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Author Topic: Cathode pin issue?  (Read 6856 times)
JS3
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« on: May 10, 2013, 10:16:42 AM »

Hey everyone!  I'm hoping for a little help, as I'm completely stuck.

I can't seem to get the ArudiNIX board working correctly.  I've tried many different sketches and wiring layouts, but no luck. 

I decided to strip down to basics to try to troubleshoot.  Here's what I know...

  • I am using a 9V, 650mA center-positive AC adapter.  It looks identical to the one sold on the site.
  • If I check voltage from the test point to ground, I get a nice steady 180V.
  • The chips seem to be working perfectly - they read 4.7V on the appropriate pins when I run a sketch that cycles through the numbers.

However, if I upload the following sketch (which just sends a zero to both outputs), I get some really weird readings on the cathode pins.

Code:
/*
  Blink
  Turns on an LED on for one second, then off for one second, repeatedly.
 
  This example code is in the public domain.
 */
 
 
 // SN74141 (1)
int ledPin_0_a = 2;               
int ledPin_0_b = 3;
int ledPin_0_c = 4;
int ledPin_0_d = 5;
// SN74141 (2)
int ledPin_1_a = 6;               
int ledPin_1_b = 7;
int ledPin_1_c = 8;
int ledPin_1_d = 9;

// anod pins
int ledPin_a_1 = 10;
int ledPin_a_2 = 11;
int ledPin_a_3 = 12;




void setup() {               
  pinMode(ledPin_0_a, OUTPUT);     
  pinMode(ledPin_0_b, OUTPUT);     
  pinMode(ledPin_0_c, OUTPUT);     
  pinMode(ledPin_0_d, OUTPUT);   
 
  pinMode(ledPin_1_a, OUTPUT);     
  pinMode(ledPin_1_b, OUTPUT);     
  pinMode(ledPin_1_c, OUTPUT);     
  pinMode(ledPin_1_d, OUTPUT);     
 
  pinMode(ledPin_a_1, OUTPUT);     
  pinMode(ledPin_a_2, OUTPUT);     
  pinMode(ledPin_a_3, OUTPUT);   
}

void loop() {
  for (int i=0;i<10;i++) {
    displaynum (0);
    delay (2000);
  }
}

void displaynum( int num ) {
  int a,b,c,d;
  // Load the a,b,c,d.. to send to the SN74141 IC (2)
  switch( num )
  {
    case 0: a=0;b=0;c=0;d=0;break;
    case 1: a=1;b=0;c=0;d=0;break;
    case 2: a=0;b=1;c=0;d=0;break;
    case 3: a=1;b=1;c=0;d=0;break;
    case 4: a=0;b=0;c=1;d=0;break;
    case 5: a=1;b=0;c=1;d=0;break;
    case 6: a=0;b=1;c=1;d=0;break;
    case 7: a=1;b=1;c=1;d=0;break;
    case 8: a=0;b=0;c=0;d=1;break;
    case 9: a=1;b=0;c=0;d=1;break;
  }
  digitalWrite(ledPin_0_d, d);
  digitalWrite(ledPin_0_c, c);
  digitalWrite(ledPin_0_b, b);
  digitalWrite(ledPin_0_a, a);
 
  // Write to output pins
  digitalWrite(ledPin_1_d, d);
  digitalWrite(ledPin_1_c, c);
  digitalWrite(ledPin_1_b, b);
  digitalWrite(ledPin_1_a, a);
 
  digitalWrite(ledPin_a_1, LOW);
  digitalWrite(ledPin_a_2, LOW);
  digitalWrite(ledPin_a_3, LOW);
 
}




If I connect my probe to a 10K resistor on A1 and the cathode pins (remember I'm sending a "0" to both tubes), I get:

Cath1Pin0: 58.1V
Cath1Pin1: 55.9V
Cath1Pin2: 59.0V
Cath1Pin3: 59.3V
Cath1Pin4: 0.0V
Cath1Pin5: 55.9V
Cath1Pin6: 60.3V
Cath1Pin7: 60.0V
Cath1Pin8: 60.6V
Cath1Pin9: 60.8V

Cath0Pin0: 71.8V
Cath0Pin1: 58.6V
Cath0Pin2: 63.2V
Cath0Pin3: 62.9V
Cath0Pin4: 75.0V
Cath0Pin5: 60.6V
Cath0Pin6: 56.4V
Cath0Pin7: 55.8V
Cath0Pin8: 75.1V
Cath0Pin9: 58.9V

I'm sure this can't be right....  Smiley
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Risen
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« Reply #1 on: May 16, 2013, 04:31:47 PM »

Actually, it's probably fine.

The tube driver chips leak current. "off" drops the flow enough to shut off nixies, but doesn't drop it to 0V. For my recent build, I tried to power small neon bulbs off them and was completely unable. I had to use a discrete transistor. My chips leaked at about 45V (but I run the Arduinix at 170V). As long as the "off" state is below the voltage needed to sustain nixies, I think the chip is considered to be working normally.

- Check the voltage out at the Arduino and see if the pins there are going as expected.
- Try turning one each of the anode and cathode pins on. Outputting a "0" is fine, but your code sets three anodes to LOW, effectively telling the arduinix to keep those off. However, I believe A1 is controlled by Arduino pin 13, which isn't being controlled in your code at all, and is probably floating. Be sure when you test that you know what all your cathodes AND anodes should be are doing.
- If those both look okay, hook up a test tube! I don't believe lower than expected voltage can hurt anything.

Good luck!
« Last Edit: May 16, 2013, 04:46:52 PM by Risen » Logged

JS3
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« Reply #2 on: May 18, 2013, 03:55:08 PM »

Thanks for your reply, Risen. 

Unfortunately, I'm not making any progress.  The Arudino's pins are AOK, and if I connect a tube, I get multiple digits firing at once.

I took the "1 Nixie Tube" code from the main site and modified it to fire a single digit.  I connected my probe and.....  I get odd, random voltages again, which would make sense given how a tube reacts when connected.
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JS3
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« Reply #3 on: June 05, 2013, 09:56:05 AM »

Well, I've made no progress.  It's disheartening, to say the least.  I was trying to get this clock done as a present for my partner, but it's now two months overdue and all I have to show for it is a mess of wires and bulbs.

Would someone who's got a working ArudiNIX out there take a few minutes and see if your pins read like mine do?
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nonentity
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« Reply #4 on: June 16, 2013, 02:36:00 PM »

Well, I've made no progress.  It's disheartening, to say the least.  I was trying to get this clock done as a present for my partner, but it's now two months overdue and all I have to show for it is a mess of wires and bulbs.

Would someone who's got a working ArudiNIX out there take a few minutes and see if your pins read like mine do?


It seems that you might have had your driver chips zapped by static.  I've seen one other case of that, and what happens is, they lose the ability to only send ONE signal, so they send multiple ones.  I can't tell from the pic, but are your driver chips soldered in, or socketed?
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JS3
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« Reply #5 on: July 02, 2013, 01:53:19 PM »

Neither.  This ArduiNIX was assembled by Bradley and the chips are simply placed, with the legs folded under.

I checked the voltages on the pins again (they were fine before) and now they do seem off. 

I'll order a new pair and see if that helps.

Thanks for your input, nonentity!
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JS3
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« Reply #6 on: July 27, 2013, 01:07:37 PM »

VICTORY!  I received and installed the new driver chips (along with their sockets - thanks Bradley) and I'm back in business!

Thank you so much guys.

Let's just say I'll be doing the rest of the work on a static bag.  Tongue
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