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by MarkHaysHarris777
Mon Jul 11, 2016 12:24 pm
Forum: Troubleshooting
Topic: Relay switch wiring
Replies: 14
Views: 2167

Re: Relay switch wiring

How large can this potential be? Depending on the circumstances, it can be thousands of volts... not much current, obviously, but enough voltaget that it can instantly destroy your PI... and this has happened more times than we would like to admit. Its one of those tough lessons learned kinda thing...
by MarkHaysHarris777
Mon Jul 11, 2016 10:38 am
Forum: Troubleshooting
Topic: Relay switch wiring
Replies: 14
Views: 2167

Re: Relay switch wiring

In reverse order, the diode is there to protect your PI from the inductive load (the relay itself). Inductive loads are dangerous to the PI because of the back EMF they produce... the diode helps to bleed off the back EMF protecting the PI circuits. The transistor acts like a switch... you activate ...
by MarkHaysHarris777
Mon Jul 11, 2016 9:02 am
Forum: Camera board
Topic: Picamera_cv colours wrong after update/upgrade
Replies: 12
Views: 3130

Re: Picamera_cv colours wrong after update/upgrade

Not seen this...

... interesting though.

marcus
by MarkHaysHarris777
Mon Jul 11, 2016 9:01 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C on Python 3
Replies: 3
Views: 2049

Re: I2C on Python 3

Please post your python trace-back...

...so that we know what error you got. thanks

marcus
by MarkHaysHarris777
Mon Jul 11, 2016 5:52 am
Forum: Beginners
Topic: different OS
Replies: 17
Views: 2241

Re: different OS

I see you're carefully ignoring Burroughs / Sperry (merged to Unisys) and Lyons / ICL who were subsumed into Fujitsu. footnotes in history; almost irrelevant as well as insignificant in the big scheme of things. Footnotes in the Great British History of developing computing................. . That ...
by MarkHaysHarris777
Mon Jul 11, 2016 5:41 am
Forum: Arch
Topic: Looking at ARCH
Replies: 14
Views: 6450

Re: Looking at ARCH

I am playing around with arch on my PineA64; similar in most respects to the Raspberry PI 3B, but with more memory on a larger foot-print (index card sized). Yes, arch is manual; which is good, because it will force you to learn gnu+linux. For instance to get wifi going you will need to manually con...
by MarkHaysHarris777
Mon Jul 11, 2016 5:36 am
Forum: Scratch
Topic: No module named scratch
Replies: 4
Views: 3318

Re: No module named scratch

You are receiving the error because 'scratch' is not a built-in and also because there is no C module on the system called scratch.so, nor is there a python module on the system called scratch.py Where did the course tell you to get scratch.py ? were you supposed to code it ? do they provide it some...
by MarkHaysHarris777
Mon Jul 11, 2016 5:24 am
Forum: Networking and servers
Topic: Allow apache to download image inside server directory?
Replies: 3
Views: 765

Re: Allow apache to download image inside server directory?

Its not a good plan to download anything into the apache directory; which makes it extremely vulnerable.

Download to another directory, or sandbox, and then host it out from there....

marcus
by MarkHaysHarris777
Sat Jul 09, 2016 9:52 am
Forum: Beginners
Topic: different OS
Replies: 17
Views: 2241

Re: different OS

DougieLawson wrote:I see you're carefully ignoring Burroughs / Sperry (merged to Unisys) and Lyons / ICL who were subsumed into Fujitsu.
footnotes in history; almost irrelevant as well as insignificant in the big scheme of things.
by MarkHaysHarris777
Sat Jul 09, 2016 8:59 am
Forum: Beginners
Topic: different OS
Replies: 17
Views: 2241

Re: different OS

Sooo ... Unix is the great-grand-daddy of both the BSD and the Linux broods ... and Windows and RiscOs come from different lineages So, apart from the pre-Neanderthal Ur Clade to which we all belong, can we say we have three families, or four? In my opinion we have four. ... and its not based on so...
by MarkHaysHarris777
Sat Jul 09, 2016 6:32 am
Forum: Graphics, sound and multimedia
Topic: [Feasibility] 4 webcams output to 1 display pi2
Replies: 3
Views: 900

Re: [Feasibility] 4 webcams output to 1 display pi2

please forgive me, but this kind of project is extremely dangerous, and in some locales illegal. The single most common cause of crashes amoung young people is distraction! This project is distraction on steroids. You need to keep your eyes out the front window at all times (scanning mirrors, yes) b...
by MarkHaysHarris777
Sat Jul 09, 2016 6:28 am
Forum: Python
Topic: LDR readings on lcd
Replies: 2
Views: 660

Re: LDR readings on lcd

Well, not only the number of elif statements (yes), but also each elif is calling rc_time and that function has an untimed counter! So, yeah, its probably going to run slower than you like; and the speed isn't really a function of python or your code, its really the time it takes to do all that unti...
by MarkHaysHarris777
Sat Jul 09, 2016 6:23 am
Forum: General discussion
Topic: 5v, 3amp ok?
Replies: 8
Views: 3310

Re: 5v, 3amp ok?

To add to Heydt's comment above, the exception these days to the rule are the new Samsung fast changers that will not only provide the right current, BUT, they will also bump up to 9v !! ... and that will blow your PI. Be very careful about PSU that claim to be 'fast' chargers because they will 9v y...
by MarkHaysHarris777
Sat Jul 09, 2016 6:20 am
Forum: Beginners
Topic: different OS
Replies: 17
Views: 2241

Re: different OS

Both unix and Linux now comply with the POSIX standard and can, for most any end user purpose be considered identical. Correct, for the most part; however, technically of the two ( bsd and gnu+linux ) only bsd can call itself unix... as can freeBSD. gnu+linux should not ever technically be called u...
by MarkHaysHarris777
Fri Jul 08, 2016 8:06 pm
Forum: Beginners
Topic: Raspberry Pi 3 Boot Problems
Replies: 4
Views: 866

Re: Raspberry Pi 3 Boot Problems

You cannot use your laptop as a monitor for a PI. Also, read the boot problem sticky. You can use your laptop (notebook) computer as a monitor for your PI (I do this all the time!) but you have to set-it-up first; and it requires the ethernet link-local connection and it also requires tightvncserve...
by MarkHaysHarris777
Fri Jul 08, 2016 7:10 am
Forum: Beginners
Topic: Operating Systems ending in .xz
Replies: 9
Views: 3078

Re: Operating Systems ending in .xz

... having trouble adding OS images onto an SD card (lots of stress over such a small thing) and I notice some of the operating systems end in .xz The .xz ending is a compression container (indicator) for tar archives; usually made with the -J switch: tar -cvJf mysample.tar.xz -C ~/directory sample...
by MarkHaysHarris777
Fri Jul 08, 2016 6:52 am
Forum: Beginners
Topic: I have some problem with DHT22(temperature, humidity sensor)
Replies: 1
Views: 1018

Re: I have some problem with DHT22(temperature, humidity sen

Hello all, I'm following a tutorial below (http://www.instructables.com/id/Raspberry-PI-and-DHT22-temperature-and-humidity-lo/step10/Set-up-the-temperature-logger-code/) You will need to contact the author of the tutorial, and ask for some advice. The tutorial may have an error (I do not know this ...
by MarkHaysHarris777
Fri Jul 08, 2016 6:43 am
Forum: Troubleshooting
Topic: File Permission Error - Accessing Samba share from Win 10
Replies: 2
Views: 1096

Re: File Permission Error - Accessing Samba share from Win 1

Try setting the permissions on the /mnt/media folder to sudo chmod 0775 ... sometimes in order to add folders to a folder the folder needs the uid and the gid to both have r-w-x permissions. Is the group id 'root' or is it samba ? The group may need to be samba , and the userids may need to be membe...
by MarkHaysHarris777
Fri Jul 08, 2016 6:25 am
Forum: General programming discussion
Topic: Weird things happening with rc.local
Replies: 3
Views: 1185

Re: Weird things happening with rc.local

There really is only one explanation for this kind of behavior in the system (other than having been the victim of a malicious intrusion) and that is that your SD card appears to have been corrupted. Have you noticed any other system errors, or other weird types of behavior ? You will probably have ...
by MarkHaysHarris777
Thu Jul 07, 2016 6:15 pm
Forum: Scratch
Topic: 1wire support
Replies: 3
Views: 2408

Re: 1wire support

All suggestions welcomed... From my experience on this forum for a couple of years... it seems that 1wire is not used that much; most of the time when it is used its the temperature sensor(s). It does not seem that performance is an issue... its more like, does the thing return a valid temperature ...
by MarkHaysHarris777
Thu Jul 07, 2016 6:06 pm
Forum: Beginners
Topic: different OS
Replies: 17
Views: 2241

Re: different OS

why there are different types of OS. Why third party OS is given. If we for example use windows 10 IOT core,will it be similar to windows 10 To answer in reverse order: "if we use Win10 IoT core, will it be similar to Windows 10?" No. Win10 IoT core is not a graphical "windows" operating system. It...
by MarkHaysHarris777
Thu Jul 07, 2016 5:59 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Rpi3 with Arduino on serial port /dev/ttyS0
Replies: 4
Views: 1783

Re: Rpi3 with Arduino on serial port /dev/ttyS0

Why is it so difficult to get this serial port problem sorted out? Because the engieers tried to get the wifi blue tooth stuff on this board before it was ready. Unfortunately, you cannot have your cake and eat it too... you need to choose. Unless you absolutely need it, just disable the bt with th...
by MarkHaysHarris777
Thu Jul 07, 2016 5:51 pm
Forum: Graphics, sound and multimedia
Topic: GPIO Sound
Replies: 2
Views: 575

Re: GPIO Sound

Ryfong704 wrote:Is there any way too hook up speakers,(small ones) or an amplifier and speakersnto the GPIO of the RPi?
Sure.

...take a look at my post here.

marcus
by MarkHaysHarris777
Thu Jul 07, 2016 5:47 pm
Forum: Python
Topic: play a specific frequency using usb speakers
Replies: 5
Views: 1027

Re: play a specific frequency using usb speakers

DougieLawson wrote:https://www.raspberrypi.org/magpi/issues/ is the catalog for current and back issues. I've no idea if there's any searchable index for published articles.
thanks bubba !
by MarkHaysHarris777
Thu Jul 07, 2016 6:15 am
Forum: Beginners
Topic: Resister sizes
Replies: 8
Views: 1286

Re: Resister sizes

Resisteors add in series. (And the divide in parallel.) Thus two 1K resistors, on after the other is 2K. Two1K resistors with both ends in common would be 500 Ohms. Heydt has over simplified.. I think intentionally... resistors in parallel don't simply divide... the result is the reciprical of the ...

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