G+_Don Hatcher Posted February 2, 2018 Share Posted February 2, 2018 cosmic Ray I'm thinking of using a 12v power supply to power the relay and a 12v to 5v step down to power the controller. Since the controller either has an output of 5v or 3.3v, a transistor will be needed to trigger the relay. Link to comment Share on other sites More sharing options...
G+_Michael Hagberg Posted February 2, 2018 Share Posted February 2, 2018 Don Hatcher He is using a relay module that has built in transistor two LEDs, current limiting resistors and a diode for surge suppression when the relay coil is deactivated. See the photo he posted. Link to comment Share on other sites More sharing options...
G+_John Sullivan Posted February 3, 2018 Share Posted February 3, 2018 Don Hatcher Well, you're right and wrong again. As I mentioned (and so has Michael Hagberg), the relay in question is not just a standalone relay, it is a relay module with other components on the board, some of which do the work of the transistor that you're thinking of. I've been saying that I don't have a 12 v relay module here to test out, but last night I found I do have a 12 v standalone relay (Porter and Brumfield item T7C5D-12), and I also have an Arduino Uno in my parts box that I didn't know I had. I hooked up the Arduino to a computer and loaded up the Blink example, which worked fine. Then I disconnected the computer and hooked the Uno directly to a 12 v power supply ( Pos to "VIn" and Neg to GND). The UNO again worked as expected, without having to convert down the power (the Uno has circuitry onboard to do that) Then I connected the output pin of the Uno (Pin 13) to the coil section of the 12v relay, and the other coil pin back to the power supply Negative. The relay did not click. Earlier today I had gone shopping and picked up a NTE brand reed relay (R56-7D.5-12) which I knew from past experiments the Arduino could drive. I hooked the reed relay coil connections between Pin 13 and GND, and the contact connections in-line with 12v supply and the standalone relays coil. Powering up the Arduino caused the standalone relay to click when the onboard LED on the Uno lit up. I then connected a separate power source and light to the output connectors of the standalone relay, and the light turned on and off in sync with the UNO. So, yes, you're right that when using a standalone relay one needs to use something in between it and the Arduino, because the Arduino does not provide enough current to energize the relay. But in the case of a relay module, nothing extra is needed. Today's experiment also proves my assertion that an UNO can be powered directly from the same 12 v source that energizes the relay, without stepping it down to 5 v. Link to comment Share on other sites More sharing options...
G+_Donald Kloss Posted February 3, 2018 Author Share Posted February 3, 2018 cosmic Ray thanks for the explanation for the other guy I’m actually going to try to do that so I don’t have to use any ubecs to step down the voltage for the arduino, I also just got my 5v relays modules in haven’t had time to tinker with it yet Link to comment Share on other sites More sharing options...
G+_Donald Kloss Posted February 3, 2018 Author Share Posted February 3, 2018 I got my 5v relays modules in and they work as promised right off the arduino 5v and ground pins, the relay fires using the blink test code on pin 13 Link to comment Share on other sites More sharing options...
G+_Michael Hagberg Posted February 3, 2018 Share Posted February 3, 2018 Donald Kloss awesome. Enjoy the world of microprocessors and programming. Link to comment Share on other sites More sharing options...
G+_John Sullivan Posted February 3, 2018 Share Posted February 3, 2018 That's good news. It looks like we're up to 55 comments on this subject (now 56). Not sure if that's a record for this KH Group, but perhaps we can considered the matter resolved? lol Link to comment Share on other sites More sharing options...
G+_Donald Kloss Posted February 3, 2018 Author Share Posted February 3, 2018 cosmic Ray yeah it’s resolved now maybe we will be on kh for questions and answers ? learned a valuable lesson buy from a reputable source ? Link to comment Share on other sites More sharing options...
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