# How do I set the speed of a 4060B chip?

Apologies if this is a bit simple, but I'm new to this!

How do I set the speed for a 4060B chip? I want it to trigger every 5 minutes (fairly accurately).

I've looked at the instructions here: http://www.reuk.co.uk/Timer-Circuits-With-4060B.htm and it looks like I need to trigger on pin 4. However, I don't get how I set the resistors and capacitor.

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According to the datasheet the formula for the R/C oscillator is:

${\dfrac{1}{2.3 \cdot R1\cdot Cx}}$

So for R1 = 10k$\Omega$ and Cx = 10$\mu F$

${\dfrac {1}{2.3 \cdot 10k \Omega\cdot 10 \mu F}} = 4.34Hz$

You can use any of the Q4 to Q14 pins for output, they have different division ratios of the oscillator speed.

Where Osc = the oscillator frequency the frequency of each Q pin is Q4 = Osc / 16, Q5 = Osc / 32, Q6 = Osc / 64 and so on up to Q14 = Osc / 16384.

So with the above example Q4 will toggle every ${\dfrac{1}{4.34Hz}} \cdot 16 = 3.68$ seconds

For five minutes you simply need to choose a compatible frequency and divider ratio. 5 * 60 = 300 seconds. If we choose the divider as Q6 then 300/64 = 4.68 seconds needed for the oscillator.

A quick shuffle of some figures gives one possible way as R1 = 204k$\Omega$ and Cx as 10$\mu$F. This would give:

$64 \cdot \left( \dfrac{1} {{\dfrac{1}{2.3 \cdot 204k\Omega \cdot 10\mu F} }}\right) = 64 \cdot 2.3 \cdot 204k\Omega \cdot 10\mu F = 300.288$ seconds.

Pretty close. I would probably use a smaller more precise capacitor and a larger resistor for more accurate timing. For best accuracy use the crystal option.

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With such a long divider chain available you can use a faster oscillator and a bigger divide ratio. If your oscillator operates at say 10 to 100 hz the components are usually much more manageable that if you need somewhere around 1 HZ BUT do what works best for you in practice. | Do not use an elecrolytic for timing or a cap that is badly temoerature affected. eg most ceramics are poor. Use a quality resistor. (Most are these days. Most.) –  Russell McMahon Nov 17 '11 at 18:15
@Madmanguruman - Thanks for the mathjax fix ;-) –  Oli Glaser Nov 18 '11 at 0:35