RG's CD4053 bypass

[alparent]

Trying out the CD4053 bypass on RG's site.
Using this to trigger it http://diy.thcustom.com/switching-relay-true-bypass-circuits-not-using-a-microcontroller/

Can I use the unused switch of the 4053 to control the LED? Or is their a better way?
(Trying to minimize part count, as always!)

Any comments or insights appreciated.

Will then design a board using SMD.

Thank you

[R.G.]

CAN you use the extra section to control an LED? Sure, as long as the LED uses less current than the data sheet says the CD4053 can conduct through the analog switch path. Quick!! Off to read the datasheet!

IS THERE A BETTER WAY? Maybe. It's not clear to me that switching high currents in the chip along with low-level signals will not transfer a bit of a >tick< when switching, expecially when the high current signal runs from the full V- on the chip to th efull V+. But it's possible the chip will just do this fine, or that some manufacturers' chips will do it OK enough for your purposes.

The real answer is to read the datasheet and try it. I actually consider the addition of one TO-92 2N7000 MOSFET to switch the LED pretty minor, but you might be able to get the 4053 to do it.

[dschwartz]

I use the flip flop output for the led.. never had an issue..

[alparent]

Thanks RG, I was hopping you would chime in 

I was also thinking of maybe controlling the LED with the same signal that would control the 4053 (the signal coming out of pin 3 of the 555) just a LED and a resistor between pin 3 and GND. If that leaves me with enough juice to control the 4053? 

Thanks also dschwartz, you answered while I was typing this.

[R.G.]

Sure, you can use the same signal that runs the 4053 as long as it can drive the LED over the full voltage. The control input to the 4053 takes so little current that it might as well be an open circuit. So if it drives the LED, it can also drive 4053 control input.

There is a useful rule in designing effects - don't use the NE555. The NE555 has huge current spikes in its power and ground supplies right at the places where its output switches. Instead, use the LMC555 or one of the other CMOS versions that do not have the big current spikes.

[alparent]

I'd say that is a very important design rule!

Thanks, I'll put all of this new knowledge to use tonight.

[alparent]

Might as well use a cd4049 then.
I was using the 555 because I have a lot of them.
4049 are more than half the price of a LMC555