Raspberry Pi Forums

tenochtitlanuk

Seen my similar setup on http://diga.me.uk/PiADC.html where my Pi was reading a photocell, or the AdaFruit tutorial...?

NB capacitors may range from pF to mF and up. That's 6 decades at least..... so you'll need a wide range of resistors. And, yes, be careful you don't apply over 3.3V to a GPIO..

tenochtitlanuk

Seen my similar setup on http://diga.me.uk/PiADC.html where my Pi was reading a photocell, or the AdaFruit tutorial...?

tenochtitlanuk

Still trying to figure how Z-Cars fitted in there.....

tenochtitlanuk

An interesting idea and helpful explanation. Must have a play. Got lots of analogue meters around still. I remember trying to mount a tiny mirror on one to make a 'spot galvanometer'! PS On your site, the rocket launcher circuit diagram looks odd. Battery symbol is back to front, & I'd have expected...

tenochtitlanuk

As far as my first PC goes, it was an 1802 Elf followed by a Kim-1. I still have the Kim-1 :) Built two variations of the Elf from the magazine articles. Second one used hand wire-wrapping. One of my students built a Kim and others built various 6502 boards. Had great fun interfacing it to our firs...

tenochtitlanuk

A different take on the same MS arrogance- it took me over an hour to get Skype running again on Ubuntu (LX) on my laptop, including Google-time trying to find why I couldn't log in, and where to find the necessary update ( not in the normal repositories). MS MUST be trying to ditch everyone using S...

tenochtitlanuk

I and many others do this. I use pairs of LiPo cells stripped out of old laptop batteries- they usually contain 6 or 9 cells, but are thrown away if one cell goes bad. Normal practice would be to feed power-circuits like H-bridges direct from the cells ( or often other cells of different voltage) an...

tenochtitlanuk

Great resource. Hope you'll fill in the bits like using the GPU....
I did a vaguely similar page at http://diga.me.uk/ExplainFourier.html but using another programming platform. I definitely want to get into high speed FFT on the Pi so your site is very helpful.
SOX is a great resource too.

tenochtitlanuk

Just a word of caution. This code implements the algorithm shown on Wikipedia. Be aware that for some sites it fails. There are subtle errors related to altitude and atmospheric conditions - rarely worth worrying about - but much greater errors affecting high latitudes. If you are inside the arctic ...

tenochtitlanuk

Wikipedia has an entry spelling out exactly where to look for the width/height in the different versions of bmp. Spells out the line-padding situation too.

tenochtitlanuk

Most such scales DO require a button push, rather than giving a continuous display. For such things I have used servos to press a button ( gives you complete electrical isolation- a GOOD idea if you are doubtful) , but if you can get at the two button contacts you can check if it's a 'pull down to e...

tenochtitlanuk

Looks interesting. I was hoping to do something similar. I got some success using a webcam 'looking' at the screen, and found that with a fixed camera position, since each segment is at a known location ( x, y) in the saved bitmap it was quite easy to detect which segments were on, and hence the num...

tenochtitlanuk

For others seeing this thread, see https://learn.adafruit.com/basic-resistor-sensor-reading-on-raspberry-pi and http://diga.me.uk/PiADC.html for the measuring of resistance. LTSpice modelled this quite nicely.. I too will have a go at reading voltage.. EDIT Of course such a voltage would have to be ...

tenochtitlanuk

Great project- glad your confidence for such a long period was rewarded.... I remember visiting Georgian Bay in the early 70's- but in high summer. Rather different! Interesting techniques for the 'smoothing' of the images. I'll be following this. For a bit of tree-surgery-removal I did a time lapse...

tenochtitlanuk

Pi has Python already on it if you use the usual image on your SD card, eg Raspbian. I'd recommend you use the Python 3 rather than the Python 2 ( both are supplied. They have noticeable differences.) Python has many nice features- particularly you can execute commands directly at a text console, wh...

tenochtitlanuk

Use of Python, pyserial and matplotlib, with one of the gui-designers like tk would allow you to do what you want. If you know RISCOS, you could use that in BBC BASIC- with my background that would probably be my choice. HOWEVER, as an extensive user of Liberty BASIC and JustBasic on XP and Wine/Ubu...

tenochtitlanuk

Yeah- put in a card reader on another machine. Copy the images to the other machine, then delete a few of the Pi images or other un-needed files. Should now work again in a Pi. Delete all the images once you've got them safely off. I tend to make a second copy and make it read-only, so if I mess up ...

tenochtitlanuk

Sounds fun. Must return to my own bead sorter- see http://www.raspberrypi.org/forums/viewtopic.php?f=37&t=42639&p=343279#p343279 You'll also see some posts in this forum by me when using tesseract OCR. I like the idea of your 'beads'. Can you get them in a whole alphabet? Could then program it to ta...

tenochtitlanuk

Are you sure about your pin allocations? Pin 7/17/Pi/BCOM/GPIO???
See http://wiringpi.com/pins/

tenochtitlanuk

Serial-control devices like this work nicely. I'd also recommend USB-connected-'serial' devices like the BitWhacker & EiBotBoard, also available from Sparkfun, which have servo outputs. It's so much easier just sending serial commands, although for understanding the code/devices it is good to progra...

tenochtitlanuk

I know it's a big install, but GIMP has a screen-capture, and a timed ability to point at an open GUI window and grab just that one.

tenochtitlanuk

If you're not yet far into coding you could look at http://diga.me.uk/PiADC.html for some simple ideas.

tenochtitlanuk

So just replace the print line with lines like

Code: Select all

    if delta_r >0.1:
        print( "Going up!")
    if delta_r <-0.1:
        print( "Going down!")

I've deliberately omitted cases where the change is between +/-0.1, because that allows for some 'noise' in the data.

tenochtitlanuk

Basically just keep updating a stored 'last value' as shown in the Python3 code here. I generate a sine wave- you'll have a routine reading the sensor. Note that finding gradients very much emphasises random fluctuations. A smoothing routine ( see elsewhere on the forum) will help here. import math ...

tenochtitlanuk

To a rather low-level Python programmer, 'deque' and 'instantiation' are frightening words! I've a bit to go yet, tho' the method looks interesting! ;) I found this kind of smoothing to work very nicely as follows. It turns your screen into effectively a scrolling x/y display. Good practice in 'bit-...

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