I am trying to make A 220 ac to 0-30 dc Using this schematic enter image description here

I connected it on the bread board three times but every time I get only a 1.25 V from the regulator but when I change my potentiometer nothing happens Here is the breadboard enter image description here

  • \$\begingroup\$ Are the two yellow jumpers in the lower right your AC input? From what I see on the breadboard, one isn't hooked to anything. Hard to tell exactly with so much hidden. What voltage do you have across C1? \$\endgroup\$ – R Drast Dec 10 '15 at 11:19
  • \$\begingroup\$ [" I get only a 1.25 v from the revelator "]. What is a "revelator" ? \$\endgroup\$ – K. Rmth Dec 10 '15 at 11:26
  • \$\begingroup\$ Get your multimeter out and start measuring all those voltages ! Check if all the pins of the LM317 have the correct voltages. My guess is that the ADJ pin has 0V which it should only be when the potmeter is at lowest value. \$\endgroup\$ – Bimpelrekkie Dec 10 '15 at 15:44
  • \$\begingroup\$ I can only see one connection to the potentiometer in the picture. \$\endgroup\$ – Simon B Dec 10 '15 at 18:35
  • \$\begingroup\$ The schematic is right. the only advice I can give you is to check the nets one by one. if it still didn't work. change the components. \$\endgroup\$ – AHB Dec 10 '15 at 20:05

The LM317 will give out 1.25 V when ADJ is connected to GND. Since you have this voltage that implies that somehow you have a permanent GND connection to ADJ.

Simon B may be on the right track. Both the green and white wires, which seem to be involved with the pot, are connected to negative. Check that you haven't connected the white wire to the black instead of the pot wiper. (If you disconnect the black wire from the pot the voltage out should increase.)


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