Monday, August 17, 2009

Fun with LEDs and CNC machines

When my cousin Ian was here during the summer, he wanted to make something cool for a girl... It's amazing what boys will do for girls. He wanted to make something really cool and personalized. I, of course, saw this as the perfect opportunity to play with my CNC machine.

First, we used a super-tiny end mill (0.020 inches in diameter!) to engrave her name in a piece of acrylic.

Then we created a base from polyethylene. While it machines OK, it absolutely sucks to cut on the bandsaw (it just melts against the blade). It was so bad, I ended up using the mill to "cut" the piece from a larger block. Here, we've added an LED. This one is a green (because she likes green, of course) Avago 1W LED. We put one at each end facing towards the center where her name will go.
Here's a test of the unit. The green LEDs shine into the acrylic, and where it hits the engraving, it comes out the front. The picture is a little over-exposed. It looks way nicer in real life.We tucked all the wiring into the base and added a barrel plug in the back that hooks up to a miscellaneous DC "wall-wart" I had laying around. The barrel plug fit nicely into the hole we machined into the base, and there was a slot in the bottom for all of the wires and a resistor (to limit the current to the LEDs). The wires and resistor were kept securely in the base using H.G. technology (that's Hot Glue, for the unacronymned).

Thursday, August 6, 2009

Tards repeated on 2 meter amateur radio

Aaron has constructed a 2m receiver and we finished aligning it. Ollie duct-taped a dual band whip base station antenna to make it vertical and we connected it to a vhf/uhf duplexer. The UHF side was connected to a 448.500 MHz transmitter at about 1.5 Watts. The receiver was connected to the VHF side at 147.740. The units were linked with a small PIC microcontroller that Ollie helped me build during the long winter. This provides Morse code ID, tail, and tailbeep, as well as timeout functions. This is all the features you need for a ham repeater which allows you to be rebroadcast from a good vantage point. After a cranky solder joint on the transmitting crystal was identified, I did a road test with KB1FLG with my HT in the car. I was able to go 4.5 miles up route 12 before things got scratchy, not bad for an antenna laying the driveway. This could be the basis of a system that is remotely located and/or solar powered. (BTW, in case you care, the TX crystal was from a toy walkie talkie at 49.830 MHz, which x3 and x3 is 448.5)