Hot answers tagged

27

You will need to check the datasheets for each part with unused pins. In many cases grounding them is a BAD idea, though in many other cases it may be CRUCIAL. And in some cases you SHOULD leave the pins floating. For example, do not connect outputs directly to ground, as this could cause a short. Do not leave inputs floating, unless they have internal pull-...


17

The transparent conductors are ITO (Indium Tin Oxide) deposited on glass. They're not easily solderable (perhaps possible with an ultrasonic soldering iron but even then they would likely be mechanically very weak). You can use an elastomeric connector (zebra connector) as Dave Tweed suggests, but you'll need a closely matching pattern (preferably gold ...


17

If you check the HW Design Manual then you'll see that it suggests the unused pins should be left floating. Please refer to Table 4 on p.15 and p.16.


13

One thing you CAN do when laying out the PCB is to ground all pins via a resistor on each pin. Then you can fit 0 ohms for a solid ground, 1K or 10K to stop the pin floating (without damage if something drives it, plus you can pull it high during test), or infinity (no resistor) if you must leave it floating. Final decision can be made for each pin during ...


10

You can't, it's a very thin layer of printed-on metal. As Dave says, you need a Zebra strip or similar pressure connector.


9

The 2-2.00 dimension (your Y) is 2.00mm, but it applies to two identical holes (2-) on the datasheet. Only one of those holes is dimensioned for length, the other is dimensioned for width, to avoid an excess of lines and dimensions cluttering the drawing. You are expected to figure out which pair of holes are the same size from the symmetry of the drawing. ...


8

You can try using anisotropic conductive tape. Adafruit will sell you a 50mm x 150mm strip. It's double-sided tape that only conducts through the thickness of the tape when you press it between two surfaces. That way, you can make multiple independent electrical connections without shorting them. Make a PCB with exposed contacts of the same pitch and ...


7

It's a perfectly valid choice. An even beefier way is to use a wire jumper on the board but that costs manufacture time. This is nice, it just happens when you flow solder. I suppose you might get the odd solder bridge if your manufacture setup isn't perfect. But easily found and fixed. Also the trace is now exposed, which will make arcing or shorting more ...


6

As mentioned by others these aren't meant to be soldered to. In theory with indium based solder it might be possible, but it's really not worth the cost of the attempt. If this originally had a thermally bonded flex cable, you can often non-destructively remove those from the original board with a hair dryer. You can then stick them to a compatible PCB ...


6

Unused output pins should just be left disconnected. For unused input or I/O pins you need to read the datasheet and/or make some discisions. As another answer points out the datasheet for your simcom device says you should leave them floating, so that is what I would do in the first instance. As a general rule though, a CMOS input should not be just left ...


4

The circular trace is an inductor, what it's doing in the circuit is hard to tell, without looking at the other components in the circuit. It looks like it's connected to a ground plane along with the screw. They removed the ground plane around the inductor to avoid capacitance with the ground plane. The thing could be an antenna. The "spark gap" really ...


4

I don't think you have to length-match the traces. In write mode, the critical timing parameter is from when the last (slowest) address or data line is valid, relative to the WE. In read mode (OE controlled), the critical timing parameter of from when the last (slowest) address line is valid, relative to the OE. By putting the meander line lengths in, you'...


4

NASA recommendations are that you support the lead on the component body side (for example, with needle-nose pliers) and make equal bends at least two lead-diameters from the body. In this case, the 'body' would be the limits of the epoxy fill in the bottom. So, grab the lead with the pliers at least two lead diameters from the body (there should be a ...


4

The copper is etched into conductive paths between components to connect them electrically. Components are soldered from their terminals to the copper, to make firm electrical connection, and also to keep components mechanically attached to the PCB. The more copper layers there are, the more complex wiring is possible.


4

It's almost certainly an astable multivibrator, or LED flashing circuit, which is a classical circuit and one which is often a first project. Here's a tutorial on one. https://www.build-electronic-circuits.com/astable-multivibrator/ Try following the tracks on the bottom of the PCB and see if you can match it to the diagram in the tutorial I linked.


3

Ethernet RX and TX pairs have literally nothing to do with one another. It's a full duplex channel. You would never need to concern yourself with this, because they are independent.


3

The size of the eMMC package is limited by the size of the silicon chip inside the package. Its size can't be reduced (with current available technology). The number of pins could be reduced, yes, but it would also make it mechanically weaker, because the package would still be fairly large. There needs to be enough pins to keep the package mechanically ...


3

I'll add it as an answer, since the comments are getting big... You should not supply 12V to the ATMega328. 3V3 would be a better choice here so you don't have to use level-shifting on the I2C lines. You are pulling up the reset to 12V, change this to 3V3 as well. You have 2 different grounds defined. This can cause problems and you should probably decide ...


3

I would have commented on the great answer but my reputation doesn't allow it. :D If you want to be precise and follow best practices on your projects always follow IPC standard eg. IPC-A-610-F.


3

It is supposed to flash the LEDs alternately. Here is a likely schematic using similar part types and values. I've made it a bit asymmetric by changing R1/R2 by +/-10% from nominal (and skipped initial condition) so it will start reliably. simulate this circuit – Schematic created using CircuitLab Below is a simulation in the Circuit lab ...


2

You are seeing "blistering". I can't really see the material you're using but if it's something like FR1 paper base phenolic it won't take much heat for very long. A typical spec would be 10 seconds. 30 minutes is a very long time. Most copper-clad laminates are made by large companies and are of rather high quality (in that they meet all the ...


2

Thanks a lot for your answers. Texas Instruments kindly explained the reason for those resistors: The in-line resistance acts as part of a low-pass filter given the input capacitance is 3pF at the START and STOP pins. This is to prevent false-positives otherwise created by high-frequency transients-glitches at these pins.


2

Use the most sensible name that will mean the most to most people. If the footprint connection is to a switch then call it SW1 or SW2 etc.. The switch is soldered to wires that connect to the circuit board so, it makes sense to provide meaning in the footprint name. If the panel switch is an SPST type you could even call it SPST1 or 2 etc..


2

One simple way is to copy the device into your own library and modify its package there. If you continue using Eagle sooner or later you'd have to make your own devices. This seems to be a good time to begin. And while you at it I'd recommend adding pin names to the display package, it might be helpful later for connecting jumper wires.


2

Several potential issues exist that I can see. Firstly, your "decoupling caps" should be as close to the pins they are inteded to decouple (usually the IC power pins). This can cause all sorts of weird behaviour in digital circuits. Your D+/D- diff pair is not routed with constant spacing, which could cause signal integrity problems due to impedance ...


2

I imagine that you can do whatever you want in the pink zone so long as you keep all the conductors as-is in the area used by the antenna (green/white zone). As for ground plane the image is a two layer board and the plane under the microstrip (the vertical; part above the socket) should be retained at the same distance to maintain the impedance match. If ...


2

The surface finish should be something like ENIG (Electrolytic Nickel/Immersion Gold) for reliable wire bonding. Here are a few other options, none of which is HAL.


2

It depends on your design requirements, such as highest signal frequency and EMC (electro-magnetic compliance). But in general for audio type signals it doesn't matter too much. The power plane will act like a ground plane next to signal layers, so you want to use as much copper as possible on the power planes as well. If your traces need to match a ...


2

I've had a read of various articles and got out few things: Length and impedance matching are two very different things Length matching has meaning when you have fast rise/fall times Documentation must somewhere state need of length/impedance matching Each bus (data, address, control) should preferably be routed on its own layer. As I ...


2

You need to edit the schematic symbol for that. In the properties of the pin, simply tick the "Draw Body" checkbutton, if I rememeber correctly.


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