Brief Description: Oxygen System - Switching Controller - Part 3
I dug out my trusty Radio Shack breadboards and started designing some circuity to tie all of these functions together in a cohesive circuit that could be installed on a circuit board. The attached schematic details the final design. I utilized a NAND gate array to multiplex the toggle switch and HX discrete outputs and then fed this to an LM555 timer configured as a debounce circuit. From the LM555, the button press signal is fed to D-FlipFlop chip configured as a divide-by-two counter. This provides the "push-on/push-off" functionality required. The output of the D-FlipFlop is fed to two NPN transistors configured for switching to the output to ground. One of the transistors is connected to a 5 volt relay and in turn feeds the EDS O2D2 though a 1N4002 diode to drop the voltage to under 5 volts required by the internal circuitry of the that unit. The output from the same transistor is also used to drive the Annunciator on the Vertical Power VP-200 Display unit. The other transistor is used to drive the electronic valve on the oxygen tank directly. Finally, regulated 5 volts is provided to the system via a standard LM7805 linear 3-pin regulator.
High Resolution PDF of Complete Oxygen Switching Circuit Diagram
