texts: Why does the output of a transformer increase when connected to a battery for charging?

texts: I have a 110VAC- 14VAC 5A transformer with me. I have the output rectified and it shows like 13.8VDC. But when I connect it to my 12V SLA for charging it output rises to 15.8V instantly and I hear a lot of fizzing from the battery. WHy does this happen?


texts: How to easily power multiple components with differing requirements?

texts:
I'm a long-term software developer who hasn't touched a soldering iron since Uni. I've been mulling an idea for a hardware project for some time, and have cajoled a raspberry pi into managing the following devices:

Touch screen
e-Ink Display
2 x Stepper Motors [Very infrequent use - <5 mins/day]
Thermal receipt printer [20cm print ~hourly]
GPS/LTE module [On for extended periods (hours)]
Arduino Zero [Not actually connected yet, but will be "always on"]

I have a bare-bones implementation running, and -now I know it's possible- I'm turning my attention to packaging it all up.

At present, I've got half a dozen DC power supplies connected to the various components.

I've started to put together a rough layout (for scale, the box is 28x18x13cm internally)

Some of the devices offer power saving modes which I intend to use when possible, but it'd be nice to be able to use it all simultaneously if required.

The pi 3 B+ itself requires 5V and up to ~2.5A. That's powering the touch screen, e-ink display and stepper motor driver board.

The motors themselves require a 12V supply (350mA/ea)

The thermal receipt printer requires 5-9V at 1.5A.

The GPS/4G module requires 3.3V/1A.

So that's....

12v/700mA [Motors]
5V/2.5A [Pi/Screens/Motor Driver/a few sensors]
5V/1.5A [Printer]
3.3V/1A [Comms]
3.3V/1A [Arduino]

I know some of those are max draw (eg the Pi) but I'm actually quite close in that case (largely thanks to the touch screen). Eg if  try to run the comms board from the Pi's 3.3v rail, it's enough to trip the pi's power.

So, my primary question is... How can I (cleanly) run all of this from a single wall socket? Due to my lack of experience, I've got a preference for keeping everything in the case low voltage (or at least keeping mains voltage fully enclosed/isolated).

Ease of integration is a consideration considering my soldering "skills" and scarcity of equipment.

I'm hoping that the subsequent step will be to use a large power pack, and have found this https://www.amazon.com/NOVOO-22500mAh-Universal-Compatible-Smartphones/dp/B07JKP3PWY but haven't really had time to look into it yet (presumably converting up to 240v and back is wasteful). I mention it in case the idea of a power pack changes the answer significantly.


texts: > 20 Minimum Hfe on a BJT Power Transistor?

texts: I'm having trouble finding what I want due to the way mouser.com limits searching on BJTs.  I'm trying to find out if anyone manufacturers a medium to high power BJT with a gain of at least 30.  The higher the better.  The classic 2n3055 has a minimum gain of 20.  I want something higher if possible.  Does anyone know if there's anything out there with such high gain and also moderately high current capability?


texts:
I know the answer is AC + ~AB, but how?

I have tried:

B(~A+C) + AC and stop.

Also, I have tried:

AC + BC + ~AB and have stopped.

There seems nowhere to go in either case.


texts: Understanding Operational Transconductance Amplifiers

texts:
I understand the high-level function of OTAs, that they provide an output current proportional to an input voltage. But what I don't understand, and what I can't seem to find any information on online, is exactly how they're used and what the function of the different connections is.

The most pressing questions I have are thus:

What is the function of \$I_{bias}\$? Why are there diodes between this pin and the two inputs? I've seen them called linearizing diodes; how do they linearize the response of the circuit?
What is the function of \$I_{abc}\$? As I understand it, it provides a scaling factor; is this correct? How does it do so?
What is the (exact or approximate) formula for \$I_{out}\$ as a function of \$V_{in+}\$, \$V_{in-}\$, \$I_{bias}\$, and \$I_{abc}\$?
What are the standard application topologies for an OTA? Op amps have the standard inverting and non-inverting amplifier topologies, and slightly more complicated summing amplifier and difference amplifier, integrator and differentiator, but are there any common circuit idioms for the OTA?
Internally, how does an OTA work? (this is perhaps best left to a separate question, though.)


texts:
I'm trying to measure a voltage across an Rsense (R2) in a galvanic isolated loop that flows a current (4 - 20mA).

My Op Amp has Vcm +20V. But I'm worried about the voltage in nodes B and A with respect to GNDA.

My intuition is that the galvanic isolation will be corrupted and GNDA and GNDB will have same potential.

What would be the voltage in these nodes with respect to GNDB if the isolation breaks?

I know that I could measure directly to R1 but I want a circuit that can be used to measure shunt resistors like in high current measurements

simulate this circuit – Schematic created using CircuitLab


texts: Can some body help me understand some parts of a schematic circuit?

texts:
I have  circuit schematic, and I do not understand what are the parts in red circles and what do they do.
The schematics are from a movement sensor using a PIC micro controller, infrared LED and an infrared receiver


texts: Matched dual 4-order active low-pass filter with two dual version opamp

texts:
I want to make two "matched" 4-order active filters, the -3db frequency will be below 100Hz. I have several choices to choose:

Choose four single version opamps. Each filter uses two of them.
Choose two dual version opamps. Each filter uses one of them.
Choose two dual version opamps. Each filter take two half-of-one-opamp.
Go directly to the quad version.
If there are more better one, please tell me :).

Is it worth to consider this when design an active filter? If so, then which choice are better? The quad version may derate in their performance, but may be routed easier. The single version may can't matched well, etc..

Any suggestions?


texts:
I am trying to design a protection circuit for a single cell lithium battery, and I was hoping for some advise on what things I need to consider.

So far, my thoughts are to provide low voltage cutoff using a comparator. A fixed voltage would be provided to the comparator using a diode, and a variable voltage from a potential divider between the battery terminals. When the voltage from the potential divider goes below the voltage accross the diode, then the comparator would turn off a MOSFET that allows power to the load. So, while the battery is above ~3V, the MOSFET stays on and powers the load, otherwise turns off and then the only current draw on the battery is from this circuit, which should be very low, and hopefully take a long time to deplete the battery to a problematic level.

I plan on having a battery charging module connected directly to the battery terminals. Is it possible that while not charging, this would allow the battery to discharge?

Can anyone tell me if the design I described is a suitable way to implement battery protection, and if there is a better way. Are there any ICs that would be recommended specifically for this purpose, and what are their advantages?

Thanks in advance.


texts: Is the transformer's secondary winding too large?

texts:
I recently took out the windings from an old microwave oven transformer and was planning to use the core for a 120 to 6.3 VAC step-down transformer (total power 160 W max).

The secondary winding (which carries the 6.3 V and 25 A) is a 12 AWG wire (shown in yellow). I noticed that the loop wasn't able to stay tightly wrapped around the core.

Is the secondary loop too large for my transformer?

Before it's brought up, I am aware that the primary loop has yet to be attached.


texts: Multi-channel high frequency signal acquisition

texts:
I have to design a test bench for a device that has more than 1000 outputs. The voltage of these outputs will be about 10mV peak-to-peak, the frequency will be in the range of 100MHz (for the carrier) and between 0Hz to 10kHz for the envelope that I am interested in.

I plan to buy 16 acquisition boards (NI PXIe-6361, X Series Multifunction DAQ (16AI, 24 DIO, 2 AO), 2 MS/s single-channel sampling rate input) to collect the data coming from the device, but I need some advice regarding how to design efficiently the interface between the device and the DAQ.

I planned to use multiplexers to reduce the number of DAQs, because I know those parts are expensive.

Do you know if there are commercial products that can take out the envelope of multiple channels?

If no, I may have to design my own board probably with one mixer and one low-pass filter per channel.

What I would like to know is : what is the most effective way to design a huge number of amplifier/demodulators to get the envelope of 1000 low-voltage signals?


texts: GoPro Hero 2 Battery Elliminator? (3.7v versus 5v)

texts:
I have an old GoPro Hero 2 who's external USB plug has failed, and I have no way of powering it externally. I need to run this GoPro using an external wired power source (available over a 5v USB).

There are battery eliminators available for the Hero 3 (example) that replace the battery unit with a USB cable connecting directly to the device's leads.

Is this product nothing more than a glorified power cable inputting 5V? Or is there a voltage regulator and thermistor dummy circuit in there? Could I build my own or modify something like this to work with a GoPro Hero 2?

For reference, the battery of the GoPro Hero 2 and 3 are 3.7v.


texts:
I have a 12kva (10kw) ups and I want to power it from a 24v battery bank. The dc input is 192dc input from the battery side. I was thinking off getting a 24 to 220 Inverter and rectifing it to output 200v dc if possible. I know a little about electronics so not to much off a noob. Thank you for your time

This is the ups that I have 8 to 18kw
https://www.jsfleming.com/wp-content/uploads/2016/07/sl-24870.pdf


texts: Simple DC voltage scaling with two ranges, lower range voltage limited

texts:
I am attempting to monitor DC voltages that can range from 0 to 250V with a micro controller. A simple voltage divider should be suitable for the broad range up to 250V, with somewhat coarse resolution. A second voltage divider for when the voltage is not more than 25V will give me improved resolution at the lower voltage levels. I have no problem using two distinct A/D ports on the micro for each of the dividers. Output of both dividers should be 0 - 5V. I've estimated the values of resistors for the two dividers.

My question is:
How can I limit the voltage seen by the second divider so it never exceeds 25V even though it is monitoring the same potential source? I've attempted to utilize a zener in the circuit to clamp the voltage to not exceed 5V but it always seems to effect the linearity of the divider on both the very low end and high end of the ranges.
I'm new to designing hardware circuits... as a software guy, I'm really starting to appreciate what's involved in developing analog hardware. Thanks for the help!


texts:
I've just placed a large FPGA in a QFP package with 144 pins in the middle of my board, and would now like to add bypass capacitors on the power supply pins.

The power and ground pins are either next to each other or at least in close proximity, so placing the capacitors manually is not that difficult, but I can see myself manually routing the entire vicinity of that IC in the process, which I'd rather avoid.

I have two kinds of I/O: About 40 pins with fmax at around 1 MHz, running a PWM coding, and an SDRAM interface; the SDRAM I have runs at up to 143 MHz. I suspect I should avoid running the latter kind through too many vias, and instead prefer to create supply vias from the bottom layer to the capacitors.

Is there a way I can automate the capacitor placement?
If not, is there a good strategy for getting good results?


texts: Trying to Gradually Increase Motor Speed

texts:
In Short:
I'm trying to create a soft start mechanism so that when a 12V DC source is turned initially connected, the motor takes 5-7 seconds to get up to full speed.
Longer Explanation:
A lot of other posts deal with preventing inrush surges on the order of milliseconds, but I could find very few that want a 5-7 second increase time. It can be linear increase in motor speed, or whatever is easiest to build, as long as it is gradual and the motor doesn't run at full speed initially. The motor will draw about 2A current, 3A max. I don't want to use a microcontroller because it seems redundant in this situation.
What chips/parts/circuits should I consider if I want to achieve this?
 Am I wanting some sort of variable current limiter?
 Some sort of inductor flyback diode thing?
 Some RC rig with a capacitor in parallel with the 12v source?
 Some thermistor circuit?
 Is there a 12v 3A motor controller than can do this automatically for me?

I'm not experienced with EE, and I would appreciate any guidance on how you would implement a circuit like that. The main thing that I'm trying to optimize for is ease of building the circuit, and reliability.


texts: Bypass button press on fan for direct power on when plugged in

texts:
I have a fan that I want to plug into a thermostatically controlled power outlet so that the fan comes on when the temperature reading reaches a certain set point.

The fan is currently wired through an on/off switch which also included a switch for a motor that operated the oscillation of the fan. I'm not using the oscillation motor/function.

Originally I was thinking I could just cut the three wires going to the motor and the same three wires going to the switch circuit board, match colors and solder them together. But there are a couple of capacitors on the board. Now I'm not so sure that would work. What is the correct way to bypass the fan switch for direct power on?

Here are photos of the front and back of the switch board.

The button on the left operates the fan.

K1, on the right, is the fan button.


texts: 'Subcircuit is undefined' when designing PWM with TL493 in PSPICE

texts:
I am trying to design a PWM for my converter using TL493 in Pspice and i am getting an error.

ERROR(ORPSIM-15108): Subcircuit model591_tl493 used by X_U1 is undefined

i am a beginner to both Pspice and circuit, so i don't know what it means. Please help me with it.


texts:
I am using relay circuit for inverter application. It's 12V relay having coil and two contacts for connecting line and neutral respectively.

But, I am not getting closed connection when I am giving 12V to the collector and Logic 1 to the base from dsPIC. Logic 1 from dsPIC is at 2 volts.

Relay is ALA2PF12. I have attached schematic.


texts: Multisim - How to create a 2-pin red/green LED in one part

texts:
I would like to pass the output of an LT1413CN8 op-amp through a 2-pin red/green LED (looks white when off) and back to it's inverted input.

In Multisim, there is a red/green LED option but that is a 3-pin configuration.  If I drag and drop a green LED and red LED from the component menu, wire them up tail to head, and transfer the design to Ultiboard, 2 separate LEDs and their footprints appear (which is expected.)

Is there anyway to build a custom component made up of those 2 LEDs, but with only 2 pins and 1 footprint?

Or, is there a component that I am not seeing in the component menu that solves this issue?

Or, is there a recently-updated library with this part?  I am using Multisim 14.1

Thank you.


texts: Were can I find a simple CPU Design tutorial / book?

texts: I basically want to know how to make(In hardware and in a simulator) a simple CPU. A book that covers low level stuff like, like logic gates, and more high level stuff like a complete CPU. Ive tried to find this book: http://www.amazon.com/Elements-Computing-Systems-Building-Principles/dp/0262640686/ref=ed_oe_p but here in Argentina it costs double to use credit card online, and I don't want to use 60 dollars on a book, i looked for a PDF of it, and I didn't find anything. I also don't want a complex collage level 1000 page book, I'm only 14 years old. The "best" and clear information on how a computer works I found were in video tutorials on how to build a redstone computer in the video game Minecraft.


texts: Interpretation of Laplace transformed function and Laplace vs Fourier

texts:
I'm used to Fourier transform, i.e. I have a good unterstanding of how to interpret a Fourier transformed function. But I'm struggeling with the Laplace transform. What's the meaning of its complex parameter \$s = o + iw\$ (where \$w\$ is the 'normal' frequency)?

I also don't see the advantage of the Laplace transform when it comes to transfer functions. It seems to me that in the end one is just interested in the spectrum of the analyzed system which coincides with evaluating the transfer function just on the imaginary axis ('normal' frequencies). So why one wouldn't simlpy use the Fourier transform to define the transfer function like this:

$$G(w) = \frac{F\left(y(t)\right)(w)}{F\left(x(t)\right)(w)}$$

where \$w\$ is real, instead of:

$$G(s) = \frac{L\left(y(t)\right)(s)}{L\left(x(t)\right)(s)}$$

where \$s = o + iw\$.


texts: Designing Precision Instruments: what to self-calibrate, what to guarantee by design

texts:
Context: I am working on a precision instrument (digital output) to measure current to systems, in the range between 300nA and 300mA (120dB).  However, I hope that this question can be answered generically enough to be a useful guidance for the design of other precision instruments.

In the design of a precision instrument, I see two principal ways of achieving precision:

use precision (low drift, high accuracy) components (amplifiers, resistors, references).  Design the instrument so that after initial (offset) trim, offset and gain are precisely what they should be.  Precision is guaranteed by design.
design in a self-test and calibration section (probably based on precision parts), and during operation of the instrument use the embedded calibration stage to (digitally) account for offset and gain variation.  Precision is guaranteed by self-calibration and post processing.

To me, it seems that (2) is not easily possible for a purely analog instrument, while it is likely more cost effective (for the same measure of precision) than (1) for systems that digitize measurements.  However, when is (1) the appropriate choice even for digitizing systems?

Which design principle is appropriate in what case, and why?


texts: Why does WiFi Signal strength increases as I touch the Wifi Receiver

texts:
I have a cheap WiFi USB receiver connected via a USB Extender. I get good strength but poor link speed specially when the device gets hot. Like sometimes hot to touch. The link speed drops dramatically when the device is heated but as soon as I touch it, the link speed gets back to normal and better (to an extent).

ADDED LATER For both the tests, I am buffering a YouTube video at 480p.

Before I touch:

After I touch (more like hold it between my fingers):

PS: It was quiet warm.

Now the question is why does this happen?

I have a few theories:

My Skin's capacitance increases the WiFi range by acting as an antenna
My (or anyone's for that matter) body is 70% water, which means it absorbs microwaves effectively, that could help the device gain signal/link strength.
I act as a heat sink for the USB device which helps it to regain its effective working (my bets are on this).

So why does this happen, is it any of the reasons I have mentioned or something different.

Regards

PS: My tags are aweful, if a mod/anyone want to change/correct them you are more than welcome.

EDIT

I just noticed something. Tighter my grip, better the link speed. So I guess it has to do with something that increases with surface area.


texts:
I am currently designing a CAN system for a 3.3 V board and I am looking for some insight regarding CAN transceivers. These are my goals from the CAN system:

No influence on the CAN bus if in read-only mode.
Terminating resistor - a unit may sometimes need a terminating resistor. Is there a method to overcome that?
Voltage - there are not too many 3.3 V operated CAN transceivers. Is it worthwhile to look for one to save a regulator or is the special transceiver with higher cost and performance worth it?
Security - the system is installed in a car. The main importance is that the system will do no harm either in receive-only mode and in trasmit mode.

What should I look for in the datasheet to accomplish these goals? Are there special methods I should look for and read about?


texts: How to connect battery pack with AC/DC out to marine amplifier with screw type terminal block connection?

texts:
I have some basic questions about powering amplifiers and connection types that I could use help with. I'm trying to power some Peavey 10 inch satellite speakers on a bike trailer using a lithium battery pack. The Lithium battery pack has an AC DC connection type ( 2.1mm X 5.5mm I think) and this connected fine with my basic Pyle 90 amplifier. The problem was that this little setup didn't give the speakers enough (they were quiet). I also got too long of speaker cables so I'm sure that diminished it too.

I'm trying to get a bigger amp, but I'm noticing that most amplifiers have the screw type terminal block connection. I'm not sure if these are compatible or not or what would it take to be able to connect my lithium battery pack into an amp that has the screw type connections.

Can anyone give me some tips here? Is it possible to connect these two?

How to connect this?

to this?

Kenwood amp link: http://www.kenwood.com/usa/car/marine/kac-m3001/


texts: Direction of resulting I through simple circuit with 2 voltage sources separated by 2 resistors in series?

texts:
I'm wondering how to find out which way the resultant current flows when you've got a really simple circuit with two voltage sources separated by 2 resistors in series. See the below circuit (the bottom part is supposed to be earthed in the original circuit, I guess this applies to any equivalent circuit for analysis). The current direction on the diagram is supposed to be the right answer:

Now how does one go about it conceptually and how would one solve this specific problem for instance. In a way it seems so confusing with 2 voltage sources, and also a bit strange that the current is supposed to go from left to right, when the voltage source to the right provides a higher voltage. One would think from Ohm's law that a higher voltage would provide a higher current (easy to see since the resistors are equal in size), so the current from the right would "win" over the other. The question refers to electron current, but use the symbol I, so I would think what they are after is the way the current flows and not the electrons (since we know that the electrons physically run in the opposite direction of the current I).

According to Kirchoff we know that the sum of currents into node m is equal to 0, since there are only 2 entries into the node, it means both currents equal each other in magnitude, however they are opposite in direction. We also know that the same resultant current runs through both resistors.
But the resulting current is not zero, and how can we find that one?

In the original circuit the bottom part is earthed, and I guess that of course would apply for any equivalent circuit when analyzing the situation.


texts: matching impedance of stm32f4-discovery board's DCMI to image sensor data line

texts:
Could you please let me know how to find input impedance of STM32F407 DCMI pins?

I'm designing a camera module using sony's IMX224 image sensor. In the future this module will be connected to STM32F407 discovery board. Thus I need to consider the impedances of them. According to its data sheet the IMX224 sensor has output impedance of 50Ω typically at high data rate. But I wonder how large input impedance the STM32F4 board has. Especially I'm interested in using DCMI to get data from the sensor. But the data sheet of STM32F407 and user manual of the STM32F4-discovery board don't specify its input impedance.

links: datasheets
     http://www.st.com/web/en/resource/technical/document/datasheet/DM00037051.pdf
      http://www.st.com/st-web-ui/static/active/cn/resource/technical/document/user_manual/DM00039084.pdf


texts: FET source body connected to the same potential

texts:
I have learn that the FET looks like this:

However industrial FETs are not built like that.The source and the substrate have common potential.However if the source and substrate have common potential that means the conductive channel formed is not wide enough to connect the source with the drain there is a gap between the n type channel formed and the source.So how does it really work?


texts: What is the most suitable? Pull Up or Pull Down

texts:
This is the IO port of ATMEGA328p according to 76 page of datasheet.

As I know, Pull up is the most suitable system because lots of voltage spikes are logic 1.So, if we can give logic 1 normally, we can avoid unwanted triggering causes by spikes.

This thread has some explanation. But,it can't satisfy me.because ATMEGA328p port is bi-directional.

Explain what is the most suitable way(pull up/pull down) when we use a button input to the port with help of diagram above.


texts: Sewing machine speed and needle position control over arduino

texts:
I need control sewing machine speed and needle position over arduino project.

Current sewing machine is: Brother X5, with 70 Watt motor with foot pedal control.

Speed of motor will controlling by triac dimmer (image attached) but want to change dimmer resistance (rheostat) throw arduino, progragrammatically. Not with servo motor.

Q1: How can I change resistor resistance to form arduino programmatically?

Q2: Can I control motor speed sending 220V AC as pulses? (without triac dimmer)

For needle position plan to use magnet sensor. "Reed Switch Magnetic Sensor" Or "Hall Sensor"
Problem is vibration of machine and spinning speed is factors,

Q3: Which sensor best suit in this case?


texts: Using a low voltage opamp for feedback with high voltage mosfet?

texts:
I've been looking at Piezo drivers lately. They are effectively 0->100v output amplifiers with 0->10v input. Which can source ~60mA, at a few KHz.

The drivers I've seen mostly use high voltage opamps on the output (Apex PA41s for example). However those opamps are very expensive. Is it possible to use a low voltage opamp to provide the feedback to a high voltage MOSFET something like the following schematic?

Or is there some other reason to favor a integrated solution?


texts: How do you read from Static Random-Access Memory (SRAM)?

texts:
I have searched online, but I do not understand very well the procedure for reading from SRAM?

I have an exam about digital electronics and two of the questions may be what is an SRAM and how the reading process works for SRAM?


texts:
I opened a small "wall-wart" power supply that had failed, and discovered the culprit to be a low-value (100µH) standard (axial, green) inductor.

This inductor had a visible crack along it, as if it had overheated and released the "magic smoke". I confirmed it to be an inductor by cutting it open.

I am familiar with the practice of using a low-value resistor in place of a fuse, but not an inductor.

Why might an inductor have been used here?
Is there any obvious reason why a resistor (or an actual fuse) couldn't be substituted?
Why did it fail? It had been powering the device it was supplied with, for around six months, when it just failed for no apparent reason.
This product was an unbranded ethernet switch bought in the UK from Amazon. Is it really legal to sell mains-powered products without a "real" fuse in them?


texts: How to sum resistors in parallel and series?

texts:
I know how to add resistors in parallel and resistors in series, but i don't understand how to differentiate between resistors in the format shown:

simulate this circuit – Schematic created using CircuitLab

I haven't been able to figure it out on my own and my lecturer hasn't helped either so i hope someone here is able to. Thanks.


texts: Identifying a BLDC and its characteristics

texts:
I have some motors to be used in copters, can anyone tell me:

a) if they are BLDC

b) how could I find what current they would draw and their power ratings?

c) what ESC should I use for it


texts: How do I figure out the windings of a transformer

texts:
I have a transformer. It is a custom wound transformer for a old linear powersupply. As is common, it has two primary windings for supporting 115V and 230V operations (or, 120V and 240V as is now more common. the powersupply is old). So, the options are the following:

The owner of this powersupply bought the device in the USA and is now in Europe, so he wants to change the wireing such that this is possible.
They desolered the transformer windings, but then got cold feet and stopped, worried they would damage the device (or themselves) if they rewired the transformer incorrectly. It was then handed to me and I now have to make sure it's done right.

However, the transformer doesn't have the wires labled. I wondered, what is the correct way to verify what pins are what coil, and more importantly, what orientation the coil has. It's obvoius in this case what the primary windings are since they were labled on the PCB, and those are the only ones unsolderd. I also know what two pins belong to the same windings with a simple continuity check.

What I'm now worried about is the "orientation". What I don't want to do is this:

I have only limited tools to my disposal for now since I cannot use univerity instruments. All I have is a simple multimeter and an old analog oscilloscope.

I was thinking about applying, with a sound card, a low-frequency (say, 1kHz) signal. Since it is so low voltage, and higher frequency as the transformer is rated for, I expect that the voltages on the secondary would be on the order of milivolts, not able to turn on any of the circuitry. I could then apply this signal to one of the windings. By then using two channels of the oscilloscope, one for each winding, I could see what way the windings are in respect to each other (if I have one connected the "wrong" way I expect a near 180 degree phase shift, otherwise almost perfectly in phase).

Is this a good method? how is this done "propperly"? I would rather not fully dissasemble the powersupply to unsolder the secondary windings as well since this requires me to pretty much take the entire thing appart.


texts:
I have a line-level audio output stage with an output impedance between 100-600 Ohms and an input stage with an input impedance of 10-20kOhms. I am looking to use an isolation transformer to connect these stages, isolate them and eliminate common mode noise between them. I am looking at audio transformers, and I have the option between 600CT:600CT or 10,000CT:10,000CT impedances.

Maybe I'm misunderstanding this, but it has been mentioned in previous posts that these impedance ratings refer to the load impedance for which the transformer is designed, as it will have the flattest output response in the region in which it is designed to operate. So am I correct in assuming that I need a 10,000CT:10,000CT transformer?

I feel like this specification is confusing, as 1:1 signal isolation transformers are not designed to transfer power, and the specification suggests that both input and output stages should have the same impedance. It also could be easy to interpret it as meaning that 10,000 Ohms is the impedance of each coil itself. Can someone please clarify?

EDIT: For anyone else looking for similar information, check out this very informative article on designing circuits using audio transformers by Rod Elliott.


texts: Mesh Wire opening size for emi filter at frequency of 30Mhz

texts:
I want to use a mesh wire and I wanted to know how do I calculate an opening size of a mesh wire that can filter 30Mhz frequency.
Your help is appreciated.


texts: The frequency rating of the snap ferrite

texts:
Snap on ferrites for power cables that are available on the the market are rated for frequencies varying from 1 to 300 MHz (most of them 100 MHz). I do not want any frequency to pass outside over my 5V, 6A, DC power cable. The source of inference is a single board computer that probably emits wide range of noise.
Would low frequency ferrite be good in stopping higher frequencies as well? Is it reasonable to put both low and high frequency ferrites sequentially on the same power cable?


texts: In connecting two separated materials with different Fermi levels we have carrier flow. Do electrons and holes always move in opposite directions?


texts: Do I have to worry about backwards crosstalk with a 1 way bus?

texts:
I'm working on a DDR memory circuit, and I'm not sure how big an issue crosstalk is on the command/address bus. I've designed for crosstalk with the DQ/DQS and CLK lines because they are high speed/bidirectional, but my command/address bus has ended up with very small spacing between traces.

With the short trace length I'm not expecting forward crosstalk to be big.

So my question is - does backwards crosstalk matter if it is only occurring at the driver end of the transmission line?


texts: Getting negative pulse on Q2 mosfet at gate to source pin

texts:
BOOST CIRCUIT:
Working on DC-DC boost converter circuit as given bellow.
Getting negative pulse of -25.6V on Q2 mosfet at gate to source pin. This is much higher then then its maximum operating voltage. Due to this negative voltage my MOSFET gets burnt. I am using 1uF of bootstrap capacitor to turn on Q2 MOSFET. Please share if there is any solution to avoid this issue and how to compress this negative voltage.

simulate this circuit – Schematic created using CircuitLab


texts: Understanding a chinese Ringing Choke Converter

texts:
I got a Chinese torch with a charger supposedly needed to charge the (removable) Li-Ion cell in it. The connection is direct to the unprotected cell, but the charger shows a spec of 4.2V +/- 0.5V.

Before tossing it away, I wanted to check how was made, to see how much cheap it was and possibly learn something out of it. So I tried to devise its schematic:

EDIT0: missing connection to the BJT's base from the Zener.

If it is correct, seems to be an RCC power supply with indirect regulation.
What I am not sure is, among the correctness of the schematic, how the GREEN and RED LEDs are working.
From a user perspective, the GREEN is "always-on" and RED turns on proportionally to the output power. I also found very useful this video to get the basics, but the feedback on that one seems different - but the rest of the product, including the torch, was very much the same.

My guess is that during the on-cycle (BJT on), the winding 2 turns-on the GREEN LED and closes the 91Ω resistor. Then, if there is need to provide output power, more energy is stored in the core, hence the off-cycle (BJT fully off) lasts more as the winding 3 has to provide more energy on the output keeping the reverse polarity for longer - energy which I presume was provided during the on-cycle for a longer time as well. So during the off-cycle, the winding 2 will make a current flow through the 91Ω resistor in the other direction, hence dropping enough voltage which is used to turn on the RED LED.

Additionally, I would like to understand, if these assumptions are correct, how that Zener is used to regulate the output voltage (as was used here, for example) - but how in this very schematic?
EDIT0: less relevant, as with the new schematic now makes a bit more sense.

So far seems that the 25uF capacitor has no usage here. Also, if the LED mechanism is right, during the off-cycle the return current used as a drop on the 91Ω to lit the RED LED, seems to be blocked by the GREEN LED. So something does not add up, essentially I don't find some returning current path - I also triple checked the schematic, but I am still not 100% sure I reversed engineer it correctly.

I had no chance to probe the circuit, as I am not comfortable to work with high voltages. Feel free to suggest any improvement to the question.

EDIT0: the zener was not correct. Now the schematics is updated and Zener relavant question updated too.


texts: What is making this LM386 circuit so distorted?

texts:
I found this circuit on a YouTube video and tried copying it down into a circuit for testing, but the audio that comes out of it is really low quality and distorted. I don't expect sterling quality out of a quick hobby circuit like this, but I do expect something better than what I'm getting. This copying comes with the caveat that I don't really know where to find the video anymore. The schematic, however, is a faithful reproduction of what I have built, complete with all alterations from spec.
I had to fudge some of the capacitor values, given what I have on hand. I added in separately the part where the two channels get mixed with 1K resistors, as I just have the one speaker here and this seems an acceptable way to mix two channels. The audio source has just been my phone, as it's the most convenient thing on hand with the jack in question. The physical circuit is built on a mini solderable bread-board without power rails on it. I know that I should have kept it on a solderless one until I had it thoroughly debugged, but I got excited and locked myself into harder changes.
My questions are:

Is there anything about this circuit that suggests excess distortion?
I think I accidentally swapped the order of R3 and C4. Most other circuits seem to have the resistor closer to ground. Is this a problem?
I had to fudge the numbers on a bunch of the capacitors, making them somewhat bigger than was called for. In general with circuits like this, what range of sizes should the capacitors be and should I err on the side of bigger or smaller when I don't have an exact match?
Just what is the purpose of C3? I see it in some example circuits but not in others. The datasheet was not enlightening for me.


texts: How can I find the origin of equation about this filter circuit?

texts: Probably everything is clear for anyone but I can't still understand how can the author found the Vo equation for this circuit. I hope somebody in here will show me the way.


texts: The concept and circuit of 2 to 4 level converter in 8-QAM

texts: I have a difficulty to understand the basic concept about 2 to 4 level converter in 8-QAM. I've google it but still don't understand much except this block is used to convert two voltage into 4 voltage, and that's why i can't start to make the circuit. Any ideas ?


texts: Electrometer amplifier circuits - surface mount or traditional

texts: I have looked at a number of electrometer amplifiers and they all seem to use big through hole passive components and through hole DIL packages. Is there a reason for not using surface mount?


texts: Ethernet transformer saturation at low frequencies

texts:
I am using a 10/100BASE-T Ethernet transformer TG110-E050N5RL (Circuit A in the datasheet) in a circuit. I am applying a 60 Hz 500 Vac hipot across C9 (T1 pin 16 and T1 chassis ground) as shown here: . Pin 14 is open, to simulate a test stand failure. Nothing is connected to T1 pins 9, 10, 11.

I am seeing nothing -- flat, 0 Vdc -- on the corresponding secondary, T1 pins 1 and 2, with a scope during hipot.

My best guess is that core saturating because of the very low frequency of the hipot signal relative to what the transformer was designed for, but I am surprised that I am seeing nothing at all. I have measured the windings' resistances, and the windings do not appear to be damaged.

What, if anything, should I be seeing?


texts: USB controllable digital output ports at >100kHz

texts:
I need to control 8 digital output pins over a USB connection at a minimum of 100kHz.

What solutions exists that allows me to do that? Preferable a COTS module if possible.

I am thinking something like a FTDI USB-to-serial, and a serial byte to parallel output pin IC. But I am unable to find any ready made modules for this.

(As a side note, would a simple arduino doing serial to parallel conversion be fast enough for my purpose?)


texts:
I know the application of PWM is controlling the brightness of led or DC motor speed, but I don't understand it, why when we change the duty cycle, it change the brightness or motor speed ? Can you explain me ? :)
Beside using microcontroller, is there any way to create PWM, Ex analog circuit ?


texts: USB 100mA unit load average/rms or instantaneous

texts:
I am attempting to understand the USB2 spec's definition of "unit load". It is clear that prior to enumeration one shouldn't draw a constant current of over 100mA. What is unclear is how this applies to pulsed current (as you might see from a switching converter for example). Is 100mA really a shorthand for the equivalent 500mW power?

In my application I'm sipping an average current below 5mA and every 2ms or so a switch opens and I have a current spike of about 200mA lasting about 2uS. Do these brief spikes violate the spec? Or am I good as long as the average (assuming a periodic power profile, bonus points for non-periodic use case) is below 100mA.


texts: Floating voltages and current path between isolated circuits

texts:
I have a bit of trouble understanding floating voltages. I thought about quite a few circuits and scenarios involving isolation transformers and floating voltages but something is still off.
Here are some points which contain a contradiction to me:

An isolation transformer separates the primary from the secondary in terms of current path (such that the current cannot cross between the two sides)
In AC, a path is not required (e.g., capacitor plates)
Voltage means there is a path for electrons to move as this "pressure" is measured. It makes sense to me that voltage measurement implies that a circuit is actually closed and that electrons are allowed to flow even though it will happen at very low currents "work needed per unit of charge to move a test charge".

With these points in mind why can someone then measure the voltage between isolated circuits where one of them is supposed to be floating? The mere existence of this voltage means there's a path for it to flow. (Here are some examples.)
My own answer would be: even though the circuits are isolated, the voltage is measured because of an incredibly small current (which would also be the maximum current in case of short circuit). This current is caused by a very large resistance. If this is the case, would a sufficiently large voltage for the floating side jump across the air resistance or winding's isolation if close enough?

simulate this circuit – Schematic created using CircuitLab


texts: Difference between Line and Neutral in AC

texts:
I want to find out what is the difference between the AC (220 VAC) lines, (phase and Neutral).

As I know that the Alternating Current (AC) has no polarity, so why do we have a "phase" line and a "Neutral" line ?!
Why one of them (the phase line) would make danger on human if touched, while the other doesn't ?!
I also want to know, what's meant by "Analog Ground"? .. is it the Neutral line ? or what ?!


texts: Problem with massive Gerber files from Eagle

texts:
I'm trying to export an 8" square design that is mostly copper to Gerber files. The top layer file size is about 14 MB and the board house is complaining that it is crashing their software.

Is there any way to get Eagle to treat the copper areas differently as to not make the Gerber files huge.  I'm currently using the Extended Gerber format.

I've read that it has something to do with the representation of the copper layers but I don't know how to change its representation in Eagle CAD.

From "Gerber File Problem 6 – Vector Fills" in a document by bayareacircuits.com:

  Often plane layers or layers with shield areas come in filled with 1 mil or 2 mil vectors. This causes the Gerber file to be quite large in size and requires us to try and contourize the data. When you panelize this type of data the files often become too large for our plotter to digest. It is better for areas to be filled using “raster” or “contour” data.


texts: design for portable pv charging for 97Wh lithium ion battery

texts:
The manufacturer of my medical device has provided a Lithium Ion battery with these characteristics:
97 Wh
Output 3.75A
Input 100-240V, 50-6-Hz, 1.0-1.5A
Protection overcharge, overdischarge, exess current, short circuit, high temperture

The manufacturer is unable to provide any assistance for charging the battery from any source except a wall outlet.

I would like to take a high mountain trek and use PV panels to charge this battery.  What components will I need to charge this battery?  What rating for the portable solar panel?  What components to connect the PV panel to the battery?

Many who depend on electical medical equipment will be very grateful for your answer.  Thank you very much!

Please let me clarify: This battery powers a CPAP machine which I need but is not life supporting.  I will not die and nobody will sue you if this charging system doesn't work.

I intend to include a photo below (if I can figure out how to do it).  Here is the info printed on the battery:
input  24v 1.64A
output 24v 3.75A
"Charge using power supply R360-760, 369102, or 370001 only"

I can get a 100 watt flexible solar panel.  I would like it to charge this battery in 4-5 hours.

You guys are great!  Thank you for your interest!


texts:
I am following this VCO design I found from a tutorial and for some reason the frequency is way too low. It doesn't state in the design what it should be, but following these instructions it is just couple of Hz. I replaced C1 with 0.01u capacitor and now it is better (30-370Hz), but still that doesn't seem correct. I tried messing around with some of the resistance values, but only managed to change the duty cycles. Is it a problem with the design or am I doing something wrong?

Updated version of my schematic:


texts: Three-phase induction motor winding terminals

texts:
According to the following diagram, when the motor is delta connected as far as I can see:

L1 goes into U1; U2 goes into L3

L2 goes into V1; V2 goes into L1

L3 goes into W1; W2 goes into L2

It looks like one winding is between U1 and U2 terminals another one between V1 and V2 terminals and the other one between W1 and W2 terminals.

Is this convention universal in the world? Is each winding always between U1-U2 V1-V2 and W1-W2 terminals? And is there a reason to place the thermal overload after the main circuit breaker but not before?


texts: Possible contradiction between Ohm's Law, KCL, KVL and Faraday's Law of Induction?

texts:
Let's say, we have a loop of wire of length \$L>0\$. Let's say, hypothetically, it is a loop of non-ideal wire. That means that the wire has a resistance per unit length \$ρ>0\$. Let's further assume that there is a changing magnetic flux through that loop of wire. Faraday's Law of Induction, as it is widely understood, dictates that a current will be induced in that loop of wire. Let's call that current \$I\$ (where \$I>0\$).
Now, for the sake of argument, let's divide that wire into infinitely many segments of infinitesimal length. Let each of those segments have length \$dl\$. That means that each segment will have resistance \$ρdl\$, and since each segment has the same current \$I\$ passing through it (KCL), the voltage drop across each segment should be \$Iρdl\$ (Ohm's Law).
Starting at any point in the loop of wire, we can sum up the voltage drop across each infinitesimal segment for the entire loop (the segments are in series):
\$\int\limits_{0}^{L}Iρdl=IρL>0V\$
Now, since we start at any point in the loop and come back around to the same point, that means that the voltage at that point (relative to itself) is both \$0V\$ (trivially) and \$IρL\$, which is a contradiction since we assumed that neither of \$I\$, \$ρ\$, and \$L\$ is \$0\$.
This is essentially a long way of saying that KVL finds itself contradicted. But I took this long way to avoid answers such as "KVL simply doesn't work with magnetic fluxes". But how can it not work? What did I do wrong in all those steps? Which assumption was incorrect?


texts: What is the difference between package description and package option?

texts: I am making an ECG sensor schematic on EAGLE and I am concerned if this is something I should be taking into account while designing?


texts: How do I design pcb keypad contacts for hard gold plating

texts:
Are there any special features that need to be added to the pcb footprint of membrane key contact in order to facilitate hard gold plating of the contact area?
In other words, how does the hard gold electroplating process actually work? Are separate contacts needed for the electroplating process?


texts: How to Add the Xilinx Library to Modelsim?

texts:
I'm trying to simulate an example design of an IP Core, but the version of ModelSim I have installed (Altera Edition/Linux) does not link to the Xilinx library. How can I permanently or temporarily add the Xilinx library to ModelSim?

EDIT:

A few more details. I'm trying to simulate an example design for the Ethernet1000Base-X IPCore. The documentation is here: http://www.xilinx.com/support/documentation/ip_documentation/gig_eth_pcs_pma/v11_3/gig_eth_pcs_pma_ug155.pdf

One page 18, it describes how to simulate the design using either IES, ModelSim, or VCS. I get the following error in ModelSim after running this command: vsim -do simulate_mti.do

# ** Error: (vsim-3033) ../../../Ethernet1000BaseX.v(9359): Instantiation of 'LUT6' failed. The design unit was not found.
#         Region: /demo_tb/dut/core_wrapper/gig_eth_pcs_pma_core
#         Searched libraries:
# ** Error: (vsim-19) Failed to access library 'unisims_ver' at "unisims_ver".
# No such file or directory. (errno = ENOENT)
#             /home/saddam/Desktop/Ethernet1000BaseX.3/ipcore_dir/Ethernet1000BaseX/simulation/functional/work
# ** Error: (vsim-19) Failed to access library 'unisims_ver' at "unisims_ver".
# No such file or directory. (errno = ENOENT)
# ** Error: (vsim-3033) ../../../Ethernet1000BaseX.v(9365): Instantiation of 'MUXF7' failed. The design unit was not found.
#         Region: /demo_tb/dut/core_wrapper/gig_eth_pcs_pma_core
#         Searched libraries:
# ** Error: (vsim-19) Failed to access library 'unisims_ver' at "unisims_ver".
# No such file or directory. (errno = ENOENT)
#             /home/saddam/Desktop/Ethernet1000BaseX.3/ipcore_dir/Ethernet1000BaseX/simulation/functional/work
# ** Error: (vsim-19) Failed to access library 'unisims_ver' at "unisims_ver".
# No such file or directory. (errno = ENOENT)
** Error: (vsim-19) Failed to access library 'unisims_ver' at "unisims_ver".
# No such file or directory. (errno = ENOENT)

EDIT 2

Software:
Modelsim Altera Starter Edition 10.0d
Xilinx ISE 14.1 WebPack


texts:
I have a circuit at a high potential compared to ground, up to 30kV, in which I have to measure a current of like 2A.
Because the whole circuit is at 30kV I could just measure it with a normal multimeter but my problem is that the whole thing should be in an isolated box for obvious safety reasons. So the "Display" needs to be connected to ground.

I know there are some wireless options like a current clamp or optocoupler but I don't know if they are isolated enough for 30kV compared to ground.
The difficulties I see with a shunt and a voltage divider is that the voltage at the resistor would be much much smaller than the 30kV so the divider would need to be super precise.
I hope someone has experience with stuff like this.

Thanks in advance


texts: Changing the Linux SDK in the embedded platform

texts: I am using an embedded platform that has Linux SDK version 2. It supports only gcc 4.9.2. Is it possible to configure the system to run gcc 8?


texts: Using PWM instead of real DC for VFD's 0-10V control input

texts:
There is a VFD which controls an AC motor through a 0-10V control. I know that this control voltage is DC voltage.

I'm wondering would a PWM work for this application? I mean instead of 2VDC, what happens if one applies 0-10V 500Hz pulse train with 20% duty cycle? In theory this corresponds to 2VDC but since it is PWM, I'm hesitating to even try.


texts: Using A/C adapters with different current ratings

texts:
Can I use an adapter AC/DC (Output 12V 500mA) instead of another A/C adapter (Output 12V 250mA) ?
If not What I will do to use the first one as the only adapter at my level


texts: Data memory usage reported by AtmelStudio for ATtiny85

texts:
I am using AtmelStudio to program an ATtiny85, which has 512 bytes of SRAM data memory.

My code includes a large lookup-table (array) which is 512 bytes:

const uint16_t lut[256] = { ... };

The project has no other global or static data, so when I compile it, AtmelStudio reports:

"C:\Atmel\Studio\7.0\toolchain\avr8\avr8-gnu-toolchain\bin\avr-size.exe" "mcp4821_attiny85.elf"
           text    data     bss     dec     hex filename
            242     512       0     754     2f2 mcp4821_attiny85.elf
    Done executing task "RunCompilerTask".
    Using "RunOutputFileVerifyTask" task from assembly "C:\Atmel\Studio\7.0\Extensions\Application\AvrGCC.dll".
    Task "RunOutputFileVerifyTask"
                Program Memory Usage    :   754 bytes   9.2 % Full
                Data Memory Usage       :   512 bytes   100.0 % Full
    Done executing task "RunOutputFileVerifyTask".

As shown, AtmelStudio reports that I have exactly filled my available data memory space. If I make the lut array one element larger, the compiler alerts me of the memory overflow. Conversely, if I make the array one smaller, the compiler reports that I have room to breathe (of two bytes).

However, when I used the code to program the chip, I found that there was indeed a memory corruption, and I received bad data when reading the last 16 bytes of the array.

For testing, the LUT is just a sine wave - and the microcontroller is writing the LUT to a DAC. The glitches in the image below reveal the erroneous data from the bad memory accesses (sorry for the poor image quality):

I resolved this problem by following the great advice found here: Memory management problems with ATTiny85

Changing

const uint16_t lut[256] = { ... };

to

#include <avr/pgmspace.h>
const PROGMEM uint16_t lut[256] = { ... };

and using

pgm_read_word()

to access the array elements. But I'm not sure why this is necessary.

My questions are:

why doesn't the array fit into the data memory even though AtmelStudio reports no error.
and most importantly, why does AtmelStudio report no error?

I suspect the answer to both is related to stack space, but I'm not sure. Thanks.


texts:
I am looking for the general approach (technique/strategy, componentry used, etc.) to implement what I am calling a power supply router, although perhaps there is a more precise/accurate term for it.

By "power supply router" (PSR), what I mean is this:

A device, say some PCB (doesn't really matter) will connect to this PSR and expect it to be its power supply, but...
The PSR itself is not an actual power supply; it is simply a circuit/component/thing that uses a simple routing algorithm to draw power from one of several actual power supplies at any given time
In other words, the router will strive to always provide power (if the device is toggled to be "on" via power button, etc.) from one of many power supplies, and can switch the actual power supply it is using at any point in time (only during operation of course) according to this algorithm

And a diagram for illustration:

In that diagram Power Supply #1 (PS1), #2, #3, #4 and #n are the actual power supplies (batteries, solar panels, whatever). The device connects to the router, expecting it to supply it with power, but the router will only be connected to one PS at any given time.

The algorithm I am looking to implement is very simple:

For all the power supplies in the system, find the first supply that isn't "nearly dead" and set it as the current supply
Once the current supply is nearly dead, obtain the next non-nearly dead supply and set that as the current supply
Only when all power supplies are dead/nerly dead is the system officially out of power

I'm sure the "nearly dead" part requires better explanation. Here, the router simply needs to be able to determine whether the given supply is almost dead, perhaps based on the amount of volts or amps its currently outputting, or based on some gas gauging component like what cell phones use to show you that your smart phone is at "2%".

I'm wondering if this type of "routing multiple power supplies" need is a well known pattern in EE, with well known solutions? Either way, what are my options here for implementing such a router & routing algorithm as a circuit? What components could be used?


texts: Is there any module that controls power supply with variable voltage by PWM input?

texts:
I am stuck for a few days already at finding a solution for controlling a motor. We can easily find a motor or LED on the market. However, those modules for motors do not have a built-in regulator as inductors can smooth out the voltage itself.

What I want is a variable power supply module with a voltage regulation function, whose output voltage (e.g. 5V to 12V) can be controlled via PWM . Does such a thing exist in the market?

UPDATE 1

I would like to use Arduino/Raspberry to control PWM signal.

As I am looking for a general solution that can be used for different Loads, I don't know the spec of the Loads, let say they are ranging from 5V to 12V and max rated current would not be >2A. You may take CNC Laser module as example


texts: Can the width of a mosfet modify the gate-source voltage?

texts:
I was solving a problem divided in two parts.
The first is a simple calculation, but the second implies reasoning, and it's here where the post question arise.
The first part importance for the second is just the following data:
$$
I_D = 1\ mA \\
\mu_nC_{ox} = 100\ \mu A/V^2 \\
V_{TH} = 0.5\ V \\
\lambda = 0
$$
With next schematic:

Where 10/0.18 is the ratio W/L.
And MOSFET is working in saturation region, so far that's all.
The second part says:
Suppose we double \$W\$ and choose \$R_D\$ to place \$M_1\$ at the edge of saturation. Is the resulting gain higher or lower than the above value?
I solved that question in both numerical and analytical ways, and they give me gain increases.
But the issue comes when I'm thinking around the analytical expressions: if I'm variying the \$W\$ with \$I_D\$ fixed, that implies \$V_{GS}-V_{TH}\$ is changing, so the question would be, is \$W\$ overwriting the \$V_{GS}\$ bias circuitry? or is this a too ideal case, that doesn't happen in real designs?
This was my solution:

Thanks!

Edition inspired by Elliot Alderson comment:
Assuming that changing \$W\$ forces the change of \$I_D\$ and not \$V_{GS}\$ (which makes much more sense), when doing the analysis, the gain voltage \$A_v\$ actually experiences no change:

But, If we continue the analysis, now with the fraction, where \$R_D\$ forces to change the \$V_{DS}\$ we see that the reduction of the subtrahend increases the gain voltage:

Again, is this right?


texts:
Is it possible to design a  very basic linear regulated power supply that can control an output of 13 volts?
I ask because doing a thorough research online leads to very complicated designs.


texts: Using Zener Diode for 12v input to Arduino

texts:
The MPGuino uses a 5.1v zener diode to read an input from the switching of an injector.

According to my very basic understanding of how zener diodes work I used the formula:

$$ I_{diode} = \frac{U_{in} - U_{out}}{R} = \frac{14.51V - 5.1V}{50k\Omega} = 0.178 mA$$

which seemed far to low given that a 1N4733A is \$5.1V\$ at \$49mA\$. Would the circuit still work at these low levels, or would a smaller resistor be needed? And would the output from this be safe to feed in to an input pin on an Arduino? I hope this all makes sense and I haven't misunderstood how zener diodes work.


texts:
So iam building a wireless charging receiver circuit.One of the options i need to use is setting a overcurrent protection is solving for RILIM.I can achieve this by solving equation 1 http://www.ti.com/lit/ds/symlink/bq51050b.pdf#20 to find R1 resistance values and place the resistors following the schematic in the pdf.The problem iam facing is when i solve for R1 is i dont see a way to solve for RFOD or can find a standard value to use for calculation.If anyone can point me in the right direction it would appreciated thanks.
http://www.ti.com/lit/ds/symlink/bq51050b.pdf


texts: How to set radio register of cc2500 and cc2511 to maximum data rate (500 Kbps)?

texts:
-I am using cc2500 at target device and cc2511 at Host device.
-I want to transmit and receive data between this two device at 500 Kbps data rates.
-My X'tal freq for cc2500 is 27MHz  and for cc2511 is 48 MHz.
-My base freq is 2410 MHz.
-I tried automatically generated register setting from smart RF studio but it's not working.
-I know that below register are affected for changing data rate .
MDMCFG4,MDMCFG3,,MDMCFG2,MDMCFG1,MDMCFG0,DEVIATN,FSCAL3,FSCAL2,FSCAL1,FSCAL0,PKTCTRL
-I tried as much as i possible but failed to communicate this two device.
help me to figure out this problem.


texts: Manual overriding a DC-motor with H-bridge

texts:
I have created the following circuit where I use a VNH7070BASTR full bridge motor driver to control a DC-motor. The goal is to open and close a drawer using a rack and pinion system. A new requirement that I have is that the drawer can ALWAYS be opened in case of failure somewhere in the circuitry controlling the driver. I want to use an external switch to move the motor in one direction. But I am not sure how to design this correctly.
I thought of shorting directly using a relay or a FET. However I am not sure how to deal with an open state of the H-Bridge. How could one implement such override?


texts:
I would like to get an anti-static mat for my bench top and found these two:

DigiKey: Table mat ESD blue 2X4' rubber
Mouser: Antistatic Control Products 2X4' blue table mat

What should I look for when shopping for an ESD bench mat?


texts: So I need help with the following exercise on op-amps (picture). I know how basic op-amps work but here I dont know how they got to the formula (circled in red). Do you need to use KVL or KCL ? I know that the gain on a normale inverting op-amp is V0=-Zf/Zi*Vi. Ok so now I applied KCL at the two nodes and this is what I got (picture 2). But after rewriting it and replacing Vs by its value, it still isn't the same equation as the answer given, what did I do wrong ?


texts: Anyone know the name of this type of switch?

texts:
Does anyone know the name of the internal switch (circled in red) in this assembly? It is a latching switch, so much to close and then push again to open. I've been Googling and hunting for about 2 hours and clearly not typing in the correct name and I just keep finding panel switches or the complete plastic assembly, which I don't need.

UPDATE: Just managed to find an application note on switches, the type of switch I am after is a push button alternate switch it seems. Still can't seem to find the type pictured though.


texts:
I am trying to multiply signed numbers on a Nexys A7-100T FPGA development board with VHDL.
See Reference manual webpage link for the FPGA board hardware information.
Also see this link (begins page 78) for Vivado's Vivado design synthesis guide user VGDL guide which shows how to use the hardware multiplier logic.
I know this will work for unsigned numbers but can this be used for signed numbers with some additional logic / code?
I also have looked at the complex multiplier within this document however I am totally unfamiliar with the concept behind it?
How do people use the multiplier hardware to multiply signed numbers?


texts: In which region does a NMOS work when its drain is open circuit? Let's say the input is high voltage lavel, how can I determine whether it is saturation of triode region when drain is open?


texts: How do I avoid a race condition in SR latch?

texts:
I have designed an SR latch using Cd4001 NOR gate IC. When both S and R are low the circuit refuses to stay in previous state even though I am using appropriate dropping resistors. Is there any way to avoid this with same CD4001 circuit configuration.

This is the circuit configuration i am using:


texts:
I am trying to add Diac component into my OrCAD v16.5 Schematic Layout. But, I only find this code below as a netlist. Even Though, I can't include the netlist into OrCAD Capture perfectly. It didn't worked. There is no Diac component in among OrCAD Capture libraries. I really searched too many times in web. The question is: How can I work with diacs in OrCAD Capture? The real Diacs are commonly named as: DB3, DB4, DB5, BR100, ER900. But there is nothing in OrCAD :(

.subckt diac 1 2
*Based on BR100 measured data
*Convergence problems often occur with this model
*If you have a better model please tell me
Vdummy 1 5 dc 0
Ediac 5 2 TABLE {I(Vdummy)} =
+ (-10.06m,-20.46) (-9m,-20.5)    (-7.02m,-20.72) (-5.98m,-20.89)
+ (-5.05m, -21.11) (-3.26m,-21.91) (-2.15m,-22.96) (-1.6m,-23.99)
+ (-7.2n,   -32.5) (-4.0n, -32) (-3.2n,-31) (-2.9n,-30) (-2.5n,-28.03)
+ (-2.3n,-25.27) (-2n,-20.15) (-1.9n,-15) (-1.8n,-7.96) (-1.5n,-1.2)
+ (0,0) (1.6n,1.24) (1.65n,5.15) (1.7n,7.91) (1.8n,10.1) (1.9n,15)
+ (2.1n,20) (2.4n,25.28) (2.9n,28.26) (3.3n,30.5) (1.6m,23.21) (2.3m,22.16)
+ (3.1m,21.44) (4.05m,20.99) (5.01m,20.65) (6.04m,20.32)
+ (6.98m,20.14) (8.09m,20.02) (9.08m,20.02) (10.12m,19.91)
.ends diac


texts: How to use a Bluetooth-controlled relay to simulate a button press on a garage door remote?

texts:
As a DIY project, I'd like to use this keypad (Danapad by Danalock) to open my garage door. The keypad communicates via Bluetooth with a "universal module" that's designed to open gates, magnetic locks, etc. I've read the manual, but don't know enough about electronics to know how to make my idea work: With the correct PIN, I'd like the relay to simulate a button press on the spare remote control that came with my garage door opener. (The communication between the keypad and module is handled by the product -- nothing for me to do there.)
Here's a link to the specs on the universal module: https://www.andivi.com/danalock-universal-module-v3/
My questions:

The module has 2 relays (one normally open and one normally closed). How can I use one of these relays to simulate a press on the garage remote?
The remote is battery-powered so it doesn't need power. I do need to power the module. I'm thinking I can just find a 12 V power supply for it and attach the module + remote to a circuit board. Am I oversimplifying or is there anything else I need to consider?

I've attached an example wiring diagram from the manual for a door strike.

Thanks!


texts: Question about this RC circuit and voltage across the capacitor

texts: I just have a small question about the below problem. How did they get Vc of the capacitor to be 12 V before the switch is opened? Doesn't the resistor use up some of the voltage?


texts:
First post here, mechanical engineer with not too much experience in designing circuits.

I'm trying to control a DC motor torque via a buck; the motor is driven, so it's acting as a brake, and I'm aiming at modulating the output current via a buck.
The first prototype is not behaving as I'd have hoped: testing it with an input tension of 5V and a load of 1K ohm, the output tension I'm reading is pretty unstable, oscillating randomly below the expected value by quite a lot (-0.6V).

The design is as follows:

simulate this circuit – Schematic created using CircuitLab

The MOSFET is driven by an Arduino UNO @ 65kHz, with constant duty cycle. Since I'm using a low frequency PWM I opted for quite big capacitors and inductance to limit output spikes in voltage and current, and simulating it in MATLAB didn't show any problem regarding output stability.

I'd love to have a feedback from you skilled guys on how to improve my design. Any suggestion is welcome!

Thanks

Edit: edited the schematic as requested


texts:
I have a basic question about the following circuit, which is introduced in the book " and is described as a "large signal transconductor":

It says that:

the capacitance value is chosen to be a short for the signal;
suppose the capacitance with no charge at the initial time. When the input signal increases, the MOSFET becomes ON and the capacitance starts charging with a current equal to \$i_\mathrm{D} - I_\mathrm{BIAS}\$. So, the source voltage increases. Then the input signal will arrive at its peak and then will decrease, and after some time the transistor will become OFF because \$V_{GS}\$ becomes lower than \$V_\mathrm{threshold}\$.

So it says that the effect of this capacitance is that of keeping the transistor ON only for a very brief time (in fact this system is used a lot in class C oscillators), as shown in the following graph:

There is also another graph which shows source voltage:

Now I have the following questions:

1) why does the source voltage have that behaviour? It seems the behavior of the voltage across a capacitor after a rectifier diode (in fact, a simple capacitance cannot determine that profile, which is typical of an envelope detector, starting from a sinusoidal signal).

2) how do we choose the value of the capacitance? Should it be high or low?

3) I have seen many circuits with a source capacitance, which was used as a bypass capacitance. Its aim was that of bypassing an additional source resistance (inserted in order to make the transistor more stable to some fluctuations of the working point), since that resistance determines a gain lowering.
From a circuital point of view, this last circuit (with a bypass capacitance) is identical to that seen now. But I have never heard that a Common Source Amplifier with bypass capacitance keeps the transistor ON only for a brief time and determines short drain current pulses. So there must be a basic difference between these 2 kinds of circuits (maybe on the value of the capacitance?).


texts: I began using a Belkin Conserve Socket and opened it to see the assembly inside. I understand the rest of the components but there is a 6-pin IC (U1) that I can't put my finger on. Pictures are attached. Would be grateful if someone could identify it for me.


texts: Is it viable to boost capacitor voltage to improve energy density?

texts:
Having a look at supercapacitors available on digikey they seem fairly expensive (say for example a capacitor with \$E = CV_{rated}^2 = 50 J\$ ).

However, an equivalent ceramic capacitor energy-wise costs far less; the problem being voltages on the kilovolt range \$V_{rated} = 2 kV\$.

Would it viable to replace supercapacitors with lower capacitance components together with some kind of boosting circuit? (presumably with a well thought out isolation)


texts: I started this circuit with stm32. But it doesn't work properly. When I set zero to all four pins and I don't want any movement, the voltage of 3 volts is at the two ends of the motor again. Or if I want the motor to turn in the right direction The MOSFETs become extremely hot and the motor does not move. What could be the problem? Is the amount of resistance appropriate? I use a 3 volts DC motor.


texts:
Can anyone identify the correct plug for this socket?

Those are 6.3mm tabs, for mains voltage and around a 10A load.

Many thanks!


texts: Calculating the resistor needed for a simple LED and battery circuit

texts:
I'm having trouble learning the most basic circuit math!

I've a 3V battery pack, two AAA, a standard plastic LED and a pack of resistors and I need to work out which resistor I need.

I'm assuming the voltage drop of the LED is 2.0V; the datasheet only states a "forward voltage" of 2.0-2.4V and some wavelengths and lumens.

The problem I have is that the math drop / current requires a value for current, but I don't know that yet. In the YouTube tutorials I've seen, I just gets written in as if its value was magically known (0.02A).

My understanding is that the current is "drawn" by the loads on the circuit, which include the LED and maybe the resistor itself.

So my confusion is that there's a circular dependency, or chicken-egg situation, I need to build the circuit to measure the current it draws in order to arrive at R and build the circuit.

What's going on? Perhaps the datasheet or testing and measuring components in isolation breaks this deadlock? Perhaps I'm just tired.


texts: Stop timer set new value and start again AVR (Interrupt)

texts:
I have AVR MCU.
I am playing with timer now.
What I need ? I have timer counting up with some frequency. In each interrupt I am incrementing variable, and somewhere I need to check value of this variable and if equals 100, I need to stop timer count, set new value for frequency and continue counting down.
I cannot get how to stop timer and set new value to compare.
I have tried to select no clock source using mux selector register, but it continue to count up.
What is correct way to do this.
Here is my code

// Arduino timer CTC interrupt example
// www.engblaze.com

// avr-libc library includes
#include <avr/io.h>
#include <avr/interrupt.h>

#define LEDPIN_UP 9
#define LEDPIN_DOWN 8
int current_value = 0;
void setup()
{
   Serial.begin(9600);
   // pinMode(LEDPIN_UP, OUTPUT);

    // initialize Timer1
    cli();          // disable global interrupts
    TCCR1A = 0;     // set entire TCCR1A register to 0
    TCCR1B = 0;     // same for TCCR1B

    // set compare match register to desired timer count:
   // OCR1A = 3123;
    OCR1A = 1562;
    // turn on CTC mode:
    TCCR1B |= (1 << WGM12);
    // Set CS10 and CS12 bits for 1024 prescaler:
    TCCR1B |= (1 << CS10);
    TCCR1B |= (1 << CS12);
    // enable timer compare interrupt:
    TIMSK1 |= (1 << OCIE1A);
    // enable global interrupts:
    sei();
}

void loop()
{
    //digitalWrite(LEDPIN_UP, current_value);
  Serial.println(current_value);
       if(current_value==255) {
      TCCR1B |= (0 << CS10);
      TCCR1B |= (0 << CS12);
      Serial.println("Reseting timer");
    }
}

ISR(TIMER1_COMPA_vect)
{
    current_value++;

}


texts: Arduino UNO, L298N Stepper Motor Drive Waveforms

texts:
I am driving an unknown stepper motor using a little red L298N board from eBay. The board is sometimes called Qunqi L298N Motor Drive Board Module. I used a 19.5V laptop power supply to power the board. Since this voltage is larger than 12V, I removed the 5V voltage regulator jumper and sourced the 5V needed by the module from the Arduino board.
The driver program is the example code stepper_oneRevolution came from Arduino kit. The motor seems to shake and turning this way and that in a rather erratic way. I played with parameters such as stepPerRevolution and saw no improvement.

When I looked at the waveforms on the four pins for the motor. I found that the waveform on the pin #2 is always flat, reading the baseline, while the other 3 have square waves as expected. I thought I fried the board and order a couple of new ones. When I got them, however, I found all of them have the same flat line waveform on pin #2.

Can someone help me out here?

Here is the code:

/*
 Stepper Motor Control - one revolution

 This program drives a unipolar or bipolar stepper motor.
 The motor is attached to digital pins 8 - 11 of the Arduino.

 The motor should revolve one revolution in one direction, then
 one revolution in the other direction.

 Created 11 Mar. 2007
 Modified 30 Nov. 2009
 by Tom Igoe

 */

#include <Stepper.h>

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

// initialize the stepper library on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, 8, 9, 10, 11);

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

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

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


texts: I was looking at figure 33 of the OP77 datasheet, and the JFET labeled D2 has an odd connection. Based on the way the circuit works that JFET must be a diode right? So why is the JFET connected as it is in the figure?


texts:
Hello,

I am looking for a usb c connector suited for three wires. I can’t find them anywhere. The picture shows the broken connector from a 65w usb c charger. Can anyone tell me where I can get a replacement connector or what they are called?

Thanks in advance.


texts: What kind of speaker can be used with an LM386?

texts:
I am trying to use an LM386 to drive some speakers. I have both a 4Ω 4W speaker and 8Ω 1.5W speaker. Would I have to build a different circuit for each of these and would the LM386 be able to drive both speakers in parallel at once?

Using the formula P=R(I^2), I would get that the 4W speaker needs 1A and the 1.5W speaker needs 0.43A, so can the LM386 handle 1.5A? Or is my logic here wrong?


texts: Why did the designer of this flyback circuit choose to set the oscillation frequency as high as possible with the smallest resistor tolerated?

texts:
This circuit uses a current mode controller with an oscillation frequency response of:
In the circuit, the designer chose to use a 10nF cap, with a 680 ohm timing resistor, which according to the datasheet, is the absolute minimum resistance that should be used in the timing circuit, as shown below:

The output frequency of this yields the MOSFET being pulsed at around 147 kHz. I was wondering if there was a reason these components were chosen in this case. I had a hunch it was because of the coupled inductors being used in this case, but I don't know where to begin on finding the best frequency to oscillate that at. And if that was the case, why not use different values to get to that 150kHz, such as a 2.4K resistor and a 5nF capacitor? Any insight is welcome on this.


texts:
I'm trying to build this simple op-amp voltage follower circuit

But I keep getting distortions on the node out. I'm using a single voltage supply and the sine wave I send in is between +/-650mv, from ground reference that is. The distortions consists of noise like patterns on the raising an falling parts of the sine wave, while the top and bottom is okay. Any ideas of what it can be?

http://s18.postimage.org/u1gpbd6fb/DSC01219.jpg


texts:
I am having some strange issues with a PIC microcontroller (PIC18F45K22) driving a SainSmart 2 Channel Relay board (http://www.sainsmart.com/arduino-pro-mini.html).

After a bit of troubleshooting I have been able to isolate the issue. Whenever I have a load connected to the relay (a solenoid in an electric door strike) and I transition from a logic low output to a logic high output, the program counter seems to jump to a random location in the code.

I have found this by running my PICKit3 without any break points. Whenever this transition happens the code will randomly break (sometimes at Program Counter 0x0, other times at random locations.) Disconnecting the load from the relay (with no program changes) consistently eliminates the issue.

I have swapped microcontrollers and channels on the relay board (even driven by a different pin from the PIC) with no change.

The output pin from the microcontroller is connected directly to the IN1 pin of the board. JD-VCC jumper is in place, powered by the same power supply as the PIC.

Setup:

TRISDbits.TRISD1 = 0;
ANSELDbits.ANSD1 = 1;
LATDbits.LATD1 = 1;

Macros used to control relay:

#define Relay_1ON() do { LATDbits.LATD1 = 0; } while(0)
#define Relay_1OFF() do { LATDbits.LATD1 = 1; } while(0)

I have an almost identical setup in another project with no issues, so I am at a bit of a loss. Any thoughts?


texts:
I want to connect 23K256 SPI RAM to ATmega. Do ISP programming will work together with SPI RAM connected.

Thanks.


texts: BJTs - Large DC Signal Analysis - Negative Voltages

texts:
So there's this circuit here. I'm a bit confused with the negative voltage in order to find out the base current.

I sort of did a hack-ish guess and did a KCL at the node at the left of the base. I assumed the current was going into the node from both +15 and -15 V sources which added up to get i_b going into the base.

I ended up with the right answer but I still don't feel like I fully grasp the concept of a negative voltage. Could someone explain this to me better?


texts: Would any voltage be induced in this scario due magnetic coupling?

texts:
Imagine a source with a 100 Ohm source impedance is coupled to an amplifier/receiver which has 1Meg input impedance and the transmission is done by using two parallel wires signal and return |XA| and |GB| in the diagram. And imagine a changing magnetic interference is varying across this page.To observe the magnetic coupling effect I use this model below:

If G was wired to J and B was wired to H, i.e if both receiver and source sides were earth grounded I can say that the voltage induced at A would be greater than the voltage induced at B because Area2+Area1 > Area1.

But what if G and J has no wire in between and similarly B and H has no wire in between, i.e they are on the air 1 meter above the earth. In this case what can we say about the magnetic interference affect? Would there still be voltage induced at A and B due to magnetic coupling?


texts:
To mount an MPXV7002 pressure sensor (SMT) on a PCB, it has to be raised above the board by about 3 mm to allow the plastic tubing to be attached to the pressure ports.  This is an 8-pin device that normally surface mounts with the ports off the end of the board, however, restrictions dictate the ports (that are at the level of the bottom of the device case) have to be within the board.  Thus the need for a way to elevate the sensor with something conductive that will surface mount to the board (or through hole) and allow the sensor to surface mount to it.  Is there such an item available, other than standard straight male pin headers?

http://www.nxp.com/files/sensors/doc/data_sheet/MPXV7002.pdf


texts:
I am using C18 compiler and I learned that acknowledge polling feature will greatly help in reducing the write time that is to remove the fixed delay in traditional methods. Well I am using EEPROM 24LC256 and there is a feature for acknowledge polling in it.

I have written a code for Acknowledge Polling.

  long eewrite_p( int address,int msg)
    {
        int my_response;
        int i;
        i2c_init();
                                    //if(!i2c_initialised) return '\0';
        StartI2C();                 //Send the Start Bit
        Nop();
        IdleI2C();                  //Wait to complete
        Nop();
        WriteI2C( 0xA0 );
        Nop();
        IdleI2C();
        //Wait to complete

        WriteI2C( address>>8);
        Nop();
        IdleI2C();

        WriteI2C(address&0xFF);
        Nop();
        IdleI2C();

        my_response = WriteI2C(msg);
        Nop();

        AckI2C();
        IdleI2C();

        StopI2C();              //Send the Stop condition
        Nop();
        IdleI2C();              //Wait to complete
    }

Well, this is an old code w/o acknowledge polling. I've read about acknowledge polling for every Control Byte/Data/Address Byte is necessary. Correct me if I am wrong. Do we need to do an acknowledge polling for every Byte written in to the chip?

Another doubt I have is if we check for acknowledgement and if it is not received then the Datasheet/App notes says wait till Acknowledge is received. Else the code is polled till Acknowledge is received.

Well, previously I tried writing EE device address, one function after another, w/o any delay in between them and I trust it must not have been written well. How can I modify the current code to make use of Acknowledge polling?


texts: New WS2801 LED strip fails while old identical ones are working

texts:
I'm trying to add an additional 2 LED strips to my current setup of 4 identical ones. Each strip consists of 32 RGB LEDs with a WS2801 chip run by an arduino which connects to a PC. However I'm running into flickering issues when using the new strips.

The LEDs seem to light up as they should during the start sequence where the arduino itself sends out a couple of hard coded, single, colors for a few seconds. After the test sequence it will start listening to commands from the PC, which will here tell it to show purple and only purple.

Video of the issue- using 1 new strip (closest to camera) with one old working strip:

https://youtu.be/MfVgBuQBV-I

Video of what it should look like - using 2 old strips together:

https://youtu.be/9lQy1iouA_g

I have drawn a crude circuit diagram of my wiring here. I'm slightly unsure about the grounding of everything since the arduino sending the signals is powered by USB. But as said it seems to work fine for the old strips.

More details and what I've tried:

It's interesting to note that using a new strip together with an old one causes the old to misbehave as well.
It's also interesting that is shows a correct color (although blue) when i stop writing color values
No software or other hardware changes were made between the two videos
Below is a photo comparing the input connectors of a new (top) and old (bottom) strip. They are also ordered off the same amazon article and should be identical
Both new strips seem to behave the same
Data / Clock lines are correct, swapping them does nothing
Using slower clock speed from the arduino doesn't help (normally using 1 Mhz)
Powersupply (10 W) should be sufficient
I've measured the supply voltage to be 5.01 V using a multimeter
Lowering brightness (lowers power consumption) does nothing
Playing around with the connector ends seem to do nothing

I would've though the new LED strips were broken if it wasn't for the first test sequence being correct. Any suggestions on troubleshooting would be appreciated.


texts: Current consumption for RS485 transceivers?

texts:
I am building a prototype that uses a RS485 BUS to communicate many devices and current consumption is a crucial part in this project. In order to set the communication up, I have been looking at several manufacturers. However, I haven't been able to find the current consumption while sending or receiving data in the datasheet specifications of any of the products. I also didn't find a graphic showing Icc(mA) vs. Datarate(Mbps) like i found in some other Maxim Integrated products. Do you know where is this information available?

This is an example of the table i was talking about.

In particular, I have identified the following products to be valid for my solution:

Analog Devices:

ADM485E
ADM1487E
ADM3486E
ADM4852

Texas Instruments:

DS1487
DS481
SN65HVD3085E
DS485

Maxim Integrated:

MAX1487
MAX1487E
MAX485
MAX485E
MAX481
MAX481E

Thank you in advance.

Edit:
First of all, thanks for your answers and comments.

As some of you have answered, the current consumption could be negligible in most cases due to the short ammount of time the transceiver is transmitting. In my case I have to send images and it takes roughly 2.5 seconds for every image sensor on the bus, which in total takes up about 14.4 % of the total time, thus not beeing negligible.

Most of you have poined out the average powed dissipation section on the datasheets of the transceivers, so I will look into that for the devices I have asked for and post here the results I come up with.


texts: Text File tranfer between PC and Atlys board (FPGA)

texts:
I am new to FPGA. While doing calculations I found that I can not input number in real time to FPGA. My instructor told me to write my numbers (or data) in a text file on PC and tranfer it to FPGA in real time through any communication link (USB, Serial or Ethernet).

After searching on internet, I found nothing but ugly new terms which I dont know. A lot is there but no one talks about which software to use or how to program FPGA.

USB transfer.
This one talks about USB but with Visual Express 2010 which I am not doing. I am simply learning and making adders and multipliers.

I have found this but its for vertix 5 board. If I can get any link like this for Spartan 6 then it will be of great help.


texts: What is the use of drain diodes in the circuit below?

texts:
This TC7920 driver will be driving a piezo electric load which may behave like a capacitive load at certain frequencies. There is another IC TC8220 which is the same except it is not having the drain diodes like TC7920.Please let me know the use of these drain diodes. Can these ICs be relaced with each other for a piezoelctric load?
Another question is the use of damp signal? Is it just to pull the output to ground or any other use?
Link for TC7920: https://www.mouser.in/datasheet/2/268/TC7920_B080613-1532304.pdf
Link for TC8220: https://www.mouser.in/datasheet/2/268/TC8220%20B080713-965140.pdf


texts:
For the following circuit, I'm trying to find the voltage at node B, so I write some KCL equations:

at node A:

$$
v_A=20
$$

and,

at node B:
$$
\frac{v_B-20}{50}+\frac{v_B}{5}-9(\frac{20-v_B}{50})=0
$$

And I get that vB = 10 V. I run this in Circuit Lab and get the vB is -80 V though. Where did I go wrong?


texts:
with a prototype of FMCW radar I'm trying to resolve the distance to the target
The Audio card characteristics are as follows:
Fs= 44100Hz
So the FMCW radar range resolution is
RR=440MHz/c = 0.34m
Ts=20ms
thus, number of points N=Fs*Ts = 882
I've tried putting the target on various distances
1m, 1.1m, 1.2m, 1.3m all the way to 2m
Does the range resolution limit me from calculating distance changes of 0.1m?
I'm new to this and would appreciate your help.
My code takes the IF difference, Does FFT of the signal with 4*N points (I don't know why but this just worked whilst testing)
I get the correct distances but my question is How?! Do targets not have to be spaces 34cm apart ?
When I produce the plot (X axis is 0 to max_range which is around 150m with the given data, and Y axis is the FFT values with 4*N samples.
Could someone point me in the right direction?


texts: INA219 current sensor allowing only 300mA of current between its VIN+ and VIN- terminals. Why?

texts:
I'm building an Arduino circuit to detect/limit the maximum charging current to a camera flash.
I decided to use an INA219 breakaout board, which comes with a R100 resistor as a shunt so it should allow measurements of 3.2A maximum.
Before assembling the circuit with the Arduino, I decided to test the sensor to see if it would allow instant high currents to pass through it's VIN+ and VIN- terminals, without connecting any supply to it, nor SDA and SCL lines.

What happened is that it limited my bench power supply source to 300mA maximum. The flash charged, but slowly.
If I plugged my flash terminals directly to the power supply, it chaarges faster, with initial peak currents close to 3A, the way I need it.

I then tried connecting just the 5V VCC and GND to the INA219 breakout board, again without wiring SCL and SDA to an Arduino. Again only 300mA of current were drawn by my bench supply, and the charging of the flash was still slow.
Why is that happening? Do I need to fully connect it to an Arduino for the INA219 to allow more current to flow through its terminals?
Edit1: Inside the flash's 3V battery compartment I soldered a DC DC buck converter that converts the 8.2V to 3V, allowing 3A maximum current.
INA219 Datasheet


texts: Can I power 4 DC motors with an AC/DC Adapter?

texts:
I have 4 24v DC motors that I would supply with a 24V 5A AC adapter I have 2 L289N motor driver board though so I wont be connecting them directly to the adapter.

Question: Is it safe if I power the 4 motors with just 1 adapter?

The motor's current draw (running current) is about 0.1A each so I figured it would be enough for it to power but I've read somewhere that unregulated power supplies (im not sure if this one I got is regulated or not) are unreliable to power motors especially because the current draws may vary because each motor I use will not work simultaneuously (e.g. at a time, only 1 or 2 motors are running, 2 are dead or 3 are running 1 is dead and all 4 may be running at the same time)


texts: Why do we need a preloader and a bootloader in many applications before even the main program

texts:
I have read the datasheet of Altera's new HPS. It shows a chart where it shows:
Boot ROM -> Preloader -> Bootloader -> OS

I am wondering, why do we need a "pre-loader" and than the "bootloader" and than the OS? I have already read questions concerning bootloaders on this great forum and have some idea of what it is supposed to do. I understand that there are different type of bootloaders and their purpose is not the same in every case.

What I am confused about is this thing that we describe as preloader, why is it there?


texts: MH-Z19 calibration. What to do for a not permanently powered device?

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I have 2 MH-z19 for measuring indoor CO2 calibration. One is running permanently on a Raspberry Pi, the other one with an Arduino Pro Micro on a handheld device, that is turned on only when I want to measure.
The specs say that the MH-z19 is auto calibrating every 24 hours. That feature can be turned off and it can be calibrated by sending a zero point calibration command.
Does this zero point calibration (400ppm) survive the powered off MH-Z19 on the Arduino?
MH-Z19 spec: https://www.winsen-sensor.com/d/files/infrared-gas-sensor/mh-z19b-co2-ver1_0.pdf


texts: I constructed a single stage differential amp and used it to make a subtractor. The input amplitudes are 2 mV and 3 mV, however the output is about 1.4 mV. Can anyone tell me why?


texts: Op-Amp - Sharing Non-Inverting Inputs in a two stage amplifier

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I've mocked up a simple circuit using a TL064A to reduce the single level of a single ended input audio source.

I'm using two stages per channel, and both stages on each channel are sharing a connection to AGND. Is there anything inherently wrong with this? I understand that the Op-Amp will force the inputs to the same voltage, and I'm concerned this may lead to interference.

Here's my schematic:


texts:
I'm trying to analyze this circuit and spend almost 2 days to make a formula for it but I don't get it , anyone know what it's called or how can I make formula for it ?
I want to calculate I1,I2,I3 currents but their rotation change at certain points .I used the mesh currents method and branch currents method but when the  current rotation change equation change too .
My goal is make a program in my calculator (R1,R2,R3,VIN,VSUPPLY  adjustable) so I can get results in future


texts: BPSK bandwidth for symbols not integer wavelengths

texts:
Most of the BPSK waveform examples in text books/online are for carrier frequencies that are integer multiples of the bit rate. This means that when the symbol polarity changes there is a discontinuity in the waveform - but it doesn't jump signal level, it just heads the other way. When the carrier frequency is not an integer multiple, the waveform does need to jump instantly from one signal level to another (ie the symbol change takes place when the signal level is not at signal level 0)..
Does this increase required bandwidth or have any other undesirable effects??


texts:
This is my op-amp

simulate this circuit – Schematic created using CircuitLab

I used superposition to find U1, where I got  $$U_{A1}=\ -U1$$

2nd part of solving the circruit when U2 is active
$$R_2+R_4=\ 2R\ \ \ \ \ \ and\ \ R_3//R_5=\ \frac{R}{2}\ \ \ \    $$

$$U_{A2}=(1+\frac{R_6}{R_1})*(\frac{\frac{R}{2}}{\frac{R}{2}+2R})U_2=\frac{2}{5}U_2  $$

There is not way I can prove if this is right or wrong so I would really appreciate some help.

Which load resistance is connected to U3 ?


texts: How to interface a BQ76PL536EVM with a MSP430 uC using the sample code?

texts:
I am trying to follow the application report : http://www.ti.com/lit/an/slaa478/slaa478.pdf to setup communication between a BQ76PL536-EVM (TI battery monitor) with a MSP430 uC board (I am using a MSP-TS430PN80USB with MSP430F5529 uC) and have made connections and setup as explained in the application report. I have further programmed the uC with the sample code provided (link for the code at the end of report) and am now trying USB communication of the uC board with a PC. The board should report battery voltages etc when I send 'p' across the serial connection. A serial connection is established but it doesnt show anythign that I type, not even the alphabets I am typing, and also doesnt show any response.

I have tested both boards individually and they work. I have tried USB communication examples on the uC board and they work too.

The battery monitor communicates over SPI and I have tried an Arduino and a Raspberry Pi too to talk to the battery monitor, but even that has not worked.

Any ideas on how I could debug the system further ?


texts: Why would an incandescent bulb produce a bright flash when burning out?

texts:
A typical way of an incandescent bulb to burn out is with a bright blueish flash and often an audible sound and (very rarely) an explosion of the bulb glass.

Wikipedia says the following:

  Since a filament breaking in a gas-filled bulb can form an electric arc, which may spread between the terminals and draw very heavy current, intentionally thin lead-in wires or more elaborate protection devices are therefore often used as fuses built into the light bulb.

But it's unclear why an arc would spread and cause very high currents.

Why would it not burn out silently instead?