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by r4049zt
Mon Jun 29, 2015 8:50 pm
Forum: General discussion
Topic: Redundancy
Replies: 21
Views: 4765

Re: Redundancy

Given that a raspberry pi B+ uses about 2 to 3 Watts, you could have eight of them always on (yes !eight) with less power than a <brand-name> rival, all running some sort of check-the-other LAN program, and tell the router that the first one which agrees with the majority is the server to get outsid...
by r4049zt
Mon Jun 29, 2015 8:21 pm
Forum: Off topic discussion
Topic: Intel Analog clone of pi
Replies: 15
Views: 1466

Re: Intel Analog clone of pi

That is only so if you count replicating sysmon.exe in and out of cache as processing, with occasional halts to trundle it off up the 240-ohm 200 lines to DDR and back. Personally, I prefer to skip all that waste.
by r4049zt
Mon Jun 29, 2015 7:53 pm
Forum: Automation, sensing and robotics
Topic: Help with external ADC and thermistor
Replies: 15
Views: 4630

Re: Help with external ADC and thermistor

Nevertheless, you'll get a theory calibration which says that it is good to +-0.01%, but does not know the temperature dependent mV where a copper wire is touching a nickelplated one somewhere. But first, put an icecube tray in the freezer, as that will be one point in your testing tomorrow.
by r4049zt
Mon Jun 29, 2015 7:27 pm
Forum: Off topic discussion
Topic: Intel Analog clone of pi
Replies: 15
Views: 1466

Re: Intel Analog clone of pi

Read up twenty year old material about RISC operating systems. Like the old IBM, the pentium was designed as a commercial chip to do lots of things and to have a few *mistakes* which software firms could rely on being there in all subsequent versions. The ARM chip was designed by purists to be Turin...
by r4049zt
Mon Jun 29, 2015 6:40 pm
Forum: Automation, sensing and robotics
Topic: Help with external ADC and thermistor
Replies: 15
Views: 4630

Re: Help with external ADC and thermistor

16 bit precision? +-0.5% is 1/256 so you should expect at best 10-bit useful precision, and more probably seven bits of useful followed by noise. I'd say i) look at the datasheet tabulations of thermister resistance at various listed temperatures and spreadsheet yourself a chart to look at 16-bit ad...
by r4049zt
Mon Jun 29, 2015 6:06 pm
Forum: Windows 10 for IoT
Topic: Camera Support? Arduino Workaround?
Replies: 6
Views: 948

Re: Camera Support? Arduino Workaround?

I don't expect that the arduino will be good for camera images. Reason is that arduino has about 2k of data memory and about 32k of program memory. The number of bits required to store a 3 colour image at 8 bits per colour of size 240x240 pixels is 1382400; or about 1350k. So no chance of getting th...
by r4049zt
Wed Apr 29, 2015 1:15 pm
Forum: Windows 10 for IoT
Topic: Windows Ten Build
Replies: 41
Views: 9217

Re: Windows Ten Build

[SNIP]
I've deleted this unnecessary post which has nothing to do with the thread subject matter.
Please play nice......
Texy
by r4049zt
Wed Apr 29, 2015 1:03 pm
Forum: General discussion
Topic: Is Unallocated space before the first partition OK?
Replies: 7
Views: 1170

Re: Is Unallocated space before the first partition OK?

probably ok. try it. Today a specially complicated multi-partition 32GB SD card which I'd made in gparted did not work. My main goal had been to define a huge swap partition before running noobs. I wiped the card, reformatted to FAT32 which I think means much the same as VFAT, copied in the unzipped...
by r4049zt
Sun Apr 26, 2015 8:38 pm
Forum: Automation, sensing and robotics
Topic: Gauge Size for Powering 17 Servos
Replies: 7
Views: 965

Re: Gauge Size for Powering 17 Servos

The question is unanswerable until you've said how much current (either measured or from datasheet) you expect to put through each servo and how much current in total you'll use from time to time. As it is, they might be industrial ones for which AWG22 is definitely way too small. As the weight and ...
by r4049zt
Sun Apr 26, 2015 8:29 pm
Forum: Automation, sensing and robotics
Topic: 5V relay - Is this a safe connection?
Replies: 7
Views: 1308

Re: 5V relay - Is this a safe connection?

I'm not too happy with only 1k from your gpio control pin to the base of your transistor because the 3mA which it might draw is a bit much for the very tiny system on a chip which drives the gpio. I'd use two of your transistors (look up 'Darlington Pair') and feed one with about 40kOhm from the gpi...
by r4049zt
Sun Apr 26, 2015 6:33 pm
Forum: Wanted
Topic: custom made display
Replies: 5
Views: 2061

Re: custom made display

For that type of TFT display technology, wire me $160 million and I'll make a quarter of a million of them for you.
by r4049zt
Sun Apr 26, 2015 6:29 pm
Forum: Off topic discussion
Topic: Op-Amp Insanity
Replies: 8
Views: 1142

Re: Op-Amp Insanity

As the opamp on the right is expected to give 1x the difference between the other two, it really ought to have +- power supplies such as +-9V and not the single supply that you've done, so that its output can go quite negative when that is the right answer. The CMMR of the 741 might cope with diffin...
by r4049zt
Sun Apr 26, 2015 6:17 pm
Forum: Python
Topic: GPIO Electrical Interference
Replies: 22
Views: 4795

Re: GPIO Electrical Interference

I second the proposal to add a 1k pullup, as that would help to make the 3V3 "open relay" state more strongly defined than the internal pullup got (thanks for sharing that line of code).
by r4049zt
Sun Apr 26, 2015 6:08 pm
Forum: General discussion
Topic: Personal purchase of RPi not allowed by Element14
Replies: 10
Views: 1588

Re: Personal purchase of RPi not allowed by Element14

If Farnell are still mucking you about by the end of this week then I'll buy an extra one and post it to you for £2 above the Farnell price. (that should cover the postage plus 50p for my efforts). I can receive paypal from your online banking or direct bank-to-bank. UK only. My account is Halifax. ...
by r4049zt
Sun Apr 26, 2015 6:02 pm
Forum: General discussion
Topic: Can we run VirtualBox on the Pi?
Replies: 9
Views: 14926

Re: Can we run VirtualBox on the Pi?

Yeah, that's my point. The ARM left out some of the mistakes prevalent in other commercial cpu designs, so there isn't a funnycircuit for virtualbox to present to the host os. Fast&flawless was the goal of the risc design, and "too slow to use if emulated by something fast&flawless" was the (alleged...
by r4049zt
Sun Apr 26, 2015 5:46 pm
Forum: General discussion
Topic: Can we run VirtualBox on the Pi?
Replies: 9
Views: 14926

Re: Can we run VirtualBox on the Pi?

I wouldn't recommend it. Much of what goes on in virtualbox software is to link contemporary names for lots of useless extra bits in modern hardware to WinXP or other system names for useless extra bits which might or might not have been present in the older hardware and which the commercial operati...
by r4049zt
Sun Apr 26, 2015 4:20 pm
Forum: Python
Topic: GPIO Electrical Interference
Replies: 22
Views: 4795

Re: GPIO Electrical Interference

ok. so 16Vac presumably to the coil of the relay might close it. Does it rattle and hum ? You've not said where you get your 3.3V from (relying on the GPIO internal pullup might be sensible, but might warm up your chip). You might want to check your code to see what pullup resistors are in place. Pl...
by r4049zt
Sun Apr 26, 2015 4:06 pm
Forum: Beginners
Topic: using a laptop skeleton to build a pi laptop
Replies: 2
Views: 647

Re: using a laptop skeleton to build a pi laptop

A few years ago I had a look at the connectors from the screen of an Acer laptop to the graphics near to the cpu. They had used a custom flat kapton ribbon, factory-made and not easily changed to a vga or any other recognisable connector which might fit an hdmi adapter to your rPi. My initial reacti...
by r4049zt
Sun Apr 26, 2015 3:43 pm
Forum: Python
Topic: GPIO Electrical Interference
Replies: 22
Views: 4795

Re: GPIO Electrical Interference

As soon as I saw the question with 16V AC in it, I imagine all those 0 to +3.3V rated transistors in your poor rPi getting smoked. Buy yourself a 1x2 inch pinboard on 1/10 inch pitch, a bag of cheap fet or transistors (it does not matter which, as long as their Vgs or Vbe is sufficient), a bag of as...
by r4049zt
Sun Apr 26, 2015 3:19 pm
Forum: C/C++
Topic: multithreaded program in Raspi2
Replies: 12
Views: 4703

Re: multithreaded program in Raspi2

"A program in Windows7" does not define whether it does a sequential task (like "compute successive decimal digits of pi", which won't multithread) or a fully parallel task (like compute the number up to 256 and colour of each pixel in an 800x800 px region from [-2,-2] to [+2,+2] of the Mandelbrot S...
by r4049zt
Thu Dec 26, 2013 11:20 am
Forum: Troubleshooting
Topic: NO COMPOSITE VIDEO, need help!
Replies: 68
Views: 52960

Re: NO COMPOSITE VIDEO, need help!

A nasty to watch out for is "updates creep". That is, something which worked last year and still works for some people on the forum just stops working for no hardware reason at your end. The only response is to not buy stuff from people who might withdraw support for known-good hardware. A more spec...
by r4049zt
Fri Nov 15, 2013 11:53 am
Forum: Beginners
Topic: Is the Raspberry for me
Replies: 4
Views: 961

Re: Is the Raspberry for me

I'd go Arduino for your application. Reason being that it does less to clutter up your workflow, and has enough in/out lines for the task. You'll need a PC to upload your programs from and debug. You can write your programs to send out a single line of text from an arduino for debug purposes such as...
by r4049zt
Fri Nov 15, 2013 11:36 am
Forum: Automation, sensing and robotics
Topic: audio output ac or dc
Replies: 5
Views: 1602

Re: audio output ac or dc

The schematic posted above showed blocking capacitors in the audio output line, so it is ac only. I think you'd be better off using one of the GPIO pins. Look up how to program your pi to set one of those. If you can get it to light an LED with 470 ohms in series below then you have a controllable v...
by r4049zt
Fri Nov 15, 2013 11:23 am
Forum: Bare metal, Assembly language
Topic: Test your compilers!
Replies: 37
Views: 6865

Re: Test your compilers!

Just in case some noobies find this page, compiling is not always so difficult. At a terminal prompt on a pi, mkdir hw cd hw nano hello1.c is sufficient to open a nano text editor and type in a hello world in correct ansi c you should find an example online to get that right. CTRL-O (yes) CTRL-X get...
by r4049zt
Fri Nov 15, 2013 11:06 am
Forum: Beginners
Topic: networking - static ip and dhcp
Replies: 5
Views: 8414

Re: networking - static ip and dhcp

The following worked for me. At the pi do nothing. It gets its ip from dhcp, from whatever network equipment is connected. Pull out the cable from your DHCP router to the internet as you don't want the mafia to see what you are doing. At your home DHCP router, login using the admin user and password...

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