Raspberry Pi Forums

tenochtitlanuk

The 'electronic' way is to isolate with a transformer; also converting down to some lower value. Now rectify with a diode and smooth with a capacitor; then feed to your AtoD & read. Store an array of readings and/or detect max, min and/or graph. Quite a lot of electronics and programming. And to mon...

tenochtitlanuk

Also consider possible overheating- a vertical orientation gives better convective cooling. Your USB load may be pushing the polyfuses into tripping. Is yours the early model with three fuses ( USB power in; 2 x USB out)??

tenochtitlanuk

Fantastic- one of those really useful jbeale replies!
I'm off to play. Can always do some pre-processing with ImageMagick...
Thanks again.

tenochtitlanuk

The representation of number outputs on displays via 7 bars SHOULD be easy to recognise as numbers. This allows interfacing all sorts of existing instrumentation, including for instance bathroom weighing scales; electricity meters; etc. I have previously written my own routines to detect the bars & ...

tenochtitlanuk

The audio file la.mp3 is at https://raw.github.com/Rob-Bishop/Raspb ... ter/la.mp3
AS I said, save it to the directory you are putting your Python files in..

tenochtitlanuk

There have been several posts about OCR on the Pi and its camera. Several have been about recognising number output on instruments with a seven-segment display but no interface to link directly to a Pi. ( I've posted before about reading pixels at appropriate locations in a BMP to get this data as a...

tenochtitlanuk

Dug out another pi. Using command line ( ie no X window) I saved la.mp3 into a folder and moved into that folder. Doing 'sudo mpg321 la.mp3' indeed worked fine, so I presume the GPIO section will work.. ( Don't know if Rob changed the mp3, or a pi upgrade has made it able to read & sound out...) Sug...

tenochtitlanuk

Can't check 'til tomorrow. The only Pi I have here is doing a timelapse film until tomorrow!
The MP3 needs to be in the same folder/directory as the ( saved) SingingJellyBaby.py file.
I don't know if the MP3 file has been changed since I reported the problem.
Will report back asap!

tenochtitlanuk

Go, jamesh! I'm one of the very happy people who got a Pi camera as soon as we could and are VERY happy with its ease-of-use and performance. Worked first-time and software has been improved. And most Pi-fans realise that the Pi developers & the Foundation are doing a fantastic job while holding dow...

tenochtitlanuk

. . . and the one I ordered online ( see earlier) turned out NOT to have the advertised USB connection. So I have all the hassle of returning it, and of course they DON'T have the higher spec model on their stock list. At least I've got them to correct their product description... and won't mention ...

tenochtitlanuk

Yes- as I implied.
The idea is to avoid losses- hence a series cap. is easiest. No resistors. Cheap diode paralleled across LED to catch the 'reverse' phase. Cheaper than a lossy zener..

tenochtitlanuk

Must say that the general level of electrical knowledge of many users of the Pi forums is abysmal. Most seem convinced a 5V 2A psu will somehow push 2A through anything connected... I recently took the trouble to disassemble a mains ( 240V) LED lamp. Instead of a resistive current limiter with atten...

tenochtitlanuk

I've just ordered a USB weighing scale to experiment with.
Google 'postal scales usb'. It cost around 20ukp.

If Linux works with it I'll report back. If not, it'll be run under XP!

tenochtitlanuk

Neat application. I hadn't heard of Beautiful Soup before... and good use of resources. Para los hispanohablantes, http://patolin.com/blog/2013/08/16/poniendo-a-trabajar-al-raspberry-pi/ I'm always on the lookout for technical Spanish articles for my language classes. Otherwise it's all news or lite...

tenochtitlanuk

Anyone happening on this thread would find helpful advice on the ImageMagick -al way of doing this kind of thing. You can script a direct compare; mask area of interest; do a difference- or do from a terminal command line. http://www.imagemagick.org/Usage/compare/ Given that my flicker-example was a...

tenochtitlanuk

Flicker comparison is certainly going to be easiest. Lighting, alignment etc are much less critical. See this quick example. http://www.diga.me.uk/comp2.gif If you go the image-processing route I concur with the comments of others- fixed camera position to near-pixel accuracy is needed unless you'll...

tenochtitlanuk

This seems an interesting project- lots of on-line references. But the only price I've found was about 180ukp for a 25mm square piece so I won't be joining in and playing with it! ( unless you can give me details of somewhere cheaper) If you have access to a CRO ( oscilloscope) or computer-based equ...

tenochtitlanuk

If I wanted to measure the slow small changes in the weight of a hive I'd hang it on a spring ( probably preloaded to the empty hive weight) and measure the extension by a variable resistor or optically. Since Hooke's Law says stress proportional to strain, PI could easily read it. Gert board, PiFac...

tenochtitlanuk

When I first got my PiCam I had similar experience until I twigged. Are you preceding the command with 'sudo'- otherwise it can't write the output file unless you've changed directory to ./home/pi. Or try specifying that output file is in a directory you have write permission for, eg '-o ./home/pi/s...

tenochtitlanuk

If you have access to Lego kit, use its 'rack and pinion' parts. A spur gear ( 'pinion') engages with the linear toothed parts ( 'rack'). I've used this several times- the rack sections stack to make what length you want. The screw thread/nut method works, but gives a huge gear ratio- it takes as ma...

tenochtitlanuk

http://www.elektor.com/news/summer-deal ... 3672.lynkx

tenochtitlanuk

Could be interesting. I've got on order the Elektor radiation detector kit ( special offer two more days) which has a small-area sensor but useful accompanying article. Hope to add a Pi interface at some stage. I've also got at least one Geiger tube around. I suppose ANY webcam sensor could be used ...

tenochtitlanuk

If raspistill -o ./home/pi/ashurpanibal.jpg does not turn camera ( red LED) on & take a picture at the location spelled out for the output then you've either a bad camera or connection- or haven't updated software.
raspistill if typed alone in a terminal will give all the options.

tenochtitlanuk

I started on something similar & then was hung up waiting for the camera. See http://www.raspberrypi.org/phpBB3/viewtopic.php?f=43&t=33912&p=297329#p297329 The camera happily takes long narrow horizontal images. ( I turn the camera 90 degrees to make this sensible) & ImageMagick happily appends thes...

tenochtitlanuk

Thanks for the hospitality- an interesting group of people, ages & projects.
Look forward to your next.......

Search found 156 matches

Re: Monitoring mains (AC) voltage with the Pi

Re: USB peripherals stop working - unless Pi on it's side!

Re: OCR optical character recognition of seven segment displ

OCR optical character recognition of seven segment displays

Re: OCR exam board Singing Jelly Baby

Optical character recognition (OCR) and Tesseract'

Re: OCR exam board Singing Jelly Baby

Re: OCR exam board Singing Jelly Baby

Re: Consider a USB camera as an alternative

Re: Attaching Weight scale or Force resistive sensor to PI

Re: how to sense 220v input -solved- I hope

Re: how to sense 220v input -solved- I hope

Re: Attaching Weight scale or Force resistive sensor to PI

Re: Raspberry Pi, a real world work for the microcomputer

Re: Challenge: Bitmap comparison

Re: Challenge: Bitmap comparison

Re: Homemade Spirometer (ADC issue)

Re: Connect load cell to Pi

Re: pi camera = no picture....

Re: Convert stepper motor rotation to linear movement?

Re: Cosmic Ray Detector

Re: Cosmic Ray Detector

Re: Picamera's problems

Re: Using a Pi as a Photo Finish Camera

Re: Exeter raspberry jam