texts:
I would like to mount a slow-moving robotic "car" to a linear track of any incline from horizontal to vertical. The track should be rigid (attached to a boom if necessary) so that it can be propped up on one end or leaned against a wall to provide the incline.

The car should be able to:

carry an 800 g load when the track is exactly vertical,
move approximately 5 cm/min,
hold position without power, and
travel several meters or more.

I suspect I need hardware such as the following, but I don't know where to begin. Can anyone help narrow my search?

Track hardware
Drive system for a small platform weighing upwards of a kilogram
Brake (to allow the car to remain at rest with zero work)


texts: verilog behavior changes with part name in iverilog

texts:
So I'm trying to build a master-slave d flipflop in verilog,

module my_d_ff (output out, out_bar, input clk, in);

        my_not clk_not0(clk_bar2, clk);    //doesn't work
//        my_not clk_not2(clk_bar2, clk);  //does work

        my_not clk_not1(clk_bar1, clk);

        my_d_ff_helper m(mid, mid_bar, clk, clk_bar1, in);
        my_d_ff_helper o(out, out_bar, clk_bar2, clk, mid);

endmodule

module my_d_ff_helper (output out, out_bar, input clk, input clk_bar, in);

        my_2x1mux_helper m(out, clk, clk_bar, out_bar_bar, in);

        my_not q_not(out_bar, out);
        my_not q(out_bar_bar, out_bar);
endmodule

module my_2x1mux_helper(output out, input sel, input sel_bar, in0, in1);

For the parts that I omitted, my_not is obvious and my_2x1mux_helper is a mux that takes the negation of the selector recalculated.

When I compile and run, during the high half cycle of the clock, the slave outputs x rather than the old value. Experimentation shows that if I change the line, then the slave performs properly.

I do recognize that I'm negating clk two separate times but if I pass clk_bar into both my_d_ff_helper instances, then I get the same x behavior.

Is this an issue with my verilog compiler? Or am I misunderstanding mutability of input parameters?


texts:
I am building an LED Cube with my kids and a launchpad.  I built a prototype with perf board and its seemed to work pretty well, except the LEDs were dim.  They were pretty cheap LEDs, I didn't give it much thought.  Well, I decided to have some boards made from seeedstudio for them.  Also I bought very bright LEDs.  That's the backstory, here's my problem:

I can't seem to get the LEDs to brighten enough.

Hooking the LED up without the transistors it works as expected on a
breadboard.

Hooking up one transistor works switching with the LED behind the
transistor.

Hooking up one transistor is dim switching with the LED before the
transistor (transistor switching to ground)

On breadboard:

3.3V -> resistor -> emitter  -> collector -> LED -> GND - OK!
3.3V -> resistor -> LED -> emitter -> collector -> GND - DIM!

Here's the schematic:

Sorry, this probably isn't well worded.  I hope the schematic can help explain.


texts: Does every block diagram for an electrical circuit have a feedback loop

texts:
I was reviewing block diagrams on this tutorialspoint page and it showed how an RLC circuit is written with a feedback loop. It occurred to me that any time a block diagram of a circuit is created, there has to be a summing joint, hence there will be feedback On the one hand, this seems natural because for a circuit to function, it has to have a path for current to flow and so there is a type of loop created. On the other hand, I have never heard it mentioned that the block diagram of every circuit must have a feedback loop. It also seems different from my intuitive concepts of feedback though I admit my intuitive concepts are wrong a lot.

Is it true that the block diagram of any electrical circuit has a feedback loop?


texts: Aircraft Harness: 32 AWG conductors to 22 AWG connector

texts:
I'm a junior electrical engineer on a new job where I design the EWIS (electrical wiring interconnect system) of a small aircraft. There is the need to connect a small Curtiss-Wright Ethernet switch to the Flight Controller. However, the Curtiss-Wright device has a power connector from Omnetics, the MNC series.

I would like to connect these wires to a D38999/26FC35PN (22D contacts) connector, which is mounted on the Flight Controller.

What do you all think are my options. Keep in mind that it is for an aircraft installation, so I can't just solder the wires, I need to use MIL spec parts and practice.


texts: What can cause magnetometer offset to be variable?

texts:
I'm a using a embedded MEMS 3-axis magnetometer. With 'embedded' I mean that I am using an Android device with a magnetometer. I am not doing the low-level control myself, only retrieving measurements. From the information I have already found, I know that a magnetometer can suffer from a hard-iron offset and soft-iron distortion.
As far as I understand, hard-iron offset is caused by magnetic fields that have a constant position relative to the magnetometer, so for example other electronics in the same device. This would make the offset (almost) constant.

Soft-iron will cause the measured magnetic strength to warp into a ellipse instead of a circle, and is caused by nearby materials that don't generate a magnetic field by themselves, but to change the 'direction' of the local field.

My magnetometer shows a near-perfect circle with an offset when turning 360 degrees while holding the device parallel to the floor (I am only interested in 'yaw/azimuth') and plotting the vectors that represent the measured magnetic 'direction'. This would, as far as I know, indicate a hard-iron offset.

My problem is that the direction of the offset vector seems to randomly change every time I run my program, the center of the circle can be in all 4 quadrants of the plane parallel to the floor and I haven't figured out any consistency yet!

Am I misunderstanding how hard-iron offsets work, and is it normal that it can change direction? If so, what can be the cause of these changes?


texts:
I'm trying to measure the dynamic response of a 16MHz crystal using a pair of op amps as shown below

Spice simulations predict that this should work fine. Experimentally, however, this configuration is unstable with both op amps drawing a large current and producing high-frequency (~70MHz) large-amplitude output (~3V). Does anybody have any ideas on how to resolve this?

Edit: Adding board diagrams. The diagram above is actually a simplified model from a larger board (but isolated from the remainder of the board, which has been disconnected while debugging this issue), but the line going to the right on the first diagram connects directly to the crystal in the second (I removed some unnecessary parts in between for clarity). The amplifier on the left seems to work on its own when the other is disconnected with the negative input shorted to ground, so I'm guessing it's either something wrong the second circuit or from the two op amps interacting. The component labeled VC4 was replaced with a 0-ohm resistor between pads 1&2 for debugging and the 1M resistor was removed as well.


texts:
As you see in the attached picture. Two component's top overlay is above
in my pcb design; I saw a error, but Altium Rule check does not inform me.
I need a rule for this error. Can you help me?


texts: How do I implement a rotate left 1 bit operation in a 16-bit ALU in logisim

texts: I'm creating a 16-bit ALU that has to perform logical AND, logical OR, addition, subtraction and rotate left one bit. I have everything working perfectly except the rotate left one bit. I think I need to implement this at the 16-bit level instead of inside the 1-bit ALU, which I've chained together to create the 16-bit ALU. Any advice on how to do this would appreciated. I'm thinking it has something to do with the carry out bit, but I can't quite figure it out.


texts: How to implement EMI filter in an N-redundant supply?

texts:
I am designing a dual supply powered system, where certain loads, depending on some conditions will be powered by one or other power rail, in order to achieve some safety levels.

The problem arises when trying to design an EMI/RFI filter for the system. First and foremost, adding the filter after the switch is not possible. This is because there are certain loads powered by the redundant power, whereas others not. Apart from the filter not being nearest to the device input, it would imply replicating filters where loads exist, which may bring more issues than benefits.
The first approach is this

But common mode filtering will never work due to the current splitting.

I have been struggling with this, and the only solution I have come up with is to use FETs as switches to open the return power path only if voltage is present in the respective positive rail.

This way, the current will flow through where is supposed to.

However, I find the solution too appealing. I have the feeling that I am missing something.

Is my solution to the problem valid? Any details/quirks to be considered, apart from the thermal ones?
Do you have any other solution to my problem?

ADDED: One of the answers suggests a 3P filter. This solution is to be applied to small scale electronics, so that would be my last resort.


texts: Linear regulators - Stability, Phase/Gain Margin, Ltspice

texts:
I am trying to understand how the output capacitor and the ESR of the output capacitor has an effet on the stability of a linear regulators. So I decided to measure the phase margin and the gain margin in function of the ESR of the output capacitor and the value of the output capacitor. The others parameters are kept constants. So in the above system, there is oscillation if :

$$|G(s)H(s)| = 1 $$
$$arg(G(s)H(s)) = 180° $$
Well, my problem is where is G(s) and H(s) in a linear regulator. Here is my simulation, I applied a technique provided by Middlebrock that I completely do not know (I will take a look on it) but analog device recommand to use it (https://www.analog.com/en/technical-articles/ltspice-basic-steps-in-generating-a-bode-plot-of-smps.html) :

So I supposed that in this position :
$$\frac{V_B}{V_A} = G(s)H(s)$$
And I observed the ac simulation for  having the gain margin and the phase margin ...
Here is the result for a output capacitor of 5µF and an ESR equal to 100mOhm

Here is the result for a output capacitor of 100µF and an ESR equal to 100mOhm

If someone can tell me how to do to observe the influence of the output capacitor, it would be nice :D I will be happy to hear any recommandations. I am actually reading a book on this subject.
Thank you and have a nice day !


texts:
Our company has designed a board for a custom SoC network processor. It has a PCIe gen2x4 interface, with a PCIe PHY.

This PHY's PLL requires a 100 MHz reference clock.
We are using the reference clock from host PC which is acting as RC and SoC is acting as EP.

We are able to lock PLL on some SoCs after doing some settings in the PHY registers and also able to get the link up (although linkup do not happen on 2x4 every time on the PC start up, but after enabling and disabling the LTSSM two or three times, it gets linked up to 2x4.), but some SoCs don't get locked with same register settings.

Then we reduce the bandwidth of PLL by decreasing the charge pump current. By doing this we are able to get PLL locked if PC is on and PLL is getting 100 MHz clock.

After this, we power off both PC and board.

Now for linkup we power on the board (EP) first and then PC (RC). But now PLL is not able to lock and therefore no linkup happens.

We have measured the RMS cycle to cycle jitter with SoC mounted on the board, in time domain which is coming around 18 ps.

PCIe gen2 spec says that RMS jitter should be around 3 ps. But they specify this jitter for some particular frequency range like 10 kHz to 1.5 MHz and 1.5 MHz to Nyquist (=Refclk/2).

So are we not meeting the specs or we have done the wrong measurement?


texts: Trouble getting measurments of my circuit

texts: I'm trying to turn the first image in a multisim circuit but i can't get the right measurements. I have tried a vcc power source but i still can't get the right result in the oscilometer can anyone give me an pointers because i'm new in multisim?


texts: Using capacitor to maintain current flow past opening of switch

texts:
This circuit turns on the motor when something blocks the beam from the LED to the phototransistor. I want the motor to remain on for 5 seconds after the beam stops being blocked (i.e. from when the phototransistor resumes conducting).

I first thought to add a capacitor in parallel with the motor, but 9V/(.120A * 5s) = 15F (I think?)

So then I thought to put the capacitor where it is highlighted in the circuit diagram, but I don't know how to determine what capacitor to use.

Will the capacitor charge in a few seconds in this arrangement? What if its positive terminal goes above the 1K resistor?
What size capacitor do I need? (The transistor is 2N2222). I'd love to see how this is calculated, but given how hairy the math seems to get with capacitor discharge there might be some rule of thumb?

I'm new to this, so would appreciate having any errors I made pointed out to me.


texts: Do solar panels generate variable current or variable voltage?

texts: Many solar panels are watt-rated. The generated power depends on lighting conditions, so either the current and/or voltage is variable. Which one is it?


texts:
Can someone help me find out what type of LVDS cable I have and point me in the direction of an adaptor to HDMI.
Thanks.

Backstory:
I recently had to throw out an old Sony Vaio All in one PC and decided to take out the monitor as it was nice and also touchscreen.
After searching around for adapters from LVDS to HDMI I realised the ports on the internet were different from the ones I have.
Searching for the model and other things didn't seem to come up with anything.
Here's some pictures:

And the original port on the old motherboard:

The monitor also has a few other cables which would be handy for someone to explain thier uses and what they are.

I realise I'm asking a lot but if anyone knows anything please reply,
Thanks.


texts:
I wonder why under assumption that \$\omega \gg \frac{1}{T}\$ then \$\int_{0}^{T} \sin(\omega t)dt \approx 0\$?

Since the integral should be like \$\frac{\cos(\omega t)}{w}\$ from \$0\$ to \$T\$ and after plugging the valued we will end up with :

$$\frac{-\cos(\omega T)+1}{\omega}$$


texts:
I am trying to design a self-oscillating flyback converter using the circuit below as a reference.

I understand the ton time depends upon the values of Rst, Cf, and Rf and the switching mosfet, M1 switches off when the potential drop across the resistor Rs is equal to threshold voltage of the transistor, Q2. But I am unable to understand how the values of the resistors and capacitors are calculated and how is ton related to Rst, Cf, and Rf.


texts: What's the role of the capacitors in this AC circuit?

texts:
I've been around electronics for a lot of time but I really didn't understand how capacitors work in an AC or DC circuits.

I know capacitor has a big role in smoothing the output of bridge rectifier. As the ripples go through the capacitor and the capacitor works as a tank that is filled upto the maximum voltage of the ripple signal and when the ripple falls to lower voltage, the capacitor is holding that max voltage and delivers it to the output, waiting for the next max ripple signal. And that's how capacitor smooth ripple voltage.

But in this circuit that have a TRIAC to be triggered with a DIAC and complete the circuit and the heater works. There's C1 I think it's a ceramic cap or something other than an electrolytic capacitor. And it works as an open circuit, so there's no current flowing through it. But my question is what its job? I learned something that in an AC circuit that has an inductive load, capacitor is very useful in bringing up the lagging voltage to a good level with the current.

Is it the job for this capacitor in this circuit?

Also what's the job of C2 & C3 ?


texts:
I am looking to drive this stepper motor from the Raspberry Pi. I have successfully followed this tutorial to get the small stepper motor used in the tutorial working correctly. I am using the L293D for the driver.

I tried switching out stepper motors (the smaller for the larger one mentioned at the beginning of this post) since the tutorial only used four wires to control the small stepper motor with the L293D I figured this would work with the larger motor. It did actually move for about 1 second and then it stopped moving now neither the small motor or large motor will function anymore.

I am guessing I burned up the L293D since I believe its only rated for something like 600mA per channel and according to the specs on the larger stepper it uses 1.5A. Is this the most likely cause for neither of them working anymore?

What would be the proper and easiest way to control the larger stepper motor from the Raspberry Pi?


texts: Registered signal and Fmax in Timing Analyzer from Quartus II

texts:
I have the following module that is a simple register:
module linear_out
(
    input clock,
    input resetn,
    input [31:0] x,
    output reg [31:0] y
);

    always @(posedge clock)
        if (!resetn)
            y <= 32'h00000000;
        else
            y <= x;

endmodule

When I synthetize it with Quartus II and I check the fmax in Timing Analyzer from Quartus II, the fmax advice that: No paths to report, but the output is registered... If instead of set only one register, I set two, the fmax already shows a value.
But, I don't get it: Why is it? Is it neccesary set 2 or more clock cycles to get a syntetyzable design with a known fmax?


texts:
I am trying to establish SPI connection between C8051F931 and SD card. One of the sample programs I have found contains the following comments.

// P0.0 - SPI SCK    (digital output, push-pull)
// P0.1 - SPI MISO   (digital input, open-drain)
// P0.2 - SPI MOSI   (digital output, push-pull)
// P0.3 - SPI NSS    (digital output, push-pull)

Do I have to connect some resistance in both the case (push-pull,open-drain) ?  if yes what values?


texts: Can we use ULN2003A to power up another module

texts: I have one requirement wherein, I need to power up one of the modules occasionally. I do not have relay in my controller board, but I have ULN2003A in my board. The module consumes around 400mA. So can I use ULN2003A to drive this external module? In case I can drive, how the connection will be? In case of relays, we give power to one side of the relay and the other side is connected to the collector of ULN.


texts:
I can't find any tutorial on how to write verilog on MKR Vidor 4000. If you have done it what software do you use to synthesize, simulate and create a bit stream to the board ?

Thanks,


texts: What does 'shunt' mean in the context of amplifiers?

texts:
So the term 'shunt' is used to mean the following according to the Wikipedia page https://en.wikipedia.org/wiki/Shunt_(electrical)

  In electronics, a shunt is a device which creates a low-resistance path for electric current, to allow it to pass around another point in the circuit.

However the term 'shunt' seems to mean something else when describing a series-shunt amplifier or a shunt-series amplifier. So what does shunt mean in the context of amplifiers?


texts: Why Is The Current Not Adding Up Through The Resistor?

texts:
Why are the currents not adding up
to the current going through the R1 resistor?
Why is it the same current in loop 1 going through the R1 resistor? What is preventing the current in loop 2 from adding up with the current in loop 1 in the the R1 resistor?


texts:
I am trying to power a Rpi project with a battery. Most of it is working fine but I would like to have a switch that allows me to disconnect the Pi from the battery because even when shutdown it draws some power. I have a mechanical switch to do that but to prevent any data corruption, I would like to bypass the switch as long as the GPIO 3.3V is up. So if anybody unlatches the switch by mistake when the Pi is on, it has no effect. Once the Pi shuts down safely and the GPIO is pulled down, the MOSFET should stop conducing and the switch position is effective again. My current circuit looks lie that (load : 12V to 5V converter + Rpi):

The problem is that my MOSFET never shuts down. I think that's because once the switch is open, there is no common ground anymore and V_GS is always greater than the threshold.
My question is: Is it possible to do that with a MOSFET and if so, how could I set a common ground without having current flow closing the circuit? Would a diode do the trick?
Thanks in advance.


texts: Thermistor calculations using B-Parameter equation

texts:
I have a USUR1000-104G as seen here.

From what I understand by these links here and here

and using the b-parameter equation from wikipedia.

I have the following values:

\$ \beta = 3890 \$

\$ \dfrac{R}{R_0} = 1 \$

This is where I get confused in converting this to a temperature.

I am not sure I follow the equation on how they solve for R in the wikipedia page under the B-parameter section.

For instance; how do I get T in:

\$ e ^ {{\beta}/{T}} \$

for \$ R = r_{\infty} \cdot e ^ {{\beta}/{T}} \$?

Sorry for the vague question; I guess I am just not fully understanding the equation and a little bit of a more detailed explanation may clear things up for me.

EDIT:

As a follow-up I have a thermistor wired to a 3.3volt 100k ohm resistor using the following schematic: here.

The voltages read from 0-1 as a floating point into my code and I have the following code in concordance to the formula discussed earlier in the problem.

 final float reading = input_.read();
 double temperature = 3890/(Math.log((reading*100000)/0.215628)) - 298.5;

However; when I display that code I get a celsius reading of 0 degrees celsius as my room temperature reading.
Which is obviously incorrect...


texts:
I want to be able to delay the signal that goes from the cdi box to the igniton coil on my moped.

I would like to be able to control the delay with something simple like a potentiometer, i don't need to be able to know how much the signal is delayed.

Besides this, the device should have some switch to turn it on or off with so that I can set the delay once and then not touch the potentiometer or whatever it may be, just the switch that controls if the signal is retarded or not.

What's the easiest way to do this?


texts: Appropriate Method of Counting counts from a Quadrature Encoder

texts:
I'm using an Mbed to drive a DC motor which will follow a trapezoidal trajectory.
What is the most appropriate way to determine position from the quadrature encoder?

Should I use interrupts, or is there a risk of the trajectory routine (which calculates theoretical position) falling behind?

Alternatively, I could poll/sample the encoder in fixed time steps, but I'd imagine this would miss out many encoder counts.

How is this problem usually dealt with?


texts: Building a 12 V DC 3-Wire Common Ground Power Supply - Model Rail Accessory Power

texts:
I'm looking for a bit of confirmation for a project I'm doing for my model railway.
I'm going to be using a piece of equipment from an maker which requires a +12 V, 0 V, -12 Vdc supply. In the literature they suggest using 2 x wall-mounted plug-type transformers and tying together the +ve and -ve from the output to create a 3-wire output of +12 V, 0 V (common ground) and -12 V.

Now I'm trying to keep things neat and I'm thinking about getting two DIN-mounted 12 V Supplies from RS:
https://uk.rs-online.com/web/p/din-rail-power-supplies/1368305/
It doesn't need to be a precise 12 V as the PCB will run with some voltage variation. Can anyone see a reason why I can't use the DIN-mounted ones from RS (or similar, as there are loads on the internet)? I can make it enclosed then and a neater job etc.


texts: I have 3 devices that I need to connect together.  They are supposed to be connected via serial port at TTL not RS232.  It only uses 3 wires, TX, RX and GND.  How can I make them communicate with each other, can I just connect all TX wires together and RX wires together?


texts:
I have a few zones and vias of the same net that should not connect (the ground return path of some components is sensitive). I currently use keepout areas, which is very time-consuming (strips around paths and zones).
Is there some way to prevent KiCad from connecting two zones or a via and a zone of the same net?


texts: Please correct my understanding of "how electric works"

texts:
Being in Information Tech, I'm good with programming languages, processor logic, and the such.  It's only natural I got curious about that outlet I plug my servers into.  Here is where I am:

I tried to understand volts and amps.  The water analogy seemed okay at first, but I have tons of issues with it.  I don't think it's exactly right.

Regardless, this is where I am currently stuck:

Do electrons physically hop from atom to atom in a circuit?  Are they really leaving one atom and onto the next, so to speak?  Just "slowly" but the pressure of this is what makes my light bulb turn on immediately?  Electrons vs. Electric Charge?  If so, does a larger charge (voltage?) make the electronics physically move quicker?

I'm trying to understand electricity 101 here and Google presents a LOAD of conflicting data, opinions and arguments.

Please set me on the right track.


texts:
I am interested in buying a high amperage relay which is AC rated (https://www.panasonic-electric-works.com/cps/rde/xbcr/pew_eu_en/ds_61A04_en_dqm.pdf). In particular it is rated for 60A @ 240VAC and I would like to use it at a max 12.4VDC circuit. Could you please advice me what is the equivalent amperage rating for DC @ 12.4VDC?
Thanks in advance and I am looking forward to hearing from you.
Best regards
George


texts:
I'am trying to run a RTOS on my STM32F407VGT6 board.
I downloaded the demo CORTEX_M4F_STM32F407ZG-SK from freeRTOS website and flashed the code using IAR IDE, however the leds are not blinking as expected.
while debugging the program i found that the program crashes here:

vPortStartFirstTask
ldr r0, =0xE000ED08
ldr r0, [r0]
ldr r0, [r0]
msr msp, r0
cpsie i
cpsie f
dsb
isb
svc 0 // The program crashes here!!!!

I made some research in freeRTOS FAQ, the section "The application I created compiles, but does not run" seems to treat the same issue but

#define vPortSVCHandler SVC_Handler
#define xPortPendSVHandler PendSV_Handler
#define xPortSysTickHandler SysTick_Handler

exists in FreeRTOSConfig.h file.
Does anyone faced the same issue? or the RTOS that I'am using is not the right one?


texts: What are the two big transistors on a ESC

texts:
Looking at an commercial electronic speed controler for a brushless motor, there is two big transistors on one side. For controling a motor, you have to switch the current on three wire, so you need six big transistor.

So, how is it possible to use only two big transistors ?


texts: I need to remove 100mV of ripple out of my 12Vdc source. What size and type capacitor do I need?

texts: I am building a very inexpensive power monitor. I need a clean 12Vdc power source for the current transducers. I currently have 100mV of ripple on the 12Vdc source i am using which is causing issues related to the output signal from the CTs. I not an electrical engineer but more of a glorified technician. I am thinking a capacitor between the +12Vdc and GND will do the trick but do not know what size or type capacitor I need.


texts:
Hello. I want to inquire the method that describes when, one side is ON/OFF(fig.17.b), and the other goes with PWM. The point is, wheather both of mosfets (high & low side) will be on/off and some extra mosfet on the power supply ground will be added, that will respond for PWM at this time now, will it keep the advantage when the power do not flow back to psu?

I guess not, but such a point)

Thank you.

In Figure 17a the two transistors in each half-bridge are both driven in anti-phase with a PWM square wave. Q1 and Q4 are gated on at the same time while Q2 and Q3 are gated on for the remainder of the cycle. At 50% duty cycle the average voltage across the motor is zero. As the duty cycle increases in one direction or the other the motor sees an average voltage at its terminals that can be positive or negative, depending on the duty cycle.
Two switches are always gated on and apply a defined voltage to the motor, as determined by the control board. Change in direction is as natural as a change in duty cycle. Current can flow in both direction and the motor can motor or regenerate.
Notice that, during the first part of the cycle (transistor current), power is delivered to the motor. During the remainder of the cycle power is returned to the supply.
The control method shown in Figure 17b uses the lower switches to determine the direction of the motor (Q4 in the example), while the upper switches are PWM-modulated to regulate the speed. This method is similar to the one represented in Figure 16. Notice that only two switches are gate-controlled on or off, while the other two have zero volts applied to the gate. In some instances the direction of the current establishes the voltage applied to the motor and it may be different from what is commanded by the control board. A change of direction requires a change-over from one transistor pair to the other, a common source of control headaches.
The first method gives better servo performance while the second method gives much lower ripple current in the motor for the same operating frequency.
With this modulation method power is not returned to the supply. Current free-wheels in the top devices and decays, as determined by the losses.


texts:
I tried building my own ring oscillator on a breadboard and ran into some issues.
After several failed designs (mostly using 2 inverters - insipired by the CD4060 oscillator), I tried to go simple and go with a classic 3 gate design as shown.

I figured based on that circuit that I could use TTL inverters (74 HC 04) with equal resistors and capacitors (R = 1 k ohms, C = 1 micro farads) and then buffering the output in order to see some oscillation (I was aiming for low frequency, around 1 Hz).

I built the following circuit which did not oscillate. I measured the voltage across the capacitors whilst trying to debug the circuit and it was around 1.8 V constantly, across all three capacitors (5V supply voltage).

Finally, after some more googling, I happened upon this Ring oscillators which described the following circuit, using the same 74 HC 04 IC that I used.

Due to a lack of available parts I replaced the 4,7 Mohm resistors with 1 Mohm ones and the 100 nanoF capacitor with a 10 nF capacitor and I could see oscillation, the circuit did indeed work as advertised.

So my questions are why did the first circuit not work? What was wrong with it? What made the second one work? And how do you calculate the frequency of such an oscillator? Do the capacitors not being non-polarized have something to do with it?


texts:
Assuming I put a 60amp fuse to an AWG 8 wire, whats the worst case scenario when a short circuit happens?

Therory about short circuits says the current goes to "infinity" however, shouldnt the fuse blow first before the wiring melting even when the fuse is "bigger" than the maximun current the wire can handle??


texts: Discharging a capacitor to a battery supply [simple circuit]

texts:
If I have the following circuit... (resistor & capacitors values are made up)

...and I hold down SW3 until the capacitor is charged, then I release SW3 then hold down SW1 why wouldn't the capacitor discharge into the negative terminal of the battery? (according to the comment I posted on this question: Capacitors and simple circuit understanding)

I think I've misunderstand some fundamentals here, as in my mind this circuit would be OK.


texts: Laser activated switch using a photo-transistor

texts:
I would like to make a laser activated switch using a photo-transistor or an LDR, by which I can switch off the lights in a room from a long distance. I just have to point the laser and it will detect my signal and the light must turn off.

Can anybody please help me with a circuit diagram?


texts: What would be the easiest way to read data from a USB glucose meter externally with a microcontroller. Not with the software that is provided. So how could I incercept the digital signals that are being sent out?


texts: lithium coin cells, safe to completely cover? lightweight method to protect from the environment

texts:
I am trying to make equipment to measure temperature in small mammals, probably attached to a neck collar. The collar needs to be very lightweight (e.g. <3g total) so I am planning to  use a lithium coin cell battery, perhaps the 16mm ones or posssibly 12mm.  I was thinking of buying one with contacts attached and just glueing it to the board to save weight.

Apart from the connection to the board I don't want to run the risk of the contacts on the battery touching anything else, and it would be better if it is somehow covered to make it much more difficult for the animal to scratch or bite (I would try to make it so that the entire collar comes off if the animal uses enough force rather than just the battery).  I'm also not sure about the requirements for waterproofing.  The animal will probably get wet and might drag the collar in a river when drinking.

Can I cover the battery (and probably rest of the circuit apart from the sensor) with some type of sealant or do these batteries need vent holes to be safe?  Any suggestions on lightweight ways to enclose and protect anything from the enviroment, (ideally which could somehow be removed later to replace the battery, even if requiring tools) would also be appreciated. perhaps I could use some type of material or something and heatshrink inside that, but I'm concerned about water also.   Thanks!!! :)


texts:
Could someone show me the methodology to solve the following problem?

If the resistance of a circuit having 12 V source is increased by 4 Ω, the current drops by 0.5 A. What is the original resistance of the circuit?


texts:
I thought it was called a "jog dial" but I can't any parts by that name.

There are five pins on the back and one on each side.

What is it called and how can I find a replacement?

It is similar to this momentary switch but it does not have the same number of pins and may actually be an entirely different component:
https://www.ebay.com/itm/231618098407


texts: Functionality of this diode configuration?

texts: What is the purpose of the diodes configured like this? If it is over-voltage protection, I am not seeing it. Please explain?


texts:
I want to build an Arduino based  chessboard using Multiplex RFID to identify pieces.
I have already build a version using reed switches see chess.fortherapy.co.uk .

Having 64 readers would be too expensive.I am assuming that by using multiplexed antenna I can keep the cost of readers down for my 8x8 matrix.

A previous post talked about using relays, but with no further detail can someone help by explaining the basic component layout I would use.


texts: I am going to be making a small robot using a Arduino Mega ADK Rev3 with 4 motors, and about a pound of other stuff. This is the first time I'm doing any major hardware project, so I'm not really sure what to look for in a motor.


texts:
We are trying to solve the following circuit using the Ideal Diode method; however, I'm having a hard time understanding why D1 is always off:

The solution sheet states 2 cases:

When Vin is +ve:

D1 must be OFF
D2 must be OFF

When Vin is -ve:

D1 must be OFF
D2 must be ON

The conclusions from #2 come from the observation that current will flow from ground to Vin (Vin is -ve)

Although when R2 is moved as in the following circuit:

We have the following cases:

When Vin is +ve:

D1 is ON
D2 must be OFF

When Vin is -ve:

D1 must be OFF
D2 must be ON

Isn't D1 supposed to be ON when current flows from Vin to Vout (Vin is +ve) in the first circuit as well?


texts: Does Wi-Fi radiation pass through my body?

texts:
I'm curious. I think I'm confused because I don't really understand the way ionizing radiation works.

So the Wifi radiation passes through my body, but has no ionizing effects within my body?


texts:
I'm new to electronics, and I have a question.
Let's imagine you have something in parallel that drives in total 100 mA.
To turn it on and off you use a pin from your microcontroller, but the pin can deliver at maximum 15 mA.

If you decide to use a N channel MOSFET, it won't help because the current is provided by the gate.
But if you decide to use a P channel MOSFET, the current should be provided by the source (let's say a power supply), and it works.

Am I right to think like that ? Does it mean that it is a big advantage when using P channel ?

Thanks you very much for your help.


texts: High or low side switching where the switch (button) is meters away from the circuit

texts:
I am making a circuit for a button to be far away from the circuit, about 50 meters round-trip. I have went decided to use an optocoupler to protect the uP from the worst of the outside environment and hopefully just get a blown optocoupler rather than a fried uP. The optoucoupler will be driven by a constant current IC to 10mA.
I have made a minimal schematic of both configuration.

What would be the difference in choosing high or low side configs? I am not particular in which offers better response time since a mechanical button can only be pressed very few times per second (but I am keen to know which one offers better response time). I am more concerned about which configuration is less susceptible to failure such as ESD from let's say a worse one, lightning. I went ahead and placed a TVS diode which should clamp at around 40 volts, the highest the CC IC can handle. I should probably increase it a bit more to make sure not to conduct so that the LED won't turn on.


texts: DC/DC buck/bost mudules vs LM317 comparing for Bench power supply circuit

texts:
I Have this two circuit, one of them based of lm317 like this:

and have some Circuit based of XL4005 or XL4015 IC like this:

Input: main using a 18V 2A transformer
Output: 0-18V
Current: 0-1.5A
Current Limiting controlled by a potentiometer
Voltage output controlled by a potentiometer

But i want the same output/input parameters for both of them like this :

  Input: main using a 24V 5A transformer or AC/DC power supply  (almost 75W)

  Output: 0-18V Current: 0-1.5A

  Current Limiting controlled by a potentiometer

  Voltage output controlled by a potentiometer

In this post said about advantage of dc/dc boost/buck modules :

  We used linear regulators like LM317, LM2940 etc. As I said before
      these are so inefficient and can't be used for a battery powered
      setup. So what you can do is, find one of those cheap DC-DC buck
      modules from any online shops and replace the linear regulators with
      them. They're more efficient (>90%), has better load regulation,
      more current capability, current limiting, short circuit protection
      and all. LM2596 is one of that kind. The buck (step down) modules
      will have a precision potentiometer on top. You can replace it with
      a "multi-turn potentiometer" and use it at the front panel instead
      of normal linear pots. That'll give you more control over the output
      voltage.

One of the important thing is having max current for 0- max voltage without considerable decrease,but i have seen this current voltage output chart for XL4005 or XL4015 base:

but don't know that chart for LM317 based!

So i like to know your suggestion about which one of this two schematic or system or better for bench power supply?

And can solve the current drop based of boot/buck converter modules (like XL4005) for this purpose?

Thanks.


texts: Compensation for dielectric losses in a coil?

texts:
Recently I built a helical resonator. It took me a good while to adjust it since I had to trim my coils much shorter than calculated. The calculation said 7.2 turns but it ended up being more like 6.5 turns. The coil was built on a custom 3D printed form (PETG material), so it's very close to ideal.

Could the difference in inductance be attributed to losses in the plastic form? If so, is it possible to estimate the decrease in self resonant frequency due to the form's dielectric constant, to allow for quicker tuning?


texts: Is there a special symbol for instrumentation amplifier, to distinguish it from an opamp? If I use the opamp symbol in a circuit diagram, it looks wrong, like it's missing components:


texts: Sequential circuit modelling using structural verilog description

texts: I'm working on implementing cordic algorithm using structural verilog description and running it on FPGAs. I want to know a way to implement D-flipflops using structural descripton. Is there a pre-defined name that would implement a DFF just like and,or,nand gates?


texts:
I am looking at a servo, which is driven by PWM.
The PWM signal itself modulates NOT DC but a sine AC, so when Throttle is set to 100%, I can see a rather nicely drawn sine wave. But when Throttle is set to values below, the sine becomes edgy, with gaps, just like PWM is supposed to do.

Now I'd like to calculate the RMS voltage. Logically, with full Throttle, RMS voltage fits (1/sqrt(2)) * Vmax quite well. Though for lower settings, a formula is needed.

I know the PWM's Frequency, duty cycles, Vmax.
Any idea?


texts: Does solder being or not being uniformly thin and shiny really indicate reliability of the circuit?

texts:
I'm currently reading an article (in Russian) and the author compares two devices (hard disks) of the same model one manufactured by Company A and the other manufactured by Company B. One of the things he compares is how solder looks like on the boards.

Company A device board has soldered parts looking like this:

and this is claimed to be "low quality tin-coating". What I see is that solder spots are not shiny and the solder layer is thinner near the spot edges and thicker far from the edges (a bit concave).

Company B device has soldered parts looking like this (that's exactly the same area of the board as on the Company A device):

and this is claimed to be "high quality tin-coating". What I see is that solder spots look shiny and the solder layer looks having uniform thickness across each spot.

So to me the first board just looks neater. From what I know about soldering once the surfaces have been properly degreased with soldering flux and the solder was melted properly the connection will be just fine regardless of how shiny and neat looking it is.

However the author claims that the Company B device is of higher quality and should be preferred because of (among other factors) the "better quality" of tin-coating. How reasonable is such claim? Can device reliability be judged based on such tin-coating analysis?


texts: Implementation of NIOS Softcore alongwith HDL modules on Aletra Cyclone IVGX

texts:
My question is not on 'how can' but 'if can'. So I believe people with sufficient experience on any FPGA family might be able to help me out here.

Problem Statement: I need to model a very basic control system on an FPGA such that the 'plant' runs as a Verilog(HDL) module on the FPGA (not just simulation) and the controller is implemented as a C executable running on NIOS2 softcore processor on the FPGA (Altera Cyclone IVGX).

All the manuals and posts that I read which use the CAD tool (Qsys,Quartus,SOPC builder etc) take only examples of how a NIOS 2 softcore processor can be flashed on an FPGA and get it doing various stuff. But can I also have a system where the NIOS2 is being synthesized along with other Verilog(HDL) modules and interacting with any code running on the softcore processor?

I understand that by posing such a question I may provoke some for a RTFMish response, but i did scroll through the design handbooks looking for such topic but couldn't find one.

All I need to know is if this can be done so that I spend more time reading the manuals even closely than before.


texts:
I'm sorry if this is too vague, I'm not thinking of a specific instance when this happened. There have been at least several times when I've been debugging the source of some unwanted electrical noise that is either mitigated or eliminated entirely when I put my hand close to the wire or trace that the noise is on, and I was suddenly curious about it again this morning.
I understand that me being close to the wire capacitively couples me with the wire, and I understand how this capacitance could introduce to some low-pass filter behavior into the circuit. I'm confused why only the noise (not the intended signal) is affected by my hand. Does it have to do with the relative drive strength of the signals?
What does electrical noise that is mitigated by a human hand tell us about the noise itself? Are there common fixes for noise that is mitigated by proximity to a hand/human?


texts: Which pins sense collisions at 100BaseT?

texts:
Background

Suppose I have the following situation...

PC with the NIC hard-coded to 100Mbps, Full-duplex
RJ45 cable, pinned EIA-568B (not that the colors in the pinout matter)
Cisco Catalyst 3560 Switch, using IEEE 802.3-1998 autonegotiation (10/100Mbps, only)

Since the PC's NIC is locked at 100/full, the Cisco's Ethernet autonegotiation fails and it falls back to 100/half. Now there is a duplex mismatch on the line.  Now, let's assume the PC and the Cisco both transmit at exactly the same instant.

  LOGICAL DIAGRAM
  ===============

                      Tx                  Tx
  100/full          ----->              <-----      100/half
  PC        -------------------------------------  Cisco Catalyst 3560

  PHYSICAL LAYER
  ==============

                    Tx D1              Tx on Rx D2??
                    ----->              <------
      568B                                       568B
      Pin  Signal                                Pin  Signal
      1   TX+ D1    ---------------------------  3   RX+ D2
      2   TX- D1    ---------------------------  6   RX- D2
      3   RX+ D2    ---------------------------  1   TX+ D1
      6   RX- D2    ---------------------------  2   TX- D1

                                         <------
                                           Tx D1

CSMA/CD's flowchart looks like this...

My questions are specifically at the decision block for "Is some other station transmitting?"  How exactly does this work at the physical layer?

Questions:

Consider the PHYSICAL LAYER diagram.  When the Cisco transmits at 100/half, is it only transmitting on pins 1 and 2 (marked Tx D1)?  Intuition says this is true, but I want to be sure I understand how a 100BaseT Ether PHY's CSMA/CD works.  I consider it possible that half-duplex would configure to transmit on all four pins (Tx D1 and Rx D2) since I have heard that the tx line driver inspects the transmitted signal to look for collisions.
If the Cisco only transmits on 1 and 2 (Tx D1), does the Ether PHY register the collision because it senses the PC's transmit on pins 3 and 6 (Rx D2)?  To me, it's counter-intuitive to register a collision if you have a dedicated Rx pair.

Please cite standards references for answers.


texts:
I am looking for analog crosspoint ICs that have a high number of channels, that can operate over 10V and are bi-directional.

Currently I am using the circuit CD22M3494 and I am looking for an alternative to it, so any MUX with channels less than 8x16 is pretty much out of the question.

The thing is I have been looking for alternatives for a few days now and all I find can pretty much be seen here.

And as I said I have been searching for a few days and I can find like 6-7 ICs at most that fit my demands. And I am wondering if it's just that I am really bad at searching for circuits or is this kind of IC not that common? I've been looking at big chip manufacturers websites and at some IC distributers like mouser for example.

And another thing, the AD8112/AD8113 alternatives in the link above is uni-directional if I understand the datasheet correctly right? Since it has input and outputs separately and not all the ports defined as input/output... Just want to make sure..


texts:
I am using the https://www.nxp.com/docs/en/data-sheet/PCA9956A.pdf chip to control LEDs.

To set the autoincrement mode three beets are needed,

But the AIF bit is marked as read-only.

Is it a mistake or there is another way of changing it but I am not smart enough to find it in the datasheet?


texts:
Ok, so I'm building a bass/treble cut switch for a guitar pedal and on the diagram that I'm following it shows an output switch with a + label on it. Which part of the jack is that ?
Also, where is the ground that I should connect the DPDT switch to?


texts: How can I program an Atmega32u4 over USB with this schematic?

texts:
This is my first time trying to program an Atmega32u4. I made a PCB with the following schematic:

Now I've soldered all the parts onto the PCB, and I've plugged a micro usb cable from my computer into J1.

I assumed that when I pressed down SW1, the bootloader would activate and and the device would register as a serial device on my computer, so that I can program it using avrdude.

However, when I pressed the reset button, I couldn't find which port it's communicating over. I tried the command avrdude -p m32u4 -P USB -c avr109 to intialise it, just in case that port happened to work, but the output was:

avrdude: ser_open(): can't open device "USB": No such file or directory

avrdude done.  Thank you.

So what's the issue here? Is there something wrong with my schematic, or with my software approach? Again, I'm a complete beginner to this, so any information at all is useful.

EDIT: I plugged it into a different USB port on my computer and now lsusb lists: "Bus 001 Device 020: ID 03eb:2ff4 Atmel Corp. atmega32u4 DFU bootloader", however when I try to use dfu-programmer (as has been suggesteed), this happens:

j4cob-antergos :: /sys/class/tty » sudo dfu-programmer atmega32u4 dump --debug 4        5 ↵
     target: atmega32u4
    chip_id: 0x2ff4
  vendor_id: 0x03eb
    command: dump
      quiet: false
      debug: 4
device_type: AVR
------ command specific below ------

0%                            100%  Reading 0x7000 bytes...
[ X  ERROR

EDIT 2: I tried to use avrdude instead again, and this happened:

j4cob-antergos :: ~ » sudo avrdude -p m32u4 -P usb -c flip1                                              1 ↵

avrdude: Warning: Failed to read USB device string 1: Input/output error
avrdude: Warning: Failed to read USB device string 2: Input/output error
avrdude: Warning: Failed to read USB device string 3: Input/output error
avrdude: Warning: USB bDeviceClass = 255 (expected 254)
avrdude: Error: Failed to reset DFU state: Input/output error
avrdude: AVR device initialized and ready to accept instructions

Reading |                                                    | 0% 0.00savrdude: Error: DFU_DNLOAD failed: Input/output error
avrdude: Error: Failed to get DFU status: Input/output error
avrdude: error reading signature data for part "ATmega32U4", rc=-1
avrdude: error reading signature data, rc=-1

avrdude done.  Thank you.

This is looking more hopeful, but at this point it seems like my schematic just doesn't work. Any thoughts?


texts: Grounding conductor meant to protect electrical devices?

texts:
I had a home inspection performed on an old house recently. The inspector noticed that some of the outlets had an unconnected third prong. He told me that the absence of a grounding conductor on the outlet wouldn't cause any harm to the home's electrical system itself, but that modern appliances that are designed to work with a 3-prong outlet could be damaged if the grounding conductor is unconnected. He used an example of a television set and mentioned that the t.v. could be fried by an unexpected voltage transient from the grid, and then mentioned something about currents travelling in the wrong direction.

I didn't feel like starting an argument so I didn't press him on this issue, but what he was saying sounded completely bogus to me. I thought the grounding conductor was meant to protect the device user from harm, not the device itself? However, he seemed like a pretty competent guy, so I'm wondering if there's actually any truth to his claims?


texts: Increasing Amplification using a MAXIM MAX492 Op Amp?

texts:
I'm using a Maxim DAC (the MAX541) with a TI microcontroller.  I output a digital audio signal from the microcontroller to the DAC.  I have the DAC's output hooked up to a typical 3.5mm audio jack.  When I plug the 3.5mm jack into typical computer speakers the volume is quite low.  I have to crank up the speakers to hear the audio.
Hooking up the 3.5mm audio jack to my oscilloscope I see the max peak-to-peak voltage output is only about 0.12 volts:

When I play the same digital audio using my phone at a reasonably loud level and analyze it with my oscilloscope I see the peak-to-peak max voltage is around 1 volt:

When purchasing the MAX541 DAC I suspected it would need some amplification so I also purchased a MAX492 op amp.  I have the analog output of the DAC going to the input exactly as shown in the MAX492 datasheet's "typical operating circuit" example:

Here's a link to the MAX492 datasheet.
However, this is only amplifying the signal to a peak-to-peak max of about 0.23 volts.  I of course need the MAX492 to amplify the signal to around 1 volt (like my phone's output level), however, I've read through the datasheet and it's not clear to me how to do this or if it's even possible.
Any help would be most appreciated.  Thank you.


texts: Routing through no connect pins in Altium?

texts:
I have an 0.5mm pitch BGA part I'm trying to route in Altium. The datasheet specifically calls out a number of balls on the part as having "no internal connection" and I've seen at least one manufacturer design guide that shows traces going through these pads as a way of having to avoid trying to do a via-in-pad or finding a place to stick a via within the ball grid.

My question is, what's the best way to handle this in Altium? I could just force certain pads to belong to the net I want to route through them but I'd rather have a rule that allows "any net" to be connected to a pad. Does anyone have any suggestions?

Thanks.

Edit:
The suggestion to force pins I want to route through to have a certain net is, I think, a good one because it forces me to make my intentions clear to the rule checker.

A follow-up question would be: is there a good way to force certain pins to NEVER be routed? For example, some pins are called out as "RFU (reserved for future use)" and I want to make sure these are never used. I tried making them all belong to a net class and making a clearance rule for that class, but it's still easy to force one of these pins to belong to a net and then route to it without the DRC complaining.


texts: Is an AB amplifier feedback like this (image inside) possible?

texts:
Whole question in the title, don't know what more information is possible:

Is an AB amplifier feedback like this possible?


texts: What voltage is a 3-LED light from a LED-TV?

texts:
I have some "NDV rev1.1 4248 back lights" from a television.

There is a print that sais "94V" on the strip, and on the wire supplying the strips it said "96V".

Every strip has 9x buttons which have 3 LED's in them. So i devided 94 by 9 and figured that every button should have 10.4V roughly, which makes sense, because a white LED is normally 3.5 volts.

I have a 12v Lithium battery which measured 11.1V so i tested one of the LED's with it and it lasted less than one second.

Are the LED's are rated for 10.4V roughly and not more?


texts: Powering stm32f3discovery board from pin/external power

texts:
I am currently making a project with the stm32f3discovery board and am ready to move it away from the computer and onto an external power source. I have a 5v ubec connected to a lipo battery and am getting about 5.2v from the ubec, when plugging it into the 5v pin it all turns on and runs fine but then after a few days the board started to not run and then got to the point where I can't even flash code to it anymore. Is this the fact that it's 5.2v and not 5v or is there something else going on here that i'm not aware about.
There doesn't seem to be anything online about how to power it from an external source except from in the user manual but it doesn't say how close to 5v it has to be.

Also what are the white circles for next to the 5v and 3v pins?
Any help will be much appreciated, thank you.


texts: Need help about cooling fan voltage adjustment

texts:
So, i built a custom cooling pad for my laptop. Built in battery, 3d-printed case, etc. And the fan that i used is a basic 80mm case fan rated only at 12v. I want to run faster so i thought: how about i run it at 15v? (Its running on a boost converter, step up from 4.2v) i dont really care if its going to be noisy.
So what? Is it gonna burn out faster? Break? Something else? Or is it fine?


texts: How to calibrate multiple light sensors at once?

texts:
I want to build a simple circuit that by adjusting a Trimpot I can regulate the sensitivity of 4  light sensors such as the QRD1114.

I prefer to regulate the gain of the phototransistor instead of the light emission of the IR LEDs

Does anyone knows a good circuit configuration to doing so?


texts: DS3231 Real Time Clock i2c 3volt battery 5V arduino

texts:
I have a doubt I hope somebody can help me

I am thinking to add to my project using Arduino Mega 5V a DS3232 real time clock. I can see on data sheet some information about the MAX voltage for SCL SDA.
I know I can connect directly to 5V the DS3231, But If I disconnect the VCC to work only with 3V battery cr2032 ...

My question is:

Will the I2C communication work?  Because Arduino will use 5V and DS3231 3V. If not, why they add option to use battery, for MCU 3v3 ?


texts: going from 5volt 1A to equivalent from a 3V CR2 Battery

texts:
I have a small camera with wifi that runs off a 3V CR2 battery. I'm trying to run it from line voltage. Could not find any small transformers that go to 3volt 750mA.
I have an Apple transformer for the iphone it outputs 5volt 1A. (I'm getting 5.33V on the crappy tester)
I've tested a fully charged 3v CR2 and it puts out 3.24volts ; I bought a NTE1904 which has a Vo 3.3V Io of 1A; when i hook it up to the breadboard I'm getting 3.25 volt output.

The mfgr of the camera said on their website that this is a 3V 750mA device; the device with the battery gives off considerable heat and only last a 1.5 hours on the battery.

When I plug it into the output of the voltage regulator straight the light comes on but it wifi doesn't work (bad because its the only way to connect to it); when i switch back to battery she works like a champ. I put 10mu caps on the output side  but light didnt even come on.

Am i missing a major concept. I'm kind of a newbie. would appreciate any help.

spec sheet of NTE1904
 http://www.nteinc.com/specs/1900to1999/pdf/nte1904.pdf
******************************
Camera Specifications
•   VGA 640x480, QVGA 320x240, QQVGA 160x120, up to 30fps
•   F2.8
•   View Angle: 60 degree
•   Focusing: 20cm to Infinity

Video Recorder
•   Motion JPEG
•   Compression mode : standard, high
•   Typical bit rate: (VGA): standard (2500 kbps), high (1600 kbps) (QVGA): standard (1100 kbps), high (800 kbps) (QQVGA): standard (600 kbps), high (400 kbps)

Video Snapshot
•   JPEG
•   Compression mode : standard, high

Wireless Interface
•   IEEE 802.11b/g 2.4GHz ISM Band

Wireless Security
•   WEP 64/128, WPA, WPA2

Wireless Range
•   Infrastructure: 20m (Typical)
•   Adhoc: 7.5m (Typical)

Wireless performance*
•   Infrastructure: 54Mbps, max. connection rate
•   Adhoc: 11Mbps, max. connection rate
•   Note: Wireless performance varies with distance and access point usage.

Antenna
•   Single, internal

Dimension / Weight
•   30mm(Diameter) x 35mm(L)
•   100g

Power Supply / Consumption
•   Battery operated
•   Voltage: 3.0V
•   Power: 750mAH (CR2)
•   Current consumption: 320mA (typical); 350mA (maximum)

RoHS
•   RoHS Compliant

User interface
•   Menu driven via Embedded Web server on module


texts: System verilog instantiation of parameterized module

texts:
If I have a mymodule that has parameters and I am instantiating this mymodule inside a top level block which has a few sub module and mymodule is also a submoulde then when instantiating mymodule inside the top level, do I need to define the parameters of mymodule inside the top level?
And if there are some signal(rem) from mymodule that I do not need its value, then when instantiating this mymodule inside the top level can I map them like below:

instant mymodule (.res(res).,clk(clk),.div(div),rem())

I am not mapping rem to any signal.
Is it legeal by compiler?


texts: LCA717 SSR connected to Arduino Digital Pin

texts:
I am trying to figure out how to go about using this LCA717 SPST-NO relay in my project. I will be sending 12V (car voltage) to a radar detector and I want to be able to turn it on/off whenever via the Digital Pin on an Arduino board (max 5V output).

As in, when the digital pin is high it allows 12v to flow to the radar. When the digital pin is low then it shuts out the 12V so no power is going to the radar.

But the problem is that I have no idea what to use for pin 5? Or if pin 4 and 6 are the correct pins to use to do what I am looking to do above?

The LCA717 PDF is here


texts:
I searched around the forum and found this post: Analog voltage level conversion (level shift)

I built a dinamic motion seat with an Arduino, H-Bridge and 2 wiper motors. The wiper motors are acting like a servo because I mounted a potentiometer to the motor output shaft.

Now my motors will turn only about 180° which will result in an analog voltage from 1.6V to 3.5 Volt.

I've built this circuit:

on a little PCB like this:

From my understanding I can use the bottom potentiometer to set offset voltage 1.6V then move the pot to the maximum position and set the Vout with the upper pot to 5V.

Now the output should be 0-5V at 180° pot movement. I use LM324n and 10k pots. Now the problem is that there is no amplification. I only can lower the voltage at Vout but max is 1.6V too.

Maybe my PCB is built wrong but I've checked it many times. Or did I understand something wrong and this is impossible?


texts: Why does a 32 bit microcontroller has only 16 pins in each port

texts: I have used 8 bit microcontrollers and each of their ports has 8 pins. So, I thought a 32 bit microcontroller will have 32 pins in each port (i.e. 32 bit data bus). But today i saw STM32F070RB pin configuration and noticed that each of its port has only 16 pins (instead of 32). Why is that so? Am i missing something here or each port can have any number of pins (irrespective of microcontroller)?


texts:
I have a large thruster that requires 48V to operate, which I've provided through an isolated supply (Vicor DC/DC isolated converters). The thruster uses a Hall-effect sensor to adjust the speed (-5V to +5V), and hands me back an encoder output that linearly relates to the screw speed somehow (though it's not clear yet how this works). The encoder output is actually a 0-12V digital signal that is powered off a provided non-isolated 12V input which should be isolated internally.

I've attached a scope trace of the relevant signals. Trace 1 is the isolated 48V line when the thruster is running, and trace 2 is this digital encoder signal. As you can see, it's incredibly noisy. I can physically isolate the signals but I don't believe that will help since the thruster wires run through a pre-wired bulkhead connection (MacArtney MCBH series, 8 wires), the wires for which run through a narrow slot all together that cannot be separated.

What I need to do is design a circuit that will filter out all of this noise and then step it all down to a standard 5V digial signal that my computer can read and decode. I'm looking for some help doing this because of the coupling; I've filtered out standard AC coupling, but this is different, I think.

I'm thinking a clamping circuit using two Schottky diodes will be the best start to remove most of the negative signal and that above the 12V. Then maybe a sequence of comparators?

Any help would be much appreciated!

EDIT:

The thruster power lines are twisted with their isolated ground, and the encoder output is twisted with its ground as well (these are separated).
I can shield both pairs only to a point; beyond that all the wires run through a narrow choke point and cannot be shielded further.
The encoder output is produced by some electronics internal to the thruster. This is, in fairness, unknown.

EDIT 2:

I've extended this question to the team I'm working with at large, and some good points were made, so I'll try to specify further. We didn't have a chance to verify, but Tony's point about the grounding is good - it's highly likely that the grounds were connected through the scope (see the attached diagram) and that's what caused the significant coupling noise.

So, given the clarification of the attached diagram and the realization that the noise will probably not be quite so severe, let's re-ask the question: given the system shown in these block diagrams, how can we extract the 0-350 Hz square wave from the motor with as few components as possible? Specifically:

Assume the signal ground is NOT connected to 48v ground this time, and there is minimal conducted noise. Also assume there may be noise severe enough to produce momentary false falling or rising edges. Keep in mind that we have a very limited bandwidth of interest: 10-400 Hz.
Assume the availability of 12v, 5v and 3.3v supplies for powering a filter circuit (passive filtering is preferred)
Know that the signal could be fed into any of the following 3 interfaces to our CPU: a 3.3v logic input (Assume a digital input pulled to ground with an internal pull up of >10k. Reducing input impedance would only be possible with an external paralleled resistor.), a single ended non inverting unity gain amp (+/-15v tolerant) or differential input amp.
Assume that our CPU interface has no hardware counters, zero-crossing or rising/falling edge detection circuitry. All inputs appear as bits in a register (either one bit for pin state or the output of an 18-bit ADC), and the only notification of their presence is a read-complete bit gets set.


texts: Can wax really improve the performance of a FM transmitter?

texts:
Why would the use of wax improve the performance of a FM transmitter?

Consider this from the video How to build a FM radio transmitter, at 4 min 14 secs:

  "Theoretically this helps decrease onboard interference between the components"

Wax in this case is paraffin wax and has a relatively low relative permittivity of 2-3 (about the same as many plastics). The resistivity of 1 x 1017 Ω•m is higher than that of air.

I can understand the use of wax for the mechanical stability of air coils (and thus frequency stability in some applications), but not for "decreasing onboard interference".

Schematics (at 0 min 35 secs):


texts:
im troubleshooting a 24v ac transformer hooked to two doorbell circuits and on one of them I am getting a 35v reading.  What could be causing this?

I am reading the voltage using a standard (cheapo) non auto-ranging meter set to 200v ac (the lowest setting)

Im not actually measuring at the secondary outputs but at the end of a 17 foot length of 18 ga wire connected to the secondary outputs.

(I dont know what 'rectified to dc' means)


texts:
I am currently using two nRF24L01+ (2.4 GHz RF transceivers) together with two AVRs to create a keyless entry system.
My problem is battery lifetime when using a CR2032 battery to power the key.

The key will sleep until a signal is received from the other unit, then wake up and respond.

The RF modules have a power-down mode in which they consume about 900 nA which would be ideal. The problem is that when the module is sleeping it won't listen for any signal and therefore won't send the necessary IRQ to wake up the AVR.

If I put the module in Standby-mode it might trigger the IRQ, but unfortunately it consumes about 26 µA which is to much.

Is there any RF receiver capable of listening for a message and sending an IRQ while consuming <10µA? The data rate doesn't really matter since it could be used only to wake up the AVR, and let the nRF do the rest. Range should be at least 3m (9 ft).

Perhaps someone has some inside knowledge of how car manufacturers have solved this?


texts:
I have been looking at EL wire inverter, and most are battery powered.
I want to power it from mains power.

I was looking at having a transformer to step down from 220AC to 110AC.
This gives me 110AC at 60Hz.
Good voltage for most El wire but too low frequency.
So now...i would like help to get a higher frequency...

Anyone has a simple idea?

Or even a different approach?


texts: Why does the voltage double in a doubler-circuit?

texts:
I’m having a hard time understanding how the final voltage is achieved.

I understand that in the first half of the sine wave the first capacitor gets charged to 1V.
In the 2nd half the first one is already charged so the 2nd capacitor gets charged to 1V as well.
But how does this account to 2V?

Looking at it, it seems like these capacitors are in parallel, so I’d expect them to only provide 1V.
Where’s my mistake?


texts: Why does this transistor circuit light the LED?

texts:
I'm trying to drive a 5v relay from an esp8266-12e via one of its digital outs (3.3v). However it doesn't produce enough current to trigger the relay. So I read how to do that from here and here.

I'm using a PN2222a transistor with an LED on a bread board to try this out, but it is not working as expected. Since the base in the NPN transistor doesn't have any power applied to it, I'd expect that the circuit would be open and the LED would not light. But it is lighting as seen in the pic. What am I missing (likely a lot)? Shouldn't it only light if I apply + voltage to the base?

If I test the transistor, assuming, the left most pin is the emmiter (e) (-) and then next is the base (B) and finally the collector (C), I am getting Veb = 7v and Vce = 7.6v.

[![

simulate this circuit – Schematic created using CircuitLab

]3]3
[]4


texts: Simple Circuit Analysis, why this cap is needed?

texts:
This is a sub-circuit that is part of larger design and I was wondering why the designer choose to use C1 inline with the BJT base? and what does the combination of R1, C1,R2,R3 do?

Since the max base emitter voltage is 5v, I would put a voltage divider at the gate to drop the 15v coming out from the flip flop down to maybe 2.5v. Any insight would be appreciated.
Thank you


texts: Problem in reading/writing bytes with atmega16 & 24LC256 EEPROM

texts:
I am beginner in MCU world.
I have learned quite few things and felt quite good.
I am trying to experiment with my Atmega16 and 24LC256 eeprom chip.
After making all the necessary connections on breadboard I uploaded my program to atmega16.
My problem is that after when I am reading back my data after writing it to the flash it is always returning 0xFF.
I am unable to figure out what's going wrong here.
Please help me find out the problem.
Here is my code:

#ifndef F_CPU                    // if F_CPU was not defined in Project -> Properties
#define F_CPU 2000000UL            // define it now as 2 MHz unsigned long
#endif
#include <avr/io.h>
#include<avr/interrupt.h>
#include "util/delay.h"
#define EEPROM_WRITE 0xA0
#define EEPROM_READ 0xA1
void i2c_init()
{
    //set SCL to 100kHz
    // CPU freq = 2MHz
    TWSR = 0x00;
    TWBR = (1<<TWPS1);
    //enable TWI
    TWCR = (1<<TWEN);
}
void i2c_start()
{
    TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);
    while ((TWCR & (1<<TWINT)) == 0);
}
void i2c_stop()
{
    TWCR = (1<<TWINT)|(1<<TWSTO)|(1<<TWEN);
    _delay_ms(100);
}
void i2c_write(uint8_t u8data)
{
    TWDR = u8data;
    TWCR = (1<<TWINT)|(1<<TWEN);
    while ((TWCR & (1<<TWINT)) == 0);
    _delay_ms(10);
}
//read byte with NACK
uint8_t i2c_read()
{
    //TWCR = (1<<TWINT)|(1<<TWEN);
    //while ((TWCR & (1<<TWINT)) == 0);
    //return TWDR;

    TWCR = (1<<TWINT)|(1<<TWEN)|(1<<TWEA);
    while ((TWCR & (1<<TWINT)) == 0);
    return TWDR;
}
int main()
{
    i2c_init();
    uint8_t readByte=0;
    uint16_t address=0x0;
    uint8_t writeVal=0;
    while (1)
    {
        for (int a =0;a<128;a++)
        {
            i2c_start();
            i2c_write(EEPROM_WRITE);
            i2c_write(address>>8);
            i2c_write(address & 0xFF);
            i2c_write(writeVal);
            i2c_stop();
            writeVal++;
            address++;
        }

        address=0;
        for (int a =0;a<128;a++)
        {
            i2c_start();
            i2c_write(EEPROM_READ);
            i2c_write(address>>8);
            i2c_write(address & 0xFF);
            readByte =i2c_read();
            _delay_ms(10);
            i2c_stop();
            address++;
        }
    }
    return 0;
}


texts: raspberry pi 3 to switch between 2 similar power supplies

texts: I put the following circuit together and it's working fine, but I still want to be completely sure I'm not missing anything. I think I read somewhere that when a relay is used to switch between power supplies, a capacitor on the pencil circled area is needed to avoid damage to the relay or other parts of the circuit because of the sudden change of power supply, but I can't find where I read it. I also read that that same capacitor (or is it a second one of other type?) would be useful to supply the load with the voltage that would cut off the time it takes for the relay to change from one power supply to the other. Can someone guide me on what value or type of capacitor to use for both purposes? And if anything else needs correction please let me know and I would greatly appreciated!


texts: Mico32 Microcontroller on Lattice ECP3 FPGA

texts:
Im trying to design an Ethernet Interface on Lattice ECP3 (versa board),
for this I have to use Lattice built in micro-controller on the ECP3 SOC from Lattice:

I cant find any reference for how to connect the Mico32 to ECP3 FPGA (pins)
I followed the Lattice Mico32 Tutorial from their website:
http://www.latticesemi.com/view_document?document_id=52209
but they connect it to ECP2 FPGA there, so I cant test it on my own board.
Someone who working with Lattice FPGAs can help me to find from where I can learn about how to use this microcontroller using ECP3 FPGA (versa board).


texts: Testing Triple Differential Driver AD 8147

texts:
I'm working on project that requires me to convert my single ended RGB signal(VGA from PC) to differential ended RGB.
I made this circuit given below the only change that I made was using a 4.7K resistance in place of R2 (4.02K).

I connected my VGA output from PC to connector P1 and left connector P2 open.
I observed the signals at the end of my cable (The end that I shall connect to my board) and I wasn't getting proper pulses of Hsync and Vsync till I connected it to my board.
I'm using a single 5V supply. So I didn't connect Vs-ve and left it open.
I used three jumpers to short:

Pin 1 of J1 with pin 2 of J1.
Pin 1 of J2 with pin 2 of J2.
Pin 1 of J3 with pin 2 of J3.

Then came the problem of observing my output signal which is differential. Now I tried looking for the procedure to observe a differential signal on an oscilloscope. I found out that :

I'll be needing two channels. One will be connected to the positive output end and the other will be connected to the negative output end.
I'll be connecting the grounds of my probes to each other and nothing else.
I'll have to keep both channels on "AC coupling"

But when I did these three things and observed my output at R+ and R- I wasn't getting a proper output.

My questions are:

Do I need to connect a load to P2 to be able to observe my output?
What kind of output I should be expecting? I tried googling images of a random RGB signal but I didn't get anything that would give me an idea of what I should be seeing on the oscilloscope.
Is my testing procedure correct?
Do I need to connect ground on Vs-ve?


texts: I want to design a DC solenoid valve that could compress a spring under 5 kg of load. All I know is the voltage (12V), load (5kg), the current range (15-20), and the cross-sectional area of the winding. kindly help me with the number of turns, wire gauge, etc.


texts: Simultaneously Charge and Discharge a LiPo

texts:
I have what seems to be a rather common problem, a circuit in which i wish to be able to simultaneously charge and discharge (use) a LiPo battery. The "charge" going "into" the battery will be coming from a solar panel, and therefore may have varying voltage, the discharge from the battery will be going through a powerboost 500 and to an iphone to charge it.
Would this be a functioning circuit, where if the iphone is not plugged, the solar panel will charge the lipo, and when it is plugged in, the solar panel and lipo will be regulated to 5V and charge the phone?

Thanks in advance, all answers are accepted


texts:
I'm planning to develop a helical heating coil wound around a ceramic rod. The purpose of this coil is to radiate heat to its nearby surroundings.

I want to know if there should be a spacing between each turn in the coil? If yes does the heat radiated depend on the spacing? If yes what should be the spacing inorder to attain maximum intensity of heat radiation, keeping all other parameters constant?

I'm guessing, the lesser the spacing more are the turns in the coil hence more heat radiation, thus the spacing should be as little as possible (but not zero) inorder for maximum heat radiation. Am I right?

EDIT: I'm interested in a high intensity heat to generate a high temperature in a small volume. Basically I just want to heat the surface just below the coil. The distance between the coil and the surface is not more than two millimetres.


texts: D.C power supplies, regulated linear power supply question

texts:
Design giving the necessary ratings and characteristics the necessary for the transformer, bridge rectifier capacitor and regulator , a 12v , 2A regulated power supply .

the available mains supply is 230v+10% @50hz

so far I have :

Regulator - Standard voltage regulator will require 2v to be maintained across it to prevent drop out , therefore input voltage should not drop below 14v

Transformer - Va atleast  50% & volt drop = 24v

Capacitor - the minimum peak voltage to the regulator input

(24-10%) x 1.414 - 2 = 28.8v

maximum peak voltage

(24+10%+10%)x1.414-1.4 = 38.9v

The minimum peak full hand voltage defines the minimum of ripple voltage
(28.8-14) = 14.8

suitable reservoir capacitor ?

I am uncertain if these figures are even correct , I think I am close but could do with some guidance

thank you


texts: Best practice to forward a Signal by using a 2.4GHz Module?

texts:
I want to control the speed of a motor by using a 2.4 GHz receiver.  I regulate the speed by sending an PWM-Info to the motor.

Its working great, if I use an arduiono and lots of wires. But I have to seperate the arduino and the motor, because the motor has to be portable. So I want to use a 2.4GHz transmitter module for arduino to control the motor.

I'd like to use this module, to receive the current frequence from the arduino and forward it to the pwm port: https://www.sparkfun.com/products/152

Is this possible as I imagine it? Is there anything else I need? When I could use an arduino, this would be very easy, but my solution has to be small. The smaller it becomes, the better.

In another scenario I use the arduino to control multiple motors at the same time, each motor has its own receiver. How can I identify the modules, so I can set the frequency for each motor.


texts: Relay Contact protection of inductive load and maintain electrical isolation

texts:
I've been reading Henry Ott's Electromagnetic Compatibility Engineering and one of the chapters is about contact protection.

Looking at the various protection mechanisms to prevent or minimize arcing from inductive loads, it seem that the components used break galvanic isolation and instead you have capacitive isolation instead (such an RCD network across the contact).

Is there a way to achieve true electrical isolation (galvanic) and to protect the contacts ? It seems that its an either or situation (have one but not the other).


texts: Has anyone worked with HX711 load cell amplifier / weighting sensor through Arduino?

texts:
I am talking about this product: http://www.ebay.in/itm/232127458591?aff_source=Sok-Goog

I need to know the following:

1) What outputs are represented by DT and SCK?

2) What inputs are B- and B+?

3) Where to connect DT and SCK on Arduino board?

4) I have load cell with 5 wires (Red, Black, Black, Green, White). What wires shall connect to B+, B-?

5) Why two wires are black? How do I find which one of them is E- and what is the purpose of second black wire?


texts: Capacitor voltage rating in a zener-only stabilized mains supply - 35 V rating OK for 24 V?

texts:
I have to replace a smoothing capacitor in the "power supply" of a mains operated device. The stabilization is done with two 12 V Zener diodes in series. The supply uses a capacitor and resistor to step down the 230 V and then clamps the voltage using the Zeners. The estimated current draw of the whole circuit is less than 50mA.

The old capacitor was rated 220µF / 50V. I don't have specifications on the old capacitor. I can't even find the manufacturer "GTH". It died, losing almost all of its capacitance.

Is it acceptable to replace the old capacitor with a (low ESR) capacitor rated for 35V?

Using a 35V capacitor (for a short test) the device was functional. The expected voltage is 24 V. The reading matched that expectation.

Here is the relevant part of the schematic. The capacitor of interest is C2:


texts: Is this ADC capable of better performance?

texts:
I am using ADS1231 to get values from a load cell,i am using the ADC in following configuration.
i am powering the micocontroller and loadcell by 5Volt supply as shown in above image. i am getting the results as expected and everything works fine.
Questions :
load cell that i am using is 2mV/volt type, and it says in the datasheet that the ADC input range is form -19.5 milivolts to +19.5 milivolts. In my case i am supplying the ADC with only 10 mV.
is there any way to increase the range ?
am i using the full potential of ADC capabilities?
Thankyou.


texts: Why is my transistor ON when charge is only going to the base?

texts:
simulate this circuit – Schematic created using CircuitLab

I am using an NPN transistor (2N4401).

In the above schematic, charge is only coming in through the base, and not the collector.

My LED is dim, but still lit. Is this the expected behavior of a transistor, or am I doing something wrong?

My expectation was that there should be no charge flowing through the emitter since the collector is not connected. Obviously, when the collector has charge applied, but the base does not, then the LED does not light up. This is expected, but it's also happening the other way around.


texts: how do i calculate stall torque 5.4kg@ 5v 1000mA?

texts: i came to this website https://www.letsbuyrobots.com/en/robot-humanoide-ls-868, and i want to know the servo spec especially the stall torque, and then i found this "2) Torque:5.4kg@5v 1000mA, Power: 5-9V Operation", what does this even mean?, how do i know the servo stall torque from that?, thanks


texts: Relationship between dynamic range and number of samples

texts:
I am working on an NI measurement system. I tried to measure the dynamic range of the system and I got about 100 dB.

On this system I can easily change the number of samples per average (for example, from 100 samples per average to 10k samples per average). When I do that, the dynamic range changes by about 20 dB.

The question is, how can I confirm by calculation that the change in dynamic range that I got is right - knowing that the receiver resolution is 16 bit?


texts: Readable and educational implementations of a CPU in a HDL

texts:
Can you recommend a readable and educational implementation of a CPU in VHDL or Verilog? Preferably something well documented.

P.S. I know I can look at opencores, but I'm specifically interested in stuff people have actually looked at and found interesting.

P.S.2. Sorry about the sucky tags, but as a new user I can't create new ones


texts:
I have a few doubts regarding the driver LM5113 (and IC's in general at this point). As can be seen in the schematic below, VDD is provided with 5.1V via the Zener Diode.

I was told (with no further information) that, the chosen resistor (R50 = 787 Ohms) value is too high, and the LM5113 would "not receive enough current". The Zener diode requires 5mA Iz in order to provide a stable 5.1V drop (as outlined in the datasheet of the Zener), thus 787Ohms was chosen.

I was of the idea that as long as the optimal input voltage was provided, then the IC would draw the required current according to its load and internal impedance.

Therefore, considering the LM5113 can source 1.2A and sink 5A, can someone enlighten me with the relationship between the input voltage, current drawn and the parameter in the datasheet (page 5) "I_DDO (V_DD operating current)".

LM5113 100 V 1.2-A / 5-A, Half-Bridge Gate Driver for Enhancement Mode GaN FETs


texts:
I'm working on a biomedical project, and need to transfer power from a non-ideal source, with a very high internal impedance (~700Kohm) and low voltage, to a load with a high impedance (~1Mohm). I need to maximize the voltage delivered to the load, and because the source has a high internal impedance, I need to have a buffer between the source and the load. Would an op-amp based voltage follower do the job (non-inverting with gain = 1)?

Also, because of the design limitations, I'm trying to find the right op-amp. The priorities are:
1- It must have a low power consumption,
2- It must have a high input impedance,
3- It has to have a low vcc.

I found this from TI http://www.ti.com/product/lpv821 , which seems to satisfy my constraints.

To summarize, my questions are:

1- Is a voltage follower the right circuit?
2- Is the above op-amp suitable for this purpose?
Thanks!

Update:

The input source is a low frequency AC signal (less than 1khz) and no DC. The peak to peak input voltage is less than 2.5V and I'm hoping to transfer the same to the load.

The maximum voltage to power the op amp would be 5V (2.5V for positive supply and -2.5 for negative) but the input wont be more than 1.25 in anplitude.

The circuit is meant to work in room temperature.


texts: Why can I use P = I²R but not P=V²/R when calculating energy lost in a circuit?

texts:
I am working through a book of problems and am confused by the answer to this one:

A 12 V battery supplies 60 A for 2 seconds.

The total resistance of the wires in the circuit is 0.01 Ohm.

Q1. What is the total power supplied?

Q2. What is the energy lost as heat in the wires?

A1:

Total power output = 12 * 60 * 2 = 1440 Joules.

All good so far.

A2:

This is the answer in the book:

P = I²R * t = 3600 * 0.01 * 2 = 72 Joules

That's fine with me. However, if I use the equivalent equation P=V²/R ...

P = V²/ R * t = 12² / 0.01 * 2 = 28,800 Joules

Both of these equations are for P, so how are they giving me different answers?


texts: US5881 Hall Effect sensor not detecting AC field

texts:
Yesterday I was disappointed to learn there is no magical IC to measure current flow in a standard appliance cord.

On the advice I received, I went ahead with a US5881 Hall effect sensor and split the conductors. I then passed only one of the conductors over the  over the sensor (to avoid cancellation of the magnetic field from having two conductors in close proximity).

I wired it up as shown below. The setup works fine when tested manually with a permanent magnet. But I cannot detect any pulses when attempting to measure against the AC line. I do not have an oscilloscope, so pulses are being measured using interrupts on a digital Arduino input.

(I also tried with a 100nF capacitor on the source voltage and a 4.7nF capacitor on the signal legs, as shown on the datasheet. The result was the same: no pulses when measuring the AC current.)

Is this just a matter of insufficient sensitivity on the US5881? From the other thread I linked, I kind of got the impression this chip could measure AC fields with this setup, but maybe not? Or is there something wrong with my approach?

simulate this circuit – Schematic created using CircuitLab


texts: Forward biasing of a BC547 transistor doesn't turn on LED

texts:
I have a setup as shown below:

simulate this circuit – Schematic created using CircuitLab

I am using the transistor as a sort of a switch. I am ensuring about 0.7 V (approx) is provided from the mid-point of the resistors to the base of the transistor. Because as I recall from my school days the breakdown voltage of silicon is 0.7V. Which means it will start forward-biasing above this voltage.

The calculated midpoint value is coming to 0.757V however. Observed is also something around .7V.

However, in this setup the LED doesn't turn on. What am I doing wrong here?

PS: I have used a standard LEDs that you use for common breadboard prototyping. Not sure the one I mentioned in the diagram is the same...


texts:
I have APC BX1100C UPS for my pc.  it has 2x7.2Ah battery. I have connected to it a router 12v 0.5a, and a monitor 19v 1.3a. Expected it to run 10 hours but it switched off after 2 hours.
Does it mean the batteries capacity has reduced from usage ? Or is my calculation off?

Edit:
Specs here:
https://www.apc.com/shop/in/en/products/APC-Back-UPS-1100VA-230V-without-auto-shutdown-software-India/P-BX1100C-IN
The specs has 173wh stated.


texts: How to setup a 16x16 led ( 4x - 8x8 Leds) with 4 shift registers?

texts:
hey guys I'm confused on how to setup a 16x16 led ( 4x - 8x8 Leds) with 4 shift registers (hcf4094)?

because the one I learned is you use 2 shift registers in one 8x8 LED dot matrix.
but how to do it with 4x - 8x8 Led matrix? 16x16 Basically.

Because when you setup 16x16 led matrix then you have to use 8 registers (2 shift Registers each), that's what ive understand.

But suddenly my professor said that you will only use 4 shift registers in the 16x16 led.

I am confused right now and searching on the net on how to setup but could find what I've need. Thank you!


texts: Transfer Function Of Multiple Feedback Filter

texts:
Can someone please give me tips on how I could prove that the transfer function of the multiple feedback filter below is

\$
   T(s) = \dfrac{ -\dfrac{1}{R_1 R_2 C_1 C_2 } }  {s^2 + s\dfrac{1}{C_1} \left( \dfrac{1}{R_1} + \dfrac{1}{R_2} + \dfrac{1}{R_3} \right) + \dfrac{1}{R_2 R_3 C_1 C_2} }
\$

I just can't figure out a way of getting an expression for

\$
   T(s) = \dfrac{V_{out}(s)}{V_{in}(s)}
\$


texts: I have problem with an lm386 op amp in an non-inverting configuration. For the resistors, I take two equal resistors so i set a gain of 2. When i put a signal of 3.3 volts on the non-inverting pin, i should get 6.6 volts on the output on the op amp, but i get totaly different measuring. I have also measured the voltage on the inverting and non-inverting pins and i do not get the same voltage but i should. Also when no voltage is connected on the non-inverting pin (when its grounded) i am not getting 0 volts on the output, but i am getting zero point something volts. I have also tried to change the ic or the resistors but it didnt worked. So now i wanted to ask am i makeing a mistake or the mistake is in the ic. Every answer is welcome. Thanks a lot.


texts:
Iam using a basic cascade voltage multiplier to boost and rectify the 0.3v ac signal. The circuit rectifies but the boost is very less. So I thought of using LTC3105 after this stage to get a regulated dc output voltage. Problem in simulation is it is taking really long time to simulate moreover LTC3105 is not boosting up below 0.5 v but according to datasheet LTC3105 starts up at 0.25 v. Can you please help me out with this?

Implement ac-dc converter for low frequency and very low voltage without external powering? - ResearchGate. Available from: https://www.researchgate.net/post/Implement_ac-dc_converter_for_low_frequency_and_very_low_voltage_without_external_powering [accessed Apr 21, 2016].


texts: LoRa RFM95/SX1276 libraries for PIC 8 bit microcontrollers

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I recently finished prototyping a LoRa RFM95 transceiver with an Arduino Uno using the RadioHead RFM95 library. I am now transitioning to designing a PCB for my project and chose a PIC16F18446 microcontroller based on my other needs.

I would like to know if there is any way to make the RadioHead Library work with the PIC? If not, please point me towards how I should go about programming the PIC to talk to the RFM95/SX1276 module. Any help would be very useful.


texts: Build PIC development board on bread board

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I have PIC24FJ128GA202 IC only. Since development boards cost too much, I would like to build a development board  on a bread board and try some sample programs on it.

Like the image below:

Is it possible to build it this way?
Thanks


texts: Common ground between battery and AC/DC adapter

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Is it possible to connect an AC/DC power adapter's ground (-) to a battery's negative side?

I am powering a car radio with a 12V AC adapter. That works fine. However, if the radio loses power, it also loses it's programmed FM stations etc. There is a separate cable to provide constant +12 V. from the car battery, but there is only one "-".

Would it work if I connect both the AC/DC "-" and the battery's "-" together to the car radio "-" lead, and the "+" sides of the adapter and the battery to their respective leads?

Or would this fry my battery, my adapter, my radio, or burn down the house :-) , or just plainly not work?

Edit:

I was thinkinkg of any small cheap 12V battery. Probably non-rechargeable. Maintaining settings memory should draw very little power.
I have no idea whether the 2 separate +12V leads are eventually shorted inside the car radio or not.
The main difference in my setup from the normal use in a car is that in a car, these 2 power leads get the same voltage (from the single car battery). In my case, they would get a different voltage (possibly up to 2-3 volts of difference?).


texts: How to identify a BLDC motor from a brushed DC motor?

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I got 2 dc motors from a broken cheap RC helicopter. How can I Identify what type of motor it is? It has 3 terminals, but only 2 where used. It takes around 2-3 Amps of current at 3.5 V.
Each trace in the board is connected to the adjacent one through a capacitor.
Here are the pics:


texts: What does the "capacitor into resistance" symbol mean?

texts: I can't understand the circled symbol and didn't manage to google it. It looks like a variable resistance and a capacitor. What does it mean?


texts: If I am writing a processor in VHDL, how can I get an assembler to ease testing?

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Provided that I have written a simple microprocessor design in VHDL where I have decided what instructions it has to do each task, I will then have to write test code in machine language which is tedious and error prone.

A simple assembler would be like a “lite text processor” where it can convert assembly instructions to machine code by parsing text of the assembly language program. Each assembly instruction is a mnemonic and the parser will also figure our how to fit the parameters into the generated machine instruction word e.g register name, variable name e.t.c

Is there an easy solution to developer an assembler of such a nature?


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I need to control output from 0-6V at max 1A (~0.8A).

Looking at the datasheet for LM25010 it looks I could control R1 and R2 feedback resistors and achieve just that.

Is it possible to get that range?
What information inside datasheet says how close I can get to Vin at Vout?


texts: Negative Voltage creating Sinking Terminal

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For powering a RS485 circuit, I am requiring a Negative Power Source.

I was thinking to split a standard power source with 0V, +6V and +12V, using the +6V as ground with LM7805, and using some LM7805|LM7905 (or similar) devices for regulate into +5V|-5V.

In this case, the +6V could become a sinking terminal if the negative voltage circuit is unloaded, which I think should not be correct and could break the source(?).

The arbitrary change of GNDs confuse me, because the GND should always be a sinking terminal, not a sourcing.

So, how should I generate +5V -5V sources in a proper way?

Also, it is a choice to generate a low power -5V from a +5V source?

Edit.

Agreed regarding RS485 not actually requiring -5V source. Please keep the example valid for other application.
Consider 0V, +7.5V and +15V for the voltage dropout.
Consider only resistive loads, DC output signals.

In the best case, I am afraid this question depends on the nature of the power source (?). For example,

Case 1: if we have two sources, one from GND to +7.5V and other from GND to +15V, then loading only the 7805 will negatively polarize (charge) the 0 +7.5V source (?), hence this design is wrong in this case?
Case 2: The proper design should have two sources from GND to +7.5V, and putting them in series (?).


texts: Increasing open loop gain of opamp by chaining

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I have an op amp, it has an op amp \$A_{DC gain} \$ DC open loop gain, its ideal

The open loop gain is \$ V_{out} = A_{DC gain} V_{in} \$ (Actually \$ -V_{in} \$ in the diagram, but you get the drift)

If I chain these two op amps together, I would get \$ Vout = A_{DC gain1}* A_{DC gain2}V_{in} \$ giving me more DC open loop gain.

simulate this circuit – Schematic created using CircuitLab

Now for the question: If I do this for two ideal Opamps with DC open loop gain in a closed loop situation I should get more DC open loop gain and be able to move to higher gains.

In the top example the closed loop gain is equal to:

\$ Gain = \frac{A_{DC gain}*\frac{R_1}{R_1+R_2}}{1+A_{DC gain}*\frac{R_1}{R_1+R_2}}\$

in the bottom chaining two opamps together should improve my open loop gain

\$ Vout = A_{DC gain1}* A_{DC gain2}V_{in} \$

so I would get this:
\$ Gain = \frac{A_{DC gain1}* A_{DC gain2}*\frac{R_1}{R_1+R_2}}{1+A_{DC gain1}* A_{DC gain2}*\frac{R_1}{R_1+R_2}}\$

(I also realize that flipping the other opamp negates the gain depending on if the positive terminal is grounded or the negative terminal is grounded.)

Would this work in the real world with real opamps that are not ideal? What would be preventing me from doing this?

simulate this circuit


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I am having trouble designing a wiring diagram for a half adder using the following two chips:

CD4069 (hex inverter)
HEF4011 (quad 2-input NAND)

Can someone guide me in the right direction?