Finder 40.61 relay coil current

Ask QuestionAsked 3 days agoActive 3 days agoViewed 47 times0

Does anyone know how much current this relay needs for its coil to turn on? And what’s its coil resistance? Here is the datasheet: Finder 40.61 It’s a 12v DC relay. And how can I turn it on using a microcontroller PIN?microcontrollerrelayShareCiteEditFollowFlagedited Dec 29 ’21 at 8:50asked Dec 29 ’21 at 8:34Momo1588 bronze badges

• 1There are 25 variants of that relay including DC and AC coil versions. Which one do you want to use? What is the relay coil supply voltage going to be? Edit your question to include that information. – Transistor Dec 29 ’21 at 8:41
• @Transistor Like I said, the relay is 40.61 and coil supply voltage is supposed to be 12 volts. – Momo Dec 29 ’21 at 8:45
• 1(1) How much coil current depends on input voltage. Usually 5V needs 70mA, 12V needs less, for the same power (See reference below). (2) You can use a 3V3/5V0 MPU/SBC GPIO pin to turn on/off, with the help of a transistor, usually NPN BJT. You also need a flyback diode, and an optocoupler, if environment is noisy. (3) Reference: My answer to this EESE Relay Q&A: electronics.stackexchange.com/questions/505318/… – tlfong01 Dec 29 ’21 at 8:57    
• 1@tlfong01 Thanks – Momo Dec 29 ’21 at 9:19
• @Mono, your are welcome. Cheers. – tlfong01 Dec 29 ’21 at 10:37   
• 1@tlfong01. How would an opto help? Optos give galvanic isolation but can still couple fast transients due to their capacitance. – Kartman Dec 29 ’21 at 11:56
• @Kartman, yes, I agree, but optoisolation is good enough in general industrial and medical applications. – tlfong01 yesterday   
• @tlfong01 the relays themselves provide galvanic isolation between the coil and the contacts so the optos add little to the circuit – to exploit the galvanic isolation of the optos would require a separate isolated supply. – Kartman yesterday
• @Kartman, Well, there is (1) back EMF which travels through, conducting wires, including ground wiring, and (2) EMI which travels through air and space. You might like to read my discussion below: (3) Ref: What is back EMF? EESE 2021apr17: electronics.stackexchange.com/questions/562294/what-is-back-emf – tlfong01 yesterday   
• 1@tlfong01 I’m no stranger to these effects. I don’t need to tell you that a well placed diode negates these effects to a significant degree. The voltage is clamped and has a well defined path, so the opto will have little benefit. You’ve yet to convince me how in a circuit with a microcontroller and a relay would benefit from an opto in the relay drive in a correctly designed and laid out circuit. – Kartman yesterday
• @Kartman, Well, I hope this 8 year old EESE Q&A might convenience you. (1) Why are relays so frequently driven by optocouplers? EESE Q&A, 2013feb27, Viewed 22k times electronics.stackexchange.com/questions/59277/…. – tlfong01 21 hours ago   
• 1@tlfong01 – i don’t think that discussion uncovered anything new. Crap design = crap results. I think we’ll stop the discussion here as there’s nothing new to discover. – Kartman 18 hours ago
• @Kartman, OK. Let us stop here. Cheers. – tlfong01 18 hours ago    

Add a commentStart a bounty

1 Answer

ActiveOldestVotes1

Figure 1. From datasheet.

From P=VIP=VI we can calculate I=PV=0.6512=53 mAI=PV=0.6512=53 mA.

^{simulate this circuit – Schematic created using CircuitLab}

Figure 2. An NPN switching circuit.ShareCiteEditFollowFlaganswered Dec 29 ’21 at 9:00Transistor156k1111 gold badges169169 silver badges353353 bronze badges

• Thank you. Can you also see what’s the coil resistance? – Momo Dec 29 ’21 at 9:19
• Do you know the formula that relates power, voltage and resistance? – Transistor Dec 29 ’21 at 10:35
• You are right. Thanks again. – Momo Dec 29 ’21 at 11:48

Add a comment