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1501  Using Arduino / Project Guidance / Re: Brewing heater element control on: December 31, 2012, 08:02:10 pm
You'd probably be best served by buying a ready made controller. An eBay or Google search for "PID temperature controller" will turn up lots of results at ~$30 and it's hard to compete with those prices when building from scratch. You would then just need a K type thermocouple (again, eBay etc.) and a hefty relay or SSR.
1502  Products / Arduino Due / Re: Using GCC directly on: December 31, 2012, 02:36:31 am
Are you asking for the basics in using GCC?

You might also want a tutorial on creating Makefiles, which kinda explains the same ... indirectly.
1503  Using Arduino / Project Guidance / Re: Automatic weight system on: December 31, 2012, 02:00:47 am
Look into bullet reloading equipment for inspiration -- the powder measuring part. A "trickler" is a horizontal, vibrating tube tee'd from a funnel for very small rates of feeding. Shotgun shell reloading equipment uses a rectangular bar with a hole in it that is pushed back and forth to measure a set amount of powder/shot; the reciprocating motion would be pretty easy with an RC servo and has the advantage of sealing your container when stopped. If you need a lot of volume to move then you'd have to go with some type of auger system. Perhaps a compression spring could be used for the auger.
1504  Using Arduino / Project Guidance / Re: Traction Control (Throttle adjustment/Boost adjustment) on: December 28, 2012, 01:26:47 am
So, I'm trying to wrap my head around the idea. PWM and Duty Cycle are relative to each other. If the pulse-width is 1 millisecond on, 1 millisecond off, then the duty cycle is 50%. So I assume that means that 'analogWrite(9, 127.5)' would be considered 50% duty cycle? Since analogWrite() uses a 0-255 value and half of 255 is 127.5?

Correct. And although 'analogWrite(9, 127.5)' works it's a bad habit to be putting floating point numbers where integers are expected.

When 127.5 is written to the motor, it continually opens. This starts to make more sense, because I've always heard that you have to keep your average duty cycle under a certain percentage or you will fry your device (I've heard it mainly on fuel injectors. I believe I have mine set to like 23% or 24% duty cycle, which correlates to the injector size? Mine are 780cc). The reason I say this starts to make sense is, I initially thought that in order to move the throttle to 100% open, you would have to write the motor 'analogWrite(9, 255)'. But actually, to maintain 100% throttle position you could initially write the pulse width to something between 200-255 to snap open fast, and then decrease the amount however much per loop, until the throttle position tries to drop under 100%.

The injectors, or any resistive devices, will have a limit to how much current they can handle. You have a duty limit so that average current flowing through the injectors will be under its current limit so it doesn't overheat. In your case it's also a concern because you'll start vaporizing your gas inside the injector if the injector gets too hot.

Back to that "it continually opens" thing are you referring to the butterfly on the carb? If the engine is not running that butterfly will always be 100% open if the throttle is anything above zero. The throttle opens the butterfly; the governing system pulls it closed and pulls harder when engine RPM is higher. The butterfly reaches an average state when a balance between the two is reached.
1505  Using Arduino / Project Guidance / Re: PWM control of many LED's from arduino on: December 28, 2012, 12:40:43 am explains everything quite nicely.

Aside from the ZXLD1360 that the driver is built around and the (unnecessary) bridge rectifier you identified, the only interesting component is the R300 (.3ohm) resistor that is used to set the max current for the driver. Per the datasheet .1 / .3 = 333ma.

I can't see in the first picture clearly due to the glare, but the pin below the "0" on the chip labeled "1360", the ZXLD1360, should be floating (soldered to a pad that goes nowhere) currently. Wire the bulb with +12V and GND, then connect to that pin through a resistor (~10K) and to a PWM output on the Arduino. Voila.
1506  Using Arduino / General Electronics / Re: Decoupling capacitors on: December 27, 2012, 07:41:35 pm
Never hurts to plan for a capacitor then leave the spot empty when you build the board. It hurts a lot more to not have a spot to add the capacitor when you need it.
1507  Using Arduino / Project Guidance / Re: Modifying the solder stop mask for a pad in eagle on: December 27, 2012, 07:35:56 pm
If you're asking to make the stop mask larger, then you would select the polygon tool, select the tStop layer, then draw the polygon so it overlaps the existing stop mask; the two will combine to create a larger area as you would expect. If you're trying to make a stop mask smaller then you would need to modify the IC package and remove the pad completely, then manually create the stop mask and pad using the polygon tool.

When your project is complete it's always a good idea to doublecheck the results using a Gerber viewer (like GerbV, etc.).
1508  Topics / Robotics / Re: which lipo battery to have for robot on: December 27, 2012, 01:37:28 pm
You likely want a "2S" (voltage is 2 * 3.7V = 7.4V) type rather than a "3S" (3 * 3.7V = 11.1V). You want the least amount of difference between the battery voltage and what voltage you'll be regulating your power to (which I assume is 5V).

The "C" rating of the battery tells you the amount of current the battery can discharge. For example, a "10C battery with 2200mah capacity" can discharge at a rate up to 10 * 2200 = 22,000ma (22 amps). HIGHLY unlikely you'll be using anywhere near that much power unless you're using some pretty big motors. "10C" is a pretty low rating for LiPo batteries so it's unlikely it'll be a concern for you.

Back to the capacity, the "2200mah" rating means it can provide 2200ma for one hour, or 1100ma for two hours, etc. Coincidentally, an alkaline AA battery is also around 2200mah so if you're running on AA batteries now then you have an idea how much more capacity you need or want.
1509  Using Arduino / Project Guidance / Re: PWM control of many LED's from arduino on: December 27, 2012, 02:30:59 am
Could I not just use a big resistor to current limit too the 3 x 1w LEDs, and chuck out the driver circuit?

Yes, but you don't want to. Looking at the "wide angle" bulb linked earlier, it's only driving the LED with 50% efficiency. A proper driver will do much better than that. Also, the high wattage resistors required are pretty expensive themselves, and then you also have the problem of them getting freakishly hot.

The drivers in your bulbs might have a PWM option that is not being used, but again only a look at the IC in question would provide the answer. At worst you could find a replacement driver for ~$2 that has a PWM option; drivers based on the PT4115 are pretty common.
1510  Using Arduino / Project Guidance / Re: Peltier-based dehumidifying cabinet on: December 27, 2012, 01:56:54 am
That FAQ and all of their technical specifications provide pretty much no detail as to thermal stress considerations, and if it were a big issue to be concerned about I would expect that they would list some specification as to the number of switching cycles it can handle. It also contradicts itself with its discussion of using mechanical relays by suggesting that the relay fails before the peltier junction does? After digging around with Google I'm not denying that PWM would be preferable, but I still can't find any decent numbers as to how much of a concern this is.

Stick with the K.I.S.S. principle. A peltier junction is ~$10, and if it does wind up failing too quickly then you can revisit how you're driving it. Drive it at a low voltage and tweak the voltage a bit until you get a reasonably low switching rate. You don't really need that much cooling; At 70F (room temperature) the dewpoint is only 50F for 50% humidity and that should be a much much lower power requirement than these devices are capable of.
1511  Using Arduino / Project Guidance / Re: Peltier-based dehumidifying cabinet on: December 26, 2012, 05:33:22 pm
So what you want to do is set the cold side of the peltier to the dewpoint so that you can collect the condensation and remove it from the cabinet.

You're going to attach some sort of aluminum plate/heat sink to each side of the peltier. The hot side will need a fan to turn on whenever the peltier is active. On the cold side you will also need a temperature probe of some type (e.g. LM35 or DS18B20) to measure the temperature of that side. Use the PID library to control the power on/off to the peltier (via relay or mosfet, preferably mosfet) to keep the dewpoint temperature of the cold side stable.

There's no PWM needed here, or putting it another way there's no reason why you'd need to switch the peltier on/off more than a couple times a second to keep a reasonably stable temperature.
1512  Using Arduino / Project Guidance / Re: Starting Materials on: December 26, 2012, 02:56:54 am
I would suggest first. They're inexpensive, ship quickly, and have a lot of good starter stuff.
1513  Using Arduino / Project Guidance / Re: PWM control of many LED's from arduino on: December 26, 2012, 02:54:36 am

Bulb #2 will take PWM fine because it's obviously using resistors for current control (low power LEDs; power input 5W but light output 2.5W). Bulb #1 and #3 are using high power LEDs and will have driver chips.

It shouldn't be possible to see flickering above 100Hz and at 60Hz any flickering should be barely noticeable (do you see flickering in a 20ma/5mm LED?). I still think your problem is just that you're making the driver angry.
1514  Using Arduino / Sensors / Re: E18-8MNK IR sensor connecting to Arduino on: December 25, 2012, 01:16:45 am
It's highly unlikely that these give an analog signal. Given no documentation, I would suggest:

Red: Connect to 5V
Black: Connect to GND
Yellow: Connect to any digital pin. The pin should show a change in state (high to low or low to high) when the beam is blocked.

Another example of these sensors:
1515  Using Arduino / Project Guidance / Re: PWM control of many LED's from arduino on: December 25, 2012, 01:05:46 am
If those bulbs have drivers in them you're probably making them angry by PWMing power to them. More detail as to exactly what bulb you're using and what is inside those bulbs would be warranted.

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