Multiplexing with IV-18

What makes it possible for an amateur like me to take on a project like this is the overwhelming amount of support that comes from a worldwide community of developers, often without their knowledge. For example, the circuit design and firmware for the icetube clock are freely available to download and re-use under an open-source licence. The clock design is similar in some ways to my own. The schematics and code don’t have everything I’ll need in the final design, but I have learned a great deal and saved hours, days, maybe weeks worth of time in procurement and experimentation, and this gave me a great tutorial for developing my own design.

I was able to light up the IV-18 tube and have it display digits, without completely understanding how it all works. I guess this is the real beauty of open-source. You don’t have to know everything, you don’t have to do everything. You find something and build on it, and bring your own contribution.

For this prototype I am using an obsolete HV518P high-voltage driver IC, which takes signals from the microcontroller and outputs high-voltage directly to the display segments in the VFD tube. I chose this one mainly because it comes in a DIP package, so I can fit it into a breadboard.

The most difficult part of getting all this to work was wiring from the driver to the VFD tube. The schematics for the icetube were for the popular MAX6921 driver, which I will likely use in the final design, but the wiring for the HV518 seems to be a bit different – so I had to cross-reference the icetube schematic and the data sheet for the HV518 to know which pins went where, which didn’t seem to work so well. It can be a bit like a rubix cube – even if it’s off by just one bit, it can take hundreds of re-tries to get it all in order. In the end I got it working by sheer brute force and determination.



Category: Alarm Clock Project, Electronics Comments Off on Multiplexing with IV-18

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