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Topic: i2c nixie tube interface problems (Read 468 times) previous topic - next topic

carbondudeoxide

hello i recently designed and built this circuit board:

and it used 3 PCF8574 port expander to control 6 74141 (Russian equivilants) thus controlling the nixie's themselves. after it was built and soldered together i am unable to get any digits to illuminate on tube and im wondering if it has something to do with the PCF8574 not being able to source enough current to operate the 74141 binary inputs.

thanks for the help in advance :)

carbondudeoxide

sorry schematic did not link :/
here you go:

Papa G

Are those 4 LEDs in parallel with no current limit resistor shown on the schematic actually there?

stoopkid

#3
Dec 24, 2012, 06:47 am Last Edit: Dec 24, 2012, 06:49 am by stoopkid Reason: 1
Yes, with no resistors those LEDs may be creating too much of a short so the 74141's aren't being powered properly.

Have to tried manually shorting the pins on the nixies to ground to see if they light? Or manually shorting one of the 74141 pins to 5v to see if 0 or 1 displays properly? Doing those two things should narrow down the problem. Just be careful, obviously.

carbondudeoxide

sorry i forgot to add the resistor into that schematic, there is one in the actual board, i have shorted the pins and the digits do light up. here is some extra info about the board:

in has a 12v power supply and this goes to the Vin and GND on an arduino uno with an Ethernet shield as well as the nixie tube voltage converter (12v to 155v)

the 5v supply comes from the 5v regulated supply on the arduino but there is also a 5v supply on the nixie tube voltage converter but that is not connected.

so far i have not shorted the pins on the 74141 to see if i can get a digit to come up but i will give it a go shortly.

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