texts: How to match Transformer output Impedance for Ultrasonic Cleaning Transducer

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I have a transformer outputting the 240VAC 40kHz. The Transducer is 50W, 4100pF, 10-20 Ohm at resonance, ~40kHz resonance)
The Secondary of the transformer is 12mH.
I am trying to match the impedance of the output to ensure the former load is right and not overloading the switching gear on the primary side.
What would be a good starting point for an L/C or R/L/C to match the impedance to the driver?
Thanks in advance!


texts: Actual Saturation Current Limit & Air Gap Based on Core Datasheet

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I'm estimating actual peak current limit & air gap height based on the actual transformer core parameter in the datasheet. This flyback transformer is designed based on 24V output with 50W rated power. Below is my procedure:

Calculate primary inductance based on minimum frequency 55kHz at minimum input voltage (85V). Based on that, I will get below value

As you can see from above image, the primary inductance, Lp = 280uH. I fixed it as 300uH with 0.307 turns ratio. Based on that, I'll get peak current 2.76A with maximum duty cycle ~45%

Then I calculate the area of product, Ap based on above value using below formula. Based on that, I will get Ap = 5303mm^4

After that, I search PQ core material that have nearest value to my Ap = 5303mm^4. From the datasheet, I choose PQ 26/25 due to the total area is 6000m^4 which is almost near to my Ap value.
From PQ 26/25 datasheet (Part No.: PC95PQ26/25Z-12
), I checked NI limit & air gap specification. From my previous calculation (Lp = 300uH, Nsp = 0.307), I will get Al = 443nH/turns^2. From the curve, when Al = 443nH/turns^2, NI = 90A.turns. See below

Questions:

Based on above, I can conclude that the total peak current for my actual transformer core will be 3.5A (based on NI = 90A.turns) which is slightly higher compared to initial calculation & air gap is 0.2mm. Correct?
From the curve, if primary turn increase, AL value will decrease, NI value will increase, therefore total peak current can be increase. Correct?

Please comment if found any missing/wrong step.

Thanks.


texts: Rh versus MHz/resistance for inductor beads

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In my previous question question I learnt I have to use inductor beads, which is also according to the MIDI specs, see below

They state  1K@100MHz, but if I look e.g. on AliExpress for inductor beads, I only see stats like RH3.5 * 6 * 0.8, see AliExpress.
How can I convert these specs?

(btw, I do not want SMD, I use DIP/normal breadboard style components).

Update:

I found probably something better: R6T 2,5T (or 3T) R6

These are according to a similar looking spec 600 or 800 ohm (of course if the components are similar, but it seems better than RH3.5's).


texts: Alternate way to read Resistance temperature detectors (RTDs) with Microcontroller

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After reading many posts with difficulties reading a Resistive Temperature Detector (RTD) such as a PT-1000, NTC with e.g. an Arduino, I am wondering if a time based approach could be used:

If I take a 1000uF capacitor and charge it via the RTD to a certain voltage (measured by an analog input), this takes time that varies depending on the R value of the RTC. One digital output of the Controller must be used to charge and discharge all connected R-Cs and to let the Controller determine the exact starting time of charging. Once the analog input reaches the threshold of e.g. 90% V+ the time is stopped and R & T could be determined.

The obvious disadvantage is that reading T takes time and limits the
sampling rate, but seems acceptable for most applications.
The obvious advantage is the simplicity of the circuit similar to a voltage divider.

Questions:

Is this idea reasonable at all?
What could be the accuracy of the reading for a PT-1000?
What are the tradeoffs in capacitance vs accuracy.

EDIT: Notes: This solution is intended for Arduino projects and not for a high volume products. The 0..1023 resolution 10 bit A/D converter of Arduino UNO's has a poor resolution for resistive devices with voltage divider yielding about 14 steps for 18 Kelvin. This is a theoretical idea and that is why it is posted here.

Update: Andy pointed out that capacitance change of the circuit could be a problem. I looked up that typically "Capacitance increases less than 5% from 25 ºC to the high temperature limit." If the capacitor is kept at room temperature, the problem could be controlled. Initial calibration due to tolerance of the capacitors could be problematic.


texts: Logisim ROM Output not matching address input

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I'm getting this really weird problem when trying to use the built in ROM chip in Logisim. First off, even though I specified a 16-bit data bit width, the ROM only stores 4 bits per address (isn't this supposed to be 16 per address?).
When I specify an address (input), instead of displaying the output 4 bits, it seems to display some bits in some places and not in others. It's a little hard to describe because each time I switch the address I get a weird output that I don't expect and I can't figure out what methodology the ROM is following for displaying output. Here is one situation in the picture below where the input address is 15, and the output is a 0001000100010001. The address 15 currently stores 1111, and I have no idea where the zeros come from and why the 1's are spaced out like that. I must be misunderstanding something about this. If there are only 4 bits per 15 bit address, how does this work?


texts: eagle cad - defining orientation of footprints of components

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I prepared a PCB layout on Eagle Cad 6.4

Here below is the end version of the PCB

As you can see the the layout is printed as the MCU will be placed from the bottom layer. However, I would like to place the MCU on the top layer and solder the legs on the bottom layer. Could anyone explain me what do I need the change on the layout so that the MCU could be placed on the top layer and foot print of its leg would be on the correct orientation on the bottom layer?

EDIT:
The layout that was printed on the paper


texts: What is the purpose of this NPN transistor in a battery protection circuit?

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I found a circuit using a HY2120 2-cell battery protection IC. The application notes differ from how it has been used in the circuit below and I don't understand why the author has not just directly connected the VSS pin to ground.

What purpose does the sub-circuit in red serve? Has it got something to do with the fact that B- and P- are both connected to GND so the protection wouldn't work if the IC was still connected to P- when the protection triggered?

Circuit in question:

HY2120 application diagram:

Huisman do you mean something like the following flow if P is reversed?


texts: Wireless sensor for location in remote wilderness

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I am using a 150 ft net to try to catch a large fish. I have buoys that I would like to monitor. If something big gets in net, it will form a V. The location is very remote (true wilderness and NO cell signals) and I will be within a mile of the nets.

Is there a system I can use to attach to the buoys to monitor their proximity?  If they get within X feet of each other an alarm would notify me?


texts:
In Verilog if we use

  always@(clock)

we can trigger a module at both rising edge and falling edge. Is there any method to do the same in VHDL.


texts: PIC : Reading and Writing to External Flash M25PE80 using pic18f67k22 controller

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I have PIC18F67K22 controller. I am making data logging system. I am using M25PE80 external flash for storing data.

I am storing session wise data in external flash. Also I am storing start and stop address of every session in PIC internal EEPROM.

So How can I delete individual session to manage all session?

For example: If we have stored six session in flash and we want to delete the 3rd session then all data after the 3rd session is overwrite to 3rd session to last session means all session is moving towards.


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I am using an STM32L053C8 and I am trying to set up an RTC wakeup event, and while I am successful, I can only do it to a max time which is a couple of seconds. I need to put it in standby and wake up days later. At the moment I am using the low speed internal 40KHz as the RTC clock, eventually i will get a 32.768 crystal.

According to Carmine Noviello-Mastering STM32 i should be able to set the wakeup delay for a pretty long time. And while I do know it says using an external clock, using the internal one of a few Khz should still be able to provide a fairly decent delay for testing purposes. I just cannot figure it out. When I chose the 1Hz setting for the wake up clock, that only means it will use the RTC clock (40Khz)/(Asynch_prediv +1 x Synch_prediv+1) = new wake up clock frequency.It calls it 1Hz because it assumes you have set up the calendar to have a 1Hz frequency. Its too bad I can use the calendar as a wake up event.


texts: Calculating the gain of a transistor in VGA

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This paper is from IEEE:

The gain of the first VGA is expressed as \$  A_1 = \frac{gm_1 R_1}{1+gm_1 R_2+\frac{R_2}{ro_1}} \$

However, I thought that since the (DC) current source at the source of M1 is considered open in small signal (AC) analysis, the gain would be: \$  A_1 = \frac{gm_1 R_1}{ro_1+ro_2} \$
The second calculation is however, more confusing:

it shows that \$  A_2 = \frac{gm_3 \times (R_4 // R_5)}{1+ \frac{gm_3 R_3}{2} + \frac{R_3}{2 ro_3}} \$

I would get that if R4 was \$ro_4\$ and the divisor was \$ ro_3 \$ but I really don't understand this. It is clearly true, because it is published by IEEE. Could you walk me through how the gain(s) is calculated?


texts: Center-tap transformer current calculation

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I have a transformer with two secondaries, one is 24 V / 500 mA and the other is 12 V / 200 mA. I want to wire them in series to make a center-tap transformer:

simulate this circuit – Schematic created using CircuitLab
I know the voltage is going to be sum of two winding.
How do I calculate the current?


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I've always found circuits containing LEDs hard to understand, please bear with me. I know most people find it easy, but I'm confused by them so some of my assumptions might not be correct, please correct me if that's the case.

So onto the question: Since LEDs are, after all, diodes, they essentially act as conductors with forward voltage, right? Which is why we need a pull-down resistor to regulate the current that flows through the circuit.

For example, let's say we have an LED with a Vf of 2 V and an operating current of 20 mA. (I think those numbers are reasonable right? Again, if not, please let me know.) And our power supply is a constant 4V. This means we need the resistor to draw 20 mA at 2 V, so it would be a 100 Ω resistor, with 40 mW going through it. That's a tiny power usage, but half of the power supplied is wasted through heat. So in this case, isn't the best case efficiency 50%? Which isn't really efficient in terms of DC power supplies, I would have thought.

So when people refer to LED's high efficiency, are they referring to the fact that the LEDs themselves convert the power they use into light efficiently, or is it considered efficient even after considering the 50% max wall plug efficiency?

Or is it just that I've given an example that happens to be a horrible circuit design that would never be found in production applications?


texts: PWM Communication without external hardware

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I'm working on project related to J1850 bus. to my understanding, it's just a PWM communication, but circuits I found online include some extra hardware (example).

What does circuit actually do? What's the reason I can't just hook bus to Arduino and read/write like regular PWM?


texts: How to force the FS312F (DW01A-G) battery protection IC to automatically enable itself when reaching the overdischarge release voltage or above

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The IC successfully cuts off the battery when the voltage goes below 2.9V (2.4V with DW01-G), but it doesn't reactivate itself when it is reaching its overdischarge release voltage. I would like to add some logic which is monitoring the voltage level of the battery and reactivating the circuitry by enabling the discharge mosfet trhough the chip select pin.
Another problem which would be solved by such a solution is the necessity of plugging in a charger, when connecting a fully charged battery for the first time to the circuitry in order to make it running. You can find a note for this case in the datasheet:

I ended up with the following shematic, where the CS (chip select) pin is pulled to ground by a 3904 NPN transistor as soon as the MAX809S voltage detector (reset/supervisor/monitor) IC is getting triggered - means the reset pin is set to HIGH at 3.2V or above, which is the case with a fully chared battery. This should have the positve effect that the circuitry is directly working without the need of plugging in the charger after inserting a battery for the first time in order to make it running.
Updated due to comments:

Like mentioned in the comments this is not working because U1 and Q1 are controlling the path to BAT- and thus there is no correct voltage measuring possible.
Here is a new try: I replaced the 3904 NPN transistor with a N-Channel Mosfet to reduce the current draw and connected it directly to the Battery, while respecting the battery cell reverse connection protection (Q2):

Any concerns about this new one?

maybe it is still not the right way to do or
maybe I should add some resistors somewhere or
maybe it is still drawing too much current or
maybe it is even dangerous, because this is bypassing some important safety features?


texts: Can I use 12V voltage regulator and a variable 0 to 30V DC power supply to control my 12V DC motor speed?

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I've got a 12V DC motor with:

Output power: 3.4 watts
Rated speed : 170 RPM
Rated current: 0.9A

Currently I have a variable voltage DC power supply which can vary the voltage from the DC power supply from 0 to 30V and an LM7812 voltage regulator.

Can I slow down the motor speed by decreasing the voltage from the DC power supply? I am still unsure what speed is suitable for my motor to rotate in my final year project.

Beside that, there is a lot of things that confuse me and I need some justification.

Some people say if I use the 12V L7912CV voltage regulator in my circuit, the current that passes through the voltage regulator is not high enough to activate my DC motor. This is the link of the data sheet L7912CV.
Some people say if I use a resistor to control my motor speed, the resistor will easily get burned up.
The goal of the DC motor is to rotate a disc which is in direct contact with a flat surface so there is friction between them. So in an ideal case, if I buy a 12V power supply and directly connect to the motor, due to the friction and the load, the rated rotating speed will decrease and is suitable for my project. So in my circuit board do I need to buy any other stuff beside a 12V power supply?


texts: Does anyone have the datasheet for this display?

texts: Does anyone have the datasheet for this display there is no serial number or Ebay link. A student came to me with this 4 digit 7 segment LED, there are 12 pins in one side, and nothing on the other side. Model number is, WP02841MGA.


texts: Need Help Understanding a Circuit (Atari 2600 XTAL Oscillator)

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Above is the image, it's the clock from an Atari 2600 Jr.

I'm new to electronics and all the books I've gone through so far don't cover XTALs. I have no idea why, seems pretty important to electronics. My searching over google/youtube hasn't gotten me any usefully direct answers either.

This particular circuit has a 3.579575Mhz XTAL, 2 PNPs, 7 Resistors, and 2 Capacitors. I'd like to know what's happening at each node and what's happening at CLOCK OUT in terms of the wave form (what's the end oscillating frequency at CLOCK OUT?).

Is there a circuit simulator (open source) that can allow you to input XTALs in a circuit? So far I haven't come across one.


texts: Does increasing voltage increase the torque of a brushless motor?

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1.) I have a brushless motor with testing data at 12V. I want to know if I increase the voltage supply, will this increase the torque?

In my research I keep seeing "current controls torque, and voltage controls speed." But that doesn't seem quite right. Let's say I have a theoretical electrically powered unicycle that is weighted. With a 5V source and 2A, the motor can't move the unicycle. But now I increase the voltage to 10V, and I believe current will also increase by x2 if resistance is constant (V = IR). So now the torque increases and the unicycle can move itself. It that a reasonable sequence of events? Can I say that increasing voltage increases torque?

2.) A similar question: if P = VI = tau*omega, then P/omega = tau, so:

2*(P/omega) = 2*tau, which means increasing power will increase torque, correct? And since P = VI, increasing V will increase P, which will in turn increase torque. Is this accurate at all?


texts: How to determine appropriate lowpass filter for Sigma-Delta modulator?

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My question may be a bit naive, as I don't know this stuff well, but bear with me.

I'm looking a encoding a time-varying signal x(t) into a pulse-stream s(t) with a Sigma-Delta modulator, and producing a reconstruction y(t) from s(t) using a low-pass filter.  What I'm wondering is what method I should use to design/tune this low-pass filter to optimize reconstruction - defined, for example, by sum_over_t((x(t)-y(t))^2).  Is this something with a clear solution, or is it one of those things with a bunch of solutions depending on your requirements/application?


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I'm an electronics hobbist with relatively little experience and I'm playing around with Multisim to try to understand how to manipulate AC waveforms.  Specifically, I would like to control the wave form with a function generator, optoisolator, and a triac.  I'm unable to find an optoisolator in Multisim that has zero crossing, which as I understand it is somewhat important when trying to manipulate the waveform.  Something like the MOC3041 (Output Type - AC, Triac, Zero Cross) is what I've been reading is a fairly standard component used to do this, but it's not listed in Multisim.  Where should I look to find something that will work?

Any help would be much appreciated!


texts: How to implement a boolean function using just NAND or NOR logic Gates

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How to implement function mentioned below  using Nand or Nor gate

Y=x1+ x2 x3+ x4'x5'

Where y is output
and x1,x2,x3,x4,x5 are inputs


texts: How can I use a pulse generator to simulate charge collection in multi-wire, proportional ionization chamber?

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I'm performing tests of the detector's breakout electronics. These are printed circuit boards that will take signals from inside an ionization detector to the rest of the data acquisition apparatus.

The key component of these circuits is a capacitor, upon which charge is collected which induced a voltage across the capacitor. This charge is the result of ionization events inside the detector, and specifically the ionized electrons being collected by wires inside the chamber.

I have a BNC Model BH-1 pulse generator (link) and I have tried hooking it up directly to the circuit boards in question. The output from the boards, viewed on an oscilloscope, is signal-like, and responds to manipulation of the pulse generator dials, as one would expect. But it's heavily warped by the interference of the two involved RC circuits.

The pulse generator doesn't simulate the expected charge collection correctly. I want it to produce a charge buildup on the capacitor as a real event inside the detector would. Perhaps I require additional circuit components to make this work? Or I don't understand the problem myself in full detail? Any help or identification of my points of ignorance would be appreciated.


texts: What is the general mathematical proof that K map and Boolean Algebra are equivalent?

texts: Is there a mathematical proof that shows K map always reduces the Boolean expression into it's minimal form?


texts:
The DUT is a relatively high-power LED driver driven by a SELV high-power +24VDC supply. It'll drive LED voltages up to 55V by specification. So everything is considered safe as far voltages are concerned but the power levels are moderate, about 620W actual, 1.2kW design limitation.

Normally I don't thankfully have to deal with UL. But on this project it's a requirement. UL reps told me I need 13mm clearance on mounting points to a non-insulated "track" for ignition hazard reasons. Apparently surface copper in the earth potential is exempt but that further raises the question whether you then have to have 13mm clearance from earth to any other parts on your PCB.

I haven't previously seen this as a reason for clearance/creepage. Could anyone point out to me where is it actually defined? In the eye-wateringly expensive UL 60950-1? IEC 60950 (or 62368) is a bargain by comparison.

Mounting holes are bolted in this case into sheet metal plate that is in contact with device chassis/earth. A device like this certainly can go up in flames albeit the external PSU and on-board fuses should kick in on a catastrophic failure.

Yes, it'd be nice to question UL guys directly but getting answers from them is a long game.


texts:
I'm not sure if I'm reading this wrong or something, but this is a trace of the DMX packet that's coming from my USB-RS485 module then being converter to UART logic levels for my microcontroller.

There are a few things I don't think are right...

What I assume is the 'break' is only the width of one frame, but by definition in the standard is is more likely to be twice this size or greater.
The 'Mark after break' is huuuuge. From the scope you can see it's about 116 us wide, when it should really only be 8
Lastly, there doesn't seem to be a 'start frame'. When set channel 1 to any value, it goes into the first frame after what I've assumed is the extra long 'Mark after break'

Am I missing something here or misinterpreting the DMX protocol? Right now I'm using Freestyler to drive the RS485 device as an ENTTEC OpenDMX transmitter. Anyone have any ideas? is it a software or set up thing? I also tested a tool called KMTronic DMX device tester, and it's given me the same sort of output.

I've just noticed after looking at the differential RS485 lines (see above picture): It looks like that low at the beginning actually is a frame (maybe the start frame?). I can see the line go from an unknown state to driving high for 4us(Mark-time-between-packets?), drive low for the frame of 44us, then drive high for 8us (typically a stop bit time). After that the line goes to an unknown state again. Really strange and confusing. If that's the case though, then I have nothing that even resembles a 'break'.

Also for those unfamiliar with DMX packet structure: http://www.dmx512-online.com/gifs/dmxpack.gif


texts:
simulate this circuit – Schematic created using CircuitLab

I'm new to electronics and wired a dc motor to a battery and switch. After the battery got really hot, I realized that it was probably a short circuit, but I don't understand why.

the positive wire from the battery and to the motor where connected to one side of the switch, while the negative of both where connected to the other side of the switch.

The motor turned very slowly when the switch was off and quickly when it was on.

Can someone help me understand what's going on or point me to good resources?

Thanks!


texts: What connectors are these and how do I disconnect them?

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I am having difficulty disconnecting two different connector-types and I am hoping someone can help me either specify which type of connectors this is or just simply how to disconnect them.

Thank you so much in advance for any help, se pictures below:


texts: What RF attentuator would be used for the HackRF?

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Background info:

The HackRF is an SDR Radio capable of receiving and transmitting frequencies from 10MHz to 6GHz.

Michael Ossmann, the creator of the HackRF, states in his wiki that:

  The maximum RX power of HackRF One is -5 dBm. Exceeding -5 dBm can
  result in permanent damage!

  In theory, HackRF One can safely accept up to 10 dBm with the
  front-end RX amplifier disabled. However, a simple software or user
  error could enable the amplifier, resulting in permanent damage. It is
  better to use an external attenuator than to risk damage.

My Question:

Is this attenuator a good idea even for normal use?

Does the external attenuator which Michael is talking about attach the antenna's SMA to the HackRF transceiver?

What value external attenuator would be used for -5dBm? (it seems to me that RF attenuators are valued at Watts; not dB)

I appreciate the help!


texts: Rectifier ripple on DC-DC buck converters

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I'm using the LMZ36002 buck converter module, which is a 1 MHz 4.5-60 V 2 A buck module. This means there is already an integrated inductor in the chip package. This device will accept any voltage between ~6V and 60V and regulates it down to my desired 5 V, 1.5 A board supply.
Normally, this device is run on 24 V DC from line power supply. Now I would like to add AC functionality by rectifying and smoothing the input.
My calculations are as following: (efficiency corrections are ignored)

5 V @ 2 A = 10 W
24 VAC * 1.414 = 34 V
10 W @ 34 V = 300 mA

I've simulated a circuit with diodes and one 470 uF capacitor in LTspice.
The load is a 70 ohm resistor. The ripple voltage on the rectified output is quite large, around 6-8V, but well within the buck converter's input range. Since space is an issue in this project, low capacitance like 470 uF would be preferred.

Will this large ripple voltage cause any problems for the DC-DC converter?
Could there be any serious problems, aside from degraded efficiency?


texts: How to write 'a signal should never have certain value before it attains some other value' in SystemVerilog assertion?

texts:
I would like to write the following in SVA (SystemVerilog Assertion) format.

signal a should never be 2 until it attains the value 1

How can we do that?


texts: Driving two motors from one power source

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I have built a little balsa wood buggy for my daughter's teddy, the idea being to drive it with solar panels.
I can get one motor working with this set up no problem, but having problems with two (one in each driving wheel).
I have two solar panels, each of which can drive one motor fine, but I don't know how to get them to work together.
I currently have the solar panels in parallel for increased current, and the motors in series (just because I was - almost certainly wrongly - thinking of LED circuits where you want the same current through both.
In this set up though, the motors run at wildly different speeds, and in anything other than full sun one runs nicely and the other doesn't turn at all.
The teddy won't complain if the motors aren't exactly the same speed, but I do want roughly the same output from both for a given amount of light.
Before I start messing around trying all the different permutations of series/parallel, is there a "correct" way to do this? Would I be better having one panel per motor, not connected together at all?


texts: Connect to "gold plate" connectors of existing PCB

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I got a Bluetooth heating thermostat that I want to modify. The board has an ATmega 169PA, and I identified JTAG and ISP "connectors". They all look like those five round golden plates in the upper right of picture. Their distance is about 2.54 mm (0.1 inch) between each.
Is there a name for those gold plates?
How do you commonly connect a programmer (e.g. bus pirate) to those "plates"? (Preferably without soldering)


texts:
update
Apparently I’m an idiot.  It took me this long (hours) to check the supply voltage of the flip flops, which was at .25 volts from a bad connection.  Rookie mistake.  Hard lesson learnt.

In the absence of registers nearby, i have opted just to use d type flip flops instead.  I have two registers (or flip flops acting as registers) so far.  The flip flops are not connected staright to the clock, since this would mean they reset everyone pulse.  Instead, they are connected to the control logic which sends a high to the clock input of the flip flop, when it wants to save the data.  Register A works exactly as intended, outputting the contents of the d lines onto the q lines On the rising edge of the clock pulse.  Register B however will not store data.  If the clock input is high, it sets the outputs high also and I have no idea why.  When the clock is low, the outputs are low.I thought maybe a bad chip, so I swapped it out but am still having the same problem.  Does anyone know what the problem could be?

Here are the flip flops used

https://www.ti.com/lit/ds/symlink/sn74hc374.pdf


texts: What effect does a logic analyzer probe have on a circuit?

texts:
I have an MCU controlling a LED sign. This sign speaks the HUB75 protocol, which is essentially a large shift register. Being a shift register, this requires a clock signal to be generated, which the MCU appears to do just fine however the sign appears to not interpret it correctly. Annoyingly, connecting a logic analyzer and probe to the offending line causes all glitches to go away, and therefore I ask: what effect does placing a probe onto the signal cause?

I'm using a Saleae Logic 8 with it's built-in probes. The datasheet cites an "input capacitance" of 10pf, however the effect is not replicated with a 10pf cap to ground.

The circuit is running at 3v, but the logic analyzer is powered off of USB, so I'd assume it has 5v -- could this mean there's a pull-up somewhere? I'm running out of ideas, and so I asked here.

EDIT: I've done some more testing and the "fixing" effect (for lack of a better term) occurs even if the analyzer has no power, just ground and the signal itself.


texts:
I am working on a project using two audio transformers for two separate circuits mounted very close to each other on a pcb as shown in the image. With the transformers as mounted, there is a bit of inductive crosstalk, as would be expected.

My question is: ignoring shielding for the moment, is there a particular orientation of the transformers (both cores vertically parallel, each perpendicular to each other) that would improve this? I am able to separate them to some degree, but not more than a few centimeters max.

To get an idea of the field strengths, with one signal active I placed 2 ungrounded scope probes' tips at different distances from the active transformer as a test. I get a higher induced voltage on the coil side (above and below in pic) than on the core side (left and right in pic). The iron core seems to keep the flux from straying as far outside in that orientation. However, I was told that it is was common in old radios to mount power and audio transformers with cores perpendicular to reduce 50/60hz cross-talk, so curious to get some other opinions.

EDIT: A schematic with a better description may help: With music on IN1, and relay on T2 closed, I can hear quiet music at out of T2. When shorting IN2 primary, it reduces the music volume, but still faintly there. Correct me if I'm wrong, but I'm generally getting the impression that audio transformer circuits should not be left open when un-used, unfortunately I haven't been able to find much info about this.


texts: What is edge trigerring and what's need for it?

texts:
I was reading flip-flops and the text-book said that we should edge trigger flip-flops.

I didn't get what is edge triggering and why it is needed. Can anyone explain me ?


texts: LED strip doesn't turn off completely by transistor

texts:
I've made a circuit with a touch switch module turning on/off a LED strip via a transistor, and the whole thing works, but in the "off" state the LED strip still shines a bit.

Touch switch module I'm using:
link to aliexpress
(I've configured it to work in latch mode)

The touch switch module is supposed to have 0V in off state, so the transistor should be in a "closed" state. Why is it allowing some current to flow through emitter-collector?

What can I do to make it turn off completely?

In the "on" state everything is fine, and touch-switching works well.


texts: I'm not an electrical engineer . I would like to know whether a normal DC motor will hold the load when the power is turned off?? Or should I need to install a controller to hold the load at that position if so what kind of controller I need to install . Please help me out??


texts: Simplest way to count quadrature encoder counts

texts:
I need to count the pulses from a high-res quadrature encoder but the prohibitively high frequency means I can't use my main processor.

I looked into the HCTL-2022 IC which does exactly what I need, although the part now appears to be obsolete.

Are there any other chips which would serve as a suitable substitution? Alternatively, how would I implement a circuit to count the pulses?


texts: Accessing odd address memory locations in 8086

texts:
I am a beginner in microprocessors. Apologies if my question is too naive.

The memory section of the 8086 processor is divided into two segments: even and odd to allow the CPU to fetch 16 bits in one clock cycle. When a 16 bit word is to be read from memory at an odd memory address say 125, the CPU first puts 124 on the address bus and gets the contents at location 125 in the higher order byte. In the next clock cycle the CPU puts 126 on the address bus and gets the contents at location 126 in the low order byte. These two bytes are then swapped by the processor because these values entered the CPU in the wrong half of the data bus.

The above operation takes 2 clock cycles. Why can't the CPU simply put the address 125 on the address bus and compute the next address and put the contents of that address ( 126 in this case ) onto the low order byte of the data bus? The low order and the high order byte can be swapped later allowing the processor to fetch a 16 bit value from memory in only 1 clock cycle.


texts: [op amp - Gain current source - current reference]

texts:
I have a question about the formula to consider for calculation of the gain for the electronic bellow.

Thanks for your support.


texts: Can someone double check if my truth table make sense to the problem statement?

texts: Just wanted to double-check. Thanks in advance.


texts: DIY Aux In connection to car stereo JVC KD-G151

texts:
I would like to connect my phone via jack cable (aux in) to my car stereo, which has no aux input (brand: JVC KD-G151). It is a CD player, so i wrote a silent disk to operate the cd player, and tried to figure out the connection points for the input signal.
Here the datasheet logic: (sorry for the shortcomings, I'm just a hobbyst wiht very limited knowledge)

From DSP_DAC  RO and LO signals go on a 1.5V channel (AC or DC i dont know)
Next is the CD low pass filter, the output voltage 4.5V (AC or DC i dont know)
Last is the E.VOLUME block where the input voltage 4.4V (AC or DC i dont know)
I connected the signals after the R595 and R585 resistors, and it works great.
But one problem: first i had to connect the jack to the phone, start the music, and connect the aux to the resistors (i am using a switch now)
In case of other order, it not works, signal not go through to E.VOLUME.

I can measure the 4.4V on E.volume input, so direct connection not sound good to my phone jack(can it damage my phone?)
Does anybody knows, where should i connect it without to damage the input source? Before the CD low pass filter? With capacitor to block the DC voltage? Thanks.
David


texts: Effect of metal on electromagnetic field / Coil performance

texts:
which forms part of a colpits oscillator circuit to determine different types of metal as they pass through the coil at a fixed speed. By analyzing the frequency and amplitude shift as the object passes through the coil I am able to compare these to my known control values and identify the material.

The coil itself is coreless - it is wound on a plastic former without any metallic content.

I am quite new to electro magnetics / coils and fields etc... so have a couple of question that I am helping someone could advise me further on.

1) What would happen if i replaced my plastic former / core with a stainless steel one? What would this do to the field, I am guess it would reduce it but would it also change its shape?

2) What would happen if I introduced a large piece of stainless steel into the proximity of the coil (think mounting bracket etc..) how would this effect the field strength and shape?

Is there a good reference source for this subject?

many thanks in advance!


texts: Is it possible to use a USB Wifi dongle with STM32F429I Discovery board?

texts:
I have been using wifi modules like ESP8266 and EMW3162, but this increases the load of work. I would like to use a usb wifi dongle (because discovery board has extra usb interface).

Is it possible? Do I need some kind of specific driver or a standard driver exists for such peripherals?


texts: Alternatives to LTSpice that are more digitally oriented?

texts:
What other alternatives do we have for circuit simulation?

In particular I would be very interested to find a tool that would allow me to simulate digital components by running C code snippets that are able to generate the output signals and then these signals would be fed into passive component simulator that will do the simulation and feed resulting signals into other digital parts that are simulated in C.

I don't want to have to design mock ups for every digital component out of voltage sources and passive components. I want to just write code to generate the output signals.


texts:
I have found a definition of phase margin of amplifier system from Texas Instruments application report. This definition looks like this:
$$\phi = tan^{-1} (A \beta)$$
where \$ A\$ is amplifiers open-loop gain (aka direct gain) and \$ \beta \$ is feedback return signal ratio - or \$ A \beta \$ known as loop gain. Now, \$ A\beta \$ would typically be a value ranging \$ 1000000 \$ to  \$ 10000 \$ (in  opamp amplifier systems, where open-loop gain is usually around \$ 120 dB \$).

Such values of \$ A\beta \$ inserted into upper definition of phase margin always equals  (approximately) \$ \phi = 90° \$. So, using that equation for definition of phase margin must be definitely wrong, because it is not possible, for amplifier's phase margin to be \$ 90° \$ in all scenarios possible. Unless we would be discussing an example with \$ A\beta < 100 \$, which is very unlikely to happen.

Also, it would seem more logical if phase margin definition equation would
be described as a function, dependent on poles of amplifier or \$s\$, damping factor or \$\zeta\$, frequency or \$\omega\$, etc.

I know how to find phase margin (and gain margin) from already drawn Bode plot, but I cannot solve it, using mathematical ways, not graphical.

Can anyone tell me, if this is the actual formula for calculation of phase margin? Or are there more data needed to solve such case? Would "fully defined" transfer function provide enough data for proper calculation of phase margin?


texts:
I'm sketching out a design for an easily and cheaply built handheld computer based on an ARM microcontroller, and thinking of using a small LCD display.  The display has an LED backlight rated for up to 80mA with a typical \$V_f\$ of 3.2V, though a smaller current will probably be enough.  I want to power it from a couple of AA cells, so some kind of voltage boost is needed.  The microcontroller will be a convenient source of a clock signal, but the I/O pins do not have anything like the required current drive.  So I am thinking of the following circuit, with push-pull drive for the voltage doubler.  A prototype seems to work reasonably well, though the diode losses are significant.

simulate this circuit – Schematic created using CircuitLab
The idea is that when the clock input is low, C1 will charge through D1 and the PNP emitter follower Q2.  When the clock is high, Q1 conducts and lifts the left end of the capacitor to over 2V, and the capacitor can then discharge into the LED (generic type shown).  For the backlight application, no smoothing of the output is needed, and the LED can act as its own rectifier.
I expect the 100kHz signal to be close to 0V low and over 3V high, since the microcontroller (like the display logic) will be on its own power supply, with a 3.3V commercial boost converter module.  Potentially, it will be able to drive the bases of the transistors a little beyond the battery voltage when the clock is high, reducing the voltage loss owing to the \$V_{BE}\$ of Q1.  I've included R1 to prevent the microcontroller from providing significant charging current for C1 through the BE junction of Q1.
Can you suggest a better, simple solution?  Is there an easy addition to the circuit that would permit measuring the average LED current with a microcontroller pin?  Should I just give up and add another IC just to power the backlight?


texts: I recently found an ultrasonic cleaner while clearing out our warehouse. I'd love to use it to remove flux residue from my prototype boards but I don't exactly know what solution I should use with it or how long I should leave a given board in the tank. Can anyone make suggestion regarding the use?


texts: Why doesn't this ring oscillator work in LTspice?

texts:
EDIT_1 :

I replaced 2 capacitors that were 22F instead of 22 μF and updated the images.
I stopped the simulation at t = 19.5μs as you can see on the image below because it is very slow, uses a lot of storage and the voltages values seem to already point to a problem.

I'm trying to learn how a ring oscillator works by simulating it using LTspice. But the various plots don't seem to be correct.
Below are two images showing the schematic and the plots.

I found the original schematic here
Made with LTspice XVII(x64) (17.0.21.0)
Does anyone know what the problem is ?
Thanks


texts: How to increase current while keeping the voltage the same?

texts:
I currently have an Arduino Uno board which has an output of around 5V @ 900mA.

Is it possible to bump up the current to around 3-4A while keeping the voltage the same? Maybe with a transistor, but I am new to this and don't know if such a transistor exists.


texts: How to properly set HIGH/LOW PORTC3 on ATmega32A?

texts:
This simple program for ATmega32A is expected to work in this way:

Set PORTC 0,1,2,3 as Output pins
Set PORTC 4, 5, 6, 7 as Input pins with pull ups
Turn on/off output pins 0, 1, 3:
3a. If input pin PORTC6 is HIGH turn 0, 1, 3 HIGH (5V)
3b. If input pin PORTC6 is LOW turn 0, 1, 3 LOW (0V)

#define __DELAY_BACKWARD_COMPATIBLE__

#ifndef F_CPU
#define F_CPU 1000000UL    /* 1 MHz clock speed */
#endif

#include <avr/io.h>
#include <util/delay.h>

int
main(void) {
    DDRC = 0x0F;    /* 00001111, set lower nibble of PORTC to OUTPUT, upper nibble to INPUT */
    PORTC = 0xFC;   /* set HIGH PORTC.3 and PORTC.2 00001100, Low PORTC.1 PORTC.0 and set pull-ups on all INPUT pins */

    while(1) {
        if (PINC & (1 << PC6)) { /* lets assume a 4V supply comes to PORTC.6 and Vcc = 5V */
            PORTC |= (1 << PC3);       /* 00001011 but don't touch PORT PC2 - it stays HIGH */
            PORTC |= (1 << PC1);       /* 00001011 but don't touch PORT PC2 - it stays HIGH */
            PORTC |= (1 << PC0);       /* 00001011 but don't touch PORT PC2 - it stays HIGH */
            _delay_ms(1000);    /* delay 1s */
        } else {
            PORTC &= ~(1 << PC3);       /* turn off all output pins */
            PORTC &= ~(1 << PC1);       /* turn off all output pins */
            PORTC &= ~(1 << PC0);       /* turn off all output pins */
            _delay_ms(1000);    /* delay 1s */
       }
    }
}

I have built flash image and loaded this into MCU using avr-dude executing below commands:

avr-gcc -g -DF_CPU=1000000  -Wall -Os -Werror -Wextra -mmcu=atmega32a -Wa,-ahlmns=main.lst -c -o main.o main.c
avr-gcc -g -DF_CPU=1000000  -Wall -Os -Werror -Wextra -mmcu=atmega32a -o main.elf main.o
chmod a-x main.elf 2>&1
avr-objcopy -j .text -j .data -O ihex main.elf main.flash.hex
avr-objcopy -j .eeprom --set-section-flags=.eeprom="alloc,load" --change-section-lma .eeprom=0 -O ihex main.elf main.eeprom.hex
avr-objcopy: --change-section-lma .eeprom=0x0000000000000000 never used
avrdude -p m32 -cusbasp -B 5 -e -u -U flash:w:main.flash.hex

avrdude: set SCK frequency to 187500 Hz
avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude: Device signature = 0x1e9502
avrdude: erasing chip
avrdude: set SCK frequency to 187500 Hz
avrdude: reading input file "main.flash.hex"
avrdude: input file main.flash.hex auto detected as Intel Hex
avrdude: writing flash (176 bytes):

Writing | ################################################## | 100% 0.19s

avrdude: 176 bytes of flash written
avrdude: verifying flash memory against main.flash.hex:
avrdude: load data flash data from input file main.flash.hex:
avrdude: input file main.flash.hex auto detected as Intel Hex
avrdude: input file main.flash.hex contains 176 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 0.10s

avrdude: verifying ...
avrdude: 176 bytes of flash verified

avrdude done.  Thank you.

PORTC0 and PORTC1 work as expected and described above, when PORTC6 is LOW multimeter indicates voltage close to 0V, when PORTC6 goes HIGH the voltage is 4.92 - 4.98 V. The problem is PORTC3 doesn't work as expected. When it should be LOW multimeter shows 4.77 V

and when it should be HIGH it is 4.21 V (!):

Why it is so? Am I doing something wrong?

[UPDATE]

Just as suggested disabling JTAG by programming fuses to hfuse:w:0xD9:m did the thing. Much better now:


texts:
I know this should probably be posted in a chemistry exchange, but I figured the parts are pretty standard electronics equipment that the question might be more relevant here.

So a couple of breadboards had been lying in a box with a rubbered aligator wire sandwitched between. They've been there for maybe a month untouched. No other chemical or electricity has been present and only ambient heat (hot summer but 30°C tops here in Sweden). I'm pretty shocked that the plastic of these two different styles of breadboards both got so messed up simply by touching this rubber:

Should I be concerned? Is either the plastic or the rubber dangerous to me?


texts: Do touchstone (s2p) files for capacitors from include the ESR/ESL, or do I need to add an ideal R/L for simulation?

texts:
Manufacturers like muRata and AVX provide .s2p files for their RF capacitors.
When modeling for simulation in my EDI software, do I need to include the ESR graphed in the datasheet for the frequency we are using as an ideal resistor component, or does the s2p file already embed the ESR (and ESL) in its metrics?
For examle, do I need the C1_ESR and C1_ESL components if I an using an s2p file?

What about capacitor DC-bias derating?  Are touchstone files even capable of understanding the presence of a DC bias?


texts: Will 5V from USB to i/o pins kill my arduino, or my laptop?

texts:
You are in no way responsible for the effects of the advice you may give.

I have a 5V source that I want to signal to my arduino to start some code when the source is on. I don't have the 5V source with me and want to test my code, and I happen to have an old usb cable handy. I think USB gives a fairly consistent 5V. But then again, I haven't taken E&M since 10 years ago in high school and have no idea what I'm talking about. Is 5V over the i/o pins from a USB cable likely to fry the board?

As a test I connected an active buzzer to the usb cable and it buzzed more quietly than it did when connected to the arduino pins. Then it stopped buzzing at all when connected to USB. Then I attached it to the arduino again and it buzzed loudly. Now my laptop is running slowly (but I'm running a numerical simulation in the background, and it could be that it has hit a complicated calculation and the slow performance is due to that) and I wonder if I did damage to my motherboard.

I wont have access to a multimeter until Monday so I'm kind of stuck.


texts:
I am making a small binary counter circuit which will toggle states of an RGB LED as a small design project to practice both design and PCB layout. My design will incorporate two CR2032 batteries in series to provide power to the circuit.

I have calculated that at times (when all three LEDs are on) the current will be at ~20mA.

I have been reading about putting a capacitor in parallel with the batteries very close to them in the circuit to help with some current pulses in the circuit. It seems that there is some controversy about doing this. I was wondering if anyone can advise if this would be a good idea and if so how to select a proper capacitance value.


texts: Prevent NPN Transistor Base-Emitter Current

texts:
I'm making a simple AND gate array out of 2n2222 transistors. Here is one cell:

simulate this circuit – Schematic created using CircuitLab

When Input "A", is disabled, and "B" is still on:

simulate this circuit

current flows from the base to the emitter of the transistor which is still on.

How do I filter out the smaller current when just the base-emitter on B is conducting, so the circuit functions like an AND gate? I've tried using larger resistors, and that solves the problem for a single gate. But the problem still exists when the gates are attached together.

Edit: Placing the LED in front of the AND gate solves the problem for a single gate too. But for an array of gates, this solution doesn't work.


texts: PMSM Rotor Design. Are these terms equivalent?

texts:
I'm working on a project with a PMSM. As I go through the literature I come across the following terms and wanted to make sure that I am getting right which ones are synonyms.

Surface-mounted PM = Non-salient pole rotor = Round Rotor = Cylindrical (in this case Inductances \$L_d\$ and \$L_q\$ are equal)

Interior Mounted PM = Buried PM = Salient pole rotor (in this case \$L_q \neq L_q\$)

Is that right?


texts: How can I make a 1K X 16 ROM chip with eight 256 X 8 ROM chips with an enable input and a decoder?

texts: I came across this, which I'm guessing is correct, but I do not understand the shortcuts made here.  What are the 8's with slashes through them?  Do those represent 8 inputs and 8 outputs?  And can someone explain the bottom part - the D(7:0) and D(15:8)?  Assuming this is correct, that is.


texts: What is the output logic levels of this STM32?

texts:
I am struggling getting my head around the input and output logic levels, mostly the output levels of this STM32 (STM32F446xC/E).
This table shows the output logic levels as dependent on if it is a CMOS, TTL, or something else which I don't know what kind of port. But how do I know if it is a CMOS, TTL or anything other? I can't find that information, only that all GPIOs are TTL and CMOS compliant, which I assume has to do with input rather than output.

What will be the output voltage levels? How do I know if my port is CMOS or TTL and thereby know which row of the table to read?


texts: I'm wondering if there's a way to use an H-bridge like a comparator- That is, if one input is greater voltage than the other, then the attached motor spins one way, and vice versa, and it doesn't spin at all if the input voltages are equal. I know I could do this using separate comparators, but I'm just wondering if there's a simpler way.


texts: In a forward bias diode, why do electrons continue into neighboring holes?

texts: When an electron from the n-type side fills a hole on the p-type side, it fills the valence shell. For reference, consider this video: https://youtu.be/7ukDKVHnac4?t=230. I learned in chemistry that atoms like this. So why do the electrons continue into neighboring holes if they are already part of a filled valence shell? I understand that part of it is from the electric potential of the battery attracting the electrons into neighboring holes. Is that it?


texts: How to design an auto-adjusted equalizer?

texts:
Think that I have a speaker and a microphone. I want to adjust the equalizer automatically depending to the surrounding the system is in with just the speaker and a microphone. How can I do that? Which equipments do I need?

When I say automatically, I meant that I should just click on some pad and then the system should take care the rest.

I am thinking of something like this:

There will be two or more speakers which can also function as microphones.
First, one of the speakers will transmit and other one will listen. Wide range of frequency and amplitude will be transmitted and other one will be listening.
Step 2 will be repeated for vice versa.
Then do some sound-signal processing.
Then equalizer will be adjusted according to gathered data.

I look up on internet for something like this and I could not find something like this. Just a few patent claims.

So I am willing to get into this but I need to be sure of few things.

1- Speakers(also function as microphones) will be still and not allowed to change their positions. So the sound check kinda be done in speakers perspectives. Would this equalizer adjustment still be valuable?

2- If it is valuable, what kind of components do I need?

3- Would it be reasonable to do equalizer-adjustment in real time?


texts: Multiple fingers vs single finger layout (MOSFET transistor)

texts:
Please, provide a summary of advantages and disadvantages of a transistor layout with multiple fingers (MF) vs single finger?

When laying out a MOSFET with a particular width and length, in an EDA tool, one has two options with regards to the shape of the gate:

1) Single stripe (classical case) (one finger);
2) Several stripes (several fingers).

Hypotheses (based on various Internet forums):

1) MF provide more flexibility in layout planning for transistor with high W/L or L/W. In other words, allows making a layout more square-like.

2)  MF allow better matching of transistors, when needed.
For example, if using common-centroid techniques.

3)  MF layout reduces gate resistance (for AC).
If so, can you explain why?

4) MF reduce current density in the gate if there are technology limitations on this.

Can someone with knowledge do a comparison of the two approaches?

Figure 1: One finger.

Figure 2: Two fingers. Two transistors in parallel (widths are summed).

Figure 3: Two fingers. Two transistors in series (lenghts are summed).


texts:
I am still fairly new to CAN bus and working to understand the bus recovery. The MSCAN documentation reads that once a node enters bus-off it "will become error active again after counting 128 occurrences of 11 consecutive
recessive bits on the CAN bus". I am trying to confirm that this is not 128 consecutive occurrences.

I believe that it is not consecutive, since the documentation does not read that way for the 128 occurrences, yet states explicitly for the 11 consecutive recessive bits.

I have also found the following post that states:

  If that were not the case then a node with a defective receiver would try to send, go bus off, then go bus on again and try to send thereby using 100% of the bus. The 128 * 11 makes it possible for 128 other messages to sneak through while this defective node goes through its bus on/off cycle.

Therefore it would seem that it is understood that it is 128 nonconsecutive occurrences of 11 consecutive recessive bits.

Is there further confirmation of this understanding?


texts: 3 leg potentiometer - what's the 3rd leg for?

texts:
In a potentiometer, I often see the 3rd leg connected to ground.

I understand exactly what a potentiometer is physically (a wiper along a log or linear resistance), but I don't understand the benefit of connecting that 3rd leg to ground.


texts: How many external interrupts has attiny85?

texts:
The title is quite self descriptive. I ask this question because I found contradicting information in the atmel web page. I need two external interrupts to control one rotary encoder. One interrupt control pulses from one pin (both rising and falling) and the other iterrupt the same for the other pin. So if I has only 1 it doesn't work for me.

Visiting the product page at atmel I read that it has 6 Ext. Interrupts: http://www.atmel.com/devices/attiny85.aspx
The datasheet I only see int0 references (page 47) , and I don't quite understand the datasheet
http://www.atmel.com/Images/Atmel-2586-AVR-8-bit-Microcontroller-ATtiny25-ATtiny45-ATtiny85_Datasheet.pdf


texts: how does program counter stores the instruction memory when program is loaded?

texts:
it is mentioned in the book computer organization and design by Patterson/Hennessy page 252 that:

  The instruction memory need only provide read access because the
  datapath does not write instructions. Since the instruction memory
  only reads, we treat it as combinational logic: the output at any time
  reflects the contents of the location specified by the address input,
  and no read control signal is needed. (We will need to write the
  instruction memory when we load the program; this is not hard to add,
  and we ignore it for simplicity.)

my question is: how is storing instruction memory when the program is loaded possible?? should we add an enable to PC which activates by operating system and the operating system then writes the address in PC?? or there are other ways??

here is a simple figure of PC and instruction memory


texts:
I need to find a inexpensive replacement stepper motor and I am wondering if all of the specs need to be matched or are there some that don't need to be exact.

Right now they are using a six wire motor, but only four of the wires are in use. The center wire on each side is cut off.

One of the motors is a Astrosyn 23LY-C205-03V

It is a .9 degree motor but if they are only using four wires does that change this spec? Can I get a 1.8 degree four wire?

Do I need to match resistance, voltage, inductance, and current? Or will it still work if they are close but not exact.


texts: Simple circuit Voltage regulator question?

texts:
I am trying to build a simple circuit that takes a 9v battery through a voltage regulator that outputs 1.5v across a load resistor . The load will be just a piece of metal that gets heated up.

My initial understanding of voltage regulators was wrong. I thought I wouldn't be wasting a lot of power using one, but from further reading I have discovered that they are just used for rectifying an ac source and when (vi-vout) is a large number a lot of power is dissipated/wasted as heat in the regulator. I want as much of the power from the battery as possible to be dissipated across the load resistor @ 1.5v.

So, my questions is how can I build this circuit with a 9v input and a 1.5v across load dissipated as heat with the smallest amount of wasted power through a regulator or other components?


texts: V/f Constant control for single phase induction motor?

texts:
I am implementing a Variable frequency Drive control of single phase induction motor. I am little bit confused about the V/f ratio and voltage level.
i boosted voltage upto 380V for Inverter . if i operate the motor at 220 volt with 50 HZ. so the 220/50 = 4.4 . am i  right . otherwise i have to use (1.414*220/50)=6.2

how can i calculate the modulation index.
please help me i am confused about the calculation of V/f constant Control techniques .


texts: LMR62421 Inductor selection for boost application

texts:
I'm trying to design a circuit that would boost a Li-Po battery voltage to 6V with 1A of current. I'm planning to use LMR62421 but I'm stuck what should be the inductance value for an inductor...

Datasheet has a detailed section for choosing an inductor, but it is too complicated for me to be honest: datasheet

Could I go with a rule of thumb to whack the biggest inductor that I have when in doubt? Or are there any downsides of using bigger inductors then you need in boost applications (other then the cost of components)?


texts: USB 5V and 3.7V Li-Ion Boosted to 5V Power-Muxing and Reverse Current Protection

texts:
I'm working on a small project that works either on USB power [connected to a computer] or a Li-Po 3.7V battery. My circuit is exclusively a 5V circuit, so I'm boosting my 3.7V battery immediately to 5V using an integrated boost IC. Currently, my load consists of about 65 LED's running at ~5mA and an AT90USB1286 MCU [and a few smaller switches], for a total current draw of approximately 400mA, with a possible spike or so above 500mA on a very rare circumstance.
Right now, my circuit pulls in USB power [VBUS], protected by a Schottky diode, into a 1A LDO 5V regulator for power cleaning and filtering. This then spits out a clean 5V for my load. Alternatively, the power source is a 3.7 LiPo battery, which gets immediately boosted to 5V by an MT3608 integrated boost IC, the output of which is protected by another Schottky diode to prevent reverse current.
As the Schottky diodes I chose have about a 300mV Vf @ 500mA, my boost IC is bringing voltage up to 5.1V and the remainder of the circuit should be fine at only 4.8V. The VBUS line should be bringing slightly over 5V, which the Schottky will also drop, and the LDO can fix [I presume?]. I'm purposely using an OR configuration here for a Make-then-Break response to a power loss with low switchover time, as I want to avoid circuit reset, but I'd also be okay with an integrated Break-than-Make solution. I do want the circuit to choose USB power whenever available however, just to save the battery and charging circuit [not pictured] from additional wear.
The schematic currently looks like this, with only 1 LED shown for representation.

Both the diodes are boxed in red, which I think should provide enough protection for the computer it's connected to and for the battery itself. However, I'm worried about the output of the boost IC damaging the LDO if it feeds back into OUT [pin 3].
Would it be prudent to move D2 over to the OUT of the LDO, or will the LDO sufficiently withstand the battery being connected? I'm worried that if I move the SS34 over to OUT, it will cause the voltage to drop a little too much with a 300mV Vf, maybe below an acceptable range for my MCU and LED's.
Would it better to use an "ideal diode" IC in place of both SS34 Schottky's? I'm okay with a little bit more BOM cost on those two areas if it helps keep the rest of my circuit running safely and smoothly.
Ultimately, I'd rather not built an eFuse or discrete MOSFET solution to save space on my already constrained board and to avoid a complete redesign of the backhall circuit.
In the scenario I envision, either power supply may come unplugged or plugged in at any time, no matter if the other is connected [battery may get plugged in which USB is powered, vice versa, etc...].


texts: Splitting laptop power supply to charge 3 NiMH battery packs, how to protect from overcharge?

texts:
I have a 20V 2.25A laptop power supply that i want to split 3 ways to charge 3 X NiMH battery packs simultaneously (5000,2000,2000 MAh each @ 7.2V).

My plan is to use 3 of these XL-4015 dc to dc step down modules to regulate the voltage and amperage. My question is how can i stop the battery from charging when its full without me having to monitor them.

I'm a hobbyist not a pro. so don't get too technical with me :-)


texts:
How does a Force-Sensitive Resistor work?

Does it work by sensing the number of tracks the user covers meaning that the more force the user pushes on the sensor the less resistance it causes?

Here is a picture of one:


texts:
Looking at the STCS1A datasheet I read:
Table 4. Thermal data

Symbol Parameter                           DFN8    Power SO-8 Unit
RthJC  Thermal resistance junction-case    10      12         °C/W
RthJA  Thermal resistance junction-ambient 37.6(1) 45(2)      °C/W

1.   This value is referred to four-layer PCB, JEDEC standard test board.
2.   With two sides, two planes PCB following EIA/JEDEC JESD51-7 standard.

About note 1: what is the standard here? The same as note 2 JESD51-7?
Here I read:
Summary of JEDEC Thermal, Multilayer Test-Board Specification JESD51-7

High Effective Thermal Conductivity Test Board for Leaded Surface Mount Packages

Material: FR-4Layers: two signals (front and backside) and two planes (internal)
Finished thickness: 1.60 ±16mm
Metal thickness:
  - Front and backside: 2oz copper (0.070mm finished thickness)
  - Two internal planes: 1oz. copper (0.035mm finished thickness)
Dielectric layer thickness: 0.25mm to 0.50mm
Board size: 76.20mm x 114.30mm ±0.25mm for packages less than 27mm on a side

If I understand correctly the two values of the thermal resistance are valid only if the IC is placed alone on a such a huge board of 76x114 mm? I hope I'm wrong...


texts: H-parameters of a BJT Transistor Amplifier

texts: H-parameters of a two port network containing passive elements can be found easily. For example "output short circuited input impedance" of the network is obtained by short circuiting the output terminal and then calculating the total impedance of the network. Can we apply the same rules (we use to find H-parameters  in a circuit with passive elements only) to find the H-parameters of a two port network with a BJT in it ? OR there is another way to find the H-parameters of such network ?


texts: Why do (microphone) preamp designs tend to limit opamp gain to max 60 dB?

texts:
Looking at many pro recording quality microphone preamps, I noticed that every design I looked at that uses an opamp (discrete or IC) limits the gain provided by the opamp to about max 60dB. While most preamps use another stage (transformer(s) or another opamp) to get to 70db or even 80dB, I wonder why they don't just use the first opamp to get there. From what I understand, there would be some advantages:

better signal-to-noise ratio as voltage gain rises,
simpler audio path,
less parts & cost.

Does it have something to do with opamp stability over 60dB?

Here is a typical schematic. R12 limits gain to 40.1dB. I'm using these formulas:

$$A = 1 + (R_{fb}/R_{in})$$

$$gain_{dB} = 20 * log(A)$$

I also noticed that complete mic preamp ICs made by THAT-Corp also have a maximum gain of 60dB.


texts: Interfacing I2C OLED display with pic18f2550

texts:
I've been trying to interface SSD1306 I2C oled monochrome display module with PIC18F2550 micro-controller without any success. the datasheet of ssd1306 controller shows the following data format

so can anyone explain the format on how can we implement this in I2C code.I'm using MikroC pro for PIC.


texts:
I'm trying to troubleshoot a (bass) guitar amp of mine. The output should be clean, but it distorts at VERY low levels. I pulled out the pre-amp board and determined firstly that the distortion is happening there, so I used an audio tracer (small amp/speaker with probes) to follow the audio signal. The preamp is divided into several stages: input/gain, bass+treble EQ, parametric EQ, then it splits to a inverter/buffer for balanced line out, and a class AB amp -> headphone output -> resistor divider -> power amp output.
I found the distortion coming from the output AB amp, so I hooked up a scope to the input/output of this amp, feeding the whole thing with a sine wave audio signal. Input was a clean sine, output showed only the negative half of the sine, but "compressed" horizontally. The peakes lined up with the input peaks, but the width of each negative half was about half the width, centered on the middle of each sine.
The amp layout is a pretty standard AB amplifier with BC547/557 transistors, 2x 1N4148 biasing diodes, and the whole thing wrapped in the negative feedback loop of a TL071 op-amp (output connects between biasing diodes, and AB output goes through resistor divider back to negative input of op-amp.

(not all values are labeled, I made this originally to better visualize what was going on)
I gathered from the scope output that the problem lies in the positive half of the amp. I replaced the transistor with a new one, but no effect, and pulled out the diode and tested it, but it passed all the tests (proper forward voltage drop, open circuit in reverse). Out of curiosity, I tried putting a short piece of wire in place of the diode, and suddenly the amp worked seemingly perfectly, even though the diode works, and I also tested with a new diode, but no change.
The amp seemed to work perfectly with the wire replacing the diode, so I left it in and put it all back together. But now, it's really bugging me WHY that worked, and what the problem actually is. Would someone be able to shed some light and help explain this to me? An idea I just had as I was writing this is that maybe the resistor connected to the positive supply is dead, preventing the transistor from getting proper voltage to turn on, and when I replaced the diode with a jumper, the op-amp started feeding the NPN base with the voltage required to turn it on. Any clues? Basically, what I'm wondering is if it's actually a problem to leave it as I changed it, or should I really keep diagnosing it? Thanks in advance!
(I am not an EE major, just hobbyist, most experience with digital circuits, so some analog stuff I still don't understand completely.)


texts: Mega2560 in circuit high voltage serial programming

texts:
Following my other question on a bricked Mega2560 I discovered that I probably locked-out myself with improper fuses values, and that high voltage programming could be the way to recover a working ICSP.

Following the datasheet of Mega2560, at § 28.5.2 "Scanning the RESET Pin", it is stated that applying 12V to the reset pin can enter the programming mode. But it is also talking of "parallel programming", and the operation mode is not detailed (or is it?).

My hope would be to use serial programming using the pins that are currently soldered to the ICSP port (MOSI/MISO/SCK/RESET/5V/GND), because the chip is a 100 pins TQFP form factor surface mounted, and it is very unlicky that I could unsolder / solder back the chip to my board, even if I do have a hot air soldering station.

The chip in-situ:

I have found several posts and layouts for high voltage programming, often based on Uno or Mega arduinos, and always targeting DIP form factors AVRs like ATTinys. None was about Mega2560 as a target, and none is about in-site reprogramming.

Can someone confirm or infirm my hopes about the resurrection of my 3D printer?


texts:
Hy guys, anyone with an information based on Part number(s) for SIEMENS QRB1 Photo Resistive Flame Detectors?
I have also attached the image of the detector I am referring to.


texts:
I want to start working on IGLOO2 FPGA, and I'm new to FPGAs.
I searched throughout the internet for tutorials and training courses for Microsemi devices. It has a bad support and resources compared with Altera and other vendors.
Can anyone help me with a starting point or any third party for Microsemi workshops?


texts: Coplanar PCB interconnect solutions - As cheap as possible

texts:
TLDR: Hardware design Newbie is lost in the jungle of options.

Base Problem: I am designing a set of PCBs that are supposed to fit into a square grid pattern and be recombined in different configurations within a construction plane. While designing these I found that the connectors used for getting signals and power from one PCB to the next are the biggest contributors to overall cost and non-logic area. I am currently using these and their counterparts on a little bridge chip.

I checked rectangular mounted versions, but they seemed to have to much of a tolerance to ensure there is no gap between the PCBs and the pins all connect.
Industrial solutions offer some nice systems, but are far to expensive.

Design Requirements:

Low cost and CotS-solution is critical (if additional pieces of PCB are required, they can be assumed to be part of the whole PCB set)
Latency, Capacity and Resistance are not critical
Mechanical stability is low priority, the whole construction is supposed to be mounted on a support structure or lay flat on a desk
The PCBs must fit next to each other with no gap between them
The connector should support at least 1 signal/power line per 100 mil of border length (including spacing between lines) used and should not require space more than 400 mil from the border (excluding mounting holes, if required)
The connection must be non-permanent and easy and quick to (dis-)connect
The connection should support a way to hook up wiring (either blank or via a dedicated connector) for debugging and point-to-point connections

Finally, the Question(s):

Does anyone know another good solution for the kind of cross-PCB connection I describe?
I thought about just putting gold fingers on the PCB borders and then creating small bridge pieces that have matching fingers on the bottom. The connection then could be made by pressing the PCBs and the bridge together with screwing connections. Could that work or would the electric contact be to unreliable?
I also wanted to include a stacking option for some of the PCBs. Do vertical connectors align with the usual sizes of distance washers commonly available?

Thank you in advance for your input :)


texts:
I would like to find out more about the purpose of a boot segment, the segment of program memory that is declared by the user, and I would like to ask the following questions to have a concise understanding.

Purpose of a boot segment?
What functionalists does it allow, that you cant do otherwise?
Can I have an example?
Have you seen any examples that made you think "That is a really smart/cool way of doing this!"

I would also like to thank you in advance for your time and sharing your experiences,

Kind Regards,


texts: Anything special I need to know about RS232 & FT232R?

texts:
I'm trying to interface an XSens IMU with my computer, and I'm running into interesting difficulties. The IMU has an RS232 connector that just uses the pins VCC, GND, TX, RX, nothing else. The SDK comes with it has a custom RS232-USB adapter that uses the FT232R and MAX3160, but apart from that it doesn't seem to do anything special.

The manufacturer claims that the IMU uses standard RS232 (and I have no reason to doubt them), so, in order to save space (their converter is quite bulky), I am trying to use a Sparkfun FTDI Basic Breakout 5V.

If I set all the COM settings the same (baudrate, parity, stop, etc), and I connect to the device, I do get data back, but it just seems like gibberish. I issue commands, the TX LED on the FTDI blink, the RX one too, and I get data, but it's nothing like what I am expecting.

Can anyone think of any "gotchas" I may be missing?
Is there a FooBar that needs to be connected to the DingDing to Actuate?


texts: Connecting sensor and avoiding ground loop

texts:
I want to monitor the output from a motor encoder inside a machine, but I am worried about blowing up my Arduino.

Can I connect the outputs from the encoder directly to the input pins of the Arduino ?
Do I connect the ground from the machine to the ground on the arduino ?
Do I plug the laptop on the AC ? I am worried about creating a ground loop.
The encoder output is 5V TTL, the reference is ME22.


texts: How to locate components individually in PCB layout in Altium Designer?

texts: I'm wondering is there any method to locate the components individually in 3D PCB board PDF file generated by Altium. I know there is an option called cross probe to check the components between schematics and PCB layout but that will be only limited to Altium users in which can be done by having project files.Considering who doesn't have Altium designer to access project files how can one view each component on the PCB layout within PDF or any other format?


texts:
What exactly does causal signal mean?

Causality,as I see it is a property of a system wherein the output at PRESENT is dependent ONLY on PAST and PRESENT values of input.Here we have a reference of Output signal Time to define PAST & PRESENT for an input.

Since an isolated signal doesn't have a concept of a STATE,how can we define past or present for a signal?

If ideas of Past & Present aren't defined for a signal,how can the idea of causality be defined for signals?

Here the definition is given but I 'm not able to get a feel of Causality of a signal?

I've a follow-up question which I've put up here.


texts: Implementation of a coplanar waveguide in the design of a Butterworth filter

texts:
I am trying to build a Butterworth bandpass from 130MHz to 140MHz (approx.). As I have already worked with microstrip lines of transmision, I wanted to give coplanar waveguides a try, as in the future I plan to work with higher frequencies (>10GHz) and I have been told that in those cases they behave more efficiently.

My coplanar waveguide is a feed line of 2mm spaced 0.49mm to ground. The board will be 1.6mm thick and use FR4 dielectric (relative permitivity of around 4.6). The expected impedance is 50 ohms.

As of now, I have finished designing my PCB, but I have two main doubts:

Can those soft curves on the upper ground plane, that KiCad adds automatically around the pads of the capacitors, affect the behavior of the waveguide?
Have I added too many vias around the signal line? And are there enough vias all over the rest of the board? I am a bit lost about vias.

Thank you in advance!

Edit 1: Thank you for the comments and answer, I have edited my design to this new PCB:

Edit 2: Thank you again for the information. This is the latest design. As I read here, it is necessary to add lots of small vias nexT to the main trace very close together. However, there is very little information about this on the internet, I cannot find any exact number/density of vias, their size or how far from the trace should thEy be.


texts: Is it harmful for power transformer operate without load?

texts:
I open chest of slide projector and there are power transformer from ~220V to ~6V and directly connected light bulb.

If light was burned out is it harmful for power transformer operate without load?

Are any special danger for user in that case?


texts:
I have been studying RC phase shift oscillators and I have the following questions:

Why does the oscillation stop when loop gain becomes less than 1 and why is clipping observed when loop gain exceeds 1?

My understanding is that the clipping occurs because too high a voltage kicks the device into the non linear region and thus the clipping. Please correct me if I'm wrong. I have no clue why a loop gain of less than unity stops the oscillation.

Which phase shift network is preferred, low pass RC network or high pass RC network?

Given a RC phase shift oscillator, the low pass filter would do the same job as that of a high pass filter. So which one would be preferred?

The frequency of oscillation is given by the formula
and the phase shift formula is given by

If we substitute the value of frequency in the phase shift formula to find phi, we get 67.79 degrees which means that the total phase shift will be 203.37 degrees, which is not what the required phase shift value (required is 180 degrees). How does the circuit still produce oscillations?


texts:
I have 132x65 dot matrix LCD. I am using STM32f303 controller in my application. I got success in displaying the normal 5x7 fonts on LCD.
 Now I what I want to do is to display 13x16 custom sized fonts on the LCD. I generated the appropriate hex code for all 95 characters for the 13x16 size.
In 5x7 i was able to send all the bytes using following routine.

void Display(uint8_t Display_Row, uint8_t Display_Column, unsigned char)
{
  uint16_t String_Pointer_Offset;

  String_Pointer_Offset = 0;

  while( '\0' != *(String_Pointer + String_Pointer_Offset) )
  {
#if (defined(DISPLAY_WRAP_TEXT_STRINGS) && (DISPLAY_WRAP_TEXT_STRINGS == YEP ))
    if(Display_Column > SHADOW_LAST_COLUMN) /* Check if it's the appropriate to wrap the row printing the exceeding character on the next line. */
    {
      Display_Column = 0;
      Display_Row ++;
    };
    if (Display_Row > SHADOW_LAST_LINE)
    {
      return; /* Ran out of space :( */
    };
#else /* if (not defined(DISPLAY_WRAP_TEXT_STRINGS) || (DISPLAY_WRAP_TEXT_STRINGS == NOPE )) */
    if( (Display_Column > SHADOW_LAST_COLUMN)
     || (Display_Row    > SHADOW_LAST_LINE  ) )
    {
      return; /* Ran out of space :( */
    };
#endif
    Display.Row[Display_Row].Column [Display_Column] = *(String_Pointer + String_Pointer_Offset);
    Display.Row[Display_Row].Touched[Display_Column] = TRUE;

    Display_Column ++;
    String_Pointer_Offset++;
  };

  return;
}

And using Display_Print(1,1,"ABC \0"); function in the main file i was able to display the string on my LCD.

But here number of bytes 26 instead of 8 so which can not be sent simultaneously on parallely interfaced LCD. Can anyone help me how to achieve this big 13x16 pixel font display task?


texts: Connecting FT2232H board (60 MHz via 2.54 mm header) to FPGA board

texts:
I am trying to connect FT2232H breakout board (http://www.digikey.com/catalog/en/partgroup/ft2232h-evaluation-board-ft2232h-mini-module/15377) to DE0-Nano FPGA board (http://www.altera.com/education/univ/materials/boards/de0-nano/unv-de0-nano-board.html) and use it in FT245-style synchronous FIFO. In general, everything works, but system is unusable, because I receive some bytes twice (usually, receive 10-15% more data than send).

FPGA is clocked only by FT2232H (60 MHz) and entire system is synchronous so I think this is happening because I connect these two boards with 10 cm prototyping wires which are not exactly suitable for frequencies this high and don't use any pull-up/pull-down/series resistors because can't figure out which ones should be used. I've tried to connect 100 ohm (50 — 300, as suggested on some forum I've googled) resistor in series of clock signal — it decreased byte repeat ratio but not entirely. Is it this or something else causing problem and how should I solve it?


texts: NodeMCU - Are all GND connctions born equal?

texts:
I'm designing a PCB which is based on NodeMCU board in its core.

On NodeMCU there are some GND pins, most of them are to serve digital outputs/inputs, or external sensors which operate on 3.3V.

Vin pin on the NodeMCU can get higher voltage (5+) which goes through a voltage regulator into the rest of the board.

My question:
When planning the connections to GND - should or shouldn't I bridge the different GND pins - between the 3.3V circuits and the 'outer' 5V input the comes before the voltage regulator?

Many thanks!


texts: Different methods to perform UIS testing on a Power Mosfet (EAS)

texts:
I am currently looking into building a circuit to test for avalanche stress of a power Mosfet.  Normally for this specific test, you would want to create a circuit that looks as follows:

simulate this circuit – Schematic created using CircuitLab

This method is commonly called "Single Pulse Unclamped Inductive Switching."  To perform this measurement, we would pulse the gate (turn on the mosfet), charge the inductor with a certain current, and finally turn off the gate of the mosfet.  Then, we would put the mosfet into avalanche breakdown mode where we can calculate V(BR)DSS and Ias.  Here is what the curve would look like and the equation coming with it:

From those curves, we can calculate the energy given by the following equation:

$$E_{AS} = \frac{L*I^2_{AS}}2 * \frac{V_{DS}}{V_{DS}-V_{DD}}$$

This energy really depends on the avalanche breakdown voltage, which can vary during discharge due to the temperature increase of the Mosfet.  But in general, if we stay within a certain range we can make accurate measurement.  I am not going to go into die temperature details here...

What I am asking is if it would be possible to switch the inductor in this circuit and replace it by a bank of capacitor.  We could therefore simply add a resistor in series and limit our Avalanche breakdown current that way.  If this is possible, how could I calculate the energy without the inductor?


texts:
In a project, I need to swap the polarity of a 12V power/signal and GND wire combination electronically.
The current flow is between 7 and 28 mA.

I'm using a DPDT relay for this - the input wires are connected to the Common terminals, NC and NO are crossed between both relay halves and then go +12V on the board (A) and GND (B).
If the relay is unpowered, 12V is connected to the first input and GND to the second one. If it is powered, 12V is connected to the second input and GND to the first.

As the relay (FRT-5) draws quite a lot of current, I would like to substitute it for an analog CMOS switch like the ADG1434 / ADG5434.

Do CMOS switches work on "reverse" current as well, with just a +12V single supply?


texts:
I know and use FPGAs quite a lot between my microcontroller and external interfaces and learned to value the flexibility of this setup.

Now I am wondering whether such a thing exists for the analogue world, too: an array of opamps, filters and comparators together with routing interconnect in a single package.

I've found a sparse selection of programmable gain amplifiers and some programmable higher-order filters at mouser and digikey but nothing with an programmable interconnect.

Does such thing exists? Or are we stuck with special made analogue interface circuitry?


texts:
I am going to put a part on a board and the position of this component needs to be perfect. I am talking about 1/10th of a mm accuracy. What is the best practice for this type of alignment issues, what precautions I can take to ensure this accuracy during manufacturing.

UPDATE
Ok. I get it, I will loose the tolerance, let me ask, what type of alignment can be achieved with ease?

This is for a complex lens system focusing on a Photodiode, the size of the active area is 2x2mm, so more error placing = less signal hence the concern.


texts:
what are elastance(daraf) and  electrostatic potential coefficient?
I wonder their physical meaning.


texts: Using an optocoupler to put an AC signal on a DC bias

texts:
Expanding from this question Can an opto-isolated input be analog?:

Can you use an optocoupler to take an AC signal and attach it to a DC bias? More specifically, can you take something like a 1V sine wave and put it on top of a 300VDC bias. As a starting point, the frequency range will be from 10Hz to 10kHz.

Edit:

I am attempting to replace the isolation transformer in the following circuit. Note, the load attached is a possible example but is able to change based upon the application.

simulate this circuit – Schematic created using CircuitLab


texts: Boost Converter for TTL circuits to drive large loads

texts:
I've got a small PIC-based TTL circuit device, powered by a 4.5V coin cell, that needs to drive a solenoid which requires 12V. Obviously my logic level device can't directly power that so I could either replace the cell with something stronger, or use a boost converter. Is there another option I'm missing?

This seems like it would be a very common problem so I don't want to reinvent the wheel here. What's the most common way to power higher voltage devices like motors, solenoids, etc from logic level circuits?

Thanks in advance.


texts:
I am designing an IoT system which uses the SIM7000A. In the SIM7000 series datasheet it says that the highest possible current for LTE is under 200mA (section 5.4 of SIM7000 Hardware Design_V1.03). However, it provides no other information - like what the waveform will be or its duration.

I am transmitting an HTTP GET. For how long will this consume 200mA of current? Will the waveform be a constant 200mA during the transmission or will it be a series of square waves? I don't have an oscilloscope so I can't check for myself.


texts: Measure antenna S11 next to another source

texts:
I have a dipole antenna designed to work on ~800MHz and 2.44GHz frequency, and a miniVNA Tiny USB device that I can use to measure return loss of the antenna. I connect the antenna directly to the DUT port of the VNA and run the measurement.
I am working from home and of course there are plenty sources of 2.44GHz emission around like WiFis, and I am wondering do the sources have a significant effect on what I see as the measured S11 return loss of the antenna? Or can I ignore their effect?
And what do you suggest for more accuracy in home working environment?
If I check two antennas at the same condition, and one gives a better (lower) s11 on desired frequency, should I say it's a better one, or worse? Since if it is better then it might also pickup the interference better!


texts:
I am designing a layout for this Chip antenna "https://www.johansontechnology.com/datasheets/antennas/2450AT18B100.pdf". In the datasheet they have Test Board as an example layout. I have a couple of questions on their test board. As shown in the below layout:

I am not sure what no ground means here?
I know that the antenna pin with the brown mark is connected to the inductor, but what is the other antenna pin connected to?
Should the ground plane be exactly 46mm? What if I need it to be smaller?
The feed line should be 50ohm, can I change the line width, and decrease the 19mm length and keep the impedance the same?

Thanks in advance.


texts: Automotive Power MOSFETs to switch 80A+ - how can it work?

texts:
I have been thinking about a method of switching large currents in an Automotive application. I asked another question about tripswitches/circuit breakers but never really found a suitable component to be able to switch 80A @ 12VDC at a low cost, electronically using an MCU.

Now I have received news of International Recifier's new range of Automotive Power MOSFETs - example, AUIRFB8405 - available here (UK site) http://uk.rs-online.com/web/p/mosfet-transistors/7870972/ in TO-220 package (and also SMD and many others) with up to 120A continuous current and 163W max power dissipation. This seems great and could in my mind (for example) take the place of a starter solenoid to drive the 80A or so required for a starter motor... they suggest applications such as electric power steering which would be a similar current I would guess.

But am I right?? I am confused because the battery and starter motor are wired up to MASSIVE conductors, maybe 100mm2 or more (wild estimate) of copper, whereas a TO-220 has a puny bit of tin leg. Can I really solder one inline and pass up to 120A safely (assuming I can dissipate the heat)?


texts:
EDIT:
For some reason Altium stopped to synchronize the Schematic and PCB for the jumper footprints. I have to set the Pads net manually. With this, the jumper method works and the second pad is assigned to the correct net once the first pad has been set manually.
This is not nice and I am afraid of inconsistencys in Schematic/PCB, but it'll do for now! Any better solutions are highly appreciated.

I am currently creating a rigid-flex PCB in Altium 15.
As a "real" rigid-flex PCB is quite expensive, I'd like to create a rigid-only pcb panel that contains the rigid sections and use flexible SMD jumpers to connect them:

I still want to handle this PCB as one PCB in Altium.
Meaning: I dont want to seperate the nets on the different sections.

My idea was create a flex connector footprint of type Jumper, giving the same Jumper ID to the pads that will be connected with the flex jumper (see image below, pins 1 and 20: jumper ID 1, pins 2 and 19: jumper ID 2, ...):

Then, create a schematic symbol that is set to jumper as well and only put pins 1..10 on this (as pins 11..20 should be connected through the jumper ID).

However, Altium does not apply the same nets to the respective pins.
Do I have to put ALL the pins on the schematic? I thought the internal jumper ID would already connect these.

I dont want 2 pins that I simply connect to the same net, as Altiums design rule check will create "unrouted net constraint" errors between the jumper pads.

Any idea on how to do this properly?

Thanks and have a great day!


texts: Can a 3 phase solid state relay be used instead of 3 single phase relays?

texts:
Apologies if this is similar to another question, but I did look before posting. I am trying to understand what exactly differentiates a 3-phase relay from a 1-phase relay. I am controlling three 1-phase lines using three 1-phase relays (all 3 on or all 3 off at any point in time); space would be optimized if I could use one 3-phase relay instead.
An example of 3-phase relay: http://www.crydom.com/en/products/catalog/53tp-series-ip00-ac-panel-mount.pdf
An example of 1-phase relay: http://www.crydom.com/en/products/catalog/ha-series-ha48-ac-panel-mount.pdf


texts: 24GHz Mixer - How to shift the frequency of a 24GHz(100MHz bandwidth) signal by +-4kHz

texts:
Why do I want this? When a 24GHz radar signal hits an object that has a relative velocity, the frequency of the signal will shift by a frequency on the order of kilohertz. I want to create this process of frequency shift electronically.

I receive a 24GHz(100MHz bandwidth) signal from the antenna. I want to shift the frequency by something on the order of kilohertz (from -4kHz to +4kHz).

(the carrier signal is 24GHz, I want to turn it into what it would have been, had the carrier frequency been 24.000004Ghz)

I have a few ideas:

(+4kHz here is just an example, it could be anything between -4kHz and +4kHz)

Using this.

I will put the received signal to LO. Put cos(2pi 4kHz t) and -sin(2pi 4kHz t) to IF1 and IF2 ports. Does this have any chance of working? Would it cause problems to put a 100MHz bandwidth signal to a LO port?

Another idea is: I can demodulate it by, say 20GHz. Put 20GHz to the IQ modulator I posted above and shift it above by putting cos(2pi 4kHz t) and -sin(2pi 4kHz t) into IF1 and IF2. And then modulating the signal by 20.000004GHz.


texts: What is the voltage at a node between two series voltage sources?

texts:
Hopefully the title explains it. As an example, what is the voltage at node one in the schematic below? And more importantly, why? I believe the answer is 0V, but I suppose what I'm thinking is: Why isn't it 125V? Thanks for any help you can give.

simulate this circuit – Schematic created using CircuitLab


texts:
I understand that when Vgs = 0, and there is a steady current Vds, there is a pinching shaped depletion region and so on. But what I have a confusion with is when Vgs > 0 or Vgs < 0.

The book states that when Vgs < 0, the Vds current will be less and the pinched depletion region will be achieved at lower Ids. My explanation is that since some of the charge from the source moves to the source between Vgs, the current/charge flow decreases, but since Vds remains same, the depletion pinched region stays the same. Is this correct?

In case of a positive connection to g between Vgs, i.e. Vgs > 0v I can't think of what happens.


texts:
I have an application where I have multiple PCBs connected to each other where each board edge is 45 degrees to the mating board. There are plenty of right angle connectors and straight connectors, but has anyone ever used 45 degree connectors? I have very low constraints in the connector, a simple 0.1" pitch 3 pole header is sufficient.

I am essentially looking for a product in between these two P/Ns (as an example): M20-9960345, M20-9990345

Another note is that I am aware that I could manually bend a straight connector to 45 degrees to accomplish this, but this would be for production so I would like an off-the-shelf solution.

Thanks!


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I was hoping to use this mosfet shield to control a "Standard 3528 12V LED strip". The shield looks like this:

However, it doesn't come with a datasheet (I guess that's my fault for being cheap) and now I'm confused about how to connect this to my Arduino Nano / Wemos D1. The black connector has +, - and s on the bottom but both blue connectors have no labeling whatsoever. So I'm not sure how to connect it to the 12V and Arduino. I've googled but haven't been able to find any documentation on this shield other than lots of sites offering it and with the same (or similar) pictures but never with any labeling. Maybe these things are so common that 'everybody knows' how to connect them?

The MOSFET is an IRF540. Also; I've read somewhere that I may need a transistor or "driver" to get the MOSFET to switch?

I have relays lying around and they work fine for my purposes but I was hoping to switch the LED strip without the noticeable click of a relay, so that's why I was looking into this MOSFET. (I also have some solid state relays laying around, but they're for AC).


texts: Improving absolute precision of ADC to balance battery voltage

texts:
I plan to use a relatively high-end microcontroller (Piccolo TMS320F28035, 12-bit resolution, +/- 4LSB offset, +/- 60 LSB gain) to measure voltage across stacked battery cells and control associated analog electronics to equalize their charge. The microcontroller will also store data in an eeprom memory (blackbox).

The current plan is to read up to 10 cell voltages. The problem is the large common mode voltage (each cell can go up to 3.5 V) - I cannot use isolated amplifiers such as INA124 or non-isolated high-precision INA117 due to high cost.

The current plan is to use voltage dividers (0.1%) at each tap and calculate cell voltages relatively to each other:

V1 is measured directly
V2 is calculated as measured V2 value less calculated V1
and so forth

The problem with this setup is that the tenth measured voltage will suffer from high voltage-divider ratio and thus could be off by too much.

Another approach is to use a battery monitoring chip and use is as an analog front end (BQ77PL900) but the cost is quite high as well.

Are there better ways to precisely read battery cell voltages?

Thanks,

SBNY


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I am working on a project with a gas engine at constant speed of 1500RPM to drive a permanent magnet generator with magnetic ball bearings.
- SKF.function is GENSET
- PM generator is water cooled.
- PM generator is horizontal positioned.

The permanent magnets Nd-Fe-Bare axial located on the rotor - radial flux PM.

From the supplier of the generator I received 2 torque ratings:

start torque: 2.9 Nm
rated torque: 191 Nm

The gas engine has a torque of 97Nm.

The generator is 3phase 400V AC - 45.6A - 4 poles -50HZ - 93% efficiency - PF 1 connected to the grid, and off grid via an inverter to a battery bank.

Will this work properly,
or do I need a rated torque of the gas engine greater or equal to that of the generator?

Assume continuous full load, as it is connected to a battery bank.

In another option it is connected to the grid.

Any specs you would need I would able to supply if possible.