Hi All. Just made these for the LED characteristics practical. Frequent problems with old ones which were just an LED and a resistor in series. If reverse connected the LED would sometimes POP and need replacing. As the voltage monitoring had to be done across the two components the resistor would swing the results. If we let them have access to the LED terminals there was the chance they would connect directly and cook up the LED. Here the LED is protected from reverse voltage by a 1N4007 reverse connected. The LED is connected by two 620R resistors so one can be used to monitor the volts directly across the LED. 620R compared to the 10meg of a DMM is negligible. I've used Toolstation 15A connectors that accept banana plugs well. This saves on buying sockets and of course keeps the profile low as the connectors are along the mounting plate, not through it. The base is laser cut acrylic from our DT dept and all is held in place with hot glue. No reason why MDF or even card might not be used if money is tight. I'm convinced that with zip ties and hot glue I could make a car.