New answers tagged

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My educated guess is either that: You have damaged (perhaps by ESD) MAX3221 chips that are creating a short across the power rails. You have a bad batch of PCBs (it's been a very long time since I've seen hair shorts on PCBs, but I have seen them from a Taiwan maker many years ago and they were in the 10-100\$\Omega\$ range. If you've purchased claimed ...


3

First, disconnect power to the circuit, then short the IN and OUT pins of the regulator to ground. Now, check your resistance from OUT to GROUND and see if it still gives you a low resistance. If you still find that 100 ohms, then start removing components from your PCB. Remove one component that connects to OUT from the regulator. Check the resistance. ...


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It depends on the current through each MOSFET. But if power comes from your 3 A Power supply strips seems wide enough to avoid any voltage drop. Pretty sure the voltage drop will be much higher in your connectors. So I think 1st PCB is OK.


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I managed to achieve a hexagonal hatch by using a solid polygon pour, and a series of hexagonal polygon pour cutouts. Its not the quickest or most accurate, but without knowledge of scripting or some complicated import process, its the simplest way to do it. Start by drawing a hexagon with lines, (you may need to do some trigonometry to be accurate) then ...


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One thing that you can do is convert the track/primitive (in my case a drawing imported from .dwg) to keepout, that worked out form me: Select the objects then go to: Tools>Convert>Convert Selected Primitives to Keepouts


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Is any of these options better from the point of view of signal integrity/EMC? Assuming your RGB signals are somewhere between 1.8V and 3.3V logic and given the fact there are single-ended signals, they will be prone to emission. If this is indeed on your concern list, I would recommend a couple of options which I've used in my past experiences: Use ...


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Thermal considerations are very very important for the proper implementation of Low-Dropout regulator designs. Texas Instruments dedicates a full section about this topic in their datasheet page 19 (https://www.ti.com/lit/ds/symlink/lm1086.pdf). Do you know how much current is your circuit pulling from 3.3V? Let's take a simple example and assume the LDO is ...


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Possibilities: LM1086 has abs max Vin of 27V. Be sure 24V supply is always < 27V You do not say what max current is at 3.3V or LDO regulator package or heatsinking. 24V to 3V3 is a LARGE drop. You dissipate 100 mW per 4.6 mA of current drawn. Minimum capacitance values are specified in the datasheet. They may be larger than expected. LM1086 needs ...


2

If you make 3.3V from 24V with a linear regulator, you will dissipate about (24V-3.3V) * drawn current = 20.7 V * drawn current. So, for e.g. 100 mA, this is 2.07W. Although the LM1086 has a thermal protection and won't get easily damaged, the thermal protection will reduce the output current or even just shut down the regulator. In both cases, it is ...


1

Are you sure you're using the 3.3V version, and not the adjustable version? This is not clear/mentioned in your schematic. You are using a linear regulator. The dissipated heat will be (24V - 3.3V) * Iout, so the output current multiplied by 20,7 equals the dissipated heat. Last but not least, a 0.1uF capacitor is not suitable to be used as filter ...


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Single ended impedance is the trace impedance with reference to ground. Differential Impedance is the impedance between two differential pair signal traces. So i think both needs to be matched if you want to work at rated high frequency. Also need to be within tolerance range as in USB case it is 15%. Reference : http://www.ti.com/lit/an/slla414/slla414....


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Mostly yes. The vast majority of 16 pin DIPs have a 0.1 inch lead pitch and a 0.3 inch width (measured from the Center of one row of pins to the centre of the other row) You do see the occasional special component though, for example I have used some high isolation optocouplers, which came in a package that was like an 8 pin DIL but with a 0.4 inch width ...


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Almost yes but No. . Please check datasheet for each part. There will be slight differences which you will be able to accept or adjust.


1

Interesting failure, and not surprising when you feel how loose the bases often are. I think you'd be more than fine with a couple drips of epoxy or non-acidic RTV silicone between the can and the plastic base before the cap is mounted. Personally, I'd use 5-minute cure dollar store epoxy.


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We use some sort of structural adhesive for these kinds of applications, where staking is required. Since this is for a high-volume ECU, I assume the proper structural/vibration analysis was done? If so, the first thing you need to do is go back to that analysis analysis and figure out where the disconnect is between the model and the real world. Then you ...


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Perhaps looking at the case, you can add some thick tape or something else that you come up with to the top part, which would push down on the capacitor (gently), since the case will be vibrating the same direction as the PCB it should be fine.


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RTV silicone is used for this (and to adhere components to PCBs permanently in general). The neutral cure kind that doesn't produce acetic acid and smell like vinegar when it cures. So not most of the stuff you will find in hardware stores. RTV-162 is one of the purpose-designed silicones for this but it's almost more than double the cost of some other ...


1

As I said in the comments, before attempting to stabilize a converter of any type, you need its control-to-output transfer function. The problem here is that the data-sheet of this Alpha & Omega chip is eloquently empty so difficult to figure out what its internals are. Anyway, I have captured a schematic using Elements, the SIMPLIS free demo version in ...


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The ground/reference plane to either microstrip or coplanar waveguide doesn't have to be on the bottom layer of a 4 layer PCB. If you are looking to reduce the width of your impedance controlled traces, you can certainly use either layer 2 or 3 for the reference plane to reduce the height.


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I just saw this question is still open. in my project I left the center pad unconnected and it works fine. I just took 1 part and measured -> the center pad is not connected to GND internally


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It means you have to worry about transmission lines effects such as ringing, propagation delays, and reflections for RF and high speed digital circuits. It also means you have to worry about leakage currents for high impedance circuits, and interplane and parasitic capacitances for circuits dependent on very small values of capacitance. You also have to ...


1

I had the same problem and after some headaches, I realized that the nucleo board I was using has the clock coming from the st-link locked in at 8MHz. CubeMX default settings had it set to 25MHz for me. Switching HSE to 8MHz (bypass mode) did the trick!


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It's just the inductance due to the plane over the distance (2). So it is part of the loop inductance. From Intel AN 574 (they have nearly the same picture): The spreading inductance is design dependent and scales as a function of the dielectric thickness (h) between the power/ground plane. It is determined by the spatial location (d) of the ...


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Press TAB while routing and it'll open the properties of the trace, then you can change it there. If your new width choice is outside your design rules it'll give you a pop up about that and then revert back to the previous width. If the latter is happening, then you need to change your design rules for the PCB.


2

I have been building my own power supplies since the mid 70s. The primary reason for doing so is that whatever power supply you buy is only just so good and I've seen hundreds of them fail. When I design, I factor in at LEAST 100% overkill. In most PS designs, the overkill is at max about 50%. That is just not acceptable to me. I have even built a couple of ...


2

A traditional power supply based on a line-frequency transformer is reasonablly easy and safe to build, since the only things on the main side are the line side of the transformer and any protective devices. All the electronics are safely on the isolated side of the transformer. However at typical electronics power levels, line-frequency transformers are ...


2

i have been working on power supply from transformer and to flyback SMPS, and some PS i create is definitely overpriced / overcost even the basic power supply with common transformer. it didn't even worth it to create "The best most stable PSU", it just not worth enough your time and cost but probbably just enough for experience, if you are not even have a ...


1

I'm going to ignore the risk of electrocution or shock, since 110V is weaksauce anyway and you'd have to be super unlucky to actually hurt yourself with it. That said, the major downside for me is that the cost of components to build your own power supply is much higher than just using a mass-produced wall-wart or phone charger. Additionally, unless you'...


3

To try to expand on a few answers a little... Firstly, if you're talking about a low-voltage PSU (ie. something that takes 12V or 24V in and pushes out 12, 5, 3.3 etc - then I'd say it is worth doing yourself, although you may find breakout boards that do a lot of what you want are available pretty cheaply. These days, little buck converters seem to be ...


3

Here's how that works in the real world. Option 1: Use a Wall-Wart that is already UL-listed. You design the DC side of the product, and pack it off to UnderWriter's Laboratories to be tested, along with some of the wall-warts. UL sees the wall-warts are already UL listed, and makes no further investigation. They focus on the low voltage behavior of ...


2

I assume it is on the PCB you want include the symbols. You can make them as mechanical symbols and add the graphics there. The symbols need to be prepared as BMP file in MS paint or something similar. Create a new mechanical symbol. Under the File->Import->Logo menu you can import a BMP file to the silkscreen layer. Select the correct file and click ...


5

Sure you could buy a supply or but if you want to learn and time for your hobby is not a problem then take a shot at a power supply. Manufactures spec sheets have a ton of info and often reference designs. A stop-gap or workbench solution if you need more power is take an old PC supply and hot-wire the startup, remembering that some require a load before ...


5

35 or more years ago, almost every kit radio and electronic hobby project required building some sort of linear power supply. Diode bridge, or even vacuum tube half wave. Most Apple 1’s, for instance, have two big transformers. A whole bunch of us old computer hobbyists, engineers, and scientists are still alive. One doesn’t learn nearly as much ...


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Even for mass-market consumer devices it's often worth it to not design a custom power supply, or even integrate an off-the-shelf power supply into the device. Going with an external power supply saves you from having to design & certify the device to avoid shock hazards, and once you do that you might as well use a commercial off-the-shelf external ...


3

As far as I know a transformer, bridge rectifier and a circuit with several LM2596 or other switching power supply IC to generate 3.3V, 5V and 12V doesn't seem hard to make, but are there any downside other than risks of shock ? Linear power supplies are quite simple to make, and the risk of shock is low if you properly insulate the mains side and keep ...


17

If you're building a few for personal use, I'd say it's not worth it unless part of your goal is to learn power supply design techniques and principles. Even then, it's much safer to get a wall wart to convert your line to, say, 12VAC for safety. If you're planning to go into production with it, you should consider your volumes first. The lion's share of ...


7

To design and implement an off-line power supply is indeed dangerous, since the 110/220 V at the mains and the rectified DC voltage can be lethal. Other than risk of shock, one need to take care of clearances and protections. I would recommend to someone without experience in the subject to buy a power supply, like your Meanwell power supply. A cheap PC/...


0

Well, it is just semantic, but a couple of thoughts: If you have any part(s) that generate significant amounts of heat (e.g. a regulator, large processor) then you would factor in where that hot air will go. As warm air rises, this would usually imply that the these components will be mounted on the top of the board so the air can flow unimpeded. For sanity,...


1

This is a frequent topic in our team and mechanical team. There is no guideline as such. More or less it is truly opinion based The PCB side which will finally face the user (examples are the PCBs which have buttons or displays facing the user) we call it top layer. If there is no such way to identify, then the side where we have components assembled (one ...


1

Your solution seems right to me. If you really need to separate AGND and DGND (which is not so obvious), then keeping DGND near the digital components and AGND near the analog ones is the best you can do. Short answer: There are no cons without further Specs.


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More common way to define is subjective. Whatever method you choose, be sure to review thoroughly with respect to recommended PCB foot print from the datasheet of the actual micro controller. We have seen variations in the package dimensions as well as special pads considerations. Apart from adjusting the pinout please verify about the pad dimension ...


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Start from a good existing one as a template.


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