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46  Using Arduino / Project Guidance / Re: proportional hydraulic valves control with arduino on: July 14, 2014, 01:21:00 am
Unless you're using a valve that has a fancy PWM signal input and requires a specific frequency you're probably on the wrong path. PWM is a duty cycle; the ratio of time that the signal is high vs. low. The granularity of the switching on/off (the PWM frequency) is not likely to be an important factor and the Arduino's default ~500Hz should be fine.
47  Using Arduino / Motors, Mechanics, and Power / Re: Building an H-bridge for very high current Stepper Motors. on: July 13, 2014, 02:40:34 am
Your mosfets are designed for ~10V at the gate before they will fully switch "on"; if you look at your datasheet you'll see the specs typically quoted a 10VGS. This is why you saw such a dramatic increase in current when you moved from 6V to 12V. A logic level mosfet (e.g. IRL540) is what you want when controlling the gate with an Arduino.

If you're really looking to build a high performance H bridge the you'll want to study up on "mosfet drivers". These are designed to drive mosfet gates from logic level signals and then do so with high voltage and current for fast switching times. An IR2181 (you'd need two for a full bridge) would be an example of what you're looking for.
48  Using Arduino / Project Guidance / Re: Visually recognize a number - dumb energy meters on: July 12, 2014, 09:52:15 pm
An optical mouse sensor reads 16x16 pixels (typical). But again it's a problem of getting the right focus on the dial. And finding a compatible mouse sensor :/
49  Using Arduino / Project Guidance / Re: Solar Charging Circuit for Onboard NiMH Charging on: July 12, 2014, 09:44:32 pm
With the panels in parallel with the battery the voltages will always appear to be the same as the battery voltage.  You should think of the panels as outputting a wattage rather than a voltage; for a fixed amount of sunlight the voltage will appear high when little current is being drawn or low when a lot of current is being drawn. Your panels might have an "open circuit" specification which refers to the maximum voltage they will output when no current is being drawn.

For a single NiMH cell, 1.3V is the 90% charged voltage, so you'd configure the TL431 to conduct right around (4 * 1.3V =) 5.2V.  If the batteries are not fully charged then they should absorb all of the current from the solar panels (minus whatever your Arduino is using). If your batteries are fully charged and you're in full sunlight then the TL431 is going to be conducting the full rated current of the panels.

Batteries can typically fully absorb a current equal to 1/10th their capacity without any problem. Your cells are 350mah and your panels are 35ma so it's a perfect combination.
50  Using Arduino / Project Guidance / Re: Solar Charging Circuit for Onboard NiMH Charging on: July 12, 2014, 01:09:53 am
Basically I'm saying you want to eliminate everything between your solar cell and your battery to keep your charge efficiency up. You could get rid of R1 and the transistor, simply leaving the zener between Vin and GND. When the solar panel charges the battery over it's upper voltage limit the zener will start conducting current to GND and keep the battery voltage within limits. A 1/2W zener should handle the current fine. And again you wouldn't need R2 because in a full sun situation the zener should be preventing excess current from reaching your battery. Just don't use too many solar cells to keep things within limits.

A TL431 (very common part) will give you more precise and adjustable regulation than a zener. It is spec'd for 100ma (150ma max) and again would be plenty for multiple panels. Plus, for future needs, if you have TL431s on hand you'll never have to worry about having the right voltage zener around.

Regarding the "LM314", assuming you meant an LM317, you'd want to avoid that part to keep your efficiency up. The LM317 has a dropout voltage around 1.5V, meaning that 1.5V times your current is lost to heat, or your battery always has to be 1.5V higher than your output voltage. An LM1117 has a lower dropout voltage (around 1V), or you can always find more modern parts like a LM2931 with just .16V dropout.
51  Using Arduino / Project Guidance / Re: Solar Charging Circuit for Onboard NiMH Charging on: July 11, 2014, 04:19:04 pm
Regarding your original circuit, you have a strategy that allows current through to the battery when the battery voltage is lower than your zener setpoint. I'd suggest rearranging it so that you shunt current to ground when the voltage is higher than the setpoint. The advantage to that is you keep the transistor, etc. out of the current path and improve your efficiency when charging.

If you have an available analog and digital pin on the ATTiny you could also program the ATTiny to dump current when voltage gets too high. I.e. read the battery voltage and if over the programmed limit activate the transistor to dump current through a resistor, etc. That would offer a bit more control than relying on zener diodes and their imperfect nature.

52  Using Arduino / Project Guidance / Re: Robot Submarine Project on: July 09, 2014, 11:40:41 am
Motor boards with L29x chips are really old tech. An RC ESC is a much better and more efficient choice; you can find them for either brushed or brushless motors (but the OpenROV site probably already explained the advantage of brushless motors).

The Servo library is used with RC ESCs.
53  Development / Other Hardware Development / Re: Banguino - Arduino made as a chip on: July 09, 2014, 03:04:34 am
Can you provide a hi-res picture of one of the chips (or board, or board chips, whatever)?
54  Development / Suggestions for the Arduino Project / Re: Does Arduino have a future? on: July 09, 2014, 02:57:18 am
Atmel's AVR chips are falling behind the ARM chips (Teensy, Maple, etc.). They need to start kicking up the clock speed and memory to stay competitive. That's my only concern.

With respect to the Raspberry Pi, Beaglebone, etc., those are not microcontrollers. There will always be tons of situations where just a simple microcontroller is warranted and AVR chips will always have their place there.
55  Using Arduino / General Electronics / Re: Circuit Correct? Help me! on: July 09, 2014, 02:39:49 am
I put the diode because I previously burn out an H-Bridge and I have fear smiley

But my question is: The diode has correct orientation? Maybe, If the diode is reverse maybe it can do the motor get low voltage.

Per your diagram the orientation and placement is correct and yes it is required. The mark on the diode will be on the side of the positive connection on the motor.
56  Using Arduino / General Electronics / Re: Proper way of splicing power cord in Ontario, Canada ? on: July 09, 2014, 02:34:26 am
I find it hard to believe that wire nuts are not allowed. The only time you'll ever find a soldered connection in home wiring is if knob-and-tube wiring is in use. Trivia: it's also called a "marrette" because it's named after William Marr -- the Canadian (Ontario) that invented them.

Any splice must be done in an accessible electrical box with a cover.

You mentioned "outdoor electrical cord". Are you referring to the type of electrical cable that is rated for outdoor/direct burial, or are you referring to an extension cord (with a plug on one end and a receptacle on the other)? I'd find it odd if the latter was an allowed type of cable, but if it were, you'd need to make sure it has an ampacity rating equal to the circuit breaker on the circuit.

Lastly, you mentioned that the cord "resurfaces in the middle of a room". I'd be surprised if it's allowed to have cables coming out of holes in the floor; you should put a proper receptacle (in a box) in the floor and plug in your appliance/lamp to that. The only time I've read of code like that refers to directly wiring machinery in a work environment (garage) to an outlet box, but that's only allowed when the breaker box is within 50 feet and in view of the operator.

Fungus: it's typically not a spring but a solid cone with an internal thread.
57  Community / Bar Sport / Re: The Cracked Pot on: July 07, 2014, 11:33:30 pm
I work with a lot of people that must have some beautiful flower arrangements on their tables.
58  Community / Bar Sport / Re: Students caught out.... on: July 07, 2014, 11:30:18 pm
I'm looking into a solder paste dispensing thingy. 

Another option for you to consider. He seems to have thought out the design pretty well.
59  Using Arduino / General Electronics / Re: Weighing scales to arduino on: July 07, 2014, 02:51:58 pm
When you're using for a load cell, the proper resistor value for the gain setting for the INA125P is typically between 50 and 200 ohms, and if you're off by more than ~5 ohms you won't see much change in the reading.

If you're seeing an output voltage (from the INA125P) of ~4V then you need a higher ohm resistor. If the output voltage is always ~1.5V then your resistor is too high a value. Keep trying different resistors until you get a value that's somewhere in-between and then at that point you'll know you're getting close.
60  Topics / Robotics / Re: fan control for parachuting device on: July 07, 2014, 11:39:29 am
I'm sure a Multiwii board (with a GPS) could be configured to do this. Just comes down to figuring out the translation of control surfaces / fan on your parachute to the Multiwii.
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