need a voltage variable resistor

[meetbpk]

in a dimmer circuit there s 100 k variable resistor ... i am going to replace it with the voltage from the DAQ kit..can any one tell me which type of device can be used for that,
if optocoupler can be used specify the type..
the output from DAQ will be around 0-5v.
this s the circuit.
**broken link removed**

 

[betwixt]

FIRST AND FOREMOST - the circuit is connected directly to AC mains and is therefore potentially lethal to touch - make sure you respect that before going any further.

There are several ways to do what you want although most use a different method to fire the triac. In your case, you absolutely MUST isolate the control circuit (0 - 5V circuit) from the live supply. I suggest you look at using a LDR to replace the 100K resistor (one of the R1s !) and illuminate it with an LED. You can then vary the LED current to set the effective resistor value and the optical barrier will give good safety isolation.

Brian.

 

[FvM]

LDR is an option, but only a few LDR types are specified for > 350V as required with 230 V AC supply. Using an opto triac (e.g. MOC 3020) and a analog low voltage control circuit or a microcprocessor based phase angle control seems better suited.