Deleted member 115935
- Joined Dec 31, 1969
- 0
Take the famous step back,
the 7805 is a LDO voltage regulator.
To a first level, It acts as a variable resistance to keep the output voltage constant.
your putting in 24 volts, and dropping that to 5 volts,
so across the "variable resistance" of the 7805, you have 19 votls,
Good old Watts = Volts * amps.
Say your relay needed 100 mA , then that 100 mA has to go through the 7805.
19 volts times 100 ,A is 1.9 Watts,
So to make the 7805 cooler, you need to either lower the current going through it, or lower the voltage going into it.
Personally, as has already been mentioned,for anything more than a few mA , I'd be looking at a simple DCDC to get me 5v from 24 v,
These are simple to use option
https://www.digikey.co.uk/product-detail/en/recom-power/R-78E5-0-0-5/945-1648-5-ND/2834904
many others around, and from other suppliers.
The other point I think I pick up, is your using a micro controller, Im guessing an Arduino, and want to control the relay.
If I read that right,
then this might be of use
https://www.instructables.com/id/Driving-a-Relay-With-an-Arduino/
the 7805 is a LDO voltage regulator.
To a first level, It acts as a variable resistance to keep the output voltage constant.
your putting in 24 volts, and dropping that to 5 volts,
so across the "variable resistance" of the 7805, you have 19 votls,
Good old Watts = Volts * amps.
Say your relay needed 100 mA , then that 100 mA has to go through the 7805.
19 volts times 100 ,A is 1.9 Watts,
So to make the 7805 cooler, you need to either lower the current going through it, or lower the voltage going into it.
Personally, as has already been mentioned,for anything more than a few mA , I'd be looking at a simple DCDC to get me 5v from 24 v,
These are simple to use option
https://www.digikey.co.uk/product-detail/en/recom-power/R-78E5-0-0-5/945-1648-5-ND/2834904
many others around, and from other suppliers.
The other point I think I pick up, is your using a micro controller, Im guessing an Arduino, and want to control the relay.
If I read that right,
then this might be of use
https://www.instructables.com/id/Driving-a-Relay-With-an-Arduino/