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by davidcoton
Thu Apr 18, 2019 5:00 pm
Forum: Beginners
Topic: How to calculate resistors...
Replies: 42
Views: 597

Re: How to calculate resistors...

I feel like I am questioning everything I thought I knew about electronics lately. Where should I measure the voltage of the LED? On either side of the LED - between resistor and GND? Or GPIO to GND side of LED? Other? It seems you are right to question what you thought you knew. You need to distin...
by davidcoton
Tue Apr 16, 2019 6:21 pm
Forum: Beginners
Topic: Relay AC/DC mix
Replies: 1
Views: 61

Re: Relay AC/DC mix

Prior question to the one about parts: Do you know enough about mains safety practices to tackle mains relays safely? In particular, how to keep the mains parts of the relay outputs safe from finger contact at all times, how to avoid fires starting from thin wires or poor contacts, double insulation...
by davidcoton
Tue Apr 16, 2019 7:40 am
Forum: Troubleshooting
Topic: Controlling LED on GPIO3
Replies: 7
Views: 136

Re: Controlling LED on GPIO3

I specifically chose the blue LED because I know it can take 3.3v You are misreading the spec. It says that, when the current is 20mA, the voltage will be typically 3V0, max 3V4. That means if you apply 3V3 without a resistor, typically the current will exceed 20mA. That is enough to damage your Pi...
by davidcoton
Sun Apr 14, 2019 8:01 am
Forum: General discussion
Topic: Powering RPI 3B+ With 24VAC
Replies: 17
Views: 501

Re: Powering RPI 3B+ With 24VAC

What if I soldered to a mini usb cable and used the standard port? That solves the fuse problem but you must make sure the wires are thick enough (18 AWG) -- this applies to power connections via the GPIO header too. Most USB cables have much thinner wires, you need one designed for charging at 2-3A.
by davidcoton
Sat Apr 13, 2019 9:36 pm
Forum: General discussion
Topic: Cluster Pi via gpio pins
Replies: 33
Views: 722

Re: Cluster Pi via gpio pins

[Off Topic WARNING] mahjongg, I love marmite, especially on old edammer cheese. (and yes, as you might guess I'm Dutch!). Good for you. Of course a nation that thinks Edam is good will be quite happy with fake cow extract. :) You should try good Stilton cheese. No need for Marmite with that. (Marmit...
by davidcoton
Sat Apr 13, 2019 9:17 pm
Forum: General discussion
Topic: Powering RPI 3B+ With 24VAC
Replies: 17
Views: 501

Re: Powering RPI 3B+ With 24VAC

If you power through GPIO pins, you are bypassing the on board power protection circuits. At the very least, put a fuse (probably best to be a polyfuse) in your power circuit to protect against overcurrent conditions. To properly protect your Pi against power supply faults, you would need to--basic...
by davidcoton
Sat Apr 13, 2019 2:18 pm
Forum: Italiano
Topic: serra automatizzata
Replies: 2
Views: 59

Re: serra automatizzata

Hi guys I would like to automate a greenhouse, the raspberry should check: humidity - air temperature, soil moisture, open a window in case of humidity or high temperature, if it's not enough to operate a fan turn off the fan and close the window as soon as the temperature or humidity drops operate...
by davidcoton
Sat Apr 13, 2019 10:30 am
Forum: Advanced users
Topic: Raspberry Pi Image Processing so slow?
Replies: 2
Views: 134

Re: Raspberry Pi Image Processing so slow?

nailcankara wrote:
Sat Apr 13, 2019 10:22 am
Now i learn new thing which is SWAP space..
Does any one know anything about this terms?
Google does https://www.google.com/search?q=swap+space
by davidcoton
Sat Apr 13, 2019 10:25 am
Forum: General discussion
Topic: Raspberry Pi is unusable as everyday computer
Replies: 67
Views: 2865

Re: Raspberry Pi is unusable as everyday computer

Gavinmc42 wrote:
Sat Apr 13, 2019 9:59 am
Pi's are more usable? Well at least they do what they are told.
Pi4 will have PiSense technology to make sure it does what you think you told it, not what you actually said. (Yes, speech input too.) :lol:
Google's search autocorrect runs on the prototype. :o
by davidcoton
Sat Apr 13, 2019 10:20 am
Forum: Off topic discussion
Topic: Why Avoid BASIC on RPi?
Replies: 1771
Views: 69580

Re: Why Avoid BASIC on RPi?

Now, all the world and his dog is jumping on Python. I find it very disturbing. I'm sure the python finds it disturbing, too. But surely after 66 full pages of this thread the one clear truth is that (almost?) all programming languages have their strengths and weaknesses. The perfect language will ...
by davidcoton
Sat Apr 13, 2019 9:54 am
Forum: Off topic discussion
Topic: Why Avoid BASIC on RPi?
Replies: 1771
Views: 69580

Re: Why Avoid BASIC on RPi?

ejolson wrote:
Sat Apr 13, 2019 7:13 am
Fortran Man and the Fibonacci Code
+1.0 :lol: :D
by davidcoton
Sat Apr 13, 2019 9:41 am
Forum: General discussion
Topic: Raspberry Pi is unusable as everyday computer
Replies: 67
Views: 2865

Re: Raspberry Pi is unusable as everyday computer

Now I'm a Win 10 maintainer. Grrr... What's the problem? Windows10 maintains itself. It will download and install updates, and even reboot without you doing anything. It can downgrade your carefully installed up-to-date GPU driver with the older "latest" M$ approved version. It even knows that an u...
by davidcoton
Sat Apr 13, 2019 9:32 am
Forum: General discussion
Topic: What's the best way to more securely fix wires to a breadboard?
Replies: 10
Views: 269

Re: What's the best way to more securely fix wires to a breadboard?

LTolledo wrote:
Sat Apr 13, 2019 6:26 am
I used colored plastic coated paper clips, whose wire diameter is small enough to snugly fit into the breadboard holes....(not too tight, not too loose),
Remembering, of course, to remove the plastic coating where the clip wire enters the breadbooard :roll: :ugeek:
by davidcoton
Fri Apr 12, 2019 3:07 pm
Forum: Off topic discussion
Topic: I know this sounds like something from a Spy novel or makes me sound a like a crazy person but...
Replies: 26
Views: 595

Re: I know this sounds like something from a Spy novel or makes me sound a like a crazy person but...

bensimmo wrote:
Fri Apr 12, 2019 3:03 pm
I have a HuaWei phone.
Remind me not to discuss any security issues with you on phone, text, or email. :lol: :roll: :twisted:
by davidcoton
Fri Apr 12, 2019 3:01 pm
Forum: Advanced users
Topic: Overvault problem
Replies: 2
Views: 97

Re: Overvault problem

Assuming you were applying power through the micro USB connector, there are a couple of things to try: 1) Leave the Pi unpowered for 24 hours. The polyfuse should have tripped and takes time to recover. 2) Remove the TVS protection diode D7 on the top of the board, near the microUSB connector. There...
by davidcoton
Fri Apr 12, 2019 10:38 am
Forum: General discussion
Topic: Run a pi3 on battery for a week ?
Replies: 7
Views: 263

Re: Run a pi3 on battery for a week ?

You forgot to calculate voltage drop over time. As you drain the battery the voltage will drop, and so the current draw will increase. True, but the starting voltage will be over 12V so the overall effect is small. Covered by the general allowance for conversion inefficiendcy and other losses. You ...
by davidcoton
Mon Apr 08, 2019 10:56 pm
Forum: Beginners
Topic: realy poor wifi ( pi2 ) ( yes another one )
Replies: 11
Views: 762

Re: realy poor wifi ( pi2 ) ( yes another one )

Imperf3kt wrote:
Mon Apr 08, 2019 10:38 pm
Then what did you mean by this?
Nataku wrote:
Mon Apr 08, 2019 9:10 pm
- and 2cm is more farther than reality between my pi and my router ><
Pay attention. Different contributor.
by davidcoton
Mon Apr 08, 2019 8:00 pm
Forum: Off topic discussion
Topic: Why Avoid BASIC on RPi?
Replies: 1771
Views: 69580

Re: Why Avoid BASIC on RPi?

ScriptBasic wrote:
Mon Apr 08, 2019 7:07 pm
Where is the best place to get a copy of Raspbian for the Zero?
Here, as always.
Most "official" software will run on all current Pi models form the same download.
Where necessary the software detects and adapts to the particular model.
by davidcoton
Mon Apr 08, 2019 7:53 pm
Forum: Beginners
Topic: raspi-config from Command Line Interface
Replies: 2
Views: 265

Re: raspi-config from Command Line Interface

For a one-off session, "startx" should start the desktop. From there you might be able to start a console and run "sudo raspi-config" to make it permanent.

But I don't know why it didn't work from the command line without the desktop.
by davidcoton
Mon Apr 08, 2019 2:59 pm
Forum: General discussion
Topic: Strange Power Problems
Replies: 7
Views: 285

Re: Strange Power Problems

nonoti wrote:
Mon Apr 08, 2019 9:43 am
I've done the measurements:
That clearly shows that the cables are too thin and/or too long, because the voltage at the PSU is good but at the Pi is not good.
The official PSU is the easiest solution.
by davidcoton
Sun Apr 07, 2019 10:45 pm
Forum: General discussion
Topic: Strange Power Problems
Replies: 7
Views: 285

Re: Strange Power Problems

Almost certainly due to either: Voltage drop on the cables, or The PSU does not maintain 5V at the current the Pi draws (chargers are notorious for this). 1) Measure the voltage at the Pi, with the Pi running.If less than 4V8 then it is a power problem 2) If possible measure the voltage at the PSU, ...
by davidcoton
Fri Apr 05, 2019 12:24 pm
Forum: Troubleshooting
Topic: I suspect My Pi is bricked, due to a failed PSU, but how do I check?
Replies: 25
Views: 565

Re: I suspect My Pi is bricked, due to a failed PSU, but how do I check?

:oops: Thanks guys, I got confused between polyfuse and TVS. :oops:
I blame morning caffeine deficiency.
Earlier post corrected.

Polyfuse is underneath on all models I checked.
TVS underneath on original B, on top on B+ 2B 3B 3A+.
TVS conponent number varies.
No polyfuse or TVS on Pi0 models.
by davidcoton
Fri Apr 05, 2019 9:56 am
Forum: Advanced users
Topic: L1 L2 Cache size in Raspberry Pi3
Replies: 2
Views: 158

Re: L1 L2 Cache size in Raspberry Pi3

avenito wrote:
Thu Apr 04, 2019 9:54 pm
Dear vkmrpi3,
You are unlikely to get an answer:

Code: Select all

vkmrpi3

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by davidcoton
Fri Apr 05, 2019 9:49 am
Forum: Troubleshooting
Topic: I suspect My Pi is bricked, due to a failed PSU, but how do I check?
Replies: 25
Views: 565

Re: I suspect My Pi is bricked, due to a failed PSU, but how do I check?

The protection diode is not like a normal diode. I believe it is bi-directional and shouldn't conduct in either direction until the voltage hits 6.0V (in this case). It's a bit like two Zener diodes connected back to back. There are TWO versions of the SMBJ5.0. 1) The SMBJ5.0A is uni-directional, a...
by davidcoton
Fri Apr 05, 2019 9:28 am
Forum: Beginners
Topic: Error when sudo apt-get dist-upgrade of Pi B+
Replies: 8
Views: 260

Re: Error when sudo apt-get dist-upgrade of Pi B+

Note: Pi B+ However, now when I boot-up, I get this message: failed to start dhcpcd on all interfaces It does get an IP address for eth0 but not for the wifi interface. Before the upgrade from Jessie to Stretch both interfaces worked correctly. dist-upgrade by itself does not move from Jessie to St...

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