Power supply to drive 8 5v Relay with microcontroller

[Shahud]

I have tried liner voltage regulator 7805 with wall mount 12v 1A supply to drive 8 5v relay. But on continuous working power supply got burned. Even 7805 was too hot on applying heat sink.
My question is which power supply to select.
Can i use smart phone charger rated 5v 2A?
Or should I use 12v relay to avoid heating of 7805.

 

[dick_freebird]

You could use latching relays and have no continuous
coil current required.

5V reed relays' coil currents vary. You could check for
lower current options.

Relays are pretty forgiving and a supply of convenience
is better than down-regulating one just for that purpose.
Let the uC drive a low side switch (like logic level MOSFET
or BJT w/ base resistor) and the switch pulls the coil from
whatever high side supply you pick.

 

[Audioguru]

A 7805 is a linear regulator. The extra input voltage and the load current causes it to heat up.
A phone charger is a switching regulator that switches on and off at a high frequency so that it does not get hot. Use it for your relays if their total current is less than 2A.
Of course you should use 12V relays that match your 12V power supply.

 

[KlausST]

Hi,

A relay needs current. You don't talk about current. If you want to use this relay then you need to know it's current rating.

Klaus