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46  Using Arduino / Motors, Mechanics, and Power / Re: Arduino Mega hanging on Solar Power on: August 22, 2014, 05:04:48 pm
Charge controllers usually have separate lugs for the battery connection only for purposes of "low voltage disconnect"; disconnecting the battery from the load to ensure the battery doesn't become excessively discharged. If you think that's a concern then I'd suggest connecting your circuit directly to the battery. You can always use a spare analog port on the Mega to monitor the battery voltage and stop your power-hungry activities when voltage is getting low.
47  Using Arduino / General Electronics / Re: HX711 - Power & Logic lines question on: August 22, 2014, 04:49:49 pm
Your DOUT line from the HX711 to the MCU would assumedly be at 5V levels and more than likely in violation of the limits on whatever MCU you have it connected to.  An AVR is VCC + 0.5V on any IO pin.

I don't see anywhere on the datasheet where resistors are on the data lines (DOUT, PD_SCK).
48  Using Arduino / Motors, Mechanics, and Power / Re: How Many amps does this transformer output? on: August 21, 2014, 05:52:52 pm
The label states it has "7.5VA" total output. That "VA" refers to volts * amps, so using the 12V output alone it's roughly (7.5VA / 12) .625 amps

Your transistor selection doesn't really depend on the output of the transformer, however, but rather the current consumption of the light or motor that the individual transistor will be switching power to.
49  Using Arduino / Project Guidance / Re: CNC Router equipment on: August 20, 2014, 02:18:27 pm
You use a CAD program (e.g. AutoCAD, FreeCAD) to create a model to cut on your CNC. You then use a CAM program (MeshCAM, PyCAM)  to convert that model into G-code -- a standard language for controlling the movements of a CNC machine. Then you use controller software (Mach3, LinuxCNC, or Arduino-based GRBL) to translate those G-code commands into signals sent to your stepper drivers / spindle control / etc.

When used with CNC the parallel port is just treated like a bunch of I/O pins. Yes, you could wire the step/dir pins on your stepper drivers directly to a parallel port cable if you were willing to accept the risk of accidental voltage spikes or miswiring blowing up your computer, but usually that wiring is done using some sort of parallel port breakout board that includes optical isolation and easy wire connections. There aren't any hard and fast rules that state what pin in the parallel cable controls what function of the CNC machine; this is always set in the controller software. Why the parallel port and not USB? Mostly legacy reasons; nobody has come up with any standards for a USB interface.

When you build your first CNC router I'd suggest starting with a mediocre design. Just use some cheap allthread for your leadscrews and tapped wood/plastic blocks for your leadscrew nuts. Stick with wood for your frame/gantry/etc. What you're going to learn from building this first, cheap machine is going to be extremely valuable when you start planning your second, expensive machine. What you don't want to do is build an expensive machine that doesn't perform well.
50  Using Arduino / General Electronics / Re: Some help with High Powered LEDs on: August 19, 2014, 12:15:11 pm
Your driver can be more than 2V output; it's the current that matters. You do want to use a source voltage and driver that matches the Vf of your LED as closely as possible however.

You need to be careful when selecting a driver that the driver is capable of PWM or "blinking" control. Switchmode LED drivers and most all AC mains-powered drivers will react poorly if you try to toggle power to them using a transistor or such. Make sure the driver you choose has either a PWM input or is otherwise described as dimmable.
51  Topics / Robotics / Re: Multiple Bluetooth/radio receivers on one Arduino? on: August 19, 2014, 11:57:46 am
Whether or not the IR would be filtered would depend on the camera.

Sounds like you should really just cough up the $300 for a Soloshot. I'm guessing that they're using GPS to track the target, and if so, it's not a good solution for indoors.
52  Topics / Robotics / Re: Multiple Bluetooth/radio receivers on one Arduino? on: August 19, 2014, 01:07:32 am
With Bluetooth modules or any commonly available RF modules this won't be possible. The signal strength data, when available, won't be accurate enough to do much of anything.

You can use an IR beacon and not deal with ambient light issues if you use IR receivers used for remote control (like your TV, etc.). The IR beacon on the person being followed would blink, for example, a 38KHz signal and the robot would have multiple IR receivers pointing in different directions (try TSSP4038 for the receiver). The IR receiver seeing the signal would indicate the relative direction of the beacon.
53  Using Arduino / Project Guidance / Re: cheap PCB printing services on: August 19, 2014, 12:52:37 am
My problem with seed is that they say it all has to be open source. That gives them a licence to just steal you work and produce a range of add on boards like they do.

Do you have a link to where they state that? I've ordered from Seeed in the past and don't recall any such statement.
54  Using Arduino / Sensors / Re: No constant IR lightbeam on: August 18, 2014, 02:59:08 pm
Common IR receivers are specifically designed to reject continuous signals -- that's what Mike is saying.

Link to a part that *will* accept a continuous signal:
55  Using Arduino / Project Guidance / Re: cheap PCB printing services on: August 18, 2014, 02:54:47 pm
I'm pretty sure Itead, Seeed, and Elecrow all use the same backend manufacturer.
56  Using Arduino / Project Guidance / Re: cheap PCB printing services on: August 16, 2014, 05:42:54 pm,, or will all give you excellent results for the price. Expect 3-4 weeks to receive your boards, however.
57  Using Arduino / Project Guidance / Re: Strain gauges on cantilever beam with amplifier circuit and microcontroller on: August 16, 2014, 05:25:36 pm
Try eBay for the HX711; comes on a breakout board for under $5. There are also a couple different Arduino libraries out there that you can use with it.
58  Using Arduino / Project Guidance / Re: Home automation PCB design idea. on: August 14, 2014, 08:30:59 pm
These CC1000 is a "dumb" transceiver; it has no standard like Bluetooth, WiFi, ZigBee... it's not anything. There's A LOT of effort to be done to make it send or receive any useful signal.
59  Using Arduino / Project Guidance / Re: Chick Incubator on: August 14, 2014, 08:16:25 pm
Coturnix quail, right? I raised bobwhite.

If you use an LED to illuminate the egg you can see if it's developing or not. It'll be obvious.
60  Topics / Robotics / Re: Recommendations Needed: Hardware Suppliers on: August 13, 2014, 10:54:39 pm has a lot of motors, bearings, etc. at very low prices. Look up Makerslide or Openrail for two nice styles of what you would refer to as scaffolding.
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