some questions about 4049 flip flop..

[dschwartz]

Hello there, i´m tinkering with a 4049ub flip flop, like the geofex one ( http://www.geofex.com/article_folders/cd4053/cd4053.htm)

and i have two questions...

it seems like it has "memory", i mean, if i leave it high, and disconnect the power, it wil start up on high ..and vice versa..

how can ai mod it to consistenly power up on a definite state?

and also, i´m worried about the current consuption of the FF..does it suck too much current? like 20mA? or this configuration is less hungry for electrons than linear mode?

cheers  and thanks you in advance for your help!

[R.G.]

it seems like it has "memory", i mean, if i leave it high, and disconnect the power, it wil start up on high ..and vice versa..

how can ai mod it to consistenly power up on a definite state?

Hmmm. I haven't had problems with that. I've used that flipflop in production pedals for years, and it always powers up in one state. I choose that state to be the "inactive" state. I have not seen it power up in just the last state it was in. More data??

and also, i´m worried about the current consuption of the FF..does it suck too much current? like 20mA? or this configuration is less hungry for electrons than linear mode?

No, the current consumption in digital mode, as it's being used here, is almost unmeasurably small. Linear mode for use as an amplifier is a high-current misuse of the chip.

[dschwartz]

thanks for your response, RG..

The Memory thing is weird..i think it´s the debounce cap charge being kept after unplugging that serves as a "memory", i am using 220nF there.. maybe if i wait longer after reconncting the circuit, the cap will discharge and  start on the low state..

anyway...i used my brain a little, and came up with a simple solution.. connecting a cap between v+ and the union of the two inverters. on power up, the cap pulses the second inverter high, so the output is low..works like a charm and pretty consistent..

also i measured the current using a 1ohm res on V+ , and measured 15mA, which i think is acceptable, but still on the high side..then i grounded the unused inverters and voilá..0.0mV, so less than 400uA..nothing!


edit.. BTW..after a minute or so, it starts on low state...i like this because if you have a hiccup on the dc supply (like, the singer kicked the wallwart), it will turn on as the last state it was. but when setting up the rig, it will start on low..GOOD..

this is the perfect flip flop/switching thingy..low current, versatile..and reliable..

[MrBinns]

I don't think I've had any problems with 4049's.

If you are using a flip-flip chip with set and reset, checkout power-on-reset



idk if that is useful to you or not.

[dschwartz]

I don't think I've had any problems with 4049's.

If you are using a flip-flip chip with set and reset, checkout power-on-reset



idk if that is useful to you or not.

yup, is the same principle i used to add the cap that made it start on low consistenly..but now that i see that it will start on low iff i leave it disconnected for a minute or so, seems that the stock ckt works perfect..