Timeline for N-channel MOSFET used to control 5V relay from 3.3V ESP8266 pin
Current License: CC BY-SA 3.0
12 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Nov 5, 2017 at 18:27 | vote | accept | ttsiodras | ||
| Nov 5, 2017 at 18:22 | comment | added | Wesley Lee | There are other level shifters with N-FETs other than the one you used such as this one, but they will have the same problem as R3 since they also depend on pull-ups. Other options would be more complicated than just directly driving the relay with your IRLZ44. (Maybe a high side N-FET? Then you would need some sort of drive voltage way higher than 3.3V for the gate..) | |
| Nov 5, 2017 at 18:20 | comment | added | ttsiodras | @WesleyLee Thanks, Wes. I was hoping for a generic solution to the 3.3->5 with n-fets, but understand from the reactions here that there is none. | |
| Nov 5, 2017 at 18:16 | comment | added | Wesley Lee | It's not that there are no good solutions, but (and I'm sorry if this sounds harsh), most sensible people would avoid providing information about how to drive a module that you yourself can't find/provide schematics of. So, no datasheet, no solution. | |
| Nov 5, 2017 at 18:14 | comment | added | ttsiodras | @ChrisStratton "the wrong part for the job" - I take this as an answer that there is no good solution to this problem with N-FETs. Can you post it as such? I respect your experience, and have followed you advice in the past - I just wanted to make sure I am not missing anything obvious. | |
| Nov 5, 2017 at 18:12 | comment | added | Chris Stratton | @ttsiodras - people are ignoring the 3.3v to 5v via an NFET as an N channel device is the wrong part for sourcing current from a higher voltage, and because level translation is tangential to an efficient solution to your problem. | |
| Nov 5, 2017 at 18:09 | comment | added | ttsiodras | @ChrisStratton I am supplying 5V at VCC - depending on IN1 (0/5V) the module connects/disconnects the NO/NC side of the relay. For some reason everyone is focusing on the relay, though - my question stands regardless of relays... From 3.3 to 5V, via an n-FET... | |
| Nov 5, 2017 at 18:07 | comment | added | Wesley Lee | @ChrisStratton - I assumed OP was always providing 5V power regardless of the input signal. | |
| Nov 5, 2017 at 18:05 | comment | added | Chris Stratton | The 3.3v signal input is probably fine, but the relay may need to be supplied something closer to 5v. However, either your original measurement of 5 mA is wrong, or this is not the circuit and component values of your relay module. | |
| Nov 5, 2017 at 18:05 | comment | added | Wesley Lee | Well, you could use a smaller R3, but it will draw more power when you want the relay to be off. I also thought it was strange that 3.3V wasn't enough to switch the transistor on.. but maaybe the base resistor is higher than 1k or, the transistor has low Hfe. Might be worth the try just adding a resistor in parallel. | |
| Nov 5, 2017 at 17:59 | comment | added | ttsiodras | About the p.s: :-) About the rest, if that was the schematic of my relay module, I don't see why the 3.3V of the ESP wouldn't work as-is; the BJT would conduct, no? But TBH, I am still hoping for a solution that doesn't involve opening the relay module - i.e. a circuit that gives a "better" 5V than my puny 3.5V (using the N-FET). | |
| Nov 5, 2017 at 17:48 | history | answered | Wesley Lee | CC BY-SA 3.0 |
