texts:
I am working on a traffic light code and the code seems to be working fine in simulation, but when implemented on the FPGA the colors do not seem to toggle from yellow to red for the main street (sc) and green to yellow to red for the crosswalk street (st). It's a simple 4-way street. I have shown the simulation bellow that is working correctly. "_sc" is the main street and "_st" is the crosswalk street.

However when I press the button on the FPGA board that means a pedestrian is at the crosswalk and the light should behave like the waveform above, but it does not work. When I press the button the light simply changes to yellow and red and then changes back to the original state green and red when I let go of the button. I have attached my code for the pedestrian bellow. I'm sure its a simple fix, but I am having trouble understanding.

timescale 1ns / 1ps
module pedestrian_st(clk, rst, ped_detected ,ped_passed, green, yellow, red,
current_state);

input clk, rst, ped_detected;
output ped_passed = 0, green, yellow, red;
output [1:0] current_state;

reg ped_passed = 0, green, yellow, red;
reg [1:0]  current_state, next_state;

parameter   green_st = 2'b00,
            yellow_st = 2'b01,
            red_st = 2'b10,
            random = 2'b11;
integer     count = 0;

always @(posedge clk)
    begin: pedestrian_SEQ
        if (rst)
            current_state = red_st; //SC has the green light priority
        else
            current_state = next_state; //put it in this state for now
    end

always @(posedge clk)
    begin: pedestrian_COMB
case (current_state)
    red_st:
        begin
             green = 0;
              yellow = 0;
              red = 1;
        if (ped_detected)   //if car is detected then stays in the same state
               next_state = green_st;
        else
              begin
                  next_state = red_st;
                  ped_passed = 0;
              end
        end
    green_st:
    begin
        green = 1;
        yellow = 0;
        red = 0;

    if (count < 6)
         begin
          count = count +1;
         next_state = green_st;
         end
    else
         begin
         count = 0;
        next_state = yellow_st;
         end
    end

yellow_st:
            begin
            green = 0;
            yellow = 1;
             red = 0;

        if (count < 3) //keep yellow on for 30sec
            begin
              count = count +1;
              next_state = yellow_st;
             end
        else
             begin
             count = 0;
             next_state = red_st;
             ped_passed = 1;
            end
        end
        random:
            begin
            next_state = red_st;
        end
endcase
end
endmodule


texts: rc battery and connector issues when used in other applications

texts:
I purchased this battery for my robotics project and this charger along with it. Since the regular use for these types of batteries is for rc cars they have very specific connectors and so i am unable to connect the battery and charger together because of the connectors and i am also unable to unable to connect the battery into a bread board for the robot. Ive done a bit of research and the batttery has a tamiya connector and the charger has a ec3 connector.

Is there a way to join the battery to jumper cables to plug into the robot or special connector that does this and what would I have to do in order to connect the battery to the charger?
I was thinking about cutting off the connectors and using jumper cables to join the cables. Would this work?


texts: How do I know whether a circuit (originally for 5 wire) will work for four wire stepper motor?

texts:
There is a very old and popular instructable 3 axis stepper motor driver, http://www.instructables.com/id/Easy-to-build-CNC-Mill-Stepper-Motor-and-Driver-ci/

As clear from the image , it's a six wire motor connected to the circuit. According to me the same circuit should also work for the four wire Bipolar stepper , as I can see that the center-taped-wires are directly connected to the bulb ( bulb is there in circuit only for testing purposes ).

So how do I actually determine whether or not this circuit work .
What could be some modifications I can do with this circuit to make it run with my four wire steppers ?

My steppper motor mode no. is :
17PM-J311-P1ST ASTROSYN
(sorry I failed to get an image of my motor)


texts: Are these BLDC waveforms making any sense?

texts:
I'm trying to drive a BLDC with a microcontroller, a discrete inverter and a sensorless network for feedback.  Here's the model I'm using and what ultimatly is my PCBA:

I'm driving this thing open loop right now, just to sanity check the waveforms, etc.  Here' what I get when I drive the motor with an 18kHz, 30% duty cycle:

Since I expect the commutation sequence to happen like this:
, this looks correct...So I think I've got that working right.

My question is, why does the floating phase look like it's carrying alot of extra baggage with it?  And if that's how it's supposed to be, then at what point would you say the zero crossings are occurring?  I was hoping it would look a little cleaner, like from this application note from Microchip http://ww1.microchip.com/downloads/en/AppNotes/01160b.pdf
  See how there's a clear, linear ramp?  I'm not seeing that on mine..

Also, I should point out that I'm only PWMing one leg, while the other is tied to a DC voltage (GND in these pictures, althought I have played with leaving VDC connected and PWMing the GND leg, but it didn't make anything into a nice ramp..It just changed the polarity of what I showed in my first pictures).

Also, just for completeness, I've added some closer views of the waveforms...Again, remember, they're running open loop, so there's no feedback...I just switch commutation state on a timer rollover that I was happy with for debug.

Here's a closer look at commutation sequence:

And here's a rising floating phase:

And here's a falling floating phase...I think it's falling...the bottom is rising, though, so maybe I'm wrong...:

Is this right, or am I doing something wrong?

Edit

Thanks to the answer below, I am now getting the motor up to speed for 100ms to get the BEMF cooking, and then I'm keeping an eye on the moment my low side of the PWM goes above zero.  I then wait a certain amount of dead time and then pull the trigger on commutation advance.  This is much better... Before, the motor would run slowly at around 112mA@12V, but now it can easily run up to 7200rpm at 40ma@12V.  Loading the motor (by pinching the shaft on the rotor with my fingers) doesn't slow it down at all, it simply increases the current draw as expected.

Pics or it didn't happen :


texts:
We have a machine which is using a timer and the timer has an LCD, a few of the displays, with no reason all of a sudden displays a black box blinking... If I switch off the machine from power switch and wait for 5-10 seconds, everything goes back to normal, but if I switch off and on very quickly, like in a second, it doesn't go away.

any leads ? ideas, you may give me would be helpful,
Thank you

This only happens, maybe 10-20 lcds out of 1000


texts: Minimum Current for Zener to Clamp Vgs of Mosfet?

texts:
simulate this circuit – Schematic created using CircuitLab

When it comes to zener diodes I find it hard to get information about minimal currents needed for it to breakdown so I thought I would ask here.

In my project I have a 12S Li-ion battery, whose voltage can vary between 50V and 36V. This is quiet a big voltage difference to layout a resistor divider, so I decided to put a zener between gate and source to limit the voltage to maximum 16V.

The capacitor is there to limit in inrushcurrent for capacitve load.

About the zener diodes I can't find information in the datasheet about the minimum current needed for it to breakdown.

For the worst case I assume a Vbatt voltage of 36V, Vgate would then be 20V (Vs-Vz). The current through the diode is then 20V / 100k = 200uA.

Would that be enough current to limit the Vgs to 16V ? If not I'd have to use lower value resistors, a bigger cap and have bigger static power consumption which is not ideal for battery operated systems.

The diode I'm planning to use is MMSZ5221BT1.

Is there some information I'm missing in the datasheet or some general rule how much current a zener needs to breakdown?


texts: How do I calculate Copper Loss in a transformer? My professors told me that it was  \$I_{OUT}^2 * R \$? , Primary Current  \$I^2 * R \$, Secondary Current \$I^2 * R \$ ? I really got confused...


texts: How to understand min/max voltage specification in datasheet?

texts:
I've seen different types of min/max voltages in this datasheet and not sure whether I've understood them correctly, so I want to double-check it here.

As shown below, there two types of min/max voltages:

Voltage available zone: The voltage provided should fall into this zone, like Reset drain voltage with min=11/max=13, which means the voltage provided to this pin should between 11v and 12v;
Voltage threshold zone: It's the uncertain area of the threshold, so voltage provided should be out of this zone, like the high level of Vertical shift clock voltage with min=4/max=8, which means the high level threshold may between 4v and 8v, so the high level of the generated clock should be over 8v.

Do I understand these parameters correctly?


texts: What does a High Time Constant for RC circuit mean

texts:
Assume a simple RC series circuit. Below are screenshots of voltage being measured across the capacitor.

Input voltage is of pulse type with the following parameters:

\$V_{on}=5V\$
\$V_{off}=0V\$
Pulse Duration \$= 20 ms\$ (On Time)
Time Period = \$60ms\$ (Off+On Time)

And RC are as follows:

\$R=1M\Omega\$
\$C=10uF\$

How do I calculate the approximate steady state value ~1.67V?

PS: I could not use the CircuitLabs simulator as it has only a square pulse input signal.


texts: SDHC over SPI: OCR Register Reading 0x000000FF, nBusy bit 0 even after IN_IDLE_STATE clears to zero

texts:
Has anyone else enoucntered this problem before?

I'm using an STM32F105VC, SPI port 1 at a speed of either ~100kHz, ~200kHz and ~800kHz.
I've tried using a 16GB Sandisk microSDHC and a 2GB Transcend microSDSC both providing the same results.

I have the Host Capacity Support (HCS) bit set when I send ACMD41, which loops until the idle state bit in R1 response is no longer set (usually after 3 repeats; seems too fast maybe?).

I have tried with the SS toggling between each Tx/Rx transaction and with it held low for the whole init procedure, made no difference. Stuff bits as 0's or 1's made no difference. Sending around 1s worth of ACMD41s before checking the OCR made no difference.

If you think you can help give me a shout for more info on my setup. Or if you can think of any obvious errors I may have made then it would all be greatly appreciated!


texts: Review of system design of motor controlled by micro-controller with rechargeable battery

texts:
I trying to build a circuit to control the motor using the microcontroller, supplied by the battery that is rechargable.
I identified the some of the components i.e. Battery PMIC, LDO, Motor Driver and Microcontroller. And also sensor and switch as additional controls.
My idea is connect these components is as shown in the figure below.

Kindly suggest if there is any other components required to be added or changes to make this possible.
I really wanted to know if I am on the right path to design such a system.


texts: QT1070 inconsistent readings on touch pins

texts:
I recently transitioned my projects capacitive touch IC from using the MPR121 to the QT1070.

I am getting irregular/inconsistent readings on one of the touch pins.  In this particular situation, it is Pin 7 (which equates to "key6" from the docs).  The pin keeps changing its state from touch to untouched, seemingly at random.

Does anyone have any experience operating this chip, particularly in comms mode with I2C?

I am using the schematic below (from the datasheet), and am using 4.7k resistors on all the touch pins.

Is it possible I have to play around with this "detect threshold" business from the docs?

  Detect Threshold
  The device detects a touch when the signal has crossed a threshold level and remained there for a specified number
  of counts (see Section 5.10 on page 19). This can be altered on a key-by-key basis using the key threshold I2C
  commands.

I should note that the resistors are not attached to anything, as it is currently operating on a bread board.


texts: Why can't conductors be used in making ICs (integrated circuits) instead of semiconductors?

texts:
I really wanted to ask why we can not control flow of electrons in conductors.
Can I not say if a current is flowing in a conductor it is 1 and when I disconnect the supply it is 0.
Can you elaborate on this point?
Can you elaborate by taking example?


texts: Noise floor raising at high RF input power after filtering

texts:
I have a USRP b205mini with AD9364 transceiver. When it receives a very high RX input of about -5 dBm at different frequencies, not in the original RX range, the noise level raises slightly. The RX is configured to 2.406 GHz at 20M sampling rate. The Tx it receives comes as a CW at 1 GHZ or 3 GHZ and should be filtered by the receiver. What really causes the noise floor to raise? Performance of filters, saturation of amplifier or else? Thank you!

Below you can see what happened.

Idle.

Now transmitting CW of -5 dBm at 1 GHZ (Rx configured to 2.406 GHZ). Note the slightly raised noise level.

The difference between these two states. Red - before CW input (idle), blue - CW is on.


texts: Through which route an SMPS propagates and picks up the switching noise?

texts:
I have seen that some switch mode power supplies are injecting noise to the electrical power network. I guess this noise is common mode noise. That switching noise then propagates through and enters to another power supply and even can appear at the DC output.

1) Regarding the switching noise originates from an SMPS, does it propagate on neutral, line or earth wire?

2) And in the affected SMPS, how does it pass this switching noise all the way to its DC outputs? From its line, neutral or earth terminal?

3) Why is this type of noise is called common mode noise?

I would like to see the actual trace/path the noise travels from the injector to the receiver SMPS.


texts:
Given a full adder with inputs $$A, B \text{ and } C_{in}$$
The formulas for the outputs are $$S = A \oplus B \oplus C_{in} \text{ , Where } \oplus \text{means XOR}$$ and $$C_{out} = AB + AC_{in} + BC_{in}$$

But when a Full Adder is created by combining two half-adders, the obtained equation for carry out is $$C_{out} = AB + (A \oplus B)C_{in}$$

The two expressions have equivalent Truth Tables, but the reason for their equality is not obvious.

Can someone please help me understand how it can easily be seen they're equal?


texts: Why are power distribution systems so prone to massive faults?

texts:
Many region-wide blackouts (like this one or this one) are described as follows: some high-voltage equipment (like a generator or a transformer) fails and the grid gets overloaded and then protective devices start tripping everywhere and millions of consumers are in the outage.

I don't get it. Okay, some generator or transformer fails, but there's dozens of such generators and transformers in the region grid.

Why is the load not partially disconnected so that the consumption matches the production again? Why would a relatively small deficit of delivered power lead to a region-wide blackout?


texts: Why a MOSFET in accumulation mode is not conducting?

texts:
In accumulation mode, the channel is not conducting, whereas in inversion mode it is conduting. But if in both cases I have free charge carriers in the channel, why isn't there conduction in both cases?

I know that the energy band diagram between the semiconductor and the oxide has a barrier for, say holes, and an accumulation well for electrons, but why would this have any influence on any barrier between the semiconductor and the source/drain?

 (source)


texts: Reset pin on ATtiny84/85/2313 clarification

texts:
I have two questions that I was hoping someone could clarify with a quick True/False. When using the ATtiny85/85/2313 the reset pin is connected to a 10k resistor which is connected to VCC.

When programming with an AVR 6 pin programmer does the reset pin on an ATtiny at that point need to be connected to the 10k resistor to VCC?
When using an Arduino Uno to program an ATtiny, the reset pin on the attiny is connected to D10. Does the reset pin additionally also need to be connected to a 10k resistor to VCC?

Or to summarize does the reset pin on an ATtiny84/85/2313 always need to be connected to a 10k resistor to VCC?


texts: Polyfuses in parallel for shorter trip time?

texts:
I'm thinking about protecting a 12V/20W transformer with a polyfuse.
Quote from the  Littlefuse datasheet:

I_Hold = Hold current: maximum current device will pass without tripping in 20°C still air.
I_Trip = Trip current: minimum current at which the device will trip in 20°C still air.

Let's take this example:
Part No. 30R185U, I_Hold 1.85 A, I_Trip 3.70 A
So this fuse will pass 1.85 A continuously without tripping, trip for any current greater than 3.70 A and yield unspecified behavior in between?
Now for the real question:
Is it feasible to use two fuses (for my example, two 30R090U with I_Hold = 0.90 A) in parallel for the benefit of the smaller time-to-trip?
Is the variance in resistance small enough that half of the current will pass through each fuse during normal operation?


texts: Why does a Solenoid driven with intermittent duty cylce produce higher force than with continuous drive?

texts:
I'm selecting some solenoids with my MechE and I noticed something that I didn't have an intuitive explanation for.

We were looking at this solenoid and noticed that at the bottom the forces available were higher when used with intermittent pulsing instead of continuous pulsing. We haven't been able to explain to ourselves why this is the case. Any guidance?


texts: Why don't motors coupled to gearboxes spike up significantly?

texts:
A 5,5KW motor is rated 11,40A for the delta connection at 400V. This motor is coupled to a gearbox that reduces it's speed from 1440rpm to around 121rpm. On the gearbox shaft is a sprocket and chain which reduces the speed even further.

According to what I know, during starting a motor will rise to about 4-7 times its rated current for certain seconds. So I was expecting this value  to be above 44A, which turned out not to be the case. In fact,  the current wasn't even double it's rated value.

Now here's the question: why didn't this value rise up as much as I expected? Since there's no back emf when the rotor is stationary, the current drawn by the motor should have been significantly higher. I'm struggling to understand why it wasn't.

NB: the motor is running direct on line, no soft starters are involved.


texts: Which bypass cap position creates a cleaner voltage and current feedback circuit?

texts:
Is the following true? Caps = 2, 1800 uF Nichicon, Manf Num UHE1V182MHD3, CAP ALUM 1800UF 20% 35V RADIAL.

"you want your bypass caps as close to what you are bypassing with the least series resistance possible. See attached sketch. If you have your shunt resistor down stream of your bypass caps the the system will have voltage ripple or noise on it due to the voltage generated by current accross the shunt resistors. Look at the data sheet for the caps, they have an ESR of 26mohms. With the shunt resistor you are adding almost 50% more ESR. Plus you have a diode drop between the bypass caps.  You are killing the effectiveness of you bypass caps with the shunt resistor and diodes. ESR is one of the most critical items for bypassing."


texts: How to reduce the leakage current of a solid state relay?

texts:
I have a zero-cross solid state relay (Crydom CKRD2420) that regulates the power output of a 2kW@240V heater using 10Hz PWM (e.g. here to illustrate). I need the power output of the heater to be under ~2W when OFF. However I measured the leakage current is 25mA RMS (2.5 times the 10mA garanteed in the datasheet, by the way...), which means that the power leakage is about 13W (the mains supply voltage reads 264V).

My first thought was a current divider, but the bleed resistor would reduce by a factor of 10 the available power, and reduce significantly the efficiency. I can't use a normal relay because of the lifetime required (I need at least 50-100M cycles of operation), and power MOSFETs would be tricky to implement. Are there any simple-ish fixes I have overlooked?


texts: Joining the output of 2 different power regulators

texts:
I'm going to use a Raspberry Pi and a Pico Pi plugged together. They are both powered by the same 5V power supply (thru the 5V pins for the Raspberry, and thru VSYS for the Pico).
So far, I've used a single 3V3 net to power other components, which is tied to the 3V3 pins of both the Raspberry and the Pico. Is this something I should avoid, and if so can you explain why?
(The 2 of them are also directly linked via UART RX/TX).


texts:
Is there anything I can use to replace this circuit?

Its a very simple electronic switch circuit, (transistor+zener diode+resistor)

The circuit is connect to a remote control, the remote control is activated via http request via the arduino. which is controlled by an iPhone app.

Remote control, when the circuit is closed (ie two wires are connected), it is activated.

Problem, when I unplug the circuit, or when my power goes down, it will set off the remote control and activate it!

I need the circuit to be normally open, when no current is applied.

USED:

Zener diodle IN4007

Transistor 2N2222

Resistor 1k

Note: I dont want to use a relay, not for something this simple!

What do I do? alt text http://img689.imageshack.us/img689/5518/circuitc.png
alt text http://img688.imageshack.us/img688/1032/201072415pm.jpg


texts:
Understand that Eb/N0 is based on (S/R)/(N/B)

S = signal power (W) R = bit rate (bps) N = noise power (W) B = bandwidth (Hz)

How can I solve this equation if I only have these values: (SN/dB): 40 dB Bandwidth: 700 000 Hz Effective data rate: 80% of maximum channel capacity.

[EDIT with my working]
I have work out the equation as follow: Eb/N0 is also = (S/N)*(B/R) therefore Eb/No = 40 * (700,000/7 759 462.4) = 3.61 (2 decimal places) 3 questions: 1) Is my answer correct? 2) Is there a unit for this? 3) What is the correct way to convert a Mbps to bps? For the above answer, I used Google for conversion.


texts:
My question is related to the following news regarding IC process technology:

  Samsung has introduced 28-nm LP HKMG and a new variant, 28-nm LPH HKMG process technology.

Following abbreviations are used in above sentence:

LP stands for Low power.
HKMG stands for High-k Metal Gate

What does LPH stands for?


texts: Charging circuit for a small capacity (13 mAh) li-ion battery

texts: I got my hands on some of Panasonic's new "pin-type" li-ion batteries – the CG-320. However, I have never had to charge a battery with such a low capacity (13 mAh). Are there charge management ICs out there that can manage charge currents this low? The closest I've found is the MCP73831, which only goes as low as 15 mAh. That won't work, right? Any tips are greatly appreciated.


texts: Implementing Safety Shut-Off Relay In Project

texts:
I am working on a project which I have poured lots of cash into that involves water, pressure and electronics in very close proximity of each other... Lately, I have been considering adding some fail-safe mechanism which will cut all power to the machine if any water is detected by some carefully placed water sensors. I am no electrical genius (really far from it) so I was curious if there was a way to create a toggle circuit which the brain(arduino) could trigger that would manipulate a relay cutting power to the device; ultimately requiring human intervention to reset.

I realize that this is most likely impossible/not ideal, and that some of you may suggest a secondary, battery-powered system to do the job.

Thanks


texts: How to improve this circuit design to meet Arduino ADC input impedance requirement?

texts:
I have a new pH sensor board, the circuitry looks like this. The Op Amp is operated at 3.3v and the input is "float" to 1.8v with a separate voltage regulator. The output is connected to the Analog Input of an Arduino Nano.

simulate this circuit – Schematic created using CircuitLab
The Arduino sketch provided by the vendor constantly reading 40 sensor values at an interval of 20mS (with an Arduino delay(20); statement) and uses the 40 values to get an average reading. Since each ADC conversion only took 104uS based on ATMega328 spreadhsheet, so I was thinking to shorten the sensing interval to say 2mS, this is when I noticed that by changing the sensing interval, I get quite different readings from the sensor board. I get the same unstable readings when switching from Arduino Nano to a STM32 Blue Pill.
A quick search on ATMega328 datasheet, under the section 24.6.1 “Analog Input Circuitry”, it said:

“The ADC is optimized for analog signals with an output impedance of approximately 10k ohm or less. If such a source is used, the sampling time will be negligible. If a source with higher impedance is used, the sampling time will depend on how long time the source needs to charge the S/H capacitor, with can vary widely. The user is recommended to only use low impedance sources with slowly varying signals, since this minimizes the required charge transfer to the S/H capacitor”.

I suspected this is what I'm facing, so I added a 10k resistor between A0 of Arduino ADC input and ground, this solved the problem. I'm able to get consistent reading no matter whether the sensing interval is 2mS or 20mS. The output voltage that I get is only about 2/3 of the original value due to the voltage divider formed by the R3 and the added 10k resistor.
My question is that although my approach to the problem seems to a workable workaround, but is it the right way to do it? or is there a better way to just simply changing the value of existing components? or do I need to add a voltage follower using an Op Amp or transistor?


texts: Why do batteries with the same voltage have different currents?

texts:
Experts say "current depends on voltage". So, if the voltage is high, current would be high. Agreed;  (I = V/R)

If the voltage is low, the current would also be low. Agreed ->  I = V/R

But why then do two different batteries available with the same voltage (say 2 V) not deliver the same current?

If the voltage is same for two different batteries, current should also be the same, right?

Which factor plays the role in delivering a different current for these batteries?

If two different batteries (with the same voltage) delivers different currents, how can we say that they are both 2 V batteries?

Why do the batteries not obey the rule? Do they have another principle?


texts: 2N7002 MOSFET gate voltage internally being pulled high, potentially dead

texts:
I am using the circuit below to switch a bi-latching relay once a wire is disconnected, i.e. to not switch as long as a voltage is present on the wire.

After assembling on a PCB, on which there are multiple instances of the circuit, about half appeared to work properly once, but after cycling the relays on/off by disconnecting the wire and resetting on the other side, all of them would stop working.

Specifically, the Q2 gate voltage appears to be internally pulled up to between 2V and 10V, and even when connected directly to GND it becomes active and brings Q1's gate to GND. Q1 appears to still function as expected.

In simulations it works as expected, and I find it strange that Q2 is the one that goes given how relatively shielded it is from the relay current and potential flyback voltage spike.

Potential solutions I see here are to use bigger MOSFETs or switch Q2 to a BJT, but I'd like to understand what could be causing this to avoid the same problems in future.


texts: How to measure tilt on a dynamic device?

texts:
I'm trying to instrument a vehicle component.  I want to measure a component's angle during a drive cycle. The component has a single degree of freedom, it has a fixed axis.  I'm trying to figure out an efficient way to measure this. I'm hoping to use Internet of Things (Raspberry Pi / Arduino) technology as appropriate. Without going into details, I must power this thing via battery. I'm assuming the testing will be done during daytime, on asphalt or concrete pavement.

Sensors that seem to offer possibilities:

Accelerometer (X,Y,Z)
Electrolytic Tilt Sensor
Passive InfraRed (PIR) sensor
Radar sensor
Sonic sensor
Laser Time of Flight

My original thought was to use an accelerometer, attach it to the bottom of the device and analyse the direction of gravity to deduce component's angle.  I know this would work on a fixed vehicle, but my situation is anything but fixed.  I won't be able to deduce vehicle travel direction. Additionally, my vehicle's speed is not constant.  I will be monitoring acceleration (but subtracting out gravity) while I'm looking for other characteristics...

Because of my huge variance in accelerations, I don't think a fluid based Electrolytic Tilt Sensor would work either.

My next thought is to accurately measure the distance from the component to ground. I'd fix the sensor to the movable end of my component, then calibrate distance observed to component angle, while vehicle is at a complete stop.
I can monitor distance in real time to deduce component angle relative to the ground.

Scratch passive infrared.  I'm pretty sure sunlight will mess that up bad.

Radar is a pretty nice technology, but seems to be oriented to metal, water or humans, and has a very slow response time.  Scratch that.

And that leads me to either a sonic distance sensor or Laser Time of Flight sensing.  At first glance both methods are cost effective and seem to work in the ranges I'm interested in.  But I have no experience here.  What I don't know is if on road testing in daylight will affect these devices.  Will ambient noise mess things up?  What about reflected sunlight?

Does anyone have any experience here with those last two technologies (Sonic Distance or Laser Time of Flight)?

Are there any technologies that offer an alternative method for measuring a component's angle (relative to the ground) in a dynamic, moving vehicle, perhaps something I've missed?

Note: I've done a lot of work using magnetometers and accelerometers (Ugh, remember the Vector Cross Product?) but I've never touched a gyro device.  Are there opportunities there?


texts: Want a 3v led to operate when 12v is applied

texts: I have a circuit with 6v and 12v. There is 1 diode between the two positives so when 12v is turned on it does not run through the 6v circuit. What I need is the led to only come on when the 12v supply is on. At the moment if the 12v feed is not on I have 6v coming through in witch the led turn's on. I only need the led to turn on when the 12v feed is turned on.


texts: Powering a RPi and a motor driver with the same LiPo battery

texts:
I have a 2-cell LiPo battery, a RPi3, and a motor driver with 2 DC motors. I wanted to use the same LiPo for both, instead of a LiPo for the driver, and a Power Bank for the RPi3.

My idea was to use a Voltage Regulator connected as below:

simulate this circuit – Schematic created using CircuitLab

I'd use the microUSB port in the RPi3 to take advantage of all the protective circuitry they have in there, instead of directly connecting to the 5v pins.

Is this correct? Or am I burning something once I plug everything in and accelerate a little bit?


texts:
I have a sample code for connecting an OV7670 to a STM32F407IGT6.

However, I'm trying to use a STM32F407VGT6 and in my sample code the STM32F407IGT6 doesn't use the default DCMI pins.

How can I change this definition?

link of sample code: http://rodfile.com/rcu46djm5q41 this sample code is in the

stm32f4_dsp_stdperiph_lib

from st official site, in directory

Project\STM32F4xx_StdPeriph_Examples\DCMI\DCMI_CameraExample

This sample code is for STM32F407IGH MCU


texts: do I need to protect my body control module any further?

texts:
simulate this circuit – Schematic created using CircuitLab

I am working on a project on my Jeep and I wanted to tap into the ground wire between the turn signal switch and the body control module and use that to activate a relay when the turn signal switch is engaged. I am worried about the voltage spike of the relay coil when it disengages. I need to make sure nothing makes it back to the body control module. I am using a Cole Hersee RC-400112-DN relay with diode. Since the switch is taking the ground away and leaving the negative side of the coil tied directly to the body control module will this cause any voltage to shoot towards the BCM? If so what can I do to protect the BCM?


texts: HM10 bluetooth module to discoverable state after connection break

texts:
I am trying to setup a HM10 (or similar Bluetooth LE to serial module) but am having problems with it.

The problem is when I am connected to the device with my phone, it works great. Now, if I force close the app while connected (or walk out of range), the HM10 module never returns to a discoverable state until it is power cycled. I could not find anything in the documentation regarding this. I am not able to connect to the HM10 manually via its MAC address either.

The only fix I can come up with is to have my app send a heartbeat signal to the MCU (ATMega 328p) and if the heartbeat is not seen within its allotted time, it should send AT+RESET to the HM10.

There has to be a better way, but I am not able to find it. Please let me know what you think.

Thank you in advance.

http://fab.cba.mit.edu/classes/863.15/doc/tutorials/programming/bluetooth/bluetooth40_en.pdf

(This happens when using any generic BLE terminal app or a custom made app)
(Android and IOS)


texts: How to connect a npn transistor properly?

texts:
I started playing with transistor earlier and i have problems i must have miss understand transistor.

simulate this circuit – Schematic created using CircuitLab

My problem is the current from base will flow to the emiter and light up the led. however if i reduce the voltage of the base and test the base dosent draw enough current from collector to the emiter, or am i miss understand the function of the transistor?


texts:
I came a cross a design problem which I need your suggestions in it.

I have 3 power sources, Main Supply which is 9-32DC, a battery pack 12VDC, and PoE Module, all are connecte to tripel output 12, 3.3, 5VDC voltage regurlators, and finally a microcontroller.

I would like to detect a power failure on the three of them, and also use one of them on power failure.

I thought about first the user must use the Main Supply first, then the uC use its ADC to check for the voltage on the battery pack, use a voltage divider to lower the voltage then measure the value and check if its lower than a value, however this method is also I want to use it for charging the batteries it self!.
The same scenario I will do with the main supply and the PoE, but the problem with the resistors that they must have high power, the current that can be drawn I assume its more than 9A. I'm also not sure which VRef should I feed the microcontroller with, it's very problematic issue too.
Do you guys havae an opinion or suggestion for better design ?


texts: Calculating capacitor discharge time constant with dc source and constant current source

texts:
I have a 1.8V dc source with 40 ohms series resistance, which models a battery. In parallel, there is a 10uF capacitor. At t<0, the mosfet is off and there is no load delivered to the output, so the voltage across the 10uF capacitor is 1.8V. At t=0, the mosfet is switched on, and is designed to deliver a constant current source of 5mA (up until it leaves saturation due to a small Vds). The constant current source charges another 1uF output capacitor. At t=inf, the voltage across the 10uF capacitor is 1.8V - 40*5mA = 1.6V, and also the output capacitor.

I would like to know how to calculate the time constant of the voltage discharge curve across the 10uF capacitor, when there is two sources acting on the capacitor.
For the maths, I would like to assume the mosfet stays in saturation well beyond the time constant of the first cap. (Maybe the 10uF cap value needs to be lowered to make this true).
As I understand, The current source mosfet has a changing impedance based on its changing Vds. This changes the R_eq seen by the first capacitor. This is where I get stuck with the maths of calculating the time constant of the first capacitor.


texts: How long can I practically power an IC with a capacitor?

texts:
If I have, for example, an IC that draws 10mA @ 3.3V, how large of a capacitor would I need to power it for 2 minutes? 5 minutes?

I understand that using capacitors to power an IC is not the most practical, since they discharge very quickly, but am curious if the required capacitance is within the range of those commercially available.

I would like to understand the math behind calculating a problem like this as well.


texts: I have a 12V starter motor that needs extra help at times.

texts: The starter motor is powered by a 12.8V LiFePo4 battery pack (14.2 when fully charged).  Sadly, even when the battery is freshly charged, the motor won't turn over unless the charger is still hooked into the circuit. (Somewhat inconvenient at remote locations.)  Can I hook a 5 cell 15.0 V (3.2V X 5) "Booster" into the circuit to give the extra push it seems to need?


texts: Can someone explain how this diode works?

texts:
I found this schematic in the Motorola Engineering Note 100, page 4.
I'm not able to understand how the diode from -12 volts going onto the serial output line works. Can someone explain this to me?


texts: Is anybody familiar with this configuration on base drive?

texts:
I'm reviewing this schematic, I wonder what's this configuration marked
with a red box.

what is the purpose of that configuration?


texts:
Good day folks :)

i just want to know if i'm understanding it right? i read the datasheet and i saw the start-up row in the switching characteristics. Does every time - let's say i execute a command on a microcontroller to do SPI communication to a slave, will it always have a this start-up time delay then continue to sck + sdo??

i have this calculation of SPI data-in to the CS5480 ic in nanosecond unit, 10-bit transmission (1 start bit, 8 data bit, 1 stop bit)

am i doing it right?

would i have to include start-up time to my computation every time i do SPI transaction?

Hope you can help me on my dumb question since i am new to this and doing self study :) thanks


texts: switiching an input between high and low state with a trigger signal?

texts:
I want to build an electronic analogue SPDT switch that switches on a trigger/rising edge.
A SPDT CMOS switch control is held high or low for either output.

This could be done with 2 outputs of a CD4017 + inverters to switch the switch states but there must be a more elegant solution than that.


texts: Can a hobbyist ARM setup be as simple as this AVR one?

texts:
I like how simple an Atmel AVR setup can be for hobbyist assembly language programming. For example:

Put a plain ATmega DIP chip {A} on a breadboard
Connect 6 pins to a USB programmer {B} connected to a computer (e.g.) . (The chip is powered by part of this connection both during writing and normal operation).
Write an assembly language program using any text editor.
Assemble the program using avra {C}
Write the program to the chip using avrdude {D}

Is the ARM world just fundamentally higher-level/more-complex or can you tell me equivalents for {A} {B} {C} and {D} that would allow a similar simple setup? Anything Windows-only is not relevant for me.

Thank you.

Note: The motive of the simple setup is assembly programming and I want to sidestep compilers and IDEs completely.


texts:
I have had this cheap set of fairy lights for a few years. Powered by 3xAA batteries.

Recently when they are turned on they start bright as they always were then proceed to get dimmer and dimmer until they reach a low light after a couple of minutes.

The lights stay dim but leaving them off for a few hours causes them to ‘reset’ and then the bright to dim behaviour happens again.

I want to fix them and I can see a resistor inside which I suspect could be broken? Does anybody know why this could be happening and what I might need to fix them?


texts: 2x rs232 communication, single wirelss connection, also rs232 to control load cell perameters

texts:
I am struggling to find any information on the ability to have 2 rs232 connections with 1 wifi connection.

I have found this wireless chip, which supports, five Ethernet ports, two serial ports:
http://www.hlktech.net/product_detail.php?ProId=62

But my question is whether such a chip or similiar would be able to wirelessly transmit and receive 2 rs232 connections through wifi.

I will be based in china, to make this project soon, and this is another information site, but its chinese:
world.taobao.com/item/524654936858.htm?fromSite=main&spm=a312a.7700824.w4002-15157484274.47.DIEyhj

I am trying to create a rs232 COMS PLC, which also has load cells connected.
I want to use a windows tablet to transmit a rs232 command to the PLC, and also send and receive load cell parameters and readings from another rs232 connections hook up to a load cell amplifier and to the load cells.
But all of this through 1 wifi connection.

Is this possible to do?
I do want to steer away from a dedicated CPU to interpret signals and send them vai wifi, i am looking for the simplest method to send and receive rs232 vai wifi.
But if this is the only method i may have to do so.

i have seen these:
http://www.usconverters.com/index.php?main_page=product_info&cPath=70&products_id=404
But i want to create a custom PCB which has a load cell amplifer, wireless rs232 connections, and customized port to connect load cells and PLCs.
All on 1 board.

Just want to make sure 2x rs232 connections is possible first before i pursue something like this.

Another question is:
i am looking for a load cell amplifier which can have its parameters changed by a rs232 connection to suit any load cell type, such as a change in excitation from 8v to 5v, this way the amplifier can suit any load bar, just by adjusting a setting though rs232.
Preferably a open source amplifer, so that i can use some of its design in my custom design.

Thank you so much for your help.


texts: Serial Communication Rx ISR logic design

texts:
If im not wrong, an ISR is supposed to do minimal processing when it receives a data serially(via UART).
Im planning on implementing such a protocol for communication between 2 systems via uart.
This is a rough situation of how i plan on coding the ISR.
Assume 2 system A & B where A is sending a message to B:
Keyword is used to indicate start of message(Established-data/length cannot be the keyword).
ChannelOK,Length of data,RxLength,RxData,Packet received flag in B's process are default 0.Length of data=no. of(all data)in bytes(ex:if all data=1,Length of data=1)

A's Process
 Send Keyword
 Send Length of data
 Send all data

B's Process
 Rx Interrupt
 enter ISR
 ISR: if(Received Byte == Keyword && !ChannelOK)
      {
        Set ChannelOK
      }

      if(ChannelOK && RxLength)
      {
       Set Length of data=received byte
       ChannelOK=0
       RxLength=0
      }

      if(Length of data != 0 && RxData)
      {
        Store Data
        --Length of data
        if(Length of data==0)
        {
         Set Packet received flag
         RxData=0
        }
      }

      if(ChannelOK)
      {
       Set RxLength
      }

      if(Length of data)
      {
       Set RxData
      }
     Reset to Interrupt Again

My doubt is: B has so many stuff to do in the ISR while A is sending continuously. Asumming A sends data at 7.5Mbps(11 bits per transfer), the ISR has to reset the interrupt ever (11/7.5M) seconds. This seems very very small. Will data be lost if i fail to reset the interrupt on time or will it be stored in the 16 byte FIFO so that an interrupt can be immediately triggered the second i reset the interrupt or must i slow down A Tx process by waiting for an ACK for each byte(slows down a lot)???

Im a newbie to ISR's.Please do help
Any ISR designs or protocols for serial data communication would be useful

Thanks


texts: do mAh on batteries (for home-use - nerf) make a difference?

texts:
I was wondering if the mAh on an battery pack is important or relevant, so you would recognize a difference?

Little bit Off-Topic:

I've read a lot about "Nerf voltage mods" where modders change the standard 3xAA NiMh batteries (1,2v each = 3,6V) against 2 Li-Ion batteries (3,7v each = 7,2v) and one "dummy" battery for better perfomance and range.

Now I'm also thinking about changing to Li-Ion (with around 1500mAh) or just buying better/stronger NiMh batteries with around 2500mAh.


texts: Incorrect orientation of components in Footprint Position File (KiCad)

texts:
I am using a PCB(A) factory where they have an online system where you can get a preview of your PCBA once you upload your files. As part of the process, I have to upload the Gerbers, the Bill of Materials (BOM) and the component placement list (or footprint position file, as it's called in KiCad).

The last one is generated through the PCB Layout editor from the File --> Fabrication Outputs --> Footprint Position (.pos) File menu and contains the orientation of the components among other information.

The issue is that the orientation of most of the components is incorrect, according to the factory's preview system. Of course it doesn't matter that much for resistors and capacitors, but as you can imagine I have to manually rotate all the rest, everytime I place a new order or do a small change.

Am I doing something wrong or is there a convention for the KiCad footprints (e.g. pin 1 has to face at a certain corner always) that I am missing?


texts: How to wire up a PSC motor from a air conditioning unit?

texts:
[
I hope someone can help with this. I have a LG air conditioning compressor motor. (PSC type motor). It has three terminals not labelled. Its new but came without a wiring diagram. I've searched the net and found various pieces of information but not sure exactly how to connect it up.
I have attached some screen shots of the motor spec and a sketch of how I think it needs to be connected.
The resistance readings across the terminals do not match the spec exactly, they are slightly higher at 4.5 ohms.
Any help would be great.

[![Wiring Diagram][3]4


texts: Can a Solid-State Relay Control AC Powered Fan Speed Via PWM

texts:
I'm working on a project where I'd like to control the speed of an AC powered box fan using a microcontroller.

I am wondering if this can be accomplished by using a PWM output to control a solid-state relay (the same way PWM can be used to control brightness of an LED, but applied to an AC powered device). This would be controlling 120VAC power with something like a 5-12V PWM signal.

I have not worked with solid-state relays before, so I wanted to check if this was conceptually solid before diving any deeper. Alternative solutions and / or parts recommendations are also much appreciated. Thanks!


texts: How to cycle through outputs ONLY given clock signal?

texts:
Purely using digital logic devices (no microcontroller) I was hoping to create something that will cycle through its outputs (only 1 pin high) given only a clock line.

Daisy chain flip-flops?

I wanted to use a shift-register to create a ring counter but then the issue how do you set the first bit high?


texts: How can I use 64-bit integers on a PIC18?

texts:
When I try to declare either a unsigned long long or a uint64_t the xc8 compiler throws the following warning:

    12: uint64_t overflow_time;
             ^ (374) missing basic type; int assumed (warning)
             ^ (314) ";" expected
                          ^ (374) missing basic type; int assumed (warning)

This eventually spirals into an error later in the compilation. Through some research I found that when using the default C90 standard the xc8 compiler doesn't support 64-bit datatypes.

The best solution I could find online was "Upgrade to XC8 2.05" - which I already had.

How can I get the compiler to allow me to use 64 bit datatypes?


texts: Programmable clock generator IC and reference circuit

texts:
I need a clock source for some data converters (DAC, ADC), and I would like the clock frequency to be as configurable as possible. I assume this would involve some kind of clock multiplier/divider, PLL, etc. The range of frequencies I would like to be able to configure at runtime would be something like 200ksps up to about 20Msps (one clock cycle per sample). I don't need extremely tiny frequency steps in this range.

The ideal answer would reference specific part numbers with detailed reference designs. I can deal with single ended or differential clocks. Configuration of the clock generation would most conveniently be with 3.3v CMOS logic, though level translation is certainly a viable option there.


texts: Selecting a suitable mosfet for Linear Technology LTC4412HV

texts:
I would like to choose a suitable P-MOSFET for power switching with the Linear Technology LTC4412HV.
This IC is just an ORing for two power supplies to select the best between two batteries.

The FDN306P in the typical application can just stand \$V_{DS}\$ of 12V, and current 2A. I would like to have a \$V_{DS}\$ of 40V, and 7A at least. I have googled around but I'm worried that there are other factors that I should consider.

Also, how much is the resistor that is needed for the required parameters? The datasheet of the IC doesn't say much about that.


texts: Design decision for dynamic firmware loading?

texts:
I've noted that some device drivers in Linux have a dependency on the device firmware. The firmware is usually a binary that the driver loads on the device (like a USB wifi dongle).

This question is based on the assumption that this kind of behavior from the Linux side is dictated by the device (a USB wifi dongle) that is dependent on that firmware being loaded.

My question is what would be the benefits of this approach from the point of the dongle manufacturer?

What benefits does designing a device that doesn't have even a minimal non volatile storage to keep the firmware on and needs an external cpu loading it on every boot?

Does it come down to costs reduction not having a minimal non volatile storage for the firmware gives? Or have I overlooked an important benefit?


texts: Using different size coil for boost circuit?

texts:
I have an iPhone 6 with no backlight. Figured out it's the coil. The coil is rated at 15UH .72A 0.9ohm

I didn't have a replacement so out of curiosity I used a random coil off a donor board part of another circuit, but the specifications are different at 2.2UH 1.2A .15ohm

It worked and I got backlight again. Can even adjust brightness.

But I'm curious how this will effect the circuit in the long run. Will it make the switching ic work harder? Will the coil burn out?


texts: Do most manufactured centrifugal pumps come equipped with soft starters, and is it a good idea to invest in one if they're going to be frequently switched on/off?


texts:
I am studying Fundamental of Electric Circuits by Alexander and Sadiku, and I am not able to solve a practice problem 13.9 about ideal transformer in Chapter 13 of the textbook. My answer is different from that provided by the textbook and I am not able to find a reference solution on internet.

As shown in the above plot, the problem asks to find \$V_0\$.

I assumes the currents of the three meshes (bottom left, bottom right and top right) are \$I_1, I_2, I_3\$ defined in clockwise directions, and the voltages at the two sides of the ideal transformers are \$V_1, V_2\$ with positive defined at the points marked by red dot. Then I wrote down the following equations

$$120 - 4 I_1 - V_1 = 0 \,\,\,\;\;\;\;\;\;\;(1)$$
$$-V_2 - 2 (I_2 - I_3) - 8 I_2 = 0\;\;\;\;\;\;\;(2)$$
$$-8 I_3 - 2 (I_3 - I_2) = 0\;\;\;\;\;\;(3) $$
$$V_1 =    V_2 /2  \;\;\;\;\;\;(4)$$
$$V_1 (I_1 - I_3 ) =  -V_2 (I_2 - I_3)\;\;\;\;\;\;(5)$$

Here Eqs.(1-3) are due to Kirchhoff's voltage law (KVL), Eq.(4-5) are due to ideal transformer, while the last one states that there is no energy loss. We note that the currents go through the two sides of the transformer are \$(I_1-I_3)\$ and \$(I_2-I_3)\$ respectively.

However, by solving the above equations, I got \$V_0=-18.46\$ V, different from the result provided by the textbook \$V_0=48\$ V. I checked several times the equations and the solutions, but cannot figure out my mistake.

P.S.

I used the following short mathematica script to solve the above equations, if it provides any convenience.

 sol = Solve[120 - 4 I1 - V1 == 0
  && -V2 - 2 (I2 - I3) - 8 I2 == 0
  && -8 I3 - 2 (I3 - I2) == 0 && V1 ==    V2 /2
  && V1 (I1 - I3 ) ==  -V2 (I2 - I3) , {I1, I2, I3, V1, V2}]
 N[8 I3 ] /. sol

Edit

Bumping my brain against user287001's nodal analysis, I found the mistake in my mesh analysis. The third equation above jumps from one side of the transformer to anther while overlooking the voltage difference. The correct one reads

$$-8 I_3 - 2 (I_3 - I_2) + (V_1 + V_2) = 0\;\;\;\;\;(3') $$

Calculations using Mathematica confirmed the result. Lesson learned.


texts: how to calculate the fourier transform of this input?

texts: I have been trying to find a relation between dominant frequency and the time period 'T'. The input is a digital ramp with an increase of 1mV per step. And each step has a time period 'T'. Will I get the dominant frequency as a function of time period 'T'? if yes how will the equation be? DC can be neglected.


texts: anything wrong with using a solid state relay to trigger a magnetic relay?

texts:
simulate this circuit – Schematic created using CircuitLab

I'm thinking to use a MOSFET solid state relay triggered by a MCU to trigger a micro magnetic relay.

I will be using a sufficiently rated flyback diode at the magnetic relay.

This doesn't seem to be commonly done. My reason is that high current solid state relays are way more costly than a low current SSR and a micro magnetic relay together.

Is there any reason to not do this?

EDIT - added schematic


texts: Digital code of the high reference voltage of an A/D of a microcontroller

texts:
I know in theory that the digital code of \$n\$ ones (the digital code for \$V_{DD}\$) is equal to \$2^n - 1\$.

For example, the code 111 is equal to \$2^3 - 1\$ when \$n=3\$. This is because
$$
1*2^2 + 1*2^1 + 1*2^0 = 2^3 - 1
$$

Why does this formula always work?


texts: Transresistance amplifier and current measuring

texts:
I was studying some shunt voltage amplifiers, and I came out with this circuit. R2 is for input voltage offset compensation only, and is the same value as R1.

simulate this circuit – Schematic created using CircuitLab

Now, I know that from various datasheets of components integrating this topology, the final gain is:

G =  R4/R1

Assuming from the classical analysis of the source degenerated transistor amplifier a R1 >> 1/gm, where gm is the small signal PMOS M1 transconductance.

Now, I'd like to build with discrete components this circuit (just for learn/fun), but I ended up with a blocking condition, at least on paper. How do I polarize the MOSFET in order to have gm >> 1/R1? I know that is taken care from the op amp, but let's say that I use an BSS84P and I have this graph from the datasheet:

How do I use this plot?

EDIT: I think that as long as the source resistor is big enough, the gm variation with the current will introduce just small non linearities.


texts: Possible reasons for differences in voltage between garage opener circuit and Raspberry Pi

texts:
I am attempting to use my Raspberry Pi's GPIO to activate a garage door opener (specifically Craftsman 139.5364812). As far as I can tell, the garage door is operated by shorting two terminal screws together (see page 17 of the manual), resulting in about 20-30 mA between them.

I'm trying to measure the voltages involved here with a simple home multimeter.

The voltage between the garage opener's red (1) and white (2) terminal screws is 17-18 volts.

However, then I plugged in my Pi into a separate wall plug, and measured the voltage between the Pi's GROUND pin and the garage opener's terminal screws. For both screws, the difference from Pi GND to screw was 0 volts.

How is this situation possible? Am I missing anything obvious? This has been tested with two different multimeters.


texts: Can i Increase the NFC range upto 50cm by making a bigger antenna? i only want to write data into a NFC enabled EEPROM?

texts:
As NFC are active upto 15cm range, i/m using a PN532 to write data into a NXP NFC enabled EEprom, which is successful, i want to increase its range by 2X by increasing the Power or size of Antenna for increase in the RF Field, My only Motive is to write a data into the EEPROM not read. will that be possible?
EEPROM has to be powered from the Transmitting End


texts: Constant current LED driver - lowering brightness with dip switches

texts: Having a 28W LED lamp with constant current LED driver which has some dip switches where I can change the current, is it safe to lower the current to reduce the brightness of the LED?


texts: Explanation of the circuit in an LED bulb

texts:
I just know the basic electronics, not an expert in the area :)

When I dismantled a broken LED lamp, I could see the circuit below (section after the rectifier, the DC part). 15 LEDs in series. There are two such lines. If they were just parallel lines I know how the circuit works, but they are inter connected here.

Two of the LEDs in a row were broken, So I thought of adding an equivalent resistor value as I did not have the right LED with me. Then the bulb started blinking when powered. Then instead of resistor I just shorted the position of broken LEDs and now it works.

Can anybody explain me the working of this circuit, especially what happens when the parallel lines are interconnected?


texts:
I build a prototype board with a STM32G431KBT6 on it.
This board simply drives some peripherals (led panel, motor) based on what commands I'm sending it over the Virtual COM port.
When connected to my laptop, I have a perfectly working prototype.

I have USB enumeration
I can send/receive commands over the VCP
It perfectly drives the peripherals

But all this changes when I connect the prototype to my client's PC
This PC isn't connected to the internet and probably can not find the right VCP port yet.
But it should enumerate in my opinion.
Nothing is shown in the device manager.
The weirdest thing of it all is that it also doesn't enumerate on my laptop and lab PC anymore
So basically as soon as my client's PC is connected to USB of the prototype, the device isn't recognized anymore.
So I thought, clearly there is something wrong with his USB cable, but when I connect an Arduino Nano on his USB cable, it is shown in device manager.
So how can Windows enumeration permanently damage the STM32 chip?
I did a full erase of the device and reprogrammed it, but nothings seems to work other then resolder a new chip.


texts: Clipping of a negative feedback amplifier

texts:
I need help solving the following exercise from my book.

I am not very knowledgeable in analyzing biasing circuits but I have understood the following:
\$R_1\$ and \$R_2\$ are feedback resistors. This is a voltage amplifier. \$R_L\$ is the load. The output stage of the amplifier is a npn-transistor. the input stage is a differential stage and the peak output voltage is \$v_L = 1.5V\$.

Should I know assume that npn-transistor is a switch and check the two cases? Or how should I proceed. Do I assume anything else about this circuit like that the base currents are 0 and that the base voltages across the differential amplifier stage is zero?


texts: Common digital "glue" chips used with Arduino/Netduino?

texts:
I have a Netduino Plus and I am trying to put together a shopping list to one of my usual vendors for digital "glue" parts I can use with it.  I am experienced in electronics but I haven't bought IC's (other than regulators) in a while.

This is a difficult question, but what digital chips are people using?  I'm not referring to specialized chips, such as an RTC (that is on my shopping list for other reasons) but to the glue chips I need to make things work with a microcontroller.  (I have several other boards, including some MSP430 boards so my question is applicable to these too.)

(I'm not considering analog or RF chips for the moment;  I have plenty of 555's and 741's;  they're like mice!)

As an example, I am looking at an 74LS595 shift register so I can use a few surplus Hitachi-based LCD's I have without the hassle of finding enough pins to directly drive it from the Netduino.  Is the 595 tolerant in the modern 3.3V logic environment?

I know, too, that I will probably use chips like the 4066 switches, so those are on the list.

Another example:  What is a good binary/BCD 7-segment driver for use these days?

It's been years since anyone could just run down the catalog of Mouser or Digi-Key and get 2 of everything with a 74/74LS or 4000 prefix and I don't expect to be able to do the same.  I'd just hate unpacking my order and finding another neat project on the net that I must have but didn't order in the box.


texts: Standing waves feedline length and dipole antenna feedline

texts:
so I have a question regarding reflections/characteristic impedance and there relation with a quarter wave transformer and its feed line.

Now I have found this video very useful for visualising what is happening with standing waves https://www.youtube.com/watch?v=M1PgCOTDjvI&t=70s coupled with the the recommended wiki link from this video. https://en.wikipedia.org/wiki/Standing_wave_ratio

I have two questions which can be applied to the following picture
1. For a quarter wave transformer it is (relatively) easy to calculate the length of the quarter wave transformer to allow for the voltage or current to be at their maximum or minimum, BUT what happens if the length of the feedline to this quarter wavelength transformer starts with the RF wave being not at a perfect division of the wave, e.g. 1/4, 1/2, 3/4 ? Does the length of the feedline to the quarter wave length transformer need to be a certain length too?

Slightly related but if I am feeding a dipole antenna, do I similarly need to make sure that the feed line length is the correct length to allow for the current distribution to be at the correct points be nulls by adjusting the FEEDLINE LENGTH?

Another example from http://colinkarpfinger.com/blog/2010/the-dropouts-guide-to-antenna-design/ - surely the length of the feeline should be specified for antenna design or am I missing something about it not effecting design if it is under a certain length.


texts:
I've been experimenting with three-valued logic (yeah, I know) and have had quite a bit of success by using voltage comparators to implement the combinatorial logic. All 27 1-input gates and many useful 2-input gates are functioning as expected. The progress is documented at
https://hackaday.io/project/6284-tern-physical-implementations-of-ternary-logic

The problem comes about when I start getting into sequential logic. Specificly, SR latches, D Flip Flops, etc. Just elementary memory elements. Not only do the circuits become quite complex but they also exhibit behavior I just don't anticipate. I'm not knowlegable enought in analog design to debug them and I don't even own a scope so I'm nearly blind as well. However, I do know that this is a solved problem because Flash chips use anywhere from 2 to 8 (maybe even higher) voltage levels. Because this stuff already exists in the realm of integrated circuits I'm not going to be picky about staying strictly away from binary-digital solutions for storage.

What I'm looking for is a relatively simple solution that will fit within these parameters:
1) will accept an input voltage between -5V and 5V
2) will store that voltage until directed otherwise (volatile is okay)
3) will output that voltage while it is stored
4) is available in a dip package

My best case scenario (even though it doesn't exist) is a family of dip IC's that are analog equivalents to 8 bit latches, shift registers, etc. My worst case scenario is throwing an arduino into the mix to read analog voltages and PWM them out.

I'm looking for a solution that falls inbtween the two. Is there a family of multi-input sample and hold chips that will keep a charge for a reasonable amount of time (at least several minutes). Or maybe an ADC with PWM output that can hold a level until directed and can accept -5 volts. Any other ideas? Thanks much for your help!


texts: Angular Acceleration: Understanding the differences between Gyroscopes and Accelerometers

texts:
I apologize for what is likely an ignorant question, but I am fairly new to electronics and have little confidence. I am working on a personal project where I am using a servo motor to move a rod back forth 90 degrees (not exactly, but this analogy should suffice), and I am interested in measuring the instantaneous (angular?) acceleration (I want to use it to calculate torque). Surprisingly, I have come across trouble while researching online for a sensor to do this. My understanding now is that an accelerometer is only capable of measuring linear acceleration (which means the object can't be rotating, right?), while a gyroscope only measures angular velocity when an object is spinning about an axis. Technically, the rod in my project isn't spinning-it's just rotating back and forth between two angles (0 and 90) on the XY plane. Is there a simply way/sensor to do this? More broadly, am I completely misunderstanding the uses of gyroscopes and accelerometers? I hope I explained the issue properly...

Edit: Sorry about the confusion. I am using a servo to rotate a rod back and forth and need to measure the instantaneous torque. While the rod is moving, there will be times at which a force acting against the rod/servo is applied, which means that the torque shouldn't remain constant between experiments.

I thought of a couple of ways to do this, and one idea I had was using calculating the torque using: torque=I (moment of inertia)*angular acceleration. To get the angular acceleration however, I figured I need a sensor. I thought an accelerometer might work, but don't know how I would implement it in my system or if it would even work.


texts: Controlling motor direction, usage and speed

texts:
I want to build a machine that can follow a set of simple rules by which it controls a motor. These rules are yet to decided, but the patterns are as follows:

Turn motor clockwise for A minutes, then pause for B minutes and then continue in a anti-clockwise direction for C minutes (and repeat from beginning after a wait of D minutes)
Turn motor clockwise for A minutes and then pause for B minutes (and repeat from beginning)
Turn motor anti-clockwise for A minutes and then pause for B minutes (and repeat from beginning)

Now, I might simplify things and decide not to include a switch between patterns and only use pattern 1, but let's include the option to have the user input which pattern should be executed.

I plan to use a low RPM motor, something similar to this 6 RPM motor. Moreover, could the speed of the motor be adjusted (for example, 1-6 RPM) as well? How?

With my lacking knowledge of microcontrollers, how could these features be achieved? Do I need relays for the motor as well? How about the speed settings? I suppose I could have a dial with a few preprogrammed pattern and speed settings.


texts: What does "driven" or "driving" mean in terms of electronics?

texts: It is a silly question to ask, but I keep seeing statements like "driven by the output signal" or "X drives the load". What does it mean to drive or be driven by X?


texts: How must be the pull up resistor circuit connected to the driver input?

texts:
I have this circuit for getting 12V or 0V from external control signals. Signals will arrive by pin connector to my board. Switches will also be out of this board.

External control signal could be high Z or GND, depending on switch state.

I Would like to bring control signals (HZ/0V) from connector to the drivers: ULN2803.

When input = HZ the idea is that driver output 0V, this is my proposal.
So when input = GND --> driver output must be 12V.

This is what I need and this driver can achieve this behavior.

I can see how my first circuit stage do:

a) When D = HZ, current goes from vdd source to driver GND because it will be ON.

b) When D = 0, current goes from from vss to vdd source (being switch on, of course).

1) But I would like tu design the previous stage correctly and efficiently. Is it any better option for connecting the external control signals to the driver?

2) Someone told me about the need of buffers before driver. I'm asking if this circuit could really need some buffering devices and what kind of buffer could fit better here in this application.


texts: How can I decrease the brightness of these BA-15 LED bulbs

texts: I'm looking at these LED replacement bulbs for the interior of my sweet conversion van. I'm looking for a more efficient alternative to the BA15 bulbs that are in there already. These bulbs appear to be really bright, and I can't seem to find a lower lumen LED light in warm white. I'm wondering if it is possible to unsolder or intentionally damage some of the LED panels to decrease the brightness of the overall bulb, or if that will disrupt the entire bulb.


texts:
i have a part in my graduation project where i need to direct some robot towards another point using local positioning system

now i dont know much about it but here is what i figured out so far
its basically dependent on the fact that you have an RSSI which is the signal strength and u calculate the distance from your current point to a fixed point , using 3 "fixed points" ( called beacons in bluetooth ) you can get the x,y,z co-ordinates(3 equations 3 unknowns, the 3 plans should intersect in a single point) of the robot at the moment

i also got to know that you can use 2 types of things for this job :-
a wifi module and a bluetooth module as you can get an RSSI from both modules

i should also use a BLE bluetooth module which is better however this is not really a possibility since these modules aren't sold in my country and i would have to pay a fortune for them when converted to my currency since cost is part of my project

i dont know if there are more types of modules that can be used for this but if there is please enlighten me

but my question is this :
can i use any kind of bluetooth module ? HC-05 for example is the one i am working with at the moment , however do i have to use a special something for this application ?

and also which is more accurate the wifi or bluetooth and how accurate are they ?

how can i increase the accuracy of the measurements ?

thanks in advance


texts: Improving SNR by increasing resistor value

texts:
I was doing some reading on noise improvement and stumbled on an article by Scott Hunt at Analog Devices.
Here is the reference link: https://www.analog.com/en/technical-articles/11-myths-about-analog-noise-analysis.html#author
According to the first subsection, due to the Johnson noise, reducing resistance helps improve SNR. However, for applications such as measuring resistance, as V=IR, the gain in voltage supersedes the increase in Johnson noise. This leads to an improvement of exactly 3dB for doubling the resistance.
Does anyone know how he obtained the value 3dB, if the resistance value itself is unknown?


texts:
I've received a prototype for this PCB I described in a different thread:
First PCB design, PWM Motor Controller feedback
I've changed the design based on the feedback I got there, I changed the gate resistors to 10 Ohm, removed the capacitor after the MOS driver. After finishing the programing I've measured everything. The PWM singnal generated by the Attiny, the PWM signal generated by the MOS driver. Everything looked fine. I put a motor and it spinned based on my adjustance on AIN.
After that I hooked the motor to some load, a planetary gear 1:25 with a small hydraulic press. I managed to output the desired pressure on the hydraulic press but D4, Q1, Q2 died and the motor kept spinning. They all became 0 Ohm resistors. No smoke and no bang, eveything looked fine until I released the trigger and the motor kept spinning. Everything else seems to still work fine, after I desolder D4, Q1 and Q2, expect that the motor can't spin anymore.
My question is, why did my design fail ? I measured 10A@14V, both MOSFETs parallel should easily be able to handle that load.

From the old thread:

Schematic:

PCB design:

Datasheets:

Q1, Q2
Q3
Q4, Q5
U1
U2
U3
D4


texts:
I need your help to find out why my lead acid battery is not fully charged when I am using the BQ24450 by Texas Instruments.

These are my calculated values based on the fomula:

Rt=150 ohm
Ra=214.79k ohm
Rb=17.21k
Rd=594.4k ohm
Rc=46k4 ohm
Risns= 0.68 ohm
Ccomp=10nF.

I connect DRVE to the collector of the external PNP (MJD32CT4) transistor I am using. I connect a resistor between DRVC and BASE of the transistor value (196 ohm.)
I am using 15V and a current limit of .65A from my external power supply.
This is the datasheet of the battery I am trying to charge.
I would like to know if my values and set up are correct and why my battery is not charging fully.


texts: Say a gate has 5 ns propagation delay. If we input a 6ns signal then does the output signal corresponding to the input last 1ns? Or do we also have to add the contamination delay to the 1ns?


texts: Can the two "high" input to a digital logic gate have different voltage values?

texts: Suppose there is a logic gate and it has two inputs.I want both the inputs to be "high" i.e logic 1, can i have two different voltage values at these two inputs? e.g 3v on one and 4v on another?


texts: Getting an ACK failure right away after writing slave address in interrupt mode for I2C [STM32F4]

texts:
I see that once slave address is written in the interrupt handler, I get an ACK Failure right away, but when I do the same thing with polling approach, I do get an ACK and goes on to read off the values from the device.

With interrupts, I see ISR gets triggered only once (in which it writes slave address) and never gets called again. My i2c configurations are fine, but there's something with interrupts that I seem to be missing out on.

Polling approach

HAL_StatusTypeDef HAL_I2C_Master_Transmit (I2C *hi2c, uint8_t *data, uint8_t size)
{
            GenerateStartCondition();

            // validate the completion of start condition
            while (!GetFlagStatus(hi2c->Instance, I2C_SR1_SB) && HAL_Timeout(5));

            // write slave address along with write bit
            I2C_WriteSlaveAddress(hi2c, WRITE);

            // wait for address to be sent
            while (!GetFlagStatus(hi2c->Instance, I2C_SR1_ADDR) && HAL_Timeout(5));

            // clear address flag
            I2C_ClearADDRFlag(hi2c->Instance);

            // write data to DR ...
}

With interrupts:

void HAL_StartI2CInterrupts() {
     GenerateStartCondition();

    // setting control bits
    hi2c->Instance->CR2 |= I2C_CR2_ITBUFEN;
    hi2c->Instance->CR2 |= I2C_CR2_ITEVTEN;
    hi2c->Instance->CR2 |= I2C_CR2_ITERREN;

void I2C1_EV_IRQHandler ()
{

    uint8_t event_interrupt = (hi2c->Instance->CR2 & I2C_CR2_ITEVTEN) >> I2C_CR2_ITEVTEN_Pos;

    uint8_t buffer_interrupt = (hi2c->Instance->CR2 & I2C_CR2_ITBUFEN) >> I2C_CR2_ITBUFEN_Pos;

    uint8_t var;

    if (event_interrupt)
    {
        //  validate the completion of START condition
        var =  (hi2c->Instance->SR1 & I2C_SR1_SB) >> I2C_SR1_SB_Pos;
        if (var)
        {
            if (hi2c->I2C_State == I2C_TX_BUSY)
            {
                I2C_WriteSlaveAddress(hi2c, WRITE);
            }
        }
         // check ADDR bit ...
     }

}


texts: Wide voltage range comparator (with zener diode)

texts:
i need to switch the transitor (Vce minimal) when input voltage (0 - 18V) is greater than 6.3V. To achieve sharp edge I use a zener diode D1. However, I also need a protect transistor base, so I use a protecting diode D2.

I run into the problem, when D2 needs a high current, but i cannot load the input voltage devider in that way due to destroying the sharp edge so  I use a 4.7K.

How to solve the clamping diode D2?

EDIT:

The characteristic should be sharp at least like this:

I tried to change R2 from 4K7 to 1K (to maintain D2 zener current)and it seems the sharpness stay there.

Any idea how to solve this circuit better?

EDIT:

To make it clarify, it will be used in circuit below. It is current limiter with, let say Mosfet protection. In case The Vds is higher than 5V, the mosfet will turn on completely, so it acts like fuse.

Due to this no need to precise comparator (4.5 or 5.5V doesnt matter).

If someone see improvements in schematic, please correct me.


texts:
On my Xilinx Zedboard, I booted Linux from an SD card and then ran a Linux application (written in C) from the SD card. This application created a server using sockets that would return whatever is sent to it. Is this possible on a Lattice ECP3 FPGA? The board I have is an HDR-60.

If its not possible to put linux on the board, is it even possible to transfer data over ethernet to and from a PC?


texts:
How to I design an antenna which produces a strong field within the antenna, but doesn't radiate out or reflect back to the source?  (as much as possible)
I'd like ideally to have a planar structure (manufacturable with PCB traces), matched to 50 ohm, and reasonably broadband at microwave frequencies (2.4-5.8GHz).
I know about the standard PCB trace antenna types eg PIFA, meander, etc;  and I can understand what makes them radiate; but it is hard to think of how to do the opposite.  It seems what is needed is essentially a capacitor (where the output field is between the plates) plus some discrete components or transmission line to match it to 50ohm and prevent reflections.  But how to broaden the bandwidth?
UPDATE A schematic using lumped elements would look something like this:

simulate this circuit – Schematic created using CircuitLab
Everything on the right is the antenna: a small inductance and tiny capacitance which is resonant at 2GHz as shown, with a resistive component a lot less than 50 ohms.  The transformer is "something" which matches the source 50ohms to the (much smaller) resistance of the antenna.


texts: SMPS output noise: Why is it amplified further away from the output capacitor?

texts:
Well this is just a general question about switch mode power supplies, but i have recently built a buck converter, and read that it is very important where in the circuit you place your probes, to measure output ripple and noise.

As output capacitance i have a electrolytic cap, and a small 100n ceramic. When i measure directly above the ceramic capacitor, i can clearly see the ideal/textbook output ripple, with a small amount of high frequency ringing, which measures to about 50mVpp. But when i move my probes to measure above my resistive load, the output noise amplifies to around 200-300mVpp.

How come? I dont understand where this noise is coming from, when closer to the circuit im measuring way less noise? Is it radiated noise picked up from the inductor coil? Or am i missing something


texts: Learning Multiplexing with LEDs, transistor switching speeds

texts:
I am working with some friends trying to multiplex.  The issue we run into is we aren't sure if we are hitting a limit on transistor switching speeds.

I am unsure if this is a hardware or software problem.  (please let me know if I am in the wrong place)

Here's an example of what we have built.

Where we have an output attached to each transistor.  We want to be able to turn them all on or individually.  We ran into a software problem and asked on Stackoverflow earlier, here is reference if needed

Here's the problem we run into:

This is where I'm not sure to post in Stackoverflow or here:

We always have a row "ghosted" behind.  So from the top (Row 3), we have it on and you can see faintly that row 1 (the bottom) is on.  If the Row 2 transistor is activated (and Row 3 deactivated) then we have Row 3 faintly on.  (with Row 1 being off entirely)

If we just disconnect the ghosted row from its output, it stays ghosted.  Somehow it is being tied to our other output.

The Column transistor is a PNP3906 and the row transistor is a NPN2222.  According to their datasheets both seem fast enough (but I don't know how to read the sheet effectively)

I have tried adding a pull down resistor to the base of the row transistors with no avail.   I also tried paralleling a capacitor to see if maybe it was a speed issue (link to reference, Russell McMahon's answer)

I would be inclined to say that it is a software bug but since the issue still exists with the output disconnected I am unsure.

One more piece of information.  We started out every 20 microseconds to switch rows.  (turn row 1 on, wait 20 microseconds, turn row 1 off, turn row 2 on, wait 20 microseconds, etc..)

This makes the "ghosted" LEDs much brighter.  The picture in this question which are much dimmer are every 5 milliseconds switch rows.  However, going from 5 milliseconds to 1 second delay does not change the "ghosted" row

I realize this might be hard to troubleshoot but thanks if you can help

3906 timing [datasheet]:

Delay Time : 35ns
Rise Time: 35 ns
Storage Time:  225ns
Fall Time:   75ns

NPN2222 Timing datasheet

Turn on Time: 35ns
Turn off Time:  285ns

EDIT:
Sorry, I didn't mention voltage.  From an MSP430G2553, the voltage is 3.3V, directly from an output


texts: Issue with my solar charger using LM2596

texts:
I am using a 20W solar panel, maximum voltage 21V & maximum current 1.23 A. I am using LM2596 to dtep-down to 5V to charge my powerbank, hich will later power my Nodemcu (ESP8266 board.)
Issue in conditions I am getting 14V and when connecting it to LM2596 it's lowering it to 1.6V and not going up to the desired 5V.
Am I doing something wrong?
Am I missing something?
Any suggestions?
Note : I am using standard LM2596 potentiometer module.


texts: Active low-pass butterworth filter design

texts:
I have a project on filtering out frequency above 2.5 KHz. The filter should be low pass butterworth. I am confused here as there are two cutoff frequencies I need to use. 1st cutoff freq. 1KHz and 2nd cutoff freq. 5KHz.

The passband is 5 amd I/p voltage is 0-5 V.

If any one can provide me some idea about this filter design? And what kind of configuration should I use?


texts:
I'm not really sure if this is the correct place but here we go.

I'm in the process of creating a robot for Uni and the hardest part for me is the hardware side of it, specifically the electronics. Thus this issue.

I'm attempting to connect my I2C bus up to my Arduino Uno, I've wried all of the devices I wish to have to my I2C bus and now have got two cables running to/ from it. 1 is the one that goes down to my motor control unit and the other is power. From there I now need to have a connection that runs from the Arduino to the I2C bus so I can just poll around the sensors and read data. Does anyone have any info on this.

I was thinking having 4 wires. 1 for power, 1 for ground, then the other two coming off to other pins on the Arduino. Does this sound about right or not? I'm really at a loss for this one as it's not my strong point.


texts: Suggestion regarding position sensing in a motor operated shaft

texts:
I'm driving an 24V DC motor through an H-Bridge back and forth, in order to position a part of my mechanical app. The motor actuates a shaft which has the said part moving according to the shaft's rotation direction.

The motor is being PWM pulsed, but I want to be able to ramp up/down the PWM in order to control the current (and improve motor lifetime) and obtain a more precise positioning setup.

I have considered using microswitches (similar to these)  that signaled the position the moving part was at, and knowing that, I pulsed the motor accordingly. I had some success with this strategy, but the microswitch option raises a bunch of concerns regarding the industrialization of said setup - I have really high variability on the microswitches' sensitivity, they are reasonably difficult to assemble in the system without compromising the positioning technique, and also, our factory workers aren't oriented or trained to understand and cope with the implications of such manufacturing process.

Other option I've considered but didn't try to implement was a linear slide actuation potentiometer (something like this). Although, as I couldn't find one with an adequate dimension, I abandoned the idea.

Hence, I'm trying to figure out what other kind of sensor could be used for such an application. I'm currently considering using a magnetic sensor and having a 3 small magnets (3 positions) placed strategically with a small harness (and glued to our part), in order to solve the positioning problem while also simplifying the manufacturing process.

So, to sum it up, I have a few different questions:

Has anyone tried this kind of sensor? Do you think it would be reliable for such a scenario?
Can you think of a more adequate solution for this problem? Can you argue it's advantages and pitfalls?

I know this question is pretty open-ended, but I don't trust many other sources to ask this kind of question.

EDIT: as requested by @DaveTweed,

The part has a motion range of 31mm from end to end in the shaft. As such, the beginning and the end of the motion range represent 2 of the positions I want to account for. The other position is somewhere around the middle of this distance, at 12.5mm of the end. This is particularly important because although I do have some leeway around this point, I can't go beyond 12.8mm from the end, nor below 12.2mm, so I need a somewhat tight control over this.

In terms of repeatability, I would say that other type of sub-assemblies in this system are being tested to work correctly for 6k cycles/year. I guess this would be a good estimate for this aswell.

By contamination I assume you are talking about factors that could hinder the operation of the mechanism. We haven't had any problems previously. At most, what could be expected is loss of lubrification in the shaft leading to mechanical friction - but we haven't had those problems before.

In terms of EMI, that could indeed be a problem as we haven't prepared for the use of sensitive equipment like this in our manufacturing process before, but I recon it might be important. What should I be looking for/expect?


texts: Troubles making a counter count from 1 to 12

texts: I can't manage to figure out how to wire the schematic in order to make it count from 1 to 12 instead of having it count from 0 to 12 like i have it right now. Any help would be appreciated.


texts: DC/DC MC34063 serial boost converter for increasing voltage

texts:
I am trying to build one ultrasonic mist IOT device for this github project. SO in the power supply part it needs to have almost 70V input voltage, so for more Voltage you can use boost converter series connections like this (USB 5VDC / Two series 35VDC by MC34063 DC/Dc Converter):

Also one try to build the schematic part of power supply:

So i like to know does this kind of schematic is correct and have your suggestion for making it better.
Update:
Based of the comments and .. this kind of connections seems dont working.
but it could be done by the 555 IC to boost from 5vDC/100V similar to this schematic in this Video( dont find it calculation!) :

that i found the duty cycle and frequency calculation for IC555 for frequncy&Dutycycle (example 200khz and 90%DutyCylce) here as you can see:

and the output signal could be given to this circuit as you can see ( from here):

But this schematic is poor and betters to have feedback to 555 as shown in the described you tube links circuit.
ALso i possible like to know about other alternative circuits.
Thanks.


texts: Can you damage DC motor by backdriving it (with disconnected leads)?

texts:
We are looking for application where we need sometimes backdrive DC-motor manually. In order to protect motor driver and rest of the electronics we're thinking of electrically disconnecting motor leads from the motor driver using FETs or relays. Is there something else you should worry about? E.g. if rotating motor shaft too fast will produce too much voltage and we damage something inside motor or damage FETs isolating it? Is answer different for brushed and brushless motor?

Motor is rated for 24V, 5A continuous, 10A peak for 2 seconds. It's geared 50:1, so we can potentially backdrive it quite fast.


texts: Op Amp Integrator Circuit - Why is there a linear current and voltage for a short time before exponential values?

texts:
Consider the following integrator circuit:

Why doesn't the current through the capacitor and voltage across it behave exponentially? There is a straight section in the beginning, up to around 2ms - why is that?

Current through capacitor:

Voltage across capacitor:

Edit:

It seems like somehow the output voltage is limiting the capacitor voltage. I can't seem to understand why though...


texts: How would an electric company detect wireless theft of electricity?

texts:
As legend goes it is maybe possible to steal electricity from power lines in a wireless way (also see this and this related questions). The legend continues that once someone does that he gets caught by the electric company.

Suppose I actually do it - dig enough wire under a power line, plant some fast growing weeds so that the fact of digging is concealed so that there's no obvious disruption and this way steal say one kilowatt of power.

How would the electric company detect that wireless theft?


texts: Proper oscilloscope connection to prevent ground looping

texts:
I have a question about proper oscilloscope connection for doing work on vintage stereo equipment (120v AC input to +-76v DC board voltage).

Our house wiring is a 1950’s 2 wire system with no ground wire to the outlets. The only earth ground in the house is a bare copper wire from the breaker box to water main. There is also an earth ground at the service transformer in the alley.

I need to know how to properly connect an oscilloscope and DUT in this environment to prevent ground looping.  Obviously, neither the scope nor DUT is earth grounded when plugged in?  What’s the potential difference between the two (are they both floating)?  If I’m probing, am I the only earth ground in this situation?  I don’t know how isolating the DUT would accomplish anything?  Would a battery operated scope be an option (still needs an earth ground) and what about probe isolation?  Is a differential probe the only real option?  I want to be able to do this safely, but reasonably too.


texts: Is there a name for the point where a Peltier cooler loses power and the cold side becomes warmer than the temperature around it and vice versa after power has been lost?


texts: Sawtooth wave generator not working in simulation

texts:
I tried to simulate the following PWM generator:

The output at the PWM node records a constant voltage, not a PWM signal. So I simulated the sawtooth generator separately

And the output of this generator too isn't what it is supposed to be:

So what might be the problem with this sawtooth generator?


texts: Problem understanding the operations of capacitor

texts:
So far I've learnt about some different types of capacitor arrangements , such as coupling , decoupling , bypass , filtering , and smoothing capacitor. Decoupling and bypass capacitors are the same and filtering and smoothing capacitors are the same(Correct me if I am wrong).

In this diagram of a voltage-divider bias CE amplifier above , The capacitor C1 is used as a coupling capacitor as it is connected in series , and blocks DC signals and passes (couples) only the pure AC signal from the source to the circuitry for amplification. And , the capacitor C2 is a bypass capacitor connected in parallel as a shunt , therefore the AC component will pass through C2 to ground and will not be superimposed on the input as feedback , while the DC will go through the resistance Re ; because , We know that the capacitor reactance: $$Xc = 1/ 2\pi f C$$
Where F is the frequency of the signal and C is the capacitance. So, If the frequency increases (ac signals) the capacitive resistance decreases , and signal uninterruptedly flows from one section to another , i.e. is coupled , while the dc signal with zero frequency is blocked by infinite resistance. Same thing happens with the bypass capacitor C2

Here comes my first question , 1. Explain me why the increase of frequency decreases the reactance of capacitor? Not by using the formula written above , but using practical theory of flow of electrons , charging discharging etc.

My second question , 2.Is the capacitor used in full wave or bridge rectifier , i.e. the filtering capacitor in coupling arrangement or decoupling arrangement or none?

3. What type of capacitor arrangement is it that is used on the input of a negative feedback amplifier?


texts: How does splitting power cables work in ATX PSU?

texts:
I came across this Gamdias 650G PSU. Its CPU EPS has 8 pins at the PSU end but it’s split as 2 x (4 + 4)  at the motherboard end. There are certain boards that now come with 8 + 4 EPS power sockets for more power hungry CPUs.

However if the pins at PSU end are still 8 and that’s split as 8 + 8  at the other end how can it meet the power needs? Your power would still be the same, what you are doing is at the same voltage splitting the current?

Am I missing some fundamental understanding here about how PSU and loads on it work?
May I get the correct understanding how splitting power cables actually work on ATX PSU?

Image sources
Youtube &  http://gamingcomponent.gamdias.com/


texts: I have been studying switch mode power supplies for a while. I have understood the working principle of several common topologies But there is a detail in the control circuit structures which I still don't understand. We use the \$R_c\$ and \$C_c\$ to "compensate" the voltage feedback. But why? I saw many sample practical designs in PWM controller IC datasheets. Almost all of them include this RC compensation technique. But none of them mention how to choose the values of \$R_c\$ and \$C_c\$. Why do we need such a compensation and how do we determine the values of these elements?


texts:
I built this 555 pump controller and it works correctly if I short the wires, however, when trying to use the electrodes in water it doesn't do anything. I am using a 12V 1A power supply so I don't think it's a current problem.

The description with the diagram says increase the 100k resistors for more sensitivity, so I made them 1M but still nothing. Why would increasing them help? Surely that will lower the current. Also is 1M enough?


texts: How to choose a properly rated power resistor for pulsed current?

texts:
Datasheets for power resistors typically provide a thermal junction coefficient or graph showing steady-state temperature increase for a given power dissipation, such as below for these ohmite power resistors:

We'd like to test some high discharge RC LiPo batteries by pulsing them at ~150-200A for very brief periods, about a quarter to a half-second or so. Supposing that the resistor is .25 ohm, we know that our instantaneous power is

$$\begin{equation}\label{eq:er1}P=I^2R\end{equation}$$
$$P = 150A^2(.25)\Omega = 5.625kW$$

This is an enormous amount of power that would cause the above resistors to eventually (quickly) fail. We obviously don't want to spec out (huge, expensive) 6kW resistors, so our question is, what's "eventually"?

I want to say that:

$$I_{avg} = I_{pulse}\frac{t_{on}}{t_{on}+t_{off}}$$

At first I tried supposing a duty cycle of 10% e.g,

$$I_{avg} = 150\frac{1}{10} = 15A $$

so

$$P = 15A^2(.25\Omega) = 56.25W$$

...which would be satisfied with a 75, 100W (etc) resistor. But this falls apart for arbitrarily long cycles, so there must be some constraint.

Given that \$Q = mc_{heat}\Delta T\$, and assuming the resistor weighs 200g, can increase 125 degrees, has a coefficient of copper (.385), does not lose heat to the surroundings, and \$Q=E\$, then it takes

$$Q = (200g)(.385J/g^{\circ}C)(125^{\circ}C) = 9.6kJ$$

to cause the resistor to overheat and fail. This happens in 1.7 seconds at 150 amps \$\big(t = \frac{E}{P_{avg}})\$, so using 1.7 seconds as \$T_{period}\$,

$$I_{avg} = I_{pulse} \frac{t_{on}}{t_{on}+t_{off}}$$

$$I_{avg} = 150A\frac{.250s}{1.7s} = 22A$$

$$P = 22A^2(.25\Omega) = 121W$$

So I'd need a resistor rated for at least this value -- like the HS150/200.

Am I correct?

P.S: Supposing I choose a fan with some arbitrary air flow rating, this will cool the resistor by some value in watts. Would the effect on the resistor be like moving left on the graph, i.e. subtracting power dissipated?