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871  Using Arduino / Project Guidance / Re: Getting into radio on: July 21, 2013, 07:49:01 pm
Jammer Shield...
it's
Sparkgapuino
872  Topics / Education and Teaching / Re: How well US students prepare for science and engineering on: July 21, 2013, 04:06:51 pm
What are people who cannot "add" doing in college at all? 
Remedial arithmetic and remedial language arts, too - in college - so they can hang out for two or three years for an "associate's" degree (drop out).
It's absurd.

I don't understand the "engineering" angst, it's not everyone's ken and that's OK.  I think the last thing anyone needs is a haircut from an "engineer".

Colleges do not turn out well-rounded people.  Nowadays they manufacture self-important excuse-makers and conceited, would-be technocrats.
873  Using Arduino / General Electronics / Re: An inverter for under 3 bucks! on: July 21, 2013, 03:40:51 pm
On the one hand, there's the raring to tear into this thing this way and on the other there's a reluctance to cobble up a little circuit from two or three components to find out what's going on.

874  Using Arduino / General Electronics / Re: lm317 current regulation. on: July 21, 2013, 01:06:39 pm
The best thing to do would be to set up that current regulator circuit on a breadboard, after calculating for a modest output (< 20mA).

Run the output into a short and measure the voltage across the "programming resistor" and that across the LM317 (input to output).
Vary the input a few volts and note the changes, if any, across those components.

Then place a smallish resistor on the output and repeat the process.
875  Using Arduino / Audio / Re: LM358 module - how to connect? on: July 21, 2013, 11:24:05 am
Provide a schematic of what you've done.
Doing this stuff verbally, and with all that back-and-forth, is a waste of time.
Draw a picture of your circuit, take a decent picture of that and upload it as an attachment.

A condenser (electret) mic requires power.
It's not like a crystal mic.

In my dwg, attached, there are some biasing resistors and coupling caps.
"+V" should not be greater than 3V.
If you don't like it, google for others.

876  Using Arduino / Microcontrollers / Re: Program Arduino Nano from Arduino Uno on: July 21, 2013, 11:09:26 am
If the IDE was up when you made the changes, they wouldn't take effect till the IDE got rebooted.
877  Topics / Device Hacking / Re: Hack garage door opener Liftmaster 973LM on: July 21, 2013, 11:04:15 am
Place the relay contacts in parallel with the existing wall-mounted switch.

(see dwg attached.)

878  Using Arduino / General Electronics / Re: Automotive relays diodes shorting? on: July 21, 2013, 10:18:54 am
Any high-voltage event would result from the coil's being de-energised (turning off), the then collapsing magnetic field's resulting a counter-emf, but not from its being energised.

...but the diode shorts out about half of the time.

So, you have removed the diode and, using the diode test function on your multimeter, confirmed that it is "shorted", or what?  Please explain.

> > > If you don't know how to test a diode then ask.  A picture of your multimeter could be helpful in providing an answer.
879  Using Arduino / Microcontrollers / Re: Program Arduino Nano from Arduino Uno on: July 20, 2013, 09:20:45 pm
I don't see anything wrong that way.
There's also the "(maybe) use a 10uF cap" and/or a "120Ω resistor".
I don't know why there's such variation.
Maybe it's differences between genuine Arduino vs clone components or something.
I'm trying to learn here, too.
880  Using Arduino / Microcontrollers / Re: Program Arduino Nano from Arduino Uno on: July 20, 2013, 07:14:40 pm
So,
  • first upload the ArduinoISP sketch to the Uno
  • connect the target (Nano) to the Uno as appropriate
  • upload the Nano's sketch, via the Uno, with Duemil./Nano as the "board"?

[Disclaimer: I have a USBtinyISP that I use for this.]

> > > http://electronics.stackexchange.com/questions/10587/how-to-burn-atmega328-chip-via-arduino-uno-as-isp
881  Using Arduino / Microcontrollers / Re: Program Arduino Nano from Arduino Uno on: July 20, 2013, 07:05:33 pm
The examples I've seen with ArduinoISP (all?) burn the bootloader to the target.

Is it the same set up and process to upload sketches to target devices without a bootloader?
Or does boards.txt require additions for a "ATmega 328 Standalone (w/ Arduino ISP)" option?

> > > http://forum.arduino.cc/index.php?topic=178517.0
882  Using Arduino / Microcontrollers / Re: ATTiny85 and Shift Registers on: July 20, 2013, 03:43:29 pm
What happens is that the shift registers light up the LED's in completely the wrong order, sometimes flickering. There doesn't seem to be any logic behind how it's driving the registers it's driving.
Am I missing something obvious?

Have you tried this with anything other than an ATtiny and had it work out right?
Maybe it's your sketch or maybe it's how you have things wired.  Possible?
883  Using Arduino / General Electronics / Re: SSR AC-motor RC snubber circuit - What type of capacitor to use? on: July 20, 2013, 12:38:24 pm
1W, 2W

Two 220Ω 1/2W in parallel = 110Ω 1W
Two 50Ω 1/2W in series = 100Ω 1W
884  Using Arduino / Project Guidance / Re: Electric go kart project on: July 20, 2013, 12:25:15 pm
That motor is approx 1/4 1/2 hp.
Gearbox or not, how go-karty will that be?

> > > I did an e-bike with a 1/2 hp motor - and it's not setting any records.
885  Using Arduino / General Electronics / Re: Automotive relays diodes shorting? on: July 20, 2013, 12:04:53 pm

There are only two reasons a diode could fail for
1) exceeding PIV
2) exceeding max forward current

It's a 1000 volt diode, so Cause No. 1 is out.
It's a 1.5 amp diode, so Cause No. 2 seems "remote".

I believe the diode is somehow shorting is this possible?

Have you removed the diode, tested it, and found signs of failure?
[You cannot test it in circuit.]
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