V0.90 schematic uploaded

[phil-barrett]

V0.90 has been built and tested. I am very happy with the results.

It works across a range of 4.5 to 28V. Current draw is 8.6 mA with the LED on, well within predictions. Temperature rise above ambient is 10C at 28V, also within predictions. Tested for 24 hrs.

Also, at 5V input voltage, the output voltage of the regulator is 3.8V on the boards I tested. I also tested it 4.5V input and got 3.3V. This is sufficient to run the 74LVC3G14 so the probe can work with 5V, 12V and 24V systems.

Note that the output is NPN, pulled high. This will work with "pull to gnd" or logic level input. Compatible with opto-isolator input. PNP output is possible. If there is sufficient interest, I will create a design. Might need someone to run with it from there.