|
I want to implement a low-pass filter with a non-linear/arbitrary group delay. That is, I specifically want to delay slower frequencies by a different amount than higher frequencies. There's lots of stuff out there on the group delay properties of different filters, but I'm not having much luck finding anything on how to specifically design for a desired group delay response. Any suggestions?
|
#
?
Dec 16, 2020 16:30
|
|
|
|
| # ? May 28, 2024 09:16 |
|
|
You could go for the all out general filter design theory. I think cameron's book has a section on group delay.
|
|
#
?
Dec 16, 2020 17:23
|
|
|
You'll probably have better luck finding material on designing filters with a given phase response rather than group delay. Group delay for a given frequency is just the slope of the phase response at that frequency, so if you take your group delay function and integrate it, you get a phase response function you can plug into a filter design method.
Stack Machine fucked around with this message at 18:20 on Dec 16, 2020 |
|
#
?
Dec 16, 2020 17:26
|
|
|
How many different bands do you need? Could you do something like band pass a signal at different cutoffs and run each band through separate delay lines?
|
|
#
?
Dec 16, 2020 17:32
|
|
|
I found a book in my collection that has a chapter on designing filters with arbitrary phase response. I don't understand it well enough to sum it up, and the book describes everything very clumsily. It is also in German : "Synthese elektrischer netzwerke und filter" by Unbehauen.
|
|
#
?
Dec 16, 2020 18:03
|
|
|
FISHMANPET posted:So let me preface this with the fact that I have no idea what I'm doing but the best way for me to learn something new is to just dive in to the deep end with a project that's way over my head. Like a year ago I started this, and got some useful information here, but the pandemic and lockdown and work from home hit, and I couldn't really get the enthusiasm to work on a project that was for a bunch of people gathering together in a room, and I dropped it for a while. Well, I'm picking it back up, and I've got another (hopefully) simple circuit question. The whole point of this is just an elaborate rube goldberg machine to push a button and send a signal, but it's all about show and ceremony. I want to control power to the device with a key. I've got a keylock, the CK-L12B. I want my device to not power on unless the key is inserted and turned (and the key can't be removed when it's on, so using the device will require the key). If the key is turned "off" I want that to cut the power. The simplest way I could do that (I think) is to put my keylock inline with the +5V coming directly off the power supply, so when it's in the "off" position it just breaks the circuit, and putting it in the on position completes the circuit, like this:  But my switch is only rated for 3A, and I my PSU outputs up to 5A. I suspect I'm well under 3A of current draw right now, but I haven't done all the math, and I might also be in the future adding additional components to this that might push me over 3A, so I'd like to not do the inline route. Based on earlier experience using a mosfet to trigger an LED (you can see by looking at my post history) I'm thinking I might be able to achieve this with a mosfet? I'm imaging something like, while current is flowing through my toggle key switch, it signals the mosfet to allow current to flow into "the thing." I made a lovely diagram, but obviously not knowing what specifically should be wired into what, or even if this is the right path, it's obviously not very detailed.  I've found some information on using mosfets to toggle power using a momentary switch (press the button, power is toggled on, press the button, power toggles off) but not using a toggle switch like this. Maybe this can't be done with a single mosfet, and I need something like this instead?
|
|
#
?
Dec 16, 2020 19:54
|
|
|
The sane solution is to get a keyswitch that is rated for 5A. With the kind of fun project you have, I would look for a nice loud and big old fashioned relay.
|
|
#
?
Dec 16, 2020 20:01
|
|
|
Switch a GPIO and power the thing from a normal battery/wall wart hidden inside it. Have the actual mcu powered normally/practically and treat all the presentation/flashy stuff as IO. That's both easier and gives you more freedom to do fancy effects. You can have a flashing light labeled 'MAIN POWER' without it actually being related to power. You could do things like have 'power' be a big chunky knife switch, or have to turn keys simultaneously if the inputs don't actually do anything to make the circuitry work (If you do just want to use that 3A switch with a 5A power supply that you never overdraw, put a 3A fuse in front of it)
|
|
#
?
Dec 16, 2020 20:15
|
|
|
Agreed that big clunky relays look cooler, but if you want to use a MOSFET, use a P-channel logic level power FET and use this circuit: The switch will only need to pass half a milliamp if you do this so it'll last practically forever. Stack Machine fucked around with this message at 03:33 on Dec 22, 2020 |
|
#
?
Dec 16, 2020 20:18
|
|
|
I would also suggest a big clunky relay if you want it to be showy and preposterous.
|
|
#
?
Dec 16, 2020 21:05
|
|
|
Foxfire_ posted:Switch a GPIO and power the thing from a normal battery/wall wart hidden inside it. I would do this, if I'm understanding correctly your proposed plan means you have to wait for the Pi to boot up? And then it also gets a hard power cut at the end? You really don't want hard power cuts with SD cards, they work by erasing huge (relatively) blocks when you have to change some data. You also don't really want to use a journaling filesystem on one, so there's a high chance of data corruption. If you want to use the switch on the power, I'd probably just ignore the rating and use it anyway in this case to be honest. I can't imagine you'd be using anywhere near 3A sustained (my official power brick for the Pi 3b is only 2.5A), let alone 5A. And since you're supposed to be in the room with it, if it does catch on fire it's part of the show, right?  Edit: You can of course throw a 3A fuse inline with it if you're concerned Forseti fucked around with this message at 22:12 on Dec 16, 2020 |
|
#
?
Dec 16, 2020 22:01
|
|
|
There's a separate button that will actually "shutdown" the pi, so I'd use that before cutting the power with the key. The primary reason for the key is to provide some (tiny) semblance of security, since the button would deploy software to our environment, I don't want anybody to just grab the box and start doing stuff (there's other things in software I can do to prevent this so the key isn't my only line of protection). The Pi itself won't draw anywhere near 5A, but I've got 7 LED switches, a 20x4 character backlit lcd display, and a couple of NeoPixel ring lights. Still I'm guessing nowhere near 3A, but I may add more to the system in the future (earlier this year in this thread I discussed adding some additional rotator switches with some LEDs). I might put this all together without the switch being functional, but at least order the parts to play around with that kind of circuit in the future, so I can get some semblance of done. I've got N-mosfets but no P-mosfets...
|
|
#
?
Dec 16, 2020 23:52
|
|
|
Ahhhh, I see, I interpreted your diagram to mean that the LEDs and such were getting their power from the GPIOs (and therefore be limited to somewhat low currents) and the 5V supply would just be going straight into the Pi. Stack Machine knows waaaaay more about electronics than I do so I'm sure there's a reason I don't know about but I think you could put an N-type on the USB port's ground side and use it to sink the current from the circuit rather than source it with a P-type?
|
|
#
?
Dec 17, 2020 00:20
|
|
|
I’m getting back into electronics now that COVID has given me enough free time to actually learn and do poo poo with it. Is the Hakko FX888D still considered a good go-to soldering station, or should I think about dropping a bit more cash on a Weller/Cooper thing?
I. M. Gei fucked around with this message at 05:46 on Dec 17, 2020 |
|
#
?
Dec 17, 2020 05:31
|
|
|
Forseti posted:If synths sound like fun to you that would be a great place to start I think. Get yourself a 4046 PLL and jump on in. Oscilloscopes are awesome but expensive if you're not sure you'll stick with it. For an audio synth though, you can probably get away with using a sound card as an oscilloscope since you'd be looking at audio frequencies mostly in such a project.. I'd get a cheap USB one so you don't have to worry so much about damaging it by feeding it too much voltage though. Shame Boy posted:If you're into synths a classic place to start is building an Atari Punk Console, which is just two 555 timers that output various square waves: Jumping in on Cheese Thief's question about learning for audio-making stuff, if I wanted to get together all the pieces necessary for four or five projects, without having to pay €6 shipping on each IC I need for the next project, and to get me up to speed right at the very start, is there a list anywhere of what I should be getting first off to start up (including the inevitable practice I need with cock ups.) Immediately I know I need a; Soldering station Flux (of some size) Wire Strippers Pliers Wire (of some size) Breadboard (of some size) Resistors (of various sizes) Potentiometers (of various sizes) Batteries Something to connect the batteries Perfboard And the ICs (which I don't even know which ones I do need.) That's a lot to put together without some guidance, never mind what I left out and filling in all the "various sizes" with actual specifics. There's no electronics shop within 200 miles of me, so realising I need something involves ordering a small piece at hefty price with a delay in shipping.
|
|
#
?
Dec 17, 2020 05:52
|
|
|
I. M. Gei posted:I’m getting back into electronics now that COVID has given me enough free time to actually learn and do poo poo with it. Is the Hakko FX888D still considered a good go-to soldering station, or should I think about dropping a bit more cash on a Weller/Cooper thing? Yeah, it's solid
|
|
#
?
Dec 17, 2020 05:56
|
|
|
I. M. Gei posted:I’m getting back into electronics now that COVID has given me enough free time to actually learn and do poo poo with it. Is the Hakko FX888D still considered a good go-to soldering station, or should I think about dropping a bit more cash on a Weller/Cooper thing? The Hakko is great. My personal iron is the older analog model and the one you linked is the model I have at work. Years of use on both and zero complaints.
|
|
#
?
Dec 17, 2020 06:25
|
|
|
Mrenda posted:Something to connect the batteries Battery holder. If you're just testing, get one that holds more batteries than what you need. It's fairly simple to connect up your croc clips and test leads to the springs inside to get the voltages you need. kid sinister fucked around with this message at 06:55 on Dec 17, 2020 |
|
#
?
Dec 17, 2020 06:52
|
|
|
Mrenda posted:Batteries I'll start with this because it's an easy question. If you're getting started with analog audio and don't want to spend the money to get a benchtop power supply of some kind, a 9V battery and a bunch of 9V battery clips will serve you well. Op-amps, transistor amplifiers, 555s and their ilk, comparators like the LM339, will all be quite happy at 9V. Nothing digital will, but using a cheap linear regulator to get to 5V or 3.3V from 9V isn't totally out of the question either. If you're more interested in digital audio synthesis/processing than analog that's a different can of worms and really the main thing I'd recommend is a nice cheap FPGA board like a lattice icestick. Those have a 3.3V pin you can use to power another chip or 2. As for what chips you'll want to have on your bench, high fidelity analog audio processing is all about op-amps. Really, just find some cheap quad op-amps, TL074 or whatever. For most circuits they'll be interchangeable. Get some comparators too if you want to do synths. They show up everywhere in oscillator-type circuits.
|
|
#
?
Dec 17, 2020 06:52
|
|
|
Stack Machine posted:9V battery and a bunch of 9V battery clips Fun fact: 9V batteries daisy chain. Somebody link the 9V series welder video.
|
|
#
?
Dec 17, 2020 06:56
|
|
|
I wish I knew more about opamps. I never got to mess with them because my professor kept cancelling class.
|
|
#
?
Dec 17, 2020 07:02
|
|
|
FISHMANPET posted:There's a separate button that will actually "shutdown" the pi, so I'd use that before cutting the power with the key. Would it be feasible to add a solenoid that prevents the key from turning while the Pi is running? I know it's overkill, but I'm swept up in the ludicrously impractical spirit of your project.
|
|
#
?
Dec 17, 2020 07:14
|
|
|
Mrenda posted:Jumping in on Cheese Thief's question about learning for audio-making stuff, if I wanted to get together all the pieces necessary for four or five projects, without having to pay €6 shipping on each IC I need for the next project, and to get me up to speed right at the very start, is there a list anywhere of what I should be getting first off to start up (including the inevitable practice I need with cock ups.) Oh man, I hate to say it, but I am not the most organized person and frequently fail to get everything I need in one order myself  I think your list is actually pretty good, one tip I've got if you want to get yourself a nice stock of passives (resistors, capacitors, etc) the E series of preferred numbers are the "standard" values that you'll most likely see in designs and will also tend to be less expensive than values not in the series. A couple months back I ordered 100 of every resistor in the E12 series from 0.1 up to 10M (IIRC) from lcsc.com in 0805 package for not a ton of money. I got a bunch of capacitors too varying between E3 and E6 numbers depending on where I was in the range (capacitors get relatively expensive as you go up in capacitance). Inductors you probably don't need to keep on hand but they are useful in audio circuits so you may want to get a spool of magnet wire to make your own in arbitrary values It looks like the project is dead now, but the hackaday article I linked has an associated hardware project on github: https://github.com/hexagon5un/klangorium. Might be worth poking around the project and seeing if there's a BOM (Bill of Materials) that lists all the components it uses as a starting point.
|
|
#
?
Dec 17, 2020 18:58
|
|
|
Mrenda posted:Shopping List 22-28 AWG are good general purpose wire sizes. You will probably want solid for connecting things on perfboard and stranded if its connected to stuff that moves. PVC insulation is cheaper, but burns more. Teflon won't melt/burn as much if you overheat it with a soldering iron Multiple colors are nice for organizing - You can get books of a few hundred of all E series through hole resistors for $5 or so - Flush cutters. They have angled blades so that you can cut pins without leaving pointy bits - Some form of multimeter if you don't already have one - A mat to work on unless you've already got a bench you don't care if gets burned by an iron - A brass wool thingy for cleaning soldering iron tips - Brand name solder wick if you want to get solder off stuff - Tweezers
|
|
#
?
Dec 17, 2020 23:05
|
|
|
Foxfire_ posted:(Assuming you are mostly looking at through hole things since the perfboard is on there) I put the perfboard down because I thought through hole stuff was the standard for "at-home" projects. If that's not the case then I need to be enlightened. It was simply that everything I saw in the videos I watched had people testing on a breadboard then putting it onto perfboard, and that seems like the route to go at the beginning.
|
|
#
?
Dec 18, 2020 02:58
|
|
|
If you're using breadboards to test, then through hole stuff is what you'll want. I need to buy an SMD kit to see if I'm any good at it, then I'll use SMD components for a project I'm working on.
|
|
#
?
Dec 18, 2020 03:08
|
|
|
Mrenda posted:I put the perfboard down because I thought through hole stuff was the standard for "at-home" projects. If that's not the case then I need to be enlightened. It was simply that everything I saw in the videos I watched had people testing on a breadboard then putting it onto perfboard, and that seems like the route to go at the beginning. If you're gonna use solderless breadboard, get a kit of precut, stripped, and bent jumper wires in a bunch of colors. Those are also cheap and convenient.
|
|
#
?
Dec 18, 2020 03:48
|
|
|
Foxfire_ posted:Through hole is best for starting out. Kinda disagree. Largish pitch surface mount tends to be a little easier, because it's all on the same side of the board that you're soldering on, and doesn't try to get away from you. Looks more intimidating than it is! All of it's easy though, I've never seen anyone have problems when they have proper gear and have read the "soldering is easy" web comic
|
|
#
?
Dec 18, 2020 03:51
|
|
|
ante posted:Kinda disagree. Largish pitch surface mount tends to be a little easier, because it's all on the same side of the board that you're soldering on, and doesn't try to get away from you. Looks more intimidating than it is! Yeah but you can't (easily) use stuff like perfboard with surface mount, you'd have to either etch your own boards or send them off to get them made. Learning a whole electronics CAD program is kinda a big barrier to entry for someone who just wants to plug some stuff into a breadboard and make a beepy boopy 555 circuit or whatever to see if they like this hobby. I mean they'd need to learn it eventually but eh might as well get them building something first before you get bogged down in layout n' poo poo. Once that's no longer really a problem yeah I agree SMD is way easier than thru-hole and I almost exclusively use it these days.
|
|
#
?
Dec 18, 2020 03:59
|
|
|
Totally fair
|
|
#
?
Dec 18, 2020 04:04
|
|
|
Foxfire_ posted:Teflon won't melt/burn as much if you overheat it with a soldering iron quote:
Regarding perf board: Adafruit's perma proto series is the best in the biz, IMO. They're laid out in the same rows and columns as a solderless breadboard, so you can transfer your design once you've tested and tweaked it.
|
|
#
?
Dec 18, 2020 05:54
|
|
|
Is there much practical difference between PTFE/Teflon and silicone insulated wires? I remember I used PTFE at my first job when making prototypes but I've been using silicone for my own projects lately. The insulation is definitely thicker on the silicone but I don't know if that's generally the case or just for the particular wires I'm comparing in my head. I etch my non-trivial prototype PCBs these days, the thinner wires are very nice for making them on perfboard though.
|
|
#
?
Dec 18, 2020 06:28
|
|
|
Silicone is noodlier than PTFE and has to be thicker to get the same voltage isolation. I think there's also some solvent compatibility differences if you're gonna dunk them in motor oils. Silicone is also usually more expensive I think
|
|
#
?
Dec 18, 2020 07:08
|
|
|
Good to know, thanks. I just grabbed silicone when I got tired of the PVC insulation on the wire I had on hand melting back when soldering. For whatever reason silicone was what first popped into my head to grab, but I never really considered the differences between PTFE and silicone. The noodliness makes it great for things like twisting together a pair to make a power lead, but PTFE being thinner makes prototype boards a lot easier if you have a lot of connections to make.
|
|
#
?
Dec 18, 2020 16:22
|
|
|
If I have a meat thermometer with a leave-in probe that's broken, what would I do to replace it? These things all have the same probe jack and Amazon has them in stock for a pretty high price. Is this a standard part I can grab from Digikey or something? I don't really know what they're called and kind of need it more regularly than Ali Express would support.
|
|
#
?
Dec 19, 2020 00:00
|
|
|
It's probably just a thermistor or thermocouple inside the metal tube, but no way to know what kind exactly without opening it up and no those aren't really standard parts. The thermistor will be but I doubt those things are made for disassembly. If you need them regularly, order a bunch in bulk from aliexpress so you always have some at hand?
|
|
#
?
Dec 19, 2020 00:16
|
|
|
The main bit is called a thermocouple and is a standard class of part but there are different types within that class. I've also never seen them with a TRS (aka 3/8" phono) connector like that or the metal stabby bit around it. The ones I see tend to look like this: https://www.amazon.ca/Connector-The...8333511&sr=8-25. Do they break frequently? Can you tell where they break? I probably wouldn't mess with the part that gets stuck into food but you might be able to patch a broken part of the lead or replace the connector.
|
|
#
?
Dec 19, 2020 00:26
|
|
|
Anyone have a take on a desktop pick-and-place? Looking to spend less than $5-6k. Was looking at the CHMT36VA.
|
|
#
?
Dec 19, 2020 06:24
|
|
|
Really want one, but have repeatedly done the cost/benefit analysis and there's no way I can justify it as anything other than a shiny toy
|
|
#
?
Dec 19, 2020 06:39
|
|
|
|
| # ? May 28, 2024 09:16 |
|
|
Knurling has been building tools for Rust; I just switched the remainder of my tooling to it. It's been making steady progress; I'm abandoning the quickstart I posted earlier for this. Compared to my prev setup with OpenOCD, ITT printing etc, it's a better experience; the printing and panic handling is more like a multi-level logging (Similar to Python's logging module, but without the config), and fast, since it's done on the host, vice the MCU. Also uses tricks to turn stack overflows into something more manageable. This stuff works with ARM MCUs like STM32 and nRF, but YMMV on others. If you're curious, I think the instructions on the page I linked will be enough, regardless of your prev experience. Dominoes fucked around with this message at 17:58 on Dec 20, 2020 |
|
#
?
Dec 20, 2020 17:54
|
|
