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by Trav
Fri Jan 31, 2014 6:03 pm
Forum: Other projects
Topic: Driving a single high power LED using PWM
Replies: 55
Views: 9575

Re: Driving a single high power LED using PWM

Here is an updated circuit: circuit_new.jpg To give a range from 0.5A to about 2.0A use the following values: CLD 3.3 mA R1 0.2Ω at 1 Watt R2 39Ω + 500Ω pot R3 470 or 680Ω TR1 & TR2 BD681 These are based on the minimum hfe of TR1, which is 750. I can't find figures for typical values. However, for h...
by Trav
Fri Jan 31, 2014 2:50 pm
Forum: Other projects
Topic: Driving a single high power LED using PWM
Replies: 55
Views: 9575

Re: Driving a single high power LED using PWM

Here is a possible CLD:
http://uk.mouser.com/ProductDetail/Cent ... TFjQ%3d%3d
Note CLDs are also known as Current Regulating Diodes (CRN)/
by Trav
Fri Jan 31, 2014 9:47 am
Forum: Other projects
Topic: Driving a single high power LED using PWM
Replies: 55
Views: 9575

Re: Driving a single high power LED using PWM

Lying in bed last night I realised I had made a mistake in my calculations :( The CLD should be a 3mA (or thereabouts) one and the 50ohms resistor and pot should be 150 ohms and 500 ohms respectively to give 1.5 to 2.1 amps I had made a false assumption about the gain of the darlington transistor. :...
by Trav
Thu Jan 30, 2014 9:00 pm
Forum: Other projects
Topic: Driving a single high power LED using PWM
Replies: 55
Views: 9575

Re: Driving a single high power LED using PWM

Change the 100 ohm resistor in my diagram for a 50 ohm resistor in series with 50 ohm pot and it will do exactly that. Or a 100 ohm pot to go from 0.75 to 2.25 A. That is for maximum currents. The PWM from the RPi can then lower the brightness from there. I reckon there is about £5-6 worth of compon...
by Trav
Thu Jan 30, 2014 7:37 pm
Forum: Other projects
Topic: Driving a single high power LED using PWM
Replies: 55
Views: 9575

Re: Driving a single high power LED using PWM

Here is a simple circuit attached: circuit.jpg This is taken from another paper ( http://www.centralsemi.com/PDFs/products/Boosting_the_CLD.pdf ) and modified for this requirement. the CLD is a current limiting diode, the BD182s are power darlingtons capable of 4 Amps. Both should be mounted on a he...
by Trav
Thu Jan 30, 2014 2:55 pm
Forum: Other projects
Topic: Driving a single high power LED using PWM
Replies: 55
Views: 9575

Re: Driving a single high power LED using PWM

<edited> just saw you are using a UBEC so my comment didn't apply.
by Trav
Thu Jan 30, 2014 2:50 pm
Forum: Other projects
Topic: Driving a single high power LED using PWM
Replies: 55
Views: 9575

Re: Driving a single high power LED using PWM

I just saw this topic, so I thought I would comment: you said "Im planning on running a 1Ohm 3 Watt resistor to it to lower the voltage to 3V" and you also said elsewhere that the LED would be driven between 1.5 and 2.5 amps. By ohms law (V = I x R where V = voltage, I = current and R = resistance) ...
by Trav
Sun Jun 09, 2013 9:42 pm
Forum: General discussion
Topic: Raspberry Pi French Version
Replies: 3
Views: 1186

Re: Raspberry Pi French Version

Note that the Swiss sockets are *not* compatible with the "Standard" Euro plug. The small two-pin French 5 Amp plugs fit Swiss sockets (and Euro sockets) but not vice-versa (Swiss plugs have a third pin - Earth) and the larger 15 Amp Euro plugs certainly do not fit Swiss sockets at all. The good new...
by Trav
Thu May 23, 2013 9:14 pm
Forum: Camera board
Topic: Automatically start raspivid to rtsp streaming
Replies: 6
Views: 13217

Re: Automatically start raspivid to rtsp streaming

A script in /etc/init.d must have the execution bit set e.g. sudo chmod +x scriptname If you paste the command into /etc/rc.local, you have to do the same for rc.local i.e. sudo chmod +x /etc/rc.local otherwise the system will ignore them. The fact that there is no mention in dmesg indicates that th...
by Trav
Thu May 23, 2013 8:49 pm
Forum: Camera board
Topic: Case
Replies: 31
Views: 22871

Re: Case

Trav wrote:I considered using a 35mm plastic film can
but I decided an SD card case was a better fit
_IGP5176.JPG
_IGP5176.JPG (31.07 KiB) Viewed 16782 times
_IGP5175.JPG
_IGP5175.JPG (18.06 KiB) Viewed 16782 times
Cheap and cheerful, but it protects the camera board and gives a larger area to gaffer tape to a support.
by Trav
Thu May 23, 2013 9:28 am
Forum: Camera board
Topic: Case
Replies: 31
Views: 22871

Re: Case

I considered using a 35mm plastic film can, but the hole for the lens would have to be so big because of the curved surface, that there wouldn't be enough protection for the board, so I'm wondering whether to sacrifice one of my old 1930's 6x9 folding cameras, which is big enough to fit the Raspberr...
by Trav
Thu May 23, 2013 8:57 am
Forum: Camera board
Topic: Automatically start raspivid to rtsp streaming
Replies: 6
Views: 13217

Re: Automatically start raspivid to rtsp streaming

I can't answer your question directly, but if you can get a bit of information from the start up kernel messages then the Linux community here will be able to offer more suggestions. After rebooting, from a terminal session type "dmesg" (without quotes). This will scroll a large amount of infromatio...
by Trav
Wed May 22, 2013 1:36 pm
Forum: Camera board
Topic: Using VLC to stream from the camera - Help needed
Replies: 166
Views: 173287

Re: Using VLC to stream from the camera - Help needed

Well. taking images work with raspistill. But if i try to store a video or even stream it, the pi shutsdown. I had a similar problem; everything worked locally, but every time I tried to stream, the network stopped working and I lost control of the Raspi and it was effectively dead. Usual suspect: ...
by Trav
Wed May 22, 2013 1:06 pm
Forum: Camera board
Topic: Camera focus distance and macro lenses
Replies: 71
Views: 58990

Re: Camera focus distance and macro lenses

Will they be any good at four for a tenner though? I remember paying a tenner for that 52mm one in the photo at least 15 years ago. The reading glasses are good enough for most things. The loss of contrast isn't that bad. Well you get what you pay for, but the same applies to £1 plastic spectacles....
by Trav
Wed May 22, 2013 10:29 am
Forum: Camera board
Topic: Camera focus distance and macro lenses
Replies: 71
Views: 58990

Re: Camera focus distance and macro lenses

You can get them down to 37mm diameter: http://www.amazon.co.uk/New-~37MM-Close-Up-Lens-Filter/dp/B003G3Z4XQ/ref=sr_1_1?s=electronics&ie=UTF8&qid=1369217543&sr=1-1&keywords=lens+filter+closeup+37mm Once upon a time you could get even smaller ones, like 32mm, but you would probably only find those at...
by Trav
Wed May 22, 2013 8:32 am
Forum: Camera board
Topic: Camera focus distance and macro lenses
Replies: 71
Views: 58990

Re: Camera focus distance and macro lenses

If you want a bit more quality, you could use photographic close-up filters. They come in 1, 2, 4 and 10 dioptre strengths and are usually made of optical glass. a set of all 4 can be bought on Amazon for less than £9, though the qualtiy may not be brilliant for that price, but still better than pou...
by Trav
Thu May 16, 2013 1:05 pm
Forum: Camera board
Topic: Any in UK get there's from CPC ?
Replies: 37
Views: 9397

Re: Any in UK get there's from CPC ?

Mine was waiting when I got home from work last night, in the obligatory squashed box. I had only ordered it the day before so I was pleasantly surprised. Although CPC is a Farnell company, it wouldn't allow me to use my Farnell log in, but also wouldn't let me use the same user id when I set up a n...
by Trav
Mon Jun 11, 2012 2:53 pm
Forum: Off topic discussion
Topic: What was your first computer?
Replies: 493
Views: 196614

Re: What was your first computer?

I first experienced computing at college in 1968; some ICL behometh running the George operating system. I handed in a deck of cards (in FORTRAN) and got a printout back. (yawn!) My first hands-on computer was a PDP8S when I worked at a University. The boot code was toggled in on a set of switches o...
by Trav
Tue Mar 06, 2012 9:28 am
Forum: Other projects
Topic: STICKY: The projects list. Look here for some ideas.
Replies: 233
Views: 412887

Re: The projects list. Look here for some ideas.

<t>fireraisr said: <br/> <br/> <br/> The Pi is supposedly going to have a camera that you can integrate later this year so you could use that natively. You might need to convert the sensor to infrared which shouldn't be too hard, just change a filter.<br/> <br/> The GPIO should be able to help with ...
by Trav
Mon Mar 05, 2012 10:27 pm
Forum: Other projects
Topic: STICKY: The projects list. Look here for some ideas.
Replies: 233
Views: 412887

Re: The projects list. Look here for some ideas.

<t>I had thought of using the board with an infrared USB webcam in an unmanned wildlife camera, perhaps later adding a camera module for higher quality stills.<br/> <br/> I would need motion detection software to start the recording and keep it going until the motion has stopped for a period.<br/> <...

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