Activity for Olin Lathropâ€
| Type | On... | Excerpt | Status | Date |
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A: How do I calculate and manipulate the inductance and capacitance of outputs to a connector on a PCB? It's not completely clear, but it seems you are asking about a circuit in a class 1 div 2 location that will drive another circuit in a class 1 div 1 location. The point of the IS barrier is to present a Thevenin source. In other words, the two important criteria are the open circuit voltage and ... (more) |
— | almost 4 years ago |
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A: Digital circuit that squares a 4-bit input No, I have not seen this circuit before, and don't know what source you may have gotten it from. However, I'm not sure that really matters. I don't know what exactly you are trying to teach, but most likely the derivation of the circuit is the real lesson. The actual circuit is of little use, an... (more) |
— | almost 4 years ago |
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Let's have a "Papers" category. Currently, we have two categories, Q&A and Meta. Those seem to be working well. New topic type available A category can now be created where there is a single post per topic, with only comments allowed on that post. The Meta site uses this for their Blog category, and the Cooking site for the... (more) |
— | almost 4 years ago |
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A: Humming noise from a boost converter's inductor First, draw schematics properly when you ask others to look at them. Your right to left flow is rather annoying. There are two main possibilities for this circuit to cause noise, the inductor and the output capacitor. Inductor The inductor can make sound for two reasons: Every bit of wir... (more) |
— | almost 4 years ago |
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A: Switch-off time of relay with flyback diode It doesn't quite work that way. You are missing the fact that the current (which the magnetic field is proportional to) decays exponentially. You are also missing the resistance of the coil itself. First, let's analyze what happens with just a diode. You basically have this circuit: Image al... (more) |
— | almost 4 years ago |
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A: When to use RTOS? RTOS A RTOS (Real Time Operating System) is much more than a bunch of interrupts. Most true dedicated microcontroller applications don't need any RTOS or any other kind of operating system. General OS (operating system) An OS adds a layer of abstraction between your application and the hard... (more) |
— | almost 4 years ago |
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A: What is a bootloader, and how would I develop one? Bootloader definition A bootloader is a program that runs in the microcontroller to be programmed. It receives new program information externally via some communication means, like a serial port, and writes the information to the program memory of the processor. This means that bootloaders ca... (more) |
— | almost 4 years ago |
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What is a bootloader, and how would I develop one? I've heard that a bootloader is code that runs on a microcontroller, and is used to get your application code onto the micro. How does that work? Is there anything special that needs to be done to write a bootloader? If a bootloader is for getting code onto a micro, how do you get the bootloa... (more) |
— | almost 4 years ago |
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A: Low loss impedance matching without a transformer As an alternative to doing the math, as detailed in Andy's answer, you can use a graphical aid called a Smith chart: Image alt text These were used routinely before computers to match transmitters to antennas. The math behind them is what Andy described. See the Wikipedia page for details, wh... (more) |
— | almost 4 years ago |
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A: Chokes, Beads and Inductors in Pi-filters Pi filters are often used to block high frequencies between a device and the power line it draws power from. In such applications, the considerations specifying the inductor include: How much power current needs to pass, preferably unimpeded by the filter. What frequencies need to be attenuate... (more) |
— | almost 4 years ago |
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A: Pi-Filter for EMC First let's define what a "Pi filter" is: Image alt text The name comes from the inductor and two caps forming the shape of the Greek letter Π. These filters are used for EMC compliance because they attenuate high frequencies. At minimum there is a L-C filter, which attenuates by 12 dB/o... (more) |
— | almost 4 years ago |
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A: Tools required to burn code in a quad flat microcontroller The days of socketed microcontrollers are long gone. In most cases, the socket would cost more than the micro. Nowadays, microcontrollers, whether in quad flat pack packages or not, are surface mount soldered onto boards along with all the other parts. There are then two ways to get the program ... (more) |
— | almost 4 years ago |
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A: Tagline/Mission Statement/etc. The short phrase is trying to capture the two broad classes of topics here: Electronic things, like opamps, transistors, microcontrollers, 20 W power supplies, and the like. Utility-scale power systems, like multi-MW generators, large over-land transmission lines, local distribution systems of ... (more) |
— | almost 4 years ago |
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A: Moving average that uses less memory? You can't eliminate all noise, use no memory, no processing cycles, and not add some lag. However, you can do much better than a brute force "moving average" filter. FIR versus IIR filters There are two broad classes of digital filters, FIR (finite impulse response), and IIR (inifinite impu... (more) |
— | almost 4 years ago |
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Moving average that uses less memory? My control system gets a signal representing the plant output, but that signal has a lot of noise on it. The control system goes nuts trying to react to the noise. I need to filter out the noise somehow, but preserve the basic plant response. I heard about a moving average and tried it. It hel... (more) |
— | almost 4 years ago |
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A: Viewing the potential live output when editing a question or answer. I recommend using native HTML for lists, and most other formatting for that matter. HTML gets around the ambiguity of what is an item and what is text following the list. The list isn't over until the </ol> tag. For more information about formatting, see the Formatting Posts document in th... (more) |
— | almost 4 years ago |
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A: Driving LED with NPN transistor from I/O pin First, let's redraw the circuit a little more clearly, with logical flow left to right. This also protects the answer from possible changes to the question. Image alt text As you say, Q1 is a switch to control the LED. Most likely, a separate transistor was used to keep the LED current out of... (more) |
— | almost 4 years ago |
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A: How to calculate pullup resistor value for pushbutton? To understand this issue, we have to look at how your circuit works and what the pullup does within it. You have a pushbutton you want to read with a microcontroller. The pushbutton is a momentary SPST (Single Pole Single Throw) switch. It has two connection points which are either connected ... (more) |
— | almost 4 years ago |
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How to calculate pullup resistor value for pushbutton? What value pullup resistor should I use for a pushbutton connected to a microcontroller input? Image alt text I've seen values from 1 kΩ to over 100 kΩ. Some references just say to use 10 kΩ because it's a "good value". How do I calculate this to decide for myself? (more) |
— | almost 4 years ago |
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A: Driving relay, transistor keeps failing The reason the transistor is dying is because you didn't put a flyback diode across the relay coil. Relay coils have significant inductance. This means the current can't change instantly without the voltage being infinite. It takes voltage applied over time to change the current thru an ind... (more) |
— | almost 4 years ago |
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Driving relay, transistor keeps failing I'm trying to drive a relay according to a 5 V digital signal, using this circuit: Image alt text It works for a while, but then the transistor fails. When I replace the transistor, it works for a while again, then fails again. The transistor is rated for 600 mA and 40 V. I'm only running 63... (more) |
— | almost 4 years ago |
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A: Replacement power supply voltage and current ratings? Voltage Rating If a device says it needs a particular voltage, then you have to assume it needs that voltage. Both lower and higher could be bad. When no tolerance or input voltage range is specified, ±5% should be close enough. ±10% will probably be OK most of the time. I wo... (more) |
— | almost 4 years ago |
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Replacement power supply voltage and current ratings? If the external power supply to a device fails, and I can't get the exact model, what do I need to specify to get the right replacement? I can re-use the old supply's connector, but what about the voltage and current ratings? How close do they need to be to what it says on the device? What i... (more) |
— | almost 4 years ago |
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Are we there yet? Are we ready to let the world know about this site yet? What, if anything, do we still need to do or set up first? I have created a bunch of help pages that are intended to give newcomers a good idea how to use the site, and what is expected of them. There is an infinite amount of information th... (more) |
— | almost 4 years ago |