texts: hacking a toy rc car I don't understand two little things

texts:
So I started hacking a toy RC car apart.

I ran across two things here I don't understand:

The motor (looks like a 6V motor) has a capacitor between the two ends. Why is there here?

The current comes in from a regular set of AA batteries. I'm assuming it won't cause any harm if I leave them there when I plan to control the motor from my own L293D hooked into an arduino? It looks like this:

There's a piece of wire coming out of the main PCB (soldered at a point). It goesinto the plastic of the car and it's soldered to a golden piece of foil.

I've never seen anything like this! Would this serve any purpose? It Isn't connected to anything.

As a side note, the car does allow me to put AA batteries and then stick a charger (with a barrel jack) into it to charge the batteries.

This looks like this:


texts:
I constructed a simple voltage doubler on a bread-board. Here's the schematic.

simulate this circuit – Schematic created using CircuitLab

The output across the 100kΩ resistor was the following. (middle waveform is input, top is output)

Now when I scaled the resistance and capacitance (for the elements on the right) proportionally - resistance went to 1kΩ, capacitance went to 1mF - the output changed as follows.

Why does the output voltage go down so much? I can't seem to analyze the circuit and see why this would happen. Might I have mixed something up?


texts: How do I pick a flux cleaner that's safe for use without industrial ventilation?

texts:
I was looking at getting this flux cleaner: Fluxclene FLU200D but then I noticed that in the datasheet, it mentions an inhalation toxicity of 300 ppm. That sounds like it's easily exceeded by just spraying the cleaner onto my PCBs, even if I have reasonable ventilation.

Should I avoid this cleaner or am I misunderstanding this parameter?

More generally, how do I pick a safe flux cleaner? I've used isopropyl alcohol and found it entirely unsatisfactory in dissolving the flux residue.


texts: Finiding composition of circuit from frequency response and bode plot

texts:
I have the following bode plot and nyquist plot result of an unknown DUT (it is a filter I asume!).

I wonder what kind of arrangement it has in terms of being a series or parallel RC or RLC network.

Since the top left plot starts at 500 and to the middle of the frequency it reaches the minimum, I assume there is a resistor involved.

Also because there is no so called half-circle in the nyquist diagram I assume there is no capacitor in the circuit.

The phase shift from -90 to +90 in the lower left graph makes my head scratchy!

What could be the circuit for this graph?


texts:
I have made thermometer with 1-wire sensor (DS18B20). The sensor connected to microcontroller via long (approx. 4m) three wires (GND, VDD, DQ). The wires has no shield.

It works, but I worry about EMI. Should I protect wires? If yes, how? Can I use ferrite bead on DQ near my device?


texts:
How to properly choose bootstrap capacitor and resistor in the common-emitter amplifier circuit, if we know that the circuit should have a low-frequency 3dB point at 100 Hz?

Here is the schematic. :

simulate this circuit – Schematic created using CircuitLab

All the values, except Cb and Rb were calculated from the previous exercise.

Here is my efforts:

1) Rb.
The network is used to increase the input impeadance and bootstrapping resistor is connected in parallel with the emitter resistor. At signal frequencies (X\$_{C_b}\$, X\$_{C_1}\$ \$\approx\$ 0), the impedance looking into the input is:

$$ R_{in} = \beta R_e || (R_{b_{eq}} + R_1||R_2),    (1) $$

where

$$ R_{b_{eq}} = \frac{R_b}{1 - (R_1||R_2||R_e)/(r_e+R_1||R_2||R_e)} \approx  20 R_b \space \space
(\text{taking re = 50 Ohms for Ic = 0.5 mA  in this case}).       (2) $$
is the equivalent bootstrap resistance, considering feedback.

To maximize the input impedance from Eq. (1), we should have
$$ \beta R_e \approx (R_{b_{eq}} + R_1||R_2)\approx R_{b_{eq}},     (3) $$

which yields:
 $$ R_b \approx \frac{\beta R_e}{20} \approx 5 \space kOhm. $$.

So far so good.

2) Now in order to get the capacitor value, we need to use the information about 3dB point at 100 Hz.

This is my equivalent scheme for high-frequencies:

simulate this circuit

In order for feedback to work properly, it should have the same cut-off point. So I assume we can just look from the emitter output back towards \$ C_b \$ and \$ R_b \$ and see a low-pass filter formed by \$ C_b \$ and \$ R_1||R_2 \$, which yields \$ C_b = 1.6 \space \mu  F\$.

1) Are these considerations correct (for Rb and Cb)?

2) Is there something else one has to take into account choosing the values?

3) Does introduction of the bootstrap affects high-frequency performance of this circuit in any way?


texts: SMD oscillator and decoupling caps placement/routing

texts:
I want to design a four-layer board with a PIC32MM0256GPM048T microcontroller. All components must be on the top of the board. I tried routing OSC1 (osc in) and OSC2 (osc out) lines, and placing the load capacitors (0402 C0G) near to the crystal (18.432 MHz, 2520 package), but I am not sure that is correct.

The decoupling capacitors (and GND line) are also near to the crystal's tracks.

Will it cause any problem?

Thanks for the help.


texts:
I am discretizing the PID equation so we have this equation

Now if we separate the integral term we get

Applying backward euler method

Now as we already have a differentiation , by applying backward euler method

and the end equation is something like this

I just want to ask if I did something mathematically wrong or did I miss a step ?


texts:
My apologies if this is the wrong stack website for this question.

We plan to use a BeagleBone Black as the control computer for an electric car. The BBB handles, among other things, communicating with the motor controllers over the CAN protocol (using can-utils).

Installation (according to a number of online guides) seemed to be going well (device tree setup, modprobe, etc), with no errors, until we actually plugged into the motor controllers... and nothing happened.

We hooked up an oscilloscope (to both the TX and RX wires on the BBB) and watched the execution of the following commands:

ifconfig can0 down
ifconfig can0 up
cansend can0 180#1234

which should send data along the bus. The oscilloscope showed the following (RX on top, TX on bottom), every time we executed the commands above.

I suspect this signal we were seeing is some sort of handshake which was not being answered.

(Note that if we tried to run cansend again, nothing would happen until we ran ifconifg down/up).

After many such execution cycles, interestingly, ifconfig reported that the RX bytes had been increased, even though nothing had been received, only sent.

A few days later, with an identical setup, the CAN bus is still not working, and we are not seeing the handshake signal on the oscilloscope. ifconfig reports dropped bytes but little else to help us.

Any ideas on where to go from here, how to debug this issue, etc.?


texts: 12v socket not providing enough current for mobile phone?

texts:
I've just installed a 12v socket to my motorcycle. The socket has a sticker saying "12V - 1A", and the user manual says that "use is possible up to a power input rating of 12W". Taking that into account I bought a USB adapter rated for 1A (the model is this one) and it seemed to work.

Now, I've been trying to use my mobile phone (a Galaxy Nexus) as a GPS (the app I use is Sygic, although I think that doesn't add much). The problem I've found is that, while using the GPS app with the mobile phone connected to the usb adapter in the 12v power socket, the "charging" icon appears, but the battery is not actually charged, nor kept at the same level. It keeps discharging, although at a slower pace. Eventually the phone runs out of battery and shuts down.

Given these facts, the problem seems that when using the GPS (haven't checked in standby mode), the energy is consumed at a faster speed than the charging speed. The question here is... does that make sense? It makes sense to me at least. The Sygic app running, plus the GPS module updating the location constantly, plus the screen at full brightness, could that need more than 1A?

I'm asking this just to discard an electrical problem. Is there a way of measuring if the 12v_to_usb adapter is actually providing 1A of current?

EDIT: There seems to be a related thread in reddit: http://www.reddit.com/r/Android/comments/nystt/galaxy_nexus_power_analysis_why_chargers_cant/


texts: USB to TTL converter: why doesn't TX need a voltage selector?

texts:
I plan to flash new firmware for a Sonoff ESP8266-based switch.

So I need a 3.3v USB to TTL for the programming. I see an inexpensive converter from China which has pinouts for

3.3v
TX
RX
GND
5v

My question: I understand the 3.3v and 5v pinouts as providing constant voltage for the load (device being programmed) with the power coming from the USB port. But why isn't a switch of some sort needed so the TX line can be set to either 3.3v or 5v output?

What I am missing here? Thanks.


texts:
I am using Lattice Diamond, I wonder how does lattice recognize the type of
signal when synthesizing vhdl/verilog.

I have a module such :

entity test is
PORT ( -- clk  : in std_logic;
      --rst    : in std_logic;
        bclk   : in std_logic; -- burst clock
        da     : inout std_logic_vector(15 downto 0);
        cs0_n  : in std_logic; -- chipselect 0
        cs1_n  : in std_logic; -- chipselect 1
        lba_n  : in std_logic; -- address valid
        eb     : in std_logic_vector(3 downto 0); -- byte enable
        rw_n   : in std_logic; -- write enable (as seen from eim)
        wait_n : out std_logic; -- wait (burst)
        oe_n   : in std_logic; -- read enable (as seen from eim)
        dout   : out std_logic
      );
end entity test;

architecture behavioral of test is

...snip....
begin

   -- the only time rw_n and lba_n appeared :
   -- rw_n, lba_n recognized as clock, while cs0_n as regular port
   da <= (others => 'Z') when cs0_n = '0' AND lba_n = '1' else data_out;
   data_in <= da when rw_n = '0' AND lba_n = '1' else data_in;

...snip....
end

Somehow Lattice synthesize lba_n and rw_n as "Clock Input" in spreadsheet view. Those are not clocks, it should be defined as regular input ports.


texts: I want to make a BLDC Hub motor for my bicycle but I am 10th grade and doesn't now so much about electrical engineering

texts:
Firstly, I want to make a BLDC motor WITH hall effect sensors to maximize the torque. I have a heavy mountain bike and I love to make long trips with it. But in my city, there are REALLY steep mountains which can be challenging with extra luggage. I want to make a compact BLDC motor in the rear or front hub which can make a little boost on the hills. I need torque, not speed. I'll use it just for boost, I won't convert my bike into a motorcycle.

So, I designed a BLDC motor that isn't so accurate for maximum torque but gives an idea for the design. I will start from inside to outside. First, we have a shaft in the center which is linked with 8 neodymium magnets around it. Then, we have the case which has the 3 phase coils and hall effect sensors in it (probably I will use 3 hall effect sensors). Then, we have the electronics which are linked with coils. And last, we have the lithium-ion batteries linked around the case. I'll add one of the lithium-ion batteries for better understanding. The volt and amp can be changed; it is for better understanding.

The magnets are not moving; coils, electronics, and batteries are spinning with the wheel.

I hope the photos will be helpful. I will also make it waterproof and dustproof so it can't have the cold wind in it. So I taught that I can fill it with engine oil. The outside will be aluminum so it will be cold I think.

Now, let's come to my questions. As I said, I'm 10th grade and don't know so much about electrical engineering.

My first question is: When BLDC motors off, do they affect my normal riding, like convert my power into electric or just make so much friction because this is a motor? I mean, when I don't pedal, does bicycle stops faster than before?

Second question: I don't know so much about how to install hall effect sensors. I googled it and find some info. But if you can tell a little bit again, it will help so much. And I know I should use ESC but I don't know how to install it, like which cables in my motor will go where?

Third question: What upgrades can I make for high torque, low speed?

Fourth question: How thick wires should I use like 250watt motor and how to wind them?

Very thanks for reading this and I hope you understand what I meant and you can answer my questions. Sorry for my bad English.


texts: MSP430 waking up every millisecond, what power usage to expect?

texts:
I have an MSP430 waking up every millisecond from a timer interrupt (to do a tiny amount of work, ie increment a counter and check a couple of input pins).  It is set up to run at 25MHz.  What should I expect as the total power consumption?  How would one calculate that from values in the spec sheet?

(The specs for this exact part say 195uA/MHz running from flash and 2.1uA in LPM3, plus "fast wakeup" I think 6us from LPM3)


texts: Differential equation for trivial RL series circuit

texts:
I would like to obtain differential equation describing behaviour of this circuit. I'm really new to this and not quite sure how to begin. We can consider situation of knowing values of all parameters of circuit: U (voltage), R (resistance), L (inductance) and iL (current).

I assume final equation should include all of the variables, so for given values it gives us idea of how the circuit behaves. I found this equation which might possibly fulfill those assumptions:

How should I proceed in case this formula is correct?


texts:
According to Barkhausen's criteria, for oscillation the feedback should be made after phase difference of 2pi and gain has to be >=1.

Now when I consider a ring oscillator if 2 inverters are connected as in:

Here the phase change after 2 inverters is 2pi. But this would actually not oscillate since output will not change. This is a contradiction right?


texts: How should I connect the windings of this induction motor to make it work?

texts:
I took this motor from an old washing machine and I'd like to make it work.

The motor has the following specifications:

Input voltage: 220 V 50 Hz
Number of poles: 2/12
RPM: 420/2820
Rated power: 0.12/0.08 HP
Capacitor needed: 14 uF / 450 V

I tried to draw a schematic of the motor by using a multimeter to measure the resistance of the windings (of course the schematic is just for connection purposes and not for modelling since it lacks inductance and slip). However I'm not 100% sure I got it right. The schematic is as below:

In the schematic, M8 is the neutral while the phase is marked with L. According to the connection box, it looks like the neutral should be wire M8. In the connection, the capacitor is connected in series with a winding and the motor should work at low speed (12 poles). What I don't understand is that when I measure the resistance across m4 and m5 I get 90 ohm instead of the expected 140 ohm (given by 70 + 70). While for all the other permutations of connection the measurements check out, this is not true for the series of m4 and m5 as you can see from the schematic.

This thing leaves me a bit of doubt on whether I understood or not the internal wiring of the motor. Could you please help me to shed some light on this?


texts: I've googled almost 100 times, unable to find what really is transimpedance. Every search displayed results about transimpedance amplifier, but didn't tell about the term transimpedence.


texts: What's the PIC FVR's gain amplifier settling time when you change the gain

texts:
I previously had configured a PIC (16F1704) to use the internal FVR for ADC reference, with gain of the FVR set to 2x, i.e. 2.048V reference.
I've since added another signal to be measured, but the signal spans 0..900mV only. I'm tempted to change the FVR's gain to 1x while reading this channel to get one bit more resolution.

The code therefore looks like:

Set FVR's gain to 2x
Read ADC channel 1:

Change ADC channel to 1
Perform ADC conversion

Read ADC channel 2:

Change ADC channel to 2
Perform ADC conversion

Read ADC channel 3:

Change ADC channel to 3
Perform ADC conversion

Set FVR's gain to 1x
Read ADC channel 4:

Change ADC channel to 4
Perform ADC conversion

Repeat

Now, while changing the ADC channels it's recommended to introduce a small delay before you start the ADC conversion, so the input capacitor of the ADC can settle. I've been using 5µs delay (after each channel change) as recommended by a Microchip tutorial. Is there an equivalent delay associated with changing the FVR gain? I haven't found a recommendation on that, nor a datasheet value on the Independent Gain Amplifiers' settling times.


texts:
I have recently become involved in FPGA design and I am just testing out some new Zync SoC hardware. I have followed a tutorial online to blink some LED's however I have modified it to blink all the LED's at different rates. My code is as follows and describes a potential 8 element LED counter:

//  Simple LED logic
// reg [28-1:0] led_reg2 [8-1:0]; // 28 bit wide, 8 element memory
reg [28-1:0] led_cnt_0; // 29 bit LED counter
reg [27-1:0] led_cnt_1;
...

always @(posedge sys_clk_i) begin // on every positive edge of system clock
    if (!sys_rstn_i) begin // if the system is reset
        // led_reg2{8-1:0} <= 28'h0; // failed attempt to describe resetting an 8 bit bank of registers to 0
        led_cnt_0 <= 28'h0; // reset the LED counter
        led_cnt_1 <= 27'h0;
        ...
    end
    else begin
        led_cnt_0 <= led_cnt_0 + 28'h1; // increment counter
        led_cnt_1 <= led_cnt_1 + 27'h1;
        ...
    end
end

assign led_o = {led_cnt_0[28-1],led_cnt_1[27-1],led_cnt_2[26-1],led_cnt_3[25-1],led_cnt_4[24-1],led_cnt_5[23-1],led_cnt_6[22-1],led_cnt_7[21-1]};

My code does as desired and they blink at rates equal to 125e6 / 2^n
- However, I am not satisfied with the layout of my code and the syntax, considering Verilog is designed to solve such problems of this nature.

My question is:

What is the correct/suitable syntax of such a problem?
I have made attempts to solve this by making a 28 bit wide, 8 element register, however I don't know how to correctly control it. I have spent quite a while looking for similar problems and syntax's but have been unable to implement it correctly. I also think a trial and error approach to this is not the way forward, as this is not simply programming.

Additionally could anybody recommend suitable reading material to learn and practise Verilog, I am familiar with the structures etc, through lecturers a few years ago but have no clue with regards to the implementation.

Many thanks.


texts:
I'm reading about op-amp circuits that use negative feedback from this article (question no.19).

What confuses me is that the negative feedback for the Op-amp (which is being used to reduce            cross-over distortion) is given directly from the output of the push pull amplifier. Does that not cause the output voltage (at point B) to be equal to the input voltage (at point A which is equal to Vin due to virtual short effect)?

Does this not nullify the Amplification
of the Push-Pull amplifier which was the aim of the circuit in the first place? Does the circuit now have unity voltage gain?

Even if we were to add resistors in the feedback loop, wouldn't the gain of the system be determined by the Op-amp itself rather than the Push-Pull amplifier which originally was the main circuit?


texts: Can a dynamic circuit extract all energy from an ultra capacitor?

texts: I understand that the energy extraction from an ultra capacitor drops the voltage to the point where the load can't function. But, is it possible to create a converter that can continuously present a consistent voltage to the load using a dynamic dc-to-dc circuit to allow all the energy in the ultra capacitor to be utilized, even if the current drops? What are the issues?


texts: Thermistor motor protection relay for thermal protection

texts:
In some of my induction motors PTC thermistor is available for thermal protection which will be integrated to thermistor motor protection relay. There are three PTC thermistors connected in series in single motor. Maximum measuring temperature and voltage for PTC thermistor are 150 degree and 2.5Vdc. In that case can I use LT3SM00M Schneider  thermistor motor protection relay for tripping the motor.

As per datasheet, voltage at terminals in the thermistor circuit:

Normal operation: R=1500 ohms; V < 2.5 Conforming to IEC 34-11-2
R=4000 ohm and V < 7.5

Here maximum measuring voltage of my motor thermistor terminal is 2.5Vdc. So as per datasheet of LT3SM00M for less then 2.5V it will have normal operation and after 2.5V it will trip the circuit, but what does it mean by "Conforming to IEC 34-11-2, R=4000 ohm and V < 7.5." Please help me in this regard. Is there any consideration of R=4000 ohm and V < 7.5 for my circuit.


texts:
We got a bluetooth bee for testing purpose on hardware. Unfortunately the device only seems to run SPP. But it seems possible to do more than that.

Here's the product:

http://www.dfrobot.com/index.php?route=product/product&filter_name=bluetooth%20bee&product_id=193#.UVinkBl9gy5

And the datasheet:

http://www.dfrobot.com/image/data/TEL0026/TEL0026_Datasheet.pdf

When I enter in AT mode, I can set the class of the device to something different to the default. While scanning, my computer could see that my blueooth device was a "keyboard" using the class 0x540

That said, while trying to PAIR it with OsX 10.8, I set the pair code to 1234 as configured but osx isn't able to pair the device. (It seems to enter the pincode correctly and wait for something to happen and then fail)

It's not possible to be in inquery mode unless you started the SPP profile. Which makes me think that it's not possible to run my own profile using UART but since we can change the device class, it should be possible to run my own profile but I couldn't find anything about it.

I'd like to know if it's possible to run different service like "hid" on this chip even if the firmware only seem to support the spp profile but allows different classes. I'd like to implement a HID device like a remote control


texts: 27 bit parallel Bus @65MHz: Use 3.3V or 1.8V?

texts:
I've a LVDS transmitter (SN75LVDS83B) connected to the GPIO bank 0 (as DPI24) of a raspberry pi compute module 3. The pixeclock is 65MHz, the 27 parallel lines are 3 x 8 bit RGB + Hsync + Vsync + DE. The length of the lines is approx. 80mm.

Now I have the choice to power the GPIO bank 0 and the LVDS receiver with 1.8V or 3.3V. Both works and I ask myself what would be the better option. My pro/cons:

3.3V pro: Higher signal to noise ration
3.3V contra: Higher electromagnetic emission and energy consumtions
1.8V: The above inverted: lower signal to noise ration but less emissions and power consumption.

Are these assumptions correct and are there other reasons to prefer 3.3V or 1.8V (both are present so there aren't additional expenses for a second voltage)


texts:
Channels 4 and 17 are received, in contrast to the target channels 12 and 25 which do not. Attempts to move the antenna from indoors to outside on the balcony did not result in reception of target channels, but seemed to improve reception of existing channels (no 'tearing').

Antenna is mounted on a balcony ~15 AGL.  Signals originate from the same location, but transmission power is unknown.

QUESTION

Is it unreasonable to expect the target channel reception (12 & 25) if channels 4 & 17 are received?

Kudos to Tony Stewart for suggesting the website and its screenshots:

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3ddfafd3f6c59f8c


texts:
I have an iMac display (thin LCD) that has the glass broken yet the LCD is fully functional and another iMac display with LCD broken but glass undamaged.
I am wondering if there is any recommended process that can do carried out to remove LCD with broken glass display and do the same in donor LCD with undamaged glass and re-laminate the working LCD with undamaged glass?


texts:
I have just broken my nexus 7 and I was about to salvage the battery. I was thinking of using it maybe to power my raspi or arduino.

My main question is how do I charge it?

I was thinking of cutting the connector from a mobile charger and putting the plus on the plus and the negative on the negative. Is this too simplistic?

Here is a photo of a nexus 7 battery. I am not sure why it has two reds and two blacks and some other coloured wires to make it even more scary :)


texts:
I was reading the datasheet for the LT1161, and dicovered the below construction in an example application toward the end of the document (Page 11). It appeared to be powering some Logic ICs.

This clearly seems to be clamping the supply voltage to something the logic IC can handle, so how does this work, and how is it better than just using a zener with a resistor?

simulate this circuit – Schematic created using CircuitLab

Context, lower left, click to enlarge:


texts:
I have a component on a PCB we are analyzing to identify components. While we have identified mostly everything on the board, there are three components labelled with the reference designator "N". I have thoroughly searched for what this could mean and the only place I could find any mention of this symbol is this IEEE site, where it just labels "N" as an "equipment subdivision" (Page 211).

Does this mean it is a custom component? I will attach a picture of the board we are studying, where you can see two ("N1" and "N3") of the mysterious components with "GR-2-103" written on them and the other "N2" component with the same long yellow shape on the far right top.


texts: Need help to identify this connector on an LED matrix sign

texts:
My step-dad has a matrix board with a control unit:

https://www.ledlightbars.co.uk/led-vehicle-message-signs/haztec-5-9305-99-led-vehicle-message-sign.html

You can plug your laptop into the control box via USB (laptop end) to unknown connection (control box). Then you can program your own signs e.g. "wide load" or "slow down" etc. Does anyone know what the connector is or what cable is needed?

I suspect this may be the cable needed, but I am not certain:

https://www.ledlightbars.co.uk/led-vehicle-message-signs/haztec-5-9301-infosign-programming-software.html


texts: Accidentally Pasted Beyond Origin in Altium

texts:
I'm new in Altium and I accidentally pasted some pads and components(the ones at the bottom corner) from another pcb file but I wasn't aware of it at first because it didn't show on the sheet on the 2D view. Is there anyway that this can be fixed/removed?
I'm afraid this will mess up in the manufacturing process since it can be seen on the Gerber file.Or will this not affect the design at all since it is beyond the sheet? Thanks guys!

Error/Bug not seen on 2d view

Paste Error/Bug in 3D View

Paste Error/Bug in Gerber


texts: voltage drop - operating a solenoid after a logic gate and a LED

texts:
I have started meddling in circuitry, but I lack any sort of formal training.
Subsequently I apologise for my ignorance.
The circuit I have made (on paper) so far has a number of issues, but I want to try to solve them individually instead of just dumping the whole thing here.
It will be an overengineered box with a bunch of switches and every switch on the box needs to be toggled in order for it to unlock.
I have ordered some parts already and I will be measuring out the values as soon as I have them, so I cannot give you the specifics already - unless you guys are ok with part numbers.

TL:DR
I want to make a box that can open only after all switches are in the ON position.

The switches and the LEDS are needed in the box (because of a pun I will be making) but I fear the logic gates and the LEDS will drop the voltage too much for the solenoid to operate.

Question: How do I make the switches and leds obligatory while still being able to only unlock the box with the solenoid if all switches are ON.

Not part of the question:
This is part of the full circuit
(only as illustration, more questions to come later)

Edit: Thanks for the suggestions and help so far.
I know I have a lot of stuff still wrong in the circuit, but I need to draw it "as is" if I want to understand it, I'll make a whole bunch of annotations on it and revise it a few times before I get to putting it actually together.
And I'll need to do that, as you guys pointed out as well, it won't work.
I know this but I can't show you the problem without having a problem to show :)
So that's where you guys with all your knowledge of components and know how come into play.
I'm already reading up on a lot of material, see picture 3 and whatever I can find on youtube and the internet.
Thanks for helping me out so far!
Box-parts and holes for LEDs are already accounted for :)

The pun in question has the answer: 'switch the lights (1) on and you will see (2)'

(1) Lights being all the LEDS that light up after switching them on.
(2) you will see: the box that will open


texts:
Why are transformer based oscilloscope probes not common?

It should be possible to put a miniature 10:1 signal transformer at the probe tip, and connect it straight to the 50ohm input of the oscilloscope to create a 10X differential probe.

I would imagine some advantages:

Poor mans differential probe.
High impedance at high frequencies.
DC isolation allows high voltage probing.
Less expensive than active probes.
Functional over a wider temperature range, allowing measurements inside environmental chambers.

And a couple of disadvantages:

Bandwidth limited to approximately 1~500MHz.
Only usable on DC balanced signals, such as Ethernet, PCI-Express, and similar. Probably useful for some RF measurements as well.

What am I missing?


texts: Timed one-shot circuit to drive laser module

texts:
I'm trying to adapt my Match Guns MGH1 (Air pistol with electronic trigger) to use trigger a laser when shooting. Currently the trigger circuit is driving a solenoid. The circuit board seems to have the trigger signal passing through a monostable multivibrator (NXP HEF4538BT) that drives a LL024N MOSFET, which in turn drives the solenoid. I don't want to use the trigger circuit to drive my laser directly as I don't want to introduce any noise in it and affect trigger performance.

I want to create a circuit, sharing power and the trigger signal, that upon trigger press (positive edge, trigger is pulled down), generates a pulse with time T, regardless of the time I press the trigger. I designed the following circuit:

The idea is that as long as I'm not pressing the trigger, the capacitor charges up through R2 and M5. When I press the trigger, the capacitor can discharge through R3 and M2. Doing an AND operation with the trigger signal and the voltage on the capacitor seems to produce the signal I want.

With the premise that this works as I see it, I would like to get rid of the NOT and AND gates with some 555 magic, or some simplification of this that I'm not seeing!

This all-FET version seems to also work, replacing the logic gates since the circuit wont have logic-level voltages.


texts: Motion-detection alarm - how to make alarm persist?

texts:
This is a basic question. I have a motion-detector, but when it detects motion I don't think the output voltage persists. So it can trigger my transistor to trigger a buzzer I have, but after the motion passes all the voltages would die back down and the buzzer wouldn't ring anymore. I want, when the motion trigger happens, for the voltage across the buzzer to persist so that the buzzer keeps ringing until someone manually comes over and turns it off.

How can I make it so that when the trigger happens, the voltages persist?
 Either forever or a really long time (several minutes). Is there a component that would allow this to happen? Would like to avoid using a microcontroller for something this simple. Thanks!


texts:
For a RS-485 Communication using a Maxim MAX3292 Driver, Full Duplex, 1/4 load unit (54 \$\Omega\$), 5 Mbps, with UTP 120 \$\Omega\$, standard cable, for each receiving unit I am thinking on a design placing two (equal) connectors, and making a tee directly in the PCB, connecting both to the Driver.

Being 10 Mbps the maximum realizable speed with this device,
Should I consider a strip geometry as Power Divider, for matching impedances (\$\lambda\sim2m\$ for 70% VF) ? or a lumped parameters Power Divider like this (with 180pF, 90pF and 2.7uH)? Or an specific device|driver? Should I take some design cautions on this tee (angle, dimensions, lengths, details), or it is enough to simply draw a "T" and minimizing the vias quantity (see the referencial PCB sketch)?

Thanks in advance.


texts:
I've set up a ESP8266 to play MP3 radio from a web server, using the ESP8266 Audio library. My circuitry is pretty much like this:
My question is, how can I amplify the volume of the sound, as it is not high enough for me. Is it merely  connecting higher voltage to the circuitry, like a 9V battery? If so, how can I know the limits my speaker and my transistor can handle? Is there a max voltage specified for speakers and transistors? Are there ready-made amplifiers for such things?
I would appreciate if someone could tell me exactly what kind of products I need in order to amplify the ESP8266. I prefer plugging to the electricity rather than using a battery.
Thanks !


texts: Why do we use S-parameters for High frequency signals?

texts:
I have read at numerous places that S-parameters are used for analyzing systems which deal with high frequency. But why only high frequency? From what I have read, I have understood the following about S-parameters:

When a system is considered a box, then the relationship between the currents and voltages from its ports combined with the impedance at each port result in S-parameters.

How does frequency come into picture here?


texts: LTSpice: Get linear results using .meas command

texts:
Another quirky LTSpice question. I am measuring input impedance and using a .meas directive to get the impedance at specific frequencies:

.MEAS AC Zi_freq1  FIND V(in)/I(v1) AT=10k

When I right click on the y-axis and change the axis from decibel to linear, the impedance in kOhms shows up. However, when I run the .meas directive the impedance is in dB again. How do I use the .meas directive to get impedance in a linear scale rather than in dB?


texts: What should I take care of while using elastomeric connectors?

texts:
I recently got this module from ebay and had trouble getting it's back light on as there were no schematics. In the process, I had to take the screen off the PCB to reverse engineer the traces. I found a rubber like connector between terminals on the PCB and the LCD. From a quick search I learnt that these are called elastomeric connectors.

In the past I have had trouble getting a display to work once one of these came off. I have had to repeatedly disassemble and reassemble displays to eventually get them to work. How do I place these right? What precautions should I use while handling these elastomeric connectors? Are these hard to use?


texts: When connecting multiple differential pairs in a D38999 connector, is it common practice to have a ground pin for each differential pair?

texts:
I have a remote interface unit that has multiple differential pairs going to a from it. Some units that are connected have multiple pairs coming to and from. Should everyone one of the differential pairs actually have a dedicated pin for ground?
Keep in mind, the RS485 reference is just referencing the voltage levels, these are not being used for serial communication.


texts: Is it possible to send data while receiving audio with a bluetooth module

texts:
BM64 bluetooth module supports the following profiles :
A2DP 1.3, AVRCP 1.6, HFP 1.6, HSP 1.2 and SPP 1.2

Using the A2DP I can stream audio output to a speaker as it is for a sink, thus a speaker.

I want to send some information from the uC to the bluetooth module and thus to whatever device is paired with the module probably using SPP.

However, is that possible while still transmitting audio from the paired device to the module?

i get that they are different profiles, but my question if it is possible to send my data over A2DP instead of SPP. even if it was not audio, while handling the software side properly.


texts: How does a fire detector distinguishes between smoke particles and others?

texts:
Many fire detectors are optic so that when smoke comes in the fire detector, it causes the light from LED reflect to the photodiode.

But the question is why don't they alarm when somebody takes a warm bath or when somebody is dust removing? What is the difference between smoke particle and other particles?


texts: Does the hole injection take place from p semiconductor to n semiconductor in a pn junction diode?  Or it takes place only in the case of a transistor?


texts: Raspberry Pi, SPI, multiple data in lines

texts:
I have a ADC that works with SPI and I am interfacing it with a Raspberry Pi 3 Model B. The ADC chip has two ADCs with simultaneous sampling. There are two data lines, one for each ADC. How would one implement this in a Raspberry Pi?

This is a quote from the ADC datasheet:

'The data output is supplied to each pin as a serial data stream. The bits are clocked out on the falling edge of the SCLK input and 14 SCLKs are required to access the data. The data simultaneously appears on both pins from the simultaneous conversions of both ADCs. The data stream consists of two leading zeros followed by the 12 bits of conversion data. The data is provided MSB first. If CS is held low for 16 SCLK cycles rather than 14, then two trailing zeros appear after the 12 bits of data. If CS is held low for a further 16 SCLK cycles on either DOUTA or DOUTB, the data from the other ADC follows on the DOUT pin. This allows data from a simultaneous conversion on both ADCs to be gathered in serial format on either DOUTA or DOUTB using only one serial port.'


texts:
I have been wondering about Beagleboard and it's possibilities of supporting many embedded OSes

What I was wondering was:

Using a SSD as a SD Card? Does it depend on the OS?
Relocation of the Usb ports?


texts: Pull up resistor on Schmitt trigger IC input?

texts:
I have two different circuits on two different boards. The output of board A, let's say, is optocoupler based and hence, it has a pull up on it. This signal is connected to board B through an interconnect board. In the board B, I have used a Schmitt trigger inverter gate on the signal (to prevent signal chattering) before connecting it to the MCU's GPIO pin for detection.

My question is, should I place a pull up resistor on the input on the Schmitt trigger IC as well or not? If I keep the pin floating (don't add a pull up), will it cause the Schmitt trigger output to be unstable?
I am thinking of a case when for some reason where there is a connection issue between two boards and the input of Schmitt trigger is left open in unknown state.

Any advice would be appreciable.


texts: Fourier transform to understand filtering on PWM

texts: Is it correct to analyse the impact of a low-pass by regarding at the Fourier transform of a PWM signal, even if this one is generated with a H-Bridge ? And deduce that the higher frequencies forming the square signal are attenuated or even disappear ?


texts: Response of a RC circuit and Frequency Response Theorem

texts:
let's consider this important result of control theory for linear systems, called "Frequency Response Theorem" (reference):

Briefly, it says that under the hypotesis of stability and linearity, if the input signal is sinusoidal, the output signal will be the original sine with phase and amplitude variations respectively equal to phase and amplitude of the transfer function of that system.

Now, let's analyze a first order LTI system, whose transfer function may be written in this form:

\$H(s)=\frac{1}{s+b}\$

It is the transfer function for instance of a passive RC circuit whose output signal is taken from the capacitor:

Now, suppose the input signal to be a sine wave. Its Laplace transform will be the following one (table with Laplace transforms):

\$V_{in}(s)=\frac{a}{s^2+a^2}\$

The output signal in Laplace domain will be:

\$V_{out}(s)=\frac{a}{s^2+a^2}\cdot \frac{1}{s+b}\$

Now we may compute the inverse transform to find the time behaviour of the output signal:

\$V_{in}(s)=L^{-1} [ \frac{a}{s^2+a^2}\cdot \frac{1}{s+b} ]=\$

Suppose a = 5 and b = 10. We get the following result:

So, I have due questions:

1) You may see that there is a sine wave, but also an exponential term. It seems to be in contrast with the initial theorem. Which is the solution of this problem?

2) How do we see this exponential term in the simulation of the previous RC circuit? All simulations I have done with RC circuits determine behaviours like this:

I see it is a sine wave, so it is correct, according to the initial statement. But it is in contrast with the computation of the time domain behaviour.


texts: Longest, thinnest trace length to decoupling capacitor before capacitor is effectively useless

texts:
I was told time and time again to always put decoupling capacitors as close to the IC pin's VCC as possible.

Sometimes when I make complex boards, I try my best to put the capacitor lead so close to the VCC pin, that the distance between the inside of the capacitor (where the pin runs into) and the VCC pin is less than 3mm.

There are times where routing the single-sided board gets so complex that I have to use 10 or 12 mil wide traces and make a track length of about 1/2 inch to even 1 inch in rare instances between VCC and the capacitor.

Whats the longest length I can go with traces between IC VCC and nearest capacitor before the decoupling effects of the capacitor become useless if the width is 10mils wide?


texts:
Good Day everyone :)

I'm new to electronics and it'll be my 2 week practicing it as my hobby though i've done a lot of DIYs and stuffs just by following tutorials but when my friend ask me regarding the maths of my projects, i can't retaliate at all since even i researched for 2 days, i haven't gone far to understanding the math specially on batteries.

I have made a DIY regarding USB charger and its block sequence is like this:

12v Sealed Lead-Acid Battery -> 5v Voltage Regulator Circuit -> 2x (Li-Ion TP4056 Circuit Module) -> 2x Smartphone Battery

I want to know how would i compute this entire project with regards how much Ah, Volts, power, battery consumption, etc. if there will be 1 smartphone that will be charged and if it will be 2 smartphone also.

Some specs of this entire project are as follows:

a) 12v SLA Battery 10Ah

b) 5v Voltage Regulator 1A output

(i don't know the efficiency of voltage regulator, i just used LM7805 https://www.sparkfun.com/datasheets/Components/LM7805.pdf)

(my 5v voltage regulator circuit is like this: https://i.stack.imgur.com/beL4b.png)

(added some:)

100uF 25v cap before 0.33uF cap
10uF 10v cap before 0.1uF cap
some 1n4007 diodes from its ground and output
feedback 1n4007 diode from its output to its input as protection they said

c) Li-Ion TP4056 charger 1A output

d) Smartphone batteries 4.2v 3000mAh

It's ok for me if only formulas will be given with respect to discharge, power, etc for me alone to do the math, i just need some guidelines because to be honest, i don't know how would i explain if my projects are efficient or later will have a drawback, doesn't last long, not practical, etc. though i really wanted to know how would i compute the battery consumption/discharge on this project.

I hope you can help me because I'm overwhelmed right now, i have a lot of tabs on my browser to search that don't have guide where to start. There's always a miss or a variable or process i don't know that applies on the answers i see on web :(


texts: Protecting 0..10 Vdc PLC input from voltage divider failures

texts:
I'm working on an off-grid PLC based battery bank monitor and dump load controller to replace commercial units that don't work really well with our lithium ion battery bank. In addition, I plan to switch hydro turbine from nominal 24 Vdc to nominal 48 Vdc by changing from DD to DW or SD connection and then run it through an SSR to do MPPT and step down to battery voltage via PWM for better generator efficiency and lower line losses.

Initially, I'd like to monitor system voltage at the following points:

Battery bank, nominal 24 Vdc (future upgrade will likely change this to 48 Vdc)
DC bus in controller I'm building. When all is working as planned, this will be connected to battery bank and running the same voltage. But battery bank safety system may disconnect the battery bank for OVP/UVP or high differential voltage between cells. In this case, we still want to keep DC bus voltage correct to protect other components and--when sufficient solar and/or turbine power are present--keep things running without batteries.
Hydro turbine input 0..60 Vdc (higher OCV to be confirmed, may affect voltage divider and zener diode needs for this input)

The present plan is to use a Beckhoff PLC (due to familiarity with programming these) and an ES3068 0..10 Vdc input card to read voltages as well as inputs from hall effect sensors to read current at various points in the system.

I understand the voltage divider concept, but this is the first time I'm applying one so I'm learning as I go. I'm thinking of using 10 kΩ and 1kΩ resistors for the divider to give a readable range in excess of 100 V while still giving good resolution in the expected operating range. Based on internal resistance of input card >130 kΩ, it seems going much higher in resistors will adversely affect accuracy. Or am I missing something here? I would like to minimize parasitic load (and heat dissipation) of resistors while maintaining sensing accuracy within 100 mV around battery voltage (24-28 Vdc).

Considering possibly failure modes, I'm thinking defined interruption behaviour resistors such as these two may be a good way to go:

Vishay #PR03000201001JAC00 1 kΩ
Vishay #PR03000201002JAC00 10 kΩ

My thinking is if the 10 kΩ resistor on the positive side of the divider fails, it should fail open to protect the PLC input from overvoltage. Zero voltage input will indicate failed resistor or other OC condition on input. However, if the 1 kΩ resistor on the negative side of divider fails open, we need a way to keep PLC input below 30 Vdc. I'd like the input to stay high in this failure case--even over 10 Vdc is okay as long as it is under 30 Vdc. Would a zener diode like the Microsemi #1N5929A 15 V connected in parallel across the 1 kΩ resistor be appropriate? Would it affect the PLC input reading when voltage is in expected 0..100 Vdc range? Or is there a better way to do this?

The overall goal is high reliability and failure modes that don't result in destruction of costly components. Am I headed the right direction, or missing something? Is there a better way to get these voltages into PLC accurately, reliably, and safely?


texts: Adafruit USB LiIon/LiPoly charger - v1.2, charging multiple batteries with series output WITHOUT switch?

texts:
On their documentation page, Adafruit offer a tutorial for using it with 2s li-ions.  However that also required a 3pdt switch, which would have to be manually thrown. Since in my project I will not have the indicator lights visible, I can easily see my self or others forgetting to flip it and either wonder why it doesn't work, or wonder why it's not charging.

The only thing I can think of using is a 5V 3pdt relay, that would have the coil terminals connected to the DC-IN terminals of the charging board (the input power would come from the micro USB port) so that when the charging cable is plugged in, it would automatically switch to charging mode.  Unfortunately a 3pdt relay is rather hard to find, especially in small sizes.

Is there another option I'm not thinking of? Or can someone point me in the direction of a small 5V 3pdt relay rated for at least 1 amp?


texts: What options do I have for a DC disconnect switch ~72VDC ~7A

texts:
I'm would like to implement a disconnect switch between my power supply and my system. Both the power supply and my system are fused, but I'd like the ability to safely disconnect the system for service.
I was looking at using something like a switchable contact block (page 13) but the majority of them won't support the voltage / current combination I intend on having.
What other options should I consider for this operation?


texts: Implementation of RTOS in irrigation embedded application on stm32

texts:
I have designed a small project in which i have two sensor nodes(stm32) with each sensing temp, humidity and soil moisture and actuating the relay based on some threshold of moisture value.
These sensor nodes are transmitting sensed data to base station(Rpi) through zigbee and UART.
Also the Rpi can send some integer value based on which sensor nodes will change their transmission rate (delay between two transmission).
Now I want to implement this system on an RTOS based system. My question is what should be different tasks (should I give different tasks for each temp, humidity and moisture or only one task for all sensors)? What priority i should assign to the different tasks?


texts:
I'm not really a hardware guy but I am thinking that this might be a simple build. With some guidance.

Basically I want to hook a physical button switch to a controlled one for my camera. So that I could say make a program that will release the shutter every minute or something simple like that.

The switch itself is simple.

However how would I hook it up to a usb controller. From reading I think I need a relay but relays seem more complicated. Is this a simple project, or a complicated one? The switch that is controlled should probably not transport any electricity to the wires shown in the picture.

Source for Image


texts:
In the following circuit, what would be the single-ended \$A_{cm}\$? I realise that there would be no current through \$R_e\$ in common mode and that this is a CE (Common Emitter). However, I am not sure whether the single-ended \$A_{cm}\$ should be

\$-\alpha\cdot R_{c1}/(r_{e5}+r_{o3})\$

or rather

\$-\alpha\cdot R_{c1}/(r_{e5}+2r_{o3})\$

I'd appreciate some help figuring it out.


texts:
As a preface, what I am asking is highly related to this question.  That said, the question linked was asked in 2011 (7 years ago), and I imagine the microcontroller world has changed (at least to some degree) since that time.

I want to include sensitive info as part of a program on some sort of uC - AVR, ARM, whatever.  I want to protect this data against people who obtain physical access to the device (if I lose it, or if it's stolen).  I want to be able to easily reprogram/re-flash this device.  I am assuming I have a perfect (but not otherwise useful) method of authenticating myself to the device that an attacker wouldn't have - so it knows it's me, but I can't use this authentication to, say, generate an encryption key or anything like that.  How can I protect my code?

Additional information: I know there are fuses to prevent hex dumps, and may just have to use those depending on the answers to this question.  I know they can be defeated by de-lidding and laser-probing the uC, but they'll keep your average hobbyist out.  Unfortunately, those also make reflashing more difficult, requiring an external programmer (which is undesirable).  I'm OK with having to add some additionally circuitry/components to the device, I really just need to see what's possible (and what's changed since 2011).

EDIT:

I have been asked for more clarity regarding my specific problem, so I'll add it in here.  I'll note that I originally decided against it because (1) I don't want to bottleneck answers into a specific vein of thought, and (2) I figured I would get more "don't do this"-type answers that useful ones.  With that said:

I'm working on a hardware password manager.  I know, there are a bunch of these out right now.  This one would read a fingerprint, and type a corresponding password (acting as a USB keyboard).  If the source code on the uC is secure, then I feel (given my potential attack vectors) this will be secure enough for my own personal use - will I recommend it to a government agency?  Obviously not.  The uC uses a special key to communicate with the fingerprint scanner, and the fingerprint scanner can respond with a digital representation of the fingerprint that could be used to decrypt a password stored on the uC.

The main problem: If physical access to the device is obtained, an attacker could obtain the special key from the uC, get the fingerprint (stored on the scanner for comparison), and decrypt the password stored on the uC again.  If the uC (or the hex from the uC) is not readable, an attacker cannot as easily obtain this information.  Thus: how do I keep the information secure, while still being able to easily-enough reprogram the uC?


texts: What is the difference between these two attiny44a parts?

texts:
I bought two Chirp plant watering alarms and I noticed that the attiny44a used are marked differently: atmel1722 and atmel1619.

What is the meaning of the numbers? I cannot find this information in the datasheet.

Are they some sort of serial number or batch?


texts: Recording Servo/Motor movement with arduino

texts:
Hi I'm really new to Arduino projects and don't really know how to start. I'have to do a project for university. The programming part should be no problem but I don't have any experiance with electronics.
What I try to achieve is to record a spezific motor movement. For expample I move a modelcar, record the movement and let arduino repeat that motion. How can I do something like that?
I've read that servo movement can be recorded but non-industrial servos are not for multiple rotations and are not very strong. It should be able to move up to 6.6 pounds record a varying movement over a distane of 10 feet.
Is it possible to record the motion with something else and do the movement with a stepper-motor?

Edit:
I want the motor to repeat the acelleration. So I move the car that the gearing mechanism makes a particular movement. I want to detect how long the motor has to run and how fast it has to be at every moment in that timeframe. I'm only interested in forth and back.


texts: Confused regarding standing waves on transmission line

texts:
I am currently learning about transmission lines form an online book hosted by a website called “All About Circuits”. If anyone is interested, the particular chapter I am currently reading can be found here: http://www.allaboutcircuits.com/vol_2/chpt_14/6.html.

Basically, the book talks about having a circuit with a transmission line that looks like this:

The transmission line is supposed to be long enough so that:

At 250 kHz, the line's length is precisely right for 1/4 wavelength.
At 500 kHz, the line's length is precisely right for 1/2 wavelength.
At 750 kHz, the line's length is precisely right for 3/4 wavelength.
At 1000 kHz, the line's length is precisely right for 1 wavelength.

The images below show that standing wave graphically depicted with the frequencies mentioned above.

At 250 kHz, 1/4 wavelength:

At 500 kHz, 1/2 wavelength:

At 750 kHz, 3/4 wavelength:

At 1000 kHz, 1 wavelength:

If you look at the standing wave for the mentioned frequencies, you will notice that the load end of the transmission line always has a standing wave antinode. I can understand this because the line is open so in my mind this makes sense.

What I don’t understand is why (depending on the frequency), we sometimes get a node and sometime an antinode on the source side of the transmission line. I don’t understand this because both the source and load sides are supposed to be endpoints which should mean that they should always be nodes or always be antinodes but not vary (at least that is my understanding).

Nevertheless, I am obviously missing something here so I was hoping someone could help me out and clarify what is going on here.

Thank you.


texts: How does an ARM processor in thumb state execute 32-bit values?

texts:
What I understand is, the ARM mode can execute 32-bit of instructions and Thumb mode can execute 16-bit of instructions.

For instance,

Here is the ARM instructions set:

And Thumb instructions set:

From these both instruction set tables, please see ADC mnemonic that describes add two 32-bit values and carry. So, 32-bit is common in both the modes.

What I didn't understand is, how a thumb mode which can execute 16-bit is able to execute 32-bit value?

I referred the other books (which I could) and in those books also same description is given. Please explain me this concept/correct me which I misunderstood.


texts: Boolean expression with only OR,NOT gates

texts: I have the expression: x'y+xy'+y'z . I want to express this with only OR, NOT gates, but the issue is I have no idea how to remove the AND functions. I was thinking of using demorgans law, but I am unsure how and if it can be used on only part of the expression. Is there a way to simplify it and remove the ANDS?


texts:
I'm studying semiconductor parameter analyzers. Those instruments are based on SMU (source and measuring unit) which can work either in the V-mode (they force a voltage on the device under test and measure the corresponding current) or in the I-mode (they force a current in the DUT and measure the corresponding voltage). Suddenly, it appears this slide:

It is just one slide and no further information is provided, but I cannot understand how this circuit works. On the web I found different configurations of this circuit.
I might surmise that the "force" and "sense" words in the picture make reference to the "source and measurement" properties of the SMU. Moreover, why do we have a variable battery? Why do we have two "force" wires (if I force a current through Rf1 like in the picture, I don't need another "forcing" action on the DUT through Rf2)? Why do we have two "sense" wires?
Thank you


texts: Wiring diagram of aller retour switch with lamp

texts: I need to connect a lamp with 2 aller retour switches. In the wiring diagram how many cables will i have between the switches if the lamp is between them?


texts: Biological 'Black Box' - how to test for underlying logic?

texts:
Firstly, I am a neuroscientist - so bear with me!

I have a collection of connected brain cells (network) and a means of recording the electrical output, as well as manipulating the input to the network in a temporally and spatially precise manner.

I want to know how the circuit as a whole, and eventually the individual components (individual brain cells), work with various inputs.

I think what I'm wanting is analogous to testing the frequency-response of a simple resistor-capacitor filter.

Whilst a frequency-response is a likely property of my brain cell network, I want to know of other means (tests) which would reveal more information about the 'black box'. Perhaps, inverted patterns of input stimulation, simultaneous activation and inactivation of different inputs.

Does any of this make sense? Any ideas or direction of a text would be greatly appreciated.


texts: Create Altium footprint from scratch for Molex connector?

texts:
I'm trying to create a footprint for a Molex connector but I don't think it is possible to do with the wizards inside Altium, so I guess I have to do it by hand, but I am completely lost. Any help, tips, tricks, tutorial, video or whatever would help me out. The component wizard has an "Edge Connector" but I think that is something different.

Here is the connector I want to create the footprint for. It's the 3 pin version.


texts:
I'm trying to design a current source / sink that will be a part of a step generator that will drive a BJT base. I only intend to drive small BJT transistors so a max base current of 10mA was decided upon (somewhat arbitrary).

The circuit I'm using is the following one:

The circuit can be re-configured by changing the polarity of the current source to sink. Using an op-amp with ultra-high input impedance / low input bias this circuit can go to nano amps and I intend to try and get close to that.

The op-amp of choice is TI (BB) OPA128 which has a typical current out rating of +/- 10mA. This seems about right, but I am a little worried that I will be stressing the device.

I have a couple of these devices, can I simply connect two of them in parallel or some other configuration so they will be able to drive a constant current of 10mA without too much "effort"?


texts: Hi I  need to replace this resistor but I  am not convinced that I have read it correctly  at 180m ohm. Can someone  confirm please?  The third band looks like pink but I ha w read it as violet.


texts: Why is programmed I/O not suitable for high-speed data transfer?

texts:
I am learning about computer architecture and organization.
I have read that programmed I/O is not suitable for high-speed data transfer because it does not support synchronous mode of data transmission that is a requirement for many high-speed peripherals like disk.
But programmed I/O supports synchronous mode of data transfer. I am confused. Can someone please help me?
References:
Assignment 10 question number 2


texts: Using C++17 static inline members in embedded MSP432 application, program fails to launch as reset occurs

texts:
I am unable to debug my embedded software since I started using static objects.
I do not think that there is much difference in memory allocation/initialization between the classic static variables and the inline static ones I am using, yet, I suspect there is a problem with the C runtime library startup lagging behind the watchdog timer when initializing considerable amount of data into the BSS.
This user manual seems to provide a solution (section 5.3), but inserting such an early-called function in my code did not produce any changes whatsoever:
static void __attribute__((naked, used, section(".crt_0015")))
disable_watchdog (void)
{
    WDTCTL = WDTPW | WDTHOLD;
}

Maybe the attributes syntax for g++ is slightly different than that of gcc?
Has anybody faced a similar issue?


texts:
My ASUS motherboard has both a winbond 25q64fvsig and a it8995e-128 chip. In a repair shop in a country I was at the time, they flashed the wrong ASUS BIOS version. I tried flashing the right version but both built-in ezflash and windows winflash (with /force parameter) refuse to flash it, giving a warning that the BIOS version is not correct for the device model. Since that time I'm experiencing graphics drivers failing to run on Linux. My first question is:
Can this wrong version of BIOS cause such drivers issue?
My second question is:
What is the function of each of those chips and to which one is the UEFI binary flashed when flashing?
Which leads to third Question:
Can a programmer dongle be used to fix the wrong UEFI version? If so, would the UEFI file from the ASUS website be good for such purpose?
Thanks in advance.


texts: The potential drop in a pn junction diode-

texts:
In the picture shown above, I was trying to learn about diode equivalent circuits. I am not being able to understand the direction of Vb taught by the instructor here. The question is-
If the n region has more potential than the p-region, shouldn't the direction of the battery be reversed.


texts:
I'm a bit confused with LoRa. I understand the CSS modulation with the chirps, but I don't get what chips are. Are chips parts of the chirps?
I saw another topic on this, but the difference is not clear. As I understand it now, is that chirps consist of chirps. Is that correct?

Thank you!


texts: STM32F4 Discovery GPIO signal generation problem

texts:
I'm trying to generate a signal to interface with a Nintendo 64 controller using my STM32F4-DISC1 (STM32F429). The signal I'm trying to generate for now is just 1us high followed by 1us low (repeat ad infinitum).

There are two problems I'm facing:

I can't seem to get the correct timing working. The main clock should be 180 MHz (as reported by the "get clocks" function, sorry forgot the full name). This should mean there are 180 cycles per microsecond, right? But when I set the GPIO to high, wait for 180 cycles (180 nops) and then set it to low again, 3.5us have passed. What am I missing here?
The signal I'm generating using the code below works well after a time, but not at first. If I look at it with a logic analyzer, then the first capture will always look like this:

As you can see above, the signal is high only for a very short time (about 0.17us). Without modifying the code though, just by capturing again, the signal changes to this:

In both cases, the code hasn't changed and waits for 180 cycles. If relevant, I'm using the Open Bench Logic Analyzer at 200 MHz sampling frequency.

Initialization code

Signal generation code

Note: 0xE0001004 is the address of the cycle counter, which is updated automatically. So there's no need to modify r6 in the wait loop.

Also note that I've tried the waiting using different techniques, including just using 180 NOPs. This had mostly the same outcome.


texts: Is it possible to power a MCU with a button press / touch?

texts:
I hope to use a piezoelectric button to harvest and produce a sufficient energy burst to power ON and bootup a MSP430 for a few ms enough to update a simple data structure (e.g. two integers stored in nonvolatile memory e.g. FRAM) and then power OFF. Note that the MCU will be completely dead before the piezo button press. This updated data structure will be used later on when sufficient energy is available to do more complex tasks (e.g. perform computation/send signal over wifi etc.).

Assume:
The FRAM-range MSP430 (e.g. MSP430FR59xx) with lowest clock frequency (32kHz), min. operational voltage 1.8V, lowest power mode that can do the above operation. I'm not sure how much current the above operation (integer updating) would require, but I assume it's under 0.5mA, lasting for under 10ms. Assume there is another solar energy harvesting element that is charging up a secondary energy buffer (e.g. a largish capacitor) to do the complex MCU actions mentioned above.

I guess the objective is to see if there is a way to capture user input in a quick and dirty fashion and react upon the input later, when sufficient energy is available from the secondary energy source.

Questions:

Can a piezoelectric sensor button or a capacitive touch sensor button produce enough energy to perform the above?
Assuming (1) is possible and there are 2 such buttons (A and B), then can the MCU obtain knowledge of which button was pressed and gave it power?


texts: Trying to identify unknown connection plug

texts:
We have a piece of foreign (Turkish) machinery and we are trying to make some adaptions to it in our workshop.  However we need to find out what the below plug is - couple of electrical shops we've been to can't recognise it and we've found nothing similar online as yet.  It looks similar to some internal automobile plugs but I can't exactly match them up with anything.

See the images below so you can see what it looks like.  The 4 hollow connections measure about 5mm in diameter, and about 24mm across all 4 connections.  They extend out from the main plug about 12mm, and the depth of the whole plug is about 26mm.

If anyone can help out with the name/code of the item or where we can source these that would be a great help!!


texts: Why are current sources not drawn explicitly in the datasheets' schematic diagrams?

texts:
Below is a schematic diagram given for an IC in its datasheet:

As you can see everything is drawn in detail in transistor level. I can see many BJT transistors and diodes for instance.

But the 3.5uA and 100uA current sources are not drawn in transistor level.
Why are the current sources hidden here and shown only as a current source symbol?
Why are not they drawn explicitly?


texts: 3 AGM batteries in parallel; does it matter what battery they are charged from

texts:
simulate this circuit – Schematic created using CircuitLab

I have 3 AGM 12v batteries in parallel.  Between Battery 1 and 2 I have a BlueSea SI-ACR Automatic Charging Relay - 12/24V DC 120A; I also have an anderson pole connector (SB175) on the last battery3.

I want to hook up a battery charger to the system.

Should I be doing this @ battery1 acting as the alternator does; or Battery2 since the ACR has already cut power between 1-2 (woundn't this unbalance the charging) or on Battery 3 where I have the anderson pole connector (this is where Iwould prefer to connect the charger though Isuspect this will only balance 2-3 and not 1 since it is isolated with the ACR.

diagram
https://1drv.ms/i/s!AmOoj1nayk49jcdVgFRUGvoiW9gjig


texts: The issue I am having is it appears many modern remotes don't have a 38kHz carrier frequency for the infrared signal. I would get inconsistent readings using an TSOP 1738. Since the remotes you can buy as a kit are always cheap and ugly, how hard is it to replace the circuitry with an attiny device to generate the correct frequency?


texts: Finding the correct capacitor for a 433MHz RF with HT12D

texts:
I have a 433MHz RF antenna connected to a HT12D.  The transmitter is powered by a 9v battery with a HT12E.  The receiver is powered by 5Vdc.  I am trying to power the unit using a 12-0-12 center tap transformer.  I have each lead of the transformer going through a diode, then they connect together and go through a capacitor to smooth out the current.  That power then goes through various voltage regulators to power different components.  I use a 5V (LM7805) regulator to provide power to the receiver and the HT12D.
When I hook the power at the capacitor from a 12Vdc power source that is already smoothed out I can take the transmitter up to 15-20 yards away and receive the signal no problem(I have a 220uF@25V capacitor connected here).
However, when I use the power from the transformer described above I do not receive the transmission at all.  I have tried various sized capacitors, 220uF@25V,100uF@35V, 470uF@35V,
1000uF@25V, 2200uF@35V, and 3300uF@35V.
At one time I could get the 220uF@25V to work at about 5 yards but now nothing.  Can anyone tell me how to calculate the size capacitor I would need and why this isn't working possibly?


texts: Characteristic of old SLA/NiCd batteries

texts:
I need service an old HVAC equipment (manufactured 1998) backuped using 6x2V SLA 5000mA Cyclone cells (http://www.ges.cz/cz/akumulator-oloveny-cyclon-x-cell-5-0ah-GES07600853.html). There is also 3xNiCd AA 600mA. I plan to replace all these cells because I suppose 17year old batteries cannot be in good condition.

I measured voltage particular cells and I'm surprised it varies significantly. Some cells have 0.9V (both NiCd and SLA), a few SLAs 2V, one SLA cell even 2.7V. Two NiCds have 1.28V. Measured as I removed from device, no load. When I put in NiCd in charger to make test cycle then charger does not recognize cell.

My question is if is possible that some batteries survived 17year in good condition, i.e. is worth testing piece by piece and replace only cells with low voltage?

What happen that 2V SLA cell provides 2.7V, is it normal feature?


texts:
Is the cathode for schottky diode hotter than the anode, as is common for most diodes, or is it reverse polarity? A schottky is a metal-semiconductor junction, with the metal at the anode. So it should be better for heatsinking, even if the cathode is actually larger, right (i.e. reverse polarity in package nomenclature)?

I'm specifically interested in the 1N5819 and 1N5822 leaded DO-41 and DO201 package.


texts: Comparing FPGA to microcontroller or SOC, assume same functionality, how big can FPGA get?

texts:
Looking at this answer to  FPGA's vs Microcontrollers --https://electronics.stackexchange.com/a/4393/127001

It mentions that FPGA is space-limited, and MCU is time-limited. So this got me to thinking.

How big can FPGA get if we assume the system using MCU has the similar application and setup as the FPGA? Would it be safe to assume that system that uses MCU and SoC has the similar answer in this case?

UPDATE:
To clarify, let's use Arduino Uno as a reference for MCU. What would be the physical size of FPGA if you were to use the similar specification of Arduino Uno?


texts: Why does my output stage rectify when I use a preceding stage?

texts:
I've been working my darnedest over the past few weeks learning more and more about amplifiers, BJTs and various topologies. As I go through Art of Electronics, I try out everything mentioned in at the very least (P)Spice.

I've run into a conundrum. When I make a class-B output stage, as the following:

Everything is kosher, and I get this output from a 3Vp sine wave:

If I replace the signal source with something more practical, like a VAS, as such:

It doesn't work out the same. I end up getting this:

Where the negative half of the waveform appears to be rectified. I notice that it appears to go to some positive DC value too, I suspect that is around the value of a diode drop, but I am not sure why. I have spent several hours trying to find an explanation for this, and what's worse, is that the circuit is almost verbatim out of the book.

If I put a DC offset on the signal, the "rectified" waveform becomes proportionally smaller, that is, with a +/-2VDC offset, I'll have alternating half-cycles of ~5V and ~1V. I've played around with resistor values to get a feel for their effect, but that again doesn't seem to help.

As I'm really trying to understand this to the point maybe in the future I can not only understand amp designs but make my own, I'd really appreciate any help in understanding what's going on. Is something wrong with my design? How can I make it work as intended, i.e., get a proper, proportional sine wave output?

My source is a sine wave, 1kHz, 3Vp, 0VDC. This is taken from Art of Electronics, Fig 2.66.

Update: I think I may understand now, it was my rather whimsical selection of resistor values. I've updated the schematic, as well as given all the components much nicer names:

The issue before, as mentioned, was that because of my biasing, the collector "had nowhere to go" (I like how that was put). Essentially, as I understand, the positive part of the waveform "comes" from resistor R1, and the negative part "comes" from VCE. Now that I've biased it so that VCE has at least ~ 7V to its name, the PNP can actually do its job. Furthermore, everything is forward biased. The only question I still don't fully understand is why it "rectified."

Here's a print of the new input/output:

I took the input from Rg as the high-pass formed by Cb/Rg does attenuate somewhat - I chose a rather small value for Cb so that I don't have to do print delays on the output while it charges (:/). I do understand a much larger cap would be necessary to pass the full 20-20kHz.


texts: Coupled current in shield in a tube from a transient surge

texts:
If a shielded cable (B) is running inside the centre of a tubular structure (A), how is the coupled current from a surge estimated in the shield?
I am trying to figure out how the coupled current between a structure, such as a tower, and a shielded signal cable can be estimated during a surge. I have been trying to do some research but without much luck.
To clarify the question, the example inputs could be:

Length L = 200m
Radius R = 1m
Surge current I_A = 200kA (10/350)µs
Diameter of cable shield = 8mm
Both A and B are terminated to a common node at the ground (Not shown in drawing)
The medium between the conductors is air

,


texts: Does a NYY or NYM cable affects a CAT6 cables transmission if they are crossed?

texts:
I get an unfinished job and really hard trying to complete it. Ex-engineer of my company had designed the cable tray system as a cable tray should used for both light current cables and heavy current cables.

I am in doubt about using light and heavy current cables in a tray. I will use a separator to keep them separate but somehow they have to pass over eachother in some points.

I am transmissing voice and image with CAT6 cables (entryphone system) and heavy current will be in 5x6 NYY cables.

Is the NYY cable affect the CAT6 cables image and voice when they are crossed?


texts: How is the fuse amp rating determined for a 12V AGM battery bank?

texts:
I would like to put 3 x 130Ah AGM batteries in parallel and attach a fuse to the positive terminal of each battery. What size fuse should I use? How is the amp rating of the fuse determined?

The batteries will be connected to each other and the inverter will be connected to the battery using heavy duty copper cable. Smaller gauge cable will possibly be connected to the output terminals with Anderson connectivity. An inverter of up to 1000W will be connected.

EDIT:

Even though an inverter of up to 1000W will be connected, the maximum power draw likely to be less than 500W. I would like to have this safety margin in case an appliance of higher wattage needs to be used so I want the system to be able to cope with a current of as high as 80A. The batteries will be charged either via solar panels or via a 20-30A 240V AC charger.


texts: Determine a known battery's instantaneous capacity through voltage? / voltage's relation to capacity

texts:
Is it possible to approximate a battery's current (the "right now" kind of current) capacity, given its absolute capacity and a voltage measurement?
An example:
I have a 1s 260mAh LiPo that is at 3.75 volts. I must charge it to 3.85 volts to store it, but I'd like to have a rough approximation of how long that should take.
I know that I can take a capacity in Ah or mAh and divide it by the charge rate (for my charger, 0.2A), which would give me the time in hours to charge that capacity (In perfect simulation). However, to do apply this to the example, I would obviously need to know the instantaneous capacity of the battery, to get the amount of mAh that I need to calculate for.
Another way to word the question: what is the relation between a battery's voltage and its capacity?


texts: Connecting potentiometer to an FPGA simply

texts:
I have a question about connecting a potentiometer to a FPGA.
I am connecting a potentiometer to an external 8 bit ADC chip that is outside the FPGA. I want the pot to represent a speed setpoint ranging from a min to max value, for example say 0 rpm to 100 rpm of a motor.
Now since I have no ALU on my FPGA, I am creating my own ALU which is no problem. However I was planning on working out the RPM setpoint based on the following equation below:
$$Setpoint~RPM = ADC_{Pot} \cdot \frac{Range_{RPM}}{2^N-1}$$
For example pot is set to ~50% and motor speed range is 100rpm: 128 ( 100 / 255 ) = 50.1 RPM.
Now the problem I run into is I require floating point numbers for my calculations. Am I overcomplicating this process of converting the pot value into an RPM setpoint by using the ALU? Could this simply be done in some code in VHDL?
I would appreciate any help, thanks.
EDIT
Ok it might be useful if I provide some information about what I am doing.
So I am making my own processing core on an FPGA. I wish to display this rpm setpoint on a LCD display. So I am working in binary with registers completely. So my pot value is inputted with 8 bit digital resolution. And say I want to represent on my LCD display a value between 0 and 100 rpm. I was going to use the above calculation with my designed ALU.
So for the calculation I was going to store the (RPM Range / Bit Size) value in memory to avoid needing to divide in my ALU and ca just multiply it with the inputted pot value but this  will require a decimal point which is confusing me.


texts: How do we solve questions involving multiple secondary coils?

texts:
An ideal transformer has two secondary coils with number of turns 100 and 150 respectively. The primary coil has 125 turns and supplied from 400 V, 50 Hz, single phase source. If the two secondary coils are connected in series, the possible voltages across the series combination will be:

A) 833.5 V or 166.5 V
B) 320 V or 800 V
C) 833.5 V or 320 V
D) 800 V or 166.5 V


texts: Packaging PCB and battery inside enclosure - foam

texts:
What's the name/type of the dense foam that's generally used in consumer electronics to stop components from vibrating around and tightly packaging everything together? In my case, this would be for mounting the battery against the back of the PCB and keeping the battery from moving around inside the enclosure. Been searching the traditional electronics part sellers and couldn't find anything suitable.

PS: Would prefer not to use sticky tape as the battery is supposed to be removable.

Thanks!


texts: Consequences of higher voltage supplied to BLDC motor?

texts: What happens to a brush-less DC motor if I supply a voltage about 1.25 times greater than the rated voltage?


texts: What is the maximum current can pass in BQ40Z50R2 (fuel gauge IC?)

texts:
I am unable to find the maximum current this fuel gauge IC can pass from its datasheet.

Can anyone tell me?


texts: Drawing equivalent circuit of transformer to determine its parameters

texts: For part a, I considered the following model of the transformer where v1 = 230 V, representing the low voltage side. For part b, I used the same model, with the right hand side short circuited rather than open circuited, except this time v1 =  4600 V because the low voltage side is short circuited. Is this the correct approach to draw the equivalent circuit diagram and calculate the required parameters?


texts: Computing ampacity a of small fuse from change in temp on breakdown

texts:
I'm trying to design an experiment for an entry-level electronics course involving burning out fuses of an unknown rating and determining their rating by the temperature they were when they failed. Is this possible with a relatively cheap (say, below $100) laser thermometer? How would I use specs of the fuse to determine theoretical failure temp?

I am aware of the serious physics problems involved in "converting" watts to a change in temperature.


texts: RC first-grade circuit with op. amplifier

texts:
I tried to calculate the voltage \$v_u\$ in this RC circuit, but I got stuck when it comes to calculate \$v_u(\infty)\$ and \$\tau\$.

simulate this circuit – Schematic created using CircuitLab

Then: \$v_u(t)=[v_u(0)-v_u(\infty)]e^\frac{-t}{\tau}+v_u(\infty)\$

First off, I notice that \$v_u(t)=-v_c(t)\$.

Then I calculate \$v_u(0)\$,\$v_u(\infty)\$ and \$\tau\$.

First step: \$v_u(0)\$

The circuit become the following:

simulate this circuit

Here the current \$i=i_1+i_2=0 \implies v_c(0)=0 => v_u(0)=0\$.

Second step: \$v_u(\infty)\$

simulate this circuit

Now \$R_g\$ is in series with \$R\$, so \$v_c=E\frac{R}{R+R_g} => v_u=-E\frac{R}{R+R_g}\$.

Is this correct? My books gives \$v_u(\infty)=-E\frac{R}{R_g}\$.

Third step: \$\tau\$

simulate this circuit

Since \$\tau=R_{eq}C\$, I have to calculate \$R_{eq}=\frac{v_c}{i_R}\$.

Let's calculate \$i_R\$: \$i_R=i+i_1+i_2=i+i_1=i+i_3+i_4=i+i_4\$

Now how much is \$i_4\$? The solution says that \$i_R=i\$. So, why is \$i_4=0\$?


texts:
this is a re-post as I was unable to get any help on other forums. I have designed and built a simple Z80 computer system with 32K RAM, Z80B at 4mhz, 32K ROM, and a UART. The only problem with it is that the system doesn't seem to work. So, I am asking to have somebody peer-review my code and schematics.

    org 0x0000
uart_init:
    ld a, 0x80
    out (0x03), a
    ld a, 12
    out(0x00), a
    ld a, 00
    out(0x01), a
    ld a, 0x03
    out(0x03),a
uart_out:
    in a, (0x05)
    bit 5, a
    jp z, uart_out
    ld a, 0x41
    out (0x00), a
    jp uart_out


texts: LCD screen with a dark patch, hot, hissing and whole screen flickering: what is happening exactly?

texts:
I've just had a problem with an LCD monitor, but this question is not about solving this problem. Google did that. I want to know what is happening at the electronic and physical level. Google didn't do that. The problem:

LG Flatron W1943C LCD monitor. Most likely backlit by CCFT. It was manufacturer in September 2011, and I think that's about the time I bought it. Today, I noticed the whole screen flickering at times, which meant the backlight was flickering. Tonight, a black right rectangle appeared in the upper left corner of the screen. The diagonal of the rectangle mixed gradually with the image. The area was much hotter than the rest of the monitor. There was a hissing sound coming from the area. Lowering brightness and contrast had no effect.

The problem is well known and Google offers several ways to fix it yourself, and it's either the CCFT or the inverter, which feeds the CCFT with high voltage. The area around the connectors may be severely damaged by the heat.

But what I want to know is what is happening exactly. If the CCFT is not working properly, why a black rectangle in a corner of the screen? I could theorize it has to do with that area being the last indices of the horizontal and vertical arrays of input, but that's a digital problem. That's why I'm so curious about this matter. This theory makes more sense if you consider some of the cases found in Google that shows a crisp diagonal of the triangle, down to the pixels.

And now a more out of topic question: is this a standard time for this problem to appear?

I'm a Computer Engineering student, so I have some knowledge of several areas of physics, electricity, electronics and computing.

Thanks in advance.


texts: Cheapest way to get motion sensor to send SMS or email

texts:
I want to build some cheap security system in to cottage without electrical network.

Burglars gets inside always by breaking the window. I think I would need some PIR or microwave sensor. Is there better way how to detect burglar in the cottage?

Then the cottage is located in uninhabited area, so simple sound alarm wouldn't work. I need to send an information about disruption wireless to the owner of the cottage. But how? I was thinking about a cell phone. If I were able to make a program, that would send SMS or email, how would I connect the cellphone to the sensor? What else would work? Could Arduino or rasberry pi send SMS or email? Does any better (cheaper) device, that would be able to send wireless data exist?

I'm searching for an advise from somebody, who has experiences with this and could share his knowledge. Maybe there is completely different and much better way, that's why I described the situation.


texts: How output signals connect when they are from different chips and banks

texts:
First I apologize for such an ambiguous title. I am reading Code by Charles Petzold during my leisure time and have a question that I can't figure out by myself.

It is about Chapter 21, in which Code tries to build a RAM for 8080 processor out of memory chips 2012. To summarize, 8080 has 16-digit addresses, 8-digit data input and output respectively, while 2012 has 10-digit addresses, 1-digit data input and output respectively. Hence, eight of 2012 chips are wired together to store the entire 8-bit, and such 8-chip group is called a bank. Each memory board consists 4 of such banks.

Then, because we have 4 banks,

  If you recall the messy details of combining RAM arrays in Chapter 16, you might assume that we also need eight 4-to-1 Selectors to select the correct data output signals from the four banks of memory. But we don't, and here's why

Here comes my first question:

Why do we need EIGHT 4-to-1 selectores? 8 chips are wired together as a whole, and their signals are the same as other ones in the same bank.  More precisely, I know 8 of them work, but I am wondering whether ONE is enough. (I understand we are not using 4-to-1 selector, just want to finish the thought experiment).

Then, it explains why:

  Normally, the output signals of  TTL-compatible integrated circuits are either greater than 2.2 volts (for a logical 1) or less than 0.4 volts (for a logical 0). But what happens if you try connecting outputs? If one integrated circuit has a 1 output and another has a 0 output, and these two outputs are connected, what will result? You can't really tell, and that's why outputs of integrated circuits aren't normally connected together.

I understand the part that circuits are not normally connected together. The question however is

When had we connected them if we ever followed 4-to-1 selector design? Were we not using an OR logic gate? (Again, I know we are not using this design, just want to make sure what would've happened if we had done it.)

A rough diagram that I have in mind is as follows (I am not sure if it is clear enough, if not, could some one points me a online diagram website and I'll try to make it as clear as possible):


texts: Choosing IGBT or MOSFET for switching application

texts:
I'm currently doing a project which requires me to design a switching circuit for a switched reluctance motor.

I have to choose a switching device and I'm going with either a MOSFET or an IGBT.

It has been suggested to me that for this application I should use an IGBT over a MOSFET.

What are the reasons for this. What advantages does the IGBT offer over the MOSFET in a switching application like this?


texts: Can a single data stream be recieved by multiple bluetooth devices without interruption?

texts:
So i know i can make a "server" and send a data stream to multiple devices one after another. But if the data stream is same for 5 devices can they all recieve it at the same time like standard FM? I saw some protocols developed by some companies that can "do it" but they only work with big manufacturers.

Edit:

Point 1:disable pairing requirement for connection (easy to do)

Point 2:disable all slave to master communication (L2CAP?)

welp


texts: I'm trying to apply Nodal Analysis here.I have found that taking reference Nodes and application of Kirchhoff's laws yields some equations and on solving these equations i will get the needed result.But in this question the current sources are not given ,in the online example i just saw there was a current source and 3 equations were formed,in this text book example they have solved it some how,can some one tell me how they have formulated the equations


texts:
I'm designing a USB-to-Ethernet adapter (actually a prototype of a piece of a larger board).  As those following my questions will know, I've had some ups and downs getting the USB part working, but now it shows up as a USB hub in Linux and I can use devices connected to it.  Now for the Ethernet part.

As far as I can tell, I have followed the various guidance in the datasheet.  The schematic is shown below.  I can confirm that VDDCORE is being generated correctly and that there is a 25MHz sine wave on the 25MHz crystal - so the chip is showing some signs of life.  But it doesn't show up in a scan of the USB bus.  Both jumpers (JX1 and JX2) are installed, though I've tried without as well.

What can I do to try to debug this?  What should I be checking for on the board?  Have I made any obvious mistakes?


texts: Does the drive circuit for a piezo buzzer require extra power?

texts:
I want to power a small piezo buzzer with a battery, and I am trying to work out the power requirements.
The buzzer has a Rated Voltage of 3V, and the battery has a Nominal Voltage of 3V.
The buzzer is an external drive type which needs a drive circuit, and I am not sure how this circuit is going to effect the power requirements. A sample circuit is shown here.

http://www.microbuzzer.com/smt-smd-buzzer-basic-drive-circuits

Does this constitute an Oscillator Circuit?
Is the transistor, resistor and diode in the circuit going to increase the power requirements for the whole circuit. Can I still use a 3V battery, or does it need to have a higher voltage?
(I am a novice when it comes to Electrical Engineering, as you might have noticed!)

Extra info about the buzzer and the battery just in case

The buzzer has a Rated Voltage of 3V, an Operating Voltage of 1~25V, a Rated Current ≤3mA, and a Generated Frequency of 4000Hz ± 500.

The battery has a Nominal Voltage of 3V, and End point Voltage of 2V, a Standard Current of 0.1 mA, a Continuous Current(Max) of 0.2 mA, and a Pulse Current(Max) of 5mA.


texts:
I have built a circuit that can drive a 3.3v AC output at a few hundred mA. The wave has a frequency of 150Khz. I want to step this up to 60-90v at ~0.5 Watts to drive an ultrasonic piezo. However, I am having difficulty finding a transformer. From what I understand, I am looking for one with a coil ratio between 1:20 and 1:30, and a relatively small VA. I would also like the transformer to be as small as possible (low height is more important than small footprint). I have looked on common electrical supply house websites like Digikey, but their filters aren't all that helpful. Coil ratio is never a filter option, and anytime I find one that I think might work, it is made to operate at 60Hz. Also, when I search "1:30," I get results for current transformers, and I don't believe that these are suitable for my application. I would greatly appreciate some guidance on how to search for a transformer and possibly some suggested devices.

Secondly, I am not positive that I am on the right track for this project. The circuit that I created is a class E amplifier. Should I be feeding Vcc 60-90v DC (by using a flyback converter, for instance) rather than throwing a transformer on the output? The idea is to prioritize making the circuit small with some consideration for efficiency. Thanks for the help!


texts: Calculate resistor value of Optocoupler & Transistor

texts:
I have a problem working out the values for the resistors R1 & R2 of a relay module.
Right now, I use R1 = 1k & R2 = 560 Ohm, but that is not working.

What resistor values should I use? And how can I calculate it?

i try to mimic 4ch relays module but not working.


texts: BLDC Motor rotor vibrates with audible high pitch beep, but does not spin. Controlled by custom motor controller

texts:
The circuit I have built (taken from the HIP4086A gate driver data sheet found at https://www.intersil.com/content/dam/intersil/documents/hip4/hip4086-a.pdf) is:

The only difference between this circuit and what I actually have is that the motor's brake is implemented mechanically (irrelevant here) and speed control has not been implemented yet - right now the duty cycle of the xHI and xLI pins are all 20%. I am using trapezoidal commutation, and so I actually have 6 pins leaving the controller instead of the 3 in the diagram (I manually invert the HI pins in the controller).

My motor is rated for 36V. When my circuit is connected to a 12V power supply with roughly 1.5A of current running through, the motor rotor vibrates, and it is physically harder to try spin the rotor manually with my hand. There is also a slight high pitched sound, but the rotor does not spin. Could this be because I am not providing enough voltage/current, or could my phases be swapped? My motor's datasheet does not provide a commutation table, so I have used this one (from this BLDC data sheet: http://cdn1.beikimco.com/Products/Dowloads_bldc_housed/motor-brushless-dc-housed-dih23-30-007a.pdf):

I know that my controller is parsing the Hall effect sensor inputs correctly and determine the correct state the rotor is in. I have also verified that the circuit is connected correctly. My main question is what is most likely to be the issue here? Could the issue be that my controller's clock speed is too low? (Using Arduino UNO but a Teensy 3.5 is available). Am I not providing enough current/voltage? Are my phases simply swapped?

My motor's data sheet can be found here: https://www.anaheimautomation.com/manuals/brushless/L010758%20-%20BLK24%20Series%20Spec%20Sheet.pdf.


texts: Why is my 8-bit counter only counting until 127?

texts:
I recently coded an 8-bit counter in Libero and simulated it in ModelSim using Verilog. When I simulated my design, it only went up to 127. Shouldn't an 8-bit counter go up to 255?
Here is my HDL Code:
module counter    (
out     ,  // Output of the counter
enable  ,  // enable for counter
clk     ,  // clock Input
reset      // reset Input
);

output [7:0] out;
 input enable, clk, reset;

reg [7:0] out;

always @(posedge clk)
if (reset) begin
out <= 8'b0 ;
end else if (enable) begin
out <= out + 1;
end
endmodule

Here is my Testbench Code:
`timescale 1ns/100ps

 module counter_tb;

 //parameter SYSCLK_PERIOD = 20;// 50MHZ

 reg clk_1;
 reg enable_1;
 reg reset_1;

 wire [7:0] out_1;

 initial
 begin
 clk_1 = 1'b0;
 enable_1 = 1'b0;
 reset_1 = 1'b1;

 #20;

 enable_1 = 1'b1;
 reset_1 = 1'b0;

 #20;
 end

 //////////////////////////////////////////////////////////////////////
 // Clock Driver
 //////////////////////////////////////////////////////////////////////
 always
    #10 clk_1 = ~clk_1;

 //////////////////////////////////////////////////////////////////////
 // Instantiate Unit Under Test:  counter
 //////////////////////////////////////////////////////////////////////
 counter counter_0 (
      // Inputs
     .enable(enable_1),
     .clk(clk_1),
     .reset(reset_1),

       // Outputs
       .out( out_1 )

        // Inouts

        );

  endmodule

Here is my simulation from ModelSim.

Thanks for your help!


texts: I have a 3 conductor DC wind turbine pushing out 12VDC to a charge controller. Wire length about 90 feet and I believe 10AWG wire. (Realizing now that it should be thicker) Battery system is 12V and an inverter. The output on the inverter is 120VAC with 3 conductor 8AWG running a distance of about 90 feet as well. Output max on the inverter is 2000W and I will probably use close to 15A. I know there is definitely a voltage drop on both of those that may reduce performance. My question now, is if I were to move the inverter to the end of the 8AWG conductors what would I need to keep the voltage up over the long distance?


texts:
I have the following assert statement in a for loop, which is within a generate block:

34   assert ((a[j] == 1'b1) || (a[j] == 1'b0))
35   else $error("Input 'a[" + j + "]' is not a digital logic value");

When I try to compile, I get the following error:

  Error: file(34): near "(": syntax error, unexpected '(', expecting property

From what I can see, I'm not missing any parentheses in the