Clock Divider

blue hell · Posted: Thu Dec 07, 2017 4:10 pm Post subject:

chatted a bit with wmonk about this puzzle ... maybe it gives some ideas?

flagada · Joined: Dec 15, 2016 Posts: 39 Location: Amsterdam

Hi Jan, thanks for thinking along and trying to find help! But I think I have found the reason for the strange behaviour. Btw: I built it on stripboard (veroboard), not on a breadboard.

I recently built the MFOS 32 step sequencer, and Ray was talking about a strange reset at some pin that he could remove by adding a 1nF cap to ground (he called it a glitch removal cap). So I took out a 1nF cap and... Bingo!

When I add a 1nF cap between pin 7 and ground, the strange behaviour is gone! (pin 7 is were the 3rd division is, just before the 4th were things go wrong).

Then I noticed that 1 of the dividers was still acting strange, even with the cap. The only difference was that it's tracks were longer than those of the other two.

I has to do with stripboard, and the fact that adjacent strips/tracks can influence each other, especially when those tracks are long. For instance by forming a capacitor, resulting in stray capacitance. But I guess that there are more effects that can occur like sensitive parts picking up electric fields. I have built many circuits on stripboard and two times before I have had issues that could be solved by minimizing the length of the tracks.

So now I have shortened the track were pin 7 is soldered as much as possible. I only could shorten it by 0,75 cm, but the total length was only 1,5 cm so I effectively cut it in two. And now, all three dividers work normal, even without the 1nF cap! That is, with the +6 Volt gates. Fingers crossed: I still have to put the switches and the wires back in place.

blue hell · Posted: Fri Dec 08, 2017 5:25 am Post subject:

Great :-)

And re. the strip board turning into a bread board .. that's what happens with chinese whispering!