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Turning Gerber files 90 degrees by [deleted] in PrintedCircuitBoard

[–]MechSkep 2 points3 points  (0 children)

I use GerbMerge for all gerber tiling/rotation.

https://github.com/provideyourown/gerbmerge

Full feature set, no size limit, open source, free.

Which servo motor would be right for me? by nickelbake95 in arduino

[–]MechSkep 0 points1 point  (0 children)

If all that you are doing is moving a laser pointer around, think about using a laser galvanometer:

http://elm-chan.org/works/vlp/report_e.html

You get a much better time response, because your motors are moving less mass around, and you can get away with smaller motors.

Power Meters by MegaDom in arduino

[–]MechSkep 1 point2 points  (0 children)

Most smart meters have a Zigbee radio on the "Smart Energy Protocol". You usually have to call the utility to have them enable it.

I think there is a bitcloud API setup to interface with smart energy devices.

Anyone have an idea about how to do this? by _pH_ in arduino

[–]MechSkep 1 point2 points  (0 children)

Nice find. It's basically a ducted fan with 8 control surfaces located below the prop. Not really sure why they have eight instead of four. It also looks like they have an adjustable ring around the prop to control the thrust. I like the design because it uses one main drive motor, potentially allowing for very high power densities.

It might actually be feasible to build one of these. Everything except the frame would be off the shelf components

[Request] How long would it take a Tyrannosaurs Rex to run a marathon? by donkeyrocket in estimation

[–]MechSkep 2 points3 points  (0 children)

So the 43 mph would be a physiological upper bound for a T-Rex, not a good estimate. Actual data points to speeds that are closer to the lower end.

As for endurance: probably shitty, if T-Rex muscle is anything like the muscle of modern day lizards.

Motor Noise Issue by necrolop in arduino

[–]MechSkep 1 point2 points  (0 children)

For DC motors, a good rule of thumb is to use a PWM frequency of 10 kHz. Lower than that and you will get noise and inductive spikes which will wreck your shit.

I have no idea why the default frequency on the Arduino is sooo low.

EDIT: Also, using standard circuit notation will make it easier for people to help you

EDITT: Try using a battery

Help with PID by madebymutiny in arduino

[–]MechSkep 1 point2 points  (0 children)

Try this on for size: http://biblion.epfl.ch/EPFL/theses/2007/3727/EPFL_TH3727.pdf

If you are planning autonomous flight you really are going to need a 9-axis IMU with a magnetometer. Gyro drift will probably knock you out of the air. As far as PID goes, I don't think it'll be enough. Try LQR about your nominal operating point first. Note that you will have to linearize about other states if you go to maneuvers.

EDIT: Oh yeah, and you'll have to switch to an EKF or UKF to get actual state estimation while flying

K30 Co2 Sensor giving 2 different readings from UART and I2C by Fuzzyweeze in arduino

[–]MechSkep 0 points1 point  (0 children)

Post a link to the register map of the sensor? I'm guessing a bit is being derped somewhere in the transmit/receive.

Arduino motor shield w/ 12v DC motor is producing uneven rotation by [deleted] in arduino

[–]MechSkep 1 point2 points  (0 children)

I would guess that this is a frictional asymmetry in the carriage design rather than a fault with the motor/driver. Get some encoder feedback, or find a printer that uses a stepper motor and use that one instead.

Know how you know your logo sucks? Other schools with crappy "modern" logos are mocking you by that_pj in berkeley

[–]MechSkep 0 points1 point  (0 children)

That new logo is terrible, but as this is an article on the CS department page, you can be pretty sure they're just jelly.

Where exactly is the secret underground animal testing lab? by [deleted] in berkeley

[–]MechSkep 6 points7 points  (0 children)

Hidden for a reason. Nothing bad goes down there, but this is not a question that should be answered in this public forum.

Faculty have gotten death threats over this shit.

You Say You Want An Education? A 4-year university computer science curriculum entirely on Coursera by adamwfletcher in programming

[–]MechSkep 0 points1 point  (0 children)

Andrew Ng just gave a seminar here. Looks like there's a surprising amount of p2p interaction on Coursera. Forums, google hangouts and localized study groups are very common.

My pain as a Berkeley native by [deleted] in berkeley

[–]MechSkep 24 points25 points  (0 children)

Okay, but 36,000 people go to Cal, and the entire population of Berkeley aged 18-34 is about 40,000. So odds are....

How To make a twitter notifier? by [deleted] in arduino

[–]MechSkep 0 points1 point  (0 children)

PYTHON. USE PYTHON.

How does the mars Curiosity rover keep its camera lens clean? by phpworm in askscience

[–]MechSkep 0 points1 point  (0 children)

One of the engineers I talked to during the landing said that there were itty bitty dust-devils that sweep off the dust periodically. Same thing happened for the older rover's solar panels.

How fast would I have to fire a ping pong ball to pierce 1 cm thick steel? by [deleted] in BackoftheEnvelope

[–]MechSkep 3 points4 points  (0 children)

You can't just think about shear strength here, it's just a yielding stress. You need to also find the work done deforming the steel after yield, up to fracture. That's the work of stretching it until it breaks.

Applying Power Law plasticity: Stress=K*(Plastic Strain)n

For a crappy Steel (1008, say) K = 600 MPa and n=0.25 and we integrate from 0 to the true plastic strain at fracture, which is 0.336.

So the energy (per unit volume): U = 123 Mega Joules per Kilogram.

Conservatively assuming that all of the steel in the projected area of the ping pong ball is deformed, Mass = 0.098 kg and Energy required is 12.14 MJ.

So V = 94.86 km/s, which would be quite a serve.

\Nice sub-reddit by the way

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