Set the initial/known state of JK Flip flop

Thread Starter


Joined Jun 16, 2021
Hi guys, this is my first post. I've been reading this forum for several weeks trying to learn about IC and electronics to make a controller pedal for my guitar pedals. I'm not an engineer, either a profesional musician, but i'm an architect, so electronics its clearly not my field. But I've enjoyed making things and seeing simple circuits finally work. So, the question, i have this JK Master Slave Flip Flop (cd4027be), well, like 6 of them in my project/attempt of circuit, and for what i've been learning, when you power up any storage-memorish-latch IC, it initialize in a indeterminate state, which is a big problem for me, because I don't want to go through each switch, reseting or clearing up all of them. So I found some solutions for this problem, and i think its something called Power-on-reset circuit, but i just don't get it. So I ask you, how can i implement that kind of circuit between A-B (or just modify all the reset circuit) so when I power this up for the first time, the JK flip flop Q output starts after lets say 0,2 or 0,5 seconds in a LOW state, and this circuit or magical IC, still allow me to clear manually with a momentary switch my JK ff when the circuit is working?
Thanks everybody,;)



Joined Jun 8, 2013

If you want Q high at power on:


When power is applied, C1 will begin to charge and short VDD to the set pin and set the Q output high.
When C1 completes charging, the set pin will be close to ground.

If you want Q low at power up, connect this circuit to the reset pin instead of the set pin.