texts:
I'm building a mechatronic system that consists of 1)XY Gantry controlled with PIC32 and a DIY motor shield and 2)control box with PIC24 three potentiometers + room for expansion, typically located fairly far away. The two systems are to be connected using an XLR line because this is in an audio setting.

In designing the system, two big concerns have been to not introduce noise into the rest of the system, and to comprehend the ground loop problem. My knee jerk as an EE student was to use Op-amps to interrupt the ground loop. The plan was to send the three signal lines from the wipers of the pots over xlr, and to use the control system ground to measure the differential voltage at the system. I went to great pains to design something that would work with a true rail-to-rail swing. Works decently well on the bench, and I think this would work for the final system, but it seems like im turning into the guy who only has a hammer in the toolbox.

So I get to thinking about I2C. Allows plenty of room for expansion, and it only takes up two lines. Potentially, this means the system that was going to take two XLR cables might only need one now. So, here is the system I envision:

This image is ommiting the pull-up resistors on the bus AND the XLR's SHIELD. I plan on having pull-ups on the three segments of the bus (pre-buffer on both ends, and on the buffer.) The CLK will be operating relatively fast, so I don't want to introduce EMI into the audi0 lines as they will all be sharing an XLR bus, So im wondering how to properly connect the grounds. I've read the RANE notes, and from what I gather, to make a functioning faraday cage, I need to connect both chassis to the cable shield to make a complete enclosure.

My confusion is this: chassis ground is becoming an extension of the shield to keep out EMI. A lot of what people write assumes that you've got earth ground handy, and that you might tie earth, signal and chassis together at some point, via a direct, RC coupled, or diode coupled connection. First off, it has occurred to me that I don't have earth ground at my circuits via DC barrel because I'm sitting on top of two different power supplies via a switched and transformer coupled power supplies. So, do I tie the shield to the signal ground (barrel sleeve)? If so, with direct, RC or diode? My thoughts are yes, and to use an RC circuit with <= 100Ω. In a bad case - where the power supply grounds 1&2 are very different - will the offset at ground affect my logic levels? The P82B715's are supposed to be 'level translating'.

Thanks for the input.


texts: I want to put together a simple library to communicate between stm32f429 and pc via usb cdc vcp. I noticed many examples from stm create a usb uart bridge on the mcu. I am trying to understand the usefulness in this. Why is the uart needed? Can you not communicate directly via usb cdc to pc? Perhaps the main feature would be setting a specific speed? Not sure, could somebody help me out. Thanks


texts:
I'm building a sort of "screwdriver antenna". In my case I have a motorized roller inductor. This motor is placed near the bottom of the coil (the coil is placed near the center of the vertical antenna. In this photo of the antenna it's still missing a few more meters of top radiator. The red wire is the lower radiator. The black wire is DC power to the arduino).

As a test, I used a small but strong servo motor modified for continuous rotation. The antenna worked OK, I got it to tune in the calculated range. My idea is to replace that small servo with a decent stepper motor (so I can just count steps to jump between bands for rough tuning).

But having an arduino up there isn't a great idea. It's RF hell. There are rather strong E and B fields which would cause it to malfunction or just fry. I'm not sure if shielding it would help.

So I thought of just using very long leads (about 6-8M) between the stepper motor and its driver. I know it's not a good idea to do this, but, will this work? Would the driver get damaged?

Most antennas of this type are smaller than what I'm building. They use a mechanical linkage and keep the motor at the bottom. I want to avoid this as this would have other problems: finding a suitable material for the driving rod (I can't find fiberglass rod or tube long enough for my application), and the tolerances required for a mechanical linkage that needs to flex with wind (I will use ropes to hold the antenna but that doesn't mean there won't be some flex). Obviously, once finished, the coil will be covered from rain.


texts: Current and Voltage opposite polarity power supply

texts:
Is there an instance where a power supply can generate a current that is the opposite polarity to the voltage, exactly 180 degrees out of phase?

If so is this power able to drive any electronic load?


texts: Effect of power supply ripple on ADC readings?

texts:
I want to use an ADC (AD7124 that is a 24 bit sigma/delta) for 14 bit readings of an external voltage. My power source is a fairly stable 24v DC supply and the ADC runs on 3.3v. I will be using the internal 2.5v voltage reference of the ADC.

I'm planning on using a MC34063 switching dc-dc converter to reduce the voltage down to 3.3 volts. Some say this is a bad idea because of the voltage ripple and spikes on the output of switching supplies.

The only effect I can think of that voltage ripple has on ADC readings, is on the internal voltage reference. According to the datasheet, the internal reference has a "power supply rejection" value of 85 db. I'm guessing power supply ripple is attenuated by 85 db and then appears as an error on the internal reference.

Question 1: Is this correct? If yes does this change with frequency? The datasheet has nothing on frequency.

Question 2: How else does power supply ripple affect ADC readings?

Question 3: If using a step down switching supply is a bad idea, will adding a L200c linear regulator solve the problem? (L200c is probably overkill but I need the current limiting function and that is the only thing I have available)

Thank you


texts: Embedded C - USB stack, arm-none-eabi-gcc settings and Matlab interface

texts:
I am using LPCOpen (latest realese available for LPC4370) and the usb stack provided within it.
I need to build a simple FSM to control the mcu with Matlab and send data from Matlab to the mcu and from the mcu to Maltab. (here another question from me on the same topic)

FSM: I'm using char as commands (e.g. Matlab sends 'o', the mcu starts data output
DATA TRANSFER: I'm sending data in bulks of 128 32 bits integers each

So as far as I understood I need to implement a CDC USB host.

LPCOPen provides the following examples to start with (and no documentation other than read-me files)

usbd_rom_cdc_uart: The example shows how to us USBD ROM stack to creates a CDC UART/Serial port bridge.
usbd_rom_cdc_vcom The example shows how to us USBD ROM stack to creates a virtual comm port.
usbd_rom_dfu_composite
usbd_rom_hid_generic
usbd_rom_hid_keyboard
usbd_rom_hid_mouse
usbd_rom_hid_sio
usbd_rom_libusb: The example shows how to us USBD ROM stack to create simple USB data pipes.
This example provides libusbdevice encapsulation with simple to use API for
non-USB experienced users to develop simple data-pipe applications.
The example is tested with http://libusbk.sourceforge.net host side applications.
The examples also shows how to handle WCID requests to install libusbk driver.
Check https://github.com/pbatard/libwdi/wiki/WCID-Devices for more details.
usbd_rom_msc_ram: The example shows how to use USBD ROM stack to creates a USB MSC example
that uses RAM. The device appears as unformatted disk with size as 32KB.

Among the above are two examples which I think could use: usbd_rom_cdc_uart and usbd_rom_cdc_vcom.

usbd_rom_cdc_uart is enterely IRQ based and it was not clear to me how I could send/receive data.
it's main loop looks like:

while (1) {
    /* Sleep until next IRQ happens */
    __WFI();
}

So I started with usbd_rom_cdc_vcom which does a loop-back:

DEBUGSTR("USB CDC class based virtual Comm port example!\r\n");

while (1) {
    /* Check if host has connected and opened the VCOM port */
    if ((vcom_connected() != 0) && (prompt == 0)) {
        vcom_write("Hello World!!\r\n", 15);
        prompt = 1;
    }
    /* If VCOM port is opened echo whatever we receive back to host. */
    if (prompt) {
        rdCnt = vcom_bread(&g_rxBuff[0], 256);
        if (rdCnt) {
            vcom_write(&g_rxBuff[0], rdCnt);
        }
    }
    /* Sleep until next IRQ happens */
    __WFI();
}

So I tested this on a terminal and then tried to move on and use Matlab.

What I found more difficult doing the small messaging.
Here some code snippets.
From matlab side:

fwrite(serial_object, K_COEFF,  'int32');
if K_COEFF ~= fread(serial_object, 1, 'int32')
 error('out of sync');
 end
pause(0.0005)

fwrite(serial_object, L_COEFF,  'int32');
 if L_COEFF ~= fread(serial_object, 1, 'int32')
 error('out of sync');
end
pause(0.0005)

C counterpart:

/*SET K*/
while(!rdCnt)
{rdCnt = vcom_bread(&param_rxBuff, sizeof(int32_t));}
K_COEFF = param_rxBuff;
vcom_write((uint8_t*)&param_rxBuff, sizeof(int32_t));
param_rxBuff = 0;
rdCnt = 0;

/*SET L*/
while(!rdCnt)
{rdCnt = vcom_bread(&param_rxBuff, sizeof(int32_t));}
L_COEFF = param_rxBuff;
vcom_write((uint8_t*)&param_rxBuff, sizeof(int32_t));
param_rxBuff = 0;
rdCnt = 0;

where vcom_bread and vcom_write are usb stack calls.

Now, this is working. Sometimes.

Some other times the communication goes "out of sync" and Matlab just hangs on printing warnings about the microcontroller not responding.
What I noticed is that this depends largely on timing and so also on the compiler settings: I am using arm-none-eabi-gcc and the more I optimize (e.g. O3) the less it works.
Does anyone have similar experience of some kind? What should be the best way of interfacing Matlab with an mcu?

EDIT1:
As suggested I tried to modify the matlab side:

fwrite(...)
pause(0.001);
flushoutput(serial_object);
flushinput(serial_object);
fread(...)

Unfortunately to no avail. Matlab is still warning me about unsuccessful read.


texts: Any way to identify "directionality" of electret microphones?

texts:
Picked up a handful of electret microphones from a local component store, and store owner claims them to be generic. He calls all components generic for which there is no data-sheet or specific part number.

Wondering, if there is any way to determine if these are uni-directional mics, or omni-directional ones ? Doing some search to see if there are any distinguishing physical characteristics, I came across pictures almost the same, just that few seem to have 3 leads, and most have 2 leads.

Edit:
This is an alternate approach I am trying, by replacing the electret microphone that came with an el-cheapo baby-monitor, which is definitely omni-directional, and currently results in pretty terrible howling, when the 2-way talk feature is activated. The other approach is in-discussion (as some might have seen/noticed) in this question.


texts: How to find efficient hardware implementation of sbox of lightweight block ciphers?

texts:
Lightweight block ciphers are usually optimized for compact hardware implementations and sbox values are computed by implementing circuit using basic logic gates(AND, XOR, OR, NOR etc).

What is the method to find an efficient hardware implementation of a 4-bit sbox?

For example, the Sbox of the Piccolo cipher is

which can be computed in hardware by

The solution I could think of is "find Algebraic Normal Form(ANF) of all boolean functions, and then make the circuit". But this does not seem to produce a compact representation.


texts: My RT8272 buck dc converter fried in my test charging circuit for arduino

texts:
I'm building a circuit to power an arduino and later a stepper motor from a 3A 24V DC source. The DC power source is a switching power supply, much like those used in notebooks.

I'll need after powering off the circuit, 3-4 seconds of charge in the arduino for selective powering down the stepper driver.

So I built this part of the circuit for testing an electrolytic capacitor as a backup energy for this power down sequence after switching off the circuit. Arduino is not connected yet for safety, only the DC-DC converter, so no load in the test so far.

I'm using a 3.300uF 50V electrolytic capacitor, but I can get one of 10.000uF if needed. I'll probably need no more than 100mA of charge in the Arduino + Stepper driver to perform this selective shutdown later.

I'm using a RT8272 based DC-DC buck Driver, as this one over ebay.
RT8272 Dc Buck Converter

I switched-on this small circuit on and it worked, charged the capacitor in maybe 4-5 seconds and, with no load connected, only the RT8272 DC buck converter, and I got 5V on the Vout of the converter.

I then switched off the circuit and even with no load, the capacitor slowly discharged (probably the DC converter drew a bit of current, keeping the 5V in the Vout as the capacitor discharged), until the capacitor gets lower than 5V.

I only kept two multimeters measuring the voltages on the capacitor and on the VOUT of the Converter (5V).

But when I turned on the switch on again, allowing the power supply to recharge the capacitor and supply the DC converter (the capacitor was at 3V, not fully discharged) the DC Converter fried...

Capacitor is still working, power supply also is still working normally.

The stepper motor and high current part of the stepper driver  are powered by a 24V line that is not in the same path of the capacitor. So the capacitor is needed just for 5V Arduino and 5V for keeping the stepper driver on for a while after it’s high current part get’s shut down. It won’t have to power the motor. But this circuit is not connected yet, just what the diagram shows so far.

What did I do wrong so far? How could I improve this initial circuit to prevent this from happening again?

Could the DC-DC Buck converter had such an increase of current when I switched back on the Power supply, to fry it, even with no load attached to it so far?

Thanks a lot for reading!


texts:
To begin with, I have two 100 watt solar systems. One on my roof, 2 panels which produce 100 watts / 13 volts DC fed too a controller rated at 20 amps.
The second is 4 25 watt panels arranged to produce 100 watts at 23.5 volts. This is my portable unit.
When not on the road I want to connect the portable unit to help charge the house batteries. Currently I have 4 12 volt 15 amp batteries connected in parallel to produce 60 watts. Looking to replace and upgrade later.
The question is how to connect the two systems together to more rapidly charge my system when at home?


texts: Replace a micro switch with the correct type of transistor

texts:
Below is a micro switch used on an existing circuit, which turns on/off a load in a DC circuit.  I'd like to replace the micro switch with a transistor, since I'm controlling the load using an Arduino which uses a high/low, and not a tristate.  But I don't know how to look for a compatible transistor.  The specifications on this micro switch seems to work for both AC and DC, despite having "VDC" listed in the specifications.  The circuit I'm working with has a load which only needs 3V.

What type of transistor should I use instead of this micro switch?

Micro Switch:

L62,Micro Switch 15A,125 or 250 VAC 3/4 HP 125 VAC 1 1/2 HP 250 VAC NC

https://www.ebay.com/itm/L62-Micro-Switch-15A-125-or-250-VAC-3-4-HP-125-VAC-1-1-2-HP-250-VAC-NC-1PL29750-/182962174497


texts: Using voltage regulators for a computer harddrive

texts:
I've got an Intel NUC (NUC8I3BEH3) that's using its own 19V, 90w power supply (pictures).

After a few issues with 4TB 2.5" hard drives, and external USB disks, I'd like to use a 3.5" drive, but the NUC's internal SATA power connector does not support this (doesn't provide 12V).

I'm considering an aluminium case (Hammond diecast enclosure, 1590DBK, 187x119x56mm), that's screwed on to the Intel NUC's 2 mounting holes, with a larger hole in the base to route the power, data cables, and maybe allow some air flow.

For power, could I run a wire off the 19V power supply (internal), in a safe way to power a 4TB Western Digital Red hard drive (WD40EFRX), which needs a 5V and 12V supply, 1.75 amperes (peak), at 4.5 watts.

Maybe using two linear voltage regulators to provide 5V and 12V (e.g. L78S05CV and L78S12CV)?

These can accept an input up to 35V, current up to 2 amperes, and have a thermal resistance of 5 °C/W junction-case or 50 °C/W junction-ambient.

Or, as per @bimpelrekkie's suggestion, a fixed switching regulator (e.g. LM2596T-12 and
LM2596T-5.0.

But I'm not sure:

Would this be appropriate for a hard drive? Can it provide a clean enough power supply, and keep running for a long period of time (4+ years).
Would it produce too much heat? I'm considering getting some 20x15x10mm heatsinks, with 3M screws, for the 3.75mm hole.
Is there a good way to connect them to the aluminium case, assuming a heatsink? I don't think solder works, or thermal tape would hold well enough, so maybe an epoxy that can also handle high temperatures (just to be sure.)
Will the 90W power supply be happy with the extra load? The computer currently uses 25W while running both of the CPU cores at 100%.
Where I'd connect the 19V supply to the 12V regulator first, should the 5V regulator connect to the 12V (so there is less of a drop from 12V to 5V, maybe helping with heat/life,) or should I connect it directly to 19V (so there is less current being pulled though the 12v regulator?) i.e. series or parallel?

Is there another way of doing this? Maybe two DC-DC step down buck converters? I've never used these before, they do look interesting, but I don't know how reliable they are.

And is there anything else I should consider with this setup?

Previously I've used a separate power supply, with an external USB hard drive, but this has introduced 2 extra wires, and where this computer will be in an office 4+ hours away, I don't want to do that journey because one of the cables have "fallen out" (at least if the computer only has 1 cable, I can get someone non-technical to check it).


texts:
https://en.wikipedia.org/wiki/Charge_pump

  A charge pump is a kind of DC to DC converter that uses capacitors as
  energy-storage elements to create either a higher- or lower-voltage
  power source.

Is it possible to create a charge pump without using capacitors? What characteristics of capacitors make them useful in charge pump applications which are normally seen in level shifters?


texts: I'm using an XC6210B332MR-G 3.3v LDO and I want to ensure good resistance to transient ringing at boot. The datasheet stipulates a bypass and output capacitance of at least 1uF for 1.8+v output. Would there be any downsides to using a 22uF X5R MLCC? I've done some research and from what I understand, larger capacitance values will help reduce the load transient.


texts: Why does the MOSFET in this circuit stay ON after a momentary trigger?

texts:
The MOSFET in this video turned ON and stayed ON after one momentary shorting of the 9V to the gate.
i always thought a MOSFET stays ON only while voltage is applied to it's gate.
at first i thought it may be a special type of MOSFET
but then i read in the description that "Any MOSFET can be used"
What am i missing here?

https://www.youtube.com/watch?v=MsEwDjl7P1Q

The circuit diagram from the video description


texts: Boost capacitor sizing, gate driver LM5106 used with N-MOSFET IPP075N15N3 G

texts:
I am using a TI gate driver LM5106 and I wanted to size the bootstrap capacitor. The application regards a synchronous boost converter. According to pag. 13 I need the \$Qgs\$ charge of the MOSFET that I am trying to switch. I am using the MOSFET IPP075N15N3G.

What IPP075N15N3G datasheet value should I use to size the boot capacitor needed for the gate driver? I am unsure if I should use the gate charge \$Qgs(max)=40nC\$ or the gate charge total \$Qg(max)=93nC\$, reported in page 3 and why.

Thank you so much,

Lello


texts: Troubleshooting noise pickup near AC motors

texts:
I have a 2-layer PCB with ADC communicating using SPI. This board is to be used with a National Instruments (NI, LabVIEW) FPGA, with a clock rate up to approximately 600kHz (higher would be nice, but this is the immediate requirement).

The board will be used near a pair of moderate-sized AC motors. When the motors are not powered, everything works fine. Once the motors are powered, I observe large amounts of electrical noise on just about everything. The communication breaks down and the data output is junk.

In case this information is useful, holding a BNC cable with two clips in the air shows voltage oscillations on the order of 500mV pk-pk; clipping these together takes it down to ~10mV pk-pk when observed using an oscilloscope.

The cabling in use is 28 AWG, 10 core (5 twisted pairs). 8 wires are signals, with a pair used for +15V and Gnd connections. Logic levels are 3.3V on the other lines. The twisted pairs aren't related, although I aimed to put the two highest frequency lines (SCLK, D_Out) with the slowest changing (essentially DC) lines to try and mitigate cross-talk.

The shields of the cabling are connected to the ground of the PCB and disconnected at the instrument end. Should this be reversed? (does it matter?) It's my understanding connecting both ends might/would lead to ground loops - is this correct, or did I completely misunderstand the principle here?

The 8 signal lines are connected to BNC lines, but the shields of the BNC cables are floating. The instrumentation specifies/expects a 50 Ohm cable. http://www.ni.com/pdf/manuals/374614a_02.pdf

How much should I be concerned about load mismatch at these frequencies? What can I do to mitigate this issue?

What should I be doing with cable grounds, connections and terminations to avoid being overwhelmed by EMI/noise?

Edit for basic drawing (even though there are 4 inputs available on the PCB for +ve, -ve PS, only two wires are available, so just one ground connection. The other can be used to connect the shield if desired):


texts: The Frequency Compensation of LT1683 in a DC-DC Converter

texts:
The fig. 10 of  Jim Williams's article presents a 2A laser current source circuit using the LT1683. I am confused about the frequency compensation circuit of fig. 10 (pin 12 Vc of LT1683). The page 8 and 16 of LT1683 datasheet describe the operation of frequency compensation using a series RC network. The RC network could be analyzed using a pole and zero theory to compensate the loop stability. But I do not understand how to use a BJT(Q3 in fig. 10) to realize it.
Could anyone give any suggestion?

Any comments are appreciated.


texts: colpitts oscillator with jFET not working

texts:
I decided to build a colpitts oscillator using a jFET (2N3819):

It seems to work fine @ http://www.falstad.com/circuit/ but when i try to build this circuit it does not work, any ideas?

Thank you in advance.


texts: Replace mechanical switch with transistor? MOSFET? Relay?

texts:
If I have a switch in some consumer electronics that I take apart, and want to replace a mechanical switch with a digitally controlled one, which component should I use? The only problem I see with MOSFET/transistors is don't I need to know if it is going to be a high side switch or a low side switch? What if I don't have access to the whole circuit when choosing?

Just wondering if there is a rule of thumb for choosing which method to replace a switch I'm missing.


texts:
I designed the following simple circuit. I used an Arduino PWM digital pin as input (500Hz at 3.3V). I choose the FDD4141 because of his Low Rds(on). It is around 18 mOhm. The dissipated power at 1.3A should be around 120mW.
When I tested the circuit I noticed at 40% of the duty cycle that the MOSFET becomes hot. About 55 degrees in room temperature. That is far from the consumption of 120mW.
Can you suggest to me another MOSFET or circuit that could work similarly?

simulate this circuit – Schematic created using CircuitLab


texts: Why are E and B field in phase in far-field electromagnetic wave propagation?

texts:
I am very frustrated with the fact that the E and B field of an EM wave are in phase in the far-field case.

Before I get into this question I am letting you know that I already read this link related to my question, but it didn't really help me so much.

First, I know that an EM wave propagates as shown in the GIF below.

But, how are E and B field in phase?
According to Maxwell's equation #3 and 4, we know that the change of E field induces B field, and vice versa. I also attached these equations below. I deleted the J term since we are talking about  the far-filed analysis which lets us ignore the B field induced by the current flowing, J, in the wire.

Let's assume that the wave propagates along the x-axis.
According to Maxwell, when there is a maximum E filed occurs (dE(t)/dt = 0) at a given point, x0, a minimum B field (B=0) should occur at the point. This should result in 90° phase difference between E and B field.

I know that we can calculate and prove that the EM wave propagates at a speed of light from Maxwell's equation #3 and 4 as shown below (source).

But the problem is that I don't know how to solve partial derivative equations (PDEs), and also I want some visualizations to understand this phenomenon better.

Is there any easy way to visualize why it is like this without solving PDEs?

Thank you.


texts: How does current flow through this Arduino circuit?

texts:
I must admit I'm rather ignorant of all things electric, so I got an Arduino with the intent of filling this gap in my education, and also learning more about the physics behind programming and do low-level stuff, but I've not found a proper theoretic introduction to exactly what's going on within the device. I can only find plug-things-like-this type tutorials.

So, for example, here is a breadboard diagram of the blinking LED tutorial (pdf)

It seems to me like the wire connected to the 5v pin is connected to the + pins of the breadboard... which are connected to nothing. There's nothing else on the + column.

So isn't this an open circuit? What exactly is that + -- 5v connection doing?

That connection is not drawn in the schematic diagram.

Nor is it clear to me how pins are connected within the arduino itself.

I know this is a basic "google it" question, but probably due to the fact that I don't have the vocabulary to do so I've not been able to find a description of current flow in an Arduino.


texts: Anomalous modelsim output, when to ignore, when to fix?

texts:
im in the process of designing a few digital circuits, and have experienced a small bug with my state machine.
Looking at the modelsim output we see:

The small 6000ps pulse should not be there. But I have reason to believe there is something more sinister going on.
For example, looking at what drives the `iLoad1 signal (which is the one causing me errors)

so here we can clearly see iLoad = (s0)(!s1)(s2), however looking at the model sim output, the three traces above iLoad, s0, s1 and s2 are all logic 0 when iLoad is asserted. So, clearly iLoad should also be zero.
The only additional information I can give is that both the NAND and inverter have a 1ns propagation delay.
Could anyone perhaps explain why I'm seeing this anomaly - should it be ignored if its only 6000picos long?
Thanks


texts: I was reading about the types of diodes, including those that can be used to generate microwaves, and I found myself confused about the material I found on it.  This link discusses the differences between three kinds of diodes, but I'm simply having trouble interpreting these diagrams that I come across, because I'm unclear about what p+ and n+ mean vs p and n in a diagram.  I think that p and n are used to represent positively and negatively doped semiconductor material, but I'm unclear with these diagrams that use pluses and minuses in addition to n and p.


texts: VU meter from line input or speaker input?

texts:
Is any of the the two following schematics for Line input? Or is it for the amplified signal that goes to the speakers?

 ( source )

 ( source )


texts:
I have testing sensor node with Arduino.The setup is Temperature sensor + Arduinoboard + Battery + Solar panel + Xbee for wireless transmission. It is placed on outside home. (hot weather).

The sensor node is using  3.7V /6600mAh battery with Arduino (Seeeduino; it is based on Arduino). The battery charged with Solar panel. I am reading Analog Pin  7 for   battery value to calculate battery %. I think it is a 8bit resolution ADC (0 to 255).

Generally, I noticed, the battery percentage curve goes higher before it dies.
Like  10 to 12 hours before it dies, i.e battery decrease.
Usually, if the Sun light is good, it last for many days. If not, the battery decrease gradually and become Low, and increase suddenly for few hours  and stop completely. When measure the voltage of that dead battery; it is around 2.8V.

I am not sure, why this sudden increase happens? Is it because of Lipo battery or Arduino (Seeeduino) reference voltage is not accurate  when battery is low.

update:

Thanks for the info. You are right: Arduino AREF is default and it is 3.3V. If i understand correctly,
Even the battery initial voltage is 4.2v but AREF is always 3.3v.So, battery is below 3.1v and regulator output also 3.1v? Right? But the ADC does not know this voltage drop and always reference from AREF voltage. Hope, i got it correctly.

Another point is is voltage below 3.2 the Zbee stops working, So, there is not much useful even if i add Voltage diver with Zener. Right?


texts: Soldering QFP with thermal pad (but with obstructions/no vias on underside)

texts:
I will start by saying that I'm a complete newbie when it comes to soldering SMD. I've been practicing with scrap boards, and I'm getting there, but not sure how to approach this one.

I am trying to replace a TSB81BA3E, which is in HTQFP package i.e. QFP with a PowerPAD underneath. I managed to desolder the broken chip OK with hot air (hard work!) and have cleaned all the pads/removed solder from the old thermal pad.

All the guides I've seen on how to solder this chip involve heating/applying solder to vias from the underside. Unfortunately this board has SMD components on the underside, and no vias to heat through. I also feel like I can't put the board in an oven as there are a lot of plastic connectors on it.

My proposed approach is the following:

Pre-heat board to 150c or so, using heat gun at a distance (and
laser temperature gun to assess temp.)
Apply tin/bismuth solder to central pad
Apply Sn63/Pb37 solder paste to pins
Heat chip at somewhere around 220 degrees until it appears to seat itself (datasheet specifies max 260 degrees for 10 seconds on this chip, so say max. 30 secs at 220 degrees?)

Does this sound reasonable? My thinking for using the tin/bismuth is its lower melting point - I'm imagining the reduced strength of its joints would be OK used on a large area such as thermal pad.

Any advice greatly appreciated!


texts:
I tried to design a step up SMPS to create ~200-300V from a 24V input with an expected power of ~12W max. Since the project is for a hobby, I chose to attempt a hybrid boost-flyback converter to get the needed voltage gain with a reasonable duty cycle. I think i have a non-stable system at some output voltages, there is a low frequency ~7Hz triangle wave of ~10V on my output of 250V. Other then that it seems to work fine with ~85% efficiency. When I tune it to a stable voltage (~50% of random voltages are stable), there is no low frequency ripple, only the expected ~1V output ripple at the switching frequency.

For compensation I made some assumptions (transformed the load / output voltage to primary side) and followed a typical boost compensation procedure. I attempted to follow suggested design steps in the PMIC (LM3478) datasheet. I added a low frequency pole but, apparently that did not work so well.

Basically I built a compensation network for ~48V output, with a ~1.5mH inductor, ignoring the fact it is a flyback. Any easy ideas of how to stabilize the output? I'm at the point to blindly play with the compensation network and see if it changes anything.

I used the following app notes for the basis of my design:
AN-5081,
AN-IPS-08

Design Info:

\$ f_s=120kHz \$ ;   \$  V_i = 24V \$ ;   \$ V_o = 200V-300V \$
Load is steady, resistive.
Transformer is 2 mil air gaped, 52uH Primary, 1.8mH Secondary, 1:5.6 ratio.

Any ideas to better stabilize the system would be helpful... Unfortunately Controls was not my forte in collage.

Image showing event I am talking about:

Steps I have Tried:

The controller uses current mode feedback as well as voltage, I overcompensated the current feedback to almost disable it per the data sheet, it had no effect. This is not sub harmonic anyways...
I have tested with multiple loads ranging from 3W to 15W, low loads exhibit this effect slightly more.
I tested this approximate design and transformer using a TL495 on a breadboard and it was successful and stable with no load, and no compensation network.

Schematic:

Bode Plots:


texts: I plan on trying to make some crystal radio sets. The only place I can do this is on the second story, do I have to add anything to the wire coming up from the ground because I'm on the second story?


texts: Understanding how an audio amplifying circuit works

texts:
I'm trying to learn electronics and electrical engineering through building small practical projects (toys mostly). I've been learning a ton from adafruit and spark fun, but I'm trying to branch out a bit and learn outside of their tutorials from time to time.

I have a couple of projects that I want to add sound to and provide volume control for. I had problems achieving this on my last project (the potentiometer "worked", but the volume only changed along a small portion of the pot's range and the change was very drastic).

I did some searching around and found a really rough video on youtube where the maker built out an amplifier for his phone. I adapted the circuit diagram to work with tone signals I'm sending out from my adafruit micro controller and it works.

The fact that it functions is great, but I don't completely understand what's going on. This is the first time I've worked with a mosfet (which I know is a transistor and operates like the NPN transistors I've used previously) and a capacitor.

I get that the mosfet is allowing me to use the smaller 3v signal coming out of my controller (p1) to control the higher 9v power source effectively amplifying the signal but I'm a little hazy on some of the other details:

Does this circuit look correct? (it physically works, but I don't know if I drew the circuit correctly :/ )
What does the capacitor actually do in this circuit?
Why do I need a resistor across the gate and drain legs?

I definitely appreciate any insight you can give.

simulate this circuit – Schematic created using CircuitLab


texts:
I have some old ~100Ah car batteries. There is no mechanical damage, they were not overcharged or incorrectly used. I assume they are sulfated.

This is a theory from Wikipedia:

  Pulses must last longer than the resonant frequency of the battery. Short pulses simply feed energy wastefully into the
  resistive components of this resonant circuit and virtually none into
  the battery. Electronic circuits are used to regulate the pulses of
  different widths and frequency of high current pulses. These can also
  be used to automate the process since it takes a long period of time
  to desulfate a battery fully.

But how to do it in practise?

What voltage and current I need?
When I should stop pulse charging?
How to determine or estimate resonant frequency of the battery?

Answering please take note that I have some electronics and microcontroller knowledge, I have oscilloscope in my workshop.


texts: When we connect a resistor to current source a finite amount of current flows through it right? Okay but how is a closed path complete?I mean the current source has infinite resistance(I'm talking about ideal) so no current flows thorough it.it's like the circuit is open right?


texts: What type of cable/connector is this 30 PIN LCD display cable?

texts:
I need help identifying the type of cable this is. It is used to connect an LCD display panel to a processor board. The width of each connector is about 15 mm and each end attaches to a 30 PIN connector with the word I-PEX on it.

What is it called so that I can order a few of them?

One end mated to connector.

Full cable.

Cable end top.

Cable end bottom.


texts: I want to know what is the difference between PHY and MAC chip


texts: Material selection for conductivity electrodes

texts: I was wondering what kind of properties i should be looking for when selecting ideal materials for electrodes in a conductivity sensor measuring the conductivity of liquids (1,1,1,2-Tetrafluorethane). The liquid is really resistive (about 10^14 ohm-cm) and is non-corrosive. I found mentions of stainless steel and titanium electrodes in commercial conductivity sensors but maybe there are others more suited to high resistivity fluids, i'm not sure. Thanks in advance.


texts: I've been reading about the EIA-485 standard and they talk about how even with twisted pair wire they need a 3rd connection for common because sometimes the devices need to be isolated. I was thinking about it and I've always taken isolation for granted, but never actually understood why it would  be necessary. Why is it that a device would ever need to be electrically isolated from another?


texts: Humidity and Moisture in Submerged Die-Cast Aluminum Enclosures

texts:
I have an electronic enclosure (5" x 5" x 4") made of die-cast aluminum alloy (A360). I plan to use it under water (~5 ft) continuously.

I first pressure test it: I monitor the pressure inside, while exposing it to 10 psi air pressure from outside for 2 min. If there is no pressure increase inside (<0.1 psi change), I consider the seals are good.

Then I submerge it in 5 ft water. I have a moisture sensor inside the box. If any water droplet bigger than 1 mm forms inside, the moisture sensor will be triggered and send a signal out.

After about 15 days underwater, the moisture sensor is triggered. I took it out and didn't see any sign of water inside. I didn't even see any water on the sensor. But verified the sensor works fine. So there must have been some moisture on the sensor surface.

So the question is: Where did this water come from? When I sealed it, the humidity inside was about 45% and the water temperature is a constant 75°F. There is no heating element of any kind inside.


texts: Why does a string of LEDs (Christmas lights) behave differently with battery compared to same voltage power source?

texts:
I have a string of Christmas lights (mini LEDs wired in parallel.)
My LEDs were too dim, so I took it apart.  I found they are powered by a single 1.2V NiCd same shape/size as 1.5V AA battery.
The NiCd is recharged by a small solar panel. Inside the controller box, there is a small chip and a few components which allow the LEDs to flicker or remain constant when you push a button.
I am pretty sure the LEDs are wired in parallel, because there are so many of them, all powered by this one 1.2V battery.  Another possible factor is that the LEDs become dimmer the further away from the source they are.  At the end of the string, there is practically no light, but there are no actual breaks or LED failures.  I couldn't detect a resistor before each LED in the string of LEDs.
Trying to repair, I replaced the NiCd by a 1.5AA battery (not rechargeable) and the string of LEDs work fine (mostly.)
Because the LEDs were a little dim for my liking, I thought I would try to use a different source of power: a bench top power supply (BTPS), set to 1.5 volts.  I connected this exactly in place of the battery; the power then went through the chip and other components before it reaches the LEDs.  When I did this, the LEDs lit up for a moment only, and then there was no light.  Turning the power on and off at the BTPS gave me the same flicker each time.  Removing the BTPS and replacing with a 1.5AA battery, the LEDs worked fine once again.
I thought this phenomenon must be an issue to do with internal resistance of the NiCd battery / AA battery, and a relative lack of internal resistance in the BTPS. Other questions like this mention internal resistance. I also read this, which insists that the parallel LEDs need a current limiter, which my BTPS I think will override.
But then I tried different voltages to try to compensate for a lack of resistor, but no success.  I didn't have the means on hand to insert a resistor in series with the BTPS. Would this have made it work properly?
Why does the battery work.differently from the power supply?


texts: Using a Dual Bidirectional I2C Bus Voltage-Level Translator

texts:
I have a module that uses this ADC powered with 3.3V (MCP3422): Datasheet

Now I would like to communicate with it over I2C using an Arduino Mega.
The problem is that the Arduino's I2C is operating on 5V level and the I2C bus of the ADC (can handle up to 5V supply but is only supplied with 3.3V) is on 3.3V level only.

Now I guess in order to ensure a stable communication I should use an I2C Bus Voltage-Level Translator like e.g. the PCA9306: Datasheet

Now I would like to power this module I have over the V_dd pin of the Arduino.
As far as I know it is not recommended to draw more than 20mA over an Arduino pin.
My board so far uses about 9mA of current. Thus, about 10mA are left to power the level-translator.
I checked the datasheet of the level-translator and im confused how much current it draws. On page 4 of the datasheet it says 64mA for Pass switch current. Is that the value im looking for?
I guess the current would also depend on the pull-up resistors I use.
Anyway, about 64 mA would be way too much current draw for my application.
However, it also says:

  Standard-mode I2C devices only specify 3 mA in a generic I2C system
  where standard-mode devices and multiple masters are possible.

Question:

What is the supply current / current draw of the level-translator?
Do you have any other recommendations for connecting the 3.3V and 5V
I2C bus domain in my case? Maybe there are more convenient methods that do not require that much current.


texts:
simulate this circuit – Schematic created using CircuitLab

Does anybody there has an ideea about how to make a synchronous boost converter only with N channel mosfets? I intend to do one, but the single design I know is the one with an N channel and a P channel mosfet (like in the attached image).


texts: How Power measured by Meters is affected by Harmonics?

texts:
I want to know how energy meters (Electro-static or electronic) measure Energy (let's assume power, ignore time) when there are harmonics present.

I know what are harmonics, how are they generated and how do they affect actual power. I read that harmonics power (in most cases) is in the opposite direction of Actual Power. That means if the utility is providing power to a consumer who has a dominant non-linear load, and in-between them is an energy meter (plz ignore class, type, etc.). So energy meter would record less power. That is understandable.

I tested this scenario like this,
I applied a linear load to meter and recorded power of ~2.3KW (230V x 10A x 1.0 P.F). But when I applied Phase-fired (90 degrees) waveform which contains odd harmonics, the power recorded by meter was ~1.1KW given the same set of V, I and P.F.

I know meter records power accurately because you can see from the waveform that rms have been decreased (as each half-cycle is 50% clipped to zero). But there lies my question.

If meters are recording less power in the presence of harmonics, then isn't it a loss of utility and benefit of consumers? While consumer is responsible for generating harmonics and is getting profit on top of it?

Should meter record actual power while filtering out the harmonics?

To me, it sounds really confusing, and I tried to search for utilities and meter manufacturer point of view, and they seem to agree that meter should consider harmonics effect while measuring power as it would be beneficial to both? How?

I tried to raise my question as much as I could find the write words, I hope that people here would understand, and help me find the answer.

Thank You


texts: Can "lead free" tips be used with leaded solder?

texts:
I've just purchased my first soldering iron, an Atten 8586. The item description claims it is suitable for lead free soldering, however I have no interest in using lead-free solder at this point.

I've read through Are some soldering iron tips unsuitable for lead-free solder? and What are the different types of solder used for? however am still confused about lead vs lead-free solder.

My understanding is this (correct me if I'm wrong);

Lead Free solder melts at higher temperatures
This means your tips may oxidise / corrode faster (due to higher working temperatures)

Will my 'lead free' soldering iron tips be suitable for use with leaded solder?


texts: Convert mechanical relay to solid state relay

texts:
I've been searching forums for a while trying to figure out exactly how to do this. I want the same functionality that a mechanical relay does.

When the "coils" are de-energized, I want the 'heel' and 'back' to be connected.
When the "coils" are energized, I want the 'heel' and 'front' to be connected.

It's easy to use an N-channel FET and the gate be in place of where the coils would be. So, when voltage is applied to the gate, it allows current through the heel and front.

But can I use a P-channel for when the coils are de-energized and I want the heel and back contacts to be connected?

Any help will be appreciated.

Update

This is what I was picturing. If voltage is applied to the gates, I want the heel to be connected to the front. If there is an absence of voltage, I want the heel to be connected to the back.

Would this work? Where do I need to put additional components and why. Feel free to alter my values. The 1k resistor is to replace the resistance of the coils of the current mechanical relays in place.


texts: I'm trying to trigger a motion sensor on a door (for fun and to learn more about these systems) using Arduino based electronics (ca 5V, ca 50mA). According to Wikipedia, these sensors (PIR sensors, passive infrared sensors) work at >8-14000nm wavelengths - can these be tripped using an Arduino as power supply - in theory / practice, or are there good reasons why this is a futile fun experiment to start with? I'm guessing a common infrared diode will not do the trick (ca 1000nm).


texts:
I just ran the DRC check in Altium for my PCB and I get errors on trace width for every trace segments on the board.

What is the reason for this ? It generated thousands of errors even tho all the traces are 4 to 5 mils wide.

All tracks width rules are set to >= 4 mils

This is the error message I get under "Rule Violations" :
Clearance Constraint (Gap=3.5mil) (All),(All)
Clearance Constraint: (Collision < 3.5mil) Between Track (52761.3mil,31343.2mil)(52769.499mil,31343.2mil) on Solder Side And Arc (52769.499mil,31340.4mil) on Solder Side

Edit: It also affects trace much much larger than 3.5 mils


texts: 1.5 ton AC on solar power through inverter

texts:
I am planning to design my design in such a way that I can run my 1.5 ton AC easily during daytime i.e. 9am to 5pm plus some load of around 500 watt.
I am planning to use following:

1 - 5000va/4000W 48vdc pure sine wave inverter (power factor 0.8)

2 - solar panels 250 x 12 = 3000 Watt

3 - 4 x 12V 200ah batteries

Will this setup work? theoretically it should.


texts: Using a transistor correctly to "connect" Maximite computer and circuit

texts:
My question is mostly if I am doing it right.

I have a snap circuit kit (kinda like a breadboard for kids). I also have a Maximite computer (kinda like a Arduino running basic with monitor out). The Maximite has some I/O pins that according to the technical details are high at 2.6V to 3.3V. Also, the maximum current that a pin can deliver is 25mA. The snap circuit kit uses between 3V and 6V depending on the circuit. What I would like to do is to use the Maximite to turn things on and off on in the snap circuit. For example, I might want to turn a 6V lamp or motor on and off.

I am pretty sure that I would want a transistor for this. In particular I think a n channel MOSFET is what I need. I looked up the datasheet for an IRF530 and see that the "Gate Threshold Voltage" is between 2.0V and 4.0V. If I understand things, that means that this MOSFET will "turn on" when the gate is given between 2.0V and 4.0M. Is that right?

Concretely, I am thinking of doing the following:

My question is really just if I am doing this the right way and if there are any other things that I should keep in mind or think of. (I would also welcome other suggestions on how I might do what I want to do.) Specifically I am wondering if it is correct to connect the two grounds/negative terminals.

simulate this circuit – Schematic created using CircuitLab


texts: Will two things in parallel on a bread board receive equal amps?

texts:
I drew my bread board here. If I plug two things into the power bus will I get equal amps to both devices? Sorry I don't have a multimeter yet to try it. I am planning a large project but I need to figure out if everything will have enough power before I go and buy parts.

More specifically is this what he is discussing in this video?
https://www.khanacademy.org/science/physics/electricity-and-magnetism/v/circuits--part-3


texts:
I am tasked with the issue of driving an IC that wants 5V input signals from an FPGA (3.3V outputs). Now, the most daunting part of it is the slew-rate requirements, with rise time \$t_r = 1.5 \text{ns},\$ hold time \$t_h = 3.5 \text{ns}\$, fall time \$t_f = 1.5 \text{ns}\$ and rest time \$t_l = 12 \text{ns}.\$ "High" is more than 4.75 V (5.0V typ) and "low" is less than 0.4 V.

If you add up the numbers, this corresponds to a period \$T=18.5 \text{ns}\$, or frequency of \$f=54.0 \text{MHz}\$. But the slew rate is

$$sr = \frac{5\text{V}}{1.5\text{ns}} = 3.333 \frac{\text{V}}{\text{ns}} = 3,333\;\text{V/$\mu$S}.$$

The Texas Instruments LMH6738 seems to be my only choice, so I can solve my problem by amplifying the signal (\$A=\frac{5}{3.3} =1.5\$). But before going that way I wondered if there were other options. After all, this is still a digital signal so I might not need to use it. A 5V digital signal at frequency $$f = \frac{1}{1.5\;\text{ns}} = 666 \text{MHz},$$ or higher would do just fine. But as far as I know, there's few logic chips working with 5V logic at those speeds.

So, any recommendations?


texts:
I was wondering what sort of tool works best for removing traces on a stripboard like the following:

Datasheet.  Product page on Mouser.

Image from http://commons.wikimedia.org


texts: Which color puts the least "strain" on an LCD pixel to avoid burn-in/ghosting?

texts:
I am developing a user interface on a cheap Kinco color LCD HMI unit.  After leaving a test UI on the screen for about 3 days, there was a very decided "ghosting" effect.

I was able to eliminate the ghost outlines by alternating a solid black and white screen over the course of about 2 days. Now the screen is back to normal and the ghosted image does not appear.

Since this HMI will be in service for several years with basically the same screens always in use, I want to build a screen-saver which will prevent ghosting. Note that users will view/interact with the HMI very little, as it's in a remote location and may be visited a couple times per week.

In building a screen saver, should the display constantly alternate between solid black and white screens, or is there a specific color which places the least "strain" on an LCD pixel, which would avoid ghosting and ensure pixels remain as bright and color-accurate as possible?  For example, is Black considered "full on" or "full off" by the LCD circuitry and pixels?  Would a black or white pixel create more prominent ghost image, or is the issue going to appear for any pixel that does not change over a period of time?

I assume either black or white would be the default/resting state of a pixel (i.e. no driver current applied to the RGB subpixel elements) but I don't know which.

At this point I don't know whether alternating between colors is better or worse than filling the screen with a single, unchanging color.  I'm looking to implement whichever scheme preserves the pixel brightness/dynamic response and eliminates ghosting.

Note that I did enable the auto backlight-off feature, but even when the backlight is off, the LCD is still displaying the image.

Your recommendations are appreciated.


texts:
<img src="https://i.stack.imgur.com/qBVDy.png" alt=" H
" />
I am trying to figure out how to find \$V_c(t)\$ for \$t \geq 0\$ in this.


texts: How bootstrap capacitor voltage is added to source voltage?

texts:
Circuit diagram below is a high side n-channel mosfet with bootstrap(while C1 is discharging)

It says that after charging of bootstrap capacitor:

  The upper optocoupler opt1 gets ON for 1s and lower optocoupler Opt2 remains OFF for 1s. The capacitor C1 now tries to maintain the 12V across it and this raises the source voltage to 12V. This makes the diode D1 reverse biased as its cathode voltage is now 24V for maintaining the 12V across the capacitor. The capacitor C1 now starts discharging through upper optocoupler Opt1 and the gate of the MOSFET Q1 develops 24V.

BUT I cannot understand how the 12 volts from the source is added to the 12 volts of the charged capacitor. I mean, at the time of discharging, the capacitor is not in series with the 12 volts source. (it seems to me that the capacitor and source is in parallel to gate of mosfet)

I think the current does added up but not the voltage. How so the source voltage is added to capacitor voltage to become 24V?

source: https://www.engineersgarage.com/contributions/driving-high-side-mosfet-using-bootstrap-circuitry-part-17-17/


texts:
I need to power a device (it's an analog bucket brigade delay) from a 9v power supply or battery. The device takes 15v. Is there anyway? I have a few 7660s IC chips, if that helps. I've made charge pumps before but they were integrated into another circuit and I'm not totally confident how they work.

The schematic:


texts: Gate driver using switches UC3842 PWM Controller

texts:
I have prepared a crude model of boost controller using PSpice simulator of  UC3842 IC

Gate driver has Ron and Roff as 1 and 100meg respectively (S3 and S5)
and Vout will go to external mosfet or a switch in boost converter.

But I dont get 16V when S3 is on it gives a large spike of 16V and settles to 8V during turn on and turn off of the switches.

Spikes at the output of gate driver.

Is there any specific way of building divers using switches what i should take care or improve this?
I am not obtaining required duty cycle due to this behavior.

I have attached images of my work, body diode on the switches S3 and S5 reduced the spikes.

But output voltage didn't match with the duty cycle is there anything where I have to concentrate on?


texts: LabVIEW outputting incorrect temperature value from TMP36

texts:
I connected my TMP36 to my Arduino UNO to A0 and I'm observing the temperature output from LabVIEW. Unfortunately, LabVIEW is giving me an incorrect temperature, with constant readings of around 40°C. I checked whether the TMP36 is malfunctioning or not and according to this website, (below) my TMP36 is functioning properly with a constant 0.75V which somewhat corresponds to room temperature.
I turned to LabVIEW to check the connections and to my knowledge, everything looks OK.

Any help? (Schematic attached below)
https://learn.adafruit.com/tmp36-temperature-sensor/testing-a-temp-sensor


texts: Separate grounding for analog and digital portions of circuitry

texts:
A datasheet suggests separate grounding for analog and digital portions of circuitry (http://www.ti.com/lit/ds/symlink/am26c32.pdf#page=12).

Is this to say that the IC's outputs should have a separate ground to the IC's power supply (VDD)?

If so, how is this possible when all components operate from the same supply?


texts:
I am using this circuit to measure the voltage of a small solar panel - around 3 or 4 V max (so instead of the photodiode consider there is a solar panel). That means Vin = -3 V. When I first built it, I didn't think about the fact that the op-amp is single supply and what effects that might have. Today, I was thinking about it and after reading some things, came to the conclusion that a single supply op-amp should not accept voltages outside its rail-to-rail range. I have 2 questions:

Why is the anode of the panel connected to ground and not the other way around? (I based this circuit on one I saw online)
Why does this circuit work? The output is exactly what I expected it to be in the first place (-0.65*Vin), but it shouldn't, because it's a single supply op-amp, right?

Thanks

simulate this circuit – Schematic created using CircuitLab


texts:
I am using ST manufacture Accelerometer(LIS2DE12) and i making a small hobbyist project for me. For this I am using ST-Microcontroller and developing the C code i am using KEIL V5 IDE. Configured the Accelerometer with normal modes, having the Data rate frequency of 200Hz and +-2g as the measurement range. (If some one needs to get the full details or configuration then let me know i will share, to solve these issue)
For calculating the speed i am using the velocity formula v = u + at. After developing this equation code i am getting wrong and continuously increasing velocity without moving the accelerometer. I don't know why this issue is for.

Waiting for the positive replies ....

Thanks
Sachin


texts: Limit Number Of Pulses From 555 Or Similar

texts:
I need as small a circuit as possible that can produce 2 pulses (say maybe 200 milliseconds long and apart) when I press a button.  My thought was to use a 555 timer and set it up for my desired pulse (exact timing not important), but I don't know how to limit the number of times it happens.

basically I will have a momentary switch as a trigger, and when I press it I need to produce 2/3 pulses in order to control something.  I'm totally open to a better way to do this as well, but the circuit must be small, and it is only controlling an low power signal to play/skip songs with an android phone, so anything passive would be even better so I don't need some kind of power.


texts: Can I use the IR break beam sensor outdoor/indoor for 4-5 meters range?

texts:
I need a sensor which can count a fast moving object. I am thinking to use IR beam break sensor. But, I think there will be a problem with the sunlight as the Tx-Rx will be 4-5 meters apart.

I also need to consider the fast response time. IR sensor has better response time than LDR. Am I right?

EDIT:

Consider, the fast moving object is like a soccer ball (a bit smaller than a soccer ball, though). Its speed is between 15ft/s - 60ft/s.


texts: What is the SAR(Specific Absorption Rate) value near a Telecom Tower?

texts: We know the SAR values of every smartphone. However we've got so many cellular towers in our neighborhood. How much of risk is there, health-wise, in being exposed to them daily? I mean is there any SAR value that Telecom Operators have to adhere to while installing their antennas?


texts:
Kind of a follow up question to this one I asked the other day. So a lot of the parts I'm looking at are listed with Vth at a certain Id. I'm not entirely understanding the graphs so I'm not sure if I wanted my desired Vth to be reached at a bigger or smaller current. For example, there are parts listed as Vth: 600mV @ Id = 1mA and also 600mV @ Id = 250uA.

Could somebody explain how the current influences the gate threshold voltage and what that would mean for low power applications such as mine? Thanks.


texts: What are the risks removing sleeve off the aluminium electrolytic capacitor?

texts:
I have a device with very strict dimensions; the space electrolytic capacitor will be installed in is exactly 5 mm. I have tried several manufacturers, and learned that some tightly fit, some do not at all. Looking to various datasheets I see dimensioning declared as 5 + 0.5 mm, or 5 ± 0.5 mm. While -0.5 mm would be great, so far I have a bunch of caps which are more than 5 mm.

Capacitor is mounted horizontally on the board, thus board at one side, and plastic casing at another (with space of 5 mm).

I am looking to ways how to put these caps in. There're actually two ways -

Increase space where cap would be installed, somehow cutting/using abrasive cloth/heat to melt or anything else on the plastic casing. This plastic casing is transparent, thus working on it will be visible from the outside of the device, and most probably will look ugly;
decrease diameter of the capacitor, and the obvious idea is to remove sleeve off it, it must save several tenths of the millimeter.

Is the second option a good idea from your experience, or I would better work on casing?

Update: thank you for suggestions so far. The capacitor is aluminium electrolytic, here's the set of datasheets: Panasonic, Jamicon and Hitano. Boards are already produced, and must be of 1.6 mm thickness due to edge connector specification.

The peculiarity of the design is that capacitors are mounted this way from the both sides, but only one side does not fit. Caps are 10 uF 25 V bi-polar, not available in 4 mm diameter body.

Here's the pic.

Update: I use bi-polar capacitors. The question is NOT about finding appropriate part, 5 mm diameter caps are already ordered and on their way. Question is about if I can remove black sleeve with marking off the cap on the picture without adverse physical and electrical effect.


texts:
I have the following problem to solve:

I am really at loss of how to design the estimator for such a system and plot the closed loop step response. This is what I have so far in Matlab:

clear all; clc

A = [0 0 1 0; 0 0 0 1; 0 -9.8 -1/80 0; 0 0 0 0];
B = [0 0 1/4 100/19]';
C = [1 0 0 0];
D = 0;
model = ss(A,B,C,D)

%%
det(obsv(A,C)); % different from zero
a = charpoly(A); a = a(2:length(a))
p = poly([(-3.83+9.24i), (-3.83-9.24i), (-9.24+3.83i), (-9.24-3.83i)]); p = p(2:length(p))

Lt = p-a
Wo = obsv(A,C)
Wot = inv([1 0 0 0; a(1) 1 0 0; a(2) a(1) 1 0; a(3) a(2) a(1) 1])
L = inv(Wo)*Wot*Lt'

Kt = p-a
Wr = ctrb(A,B)
Wrt = inv([1 a(1) a(2) a(3); 0 1 a(1) a(2); 0 0 1 a(1); 0 0 0 1])
K = Kt*Wrt*inv(Wr)
kr = -1/(C*inv(A - B*K)*B)

newA = [A-B*K B*K; zeros(4,4) A-L*C]
newB = [B*kr; zeros(4,1)]
newC = [1 0 0 0 0 0 0 0]
newD = 0

newmodel = ss(newA,newB,newC,newD)
step(newmodel)

I don't know if what I'm doing is right because the professor for this course hasn't really taught us how to handle such systems. Please help in any way possible. No one is giving me guidance and I am a really desperate college student trying to understand control theory concepts.

EDIT: I do have some knowledge of what I am doing. I know how to design control laws of the form \$u = -Kx + k_rr\$ to get state feedback, and where the new closed-loop system will be governed by the new dynamics matrix \$A - B*K\$.


texts: Trying to determine the switch type I need to shop for

texts:
I am trying to find a double-illuminated 12v rocker or pushbutton switch (one light for off, 2 lights for on, or at least different colors for on/ off), single-throw, on-off, but...

The circuit I want to close with the switch is a 5v continuity line that should be electrically segregated from the power going to the switch light.

Is there a standard switch type that does this without employing a relay of some kind?  Trying to keep this (relatively) simple.

Scenario:  I'm installing an AIS transponder in my boat that will receive and transmit telemetry (course over ground, size, type, name, and speed of vessel) over VHF to other vessels with the same type of equipment, but it's generally bad "manners" to transmit when you are in a marina or at anchor... so the unit has two wires coming out of it that, when connected, you transmit, and when disconnected, just receives.  I want to install a switch I can easily see in the dark that lets me know if I am transmitting or not.

If someone could tell me what I should be looking for, I'd really be grateful.  That way I can look it up on common websites and (hopefully) get one with a custom face for it.

Thanks for your attention.


texts:
I need to build a current limiting circuit in order to protect a circuit board.
It is for a solar power application. Currently the circuit board only can handle 1.6 amperes but the solar panels that are being used deliver up to 4 amperes.
I know the easiest solution is to replace the panel with a smaller one, but unfortunately that is not possible, so I am looking for a simple circuit that will do this.
I have found lots of circuits with MOSFETs online but not really sure how well they work.
The input voltage ranges from 20V to 28V from the panel and that is no problem. I just need to limit the current to maximum 1.6A, so it will be 24V 1.6A
Any ideas?


texts: Can I connect an amplifier to a Crystal Radio?

texts:
I am wanting to create a crystal radio that connects to my amplifier (It is for a guitar and has 3.5mm and 1/4" jacks). The diagram is as shown:

Would this be possible and work?  If not, please describe how I could make it work.


texts: looking for a sensor that activates when hit by a certain frequency burst

texts:
I have a question that may seem silly, but I am only new at this type of thing:  

Is there a sensor that I could connect to an LED (via an integrated circuit of some description, I assume) that would allow the LED to light up when the sensor came into range of a certain frequency?

I would like to run this setup from a 9v battery, if possible.

If this is possible, could I get a parts listing for what I would need for this setup?

Added:

What i was trying to achieve was a small device that incorporated an led that lit up when it detected a certain frequency/radio wave from another device (possibly a vehicle). Maybe an antenna instead of a sensor might be the go? Not sure yet and I am still very green with this. It was just an idea I had that may be useful for my work environment.


texts: Is it possible to charge a capacitors, and in return charge a battery?

texts:
If suppose I have a Li-ion battery of 10000mAh
Input/Output: 18W Max (5.1V/2.4A ,9V/2A , 12V/1.5A)
How many 1000F capacitors would I require to charge the battery?.

Ok, simply put, I am trying to charge a Mi power bank(10000mah) using capacitors. How many capacitors of 1000farads would I require?.

I found there are ultracaps, for ex:- Maxwell Ultracaps 2.7v BCAP0350 , that can store 1300Joules.
Now how should I make the capacitor charge the battery?

Won't the current flowing from the capacitor damage the battery?. Will using a resistor prevent the damage?


texts:
I'm trying to measure whether a gyro i'm using is damaged. I've got raw data coming off, and a total RMS noise value from the data sheet of 0.38 deg/s-rms. I'd like to look at the raw data and compare it to this value. Is it really just a matter of root-mean square of the raw data, or is there some more complex formula?

right now i'm doing

$$\sqrt{\frac{1}{n} \sum_{i=1}^{n} Gx_k}$$


texts: Why is the slope of the op amp graph 20 log (AB) in this application note

texts:
I am going through the following guide for op amps :
http://web.mit.edu/6.101/www/reference/op_amps_everyone.pdf
On page 87 (screenshot attached) there is a bode plot which has got me slightly confused.
I've usually seen two bode plots on such plots, one for open loop gain (starts of high and then has a roll off based on the pole zero configuration) and then the closed loop gain which the designer sets using passive components is usually (ideally) much lower than open loop and then intersects with the closed loop to form the bandwidth of your op amp circuit.
In this image they state the flat bit is set by the DC gain. What are they referring too? This isn't the closed loop gain right? Is this the difference between closed and open loop? But that isn't the circuit gain?
Also why is the slope 20 log (Abeta)? If this was loop gain wouldn't it be 20 log (1 + Abeta)
Thanks!


texts: How to make lightbulbs filament stronger?

texts:
If I make the tungsten filament in a lightbulbs thicker could it then handle high electricity flowing through it without burning up so fast. Also could making it thick, allow it to handle being cut off and on very rapidly, a few thousands times for hours on end and still not metal?
This is for a special fun project I'm working on f.y.I and I need to know if I can make the tungsten filament handle more power at a rapid speed for a very long time.


texts: What makes compact florescent lamp wear out so fast?

texts:
I notice that a compact florescent lamps (CFL) wear out faster than its lifetime.
My personal experiment was on 15 watt / 220 V / 50-60 Hz / 690 Lumen spiral lamp. Its rated lifetime is 8000 hours (about 11 months). But it is burned after 3 months only. It is repeatedly happens that each new lamp live for 3 months only then it is burned. What could be the reason? I don't light the lamp all the day. I light it while the periods of breakfast, lunch and dinner.

I guess it is the temperature, because a lamp is rated for -5 deg to 40 deg and I live in a country where the temperature reaches 40 deg. So, I think the temperature inside the lamp is higher than 40 deg and the lamp is overheated.

Thank you very much,


texts: Is there any method to output VGA with Arduino?


texts: How to determine if an RFID system supports reading multiple tags at once?

texts:
In this answer the following is stated:

  Most RFID protocols include singulation so that if you put dozens of
  RFID tags in front of it, and then turn on the RFID reader, it can
  read the correct serial number from each and every tag.

How can you determine what protocols and devices do or do not support singulation? When performing searches on RFID singulation most of the results are related to the theoretical side and not what components or protocols support it. Are there any more proper terms to be using for this type of "feature" in RFID?

For some context, I am looking for a way to read multiple passive objectives that may or may not be stacked on top of each other.


texts: How to construct an SMA feedline for a horn antenna

texts:
I'm constructing an sma coax to waveguide transition for a horn antenna. Here's a cross-sectional view of what the device will look like

I can 3d print the waveguide portion (I use a conductive paint on the inside) but I'm wondering about how to get the coax connector right. I was thinking about purchasing a panel mount sma with a long feedline like this and then cutting the insulation with an xacto knife and clipping the metal feed with some sort of metal cutters (e.g. these). I'll cut the insulation so that it doesn't extend into the waveguide portion of the transition and the feedline to be half the height of the waveguide. Are there any issues with this plan?

Would it be better to get an sma mount with a shorter feed and solder a piece of wire to the end to get the right length? If this is the case, can I get away with 18AWG solid core copper wire?

Is it a problem that there will be a portion of the waveguide inner surface that isn't conductive (where the insulation of the coax connector ends)? Any other thoughts?

I know this device will be far from perfect. It's for personal, recreational use so that's ok. But I would like it to be as good as possible with the materials I have.


texts: What happens when the voltage applied to fully charged capacitor becomes lower than initial voltage?

texts:
I have 24 volt capacitor and I charged it fully using 24 volt power supply. What happens if the power supply voltage becomes 20 volt which is connected to the capacitor that is fully charged at 24 volt.

Car's cigarette lighter socket is used as source power supply. I am trying to use capacitors to provide more current at peak times of load. Power supply voltage can be changing from 12.6 volt to 14.4 volt.


texts:
I'm working on a circuit that feeds a microphone into the ADC of the STM32F4 Discovery and then outputs that exact signal out of the microcontroller's DAC and then to a headphone jack.

I am able to hear everything that the microphone picks up, but I am getting a humming noise when listening to the circuit. The humming noise is present no matter if the microphone is attached or not. I've done the following to try and isolate the problem:

Connected the ADC pin to the DAC pin (still hums)
Disconnected the ADC pin (still hums)
Disconnected the DAC pin (no hum)
Grounded ADC pin (no hum)

I'm a little confused as to the what the problem could be. Judging by the tests I would think the problem would be in the Sallen-Key Filters after the DAC, but I have no idea how to alleviate it.

simulate this circuit – Schematic created using CircuitLab

Are there any glaring problems with the circuit above that would cause the hum?

EDIT: Sorry the 100 Ohm Resistor R5 is supposed to be 100k Ohms


texts: Are activated open-collector and open-drain circuits wasting energy?

texts: Consider the following reference circuit for a 6N137 optocoupler. My understanding is that this circuit uses a pull-up resistor on the output node so when the optocoupler led is activated, the transistor gate opens and the output is pulled to ground. This seems to be a standard configuration for open-collector or open-drain circuits. What puzzles me is that it seems inefficient. In order to switch the output off, I need to effectively short the circuit in order to pull it to ground. Is my interpretation correct? If not, why not?


texts: Layout design in a board with Ethernet Controller and Connector

texts:
I received a task to review a board with ethernet controller W5100 from Wiznet and Ethernet Connector. It has SIM800L module as well ESP8266 uC. I cant give lot of details because confidentialitty.
As I know, for ETH controller and Conn, It has differential signal pairs because ETH interface with RXIN, RXIP and TXON, TXOP RJ45 connector.  For this board, I have only 2 layers and I dont know if I need to decide and go through 4 layers because Ethernet Interface. I attached pictures from this layout and I would like suggestions how to improve it. Besides it theres a battery charger CI and holes where I will place a switch power supply module. I indicated So my questions:
1) Keep 2 layers or go through 4 layers? (1 gnd plane and 1 power plane, 2 signal layers)
2) How to make a correct differential pair for ethernet controller wiznet W5100, I did some serpentine to tune impedance on 50 ohms, and tune differential pair skew to 0mm.
3) Theres a need to use serpentine together with differential pair and which rules I should use, general rules, i find this reference design: https://wizwiki.net/wiki/doku.php?id...hardware:start
4) What to improve looking for this board?
5) I have SIM800L module, Esp8266 uController and Ethernet interface what to improve looking for this design and its reasonable this way or need to make rework, like place multilayers and its correct to use vias to do differential pair for ETH as was done? Well, whole board was done using auto router by coworker here...


texts: I want to make a cd4049 cmos inverter spice model

texts:
I know the cd4049 is just two FET's but I don't know how I can model those transistors to be at least near what one would expect from the behavior of the IC.

Also, what parameters are absolutely needed when modelling a FET? Can I leave some out? I have seen different models with different complexity, that is confusing. I'm pretty new to modeling components in spice, in other words, this will be my first.

[EDIT1]

Ok, I found an excellent tutorial on how to do this using pspice.

http://tuttle.merc.iastate.edu/ee201/spice/pspice_mosfets.pdf

They take PMOS and NMOS FETs' models and specify only the parameters that are different from those default. This is what I want to do, but how can I know the parameters of the FETs from the datasheet?.

https://www.fairchildsemi.com/datasheets/CD/CD4049UBC.pdf

[/EDIT1]


texts: Does 18650 cell voltage sag have a direct relationship with its internal resistance?

texts: When a cell is connected to full load does it drop some of its voltage due to internal resistance and quickly jumps back to normal whenever the load is taken off??


texts: General Steps (guidelines, formulas and matices) in selecting wire-gauge for copper wires, when knowing the load characteristics?

texts:
I would like to ask if someone could summarize the steps/process we follow in order to select an appropriate diameter of copper wiring for an application in which we just know the main characteristics for our load, like: the desired Amps we need for our load, the thermal conduction of our load in W/(m·K) and its resistance in Ω·cm. The wire will be soldered to the load which is made of Ti-alloy and it won't be very long (length is considered a known parameter, L in cm; same for our source, V_s in volts).

These steps may include formulas to calculate some factors/measures, or matrices from which we take specific values to consider for the final choice.

Since this is very general, because the process followed is what is asked, but as an example: let's say we need 3 Amps for our load, and that we know that the thermal conduction of our load is 6.7 W/(m·K) and its resistance is 17.8·10^(-5) Ω·cm.


texts: Simple circuit transfer function and output graph

texts:
I have this simple circuit and I need to graph the circuit transfer function and also graph the output as a function of time. The output is marked A-B and the source voltage is 10 V peak.

I know that when the source is between 0 and 5 V, the diode is polarized direct and the output is 0V. But I don't know what happens when the source is in the range of 5 to 10 V and 10 to 5 V


texts: I've search all over to no success. I tried the data sheet, but couldn't make heads or tails of it. What is the voltage of an output pin of the ATtiny 85 when high? is it just the same as the input voltage a vcc? Also, what is the maximum current output when run at 3.3v?


texts:
I am reviewing a 4 layers PCB (2 layers + GND + Power layer with different rails on it) which is hosting a Lipo battery charger being capable to deliver up to 2.5A on the output named SYS.

We have one track wich is connecting two components (an inductor and a capacitor). We are hesitating wether we should keep this track on the top layer or if we should better create two vias and send the track on the power layer.

What is best ?

PS: We are not on high frequencies


texts: Reasonable Li-Po Battery Protection Circuit?

texts:
I'm designing a circuit to monitor the voltage of a Li-Po battery (single cell 3.7v, 2500mAh, 25A) and switch off the battery when the voltage drops to a certain threshold.  The Circuit will also pulse an LED to indicate the Battery needs to be recharged.

The ATtiny85 will be programmed to monitor it's internal Vcc voltage and turn on the MOSFET if the battery is above 3V.  When the battery is below 3V it will turn off the MOSFET and pulse the LED every couple of seconds.  The micro will use sleep mode to reduce the battery drain of the monitor circuit.

Does this seem like a reasonable circuit to accomplish this task?
Is the value of R2 reasonable? (not sure how to calculate this value)
Can the ATtiny85 maintain the output on PB1 when it's in sleep mode?
What kind of parasitic losses on the battery does the use of the MOSFET introduce?

Also, as the battery voltage decreases the voltage driving the gate (PB1) will decrease as well.  I don't think this is a problem but not sure.


texts: Is my LED driver fundamentally incorrect, or can I compensate it somehow?

texts:
I'm driving 3 tricolor LEDs from 3 PWM pins. They can't source enough current to drive them directly so I have them switching on some 2n7000s. Works great when each PWM corresponds to one color but...
I wanted to have each pin drive a different LED colors (e.g. PWM1 drives Led1.Red, Led2.Green, Led3.Blue, etc.), so they'd always be different colors. The drivers are staggered as shown (https://imgur.com/a/hi1f6qa). It didn't work at first or had apparently strange behavior. Eventually I realized, of course, the B/G LEDs have a Vf of around 2.8 and the R LEDs are about 2.3. So if I had the Red channel turned on, the Blue and Green were either extremely dim or just off entirely. I was trying to create 2 voltages simultaneously at the drain of the FET.
Is this design fundamentally incorrect, or is there some small change I could add to compensate?


texts:
I bought a "Solder Paste". It is in quote because I'm not really sure if it's a Solder Paste itself.

I researched about what Solder Paste is and, by definition, is defined as a mixture of small solder spheres with flux. It's also grey-like in color since it has tiny solder spheres.

So, it can be directly applied to the pads of the PCB and perform reflow soldering afterwards.

But here is the actual product I bought:

As you can see, it's brown-ish in color and I don't think there are tiny solder spheres in there.

And the direction in using this is to put ample amount on the pads then apply solder with iron or torch

So my question is, is this really a solder paste or just flux?
How can I use this, then?


texts:
I’ve been doing much research the last couple of days about electricity. I have a pretty good understanding of Watts, Joules, Coulombs, Amperes, Ohms, and I know Ohms law finding voltage and all and I understand that Volts measure the electric potential between to points on a circuit and that Volts are the “pressure” force that push the electrons through the circuit.

What I can’t seem to understand is how to know what creates that “pressure.” Is it based on how many free electrons are on one side of the lightbulb, for example, compared to the other?
Can you create more voltage by loading more electrons into one side?

I understand there isn’t a simple answer to this question so posting any article links or video links would be what I am looking for.


texts: Power Supply Sees Electromagnet as a Short Circuit

texts:
I'm designing a circuit in which current periodically passes through a copper coil (with an air core), which acts as an electromagnet. The resultant magnetic field then repels a neodymium magnet attached to a rod, such that when the current stops, the magnet+rod returns to its original position.

In the circuit I'm presently trying (below), the periodic output from a 4060 counter is amplified by a BC547 NPN transistor, which then charges a relay that switches 9 volts through the coil. The power supply is a Mastech benchtop HY3005f-3.

I'm presently using quite thick wire (24 SWG, 0.56 mm), and so the resistance of the coil is only 0.5 ohms, which gives a large enough current to do the job (the magnetic field of an electromagnet is a function of both the current in the coil and the number of turns in it). However, the problem is that the power supply sees the coil as a short circuit, and so the short circuit protection in the supply is activated whenever the coil is charged. One way around this is would be to wind the coil with thinner wire and more turns, so that it has a sufficiently high resistance to not appear as a short circuit to the supply.

My question is, is there a way to design the circuit so that I can keep using my present, low resistance, coil without the supply seeing it as a short circuit? Perhaps by discharging a capacitor through it? Or is the only way to go with thinner wire and more turns?


texts: Ferrite Magnet as Ferrite Inductor Core?

texts:
I have a toroidal “ferrite” ceramic magnet lying around and am wondering what the similarities are (if any) between one of these that has been put in the oven to remove most of its magnetization and a standard ferrite core used in inductors.
Could I make an inductor with one of these + magnet wire and if so, just how crap of an inductor would it be?


texts: Size to power trade off with solar panels

texts:
I'm looking to power a remote controlled car with a solar panel on its back.

What size to power am I going to get?  Is there one light enough that it wont slow the car down?


texts: Effect on battery characteristics of a zinc-air button cell from oxygen starvation?

texts:
How would the performance of a zinc-air battery would be impacted by oxygen starvation - a sealed container with the available oxygen gradually decreasing over time.

Would this just decrease the maximum available current or would there also be a drop in voltage?

I am wondering if there could be some way of deriving changes in oxygen levels inside the container based just on the battery characteristics.


texts: PCB features that cause EMC problems and track on ground plane for return current

texts:
If I have understood correctly the return current for AC voltages will follow the red signal track but on the ground plane. For DC voltages the return current will spread out across the ground plane. Could adding the track shown in white on the image on the ground plane contain the DC return currents?

Also would the main EMC problem be the track acting as an antenna? What else could it be?

Thank you for any help you can give. Hopefully this makes sense


texts:
I'm currently designing a PCB at which I have an lithium ion battery (4.3V max) attached. The battery is charged via USB (5V).

The charging controller is enabled by a microcontroller which should detect when USB is attached. Due to power saving and money saving design considerations the plus-pole of the battery and the 5V-USB pole are connected to each other (diode is there for direct-charging-protection).

Anyway, before I had these design re-considerations I had a simple voltage divider at the 5V-USB (150k/100k) to detect a connected USB charging cable directly by the microcontroller via a simple GPIO interrupt.

Now I have to detect without an ADC (already used) if the voltage on the line is sourced by USB (5V) or by the lithium ion battery (4.3V). Is the microcontroller's analog comparator (ACMP, using SiLabs, EFM32G222 microcontroller) an option to use? Then I could just compare if the signal is below or above 4.3 V (or let's say 4.4 V to add some safety space)?
I would use a voltage divider to scale down the 4.3 V/4.4 V to the voltage are of the microcontroller (2.1 V).

Is this a reasonable idea?

Many thanks in advance for your help!

EFM32G Reference Manual: https://www.silabs.com/documents/public/reference-manuals/EFM32G-RM.pdf

Used Specific MCU Datasheet: http://www.farnell.com/datasheets/2170296.pdf


texts: xilinx create schematic of top modul with lower level moduls

texts: I have a top modul VHDL source file, which has a few instances of lower-level modules (VHDL) and signals which connects these lower-level modules. How can I generate a schematic for this? I mean, I would like to see the top module, inside it, the lower-level modules and the signals. (xilinx ise design suite 14.7)


texts:
I’m curious about current flow through an oring diode configuration. I’m using oring diodes to “autoselect” between two power sources: a 4.2V (max) battery, and a 5V USB line. The battery has one diode on its branch, and the 5V line has two diodes in series (for a higher desired voltage drop). I have a few questions regarding this configuration:

I’ve read that oring diodes will allow the circuit to choose the higher voltage power source (the USB line, I think, in my case). Is the “comparison” considered before the diode voltage drop or after?
When both are connected (battery will always be connected), will current be drawn through exactly one branch only or a mix of both? In testing, I detected a small (~0.2V) forward voltage across the battery line’s diode, but I’m not positive if this means there’s any current flowing through that line.
What effect does having unbalanced diodes have? That is, does the fact that one line has a higher forward voltage than the other effect the way the circuit “chooses” a power source?

Thanks for your input! Apologies for not showing a diagram — I’m on a mobile phone — but hopefully the circuit is simple/common enough to understand.

UPDATE 7/11/18

I had some time to sketch the circuit. Here it is with some more details.

This device is powering something that must run on about 3 to 3.6V and draws about 100-150mA. I don't want an LDO regulator because the device its powering has a low-battery indicator that I want to work properly (if I used a regulator, I'd get little warning before the battery dies). I want diodes because they provide the necessary voltage drop. My goal is to allow the battery charger to continue to charge the battery while the loading device is powered on. The USB input provides up to 500mA current, so there should be roughly 350-400mA left to charge the battery. I've verified that this all works empirically -- I'm just trying to understand exactly why.

Each diode has about a 0.55V voltage drop at my load current. Notating the node voltages while thinking about your answers really helped me understand what's going on. Please correct me if needed. The voltage after Du1 and Du2 is about 4V. This explains the approx 0.2V drop across Db (which allows very little current for my diode, based on its spec sheet).

At first, I was not sure why the 5V line dominated rather than the battery line -- then I decided to see what the alternative voltage at the junction (before Dc) would be if the USB were unplugged: it would be 4.2V - 0.55V = 3.65V. Because this voltage is definitely less than the 4V that it would be if the USB were connected, the 5V USB line wins and the node takes that voltage.


texts: For pills there exists a service which can ID them based on markings, shape, color, etc. I buy the grab bags of ICs from Jameco and sometimes get a part or two that I can't identify within a few pages of a google search. Does such a service exist for ICs and other chips?


texts: I have a custom board with a STM32F411 and a MCP25625 chip, which I did not create. But now I need to write a firmware on it so that this board communicates with another board via the CAN bus. I know on which pins the MCP25625 is connected to the mcu. But I cannot find libraries and examples of how they can be connected programmatically so that the CAN bus can work. The only library that I have found is CANnuccia, but it seems to me that it will not work for this case, and even more so, I have not found any examples using this library. Well, the question itself - which library should be used in this case and how to link them programmatically. (I already know how to upload firmware to this board, write PWM to it, etc.). Most likely this question will not be correct for this site, but I hope for any help and advice. Thank you.


texts: a solderless breadboard alternative allowing point to point wiring by pushing the wire between special bifurcated pins?

texts:
Does anyone remember what was the name of the manufacturer who made a solderless breadboard alternative allowing point to point wiring by pushing the wire between special bifurcated pins on the back of the board. All that was needed was a little plastic "pusher" tool. I picked one up at the Ideas In Science and Electronics" show in Albuquerque in the '8os, but passed it on to someone else.

I used it and it was a LOT faster than wire wrap, and was claimed to offer as good or better contacts.

Thanks for answering. The bifurcated end of the pins were like opposing miniature knife blades that cut through the insulation and a bit into the wire to make a gas-tight connection. You could push more than one wire - I think as many as 3 - onto the same pin. The only drawback was that since you were working on the bottom of the board, there was the problem of keeping track of the pin order. This was helped by getting little number-pattern labels that were made just for this purpose and pushing them over the pin layout of the IC, only from the bottom. Then no problem.

I've been searching, and Speedwire is the system that seems closest, but it's no longer available, and I think what I'm searching for was an American-made product. I'd get a Speedwire board immediately, 'tho.


texts: What are the differences and similarities between FPGA, ASIC and General Microcontrollers?

texts:
I have read this post and it does not answer my question in its entirety:

I think of a microcontroller as anything that has some memory, registers, and can process a set of instructions such as LOAD, STORE and ADD. It contains logic gates and such to perform its role, but its main task is to be a universal processor of bits. I think of a Microntroller as a system of interconnected ASIC designs to create the ability to store and process instructions.

I think of an ASIC device as a circuit that has been specifically constructed using logical and electrical components to perform one single task, with no other task in mind nor extra hardware included.

I think of an FPGA device as an ASIC device (a low-level device) + a bunch of unused stuff left over, used to implement a particular truth table.

Despite its name, an FGPA feels very "application-specific", since it must be rewired to perform a new and different task. This leads to confusion with ASIC. Albeit, in the case of rewiring an FPGA, all necessary hardware should be present. Also, FPGA's are meant to be programmable, but isn't that what a Microcontroller is meant for?

The post above I referenced also mentions HDL, with which I am familiar. Can't HDL be used for both ASIC and FPGA, and by proxy to design an entire microcontroller?


texts:
Does anybody know if this epoxy resin can be reused? I do not need all the resin in the package at this time and I want to store it for later use. I am asking because it says in the specifications that the useable life is 60mins.

If it cannot be reused, is there a resin that can be reused? Or at least, in smaller packages?


texts:
I'm implementing some modules using VHDL and for some of them I need the FPGA's global clock signal, and for some others I need to update to two different frequencies. A common solution to this is using frequency dividers based on counters, so if I have a 8MHz clock and I need 2KHz, I can just count up to 4000 and generate and enable signal for the other components.

But when many clocks are needed, a way of reducing the size for frequency dividers could be cascading them. For example, to generate 2KHz and 1Hz, I could count up to 2000 using the previous generated 2KHz enable signal.

My problem is that, since it's a good practice for scalability and performance the use of a single global clock, using the previous clocks as enable signals causes delays on subsequent clock generation. This is my VHDL code to generate two new clocks based on the global one:

library ieee;
use ieee.std_logic_1164.all;

entity clock_generator is
    generic(
        global_freq  : integer;
        display_freq : integer
    );
    port(
        clk      : in  std_logic;
        reset    : in  std_logic;
        clk_2KHz : out std_logic;
        clk_1min : out std_logic
    );
end clock_generator;

architecture behavioral of clock_generator is

    constant MAX_2KHz : integer := (global_freq / display_freq) - 1;
    constant MAX_1min : integer := (display_freq * 60) - 1;

    signal cnt_2KHz : integer range 0 to MAX_2KHz;
    signal en_2KHz  : std_logic;

    signal cnt_1min : integer range 0 to MAX_1min;

begin

    gen_2KHz : process(clk, reset)
    begin
        if reset = '0' then
            cnt_2KHz <= 0;
        elsif rising_edge(clk) then
            if cnt_2KHz = MAX_2KHz then
                cnt_2KHz <= 0;
            else
                cnt_2KHz <= cnt_2KHz + 1;
            end if;
        end if;
    end process;

    en_2KHz <= '1' when cnt_2KHz = MAX_2KHz else '0';

    gen_1min : process(clk, reset)
    begin
        if reset = '0' then
            cnt_1min <= 0;
        elsif rising_edge(clk) then
            if en_2KHz = '1' then
                if cnt_1min = MAX_1min then
                    cnt_1min <= 0;
                else
                    cnt_1min <= cnt_1min + 1;
                end if;
            end if;
        end if;
    end process;

    clk_2KHz <= en_2KHz;
    clk_1min <= '1' when cnt_1min = MAX_1min else '0';

end behavioral;

If I simulate its behavior, we can see that the first clock is generated synchronized with the global one, but since the second depends on the first one's activation, it's delayed one cycle of the global clock:

So my questions are:

How can I get full clock synchronization without using individual frequency dividers?
Could this synchronization cause any problem on some kind of special systems or is this just negligible?


texts: Half-etched fiducials Vs through-cut fiducials

texts:
While making PCB, I added 8 fiducials (fids) marks so that pick and place machines use these marks as referent points on the PCB to position the surface mount components (Packages) during assembly.

But when I sent same Gerber file to stencil manufacturer, they asked me "do you require fiducials half etched or through cut".

I don't have any idea about half-etched fids. Could someone explain the difference between these two?

All I can found a web link but it does not serve the purpose.


texts: Voltage divider resistance/wattage sizing

texts:
I am working on a small project currently -- I recondition hybrid car battery packs with a grid charging system, and I am working on a voltage sensing circuit that's monitored and available via a network. The voltage sensor I currently have is only capable of measuring 250VDC, and some battery packs exceed this.

I was going to make a simple voltage divider with like-sized resistors to just cut the voltage in half, which would bring me well within the 250V range. The voltage sensor is obviously an extremely low load, so what value resistors would I need for this? And what wattage rating should the resistors have?

Thank you.

Edit: here is the link to the voltage sensor I plan on using. http://www.yoctopuce.com/EN/products/usb-electrical-sensors/yocto-volt

Also, maybe I'm thinking incorrectly, but if I connect two resistors in series(and use the center tap as the half voltage) to a 250vdc battery, aren't the resistors just going to blow? I really feel like I should know this :/