Converting 8v dc to 1.2v dc..

[tcmtech]

Just use three small diodes in series to produce the 1.5 volt reference voltage with a 10K - 15K resistor for the voltage dropping component. After that use a large value low voltage capacitor as a backup power source for line power dips and outages.

5 components and thats it all salvageable from almost any common circuit board.

 

[JimB]

any help will be appreciated ! JimB

OK, have a look at the attachment.

This is what I suggest (others have suggested a similar arrangement).

I suggest using two diodes, I notice that TCM has suggested using three.
However I think that three may be too much.

I just did a quick test using a bunch of 1N4007 diodes and got a forward volt drop of 0.71 to 0.72 volts across each diode.
Using two of those diodes in my proposed circuit would give your clock a supply of 1.42 to 1.44 volts which should be adequate for normal operation.

JimB

 

[tcmtech]

I suggest using two diodes, I notice that TCM has suggested using three.
However I think that three may be too much.

Yep you are right. I am at work and mostly asleep at the computer right now.

For a 1.2 - 1.5 volt low current reference source the two diode suggestion is correct.

 

[4pyros]

There are many components inside the smps charger ! To gain 1.5v what should i change !

Start by looking up the data sheet for the switching chip thats in it. What is the number on the chip?

 

[Electroenthusiast]

Better use a 1.5V battery, because the current range in your case is in uA. You wont save huge using an adaptor.

But, if you still want to use a adaptor, then 7802 would also work. 1.5 or 2 wouldn't make a large difference. LM117(/LM317) is a better opt, but if you are unable to rig up the circuit/if you want it much more fast, then you can go with 7802IC. But take expert opinion, i might be wrong.

 

[tcmtech]

Better use a 1.5V battery, because the current range in your case is in uA. You wont save huge using an adaptor.

Stick a 99 cent D battery on it. you will die of old age before it runs out of power from the clock draining it down.