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by r4049zt
Thu Nov 07, 2013 5:49 pm
Forum: C/C++
Topic: Default "C" subroutine values
Replies: 4
Views: 1721

Re: Default "C" subroutine values

Yes, by adding a couple of extra lines with an 'IF' to test values before your subroutine call and replace with defaults if not sensible. You can always write a new subroutine to hide those extra checks and call the old one.
by r4049zt
Wed Nov 06, 2013 6:33 pm
Forum: Troubleshooting
Topic: Blank screen after power-cycle tv oder replugging hdmi
Replies: 3
Views: 984

Re: Blank screen after power-cycle tv oder replugging hdmi

I have noticed that some hdmi TV screens "do nothing" unless they get a response from the device end. My rPi device HDMI will do nothing unless it gets a response from the TV end. It is possible for the rPi to power-off its HDMI output whilst the TV is off. Yikes!. There are days when I see nothing ...
by r4049zt
Wed Nov 06, 2013 6:19 pm
Forum: General discussion
Topic: Need for Industrial Quality RPi System
Replies: 27
Views: 10959

Re: Need for Industrial Quality RPi System

I'm not aware of the educational goals of the raspberry pi home computer including cost reduction of industrial automation hardware for critical systems in hostile environments. By all means buy an IP55 box and do something, but don't moan that one is not included in the home computer and learning k...
by r4049zt
Wed Nov 06, 2013 6:03 pm
Forum: Automation, sensing and robotics
Topic: Room by Room central heating control
Replies: 31
Views: 32816

Re: Room by Room central heating control

My Luddite Opinion Each room can have a self-contained bimetallic thermostat on each radiator. The effort of changing the radiator thermostat from "4" to "2" is about the same as finding an iphone app to do that with much less wiring to get it set up. == none. I suppose that you are after the data l...
by r4049zt
Wed Nov 06, 2013 5:47 pm
Forum: Beginners
Topic: Backup of SD Card
Replies: 3
Views: 770

Re: Backup of SD Card

get your 2GB copied. Your installation may contain an option to 'inflate the filesystem' to fill up the 8GB card, and if you have not got to that stage yet then a smaller content is likely. It is so that the installer is unchanged for 4,8,16GB cards.
by r4049zt
Wed Nov 06, 2013 5:43 pm
Forum: Other projects
Topic: What board to get for my project(s)?
Replies: 4
Views: 1220

Re: What board to get for my project(s)?

I'm using an Arduino for something similar. It has six 0-5V a/d pins which can look at a home-made potential divider to log your battery and solar voltages. Mine uses an 18V zener to log "24V" battery -18V. The arduino is also sufficient for simple logic such as "while the battery is sufficient, swi...
by r4049zt
Wed Nov 06, 2013 5:29 pm
Forum: Teaching and learning resources
Topic: Noobs screenshots howto ?
Replies: 9
Views: 5214

Re: Noobs screenshots howto ?

I recall there being some one-way write to GPU in an early draft specification which would rule out using the usual linux screenshot mechanism in raspian. I don't know Noobs. Pidora uses part of normal memory for screen X-display so that has a screenshooter application. Guessing that you cannot give...
by r4049zt
Wed Nov 06, 2013 5:14 pm
Forum: Advanced users
Topic: Repeating Keyboard Characters
Replies: 24
Views: 5349

Re: Repeating Keyboard Characters

I don't like wifi so do not comment on that.
If you had a known good usb keyboard and it still won't log in, maybe try flashing an sd card with pidora and see if that works. If not then you have duff hardware and should try asking the seller for a return replacement.
by r4049zt
Wed Nov 06, 2013 5:08 pm
Forum: Troubleshooting
Topic: Damaged Pi
Replies: 8
Views: 1114

Re: Damaged Pi

So you snapped off the input smoothing capacitor? I'd recommend putting something back there, as a less than urgent job. 220 microFarad capacitors for 5V (pref a little more) are usually physically bigger. If you found say, 470microFarad 16V rated, that should also work. As it is, yours depends on t...
by r4049zt
Wed Nov 06, 2013 5:00 pm
Forum: Other projects
Topic: Battery Pack / PSU for Pi ?
Replies: 27
Views: 28146

Re: Battery Pack / PSU for Pi ?

I'd suggest some caution here. Testing in 2012 a 256Mb Pi with 4x 2000mAh AA batteries (NiMH), it would not boot from 5.2V,5.3V nor 5.5V fully charged. It booted and worked fine for a couple of hours if batteries were at 5.0 V to start and continued to work down to batteries 4.4 V when the mouse con...
by r4049zt
Mon Oct 28, 2013 9:25 pm
Forum: General discussion
Topic: Interfacing with Solar Charge Controller
Replies: 39
Views: 12288

Re: Interfacing with Solar Charge Controller

OK, so it is 38400 baud. Try looking up printf("%x",number) which in a c program converts number to hex and prints it formatted that way to stdout. You'll want to get the hang of that, building suitable messages and inspecting them at a terminal. I've been doing the other way around, recieving data ...
by r4049zt
Mon Oct 28, 2013 9:16 pm
Forum: General discussion
Topic: Interfacing with Solar Charge Controller
Replies: 39
Views: 12288

Re: Interfacing with Solar Charge Controller

Your raw cat</dev/AMA0 looked like what I'd see from serial data at either the wrong baud rate or something corrupt. I don't think that you can do much without knowing the pinout, signal voltage, and baud rate of the serial line. I've been dabbling with an arduino connected to rPi and suggest that a...
by r4049zt
Mon Oct 28, 2013 8:56 pm
Forum: Troubleshooting
Topic: Failing to Recognize USB Hub
Replies: 4
Views: 4440

Re: Failing to Recognize USB Hub

I tested power supply requirements of my 2012 raspberry pi and with 5.15V it would not boot but 5.0 was ok. I have had other problems with a cheap 2012 usb hub which used to work with 2012 raspberry pi and 2013 rPi but does nothing now. It also stopped working with an intel desktop PC running linux....
by r4049zt
Mon Oct 28, 2013 8:35 pm
Forum: Beginners
Topic: Electromagnet with pi
Replies: 40
Views: 10529

Re: Electromagnet with pi

I'd say don't be a hero, and get it doing something on a small scale to get the hang of it. That is, instead of having a car battery or equivalent heavy power supply, have 4 to 8 AA batteries (5 to 11 volts), and switch that with a medium sized 3 legged N FET of some sort. The batteries won't delive...
by r4049zt
Wed Oct 23, 2013 12:24 pm
Forum: Other projects
Topic: 12v Li-ion charging circuit?
Replies: 14
Views: 7352

Re: 12v Li-ion charging circuit?

I don't know the Li batteries but can vouch that eight NiCad AA batteries from Maplin can simultaneously store charge as it arrives off a small solar panel and provide power to a 1Amp rated DC-DC buck regulator set to 5.0V which powers my rPi. NiCad batteries prefer to be kept topped up for most of ...
by r4049zt
Wed Oct 23, 2013 12:07 pm
Forum: General discussion
Topic: Power supply amperage
Replies: 10
Views: 5216

Re: Power supply amperage

You must check that your power supply is in quite a small range; about 4.9 to 5.0 volts. If it is then it will work. Don't worry that your supply is capable of 4 Amps. So long as it can do >=0.8 Amps it will work. I solder wires onto component D17, as the microusb connector is not convenient. If you...
by r4049zt
Wed Oct 23, 2013 11:57 am
Forum: Beginners
Topic: Power Supply question
Replies: 4
Views: 1019

Re: Power Supply question

5.1V 1A might be ok. When my rPi is working, a voltmeter across component D17 on the rear of the board and near to the power supply connector shows between 4.85 and 5.0 volts. If 5.2V there it does not start. I tested up to 5.5V (from four AA batteries fully charged) and nothing happened. After runn...
by r4049zt
Wed Oct 09, 2013 1:26 pm
Forum: C/C++
Topic: hello world for beginners
Replies: 10
Views: 6166

hello world for beginners

This has been covered countless times before, but as I could not find it I'll post again because this should be tested before you write more proper programs. pidora on a 4GB card was booted on a 2012 256MB rPi and configured (1/2 hour) pidora was rebooted. HDMI was a bit slow to start but got there ...
by r4049zt
Wed Oct 09, 2013 12:42 pm
Forum: Beginners
Topic: Could a phone line power a Pi?
Replies: 5
Views: 2166

Re: Could a phone line power a Pi?

Don't do that. See above comments on 50+V AC which would immediately damage your pi. I am writing from a 2012 rPi using a spare mains powered mobile device charger rated 5V 800mA. That works fine. Sometimes I use a small DC-DC buck regulator rated at 1 Amp and set to 5V by its screw pot. Those are q...
by r4049zt
Mon Oct 07, 2013 2:56 pm
Forum: General discussion
Topic: best basic USB hub for the Pi?
Replies: 14
Views: 87878

Re: best basic USB hub for the Pi?

My cheapest usb hub worked until July 2012 and then stopped working. On my PC's, it stopped working after updates. By 'not working', I mean that linux can see and list a usb hub but can no longer list the devices which are on it. The problem from my rPi is exactly the same. My single USB to PS2 keyb...
by r4049zt
Sun Oct 06, 2013 3:46 pm
Forum: Off topic discussion
Topic: Intel Galileo
Replies: 46
Views: 16827

Re: Intel Galileo

Hmm. I think I smell Intel marketingbots. Who in their right mind would use a 32bit nondeterministic chip to do a job for which a smaller lighter chip would suffice? Cue ta-da! enter stage right a whole chorusline of marketingbots wearing brightly coloured tutu's and tap dancing.
by r4049zt
Sun Oct 06, 2013 3:35 pm
Forum: Automation, sensing and robotics
Topic: Power supply possibilities
Replies: 4
Views: 1118

Re: Power supply possibilities

Turn over your rPi board and find component D17 near to the microusb 5V in. Solder your supply ground wire at the side of D17 nearest to the edge of the board. Solder your supply 5V to the other side of D17, about 1/4 inch inboard. Mine works while supply is in the range 4.9 to 5.05 V. As your batte...
by r4049zt
Mon Feb 11, 2013 12:39 pm
Forum: HATs and other add-ons
Topic: Isolating GPIOs and using alternate power source
Replies: 20
Views: 13613

Re: Isolating GPIOs and using alternate power source

Common Earth I worry about this thread because I can envisage a Pi running with 0V at earth, connected to a gertboard driven external circuit which might have battery powered heavy transistors. You did not say that, but what you said did not rule it out. Here are two possible solutions, the best dep...
by r4049zt
Thu Feb 07, 2013 1:39 pm
Forum: Beginners
Topic: Powering the Raspberry Pi
Replies: 5
Views: 1910

Re: Powering the Raspberry Pi

It should not work from 7V. Don't do that. My tests found OK at 4.9V OK at 5.0V OK at 5.1V no boot above 5.3V max for my 4x AA rechargeables was 5.5V, which did not work but did no obvious damage. Try looking up raspberry pi at 40000m. The balloonist had six AA batteries and a lossy regulator to dow...
by r4049zt
Thu Feb 07, 2013 1:26 pm
Forum: Beginners
Topic: Can someone help me find a power supply?
Replies: 18
Views: 2814

Re: Can someone help me find a power supply?

I've seen reported success with a 5V 800mA rated blackberry power supply. If you have something else which does about 1A at 4.9 to 5.2 Volts then it is possible to solder wires onto your rPi board; ground near to the board edge and 5V across component D17. Alternatively, you can buy a 5V 1A supply w...

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