texts: GND vs COM? Which one should I connect the ground to?

texts:
I have a cassette in my car, I was using a cassette-aux adapter to play music through my phone. It looks like this:

After searching a bit about how it works, I found out that it's nothing but a tape head that is connected to an aux cable. By having the two tape heads close to each other, the signal is transmitted from the first to the other.
I believe this will pick up some noise along the way, so I decided to solder the aux wire directly to the cassette where the tape head is soldered. This way, I don't have to use tape heads at all and have a cleaner signal.
When I opened the cassette, I saw that there are 6 points to solder to:

RL (Rear Left)
RR (Rear Right)
FR (Front Right)
GND (Ground)
FL (Front Left)
COM (Common)

I'm not sure if I've understood correctly.
Here is what I found:

I'm planning to solder the aux cable as follows:

Right to RR and FR
Left to RL and FL
Ground to ??

Where should I solder the ground? Should I solder it to both GND and COM?
How should my wiring be?


texts:
I've been trying to connect a 2+ meter wire to a nema 17 motor.  Usually the motors I buy come with a 1m cable, which is too short for this application. The Nema17 needs a 4 wire connection.  So I figured I'd just use a normal 4 conductor 20awg insulated wire and attach a 6-prong jst ph connector on the end which mates with the connector on the stepper I bought.
I am noticing that many stepper motor's external wires are 4 conductors but they are all side by side (like picture below) instead of twisted and insulated together like I am accustomed.  Is there a reason for this, or are the manufacturers doing this just because it's cheaper.


texts: How to go on from here (Thevenin circuit)?

texts:
Basically, I've discovered the "total" resistance, being 6/11 Ohms. Same resistance would be found in Norton's circuit.

Now, I know that the sum of all voltages should be zero. I was thinking to go with 2.2-1*I+11-1.2*I=0 and get I=6A (1.2 is the total resistance of the resistors of 2Ohm and 3 Ohm which are in parallel). But if I do get I to be 6 A I can't find Vth to be 10.2V.
Could you help me?

PS: This is NOT Homework


texts: Boost Converter Stuck at Around 80 Volts

texts:
I'm building a boost converter that utilizes a 555 timer switching at 60 kHz at a 96% duty cycle which drives an IRF3205 MOSFET to power a hand wound inductor (calculated to have ~330 uH) with a 6A10 diode and a 400 V, 80 uF capacitor at 5 volts. My goal is to achieve 360 volts.

The problem I'm having is that the circuit consistently maxes out at around 80 volts and attempting to increase the voltage e.g increasing the inductance of the inductor by adding an iron rod, adding another inductor in series, increasing the duty cycle of the 555 timer and even increasing the voltage has no significant effect on the voltage. I can only lower the voltage using these methods.

I think it may be because of the diode limiting the current as replacing the 6A10 diode with a higher resistance one seems to decrease the voltage to ~60 and further attempts to mess with that also fail.

I do not have any more diodes that I can use and so I am wondering if it is current available to the inductors which is limiting the output before I buy any more diodes.


texts: Similarities between flash memory and a camera flash?

texts:
This story is repeated in a number of places. What about flash memory would have reminded him of a camera flash?

  The name “flash” was suggested by Dr. Masuoka's colleague, Mr. Shoji Ariizumi, because the erasure process of the memory contents reminded him of the flash of a camera.

https://books.google.com/books?id=abfBAAAAQBAJ&lpg=PA6&ots=gd_v3zpNPg&dq=name%20flash%20suggested%20mr%20shoji%20ariizumi&pg=PA6#v=snippet&q=%22flash%20of%20a%20camera%22&f=false


texts:
I know this question is asked a lot and answered well in many posts, however, I'm still confused.

A switch transistor works by using a semiconductor to pass the current from an emitter to a collector, thus opening the switch, by applying a current to the base.

I understand this, however, I don't get how this removes the need for human interaction. What/Who applies the current to the base to open the switch?

I'd like to know how this works on a larger scale, but if I can't get my head around one switch then I don't think I can proceed.
Thank you.


texts:
I have been given a circuit and asked to find the voltage across the diode (both the DC and AC parts).

I believe the right approach is the ignore the ac source initially and find the IDQ. I know there is 0.6 V across the diode so I found IDQ to be 14.4 V/1 kΩ = 0.0144 A by analyzing the resistor.

I know there is an equation for dynamic resistance: $$r_d = \frac{nV_T}{I_DQ}$$ I am given n = 1 and VT = 26 mV so I get rd = 1.86 Ω. I interpret this as: in this setup, because the ac signal is small and the diode will always be forward biased, we can effectively treat the diode as a resistor of value rd.

But if I look at the voltage across the diode at the Q point using the voltage divider: $$V_D = \frac{15r_d}{r_d + 1\mathrm{\ k\Omega}} = 0.028\mathrm{\ V}$$
But it should equal 0.6 V. Have I done something wrong in my calculations? Or am I interpreting rd incorrectly?

I know I haven't finished the given question yet, but I thought I would make this check and it would show me if I am on the right track or if I have already made a mistake.


texts:
So I was implementing a 16-bit square root function using this algorithm.

The components contains several 8-bit multipliers and 16-bit comparators, with gates addressing the cycle mechanism mentioned in the algorithm. Here's the highest level schematic:

All ARGs are exactly the same (The first one looks a bit large, but still the same):

On the top right is a 16-bit comparator, nothing wrong with it. The error is in the lower left 8-bit multiplier.

As you can see, one of the output wire is red, indicating some errors.

It turns out that it was from one of the full adder in the 8-bit multiplier, as such:

1.

2.

3.

How come the output of that particular Full Adder becomes blue(unkown)?

After I investigate that full adder, all its wires are blue, which makes little sense to me, since its inputs aren't unknown at all!

Here is the circuit file.


texts: How to use and bias LM285 shunt voltage ref for virtual ground?

texts:
I'm adding a lab to my course, unfortunately at the last minute.  I'm going to have them work on a single-sided biopotential amp, working off a 5V supply.  I guessed at parts I'd need, and got LM285 2.5V shunt voltage refs, and now I have to figure out how to use them.

I'll be using them to handle Vref on AD623 instrumentation amps, and as a virtual ground for filters and subsequent gain stages.  For the 623 Vref needs, I figured on buffering the LM285 with a follower (100mA capable output on op amp), but I'm not sure I need to.  I suppose I can do the same thing for the virtual ground point.

Does this approach sound OK?  How would I choose a bias resistor for the LM285?


texts: How much current will LM317 pass in this circuit?

texts:
The formula for the output current of a LM317 is:

In this schematic, what will the output current be?

simulate this circuit – Schematic created using CircuitLab

MY approach:

I thought R in this formula is the resistance LM317 sees. so I should calculate the whole resistance. it will be:

$$\left( \frac1{R_1}+\frac1{R_2+R_3}\right)^{-1}$$

but how can I neglect the node R2-R3 which current is being sunken through?

So I tried Delta-wye conversion :

$$R_{13}=\frac{R_1R_3}{\sum R_{\Delta}}$$
$$R_{12}=\frac{R_1R_2}{\sum R_{\Delta}}$$

So  the resistance LM317 sees will be R13 + R12.

Which approach is correct? Am I right at all?


texts: Radioshack's theremin circuit - how does this work?

texts: Can anyone explain why this works? What's going on? I built this kit today and it works great, but I don't fully understand what each part is doing. Is the 555 timer being used for pulses or ossilation? How's that working? And what are the other capacitors doing? Can anyone give a simple explanation of this circuit? See attached image. Thank you!


texts: In this transistor circuit, what is the purpose of the diode across the motor?

texts:
I am trying to follow an Audrino tutorial with my kid and I am confused by the role of the diode in this circuit.

In particular, I have the following questions:

It looks like the circuit will work without the diode. The purpose seems to be to allow the current flow from the pin9 power source, but why do we need that?
Does current flow from pin 9 through the emitter to the ground?
More generally, when someone says “the current” is in this direction, do they mean that is the + => - direction, or the flow of the electrons?


texts:
I want to build an RTC clock for the Raspberry Pi. Adafruit has a guide to accomplish this with Dallas DS1307. On the schematic they put a 2.2K resistor between VCC and SCL and do the same for VCC and SDA. SQLW is just wired out. But on the IC's datasheet, the resistors are proposed to be elsewhere:

Serial Data Input/Output. SDA is the data input/output for the I2C serial interface. The SDA pin is open drain and requires an external pullup resistor. The pullup voltage can be up to 5.5V regardless of the voltage on VCC.
Square Wave/Output Driver. When enabled, the SQWE bit set to 1, the SQW/OUT pin outputs one of four square-wave frequencies (1Hz, 4kHz, 8kHz, 32kHz). The SQW/OUT pin is open drain and requires an external pullup resistor. SQW/OUT operates with either VCC or VBAT applied. The pullup voltage can be up to 5.5V regardless of the voltage on VCC. If not used, this pin can be left floating.

So the question is: why there is a resistor at SCL and why there isn't any at SQW?


texts: Slew Rate and Bandwidth of Transistor Amplifier

texts:
How can I calculate the slew rate and bandwidth of a typical transistor amplifier such as the following? What are the parameters I need to consider?

simulate this circuit – Schematic created using CircuitLab


texts:
Can somebody enlighten me on when and how much current flows in/out of the supply and/or ground leg of an opamp?

What happens if there are resistors in those legs?

Update 1:
Here is the circuit that sparked my curiosity: (from the opamp's datasheet)

Thanks to Jason's answer I understand how the circuit works to create the output but I am not clear on how the clipping voltage can be found.

Also: why does clipping occur at all - rather than the opamp just switching off due to a supply range that is too small?

I.e. The max sink current is 500µA. Assuming a very large Isense, this means max(Vout) = RB*500µA: this can easily be 5V. Assuming Vsupply = 3V, this should push the supply range quickly below its required minimum and switch off the opamp. - Resulting in a on/off oscillation, no?


texts: Why does reflection off a PCB via look like this?

texts:
My question is related to http://mobius-semiconductor.com/whitepapers/ISSCC_2003_SerialBackplaneTXVRs.pdf.

On the page 18 there are a few figures of "TDR off Diferent Types off Vias". I am confused regarding the capacative, inductive and L-C-L titles under the different vias. What is the explaination for why graphs look the way they do? What is the meaning of the titles gives under the graphs? I am not sure why one is capacative and another is inductive and another is L-C-L. I am also not sure as to what blind via and counter boring means.

I do know somewhat about transmission lines and matching impedance, but I have never encountered these type of graphs and reflections at vias before.


texts: Multiple transformers to generate high voltage

texts:
I'm trying to generate high voltage from a 5 volt battery source.
Currently I have some normal transformers from my old devices that I think can transform 5V to 220V. If I connect several of these transformers together can I reach very high voltage?  For example: 5V * 44 = 220V, and then 220V * 44 = 9680V?


texts:
I am working on a project using a microphone/microcontroller combination to detect if a clap has occurred.

Thus far, I am using the Electret Microphone Amplifier - MAX4466 with Adjustable Gain from Adafruit, which uses a CMA-4544PF-W Elecret Condenser Microphone as well as the MAX4466 LNA.

For this project, I need to be able to detect claps from up to 30 ft away. After some testing with the microphone on maximum gain, I found that the microphone can certainly pick up sound from that distance but only strong, loud sounds. Thus, I am inclined to believe that I need a bit more gain from my microphone.

I don't know too much about audio amplification, and am curious what direction to proceed in. I would estimate that I need a gain in the ballpark of ~6dB-20dB ON TOP of the already existing microphone amplifier that I linked above.

Thus far, my thought process has led me to 3 options:

Cascade another LNA with the current amplifier.
Use a single-ended op-amp with a low gain. My logic here is that an LNA in the adafruit mic/amp has already amplified the signal ignoring as much noise as possible, I could possibly just use a standard amplifier at this point.
Use a completely different LNA with higher gain with the microphone. This was my first idea, but I was finding that the MAX4466 already has a gain larger than most of the other LNA's I was looking at.

Any input or other ideas would be appreciated!


texts: Cost effective way to protect circuit from overvoltage

texts:
Which is the most cost effective way to protect a DC circuit that requires 5V input (and draw up to 1A) from external power supply?
Suppose that a careless user can accidentally attach an external power supply and power up with 6-9-12-24V, this situation can literally blow up my circuit!
This can appear to be a silly question but i don't have any ideas!


texts:
I need to find a solution to start a relay with a momentary pushbutton and stop it with a hall sensor. The rellay would control ~1000W.

I was thinking of two possible solutions:

analog: pushbutton activates latching relay and hall sensor deactivates it.
digital: pushbutton tells microcontroller to latch regular relay until the signal from the hall sensor is detected.

I was also thinking to add a short delay when the hall sensort triggers and I guess in the first case I could do it with a 555 timer and in the second case, it would be easy to do that in software.

What is the recommended way to do this? Does anyone know if an off the shelf solution exist for something like this?


texts: What is the usage of the negative voltages on a PC motherboard?

texts:
What is the usage of theses negative voltages? Are they there only for backward compatibility?

In nowadays PC power supplies, we have:

+12V
+5V
+3.3V

but also:

-12V
-5V

But the current rating of the negative rails are much smaller than the positive ones.

If we were back to the 80' where op-amps were always powered symmetrically at +12V -12V: Okay.. But nowadays, almost everything you may find on a motherboard is digital logic only powered by positive voltages.

Except for the RS232, which is an almost obsolete bus, I don't see any reason for having negative rails distributed by the power supply.

Because it's very high volume, I suppose that cost drives everything here. Thus, why each PSU has to deliver those voltages if they are barely used ? (the very low current rating of the negative rails of PSUs let me suppose this).

Wouldn't it be less expensive to let every hardware provider to add their own embedded SMPS when a negative voltage is required?


texts: STM32 UART reliability with high baud rate

texts:
I am using STM32F4 (bare metal with HAL library) as an HTTP Server. I don't implement TCP layer, because that is done for me by the WiFi232 D2 module - all I receive in the uC through UART is a string with pure HTML request (and all I send is a string with pure HTML response). The requirement of the application is to send one large response with SPA web page (almost 300k characters) and several tiny responses as AJAX (~200 chars). With 57600bps all works fine, but the big response takes 50s to load on the client, so obviously I have to raise the baud rate.

That was the scenery introduction, now the main play, where the problem begins: with everything above 57600bps, I loose message characters on the way to the browser. I loose them randomly - it's usually a row of contiguous characters; sometimes several, sometimes above hundred of them. Initially I played with blocking UART transceiving. When I noticed the problem, I changed for DMA and it made absolutely no change. I tested both cases sending through UART to FTDA -> USB -> Termite terminal instead of the WiFi module, and saw the same symptoms. Since every single simulation lead to the aftermath of lost data, I went to the extent of even crossing STM Tx with Rx and checking if everything works okay on the shortest of possible circuits and... it of course worked perfectly :) So the uC is excluded from the suspects.

So is it even possible to achieve reliable UART transmission? Do you have any clue for how to send HTTP msgs by UART at high baud rates? I feel that I exhausted all the possibilities, but it seems unprobable that 115kbps is to much, not even mentioning Mbps... Maybe I'm missing something simple? Applying hardware flow control corrects the transmission only a tiny bit, I still get errors on 115kbps (although less frequently then without it).

*Note, that I keep talking about HTTP msgs, because of their particular nature - I can't implement any framing nor software flow control algorithm, because I don't have power on the browser side of this communication chain.

EDIT: Some more observations:

With RST/CST flow control I can see a pattern in transmission (@230kbps): contiguous ~45056 OR ~28672 characters are sent correctly, then I loose a couple of characters, and then again - ~45056 OR ~28672, then loose couple of chars etc. Note, that the number of contiguous correct characters is always one of the two mentioned (+/- a couple).
Without flow control I (as anticipated) get the following pattern: transmit EXACTLY 8191@115kbps or 4095@230kbps contiguous correct characters and then loose around 90@115kbps or 110@230kbps characters. What is strange though, is that I don't loose characters in any other spot...

In accordance to those observations, I prefer to use no hwfc and simply add some delay at the well-known spots (after every 8191st or 4095th char, depending on the baud rate). However this is very hackish, I hate this solution and I hope there still is some better way to solve that problem.


texts: Digital circuit to sense both high side and low side switches

texts:
Currently, I have a digital circuit running parallel to a LED to measure if it is driven high, with a zener clipper circuit to clip the voltage to 3.3v (max safe for microcontroller).

Current circuit is:

This senses if S2 is closed but does not check if S1 is closed.

I want to have a digital circuit that checks if both S1 and S2 are closed.

Thanks in advance


texts: Determining how to make 7 wire DC motor run?

texts:
I have got these motor. I wanted to make it run. It has 7 wires.

The only information i got online is from its similar model: http://www.dhgate.com/store/product/original-ebmpapst-r1g175-af33-06-12v-120w/202162639.html

Which tell me that its centrifugal blower wheel and it has 7 wire termination.

The thing that confuses me are the colours of wire. It has 2 red and 3 blue wires. How to make the connections to run it.

[

]1


texts:
I am using this circuit to supply current through R1 which is a 50Ohm coil. Opamp is Lm124 supplied as shown in the schematic. Vin is a voltage that can be between 2.5V and 3.5V. Everything works fine except when Vin is between 2.8V and 3.1V. In this case the output of the opamp gets really noisy with constant noise exceeding 500mV which makes measuring the output voltage with an adc impossible. Did anyone encounter something similar or sees where the problem is? I already changed the opamp and checked all connections and everything seems to be fine. A 100pF capacitor over 100k reduces this but it is far from enough. Does anyone know other circuits that could achieve this voltage dependent bidirectional current through R1?

simulate this circuit – Schematic created using CircuitLab


texts: How does USB Type C handle reverse polarity / signal duplication

texts:
The new USB Type C connector doesn't have a physical reverse polarity protection any more. You can plug it in any way you want on both ends, there is also no A and B end any more, it's all the same.
So how does this new USB type handle that the polarity doesn't end up being reversed or signals being routed to the wrong point?
Is there some sort of routing going on in the connector and the devices don't have to handle anything and can be sure the polarity is always correct?
This is assuming that not half the signals in the cable are redundant.


texts:
I am looking for different option of interfacing to the JTAG port on a PogoPlug board. I have found the picture below which has silkscreen (my board doesn't),
I have used JTAG before, but it was built into the board (using an FTDI chip).

I am not quite sure what type of dongle can I possibly purchase.

I also have a few devices which could be made to do the job, I think I could use
usbprog-jtag code on an Arduino, however that will also require a level-shifter (which I don't have). I have a few other devices, including an mbed board
(cortex-m3) and an Econotag (arm7).

Is there a cross-platform example that I could compile with a customized GPIO mapping header and use that with OpenOCD?

I don't have a parallel port on my new machine, though I don't really feel like
fiddling with parport any more, a USB dongle device is a preference really.

I know that FT2232 chip can be used for JTAG using libftdi, however I only have
a FT232R cable, I suppose that cannot be use really, is that right? Though I manged
to run bitbang command from libftdi. Probably the FT232R is missing some important pins that would make it usable as JTAG tool ...

Update 1: I have had a conversation with one person who suggested that there should
be a way of using FT232 in bitbang mode, since you can set TX/RX to be GPIO and
apparently this blog describes how to use the FTDI cable as AVR ISP.


texts: Is there a maximum amount of time a circuit or system is allowed to have a short circuit present? I'm asking this because I'm thinking about how fuses and Over-current IC's perform. There is a set amount of time where the circuit will be outputting more current than it should with these type of devices, so I was just curious if there was some kind of rule of thumb to follow when designing a Over-current or Short Circuit protection circuit.


texts: Why are constant current drivers 10% less efficient than constant voltage drivers?

texts:
I want to drive a CREE XP-G3 LED with 2.73V, 350mA. My power supply is a car battery (10.5-14.5V).

I went to the Texas Instruments website and inputted the above specs into their WEBENCH designer, once for a constant voltage supply and once for a constant current supply. The constant current regulators topped out at 83% efficiency but the constant voltage ones reached 89%+ I looked on Digi-key for non-TI parts and it was a similar story for my specs.

Is there a fundamental architecture difference between constant-current and constant voltage regulators? They both look like their feedback input is just a voltage.

If all my Cree XP-G3 LEDs are the same, can I just use a constant voltage supply tuned to 2.73V?

Constant voltage:

Constant current:


texts: Need help identifying antique porcelain fuse block

texts: This is an antique 30 amp porcelain fuse block from a house, built before electricity, that was first wired around 1900. I would like to identify the manufacturer and the year of manufacture of this fuse holder. The reason I removed this from the house is because I am trying to identify the exact year this house was first wired and I had read somewhere that some of these fuse blocks have the year of manufacture written on them, but this one doesn't. If I'm not mistaken, most home electrical systems were 60 amps at this time, and so I assume there was (or still is) another one of these somewhere else in the house (it was located about 15 feet from where the power appears to have come in, but didn't appear to have any wires above 14 AWG connected to it). I assume that number on the back is a serial number.


texts:
What is the difference between reading PORTA and PINA?
What is the relation between a port and its pins?I'm really confused!!!
sample of reading PORT:(reading pin is not useful here)

Assembly
f=1MHZ
ATmega8
I need to complement PORTB every 1ms.(Dutycycle=50%)

    LDI R16,$FF
    OUT DDRB,R16
    MAIN: LDI R16,00
    DELAY:CPI R16,200
    BREQ LOOP
    INC R16
    RJMP DELAY
    loop:IN R17,PORTB
    COM R17
    OUT PORTB,R17
    OUT R17,PORTB
    RJMP MAIN


texts: Controlling electricity flow via MIDI to power lamps

texts:
I'm looking to build an interesting lighting rig comprised of lampshades for my band. Here's an image of what I want to achieve:

I have Logic pro running in my Macbook pro. I want to create MIDI tracks that control each lampshade.

I'm looking to map each lampshade with a corresponding note. So that when I play a MIDI track, each lampshade will light up when a note in the MIDI track is played.

Here are some things that I want to achieve as well:

Accept MIDI velocity parameters (0 - 128) to determine lampshade brightness and fade-ins/outs
Allow combinations of notes (e.g. playing C#1 and E#2 at the same time will trigger two lampshade simultaneously).

Here are my questions:

Is this feasible?
What's the best way to get started?
Is there a concern for blowing any fuses with this setup? (We plan to play in several clubs)
Are there any methods I should consider, or things I should be concerned about?
Do you have any ideas to make this lighting rig much more interesting?

I have some previous experience with Arduino. It's mostly lost to me now, but I'm willing to get back to it.


texts: What is the difference between EEPROM Data Memory and RAM

texts:
Since a few days I've been messing around with PIC microcontrollers and a Pickit 3. I was writing some test programs in MPLAB where I came across a nice statistics chart like this here:

After making some variables and expanding my program, I noticed the "Data 25" part to increase. After making some integer arrays and compiling those the data was 100% and the program couldn't compile because of insufficient memory. I unfortunately do need this extra memory to finish my program.

Here I come to my first questions

Is it true that the Data 25 equals the variables used?
Is it true that the Program 512 the amount of memory used to store the program?

These are two side questions I have, here comes my main question.

Assuming my two statements were true, I headed to the microchip website to look for a chip with more Data (RAM) available. Here's where I looked. As you can see there is also a column which says "EEPROM Data Memory".

My question is: What is the difference between Data (RAM) as shown in the picture and this EEPROM Data Memory? What is the EEPROM Data Memory useful for? I'm new with electronics and have been messing around with a pic12f508 so far. Hope someone can clarify this for me since I don't understand this concept. Thanks!


texts: Triangle wave input with Zener and diode

texts:
I've found a problem posted as a question in one of the past exam periods. I've tried reviewing it with my peers, and we all get to different results, which makes me think my understanding is compromised. I've posted the circuit below. The problem states that Vi is a 10V triangle wave generator, the resistors are all 1KΩ and the required potential for the Zener and diode to conduct are 3V and 0.7V, respectively. We need to calculate Vo as the voltage drop output at R3, and draw the output graph.

simulate this circuit – Schematic created using CircuitLab

My issue lies with understanding when a diode in series actually conducts. One of my peers insists that D2, for example, conducts for Vi > 0.7V. However, I don't see how that's that case -- isn't there a voltage drop across R2? Can you help me understand the logic behind it so I can attempt my own solution? There is no similar example for me to study in the textbook.

Thank you.


texts: Delayed, active low, short pulse for reset

texts:
I am attempting to create a circuit using a TUSB2036 usb hub IC that automatically starts when it is powered on.

The datasheet states for the inverted RESET pin

  RESET is an active low TTL input with hysteresis and must be asserted at power
  up. When RESET is asserted, all logic is initialized. Generally, a reset with a pulse width between 100μs and 1 ms is recommended after 3.3-V Vcc reaches its 90%.

My understanding is that this means I have to supply a delayed (to allow the power to fully initialise), active low (because the RESET pin is active low), ~1ms pulse that is triggered when the power is connected. Is this correct?

If so, how would I go about doing this? I have tried using a 555 timer but I can't get it to work. I tried looking up monostable 555 timer circuits but they all the ones I found are effectively pulse extenders which is not what I need. I also found this question that also used a 555 timer but I was unable to use the circuit in the answers to generate a pulse that is short enough.

Is using a 555 timer the way to do this or is there a different IC that do this simpler. I don't really have any particular constraints apart from the usual cheaper and simpler.

Thanks.


texts: Confusion on the purpose of using active current-meters

texts:
I was reading about current to voltage converters and simple opamp current-meters.
I found myself in confusion comparing them to passive current meters.

Active current-meter:

As you see above the Iin passes through R and the voltage drops to -Iin*R as Vout. So Vout is linearly changing and with Iin.

And below is measuring current without an opamp:

Passive current-meter:

Above the same logic, the Iin passes through R and Vout is linearly changing with Iin.

Can someone explain what is the point/benefit to use opamp here? What is the advantage of using opamp/active version over the passive one?


texts:
As part of my current project I need to ensure that my MCU (namely PIC18F4520) runs smoothly, minimizing the possibility of any interruptions. The datasheet specifies that a series resistor, Rs of value 330 ohms, should be used for AT strip-cut crystals.

  A series resistor (RS) may be required for AT
  strip cut crystals.

  If HS is
  selected, it is possible that the gain of the
  oscillator will overdrive the resonator.
  Therefore, a series resistor should be
  placed between the OSC2 pin and the
  resonator. As a good starting point, the
  recommended value of RS is 330Ω.

By my understanding, AT strip cut crystals can be (generally) identified by square shape. I'm using ACT HC49/US. The datasheet, sadly, does not answer whether the crystal is AT strip cut or not. Hence my question: is it? And is 330 ohms a suitable value to be used?


texts: Will mains kill me if I'm using an adapter?

texts: I'm sorry this is an ignorant question. I am working on hooking up leds for my raspberry pi. I keep hearing about mains power and how dangerous it is. I'm using a 5v adapter that is plugged into an outlet. If something goes wrong and I get shocked will I be okay? This might be a really stupid question, but I figured I would be better safe than sorry.


texts: SX1272 - LoRa - What is the minimal schematic (needed capacitors/resistors) to use that device?

texts:
I'm interested in SX1272 by Semtech. It's a LoRa modem.

I'm not the best at reading datasheets. Maybe it's because of my poor English. I wonder what is the minimum schematic of such a chip? What capacitors, resistors, inductors do I need and where?

On the Semtech's website I found something like this:
868 MHz - Combined RFI and RFO (high efficiency PA) design, switchless
This PDF contains a scheme, but a lot of values of capacitors are not specified. Do I need to somehow calculate them by myself? How to do it?
Is it minimal connection needed?

I just want to connect SX1272 to ATmega88.

BTW. As I understand, the SX1272 can not be programmed? - Ie. Upload your own program? But on the other hand, what would be the use of GPIO pins?


texts:
Sorry for this basic question but I am not finding a simple answer to it

Lets say we have a input signal(a node) that we expect to be in the range from 0V to 5.4V. To make sure that it never exceeds it, a schottky diode with +5V on cathode is added.

This way, when the input voltage is 5.4 (assuming Vf of diode as 0.4V), then the diode becomes forward biased and the node is prevented to see voltage greater than 5.4v.

My question is does this have any adverse effect on the +5volt supply? What is the input signal sees a voltage of 12V? What will happen to the +5 supply then?


texts:
I'm working on a TINA-TI circuit. I'm no expert in the electronics field or the medical engineering so I am having a hard time figuring out how to construct my ECG circuit. This signal will be connected to an Arduino, so I want the Vout to lie between 0V and 5V, to use the whole workspace of the A2D in the Arduino.

A couple of things I wonder about:

When I run a Transient-analysis, the graph tells me that my Vout is between 2.50V and 2.50V and I cant seem to figure it out. I want the signal's virtual ground to be 2,5V (or maybe less) and the signal to swing from 0V to 5V.

I'm also unsure about the supply minus voltage on the INA333 and the OPA333. Which should be me virtual ground, which should be ground or if some should be negative Vcc. As I've already mentioned my electronics skills are not good, so excuse me for any obvious mistakes.


texts: Systematically, what would happen if I give a crank at the shaft of a motor?

texts:
In particular, I would like to know what would happen if I crank the shaft of the following kinds of motor: brushed DC, brushless DC (the kind used in computer fans now) and 6-coil 3-phase AC permanent magnet synchronized motor (the kind that coils are used as stator and a permanent magnet rotating in the middle).

Would the cranked motor 1) energize a otherwise powerless line, or black start the line, 2) pushing out energy into a energized line, at least when the motor start get cranked, but does not work otherwise or 3) does not push out energy, and probably catch fire if cranked hard and long enough?

Assume that I have hooked the wires to a few resistors, and maybe an appropriate power source.


texts: How to resolve VHDL packages constant name clash?

texts:
There are 3rd party packages where there is clash because

There are constants with same name in both.
Procedures with same name in both.

How to prevent this clash and make sure that the project will compile and simulate and I can access specific constant or procedure in my testbench without trouble?


texts: Voltage drop in ESP32 ADC reading when adding devices

texts:
I've setup an ESP32 for reading a voltage from its internal ADC as follows:

simulate this circuit – Schematic created using CircuitLab
I have the ESP32 ADC configured to sample from ADC_UNIT_1 on pin ADC1_CHANNEL_7.  I am using the attenuation ADC_ATTEN_DB_0 and width ADC_WIDTH_BIT_12.
The documentation for the ADC_ATTEN_DB_0 attenuation shows that the suggested range of input is from 100mV to 950mV.
I am measuring a pressure sensor that outputs 4.5V at its maximum reading (100psi) and 0.5V at its minimum reading (0psi).
I chose the 5.6kΩ and 1.5kΩ resistors so when the probe outputs 4.5V, the resistor divider output at VOUT is 951mV and when the probe outputs 0.5V the resistor divider output is 106mV.
The 100nF capacitor was chosen based on Espressif's Minimizing Noise documentation, and I am following their sample code and recommendations for multisampling.  Additionally, the ADC is characterized using the factory-set efuse reference voltage.
When configured like this, all is well.  For any range of VIN values from 0.5 to 4.5V, I get the expected VOUT value and the ADC reads the VOUT value very accurately.
The problem comes when I add additional devices to the circuit, like so:

simulate this circuit
Now, when I read the ADC value, I notice a voltage drop, and the drop increases as the peripherals draw current (though not strictly linearly).  For example:
With no peripherals,
VIN @ 4.5V shows 952mV at VOUT on the multimeter and the ADC reads 953mV (close enough, OK).
With one peripheral drawing 20mA, I now see:
VIN @ 4.5V shows 952mV at VOUT on the multimeter but the ADC reads 950mV (this is very consistent).
When that same (or another) peripheral increases the current draw to 87mA, I see:
VIN @ 4.5V shows 952mV at VOUT on the multimeter but the ADC reads 941mV.
Is the voltage drop I'm reading caused by noise?  Or is there some critical thing I've left out of the circuit (I do have bypass caps on the ICs, but I didn't show them in the schematics for simplicity)?
I'm a total electronics noob and this is only the second PCB I've made so I think it's likely I have a ground loop (I was careful not to make one with my traces and used a star ground, but then I did a ground pour so I probably made a ground loop anyway).
If there are any other likely causes I should look at please let me know.  I'm learning all the time, thank you for your time to reply.
EDIT:
I've updated the schematic to show how I'm powering things.  I'm using a 7.5V, 1A wall wart that connects to a ST LD1117 3.3V fixed-output linear regulator.  I have both required capacitors (datasheet page 8) attached, the 100nF capacitor is a ceramic capacitor, the 10uF is an electrolytic (it's what I had on hand, not sure if it makes a difference).  The regulator is capable of delivering 800mA.
When I measure the VDD33 pin of the ESP32 (connected directly to the supply) with no peripherals attached, I see 3.315V.
As I attach peripherals (which use the same 3.3 supply as shown in the second schematic), I see the voltage at the VDD33 pin rise slightly with each component.  The first component causes the supply voltage to rise to about 3.330V, and when I add four components it goes all the way up to 3.370V, so there's a rise of about 55mV when multiple components are connected.
The components I'm adding are Electrically Isolated Carrier Boards from Atlas Scientific and to those various sensors such as their EZO-pH sensor.
The schematic on page 5 of the electrically isolated carrier board's datasheet is shown below (note that it's an internal schematic -- the only thing exposed to my device are 5 pins, VCC, GND, EN, SDA, and SCL, where VCC is 3.3V from my LD1117 and EN is pulled to VCC through a 10kΩ resistor).


texts:
I have a solar screen in my motor home that is motorized with a DC motor (24V.) Today, I tried to move it but no response. I removed all the solar screen and inspected the motor. I saw it has a PCB and on it, something burned. I know it's a capacitor from the shape before I removed it. I removed the dirt, safe the pin and try to operate my screen, but the relay only switched "On/Off" quickly.
Can you help to understand the use of this PCB and if I can use my motor without it?
The burned capacitor is C5 on the schematic of the PCB I've produced. I don't know which type of capacitor it is.

Improved size schematic:


texts:
Consider this shift register:

I want to find to find the time offset between A and B if the frequency of the signal 'x' is fs and the shift register is clocked at the positive edge of 2fs
I failed to find the time offset between A and B.
Any hints or suggestions?


texts: Would I be able to use a rechargeable battery in a Fluke 87V (based on specifications)?

texts:
Would a Fluke 87V meter be able to run on a 9V Li-ion rechargeable battery capable of 550mAh?

In general (for any device), what information (device specifications) would I need in the future in order to be able to answer this sort of question? Current? Power consumption (how long a battery lasts in the device)?


texts:
I have written some measurement commands in LTSpice to calculate the weighted harmonic distortion (PWHD)

.meas a1n INTEG (I(Lgra)*cos(2*n*180*fg*time))

.meas an PARAM a1n*2*fg
....

(if somebody wants it I can give you the full text. It works)

The problem is that I want to run it for harmonics n=14 to 40.
Is there a way to do that without running the simulation again for a different n? (I have already tried the step command and it takes too much time)


texts: What is 'best' temperature sensor for an array of sensors

texts:
I'm looking to make an array of sensors to record the temperatures in a house at various points

eg. Above flat metal roof,
    inside flat roof cavity (above 1st floor),
    ceiling of room (1st floor),
    floor of room (1st floor),
    floor cavity (first floor),
    ground floor room ceiling,
    sub-floor/basement space.

I guess I need accuracy tolerance of about ± 1ºC. More important is that once initially calibrated, the sensor do not drift relative to temperature or the data comparison will be bunk. I hope to run the sensors for weeks in winter, summer, spring, autumn to get a full profile of the thermal performance.

So which sensors are good for me. Few seem to be good for ± 1ºC and I need a way to deal with the wiring of them too. So I2C or another digital bus might be good, anything that stops the length of the wire introducing errors into the values. Digital also means I can run a cat5 daisy chain of sensors rather than a separate lead to each sensor which seems reasonable.


texts: DC-to-DC conversion for solar, off the shelf or custom?

texts:
I am working on a small solar power system. The critical problem right now for me is how to do the DC-to-DC conversion. Essentially, the problem is that you have an array of large 12V lead-acid batteries and need to power a wide variety of different DC devices which typically require voltages like 3, 5, -5 and 9. Also, you may have 12V devices but need a regulated supply so even for hooking up the batteries to a 12V device is not trivial.

Problem #1: confusing multiplicity of circuit possibilities

The main off-the-shelf options seem to be either buck converters or DC switchers. One problem is that there are many different ways to design such devices and what you can buy is often a black box, so you often don't know what kind of circuit you are buying. The manufacturers claimed efficiency is often much different than the real efficiency you actually get when you plug it in and measure it. Therefore, it is hard to know without a lot of trial and error which products might be good or bad.

Problem #2: compromise circuits

A lot of switcher products accept a range of input voltages, thus they may be "compromise designs" that sacrifice efficiency for flexibility. In my case I have just ONE input voltage: 12V, so I don't need a chip that accepts a range of input voltages. So, if I a buy switcher chips I may be unnecessarily losing efficiency to get flexibility I don't need.

Problem #3: single-input single-output designs

Virtually all commercial products are not designed to output a range of different output voltages; they take one input and generate one output. Therefore, to use off-the-shelf components, you have to use a whole bunch of different independent converters, which is bulky and probably a lot more inefficient than an integrated design.

Custom Design

To avoid these problems, the alternative is to make a custom design: a board that takes a large 12V input, divides and regulates it to a range of different smaller voltages according to what is wanted. So, for example, the board could have 6x 3V outputs, 8x 5V outputs, 5x 9V outputs, etc, whatever I want. The challenge is that making such a board, especially one that would have good efficiency is potentially extremely complicated. For example, I have been reading the book "GaN Transistors for Efficient Power Conversion"
by Alex Lidow and "Switch-Mode Power Supplies" by Christophe Basso and it is evident that making a such a board could be extremely complicated and take a long time, at least for me. Although one alternative I guess would be to pay an expert to design it.

There is a halfway solution here and that is to make a custom board, but to use switchers, which come in SMD packages. You just plaster a bunch of switchers on the board, so you solve the bulky multiplicity of devices problem, but the design is not really integrated--it's just a large number of switchers in the same box.

So, what would be a good solution here? If I am trying to get >95% efficiency, is cobbling together commercial products "good enough" (Option 1) or should I look at a multi-switcher box (Option 2) or go whole hog and try to make a custom board (Option 3)?


texts:
My problem is about AND-gate when its inputs are open. I want to know: What is the output when inputs are open? The output is Z (open) or 0?

What is your idea about this AND-gate transistor structure?

(Image source)

My answer to the above structure is that the output is 0 when the two inputs are open, or at least one of them is 0.


texts: Circuit design for triggering multiple optocouplers at constant voltage level

texts:
I have theoretical understanding of general electronics basics, however I do not have any practical experience in circuit design. Therefore I need some advice of what would be the best practice on how to set up a circuit that has some requirements.
I have multiple industrial cameras that are triggered by one master camera. The master camera has an internal mosfet and the slave cameras are triggered by an internal optocoupler. Furthermore the trigger event should also go into a MARK_IN pin of a gps receiver which has an 3.3V high and 0.0V low level and registers the triggering event on a falling edge.
I set up a basic circuit in a simulation that I can think of that is shown below:

Here the 820 ohm resistors with the diode (led) are the internal trigger_in optocouplers of the slave cameras. The mosfet is the trigger_out when an image is taken by the master camera. Furthermore I thought about connecting the MARK_IN pins of the gps receiver like shown (I do not know how the internals of the MARK_IN pin looks like, datasheet only say it should be 3.3V with falling edge).
However, with my design I see a lot of problems:

The voltage level does change at MARK_IN when the number of connected slave cameras changes. For example just one slave instead of 2.
The energy consumption is about 150mW when the mosfet pulls the line on ground, which I think is quite a lot.

So I am wondering if there is a typical approach how to realize such circuit? That can handle a varying amount of slave cameras and still keeps the MARK_IN pin on 3.3V level. Am I on a right track or completly wrong? And furthermore, a circuit that is more energy efficient.
Apart from that is there anything wrong with my circuit in general, or something that I am missing?


texts: Digital Potentiometer Capacitive Feedthrough?

texts:
I am trying to use a digital potentiometer to reduce the amplitude of a square wave. I am getting what appears to be capacitive feedthrough on the rising and falling edges.  This is getting amplified by later stages and causing glitches in the output.

Looking at the scope screen shot below, the cyan trace is the ~12v/us square wave input and the yellow trace is the wiper output of a MAX5387 100K digital pot set for about a 96K : 4K divide.  After recovering from the initial glitch, the yellow trace exponentially settles to the expected value after about 4uSec.

I have looked up capacitive feedthrough for digital pots and have not found anything.  It is not spec'd in any datasheets that I have seen.  ADI lists digital feedthrough for some of it's pots, but that's about it.

I assume that digital pot capacitive feedthrough is a known phenomenon.  Any idea which particular pots minimize it or how to mitigate it in general?

At this point my only option seems to be slew rate limiting the input square wave to a slope similar to the post glitch RC slope.  This takes an extra op amp stage.  I don't want to just put an RC on the input, since I need the edges to be symmetric and as fast as possible.    Any other ideas on how to avoid the initial glitch?


texts: Wrongly documented TI LM324 unity-gain bandwidth?

texts:
I was reading the datasheet of the LM324 from TI (http://www.ti.com/lit/ds/symlink/lm324.pdf).

They specify a generic GBW of 1.2MHz. This is usually done with no output applied, from what I understand.
Then there is the \$ A_{vd} \$ which is max 100K (100 V/mV). This is the open-loop gain measured with a load, so taking into account loading effects, if I get it right.

Is this gain really reducing by a factor of 10 with few \$ k \Omega \$ on the output?

To understand this better, I read the SLOA11 from TI. They mention \$ B_1 \$ to be the bandwidth at unity-gain with a load specified under the \$ A_{vd} \$ measurement, which should result in a BW of 100kHz. Making it different from the GBP measurement with no load (resulting in unity BW of 1.2 MHz). But in the LM324 datasheet, \$ B_1 = 1.2MHz\$ instead of \$ 100kHz \$. So I am not sure here what are the correct terms and how to use them.


texts: Maximum Data Rate on BLE Dual Mode Device

texts: Can a Dual Mode BLE device transmit data at the BT (BR or EDR) speeds? I am working on a project that is power sensitive and usually transmits very little data - so BLE makes sense but the device will occasionally need to dump several Megabits of data very quickly so I want to make it switch to standard BT for those high data transmissions. Is this possible?


texts: Is it bad to load one rail of a power supply vastly more than the other?

texts:
I am trying to modify a Delta DPS-400AB-17 server 1U power supply to support a desktop motherboard and graphics card. The power supply has an 8 pin 12V EPS connector attached to a 21A 12V (252W) rail. My plan is to turn this into a 4 Pin ATX connector + a 6 pin PCIe connector (my motherboard only has a 4 pin CPU plug).

This theoretically shouldn't be a problem as I am not splitting up any wires, each receptacle is getting its own wire from the power supply (except the sense wire - which my understanding is doesn't actually complete a circuit). However, this would mean the rail that this is connected to could be at 70-80% utilization, meanwhile the other rail (which only has a 24 pin motherboard and some unused SATA connectors) could be at only 10%. Is having this kind of differential between the rails a bad thing?


texts: Thermocouple on a grounded stainless steel box

texts:
My present project is a ~6kW switching converter in a sealed stainless steel box. The box is grounded well. When I put a thermocouple on the surface of the box, the reading is noisy. Even if I put some tape between the box and the thermocouple, I get the same result. All thermocouples in the box give reasonable results, but the one on the actual box surface gives me so much noise as to be useless. My PC temp logger box rejects all the results as outliers and never updates. A calibrated multimeter gives me readings 30C higher than three IR guns (pointed at black tape on the box) and a PN junction temp meter give me. This problem only seems to occur when the unit is running. Grounding or not doesn't seem to matter. Two brands of thermocouples give the same results.

Why would I be getting such bad thermocouple readings in that particular circumstance? Are thermocouples just that untrustworthy and I'm getting unlucky? Or am I missing something?


texts: Replacing a missing/obsolete AC power supply with DC power supply

texts:
I am trying to replace a missing power supply for a TRS-80 model 1. The original power supply provided unregulated DC ~20V, unregulated AC ~10V and ground. Internally the computer connects the AC to a full wave rectifier with smoothing capacitors. TRS-80 model 1 technical manual, schematic is on page 37 and 38

My understanding is that if I supply positive and negative DC to the AC lines and account for the voltage drop through the rectifier, I should be ok. I would like to keep the original computer unmodified, if possible.


texts: Can I charge a large capacitor with a small resistor?

texts:
I am working on a simple Arduino capacitance meter.

This project uses twp resistors: a 10 kohms resistor for charging and 220 ohms resistor for discharging.

The Arduino is programmed to measure the time constant T=RC and eventually calculate the capacitance.

Now for large capacitors such as a 3900 uf capacitor, the time between the readings took several minutes.

I was wondering if we can fix that buy changing the charging resistor(10 kohms) with a small resistor say 220 ohms or something.


texts: Finding transfer function of a compensator circuit similar to a type 2 compensator topology

texts:
I know how to find transfer functions of op-amp circuits using equations derived from using Kirchhoff's current law (nodal analysis), and normally I don't have any problems solving them. However, I came across a design of a circuit that very closely resembles a type 2 compensator, with one difference - there's an extra resistor between the voltage divider and the feedback impedance.

This circuit is used in a switching regulator, so Vout is fed to further electronics internal to the IC, and Vin is the regulated output voltage feedback of the system.

simulate this circuit – Schematic created using CircuitLab

When I use nodal analysis to solve this circuit, I always end up with an extra constant term in the equation, making me unable to get a Vout/Vin relationship.

The simplest equation I can get looks like this:

$$
\left(\frac{V_{in}}{R_1}\right)+V_x\left(\frac{1}{R_3}-A\left(\frac{Z_f+R_3}{Z_f}\right)\right)=-AV_{out}
$$

where

$$
A=\frac{R_0R_1+R_1R_3+R_0R_3}{R_0R_1R_3}
$$

and where Zf is the feedback impedance consisting of C1, C2, and R1.

The problem I encounter is with the Vx term. I'm not sure how to get the transfer function Vout/Vin from this equation. In a normal type 2 compensator, R3 isn't there. My algebra might be off a bit, but I double checked a few times and don't see any problems. Even if the algebra was off somewhere, I expect Vx would still show up.

I suspect R3 plays into the input resistance, which is normally determined only by R1 in a typical type 2 compensator, but I cannot be sure that the resistance for the compensator would simply be R1+R3. In the past, I've designed type 2 compensators that utilize a voltage follower between Va and R3 so you can adjust the input resistance without having to tweak the other side of the voltage divider, but while similar, this design forgoes the follower.

Any help would be greatly appreciated. And, to be clear, this isn't a homework problem.


texts: Voltage increase with capacitor... what's the "true" voltage?

texts:
The board on an old battery charger went bad, but the transformer was good. So I've got about a 12.3VDC output when I connect the transformer to a bridge rectifier. However, if I decide to wire in a capacitor, the voltage jumps to over 20v. When I hook up a 12v load (light bulb) it goes back down to around 13v.

Why is this voltage increase happening with the cap?
If this 20v isn't my "actual" voltage, what is? Is it the voltage I see with a load attached? If load decreases the voltage in the circut, how do I know I'm not sending too big a voltage to my load?


texts:
Consider this circuit:

simulate this circuit – Schematic created using CircuitLab

(this part is preceeded and followed by other components).

$$I_1 + I_2 = \displaystyle \frac{V_1}{sL_{12}} - \frac{V_3}{sL_{12}} \left( \displaystyle \frac{L_1}{L_1 + L_2} \right)$$

with

$$L_{12} = L_1 || L_2 = \displaystyle \frac{L_1 L_2}{L_1 + L_2}$$

How can this relation be obtained? Any hint?

The ratio \$ \displaystyle \frac{L_1}{L_1 + L_2} \$ seems a voltage divider; but I can't see anything similar. Moreover, \$ L_1 \$ and \$ L_2 \$ are not parallel.


texts: Does turning a lighbulb on and off repeatedly use more energy than just leaving it on for hours?

texts: Let's say I have a 60W bulb in a lamp in my bedroom. If I kept the lamp on for 2 hours straight but the next day, I switched it on and off 10 times in intervals of 5 minutes. Which scenario would use more energy?


texts:
I'm trying to figure out \$V_x = V_x' + v_x''\$

For \$V_x'\$, I had open the current source, and tried to solve using KVL.

Obviously, \$i_2 = 0.1v_x\$. The equation I concocted was \$-10 + 24I -.4V_x = 0\$. However, I am stuck at this equation.

For \$V_x''\$, I shorted the voltage source, and solved by simplifying the two parallel resistors to \$3.33\Omega\$. Thus, I could just do nodal analysis at \$V_x\$. is this correct?


texts: Passive-ish isolated IGBT driver with PWM design review

texts: I would appreciate if anyone could give me some critique of my design proposal, is there any way it could be improved e.g. increased di/dt and dv/dt, sharper and more uniform gate signals? I am aware that there are many other more sleek end modern driver topologies out there, but I want to use exactly this presented topology due to its ruggedness.


texts:
I want to know if it's possible to have a push button so that when it's activated, it turns on my 9 volts circuit for 10 minutes and then turn it off. Also, I don't want this circuit to consume electricity when it is close.

Thanks you


texts:
I am trying to sample sin wave using Lpc1769's Adc.
I am sampling signal using adc and send this data to pc using serial port (115200 baud rate). My sampling frequency is 1.5 kHz. When I sample 100 Hz signal, and then send this data to dac, dac output is 100 Hz signal. So this is good. But when I send this data to the pc the graph is wrong.
Here is my screenshots.

By the way, I am using zedgraph for drawing the signal in the pc side.
Also I checked the data missing condition. There is no data missing.

One interesting thing for me is, When I decrease the peak-to-peak value of the signal, I can see right graph in the pc side.

So Do you have any advices ?
Thanks for your response.


texts: Is there a general method for switching between PCB power sources?

texts:
I'm working on PCB design that will typically be battery powered. However, the device needs to be programmed and thus will be plugged into a computer occasionally.

I'm running into the problem of switching between a battery supply and a PC power supply, and specifically making sure I won't be applying power from both sources at the same time.

Is the general method to use relay logic to switch between power supplies? I assume I could design something that disconnects the battery supply when the device is connected to the PC. However, I assume this is a common problem and am curious if there are other methods for addressing this.


texts: Trying to program a DSD TECH SH-A10 iBeacon with Sparkfun FTDI Basic

texts:
I ordered some fairly random iBeacon (DSD TECH SH-A10), and I didn't realize that its configuration software is Windows only (http://www.dsdtech-global.com/2017/11/dsd-tech-bluetooth-config-tool.html), and I have a Mac. Nevertheless, I installed Wine and tried to run the software that way - but it doesn't recognize that my FTDI Basic is connected (there is no UART port option to subscribe to in the top left of the software). Next, I decided to go the more manual route of AT commands. I connected the iBeacon to my FTDI, and opened up CoolTerm (a serial terminal), and tried the standard "AT" test command. It didn't work, no response. I can see on the FTDI Basic that the transmit (TX) light flickers when I send the command, but nothing is received (RX).

I should mention that the whole time I am trying, I can see that the beacon is operating (or at least appears to be) because there is a red light that goes steady on and steady off. I think it is transmitting, but I think it has a default power of 0db (I was unable to detect the beacon using the default UUID and if the power is at 0db this would be why).

I can see the power level (and all the other parameters) in the configuration software when I run it with Wine, I'm just not sure if it is filler data/parameters or if it actually represents the data that pertains to my device...as I never connected the device to the software. I'm assuming each device comes with the same default data/parameters/settings, so there is no reason to believe that what I am seeing in the configuration software for settings is not correct.

Here are some pictures of the wire/FTDI/iBeacon setup:


texts:
I'm designing an altimeter based on a pic microcontroller and a freescale pressure sensor.

I'd like to output the altitude from the pic using an analog gauge. I found some useful information here.

What I want to know is where to buy analog gauges that allow me to put my own scale (I'm basically looking for the raw ammeter)


texts:
I have a clock with a time period of 1ms. I want to generate a signal which has the following characteristics:

Some \$\hat a = 3.7, \delta = 0.1\$ . At a particular clock cycle, the signal must have a voltage which is from the uniform distribution \$[\hat a -\delta,\hat a + \delta]\$. Say this value is \$a_1\$. At the next clock cycle, the voltage \$a_2\$ must be such that \$a_2=2\hat a-a_1\$. This will give the average voltage in two clock cycles always equal to \$\hat a\$, which helps me a lot with my analysis

The first part of getting a value from uniform distribution is easy. How do I do the second part? Is there any way to write a loop in PWL such that the first voltage will be chosen randomly from the interval, and the second will be as given in the above condition, and this is repeated forever? I have no idea about the concept of memory in Ltspice. Help appreciated. Thanks!


texts: Why can mobile microphones handle high noise now?

texts:
I'm wondering why mobile microphones can now record just fine in very noisy environments? (like loud rock concerts) when just a few years ago the sound would be cracking so terribly that you could barely hear the recording.

What changed in mobile microphones that made this marvelous feat possible?


texts: Why should PCB design be mirrored before toner transfer?

texts: I am currently designing a PCB to make with the toner transfer method for the first time. I was reading a guide that said to mirror the image before printing it to the paper. However it seems that the paper should not have a mirror image because when you are designing the board it is like looking through the board onto the other side and in turn drawing directly on the paper. Does the PCB design need to be mirrored to work?


texts: Connecting Ground Paths of Low-Current and High-Current Circuits

texts:
A small (3.3V/10mA) uC circuit requires a ground.  I designed the circuit’s PCB to use a nearby ground wire that is attached to the car’s frame in at least two places and used by the 2A windshield washer motor (other devices may use it as well).  I created a break in the ground wire (denoted by A and B) and it is soldered to the PCB onto two pads nearly touching and connected by a 100 mil trace (2 oz), more than adequate for the washer motor. (The trace width calculator indicates 8 A conservatively.)  Connecting the remaining ground wire C completes the uC circuit and everything works fine; the washer and the circuit.  Both are on the same 12V supply but I’m curious if there is anything inherently wrong with this approach.  Ideally, (from what I’ve read) I would add another separate ground wire for the uC circuit, but I would like to avoid adding another wire if at all possible.  The uC is only controlling a relay.  Should I isolate the A-B pads from the ground pour using a polygon cutout and then connect the uC circuit grounds to those pads with a single connection instead of having A and B directly connected to the ground pour?  Does it matter?

There are numerous threads about connecting grounds, but the many I've read address noise and different voltage potentials; I have not seen anything that addresses sharing a ground with another higher-current circuit.

simulate this circuit – Schematic created using CircuitLab


texts: about grounding on different circuit board

texts: I got a STM32 development board, which is used to control another board for DDS output. The STM32 board send digital signal (TTL) for output control on the DDS chips. The STM32 board and the DDS board are powered in different supply. I wonder in this case, do I have connect the STM32 board and the DDS board in common ground so to make it work?


texts: Hand-made interface to SWD to write flash of ARM chip

texts:
I'm interested in creating simple interface to SWD to be able to write flash memory of ARM chips. I.e. to create a make-shift programming device - more for sake of exercise.

I started reading the documentation and searching for examples (for I think people already tried this). Currently I have a few questions, for which I would be thankful for guidance:

I'm going to configure SWDCLK as normal output, and SWDIO as an open-drain (acting as input when it is in high-Z, see below) - I suspect that it is also open-drain on the side of the target device, so with the help of pull-up I will never have a short-circuit by mistake - is this correct?
is there minimum allowed clock period? or anything will do, even just a few Hertz? Or perhaps this is dependent on target device?
is it correct that in waiting mode both lines are driven HIGH on the host side, and when the communication begins, the first edge on SWDCLK is falling?
HOST should change SWDIO on falling edge of SWCLK - and sample data from target (when needed) on falling edge of SWCLK either - right?

I think currently that's enough (though I would be also thankful for short sample of commands sequence to read / write the flash - but I believe I'll find it out anyway soon) - thank you in advance!

Currently I'm trying to use Arduino to create a basic prototype, though I can switch to plain Atmega or LPC111x with FTDI cable at any time... Though I believe this is not important.

P.S. to explain better about SWDIO - with AVR's for example I put the pin to LOW state and then if it is switched to output, it produces 0. However if it is switched to input, it is in high-Z state and really works as input. I.e. I manipulate not PORTx bit, but DDRx instead (while PORTx is permanent 0 and PINx is used for reading).


texts: Using internal pull-ups for TWI on AT32UC3B?

texts:
Does anyone know if it's possible to use the built-in pull-ups for TWI on the at32uc3b chips? I've been adding external pull-ups to my TWI circuits in the past because I couldn't find any concrete info about this. But if it's possible to just use the internal pull-ups, I'd much rather do that.

Thanks!


texts: Testing the integrity of cable shielding for suitability

texts: I am currently working with an ECG cable, is there a way for me to test the integrity of the shielding of the cable without using it directly on an ECG monitor to check for interference.


texts: High voltage (2-6 kV), high frequency (20-50 kHz) power supply how to achive

texts:
I need to make a high voltage (2-6 kV), high frequency (20-50 kHz) power supply in order to generate cold plasma (in Ar gas). I use a fly back circuit (found in web) could allow me to to that. The high frequency will be generate by the self oscillating fly back transformer.

I made a transformer myself, with 3000 turns on the secondary and (4+4) on the primary and everything works. Input is 12V and I could get ~ 5 kV output at 10-30 kHz. But there is a problem that the oscillating frequency only depends on the feritte core and the number of turns in the flyback transformer (e.g.: 4+4 or 5+5), therefore it is difficult to control.

I have few questions:

(1) Can I achieve my goal with an IC use to generate the high frequency pulse and feed it to my transformer? That way, I can control the oscillating frequency well.

(2) I found a circuit online use IC555, but it is for car ignition. Will it work in my case? If not, what I need to change in the circuit?

(3) I realize that flyback transformer was used much more common that an IC controlled one (like in an plasma ball). Why is it? Is it more efficient?

Many thanks for any advice/suggestion!


texts:
I'm looking for a way to improve the rise-time of a current mirror.

My problem is as follows: I want to interface with an obscure single wire protocol.

I'm starting with a digital signal that has a high level that can be anything between 1.8 to 5V (shown in the graphic as DigIn). I need to load this signal based on a different digital signal with a fixed voltage (I'm generating this signal). This signal is shown as ModulateIn in the graphic.

The current that I draw from the DigIn signal should be independent of the signalling level of DigIn. Around 1mA, but there is some wiggle-room.

To do so I load the DigIn signal using a standard current mirror as shown below:

The circuit works as it should except for one thing: I'm not happy with the rise-time. If ModulateIn goes high, it takes a while until the transistors start to conduct. This can be seen in a small delay in the current drawn from DigIn.

I'm dealing with frequencies of roughly 4Mhz here, that's why I picked fast RF transistors.

Question: How can I improve the response-time of the current mirror? I tried speed-up techniques from transistor switching applications like adding a speed-up capacitor parallel to the base resistor, but that does not work.

Any idea how to improve the rise-time except for picking even faster transistors?


texts: How to bring out internal signals of a lower module to a top module in VHDL?

texts:
How can I bring out the internal signals of my VHDL source code to my testbench so that I can view them as waveforms? I use Active HDL. I would like to know if there is any tool independent method of achieving my objective. Any help is appreciated.    I get this error now.

My source code is

entity SPI_DAC is
    Port (
    -- inputs and oututs
    )
end SPI_DAC;

architecture Behavioral of SPI_DAC is
    --These are my internal signals
    signal ch1_byte_data_sent       : STD_LOGIC_VECTOR(23 downto 0)     := x"000000";
    signal ch1_byte_cmd_sent        : STD_LOGIC_VECTOR(23 downto 0)     := x"000000";
    --and a few other signals
begin
    --functionality
end Behavioral;

My testbench code is

entity tb_spi_dac is
end tb_spi_dac;

architecture behavioral of tb_spi_dac is
    component spi_dac
    port(
    --declaration, inputs and outputs
    );
    end component;
begin
    uut: spi_dac port map(
    --map ports
    );
    --stimulus process
end;


texts: DC choppers output voltage in ccm and dcm mode with no load

texts:
I was wondering what would happen to the steady state output voltages and currents of the
Buck, Boost and the Buck-Boost converters, working in

1 - Continuous conduction mode (CCM),

2 - Discontinuous conduction mode(DCM),

when suddenly their load gets disconnected due to some fault.
All three converters are assumed to be in ideal conditions with all ideal components. The load (purely resistive) in all three is connected across an output filter capacitor. The switches in all three are controlled by PWM scheme.

Further assume that:

All converters are having an Input of say 20V,  and a fixed duty ratio of 0.8. The resistive load is of say 20 ohms and the switching frequency is 100 kHz.

My thinking in the case of CCM is:

- For Buck converter, the capacitor will charge to full voltage and then no current will flow.

- For Boost, the inductor will keep giving its energy to the output capacitor and after a certain point when voltage limits of the capacitor exceed, burnout of switch or diode may occur.

- For Buck-Boost, similar to buck or boost scenario depending upon the duty ratio.

I have no idea about what might happen in DCM.

For reference the schematics of the three choppers are given below:-

So, please answer, review and help!

Thanks!!


texts: Is it a good idea to use the motor voltage as a source for a logic regulated voltage?

texts:
I'm creating a circuit for controlling a NEMA17 step motor with 1.7A per phase. This motor will be driven with +12V. The logic part of the circuit will use +5V though.

At the beginning, I was planning to use a different voltage source for each part of the circuit (motor power and logic), but then I was thinking if it'll be a good idea to use the +12V that goes to the motor to also be used together with an AMS1117 (5V) to provide a regulated voltage to the logic circuit like the image below where VMM is the power of the step motor.

Is it a good idea or not? My concern is about the stability of the output regulated voltage from the AMS1117 when the motor is running even though I added the electrolytic capacitor at the output as recommended by the datasheet.

I think it's good to tell that the 12V comes from a source like this one:

Can you guys tell me your opinion/experiences about that? Have you already created a circuit like that?


texts:
In Amplitude Shift Keying, the bandwidth required is given by \$B=(1+d)S\$ where B is bandwidth, S is the signal rate, and d is a value of either \$0\$ or \$1\$.

But how could the required bandwidth be just some multiples of the signal rate when one signal element itself could have higher frequencies?

Say in this picture:

The baud rate is 5, which implies the signal rate is also 5 signals per second. One signal itself would need 3 cycles. Then the worst case scenario is where all the bits are 1 and the thus the highest frequency is \$ 3 \times 5 =15Hz\$ and so the minimum bandwidth required of a channel to allow this modulated signal to pass through is still 15Hz. Is this right?

However, if I were to follow the formula \$B=(1+d)S\$, I would get...

If let \$d=0\$, \$ B=(1+0) \times 5 = 5Hz \$

If let \$d=1\$, \$ B=(1+1) \times 5 = 10Hz \$

But is 5Hz or 10Hz be sufficient for the signal in the picture? Why does the formula say that the bandwidth is either equivalent or maximum 2 times the signal rate? How is it so?


texts:
I have build a stepped tone generator (aka Atari Punk console) which are 2 555 timers connected together (one 555 is configured as a astable oscillator and drives the second configured as a monostable oscillator; more info here).

The circuit works as expected (I am using a 556 in place of the two 555).

I would like to control the frequency of the 555s from a midi keyboard. For this I would like to use a MIDI to CV converter that translates midi signals to voltages. I also build this circuit, which is based on an arduino and 2 DACs (MCP4922) and works as expected. (I can control another analog synth with it).

However, if I connect the MIDI to CV converter to the CONTROL pin of the 555, it does not work: whatever the output of the DAC, I measure around 5V on the CTRL pin.   I believe this comes from the fact that the CONTROL pin of the 555 is at a voltage of 2/3 Vcc by default. How can i control the voltage applied on the control pin of the 555s with such a system ?

I am relatively new to electronics and this might be a complete newbie question. I am sorry if this is the case but I could not find the answer anywhere on the internet.


texts: What's the easiest way to get fast USB serial communications?

texts:
What's the easiest way to get fast USB serial communications from an Atmel SAM microcontroller? I consider fast to be faster than 1 Mb/s.

In my previous projects I've used an FTDI module, but I've had lots of issues with drivers on the Mac. In OS X Mavericks Apple released their own FTDI driver, but it doesn't support non-standard baud rates. Getting users to disable the Apple FTDI driver and then enable the FTDI's own driver is causing too many support issues.

The Atmel software framework comes with a serial driver, but OS X and Linux only support serial ports at standard baud rates and seem to top out at 115.2k.

Are there any other USB protocols that are easy to implement, or an inexpensive stack / driver is available, that let me communicate like a serial port. I just want to read/write streams of bytes, blocks of bytes would be ok too.


texts:
I'm building a circuit for a home brewing application which will use the MAX31865 chip to read in temperatures of liquids from a RTD100 sensor.  The chip does this by reading the current that flows through the RTD and comparing it to the same current that flows through the reference resistor to get a ratio (and therefore the resistance value of the RTD which can be translated into the temperature).

The datasheet specifies that RRef should be 400Ω to cover the entire temperature range that the PT100 can handle (-200°C to 485°C), but I only need to cover from 0°C to 100°C, as the liquid will never go above that (it'll boil instead).  I thought I'd be able to specify a smaller resistor (say 150Ω) and get better precision from the 15 bit DAC, but the datasheet specifies a minimum Rref of 350Ω.

Does anyone have enough experience with this chip to tell me if a smaller value resistor would work? I know its a violation of the specs, but I don't see why it wouldn't work. Too much current for the Vbias?

In the end, I can use a 400Ω resistor if I need to, but I thought I'd see if I can optimise it.

Thanks!


texts: Art of Electronics, Second edition pp. 73-75 -- question about pull-up resistor and the logic of current setting

texts:
Edit:  As you can see in the comments, I got a great explanation about the pull-up resistor question.  I also wanted to make more of a bullet point of the PNP question as follows:
When it comes to setting the current in a PNP circuit (like a current source or emitter follower), is the procedure the same as for NPN, i.e. base voltage determines emitter voltage (as long as Vee is high enough), which will be a diode drop higher that the base voltage, then the emitter resistor is chosen to set the current based on that and I=V/R? If so, why does the voltage stabilize at that level? It seems that Iec is bringing Ve down from Vee, but why would it stop at Vb+.6V?  I could imagine the transistor constantly turning off and back on.
Original post:
I was really grateful for the answers to my last question and am hoping not to wear out my welcome by asking about everything I come across, but this question involves something that has confused me all along in reading this book, which is the logic of setting voltages and currents in transistor circuits, and another issue is what is meant by pull-up resistor in this context.
On pp. 74-75 (see attached image), the authors state that R3 in figure 2.23 is a pull-up resistor for Q1.  First of all, I don't think they ever introduced the concept of a pull-up resistor in the foregoing, but putting that aside, I'm not sure how this is a pull-up resistor or why one is needed.  I think I must not know what the term means -- when I look it up, the definitions usually have to do with logic levels and using resistors to tie a node to either ground or +5, and that makes sense to me.  It doesn't seem as though there is any shortage of either voltage or current in that location, and although I see that Q2's base is drawing current from the emitter of Q1, it doesn't seem as though it would be enough to cause any deficiency.  What am I missing?
Trying to understand that comment led me to think about how a PNP transistor circuit is set up and how often the logic seems confusing (to me).  In the NPN circuits like the emitter follower and current source, the base voltage is supposed to set the emitter voltage, then the drop across the emitter resistor determines the current according to ohm's law as in figure 2.22 A and B.  This seems to make sense, since the emitter should be at ground (in these examples) before voltage is applied to the base, and then the applied voltage overcomes the diode threshold voltage and the emitter is separated from ground by the resistor, allowing the voltage to rise to VB-.6V.
But in the PNP case (2.22 C), if there were no diodes or emitter resistor, the base and the emitter would be at +10V, and the transistor would be in cutoff.  When the diodes are added, the transistor is biased and turns on -- what happens then?  I guess the +10V on the emitter would cause the base voltage to rise until there is less than diode drop between them?  And possibly destroy the transistor with a giant current through the base?
But when I look at the 560 Ohm resistor, I think, well, that would create a 1.2 Volt drop if the current were 2ma, OR it would produce a 2ma current if the voltage drop were 1.2V, but can it really set both values at once?
Now that I think of it, I guess that with no emitter resistor, once the transistor is on, a giant current flows to the collector, and that will destroy some components.  But as long as there is any resistor on the emitter, the current flowing to the collector will cause the voltage to drop to VB +.6V, and that is how the voltage is set to allow the resistor value to be the determinant for the current.  Does that sound right?  And if so, why doesn't the voltage drop any further and cause the transistor to constantly turn on and off?


texts: Gyroscope questions: building a stable platform

texts:
I'm embarking on a summer project and have a few questions. I'm planning to build a 3-axis stable platform for electronics. (Picture a flat surface that stays parallel with respect to the ground while the supports for this platform are free to rotate in any axis)

My questions are:

Is it better to use 3 1-axis gyros each located on the center of the axis of rotation or 1 3-axis gyro located in the middle of the platform?
Could I accurately compensate for gyro drift by using accelerometers and implementing a kalman filter?
I need an accurate and fast gyro for this application. I've been looking through a digikey catalog (http://www.digikey.com/product-search/en/sensors-transducers/gyroscopes/1967243?k=gyro&ColumnSort=1000011&fid=0&pageSize=25) and was wondering what specs I should look for. Do I want a gyro with high sensitivity (mV/°/s) or high range (°/s)?

Thanks Guys!!


texts: A question about how RS latches work and the time an input needs to stay high after it has been supplied!

texts:
I have a RS latch constructed of 2 NOR gates, without enable input.

Lets say that the in the beginning the output is set to Q=1, Q'=0. (pic1)

In a given moment R is pulsed high, and Q is calculated as (R+Q')'=(1+0)'=0. (pic2)

So now Q supplies 0 instead of one to the other NOR gate.

Now Q' is calculated as (0+0)'=1.(pci4)

Now as i can see from the picture while the propagation of the signal from the first NOR to the second, and then back from the second to the first lasted, the pulse at R stayed high. Therefore in this moment both signals to the first NOR gate are high. Q is again calculated as (1+1)'=0, so it doesn't change.

The moment comes when R becomes 0 again and Q is calculated again, Q=(0+1)'=0, but still doesn't change.(pic 5)

At this moment both inputs are low and the latch is in a stable reset state.

The pictures are from an animation, but all of this wasn't clear to me until i separated the animation. This might not have been that much of a question but a discussion, because i need someones confirmation if i'm right. Does this mean that the input has to stay high for at least the time needed for the first NOR gate to be calculated, the new pulse supplied to the second gate, and that pulse supplied back?


texts: What is the purpose of a "BUF" in Xilinx ISE schematic?

texts: I'm working on a schematic for a Xilinx CPLD using ISE. The schematic has a triangle symbol labeled "BUF" before every output, and also between some other nets. I can't really tell why some connections have "BUF"s and some don't. I read the documentation (Page 72 of this pdf) and it just says "This element is not necessary and is removed by the partitioning software (MAP).". So if it isn't necessary what is the purpose of adding them to the schematic?


texts: How do I find JEDEC registered specifications?

texts:
If I'm sharing a circuit for educational purposes, I want to make sure that my parts are common generics.  I'd much rather specify "2N3904" than "ON Semiconductor MMBT3904".  But not all 2N3904s are created equal.

To use an even simpler part, the 1N4148 diode, the ON Semiconductor datasheet specifies IFSM at 1μS to be 4A.  However, the Vishay and Diodes Inc datasheets specify 2A.

Suppose I design a circuit that does have a big inrush that rapidly drops (for instance, charging a capacitor).  If I look at the ON Semiconductor sheet, I think that it can handle 4A, so I calculate accordingly.  Then, I write "1N4148" on my schematic, post the design to the web, and move on.  Somebody reads my article, pulls a Vishay diode, and tries to build my circuit, only to see the magic smoke escape their diode.

If I'd read the JEDEC-registered datasheet for the 1N4148, then I wouldn't have this problem.  I'd know the ratings that every 1N4148 must meet, and could design around that.

If you think the IFSM example is farfetched and want a different one, note that the VRRM is 100V for the ON Semiconductor and Vishay diodes, but only 75V for Diodes Inc.  Or just try to find a 2N2222 datasheet at all (i.e., one without a trailing A, leading P, etc).

However, I haven't found an archive of the JEDEC datasheets for jellybean parts like this.  Does anybody know how I can get this information?


texts:
I'm trying to get some ideas for dropping 1.8kVdc to 700Vdc using simple voltage dropping techniques/topologies. I am using a SMPS (Switched Mode Power Supply) to regulate the low voltage outputs from there. The load power is roughly 20W. Could someone suggest me a way forward?
Edit1: Adding more details-20W is the maximum load power, load power is variable. I have achieved efficiency of 87% with the second stage(i.e.700Vdc to low voltages SMPS). This smps would be delivering power to control electronics. Product is industrial requirement, PD2 rated, has to operate with internal ambient up to 85degC.
Need to select topology for the first stage considering simple & cost effective design because the second stage is well regulated. I don't have a figure on the new efficiency requirement; need to get the best efficiency possible.
Edit2: Second stage is not removable due to multiple use of this SMPS in various products. But this is editable, For eg: transformer, mosfet etc., could be re-designed. It is preferable to opt for dropping 1.8kV to 700V though. 700Vdc needn't be strictly regulated.


texts: Abracon RTCC - no startup oscillation, no SPI

texts:
I'm trying an Abracon AB1815 Real-Time Clock/Calendar (SPI interface) in a "fun" QFN16 package. It has a 17th VSS pad which is grounded. It is on a QFN17-to-DIP expander for prototyping at 1.8v. I reflowed it with quality needle-syringe solder paste and a digital hot-air iron. All joints look good under magnification. But the "XO" pin (the oscillator output?) never does anything visible on a 10x probe/100MHz Iwatsu DSO. Not even a startup blip. And the device is unresponsive to SPI commands.

Now this datasheet is "one of those" in which many things are assumed or not covered clearly. The "Typical Application Circuit" on page 4 is grossly simplified; little to no mention is made of the various watchdog, interrupt, reset pins, etc. which MUST be handled. The initial configuration of the device is not stated, it must be inferred from each entry in the register section. (It has an internal RC oscillator, but requires an external resonator - not mentioned in the datasheet except for default register bits.) And the naming convention of the pins is also quite mind-numbing, such as

\$\text{nCE}\$ for \$\overline{\text{CS}}\$

\$\text{EXTI}\$ for External Interrupt (apparently active-low due to page 4...)

\$\text{WDI}\$ for Watchdog Interrupt (no mention as to active state, needs pull-somewhere)

\$\text{nEXTR}\$ for External Reset (active-low, needs pull-up)

I've tried toggling through all states of these with power applied, no oscillation, no SPI.

The device is powering up, as nRST (reset output) and a few others are driven low. No oscillator change at 3.3v. I'll get current measurements soon.

I even ordered the recommended Abracon ABS07-120-32.768kHz-T tuning fork. 0.1" wide, soldered to a SIP2 header, plugged into board. Ditto - no oscillation.

I measured the inter-segment capacitance of the breadboard. 2pF repeatable. If that were affecting it, I should at least get some signal for a brief instant, right?

All out of ideas here. Anyone use one of these, or have some ideas I can try? Have another one if it's damaged, but perhaps it's something I've overlooked.

Edit:

simulate this circuit – Schematic created using CircuitLab

So I poured over the eval-kit schematic vs. mine and can't see any difference. Still, I added 10k pull-ups to all inputs except nCE and SDI as these are driven totem-pole from a PIC18LF. (nIRQ3 is a totem-pole output.) Using a 0.1uF bypass cap.

Confusingly, the eval board refers to XO as "Clock Input." I don't know if that is true or not, but I'm still getting no response from SPI and nothing on XO or XI using a 10M probe on 10x setting (down to 1mV/div.)

To be clear, I am sending the AB1815 the following: 0x0F (read status reg), (no response), (no response.)

The blips on MISO show where the SCL line toggles, around 65kHz.
nCE is correct (low only during transaction.)
Tried all manner of CPOL and CPHA.
The eval kit includes C code, but it doesn't contain any "init" or "main" function.
Default bits set device for crystal resonator operation.
Shown are MOSI and MISO: 0x0F (read status reg), nothing.

The SPI pins are multiplexed with another device (separate SS line), and that works fine. Here is a photo of MOSI and MISO during communication with the other device. (Command: 0x0B (read register), followed by a 0x00 (Device ID), returns 0xAD):

I doubt just XI or XO are not soldered properly, as all other pins seem to be working fine. Is some kind of SPI initialization required for the AB1815? About to try sending it a reset command upon startup. Thanks for any insight you can give!


texts: swapping a 1uf 200v axial capacitor for a .9uf 200v axial capacitor

texts: I have a bad axial type .9uf 200v capacitor in the power supply of an old turntable. Can I substitute a 1uf 200v axial capacitor in its place?


texts: I have a stream of water, it flows at 1 gallon per minute into a water wheel. The water wheel produces about 75lbs of torque. How much electricity can I make with this? Where can I get more info on how to compete this project?


texts: Why does this MOSFET switch on so slowly?

texts:
I am learning Tina and drew this simple MOSFET switch:

Adjusting P1 will at a certain point switch on the MOSFET, which I expected to  saturate immediately. However when I look at the DC transfer characteristic, it turns on 'slowly' when the gate voltage moves between 3.5V and 4.7V

I confirm this by setting P1 to 4.3%, where the MOSFET seems to be half-conducting and thus dissipating 249W:

How can this be? I thought that this kind of MOSFET was a switch but it seems to behave like a BJT (albeit in a narrow gate voltage range)?

EDIT: Thanks to for the answers, all +1, which thoroughly enlightened me; I accepted Andy's answer simply because it corresponded best to my lack of understanding.


texts: How to program SoC chips like CC2541F128RHAT

texts: I am working on a BLE project. As per initial research, decided to use the cc2541 chip as BLE module. I have found one here. As per the datasheet, it shows it contains BLE and MCU. I need to program the MCU for accessing the GPIO pins. Can I connect a USB-TTL converter and program SoC like this or is it requires special development kits for development.


texts: Why is base resistor of a transistor important?

texts:
I know that this is a very basic question but I really do not know the answer.

I was making simple logic gates using transistors and I used PNP transistor as NOT gate.

I made the following circuit: (A) AND (B) AND (NOT C)

This circuit does not work without the resistors R1,R2 and R3. Why are these resistors important ?

simulate this circuit – Schematic created using CircuitLab

The Following NOT gate does not need a base resistor. I connect Vcc or ground directly to base and it works.

How can it work without resistors although it is very similar to the previous circuit ?

simulate this circuit


texts: Powering an SN754410E from Arduino logic pins

texts:
I want to run a very small stepper motor using a 5V source (specifically, a stepped-up Lipo battery). Since both the stepper I have and the SN754410E are rated to operate from 5V up, I figured this would be fine. My first question is, can I simply connect the pins together with a trace, with a single decoupling cap providing for both, or should I have one on each pin?

I have also currently got pins 1 and 9 on the SN754410E connected to one of the digital O/P pins of an Arduino Nano so I can easily switch the SN754410E on and off as I need it. Have I got this right? I'm concerned about current draw on the arduino pin going over the rated 20mA, so should I just connect pins 1 and 9 directly to the 5V net? I am wanting to reduce the circuit's quiescent current as much as possible.

Here's the datasheet for the stepper I am using.


texts: How is the following ground symbol different from conventional ground?

texts:
I've seen the following ground symbol in quite a few schematics:

How is this different from the typical GND symbol?


texts: Combining perfect voltage and current sources

texts:
I am attempting to reduce the circuit shown into a form of a single voltage source and resistance in series using Thevenin and Norton conversions.

I approached the problem by first considering a Thevenin equivalence circuit to reduce the 6V source, 6 ohm resistor and  5 ohm  resistor to a 30/11V source with a 30/11 ohm resistor in the position of the 6 ohm resistor.

I then did a Norton conversion for the 2A source, reducing the circuit to a 30/11 V source on the LHS and 60/11 V source in series with a 30/11 ohm resistor on the RHS, which reduced to a 30/11 V source in series with a 30/11 ohm resistance. This was incorrect.

Any advice on how to correctly reduce the circuit would be appreciated: I'm not sure which of the reductions I made were invalid.

[![enter image description here][1]][1]

The circuit should reduce to an 18V source with a 6 ohm resistance in series across the 2 wires on the right


texts: Why do blue LEDs have more candelas of luminous intensity than the green ones, in general?

texts:
I have been going through datasheets of a lot of LEDs, manufactured by a plethora of manufacturers, like Vishay, Kjell, etc.

The Blue LEDs, as per my observation, have more luminous intensity than the Green LEDs that I have been going through, for the same manufacturer. That doesn't make any sense to me. Green LEDs have their spectrum of illumination in the most sensitive region of eye, that means for low radiant power, you'll get almost the same luminous intensity. However, for Blue LEDS, they certainly need to have a huge radiant intensity, because their spectrum lies in the less sensitive part of the eye, and, hence, cannot match the green LED, in its brightness. However, for e.g. Vishay has SMD LEDs with their Luminous intensity lying in the region 0.7 to 70 MilliCandela, while Green LEDs' variation is just 7.2 to 12 MilliCandelas. If I want equal Radiant intensity for Green and Blue, that won't be possible because Blue has a photopic response somewhere around 0.009 to 0.08, in general, however, Green's photopic response is 0.85-0.92

Thus, my questions are:
(a) Is my analysis correct?
(b) Can one have equal radiant intensity for Green and Blue LEDs?


texts:
I'm looking for a way to amplify a signal from 5v -> 24v.

This signal is a PWM with a frequency of 150kHz.

Amplified signal will have a fixed load of 20mA to power a LED with a Vf of 1.25v.

I've thought about an opto like TLP293, but too much current. I've done a test with 2 NPN and 1 PNP but didn't worked like expected.

Do you have suggestion to analyze?

UPDATE:
It's a test circuit. Main use will be to light a LED of an optoisolator at 20mA, but I'll use it also for different test purposes. That's why I didn't specify more.

Here's what've used:

simulate this circuit – Schematic created using CircuitLab


texts: Shannon-Nyquist - only for repeating signals?

texts:
This was triggered by the comments in this question.
I'm using this definition of the Shannon-Nyquist theorem (form wikipedia):

If a function x(t) contains no
frequencies higher than B hertz, it is completely determined by giving
its ordinates at a series of points spaced 1/(2B) seconds apart.

I was under the impression that the Nyquist theorem is theoretically true in the following sense: if you decompose a signal into sinusoids, and then sample at 2x the highest frequency sinusoid, you can perfectly reproduce the original signal. This is because there's only one sinusoidal curve that fits all the samples at or below 1/2 the sampling rate, and if we're considering the highest frequency component in the original signal, it must be a sinusoid (or else it wouldn't be the highest frequency in the signal).
But others commenting on the question linked above said this only applies to continuous signals. One person elaborated on this as follows:

think about continuous signal reconstruction from discrete-time
values: in theory, every value between two sample instants requires
the sinc sidelobes of all countably infinitely many samples before and
after. That's a bit problematic, especially because we don't know the
future. Assuming periodic repetition is one of the common tricks to
get around that, so that with only a limited amount of past and no
future, we can reasonably sinc-interpolate

I don't really understand this - does it mean that what I said above about the Nyquist theorem is not completely true?


texts:
I am using a LM317 to create 12V into 7V which is driving a load that draws 1A. So I have to dissipate 5W from my voltage regulator. Datasheet is here.

According to the datasheet Rja is 65 C°/W (Case 221A) so the heat on the chip is 65*5=325C° which is way too much obviously.

So I need to choose a heat sink but not sure how. One confusion I have is, each heat sink has a thermal resistance associated with it but I'm not quite sure what to do with that number or what to calculate next.

If I pick a heat sink with a thermal resistance of lets say 4 C°/W then does that mean the heat on the chip will simply be 4*5=20C°? So I've solved the temperature problem?