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by rpdom
Thu Apr 26, 2018 8:35 pm
Forum: Beginners
Topic: Disk Full
Replies: 4
Views: 85

Re: Disk Full

You've got an 8GB card with NOOBS, by the looks of it. NOOBS (not the Lite version) uses a fair chunk of space for the Raspbian installation image, over 1GB, so that won't be available to you. Neither will the sapce that NOOBS itself uses, so 5.7GB sounds about right for the remaining space. You can...
by rpdom
Thu Apr 26, 2018 4:04 pm
Forum: General discussion
Topic: Controlling three solenoid valves with 12 mA limit
Replies: 21
Views: 551

Re: Controlling three solenoid valves with 12 mA limit

There's nothing in any of those circuits that would need a high wattage resistor.
by rpdom
Thu Apr 26, 2018 10:52 am
Forum: Python
Topic: How ist the best approach for task sharing in Py?
Replies: 9
Views: 165

Re: How ist the best approach for task sharing in Py?

Creating files in /dev/shm may be an option. That is basically a ramdisk, and fine as long as there is enough free RAM. After that it will use virtual memory (swap file) and that will hit the SD card. Are you going to be producing many MB of data at a time?
by rpdom
Thu Apr 26, 2018 7:29 am
Forum: Raspbian
Topic: what time raspian will show if internet is offline?
Replies: 6
Views: 156

Re: what time raspian will show if internet is offline?

DougieLawson wrote:
Thu Apr 26, 2018 6:55 am
The default with fake-hwclock is seventeen minutes past the last hour before you shut it down.
It is supposed to save the bcurrent time when you shutdown cleanly. It also saves the time at 17 minutes past each hour, which is what will show after an unclean shutdown/reboot.
by rpdom
Thu Apr 26, 2018 5:43 am
Forum: Advanced users
Topic: Mean of 60 temperature sensors
Replies: 11
Views: 285

Re: Mean of 60 temperature sensors

I can't immediately think of a (wired or wireless) approach that would be likely to work without using a fair number of Pis as data collection hubs. Does anyone have any bright ideas on the data collection side? Is there a limit (system, not the physical problems) on the number of one-wire-bus (Dal...
by rpdom
Thu Apr 26, 2018 5:35 am
Forum: General discussion
Topic: Controlling three solenoid valves with 12 mA limit
Replies: 21
Views: 551

Re: Controlling three solenoid valves with 12 mA limit

DCV Solenoid Circuit 2-min.jpg How's this circuit? Is that really all I need on the DC side? If so, how much current will the Pi have to source for this circuit? Yes, that is all you need on the DC side. The Pi only has to drive the low current LED inside the SSR module to turn it on. I'd have to c...
by rpdom
Wed Apr 25, 2018 5:02 pm
Forum: Raspbian
Topic: Bash script: double ascii stream to hex .. and back
Replies: 24
Views: 419

Re: Bash script: double ascii stream to hex .. and back

PeterO wrote:
Wed Apr 25, 2018 5:00 pm
B.Goode wrote:
Wed Apr 25, 2018 4:45 pm
Now we need a wrapper that converts 30323441 into 024A before invoking .hexstr.sh
What is the algorithm for that conversion ? I can see no relation between 30323441 and 024A.
PeterO
ASCII Hex values
0x30 = "0"
0x32 = "2"
0x34 = "4"
0x41 = "A"
by rpdom
Wed Apr 25, 2018 3:36 pm
Forum: Troubleshooting
Topic: Raspberry PI 3 "Under Voltage"
Replies: 9
Views: 226

Re: Raspberry PI 3 "Under Voltage"

I have a number of USB chargers, cables and power banks with uUSB connectors that just don't mate properly with any of my Pi's (Too loose) That's why I gave up using them. I have the opposite experience. Every charger/power supply/whatever with MicroUSB connectors have had no problems connecting to...
by rpdom
Wed Apr 25, 2018 2:47 pm
Forum: General discussion
Topic: Determining 3B board age
Replies: 2
Views: 150

Re: Determining 3B board age

I believe the numbers 1610, 1637 and 1643 are the manufacturing date codes. 2016 weeks 10, 37 and 43.
by rpdom
Wed Apr 25, 2018 3:47 am
Forum: Camera board
Topic: What resistor value is C3 on the camera?
Replies: 4
Views: 154

Re: What resistor value is C3 on the camera?

It should be a 1uF capacitor, according to the schematics which have just been released https://www.raspberrypi.org/documentati ... a2_2p1.pdf
by rpdom
Tue Apr 24, 2018 5:13 pm
Forum: General discussion
Topic: SenseHat Callibration for Compass
Replies: 11
Views: 295

Re: SenseHat Callibration for Compass

MMrmcnich wrote:
Tue Apr 24, 2018 4:34 pm
Ah I always just update and upgrade I never repeat update after.
Yes. Usually that is fine. This is an exceptional case due to the particular upgrade.
by rpdom
Tue Apr 24, 2018 1:55 pm
Forum: General discussion
Topic: Enable Predictable names
Replies: 19
Views: 310

Re: Enable Predictable names

root@hitchhiker:~ # dpkg -l | grep raspi-config What is that "grep" doing in there other than to make more work for your poor raspberry? pi@raspi7:~ $ dpkg -l raspi-config Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend |/ Err...
by rpdom
Tue Apr 24, 2018 12:18 pm
Forum: Troubleshooting
Topic: Official touchscreen is upside down.
Replies: 6
Views: 146

Re: Official touchscreen is upside down.

I got it to work, however, the viewing angles are worse with the display like this, can you put the display in the other way around? That's the reason the image appeared upside down. The original design of the screen was the wrong way round for the viewing angles. Also, there are black borders arou...
by rpdom
Tue Apr 24, 2018 12:09 pm
Forum: Advanced users
Topic: How to expand Virtual Memory on RPi B3 +?
Replies: 27
Views: 581

Re: How to expand Virtual Memory on RPi B3 +?

WHY NOT, THE SPACE IS THERE! If you are needing to use virtual memory (swap space) on a Pi (or almost any other server really), you need to reconsider things. Are you using the right hardware? Is your application being too memory hungry? Using virtual memory on a Pi is even worse than using it on a...
by rpdom
Tue Apr 24, 2018 10:01 am
Forum: General discussion
Topic: Is there a way to have a single button initiate a call to play a prerecorded message.
Replies: 4
Views: 111

Re: Is there a way to have a single button initiate a call to play a prerecorded message.

I'm not sure it would be quite as simple as people are implying to script it to use SIP (as the OP requested). It is possible though.
by rpdom
Tue Apr 24, 2018 4:39 am
Forum: General programming discussion
Topic: SMI Documentation ?
Replies: 17
Views: 3895

Re: SMI Documentation ?

Some details are given the the BCM2835-ARM-Peripherals file (here). I think it was on page 102 or near there that most of the GPIO alternative pin mappings are listed. ALT1 on most pins is for SMI. The https://pinout.xyz site also shows them, but you have to check each pin to find its SMI function.
by rpdom
Tue Apr 24, 2018 4:25 am
Forum: General discussion
Topic: SenseHat Callibration for Compass
Replies: 11
Views: 295

Re: SenseHat Callibration for Compass

Yes I have done sudo apt-get update and upgrade and after attempting to install I got the same error message. I even wiped and restarted the sd and then followed the same steps after updating to no avail. Aha! Please do sudo apt-get update again. Then try the install. On a recent upgrade the packag...
by rpdom
Mon Apr 23, 2018 7:44 pm
Forum: Advanced users
Topic: How to expand Virtual Memory on RPi B3 +?
Replies: 27
Views: 581

Re: How to expand Virtual Memory on RPi B3 +?

That is up to the RPF to make that decision. Their decision is right now to keep that compatability since one of their goals is to provide an affordible computer to teach stidents worldwide including third world countries where even a $35.00 is an expensive purchase for many. It is nothing to do wi...
by rpdom
Mon Apr 23, 2018 7:09 pm
Forum: General discussion
Topic: Controlling three solenoid valves with 12 mA limit
Replies: 21
Views: 551

Re: Controlling three solenoid valves with 12 mA limit

From the Fairchild Semi datasheet
30N06L.png
30N06L.png (15.62 KiB) Viewed 287 times
by rpdom
Mon Apr 23, 2018 6:26 pm
Forum: Beginners
Topic: Simple question about updating Raspbian after new version released...
Replies: 5
Views: 137

Re: Simple question about updating Raspbian after new version released...

The main difference between doing an upgrade and installing a new image is that if an extra package has been included in the new image, and isn't referenced by any existing (updated) packages in the old image, then it won't get installed. (For the benefit of the readers, including me) Can you give ...
by rpdom
Mon Apr 23, 2018 5:11 pm
Forum: Beginners
Topic: Simple question about updating Raspbian after new version released...
Replies: 5
Views: 137

Re: Simple question about updating Raspbian after new version released...

Hi guys. i started my journey with linux when Raspbian was released on 2018-03-13. Now we have 2018-04-18 available. My question is... To get all the functionalities from new image do i have to reflash my SD card and configure everything from scratch? To update my Pi i use: sudo apt update sudo apt...
by rpdom
Mon Apr 23, 2018 4:40 pm
Forum: General discussion
Topic: Controlling three solenoid valves with 12 mA limit
Replies: 21
Views: 551

Re: Controlling three solenoid valves with 12 mA limit

the FQP 30N06L turn on voltage (Vgs) is spec'd as 1.0 to 2.4 V to turn on the FET The spec sheet I'm looking at says different. Min 2.0 and max 4.0 for a drain current of only 250 micro-amps. vgs.png There is a difference between the 30N06 and 30N06 L . Lower gate threshold voltage for a start.
by rpdom
Mon Apr 23, 2018 3:59 pm
Forum: Beginners
Topic: Stretch problems
Replies: 8
Views: 267

Re: Stretch problems

The things was that one of the upgrades changed the repositories. It invalidated the old one, so no packages in that repo showed as existing, until the index was rebuilt for the new repository by doing an update.
by rpdom
Sun Apr 22, 2018 9:58 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: How much external power from Zero?
Replies: 14
Views: 411

Re: How much external power from Zero?

Few things stand up from "schematic" There are two 3,3V pins on header - nice This is a well known fact. The layout of the 40 pin header is standard across the Raspberry Pi range (other than the early models with 26 pin headers and the CM modules). The "processor" runs on 1.8 V - so how does it man...
by rpdom
Sun Apr 22, 2018 8:42 pm
Forum: Beginners
Topic: Do you browse Facebook on your Pi ?
Replies: 9
Views: 183

Re: Do you browse Facebook on your Pi ?

I'm quite surprised that any of the forum regulars are willing to admit that they even know what faceblob is, much less, that they (some of them) actually use it. Somehow that doesn't surprise me. I mostly to use it to keep in contact with certain members of my family and my large circle of friends...

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