Strange Screening Problem

[Xenobius1]

Hello all,

I have built this circuit http://www.electronics-lab.com/projects/sensors/008/ and it worked. However I have a problem. I am using a DC adaptor to give it 12v and so im not so sure if its pure dc. The problem is that, IF I touch the positive metal part of the power supply, the circuit works perfectly... if I remove my finger from the positive of the power supply, the RED led (of the circuit LED1) turns ON until I touch the + again.

Could this be a filtering problem of the power supply? I put 10uF and 68nF in parallel across the power supply but no luck.

Thanks all

 

[ante1]

Have you grounded the circuit like it shows in the diagram?

The

 

[Xenobius1]

Cool thanks a lot

I had 2 problems. The gnd was not earthed as you said but also the power supply that I was using had just one diode to make ac into dc and thats was another problem.

Thanks