One option to consider is the Variable 3 24 Volt/3 Amp Power Supply. This regulated power supply can be adjusted to deliver anywhere from 3 to 25 volts, while also limiting current to a maximum of 2 amps. If you need to increase the current limit, you can select a smaller current sense resistor (0.3 ohm) to increase output to 3 amps or more.
To control voltage regulation, the circuit uses half of a 1558 or 1458 op-amp. While either option can be used, it's recommended that the supply voltage to pin 8 be limited to 30 VDC by adding a 6.2 volt zener or 5.1 K resistor in series with pin 8. The maximum DC supply voltage for the 1458 and 1558 is 36 and 44, respectively.
When selecting a power transformer, it's important to choose one that can provide the desired current while maintaining an input voltage at least 4 volts higher than the desired output. Be sure to also make sure that the maximum supply voltage of the op-amp is not exceeded under minimal load conditions. The power transformer shown in the circuit diagram is a center tapped 25.2 volt AC/2 amp unit that produces regulated outputs of 24 volts at 0.7 amps, 15 volts at 2 amps, or 6 volts at 3 amps.
To achieve the 3 amp output, simply use the center tap of the transformer with the switch in the 18 volt position. All components required for the circuit should be readily available at Radio Shack, with the exception of the 1558 op-amp.
In summary, a 24 volt AC power supply is an essential component for powering many electronics devices. With Radio Shack's Variable 3 24 Volt/3 Amp Power Supply, you'll have a reliable and versatile option for your power needs. And with the added convenience of online shopping, it's easier than ever to find the right supply for your needs.