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by Ravenous
Tue Feb 10, 2015 3:49 pm
Forum: Other projects
Topic: Pi Compatibilitywith a Unihedron Sky Quality Meter
Replies: 1
Views: 2159

Re: Pi Compatibilitywith a Unihedron Sky Quality Meter

They appear to have Linux drivers, but they may not be suitable for the Raspberry Pi. You should probably ask them if they support Linux on ARM devices. (I notice they have a forum.)
by Ravenous
Tue Feb 10, 2015 2:34 pm
Forum: Off topic discussion
Topic: Lasers...
Replies: 29
Views: 3488

Re: Lasers...

rurwin wrote:Semiconductor lasers have a widely diverging beam, hence the collimating lenses.
Ah thanks, that's what I was missing. (I was thinking that magically they all had the same beam divergence.)
by Ravenous
Tue Feb 10, 2015 2:28 pm
Forum: Raspbian
Topic: A SERIOUS Raspbian issue
Replies: 22
Views: 3197

Re: A SERIOUS Raspbian issue

It is a shame that the PI guys don't invest in this, since there is already a GPU over there which is good enough to handle the LXDE :\ With respect, this is not "A SERIOUS Raspbian issue". Do you think they aren't investing in several things at once? Please show them at least a little bit of respe...
by Ravenous
Tue Feb 10, 2015 2:06 pm
Forum: Off topic discussion
Topic: Rasp Pi 2 Vs. ODROID-C1 : Benchmarks!
Replies: 8
Views: 13516

Re: Rasp Pi 2 Vs. ODROID-C1 : Benchmarks!

What does the bit at the end mean - RPi 113, odroid 41, despite the RPi's lower figures elsewhere? Is that just graphics performance?
by Ravenous
Tue Feb 10, 2015 2:01 pm
Forum: Off topic discussion
Topic: 3D Printing
Replies: 56
Views: 7079

Re: 3D Printing

I think you are - I'll guess a 220V supply will be OK for the UK market - but as I say, search for more opinions before committing £70.
by Ravenous
Tue Feb 10, 2015 1:57 pm
Forum: Advanced users
Topic: Pi Car with L298N
Replies: 1
Views: 1284

Re: Pi Car with L298N

You certainly can. Have a look around the Automation, Robots etc. forum. And do a search, you'll find lots of links.

Also have a look at the Magpi magazine (it's free online) for several similar projects.
by Ravenous
Tue Feb 10, 2015 1:45 pm
Forum: Off topic discussion
Topic: 3D Printing
Replies: 56
Views: 7079

Re: 3D Printing

Eek - sounds very dangerous. Instead I suggest covering yourself in bacon then playing with a hungry lion! I suspect the supply you have will be fine, though wait for a few more opinions first just to be safe. But in the unlikely event it's not safe: I've seen transformers that drop you from (in old...
by Ravenous
Tue Feb 10, 2015 1:37 pm
Forum: Off topic discussion
Topic: Lasers...
Replies: 29
Views: 3488

Re: Lasers...

jamesh wrote:Beyond the blue event horizon?

(Brownie points for the author)
I admit I had to search the phrase, as I've never heard of it!
by Ravenous
Tue Feb 10, 2015 12:02 pm
Forum: Off topic discussion
Topic: Lasers...
Replies: 29
Views: 3488

Re: Lasers...

...creates a singularity out of all that mass which is about the size of an atomic nucleus and that will last for about a century. You then manoeuvre a concave reflector close to it and the Hawking radiation drives your spaceship up to close to the speed of light in a few decades . They don't menti...
by Ravenous
Tue Feb 10, 2015 8:51 am
Forum: Off topic discussion
Topic: Lasers...
Replies: 29
Views: 3488

Re: Lasers...

"Okay, so, she's a dog..."

Back to lasers: I've wondered why the cheapo laser pointers out there apparently have focusing lenses on them... fine for a CD player that needs to do certain clever things with the beam shape, but why laser pointers?
by Ravenous
Mon Feb 09, 2015 6:05 pm
Forum: Troubleshooting
Topic: Why is the PI2 camera-shy ?
Replies: 162
Views: 266156

Re: Why is the PI2 camera-shy ?

Any fluid you paint over a BGA package is going to get wicked underneath around the solder balls and die surface, and even a little bit of conductivity or corrosiveness could be an issue. I guess the only materials actually tested for that application are the plastics (epoxy?) used for chip packagi...
by Ravenous
Mon Feb 09, 2015 2:58 pm
Forum: Troubleshooting
Topic: Why is the PI2 camera-shy ?
Replies: 162
Views: 266156

Re: Why is the PI2 camera-shy ?

Peeling it off the HDMI port was a job my little 5-year-old goblin... er,daughter Beatrice considered to be a crucial part of setting up a new Raspberry Pi. Now give her the job of painting a small blob of dark coloured nail varnish on the offending component! :) (Or perhaps the job of soldering a ...
by Ravenous
Mon Feb 09, 2015 2:42 pm
Forum: Troubleshooting
Topic: Why is the PI2 camera-shy ?
Replies: 162
Views: 266156

Re: Why is the PI2 camera-shy ?

The discharge time for a lamp is of the order of 10s of microseconds which interferes with the control loop response in addition to the output voltage. Thanks, that's interesting (it was purely academic interest in my case) - I think this means there's both a steady state offset from bright light (...
by Ravenous
Mon Feb 09, 2015 2:24 pm
Forum: Troubleshooting
Topic: Why is the PI2 camera-shy ?
Replies: 162
Views: 266156

Re: Why is the PI2 camera-shy ?

Trivia question: is it a flash (ie a brief transient) or can a constant but very high intensity light cause this? I'm thinking of the step response in the control circuits of the regulator chip - will it be stable under a sustained light level? If so, sunlight is less likely to be a serious problem....
by Ravenous
Mon Feb 09, 2015 1:41 pm
Forum: Beginners
Topic: Driving Actuators
Replies: 2
Views: 490

Re: Driving Actuators

Do I understand this correctly - you currently have the raspberry pi producing an analogue or square wave output (somehow) then go through an audio amplifier to drive the gadget? If a square wave signal is good enough, I suppose you could drive each through a darlington transistor, provided there's ...
by Ravenous
Mon Feb 09, 2015 1:20 pm
Forum: Troubleshooting
Topic: Why is the PI2 camera-shy ?
Replies: 162
Views: 266156

Re: Why is the PI2 camera-shy ?

So has anyone said it yet... Is the raspi compatible with Flash? (Sorry.)
by Ravenous
Mon Feb 09, 2015 12:05 pm
Forum: Beginners
Topic: Gradiometer for archaeology
Replies: 21
Views: 4875

Re: Gradiometer for archaeology

The PIC16C54 has no analogue inputs, so these sensor signals must be digital. Why not connect the sensors directly to the Pi and do all the calculations yourself? Then you don't need the SCL007 at all. Oh! That's it. Well spotted. I just looked up the sensors themselves (not the SCL007). From the d...
by Ravenous
Mon Feb 09, 2015 11:46 am
Forum: Troubleshooting
Topic: Why is the PI2 camera-shy ?
Replies: 162
Views: 266156

Re: Why is the PI2 camera-shy ?

Might be too opaque. Wondering if maybe some nail polish would be enough?? :D scene: Standing bewildered at the Boots makeup aisle - surrounded by bright lights and thin expensive plastic containers. "For your Raspberry Pi 2, did you say sir - Of course sir. :lol: I used to play a lot of classical ...
by Ravenous
Mon Feb 09, 2015 10:36 am
Forum: Automation, sensing and robotics
Topic: Motor Direction Control
Replies: 10
Views: 2897

Re: Motor Direction Control

Oh by the way, I don't recommend the 6V batteries directly to the pi. Some people have tried it and it wiorks, but may be a little risky. The little switched regulator you show should work fine, though as you say 6V may not be enough to make it work well. It may need 7-8V. (You can get 8 AA, 10 AA b...
by Ravenous
Mon Feb 09, 2015 10:28 am
Forum: Automation, sensing and robotics
Topic: Motor Direction Control
Replies: 10
Views: 2897

Re: Motor Direction Control

Most motor direction circuits I see tend to use double pole relays, yours seems to use single pole. However I think it'll work. Connect two relays so their contacts are on 0V and the +V supply (whatever it is). Then for each relay, connect the pole to one of the motor wires. Here's a circuit I found...
by Ravenous
Mon Feb 09, 2015 9:27 am
Forum: Off topic discussion
Topic: Raspberry Pi Pony and other memes
Replies: 32
Views: 11850

Re: Raspberry Pi Pony and other memes

That's just too topical :)
by Ravenous
Fri Feb 06, 2015 6:07 pm
Forum: General discussion
Topic: where in the uk can you pick up a pi 2 for $35?
Replies: 19
Views: 2267

Re: where in the uk can you pick up a pi 2 for $35?

Oops! I take it back. (I was doing a conversion from Farnell's price, which was over $35 for me.)

Boy do I have a red face :oops:
by Ravenous
Fri Feb 06, 2015 6:01 pm
Forum: General discussion
Topic: where in the uk can you pick up a pi 2 for $35?
Replies: 19
Views: 2267

Re: where in the uk can you pick up a pi 2 for $35?

They're made in Wales! Third parties like Maplin can charge any price they like. Thats the ironic thing. Here in the US one of our smallish PC/electronics stores Microcenter sells the for 34.99 right on the shelf. So glad they are decent enough not to gouge us. The annoying thing is, even here in t...
by Ravenous
Fri Feb 06, 2015 5:55 pm
Forum: General discussion
Topic: where in the uk can you pick up a pi 2 for $35?
Replies: 19
Views: 2267

Re: where in the uk can you pick up a pi 2 for $35?

They're made in Wales! But as you rightly say, add 20% VAT. Also add postage, if buying mail order. Third parties like Maplin can charge any price they like. The two official distributors (fruitofthelom has linked them, above) are supposed to sell them for the equivalent of $35 (+VAT +postage) but t...
by Ravenous
Fri Feb 06, 2015 4:47 pm
Forum: Off topic discussion
Topic: Fresnel Lenses
Replies: 23
Views: 3843

Re: Fresnel Lenses

Some other diagrams before I forget:
http://hkier.fed.cuhk.edu.hk/journal/wp ... _85-95.pdf
http://kaushalgrade10optics.wikispaces. ... +Projector
Indeed the collimator/condenser arrangement near the olde fashioned bulb is a bit more complicated than I thought...

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