toggle circuit doesn't work

[turner]

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:



the truth table of the 4027 is the following:



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

[Perry Babin]

Have you tried adding a capacitor across B+ and ground?

Have you tried grounding the reset pin?

This is a circuit I built for someone. If you have a CD4013B, you may want to try it. You have virtually all of the other parts you'll need.

http://www.bcae1.com/opamptemp/flipflop01.swf

[turner]

Hi,

what do you mean with B+? reset is low, this shouldn't be the problem i guess ...

so long
Turner

[Perry Babin]

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?

[I_Forgot]

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/homep...wden/page9.htm

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

I_F

[cpemma]

Originally posted by I_Forgot
You are assuming that the switch behaves perfectly, opening and closing without any bounce. That's the problem with this type of simple circuit.

Some tried & tested bounce-free circuits.

The Winfield Hill one is cheap and simple (and with that provenance...)