texts: How can i find the source of a high pitched noise

texts:
I have one old power supply, it was dead but i decided to attempt to fix it.
Replacing all bad capacitors made it power on again.
Since i didn't had one 2200uf 10v capacitor i used one 2200uf 25v capacitor but i guess this should be fine.
but then i noticed that terrible whine.
https://www.youtube.com/watch?v=NKsqcYnQ_v4
i'm almost sure that it might be a coil or transformer whining on the second stage of the psu(the stage of the high frequency switching), but is packed in a tiny area it made almost impossible to pinpoint where is this whining part.
I'm sure it isn't a fan because even unplugging the fan the whine continue.
And i can't get a new atx psu because nowadays ATX psu have a strong 12V rail and older ones have a strong 5V rail(for example one Corsair CX600 is a 600W psu but only has 25A rating on the 5V rail, this 'revived' psu has 60A rating)


texts:
I am designing an battery powered instrument with around 20-40Ah 3S li-ion batteries in it along with a 10A 3S(12.6v) external charger.

Due to ease of availability and the current capacity I have used an IEC 60320 connector to charge the battery.

My problem is that the same connector is a standard connector used for AC power usually for PC's and other electronics. I don't want someone to plug in a power cord directly in here because it is directly connected to the battery.

I have looked into over voltage protection using crowbar circuit but it seems it blows the fuse every time,

so is there any smarter way of doing this?

Thanks for your help


texts: Does this solar charger PCB design satisfy the layout requirements of the step down charger?

texts:
I'm implementing the reference design for lead acid batteries for the LT3652 battery charger for solar power IC (see datasheet page 26).
My circuit is identical to the reference design except for the addition of two status LEDs and the removal of temperature compensation.
Solar powerd 3-stage 12v lead-acid fast/float charger

I'm not very familiar with the layout considerations for switched mode supplies and have tried to follow the datasheet suggestions. From page 21:

The LT3652 switch node has rise and fall times that are typically less than 10nS to maximize conversion efficiency. The switch node (Pin SW) trace should be kept as short as possible to minimize high frequency noise. The input capacitor (CIN) should be placed close to the IC to minimize this switching noise. Short, wide traces on these nodes also help to avoid voltage stress from inductive ringing. The BOOST decoupling capacitor should also be in close proximity to the IC to minimize inductive ringing. The SENSE and BAT traces should be routed together, and these and the VFB trace should be kept as short as possible. Shielding these signals from switching noise with a ground plane is recommended.
High current paths and transients should be kept isolated from battery ground, to assure an accurate output voltage reference. Effective grounding can be achieved by considering switched current in the ground plane, and careful component placement and orientation can effectively steer these high currents such that the battery reference does not get corrupted. Figure 11 illustrates an effective grounding scheme using component placement to control ground currents. When the switch is enabled (loop #1), current flows from the input bypass capacitor (CIN) through the switch and inductor to the battery positive terminal. When the switch is disabled (loop #2), the current to the battery positive terminal is provided from ground through the freewheeling Schottky diode (DF). In both cases, these switch currents return to ground via the output bypass capacitor (CBAT).

The datasheet has the following recommended layout:

My design is as follows:
Front side (40 x 31mm)

Rear side (40 x 31mm)

Does this design address the layout considerations raised in the datasheet or am I likely to run into problems? You'll also note that the vias connecting the front and back ground pours are all over the place. Is there any recommendation to reduce the chance of running into trouble?


texts: Find the current flowing in the load of a transmission line?

texts:
My Try:

\$Z_{in}=Z_0*\frac{Z_L+jZ_0tan\beta l}{Z_0+jZ_L tan\beta l}\$
Now
\$\beta l=\frac{2\pi\times37.5\times10^6\times10}{3\times10^8}=\frac{5\pi}{2}\$
so its becomes
\$Z_{in}=\frac{Z_0^2}{Z_L} \$
\$Z_{in}=\frac{200\times200}{100}=400\Omega\$
So for part \$(a)\$
\$I_{i}=\frac{200}{600}=\frac{1}{3}A\$ also \$V_{i}=\frac{400\times200}{600}=\frac{400}{3}\$
Now for part \$(b)\$ from the generator we know the equation for lossless line is \$ I(z)=\frac{-j}{Z_0}sin\beta z V_i+Cos\beta z I_{i}\$
so current at the load, that means at \$\lambda/4\$ distance from the generator will be
\$I=\frac{-j}{200}sin(\frac{5\pi}{2})\times\frac{400}{3}+0\times\frac{1}{3}=\frac{2}{3}\angle-90^{\circ}\$
but for part\$(b)\$ the actual answer is \$\frac{1}{3}\angle-90^{\circ}\$
What is the mistake i am doing can anyone help please?


texts: i' m working in an exercise of integrating between pic16f877a and Matlab GUI. Although spending much time searching, i still have not found out how to display ADC value on a GUI panel. Hope you could help me with this. Thank you so much.


texts: Homemade printing and soldering for small components.. the best way

texts:
Which is the best way to solder small components such as SOIC or QFP44 packaged components to a PCB without using adapters?

And how can I manage to print PCBs with small track distances and widths for those type of packages?


texts: How to debug Cortex M3 with STLink V2 over SWD?

texts:
I have a SAM 32bit cortex 3 board(arduino Due clone) and an STLink V2 mini clone. Supposedly all cortex M3 should be able to be debugged via SWD which the STLink V2 mini clone uses.
What's not at all clear to me is what the process is. In particular I am confused on What software would be used to interface a windows PC with the STLink V2 clone? The provided ST software only targets ST boards.


texts:
My requirement is 3.3V 1A output from 5V (this 5V is derived from DC-DC regulator 24v to 5V 1.5A)

i have chosen NCP5662DS33 LDO , but which is best one to use for this current requiremnt ?
i have already used Dc-Dc for 24V to 5V, if i use one more DC-Dc for 5V to 3.3V the noise emsissions, ripples will effect?


texts: Is it worth to try making peltier based refrigerator?

texts:
I built a box from 5cm thick Styrofoam with outer dimensions 60x55x80cm. I wanted to use it as a fermentation chamber for home brew purposes. The reason why I did not choose regular (some used cheap) refrigerator is I need to have it in a small chamber with floor dimensions of 80x130cm. Also door of that chamber is only 55cm wide. So getting inside some refrigerator would be most likely impossible.

I decided to buy 2 peltier modules - TEC-12715 and attached them to a "hot side heatsink" of dimensions 23x17x4cm and "cold side heatsink" of dimensions 10x17x5cm. I am powering each separately from the dedicated ATX power supply which each can handle 18A max at 12V, so there is a reserve. Hot side is being cooled by 5 fans removed from old cases and atx power supplies. The smaller, cool heatsink is inserted into the top part of the box and sealed. On the cold heatsink there is one 12cm fan.

Unfortunately I can only get max of approx 18 degree Celsius inside (35L barrel with approx 20L of a beer inside + 4x 1.5L bottles with water just as a accumulation of the "cold").
Hot heatsink has most of the time 50 degrees Celsius (I have a temp sensor sticked on it's middle part (near to the peltiers which are also in the middle)). Ambient temperature is now 29 degrees Celsius. So it is a difference of max 11 degrees of Celsius.

Should I consider this to be "normal" when considering inefficiency of peltier modules? Or should I be able to squeeze more cold inside? I read somewhere on the internet the peltier's efficiency is terrible once the hot side is over 40 degrees, but I am not sure if this is true. I planned to do some temp regulation as well, but as I wanted to get closer to 15 degrees Celsius, this does not have the reason now.

Any ideas, suggestions?


texts:
I'm currently doing a home automation project which involves my intercom system being controlled by a NodeMCU. The intercom system runs off 12V AC. As for the actual automation/wiring itself, I think I have that fairly well covered. However, I would love to be able to power the NodeMCU directly from the 12V AC rather than having to bring in an extremely long extension cord just to supply 5V DC.

Whilst I am aware that there are plenty of options available for getting 5V DC from 12V DC, I have been almost completely unsuccessful in finding a simple convertor to do exactly what I intend at a low price.

I would really appreciate it if someone could give me some guidance as to how they may think to overcome this problem.

Thank you in advance for any help.


texts: Help getting the transfer function of a circuit

texts:
I have been trying to get the transfer function of the circuit below for some days now and I eventually get to an expression but I don't believe I am geting the correct expression and here's why (the words "Circuito" translate directly to "circuit"):

Ignore the dotted lines, those are meant to guide the analysis. I have tried to get an expression by using the superposition of the two circuits that the dotted lines enclose. So I would have:

$$
V_{outA}=\bigg(1+\frac{R_{5}}{R_{4}}\bigg)V_{in}
$$
Since its just a mere non inverting configuration of the OpAmp. For the circuit B I would have:
$$
V_{outB}=\bigg(1+\frac{R_{5}}{R_{4}}\bigg)\bigg(\frac{R_{2}}{R_{2}+R_{3}}V_{+5}\bigg)
$$

and the total response at the opamp would then be:
$$
V_{out}=V_{outA}+V_{outB}=\bigg(V_{in}+\frac{R_{2}}{R_{2}+R_{3}}V_{+5}\bigg)\bigg(1+\frac{R_{5}}{R_{4}}\bigg)
$$

Finnaly at the passage through the RC filter it would be:

$$
V_{out}=\bigg(V_{in}+\frac{R_{2}}{R_{2}+R_{3}}V_{+5}\bigg)\bigg(1+\frac{R_{5}}{R_{4}}\bigg)\frac{1}{1+j\omega R_{6}C_{3}}
$$

when left in complex form. To get something to work with I wrote:

$$
|V_{out}|=\bigg|\bigg(V_{in}+\frac{R_{2}}{R_{2}+R_{3}}V_{+5}\bigg)\bigg(1+\frac{R_{5}}{R_{4}}\bigg)\bigg|\frac{1}{\sqrt{1+(2\pi fR_{6}C_{3})^{2}}}
$$

$$
\phi=-\arctan(2\pi fR_{6}C_{3})
$$

However, when I use this expressions, and I fix the values of R1,R2,R4 o 1kOhm, R6 to 12kOhm, C1=1uF, C2=100uF and C3=150nF The values I get for a resistance in the places of the potentiometer are R3=5100Ohm and R5=2500Ohm when Vin is a 0.8V sinusoidal signal and Vout will be a 2.5V sinusoidal signal with a 2.5V offset. But in practice I had to use a 20k potentiometer in R5 and a 10k for R3 so My intuition is that my expression is wrong, and the simulations in multisim also point in that direction. Where is my mistake?

PS: This circuit as appeared in two other questions here in the stack  but I am a bit desperate to get a correct answer and its killing me not knowing where my mistake is.


texts: Alternative for PTC Thermistor NXP KTY83/122 SOD68 1.02kohm

texts:
I am looking for an alternative part to replace an existing thermistor (type: Thermistor NXP KTY83/122 SOD68 1.02kohm). This part appears to be discontinued so that's why i need an alternative.
I will be using it to measure motor temperature (Brushless DC motor), the sensor will be connected to the BLDC motor controller (which is designed to work with this particular thermistor). A max temp. rating of approx 150celcius would be desireable I think.
I am not sure what specs/details to look for when searching for a suitable alternative. Would any PTC with same Resistance @ 25 °C, a somewhat similar Thermal Time Constant, and approximately the same temperature ranges (max and min working temperature) be suitable? I was looking for a number indicating how much the resistance changes per Celcius temperature increase/decrease for a certain thermistor and came accross the "TK" aka "Temperature coefficient" value in the datasheets? Is my assumption correct that this value indicates how much the resistance changes per increase/decrease of temperature?
Datasheet of original part: https://docs.rs-online.com/4af3/0900766b812d0c2e.pdf
Perhaps this is a suitable alternative?:
part name: NXP KTY81/110,112 Thermistor SOD70 1.01kΩ
datasheet: https://docs.rs-online.com/17a2/0900766b812d0c2c.pdf

Similar resistance @25C (1,01kohm compared to 1,02kohm for the original part)
Max working temp=150 Celcius (should be enough for my purposes)
Similar temperature coefficient (0,79 %/K for this part compared to 0,76 %/K for the original part)
Resistance ratios listed in datasheets also look quite similar (although I am not really sure what this means/if it is important)
Thermal time constants are higher at 3/5/30seconds instead of 0,5/1/20seconds (flowing liquid, still liquid, air) but I think that shouldn't be an issue for my applications since I'll be gluing the sensor directly to the aluminum core of the motor (so it should eb comparable to the thermal time constant value for "still liquid") and there shouldn't be any rapid temperature changes in the motor so a delay of approx 3 seconds is acceptable

What approximate inaccuracy in temperature measurement do you think would result from replacement of the original part with the alternative mentioned above (since it has slightly different values), will the inaccuracy be significant? (more than 2 Celsius for example)?
Thank you very much for any input, it is greatly appreciated :)


texts:
I hope this thread is allowed. Based upon my previous topic, which turned out to be the exact opposite of what I needed to accomplish, I have a few questions.

I have a 240W 24V Supply: https://www.us.tdk-lambda.com/ftp/Specs/dpp120-240.pdf

I have a coil with a 750W turn on rating and a 5W hold in rating: http://www.kvc.com.my/EnterpriseChannel/SharedResources/Datasheet/0/?ProductId=1000066755&Filename=SCHNEIDER-LX4-FH024.pdf

The device will also be used for some sensitive equipment, so I want to be safe and not allow too much voltage fluctuation.

50ms (closing time) * 30A= 1.5C (Thanks @DaveTweed)
To be safe, 1.5C/4V= 375,000uF

What voltage rating? I've read to derate 2-3x.. for a .4F 50V cap and above, I'm looking at $1-200 per capacitor. Am I playing it way too safe with these numbers, or is this really what I need?

Ok, so if my above power supply uses a forward folding method of current limiting, do I need to use a resistor/thermistor to ensure the capacitor itself doesn't overdraw my supply after it's emptied? I will probably have at minimum a minute of time for the cap to recharge.

As far as wiring, since there are other items in my circuit, I want the capacitor in parallel with my coil rather than directly off my supply, correct? If I were to need a thermistor/resistor would that be in series with the + side of the coil, prior to the capacitor?


texts: Controlling a 3-pin 12V 3A fan using a Raspberry Pi

texts:
I have a Highfine FFC1212DE 120mm fan that operates at DC 12V 3.0A max and want to control it variably using a RPi. The third pin on the fan is a tach reading, not pwm control.

I'm looking to change the speed of the fan based on temperature input so using a relay isn't a good solution.

What is the best way to do this? Can I use a higher rated digital potentiometer?


texts:
I am looking into a electric vehicle charging system and using a cell that can charge at 1.6 A and a voltage of 4.2 V. Therefore I believe the max power I can expose this cell to while charging is:

P = IV = 1.6 * 4.2 = 6.72 Watts

Would I be correct in thinking that if I were to connect 90 cells in parallel then I could expose this system to:

6.72 * 90 = 605 Watts ?

Would it also be the case that if I connected two of these set of 90 parallel together by a series connection could I expose with system to:

605 * 2 = 1210 Watts ?


texts: Arduino serial communication with printer

texts:
I'm working on a project with an Arduino Mega 2560. I connected the board to a MAX232CPE in order to communicate in serial mode with a thermal printer.
I connected the MAX232 to one of the 3 extra serial ports of the Mega 2560 and did all the required wiring adding capacitors. I did not connect the RTS terminal.
No message seems to be sent to the thermal printer, but the communication works perfectly when trying to send a message to the debugging computer.
The very same computer communicating with the printer works perfectly, opening a serial port and sending some data.
In example, If I send the command PRINT XYZ, the printer will print the message when communicating with the computer, but nothing when communicating with the arduino. the very same message has been successfully read by the computer when connected to the RS232 port of the arduino.
What could the problem be?


texts: How much clearance should you include in through-hole component holes?

texts:
Is there a general rule as to how much clearance you should add to through-hole components' holes to allow them to fit easily?

For example, if I have a component with 1mm pin diameter, what should the diameter of the holes for it's pads be?

Using my calipers on a PCB I have handy, it looks like about 0.1mm is added to some holes, but I don't know if that's "normal" or not.


texts: Operational amplifier circuit, but one of Kirchoff laws doesn't work

texts:
In this circuit i have to obtain all the voltages and intensities assuming the operational amplifiers are ideal, but I'm having trouble.

I've found the voltage on the point right in front of the plus entry of the first opamp (\$v_1=9/23\$V). The voltage at the black dots is 0 for both, the voltage that comes out of the first opamp is \$v_1\$ too, and the voltage that comes out of the second opamp is \$v_2=-63/23\$V.

Easy so far, but when i try to sum the intensities that go from \$v_1\$ to ground (through the 1k\$\Omega\$ and the 3k\$\Omega\$ resistors) and from \$v_2\$ to ground through the 4k\$\Omega\$ resistor, they don't add up to 0, which bugs me and my whole class. Can you help please?


texts: Phase Crossover Frequency at 0 deg or -180 deg

texts: I've learned in school to calculate gain margin by first finding the phase crossover frequency at -180 deg, but sometimes I see people calculate gain margin by finding the phase crossover frequency at 0 deg which doesn't make sense to me. I'm confused as to why that method is used? I can't find any explanations online so any help is appreciated.


texts: How to get NTC resistor's temperature vs resistor curve?

texts: I have a thermistor MF52203 whose rated resistance is 20k. However, the datasheet seems like not providing the temperature vs resistor curve. Without this curve, how can I get the corresponding resistance for a specific temperature, like 40℃？


texts:
Is there any GPS tracker available in which I can set server's location (some IP) to which that device will send notifications (GPS data).

I want to create my own GPS receiver server.


texts: Raise SNR of pulse signal by passive LC filter

texts:
I have a weak pulse signal, rise time 1us, fall time 10us, 0.01 to 200 pulses per second, dead time between pulses is random, along with mostly ‘white’ noise.

The system has two goals of extracting information which is peak pulse amplitude among a noise background.

For the first goal, if I have unlimited budget, I would use a fast ADC, says 40 mega samples per seconds, to digitize the waveform and get the peak amplitude of the raw un-processed signal. Mission accomplished.

For cost limited DIY project, I would like to use either a 'pulse stretcher' (low pas filter of some type), or Op-Amp integrator, to lengthen the pulse width so that it can be digitized by low cost MCU built-in ADC.

I am hoping that the ADC 'area under the curve' of the 'lengthen' signal will be proportional to the peak pulse amplitude of the original signal.

That is, instead of measuring peak amplitude of the raw signal, it is measured 'indirectly'. Test signals can be used to 'per-calibrated' and establish relationship between the 'area under the curve' against peak amplitude of the original raw signal.

For the second goal, first, I would like to measure frequency domain spectrum of the raw signal using DSO as high speed ADC. Then, filter out 'out of band signal' to improve SNR.

Hardware has not yet built but from literature research, signal characteristics are as follow:

Signal is a few times higher than noise.

I want to raise the signal to noise ratio to, says reduce noise to 1 to 5% of signal amplitude.

The filtered signal is then feed to a passive RC or LC low pass filter or active OP-Amp integrator to 'stretch' the pulse width to, says 1ms, so that it can be digitized by build in ADC of MCU at, says, 44k to 192k samples per second (PC sound card rate).

Would appreciate pointers on how to:

Buy a digital oscilloscope (like ‘DIY affordable’ Rigol at 1G samples per second).

What sample rate should I set it to?  What file format to
    save the captured pulse to USB drive.

Use a software spectrum analyzer on PC to find out the frequency
contents of the signal.

There are settings like, fft window size and
    others. How these setting related to the signal to be analyzed? What
    should I set them to?

Apparently, there are many PC software designed to work with PC sound card.

How can I edit the ‘file header’ on says, sampling rate, to ‘fool’ the software that the signal is audio range other than the real sampling rate and signal frequency of a few MHz.

Which software is suitable for DIY, free and/or open source?

Design a passive LC filter to filter out off-band noise. Should I use band pass, low pass or others?

At frequency of around 1.5MHz, is it cheaper and easier to choose passive LC over active OP-Amp filter needing high gain bandwidth product OP-Amp?

For keeping minimum distortion of signal pulse waveform, should I use Butterworth, or other filter type?

What is the ‘suitable range’ of filter order?

Which LC filter design software can create Butterworth and several other configurations, plot curve and is more suitable for DIY, free and/or open source?

Is ‘Resistor shape coil’ or SMD chip coil more suitable for this particular application?

I tried Coilcraft filter designer version 3.4 for 1.5 MHz low pass design of 5th order low pass Elliptic.

Changing SMD coil size, but not inductance value, caused significant change on filter curve. I am surprised to see that, other parameters apart from inductance, have such a strong influence at relatively low frequency of 1.5MHz. Or I missed something?

What is the appropriate load impedance for filter driven by low cost OP-Amp?

Design tools, like this, allow setting of impedance. Presumably, there is no point to use 50 ohms as it would be too heavy to be driven by OP-Amp, right? What impedance should it set it to?
example passive LC filter design tool

Should I use passive RC or LC low pass filter or active OP-Amp integrator for pulse width stretching?

Many thanks in advance


texts:
I am designing a board that will eventually be connected to a front panel with LEDs. In the meantime, I have a set of LEDs mounted on the board itself for debugging and whatnot. To debug this board I will be running it off of a 5v arduino, but my final circuit will be run off of a pic24 at 3.3v.

Here is what my circuit looks like:

During assembly and debugging, D2 will not be connected, so all current will go through D1. R1 is calculated to give 20mA through  D1 at 5V. Once the panel is connected, D2 will be connected and R2 should give 20mA to D2 at 3.3 V.

What will happen to D1 at that point? My intuition says that current will not flow through R1 since it is higher resistance than R2. This is what I want. I definitely don't want to put 5V through after D2 is attached or I may overload it. I could just unsolder R1 and D1 once I am done debugging, but I would rather not.

Is this safe to do? I don't want to plan on this strategy under false assumptions and blow up leds. Is there any safe way, short of replacing R1 when switching, that D1 would still work once D2 is attached, so that it works at 5v or 3.3V?


texts: Drive 8 leds with On/Off and PWM using 8 pots and 1 pwm

texts:
I have 8 leds in a line, and a PIC microcontroller with 8 free digital outputs and one free pwm output.

I need to control the leds in a way that at first they are all on, then the rightmost begins to fade to zero, once it reaches zero it stays off and the seventh begins to fade and so on untill all are off.

Can this be done using only 8 outputs and a PWM?

I thought to power the leds directly with the output, wether they are on or off, and to use the pwm with diodes to PWM the turned off leds. Problem is that with this solution all the off led's turn on by the pwm.. I need only the very last one to be fading.

Can this be done using only very basic components like diodes, and similar?

Thanks


texts:
I have a shielded cable, but the shield is not very efficient because the EM radiation leaked from the cable still interferes with nearby equipment. It is still better than a no shielded counterpart, but still not efficient.

So I am thinking of putting another shield around the cable.The cable is insulated already with a rubber coat at the outside.

I am thinking of wrapping aluminium tape around the rubber coat, all the way from one end to the other end. The cable ends with a metalic connector back-shell.

Would this method decrease the amount of EM radiation from the cable?

I have also read that it's better to keep the insulation layer on, and put the 2nd layer of the shield over the insulation, so there is always a layer of insulation between the 2 shields.

I have read on other forums that the outer shield has to be bonded 360 degree to the back-shell, on both sides, tightly. While the inner shield has to be connected inside to the backshell.

Does this mean that all shields have to be connected to the backshell, and the outermost shield has to be wrapped all around it in 360 degree?

Also is it more efficient to leave a layer of insulation between shields, than to have all shield layers next to one another. Some forums say it's more efficient to have a layer of insulation like air, plastic or the rubber between the shields so that the shield has better reflectivity.

I have drawn an illustration how my cable would look like:

So to recap: currently it has 1 shield and 2 insulation layers protecting the signal wire and the outside. After I'm done I would all another shield around the outside rubber coating, and 1 more insulation layer around the shield. The outside shield would be bonded to the back-end connector, that is metalic.The metalic backend connector is connecting to a chassis, that is grounded properly.


texts: Why hasn't the industry standardized sink/source according to sensor/plc component type?

texts:
I know quite enough to understand how sink/source works when connecting sensors and PLCs, as well as how it works concerning the electronics components and circuit diagrams. What I don't understand is why the manufacturers have the freedom to choose beetween sink/source when producing a sensor or PLC.

Wouldn't it be easier if all the sensors were standardized as sink and all the PLCs  as source, the other way around could work as well.

I am probably missing something regarding this claim so I'd really appreciate if someone could help me understand this matter.


texts: What is the use of CC_to_GND option in starrc extract?

texts:
While doing parasitic extraction using starrc tool, I see there is a switch CC_ti_GND. It combines all the coupling caps and gives the cap with GND.

So my doubt is, in which case would it be useful to convert coupling cap into cap with GND?

I don't understand the usefulness of this switch.

Can anyone throw some light on this?

thanks.


texts:
I am currently using a DAC (mcp4922) and want to send the output voltage (0 to 5V) to 1 of many (14) inputs on an Arduino Mega.

I am currently using some VN2222 fets for switching (because I had them laying around) but would like to get something with a higher density. They are all connected to the DAC output and switched with 14 output pins from an Arduino. I know there is a DIP 20 part with 4 fets on-board, but I would still need 4 of them to get the number of pins.

Does anyone have suggestions on other parts that would do something similar Hopefully a single DIP style case? Note that the switching is done to only one of the inputs at a time and typically for several milliseconds before it is switched to another one, so no high-speed pulsing-timing here.

Thank you!


texts:
I currently have a program that runs at X frequency, with the clock input generated by a slow clock module that divides the default clock via the counter increment method.

However, I wish to be able to switch between 3 frequencies, X, Y and Z using button presses. I have debounced the buttons with a single pulse signal generator module (using d flip flops). How can I go about doing it using rudimentary concepts only (multiplexer, etc)? Also, should the logic be implemented inside the slow clock module or in the main module?

Thank you.

simulate this circuit – Schematic created using CircuitLab


texts: I have a circuit with 2 anti parallel mosfets driven from a gate driver IC. I understand how mosfet gate charging works. A big gulp of current is necessary to switch the mosfet fast. After that gate current is as good as zero(except the leakage current). But when discharging the mosfet i see a current flowing into the source. What is the reason for this? I thought the mosfet would also discharge via the gate( as the mosfet driver IC has a push pull configuration. Can anybody explain me what's going on?


texts: Sensing magnetic pulses from a rowing boat impeller

texts:
I'm a mechanical engineer at uni who has some basic experience in electronics and programming. I'm building a system for my rowing boat to help me with my training. This will give me feedback on a variety of things like speed and rudder position. I'm using an arduino to build the project. I'm having a little trouble finding out what to use for the speed sensor. I have an rowing boat impeller which looks like this:

Basically the flow of the water causes the impeller to turn. Either side contains a magnet so there is effectively two pulses per rotation. The problem I'm having is picking up the pulses of the magnet. I bought a cheap reed switch to test this out and it only picked up when the magnet of the impeller is almost touching the switch. This is not ideal as it the impeller fin holds the impeller about 15-20mm from the hull of the boat. The sensor needs to be also mounted inside the hull therefore you have to factor in the thickness of the boat which is 5-10mm. So overall I need a sensing range of about 30mm. I've read that reed switches can sense up to 40mm effectively and read that the pull in range is to do with sensitivity (the lower the AT the higher the sensitivity.) Now I'm assuming this 40mm includes a strong magnet as the impeller uses a weak magnet I assume this is less. This website is doing the current thing that I want to acheive. They are charging £240 for the sensor. They will not tell me what sensor they are using. They claim they can measure accurately up to 60mm away and have measured up to 200mm on this website: http://www.peachinnovations.com/moreboatsensorfeatures.htm. They are using the same imepeller as me. I guess they are not using a reed switch. So basically my question is what are they using? And if it is a reed switch can you help me find one which would be suitable as I am struggling to know which ones are. Another website also claims they can measure up to 11" here: http://www.nkhome.com/support/troubleshooting/speedcoachgold.html (about a third of the way down)


texts: Sawtooth/ramp waves with fixed amplitude from sine or square clock source?

texts:
I hope someone can help me out!

A bit of background info:
I have created a DDS based signal generator (Using PIC MCU to drive a AD9833 for DDS output). The generator is capable to produce sine, triangle and square waves up to 12.5Mhz. However the output at higher (more than 2 Mhz) frequencies is far from perfect (nowhere near the desired wave forms). Anyway, currently I don't need more than 2MHz.
I have added a 7-th order elliptic filter to smooth the sine output from the DDS. After th? filter I use a Schmitt trigger in order to obtain a rectangular wave forms (I can adjust the duty circle as well). The problem is I don't know how I can create sawtooth/ramp or a triangular wave forms based on the DDS signal as a reference clock source (either rectangular or the filtered sine). My most important requirement is for a sawtooth waveform, with adjustable frequency and a constant amplitude in the frequency range from 1Hz to 2MHz.

My query is:
Is there a cheap, easy for implementation solution, which could generate sawtooth/ramp waveforms (triangle as an extra is welcome too) with linear slope (without aliasing or discretization artifacts), adjustable frequency and fixed amplitude in wide frequency range?

Unfortunately I'm not able to find decent solution to that problem.
The only thing that I have found was a post in a forum:
http://www.eevblog.com/forum/blog/eevblog-483-microcontroller-voltage-inverter-tutorial/msg247080/#msg247080, which suggests usage of 4046 PLL chip, that generates a higher frequency square wave, which tracks the input and a 4024 binary counter, which is then fed into a cheapo r2r DAC consisting only of a resistor ladder. Incorporating that, possibly I could generate arbitrary frequency sawtooth with fixed amplitude. However the frequency range that I could get from 4046 PLL will not cover requirements (this is my opinion based on the formulas given in 4046 datasheet, that specify the frequency range), also there will be staircase artifacts because of the ADC conversion.

It will be best if I could cover the range from 1Hz to 2MHz.

Can anyone recommend something, which could do thе things properly?

Sorry for the long post, I hope that I managed to explain the problem (excuse me for my English, as it's not my native language).

Thanks,
Osvaldo


texts: Main water line TDS measurement grounding

texts:
I am trying to implement a TDS sensor to measure a main water line connected pipe, with circuitry that is powered from the wall.

My TDS circuit is essentially a two electrode conductivity probe with one end having a square wave signal and the other a resistor divider referenced to ground.
When the TDS goes over 1000 ppm NaCl the readings become very different to the battery powered TDS meter I am referencing against. My thought is that as the ppm increases the conductivity of the water also increases, and since the water itself is grounded through the pipes to earth ground that there is an alternate path messing up the measurements.

Has anyone had any experience like this with high TDS inline water measurements? Running on batteries is not an option. I am considering an opto-isolator or transformer but I have not seen anything like this talked about online.


texts: pH measurement in cascaded tanks -- Ground loop

texts:
I am doing a mini waste water plant with cascaded PVC tanks (and PVC fittings) for my university project. Each tank has a mixer (the motor is grounded). I made a pH amplification PCB which works with its own battery then send wirelessly the information to my computer.

I was advised that it could be a ground loop, I trace the supposed path on the graphic. Near 1 unit of pH error in the 2nd tank if I compare with a sample taken in a beaker. The error seems proportional to the water flow.

What could be the best approach to solve the issue? Independent PCB for each pH-meter? ground electrodes like stainless steel faraday cages around electrodes connected both together? Or even connected together and with the negative pole of the battery?


texts:
Can anyone please explain what the purpose of the zener diode is in the circuit shown?  The circuit is taken from Figure 3 in the datasheet for the STN1170, an OBDII interpreter IC.

simulate this circuit – Schematic created using CircuitLab

DLC_RAW is the unfiltered, raw +12V from an OBDII bus (i.e. the car battery voltage, so should be in the order of +12.6V). It is also therefore going to be full of transients etc.

The op amp is a non-inverting buffer followed by a LP filter, and the overall purpose of the circuit seems to be to measure the voltage of the car battery.

I'm not sure what the zener is for.  What would be a suitable value for the zener diode?  And does this not mean that in the event of a large spike coming from the battery (such that the voltage divider output is greater than 3.3V) then the transients will find their way onto the 3.3 supply line?

There is a slightly simpler circuit shown which also achieves the same aim, shown below. I don't know what the zeners do - clamp the voltage to within 0V and 3.3V, perhaps?  I have the same question about whether transients then appear on the 3.3 supply line.

simulate this circuit


texts: Implementing a SN74LS245 Octal Bus Transceivers With 3-State Outputs in Logisim

texts:
I'm testing out different circuit simulator programs and I was able to build the integrated circuit SN74LS245 Octal Bus Transceiver in a program called Digital Works. Here is the datasheet SN74LS245 pdf.

In Digital Works you set up the logic gates that you need, and for the pin I/O in this application it has a tag device in which you can associate that tag as an external pin to the IC. In Digital Works, I'm able to save this circuit and its template as a macro and then be able to include that into another circuit.

Within Digital Works I was able to create an 8 bit bus and connect multiple devices to it using this 74LS245 chip. I can use the ~OE pin which is active low to allow the chip to be either active or inactive to the bus. I can then use the DIR pin to set the direction of the I/O. If DIR is set HIGH or 1 then logic will flow from pins [A1..A8] to pins [B1..B8]. If DIR is set to LOW or 0 then direction flows from [B1..B8] to [A1..A8]. This is the desired and expected behavior of this chip.

I will show some screen shots of the logic implementation and the different simulated states it can be in.

Here is the logic diagram within Digital Works when all of the pins or external connections are defaulted to 0 or LOW input. This is the internal design of the IC macro circuit.

Now I'll show you a series of images in it's different states: I'll only be using 4 pin I/O's for this demonstration. I will have A's bus inputs as 0011 and I'll have B's inputs as 1100 just to show how it only flows in a single direction or doesn't flow at all or disconnects when ~OE is set to HIGH. First here is the truth table of the 4 states:

~OE  | DIR | BUS A - in | BUS B - in | BUS A - out | BUS B - out
 0   |  0  |    0011    |    1100    |    1100     |    1100
 0   |  1  |    0011    |    1100    |    0011     |    0011
 1   |  0  |    0011    |    1100    |    0011     |    1100
 1   |  1  |    0011    |    1100    |    0011     |    1100

 Here are the 4 images of the respective states:

I tried to do the same thing in Logisim but I'm having issues with it's pins for I/O. It seems that Logism is expecting for it to be either an input or an output. However, there is an option to set it to 3 states, but I'm not getting the desired behavior that I am seeing within Digital Works. Can this type of circuit with bi-directional capabilities be simulated within Logisim? If so; how would one do this, what am I missing or over looking?


texts: How to determine whether a system is in resonance with an externally applied voltage - RLC Circuit

texts:
Forgive me if this is the wrong forum. This is a problem in my Differential Equations class involving RLC circuits, but we have not gone over the concepts of these circuits in class. I'm given the following differential equation for the RLC circuit and asked if the system is in resonance with the externally applied voltage.

q'' + 0.2q' + 0.01q = e^(-0.1t)cos(10t)

I've solved this much:

q(t) = c1e^(-0.1t) + c2te^(-0.1t) - .01e^(-0.1t)cos(10t)

Where c1 and c2 are arbitrary constants from integration. From what I think I understand the external voltage is the function of 't' on the right hand side of the original differential equation. After brief research it seems that the resonance of an RLC circuit can be solved using:

Wr = sqrt(1/LC - R^2/(4C^2)

Using L=1, R=.2, 1/C=.01, I get Wr = sqrt(0.009999)

I'm not sure how to relate this to q(t). I apologize I don't have a background in electrical engineering.


texts: Unoccupied SMD and TH pads and noise/interference/capacitance

texts:
Imagine a rather noise sensetive application, My question is if there are unoccopied pads for SMD and through-hole are existing on the board and somehow connected to other components through theire trace lines, what would be the side effects?

I have the following PCB which capacitors or resistors are soldered on it (only one of the footprints will be used). What will be the effect of the unsed pads? (This is to measure capcitance/Inulation Resistance):


texts: How do the collector and emitter terminals of a BJT operate when no power supply is present?

texts:
let's consider an example of transistor amplifier:

Let's consider the case in which power supply is not connected (so between VCC and GND there is an open circuit). What will I read at the output terminal? 0V (i.e. Collector and Emitter are short circuited when the transistor is off) or Undefined Voltage (i.e. Collector and Emitter are separated by an open circuit when the transistor is on)?
I have also the same doubt about MOSFET transistors.
I'd say that, since the material between collector and emitter is a semiconductor, it acts like a "mean" resistor (not open circuit but also not short circuit). So I'd say that without power supply, the output of the amplifier is 0. Is this reasoning correct?


texts:
I am a newbie with these type of applications, but I am trying to see if this idea would work out.

Essentially what I am trying to do is build a large panel 2ft x 20ft that will act as one large light strip. I want to have light dissipating material to spread the light evenly over the entire thing. Behind that I want to use a number of LEDs to provide a low-power and low-heat solution.

Right now I am looking at LEDs in the range of 25-50 lumens. Would this work out to provide more even lighting, or would it be better to use LEDs with higher output?
Would I still need a heatsink? Say I use this 26.8lm LED, each individual LED would consume just 0.2 watts. I would be putting this in a grid with roughly 30 LEDs per 2ft x 2ft tile, but I'm not sure how much energy would be wasted as heat.
Is there an idea material for the panel so that the lighting is most evenly distributed?


texts:
Hey, I came across this Low Volatage Shunt regulator on a Hobby RC forum, I am trying to figure out how the resistor Values are Calculated,

http://www.rcgroups.com/forums/attachment.php?attachmentid=210702

the one shown here, uses a TL431 regulator and a 2N700 transistor connected with Lithium Polymer batteries of value 11.1v or 7.4v, the circuit trips the alarm at a particular voltage in this case it is 9v when an 11.1v battery is used and 6v when a 7.4v battery is used. If anyone can help this would be super awesome thanks


texts: What are those black things on the board?

texts:
I'm a beginner in electronics, and I'm ignorant of many basic things.

Check out these black things on the board:

These are from a keyboard.

I'm disassembling it and I want to connect my own switches to it. All the connections seem to go to these black things. But I have no idea how to connect to them. How can I do that?


texts: What is the universal name for this cable and where can I get PCB connectors for them?

texts:
What is the name for this style cable? I've always known them as nano-cables or micro-cables but I've seen them called sensor-link cables too.

I typically get the cable from here. However, I don't know that this is a standard name for this cable.

Regardless, what I am really after is a source for a PCB mount connector for this style cable. Having the correct name would help my searching.


texts: No grounding system available for oscilloscope, what other options are available?

texts:
Many old buildings/houses in Europe are so old that they were not built with a grounding system. I happen to live in one were this is the case. The problem is that if I want to use an oscilloscope, it picks up mains disturbances up to 1 Vpp due to the absence of grounding.

What options do I have?

My building has a grounding only on some outlets and while I have the option to run a power cable across the building where there is earthing, I'm pretty sure this would lead to further 50 Hz radiated disturbances on the cable, I will test this as it currently is the most viable option.

I don't need to work on hazardous voltages (at worst I'll be working on 24 V DC).

Please do not remind me of why I need grounding (other than for having a decently working oscilloscope). I am aware of that, and I try to be as cautious and safe as possible when dealing with any kind of electrical system.


texts: How can I use/model a custom diode in LTSpice?

texts:
I would like to simulate the behaviour of a zener diode in LTspice. Consider the following schematic

simulate this circuit – Schematic created using CircuitLab

I'm interested in simulating its performance when Vcc changes from the rated value (say 12V), for example when Vcc varies from 11 to 15 V.

Now, I know how to simulate this behaviour in LTspice for a generic diode or even for a particular diode which is available in the model library, but when it comes to using a custom diode, I have no idea on how to specify the diode parameters.

Looking into the documentation I was able to come up with a setup that is the correct one, that is, I can specify a custom diode model but now I'm having problems in understanding where to find all the parameters since the datasheet of my diode of choice does not provide all of them. In the LTspice model shown below I've picked a 4.7 V zener diode that was available just to have a base model to edit (and a 1k resistor just for reference).

The diode I'd like to use is a 3V BZX55C3V0. How can I simulate, as realistically as possible, the behaviour of this diode given the few parameters available in the datasheet?


texts:
I have to solve the task shown on the image below. (The diodes should be ideal with a forward voltage of 0.7V)

I tried solving it but always got the wrong current for D1 and V. First I drew it new like the schematics below.

simulate this circuit – Schematic created using CircuitLab

How do I need to approach such a task? I don't fully understand the -5V source.


texts: Why should a diode be placed parallel to the coil?

texts:
I'm looking at connecting relays,

In the schematic found on this site, the diode is placed in parallel. Why would this be the case? If the diode is there to circumvent large voltage flow back, wouldn't this skip pass the diode and go straight to the arduino?

http://www.ecs.umass.edu/ece/m5/tutorials/relay_tutorial.html


texts: Smallest Voltage that a comparator can detect

texts:
What is the smallest voltage a comparator can detect?
Is it possible to set the reference voltage to a few millivolts, just above the noise margin for using a comparator circuit?


texts: Addressing individual distributed RGB LEDs

texts:
I want to have a set of RGB LEDs and to be able to define the color for each one individually. The LEDs will be in different locations but in the same room. Some solutions I'm considering with wired and wireless approaches:

Each LED has its own Arduino (or similar), all Arduino are connected with I2C, the "main" Arduino sets the color for each
Each LED has its own ESP8266 (or similar), through wifi, the "main" board set the color for each
Use TTGO with color display, instead of LED I can set the color on the display, wifi also.

Is there any simple solution? Are there LED strips where each LED can be addressed independently?


texts: Why do ICs have NC (No Connection or No Function) pins?

texts: In case they have no use to the end users and have no function, why are they given as pins instead of being just closed? Some ICs have even 4-5 NC continuously (in accordance to their pin number).


texts:
I built an attenuator for my guitar amplifier. I took the circuit from here but left out the 4 ohm toggle since my amplifiers all have 8 ohm outputs. Below is a simplified schematic of the circuit (with the L-pad set to 20 dB attenuation):

The 4.7u capacitor is supposed to be a treble bleed. My intuitive understanding is that the capacitor allows the high frequencies to bypass the L-pad while the low frequencies are still attenuated. However, I don't notice any difference with the switch open or closed while playing.
I tried to measure the frequency response of the whole attenuator with a signal generator and a scope. The amplitude of the output signal did not change when toggling the capacitor for any frequency up to 20kHz. However I realise that the signal generator and scope have very different output and input impedance compared to the amplifier and speaker, so I don't really trust these results.
My next idea was to calculate the expected cutoff of the treble bleed, but I am not sure how exactly the high-pass filter equation applies here. My understanding is that the speaker is part of the filter, so
$$
R = \frac{1}{\frac{1}{0.89}+\frac{1}{8}}
$$
$$
f_c = \frac{1}{2\pi\times4.7\text{u}\times R} = 42281
$$
42 kHz is of course too high for audio, so now I am not sure if my analysis is correct.

What is the correct way to analytically determine the treble bleed cutoff frequency?
How can I reliably verify this using the signal generator and scope?


texts: In electronics there are two values 0 and 1, so in edge triggered flip-flops what is the value of voltage at the edge, is it 1 or 0?


texts: Augment battery-run device power with 100mA solar cell?

texts:
I may be running a microcontroller for an extended period of time in a portable manner under battery, but do not want its life to be reduced by a silly load such as an LCD screen (5v + backlight) which may easily be drawn from my solar cell.

It is not enough to run the Microcontroller unfortunately (nor would I trust it, if it is intermittent) however wonder in what scenarios I can use the solar cell's power instead.

The LCD example is simple, I can regulate it and power it, only the data pins touching the Microcontroller, however there may be other components. Can I pair together both battery and that @ regulated 5V? Would it prefer one over the other since the solar cell may be closer if connected near or in between?

It would just be nice to get my money out of the solar cell.


texts: Difference between select lines and control lines in Digital circuits?

texts: I want to know about the conceptual difference, not a specific case.


texts: How to determine which harmonized standards are relevant to achieve CE conformity declaration

texts:
We are aiming to develop our first product to achieve a CE marking. So far i understand that there are a few directives like Low Voltage Directive (LVD), ROHS, EMC, etc, which can be implemented by sticking to harmonized standards (e.g.:EN55022 for the EMC directive). My problem at this point is that there is a ton of harmonized standards (especially concerning the LVD) and I am not sure how to determine which of them is relevant to comply to the directives and achieve CE conformity.

The product is basically a computer system which is used for hardware in the loop simulation and inherited in a 19 inch rack system. It will be supplied from mains, the main power supply will be a purchased part though. There will be more or less hazardous DC rails inside (~100V). Almost everything else inside the 19 inch box was developed in house years ago.

Is it generally the right approach to determine the relevant directives and then looking for the most suitable harmonized standards to fulfill the directives? And if yes how to determine which standards are relevant?


texts:
I am developing an OSD project which also manipulates audio signals.

The aim is to add a 'mux' system, which allows a microcontroller to select between the input audio and an internally generated audio signal as the output. This allows it to add a voice to the signal or transmit data in the right audio channel.

Does anyone have any solutions for this? I would like to avoid something like a 4066 which takes up valuable space. Also, since line level is alternating current, it needs to somehow work well with this.


texts:
In order to prepare for an exam in electro technics I have a specific task:
I have the following measurements of an unknown circuit:

\$(1)\quad U_{2(1)} = 4.28V \quad @ I_{(1)}=0.67A \$

\$(2)\quad U_{2(2)} = 1.38V \quad @ I_{(1)}=4.91A \$

Now I have to calculate the internal resistance.
The formula therefor is either \$ R_i = \dfrac{\Delta U}{\Delta I}\$ or \$R_i = \dfrac{U_s}{I_c}\$

where \$U_s\$ is the source potential and \$I_c\$ the short-circuit current.

I don't want to use the delta formula because I need the other two values in a later task anyway.

How do I calculate the source potential just having the both values?


texts: Can I constantly run motors for an extended periods of time?

texts:
I want to run a small DC Pittman gearhead motor rated at 12VDC continuously for an art piece.

Can the motors withstand running 12-14 hours on a lower than 12v?

The load is very small.


texts: How can I find or build a passive RFID tag with a range of 6ft, as well as an associated reader?

texts:
I am looking to implement a RFID system that uses trilateration to localize a RFID tag.

I have no experience with RFID, and although I have done some basic research, I have no idea where to begin. Can anyone help?


texts:
It's from Sedra. It's about how the offset current messes with the input of an inverter. It's "easily seen", but no so for me. Can anyone explain to my "not easily seen" brain how the output is $$V_{out} = V_{off}(1 + \frac{R_{2}}{R_{1}})\text{?}$$
Thanks a bunch!


texts:
Hopefully this is something not too difficult!

I am trying to get a voltage divider which has a positive and negative rail such as this:

simulate this circuit – Schematic created using CircuitLab

I know with a standard voltage divider the equation for Vo would be (R2/R1+R2)*Vin which is fine.

I know if R1 and R2 are equal, you get half the supply. I know this works with a positive and negative rail also, for example:
V+ = +5V
V- = -5V
R1 = 100R
R2 = 100R

Then I know Vo will be 0V as this is the halfway point.

My question then, is what if the value of R1 or R2 changes? I have done simulations, for example, when I make R2 half the value of R1, my simulation tells me the Vo is -1.67V.
When R2 is a quarter of the value, then Vo is -3V.

Also, If I change the value of R1, then it gives me the same results, but positive, rather than negative.

I have tried to search for an equation to calculate Vo but cannot find one. All the voltage divider calculators online just assume that V- is GND. I have tried to find some way of calculating it by putting the -5 in the equation somewhere but I never get the same result as the simulation.

Does anyone know if there is an equation for this, and of so, what is it? Would be useful for a project idea I have in mind!

I hope I have worded this well enough and have supplied all the appropriate information, if not, please do not hesitate to ask if I have not communicated something properly.


texts: Any DC-powered, low flow-rate, inexpensive water pumps?

texts:
Looking for small water pump, which can pump up water from a container, kept at ground-level to another container, placed 10 feet above ground. It should ideally be DC powered, and be able to transfer about 10 liters/hour.

In my search I've come across, pumps called "Rolling Pumps", and another type called "Dosing Pumps". Searching for "Rolling Pumps" brings up "Peristaltic Pumps" page on Wikipedia. Searching ebay for "Peristaltic Pump", returns "Dosing Pump" results, but not sure if they are similar. Oken Sieko (who make "Rolling Pumps") website shows a twin-diaphragm based approach.

The "aquarium pumps", I believe are all air-pumps, right ? They suck-in and pump-out air, to oxygenate the water. They are not water-pumps, right ? These seem to be fairly inexpensive.

What kind of pumps do the small table-top fountains use ?


texts: Reactive-Voltage (QV) Droop Curve and droop constant of Statcoms

texts:
I have a question about voltage droop curve of statcoms. I read many articles about it but I did not figure out how to calculate it and how to add droop curve in control systems.

My system parameters in simulation:

Statcom:Three Phase Two Level (50 Hz)

Vsupply=400 V(L-L)

Qstatcom=100 kVA in one module.

According to my researches,
The droop constant is added directly to control loop as feedback as shown in below.

But here;

As I understand correctly It depends on Vmax,Vmin of supply and also droop constant can be set any value between 0-10 %. How can I find a right value of it? And what is the differences between these values?

If you give an application example, I will be appriciate it.
Thank you.


texts:
I am building a controller for a snow plow and have run into one small problem with valve operation. The controller uses multiple contacts switched by one handle. In operation the switch closes two contacts, one for the motor relay and the other for a coil on a hydraulic spool valve. When the circuit is turned off, both motor and valve stop at the same time and cause hydraulic slamming.

I would like to keep the valve (coil) on for approximately 2.5ms longer to avoid the slam. Could I use a capacitor? If so, of what rating would it have to be? The circuit is 12 volts and the coil draws 1.7 amps.


texts: How to remove kapton tape from soldered parts in bulk?

texts:
I have PCBs with SMT nuts (SMTSO2060MTJ) which has been assembled onto a PCB - the nut has kapton tape on top to allow easy pickup for assembly.

However, removing the kapton post reflow is proving very time consuming.  We have a few thousand to remove.  Currently, we are using a pointy edge of a needlenose tweezer, and a kind of angled stabbing motion to spear the tape - when this works, it allows perhaps 20 to be removed before needing to remove the tapes from the tweezers.  However, it's not fast.  We have also tried a modified "fishhook" barb but this ripped the kapton and it wouldn't come off in one piece.

How can we do this faster/what's a better method?  I have wondered if we might be able to blow them off with compressed air from the back side but the tape is quite sticky.


texts: finding transconductance for common source amplifier

texts:
I wanted to check the transconductance formula I am using is correct when I am dealing with an amplifier that has a small signal (Vsig) and a DC signal(Vs). The schematic below is a little unclear but lets assume that it has a small signal and a DC signal as input to the gate.

I want to bias the amplifier so that when the amplifier is in the mid band frequency range of small signal input, there is an amplification of 11 V/V. I know that we can find the gain at mid band by treating the coupling and bypass capacitors as short circuits which leads us to the gain equation:
Am =-(Rg/(Rg+Rsig))gm(RD||RL)
When I look for gm online I found many different forms and it kinda confuses me (are some forms of the equation more useful for certain applications?). I decided I would use this form:
gm = Kn(VGS-Vt)
where kn = kn'*(w/L)
and VGS is the DC component of the signal that is being fed into the gate. Is this correct?


texts: For the CAN bus, is it OK to swap CANH and CANL lines?

texts:
Similar to question In a USB cable, is it OK to swap the D+ and D- wires?, is it okay if we interconnect CAN-H and CAN-L lines?

CAN is a differential protocol. Is it that dominant and recessive bits are nothing but voltage differences on these lines?

Information about other differential protocols would also be useful.


texts: Why is the Collector current of a BJT transistor independent of the Collector Base voltage?

texts: Ignoring the modulation of the effective base width, why is the collector current independent of the reverse bias voltage across the Base-Collector P-N junction? On one hand, it is easy to see that KCL must be obeyed, so the Emitter current flowing into the base must exist through the collector; but how is that "obeyed" given the large electric field the carriers roll down when they reach the Base-Collector junction. Surely the electric field in the depletion region accelerates the carriers which by the Drift current equation: , increases the current as E can be very large?


texts: Can I read EEprom in circuit when connected to a SH7055 MCU?

texts:
I am trying to read a microwire 93C66 EEprom which is connected to a Hitachi SH7055 MCU. The device is a complete automotive ECU. I need to be able to do this in circuit.

Currently I get an error when I try to read so I assume I need to hold the MCU in either reset or hardware standby mode.

The Eeprom is connected to the MCU  as follows:

Pin1 - PIN193 PJ15/TI9F

Pin2 - PIN192 PJ14/TI9E

Pin3 - PIN191 PJ13/TI9D

Pin4 - PIN190 PJ12/TI9C

Can I just tie the HSTBY pin to GND or would I have to power the whole board?

Datasheet for the MCU

Datasheet for the Eeprom

What else would I have to do in order to read this EEprom in circuit?


texts: Reason fo use or not use a microcontroller to drive a buck DC/DC regulated converter

texts: Is there some reason not to use a microcontroller ( like ie an Arduino ) to drive with PWM a Mosfet and use an analog input to provide voltage feedback and regulate the output, and maybe another analog input to provide some current sense to add a current limit. Frequency would be around 32Khz. Any suggestion in designing capacitor and inductance? Please note this would be an experimental project, but result will be used as a laboratory power supply, so if it is not suitable for this purpose, I will not continue investigate more.


texts:
Recently I dropped my Bluetooth speaker remote and it stopped working. After testing it with remote control diagnostic tool (one of the cheap component testers from eBay that also decodes remote control signals) I noticed that the remote does not send any IR signals. After testing it with a scope I pinpointed the issue to the IR diode (It was cracked inside). Sadly, there is not much documentation for the device therefore all I have is IC code. After reviewing the datasheet:
https://html.alldatasheet.com/html-pdf/35109/PTC/PT2221-001/211/4/PT2221-001.html
I can confirm that the circuit on page 4 represents the circuit in my remote (current limiting resistor in series with IR diode and BJT. I believe the resistor in my remote is also 1 Ohm this can be changed depending on the replacement diode and its voltage/current characteristic. One thing I am unsure of is the wavelength of the diode. Perhaps someone could advise on what wavelength it would most likely operate at. Thanks.


texts: How to program MCUs and test PCBs in mass production?

texts:
I am working on a PCB which includes an microcontroller (STM32), some sensors and a BLE module. Right now it is still a prototype, only 3 units have been produced.

To program the microcontroller, I am using the programming probe provided by STMicroelectronics (ST-LINK/V2).
To check that the hardware is fine, I send a BLE command to the PCB : the microcontroller verifies that all the sensors are responding and if the test is passed, a green LED is turned on (otherwise a red LED). It is not an exhaustive test procedure but it is convenient for my needs (for example I do not test the red LED nor the values of all the resistors nor the measurements of the sensors).

That works for small quantities, but if the prototyping phase is conclusive it might be produced in large quantites (some thousands), so I will have to change the way the MCU is programmed and the PCB tested. I have never done this before, so I have trouble finding what is expected of me and of the EMS.
Programming
How can the MCUs be mass-programmed ? Let's consider I will not ask STMicroelectronics to deliver the MCUs with my custom firmware (because that solution is "easier"). I suppose I will need to make the programming pins of the MCUs accessible. But can I just send the .bin file to the EMS who will take care of the whole programming procedure ? Do I need to specify the programming procedure ? Or do I need to design another electronical card whose goal will only be to program the MCUs ?
Testing
I do not have any idea how to industrialize a testing procedure. Once again : can the EMS take care of the whole procedure based on my schematics/layout ? Or do I need to design another electronical card ?


texts: Pinning convention for Panasonic P5KS connectors AXK5S24047YG and AXK6S24447YG

texts: I am making KiCAD libraries for this connector pair. What is the standard pin number convention for such connectors ? What is the first pin ? The datasheet by Panasonic does not tell much on pin numbers.


texts: How to make single ended voltage measurements

texts:
I’m in the process of setting up a test rig to automatically measure and test induced PCB voltages. The device I’m using (we’ll call it the meter) makes single ended measurements. The PCB output drives a 24V volt fan via two pins (which I assume are analogous to live / neutral) when not connected to the test rig.

Firstly I’m confused over the concept of single ended measurements (I’ve been working in purely SW for several years now). If I wire the live and measure it relative to the meter’s internal ground surely I could get a zero voltage back as there is not necessarily a completed circuit if the meter’s ground doesn’t correspond to the PCB’s ground?
    A slight aside: I tried an experiment where I wired a single terminal of an AAA battery through a meter to the chassis of my PC and got a zero volt reading. I’m having difficult conceptualising this as I would expect that if V(batt) = 1.5V then V(+ve/earth) - V(-ve/earth) should also be 1.5V. I’ve asked a couple of people this question and been given the not very satisfying answer of “it’s not a completed circuit”. If that is the case would you not expect current to flow from a charged balloon into earth through a wire?

An alternative could be to simultaneously measure both the live and neutral pin relative to the device’s earth and perform a subtraction. However, I want to preserve as many screw terminals on the meter as possible as there are several other voltages that require testing with the rig.

The meter also has screw terminal labelled GRD and SGRD. Can I wire in the fan pin neutral to this terminal and get a single end measurement relative to the PCB’s earth?

Hope someone can give me some clarity here. Electronics is not my primary field so if some of these seem basic concepts good links and also terminology would be useful (although I'm in the process of trawling the net for answers).


texts: Is it possible to determine load on a stepper motor when stopped

texts:
Is there a way that the torque on a stepper motor can be determined without some kind of additional force sensor.

Additional electronics such as current shunts etc would be acceptable.

I would like to use the stepper in a winding mechanism and want to be able to check if the stepper is under load before I swap to freewheeling mode.

As far as I understand I would not be able to tell directly when the stepper motor is stopped directly. However I thought some kind of trick like jogging the stepper backwards and forwards a step and watching the current may be plausible.

Does this sound plausible? Or does anyone have a better idea.

Edit: To clarify I am not that interested in the precise value of the torque, I am more interested in checking that there is no significant torque.


texts: I'm currently trying to fix my headphones with a TRRS jack that I recently purchased. I'm using my multimeter and have figured out that green/blue wires together make up the left audio channel and red/black make up the right audio channel. How would I wire this? It seems that there are two grounds but I don't know which is which. Thank you in advance.


texts: Practicality of driving LEDs with high voltage?

texts:
After watching someone build a fairly wasteful project, I wondered if there was a better way. The LEDs are cheap chinese variety, with a forward voltage of around 34-36V @3A, and they throw off about 10,000 lumens. They used a SMPS, putting out 24V, and a cheap boost converter to get upto 36V. For each of 10 LEDs. I thought that was a pretty crappy way to drive 10 of these, an expensive at that.

The way I would do it, is with one large SMPS at a common and cheap voltage, like 24V, and step up the voltage to 360V and control the leds with current. Is this a practical approach? I see a lot of chips to control LEDs at 350mA, but not a lot for 3A. Are there design limitations I'm not considering? I've done some HV stuff, but it was just a plasma speaker.


texts: Why are the power transmission/distribution systems AC and not DC?

texts:
Is there a good reason why we are not in the process of completely converting our electrical transmission system to DC? The main reason for using AC on the grid (no offense Tesla, I love you man) was to enable transformation to higher voltages in order to drop line losses (\$P=IE=I^2R\$) and if the conductor size remains the same, when \$E\$ is increased in the equation \$E=IR\$ then \$I\$ must necessarily decrease, in turn decreasing losses as the square of \$I\$). But now we have the ability to transform AC (at all thermal, hydro and wind generators) and DC (at solar generators) to any level of DC we desire and transmit, usually to residential or commercial loads which tend to use DC anyway. If need be it can be converted back to AC at industrial loads (motors usually).

In this way many transformers, capacitors, spacing issues, etc. can be eliminated from the electrical grid, increasing efficiencies dramatically, and in turn decreasing emissions and costs.

Am I missing something here?


texts: What's the use of the average voltage in rectifiers?

texts: I've noticed that there is much talking about \$V_{dc}\$ in rectifiers (specifically, the half-wave rectifier) and less focus is given to \$V_{rms}\$. Why is that? I thought the RMS value was the much more important one (because it's the value of the DC signal that delivers the same power within the same time interval), but what use is the average voltage? Why do we even bother to calculate and emphasize that \$V_{dc} = \frac{V_{MAX}}{\pi}\$?


texts: I have done a simple electronic circuit with a bridge rectifier diode and I have observed an issue when I display the output signal. The output signal on some harmonic doesn't reach the 0 point as shown in the capture screen of my oscilloscope. Can any one explain the root cause of this issue? I have used the DF08 bridge rectifier.


texts: Whats the relationship between capacitors' ability to filter high frequencies and i=C dv/dt

texts:
Whats the relationship between capacitors ability to filter out high frequencies and the equation i=C dv/dt?

Thanks


texts: Circuit to switch about 5W of 12V using CMOS logic inputs using N-channel MOSFET?

texts:
I want to switch some 12V landscape light LEDs, totaling about 5 watts, using MOSFETs, with the control signal provided by a digital output line from an Arduino microcontroller running at 5V.

I thought I had some logic level N-Channel MOSFETs lying around, but apparently not.

What I have is several 400N80Z and IRLB8721PBF power MOSFETS. I tried using the 400N80Z in m circuit, but the LEDs don't light fully.

I have a variety of low to medium power NPN and PNP switching transistors on hand (BC33716, PN2222A, and 2N4401 NPNs, various others, plus a few TIP120 NPN power darlingtons.

Clearly logic MOSFETs are the right tool for the job and I need to order some. In the meantime, though, can I rig up a circuit that will fully saturate one of my power MOSFETs with a 5V CMOS logic signal from an Arduino?

I'm a software guy, and only passingly familiar with analog circuits.


texts: Low output impedance vs high output impedance of an amplifier

texts:
I read that a low output impedance is desirable for an amplifier. I am unable to understand why from my analysis of the output side of the common emitter amplifier. So looking at the output of the Common Emitter amplifier below, the output impedance is \$Z_{0}=r_{o}||R_{C}\cong R_{C}\$.

The load and \$R_{C}\$ will be in parallel with respect to the current source.

Let's consider the two extremes:

\$R_{C}=\infty\$ : \$R_{C}\$ branch is open so all the current will be flowing through the load. The load voltage is, \$\beta I_{b}R_{L}\$.

\$R_{C}=0\$ : \$R_{C}\$ branch provides a short for the current source so no current reaches the load. Load voltage is 0.

So what's going on? How come a low output impedance is desirable? Surely, something must be wrong with the way I'm analyzing the circuit!


texts: How do we communicate computers(NETWORK Adapter) using two different data encodings?

texts: For example, one of the computers use NRZ encoding, and the other one use manchester encoding. How should the communication be? Or what would be the result if we used a repeater? Is it possible ?


texts: multiplexer resistance increasing is that means its dying?

texts: I have a multiplexer 16 channels for arduino  suddenly its stop working and when i measured this with multimeter each pin from mux produce 2k ohm, and when i measured this with arduino pin it measure no resistence at all.  is that mean it is dying? or the arduino is dying what is the sign that my mux is broken ?


texts: Logic circuit to limit motor travel based on a sensor 0/1

texts:
I would like to create a very basic 5v logic circuit to control a motor's movement. The control should follow these rules:

Allow the motor to move in one direction until the a current sensor detects that the motor is drawing too much current.
Once the motor is stopped (because it reached the current sensor limit) do not allow the motor to continue moving in that direction, even after the current sensor reports acceptable current limit.
Wait in until a signal arrives that says to drive the motor in the opposite direction. This signal will also reset the opposite direction's sensor limit latch.

I'm using a BA6286 which is a basic H-Gate for 12vdc motors and this works as expected. I'm also using a circuit which correctly detects the over current limit and gives me a logic 1 when the current is at an acceptable level, or a logic 0 when the motor draws too much current.

My question about setting up a latch to store the sensor bit that says you can no longer travel in this direction, and getting this latch to be reset when the motor goes in the other direction.

I would prefer to do this in logic, instead of a full up controller chip.


texts: VHDL: Is there a tool that automatically generates the signals (for use in testbench) and a component instantiation if an entity is given?

texts:
When writing testbenches, it is a routine to take the entity we want to test, replace the entity word with component and put this into the architecture of the tetsbench before begin. Then create signals with the same name as the ports in this design to be tested and then created a component instance where we do the port map and generic map.

It is not a lot of work but gets annoying when it has to be done over and over again, certainly a tool must exist that can generated this text automatically?


texts: Is there truely such a thing as a negative DC voltage (with reference to earth ground)?

texts:
I understand the concept of a negative voltage.  Ground is a reference point and it's easy to get a negative voltage if your ground reference is above earth ground.  Does a differential power supply actually produce a negate voltage (referenced to earth ground) or does it just use a voltage offset from ground as a ground reference.

For example a +-5V power supply can easily be created by using two voltages (+10V, +5V) and GND. If you use +5V as ground, it will make +10V the +5 equivalent. GND will become the -5V equivalent.  The problem with such a circuit is that ground isn't compatible with earth ground.  For example you can't then tie your newly created (+5V offset) ground to earth ground without creating a short circuit.


texts:
Edit: A p-channel mosfet to keep DC boost circuit separated from main circuit until its charged worked like a charm.
I'm trying to build a DC-DC boost converter, controlled by a 200kHz PWM signal generated by a PIC16F887 microcontroller to produce a 10V DC out of a 5V USB port as a part of hobby project.
When I seperately supply my PIC and DC-DC boost circuit, they both work well. But when I try to supply it from same line, this happens. Periodically, the power circuit's inrush current causes a voltage drop, which causes a reset. Then it all starts once again until the next reset.
I just read that on some sources it's called a "hiccup fault," but couldn't find a proper way to deal with it. Any suggestions?
circuit irl
sim circuit
(p.s: The load and output current will also be clocked next. The Zeners are to keep the DC-DC boost from over boosting during no-load situation.)
edit: pictures are inlined on request


texts: VHDL simulation shows 'u' by read the input

texts:
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;

entity TestRun01 is
    Port ( Clk : in  STD_LOGIC;
           Din : in  STD_LOGIC;
           Dout : out  STD_LOGIC_vector(11 downto 0));
end TestRun01;

architecture Behavioral of TestRun01 is

signal regr : std_logic_vector(11 downto 0) :="000000000010";
signal reg  : std_logic;

begin

    process(Clk,reg)

    begin
        if falling_edge(CLK) then

            if Din ='1' then
                reg <='1';
            elsif  Din='0' then
                reg <='0';
            else
                reg <= reg;
            end if;

regr<=regr(10 downto 0) & '0';
regr(0)<=reg;

        end if;

    end process;

    Dout<=regr;

end Behavioral;

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;

ENTITY Test1 IS
END Test1;

ARCHITECTURE behavior OF Test1 IS

    COMPONENT TestRun01
    PORT(
         Clk : IN  std_logic;
         Din : IN  std_logic;
         Dout : OUT  std_logic_vector(11 downto 0)
        );
    END COMPONENT;

   signal Clk : std_logic := '0';
   signal Din : std_logic := '0';

   signal Dout : std_logic_vector(11 downto 0);

   -- Clock period definitions
   constant Clk_period : time := 10 ns;

BEGIN

    -- Instantiate the Unit Under Test (UUT)
   uut: TestRun01 PORT MAP (
          Clk => Clk,
          Din => Din,
          Dout => Dout
        );

   -- Clock process definitions
   Clk_process :process
   begin
        Clk <= '0';
        wait for Clk_period/2;
        Clk <= '1';
        wait for Clk_period/2;
   end process;

   -- Stimulus process
   stim_proc: process
   begin
--      wait for 1 ns;
        Din <= '1';
        wait for Clk_period/2;
        Din <= '0';
        wait for Clk_period/2;
        Din <= '0';
        wait for Clk_period/2;
        Din <= '1';
        wait for Clk_period/2;
   end process;

END;

Why there's a U?
And how can I get rid of it?


texts: Alitum: polygon pour with a fully included round hole

texts:
I need to draw a round hole on a polygon pour.

I've followed this documentation (see video in
"Subtracting Selected Polygon Pours" paragraph). It explains that you must first selected the reference polygon and then all the polygons you want to "remove" from the reference polygon.

My concern is that I can't select the other polygons while they are fully inside the reference polygon. If I click using the shift key. It deselect the reference polygon...

How to do that?

Edit:
I need to remove the highlighted circle from the disk but not the other
copper region:

Starting from this:

to this:


texts: Get 12 volt power supply from Dell Laptop

texts:
Is there any way to get a 12V supply out of my dell inspiron 9400 laptop?
I have an external 2.4Ghz video receiver which I want to power from my laptop without using a separate battery.

Could I just take power out of the charging port?

Obviously if I wanted 5V I could use a USB port as a power source, but I need 12V.


texts: What comes after you have programmed a Bluetooth Low Energy chip with Nordic SDK and are ready for deployment?

texts: I am working on this project with bluetooth low energy and it seems I will have to order the Nordic Semi DK kit for one of their nRF51 series chips.  I am just curious (and an amateur at this), once one has written the program to be compiled and stored in the chip and tested the program with the DK board, you still obviously have the dev board attached to the chip. Once youre ready to manufacture a PCB do you just order the chip itself and load the compiled program in via an input mechanism on one of the chip's inputs or how exactly does that work most of the time?


texts: NUCLEO-STM32L432KC: How to use UART through USB?

texts:
Back with my STM32 adventures(data sheet). This time trying to get UART data through the USB. Essentially I want to be able to print over usb to start printing out variables to further debug code.

I am using the classic NUCLEO-L432KC board and I read somewhere for debug purposes you can print through the USB (ST-LINK) by setting up UART on the PA_2 pin.

What I have tried doing is setting up PA_2 to be a UART_2_TX pin and transmitting a constant decimal number (0x50) then using my mac terminal to 'screen" into the com port of the NUCLEO board. However I am getting this? The UART is working as on the oscilloscope scope I am getting data through. Any idea whats going on?

In terminal using: screen /dev/tty.usbmodem1423 9600

The code:

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  *
&copy; Copyright (c) 2020 STMicroelectronics.
  * All rights reserved.

  *
  * This software component is licensed by ST under BSD 3-Clause license,
  * the "License"; You may not use this file except in compliance with the
  * License. You may obtain a copy of the License at:
  *                        opensource.org/licenses/BSD-3-Clause
  *
  ******************************************************************************
  */
/* USER CODE END Header */

/* Includes ------------------------------------------------------------------*/
#include "main.h"

int main(void)
{
    RCC->APB1ENR1 |= (1<<17); // Enable USART2 Clock
    RCC->AHB2ENR = (1<<0); //Enable GPIOA Clock
    RCC->CCIPR = (1<<2); //Use the System Clock for USART2

    GPIOA->MODER &= ~(1<<4); //Enable Alt Function for PA_2
    GPIOA->AFR[0] = ((1<<10) | (1<<9) | (1<<8)); //Enable USART2_Tx for PA_2

    USART2->CR1 = (1<<3); //Enable Transmitter
    USART2->BRR = 0x1A0; //9600 baudrate
    USART2->CR1 |= (1<<0); //Enable USART2

  while (1)
  {
      USART2->TDR = 0x50; //Put data in the Transmitter reg
      while(((USART2->ISR) & (1<<7)) == 0); //Wait till transmitter reg is empty
  }

}


texts: What is the TDS and Conductivity of Ice from freezer, when, it has turned liquid?

texts:
Condensation of water vapors makes it distilled. I was wondering if the Ice formed inside the freezer top chamber can be used as distilled water. I tried checking the resistance with multi-meter, could not get a better result. Has anyone tried this before? What will be the TDS and Conductivity of such water ?

It is the atmosphere air condensation and not Ice formed inside a tray filled of regular water.

What will be its pH?


texts: I am a newbie at electronics and was hoping I could find some help. I have a coil with a removable iron core, photo for which is given above. I tried to find L1 or the inductance of the coil. I was using the circuit shown in the diagram and a cheap multimeter. I tried applying AC and DC voltage to it. I was wanting to find the voltage drop in R1 so I can use it to find XL or the Inductive reactance, which I would use to find L1. But I am not getting any voltage drop in the resistor across points AB (my multimeter might not be good enough to measure a really . Both in AC and DC. Is it because the coil I am using will have such a high L value that all the voltage is dropping across the coil? Is there anyway of doing this without an oscilloscope, function generator and such tools?


texts: Can you find an analytic expression for the (beta)hfe of a BJT?

texts:
I understand there are two models \$Ic=\beta Ib\$ and \$Ic=I_s exp (\frac{V_{BE}}{Vt})\$ for a bipolar junction transistor.

However (correct me if I am wrong), I have not seen any textbook derivation which actually finds \$\beta\$ as a function of the circuit itself.

Is there some reason for this? I am asking this question because I wanted to know if there could be an expression for this behaviour:

Taken from BC547 datasheet.

In other words, given only \$I_C\$,\$V_{BE}\$,\$I_S\$ (is \$V_{CE}\$ required?) can you work out \$\beta\$ without going out and experimentally finding it?

To begin with (in active region), I think there is a forward biased pn junction between the base and the emitter. Thus it would be a case of finding the diode current (\$I_B\$) for the applied voltage (\$V_{BE}\$)? And then relating this to the \$I_C\$?

Small related question, is the \$I_S\$ in the \$Ic=I_s exp (\frac{V_{BE}}{Vt})\$ stated anywhere in a transistor datasheet?


texts:
I am not a genius in eletronics but I know some information about converting 12v to 5v. There are different devices that can do these stuff like linear or switching converter, and I read that switching converter is the best one.

Now, my problem is to understand what is my relation between device using 5V@300ma from a 12v battery that has the capacity of 100Ah.
How do I calculate the life time of my battery? I am very confused even because I got a very big battery (100Ah) that should run my Raspberry Pi for a while ( hopefully over a month ) but not sure.

I got a  HKU5 5V/5A UBEC from hobbyking that converts from 12v to 5v.


texts: Altium Designer - Drag a component and all traces attached to it

texts: In the PCB editor, I am trying to move a component and also the traces that it is connected to. I tried using the Drag command but the component still becomes disconnected from the traces.


texts:
I am designing a PCB and I will use a 2 dBi antenna like this image. But the point where my radio should connect has a 9 dBi antenna like this picture here.

I know everything will work perfectly, but the question is: this antenna 9 dBi is very expensive and it really will make a difference in the whole set? I say this because I think that to take advantage of all pontencial this antenna I would need to have two identical antennas.

I think my antenna 2dBi (placed on the radio) is that will dictate the maximum distance of communication and not 9dBi antenna. I am very wrong? Would not the same just use two equal 2dBi antennas?


texts:
So I've decided to make a circuit based on this:

I have a few questions. First of all, when the photo-transistor switches off and Q1 switches off, as per the article, what is the voltage going through Q1? Can anyone explain R3 and Q1. I know how it functions generally but as the photo-transistor forms essentially an open circuit with R4, wouldn't there be negative voltage going through R3? If anyone can explain that It'd be much appreciated.

Also, how would I go about choosing resistor values (mainly R1, R3, R4)?


texts: Sizing cables in pulsed power applications

texts: I am looking for rules for sizing cables for short pulses.  For example, if I were to run 2000A DC current for 0.5 seconds in a cable, what size would I need? Sizing as if it were continuous current seems like overkill.  I could calculate the temperature rise for each wire size and then pick one, but how do I determine an acceptable change in temperature?


texts: How to tune GPS Antenna with a PI circuit and spectrum analyzer?

texts:
I am designing a wearable product that uses GPS. In prototypes up to now we have used a patch antenna, and it worked great, however in this revision to cut down on size, we put in a chip antenna, along with a circuit to do antenna tuning.

When I run the GPS I get very consistent results, but they are quite far away from where I actually am. They tend to be about 0.014 degrees south and 0.139 degrees east of where I am.

I have a feeling that antenna tuning is causing the problem. My circuit schematic and layout is below. I believe that I have followed all of the antenna manufacturers guidelines in regards to layout around the antenna.

I do not have / have access to a network analyzer to help me tune the antenna, so my method of tuning will likely be guess and check. (Update: I can afford the low end Rigol spectrum analyzer)

How do you use a Pi circuit and spectrum analyzer to tune an antenna? What values of parts would I need to try and such?

The antenna I am using is: JTI 1575AT43A0040

The chip I am connecting it to is: SIM868

The keepout square around the antenna is 18.8mm x 10.4mm

I am working with standard US GPS frequency.


texts: Measuring AC Voltage from Floating Power Supply

texts:
In the schematic below I'm measuring the scaled-down AC voltage of a floating power source @120VAC (model is FC 205 from Adaptive Power). Both the op-amp (any standard op-amp) and ADC (ADS131E04) are running off Vss=-2.5V and Vdd = 2.5V from an isolated supply.
To address all safety concerns: instead of using a transformer on the AC voltage from the FC 205 to give the ADC and op-amp an isolated signal, I’m feeding the scaled down FC205 voltage in directly while powering the ADC and op amp off an isolated +/-2.5V supply. For communication I’m also using an isolated SPI module. So the isolation factor needed between the AC line and the end user is still there, just not shown in this schematic.
The ADC is missing all connections aside from the one analog input because they are not relevant to this question and have been removed.
My question here is: when measuring the voltage between IN1P and IN1N, does it matter that the Neutral Line from AC Source is not tied to the same ground as the ADC? I need the Neutral line of the AC Source to be separate from the ADC or Op-Amp's Ground Rail for other measurements I need to perform (the rest of that circuit is not relevant and not shown), but want to measure voltage directly without isolation (ADC and OP-Amp are powered off of isolated supplies, so there is no safety hazard).
I'm having a hard time figuring out what the voltage difference between the Neutral Line of the FC 205 and the -2.5V Vss supply would be, and if this could blow the ADC. (so looking for V_Neutral - Vss). Thanks for your help!


texts: Why is the temperature range of industrial and military products so high?

texts:
From Wikipedia the common temperature range for electrical components is:

Commercial: 0 to 70 °C

Industrial: -40 to 85 °C

Military: -55 to 125 °C

I can understand the lower part (-40°C and -55°C) as these temperatures do exist in cold countries like Canada or Russia, or at high altitudes, but the higher part (85°C or 125°C) is a bit confusing for some parts.

Transistors, capacitors, and resistors heating is very understandable, but some ICs have approximately constant low heat generation (like logic gates)

If I am considering a microcontroller or operated in a Sahara deserts at 50 °C ambient ( I don’t know if there is higher temperature on earth) why would I need 125 °C or 85 °C?  The heat built up from power loss inside shouldn’t be 50 °C or 70 °C otherwise the Commercial part would fail immediately in for example, 25 °C environment?
If I live in a moderate climate where the temperatures can only fluctuate in the 0–35 °C range all year around, and designing industrial products for the same country only (no export) could I use commercial grade components (assuming no certification, legislation, and accountability exist and only engineering ethics govern your actions)?


texts: Repairing a PS/2 mini-DIN connection w/o clock pulses

texts:
I have a Fanatec CSR racing wheel with an optional sequential shifter. Since I last used them I lost the stock PS/2 cable and haven't been able to locate it. I bought an off-the-shelf PS/2 cable but found that only the upshifts on the sequential shifter works, not downshifts (up and down need to register).

I had a look inside of the shifter and the circuit is very simple. It has a square ps/2 female as shown on this page. The connections as shown, excuse the artistry

I am very inexperienced in electronics but this is the entirety of this device's circuitry so I would conclude there is no clocking.

Should all work fine by my approximation (and does for upshift). Examination of a female port as in the link shown above details that it connects to one of the NC pins of the mini-DIN format (left black wire in diagram), thus I am coming to the conclusion that the off-the-shelf PS2 replacement cable does not cater a connection for this pin, does that sound rational?

Edit: I have now solved the issue with the shifter in terms of physically managing to make it work. For anyone encountering a similar issue it transpires that if when looking at a diagram like this on a female connector, pins 6 and 5 are downshift and upshift respectively, each having +3.3V when wheel is powered. Grounding either 5 or 6 to pin 4 (ground pin) will cause an upshift/downshift event to register. My purchased cable and a faulty switch were causing the issue for me


texts: Is there a standard way to build a configurable circuit topology mesh using mechanical or solid state relays (or/and other components)?

texts:
Preamble:

The motivation is to build a hybrid analog/digital computer this is reconfigurable (the topology of the opapms, resistors, capacitors, adders are all wired automatically -- without human hand)
For that I need to be able to route/connect analog signals (and loads)
There is no need for high speed switching
Though there is a need for low noise, low cross-talk and low resistance, impedance, capacitance across the connections.
Although I do not know too much about them -- I reckon I could extend how cross-bar switches in the old telephone exchanges worked
Cost is an important factor
Solid state would be preferred over mechanical
Digital FPGAs are not candidates for this soliton as they only deal with digital signal
FPGAs have digital cousins (see this question) -- but they seem to have a very low analog component count -- 2 OpAms, 2 comparators, and seem to suffer from noise and some of the challenges I cited above.

I want to build a configurable circuit topology mesh using mechanical or solid state relays (or/and other components).

What I envision is that I have a set of electrical pins: 1 through N; The pins could be left open; connected to a pin of a component like a capacitor, inductor, OpAmp, Adder, Multiplier, etc.
I have a digital (bus?) that specifies the topology of the circuit by a set of pin short circuit specifications:

A set of pin short circute specifications looks like:

Short pins: 1, 11, 13
Short pins: 22, 12, 43
Short pins: 44, 66, 89

Note the short circuits are intended to create circuit nodes (as in Kirchoff's laws nodes)

I've tried to illustrate this using the diagram below.

Is there a standard way of constructing such a routing mesh?


texts: May immersion cooling cause components to crack?

texts: Just wondering if a component that has Moisture Sensitivity Level greater than 1 may also absorb ethanol or other coolant liquid used for immersion cooling and then crack when its boiling temperature reached. PCBs with its porous structure worry me even more.


texts: Need Help Creating SATA Power Cable for Lenovo C540 AiO

texts:
I need expert help. I have an old Lenovo C540 AiO desktop that I am trying to salvage. This model is prone to a failure in the SATA power cable, at the HDD connector end. I have found video guides on how to create your own power cable using a spare SATA power cable and the mini motherboard connector from the original cable.
https://www.youtube.com/watch?v=ysX7qb2MFMo

Unfortuntely, I cut off the original motherboard connector end before I made note of which black connects to which black end to end.
The guy who made the video told me that matching the black does not matter. This seems correct, but I want to get this right and could use a second opinion.
I have looked at pinouts on the standard SATA end, and the blank are just labeled as "GND" but the 11 pin is labeled as "Staggered spinup/activity". I can find no pinout for the motherboard connector.
I have tried to contact a seller on ebay who has torn into this model before to see if he could confirm the original design, but he has not replied since our original contact.
Can anyone confirm that I can connect either black to either black? I don't really understand why they don't just put them in the same order on both ends to avoid confusion.
Thanks.


texts: How to make sense of a PCB in electrical circuit terms,

texts: How can I 'read' a PCB? An electrical circuit schematic is one thing, but this is a whole nother ballgame to me. Are there any standard ways to go about things when deciphering a printed circuit board in terms of the electrical circuit layout of the electronic components soldered to it? How is this normally done?