Fridge Timer UpdateOK so I have wired up a 4060.
These old CMOs chips aren't as fragile as people say... Mine have been stored in a small plastic bin for 30 years, all teh chips entangled with each other, touching pins, me grabbiing and handling them with my big fingers with no ESD protection other than me discharging my fingers to earth just before grabbing the chips and..... freaking chip still works just fine !!!
so first thing was to see if it's alive. I calculated that to get my 4.55Hz target frequency, I would need a 100ms RC time constant given, the formula in the datasheet for the built-in RC oscillator.
At first I wanted to put a 1uF cap with a 100K of course, as it's easy round numbers, but I couldn't do that because that means the second resistor needed in this oscillator, which needs to be 2 to 10 times larger than the R in the RC, would be 200 K to 1M, and my resistor selection stops at about 150K sadly. So instead I halved R from 100K to 47K, and doulbe C from 1uF to 2.2uF. this way I could use 100K for the second resistor.
Reset pin : I didn't even put an RC network because the datasheet doesn't call for it. They simply tie the pin to ground permanently and call it done, so I did just that...
Then.. I applied power...
As a first step I scoped the output of the built-in oscillator to see if it was running, and what the frequency was like. See below.
It worked just fine, this old chip is alive !
Frequency wise I got 4.15Hz at first, a bit low, a bit less than 10% too low. So I sped things up by about the same amount by replacing the 47K resistor with a 43K one. That brought the Freq up to 4.55Hz, spot on !
Then I checked the dividing chain / counter outputs. 14 stages, number starting at Q1 not Q0. Q1/2/3 and 11 are not available because of lack of pins on the 16 pin package. So the fastest output I could check was Q4, hence divides by 8. As you can see that works just fine
So I will assume that the other outputs work too... and move on to the next step : add the NOR gate on the last 2 outputs to get the modified duty cycle.
I have no 4001 CMOS so will be trying with a TTL equivalent. Should still work I think... the totem pole output of the 4060 should be plenty capable enough to sink the current required to drive a TTL input low. As for logic high, it does not require any drive so it can only work I guess !
Let's see !!