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1  Community / Bar Sport / Re: What have you made out of old circuit boards? on: April 14, 2013, 12:48:47 pm
While working at a used computer store / electronics recycling depot, I covered a wall in the lobby with 600+ used motherboards.  It was pretty sharp (looking).

Sorry.  No pics...
2  Using Arduino / Motors, Mechanics, and Power / Re: Motor works only when ammeter is in series on: November 02, 2012, 11:13:50 pm
It may work, depending on the inductance of the motor.  Low duty cycle PWM may make the motor look like it's starting softly, but there could still be a lot of reactive power in the windings.  20kHz seems like a high enough frequency to cause a decent amount of impedance in modestly inductive motor windings.  I'd still run the test with the inductor first, and add it to the final design if the power supply continues to fail without it.

3  Using Arduino / Motors, Mechanics, and Power / Re: Motor works only when ammeter is in series on: November 02, 2012, 06:28:02 pm
Yup... Series, just like the ammeter was.

That coil looks good to me, if indeed the inductor would solve the problem.  More empirical evidence would be needed to say for sure.  So, rather than ordering a part, perhaps you could find something to cannibalize.  Computer power supplies are chock full of inductors, as are old TVs.

Still...  A much larger power supply that's meant for inductive loads would be the best measure.  Check the following link for another possible solution regarding NTC resistors
4  Using Arduino / Motors, Mechanics, and Power / Re: Motor works only when ammeter is in series on: November 02, 2012, 01:48:19 pm
What specs do I need to look for and what size inductor would you consider good?

The value of the inductor is not terribly critical.  I'm thinking 100uH should do the trick.  Something like this...

If you can find a toroid to use, it would be the best choice.  They don't radiate a lot of EM.  The definitive solution would be to use a bigger power supply.
5  Using Arduino / Motors, Mechanics, and Power / Re: Motor works only when ammeter is in series on: November 02, 2012, 03:05:39 am
It must slow down the initial surge of current somehow, to a point just below the threshold that trips the power supply?

You could try an LC filter to test your theory.  I suspect a large inductor would be necessary.
6  Using Arduino / Project Guidance / Re: GinSing on: October 22, 2012, 07:04:03 pm

That page may be of some use as well.  Keep digging.
7  Using Arduino / Project Guidance / Re: GinSing on: October 22, 2012, 06:50:51 pm

Click on "read more" under the mode examples.
8  Using Arduino / Audio / Re: LM386 speaker hum on: October 10, 2012, 12:19:05 am
Try connecting a small value capacitor between the inverting and non-inverting inputs on the amp.  Start with .001uF, and if that's not enough, work up to a value of .1uF, then stop.

This has worked for me in the past.
9  Using Arduino / Programming Questions / Re: ATmega328 on BreadBoard Bootloader Question on: October 09, 2012, 11:58:25 pm
Post a picture of your assembled breadboard, connected to the programmer.

You may have made an error in reading the fritz diagram, like you did with the DTR capacitor.
10  Using Arduino / General Electronics / Re: Momentary reset switch Cap question on: October 08, 2012, 11:30:51 am
Take another look at the diagram.  You should notice that the capacitor is not in series with the switch.  Instead, it's in series with the DTR line that would be connected to a serial port for auto-resetting before uploading.  According to the diagram, the only thing in series with the manual reset switch is a 220 ohm resistor, which should be more like 10k according to the datasheet.  220 ohms should work, but seems quite small to me.
11  Using Arduino / General Electronics / Re: Protecting PCBs against tarnishing - on the cheap? on: October 04, 2012, 07:37:21 pm
The most important thing I've found is to not get any fingerprints on the copper.  Oils and salt from your skin will corrode the copper quite quickly.

My favorite coating is a clear acrylic made by tamiya, with one drop of glycol added per ounce of coating, to give it long term flexibility.  I often use food coloring as the glycol source so I can keep tabs on what's been coated, and how thickly.  I apply it with a brush.
12  Using Arduino / General Electronics / Re: Connecting an 8 ohm speaker to Arduino on: July 13, 2012, 06:29:06 am
Digital components with low current capability shouldn't be directly driving reactive loads unless very high series resistances are present.  Even through a 120 ohm resistor, the kickback can develop a very high voltage across an output pin, and it's of the wrong polarity.  It causes a current to flow between the substrate and n-doped well in any PMOS devices present on the chip (if any, I haven't seen atmel's schematic for it's mega series).  This can crash the processor, cause memory errors, and may even damage the chip.

Use diode protection, and a drive transistor if you can.
13  Using Arduino / Motors, Mechanics, and Power / Re: H-bridge chip vs a stepper motor controller on: October 21, 2011, 03:22:52 am
One thing that I can think of, is that many stepper controllers act as constant current supplies, so that you don't have to wait quite as long for the magnetic field to build up after you make a step.  This gives you more torque at higher running speeds.
14  Using Arduino / General Electronics / Re: Distinguishing an IR LED from an IR sensor. on: October 08, 2011, 03:00:38 am
Any CCD type of camera will detect IR.  A webcam or even a digital still camera will work for you.

My guess would also be that the tinted device would be the sensor.  The tint is there to filter out wavelengths that don't match those produced by the emitter.
15  Forum 2005-2010 (read only) / Troubleshooting / Re: Low frequency tone issue on: September 07, 2010, 06:50:54 am
Thanks for the great info, guys.  It really should be mentioned in the tone reference page.

I guess I'll just have to resort to the blink example to get the frequency I need.  OH, THE HUMANITY! smiley-razz
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