MC14538B as astable ?

Thread Starter

inwo

Joined Nov 7, 2013
2,419
I would like to use 1/2 for retrig. monostable and 1/2 for astable if its possible.
Or find a dual timer that does both. ~12v
555/556 type isn't a good choice for retriggering. IMO
 

hp1729

Joined Nov 23, 2015
2,304
I would like to use 1/2 for retrig. monostable and 1/2 for astable if its possible.
Or find a dual timer that does both. ~12v
555/556 type isn't a good choice for retriggering. IMO
I don't have an example made up but if you put a power on reset circuit on the reset line and tied the Q0not output to hi trigger input it should go astable but only be in the reset state for about 50 ns. On power on it comes up reset, triggering it. When the timing times out Q-not goes high again, clocking it ...I don't think I ever tried it since I don't have it in a drawing, but in theory it should work.
 

AnalogKid

Joined Aug 1, 2013
8,590
A CD40106 or CD4093 can do both functions in one chip.
Does the retriggerable gate the oscillator?
What is the freq range of the oscillator?

ak
 

GopherT

Joined Nov 23, 2012
8,012
I would like to use 1/2 for retrig. monostable and 1/2 for astable if its possible.
Or find a dual timer that does both. ~12v
555/556 type isn't a good choice for retriggering. IMO
What is your goal and what are the constraints. Any reason for limiting to a single chip?
 

jpanhalt

Joined Jan 18, 2008
10,225
If you are looking for how to connect the MC14538 as an astable, this might help (you may want the whole application note, see link below):
upload_2016-8-10_4-13-4.png

Source: Fairchild AN366 (available here: http://www.scarpaz.com/Documents/AN-366.pdf)

As just an FYI, MC1xxxx numbers are usually equivalent to NNxxxx . That is, to find circuits for MC14538, try searching on CD4538 or any other chip with just 4538 in its ID.

John
 

GopherT

Joined Nov 23, 2012
8,012
If you are looking for how to connect the MC14538 as an astable, this might help (you may want the whole application note, see link below):
View attachment 110234

Source: Fairchild AN366 (available here: http://www.scarpaz.com/Documents/AN-366.pdf)

As just an FYI, MC1xxxx numbers are usually equivalent to NNxxxx . That is, to find circuits for MC14538, try searching on CD4538 or any other chip with just 4538 in its ID.

John
Nice find. Very interesting things in there. I have been looking for the answer to @inwo 's question for a long time and I assumed it couldn't be done.
 

Thread Starter

inwo

Joined Nov 7, 2013
2,419
What is your goal and what are the constraints. Any reason for limiting to a single chip?
An exercise in kiss.
Circuit from my other thread works with a retriggerable monostable into an astable 555.

Making sure I'm not missing a simpler way to do it.

For those who missed it.
Project has a signal in from <10 to 500hz.
Output needs to follow input to ~350hz.
This is where I'm at so far using TTL.
Just got in some more parts.
Over 350hz output = 350retriggermono123a.png hz.
 

Thread Starter

inwo

Joined Nov 7, 2013
2,419
I have 14538 now.
Quite sure that 1/2 will work as my retrig-mono.
If the other 1/2 can be a gated astable, I'm in business. One chip solution.........

If not I'll go back to adding a 555.
 
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