Hi,
I need to activate a 60W light bulb when touching a metal door. So, I designed a simple touch-switch ckt using a 555 chip. For the PS I used a HI-LINK AC to DC power module and for switching the AC line, a relay module as shown in the diagram below.
On my workbench all worked fine, but when I tested the project in the field by connecting the touch-wire to the metal door, the 555 chip burned out. At power on, the relay activates but doesn't turn off after the 30 programmed seconds. The door doesn't have any other wires going to it but it's bolded to ground.
I did notice, when I connected the touch-wire to the metal door, a tingling sensation on the door. Unfortunately, I didn't have a DVM with me to check the voltage on that door as I didn't expect problems but... if I had to guess the amount of AC voltage on door, I'd say between 15 to 30 VAC.
The question is, How could that be possible if the PS module lists as isolated?
TIA
I need to activate a 60W light bulb when touching a metal door. So, I designed a simple touch-switch ckt using a 555 chip. For the PS I used a HI-LINK AC to DC power module and for switching the AC line, a relay module as shown in the diagram below.
On my workbench all worked fine, but when I tested the project in the field by connecting the touch-wire to the metal door, the 555 chip burned out. At power on, the relay activates but doesn't turn off after the 30 programmed seconds. The door doesn't have any other wires going to it but it's bolded to ground.
I did notice, when I connected the touch-wire to the metal door, a tingling sensation on the door. Unfortunately, I didn't have a DVM with me to check the voltage on that door as I didn't expect problems but... if I had to guess the amount of AC voltage on door, I'd say between 15 to 30 VAC.
The question is, How could that be possible if the PS module lists as isolated?
TIA