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by Burngate
Thu Aug 06, 2020 5:55 pm
Forum: Device Tree
Topic: How to set GPIO Output to LOW at shutdown
Replies: 7
Views: 464

Re: How to set GPIO Output to LOW at shutdown

Since the internal pull-up is of the order of 50kΩ, could you add an external pull-down of around 10kΩ? Less space needed for one resistor than for a transistor and its associated paraphenalia, but it's your pcb.
by Burngate
Tue Aug 04, 2020 9:59 am
Forum: Other projects
Topic: electromagnets and a pi
Replies: 3
Views: 250

Re: electromagnets and a pi

In addition to pcmanbob's post regarding transistor interfaces, I would strongly suggest diodes across each electromagnet, to control the back-EMF when each electromagnet is switched off - its inductance will attempt to keep the current flowing, and a diode will provide a low-impedance path for the ...
by Burngate
Mon Aug 03, 2020 10:37 am
Forum: General discussion
Topic: Re: Useful Accessory?
Replies: 15
Views: 951

Re: Useful Accessory?

[moderator removed first post which was post edited with a large spam in vietnamese poster was banned]





What spray? Any details?
by Burngate
Mon Aug 03, 2020 9:48 am
Forum: Beginners
Topic: Output pin and internal pull resistors
Replies: 2
Views: 140

Re: Output pin and internal pull resistors

A couple of questions 1k resistor + LED to GPIO7 Do you really mean GPIO 7 (on pin 26), or do you mean pin 7 (which is GPIO4)? I've wrote a program Can we see it? when driving GPIO7 LOW I could measure 1.6V at my 1k resistor. I changed the resistor to 40k an could measure 2.2V Which end of your resi...
by Burngate
Mon Aug 03, 2020 8:42 am
Forum: Troubleshooting
Topic: Raspberry Pi 3B - Does not boot, only red LED
Replies: 3
Views: 198

Re: Raspberry Pi 3B - Does not boot, only red LED

Not sure this is the same problem. The OP, gearheart89, says he's tried already a different PSU without result. And as Hippy says on that other thread, Butchkemper only had the problem after upgrade. Constant red LED => PSU ok No green LED activity => SD card not being read Second Pi works with same...
by Burngate
Sat Aug 01, 2020 5:43 pm
Forum: HATs and other add-ons
Topic: Pi4 won't boot w/ PoE HAT - flashing red light
Replies: 4
Views: 432

Re: Pi4 won't boot w/ PoE HAT - flashing red light

Have you tried swapping that HAT to a different Pi, and that Pi to a different HAT, to confirm that the problem follows the HAT rather than the Pi?
by Burngate
Thu Jul 30, 2020 5:53 pm
Forum: General discussion
Topic: Raspberry as an all around the world transmitter?
Replies: 8
Views: 447

Re: Raspberry as an all around the world transmitter?

It may be an obvious reply (if so, ignore me), but can you not download to a usb dongle and use the post to send it?
There might be a delay of a few days, but the cost is going to be less than satellite, and the bandwidth could be at least terabytes per week.
by Burngate
Tue Jul 28, 2020 5:59 pm
Forum: Beginners
Topic: RP0 Header
Replies: 10
Views: 352

Re: RP0 Header

The advantage of the "unpopulated" version (besides cost) is the saving of a few mm in height.
You can solder your own wires where you want them, without requiring the header.
by Burngate
Sat Jul 25, 2020 6:08 pm
Forum: Graphics, sound and multimedia
Topic: NTSC/PAL through speaker channel possible on Pi 4?
Replies: 7
Views: 488

Re: NTSC/PAL through speaker channel possible on Pi 4?

I disagree (just for the sake of). It very much depends on how fast you can allow your video to change, and how long you can wait for the result. Starting with a standard PAL frame, turn it into a JPEG file then send that as fast as you think you can get away with. Once it's reached the far end, rec...
by Burngate
Fri Jul 24, 2020 8:41 am
Forum: Troubleshooting
Topic: Rpi 4 B 8GB overriding other tv HDMI inputs
Replies: 1
Views: 136

Re: Rpi 4 B 8GB overriding other tv HDMI inputs

I tried posting this in the beginners section to no avail. I am truly a beginner at this. Not getting any response in the beginners section doesn't mean we think you're not really a beginner; rather it means we have no more idea what to do than you do! That said, it seems to me to be a problem with...
by Burngate
Fri Jul 24, 2020 8:29 am
Forum: Troubleshooting
Topic: PI Zero: no HDMI output unless powered by my PC's USB port
Replies: 12
Views: 507

Re: PI Zero: no HDMI output unless powered by my PC's USB port

... the pc has it's own display and the pi is plugged into a separate TV., there's only one HDMI cable ever plugged into the pi- it's the same one in the working case and the non-working case. If the pc has an earthed power supply, then using its USB to supply the Pi ties the Pi's ground to your ma...
by Burngate
Thu Jul 16, 2020 6:15 pm
Forum: Off topic discussion
Topic: Pis...the answer is Pis!
Replies: 64
Views: 4145

Re: Pis...the answer is Pis!

.... The article stated that the press were kept "at least 331 feet" away from the VIP's plane. I can tell what the original dispatch said (100 meters) and what would have be a more *accurate* statement (100 yards)--the precision to the nearest foot being completely unwarranted. Clearly some fool o...
by Burngate
Mon Jul 13, 2020 5:30 pm
Forum: Off topic discussion
Topic: Worst "production" Pi hardware installation
Replies: 26
Views: 2103

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: 365

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: 365

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: 579

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: 280

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: 508

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: 713

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: 346

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: 884

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: 524

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: 497

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...

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