Michael Silverman documenting innovation at work


Nixie Clock Update: Prototype


I wanted to give an updated on my nixie clock. I've been very busy with classes the last few months but I have had some time to work on the clock. I have created a prototype that will effectively test the majority of the circuit and all the microcontroller related functions.

I'm using a 7SEG display in place of the nixie tubes. This is because the nixie tubes do not fit in the protoboard easily. This substution still replicates the final design in implementation because all the displays are hooked up the same as the nixie tube. Each digit has a transistor connected to it's anode. The 74LS chip which drives the digits also has a BCD input, the same as the 74141. One of the ICs are comprised of NOT gates. I needed to flip the output of the 74LS driver to work correctly with the active low inputs of the 7SEG displays. The displays are hooked up all multiplexed and turned on individually in the same manner the nixie tubes will be.

You can also see the two pushbuttons which are used for setting functions. The MAX232 which is used to convert the RS-232 voltages to TTL level for the PIC. The clock OSC on the PIC is using the simple RC method as outlined in the datasheet. I wanted to get some testing done and have yet to determine which crystal/cap combo I will be using.

Also the programmer I am using is from a company called Cana Kit and functions the same as the PIC Kit 2. Here is the link on SparkFun, although I purchased it on eBay for cheaper. It is working great for programming and in-circuit debugging (ICD).

I am going to be sparse with the details but I am getting closer and closer to ordering a real prototype PCB and getting things started!

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