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Circuit building: stop using antique parts (2014)

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Re: Circuit building: stop using antique parts (2014)

#151

Post by throwanem »

paulannesley wrote: post #126
mrob wrote: post #27

Earlier quoted context omitted.

If I count as a critter, I can easily tell the difference by moving my eyes and seeing the phantom array effect. If you're already using resistors for current limiting then putting a big enough capacitor across the LEDs will filter them without much difference in power consumption. I have no idea if the fish will care.

That effect drives me nuts too; but it seems to bother a minority of people. I've always assumed/guessed it's in the order of 50–100Hz; the 500–1000Hz mentioned may be fast enough to appear continuous to sensitive humans and maybe fish...

The most usual source of that flicker these days is driving LEDs (usually in a string of Christmas lights) with half-wave rectified AC, which can be considered PWM with a 50% duty cycle over the same period as the input signal - 60Hz in the US and I think Japan, 50Hz most other places. That's slow enough to see easily; it would surprise me to learn that PWM at ten times the rate is slow enough to see at all.

Looking at the code I wrote a while back to drive a four-digit common-cathode LED display (you know, a TV bomb timer!) as a clock, I find that after all the tuning I did to get rid of flicker, I ended up activating each digit for 1ms at a time. Granted, running under Raspbian this is going to flicker anyway from time to time because multitasking, but that aside, I found no PWM flicker perceptible, even at what is effectively 20% duty cycle over a 5ms period. (The decimals are implemented as a fifth "digit".) So I'm going to guess that .5KHz and up are fine for most humans. Fish I don't know about; (1) cites a flicker fusion rate between 2 and 40Hz for swordfish, but for goldfish I've no idea, other than to guess that .5KHz and up is probably fine for them too.

(1) https://www.google.com/amp/amp.livescience.com/3799-fish-eye... (Sorry for AMP, but taking it off the front nets me a timeout from livescience.com. Something broken there, I'm guessing.)

Re: Circuit building: stop using antique parts (2014)

#152

Post by mrob »

throwanem wrote: post #151
paulannesley wrote: post #126

Earlier quoted context omitted.

That effect drives me nuts too; but it seems to bother a minority of people. I've always assumed/guessed it's in the order of 50–100Hz; the 500–1000Hz mentioned may be fast enough to appear continuous to sensitive humans and maybe fish...

The most usual source of that flicker these days is driving LEDs (usually in a string of Christmas lights) with half-wave rectified AC, which can be considered PWM with a 50% duty cycle over the same period as the input signal - 60Hz in the US and I think Japan, 50Hz most other places. That's slow enough to see easily; it would surprise me to learn that PWM at ten times the rate is slow enough to see at all. Looking…

In my own testing I could see flicker at 10kHz, during fast eye movement only. This has nothing to do with flicker fusion threshold. Instead it's a failure of saccadic masking. At 10kHz it's subtle enough that it's not at all annoying, but I do find 1kHz slightly annoying. The commonly used 200Hz is definitely annoying.

Re: Circuit building: stop using antique parts (2014)

#153

Post by pareidolia »

Florin_Andrei wrote: post #81
aexaey wrote: post #72

Earlier quoted context omitted.

There is a purpose-designed Chinese chip exactly for your situation - control brightness of a LED strip based on PWM input. Compared to a bare MOSFET, this chip gives you higher efficiency, current-controlled (i.e. flicker-free) output and ability to drive LEDs directly (without current-limiting resistors). PT4115, pretty cheap on ebay and other usual places.

Well, the LED strip I use is a black box (from an electrical perspective). It just needs 12V, no external resistors. So I just hooked it up to 12V via the MOS-FET. The PWM signal from the Arduino (plugged into the MOS-FET) does the job of changing the apparent brightness. No need for magic chips in this context.

Your ledstrip probably also consumes about 15 watts per meter since integrated current limiting resistors dissipate most of the energy; a black box with the efficiency of a lightbulb.

Re: Circuit building: stop using antique parts (2014)

#154

Post by etatoby »

mveety wrote: post #138
busterarm wrote: post #33

Earlier quoted context omitted.

Guitar d00ds having obscure, nonsensical reasons for things because "mah tones!"? Say it ain't so. I mean, nearly every tube head on the market has an essentially pointless standby/bypass switch because of the mistaken belief that you need to warm up your tubes for some arbitrary amount of time in a modern amp and keep them warm. I forget which manufacturer it was that dropped the switch on one model and saw sales pl…

Well tube amps do actually need to warm up, but people think it takes minutes to hours for them to warm up when it really takes like 2 to 5 seconds. That, I think, comes from a lack of knowledge about how tubes work and the general cargo cult surrounding sound electronics.

"Cargo cult" summarizes that attitude well.

Re: Circuit building: stop using antique parts (2014)

#155

Post by r3boots »

CamperBob2 wrote: post #102
jacquesm wrote: post #21

Earlier quoted context omitted.

RF grade relays will cost you an arm and a leg though.

To that point, another mistake a lot of amateurs make is that they buy expensive things on DigiKey without looking on eBay first.

Amateurs are often poorly positioned to diagnose problems stemming from floor sweepings, parts recovered from e-waste, cheap knockoffs, or outright counterfeits. eBay parts not in those categories are often free samples you can request yourself.

Paying a premium for a new part with predictable characteristics isn't always a mistake.

Re: Circuit building: stop using antique parts (2014)

#156

Post by moron4hire »

Kliment wrote: post #148
retrogradeorbit wrote: post #132

Earlier quoted context omitted.

"easier". Just pull apart a toaster oven. Reconfigure it. Rewire it. Get some paste. Make a stencil. You know. Easy peasy. Get the software. Learn how to use it. Get the stencils printing. Easy. Oh, you've got registration problems. Come on! Its easy! So much easier than spending one minute ordering a through hole component. You see, its not actually "easier". Its "easier" to you because you already have the equipmen…

Hey, I teach SMD soldering to absolute beginners, many of whom have never done ANY electronics. Within an hour and a half they have a working board with "advanced" components like QFNs and 0402 passives attached. Nobody goes without a working board. Only equipment needed is a pair of tweezers, a metal squeegee for paste deposition and a plain off-the-shelf $10 hotplate. No fancy anything. It's not a setup you'd use f…

How do you make the solder paste stencil? How do you make the PCB traces?

Re: Circuit building: stop using antique parts (2014)

#157

Post by PeanutNore »

mveety wrote: post #138
busterarm wrote: post #33

Earlier quoted context omitted.

Guitar d00ds having obscure, nonsensical reasons for things because "mah tones!"? Say it ain't so. I mean, nearly every tube head on the market has an essentially pointless standby/bypass switch because of the mistaken belief that you need to warm up your tubes for some arbitrary amount of time in a modern amp and keep them warm. I forget which manufacturer it was that dropped the switch on one model and saw sales pl…

Well tube amps do actually need to warm up, but people think it takes minutes to hours for them to warm up when it really takes like 2 to 5 seconds. That, I think, comes from a lack of knowledge about how tubes work and the general cargo cult surrounding sound electronics.

They usually specify a warm-up time on the datasheet. For most 12A_7 preamp tubes it's 11 seconds

Re: Circuit building: stop using antique parts (2014)

#158

Post by CamperBob2 »

r3boots wrote: post #155
CamperBob2 wrote: post #102

Earlier quoted context omitted.

To that point, another mistake a lot of amateurs make is that they buy expensive things on DigiKey without looking on eBay first.

Amateurs are often poorly positioned to diagnose problems stemming from floor sweepings, parts recovered from e-waste, cheap knockoffs, or outright counterfeits. eBay parts not in those categories are often free samples you can request yourself. Paying a premium for a new part with predictable characteristics isn't always a mistake.

How else do you suggest they learn? China == cheap education.
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