texts: Reclaimed LEDs from fixture. What kind of power supply can I safely use?

texts:
I recently harvested 5 bright white COB LEDs from a light fixture and am trying to figure out what kind of power it would take to power them individually.

The fixture contained a transformer with an output of 36VDC 0.47A Max and was epoxy potted so I can't see if there were any resistors inside.

The LEDs were simply wired in series, so ignoring any resistors, can I assume that the voltage drop across each LED is somewhere around 7.2V? I tried measuring the Vf of an individual LED on my meter but couldn't get a reading. (36/5=7.2) If not, is there any way to calculate/estimate what it would take to power these LEDs individually?


texts: electromagnetic energy harvesting LTspice simulation problem

texts:
In my project I need to use electromagnetic energy harvesting that provides below 1V. Rectification and voltage level boosting are required to meet the power supply requirements of typical electronic circuits.
In the paper Ultralow Power, Fully Autonomous Boost Rectifier for Electromagnetic Energy Harvesters, the author used a 5.35mH inductance coil with a coil resistance of 80 ohm. The problem is when I do the simulation in LTspice the output converter are corrected  when I delete the 80 ohm coil resistance. I don't know what the problem is, exactly. What is the importance of this resistance?
The signals (PWM1 and PWM2) that commands the two MOSFETs and the schematic circuit in the figures below.


texts:
I need a circuit which can step up the voltage from my 3.7V Li Ion battery to 7.5V.
The current requirements are pretty small (up to 50mA max), but I have a latching solenoid which requires a short 7.5V pulse @ 350mA and so the step up circuit must be able to supply this too. I designed one based on the MC34063A but the Ipk value was around 2A and I don't think the IC can cope with that.
Would anyone be able to recommend a differnt IC that I could use. Power consumption is the main concern since it's a battery powered project and so ideally I want the power consumption of the IC to be proportional to the output power, i.e. I don't want it to draw a lot of power while it's only using up to 50mA in order to cope with the larger pulse.


texts:
What does it mean when it says '0' after a resistor value, for example 1k00 or 11k0? Two examples are R7 and R8 in the schematic posted below:

What are the extra zeros?


texts: How to generate 5 MHz clock with 50% duty cycle?

texts:
How to generate a 5 MHz clock with 50 percent duty cycle? I have an application that requires a continuous clock signal to operate. 555 timer is an easy option but it generates only up to 1 MHz frequency. I know that there are various crystal oscillators available but not sure how to connect.
The application is for a printer. The data is loaded into the printer ICs clock signal is high and with a constant frequency of 5MHz.
I need to design a clock generator to load this data into the ICs. The interface connector has 2 input pins, one for data and the other is for clock signal.


texts: Adding phasers in a parallel circuit problem

texts:
Below is a practice question that I am having trouble progressing further with.
The (abbreviated) question and progress as follows:

A circuit of 90V's supply is in parallel with two branches.
Branch 1: Capacitive reactance of 3 Ohm in series with 6 Ohm resistor.
Branch 2: Inductive reactance of 5 Ohm in series with 4 Ohm resistor.
Find the total current and current across each branch.
Confirm these results with a phasor diagram.

My progress:

B1 = 6 + 3J and B2 = 4 + 5J
B1 into polar: Root(6^2 + 3^2) = 6.7082 , Tan^-1(3/6) = 26.565.
B2 into Polar: Root(4^2 + 5^2) = 6.4031 , Tan^-1(5/4) = 54.340.

I=V/r or I=E/Z

B1I = (90/6.7082 angle 26.565 = 13.4164 angle 26.565) and`
B1I Rect = (13.4164 cos 26.565) + (13.4164 sin 26.565) gives 5.9978 + 12.00100J

B2I = 90/6.403 angle 51.340 = 14.0559 angle 51.340
B2I Rect = (14.0559 cos 51.340) + (14.0559 sin 51.340) gives 8.7806 + 10.97578J

Kirchoffs law and common sense states the two currents in parallel added will give total current:

Polar:(13.4164+14.0559) ang (26.555 + 51.340) =  27.4723 angle 77.895

Now converting to rectangular:

27.4723 cos 77.895 =  5.760 and
27.4723 sin 77.895 = 26.861J

Therefore total current should be 5.760 + 26.861J

Assuming my calculations are correct how would I then prove this using phasers ?
I have only done phaser calculations using non-imaginary ; I am told this method is easier.

I have attempted to prove this using further polor to rect calculation and they don't appear to add up ;although this could be due to a lack of sleep.

Progress update
Thanks for edits and info thus far.

Update given capacitive reactance is negative:

B1 = 6 - 3J
Into polar: 6.7082 , Tan^-1(-3/6) = 333.433 (-26.565)

Calculating Current rectangularly first:

Total current would be
    90/((6 - 3j) + (4 + 5j))
    = 90/ 10 + 2j

 =(90/10 + 2j) * (10 - 2j)/(10 - 2j)
 = (900 + 180j) / (100 -20j + 20j -2j^2)
 =  (900 + 180j) / (102)
 = 8.8235 + 1.7647j

To polar :

Sqrt(8.8235^2 + 1.7647^2) = 8.99824 , Tan^-1(1.7647/8.8235) = angle 11.3099

__
 Assuming this is correct how would I prove with phasers ; again I am unsure due to only using phasers with real values.


texts: What exactly does OTG_FS_SOF do? Is it vital or imperative to USB host mode?

texts:
When using the USB host mode, the STM32 has a pin named OTG_FS_SOF that ST gives very little useful information (in both Datasheet and USB tech documents) other than it has something to do with syncing when driving Audio devices.

However, I've seen various designs where no audio application was used but the SOF pin was connected anyway — pull up with 47k under most cases. Why is that? Is it very important to host mode? Must I connect it, or data wouldn't be sent and received properly? What does it do anyway?


texts: Normally On Circuit with Positive Trigger?

texts:
Pardon my lack of technical terms here; essentially I have an under glow kit on my car (along with some other lighting) that I want to expand the circuit on. I bought a pair of 5 pin relays to accomplish my task. Essentially the running board lights will constantly be on, until I use my turn signals in which case the appropriate running board light will blink like my turn signal.

The lights have four wires, a positive, and three negatives that create the colors.

This is the relay I bought:

Here is the diagram for the normally off circuit they have:

Here is the wiring harness:

And here is the diagram I came up with to accomplish my task. As I stated before, I’m not great with technical terms so please pardon that.

simulate this circuit – Schematic created using CircuitLab

Now, for testing I’ve scaled this down to just the relay and a single light; for some reason, I can’t seem to get the light to come on even with the turn signal on. When I attach the light straight to the battery, it comes on.

I feel like I’m just doing something wrong and can’t figure it out.

For clarity, the goal is to have the light on when the turn signal is off, and blink when the turn signal is on.

Also, if the above isn’t possible, even the normally off diagram didn’t work; how can I correct to achieve it?


texts:
I have just had a frustrating experience with an NPN transistor that came from a pack of 15 "switching transistors" from Radio Shack. The specs on the packaging say "Typical hfe: 200" but when I measure and calculate the values from an actual operating circuit it looks like the hfe is more like 8. (If I am calculating correctly, 35ma measured on the base is allowing only 280ma to flow.)

Is it possible this transistor was simply damaged by ESD or something?

I am fairly confident my circuit is sound, because when I replace the transistor with a different type (and changed my base resistor appropriately) the circuit functions fine.


texts:
I’m looking at the Panasonic 600V 40mA relay AQW216A (https://www.mouser.com/ProductDetail/Panasonic-Industrial-Devices/AQW216A?qs=QVBMgXxBiLwcjOQSSsoh0w%3D%3D) for a dual Voltmeter/Ohmmeter circuit. When the relay is open, it will experience AC voltages in the range of 120-347Vrms.
On the surface this relay looks like a good fit because it can handle up to 600Vpk. My question here is: should there be a larger cushion between my Vpk (~490V) and the rated maximum? This circuit will be protected with bidirectional TVS diodes so I hope to quickly snuff all overshoots, but am still unsure if I need a larger difference between my Vmax and the spec. (Like if I need to use a 1kVpk, or 1.5kVpk relay instead)
Thanks for your help!


texts: Ways of PCB Etching other than Photosensitive Spray or Toner Transfer

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Toner Transfer is not an option for large quantity or quick production and in my area I could not find any photosensitive sprays.

I tried with screen printing emulsion, but it does not stick with the copper quite well after exposure. I tried also with plastic paint by screen printing process, but I couldn't achieve the resolution I wanted (12 mil trace with 12 mil clearance).

The plastic paints sticks with the copper quite well but it is not VU Curable. Does mixing the plastic paint with the emulsion will make any use to me?

If it still don't work I got a last option of this.
But it is not available in low quantities. They provide a minimum of 20kg. But for my need 1kg will be enough.

What should I do?


texts: How do I tackle phone-microcontroller BlueTooth communication?

texts:
I have this bluetooth module I bought on RS a while back, and I was pretty keen to set it up with an STM32L152 development board I have handy. The only thing is, I'm not really sure what steps I have to take to get to that point, I'm finding the whole datasheet very overwhelming.

I can handle the SPI communication stuff, or at least figure it out eventually on my own, but the bluetooth protocols/handshakes, etc. are a total mystery to me and I don't have a clue how to go about even pairing the module with my phone which would be a step towards my eventual goal.

Suggestions, advice, links, and ideas that can help me get to where I want to be would all be very much appreciated.


texts:
I've opened up a knockoff game cube controller and I want to know what the power via is labelled as. There is a 5v which is fine but what are the 'v' and 's' pins? Photo attached. The cable is a standard game cube plug but I'm wondering if its just USB and if I can therefore splice it into a USB plug.
Cheers


texts:
I have a PC with a DisplayPort monitor. When the monitor sleeps or is powered off, the OS loses track of the current display resolution. My research indicates this is probably due to the Hot Plug Detect (HPD) pin being brought low when the monitor enters sleep mode or is powered off. To remedy this, I'd like to have DisplayPort's (DP) hot plug detect (HPD) always report that it is connected.

For HDMI, there's a device that puts a 1K resister between the power and HPD pins. I think something similar would work for DP. I can't find any easy-to-open DP to DP adapters but maybe I can hack a cable.

Further research indicates that in DP 1.1 there is a power line but it's not available in DP 1.2. (The specs seem to say that the power is connected at the port but cables should not pass it through in DP 1.2 like they would in DP 1.1.)

USB seems a viable alternative for power but HPD uses a 3.3V supply while USB is 5V. Since it's a cable hack, I think keeping the component count down is necessary. Maybe a zener diode based regulator would do the trick, sort of like this:

Spice simulations seem to indicate the voltage would fall within what is necessary to pull up the HPD.

So far this is all theoretical. I don't have access to the official DP specs (or the official USB specs for that matter) and I'd rather not fry my video cards or monitor.

I'm hoping there's someone familiar with DisplayPort here that can either tell me if this is likely to work or can point me in the right direction.

(Using other video connection types is not an option.)


texts: Slow slew-rate of photodiode circuit output

texts:
I've built an LED driver and a photodetecting circuit.

Basic forms of the driver and the detector were made.

Driver

Detector

FYI: Parts used and their datasheets

LED: Seoul semiconductor W42182 (datasheet)
Photodiode: Hamamatsu Si PIN photodiode S6036 (datasheet)
Op-amp: TI TL792IP (datasheet)

In this configuration, I want to driver an LED and detect it as fast as hundreds of kHz.

But, output from the photodetector shows a sawtooth form not a square form even with a very low frequency, 10 Hz:

The blue line is the V_OUT in the dirver circuit, the photodiode outputs, V_OUT in the detector circuit drawn with the yellow line.

As you can see a **slew rate of the detector is not fast as the driver. So I made a list of candidates that may cause this problem.

Candidates of the slow slew rate problem

V_OUT in the driver is different from an actual voltage value across the LED. (i.e. I am probing a wrong point. And brightness of the LED may not be a square form as the blue line.)
Reverse voltage applied on the photodiode is not sufficient. In datasheet, BW > 10 MHz when V_R = 12 V. Thus, I need to apply 12 V as the reverse voltage across the photodiode.
R1 (gain) in the driver is too large. So, I need multistage low gain op-amps.
Photoconductive mode doesn't suit. It's better to use photovoltaic, etc. (But, I think photoconductive mode is nothing wrong.)
(Si PIN) photodiode doesn't suit. It's better to use photoresistor, phototransistor, etc.
(Feedback or any) capacitors have too low/high capacitance.

Which one do you think is the keypoint of the problem? If I got everything wrong, please correct me.


texts: How can I calculate CM and DM gains for this model?

texts:
Regarding the second page of this document, at the first example it calculates the DC CMR due to line imbalance Rs and explanation is given in the first paragraph below(ignore the second example):

But I don’t understand where the numbers 0.9990 and 0.0009990 come from.

I redrew the circuit model to simplify it and named the nodes as follows:

Can’t we show the path taken by the differential current flow direction using the nodes order such as a, b, c, d, e and the common mode currents direction as a, b, c, m, k and e, d, c, m, k?

If true the differential voltage gain and common mode voltage gain seems not as given in the document. For instance the differential gain to me seems like 20Meg/(20Meg+10k) but the document shows it as 0.999. Im confused how to calculate both differential and common mode gains mathematically here. How should they be calculated separately to find out the CMR eventually?


texts: LM3466 circuit symbols, SEN/SRC to ground?

texts:
I'm reading the LM3466 datasheet (page 9) and am confused about the symbol downstream of the SEN/SRC pins and  R(sen). Is this a ground symbol? If so, why do they use multiple different ground symbols in this schematic?

Cheers,
Fin


texts: Light bulb LED equivalent of a CFL (Compact Fluorescent Lamp)

texts:
If I have a CFL light bulb of 100W what would be (how many watts ) its equivalent in LED.

In the place where I live LEDs have taken over and CFLs are no longer available, but I need stron bright lights and with LEDs it ranges from 6 to 14 watts.
While searching online i saw phillips selling LEDs with equivalent characteristics to CFLs. how can I do that by myself ? with local LED light bulbs available here ?

what matters to me is the brightness.

EDIT
Is there anyway I can somehow evaluate how bright and LED light will be if I'm given only something like 14W and the voltage .?


texts: How to pick a Balun and transformer for this power line measurement circuit

texts:
I was reading this paper here about measuring power line impedance using a network analyzer.  It has a little circuit that they used but of course they're not nice enough to include a BOM :)

How would I go about choosing a Balun and transformer like the one they used here?


texts: What does VA rating of a wall receptacle means ? Just started using Revit for Electrical Design (120V/208V) and came across wall receptacle rated as 180 VA. Just trying to wrap my head around that 180VA rating as I understand the maximum load that can be connected to a receptacle would be 120*15=1800 VA.. So what does 180 VA means ?


texts:
I'm using an AAT1217 for the boost converter in my circuit. The reference circuit I'm using is:

The datasheet suggests several inductors:

It suggests using these fairly large inductors, the ones that you can see the coils. My question is why aren't the normal 0402/0603/0805 SMD inductor packages being used instead? For example, the MLZ series from TDK has a similar DC resistance and a fairly large DC current rating of 500 mA. The fine print does mention that "Current assumed when inductance ratio has decreased by 50% max". When does the inductance ratio change?

Also, I've run some experiments with both the CR43 and the MLZ inductor and they are both able to drive the servo motor (MG90S) fine. Am I missing anything? Or is it perfectly fine to switch to a smaller, more compact inductor? (the other thing that I am wondering is if the AAT1217 datasheet was written a while back when small inductor packages did not exist).


texts: Constand output voltage from batteries / rechargable batteries

texts:
I'm trying to make myself a battery pack for my DSLR camera.

The original battery of the camera has 7.2 V and 1200 mAh.

I've also bought a coupler ( a dummy batterie for external DC input ) which has a AC/DC adapter with 8.4 V and 2000 mA output.

So I am pretty sure, the camera can hadle anything between 7.2 V and 8.4 V input voltage.

I was thinking of using two 6x AA battery clips.

So if I wire the battery clips like so ( seriel & parallel ):

[##]   <--  AA battery

+--[##]---[##]---[##]---[##]---[##]---[##]--+
|                                           |
+--[##]---[##]---[##]---[##]---[##]---[##]--+-----  (+)
|                                                         INPUT
+-------------------------------------------------  (-)

...I should either get:

A. Using normal AA batteries:

6 x 1.5 V = 9 V

B. Using rechargeable AA batteries:

6 x 1.2 V = 7.2 V

So is there an effective way I can get a constant output with anything between 7.2 V and 8.4 V ??

thank you.


texts:
Can anyone recommend a hobbist linear motor?

The motors are often described as being a rolled out version of a DC motor (is that true btw). If this is the case then how does one "drive" a linear motor. I'm trying to understand what kind of signals need to be sent to the coils to make it move.

Any info welcome.

EDIT: For clarity, I'm asking about the  "stepper" type linear motor


texts: STM32 one timer for multiple push buttons

texts: I have a small project where I set up a timer interrupt  to check the state of few buttons. Do I need to set up 1 timer per button or can I check 2 or 3 with 1 timer?


texts:
I'm integrating an nRF24L01+ chip into a PCB I'm designing, but I'm a little confused about the best PCB antenna design. In the datasheet for the chip, they specify an antenna like this:

However, all of the boards you can buy with this chip use a different design:

The design is quite different. Not only is it a different shape, it also has that extra stub track with a via.

What is the reason they do this? Is it a more effective antenna, or does it just take up less PCB space?

If it is a superior design, how can I create my own? Do I just draw a wiggly line that looks roughly similar, or do I have to get the dimensions precise for it to work properly?


texts:
I would like to design and build a tunable lowpass filter. I would like to adjust the cutoff frequency from 1 MHz to 500 MHz.  Requirement on the resolution would be something like 10-50 MHz, obviously, it's not that critical.

I am going to send a programmable clock signal through this filter and want to reduce the high frequency harmonics.  I am only using the clock signal as a simple way to get a programmable sinusoidal signal, hence the need for the filter.  I was considering using the ADF4110, ADF4350, or one of the Silicon Labs Si570/571 as the programmable clock.  I was told that a tunable lowpass filter over this range may be tricky, so I thought it best to consult the StackExchange.  I am open to any suggestions.

Ultimately, what I'm trying to accomplish is get a sinusoidal signal that will sweep from 1-500 MHz.


texts: Have my AGM batteries reached EoL or is my charger defective?

texts:
My setup: two 12V 20Ah AGM batteries in series for 24V. Typically discharged to about 50% depth on average about 3 times per week (less often in winter, batteries are kept indoors). The current set of batteries is about 3 years old, so are likely reaching the end of their lifespan (average of about 150 cycles/year, so around 450 half-depth cycles now.)

I have a 24V 2A smart charger that is relatively new (about 2 months old), since my old charger started making weird sizzling noises. The new charger has worked fine for the time I've had it.  Normally, the batteries are always connected to the charger when not in use, and the charger will show a green "Charged" indicator, which according to its specs means it's delivering an appropriate float charge.

Yesterday morning, I connected the batteries to the charger as usual, and it went into charge mode. I left it as usual. This morning, about 24 hours later, I noticed the charger was still in "charge" mode. The LED was still blinking red (indicating charging) and the transformer was quite warm to the touch (typical when it's delivering its full load). The batteries were also quite warm to the touch - not uncomfortably warm, but definitely above room temperature.

Which is more likely?...

that the cells just reached the end of their lifespan and thus their voltage characteristics during charge differed enough to confuse the charger, or
that the charger itself is defective and kept charging the batteries even after their voltages reached the appropriate cutoff point?

The cells were functioning OK during the last cycle, in other words I didn't see any significant capacity drop or voltage drops. Obviously though, I now need to assume these batteries are probably either seriously degraded or otherwise useless. Basically, we have a 20Ah cell that was discharged to about half its capacity, then charged at a full 2A for the next 24 hours (48Ah). That extra energy went somewhere - and I think it's a safe bet that even though it's a sealed AGM cell, it probably lost some of its electrolyte.

But the reason for this question is to figure out - do I need to also replace the charger? I'd hate to buy a brand new set of cells and then have them also immediately damaged by the charger.

Perhaps a more technical direct question: do the voltage characteristics during charge change significantly in an AGM cell such that, when the cell is nearing end of life, the voltage might not reach the level that chargers will read as a full battery?


texts:
I am designing an FSK transceiver that operates from roughly 902-928 MHz with at least 18 possible channels. Using the 5-bit DAC in my microcontroller, I plan to control a Crystek VCO (CVCO25CL-0902-0928). The voltage vs. frequency equation is as follows:

$$\\(0.5V,902 \text{ MHz})\\(3.5V,928 \text{ MHz})\\ \therefore f_\text{MHz}(v)=\frac{26}{3}v + \frac{2693}{3}$$

The 5-bit DAC at Vdd=5V will provide 18 unique frequency channels, however, I am uncertain of how my microcontroller will identify each of them. Below is a receiver block diagram:

900 MHz is far too high for the ADC of the MCU to sample but is there some sort of frequency divider to bring it down? Some FSK receivers have two band-pass filters for the mark/space frequencies but I plan to have 18 with a 1.355 kHz separation - that would require 18 tuned band-pass filters. My hope is to avoid using a DSP as well.

In other words:

How can the MCU infer each individual channel with 1.355 MHz spacing?
Is 1.355 kHz spacing to little (i.e. should I reduce the number of channels)?

EDIT
@Andy aka: The reason I have only 18 unique channels is because of the DAC resolution. A 5-bit DAC provides the following table of voltages. Plugging them into $$f_\text{MHz}(v)$$ gives:

The SAW filter I was thinking of using has a center frequency of 915 MHz (AFS14A26-915.00-T3). Haven't thought about interference as of yet but I plan to use a unique communication protocol depending on how many channels are used. If just two channels are used (2FSK) then I could have an address byte to identify the slave/master (somewhat like I2C). Alternatively, the PIC could switch to different channels that are less noisy. If you have more thoughts on this I would be interested!


texts: Basics of board level shielding and grounding

texts:
I have been designing MCU based PCB that must be withstand hard EMI tests. This PCB includes ethernet transceivers, can transceivers, rs485 transceivers, II2 chips, 25MHZ oscillators, optoisolators and some inputs.PCB will be connected to metallic enclosure by screws. There isn't any RF antenna on my PCB. I need an expert device about shielding and grounding.
My plans and current situation are:

There will be a outer border plane for chassis ground. It will be
connected to metallic enclosure. And this chassis
plane will be connected to ground by 22nF 1000V capacitor at one
point (I will put spare capacitor connection for all edges but for
first I will placed just 1) I used this method on my other PCB and it was very good for ESD.

I'm planning to use board level shielding. Firstly I have been
decided to cover MCU,oscillator and nearest coupling capacitors in 1
shield. Other Ethernet transceiver and capacitors will be covered by
other shield.

My basic questions are :

Need I faraday cage between chasis plane and ground plane ? Will It
be helpfull to reduce any EMI ?

How can I draw traces that must be connect any point where is out of
shield? Is below figure proper? Can I draw traces just between the
shield pins/pads. Won't it break the shielding? Or I have to use vias
and draw trace on bottom layer?

Which components I must cover? My covering groups that I explained above is proper? Or I must cover all components in 1 shield. Or any other combinations ?

Where shield pads must be connect to ? Directly to the ground or chassis or anywhere?


texts: PID temperature controller with Arduino using a NTC thermistor and a Peltier Cell

texts:
I'm trying to control the temperature of a LED laser (which have a thermistor as temperature sensor and a Peltier Cell, both integrated with the laser) and what I'm implementing is a PID controller with Arduino Uno. The project is going as follows:

1.- I set the Setpoint and get the value of the thermistor with the next cirtuit (the obtained raw data are processed in arduino and transformed to the corresponding temperature):

2.- I'm using the PID arduino library, so with the value of the temperature, the setpoint and the chosen Kp, Ki and Kd I'd get the corresponding output. And with this output value is where I have the problem, which I'll explain later.

3.- The idea is to send this output given by the PID to a PWM pin and then, depending if we need to increase or decrease the temperature, generate a positive or negative current in order to feed the Peltier Cell. The PWM signal will go from 0 to 4V (0-2V when we want to cool down and 2-4V when we want to heat up). To generate the corresponding currents I've implemented the next circuit:

It sets 2V as threashole, which is compared with the arduino DC signal, generating then a positive or negative value. Then I amplify this small current at the output of the comparator (U1A) with the Darlington transistors (one for positive and the other for negative values) and that will be the current that goes through the peltier cell.

As you see, I need to set up the output of the PID in arduino in a way that gives me 2V in case that there is no error, 0-2V when the error is negative and 2-4V when the error is positive. I don't know how to do this with the PID arduino library, so if someone has any idea please help me!!

I know it can be a long question just for this, but I wanted to explain a bit some of the system so it is easier to see the situation and also it can be of help for other people. Anyway if something is still not clear, please ask me.

Thanks!!


texts: NPN or PNP for multiplex seven segment display?

texts:
I want to put three multiplexed seven segment displays on a pcb module which then will be connected to another board through a 1x12 Pin header housing an ATMega (so assume in the following that Pin 11 is GND).

I created two circuit designs one using PNP transistors for multiplexing (as seen in most tutorials):

and one with NPNs:

Wouldn't there be a benefit of using NPNs as we can avoid the 0.6V drop? How is the recommendation in this use case?


texts: Calculating data retention rate of SLC NAND

texts:
Background
I am a software developer trying to calculate data retention rate of a NAND memory ic. I have minimal knowledge/experience with electronics.
I have a constraint on data retention, 15 years. I am trying to calculate data retention rate of a 256 MB SLC NAND with ECC. This NAND will be used alongside with a host controller for a custom module.
I have the following application parameters:

Operating temperature range is commercial, 0 - 40 Centigrade Celsius.
512 bytes of data will be written to a fixed address range sequentially on NAND 3 times per day
31 Bytes of data will be written to a fixed address range sequentially on NAND 10 times per day
512 bytes of data will be written to a fixed address range sequentially on NAND once daily.

Issue
Datasheet for NAND IC includes just a graph with logarithmic scales under Reliability:

Also I found the following article: Understanding Life Expectancy of Flash Storage, unfortunately I cant make a connection between parameters mentioned in article and my application parameters.
Questions
What is Write/Erase Endurance Cycles?
How is related to application parameters mentioned above?
Is there a formula to calculate data retention rate based on application parameters mentioned above?


texts: Using an analog temperature sensor near 3-phase 150V , 40A Motor Controller?

texts:
I'm looking for suggestions on what type of temperature sensor to use. I need to have it attached to the heat sync of a 150V, 40A 3-phase motor controller. The motor controller is in a enclosed space and I need the monitor the heat being dissipated by the controller remotely.

Whenever the motor controller is run, I see a massive spike in the temperature reading, due to it being analog, coming from the induced voltage from the EMF produced by the 3-phase output.

Currently I have this sensor attached
http://www.analog.com/media/en/technical-documentation/data-sheets/TMP35_36_37.pdf

My current thoughts are to use a simple thermistor with a shielded twisted pair attached to it, but I thought I'd see if anyone had an idea about a way to have a sensor that would be agnostic to the EMF.


texts: How does the arc extinguisher work in a miniature circuit breaker?

texts:
In a miniature circuit breaker, as shown below, the distance between open contacts is much less than the distance between metal bars in the arc extinguisher part (the gap gets progressively longer from contacts to arc extinguisher.)

So why does the arc move from the contacts to the arc extinguisher?

i.e. Why doesn't it stay between the actual contacts, where the gap is minimum and has the least resistance/breakdown-voltage?


texts: FCC Requirement for device to device output power variability?

texts:
I'm working on a BLE capable device using the Nordic Semiconductor nRF52 SoC, and we're going to have to go through FCC testing.  But one thing that I am not clear on, at all, is the tolerance in output power from device to device.

For example, let's say my target output power is 0dBm on BLE channels 37, 38, and 39 (2404MHz, 2426MHz, and 2480MHz), and the sample we send to FCC testing transmits at exactly 0dBm on all 3 frequencies.  How much variation is allowed from device to device?  Is okay to be at 0.5dBm? 1dBm? -0.5dBm?  Or is it more of a "thou shalt not transmit more than sample + xdBm"?

The nRF52 chip only gives 4dBm steps in RF output power, and I'm worried that might not be enough control to get every device close enough in terms of RF output power, but I have not found anything authoritative on what the FCC requires for device to device difference in RF output power.


texts: Why do electrolytics have a different charge and discharge rate for the same current

texts:
I am measuring the charge and discharge rate of a HV electrolytic capacitor (actually three 560uF, 250V capacitors in series) to calculate the capacitance.
Note: The capacitors are hand picked for an effective combined AC capacitance of 155uF.

During charge I source 20mA and measure (digitize) from 35V to 695V.
During discharge I sink 20mA and measure (digitize) from 695V to 35V.

The curves are really flat (the charge has a very slight curve).

Computed capacitance (20 runs) using C=\$I / {dV\over dt}\$ is:

Charge    - 166.13uF +/-0.7uF (2nd order polynomial fit)
Discharge - 185.16uF +/-0.08uF (linear fit)

Why is the discharge capacitance consistently 11% higher?

Note: Reforming is not an issue as the test was repeated 20 times in quick succession with consistent results.

Test is performed by sourcing the current with a Keithley 2410 SMU.  Voltage is measured using a calibrated 1000:1 divider into a waveform digitizer. The voltage divider is buffered and has a 10M input impedance.

Here are the charge and discharge curves.


texts: I've worked with the AVR-series of microprocessors before, as well as twiddling around with digital ICs. Recently I've gotten interested in analog design, but I don't understand it very well. I've looked around for resources but most of them assume that you already have prior knowledge. Are there any good ones for beginners?


texts: How to determine if a Carry Look Ahead Adder Overflows

texts:
I am implementing a 32 bit CLA Adder like how a 16 bit adder is implemented in Wikipedia

Problem is how do I determine if the block overflows? I will need the carry into bit 32 (which is now in the last 4 bit CLA Adder) and XOR with carry out of bit 32(Check difference in MSB)?

UPDATE

Is my overflow logic correct

where Cin is the carry into the whole 16 bit block, P* is the Block Propagate, G* the block generate, and carry into bit 32 (typo, bit 16 MSB actually)


texts:
I'm planning to buy a photo-interrupter, and I had a look at the spec sheet, but I didn't see much on the current/voltage of the device.

I was thinking that it could run on 20mA, but I am confused about the maximum voltage.

I saw something about collector/emitter and emitter/collector voltages, but I don't know what to make of it.

So, my real question is, would it work well at about 20mA and 5V?

If not, could someone please explain how to find the ideal current/voltage?


texts:
I am new to this site, but I have got a problem and You might be able help me out.
I have got a car cluster which talks and listens to a 0V/+12V serial line. My goal is to send some extra commands to the instrument cluster.
I'm using the MEGA's Serial2 for this and Serial to monitor the whole network.

The problem is, I have to wait still the line goes idle / silent so my message does not interrupt any other lines sent by other devices on the network.

I have got this so far:

#define Kbus Serial2
#define get_Kbus_data serialEvent2
#define Kbus_rx 17
#define Kbus_tx 16
byte Kdata;
uint8_t left_blinker[10]={0xD0, 0x08, 0xBF, 0x5B, 0x20, 0x00, 0x04, 0x00, 0x00, 0x18};
int time_Kbus;
void setup()
{
  pinMode(Kbus_rx,INPUT_PULLUP);
  pinMode(Kbus_tx,OUTPUT);
  Serial.begin(9600, SERIAL_8E1);
  Kbus.begin(9600, SERIAL_8E1);

}
void loop()
{

if(millis()- time_Kbus > 1 ) Kbus.write(left_blinker, sizeof(left_blinker));

}
void get_Kbus_data()
{
  Kdata = Kbus.read();
  Serial.println(Kdata,HEX);
//  Serial.write(Kdata);
  time_Kbus = millis();
}

I am using two opto-isolators to get the proper 0V/+12V signals.

simulate this circuit – Schematic created using CircuitLab

I'm using 4N35 optos and a 2N3904 as Q1

I have noticed one thing while working with this. The Arduino does not send the starting zeros of, like 0x08 goes out as > 8 so maybe the recieving end does not recognise it?!

I can read the line using this circuit and an other code, but I haven't tested the "sender" side of it.

I think this is all I have.

UPDATE #1 = Missing junction between the two optos and GND line fixed.


texts: What is the importance of a 4-terminal shunt resistor? What is real purpose behind using two seperate terminal for the voltage measurement across the shunt resistor?


texts:
I bought a 115 to 15V toroidal transformer.The turns ratio of this should be (115/15)=7.66 ideally.

Now the problem I'm facing is that upon wiring it I'm getting a calculated turns ratio of 6.97, which doesn't match the datasheet.

I plugged it into my wall outlet and measured 122 V with my voltmeter coming into the primary side. On the secondary of the transformer I am getting an output voltage of 17.5 V.

This give me:
(122/17.5)=6.97 turns ratio.

Why is this? The toroidal transformer also had this wound plastic which encircled the coils and I cut that off. Could that be the reason why this is happening or is it just how things in the real world work?


texts: Can the transformer from an SMPS be used for step-up?

texts:
Problem: Stepping up voltage of a high frequency sine wave = 50 KHz to 100 KHz range.

Inside SMPS circuits I find a donut shaped transformer that I think is used to step down the voltage from the high voltage circuit plus isolate it from mains. I have read that SMPS oscillators work at frequencies in 10s to 100s of Kilocycles. From what I read transformers can be used in either direction but not equally well.

So I have a sine wave generated around 50 to 100 KHz and 0 to 5 volts can I simply use the round transformer with the connectors reversed to step up this voltage to whatever ratio that the transformer was originally stepping down?

Even if it is not a perfect solution will it work at all and what part will not work? What can I do to make it work? I do not want to use a amplifier because the amplifiers I can get are all up to 20 KHz and I do not have a 20 voltage or higher and a + - power supply or SMPS that the amplifiers need. Oh and I have many broken SMPS units I can take apart.

Thank you.


texts: What is the Address of the first LUT in a Spartan 3E?

texts:
I've been reading the document Spartan-3 FPGA Family Advanced Configuration Architecture and I'm having trouble figuring out what the address of the first LUT is. Can anyone point me in the right direction?

EDIT: I'm trying to setup a Spartan 3E. In order to configure the first LUT as a NOT gate and connect it to outside world, I need to know what value to send to the configuration so that LUT becomes a not gate connected to the pins on the IC that I want.

I am learning about FPGAs and I need to know how they work from the transistor up.


texts: I want to simulate the behavioral model of CD4006 chip in LTspice. It is a CMOS 18-Stage Static Register. Looking at the Datasheet  I see the one stage logic diagram that consist of inverting buffers and flops. But this stage has D, Q, !Q, CL and !CL i/os. CL - is for clock. D - is for DATA, Q and !Q - outputs, but what is the !CL input ? Is it CLR, that is usual attribute for FLOPs in LTspice?


texts: How much energy does a transistor use? Is it worth building a NOT circuit for a relay?

texts:
I'm a super beginner, but I've developed a circuit that appears to work. My question is if there is a better way to do it.
I have two power supplies. The primary supply will power a load. When the primary supply is cut, the secondary should power the load.
There are two possible solutions:

Use a transistor in a not circuit. When the power fails, it allows power to the relay to switch it.

Use the relay, have it always on, and when the power fails, the relay falls to its natural state connecting the secondary supply.

I know we're talking about very little power, but I'm curious which one uses more? If the relay requires 20ma to stay activated for the primary power, then it's always using that. If I use the transistor/NOT circuit, then the relay is using 0ma to connect the primary power, but the transistor looks like it is using 20ma instead to just short the relay circuit.
So my question is, is one of those preferable over the other? Or is there a way to build a NOT circuit that uses less power than the load it needs to power?


texts: PWM dimming using the TLC5916 current limiting LED driver

texts:
I'm using a TLC5916 which is a constant-current LED driver. I want to dim a LED and have setup a simple board with a particle chip. Try as I might I don't get the LED to be dimmer without flickering (to be honest it just flickers and doesn't really dim).

My question is: Can LED dimming be achieved with constant current drivers? If it can be achieved a clue on how would be nice, so I can do a triple (thousand) check on my source-code on what I'm doing wrong.


texts: Which of the following methods should I use to actuate a solenoid from a microcontroller?

texts:
I've been studying the PICAXE microcontroller as a driver for a set of three 12VDC solenoid valves (though I may choose the 24V models).  For reference, the controller will use a temperature sensor to determine when to actuate the solenoids, in addition to elapsed time (via the firmware).

Conceptually, the use of a relay to control each solenoid makes sense to me since they operate at a higher voltage than the microcontroller.  However it has been about 20 years since I last studied electronics in high school, and I get a bit confused when I see slightly more complicated solutions to this problem.

Here is a schematic of how I thought I should build the circuit, simplified to one output pin and one solenoid for brevity.

I then found the "Standard Circuit" in the PICAXE Interfacing Circuits manual, which is represented as follows.

Why is a transistor is required to actuate the relay?  Perhaps the output current of the microcontroller pin (~20mA) is insufficient to power the coil in the relay?

Finally, I became concerned with the space that three relays would occupy on my circuit board and though I might be able to use an AND gate chip as follows.  The benefit being that such chips usually contain four gates, and thus replacing three relays with one smaller chip.

In this example, one gate input is fixed at 12V.  Is this gate solution feasible?  That is, if the two "high" inputs are different, but recognized as a high by the chip, will the output voltage generally be the max of the two inputs?  I found a data sheet for the BU4081B chip, but I am having difficulty finding the answer to this question in it.


texts: DC output of DC-controlled SSR does not turn off in simple circuit

texts:
The following simple circuit turns a LED ON/OFF. It includes:

DC power supply 12V (EDR-120-12)
SSR (rated for DC input and output, DR10D12, datasheet)
LED, 400mA, 2.85V forward (L2-MLN1-S, datasheet)
resistor 50 Ohm
pushbutton (PVA6LRE21241, datasheet)

My problem is that the SSR output remains ON and can only be turned OFF with turning the power supply OFF.
When the pushbutton is ON:

the small LED of the SSR is ON
the LED is ON and the measured current flowing through it is 198 mA (supposed to be 195 mA = (12 V - 2.85 V)/47 Ohm)
when there is no load at the SSR output, the resistance across the SSR outputs (1/L1, 2/T1) is 0 Ohm (and my multimeter says it is the same potential)

When the pushbutton is OFF:

the small LED of the SSR is off
the LED is ON and the measured current flowing through it is 185 mA
when there is no load at the SSR output, the resistance across the SSR outputs (1/L1, 2/T1) is 3 MOhm

With the SSR LED turning correctly ON and OFF I believe that the issue is on the output side.
I do not understand where these 185 mA come from when the pushbutton is OFF. (I think the 13 mA difference (198 mA - 185 mA) is the small LED of the SSR turning ON and OFF).
I've read about possible solutions (use a bleeder resistor in parallel to the load to remove a leaking current?) but I am still not sure I understand what is happening here, so I thought I would ask a clear question here for the record.
Thanks for any help
Edit: for clarity, removed the circuit for the LED illumination of the pushbutton
Edit: answering questions from comments

"Is this SSR designed for DC?" from @user253751. Yes it is:

Diagram of the SSR with DC control input and DC output.


texts:
I am trying to come up with a driver logic for an H-bridge (seen in the image attached) which would provide a single-ended or a differential pulse based on a user choice.

Input signals: clk (clock, duration can vary), por (power-on-reset), en (enable for the circuit), sel (select the mode, 1 for differential).

Outputs: A1, A2, B1 and B2

Terms: low - 0, high - 1

Operational logic:

Initial conditions: A1 and B1 are high if A2 and B2 are low (prevents crowbar current).

If 'por' and 'en' are high, the circuit is enabled.

If 'sel' is low, single ended drive is run (same for A and B branches, so will just describe A):

When 'clk' goes high, A1 goes low; A2 goes high, but only when A1 is low.
When 'clk' goes low, A2 goes low; A1 goes high, but only when A2 is low.

If 'sel' is high, differential drive is run:

When 'clk' goes high, A1 goes low; A2 goes high, but only when A1 is low; B2 is low and B1 is high.
When 'clk' goes low, both A2 and B1 go low; both A1 and B2 go high, but only when A2/B1 are low.

The code I currently have is:

module non_ov_gen (
input clk, por, en, sel,
output a1out, a2out, b1out, b2out
);

wire a1 = a1out, a2 = a2out, b1 = b1out, b2 = b2out;

case (por && en) // if power-on-reset goes high, initiallize the device

    always @(posedge clk)
    begin
        if (sel)        // if differential drive is selected
            assign a1out = 0;       // turn off a1
            assign b2out = 0;
            assign b1out = !b1;
            assign a2out = !a1;     // turn on a2 if a1 is low
        else
            assign a1out = 0;       // turn off a1
            assign a2out = !a1;     // turn on a2 if a1 is off
            assign b1out = 0;       // turn off b1
            assign b2out = !b1;     // turn on b2 if b1 is off
        end
    end

    always @(negedge clk)
    begin
        if (sel)
            assign a2out = 0;
            assign b1out = 0;
            assign a1out = !a2;
            assign b2out = !b1;
        else
            assign a2out = 0;       // turn off a1
            assign a1out = !a2;     // turn on a2 if a1 is off
            assign b2out = 0;       // turn off b1
            assign b1out = !b2;

default // set initial states
    assign a2out = 0;
    assign a1out = !a2;
    assign b2out = 0;
    assign b1out = !b2;
    end
endcase

This is the first time for me using Verilog and I am confused whether this is appropriate or not and whether I am taking the right approach.

Can you please help me out with getting this to work?


texts:
I would like to build a circuit that adds a "vibrato" audio effect to a simple sine wave input.

Sample audio clip from Wikipedia:
Vibrato, Sound Frequency 500Hz, Frequency Modulation 50Hz - Vibrato Frequency 6 Hz
https://upload.wikimedia.org/wikipedia/commons/e/e7/Frequenzmodulation.ogg

This sample effect is exactly what I want to create. I already have a circuit that generates a sine wave, and I can easily generate a 50 Hz frequency modulator. I'm just unsure of how to create a circuit that would provide that 6Hz vibrato effect and combine everything together to get the desired sound.

Does anyone have any ideas of things I can try to replicate the sample audio with the effect?

Thanks


texts: Float calculations hangs on Kinetis K20 (arm-m4-no-fpu) when PWM interrupt is on

texts:
I will use this ARM to control Induction Motor with three-phase inverter.
When the program encounters any float operations, like simple plus operation, the system hangs but the pause of debug works well.
I increased the stack, I turned types as double, I increased the period that the interrupt ocorre (before 50us, changed to 1ms) however only work when this interrupt is turned off.

Kinetis K20 Without FPU
CodeWarrior 10.4
Timer Overflow period 50uS
Stack greater than 2048b
Combined-complementary PWM mode


texts: DC Motor + Pull Solenoid + 2 Microswitches --- Rigging and Timing Question?

texts:
so my senior design group at UCF needs some help with the electrical engineering aspect of our project as we are all ME majors and lack confidence in this area.

Our design is driven by a DC gear motor that has been geared down to rotate at 0.9RPM.  From the motor is a rotary shaft that is 9" long and 1" in diameter and will rotate the system from 0 degrees to 90 degrees and from 90 degrees back to 0 degrees in the XZ plane.  At each of the two positions (0 and 90 deg.) the system needs to remain locked in that position. A plate attached to the rotary shaft with a diameter of 3.5" has 2 holes for the pull solenoid to enter and hold the system.  With the integration of microswitches that are timed to power/unpower the solenoid is able to lock/unlock at the required times/positions.  The shaft will have indents that push the microswitch buttons in and out at the appropriate times.  While the system is moving from one position to the other we need the solenoid to be powered on and the motor to be powered on.  Once the system reaches one of its locking positions (0 or 90 deg) the motor needs to power off and the pull solenoid needs to power off and drive itself into the locking hole thats on the plate attached to the shaft (a spring on the solenoid shaft will allow for this motion once the solenoid is powered off).

We are planning to us a DPDT switch to power the system and allow the DC motor to be reversible.

Our groups main struggle is how to wire the system as a whole and also how to time the system so that the motor does not power up simultaneously with the solenoid because that situation would jam the motor up and also put to much force on the pull solenoid to be able to pull out of the locking hole.  Another concern would be the motor powering off simultaneously as the solenoid shaft enters the locking hole.

In summary, locked at 0 degrees our system will unlock (pull solenoid powered on) and motor power on and move out to the next position of 90 degrees.  Once he motor drives the system to 90 degrees the solenoid will turn off and the spring will drive the solenoid shaft out and into the locking hole on the rotary shafts plate.  At the same instance, the motor will power off.  From here, the system needs to repeat the process to move from 90 degrees to 0 degrees and lock again.  The time that the motor takes to move from each position is 25 seconds.

Hopefully this is not to confusing in words....all help is greatly appreciated and let me know if I can clarify anything to help!


texts: Capacitance and Inductance properties of coaxial transmission lines

texts: I'm interested to understand what affect the capacitance (between cable core and shielding) and the inductance have on a signal transmitting down a coaxial cable.


texts:
I'm trying to sense IR wave with a phototransistor circuit. The circuit operates well under DC operations (I mean 3V or 0V through inputs). However, if a square wave is supplied from UART input, propagation delay increases after some frequency due to bandwidth of phototransistor(I suppose). What should I consider to increase bandwidth? There is 1.5cm space between IR & phototransistor in vertical axis. LED draws about 15mA current when it conducts.

For example;

When 8kHz, %50 DC, square wave input is applied from UART pin, the DC of output decreases to 27% with about 20us propagation delay.

I've tried increasing the distance between IR & phototransistor to decrease photocurrent gain. Is it a good approach, or should I vary resistance values to decrease gain? Lowering the value of R2&R3 gave me better result; but, what other effects should I take into account?

Here are the datasheets:

bc848b: http://www.nxp.com/documents/data_sheet/BC848_SER.pdf

bc858b: http://www.nxp.com/documents/data_sheet/BC856_BC857_BC858.pdf

phototransistor: http://www.megasan.com/service/pdfhandler.ashx?fileid=3565

simulate this circuit – Schematic created using CircuitLab

edit: Problem has solved according to values of updated schematic.
For square wave input with 3Vpp, 50%DC up to 9.6kHz has been tested.
@4.8kHz -> DC: 45%, propagation delay: 10us
@9.6kHz -> DC: 40%


texts: How to prove the SOP and POS are equivalent to one another in XOR Funtion?

texts:
Write two Boolean expressions for the Exclusive-OR function, one written in SOP form and the other written in POS form. Simplify both expressions using Boolean algebra reduction and show that the two expressions are equivalent to one another. Draw the simplified circuit diagram for this function.
So, I've got
A B Output
1 1 0
1 0 1
0 1 1
0 0 0
SOP: A(B)'+(A)'B
POS: ((A)'+(B)')(A+B)
How to show that A(B)'+(A)'B = ((A)'+(B)')(A+B)


texts: What do capacitors C0 and Ce do in this RC phase-shift oscillator?

texts: what is the use of the capacitors Ce and Co in the given circuit.


texts:
I draw a new schematic, which uses a operational amplifier to turn on a n-channel mosfet when the night comes.

I used a article from internet to make the connections of the unused operational amplifier.
I tested today the schematic and it works.
The power supply is an 12V, LM317 power supply, but I am planning to use a 12V 2A SMPS for this project.
The LED_load connector is for connecting a few leds with series resistor. The total power consumption of the leds will be about 100-200mA.

This is the schematic: View post on imgur.com

Please have a look at the schematic and tell me what you think. I am interested especially if the connection between the operational amplifier and mosfet is good.

Is the schematic correct ?


texts: Why output voltage of power adaptor is increasing when more load is applied instead of dropping?

texts: I use a cheap power adaptor 5v 3Amp When I power arduino with modules it is stable 5.4V but when I add thermal printer that consume 1.5Amp peak output voltage is going 6.7V (when it is printing or sleeping). Also I have seen this when was powering some 1W relays. When I disconnect it it need some minutes to go back on 5.4V. I measure  vout with multimeter always onload. This may damage other modules. What may cause this and how to deal with it?


texts: my question is on how to calculate battery capacity

texts:
I got this from a search google, this example was given but didn't understand they got to the answer, here is the example let say you run a 250watts, 110vollts light bulb from an inverter for 5 hours.Amp-hour( 12volts) = watts-hours/12volts = 1470/12 = 122.5Ah.So i didn't get were this (1470) came from for i was expecting to see but 250 watts * 5hours which would have given me this 1250/12 = 104.16Ah.

Then this second question, How long does it take to charge a 12 volts battery with a solar panel? This is what i got from a search on google, to find the charging rate , divide the wattage of the panel by the voltage of the battery. (Amp = watts divide volts) which is 245watts/12volts which is equal 20.42Amp. So the equation now leads 140.875Amp-hours divide by 20.45A which equals about 6.9hours.I'm just lost from were they say the equation leads to 140.875 Amp-hours. Thanks.


texts: Can you identify this 14-pin DIP resistor network?

texts:
I'm trying to positively identify this resistor network. Has anyone encountered them before?

They were found on a backplane with 96-pin DIN 41612 connectors. It's not a VME bus — A/B/C1-3 are a big rail, possibly ground, and so is A/B/C32 (possibly Vcc). The bus pinout may be ad hoc. It's a relatively old device: early Nineties at the absolute latest, probably mid to late Eighties.

(Apologies for the graininess, it's an available light photo)


texts: Basic of a charged piezo : pC/G, mV/G, Signal analysis

texts:
This is the first time I use a High impedance piezo sensor and the problems went pretty quickly.

Here is the piezo I used :

Manufacturer part number :   PKGS-00GXP1-R
Rating : 0.35pC/G (+/- 15%)
Range is between 0 to 50 G.

I read that we always need to amplify the piezo signal when it's a charged piezo.

So, I'm trying to make an amplifier for this but I can't make any correlation between the G and the voltage I get from this.

Might as well say that I don't even know how to read the output from the piezo signal!

Here is the amplifier schematic:

simulate this circuit – Schematic created using CircuitLab

Here is a scope view of a small shock.

Ch1 yellow : ADC (amplified output signal)
Ch2 blue : BS170 Gate (piezo output signal)

How to read a piezo signal like the signal on the scope? Should I read only the first Edge from the signal like in the image below?
What is pC/G ?
How to make a convertion pC/G to V ?
Is my Amplifier even correct? Any other low-cost suggestion ?

image taken from the manufacturer of the piezo (murata)

Lectures about High Impedance sensor:

https://www.analog.com/en/technical-articles/signal-conditioning-for-high-impedance-sensors.html
https://www.allaboutcircuits.com/technical-articles/understanding-and-implementing-charge-amplifiers-for-piezoelectric-sensor-s/

Precision :

When I said low-cost, I mean, the lower the better. If I can make it under 2$ (piezo not included) it would be awesome.
The sensor is near the MCU. I want to log any shock made to the device. So physically, the piezo is at 5mm of the amp-op input and the amp-op output is direcly linked to the ADC input of the MCU (Will probably add some protection). Everything is on the same PCB.


texts:
I was planning on flashing my mini os onto my NXP - LPC1313FBD48 (here is a link to where I bought it) but I wasn't really sure how. So I asked but I was told that I would need a serial to usb connector. I wasn't sure if they meant something like This or something like this. So my questions are

Which connector do I use and how do I pick the connector?
How do I use the connector with my MCU (ex. Plug one end into my usb connector and put Jumper wires onto certain ports of my MCU inorder to send the data)?


texts: Using a battery as a voltage source in a DC DC converter to supply a second battery?

texts:
I was wondering if I could use a battery as Vin to a DC DC converter to charge another battery.

Example:
Using a Li Ion battery pack and having it go through the DC to DC converter to charge a LiPo battery pack.

More specifics:
My idea was to have a Li ion pack be able to charge a Lipo pack by going through the converter or press a switch to have the Lipo pack charge the Li Ion pack. I'm wanting to be able to charge either batteries while using it. Like flying a drone or using an eboard etc.

While in flight for example be able to use a Lipo pack as the source supplied to esc while being charged by the Li ion pack, or use the Li ion pack as the source supplied to the esc while being charged by the Lipo.

Batteries:
Li ion 4s2p (3.7/4.2v 20/40 amps per cell)
Li po 4s (1500 mAh supposedly 120c)


texts: Charging a battery without overloading the rest of the circuit

texts:
I have a charger circuit (BMS) V1 which charges my LiFePo4 V2 battery, the battery also attaches to a circuit which can take a little more than 3.3v, however if for what ever reason the battery fails I don't want all the power from the changer shunted to the circuit.

Should/Can I insert a zener diode D1 and clamp the voltage to 3.3v to avoid the charger destroying the circuit? Or should I add some logic which disconnects the circuit I want to protect when charging?

How would you do it otherwise?

simulate this circuit – Schematic created using CircuitLab


texts: Unknown characters in the serial monitor

texts:
I am trying to sniff the UART communication line of a commercial BLDC controller. The UART port connects to the Bluetooth module and the Bluetooth module connects to an Android App. I am able to get the baud rate right with some hacking, but it seems that after the successful connection of the Bluetooth module to the app, the app sends some characters to the Bluetooth module, and expects some characters in return because the Bluetooth module is connected to my PC via FTDI converter and not the controller.

It does not get the desired reply hence, the Android application shows "Open Flash Error." Now I do not exactly know what the error is but, in the Arduino serial monitor I see four characters (when the Bluetooth module is connected to app) represented by blocks as the serial monitor does not have the right font I guess.

What should I do in order to decipher what are those characters or how should I get the ASCII values of the characters received?


texts:
I am trying to analyze a PMOS circuit, but cannot seem to set it up correctly. Here is the circuit:

$$K_P=\frac{250 \mu A}{V^2}$$ where $$V_T = -1V$$

I have simulated the circuit with Pspice, but cannot get the same values by hand.
I am mainly trying to solve for Vs:

$$V_S=5-1200\times I_\text{ds}$$ where: $$I_\text{ds}=\frac{V_S-5}{1200}$$

$$V_\text{GS}=V_G-V_S=0.174 - V_S$$

$$\frac{V_S-5}{1200}=250\times 10^6\times (0.174-V_S-1)^2$$

However, the above equation does not lead to the correct value for Vs (which is 4.1269V).

If someone can just point out how I am setting up the problem wrong, that would be very helpful.


texts:
This question comes from text from the AOE 3rd ed. It's about unintentional capacitive coupling right after differentiators in chapter 1. I've included the text. Please read the first excerpt. That is where my question is from. The second photo includes a graph Figure 1.45 that I reference.

I dont understand: “resistor termination on your signal line.” and “reduce the source resistance of the signal line.” I understand how capacitors, charge, voltage, and current, differentiators supplied DC, sin, and squarewaves so Figure 1.45 makes sense. I've written and attached a 7 page document about capacitors I'm currently working on. Would you please help me by rephrasing the parts of the text I don't understand, providing an example, and or explain like I'm five (elif). Thanks.

https://docs.google.com/document/d/12gug-CDFmSIw96a-6j31GgybIcRjOr09F0q_aluErJ8/edit?usp=sharing


texts: Can you use a single Bipolar Transistor as an AND gate?

texts:
I have recently began electronics as a hobby, and I am curious about the use of Bipolar Transistors in AND gates.

Simply put, if I was to use the collector and base as inputs, and run small (~1 volt) currents through them, could the single transistor function as an AND gate, even if the base and collector voltage were approximately equal?


texts: Easiest/Cheapest alternative of an oscilloscope to observe PWM signal, if any

texts: Is there a tool/method that I can make use of instead of an oscilloscope to be able to display or at least gather information such that its frequency and on-off times of a PWM signal, out of a microcontroller let's say. A cheaper alternative, of course.


texts: How can I describe and explain SMPS on a very basic level without diving down in heavy maths / EE lingo?

texts:
I'm writing a book about repairing electronics. The audience level for the book is "very little knowledge about electronics" and it's mostly about the mindset and mindtools for finding problem sources and how to correct them. It's not buried in maths or anything like that, as it's not a electronics book per se.

That being said, I'm currently a bit stuck on the current chapter about power supplies. I've been describing the very basics of linear supplies (fuse, graetz-bridge, filter cap, regulator, output cap), where error sources most commonly appears, et cetera. I think I've managed to capture the spirit of the linear supplies, but I have a very hard time describe SMPS on a very basic level and this is what I'm asking for input of.

I could slam the reader with block diagrams, schematics and describe the basics of this very complex topic, but I'm afraid I will miss the audience the way I've been trying to pinpoint it all. There's an awful lot of maths and electrical engineering behind SMPS but I want to avoid all that and just show-and-tell the very spirit. Showing a schematic like the one below (not mine) will only boggle the reader, I think, but somehow I have to highlight at least one schematic and point at which components fail most, etc.

How can I express myself about this topic, on a basic level?


texts: 5v vs 12v dc pcb mounted relay selection

texts:
I'm newbie and just got stuck at design decision whether to go for 5 volt dc relay or 12 volt dc relay in power circuit.Both relays equally mentions power dissipation as 170mW according to their datasheets.

Originally I selected the 5v one since mcu and other wireless controller are 3v3 ones.But then one of my friend suggested that current consumption in 5 volt would be higher.

Since circuit will be running 24X7,I intend to keep heat dissipation as low as possible.I have also attached possible design combo.Should I go with 1 or stick with 2.


texts: Is there a freeware VHDL editor out there that supports intellisense and lint? There are plenty for other programming languages but seems like none for HDL.


texts: What component values could be deduced from this graph? It is for a restricted DC motor, A vs T

texts: What components cause this graph to look like this, what values could they be given? the DC motor has a P magnet and a split ring commutator and is powered by 9V supply. Why did current take time to reach final value? The motor was restricted from moving ( like a high load) at power up.


texts:
What exactly is the difference between Tesla Coil and Tesla Tower? What does the tower do? How does it affect the propagation of electric energy?

A Tesla coil can generate voltages of high potential. I have seen videos of how this thing works but never saw a Tesla coil in combination with the tower.

What is the original purpose of Tesla tower?

  "In the course of certain investigations (...) I observed that
  sensitive receiving instruments (...) at times failed to respond when
  they should have done so, and (...) I discovered it to be due to the character of
  the electrical waves which were produced in the earth by the lightning
  discharges and which had nodal regions following at definite
  distances the shifting source of the disturbances. From data obtained
  in a large number of observations of the maxima and minima of
  these waves I found their length to vary approximately from
  twenty-five to seventy kilometers, and these results and certain
  theoretical deductions led me to the conclusion that waves of this
  kind may be propagated in all directions over the globe (...).
  Recognizing in the existence of these waves an unmistakable evidence
  that the disturbances created had been conducted from their origin to
  the most remote portions of the globe and had been thence reflected, I
  conceived the idea of producing such waves in the earth by artificial
  means with the object of utilizing them for many useful purposes for
  which they are or might be found applicable." -- NIKOLA TESLA U.S.
  PATENT 787,412

Here's how Nikola Tesla began to think about creating lightning discharges artificially. Through observation of the results of measurements and theoretical deductions, he came to conclusion that electric waves created by lightning travel all over the globe.

What do you think about the accuracy and validity of his conslusions? What kind of instruments did he had? Do electric waves really travel throught he Earth as he described?


texts:
I know we can connect two or more transistors in parallel to increasing the maximum switching current, but what about increasing the maximum voltage?

Can we connect them in series?

For example, connecting two 2N3055 to give 100V 5A rather than 50V 5A?


texts: On-line arithmetic vs digit recurrence, are they different?

texts:
I'm looking at some reference to "On-line arithmetic",in chapter two of this PhD thesis there's a description of such methods. There's a recurrence derived at some point in such thesis that reminds me of the "digit recurrence methods", are they somehow similar?

(Specifically I saw an equation that reminded me of the division by digit recurrence).


texts: Most significant Bit first Vs Least significant bit first

texts:
I am studying protocols and came across a concept of MS bit first(in I2C) and LS bit first(in UART). I couldnot understand the advantage/limitations one has over the other?
 on what basis is it decided that we shall have msb first or lsb first for the device we are designing?


texts: Why is the voltage regulator's output current not what I'm expecting?

texts:
I've recently bought a couple of Sanyo LA5003 voltage regulators (datasheet). From the datasheet, I understood that the highest possible current on the output can be 60mA. However, when I connect it to several (2 or 4) series-connected 1.5V AA batteries, I get, respectively, around 120mA and around 140mA.

Here's how I'm testing the current:

(pin 1 is on the right)

What am I doing wrong and/or misunderstanding?

PS. I've tried measuring on more than one of them, obviously.


texts:
I know there have been a lot of questions about lookup tables and their design, but even after reading them and scouring the web, I still don't quite understand how the LUTs are filled with corresponding boolean function's outputs from SRAM.

What is an LUT in FPGA?

The top answer to that question mentions something about using LUT masks. Are LUT masks the key to filling LUTs based on the boolean function from SRAM? Could someone elaborate on LUT masks please?

Also, say we have a 4 input LUT. That means we have 16 outputs, and 65535 possible combinations of outputs (0000000000000000 to 11111111111111). Does that mean all 65535 combinations will be stored in SRAM? And if we had 6 input the number would jump by a lot, and it doesn't seem like all that could be stored in RAM?

I think I may be misunderstanding something fundamental about FPGAs/LUTs horrifically. Any insight would be helpful!


texts: RJ-45 with magnetics transformer (Ethernet port) connections

texts:
I am working on circuit having RJ45 connector with built-in magnetics transformer.
The schematic diagram of mentioned circuit shows following connections with Rj45 magnetics connector.
At first I did not connect the RC circuit (consisting of R17-R18-C10 ,R19-R20-C8 ) to the Rj45 magnetics connector....circuit worked but gave some random behavior.
After that i connected the RC circuit and then circuit worked perfectly...
I want to know- what is the need of that RC circuit in this???...how it helps in improving the performance..??

Any kind of help is appreciated !!!
Thank you


texts:
I was programming my PIC microcontroller to the 16x2 LCD (Hitachi HD44780) to test out some codes, but when I tested my circuit again, my LCD started going haywire displaying some fuzzy or corrupted characters.

It eventually went to displaying white blocks on both the top and bottom rows on the right side of the LCD.

I was programming my circuit at 5 V all the time, but I don't know why the LCD doesn't work anymore. I tried adjusting the contrast voltage on the potentiometer, but nothing else works.

Anyway to fix this issue?


texts: Using a Micrel MIC2940A-3.3 LDO regulator without additional circuitry?

texts:
I'm designing a basic table-top toy based around a dsPIC33 MCU. It'll be battery powered and I'm using a Micrel MIC2940A-3.3 regulator to produce the 3.3v for the chip. (I've fitted a PP3 clip, with the intention that my device can run from a 9v battery or 3x or 4x AA batteries in a cage with a PP3-clip.)

I'm currently using it in the basic configuration with a couple of capacitors to make the MCU happy. (The typical applications from the datasheet just give it used like this.)

That works, but I've read elsewhere that the 3-terminal regulator can be used as a voltage reference in a feedback loop to a power transistor, so that the power current comes from the supply rather than the regulator.

Is it common practise to use these regulators bare in a simple application?

And is the more complex configuration only necessary when a large amount of power is drawn? (And would using it as a reference be more efficient/stable than the regulator by itself?)

Edit - More info: With the MCU running in its 40 MIPS mode and LEDs and other outputs all on this 3.3v output, it comes to 85mA max draw.


texts: Can I make a 20-bit ADC if I combine two 10-bit ADC's?

texts: I know that the opposite is possible  i.e. using 2 DAC's to get a higher quality output, but is it possible with ADC's?


texts: How to implement mutually coupled inductor in SimuLink

texts: I want to make a mutually coupled boost converter but I could not find any mutually coupled inductor block in MATLAB SimuLink. Please help, thanks in advance


texts: LNA using Common Emitter with feedback collector

texts:
I am trying to design an LNA with input impedance of 50 Ohms, I am considering the topology illustrated below. I have found an online calculator that computes this however when I try to work out the answer by hand I do not get the same answer for the impedance.

I am very confused because when looking at the small signal according to

The answers do not match up: Note I am using a NPN 2n3904 transistor, also I am not sure If I am reading the datasheet correctly. My overall goal is to have input impedance of 50 and a decent gain of 20dB.


texts: How to calculate telescopic antenna impedance?

texts: I'm designing a 27 MHz transmitter for controling RC toy using TX-2B and RX-2B ICs. Thre is my output stage schematic (see attachment). Output impedance 50 Ohm. I know that antenna length on 27 Mhz should be l (wave length)/4 = 2,77 m (quarter wave antenna) and impedance of that antenna is approximately 36 Ohm. But its too long antenna. I want to use small chineese telescopic antenna (97 cm) . Antenna lenth can be reduced connecting serires inductor. According to this https://m0ukd.com/calculators/loaded-quarter-wave-antenna-inductance-calculator/ in my case loading inductance should be 5.12 uH. Now our antenna reactance is zero: $$Im(Z_{a})=0$$How about antenna resistance $$R = R_{Radiation} + R_{Loss}$$ How i can calculate it?


texts: Field Oriented Control Feed Forward Term

texts:
I implemented a Field Oriented Control (FOC) controller for a synchronous motor, which works already pretty good. Now the I-part of the PI controllers is necessary to achieve a good reference tracking, but slows down the dynamics drastically. I heard that a feed-forward term and prefiltering can be used to get rid of this problems, but I actually don't know how this could be achieved. The motor will mostly be driven at very slow speeds, but also here, a huge current seems to be difficult to track.

I heard that the plant of the BLDC motor for each phase can be simplified as follows:

$$\frac{1}{Ls + R}$$

Such that the output current is related to the Space Vector Modulation (SVM) voltages, but I don't see how to go from here.

How can prefiltering and feed-forward control be used to achieve better performance in Field Oriented Control (FOC)?

Edit: What I find is mostly the feed-forward part to compensate for the speed of the system, but this is not necessary in my application, since it is used for position control or slow speed only.

Is there a way to take feedforward terms into account to achieve better current control? Maybe I'm just bad at tuning my PI-controllers for current control, but it seems that the current is very sensitive to the P-part and so to get best current tracking mostly the I-part is used. So I'm interessted in how to achieve better and faster control of I_q and I_d.


texts: Essential parts of a USB connector, stripping to bare bones

texts:
I have a very specific question.
I want to create a very thin storage device solution.
A picture is worth a thousands words so here you can see the hardware I have:

This is the image of a USB pen drive without the outer casing.
Now, I am very happy with the circuit board, NAND chip etc. in terms of performance and thickness.
However the USB connector is 12mmx11mmx4mm much too thick. Pretty much a deal-breaker.
When I peer into the USB connector hole, I see 4 golden strips.
Can I remove the outer casing for the USB connector and simply keep the four golden strips and still connect functionally to USB ports, or does the outer casing of the connector(with two holes on top and two on the bottom) contain some crucial components for I/O?
Finally, can I find a very thin port for this USB flash device so that the whole structure will be less than 0.5-1mm thick?
Structure:
USB circuit board -- USB connector -- USB port -- cable
As you see, both the first part and the last part are thin enough,I am trying to reduce thickness on the intermediate parts.


texts: Uncertainty(jitter) in setup and hold calculation

texts:
In setup calculation, the launch flop is triggered by 1st edge and capture flop is triggered by next edge. And in calculation we take jitter into account only for the clock path of capture flop. There is possibility that the 1st clock edge coming to launch flop having positive jitter and clock edge coming to capture flop having negative jitter(worst case possible) So in this we should take twice the value of jitter in calculation right?

And for hold calculation, since same edge is being used, there won't any effect of jitter right?
Please correct me if I am wrong.


texts:
I'm going to build a switching device for my guitar effect units. I want to integrate some simple form of memory, which should be able to store some on/off states, even when power is off. However, I still don't know much about electrical engineering, and I really don't know where to look for the right information. Thanks to google I came up with 3 possible solutions myself already:
-Use latching relays. However, this is quite expensive, and I don't know how well the relay keeps its state when moved.

-Use EEPROM or something like that. However, since I'm still a beginner, I really don't understand how these things work and how I can control these things

-Use CPLD. Seems like the best solution. Only problem is that I need to buy some expensive cable to connect the chip to my computer.

Can you please give me some advice on how to do this? I really don't know what to look for!


texts: Why in the world would the tab on a TO-220 package have a connection to anything (but GND, if applicable)?

texts:
I know this is in some way a different version of the prior question In i.e. a TO-220 package, why is mounting the (pin connected) tab to case safe?

But I am not looking for ideas what to do to mount a TO-220 (in my case an SCR that has the anode connected to the tab. That's the input with the highest potential from ground!)

What I am asking is why in the world would they have designed it that way? These things even have a hole to screw it to a heat sink and you'd want the best contact to the heat sink, not layers of plastic in between.

Now I am certainly not the first one discovering that this is rather annoying. So why did the engineers so unanimously design things that way? Why not just leave it disconnected?


texts:
I am trying to find a suitable diode to place on the wire that connects c and e in the circuit, with the cathode on the right hand side. I need to justify why I chose the specific diode as well.

However I have no idea on what to chose in terms of forward current and voltage rating as when I start putting other diodes in the circuit later (which is the next step), the currents and voltages through that wire change.

I suppose my question is, am I suppose to find out what the highest current is in that wire out of all possible future diode configurations and then use that?

And would I be right in using a power (rectifier) diode rather than Zener etc?

simulate this circuit – Schematic created using CircuitLab


texts: Assign I²C address to multiple devices on the same bus

texts:
I've got a couple of ADCs on the same I²C bus, which all default to the same address. My first instinct tells me to use an I²C multiplexer like the TCA9544A but that would require sending a byte to the MUX before getting the data from the ADC and I'd like to avoid that (since I need to continuously read data pretty much as quickly as I can).

The ADCs do support custom address assignment through I²C so I just need to make sure, that I'll send the configuration byte to one single ADC. I could include a FET into the SDL line to every ADC so that I'd have only one ADC connected during address assignment but there's probably a much more elegant solution since there must be a bunch of people out there having the same issue. My google search terms are just not good enough to find the answer :(


texts: Which symbol to use for polarized capacitor?

texts:
Ok guys, this has been driving me crazy and I would love an absolute universal answer (even though I know there are disputes)...

Which symbol should I use for a polarized capacitor? At school they taught us to use the "two straight lines with a + indicator", however, online I mostly come across the "one straight and one curved line", sometimes with a + indicator. And then there is the unholiest of all that is unholy, the "white box for positive and black box for negative" approach.

I googled PSU schematics to try and get a good picture of which once were most used, but out of the top three schematics, they used all of the above mentioned conventions.

So, to sum up: Which symbol should I use from now on?


texts: Rectifying a spark coil that produces 10 kHz

texts:
I am working on a project where I want 10 to 30 kV DC (to energize two capacitors in series rated at 28 kV per capacitor). I bought a couple of 25 kV HV rectifiers (one to generate a positive voltage and one to generate a negative voltage) and hooked them up to spark coils.

The first hookup was a couple of motorcycle spark coils and, although I was getting 20 kV P-P into the rectifiers, the rectified voltage was only about 1 kV.

I tried an automotive coil (with a built-in solid-state triggering device and with an external voltage control potentiometer attached) and even though I was getting 20 kV P-P, I still was only getting 1 kV DC through the rectifiers.

After having played with this for such a long time, my conclusion is that my HV rectifiers don't have the frequency response for the 10 kHz signal the automotive spark coil produces. The circuit is so simple this is about the only conclusion I can come to.

The question is: How do I get around this? Are there HV rectifiers available (at reasonable cost) rated at 30 kV and can operate at 10 kHz? Any help in this would be appreciated, thank you.


texts: I have been reading about FPGAs recently and found that they have a lot of applications in many fields. I also read an article that they are used for testing purposes alone. Are FPGAs only for that? Also please tell me the disadvantages of the FPGAs compared to the ASICs. Are FPGAs slowly being used more in many fields like military, space, image processing etc? Are they very useful compared to the ASICs?


texts:
I'm trying to use an ATtiny88 to detect data on a USB line. I have an USB data connection going to a hub and a secondary system and I want to use the ATtiny to detect if any peripheral hardware has been plugged into the USB port.

The idea is to simply the the USB D+ line and connect it to the ATtiny. When there is data on the line, the signal will pulse and this can be detected in the ATtiny.

Are there any electrical considerations I should take when doing so, or can I just connect the data line directly to the ATtiny?


texts: Low-complexity generation of single pulse using RC circuit from a fixed DC supply without the use of a controller

texts:
I was looking for a similar solution to this question:

I want to generate a pulse (high) of 2 seconds when that DC supply is turned ON.
Is there a solution where we can implement this without using any microcontroller, timer IC or any delay IC? The circuit can contain resistors, capacitors, transistors or diodes etc.

The last answer was my approach, but this does not discharge the circuit when the power supply is taken away. So it only works once.

Is there an easy way to have the capacitor discharged (in less than 1 second) when the 'POWER' switch is opened again?
And with easy I mean with less components than this answer, which uses 8 resistors, a single capacitor and 4 transistors.
EDIT
The goal is to power a DC motor for maximum 2 - 10 seconds (adjustable with potmeter) every time the power is turned on.
If the power gets turned off the motor will also stop running.
The actual load will be a 5W DC motor, but this will be done by using another transistor or mosfet.
Timing diagram:
                __________       __    ______
Power      ____|          |_____|  |__|      |_______
                ____             __    ____
Motor      ____|    |___________|  |__|    |_________
                <--> = 2 s

EDIT
I edited the restrictions in the title because timer IC is being considered.


texts: Transimpedance-amplifier with 2nd order filter (termination and derivation of transfer function)

texts:
I have this schematic from the datasheet of the amp OPA380 (page 12, figure 6c) with a low noise 2nd order filter. I would like to derive the transfer function analytically of this op-amp to get the frequency response.

My first question:

Is this the proper way to drive a coax cable with \$Z_L=50\Omega \$ termination (\$Z_S\$  is my output impedance), or is it necessary to decrease \$R_{Filter}\leq50\Omega\$, although it is in the feedback loop?

The second question is about the derivation of the transfer function with the following equations:
$$s = i \omega $$
$$ V_1 = \frac{I_D}{s\cdot C_D}$$
$$I_D = I_{CD} + I_{Cf} + I_{Rf}$$
$$ V_1 = V_{Cf} + V_{R,Filter} + V_{o} $$

What is my current through \$R_{Filter}\$? Is \$I_{R,Filter} = I_{C,F}\$?

\$I_{CD}\dots \$ current through \$C_D\$ (Capacitance of photodiode)
\$I_{Cf}\dots \$ current through \$C_f\$ (feedback capacitance)
\$I_{Rf}\dots \$ current through \$R_f\$ (feedback resistor)
\$V_{Cf}\dots \$ voltage over \$C_f\$ (feedback capacitance)
\$V_{R,Filter}\dots \$ voltage over \$R_{Filter}\$ (filter resistor)
\$V_{o}\dots \$ output voltage over \$C_{Filter}\$ (filter capacitance)

Edit1: feedback of op-amp drafted wrong

Edit2: Changed Vcc of op-amp
Thank you in advance!

UPDATE (2016.06.21):

Thank you CX05 for you help.

For better understanding I post this adapted schematic (forgot to adapt the right op-amp names):

I have derivated the schematic like you with some exceptions:

I assume your \$I_N\$ is the negative input current of the op-amp, I neglect that.
I wrote the equation with opposite potentials, but this should not matter much.

$$ I_D = I_{CD} + I_{RF}+I_{CF}$$

I can calculate \$V_n\$ from the equation as you mentioned [eq.2,pg.2]:
$$ V_o= -A_v\cdot V_n$$

\$ A_v\dots\$ open loop gain

Is your \$R_L\$ the resistance of the coax load? If so it should disappear now with the unity gain amp.

If I understood it right, this should be the current divider (with assumption \$V_n=0\$) which you have spoken of?
If so, I get:
$$ V_{o2} = V_o\cdot \frac{Z_{fi}\|R_{f}}{R_{fi}+Z_{fi}\|R_{f}} $$
\$Z_{fi} \dots \$ Impedance of \$C_{fi}\$

If I consider the open loop gain \$A_v\$ to calculate \$V_n\$ it seems more complex, is this the correct way to go?

$$ V_{o2}= V_n\cdot \frac{Z_{fi}}{(Z_f+R_{fi})\|R_f+Z_{fi}}$$

\$Z_{f} \dots \$ Impedance of \$C_{f}\$


texts:
Consider the following circuit:

[edited schematic]

DC_gen1 and DC_gen2 are two +28V dc ideal generators. Fuse is real component and it has a finite and small resistance (0.1 Ohm for instance).

I need to design a Sense circuit that detects that the fuse is broken. I have already considered a few possibilities:

A differential amplifier could sense a voltage across the fuse. Anyway, since the two generators have the same voltage, no current is flowing through the fuse and therefore there is no voltage drop on it.
A galvanically isolated power supply could inject a current in A point to B point to create a voltage drop across the fuse. Anyway, the injected current would flow through DC_gen1, ground and DC_gen2, and therefore no voltage drop would be createdo on the fuse.

Can you please suggest how to sense the broken fuse?

EDIT:
Following comments, I edited the circuit to add details:

The two generators are connected through a long power cable; the purpose of the fuse is to protect DC_gen2 from short circuits on the cable itself. DC_gen1 already implements its own protection so no fuse is required.
Due to physical constraints, the sense circuit must connect next to the fuse, at point A and B.


texts: Making a plant stable with a compensator based on given requirements

texts:
I have a transfer function of the plant modeled as the following:

I'm trying to design a compensator that satisfies some requirements.

a.  The maximum control bandwidth (0 dB crossover frequency) is 100 rad/s.

b.  The minimum phase margin at crossover is 30 deg.

c.  The loop transmission magnitude at 2000 rad/s must be less than -6 dB.

d.  The step response overshoot of the closed loop system must be less than 20%.

e.  The 2% settling time must be less than 0.75 s.

f.  The steady-state error to the unit step reference is less than 1%.

Open loop poles reside in -0.05 +/- i and - 5 +/- 2000i, so there is a lot of potential for instability for some variable gain K. This means that I would need a two zeros for the poles to sink in.

Designing a compensator that makes this system stable is easy, I can throw in two zeros in the LHP such as s^2 + 2 s + 8. What I'm not too sure on is the method of satisfying the requirements. Normally, I'd use a PID controller to tune the settling time, step response etc. But in this system, a PID controller cannot be applied, because the addition of pole would make this system unstable. (Edit: Well I guess I could use PID, as long as I define the bounds for gain K, but this seems like a crummy solution as the range of K would be really small)

What are some alternative methods of achieving the requirements while making the system stable?


texts:
This question is based on my previous question - Measuring voltage drop across a diode in a switched circuit

I have started a bounty on that question. At the same time, I am trying to understand why is that happening as I still didn't get a proper answer.

So, I tried to understand by trying different simulations.

I tried simulating just a voltage source, with adding parallel diodes and a load.

My questions :

When I have only one diode connected to the load, the voltage at the load is around 4.474V
When I have 2 diodes in parallel and voltage at the load is around 4.50V
When I place 3 diodes in parallel as shown in the image above, the voltage at the load is around 4.53V

What is happening here, when I add diodes in parallel?

Yes, I agree and have been told that adding diodes in parallel is not a good thing to do. But I am just trying to understand the basics of what might happen when diodes are in parallel?

If could also help me with my previous question, it would be beneficial for me.


texts: Using 2N2222 as level shifter for TIP127: simulation works, circuit does not

texts:
I'm building an H-bridge with complementary Darlingtons, TIP122 and TIP127, as they are cheap and the nearby shop has them (i know about the high power dissipation, it doesn't matter), and i found trouble with the high side driver.

I tried to use a 2N2222 as the driving circuit to turn on and off the TIP127, and as far as EWB tells me, my idea should work, at least in theory...

I am building this sample circuit to test the current absorbed by the 2N2222 to see if it's within range of the microcontroller's GPIO i have available (the STM32F205).

In the real circuit, if i use the depicted resistor values, i can't seem to turn off the darlington, and i suspect the issue to be the 2N2222 leakage current in its off state, but i'm not sure.

I swapped the R4 pull-up resistor and the R2 resistor with 5k trimmers, and i managed to find a spot where the TIP127 does actually turn off; but then when switching again S1, it doesn't turn on anymore :|

What did i forget to take into account?

EDIT, clarification:
The circuit i built was behaving differently from what i predicted, so i thought there was some design mistake due to inexperience. My question was if an erroneous calculation of the resistor values (or some other error) in a circuit as the one shown, could lead to such an unforseen behaviour.
In the end, i was working with the wrong transistor (or the wrong datasheet, should you switch point of view), hence the question itself is rather pointless... Took me someone from the other side of the globe to make me take a closer look, so, my bad.


texts: noticed this inside a old-ish Kindle. It's a cup with a single pin. Wondering what type of connector this is called and maybe who supplies it.


texts: Convert ALTIUM file to Autodesk EAGLE: what is the most recent procedure?

texts:
I would like to convert following Altium file to EAGLE:
https://www.st.com/en/microcontrollers-microprocessors/stm32wlex.html#cad-resources
To do so I have opened the file in Altium and exported it to P-CAD ASCII according to some forum posts on the Autodesk forum:
https://forums.autodesk.com/t5/eagle-forum/importing-files-from-altium-designer-to-eagle/td-p/6827258
I could import it in Autodesk EAGLE but the design is broken at many pads:

I've also observed a couple of errors when importing the Altium-generated file like 'Couldn't place smd4 on padXX'.
My questions are:
What are the most recent or best ways to import Altium files in EAGLE?


texts: Private star network topology on Sub-1GHz

texts:
I have a project which there is a need to be implemented many sensor nodes in a star network topology. One collector-gateway and multiple transmitters.

The farthest sensor node from the "collector-gateway" would be about 2km.

All sensor nodes would work with battery and would take measurement from their environment such as soil moisture, air temperature, air humidity, sound level and some other "internal data" about its status like internal battery level etc...

The number of transmitters may be more than 20, or in some cases it may exceed the number of 100. It depends on the needs. So I need something that I can customize easily.

First, I was thinking about using TI's CC1310 but I have second thoughts to go with LoRa.

What physical interface or technology would be fit better in my case?

Either way I intend to use my own GSM based gateway and my own server with my own protocol based on HTTP connection.


texts: What is a suitable material to cover photo voltaic panels?

texts:
I'm building a small, portable, modular solar panel array to charge 5V power banks, phones, etc.

I got most of the electronics down, the Step-Up converter, by-pass diodes, blocking diodes, as well as JST connectors are somewhat in place, but now I'm struggling a bit in building an enclosure for them.

The idea is, the cover or case should be made from soft material, I was thinking Dacron backing, and using either Nylon or Polyurethane fabric as cover.
But the tricky bit seems to be the cover for the active surface, that gets exposed to light. The problem is, using a material that doesn't impede the functionality of the panel too much. It doesn't have to be soft, as the panels aren't bendy themselves. I was thinking perspex (Plexi-Glass), but I'm not sure if that will filter out the wavelengths important to the panel.

There are these waterproof bags for tablets and smartphones available, they have a translucent front, which is soft and glued/welded to the rest of the plastic container. Unfortunately, I wasn't able to find out what sort of material that is (otherwise I'd have ordered a sample of it from AliExpress or something).

So, what sort of plastic should I use to cover the panels with?

I don't wan't to use glass. It's supposed to be carried either in a pocket or a backpack, so something that can shatter like glass would be too dangerous, obviously.


texts: Has anyone had any luck converting Hspice or IBIS model files to formats LtSpice can use? Any help much appreciated, thank you!


texts: Cannot Initialize 8GB SDHC CMD8 responds with (0xFF)

texts:
I am trying to interface a 8GB SDHC with STM32L0 controller through SPI.

Followed this tutorial.

As this thread suggests, I followed the the Command Sequence as follows:

CMD0 arg: 0x0, CRC: 0x95 (response: 0x01)
CMD8 arg: 0x000001AA, CRC: 0x87 (response: 0x01)

I am sending some clocks with CS Activated and Deactivated in between these commands as discussed here.

Somehow, I get the response from CMD0 as 0x01 but CMD8 always responds with 0xFF.

Following is the code I am using to init my SD card:

void SD_INIT(void){
    CS_HIGH;
    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }
    CS_LOW;
    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }

    uint8_t txBuff[] = {0x40,0x00, 0x00, 0x00, 0x00, 0x95 };
    HAL_SPI_TransmitReceive(&hspi2,txBuff,readBuff,6,100);

    //count = 255;   //Try 255 times..
    for(count = 255;count>0;count--){
            uint8_t dummy[] = {0xFF};
            HAL_SPI_TransmitReceive(&hspi2,dummy,readBuff,1,100);
            if(readBuff[0] == 0x01){
                    status = 1;
                    break;
        }

    }

    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }
    CS_HIGH;
    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }

/*-------------------SDHC TRY----------------*/

    if(status==1){

    //status=0;
    CS_LOW;
    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }
        //HIGH CAPACITY 0x000001AA
    uint8_t tx1Buff[] = {0x48,0x00, 0x00, 0x01, 0xAA, 0x87 };
    HAL_SPI_TransmitReceive(&hspi2,tx1Buff,readTempBuff,6,100);

    //count = 255;   //Try 255 times.. //10ms = 160000
    for(count = 100;count>0;count--){
            uint8_t dummy[] = {0xFF};
            HAL_SPI_TransmitReceive(&hspi2,dummy,readTempBuff,1,100);
            if(readTempBuff[0] == 0x05){  //Invalid Command
                    status = 3;
                    break;
        }
    }

    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }
    CS_HIGH;
    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }
    }

void SPI_SEND_CMD_DUMMY(void){

        uint8_t txBuff = 0xFF;
        HAL_SPI_Transmit(&hspi2,&txBuff,1,100);
}

The response I am getting in readTempBuff is:

readTempBuff[0]  :  0xFF
readTempBuff[1]  :  0xFF
readTempBuff[2]  :  0xFF
readTempBuff[3]  :  0xFF
readTempBuff[4]  :  0xFF