Capturing Display Data

Capturing Display Data

What would (fill in name here) do!?

This has been a lingering problem I’ve been chipping away at for the past 4 years.  It’s the reason I choose to restudy electronics.  It all started when I purchased a watt meter for my ebike setup.  It displayed information about my battery voltage level, watts used, and amp hours used.

The watt meter has large guage pigtails to patch into the power source and load.  The problem was these wires were too large and ackward to run along my bike frame so I could mount the meter on the handlebars.  I had tried this one time before and the meter got wet, then malfunctioned.

Since then, I’ve learned how to take shift registers and send the data directly to a LCD using small guage data cables.  Having a readout is great, but I want to do more now.  I want a historical view of the enegry used and I can do this using a data logger.  I’ve used data loggers before with GPS and video data to create impressive details of that data.  Now I want to do the same with my power use.

Capturing the data that is meant to be displayed on a LCD, whether it be character or graphic is difficult to near impossible.  I had recently purchased another volt/amp meter with hopes of capturing the data from it.  Albeit was simpler, it uses 7 segment LEDs for output, I would still need to use a large amount of I/O’s or shift registers to do this.  The complexity of sniffing the data will require more effort.  The trade off isn’t worth it when compared to creating a system from scratch.

It’s interesting to look back and recall my intial ideas to the problem.  The inocence was enpowering becuase I wasn’t hindered by the awareness of what was possible.  There is wisdom in that realization.  Too often, season engineers will use logic and experience to excuse ideas that might lead to something new.  The chance outcome is never taken becuase the comfort of solid predictable results pacifies.  I’m not suggesting that anyone throw away what they know or rely on.  I just find it peculiar that we forget how we used to think.

With that all out of the way.  It’s clear that I will not want to spend the time and effort capturing data.  I’m simply going to create a new dedicated device to do this and use the old device to test, calibrate, and verify its operation.  The sensor that I’ve choosen is the INA219 High Side DC Current Sensor supplied by Adafruit.  I currently have a Volt/Amp meter that uses a shunt, but I’m considering using this Panel Volt Meter also supplied by Adafruit.

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