Pin 11 is the inverting input of an op-amp, we are setting this to a voltage mid-way between the power rails – this gives the op-amp a definite threshold which the non-inverting input on pin 1 must cross to switch the op-amp’s output.
The reed switch will connect pin 1 to 0v when it ‘makes’ (magnet close-up) and allow the 10k resistor to pull pin1 all the way up to 9v when the reed ‘breaks’.
We can now force pin 1 to go both sides of the voltage set on pin 11. These three 10k resistors are all non-critical; if you have 6k8 (6.8k – we use the multiplier in place of the decimal point) or 22k – anything around there will do.
Also changed is the output circuit – the original drove a current meter, we want a voltage, so dump the mA meter and connect pin 8 to 9v. Pin 10 connects to pin 5 and this produces the voltage. It wouldn’t hurt to leave the 12k resistor in for now and just watch the voltage across it. This whole output section of the IC is just acting as a buffer for the voltage across the charge pump capacitor (your 1.0uF)
When testing with your motorised wheel can you watch the effect on the output. If it shoots from 0v to 9v while the wheel is spinning I would suspect the speed of the wheel is too high. We can adjust the circuit easily later for this.
I think the maximum input frequency will be 100Hz ???