Soft On/Off switch
Wonder how soft electronic switches function? Well here is one pretty simple way to do.
For one of our scientific labs we use a special cooler connected to a calorimeter. There were some issues with the software which controls the calorimeter and the cooler. In order to control the cooler independently I designed a very simple circuit which in principle can be used to control other electrical devices.
The circuit is basically build using the famous timer chip 555. The circuit diagram is show below. The operation of the circuit is quite simple, it works in the bistable mode and the output of the chip (ON or OFF state) can be controlled by how the reset and the trigger pin is momentarily connected to the ground (flip-flop mode of operation). The circuit is electrically isolated by employing a small relay, which determines the intracooler's or any electrical device state.
I enclosed the whole circuit in an elegant enclosure with two momentary switches and LEDs to indicate the mode of operation. The flywheel diode is a must to prevent the damage of timer chip from back emf produced by the relay RL1. Q1 can be any low power NPN transistor. I will be more than happy to share the PCB layout for hobby enthusiasts like me.
For one of our scientific labs we use a special cooler connected to a calorimeter. There were some issues with the software which controls the calorimeter and the cooler. In order to control the cooler independently I designed a very simple circuit which in principle can be used to control other electrical devices.
The circuit is basically build using the famous timer chip 555. The circuit diagram is show below. The operation of the circuit is quite simple, it works in the bistable mode and the output of the chip (ON or OFF state) can be controlled by how the reset and the trigger pin is momentarily connected to the ground (flip-flop mode of operation). The circuit is electrically isolated by employing a small relay, which determines the intracooler's or any electrical device state.
I enclosed the whole circuit in an elegant enclosure with two momentary switches and LEDs to indicate the mode of operation. The flywheel diode is a must to prevent the damage of timer chip from back emf produced by the relay RL1. Q1 can be any low power NPN transistor. I will be more than happy to share the PCB layout for hobby enthusiasts like me.
Proper care must be taken when handling the mains side of the relay.
