Visa gift card (credit card)

I recently participated in a usability study and was given a Visa gift card to thank me for my time. Unfortunately, the gift card is not as easy to use as cash or a check, but I found a good way to handle it.

The gift card cannot be used at an ATM or bank to get cash. If you try to charge more than the card's balance at a merchant, the entire transaction will be denied. A merchant cannot check the card's balance. So, if someone receives a Visa gift card, uses it a few times, then wants to use all of the remaining balance, he or she has to check the balance by calling an 800 number or going to a website, then go to a merchant and say "Please charge eg $23.14 to my gift card and I'll pay the remainder with another credit card." If the amount charged to the gift card is even 1 cent over the balance, the transaction will be denied. Also, the card's balance will deduct by $2 every month ("maintenance" fee), so you'd better check your balance on the exact day you plan to use it. I guess this fee only applies 13 months after the card was purchased, so not quite as brutal, but the card's value simply disappears after 2 years.

As you can see, Visa must be making a lot of money on unused balance, maintenance fees, and the $5.95 that the gift card's purchaser spent just to burden you with this pseudo money. Here's how to beat the system: Pay your utility bill with the gift card. As soon as you get the gift card, use it to pay the card's full value into your phone, cable, etc account. The utility company will just credit your account, and lower the amount due for the next month or two. This way, you can use the full amount of the card without ever checking balances or worrying about fees. Now spend your utility bill money on something fun.

Comcast internet

Comcast cable internet is cheaper and much faster than AT&T DSL in the SF Bay Area. Here's the comparison:


AT&T DSL. $33/month plus basic phone line charges of about $12/month. 2.5 Mbit down / 0.42 Mbit up.


Comcast Internet 15/3 plan: $19.99/month (even for new customers who are not buying TV or phone). 17 Mbit (average 15 ) down, 5 Mbit up.


Here's what I learned:

Do not call Comcast's phone number. Instead, use their online chat feature. It seems the people in the call center are unable or less willing to make a deal than the chat room people.

Each CSR (rep) acts as his or her own negotiator. They all have different quotas and desire/ability to make deals. Start a chat session and just ask for current promos. If nothing sounds good, refuse politely and try again in a few minutes/hours/days. Different reps will offer different deals.

In one chat session, I mentioned that I currently had AT&T DSL. A few minutes later, the Comcast rep offered me cable internet for $33/month. What a coincidence! That's exactly what I was already paying for DSL. The reps have more information than I thought. The rep would not go lower than $33/month and I eventually refused.

Buy your own cable modem. eg http://homestore.cisco.com/viewproduct.htm?productId=54377589
For $30 or less, you can beat the $5/month rental pretty fast.



The "internet-only" service apparently comes with some basic cable TV channels:

I do not want cable TV service (even for free), but I brought in my shop monitor from the garage to test if cable TV was indeed available. It appears so. The Comcast tech did not install any sort of filter between my house and the poll. I flipped through it, and it appeared to be all working. The only thing that caught my eye was an old Star Trek The Next Generation episode. I will return the TV to the garage and not even worry about "stealing" cable TV.



Here's a photo of a device that the Comcast tech called a "trap." It's not a trap in the electrical sense. It's more of a mechanical security device.

The tech left it on the ground after completing my installation, so I decided to cut it open to see its internals.

If this were a 1/4" left-handed drill bit, it might grab the inner piece of metal enough to turn it counter-clockwise.

Remote focus control for telescope (remote follow focus)

The chips in the control circuit are:

Avago HCTL-2032-SC quadrature decoder
E-lab EDE1200 stepper control
Generic 558 timer for simple oscillator








Hi-res version


Moon at f/6.3 1/320 at ISO100. The lens is approx 1260mm (telescope with focal reducer).



Composite shot of Jupiter with its moons.

Terrestrial photography with a telescope and DSLR

I setup my 8" Celstron Nexstar with f/6.3 focal reducer and Lumix GH1 to try out some "terrestrial" photography. I picked a public road in Redwood City, CA that has a good view and easy parking nearby. As far as I know this is a public sidewalk here.

Here is a shot with the GH1's stock lens at 14mm. The red squares indicate areas that I will image with the telescope.

Here's the stock lens zoomed all the way out to 140mm. This area is centered on the left red box in the first image.

This image was taken through the telescope and f/6.3 redcuer, so it is effectively 1260mm f/6.3.


This image was taken through the telescope at prime focus 2000mm f/10. Note that with the GH1 crop factor, the field of view here is comparable to 4000mm in standard 35mm SLR terms. Most of the blurriness is coming from air currents and haze. I will try again on a cool, overcast day, and I would expect better resolution. I am also eagerly awaiting my telescope remote-focus project to be completed. It's extremely difficult to achieve perfect focus while touching the telescope's focus knob, so it's possible this photo was taken slightly out of focus.



The distance is about 2.4 miles.



Here is a cluster of antenna across the Bay.

22 miles.

Here's another post of photos that I took many years ago with the same telescope and a Nikon 35mm film camera.
http://benkrasnow.blogspot.com/2009/09/telescope-magnification.html

I forgot that I even had an eyepiece projection adapter. I'll try it out next time, but I suspect the limiting factor will be air clarity not the telescope optics.

Web-controlled watering can and vortex tube

UPDATE: Code added at the bottom of this post.


This is an interactive art project that I have been building for an upcoming exhibition. The idea for a web-controlled watering can come from the first "iphone watering can" that I helped build with a friend for Maker Faire a couple years ago. Search the internet/youtube for "iphone watering can" for details.





This new version uses a different drive mechanism and a PD control loop to make the watering can track the desired position in realtime. The interface works with any webkit browser. My collaborator and I have discussed using the iphone or android accelerometers to achieve control through phone tilting. I'm not sure if the tilt data is available to the web browser, though, and we are trying to make the interface run on as many platforms as possible. Any ideas?

The siteplayer webserver is extremely old technology and has many problems, but does work. I would explore using a hacked WRT router in the future for similar projects.






HTML file from Siteplayer webserver:
http://www.magconcept.com/watering/can.htm.txt

SPI file from Siteplayer webserver (simply to establish a server response):
http://www.magconcept.com/watering/serial.spi

Arduino code to get serial data from webserver and effect the PID control loop
http://www.magconcept.com/watering/watering_can.pde