Help With Circuit,, Auto Dimmer, cant find one

Discussion in 'The Projects Forum' started by jgraham83, May 13, 2009.

  1. jgraham83

    Thread Starter New Member

    May 12, 2009
    :confused:Hi everybody, im new to the site. Im looking for a project for my final term of my electrical apprentiship. Im on the hunt for a lighting circuit that incorporates a variable brightness in relation to the surrounding ambient light. The light when switched in the on position would be at full brilliance in complete ambient darkness, half brillience at dusk or dawn situation and not come on or minimul output at full ambient brightness.

    For some reasons ive searched and searched and cant seem to find a decent circuit drawing that would work for my idea. Im assuming i need an LDR or multiple ones scrs and op amp but i dont know where to start. im in an Advanvced electronics class but my level is certainly not advanced. also id like to use a 12 volt dc auto tail lamp if i could. This project is just a plug and play proto bread board type.

    If any one has any suggestions or even better a working circuit diagram. id greatly appreciate it.

    Thanks in advance.

    Senior Member

    Jul 1, 2008
    I would recommend that you not use a backup light as your lamp. Using it will put additional current demands on your circuit. To demonstrate your circuit a small 12V panel lamp will suffice.
  3. jgraham83

    Thread Starter New Member

    May 12, 2009
    Would anyone have a diagram for a circuit like this?. I honestly dont know where to start.

    If not maybe some other project ideas,. it needs to be some sort of auto adjusting curcuit.
  4. SgtWookie


    Jul 17, 2007
    Why don't you look at using a 555 timer to build a PWM circuit where the control element is an LDR?

    Better use a transistor or MOSFET connected to the 555 timer's output to control current flow through the lamp.