The 24 volts power supply circuit is very simple. It uses a zener diodes and Darlington transistors type TIP122. Output voltage is set at 24 V with 2 amperes current output.
Lowering the voltage 230 V sector is provided by the transformer TR1, whose secondary voltage is 24 V. Available voltage after rectification and filtering is the order of 32 V to 34 V (depending on transformer and voltage).
Electrolytic capacitor C1 provides filtering rectified voltage to obtain the required output voltage. Its value depends on the maximum output current that you want to get, 4700 UF set here will allow you to simply filter 2 A output current. You can reduce it to 2200 uF if you dont need more than 1 A. The proposed circuit allows the implementation of one or two radial capacitors 2200UF-4700 UF, the choice is yours depending on the size of the capacitor that you can get.
The voltage stabilization is entrusted to a zener diode, which is supported by a Darlington transistor for output current capability greater (TIP122 transistor carries a collector current of 5 A continuous, so this is fine). In fact, if you look at the diagram, you find that there are two zener diodes instead of one. This choice allows you to change easily the output voltage by choosing other values of zener diodes. For this model, It used a 12 volt zener (BZX55C12) and a 13-V (BZX55C13), so that the output voltage is close to 24 V output current max. The output voltage depends a little on current consumption, this is quite normal for this type of scheme.
The power dissipated by the transistor Q1 is connected to the voltage difference that exists between its collector (regulated voltage of about 32 V) and its emitter (regulated voltage of 24 V), and supply output current (2 A max). Therefore, in 16 W at full capacity, which requires the use of cooling radiators in Q1.