Author Topic: Vacuum Fluorescent Display Driver  (Read 46483 times)

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Offline pqass

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Re: Vacuum Fluorescent Display Driver
« Reply #175 on: January 07, 2025, 06:50:37 pm »
Page 53 on the schematics show things like VFDSCLK, but the label changes to BVFDSCLK. On the front panel schematic it's shown again as VFDSCLK.

I've soldered the wires to the three pins (12, 16, and 18), but wanted to verify this is correct. Normally the "B" would indicate a different node, but I'm guessing this was done because they go through the series current limiting resistors and the two nodes can't have the same name.

It's just odd they revert to removing the "B" when it goes to the front panel board.

This should be fine.
I don't think you'll have an issue driving the extra inputs of the 1488 through the 1K resistors.
Schematics don't always make sense; can be contradictory.
 

Offline bostonmanTopic starter

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Re: Vacuum Fluorescent Display Driver
« Reply #176 on: January 08, 2025, 12:17:55 am »
Thanks.

Seemed odd to rename the node names, but, as you stated, schematics don't always make sense.

I agree and assumed the 1k resistors (1.92k on VFDSEN) won't affect anything. Just wanted to confirm I wasn't overlooking the nodes going elsewhere.

 

Offline bostonmanTopic starter

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Re: Vacuum Fluorescent Display Driver
« Reply #177 on: January 24, 2025, 03:17:36 am »
I began building the external display circuits on a perf board, however, I got annoyed at trying to run all the jumpers, so I made a PCB.

Attached is the schematic. It began as a simple circuit, but I didn't want to make two separate boards, and put everything on one board with the idea I'll only populate what is needed for each board.

Unfortunately I didn't create a good schematic because I used too many ports. I should have placed the connections next to the IC rather than separate the circuits with ports. Also, my pet peeve is placing too many circuits on a single page, and I did just that.

I'm uncertain whether I'll use all the "features" I placed on the board, but thought have LEDs would be cool, connectors for future troubleshooting, and a regulator should I need one rather than use the one on the Arduino.
 

Offline bostonmanTopic starter

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Re: Vacuum Fluorescent Display Driver
« Reply #178 on: Today at 12:36:16 am »
Thankfully this past weekend I made time to somewhat complete the external display.

The "transmitter" board (the SN75188 portion) is installed in a 3D printed box mounted to the inside side panel. All connections from the counter PCB go to this box, and then an eight wire twisted pair Ethernet cable goes from this box to the rear panel where I installed a connector.

The external "receiver" board (the SN75189 portion) is connected to the same type eight wire twisted pair Ethernet and plugs into the rear panel of the counter where I installed the connector. Due to not knowing whether this would work and location of the external display, I left this cable long, approximately 3' (1m).

This "receiver" board makes all the connections (currently a hacked wiring job) to the Arduino; and then from the Arduino to the display (also currently a hacked wiring job).

For the external display, I went with: HiLetgo HD44780 2004 LCD 20x4 2004A Character LCD Screen Display Module Blue Backlight with IIC/I2C Serial Interface Adapter

Things seem to work well except for two issues. The first is poor refresh rate on the external display. I increased the counter gate time to two and three seconds, and both still showed ghosting. It's quite poor quality and not exactly ideal for taking measurements. I thought this size display would be nice and why I went with it.

Any suggestions on a nice size display with a good refresh rate?

The other is the counter front panel displays fine, but the external display places an 'X' where any and all numerical digit 3s' go. Unless it's also missing something else that hasn't been displayed yet (or I overlooked) all numerical digits display fine except the number '3'.

Maybe I overlooked a connection or a wire broke, but would think a missing connection would have more than just a single number display wrong.
 


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