|7441 / 74141 nixie driver tester|
Schematic - Hand wired proto
This tester is essentially a 12 channel A/D with logic setting and power control for the unit under test (UUT). The Vcc of the UUT is supplied by a pair of GPIOs to provide a 50mA current limit in case the part is dead. A high voltage bias is switched on during testing to measure both the active low current handling of active outputs as well as the leakage current of inactive outputs. Data is collected and sent to a PC for processing and Pass/Fail determination which allows the identification patterns as well as device family specific test parameters to be soft coded and stored in a plain text file that can be updated as new devices are encountered. Test time was about 2 seconds per unit including handling.
The links to the left are the output screens of the 7441 tester GUI in the
Calculators program. When the button on the box is pressed, both
the red and green LEDs are lit and a "Test-me" command is sent to the
connected PC. For each possible input state of 0000 to 1111 the
following data are collected:
After all 150 pin combinations are measured, the logic high (1) or low (0) for each state is determined from the selected parameter set. Any pin that is in between a valid logic high or logic low is grayed out and given an "X" in the pattern window. The resulting pattern of 1's and 0's (Any "X" is an automatic "Fail") is then compared against known device patterns and if a match is found then the red LED is turned off indicating a "Pass" or else the green LED is turned off indicating a "Fail".
Any questions or comments?
This page last updated on June 08, 2009