texts: How to fix EMC problems for existing designs?

texts:
I'm going to be looking at a few products that have failed EMC radiated emissions testing and will need to apply fixes in order to make them pass (unfortunately, in these cases, two of the designs can't be modified to fix the problem at board level).

NOTE To see high resolution images of the scans, right click on the images and open in a new tab/window

In my particular case, the problems seem to stem from the following:

Product 1 is in a metal enclosure with a cut out for a TFT display and keypad, and several cables running out of the enclosure. The system is microcontroller based, with unshielded power, shielded CAN and shielded RS232 interfaces exiting the enclsoure. The problem seems to be coming from a 25MHz crystal that is driving the graphics controller and is leaking out from the cables and also from the front of the screen.

Product 2 is also in a metal enclosure but with a plastic window and cables running out. This system is microprocessor based (Linux) with unshielded power, shielded CAN and shielded RS232 interfaces exiting the enclosure. The problem in this cases appears to be stemming from the 3A, 5V switching power supply on the board (Lot's of 3kHz harmonics). There's also a lot of 45MHz harmonics stemming from the SD card. This product is open to design modifications

Product 3 is in a plastic enclosure with a large plastic window for indicators and cables running out. The system is microcontroller based with unshielded power, shielded CAN and unshielded GPIO interfaces exiting the enclosure. The problem seems to be stemming also from the same 3A , 5V switching power supply (same design as the previous item).

All three products are double layer boards.

What steps can I take and what solutions can I use to help reduce the radiated emissions of this existing design? What reference material (books, articles etc) can I use that discuss this topic?


texts: I heard it is usually better not routing at 90 degree angles. However what about with via, as I've read that it is usually recommended to use one layer for horizontal and another layer for vertical. Can I route safely like the picture below?


texts: Address decoder design and memory tables (recommended books)

texts:
i have been self studying and i encountered with an exercise of address decoder design, i have seen videos and i have searched in this book "Digital design by M. Morris" which is the one im using for studing digital design but it doesnt explain how to approach to this kind of decoder. I would like to be capable to that myself without look any videos so thats why i wonder where i can find this information, do anyone know in which book may i learn how to design this kind of decoders.

The address decoder that im trying to do have the next requisites

X is low active in the range 00 to 0F

Y ..... 10 TO 2F

Z ..... 30 to FF

E is the enabled input which is low active too


texts:
I have a camera outputing parallel data and I want to interface it with iMX6 module which accepts CSI-2 camera data.

Are there any ready & cheap solutions to convert parallel into CSI-2.

Lattice have some FPGA solutions but I do not want to pay for development software licenses just for this purpose.

thx


texts: Can I connect various LED fixtures to one driver?

texts:
Let's say my driver is 32W (700mA). I should be easily able to connect 5 x 5W 350/700mA LEDs right?

My idea is to use driver with DALI interface and control 5 LED's using just one address.


texts: Choosing equipment for 3 phase wind generator?

texts:
I want to be able to move the windmill I am designing out of the wind when the power output is to much (high wind scenario). To do this I need to measure the output of the power. To set everything up I need to be able to select my equipment for max current/voltage/power/etc. The generator I am planning to use for now is this generator. The max output from the graph seems to be about 800V DC rectified. At max RPM however the max OC DC rectified voltage is about 675V. Some calculations later I figure about 500VAC LL output @ 675V DC rectified. This is assuming a balanced load and current flow but there is none at the open-circuit point. I am assuming the voltage will be lower under load. Being under load all the time (diversion unit in place) will allow me to "safely" use equipment rated for typical 3-phase AC voltage of 480V?

Also for testing and maintenance since this is a prototype I wanted a shut off switch to be able to work on the control section. I am thinking the best way is to have a 3 phase 480V knife switch (lock out tag out method) in series between the diverting modular and the control modular. Any other suggestions?


texts: I can't understand the logic with power = voltage * current

texts:
I mean, if I have a 2000W device and plug it in a 220V outlet, it will produce about 9,1A.

But if somehow the outlet is not delivering 220v, but less, like 180V, according to the equation, it will produce 11,1A.

But how decreasing voltage increases current if voltage is the 'provider' of current?


texts:
I built a very basic circuit to get around 5.5V from a +15V source

I have a 220 Ohm between Adj and Vout and one 470 Ohm, one 220 Ohm and two 100 Ohm in parallel between Gnd and Adj summing up to about 740 Ohm
that should give me about 5.45V between Vout and Gnd.

With a 1.5k Ohm Load between Vout and Gnd I get 5.5V. However with a 470 Ohm Load I only get about 3.7V.

Putting in 100nF capacitors between Vin and Gnd and Vout Gnd did not help

simulate this circuit – Schematic created using CircuitLab

Any Ideas what I'm doing wrong?


texts: Unable to connect amplifier output to comparator in opamp

texts:
I am amplifying a signal for a current transformer (CT) with an op amp. This amplified output signal I need to compare using op amp comparator.
The supply voltage is 12V and the IC is an LM358. When I give the output of the amplifier to the comparator, the comparator gives an output signal of 7 volts irrespective of voltages at inverting and non inverting terminal, which should be either high Vcc or low 0V as it is a comparator.
Can you help me with a solution?


texts: Using latching Hall sensor to toggle a LED - brightness issue

texts:
I'm using a U18 latching Hall sensor (datasheet) to toggle a LED. I'm driving it off a 6V L1016 battery.
My issue is that the LED is very dim.
My understanding is that the U18 limits the output current to 20~ish mA. In theory my LED wants 20mA forward current.
So I am not sure why it is not very bright. Testing the LED directly with the same battery both 150 & 300 ohms resistance it's much brighter.

simulate this circuit – Schematic created using CircuitLab
Original and tidied-up schematic.
How can I make this brighter? Would the best solution would be an op-amp? Is there something else I've overlooked (in terms of setting it up incorrectly)?


texts:
I'm working on an Ethernet connection for a PIC18F4620 with the ENC28J60. I found a useful article here, with a schematic:

I see I need transformers between the RJ45 connector and the Ethernet chip. I've heard people talking about connectors where the transformer already is included. I'm thinking of disassembling the connector from this board:

My questions:

Would this connector have built-in transformers? Or how can I check this?
If the connector does not have built-in transformers, can I use the chip next to it for that? The numbers on it are "bel 0120S1B S558-5999-46" and a search for "S558-5999-46" returns this. Would this "transformer module" be compatible with the ENC28J60?


texts:
The IV curve of this solar panel looks okay, but the axes values don't seem to match up with the tabulated values. Datasheet states that 6.70 V, 36.6 mA at mpp. Can anyone tell me the relation between these and the graph?

http://ixapps.ixys.com/DataSheet/SM940K12L.pdf


texts:
Usually pullup resistors are needed for i2c but if I have pullups in master and hosts devices and when I add another one device to I2C bus then bus stop working. I cann't remove pullups. Does it make sense to add pulldown resistor to compensate pullups? or even resistance regulator to find optimal radio for pullup and pulldown?

PS My device is quad with matek 405 ctr. I am adding GPS TS100 mini. I watched a set of videos. They say that there is a zillion of fake magnetometers. hmc5883, qmc5883, qmc5883 that is flashed to be hmc5883. I tried 3 GPS (not just TS100) and I pulldown resistor is just another hack I thinking to try and I wonder how common this is and what could be wrong. I am a bit out of budget to get 4th GPS.


texts: Calculating at which source voltage, Zener regulation begins

texts:
I've been trying to understand how to get to the voltage at the source with which the Zener starts limiting the voltage. Circuit and graph in the end.
The diode model used was from Motorola. The program is LTspice, by the way. And this is what I did to try to get to the 17.08 V shown on the graph.
So from the datasheet I found from Motorola (https://www.datasheetarchive.com/pdf/download.php?id=7331c4726472d5aca3cd9a2eafe52096f4155e&type=O&term=motorola%25201N4740A), 250 uA is the knee current, at which the impedance is 700 Ohm. What I understand from that is that at 250 uA, there's more or less 10.1 V across the diode, and the resistance is 700 Ohm (which is VERY confusing to me because \$R = \frac{{10.1}}{{250 \times {{10}^{ - 6}}}} = 40.4\;k\Omega \$ - why is it giving a different value here?). So from that, I'd say I have there a current divider. So I just used the values I have:
\$250\;\mu A = \frac{{200}}{{700 + 200}} \times I \Leftrightarrow I = \frac{{250 \times {{10}^{ - 6}}}}{{\frac{{200}}{{700 + 200}}}} = 1.125 \times {10^{ - 3}}A = 1.125\;mA\$
So that's the circuit current (R15 current). Then I have 10.8 V of potential one one side and X on the other. So:
\$1.125 \times {10^{ - 3}} = \frac{{V - 10.8}}{{124}} \Leftrightarrow V = 10.94\;V\$
And that's wrong, acording with the graph. Should be 17 V... Actually before that, the circuit current should be at least 53 mA, since that's what's on the graph and I only got 1 mA...
I've also thought D14 may not be working at such a small current, so it may not be 10.8 and yes 10.1. But I don't see mention of the minimum forward current on the datasheet, so I'm not sure if D14 is working or not. Aside from that, I've also thought there may be some forward resistance on D14 to add to the 700 Ohm of D12, but no graph at the datasheet, so no idea again - though it would not be as high as I say bellow... (right?).
Then I tried to see what resistance the diodes together would have to have for the potential on the left of R15 be 17 V. Seems it should be about 20 kOhm... Though, the current there would be 25 mA and not 50 mA. If I get the current to 50 mA and forget the potential, I get 40 kOhm... Where do I go get those resistance values from the datasheet??? I only saw 700 Ohm at 250 uA, not 40k or 20k!! 40k only from what I calculated above which is VERY different from the 700 Ohm - not sure where the 20k comes from then, as at least I got 40k at another place, but no 20k. Or (probable)... I didn't understand anything of what I saw?
Thanks in advance for any help!
EDIT: Wrong calculations. No 20 kOhm. No idea where I got that from. The correct result should be the 40 kOhm, approx., for the source voltage be 16.18 V.


texts: I'm wondering if MAX712 would charge 4 Eneloop batteries in series. I don't know if it will charge them safely and if it will charge them the correct way. How much voltage will need to be provided to charge the batteries?


texts: How to compile .ccf file using CMI in Sentaurus TCAD?

texts:
I have gone through the Compact Model interface manual provided by Synopsys. They only mentioned to compile the .ccf file using cmi compiler and generate .so.arch file. However, there are no more details regarding this. I couldn't find much help from anywhere else. Hence, It would be really helpful if someone could guide me in this.
Thanks


texts: Would this shift register schematic avoid master/slave if I extended it to four billion bits?

texts:
simulate this circuit – Schematic created using CircuitLab

The basic data structure for the machine I want to build is a shift register. Quite some time back someone told me that if I could implement it without a master/slave architecture then I really should. So I came up with the following schematic for a shift register of four bits. I'm banking rather heavily on my ability to time each assertion of (shift) just long enough to move each bit of data from one position to the right, perhaps a little over two transistor delays, and definitely less than three transistor delays.

I may be able to get this to work for four bits, but my machine is going to need a shift register as large as four billion bits long to do what it needs to do. If I extend this schematic to four billion bits, can I realistically expect to be able to assert (shift) long enough to move each of the four billion bits just one position to the right and no further?

This article was marked as a duplicate of another article, and I was told that if I disagreed that it was a duplicate I should edit it to point out why it's not a duplicate. The original article used BJTs instead of MOSFETs. I was told that the output of M1 and M2 couldn't be amplified by M3. I changed all the BJTs to MOSFETs in an attempt to fix that, but nobody commented on the change. So I started this article out with MOSFETs instead of BJTs in order to prompt people to tell me what's wrong with my design, to tell me why it won't work as a shift register. That's the difference from the original article.


texts: Can't connect ESP8266 to Raspberry serial

texts:
I have been trying to get ESP8266 WIFI module (ESP-12E) to connect to Raspberry PI 3 serial port, but I've tried everything I could think of, but still can't get it to connect.

Connection

I have connected it directly to Raspberry Pi 3 the following way:

I followed this datasheet: http://www.kloppenborg.net/images/blog/esp8266/esp8266-esp12e-specs.pdf

Which states:

  MODE        GPIO15     GPIO0     GPIO2

  UART        Low        Low       High
  Flash Boot  Low        High      High

So far so good, but when I apply the power, nothing happens and when I touch the module, I can feel that it's warm. If I disconnect the GPIO2 pin, the blue LED blinks once on power up, but according to the manual, it should blink twice. Manual also states that there should be a red LED, which apparently doesn't exist for this version.

Raspberry

I ran raspi-config and disabled "Login shell over serial"
I edited /boot/config.txt and added "enable_uart=1"
I edited /boot/cmdline.txt and it currently looks like this:

dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait
dmesg | grep tty returns:

Kernel command line: 8250.nr_uarts=1 dma.dmachans=0x7f35 bcm2708_fb.fbwidth=656 bcm2708_fb.fbheight=416 bcm2709.boardrev=0xa02082 bcm2709.serial=0x99a45a3 smsc95xx.macaddr=B8:27:EB:9A:45:A3 bcm2708_fb.fbswap=1 bcm2709.uart_clock=48000000 vc_mem.mem_base=0x3dc00000 vc_mem.mem_size=0x3f000000  dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait
console [tty1] enabled
3f215040.uart: ttyS0 at MMIO 0x3f215040 (irq = 59, base_baud = 31250000) is a 16550
3f201000.uart: ttyAMA0 at MMIO 0x3f201000 (irq = 87, base_baud = 0) is a PL011 rev2
systemd[1]: Starting system-getty.slice.
systemd[1]: Created slice system-getty.slice.

Finally I tried to connect using the following commands:

picocom /dev/ttyAMA0 -b 9600
picocom /dev/ttyAMA0 -b 57600
picocom /dev/ttyAMA0 -b 76800
picocom /dev/ttyAMA0 -b 115200

picocom /dev/ttyS0 -b 9600
picocom /dev/ttyS0 -b 57600
picocom /dev/ttyS0 -b 76800
picocom /dev/ttyS0 -b 115200

But I can't type anything and when I restart the ESP8266, I see the blue LED blinking once (if GPIO2 is disconnected), but no data. Any ideas what am I doing wrong? Thanks!


texts: 12AX7 Valve Overdrive/Distortion Effect Pedal

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I'm following the schematic below using the recommendations plus a couple of extra LEDs. With the footswitch in the enabled position, I'm not getting any sound. In the bypass position, the input and output sockets are connected as expected.

The valve I am using is very old so could be faulty, is there any way to reliably test it or is there anything I have missed in my variation on the original?

My version:


texts: Using a solid state relay/ photoMOS relay

texts: I'm trying to use solid state relay (Panasonic's AQY277 / AQV215) to switch a light bulb (100 V AC). To control the input, I'm using a signal generator in DC mode with 5 V as input. I have not yet succeeded in making it work. Anyone having any idea about wiring details of these relays?


texts: Can anyone tell me what is the purpose of diodes at the output of a chip?

texts: I am new to engineering, and now I am puzzled. My friend bought the product and he gave me the circuit diagram. But I don't know the purpose of diodes D10-D17. Can anyone give me an answer?


texts: Is it okay to replace voltage feedback op-amp with current feedback op-amp?

texts:
I have an LED driving circuit and a photodetecting circuit drawn as below:

LED driver

Photo detector

TL972IP has GBWP of 12 MHz. But my application requires a very high bandwidth up to 30-60 MHz.

So I've been searching an op-amp with high GBWP and found AD8001ANZ. It has a GBWP of 800-880 MHz. Thus, I thought that it is what I am looking for. (Of course I can make bandwidth wider by lowering gain.)

One thing is, I found that it is a current feedback op-amp and that CFA's output voltage is deterined based on a current between (+) and (-). In addition, it is good for high frequency application since CFA's gain is independent to frequency.

But I am curious if it is okay to simply replace TL972IP with AD8001ANZ with a few number (resistance, capacitance) changes? but without a big modification on the schematic and a physical layout?


texts: A tutorial I am following requires the HL1606 Addressable (digital) LED RGB strip, but this is no longer available. Can anyone either suggest an alternative or equivalent?


texts: Quieting headphone pop: Would it work to put a discharge resistor in a custom dongle?

texts:
When I leave my favorite headphones connected to my favorite smartphone or laptop when I'm not currently playing any audio, I periodically hear a small pop/click/crackle. I suspect it happens when some process "opens the headphone port", even if they don't immediately start playing audio.

Please note that I don't get any pop/click/crackle at other times, no matter how much I rotate or wiggle the plug or cord; so I have no reason to suspect flaky connections of any kind, such as dirty connectors, broken wires, etc.

I saw this answer to a similar question…
Loud pop noise while plugging to a headphones jack
…and I wonder if that applies to my situation.

I'm wondering if the small pop I hear might have the same root cause (charging a DC decoupling capacitor). I'm also wondering if I could implement the proposed solution — wiring a ~100Ω resistor from line to ground — in an external dongle I would place inline between my headphone cord and my audio source device.


texts: What does it mean by P:N ratio of a CMOS inverter with equal rise and fall times?

texts: Can someone explain what does it mean when one say P:N sizing ratio of an inverter. FO=4 and equal rise and fall time.


texts: Two logic circuits controlled from two SPST switches?

texts:
I have two low power 12 volt circuits (C1, C2) that operate relays. I want to control these with two SPST switches (S1, S2) in a Boolean manner: (S1 OR S2) for C1, and (NOT S2) for C2.

Can these circuits be wired in parallel off the same two switches, using relays for the logic gates as shown below?  Will there be any negative interactions between these logic circuits, or these and the relays that C1 and C2 themselves control?


texts:
Charge pumps are very cool circuits because they challenge my ideas about how voltage works.  I'm very comfortable with the math behind line integrals, so to define "voltage" as the work done to move a coulomb from one point to another is perfectly acceptable for practical purposes, and I believe I know how to apply formulas to get circuits that work in practice.

It just seems so abstract.

Let's neglect all magnetic and/or inductive effects, and assume ideal and identical parallel plate capacitors and ideal switches.  My understanding is that with ideal parallel plate capacitors, a Volt is literally a Coulomb per Farad -- in some sense, it is a difference in "density" of electrons and protons between two places, where that "density" is with respect to capacitance.  Going further, I am tempted to view all voltages in this way, just by assuming a low value parasitic capacitor across any two points on the circuit.

This way of viewing voltage is a lot more appealing to me than some vague reference to "energy" -- in particular, since conversations about energy in electronics seem so often run into bandgaps and other quantum mechanical nonsense.  With this Coulombs per Farad viewpoint, you just count electrons and protons, and then divide by a capacitance value that's determined by the geometry and material properties of a particular part of the circuit, and that's your voltage.

Please note: despite my tongue-in-cheek use of the word "nonsense", I have great respect for quantum mechanics.  But QM can be non-intuitive, and I feel that there should be a classical explanation for the behavior of a capacitor.

My view of voltage does fine until I try to comprehend a charge pump.  Take the following circuit:

simulate this circuit – Schematic created using CircuitLab

Suppose that ahead of time, perhaps with more switches, we charged both capacitors to 1V and then disconnected the power supply.  Because of the resistor, VM1 reads 0V with the switch open, and VM2 thus reads 1V.

Because the capacitors are identical, they each have the same number of protons on each plate, so we can compute the difference in number of electrons between the plates in each capacitor as 1V*1uF=1uC=6.241 * 10^12 electrons.

Now, before C1 can discharge through R1, we close the switch.  Instantaneously, the voltage across SW1 goes to zero, whence VM1 reads 1V and VM2 reads 2V.  Because the voltage across SW1 is zero, does that mean that the number of electrons on the bottom plate on C1 is the same as that on the top plate of C2?  I lean towards no, but if not, how is it that this apparent difference in charge does not result in a voltage?

The reason I lean towards "no" is that if the bottom plate of C1 has the same charge as the top plate of C2, then either the charge on the top of C1 has gone up, or the charge on the bottom of C2 has gone down.  But if that's the case, where did the extra electrons come from or go to?  There's nothing connected to those terminals but voltmeters and R1, which we assume draw negligible current.


texts: Beginner Question about the logic behind Ohm's Law?

texts:
In all the physics i learned and practiced many subjects But understanding Ohm's law used to be a big problem for me... Here is what i mean  :

We have a 5 volt battery. And a 3 volt/ 20 mA led.
So general approach to this schema is i learned:
The led needs 3 volts. So we should control 5-3 = 2 volt with a resistor .

V = I*R  & R = V/I
Here as i assume : R = 2 V / 0.02 mA = 100 ohm resistor we need ..
I hope this is correct..

But in this formula we use the voltage that resistor will control : 2 volts .. Since this voltage is resisted against; 3 volts will reach the Led.
But we find the current in formula using the voltage resistor will control and what it has to do with the LED's required Current ? Cause only 2 volts reaching to LED.

I really do not understand the logic behind this ; connection this two unrelated values..
Usually tutorials uses Pipes analogy.. Even with pipe analogy i can not clarify this ..
Example : In a pipe system , If a narrow pipe is stopping 2/3 of water ; the water tribune placed after this will receive 1/3 of the water. So no way to use 2/3 water to calculate anything about the water tribune and no effect on this tribune at all.

Is there any logical explanation of this ?

Thanks in advance from confused person..


texts: MOV C, B instruction in 8085 takes 4T cycles so when and how does the data copies from B to C

texts: As specified all over the internet, MOV C, B instruction in 8085 only takes 4T states to execute but the opcode fetch and decode take 4T states, which means the transfer of data from one register to another does not take any clock cycle. Now there is only one 8 bit bus for data in the architecture of 8085. So if the MOV instruction is using the bus and let the next instruction is one which requires the data bus, which is not possible. So how does the data get transferred from register to another, is there an internal buffer or any other mechanism?


texts: Why is a resistor added after the DC blocking capacitor of the op-amp input?

texts: I read somewhere that the addition of R2 provides the DC return to ground however this would reduce the overall input impedance of the op-amp. Input impedance must be high for an op-amp. How to solve this problem?


texts: Why SATA ALIGN primitive is shifted or swapped on 7-Series GTXE2 transceiver RXDATA output?

texts:
I am using a Xilinx 7-Series GTXE2 Transceiver configured as SATA host PHY. This transceiver is interfacing with an SATA Host controller and an SATA Gen1 device.

During initialization, I am able to see COMRESET, COMINIT and COMWAKE from host and device. They have been captured on RXDATA/TXDATA. TX/RXELECIDLE are de-asserted correctly. The host controller is able to receive and response to complete OOB sequence.

After that, the host is sending D10.2 at 1.5 Gbps to start speed negotiation.  The device is responding with \$ALIGN_p\$ primitives, which are send at 1.5 Gbps.

However, from RXDATA, I can only see D27.3 D10.2 D10.2 K28.5 symbols appearing for only one clock cycle, which is 20'haaaaa, follow by 20'h5f0e4. After that, I am seeing 20'h55555, follow by 20'h5f0e4. The D27.3 and K28.5 character appeared to be correct. D10.2 appeared to be either swapped or shifted. Because the GTXE2 transceiver is unable to decode \$ALIGN_p\$, the speed negotiation failed.

I have set RXCDR_CFG to (72'h0380008BFF40100008). The FPGA is connected to a Gen1 device.

I have implemented a control signal to release RXCDRHOLD when I find 20'haaaaa follow by 20'h5f0e4 in the data stream. After I release the hold signal, it becomes 20'h55555 and 20'h5f0e4. If I don't release RXCDRHOLD, I see garbage on RXDATA. So it seems that releasing RXCDRHOLD only improve part of the \$ALIGN_p\$ characters. K28.5 and D27.3 was right. D10.2 is bit swapped or shifted.

I have came across another post, wherein the author may have experienced similar problems. He modified RXCDR_CFG: Configuring a 7-Series GTXE2 transceiver for Serial-ATA (Gen1/2/3)

I was wondering, if anyone has experienced this problem with Xilinx 7-Series GTXE2 transceivers.


texts:
Calculate Inverse Discrete Time Fourier Transform of the following where \$|a| < 1\$:

$$
  X(e^{j\omega}) = \frac{1-a^2}{(1-ae^{-j\omega})(1-ae^{j\omega})}
$$

Plugging this directly into the IDTFT equation, I get:

\begin{align*}
  x[n] &= \frac{1}{2\pi} \int_{-\pi}^\pi X(e^{j\omega}) e^{j \omega n} d\omega \\
  x[n] &= \frac{1}{2\pi} \int_{-\pi}^\pi
         \frac{(1-a^2)e^{j \omega n}}{(1-ae^{-j\omega})(1-ae^{j\omega})} d\omega \\
\end{align*}

I am having trouble getting started. I'm not sure what to try. None of the standard Fourier Transform property laws seem to directly apply to this.

(This is problem 2.57 from Oppenheim textbook on Discrete Time Signal Processing)


texts: Why does this component on my Arduino UNO heat up?

texts: Every time that I plug my Arduino into the computer, this chip immediately gets burning hot, way too hot to touch, this wasn't something that i noticed happened after a particular event, I just noticed it one day. On the chip it reads "52 TI MSP" I googled this but I couldn't find a datasheet. So what does this chip do? And what could have caused it to break and heat up? I have noticed that the board still works, but is it safe for me to keep using it (for the computer and the rest of the components on the board... and myself)?


texts:
I have written the following code to generate PWM and to change the duty cycle when a button is pressed. In simulations it works fine. However when actually implemented the circuit, the PWM starts when the button is pressed. But after an about 2 secs it will stop. PWM is not generated continuously. Is there any reasons why this is happening?
(eg: PIC is defect, error in assembly code)

*I'm using internal clock of the PIC

 PROCESSOR PIC16F628A
#INCLUDE <P16F628A.INC>
#INCLUDE <BANKSEL.INC>   ;a macro is used to easily change the banks

org 0x00

;set the PWM period
  Bank1
   movlw d'249'    ; PR2 is 249 when Fosc=4MHz, TMR2 prescale=4
   movwf PR2

;set the PWM duty cycle- initially set to zero
Bank0
 movlw d'0'  ; set bits 9 - 2
   movwf CCPR1L
   bcf CCP1CON,CCP1X  ; set bit 5
   bcf CCP1CON,CCP1Y  ; set bit 4

  ;Make the CCP1 pin an output
  Bank1
  bcf TRISB,3

  bsf TRISB,0;make RB0 as input

 ;Set the TMR2 prescale value
   Bank0
   movlw b'00000101'   ; TMR2 = on, prescale = 1:4
   movwf T2CON

 ; enable pwm mode
   bsf CCP1CON,3
   bsf CCP1CON,2

l
btfsc PORTB,0 ;bit test f skip if clear
call inc
goto l

inc
movlw d'50'
addwf CCPR1L,1
return

END


texts: My physics teacher said that on a LC based radio receiver, the frequency knob changes the capacitance of the capacitor, thus changing the resonance frequency. How is that done?


texts: When/why is the solution for an RLC circuit differential equation actually useful?

texts:
Maybe it's an obvious answer that I'm missing, but I was trying to apply the Laplace transform to a differential equation for a maths assignment, and an RLC circuit differential equation was one of the few applications of a sufficiently complicated differential equation that I could justify using the Laplace transform for. But I need to actually justify why this application is useful, and I really don't know why. I have found the solution for my differential equation describing the RLC circuit so I guess I now have a time-varying current function.
But when is this useful?
Sorry for knowing nothing about circuits, in retrospect I should probably have found a different application.
Also, I feel like I should mention this is the method I am following since sometimes I see a Laplace method for RLC circuits seems to go in a different direction.


texts: BLDC and Stepper motor torque ration meaning

texts:
Ok so after searching on the internet for a pretty long time there are a lot of undefined or roundabout articles about torque for both motors.
Hybrid bipolar stepper motor torque. This one is a little bit better defined.
Is the holding torque measured when there is equal current flowing through both of the windings (the rated current / phase)?
PMSM / BLDC holding torque. I really have no idea about this one. They have rated current. Here is a kollmorgen datasheet and chinese servo datasheet.
[

Explanations:

And chinese servo:

Are continious and peak current defined as max current through one winding at a time or total amount of current going through all 3 windings at a time?
To clear any misunderstanding bldc driving techique is FOC / Sinusodial drive with 120 deg out of phase currents.


texts: Two devices on Y 9pin Serial cable to 25pin printer input - Data Corruption

texts:
I have't been able to find a solution, and was hoping for some clarity. I have 2 machines (one is a bill counter, one is a coin sorter) that both support printing over DB9 serial connection, and one printer that has a 25 pin input.

The goal is to have the single printer handle printing for both units through a y-split. On the bill counter in this setup, I am able to print from the bill counter with minor data corruption (a few odd characters interspersed), but am unable to print anything from the coin sorter. Either singulated unit plugged into the Y cable works independently with the other unit not plugged in, the cable integrity and pinouts seems fine. For both units, in theory, they should only be communicating with the printer when a manual print request is initiated, but I do not have access to either protocol manual, or port testing equipment, just a standard DMM.

Do I need to filter each comm line with diodes?
Any insight as to why the other unit wouldn't print when both devices are attached?

Please let me know your thoughts or what additional information I may provide to help drive finding a solution.

Thank you!


texts: Does any MPLAB compiler e.g XC8 have built in functions to control PIC peripherals like in CCS PIC C

texts:
The CCS compiler provides a lot of built-in functions to access and use the PIC microcontroller's peripherals. This makes it very easy for the users to configure and use the peripherals without going into in depth details of the registers associated with the functionality.

Examples:

D/A conversion:  dac_write(), setup_dac()

RTOS: rtos_await(), rtos_msg_send(), rtos_run(), rtos_disable(), rtos_overrun() e.t.c

Non-volatile memory: erase_eeprom(), read_external_memory(), write_eeprom( ) e.t.c

Timers: get_timer_x(), set_timerx(), setup_timer_0() e.t.c

Is it possible to somehow get the same functionality in the MPLABX IDE as well or shall I have to write my own library functions like the ones shown above by writing code that tampers with registers at low level? I am using the XC8 compiler.

The CCS C Compiler having these type of functions is the main reason why I have used it in the past. But now I want to move over to MPLAB.


texts: Speaker systems: When is 25 volt used vs 70 volt?

texts:
I am doing research on installing a small constant-voltage speaker system using a ten year old TOA BG-115 Integrated Amplifier, and I am trying to determine what the reason is for the existence of 25 volt wiring for distributed audio background music / announcement building speakers.

Speakers, with integrated multitap transformer and 25/70v voltage selection:
http://www.specotech.com/index.php/products/audio/speakers/surface-mount/item/572-wb86t

And what this is for anyone who is not familiar:
https://en.wikipedia.org/wiki/Constant-voltage_speaker_system

The more common distributed audio design is to use 70 volts. The only specific answer I have been able to find so far is that "some building safety codes require the use of 25 volts". Yes, but why, exactly?

As far as I understand the main benefit of 70 volt is operating at a higher voltage allows audio signals to travel much further through the distributed wiring network to the speakers.

25 volt will apparently have a correspondingly shorter operating distance for the same amount of line losses, and will lose more signal to resistance. How much this matters is unknown.

Apparently 70 volt can give you quite a shock even compared to 120 volt AC due to the high frequency components of audio signals. That is why a plastic cover is over the audio transformer output terminals of this amplifier, to reduce the risk of shock.

Is this part of the reason for the use of 25 volt systems, less or no shock hazard?


texts: Electronic controlled trash can lid eats batteries

texts: I have installed a nine volt DC power source to take the place of the six 1 1/2 volt series-ed AA batteries, because the trash can lid circuit eats batteries. I installed the power pack after the switch which cuts out the  batteries, so in case of a PG&E power outage I can close the switch and run trash can on batteries. I want to know, if I replace the standard AA batteries with rechargeable AA batteries, can I just leave the battery switch closed with no issue of the batteries and power supply being paralleled together?


texts: Simulation isn't working for high voltage amplifier

texts:
Been trying to simulate on multisim a circuit I saw about high voltage amplifier:

The input is 8 Vp-p and 100Hz and reached to output of 1800 Vp-p and 100Hz.
The publisher mentioned he used the following parts to build it:
OP07 , LM356,  MTP2P50E and BUK456800B.
In the multisim database, I couldn't find these exact parts (perhaps because companies stopped creating them). So, instead I used the following parts for the following simulation:
OP07, LF356H, MTP2P50EG and NDD03N80Z-1G.

For input 8 Vp-p and 100Hz, I got the result of approx. 8 V:

And I can't figure out whats the problem with the design I implanted on the multisim, as I don't get the high voltage that is desired.
Thank you for anyone who reads this and tries to help me, much appriciated !


texts:
I have a water tank that I want to fill up with a well. I have a float switch at the top of the tank and another float switch in the middle of the tank. What I want to do is have the pump only turn on when the middle tank switch opens and to keep pumping until the top switch closes.

This is trivial with a microcontroller but I feel there must be a way to do this with solid-state components. I can convert logic-level to what is needed to drive my contactor - I just need to get the actual logic circuit sorted out. I feel I'm missing something obvious and would appreciate any guidance. Thanks!


texts:
I am learning programming with 8051 and 2051 using Assembly language. About the pound sign (#) I found that it should be used when I am considering an immediate data. Like I found here http://what-when-how.com/8051-microcontroller/inside-the-8051/

MOV A,#23H ;load 23H into A (A=23H)
MOV RO,#12H ;load 12H into RO (RO=12H)
MOV R1,#1FH ;load 1FH into Rl (R1=1FH)

But when using Indexed addressing mode, I found that I have to use # sign to indicate address. And I didn't find it anywhere. This is a simple program I wrote -

ORG 00h
MOV A, #00h
MOV DPTR, #Y
MOVC A, @A+DPTR

MOV A, #00h
MOV DPTR, #Z
MOVC A, @A+DPTR

ADD A, R1
MOV P1, A

Here: sjmp HERE

X: db 00h
Y: db 100
Z: db 50
END

Is there any other way to get value from a variable which is in code memory?
And is DPTR considering #Z as the address of Z? Should not it get data rather then address?

I searched for that pound sign thing but seems I am finding in wrong place.
Thanks for helping me understand in advance.


texts: How many 18650 cells in series for 48V Li-Ion pack

texts:
I'm looking at the Samsung 35e and trying to build a 48V pack.
I'm trying to figure out how many I should put in series to get 48V. I'm assuming I use the nominal voltage to spec that (3.6V/cell)? Should I do 13 in series (3.6V/cell * 13 cell = 46.8V) or 14 (3.6V/cell * 14 cells = 50.4V)?


texts: I am asking a question as a part of library maintenance for electrical equipment.  We have installed a POS machine with credit card swipe on the same outlet as a laser scanner (used to check in books).  Apparently, the POS gets a signal immediately that a swipe has occurred and failed before a swipe occurs.  If the laser scanner is plugged into a different outlet (we are using an extension cord), everything works.  Using extension cords in a commercial facility is prohibited, so does another outlet need to be added?  What could be causing the POS to get a swipe signal? Thanks in advance for your help!


texts: "Dynamic" shifter in priority queue implemented on FPGA (SystemVerilog)

texts:
I'm implementing a priority queue on FPGA such that if some external signal is up (\$w_r\$) the priorities are evaluated and the priority queue us updated accordingly. The schematic is the following:

My approach is:

module priorityQueue(
input logic [13:0] dataIn,
input logic clk,
input logic wr,
output logic [7:0] out1,
output logic [7:0] out2
);

logic [13:0] dataInQueue [7:0];
logic [7:0] we;
bit [2:0] trigger = 0;

always_comb begin

for (int i = 0; i < 8; i++)
    we[i] = (dataInQueue[i][13:8] < dataIn[13:8]);

if (we[7])
    trigger = 7;
else if (we[6])
    trigger = 6;
else if (we[5])
    trigger = 5;
else if (we[4])
    trigger = 4;
else if (we[3])
    trigger = 3;
else if (we[2])
    trigger = 2;
else if (we[1])
    trigger = 1;
else if (we[0])
    trigger = 0;
end

always_ff @ (posedge clk)
    if (wr) begin
       dataInQueue[trigger] <= dataIn;
       case(trigger)
        3'b111: begin for (int i = 6; i < 0; i--)
                    dataInQueue[i] <= dataInQueue[i + 1];
                    end
        3'b110: begin for (int i = 5; i < 0; i--)
                      dataInQueue[i] <= dataInQueue[i + 1];
                      end
        3'b101: begin for (int i = 4; i < 0; i--)
                      dataInQueue[i] <= dataInQueue[i + 1];
                      end
        3'b100: begin for (int i = 3; i < 0; i--)
                      dataInQueue[i] <= dataInQueue[i + 1];
                      end
        3'b011: begin for (int i = 2; i < 0; i--)
                      dataInQueue[i] <= dataInQueue[i + 1];
                      end
         3'b010: begin for (int i = 1; i < 0; i--)
                      dataInQueue[i] <= dataInQueue[i + 1];
                      end
         3'b001: dataInQueue[0] <= dataInQueue[1];

        endcase
   out1 <= dataInQueue[7][7:0];
   out2 <= dataInQueue[6][7:0];

    end

endmodule

I'd like to focus on the always_ff part. Note that there a shift occurs depending on which \$w_e\$ was triggered. So, the shift depends on that factor. So far it seems to work, but is there a better to way to approach this in order to avoid redundancy?

note: the two "outs" are used only to visualize the queue in LEDS in the target.


texts:
Suppose I have some signal input which I know.
The signal is 85 seconds long and its not something I can describe with equation but It looks as follows:

Now, I have made a simple PWN controller that basically compares between the input (this signal) and some repeating sequence signal and whenever it is small it should return 1 to activate and whenever it is larger it should return 0:

However, Inside this repeating sequence signal block there is a need to define the time values and output values to define the signal.

My question is how do I know what amplitude I had like the repeated sequence to be?

Since if I set the triangle tip at amplitude higher than my whole input signal it means that the PWM will be mostly OFF and if I set the amplitude lower than my signal than it would give ON signals.

Thank you.


texts:
This might be a basic question...but I'm having a hard time understanding reverse saturation current in collector-base junction in the active region(Is),
Could anyone explain about it?
Its temperature dependent right?
If so is there a fixed value at room temperature?
How does it change over different transistors?


texts: Want to control 30V LED strip with a microcontroller, any help or ideas?

texts: Like the title says i want to control around 30volts of current (multiple LEDs that will be running all at once, added up to about 30volts.) i want to use a micro-controller to control it so i can add some effect to it, the controller will control 4 LED strips which take about 4.5V ea. and a 12V light strip. any help or ideas to control this project would be great


texts: essential ESD protection for embedded engineering

texts:
For an embedded software engineer who is working and handling prototype boards (microcontroller systems, no crazy stuff like bare wafers or so):

What is a good ESD protection setup?

Background: I want to improve the ESD situation at the office. Right now there is no protection at all and we could clearly improve here. Then again we don't need 100% protection. If we can avoid most ESD issues it'll be fine.

On my list I have an ESD mat and some ESD trays to move boards from one desk to another.

Is a wrist strap essential? From my experience people just ignore these for various reasons even if the company tries to enforce the usage. One argument that I've heard is, that you'll be in contact with the grounded mat anyway, so the risk of a potential difference between you and the device you're working with has already been taking care off. The wrist strap adds no benefit.

Also, besides mat and trays, what would you consider to be the essential and practical equipment to have for the workplace?


texts: MOSFET selection for high current application

texts:
I am designing a reverse polarity protection using the LM74610 chip.Now, my circuit can take peaks of about 90Amps and constant of 50-52Amps. This is quite a load and I want to select the right MOSFET. I have been thinking of the GaN MOSFET family for this application. The requirements -

VDS - 24V,
Id - 50Amps, 90Amps (peak bursts).

I was looking at the EPC2024 MOSFET. It has the following charachteristics -
. It has an Rds = 1.5mOhms

Now, supposing I consider a continous current of 50Amps.
Pd = IdIdRds = 50*50*0.0015 = 3.75W. This is the power dissipated in the form of heat.

Now, my thermal calculations are as stated -

Rja = 42degC/W.
=> Temperature = 42*3.75 = 157degCel. This is beyond the operating temp. So, I will need immense amount of cooling for this. Also, in the maximum ratings they have mentioned a factor of 6degCel/W for 90Amps continuous current. How is this achieved ? I cannot go beyond the 1sqinch,2Oz FR4. So, will this be a bad choice ?

Is using such MOSFETs in high current applications unadvisable ? Can anyone suggest a different MOSFET ?

I then decided to check the PSMN1R0-30YLC MOSFET. This has even lower Rds. But the thermal Rja is not mentioned. Also, the graph below shows that I can use it in DC mode for 24V for drawing only 1.5Amps only. Please check graph below -

So, using MOSFETS the bets approach in such applications ? Can I us 2 MOSFETs to split current flow ? I know it wont be ideal but even if some level of splitting is achieved it is good. I can use 2 GaN MOSFETs to do it.


texts: fast voltage follower (from datasheet of LM318) and current of input terminals

texts:
I was looking at the datasheet of LM318 and found the op-amp configuration below (first image). I think the voltage at input terminal 2 is V input.  But I wasn't able to figure out what V out is going to be.

I can figure out what the V out is going to be for the second circuit, knowing that the voltage at the negative input has to be V in and the current flowing through R1 down to GND also has to flow through R2.

Also, can input terminals of an op-amp output current? (I know that due to high input impedance, no current flows into them)


texts: What is that sugar like thing in the porcelain body of NH2 fuses,315 amp,400v?

texts:
On breaking down a 415v,315 amp Siemens NH2 fuses, I saw some white sugar like material.
What is that?


texts:
this is more of a 'I have no ideas how to route this part' than 'I don't how to technically route this part'. Or maybe both. Basically I have no ideas how to route and what to do here.

R35 cant access those pins which is a big problem. Any ideas?


texts: I'm looking at building a hobby project featuring led strips. I'm looking at 5v RGB addressable LED strips The Strips. I've already more or less figured out how much I need to cut for each section and the total power consumption. Each strip that needs to be cut is < 1 meter in length. In total I am going to have 12 strips. No strip will be longer than 1m individually, but there are 2 sections where the total of the strips in that section will be longer than a meter. What do I need to to to ensure each section has the appropriate power?


texts: Is a "self-bootstrapping" zero-crossing AC power switch possible?

texts:
As a follow-up to this prior question I'm looking for a zero-crossing mains (120V) power switching solution to mitigate the bounce-related EMI I'm getting using the "stock" traditional ON/OFF toggle switch connected directly to the step-down transformer.

In the abstract, what I'm looking for is this:

As I search on the web, I haven't come across anything so far that doesn't require a separately powered "control" circuit, with its own 24V (or whatever) DC power supply.

What I envision is something like one of those dimmer switches that fits into a wall junction box and takes whatever power it needs directly from the mains (without needing a transformer of its own).

Is there such a thing? I vaguely sense I just haven't found the right search term yet. I've been using "zero crossing triac circuit".


texts: Chebyshev filter design (lowpass to highpass with specifications)

texts:
I have been trying to solve the following problem:

Design a band pass filter with 2nd order Chebyshev filters: Low-pass to high-pass (both 2nd order in cascade.) Find the component values (resistors and capacitors.) Use Matlab.

simulate this circuit – Schematic created using CircuitLab
Parameters:
-> Ripple[dB] = 3
-> flp = 10kHz
-> fhp = 3.2kHz

From the following code I have been able to find the transfer function for the low-pass:
n = 2;
ripple = 3;
[z,p,k] = cheb1ap(n,ripple)
H = zpk(z,p,k)
bode(H), grid on, shg

The output transfer function for the low pass filter:

 &nbsp
 &nbsp
I only know some basic equations:

 &nbsp
Circuits:
 &nbsp
Low-pass 2nd order

simulate this circuit
 &nbsp
High-pass 2nd order

simulate this circuit
 &nbsp

My real trouble is knowing the equations I can use to find out the resistor and capacitor values to implement the circuit in a lab. What would you recommend?

Are there Matlab functions I can use for the highpass?


texts:
I'd like to build a UHF (~800 MHz) FM audio transmitter. I have no experience in electrical engineering but I study physics and I'd like to acquire practical experience in electronics. In fact my goal is (almost) entirely didactical, with the purpose of self-learning.

I suppose I will need an oscillator, an FM modulator (let's say I pick the audio signal from a computer through an audio cable, and not from a microphone) and some sort of antenna. I'm asking you how to build all these elements, possibly from scratch.

I guess the biggest problem would be the oscillator, because 800 MHz is really a high frequency and even the function generator we have in the laboratory isn't capable to produce such a signal. On the other hand computers and microprocessors have oscillators in the range of gigahertzes so it should not be an impossible task, either.

If the problem of the oscillator is settled I will also need to interface it somehow with a FM modulator and get a frequency-modulated signal. I don't know how to do this but I am willing to learn

Then comes the antenna. In class we have learned about the dipole antenna, but I guess for my purposes I need another type of antennas. I'm saying this because the length of a dipole antenna should be the wavelength of the generated frequency, at least according to my textbook, and I see that the a UHF transmitter has an antenna shorter than 30 cm.

The reason I want to build a UHF transmitter is that I'd like to transmit a signal to a receiver that is already tuned to that frequency. If this reveals to be too difficult I will do something other instead.


texts:
For learning purposes I mounted basic audio amplifier on breadboard, schematic below:

Basically it works, meaning voltage has been slighly icreased as well as current and as a result I hear the sound in small 8 Ohm, 0.5W speaker. Nevertheless I have a few questions. Thanks in advance for detailed answers:

1.Looking at the schamatic we see point B (red dot). If I remove the C2 capacitor I have no output signal. My explanation to this is, without C2 audio signal is "shoted" to ground immediately before it reaches Q1 base. With C2 however, its right plate is constantly charged and discharged and therefore the signal has the chance to reach Q1 base. Is that good explanation?

2.Even though I use samll values resistor across the circuit I have small voltage and current amplification. Especially I would expect high current gain but it's not so. It's enough to put ~100 Ohm on the emitter terminal and I don't hear anything form the speaker. Below scope capture shows voltage levels having the gain of max 3. It did not help if I powered the circuit from 9V battery instead of 3. (changing base bias of cource). So why I was able to achieve only tiny gain?

I am a bit suprised that it works at all, since audio input signal has positve as well as negative components. While positive components are ok, negative swings should stop transistor operation. My explanation is that the negative swings on left capacitor plate rises right capaciotr plate to positive value with magnitute two times bigger and therefore traniststor is ON. Does it make sense?

Blue signal - Audio_Out

Yellow signal - Audio_In


texts: Large LED Matrix Display of 10 lines of 12 rows x 128 columns

texts:
I need help to drive 10 LED matrix display each of 12 rows x 128 columns.
I am unable to find LED driver that can drive 12 x 128 LED matrix display.

My project requirements are:
1. All 10 LED matrix display has Monochrome LEDs

Is it possible to use daisy chain technique to tie up multiple drivers ? How ? If not possible, what could be the alternative ?
How to supply power this huge LED display matrix ?
Also suggest me the driver chip suitable for my requirement.


texts: I have the following transformer that takes in 117V and steps down to 12V and 9V. However, I don't understand the label. "PUR" and "RED" are listed as 117V, does that mean PUR is power and RED is ground? Or is PUR power and BLK ground (since its 0)? Basically, which two wires do I connect to the power outlet wires? And what about the secondary wires? I'm new to transformers so I don't want to take any chances by wiring it up wrong. Thank you.


texts: What matters, the rms or peak value of the Analog signal to choose appropriate ADC for digitization?

texts:
i have an 23 bit ADC with voltage reference of 1.4 V.
If my input Analog signal is AC with frequency 50 HZ and its rms ranges from 0.2 Vrms to 1.3 Vrms. Then its peak voltages will vary from 0.28 V to 1.838 V.

Now, considering ADC high value that it can digitize (1.4 V). What does it mean?
I mean, if i consider input Analog rms values or peak values to find out that this adc will work for my inputs. Because if i consider rms value then it probably would work, but it ADC is concerned with max peak of incoming Analog signal then my inputs with peaks higher than 1.4 V won't be able to digitized correctly.?

Please guide, what is considered by choosing ADC, is it the rms of Analog or peak.?

And if it is peak, then what would happen if Analog value is higher than adc specified value? Will all values higher than 1.4 V will treated as same digital value??

Thanks in advance..


texts: How to use pir motion sensor to light up 3.8v dc bulb using battery and relay

texts:
I would like to detect motion to turn off my 3.8v 0.3A dc light bulb using pir motion sensor.

Recently I tried to connect it with 5v relay, arduino uno and 2×3.7v li ion battery and the bulb seem to burnt out.

Any ideas on what should I do to my circuit, what values of battery that I need? Or should I put a resistor instead?

*Still a learner!
I try to modify the schematic with battery and dc light bulb referring the schematic from https://www.electronicshub.org/automatic-room-lights-using-arduino-pir-sensor/
(https://i.stack.imgur.com/ndQdV.jpg)


texts: Why do we use a low resistors on Data lines for an ADC for example or a clock?

texts: Why do we use a low resistors on Data lines for an ADC for example or a clock ?


texts:
I am working on a Z80 computer and needed to write data to an EEPROM. I am using the Xicor 28C64AP-25 chip (datasheet). I wrote a program for the Arduino Uno that writes data to the first 4 addresses and then reads the data back. Since I am only using the first three address pins, the rest are tied low. Here is my code, sorry if it seems too cluttered:

#define WE 11
#define OE 12
#define CE 13
#define NUM_ADDR 3
int DP[8] = {A0, A1, A2, A3, A4, A5, 2, 3};
int AP[] = {4, 5, 6};
byte data[] = {0x3E, 0xAA, 0xD3, 0x00, 0xC3, 0x00, 0x00};
void setupDataBus(int mode) {
  for (int i = 0; i < 8; i++) {
    pinMode(DP[i], mode);
  }
}
void setupControlPins(int mode) {
  pinMode(WE, mode);
  pinMode(OE, mode);
  pinMode(CE, mode);
}
void setupAddressBus(int mode) {
  for (int i = 0; i < NUM_ADDR; i++) {
    pinMode(AP[i], mode);
  }
}
void writeByte(int address, byte data) {
  setupDataBus(OUTPUT);
  setupAddressBus(OUTPUT);
  setupControlPins(OUTPUT);
  Serial.print("Write Byte: ");
  for (int b = 0; b < 7; b++) {
     digitalWrite(AP[b], bitRead(address, b));

  }
  Serial.print(address, HEX);
  Serial.print(", ");
  Serial.print(data, HEX);
  Serial.println();
  delay(1);
  // Enable write
  digitalWrite(OE, HIGH);
  delay(1);
  digitalWrite(CE, LOW);
  delay(1);
  delay(10);
  for (int b = 0; b < 8; b++) {
    digitalWrite(DP[b], bitRead(data, b));
  }
  unsigned long time_i, time_f;
  time_i = micros();
  // Start write
  digitalWrite(WE, LOW);
  // End write
  digitalWrite(WE, HIGH);
  time= micros();
  Serial.println(time_f-time_i, DEC);
  delay(1);
  digitalWrite(OE, LOW);
  delay(1);
  digitalWrite(CE, HIGH);
  delay(1);

}
byte readByte(int address) {
  setupDataBus(INPUT);
  setupAddressBus(OUTPUT);
  setupControlPins(OUTPUT);
  byte val;
  digitalWrite(WE, HIGH);
  delay(1);
  digitalWrite(CE, HIGH);
  delay(1);
  digitalWrite(OE, HIGH);
  delay(1);
  Serial.print("Read Byte: ");
  for (int b = 0; b < 7; b++) {
     digitalWrite(AP[b], bitRead(address, b));
  }
  Serial.print(address, HEX);
  Serial.print(", ");
  delay(1);
  digitalWrite(WE, HIGH);
  delay(1);
  digitalWrite(CE, LOW);
  delay(1);
  digitalWrite(OE, LOW);
  delay(1);

  for (int b = 0; b < 8; b++) {
     bitWrite(val, b, digitalRead(DP[b]));
  }
  Serial.print(val, HEX);
  delay(1);
  digitalWrite(OE, HIGH);
  delay(1);
  digitalWrite(CE, HIGH);
  delay(1);
  digitalWrite(WE, HIGH);
  Serial.println();
  return val;
}
void setup() {
  setupDataBus(OUTPUT);
  setupAddressBus(OUTPUT);
  pinMode(WE, OUTPUT);
  pinMode(OE, OUTPUT);
  pinMode(CE, OUTPUT);
  Serial.begin(9600);
  }
  void loop() {
  // init
  digitalWrite(OE, HIGH);
  digitalWrite(CE, HIGH);
  digitalWrite(WE, HIGH);
  Serial.println("Initializing pins for write...");
  delay(1000);
  for (int i = 0; i < sizeof(data); i++) {
    writeByte(i, data[i]);
  }
  for (int i = 0; i < sizeof(data); i++) {
    readByte(i);
  }
  while(true);
}

All those delays are just to make sure I'm not going too fast for the EEPROM.
I can tell via some LEDs that the Arduino is outputing the right data onto the I/O pins of the EEPROM, but when I read the data back, all I get is 0xFF. Here is the serial output.

Initializing pins for write...
Write Byte: 0, 3E
/WE enable time: 12
Write Byte: 1, AA
/WE enable time: 12
Write Byte: 2, D3
/WE enable time: 12
Write Byte: 3, 0
/WE enable time: 12
Write Byte: 4, C3
/WE enable time: 12
Write Byte: 5, 0
/WE enable time: 12
Write Byte: 6, 0
/WE enable time: 12
Read Byte: 0, FF
Read Byte: 1, FF
Read Byte: 2, FF
Read Byte: 3, FF
Read Byte: 4, FF
Read Byte: 5, FF
Read Byte: 6, FF

I have tested an earlier version of the above program with a static RAM chip and everything works great. It just doesn't work with the EEPROM.

Any help would be much appreciated.


texts:
I'm trying to design an integrated power supply to use in IoT projects that I'm working on, some including microcontrollers like the ESP8266 or ESP32. In previous projects I've made, power supply ripple was extremely important to keep low so I just used a linear regulator (along with alkaline batteries since it was a portable product). This time, I'm making projects that are stationary and outlet powered so I'm wondering if this circuit is a way that I can integrate the power supply onto my PCB's directly or if I should just use a wall-wart instead.

The transformer I'm using steps down the input \$120V_{AC}\$ to \$12V_{AC}\$ with a maximum current of 200mA. The target output power for the power supply is 3.3V @ 250mA or approximately 825mW. The BOM list can be found here if component choice would matter overall.


texts: Where does this current source symbol come from?

texts:
There's an old symbol for a current source that's just two overlapping circles, reminiscent of a Venn diagram. There is more than one question on here with people asking what the symbol is, but I'm interested to know where it comes from; is it just an abstract symbol with no meaning behind it, or is it meant as a simplified drawing of something?

Symbol d in the above image (taken from wikimedia commons) is the one I'm asking about. Symbol a is the one that I am most familiar with, and I've never seen symbols b, c, or e before.

I'm aware that the precise reasoning behind any given symbol doesn't really matter, but I simply have an interest in... "etymology", I guess you could call it? ...now I've gotten to thinking about circuit diagrams as a language, and studying them from a linguist's point of view....

That's for another website, though.


texts: What is the meaning of biasing in electrical/electronics circuits? What is the need for biasing in BJT/MOSFET? What will happen after biasing when we apply input signal(AC/DC)? Will biasing signal and input signal superimpose?


texts: How is 10G Ethernet physically possible?

texts:
10 gigabit Ethernet means that 10 billion bits are transmitted every second, but I don't understand how this is physically possible (let alone 100G Ethernet). The fastest CPUs today only run at ~8GHz, but even if transmission doesn't require a CPU, it still seems problematic.

At 10G, each bit lasts only 100 picoseconds, and in that time span, I would think that gate delays become an issue. It's not as simple as setting a line high or low for each bit, surely hundreds of transistors are required in order to output the complicated Ethernet waveform.

This seems like even more of a problem on the receiving end, since the waveform must be sampled at a very high rate, and if this uses ADCs, that introduces even more delay.


texts: Altera Quartus - How do I simulate a different Entity

texts:
I tested the first entity in my project successfully. Now, when I try to create a Vector Waveform File for my second entity, it only lets me add the pins of my first entity. I did set my new entity which needs to be tested as a "Top Level Entity".

I am using Quartus 9, which uses vector waveform files, since I am working on an old FPGA. When creating the vector waveform file, I have to specify what signals go to which pins. I can't select the pins from my new entity there, any ideas?


texts: ST7590 Power Line Communication chip integrated with a PIC18 microcontroller

texts:
I am using the ST7590 chip for PLC purpose which integrates with an STM controller, but my company uses Microchip controllers. I have signed an SLA so I will not post or talk about the non-public information. The public info that I refer to is the chip datasheet and the design guide.

I have followed the design guide to the letter in the hardware apart from the STM chip being used, USB, SDC reader and the JTAG (but these are peripheral).

I am using the PIC18F45K40 to control the ST7590. The EUSART, 8MHz clock, Digital IO and Analog work on the PIC18.

In setup:

Enable Clock;
Delay;
PLC_RESET=0;
DFU =0;
Delay;
PLC_RESET=1.

In main:

Set EUSART;
If(CTS ==0)
    // send the appropriate string of bytes through EUSART;
Delay;
If(CTS ==1)
    // send the appropriate string of bytes through EUSART;
//long delay and Loop.

I monitor the TX of the ST7590 with a Logic probe and get no response.

In the main loop, I have also tried toggling the DFU pin between sending strings of bytes.

The strings of bytes I send I have checked multiple times, but if they were wrong the chip would still send an error response. Therefore I can only assume that it is the chip's firmware that is damaged or lost; alternatively that it is not in the state to be sent commands.

I have also replaced the chip with a fresh one multiple times to make sure the firmware is working.

Do you have any suggestions?

I know I have given very little information, but my hands are tied and the support for this chip with a tertiary controller is limited.


texts: Marlin temperature update frequency 3Dprinter

texts: I would like to know at what frequency is the temperature information pulled by the marlin software. I have looked into the code but it insn't obvious to me.


texts: In actual OFDM trasmitter, is the stepwise waveform after IFFT put on the carrier as it is?

texts:
I simulated OFDM on MATLAB,though,the spectrum of it is not white(flat shape).
Why?
IFFT circuit of actual transmitter uses higher IFFT order than the count of subcarriers?

P.S.

I simulated with the following MATLAB code.

MATLAB code

Generate a random number sequence of size 500 → Generate a waveform with IFFT → Apply step-like interpolation → Multiply the carrier wave → Perform FFT


texts: PCIe riser card: Does it generate a local PCI clock on riser board?

texts:
Does anybody know if a "PCI riser card" generates a local PCIe clock on the riser board that is asynchronous to the PCI clock on the Motherboard, or does the PCIe clock come only from the adapter cable that plugs into the PC motherboard (blue USB cable with 1x pcie connector for PC motherboard)?
the reason why i'm asking is because I was curious if I could use a riser card to plug in a "Xilix FPGA card with PCIe edge connector" to obtain a PCI Clock, Specifically, without pluging in the USB-like cable to the PC motherboard PCIe slot to get the PCIe clock from the motherboard.
I'm hoping there's a PCIe bridge chip sitting on the riser card, with a local pcie clock generation circuit... is that the way a riser card works? Anybody know where I can find a schematics of a typical riser card?


texts:
I'm currently redesigning a board that has a high failure rate.
The design consist of three power rails 3.3v 12v and 24v

3.3v is coming from an USB powered Nucleo STM dev board
24v is my input power from a DIN rail PSU and is distributed via a copper plane on the entire board.
12v is generated with a LDO from the 24v rail.
GND is all interconnected with a copper ground plane.

The board has six Geckodrive stepperdrives mounted on it, those are definitely causing the failures.
Geckodrives have two ground pins, one for logic and one for powering the steppermotors.
They say I should first of all route the 24v as a track to each Geckodrive instead of using a 24V powerplane. (star network)
And also never interconnect the two ground inputs.
So what I was planning to do is giving all 3.3v & 12v devices + Geckodrive logic ground the ground of my Nucleo board.
And the Geckodrive power grounds are connected to my 24v PSU ground.
But how to split the ground at the LDO?
It has only one GND pin.
If I give it PGND do my 12v powered device perform perfectly by having the GND of Nucleo board?
I'm only allowed to share a snippet of the PCB design that shows how the Geckodrives are interconnected.

At the left you have the logic GND of the Geckodrive.
At the right the Power GND.
Both grounds are connected to same GND plane
The brown polygon is the 24V for all six Geckodrives to my surprise it barely makes a connection to the desired Geckodrive pin!!
So in this design all grounds are interconnected.
And one big 24V polygon is feeding all six Geckodrives (so far from star formation)


texts: Understanding MOSFET operating transitions

texts:
I'm trying to conceptually understand the output voltage and the operating condition transitions that the MOSFETs in the circuit below go through as the input voltage is swept from 0 to VDD.
It's not labeled in the circuit but I'll refer to the node between M1 and M2 as \$V_m\$.

Is it guaranteed that M3 goes into saturation before M2 goes into triode? I think this depends on various things like M3's bias voltage but I'm not sure.
Why does the slope of the graph become less steep from the transition of M2 being in saturation to M2 going into triode? I think it's because \$V_m\$ decreases more, which slightly suppresses the magnitude of current increase forced by M1 (since M1's drain-source voltage is now going down much more significantly). So then the output voltage doesn't need to change as much.
Shouldn't the labeled output voltage transition point \$V_{b1}+V_{th2}\$ be \$V_{b1}-V_{th2}\$?


texts: Is there any definitive I2C pin-out guidance out there? Not looking for a "STANDARD"

texts:
EDIT: This has been repeated several times, so putting it on top: Yes, it is well known that there is no "standard" for I2C inter-device connectors, but surely this community can formulate a list of "guidance" points for making such interconnects, based on signal behavior, noise minimization, and mitigation of risk due to wrong connections.

NXP defined the I2C standard without specifying a pin-out for I2C connectors, is my understanding. The only guidance from NXP seems to be a mention of placing a Ground and / or Vss between SDA and SCL if Vss / Gnd are carried across the interconnect.

Purchases of various I2C modules has left me with a variety of I2C pin-outs, and a bit of a task keeping track of the various little ribbon-cable-switching shims I've had to make for them.

e.g.

Mono OLED module: SCL, SDA, GND, 5V (obviously not ideal, since clock and data are next to each other.
Sensor Shield for Arduino: SDA, SCL, GND, 5V (again not ideal, plus switched SCL/SDA)
Color LCD module: SCL, GND, 5V, SDA (Yay!)
No-name I2C repeater: SCL, 5V, GND, SDA (ouch, they switched power pins! Nearly let the magic smoke out.)

So my question is this:
Is there a definitive / authoritative guideline for the I2C 4-pin connector pin-out sequence to use, where both Vss and GND are to be carried from host to device?

Failing this, is there any directory, however incomplete, of I2C modules / devices listing the pin-out each has adopted?

Clarification: Looking for guidelines such as "put Vss closer to SCL because..." rather than a defined standard which clearly does not exist.


texts: Will an ATMega128A work with a 12.8MHz external crystal?

texts:
Ultimately I am trying to create a timer that interrupts on a 50kHz cycle. Using the equations in the ATMega128A datasheet, I've determined that I would have to scale down a 12.8MHz crystal.

In the datasheet I've found language like, "for resonators, the maximum frequency is 8MHz with CKOPT unprogrammed and 16MHz with CKOPT programmed ..." and also, "... Max operating frequency 16MHz ... " There is nothing in the datasheet that concisely tells me whether or not a 12.8MHz crystal will work.

Is there no minimum frequency? I just don't understand this, I guess I'd expect them to give me a range of working frequencies somewhere but I guess not. I would also like to add that I am relatively new to microcontrollers and this may be something I just don't understand in general.


texts:
So I looked around electronics.stackexchange for this one and here is where I landed:
What type of USB Protocol for Datalogger

Basically, I would like to sample a voltage (specifically, from a photo diode through a trans-impedance amplifier) and send it to the PC. Though, I just don't want to send it to a hyper terminal, I want to graph it in my own GUI and do fun things like showing a FFT of the data. So I see two parts to this project; microcontroller and GUI.

Thing is, I am not sure where to start. The microcontrollers I have experience is with BASIC STAMP 2, PICAXE, and some Arduino. But I want to use something that would be more popular in industry. So I decided that I would perhaps go with the dsPIC series and learn it through mikroC's online book.

I was going to learn to use HID support on the dsPIC and send it to the PC (I know, easier said than done). I read info on the internet that CDC is better since it is not interrupted but I like the idea of not having to download drivers. With a quick google search, I see that other companies make HID dataloggers so it must be okay?

As for the GUI, I have basic academic experience with C++ and Java. I have used Java Swing to make some desktop GUI applications but they were fairly simple compared to what I want to do here. I am also not sure how to "read" the USB port for data to use as inputs for my GUI. I was thinking that I was going to use (well, once I learn it) C# since I read somewhere that it is fairly easy to grab data from a USB port for a program and show in a GUI. I was going to start with the GUI part and attempt to use dummy data like a mouse to make sure it works, maybe even use an actual datalogger for testing. Then muddle with the dsPIC part.

So I guess my bottom line question is am I approaching this the right way? Is what I proposing even possible?


texts:
I'm new to the forum, have no electronics background  and I've just started learing PIC programming (Mplab X c-compiler) so please forgive me if this question is irrevelant, stupid or both.

Short background to my question:

There is a lot of info in datasheets and on forums about reading 16 bit timers on 8-bit PIC:s and I think that I have a basic understanding of the overflow problem that could occur when reading the high and low registers separatly.
I've seen that some PIC18 (e.g. PIC18F45K22) have a hardware buffer of the high register to avoid this problem.
I'm using the timer1 module of a PIC16F1783. In my understanding this timer can count EXTERNAL signals in both ASYNC and SYNC (at least for moderately fast signals) mode.

My question:

In the datasheet for the PIC16F1783 on page 177 (http://ww1.microchip.com/downloads/en/DeviceDoc/40001579E.pdf) there is a paragraph called: "READING AND WRITING TIMER1 IN ASYNCHRONOUS COUNTER MODE".
For the PIC1845K22 there is a similiar paragraph on page 165 (http://ww1.microchip.com/downloads/en/DeviceDoc/41412F.pdf).
Why does is say ASYNCHRONOUS here? Wouldn't the same problem occur if timer1 was used as external SYNC counter OR internal/external timer?
Does it mean that it's somehow possible to read both the high and low registers consecutively and get a valid read when external SYNC counter mode is used (even without hardware buffers or software tricks)?

Thanks for your time!
Kind regards / Henrik


texts: Isolating polarities on a series wired battery bank

texts:
Can anyone, with 100% certainty (that means you know what you are talking about) tell me how to "isolate" the positive from the negative posts electrically in one direction so I have a true 'positive' and a true 'negative' in a series wired battery bank with 3 12 volt marine top post batteries. I already know about Schottky barrier diodes but I am looking for a better product that does not have as much reverse leakage. I also am learning about N MOSFETS. Forward voltage will be 34- 36 volts and trying to convey a maximum of 180 Amps with a minimum of 140 Amps.
    Please help; thank you.


texts: What is the voltage across the circuit shown?

texts: I'm having trouble finding the voltage between the points 0 and 1. Can anyone help me? By applying KVL on each closed loop I find that Vi+IiRi is constant for every "i" but I don't know how to find the current flowing trough each resistor and therefore the corresponding voltage.


texts: Is a Type 2a PID(ish) controller just an example of an augmenting integrator?

texts:
In a previous question I finally cracked the code on deriving for myself the transfer function for a Type 2(a) compensator like this one, built around an op amp.

As it turns out, for AC analysis purposes, that configuration is exactly like an augmenting integrator circuit, depicted below, except that the feedback resistor (\$R_O\$) and capacitor (\$C_O\$) are transposed in their branch. (Note that the resistor denoted above as \$R_{lower}\$ "disappears" from the Type 2a controller in AC analysis. The op amp inputs are equal (or very close to it) so no current flows through that resistor.)

Unsurprisingly, I get the exact same transfer function, regardless of the order in which the two local feedback devices appear.

$$\frac{1 + sR_OC_O}{sR_IC_O}$$

So my question is: Is the Type 2a controller circuit just an example of an augmenting integrator? Does it matter whether the capacitor is connected to the output node or the inverting input?

I've seen the Type 2a circuit referred to as an "integrator" or "integrating element" in various sources, but with no further elaboration. I was initially puzzled by why it didn't look like a classical op amp integrator, which lacks the resistor in the local feedback loop, and am suspecting this may be why. And, mathematically, at least for impedance, the order of those two components doesn't matter. Intuitively it seems like there must be some difference, although perhaps a subtle one. In actual circuits the capacitor invariably appears on the inverting input side.

Can you illuminate? Extra admiration if in the process you can explain how an augmenting integrator is different than a regular one (which also appears in PID controllers) and intuitively why an augmenting one is the right choice here. If that's really a separate question just let me know and I'll post it separately :)


texts:
I am reading a textbook Circuit Design with VHDL, 3rd Edition by Volnei Pedroni. There, he claims that there exist 3 categories of finite-state machines - namely, regular, timed (where the output depends on the time as well as on the input), and recursive (where the output also depends ont he previous outputs):

So here's the question: to those two other FSM categories fall under the strict mathematical definition of an FSM? Is it even valid to call them finite-state machines?
UPD: Is the circuit below (which has an "auxiliary register" in addition to the state register) still an FSM?


texts: Problem with using SCR to control power for an electric grill

texts:
I'm doing a power controller for an electric grill, where through PWM I allow to pass x number of cycles from the 124V @ 60 Hz source of my lab.

Here you have the diagram:

simulate this circuit – Schematic created using CircuitLab

It consists on a triangle signal that joins the LM311 comparator on one pin, and in the other one the input is the LM35 signal multiplied x 7. The system has been designed to get thinner pulses from the LM311 as the temperature on the sensor gets closer to 60 °C, where pulses must disappear. The PWM signal goes directly to a MOC3011, whose job is to excite the Gate pin from the SCR TIC116. I've checked everything so far with and scope. So, so far, so good.

As you may see, the frequency of the square signal that generates the triangle one, is 0.6 Hz. This means that in a whole pulse, 100 cycles from the 60 Hz might be involved. So, when the Gate is on, the grill would be working the number of cycles that are "inside" the gate pulse according to the temperature on the sensor.

Here comes the problem: the grill keeps working even when there is not any signal at the comparator output. I haven't seen the voltage signal at the grill because I have no way to isolate the scope from ground (it is not mine so I don't want to break it). But, anyway, something is happening in between the moc and the scr.

I can't use a TRIAC, my professor banned it.

EDIT: Do you think that replacing the moc3011 with a moc3041, the one with zero-cross circuit inside, may help to solve this? What would you be so kind to suggest?

Regards.


texts: Finding the maximum storage of a CD from measurements of pits and lands?

texts:
Full disclosure: This is schoolwork. I'm not asking for anyone to solve this for me, I am only asking if I'm on the right track with my thinking.

I have imagery of a CD from an atomic force microscope showing the pits and lands. Using Gwyddion I have measured the lengths of 150 different pits.

The task I am currently stuck on is finding the maximum amount of data the disc can hold. My thinking is that if the minimum size of a pit is 3 channel bit periods, this represents 2 bits of data. I could use my measurements of the smallest pits to find the area per unit bit, then use the area of the writeable surface of the CD to find the total amount of bits a CD can hold.

My issue with this is that the AFM imagery is not perfect, and area calculations of the pits and lands may be rough. Is there a better way of doing this or am I on the right track with my thinking?

Thanks!


texts: PCB vs SMD antenna for 2G cellular IoT device

texts:
I am designing an IoT module to read water sensors in an Agricultural field, then send the data through cellular to the cloud. My design uses the SIM800H, a quad band cellular modem, to send and receive signal.

I need to decide what kind of cellular antenna to use: SMD or pre-made PCB. I found a few options here, but no general guidance on how to choose one. Note I am not going to build my own antenna in the PCB, but instead will buy a pre-made PCB antenna. The SMD antennas are smaller and easier to mount (just soldered with the other parts), but will they have the same range as the PCB antennas? What are the pros and cons of each type?


texts: LTspice Monte Carlo with different model libraries

texts:
I'm trying to figure out how to do my first Monte Carlo analysis in LTspice. I have a very simple schematic that includes the SPICE model for PN 74LVC3G17DC (vendor link).

The distribution from the vendor includes 3 library files, 1 for fast/nominal/slow performance of the part. (There are also multiple netlist files for the performance of the different IC packages available).

I want to run a Monte Carlo where not only are my resistors/capacitors varying, but also the performance of the IC varies (as defined in the different libraries provided). Right now I have a spice .INCLUDE directive at the top level that defines which library to use; and then I run the simulation multiple times to compare. There has to be a better way... right?


texts: How to take Time Measurements using LT Spice

texts:
I've been fooling around with LT spice .MEAS feature for a while now and I just can't seem to determine how to take the time measurements I need for an assignment.

I can look at the time values on the waveform viewer and determine an estimated time, however given that LT spice is equipped with a measurement feature I'd like to be precise.

I have a simple circuit of a voltage source in series with a resistor and capacitor and I need to find the time that the voltage at the capacitor reaches 63% of the Voltage input. I think this is called Rise Time?

the command I've been trying is:

.MEAS Tran res1 FIND time WHEN V(Vout)=0.63(Vin) cross=5 TD=1m

essentially I need to find the time that it takes Vout to reach 3.15v (63% 5V(Vin))

Thanks


texts: Cant recognise a Damaged component of switched-mode power supply

texts:
I was repairing an smps ATX power supply I found a damaged component that I could not it recognise. I thought it's a power switch since it was mounted to a heat sink along with tow D13007 NPN power transistors and I could not find the datasheet due to the missing part number after explosion .Can someone with expertise in this type of circuits guess what this could be?
EDIT :

EDIT :


texts: Reed switch melting closed in simple LED circuit -- What resistor to use?

texts:
Made a simple circuit with a reed switch, wall power source and LED strip (for a bathroom occupied sign).

Worked as I’d hoped at first.  But, after a while, THE REED SWITCH MELTS CLOSED--leaving the light stuck on.

Im guessing I need a resistor?  Can you help me figure out what type and where it should go?  I tried reading about this but I was quickly overwhelmed.

Or is the problem is more fundamental? (e.g., I read that I may want to use a relay to separate the LED/power source from the switch.  Is that overkill?)

Thanks for holding my hand. I know it’s a very, very simple question--but ya'll are saving my life. :)


texts: What's difference among impedance analyzer, spectrum analyzer and vector network analyzer?

texts:
Spectrum analyzer and vector network analyzer are the common instruments in the measurements of high frequency for electronic component.  I think two of the most important issue in the high-frequency measurement probably is the impedance and S-parameters.

I have the following questions:

Why don't we use the impedance analyzer to do so?
Can we use a impedance analyzer to measure impedance or S-parameters?
If we can't, what's the problem when we use the impedance analyzer?
Can impedance analyzer be replaced by spectrum analyzer or vector network analyzer? Why or why not?

Original question:
Impedance analyzer, spectrum analyzer and vector network analyzer are the common instruments in the measurements of electric circuits at high frequency.  I want to wonder what's the difference among these instruments?  What's their major functions, advantages and disadvantages?


texts: LM336 Zener diode and LM759 opamp circuit as a stable DC 5 volt power supply generator

texts:
I would you to help me to understand a circuit I have in my notes which is reported in the following picture.

First of all it's my first time in which I see the supply voltage in some ways connected to one of the opamp inputs, which looks a little bit weird to me. Secondly I would expect a 2.5 V as output voltage instead of the 5V reported here.
In fact, according to my knowledge, the opamp is in a kind of non inverting configuration, where the gain should be
\$ G = 1 + \frac{R_g}{R} \$
since \$R_g\rightarrow 0\$ and \$R\rightarrow \infty\$ then the gain is \$G = 1\$.
Furthermore the LM336 has a breakdown voltage of 2.5 V, honestly I am not sure the voltage drop is large enough to guarantee a breakdown configuration, but I don't see any sense in putting a Zener diode in confinguration which is not the breakdown one.
From these considerations, I argue that the opamp, with its gain \$G = 1\$ provides a stable tension of 2.5 V in its output, and that the current passing through R should be \$(12V-2.5V)/1k\Omega\$ which is something less than 1 mA.
Is there anything wrong with my considerations? Furthermore, why do I need this configuration to have a stable 2.5 (or 5 V in the case in which I am wrong) power supply voltage? Is there any difference with a power supply obtained with a much more usual non inverting op amp?


texts: How does one get started with electrical engineering?

texts: Total beginner here. I know absolutely nothing about anything, but I want to build stuff. Preferably for cheap. Books, kits, anything?


texts: How do I build a micro controller based laser detector

texts: I want to build a laser detector using a photoresistor and a pen laser. Ideally, I would like to increase the surface area that detects the laser beam, perhaps through refraction or diffusion. I'm also wondering if it's possible to either filter the light, so that it will only detect a red laser, or somehow implement using a photoresistor that is only sensitive to laser light. Has anyone implemented something similar before ?


texts: RC Circuit response to different input voltages

texts:
For an RC  time constant circuit like below, what is the behavior of the circuit for different inputs:

A Linearly rising input.
A repeating Sine wave
Square wave

Based on the values I do understand, that time constant would be 1/RC. But I could not intuitively understand the working of the circuit.
From the circuit, it looks like the C would first allow flow through till it charges, after which I should just expect the input voltage + Cap voltage at output, and this process would repeat.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm using a CD4017 to control 8 Mosfets. But my problem is that I only get a output from just 1 pin, this pin is random every time i power up the ic. I wired it up like that
I shorted reset and output 8 to reset the ic and restart with 0. Is that the mistake or do I have a thinking error?

Schematic with Mosfets


texts: Using piezo buzzer to play complex waveforms

texts:
Would it be possible to play complex waveforms(sine waves, triangular waves, multiple voices and suchlike) using a normal piezo buzzer? The buzzer in question doesn't have internal oscillator. [Datasheet]

I have only ever seen piezo buzzers used to emit square waves(via PWM) and speakers with magnets to play more complex waves/music. Is there some inherent flaw in piezo buzzers that makes it unsuitable for playing complex waves/multiple voicings?

I intend to use an R-2R ladder DAC on a SI-PO shift resistor driven by an ATtiny13 to create waveforms to drive the buzzer.


texts:
I'm working on a project and I need some assistance.

I have an audio tube amplifier output stage that I need to have adjustable operating points while maintaining a DC null at the output.

[![enter image description here][1]][1]
As you can see it's a white cathode follower with a DC offset servo to null the output.
I need to be able to adjust the load line but if I adjust the operating point I must also adjust the servo offset.

R12 is the variable resistor to set the CVS voltage but in order to maintain 0vDC on the output of the amplifier and keep the current of the tubes balanced I need to decrease the negative supply voltage of the servo when I increase the resistance of R12 and I need to increase the supply voltage of the servo when I decrease the resistance of R12, up to -300v.
Sadly opamps with the required supply voltage and output swing don't exist unless you want to pay $500

So I have 2 problems, I need to have some sort of servo that will adjust the supply voltage of the DC offset servo as I change the resistance of R12 and I need to figure out an alternative way to an opamp for use as a DC offset servo since no opamp worth paying for is going to handle the needed voltages.


texts: Reflections of Low bit rate signal and High bit rate signal

texts:
I was reading wikipedia page on Signal Integrity and got stuck with this paragraph. It says:

  The channel flight time (delay) of the interconnect is roughly 1 ns per 15 cm (6 in) of FR-4 stripline (the propagation velocity depends on the dielectric and the geometry). Reflections of previous pulses at impedance mismatches die down after a few bounces up and down the line (i.e. on the order of the flight time). At low bit rates, the echoes die down on their own, and by midpulse, they are not a concern. Impedance matching is neither necessary nor desirable. There are many circuit board types other than FR-4, but usually they are more costly to manufacture.

As far I know, Digital signal bandwidth is function of it's rise and fall time. Hence, Reflected power will dependent upon rise and fall time of the signal, not on bit rate of the signal. However, in the above paragraph, it is mentioned that for low bit rate signal reflected power won't effect the original signal. I am not able to understand the above statement. Can someone help me?


texts: Simple Li Ion integrated Charger and balancer

texts:
I am currently working on a project, which should contain a Li-Ion battery pack in the form of 8 18650 cells in 4S2P.
The main consumers of the build are a class D amplifier and a single board computer, probably a Banana Pi Zero.

I would like to have a charger and balancer circuit integrated in the project, which would ideally be controllable in some form by the SBC. A charging voltage from 16V DC (or higher if needed) would be supplied by a power jack.

I have looked for charging and balancing ICs, the only suitable one I found, is the BG24702/3 from TI. It could handle the charging, but requires a huge amount of external circuitry.

Other ICs I’ve found, are only offered in QFN packages or similar. But I want to be able to solder everything by hand

Do you know a good and/or simple method for charging and/or balancing?
Is it possible to get a simple CC/CV power source and then charge and balance periodically?


texts: Can anyone identify this IC (in a Sebo Automatic X4 Extra vacuum cleaner)?

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This IC in on the controller board of our Sebo X4 vacuum cleaner, which suddenly stopped working. At first, I thought it was just a case of dirty contacts, because I dismantled it, cleaned everything, reassembled it and it worked again, but only for a day, then it died again.
There's not a lot on the PCB, just this chip, the blue 8 MHz ceramic resonator (its outer pins connected to pins 3 and 4 on the IC), what seems to be an op amp and a triac, a few  capacitors, diodes and LEDs and a load of resistors. For so few components, a replacement board is ridiculously expensive at £100+ and as the vacuum is almost 10 years old it's not worth spending that amount to fix it. Therefore I'd like to try to diagnose it, but without knowing what this chip is, I have no idea what readings to expect from it. I've spent ages in Google, on Mouser, Farnell and various other suppliers trying to find a datasheet but with no success.
I'll happily supply any other photos of the board or any other info that people might find useful. Any help or suggestions would be very much appreciated.
Thanks in advance.


texts: Is current source also a voltage source?

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I'm confused between current and voltage sources; I get the text book definition but I am not able to understand real world difference. To me both current and voltage sources seem as the same. I understand that ideal sources doesn't exist.  What is an example of practical current source? In order to produce current, we need voltage, so then isn't a current source also a voltage source? Since a battery is a voltage source and it produces current when connected to a circuit, isn't it also a current source?

Please help me understand real world example and usage of current source and how it is different from a voltage source.


texts: Unable to use the VGA port correctly, De1 Soc distorts signal depending on the output pin

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This is a followup to my previous question.

The code I was using, pin assigmnets and the theoretical timings for VSYNC and HSYNCH were correct.

I have used to oscilloscope to look at the signals, and have gotten very weird results that I am unable to explain or fix.

The signals generated when displayed on one of the GPIO pins and shown on the scope have the correct duty cycle, frequency and amplitude.

If if i send the same signals to the VGA outputs and measure the voltage at the actual pins of the VGA I get very differnt results.

VSYNC displays exactly the same as it does on the GPIO, while HSYNC has a pulse which is around 0.33V and its frequency and duty cycle matches the one of the VSYNC.

I think this is very interesting as VSYNC is derived from HSYNC yet VSYNC is correct while HSYNC is distorted.

I am beginning to think that the FPGA board is faulty, rather than this being some fault due to my design as I didn't even know you can unintentionally drive a signal at 0.33V.

My query is, has anyone had a similiar problem or knows how it may be possible to fix it from quartus window or should i just dump the board.

cheers


texts: Old-school pseudorandom pulse generator (requesting assistance with hardware design)

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I would like to design an old-school pseudorandom pulse generator to trigger various types of events (hardware suggestions only please - no programmable ICs). The events that I want to control need to happen, generally speaking, in the following categories of frequency: many times a minute, a few times a minute, once a minute, once every few minutes, once or twice an hour. Within each category of frequency, the event should occur "randomly," which is to say, the event's recurrence should not be exactly predictable. To give you a sense for why I want to build this: imagine a video game that has various scene elements, some of which occur very often, some that happen pretty frequently, and others which are infrequent... you get the idea, I hope.

The reason that I would like a hardware-only solution is that I am purposefully trying to learn about discrete logic - things like shift registers, multiplexers, Boolean logic, etc. Efficiency, speed, size, and cost are not my primary concerns. Hopefully there are some vintage electronics fanatics out there who will help me in my quest for knowledge! Thanks :-) PS: a drawn schematic would be tremendously appreciated since I am learning and probably won't be able to understand or build vague suggestions.


texts: Solveability of a circuit(schmitt trigger)

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I was reading about Schmitt triggers and something is bothering me. Given that each component is memoryless- shouldn't the circuit be solvable(as in, for any input voltage it should always be immediately at a steady-state)?

Why can't it be described by a set of time independent algebraic equations since the V/I relationships of all components in the circuit are time independent?


texts: Energies carried by electric and magnetic fields in plane waves

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This is a newbie question. I'm trying to understand what I think must be a very basic concept with an obvious answer, but I want to be sure.

Do plane wave electric and magnetic fields of equal strength at the same frequency and same waveform carry equal amounts of energy?

In other words, if a dipole and a loop antenna of equal length encounter plane waves in free space at the same frequency and with the same waveform, and signal source power levels are adjusted so that the electric field to which the dipole is exposed is equal in strength to the magnetic field to which the loop is exposed, and all other variables are equal, is the current induced in each antenna equal?  Please assume ideal antennas that convert all of the energy they receive into current and that have no other properties that affect the results.


texts: LED as Zener: is this a good way to lower the BOM cost?

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I had an old AM radio board designed to operate with a 3V CR2032 coin cell. I want to revitalize this old junk with as few parts as possible and convert it into a USB-powered AM radio with a built-in speaker. Parts I have for this project include three caps, two resistors, a blue LED, an 1N4728 3.3V Zener, a speaker and an LM386 audio power amplifier.

simulate this circuit – Schematic created using CircuitLab

My question is that can I get away without the Zener and use the blue power indicator LED (my bach have a forward voltage of about 3V) instead like this:

simulate this circuit