Can anyone help me with the attached schematic, I don't really understand were the line of " VREF" connects to , maybe I can not see the trees for the forest!



spikeVelleman MK 120 Hi

Thank you all , for all your replies, I have tried to do a schematic that I can understand from the schematic I first put on here, would anyone be able to have the time and patience to check it out!

Cheers and again thanks, what a great site, and nice people willing to help people like me that are very new to electronics.


enter image description here

  • \$\begingroup\$ I am not a school child , I don't need anyone changing or altering my wording . \$\endgroup\$ – Spike1947 Apr 11 '16 at 18:42

Vref is generated by IC1D, and it serves as a DC bias for all other stages, so they can work with ac coupled signals.

| improve this answer | |
  • \$\begingroup\$ Thanks for that info , do I take it that 14 , 3 , and 5 of the IC LM324 are linked together ! , and were does COMP link to ! , sorry for all the questions I am just a newbie .chhers spike \$\endgroup\$ – Spike1947 Apr 10 '16 at 8:55
  • \$\begingroup\$ No problem, yes you should take it as an internal connection, it is just to avoid having a wire line going all through the schematic. Comp goes from C3 to the inverting input of IC1C, which is acting as a comparator. \$\endgroup\$ – payala Apr 10 '16 at 9:03
  • \$\begingroup\$ Thanks all , for your replies , there is just one more problem with this schemtic , that is the time period when activating the alarm is very short , is there a way of increasing the time on to the alarm ! .cheers spike \$\endgroup\$ – Spike1947 Apr 10 '16 at 9:41
  • \$\begingroup\$ I would say increasing C3 value should give a longer time to detection. But I'm not sure how much time you are thinking about, you could require something different. \$\endgroup\$ – payala Apr 10 '16 at 9:44
  • \$\begingroup\$ Hi , thanks for your reply , I am wanting to replace the Buzzer with a relay hopefully ( not sure of the current to the buzzer ) , so I would of thought about 3 seconds , I think this circuit is quite short maybe 1 second ! .cheers spike \$\endgroup\$ – Spike1947 Apr 10 '16 at 10:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.