Saturday, February 14, 2015

Transistor Tester

I had ordered a Transistor Tester a while ago on eBay. I have been having trouble reading the markings on some of my diodes and capacitors so I was hoping to find a measurement tool for them. I was shocked to find that kits of the OSS Transistor Tester circuit run around $15 - seems like a no brainer to buy one and try it out. I finally built mine today and I love it.

This particular one can be found by searching ebay for M168 Transistor Tester. You get no instructions in the kit but you can search for Karl-Heinz Kubbeler transistor tester and get instructions there if you like. In short, you plug something in, press the reset button, get some nice info, and then the display will shut off in a couple seconds.

Friday, January 02, 2015

perf version of IR Repeater

Michael did the tedious work of laying out this version of the IR Repeater with VeeCAD on a perf board. I finally got this version built and am excited to be testing it out. Michael has also done the layout for a printed circuit board so I hope to send away for that while the perf board version gets exercised.

The picture above shows the perf board in use. Instead of a micro USB cable I'm using a standard USB B cable for power. The picture below shows the completed perf board version.

I made a lot of mistakes in building it so it took me quite a long time to get this done. Most of the mistakes were due to getting myself confused from flipping the board over differently than I was thinking and soldering things incorrectly. I'm lucky I didn't burn out anything soldering / desoldering over and over. I moved a few things around based on late component changes that I made: PR1 and JP2 are completely different shapes in this than in the original specs I provided. Those changes also caused me to make some mistakes.

This is the underside of the completed board including a major mistake. I had the ground hooked up incorrectly on the RJ45 header: pin 5 instead of pin 4 - oops. I didn't catch this one until I started testing. I didn't hurt anything - the LEDs were just always on so it was pretty easy to spot quickly. Below is the corrected version.

There is one other major mistake that I made that I couldn't correct with desoldering: I was mistaken about what pin 1 on RJ45 was so I have the RJ45 backwards. Pin 1, at least on this SF breakout, maps to brown rather than white-orange. I tried to desolder and flip the breakout from the header but I couldn't get it off. I didn't want to redo the header connections so I ended up making a temporary RJ45 cable that just had all the wires backwards on the one side.
It isn't ideal that I ran wires on both sides of the board but I found that easiest. I really appreciate Michael's work laying this out - its awesome to have a compact version running with near-final connectors and a layout closer to what will be on the printed circuit.