# LM2956 Buck Converter, 12V, and 5V Single Channel Relay **URL:** \ **Category:** General Guidance\ **Created:** [August 13, 2025, 1:24pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061 "2025-08-13T13:24:10Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![astral420](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/astral420/32/1147292_2.png) [@astral420](https://forum.arduino.cc/u/astral420)\ **Post date:** [August 13, 2025, 1:24pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/1 "2025-08-13T13:24:10Z")
Hi all, I am working on a project which involves an LM2956, a 12V female jack, and a 5V Single Channel Relay module. I am planning to use the relay to power a solenoid lock as well but I am a bit confused as to whether I can split the power between the buck converter (which will power my ESP32 through its VIN) and the 5V relay through wiring, or is it actually risky? ---
**Author:** ![kmin](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/kmin/32/1147370_2.png) [@kmin](https://forum.arduino.cc/u/kmin)\ **Post date:** [August 13, 2025, 1:29pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/2 "2025-08-13T13:29:41Z")
All depends on your solenoid and 12V power supply. Which you didn't tell anything about.. Please post current ratings for both. ---
**Author:** ![astral420](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/astral420/32/1147292_2.png) [@astral420](https://forum.arduino.cc/u/astral420)\ **Post date:** [August 13, 2025, 1:33pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/3 "2025-08-13T13:33:31Z")
My bad. The solenoid that I am planning to use is a 12V one 500mA with 0.6A current and power supply wise, I want to use a 12v 2A wall adapter (with maximum 24W) to power both the ESP32 and the lock itself. ---
**Author:** ![jim-p](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/jim-p/32/922840_2.png) [@jim-p](https://forum.arduino.cc/u/jim-p)\ **Post date:** [August 13, 2025, 1:34pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/4 "2025-08-13T13:34:58Z")
Yes, you can power the ESP and relay from the buck. However are you sure your 5V relay will work with the 3.3V ESP? ---
**Author:** ![astral420](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/astral420/32/1147292_2.png) [@astral420](https://forum.arduino.cc/u/astral420)\ **Post date:** [August 13, 2025, 1:38pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/5 "2025-08-13T13:38:47Z")
Umm yeah supposedly if I have it connected by 5V right? But I was confused about the buck also taking the 5V pin as well so my original plan is to split the wiring between the buck converter (so it solely powers the ESP32 and such) and the 5V relay so they both use the 5V pin of the ESP32. ---
**Author:** ![kmin](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/kmin/32/1147370_2.png) [@kmin](https://forum.arduino.cc/u/kmin)\ **Post date:** [August 13, 2025, 1:39pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/6 "2025-08-13T13:39:53Z")
> [@astral420](#): > > is a 12V one 500mA with 0.6A current do you have any specs about "pull-in" current, starting current of your solenoid? ---
**Author:** ![jim-p](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/jim-p/32/922840_2.png) [@jim-p](https://forum.arduino.cc/u/jim-p)\ **Post date:** [August 13, 2025, 1:43pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/7 "2025-08-13T13:43:35Z")
> [@astral420](#): > > and the 5V relay so they both use the 5V pin of the ESP32. No. Connect the 5V buck output to the ESP Vin and also to the 5V on the relay module. > Umm yeah supposedly if I have it connected by 5V right? Depends on the module, some work some don't. ---
**Author:** ![astral420](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/astral420/32/1147292_2.png) [@astral420](https://forum.arduino.cc/u/astral420)\ **Post date:** [August 13, 2025, 1:44pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/8 "2025-08-13T13:44:32Z")
Unfortunately, in the description of the page/shop I am planning to buy it from, it doesn’t show the full specs such as the pull-in and the starting current. But, I can ask by the time their sales rep is online. ---
**Author:** ![kmin](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/kmin/32/1147370_2.png) [@kmin](https://forum.arduino.cc/u/kmin)\ **Post date:** [August 13, 2025, 1:48pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/9 "2025-08-13T13:48:52Z")
It's good to have the specs anyway. Your buck doesn't draw a lot to power esp and relay, so probably 2A supply is sufficient. You need to place "kickback" diode across your solenoid. Like jim-p wrote, not all 5V relay modules are compatible with Esp 3.3V trigger signal. Post a link to the one you are willing to use. ---
**Author:** ![astral420](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/astral420/32/1147292_2.png) [@astral420](https://forum.arduino.cc/u/astral420)\ **Post date:** [August 13, 2025, 1:58pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/10 "2025-08-13T13:58:28Z")
Hmm ok, I guess wiring like this would work? ![schematics_try](https://europe1.discourse-cdn.com/arduino/original/4X/5/2/b/52b21394615332ab3aa0549aeae9d0ee4aae7e02.png) and this is the 5V Relay, I am planning to use: ![5v_relay](https://europe1.discourse-cdn.com/arduino/original/4X/0/9/0/090c121887cbcb3ff49f3ca339c628961269296a.png) > **[1 2 4 8 Channel 5V 12V 10A Relay Module with Optocoupler](https://www.makerlab-electronics.com/products/1-2-4-8-channel-5v-12v-10a-relay-module-with-optocoupler?%5C_pos=1&%5C_sid=18cd08c42&%5C_ss=r&variant=43922027905215%3Fvariant%3D43922027905215)** > > NOTE: Please Select only 5V for Arduino, Orange Pi, and Raspberry PiNOTE: Please Select only 5V for Arduino, Orange Pi, and Raspberry PiNOTE: Please Select only 5V for Arduino, Orange Pi, and Raspberry PiRelays are used to control or switch devices... ---
**Author:** ![Paul\_KD7HB](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/paul_kd7hb/32/1127958_2.png) [@Paul\_KD7HB](https://forum.arduino.cc/u/Paul_KD7HB)\ **Post date:** [August 13, 2025, 2:04pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/11 "2025-08-13T14:04:19Z")
> [@astral420](#): > > I am planning to use the relay to power a solenoid lock Is this lock of the type that needs the current reversed in order to unlock? Or is it spring loaded and your solenoid is UNLOCKING the lock. How much time will you be applying power to the solenoid lock? ---
**Author:** ![astral420](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/astral420/32/1147292_2.png) [@astral420](https://forum.arduino.cc/u/astral420)\ **Post date:** [August 13, 2025, 2:07pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/12 "2025-08-13T14:07:48Z")
It is this one and I am planning to apply power to the lock for like 5-10 seconds > **[12V Solenoid Lock Philippines - Makerlab Electronics](https://www.makerlab-electronics.com/products/12v-solenoid-lock?%5C_pos=1&%5C_psq=12v%2Bsolenoid&%5C_ss=e&%5C_v=1.0)** > > Our 12v solenoid lock in particular is strong, has a slug with a slanted cut and a good mounting bracket. It's designed for a basic cabinet or door. ---
**Author:** ![Paul\_KD7HB](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/paul_kd7hb/32/1127958_2.png) [@Paul\_KD7HB](https://forum.arduino.cc/u/Paul_KD7HB)\ **Post date:** [August 13, 2025, 2:12pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/13 "2025-08-13T14:12:21Z")
Ok, I thought do. Power to unlock. What type of door will this open? Metal or wooden? Do you have the striker plate for the door, so it can push back the locking pin when the door is closed? ---
**Author:** ![astral420](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/astral420/32/1147292_2.png) [@astral420](https://forum.arduino.cc/u/astral420)\ **Post date:** [August 13, 2025, 2:14pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/14 "2025-08-13T14:14:58Z")
It does + the door is metal but for now, this is just a school project (so its leaning more towards a demo rather than something that is going to be used as of yet). Planning on mixing this with an actual application that involves firebase and 2x RC522 readers as well (one for in and one for out). ---
**Author:** ![kmin](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/kmin/32/1147370_2.png) [@kmin](https://forum.arduino.cc/u/kmin)\ **Post date:** [August 13, 2025, 2:26pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/15 "2025-08-13T14:26:40Z")
> [@astral420](#): > > It is this one The description says: "To drive a solenoid lock with an Arduino you will need a relay module fairly good power supply, as a lot of current will rush into the solenoid to charge up the electro-magnet, about 500mA" So If that 500mA is the inrush current, your power supply is ok. > [@astral420](#): > > and this is the 5V Relay, I am planning to use: If that relay is "low-level trigger type", you shouldn't drive it directly from Esp. Use NPN transistor to drive it or use a relay that has high-level trigger or separate pins for coil . ---
**Author:** ![jim-p](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/jim-p/32/922840_2.png) [@jim-p](https://forum.arduino.cc/u/jim-p)\ **Post date:** [August 13, 2025, 2:42pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/16 "2025-08-13T14:42:34Z")
> [@astral420](#): > > Hmm ok, I guess wiring like this would work? Thta's OK but you also need to connect the OUT- to the relay DC- AND the ESP GND > and this is the 5V Relay, I am planning to use: It may or may not work with 3.3V I/O from the ESP There is not enough information on the webpage. ---
**Author:** ![astral420](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/astral420/32/1147292_2.png) [@astral420](https://forum.arduino.cc/u/astral420)\ **Post date:** [August 13, 2025, 2:54pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/17 "2025-08-13T14:54:46Z")
> It may or may not work with 3.3V I/O from the ESP > > There is not enough information on the webpage. I’ll ask through their page and in person by the time I’m buying the materials I need. > Thta's OK but you also need to connect the OUT- to the relay DC- AND the ESP GND Yeah of course. But, for COM, I’ll have that connected through my solenoids positive and for the negative is the NO of the relay? ---
**Author:** ![jim-p](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/jim-p/32/922840_2.png) [@jim-p](https://forum.arduino.cc/u/jim-p)\ **Post date:** [August 13, 2025, 3:11pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/18 "2025-08-13T15:11:01Z")
Like this ![image](https://europe1.discourse-cdn.com/arduino/original/4X/f/d/a/fdab70f42ad0e63b6becca80e48196c70789cd50.png) ---
**Author:** ![astral420](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/astral420/32/1147292_2.png) [@astral420](https://forum.arduino.cc/u/astral420)\ **Post date:** [August 13, 2025, 3:27pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/19 "2025-08-13T15:27:13Z")
1 last question since my barrel jack goes to +in/-in of my buck. Where do those 12v +/- connect to? ---
**Author:** ![kmin](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/kmin/32/1147370_2.png) [@kmin](https://forum.arduino.cc/u/kmin)\ **Post date:** [August 13, 2025, 3:29pm UTC](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061/20 "2025-08-13T15:29:16Z")
To the same point. Your buck has barrel input? [Next page](https://forum.arduino.cc/t/lm2956-buck-converter-12v-and-5v-single-channel-relay/1402061.md?page=2)