Dollar Store Busts

After stopping by the local Harbor Freight today and finding myself un-enthused by the offerings, I poked my head into the adjacent dollar store to see if there were any interesting electronic items that would be interesting to take apart. I came away with three hopefuls: an electronics kitchen timer, a 4-function calculator, and an 1/8″ to cassette adapter.

IMG_0878
Dollar Store Spoils. Total Cost: $3, of course.

The first victim of the hobby knife and screwdriver was the kitchen timer. Unfortunately, it turned out to be the most interesting of the three items, having a whole four accessible components: a button cell battery, a piezo-electric element, an oscillator crystal (measured at be around 33 Khz) and a tiny SMD capacitor. (I’m not counting the LCD display.) All that, and a solder blob. Perhaps the piezo and crystal will be useful for something.

Next, the calculator. This one was even more inaccessible: one solder blobbed chip and a battery. Oh, and a tiny SMD cap as well. I assume this is a calculator on a chip.

Finally, the tape adapter. This one has no accessibly parts at all, just a direct connection to the magnetic tape head and a gearing arrangement to fool the tape drive into thinking all’s well.

IMG_0882.JPG

So much for dollar store teardowns. But hey, I got two button cells with clips, a piezo buzzer, a little crystal, and some good fun out of it.


In brighter news, I did pick up a nifty old Crescendo Systems RTC2000 for a couple bucks from FreeGeek today. It’s apparently an old component to RGB converter, but that doesn’t really matter: what I really want is the case. I think it’s a nice form factor for a little field radio – I figure I’ll punch through the rear panel and use that as the face plate, or maybe ask the folks down at the Harold Washington Maker Space to help cut a new faceplate.

Hear you on the Air.

73

Advertisements

Fried Green Arduinos

It was only a matter of time until something blew up. And last night, it was TWO things.

The first one was my own darn fault  – I’ve been playing around with some simple transistor amplifier circuits, and mis-read one of the transistor data sheets. When I hooked it up a 12V power source… BANG!

IMG_0064You can see the TO-220 package there, literally split in half by the power of electricity. Zam zam! Turned out I had grounded the emiter and applied 12V to the base of the transistor. It blew apart in my face in a shower of sparks.

So, I desoldered that transistor and replaced it with a little J110 FET I had a pile of from my last trip to California. While messing around with the supply voltage, I kept switching a clip lead back and forth between 5V coming out of the 5V rail on an arduino an 12V directly from and SLA battery. Unfortunately, at one point, I disconnected the clip from the circuit and ended up connecting the Arduino directly to 12V…

IMG_0069

You can’t make radios without breaking a few toys. Thankfully, the Si5351 breakout and the nice LCD screen I had hooked up were unscathed. Another sacrifice to the radio gods.

73

Update 2/29: I’ve toasted another one! I’ve been using my old Duemilanove to work on a transmitter project, and apparently relying on its little 5V regulator to power an LCD screen, an Si5351 breakout, and provide bias current to the finals was just too much for the little thing….