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The LM383 Story

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Re: The LM383 Story

#41

Post by CamperBob2 »

phkahler wrote: post #34

Load dump is not about connecting two batteries in series to achieve 24V. It's about (accidentally?) disconnecting the battery while charging from the alternator - which is an inductive source. When the load taking the current is disconnected that current is going to continue flowing through the vehicle electrical system which will cause a voltage spike until the current goes down. On a related note, I heard this 2nd…

Yes, that was a weird mistake for someone in the author's position to make.

That said, I may not understand what a 'load dump' condition is, myself -- I always thought it referred to the common case where a high current load is switched off abruptly, causing the voltage to spike until the alternator's regulator circuit can respond by reducing the field coil current.

Disconnecting the battery would not be expected to cause such a condition, since the charging current is not all that high most of the time compared to other loads. I wouldn't expect much of anything to happen when disconnecting the battery from a running car. It should just keep running.

Re: The LM383 Story

#42

Post by jimnotgym »

JohnBooty wrote: post #28
aidos wrote: post #8

OT but it seems like a good place to ask: this week I’ve been looking into making a wireless speaker similar to a Sonos play:1. In terms of the streaming mechanism is was going to use a raspberry pi running as a snapclient, wired to a class-d amp board and a, say, 3” driver. I thought I would find a load of projects using a pi + amp + driver in a small box combination, but I must be looking in the wrong place. Does a…

If you want a box with two tweeters and a woofer for some really legit sound, here's a design from a superstar of the DIY speaker design world: https://sites.google.com/site/undefinition/isetta He mostly just lays out the speaker and crossover design; but as he mentions a search for "TPA3116 2.1 amp" will give you lots of results on Amazon, AliExpress, and Parts Express. PE's forums are good, lots of people have tack…

I would love a C-note or the Overnight Sensations. Unfortunately UK shipping is a bit pricey! $90...

Re: The LM383 Story

#43

Post by fernly »

"My neighbor had just got a dog that was always barking. So I got tweeter, built up a simple 30kHz oscillator using a LM324. Set the two LM383 to swing rail to rail. Got a lantern battery that could put out the power. Then connected the tweeter."

Paging Steve Gibson: somebody reinvented your dog silencer[1][2]!

[1] https://www.grc.com/tqc/TheQuietCanine.htm

[2] https://groups.google.com/forum/#!topic/portable-sound-blast...

Re: The LM383 Story

#44

Post by icefo »

CamperBob2 wrote: post #41
phkahler wrote: post #34

Load dump is not about connecting two batteries in series to achieve 24V. It's about (accidentally?) disconnecting the battery while charging from the alternator - which is an inductive source. When the load taking the current is disconnected that current is going to continue flowing through the vehicle electrical system which will cause a voltage spike until the current goes down. On a related note, I heard this 2nd…

Yes, that was a weird mistake for someone in the author's position to make. That said, I may not understand what a 'load dump' condition is, myself -- I always thought it referred to the common case where a high current load is switched off abruptly, causing the voltage to spike until the alternator's regulator circuit can respond by reducing the field coil current. Disconnecting the battery would not be expected to…

The battery acts as a big capacitor to smooth the voltage and depending at which speed the alternator is turning I'd expect the voltage to vary wildly. This may make weird things happen especially on newer cars

Re: The LM383 Story

#45

Post by jhallenworld »

So the new LM386 is the Nsiway NS8002. This chip is better in that the output capacitor it not required (it has two LM386s making an h-bridge). On lcsc.com, they are $0.0329 each for QTY=10, or $0.90 for boards (each) on eBay. They are nice if you don't want to deal with class-D switching noise.

Cheap clock radios use them. They also use an 8-pin AM/FM digital radio IC: pins for 32 KHz crystal, I2C, antenna (loopstick for AM), and audio out. No coils, inductors or filters needed.

Re: The LM383 Story

#46

Post by madengr »

yitchelle wrote: post #37
squarefoot wrote: post #26

Earlier quoted context omitted.

EE aside, keeping the magic smoke confined inside the components requires also some good witchcraft knowledge:)

The real crazy stuff is RF electronics. That stuff is voodoo.

It’s not, you just need to know what you are doing.

Re: The LM383 Story

#47

Post by upofadown »

phkahler wrote: post #34

Load dump is not about connecting two batteries in series to achieve 24V. It's about (accidentally?) disconnecting the battery while charging from the alternator - which is an inductive source. When the load taking the current is disconnected that current is going to continue flowing through the vehicle electrical system which will cause a voltage spike until the current goes down. On a related note, I heard this 2nd…

Just to expand on this a bit. The load dump is not directly caused by the inductance of any component. That would only produce a very short voltage spike that would be easy to suppress. A load dump can involve greatly increased voltage for up to half a second.

Alternators tend to produce a constant current in proportion to the field winding current (the variable the voltage regulator controls). When you disconnect the battery the alternator attempts to maintain that current by increasing the voltage. The voltage regulator has to reduce the current in the field to close to zero to stop this voltage surge. The field has some magnetic energy (inductance) that the voltage regulator has no good way to get rid of quickly. So the output voltage zooms up to maybe 10 times the normal voltage for an extended period and any electronics in the car might be very sad.

Re: The LM383 Story

#48

Post by jcims »

yitchelle wrote: post #37
squarefoot wrote: post #26

Earlier quoted context omitted.

EE aside, keeping the magic smoke confined inside the components requires also some good witchcraft knowledge:)

The real crazy stuff is RF electronics. That stuff is voodoo.

You mean 'weird messed-up alien voodoo black magic stuff'?

This is coming from Mike at mikeselectricstuff no less, lol: https://www.youtube.com/watch?v=eyA2lWQrxwg&feature=youtu.be...

If this is intriguing, Shahriar from The Signal Path does know how this stuff works and does some amazing teardowns and repairs of six (and likely seven) figure RF equipment.

https://www.youtube.com/channel/UCKxRARSpahF1Mt-2vbPug-g

Re: The LM383 Story

#49

Post by JohnBooty »

jimnotgym wrote: post #42
JohnBooty wrote: post #28

Earlier quoted context omitted.

If you want a box with two tweeters and a woofer for some really legit sound, here's a design from a superstar of the DIY speaker design world: https://sites.google.com/site/undefinition/isetta He mostly just lays out the speaker and crossover design; but as he mentions a search for "TPA3116 2.1 amp" will give you lots of results on Amazon, AliExpress, and Parts Express. PE's forums are good, lots of people have tack…

I would love a C-note or the Overnight Sensations . Unfortunately UK shipping is a bit pricey! $90...

The C-Notes are still a bargain at that price!

There's about $80 worth of drivers in there, which is bonkers for a $100 kit that also includes crossover parts and MDF cabinets.

For comparison, the $130 Overnight Sensations kit contains about $55 worth of drivers. That's a good deal, and consistent with other DIY kits... and it illustrates what an outlier the C-Notes are.

(The reason why the C-Notes are so affordable is because Parts Express and Dayton share corporate ownership, so presumably they're about to source those Dayton drivers for next to nothing)

FYI there's an MTM (two woofers, one tweeter) version of the C-Notes coming in ~45 days for $100/speaker ($200/pair)

Re: The LM383 Story

#50

Post by stergios »

phkahler wrote: post #34

Load dump is not about connecting two batteries in series to achieve 24V. It's about (accidentally?) disconnecting the battery while charging from the alternator - which is an inductive source. When the load taking the current is disconnected that current is going to continue flowing through the vehicle electrical system which will cause a voltage spike until the current goes down. On a related note, I heard this 2nd…

Mig welders are used as temporary power supplies all the time. They allow for variable DC voltage (some offer AC), current, wave forms, and the bigger one have close to 100% duty cycle. Here's a guy using a mig welder to power a 15 ton radial arm dill. https://www.youtube.com/watch?v=2zYrabDGIEg
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