texts: How to adjust this BJT design to increase brightness of LED without changing PCB?

texts:
I am having issues with this previously designed circuit from a former co-worker. What we want it to do is turn on the LED when IN1 of TPS2121 (Power mux) is chosen as the output. According to the datasheet ST is pulled high when the output is Hi-Z or IN1 and pulled low when IN2 is powering the output. The LED is part of the switch PVA6LRE21141 I can't find the forward voltage it requires but with the current design, voltage across the diode is only 2.6V.

I do not understand his BJT circuit, the LED is not very bright at the status pin I only see 3.1V. I am trying to get it to turn brighter. Can someone explain the purpose of R14 and the way it is connected. Only R13 seems to affect the brightness, except I cannot decrease it any lower than 6K or I would violate the specifications of the TPS2121 ST pin. The ST pin requires a pull up from 6K-20K.

I think he used a BJT with C8 and R15 to create a ramp up effect for the LED. I do not think the ramp up is that necessary. Is there anyway I can change this design without having to change the PCB or as little as possible so that the LED can turn on brighter? I am considering changing Q1 to a mosfet with common footprint and removing C8. Thanks in advance for your help!


texts: Term for a guarantee a manufacture makes that a product will be produced for a number of years?

texts:
Sometimes manufactures of electrical components guarantees that a product will be produced for a number of years so you can rely on getting new components for future production runs. What is the term for such a manufacture guarantee?

Sometimes this is something that you can buy, you can pay the manufacture up front for a guarantee that you will be able to buy the component X years from now. I know there is a specific term for this, but I cannot find it.


texts: GPS antenna ground plane design considerations and limitations

texts:
I have a PCB design which incorporates a GPS unit.  I'm looking at refining the PCB, and I'm looking to do away with the long cable length, occupation of space within my enclosure, current consumption, and reliability issues that I have experienced with using an external GPS antenna.  I'd like my new PCB design to incorporate a ceramic GPS patch antenna right on the PCB itself.

I have quite a bit of PCB real estate that will be facing the sky once installed in it's enclosure.  I'm hoping the enclosure itself won't block the GPS signals too badly, as it is made of plastic that's about 3mm thick.

I know that in order for a ceramic patch antenna to be effective, I need to place a ground plane underneath it.  I'm planning on allotting a 40mm x 40mm ground plane underneath the patch antenna, but I'm wondering this:

Can I have part of the antenna ground plane located underneath another small pcb that is mounted on top of the PCB with the ground plane on it?

See the following picture:

Here are the specs for the hardware I am proposing:

-PCB antenna ground plane is 1oz per sq ft (1.37 mm) thick

-SIM908 GSM/GPS module from SimCom

-YAGEO     ANT1818B00DT1516S GPS patch antenna

Also, a pretty newb question:

Do I connect the antenna ground plane to the ground of the entire PCB?  If so, where should this connection be made?


texts:
I had picked up a beagleboard a few weeks ago and had then looked into the USB sniffer project that had been created a while back. (https://gitorious.org/beagleboard-usbsniffer/)

I understand that the project is based off a proxy driver in which is registered as both a USB device/gadget driver and forwards the data between the both whilst logging the data.

The question I have is as to how this is done without actually interferring the data being sent through the two interfaces (the beagleboard is invisble between the two interfaces).

Cheers


texts: How to protect a P-channel MOSFET when driving a motor?

texts:
I want to switch a 12 V DC automotive fuel pump in a bench test rig using a P-channel MOSFET, as follows:

simulate this circuit – Schematic created using CircuitLab

This is a simple on/off switch, no PWM is used. The datasheet for the FQPF47P06 gives its maximum Id as 30 A continuous, 120 A pulsed. Vdss max is -60 V and Vgss is +/-25 V. The data for the pump shows a maximum current draw of 20 A, but the most we observe in the application is about 5 A.

In a previous version of this circuit I didn't include D2 and underspecified the fuse rating; the fuse failed and the MOSFET was destroyed (became short circuit source to drain). I've guessed that this was because the motor inductance created a large negative voltage spike from drain to ground on disconnection, so I've added D2 to handle this situation.

Does this look like a suitable setup to switch this load reliably, or have I overlooked anything?
What diodes are suitable for D1/2 - is a 1N4007 OK or should I look for something faster and/or with a higher current rating?


texts: Does the Microchip/SMSC PHYBoost technology help with Rx, or does it boost Tx only?

texts:
So I'm doing some configurations on a product which has a LAN9514 chip (datasheet), that features the "PHYBoost" technology.

Microchip's website is very vague about the technology, and my impression, after reading the datasheet, is that this feature will only increase the amplitude of the signals sent by the hub.

So my question is: Does it do anything for the signals which the hub is receiving?


texts: I don't understand how this circuit works. I'm not sure if it's correct. It should give a DC output, but how would it do that?


texts: Does the distance between the signal lines (in terms of noise immunity) matter when wiring the board?

texts:
Studying the design of many boards, I noticed that the signal lines go very close to each other.

A small distance between the tracks improves noise immunity or is it a matter of beauty and compactness?

I make a large distance between the tracks (0.7-1 mm). Should I reduce it if the size allows?


texts:
I'm trying to implement a simple current control circuit for an LED from here: https://www.allaboutcircuits.com/technical-articles/the-basics-behind-constant-current-led-drive-circuitry/

The principle of the circuit seems straight forward- the voltage at the inverting input should be controlled by the current passing through the resistor, which in turn is the current passing through the LED minus the input current of the op-amp (1 pA according to the datasheet). For the control voltage on the non-inverting input I am using a DAC output from a microcontroller.
My problem - even when my control voltage is zero my LED lights up. In fact for 0V input I am getting 2.4V across my diode and 0V across the load resistor which corresponds to about 5mA of current through the diode.
With increased control voltage the voltage starts to increase across the resistor but the output soon saturates. and the voltage across the resistor does not match the control voltage. The op amp I am using is a MCP6241 which is a single supply rail-to-rail op amp and I'm running it at VCC = 3.3V.  So I am guessing this may be something to do with the single supply?
Is there a solution using this op-amp?


texts: Is this switching power controller compromise wise?

texts:
TL;DR: Looking for all kinds of advice :-) Especially related to pushing "backwards" power into a MC34063 based step-up switching controller at times.

I'm building a device with an AVR microcontroller, some I/O (rotary encoder, button, LED digits and a buzzer,) a wall wart power in, and a 18650 LiPo cell for unconnected power.

I want the device to run well on connected wall wart, as well as charge the LiPo battery. The AVR will disconnect the charge voltage when the LiPo voltage gets to 4.1V. (Data sheet says to charge to at most 4.2V, so that leaves a little safety margin -- the cell also has built-in protection)

The chain is something like "jack in -> linear regulator -> switch -> battery -> switching step-up -> AVR" with a diode from linear regulator to AVR to run on wall power even when the battery charging is switched off.

I built a version of this that used a 5V 1117 regulator and a depletion mode MOSFET for the switch. Sadly, the MOSFET had a Rdson of about 3 ohm, which significantly limited the charging current once it got above 3.7 volts or so. This made it take forever to charge. The regulator also runs hot, but I have a heat sink on that, and on the MOSFET.

For a second try, I'm thinking of using the variable 1117, set to 6V out (with a 0.85V rectifier drop that to 5.15V for the AVR) and a P-channel MOSFET as a switch. This will not stay "on by default" as the depletion mode did, but with the shunt diode to the AVR, it will come on with wall wart power only anyway. Initially, I did not have that diode, so power "on by default" was important. The P-channel MOSFET has an Rdson of about 0.2 ohms at -4V, so it probably won't even need a heat sink.

I will then depend on the current limiting built into the 1117 to not deliver more than one amp into the battery while charging. While this is going on (voltage < 5V) the switching step-up controller will actually power the AVR, in parallel with the battery being charged. Further, even when the battery charge switch is turned off, the battery will be in-line with the step-up converter, although that converter will be running "idle." (It's a mc34063 based converter) I imagine I'll need hysteresis in the charge on/off switch -- say, charge to 4.1V, discharge to 4.0V, repeat. Hopefully, that cycle is long with this design while plugged in. The device will be un-plugged every day and recharged overnight, generally.

Finally, I'm enclosing both the schematic and the layout. The biggest annoyance with the lay-out is that the inductors I have are laying down, and thus take up a square inch of the board :-/ That also makes the traces from the switcher to the inductor longer than needs be. On the final board, I will overlay a ground polygon on both sides of the board (2-sided only, no real "planes," sorry :-)

Please be gentle but firm!

https://watte.net/timer-schematic-revB.png

https://watte.net/timer-board-revB.png


texts:
I'm trying to design a circuit to measure power of 230VAC (MAINS), with the ADC of a small MCU.

I have designed the part of the circuit to measure current, but my solution to measure voltage is getting a bit messy.

If have come up with a solution using an opto-coupler, but I'm not sure, it is the best way to do it.
I have also looked at transformers, but the seem expensive and kinda big.

Please come with some good suggestions?


texts:
I'm presently writing the code for SAMD20 micro-controller and SDCard. I'v successfully written code for single block read and multi block successfully. I'm testing my code with San-disk 16 GB SDCard with HC-1 specs.

I'm stuck with writing the code for single block write.

I've followed following process:

Sent CMD24 command (with sector number 2001:just after first block of FAT32 FS )
Based on response started writing buffer with incremental data (0x00,0x01,0x02,0x03........) (After Sending data token 0xfe)
Now after this, I'm waiting for data response (i.e. 0x05 for successful data write), which i didn't get. MISO line goes BUSY (0x00) after that and after some time, transit to high (0xff).

If I send CMD13 (arg=0x00) after this, I should get card status, but It is returning back with 0xC1 0x3F.

After reset, if I tried to read sector no. 2001. I get following results

I think this is the correct procedure for SD Card write.

Any help will be appreciated.Thanks in advance.


texts: Filter Design for Charge Output Transducer (accelerometer)

texts:
I am designing a low-pass filter for a charge output transducer. The filter must be passive and provide a 2nd order Butterworth response, no more than 0.01dB of ripple in the passband is acceptable.

I have a filter available that does not meet my cutoff frequency requirements, but, as it operates on charge I am not sure how to approach analyzing or redesigning it.

The attached image shows a model that I built to simulate the filter. The design shown gives an approximately 3 kHz cutoff.

The transducer is simulated by the voltage source, transformer and series capacitor.
An example of the lowpass filter topology is shown at the output of the simulated charge source.
A textbook charge amplifier has been included at the filter output (the choice of op-amp might not be ideal here).

simulate this circuit – Schematic created using CircuitLab

Can anyone offer insight into the design and analysis of the filter topology shown? Specifically, I would like to understand what method could be used to select the components to achieve a Butterworth response.

EDIT: The ripple and filter type requirements could be modified. The biggest challenge( for me at least) is designing a filter for charge signals. I am not sure how to use any standard technique to design such a filter.


texts: How do I define a module with a modified parameter in Verilog?

texts:
I want to define an add module which has a modified parameter in my declaration of the new instance but it doesn't go well.

It is in Verilog.  I want to define an instance of this module:

module add #(parameter wd=1) (input wire [wd-1:0] a,b, output wire [wd-1:0] o);
   assign o = a + b;
endmodule

I tried this line but I get an error:

 add len_plus_1 #(8)(.a(len),.b(8'h1),.o(lenPlus1));


texts: Using Solar Charge Controller with AC Power instead of Panels

texts:
I'm working on a project here which needs to have a small SLA backup battery.

I have a cheap PWM solar charge controller already and I want to use plugged into an AC power supply (48V DC out) in place of solar panels.

I've tested it on my bench and it works but is there anything I should be worried about long-term with this setup?

Edit: Here is the datasheet - Tycon Syetems model TP-SC24-20


texts: Is there such a thing as a momentary SPDT off-on-on switch? "off-(on)-(on)"

texts:
I'm looking for a toggle or slide switch that has an off and two on positions and is spring loaded to automatically return to off, but one of the on positions is past the other one.

So instead of "on-off-on", I want one that is "off-on-on"

Or maybe "off-onA-onB"

And it should be momentary, so maybe that would be "off-(on)-(on)"?

So you push it to the first click to turn on the "onA" circuit, and then can push it further to turn on "onB".

For my application it would be fine if the second load is only an additional "on" (in other words, onA is also still on when we switch to onB), much like a car key ignition.

But if pressure on the switches is released, the switch automatically returns all the way to off.

Anyone know where I can find a switch like this?


texts: EEPROM chip always toggling bit when reading

texts:
I have a parallel EEPROM, the AT29C020 (doc: http://pdf.datasheetcatalog.com/datasheet/atmel/DOC0291.PDF)
In order to read it I'm using an ATMega8535 as it has enough pins.
At first I thought reading the chip would be easy but after several attempts I have to admit I don't have a clue about what is going on here.
If I correctly understand the spec, you put the address on the address lines, then you put CE and OE low to enable the chip and the reading process and finally after some time (far less than 1µs) the chip outputs the content on the data pins.

I'm doing this and it doesn't work.
More precisely, here is what I do:

everything as output (DDR* = 0xff)
everything high (PORT* = 0xff, thus including WE)
CE low
(*) data lines as input
put the address on the pins
OE low
1µS sleep
read data pins
OE high
1µS sleep
go to read next address => (*)

Instead of receving the data, I have the pattern that the doc describes as the I/O6 bit toggling, which is a method during the write operation to know if it has finished.
This means every read returns the same value except for the 6th bit that toggles for each read.
For example I saw 31/95 and 159/223 patterns. Also, it never ends and doesn't depend on the input adress.
TOGGLE BIT: In addition to DATA polling the AT29C020 provides another method for determining the end of
a program or erase cycle. During a program or erase operation, successive attempts to read data from
the device will result in I/O6 toggling between one and zero. Once the program cycle has completed, I/O6
will stop toggling and valid data will be read. Examining the toggle bit may begin at any time during a
program cycle.

Obviously I'm neither programming nor erasing so I really don't get why the chip reacts this way.
I searched a lot before coming here but sadly I can't find anything.
By the way I don't think it's hardware related because I tried to put a long pause while reading and the address/CE/OE/WE are correct.


texts: YIG oscillator - where is the oscillator?

texts:
In this excellent article, the author gives the following schematic of a YIG oscillator:

I don't recognize any oscillator like Colpitt etc. or those listed in Wikipedia "oscillator" article.

What or where are these oscillators?

Related question: in the first two schematics, there is an RC circuit. What is his role?


texts: How to regulate a 3.6 V battery to two power rails (3.3 V and 1.8 V)?

texts:
I have a 3.6 V battery from which I need two voltage rails, one that is 3.3 V and one that is 1.8 V. How should I design this circuit such that it is the most power efficient?

Here is what I was thinking:

Using one voltage regulator to regulate the 3.6 V down to 3.3 V, and using voltage division after the 3.3 V to create a 1.8 V
Using two voltage regulators to regulate the 3.6 V down to 3.3 V and 1.8 V

Are either of these good options? What else might you suggest?

Follow-up question about using two regulators: Should I put them in series or parallel?

i.e.

Series: Regulate 3.6 V down to 3.3 V, and then regulate this 3.3 V down to 1.8 V.

Parallel: Regulate 3.6 V down to 3.3 V, and separately regulate 3.6 V down to 1.8 V.

simulate this circuit – Schematic created using CircuitLab


texts: why must \$"i"\$ of the current source in the figure be the \$"i_{rms}"\$,not \$i_m\$?

texts:
Calculate the average power which  \$5Ω\$ resistor consume

The solution is

To be honest,i don't know why can the current be calculate like that,that is ,\$\sqrt{\frac{i_{rms}^2 \times t }{T}}\$

Here is my calculation,but the answer is not 52.5W

\$P_{avg}=\frac{P_{total}}{T}=\frac{P_{total}}{3}\$,and \$P=IV=I^2R\$
,so

\$P_{total}=P_{1s}+P_{2s}+P_{3s}=[(\frac{6}{\sqrt{2}} \times \frac{15}{15+5})^2+(\frac{4}{\sqrt{2}} \times \frac{15}{15+5})^2+(\frac{1}{\sqrt{2}} \times \frac{15}{15+5})^2\ ]\times 5 =78.75\$

\$P_{avg}=\frac{P_{total}}{T}=\frac{78.75}{3}=26.25W\$

Now ,i find what is the main reason that my answer is not the same as solution,i think the \$"i"\$ of the current source in  the figure is the \$i_m\$,but the solution think this \$"i"\$ should be \$"i_{rms}"\$ ,and the relation between \$i_m\$ and \$i_{rms}\$ is that \$i_{rms}=\frac{i_m}{\sqrt{2}}\$,so i want to ask why must \$"i"\$ in the figure be the  \$"i_{rms}"\$,not \$i_m\$?


texts: How to replace an LED with a diode and stop LED after timer ends?

texts:
So I have been working on this circuit that basically will activate an LED when the lux levels drop low enough. The time that the LED will remain active for is determined by VR4. I'm having two issues that I want to overcome, however.
The first is that I want to make it so that LED "D6" will turn off after the time that I have chosen has passed (say 10 seconds, etc) and not turn back on again until the lux levels have risen above the threshold and then dropped below again.
The second is that I want to remove LED "D5" from the circuit without altering functionality, as it is only on when lux levels are high, but the point of the circuit is that no LED is on when the lux levels get to a certain level or after the set time has passed.


texts: building a remotely controlled remote controlled car :)

texts:
I am a newb to EE (I am a web developer). My friend works remotely and this is what I would like to accomplish:

Build a web interface like this:

When he visits this interface from a remote location, he can press the buttons and (using an infrared signal emitter on our end) control a remote control car with a camera on it.

Any idea if something like this can be accomplished with standard web technologies? I have never done anything with robotics but I have heard about things like Arduino and tools like Raspberry Pi.

Just looking for some basic suggestions to point me in the right direction.


texts: Vivado Zynq DMA unconnect automically generated AXI-Lite interface from AXI Interconnect?

texts:
I am trying to initiate a MM2S stream read from the programmable logic of a Zynq board. I have inserted the AXI DMA IP, and intend to use the AXI-Lite interface on it to program the registers in the  Programming Sequence from p70 of the user manual
However, Vivado seems to be automatically connecting the AXI-Lite interface on the DMA to the ps7_0_axi_periph  (AXI Interconnect), as shown in the read-only automically generated verilog file below. It remains this way even after I reset the output products with the connection absent in the block design.
Basically I just want to use the AXI-Lite interface from inside the sandbox with my own signals to write to the registers that would be required to read data into the sandbox, but Vivado is not letting me disconnect the AXI interconnect from the DMA.
Am I doing something wrong?

Update
Turns out a had a misconception. The AXI DMA Master looks like it is automatically an ARM/CPU master, and Vivado doesn't let me change it (see image). How can I connect a PL-based master to the DMA IP to read data into BRAM?


texts: PIC16F57 timer how to trigger an interrupt

texts:
I'm trying to make a simple delay turn-on function using Timer0 inside the PIC16F57 itself.All the example I can find on internet mostly come with build-in interrupt function which the PIC16F57 doesn't have,at least on the datasheet.Any way or hint to workaround?

Objective is quite simple:

a switch was pressed(input stay HIGH)
LED will turn ON after 3s
LED will remain ON if switch is still being pressed/latched
if switch input is LOW logic level,then LED will off

Did try with normal __delay_ms(3000) but it's not practical since switch off the LED also need to wait for 3s if the switch on routine is not completed.

I'm using MPLAB XIDE in C language and no way to change the mcu to other model as the PCB is already fixed for PIC16F57.


texts:
I'm trying to find solutions for the security of an outdoor area (2km long and 1km wide). We want to detect any breach through the borders of the area, if someone sneaks in and/or someone goes out.

What I'm trying to achieve is to have the least detection nodes possible on the borders that use solar power packs to take their juice from. Let's assume that we can have 5-10 nodes in 2km length (max of 1 node each 200m) and 5 nodes in 1km width of the area. We'll have a gateway that receives the data from these end devices once motion is detected through RF (and that's not a problem). These motion sensors should be able to detect movement up to 200m away (until the next node), only detect human movements (not pets, cars, etc.), work with arduino or RPi and don't be in need of too much power.

I've done some research already, but I thought maybe someone could introduce me to an specific sensor or solution.


texts: Finding the FET with lowest channel length modulation

texts:
I'm looking for the FET (JFET, MOSFET and other more advanced variants like Heterojunctions) that has the lowest channel modulation or perhaps among the lowest. Now, before anybody argues if other FETs do have it, then at least JFETs also have it, as some sources will say. It's just that it's most pronounced with MOSFETs (along with other short channel effects), seeing they are scaled way down with the CMOS process.

But, as most of you know, it's not a parameter listed in datasheets. So I'm trying to resort to deriving by other parameters. Although I've ran into some problems. \$R_{OUT}\$ or \$R_{DS_{ON}}\$ is calculated as:

$$R_{OUT} = \frac{1 + λV_{DS}}{λI_{D}}$$

I believe that to more accurately derive \$λ\$ it ought to be (assuming \$λ\$ is a constant, giving a linear growth for the channel length modulation -- a simplified model):

$$R_{DS_{ON}} = \frac{1 + λV_{DS_{SAT}}}{λI_{D_{SAT}}}$$

$$λ = \frac{1}{R_{DS_{ON}}I_{D_{SAT}} - V_{DS_{SAT}}}$$

where pairs {\$V_{DS_{SAT}}\$, \$I_{D_{SAT}}\$} are any point past the beginning of saturation region where channel modulations has started to take effect.

Now, in the datasheet, typically, \$R_{DS_{ON}}\$ is listed with \$V_{GS}\$ and \$I_{D}\$ given. It's implied for the most part that all parameters are tested at some point in saturation. So, some \$V_{DS_{SAT}}\$ is \$V_{DS_{SAT}} ≥ V_{GS}\$. So we can have

$$V_{DS_{SAT}} = V_{GS} \quad (given) $$ $$I_{D_{SAT}} = I_{D_{RDSON}} \quad (given)$$

Though, of course, we are simplifying and linearizing clm, so we need a \$(V_{DS_{SAT}}\$, \$I_{D_{SAT}})\$ that is well within the clm effect and not at what probably is just the meeting point of the peak of the linear region and the start of saturation region. So that's the technical problem.

Other than the last paragraph, what other problem do you guys think there is?

EDIT:

I meant:

$$V_{DS_{SAT}} = V_{GS} \quad (given) + V_{extra}$$

So in the more ideal case that \$V_{DS_{SAT}}\$, under which everything is tested, it is well within the clm taking effect, we need the offset \$V_{extra}\$.

EDIT:

corrected the formula to \$R_{OUT}\$. My mistake.


texts:
I have seen the same issue posted here with TL494, but The feedback pin set up in that IC, seems to be different- so that I cannot adapt it here.

I got an idea about how to implement a closed loop system. Vref to non inverting pin and scaled output to inverting pin.
But I need a open loop system where I can Vary the PWM duty cycle within the range using a potentiometer without taking a sample from output.
Is it possible with this chip?


texts: How to find a replacement for an antiquated transistor 2N2148

texts:
I need to replace a transistor in my guitar amplifier.  The model number listed on the original schematic is 2N2148.  It is in a TO3 package and the rest of the specs are listed here.

I am having trouble trying to find a suitable modern replacement and I am unsure whether I should buy a NOS given that it is a germanium component.  I found a few on Ebay here and here
but I could really use some advice as to what to do in this situation.


texts: How does someone design a low frequency FM radio transmitter?

texts:
I'm relatively new to the topic but I'm intending to transmit some data from a measurement system in a cave to a receiver on the surface. I understand that I can use a SDR (software defined radio) to receive radio signals on the surface but from all of the tutorials and material I've come across online I can't seem to find a way to to transmit data at frequencies around 80 kHz to the surface. I've chosen 80 kHz because frequencies such as 88 - 108 MHz would encounter far too much attenuation whilst attempting to penetrate the ground and frequencies around 80 kHz are used by commercial cave radios that utilise voice links. However, I'm not interested in transmitting voice links but rather simple files. I've been told that using VCO circuits to simply generate a low frequency signal and modulate it with an input signal would be unstable and unreliable so my understanding of FM radio has proved useless at this point.
I suppose my question is what is the best method for transmitting signals at these low frequencies to the surface? How do I even begin to consider the design of a system that does this? I'm still a beginner with RF engineering so any help would be valuable.
Edit: I'd like to make it clear that I'm not aiming for "line of sight" transmission through air but instead "through the earth" (TTE) transmission through a conductive ground medium. Limestone, to be exact.


texts: Quartus: What is the purpose to "register output port" when RAM or ROM megawizard?

texts:
The RAM and ROM megawizards in Altera Quartus II give the following option in the GUI "Which ports should be registered?" The options vary but are:

‘data’, ‘wraddress’, and ‘wren’ write input ports
‘raddress’ and ‘rden’ read input port
Read output port(s) ‘q’

How do I know if my design requires the outputs of the memory block to be registered or not? If it is a good practice I guess it would be registered by default right?


texts: I'm trying to design a board that powers an MCU and a strip of Lights. The lights draw about 4A at 5V. In calculating the potential copper thickness of the PCB I'm a little lost. If i make the trace wide enough say 2cm, will that allow sufficient current flow? or do I have to create some sort of bus bar?


texts: Parasitic oscillation in BJT booster stage of voltage controlled current source

texts:
I have constructed a voltage controlled current source for driving high power LEDs. In essence, it is a power N-channel FET in series with the LED whose gate is driven in reference to a 1 Ohm low-side sense resistor. I have included a BJT booster stage inside this feedback loop to enable high-frequency modulation of the gate voltage and therefore load current. I'm targeting ~100ns 1A turn on times. The circuit is shown here for reference:

simulate this circuit – Schematic created using CircuitLab

The feedback loop is stable and operating as desired. However, there seems to be a parasitic oscillation in the emitter follower formed by Q1 within the BJT booster stage. This results in an ~20 mA ripple riding on top of the LED current for DC reference signals. The oscillation is seen riding on the of the LED current but is not present in the reference voltage.

Scope trace showing reference voltage (yellow) and LED current pulse (blue, 1A/V) with the small oscillation riding on it:

Same as last image with 1A offset and zoomed:

I believe this a local, parasitic oscillation rather than instabilities in the feedback loop because:

If I break the feedback loop and apply DC voltages to the base input node (labeled "A" in the circuit diagram), the oscillation persists.
Poking the base of Q2 (labelled "B" in the diagram) with a pair of metal forceps while my hand is also touching a ground point removes the oscillation for the first part of the pulse. The oscillation seems to go away at the start of the current pulse, but it quickly returns 10 usec or so into the pulse. I have pictures of this but I'm not allowed to show them because my rep is too low.
Increasing the value of the compensation capacitor (C6) does not affect the frequency of the oscillation.

I've tried playing with the values of base stoppers (R1, R2) adding capacitance between various terminals of Q1 and Q2 and I have not found a solution that totally gets rid of this oscillation. Any advice would be much appreciated.

EDIT Fixed schematic to include power supply decoupling elements.

EDIT Fixed schematic to include MAX4564 analog switch series resistance.


texts: What is the minimum current for my load to see TTL?

texts:
I have an inverter that can output +/- 25 mA.
I would like to split that output 3 or more ways, and deliver it to as many loads.
So my question is: how many times can I split it before the current is too low to reach a TTL level (5, 3.3 or 2 V)?
My loads' input impedance is 8.2 MΩ. So, naïvely, I would say that the minimum current for TTL to be "seen" is I = V/R = 5 V / 8.2 MΩ = 0.6 µA. Is this reasoning too simple? Is it wrong?


texts:
Let's say we have a ferrite core inductor connected to an AC sinusoidal source with period \$T\$.
Thus, we have voltage \$u(t)\$ across the inductor and current \$i(t)\$ through the inductor. How can we find the equations which describe the power and energy loss due to hysteresis over one period?
We know that power at any point in time is given by: \$p(t)=u(t)\cdot i(t)\$ and the energy loss over one period is:
$$W(T)=\int_T{p(t)dt}$$
But, where do we go from there?


texts: Identifying SDA and SCL wires in I2C device

texts:
I have a IR proximity sensor with 4 wires sticking out, I know which the GND and V+ but I cant figure out which the SDA and SCL wires are (even from looking at the datasheet). Any ideas what the Blue and Yellow ones represent, from the schematic / image below and code:

/***************************************************************
  Arduino GP2Y0E02B example code
  Gets range from GP2Y0E02B and prints it to the serial monitor.

  By James Henderson 2014
***************************************************************/

#include <Wire.h>

int distance = 0;                // Stores the calculated distance
byte high, low = 0;              // High and low byte of distance
int shift = 0;                   // Value in shift bit register

#define ADDRESS       0x80 >> 1  // Arduino uses 7 bit addressing so we shift address right one bit
#define DISTANCE_REG  0x5E
#define SHIFT         0x35

void setup()
{
  // Start comms
  Wire.begin();
  Serial.begin(19200);

  delay(50);  // Delay so everything can power up

  // Read the sift bit register from the module, used in calculating range
  Wire.beginTransmission(ADDRESS);
  Wire.write(SHIFT);
  Wire.endTransmission();

  Wire.requestFrom(ADDRESS, 1);
  while(Wire.available() == 0);
  shift = Wire.read();
}

void loop()
{
  // Request and read the 2 address bytes from the GP2Y0E02B
  Wire.beginTransmission(ADDRESS);
  Wire.write(DISTANCE_REG);
  Wire.endTransmission();

  Wire.requestFrom(ADDRESS, 2);

  while(Wire.available() < 2);

  high = Wire.read();
  low = Wire.read();

  distance = (high * 16 + low)/16/(int)pow(2,shift); // Calculate the range in CM

  Serial.print("Distance is ");
  Serial.print(distance);
  Serial.println("CM");

  delay(50);
}


texts: Is it safe to run Logic ICs at their maximum output current?

texts:
I am building a circuit that will ultimately output to 8 7-segment displays. I am going to be multiplexing these displays.

The displays I chose are https://uk.farnell.com/kingbright/cc56-12surkwa/display-seven-segment-14-22mm/dp/2478714 (common cathode) which lists the DC forward current as 30mA on the datasheet.

I am planning on running the data lines for this display from the 4094 (SIPO register) and the cathodes (to do the multiplexing) from a 4017 (Decade counter).

In the case of the 4094, the datasheet (https://assets.nexperia.com/documents/data-sheet/HEF4094B.pdf) lists the maximum input/output current at 10mA.

My question is two part. Firstly, am I right in assuming these values given are per led / per pin and secondly, if that's the case, am I safe to run the 4094 at the maximum current output without using a resistor to go to the display?

I know I should probably use a driver chip or something, but I just wanted to clarify my query about pushing the maximum ratings on an IC.


texts:
This may be a little basic for some. Sorry in advance...

I would like to use a large 3ph motor to perform a fast, controlled, stop.

The rated motor torque is 850Nm @ 242A.

My inverter claims to be able to deliver a short duration current of 460A.

Calculating the torque constant KT = 3.51Nm/A (from the rated figures 850/242 = 3.51)

Could I realistically expect 460A x 3.51Nm/A = 1615Nm of reverse torque for a short duration?

Or in fact, like when a motor is starting would the ratio of current to torque be a non-linear relationship?

(The motor would be running at normal load and speed and then attempt to decelerate as fast as possible.)


texts: Does a MicroControllers resistance change with computation?

texts:
Does the load resistance of a micro-controller change based on particular programs or instructions that it is currently running? Does adding in extra functionality of the device also have an effect on the resistance, such as Timers, ADC, Interrupt Service Routines etc?

For a follow up question, I see in a lot of the electrical characteristic sections of uC datasheets that higher frequency requires more current from the supply source. What is the actual cause of that? Shouldn't the overall current draw be unaffected by the clock speed? That is to say, on average, if I've got a program that spends half the time executing x instruction and the other half of the time executing y instruction, speeding that process up doesn't change the relative proportions of time spent in the different states. From the datasheets I've seen, it's not a 1-1 relationship, so doubling the speed won't double the current draw. So is it correct to assume that it's got to do with switching losses in the digital gates?


texts: How to dial a phone number via DTMF tones?

texts:
I want to dial a phone number on a landline with DTMF tones generated by my phone. I tried soldering a 3.5mm audio jack to a phone cable and using my regular phone app, but nothing happened.
In this video, this is done by simply playing the tones in to the speaker, but that wouldn't work on my phones either.


texts:
I have a nice looking purple PCB from Laen's batch service, which I have assembled using rosin flux. I have cleaned the board as best I can with isopropyl alcohol, which gets rid of the tackiness of the rosin, and also improves the dielectric behavior. However, as you can see in the pictures, it leaves a white powdery flux residue which looks unprofessional.

I tried 1631-16S flux remover, as well as just blasting it with compressed air, but it doesn't seem to get rid of the residue. How do professionally assembled boards manage to look so clean?


texts: Gating TTL UART Tx pin to simulate BREAK for arbitrary time periods

texts:
I need to gate a TTL Tx pin @115000bps as the chipset that drives the RxTx lines do not implement UART BREAK for arbitrary time periods.

Thanks to this community's feedback (Selecting proper vales of Rb, Re and and Rbe in a NPN transistor emitter follower configuration?) I have come up with the following configuration that I will connect to the TTL Tx pin of the said chipset, at TTL.TX.In.

The Tx output from the whole device will be tapped from TTL.TX.Out

BREAK is the gating input that controls whether TTL.TX.Out will be in BREAK condition or not.

BREAK is an output pin of a typical FET Microcontroller - say AVR, MSP430 or PIC.

The TTL levels can be ~5V DC or ~3v3 DC.

My questions are:

What should be the proper value of R1 and D1? (I am thinking R1 = 1K and D1 = 1N4148 but that is very arbitrary)
Is this a proper design that will allow me to implement BREAK for arbitrary time periods without affecting the "usual" transmission (When BREAK is off and all signals should go through)?

My fears are:

i. The Vf drop, typically 0.7V can degrade the output signal quality
ii. The 1N4148 is speced to work upto 4ns but it's capacitance is around 1pF and taking stray capacitance into account, I am not sure how the output signal would look like @115000bps.

Would you have reason to believe that the UART signal outputs could become severly degraded?

I have shared the schematic here. Feel free to make copies and modify it: https://www.circuitlab.com/circuit/gh3g6z/ttl_uart_gating_public/


texts: Hspice measurement without re-running simulation

texts: is there any option to use existing tr0 or fsdb file and use measurement using hspice or finesim without re-running simulation ?


texts: Matrix of small incandescent lightbulbs - problem with buzzing

texts: I am prototyping a circuit for controlling matrix display of small incandescent lamps with Arduino (each lamp is 6.3V 0.3A). I designed the circuit in Yenka and built it. It is composed from 3 types of transistors: IRF640N, BD244C and TIP122. All of the resistors in my circuit are 1KΩ. I am controlling the lamps by multiplexing: one column of lamps is lighted up at each 1 millisecond. There are 20 columns of 7 lamps in my real circuit, divided in 4 groups, but only 6x3 divided in 2 groups are shown in the diagram here, connected in the same way. Everything works good, but I have small problem with the noise coming out from the electronics (it is not loud, but noticeable). At first, I though that the IRF640N transistors are causing the problem, but thanks to the suggestions I get here, I concluded that the lamps itself are the source of the noise. If I increase the pulses speed, the noise gets higher frequency. I noticed that the noice is stronger when there is a column in which all of the lamps are turned on. It also becomes louder if I try to dim the lamps intensity by adding delay between the pulses. I chose this design because it worked in Yenka. I am beginner and didn't know too much about designing circuits like this one. I would be very thankful if somebody give me directions and help me about fixing this design to eliminate the buzzing.


texts:
I have been thinking of starting a new home project: I want to automatize some stuff at my home, starting with the heating. To do this I looked at the FHEM project. All looks pretty good and interesting, but I realized quite early that I needed a small device to send and receive radio signals to all the devices of the house that I want to install.

The website suggested to get this one, but looking at the price it looked quite exagerated (plus the website does not look very reliable). Looking around on the internet I saw this other item. I am not very skilled when it comes to electrical things, but I could swear it is the exact same thing (Am I wrong??). the only difference I notice is that it does not have the USB jack solderer in. Fortunately I know someone that knows how to solder this kind of stuff. He agreed to help me with the project, but he told me he would need the schematics to figure out how to weld it.

Could someone please help me find those schematics, since I have no idea where to look for them?


texts: Does a wide-band, high-current, inline ammeter circuit already exist?

texts:
I have an application where I would like to measure currents up to 1000 A, inline, but am also interested in using the same circuit for a low current part of the cycle. The thought is that if I can use a low resistance shunt and amplify the voltage across it using a log scale amplifier, then I could have a 0-5 v signal crossing the range of 0.1..1000 A, that I can then digitise. I know there are concerns about signal noise and effectively variable resolution, but these are manageable should the method ultimately work.
Do products already exist that do this? Is there a specific name? Should I just go ahead and design it?


texts: If ground and neutral are bonded at main panel, why aren't all grounded device chassis energized?

texts:
I know this is a question with variants that have been asked countless times on the internet and on this site. Believe me that I have scoured through these questions and answers in search for a satisfactory answer but that I have not found one.

In your home electrical wiring, the rule appears to be that you should never connect ground to neutral anywhere else than at the main panel. The reason for that (from countless individuals/websites online) is that once you do that, you would be a using a device's ground and neutral returns in parallel, and once the ground in a system is energized, this effectively energizes all other objects connected to ground in the system.

But given that ground and neutral are already connected together at the main panel, doesn't that do exactly what is meant to be prevented with this rule? Once you have conductors (ground/neutral wires) at equal potential somewhere in the system, how does connecting them elsewhere change their relative potential?

I know that my thinking is wrong at some point, since clearly every chassis in every home isn't energized. I just don't know where my understanding goes wrong.


texts: SCR (thyristor) - Practical Dimmer Circuit

texts: Could someone please explain the main function of the capacitor C3 connected between the gate of the thyristor (through the diac) and the cathode of the thyristor, in this Dimmer circuit schematic


texts: Delay ON LED circuit with motion sensor OFF

texts:
I'm trying to make a circuit that goes:

Delay ON > Run for 5 minutes > Off.

But it also has a motion detector that will immediately switch the circuit off when it detects motion. I am referring to this circuit diagram for the Delay ON part:

https://circuitspedia.com/on-delay-timer-circuit-diagram-with-relay-using-capacitor/
But other than that, I'm at a loss on how to integrate the motion sensor part. Can anyone please help? I'm new but I'm willing to learn. I am using 12V batteries and some LED strips (120 led/m).


texts: How are in practice input output impedance measured of a prototype circuit?

texts:
When an analogue circuit like an audio IC or an ADC for instance is implemented, is there a dedicated instrument/device which measure the input output impedance of the circuit or one has to perform his own setup?

I am very curios how are such tests are performed and cannot find any information in literature. I basically wonder what professionals use in testing their prototypes besides oscilloscopes and function generators.


texts:
I have a 5000 VA UPS which is connected to eight 65 AH batteries. I am looking to replace these old batteries with new ones. I was wondering whether the UPS will run safely with less number of batteries or with less battery capacity.

I did some research and found out that the formula for calculating the battery capacity goes something like this:

Battery capacity = (Load / Voltage) * Back up time

I am assuming that the load is 5000 VA which will roughly convert to some 4000 Watts and its a 12 V battery. The back up time required is 30 minutes.

So battery capacity = (4000 / 12) * 0.5 = 166.

Is my formula wrong? I don't have an electrical background. Any help would be appreciated. Thanks.


texts: How to calculate a differential ADCs resolution

texts:
I have a differential ADC with two internal reference voltages. The bottom voltage is 1V the top voltage is 3V with a 14bit resolution. I want to calculate the resolution in V.
For a single ended ADC you can calculate the resolution in V with this formula: Ref.voltage/(2^(bitresolution))
How can you calculate the resolution in V for the differential ADC?
My guess would be : (TopRef.voltage - Bot.Ref.voltage)/(2^(bitresolution))*
Is this correct?


texts: Using a transistor to add to max current output from a opamp?

texts:
I thought I understood transistors but now I'm confused again.

I have a basic opamp circuit to amplify the input of a electret microphone. The output of the opamp will vary within 1-4V. Now I want to connect this output to a load (laser) and this modulate the light intensity via the mic.

The driver of the laser is not a constant current one, and output does change if input changes, thus modulation is possible.

The thing is that I cannot connect the laser directly to the output of the opamp circuit because the current flow will be to high (+-300mA), so this means I need to use a transistor right?

So I thought I can just connect this output to the base pin of the transistor(2n2222), the load from +5V to collector, and emitter to ground. The base input then controls the current over the proportionality.

So basicly a input of 1-4V on base must control the collector current also from 1-4V but allowing a larger current to flow.

I read that the base-collector current must not be the same and this shuts down the transistor. I tried a basic circuit and obviously it didn't work.


texts: Pin assignments do not appear to be assigning in bdf - Quartus 17.1

texts:
Following the pin assignment diagram in the device manual for my Max 10 DE10-Lite, I assigned all the correct pins to their associated inputs and outputs as seen below:

However, when I go back to my bdf file and run the full compile, the pin assignments do not appear, as they have in the past.

I thought to myself, maybe they just aren't showing up, but they are actually still assigned. So I programmed my board, and it simply remains black, with my circuit not working at all. Has anyone seen this before? I have tried creating a new project, and still nothing.


texts: Need help identifying a mystery component with double-diode marking

texts:
I've found this MOSFET-shaped component inside a Dell laptop power supply (I've lost the case so I can't tell you any details, sorry):

The problem is that I can't find any datasheet for it anywhere.

I will try and describe it in terms of the lines of text on the front:

Line 1: C6312
Line 2: A picture of two diodes facing each other.
Line 3: 004

For the most part, it looks exactly like a MOSFET, metal back etc, and it is also mounted on a heat sink if that is useful.

Through some research I think I've narrowed it down to a Schottky barrier rectifier stack based on the symbol of the two diodes facing each other.

This isn't super serious or urgent, but I'm really interested to know what it is!


texts:
I am using a PIC 16F884 to run 2 motors and 2 servos.  The motors are using the onboard PWM module, and I am bit banging PWM for the servos on Timer 2.

With only one servo being controlled, it works perfectly, but when I add a second servo control, the timing becomes off because of the number of commands that are being issued during the interrupt period (at least this is what I've seen when I've hooked it up to an oscilloscope).

My question is: Can I issue a command to a servo, wait until its reached to proper position, then turn off the pulse and expect it to maintain position?  If this is the case, then I should be able to control both servos with 1 timer.

I saw a similar question here: Will a servo hold its position without a signal? with no definitive answer.


texts:
I'm trying to connect my atmega328P to the following H bridge, but I'm using 5V source and 2N3904 & 2n3906 transistors instead of 12V as shown in the picture:

The problem is that two of the transistors are PNP, but I always used NPN's as a switch by connecting micro-controller's output pin to the NPN's base, but I don't understand how can I 'output' a negative signal to trigger the PNP's from the micro-controller. Any suggestions?


texts:
I want to put a LED inside a door and to get the current to the door I was trying to find a device that could conduct while the door is closed like so  https://www.ebay.com/itm/Two-Function-Magnum-Shooter-Dakota-Digital-MGS-2/231532017929?epid=1037725533&hash=item35e8623909:g:FU8AAOSwJTta1hxY:rk:7:pf:0

but I'm sure that there is something more specific(and cheap)then that, I just don't know what to search

Does anyone has an Idea?

Tanks

-------Edit------

Well, Sorry for the lack of information in the original post. My bad.
Here's the photo that's in the  link

The Purpose of this is that I want to do an electric locking for a bathroom door in my house and I want a LED to light everytime the locking system is switched on. I want the LED to be placed in the door itself(design preference) and to do that i'm looking for a way to "electrify" the door

Thats it


texts: Choose which led that will light up, (Digital circuit)?

texts:
So I am supposed to construct a digital circuit that have 3 inputs and 2 outputs. The first input is used for "settings", in the second input you can choose which one of the LED lights you want to be affected by setting, the third input is then used to carry out the setting for the lamp you chose. the outputs are 2 LED lights.

The first input is a light switch, with this light switch you are supposed to choose if you want an LED to be on or off. 0 is off, 1 is on.

The second input is a light swhitch, with this swicth you are supposed to choose which LED you want to be affected by the setting in input 1. 0 is LED 0, 1 is LED 1.

The third input is a simple button, when you push it the setting that you chose for input 1 is supposed to affect the LED that you chose in input 2.

I am supposed to do this with only D flip flops, multiplexers and logical gates but I have no idea where to even start? What's the first step in a problem like this?


texts: Is synthesis tool supposed to generate two copies of logic for this piece of code?

texts:
Here is line of code:
diff <= (t0 - t1) when (t0 - t1) >= 0 else 0;

Some saturation is being applied, so diff is always >= 0
Is synthesis tool supposed to generate the subtraction logic twice since it has been repeated twice in the statement?


texts: Why do electrons and holes in the base have to recombine in order to create the base current

texts:
Khan academy link
In the video above, it is said, that in order for the base current to appear, electrons have to recombine with the holes in the base region.
Why can't they simply go to the base electrode directly?
Is it somehow related to the semiconductor-metal junction as in Shottky diode?


texts:
I'm using an interrupt to wake the microcontroller once the value has been reached. I see that in the Capture/Compare Control Register there is a Capture Overflow bit. I can't seem to find an example of checking for this bit once the value has been reached. One example interrupt looked like:

#pragma vector = TIMERA0_VECTOR
__interrupt void CCR0_ISR(void) {
    if (++i == 120) {
        P1OUT ^= RLY1;
        i=0;
    }
} // CCR0_ISR

But this doesn't check the value of the bit. So how do i check to see if the timer has overflowed?


texts:
I want to connect a light sensor to my PC ( serial or usb ) and read the values of that sensor.

Is there a way i can do this without a microcontoller?

I am looking into the cheapest method of acheiving this functionality.I must say i am a n00b in electronics so i would be grateful for any detailed explanation.

Thanks.


texts: What could be the output current rating of the following shunt regulator?

texts:
I am trying to solve the 2013 paper set by ISRO for electrical engineers. I wanted to verify if my answer to Question no 18 is correct.

So \$I_L\$ is being drawn out of the circuit shown. Since the zener diode operates in reverse bias, let \$I_Z\$ be the current that flows into the ground through the zener diode. Since the power rating of the diode is \$0.4 \ W = 5\times I_{max}\$, we know that \$I_Z\$ can at max be \$\frac{0.4}{5} = 80 \ mA\$.

By the current law,

$$\frac{10-5}{50} = 100 \ mA = I_Z + I_L $$

So \$I_L\$ can't go below \$ 20 mA\$ or the power rating of the diode will be broken. It can't go above \$ 100 mA\$ or the diode will no longer be in reverse bias.

So the answer is B? Anything wrong here?

From what I know isn't there some minimum current that has to pass through the zener diode for reasonable regulation? Izk? Should we just assume that the value for that is near zero? Because then the upper limit might not hold.


texts: Convert low power USB to high power USB in car stereo.

texts:
Could I connect the D+ and D- to my car stereo's USB input, then connect the red and brown (+/-) to a 2amp cigarette plu'sg USB? My issue is that the USB in the head unit is low power and doesn't charge my iPad I use to play through it so I'm trying to figure out getting a high power source in there.

Would this work?


texts: Minimum distance between two connectors in a high voltage PCB design

texts:
My application will have low current (mA) but high voltage lines. High voltage will arriving from external source using banana jacks on the case.

I am looking for an example in which someone uses PCB connectors (i.e., terminal blocks) that carry high voltage (e.g., 5KV). But I'm not having success.

I have not found any connector with more than 2.5kV dielectric strength. But I must put external 5kV signal at one connector and 0V to the other one, if it's possible in the same PCB.

I would like to know how can be calculated the distance between two (separated) connectors that have a 2.5KV breakdown voltage but they need to support a bigger voltage difference between connector 1 and connector 2: 5kV.

Connector 1: VCC+ (5KV)
Connector 2: VSS- (0V)

With BV = 2.5KV for me it's clear that bringing the two connectors so close to each other the material will break. Maybe I'm wrong.

I know the creepage and clearance techniques, but if I understood well it's referred to the sheet material and the copper over it, that has its own breakdown voltage/mil. But what about connector material? I thought that E field will be constant between two connectors, but voltage will be decreasing equipotential lines.

So, could I find a distance between both connectors in which the VCC+ connector and VSS- connector will be safe from breakdown?
Whereas trace and pad spacing literature suggests for certain kind of material to divide nKV/30cm to obtain safety distance between pads or traces with high voltage differences, what can be applied to the gap of connectors? How to get the minimum distance between two connectors with higher voltage level than its breakdown voltage? I need to be sure of minimum distance in which I could solder them in a board without damage.

Take into account that I'm not talking about connector (copper) pads to another printed pad/trace distance. I know how to calculate the minimum clearance and creepage.

I try to say that I will use 2 separated connectors, one for V+ and other one for V-, as far as they can from each other. But how to relate the manufacturer parameter limitation (1kV) with the distance needed for 5kV (or whatever) between them? That's the point of the question. If connector dielectric parameter is negligible, please let me now.


texts: CE marking of device that contains CE certified module

texts:
I am using a bluetooth module in an electronic product. This bluetooth module is CE certified.

When it comes to CE marking of the whole product, do I need to perform tests of the bluetooth part of the product?


texts: Multiple micro controllers to control LED matrix

texts:
I am planning to use 5 40 pin  Picaxe micro-controllers to control a 70x70 LED board matrix. My plan is to use 4 of the micro-controllers to control the LEDs and the 5th to tell the other micro-controllers which lights to turn on and off. first of all is this the best plan for the system and second of all how would I communicate between the main micro-controller and the other ones.

Also is anyone has a better idea to control a 70x70 LED board fire away :)


texts: Is it bad design to use logic gates for multiplexing?

texts:
I have a PIC18F4550 which uses the same pin for UART RX and SPI data out.

Would it be bad design if I used a GP I/O pin and a logic gate to control the multiplexing of that pin?

When the IO1 pin is on, CTS (clear-to-send) will be turned off so the other module doesn't send any data.

When this is the case, IO2 pin will be asserted as well and therefore enabling data to flow to the SDI pin of another component. When SPI data is sent, IO2 and IO1 pin will again be de-asserted therefore stopping flow to the SDI pin and allowing DOUT to continue sending data to the RX pin.

IO1 and IO2 can be the same pin (this was quite stupid of me).

Would this be a good design or are there better ways of accomplishing this?


texts:
So I was taking a look at some of the example schematics in Eagle and I came upon this weird OpAmp configuration in which both inputs are connected:

I'm not sure what this is meant to do, my best guess is that this was done in order to stop the output from swinging due to both inputs being unconnected. Does anybody know if that is the case? And if so, why would that be a problem?
Also, there is something else that might be important: the same IC has another OpAmp which is being used as a comparator in this circuit.

Edit.
This is where the other OpAmp from the same IC is used.


texts: Why do we need 4 resistors for a common emitter amplifier?

texts:
I'm studying the 4 resistors bias configuration, I'm trying to understand why we need everyone of these resistors.

If I understood correctly, Re is used to make the Q-point stable, while R1 and  R2 are used to determine Vbe, but I can't understand why we need RL.
I also would like to ask why in the common base configuration we have a bypass capacitor in parallel with R2 and in the common collector we have a capacitor between the collector and the ground. Why we need to bypass these resistors in these cases?
I understood that in the common emitter we bypass Re because it reduces the gain, is it the same thing in the others configurations?
Thanks
Answer
We need RL otherwise the output voltage would always be equal to the supply voltage, this is true for the common emitter amplifier,but if we take the emitter voltage as output voltage(common collector configuration) we don't need RL anymore.
Moreover the DC component of the output voltage depends on RL
About the bypass capacitors, we use them because some resistors reduce the gain(but we need these resistors during the bias).
Thanks to eveyone.


texts: Can I connect multiple STM32 to single CAN transceiver?

texts:
TL;DR: This question is about saving unnecessary CAN transceivers by sharing one among 3-4 equal MCUs on a small, single board.
Imaginary situation:
A board with multiple, equal, CAN-capable STM32-MCUs needs to chat with other equally-made boards via CAN bus.
There's one transceiver on each board (most probably an MCP2562FD), meant to be connected to all MCUs in parallel, sharing bus access.
Please see the following pseudo-schematic for clarification:

The "secondary MCUs" on the left half will "just passively listen" and use individual ID filters to only get relevant data for their task.
The respective "main MCU" will be the only active communicator on each board, officially talk / respond / ACK on the bus.
The point is to reduce transceiver IC count per board. Normally, I would put a dedicated transceiver for each MCU. To me, however, a CAN transceiver (not: controller) looks like an "active access point" / "medium translator" that's not necessarily bound to be connected to a single client MCU only. I further assume, that if the main MCU was able to understand a message (and "ACKed" it), the secondary µCs should have received it correctly, too - since all lines are kept short and away from noise, and interference should be most likely to happen on the other side of the transmitter. The tx lines of the secondaries will be omitted, most probably, to enforce passivity.
To me, this concept looks feasible, electronically and logically. Yet, I'm unable to find any resource describing that it could work or wouldn't at all.
If any CAN / STM32 pro could shed some light on this, point me to the right direction (*), name pitfalls, confirm or refute my thoughts, I'd highly appreciate that!
Thank you for your time and attention!
(*) without discussing the multi-MCU-approach as a whole or switching to / introducing other means of multi processor communication - I love and want the high abstraction level by ID filtering and mailboxes all-in-hardware goodness ;)


texts: Can anyone explain to me how a carry select adder works?

texts: Doesn't get more complex then the question above. I've been looking through textbooks and using google and I feel like the explanations are not suffice or unclear. Can anyone explain this to me well?


texts: Looking for part number of 0.05 pitch of SWD and STDC14 headers

texts:
I'm looking for pin headers for SWD/JTAG and STDC-14 (SWD + VCP) interfaces.
The ones that can be used together with a STD14 cable from STLink V3 mini.
I found the 10-pin connector that I need on digikey:

Could anybody help me to identify the part number for a similar part for 14-pin connector? Like on this board:


texts: Why did the datasheet mention this interface?

texts:
I have a ST32F103RET6 MCU. I got the datasheet (and refrence manual). When I read the datasheet (and refrence manual), I found this section:

Now I have several questions about it:

Why does the datasheet (and refrence manual) mention this interface?
Is it a peripheral? Obviously not, because you can't find it in peripheral's section). If not, then why did the datasheet (and refrence manual) mention this interface?
Why did it mention this interface at memories section?


texts: Sniffing lowspeed CAN bus with highspeed device

texts:
Is it possible to use a highspeed (HS) CAN interface for listening to a lowspeed (LS) CAN bus? If so - Is it in any way questionable to do so in a real world car or moped?

As far as I know, LS CAN supports failsafe operation when one signal is broken. I assume, this will not be supported by a HS transceiver.

In my application, I can insure (by means of hard- and firmware measures) that my device is not writing messages to the CAN bus.

So, which risks should I keep in mind when listening on a LS CAN bus?


texts: How to construct the DC equivalent circuit of a BJT amplifier

texts: How would the DC equivalent circuit be constructed? I have a vague idea knowing that AC voltage sources are connected to the ground and capacitors are open circuited but what happens to the resistance \$R_B\$? I have seen some solutions where the whole branch is connected to the ground but that doesn't sem right


texts: Mesh Analysis with voltage and current source

texts:
I've spent all day trying to figure out where I am going wrong with this problem:

My mesh analysis attempt must have something fundamentally wrong with it as my results are giving me crazy numbers:

I have also atttempted Nodal but I can't post it in this question as I have reached my image limit. Any help would be massively appreciated. I've spent pretty much all day on this one problem and I'm sure that I'm 90% of the way there.
Thanks


texts: Can I use a diode as a level shifter, and which way should it be?

texts:
I think so, in https://cdn-learn.adafruit.com/assets/assets/000/024/745/original/adafruit_products_schem.png?1429900999

RXD_5V is connected to RXD with a diode labelled 1n4148.

But in my mind I imagine the diode would be facing the other direction. What am I missing please?


texts: finding air gap shear stress in a permanent magnet generator

texts: I have found that the air gap shear stress is a limiting factor when sizing a generator, but how do I find the value for it?


texts: Most efficient way to select between 10 large buses?

texts:
I need to select between 10 different 164-bit buses using four-bit BCD (8421, unsigned binary). What is the most efficient way to do so?

Currently I have the following SystemVerilog implementation

case (bcdIn)
  4'd0: muxOut = optionA;
  4'd1: muxOut = optionB;
  4'd2: muxOut = optionC;
  4'd3: muxOut = optionD;
  4'd4: muxOut = optionE;
  4'd5: muxOut = optionF;
  4'd6: muxOut = optionG;
  4'd7: muxOut = optionH;
  4'd8: muxOut = optionI;
  4'd9: muxOut = optionJ;
  default: muxOut = 'x;
endcase

where muxOut and each of the "options" are 164 bits wide. The timing report for this snippet reveals a huge delay due to the fanout of the select lines (the digits of bcdIn).

Is there a more efficient way of selecting between large buses? Perhaps a tree construct of MUXes of some sort?

I am willing to code this by hand using assign statements and the like, but if there's a way to infer faster logic using case, I'm all ears.


texts: Audio oscillator cross-talk on small synth project

texts:
I am making a small 9V battery powered synthesizer with a square wave oscillator built around a 40106b Schmitt trigger (reference: http://richdecibels.com/blog/?p=11) and a few other components, one of which is a white noise generator (similar to this build: https://www.flickr.com/photos/secondhandsynth/4501573713/)

My problem is, the square wave oscillator is bleeding into every part of the circuit. It's really loud, and its leaking into other sound generators on the circuit board that it's not even connected to in any way besides power and ground. As I probe the circuit board with a speaker input, I can hear the oscillator ring through every part of the build.

Is there a way to isolate a loud oscillator from the rest of the circuit? Or prevent signals from cross-talking on a common ground?

thanks.


texts: Can I send an SSH command via Nucleo Board?

texts:
I'm in a very embryonal phase of my project, so I'm just putting the pillar on possible solutions.

I'd like to have an opinion or suggestion by experts about this question:

For the above-mentioned project, I should send an SSH-based command to a final device.

Note: the final device can communicate only via ssh.

Although send an SSH command can be simple by using a computer (e.g., by using pink or PuTTy), is there a way to do the same via the Nucleo L476RG board?

Ultimately, can I open an SSH connection by using a Nucleo board and send commands?

Note: The project could admit the purchase of other hardware components if necessary (e.g. wifi modules).


texts: What are these elements and what they do?

texts:
I have a telephone circuit (Model No. Panasonic KX-TS500MXB) which has following item between TIP and Ring. Do you have any idea what it might be? At first I thought it might be a back to back zener diode but after some testings I doubt if I am correct.

The following item is as well unknown to me. I have searched the part number but I couldn't find any item similar to this!!

EDIT:
Here is the symbol that corresponds to first image:

Thanks


texts: Why does the 802.11b DSSS signal have 22 MHz of channel width? How does the information get spread over that width?

texts:
This topic has got me so much confused.

In terms of Wi-Fi, when we say the 802.11b has 22 MHz of Channel Bandwidth, what does it mean? When we refer to a particular Channel No. say Channel 1, it has its center frequency of 2412 MHz, but it spans from 2401 MHz (-11 MHz) to 2423 MHz (+ 11 MHz) to form a 22 MHz channel. Why is that? Why can't the channel be just 2412 MHz signal?

How does the data utilize the 22 MHz width?

Also how does increasing the Bandwidth help in increasing the throughput (not data rate)? No highway examples please, because those are layman and incorrect analogies.

Thanks


texts: CMOS/RTC battery standard connector type?

texts:
Most CMOS/RTC batteries have a standard connector type, however after exhausting tons of time searching I cannot seem to find the type of connector these use.

It's a 2 pin connector with 1.25mm pitch. It reminds me of a JST type connector however it's not that, and I've also search to see if it was apart of any molex mini series. Pictures for reference:

I'm looking for connector B in this picture, connector A seems to be a JST-SH 1.0mm pitch.

Another example:


texts: Choosing industrial grade components after a consumer grade proof of concept

texts: I assembled a basic prototype with an ATSAMD21G18 based microcontroller and what I believe are consumer grade sensors (LSM6DSOX, LIS3MDL) to test out a proof of concept for product that would need to operate in an industrial scenario where the main factors are temperature and vibration. What are the major considerations necessary when looking to graduate from a simple idea into industrial grade components and PCB's?


texts: Is this a viable mini wind turbine setup?

texts:
I'm going to build my first wind turbine. I have already constructed the prop, 5 blades 50cm long from PVC pipes. I've searched for a decent sized motor and charge controller. The turbine will be located in the city, so winds will hardly ever go above 10-12 m/s. The battery i'm planning on having permanently connected is a 12v lead-acid 6-7Ah

How is this for a setup?

Charge controller: http://www.ebay.com/itm/5A-CC-CV-Buck-LED-Drive-USB-Lithium-Charger-Power-Current-Voltage-Display-Module-/400976105382?hash=item5d5c09cfa6:g:vf8AAOSwjVVVyrFl

Motor:http://www.ebay.com/itm/161763982868

I also have a boost/buck converter lying around (No current regulation) , would it be a good idea to connect that first, in order to boost the voltage and get less power loss through the wire and then connecting to the buck converter (with CC) as listed above.

Note: The buck converter has a really low minimum input voltage of 2.8v (max 32v input) so using this as a first step would make sure that the battery is charging at 13-14v even though the voltage from the motor is between 2.8v and 14v.

If anything is unclear please ask me. Thanks!


texts: Is there an advantage to using one or the other?


texts: How to drive and control capacitive load?

texts:
There is electrochromic film (which is  some kind of capacitive load) that need to be driven with 50Hz alternating current, load voltage should be controlled in range 0-100V (with 8 or more fixed voltage levels or with continuous change in given range) by ARM processor with PWM or any other way.

Film segments of desired size have around 50KOhm impedance magnitude and should be driven by AC in order to function properly. Load power consupmtion is aproximately 0.001-0.01 watts at 100V.

I want to control many segments in parallel so per segment part of the circuit price and complexity are significant, so scheme with shared ac source design will be better.

The only idea i have for now is to produce low voltage alternating current with PWM and low pass filter and then use step up transformer to get high voltage output, but it looks over complicated for me and i'm not sure it will work at all.


texts: Can we estimate the remaining lifespan of a Lithium (Iron Phosphate) battery by its energy efficiency?

texts:
All manufacturers that publish the energy efficiency of their lithium (iron phosphate) battery claims that it's 99%.
https://www.sciencedirect.com/ claims that:

Lithium Battery - an overview | ScienceDirect Topics
The efficiency of Li-ion batteries is almost 100%, which is an important advantage over other batteries. They have fast charge and discharge time constant defined as the time to reach 90% of the rated power of the battery, which is around 200 ms, with a relatively high round-trip efficiency of 78% within 3500 cycles.

I can not find any other similar information comparing efficiency and the cycle count for lithium batteries. Is there a well known relation between those two?


texts: How current is steady after pinch off voltage?

texts:
I was studying the JFET. In the books and other material it is mentioned that when the voltage between the drain and source is increased then drain current is also increased. After a certain point (Pinch Off) the drain current becomes constant and will remain constant even if the drain voltage is increased.
If we see the physical structure of the device the depletion region will start to increase when the voltage between the drain and source is increased. After the same certain point (Pinch off Point)depletion region touches and then current cannot move forward.

My question here is that then how the current becomes steady or current will pass when the depletion regions are closed. Doesn't the current become zero ?

If the depletion region is closed by Voltage between drain and source then what is the role of voltage between gate and source. Although I can see the steady current value is changed at different Voltage gate to source and a logic of faster build of depletion region (Through Voltage to Source and Drain to source) also comes in mind but what is the main logic behind it ?

Before replying please consider me as basic learner. Thanks


texts: Formula derivation of Doherty power amplifier from circuit diagram

texts:
I'm having a hard time understanding how formulas are derived from the diagram of a simple Doherty power amplifier circuit, as pictured below.

While I understand the concept behind load modulation and thus the necessity to introduce a λ/4 transmission line, I'm having trouble deriving the formulas shared by most of the literature I've explored and that I've pasted below. (Diagrams are in German, U stands for the voltage V.)

The main amplifier and the peak amplifier are represented as current sources I_H and respectively -jI_S. There's a load R_L, Z_H and Z_S are the impedances seen by the two current sources.

QUESTION 1) I understand that, looking from the node between resistance R_L and current source I_s into the transmission line, the high-ohmic impedance of current source I_H will look like a short circuit due to the length λ/4 of the transmission line,
but I don't see how this implies that:

That is " the voltage at impedance R_L is only dependent on I_H."

How is this possible considering I_S is there, too? Also, is 'minus j' multiplied with I_H because the transmission line creates a phase shift in I_H?

QUESTION 2) How is following formula for the voltage at current source I_H defined? I've read that superposition is used here, so I guess one current source is observed in the circuit while the other is open-circuited and viceversa, then the two formulas are superposed. Yet, how was this done?

QUESTION 3) Lastly, I'm completely clueless as to why this is the impedance seen by current source I_S:


texts:
Currently following an schematic for NanoPI NEO4 to make my own RK3399 board.
On their schematic for the K4B4G1646D-BCK0,I noticed for pins DQ1-DQ15 on both chips connect to a randomised list of connectors from DDR0_D1 to DDR0_D31 and I was wondering why is that?

And also why are the numbers on the connectors different to the lines that they're connecting to, for example DQ7 I would expect it to connect to DDR0_D7 but instead it connects to DDR0_D3.

Second question in relation to the LDQS(F3)/LDQSN(G3) & UDQS(C7)/UDQSN(B7) connectors I plan to change out the ram chips for a different chip which is more widely available to purchase (AS24C256M16D3LB-BIN); however I've noticed that the LDQS/LDQSN & UDQS/UDQSN pins are completely missing from the datasheet and instead have been replaced with DQSL (F3/G3) & DQSU (C7/B7). So I was wondering how do I exactly go about connecting these up to the previously available connectors on the RK3399?

Finally I noticed on the manifesto for the Nanopi Neo4 that its meant to use 1GB of DDR3 Ram but in the schematic these K4B4G1646D-BCK0 are actually 4GB each so I was curious as to whether the wiring they have in their schematic for the DDR Controller on the RK3399 & DDR3 schematic properly utilises the 2 4GB DDR3 ram and allows the RK3399 to have the 8GB DDR3 ram readily available?

If anyone able to help answer and/or point in the direction of an answer, would be greatly appreciated.

DDR3 RAM Schematic

DDR Controller

AS24C256M16D3LB-BIN

**Neo4 Spec List*

Samsung Webpage for the K4B4G164D-BCK0 can be access via the link below:
https://www.samsung.com/semiconductor/dram/ddr3/K4B4G1646D-BCK0/

Edit: I was doing some digging about in the schematic and I noticed that the DQLS & DQSU on the AS24C256M16D3LB-BIN is essentially the LDQS & UDQS but the letters have been placed in a different order, so I would assume those are the pins I would be connecting. And as there is no connector with an 'N' on the end I would also assume I would simply be connecting up to DDR0_DQS0P-DQS3P and just ignoring the DDR0_DQ0M-DQ3M connectors on the RK3399?

2nd Edit: AS4C256M16D3LB-12BIN Datasheet: https://www.mouser.co.uk/datasheet/2/12/Alliance_Memory_4Gb_256M16_AS4C256M16D3LB_Bdie-Rev-1288929.pdf


texts: Why is it so expensive to produce cameras for non visible light?

texts: Typical consumer cameras can capture wavelength of 390-700 nm 400-1050 nm. But why is it so difficult and expensive to produce cameras for infrared, ultraviolet, hard x-rays, etc.? The only thing which differs them are the wavelength and the energy eV.


texts: Fuse configuration AVR dude for external 12MHZ crystal in Atmega 168

texts: I have 2 microcontrollers (Atmega 168PA-PU). So far I have run the following program in one of them (say mc1). Now when I run the same code in the other one it gives erroneous results. Someone suggested that the inbuilt RC oscillators give +/- 10% error in system frequency and that is enough to throw the device out of balance. So I have decided to use external 12MHz oscillator crystal and connect them to XTAL1 (pin 9) and XTAL2(pin 10) with 22pF capacitors (ceramic). I burn my programs with avrdude. What is the appropriate fuse setting I should use? The AVR fuse calculator confused me even further.


texts: Calculating Solar Requirements for a Refrigerator

texts:
I am attempting to run a refrigerator on solar power, it's "Energy Guide" says 410 kWh/year, so I assumed that it uses 46 W each hour (410 kWh / number of hours per year = 410 kWh / 8760 = 46 W), I really double that a refrigerator would require that very low power, or this is the running power?

The power consumed while the motor is running? and not starting?

Since I have seen that the power required to start the refrigerator is 10x that, so 460 watt required from my solar panel to run this fridge?


texts: Do I need more capacitance for my crystal?

texts:
I've used the formula "CL = (C1 * C2) / (C1 + C2) + Cstray" (where C1 = C2) to calculate the capacitors I need for my board.  CL is 18pF, I ballparked Cstray at 5pF, meaning I should use 26pF capacitors.  When I did so, I got this waveform:

Note that the center line is 0V, so this seems to have a good amount of swing above 0V, but then freaks out and doesn't go below it.
I don't feel like I understand the operation of this very well, and I'm trying to decide if this means I need more capacitance or less.  Is this an expected waveform, or have I done something wrong?


texts: Efficiency of Half wave Rectifier and input RMS value

texts:
Efficiency of the half wave rectifier is given by
\begin{align}
  \eta &= \frac{dc\ output\ power}{ ac\ input\ power} \\\\
\end{align}

with ideal diodes for the given Vin, we get the Vout as in the figure.

So for calculating the dc output power we consider only one half cycle, since diode is conducting during one half cycle.

My doubt is why do we consider one half cycle of the AC input to calculate Vrms and why not one full cycle. Peak inverse voltage of the diode is given by negative peak value of the input.


texts: DFRobot LCD shield minimum pin connections

texts:
I am connecting a DFRobot LCD shield (http://www.dfrobot.com/index.php?route=product/product&product_id=51#.UYWE0itxsVk) to a bareduino.  There will be no shield placed on top of the LCD and am looking to minimally connect it to the bareduino.

What I believe must be connected:

D4-D10
A0
5V
GND

Candidates for not being connected:

Reset
A1-A5
D0-D3, D11-D13
AREF
2 GNDS
3.3V
VIN

What pins must be connected?


texts: Does a simple bug detector detect electric field or magnetic field?

texts:
Hi.

This is a very cheap and simple bug detector that is supposed to make sound
when it detect RF signals between 100Mhz-2600Mhz.
I found out that it doesn't do what it supposed to do,since its
sensitivity is very poor.It detects signals of some mobile phones(while some mobile phones it doesn't detect),wi-fi transmitters,garage doors remote control signals etc.at a distance of maximum 5 cm in the best case.Thats all.
Regard to my description,What may be the method of that cheap bug detector:detection of magnetic fields,electric fields or maybe both?

EDIT:
This is the pcb circuit of the detector.


texts:
I've been working on some digital designs with I2C command & control and need a PC-based tool to test my interfaces. -- In the past, I've used iPorts (MCC) to do these tasks but the price tag of approx $500 each has always seemed steep.

What are some other available (hopefully cheaper / more robust) tools to help with this task?


texts: Mains Filter for Power Line Comunication

texts:
I have two questions about Mains filters and their impedance effect on PLC.

1) With respect to signal propagation relative to the Line impedance:

As the signal is sent, via the power line, it will take the path of least resistance. Therefore the line to the PSU needs to have a high impedance (greater than 50 Ohm) to ensure the signal is not sent to the PSU. What is the Max impedance I can add to my filter before the PSU stops working?

There are two PSU's I am using. The 5 Watt PSU and the 10 Watt PSU.

simulate this circuit – Schematic created using CircuitLab

2) With respect to the prescribed circuitry in the 5 Watt and 10 Watt data sheets.

There are a fuse and an NTC used in series with one another. The fuse is required to prevent fires from starting. I would like to know if a PTC could replace the function of the fuse. If so would having a PTC in series with an NTC be contradicting in their functionality, or would they just need to be placed far enough apart so that their temp's do not interfere with one another?

For question one the PTC and NTC resulting impedance will be included in the overall impedance of the filter.


texts:
I have a Tektronix 531A tube oscilloscope from the late 50s.  I recently bought some 20$ probes and noticed a lot of noise on the 0.005 volt/cm setting when that spring loaded hook attachment was clipped on.  When I bring my hand in closer to the plastic of the probe the ripple on the scope goes crazy and when I'm actually holding the plastic, it goes off screen on the 0.005 volt/cm setting.  When the spring loaded hook attachment is removed the noise level is normal and when I touch the scope's chassis with the same hand the probe is in, it returns to normal levels as well.

My question for this part would be if this was to be expected from a 20$ probe and if there is any way I can get less noise with this clip.  One thing that I should've mentioned at the beginning was that my house is old and has no mains ground in any of the wall sockets.  I mean the hole is there but it was never wired when the new standards came in.  I have done my best to ground the machine from its ground clip in back to my radiator, which has solved a lot of noise problems already on the higher settings like 0.05 volts/cm.  Now its just the noise at the 0.005 volts/cm as mentioned above.

This brings me to my second and last question.  Is it safe to take measurements with a "floating" oscilloscope that has no mains reference/grounding?  Will people be shocked if they're next to that radiator now?  I have read that if your machine is grounded, it is safe to measure battery powered equipment, isolation transformer stuff and basically anything else that doesn't have a ground connection where the circuit can be completed.

But what if your scope is not grounded?  (Haven't found much helpful information on this for such an old scope as mine although I have seen some for the newer scopes)  Is it still safe to measure battery powered and isolated stuff or is that now dangerous?

P.S.  I only do this for a hobby.  I have basic understanding of electricity and use my tools to repair tube powered equipment where voltages are in the 500+- range.  Is there any dangers I should be aware of and any fail safe techniques that I could use to save my oscilloscope because its the only one I've got.


texts:
Velostat and some other type of conductive fabrics change resistivity based on pressure, but I did not found information about its sensitivity regarding the temperature.

Is the velostat resistance very sensitive to temperature?


texts: Capacitive voltage divider frequency response and cut-off frequency

texts:
I'm working on designing a guitar pedal based on the topology of an old tube amplifier I own.
Between the amplification stages I found an inter-stage filter that I cannot understand in the frequency domain. After some research I understood that it is a capacitive voltage divider:

simulate this circuit – Schematic created using CircuitLab
I know that the filter is used for mixing some frequencies of the preceding stage (which produces the "clean", or un-distorted sound,) with the signal coming from the lead stage that is in parallel. However, for simplicity I'm focusing on the case of clean sound (lead circuit is open.)
I simulated the circuit and in this case the frequency response it is similar to that of an high-pass shelving filter, but the highs settle at about -10.5dB instead of 0dB.
Altering a single component value alters both cut-off and gain, eventually changing also the kind of filter. Indeed, I found an article stating that the transfer function of the voltage divider is:

Even knowing the transfer function I cannot find out what the zeroes and poles are, since I cannot turn the equation in to.canonical form.
I need a way of expressing the two cutoff frequencies and possibly the high and low frequency gains in order to adapt the circuit to my amplitude and impedances values, while keeping the same frequency response (or even altering it in a rational way, understanding what feature is affected by each component.)
Could anyone point me in the right direction?


texts:
Since my sleeping is very deeply, I can't wake up with alarm clock, I thought for a simple PIC-microcontroller project to wake me up. I will suspend a "bucket" full of water from the ceiling above my bed, and at a certain specific time, the PIC will move a motor that causes the water to fall on me :D :D.
But that is not a joke!!
Actually I can write some simple programs with mikroC for dimming a LED, making sound frequences, switches, transistors and relays, for example.

I have searched the web, found many motor types: DC, AC, servo and stepper, but have no idea about the suitable one for my project (it should be able to load a fully bucket). I want also to know how to run it.

Any help would be appropriated
Regards

EDIT:
I want the water to fall by degrees, hence the motor, not toppling it directly.


texts: How to Run 12v 1A Electromagnet From Arduino (3v) Without External Power Supply

texts:
I have a project that I am working on that uses a micro controller to control an electromagnet that I want to run with a 3.7 volt battery. I would like to reverse the polarization on the electromagnet to push and pull the magnetic fields to attract and repel a magnet (change poles). I understand that I need an hbridge to reverse direction of the polarity. I also understand that the h bridge can manipulate a higher voltage than what the microcontroller can supply.

My question is, How can I use the energy from the battery to spike to 12v on the supply voltage of the h bridge? The 3.3 volt is not enough energy to overcome the pole on the magnet. I tried with a 12v 2 amp power supply and the magnet flew across my desk ( this is the desired force). In the link below I am following this tutorial and design but they are using a 12v power supply. I would like to keep the power source singular.

I have researched inductors, capacitors, and even OP amps. My goal is to try to use the 3.7 battery that powers the microcontroller to increase the voltage/amps quickly and have the voltage available to the high input side of the hbridge and exclude a 12v power supply.I have been leaning towards an inductor but I am not sure. The voltage increase will only be for about 500 miliseconds to release a magnet.What should I use?

If there is a big fundamental that I am missing, I apologize.

Here is the setup so far:
Following tutorial here:
http://www.instructables.com/id/How-to-Control-an-Electromagnet-with-an-Arduino/

Arduino Uno or Teensy 3.1 (3.3v supplied by 500mah LiPo)
Hbridge SN754410


texts: Max input/output voltage/current of CD4060 & other ICs

texts:
I’m learning to build clocks using sequential logic. One thing I don’t quite understand from the data sheets is the max input and output current that comes out of ICs like the CD4060 and CD4026.

I’ve chosen to run my project on 5V DC. I want to operate the ICs within their recommended currents but I don’t really understand all of the values listed on the data sheets.

For instance if I power my CD4026 on X amount of current, what will the current be on those output pins which go to my LED displays? Equal to the inputs?


texts: Can I measure current in antenna? What is the difference between current in closed AC circuit and current in antenna?


texts:
When we say, for example, an antenna has spec of 22 dBi;
Does it mean that its power is 22 dB stronger for any point at fixed direction than if it were to emit spherically?


texts:
I want to build a real-time phase error correction circuit to correct the phase degree error of a feedback loop to prevent oscillation.
For this I need an electronically controlled phase shifter for frequencies between 10hz and 20khz.
I want it to simply offset the phase of the entire input signal fully intact.
Can this be done?


texts:
I have a question based on low pass filtering. If I input a signal to this low pass filter, why does the output file have an AC (of very low frequency).

The input signal is$$ v_i(t) = 2 + sin(2*pi*100Mhz*t)$$ According to the filter response, the $$ sin(100Mhz*t) $$ should be attenuated by a very large number, thus resulting in a coefficient << 0 and leaving the DC component of 2 left.  The output however is $$ v_o = 2 + sin(2*pi*0.1t) $$

Where does that AC signal come from?


texts: Why adding capacitor to a 10x passive oscilloscope probe

texts: I'm trying to understanding input impedance and its circuitry of a simple, passive oscilloscope 10x probe. From reading Input Impedance of an Oscilloscope and the video EEVblog #453 - Mysteries of x1 Oscilloscope Probes Revealed, I don't understanding why we add these capacitors in the probe circuitry and make things more complicated. The point is to add enough impedance to a passive probe to minimize loading effect of the circuit being measured. A big enough resistor will do and the with just resistors, voltage divider works the same for both AD and DC source regardless of frequencies. If there are intrinsic reactances in the wiring, then can't we just add a big enough resistor in series with those to make any reactance negligible?


texts: low voltage cut off for 1-cell lithium battery

texts:
I am designing a device running on a 1-cell lithium battery.

I am really struggling to design the low voltage cut off.

This document seems to be a very good solution, but those old parts can't be found anymore.

Later on, I found this link. I think it could be a good solution but this circuit draws 100uA which seems to be a lot...

Do you have any good and cheap solution for a low cut off voltage for a 1-cell lithium battery ?

If you think that using TLV431 is still a good solution, then could you help me selecting the right resistors values as I can't find what those should be in the datasheet?

If it can help, I already use an LDO 3.3V regulator: MCP1700

Thank you very much!


texts:
In a neon tester, how does the body complete the circuit even when it's insulated from the ground by footwear and the bulb glows?
I mean is current flowing to the neon bulb?


texts: Can a capacitor be used for overvoltage protection?

texts:
I'm replacing the capacitor for a start motor that had previously burnt up. I'm new at this. I previously referenced the following questions about replacing caps with higher ratings than spec'd:

High Voltage Capacitor, in a low voltage system?

Can I swap an electrolytic capacitor with one with a higher voltage?

selecting voltage rate for capacitors

The general consensus from the answers above, is that it's best to run a bit higher, typically 1/3-2/3 over. My motor's cap is spec'd at 250vac. I'll be running 120vac, where my motor is spec'd at. I can only find 440vac's readily available.

My question is, with LARGE voltage differences above a spec'd capacitor/equipment rating, is there not risk of damaging equipment not rated for those potential maximum overages? For instance, a 440vac cap may let 400vac by, whereas a 250vac cap would in theory have already failed. In essence, do capacitors act as potential fuses during surges and should one take this into consideration when trying to protect equipment behind them?


texts: Triggering of TRIAC for Crowbar Protection

texts:
I am reading the datasheet of TRIAC (T1235T-8G). I am not sure how to trigger the TRIAC and what do they mean by maximum Vgt voltage (Page 2, Table 3).

Basically, I want to use that TRIAC for crowbar protection and I want to select a mechanism to trigger the TRIAC.

Note: Ignore the LM431 in the picture as I would be using some other reference IC.

Picture taken from here.

I want to use the TRIAC in Quadrant 1 (because of it's sensitivity). I have few queries:

Does TRAIC for Quadrant 1 will be triggered for any positive gate voltage (but gate should have minimum Gate current of 1.75mA)? So, how can I calculate minimum gate voltage required to latch the TRIAC?
What do they mean by Maximum Gate Trigger Voltage? Does it mean if I apply more voltage than the maximum, then TRIAC may get damage?


texts: Clock frequency of FPGA circuit and 4-bit counter

texts: I have implemented a 4 bit counter using HDL. Now I have downloaded the code to an FPGA kit with a 50 Mhz oscillator. This means that the clock period will be equal to 0.02 microseconds and consequently we will not recognize the counting process if the 4-bit output will be implemented on a 4 LEDs. So to solve this problem, I have changed the code so that the counter output signal will be equal to 28 bit and then I have coupled the 4 LEDs with the 4 most significant bits (24,25,26 and 27) so that I can recognize the counter as now the counter will count on 28 output bits instead of just 4 bits. Now, I need to prove these using equations or in other words, I need to quantify this effect to prove that this will work and the counting process will be notified by users of FPGA in my presentation for this small project. So how do I quantify it?


texts: How can I drag-select components in a room in Altium?

texts:
I have a PcbDoc in Altium Designer with several components in a room. I want to select some components by dragging a box around them.

I can select them if I start dragging in the gray or black areas. But if I start in the red room, I reposition the whole room.

So I double-clicked the room and locked it.

Still, I can't start a selection box inside the red area. What's the trick?


texts: This is probably relevant for all SPI compatible chips but I'm asking for the DRV8711 in particular. The data sheet lists the SPI timing requirements and I was wondering how to get the maximum data rate supported by the device. The host MCU is STM32F103C6 and it needs to set a prescaler value to set the data rate.


texts:
I have a JTAG chain connecting 4 Spartan 6 FPGAs that I program using ISE iMPACT. The software can program any strict subset of the 4 FPGAs in a row successfully, and in any order. However, when I attempt to program all four FPGAs, the DONE pin of the last FPGA does not go high, and the programming fails.

What could be causing this strange behaviour?

Notes:

After programming three of the FPGAs, the INIT_B bit of the status register for the fourth FPGA is 0, although the INIT_B pin is high. Right before programming the third FPGA, that bit was 1. This suggests the fourth FPGA has locked up.
When programming with SelectMap, I can program all four FPGAs without any problem.
When I program three of the FPGAs using SelectMap, the fourth one still cannot be programmed using JTAG.
Each of the four done pins are pulled-up to 3V3 through 4.7K Ohm resistors, and then tied together.

Things I have tried:

Disconnecting one of the FPGAs from the chain allows for the remaining 3 FPGAs to still be programmed.
Swapping the 4.7K Ohm pull-up resistor of the last FPGA for a 330 Ohm resistor doesn't solve the problem.