there are two buttons On and Off. When the On button pressed a light turns on and stays on regardless of how many times the On button pressed. The light could be turned off only by pressing the Off button (providing that the Off does not turn back into ON)
I have a power supply 15 volts and I'm looking for a chip (CMOS) that I could buy fom Digi-Key
thankx

 

This could be done very easily with a SCR. Press button to fire the SCR, it will now stay on as long as sufficient DC is flowing through it, then when you press the other button, it opens the circuit, the SCR turns off, and stays off.

All you would need is a normally open switch to turn the SCR on, a normally closed switch to turn it off, and 2 resistors to connect to the gate of the SCR to fire it from the first switch.

The SCR you get would depend on what the load is, and how much current it draws.

 

yeah 15 V is at the upper limit of CMOS...

 

Try Mouser instead of Digi-Key, no minimum order. www.mouser.com

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thanks everybody for an answer, but I guess I did not explained myself well
by using a word "button" I wanted to show how I want the signal to work, I was not talking about actual buttons being there
I'm looking for a chip that would perform such a function

 

Mouser does have minimum buys.. depends on what it is.. Digikey also lets you buy small quantities on most things.. they are similar in this regard. Wonder why you think mouser is better in this regard? In my experience, Ive run into the quantity problem more times with mouser than digikey.. but overall, I think they are similar.

 

I checked some manuals and 15V is the upper limit on some , but not all CMOS chips , others are 18V .. so your 15V should work.But check the specs before ordering..S1 turns Led on S2 turns Led Off..R1's value depends on what you want to use as an indicator..R2 & R3 Should be 100K to 1Meg..
R4 = 100K ohms..
R5 & R6 =100K to 1 Meg

EDIT : Revised circuit..

Attached Thumbnails

 

 

Thank you, that what I need , but what about D and CLK inputs, should I leave them how you showed, or put on high or low level .
thanks again .

 

They can Float ..

 

CMOS ic inputs cannot be left floating, as will damage the IC. Also U have to tie all the other inputs, of the unused section to GND.

Gajanan Phadte

 

i stand corrected.. ok then ground all unused inputs
please dont ground any unused outputs..

 

thanks for your help.