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121

1. Capacitors There are a lot of misconceptions about capacitors, so I wanted to briefly clarify what capacitance is and what capacitors do. Capacitance measures how much energy will be stored in the electric field generated between two different points for a given difference of potential. This is why capacitance is often called the 'dual' of inductance. ...


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Development to 50,000 units every six months? I wish all my projects went like that :) If you don't have the experience there's no reason you can't hire a consulting company to make the board for you. It won't be cheap but they'll get the job done. It's a little riskier too if you don't know the guys you're hiring enough to trust them with the design. 50,...


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For example, why do I see it suggested to use ceramic caps for power decoupling per microprocessor & a larger electrolytic capacitor per board? why not use electrolytic all around? The three main types have differing characteristics - I suggest you do some research on them but the main things to look for are self-resonant frequency (brought about ...


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First things first. You do not, repeat not, wait until the board is laid out to design the enclosure. Not if you want to be a professional. The circuit designer must work closely with the mechanical designer. For equipment incorporating pcbs, the following need to be considered: power supply location and dimensions, thermal limits (both from the board AND ...


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Engineering is not only about creating robust designs, but is about creating a design that meets some specifications. Usually young designers don't fully understand that economic factors are part of the specification. The problem is that sometimes those economic factors are not well specified (that's often a management's fault), but a good designer is ...


49

You are looking for a slip ring. This is a device designed to do exactly what you describe - transmit power and/or signals to a rotating object. Generally, they work by having a rotating circular contact on one side and a spring-loaded pin which pushes against it on the other. They are not super reliable long term or in harsh conditions, but should be ...


47

An alternative to slip rings is the rotary transformer. This consists of two cup-shaped cores that face each other, with the windings inside the cups. If you drive the primary at a high frequency (we used 25 kHz), the cups can be ferrite and the whole thing can be quite compact (we did about 100W in a unit that was about 1" thick overall and about 3" in ...


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I'm a professional electrical engineer who routinely designs new circuits for volume production, and have been for over 35 years. Yes, I frequently do calculations to determine the exact part specs. There are also many cases where experience and intuition are good enough and the requirements loose enough that I just pick a value. Don't confuse that with a ...


41

Advantages of holes in shield: Allows some air flow for better heat dissipation. This is the primary reason. Less weight. Small holes don't really compromise the shield, as long as the holes are significantly smaller than the wavelength of what you want the shield to attenuate. As a aside, you won't ever see long slots in RF shields. If a larger overall ...


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In my experience the widespread use of simulation of entire boards is mostly a myth outside of physics simulations in RF. Simulation rules for IC design of course, because the prototyping costs are so insane, and for anything involving HDL design, but for general electronics, not so much. Where the sim really helps is for things like filters and control ...


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Everyone can edit source code at home, very few people have a chip fabrication plant to knock out a couple of custom chips. Bytes are free to create and distribute, materials are not. There's also the issue that source code is portable, and although CAD files etc. are sort of portable, there's a lot more overhead & errors & setup cost wasted ...


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To answer your comment on three-phase torroidal: Because it seems, per wikipedia: Toroidal inductors and transformers, that the design should be superior. But I see no mention of three-phase usage, only single-phase. Figure 1. 3-phase transformer flux. Source: NPTEL. In a three-phase transformer each primary and secondary pair are wound on the same "...


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Three coils, in magnetic series as you've drawn them, will not make a 3 phase transformer. There would be only one value for flux which would be common for all three coils, as each coil surrounds the entire core cross section. In a real three phase transformer, each coil surrounds only part of the core, so that each coil can operate at a different flux. A ...


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If your project is going to use an FPGA for the grunt work, and it has the spare capacity, why would you go to the expense of an extra chip when you can just implement it in the FPGA? For many procedural control environments it can be considerably easier to implement the required setup in a language like C than trying to do it in VHDL or Verilog. By adding ...


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Benefits: blazingly fast interface between the microcontroller and any custom interface or I/O logic on-chip. customizable processor and debug interfaces also, often easier control logic than writing the control code with, say, VHDL Downsides: Possibly more expensive FPGA is needed to fit both the microcontroller and the custom logic, compared to just ...


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Why not just leave it disconnected? Because of the way the IC is made. It starts off as a (relatively) large piece of doped silicon, and the features are deposited / etched / implanted into one side. That leaves the back side of the die electrically connected to one node of the circuit. Which node it is depends on what circuit is being made. Generally ...


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Precision. Internal clocks are not precise, can be affected by noise. Temperature independent precision. Typical oscillators can vary wildly. Specialty temperature compensating oscillators can be needed in low or high temp applications, or if temperature varies wildly. Speed. Internal oscillators may not reach the highest speed of the IC. External ones can ...


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The points highlighted in this image (produced by @AnindoGhosh): Are called Fiducial markers. A fiducial marker or fiducial is an object placed in the field of view of an imaging system which appears in the image produced, for use as a point of reference or a measure. It may be either something placed into or on the imaging subject, or a mark or set of ...


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Saturation is always an issue in both transformer and inductor design. If we're going to spend money on a heavy and expensive iron core, then we want to work it as near to saturation as we can. The reason inductors are gapped, and transformers are not, is that they are trying to do different things. The purpose of an inductor is to store energy. This ...


23

There are several aspects influencing the grade of detail the structuring of a project needs. For me one of the main factors is whether I'm the only one coding (what seems to be the case for you as you write you're the only EE) or if there are others involved. Then there's the question of what "large" actually means. Usually I divide the design process into ...


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Frizting looks like the ideal tool for this: Free (GPL license) Multi platform (Linux, Mac OS, Windows) Integrates a large library of components The stripboard can be resized, you can chose the strips to be vertical or horizontal. You can also cut the contacts with your mouse like you would do in real life. Example circuit: Edit 30/10/2018: Make sure you ...


22

If you're only making one it's entirely reasonable to just order a plastic project enclosure (all sizes are available) and then drill and cut holes yourself. The issue it seems you're trying to overcome is a lack of craftsmanship, you can help alleviate that problem by purchasing the correct tools for the job. The other keys are practice and patience. ...


22

I program small micro-controllers in C++, which achieves exactly what you want. What you call a module is a C++ class, it can contain data (either externally accessible or not) and functions (likewise). The constructor (a dedicated function) initilializes it. The constructor can take run-time parameters or (my favourite) compile-time (template) parameters. ...


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Personally for hobby projects I tend to use the most powerful microcontroller in the family with the right footprint. I then develop the PCB, write some code and produce a prototype. This has the advantage that I know the small number of microcontrollers fairly well, so I can rapidly prototype without having to read a whole datasheet. I also have breakout ...


20

I'm with you 100%. That said, there are things (for example hFE) where you have to trust that things don't go too wonky between (say) two guaranteed points and that nothing in the physics and typical curves would suggest any kind of weird behavior. If you using a cut-and-try approach, which may actually be the practical way to deal with complex parasitics ...


19

Limiting the current and the voltage effectively limits power, since power \$P\$ is the product of voltage \$E\$ and current \$I\$: \$ P = IE \$ Since bench supplies are commonly used for prototyping, where faults are commonly introduced mistakenly, this is a big win. Many faults that would normally destroy a device will instead not destroy the device if ...


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I have been designing some PCBs recently and I would suggest you NOT to use auto-placer or auto-router for your final product. (Proteus has auto placer.) First of all - Your software is as intelligent as an earthworm when it comes to auto placement or auto routing. In other words, it's dumb as a potato. Auto routing would not know which placement will get ...


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A common way of doing this is with a self-locking worm drive The worm drive has a gear ratio that provides high mechanical advantage and depending on the helix angle of the gear, the output can't backdrive the input, so it is self locking. You can find one here at Servo city or try to DIY with hardware store threaded rod and an off the shelf gear. Another ...


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Even though the Motorola 68000 and the Sega Genesis are quite old (early 1980's), you are not going to find a low-end (i.e. 8-bit) AVR that can emulate the entire game machine. The Sega Genesis ran at 7.61 MHz and had 72KB of RAM (plus an additional 64KB of video RAM). However the game programs resided in ROM, so you will need additional RAM to hold them (...


18

The best error catching technique is to show it to someone else and step him or her through the design. You would be amazed how often you find something obvious.


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