toggle circuit doesn't work

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hi folks,

i build a toggle circuit to switch on my diy amp with a pushbutton (not a switch!). the toggle circuit is based on a 4027 mos, the circuit is shown below:

An externally hosted image should be here but it was not working when we last tested it.


the truth table of the 4027 is the following:

An externally hosted image should be here but it was not working when we last tested it.


when turned on, Q is high and the "off led" is on - fine and ok.

when i push the button, Q/ is high and the "on led" gets on and the relais closes - fine and ok, too.

this state should last until i push the button again, but as soon as i put my fingers off the button, Q/ gets low, Q high and i can see the "off led" laughing at me.


so anybody an idea, whats wrong with the circuit? i changed already the 10uF cap at clk and put a smaller one in - 0,22uF - but without any result, all the same.

thanks for help

so long
turner
 
B+ = 12v

I was concerned that the reset line may be picking up some noise from the B+ line. This could cause it to reset.

Does the circuit work properly if you remove the relay? Replace the relay with a 1k ohm resistor to see if the relay is causing the problem.

Are you 100% sure that the IC is in good working order?
 
You are assuming that the switch behaves perfectly, opening and closing without any bounce. That's the problem with this type of simple circuit.

When you open or close a switch the contacts bounce for a few ms. That is plenty of time for the circuit to switch.

Have a look at some of the circuits here:
http://ourworld.compuserve.com/homepages/Bill_Bowden/page9.htm

The 555 timer based circuits should work more reliably...

I_F
 
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