Log in

10 March 2010 @ 03:53 pm
So I bought some stuff from sparkfun, including a 1-wire temperature sensor, and a serial LCD to use with my Arduinos. That was pretty cool, although I thought I was getting an I2C LCD, and I thought 1-wire = I2C. But it turns out that I2C = 2-wire which is very much not the same. You see 1-wire needs two wires where 2-wire needs four. Got it?

I rigged those up and even added some LEDs to make sort of an electronic Galilean thermometer. That was pretty neat.

Then I decided to get fancyCollapse )

If I can get this to work, I'll try to add some relays so I can use this rig to do some gardening. I have some other plans too, like making a helio/lunar-tracker.

Wish me luck.
21 December 2009 @ 07:46 pm
I did some googling, and was disappointed at not quickly finding any joule thief designs that only turn on at night.

After some fiddling I came up with this modification of the previously mentioned design:

I bought the cheapest phototransistors I could find a Digikey. They are apparently only sensitive to infrared light. As a result, it took me a while to figure out if they were even working. Most of my lights are now CFL, or LED and apparently aren't very bright in the deep infrared. I had to go digging to find an old halogen light and was finally able to prove the part works. I guess we'll find out tomorrow if daylight really works effectively too.

More things to look forward to tomorrow and some doubts too behind the cut.Collapse )Today was supposed to be "robot Monday" but without good mating to the motors, it has turned into "make-ready-for-Tuesday Monday" instead.

[Update: The phototransistor does turn out the light, but not as hoped. It would seem that while I'm indirectly closing the "free path" to ground, I'm still using more current/power than is helpful. So rather than the power consumption nearly stopping until nightfall, I continue to pour energy right out of the battery and into space only none of it visible. I will now try to verify this new hypothesis. And if true, probably move the phototransistor to the base of the other transistor.]

[Update again: I have modified the circuit and the image, and tested the power consumption using this design, As hoped, with the phototransistor is activated the total current was 1.0 mA as opposed to 35 mA which it was pulling in the dark.]

[Update again again: I recently verified the previous modification. It was only drawing half as much current in the presence of light. And even then, I suspect that I'm using DC measurements to compare a DC value (in daylight) and an oscillating value. So presumably half is actually better than it seems. Still, it doesn't quite explain how quickly the two thieves died after that modification. But then, they were randomly selected dead batteries, it may just have been their time.]
17 December 2009 @ 11:10 am
So last night I tried out a new motor, a "SolarBotics Gear Motor 3". The most difficult bit was mechanically adapting it to the LEGO pieces. Eventually I got something pulled together, but it is far from perfect. Applying power to the motor, though, shows that it has more than enough torque for the job.

I still have to figure out if it will run OK off USB power. And to figure out now how to adapt that to the iSight in the form of a reasonable mount.

If I manage to get it half-working, I'll post some photos.
12 December 2009 @ 11:15 am
Finally I was able to get a Joule Thief working. I found this design:

which you will note does not include any sort of hand-wound transformer. It isn't that I oppose this sort of thing, but !@#%!#$ where do you find ferrite beads?

And some udpates on other projectsCollapse )

Onward and upward!
20 November 2009 @ 01:13 pm
One particularly annoying thing I've run into a few times with these DIY projects is exemplified by This 3D Camera Adapter Project.

Basically these projects are the equivalent of "Make this awesome x! It is Easy: Start with all the x parts and then put them together!" While never revealing where one gets the most critical parts.

In this example, I was unable after some searching to find anything like the beam-splitter (half-silvered mirror) in question online. Unless you count the mult-hundred-dollar laser accessories.

At the same time I've been totally thwarted in making a Joule Thief for lack of any way to specify or acquire the necessary toroidial ferrite beads.
16 October 2009 @ 01:09 pm
I'd seen a Joule Thief mentioned several times over at Make. But only just yesterday did I look into it.

Unfortunately the explanations of how it works didn't really help or satisfy me in any way.

It was only after digging through three levels of wikipedia articles that I started to get it.

First a little explanation: The Joule Thief is a simple device to turn otherwise dead batteries into a usable LED flashlight. It does so by scrounging up current deliver shorter pulses of electricity at a high enough voltage to make the LED work. [Most LEDs are not continuously illuminated anyway, but are pulsed quickly enough to seem like they are always on.]

Fear not this is not free energy of any sort. LEDs have a required voltage to light up, and a dead battery usually can't muster much voltage at all. However, they still trickle current at that meager voltage. So this device is how you make higher voltage lemons out of available current lemonade.

But how does it work? [This was what took me a while to really get.]Collapse )

Even if you don't have a dead battery, the usual AAA battery puts out ~1.5 V and the typical LED needs 2.5-4 V to illuminate. So you could use this design instead of stacking batteries. Apparently they use a similar strategy in the Prius.

As a bonus, I'd never before realized that I was not the only one to use water analogies to understand electricity. To my knowledge nobody ever mentioned or explained this to me. I wish they had.

[Update: I've tried three different inductor/transformers with absolutely no luck. Granted none of them have really looked anything like the two examples available on the internet. But still... sometimes I have to wonder.]
01 October 2009 @ 12:47 pm
So I've been going back to my roots over the past year and fiddling around with electronics again.

I'm still an idiot in many ways. [For example, I was completely turned off by the whole thing a few years ago because I'd chosen the wrong solder. It just would not melt and caused me to burn a bunch of very fancy ultrabright LEDs.] However, I still find these things endlessly fascinating. So I'm going to add topics like this to my blog as public content.

One of the topics that has been very eye opening has been an increasing appreciation of/for power.

This entry would've been much cooler if I'd posted it when I wrote the first draft, as the day after this comic came out.

Rather then spend too many words I made this table to try to illustrate what the different measures of electricity mean by comparing them to something we've all had experience with (I hope), water:

Electrical Unit

Water analogy

Volts (V)

Water Pressure

Amps (A)

Water Volume

Watts (W)

How much water going by at a given moment.

Kilowatt hours(kWh)

How much water is in the Pool after you've turned off the water.

This isn't perfect, but it can help you to understand that a line with a lot of pressure but not much capacity can fill a pool just as fast as a line with very low pressure but a lot of capacity.

In electrical terms, Watts = Volts * Amps, or Power = Voltage * Current.

Kilowatt hours (literally Power * time or Watts * Seconds / 1000) are important because that's what they bill you by. The addition of time is critical here. You can spend a lot more money on something using only a few Watts which stays on 24/7 than something very power hungry (like an espresso machine) which you only use for a few minutes a day.

Unfortunately getting a bill once a month without the sort of itemization you might expect from your phone company doesn't really help you understand where your money/power is going. And if you want to learn about how AC vs DC fits in, the two topics are actually related. But that's a separate post.
08 July 2009 @ 01:32 pm
I am not really a fan of Lindt chocolate. To me it has a starchy flat taste. But somehow or another I found myself with a touch of sea salt bar. And what a difference! That flat flavor was nowhere to be found.

[I'm sure this is where Someone (someone without high blood pressure) would try to point out that "everything is better with salt.]

Perhaps I should re-try the other Lindt chocolate kicking around only now adding a touch of salt.

PS: Despite signs to the contrary (and the news of the day) this blog has not been abandoned, but merely neglected.
13 March 2009 @ 05:34 pm
I suddenly got a vague whisper of a scent... the smell of vanilla frosting on a chocolate cupcake. Now I would kill to dip my finger a mixing bowl of the stuff.
Current Mood: sleepydrowsy
30 October 2008 @ 01:16 pm
I was at the food museum yesterday to get Someone cilantro and the fage and I couldn't help but noticing a special on Dagoba chocolate bars (2 for 4$). So I picked up a couple and last night I got to enjoy roseberry.

I love raspberry to begin with, and am fond of rose. So it was a special delight to enjoy them all at the same time. While not truly a hard-core chocolate experience, it was a delightful treat I felt I had to mention.
Current Mood: blahblah