texts: Regulating LED brightness using headphone output

texts:
My PCs headphone jack (green) outputs a 4Vpp (2V amplitude) sinusoidal signal at 100% output level set in the sound preferences. What kind of circuit would I need to drive a red LED (2.2V forward voltage, 20mA forward current) based on the voltage level present at the headphone jack?

The LEDs luminous intensity behaves linearly in the range from 0 to 30mA. My idea would be to balance the LED current like follows:

Soundcard output:

+2V: driving the LED with 30mA

0V: driving the LED with 15mA

-2V: driving the LED with 0mA

I experimented with a circuit that puts the signal in parallel to a 9V battery that provided DC bias voltage. And I also tried to use a BC547C npn transistor in combination with the 9V battery. Unfortunately unsuccessful. The outcome was always a offset of the LED current: e.g. +2V: 28mA, 0V: 22mA, -2V: 16mA

I was not able to balance the current through the LED as described above. I guess to achieve this, a much more elaborate circuit is needed.

I would really appreciate any advice. Thank you very much!

Best regards,

Zelyev

Edit:

I would like to modulate the LED with the frequency of the audio signal.

A receiver catches the signal using a phototransistor.

I achieved the transmission using a simple Common-Emitter-Amplifier, the outcome was OK. But I want to make use of the whole LED intensity spectrum (0-30mA).


texts:
I can see that OpenOCD is RTOS aware and it supports FreeRTOS, which I'm using at the moment.

I have looked at various sources and cannot seem to figure how to use this feature.


texts:
I have 2 pcs 24VDC 3Amp ITE adaptor and i want to make split supply for 24v +/-
1 of the adaptor i remove the earth wire on the wall plug 3 pin and 1 is connected with earth.Adaptor A conected with Earth and adaptor B without Earth connection.I put diode on both adaptor + and - output.
I have try this and the adaptor accept the conection.But i test it just for 1 minute.Im wondering if this connection is safe and can be use on long period.
If i remove earth wire on both A and B adaptor,the 24VDC out absolute deadly :)So only 1 adaptor is connect with earth.Can i use this connection for split supply?The adaptor is same brand.Should i add anything for this connection?Im noob lol.
Sorry my english it's terrible.


texts: Analytic solution of a Graetz bridge rectifier with inductive filter

texts:
how could I solve the following circuit?

In particular I would find the analytic expression of current on inductor. I tried to solve the differential equation (hps: S1 and S4 on):

$$L \cdot \frac{di}{dt}+R \cdot i = sin(t)$$

which solution is (if R=1 and L=1):

$$i(t)=C \cdot e^{-t}+\frac {\sqrt(2)}{2} \cdot cos\left(t-\frac{3 \cdot \pi}{4}\right)$$
If
$$i(0)=0$$
then
$$L \cdot \frac{di}{dt}+R \cdot i = sin(t)$$ whose solution is: $$i(t)= \frac{1}{2} \cdot e^{-t}+\frac {\sqrt(2)}{2} \cdot cos\left(t-\frac{3 \cdot \pi}{4}\right)$$
This solution is right until i>0, after I solved again the differential equation with the same initial condition, but my plot is not the same of LTSpice.
Thank you for your help.


texts: Why doesn't my car hardwire USB C loom work?

texts:
I decided to tap off the negative and positive wires for a 12V cigarette lighter and wire in a USB C charger to discretely provide permanent power to a Bluetooth receiver in my car. I have a 4A inline fuse which then leads to the USB C cable. I'm confident I've done the wiring correctly, the cigarette lighter socket still works, heat shrink solder joins look good everything should be connected but both my phone and Bluetooth receiver won't charge using the cable.

I have a friend who's suggested this is because I haven't stepped down the 12V power to 5V before it gets to the USB C cable and my devices aren't recognising the out of spec 12V signal.
I just wanted to check if this sounds correct and a 12V - 5V regulator should solve the problem?
Thanks.
UPDATE:
Fitting a 5V regulator resolved the issue!


texts:
For a switching application I want to make two HDMI signals synchronized, is there a way to negotiate clock signals between an HDMI source and sink or two sources (preferably without taking devices apart and introducing my CLK)?

Also is it possible that internal clocks for processing (not HDMI clocks) may differ in the sources, so a global forcing a global CLK may not be a possibility?


texts: Translating a datasheet into a PCB design (TPS63001)

texts:
I'm in the process of leaning to design PCB's and leaning to solder tiny QFN parts. As part of this process, I'm trying to create a circuit with the TPS63001 (Datasheet) buck-boost converter, which I would like to use to power a ESP8266 (which requires 3.3v) by a lipo.

According to the datasheet, the circuit should be:

And in the same datasheet, they even provide a layout example:

This layout is for the Adjustable Output Voltage version, I will be using the fixed voltage version.

With the information in the datasheet, I created this layout in eagle:

Now there are a few things I'm wondering:

There are three dots underneath the chip in the example in the datasheet. I guessed that these would be via's, and created a ground plane on the back of the board. I guess this is for heat dispensation, did I interpret this right?
I connected VINA, EN and PS/SYNC together. In the layout example EN and VINA just move out of the picture, but according to the schema, they should be connected, did I do this right?

Are there any other dising rules / recommendations that I should take care of?


texts: Is it OK to use a lower voltage to operate a relay coil than rated coil voltage?

texts:
I want to know if I used a lower voltage than what was labeled on the relay was OK. The relay was a 24V relay.
I check that the relay turns on when the voltage when the voltage was 13.5v.
If I apply that voltage is it reliable?.
EDIT: I do not have a datasheet but here is the part number: HTCA024V


texts: I want to know if the words electric, electrical, and electronic can be used interchangeably. They all seem to mean about the same thing... Any suggestions?


texts: Why are DC signals bad for loud speakers?

texts:
I googled and found out through some forum that:

  DC has a constant amplitude which overheats and destroys the voice coil of the speaker.

Could someone clarify if this answer is complete and accurate?


texts: Use transistor to auto swap power source

texts:
Basically I'm looking to use a simple transistor circuit to diconnect one V+ (or ground) when another is connected and automatically switch back when the switching source is removed.
Like having a small lithium batt in a device with charge circuit external. When the charge supply is connected I'd like to run the device from the external supply while charging the battery and automatically swap back to battery supply when the charger is removed.
Planning to work with 5VDC.

Basically looking for pointers on how to setup such a switch?
already have the external charger worked out.

For clarity's sake:
I'd like to charge the battery while still in circuit with the load device while powering the device.
Wouldn't the batt need to be removed from load to do this safely? Could this be achieved by detecting the charger input with transistor switching and how?


texts: Blue 5mm flashing LED flashes for a while then goes static

texts:
This isn't my strong point by far so please bear with me!

I have some 5mm blue flashing LEDs 4.5v - 6v operating voltage and my power source is a 12v 1A mains adapter (for CCTV camera) over CAT5e.  I want to install an LED to an external junction box used for CCTV camera connections for added visual security.  I've got 400 Ohm resistance (resistors) and the LED flashes perfectly for several minutes then stops flashing and goes static.  Why does this happen and can you suggest a possible fix please?

FYI - I'm using same LEDs with a 6v AA battery pack and 100 ohm resistor and this setup works perfectly.

Any help and advice gratefully received.

Many thanks.


texts: How to add voltage thresholds with hysteresis to the input of a voltage regulator?

texts:
Device to be used in: solar-powered microcontroller with some peripherals attached.

Meant to operate whenever sufficient power is supplied (light is bright enough for a while). No battery, weather reasons.

Device is powered from a mp1584en buck voltage regulator, with large caps on both input (useful for solar, I think) and output (in case device needs more current for its nrf24l01 radio).

What I want to accomplish is a behavior where the buck gives no output when voltage on input side is too low (threshold to be determined later, expected ~9V of max 25V), but also to avoid it repeatedly turning on/off in low(ish) light, so turning back on shoud happen on a higher voltage (16V?).

Low-component-count solutions preferred, I'm not skilled enough not to mess up otherwise.


texts:
I have followed a guide to generate gerber files in altium designer.
This guide first goes to "File/Fabrication Outputs/Gerber Files" to generate gerbers and to open a CAMtastic file where you can see and edit them.

Until here everything is clear, but then the guide exports gerber files from CAMtastic to another folder, where gerbers are saved.

The thing is that some gerber files generated through the "Fabrication Outputs" option in the File menu have different size from the ones generated from CAMtastic throught the export command, although I didn't edit them at all in CAMtastic.

I am confused... why are they different? which ones should I use?


texts: How to wire a PPTC polyswitch + blown indicator LED to protect a bi-directional DC motor from stalling?

texts:
I have the following setup and it works well as is, except that I would like to protect the 12V DC motors (Reverse High Torque Permanent Magnet 12V DC motor) with a PPTC polyswitch + a LED to indicate a temporary overheating/blown state to the user.

I understand that by simply inserting the PPTC along the positive wire that goes to the DC motor will work.  Tough, I would like some advice on how to additionally connect a 12V LED (1W) to that circuit.


texts: Looking at the schematics of the Pro Micro, the LED in PD5 (bottom-right) is connected to VCC instead of GND, same for PB0. Why? Shouldn't they connect to GND?


texts: What is a term for voltage that does not involve the unit?

texts: Basically the title. What is the term that means the same thing as "voltage", but does not invoke a specific unit (in this case, volts)?


texts:
Is it possible to create multiple submodules (hierarchical sheets) that represent separate pcbs and are connected by terminals/wires in the master scheme?
If so, how?


texts: Need help with simple digital circuit that can change state and reset

texts: It's been 20 years since I have used any digital logic circuits, so please explain things well and be patient. I just need a simple digital circuit that does the following: When the input state changes (Low to high or high to low) the output goes to high. Then there needs to be a momentary switch to reset the output back to low. It's as simple as that. I have searched Google, but I think I that I just don't know the correct terms to be using or maybe the answer is staring me in the face and I just don't know it. Any suggestions are examples would be appreciated.


texts: Common source amplifier using mosfet: Why is my Id dependent on my Rd?

texts:
Since I'm (trying to work) in the saturation mode, the following formula should be valid:

Since Vto is a static parameter it shouldn't change, same for K. And Vgs is 2 as determined by the voltage divider circuit. My DC operating point simulation confirms this. This leads met to believe that Id should be stable if you change the resister R1. However, according to the simulations this isn't the case. (Even though Vgs is 2, and Vds is higher than 2. My Vto should be 0 so I should be working in the saturation region)  If I make R1 higher, Vds becomes lower and Id also becomes lower. Can someone explain this to me?


texts: Universal motor DC vs AC which will give more speed and torque

texts:
I have shortlisted a universal motor for a DIY project requiring High speed and torque of the motor.
Motor looks like below and some characteristics.
DC Motor : Washing Machine
Input Power: 750 Watt
Voltage: 230 V 50 Hz
Current: 0.95 – 1.1 A
Speed: 16500 - 20000 rpm (3 speed)
Rating: 30 Minutes
Insulation: Class B
I see it being a universal motor can be powered by 230v AC or 230v DC supply.
Will AC or DC give more speed and torque for a 30 min continuous operation ?


texts: Battery connectors: how are they called?

texts: How is this 3 pad connector called? I'm trying to build something similar into a product but can't seem to find anything similar.


texts: Can I use software serial rx on attiny84 pin 0?

texts: Please address using ATtiny84 physical pin 13 (logical pin 0) (RESET) ("D10"?) as a software serial RX.


texts:
I'm developing board which have STM32F103VET6. I don't need RTC so is it OK to not connect the OSE32_* pins to external oscillator? Will there be any side-effects? All the reference design I found all have a 32.768KHz oscillator connected to them. So I'm afraid losing other functions besides RTC.

The datasheet is here.


texts: is it possible to wire bond to a perfboard pcb?

texts:
Can a wire bonder bond wires to contacts on a board like this one:
https://www.sparkfun.com/products/8808


texts: What is the most common logic family in modern CPUs?

texts:
I know there are a lot of logic families, from the old RTL to LVC, but which is the most common of them?

Can you also explain the reasons?

I also wanted to know: which is the fastest and which has the lowest power consumption?


texts: what role does transmission line termination take in long distance power lines?

texts:
Does transmission line theory and transmission line termination take any significance when dealing with long high-voltage power lines? Do power companies terminate their power lines to avoid reflections in their power lines over great distances? (say 1000 km for example)
If so, how do they do it (in general terms)?
Most of the sources I have found talk about electronic and PCB design, I have not been able to find anything about this phenomenon in the electrical power industry so far.
Any article or reading material suggestions are very welcome in the comments.


texts:
I will have a wire that will run up to 1000 m with many nodes connected to it. The wire will run along a CAN bus and a ground wire and must transport a 1 kHz square wave 50% duty-cycle clock signal to each node.

I will run this from a 3.3 V microcontroller and the signal will be received by a 3.3 V microcontroller and a time measuring circuit as well.

In short, the clock will be used as a global time and the time measuring circuit will determine the time difference between an event and the clock edge. This circuit is able to measure with around 0.1ns precision. The ideal scenario is to have the clock be as precise as the time measuring circuit.

Any delay from the master to a node is measured/known and is accounted for.

What can I do to increase the reliability and stability of this wire/signal?

Because it's a very slow clock, I imagine that no extensive work has to be done and that something simple like a Schmitt trigger at the nodes would do just fine.

Here's a diagram:

To measure the delays to all nodes, the master stops all nodes from doing work
(Over CAN it communicates that).
Then it asks the first node to reflect the signal it will receive over the other line.
All other nodes will leave the wires floating now.

The master sets its right wire high, triggering the timing circuit to start.
After some delay, the signal will get to the node which will then let it through on the second line.
After another delay, the master will receive it back which will stop the time circuit.

Now the master can read the time circuit value and determine the delay.
When all node delays are known, the master will start the operation.
All nodes will leave the return wire floating and will take the clock (master's right) wire as input.

When an event happens at one of the nodes, that will trigger the time circuit.
The next pulse of the clock will stop the time circuit.
We now know the time between the start of the event and the the next clock pulse.
The node sends back at which clock count the event was detected and how much time the time circuit indicated. Together with the measured delays, the master will be able to get the global time of the event.

Oh, about what accuracy is acceptable: the target is 1 ns, would be happy with 3 ns and would be ok with 10 ns. Depending on the final design of the system, there might be a possibility for getting the event triggered multiple times and having the results be averaged, which would also improve the accuracy.

The actual timing isn't made by me, but by TI.
TDC7200

The application is TDOA. The event times are fed into an algorithm to determine where the event originated from. The event is the detection of a radio signal (which will be a challenge as well to get as accurate as I want).


texts: Using two diodes as a simple power supply backup switch

texts:
I saw this module as a "battery emergency switch module" for $2 on aliexpress:

which is just a relay energized by the external power supply, and when the external supply is gone, connects the battery to output.
despite a relay could switch higher currents than a same priced diode, it is slow and the chances that the circuit resets are high. also, the relay may stay energized with lower voltages than the nominal supply, while the circuit has turned off because of low voltage.
what could be the problems with a simple circuit like this ?

simulate this circuit – Schematic created using CircuitLab
it is cheaper (for some applications at least) and much faster than the relay. it doesn't have the problem of low voltage mentioned above.


texts: Feasible to capture data to/from a 1970s RAM chip?

texts:
I have a 1978 Bally Playboy pinball machine. The processor is a 1Mhz 8-bit microprocessor Motorola 6800. I would like to build a way to extract/watch game state from outside of the machine. The best place in my mind to do this would be simply watch the game memory. The 6800 microprocessor communicates with a 6810 RAM module and a 5101 CMOS RAM module. I'm most interested in the data stored in the 6810 RAM. Effectively I'm looking to "packet capture" the memory, to be processed later to extract information about the game.
I see a few options and I'm not sure what is feasible with today's hobby-style boards like Arduino and Raspberry Pi. I do have a 8-channel Saleae Logic Analyzer I could use, but I don't think it's enough monitoring points to capture all the data I need.

Watch the I/O pins on the RAM chip(s). I could maybe even get away with just monitoring the inputs and keeping track of them in my own application's memory. Basically as addresses are updated/retrieved interpret the signals and store the data myself.
Emulate the RAM chip itself, re-implementing the functionality of the IC in code. Of course since I'm tracking the values FOR the microprocessor I have easy access to them.

Am I totally off base? Are these 40 year old microprocessors still too fast to be tracked with modern consumer hardware? Are there any relevant search terms I could use to research if someone else has attempted anything similar?


texts: How to create a circuit to reduce my H-Bridge Inputs from 4 to 2, much like the 4427 Dual Driver does?

texts:
My H-bridge is identical to the one here:
http://www.robotroom.com/BipolarHBridge2.html

I'm trying to reduce the number of inputs from 4-2 so I can control it with my arduino using the 2 inputs.

In his book, the creator of that website mentions using the IC1 4427 Dual Driver (non-inverting)

Why not just use 2 transitors, one which activates both R1/R4 and R2/R3? (forward, reverse, 2 inputs)  I'm assuming it has something to do with applying the exact equal power to both transistor bases?

If that is the case, how would I manually create a circuit that accomplishes what the 4427 dual driver does?

What I'm really curious about: what are the advantages to using a 4424 Dual Driver to turn on the 2 inputs at a time as opposed to 2 more transistors?


texts: How would I go about analyzing this SDR-captured 300 MHz radio signal?

texts:
I am attempting to reverse engineer the signal from a 300 MHz garage signal as a learning experience rather than an exercise in efficiency. My intent is to purchase a 300 MHz broadcaster IC and connect it with a microcontroller so that I can have a neat gadget that controls a few gates. My quest has led me to software defined radio. I purchased the recommended dongle, the R820T, and fired it up. After much tweaking I was able to isolate the frequency.(much happy)

I found the signal, then recorded and extracted the .wav. Then I zoomed into the desired signal from the .wav file in Audacity.

I've heard the 10 digit key (each one in one of two positions) should be readily apparent
from the signal.

Can anyone help me understand how I can get the key from this signal or any other tips on deciphering?

Here is the current remote config for this signal:

Here is the Multicode 3089 remote that i received the signal from: http://multicoderemotesonline.com/Multi-Code_Remote_3089-11.html
Here is the quick start guide I used:
http://www.rtl-sdr.com/rtl-sdr-quick-start-guide//


texts: Is there a problem connecting PSU grounds to earth for an isolated signal chain in this scenario?

texts:
For a precision and simultaneous analog signal data acquisition;  several force, temperature and acceleration transducer outputs are coupled to a daq board input channels through signal conditioning modules for each channel. These modules acts like differential inputs they have very high CMR, they provide ch-ch isolation and also provide built in anti-aliasing filters.

So far so good, but I still have AC line interference coupling through power supplies. And if I connect power supply DC ground terminal to earth terminal the interference disappears.

I tried to draw the scenario below where switches indicates connection option between the power supply DC ground and the earth. In the diagram two channels shown as example and in real there will be around 15 where cable lengths are around 12 meters:

(Tr indicates a transducer)

Is there any issue with such a scheme for the above diagram? I know if there would be no isolation modules there would be ground loops but in this case there seems to be complete isolation but still I don’t have more experience beyond this argument for the overall system here.


texts:
In my current project, I need a microcontroller to retrieve the temperature of 60 temperature sensors which are located on the same PCB with distances not exceeding 50 cm. The temperature sensor's reference is MAX30205. It communicates using I2C and offers 32 different I2C addresses.

I was thinking of using three I2C buses (which is the maximum with my microcontroller), and putting 20 sensors in each bus.

I do not have big contrains regarding the bus clock, as I will only need to get the temperature of sensors from time to time, so we can suppose I will use I2C in its standard mode (speed = 100 kHz).

The MAX30205 will be supplied at 3 V, meaning that the minimum possible pull-up resistors value is 1 kohm (because I2C spec dictates a maximum current of 3 mA on SCL and on SDA). Given the number of sensors, I will choose R as small as possible, so maybe around 1.1 kohm.

The MAX30205 has an input capacitance of 3 pF, and the microcontroller has an input capacitance of 5 pF, meaning each bus will have at least a bus capacitance of 103 pF. The maximum capacitance for standard mode I2C is 400 pF. There is a remaining bus capacitance due to PCB and traces.

Is it possible to estimate it ? Can it be close to 300 pF ?
Do you think I need an I2C buffer ?


texts:
My question pertains to different types of the Li-ion batteries currently available.

http://investingnews.com/daily/resource-investing/energy-investing/lithium-investing/6-types-of-lithium-ion-batteries/

Many of them address relevantl issues which are generally faced with the current type of Li-ion used in everyday electronics, probably the Li cobalt based battery.

Like Li-manganese based cells which are considered thermally stable than most other types or Li-NMC which in my opinion should become the battery type of choice to be used for everyday electronics, having better energy density, longer life and obviously safe. (It even has the same nominal voltage and cut-off power, can be replaced?)

Obviously, these may not be revolutionary in its ultimate objective, but it definitely is better than the current choice used, considering even that was used to replace the erstwhile Ni-Mh based batteries as, only, a better upgrade after all.

So technically speaking, why isn't Li-NMC, for eg, not being used in laptops or smartdevices, etc? Is there something else missing, in the engineering choice of it?

PS - Not referring to the cost or industry adoption rate, etc


texts: TMP36, trouble understanding the schematic

texts:
Big electronic noob here. I've got a microcontroller with an ADC (connected to TEMP3) and I'd like to work out the temperature using a TMP36 connected on P11.
It's output pin is connected on 2, where I measure around 3.1V (environment temperature is around 20 degrees C). I'm clearly seeing the voltage change if I heat up or cool down the TMP36. For example, at around 30 degrees the voltage drops to around 3.0V.

The datasheet says that I should get something around 0.6V at this temperature, and it should rise as the temperature goes up.

Clearly the circuit is changing this, but I can't quite work out how.


texts: Why are Alkaline, NiMH, and Li-ion AA measured differently (mAh, mWh, etc)?

texts:
Looking around Amazon, it seems that different types of batteries are measured differently:

Does anyone know why?

Li-ion are measured in mWh

1200mWh Cheap-Os
3200mWh Deleepow
3000mWh AmpTorrent

NiMH are measured in mAh

2000mAh Eneloop
2800mAh EBL

Alkalines are typically not measured

"Long Lasting" Duracell
"Longest Lasting" Energizer

I assume that Alkalines are not measured for some sort of historical reason with marketing departments?

... or is it that alkalines so mystical and unreliable that giving them a measurement is too aggressive? Or that switching to non-toxic / non-mercury was such a bad move in performance that measurements had to be removed in the 90s so people wouldn't know?

Perhaps NiMH are measured in mAh because the voltage can very so greatly and mWh doesn't make sense?

Are Li-ion measured in mWh because that's more consistent with non-battery measurements and they do deliver reliable voltage?


texts:
(NB: I feel this is better here than super-user because it is hardware based)

Trying to connect my laptop's S/PDIF output to some headphones. Setup is:
Laptop -> 3.5mm to RCA cable -> Co-ax to Toslink converter -> toslink optical cable -> headphone decoder box -> headphones

Everything from the Co-ax to toslink converter works fine from an alternate source RCA S/PDIF connector on my desktop's motherboard.

Using a random 3.5mm mono jack to RCA cable works but it is very quiet (as in laptop volume settings maxed out, and headphone volume control (active (yes they need their own power supply!)) also maxed out and I can barely hear the sound above the noise.

Would a genuine 75\$\Omega\$ cable (eg. this) sort out the attenuation issue?

I am thinking that the laptop lacks the impedance matching output system my desktop has, so the laptop is setup for:

spdif ----
        |
      ----
      |  | 75 ohm
      |  |
      |  |
      ----
        |
      ---- GND

hence provides \$I=\frac{V}{R}=\frac{0.5}{75}\simeq6.7\mbox{ mA}\$

but because of my random cable (which multimeter measured at ~2\$\Omega\$)
sees:

spdif ----
        |
       ----
       |  | 2 ohm
       |  |
       |  |
       ----
        |
       ---- GND

hence the voltage across the load (the converter box) is \$V=IR=13\mbox{ mV}\$ instead of the \$0.5\mbox{ V}\$ it should be.

Is this anywhere near correct? And is a proper 75\$\Omega\$ cable the solution?


texts: Why won't my BJT transistor work as intended?

texts:
I am trying to hook up an NPN transistor to emulate the circuit design here

The poster calls for an SS8050 NPN transistor (datasheet is here) but all I have on hand is a BC547B (datasheet is here).

My circuit doesn't work so I removed the controller and wrote a simple program that just "turns on" the transistor for 5 seconds, then off for 2 so I could see what is going on with this thing. One thing I found is if I take the voltage between the collector and emitter when the base is on I get 0.275VAC which doesn't make any sense to me. Why is it outputting AC voltage when I'm not changing the gate at all? I assume this is the reason why my circuit doesn't work but the datasheet for this transistor doesn't mention AC voltage at all.

Can anyone shed some light on this? I'll buy some of the SS8050's that the poster recommends but I just want to know what is so different about my transistor that it refuses to act as a switch.

For people asking about the schematic. In order to reduce error on my part I duplicated the schematic provided by the poster here. The only difference between mine and his is my transistor is different and I unplugged the controller because it wasn't working as intended.


texts: Simplest way to reduce voltage from ~48v to ~36v

texts:
(I'm very much a beginner with electronics, so I apologise in advance)

I’m trying to use a 48v battery on my 36v ebike controller. The controller itself can deal with the higher voltage, but it has a hardcoded limit of 44v, which it reads from a wire coming from the display.

So my aim is therefore to lower this voltage somehow. The parameters are:

Input is 39-55v, output needs to be between 29-44v
Current on the wire is 80-120ma
It would be great it if this could be done proportionally, or with a
constant voltage drop, instead of just regulating to a set output
voltage
Single component solution would be best, since it would be easier to
wateproof for riding in rain

Solutions I have researched so far:

Tvs diode:

Guy here used one for this purpose (52v battery but otherwise same
situation) and he said it worked
But I’ve read that they’re not supposed to be used continuously like
this, only for spikes in voltage - does that mean it could fail if
used like this?
Also have no idea how to choose one for specific voltage drop - have
read many explanations and data sheets but don’t understand
difference between clamping, breakdown and working voltage. The guy
in the linked post seemed to choose based on breakdown voltage =
desired voltage drop, but this doesn't seem to be what breakdown
voltage should mean?

Zener diode:

To calculate the series resistor, I would need to know the resistance
of the load, correct? I’m not sure how to find this - do I measure
resistance across the voltage sense wire and ground while the display

Step down converter:

I have one of these (appears to use a LT3800) This has a constant
output and is large, so not ideal. But I would also worry that it
would draw too much current? I've tried to measure the current it
draws with no output, but I doubt that is particularly useful
information. I tried to figure it out from the datasheet, but I don't
really know what half the symbols mean

Resistor:

Every mention of using a resistor for this purpose (that I've seen)
has said not to do it, but not said why (although I assume this is because fluctuating current would change the resistance too much?)
Also wasn't sure how to select the resistor value for a desired
voltage drop. Is the V in V=IR meant to be the drop, or the voltage
of the circuit?)

Voltage divider

From what I’ve read, this doesn't work once you apply a load?

Other ideas:

Only just found these so haven't looked into them: using high power
LEDs in series, or zener + transistor circuit

My main reasons for asking instead of just trying these things are:

Not wanting to exceed the mA level that I have witnessed on the line,
because I don’t want to break anything
Not knowing whether my lack of understanding might lead to something
breaking
Need something reliable, i.e. that won't fail halfway up a hill

Sorry if I've missed anything obvious - I feel like I could have researched some of these things more, but I did try. And in fairness they are bloody confusing if you have no real prior knowledge!


texts:
What are some of the factors that makes a microphone preamp good or bad?
noise, cancelling reverb and other factors.

I'm trying to build a electrec Mic that will handle voice recognition, from a distance in a room. It will connect into a Computer Audio input.

I need to talk all factors into account.
mic needed range around 10 feet. I have looked over several microphones pre amp schematics.

If there are good examples I would love it.

Thanks


texts: Confusion between register size, address size, data size

texts: I started learning about pointers in C++ and I figured I should educate myself a bit on how memory works and is accessed. I read that when we say a processor is 64-bit, it has a 64-bit register and can access 2^64 address locations. I also read that it can fetch 64/8, so 8 bytes of data at a time, but the data bus is not the same thing as the register right? Do they need to be the same size or does that just happen to be the case usually? And is it the size of the register or the data bus size that determines what we refer to it as, such as 32/64-bit? Also is there a difference between register size and address size?


texts: Identifying live, neutral, and ground wires cold

texts:
I have a European (230 volt AC motor, no markings), 1 phase (I think). It is roughly 6 inches long, just to get a sense of the scale.

It basically wobbles when current is supplied to it.

1) I need to figure out which leads connect to ground, neutral and live.

2) I also need to figure out what kind of transformer I need to use. All I know is that it needs to convert the voltage from 110V (in the US) to 230V (so that the European motor can use the power).

I read about how to do it when there is live voltage, in a situation where you need to figure out which wire are which in a house with running current. How do you do so with a cold circuit? How do I do it without first connecting (and possibly shorting) the motor to a transformer? How do I know which wires to connect to what before doing so?

All I have is this shabby old multimeter, but it works.

Motor is .2Amps 240V and 45 watts.


texts: Laptop battery voltage vs input voltage (18.5 V)

texts:
Let's say I have a laptop whose battery is labelled 10.5 volts, 4000 mA but the laptop itself
has an input voltage of 18.9 volts. I have traced circuitry and couldn't find a boost or buck
converters in particular related to power supply.  Can you guide me understanding how it's wired or what are the working voltages?    Could the motherboard power the battery at 12 volt straight from the vias which had the dead mosfet? or should i look for a subcircuit in particular providing those 10.5 volt aside from the aparent 12v mains buck?
Thank you.


texts: Why feedback is needed in PLL FM Demodulator?

texts:
I am trying to build FM Demodulator in FPGA. The architecture I am trying to use is PLL-based FM Demodulator like the one below. I searched for the working principle of this demodulator but there is one thing I couldn't understand and I couldn't find an answer to. Why do we need this feedback to the NCO (d(t) in the diagram)?

I think it doesn't make sense because the NCO should run on the centre frequency, that is the carrier frequency of the received signal, why should I change this running frequency while detecting the phase, thus extracting the information signal?

I have implemented this demodulator, and simulation assures my point of view. The output signal of demodulator with feedback to NCO is distorted and has no relevance to the input signal (of the modulator), on the other hand, the output signal without feedback to NCO is very similar to the transmitted signal.

Any explanations?


texts: Is 'hot-wiring' two contacts a proper way to bypass a broken button?

texts:
I have a broken cell phone, and its power button is not working at all.

Examining the device's motherboard I have discovered the button has five pins. As seen on the manufacturer's service manual, the connections look like this:

My theory is that it could be possible to join the four ground pins into one and create an equivalent circuit by placing two wires out of the motherboard: the first coming out from the GND and the second from the positive part of the chip (the one in the right of the picture).

With this setup, would connecting the two wires one to each other bypass the broken button action and simulate a press to power on the device?


texts:
I am using the ADC4245-EP (enhanced product) adc chip. It has a normal version as well of it.There are 2 options of interfacing thiis ADC to an FPGA. They are CMOS or LVDS. The advantage of the LVDS being a better immunity to noise.  Now, the idea of LVDS is that we have signals that are complementary and hence the noise immunity is enhanced.  But, suppose I go for a simple CMOS voltage level, I must make some provisions for noise immunity.
The 1st thing that I will do is designing the bus with length matched tracks. This will help make the signals arrive at the FPGA at the same time (more or less) and hence make the design robust.

Is there any other aspects that I need to take into consideration when doing this layout ? Suppose if the tracks are not length matched, what is the impact ? How is the signal delayed or the extent of delay with increase in length (say even a few mils) . Can anyone direct me to any application note for such designs please ?


texts: Step up converter 1-3V to 5V fixed for supercapacitor

texts:
I would like to use this step up converter, LT1073 - Micropower
DC/DC Converter
Adjustable and Fixed 5V, 12V, to drive an input in the range of 1 V to 3 V (input is a supercapacitor).

In the datasheet there are examples of voltage inputs from 1.05 V to 1.55 V to get a fixed 5 V output. Could this IC work with an input range of 1.05 V to 3 V to get 5 V voltage at the output?

The capacitor I am using is 2.3V 50F, so if you have any suggestions how to use it at highest efficiency, please share your advices.


texts: Use Arduino to detect momentary 120VAC interruption

texts:
I'm trying to figure out how to notify an Arduino controller that there's been a momentary interruption to a 120V AC circuit that is normally powered.  When a spring-loaded switch is pressed, it opens the AC circuit until the switch is released (typically about 0.1 to 0.3 seconds in duration).  I don't care about measuring the current, I just need to know if the circuit has power or not.

At first I was thinking a relay would be appropriate, but it seems like most relays are designed to let low voltages control higher voltages, not the other way around.

Using a CT may be a possibility but it's a somewhat cramped area, so it may be difficult to fit a CT in and get it wrapped around the line I need to watch.

What other options might I have?


texts:
I've been trying to make a simple audio player using the STM32F302CBT6, however, the VCC and GND pins of the MCU keeps on getting internally shorted when a 3.3V power supply is provided and a faint burning smell starts to come out of it but it does not get very hot to the touch. The PCB was tested for shorts using a multimeter before powering on.

I'm certain that short is due to the microcontroller because desoldering it removes the short from the board.

Initially, I thought it was a soldering problem but all three PCBs which I soldered have had this issue, including a PCB which was soldered with just the MCU, clocks and a 3.3V low dropout regulator, i.e., these components:
The power to the PCB was being supplied by the 3.3V and GND pins of an Arduino Uno connected to my computer via USB.

My PCB is laid out like this (note the ground copper plane was hidden for visibility):

Are there any visible design flaws or issues I have overlooked which could be causing the internal short?


texts: Effect of increased leakage of PMOS in reversed inverter configuration

texts:
I have built the standard CMOS inverter in reversed configuration by putting NMOS on pull up side and PMOS on pull down side. This will work like a buffer but the the upper and lower bound of the output will not be the Vdd and Gnd. Instead, as NMOS passes weak '1', the upper bound will be Vdd-Vth. The PMOS passes weak '0', the lower bound of output will be Vth of PMOS.

But the question is, what happens if the PMOS leakage increases. Will it affect the lower bound of the output, bringing it below than the Vth of PMOS?


texts: Is this current source (or mirror)? How does it work?

texts:
I'm trying to understand this schematic of this differential probe:

There are several things I do not fully understand. One of them is this section:

I would guess it is a constant current source (or current mirror). Is my assumption correct?
How does it exactly work?

I understand that D3, R19, R18, Q2 form a current source (several milliamps). But I don't know what the other 4 transistors do. Could anyone explain this to me?


texts:
I have a quick question, how do I know how many phases a BLDC has? For example, an E-bike motor kit has three motor wires: yellow, green and blue. It also has three wires for the hall effect sensors: yellow, green and blue plus two more wires for powering up the sensors: black and red. By intuition, I believe it is a three phase BLDC because it has three signals for motor control plus three signals for feedback. Is that correct?

Best,


texts: How to use N-channel MOSFET as high side switch (non-buck switching)

texts:
I have an application with some constraints for which it feels difficult to find a solution.

load current more than 10A, so N channel MOSFET is preferred;
working voltage is a bit high, between 50-80V;
logic switch control signal, no driving capability while expecting very fast response;
due to some reason, high side switching is required. That is, the MOSFET will be between power source and load. The load is non-inductive like one in buck converter.

I have searched the web for high-side MOSFET driver, but all are with buck type of application, coming with external capacitor connected to source of MOSFET to get ground rail to be charged. Which I don't think it works in my application where no ground rail exists after switch-on.

I found few drivers with charge pump built-in, but below 36V.

I know a workaround that uses a battery and connects the negative of the battery to source of MOSFET, but this is not a solution as I have no way to charge the battery and so it has to be replaced regularly.


texts: 6 layer PCB layout with RF antenna track

texts:
I am doing my first 6-Layer PCB with RF antenna connection tracks.

I am using this stack-up:

L1 Signal Layer

L2 Ground Plane

L3 Power Plane

L4 Signal Layer

L5 Ground Plane

L6 Signal Layer

I have some questions in my head:

The power plane is splitted into 3 different voltages. As every signal layer has a reference solid ground plane close to it, it is not that important to cross power planes sections in signal layers because the return path will flow in those ground planes, right?
In the bottom layer there are two antennas (one chip antenna and one ufl connector). In this case I think I should place a GND polygon pour in the bottom layer with many stitching vias to the ground plane, right? if so, is there any rule for placing those vias? (how many? where?) and what via size should I use? Should the polygon cover the whole PCB or just the zone containing the antennas?

A lot of questions, sorry! :)


texts: Does the order of connecting the low pass and high pass filter make any difference?

texts: Is there any advantage in connecting up high pass filter first and then low pass filter to achieve a simple band pass filter. Or the other way around is better? Will there be any change based on the order of connection of filters?


texts: How do I bias a phototransistor (TCRT5000) to scale the effective range?

texts:
I am attempting to measure smoke in a small chamber through optical obfuscation using a TCRT5000 phototransistor. I'm taking measurements with an Arduino Nano.
My current configuration is:

\$R_l\$ is a 10k resistor
\$V_{cc}\$ is 5V
The IR diode resistor is 100ohm

The problem I am facing is that the sensitivity with this configuration is too low.
Here is a graph of the recording:

As you can see, the effective range is between 232 and 214 (this is the 10-bit ADC values bitshifted down to 8-bit).
What I need to do is change \$R_l\$ to move the range of the phototransistor to be more sensitive within this range since I do no expect values smaller than about 200.
What are the steps to calculate the \$R_l\$ value on my desired range?
Edit
Here is the schematic:

(source: northwestern.edu)
I have the circuit configured as the Common-Emitter Amplifier type. In this case, my above reference to \$R_l\$ should be changed to \$R_c\$
Am I able to just adjust \$R_c\$ to change the range of the circuit?


texts: 3-Phase Permanent Magnet Alternator with Regulator/Rectifier (SCR) Output Waveform

texts:
So I've been troubleshooting some electrical problems with a motorcycle charging system, and I need a little assistance understanding the output waveform:

Per an article (which I don't have enough reputation points to link to...), I interpret the first half as "good" and the latter as "bad", though the latter does not 100% match any of the bad scenarios. The switch between these two different waveforms happen quite often and with no outside stimulus. Unfortunately the R/R is a "black box" so I can't measure the rectifier output before the regulator.

I suspect that the dips I'm seeing in the latter half of the waveform represent the regulator periodically shunting current to ground in order to do it's regulator thing but I'm looking for confirmation\alternative explanations.

Here's a schematic of this particular system:


texts:
I'm having a quiz show project with LEDs, and a buzzer. One LED must be lit up and the buzzer should work for about 0.5 sec.
I am stuck on the problem that using circuit output state (which gets high and remains high till reset comes), I will set the trigger pin of timer555 low, but since it's continuously low, the buzzer, which is connected to the output of timer555, buzzes repeatedly.
 I'm wondering what I could do to convert a constant output to a fixed 0.5 pulse using a timer555.


texts:
Possible Duplicate:
  How to measure power consumed by mains device

I have the following question:

In my home I have certain devices such as my fridge etc. of which I would like to measure their powerusage. For practical reasons I would like to use current convertors (CT's) to do the measuring for me.
At the moment I have some current convertors with a rated secondary output of 1A. Yet I do not seem to find a device that allows me to accomodate this output and convert it to kwh.
As a plus I would like that the measuring devices has a pulse output for usage in an other project I am working on.

Can anyone give me advices on this matter?

Sincerely


texts: Linear Voltage Regulator Maximum Input Current

texts:
I am trying to understand why the maximum rated input current is not listed as a parameter on linear voltage regulators. For example, the LM1117 lists nowhere on the datasheet the maximum input current. The maximum input voltage is listed but not the input current. At first I thought it may have just been the particular regulator I was looking at; however, if you go on Mouser maximum input current is not even a selectable parameter. I find it hard to imagine the input current doesn't matter especially when the maximum output current is often listed.

Any clarification anyone can add to this would be very helpful.


texts:
I'm trying to create a circuit that will pass a 12V pulse on the rising edge of a push button (it can be triggered by the entire input pulse but rising edge preffered). I've had some experience with microcontrollers but I'm very new to ICs. I believe I can use a monostable multivibrator, constructed with a 555 timer.

Datasheet: http://www.ti.com/lit/ds/symlink/ne555.pdf

The below circuit is taken almost directly from the datasheet (pg. 10) with the addition of the trigger configuration. My understanding of the graph in figure 10 of pg. 10 is that the pulse is generated on a "low" input at the trigger, would my configuration below create this low input when the button is pressed (pull up resistor, I believe)?

simulate this circuit – Schematic created using CircuitLab

The output pulse length is found approx by: \$T=1.1{\times}R_1{\times}C_x\$

I'm having trouble wrapping my head around what the threshold and control inputs do and so in the above equation I'm unsure which capacitor value to use, \$C_1\$ or \$C_2\$?

When triggered, is the output pulse equal to the input source \$V_1\$ or another value?

Not 100% on choosing a value for \$V_2\$, graph would indicate using a value of \$\frac{V_1}{2}\$ works?

Sorry, I know this is a lot of questions, thank you for any and all help.


texts: Resistor parallel to optocoupler LED in Zener-stabilized circuit

texts:
I was watching a video about phone chargers where the following schematics was presented:

simulate this circuit – Schematic created using CircuitLab

In the video it was stated that this schematics is for the feedback circuit of a phone charger and that the resistor R1 is for stabilizing the optocoupler.

Question 1: How does the resistor stabilize the optocoupler, and why would one need to stabilize the optocoupler?

Question 2: I would argue that the voltage drop over R1 is limited to the forward voltage drop of the diode within the optocoupler. Does that make sense? If so - Why would one place a resistor there, doesn't that limit the current supplied to the led, resulting in a slower turn on time for the transistor of the optocoupler?

Thank you for your help :)

For reference video (Timestamp: 08:20): https://www.youtube.com/watch?v=bNoGCdX1IdQ&t=500s


texts:
This is for a GE refrigerator control board.

It is fairly close to a Molex 496 KK series (6 position) pn# 0009508063
However, that particular part has taller posts along the side & the ramp is too tall and thus interferes with the plug when trying to plug in.

I'm needing to ID the connector marked "ORG".
The back has a marking of AMP.

The measurements that i'm sure of are:
Pitch = 3.96mm
length = 23.81mm
width = 6.45mm (8.59 including the post)
hight = 16.96mm

It would be a great help if one of you can help point me in the right direction.
Thanks so much!

Photos


texts: Arduino project LCD displays gibberish when water pump is activated?

texts:
The setup is I have connected 9v battery to motor and I have tried using mosfet and but both works fine . I used cap between vas and V can pins of LCD it solved but the values are 20 percent high than original .Arduino project LCD displays fine when water pump connected to it off , when it gets activated LCD display shows some gibberish.This is aurduino activates water pump as value of humidity drops as in program . The program is

#include <LiquidCrystal.h>

//initialize variables for sensor pins
int moistPin = 0;
int tempPin = 1;
int lightPin = 2;

//initialize variables to store readings from sensors
int moistVal = 0;
int tempVal = 0;
int lightVal = 0;

//initialize variables for LED pins
int redPin = 11;
int greenPin = 10;
int bluePin = 9;
int waterPump = 13;

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);

void setup()
{
  //initialize the serial port
  Serial.begin(9600);

  //set LED pins to output mode
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);
  pinMode(waterPump, OUTPUT);
  //set LED pins to off
  digitalWrite(redPin, LOW);
  digitalWrite(greenPin, LOW);
  digitalWrite(bluePin, LOW);

  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
}

void loop()
{
   int humidityRaw = analogRead(A0); // 1023 to 0 ===> 0 to 100%
   int humidityReal = map(humidityRaw, 1023, 0, 0, 100);

  //display moisture reading on lcd
  lcd.clear();
  lcd.print("moisture %   ");
  lcd.print(humidityReal);

  Serial.println(humidityReal);

  delay(100);

  if (humidityReal < 60)
  {
    digitalWrite(waterPump, HIGH);
  }else{
    digitalWrite(waterPump, LOW);
  }
  //turn on LED to blue, others off if moisture pins are touching together
  if (humidityReal > 60)
  {
    blue();
  }
  else
  {
    off();
  }

  //wait 4 seconds
  delay(4000);
   //display moisture reading on lcd

  tempVal = analogRead(tempPin);

float mv = ( tempVal/1024.0)*5000;
float cel = mv/10;
float farh = (cel*9)/5 + 32;

  lcd.clear();
  lcd.print("temperature ");
  lcd.print(cel);

  if (cel >29)
  {
    red();
  }
  else
  {
    off();
  }

  delay(4000);

  lightVal = analogRead(lightPin);
   //display moisture reading on lcd
  lcd.clear();
  lcd.print("light ");
  lcd.print(lightVal);

  //turn on green if light sensor reads 600 or brighter
  if (lightVal > 20)
  {
    green();
  }
  else
  {
    off();
  }

  delay(4000);

}

void blue()
{
  digitalWrite(redPin, LOW);
  digitalWrite(greenPin, LOW);
  digitalWrite(bluePin,HIGH);
}

void red()
{
  digitalWrite(redPin, HIGH);
  digitalWrite(greenPin, LOW);
  digitalWrite(bluePin, LOW);
}

void green()
{
  digitalWrite(redPin, LOW);
  digitalWrite(greenPin, HIGH);
  digitalWrite(bluePin, LOW);
}

void off()
{
  digitalWrite(redPin, LOW);
  digitalWrite(greenPin, LOW);
  digitalWrite(bluePin, LOW);

}

void on()
{
  digitalWrite(redPin,HIGH);
  digitalWrite(greenPin, HIGH);
  digitalWrite(bluePin, HIGH);
}


texts: I have two V38238 IR receiver's but one acts as active low and other as active high. What could be the reason? Is there a difference in the part number?( both had 69 DRZD V38238 specified on it ) I am using the following IR receiver circuit. I checked both the receiver's using the same circuit.


texts: Spiral hoar frost and spiral device around telephone or electric landlines

texts:
I live in Germany.
When I travel by train, sometimes there are cables that run from pole to pole parallel to the train track.

From the lack of insulation between wire and pole, I guess these are telephone landlines, or electrical cables with low voltage.

Sometimes on these black, rubber-covered cables in the summer I see a thick, shiny, metallic or white spiral wound around them for about a metre (3 feet).

It looks something like this sketch:

When it is cold enough for hoar frost to form, the frost on the cables takes on a spiral shape as well. This spiral hoar frost forms not only on the device, but beyond it and along the whole length of the cable.

What is the purpose of those spiral devices on the cables? And why does the hoar frost form spirals?


texts:
I am trying to use a DAC8571 (datasheet) and I'm trying to set up a communication between this convertor and an Arduino Mega via I2C.

The communication between the Arduino and my computer is done using LabView and LINX VIs (MakerHub).

My I2C communication is already working between a sensor and the Arduino Mega and I just would like to add the DAC. The problem is that the DAC does not react at all when I write on the I2C with the Arduino.

My first worry is that the DAC is not working at all (could I have broken it with the heat while soldering?). I have two of them and I am testing them on a breadboard. When I connect them (pin1 = 5V, pint2 = 5V, pin3 = not connected, pin4 = voltmeter, pin8=gnd, pin7,6 = I2C with 10k pull-ups, A0 = gnd), no one gives 0V at the output as I would expect and they give different outputs (I guess at least one of them is broken). Is there a way to test the DAC without using the I2C communication? I want to avoid the I2C communication because maybe the mistake is there.

Just for additional information I add the VI I used to test the DAC:

SITUATION UPDATE:
I tried to read the I2C bus at the DAC address (76) and I get a sequence of bytes (0, 30, 16), which is exactly what it should give because it is what I have set... BUT, the DAC output doesn't change :/.

ADDITIONAL INFO:
To set the value of the DAC (address 76 = 1001100 plus write bit = 0) I use three Bytes: 16 = 00010000 (Command = Write temporary register and load DAC with data), x (first 8 bit to be loaded starting from MSB) and y (second group of 8 bits). In the picture x = 0 and y = 30. When I read from the DAC, it gives me its status 0, 30 and 16, but the output had not been updated.

I have tried both my DAC and they both react in the same way with respect to the I2C, but one has a fixed output at about 0.5V and the other at 5V.


texts: Why does CST give "Error in field monitor calculation" after I change the frequency of the simulation?

texts: I'm using Integral Equation Solver (IES) in CST (Computer Simulation Technology). I have one E and one H field monitor that are each 100cm^2. The simulation runs well at 100GHz, but when I up the frequency to 200GHz, CST says "Error in field monitor calculation" after completing the simulation. I'm changing the frequency of the simulation, the frequency in the field monitor definitions and the frequency of the excitation source, so it's not a matter of mismatched frequencies. I have about 100GB of free memory leftover during the 200 GHz simulation so I do not believe it is a memory issue. Does anyone have any idea what could cause this?


texts: How can I find a relative yaw value from an IMU (MPU-6050) based on which direction is currently up?

texts:
I'm having a hard time putting this question into words but basically I have an IMU (MPU-6050) and am able to get the data to stream using the i2cDev library.

The IMU is in a box and I want to be able to determine which side the box is on (which I assume will be easy using using the gravitational direction as a reference point) and then have that side's yaw be calculated.

In a sense, I want to pretend that the absolute Yaw, Pitch, and Roll don't exist for the device and instead that each side of the box has a relative Yaw.


texts:
Please forgive my lack of knowledge as all of this is VERY new to me... old dogs and new tricks and all ;)

I want to wire a usb cable to a simple momentary button to use as a push-to-talk button. I've done some LIGHT FIT stuff; built button boxes with zero latency boards and such, but I'm not sure how to find this answer. Heck, I'm not really sure how to search the question.

The button is 2 prong of course. I don't want to utilize a board (learning arduino now, but there's no room for a board in th his project) if it can be avoided, but would rather just have the button connected to the cable and plug it in to have Windows recognize it as a button.

Can I simply wire this button to a usb cable? If so, what fills the remaining 2 positions on the USB connector (data pins I believe) if anything? I don't want to blow up my newly built pc ;)

Thanks in advance for entertaining my ignorance.


texts: can't figure out why dsPIC digital input is not working

texts:
Having trouble getting a basic digital input to work correctly.  Just trying to use it as an additional condition for an LED flasher to work.  Right now their example code works just fine but when I try to add my additional condition on PORTA pin RA1 is just always reads it as 0 no matter what input I apply to the the pin.  Total noob to microcontrollers so I'm sure the mistake is basic, but here is the code:

int main ( void )
{

    /*  Initialize ports */
    //LATAbits.LATA0  = 0;          // set latch levels

    TRISA = 0x0002;                 // set pin RA1 as an input
    LATB  = 0x0000;                 // set latch levels
    TRISB = 0x0000;                 // set IO as outputs
    InitTimer1();                   // start the timer

    /*  endless loop*/
    while (FOREVER)
    {

        if (timer_expired && Counter == FLASH_RATE && (PORTAbits.RA1 == 0))
        {
            LATAbits.LATA0 = ~LATAbits.LATA0;
            LATBbits.LATB0 = ~LATBbits.LATB0;
            Counter = 0;
            timer_expired = 0;
        }

        // or do something else
        Nop();
        Nop();
        Nop();

    }

}

I didn't include the timer code because that is all working fine.  The problem is with trying to read the RA1 pin using ... PORTAbits.RA1.  I know I have the tri-state register initialization correct because I put a pull-up resistor on the pin, initialized the whole LATA to 0's and then switched TRISA from 0x0000 to 0x0002; in the first case, the pin was driven low, in the second case, it was pulled up by the resistance.  I looked at dsPIC's documentation here and couldn't find anything which explained why I can't seem to read a value from it.


texts: What is the maximum supported I2C mode in the FS32K146?

texts:
In the S32K146 user-manual guide, it is mentioned as High-Speed mode is not supported by this device. (Page 1481).

But in the coming section of the user-manual it is mentioned as device support HS mode (page 1483).

Both seems bit contradictory for me. What are the I2C modes supported by S32K146? And what is the maximum speed of I2C clock frequency?


texts: My VHDL doesn't detect all transitions of a signal

texts:
After a few tutorials, I'm writing my first VHDL entity of my own.

Given an input signal and a 50MHz clock, it's supposed to emit a 6-clock-pulse strobe (120μs) when the time between two transitions in the input signal is longer than 21 clock pulses (420μs), and emit nothing if the transitions are shorter.

It revolves around a 5-bit binary counter. At each clock pulse it samples the input signal and compares it with the previous sample to see if a transition has occurred. If no change, keep counting; otherwise, set the strobe high if the counter reached 21, and reset it in any case. Also reset the strobe at the sixth clock pulse after the last transition.

While it works fine in ModelSim (using a stimulus taken from a real-world signal), IRL it often fails to recognize a transition, causing problems downstream. Here's a screenshot from the logic analyzer:

Here the pulses are shorter, and the counter is supposed to reset at 16-17 (note the bit 0 isn't shown, it switches too quickly for my 24Msps logic analyzer). I'd expect the counter ot_count to reset at every transition of i_data/ot_last_data, but sometimes it keeps counting.

Here's the code:

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.numeric_std.all;

entity SpdifAmp is
    port(
        i_clock: in std_logic;
        i_data: in std_logic;
        o_strobe: out std_logic;
        ot_last_data: out std_logic;
        ot_count: out std_logic_vector (4 downto 0)
    );
end SpdifAmp;

architecture rtl of SpdifAmp is
    signal r_last_data : std_logic := '0';
    signal r_count : std_logic_vector (4 downto 0);
    signal r_strobe : std_logic := '0';
    constant c_zeros : std_logic_vector(r_count'range) := (others => '0');

begin
    SyncFinder : process(i_clock, i_data, r_strobe, r_count, r_last_data)
    begin
        if rising_edge(i_clock) then
            if i_data = r_last_data then
                r_count <= r_count + 1;
                if r_count = 6 then
                    r_strobe <= '0';
                end if;
            else
                if r_count > 21 then
                    r_strobe <= '1';
                end if;

                r_count <= c_zeros;
                r_last_data <= i_data;
            end if;
        end if;
        o_strobe <= not r_strobe;
        ot_last_data <= r_last_data;
        ot_count <= r_count;
    end process SyncFinder;
end rtl;

Seems like the if i_data = r_last_data then is under some race condition; being new to VHDL I don't understand what's wrong and how to fix this.


texts:
I am just beginning to understand how electricity really works. I understand there is voltage, amps, and resistance. If electricity is water, voltage is like the pressure of the water and amps are the amount of water flowing through a specific point in a specific amount of time. Resistance is like the width of the water pipe.

I also know that electricity must flow in a "circuit." Basically, around and around. In other words, it has to have somewhere to go. If there is no circuit, there is no electricity.

I also know that a MOSFET transistor is "voltage controlled" not "amp controlled." I also believe that a MOSFET works a little bit differently than a Bipolar Junction Transistor because the electricity from the gate does not actually flow to the drain in a MOSFET because there is an insulator stopping it.

However, this makes me wonder about the fundamentals of a "circuit." From what I have seen in some explanations of online simulations of CPUs, such as this blog post from Ken Shirriff, the wire that goes to the gate of a MOSFET stops after it gets to the gate. This makes me think there is no "circuit" for the gate wire of a MOSFET since it just stops.

I can think of two possible explanations for this:

If you connect a wire to the positive terminal of a battery, it has volts even though there are no amps flowing because there is no circuit. In other words, volts don't require flowing electricity to exist. This would explain why the gate wire of a MOSFET doesn't actually need a "circuit" to control the transistor.
There is actually a circuit, it's just that the wire flowing to the gate of the MOSFET is actually just an offshoot of another wire that is completing a circuit.

Can you please help me clear up this misunderstanding.


texts: Found this circuit for a 555 timer. I can't understand the use of the d-type flip-flop. Please explain.. And is the variable resistor used to adjust the frequency?


texts: Covering electronic device with plastic film wrap

texts:
I hope someone can help here with an electronics issue I have.

I am currently shipping an electronics device, an audio reel to reel to be exact. It was suggested that I wrap it in plastic film wrap, which I did. As I was wrapping it I started getting small shocks (not painful, but constant). I didn't realize there is anti-static film wrap, which is what I probably should have bought. I am now worried that I might have damaged the device by using static plastic wrap. It has been removed for the time being.

I have to questions:

Is it critical that I use anti-static plastic film wrap when wrapping electronics?
Is it possible that I damaged my device?

This is an expensive piece of equipment, so I am freaking out here. If anyone has any insight it would be really appreciated. Thanks for reading.


texts:
I bought a cheap USB battery pack to power a portable project.  It works great, except it shuts itself down if there's a current draw lower than a certain amount (haven't pinned it down, but I think it's around 60mA). Some of the time, my actual load is less than that (it's an arduino and some LEDs), although it can run quite a bit higher, too.

I can keep the battery pack on by just putting a resistor in parallel with the load, but obviously that's just burning power. Is there a simple-ish circuit I can build that would ensure that there's always a minimum current being drawn, but draw less or no current when the real load increases?  That is, if the LEDs were off, it'd be drawing 60mA, but if the LEDs were drawing 200mA, it wouldn't draw any current?


texts: FT232 Custom Display Name and Device Description

texts:
I have put a FTDI FT232RL onto a PCB to control a Microcontroller via USB. It's working fine. When I connect the board to my Windows 10 PC, the FT232RL is recognized as USB Serial Port (COMx).

I want to customize this name. I downloaded the FTDI FT_Prog utility, in which I could change the Product Description, Manufacturer etc. I successfully wrote the changes to the EEPROM according to FT_Prog.

This website described the exact procedure to follow, which I did, but in the Device Manager the name does not change (nor after reboot). I also checked the device name on a Ubuntu 18.04 device by running ltusb, but my custom name is not showed there either.

Can someone tell me if it is even possible to change this name on the chip side, without changing any local drivers? And if it is possible, how to do it?


texts:
This is supposed to be a followup to my previous question how to get a FPGA design that will definitely work on actual hardware. I have made a lot of progress since I asked the above question (thanks to amazing advices and comments). I have now moved on to designing much larger FPGA designs, and have learnt a lot, and am now facing much more difficult to solve problems (nothing that I don't like, but some occasional advice is always good).

I am now very familiar with the various design methodologies and practices that need to be undertaken while designing FPGA circuits. However, once in a while I manage to screw things up by writing something stupid in the code that costs me a lot of time and energy. Also, as my designs have been getting much more complicated (recently I have been working on using the Memory Controller inside the Xilinx Spartan 6 FPGA and writing a traffic generator for the same) and the simulation in Xilinx ISim now takes a hell lot of time (sometimes I have to wait for half an hour to check whether my design works, only to find that I made some stupid mistake, and start over again).

This has become frustrating now, and I need some advice. Until now, the fool proof plan I used to ensure everything in my design works properly was to check the value of each and every register and wire in my design and checking if their values are as expected, and sometimes looking at the RTL schematic. It has become very tedious now (because of the reason stated above) and I am wondering whether there are better ways to debug an FPGA design, and ensure that they work properly :

maybe a better way of debugging circuits
maybe a better simulation software

The advice that I have gotten on similar topics in the past has been gold, and I thank you all for your efforts.


texts:
I have a square signal (fixed but can be between 12MHz and up to 48MHz) and I would like to create every 8 clocks a pulse as brief as possible, no more than 1/4 of the period.

First, a couple of loose constraints:
- voltage is at 1.8V but I could have a shift level up to 5V if needed.
- I need the pulse every 8 times, but I would be fine with every 16 or every 32 times.

The key objective is to have the most SIMPLEST approach. Please avoid any answer suggesting a teraflop super computer!

Similarly, FPGA would really make sense but it's like killing a mosquito with a bazouka.

One option consists of using an Atmel 8-bit chip such as AtTiny85 but it's limited to 20MHz so I'm not sure if it could really work or not.

I have read this page with great interest: http://ued.udjat.nl/counter/ and I'm wondering if I could use a similar stratagem.

I prefer AtTiny because of the small package, then Atmel, then Cypress, then Microchip but I'm listening for any option. Is there any option to do something without a "micro processor"?


texts: Find out how much current a mains adapter can supply?

texts: I have a mains adapter without an enclosure which delivers 12V. Is there a way to find out how much ampere I can draw from it max/safely?


texts: I'm working on a project to control a TIG welder digitally. The dial that changes the main for the welder starts at basically 0v and at the top end gets to 8.52v. I'm currently using an Arduino that is externally powered to control an MCP4131, which then controls how much of the main amperage is used. The MCP works perfectly up until it gets to 5v and then dies (duh). What is a good solution for this? I need it to work at every voltage between 0-8.52v


texts:
This is my first ever posting on Stack Exchange so I’ll try to be thorough in my description.

I have some 18650 batteries that are about 18 months old. I have mainly used them in a gimbal for my GoPro and I’d say I’ve used that no more than a couple dozen times - so certainly not heavy daily usage. I charge them with a DFmicro Smart Li-ion battery charger I bought from Amazon.

I do have a bad habit of leaving the batteries in the gimbal after I’ve finished using it. On several occasions, I’ve found the gimbal to be totally dead. Last weekend we put the batteries fully charged into the gimbal. We didn’t end up using it but checked yesterday and the batteries were totally dead.

The charger refused to charge one of them at all - just said “Err” on the screen. I put my DMM across it and the battery voltage was 0.58V! To try and recover it, I set my benchtop power supply to 4.2V and held the connectors to the ends of the battery. It drew ~2.4A for about 15 seconds or so. I checked the voltage again and now the battery read 3.06V. Placing the battery back in the charger, it now started charging.

The other battery was recognized by the charger, which showed the voltage to be about 0.6V. However, even at a charging current of 0.5A the voltage rose quickly. In a few minutes it had risen to around 3V and continued to rise as it charged.

Questions:

Are both these batteries irrevocably damaged and hence should I just dispose of them?
If so, were these likely to have been faulty cells or did I damage them by leaving them in the gimbal for prolonged periods (or something else)?
What would cause an 18650 battery to drop to 0.6V and why does it rise so quickly when charged - e.g. even chemically, what’s going on?
Was it unsafe of me to “jump start” the dead battery using my benchtop power supply?

Thanks in advance!


texts:
I have a need to read out the flash memory of a read-protected PIC16F57 (this is for legal purposes). From my basic research, there appears to be no way of doing this short of decapping it and reading it out with a microscope, or selectively resetting the security bits with UV light by somehow masking out the rest of the die.

However, I've just contacted a company who advertises themselves as capable of dumping the flash off read-protected PICs. They quoted me $100 for a hex file. They claim a 100% success rate, so assuming they're not straight up lying, they can't possibly be decapping the chip, and instead must somehow be resetting the security fuses.

Is this possible? How? Or, like I suspect, are they scammers? Any way I can do what they're doing myself? I have 2 chips with identical firmware, so that gives me a little protection against frying it by dumb mistakes.


texts: Why is it that "a single supply voltage is seldom used for audio mixers"?

texts:
I'm reading "A Single Supply Op-Amp Circuit Collection" and in the paragraph about summing (page 9) I read "a single supply voltage is seldom used for audio mixers. Designers will often push an op amp up to, and sometimes beyond its recommended voltage rails to increase dynamic range".

Does this still apply? Do contemporary single-supply op-amps have limited dynamic range for mixing applications? If this is the case for how many channels does summing signal dynamic range need split-supply op-amps?


texts: What's the differences of these usage of PNP, NPN transistors?

texts:
I am reading the book Electrical Engineering 101.

When talking about NPN and PNP transistors, the book said this:

  Use an NPN to switch a ground leg and a PNP to switch a Vcc leg. This
  might seem odd to you at first. After all, they are both like a
  switch, right? Well, they are like a switch, but the diode drop in the
  base causes an important difference, especially when you only have 0
  to 5 V to deal with.

And below are the example pictures quoted from the book showing different designs with different robustness. But I cannot figure it out why.

Scenario 1

Scenario 2

Add 1

Thanks to Photon's reply, I found this reference: Active Mode of BJT.

There're 3 modes of BJT:

cut-off
active
saturated

If working in active mode, I think the voltage over Load is heavily affected by the Vin in ALL 4 pictures.

If working in saturated mode, I think the BJT are just switches and the voltage over Load are no different in each scenario respectively.

So how come the robustness difference?


texts: Low power, low voltage, slow (0.1Hz) oscillator?

texts:
I had the opportunity to analyze a very interesting circuit today using a programmable unijunction transistor as a timer.

The power supply varies, and the circuit must operate on under 10uA of current (not counting charging the cap).  It triggers an SCR every 10-30 seconds as long as the power supply is above 1.8VDC, and must operate across a range of 1.8 and 7.0 VDC.

The timing isn't critical - around 10-30 second intervals to trigger the SCR is fine (a short positive pulse). The lower the voltage, the longer the time interval is fine.

The kicker is the low current requirement (10uA or less), low voltage requirement (1.8V) and, as always, low cost (ie, replacing a 10 cent PUT with a 30 cent microcontroller would not be ideal).

What other options should I be looking at for a cheap, low current, low voltage, low accuracy timer design?


texts:
I am given the following problem:

When the switch S is closed, current I=(3-j) A. Find complex power of current generator Ig1, when the switch is opened, if it is known that when switch is opened, complex power of Ig2 is $$\underline{S_{g2}}^{(o)}=(10+j6) VA.$$
The following data is given:
$$\underline{Z}=(2-j2) \Omega$$
$$\underline{Z_1}=(1+j2) \Omega$$
$$\underline{Z_2}=\underline{Z_4}=(2+j4) \Omega$$
$$\underline{Z_3}=(2-j4) \Omega$$
$$\underline{I_{g1}}=(0.5+j1.5) A$$
$$\underline{E}=(7+j3.5) V$$

Circuit:

Attempt:

When the switch is closed, by using Potential of nodes method, we get the system of 3 equations with 4 unknowns, that is not solvable. If we use Contour currents method, we get the system of 2 equations with 4 unknowns, that is not solvable. In this case, we have the following unknown data: E2, E3, Ig2.

When the switch is opened, we get the same number of unknowns.

How to solve this problem?


texts: I need to connect to a Bently Nevada 990 transmitter BNC output but it is not isolated, would a galvanic isolator work?

texts:
I need to monitor the proximity probes on a steam turbine. Normally I would connect my datalogger to a buffered output using BNC cables. This turbine instead is using a Bently Nevada 990 transmitter. This converts the signal from the sensor to a 4-20ma loop fed to a PLC.
The 990 transmitter does have a BNC output for connection but this is non-isolated so unable to connect logger is case it interferes with the 4-20ma loop and cause trips etc. Bently Nevada did sell a unit that would connect to the BNC output and isolate this signal exactly for this use but this is no longer available.
The device performs the following functions:

Shifts the phase of the PROX OUT signal by 180 degrees
and changes the voltage from positive to negative
Isolates the transmitter from diagnostic equipment so that grounded equipment will not affect the transmitter's 4-20 mA loop

Am I correct in thinking that a standard voltage type galvanic I
isolator would perform the same function?


texts: Watchdog Signature in Flash memory or RAM?

texts:
We used to use Watchdog signatures in our control applications.

Basically we used to allocate a reserved memory in RAM(uninitialized) and used to store the watchdog signatures.

On power on, the system checks for the watchdog signature and based on that we used to find out whether it is watchdog reset or normal reset that has happened.

My question is, which memory is better for storing the watchdog signatures whether it is RAM or Flash?


texts:
When I was looking at someone's Verilog code, I found "+:" in Verilog.
It looks like an arithmetic function but I'm not sure. I never seen before. Does anyone know this usage?

Update:

csum= csum + one_cnt[i* ('DPC_shift +1) +: ('DPC_shift +1)];

I have a query, is this synthesiable?


texts: Replacing a charged capacitor with suitable components to form equivalent circuit

texts: If we have an initially charged capacitor (say 5V) and capacitance C, in a circuit, can we replace it with a constant voltage source of 5V and an uncharged capacitor with same capacitance C, both in series?


texts: Resistor for solid state relay (CPC1008N)

texts: I have solid state relay (CPC1008N) Dataheet here. What is the resistor I need to use to connect it to a power supply with an output voltage of 4.5 volts?


texts: Why "Supports 5V VCC operation" appeared in LVC family datasheets?

texts:
Looking into the LVC logic chip family I was aure that it is 3.3 V supply devices. One of our fellows also confirms it here. This manual dated 1999 states that LVC is 5 V tolerant (version A), but not that it can be powered by 5 V. This manual (dated 1998) states maximum absolute voltage to be 6.5 V for all the listed LVC chips, and operating voltage is 3.6 V max.

However looking through numerous "current" datasheets (example) I see this "Supports 5V VCC operation" statement, absolute maximum 6.5 V, but recommended supply voltage up to 5.5 V.

Is it that LVC family - new manufactured chips and old ones - was upgraded or certified for the 5V operation? Or maybe 5 V supply applies to 1G/2G devices only - and LVC without these grades are still 3.3 V?

What are the cons for using 1G/2G LVC family for 5V power systems? Spikes/oscillation above 5.5 V at the inputs? Anything else? Let's consider that 5V is well regulated.


texts: Selecting a ceramic capacitor: Rule of thumb for required DC voltage rating

texts:
What is the rule of thumb for the DC voltage rating when selecting a ceramic capacitor (MLCC).

Example: selecting a X7R decoupling capacitor, system voltage is 5V. Can I safely chose a capacitor with a DC voltage rating of 6.3V? Or should the voltage rating be at least twice or even more times as large as the system voltage?


texts:
I'm interfacing a dsPIC33EP512MC806 with a set of analog systems. The analog systems manage a battery and have vregs for the digital systems. The analog systems measure the voltage and current consumption of the battery providing feed back to the micro. The current is measured with a low quiecent current IC (ZXCT1010). The voltage is measured with a low quiecent current opAmp in a divide by four configuration.

It is the opAmp that concerns me. The digital side will get shut down by disconnecting power from the analog side. The analog side will remain powered on. Because the analog side remains powered on the opAmp still applies about 2.1 volts to the pin of the processor. When the processor is powered on there is no current or at least less than the meter can measure. With the processor turned off there is about 300uA of current from the opAmp into the pin. I believe that an ESD diode is being forward biased. There is a 1k resistor and a 0.1uf capacitor serving as a low pass filter. Also there is another 1k resistor serving as input protection to the pin. This makes for 2k of resistnace between the op amp and the pin of the micro controller.

I'm having a hard time finding any information on what the ESD diode can tolerate. Can the opAmp remain connected to the micro controller indefinitely if the micro controller is shut off?

simulate this circuit – Schematic created using CircuitLab


texts: I am trying to get a robotics club started in my school. But I am wondering if I started what could I get the kids to make. They would be aged between 14-18, some with electronics knowledge. So I need some cheap project ideas. I am looking for a project cost of about £3 per device, this only applies to specialised parts such as motors, relays/H-Bridges, sensors and materials for chassises. Other parts such as microcontrollers we have lying around.


texts: Add MIDI to music keyboard without disrupting its functionalities

texts:
As a DIY project I would like to add MIDI capabilities to my Yamaha PSR F51 keyboard.
I've found some projects on the Internet as this one, but unfortunatelly in this way the keyboard would not work as a normal keyboard anymore: its output would be only MIDI. My goal is, instead, to maintain its functionalities and add a MIDI USB port.
The keyboard's motherboard has one 13 pins ribbon cable going in and one 11 pins ribbon cable going out, which seems to suggest a 13x11 scan matrix.

Instead of using a couple of 74HC565 shift registers to send signals to probe which key is pressed, as in the projects I found, I am thinking to use some 74HC165 to poll what the Yamaha uC is doing.
Can it work? I should find out how the Yamaha MCU is scannig the keyboard. Is it something already documented somewhere?
Edit: after reading the comments I am thinking on a different solution: the new MIDI board should completely bypass the original circuitery when powered powered on. When powered off the keyboard should work as before. In this way I could follow the same approach of the one in instructiontables.
Can it work? How can I electrically isolate the original circuitry?
Edit2: I’ve found the service manual of a similar model and it seems that MIDI is already available via UART. I’ll give it a try with my scope.

Edit3: unfortunatelly I wasn't able to find where pin 54 goes. I should remove the ribbon cables from the board but I am worried about those molex connectors: they don't hold the cable well.

I cannot solder near the chip's pin, it's too small. I am afraid I should give up.


texts:
I'm making this circuit:

I've bought an Omron G5LA-1 non-latching SPDT relay. It looks like this (from the datasheet):

I'm struggling to figure out how I wire this up though. I believe I need to ignore a pin, but I'm not sure which. I also don't know what gets wired to which pin.

I have the circuit wired up with the power, tumbler switch, and capacitor so far.

The keyboard just looks something like this, where 2 of the 26 contacts would be connected:

Any guidance with figuring out what goes to which pin is much appreciated!


texts: ADM2483 or MAX485 Design: Modbus RS485 RTU bus in harsh environment

texts:
I'm currently out of ideas, i have a simple Wigoneer RS485 TTL interface (Sch link here) with MAX485 wired to my ESP32 based board, in my lab everything works like a charm with 1300 meters of CAT6 UTP Cable, but when i try to put in production with 800 meters of CAT6/FTP cable nothing works (using ModbusMaster library i get 224 error)

keep in mind that the cable it's placed in a cable duct with three phase lines, so it's a totally different condition instead my lab and it's placed in a harsh environment with motors, solder machines and so on...

Anyway, i've decided to redesign my RS485 breakout board using an isolated transciever, in this case the ADM2483: it's a good idea? maybe can help me to solve this problems that i'm encountering in harsh environments?

This is the schematic reference that i'm planning to use:

VDD1: 3.3V - VDD2: 5V


texts:
I'm curious about this comment. It says what

  ... in the US or UK you should be able to go to a hardware store and buy
  an outlet tester for very little money. This is a little plastic
  housing which plugs into a wall socket and has 3 LEDs. The pattern of
  which LED lights up will tell you if your wall socket is properly
  wired.

But North American standard power connector isn't grounded, so 3 LEDs looks too many for me. Moreover, there is Japanese version of this connector which is polarity-agnostic even!

What is "mains outlet tester" (for proper wiring) in the context of US power connector standard? What extra LED indicates? Am I correct assuming what Japanese outlets are not testable at all?


texts: What is the purpose of the capacitors on the input and output of this circuit?

texts:
In the circuit below,  I'm having trouble understanding the purpose of C1, C2, C12, C13, C14, C15.
The circuit takes a differential pulse input and has an amplified differential pulse output.
It's got a low pass filter in the front, so C1 and C2 kind of make sense to shunt some high frequency energy to ground. How do people even choose the capacitance value for caps for that purpose?
The output capacitors C12-C15 make less sense to me. Why is the output AC coupled?


texts: The purpose of getting IC temperature or the die temperature?

texts:
In a brief time of working with Electronics IC , I have came across various IC's that provide the temperature sensor inside the die for the access of Engineer or embedded programmer.

The recent one I came across is MPU6050, I ran some Google search and came to an conclusion that it is being used for Thermal Compensation in order to improve accuracy over the varying temperature.
What I want to know is, What exactly is the purpose of providing that information and what's the procedure to do it When one doesn't have an Hi Tech laboratory to take the IC reading @ Various Temperature?MPU6050 Datasheet


texts: Choosing the right MOSFET for 5V power relays

texts:
I am planning following circuit

PR_SIG: a 5V logic level coming from a uC
+5V: is powered trough a external power supply (max 10A)
Power_relay: 5V, needs 70mA to switch

My problem now is choosing the 'right' MOSFET. I used the search on Mouser using the parameters that come to mind:
 - Vgs = 5V
 - Id > 250mA (3x70mA when all relays are switched on)
 - Another parameter is the power loss, but can also be neglected

With my research I found two candidates
PMF250XNEX,
DMG1012TQ-7

Comparing the two both should work as switch but I am not sure that I consider all necessary parameters, since there are ~450 different MOSFETS which apply to my search.

Do I need to look at more characteristics or can I choose the MOSFET using only Vgs and Id?


texts: LTSPICE how to use the TSTOP and TSTART in Subckt?

texts:
For years I am using an automated potentiometer in LTSPICE that changes the position of the wiper from one side to another proportionally with time, I specify that time in two variables used in Subckt of the potentiometer, Tstart and Tstop. Those variables appear at the potentiometer.asy, so right clicking the part before the simulation I can change them according to my need.  That in fact work very well for observing as a circuit behave when changing something like that.  For other uses where a simple changing resistor value, I use a simple resistor and define its value as R=0.001+Time*10k, so if running a 100ms simulation, that resistor changes from 1mΩ to 1000.001Ω, what is neat for some testing and adjusting purposes.  This approach with the resistor works, but its value depends on time, and I need to pay attention, for example running a simulation of 1s and wanting the resistor to change from 100Ω to 1kΩ during this 1s, I need to enter the correct formula, such R=100+time*900.  This is not the case on the potentiometer subckt, since its total value is already defined, the change of the wiper must happen within a specific period of time, not just "time".  What I wish is for the wiper to swing from 0 to 100% for the simulation time specified at the .TRAN

So, it is possible to use "time" as a value into a subckt calculation, what else can we use?

Now, I wish to use the potentiometer TSTART and TSTOP variables at my lib (potentiometer subckt) to copy the values stated at .TRAN "tstop" "tstart"...
How can it use those values if I omit them at the ASY?

The potentiometer subckt used is:

.subckt potentiometerx 1 2 3

.param TFTI=Tstop-Tstart

R1 3 2 R={if(time>Tstop,Rtot,Rtot*(time-Tstart)/TFTI*int(0.9999+((time-Tstart)/TFTI))+1m)}

R0 1 3 R={if(time>Tstop,0.0001,Rtot-(Rtot*(time-Tstart)/TFTI*int(0.9999+((time-Tstart)/TFTI))+1m))}

.ENDS potentiometerx


texts: Exam Question : Using a 74163, implement the following counting sequence

texts:
During a past paper this question was given
Using a 74163, implement the following counting sequence

Professor also added his own solution can be seen here :

Can anybody explain to me thoroughly how can i reach the same answer?
Thanks in advance.


texts: Looking for advice on how to move stepper motor on TTL signal reception?

texts:
I have a full-blown motor controller that moves a stepper motor ; it is able
to receive a TTL signal (3 volts, raising edge) to trigger a +500 steps
motion on the stepper motor. It is also able to do a home signal search to
put the system at a known position.

EDIT: the stepper motor is bipolar, 2000 steps for 360 degrees

Speed and acceleration are fixed, and configured since the beginning.

This motor controller is quite expensive and I have the feeling the same can
be done very easily with another piece of hardware ; but I have no idea
where to look for.

I am a software engineer so I don't mind having to write some code to make
it work.

I looked at a Wago controller ; I imagine a lot of simpler alternatives exist.
I am looking for a simple
stepper motor controller with external TTL input to trigger a configured
motion, or some more DIY solution.

It seems I can also use something based on a Raspberry PI: https://www.pololu.com/product/2753


texts: TLC 5940 PWM driver blank input and pull-up resistor

texts:
I've read some of the data sheet for the TLC 5940 and it states the following about the BLANK input:

  Blank all outputs. When BLANK = H, all OUTn outputs are forced OFF. GS counter is also reset. When BLANK = L, OUTn are controlled by grayscale PWM control.

Looking at this image:

... from the Arduino playground about using the TLC chip with Arduino it shows a 10k pull-up resistor to reset the chips when the device is turned on.

I read about pull-up resistors so I get that when power is supplied the resistor allows BLANK to read a high input. What I don't get though is how the chip works after that. I don't see anything that sets BLANK to low.

How is the BLANK input getting set to LOW so the device can operate normally?


texts:
Everything is in the title. Let's say I design a PCB layout. It has 4 layers. How do I decide:

The material to use for the PCB (difference between FR TG 130, FR TG170, Aluminium, or other materials)
PCB Thickness (I suppose this is partially dictated by the stack and by requirement of potential impedance matching, but does anybody can explain with an example?)
Surface finishing (when to use HASL vs ENIG, vs OSP vs Gold or vs Immersion tin)
Copper weight (1,2,3,4 oz)

Thank you in advance for your help.


texts: 30 minute timer that has normally closed circuit. It goes off when timer activated

texts: I need normally closed timer that I can set to turn lights off for 30 - 60 minutes then have them come back on. when timer expires.  This is a situation where we have a motion detection light that comes on as it should but clients wants to be able to disable (turn off light) for 30 to 60 minutes.  Don't want to disable the motion sensor as it would not be re-enabled.  With a timer they won't worry about motion sensor not working the next time, timer would re-set it.


texts:
I have made a button box, using an Arduino mini pro, which includes LEDs and buzzers. I am using a shift register (74HC595) with a ULN2003 (to use 12v on the LEDs) to decode the SPI.

See the top right in: (sorry about the schematic, but I am quite new to electronics.)

Click for magnified view.

When I power it ON, the buzzers beep (most of the time).  But if I do a reset on the Arduino mini pro, using the reset button, then power OFF, and then power ON again, there is no beep.

I have reduced the Arduino code to the minimum to try to figure out why this is occuring. If I do the following, the beep does not stop:

const int SS10 = 10;
void setup() {
 pinMode(SS10, OUTPUT);
 digitalWrite(SS10, HIGH);
 SPI.begin();
 SPI.setClockDivider(SPI_CLOCK_DIV16);
}
void loop() {
}

Can it be that on startup, the SPI is using a setting it had on the most recent power off? Can it be inrush current flowing through the buzzers?

Any help would be greatly appreciated.

Here is the schematic on which I based my use of the ULN2003. It is from the datasheet.

Thanks in advance.


texts: How do I measure the characteristics of a voltage divider in a QUCS simulation?

texts:
How do I measure the characteristics of a voltage divider in QUCS?

Below is what I have tried thus far, using Qucs 0.0.15 on Ubuntu 10.04

I want to measure how the voltage at the center of a voltage divider changes based on R2 in the schematic below.  I am attempting to simulate this in QUCS using a DC simulation and a parameter sweep.

This is how I have it set up below, but the output is constant from what I can tell, which does not make sense.


texts: Maximum SPI clock speed specified in data sheet

texts:
For integrated circuits that use SPI interface, they specify maximum clock frequency in their datasheets such as attached below.

The question is that if the datasheet speficies the maximum frequency as 6MHz, can I decide that it will be safe to set up clock speed exactly at 6MHz(accuracy determined by crystal used for MCU)? Or It is safer to have some margin?


texts:
This seems to me like a pretty silly question, but how would I go about drawing thermal vias under a thermal pad on an LED in Eagle CAD 6.5?

I am using the Phillips Luxeon T series which has an electrically isolated thermal pad.


texts: How is energy consumed in a PN junction?

texts:
In the schematic above, there's a PN junction with a source \$V_d\$, the barrier potential \$V_J\$, contact potentials \$aV_{J0}\$ on the P-side and (1-a)\$V_{J0}\$ on the N-side. \$V_{J0}\$ indicates the barrier potential of the PN junction with no source connected, \$V_J\$ the barrier potential with this source present and 'a' is a fraction in \$aV_{J0}\$.

How can we interpret the whole circuit in the point of view of erergy-providing and energy-consuming?

1)  There are voltage drops \$aV_{J0}\$, (1-a)\$V_{J0}\$. Does that mean a test positive unit charge will "loose" energy while going from the (+) side to the (-) side? If so, in what means does the test charge get it's energy? What kind of form of energy is it transferred to?

2)  Across the depletion region from P to N-side, there is an electric field pointing to the P-side. I guess there must be a reverse electric field acting on a test positive charge for it to pass through the build-in field. Where does that reverse electric field come from?

3)  If the external source \$V_d\$ > \$V_{J0}\$(the barrier potential of the PN junction with no source connected), will there still be a barrier voltage inside the PN junction?

Thank you!


texts: Thurlby PL310 bench power supply: what does these resistors do?

texts:
I have an issue with my PSU showing 'ofl' on its voltmeter, despite the output working fine.

Could you explain to me what the resistors in the red box are for and why it needs them?