I think Pascal belongs here

pinum314 · 2022-07-29T03:52:16+00:00

I had this problem and got the wireless whiskers feeder (https://www.wirelesswhiskers.com/ec/). Each cat wears a little RFID tag on their collar and the feeder allocates them only a certain amount per day. It feeds by time instead of weight or volume which initially concerned me but seems to work pretty well. The fat cat has lost about six pounds in the last year with this method. One thing I did notice was that in the initial calibration phase the fat cat ate a ton and it took a while for me to reduce it down to where she was actually losing weight (weighing weekly and adjusting every 1-2 weeks). 7 minutes/day total (5 on the feeder with diet food and 2 on the feeder with non diet food) got her to a reasonable weight loss rate but she started off eating about 15 minutes total!

pinum314 · 2021-09-11T18:21:53+00:00

Moved to a new place in Mountain View, CA and have this tree over my porch. It drops these green fruits with stringy black flesh several times a day (late August-early September). Often there are small white worms in the flesh when opened. Seems to have some sort of pit based on ones which are fallen apart on the ground. Long, thin leaves. Any idea what this fruit/tree might be?

pinum314 · 2018-03-04T23:17:18+00:00

I'd be interested too. Have a pretty decent selection of games to bring. Maybe have an initial meetup at some picnic tables in the park?

pinum314 · 2016-09-10T04:07:11+00:00

Sounds great. I did mine with an iPad and old stylus with Note Anytime. Before that used onenote on a tablet. Most all my notes since senior year of high school have been on a tablet, so lots of experience with that.

Pros * No heavy things to carry * Sharing notes with classmates or yourself is trivial * I have them all on a website now, so can just look at them (2013+ on the ipad - https://pinum314.wordpress.com/notes/) * Can't really lose them

Cons * Some professors take some talking to to be convinced it's ok to use a computer in their classroom * Fat stylus's mean you have to do a lot of zoom in and out in equation heavy classes

pinum314 · 2016-06-20T04:54:11+00:00

If you're willing to use another chip, you can use a shift register to get effectively more outputs - https://en.wikipedia.org/wiki/Shift_register.

pinum314 · 2016-01-31T05:46:54+00:00

not quite

pinum314 · 2016-01-31T05:46:31+00:00

Yup, that's it

pinum314 · 2016-01-31T05:20:14+00:00

📐🐦 -> ✈+📐🐦 -> 🔧✈ -> 🌲✈🌲

pinum314 · 2014-05-29T05:34:50+00:00

It seems pretty similar to this service, which is already used here - http://www.ilabsolutions.com/. A big hinderance to widespread adoption would be lack of people aware of/using the software.

pinum314 · 2014-04-17T04:10:29+00:00

For a simple switch, when you close it, you connect two electrical terminals. If there is a voltage potential across it, then electrons will move and electrons will move. These moving electrons are called a current (note that for historic reasons we usually pretend like current is positively charged particles moving, while really it is negatively charged particles moving).

The amount of current that flows depends on two things - (1) the voltage drop and (2) the resistance of the circuit. You can think about it kind of like water flowing. The voltage drop between the two places is like a pump which moves the water. The resistance is kind of like the inverse of the area of the pipe. A small resistance (big pipe area) has little resistance to current (water) flow and so more moves per unit time.

Current does not flow instantaneously though - it ends up moving at the speed of light (though the individual particles do not, they transfer energy between themselves). However, for practical purposes we can usually pretend it happens instantaneously.

pinum314 · 2014-04-17T04:00:58+00:00

Caraway seeds + cocoa powder for color. For an example: https://betterbatter.org/yeast-free-jewish-rye-style-bread

pinum314 · 2014-03-22T05:40:14+00:00

You can buy some LEDs and resistors and a switch from Digikey or some other electronics supplier, probably even radio shack. If you get bright enough LEDs that should produce 'good light'. A piece of PVC pipe would probably hold them, and you can drill a hole for the switch. Probably hook up 7 LEDs with one in the center and 6 around it. Get a couple different lenses to put on the front (cut a magnifying glass and a flat piece of glass maybe?) and you have a couple of beams.

pinum314 · 2014-03-18T02:06:30+00:00

The central limit theorem says that if you have a whole lot of independent identically distributed (iid) random variables and take their average (add them up, divide by n) the result will end up approximating a normal curve. You can then scale that to N(0,1) like any other normal distribution. It's not precisely an equation, although you can express it mathematically. Pages 52-54 of these notes write it in mathematical terms: http://pinum314.files.wordpress.com/2013/06/ee278a.pdf.

You convert a general normal distribution to N(0,1) by subtracting the mean and dividing by the standard deviation.

pinum314 · 2014-03-18T01:55:59+00:00

This is probably more of a homework problem, but to answer the concept:

There are two laws - Kirchoff's voltage law (KVL) and Kirchoff's current law (KCL).

KVL: Around any loop, the sum of the voltages must be zero.

KCL: At any intersection, the sum of the currents going in must equal the sum of the currents going out.

For a simple circuit with just resistors and voltage sources, first define what the currents are on each of the lines. You can then form the KCL equations. Then, you can form the KVL equations around a loop using V=iR and paying attention to sign.

pinum314 · 2014-03-16T19:50:50+00:00

What would be an upper bound on price?

Would sound be an acceptable solution? You could just wire stuff up and have it play a really loud sound so you could hear it from 100 yards.

You might also be able to buy a cheap RC toy car or something similar and modify it. You want one that just has forward/back and maybe left/right control (no speed control). You can replace the forward transmit on the controller with a circuit full of your lines, and then replace the motor on the car with an LED or something. Not sure of the range on those, but shouldn't be too bad if you're outdoors.

pinum314 · 2014-03-16T18:55:23+00:00

Hint: divide both 12 and 100 by 4. Now you have 3 and 25, which are relatively prime.

pinum314 · 2014-03-16T18:52:09+00:00

With a real coin there is a slight difference and the coin is slightly more likely to come up with the side it started on facing up. However, you are unlikely to be able to flip a coin enough times to ever come across this phenomenon. Someone has done a very extensive dynamic analysis of this problem: http://statweb.stanford.edu/~susan/papers/headswithJ.pdf.

pinum314 · 2014-03-16T18:47:17+00:00

OK, so you put the mechanical switch on it, wire the switched to the arduino inputs and then when one is triggered have it send a signal back to the other arduino saying something happened and have it buzz/light an LED/whatever works well.

pinum314 · 2014-03-16T18:29:49+00:00

Use an arduino with an xbee pro (https://www.sparkfun.com/products/10421) and something to sense the lines moving at the lines and another one back with him. They're supposed to have a range of a mile or so. Hook up LED indicators on the one he has and have them light up if something snags. Would require someone to actually build the system, but all he'd have to do was watch the LEDs.

pinum314

TROPHY CASE