Hi guys,
I have designed a nixie clock using Russian 74141 equivalents. Im using the arduino to write 4 bit data to a Latch and then stobing the latch whenever I want the data to change. Sounds great in theory, but i'm having issues. My outputs all sit at roughly 1.5-2V. Ive checked my input voltage seems good, roughly 4.5V. Can anyone see any major issues with my design?
Thanks!!
NIXIE.pdf (112 KB)
What is the purpose of R9 and R5? I don't like your design for the 170 volt nixie driver. You are getting this voltage directly from the line voltage. Not a good idea. I bought a neat little Hv power supply from a guy on eBay for about 12 bucks. It works great. Search on eBay for Nixie power and you will find it.
Also, why are you wasting chip resources? You could use the 373 to drive both the units and tens digit.
What is the state of OE? It looks like the signal is tied to all the 373 chips. OE must be low to enable the outputs. If you bring it back high the outputs of the 373 chips will float to about 1.3 v. You could just ground this signal at the 373 chips and not even drive it from the processor.
Do you get any numerals on the nixies? Pull the 373 that drives the decoder for one of the digits. ground all four inputs to the decoder and you should light the Zero digit.
Do you have any code written? Now that I am in the middle of this response, what are you doing for your LE signal for your 373 chips. You will need one for each digit. I will look at the schematic again to see but right now I would bet that you only have one LE for all the 373's.
RWW
I see you do have a clock for each digit. Sorry for doubting you. Do you have access to an oscilloscope?
What do your power supplies measure?
RWW
Roger,
Thanks for your response. R9 and R5 were designed in before I had a driver IC to test with. I wasn’t sure if I needed 5V to the IC or +170V so I used two 0 Ohm resistors and I didn’t populate the 170V jumper.
I used one IC per to make it as easy as I could to program, I'm not the most advanced programmer and this would be easy for me to implement.
I have OE driven low to enable the output, one thing I may have not made clear is that my Arduino outputs are at 1.5-2V NOT the 373 outputs. I don’t understand how this is possible, the inputs to the 373 are high impedance and the output of the 328P is a push pull driver.
I have the most significant hours digit connected now for testing, no others. The nixie tube glows funkly (word?), no individual digit is lit up fully, just a big blurry mess.
Power supplies measure at +4.52V and +159ish. The reason I use one OE is so that I could possibly dim the signals in the future if I wanted to.
With the proper safeguards I should have no issue with my PSU, I wanted to use an isolation transformer, but I never got to it.
The interesting thing is that the program works perfectly off on the arduino board. I used some LEDS to check the bus and clock signal, works perfect.
Andrew
Is the 328 running on an Arduino board or is it running on a board of your design? If it is running on your design pwb what have you done to verify correct function of the 328? I have never tried to make an AVR run on a breadboard or a self designed pwb. I do know that the routing and de-coupling of the VCC & GND wires to the chip is critical. The clock design is also critical as far as placement and routing on the pwb is concerned.
Did you try my tip to ground the inputs of the nixie driver to see if you get the zero digit lit?
How are you programming the device? I would suggest a very simple sketch to blink an led that you could tie to one of the output pins. Then one to count 0 - 9 and send the output to one digit at a time.
Did you have your processor running on a breadboard?
RWW
Roger,
The 328 is on my PCB, ive done this numerous times in the past and have had no issues what so ever. (LAVe Unloading- Wentworth Institute of Technology - YouTube this has a 328 mounted to the PCB check out the PWM video.) I am decoupling VCC, not GND but again ive done this in the past.
I have not grounded the inputs, but i will later.
For the time being I am programming on the arduino board and transferring the IC over, when I get it running correctly il program on the PCB.
My current program has it running 0-9 with one second increments, with OE low. Ive tried strobing the clock line as well as holding it high. No luck.
I just dont understand the outputs being at 1.5V, seems like something is way wrong but I cant see it!
Thanks a lot!
Andrew
Have you tried running your program from the Arduino, jumpering the signals to your clock board? Should be easy to do if you can put yor hands on a dip-clip. You might want to try and drive just one of the 373's. One of your videos shows a scope in play. Can you still use it?
RWW
Yup, still have access to that scope, and a much better one. 
I'm going to mess around with it for a bit, real problem is that the 373's are SOIC's... But not a worry, ive been in worse situations.
I was looking at the PCB, when the 328P is not in its socket I get 2V's or so on the data bus. When I plug in the 328P bus voltage drops to roughly 1.7V.
I threw an ammeter on the input side, I figured out that im drawing 200mA on the 5V supply which is way more than I should be. I think this is a attributed to the 373 attempting to keep the bus high (which I dont understand how it would do that...) and the 328P is trying to drive it low.
I grounded all the inputs to the 74141 and I did get a "0" output, I was able to get a few digits out by changing the input bus value. So I know my nixie tube and driver are working.
I figure that my problem lies directly with the 373 latch, I removed them all one by one to see if one was bad. They all did the same thing and held the bus high. Am I correct in assuming that the output of the 328P is a push-pull?
Andrew
Sorry, I do not know what the output circuit is on a 328p. Did you measure the buss with the latches and the processor pulled? I would expect zero volts. if not then you need to find where that voltage is coming from.
RWW
Have you talked this problem over with your school buddies?
RWW
With the processor pulled I get about 2V on the bus, which is normal for LS (ttl) logic since they have internal pull ups.
Not in school anymore, had to jump into the real world, sigh... All kidding aside, love my job, they allow me to build wacky stuff like this all the time!
Thanks
Pretty sure I just figured out my problem, I forgot to connect the AVCC pin to5V... AVCC powers some/all of port C, makes sense!! All of my bus lines are on Port C.
I left the board at work, so I'll have to try on monday. It was frustrating, I rechecked my device pinouts numerous times and never found an issue. Hopefully this will fix the problems!
Thanks for your help!
Let's hope you found it.....
RWW
Did connecting that AVCC pin to 5 volts fix your problem?