7805 | Electronic Project Circuits

Posts Tagged ‘7805’

Uninterruptible Alarm Power Supply by 7805

Although this Power Supply was designed for the Modular Burglar Alarm – it has other applications. It provides an output of 12-volts – at a current of up to 1-amp. In the event of a mains failure – the back-up battery takes over immediately. And when mains power is restored – the battery recharges automatically.
The 7805 needs the larger heatsink because it has to dissipate a lot of energy – especially when called upon to recharge a flat battery. Its heatsink is at 9v1 – and must NOT be connected to ground. The 7812 never has to dissipate more than 2-watts – so its heatsink can be smaller.
Many of the components, which are shown lying flat on the board, are actually mounted standing upright. The links are bare copper wire on the component side of the board. The heatsinks are folded strips of aluminium, about 2mm thick. Use a well-insulated panel mounted fuse holder for the mains supply to the transformer – and fit it with a 1-amp fuse.
Use a genuine alarm type back-up battery. They are maintenance-free. Their terminals can be held at 13v8 for many years – with no apparent ill effects. They have a life expectancy of about five years. However, they tend not to recover from a very deep discharge. If you wish – you can use a smaller or larger capacity battery.

Read More Source: http://uk.geocities.com/ronj_1217/al1/psu.html
Thank you.

Be the first to comment - What do you think? Posted by admin - March 20, 2008 at 11:02 am

Categories: Electronic Control, Power supply Tags: 7805, 7805 psu, alarm power supply circuit

12V jacking up the 7805 Regulator

The output voltage of a supply can be increased by “jacking up” the voltage produced by the 7805. The way the 7805 works is this: It maintains a voltage of 5v between output and common terminal. If the voltage on the common terminal is increased (jacked up), the output voltage will be 5v higher. The 7805 always maintains 5v between output and common. The circuit below produces an output of 12v.

Read More Source:http://www.talkingelectronics.com/te_interactive_index.html
Thank you.

Be the first to comment - What do you think? Posted by admin - March 8, 2008 at 1:17 pm

Categories: Power supply Tags: 12V, 7805, dc voltage regulator

5V to 24V DC Variable Regulator by 7805

The output voltage can be adjusted (varied) from 5v to 24v via a potentiometer connected to the common line of the regulator. The input voltage and heatsinking of the regulator must be sufficient for the output voltage and current. The output may not deliver more than 100mA @ 5v due to the heat produced by the regulator if the input voltage is say 24v – 36v. This is one of the disadvantages of a variable power supply if this design.