texts:
I recently designed a PCB and have been testing it.The PCB mainly consists of the Bluetooth Module BMD-350 and HX711.( There is an accelerometer and RGB-LED as well but we haven't mounted them yet). The schematic is attached herewith:

While testing it, I was baffled by the strange current consumption pattern of the device. We are powering the device up by a Li-Po battery 3.7V 1500mAh.And we have programmed it in such  way that for 30 seconds, HX711 is active and sending weight data and BMD-350 is active and transmitting packets. For the next 30 seconds, we put the HX711 in low power mode while BMD-350 is still active and sending earlier info. Thereafter, the BLE also enters deep sleep mode.
As it is a battery powered device, we wanted to monitor current consumption and hence we connected a multimeter to the device terminals. The PCB is displaying different current consumption patterns:

Generally, every time I power it up, the device goes into either of these two states.I guess state B is the desired behavior. However, out of every 10 attempts on switching on the device, 3-4 times, it enters into state A and consumes high currents, even in sleep mode.And whats even more strange is that sometimes,when device is consuming 9.4mA in state A third mode, after 30 odd secs, it suddenly starts consuming 0.03mA. So the behavior is kind of erratic.
I de-soldered the HX711 section and the strange current pattern kind of still continued which makes me think that the problem is with BMD-350. The BMD-350 has been programmed to transmit in DC-DC Enable mode in active state and goes to deep sleep with sd_power_system_off.
Could you it be the firmware or the floating pins causing this issue ? Has anyone here faced similar problem while testing a device ? Any help will be appreciated ! Thanks.


texts:
What current is best, longevity wise, to run an LED at?

For example in the below data sheet, an RGB LED from sparkfun, the absolute current limit is listed as 20ma. However running an LED at 20ma or close to it is likely to degrade that LED an an accelerated rate, correct?

If I want to achieve decent brightness but maintain a long life for the LED what current should I provide to an LED?
And if I do provide less than optimum current in order to increase life time, what sort of returns are expected?

Is it negligible or worth it?

https://cdn.sparkfun.com/datasheets/Components/LED/YSL-R596AR3G4B5C-C10.pdf


texts: Pressing a physical button, but digitally using an Arduino in an existing circuit

texts:
I have a pair of speakers that by default select their input as bluetooth and I have to press a physical button (every time I power them up) to switch their input to auxiliary.
So I'm thinking of a small arduino based project where every time the arduino starts up (I will wire it to get 5V when the speakers start) it will simulate a button press.
The software part is easy, when the arduino starts, just output the correct voltage on one of the pins, connected to the switch.
Trouble is that I need to press the switch just once (if I press it more than once, the inputs will cycle) and I cannot really understand the electrical schematic.

So as you can see there are 5 switches, all connected to the pin 45 of the MCU.
I want to simulate a single press of the SW10/INPUT button.
Conceptually I think the pin 45 measures the voltage (since every button is series with a different resistor) in order to find out which button was pressed.
So, is the AD_KEY line connected to the MCU between pin 45 and the 3,3K resistor?
Just like a voltage divider?
If yes, does this mean that on startup, and only on startup, it is sufficient to output 1.2V [a] from the arduino to the AD_KEY line (which leads to pin 45, where the speaker's MCU will read) in order to simulate a button press?
Electronically, is there a way I can do this just once at the beginning, without wasting an mcu/arduino (even if just a micro arduino) here?
[a]: If we're talking about a voltage divider then when SW109/INPUT is pressed we have:
$$
V_{pin45} = V_{in}\frac{R80}{R80 + R1} =>
$$
$$
V_{pin45} = 3.3V\frac{2K\Omega}{2K\Omega + 3.3K\Omega} = 1.24V
$$


texts: Do force-sensing resistors draw current?

texts:
I know that a resistor in a series and parallel circuit would draw a certain amount of current. However, would a force sensing resistor wired with a 10k pull-up like in a typical microcontroller application draw current with no force applied to it? And how about with force applied to it?

Thanks for your help.


texts: How do I stop my light flickering in a relay motion circuit?

texts:
simulate this circuit – Schematic created using CircuitLab

My circuit has a motion detector that is only active when the solar panel has light upon it. (Night activated light) the output of the motion detector activates a relay which in turn activates a 230v light.

My issue is that in around 30% light the relay clicks on and off very fast as there isn't quite enough current to fully activate it causing the light to flicker quickly

I cannot modify the motion detector circuit only the wires going to each component.

Any ideas?


texts: What would happen if write strobe signal is asserted in asynchronous SRAM as data & address are toggled

texts:
This question is about SRAMs, specifically the ISSI IS61WV102416. This is an asynchronous SRAM. To write, we asserted CEn, put the data and address on the signal lines and then toggle the WEn signal high to low and then high. I think that the WEn could be called write strobe though I do not know what strobe generally means in this context.

Rather than toggling the WEn signal each time I put in a new data and address value, what would happen if the WEn is kept low and the address and data are changed simultaneously? I do not know if this will work since in physical hardware there will be a small difference in speed at which they toggle i.e all address and data lines will not change to new state simultaneousl. Therefore, I get the impression that the data may get corrupted in the memory. Is that correct?

I assume that if we don't have to toggle WEn each time new data is to be written, the data writing process shall speed up.


texts:
Why don't we keep low voltage winding of transformer at one loop and adjust the rest of the circuit accordingly? Like in clamp meters.
Also is there any software where I can model unorthodox shapes for my transformer and simulate it's flux flow etc?


texts:
I have an MPU-6050. I have known that it uses I2C bus for communication, but I have no experience of the I2C bus. I know that SDA and SCL serial wires are used in this communication. I have got knowledge about writing and reading from an address on I2C bus from Implementing I2C in Assembly.

In this article, it is said that one should initialize I2C bus, then send the address of location on I2C bus, and then read or write.

My question is this: Is it such that I send the address of gyro's x/y/z on the MPU-6050's I2C bus and then the data of that address will come on the SDA line? Are the gyro's x/y/z addresses the address that are mentioned in the I2C articles?


texts: One Gate Voltage to Control Multiple MOSFETS

texts:
I am wanting to control 5 voltage signals with MOSFETs (0-1V each, through drain-source of each MOSFET) from BNC connectors to then observe with an oscilloscope. The circuit is optically isolated and activated by a transistor on the 12V VCC line.

I have a few questions about the feasibility of this due to my basic knowledge;
1) Is it actually okay to connect MOSFETS like this, will they operate correctly/simultaneously or will the small voltage signal not flow?

2) I understand that the capacitance of the MOSFETS will slow down the switching, how do you calculate this effect?

3)Is 12V enough to switch all of the MOSFETS?

4)Are the pull down/gate resistances appropriate?

Please note I am very new to circuit design/electronics, any direction on this would be much appreciated.

The MOSFET I have available to me;
http://www.mouser.com/ds/2/149/FDV305N-888896.pdf
but can change it very easily
The optical transistor; http://datasheet.octopart.com/HFBR-2522-Avago-datasheet-7278264.pdf


texts: Can a metallic rectangular waveguide support hybrid modes?

texts: Studying the basics of guided waves in metallic rectangular waveguides, filled with homogenous dielectric material, I see that there is always a distinction between TE and TM modes. I understand that a TEM mode is impossible in such a configuration, but I'm wondering if hybrid modes (i.e. modes with both longitudinal components of the electric and the magnetic field nonzero) are possible and allowed by Maxwell's equation.


texts: Adequate decoupling / noise reduction for two accelerometers?

texts:
This is my first PCB, so please forgive some of my ignorance! I'd like to mount two accelerometers (ADXL193: +/- 250g), orthogonally, on the same PCB, and have a question about noise.

The current design is to have 5 strands of a ribbon cable soldered to the PCB, shown below: 5V, GND, X_OUT_1, NC, X_OUT_2. The "NC" is connected to GND on the DAQ board, but has no connection on the accel PCB, intended to reduce noise between the signal lines. They are single-ended, collected simultaneously.

C1 and C2 are 0.1uF and 1uF ceramic capacitors, respectively, intended to decouple noise from the power supply.
ribbon cables to these PCBs from the DAQ board will be up to 16 inches long, and could have ferrite cores along the ribbon cables

Questions:

Should this combination of the ground plane/capacitors effectively reduce noise?
If I want to use a radio on the DAQ, will it take a lot more decoupling?

I appreciate any help! I plan to make this design freely available after having it made and tested.

RECENT EDITS:

swapped the power plane on the top of the board for a ground plane that's tied to the bottom
added larger keepouts (top + bottom) around the drill holes for #4-40 socket cap screw head
moved the self-test pins onto the 0.1" grid. unfortunately doing so removed 2 other labels from the board...

Images:


texts: Isolator’s (ISO7720) recommended current

texts:
I have a design which uses an ISO7720 digital isolator, with a 3.3 V supply voltage.

My output load is 500 Ω. Due to area constraints, I’d like to avoid adding a buffer on the output, if I can.

The datasheet specifies an absolute max output current of +/- 15 mA, so I would be well within that rating. But the recommended current is +/- 2 mA.

Maybe the recommended current is just to keep the output voltage within some tolerance of VCCO?

I don’t see any rationale in the datasheet as to why the recommended current is so low, other than Figure 11, which plots the device’s voltage loading vs output current:

If my design can tolerate the reduced voltage1, is it safe to proceed? Am I overlooking something?

My data rate is ~30 Mbps.

1 From the curve, it looks like my output might be around 3.1 V


texts: Do I have the right circuit drawn?  Please help


texts: TVS diode replacement - top marking P450 DEM

texts:
I got a Hikvision camera DS-2CD2332-I that was mistakenly connected to 48 V power supply instead of 12 V. I checked the board and found a TVS diode is getting hot. The power supply LED was blinking at some regular interval while connected.
I removed the diode, connected the camera and surprisingly it worked! So I guess, before using it for surveillance, I need to get new part instead of fried one, so another V spike doesn't kill the board.
I have a problem identifying that diode. All I could find is manufacturer is BrightKing, but can't get any specs about power/voltage... Markings are P450 DEM
Any hint? What would be proper replacement?
Thanks


texts: Using a development board to charge a lipo battery

texts:
Ok, I'm not specialist in electronic but just enthousiast.
I'm searching a solution to charge lipo battery in-board (to build tablet with a micro computer like Raspberry Pi)

So, I have seen this development board, because I need a lot of power (5V 4A during 5~6 hours)

The board is a microship MCP1630V

I have understood that the battery must be plug at the same place as the input power, but how about the balance circuit ?

For example this battery (14.8v, 10400mAh), is it possible to charge it with this board?

Sorry by advance for my bad english, and my non knowledge about the subject, so be indulgent!

However, any help for my project is welcome!


texts: How differential pairs should be called out on fabrication print?

texts:
I have a design that the diff-pairs (100 Ohm impedance) and single-ended (50 Ohm impedance) are routed on the same layer. To specifying the impedance, on the “Lamination Stack-up”, I am going to add the information like this;
INT1 (TW=0.006” Z0=50 ohm / Z0=100 ohm DIFF-PAIR). Is this OK?

In this case, the fabrication vendor will determine dielectric thickness based on the TW, trace spacing, and material on their own to achieve required impedance. Right?

In other case, if the trace width of the diff-pairs are different to the trace width single-ended, can I apply this way to call out?


texts: Supply desgin for two TDA2003 amplifiers and TL072 stereo operational amplifier

texts: I made two TDA2003 amplifers, one for each channel to act as stereo device. For preamplifier I want to use TL072 stereo opamp, but supply od +12 and -12 for IC is giving me a problem. How can I make +-12 split supply for TL072 from toroid transformer that has two 18V secondary windings. On each winding is LM317 regulator limiting voltage to 18V.


texts: Understanding mixed-signal PCBs, in most simple sense

texts:
I understand that mixed-signal is a circuit that obviously has both analog and digital circuits. I am trying to understand what really would be classified as mixed-signal. If you had a PCB with some sort of sensor collecting data and that data is processed by an ADC internal to say an MSP430, is that considered mixed-signal technically? Would most job employers consider this mixed-signal or would the ADC need to external to the microcontroller?

I've done plenty of boards with micros on them and some kind of sensor interface, but I'm not sure if I could call that experience 'mixed-signal' or not.


texts:
How do you choose a micro-controller for your project? My hardware requirements are :

I2c
SPI
ADC channels
SMD package
3.3V operating voltage
A few GPIOs.

There are so many microcontrollers available from various companies which satisfy these hardware requirements(almost all I know of satisfy 1,2,3,4,6)? So then should I choose the microcontroller based on my familiarity with the controller and resourses/documentation available about it or is there any other method to choose one?


texts: Which datasheet parameters describe the switching perfomance of a BJT?

texts:
I have a Fairchild BC547 (NPN) that I'm going to use as a switch.

What parameter(s) should I look at, if I want to know how long time the transistor will take to go from cut-off to fully saturated?


texts: How much slower does a photodiode become in photovoltaic mode?

texts:
Take for example this photodiode, the main differences between using it in photovoltaic and photoconductive mode is the rise time and the Dark Current, aren't they?.

I know exactly how the Dark Current will change depending on the bias voltage, but, what about the Rise Time?, how can I know how it changes as I increase the voltage?.

All of this is because I'm trying to find out in which mode should I use the diodes.


texts:
I have an electronic project about a OCR that could be held in hand and used like a Tipp-Ex mouse (image) to scan words. As I am an amateur in electronics, I don't really know what sensor(s) I can use to get a complete image of the word that I could process afterward. I thought of a gyroscope/accelerometer to track movements and an image sensor.

My questions are about the later:

What kind of image sensor should I use ? (Resolution, focal point, on chip features,... )
Is a LED enough to light the text or should I have some laser ?

I think these questions can be (partially) solved using Google but I am more looking for your experience in this field.


texts: L-C Circuit (Series) connected with AC power

texts:
Good morning
I am learning about L-C circuits, because it is very interesting, so in my simulation software I built the circuit, which can be seen in the below image.

Why, and how i build it ?

I wanted to see in action, the reaction of L and C, resistance, while i increase and decrease the frequency. I know that, in low frequencies, the Capacitor's resistance, increase, and the Coil's resistance decrease (and vise versa), and in resonance these two, are equal, so the Volts value of these two, became opposites and cancel each other, and this means, if i understand well, that there is no Volts against the Volts of the source, so the circuit acts like a close, one.(in a series connection between L and C)

I calculated the frequency of the source, in order to be resonance between L and C, and i found must be 79.577 Hz. When I, first, connected the oscilloscope,  the V(L) and V(C), were both, increasing (while they execute their cycles), with no end.

So  adding resistance, between L an C, and this, stopped this increase and hold Volts stable. After that, Volts(of L) and Volts(of C) had opposite phases and equal values, as expected. But when I tried to measure, Volts, at the ends of Coil(L) and at the ends of the Capacitor(C), I received these indications : 119.964 Volts with only 12V applied.

My questions are:

Why before i insert the resistor in the circuit, the L and C volts, were increasing continuously ?
Why the resistor, stable the Volt sinusoidal movement ?
Why Volts in the ends of L and C are 119 Volts ? The Vrms of the source is 12, and as far as i know the relationship between Vrms and Vpeak is Vrms=0.707Vpk, thus the Vpk should be 16.97 Volt.

I need to know what is happening, in general, because this relation between L and C it is a kind of magic, to me. I mean, i am fascinated.
Is there a good tutorial, to understand?


texts:
In hydraulics, I think perfect sealing is achievable - it is not science fiction to consider a material whose pores are smaller than a water molecule (or is it?), which would yield zero flow rate.

However I can't apprehend a material which would reflect electrons - given that the number of electrons in an atom if fixed for it to be stable, and otherwise it can re-emit then in any direction, including through the material.

So it seems it's impossible to get perfect insulation. To prove it's right or wrong, a recap of how insulation works would be nice.

I hope this is the right stackexchange.


texts: convert neagative out put signal of sensor to apply adc

texts:
I have a problem in convert out of RPM sensor that has -10v - +10v analog output signal.
How can I convert the output signal to 0-5v by practical circuit to apply in ADC of micro?


texts: Cascaded flip-flops and shift register timing

texts:
In the D-flip flop at the edge triggering of the clock, \$Q(t+1)=D\$.
In the figure below, shift-register using cascaded flip flops, why don't we assume that at clock edge triggering
\$Q_1(t+1)=D_1\$ and \$Q_2(t+1)=D_2=Q_1(t+1)\$...etc.
so \$Q_4(t+1)=Q_3(t+1)=Q_2(t+1)=Q_1(t+1)=D_1\$?
Is the propagation delay what makes the schematic below a shift register?
How can I put that into consideration?


texts:
I'm trying to fix a Vestax PMC-07 Mixer and I'm puzzled by the schematics.
It is fed by a single +12V wall-wart switching adapter through a DC Jack.
Can this configuration really produce a negative 10V rail using this combination of a NJM-7910 for the negative and a NJM-7810 for the positive?
The full service manual can be found here:
VSS-PMC-07PRO.pdf


texts:
I don't think that there is an easy (or even any) solution to this, but maybe somebody can help me:

I got a GPS module connected to another MCU. The GPS module works on its own and should wake up the MCU when its ready. Therefore, the GPS module has an analog pin that continuously outputs one-second high-level followed by one-second low-level when it is NOT ready (HLHLHL...), and continuously low-level (LLLLLL...) when its ready. The MCU has an input pin that wakes up the MCU on high-level (Hxxxxx...). Obviously, this doesn't fit.

Is there any (easy?) solution to this problem? So I would have to switch HLHLHL... to LLLLLL..., and LLLLLL... to HHHHHH... (or at least Hxxxxx...), so there is at least a short high-level signal, when the GPS module is ready, and no high-level when it isn't. So the analog output of the GPS module has to be inverted.

                        _   _   _   _
Input (GPS Output):   _| |_| |_| |_| |____________________
                                           _______________
Output (MCU Input):   ____________________|


texts:
I have the circuit below using PIC16F627a, which should support ICSP (drawn in autocad instead of built in editor). IO pins which are not relevant to my question are omitted.

Outputs RB5 and RB6 have to be fed back to inputs RA5 and RA6 respectively. Those signals named 'reset' and 'inhibit' need to be combined with corresponding signals of identical units in two global signals for the whole system. All reset signals are logically ANDed, because all units have to agree on a global reset. Inhibits are logically ORed, because a single unit should be able to initiate this function.

As can be seen, 12V programming voltage would be fed back to output RB5 via diode D2, possibly damaging the PIC. To eliminate this danger, a 2k2 resistor R1 is included in the system, limiting the current that could flow back to RB5.

A similar concern may apply to IO pair RA6/RB6 but only when ICSP CLOCK voltage is low would RB5 be pulled to ground. I don't see any inherit dangers here, the diode used here is just to play it safe.

Will this simple solution applied to VPP eliminate the danger of getting 12V on RB5, destroying the IC?

Note: the additional units inside the cloud are to enhance to IO capacity of the system.


texts: Converting two's complement hex values to binary?

texts:
I'm reading x-axis accelerometer data from an IC via the I2C bus using I2C-Tools ( specifically i2cget ) in Linux.  Here is the code that is reading these values:

$OUT_X_L_A = shell_exec( 'i2cget -y 1 0x19 0x28' ) ... eg. returns 0x20
$OUT_X_H_A = shell_exec( 'i2cget -y 1 0x19 0x29' ) ... eg. returns 0xfc

The documentation for this accelerometer states that these values ( 0x20 and 0xfc ) are expressed in 2's compliment.  This accelerometer has 16 bit resolution.

From another application I'm running that is reading this data in C, I believe that these values, when converted to a decimal value, should equal ~65,475 ( essentially no acceleration as the device is sitting on my desk ).  Some other documentation I've found suggests that $OUT_X_L_A is the Least Significant Register and $OUT_X_H_A is the Most Significant Register.

I've done some research, but am generally unfamiliar with Two's Complement and LSB and MSB.  How do I calculate the full decimal value ( 16 bit resolution ) from the two hex values returned by the device?  How am I supposed to tell from the documentation which register is the most significant?


texts:
I found a strange and old electrical device. It seems it could be plugged into the wall and you could plug another equipment in it. Inside there is a sort of heating resistor, I'm not sure. I don't know what is it or where it comes from. Has someone already see that?
Thanks for any suggestions

EDIT
I live in France so we have 220v 50Hz but before we had 110v 50Hz, so maybe it could be a adaptative device?


texts: Programming ATMega16L over ISP interface

texts:
Sorry if the question seems silly, but I really need some expert guidance. My question is as follows:
What are the necessary pins to program an ATMega16 chip over ISP interface? I've bought a locally made ATMega16L target board. I intend to use a standard USBASP (Fischl design) AVR programmer. Unfortunately, ISP headers on both devices are different. I'm really confused what pins to connect and what not. My AVR programmer has no Vcc output, while the target board ISP header has a pin marked Vcc. Do I need to power my target board with my programmer while writing to the chip, or the DC power of my target board would suffice?

My Target board ISP header has following pins:
1. Vcc (+5V)
2. Gnd
3. MOSI
4. RxD
5. MISO
6. TxD
7. SCK
8. No connection
9. SS
10. RST

AVR Programmer ISP Header:
1. MOSI
2. N/C
3. RST
4. SCK
5. MISO
6. N/C
7. N/C
8. N/C
9. Gnd
10. Gnd

If only MOSI, MISO, RST, SCK and Gnd pins of AVR programmer are used, where do I connect Vcc, TxD, RxD, SS pins of target ISP header. I'm willing to do some cross-over connections between, programmer and target board ISP headers. Please help!


texts: What does the waveform for a Digital Addressable LED Strip look like?

texts:
I want to use this Digital LED Strip but with my own controller (i.e. NOT a raspberry Pi).

The link has sample code but I want to be able to understand clearly in terms of hardware waveforms what does the Clock IN (CI) and Data IN (DI) pins correctly look like?

Here is the spec of the IC, but it does not show the waveforms either. What protocol is used here? How do I go about finding that?


texts: Installing Microsemi/Actel Libero on Ubuntu

texts:
I am trying to install the latest version of the Libero SW tools set from Microsemi/Actel on my Ubuntu laptop.

The web site of the company says that their SW only supports the RH linux and they don't mention Ubuntu anywhere on their site. But I only have access to Ubuntu and therefore need to find a way to install it so I can work on my project.

I have followed the instruction of Microsemi and installed all the necessary libraries before running the installation program, but I still can't get this to work.

Does anyone knows if SW for RH can be installed on Ubuntu? Do I need to add extra libraries that are not part of current installation I have?

My installation is "Linux 3.8.0.32-generic x86_64"

Thanks in advance for your help.


texts:
I was reading a blog about someone's application to ingest a TTL signal to a device and got perplexed.
The author connects what appears to be a 3.3V TTL signal directly to a RS232 port (and it apparently works!). Shouldn't it just read 0 and undefined since 232 is 1: [-3,-25] and 0: [3,25]? Does the undefined maybe count as a change that essentially acts as not 0?
Am I missing some simplification or principle?
The blog is here


texts: Single LED single transistor circuit not working

texts:
I was making a circuit with 1 LED and 1 transistor. pretty primarily i was trying to use the transistor as a normal switch. Here is the diagram below.

So, this is an NPN transistor and i connected the -ve part of the D1 (transistor) with the -ve part of the LED and the other -ve leg of D1 to ground. I connected the +ve part of D1 with the positive end of 9V dc power supply. The LED should light up and if I disconnect the wire connecting the +ve part of D1 , the LED should turn off. But the problem that I am facing is that the LED isn't lighting up when I connect all the points and follow the schematic.

Also another problem that I am facing is that when I connect a wire with the +ve leg of D1 and don't connect the other end of the wire with the battery and just hold the wire by my fingers, the LED turns on but emits very little light. Is there any mistake in my schematic?


texts: Index into std_logic_vector using signal

texts:
I need to modify a certain portion of a register, but the upper and lower bound of the modified part depend on the input. Can the following code:

(1) be synthesised?

(2) if so, what circuit do the tools produce?

reg (to_integer (unsigned(upper1)) downto to_integer (unsigned(lower1)))
 <= input (to_integer (unsigned(upper2)) downto to_integer (unsigned(lower2));

(edit: the syntax might be wrong, but I hope I've got the idea across)


texts: Does this AC axial fan need a capacitor?

texts:
I recently found this old axial AC fan in my collection of old vintage electronic stuffs. Its a Rotron Whisper WR2H1 115V 7W 50/60Hz fan, probably from some sort of server computer or something I guess since it isn't a very large fan. My question is does this fan need any sort of capacitor for starting or it can be directly connected to my 110V outlet? I've not played much with AC motors except one from an old exhaust fan and it had a small capacitor connected to it in parallel, without it I guess the motor would heat up and get damaged. I've attached a few pics of the fan below.

Hope that helps. Thank you.


texts: Choosing an OpAmp for MEMS mic preamp stage

texts:
I am trying to create an updated version of a mems mic board, like this one from sparkfun. They use an INMP401 mems mic (which is not recommended for new designs) and an OPA344 for the preamp stage (20 years old, from the datasheet creation date).

My objective is to improve it a bit in terms of a wider frequency response, better noise tolerance, low power, etc. using a different mic and a different opamp. By "different" I mean more recent.

I have been checking some application notes on the topic, like this one from AnalogDevices and this one from ST.

In the end, I have some parts that I am comparing but couldn't decide which one to select. The only feature for the OPA344 that is better than the others is its low power consumption, but for Slew Rate, Noise, THD, and Bandwidth, all are better than it. Here is the comparison table: (green boxes are what I think are pros of each part).

Is there any tip about which additional feature I should look at when designing a preamp stage? Any suggestions from the previous list? In case low power is not a requirement, which opamp could be selected instead?

Thanks.


texts: How is the smallest erasable unit of flash memory called?

texts:
Flash memory cells are erased for reprogramming not individually, but in large units of certain size. Here they are called segments, here — sectors, and here — simply blocks.

What is the correct term for the smallest erasable unit of flash memory? If there is no official one, which word could be used in vendor-neutral text?


texts: Is it reasonable to use Ethernet or USB to input video into FPGA?

texts:
I want to use FPGA to do video processing and I need one video input and one output. The problem is most FPGA boards have one (HDMI or VGA) port and the price significantly rises with the boards which have two HDMI\VGA.
So my question is: Is it reasonable to use Ethernet or USB to input the video from PC to the FPGA considering the extra development complexity?
Edit: The video is 1080p and 30fps. The processing is rather light. By using Ethenet, I can go from a $400 board to a $150 board and I want to develop the interface myself to save cost


texts: Is this circuit ok for MCP9700 temp sensor?

texts:
I am trying to use multiple MCP9700 temperature sensors and probe certain power IC heatsinks for sensing the temperature through an attiny85.

I have two parts in the overall schematic. For each MCP9700 temperature sensor I am having a circuit similar to this inside the control board where the attiny85 and 3.3V power source is located.

And then I am using 3 small distance wire for about 17cm each (max) to the physical MCP9700 temp sensor which is attached to the power mosfet heatsink for ground, vcc and signal. And also I am including a 1uF capacitor close to the temp sensor on its vcc and gnd pins and one 10R resistor close to the temp sensor signal pin which then connects to the board TS5 pin through the signal wire. And then the TS5 on board goes to attiny85 analogread pin for reading the temperature.

Is this a good application circuit design for the MCP9700 and attiny85 measurement? Should I adjust any resistor and capacitor values to get more stable and accurate temperature readings? Not really sure if my circuit is ok, so, would appreciate any tips and suggestion on this.


texts:
How quick does a signal have to be in order to be considered a high-speed signal?
What are the limits and threshold where you can get away without special PCB layout?


texts:
I just bought the Arduino Wifi Shield. I've followed the setup instructions and uploaded their code but I get the error: "WiFi shield not present". No LEDS are ON on the Shield . I use the Arduino Uno 2009. Not the newest R3 version, so I did the connection for the 3.3V. Why the code is not working?

The Code

/*

 This example  prints the Wifi shield's MAC address, and
 scans for available Wifi networks using the Wifi shield.
 Every ten seconds, it scans again. It doesn't actually
 connect to any network, so no encryption scheme is specified.

 Circuit:
 * WiFi shield attached

 created 13 July 2010
 by dlf (Metodo2 srl)
 modified 21 Junn 2012
 by Tom Igoe and Jaymes Dec
 */

#include <SPI.h>
#include <WiFi.h>

void setup() {
  //Initialize serial and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }

  // check for the presence of the shield:
  if (WiFi.status() == WL_NO_SHIELD) {
    Serial.println("WiFi shield not present");
    // don't continue:
    while(true);
  }

  // Print WiFi MAC address:
  printMacAddress();

  // scan for existing networks:
  Serial.println("Scanning available networks...");
  listNetworks();
}

void loop() {
  delay(10000);
  // scan for existing networks:
  Serial.println("Scanning available networks...");
  listNetworks();
}

void printMacAddress() {
  // the MAC address of your Wifi shield
  byte mac[6];

  // print your MAC address:
  WiFi.macAddress(mac);
  Serial.print("MAC: ");
  Serial.print(mac[5],HEX);
  Serial.print(":");
  Serial.print(mac[4],HEX);
  Serial.print(":");
  Serial.print(mac[3],HEX);
  Serial.print(":");
  Serial.print(mac[2],HEX);
  Serial.print(":");
  Serial.print(mac[1],HEX);
  Serial.print(":");
  Serial.println(mac[0],HEX);
}

void listNetworks() {
  // scan for nearby networks:
  Serial.println("** Scan Networks **");
  int numSsid = WiFi.scanNetworks();
  if (numSsid == -1)
  {
    Serial.println("Couldn't get a wifi connection");
    while(true);
  }

  // print the list of networks seen:
  Serial.print("number of available networks:");
  Serial.println(numSsid);

  // print the network number and name for each network found:
  for (int thisNet = 0; thisNet<numSsid; thisNet++) {
    Serial.print(thisNet);
    Serial.print(") ");
    Serial.print(WiFi.SSID(thisNet));
    Serial.print("\tSignal: ");
    Serial.print(WiFi.RSSI(thisNet));
    Serial.print(" dBm");
    Serial.print("\tEncryption: ");
    printEncryptionType(WiFi.encryptionType(thisNet));
  }
}

void printEncryptionType(int thisType) {
  // read the encryption type and print out the name:
  switch (thisType) {
  case ENC_TYPE_WEP:
    Serial.println("WEP");
    break;
  case ENC_TYPE_TKIP:
    Serial.println("WPA");
    break;
  case ENC_TYPE_CCMP:
    Serial.println("WPA2");
    break;
  case ENC_TYPE_NONE:
    Serial.println("None");
    break;
  case ENC_TYPE_AUTO:
    Serial.println("Auto");
    break;
  }
}


texts: What is equivalent to a daily build (and smoke test) for schematic designs?

texts:
Daily build in software is taking the source code, compiling it and generating the executables, then running that nightly.  This is considered a best practice since it catches errors that prevent the build sooner rather than later, which makes it easier to fix.  And if the build works, then others can make sure they aren't introducing errors.

What would be the equivalent for a schematic design?  Clearly I can't build the PCB, but there might be something more than generating the netlist.

Edit 1/21/11: Also a smoke test is running some tests against the build.  Again, not possible.  I like the DRC (design rule check) idea, I'm thinking of checks such as that.

Edit 1/24/11: I was think of the schematic since that's what I do, rather than the PCB.


texts: how do the micro-inverters stay in sync(phase-lock) in a grid-tied residential solar panel system

texts:
I'm looking for a little more detail on how the all the micro-inverters sync up to the phase on the grid 60Hz.
In communication circuits phase/frequency locking is done with a PLL(phase lock loop). And I assume something similar is used in the micro-inverter. That is each micro-inverter has a PLL to achieve phase and frequency lock. But this can't be an analog PLL, as the
loop filter components would be huge(big capacitors, ...) So I guess a company like
Enphase uses a digital PLL to do the phase/frequency locking. Does this sound right ?
Or does Enphase use something simpler like a zero- crossing detector, with additional information about the slope(at the zero-crossing) to maintain phase/frequency lock with the grid 60Hz.


texts:
I'm creating a dead simple motor driver:

simulate this circuit – Schematic created using CircuitLab
I apologize for any mistakes in the schematic, I tried to portray the motor as it's equivalent components in the editor but I don't really know what the actual values for them should be. It is a 36V ~25A motor.
I'm planning the frequency of the PWM signal to be 22kHz.
I learned that there come a bunch of problems when you start switching FETs fast such as voltage spikes, increased current consumption for energizing the gates, something about capacitance between gate and source which I don't fully understand and possibly more.
To tackle all of those I should use a MOSFET driver IC. I found TC4420 which has a continuous output current of about 1.5A which should be well above what those gates will waste. Is it possible to use a single TC4420 IC to control all 8 FETs?


texts:
I want to create an assignment which takes care of pull-ups from a port pin. I wrote the following:

module test5;

reg value;
reg output_enable;
reg pullup_enable;

wire pullup_helper;
wire value_helper;
wire outp;

assign (highz0, pull1 ) pullup_helper = pullup_enable;
assign                   value_helper = output_enable ? value : 1'bz;
assign                           outp = value_helper  + pullup_helper;

always @(pullup_helper) $display ( "pullup_helper %b", pullup_helper );
always @(value_helper) $display ( "value_helper %b", value_helper );
always @(outp) $display ( "outp %b", outp );

initial begin
    $display ("Start");
    pullup_enable = 0;
    output_enable = 0;
    value = 0;
    #1
    $display ("1");
    output_enable = 1;
    #1
    $display ("2");
    value = 1;
    #1
    $display ("3");
    value = 0;
    #10
    $display("End");
end

endmodule

I got the output:

Start
pullup_helper z
value_helper z
1
value_helper 0
2
value_helper 1
3
value_helper 0
End

Q: Why does outp never change?

EDIT: Because the full answer is related to some comments on the given answers I will summarize the results:

As with support from Greg the answer to the problem is in two steps:

The default installation on Fedora 22 is Icarus 0.9.6. This version is buggy. As Greg tested also version 0.9.7 has the same bug. I installed the latest released version v10 (changed version conventions?)

The second part is simply let drive to assign statements into one wire.

assign (pull1,pull0)  bus = pullup_en ? 1'b1 : 1'bz;
assign                bus = output_en ? value : 1'bz;

With Icarus Verilog V10 it works as expected.


texts:
My usecase requires me to send Computer (USB) -> Teensy 4.0 -> SPI -> Peripheral
I am attempting to send data over USB (potentially USB serial or is there any other way). My data transfer requirement is sending 40,16-bit data, 4000 times a second, which translates to around 2.56Mbits per second.
I plan to cache 1 second of data, which is 2560000 bits or 320 Kilobytes or 312.5 Kibibytes
I am looking for guidance regarding:

Caching mechanism (mutex), and 1024 bytes of RAM availability, parallelly transfer data from USB to Teensy 4.0 to SPI. i.e. Threading within Teensy / Arduino.
How to effectively transfer 320kb of data per second over USB to teensy 4.0?
Text-based serial transfer or hex bytes? Any links or articles.
Is there any other language to program Teensy 4.0 for this purpose that could be more effective than Arduino (TeensyDuino)?


texts: Completing circuits with transistors and arduino

texts:
Hello and thanks to anyone who helps.

I am trying to create a test bench for a control board we commonly work on at our business. One control board has 11 pins that a ribbon cable would be connected to. To use the functions on the board we use a wire to short different pin connections on the board. For example: pins 4 to 5 initiate the broil on a certain oven control board.

What I want to do is see if there is a way to do this without using the wire. I want to be able to use an arduino to short the different connections automatically or by a user on a computer.

So I was thinking, could I use a transistor to represent each pin. While being able to still have the function of shorting different pin combinations?

Thanks to anyone who helps. I can provide more info if needed.


texts: Reverse universal motor from a sewing machine

texts: I have purchased a sewing machine motor from aliexpress. The issue is that it spins in the wrong direction. I opened it and only see 2 wires going to the brushes.


texts: How Much Current Draw From Speakers/Amplifier?

texts:
So I plan on using the VS1053 Codec connected to a class D Amp (2 x 2.8W channel) with two 3W 4 Ohm speakers. If I supply 5V to this setup, what would the current draw be at full use?

Codec: https://www.adafruit.com/products/1381
Amp: https://www.adafruit.com/products/1712
Speakers: https://www.adafruit.com/products/1669


texts: line regulation factor with 2 zener diodes

texts:
i want to calculate the line regulation factor  of this circuit

You can check below my work.
is it right or not  ?

Correct me if  i'm wrong
Can we consider that  Z1  has  a similar function  as the zener diode in the picture below ?


texts:
I'm trying to understand the below circuit:

I have to analyze an amplifier circuit from a microphone to a speaker and don't understand how it works. I know that the first stage is a voltage divider, but I can't figure out what the second stage is or how it works? In which stage does the amplification take place? I would really appreciate any help!


texts: What is initial contact resistance in relays?

texts: I am reading datasheet of a relay. I see a term, initial contact resistance in relays. What is the definition of this parameter? Thanks.


texts: Darlington Transistor Array Overheating and failure

texts:
I own some animatronic robots that use solenoid valves to operate their mechanical movements.

Recently I created a pcb that uses three 8 channel Darlington Arrays ULN2803A to control the individual solenoids and make the robot move. Each Solenoid is 6.7 watts (or about 300milliamps) and 24 volts. The power supply I use is 4.16 amps and 24v. I use an arduino to control the darlington arrays. When I first tested the darlington arrays, the robot moved and it's solenoids were triggered by the darlington arrays, but upon inspection of the board, the darlington arrays began to smoke. I replaced them, and tested them again. I tested them multiple times having similar results, only twice did they work without failing. When they didn't fail, I noticed the chips get extremely hot. This has concerned me, because I know someone who also uses them and has had no heating or failure issues with them. I did not use diodes for the outputs as it says they have built in output clamps diodes.  I don't understand how I could possibly be overloading them because they can handle up to 50 volts and 500 milliamps. Is there any output protection I should have used? perhaps addition of some resistors? Thanks


texts: Arduino: How does one extend the pins to accommodate multiple sensors?

texts:
This is a fundamental question about the Arduino system. I've been trying to find answers all day, but keep getting answers either unrelated to the Arduino or completely off topic.

I'm building a robot that consumes most of the pins on the Arduino for motor and IR sensor modules. The robot works great (Robot Starter Kit by OSEPP). Now I want to get on with adding several more sensors and an LED output module, but I've run out of pins. I've seen prototyping boards and shields that seem to extend the pin count, and I've read several articles on the address bus helping to uniquely ID all the components, but I'm lost at step one...

How does one address various input / output connectors or pins on prototyping boards?

Sorry for the noob question, but as with all tech, the simplest first steps are always the least documented. Any links to great tutorials would be greatly appreciated.


texts:
wondering if anyone could help me out here. I don't work with PCBs, but troubleshooting a salt chlorine generator for my pool and believe the board in the pics below is the cause. My question is, does the level of corrosion shown seem like something i can clean with isopropyl alcohol and a toothbrush? I won't even bother trying to remove the damaged components and replace, I've never soldered anything before in my life and I'm sure I'd do a horrible job.
The part isn't easily replaceable as it is no longer manufactured by the vendor so trying to salvage if I can before spending thousands on a new system.
Thanks for any help you can provide.


texts: Power Transformer question to power a motor load

texts: So I bought a toroidal power transformer that can output 117Vac, 12.8A and has a power rating of 1.5kVA in order to power a motor that requires 115Vac, 13A. I wanted to see if this would be viable to power the motor or if I should try another solution? Below is attached the motor requirements. Hope to get some feedback.


texts:
I must have spent 20 hours on this question and still i have not prevailed with an answer.

simulate this circuit – Schematic created using CircuitLab

simulate this circuit

Every time i end up stuck with to many unknowns.
So circuit 1 is the general circuit, circuit 2 is DC model, Circuit 3 is small signal model

So from the beginning.

Assume saturation mode.
Because drain current is given and gm, VGS(DC) can be accordingly be solved. Gm=1mS VGS(DC)=1.5 V
Issue in DC analysis. when drawing DC model you short all small signal voltage sources. Now at Vin in the second schematic. does that get short circuited because somewhere behind that point there must most definitely be an small signal source. If it it short circuited the VGS DC value of 1.5 V is not possible.therefor presumably it must be left as an open circuit? to have a 1.5 VGS value? This delema would not be an issue if there was a cap in the diagram and then the Vin source. unfortunately not the case.
Vout in dc analysis left as an open circuit
Move to small signal analysis
See working out in attatched image. KVL from Vin->R1-> Ground and KVL            vin->R2->R3->ground applied. Not that Rin = Vin/Iin. Apply 1 V test voltage to Vin. coresponding I Test= 2x10^-6 A.
Results in expression for R2 in terms of a constant and I2 and an expression for R1 in terms of I1
From here? I'm not sure


texts: Lab 30V 10A PSU - no current in CC mode when shorted

texts:
I have problem with my PSU, which is similar costruction to Mastech HY3010 (exactly this is MCP lab electronics M10-SP-3010E)
When I short the output, no matter what I set on potentiometers, there's no current at the output. It goes into CC mode, but stays at 0 amps. When I connect some higher resistance it works fine, until the voltage drops somewhere below 0,8V. Then no matter how I manipulate the gauges it stays at 0A. When i disconnect the load, and set higher current it works fine. What is even more interesting - when I touch D11 diode with my finger ,when output is shorted, something is happening at the output, the current shows up for a while. What can cause that problem?
Edit:
I've already chcecked all wires, all soldering points, and everything is fine. Also done some measurements on U2 and U3 op-amps and checked all supply voltages. Still cannot find any problem :/
I don't understand why LED1 an LED2 are connected between op-amps outputs, and transistor base. Can somebody explain me that circuit?


texts:
I'm having trouble reconciling my understanding of motors and generators.

Let's examine a simple DC motor at rest.

Applying a voltage (\$V_{applied}\$) to the terminals generates a large current and a corresponding large torque which rapidly accelerates the motor shaft and any mechanical load. Let's say the rotor spins counter-clockwise (CCW). As the rotor speeds up, an increasingly larger back-EMF (\$E\$) restricts the current in the windings until motor reaches mechanical equilibrium with the load (no more excess torque to accelerate the load) or until \$E = V_{applied}\$ (the motor's no load max speed).

What happens if we suddenly remove the applied voltage and externally spin the motor at a constant speed in the same direction (CCW)? Now the back-EMF becomes the voltage source, and current flows in the opposite direction (assuming we've shorted the circuit, \$I = E/R_{windings}\$).

Does this current generate a counter-torque that resists the externally-applied rotation of the motor? If so, does this torque and the external power source (such as windmill) reach some equilibrium state like in the motor case?

Side question: In a powerplant where steam spins a generator to produce very big EMF, does the "grid" serve as an additional resistance in the generator's circuit that limits the current?

I've read that motor manufacturers will often characterize their motors using other motors. To test a motor's torque/speed performance, they will mechanically load it with another motor and feed the power generated from the second motor back into the driving motor. Is the 2nd motor's counter-torque (as hypothesized above) what provides a mechanical load on the first motor? Otherwise, the first motor would just spin a dummy mass.


texts: I have been trying to simulate a full bridge sine wave inverter for 350W using an LC filter. I referred a Texas instruments reference material for the design of LC filter. Switching frequency of 39.5 kHz and 50Hz output frequency. The cut off frequency was chosen as 4kHz. The value of inductance is 5.62 microhenry and capacitor of 281 microfarad. But the output V drops from 230V for greater than 40W and even if I simulate for 350W the issue is the voltage drops to 160V from 230V and the power measured across the load is 180W and not 350W. Can someone suggest me reference materials or help me to design this filter.


texts: Decoupling capacitors for circuit with two voltage converters and stepper motor driver

texts:
I have two questions regarding my first design - a simple speed/direction controller for a small (24V, 0.7A) stepper motor.
How it works:
12V from DC plug is converted to 5V to power Atmega and a4988 (driver) and to 24V to power motor.
Atmega controlls stepper speed and direction by reading two user inputs: 3-pos rotary switch (CW, Off, CCW) and 10k potentiometer (speed control).

Questions:

are decoupling capacitors ok? anything is missing?
I'm aiming at EMC compliance in the near future, what other obvious things I should consider at this stage? (my next question will be about PCB design but first things first)

Thank you!
Datasheets:
step-up converter
voltage regulator
Atmega328p
a4988 stepper driver module
a4988 complete driver
quartz


texts: S-parameter measurement of thin polymer film

texts:
I need to obtain S11 and S21 to calculate loss tangent of polymer(PVDF) in C-band. I have an access to vector network analyzer, to use it I must somehow attach 2 SMA connectors to polymer and here starts the hard part.
Polymer film is roughly 0.1 mm thick with aluminium coating on both sides(around 100 nm thick). Melting temperature of PVDF is 175 degrees C so I can't solder something directly to film.
 At first I thought that I can just take PCB, solder one SMA to it and glue film to board with second SMA glued to top side of film (with conducting glue). But it wont work correctly because of amount of places where waves will reflect because of glue. Some additional info you should know:

I can't use cavity perturbation method.
I only have this film. I can't obtain this polymer in other form.
I can remove aluminium from film where needed by using PCB marker and ferric chloride.
I can cut the film, I think square shape will be the best solution to ease further calculations.

So you can imagine it as square thin film capacitor. Any ideas?


texts:
I have all the units and calculations I need but I'm not sure which formula to use, and how to go about it. Please help.

Frequency - 10.53 Hz
Duty Cycle - 52.63%
C2 - 100 uF (e12 value)
Time High - 49.97 ms
Time Low - 44.99 ms
Ra - ?
Rb - ?


texts: Problem in Clock Gating Control with ARM Tiva C

texts:
When I access a peripheral register (such as a GPIO port) just after enabling the clock gating of the peripheral, a hard fault happens. For example:

This code doesn't work (generates a hard fault):

/* enable clock to GPIOF at clock gating control register */
SYSCTL_RCGCGPIO_R |= SYSCTL_RCGCGPIO_R5;
/* enable the GPIO pins for the LED (PF3, 2 1) as output */
GPIO_PORTF_DIR_R = 0x0E;
while(1) {}

But with this little nop tweak, it works:

/* enable clock to GPIOF at clock gating control register */
SYSCTL_RCGCGPIO_R |= SYSCTL_RCGCGPIO_R5;
asm(" nop");
asm(" nop");
/* enable the GPIO pins for the LED (PF3, 2 1) as output */
GPIO_PORTF_DIR_R = 0x0E;
while(1) {}

The code should work fine with no delay after enabling the clock, but I need to know what is happening here?

Long Story:

If I run the first code it gives me a bus error. I tried other ports in GPIO and also tried some UART channel and the problem persists. What I got is that: just adding sufficient asm(" nop"); instructions in the right place make the code works.

It appears that the problem is with the delay time between enabling the clock gating of a peripheral and accessing it's registers. Any solution that implements adding a sufficient delay works. I tried different things  like using a delay function or using asm(" nop") instructions or just adding a debug breakpoint in the line just after enabling clock. Is this have something to do with clock gating latency or clock skew or such expressions?

I've debugged the code according to this document form TI. My fault register reads a value of 0x0000.0400 after fault which means that "A bus fault occurred, but that the exact faulting address is not known". I've checked the exception stack frame and analyzed the disassembly code that is executed before the fault happens and it seems that there's no problem. The document says that this fault occurs usually due to the STR instruction, but I've checked the memory pointers and it's all fine.

Disassembly of the not-working code:

11            SYSCTL_RCGCGPIO_R |= SYSCTL_RCGCGPIO_R5;
          main():
0000026c:   4913                ldr        r1, [pc, #0x4c]
0000026e:   6808                ldr        r0, [r1]
15            GPIO_PORTF_DIR_R = 0x0E;
00000270:   4A13                ldr        r2, [pc, #0x4c]
11            SYSCTL_RCGCGPIO_R |= SYSCTL_RCGCGPIO_R5;
00000272:   F0400020            orr        r0, r0, #0x20
00000276:   6008                str        r0, [r1]
15            GPIO_PORTF_DIR_R = 0x0E;
00000278:   200E                movs       r0, #0xe
0000027a:   6010                str        r0, [r2]

Disassembly of the working code:

11            SYSCTL_RCGCGPIO_R |= SYSCTL_RCGCGPIO_R5;
          main():
0000026c:   4914                ldr        r1, [pc, #0x50]
0000026e:   6808                ldr        r0, [r1]
00000270:   F0400020            orr        r0, r0, #0x20
00000274:   6008                str        r0, [r1]
00000276:   BF00                nop
00000278:   BF00                nop
15            GPIO_PORTF_DIR_R = 0x0E;
0000027a:   4912                ldr        r1, [pc, #0x48]
0000027c:   200E                movs       r0, #0xe
0000027e:   6008                str        r0, [r1]

From my experiments, it seems like after enabling clock for GPIO requires more than 1 clock cycles before accessing the GPIO port registers. For UART it is higher, about 5 to 6 clock cycles (I've measured that with the debugger).

IDE: Code Composer Studio.
Compiler: TI v18.12.2.LTS (with optimization level of 2).
OS: Ubuntu Bionic 18.04.2 LTS.

So, is that delay required? or unfortunately, I have a hardware problem?


texts:
Disclaimer: I know you aren't supposed to ask about specific IC's as it is not helpful to the community in general, but I am at my wit's end here so I will try to make this as relevant as possible.

I would like to add audio to a good ol' Raspberry Pi Zero. Specifically I would like to take the audio generated by the PWM pins (GPIO 18 and 19) and feed them into a small 8 ohm speaker and a headphone jack. To do this with the raspberry pi an amplifier would need to be used. I would like to use one amplifier for both outputs so I can control the volume of both outputs with one potentiometer on the input to the amplifier.

I found one family of amplifiers that I thought could do the trick, namely the Diodes Inc. PAM8009. The PAM8019 would also work, but it has the same issues. The problem is that I don't know what to do for the Undervoltage Protection (UVP) pin. There is a small circuit connected to the pin with three resistors and it gives a couple of equations for desired UVP voltage and hysteresis. The problem is that I don't know enough about audio AMPs to know what my desired UVP voltage and hysteresis should be, much less the values of the three resistors. Sadly, Diodes does not provide an evaluation board for this chip and my attempts to contact them have gone unanswered for weeks. They have no public forums to seek help from other people. I really have no idea what their values should be and I don't want to apply a "try random values and see what happens" approach if it can be avoided.

If you know of another amplifier that can do the trick that does not use I2C control for amp volume (because I don't want to have to right a driver for that and the I2C buses already have a few devices on them) then please let me know. Otherwise any help with the PAM8009 would be greatly appreciated.

Again I know this may be against the posting rules, but this is the last place I can turn to for help. If you know somewhere better to ask then let me know.


texts:
I've been reading about "dirty electricity" lately and while I know there's much controversy whether it causes adverse health effects this question is not about that subject. I'm simply trying to understand the facts and physics regarding "dirty electricity".

According to GreenWave Filters (which produce and sell filters to "remove" dirty electricity):

  Dirty electricity is erratic spikes/surges of energy traveling along
  power lines and wiring where only standard 60Hz AC electricity should
  be. It is created by electronics, energy-efficient lights, and many
  other devices, as they manipulate electrical current to operate. Dirty
  electricity can circulate throughout a building and to other
  buildings, radiating potentially harmful EMFs as it goes.

1) What exactly is "dirty electricity"? Based on the above text, I understand that certain devices may draw electricity in aberrant ways causing it to spike/surge. What do we mean by electricity "surging"?

2) Do devices that generate "dirty electricity" contaminate all of the wiring in the wall? Or is it just around the outlet they draw power from? Or perhaps just around the device itself? If it does contaminate everything, how does the electricity from the device go back and contaminate the wiring in the whole house?

3) Most importantly, does this "dirty electricity" somehow radiate outside the walls (like WiFi) or is it something that just effects the flow of electricity in the wires? If it does radiate, does it radiate in a single frequency or multiple frequencies? Finally, does the amount of "radiation" depend on the amount of energy drawn by the device? Is there a way to measure it?

I understand it may seem like I'm asking several unrelated questions but I think all of my questions stem from a lack of understanding of the simple physics of dirty electricity. I think that if I understood exactly what dirty electricity is, all of my questions would be answered. This is why I'm asking it as one question.

P.S

I realize there are other threads on stackexchange that address some of the health concerns related to "dirty electricity". Once again, my question is not related to health. I'm just trying to understand the physics of how it all works - what creates it, where does it exists etc. Also, this question seems to address how dirty electricity effects electronics plugged into the wall but of course we are not plugging people into the outlet. So I'm trying to understand the physics of how it interacts with humans.


texts: Is an Arduino capable of managing a 3D printer and additional modules?

texts:
I have the electronics for a RepRap 3D printer (arduino MEGA 2560 + RAMPS) and I would like to add a few additional modules:

Cameras to use as a surface scanner (even something kinect-like). They are used only to detect the shape of an object already present on the base before printing.
A syringe interchanger (possibly using magnets)
A RFID reader to identify the syringes.
SD Storage

I'm at the starting phase of the project and don't know very well where to begin. Do you think the arduino will be enough to manage all the modules?

Any pointers on resources or problems I could find will be much appreciated.


texts: Best practice for multiple SMPS-generated power rails at different voltages on PCB

texts: When creating a PCB design with multiple power rails at different voltages, all drive by switching power supplies, is it better to generate all of the voltages from a single input voltage, or two derive small voltages from other power rails? For instance, in my current project I have a 24V input, a 10V rail and a 3.3V rail. Would I be better off with a power supply that converts 24V to 10V, and 24V to 3.3V, or a power supply that converts 24V to 10V, and then 10V to 3.3V? The latter seems like it would offer some efficiency benefits at the cost of increased power supply transient noise.


texts:
I am not too familiar with designing snubber circuits.

Can somebody sanity check the following sizing calculation for a snubber circuit?
Also: Is the undampened rise rime of the voltage due to the missing capacitor an issue if the absolute value stays below the critical values for the switch?

I want to switch an inductor L1 with ESR R1 with a BJT Q1. Given that I want to limit the voltage across Q1 to a safe value $$V_{Q1} = x\times V1,$$ I am looking to size R2 appropriately.

Assuming D1 has a negligible forward voltage drop, the current in the inductor should drop as:
$$ I_{L1} = \frac{V1}{R1}\exp(-\frac{(R1+R2)t}{L1})$$

This means the maximum voltage across R2 is $$V_{R2} = R2 \times \frac{V1}{R1}$$

The voltage from the voltage source and across R2 add to give the voltage across Q1: $$V_{Q1} = V1+V_{R2} = V1+\frac{R2}{R1}\times V1=x\times V1$$

It follows that to limit $ V_{Q1} $ to $ x \times V1 $, R2 is to be sized as:
$$R2 = (x-1)\times R1$$

Note: please ignore the model numbers for D1 and Q1. I could not find a way to remove them.

simulate this circuit – Schematic created using CircuitLab


texts: How to effectively avoid current drops while stepping down the voltage?

texts:
We are using a PC power supply to power our project, which is a Robotic arm. Since our power supply has a 12V output voltage, can anyone please advise how to step down the voltage (12V) to 6V.

Using a buck converter to step down the voltage to 6V is heating up the circuitry. It's also reducing the maximum rated current, which makes it unsuitable for the motors.

The L7806 regulator is also an option, but it drops the maximum achievable current. How to avoid this problem, where the current drops along with the voltage?

NOTE: We are using 5 servos, and looking for the simplest possible solution to step down the voltage to 6V and still deliver 7.5A.


texts:
I have a quite basic question about crystal filter impedance termination.
F.e. ECS-45K20A 45Mhz IF filter - it has specified terminating impedance 910 Ohm / 2.5p.
https://pl.mouser.com/datasheet/2/122/mono%20crystal%20filters-309914.pdf

According to Murata application note impedance matching is described as resistor / capacitor combination and it shows effects of incorrect match.
https://www.murata.com/en-sg/products/filter/crystalfil/matching

1) As I understand - that values (refering to Murata a.n.) are correct for 50 Ohm source and load. How impedance terminator should be defined in 2-3 series connection?

2) It is necessary calculate values if load or source have impedance other than 50 Ohm?

Thanks for any answers.


texts: Current limiting a dc-powered heating element

texts:
What would be the best way to limit the current into a 2.1Ohms, 12V max heating element fed with a range of known dc voltages (5V to 12V) with also known maximum input currents (2A to 5A)? The load can only be switched from the high side as the low side is shared with a thermocouple.

My first experiment was using a +/- 40 kHz to 400 kHz pwm signal to control a high side mosfet, with the duty cycle as a way to modulate the average current consumption. That led to big inrush currents, even at 1% on time.

So my second idea was to used a buck converter. Given a known input voltage and current sourcing capability (let's say 5V, 2A = 10W) and a estimated efficency of the buck (90%), that gives a certain amount of power that can be fed to the heating element (9W). Finally using ohms law, \$V = \sqrt{P * R}\$, I can determine the output voltage of the buck (in this case 4.34V).

The second idea works quite well, however I'm aiming for a compact solution, and the coil and the input/output capacitor end up quite having to be quite large when running simulations.

So I thought I would reach out to the community for any other possible solutions. Thanks in advance for your inputs!


texts: coupling coefficient & effective turn ratio

texts:
In the fundamentals-of-power-electronics this book, Chapter 13 Transformer Modeling

How to derive the coupling coefficient (13.52) & effective turn ratio (13.51)
I can use the ideal transformer to derive but non-ideal is difficult to me


texts: Who is creating/maintaining the Unified components for PCB?

texts: In Altium, I noticed that there are 'Unified components' - the repository that contains symbols/footprints that are already created. I am keen to know more about this repository. Who is maintaining it? Who created the symbols/footprints inside it? And why isn't it a global thing to have it done for all ICs and not a select few?


texts: How increase pressure sensor breadboard sensitivity?

texts: I build a pressure sensor breadboard according the schematic. It works, but has quite low sensitivity - it shows some pressure only after big pressure is applied. Is there a way to increase sensitivity by replacing some components with different values , without redesigning PCB?


texts:
I'm trying to get LaTeX mode to work in XCircuit.  It really doesn't seem to produce a tex file when I save.

Here are the steps I'm following.

Open terminal in Linux, execute xcircuit, program starts up and I go edit -> latex mode, then it checks the latex mode thing and I press t, then I type some random word.  Then I go file -> format page output, I give the file a name, hit Write File and then I have a look and only a postscript file was created...  No tex file was created...

I've been trying to get this to work for ages.

Anyone actually got this working?


texts: In Figure 3 of https://www.systemverilog.io/understanding-ddr4-timing-parameters#refresh , why tRAS is defined as the max timing between two REFRESH commands ? This seems contradicts with Micron document.


texts: Electrical and electronic engineering magazines

texts: What electrical and electronic magazines can be recommended in order get up-to-date information about the latest technologies? I would like magazines listing from hardware hacking to proper professional design.


texts: Convert microcontroller 3.3V output to 6V

texts:
I have built an h-bridge from 4 MOSFETS (PHP21N06LT) shown below. This bridge is used for motor speed control in either direction and fast stop. I have a dev board with C8051F020 microcontroller on board. I have noticed that if I provide 6V to the gate of the mosfets the motor runs much faster than providing 3.3V (same as output from microcontroller GPIO) to the gate and the motor does not run as fast.

I need to somehow pull up the gate voltage to 6V when microcontroller GPIO goes high and vice versa. I tried the circuit below but it does not do what I intend to do.

Am I going in the right direction? Can someone suggest something?


texts:
I have a 5 ns pulse width High coming out of a comparator that is asynchronous.  I am attempting to count this pulse.  My current  microcontroller  (dsPIC33FJ) has an asynchronous counter on board, with a min spec of at least 10 ns pulse width High.

What are my options to lengthen/elongate this 5 ns pulse so it can be read by the counter?  I am open to switching to a different microcontroller or using a more qualified front end counter, but I would prefer to use passive/simple circuitry instead.  Is this possible?

What I have researched so far:

I have tried tying a .1uF capacitor to between the output signal and ground in hopes that the discharge would slow it down, but all that did was heavily distort the signal.  May I use a way lower value?
I researched sample and hold IC's, but the shortest acquisition time I could find is around 200 ns which is not suitable for my application.


texts: How different are 8-bit microcontrollers from 32-bit microcontrollers when it comes to programming them

texts: Right, so we have 8-bit, 16-bit and 32-bit microcontrollers in this world at the moment. All of them are often used. How different is it to program 8-bit and 16-bit micrcontrollers? I mean, does it require different technique or skill? Lets take microchip for example. What new things does a person need to learn if they want to transition from 8-bit microcontrollers to 32-bit microcontrollers?


texts:
I am reading this paper : Upgrade of a low-temperature scanning tunneling microscope for electron-spin resonance and found that for thermalization, they use 0 dB attenuators.

  Page 6: Having the finite cooling budget of our cryostat in mind, and noting
  that the heat transfer of the RF line is dominated by the micron thick
  Ag coating of the center conductor, we thermalized all SR  cables
  using  0dB  attenuators

I understand attenuators reduce signal intensity (power), but what does it mean to have a 0 dB attenuator?

What is the general purpose of 0 dB attenuators and in the paper is it just being used for thermal coupling?


texts:
There is a electrical scheme of my board:

That's what I see on output, when stepper motor is not connected / is connected:

The stepper motor doesn't move and produces a squeaking sound and vibration, but I feel torque a little bit on stepper motor. Can't figure out what's wrong.

V motor is 12V, VREF = ~1.1V. Stepper motor 17HS4401.

There is a PCB layout:

UPD:
Now I put the driver on breakout board and repeated Polulu scheme. Still didn't succeed.

This oscillogram is for STEP pin of DRV8825:
STEP pulse duration HIGH and LOW are both more than 3us

This is for R10 and R11 (mean amplitude is near to 100mV):


texts: Thevenin equivalent with non-constant voltage

texts:
Does Thevenin's Theorem cover the case where the voltage source is changing with time?  As an example of such a circuit, I'd like to replace a sensor, that produces a voltage, with a Thevenin equivalent in a model.  Presuming I have a model of the internal resistance of the sensor and a model of the voltage change with respect to stimulus change, am I allowed to say that by Thevenin's Theorem the equivalent circuit is a variable voltage source and a resistance in series?

Note that I am asking specifically if this is permitted under the theorem.  I know that I can model my sensor this way, I'm just not sure if I can invoke Thevenin as justification.


texts:
I would like to switch a 10A AC load with a solid state relay (SSR) and I am wondering if a higher current SSR (e.g. 40A) would be more efficient and produce less heat than a lower current rated SSR (e.g. 25A).

Is the SSR's loss resistive (like a MOSFET) and improved with a higher rated SSR, or is it based on a forward voltage drop (like a transistor) meaning the wasted power would be unrelated to the SSR's current rating?


texts: Reading a single byte using 3 wire interface

texts:
I am trying to communicate with DS1302 (RTC) using P16f877A MCU. I tried to read a single register (let say Hour-register) of DS1302 and put its value on a certain PORT/LCD. But I am doing something wrong because everytime i get the same value i.e. 0x01 when I read either date,hour,minutes or seconds etc.

Here is how i am doing to read the byte from RTC.

sbit EN at PORTC.B2;
sbit SCLK at PORTC.B3;
sbit SDI at PORTC.B4;
sbit SDO at PORTC.B5;

sbit EN_Direction at TRISC2_bit;
sbit SCLK_Direction at TRISC3_bit;
sbit SDI_Direction at TRISC4_bit;
sbit SDO_Direction at TRISC5_bit;

// SPI Initialization Fucntion

void SPI_init(void){

          INTCON |= 0xC0;     // GIE and PEIE enable
          SSPSTAT.SMP = 0;    // Sample at MIDDLE
          SSPSTAT.CKE = 1;    // Data send on Rising Edge
          SSPCON |= 0x21;    // Serial Port Enable, Idle state Clk is Low, Clock = Fosc/16 => 31 KBytes/sec
          SCLK_Direction=0;
          SDO_Direction =0;
          EN_Direction  =0;      // Output Ports
          SDI_Direction =1;
          EN  =   1;
}

// ============== Main function =============

void main(){

           SPI_init();
           EN=0;                       // Active low signal
           SSPBUF = 0x85;         // Hour Address
           while(SSPSTAT.BF == 0);     // Adress Transmission not complete ? Stay here
           value=SSPBUF;               // Read to Clear BufferFullStatusBit
           while(SSPSTAT.BF == 0);     // Recieve byte not complete ? Stay here
           value=SSPBUF;               // Store the recieved Byte
           EN=1;                       // Fininsh Reading
           PORTB=value;                // Transfer byte to PORTB
}

The timing diagram of RTC is as follows


texts: HDMI triggering the Ground Fault Circuit Interrupters via Projector

texts:
Overview: A colleague of mine took her HP laptop from Canada (19.5 V, 1.4 A DC rated) to work in Brazil and experienced ground fault trips on the outlets when she connected an HDMI to a projector during a presentation. Please see my key points for more detail.

Key Points:

Brazil uses Type N connections
During the presentation her laptop was not connected to the wall and instead was on battery
However due to the different wall outlet she did borrow a charger for her time in Brazil (but did not have it plugged in during presentation)
The other Brazilian colleagues use Dell laptops rate at the same voltage and current but do not have this issue
The HDMI cable was their cable (incase there is a difference between Canadian and Brazilian make)
The fault did not happen immediately but after (as she described) 5 minuets
This issue occurred twice until they decided to switch to another (Brazilian) laptop at which point it did not occur.

Research:
I did some research to see what could be the case and found that people experience a lot of HDMI issues that may be caused by incorrect grounding or pre-charged circuits from DVR's to TV's. I feel this might be relevant so here is a link to a forum response on CNET.

My possible explanations:
Considering that this was tripping a GCFI instead of an overcurrent breaker my guess is that it's not a "drawing too much power" issue but instead a difference in grounding between the Canadian equipment (laptop) and the Brazilian equipment (HDMI and projector). I also believe that perhaps these differences are creating a charge to build upon an insulated part which is reaching a critical flashover point and then being discharged through the case to ground and perhaps this explains why there is a time delay.


texts: What is the purpose resistors and capacitor in this 555 circuit?

texts:
What is the purpose of the capacitor , the resistor , and the variable resistor ?

Do they work like clock pulses for the 555 timer?


texts: MCU controlled adjusting LED current with current sensing regulators?

texts:
I'm really sorry for the noobly formulated question, if I knew how to formulate it I'd probably find what I need by searching, this has to have been asked and dealt with many times.

I've been using some regulators / LED drivers (CAT4101 for example) where I can easily adjust the current from a MCU by using a digipot. The sense resistor is between sense pin on the regulator and GND. To obtain max specified current for the CAT4101 the resistor needs to be 549 ohm. With a 256 step 5K digipot in series with a resistor (549 - wiper resistance) I can control the current easily with good enough resolution.

Now I've been looking at some other regulators of interest but they require current sensing resistor to be in series with the LEDs. Is there a similarly easy method to adjust current with these kind of regulators? I can't seem to find a method of doing it.

Note: I know I can use PWM to adjust LED brightness. I'm not asking about that.


texts:
I have the following 5V relay board:

Please ignore the light bulb hook up. That was an example on the website that had the same relay :)

And I am looking to hook one of the relays up to a monetary switch:

Now this is what I am guessing is the way I connect the switch to the relay board:

Connecting the ground to both the left connector pads on the switch and shorting them together "presses" the button. I just want to make sure the hookup I have drawn there is the way it should be connected to that relay board?

So when I apply 5V to the pin 1 on the relay board (Arduino Digital pin 3 goes high) it will close the circuit in relay 1 which will act as if I "pressed" the button?


texts:
I'm making my own board and using an ATmega 328 with the Arduino bootloader. I have a DIP switch to select either an FTDI chip (for programming) to be connected to the ATMega's Rx and Tx, or a GPS that outputs serial to be connected. I was looking at this schematic for reference:
http://arduino.cc/en/uploads/Main/ArduinoNano30Schematic.pdf

Why are there 2 resistors on Rx and Tx coming from the ATMega? Do I need those just for the connection to the FTDI chip, or do they need to be there for the GPS too?


texts:
Preparing a lab excercise, where we are tasked to generate a 1 Hz clock out of the 50 Mhz system clock of a FPGA. This should be achieved without using any libraries besides ieee.std_logic_1164 and ieee.numeric_std.

The obvious possibility would be, to run a counter. When it hits 25*10^6 ticks, a edge can be transmitted (alternating between rising and falling edged). Then reset the timer. This would require a 25 Bit timer and a 25 bit comparison. As our overall excercise is not that complex, we should not run into limitations of the FPGA ressources. However I wondered how this could be implemented more efficiently. E.g. one could compare only the first couple of bits thereby loosing accuracy of the clock frequency.

The excercise documentation notes, that such timers are usually only loocking at one bit within the counter. So one possibility would be to count faster, so that after half a second one specific bit would swap. This could be done by counting to 2^n and increasing the counter steps. However this would create an error due to the truncated remainder in the step size. E.g. counting to 2^30 with a step size of 43 would result in an error of 0.1% , whereas counting to 2^27 has an error of 6.9% with a step size of 5.

Are there more ressource efficient concepts to generate such a clock? Preferably using a counter and loocking at a single bit for clock generation.


texts:
I have gone through many of online blogs and websites for guidelines about selecting Peltiers but somehow I am still lost in the middle. I am still missing major numbers to be able to select which peltier to use.
So, here is my application in case someone can guide me in detailed way about calculations. Thanks in advance.
I have glass slide 25*75 mm with thickness 1.1 mm, and above this glass will be some biological sample. The whole experiment starts at room temperature ~27 c. At some point later, the temperature above this glass slide will increase to around 60 C in a matter of 10 seconds and I need to maintain it back to around 37 c (suitable temp for bio samples to survive). I will need to maintain this temperature for around 5 minutes.
So, to select Peltier I need to know my heat load ... and also heat that will be generated by peltier itself to cool down my sample.
Can someone guide me into that ,,, I know more or less the data sheets and I will need heat sink and fan but cant do full calculations to come to the point to choose a peltier.
Thank you in advance.


texts: How can I tell from a datasheet if a thermocouple amplifier IC will work with a grounded thermocouple?

texts:
There are several different solution available for thermocouple amplification such as the MAX31856, AD8495, and LTC2983. Some of these support grounded thermocouples (AD8495) and some don't (MAX31856). This is not explicitly stated in the datasheets. How can I tell? My best guess is that I needs to look for a common-mode voltage rejection down to 0V. Is this correct?

Below is a picture of a "grounded thermocouple" configuration.


texts:
I am using an H-Bridge chip, given inputs from a PIC16. My problem is that when a motor is NOT attached, I can measure the voltage across the wires that are supposed to be connected to the motor and it is 5V (which is what I want). However, when I connect the motor, it drops to 0.5V, and the motor barely turns.

What could be the problem?


texts: I killed my Tiva C-Series LaunchPad. Can anyone rescue it?

texts:
I have a Texas Instruments Tiva C-Series LaunchPad (Part Number: EK-TM4C123GXL). I've got the LaunchPad for only a month. Most recently, I used Energia to upload the following code into my LaunchPad:

https://gist.github.com/phil3c7r0n/4e22cd686ae196f92e6b

In my code, I used the following pins: PB_7, PE_5, PB_6, PB_4, PE_0, PD_0, PD_2

And here is the guideline of the LaunchPad:

As you see, in my code I wanted to use PB_7, PE_5, PB_6, PB_4 as OUTPUT with Pulse Width Modulator (~PWM). However, for a stupid reason that I forgot about the guideline included in the LaunchPad's box, I messed them all up: I used Analog pins for Digital-purposed pins and Digital pins for Analog-purposed pins.

Importantly and deadly, I used PB_4, which has main functionality as "SPI CLK" (according to the guideline), for ~PWM (!!!). I also did the same thing with PB_6 and PD_0, which both have functionality as "SPI MISO" (according to the guideline).

Now my LaunchPad is dead now, and this is exactly how it looks:

Let me describe it: A steady half-green-and-yellow light indicating the power on, and that's all. I strongly want you to know that I PLUGGED the LaunchPad in my computer and it did NOT CONNECT to the computer AT ALL:

The computer didn't play the sound as usual when it detected USB connection.
There is no driver appeared in Device Manager although I had already viewed all hidden Devices:

There should be Stellaris Virtual COM Port located inside Ports, and there should be Stellaris In-Circuit Debug Interface (ICDI) driver as well. They disappeared, all of them.

From 1 and 2, I'm pretty sure that there is no way to erase and reset the factory settings for the LaunchPad.
I had already used LMFlashProgrammer from TI:

I had already used other USB ports on my computer.
I had already used other computers.
I had already tried to press the Reset button, even SW1 and SW2, but nothing happened.
Please don't tell me to upload the blink example (or any code) to the LaunchPad. I had told you, the computer didn't recognize the LaunchPad AT ALL.

[Editted] My schematic:

IMAGINATIVELY, IT WAS LIKE I LEFT THE KEY IN THE ROOM AND LOCKED THE DOOR.

Please help me with this problem! I feel frustrating now, and I need the LaunchPad back. I'm in an online course and it is in session!
SINCERELY THANKS!


texts: CI HT12E enable control to reduce power consumption

texts: So, following this datasheet (check out Application Circuit 4), I managed to transmit a signal and receive it on the other end. The thing now is: the whole circuit is drawing 2 mA, and that is because it is always active, meaning that, the TE pin is always grounded. My efforts now are to only enable TE when the button is pressed, so I changed the circuit a little bit, so that the switch would ground both TE and the AD pin. After tweaking with it a little bit, I figured out that that the TE pin should be grounded a little longer then the AD pin, and I would like to know how to do that.


texts:
What are the steps or the algorithms to verify that an EEPROM is working ?

Right now I just write 10 bytes and I read 10 bytes from 10 addresses, and that's naïve approach. Is there an algorithm or an approach to verify that the eeprom is correct ?   or also the problem for flash memory testing ?


texts: using led stripes with external battery: any side effects?

texts:
i have to power some led stripe from ikea with a drill battery:

On led stripe power is written: 12V 0,25A. and on drill power: 12V 2A.

Now i want to power n led strip (for example: n=4) and i want to understand if there are some side effects or some safety way to do it: do i have to add some resistor? and how to have the best result (=more light) for example mayebe if i use more then 10 stripes the light is reduced or whatever..

and if i want to add more kind of light? (ex: 4V lamp like this black one below)

i had some trials and it seems that there are no problem with 4 stripes in parallel, and i think that there is no need for resistors because both the parts works with 12 volts, but my theory knowledge is very poor (i have only some trial and error experience) and i have no idea with 4V lamps (i think that here i need some resistor) or if i change the power and if i use a different power supply (or even some normal battery like 2 or 3 9V battery in series)

mayebe here there are someone that can explain me how things works and how to design the circuit when i have decided how many light i want.


texts:
I want to interface a cc2500 module with the 3pi robot...How do i do that...I just have the cc2500 module(the one here)
I want my 3pi to move accordingly to the instruction given by another transciever.


texts: Having issues with clocking a 74S374 (D Flip Flop)

texts:
I'm having issues setting the state of any of the D Flip Flops, I have jumpers and a multimeter to work with. does the clock pulse have to more precise than touching the jumper to +5v?

 74s374J
data sheet


texts: STM32 UART: combining interrupt and DMA modes

texts:
I am trying to use UART3 of STM32F103K8 to rx data in interrupt mode and tx in DMA mode.
Reception works well, but transmission has a bug: first portion of data is transmitted just fine and ISR is called.
After that, huart.gState == HAL_UART_STATE_READY is never achieved and any subsequent transmission fails.

So, the questions are:

Is it OK to use interrupt mode rx and DMA mode tx for single UART? Are there any examples?
Given that all DMA channels have same preemption priority and are used havily and simultaniously, can it potentially result in data loss, IRQ conflicts or have other negative consequenses?


texts: How to calculate how much voice channels is being multiplexed

texts:
I would like to know how I could calculate from the bitstream which has a bitrate of 2,048 Mbps into how much voice channels is being used. I know that the syn has 32 bits and sign is 16 bits.
Bitrate = sampling frequency * bits/frame
If we would model the dataframe then we would get something like this:
syn + S1 + S2 + Sn...........+ sign
Now the problem is that we want to know how much Sn(t) there is which must represent the voice channels.
But when I use the bitrate of 2,048 Mbps and subtract the syn and sign and divide that with the 8000 Hz sampling frequency and then each voice channel is 8 bit then I get a huge numer which I think is not logical.
Before I can do the other questions the first question is quite tricky ;-)

Asked:
a. Calculate the number of voice channels that are multiplexed in a primary group.
Let's see how you do that.
b. Draw the composition of a data frame of a primary group
Indicate clearly the duration of the frame and the number of bits per sample.
c. How many bits of the frame of the primary group are now "lost" to the
signalling and routing information? What percentage of the frame now consists of
real voice information?
d. How many voice channels are there in a supergroup? How many percent of the
frame of the supergroup now consists of real voice information?
e. What is the baud rate on the connection? Motivate your answer.
f. What is the required transmission bandwidth BW on the cable?
Please justify your answer.


texts: What might cause a fluctuating resistance of a generator winding?

texts:
Before assembly of a machine that contains a three phase generator I check the resistance between the 3 phases of the generator with an ohmmeter. The generator is kept stationary and the temperature is somewhere around 20 degrees centigrade.

The measurement ensures that the generator has no internal wiring fault.

The success criterion is that the resistance between the different poles is equal and matches the resistance specified by the manufacturer (58 Ohm).

Now I have a generator that has a correct measurement between phase 1-2, but any measurement involving the 3rd phase shows me a varying resistance value.

The value jumps around (from 20 to 140 Ohm), converges to the correct resistance value after 20-30 seconds and then starts diverging again.

What could cause this odd behaviour?


texts: Cockcroft-Walton Multiplier strange voltage values

texts:
I am building a circuit that allows me to generate high DC voltages that can be used in conjunction with a 3He counter tube to detect slow neutron radiation. The circuit was designed by someone else but I have transformed the schematic into a PCB and have been testing it. My problem is that the voltage on its output is much smaller than what I am expecting. I am able to read up to 800VDC on the final stages of the CW-multiplier (my current build is seeing more like 120VDC so this is for previous builds) but the output only measures around 60-90VDC. I have a few theories, but I am still not certain as to the cause. The design is based off the one outlined in this paper by Bob Higgins (http://physicsopenlab.org/wp-content/uploads/2017/02/SlowNeutronCoronaCounterTubes_1v10-1.pdf).

The basic explanation to the circuit is 5VDC is fed into the MAX1605 switching regulator and also a nearby transformer (1:20) which steps the voltage up to about 100V (~175KHz). The transformer's primary is grounded through the switching regulator and by controlling the current flow through the primary, (switching on and off quickly) it creates the changing magnetic field needed by the transformer. This 100VAC signal is fed into the 5 stage CW multiplier were it is boosted to around 1.8KV. This is connected to a 4.7M resistor whose other side is connected to the feedback line to the MAX1605 (100M and 50M in series) and the HV output (100M resistor trace). The feedback line is supposed to drop the output to 1.25V which is the switching threshold for the regulator. When the HV output is connected to the 3He tube and a neutron interaction occurs, the tube should draw current and R6 drops that 1.8kV down to ~750V to regulate the current flow. This small current is detected by another circuit and then produces a smoother signal (but this is unrelated). A more detailed explanation can be found in the paper linked above.

Theory 1: The feedback line to the fast switching regulator (MAX1605) may be creating a voltage divider that drops the voltage at the intended HV output. This seems to be the most likely case, however when I measure the voltage drop from the output of the multiplier (left side of R4) to the HV output I only measure .6V so I am a bit confused as to where this drop occurs.

Theory 2: I have gone through several iterations of the board as I thought maybe there were issues with the regulator (burnt out from hot air soldering), this is why my output voltage readings vary so much (60-90VDC). When I measure the feedback voltage at the regulator I see 133mV DC. This makes me think that the regulator is not working correctly but I am still able to measure higher voltages at the multiplier output (R4). My current build is only outputting around 130VDC measured at R4 (but previous ones have gotten as high as 8-900VDC as mentioned) so there definitely seems to be an issue with the regulator in this build, but the transformer still seems to be doing its job so it must be switching. Maybe the there is an issue in the CW multiplier like a blown cap or diode?

Any ideas are appreciated, I know this is a wall of text but I wanted to be thorough. If you have any questions dont hesitate to ask.


texts: Bi-directional motor control with 3 push buttons

texts:
I am trying to create a system where there are 3 input buttons (PTM) and a dc motor output. The motor needs to be bidirectional.
The 3 buttons are: forwards, stop and backwards.
once the forwards or backwards button is pressed, the motor keeps running until the stop button is pressed, or if the other button is pressed in which case the motor will turn in the opposite direction.
It would need to be a latched system (I don't need to hold down the button) and have some protection against unintended input (for example if I accidentally press 2 or all the buttons at the same time, it should ignore it).
I am trying to not use any microcontroller (Arduino) or software on this project. Ideally, something with logic gates, transistors and a motor driver chip (l293d) will be good.
Any suggestions on the circuit for this project or where I can start?


texts: Determine average supply current of switching regulator in DCM (calculate dutycycle)

texts:
For a project, I need to calculate how many hours my battery powered device can operate. The device consists of a ESP32-WROOM-32D, display, reed-switch and switching regulator.
The device is powered by 4 AA batteries in series, which gives me 2800mAh at 6V.
The operating hours, are where the ESP32 is in deepsleep and using the ULP co-processor to count the pulses from the reed-switch. When this happens, the display is fully turned off. So it can be expelled from the operating hours calculation.
The ESP32 draws 0.1mA when the ULP is active during deepsleep at a duty cycle of 1%. Source, p31:
https://www.espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf
The switching regulator IC I use is the LM3578A by Texas instruments. Using this IC is a must given by my supervisor... This IC claims to have a power consumption of 2mA at output OFF and 14mA at output ON. Since the ESP32 only draws 0.1mA in deepsleep, the regulator will operate in Discontinues Conduction Mode (as I understand it).
Now this is where it gets tricky for me.
How do I know the duty cycle of this IC? When is it drawing 14mA and when 2mA? Without this data it is impossible to calculate the operating hours.
I've seen this calculation for calculating the duty cycle of a DCM switching regulator. But I do not fully understand it. Source: https://www.allaboutcircuits.com/technical-articles/discontinuous-conduction-mode-of-simple-converters/

If any clarification is needed, please let me know!


texts:
Background

If you look at my profile description, you'll see that I'm involved in building and wiring up Carnival floats that are powered by an 800KVA, 415v, 3 phase Generator. Electrically, they generally have about 10 or 15 motors, thousands of light bulbs and a 20KW sound system.

Problem

3-phase induction motors are used to drive big spinning steel structures which carry a lot of weight and have a lot of momentum, and therefore need to ramp up (and down) the speed over a period of around 10s so as not to put too much stress on gearboxes, chains and bearings, etc. The running speed also needs to be adjusted to fit the float design, which needs to be done electrically as changing gear ratios is not practical once built.

To control the motors, an Inverter Drive is needed, which is a very expensive piece of kit that has a huge array of parameters that can be adjusted to control motors in all different situations. We have 2 of these units that control a few motors each. So the problem I have is:

A big single point of failure - one unit fault causes many motors to fail.
Many of the motors are limited to being driven at the same speed, when individual speed control is sometimes needed.
Costly.

As we struggle to raise the funds to build our carnival float every year, we cannot afford to buy any more Inverter Drives (unless someone is kind enough to donate one as they have with the two we've got).

Solution

I would love to be able to build my own for a fraction of the cost. I don't know if I'm setting myself an impossible task and am setting my sights way too high, or if this is indeed achievable. Looking inside an Inverter Drive, I can see several SMD circuit boards, some huge capacitors/inductors, and some heat sunk transistors.

I have experience of switching/dimming resistive loads using pic based control circuits, but although I know the theory, controlling a 3 phase inductive load at the moment is beyond my skill level.

Question

Can any one guide me to where I should start with this. I suppose initially I'm looking for a block diagram of the modules (with a little detail) that I would need to build a home-made inverter drive (e.g. PSU, microcontroller, output stages, etc), and how they fit together. I can then work out if indeed its even worth attempting this, and if so work out which parts I can happily design and make myself, and which parts I'll need more help with.

Specs

Input: 240v single phase or 415v 3 phase.
Output: 415v 3 phase variable frequency motor drive.
Controls: Stop/Start, Ramp up speed (seconds), Ramp down speed (seconds), Running speed (Hz), Emergency stop.
Display: Current speed (Hz), Load (A)
Motor wiring: Star

UPDATE (31st Jan):
From the information provided by pingswept and bt2 in their answers, I think I've come up with a simulation of the bare bones of what I need... Rectify the 3-phase to get 586V DC and use 6 IGBTs controlled by an IRS2330 which is controlled by PWM from a microcontroller.