I am going to design led torch using small watch batteries. ( this image type)

I need to use push button instead of slide button
problem is I can't use IC since here I have 3V only

what is the best circuit for that
assume led needs 50mA

thanks

 

I have idea about 555 ic based circuit. but if I use it i think I need 5V
also I need to know how to calculate the lifetime for a one battery of torch
I can do it by measuring power requirements
but I do not know battery details

 

What is the forward voltage drop of your LED?
Look at the battery makers data sheet to see what is the maximum current that the battery can deliver. (I dont think it is even close to 50mA).

 

Hello,

The ML2016 can not deliver the wanted 50 mA.

Bertus

 

The capacity of that battery is only 18mAh or ~25mAh (depending who's figures you believe). So even if it could give ~50mA a charge wouldn't last long.

 

ohh that a big problem
so no matter then is there any circuit ?
which can use push button
once pressed led on
then press off

 

ohh that a big problem
so no matter then is there any circuit ?
...

No "circuit" can make up for the fact that the battery does not store enough energy to do what you want.

Look at all the available high-output flash lights. Do you see any that use a coin cell? Three AAA or AA is the minimum.

 

its already been invented....

http://www.ebay.co.uk/itm/290980298083?redirect=mobile

 

its already been invented....

http://www.ebay.co.uk/itm/290980298083?redirect=mobile

But that is no 50mA LED, more like 10mA

 

yes. also that is use push button which can't keep turn on without force.
is there any mechanical type push button once pressed turn on next press turn off.
I know they are available but I need one that height is less than 3mm

 

Why are you looking for that switch if the battery won't do what you want??

 

My working glasses uses two small coin cells and has a push button. No need to make just buy it.

 

you can see a pushbutton circuit here
http://ledmatrix16lf1709.hitechworld.org/?p=19