1 sec alternating polarity circuit

[wombweller]

Hello all.
Please see the attached photo of a circuit I’d like to copy. I don’t have the actual board a friend of mine sent me the photo.

It’s a circuit to produce 1 second alternating pulse using the following IC’s-
CD4017B x2, CD4060B x1 and a CD4024B.

Can anyone point me to a circuit diagram for this, maybe there is something online, if there is I’m unable to find it.

I think this circuit is used so it can run on 3v so low power. It’s for pulsing a low voltage Brillie slave clock and needs to be a small footprint so it can go in to the back of the clock and run on batteries.

I look forward to hearing from you.

Regards
Mark

 

[wombweller]

Here is a first pass at a re-work of the #22 schematic. I did not verify that this is a correct schematic for the board in Post #1. Click on the schematic for a larger image.

Note: Adjust R1, R2, C1 and C2 for the crystal being used.

ak
View attachment 148305

Hi All.
What is the purpose of using 5% resistors ?

 

[Nigel Goodwin]

Hi All.
What is the purpose of using 5% resistors ?

None, it's just that it's a VERY, VERY old design, when 5% resistors were commonplace - nowadays you'd usually use 2% or 1% resistors.

Going back even further 10% (silver tolerance band) were normal, and before that 20% (no tolerance band at all).

 

[AnalogKid]

My design libraries have parts created by seven different people over a couple of decades, so my concept schematics often have things like a 20 amp FET where a 1 A part will suffice. 5% still is the most common tolerance for small through-hole resistors, but there is nothing critical about the base-current-limiting resistor values.

ak