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Circuit building: stop using antique parts (2014)

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

#81

Post by Florin_Andrei »

aexaey wrote: post #72
Florin_Andrei wrote: post #16

Earlier quoted context omitted.

The article seems mostly right when it's about interfacing logic circuits with loads that require even moderate currents. FET is king in this field. I've a little aquarium and I've noticed how fish always get scared when lights turn suddenly on or off. So I took an Arduino and wrote a timer app for it, using PWM to slowly drive the output up over 60 minutes (sunrise), keep it at max for a few hours, then drive it dow…

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.

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

#83

Post by AceJohnny2 »

I've recently gotten back into hobby electronics, trying to revive all that EE knowledge I haven't used in 15 years, and one thing I sorely lack is knowledge of common components to use.

Online electronics stores are no help because of the overload of possible components.

Is there some sort of Cookbook out there I could refer to for up-to-date examples of common circuits and electronic tasks? I mean, I otherwise totally would've used a 2N2222 transistor for some tasks, because I wouldn't know better.

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

#85

Post by cylinder714 »

coreyp_1 wrote: post #22

Don't tell me that a LM386 is bad without telling me why and what to replace it with. If you don't, then you're not actually helping me at all, but rather it just sounds like you're spreading FUD.

The very first article of the book More QRP Power discusses surface-mount tech and why amateur radio people should embrace it, and the author specifically mentions an SMD chip with better specs than the LM386...but I don't have the book handy. I'll search for it later.

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

#86

Post by mdb333 »

nitrogen wrote: post #80
sounds wrote: post #29

Earlier quoted context omitted.

I would love to see something on digikey or mouser that allowed me to search for MOSFETs in a way that was less painful. Let's say you wanted to do a special purpose switching power supply. Digikey doesn't have a column for gate capacitance (for the mosfet), or Q (for the inductor). All that manual work to read datasheets is terrible, especially if your design takes a little while to perfect and some of the component…

Is the Octopart search engine still running? Or something like it?

it is, https://octopart.com/search?q=

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

#87

Post by chuckdries »

AceJohnny2 wrote: post #83

I've recently gotten back into hobby electronics, trying to revive all that EE knowledge I haven't used in 15 years, and one thing I sorely lack is knowledge of common components to use. Online electronics stores are no help because of the overload of possible components. Is there some sort of Cookbook out there I could refer to for up-to-date examples of common circuits and electronic tasks? I mean, I otherwise tota…

I've been looking for the same thing for weeks, I ended up just texting my electrical engineer friend

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

#89

Post by julian_1 »

blackguardx wrote: post #9

There is nothing wrong with bipolar transistors. They aren't antiquated. FETs have definitely overtaken them in power applications (for good reason) but it seems hard to displace them for small signal applications. Small signal FETs just aren't that plentiful or cheap. There are many instances where a small signal FET makes sense (level translators, etc) but the cost doesn't justify its use. Using a 2n2222 and the li…

Higher gate capacitance of FETs is also a drawback. Often you need a bjt or even dedicated gate-driver IC to drive the gates quickly. The extra pole can also make negative feedback more complicated. And there's less component choice when you want more control in the ohmic region versus switching - for a non emitter/source follower circuit. Another issue is the higher gate voltages required - compared with bjts even using logic-level FETs.

The article would have been much better with a different title - "How to use FETs effectively and when to use them", not a binary oppositioning of "antique" versus "modern".

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

#90

Post by WalterBright »

failrate wrote: post #55
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…

If I ever made analog audio equipment professionally, I would add an entire series of switches and dials that weren't wired up to anything.

Back in the 70's, a friend of mine created a formula where the inputs were number of switches, number of dials, and number of meters and would output the price. It was remarkably close at predicting the price of most any stereo receiver/amplifier in the stereo store.

One standout anomaly was the Heathkit 250W amp, which just had an on/off switch and 2 meters.

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