Electronics

19th March
2011
written by Todd Harrison
This is Part 4. You may want to read (part1), (part2) & (part3) first.
I’m trying something new. This posting will be a video blog posting. All the content is in the video. I’m limited to 15 minute videos on YouTube so I had to split the content into two clips (1a & 1b).
It is be kind of a trouble shooting tutorial slash what am I trying next video. I will also post some photos and links as normal but let me know if you like the video format better. I know the camera and sound sucks but I have to use the equipment I have which is a 15 year old Sony digital 8 Handycam with built-in mic. Sad I know.
After the videos are some oscilloscope screen shots of some test points and what they mean.
(video)
(oscilloscope screen shots
Key:
yellow trace: ch1 (+ test point)
blue trace: ch2 (ground plane at rectifier)
red trace: (ch1 – ch2)
((This first screen shot is the signal across the bridge rectifier showing full rectification as the 152v peek-to-peek (20v to 172v) pulsing DC red trace. The math is displayed on the right for the red trace. I disconnected the bridge rectifier from the circuit so no filter caps are present to smooth out the dc pulses.))

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24th February
2011
written by Todd Harrison

This is Part 3.  You may want to read (part1) & (part2) first.

In this part I was going to probe the board to find where the signal was being lost for the controls. After mapping out all the connections and looking up the functionality of the ICs in the earlier postings I was confident I was going to track down the problem. I had the motor secured in my bench vise, the power supply and speed control board connected to the speed sensor feedback and mains 120v to a switch. When I turned on the 120v mains power I could smell something getting hot real fast. I had to work 30 second at a time and let the control board cool between tests. Something was not happy in the power supply! The heat was coming from a large 4watt 1.8K ohm resistor. I didn’t dare probe for more than 30 seconds because it was clearly getting too hot. But I pushed my luck too far (KA-BAM!).

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20th February
2011
written by Todd Harrison

I was helping HeatSync Labs with their amateur high altitude balloon launch back on August 27th 2010. I finally got time to post the photos and the video. It was a great launch and recovery.

We launched the balloon at 8:04am and recovered it at 10:18am. Here is a link to the GPS tracking data from the balloon.
This flight tracking data may not be available, sorry.

Everything survived the landing. We landed in some farmland just off a dirt road and the transmitter worked the whole time so it was an easy recovery.

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