Tag Archives: China

CNC board and USB microscope

While in China I picked up a USB microscope for $25 USD. It’s an “2MP HD microscope with 600x magnification” according to the box and has 6 LEDs around the camera. I plugged it in and it was found right away by Linux as a video4linux device and works with VLC and Cheese. It’s been sitting next to my computer for about 2 weeks since I got back from China and I’ve been itching for some reason to use it. Tonight I made a small board on my CNC to test some new footprints and I thought it would be the perfect time to use the microscope to check out the cuts made by the bit. Using Cheese I was able to get some good shots of the PCB traces. The pictures are only 640×480, so I’m not too sure where the 2MP claim comes from.

I used my gcode_03 ULP script for Eagle (from my older site) to export the PCB to G-code. When I started working with the CNC for PCB routing I was using a 0.8mm end mill carbide bit, however I’ve noticed I get pretty clean cuts with a 30 degree “V” etching bit run at the max speed of my manually controlled spindle (Yes I know I need to find out the RPMs of that thing). The cuts made by the CNC are impressively clean and without burs. Each cut goes down 0.16 inches and the feed rate is 300mm/minute. The footprint is SOIC-8, the pads are 1.27mm x 0.635mm and the traces are 20mil. The cut is close to 0.5mm. The microscope did show what looks like copper particles in the track which was interesting to see. I’ve made a bunch of breakout boards and switch boards without shorting issues so I don’t know if these particles are big enough to cause a problem. Here are some pictures of the board using the microscope.

microscope image of board compared to a dime microscope image of the board microscope image zoomed in on traces

microscope image of cnc cut - two traces microscope image of cnc corner cut microscope image of cnc particles microscope view of SOIC-8 chip on pad

Problems with cheap electronics on Ebay

I have an electric scooter project that has been on and off again for a while now, I get to it when I can when it’s not cooking or freezing in the garage.  The scooter runs on six 12V batteries for a total traction voltage of  60V, the lights/horn/blinkers/etc all run on 12v which requires a 60v to 12v DC/DC converter.  I found a cheap 72v to 12v converter on Ebay from a manufacturing company in China (similar to this one) and figured I would spend the $30 and see how it performed.  Well what I got in the mail wasn’t a DC/DC converter, but a 24v electric bicycle controller for a brushless DC motor.  The interesting thing is the mailing envelope had “Motor controller” on it and not “DC/DC converter”.  Here’s the new rule, you get what you pay for.  Because I’m sure sending a $30 unit back to China is going to be more trouble than it’s worth, I think I am going to keep the controller and maybe make an electric bike some day…if I can figure out the non-documented pin out of the thing!

Cheap electronics, wrong part sent from China