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16  Using Arduino / Project Guidance / Re: How to increase the dc motor's speed(andFrequency)value more than255(and64KHZ)? on: April 17, 2014, 01:51:14 pm
Go, Grumpy_Mike.

This is why I'll continue to say that delay() is one of the worst things to teach a newbie as a first lesson. It has its uses.
17  Using Arduino / Project Guidance / Re: Blocking -VDC on: April 17, 2014, 01:48:28 pm
Just commenting on the idea of using a motor as a generator to determine direction:

Connect one terminal of the motor to a voltage divider at Vcc/2. Connect the other, through the appropriate resistors and diodes to protect the Arduino and capacitor to smooth the signal, to an Analog input pin.

Motor spins one way, voltage>2.5V. Motor spins the other way, voltage<2.5V. You could connect a second Analog input to the voltage divider to get an accurate read of zero speed voltage.

Load the motor down with the right resistor across it, and you can probably get a reasonable indication of speed, too. The resistor should go right across the motor.
18  Using Arduino / Project Guidance / Re: [ Guidance Needed ] How to make my own Arduino. (for USB com) on: April 17, 2014, 01:38:16 pm
ATMega8, sure. This page covers using it:

http://playground.arduino.cc/Learning/AtmegaStandalone
19  Using Arduino / General Electronics / Re: How do I replace a moral rectifier part? on: April 17, 2014, 12:02:30 pm
If you can get more Magic Smoke, you can repair it.
20  Using Arduino / General Electronics / Re: criticism over my circuit.. on: April 17, 2014, 12:01:36 pm
SteveSpice still works pretty well. ;')
21  Using Arduino / General Electronics / Re: criticism over my circuit.. on: April 16, 2014, 11:25:22 pm
Don't forget my correction...
22  Using Arduino / Project Guidance / Re: How to increase the dc motor's speed(andFrequency)value more than255(and64KHZ)? on: April 16, 2014, 06:25:31 pm
http://www.ti.com/lit/ds/symlink/l293d.pdf
23  Using Arduino / Project Guidance / Re: How to increase the dc motor's speed(andFrequency)value more than255(and64KHZ)? on: April 16, 2014, 06:25:11 pm
Quote
When I take of this jumper ( at the above screenshot that is on my motor shield ) I can put 1 power supply to power shield and 1 power supply to my arduino at the same time without any problem, right ? thanks.

Yes, that is the jumper I thought you were talking about. Take that off and you can power the motors with their own supply.

The grounds will be connected together through the motor shield, as long as you connect both leads to the Ext_Pwr pins.

As for the current, the two outer ICs are the motor driver chips; read the numbers and Google for the datasheets. I think that might be the same motor shield that I have, it has two L293D chips on it. They are rated at 600mA max, 1.2A peak.

However, without a heatsink, they may get quite hot at 600mA.
24  Using Arduino / Project Guidance / Re: How to increase the dc motor's speed(andFrequency)value more than255(and64KHZ)? on: April 16, 2014, 01:53:18 pm
The motor shield may have a jumper that connects the motor driver chip to the Arduino's 5V.

If you do not remove this jumper and you connect 9 or 12V to the Motor Power Input, you'll be applying this directly to the Arduino's 5V buss and fry it. If you have not removed the jumper and haven't fried your Arduino, it is probably because a small rectangular 9V battery can't supply much power.
25  Using Arduino / General Electronics / Re: criticism over my circuit.. on: April 16, 2014, 01:49:01 pm
Hah! Yeah, I don't think we need to limit "General Electronics" to strictly Arduino related or nothing.

How about this? It relies on only about 15uA pulled from the 5V supply to the base of an NPN, then that draws about 140uA through a resistor from the 14.4V supply. No other power when the 5V supply is present.

When 5V goes dead, the 2nd transistor gets turned on through the 100k resistor. This pulls the base of the 3rd transistor, a PNP, low through a 10k resistor and turns it on. lighting the LED.

The 10k from 14.4V to the PNP base is to make sure it is kept OFF when the 2nd transistor is OFF.

Edit: That first resistor should be 3.3M. Somehow my decimal point got lost... and 1.3uA from the 5V supply. I'd feel more comfortable with a slightly smaller resistor here, like 1M.
26  Using Arduino / Project Guidance / Re: [ Guidance Needed ] How to make my own Arduino. (for USB com) on: April 15, 2014, 03:57:10 pm
Arduino the -best- choice? In what terms?

It should be sufficient. It doesn't take much CPU power to keep up with input from a person.

There are a -lot- of alternatives to ATMega. PIC, Propeller, TI, ST, Freescale, Si Labs, etc. and more etc. It seems like just about every IC manufacturer has their own microcontroller.

For price, TI has an ultralow power 16 bit MCU, the MSP430, some versions way under one US dollar. The Propeller has 8 cores in an 80MHz chip for $8.
27  Using Arduino / General Electronics / Re: criticism over my circuit.. on: April 15, 2014, 12:26:37 pm
How about a CMOS 555 timer? Some aren't meant to run from more than low Vcc, so make sure the one you choose does. Should draw on the order of microamps when the LED is off.

The TS555 is rated to 16V. Just put an appropriate resistor on pin 5 so pins 2 and 6 trigger when the 5V line drops to where you want it to trigger. Built-in hysteresis. It acts as an inverting schmitt trigger.


28  Using Arduino / General Electronics / Re: Running super bright IR LEDs at 38khz off PN2222 on: April 15, 2014, 10:13:05 am
38kHz isn't really fast, though.

I suspect this has more to do with not enough difference between 6V and the total LED drop.

The suspicion that the transistor has C and E reversed is a good one, too. Generally, a BJT will work with them reversed, but at a much lower gain and seriously degraded saturation.
29  Using Arduino / General Electronics / Re: My First Oscillioscope on: April 15, 2014, 10:10:51 am
2M memory vs 40k? Just that alone is worth the extra $100.

As for bandwidth, fungus is right on. Square waves have odd harmonics, the more that get lost, the more it looks like a sine wave. I consider the 9th harmonic the minimum, and the bandwidth is measured where the response is -3dB down, so 10x the square wave frequency is a good rule-of-thumb.
30  Using Arduino / General Electronics / Re: Measure a battery amps on: April 14, 2014, 10:05:59 pm
I think there was a misunderstanding and the OP connected his meter set on Amps directly across the battery.
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