Hello all,
I have a project with Arduino Mega 2560 and i would like to control some relays (15 relays) but i am not shure how can i do this.
The relay coils are working at 5V and they need a 72mA current.
Can someone please help me with this ?
Many thanks to all
Hi
Use small transistor like BC547 or similar for controlling each relay. With transistors you'd avoid arduino to burn up 'cos of over current. To be absolutely sure add optocoupler also to prevent voltage peaks from primary coil when you'll turn'em off. There are also optocouplers in the markets which you could use without transistor, in other works, optocoupler can stand that 72mA. You'll need one optocoupler for each relay. Transistor and optocoupler should be between ground and relay coil, 5V voltage is attached directly to the coil.
There are relay modules up to 16 channels in ebay for example which are equipped already with transistors or/and optocouplers and you could attach them directly in to the i/o pins of your arduino. I'd recommended to pick one of those is electronics isn't your hobby.. 
Also, you'll have to make external voltage feed for these relays. If you'll try to feed them thru Arduino's 5V supply, you'll propably will burn on board regulator. If all of those relays are pulled at the same time, it will need more than 1100mA which is too much for it.
TommiP
Two TPIC6*595 shift registers with inbuild mosfet switches.
No extra parts needed, except for maybe a decoupling cap across the supply.
Two chips for 16 relays use only three Arduino pins.
Leo..
Wawa:
Two TPIC6*595 shift registers with inbuild mosfet switches.
No extra parts needed, except for maybe a decoupling cap across the supply.
Two chips for 16 relays use only three Arduino pins.
Leo..
Would a shift register not cause intermittent signals and result in relays flickering when they lose their signal? Chances are these relays are simply momentary, not latching.
Shifting in/through bytes is done in the background.
When this is done, a different pin then transfers the data to the outputs.
So no relay chattering when it's done right.
Leo..
I have relay board that is controlled by shift register:
http://www.crossroadsfencing.com/BobuinoRev17/
