texts: How do I design a circuit for a bi-color led to display power?

texts:
I'm trying to create a simple circuit that will turn a Red/Green LED green when the power is on and red when it is off. I figure the simplest way to do this would be using a SPDT switch, but the switch in the circuit I'm designing is a 40 amp relay, and I found a SPST one for about a buck while the SPDT one was almost 4. For future reference, and also to cut the cost of designing my current circuit I'm trying to come up with some way to wire it up and basically make a "normally on" switch for the red and "normally off for the green.

The closest I've come is finding this circuit which would work except for the fact that the bicolor led shares a cathode.

Is there any way to change up the circuit, or is there something else I can try which would free up the cathode to make it so I can independently switch on the two LEDs?


texts: Closed-loop gain with source degenerated amplifier

texts:
The following circuit needs is modeled with parasitic capacitances to be analysed in frequency. I need to drive it with an MCU that can output a signal that can be some tens of kHz and I need to see if can be supported:

simulate this circuit – Schematic created using CircuitLab

I tried to find some help inside the Grey-Meyer book of analog electronics. I tried to do some calculus but some results are fuorviant. Then I choose to ask here how if the initial conditions/approximation that I made are correct. In that case I'll continue to try.

First, the Rd could be a LED or any device that can be not a resistor. If an LED, I've considered as a short circuit (here just to be more similar with the book's example of voltage buffer analysis made on it): but I know that shorting the Rd this become a common drain configuration. Then I've considered only the Cgs. And finally considered the Rout of the opamp of 0 ohms (ideal).

Basically, under these previous assumptions, I find

$$\frac{V_{out}}{V_{gs}} = \frac{R_s(G_m + sC_{gs})}{1+R_s(G_m + sC_{gs})}$$

Now, just to finish my question, I assume these assumptions as correct and that the formula makes sense.

I have some (bigger) trouble in the formal application of the formula to find the relation with the \$V_{in}\$.

I know that \$V_{gs} = Ad(V_{in} - V_{out})\$, which bring to:

$$V_{gs} = Ad_{0} \cdot V_{in} \cdot \frac{1+R_s(sC_{gs}+G_m)}{1+2R_s(sC_{gs}+G_m)}$$

in which, more than make me feel blind about any T (closed loop gain) analysis, seems also non sense, because tend to divide only by 2 the open loop gain: but in reality the opamp has a lower lower value, a bit more than unity. I know that this little more than one gain is due to the relative high threshold voltage of the power MOSFET and the relatively lower value of \$V_{in}\$. If you can point me out where I am wrong I would really appreciate. Sorry for the big mistakes.

EDIT: it seem that I find some reasonable results. The equation above describing the \$\frac{V_{out}}{V_{gs}} \$ relation, with my approximations, seems to be correct if I consider the \$V_{gs}\$ relative to ground, so changing it name in, for example, \$V_{oa}\$, as outputted by the OA. That was the confusion, I think. The \$R_{d}\$ does not count since it is separated by the current generator, which is not dependent on that voltage drop. Then many books neglect the other capacitances and in my case, since I want to find the slowest frequency change (to be in the worst case) seem to be fine, and btw the result would be instead insanely complex. So, the expression is equivalent to:

$$V_{out}= \frac{R_s G_m}{1+R_s G_m} \frac{1-\frac{s}{z_1}}{1-\frac{s}{p_1}} V_{oa} = k V_{oa}$$

with $$z_{1} = -\frac{g_m}{C_{gs}}$$ $$p_{1} = -\frac{1}{C_{gs}\frac{R_s}{1+g_m R_s}}$$

My misconception about the OA seems also to be solved. The differential voltage is:
$$V_d = V_{in} - V_{out} = V_{in} - k V_{oa} = V_{in} - k V_d A_d $$ but with another point of view is also $$ V_{oa} = V_d A_d = (V_{in} - k V_{oa})A_d $$ leading to: $$ V_{oa} = \frac{A_d V_{in}}{1+k A_d}$$ where the closed loop gain is $$ T = A_d k $$ and finally to \$k\$ apply the frequency response made just before. Here seems logic since the voltage gain of the OA is near unity and it is the loop gain to be far different from the unity. From here I can continue an analysis with some real components in terms of resistors choosen.


texts: Why does isolation transformer protect from shock?

texts:
Perhaps I can best explain the question with two examples:

(1) there is PC powered directly from 230V mains (unprotected by RCD or similar), and there is fault in PC that causes line voltage to connect to PC case. When user touches the case, he will be shocked (perhaps fatally)

(2) the same PC with same fault is connected to 230V mains via isolation transformer. Now user touches the case, but (s)he is safe from electrical shock (or at least much safer).

Now I understand why (at least I think I do), from the electricians point of view:

In first case, star of the transformer that powers the mains is connected to the ground, so electrical path is closed by human touching the case - current can go from power transformer line through case through human to the ground and back to the star of the power transformer - as explained in this question

In second case, there is no connection from secondary windings of isolation transformer to the earth, so current will have no incentive to flow from case to the the ground via human touching the case - electrical path will thus be open, so no shock.

Correct so far? I guess that measuring voltage between ground (on which uses is standing, which is same as protective grounding in electrical outlet, right?) and either end of secondary winding will show 0 volts (otherwise user standing on ground would get shocked by touching either end of secondary winding of isolation trafo).

What I am having problem is physics explanation WHY is that so? (I realize this might also belong on physics.SE, but thought this might be better place to ask than to explain isolation transformers and star topologies in p.se).

As I understand it, voltage is simple difference between two electrical potentials, and every object (be it any of secondary winding of isolation transformer or the ground) must be at SOME potential. But I guess that is probably flawed, because if one end secondary winding was at potential A, and other end of secondary winding was at potential B, and ground was at potential G, than it should stand:

difference between potential of A and potential of B is 230V (or we couldn't power the PC from isolation transformer)
difference between potential of A and potential of G is 0V (eg. they are at the same potential) -- or the user standing on G and touching A would be shocked.
difference between potential of B and potential of G is 0V (eg. they are at the same potential) -- or the user standing on G and touching B would be shocked.

So, if A=G, and B=G, it would follow that A-B=0, which is obviously not true (as first point above says that A-B=230). So I know I'm wrong somewhere in my assumptions.

Could someone explain in basic physics (like movement of electrons and stuff) where I went wrong - what happens in first example, and why it doesn't happen in second example?


texts:
I know there are other questions on this site about decoupling, but I do not feel they accurately cover the full decision process.

I am interested in knowing the decisions that go into choosing decoupling caps. I do not mean a microprocessor with a well laid out datasheet containing proper diagrams of the capacitors, and I do not want to concern this questions with layout as decoupling in layout is separate and a huge subject.

Let us take an i7 as an example. What are the steps that one would take in choosing decoupling caps? Certain things in the datasheet to model? ESR models? Signal speeds? I am just curious what rabbit holes I should go down if I want to be diligent and not rely on the manufacturers recommendations (which I am aware are important).


texts: Solid ground-plane vs Hatched ground-plane

texts:
So recently when i was routing a PCB , I came across the option to either fill/pour my ground plane with either solid or hatched copper. I've also noticed that the old arduino duemilanove also had a hatched ground plane.

So what benefits does a hatched ground plane have over solid ground plane and vice versa.


texts: Does this appliance break UK safety laws?

texts:
Good evening.

I recently purchased this active suction SMD pick-up tool from AliExpress:

When it arrived, it seemed to work fine. However, when I opened it up (to investigate the feasibility of adding a switch), I was less than impressed with the build quality and safety of the unit. (I was also staggered at the amount of empty space inside, but that's beside the point.)

The inside looked like this:

Closer examination showed obvious green corrosion on the ends of the wires; poor soldering; and damage due to a lack of strain relief:

I also noted that the capacitor was rated for 100V, which is far less than the operating voltage of the unit. Tests determined that the AC voltage drop across the capacitor was far less, however this probably did not take peak voltage into account.

At the very least, I would need to fix the solder joints and heatshrink the exposed contacts for safety. Either that, or demand a refund from the seller - and if I'm going to complain, I need to know what exactly I'm complaining about. I need to know if this device can legally be sold.

Therefore, my questions are:

Does this device break any specific UK laws or regulations, that I could complain to the seller about?
Do I need to replace the capacitor with a higher voltage one? If so, what voltage? I'm running on a standard ~240V supply, but I gather capacitive droppers should ideally be rated higher than that.
Presumably I need to add a fuse of some sort? (Again, does the lack of a fuse violate UK law?)


texts: 5 wire, Logic Output Photointerupter/Slotted Optical Switch

texts:
I am trying to get a digital output from a 5 wire photointerupter.

The p/n is OPB903w55z, it is configured as an inverted open collector.

I have used 4 terminal transistor output photointerupters before with success, but I am really striking out on this one.

What I have so far:
Photo Diode --->Anode going to +5V through 220 ohm resistor, Cathode to GND.
Photo Transistor ----> VCC to +5V through 220ohm resistor, Output disconnected, GND to GND through 10 Mega-ohm pull down resistor and arduino A0.

I am able to get a 1.7V when the photo-gate is clear, and 0.7V when it is interrupted.

In order to get a digital ouput, I need 3.3V on interrupted or non-interrupted state, and ideally 0V on the alternative state.

I have have tried experimenting with as many combinations I can think of on the phototransistor, pull-up resistors on VCC, pull-up/pull-down on the gate/output, voltage dividers on the GND, and still no further progress.  I have also tried just putting the Output straight to a A0, but it will show only 0V regardless of the interrupted condition.

Hoping someone smarter than me can help!

Thank You!

https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Optoelectronics/Datasheets/OPB900-913.pdf


texts: Can there be a voltage spike from ULN2803 to MCP23017?

texts:
I would like to ensure I have designed my circuit to operate safely. I am trying to control a 12V electric lock using Raspberry Pi.
I have connected my SCL and SDA to MCP23017 and the output of MCP23017 to ULN2803. I have connected +12V source power to ULN2803 COM and + of the electronic lock, while -12V to ULN2803's ground.

Do I need any resister to have my circuit operate safely without current spikes going back to MCP or Raspberry Pi?
Is it a problem to connect all the grounds back to Raspberry including -12V?

I am using 10K resister for MCP'reset.


texts: Location for placing ESD components for UHD video

texts:
I am implementing ESD protection for HDMI video input. The HDMI video goes through a custom cable of ours, into a connector board attached to our enclosure, through an edge card connector, into our main board and into the receiver chip.

I usually add the ESD protection circuit on our connector board because that's the first part where the high speed signals make contact from a cable to a board.

Would it be bad practice to add another ESD protection circuit on the main board since the signals will go from the connector board to the main board via edge card connector?

I'm worried that adding extra capacitance to the high speed signals will cause signal integrity issues and that it will be overkill.


texts:
I am trying to establish a unidirectional connection over a RJ45 cable (not an optical fiber). I saw in the IEEE 802.3 standard that the clause 66 describe how unidirectionnal chips should work. However, I do not find any chip that implement this clause. So here are my 2 questions :
- Do you know if there are some chips that are capable of establishing a unidirectionnal connection over a RJ45 cable?
- Is it possible to reprogram an existing chip?
Thank you!


texts:
I'm using CC2640, and N25Q128A (Micron Serial NOR Flash Memory).
SPI is working well, erase and write commands are changing the status register so busy flag rises and i'm waiting until it's clear.

The only problem i'm facing is read command, when i'm sending the read command with 3 byte of address the memory is rising miso pin and does not release until c# pin is rise again.

I cleared the ReadLock register and set the WriteEnable register, and now here i am... asking why it's happen and how to fix the issue?


texts: Testing old lithium cells with Zanflare chargers, second test shows more capacity?

texts:
I've been salvaging 18650 cells.  The first I salvaged was from an old laptop battery that has been laying around for a year or so.  It was still good, as far as I know - the laptop was just no longer around.

I pulled 9 green cells out of it, they all still had some voltage, but I don't remember what exactly.  I charged and tested them in Zanflare chargers.  Normal test, which I believe charges them to full voltage, does a drain to test capacity, then recharges.  The first time I did them, 3 of the cells came out at 1100-1200, 3 around 1000, and 3 around 1450mAh.

I've been using a few cells for various thing and threw them back in the charger. I ran the normal capacity test again just out of curiosity.

Two of the cells in the tester previously ended at 1175, but this time they came out at 1455, and 1292.  The third one was 1256 previously, and this time 1410.

So, are these cells regaining some life after sitting so long?  Or is my tester not as accurate as I would hope?  I guess I could run a 3rd test, but it makes me wonder if at least a second test should always be run on salvaged cells.  Ultimately I'll be making battery packs with these, and if in series I'll want to know accurate mAh ratings.

UPDATE:
Here is a table of 1st, 2nd, and 3rd tests:

 1st |  2nd |  3rd
------------------
1174 | 1455 | 1552
1175 | 1292 | 1323
1256 | 1410 | 1421

The last cell isn't as wild, but the first two seem strange.


texts: Turn gate on and off while on rising edge of a signal

texts:
I am measuring a voltage which looks something like the positive half of a sine wave and I want to drive the gate of a FET while this voltage is inbetween two certain points.

So for example the voltage has an amplitude of 10 V, the gate should go from low to high when the measured voltage reaches 1 V and turn low again when it reaches 6 V.

What is the easiest way to do that? I tried with a Schmitt trigger but could not get the gate to low again while still being on the rising edge of the measured voltage.


texts:
I know how to compare unsigned binary numbers.

But can you help me compare any signed binary numbers?

Above is my simulation but I don't know how to integrate those signed bits in my circuit correctly. In that setup, my output also reads my signed bit as one of the input not as a polarity.


texts: How to jumper differential pair wires for USB 3.0 Superspeed?

texts:
Building a USB 2.0 speed cable is almost trivial. Simply connecting D+ and D- through any sort of wiring seems to allow full 480 MBps speeds.

Now I want to jumper a USB-C connector to a USB3.0 Type-A connector as shown. The distances involved are short as you can tell.

I can achieve USB 2.0 speeds no problem by connecting D+ and D- using jumper wire. Easy.

However, using twisted pair wires to jumper SSTX+/SSTX- to TX2+/TX2-, and SSRX+/SSRX- to RX2+/RX2- fail to allow the device to negotiate up to USB3 Superspeed. Note: The device still connects as a USB 2.0 device and operates properly at USB2 speeds.

If I connect the device directly to the computer, it properly negotiates USB3 superspeed and operates at USB3 speeds.

Yes, the same problem occurs if I use TX1 and RX1 - the orientation of the USB-C doesn't matter.

Help?

Note: The USB-C cable is actually a USB-A to usb-C superspeed cable. Yes, I have verified continuity on the breakout PCBs shown by connecting them to both ends of the same cable. Circuit continuity between the differential pair pins is verified.


texts: Comparator - get the difference between inputs?

texts:
Is there any way to have a comparator (say LM339) output the difference between its +V and -V ??
For example, if +V is 6.3 volts and -V is 5 volts, how to get a 1.3 volts signal?
Put another way, I guess it could be how to substract the -V from the +V voltage..
This is probably simple, any ideas?


texts: How to create phase (hot) and neutral in single phase inverter?

texts:
simulate this circuit – Schematic created using CircuitLab
I have made a single-phase 50 Hz-220 volts (RMS) inverters. I thought that one of the outputs will be hot and another one will be neutral. But both of the outputs are working as hot (AC tester glows).
Is there any circuit that will provide me a phase and a neutral?
Additional information:
1.Gate Pulse.

I used IRF3205 N-Channel MOSFET. (I tried power BJT too)
Tried various transformers. Like 12-48, 12-220, 24-48 , 220-55. This is the secondary output of a 12-220 (5A) with a 500-ohm load. The voltage has dropped because I have not implemented feedback yet. I'll do that later.


texts: Stable 200uA Current source by cascading REF200's Current source and Current mirror

texts:
I am trying to work on above circuit. A common operating point of ISFET pH sensor is a drain-source current of 100 uA and a drain-source voltage of 500 mV. I am using REF200 current source to feed 100uA i.e. 'I' and for 2I, I am cascading REF200's another current source and current mirror to generate 200uA as shown below.

I am unable to maintain I and 2I constant. Could experts please help me understand why isn't it working?

Thanks in advance.


texts:
How can you tell if an ESC, brushless motor and Li-Po battery will work together. Specifically, I have a A2212 Outrunner Brushless Motor KV2200, 30A Brushless Speed Controller ESC and I am looking for a battery to run this system.

Motor

ESC


texts: Skin effect of copper in a high-strength AC magnetic field

texts:
I'm trying to determine the thickness of copper foil required to construct an enclosure that attenuates a very fast-rising, very brief pulse of AC magnetic field at a frequency of 1 MHz and field strength of 133 A/m by 50 dB. Using the equation
$$
A = (3.338)(10^{-3}) t\sqrt{\mu fG}
$$
where A is attenuation, t is thickness in mils, μ is relative permeability referred to free space, f is frequency and G is relative conductivity referred to copper, I get a thickness of 380 microns.

Someone answered a previous, related question of mine with the following equation, which he identified as "Maxwell's equation plus Stokes",

$$
\oint_{\partial \Sigma} \mathbf{E} \cdot d\mathbf{l} = -\mu\int_\Sigma \frac{\partial \mathbf{H}}{\partial t} \cdot d\mathbf{A}
$$

which means that the electric field, integrated along a contour Σ (i.e, potential) is equal to the integral of the time-derivative of the H field times the medium's μ. He concluded that according to this equation, a strong AC magnetic field at the frequency of interest would induce a current strong enough to fill a thickness of copper, calculated as above, and couple to the contents of the enclosure.  I've asked the poster for clarification, but they haven't responded in 5 days.

So, my multi-part question is:

Would someone please confirm that the Maxwell/Stokes equation is applied properly to answer my question, and that the poster was correct in concluding that my copper foil and its contents would be in danger in the presence of a 133 A/m H field, and if so, why?
Could it be because skin depth is greater at 133 A/m than it is at a lower field strength? "The relative permeability of any material at a sufficiently high field strength trends toward 1 (at magnetic saturation)" (Wikipedia). And lower μ means greater skin depth. But I don't think this affects copper, because its relative permeability is 0.999994. Also, I'm not sure if magnetic saturation applies to copper in an AC magnetic field. So is there another property of copper that results in increased skin depth in a high-strength H field?  Or,
Does the formula that I used to calculate thickness provide only skin depth, so that an additional thickness of copper is required to separate the point of deepest current penetration from the inner wall of the enclosure? Or,
Does heat build up in the copper due to the high induced current, causing it to melt? (This seems unlikely to me, because the EMR of interest is produced as a very fast-rising but very brief pulse.) Or,
Have I specified insufficient attenuation?  If a 133 A/m H field is attenuated by 50 dB, the resulting field strength is 420 mA/m. The only electronic components that might couple strongly at 1 MHz might be things like the coil antenna in an AM radio. Given that the H field of an AM broadcast signal might have a field strength of 76 mA/m at a distance of 100m (see this article), and that an AM radio must be sensitive to much lower-power signals, would 420 mA/m be enough to fry an AM radio? Or,
Does some other phenomenon apply?


texts: Why doesn't this 950 MHz to 2200 MHz Colpitts VCO circuit work in Multisim?

texts:
I found a 950 MHz to 2200 MHz Colpitts VCO circuit from this web page.
I tried to design it in Multisim, but doesn't produce any signals. Why?
I used BB130 diodes instead of SMV1232 because Multisim has that varicap diode, but it doesn't produce any signal. Why?


texts: Combining buck and boost converter with a single potentiometer

texts:
I'm designing a buck boost converter for a simple variable power supply by connecting a boost(LM2577) converter circuit and a buck(LM2596) converter circuit in series. They each have a potentiometer to control the feedback pin. Is there anyway where I can combine both the potentiometers into one?
Plus, I do not want to get a buck-boost converter module because from where I from its really expensive.

Edit: The 3 euros buck boost converter has low power and after conversion rate in my country it's not worth it since I have the individual modules already. Regarding the power rating, the input will be 12V and have an output range of 1-28V 3A.

These are the images of the buck boost converters respectively.

Thank you!


texts: Instrumentation Amps for AC signal measurement

texts:
I am trying to measure excess resistance fluctuations in resistors. The circuit itself is very simple. Its a wheatstone bridge excited by a AC drive. the idea is that this drive will modulate the fluctuations to a higher frequency which is then demodulated and measured using a lock-in. The demodulated output should reflect the excess resistance fluctuations which have a '1/f' power spectrum. The circuit consists of a voltage source driving a bridge of identical resistors, the bridge difference is amplified by an instrumentation amplifier(As I do not have to worry about source impedence matching with the amplifier) and then locked at the drive frequency using a lock in. The problem is that the final output power spectrum, shows a sharp roll off of about 20-30 dB/decade instead of the expected 10dB/decade. A sort of filtering is happening in the circuit somewhere, I have kind of isolated the problem to lie in the AD620 in-amp I am using. Could this happen in an in-amp? or in other words are there special precautions to be taken when amplifying ac signals with an instrumentation amplifier? Would using a different instrumentation amp(AD8221) help?
P.S: I have taken care of the basic errors that could happen like ensuring a proper return path of DC Bias currents, etc.


texts: Do I still need a resistor in this LED series design?

texts:
I'm designing an aluminum PCB containing a series of 1W LEDs. The series of LED will be powered by 24VDC and N-MOSFETs will be placed between the ground and every series of LEDs. The gates will be attached to Arduino PWM pins.
Here is the example schematic:

The number of LEDs in a series is determined by dividing the 24VDC with the forward voltage of each LED. For example, the white LED has a forward voltage range of 2.8-3.4V and a forward current of 350 mA. Dividing the 24V by the forward voltage, I can have 8 white LEDs in series. Now the question is do I still need the resistor added in the series or is the number of LEDs enough to limit the current to around the 350 mA range?


texts: Boosting wifi antenna with aluminum foil: ideal placement/size?

texts:
On more than one occasion I have successfully (and significantly) improved the wifi signal a desktop computer was getting simply by taking a flat sheet of aluminum foil and curving it into a semicircle around the antenna.

Currently, I'm trying to boost signal on a desktop I have placed face down so that the dual antennas from the network card are facing straight up and I have placed foil behind them as described above.

Are there any simple rules to follow when doing this to achieve the best size 'satellite dish' and optimal distance from the antenna?


texts: Confused on how to wire a Laptop Heatsink/Fan

texts:
thank you so much for taking some time out of your day to answer my question.

I have bought this Laptop HeatSink/Fan combination and it comes with a molex connector at the end of the wire to attach to a male molex connector.

As you can see on the bottom left corner, the Molex connector is present; however my project involves hooking the fan up to a USB to power the device. What went wrong the first time I did this is that when stripping and soldering the wires, they were so fragile and small that they broke easily.

So, I was wondering is there a way that I can connect this molex connector to a male molex (more secure than soldering thin wires) and somehow get power to the fan still?

I can't seem to find a molex connector and wire the same size as the one in the picture, and neither can I find some way to connect the wire to a place in which I can power the fan from a USB cable.

As a side note I only need power, no speed or power adjustments as I want the item to run at maximum speed always. Thank you.


texts:
Hello I am making a VHDL project in which I am doing some image processing. Color data of pixels are held in Rom and operations are done on Ram. However, when I try to reset the ram from the rom. It is not reset as intented. What I mean is that in place of what should have been the default picture on the moniter, there is a square which is consisting of just one color. When I reset the ram, what should happen is that I should see the default picture on the monitor but I cannot. I tried to debug code but could not see the fault. There could be some other problems in the code given below. How can I solve this problem??
Also I get this warning

  [Synth 8-6014] Unused sequential element address_rom_reg was removed.

Here is what I have::

Reading_Writing_Resetting_Ram: process(clk,rst) is
begin
  if rst = '1' then
    done <= '0';
  elsif rising_edge(clk) then
    if done = '0' then
      if address_rom <
        conv_std_logic_vector((PICTURE_WIDTH_HEIGHT*PICTURE_WIDTH_HEIGHT),16) then
        write_enable <= '1';
        data_in_ram <= data_rom;
        address_ram <= address_rom;
        address_rom <= address_rom + 1;
        if address_rom =
          conv_std_logic_vector((PICTURE_WIDTH_HEIGHT*PICTURE_WIDTH_HEIGHT),16) then
          address_rom <= (others => '0');
          write_enable <= '0';
          done <= '1';
        end if;
      end if;
    else --if done = '1'
      if (pos_x < PICTURE_WIDTH_HEIGHT)
      and (pos_y <PICTURE_WIDTH_HEIGHT)
      and (pos_x >= 0) and (pos_y >= 0) then -- if within picture
        address_ram <= (conv_std_logic_vector((pos_x +
          pos_y*PICTURE_WIDTH_HEIGHT),16));
        if (pos_x > control_cursor_pos_x - 1)
        and (pos_x < control_cursor_pos_x + length)
        and (pos_y > control_cursor_pos_y - 1)
        and (pos_y < control_cursor_pos_y + length) then --if within cursor
          data_in_ram <= output_of_operation;
          if enable = '1' then
            write_enable <= '1';
          else
            write_enable <= '0';
          end if;
        end if;
      end if;
    end if;
  end if;
end process;

and

U3: Block_Rom port map(addra => address_rom,
                       clka => clk,
                       douta => data_rom);

U4: Block_Ram port map(addra => address_ram,
                       clka => clk,
                       dina => data_in_ram,
                       douta => data_out_ram,
                       wea => write_enable);

component Block_Rom
port(addra : in std_logic_vector(15 downto 0);
     clka : in std_logic;
     douta : out std_logic_vector(11 downto 0));

end component;

component Block_Ram
port(addra :in std_logic_vector(15 downto 0);
     clka : in std_logic;
     dina : in std_logic_vector(11 downto 0);
     douta: out std_logic_vector(11 downto 0);
     wea: in std_logic);
     end component;


texts:
I bought different type of CAN transceivers: Two with an CJMCU2551 (left in the picture below). and four with TJA1050 (right in the picture below).

CJMCU2551 (left) has pins: VCC, GND, CTX, CRX, CANH, CANL, chip: MCP2551I (I think last is an I), written on back: CJMCU-2551

TJA1050 (right) has pins: VCC, GND, TX, RX, CANH, CANL (thus the same), chip: TJA 1050, written on back: LC Technology, www.lctech-inc.com

I have the feeling these are similar, although I see some difference, like the TJA1050 has an 120 ohm (terminator) resistor, but the MCU2551 has not.

Question 1: Are they interchangeable or not? (and if not, what should I take into account, like adding a 120 ohm resistor?)

I soldered pin headers to the pin holes, and I found out that all are not with 90 degrees angle. For the MCU2551 this was my own fault (I probably pressed to hard on the soldering iron so the angle is less than 90 degrees).

However, for the TJA1050 I could put both ends on a breadboard and the only way it fitted was like this: but when I took them out I saw the pins are in an angle.

Question 2: Why aren't the pins made in such a way both row ends (VCC, TX, RX, GND and CANL, CANH) fit in a breadboard with 90 degrees angle? (see pic below)

(I want to use them for STM32 (STM32F103C8T6 and STM32F407VET6) which all have CAN supported by GPIO pins).


texts: Type name conflict between FPGA libraries

texts:
I've procured FPGA cores from two different vendors, both written in VHDL. Both cores have a type defined called ahb_slv_out_vector but the two types are not compatible. I need to use both types in my top-level module but there is an obvious conflict.

The libraries are imported from

work.amba.all

and

<vendorname>.amba.all

How can I disambiguate the two type names in my top level module while allowing other files that import them to continue using them with their current name?


texts: Advice for pcb that didn't print correctly

texts:
I designed a schematic with quite a lot of connections (88 comparators into 14 MUXes) I created  ground planes on the top and bottom layers to assist with the many ground connections. I just got the PCBs from pcbway.com and I tested the ground and power connections using continuity mode on my multimeter. What I found is that the ground pins and vias with point to point connections visible on the top layer are all connected, but the ones that should have connected to the ground planes on the bottom or top layers are not connected to any other ground pin on the board. So my question is, did I do something wrong when I built the PCB design in eagle? What can I do differently to have some assurance that the board will print correctly next time? I have included links to download the schematic and the board files below.
Schematic - Eagle
Schematic - PDF
Board - Eagle
Board - PDF


texts:
Today I had a bad experience on my cycle commute home from work - my battery pack died and I was left without a front light for 20 miles of my journey home.

So I want to see about creating a new, backup battery pack as a spare.

It will obviously need to be waterproof and robust enough to handle vibrations from the road.

My light and battery pack came together, so my question relates to compatability.

The battery pack is a 7.4v 4600mah lithium ion pack. The pack connects to the light (and charger) via a barrel connector.

Can I create a new pack in this instance relatively easily? I am not an engineer, and not clued up at all. Can any body give me some advice or point me in the direction of some materials I can use to create a new pack?

I would just order a replacement pack, but my model of light is discontinued. Thanks for any help, it may just save my life! :)


texts: Using a Spectrum Analyzer to measure VSWR

texts:
I need to measure the VSWR of a coaxial wire that has a length of 100 metres and a characteristic impedance of 50 ohms using a Spectrum Analyzer (I don't have a Network Analyzer). I found this website: https://rigol.desk.com/customer/en/portal/articles/2270018-how-do-i-measure-vswr-using-a-spectrum-analyzer-

And I don't know if I understood right the testbench. Would it be something like this?

If that is OK, what do I have to put in the green box? A short circuit? Open circuit? Why?

The coupler is a unidirectional, isn't it? I understand how a coupler works but I don't know how the tracking generator and the coupler work together.

Thanks


texts:
I want to get the idea behind determining states of a FSM. I would appreciate a hint for the following problem as to where to look for the states.

"A FSM should send out a signal to open a door. If you are authorized by wearing an ID, a sensor detects you and the door opens (out to in, always). However, between 9PM and 6AM, the door does not open if you're inside (night lock). At other times, the FSM also opens the door from in to out."

Where do you start? Are night and day the states, or open and closed, are 'states' a combination of those?


texts: DIY FP - Implementing floating point math on a microcontroller without a hardware FPU

texts:
I'm working on a little personal project (targeting a Parallax Propeller, but this should be pretty generalizable) that needs floating point math.

The micro-controller I am working with does not have native floating point, or a stock floating-point library.

Are there any good resources or tutorials on implementing software floating-point math? Preferably on really limited resources (I don't even have a stack!).

I'd like to support double sized floats. The propeller is a 32 bit MCU, so I'll have to use multiple variables for each float.

I know there is one software-floating-point library for the propeller out there, but it only supports single sized floats.

No, I probably don't really need double sized floats, but this sounds like a really interesting project. Half the reason I want to do this is because I'll learn a lot along the way.


texts: VFD configured for six-step output instead of SPWM?

texts: I need a transformerless inverter which generates a 3 phase 230 VAC modified sine wave output from 325 VDC input. Unfortunately, it seems these are rare, at least high power models. Can a VFD (with DC bus) be used instead? As I understand it, most modern VFD use Sinusoidal PWM. Are there any models which can be configured to output "six step" instead of PWM?


texts: How to add power-LED to my small amplifier?

texts:
I have a simple PAM8403 that I use to amplify sound,

The volume switch also works as power-off, if I slide it all the way down it makes a click and its off.

My girlfriend is the user of this device and she often forgets to turn it off because its easy to overlook, therefore I want to add a LED that lights up when its on and off when its off.

How would I go about customizing it to achieve that?


texts: Planning of integrator and derivator circuit

texts:
I have to plan a circuit given by the series of an integrator and a derivator circuit. I haven't planned a circuit before, so I ask you if my reasoning is correct.

The only condition that I have to satisfy is that the angular frequency I will apply to my circuit must be in the range beteewn 1k rad/s and 10k rad/s.

The fist part of the circuit has to be an integrator and the second one a derivator.

Let's call \$R_1\$the resistence and \$C_1\$ the capacity of the integrator.

Let's call \$R_2\$the resistence and \$C_2\$ the capacity of the derivator.

I have to satisfy these two conditions: \$\omega_1<<\omega\$ and \$5\omega<<\omega_2  \$, where \$\omega_1=\frac{1}{R_1 C_1}\$ and \$\omega_2=\frac{1}{R_2 C_2}\$

I consider \$\omega_1=\frac{1}{10}\omega\$ so its value can be between 100 and 1000 rad/s.

If \$\omega_1=\frac{1}{R_1 C_1}\$=100 -> \$R_1=\frac{1}{\omega_1 C_1}\$ and, if \$C_1=47*10^-9\$ F, \$R_1=2.1*10^5 \Omega\$

If \$\omega_1=\frac{1}{R_1 C_1}\$=1000 -> \$R_1=\frac{1}{\omega_1 C_1}\$ and, if \$C_1=47*10^-9\$ F, \$R_1=2.1*10^4 \Omega\$

So I can choose a resistence between 2.1*10^4 and 2.1*10^5 ohm.

I have choosen it such that \$R_1=5*10^4 \Omega\$

So \$\omega_1=\frac{1}{R_1 C_1}=4.25.5\$ rad/s

And \$\omega=10 \omega_1=4.25*10^3\$ rad/s.

Then, this is the proceeding about the second condition:

\$5\omega<<\omega_2\$ -> \$5\omega=\frac{1}{10}\omega_2\$ -> \$\omega=\frac{1}{50}\omega_2\ = \frac{1}{50R_2C_2}\$

If I choose a capacity of 47 nF, I obtain the second resistence \$R_2=100\Omega\$

Is my proceeding correct? Thank you so much!

(The image of the circuit is here)


texts:
Is there a clever way using KVL and KCL to calculate the voltages across the components in this circuit:

simulate this circuit – Schematic created using CircuitLab

If there would be no parallel path it would be easy to calculate the voltage across the remaning resistors by splitting the 12V-7V5 = 4V5 according to the resistors' values. But I can not wrap my mind around what's happening due to the parallel path with the 6V8 z-diode.

Any advice is appreciated!


texts:
I am trying to find the v1, v2, v3 and i5 using nodal analysis.

I gave the name to the current over the respective resistors i3 and i4 and put it as i0 - i3 - i4 = 0 also write the equations as i3 = (V2-V1)/R3 and i4 = (V2-V3)/R4 but couldn't progress further to find i5 and others.

The only info about the direction of currents flow was, i5 is flowing clockwise (to left).

This is my first question on the exchange so please let me know if I'm doing something wrong.

Thanks

simulate this circuit – Schematic created using CircuitLab


texts:
I have a non-magnetic(aka card with chip) credit card. I had the classic accident where it took a quick bath in the washing machine. :)
Some questions came in mind immediately:
- Are they water proof?
- Lets say I try it and works. What are the chances that it will break eg 4-5 weeks later due to the wash?


texts: Using PS2501A-1-A Optocoupler. Need help understanding datasheet

texts:
I'm experimenting with circuits to trigger my camera shutter and camera flash. My plan is to build a 2-stage trigger for high speed photography that triggers the camera a fraction of a second  before an event like a balloon popping, and then a second trigger for the flash using sound, vibration, breaking an "electric eye" light beam, etc.
Both cameras and flashes use a 2-wire trigger that applies a DC voltage. When the 2 wires are connected with a near-short, it triggers the flash to fire/camera to take a picture.
Different cameras and flashes use widely varying trigger voltages. Older flashes sometimes use trigger voltages as high as 300 volts, although those are uncommon in modern flashes. It looks like the phototransistor is rated at 250VDC max, so it would probably be destroyed with a flash who's trigger voltage exceeds that level, but that's fine. Better to sacrifice the optocoupler than burn out my controller or my camera.
So far I'm using analog electronics for my trigger circuits, but I plan on using CMOS logic circuits (run at 5VDs) built around a micro controller. The microcontroller will allow me to add things like variable delay, enabling/disabling the whole setup, sequencing the triggering, quenching LED room lights just before opening the shutter, etc, etc.
The circuits I've built so far use a low-power PNP switching transistor like a C1740 to do the final triggering of the flash or camera. (I just connect the flash/camera trigger directly to the collector an emitter of the PNP transistor.) That works fine, but I wanted to provide some protection to both my trigger circuit and to my cameras/flashes. I've been using a 5-6 volt supply for my test analog circuits in anticipation of using regulated 5 volt supplies for my digital circuits.
I use Nikon cameras and flashes, which use very low voltage triggering (According to my meter, my hotshoe flash puts out about 3.6 volts. I haven't measured the trigger voltage from the camera, but I think it's also <= 5VDC.)
I bought some PS2501A-1-A Optocouplers, and am having trouble understanding the data sheet. Here's a link:
Datasheet for PS2501A-1-A Optocoupler
My questions:
Is the "diode" mentioned in the data sheet the LED on the trigger side of the photo coupler?
What is the minimum current needed at 5VDC to trigger the optotransistor "wide open"? It looks to me from the data sheet as if the LED needs 30 mA, but that it can tolerate .5A forward current. Is that right?
If I drive the LED at 30 mA and 5 volts, can I push 250V through the phototransistor? (I don't know how much forward current one of the older high trigger voltage flashes needs to trigger. It's my understanding that it is a transient voltage though. I believe that for these older flashes, the flash feeds it's flash tube voltage through the trigger line to a step-up transformer that generates something like 10kV, which ionizes the xenon gas in the flash tube, triggering the flash. If that's the case the current would be quite high for a tiny fraction of a second.)
If my trigger circuit can't trigger these old flashes that would be ok, although not ideal. At least the optocoupler would prevent damage to the other components in the system.


texts: How triac acts as a diode and two transistor?

texts: I'm constantly reading this fact that a Triac acts as a diode and two transistor. Can someone explain it.


texts: choice of parity bits for linear block codes

texts: We know that in linear block codes the codeword for a given a message is generated by multiplying the message with the generator matrix G . The generator matrix consists of a sub-matrix which is the transpose of the submatrix of H matrix which contains the parity bits. and another sub-matrix which is an identity matrix.I am curious to know how is the set of row vectors for the H matrix chosen . For example in the case of a (6,3) linear block code the H matrix contains a sub-matrix whose row vectors are made up of the parity bits . However only 3 possible combinations of 1's and 0's for three bit numbers are allowed to form the row vector of this sub-matrix . How do we decide which three bit numbers are to e chosen to form the row vector ?


texts: What do the "F+" and "F-" pins on a power supply unit stand for?

texts: I have a power supply unit I extracted from a media player and there is a pin connector with the labels "-24V", "GND", "F+", "F-". I know what the first two mean but what do the last "F+" "F-" mean? Also bonus points if you can tell me why there is a negative 24V rail but not an opposite positive one (24V)?


texts: I'm using nRF52 DK with 14.2.0 SDK. I created a LED blink project for testing and extract its HEX file. I uploaded the program to the nRF52 over USB (J-Link-Keil IDE) and the HEX file over ESP12E (SWD) to compare the register values between the working one (USB) and the non-working one (SWD). There is no difference between them. I could not understand why its not working when I uploaded the code over ESP12E. Isn't it enough to just write the hex file into nrf memory. I did some search on the web but I could not find any solutions working for me. Waiting for your replies. Thanks in advance,


texts:
Let's have a look at this photo:

It shows a simple preamp with C1 capacitor placed to avoid amplifying DC voltage (the loop closed for AC and open for DC). Unfortunately this capacitor limits the bandwidth and cuts off low frequencies. The higher the value of C1 is, the lower loss in bandwidth is achieved (and i don't want to lose bandwidth). So... I saw many circuits with 220 µF cap as C1 but not higher. Spice simulation shows, that rising the value to say 1000 µF visibly widens the bandwidth. Are there any negative consequences of rising the value of C1?


texts: Protecting 0/4 - 20 mA loop from over voltage/current?

texts: I'm building a device to read 0/4 - 20 mA loop currents using a 250 ohm precision sense resistor. The power source inside the receiver used for driving the sensors is current limited to 30 mA. Suppose that due to some fault or operator error, an external 24 volt supply (that is not current limited) is directly connected to the system input thus putting 24 volts across the 250 ohm resistor. This would result in 2.3 watts of dissipated power. Is there any way to protect the 250 ohm resistor from such voltages or am I forced to use a high watt rated resistor?


texts: Calculating Average voltage with integrator

texts:
I need to output a signal that is the difference between the average of two input signals, for this i have used the integrator circuit below:

how can i make the integrator output the average of input signals for each 1ms?
I want that the integrator calculate the average of the values in 10us, then start over again and calculate the average for other 10us repeatedly.
Appreciate the help, and sorry if my question isn't clear, i'm not that good in English.


texts: A question about a sensor in a metallic enclosure

texts:
I need to mount this sensor inside an aluminum or metallic enclosure. Then the sensor will stay inside the enclosure. The enclosure will be mounted outdoors on a bridge concrete or some part I dont know.

In above figures, blue is the cable for sensor wires, gray is the enclosure. Enclosure has IP67 rating so waterproof ect.

The sensor's metallic case is not connected to sensor ground. But when I inject earth noise to the case it somehow capacitively couples as noise.

I have too option: either I will directly mount the sensor's metallic case to the enclosure or I will mount it on a wooden or plastic plate and isolate the direct contact with enclosure.

Is it better to mount the sensor as in Figure 2?


texts: In a 2 layer PCB with a top layer densely populated, from an EMI & EMC point of view should the ground plane be on top, bottom or both and why?

texts:
Suppose I have a 2 layer PCB with the following characteristics:

Top layer is relatively densely populated by both THT ad SMD components
Bottom layer has very few traces

Among the following, what is the best option from a theoretical EMI & EMC point of view and why?

Top ground plane (copper pour)
Bottom ground plane (copper pour)
Both top and bottom ground planes with connecting vias

If you think another option not listed might be better please do propose it and explain why.

This is a theoretical question so I don't have a concrete example to show. Feel free to report some practical examples.

My guess is that option 2 would be the best since it allows for the current to choose the path of least resistance and avoid large loops, although maybe depending on the layout option 3 might also be reasonable.


texts: Is it wattage that kills you and not specifically amps

texts:
First of all the actual amounts needed to kill and the body resistance is not important for this scenario.
Let's say we are working with dc.
Let's say that 100ma is enough to kill across the chest give or take.
Let's say we have a generator with a constant voltage and maximum current of 10kv and 10ma.
In the right conditions, this could put 100 watts of power across the chest. How can this not kill?
My question is based on watts = volts times amps.
Exsample 10v 1a motor should give the same wattage as a 1000v 10ma motor.
Is it more likely there is not enough current to stop the heart but you would die eventually by being cooked!
I have asked this question many times but nobody can give a suitable answer. Or perhaps more like the reason for the answer.


texts: Is it possible to subtract one voltage from another without the use of an op-amp?

texts:
I've been watching a video on the early techniques used to create truly flat surfaces for precision engineering, and started wondering when it would first have been possible to develop an LVDT for measuring displacement.

The reading is the difference between the two vOut, meaning a subtraction is required.

Would this have been possible without an op-amp? And if so, how?


texts:
If you have a 12 bit adc, as the one in STM32F437, which of the following formulas do you use to calculate the analog value?

V = ADC_sample / 4095 * 3.3

or

V = ADC_sample / 4096 * 3.3

My question is similar to this one, however, I find the answers somewhat conflicting:

https://stackoverflow.com/q/892723/7689257

One answer linked to "The Data Conversion Handbook" and said that it should be the latter equation.

https://stackoverflow.com/a/7895054/7689257

The consensus in the answers dictate that you should refer to the datasheet of the adc, which is where I fail. I have tried to find the answers in the datasheet and reference manual:

https://www.st.com/resource/en/datasheet/DM00077036.pdf

https://www.st.com/content/ccc/resource/technical/document/reference_manual/3d/6d/5a/66/b4/99/40/d4/DM00031020.pdf/files/DM00031020.pdf/jcr:content/translations/en.DM00031020.pdf

I understand that the difference has no practical difference and perhaps not even measurable, but I want to understand the theory. Not only for the  stm32f4 but with other adc's as well.

Update:
Thank you for all answers, I am still not quite sure what to make of this.
 The comment from Scott Seidman on Ron Beyers anwser says that:

  Many ADC's can only go up to Vref-1LSB. If Vref is 3.3, the ADC has no
  code for 3.3V -- it is out of range."

How can you tell if the ADC goes to Vref or Vref-1LSB?

A post by Adrian S. Nastase, states that an ADC will never go to Vref:

https://masteringelectronicsdesign.com/an-adc-and-dac-least-significant-bit-lsb/

Update 2
After searching some more I found an application note for STM32 microcontroller ADCs (AN2834):

https://www.st.com/content/ccc/resource/technical/document/application_note/group0/3f/4c/a4/82/bd/63/4e/92/CD00211314/files/CD00211314.pdf/jcr:content/translations/en.CD00211314.pdf

Under section 2.2.1 it is explained about reference voltage noise, and the following equation is used to calculate the digital value if the input is 1 volt.

(1/3.3) * 4095 = 0x4D9

And with the same formula instead have a 3.3v input would give:

(3.3/3.3) * 4095 = (1) * 4095 = 4095

And the answer to this question is therefore(?):

V = ADC_sample / 4095 * 3.3

Because this is how the ADC works on STM32 microcontrollers, which is/might be different on other vendors.


texts:
I am trying to figure out how to configure the USART of the mentioned discovery board for a transmission of 14400,8,N,1. My problem is that I don't know what to put in the USARTx\$\rightarrow\$BRR register. I know it has something to do with the following formula (according to the manual):
$$Tx/Rx\;Baud=\frac{f_{CK}}{8\times(2-OVER8)\times USARTDIV}$$
And the BRR register has the following format:

What I know is that for a communication of 9600,8,N,1 the value used is
USART1\$\rightarrow\$BRR=0x00000D05 (is this supposed to be 9600?). I have understand the 8,N,1 part that are configured in the CR1 and CR2 registers.

I know that \$f_{CK}=32MHz\$ (I don't know if it can be changed somehow). The \$USARTDIV\$ value seems to be the one to be written in the BBR register, like in this example:

\$OVER8\$ is configured in CR1. Some tables like these appear in the manual that are supposed to help to compute the baudrate:

The clock tree used is the following:


texts: CNY70 and LM358 amplifier circuit not behaving as expected

texts:
I have reproduced a circuit proposed by Nicholas Burnett in 2013:
An improved noninvasive method for measuring heartbeat of intertidal animals please see Fig. 2
which looks as follows:

The circuit heavily reacts if I move my hand around it (also pretty far away), which can be seen by the indicator LED. It's a sign for me that it kind of works. However, it seems to be very noisy to me.
Is there a way to make this amplifier circuit more stable either by electronic parts, shielding or grounding it somehow?
EDIT1: The circuit was built as a PCB (source: Chinese manufacturer), please see a screenshot from EAGLE below as well as a photo:


texts: Doubt regarding the CMP instruction of the 8086 microprocessor

texts: In 8085,we've learned that the carry flag is SET,when the content of the memory exceeds that of the accumulator and that,comparison is always with respect to the accumulator.But in 8086,comparison doesn't always take place with respect to the accumulator.So how is the carry flag SET or RESET in this case?


texts: H-Bridge Transistor Smoking (Bipolar BJT Transistor)

texts:
I'm using the following circuit: Applied to the motor is 12V, and either high (5V) or low (0V) to each transistor through a 1kΩ resistor. The transistors are TIP 142 and TIP 147. The diodes are 1N5817.

When I apply 0V to R2, R1, and 5V to R3, the motor runs fine; voltage across it is 8-10V. However, whenever I connect 5V OR 0V to R4, the voltage across the motor is 1-2V, and the transistor at R3, starts getting really hot and smoking.

Why does applying anything to R4 cause this?


texts:
I have an input signal that is the sum of a DC and AC component. Lets say DC = +2.5V and AC = +-2.5 MAX (it can vary with time), 50Hz.

I know that I can implement a high pass filter with a simple RC network (maybe just enough with a Capacitor in series) but I wonder what could I get from an AD737 if I just use a passive resistor divider to move the 0-5V input range to 0-200mv required by AD737.

Could I, with this configuration, ignore the double supply requirement of AD737 and just connect VS- to ground?.

What about the LTC1966?.

PS: Input is a hall linear sensor measuring mains current.

Thanks!


texts: Controller to increase phase or gain margin

texts:
I can't find any good sources on this one. The only textbook I have says nothing about it. I've been restricted to the use of some formulas given by our teacher which I don't understand why they achieve the increase. He didn't want to work much on this kind of controller due to the little time we had left.

So how do I go about designing a controller which increase the gain or phase margin?

One thought: The gain margin is the gain for which the system is critically stable. Therefore moving the dominant pole further away from the origin could help increase the gain margin. As for increasing the phase margin to a specific value I have no idea. Phase margin is my main concern to be honest.


texts: Why weights on cables between utility poles?

texts:
Yesterday I saw what look like weights hanging from a cable between utility poles.  This was in northeast Arizona on Route 60 between Show Low and Springerville.  Here is a picture of a whole span:

The white blobs are the weights.  Here is a closeup of a single weight:

They appear to be just concrete blocks with no dashpot or any other apparent way to dissipate power.  These weights seem to be at 1/4 and 3/4 of each span, which would be the nodes of the first harmonic standing wave.  They would add inertia and affect the frequency, but is that really their purpose?  I can guess some possibilities, but I'd like to hear what these things are for from someone that actually knows.

Due to being a single cable, it must be for communications, not power, but I'm guessing that doesn't matter.

Added

Sorry, I added this note earier, but apparently somehow aborted the editor so that it wasn't posted.

To answer PlasmaHH's question, yes, these were on just about every span.  The bottom of the cable was quite high, and a little lower didn't look like it would have been any problem.  The bushes you see in the first picture are well in front of the cable.  There is a lot of clearance below the actual cable.  Even if there was a tall bush there, there would still be a lot of clearance.


texts: Doubts regarding via creation using pad designer

texts:
I have following doubt on via creation.

Is a via surrounded by soldermask or not? If it has a soldermask layer then what happens if there is no soldermask layer around pad?
Give me brief explanation about types of vias?


texts: Looking for a small inductor buck converter in a SOIC-8 package

texts: I'm looking for a buck converter in a SOIC-8 package which requires a small inductor (preferably ≤10µH) which can convert 6V-16V to 5V @ 1A. Unfortunately the package must be a SOIC package, because the person I'm designing for requires the SOIC package to be easy to place and solder. At the moment I've drawn a blank: all the high speed buck converters I have found only have a 6V or so maximum input voltage or they come in strange packages which are difficult to hand solder.


texts: Simple circuit analysis question?How to get 1V?

texts: The circuit.And why is there a negative 5V at the bottom?


texts: Can a USB device attempt to be bus-powered and then fall-back to self-powered?

texts:
The device has a battery, but it would be nice to be bus-powered when available.  A computer will typically supply 500 mA, for instance, while a smartphone in OTG mode is only required to supply 8 mA.

Is it possible to do something like this?

request 500 mA
if accepted: power from computer and charge battery from computer
else: request 200 mA
if accepted: power from computer
else: claim self-powered, power from battery

This seems to be what configurations are for:

  Therefore it is possible to have two configurations, one for when the device is bus powered and another when it is mains powered. ...
  Once all the configurations have been examined by the host, the host will send a SetConfiguration command with a non zero value which matches the bConfigurationValue of one of the configurations. This is used to select the desired configuration.

Is it enough to specify multiple configurations in the descriptors, one for each current requirement?  Does the OS automatically try them in order and move on to the next if one fails?

Multi-config USB devices and Windows seems to say that's how it works:

  During enumeration, USBCCGP will first attempt to select the configuration whose descriptor is found at the specified “original” index. If the attempt fails, normally due to the configuration requiring more than 100mA while the device’s upstream hub has only bus power, then USBCCGP attempts to select the configuration found at the specified “alternate” index instead.

However this doesn't work in practice?:

  “Microsoft drivers invariably work with just the first configuration of a device. The Microsoft support for composite devices won’t engage if the device has multiple configurations. Consequently, multiconfiguration devices seem to be rare in practice, and Microsoft discourages people from designing new ones.”

and:

  Microsoft drivers will only ask for the first configuration - and if that asks for too much current, so be it.

and:

  it is not common to have more than one configuration. Windows standard drivers will always select the first configuration so there is not a lot of point.

If multiple configurations don't work in practice, can the device detect that it's been rejected, simulate a disconnect and reconnect with a different set of descriptors?

(This is a question about the USB enumeration/communication part, not the hardware implementation of how to connect the battery, etc.)


texts: Looking for a three state relay or switch

texts:
I need to control the link between three wires:

Nothing touches == State 1 == Light is off
Red touches brown == State 2 == Light is on
Red touches grey == State 3 == Light blinks

A little drawing: edited by irfanview TS..

I control it through a raspberry.

I have it solved with 2 relays:

But I am wondering if there is a single electronic part that can manage this function (then save one relay?).

Any idea?


texts: What is the importance of Bypass capacitor of Common-emitter amplifier? Will the gain be reduced when it is removed?


texts: Sending data from Simulink Matlab to development board F28379D

texts:
I'm fairly new to Simulink programming so bear with me.

My project is to measure some parameters with the ADC of the board and send them over serial (SCI_A) to a Simulink file I'm running on my PC and then graph the data.

So far I've succeeded in doing just that, by uploading a program to the board that sends the data (using the SCI transmit block) and another program that's only run on my PC, reads the data using SCI receive (and of course a com port select block and a Scope block to plot the data)

Now I want to save the data that I get into a Matlab file, but since I plan to save days or weeks of data (multiple times per second), the file would become huge and I wouldn't want it to get corrupted.

So my first question is: Is there a way to SAVE the data (I've tried using a To File block) in chunks, say 1000 samples, then open a new file and start saving the new incoming data to that, so I'll end up with loads of separate data files?

My second question is: Uploading a program to my board takes loads of time and I have to do it each time I want to change a parameter. Is there a way I could receive the data I want to, but also use the same program running on my PC to send data back to the board and change its parameters?

To clarify: Let's say, for example, I want to measure an ADC input with the board, multiply the data by a number X and send that to my PC where I could plot the data and save it into multiple files when one file exceeds (for example) 1000 samples. If I choose so, I would also like to send the number X from my PC to the board, so that the multiplication factor changes.

I hope I've clearly stated my problem and I thank you for your answers in advance.

P.S: Again, I'm new at this so please be specific when answering, I would very much appreciate "explain this to your granny" answers.


texts: Interconnect capacitance and speed of data transmission?

texts:
Is the interconnect capacitance in a transmission cable is having an impact on the maximum data transmitting rate ?

Or is it only producing "crosstalk" ?


texts:
I have two multimeters. One is very good, the other one is quite cheap. I am measuring a regulated power supply to see if it is in indeed regulated. Both so 5.4 V, unloaded and loaded. This seems to indicate that it is in fact regulated.

When I measure AC voltage, the cheap multimetre shows 10 V, and the good multimetre shows 60 mV. I assume the cheap multimeter value is incorrect. Do you have any idea why this would occur?

Also, I am using this power supply for powering an Arduino 5V, supplying voltage at the 5V pin. It seems to work just fine. Do you think the extra 0.4 V will cause problems over the long run?

Thank you very much for your help.


texts: Desoldering/soldering 1/4" chip with eight pins

texts:
I need to transfer a working eight-pin 1/4" (4 mm) chip from the top PCB to the bottom PCB that has a non-working chip. Is there a special soldering tool for such micro soldering? Has anyone tried desoldering/soldering something this small?

Any special technique for this or can it only be done by machine?


texts:
I have used two X1 safety capacitors in series with an isolator (ISOW7842DWE). I have fault on EMC test on 64MHz. When I remove the capacitors, the EMC issue is reduced by 6dB.

I have used two safety capacitors to obtain 8kV spike protection.
I do not know why there are more radiated emissions on the board when I use the safety capacitors with the isolator.


texts:
It is time to choose the proper enclosure for a high voltage PCB. We will need to do holes for LV external connectors and external connectors for high voltage wires. I was looking for standard boxes from different providers' catalog and the most are offered in metallic (aluminium) material. I know that this material is often used due its conductivity. But I'm wondering how it may to have influence on isolation between conductors if I have some case surface connectors (bananas) at HV and the other ones at LV (or 0V). They will connect external wires with board components through internal wires soldered to the bananas copper connector (internal side). In other words, I would like to apply clearance and creepage distances between connectors at case surface, but they depends on kind of surface material, normally air gap or PCB sheets material. I don't know what happen when surface material has high conductivity like aluminium.

I have seen high voltage source (few kV), that has metallic cases and red banana plug is about 3 cm separated from black banana jack datasheet here

So if this is commonly done it would has a coherent explanation for not to use/offer another isolation material, as for example plastic since aluminium conductivity is "similar" to the copper, how can people deal with this? How can it be used for these applications?
If yes, what clearance and creepage distances will we need?
If these boxes were not correct for a portable device like this (V < 7 kV), how does developers get the correct enclosure for a high voltage PCB?

Notes:

PCB will be covered by conformal coat
A kind of silicone paste for coating the banana copper-wire junctions.
Kapton mask instead of solder mask.


texts: What's causing my 7.3728 MHz xtal to be unstable?

texts:
I'm using a 7.3728 MHz HC-49 crystal with 22pF disc ceramic load capacitors. I'm doing this on a breadboard, but I've had prior experience with using a breadboard for this and it has worked well, so I'm hoping this is not the problem. On the crystal, the following is written: "ACT Fo 7.3728SCA" and I've tracked the datasheet down to this one. The load capacitance is correct it seems - well within the specified 12pF to 32pF. I'm using with a PIC24FJ64GA002 microcontroller and the microcontroller is set to HSPLL mode, to generate a 29.4912MHz clock. The clock is a baud multiple, and it's very important it's stable. The expected clock is 7.3728 MHz within 50ppm, but the achieved clock is unstable and I can just about measure 20 MHz using my scope, but even that's tricky because it won't trigger well on such an unstable waveform.

Here's the waveform I'm talking about. Notice how unstable it is. Since I tried last night, it changed frequency from 20 MHz down to 10 MHz. What is going on??

My scope only has a limited sample memory of 1K and doesn't sample nearly as fast as a modern one (it does 10 MS/a real time, 10 GS/a equivalent time), but even so I should still be able see a clock frequency.


texts: does the battery determines the amount of current flowing in the circuit?

texts:
suppose a 9v battery is connected to a load which draws 2 amps of current. so how does the battery determines that load requires this much current ?
I mean if the battery throws about 3 amps, then it would just blow the load, so how the battery just supplies 2 amps and not just any other value?


texts:
Where is collection of data sheets of large table with parameters as columns and models as rows?

Something like:

Model        Breakdown_voltage On_resistance <other_values>
QWERTY122AS  120V              6_Ohm         ....
AWERTY123SD  30V               1_Ohm         ....
<all other popular models>

for transistors, diodes and other parts.

When searching Google it usually provides data for one/few models or even offer download a PDF file. Where to find it in bulk?


texts: Deriving currents of parallel mutual inductors

texts:
This is possibly just a math question, not sure.

In Irwin's textbook "Basic Engineering Circuit Analysis," 7e, there's a quick derivation for current in parallel inductors I don't follow:

The KVL equations are fine and make sense but the solutions for I1 and I2 don't. I generate a half page of algebra (when trying with substitution and subtraction of the linear systems of equations for V) and don't get there and Wolfram Alpha also doesn't come up with that simple of an answer. Is there a simple algebraic answer here?


texts: Increasing frequency response instead of gain for a Cascode circuit

texts:
so this a homework problem that I am working on and I'm not looking for a flat out answer, just a good place to start and some help on the concept. So the question is as follows:

Suppose our objective is not to increase the total cascoded gain, but rather keep it at the single common-source stage's gain of gmRL, and extend the frequency response. Develop the theory needed to modify the Bode plot to show the new cutoff and unity gain frequency.

So what I understand so far is that the corner frequency is dependent on both internal and external capacitances of the circuit and transistors. I know that I have to account for the miller multiplier so the internal gate-drain capacitance appears larger, making my corner frequency smaller? and I also know that the corner frequency is w=1/τi where τi is the sum of the time constants, and the time constant is the resistance multiplied by the internal and external capacitances. Would adding more capacitors at the output or input to lower the total capacitance? I think that both of those solutions actually increase the time constant so it's not the direction I should go in. what about placing a small resistance between the input and output of the individual transistors?

Thanks for the help!


texts: What types of fault protection is recommended for low voltage power supplies?

texts:
I'm building an AC-DC 120/15 V isolated power supply using a transformer, buck regulator for constant voltage, and a diode bridge rectifier.

I'm not sure what type of fault protection to implement, and what phase of the power supply it should be integrated into. I considered hiccup mode protection but it's very expensive and I'm looking for something cheap and simple. Any suggestions would be appreciated.


texts: How to derive formula for emitter current flowing through Re?

texts:
Ie = Ve/Re

I was thinking about using that approach but i have been doubting myself if that is the right approach to go with, because then i have to express the emitter current in term of alpha and beta
Can anyone clear my doubt please?


texts: Why don't microwave oven transformers state their output voltage?

texts:
This is a simple question that I haven't found in anywhere before: Why don't MOTs state their output voltage?
I mean, I've been in a junkyard looking for MOTs and I've found about 30 MOTs of 5 different manufacturers maybe, none of them state their output voltage and neither does the info I found online about them (when I search their code only I only find the same info that's on their label again, input voltage, power, sometimes input current).
I know that measuring the primary-to-secondary ratio is damn simple, I just need to feed the secondary with line voltage instead and measure the primary, and I also know the output is < 2.1 kV because of the capacitor used.
But why don't they even mention it?
I couldn't be sure of what one had the highest output voltage while in the junkyard.


texts: Modifying 12V PSU, how do I identify the +12V Return Sense?

texts:
I'm trying to build a 13.8V/14.4V @ 30A power supply, to charge a lead acid battery bank.

For the purpose, I've read that some server PSUs are excellent for the purpose. They are typically able to provide high currents at 12V, and have sensing circuits that can be fooled into supplying a higher voltage, typically up to 14.2V.

Here is an example: https://www.rcgroups.com/forums/showthread.php?1005309-A-simple-high-quality-12Volt-100Amp-Power-Supply-Part1/page107

I've purchased a Dell PS-2521-1D, which was advertised as AA23300, and I've read that they should be the same. It can provide 12V at 44.5A.

Unfortunately, after opening the case, I see that the PCB is a completely different design, yet the pin-out has the same AA23300 layout.

I've tried to identify the voltage sensing circuit by using the multimeter to test for short circuit between the +12V and any of the chip pins. I didn't find any connections direct connections.

The MOSFETs have ~26V on the drain side when powered on, and 12V at the source side.

The gate of the MOSFETs are all connected with a short circuit (0ohm), to the pin in the pictures below. This is the only pin connected to the gates of all the chips.

I've looked at the chips, but the protective coating makes it difficult to read the names.

The names of both chips is EZ22601 with an "ST" logo. But I didn't find anything on Google.

The PSU provides 12V@44.5A and 3.3V@4.9A. Perhaps these two chips are for regulating those two voltages?

Is this the correct voltage sensing pin?

In the other tutorials, they seem to just slap on a different voltage. But since the resistance is ~0 ohm, wouldn't it be necessary to isolate the pin from the 12V sense?

UPDATE:
I've identified some additional information.


texts:
I need to communicate from FPGA to ARM with about 16GBits/s...
Is there a Bus which I can use? Or how to solve this problem?

The FPGA receives data over LVDS. This data schould be post-processed in ARM (User can write some linux-based software to store the data on SSD)

btw. FPGA and ARM will be on the same board ;)


texts: Building a small 4-bit adder on a breadboard

texts:
I am very new to using IC and basically a breadboard in general, but I am doing a project on how computers add and thought it would be nice to have a practical demonstration.

My main question is, for the parts that I am going to list out, would a 5 volt input be ok? What size of resistor should I use to get a 9 volt battery down to 5 volts? And what size resistors would I need to use for the LEDs?

Parts:

C&K BD01,
Lumex SSF-LXH400SRD,
ST M74HC08B1R,
TI SN74LS32N,
TI SN74HC86NE4,

I am new to all this.


texts: Li-Ion Battery Charging using current controller

texts:
For a single Li-Ion battery cell charging process, one needs to do a CCCV cycle, in which first the li ion cell is charged using a constant current (of rating 1C normally), and when a specified voltage (4.2V) is reached, the battery is charged in a CV constant voltage cycle where the battery of the voltage is kept constant until the charging current falls to a specified value (normally 0.1C).

If i am charging my battery cell using a buck converter (a buck converter taking a PWM input from a micro-controller which is continuously monitoring battery's currnet, voltage and temperature), and i have designed a current controller for my buck converter to charge the battery, i will force some amount of current into the battery cell during the CC cycle by varying the duty cycle of the PWM (the amount of current would be increased and decreased by varying increasing and decreasing the duty cycle of my PWM respectively). When the battery cell Voltage reaches 4.2V, i have to now apply CV cycle to continue the charging process.

My question is regarding this Constant Voltage cycle. And the question is that would i apply the constant voltage cycle the same way i was applying the CC cycle? except now i would consider the battery voltage to be controlled, and against it i would be decreasing my PWM duty cycle in a way that the this voltage remains constant, and as a result of decreasing my PWM cycle my charging current would be continuously decreasing until it reaches a pont where i stop the charging. Am i right ? I mean to ask if the current control method would be enough for both the CC and CV method ? Which means ultimately in the CV cycle also, i would be controlling the current by decreasing it continuously, in such a way that my battery cell voltage doesnt go above 4.2V, am i right about it ?

I hope i made myself clear about my confusion.

Your helpful suggestions would be appreciated.

Thankyou!


texts: How to connect PBI to detect an open door

texts:
What's the best way to connect a wired magnetic contact stripe [edit: a "reed switch"] to the door, in order to detect whether or not it's open.

I'm not interested in a wireless one, I'm building all the circuits from scratch, so I want a wired one.

The way I thought to do that is, to use a push button interface (in my case, a KNX PBI), and connect it to the a magnetic contact stripe on the door.

Here is an example for a KNX PBI.

On the door the magnetic contact stripe would close/open the circuit and notice the PBI when the door is closed/opened.

My question is, what's the best location to place the PBI? Should I place a switch near the door, and put the PBI behind it?

Should I pull the cables of the PBI far, to the fuse box?

(Migrated from home improvements SE site, as seems more relevant here.)


texts: Issues using an Ultrasonic Sensor with Raspberry Pi

texts:
I am conducting a project which needs to use a precise ultrasonic sensor but I am having trouble working it with the raspberry pi. The sensor I’m using is the Senscomp 600 series; the manual isn’t available online but I’ve posted a few relevant pages here. I realize the sensor works on 5V logic but I figured a 3.3V signal would be enough to set the Trig port to logic 1 (as it was enough for another 5V logic sensor I’ve used in the past) and I could simply use a voltage divider to bring the output Echo signal down from 5V to 3.3V. However after connecting the circuit it does not seem to work. The issue could be that the sensor requires a higher Trig voltage (it says +4V in the manual so maybe that’s the minimum), in which case how could I increase my signal voltage? I’m not very familiar with this, but I’ve read of people using a transistor to output a 5V signal using a GPIO pin and the 5V pin.

Alternatively the issue might be my set-up. The manual calls for a pull-up resistor to be established to a 5V power supply, but since the logic is 3.3V for Raspberry Pis, I have the Echo pin pulled up to 3.3V. Here is a diagram of my circuit:

I am pretty new to circuits, but as I understand it, the echo pin with a pull resistor acts like this:

 when the Switch (in this case the echo pin from the sensor) is open, the MCU (in this case the Raspberry Pi) will read VCC (logic 1), and when the Switch is closed, the MCU will read 0V (logic 0). If this is how it works, pulling up to 3.3V should work perfectly find for the raspberry pi (I think).

Also note that I have the sensor connected to an external 5V power supply and is not drawing power from the raspberry, as is suggested in the manual. The python code I’m using measures the time from when Trig is set to True, to when Echo is measured to be True, then multiplies it by the speed of sound. Any advice on what I could try would be much appreciated. As always, thank you very much!


texts:
In my textbook, the author showed the calculus derivation of what value of load resistance is needed such that it will absorb maximum power from the source, while keeping the Thevenin voltage and Thevenin resistance fixed.
After that, the author asked us to repeat the derivation for the case where the load resistance is fixed while the source resistance is variable. It seems logical that the the source resistance has to be zero for maximum power transfer to the load. However, I can't seem to get the answer via differentiation.
I tried differentiating with respect to the source resistance but the numerator has no Rt term.


texts:
Curious on your thoughts for an application and the pros and cons of using a relay or a MOSFET or IGBT.

The application involves switching a 96V lead acid battery pack on and off for periods of 5 minutes upto 1 hour, there is no PWM involved so just hard switching.  The load is just resistive and the current will be in the region of 20A.

For this sort of application I like the idea of a MOSFET as lower drive current and voltage, but would be interested in the pros and cons as far as reliability etc.


texts:
I need to produce an extremely low noise SPDT switch. This switch will take two different inputs to a single 16 bit ADC. The inputs are 50 ohm BNC outputs from trans-impedance amplifiers. The amplifiers take a small current and convert them to 0-10V DC (they operate between 200 KHz and several MHz). This signal is then sampled at a rate of 1 MHz to 80 MHz, depending on application.

Currently I use the following component:

http://www.jfwindustries.com/products/50S_1313_12_SMA_Electro_mechanical_Switch_from_JFW_Industries-368-76.html

I tried to design a simple PCB using an OMRON relay. However, this introduced significant baseline voltage as well as noise (100-250 mV plus noise).

Does anyone have any ideas on how to design such a circuit? I tried some off-the-shelf RF switch ICs demo boards but nothing handles DC and/or they clipped at VCC = 3.3V and I need transmission to the full 10V range.

Is there something special about getting a board built at 50 Ohm controlled impedance? I used a single IC to power the relay and a 7805 regulator to provide 5V (the ground is shared with the SMA connectors and power supply).


texts:
I am currently doing a project which requires the measurement of forces on a surface and to achieve this we are using 3 wire load cells.
The problem that I am running into is no matter how I orient the load cells in a circuit, I cannot seem to notice a notable difference or consistency in voltage supplied to the analog input of my board. I have most recently tried a Wheatstone Bridge layout which I found online. It seems as though the voltages measured through the circuit are always consistent, regardless of what I put on them.
I have achieved success in an online implementation with an Arduino Library, however I had to be using a Arduino board and I do not have this luxury. In my project we are using the CC3220SF Launchpad XL by TI for its wireless communication abilities in another portion of the project.
Does anyone have any ideas which may be able to help me achieve some sort of a measurable reading with these load cells?


texts: Need for ''stiff'' bias voltage in this emitter follower?

texts:
Here is my circuit:
It is intended to drive headphones with low distortion, and be driven by fairly high impedance source (~500R).
The trouble is maintaining a very high input impedance with high quiescent current, the values for a voltage divider needed to create a 'stiff' bias voltage (10 times the base current) on the base are quite low, the values in the schematic are already assuming a generous Hfe of around 200.
I think the CCS helps with this, with the bias current remaining constant with changes in emitter voltage, so only current to the actual load will affect beta
So instead the divider could be sized to 10 times the peak load current which is much lower...
Correct me If I'm wrong on anything.
I'm wondering what the effect on the ratio between the divider and base current (or in this case load current divided by beta) has on the output signal (distortion etc.)?
'1/10th' seems to be just a general, minimum figure and may not be ideal choice for this..
While the CCS may allow to use higher values in the divider and still have 1:10 ratio, it could also let me use a higher ratio (e.g 50:1) using lower divider values for a bias voltage.


texts:
I'm trying to figure out how to model a transformer in order to estimate the number of transformers on a bus line. Each transformer is connected in parallel and may or may not have a connected load. I've been able to collect some empirical data from an available device, but I'm having trouble formulating an equation to satisfy that data.

I would assume that, ignoring hysteresis and eddy currents for simplification, calculating a bus like this would be a simple matter of combining the primary-side resistance/reactance with any referred secondary-side resistance/reactance and then adding these resistances in parallel with all other transformers connected in the bus. But when I perform actual measurements, my calculated numbers are off. When testing a circuit with  (transformers are a simple 1:1 ratio), the measurement is closer to 75 ohms rather than approximately 71-72 ohms (adding 13.52k + 5k + 3k + 75 in parallel). The measurement will also continue to stay relatively close to 75 ohms rather than dropping to the low 70s/high 60s that I would expect when introducing lower load values.

What exactly am I missing here?


texts:
For example, if a phone comes with a charger rated at 5V and 0.7A, when it's plugged in to charge, what dictates the current the phone draws, is it the resistance of the phone?
If I = V/R, do phones typically provide little resistance so that the current is the max the charger can provide? i.e in the above example, if the phone was off, would it constantly be drawing 0.7A, and if the charger was changed with one rated at 5V and 2A, would the phone draw more than 0.7A? could it reach 2A?
...bit of a side question, but when the phone is done charging, how does it stop drawing current? again if I = V/R, does the phone have to alter the amount of resistance it is providing? how does it do that?

I'm only looking for fairly simple answers to be honest as this is just a general query and not something I need to go in depth with.

Thanks.


texts:
First off: I realize that my problem could be solved by simply using a few power strips with built in on/off switches, but I do not want to do that. I look at this project as being a learning opportunity.

For aesthetic reasons I have hidden most of my electronics (PC peripherals etc...) under my desk. However in doing this I have sacrificed ease of access. Since I do not want to have to continually plug/unplug my devices but also do not want to leave them constantly running, I would like to add a switch box (to the side of my desk) where the power cords for a variety of these devices each are connected to a switch.

There are two types of power supplies I would like to add a switch too:
1) 120V AC
2) 5-20V DC (what comes off of many of the AD/DC converters that come with my devices).

Note for each of these devices I am not dealing with particularly high currents (again think normal household electronics, speakers, monitors, laptop...)

If, for each of these devices I have just two wires (+) and (-/Neutral) is it safe to simply cut one of them and add a switch?

If not what would be the proper way of handling this? Do I need a different approach for High Voltage AC and Moderate Voltage DC power cords?

Thank you very much for your help!


texts:
I have an Arduino BT V06 that I could connect to my Mandriva 2010 linux laptop: "rfcomm connect" is working, /dev/rfcomm0 virtual serial port is created, "hcitool con" shows the connection and "hcidump" displays my upload attempts.
However when I try to upload the BlinkWithoutDelay example I got the following error message (upload.verbose set to true in .arduino/preferences.txt):

/usr/local/arduino-0021/hardware/tools/avrdude -C/usr/local/arduino-0021/hardware/tools/avrdude.conf -v -v -v -v -patmega168 -cstk500v1 -P/dev/rfcomm0 -b19200 -D -Uflash:w:/tmp/build8547029001705996442.tmp/BlinkWithoutDelay.cpp.hex:i

avrdude: Version 5.4-arduino, compiled on Oct 22 2007 at 13:15:12
        Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/

        System wide configuration file is "/usr/local/arduino-0021/hardware/tools/avrdude.conf"
        User configuration file is "/root/.avrduderc"
        User configuration file does not exist or is not a regular file, skipping

        Using Port            : /dev/rfcomm0
        Using Programmer      : stk500v1
        Overriding Baud Rate  : 19200
avrdude: Send: 0 [30]   [20]
avrdude: Send: 0 [30]   [20]
avrdude: Send: 0 [30]   [20]
avrdude: ser_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding
avrdude: Send: Q [51]   [20]
avrdude: ser_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding

I was struggling for several hours to solve the problem.

I am using Arduino-0021 but I have also tried it in 0018 and 0015 without luck. I have also tried with board type BT Atmega 168 and BT Atmega 328. My Arduino Duemilanove works fine with the same computer, Arduino 0021, and settings.
I have seen several question with the same topic http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1290646119/1 or http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1247005623. They mention differing error messages and anyway I cannot see how can I press the reset button on the Arduino during the upload when I have to type the PIN in a different window.

What could be the solution to the problem?

What I could imagine is to buy a BlueGiga WT11 chip extension to my Duemilanove and do the upload via USB. But how could I be sure that the connection for the communication will work?
Moreover I still would like to use the not-so-cheap Arduino BT board.

Update:

Based on Nick T's answer I have tried again but the BT still does not work.
I have tried to press the reset button
- 3 seconds before,
- just before,
- at the same time of the upload button hit
and
- when the first two/three avrdude lines appeared
- after the first two programmer is not responding lines appeared.

Altogether 20 times without success.

Even when the arduino environment has not been started and I press the reset button on the board the connection is lost (checked by hcitool con) after 1-4 presses.

Are there any other ways to solve the problem?

Do I have to buy a BlueGiga WT11 and hope that the bluetooth connection will work while the USB connection stays OK?


texts: How to find a design house with dynamic memory device support?

texts:
I am looking for a design house with dynamic memory device support. Design houses, I found on the web, support only analog, mixed-signal, high-voltage designs and so. I found no design house with dynamic memory support. Whatever I missed, I have no idea. To be honest, I am totally lost in the practice of the microelectronics industry.

Could anyone please point in the right direction, which design house should I contact? Also, thank you for any advice in advance.


texts: I have a little bit confusion about the current in the 40 ohm resistor given in the picture below. Will the current be zero?


texts:
I was looking for a SMD diode to add reverse-polarity protection to a circuit I was designing, and the PMEG3020CPA looked like a good fit with regards to my current and voltage needs.

What confused me is why the data sheet shows two anodes, so I have a few questions about that:

Are the two anodes meant to be connected? E.g. the two internal diodes would be in parallel. Or should only one be used?
Are the current and voltage ratings given for each of the internal diodes, or both together?
Why is it designed or diagramed like this?

I ran into this question about three-terminal diodes but that seemed to be one diode and a floating third pin, which isn't really relevant.


texts: Electronics components casing or packaging style types and diferences?

texts:
Is there any good visual guide or reference that explains the different types of casing styles like these ones that I come across every time I try to buy a component on farnell website:

017AA, 0201, 0402, 1005, 403A, 403C, Axial Leaded, DFN, DO-15, DO-201,
DO-201AE, DO-202AA, DO-204AC, DO-204AL, DO-214, DO-214AA, DO-214AB,
DO-214AC, DO-215AA, DO-216AA, DO-218AB, DO-221AC, DO-222AA, DO-41,
Flip Chip, FlipChip, MicroSMP, MLP, MSOP, NSOIC, P600, R6, SC-70,
SC-74, SC-75, SC-88, SLP1006P2, SLP1616P6, SLP2510P8, SLP2626P10,
SMD, SOD-123, SOD-123FL, SOD-123W, SOD-128, SOD-323, SOD-523, SOD-923,
SOD-963, SOIC, SOT-143, SOT-23, SOT-323, SOT-363, SOT-523, SOT-553,
SOT-563, SOT-666, SOT-723, SOT-953, TO-263, TO-277A, TSLP-2-19,
TSLP-2-20, TSOP, TSSLP-2-3, TSSLP-2-4, TSSOP, UDFN, UQFN, WLCSP, WLL-2-1

Often I buy through hole components and I would want to know which of above casings fit my needs but I have no clue (Except from the "Axial leaded" one which is obvious), but also I want to learn about the other types.


texts: High efficiency pwm current limiter for charging supercap from alkaline battery

texts:
I'm designing device which uses two alkaline C-batteries in series as power source, and sends SMS messages using SIM800. On average 1 message per day is sent. Goal is to maximize battery life.
Allowed operation voltage for SIM800 is 3.6V-4.4V, and peak current around 1000mA while sending. Alkaline batteries are known for NOT having good recovery effect with pulsed discharge, so plan is to limit the current around 50mA-100mA and slowly charge the 1F supercap, then using power from cap to send the message.
The whole idea of using current limited charging is to improve overall battery efficiency, so obviously current limiter should be as high eff as possible.
I figured to put the current limiter to low-side, as N-channel mosfets are better in general, lower Rds, lower gate charge, so better efficiency and can be driven with MCU gpio as is.
I came up with a low-side design like this:

There is MCU on board, and PIC[1..12] bus goes there. VCAP_MEA measures low side voltage and VCAP_DRV drives the mosfet. There is no current sense, but as ESR of C1 and coil L2 properties are known and pretty much static, i figured i can make it close enough with measuring the voltage and ramping up the PWM as voltage rises..?
For coil L2 i planned to use NR6028T101M.
Vdd is 4.3V and comes from TPS61023 based dc/dc boost converter, 1.6V-3.6V from two alkaline cells is boosted to a 4.3V.
The problem is, i have very little to no experience with custom switching circuit designs. Would that design even work as planned?
What would the efficiency be, does it make any sense to use approach like that or am i better off getting the 1A peaks straight from the batteries?
How will switching frequency affect the efficiency? I did some simulations with 100kHz and picked the coil accordingly, so that the simulated voltage looks reasonably smooth.
Part descriptions:
Coil L2 - NR6028T101M - 100µH Shielded Wirewound Inductor 660mA 780mOhm Max
https://www.digikey.fi/product-detail/en/taiyo-yuden/NR6028T101M/587-2105-1-ND/1866245
Mosfet SSM3K127TU,LF
https://www.digikey.com/product-detail/en/toshiba-semiconductor-and-storage/SSM3K127TU-LF/SSM3K127TULFCT-ND/10380188
Capacitor DGH105Q5R5 - 5.5V, 1F, ESR 260mOhm.
https://www.digikey.com/product-detail/en/illinois-capacitor/DGH105Q5R5/1572-1771-ND/7387509


texts: I'm connecting 3 phase motor to frequency converter and I don't understand why to use shield cables. Is using shield cables a must in every situation or only when nearby is running a Profinet or other sensitive signals?


texts: Need chargeable momentary 15 watt regulated voltage source

texts:
I'm working on a RF telemetry side-project that requires an amplifier IC to be run for about 5 seconds bursts between charges. The system is portable and runs off of a 3.3V battery that can supply about 100 mA. The IC runs at 10V and draws 1.5 Amps, so 15 Watts. I can't simply use a boost converter on the device's battery because it can't supply nearly that much power. So I need to store the necessary charge and then dispense it at a regulated voltage.

The output voltage of my charge storage system should be well regulated at 10 volts, and I need it to be able to supply a constant 1.5 Amps for at least 5 seconds, after which I will turn it off and recharge it.

The goals here are to minimize size and amount of time it takes to charge the thing. I assume the solution is either going to be some sort of battery or capacitor with some circuitry to regulate the voltage output.

I don't know very much about practical charge storage and power regulation, but if someone knows a good general approach I can look into the details.

edit: Assuming money is no object, anyone interested in elaborating on using a super-cap?


texts: Can I link mismatched parts with jumper wires?

texts: I'm out of my element here and I don't know much about electrical engineering so please excuse the bad terminology. A light on my car stopped working and it's a long story but the easiest way to fix it is to retrofit a newer light to the old connector. The female adaptor of the old part is square while the new part is supposed to take a round adaptor. I wanted to know if I can connect the two parts with jumper wires rather than doing what others have done like shave the sides of the original adaptor or trying to solder the exposed terminals inside the round socket.


texts: How much background "noise" is normal on an oscilloscope

texts:
Following this question, I purchased a DSO-2090 USB oscilloscope.
When I power it up, I see lots of small fluctuations in the waveform, whether connected to nothing, a battery source, itself (small waveform generator on the back) or by shorting the ground clip.

(See the large version)
In the screenshot above, the CH1 is connected to a small, battery powered circuit of mine. CH2 does not have the probe connected at all.
I have spoken to a colleague about this and was told that I should see a flat line so I am worried I have purchased a faulty unit.
My question is whether or not background noise like this is normal in an oscilloscope?
Edit 1
Added 1kHz waveform example as per comment:

(See the large version)


texts: What is the purpose of the three part circuit?

texts:
I'm studying for my final on introduction to circuits and came across a question about this circuit:

The question is:

Identify and describe the three parts of the circuit used for a measurement system for signal conditioning.
Describe the signal conditioning one intends to use the circuit for.

From what I can tell the R1 and R2 resistors are the first part of the circuit used to use a fraction of the incoming voltage. The second part is the voltage follower used to move all of the incoming voltage to another circuit. Lastly there is a low pass filter used to filter off the high frequency voltage.
The second question I'm not sure of the answer.