5v 8 channel Relay to control 7 house fans

Hello, im new to forum and new to electronics im currently creating an art project and i have hit a dead end.

i am using a http://www.ebay.com/itm/8-Channel-5V-Relay-Module-Board-Shield-for-Arduino-PIC-AVR-MCU-DSP-ARM-US-Stock-/360717697832?pt=LH_DefaultDomain_0&hash=item53fc734328

and am wanting to control 7 house fans switching them on and off.

however the way i have configured them i seem to only be able to power 2 of them before the relay looses power and can't open to switch the 3rd on.

i am using no external power but i feel i should be?

i am connecting

  • ardunio dig pin 7 to channel 1 on the relay
  • gnd on the ardunio to the ground on the relay
  • and using the 5v from the ardunio to run the VCC

the ardunio is an uno?

i also made this today in the hope it would help but it doesn't seem to open the relays just keeps the light on?



Your power supply may not be able to supply the current to activate multiple relays. You may need a bigger (higher current capacity) 5V power supply.

Each relay requires a little less than 100mA and there is some additional current for the LEDs & transistors on the board. With all 8 relays activated, you are getting close to 1 Amp.

Does Relay-3 work by itself? Maybe that relay (or it's associated circuit) is bad.

Do you have a multimeter to check the 5V?

How much voltage are you running into the Arduino? A higher voltage means more voltage drop across the Arduino's 5V voltage regulator, so it will overheat (and possibly shut down) with lower current when the supply voltage is higher.

can you recommend a good power supply that i can use as im currently just using the 5volts from the arduino?

i have seen on video's people using buck converters like these http://www.amazon.com/DROK-Switching-Regulator-Adjustable-Stabilizers/dp/B00BYTEHQO/ref=pd_sim_e_53?ie=UTF8&refRID=150YT21AKCMYYYBN7HCK

but im unable to see which pins they are connecting too.

yeah all the relays work by themselves it's just as soon as i turn on the power for fan 3 it isn't able to close/open the relay.

the arduino is just being powered by my laptop usb voltage.

I use the 1A and 2A supplies from here all the time. http://www.dipmicro.com/store/index.php?act=viewCat&catId=690

CrossRoads: I use the 1A and 2A supplies from here all the time. http://www.dipmicro.com/store/index.php?act=viewCat&catId=690

so you think 2amps will be enough to drive 7 relay channels at once possibly?

also do you know what pins i would need to connect a power supply to?

or is this to power the arduino itself?

  • Cheers for your help so far people!

2 amps should be more than enough.

Search "5 volt power adapter" on ebay, amazon, etc will turn up lots of results.

and this is to power the Relay directly is this connecting to the JD vcc jumper?

sorry for the array of simple questions.

Found this in another forum is this what i should be doing?

can i use the power from my usb connection instead of using dc to power the arduino and then using a 5v dc to power the relay?

  • Cheers Aaron