The 24-volt on-board power supply is found in buses, trucks, and other large vehicles. This creates difficulties when installing car radios and other electrical loads in them, designed for power supply with a voltage of 12 V.
Instructions
Step 1
Find out from the instructions for the radio tape recorder or other device the current indicator that the equipment needs in the most severe mode. Calculate the power dissipated by the gimbal when operating in linear mode using the following formula:
Pst = (Uin-Uout) * In, where Pst is the power dissipated on the stabilizer in units of W, Uin is the input voltage, 24 V, Uout is the output voltage, 12 V, In is the maximum load current in units of A.
Step 2
Choose a switching or linear regulator chip. It must have the following parameters:
- output voltage - 12 V exactly;
- input voltage - not less than 30 V;
- maximum load current - not less than 1.5 of the maximum current consumed by the device;
- the maximum power dissipated on the stabilizer is not less than 1.5 of the calculated value according to the formula given above (for switching stabilizers it can be reduced several times).
If you want to listen to AM radio stations, use a linear regulator - the pulse regulator can interfere.
Step 3
After purchasing the microcircuit of your choice, attach it to the massive heatsink. For example, a heatsink from a large processor (Pentium IV class) will do. The fan can be used from the radiator kit. Be sure to apply a thin layer of thermal paste between the gimbal's heat-dissipating flange and the heatsink. Make sure that the flange is well pressed against the heatsink.
Step 4
Switch on the microcircuit according to the standard wiring diagram. For example, if this is a 7812 type microcircuit (suitable only for car radios with a current consumption of no more than 2 A), place it with the marking facing you, with the flange up, with the leads down. In this case, the left terminal will be the input (+24 V), the middle one - the common (ground), and the right one - the output (+12 V). Shunt both input and output with 1000uF, 50V electrolytic capacitors in correct polarity. In parallel to each of them, connect a ceramic capacitor of any capacity (they are not polar). If a fan is used, connect it to the output of the stabilizer. Switching stabilizer microcircuits may require the connection of additional elements: resistors, chokes to specially designed pins.
Step 5
Connect the power input of the car radio, observing the polarity to the output of the stabilizer, and the stabilizer itself through a fuse selected according to the current consumed by the radio tape recorder, to the vehicle's on-board network, also observing the polarity. Check the device in operation. Place it in an insulated jacket with cooling holes. Place the finished structure so that it is not blown by the warm air flow from the engine, and so that splashes of oil, gasoline, water cannot enter it.
