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16  Using Arduino / Project Guidance / Re: Help With Powering/Wiring of a CNC-Style Setup on: July 21, 2014, 08:58:43 pm
I bought a bunch of VGA/RAM heat sinks. Just the right size for the A4988. Many come with thermal double-stick tape on them, if not, buy some.
17  Using Arduino / Project Guidance / Re: How rugged is Arduino? on: July 21, 2014, 08:50:13 pm
Short, clear, code. The hardware affects the reliability, too.
18  Using Arduino / Project Guidance / Re: Poll: How Should I Unlock My Door on: July 21, 2014, 08:48:01 pm
DIY RFID?

http://playground.arduino.cc/Main/DIYRFIDReader

As others have said, the unlock mechanism may take your entire $20.
19  Using Arduino / Project Guidance / Re: How rugged is Arduino? on: July 21, 2014, 08:41:55 pm
Quote
Should i use a watchdog timer for reliability?

Yes, absolutely. Never assume that it can be made to never lock up. ESD, nearby lightning strike, stray cosmic ray, etc.
20  Using Arduino / General Electronics / Re: Circuit Correct? Help me! on: July 21, 2014, 08:14:36 pm
Wow! No wonder your AA batteries are pulled down so far. There is no way they'll supply 1.5A at full voltage, or for very long.
21  Using Arduino / General Electronics / Re: Circuit Correct? Help me! on: July 21, 2014, 04:46:12 pm
Do you have a 10A range on your meter? Connect the meter in series with the motor and connect them to the batteries without the MOSFET.

And change those resistors!

There is no point in placing capacitors in the circuit until you either use larger batteries, or find out that your batteries are merely worn out and you replace them.
22  Using Arduino / General Electronics / Re: Circuit Correct? Help me! on: July 21, 2014, 04:26:48 pm
No, get bigger batteries. Capacitors will only make up for spikes in current draw. Fix those resistors, and use larger batteries.

How much current is this motor drawing?
23  Using Arduino / General Electronics / Re: IR Led and Phototransistor connection give always 0 value on: July 21, 2014, 04:25:15 pm
Some phototransistors bring the Base lead out for biasing.
24  Using Arduino / General Electronics / Re: Getting 0-5V with PWM on: July 21, 2014, 04:23:57 pm
An entire industry disagrees with you. Page 44 of the good old Simpson 260 VOM (page 23 of the PDF) has the schematic. No smoothing capacitor when using the ACV range.

http://www.simpson260.com/downloads/simpson_270-4_user_manual.pdf

Same with the 160:

http://www.simpson260.com/downloads/simpson_160_schematic.pdf

Some other brands:







In VU and dB-spl meters, capacitors are added to slow the response time of the meter.

In any case, what I said about peak readings still stands.
25  Using Arduino / General Electronics / Re: Circuit Correct? Help me! on: July 21, 2014, 02:13:53 pm
OK, good, that should be good. How is it working now? Is the MOSFET cooler?

That 8.3V --- read on a DMM during operation? I don't see a capacitor in there. You should have something like a 470uF or larger capacitor and a 0.1uF ceramic capacitor across the 9V power source, as close to the MOSFET as possible.
26  Using Arduino / General Electronics / Re: Getting 0-5V with PWM on: July 21, 2014, 02:07:23 pm
No, he wants to read the average of a PWM output. He could do so using a lowpass filter and buffer amplifier, or he could just connect the meter and allow the intertia of the movement to smooth PWM to a static needle position. No capacitor required.

To read the peak, he'd need a diode and capacitor. But the peak would always be 4.8V - 0.7V or 4.1V.
27  Using Arduino / General Electronics / Re: PWM 12V 150Amps output signal using arduino is it possible ???? on: July 21, 2014, 11:21:13 am
I seem to recall that the maximum efficiency of electrolysis of water is only about 70%. And that the maximum theoretical efficiency of the Carnot cycle in an engine is just under 70%, but the actual efficiency in modern engines is considerably lower.

So already 50% of the power is gone. IE, 2hp (about 1500W) from the alternator nets about 1hp additional power at the engine. Then the alternator is not 100% efficient. The battery is not 100% efficient at storing and releasing power.

Even if everything was 100% efficient, you'd have broken even.

BTW, there is no such thing as "HHO gas". It is H2 and O2 mixed.
28  Using Arduino / General Electronics / Re: bad design? on: July 21, 2014, 11:12:22 am
Maybe you should tell us what you are trying to accomplish.
29  Using Arduino / General Electronics / Re: IR Led and Phototransistor connection give always 0 value on: July 21, 2014, 11:11:07 am
Schematic? Please trim white space and resample to 600 or 800 pixels wide. Take voltage measurements and post those, too.
30  Using Arduino / General Electronics / Re: Circuit Correct? Help me! on: July 21, 2014, 10:27:10 am
No, no, I mean I made a typo. I meant to say to change R4  to 100ohms. Leave R3 alone, change R2 and R4.

Please, just try it.

As long as the 9V supply isn't sagging, 9V should be enough to turn on even a non-logic level MOSFET as good as all the way.

Non-logic level MOSFETs generally are rated at 10V for full saturation. However, there should be very little difference between the On resistance with 9 or 10V.
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