The charge controller’s LED presents us with both an opportunity and a challenge. We want it to provide a useful amount of feedback to the user, but at the same time consume the minimum amount of power possible, particularly during the battery’s bulk charge phase.
Information we have available for display includes:
Battery voltage
PWM duty cycle
Error conditions
Battery [...]
The prototype charge controller has served it’s purpose well, but now a new design is needed, one that will more closely resemble the finished product.
The new layout is rectangular and fits onto a piece of Veroboard 14 x 16 holes in size. The FET is laying flat on the board this time, the tallest component [...]
The prototype charge controller works, but there are a couple of issues that need looking into. One is instability in the feedback control mechanism and the other is that you can’t switch the thing off.
Let’s have a look at the second problem first. If you disconnect the charge controller from the 12 volt battery, it [...]
This is the regulator circuit that generates 5 volts for the PIC microcontroller. The 1N4001 diode decouples battery voltage Vbatt from the regulator circuit. The various capacitors provide smoothing and decoupling to provide the microcontroller with a clean stable power supply. A 100n capacitor is connected as close to the PIC supply pins as possible.
The [...]