Saturday, November 7, 2015

Momentary Pulse for Latching Switches



We are making some great headway in being able to have the latching DPDT lighted rocker switches of the upper console able to generate a short momentary pulse for the random DTMF tone request of the Voice box using the LM555 timer chip and a few other components.

Here is a diagram showing how I have the switches wired up to the 555 timer circuit. this is really great because originally I thought I was going to need a separate circuit for each on on the rockers. by this method I can get away with once circuit for the upper console's latching switches and one circuit for the lower console's latching push buttons. I should mention that I change the value of R1 to a 200 K resistor and this allows me to flip the switches fairly quickly and still get the needed pulse for the DTMF request. Also for 10 switches R2 is being swapped for a 470 K Resistor. Not that 10 switches can be on at any given time as there are 5 DPDT rockers so only 5 devices can be on at any given time with this circuit so it should be fine I am told.