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1291  Forum 2005-2010 (read only) / Interfacing / Re: Beat detection on: January 30, 2009, 05:18:53 pm
A strong "beat" is normally associated with 2 things; a lower frequency and a higher amplitude.

The simple way (requires parts)  I would do it is to pre-process the analog stream with a low pass filter and then follow that up with a  comparator with adjustable threshold.  (THE AVR has a comparator but you have little control over it)

The low pass filter might involve 1/2 of a generic op amp and the comparator function can be done  the other half of the op amp comparing the filter to say an potentiometer value.  You could then use digital read to determine a 1 or 0  for beat or no beat.

Yeah, it needs external parts...  but there are many google hits if you want examples of Low pass audio filters and op amp comparators.

1292  Forum 2005-2010 (read only) / Interfacing / Re: sht15 problem running code from sensirion on: January 27, 2009, 09:56:36 pm
I have the SHT11 code running great (posted code in the forum) with no temperature issues. I cobbled routines found here with routines found elsewhere.  I'm pretty sure the interface for both parts is similar.  The code I used was originally based on the Sensirion sample code so it will save you the trouble.  (I'm not the original author...  I only tweaked stuff a bit for my own needs)
1293  Forum 2005-2010 (read only) / Interfacing / Re: analog out 0-10V With Arduino on: January 22, 2009, 10:25:12 am
The Triangle:
1294  Forum 2005-2010 (read only) / Interfacing / Re: simple serial issue on: January 22, 2009, 01:39:02 pm
don't assume that baud rate mismatch will do something... very often a mismatch will result in nothing being displayed.
1295  Forum 2005-2010 (read only) / Interfacing / Re: circuit for automatic air organ on: January 24, 2009, 11:03:00 am
Oh.  Well, I guess we misunderstood.  Technically, that's not truly a solenoid as much as it is magnetically driven linear actuator. (now that I see it work)
1296  Forum 2005-2010 (read only) / Interfacing / Re: circuit for automatic air organ on: January 22, 2009, 11:10:52 am
I also agree.  A solenoid will actually "hang on to" the pulses... and only when enough holding current is drained from the coil will it release. The PWM pulses will not make a solenoid open and close if they are very close together... which is what PWM... is. (very close together pulses).  

The solenoid is clearly a binary device and you want it to behave like an analog device.  In my opinion, your theory about slow opening and slow closing of a binary device needs a better explanation.

You can achieve the same results with a solenoid driver chip and making them turn on and turn off  with timed controlled delays directly with software control.

Or, sadly... you are in the land of "SERVOS" if you want control over opening speed.
1297  Forum 2005-2010 (read only) / Interfacing / Re: circuit for automatic air organ on: January 19, 2009, 10:48:17 am
Power Shift Registers might make more sense...

Like maybe these:  L9822E

Available from Mouser
1298  Forum 2005-2010 (read only) / Interfacing / Re: Questions about transistors, capacitors and diodes on: January 22, 2009, 10:35:30 am
While I'm not certain, since the 2N series are easier for me to get, the BC557 is considered to be the PNP equivalent to the BC547.
1299  Forum 2005-2010 (read only) / Interfacing / Re: what is the best ethernet shield? on: January 16, 2009, 03:34:35 pm
The limitations are not necessarily  with the shield or the ENC28j60.  The Arduino is very limited in memory space (from the perspective of what is needed by the TCP/IP STACK)  You would even have trouble if you programmed it in straight AVRGCC with just an AVR168.
1300  Forum 2005-2010 (read only) / Interfacing / Re: Analog output on: November 17, 2008, 10:22:33 pm
LED + resistor = ALWAYS -> to save the life of the LED and the I/O port since the LED resistor is about CURRENT not VOLTAGE.
1301  Forum 2005-2010 (read only) / Interfacing / Re: Slot Cars Hack on: November 17, 2008, 10:54:50 pm
for lack of a better term, the PWM from the Arduino needs to control transistor throttles that are added to the I/O pins.  The Transistors in the throttle circuits carry the current from the "game" power pack. The Arduino just sends low current  PWM to the transistor  throttle.

1302  Forum 2005-2010 (read only) / Interfacing / Re: relay missing on: November 18, 2008, 09:46:36 am
How are you powering the relays?

Is there ANY possible way that the RELAY COIL being energized can feed back into the Arduino's power supply as a SPIKE that is not filtered.

Is it possible to supply the power to the coils via common Ground and Separate Supply... like a battery... to test the theory that glitches are causing unreliable changes on the I/O pins.

You could try adding some additional BYPASS CAPACITORS on the Arduino MCU supply to help catch spikes.  Maybe the Sanguino is more sensitive or has fewer caps.

1303  Forum 2005-2010 (read only) / Interfacing / Re: Arduino voltage? on: November 17, 2008, 09:56:17 pm
1st,  What do you mean "advertised"?

The example showed an LM35 that reads Millivolts per Degree C  and your LM34 reads Millivolts per degree F.

It's the chip USED that defines Celcius or Fahrenheit... not the math.

The math does makes sense.  The *100 converts the Millivolts to volts.

The 5 and 1024 are for scaling the MAX A/D voltage against the MAX A/D resolution.

temperature = (5*val*100/1024)


TEMP F = 5V MAX * A/D VALUE READ * 100 (Millivolts to Volts) divided by  A/D resolution  (again, this is called SCALING)

If you just read RAW values... it will not make sense... as you have noticed.

The A/D on the Chip reads 0-5V with 1024 Bits of resolution.   Halfway between 0 and 5V (like 2.5v) the A/D value = 512.

Based on my understanding of your circuit and results  160 = 78.2 Degrees F.

Sounds Right to me.

By The Way, if you want a chip that send you REAL temperature values, try the 1-wire DS18S20 or 3-wire serial DS1620.
1304  Forum 2005-2010 (read only) / Interfacing / Re: Arduino and Parallax GPS on: November 13, 2008, 02:09:25 pm
In my case, I really don't want to lose the Diecimila host connection to talk with the Serial stream from the Parallax GPS.  So far, the Arduino Software.Serial library work good for me.  (It was designed to allow RS232 type serial communication on non-uart pins using the Bit-Bang Method)

This does mean you need to write code in such a way that you don't "miss" incoming data...  but it's not that hard.
1305  Forum 2005-2010 (read only) / Interfacing / Re: 2N2222 vs 2N2222A on: November 13, 2008, 02:15:36 pm
Here is a nice tidbit of RETRO ELECTRONCS reading material...   it also somewhat explains why you should just consider  lovely 2N2222 a recommendation and not a requirement.
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