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Converting 8v dc to 1.2v dc..

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yusuf

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Hi friends once again...

I have recently brought a simple analogue alarm clock for my bedroom...

It need only one 1.5v pencil cell as power...

I want to remove this cell and I want to convert my 8v dc regulated power supply to 1.5v to power my clock..

I want to power my clock with 1.5v , by converting my 8v dc power supply... to 1.5v

Any help will be appreciated !
 
Look at the LM317. If you use resistor values of 240 and 47 ohm you should get 1.5 volts out.
For a smaller version, look at LM317L in a TO-92 plastic case. It is good for 100mA.
 
You can use an LM317.
You didn't say how much current you need, but that should get you started.
can you post any circuit diagram for better understanding ...
 
Or....
Is there any solution for gaining 1.5v dc from 8v dc... By adding some resistors...
 
NO....well not with out knowing how much power the clock needs. The clock needs to pull the same power all the time.
 
Clock needs 1.5v and 50ma current to work properly...
 
Clock needs 1.5v and 50ma current to work properly...

If you make a voltage divider that uses 200mA then a resistor divider will work.
______________________________
Another thought.
Resistor from 8V to 1.5V will have 6.5 volts across it. Pick a resistor that will conduct 60mA.
From 1.5V to ground connect the clock and a high current red LED. The LED works like a Zener diode.
 
I doubt your analog clock needs 50 mA from 1.5 vdc, unless the circuit within the clock is defective. An AA sized alkaline battery is about 2000 mA-Hrs of capacity so a 50 mA draw would have the cell lasting about 40 hours. AAA sized battery would be about half that time.

As you say it is an analog clock I assume you mean there is an electronic timing solenoid like in most analog dial wrist watches. They have a 32.768 kHz quartz crystal oscillator that generates a one pulse per second output that drives the timing coil.

They draw very little current, in the order of 1 to 5 uA average. There is a small current current spike when the coil is triggered. Any 8 vdc DC power supply will likely draw orders of magnitude more power then the actual clock, but if you insist on having it AC powered you would be better off just making a direct AC to 1.5vdc power supply. Clock will stop when AC goes out. If you put a large, low leakage filter cap you will ride across short AC outages.
 
RC,
I was just thinking the same thing. uA! not mA!

Using a red LED as a Zener; Use a 600 to 1000 ohm resistor to give the LED some current in the range of 5 to 10mA. Then attach the clock across the LED.
You might have to sort through some LEDs t find one that turns on at 1.2 to 1.5 volts.
 
yaa It is ua ! not ma !

Can you give friends a good circuit diagram.. because I am new and i understand better from looking at circuit diagram...
 
Empty post ! Sorry for double post !
 
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Just us the battery, you are going to be wasting so much energy its ridiculous.
The regulater will be using more power than the clock.
Get an old SMPS cell phone charger. It will have a lower voltage to start with.
 
Get an old SMPS cell phone charger. It will have a lower voltage to start with.
I have a old smps cell phone charger ... but it output's 6v... dc
I want 1.5v dc...
 
I have recently brought a simple analogue alarm clock for my bedroom...

It need only one 1.5v pencil cell as power...

I want to remove this cell and I want to convert my 8v dc regulated power supply to 1.5v to power my clock..

I want to power my clock with 1.5v , by converting my 8v dc power supply... to 1.5v

Why?????

The clock will run for months/years from the 1.5v cell.

Running from a power supply will give what advantage?
When the mains power fails, the clock will lose its time setting.

Are you trying to save on the cost of batteries?
The power supply will waste many times more power than the clock uses.

The only advantage of this project is as a learning exercise,
the practical advantage is zero.

JimB
 
The only advantage of this project is as a learning exercise,
Ya ! I want to make this project for only learning purpose...
My friend...
any help will be appreciated ! JimB
 
OK then open up your cell phone charger and chang the SMPS voltage to 1.5 volts.
 
Yusuf, you have already stated in other threads that your local mains supply is frequently absent. Therefore it's unsuitable for a clock. Are you trying to make life difficult for yourself? What's wrong with using a battery?
 
Yusuf, you have already stated in other threads that your local mains supply is frequently absent. Therefore it's unsuitable for a clock. Are you trying to make life difficult for yourself? What's wrong with using a battery?
Alec, thanks for your reply !

I have completed that project ...

But ,just for learning I want to power the clock without battery !

OK then open up your cell phone charger and chang the SMPS voltage to 1.5 volts.

There are many components inside the smps charger ! To gain 1.5v what should i change !
 
Editor is double posting things.
 
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