Member Since: January 26, 2007

Country: United States

  • When I was a kid I learned that a diode passed current in one direction but not in the other. So I was dumfounded when I was looking at the schematic of a frequency counter and saw two back to back diodes near the input going to ground. It looked to me like it was just shorting the input to ground whether the input was positive or negative. It was only years later that I learned about the voltage drop across a pn junction and realized that I had been looking at an input voltage limiter. The AHA moment was very satisfying.

  • Really? That is surprising. And confusing. And disappointing.

  • I opened up a Stanley FatMax a while back. I poked around on the connector between the main circuit board and the measurement head. Here is what I found starting with connector pin 1 as the one nearest the edge of the board….

    (1) - 4v power I think (2) - looks low (3) - low (4) - 3.4v 5.0 mhz after shot, 10mhz before shot (5) - 10mhz before shot, 5mhz after. AC coupled 200mv or so (6) - 50 uS low-going pulse on trigger (7) - looks like serial clock pulses - 24 pulses multiple times during measurement (8) - ground i think - connected to pin 3 (9) - looks like serial data pulses (10 - seven pulses, 12.5ms long at 50ms intervals (11) - looks like constant 1 volt (12) - 18 pulses 2.3ms long, about 4ms apart. missing pulse after pulse 2 (13) - 3.6v whenever power is on (14) - 3.36 v normally, but dips very slightly, apparently as the unit seeks distance (15) - powers up during measurement, powers down with slight decay after more or less ½ second (16) - gnd (17) - complicated - initial pulse from 1.7 up to 3.6, then series of 7 up down spikes (18) - even more complicated

    I didn’t have a logic analyzer at the time, so I didn’t go any further with it, but pins 7 and 9 look very promising to me.

  • Stopped by the Houston store on my way through town, just to support your retail effort. Nice display by the book section. Out of stock on a lot of stuff. Overspent my months hobby budget in one stop. Go Sparkfun!

No public wish lists :(