a PWM to obtain pulses:

Is there some mathematical formula as shown above for a different case or some method to obtain the PWM for unregular reference shapes?

Thank you very much.


texts:
I am developing the automated test system depicted in the following picture.

The system receive commands and returns result data via Bluetooth to a remote computer
DK52 is used to fine tune the control software and will be replaced by a custom board based on nRF52832
Control Circuit generates testing signals according to the received commands
ADC measures voltage applied to the DUT and drained current
To respect the ADC specs the two circuits are isolated by ISO7741

Everything works fine.
To simplify the system I replaced the power supply 2 with a isolated DC-DC converter (DPAN02A-05) connected to power supply 1.

After that the current measurements (differential voltage across R1) are completely screwed up. Measured current is definitely lower than the correct value and it is negative instead of positive.
Conversely, voltage measured across DUT is correct (even if a little bit lower than the expected value. Maybe because the supply voltage is noisy since the DC-DC converter).
I measured +5V and +3.3V and they are correct.
I have been bumping my head on the wall for days trying to figure out what's wrong.
Please, give me some help!


texts: Microcontroller self-shutdown with MAX682

texts:
I have read How to implement a soft power switch controllable by microcontroller? and am wondering if something similar would be possible with a MAX682.

What I want, is a device that is turned on by pressing a single button, and that turns itself off. I'm using a PIC16F88, but because my battery has 3.6V and I need to drive a 5V LCD, I'm using the MAX682 to step this up.

The problem is that according to the datasheet, the /SHDN pin of the MAX682 should be connected via a resistor to its input voltage. What I would suggest is using its output voltage as an input for /SHDN, like this (only relevant pins are shown):

simulate this circuit – Schematic created using CircuitLab

When the user wants to start the device up, he presses the button to activate the MAX682 and thus the PIC (R1 is required for the MAX682). The PIC is programmed so, that it directly puts high on P1. R2 and R3 form a voltage divider to make 3.6V (I didn't calculate them yet). R4 has then the same function as R1, and makes sure that the MAX682 keeps running. When the PIC wants to shut itself down, it pulls P1 to ground and the MAX682 shuts down.

Would this work, or would the MAX682 have problems if the /SHDN pin isn't connected to IN? And if it would work, could I also remove R4 and connect the 'output' of the voltage divider to the point between SW1 and R1, to save a resistor?


texts: Amplified Active Low Pass Filter with Capacitor in Place of Resistor

texts: I'm an electrical engineering student learning about OP-Amp circuits, and I ran accross this circuit for an amplified low pass filter. I was wondering how the output of the circuit would be altered due to one of the resistors in the voltage divider that normally provides amplification being replaced with a capacitor. What is the output formula of this type of circuit. Is it the same as that of a standard amplified low pass filter?


texts: How would I measure current using current sense resistor at high voltages(-50 / +50V)

texts:
I am looking to measure voltage drop across current sense resistor. The waveform which occurs at the resistor is specific and consist of parts which are at voltages of +50V and -50V relative to ground.

The actual current is pretty small, about 50mA. So if I use 0.5ohm resistor, at 50V, there is going to be 25mV voltage drop across it.

Since voltage is changing, the direction of current is changing, too, so for start, I would need bidirectional measurement. I am looking to be as much as possible cost efficient here, too.

There is quite of options which I considered but none I have found to meet all the requirements:

a) using shunt amplifier, for example INA170 - the common mode voltage range is not big enough (best I have found is LMP8601 with -22 to 80V)

b) using shunt amplifier + voltage divider at Vin+ and Vin- pins - I would loose precision, only 25mV difference!

c) using differential bipolar ADC(for example MCP3424) - the max. voltage on pins is too small, too

d) ??? - I have no idea

Thanks on your time, as usual!

EDIT: The +50V and -50V voltage which creates the output is coming from the isolated power supply. If I use shunt amplifiers / ADCs / any other device which is connected to the other ground of the other power supply, the output is not isolated anymore, right?


texts:
In multi cycle path of 3 cycles, the setup for data D1 is checked at 3rd cycle. But for the next data, D2, the setup will be checked at 4th cycle or 6th cycle?

I have this doubt because, data takes 3 cycles to propagate, so that means after 1st launch the data will reach by 3rd edge and similarly data launched at 2nd edge will reach by 4th edge.

I am thinking like... data propagation as car travelling in a road. At a time two cars can be at two different positions in the same road(net).


texts: Why would some circuit designers prefer a tantalum or a ceramic capacitor instead of the popular electrolytic ones? In circuit schematics, all capacitors are all the  same. So what factors will be considered when choosing which capacitor to use?


texts:
I am trying to simulate an experimental setup, where the signal of a diode is amplified with a broadband amplifier and then registered by an oscilloscope.

As there are no many information available for the amplifier I was told to simulate it by "using a a simple Spice model with a transfer function with 20 dB gain, a lower cut-off frequency of 1 MHZ and an upper cut-off at 2 GHz".

How could I select the right spice model based on the info given above?


texts:
My teacher gave me a task to design a circuit board in P-CAD 2006. There is HC-06 Bluetooth module on the board. Unfortunately it has no usual smd or dip pins. Instead it looks like this (red arrow):

My teacher told me that It should be designed in powerful cad system like Mentors Graphics or similar. P-CAD 2006 doesn't provide such kind of pins and I have to design this pins like rounded rectangle smd.

I made this in P-CAD but now I have to make a 2D drawing in AutoCad of setting this module on the board. It should look something like this:

The main problem that I cannot find the image or drawing of this in Internet and I cannot find the technology of making this. What soldering or gaskets should I use? I really must do this drawing in AutoCad. Can you help me with this? Maybe you have some pictures that I can make a drawing from it?
I appreciate any kind of help.

Thanks.


texts: BTA16 (snubless version) triac was killed with 02 laptop adapter, please advice on how to overcome!

texts:
I found some threads asking on inductive load for triac can kill the triac with over clamping voltage, however, the thread is no longer open so let's me make a question here with a hope that the community would be so kind to to help.
I use a BTA16-600BRG with MOC3020. I make a test with normal resistive load and it worked fine with even 5A for short while without heatsink. Tests with fans, drilling tools were also fine. However, when I plug in 2 laptop adapters, the triac dead upon 1 (one) switch off and T1 and T2 become always connected (replacement of another Triac makes the relay work again and I test again with 2 adapter and the BTA16-600B got killed again).
The datasheet of the BTA tells that this is a snnubless triac. But it seems that the internal protection is not enough. In this case do I have to make a snnubber circuit for the BTA and how much would be the value for C and R.
Note: My actual PCB has no BC 547 as it not needed, I drive triac with MOC3020 only. I replace the dead BTA16 with a new one and it work again (of course, I dont want to try a test with 2 adapters again). My concern it: What was the problem that cause triac to die?
Thank you very much for your attention.

I revised the schematic with  but have not tested yet!


texts:
I want to understand how LM2574 step-down regulator works and I can not find the logic of the comparator in the following picture:
Can anyone explain ?


texts:
I've searched the forums but can't find an answer for my issue. I've got a simple LED circuit powered by 5V DC. When the switch is closed, I've got 2.8V across the resistor, 2.2V across the LED, and 0V across the switch (as expected).

However, when the switch is open, I get 3.45V across the switch but no other noticeable readings (0V across resistor and 0V across the LED). Where did the other 1.55V go? If I shunt across the LED, I get the expected 5V across the open switch connections. How is there a voltage drop across the LED in an open circuit and why can't it be measured with a DMM?

simulate this circuit – Schematic created using CircuitLab


texts: Do battery connectors handle more amperage than the charger port?

texts:
I have a tiny device (similar to a stripped down cell phone), and it has an unmarked battery connected with +/- wires.
It also uses an power adapter to charge the battery, the power adapter (with USB plug) says 5V 0.2A

A connector / wires for battery
A connector that gets power from wall adapter (0.2A)

I wanted to permanently connect it to another power source that is 5V and ~1A and use the battery connectors for that (unsolder the battery).

Is it safe to assume the device can handle more amperage on the battery connector than the 0.2A that it gets from the charger on the charger connector ?

// Maybe there is a way to decide how much amperage it can handle on the connector coming from battery ?


texts:
For my final lab this semester, I've been tasked with designing a multi-stage amplifier that serves as a receiver in a laser tag set that we've been building over the course of the class. I've searched various forums, but have only found loose advice on how to go about designing the amplifier.

Here are the specifications and what I've designed so far:

Specifications:

Gain: 5000 V/V
Maximum output voltage: 1 V
Built in bandpass filter with a lower corner frequency of ~200Hz and an upper corner frequency of ~20kHz
Total current draw of less than 1 mA
Final stage is a common collector

Here's a circuit design that should be able to fill the parameters:

simulate this circuit – Schematic created using CircuitLab

The input voltage depends on the signal received from a photodiode/resistor circuit (not depicted here). The signal will be on the magnitude of about 50 uV at the smallest.

So, as you can see, I have a 4 stage amplifier in the pattern of CE, CC, CE, CC. The way I see it, I have at least three major design steps to this project. First, I must determine the resistor values 1 through 14 such that my gain is the adequate amount. Second, I must determine the capacitor values to make the amplifier also function as a bandpass filter. Lastly, I need to limit my output to 1 V.

I'm fairly inexperienced with the design process. I know I'll need to calculate the gain, input resistance, and output resistance for each individual stage, but after that, I'm uncertain of which values to start tinkering with or adjusting to attain my goals. Before anyone jumps down my throat for wanting people to do my work for me, let me make my goal clear: I am looking for design techniques and a process that will help me solve this problem--hints in the right direction. I would be disappointed with this great community if anyone simply solved it for me. Would someone be willing to point me in the right direction?


texts: Is there any way to calculate milliseconds from DS1307

texts:
I have a DS1307 and I have done its program and taking out time from it. In my program I have sec1,sec2 which holds the digits of seconds and same for min1,min2 & hr1,hr2. I am saving all in a variable TIME

sprintf(TIME,"%s%s:%s%s:%s%s",hr2,hr1,min2,min1,sec2,sec1);

Now TIME contains the value of Hour, Minutes, Seconds. But I also need the value of milliseconds.

Is there any logic which I can use in code or any other way to calculate values for milliseconds

CODE FOR MilliSecond

 //MSECOND is variable to hold millisecond
   int count = 0;
    do
    {
        count++;
        sprintf(MSECOND,"%d",count);
        sprintf(TIME,"%s%s:%s%s:%s%s:%s",hr2,hr1,min2,min1,sec2,sec1,MSECOND);
        putsUART1("Time: ");
        putsUART1(TIME);
        putsUART1(" \n ");
    }while(count<=999);

EDIT

This question is in reference to my older question: Where to save DS1307 program to get real time value?. I am using PIC32MX795F512L MCU. I have not posted the complete code. Its in the link.


texts: Can a semiconductor device discharge power capacitors

texts:
Trying to figure out how to discharge a capacitor yielding 75 Joule - 177v @ 4700uf. I am uncertain which or even if a semiconductor device is up to the task. Can semis do it? If yes then which can do it and do it constantly (~2x second)? How do I determine heat rise in device?

If scr's can do it please specify answers in regards to scr's.

Thank you.


texts: How to design high-current through hole solder connection to large planes

texts:
We have a power connector, which is capable of delivering 20Amps to a PCB. On the PCB, one layer is dedicated to Vdd, which is 5V. The board is quite large, 200mmx300mm.

The power connector is through-hole. In order to solder the connector, we assumed we would need thermal reliefs on the pads so that during soldering, we can heat up the pads properly. But then on the other hand, thermal relieving the pad reduces its current carrying capacity, increases resistance, and increases power consumption. Is this a correct assumption?

What are the issues that should be taken into account when designing for high current power inputs to large power planes?


texts: Should the output of logic gate have pull-up or pull-down resistor

texts:
I am a bit confused whether my chosen AND gate should have pull-up or pull-down resistor on the outputs, as I don't see any sentence containing words like pull-up/down or sink or source ... but as far as I understand then TTL IC's usually need pull-up/down resistor on the output. When I am looking at the schematics then I would say it is capable of making both high and low, as there are transistors connecting the output to both Vcc and Vdd. Here's the datasheet: triple input AND.

I am also using NOR gate which states that it is totem pole output: Diodes Incorporated and part number: 74AHCT1G02W5-7 (sorry, not enough reputation to post more than 1 link :D). Am I right that it is capable of making both low and high output, but the high means it is only 3.5V as there are voltage drops across transistor junctions so I would have to use pull-up resistor on the output so it would be 5V.

Schematic snippet I have at the moment:

Some additional explanation is also much appreciated so I would have the know-how for the future how to read out the necessary info from the datasheet.


texts:
I was looking over LTC2990, which is a voltage, current and temperature monitor.

It is perfect for my project as I'm newbie. I want to build a power supply which will show on a display the voltage, current and the temperature using the arduino Atmega328. But the input voltage of the IC is maximum +0.3V over the VCC voltage. Is there a way of raising that value up to 15V?


texts: I have a 5V PWM signal around 500Hz. I want to have 0-10V analog output from this. I considered using a MOSFET to step the 5V PWM to 10V PWM and using a low pass filter at the output to achieve my goal. However, I want to see other ways of doing this. What are my options?


texts: Input power with PF, impedance on transmission line and transformer

texts:
I've just had and exam (Renewable Energy) and we had a problem that I'm not sure if is correct. The answers should be simple as we haven't studied tranmission lines at all.

Okay, here we go.
We have an AC signal, tranmission line with impedance and transformer at the end.
At the beginning of transmission line we have a signal with(max values):
V=240kV
I=400A
PF=0.85

First question was to calculate apparent power etc. what was straightforward, but the second question was:
There was voltage drop of 1kV on the transmission line.
The impedance of transmission line 0.1+0.1j per km.
So Vin=240kV sin(alpha)
Phase angle was arccos(0.85)=32 degrees
Iin=400A cos (alpha + 32)

How can we calculate what was length of the line?
Won't this initial phase shift somehow make it more complex?
Also, do transmission line do have inductance or they just have characteristic impedance?

Maybe I'm overthinking it and the answer should be just
V=IR -> 1000V=400A*(0.1*l) and therefore l = 1000/(400*0.1)=25km
Or maybe, as sqare root of (0.1^2+0.1^2) = 0.14
V=IR -> 1000V=400A*(0.14*l) and therefore l = 1000/(400*0.14)=17.85km

After calculating this we were asked what is be impedance on the secondary side of transformer with turn ratio = 16 (i.e. secondary voltage = 15kV).
Could you please help me with that?


texts:
I've opened up the battery box of a string of fairy lights (like pictured at bottom) and found a resistor, plus what looks like a capacitor in series with the lights. Is this really a capacitor? If so, how does it work in a DC circuit like this?

simulate this circuit – Schematic created using CircuitLab

My aim is to convert these to run on 12v. Does this circuit look ok? How can I determine the right value for the current limiting resistor?

simulate this circuit


texts: Is buffer needed for very long coaxial cable carrying DC analog signals coupled to an ADC with a huge input impedance

texts:
I know the topic is immensely broad but I dont have the practical knowledge on the following issue:

Let's say I have a very long like 1km BNC cable carrying DC signal around 1V analog voltage signal coming from a transducer.
And let's say the BNC goes all the way straight to an ADC with 100 Meg-ohm input impedance at the end.
If the measurement should be very accurate, do we need to buffer this signal?

BNC cable even 1km long has very very low resistance comparing to ADC's huge input impedance.
Theoretically form this point I would think one wouldn't need a buffer.

But how would that be implemented in practice for 1V DC level and 10mV DC?


texts: Looking for datasheet for SHARP LS030Y3DX01 Display

texts:
I am looking for the datasheet for the LS030Y3DX01  LCD display from Sharp.

The display is a 3 inches with the resolution 480x800 pixels.

The only thing I have found is on this web site that requires a paid subscription:

http://www.panelook.com/LS030Y3DX01_SHARP_3.0_LCM_overview_14230.html


texts:
I was designing the start up circuit for one of my circuits as shown in the figure below . I was able to understand how a start up works clearly but I stil havent figured out how exactly the 0 current state would be made possible.

I know that when the mentioned nodes reach Vdd or 0 volts then yes of course the current in the circuit would be 0 but what would cause these nodes to be Vdd and 0 ?

The circuit is a design of a bandgap reference. I just want to know how the mentioned nodes in the figure could reach Vdd or 0 Volts. If I understand this then I am clear with the entire startup issue.


texts:
I am interested in using this Tubular Solenoid at 3 DC voltage to operate in Continuous (100%) Duty Cycle. According to the specifications the solenoid can operate at a:

  Continuous (100%) Duty Cycle when supplied with voltages equal to or
  less than 24 Volts DC, with an approximate Input Power of  2 Watts

Can I successfully drive these types of solenoids using an
Arduino UNO/Teensy 3.1?
How can I make sure an Arduino can accept 2 watts?


texts: Are Gerber files of inner layers interchangeable?

texts:
Regarding the Gerber files of a 4 layer PCB with 2 inner layers:

Top layer: Analog signals
Inner layer 1: Digital signals (SPI and I2C)
Inner layer 2: Power planes (+3.3V and +12V)
Bottom layer: GND plane

For better isolation between analogue and digital signals and to prevent digital noise from coupling back into analog signals, I would like to swap the two inner layers, so that there is a power layer between analogue and digital.

Unfortunately, my EDA software (KiCAD) does not permit to reorder the stack.

This is why I'm wondering if it would be possible to simply rename the two Gerber files before sending them to the producer, so that the layers get swaped?

My guess is that the layers are only connected through vias and PTH's for THT components. Am I missing something here, that might break the PCB, if I manually rename the files ?


texts:
I have an application where I'll be receiving an audio stream, much like using headphones, into my processor. I would like to run FFT and various DSP algorithms on the sampled audio and then spit the audio back out as if the device wasn't there. Basically doing DSP in real-time in between samples I guess. The processor I'm using is the MKL26Z128xxx4, mounted on the FRDM-KL26Z development board. It has a single ARM Cortex M0+ core and is programmed in C/C++ and can use the THUMB Assembly instruction set.

How would I do this without losing any of the streamed audio?


texts: What is the purpose of these components in an LC Balun?

texts:
I'm trying to understand an antenna impedance matching / balun network that I came across in the receiving signal path in the schematics for the STEVAL-FKI868V2 S2-LP Evaluation Board, shown in the picture above.

RXP / RXN are the balanced LNA input pins of the transceiver IC, which has an input impedance that is given in table 17 in its datasheet:

The anennta's characteristic impedance is assumed to be 50 Ohms.
Now obviously, C14, C17 and C16 are just DC blocks and large enough to be neglected.
C13, C18, L3 and L5 form an LC balun. C15 is not fitted.

But what exactly are L4 and C38 (marked red) for? How did the designers come up with their values? Is there a name for this kind of circuit?

Especially C38 looks odd to me, it makes the whole balanced line asymmetric.
Any hints are greatly appreciated!


texts:
I'm an electronics engineering student and I want to state that this question is not my homework, it is a tiny part of my project (PWM encoder) but I couldn't pass it.

I'm trying to make a "frequency to voltage converter" but 3 days of web search didn't allow me to do that. (Seriously, even in SE there are no clear topics about frequency to voltage converters) I know some ICs can do that but I want to do my project without any IC, using only primitive components so I tried RC low-pass filter as an integrator to make frequency to voltage converter.

The input is a square wave between 10-20kHz

Design objectives are :

The converter should handle frequencies between (all frequencies at that range) 10kHz and 20kHz.

And it should converge under 10 cycles

I made 2 different circuits and simulated but in first circuit output voltages are the same and they are not converging fast enough.

Here is the first circuit scheme and simulation results:

And in second circuit output voltages are different but too close, I need like 4 volts for 20kHz and 2 volts for 10kHz. How can I separate them? And again it is not converging fast enough.

Here is the second circuit:

To be honest, I took the left-hand side circuit from the internet and couldn't understand the principle behind it. The diode was between the schmitt output and ground (parallel to the first capacitor) but since I don't know its purpose, I tried different combinations and decided that this version is better.

In both circuits, the more outputs separate, the more time needing for converge and more ripples occur. Is it always a choice between one or another? Are there some ways to make it better?

I am not wanting full solution or design (if you can provide I'll appreciate), I'm just asking for guidance and tips/tricks.

Edit : Additional Information

The circuit below is designed for PWM encoder which generates 25% pulse width for data "0" and 75% for data "1" between 10-20kHz. Monostable Multivibrator(MMV) pulse width is depended on RC on its Rx, Rx/Cx pins and the voltage on the RC part. The Difference between the three images below are clock frequency(first is 10kHz second is 15kHz the last one is 20kHz) and the voltage on RC (Top left Voltage source will be replaced by Frequency-To-Voltage Converter) are 5v, 7.5v, and 10v respectively. These three values are for example. I need correct voltage on RC part for every frequency so I need to obtain voltage value from clock signal. The question is about it, how can I obtain voltages between 5-10v as precise as possible by connecting Frequency-to-Voltage converter between MMV's RC part and clock signal.

10kHz - 5V

15kHz - 7.5V

20kHz - 10V


texts: What's the use of the LODRV pin in the 2BQ24650 mppt batery charger circuit

texts:
I'm looking at the datasheet of the ic and I kind of understand what's going on.
Apart from the typical sensing and signaling pins there are the HIDRV and LODRV pins which drive Q1 and Q2 respectively. (Typical Application, page 1)
Q1 controls the current flowing from a solar panel to the battery pack.
Wouldn't Q2 just drain the battery pack?


texts: What are the component values needed to design a cuk converter

texts:
I have been trying to make a cuk converter for a long time now, I am using a 555 timer to control the switch, the maximum output voltage that I get is -1.5V in my design, also in my circuit, though i give an input of 9V, whenever i measure the input across the battery after connecting, it drops down to 4V and even less for some reason

Even if the voltage drops to 4V i want it to still be giving to me atleast greater than 4V if not 9V. I am attatching the circuit configuration that i have used, the inductors are 1mH and 0.25mH while the capacitors are 1000uF and 1200uF, i have tried interchanging the positions kf these four components as well but it yields not much of a difference


texts: Solving for a current using node-voltage analysis

texts:
I wish to know how I can find out what \$i_a\$ is. The answer is, according to the textbook, supposed to be 1.33 A.

If I select the top node as a reference node, my understanding is that we then know the voltage over \$R_2\$ is 10 volts as well? I'm very confused as to how I can analyze this simple circuit.

Any help appreciated.


texts: Rail to rail OpAmp Parameters for signal conditioning

texts:
I am currently making some calculations and also simulations on a PT100 circuit, the circuit itself and calculations are not an issue, but I am trying to look at the best rail to rail opamp.  An image of the circuit is below:

Currently the university were I am studying has TLV272 and I intend to build a prototype for calibration and testing, with tweaked values pending what 1% resistors we have.

What I am interested in is the benefits of using an OPA188 opamp as opposed to the TLV272, I don't have a Pspice model for the OPA188 so cannot check.  I know the OPA188 is stated as low noise, I don't believe parameters which are speed related are an issue here as it's a low speed signal conditioning circuit.  Input current yes so Iq per channel, not sure the significance of IIB as the value seems counter intuitive to me and not sure I fully understand the implications of a large or small value here?

OPA188

TLV272

Any further advise would be welcome, I am also thinking of adding a small pre-amp stage to boost the range of the output, then add this circuit afterwards as have 2 Opamps per package.


texts: USB power pack in wearable electronics: Is it safe?

texts: I'm developing a wearable electronics product that runs on batteries. I would like to use a USB power pack like this as the battery, but I need to make sure it's not a fire hazard because it's going to be part of a clothing item. The power pack says it's UL listed, but I don't know how to find out what exactly that guarantees. Does anyone have any suggestions? Given the recent hoverboard incidents I'm inclined to be very cautious with Li-ion batteries.


texts: In my book there is the architecture of a basic circuit with a half adder with 1 AND and 1 XOR for the carry, and a "maimed" half adder with one XOR for the previous carry. Then book say that minimum time of an operation is $$t_{min}=t_{xor} $$ (without carry) and the max time is $$t_{max} = t_{xor} + t_{and}$$ but the max time should not be $$t_{max} = 2t_{xor} + t_{and}$$ ?


texts: Likely to use more power - phone screen or bluetooth le?

texts:
Just as a theoretical guesstimate, would a phone screen likely to be more of a battery drain than a bluetooth le connection?

Of course this is going to vary on the amount of data being sent the screen brightness etc etc.

But my uneducated thinking... as an example:

Is it more power efficient to use the music app on a pebble smart watch than to change music track v.s. turning on (e.g. an iPhone 4s) screen to change track?


texts: How charge moves through a diode during the reverse recovery time?

texts:
My textbook says something like this :
When a diode is switched from forward bias to reverse, the current changes direction but the magnitude doesn't decrease immediately. The charges continue to flow and the diode draws the power from the battery through out the reverse recovery time.

During forward bias, there exist some "excess" minority carriers near the junction. These contribute to the current during reverse recovery time.

In forward bias, negative plate of the battery pushes electrons from n side to the junction, then the electrons recombine with holes and travel in the valence band through the holes of p side and reach the positive plate of the battery. It seems electrons only travel in valence band in p side. I'm happy having this mental picture for the charge movement during forward bias. But I'm failing to visualize a similar picture for the charge movement during reverse recovery time. I keep getting questions like :

1) Does the negative terminal of the battery put electrons at the edge of the p side, then these electrons fall into holes, the electrons then travel through the holes to the junction and they see depletion region! Then what happens ?
2) What happens to the excess minority carries on the p side near the junction ? Do they feel the battery and move to the n side ? Even if they move to the n
 side, the excess electrons on p side are never going to disappear because an equal number of electrons seem to enter from the negative terminal of the battery...  Highly appreciate any help. Thanks!


texts: 1V voltage reference and temperature coefficient

texts:
There are precision 1V voltage references like ADR510 which I don't have access to, though I do have LM385 1.2V, LM336Z5 5V and the famous TL431 at hand.

The easiest solution is to use a voltage divider:

simulate this circuit – Schematic created using CircuitLab

But using voltage dividers is not temperature coefficient, in page 6 of LM336 datasheet there's a schematic which claims:

  If minimum  temperature  coefficient  is  desired,  four  diodes can
  be added in series with the adjustment potentiometer as shown in
  Figure 2. When the device is adjusted to 5.00V the temperature
  coefficient is minimized. Almost any silicon signal  diode  can  be
  used  for  this  purpose  such  as  a  1N914,1N4148 or a 1N457.

How diodes makes above circuit temperature coefficient?
How do I achieve a temperature coefficient 1V voltage reference?


texts: Simple transistor circuit with unconnected gate pin acts strangely

texts:
My brother and I were playing around with some new transistors we ordered (2n7000 n-channel MOSFETs), trying to make a simple switching circuit: connect a switch, LED turns on; open the switch, LED turns off. Here's a link to the circuit we were attempting to make.

Here's a picture of what we implemented in a breadboard. There's one difference from the above circuit: the switch is not actually complete. We just have a single wire connected to the n-MOSFET's gate. So this is what we actually have in the breadboard.

As far as we can tell, from our limited electrical engineering experience, the LED should never be on, since there is no connection from the +5V power to the transistor's gate; the transistor should not let any current through. However, there were two interesting things: first, the LED turned on as soon as we powered on the circuit, even before we connected the transistor's gate to power. Also, whenever we touch/tap the wire connected to the gate (labeled by "??" in the circuit), the LED randomly switches between three different levels of brightness (on, medium, off), and will even "stick" at a brightness setting, even between power cycles of the entire circuit. The single transistor appears to act as a flip-flop!

So, the question is: why does touching the unconnected wire change the LED's state?

And, secondarily, how is the LED on, even if the transistor has no voltage source attached to the gate?


texts: On button press, use battery if no power is provided via USB

texts:
I'm making a binary clock that is normally powered using USB 5V.

I already have a battery (CR2032) for the RTC chip. So I want to also use this battery to power the board, when a button is pressed (and USB isn't connected). So you can tell the time, when you don't have a USB port nearby.

This is the schematic I came up with:

Now my question is: when the board is powered via USB, does the PNP transistor prevent the 5V from going into the battery (when the button is pressed)?

Also, since the IC-INPUT has a pull-up to 5V, is there any danger in that 5V is coming into the battery via the pull-up (~30K), 3K3 and 33K? When applying Ohm's law I get around 0.03mA of current, so I guess I'm good. But I don't want to have the battery explode on me.

Note that I'm also using the button as an input for the microcontroller.


texts: arduino boot up button and shutdown mode on regulator

texts:
We've a projet with an important autonomy concern. We use an homemade arduino (atmega328), and for the moment we're using interrupts on buttons to wake up the atmega.

so we have: sleep ->(button pressed) -> wake -> (user RFID identification) -> (RF Communications) -> sleep.

We've optimized the total consumption with advanced sleep, modules isolated from current with transistors and so on...

I was asking myself if we could use a voltage regulator with a shutdown pin, and link one button and one pin of the atmega with it.

We would have this cycle:
shutdown -> (button pressed) -> shutdown pin HIGH -> atmega is powered-> atmega set shutdown pin HIGH during sketch configuration -> user RFID identification) -> (RF Communications) -> atmega set shutdown pin LOW -> shutdown

You get get the schematic here:

So to summarize: I need the button during my sketch, so when it's pressed and get the shdn pin high on the regulator, the first thing the arduino makes is maintaining this high with its pin 4. Furthermore, it restore the pull-up configuration of the button by reconnecting it to the ground through the npn transistor. When arduino is shutdown, button is linked to VIN as the npn make a NOT function with arduino state (HIGH or LOW).

Do you think it could work? If something is unclear don't hesitate to tell me :-)

Thank's a lot!


texts: I am trying to control a SainSmart 4 channel 12VDC relay from Labview and having some trouble.  I was hoping to control the module via serial comms but this does not seem to be working. Can anyone suggest an example that I might follow to set this up?


texts:
I am planning a circuit that requires two-way communication between one esp32 and 3 others. I want to use a master/slave architecture as shown here:
They need to be able to communicated via hardware, not wirelessly!
Is this possible using the following circuit?

(in this circuit, the CLK pins are serial clock pins and the SD pins are serial data pins, i plan to use i2c (which may also need the arduinos to have a common ground...))

Any solutions/ideas are appreciated


texts: Positive and Negative Sense Circuit. How/why does this work?

texts:
I am trying to build a centre-off model railway controller, no reversing switch. I am working on the overload/short detection part of the circuit based on sensing the voltage across a 0R68 resistor. I want to trigger at about 1A, i.e. approx. 0.7V across Rsense. The current flow will be bi-directional.

The "detection" is done by two comparators using diodes to give the 0.7V references, which worked fine. My next step was to use a rail-to-rail OpAmp to invert/shift the negative pulses to positive ones. In working through a circuit in LTSpice I  hit "Simulate" before I'd hooked everything up and ... it did exactly what I need! But it bugs me that the inverting input of the OpAmp is floating. When I try to connect it I cannot get the correct result.

Could someone please explain how/why this works? And am I OK to let the input float?

Diagram and waveforms below.

Thanks,

Duncan


texts: Multiplication of two binary numbers in fixed point arithmetic


texts: Requirements for PCIe Bifurcation on SBC

texts: I'm looking for clarification on what actually needs to happen in order for a device to support PCIe bifurcation. Some forums say it's motherboard dependent, making me think it's not tied to the processor I choose, but all that is in the realm of PC hardware. My application is on an single board computer (SBC). To clarify, my application is splitting the x4 PCIe 2.1 Lanes from a RK3399 into 2 x2 lanes for 2 SATA adapters. As far as I'm aware, bifurcation is what I want, but even that I'm not completely sure of. Sorry if this is too broad, but nowhere online can I find the information I'm looking for.


texts:
I bought one of these: https://www.ebay.ca/itm/High-Power-Warm-White-DC-32-34V-100W-LED-light-Lamp-SMD-Chip-9000-10000LM-LM/272210214196

I am powering it with a 12v 8ah battery and a voltage booster: https://www.ebay.ca/itm/150W-DC-DC-Boost-Converter-10-32V-to-12-35V-6A-Step-Up-Voltage-Charger-Power/171907240597

I adjusted the voltage booster to output 34v exactly (measured with my multimeter)

Problem?:
It's not as bright as I would have hoped ... so with my multimeter I measured the current flowing from the battery and it is only drawing about 4amps from the 12v, so about 50W.

Am I missing something or is the seller just selling under wattaged chips?

Thanks!


texts:
Circuit structure:

An AC to DC power converter MeanWell 220V to 5V. The output is 5V. The power grid runs at 50Hz.
We build DC-DC converters(Power Module) with multiple orders of Low pass filters to provide different DC voltages needed for our main circuit: +5V, +15V, -15V
Main circuit uses the voltages generated above. It provides control signals to its target and reads feedback signals. It connects with target through 2.54 mm dupont wires, which are around 0.3 meters long. It will adjust control signals according to the feedback signals. The target device has purely differential receiver and shall not be influenced by common-mode noises.

Problem:

The whole circuit runs normally at our companies lab. The circuit is not connected with earth.
When used in some Lab with many devices(scopes, signal generators and etc.), it does not function well any more. The feedback signal looks like following, which is 50Hz noise.

When the circuit ground is connected with earth, the 50Hz noise will be reduced greatly. It starts to work.
There are still 50Hz noises which do not exist when in my Lab and it harms the device performance.

Questions

Where are the 50Hz noises from?
Why the noises are reduced when connecting the circuit with earth?
How to remove the 50Hz noise totally?


texts: Resistor value labeling, what does the second number refer to?

texts:
Possible Duplicate:
  µ in the Middle of a Capacitor Rating
  What does 3V3 or 1V8 mean

I have been looking over some schematics for an industrial Laser. Some resistors which have low values, say 100 Ohms, are labelled 100R. Makes sense. Same goes for 1000 ohms, 1k. again makes sense. But there are a few that have a additional number. For example I see one labelled 5K1. I assume its a 5k ohm resistor but what does the 1 mean? I was looking at another schematic and it has a bunch of resistors but two of them are 3K9. Again whats with the 9?


texts: Melting a connection in circuit while operating

texts:
If I take a circuit, for instance an RC circuit, on a PCB while attached to some AC source or network analyzer and measure the voltage drop across one of the components, when I melt one of the connections, e.g., with a soldering iron (but with the component(s) still in place and in mechanical contact with the corresponding track(s)!), will then the circuit stop working?

I haven't tried it yet just in case something goes terribly wrong.

From a theoretical perspective, the junction I melt is then not in solid state, which means that all the quantum treatment of the valence-conduction bands is no longer valid. On the other hand, tap water, which is liquid, is a good conductor, so I don't know if electrons will be free to flow or not at all in the circuit through the melted junction.


texts: Can I operate a 500kW/1500rpms motor at 35Hz with 400kW inverter?

texts:
In stock we have a 3 phase induction motor with a rated power 500kW and 1490rpms.

What is the smallest frequency inverter which we can use to operate this motor in a machine with a maximum power/speed 315kW/1000rpms

I think 315kW inverter (or for service factor 355kW) is enough.

But the specialists who are selling the inverter explained me that we need 500kW inverter for it, but I did not understand why?


texts: How to generate wait until division is over in verilog?

texts:
I am using a division module which has two signals other than inputs
"go" to indicate start of division.
"done" to indicate stop of division.
It is taking approx 300 clock cycles for the division to complete

How do I stop the rest of the circuit from executing while this is being done?

I have to generate the following code

if x>p
    c=-p/x;
    m=(c+10)f
else
    c=-x/p;

The division here is taking 300 odd clock cycles to complete and I have to stop the assignment of m until value of c is calculated from division
thanks for the help :-)


texts: How can the value of a resistor be measured if it goes straight to ground?

texts:
I'm looking to integrate a LiPo charging circuit into my PCB, and found the MCP7831 IC. It's got a PROG pin, that allows you to change the behavior of the IC by use specific resistor values between that pin and ground.

But I'm wondering how it knows the value of the resistor?

I would think to know the value of the resistor your + voltage is applied to one side, and the other goes to an input pin of an IC that measures the lowered voltage. But if it connects straight to ground, how does the value get measured?


texts: Auto-switching between power sources with multiple voltage outputs

texts:
I'm looking for a bit of initial direction or input on a circuit to accomplish two relatively simple tasks: (1) automatic switching between a li-ion battery pack and 120VAC and, (2) supply multiple output voltage taps. I made up a rough diagram of what I'm thinking, which isn't technically accurate but hopefully explains my general plan. I'm really hoping to minimize the number of PSUs due to space (and cost), and if I could eliminate a battery charger that'd be great too. But, I've been unable to identify a li-ion charge circuit that would support my 12S battery design.
The power amp is the primary draw, and it has a wide voltage tolerance (25-50VDC) but requires a higher voltage to maximize the output. So, my thought is to design everything to supply as close to the 50VDC as possible and step down from there in order to power the other devices directly. There's also a 120VAC device that contains an internal PSU with multiple DC voltage taps, which I'm trying to determine how to power when on battery. Obviously I could use some sort of inverter, but I'm not sure how that would fit in to everything.
Any input, advice, or initial direction would be much appreciated!


texts: What is a Thyristor Switched Series Capacitor (TSSC)?

texts:
I'm struggling to understand the physical difference between the Thyristor Switched Series Capacitor (TSSC)  and the Thyristor Controlled Series Capacitor (TCSC).

From this book, I understand that a  TSSC permits discreet control of capacitive reactance, while TCSC permits continuous control of capacitive and inductive reactance. The book also mentions that TSSC is more comonly employed, however, when continous control is desired, the TCSC is employed.

This paper gives a good outline of what a TCSC is and how the thrysitors are controled. The diagram for a TCSC is shown below:

However I cannot find a diagram for a TSSC. How does the system differ from the TSCS? And what would the diagram of the TSSC look like?


texts: Measured VS Ltspice Difference in P-Chan JFET Attenuator

texts:
The following circuit is a slow switching +-15V audio signal attenuator:

Why are the measured voltages (shown in white boxes) so different from the SPICE values (shown in the graph)?

Note that circuit works fine in practice because the J175 pinch off voltage is only 6V. I just want to understand:

1) where the voltage drops are coming from and
2) why LTSPICE didn't simulate them.

Specifically, if the voltage drop across R4 is 12.6 - 9.2 = 3.4 and we compute the current of 3.4 / 470K that's 7.2uV. I don't see where the 7.2uV could be going?

I thought the gate current of a JFET was picoamps? If I temporarily remove the capacitor the voltages don't change at all so it's not the cap leaking. I've reproduced this on a soldered board and then bread-boarded with completely different set of parts.

I got the J175 model from a popular fet library on the Interweb. Graph lines are control signal blue, NPN collector green and gates red.

What am I missing here?


texts: DC-DC Converter Datasheet - What does "Temperature Coefficient" Refer to?

texts:
I am trying to understand all aspects of DC-DC converter datasheets. One thing I am unsure of is what is referred to as "Temperature Coefficient." An example of this can be seen in the "Output" section of this datasheet.

I am thinking it may refer to efficiency? So the rated efficiency drops 0.03% per degree Celsius of temperature rise? It seems like it should rise more than that.. Or does it perhaps refer to voltage accuracy?

Is there a general rule for this sort of thing across DC-DC converter datasheets, or is it necessary to email the individual company?


texts: Nodal analysis how to determine high and low potential for current

texts:
The rules for nodal analysis is that current flows from the higher potential node to the lower potential node, with the mathematical equation being:

\$I = \frac{Vhigher-Vlower}R\$

However, how do we determine which node has the higher potential. Ground node against any other node is easy because ground is always \$0v\$, but for other nodes (say Node A to Node B), how do we determine which is higher.

Edit: In the current question I am doing, I am given the arrows for the direction of the voltage, along with the direction of the current (This is just a practice question). So I am assuming it is related to one of these two but which?

So far I have gotten the KVL and KCL, along with \$VoltageA = 6v, VoltageD = 0v\$.

I have no idea how to proceed from here


texts: A better power supply for microcontroller circuits

texts:
I've been playing around with PIC microcontrollers for a while now, and have had a fair bit of success, however I sometimes get unexplained resets and sometimes need to cycle the power a few times to get my device to start working.

I think this is down to my simplistic PSU.

I normally throw together a mains transformer, bridge rectifier, linear regulator and a few capacitors.

Does anyone have a circuit diagram of a better more efficient PSU that is easy to build on stripboard and doesn't cost too much?


texts: What happens in a generator so that we get a sinusoidal voltage as an output?

texts: I read this online, " For a travelling magnetic field in a circle, the induced magnetic field in the armature of the generator will be sinusoidal. That's why the generated voltage is a sinusoid, exactly at the same frequency as the generator is turning."  I understand that the angular motion is responsible for the sine wave, however, I am very confused about what induces which. I thought magnetic field was either created with a permenant magnet or flow of charge, and that what magnetic field induces was emf, not another magnetic field. Sorry, if these all sound stupid, it all gets confusing after some time, and I don't know where to start.


texts:
I'm trying to control some ESC and brushless motors using a raspberry pi. I used the pigpio library to control them using servo pulses. But it seems  that my motors wont increase rpm after a limit near 1740 (servo pulses). Whenever I exceed this level, the motor slows down to a certain speed and wont increase speed again. Also, it wont start rotating until the level of 1660. If there is anyone who had this problem before, please inform me because I'm a bit newbie to this kinda stuff. My motor and ESC's are these by the way:

https://www.banggood.com/Racerstar-3660-Brushless-Waterproof-Sensorless-Motor-80A-ESC-For-18-110-Short-Course-Rally-Car-p-1069993.html?rmmds=search&ID=511868&cur_warehouse=CN

Thanks for any answer...


texts: CAN - duplicate message at receiver possibilities?

texts:
This Link says a that :Use of sequence numbers fixes the duplicate error.

When can duplicate message end up at a receiver?

If a node detects an error, it sends out an error flag and when all the other receiving nodes detect the error, they too send out error flags and destroy the received message. The transmitter then resends the message again.

Im not aware of the possibilities of a duplicate messages being received...

Plz Help as i must decide if sequence number must be used or not in my messages.

Thanks


texts:
I thought I'd be able find this easily via google, but apparently not, so:
What pressure can 'normal' consumer-packaged chip withstand?

(To give a specific example, say the OMAP4430)

I'm presuming it's complex parts like this that would break first under high pressure, instead of simpler passive parts, or the PCB itself.

I'm also assuming the pressure is applied hydrostatically - so air gaps under components, provided they are not completely sealed, will be the same pressure as the external pressure.


texts: Why would a switching power supply fail with a battery supply?

texts:
I have this power supply circuit I have been using for a couple of years:

I have put it on a lot of boards, and ranging input voltages up to 50 volts (as long as the capacitors are rated that high). I had never been able to get it to fail, and I even load tested it drawing the maximum off both rails, and it shutdown before it failed. However, I had always powered the input from an AC/DC converter.

I recently began using a board with this supply on it in a battery powered application (24 volt - 2 12 volt lead acid in series). Everything worked fine for months. I was charging the batteries separately using a car battery charger. I then bought a 24 volt charger, which seems to work well. After charging the batteries (there are two supposedly identical systems) I powered up and one of the power supply circuits blew on the board. In the second system all was fine.

To summarize my troubleshooting from that point forward: that one board that didn't fail on the original power up after charging is the only one that I can get to work on this charged battery system. I have replaced the LT3988 and tested it in the lab off a lab supply (up to 40 V) and AC/DC brick, and it works perfect. I take it back to the fielded unit and plug it up to the battery (only the supply connected) and the switcher immediately smokes. I populated an entire new board, the switcher works on a lab supply, and immediately smokes on these batteries. The one that works, works on both systems...but I cannot recreate it.

So...what problems can you guys think of when using a battery supply that are not encountered on an AC/DC converter? I can think of a lot of more problems powering a switcher with a switcher, so I need your help.

Edit: When powering this circuit from an AC/DC brick, I usually have the brick plugged into AC and just plug the barrel jack connector into the power input on my board. When powering from a lab supply, I obviously just press the button. When powering from the batteries there is a switch in the line between +VDC and my board.


texts: I am working on a project to print and CNC PCBs double sided simultaneously. The design for this project would require me to install my printer upside down. Can anyone think of any part of the printer that would have trouble working against gravity? Would I need special ink cartrages/Print heads? Would it even be possible?


texts: Do MOSFETs have a diode built into them?

texts: I have noticed that a MOSFET symbol has a little diode in it (or at least what looks like a diode). Does this mean I do not have to worry about using a diode in a circuit that runs a motor using one? I would have used a diode in order to prevent reverse voltage from turning the motor by hand.


texts: I have a drawing border in DXF format that I need to get into PADS.  Is there a sensible way of doing this, without needing some add-on software?


texts:
I'm reading the datasheet of this DAC. Page 27 states:

  In many industrial process control applications, it is vital that  the
  output voltage be controlled during power-up and during  brownout
  conditions.

What are "brownout conditions"? Why is it "vital" that the output voltage be controlled during brownout conditions?


texts:
I'm designing STM32f446 chip in PCB in a project. It will be programmed through SWD.

but I'm stuck with (BOOT0) pin. I want it to be (0) as recommended.

The thing is that there is no enough info. about it.

I've looked at the data sheets to find the rating (voltage and current), I just found the voltage to be 9V !

I need to select the pull-down resistor, what should I do?

thanks,


texts: What is the purpose of this disk over a Samtec connector?

texts:
With beautification in mind I decided to attach 3D-STEP models to elements on my PCB.

One of them is a connector from Samtec. They do provide a STEP models for a download, but it was immediately suspicious to me, that the preview had this weird disc over the connector. At that moment I thought it was some kind of glitch and proceeded downloading STEP model regardless.

See the image below:

Attaching the downloaded STEP model I was surprised by this disc again. Turns out, it was also exported into STEP model along with the connector. Unfortunately, this serves bad for the purpose of "beautification" :)

Questions are:

What is the purpose of this disk?
Is there any way to download a STEP model of Samtec connector without this disk?

For a reference, the connector is QSH-030-01-F-D-A-K


texts: Is there a reference PCB design for hobbyist manufacturers?

texts:
I'm considering using a PCB manufacturing house to make me some boards.  Since you have to pay, I'm trying get my PCB designs correct but will unavoidably have to go through a learning process.  My concern is that this process will be expensive as I design a board, send it off, see the mess that comes back and so on till I get it right.

In KiCAD the plot menu has about 10 options x several layers which equals a lot of combinations and perhaps cost.  It also will take time as boards go back and forth to the manufacturer.  If that manufacturer is in say China, that's even more time.

It would be very useful to have a reference file(s) that is formatted to industry norms.  I've looked at some manufacturer's web sites ard they all seem short on helping newbies even though they are intended for hobbyists. They seem far from friendly and warming.   The issue seems to be that one size fits all.  KiCAD can produce a PC motherboard, and some of the PCB manufacturers can make one.  I want a circuit that blinks a single LED with a DIP timer chip and a couple of mounting holes.

I would expect it to have correctly laid out tracks.  Some mounting holes, perhaps logos /graphics on the board.  Correct sized component holes.  Just the basics really to cut my teeth on and save a lot of needless waste.  We all have to learn to walk before we can run.

Do such reference files exist?  Where is my "Hello World" PCB example?

Just to be crystal clear, I'm not asking for recommendations for cheap PCB manufacturers.  I'm asking for reference layouts of how I should layout to industry standards whilst being a hobbyist.


texts: Design recommendations for an array of different forward voltage LEDs

texts:
I'm putting together a custom aquarium lamp as a hobby project and I'm not sure of the best way to configure the LEDs.

All the LEDs are Cree and I am looking to push ~800ma through them.

5x whites with a forward voltage of 3.4v (XTEAWT-00-0000-000000H51)

2x blues with a forward voltage of 3.4v (XTEARY-02-0000-000000Q04)

3x reds with a forward voltage of 2.1v (XPERED-L1-0000-00801)

I am not sure whether to go with a dedicated LED driver or a standard 12v strip supply. I would prefer a 12v supply as they are available locally.

I figured to run with 12v:

3.4v - 3.4v - 3.4v - 2.20hm 5W resistor = 818ma, 1.5w in the resistor.

parallel

3.4v - 3.4v - 3.4v - 2.20hm 5W resistor = 818ma, 1.5w in the resistor.

parallel

2.1 - 2.1 - 2.1 - 3.4 - 2.7ohm 5W resistor = 851ma, 1.8w in the resistor.

I am concerned about the power dissipation in the resistor being high and adding to the thermal load.

Is there a better way to go about this? I looked for 'dual channel' LED drivers so I could hook up two strings of 3.4v and 2.1v but they don't seem to exist.

I considered using two 800ma drivers into one series line of 3.4v and one series line of 2.1v but that seems ugly.

I looked into some preassembled aquarium lamps and they seem to use SMD resistors only, so there must be a trick I am missing.


texts: Controlling multiple PIC microcontrollers with a 2-wire setup via GPIOs

texts:
I am working on a small project that consists of a PIC18F4550 acting as a master and other various PIC18F4550 acting as slaves. The distance between the PICs will be more likely about 30 meters (~100Ft). I would like to communicate between the PICs via a 2 wire interface as the image below:

The blue wire ON RA0 will be sending a clock signal so that the PICs will sync with each other and sending data will be more reliable (at least I think so).

The red wires will be connected to other PICs.

The target is to send an array of bits on the GPIO like :

Command: PorchControl("BULBS ON")
This will be converted to binary
01000010 01010101 01001100 01000010 01010011 00100000 01001111 01001110
binary streamed via RA1
SLAVE 1 will convert binary back to text
SLAVE 1 will parse the command and switch on the bulbs in the porch
SLAVE 1 WILL SEND a confirmation BACK.

Questions:

-1- Is it possible to do in a much more convenient manner?

-2- Any tips for the programming piece about Txing and Rxing the bits?

Thanks,
J. Wayne


texts: The title may seem ridiculous, but I am unable to find a ChipFet that has a 3V gate, and can switch 12V, I am unable to provide 5V to the gate. Are there any well known SMD small and compact Mosfets that can be activated with 3V/3.3V? Thanks!


texts: How to calculate the expected output current being drawn by a speaker?

texts:
I'm trying to calculate the current that will be drawn by a 4ohm 3W speaker from a MAX98357a IC amplifier. From my understanding, the amplifier takes in a I2S audio signal (which originates from an ESP32), converts this digital signal to analog then passed through an amplifier with a programmable gain that will be outputted directly to the speaker.
From this I don't fully understand how I can calculate the expected current that will be drawn by the speaker. It is important since this circuit will be powered from a 2500mAh 5V lipo battery and needs to run for a reasonable amount of time.
By searching through the internet, I can see that power output is the important factor in this calculation. Looking at the amplifier IC datasheet, I can see that the output signal level can be calculated by the below equation.
Output signal level (dBV) = input signal level (dBFS) +
2.1dB + selected amplifier gain (dB)
From another stack exchange question, assuming the input signal uses the maximum range, it will result in 0dbFS and choosing a gain of 12dB, the output will result in 14.1dBV. With this number and using the decibel voltage equation 20log10(V/Vo) or 20log10(V) = dbV, the output voltage that will be seen from the speaker is 5.06V.
Using that number and I=V/R I can calculate that the expected current draw will be around 1.26A but that seems to simple and ignores a lot of other things. Overall this all confuses me and don't have any clear ideas on how to tackle this problem.
Any explanation on the principles of how this circuit will play out is best or just any guidance to any other material I can read on.
P.S. This is my very first post on Stack Exchange so sorry for any mistakes in advance.


texts:
I have a question regarding setting timing constraints on enable signals.

In my vhdl design I use an enable signal, to gate when the process needs to sample my input data. The enable signal is derived from the input data, using another vhdl component.

My clk is 27MHz, but the enable signal is maximum present at every 2nd cycle, so its period is minimum: 1/13.5MHz.

When I compile my design, I get warnings on the clk timing constraints, due to my algorithm. But can I make some timing constraint on the enable pin, this could probably make the vhdl code compile without warnings, by effectively only requiring half of the clk period.

test : process(reset, clk)
begin
  if reset = '0' then
     ...
  elsif rising_edge(clk) then
    if en = '1' then
      ... vhdl algorithm is here ...
    end if;
  end if;
end process;


texts: the output in buck converter multi sim 14 is too low

texts: it is required to use UC3842 to make a Buck converter that has 68V input and 29 output. i did the calculations for the buck circuit however not for the UC3842. i dont know how to calculate it. i been playing with its values for a while , the max i got was 9.8 volt. any help would be great. best help is telling me how to calculate these values or just telling me the values .


texts: Micro SD card operating voltage: 1.8 V specified?

texts:
All manufacturer SD cards work in 3.3V based on SD specification.

In our recent design we have tested SD card connector power to 1.8V, I thought no SD card will boot but some of the SD card are boot some of them are not booting.

Could you please clarify me if there is any specification changes in recent microSD cards standards?


texts: About impedance matching for high frequency and divider effect

texts:
----- 2013/11/08 modify my question

I have an 'A' source has 5 MHz signal (0-5 V square wave) without knowing input impedance and a receiver 'B' has 75 ohm input impedance.

As I know I have to match the impedance match to avoid the reflection effect, but I will have the divider effect if I parallel a resistor to the 'B' input end or series connect a resistor to the 'A' output (means not 0-5 V input for 'B' anymore).

Should I do a 2x amplifier circuit to make it 0-10 V first to avoid the divider effect and use this op as a buffer and series connected to a 75 ohm to make the output impedance as nearly 75 ohm?

If there is any information I can study, please let me know.

Thanks for the help.

-----2013/11/08 upload the 'A' spec

-----2013/11/08 upload the 'A' output via Oscilloscope

sync output with 50 ohm parallel

sync output without 50 ohm parallel


texts: A question about the Clock control register high of I2C bus

texts:
While reading the part about I2C bus of reference manual of STM8L MCUs, I found that there is this register named Clock control register high (I2C_CCRH). Its 6-th bit, referred as "DUTY", can be used to set the duty cycle under fast mode. When it is set to 0, it means that the ratio of t_low (low phase time bus clock)  to t_high (high phase time of bus clock) being 2/1. When it is set to 1, it means the ratio being 16/9.

My question is: What is so magical about the ratio 16/9? In other words, how was this number determined in the first place?


texts: I am trying to make a touch switch using an Arduino and a MOSFET. I have managed to get an LED to turn on when the pad is touched and it seems to work well (fully on when I touch it and fully off when i don't). However, when I try to replace the LED for an Arduino pin pulled high (internally) I run into problems. Sometimes the switch is read as low when I touch the pad, but other times it just becomes unresponsive. Could anyone see where i am going wrong? Thanks.


texts: Micron NOR Flash datasheet clarification

texts:
I am working to create a controller for a Micron NOR Flash Memory (MT25QL128ABB) and I am having difficulty writing/reading the device. I would like to know if my procedure is correct:
Write Procedure:

Send the write enable command (06h)

Latch the write enable command in by raising the #S line

Lower the #S line

Send the page program command (02h)

Send the write address (24 bits)

Send the write data (I am writing 96 bits)

After the last bit of the write data has been sent, raise the #S line

Read Procedure:

Lower the #S line

Send the read command (03h)

Send the read address (24 bits)

Continue sending clock signal for 96 bits

After the last clock has been sent, raise the #S line

The datasheet is as follows:
For a read:

For a write (page program):

After I attempt a write, I read the status register and I see that the "write enable" bit is still set. The datasheet indicates that the write enable latch should be cleared automatically after a page program command whether or not it was successful. This indicates to me that the page program command is not being executed.
When I attempt a read, I would expect since I haven't successfully programmed the memory I would get all 1's. The device does indeed return all 1's on a read however it continues to output for a set amount of time even after I have stopped the clock and raised the #S line.
Note that I am able to successfully read the status register, flag status register, device ID, set the write enable latch, and clear the write enable latch at will. Before attempting a page program command I always send the bulk erase command to ensure the device is erased. I am running the CLK to the memory device at 20 MHz, well below the max. frequency.
Here is the timing diagram of what I see when I try a read:
(not to scale)

Here is what I send for a write:
(not to scale)

Note that these diagrams do not show the actual number of clocks