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586  Forum 2005-2010 (read only) / Interfacing / Re: PLEASE HELP~ How can I dim two 220v ac lamps? on: January 07, 2009, 07:18:35 am
i would use
12V LED lamps, which use not so much power (2W for a "60W-light"),
and a L293 (1A driver) (or a thyristor/transistor or so) at a arduino PWM pin...

u would need a 12V voltage source (PSU), which should be properly shaped, so that u dont waste the saved energy in that PSU... :-)
a Switched-mode power supply would be fine, i think...
587  Forum 2005-2010 (read only) / Interfacing / Re: how can i build keys? on: December 09, 2008, 02:15:16 am
good idea...

i found in an old defective keyboard this:
3 rubber foils in a "sandwich"...
the middle layer had holes...
the other layers had metallic coats...

i made a bigger hole and glued the metal foil on the rubber foil...  8-)

case closed... (i liked steve martin in "the pink panther")  ;D

588  Forum 2005-2010 (read only) / Interfacing / how can i build keys? on: December 01, 2008, 03:34:29 pm
hey yo!

i hope this is not too much off topic... :-)
i dont know another hardware forum...

i have to lie in bed when i use my computer (because i dont want to buy a table and a backbone-friendly chair). an engineer built me a thing that holds the monitors over my belly. but now i need a keyboard, that can be used by 1 hand. i found a one-hand-keyboard and use linux' evdev to read from that device and inject the translated keypresses into the PS/2-evdev-device (e. g. thumb+finger1 --> 's', finger4 --> 'e', finger1 --> SPACE, finger2 --> BACKSPACE).

BUT: the keys of that keyboard are soooooo difficult to press, that it hurts after some thousand presses, and that increases the typo-rate...

how can i build my own keys?
i have 6mm-rubber-straws and some silicone-glue and duct tape and metal-foil...

i would connect them to an arduino via a 1-to-16 DEMUX chip (16*2 buttons r connected to GND; each button-pair is connected to the same 2 pulled-up input pins).

do u know a better one-hand-keyboard?


589  Forum 2005-2010 (read only) / Interfacing / Re: Best Choiuces for Sensing Fire... on: November 19, 2008, 10:52:24 am
I apologize if I sounded harsh or critical, especially of Riddick, as that was certainly not my intent.
no problem - i found it funny... at work i had to attend a "1hr" (on my watch 2hrs, but i'm no "doctor of chemistry") network shutdown, because some officers of the state wanted, that we use "10.X.X.X" IP-addresses in our private network (and no longer IP-addresses, that r assigned to their agency) back in 2000.  ;D

Should i be able to build one on my own using these...
ok - this 4USD-sensor (plus lense or plus a radar-like device) looks sweet and possibly does what u need...
590  Forum 2005-2010 (read only) / Interfacing / Re: Best Choiuces for Sensing Fire... on: November 19, 2008, 10:12:12 am
Why would one make a smoke or any other fire detector difficult to get?

hmm - the argumentation goes as this:
when it is said to be a smoke detector, people in the "sense area" might feel safer than they really are (e. g. because the smoke detector died 2 years ago when the battery failed)...

I'm no native speaker... sorry if i use misleading words...
here is my source:
public information campaigns have been created to remind people
was saved in my brain as "legislative means"... :-)
591  Forum 2005-2010 (read only) / Interfacing / Re: Best Choiuces for Sensing Fire... on: November 19, 2008, 08:33:17 am

i use a CO2 meter, that costs 90€ (about 126USD)...
it delivers 0V (0ppm CO2) to 5V (2000ppm CO2) and takes 2500mW (max, at a supply voltage of 5V)...

1000ppm CO2 r ok...
2000ppm CO2 r a reason to leave the work place in some countries...
permanently >40000ppm CO2 (4%) r toxic... for "kiss of life" (first aid) 4% CO2 r good, because the breathing-center feels stimulated then...

u should ask the local fire fighting authority for assistance...
in the USA fire detectors might be subject to legal regulation...

592  Forum 2005-2010 (read only) / News / Re: Arduino 0013 released. on: February 27, 2009, 06:19:53 am
i just installed rxtx.x86_64 (for fedora 10 currently: 0:2.1-0.2.7r2.fc10)...
and removed the lib/ file in the arduino 0013 directory
and soft-linked /usr/lib64/rxtx/ to lib/

it can compile and upload on amd64 now... natively... :-)

593  Forum 2005-2010 (read only) / News / Re: Arduino 0013 released. on: February 26, 2009, 12:58:26 pm
i think, the amd64 version would use the normal libraries and java-amd64?

but the 32-bit version would need a lot of fumbling... :-)

e. g.: lib/

or did that change?
594  Forum 2005-2010 (read only) / News / Re: Arduino 0013 released. linux amd64? on: February 25, 2009, 01:05:15 pm

when can i upgrade my 0012-linux-amd64 package to 0013?

595  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Help - Random function not working on: November 20, 2008, 05:42:09 pm

What if u use
instead of
This would use some upper bits of the random numbers... The lower bits r sometimes not really random... *giggle*  smiley-wink

Do u call random() just once between two board-resets?

do u call
or so, too?

random() uses GNU CC's rand() function, which should deliver quite good pseudo-random numbers...

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