I am new to Arduino and this Forum is hope I am in the right place. I am using Uno R3 to control 12 relays on opto-isolated boards. The Uno is powered through the barrel jack. They are 5-volt relays. In a previous post (June 2022), it appears that if the Uno is powered using the barrel jack, the relays will likely draw too much current from the Uno’s regulated power supply. I seem to confirm that as my breadboard test, while working, results in some heat on the back of the Uno. I am currently powering the relays from the 5V terminal on the Uno. I have access to a 5-volt regulated power supply. Would it be OK to power the Uno with that supply and feed it into the Uno via the 5v terminal? I am confused that I can take power off that terminal or use it to power the board. Thanks for any advice.
Stop doing that immedeately.
What's the other data for that power supply? You need to think about the current needed for both the controller and the relays.
That's wasting energy but can be used. What's the source?
Activating all 12 optos at the same time can be too much load for the Arduino. The recommended combined output is 200mA.
What is the part number of the relay modules?
If you keep doing this I expect you will be buying more Arduinos to replace the fried ones. Use an external power supply for all loads, with the exception of a LCD and a few small loads.
This should save you some money:
Gil's Crispy Critter Rules, they apply to processor hardware:
Rule #1. A Power Supply the Arduino is NOT!
Rule #2. Never Connect Anything Inductive to an Arduino!
Rule #3 Don't connecting or disconnecting wires with power on.
Rule #4 Do not apply power to any pin unless you know what you are doing.
LaryD's Corollary's
Coro #1 when first starting out, add a 220R resistor in series with both Input and Output pins.
Coro #2 buy a DMM (Digital Multi-meter) to measure voltages, currents and resistance.
Violating these rules tends to make crispy critters out of Arduinos.
Hint: It is best to keep the wires under 25cm/10" for good performance.
The opto coupler of a common relay board only draws 2mA.
So you can have a relay on each Arduino pin.
The problem is relay coil current. That's about 75mA per "active" (5volt sugar-cube) relay.
Opto isolation is usually not enabled by default, and requires specific a wiring scheme.
And if you need opto isolation, then you need two separate supplies. One for the Arduino, and one for the relay coils. And no shared ground between Arduino and relay board.
If you don't need opto isolation, then you can power both relay board and Arduino on the 5volt pin. You must however disconnect the 5volt link to the Arduino when connecting to USB to upload new code. Post a link to that 12-relay board.
Leo..
With what voltage?
Post a picture with details of the hardware set up.
Yes, that's fine.
5 v Powers supply good for at least 2amp The barrel plug source is a wall wart 9 volts 600 ma. From all of the responses, it appears I may use the same 5V supply to power Uno and the relays. The issue will be what ground I use. The relay boards have the normal Vin and Gnd pins in addition to the trip pins. mancera1979 wants a part number for relays. No idea, got them on eBay. Actually they are an 8 bank and a 4 bank.
9 v 600ma
See my reply below, How do I not have a shared ground unless I buy a second power supply? Have seen some circuits on the Internet that use the same 5V supply, both use the same negative side of the power supply that goes to ground. Thanks
No idea I got them on eBay. Actually there are two sets one is 8 relays the other is 4.
No idea I got them on eBay. Actually there are two sets one is 8 relays the other is 4.
Thank You.
Thanks to all for the great information and advice. I believe you solved my issue. A great forum for answers.
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