Coding classes in East Renfrewshire

The basin is invented, not a copy of anything at Waulkmill Glen. Water leaves it all day as a town draws its supply, more in the day and less at night, with some randomness on top. Water enters through a sluice that delivers 0.09 cubic metres a second when open. The aim is to hold the level near 2 metres. A sensor reports the level once a minute, and like every real sensor it is a little noisy, off by about 2 centimetres either way. The learner simulates a week and tries three rules.

The first rule looks perfect on a graph, since the level hardly moves. Look at the valve, though. Whenever the water sits near 2 metres, sensor noise alone makes the reading hop above and below the line, so the gate flips open and shut minute after minute: 5,088 times in a week. Engineers call this chatter, and on a real gate it wears out the machinery. The second rule adds a dead band. The gate opens only when the level falls under 1.8 metres and stays open until it passes 2.2 metres. That gap, called hysteresis, cuts the switching to 161 times in the week, and the price is water that swings further. A home thermostat uses the same trick.

The third rule opens the gate part of the way, more when the basin is low and less when it is nearly full. The level stays between 1.90 and 2.09 metres and the gate never slams, though it is adjusted constantly, and in real designs a purely proportional rule can settle a little away from its target. Choosing between the three is a trade-off between accuracy, wear and simplicity, which is what control engineering is about. We make no claim about how the 1840s sluice actually worked; that is for historians, and the listing itself is uncertain.

Coding is still worth learning for an East Renfrewshire teenager in 2026, because someone has to check what the machine will really do. The longer argument is in why teenagers should still learn to code in 2026.