555 timer examples in falstad circuits

Few 555 timer chip examples built digitally in falstad circuit builder.

This one is Schmitt trigger with 2/3 and 1/3 Vcc hysteresis.
Check out extra sliders and see how current through led changes.

Simulation is here - http://tinyurl.com/y4rnjs4o

Another one - LDR logic board. Similar, but without hysteresis as threshold pin is connected to stationary 10k resistor, so the output is passed on at strict threshold level chosen by adjusting the variable resistor.

And the simulation - http://tinyurl.com/y6l7blt2

Here is a monostable circuit. Use switch as a push button and the LED will stay turned on for a certain time.



Telnet and ssh from cygwin on windows xp in virtualbox

Another way how to play with shell commands.
By default new cygwin is not possible to install on Windows XP.

1. Get a cygwin installation which suppors windows xp


2. Create shortcut for cygwin installation file and add -X (*capital X) in target field.

3. Use fruitbat mirror where to get files from

32-bit ftp://www.fruitbat.org/pub/cygwin/circa/2016/08/30/104223
64-bit ftp://www.fruitbat.org/pub/cygwin/circa/64bit/2016/08/30/104235

4. Add wget from mirror

5. Backup cygwin1.dll from /bin folder

6. wget apt-cyg

wget https://raw.githubusercontent.com/transcode-open/apt-cyg/master/apt-cyg
chmod +x apt-cyg
mv apt-cyg /usr/local/bin

7. install telnet using apt-cyg (telnet is in inetutils package)

apt-cyg install inetutils

8. install ssh using apt-cyg (ssh is in openssh package)

apt-cyg install openssh

9. Enjoy!


That string is date or float?

Got an interesting situation where I had to distinguish if the piece of string is float or date in Python 2.7. No problems to do that when there is dateutil.parse library in Python. But in my case the tricky situation was that piece of string which actually is float, can be interpreted as... date.
So,  I came to solution - let there be two separate functions.
Checking if the string is float is straightforward.
def is_number(s):   
    return True   
   except ValueError:   
    return False   
Checking if the string is date - first of all, I check if it is a float. And if it is - lets return False.
 def is_date(d):  
   if is_number(d):  
     return False  
     print parse(d)  
     return True  
   except ValueError:  
     return False  
And that`s it.



How to download videos from facebook or vimeo (or youtube or any other service)

I hate long "how to" videos.
So here are my versions of how to easily save videos using just a web browser

Facebook video download steps:
1)open video page
2)change to mobile version
3)play the video and save it using right mouse button option

Vimeo (youtube and many more service) download steps
1)copy the video link
2)paste it in some service (keepvid or ssyoutube or savefrom.net)
3)download it


Sharing more than one main folder in Dropbox?

No. I haven`t found how to do that.

But why would anybody do that? Does it make any sense? Why it is not enough with only one main Dropbox folder?

There are some cases related with programming, when it is easier to have all scripts in some specific place, e.g. C:/scripts, instead of some complicated Dropbox folder path like C:/Documents and Settings/whatever/user/space in folder/name creates problems/Dropbox/specific folder for scripts/any programming language/scripts...

But how about duplicating the contents in the main Dropbox folder? You can still work in your C:/scripts, and all updates will be synced in your specific folder inside Dropbox main folder.

Synchronising between folders. That`s the key. DSynchronize.

Features include - real time sync and bidirectional sync.