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by Burngate
Mon Jul 13, 2020 5:30 pm
Forum: Off topic discussion
Topic: Worst "production" Pi installation
Replies: 24
Views: 824

Re: Worst "production" Pi installation

I don't see a problem - all my Pis are mounted like this. It has the advantage that you can't drop a screwdriver on it, and it can't accidentally touch a conductive surface. Though admittedly I think the ethernet cable should have a half-hitch to hold it in place, otherwise it'll unthread itself whe...
by Burngate
Fri Jul 10, 2020 10:23 am
Forum: Python
Topic: atm - return required sum using minimum amount of 100, 50 and 20 banknotes
Replies: 7
Views: 225

Re: atm - return required sum using minimum amount of 100, 50 and 20 banknotes

Yes, but ... Barman, customer ... The barman was adding it up as he was pulling the pints, and tells the customer what amount he needs. The customer knows what's in her purse, hands over some amount that's convenient for her, maybe a twenty or two tens. The barman has to take into account what chang...
by Burngate
Fri Jul 10, 2020 9:13 am
Forum: Python
Topic: atm - return required sum using minimum amount of 100, 50 and 20 banknotes
Replies: 7
Views: 225

Re: atm - return required sum using minimum amount of 100, 50 and 20 banknotes

Not a Python guru, so can't help with that side, but two things stand out for me. First, there ain't no answer if you start with 10 or 30, so it might be worth checking for that before you start. Second, why start with the largest notes and work down - the 100s, then the 50s and end with the 20s? In...
by Burngate
Thu Jul 09, 2020 6:01 pm
Forum: Beginners
Topic: LED help
Replies: 17
Views: 417

Re: LED help

... 3v ultra bright water clear LED's ... Just to say I'm dubious about the 3v bit of the description. Does the seller expect you to connect them to a 3v source - in which case they should have a resistor built-in? Or is it more of a pious hope that not too many buyers want their money back, becaus...
by Burngate
Wed Jul 08, 2020 5:04 pm
Forum: Automation, sensing and robotics
Topic: Recommendations for understanding electronics / GPIO?
Replies: 5
Views: 192

Re: Recommendations for understanding electronics / GPIO?

There are several members here who can explain things simply and clearly; two that come to mind are pcmanbob and drgeoff. Have a look through their posts - though they each have rather a lot, in the 10k region. Also look at the posts by any of the engineers - they are rarely wrong, though they might...
by Burngate
Tue Jul 07, 2020 5:56 pm
Forum: Troubleshooting
Topic: Raspberry Pi 1 B not starting up
Replies: 14
Views: 358

Re: Raspberry Pi 1 B not starting up

... RPi 1B Rev 2.1 - PWR (red) LED stays on for 1-30 seconds, then goes off - the 220 CFP 35 (capacitor?) and a couple of components get hot after plugging in power - the mentioned components stay hot even after the PWR red goes off Since the red LED comes on to begin with, the polyfuse hasn't acti...
by Burngate
Fri Jul 03, 2020 10:18 am
Forum: Automation, sensing and robotics
Topic: Unidirectional logic shifting (3V3 to 1V8) with minimum components?
Replies: 10
Views: 536

Re: Unidirectional logic shifting (3V3 to 1V8) with minimum components?

... pulls down 1.8V for 2 seconds and then the external device powers on... How close to 0v does it need to get? How much current will it source? If, for example, the device's input is one input of an old-fashioned 74LS logic chip, it only needs to be pulled down below 0.8v, and to do that you need...
by Burngate
Thu Jul 02, 2020 10:12 am
Forum: Beginners
Topic: Yet another question about LEDs and resistors...
Replies: 7
Views: 248

Re: Yet another question about LEDs and resistors...

Ok, found the source of your screenshot https://www.ledsupply.com/leds/5mm-led-orange-610nm-30nm-degree-viewing-angle And I have a screenshot you may find interesting - it's from a Kingbright green LED datasheet, but the basics should apply to most LEDs. L-934GD.png As you can see, although it's spe...
by Burngate
Thu Jul 02, 2020 9:26 am
Forum: Off topic discussion
Topic: Biomimicry in PCB Design
Replies: 6
Views: 487

Re: Biomimicry in PCB Design

... naturally designed to maximize the space inside of it by increasing surface area (has lots of folds going back and forth) That confuses me - doesn't the folding, at least of the endoplasic reticulum - minimise the space taken up? But I'm not convinced that somewhat random folding of a circuit b...
by Burngate
Tue Jun 30, 2020 9:44 am
Forum: Beginners
Topic: Electronics questions
Replies: 7
Views: 442

Re: Electronics questions

I was thinking to switch the MCP3008 to 5V ... Don't. If you use 5v, the output from it to the Pi will approach that, and the Pi will be damaged. ... so it will sample at 200ksps. The maximum frequency of the signal must be 100KHz, how can I be sure that I won't wiggle the potentiometer too fast? W...
by Burngate
Mon Jun 29, 2020 6:22 pm
Forum: General discussion
Topic: No red LED Pi 4B
Replies: 9
Views: 425

Re: No red LED Pi 4B

You have, naturally, probed with your meter round that LED, haven't you? Bottom end is GND, obviously. If the LED is open circuit, you should see 4.somethingV at its anode. If R17 is broken, you should see 0V, and the same if it's being held off by Q1 In the latter case, Q1's gate should be high unl...
by Burngate
Mon Jun 29, 2020 10:45 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Pi4 3.5mm audio out cuts off at 19kHz
Replies: 7
Views: 418

Re: Pi4 3.5mm audio out cuts off at 19kHz

The low-pass filter shown there gives 6dB/octave with a 3dB turnover at 145kHz. Not what's shown on his graph, which has a 3dB turnover at 19kHz and thereafter something in excess of 18dB/octave. What frequency does the Pi's PWM work at? What does the Pi do to the audio before it feeds into the PWM?...
by Burngate
Sat Jun 27, 2020 5:50 pm
Forum: Off topic discussion
Topic: Wish list for the foundation
Replies: 45
Views: 2280

Re: Wish list for the foundation

Just a minor gripe of mine. The idea that everybody should re-invent every wheel, is, well, just not in keeping with the modern world. One of those things that everyone says, without thought. If inventing wheels were easy, it wouldn't have needed the Egyptians to do it - Neanderthal Man would have h...
by Burngate
Sat Jun 27, 2020 11:00 am
Forum: Troubleshooting
Topic: I removed the back feed, still won't boot if USB HDD is attached.
Replies: 14
Views: 381

Re: I removed the back feed, still won't boot if USB HDD is attached.

If you don't remove the power feed to the Pi - which you aren't, since you're just trying to reboot - then whether or not the hub back-feeds power to the Pi is irrelevant. It seems more likely that the Pi is waiting for a reply from the drive, and unplugging the hub tells the Pi that the drive is no...
by Burngate
Fri Jun 26, 2020 10:03 am
Forum: Beginners
Topic: Driving SMD5050 LED strip using IRLZ34N
Replies: 5
Views: 236

Re: Driving SMD5050 LED strip using IRLZ34N

I think your best bet would be what's sold as a logic level converter. They're generally meant to translate 3v3 signals to 5v, but would work just as well translating to 12v And the advantage for is you can get them as four on one board - one for each colour and one spare! 3-12v.png Just read 12v in...
by Burngate
Fri Jun 26, 2020 9:31 am
Forum: General discussion
Topic: Raspberry Pi integrated storage
Replies: 59
Views: 2241

Re: Raspberry Pi integrated storage

Given what a Pi is meant to be - not bank-breaking if you break it - keeping the OS on a separate, cheap, disposable SD card is a far, far better thing than anyone else has ever bothered doing, at least according to Charlie Boy.
by Burngate
Thu Jun 25, 2020 10:04 am
Forum: Beginners
Topic: Remove the wireless card
Replies: 24
Views: 1319

Re: Remove the wireless card

It strikes me as weird that the 3B / 3B+ / 4B have both WiFi and PoE, while the 2B has neither. With the 4B, If you use PoE, WiFi is redundant; WiFi implies no cable so you'll have to provide power some other way. With the 2B, either option needs desk-clutter. That's without considering the down-sid...
by Burngate
Thu Jun 25, 2020 9:17 am
Forum: Beginners
Topic: Driving SMD5050 LED strip using IRLZ34N
Replies: 5
Views: 236

Re: Driving SMD5050 LED strip using IRLZ34N

Hi, may I suggest you're using a logic level FET, but driving it from 3.3 not 5. The IRLZ34N is a FET, it's a 3.3v max gate voltage MOSFET Not quite true. Its max gate voltage is 16v - it'll survive if you give it that much - but its gate threshold voltage is typically between 1v and 2v. That means...
by Burngate
Sat Jun 20, 2020 5:26 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SRF08 power
Replies: 2
Views: 196

Re: SRF08 power

Just make sure you don't add pull-up resistors to 5v on the SDA & SCL lines.
The Pi already has pull-up resistors to 3v3, so no more are needed anywhere.
by Burngate
Sat Jun 20, 2020 10:10 am
Forum: Off topic discussion
Topic: Animal question
Replies: 21
Views: 1937

Re: Animal question

If the Raspberry Pi were an animal, ... Why are we limited to the Animal Kingdom? There're far more interesting things elsewhere! There's the bacteria, of course, and viruses, but they're not really very interesting unless you catch one. We could ignore the Plant Kingdom - sitting there doing not v...
by Burngate
Sat Jun 20, 2020 8:20 am
Forum: Graphics, sound and multimedia
Topic: Outdoor audio and high wattage speakers
Replies: 15
Views: 3768

Re: Outdoor audio and high wattage speakers

The difference between 60w and 100w is generally undetectable to the average human. You need 4x or 10x to make a difference. People in general are piss poor at judging output power. 60W to 100W is less than 3dB. The human ear can't usually detect less than 6dB Back before Covid-19, you went to see ...
by Burngate
Fri Jun 19, 2020 10:22 am
Forum: Troubleshooting
Topic: I think my Pi3 is almost dead
Replies: 7
Views: 372

Re: I think my Pi3 is almost dead

Hmph. Need more coffee
by Burngate
Fri Jun 19, 2020 9:23 am
Forum: Troubleshooting
Topic: I think my Pi3 is almost dead
Replies: 7
Views: 372

Re: I think my Pi3 is almost dead

GPIO pin 1 and 2: ~5.1V and ~3V3 respectively. PP1: 5V, same as input. PP10: ~1.8V (is acting as a browndown detector?) I guess there's a problem here. PP21: Should be high at 3V3 but I got ~0V PP25: ~0V when it should be 5V on the USB bus. (I'm assuming this is a 3B, not 3B+ or other variant) PP1 ...
by Burngate
Thu Jun 18, 2020 9:32 am
Forum: Beginners
Topic: Raspberry Pi OS Imager does not find SD card
Replies: 12
Views: 511

Re: Raspberry Pi OS Imager does not find SD card

Could it be that both the tower's slot and the USB card reader aren't SDXC compatible? They can read but not write?

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