Go to advanced search

by emma1997
Sun Dec 15, 2019 6:02 pm
Forum: General discussion
Topic: Is It Safe To Buy A Raspberry Pi 4b From AliExpress
Replies: 4
Views: 258

Re: Is It Safe To Buy A Raspberry Pi 4b From AliExpress

Last few years I've purchased literally dozens of Pi on Ebay and very pleased. Two defective: one replaced, another refunded. Quickly. Recently six Pi4 (four 1gig, two 4gig) all fine. A couple 'pre-owned' at less than half price checked out ok too. A few came with free (real) 3a dual wall warts w/US...
by emma1997
Sun Dec 15, 2019 5:48 pm
Forum: Advanced users
Topic: Can I power up Raspi Zero by connecting it to a Raspi 4 GPIO
Replies: 6
Views: 124

Re: Can I power up Raspi Zero by connecting it to a Raspi 4 GPIO

Language corrupts evolves. OP is not using a port bit. He stated "5 V + Ground from Raspi 4". As mentioned there should be no problem getting power from the GPIO connector or USB.
by emma1997
Sun Dec 15, 2019 5:22 pm
Forum: Troubleshooting
Topic: Raspberry pi 4b shutting down when standing up from chair
Replies: 13
Views: 301

Re: Raspberry pi 4b shutting down when standing up from chair

Lol, it's always fun to see Rube Goldberg insinuate into these tales of trial and tribulation. I suspect just a shorter or twisted wire will fix it. If not the series r definitely will. A long time ago I had the same thing on a PC. Sometimes when I stood up it reset. Actually any motion nearby. Prob...
by emma1997
Sat Dec 14, 2019 8:36 pm
Forum: Raspbian
Topic: Show Raspberry Pi IP-address on PWR led on boot
Replies: 4
Views: 174

Re: Show Raspberry Pi IP-address on PWR led on boot

A great solution but IMO basic decimal blinks would make it easier to enter IP in the other computer. Flag semaphore or whatever the new one is don't seem ergonomic. Might be easier to decode realtime if it was more familiar?
by emma1997
Sat Dec 14, 2019 7:59 pm
Forum: Troubleshooting
Topic: Raspberry pi 4b shutting down when standing up from chair
Replies: 13
Views: 301

Re: Raspberry pi 4b shutting down when standing up from chair

It's a real resistor not internal to the chip so I doubt it makes a difference but who knows? Experienced similar problem with couple feet between button and pin. Shortening to less than an inch fixed it. There is definitely a minimum distance that works (ie no button at all) so it's only needed to ...
by emma1997
Thu Dec 12, 2019 6:15 pm
Forum: Raspbian
Topic: Buster bug report thread
Replies: 278
Views: 47640

Re: Buster bug report thread

Space character %20 is hex (aka $20, 0x20, 20H, 32dec 0b00100000 etc). IIRC octal would be 040.

lol, just in time p!
by emma1997
Thu Dec 12, 2019 5:23 pm
Forum: General discussion
Topic: New Pi 4B v1.2?
Replies: 172
Views: 11971

Re: New Pi 4B v1.2?

Traditionally 'revision' number related to the PCB itself and not so much components on board or software (we had 'version' for that). Of course there were many exceptions by creative engineers and companies, making life slightly less convenient for everybody else, but what ya gonna do? I think if a...
by emma1997
Thu Dec 12, 2019 5:03 pm
Forum: Troubleshooting
Topic: Pi4 solid red and green led
Replies: 34
Views: 1931

Re: Pi4 solid red and green led

we should not splash out along with dirty water from the basin of the child =) Hi, renice123. I see now you are probably from another country and smart and not just too young or other problems. Maybe we can blame bad google translate. It's not required but showing approximately where we are from in...
by emma1997
Tue Dec 10, 2019 10:29 pm
Forum: Beginners
Topic: Fried pi?
Replies: 16
Views: 402

Re: Fried pi?

yummmmmmmmm....
by emma1997
Tue Dec 10, 2019 9:48 pm
Forum: Beginners
Topic: Connecting 5V pullup to Pi GPIO
Replies: 33
Views: 929

Re: Connecting 5V pullup to Pi GPIO

Being stuck in real universe, on more than one occasion, I've been accused of being 'pedantic foo...', no wait, that was... lol

Anyway:
emma1997 wrote:
Tue Dec 10, 2019 8:13 pm
capacitance would be associated with the 'logic' part, not the pin.
by emma1997
Tue Dec 10, 2019 8:59 pm
Forum: General discussion
Topic: New Pi 4B v1.2?
Replies: 172
Views: 11971

Re: New Pi 4B v1.2?

Just surprised you were so sure supply had nothing to do with Pi problems. I was shocked top King of Links and guy I learned so much from last few years did not run out to get in line/setup tent at midnight to be first when doors opened. Maybe not that odd because I wasn't so hot on them myself orig...
by emma1997
Tue Dec 10, 2019 8:27 pm
Forum: General discussion
Topic: New Pi 4B v1.2?
Replies: 172
Views: 11971

Re: New Pi 4B v1.2?

Spoken by a fellow who does not have even one yet? Or maybe finally grabbed one recently? ( your honor... I move to question the expert testimony... lol ) Anyway they are a dime a dozen now and grow on trees and more fun than a barrel of monkeys so all's good.
by emma1997
Tue Dec 10, 2019 8:13 pm
Forum: Beginners
Topic: Connecting 5V pullup to Pi GPIO
Replies: 33
Views: 929

Re: Connecting 5V pullup to Pi GPIO

Since it isn't show in the diagrams how can you be so sure ?. And if was after the charge/discharge times would be a major limiting factor ! AFAICS it is shown. Any capacitance would be associated with the 'logic' part, not the pin. Capacitance at the pin (driven) end of this resistor would be of l...
by emma1997
Tue Dec 10, 2019 7:19 pm
Forum: Beginners
Topic: Connecting 5V pullup to Pi GPIO
Replies: 33
Views: 929

Re: Connecting 5V pullup to Pi GPIO

Glad to hear that. BTW I don't need any ambulance to experience the memory thing. lol Gesundheit.
by emma1997
Tue Dec 10, 2019 7:11 pm
Forum: General discussion
Topic: New Pi 4B v1.2?
Replies: 172
Views: 11971

Re: New Pi 4B v1.2?

Unfortunately I'm stuck in the real one so, yes, you guys have described me to a t (except maybe the apple part, lol). That first one did help give me a huge jump instead of waiting a month from overseas to save 2 dollars or driving 60mi to Cambridge Microcenter for even less savings. I more than ma...
by emma1997
Tue Dec 10, 2019 6:41 pm
Forum: Beginners
Topic: Connecting 5V pullup to Pi GPIO
Replies: 33
Views: 929

Re: Connecting 5V pullup to Pi GPIO

why should it take that long to switch, if the gate capacitance is before the (nonexistant) resistor? Actually in those diagrams it's after, not before. PIN capacitance might be before but who cares about hundredths of a puff. IMO that resistor is not even close to how CMOS actually behaves. Might ...
by emma1997
Tue Dec 10, 2019 6:02 pm
Forum: General discussion
Topic: Noise Level Detection - Wi-Fi Based Noise Monitoring Systems using Raspberry Pi in Library
Replies: 2
Views: 169

Re: Noise Level Detection - Wi-Fi Based Noise Monitoring Systems using Raspberry Pi in Library

Unless somebody comes along with 'relevant' code the choice seems obvious if expensive. Software is often 99% the time/effort/cost.

I was able to log noise events using five cent electret connected directly to Pi but only above/below certain Db. Not good for very low frequency too.
by emma1997
Tue Dec 10, 2019 5:26 pm
Forum: Automation, sensing and robotics
Topic: Choosing NPN BJT as a switch for RPI to control motor by PWM
Replies: 10
Views: 346

Re: Choosing NPN BJT as a switch for RPI to control motor by PWM

Bottom line: ain't going to do it with one BJT. Specially if there's '3055' or 'TIP' in the name. For cost effective solution at 6a we need some paralleling here. Good power BJT are so cheap 3 or 4 on the output and darlington input would work. Or one HEXFET for about 1/10th the cost.
by emma1997
Tue Dec 10, 2019 5:05 pm
Forum: General discussion
Topic: New Pi 4B v1.2?
Replies: 172
Views: 11971

Re: New Pi 4B v1.2?

At first release they were about double list on Ebay etc. Within a month or so only about $15 more. BO and bid 1g and 4g. Stayed the same for months. Then few weeks back, not long after buzz started about the big apple PSU 'disaster', prices dropped to $5-$10 over which is hard to resist. Lots more ...
by emma1997
Tue Dec 10, 2019 4:48 pm
Forum: Beginners
Topic: Connecting 5V pullup to Pi GPIO
Replies: 33
Views: 929

Re: Connecting 5V pullup to Pi GPIO

Am I the only one giggling at these resistor model representations of bias current? Highly unlikely there is actually any 100meg resistor in series with any logic. Considering gate capacitance it would take a month for the logic to switch. lol
by emma1997
Tue Dec 10, 2019 4:31 pm
Forum: General discussion
Topic: New Pi 4B v1.2?
Replies: 172
Views: 11971

Re: New Pi 4B v1.2?

I think hysteria over that resistor issue may be why the recent street price drop. Anticipation of this new rev or maybe just oversupply. So a bonus of the hype let's me pick up a couple more1g and 4g for not much over MSRP or used ones a lot less. I am keeping fingers crossed the video/usb3/wifi pr...
by emma1997
Sun Dec 08, 2019 11:22 pm
Forum: Beginners
Topic: Will I burn my RPI if I accidentially provide a large voltage to any 3.3v GPIO pin?
Replies: 15
Views: 443

Re: Will I burn my RPI if I accidentially provide a large voltage to any 3.3v GPIO pin?

Well I'm not so experienced in that realm but my understanding is there are issues associated with negative resistance and similar phenomena which do not equate to exactly 0. AFAIK kinda flutters around or pass through that point. So I would have to say you are correct in the same way as a dead cloc...
by emma1997
Sun Dec 08, 2019 10:47 pm
Forum: Beginners
Topic: Will I burn my RPI if I accidentially provide a large voltage to any 3.3v GPIO pin?
Replies: 15
Views: 443

Re: Will I burn my RPI if I accidentially provide a large voltage to any 3.3v GPIO pin?

True. I was referring to an actual electrical "circuit" which does seem to need a bit of each. No such thing as perfect short or open on this planet. My measurements showed inputs somewhere above 10Gohm but less than 100Gohm the limit of my gear. That might be moisture between pins or other epoxy ad...
by emma1997
Sun Dec 08, 2019 10:28 pm
Forum: Beginners
Topic: Will I burn my RPI if I accidentially provide a large voltage to any 3.3v GPIO pin?
Replies: 15
Views: 443

Re: Will I burn my RPI if I accidentially provide a large voltage to any 3.3v GPIO pin?

the current that causes the trigger can be tiny, so current limit resistors won't help. it is the voltage that matters, not the current. The GPIO inputs are like FETs - they are voltage driven, not current. It's surprising even top experts are not 100% aligned. My understanding is there can be no c...
by emma1997
Sun Dec 08, 2019 5:03 pm
Forum: C/C++
Topic: How to drive max7219 8digit 7segment tube via pigpio spi?
Replies: 5
Views: 198

Re: How to drive max7219 8digit 7segment tube via pigpio spi?

Those low cost max 8 digit ('tube' in chinese, lol) are among my favorite display type. Exceptional visibility, easy coding, simple interface, cheeeeep, what's not to like? However I think what scruss says cannot be stressed enough. First the modules only work reliably as-is off 5v so be careful int...

Go to advanced search