how to get right value out of adaptor

i had a question that is confusing me

if u had an adapter which gives 1.5,3,4.5,6,7.5,9,12 volt using a switch

when u move the switch let's say to 3v and measure it with voltmeter it gives 5.5v and when i move the switch to give 12v and measure it with voltmeter it gives 18.5 volt

i read on a site that u only get this voltage at full load so if the adapter is 12 1A
u must use all of the 1A to get 12v out put


and here comes the question let's say i am making a digital clock circuit and in the schematic it says use 5.5 let's say 6v how to get this value from the adapter as when i move the switch to 6v i will get may be 8.5v output as the clock will not consume all of 1A adapter and so making it at full load

also for this example of circuit types u can't calculate exactly the ampere needed to use adapter of the exact value

so how can i get the right value

Buy a regulated adaptor, the un-regulated ones (like you have) are completely useless.

Or put a regulator in your clock. Then it would be able to handle a much wider range of input voltages.

Try measuring it with a load on it.

Nigel Goodwin said:

Buy a regulated adaptor, the un-regulated ones (like you have) are completely useless.

Click to expand...

That's not true, unregulated adaptors are good for projects with built-in regulators or which don't need a regulated supply.

My advice in this case is to add an LM7805.