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by mahjongg
Sat Jul 31, 2021 10:26 pm
Forum: Beginners
Topic: LEDs?
Replies: 36
Views: 749

Re: LEDs?

Oh? You claim they could not, and yet the OP has built it and it works. theoretically two 2.5V LED's in series CAN NOT work when powered from 5V because 5V - 2.5V -2.5V = 0V (for the current limiting resistor) THAT IS A FACT, but then as I said what can't work in theory sometimes works in practice....
by mahjongg
Sat Jul 31, 2021 1:19 pm
Forum: General discussion
Topic: I have a monitor hp compáq la2205
Replies: 2
Views: 60

Re: I have a monitor hp compáq la2205

Your monitor has DVI, which is the predecessor of HDMI, only without sound. all you need is a a HDMI cable, and a small passive HDMI to DVI adapter and it should work, probably you need to switch input channel to DVI before turning the PI on.
by mahjongg
Fri Jul 30, 2021 10:33 am
Forum: Beginners
Topic: LEDs?
Replies: 36
Views: 749

Re: LEDs?

Or those LEDs could be in series, with one dropper resistor. No, they couldn't. The V f of these LEDs can be 2V5. hat is too high for reliable operation in series with a 5V supply. Oh? Yes they could. No, they could not, unless my calculator is broken 2.5 + 2.5 = 5V leaving exactly ZERO volt over t...
by mahjongg
Thu Jul 29, 2021 10:39 pm
Forum: Python
Topic: GPIO goes to 2.5v
Replies: 3
Views: 95

Re: GPIO goes to 2.5v

two questions: Did you use an external pullup resistor to 3V3, using a correctly sized resistor (say 4K7), the soft pullups are very weak at about 50K. did you use a current limiting resistor in series with the LED, such a resistor is absolutely necessary, as a LED is a diode and as such does not li...
by mahjongg
Thu Jul 29, 2021 12:42 pm
Forum: Compute Module
Topic: Possible migration from Compute Module to other SOM
Replies: 17
Views: 916

Re: Possible migration from Compute Module to other SOM

You got at least four days after your ban ended, I made sure of that, but yeah probably should have waited a bit longer. :mrgreen:
by mahjongg
Thu Jul 29, 2021 12:40 pm
Forum: Troubleshooting
Topic: Battery pack on raspberry pi 4
Replies: 1
Views: 43

Re: Battery pack on raspberry pi 4

cigar plug converters were often used to power early PI's, who used less than 1A, and were a cheap solution, but the RPI4 needs much more power, so you will need a converter that can deliver at least 2A, also use a thick and short USB cable or you cable lesses will be prohibitive. You can also use a...
by mahjongg
Thu Jul 29, 2021 12:28 pm
Forum: Troubleshooting
Topic: Raspberry PI4 rainbow screen Frezze on startup
Replies: 1
Views: 29

Re: Raspberry PI4 rainbow screen Frezze on startup

This is the result of the GPU test, and is the last thing it does before trying to boot up the ARM code. It means the ARM code is bad and unbootable.
The RPI uses the GPU to boot up the system.
by mahjongg
Thu Jul 29, 2021 12:24 pm
Forum: General discussion
Topic: Powering pi 4 model b with 7.4 volt 2200mah battery
Replies: 4
Views: 163

Re: Powering pi 4 model b with 7.4 volt 2200mah battery

NO!

you need a good (switching) voltage regulator that can deliver enough current, and with the required stability!
by mahjongg
Wed Jul 28, 2021 11:53 am
Forum: Automation, sensing and robotics
Topic: How do I make 2-way light switch automated with a RPi?
Replies: 2
Views: 206

Re: How do I make 2-way light switch automated with a RPi?

, but I'm willing to take the risk. Are you also willing to electrocute someone else? I have just one suggestion (other than don't do stuff you are not allowed to do) and that is to separate the task of changing the switch to a PI controlled relay in two separate tasks, controlling the relay with a...
by mahjongg
Mon Jul 26, 2021 7:12 pm
Forum: Other projects
Topic: Pi Zero as middle man between pc and keyboard
Replies: 5
Views: 230

Re: Pi Zero as middle man between pc and keyboard

You could try to use a PS/2 keyboard, it doesn't need an USB interface, and the interface can be "bit banged" with GPIO's.
by mahjongg
Sun Jul 25, 2021 7:19 pm
Forum: Compute Module
Topic: Possible migration from Compute Module to other SOM
Replies: 17
Views: 916

Re: Possible migration from Compute Module to other SOM

Okay OP has not replied to my demands so I have deleted his first post, and perma banned him Hi all, as we are all well aware of the current world wide chip shortage, availability of any type of RPi Compute Module is being pushed back further and further. So it could very well take another year befo...
by mahjongg
Sun Jul 25, 2021 6:52 pm
Forum: General
Topic: Power a 24v 11amp halogen bulb with pi and relay
Replies: 11
Views: 452

Re: Power a 24v 11amp halogen bulb with pi and relay

dbrion06 wrote:
Mon Jul 12, 2021 11:14 am
Excuse me, but is it a Rapberry Pi thread or a Pico Pi thred?
Actually as the Pico also has 3V3 GPIO's so the Sticky is valid to both RPI's and Pico's, but Pico's are not as latchup sensitive as RPI's, but the are still not 5V tolerant! (slightly updated the sticky).
by mahjongg
Sat Jul 24, 2021 7:56 pm
Forum: Troubleshooting
Topic: Low voltage warning despite official power supply?
Replies: 8
Views: 277

Re: Low voltage warning despite official power supply?

Duffl wrote:
Sat Jul 24, 2021 5:51 pm
Or may it be that this is a known bug, is it possible that the warning is somehow faulty?
In my experience that is highly unlikely.
Many low power situations exists because unsuitable cables are used.
by mahjongg
Sat Jul 24, 2021 7:43 pm
Forum: Beginners
Topic: How do I combine several components to GPIO
Replies: 4
Views: 202

Re: How do I combine several components to GPIO

Not a joke, but buy a soldering iron, and learn to solder, and you will never have a problem permanently connecting two metal wires together again.
Learning to solder is a must for every engineer. :mrgreen:
by mahjongg
Thu Jul 22, 2021 8:55 pm
Forum: Troubleshooting
Topic: unfrying a raspberry pi 4 (applied 12v to 5v pin, oops)
Replies: 11
Views: 257

Re: unfrying a raspberry pi 4 (applied 12v to 5v pin, oops)

throw the PI in the bin and buy a new one.
by mahjongg
Thu Jul 22, 2021 12:26 pm
Forum: Advanced users
Topic: Rearranging partitions on SD Card
Replies: 5
Views: 347

Re: Rearranging partitions on SD Card

a Raspberry PI can only boot from a FAT32 partition, so the FAT partition is a necessity.
by mahjongg
Thu Jul 22, 2021 12:24 pm
Forum: General discussion
Topic: Plug in monitor HDMI cable after boot up
Replies: 4
Views: 172

Re: Plug in monitor HDMI cable after boot up

Yes, that is normal, as the PI only reads out the monitor info during boot, if it can't then it switches to generating composite video.
If you want a fixed monitor setting you can make an entry in config.txt
by mahjongg
Wed Jul 21, 2021 11:53 am
Forum: General discussion
Topic: NTP uninstalling itself
Replies: 29
Views: 990

Re: NTP uninstalling itself

Locking this posts, as it is going nowhere! I would suggest starting over with a slightly different question "Why is NTP uninstalling itself", I will look the other way as technically it is a duplicate, and we normally don't allow duplicate posts. Ill advice agains using snarky language, a...
by mahjongg
Tue Jul 20, 2021 10:13 am
Forum: Astro Pi
Topic: Sense Hat IMU Sample Rate - Python
Replies: 1
Views: 275

Re: Sense Hat IMU Sample Rate - Python

deleted duplicate copy
by mahjongg
Mon Jul 19, 2021 12:59 pm
Forum: Troubleshooting
Topic: [SOLVED] Adding sound output to Pi Zero W ?
Replies: 14
Views: 533

Re: Adding sound output to Pi Zero W ?

The solution I would prefer is that they would route out the two (original) PWM signals to two solder pads. or even better pin holes.
then you would only need to add your own filters, and it would be software compatible with older systems.
by mahjongg
Mon Jul 19, 2021 12:55 pm
Forum: Other programming languages
Topic: Cobol in schools
Replies: 99
Views: 3087

Re: Cobol in schools

The last time there was any use for Cobol programmers was when the "year 2000 bug" happened, and a lot of cobol had to be checked and changed to make sure it would keep working after the year 2000. I seriously doubt such a thing would happen again.
by mahjongg
Sat Jul 17, 2021 12:45 pm
Forum: Beginners
Topic: USB Power Supply
Replies: 14
Views: 558

Re: USB Power Supply

No RPI has a battery, so it should not be used with a battery charger. :mrgreen:

That said, with the very first PI you could generally get away with using one, but not the later ones, especially WiFi modules absolutely demand a stable power supply.
by mahjongg
Sat Jul 17, 2021 12:33 pm
Forum: General discussion
Topic: I'm new here, need a guide!
Replies: 7
Views: 443

Re: I'm new here, need a guide!

For starters, post in the right thread, or create a new one! you posted this in the introduction sticky, but this is not an introduction, so I split it from that thread, and started your own thread. Don't be bashful though, you can still post in the introduction sticky and introduce yourself. You co...
by mahjongg
Thu Jul 15, 2021 11:37 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Occasional unhandled IRQ on Pi4
Replies: 3
Views: 251

Re: Occasional unhandled IRQ on Pi4

Moved back from where I THOUGHT it came from, if I'm wrong please flag me again.

And sorry but I thought IRQ handlers would always be bare metal....

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