texts: Series resistance for DC brushed motor with PWM drive

texts:
I'm looking for double-checking my math/assumptions, and if possible, a physical explanation of the "rising corner frequency" phenomenon.

When controlling a DC brushed motor with PWM, typically by switching MOSFETs in a bridge configuration (or a single MOSFET plus reverse diode when driving in only one direction,) it is possible to limit the maximum amount of current seen by the MOSFET by measuring resistance and inductance of the motor, and setting the PWM on-time to be no more than an appropriate time.

For example, for a 16V drive of a 20 uH motor with internal resistance of 2 Ohm, the time constant is (0.000020 / 2.0) or 10 microseconds, and the current achieved after that time is 16V * (1 - 1/e) / 2.0 Ohm = 5.06A. Alternatively, if I have a fixed PWM frequency, the duty cycle has to be set appropriately to make the on-time be at the given length. For example, with a duty cycle of 20%, the total cycle time is 50 microseconds and the frequency is 20 kHz.

I want to reduce the risk of overloading the output MOSFET in the case of a short, so I add a 1 Ohm series resistor (rated for appropriate wattage at the expected duty cycle -- this is an example!) The time constant now shifts to (0.000020 / 3.0) or 6.7 microseconds. In effect, the corner frequency of the low-pass filter of the RL circuit has gone up; it now passes more high-frequency signal. This means that at the same 10 microseconds as before, the circuit has reached a higher percentage of its "final" current.

First: Am I missing something, or is this correct? (to the first order -- motors seem tricky when you want to model everything!)

Second: It seems unintuitive to me that adding resistance increases the passband of the filter. Is it correct to say that the reason for this is that the time constant measures "time to 1-1/e of final current," and the additional resistance makes "final current" lower? I e, the actual current growth / voltage drop "speed" in the inductor doesn't change; instead it's the "goal" that changes? The math is very clear that this change in time constant (and thus frequency response) happens, so I'm trying to find the right "hook" to anchor my physical understanding to.


texts: How to convert arcade RGB video (2-5v p-p) to VGA (0-0.7v)?

texts:
I'm trying to convert arcade video signals (JAMMA) to VGA specifications.

From what I've gathered, arcade video signals aren't standardized.  They can range from 0v-2v or 0v-5v, etc.  However, VGA requires 0v - 0.7v p-p (75 Ohm double terminated).

Are there any ICs that can detect RGB voltage and then convert it to VGA level?

Can anybody give me any advice?


texts: Why can't I light a LED with a 1.5 V battery?

texts:
The LED I am using requires a higher voltage to light than I have supplied, and as a result, it doesn't light at all.

I would expect at least a dim light, but light is not generated.

Why this behavior of "if there isn't the required voltage level there's no light"? What is going on inside the LED?


texts:
As far as I know per unit system removes the transformation ratio, having only one per unit impedance on both sides of the transformer. However, the question below gave different per unit values for the same transformer windings WHY?
Source:
https://courses.electricalpereview.com/courses/take/electrical-power-review-course/quizzes/14677216-quiz-transformers


texts: What type of mask to be used in lead free soldering?

texts:
Is it safe to use mask for lead free soldering in solar string soldering?
What type of mask to be used?
What is the difference between lead based and lead free flux?


texts: LED strip brightness and its measurement - did I get ripped off?

texts:
I recently bought two 5m rolls of red and blue LEDs for building an hydroponic lettuce light. Each of them is supposed to have the following properties:

300 SMD 5050 LEDS
72 Watts
12 Volts
4500 Lumens
Beam Angel 120°

See Amazon

Naturally the high lumens were the thing that made me buy these ones. But I had my doubts so I started measuring their power consumption first:
Red: 92,5 W Blue: 71,6W
So red is drawing way to much current - still no big problem as I am interested in light intensity.

Here is a schematic:

simulate this circuit – Schematic created using CircuitLab

Then I measured all the LEDs and resistors and found the following:

Red: LEDs(2.1V), Resistor(2.8V),
Blue: LEDs(3.06V), Resistor (1.3V)

That suprised me:
As there are always 3 LEDs and 2 resistors in series, the resistors in the red strip account for about 46% of power consumption. The resistors in the blue strip for 22%. Is that normal? Or is it just bad engineering?

That seemed legit from datasheets of other vendors (they did not include any data sheet).
Finally I measured the luminous emittance with a Voltcraft MT-52 (cheap multimeter...).
I made a box where only one LED could fit and positioned the multimiter 10cm beneath it. I measured:
 - Red: 55 lux ~ 1.73 lm
 - Blue: 115 lux ~ 3.6 lm

If you multiply that by 300 LEDs per strip you get 520 lumens for red and 1086 lumens for blue - but they promised 4500lm for each one!

I know that my multimeter isn't exactly made for measuring this and probably has a quite big measuring error - especially for LEDs. But can the error be that big?
And are there even 5050 LEDs that could give me 15 lm a piece?

Finally a pic of the LED strip (notice the weird circuit: LED--R--LED--R--LED)


texts: Help calculating the value of a smoothing capacitor

texts:
I prefix this with I know virtually zero about electronics, sorry.

Preface

In an attempt to try and gain some basic knowledge and learn a lower level programming language (usually work with more abstracted languages) I'm working on a project to create a power folding mirror module with an Arduino.

My current progress is located here if anyone is interested.

It currently works. I listen to door lock CAN message and simulate ignition through an Arduino pin. Using a couple of relays it controls the mirrors.

However I can't seem to decipher ignition signals of from CAN messages so I need to take a 12V feed and bring it down to the safe 5V level my Arduino can work with.

I have an of the shelf offering which I have opened up and am trying to use as a reference to some of the circuitry and design.

Question

Based on my off the shelf offering I have traced the following circuit.

simulate this circuit – Schematic created using CircuitLab

It is my understanding that R1 and R2 make a voltage divider and bring the voltage down to about 4.5v.
It is also my understanding that R3 will act as current limiting. I assume not for the benefit of the Arduino but more to protect anything I may have taken the original 12V feed from.

The part I'm having trouble deciphering is C1. Based on my attempted research i think this is acting as a smoothing capacitor.

How can I work out its rating? I have no equipment capable of measuring it. Are there any sort of generic default values such a component could be in this context?

Iv'e tried looking at the rules for calculating it and the various equations I've seen are just a little mind boggling (maths is a sticking point for me, which is odd being a programmer writing HR and payroll software.)

Thanks for any advise. This is the first question I've written in this domain so hopefully it is acceptable.


texts:
I need some some Magnifier for SMD soldering so I bought these Magnifying glasses:

http://www.ebay.com/itm/381555608061?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

It is good for PCB inspection but it's not for SMD soldering: for 10x magnification glasses need to be only few centimeters away from PCB and for greater magnification, distance is of course smaller so it is not possible to use it for SMD soldering. My question is, is there any cheap solution? I'm not good at optics, but smaller magnification mean larger distance, right?
What do you think about these glasses:

http://www.aliexpress.com/item/Magnifying-Glasses-2015-Rushed-Top-Fashion-Glass-Surgical-Loupes-1x-1-5x-2x-2-5x-3/32381736388.html?spm=2114.30010308.3.52.SCX8Jl&ws_ab_test=searchweb201556_9,searchweb201602_1_10034_507_10032_10020_10017_10005_10006_10021_10022_10009_10008_10018_10019,searchweb201603_6&btsid=8d9303e9-107a-4a6d-b3b4-eabeec9ed4cc
?

Here are specifications:

Color: Black

Material of Lens: Acrylic Lens

Battery: 3 * LR1130 Button Batteries (included)

Lens: 1.0X / 1.5X / 2.0X / 2.5X / 3.5X

Field of View:

1.0X: 250~350mm

1.5X: 200~300mm

2.0X: 175~275mm

2.5X: 150~250mm

3.5X: 80~120mm

Size of Lens(1pc): 85 * 8.5mm (L * T)

Item Size: 220 * 145 * 55mm / 8.66 * 5.7 * 2.16in (L * W * H)

Package Size: 22.0 * 17.7 * 4.7cm / 8.66 * 6.9 * 1.85in (L * W * H)

Package Weight: 270g / 9.5oz

What does "3.5X: 80~120mm" mean exactly?


texts:
In the following you can see the channel A ( above ) and the Channel B ( middle) output of an optic encoder that is connected on a rotating shaft.

My questions is: Does the impulse width impact the way you need to count the distance? To me , it seem that channel A is in advance from channel B therefore I just need to add distance to my current total distance ( convention A in avance on B = increment in position)
Could you see it as the distance going back and forward therefore explaining the larger pulse on channel A and smaller pulse on channel B?
[EDIT]
Here is the link to the encoder that will be used
Encoder Datasheet


texts: Impedance matching with complex impedance source

texts:
The method/steps to use a VNA to determine a matching network for a 50 Ohm (or whatever impedance) antenna seem mostly clear to me now. My current knowledge assumes though the transceiver (source) is basically the same impedance as the desired impedance (well, complex-conjugate) of the feed line + antenna. That's the whole point after all, to match them to the transceiver.

What I don't really understand, is how to tune the system when my transceiver is known to have a complex impedance other than the antenna (in my specific case the manufacturer specifies it to be 35+10j Ohms).

Say my source is Zs and my load is Zl. Is my goal then, when measuring the impedance using a VNA, to see Zl when my probe is placed at the antenna in, and to measure Zs when measured at the point of the transceiver? Should the transceiver be connected during these measurements at all? Should it be powered (but not sending)? How does this comply with the general advice of connecting the probe at the point of the matching network?


texts:
I'm making a guitar pedal project,  and I have a very basic understanding of electronics, so I'm having a hard time understanding some of the logic behind the schematic I have.

Why would I need to connect the battery to the jack input?

My original question was why would I need a stereo jack input if a guitar uses a mono jack, but looking at the schematic just made things worse for me.


texts:
I am currently working with a project where i am creating a small embedded board consisting of a 9DoF IMU which is transmitting its data with RF (BLE or normal RF). Furthermore there will be a battery attached extremely close to the unit.

I have few questions for this application:

Can i have a RF antenna close to the IMU and how will it impact the electronic compass?
Can i have a battery on the back or top of the board very close to it, and how will it impact the electronic compass?

Which type of battery would be suitable: LiPo, Pure lithium, LiFe

I plan to use a Invensense IMU for the purpose.


texts: How to toggle relay with single push-button

texts:
I believe there is a simple circuit, that uses a single non latching push button (1 or more pole possible?) to toggle  12V relay. 1 press - ON state, another press - OFF state and so on.
I can't find it anywhere, I searched over the internet as much as I could.


texts: Virtual ground in two-stage OpAmp for slew rate calculation

texts:
I am reading about slew rate of two-stage OpAmp from this page.
However, I don't understand why the node voltage at drain of M2 or M4 is assumed to be a virtual ground here.

Could anyone explain that?

PS: I have just seen a paper here saying that the output voltage is also the voltage across the capacitor.
Could you explain why the voltage across the current source M0 is almost zero?


texts: PCB routing: EMI and signal integrity, return current questions

texts:
If there's any EMI/SI lesson I've taken in, it's to minimize return loops as much as possible. You can work lots of EMI/SI guidelines from that one simple statement.

However, not having or ever even seen Hyperlynx or any sort of full RF simulation tool... it's somewhat hard to imagine what specifically I need to concentrate on.  My knowledge is also entirely book/internet based...  not formal or based on too many discussions with experts so I likely have weird conceptions or gaps.

As I imagine it, I have two main components to a return signal. The first is a low frequency (DC-ish) return signal that follows generally as you'd expect...  along the lowest resistance path through the power network/plane.

The second component is a high frequency return signal which tries to follow the signal trace on the ground plane. If you switch layers from say the top layer through to the bottom layer on a 4 layer board (signal, ground, power, signal) the HF return signal will as I understand it try to jump from the ground plane to the power plane by detouring through nearest available path (nearest decoupling cap, hopefully... which to HF might as well be a short).

I suppose if you put these two components into terms of inductance, then it's all the same thing really (near DC resistance is all that matters, at HF lower inductance means following along underneath the trace)..  but it's easier for me to imagine them separately as two different modes to deal with.

If I'm okay so far, then how does that work on internal signal layers with two adjacent planes?

I have a 6 layer board (signal, ground, power, signal, ground, signal).  Every signal layer has an adjacent ground plane that is entirely unbroken (except for vias/holes, obviously).  The middle signal layer also has an adjacent power plane.  The power plane is split up into several regions.  I tried to keep that to a minimum, but my 5V split for instance takes the form of a large thick "C" shape around the outside of the board. Most of the rest is 3.3V, with a 1.8V region under most of a large BGA, with a very small 1.2V region near the center of that.

(1) Will my split power plane cause me issues even if I focus on ensuring the signals have good return paths through the ground planes? (2) Will the low frequency return path taking a wide detour on my "C" shaped 5V plane split cause trouble? (I'd generally think no... ?)

I can imagine that two unbroken planes with nearly equal inductance would possibly induce return current to flow in both... but my wild guess is that any significant detour required on the power plane would make the return signal heavily bias itself towards the ground plane.

(3) Also, the middle and bottom layers share the same ground plane. How big a problem is that?  I'd intuitively guess that traces directly over eachother sharing the same ground return would interfere with eachother more than simple adjacent trace coupling on the same layer. Do I need to work extra hard there to make sure that doesn't happen?

I'd suspect there may be a "yeah generally, but you can't know without simulating it" comment coming...  let's just assume I'm talking generally.

EDIT: Oh, I just thought of something. Would crossing a power plane split screw up trace impedance for stripline?  I can sort of see how the ideal trace impedance is lower based partly on having two planes...  and if one is broken up could that be a problem...  ?

EDIT EDIT: Okay, I've partially answered my question on sharing a plane between signal layers. Skin effect depth probably mostly limits the signals to their own side of the plane.  (1/2 Oz copper = 0.7 mils, skin depth @ 50MHz is 0.4 mil, 0.2 mil @ 200MHz..  so anything over 65MHz should stick on it's side of the plane. I'm mostly worried about 200MHz DDR2 signals, but < 65MHz components of that could still be a problem)


texts:
I am looking to replace a 4.3 inch TFT (480*270 px - 400-500 mA @ 5V) by a more energy efficient one (other sizes welcome) to go with my raspberry pi driven handheld emulation console.
What is the minimum intake that I have to take account, if I can find a screen that runs natively on the 5V or 3.3V that my battery or the Raspberry supplies?


texts: How do you make custom THT (through-hole) connectors?

texts:
I have a project that requires a connector that is no longer manufactured which would interface with an old device. For prototyping, I have been salvaging this connector from old peripherals that used it, but I need a way to get these connectors in bulk that doesn't rely on using other devices for parts. Specifically, I need the THT (through-hole) version of this connector.

Is there a way to either make the connector myself or to get them manufactured? The connector plug is like any other USB, HDMI, DVI, or similar THT plug, it is just of a completely custom design.


texts: Cypress MCU strucks in Hard Fault Handler

texts:
I have started using Cypress MCU Cortex M0+ but I am seeing that Debugger always gets struck into Hard fault handler. Behaviour is random, sometimes it goes into hard fault handler at the start of execution of code and sometimes after executing the half/full code.
Any idea, what could be the issue? What all I can check.
Moreover, If can I doubt on hardware or firmware is the culprit?


texts: Can this work as an ADC Input setup and is it common?

texts:
Would this work? I'm pretty sure in theory it should, but I don't see it often or at all. In theory, the voltage divider from 2:1 to 1:2 should give 3.3v at one end and 1.6v at the other end of the pot, giving the ADC a wide range to work with. And if the button is pressed, the R1+RV will act as a max 20k pullup, so the line would be down to 0v, which the ADC can be coded to recognize as a unique event, allowing both a button and a pot to exist on the same input pin, allowing the ADC to serve both purposes.

An input pin is saved, without any significant code changes, as the adc is already being polled for the pot.

simulate this circuit – Schematic created using CircuitLab

Would this work, and if so, as a curiosity, why isn't this more popular.


texts: I am attempting to set up an I2C bus off of a Raspberry Pi that will have two slave devices. One of these devices already has built in pullup resistors, but the other does not. Is there any way to run them both on a single bus? Can I add a pullup resistor to the bus and expect them both to work? Or is this maybe something I can only figure out through testing?


texts: Why not make soldering iron tips out of tin?

texts: It seems illogical to me to make a soldering iron tip out of steel coated copper. If tin is a superior material (notice the anachronistic use of the term "tinning" used today), then why not just make the tips out of tin? Is cost the only reason? Seems crazy to me to put up with difficult soldering just to save a few dollars on the tip.


texts:
How does a dual gate MOSFET reduce Miller effect? I am trying to gain a global understaning of the physics behind them, not necessarily exact formula's that come with it other than maybe some for practical use. The Wikipedia article refers to a tetrode article based on tubes, where I get slightly lost.

I guess the questions in order are:

What is a tetrode (in discrete transistor/MOSFET speak);
How is a dual gate MOSFET similar to a tetrode, what are the 'mechanics' behind it in global terms? (Trying to get a feeling for the physics behind it).
How does it reduce Miller effect and is a dual gate MOSFET different from a discrete tetrode in this.
Is a dual gate MOSFET any good for other properties?


texts: Speed control using direct torque control of induction motor

texts: Is there any steady state error present in speed output at any load in direct torque control of induction motor?


texts: Custom spot welder design for very small scale

texts:
This is an R&D project to test feasibility.
I need to try and weld a fine tungsten wire (50 micron) to a small piece of copper.
The obvious solution (to me) is to place the wire on the copper and compress both side with an insulator, then feed in a current pulse.

If it works, local melting/bonding would take place.
The bulk of copper, being much more massive than the wire, could sink a lot of heat. The tungsten wire - well, it melts at over 3000degC so I am assuming most of the local melting happens at the copper interface.

So, the electronics question.
Given a capacitor, how do I discharge a massive current in a very short time? A mechanical switch would weld or be destroyed and I am not sure a MOSFET would do the job. I am assuming a ballpark energy of 10J to 100J

Has anyone done anything similar?


texts: How to connect LDR to LED by using battery 5V

texts:
I connect LDR to LED by using battery 5V like this circuit.

I adjust value of VR and LDR but it's not work. LED still 0.00V.
How to fix circuit for make LED to 5V


texts: Need help sizing zener diodes and varistor for 12v automotive power supply protection

texts:
I have built an astable 555 timer circuit to control a MAC valve that will allow me to change the turbo charger boost levels on my S10.

The circuit works great as is but I skimped out on the circuit protection side of it.  Currently there is a diode across the MAC valve and just a single .33 uf cap on the 12v side of the LM2937-5v voltage regulator.

After doing some research it looks like I should consider installing both a varistor and a zener diode to help protect against voltage spikes.

Here are some good articles I found:

https://www.electronics-tutorials.ws/power/transient-suppression.html

https://www.electronicdesign.com/power-management/article/21800530/select-the-right-varistors-for-overvoltage-circuit-protection

Here is a link at Mouser of some varistors I am looking at
https://www.mouser.com/Circuit-Protection/Varistors/Automotive-series/_/N-5g3h?P=1yzt5irZ1y7yila

Running voltage is around 14 volts and according to the document above I should size for 20% over so I should look at around 17 volts.
What should I consider for peak current in an automotive environment?
Is the only reason to consider a varistor with a lower peak surge current just physical size?  So if I had all the room in the world then I just go with a 2kA and be done?

Another item I have been using for some back ground information is the schematics for a megasquirt ECU.  For those of you that are not familiar with MegaSquirt ECUs they come as DIY ECU kits that you solder together and assemble based on your engines needs.

Here is the schematic of the voltage regulator and circuit protection.
I guess my question is what is the difference between MOV1 and the D13/D11/D12 combo?  I thought a MOV essentially acted like a back to back zener diode package.

I guess can someone help kick me in the right direction.
What exactly am I trying to protect against?  Someone hooking 2 batteries in series?  hooking up jumper cables backwards?  Large rush of current during cranking?

Thank you everyone for your time and input!


texts: Can I connect 2 USB ports to a device with a Y cable and therefore double the current output?

texts: Say I have a portable power bank with two USB ports providing 2a each. If I connect both the ports to the same device using a Y cable would I therefore have an output of 4a?


texts: Measuring SNR on a mulltiplexed coax power and data cable

texts:
Please excuse the basic knowledge I have in this field.
Within my workplace, we constantly use long 300m-6km coax cable which carries HV (Up to 400VDC) and DSL data.
We have encountered problems whereby using a cable length too long has resulted in interrupted data, as well RF pickup in some instances that interrupt data.
I would like to be able to carry out physical tests on cables not only for my own sanity so I can see exactly what is happening and when, but also to aid in isolation of where problems are occurring and to be able to send visuals back to the office demonstrating where our problems arise.
I have been looking at different options, ie, tablet based oscilloscope (Handy as it makes the unit easier to carry/use in the workplace), PC based oscilloscope (Pico), etc. I'm not sure on the best route to take here.
Could some recommend not only an ideal test tool, but a method for measuring Signal strength, SNR and RF pickup (This tends to happen when we operate motors in close proximity).
As I say, my knowledge in this field is extremely limited, but as well as just being able to carry out the test, I  am hoping to learn an understanding of what is happening etc.
Thank you in advance.


texts:
I'm still not entirely clear on TTL, so please, forgive my ignorance in this.

I have a sensor and a microcontroller. The sensor is a BMI055 Gyroscope and accelerometer. The microcontroller is the Atmel AT32UC3C0512CAU-ALUT. With these two, I want to connect them with a correct 4-wire SPI interface.

Here is my proposed layout:

pins 13-17 are as follows from the datasheet (above):

13: (Function B) SPI0 MOSI

14: (Function B) SPI0 MISO

15: (Function B) SPI0 SCK

16: (Function B) SPI0 NPCS{0} (NPCS is chip select pin)

17: (Function B) SPI0 NPCS{1}

Thing I have questions on: Am I correct in using pull-down resistors? I hear Pull-up is more common, but I'm not sure why. Another thing is how would you make this schematic prettier? it's pretty bad right now. and my final concern is the value of these resistors. I'm not sure how to calculate that.


texts: Is there a way to utilize a old screen using electronics that can be handheld?

texts:
So, I guess this is a follow-up question to my previous one: Is there a way to output high quality pictures to a monitor with VGA using an Arduino?. Obviously, the answer did help me to get rid of the Arduino approach which would have cost both time and resources on my part (so thanks :)
But my question today is the following one: Suppose I have a laptop screen. I have its connector with it (it's with the screen). So, basically, it's just been disconnected from an old laptop from the 2009s. Is there a way to utilize it? I know I can use a PC to show pictures on there or, well, run windows. But is there something the size of an Arduino or something that can be handheld that will help me control the screen and input to it?
Edit: So, I don't know if this is a datasheet (I'm still a beginner in reading datasheets and patents per se), but this could be it: 15.4” WXGA+ TFT LCD


texts: Simulating Multiple Feedback Low Pass filter using LTSPICE

texts:
I am trying to simulate the follwoing circuit in LTSpice IV. What I am looking for is overall performance in frequency domain.

I downloaded and readed a lot of LTSpice guides, but none of them were speaking about how to do for this kind of circuit. If you know how-to, I would really appriciate yuor help! Maybe it is stupid but I do not know what voltage source (AC, DC, sine or ...) I should use and I do not know which simulation type will be what I need.


texts: Filter design for high power voltages Partial discharge detector

texts:
Hell all,
I have a signal imposed on a 60Hz 800V AC voltage that I need to retrieve via MCU. The signal is in the range of 10KHz to 50KHz with peak to peak voltage ranging from 5 to 50 volts . The signal waveform is as can be seen in attached image. I have never worked with such high voltages before and tried a few methods to retrieve signal however I failed. (I tried dividing the voltage and and taking a sample however that failed, I tried a transformer however the signal was lost in the transformer and more noise was introduced).
This signal is that of a Partial discharge/corona that I need to detect for an extremely small part in a certain environment.
My question is as follows, are there any active amplifier designs that handle high voltages, up to 1kv. Also, where can I find such high voltage components?
Any design suggestions would be greatly appreciated.

Thanks in advance for all your tips.


texts: HDLCompiler:251 - Cannot access memory directly Error

texts:
I'm giving a 2d array to a VHDL module.This 2d array is valued in a verilog module.
The error that ISE is giving is that the 2d array is assumed a memory and can not be accessed.
I've googled the error but there were no answers to this specific case.
Please help me on this.
Here's the definition of the 2d array.

wire [IN_FIFO_DEPTH_BIT:0]  depth_of_fifo[NUM_QUEUES-1:0];//storing the depth of all FIFOs
wire [IN_FIFO_DEPTH_BIT - 1:0] packet_size_temp[NUM_QUEUES-1:0];

Here's the part of my verilog code that is the source of the error.

Deficit_Round_Robbin_algorithem
#(
.Quantom(),
.Num_queues(NUM_QUEUES),
.IN_FIFO_DEPTH_BIT(IN_FIFO_DEPTH_BIT)
 )
algorithem_module(
.clk(axi_aclk),
.axi_resetn(axi_resetn),
.m_axis_tready(m_axis_tready),
.packet_size(packet_size_temp),  //Line 247
.fifo_out_tlast(fifo_out_tlast),
.empty(empty),
.rd_en(rd_en),
.pkt_fwd(pkt_fwd)
 );

And here is the error message

ERROR:HDLCompiler:251 - "K:/final project/codes/v3/input_arbiter.v" Line 247: Cannot access memory packet_size_temp directly
ERROR:HDLCompiler:598 - "K:/final project/codes/v3/input_arbiter.v" Line 46: Module <input_arbiter> ignored due to previous errors.


texts: Alternatives to motorized variable capacitor?

texts:
I want to dynamically fine-tune the capacitor (about 100pF) of an RLC series resonant circuit, so as to keep it tuned despite variations of the coil's environment. Operating frequency is f = 13.56MHz, Q ≈ 30, about 0.1W power dissipation in R (mostly hidden in the coil). I only need like ±10% adjustment of C.

I see that I could use a motorized capacitor (approriately scaled with fixed capacitors), but what I find is way overkill and over-expensive.

What are my options ?

I vaguely see that a varicap may help (although polarization might be tricky), but I have no experience with these, and I even wonder if a varicap is at all compatible with my high-Q requirement.

I'm pointed that the voltage across the capacitor is critical in the varicap scenario. It can be estimated from the givens; I get:
(Q R)2 C = L
and (2π f) 2 L C = 1,
thus R = 1/(2π f C Q) ≈ 3.9Ω
thus IEFF = (P/R)1/2 ≈ 160mA,
thus UEFF = IEFF/(2π f C) ≈ 19VEFF across the capacitor.

With some margin, I believe 80VPP will never be exceeded.

Currently my capacitor has no grounded side; but that polarization issue seems fixable.


texts: Connecting an FM radio receiver circuit to a speaker via 3.5 mm audio jack?

texts:
As an experiment and for educational purposes, I wanted to build and connect an FM receiver to some old computer speakers via a 3.5 mm audio jack.

So I tried building a circuit like this on a bread board

My FM receiver circuit with pre-amp to 3.5 mm audio jack

Note: The 22pf capacitor on the far left is actually a variable capacitor that I can adjust between 8pf and 40pf.  And hopefully, I used falstad correctly to depict my actual circuit.

The circuit on the left consisting of the two transistors is something I found in most FM receiver tutorials.  And I figure I couple it to a NPN transistor pre-amplifier circuit on the right.  I then connect the output to the tip of a 3.5mm jack.

When I power up the circuit, my speakers are silent.  If I touch the antenna with my fingers, my speakers produce a low frequency hum.  I disconnected the 3.5 mm jack and hooked up an oscilloscope probe to the output and confirmed there is no signal...in fact I don't even see any noise waveform unless I touch the antenna with my fingers.

Does anyone have suggestions on what I might do next to receive an FM radio signal or at least noise from a blank FM channel?


texts: Wiring a car radio with two power sources

texts:
This is on a land rover I'm helping sort out for an off-road expedition

I'm trying to wire up the radio with two different power sources, but what I've got at the moment is having some undesired effects.

I'd like the radio to be:

Always powered when the ignition is on, but without the dashboard LEDs
Also able to be powered from the battery (A secondary battery, not the main car battery) if switched on.

If the switch is on then the dashboard LEDs should be on too.

If the switch and the ignition are on, I don't really care which source the radio uses.

Currently it's wired like this:

However there are problems:

The dashboard LEDs are always on when the ignition's on, and
If the switch is on and the ignition's off, the wipers start going

I thought about fixing it by putting diodes on the ignition-switched source, and between the switch and the radio (after the LEDs), I'm not where to get a diode that I can put 20A through or whether that's a good idea.

Thanks in advance for your help!


texts:
As I was trying to validate our pcb design, I measured the impedance matching on the digital transmission lines, and got stuck with the oscilloscope not showing what I expected. We are using the PicoScope 4227, but I suspect that the strange measurement is not directly related to the specific oscilloscope but more to general on how to measure digital signals.

My setup is as follow:
I measure the output-pin of an FPGA with both oscilloscope input A and B.

Input A (blue) is measured using the oscilloscope probe set to x10.

Input B (red) is measured using a 50-ohm coxial cable terminated at the scope input with 50-ohm.

As you can see, Input B seems correct, no reflection ect.

But Input A (the probe) has some overshoot, and ringing.

The probe should be calibrated and valid to 250MHz, so I don't get was is wrong. ?

I suspect that the small probe-clip adds some inductance, and therefore we see the ringing. But I really don't know.

EDIT
After reading your answers, I walked got into our lab storage and started looking, and found a probe GND clip like the one showed in the answer below.

When I use that clip, I get the output below. Which is really a huge improvement.


texts: How do computers understand decimal numbers?

texts: Computers calculate numbers in 0s and 1s. A bit can be either but not in between. So if you enter 3/2 into a calculator, it should return either 1 or 2, right? Wrong! It gives you 1.5, the correct answer. Even on problems with more complexity, the calculator answers with the right number. So my question is, how does all this work? If a computer can only use 1s and 0s, how is it able to interpret a number in between 1 and 0 correctly, and is there a way to build a schematic for a machine that understands decimal?


texts: How to mimic running lights, turn signals and hazards with LEDs for diecast model

texts:
20 years ago I took electronics in school. Did very well, but never used it much since so I have forgotten just about all of it.

I have been testing in LTspice and just cannot get anywhere with this. Spent about 12 hours total before searching google. Found this wonderful site and searched and browsed for hours and tried a few ideas I found but nothing worked.

Here is the needed setup

3 LED's per side of the vehicle
Using a simple on/off micro switch will turn on/off the running lights which consist of 2 of the 3 LED's per side
A 555 timer circuit (I have this part figured out) for the flashing (turn signals and hazards)

simulate this circuit – Schematic created using CircuitLab

A 4 position switch to now control the states of the LED's.

1st position: nothing.
2nd position: flash all 3 LED's on left side.
3rd position: flash all 3 LED's on right side.
4th position: flash all 6 LED's.

I have tried using NPN's in all sorts of configurations. DT switches to control where power goes... I am now at a loss, brain has run out of ideas. If we had SMD LED's with dual SAME color, this would be easy.

If there is any part someone doesnt understand, I can try to explain further.


texts: Parameter range to ensure stability using Routh Criterion

texts:
I have a question regarding Routh Stability for a characteristic equation of the form,

$$ 2S^4 + 2S^3 + 4S^2 + (k+1)S + 4 = 0 $$

I need to find the range of K for which the system will be stable. Upon using the Routh Criterion,

I ended up with two inequalities for K namely,

\$ K < 3\$ and \$ -K^2 + 2K -11 > 0 \$

The solution to the quadratic in K leads to two complex poles. How can I comment on the stability of the system?

I have attached a picture of the Routh table.


texts: How do I read these (Arduino) schematics?

texts:
I am currently trying to learn about circuit boards and microcontrollers. On the Arduino webpage I found these schematics of the Arduino Uno. But I am not sure, how to read that.

There is a big circuit with the Atmega chips, everything is wired and connected with several other components. On the top there are smaller circuits that in the drawing are not connected to the rest. How do I read that? Are there connections omitted?


texts:
I've been working on building a frequency to voltage converter using discrete components (before you suggest an LM331 or similar, I wish to implement such a device using discrete components, not use an IC), for this I've used a low pass filter (because noise is high frequency so I figured I should filter that out) to provide a frequency-dependent transfer function, and implemented it this way:

So far, It's linear in the frequency range I wish it to, however I have a problem: It reaches a value and then tends to oscillate around that value (reaches 7.41, then 7.42 then 7.38 then 7.41 again, etc), which of course is not behaviour you'd want from such a device.

My question is: How can I minimize or get rid of said oscillations?

Thanks a lot for your help


texts: How do I work out the correct PWM frequency for my application (motor)?

texts:
I am working on a project and want to drive a motor with a 12V PWM signal (Motor connected to 12V and the Motor- net on the diagram).

I have it working, however i'm not sure how to work out the optimum frequency for my PWM to operate at for the motor i'm using. It's a brushed DC motor. I have attached the only information I have on the motor in case that helps.

Any advice or input is welcome. Thanks in advance.

Circuit Diagram

Motor Spec


texts:
I want to power my DIY stuff with a MacBook Pro USB C charger. The label on a charger says that it can provide three different power profiles:

20.2V - 4.3A
9V - 3A
5.2V - 2.4A

There is a ton of information about what USB-C power distribution is capable of, but I can't find any examples of how exactly to do it.

Is there an easy way or workaround to request one of those power profiles without using a microcontroller?

For example, I got apple MacBook Pro charger, apple USB-C cable, and a breakout board like this one:


texts: Trimpot potentiometer rotational life Vs load life

texts:
I'm dealing with an application which makes use of an adjustable linear voltage regulator (LT3080). A trimpot potentiometer is used in place of the set resistance Rset to regulate the output voltage. A constant set current of 10 uA flows into the Rset and gives the output voltage following the equation Vout = Rset*Iset
The linear regulator is powered by a 12V DC input source.
I would like the output voltage to vary between 5V DV and 12V DC (minus the voltage dropout). Therefore I would split Rset in the series of two resistors: a 500 KOhm fixed resistor and a variable trimpot of 1 MOhm. In this way the minimum Rset will be 500 KOhm and therefore the minimum output voltage will be 5V. The maximum Rset will be 1.5 MOhm and the output voltage will go at maximum allowed. I was keen in choosing a high accuracy (0.1%) fixed Rset resistor and a good accuracy (10%) trimpot.
I'm now concerned about the life of the trimpot. The datasheet of the trimpot I chose (BOURNS 3362P-1-105LF) states that rotational life is 200 cycles. I'm aware that cermet potentiometers like this one have limited rotational life. On the other hand, there is one value I am most concerned about: load life. Here again, the datasheet states 1,000 hours 0.5 watt @ 70 °C. Since I am burning a meaningless amount of power in the potentiometer, can I expect longer life?
And the most important question here: What will happen after these values have been passed? Will the potentiometer be like a shortcut or and open circuit? Or there will just be derating from the set resistor value?
The system is expected to work in standard room conditions, at an ambient temperature of +25C, non condensing.

simulate this circuit – Schematic created using CircuitLab


texts: How to fix a frequency shifted audio part of an RF signal?

texts:
I tried to connect an old Japanese (NTSC, System M) video gaming system (an original Famicom, HVC-001) to a rather modern multisystem LCD TV-set (Sharp LC-43CFE5222E). The TV tuner is capable of tuning to the signal, but I can’t get both clear image and sound at the same time.

As can be seen in this video, the image is clear at 91.750 MHz. However, on this frequency the sound is not. If I use the fine tune control to adjust the frequency a bit higher to 92.125 MHz, the sound becomes clear, but image becomes distorted.

The game system has a channel switch with two options: CH1 and CH2. This problem happens on both of them, only the absolute MHz values are different.

Since I know only little about electronics, I would appreciate help finding the source of the problem. Is the game system broken? Is the TV tuner of low quality? Even if so, would it be possible to build a device that would shift the audio part of the signal this tiny bit?


texts: Putting electronics in sand to keep them cool?

texts:
I am running some RTL-SDR software defined radio USB dongles.  They have metal cases, and can get pretty hot.  I saw it mentioned that they can be cooled down by burying them in sand.  Since i won't need to touch them after they're set up, is this a good way to go?

I could attach a heat sink to each of them but it would require some work (cutting, etc.)


texts: How can power line devices be affected by a power supply?

texts:
I have two power line adapters plugged into mains and I've noticed that whether a cheap power supply is plugged in, the data transfer rate drops dramatically or even drops to zero.

What's the theory behind that?


texts: Purpose and explanation of resistor near output of LM317, high-current, adjustable-regulator circuit

texts:
I'm trying to make a high-current, adjustable-voltage regulator using LM317 data sheets. Specifically, I am using the schematic below.

So, what is the point of the resistor related to Note A? Is it supposed to represent the load? What does it mean that the minimum load current is 30 mA, and can or should that value change? Also, what determines that value? Basically, I'd be happy to learn as much as possible about that resistor.

Edit: The figure above is incorrect in that the TIP73 is depicted as a PNP transistor. The figure below is from a more recent LM317 data sheet, correctly showing the TIP73 as an NPN transistor.


texts: Is there any way to retrieve data from a PIC16F877 if VCC and GND are shorted? I want to get the existing program and load it into a new device.


texts:
I have a toy that takes 4 AA batteries that I would like to modify to take AC power. I googled and found plenty of AC to DC power supply cables with the small socketed end. I know I could get one of those and cut off the socket and strip the cables and either solder or clamp them to the contacts in the toy. I'd like to do something a bit more clean, and find the receptacle socket for that ubiquitous AC->DC power cord. So I could mount that on the outside of the toy and solder its leads to the battery terminals. My google searches have failed, probably because I don't know what I'm looking for.

Can someone give me the name of the component or a link to one?

Here's the power cable I've found in case I'm not describing it well. https://www.amazon.com/ZJchao-Adapter-Precision-Pressure-Monitors/dp/B009SNJ0NS


texts: Why are radio signals clearer near the human body?

texts:
In Asia, specifically in Bangladesh, we often listen to FM radio. But the signal is not clear everywhere, that means it produces some noise.
From my childhood till today, I have observed that, if I keep the radio in a fixed position and I increase distance between me and it, the signal starts to be more and more noisy.
And sometimes, if I touch the antenna, the signal become more clearer. This is an observation from real life. But I don't know the exact reason behind it.
Would you please describe the exact reason behind it?
Note:
This question came in my mind few days before, but I was confused which site best suits for this question. However, I thought this site is the most suitable one to ask the question. If you think it is off-topic here, then don't hesitate to have a migration request to the appropriate site.
I am also sorry for my bad English.


texts:
Why is there no drive current available from the circuit below when R is connected to 0V?

The last sentance in this extract from wikipedia states that

  If R is connected to 0 volts it will have no drive current available to drive the next circuit; practical diodes need a bias current.

If diode A had +6V at the input, R was 1k and connected to ground; then A would be forward bias ("fully on" as +6v >> 0.7V required) leaving B and C in reverse bias. Providing the +6V rail was capable of supplying more than the (6mA) required for the resistor I would have thought that there would be current left over to drive the next circuit?


texts: Stability of closed-loop systems at -180 degree frequency

texts:
Say e(t) is sine wave and y(t) is sine output.

If y(t) has the same frequency as e(t) with phase shift of 180 degrees, we can only get stability of the system, if the gain of open loop at this frequency is less than 1.

This makes sense to me, in order for y(t) to gradually descend toward 0, the gain obviously has to be less than 1.

In order for that to happen, the polar plot of open loop G(iw) at this frequency (where it crosses the (-x)) has to lie between points (-1,0) and (0,0).

Why? What does the location of that exact point tell me about gain of this system?


texts:
I'm trying to design a peak detector which can be cleared by using an pin on the arduino. To design the peak detector I was following this guide-How to make a peak detector circuit. I used the circuit shown in that post and it works fine.

I made some changes to the circuit to use mosfet as switches in order to clear the peak value stored and another mosfet to allow the output to the stored value for certain times.

The switch s1 is used to clear the stored value and the output across load r2 appears when the clock u1 is high

The problem: Now the problem i'm running into as you can see from the graph is once the switch s1 is closed and opened again, the peak detector stops working. Also how do i remove the spikes appearing at the output whenever the clock u1 is switching?


texts: How do I calculate the energy (kWh) consumed by my 5V smartphone charger?

texts: I'm having a little trouble in figuring out how much power is absorbed by my 5v smartphone charger. I'm curious as to how to account the energy loss due to stepdown.


texts: Is a special BJT transistor to use in Common Base configuration?

texts:
Revisting multistage amplifier consists of Common Source-Common Base-Emitter Follower in cascading, I found the attached page of MPS-H85 PNP transistor that is proposed special for common base application.
Is any unique characteristic for CB amplifiers?
Surpriselly, when I used many transistors in simulation, I found very few that can give a good gain and low distortion in CB configuration even at 1MHz


texts: How to limit current while almost keeping voltage same

texts:
I am supposed to design a power supply to a project. I have 3 alternative power supply designs for this purpose. However, one of them sucks huge current while giving enough current. My design is given below:

I have searched a lot to find a way to limit this current. I have found current limiter including 2 transistor and the power supply including current limiter is given below:

As it can be seen, Although stated as low voltage drop, just after the limiting block, voltage almost hit the ground. Please offer me a way to limit this current somehow by depending on the design, please. Thanks in advance.


texts: What happens if I power arduino with an external power of 12V/2A

texts:
I am connecting a device which needs 5V/150mA and a micro sg90 servo.
Would it be ok if i connected them via external adapter of 12V/2A.Normally if i connect them with a USB, my servo is giving jitter.


texts: Why is a 15 stage binary counter/divider so cumbersome?

texts:
There seem to be many ways to take a 32.768kHz signal and turn it into 1Hz.

I can use a CD4060, but still have to add a flip-flop... so 2 "large" chips with excess (potentially) unused functions there. Sure the other 4060 outputs could come in handy, and I might find a use for the other flip-flop on board, but still a lot of real estate for a pile of maybe with a built-in oscillator likely as accurate as a 555 - negated by a crystal anyhow.
The "Swiss Army Knife of dividers" - I can use the programmable CD4536, which provides a single output from any stage from 1-24. But again, with chip size and "wiring" for programming - a lot of real estate for one function - and again with the on board oscillator.
The picture of simplicity, Nexperia makes a small 5-pin 14-stage divider. Oh so close. Still need to add a flip-flop, but at least the '4214 is not a 16 lead divider like the '4060.
Just for fun, I could cascade 8 CD4013s.

There are other counter/dividers that fall very short or way beyond 15 stages as an option. It seems that 15 stages of binary division is not nearly as important as I would suspect.

So my question is: With the 32.768 kHz Crystal being so prolific, and the (I would think, common) need to yield "seconds" with clocks and timers, why is there no discrete solution for doing so? Am I missing something?

P.S. I know that microcontrollers, GPS RX, RTCs, and other modern devices can provide all the timekeeping function one might need, but with all of the other "archaic" technology still available, I find it hard to believe such a device doesn't/didn't exist.

Addendum I seem to have created some confusion with my example, where I was personally looking for a 1Hz signal from what I thought was a "jellybean" frequency. But, it's about the stage count availability, not the frequency yielded. My example is my discovery of a lack of devices with a specific intermediate division capability - regardless of the input frequency - where the output of \$2^{15}\$ (and 16th and 17th) seems to be almost avoided, and that with the exception of one example, an additional device is required to achieve that number.

I already had my 1Hz solution before this question, but got curious and sought out what I thought was the "old way" of achieving this frequency in small, cheap timing products. So, my search was for a 15th stage readily available within a single device. Maybe the 32.768k wasn't part of the old way at all. Regardless, it seemed odd that all of the available preset counters/dividers I found that provide select ranges between \$2^0\$ and \$2^{24}\$ seemed to beat around that \$2^{15}\$ bush.


texts:
We have designed a circuit which is enclosed inside a plastic enclosure.
The equipment was tested on a standard ESD testing site (on top of a isolated plate placed on a HCP).
The equipment failed the ESD test at -3kV shot directly to the HCP. The MCU halted operation, it did not reset, just halted operation.

I have a question:

Would it help (make them more resistant) to set unused (tri-stated) MCU pins as output? (EDIT: I have a JTAG-port/connector which I suspect is the one causing the problem)


texts: How do I calculate the frequency accuracy of a Fluke DMM?

texts:
I have a Fluke 8846A and I want to make a frequency measurement with an error less than 1 mHz. I'm having trouble interpreting the manual as to calculate the error of a 120V 60Hz measurement.

Manual: https://www.instrumart.com/assets/Fluke-8845A-8846A-Manual.pdf

On page 1-12, the 100V, 10Hz-20kHz, 1 year (its calibrated every year) is states the error is 0.06% of the measurement + 0.03% of the range.

Say I measure 60Hz exactly, does that mean my error is (60 Hz * 0.0006 + 0.0003 * (20 kHz - 10 Hz)) = 6.033Hz? That seems too high of an error though.


texts: Low frequency Pierce oscillator with transistor

texts:
I am trying to built an oscillator at low frequeny (32768 Hz). After some research i have chosen to build a pierce oscillator.
Here is my schematics : discard

simulate this circuit – Schematic created using CircuitLab

I have tested the amplifier with a function generator producing 32Khz and it worked well, i have observed a gain of approximatively 3.7.
The load capacitance of the cristal is about 12.5pF.
I am not seeing any oscillation at the collector. Any idea about what could be wrong in my setup ?

Thanks !


texts: Is USB-C a technically viable substitute for SATA Express connectors?

texts:
SATA Express, the successor to SATA, is too new to be widely used yet, but the advancing speed of SSDs appears to make it inevitable, the same as SATA replaced parallel IDE. Despite the name, it isn't SATA at all; it's either the AHCI or the NVMe protocol over PCIe, similar to what SOP (SCSI over PCIe) does. The SATA Express connector directly passes two full speed bidirectional PCIe lanes via four signaling pairs, with no protocol encapsulation or translation, and the AHCI or NVMe controller is integrated into the HD or SSD rather than the AHCI controller being on the motherboard as for traditional SATA.

This summer, the USB-C specification was finalized*, with a feature called Alt Mode, which enables use of non-USB protocols through a USB-C port. In particular, it enables passing two full speed bidirectional PCIe lanes via four signaling pairs, with no protocol encapsulation or translation (unlike Thunderbolt, which encapsulates PCIe). Unlike the big and specialized SATA Express connector, which is only used for the SATA Express protocol, USB-C is small and general, and is widely expected to soon become ubiquitous and replace all other USB connector types (all combinations of full-size, mini, and micro type-A and type-B connectors for both USB 2 and USB 3) on all types of devices and hosts, and even replace Displayport connectors since USB-C's Alt Mode enables passing the Displayport protocol.

My question is for an engineer who works with these kinds of interfaces, and it's this: would it be technically feasible and cost effective to use USB-C instead of the specialized SATA Express connector for connecting SATA Express devices (i.e. devices that use AHCI or NVMe over PCIe) to motherboards? It appears that the SATA Express connector was created simply due to lack of better options at the time, but since USB-C can directly pass PCIe (and power too, including an option for the 12V commonly used by 3.5" HDs), it looks like it would be a technically feasible substitute and maybe even cheaper since it's smaller and consumes less PCB space. But since I don't engineer these kinds of things, I want to ask somebody who does, to see if my analysis is accurate.

Of course, technical feasibility and cost effectiveness are necessary but not sufficient for HD and SSD manufacturers to use USB-C in this way, but the other factors (especially inter-company politics) are outside the scope of my question. If manufacturers were to use USB-C connectors on their new SATA Express HDs and SSDs, then there would be a transition period in which motherboards would include both USB-C and SATA connectors, the same as motherboards included both SATA and parallel IDE connectors during that transition.

*See http://www.usb.org/developers/docs/usb_31_102214.zip


texts:
I found this instrument at a garage sale a while back.  It consists of two parts: a bent sheet metal housing with a stand near the front and rubber feet on the bottom; and an insert.

I haven’t been able to find a lot on it.  The only clue I have is the manual for HP’s vacuum tube voltmeter model 410b that I bought with it. The plug on the back matches one of the accessories used with the voltmeter mentioned in the manual.

My initial thought was that it was an oscilloscope, by the front switches being label DB, instead of dB shot that theory out the window.  I couldn’t find any units that looked like that since.

Can anyone help me out? I would be willing to answer any questions about interior items that I can.

Link to more images

Update: I just dismantled the instrument.  I do think more concretely that it was a dBmV meter or a signal strength meter of some kind.  The 4 Black rectangles turned out to be variable inductors.  The three switches on the side of the front panel turned out to be toggling resistor filter for the top coaxial plug.  The plug on the back is for AC current to recharge the batteries inside, since one of the lines from the plug leads to a diode and a “Ohmite”.

I would be willing to post pictures of the individual components if any want to see


texts: Trying to figure out an RC Plane Solar Charger

texts:
So for a project I am looking at making a solar charge controller for a 3S Li-Ion battery system used in an RC Plane.
The issue I am running into now is that I am unsure how to go about designing the charge controller for specific performances.
So currently our battery pack is going to be 5000 mAh. However based on our calculations the maximum current from our solar array is atleast 6 Amps. The problem is that we want to be able to control the maximum current coming from the solar panel to the battery while it is in use.
What I mean is that while we are flying we might be drawing 5 amps from the battery for the motors but charging 10 amps from the solar array which leaves us at a safe 5amp charge. However, if we go below this in motor draw, say 4 amps, that means we are now charging at 6 amps which is over the recommended charge rate for the li-ion batteries. Does anyone know of a way we could somehow adjust the current going to the system to prevent the battery from overcurrent? The mppt charge controllers we have looked at like the LT8491 do not have a method of controlling the maximum current except for the resistance values you pick when you create the PCB.
I wasn't sure if there was a way to just shunt of the current safely without wasting a lot since we are trying to get the RC plane flying as long as possible.


texts: Does a capacitor respond faster than a battery?

texts:
I grew up with the rule of thumb that you should always put a 47 uF tantalum capacitor wherever power enters a PCB. Perhaps that's a little dated now. I then recently built a battery powered circuit and followed this rule.
Is there any point including the capacitor?  Would you decouple a good alkaline battery?  My understanding is that the electrical power is derived from a redox reaction within it's metals or their oxides. Wikipedia says:-

Redox reactions can occur relatively slowly, as in the formation of rust, or much more rapidly, as in the case of burning fuel.

Rusting and burning (even exploding) fuel doesn't seem to operate at GHz speeds. A capacitor can. Chemicals have mass and volume. And they're gooey. So is a capacitor faster at responding to demand than a chemical battery?


texts: What does (PNP) BJT with shorted C-E do?

texts:
I was browsing through the TI datasheet for an LM78L05 and noticed this application schematic:

Note how Q2 has its collector and emitter shorted. I can't say I've ever seen that before and search didn't turn up anything.

What role would Q2 play in that configuration?

I kind of suspect a diode, but can't figure out why a plain old diode wouldn't work better and be a lot cheaper. The 2N4033 datasheet describes it as a General Purpose PNP Silicon Planar RF transistor.


texts: How can smart car keys work with such a small battery?

texts:
On my old car, I used to have a push button based key for my car. I push the button in the key, and the radio transmitter opens the locks. The battery lasted for 5 years. Easy to understand why the battery lasts, as the radio is operated only when pressing the push button.

On my new car, the key is a smart key: I put my hand inside the door handle, the car detects my hand, then it detects that the smart key is nearby and the car thus opens the locks. I don't even have to remove the key from my pocket.

Now, to me it seems that the radio transmitter in the smart key would need to be continuously operating (or if not continuously, at least in bursts every second or so). This has left me puzzled: how can a small coin cell battery power a continuously operating radio transmitter for years?

So, how are the smart car keys actually implemented? How is it possible that the small coin cell battery lasts for an acceptable duration of time?

What is the transmit power and duty cycle of these smart keys? Or do they instead of transmitting operate as a receiver, detecting the signal transmitted by the car, and start to transmit only if the car is detected nearby?


texts:
Thank you for taking some time out of your day to read my question, I have improved the specifics of my question:

I have a project in which I cool a very low power Peltier device (none of this question will regard any Peltier specifics) using a laptop fan keeping constant voltage and current to the Peltier. Peltier is 5v 1.5A, and I am using Artic Silver Thermal Paste on all mounting devices. Here is what is troubling me:

1) Using this fan, I get the cold side of the Peltier to 30 Fahrenheit:
Some description of the item:

The Heatpipes are 2mm thick (almost flat), the fan runs .45A 5V, the mounting pad for the Peltier (copper plate) fits the Peltier Entirely (30mmx30mm Peltier, same dimension fan).

2)  Using this fan, I get the cold side of the Peltier to 43 Fahrenheit:
Some description of the item:

The Heatpipes are 3mm thick (have some thickness), the fan runs .21A 5V, the mounting pad for the Peltier (copper plate) does not fit the Peltier Entirely (30mmx30mm Peltier, 20mmx20mm copper pad, only fits the center). The end portion which the fan blows into has a quite thick aluminum sheet vent vs the last fan is less substantial aluminum vent.

3)  Using this fan, I get the cold side of the Peltier to 45 Fahrenheit:
Some description of the item:

The Heatpipes are 1mm thick (paper flat), the fan runs .5A 5V, the mounting pad for the Peltier (copper plate) does not fit the Peltier Entirely (30mmx30mm Peltier, 20mmx20mm mounting pad, only fits the center of the Peltier).

Question:
 - Despite the double higher amperage of the last fan, but same "mount" size as the second one but smaller heat vent and heat pipes, the second fan cools better than the third fan.

So, using the first fan as a guide for proper mounting/size of vents and heatpipe analysis, what makes the second fan a better cooler than the last fan despite having less than 1/2 the current? What should I be looking at in a smaller fan (mainly concerned with the last two) that will allow it to cool more than what I currently have presented. What are the determining factors in cooling power, as seen current is not a factor as 1/2 the current cooled better? Heat pipes? Vent size? Mounting Size?


texts: power consumption with MIPI CSI-2 vs parallel interface

texts:
I wanted to understand, if MIPI CSI-2(LVDS-like) should result in a larger   power consumption than the traditional signle-ended digital parallel interface. The MIPI is widely used today, but the parallel interface is also used for low resolution image sensors. So if one should use a sensor that supports both MIPI CSI or parallel interface, then the person must choose one. In terms of performance, MIPI would be better, due to its lower noise and EMI. However, is it normal to expect that using the MIPI would result in a larger power consumption?

Let's say one controls an image sensor using an FPGA and a SDRAM. The frequency of the parallel signal is 50Mhz, and the bitwidth is 8-bits, while the frequency of the MIPI CSI-2 is 200Mhz, and it uses two lanes. Also let's assume the SDRAM clock frequency is 133Mhz, which means the FPGA should be fast enough to handle the SDRAM as well.

Thinking about the dynamic power consumption of the CMOS I/Os, the parallel transmission seems to consume less power, because 50Mhz x 8 lines  < 200Mhz x 4 lines. Also clocking FPGA to cover 200Mhz signals would increase the power consumption of the FPGA even further. Does this reasoning make sense?


texts: Do IC's in DIP sockets require an extraction tool?

texts:
Am I correct in that the IC extraction is used to extract an IC from a DIP socket for swap/extraction in a safe manner? Or is it used for something else?

I doubt I will need this behaviour, however if I damage the socket it is worth a few dollars to own such a tool.


texts: Controlling a digital switch using Python through USB

texts:
I have an RF digital switch that takes two digital inputs (AB) in order to decide from which antenna port to take the input. Is their a simple way to use Python to send the AB values through the USB port to this switch?

The pseudo code would be something like this:

while(1):
    Switch antenna
    Read the input
    Do some processing

Thank you very much.


texts: Backup power supply boost converter TPS61030

texts:
I'm developing a backup power supply using a supercapacitor and a  TPS61030 boost converter based on this Texas Instruments circuit design.
This is the circuit shown in the reference guide:
and it is explained that the VOUT is set through the feedback resistors R6, R9 and R10. When the Vsys is present, the voltage at the LBI pin is above the threshold and the pin LBO is at high impedance so the resistor R9 is not affecting the others feedback resistors, setting the (so called in the guide) Vout_re to 4.5V, so lower than the Vsys after the D1 diode. In the case Vsys disappears, the pin LBO is connected to GND, modifying the feedback network in such a way to obtain 5V at the output. You can find the calculation at page 5 of the reference guide. This is functional block diagram from the datasheet:

I don't understand why they are differentiating VOUT and Vout_re, because since the feedback resistors are used to set the VOUT voltage, those 4.5V should be also present at the output, lowering the value of the Vout when the Vsys is present. What I would expect, since this is a backup PS, is that as long as the Vsys is present, the boost converter goes in some kind of high impedance state, and not output 4.5V. I think I'm missing something, probably the IC is not outputting this voltage, but I cannot find a proof of that neither in the datasheet nor in the reference guide. Thank you in advance for your help.


texts:
I'm using a TIC116 to control the power over an electric grill. However, I didn't use a heatsink and it got very warm. On the data it says that its upper limit is 110 °C.

I suspect that the gate is not doing its job as expected, I think I have a leakage current. To test it, I tried with a continuity probe on my multimeter and it showed indeed continuity between gate and cathode. What does it mean? Is there another way to test it?


texts: How to generate a single pulse using RC circuit from a fixed DC supply without any controller, timer or delay IC?

texts:
I have a DC supply (5 V) to turn some circuit on and in that circuit there is a module which uses a specific mechanism (i.e. a 2 seconds width high pulse) to turn on (even if a supply is connected, that module will turn on only by this mechanism i.e 2 seconds pulse).

So I want to generate a pulse (high) of 2 seconds when that DC supply is turned ON.

I know we can do this using timer ICs like 555 timer, or any microcontroller, or using gates (but this uses IC, RC components etc,) but I was wondering if I can make a circuit using only R and C as components.

Problem:
When DC supply (5V) is turned ON, the circuit gives '1' (5 V) for 2 seconds and then give '0' (0 V) for the rest of the time supply is connected.

Question:
Is there a solution where we can implement this without using any microcontroller, timer IC or any delay IC? The circuit can contain resistors, capacitors, transistors or diodes etc.

Edit:

This pulse is used as a trigger to turn on the module, there is no load attached to that pulse. Currently, there is a push button that does this job. I have to press that button for 2 seconds to turn that module on. I want to remove that button and want to automatically turn the module on when supply is connected.


texts: Film capacitors, replacing with ceramics

texts:
I've been watching through hole film caps disappear.  I've used a bunch of these in thermal control loops,

http://www.digikey.com/product-detail/en/ECQ-E1106KF/EF1106-ND/56416

Still making 'em, but I'm seeing a lifetime buy in the future.

The current project will again need thermal control.
Can I use a ceramic X7R as an integrator? Maybe one of these (50V 10uF),
http://www.digikey.com/product-detail/en/CL32B106KBJNNNE/1276-3387-1-ND/3891473
I'd run it from +/- 15 V supplies. Time constant no more than one minute.

The question really is, what's the leakage current, and what's the voltage, temperature dependence?

I can hear many of you saying "George, get with it! and get a uC."


texts: Is it possible to find the critical path in specific part of the design?

texts:
I have written RTL description of a circuit in VHDL which is hierarchical and I am using Altera Quartus II; my design meets timing. I had set 50MHz clock frequency (20ns period) constraint using create_clock for now.

I have a slack of about 10ns in the design at present. The design contains a Nios II connected with a custom design which is rather a complex design with multiple levels of hierarcy. Provided that I want to find the worst case path inside my custm design starting from a certain block and thus including all things under it (in hierarchy), how would I do that in TimeQuest? Is it possible? At present, the timing bottleneck seems to be the Nios II.


texts: How to turn off and turn on LCD 16*2 display?

texts:
I build a device in which I check data on LCD display 1 or 2 times a day. So when I tried to turn off my 16*2 display and re-plugin in the middle of running the machine it gives some garbage value.
How can I turn on or off my LCD with the I2C module on my running device?
Is it possible??


texts: HO defaults "On" on high side/low side driver

texts:
I have an application where I need to drive 2 piezoactuators in a push-pull arrangement (voltage 180deg out of phase with each other) where the charge/discharge time is about 50 microseconds and the actuation is not periodic but on-demand and occurs at least 1 time/second. After some very useful help here I started using a proper driver for high side and low side power switching, and everything works when cycled continuously with a square wave, but there are problems when the time domain increases and I try to keep the voltages static. I mirrored the circuit below to drive each stack actuator.

When Vcc and the source voltage are applied, HO defaults to ~3/5-4/5s of Vcc while Hin=0V (Vcc=15V, HO is ~9V in one side, ~12V in the other side), and this seems to allow the voltage at the load/piezos to match HO.

Is there anyway to keep HO=0V on power-up?

https://www.infineon.com/dgdl/irs2186pbf.pdf?fileId=5546d462533600a40153567716c427ed

https://www.st.com/content/ccc/resource/technical/document/datasheet/66/f9/3f/68/12/26/40/75/CD00144165.pdf/files/CD00144165.pdf/jcr:content/translations/en.CD00144165.pdf


texts:
this is my first question on electronics, so I hope I will get it right. :)
GSM and GPS are topics which are quite new to me, but I will try to be as clear as I can.
Is it possible to collect data about all the present GSM devices in the room or on a floor, with my device, and then calculate via GPS the distance between my GSM device and all the others? Can it be done via GPS or should it be done via GSM module? Can that kind of collecting be done, at all?
Thanks in advance!


texts: I used a LC filter to the input of a DC/DC isolating converter to help with EMC. On the PCB design +Vin goes to the inductor first then to the inductor /capacitor junction. Capacitor then connects to GND. The reference design of the DC converter shows it the other way around...makes sense as we are filtering from the converter back into the supply. My question is have I created a problem here ? . Its still acting as a low pass filter but maybe the impedance has been effected ?...will it still work


texts: Switch off this single cell lithium hi-power LED driver with protection circuit

texts:
I've been goofing around the internet trying to build my own flash light with a single 18650, with low voltage protection circuit.

For now this circuit can already achieve following ideas:

Standby at very low power: with T1_1 pin at 0 volt and T3_1 pin at Vcc
Lit the power LED: Press the SW1, T1_2 goes low, T1_1 goes high
Cutoff the whole circuit when Vcc drops below ~3.3v
Lit the warning LED D2 if Vcc<3.3 w/ SW1 overiding protection circuit.

Now, I want to figure out how to shutdown this circuit. Currently SW1 is sort of both "turn on' and "override", but how do I turn off?

If simply disconnect the Vcc it would mean you have to push SW1 every time reconnected and that's just one step too much.
Right now, if the battery is charged, the SW1 would turn ON, but never OFF. This does not look like override to me.

I've tried multiple connection around T1 so far, and even thinking about using some caps to create some sort of histerisis so a single switch can act differently at different state. But still no success. So I'm hoping someone can help me here on:

How to add a proper ON/OFF switch? (so when turned OFF, everthing goes back to low power standby state)
How to add a proper override switch? (that lit the warning light but still enable T3)

p.s.
Yes, I know the circuit probably seemed weird because it's too complicate to achieve some simple tasks. I'm doing my best to try to learn (doing googling) here. Please forgive me for any noob question, I really appreciate any opinions of all kind.


texts: How can I calculate Exponential using CORDIC for numbers outside [-1, 1]?

texts:
I am not able to understand the math behind calculating exponential of a number outside the range [-1, 1) (actually I am not sure what is a good range to compute exp using CORDIC, some place I read [-pi/4, pi/4] and in others I have read [-1, 1)) using CORDIC algorithm. Can someone give an example?

I read following statement at http://zone.ni.com/reference/en-XX/help/371599G-01/lvfpga/ht_exponential/:

"x must be in the range [–1, 1). To compute exp(x) when x is outside this range, find an integer q and a real number r, where r is in the range [0, ln(2)), such that x = q × ln(2) + r. You then can compute 2^q × exp(r), which is equivalent to exp(x). Because r is in the valid range of [–1, 1), you can use this function to compute exp(r)."

But it doesn't make much sense to me as to how can I find q and r?

Second approach I found was at http://www.xilinx.com/support/documentation/application_notes/xapp552-cordic-floating-point-operations.pdf which tells us to use to equations after dividing the number into integer and fraction part:

cosh(int + frac) = cosh(int) * cosh(frac) + sinh(int) * sinh(frac)
sinh(int + frac) = cosh(int) * sinh(frac) + cosh(frac) * sinh(int)

cosh(int) and sinh(int) are taken from lookup table. But this approach is more computationally intensive so I prefer the previous one.


texts:
Sorry to ask a question that I feel I should be able to google, but I'm kind of stuck.
I have some different 5v AC/DC power supplies that I need to plug into the wall and use to power rgb LEDs.
The max currents that I need to draw from these supplies are 2,4A, 1,2A, 0,9A, 0,6A, so I use one power supply 2,5A, one 1,5A (this one is variable 3-12V, I'm assuming that I get minimum 1,2A at 5v) and the rest 1A.
What value capacitors do I put across 5v and gnd in these particular circumstances?
I get that they should be rated for 10v as a safety, but I don't know how to get to a good number on capacitance. No datasheets available to me on the power supplies, but on the 1A supply it says 300mV ripple on the web site where I buy them.
Thanks!

EDIT: Schematic

EDIT2: Updated schematic


texts: Microchip PIC - How to recover the context saved in interrups or disable the automatic saving of the context?

texts:
I'm building a dispatcher for PIC microcontrollers to switch tasks saving their contexts.

The dispatcher is triggered when an interrupt occurs. The problem is that the compiler I'm using (C18 V3.x) saves/restores the context automatically when an interrupt occurs, but I don't know how to recover the information saved.

I want to disable the automatic saving of the context and make it by myself, choosing just the registers I want to save.

Part of the ISR's code is:

void isr_dispatcher()
{
    uint8 w_temp, status_temp, bsr_temp;

    INTCONbits.GIE = 0;

    // save the context
    _asm
        movwf   w_temp, 0
        movff   STATUS_REG, status_temp
        movff   BSR_REG, bsr_temp
    _endasm

    // ...
}

When an interrupt occurs (TMR0 overflow, in my case), isr_dispatcher begins to execute. The problem is that the compiler translates my isr_dispatcher to this assembly code:

!void isr_dispatcher()
0x1308: MOVFF FSR2H, PREINC1
0x130A: NOP
0x130C: MOVFF FSR1H, FSR2H
0x130E: NOP
0x1310: MOVFF FSR0, PREINC1
0x1312: NOP
0x1314: MOVFF FSR0H, PREINC1
0x1316: NOP
0x1318: MOVFF TBLPTR, PREINC1
0x131A: NOP
0x131C: MOVFF TBLPTRH, PREINC1
0x131E: NOP
0x1320: MOVFF TABLAT, PREINC1
0x1322: NOP
0x1324: MOVFF PROD, PREINC1
0x1326: NOP
0x1328: MOVFF PRODH, PREINC1
0x132A: NOP
0x132C: MOVFF PCLATH, PREINC1
0x132E: NOP
0x1330: LFSR 0, 0x0
0x1332: NOP
0x1334: MOVLW 0x14
0x1336: DECF WREG, W, ACCESS
0x1338: BNC 0x1340
0x133A: MOVFF POSTINC0, PREINC1
0x133C: NOP
0x133E: BRA 0x1336
0x1340: LFSR 0, 0x14
0x1342: NOP
0x1344: MOVLW 0x7
0x1346: DECF WREG, W, ACCESS
0x1348: BNC 0x1350
0x134A: MOVFF POSTINC0, PREINC1
0x134C: NOP
0x134E: BRA 0x1346
0x1350: MOVF POSTINC1, F, ACCESS
0x1352: MOVFF FSR2, POSTINC1
0x1354: NOP
0x1356: MOVFF FSR1, FSR2
0x1358: NOP
0x135A: MOVLW 0x3
0x135C: ADDWF FSR1, F, ACCESS
!{
!    uint8 w_temp, status_temp, bsr_temp;
!    INTCONbits.GIE = 0;
0x135E: BCF INTCON, 7, ACCESS
!    // save the context
!    _asm
!        movwf   w_temp, 0
0x1360: MOVWF nova_tarefa, ACCESS
!        movff   STATUS_REG, status_temp
0x1362: MOVFF STATUS, status_temp
0x1364: NOP
!        movff   BSR_REG, bsr_temp
0x1366: MOVFF BSR, bsr_temp
0x1368: NOP
!    _endasm

As you can see, the compiler inserts several assembly instructions before my original isr_dispatcher code. I wish the compiler did not do it. Just so I could save the context.


texts:
I am trying to run an experiment using a piezo ceramic cylindrical transducer (32X30X10MM 29 KHZ) to send a signal from the inside of a water-filled test metal tube to a transducer mounted on the outside of the tube, and I could use some input on how to get the transducer to operate in water.

I am trying to avoid potting the transducer in a urethane for fear of bubbles (i don't have a vac chamber), can I operate in a pipe filled with distilled water for short time periods?
Or would I need to use mineral oil (messy!)?  If so, what kind?
On these cylindrical transducers, where do I solder +/-?  I assume inside and outside surfaces.  Should I use a special wire to prevent interference?

Any help would be appreciated!!


texts: Reasoning Behind Placement of Various Components in Radio Receiver Circuit

texts:
I have been working on a Science Fair project recently, but I have been unable to understand the reasoning behind several components in a circuit I am using. The circuit is shown here: Radio Receiver Schematic
The components I am struggling with are as follows:

C10 - I do not fully understand the reasoning for placing a coupling capacitor between the antenna and the AM input to the SI4844-A10. My understanding of coupling capacitors was that they block DC current. What is this capacitor doing if RF signals are AC?

C13 and L1 - It appears to me that C13 and L1 are high pass filters. This would result in high frequency signals reaching the FM input on the Si4844-A10. What is the value of using two high pass filters? Furthermore, am I correct in my assumption that these are high pass filters?

C1 and C2 - Why use capacitors on the audio output line?

If anyone has any information that may prove valuable to my understanding of these components, please respond. Moreover, if anyone has any suggestions for improvement of my question, please leave a comment.

Thanks!


texts: ISO standards test for vibration resistance of electrical equipment

texts:
I would like to test some electrical contacts for oxidation wear resistance in indoor environments and in cars including off road vehicles with a lot of vibration.

Are there some ISO standard tests which involve putting various currents through a contact and tying it to a jackhammer or something to test it's performance under duress?

I would like to also test the contacts at moderate vibrations and with chlorine or moisture to simulate many years of usage and to estimate a MTBF.

Where can I find a list of that sort of test?


texts: How to secure flimsy wires from RGB LED strip in Arduino Uno breadboard?

texts:
I just purchased an RGB LED strip to make my first 'non arduino starter kit project'.

It has red, green and blue wires coming from the end of it, which I am trying to put in the breadboard sockets adjacent to the drain of each required MOSFET.

I am finding, however, that only the very tip of the wires are rigid and they are not 'sticking' in the breadboard sockets (if i move the wire slightly, they just come out).

Is there a well known 'hack' to make sure the wires are fastened securely in the breadboard sockets?

I'm new to electronics, so I wasn't sure if there was some sort of connector designed exactly for this - perhaps something with one female end that could clamp the flimsy wire, whilst the other end had a more rigid pin that could be secured in the breadboard?


texts:
I need to design a power supply that is powered from a single Li-ion cell (3-4.2V) and provides 3.3V up to 500mA and 5V up to 1A. I have three solutions in mind, one is boost converter to 5V and then a LDO for 3.3V, second is a buck/boost for 3.3V and a separate boost converter for 5V and the third is boost converter for 5V then cascade (input for 3.3V conv. is 5V) a buck converter for 3.3V.

Since I am using batteries a LDO seems inefficient (cca. 64%). So I am curious which of these solutions is better in terms of efficiency? And would I have issues if the dc-dc converters were running on different frequencies?


texts: Multiple DTMF circuits able to detect the pressed keys but fails to read caller's number!

texts:
This is a follow-up question of "Multiple DTMF circuit interfaced to one microcontroller, will it work?

Multiple DTMF circuit interfaced to one microcontroller, will it work?

I used the differential mode of the CM8870 DTMF decoder IC to isolate the three phone lines from the ground. I have finished the board. When I connect the phone line to the RJ11 jack, I do get a dial tone. When I pressed a number, I also get the number pressed displayed in my console. But when I try it to get the caller's number, I do not get anything anymore. Here is the circuit.

Analysing and comparing the circuit from the previous one (note that the previous one worked!), I thought of increasing the signal gain might solve the problem. I increased it to have 3.3 signal gain and added a capacitor of 0.1uF in pin 17 and pin 18 to filter noises (since I realized that this is really needed.) Unfortunately, it still didn't work.

Comparing the previous circuit to the present one, it seems there are differences which are as follows:

(Present) versus (Previous)

1.) Differential mode versus single-ended mode.
2.) 330K ohm resistor versus 390k ohm resistor in pin 17 and pin 16.
3.) pin 5 and 6 are grounded, as opposed to floating.
4.) 100pF series capacitor versus 0.1uF series capacitor

Am I missing something?


texts: 3.6V NiMH smart charger, microcontroller, auto switch over from DC in to battery

texts:
I'm working on an agricultural pump monitor project using a microcontroller.  It needs to be able to operate ~1 hour after power failure, and signal same.

I'm hoping there are maybe single chip, or simple circuits using a smart chip, that will continually charge/monitor the 3.6V 700MAH battery, then to assume load on failure of the DC input power.  My searches are returning overnight, timed, and wall-plug discrete cell chargers.

Is Maxim 712 my only $$ choice?

Any suggestions appreciated.


texts:
i would like to protect a 3 mosfets and 3 leds connecting to this mosfet from over voltage or transient voltage spikes.

Attached is a scheme with a capacitor in paralel prior each mosfet.

vin = 12v from regulated wall adapter, vload =12v, 2A each load, load is a led.
mosfet i am using is FDMA430NZ.

Mcu to gate 5v, 25ma max.

Apreciate for any advice for determining the capacitors values so they will be efective in protecting? or is a 0.1uf is the right value base on these details?

What If i will use a tvs diode instead of the diode in beginning of the circuite, will it cover all this circuite protection for over voltage spikes?

Thank you


texts: How to draw current from a telephone line?

texts:
My landline phone comes with a lcd display caller id and clock.
Even if I remove the 2 AA 1.5V batteries, the lcd still shows time even if I'm not busy on a call.
The lcd has no other source of power as is turns off when I disconnect the line.
I'd like to power up a 1.5V quartz analog clock using the phone line.
Is that possible?
Any circuit suggestions welcome.
Thanks.

Edit:
The phone line has had no failures, at least since 2005, since they switched to fibre optic from copper wires.
And it's not illegal in India to connect low voltage devices like caller ID, tape recorders aka call recorders, answering machines and external ringers to the phone line, or so says the govt. owned company.
I'm crazy, officially:-P
But has anyone got circuit diagrams?


texts: Does a 3rd-Party Cable cause any harm when charging your Phone with the original Power Brick?

texts: When using the original Power Brick the Smartphone came with to charge it, does a 3rd-Party cable cause any harm to the device or is there no difference to using the original cable?


texts:
I have ESP8266-01 this model

I Updated the frimware to nodeMCU and uploaded the web server code and tested by blinking led via web browser. Now I want to test that if I can send text data from web browser to ESP8266 and show that text on LCD screen similer to thi one

I know how to operate this LCD and display text on this LCD but my problem is that in this ESP8266 there are only to GPIO pin GPIO0 is for uploading frimware and GPIO2 is that free for send signal to outer device. I have not much knowladge about electronics so is there any way to achive this with minimum extra components if required.

Update:-

I found some link where they are showing its working but I am not able to figure it out how.

here are the links

ESP8266 WITH 16X2 I2C LCD
Image


texts:
I'm trying to switch the colors of a 4-bitmap image using VHDL .
In a 4 bit-image .
Which means we have  these types of colors .

r_in : in std_logic_vector(7 downto 0);
g_in : in std_logic_vector(7 downto 0);
b_in : in std_logic_vector(7 downto 0);

r_out : out std_logic_vector(7 downto 0);
g_out : out std_logic_vector(7 downto 0);
b_out : out std_logic_vector(7 downto 0);

Assuming we have these vectors  in the entity .
Is it possible check the color of the image using the Hexadecimal code ?
for example :
if ( r_in = #16#AA0000 )
THEN
r_out <= #16##0000AA;
b_out <= #16#AA0000;

Something like that .
Otherwise what can I do instead ?


texts: How to choose the MOSFETs for BLDC motor drive?

texts:
How to select the proper MOSFETs for Brushless DC motor drive circuit?
The Motor will work at 22.2V max. voltage and 40A max. current.


texts: How to drive high power LED and Arduino by the same power source?

texts:
I am building a plant light consisted of 24 high power LEDs (Cree ML-E) and an Arduino Uno. I would like to power the LEDs and the Arduino by the same power source. Since creating circuits for dealing with household power requires quite a lot of experience and also can be potentially dangerous, I decided to go for a commercially available AC-DC power supply similar to the ones for laptop, such as this (TRANSFORMER DESK TOP 24V 60W).

Coming with computer science background, here are some problems I would need advice for:

The fundamental problem: can these LEDs and the Arduino share the same power supply?
I suppose the power supply should have output voltage high than 12v, which is the maximum that an Arduino can take. How do I lower the voltage to the safe range of 7-12v?
The forward voltage for the Cree ML-E is 3.2v, therefore the wiring I can think of is first to create three series of LEDs, 8 in each. Then connect these three series in parallel. Is this a proper way of wiring or I was wrong?
I found there are LED drivers ready for use out of box, such as this (POWER SUPPLY LED 36W 700MA). Is it a good idea to use it to mainly power the LED and "fork" another power source from it for the Arduino?

Note: The Arduino is for the sensors placed at the same spot as the plant light


texts:
I'm trying to diagnose a faulty car usb power supply. I can't identify one component however. I tried to take a picture

The part on the bottom left. Its light blue and the only thing on it is a big O. I couldn't get a better picture, unfortunately, as it is very small. It sits right between positive power and the resistor above it. I thought it might be a fuse or a diode. Seems not right though, when I use my multimeter in diode mode, it lets current through for a second or two, then stops. Switching the probes shows the same result, letting current flow for a while, then stops. So it might be a capacitor? It shouldn't be, though, as the only other connection from positive input to the rest of the circuit is through another 330uF capacitor, and the input is DC.


texts: How do I determine \$R_o\$ for an op amp?

texts:
I understand that when driving a capacitive load with an op amp, the output resistance, \$R_o\$, of the op amp interacts with the load capacitor to form a low-pass filter, introducing a pole in the loop gain that can cause instability.

One of the compensation strategies involves adding a resistor that interacts with \$R_o\$ and \$C_{load}\$ to add a zero in just the right place to counteract the unwanted pole. The calculations require knowing the value of \$R_o\$.

I understand why the compensation works and where to place the components. What I don't know is where to find the value of \$R_o\$; I've yet to find an op-amp datasheet that publishes a value for \$R_o\$ or \$Z_o\$.

(Note: there is another question here about how to compensate an op-amp for a capacitive load, but it does not address \$R_o\$ or mention where to find it.)

Am I just unlucky? Or perhaps the value is obvious (although I understand it can vary between tens and thousands of ohms)? Or am I looking in the wrong place? Or do I need to determine it by bench measurement somehow? Or perhaps I don't really need it as badly as I think?

What do the pros do in this situation?


texts: How to switch SMD part for through-hole part in EasyEDA?

texts:
I'm using EasyEDA for the first time. I have about zero experience with CAD. I drew this schematic

And generated this PCB layout

But I really wanted to use a through-hole DIP package for the ATTiny85, not the SMD part.
Is there any good way to replace the SMD part on the schematic with a DIP part in a way that will minimise the amount of work needed to redo the tracks?
(Any other comments also welcome)


texts:
i am doing a cycloconverter single phase design and i have a problem , i use microcontroller to control the firing angle ,i have used zero crossing voltage (741) to trigger INTERRUPT port of MCU , i have controled two positive  waves well but two negative waves dont work in reality .
my question is " i want to use directly MOC3021 to control the two negative waves with load resistor 100ohm ?"
And i will use MOC3021 inside triac to control negative waves instead of 2 SCR negative direction but it doesnt work.Can the MOC3021 drive directly load 100ohm Vin=6VAC

[![enter image description here][2]][2]

VIN=6VAC
Rload=100ohn

Thanks guys!


texts:
This is my first electronics project - apologies for the noob question.

I wish to control a power relay, trigged via motion / PIR.  After the PIR triggers the relay, the relay should stay "on" for a user selectable time, of 0.5 to 4.0 hours duration. (approximate, timing does not have to be accurate)

How can I build a end-user-adjustable timing circuit, with that range of time delay?
e.g it needs a knob the user can turn.

Also, is it realistically feasible to do this without a micro-controller? For learning purposes.


texts: Am I risking a short circuit/gaping situation?

texts:
I am rather new to the DIY/hobbyist electrical engineering scene. I am working with an arduino, a 9V power supply, and a few 7805 voltage regulators. I bought some sort of run of the mill PCB board with many many copper squares and pin holes on it, and I have been using that to construct my project. In the end I am trying to drive up to about 100 LEDs.

The copper squares on the pcb board seem really close. And yes, I am sure the wiring/soldering job I have done is rather horrid, but I have a limited budget and knowledge.

What I would like to know, as I have had a hard time tracking down an answer, is whether or not my solder joints and the contacts of my various components are too close together and I am risking a situation where an arching might occur. I am really not all too sure on how much distance it takes for 5 volts to gap. So far I haven't had any issues, but since I want to make a gift for someone I care about, making sure its relatively safe for them to possess would make me feel comfortable giving it to them.

I have linked to two pictures, one of the underside of my board, and the other of the side of the board with the 7805s in sight, so that hopefully some rough idea of scale here is possible.

Thanks much in advance!


texts: Testing the strength of a B filed from loop of wire and limitations of a function generator

texts:
I built a coil that receives magnetic fields (Rx) from a sending coil (Tx) a few centimeters away. (wireless power transfer) I send waves to the Tx at the Rx's resonant frequency since its a loop with a capacitor in parallel. (RLC circuit) Wave sent to the Tx is in the 200kHz range so no impedance matching
Im testing if the addition of a iron like material increases the voltage. Almost like a transformer with an air gap.
It turns out it did, not much surprise but Im wondering by how much.
Then I thought. The addition of the material brought down the resonate frequency I was sending the B field at. My test coil (No iron) had a resonant frequency at 212kHz and my coil with the iron had a resonant frequency of 191kHz. Think this checks out because f resonant has a 1/sqrt(L) relationship, so the iron raised L and brought down f.
My issue. The two different frequencies will have two different impedances on my sending coil. Since one test had a frequency of 212kHz and one 191kHz, the 191kHz Tx sends slightly more power because the 191kHz experiences less impedance. Is this correct? Did some rough math (I know the L value for my Tx coil) and a 10Vpp wave experienced like 2.6 ohm for 212kHz and 2.4 ohm for 191kHz. This is like around 9 amps for 212kHz and 8 amps 191kHz. The function generators spec sheet said that it has a .2 max amp output. So did both my tests receive this max current of .2 amps?
If there was no current output limit, the impedance of my Tx would effect the B field?
Also may be silly question but if your sending a 10Vpp wave down a wire with little resistance, how does the function generator limit the current to .2 amps. Thank you


texts: How can I use a BMS to charge 4 LC18650s in series?

texts:
I have a collection of 4 LC18650 batteries. I need to draw at least 12V with a current of at least 1 amp, hence the use of lithium batteries. I know I could use lead acid but environmental impact, energy density, and compactness of the system are high priority concerns. My best option is to use 3-4 lithium batteries connected in series.
I also have a battery holder that connects the batteries in series to output the combined voltage. At full charge, the bank should output ~16.8v, and ~12.0v at low charge.
My understanding is that doing this wouldn't be a problem, however recharging the batteries without removing them would be. I personally find the idea of removing the batteries in order to charge them distasteful and unprofessional, but keeping them from exploding is much more important. To that end, I've acquired a BMS from my local electronic component store, which unfortunately did not supply a datasheet.
As I understand it, I connect the 0v pin to the negative terminal of the first battery. I then connect the 4.2v pin to the positive terminal of that battery and the negative terminal of the second battery. I repeat this for all remaining batteries. Next, I connect the 0V pin to the ground supply of my device and the 16.8v pin to the V_BATT connection. I can then charge all the batteries from said device exactly as I would a single battery. Is my assessment accurate? How exactly does my BMS work? If I'm wrong, how would I design such a system?