itsmoked
Electrical
- Feb 18, 2005
- 19,114
A regular problem in industrial controls is the range of voltages one must sense. Users may have 12Vdc, 24Vac, 120Vac, or 240Vac signals that need to be sensed.
Classically one uses two 1/2W resistors(240V), one in each leg feeding the input of an AC opto coupler. Then on the other other side of the coupler you have your micro looking at the level.
It's a pretty fine line to walk between 12V and 240V. It often results in a lot of power dissipation because the resistor values have to be low enough to work for the 12V and are cooking at the 240V level.
Does anyone have ideas for robust general sensing input?
Keith Cress
kcress -
Classically one uses two 1/2W resistors(240V), one in each leg feeding the input of an AC opto coupler. Then on the other other side of the coupler you have your micro looking at the level.
It's a pretty fine line to walk between 12V and 240V. It often results in a lot of power dissipation because the resistor values have to be low enough to work for the 12V and are cooking at the 240V level.
Does anyone have ideas for robust general sensing input?
Keith Cress
kcress -