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31  Using Arduino / General Electronics / Re: Controlling 4 electromagnets with Arduino on: May 22, 2013, 12:39:28 pm
You'd connect/wire your electromagnets using a Logic Level Mosfet to turn on/off the magnets. The Mosfets will act like a switch, controlled by the Arduino.

You'd need a lot of power to turn on/off this electromagnet. 5 Volts wouldn't cut it. So a separate PSU just for powering the electromagnets is recommended.

Yes, you can try building your own electromagnet. It's not rocket science. I don't understand your question "would that be compatible with Arduino?"  -- what exactly do you mean by that question?
32  Using Arduino / General Electronics / Re: Geezer electronics or a short history lesson... on: May 17, 2013, 07:31:08 am
Thanks for sharing.
33  Using Arduino / Project Guidance / Re: Cleaning a 12v Supply on: May 16, 2013, 10:53:28 pm
My "beef" with Chinese PSUs is they say one thing, but actually do another.  So I'd say test and verify that it's true.
They may say 30mV, but does it really measure 30mV on your scope? 

If it's really 30mV, then it's probably going to be fine. 

UPDATE: I did a quick check on the 2596 datasheet, and typical performance graphs show ripple is 50mV-100mV. How can they claim 30mV,  better than the datasheet? As I said... test and verify. Don't trust those lying chinese. Maybe that 30mV is for a no-load condition.

34  Using Arduino / Project Guidance / Re: Cleaning a 12v Supply on: May 16, 2013, 09:43:31 pm
The buck converter will have a small capacitor in front of it. But you may want to "clean" the output of the buck converter if the ripple/noise is too high to your taste.  I don't know which buck converter you're using. Some buck converters have built-in linear regulators at their output. Others don't have.

Of course, you can add your own linear regulator to your DC/DC converter's output. By using a post-linear regulator at the outputs of your DC/DC converter, you can bring down ripple/noise to 10mV peak to peak.
35  Using Arduino / General Electronics / Re: My serious fail with ribbon cable on: May 16, 2013, 09:39:35 pm
Or a good way to connect the two devices without single strands?
The female connectors have "teeth" in them, that puncture the insulation of the ribbon cable.
That's why they're called "IDC", for Insulation-displacement connector.
So all you need to do is align them, then snap the bottom and top part, letting the "teeth" dig into the insulation and make contact with the conductor. No soldering needed.

You can buy these kind of female connectors from
For the cable, you can try eBay or mouser/digikey.

36  Community / Gigs and Collaborations / Re: Programing Code Assistance For Led Mouth on Ten Foot Costume on: May 16, 2013, 10:15:06 am
You don't need an Arduino for this... Just any LM3914/3915/3916 LED VU driver, and a small amplifier in front of it for the mic is all you need. Each LM39xx chip can handle 10 LEDs, and you can cascade them even if you need longer (20, 30 Leds, etc) .... or if you only need less than 10, then skip some of the output pins.
37  General Category / General Discussion / Re: Make Your Pitch - My Business Idea! on: May 07, 2013, 01:20:43 pm
Great idea.

Some comments:

Background music is distracting*/loud  (doesn't help that your vocals sound echoey... sounds like recorded in a hallway? i.e. you're not using a mic, just using the built-in mic of your camera). Lower the music volume so it doesn't distract from your message.

** this is the distracting music effect. starting from 00:40, then again at 1:07, 

38  Community / Bar Sport / Re: Super Computer Power AND piping hot 24/7 hot water? on: May 03, 2013, 10:56:25 pm
Two Questions about your grandiose idea:

1. What are you smoking?

2. Can you send some?
39  Using Arduino / Project Guidance / Re: simulation software? on: April 29, 2013, 01:22:55 am
Try this.... runs on your Chrome browser.
40  General Category / General Discussion / Re: Arduino board used as detonation device in Boston? on: April 28, 2013, 07:34:42 pm
If anyone has any information on somebody asking how to write code, let the proper authorities know!!!

Like what kind of suspicious question?

How do you turn on an LED light in Arduino? 
and how do I add remote control to my Arduino to turn on an LED lamp?

41  Topics / Product Design / Re: PCB fab suggestion? USA or Canada? on: April 28, 2013, 05:56:02 pm
Oshpark is great. But they deliver in multiples of (3).  A 2x2.5" will be about $25.10 total for 3pcs.
42  Using Arduino / General Electronics / Re: Convert 48V Phantom Power to 9V on: April 28, 2013, 05:43:56 pm
Yes you can use a regulator to regulate that down to 9V. Just use a big heatsink.
I'd suggesting using a LM317HVT <--- note: HV type

You probably don't want to use DC/DC switching regulator here as any EMI/RF noise may travel back to your mixer and may be heard as noise.
I said *MAY* because in general, the CMRR of your preamp should take care of that noise and you won't even hear it. 
But who knows.

The max. voltage differential (Vout - Vin) of the LM317HV type is 60V.  So you're okay*.

* Just use a big heatsink because that will be dissipated as heat.
43  Community / Bar Sport / Re: Flying with Arduino on: April 27, 2013, 05:34:49 pm
In other countries, banks have posted armed guards posted by their entrance. These guards are loaded with sidearms, shotguns or M16 rifles.
You don't f*ck with them.

Well, me and my officemate were going to a client's site but she decided to stop by the bank to do some personal business first.

Before entering the bank, the guards try to feel my gym bag's content with their hands.
Sure enough, they felt something heavy and bulky. Asked me to open the bag.
I opened up the bag's zipper for inspection by the guards, so they can peek in.
The guard saw something and he pulled out this metal cylindrical thing, with lots of wires sticking out. (I was carrying several stepper motors.)

DANG! Some guards were ready to draw their guns! It surely got their attention!
"What's this?" he asked.
"It's a motor" I said nonchalantly.
They recognized my friend so they waved us in.

But they were very wary of me.

So I'm sitting on the sofa in this big lobby, while my friend conducts her business by the teller.

I see 2 guards with shotguns walking around the 2nd-floor balcony, overlooking the lobby, keeping an eye on me.
Another 2 guards by the door looking my way, and the 2 guards outside the bank peering in the glass doors also keeping an eye on me.
Another guard is walking/standing by my vicinity, maybe 30ft away.
They were really observing me.

Never again will I bring stepper motors inside that bank! 
44  Using Arduino / General Electronics / Re: Opamp mystery on: April 24, 2013, 06:28:53 pm
I would think all opamps should behave pretty much the same.

In the real world, some opamps are more prone to oscillation. Need proper bypass capacitors.

Is your output oscillating, and that's what you're measuring?
45  Using Arduino / Programming Questions / Re: SIN COS TAN Decimal Precision for 32-bit Float / 64-bit Double Arduino on: April 23, 2013, 06:06:39 pm
Can your stepper motor/mechanical design resolve to that accuracy of 6-7 digits precision that you need it in the firmware?
Just asking...
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