Hi
I have a small PCB used to control a 240VAC heater and motor.
There is a low voltage control circuit on the board including a micro-controller.
To produce the low voltage required, the following equipment is used.
1 x Hahn transformer 230V 50-60 Hz (BV EI 304 2086)
Sek 1: 9 V 1.05 VA
Sek 2: 9 V 1.05 VA
This is fed through a fairly standard surface mount rectifier and then on to a 5 Volt regulator.
On both the live and neutral lines from mains supply to the transformer, there is a 100 ohm surface mount 1206 resistor, these are what have raised a query.
I had never taken much notice of them until now as i need to update the saftey testing file and need approvals for all componets that are exposed to the mains. The rating of any resistor like this that i have looked at are all in DC....
Does anyone know why these resistors would be here on the AC input to a transformer. And do they need to be special resistors to use in an AC line?
Is it a strange set up or fairly standard?
Ive attached a picture of the arrangement on the circuit diagram for reference.
any help appreciated
justin
I have a small PCB used to control a 240VAC heater and motor.
There is a low voltage control circuit on the board including a micro-controller.
To produce the low voltage required, the following equipment is used.
1 x Hahn transformer 230V 50-60 Hz (BV EI 304 2086)
Sek 1: 9 V 1.05 VA
Sek 2: 9 V 1.05 VA
This is fed through a fairly standard surface mount rectifier and then on to a 5 Volt regulator.
On both the live and neutral lines from mains supply to the transformer, there is a 100 ohm surface mount 1206 resistor, these are what have raised a query.
I had never taken much notice of them until now as i need to update the saftey testing file and need approvals for all componets that are exposed to the mains. The rating of any resistor like this that i have looked at are all in DC....
Does anyone know why these resistors would be here on the AC input to a transformer. And do they need to be special resistors to use in an AC line?
Is it a strange set up or fairly standard?
Ive attached a picture of the arrangement on the circuit diagram for reference.
any help appreciated
justin