Ax Man Clock


Ax Man surplus in Minneapolis is a magical place.  They have tons and tons of electronic and industrial surplus, plus a bunch of just general weird crap.  It helps that the place is packed with the bizarre inventions of the owners and employees (robotic mannequins with mismatched limbs, motion sensing babies that cry when you walk by with a chilling robotic scream, etc.).

Last time I was up there, I found a board with a bunch of seven-segment displays, a chip, and a 6-pin connector.  I thought the chip might be an LED driver I could look up, so I took a $2 bet and bought it, figuring I might be able to reverse engineer it.

The chip turned out to be a common LED driver, the MAX7221.  I applied the circuit tracing technique I described earlier, and found that the connector easily mapped to power, ground, and signalling for the chip.  So I made a clock out of it.  Also, I spotted why the board was sent to surplus:

IMG_0396 typo

What a waste for Tactile Systems Technology…a whole run of boards fully populated, thrown out because of a silk screen typo :-).  That company is still around — they make medical gear, so I guess the thought of a life saving device with a typo was a non-starter.

Build directions after the break.  Continue reading

E-tweezers: a $6 way to make multimetering easier


A while ago, I read a post about “Smart Tweezers” on Hack a Day, as well as a DIY version as well. These are good designs to measure components without trying to hold two probes and the component at the same time.  These designs are overkill (and overpriced) for what I do, though…I don’t need a whole meter built into my tweezers.

That inspired me to build this cheap hack: E-tweezers.  Basically, I just made the tips of some plastic tweezers conductive, and wired them down to some alligator clips to hook to my multimeter:


Build directions are after the break.

Continue reading