Let’s have a little tinker with a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor). This is an IRFZ44N device which according to the data sheet can handle 49 amps maximum! Take a look at the video of a car headlight bulb being switched on and off, which at only 5 amps still managed to [...]
Although it’s perfectly possible to design a feedback control system using analogue electronics, it’s fairly clear to me that a digital microcontroller solution is the way to go. For one thing, the component count will be lower and that will almost certainly mean lower cost too. The switch element will be a MOSFET due to [...]
Let’s enter the world of analogies and metaphors to help understand how the controller might operate. First, here’s a real world example of negative feedback. A light aircraft will normally fly straight and level if its joystick is in the centre position. When a gust of wind tips the aeroplane over to the right, the [...]
The voltage regulator operates as a closed-loop control system employing negative feedback. To understand what this means, we need to delve a little bit into control theory. But we’ll tread carefully, and certainly steer clear of the very complex mathematics that this subject can involve.
The diagram shows a generalised feedback control loop. The box labeled [...]
This circuit shows a solar panel connected to a battery via a switch. If the switch is closed, current will flow into the battery causing its voltage to rise. When the battery voltage reaches 14.5 volts, the switch must be opened. But instead of leaving it open (which will allow the voltage to start falling [...]
Perhaps more by luck than judgement, the simple relay circuit has an inherent hysteresis. Hysteresis is often desirable in voltage controlled switching applications to prevent instability at the trigger voltage. In the case of the simple regulator above, there are two trigger voltages, an upper one above which the solar panel is disconnected, and a [...]
Here’s a very simple voltage regulator circuit. It doesn’t have all the features of our fully specified device, but it does perform the basic function of battery protection.
The solar panel is connected to the battery via the normally closed contacts of a 12v relay. A transistor energises the relay coil when the battery voltage rises [...]