I am trying to construct a latching circuit with a 1-2 minute shutdown delay so I can soft start/stop a 240V-5V power supply.
I am looking for a momentary push latching (on-off) circuit to switch the 240V supply that will work like this:
—Push once (irrespective of push duration) the circuit latches and switches the 240V supply to a 240V-5V power transformer.
—Push again (irrespective of push duration), the latching releases but the 240V supply continues running to the 240V-5V transformer for a set time (approximately 1.5 minutes) and then the 240V supply is disconnected.
I have previously used a latching circuit I found online http://www.electronics-lab.com/project/toggle-on-off-switch/ and have found a "Power off delay" thread here How can I add a power-off delay to this circuit.
Because my skill level is low I am thinking about combining the two circuits with the relay in the latching circuit replacing SW1 in one of the options provided by Olin Lathrop and EM Fields.
So my current plan is to simply use a rely to connect the seperate soft start and power off delay circuits. However I am wondering if there is a simpler way (I am sure there will be) to integrate the latching circuit into one of the Power off delay options? Or is there a better alternative?
Regards
Best Answer
Good news, I have hit it with a stick a lot, made some guesses, then some changes and have managed to get a result...
I couldn’t get the existing flipflop to work without the timer so I looked at some CD4013 on-off circuits online (and built one to make sure my components weren’t faulty). The result being I combined the flipflop I built with the circuit provided by Jonk. The timer circuit is the same, but the flipflop C2, D4 and R4 area is now a bit different and I have grounded pins 4 and 6 on the CD4013. LED 1 and R6 don’t have an impact on the operation; they are there so I can see when the flipflop switches.
When the circuit is off I am seeing the base of Q2 sitting at 11.27V (collector at 0.01V) and when the button is pushed the base drops to 10.95V (collector rises to 11.65V). The power supply is stable at 11.8V. In its off state (standby) the circuit appears to be consuming about 21mA including LED1 which is on when the circuit is in standby. When active it consumes 87mA which includes the relay and 2 LEDs indicating the relay has switched to the NO pins.
I am interested to hear if this circuit can be improved and/or if the Volts and mA I have recorded are good or could be better...
Thanks.
Edit; I have found the circuit switches on and switches the relay when the power is connected. The flipflop and timer delay work correctly after that. Is there a way to prevent the self starting with power on/the main power supply is connected?