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436  Using Arduino / Project Guidance / Re: Controlling 12v 25w Heater on: March 16, 2014, 08:25:49 pm
Quote
 2n222  
=>2N2222
SEE ATTACHED.
I guess that means the heatsink is anywhere but on the TIP120 ?

Quote
The emitter on the 2n222 is connected to +5 rail. The collector is connected to the base of the TIP120. This configuration does work.  
The emitter on the 2n222 is connected to +5 rail. (damn! , now you got me doing it...)
The emitter on the 2n2222 is connected to +5 rail.
The collector is connected to the base of the TIP120
 I think you better look at the datasheet. The only way it could be working is if the COLLECTOR is connected to +5V and the EMITTER is connected to the base of the TIP120.
FYI,, It is really not a good idea to omit the current limiting resistor on the base of the transistor. It is going to get very cross with you . It's probably already pissed off for you not putting a heatsink on.


How often do you get into arguments with electronic components? smiley
437  Using Arduino / Project Guidance / Re: Newbie series LED issue on: March 16, 2014, 08:20:31 pm
If you don't have time to rewire it, you're out of luck.

Each pin and a resistor can handle 1 led, placing leds in series will not work, too much voltage drop per led.

(Use a shift register, or individual pins for each led, or if you must a higher voltage with transistors)
438  Using Arduino / General Electronics / Re: How to get 3.3V from Arduino nano, mini, or lily? on: March 16, 2014, 11:19:38 am
You're probably best sticking with the atmega chip, no external circuitry (eg usb to ttl ic)..

Tricky part is supplying the 3.3v , you could power the processor using just the batteries (providing it's not over 5v) getting a regulated 3.3v...

Maybe a LDO (but as soon as the voltage sags, there's not much head room)
Maybe a 3.3v zener diode and a small npn transistor

439  Using Arduino / Programming Questions / Re: Need help with "speed optimization" on: March 16, 2014, 11:04:48 am
Bugga...

I even designed a circuit !

440  Using Arduino / Programming Questions / Re: Need help with "speed optimization" on: March 16, 2014, 10:47:10 am
I'll take a stab in the dark (I'll wait for mike if I'm wrong lol)

But... I think the voltage is not high enough or is just on the borderline to trigger a rising edge.

If that's correct, you may need to boost the voltage signal.
441  Using Arduino / General Electronics / Re: Button state on: March 16, 2014, 10:11:16 am
http://i00.i.aliimg.com/img/pb/713/166/439/439166713_402.jpg

When pressed these buttons latch keeping it in the on state until you press the button again... esp made for feeling (it's dark when youuse one)
442  Using Arduino / General Electronics / Re: Button state on: March 16, 2014, 10:06:15 am
Then a flashlight style button would work..

Push in the button (on)
Push in the button again (off)

?
443  Using Arduino / Programming Questions / Re: Need help with "speed optimization" on: March 16, 2014, 09:57:27 am
Is serial communication affecting the speed?

Next, how much noise is on the reset interrupt?  Maybe it's not getting a clean rising edge?
444  Using Arduino / General Electronics / Re: Button state on: March 16, 2014, 09:51:58 am
Capsense? As your finger gets close arduino sees it?
445  Using Arduino / Motors, Mechanics, and Power / Re: 5v power supply output smoothing on: March 16, 2014, 09:49:38 am
Load cell? You're trying to charge a cell directly from an arduino pin?
446  Using Arduino / General Electronics / Re: Understanding anti-parallel clipping diodes on: March 16, 2014, 07:22:52 am
ahh! - finally, understand it lol.

Thanks smiley
447  Using Arduino / General Electronics / Re: Understanding anti-parallel clipping diodes on: March 16, 2014, 04:19:46 am
I understand zeners... I'm confused as to the clipping in the 0.6v range
448  Using Arduino / General Electronics / Re: Question with level shifter CD4504B on: March 16, 2014, 03:58:21 am
Basically,  the resistor on the led side can be dropped, + to positive (from the logic shifter ic) while ground is switched depending on the 5v signal, no signal the IC is powered down.
449  Using Arduino / Motors, Mechanics, and Power / Re: Series resistor for MOSFET - is it needed? on: March 15, 2014, 07:14:54 pm
The capacitance is what worries people, for brief moment in time the io pin has to supply the current, a resistor just ensures the pin does not supply > 40ma
450  Using Arduino / General Electronics / Re: Understanding anti-parallel clipping diodes on: March 15, 2014, 06:54:04 pm
Mark, are you saying they behave more like zeners in this combination?
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