texts: Minimizing PCB size of a 192 RGB LED array

texts:
I'm working on the design of an LED lamp house for my film scanner. I need RGB LEDs, plus IR LEDs. I'm figuring on a 2"x2" grid of SMD LEDs. Datasheets for the ones I'm using below. The current design is based on the common cathode schematic at the bottom of this post: https://electronics.stackexchange.com/a/64623

I've got this working on a breadboard with similar thru-hole LEDs, and will be making a PCB for the final setup. However, this is a lot of resistors and they take up a lot of space. I'd like to keep the size as small as possible - not a lot bigger than the 2"x2" LED array, if I can. I'm using a Quad PNP transistor array with an isolated resistor array, which has a fairly small combined footprint. There are also bussed resistor arrays for each row of LEDs in my prototype, which obviously saves some space over using separate resistors for each LED, but the smallest I can get my board design is something like 5" wide by about 3" high. I'd like for it to be smaller - as close to the 2"x 2" LED array size as I can get, ideally.

So I'm wondering if maybe I should use some kind of LED driver IC for this instead of the setup I have now. I'm basically controlling a total of 192 LEDs. In all cases, all the LEDs of a given color will be all on, at the same intensity, or all off. When I do white, it'll be a mix of RGB. I'm using an Arduino Mega (with an external power supply for the LEDs) and am planning on using some of the PWM pins to calibrate the intensity of each color channel as needed.

Any suggestions for how to approach shrinking/simplifying this, or specific ICs I should be looking at? I've never used an LED driver, and I'm not really clear on how they work, but from what I'm seeing/reading, it seems like it'll save me a lot of space. Is it possible to use one driver chip to drive all the LEDs of one color at once, or even with a driver do I still need one resistor per color per LED?

What about alternatives to the bussed resistor arrays? Anything I can use with an even smaller footprint?

Thanks!

Datasheets for my LEDs:

Lite-On LTST-G683GEBW RGB SMD LED: http://www.mouser.com/ds/2/239/S_110_LTST-G683GEBW-337108.pdf

Kingbright APT2012SF4C-PRV IR SMD LED: http://www.mouser.com/ds/2/216/APT2012SF4C-PRV-55109.pdf


texts:
I was originally considering using a 10 µF 6.3 V 0603 ceramic capacitor for stabilising the onboard voltage regulator on my microcontrollers. However, it may not be capable because of temperature coefficients, tolerances and applied voltage (losing up to 60% of the rating). Therefore, I am considering moving to using tantalum capacitors.

The microcontroller LDOs output 2.25 V - 2.75 V for powering the internal core. I am using a PIC24FJ64GA004 and dsPIC33FJ128GP804. Would it be fine to use a 4 V capacitor here? I have always used 2-3x rating for electrolytic capacitors, but maybe the same problems with aluminum electrolytic capacitors as for tantalum capacitors do not apply (with lifetime decreasing over applied voltage considerably.)

Ideally I'd like to reach a 50,000-100,000 hr MTTF. If tantalum capacitors aren't an option I'm considering using a 22 µF 6.3 V 0805 ceramic capacitor in place (I might have to resize the footprint), because even with a loss of 60% it stays within the minimum requirement of 4.7 µF. Any tips? Has anyone used tantalum capacitors before? What about ceramic capacitors for microcontroller LDOs?


texts: Can any one explain me in detail the magnetizing current and working currents that occur in no load conditions? I know that they are the vertical and horizontal components of no load current.. But how? Explain practically?


texts:
I am currently working on a device in which I need to implement internet connection. For that I intend to use a GSM module, for example this one: SIM5320. This is a 3G module. I have been reading about 3G vs LTE power consumption comparison (this is a good one: Comparing LTE and 3G Energy Consumption) and it seems that LTE consumes more power. I however, dint intend to use high throughput here. I just need the least power hungry module. I have heard a rumor that at low transmission speeds LTE module would be less power hungry, but I cannot find any data to back this up.

Is that a true statement? I would appreciate all help regarding the topic.


texts: Blue Yeti failed component identification

texts:
I have a Blue Yeti microphone that has had an on board component fail (lack of audio out and extreme heat from the chip in question). Based on some tracing it likely has something to do with the 3.5 millimeter headphone output jack and the volume knob.
The text on the chip appears to be AIF BAN or A1F BAN. I do not see any obvious manufacturer markings.

Image of chip with ruler for scale.

Whole board in context with the chip indicated with an arrow and the surrounding components circled.


texts:
Given the following circuit:

I know that I1 = I2 + I3, but what would be the relationship between I2,I3,I4, and I5?

I would assume if there are 5 unknowns, we'd need to have five equations to solve for this, so something like:

# voltage
I1*100 + I2*200 + I4*500 = 5 # top
I1*100 + I3*300 + I5*400 = 5 # bottom
I2*200 + I4*500 - I5*400 - I3*300 = 0 # I2->I4->I5->I3 loop

# current
I1 = I2 + I3
I2 + I3 = I4 + I5

But then, if I plug these equations in, it doesn't seem like it's enough to solve for all the currents. Am I missing any equations in the above to solve for I1-I5?

By the way, I tried plugging in what I got into an equations solver, and got the following error:

import numpy as np
A=np.array([
    # current
    [1,-1,-1,0,0], # i1 = i2+i3
    [0,1,1,-1,-1], # i2+i3 = i4+i5

    # voltage
    [100,200,0,500,0],
    [100,0,300,0,400],
    [0,200,-300,500,-400],
])
B = np.array([0,0,5,5,0])
A_inv = np.linalg.inv(A)
i1,i2,i3,i4,i5=np.matmul(A_inv,B)
> ERROR: numpy.linalg.LinAlgError: Singular matrix

Which equation(s) does it seem like I'm missing or getting incorrect here?


texts: Starting the VFD from a specified frequency instead of 0 Hz

texts: I have Hyundai N100 inverter. PLC is sending 0-10V analog signal to the inverter. It starts from 0 Hz and then reaches the maximum frequency of 50 Hz. Now i want it to start from 40 Hz instead of 0 Hz but it always start from 0 Hz even though i set the minimum frequency as 40 Hz in minimum frequency parameter. It is driving a conveyor motor and it starts and stops when PLC sends the run command. Is there any way i can make it to start from 40 Hz instead of 0 Hz?


texts: MOSFET High Side conducts when low side switches in H bridge circuit

texts:
I have designed an H-bridge circuit using IR4110 Mosfets.
Q1 and Q4 are OFF, Q2 and Q3 are conducting. Gate of Q1 is left floating. Q2 being high side, its gate is connected to Vcc + 12V. The gate of Q3 is connected to a PWM signal (12V square wave 15kHz, 70% duty cycle) for motor speed control through a 10 Ohm resistor. Gate of Q4 is grounded through 10ohm resistor. All MOSFETs have a 10k resistor between their gate and source, though it is not shown in the diagram.

Now, when gate of Q3 is high, it conducts, but at the same time Q1 also conducts for a brief moment, causing shoot-through and heating up Q1. When I hooked up the gate pin and source pin of Q1 to a DSO, it is observed that \$ V_{gs} \$ of Q1 goes above its threshold for a brief moment, turning it ON, which is undesired. The exact reason is unclear.

This never happens for IR4115 MOSFETs, which I am currently using without any such problems. Maybe it is because \$ V_{gs} \$ threshold of 4115 is higher than that of 4110.

Any explanation or suggestions for design modification will be highly appreciated.


texts: My boss has asked me make a device which is capable of scanning rooms for bugs!

texts:
Well this as I searched on the net is advertising, making money and fools out of those who want to make/buy such a bug scanner.

I am not an electronics engineer but am being forced to.
I do have access to all the hardware I may need.
There are lots of shops claiming that they have devices which can scan a area to see if there are bugs or spy listener devices installed, but how do I know if these work?
Personally I think this type of device only exists in James Bond movies :))

My boss's reason

He seems to hear some sound in the conference room, and his room where he has to stay for another month.
He claims the sound is something like "tii-eee, tii, teee ti ti" and so on. lol

Deliver

Okay, so now I have to reply to him with a gadget to scan his rooms for potential wireless transmitter bugs.


texts: First PCB design, PWM Motor Controller feedback

texts:
EasyEDA Project
I made my first PCB design and I would like to hear a quick feedback to it. It is a motor controller board, with two MOSFETs parallel, driven by a MOS driver IC and the PWM signal comes from a Attiny85 IC. The USV signal will measure the battery voltage and stops operating the device if below a certain voltage. USV is a simple voltage divider and will drain the battery, I am okay with that design flaw. AIN will measure a analog signal and adjust the PWM regarding to that. There is also a ISP connector to program the Attiny.
The DC-DC Converter should be a standard application. Everything regarding BAT DP is experimental, I don't know if this will work, I can't even explain how it will work since I have no insight of the battery circut. I found a old reference design and copied it, hopefully it's okay.
The design should operate with 180W and I will test it up until ~600W and see what happens. VCC will be from 14-20V.
If someone feels like giving me tips or finds mayor errors, I would like to hear that.
Schematic:

PCB design:

Datasheets:

Q1, Q2
Q3
Q4, Q5
U1
U2
U3
D4


texts:
I am trying to calculate the CMRR of following circuit. I am aware that similar circuit has been posted here before but I have read through them and they don't answer my question.

Based on my research so far, this circuit is one of the way to measure the CMRR of op-amp assuming that the resistor values for \${R}_{1a}\$, \${R}_{1b}\$, \${R}_{2a}\$,\${R}_{2b}\$ match perfectly.
In this circuit, i assume that the common mode input \${V}_{CM}\$ is \$ {V}_{IN} \frac{{R}_{2b}}{({R}_{1b} + {R}_{2b})} \$
And I learnt that the \$ CMRR = \frac{Differential-mode-Gain}{Common-mode-gain} \$. So, normally, i would find the common mode gain \$ {A}_{CM} \$ and differential mode gain \$ {A}_{DM} \$ separately.
However, i noticed, in  most of the online sites, they simply measure the \$ \frac{{V}_{out}}{{V}_{in}} \$ and considered it as \$CMRR\$
My Question is: Why is the \$ \frac{{V}_{out}}{{V}_{in}} \$ of this circuit is equivalent to the \$ CMRR \$ of the circuit?
Can someone point me in the right direction?
EDIT 1:
I have added some link to the similar questions per @MarcusMuller request.
operational amplifier CMRR measurement
This question was asking what is the correct common mode input voltage. I am well are that it is \$ {V}_{IN} \frac{{R}_{2b}}{({R}_{1b} + {R}_{2b})} \$ so it doesn't help me.
Op Amp CMRR problem
This question was asking about his particular issue regarding common mode gain.


texts:
I'm generating a clean sine wave signal of about 4V of amplitude from the IC XR2206 and I need to amplify the signal to about 10V of amplitude, I'm using the following amplifier:

Still, on the oscilloscope, the output signal is completely damaged, it is basically a triangle wave with about 1V of amplitude.

I have simulated a 600 ohm resistance as it is supposed to be the output impedance of the XR2206.

Any solutions?


texts: How can I convert a latching relay to two discrete momentary outputs?

texts:
I can find some questions that have some similarities to this one, but I think mine is different in the sense that I need to control two discrete outputs, one when the relay closes and one when it opens.

I have a device that I would like to control with a relay that can be controlled remotely (which I already have). Basically I would need to momentarily close a volt-free circuit with a 2k2 resistance when the relay closes and momentarily close the same circuit with a 6k2 resistance when it opens.

Here's a picture that might shed light on my clumsy description:

Any help is much appreciated!


texts:
I see a lot of h bridge diagrams on the internet, more or less like this:

If I wanted to connect let's say 4 motors in h bridge configuration while using the same power supply (12v) for all 4 of them and would also like each motor to be able to work independently, what do I need to do? Is this feasible (without a motor driver IC)? Would hooking up more than one h bridge to the same power source affect the current that goes through each motor? If so, how to remedy that?


texts:
QUESTION
 In the circuit, if current gain βdc of transistor amplifier circuit is 200, then what will be the voltage drop across resistor R under quiescent conditions? Assume quiescent base current is 1 mA.

ANSWER
okay now if Ib=1mA.
Ic=(Beta)*Ib
Ic=200mA
which means voltage across the resistor 4.7 k-ohm will be (200/1000)*4.7*1000(since resistance was in k-ohm).
well this much voltage drop is not possible. i know my analysis is going wrong, but how? i am sure i am missing something but what is the fault in my method and what is the correct approach for this question?


texts: Voltage source in series with dependent curent source. How to solve for voltage source?

texts: I am trying to calculate the high frequency cut off of a common collector BJT circuit.  I replaced Cu with a test voltage and open circuited the other capacitors.  The circuit I came up with has the test voltage in series with a current source.  I am just unsure how to find the test voltage.  Here is the work I have done so far.  I just can't figure out what an expression for Vt would be or how to relate it to the other variables.  I needto find Vt/it


texts: Using Simulink to simulate FOC of a PMSM motor

texts:
I am building a simulation of Field Oriented Control of a PMSM in Simulink. The goal is to approximate the behaviour of a uController sampling the position of the rotor and the stator currents at 10kHz, and generating SVPWM signals at 10kHz to control a DC/AC converter connected to the motor. The motor parameters are from the PMSM Emrax 228 Medium Voltage (datasheet here). The controller's goal is to control the electromagnetic torque produced by the PMSM.

There is no speed control loop since the input of the controller is directly the torque generated by the motor. Also, the reference current Id is set to zero so that the torque may be directly controlled by Iq (given by T = 3/2 * #pair_poles * Phi_m * Iq). This is essentially equivalent to MTPA control given that Ld is practcaly equal to Lq for this PMSM.

The problem: The simulation results are complete garbage. The PI loops are unable to control the electromagnetic torque without ridiculous oscillation. As far as I know the FOC algorithm is implemented correctly, and so is the model of the motor. The PI gains may be incorrect, but the controller doesn't even seem to work with a simple P gain. I have tried various times to tune de PI gains with no success. I have also dabbled in changing the Simulink simulation settings (such as decreasing the maximum simulation step time), to no avail.

For the life of me, I can't figure out what is wrong. Why am I seeing these results?

Simulink file here.


texts: What is the effect of this delayed statement in the following process?

texts:
Hi guys in the following process how the delayed assignment should be interpreted?

clk_process : process
begin
        clk <= '0','1' after 5 ns;
        wait for 10 ns;
end process;

Is it intepreted as...

clk is set to '0' for 5 ns then i changes into '1' and after 10 ns it is set again to '0'?
or it is simply '0' for 5 ns and '1' for 5 ns?

I'm a bit confused...


texts: USB to Serial (RS-232) cable not displaying data on Arduino serial monitor

texts:
My previous post (Pictures from the previous post as well)

So far all of the answers and comments yielded no solution to my problem.
This post offers a different method to communicate serially with the reader.
I bought a serial to USB connector cable.
I connected this to my reader and then to my PC's USB port. I opened the Arduino serial monitor and behold my amazement I was reading data correctly. So I thought why couldn't I strip the USB connector and expose the Vcc, GND, TX and RX wires. So I did.

I then connected the Vcc to +5V (Arduino), GND to GND (Arduino), RX to TX and TX to RX. I then opened up the serial monitor after uploading the serial code but still no data. I then changed the RX to RX and TX to TX and still no data.
However, when I connected the serial to USB cable straight to my PC (before striping the USB connector) the serial data was been correctly transmitted and viewed from the serial monitor. So why when I put my Arduino as the "middle man"  the data does not go to my PC serial monitor?
The baud rate was 115200. I cannot change this baud rate because it is the spec of the reader. Additionally, I transmitted data successfully at 115200 by using my PC as the host (using Putty at 115200). So the baud rate is not the issue.


texts: Common mode range and DC common mode interference

texts:
Here is my basic understanding of common mode range for diff input amplifiers:

As far as I understand the common mode voltage is nothing but the offset at which the diff signal is travelling above a common reference.

And if this CM voltage exceeds the amplifier rail voltages due to capacitive coupling or EMI, this is a problem. So as a remedy, common mode chokes(for high freq.) or filters(for lower freq.) are employed to attenuate this CM voltage so that the amplifier can operate well.

It seems like chokes and filters are frequency dependent and they attenuate CM voltages if the CM voltages are alternating/varying in time.

But can there be an interference or noise source which causes increase in CM voltage as DC? In other words is there a phenomenon called DC common mode interference in practice? If so, what are the ways to eliminate it?


texts: Why don't people power LED strips in parallel instead of using amplifiers?

texts: The common pattern to run long LED strips seems to use separate transformers and amplifiers in between the individual strips. Why not use a single transformer, controller and appropriately thick cables to wire the strips in parallel? Given a certain thickness (>1mm), the power loss for runs within a single room seem to be insignificant...


texts: I am confused with how to implement a method of filtering out the impedance from the ground path of an IC. I'm thinking that I should use an RC filter circuit in order to smooth out the current and lower noise, but from what I've found online (here), a bypass capacitor would function similarly and is specifically designed for shorting to ground. Which one is better in this scenario? Are they both the same thing?


texts: getting rid of dc offset at input of unity gain difference amplifier

texts:
I have a question regarding how to tackle an issue i am facing regarding DC offset at the input of unity gain difference amplifier difference.

Following are the details of my circuit :

I use a LT6375 IC for a howland current pump circuit.
The -ve input of the difference amplifier is at ground and the positive input is the output of a sallen-key filter (IC AD8028),which is Vout =  Vdc + Vac (Vdc = Vdd/2 in this case.
To get rid of the DC offset from the filter stage i use a DC-blocking cap (see below). However there still seems to be an offset present after the cap.

Here is the circuit and simulation result (using LT Spice)

Transient simulation result :

As you can see above, the voltage at node "Vin" which is after the DC blocking cap is around 1.2 V.
I am unable to understand how to analyze where the DC offset is coming from. My simulation results match what i have measured on the PCB.

Also if i set the negative input to the DC offset seen at the positive terminal (of the IC)i get the desired results.

Could the offset arise because of some ESD ciircuit at the input pad of the op-amp?
The output current of this circuit depends on the difference of voltages seen at the differential terminals and that explains probably why i get the desired output once the -ve terminal was connected to the same DC level.

Can somebody help me analyze this? Any help will be appreciated.

Thanks


texts: Working of a transistor in a TTL inverter circuit

texts:
I was referring to TTL inverter circuit in the book Digital fundamentals by Thomas Floyd and its working principles first proposition went as follows:

When input is HIGH,  Base emitter of Q1 is reverse biased and base collector is forward biased.
This permits the current to flow though R1 and into Q2's base, hence turning on Q2.

My doubt is:

1.How can you say that base emitter of Q1 is reverse biased?

We only know that Emitter of Q1 is high.
We do not know what the voltage at the base of Q1 is because there is R1 between Vcc and the Base.

2.How can you say that the base collector is forward biased?

We do not know the voltage at the collector of Q1, because we do know the state of Q2 or the rest of the circuit.

-Also how can Q1 conducts current through base collector, because if base emitter voltage is reverse biased the transistor is in open circuit or off state.


texts:
I am working on DIY-ing a handful of USB cables (USB-A to mini for PC peripherals and phone charging), and I'd like a professional take on two dilemmas that I have:

1) I have the option of using either 28AWG tinned copper wires throughout (for both power and data), or the option to use 28AWG for the data and 24AWG for the power. The 28/24 seems like the better way to go (more power = faster charging), but I'm not sure if that would cause trouble in any way. In either case, the four internal wires would be wrapped in foil and shielded in a tinned copper braided shield.

2) Also, the wire I have found is rated at 300v. I know USB ports typically put out only 5v...so is a 300v capacity wire trouble? Or is that irrelevant?

Thanks so much in advance. All the best!


texts:
I'm using an IRF540N power MOSFET in a 12V to 24V DC converter. But the MOSFET getting over heated when its connected to source.  Before providing a gate pulse its getting very hot.  I have attached the schematic here. And the load is a LED lamp of 15W. Battery capacity is 26Ah,12V battery.

MOSFET is driven from a PWM of 100KHz with the duty cycle of 0.7.  But is hetting up more before connecting it to the gate pulse.

What might be the possible reasons? Please help me to improve the design.


texts: Learning process automation starting from general engineering background

texts:
I'd like to study process automation by myself, could you suggest a good entry-level book to start with?

I have engineering college math level and I remember a bit of Laplace transforms to model systems. I have successfully implemented many simple PID and fuzzy logic control with microcontrollers, like tank-level control, pH and more.

My goal are to model systems, test automation strategies in Simulink (instead of time-domain simulations like I did until now), and be able to solve multivariate/interactive situations through decoupling (RGA etc.)

Any suggestion would be very appreciated!

Best,


texts: What is the main advantage of Switched-Capacitor filters?

texts: What is the main advantage of Switched-Capacitor filters compared with passive LC filters and active RC filters?


texts: Car battery(12v) to 7v 2a (to power fan controller)

texts:
I recently installed an amplifier and sub woofer in my car and it is gets up to 40C where I live so my amp gets VERY hot. I want to build a box/amp rack for the amp which will have fans on each side on push pull with a fan controller to turn them on/ramp them up depending on the temperature of the amp.

This is the controller that i want to use https://www.acinfinity.com/cabinet-fan-systems/controller-2-intelligent-thermal-fan-controller-single-zone/#product-warranty
There are controllers that I can simply power off a USB plug but those don't have the features I need.

You can see on the picture that the controller accepts 7V, 2A DC power through a DC plug, which is meant to be plugged into the wall and installed in a media cabinet or something similar. So now I am trying to figure out how I can hook it up to my car battery.

I was thinking of using a DC-DC regulator like this one I found on amazon https://amzn.to/2PluCe8 . Would I be able to wire that to the REMOTE connector from my head unit(12V) and the ground wire from my amp (so it only turns on when the head unit is on) or would there be a better way to go about doing this?

TLDR : Trying to install fan controller that accepts 7V 2A in my car to cool amplifier.


texts:
I'm using an arduino to send a 5v signal to other devices. I'm using the uln2803apg
to drive a 5v 3ampere signal.

The problem, when i look at this output signal i'm seeing a lot of noise, which is not visible on the pin controlling the uln2803apg.

Within the peaks you notice the noise,

I'm clearly not an experienced electrical engineer, however any ideas or comments
would be greatly appreciated.

Regards Auke


texts: Can two super capacitors connected in series back to back be used as DC blockers when in series with an AC supply and load, regular polarized capacitors can be used in this mode, but is there something different in the construction of super capacitors which precludes this.If yes are diodes required to prevent reverse charging.


texts: DC current transmission loss vs. conversion loss

texts:
I'm going to transmit about 7 Watt DC over 4 meters long twisted pair Ethernet cable. I'm thinking of using Buck and Boost converters to step-up to 30 V and step-down to 5 V the voltage before and after the transmission to reduce path loss.

My question is can DC-DC conversion cause to more power loss than the path loss?

EDIT

Another requirement is ~4A @ 5V and the cable is 10m long. Then ~20W has to be transmitted.


texts:
I know that current is amplified by junction transistor but what about voltage? Is voltage also amplified at same time as current or not? In school professor was explaining me about this and I still don't get it. He was mentioning resistors or something like that.

I hope someone can explain me this more detailed and understandable about transistor gain, whether amplifies current or voltage.


texts: How does a negative current start in the inductor in ac circuit?

texts:
As shown in this image, how does a negative current appear at the beginning, when the voltage starts to increase ?

I understand the current lead lag mathematics behind it. I just can't figure out, what is going on with the electronics inside the wire. How can an increasing voltage, cause a reverse current ?

Update

Thanks to Andy aka for pointing out the right solution with correct references. I realised that the answer to the anomaly lies in the equation of the inductor.

Since for an inductor v = L * di/dt

Therefore current = Integral (v/L * dt)

Integral of Vsin(wt)/L = -Vcos(wt)/L

And the TRICKY part is to take integrals between 2 points A and B

So the current at a time t = -Vcos(wt)/L - (-Vcos(0))/L = -Vcos(wt) + V/L

The cos(0) is the DC component that "lifts" the entire current wave above the 0-line so the current keeps flowing only in positive direction (assuming a 0 resistance path). This is mentioned here -

http://licn.typepad.com/my_weblog/2012/03/to-zero-cross-or-not-to-zero-cross-john-dunn-consultant-ambertec-pe-pc.html

Observation

This is probably why the SMPS of my CPU cabinet makes a loud noise right when I turn it on. The sound persists for about a minute and then fades away. Because the voltage supply starts with a 0V at t=0 and the ac current flows only on the positive side of the graph above the 0 level, giving a higher dc value.

Notes

I tried reading a few more online tutorials on circuits to understand the very basics of RL and RC AC circuits.

Every RL and RC ac circuit has 2 currents. One is the steady-state current I(ss) and another is the transient current I(tr).
The phasor method calculates only the steady-state current of it. Which many believe to be the "real" behavior of the circuit, while it is not.
This link shows the calculation of the transient current in a RL ac circuit -
http://www.ee.nthu.edu.tw/~sdyang/Courses/Circuits/Ch09_Std.pdf
I have created a partsim simulation of the RL ac circuit, which shows the whole thing nicely -
https://www.partsim.com/simulator/#69215


texts: Lead Free Soldering and bad looking joints

texts:
For years I've been soldering with normal Sn60Pb40 solder wire. But now I try to switch to lead free solder. In many forums over the internet I found the Amasan BF32-3 solder wire. It's a Sn95Ag4Cu solder wire with 3.5% flux.

So I tried it and was very disappointed. Nearly every solder joint was looking different. Some of them were (partially) shiny; some (the most) of them were dull. And the worst thing was, that even with additional flux, the solder didn't flow like the leaded. So there is no way, I could solder fine pith SMD stuff with it.

I’m using a JBC soldering iron station with a C245-907 2.2mm chisel tip and tried different temperatures starting with 290°C to 360°C. The best results I get with about 315°C, with 350°C I got the worst results. I used the Amtech NC-559 Flux – the original, not the fake from china.

Some other guys told me, that maybe the solder wire is not the best. That's why I'm looking for other soldering wires. But there are so many on market. Some with copper, some are Sn96.5Ag3.5 like the Amtech ASN96A3.5-0.50.

So can someone tell me, with what type of solder wire or what product I can get nice shiny solder joints. And yes, I now that dull joints were not a sign for a bad or even cold joint.


texts: Motor power supply issues causing 'judder/jitter'

texts:
I have an Arduino project which uses a L298N to control a 12V DC brush motor (with an apparent 1.8A stall current rating). The motor is equipped with an encoder but I don't think that is relevant to my problem.
While prototyping I have been using an ATX PSU for a PC which I modified for a 'bench supply', which provides 5v, 9v and 12v with ample current.
With this PSU, everything is great - no problems, motor is smooth. I thought any old 12V power supply that could provide at least 2A would be sufficient as a replacement.
However, every other power supply I have tried does not perform nearly as well as my ATX PSU; the motor feels weaker but most importantly it sounds like it's having a bad time. It's hard to explain, but the motor makes a whole lot of mechanical noise, especially when under load. I don't mean a PwM whine, but more a noise like it has bad bearings or gearbox or something. The motor jitters/judders/vibrates as it moves instead of giving nice linear feedback/movement.
As it works fine with my ATX PSU, I can only assume this is a power supply issue. Also I think I can rule out lack of current based on the specs of the ones I have tried:
I tried this first:
EFISH Power Transformer 12V 2A 24W,AC 100-240V to DC 12V Power Supply Adapter
https://www.amazon.co.uk/gp/product/B07KZB5TQX
Then this, as I thought the first one might just be a cheap unit that wasn't as capable as it said:
BW High Quality 12V 5A 60W DC Power Supply
https://www.amazon.co.uk/gp/product/B00C676JNM/
Finally, I tried this, thinking a more 'dedicated' regulated switched mode power supply would do it:
Velain 12V 5A DC Universal Regulated Switching Power Supply Converter, 60W Adapter Transformer
https://www.amazon.co.uk/gp/product/B01N0Y5E8K/
Motor specs:
Gear Motor 12V-DC 12V Encoder Gear Motor Speed Reduction Pure Copper Coil Motor (500RPM)
https://www.amazon.co.uk/gp/product/B07XRDVXRZ/
Rated speed (RPM): 500
Reduction Ratio 9.6
No Load

Speed ±10%RPM 620
Current A 0.07
Rated
Speed ±10%RPM 500
Current A 0.3
Torque KG.CM 0.2
Stall
Torque KG.CM 0.9
Current A 1.8
Rated Voltage 12V

Any help much appreciated.


texts: I have a board in Kicad that uses a mixture of plated and non-plated through holes. It generates two drill files for these. However, manufacturers seem to expect only a single file. If they don't support NPTH, how can I generate a single file? Can they be safely concatenated?


texts:
I was wondering what is the easiest and cheapest way to have a high power led (3 Watt) turn on/off and blink remotely from a distance (60m-100m).

I've been looking at some microcontroller solutions (simple decoders and relays combined with a 433MHz transmitter) but I'm not sure which way would be the simplest.

Can anyone help me with this?


texts: What is the correct way (read "correct way according to the law") to choose the section of a power cable in the EU and UK?

texts:
I am wondering if there is a standard process across the EU in particular Germany, France and the UK, for choosing the the section of a power cable.

Suppose that:

the cable is to be installed in an industrial/civil low voltage application (400V three phase or 230V mono phase, your choice, if it makes any difference, please explain why).
The power factor is given
The cable is isolated with PVC.
The cable is protected with a fuse or an automatic switch.
There are no other special requirements.
The user is using the line at full power all the time (think of an industrial motor running 24/7 for instance).

How would you need to choose the section of the cable, the size of the fuse/automatic switch in such countries according to the law? Is there a common framework?

If you need a specific case to study, please refer to a common home appliance that should be able to provide, at worst, 4kW continuosly.


texts: schematic for battery and solar cell in parallel

texts: I have a thermometer, that the sender uses 2 batteries AA (2 x 1.2V). I would like to add a solar cell to use it to load the battery. I tried to connect both (battery and solar cell in parallel) with a diode in front solar cell to avoid any reverse current into the solar cell. Somehow it didn't work, it means, the thermometer stopped to send information to the base. As soon as i removed the solar cell, it started back to send information to the base. so I would like to ask if there is any schematics that I can use as example.


texts: Filter before or after switching regulator?

texts:
I will be passing a power line (12V-60Vdc depending on the circumstance) with a lot of noise, 300Hz and above, riding on it through a buck regulator. I want to remove this noise with a filter. I don't know whether to place the filter before or after the regulator.

The choice that seems more obvious to me at first is to filter after the switching regulator - the power will be attenuated and it's easier to filter a smaller signal. However, I am not sure if this is correct, because this assumes that the AC noise is reduced like the DC power in the regulator. Is this the case? Or does an AC signal in a buck converter behave differently?

In summary, I want to attenuate and filter noisy DC power. I'm not sure whether to place my filter before or after the buck converter.


texts: Light load efficiency of DC-DC Switching converters

texts:
I have been working with DC-DC Converters theoretically.

What is it that I don't understand is that how the efficiency is very less at light loads? How does the switching and the output get affected?

Light load means that the IC output has the stable output voltage but Load Current is less?

Can someone help me understand the light load behaviour of DC-DC converters in simple terms?


texts: When a PN diode junction forward conducts heat is generated due to the product of forward volts and current.Is the heating evenly distributed between the P and N junctions ? or is it the P? or is it the N?.What is the story with a shottky does it go to the metal? Is this why common cathode is more common ? .


texts:
Shown below is the circuit I would like to implement. (the circuit is from this paper).

Basically, it's a circuit designed to cut off voltage when electrochemical etching is done. The sudden drop in current flow is taken as the signal to stop the voltage bias.

I circled the two parts I would like to better understand.

Given the schematic of the circuit, I would like to know the voltage difference between 'WIRE' and 'RING' (circled in blue), assuming the state where Q1 and Q2 have zero Gate voltage and hence all the current is just flowing down to WIRE and RING.
There is a switch (circled in red) connected to CLR pin of the flip-flop.  I looked at the datasheet of DM7474 flip-flop.  I initially thought it was some manual switch that maintained the voltage between 'WIRE' and 'RING' but given the output of Q's dependence on CLR input, it doesn't seem so obvious. Neither high nor low of CLR fixes the output of Q.

-----added-------

Thank you for your suggestion.
After your explanation, I wrote down what voltage value the gate of Q3 would get as a function of resistance values of 'WIRE/RING' and potentiometer.

Since no current goes into Q3 gate, I \$= \frac{8V}{R_2 + x_w + x_p} \$.

So I guess I have to choose my potentiometer value such that the gate voltage of Q3 gets some voltage above the threshold when in the process of etching and gets zero when the etching is over (since when etching is done, the resistance value will shoot up).

-----added-------

I circled the potentiometer, capacitor, and another switch.  I think I understand why the potentiometer is there. It is to introduce a potential value change to the input of the flip-flop.

I am not sure what role the capacitor and switch in parallel with the potentiometer serves.


texts:
I have a 555 timer clock output controlling a few things,  one of them is the coil of a 24v relay.  How can I take the 5v coming from the 555 and pump it up to 24v. ?

simulate this circuit – Schematic created using CircuitLab

What I am doing is using the clock cycle to turn relay on/off . Then the 5v threw the contacts is being counted. Thus if I turn on off the relay 100 times, I should get 100 counts at the counter.  The logic works for a 5v relay, but unsure how to change this for a 24v relay.

Thanks
Glen

UPDATE
Added circuit as suggested, now the relay will get 24v across coil when signal is high and 16v when signal is low(not low enough to turn off relay). Below is image of circuit.


texts: CAN communication on tms320f28377s using usbToCan driver with db9 connector

texts:
I am using launchpad xl f28377s. It has a CAN transceiver which is intagreted. How can I connect this card to usbToCAN ixxat driver using db9 connector ?

Thanks,
Regards.


texts:
I have seen the crystal oscillator output in the oscilloscope and it looks something similar to a sine wave (at least nothing similar to a square wave and with a hard to calculate duty cycle)!

So how does a type 1 phase frequency detector (the xor gate) functions with such a reference signal from the crystal oscillator as one of its input?


texts: Is it possible to create a homemade programmer for PIC16F84A?

texts:
Is this simple circuit able to program a microcontroller? Or Does it need any other components?

After looking at this question, I can know where D+ and D- of USB cable are, by looking at the colours of wires.

After reading datasheet, I think that D+ and D- should be connected to pins 13 and 14. But I don't know which one I should connect to which. for eg. should I connect pin 13 to D+ or D-? If I connected them in a wrong way by mistake, Does that damage the microcontroller?

What is the best software to communicate with this circuit? I want windows to recognise or add this new hardware without getting in troubles.

simulate this circuit – Schematic created using CircuitLab


texts: Making a two speed motor - TRIAC and PWM question

texts:
I would like to create a dual speed blower which goes into HI when an SSR from a PID is activated.  I would like to be able to control the speed of each of the high and low settings.  When the SSR is not activated the blower would be in low.

For an AC motor, using TRIACs:  If I set the low speed controller to my desired setting and use this to power the fan and then connect another TRIAC speed controller in parallel to the first, where the second on is activated via the SSR, will these operate correctly in parallel and "boost" the blower?

Or would there be some sort of feedback? If I set each to controller to say 50%, in low would we be operating at 50% fan speed then in high we would have full speed or are these not additive?

Second part of this would be if I were to use a DC motor and PWMs.  Would a solution to this be to have the SSR switch between the two PWMs so that only one is operating at a time?  And if so, what would be a good approach to this - would I use two SSRs and a NOT to switch between the two?  Something like:

I would really appreciate any thoughts, or if you have better ideas please let me know.

Thanks for any input.

[edited based on comment below]

Motor contenders:
I'm not really sure what type to get - whatever is most easily controllable, and I'm not that familiar with the motor types.  Some contenders were a 115V Dayton shaded pole blower (e.g. dayton-model-1tdp7-blower-146-cfm-3100-rpm-115v-60-50hz-4c446 (sorry can't post full links because I don't have a reputation)), but these say "not recommended for speed control" so that doesn't sound too promising.   The 12V version (very similar) also says not "recommended for speed control".

Finally there is: www.spalautomotive.com/files/centrifughi/catalogues/004-A41-28S.pdf
Which is interesting because it has 3 resistors on it for high, med and low.  So I think it is a different type of motor from the Dayton.  I submitted a question to the manuf about acceptable speed control, but I haven't heard back.

Note that the speed difference I am looking to implement would probably be about 10% different while running close to the max speed (I'd choke off the input to reduce flow).   I believe speed control issues are usually related to running too slowly and causing overheating so that might be the reason for the Dayton warning.

Any recommendations about the type of motor would be appreciated also.  I need something relatively high pressure and CFM (1-2", 150CFM).

Thanks.


texts: Two grounds when using transistor switching

texts:
Background

I'm designing a small circuit in which an MCU and all its peripherals should be shut down unless a certain condition is met, which is represented by a switch in this simplified schematic.

The MCU requires a 5V power source from which it supplies 3.3 Volts for the peripherals.

In its simplest form I came up with the two solutions below. The measurements reflect reality -- I probed both circuits on a breadboard.

Question

Which alternative is more suitable for this:

Observations:
In case 'A' the MCU receives 4.3 V, which should be sufficient for the internal regulator to operate and output a proper stabilised output, however, two separate grounds will result. Digital ground will be comparatively higher than 'real' or analogue ground. Peripherals will have to stick to using the digital ground, everything else (i.e. not connected to the MCU) may use the real one.

Observations: I case 'B' digital and analogue grounds are the same but the MCU only receives 3.7 V instead of 5 V. It still operates and establishes the 3.3 V output, but I think this it is really pushing it and is bound to fail intermittently.

Is either of these a viable solution, or should I do something along the lines of this (which will increase the part count):


texts: Mosfet failure in DC-DC switching converter: root cause analysis and countermeasures

texts:
I'm dealing with a pilot project which involves several units on the field (around 15 units) powered by a control card which needs to drive two resistive loads in DC in the range of 13-5 VDC. Each of the two loads is rated 60W
One of the cards from the field reported a failure, after circa 18 months operations, 5 days a week, 8 hours/day. I investigated the card and I found out that one of the Mosfet appears to be blown.
At a closer inspection I realized that small flux balls have built up in between of the Mosfets. The bottom pads of Mosfets Q17, Q18 and Q19 appears to be shortcut, according to the multimeter used.

I compared the defective control card with a new one, and the new one appears to be free from defects.
The mosfets are controlled by two LM27222 in push-pull configuration. The mosfets are FDMS86101DC.

Are the flux residues likely to be the root cause of the failure?
I heard that flux is quite hygroscopic, and, in my analysis this could have let to flux bridges build-up.
The cards are enclosed into a metal case, but levels of humidity can be high. Should we try to coat the cards with compound? Would this be a valid countermeasure?
Here's the schematic and the PCB layout.


texts: How do I calculate a PCB antenna trace width?

texts:
I'm totally stuck here trying to find a single source that describes how to determine a PCB antenna trace width. I understand how to determine the length based on the targeted wavelength, but the width is lost on me.

To preface, I'm very new to this and am trying to design a half-wave curved dipole PCB trace antenna. The guide I'm using as a reference is from Texas Instruments. Click design guide at this link.

In this TI DN041 guide it says the following in section 4 Designing a Half Wae Dipole Antenna on a PCB:

  The width of the trace does have an impact on the antenna performance, particularly the bandwidth. In this design note we will stick to a width of  300  um (12 mils), and refer the reader to more thorough papers on antenna theory if they wish  to  probe  deeper  into  this  particular  property of  the  dipole.

So I went on a hunt to try to find these "thorough papers on antenna theory" and came up short. I did, however, find a few resources that pointed me to a broken link for an online "microstrip" calculator. I did some digging and found a new link to it here (click "Microstrip Trace").

Now I'm not sure that a PCB trace antenna counts as a microstrip trace because PCB trace antennas are not supposed to have anything on other layers above or below it so that the antenna performs well. Yet a microstrip has a groundplane underneath it as illustrated below:

Then I did some digging and found that this is used to calculate transmission lines and  that "PCB antennas are not transmission line."

Someone on this very site tried to use this calculator for that purpose and it was mentioned that their use of the microstrip calculator was incorrect due to the ground plane. So using a microstrip calculator seems to be incorrect (even though some people used it as such). So then how do I calculate it?

So to summarize into a single question, how do I determine the width of a PCB trace antenna?


texts:
I am interested in finding out the memory usage of my code running on an ATMega328P (16 MHz) using the avr-size utility bundled with WinAVR 20100110. Using the Makefile included in the distribution I obtained the following memory usage for the code below:

#include <avr/io.h>
#include <stdint.h>

int main(void)
{
    while(1)
    { }
    return 0;
}

The console output is:

make all

-------- begin --------
avr-gcc (WinAVR 20100110) 4.3.3
Copyright (C) 2008 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Compiling C: src/main.c
avr-gcc -c -mmcu=atmega328p -I. -gdwarf-2 -DF_CPU=16000000UL -Os -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wall -Wstrict-prototypes -Wa,-adhlns=./src/main.lst  -std=gnu99 -MMD -MP -MF .dep/main.o.d src/main.c -o src/main.o

Linking: src/main.elf
avr-gcc -mmcu=atmega328p -I. -gdwarf-2 -DF_CPU=16000000UL -Os -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wall -Wstrict-prototypes -Wa,-adhlns=src/main.o  -std=gnu99 -MMD -MP -MF .dep/main.elf.d src/main.o --output src/main.elf -Wl,-Map=./src/main.map,--cref     -lm

Creating load file for Flash: src/main.hex
avr-objcopy -O ihex -R .eeprom -R .fuse -R .lock -R .signature src/main.elf src/main.hex

Creating load file for EEPROM: src/main.eep
avr-objcopy -j .eeprom --set-section-flags=.eeprom="alloc,load" \
    --change-section-lma .eeprom=0 --no-change-warnings -O ihex src/main.elf src/main.eep || exit 0

Creating Extended Listing: src/main.lss
avr-objdump -h -S -z src/main.elf > src/main.lss

Creating Symbol Table: src/main.sym
avr-nm -n src/main.elf > src/main.sym

Size after:
AVR Memory Usage
----------------
Device: atmega328p

Program:     134 bytes (0.4% Full)
(.text + .data + .bootloader)

Data:          0 bytes (0.0% Full)
(.data + .bss + .noinit)

-------- end --------

When I run the same code with the while() construct removed the program size is reported to be 138 bytes. Same happens if I comment out both while() and the return statement. How can the program size increase when I remove a loop construct? The Makefile uses the -S optimizer for gcc. Does it have something to do with it?


texts:
I am looking at the specifications of an EMI filter for single a phase ac application, and I noted that the datasheet specifies an operating frequency from DC-400Hz? Do you have any idea of what this means?

Thanks


texts:
I have an AC/DC converter:

input AC 220-240V 50/60Hz

output DC 3.6-10.8V 1.5A.

It is a charger for an electric drill battery (Li-ion 10.8V 4Ah).
What would happen if I were to plug this converter on a 110V circuit? Would the DC voltage be half what it is supposed to be?
Would the battery charge at all, albeit slower?


texts:
I am new to electrical engineering. Just a question on lack of synchronization problem. Below is a picture from my textbook:

I am very confused, time is unique to everyone in the world, so if both sender and receiver agree that, for example, the pattern of 0.001s represents a bit, so we won't have any synchronization problem any more, isn't it?


texts: Simulation LTSpice Miller plateau and reverse recovery diode

texts:
I would like to do a simulation in order to better understand the losses in switching power supply. I m trying to a simulation with the following circuits :

I'm working at very high frequency in order to better see the effect of the reverse recovery diode. Nevertheless, in any case I have a problem that I do not understand. Why my Drain voltage of the MOSFET is never near to 0 V ?

I'm totaly a beginner on LTspice...

Thank you very much and have a nice day !


texts:
Estimate the gain tolerance (+/- X%) of the non-inverting amplifier in Fig. 3 assuming that the tolerance is solely determined by the errors in the resistor values. Only resistors involved in the gain definition contribute. Their tolerances are simply added up. You have 5%-tolerance resistors.

Fig. 3:

I understand that $$A = 1 + \frac{R_2}{R_1}$$ for non-inverting op-amps, but I don't understand what this question is asking.


texts: How to make LED bar graphs to measure intensity

texts:
I'm working with this design.

I would like to make those LEDs into LED bar graphs that will show the intensity. For example, I want a song with a loud base to make the bar graph shoot up to the top. The bars of the LED bar graph I would like to just be individual LEDs. I was getting the effect with an arduino but I was hoping there was easier way to do this.


texts:
I'm trying to make a "Toggle Latch" or toggle flip flop. The S-R latch works properly (The two NOR gates). when I add the two AND gates, the output led turns off and it does not respond to the inputs J and K !

I tried to add pull-up or pull-down resistors but it does not work too.

The IC's I'm using are 7408 and 4001 and I'm sure they are working.


texts: Generating negative voltage rail using P7805 DC-DC converter

texts: I need to create a negative voltage rail (from positive supply rail), say -5V to keep a P-MOS transistor in ON-state even when the voltage on its [S] source is 0V. So I found this schematic in an answer of another question here, but does this actually work?


texts: How to choose value of base protection resistor for TRIAC

texts:
I'm using the following circuit to allow an ESP8266 to trigger a mains TRIAC via an optoisolator. I'm aware that there should be a resistor between the OI and the base of the TRIAC (R1 in my diagram).

How do I choose the value of the resistor? It's mains in the UK, so 230V RMS. The TRIAC has a max gate trigger voltage of 1.5v, and a max holding current of 15mA. The original circuit suggested 470, but my (probably wrong) maths suggests 20K. What is the correct way to calculate it?


texts: Effect of PWM output from Variable Frequency Drive to PSC motor

texts:
I looked at VFD diagram and seem like it use Sine-PWM Output without any filter to drive psc single phase ac motor
Inductance and capacitance seem to work with pure sine wave but PWM output have a lot of harmonic frequency.
The question are as following.

can we put PWM output directly to motor, how the system behave?
Does it need additional filter to convert pwm to sine wave?
Is that practical?, how we do for practical use?


texts: Bi-Directional MOSFET level converter problem

texts:
I am using standard schematic of level shifter.

It is used to communicate with avr and sometimes reset it. Everything works fine except for reset line. After the first pulling down I am not able to make it high again.

Screen from LA:

Closer look:

I have tested it on three different boards. I have checked everything. Nonetheless reset line is still going bananas.

For me it looks like the transistor is closing and opening quite fast. Why I can not imagine. The only difference between reset and other lines is that it has one more pull up(the first one is on the shifter) through 10k to 5v.

What is going on here?
Thanks!

UPDATE

Have revealed that disconnecting arduino/avr from the device results in normal reset line operation. I am trying to load file into avr memory if it makes it clearer.

SCHEMATIC

Connected avr is arduino uno/mega. Here it is its shematic. You should be interested in ICSP connector.
For the controlling device I use cc3200-launchlx board from TI. It connects to arduino over ISP connector.

For cc3200 I have this simple shield:

So.. I pull P61(H_RST) down and it sets reset line low. However when I pull it up after that I get infinite switches between low and high levels on it.

Here is also my handmade atmega16L board schematic which faces the same problem:


texts: Safe Variable VAC Power Supply using Switch

texts:
I want to make a variable VAC power supply, maybe using 3-5A transformer. I provide the simple circuit diagram below.

What should I add to ensure its safety? Thank you.


texts: How is it possible that an LC Oscillator create a sine wave?

texts:
I have a question, for example look at this circuit:

1)How is it possible if this circuit can oscillate, for example taking on the capacitor full charged, and the inductor full discharged, the capacitor, since there isn't a resistance is shorted, so how can it create a sinesuoidal wave?

2)How is is possible, taking on the capacitor full charged, and without a resistance, that this circuit swinging will create a sinusoidal wave, and not for example an exponential signal [In voltage], like for example in an RC circuit, like that:


texts:
I'm designing a system with a master board and a variable number of identical daughter boards that I would like to connect in a chain.  The master board contains a microcontroller but the daughter boards don't contain anything intelligent. The master board will only connect to one daughter board, and each daughter board will be able to connect to a next daughter board.

I'd like to figure out a way for the master board to be able to detect how many boards are connected to it, and be able to send signals to each board depending on where that board is in the chain.

Does anyone have a good idea for this?  The simpler the better.


texts:
I am trying to design a PWM inverter in Orcad PSPICE where i am using a Vpulse source from library to generate MOSFET triggering pulses for H-bridge and it works fine for square waves.

But i  if i want to generate sinusoidal pwm to drive the h-bridge how can i accomplish it in orcad pspice and drive the mosfets accordingly.

Previous method:

Desired PWM output in simulation

  I figured out that sinusoidal pwm is generated by comparing a
  sinusoidal wave with triangular wave.Is there any way we could
  simulate sine pwm in orcad pspice and drive the h bridge accordingly
  different switching topologies.?

  I would appreciate any help or suggestions that will help me to
  achieve my intended purpose of making prototype of sine wave pwm
  generation like as mentioned above in picture using orcad pspice.

  Thank You for your time :)


texts:
I am seeing a strange behaviour on an I2C waveform, and it is causing an incorrect bit to be read by the master. The master device is an ET1200 EtherCAT ASIC, and my slave is a CY8C3666LTI PSoC which is emulating a 16-bit address EEPROM.

The master is attempting to read a few bytes from the 'EEPROM'. On the logic analyser and oscilloscope, the waveform looks like this:

The logic analyser is interpreting the waveform correctly. The bytes 0x24, 0x04, 0x30, 0x05, etc. can be seen written along the top. However, the ET1200 is seeing every other byte have the top bit set. So it's seeing 0x24, 0x84, 0x30, 0x85, etc.

Looking closely at those bits on the oscilloscope, we can see a malformed clock pulse there. And it's also so close to the preceding data bit, that it's not surprising that a 1 is being seen.

My question is: What could be causing this malformed clock pulse? Has anyone seen this before?


texts:
I'm working on a project that relies on the Roomba vaccum cleaner's reference document (shown below), there are two positive terminals and 2 ground terminals. I'd like to understand:

Why there isn't a negative terminal, only positive and ground (this isn't a typo, I measured the +ve-ground terminals with a multimeter).
Why there are two positive and two grounds instead of just one each (couldn't a user easily break a single terminal into two if he needed to?).

Please refer me if this question already has answers elsewhere; my google-fu may not be up to the mark.


texts: Maths behing implementing temperature compensation on a signal

texts: I have a fluid pressure sensor (blue line) whose measurements are affected by outdoor temperature (yellow line). So there is a 12 hours cyclic component (day/night) in my pressure measurements. How can I use the temperature variable to compensate (or "decycle") the pressure readings accordingly? I'd appreciate if you could direct me in the right direction, what are the mathematics concepts to look at?


texts: Ingress protection(IP Code) at connectors

texts:
What does the IP code exactly describe when applied at bulkhead receptacles?
The ability to seal the conductors inside of the connector from the environment or the ability to seal the enclosure from the environment, when the receptacle is installed or both?

For example this SMA connector says in the datasheet "SMA IP67 bulkhead jack to SMA plug RF coaxial cable assembly", but on the picture I can't see any sealing for the enclosure, so I can't imagine that only metal on metal could make a waterproof seal in this case.


texts:
I am a bit electronically challenged and need to hold an input pin high for about 8-10 seconds. I am implementing this solution: https://github.com/NeonHorizon/lipopi/blob/master/README.power_up_power_down.md, which works fine, but I have to hold the power on switch for 10 seconds before the Pi sets the UART pin high (and keeps it high). I looked at some explanation of RC circuits, and they seem to all have the same charge delay as discharge delay. Maybe I need a diode in there somewhere? Basically, I'd like to have the capacitor charge quickly, and discharge slowly through the resistor.

Following onto Flàvio's suggestion, can anyone tell me if using a transistor for isolation will work, something like this? The hoped for outcome is:

Press switch
Capacitor charges
When switch is released, capacitor keeps base of transistor high until GPIO 14 goes high as a result of the Raspberry Pi powering up.
By the time the capacitor would have
discharged, GPIO 14 takes over to keep the transistor conducting, and
EN remains high.
To power down, when the switch is pressed again, the
Raspberry Pi reads GPIO 18 and a script instructs the Pi to power
down
After shutdown, GPIO goes low, the capacitor discharges, and the
powerboost cuts power to the Pi.

(fixed transistor orientation)


texts: IC Price Discrepancies (General Information)

texts:
Looking for some insight into what drives IC price discrepancies across suppliers. Espcially comparing places like digikey and mouser to aliexpress

For example:

I'm looking into buying Maxim Integrated ICs to control LEDs.

I've bought some Dot Matrix modules (with 4 MAX7219 chips each) for around 5 dollars.

On mouser and digikey the hugely popular MAX7219 chips are 8 dollars each. On Aliexpress you can get them for around .60 cents each.

However the less popular MAX6954 are 30 dollars each on digikey, and the same price on aliexpress.

While I know we can only speculate here, I'm wondering what are some of the common causes (I'm new to the world of buying ICs).

Is counterfeiting of ICs a big problem in the electrical engineering world? I know several vendors can make similar chips that do the same thing, or even knockoffs. But, is it common to see counterfeit ICs complete with name brand logos from places like Maxim and TI?
How bad is middleman markup in the IC world? Are prices controlled more by the manufactures or the distributors? Mouser and Digikey seem pretty simliar in price. But Aliexpress is all over the place.
Are there any reputable IC surplus sellers where I am getting surplus parts instead of counterfeit?


texts: Need help to understand inductor based non-isolated offline buck converter

texts:
Here ADGJ IC is used in offline buck topology.
Can anyone share the schematic of it.
Picture taken from sonoff mini and shelly1 board is attached below


texts: Will assigning a value to the W-reg in PIC16F84A during an interrupt, save it after the interrupt is disabled?

texts:
Okay so, I'm having this part of my program that needs a value to be checked to continue.
basically, here is what it is doing:
WAIT_INT   ; wait for interrupt
     CLRWDT
     BTFSS TO_LOOP_OR_NOT    ; will be set after interrupt runs
     GOTO WAIT
     ; interrupt assigns a value to W-reg
     ; When it exits, it will be compared here below
     SUBLW 01H
     BTFSS STATUS, Z            ; checks if equal
     GOTO WAIT_INT

     ; rest of code

I am stuck in this part and I don't know if the value W-reg is saved after being assigned in an interrupt.


texts:
After searching online for an answer to how to convert a toggle switch to a momentary switch I found the circuit below. I've simulated it and it works in CircuitLab.

simulate this circuit – Schematic created using CircuitLab

I'd like to do the same thing using a transistor instead of a relay but so far I haven't been able to make it work in CircuitLab. Can I convert a toggle switch to momentary switch using a transistor and capacitor?


texts: Interpreting garage door sensor signal using a microcontroller/opamp

texts:
Edit 3: I had more information to share regarding my question.

I am trying to use this garage door sensor in one of my projects. I am trying to use the sensor to detect if a person tripped the sensor. There is really no documentation for the sensor except for the patent information.

The sensor has two terminals '+' and '-'. I was able to read the data from the '+' line. The sensor is powered by a 12V source and the response is a square wave that I was able to capture by turning on the AC coupling.

As seen from the capture, the signal is really noisy. When there is no beam interruption, the output is a square wave while there is none when the beam is interrupted. How do I detect a square wave of such a small amplitude?


texts: Measuring veloctiy by detecting objects with an analog sensor

texts:
I have a sensor (DRV425) which outputs an analog voltage. The voltage level changes to a lower voltage when the sensor pass an object. Please take a look at the screenshot. It shows the output signal of the sensor after passing 6 objects.

The length of the spikes depend on the velocity of the sensor and I want to measure the time between each of this spikes to calculate the velocity of this sensor. My actual idea is to measure the voltage with an ADC and calculate the average of the signal. But this idea is not very robust against some noise or some kind of peaks in the output voltage. So I´m thinking about some better ideas.

Does it make sense to use a moving average (exponential moving
average) filter on this signal? As far as I know the exponential
moving acts as a kind of low pass filter and so I don´t know if this
works.
Does it make sense to average the data points and check if the average changes to detect if the voltage is above a threshold. This can start a counter and I stop it when the voltage is under a threshold to measure the length of the peak? With this I can calculate the time, by knowing the sample rate of the ADC and with the width of the measured objects I can calculate the velocity.


texts: Safe way to interface directly with HomePlug / Powerline

texts:
I'm looking to do some research into the actual messaging used by powerline adapters. I'm aware of the standards, but I'm specifically looking to see where real devices deviate from the standard, and how they might be played with from a security standpoint.

What's a sensible way to interface with the powerline adapters safely? I envision some kind of high-pass filter on the mains which pulls out just the HF components (>1MHz), but then I'm not entirely sure what kind of voltage levels the resultant signal would come out at. I'm looking to translate them down to save levels (e.g. ±1V) for analysis.

Is there a simpler option, perhaps a chipset that can be interfaced with from a microcontroller that supports direct messaging rather than an Ethernet abstraction?


texts:
We are trying to create a chaser circuit using a CD4017 counter with the output of a 555 timer as the CD4017's input. The schematic diagram used is here (photo taken from circuit digest):

When probing the outputs, we get this waveform

Can someone explain why or what causes the /\ /\ /\ /\ /\ portion on the output waveform?

[edit]

Probing the output of 555 and the capacitor produces these waveforms:

Unfortunately, we weren't able to include both the output waveforms (that of the 555 and CD4017) at the same time on a single display. (lol :( ) Also, we forgot to set the traces on the same volts/div and sec/div


texts: Is it possible to conceive of a system that would use a stationary camera with a fish-eye lens to effectively provide the same images as a camera that was actually panning and tilting.


texts: Selecting a transistor, is there a go to transistor for typical projects?

texts: I'm a HVAC tech who is interested in electronics. I have 3 kids and not a ton of time to really get involved with the data sheets or a real understanding of electronics. I just want to make some simple electronic devices. Some things I've done are a solid state water make up control for the Keurig and a peltier heater / cooler. My problem is that I don't really understand transistor ratings and abilities. Is there a, or a small set of, go to transistors that have a wide range of applications?


texts:
I'm currently trying to size some logic inverters (CMOS IC Inverters, not power converison) based on the Logical Effort Approach. This approach requires that you know the input capacitance of an x1 size inverter.

I've run a DC operating point simulation in Cadence Virtuoso and selected the DC parameters of my PMOS and NMOS device of my x1 inverter. However, there are so many capacitances that it shows, some don't make complete sense to me.

For example, there is Cgd and there is also Cdg are they are different values, how does that make sense?

In short, which capacitances do I sum up to find my total input capacitance for use in my logical effort equations?


texts: 36V Li-ion Charger - how do we make it actually work?

texts:
I have a Hitachi Li-ion charger (without the case) that suppose to charge 10 18650 cells in series (hitachi powertool battery made of 10 high drain cells). That's an official 36V rating of the charger that suppose to deliver at least 42V to fully charge a 10-cell li-ion battery.

The charger was used initially exactly for its purpose. Now I wanted to use it to charge various 36V rated batteries but it seems there's a problem: it does not activate (even with almost fully charged battery).

Measuring it not connected does not give a relevant reading.
Connecting a 36V rated battery (+ and -, also made out of 10 cells) to it does not activate the charging process (a LED suppose to go active to signal charging state).

Now, there's a 3rd contact in the charger (that was going to be connected to a 3rd contact of the original battery) but I have no idea what that connector suppose to do. My guess it's a reference or something signaling the charger that a battery is connected so it starts charging.

What else could I try ? Where that 3rd contact suppose to go to activate the charging process ?

I can add a picture of the charger if it helps.


texts: How to rotate part in Eagle (schematic view) using hotkeys only?

texts:
I'm fairly new to eagle. So far i was unable to figure out how to rotate a part in the schematic editor using keyboard shortcuts only.

I'm using 7.5.0 on Linux


texts: Arduino Project Idea: RFID or Bluetooth or What

texts:
I am planning on creating interactive building blocks that talk to each other and know which block is beside each other. I am using an Arduino Uno SMD Edition to create this project.

My question is: for the communication between blocks, what system should I use? Please keep in mind that the blocks have to know which block is beside it.


texts: I'm trying to design a common-emitter amplifier with a gain of 25. I seem to have gotten the correct gain by guessing with my resistor values. Can anyone tell me how to calculate resistor values and verify that I am indeed getting a gain of magnitude 25?


texts: How to add connection points on layout (ADS)

texts:
As I have shown below I want to connect a resistor between the leftmost edges of CLin3. The way I wanted to do so was to define two ports at the edges. That way hopefully I'd be able to cosimulate the resistor and the rest of the layout in a separate schematic window.

Actually that hope soon turned into a shame as I ran into a warning when I added a pin named Pin 4 to the up joint. The warning keeps saying:

The port setup needed to be corrected: Calibration will not be used
for port "P4" (pin "P4" is not on the edge between a conductive and a
nonconductive region).

I'm actually stuck thinking what caused the warning. Almost no idea what made the warning message and how it can be fixed. I tried a lot of variations but non fixed the problem. Is there another alternative on how to do this?


texts: Split output from portable laptop charger

texts:
I'm looking for a safe way to power two devices from my portable power source which only has one output. The power source is an Intocircuit® Power Castle 26000 mAh External Battery. Which can output 12 V, 16 V or 19 V.

And I want to power a Raspberry Pi 2 - which takes 5 V DC (maximum).

And this LCD, which needs 6.5 V if I am reading the data sheet correctly,

  Power Supply Voltage, VDD, Vss-0.5 6.5 V (1)

I figured it would be best to ask the experts rather than fry my electronics.


texts: PIC datasheet is unclear on clearing framing error

texts:
On the PIC16F1829, FERR reflect the framing error status of the top byte in the two byte serial receive FIFO. Thus, assuming no new bytes arriving with framing errors, two reads of RCREG should always clear FERR.

However, it is possible I'm reading way too much into this Note in the PIC16F1829 datasheet for the USART. The relevant section is 26.1.2.4 on page 287:

  If all receive characters in the receive FIFO have framing errors,
  repeated reads of the RCREG will not clear the FERR bit.

This seems to imply that if both bytes in the FIFO had framing errors, FERR would be stuck forever. This seems a little unlikely to me but, at the same point, the datasheet describes how to force clear FERR by resetting the EUSART.

Does anyone have any clarification? I was going to count if consecutive bytes resulted in a framing error but if I don't have to, that would be nice!


texts: Is it logically explainable that current is lower when torque higher?

texts:
I am modelling a motor with a little simulation script. The principle is:

Input is the traction force needed to be provided by the motor
Output is the current to be provided to the coil of the motor (DC, rotationnal motor)

But with my simulation, I am getting a lower current when the traction force is higher. I think that speaking of energy, it does not make sense.

I don't know yet how to calculate the Voltage needed with the current, so maybe it could explain something?

Thanks in advance for insights

EDIT:
I replace "solenoid" by "coil"
Thank you for the answer in comment, but then I have another question to solve my problem:

What are the numerical relation between Voltage and Speed, and the numerical relation between Current and Torque?


texts: My very basic voltage-controlled amplifier gives an asymmetric waveform?

texts:
I want to build a voltage-controlled amplifier. The Wikipedia pages on voltage-controlled amplifiers and voltage-controlled resistors suggested using the following approach: first I would simply build a voltage amplifier using an opamp and this familiar topology:

I would then replace one of the two resistors with a voltage-controlled resistor to yield a voltage-controlled amplifier. Wikipedia suggested using a JFET, which to me seemed quite reasonable. I thus made the following circuit in LTSpice:

I've attached the LTSpice-file at the bottom.

My problem now is the following: by varying the voltage on the gate of the JFET, I can indeed vary the gain of this circuit. However, when I input a sine-wave with no DC-offset, the circuit outputs a sine wave with more gain in one direction than in the other. In the LTSpice circuit on the picture, for instance, a 200 mVpp input sine gives an output sine going from 750 mV in the positive direction to only -700 mV in the negative direction. Obviously something is wrong here!

I can't quite make out whether it is just an offset or the output is really not a sine wave anymore. My main question would be why is my output waveform asymmetric with respect to the time-axis? but if this circuit is a dumb idea in general I wouldn't mind hearing too.

LTSPice file: http://g2f.nl/002hube


texts: I uploaded my first program to ATmega328p and now i cannot upload anything

texts:
Ok guys, I wanted to make simple electronic device (mostly RGB display) so I bought all the stuff.

I have read like dozens of diffrent tutorials and I managed to connect ATmega328p to breadboard, I burned bootloader to it with my USBasp (internal 8Mhz clock). Everything seemed fine so I upload a Blink sketch from Arduino IDE. It worked great, the LED was powered from Pin13 (same as SCK from USBasp) and it was blinking. So I wanted to try Fading Sketch. But The Led kept blinking.

I was trying to upload ther sketches, empty sketches, burning bootloader, more sketches, more burning, diffrent bootloaders (even external 8Mhz clock), and still...
Always the same error (sck period while bootloader and not in sync from avrdude) - even though each time the IDE says all went fine.

I checked connections twice, can you help me out with this? I am desperate at this point. My old (first) program with blinking LED is on ATmega and I cannot upload anything else.

can someone give me valid boards.txt file to properly configure and burn bootloader?

Thanks in advance!!


texts: A question on sizing a blocking capacitor

texts:
When I was trying to find an answer for an optimum capacitor value for entire DC removal of a signal I encountered the following:

  In general, DC blocking capacitor shall behave like a short at working frequency. Calculate the reactance in ohms of the DC blocking
  capacitor for a minimum value at your working frequency:
      Usually Xc(ohms) = 1/(2×3.14×f×C) shall be less than 2 ohms at working frequency.

If this is true, and lets say I want to completely remove DC of a periodic waveform which has 1kHz fundamental freq.

So if I follow that logic (setting Xc=2 Ohm), C = 1/(2×pi×f×|Xc|) and at 1kHz:

C = 1/(2×pi×1000Hz×2ohm) = 79uF

So I guess I should choose 100 uF

If now my understanding is correct, my question is what should be the upper limit and what would be an example to a bad affect of choosing overlarge cap for DC removal. Say you calculate the blocking cap 100nF but in your circuit you use 100uF. What kind of consequences can that have?

Edit: One of the reason asking this is I always see that decoupling caps around opamps are 100nF. What if I use 100uF instead. I know this is not blocking cap but similar confusion.

Whenever we need a capacitor with capacitance C, what I understand using higher value is not a problem for both decoupling and blocking caps. Is that correct? What determines the upper limits?


texts:
I have a Samsung HM1300 headset and want to emulate the call button signal via a microcontroller.

Here is a pic of the inside of the headset:

(Original)

The gold button is the call button. I see the solder points (the 4 points around the button). Do you think it's plausible to solder other wires to those points? I would like to simulate a button press via an Arduino to the Bluetooth headset by soldering wires to the current button circuitry.

What do you think? If I am not clear on the question, please let me know.


texts: Can you explain the resistors in this PIR circuit?

texts: The circuit is a motion detection alarm circuit, I know what the circuit does but I want to know about the resistors attached (R2 is attached to the transistor for amplifying the output to 5V). Why R1 and R2 are attached? Anything do with the delay? Can you explain to me the relay circuit of npn transistors?


texts: What transistor do I need to drive many LEDs and how should I hook it up?

texts:
I know that a transistor amplifies a signal, but I've never used one. I have this design here and I want to add 15 LEDs connected to each pin, instead of 1.

How I could incorporate a transistor to help me achieve a strong enough current to power the LEDs ?


texts: Can I write a bootloader to Atmega using serial port

texts:
There is a really grand price difference between an empty Atmega328 chip and the one with the Arduino bootloader installed. In my country, this difference is 1:3. This means that uploading bootloader manually would save me a lot of money, while this operation takes about 5 minutes altogether.
I've heard (but not read) about the possibility to make an Arduino upload the bootloader on another Atmega. This has at least 2 disadvantages:

You need to have one Arduino first.
You must turn that arduino into programing device - so you cannot have fun with it.
The process will be hard to control until some advanced techniques are implemented (control leds, start button)

I own a few old PCs with standard real serial port and I also have a USB to serial converter.

Is there any chance to create a little PCB that connects dirrectly to
a PC and would serve to upload the bootloader to the chip?
Is it thinkable for me, to create an application for this in C++?
(I'm a begginer, but I don't give up fast) Or does it already exist?
Could you please provide links to any tutorials concerning this
matter?


texts: Is signal reflection dependent to PCB track length?

texts:
We add a termination resistor at the end of a transmission line in order to prevent its signal from reflecting back. I have deduced from some discussions that the termination resistor is not necessary if the track is short. (for example, this topic).

Have I correctly deduced? Is it a general rule? If so, why does not a signal reflect back in a short track? and how is a short track determined? Is it dependent to the signal frequency?


texts: How is lithography actually used to "print" transistors?

texts:
In one of my classes, we skimmed over lithography, but mostly the optics side of things (the diffraction limit, liquid immersion to increase angle of incidence, etc).

One point that was never covered is how the light actually dopes the silicon, and creating a transistor. I've tried to stumble around on the net but every article is either way over my head, or way too vague.

In short, how does a focused beam of light directed at a compound like silicon lead to a "printed" transistor, for lack of a better term?


texts: Switch at output of operational amplifier

texts:
I'm currently designing an active filter which has to pass an analog signal between two cables (PLC). I'd however like to not let it pass in case the signal is already present (up to a certain amplitude) on the second cable, to avoid harmonic distortions and presence of multiple frequencies.

I was thinking of using a CMOS analog switch (as indicated here for instance Switching op-amp gain resistances - how?) at the output of the OAP which I'll turn on when I need it.

The biggest problem is that: the resistance is highly non-linear (because in the circuit I have I can have down to 2 Ohms of load) and I may have to drive up to 1A (the output amplifier is a power amplifier).

Another solution I though was simply using an inverting amplifier with two feedback resistances: one very small (no transfer) and one equal to the resistance put in front of the inverting input (unit gain).

The bandwidth is about 100kHz. No problems concerning gain, since I already amplify the signal before (using a static gain, or even a programmable gain operational amplifier). The problem is how to connect the output only when I need it. Another potential problem might be the small amplitude of the signal: 2V_RMS (a sine wave at about 100kHz).

Switching has to be relatively fast: less than 1us.

I was even thinking of using static relays but I'm not really sure either. Normal or even reed relays seem to be quite slow and deteriorate with time.

Basically I was looking for a switch with: low R_ON, high R_OFF (>> 1MegaOhm), quite fast, bidirectional (supporting ANALOG signals in sine form of low amplitudes), low THD, and possibly easy to control. If there can be 3,6 or more switches inside a SOIC (or other IC) package it would be very good, since I have very limited space.

I'm hoping to see if there are other (better) solutions available.

EDIT: I though it would not work, but what about using an OAP with a switch to control power supply ? I did a simulation with PSPICE and it seems to work. It only produces a small voltage offset output. This is not a problem since there is a decoupling capacitor in series at the exit, so DC voltage/current doesn't pass through. Could this actually work ?

OAP power off http://img140.imageshack.us/img140/7462/opampturnedoff.png

Relays should be able to take as much as 230V_AC when turned off (open circuit): there is a decoupling capacitor at output, but its impedance is pretty low at 50Hz/60Hz (200kOhm) compared to that of the open relay. I haven't found those with a low ESR yet.


texts: Two 24V switching power supply in one fused switch?

texts:
I have two Meanwell 500w 24v 21A PSU that are going to control different heaters on a 3d printer but I don't know how to connect them in a single IEC C14 fused plug switch. They need to operate independently of each other, just turn on/off by the same switch. I have made a wiring diagram of what I have now and what I'm aiming for, just have to figure how to use the input for PSU 2.
Thanks

edit: I'm asking about connecting the fused switch (1) to the both of the PSU inputs and if its safe?
picture for reference

[![Wiring Diagram][1]][1]

[1]: https://i.stack.imgur.com/eBWol.png


texts: How do I calculate the proper width of a copper trace based on a given gauge (AWG) of wire?

texts: I am designing a PCB which I will etch at home, but I need to know how to convert a wire gauge into the proper corresponding width of a copper track on the PCB.  Is there a standard formula for this?


texts: Transistor as a switch not working as expected

texts:
In the above circuit, the transistor is an NPN 2N2222 model. The RC resistor is actually a very small water pump (which I believe is a DC motor) that uses about 60mA across a 5V potential difference, hence the 85 Ohm resistor to represent it.

My issue is that when I set this up in real life with a Raspberry Pi supplying the 5V and 3.3V from its pins, the motor does not turn on.

Sometimes if I power the base then disconnect and reconnect the power, it briefly turns on.

Wierdly, when I measure the current going through the pump (with  the base pin high), it increases to about 240mA then goes to 0. If I disconnect and reconnect the power this happens again.

I'm quite new to transistors so would be grateful for any help possible. If changes need to be made to my circuit I would be grateful to end up with as simple circuit as possible with as few transistors as possible as well.

Many thanks in advance!


texts: I am trying to create the layout of my design for an 8 bit multiplier accumulator in SoC Cadence encounter tool. After routing the design using wroute command, the tool is generating many shorting and overlapping errors. How can I solve these?


texts: How do I add existing files to a newly created group in Keil u Vision 4

texts:
I have struggled with this problem for hours now. I have created a new group in the project structure called inc. I have some existing header files that initialize the  hardware in a separate folder on disk. I have tried to add these files in the newly created group, but every time I include one of the header files in my main program, the compiler complains that the file can not be found.

I have posted a screenshot of my project structure below.

Below is the error


texts: Is it possible to make a usb charger to power multiple devices?

texts:
I was thinking how nice it would be to have a single wall plug with multiple (4-6) USB ports that would be capable of supplying enough power (at 5v) to charge say an iPad, smartphone, bluetooth headset etc. simultaneously at full capacity. But I haven't been able to find such a thing anywhere.

So I am contemplating making one. I don't have any knowledge of electronics and only a rudimentary knowledge of electrics (I can wire a plug) and would appreciate it if someone could tell me how viable this would be from an electrical/electronic point of view. Assuming it is feasible, I'd also like to know whether the work required to make such a thing could be done by an enthusiastic beginner.

Of course if someone can recommend somewhere I could buy such a device I'd happily buy it instead ;-)


texts:
My verilog module is instantiated in a VHDL top entity. I want to pass integer design-time configurations to the verilog module. These are the initial configurations that should appear at reset.

module abcmod
#(
  parameter  [23:0] VT_PARAM1           = 1280,
  parameter  [7:0]  VT_PARAM2           = 53,
 ..
)
( .. );

reg [31 : 0] params;

always @( posedge Clk )
  begin
    if ( Resetn == 1'b0 )
      params <= {VT_PARAM1,VT_PARAM2}; //Assign default 32-bits
    ..

The above examples compiles with Xilinx ISE 14.4, but does not function. VHDL parameters are not passed to verilog parameters with [L-1:0]. Only parameters with unsized parameter par_name = DEF_VALUE, format works.

So I have to pass integer parameter values, unsized, then verilog should expand them to 24 and 8 before concatenate them. How could I possibly do this?


texts: How to amplify DC Voltage to be used like supply to 2km?

texts:
I want to turn on a device away from the voltage source to 2 kilometers. My device operates at 24VDC or 48VDC / 35W.

I need to know how is it possible to amplify the voltage from 24Vdc to 240Vdc or higher. In this manner the current needed is lower and loss due to resistance too.

I don't know how to specify the characteristics of my current cable.

Is there something to help me to reach this goal?


texts: Braking Methods of Induction Motor in VFD

texts:
As you know, we can stop an induction motor by plugging or regenerative braking. What I'd like to know is that when controlling induction motor with VFD, which braking way VFD uses? It seems to me always VFD stops motor by regenerative braking because plugging may damage motor (also enery is consumed and can't be used again) but I can't be sure.

Is it always regenerative braking? Or depending on ramp-time may it be also plugging?


texts: Does anyone know the part number for the package with marking code "MAAC A65A"?

texts:
It's a 8-pin, MSOP Package component.

Can you provide a datasheet for it?


texts:
I work for a Utility that has several hydro generation facilities.  We have a consulting firm performing a full load rejection transient analysis on the penstocks at one of the facilities. One of the data points they have requested is upon a full load rejection how quickly does the electrical torque drop to zero.

Can the electrical torque be calculated, what is formula and parameters needed?


texts:
Apologies if this is a bit simple, but I'm new to this!

How do I set the speed for a 4060B chip? I want it to trigger every 5 minutes (fairly accurately).

I've looked at the instructions here: http://www.reuk.co.uk/Timer-Circuits-With-4060B.htm
and it looks like I need to trigger on pin 4. However, I don't get how I set the resistors and capacitor.


texts:
Where does the Vth=2.571 come from? I get the resistance is (4+6)4/(10+4)+5.
This is how Hayt's solved example pattern right before would look like if applied here:

simulate this circuit – Schematic created using CircuitLab


texts: How a switching PSU inductor overcomes the problem of saturation current?

texts:
If you open a switching step down converter like the one used in your desktop computer, you will only find that a relatively small torroidal transformer ultimately provide the power to the user.

Sure, the flyback operates at high frequency, which raises the impedance enormously, and there is a whole regulation mechanism, but that's not the point: These PSU can easily provide 7A or much more (15A not unusual). This high current is ultimately provided by the small transformer. Without the magnetic effect, nothing would happen.

My question is: how these transformers can handle such high a current without saturating?


texts: Control LED using usb to parallel converter

texts:
I am using a laptop ( windows 7 and 64 bit)
I bought usb to parallel connector as i want to control the LED's through the data lines of the parallel pin( 25 pins)...
So i am trying indirectly to use a LPT port..
please tell me how to go about..
The code works fine on desktop PC when connected to parallel port..


texts: Why is negative logic usually associated with low-level signal? If negative logic is just one possible way of achieving results, why do textbooks associate negative logic with low-level signal?


texts: How to scale down voltage of the the video signal without affecting input wire impedance

texts:
This is a question stemming from this one where I search for the root cause of AD725 displaying wrong colors. Current step have shown that I must be out of the spec for the input of the chip: my RGB video signal is 1 Vpp (while AD725 accepts max 0.741 Vpp - and that's why CXA1645 shows perfect pic and AD725 may go crazy).

Here's one of the RGB signals, measured on the AD725 pin after decoupling capacitor. There's DC bias of about 3V before the cap.

I can follow the reference circuit in the datasheet on page 12 lower part putting 470 pF caps in series on input and making opamps gain of 0.741 and putting decoupling caps on outputs which are to be connected to AD725. But:

prefer +5V or +12V supply only circuit;
can not find AD8073 or similar opamp available to use;
circuit must not affect input wires as much as possible (they go further to other parts of the board), thus this solution does not look good.

Is there any more suitable circuit to do the task? Dot frequency is 25 MHz (PAL/NTSC). There're 2SC1815 transistors in the video signal conversion circuit in one of the other circuits attached to RGB lines, thus these transistors may do the task.

I am strong in digital stuff, but must improve in analog...


texts: What is a safe max. discharge rate for a 12V lead acid battery?

texts:
I've got a 12V 2.4Ah lead acid battery which I plan to connect a water pump to. I've looked at various pumps, but the one I'm most interested in draws 2.2A.

I'm not so interested in how long the pump can run, as it only will need to run for about 5 - 10 minutes/day. So, I'm assuming the battery is plenty for that. The battery will be charged via solar cell panels.

However, I'm more concerned about the discharge rate. I've read that lead acid battery not should be discharged too quickly, as this might result in overheating the battery (and cause damage to it).

How do I figure out what a safe maximum discharge rate is for a 12V lead acid battery?


texts: Software (or website) to visualize binary sequences

texts:
I am looking to visualize a binary sequence for a tutorial.

For example, I have an oscillating CLK signal. Also there is serial data being inputted on INPUT pin. I want a graphical visualization of this timeinline, exactly like you would see on a logic analyzer.

i.e. to take an image from a previous post of mine:

It doesnt need to be as fancy showing ACK or anything like that. There must be a solution other than writing VHDL code and simulating or actually creating the circuit and capturing the output.


texts: Replacing a DDR2 memory with another that is faster

texts: Are there any known timing issues with directly replacing on board one DDR2 SDRAM with another package and pin compatible DDR2 that is slightly faster?


texts: Is it possible to get accelerometer magnitude value lesser than 1G?

texts:
I'm using lsm9ds1 accelerometer.  I retrieved row data in mg for Y, Y, Z accelerometer axes every 10 ms and calculated the magnitude sqrt(x^2 + y^2 + z^2) but this magnitude is sometimes less than 1g.

How can I get magnitude < 1g? Is that physically possible?

magnitude in mg


texts:
Could someone tell me where my calculation is going wrong?

So I integrate  $$\int_{-1}^1te^{-jn \pi\ t}\ dt$$ and get

$$\frac{e^{-jn \pi\ }}{-jn \pi\ }\text{+}\frac{e^{-jn \pi\ }}{-(jn \pi\ )^2}\text{+}\frac{e^{jn \pi\ }}{-jn \pi\ }\text{ - }\frac{e^{jn \pi\ }}{-(jn \pi\ )^2}$$

which I can get to

$$\frac{e^{jn \pi\ }}{-jn \pi\ }(1-\frac{1}{jn \pi\ })+\frac{e^{-jn \pi\ }}{-jn \pi\ }(1+\frac{1}{jn \pi\ })$$

The simplified answer is

$$\frac{e^{jn \pi\ }+e^{-jn \pi\ }}{-jn \pi\ }$$

I can do some simple simplification but I can't figure out how to get to that final answer


texts: A regular on / off switch AND a momentary one

texts:
I'm building a drill press and I'd like to be able to turn it on with a momentary switch on the handle, but sometimes I need both my hands free while it's running. Ideally, I'd use a "lockable" momentary switch if I could find one, or even build one (ideas welcome) but so far no luck. So what I have now is :

A wall outlet to plug the drill in ;
A regular on/off switch ;
A momentary switch (the - big - PCB type)
A small 3-way toggle switch (to toggle between momentary and on / off, and yes I know it sounds clumsy and somehow counterintuitive) and ;
A mosfet module to connect the switch(es) but I'm not sure they're of the right type / voltage, I use them in my 12V builds, should I use a different module for alternative current?

The only thing left is the diagram... How would I go and wire this ?


texts:
I'm trying to understand how an I2C master module (in Verilog) works.

I've found in Github this module, which seems not too much complex.
https://github.com/manojvishy/I2C_Project/blob/master/i2c_master.v

It has an input called open_drain which always is at high level in its testbench.

I can't figure out for what does it worth.

Any idea?


texts: How to use two antennas with a single Bluetooth module? (BLE repeater)

texts:
I am working on a project that uses small Bluetooth low energy (BLE) beacons to track important items.  However, we have run into a situation where one location will store these items underground in a metal storage container, causing the system to be unable to "see" the beacons inside, and thus thinking they have been lost, stolen, etc.

The idea to fix this is to design a BLE repeater, that sits inside the underground container and picks up the beacons' advertisement packets and then re-advertises them outside the container where the main system can see the signals. (The beacons only advertise once every 10 seconds, so data bandwidth is not an issue.)

The problem is that we would need an antenna inside the container to pick up the advertisements from the beacons, but also an antenna outside the container to retransmit the data.  I'm no RF expert, and just beginning to dip my toes in the BLE world, but is there a way to connect two antennas in such a way to a single BLE module that could either listen/broadcast on both antennas or multiplex between the two?

Or would the best solution be to have two BLE modules, one responsible for scanning for beacons and the other one responsible for retransmitting the advertisements, with a communication link between them on a PCB?

Thank you for any input you can give!


texts: Why do characteristic impedances matter only when traces are longer than half a wavelength?

texts: Why are characteristic impedances of traces not considered when the traces are shorter than half a wavelength? I've had the same issue with light diffraction, which happens when pinholes are smaller than half a wavelength - it sort of makes sense somehow, but I can't "see" it, I don't understand how wavelengths are related to reflections (which I assume are the only reasons why we care about impedance matching). I'm trying to make the ocean wave analogy work but... Well, the fact that I'm asking this says it all.


texts: How long will a CR2032 battery take to exhaust powering two 5mm blue LEDs

texts: I read on the Internet that a typical coin cell battery has an ampere hour of 225mAh. I connected up a CR2032 battery to two blue LEDs and left it switched on expecting it to take approximately 5 and 1/2 hours before the battery was exhausted, but 9 and 1/2 hours later the LEDs are still glowing brightly. How long should it take before the battery is dead? Is there a reliable way to calculate this?