I wonder if any one can help me, I have tried several different configurations and I can't get it. What I want is that when darkness comes the LEDs should glow less according to darkness (but not fully off) and when sun rise then it will rise according to the daylight.

enter image description here

enter image description here

In the schematic is an jumper for the LEDs (display 12v isolator) here I will have an LDR that do what I meant above. Any one that can provide me with a schematic so I can make the project clear.

Thanks in advance.

  • \$\begingroup\$ If you can provide the whole of that very tightly cropped schematic someone here might be able to help. \$\endgroup\$
    – stefandz
    May 25, 2016 at 9:43
  • \$\begingroup\$ I send the schematic \$\endgroup\$
    – Lenny
    May 26, 2016 at 14:31
  • \$\begingroup\$ Are you having issues with making an ambient light sensor, or with the dimming of the display? \$\endgroup\$
    – W5VO
    May 26, 2016 at 15:58

1 Answer 1


enter image description here[![enter image description here][2]][2] Many years ago I build a circuit to do just what your doing. It controlled the brightness of a LED digital dash I built for my 37 Chevy. After looking at the schematic it looks as though 4 PNP transistor have their emitters tied to the 12 volt source. SK4 to SK10 I used a photo opto device with buffer to drive a 2n3055 transistor base. 12 volts on the collector and the emitter as the source.
I had to install a very large capacitor at the emitter of the 2n3055 to keep the brightness constant. flickering(1000uf to 5000uf capacitor) Since I no longer have exact valves you will have to design this yourself. The 4 PNP transistor emitters will have to be removed directly from the 12V source and attached to the new emitter source. Worked very well. Bright during the day auto dimming at night. In order to get maximum 12 volts from the 2n3055 emitter. I had to over drive the base through a series resistor, with near as possible 12 volts on the base. 2n3055 15 A, 60 V NPN Bipolar Power Transistor TO3 Case.


This site is temporarily in read-only mode and not accepting new answers.

Not the answer you're looking for? Browse other questions tagged .