# Design glitches: Arduino Nano supply voltage **URL:** \ **Category:** DIY STUFF\ **Created:** [May 3, 2020, 10:09am UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795 "2020-05-03T10:09:42Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![fredrik](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/fredrik/32/682_2.png) [@fredrik](https://lookmumnocomputer.discourse.group/u/fredrik)\ **Post date:** [May 3, 2020, 10:09am UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795/1 "2020-05-03T10:09:42Z")
(thought I’d collect my nano supply notes in one place to make it easier to link to) A common design glitch in circuits that use an Arduino Nano is to connect regulated 5 V to the VIN pin instead of the +5V pin. This results in the Arduino running at a lower internal supply voltage, often 4 V or below, which may be a problem if the design depends on analog inputs or digital output levels. Voltages below 4.5 V are also out of spec for the 16 MHz clock used by the Nano. Details below, but TL;DR if you have regulated 5 V, connect it to the +5V pin, not VIN. To see why this happens, here’s the general layout for the onboard power supply on an Arduino Nano: ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/9/9166c47adc54aab2dcc155fe9cd22de319ac1d56.jpeg) The +5V input (pin 27) is connected directly to the main internal 5 V VCC rail on the Arduino. If you provide power via VIN or USB, this is an output. The VIN input (pin 30) is connected to a voltage regulator, which brings the input down to a regulated 5 V. This circuit causes a voltage drop as the current passes through the regulator’s internal circuitry. This drop is typically between 0.8-2.0 V, depending on what Nano you’re using, so if you feed in 5 V here, the “5V” rail (internal and 5V pin) will be at between 3.0 and 4.2 V: - The Arduino Nano 3.2 uses an [LM1117 low dropout linear regulator](https://www.ti.com/product/LM1117), which has a 1.2 V dropout, and internal rail will be ~3.8 V. - Cheap clones often use an [AMS1117](http://www.advanced-monolithic.com/pdf/ds1117.pdf) instead, which has similar specs. - The Arduino Nano Every uses a fancy $3 [MPM3610 step-down converter](https://www.monolithicpower.com/en/mpm3610.html) which can handle higher input voltages (up to 21 V) and more power, and do that more efficiently. It has a dropout equivalent of ~15% of the input voltage, so internal rail will be ~4.25 V. - The older Arduino Nano 3.0 uses a [UA78M05 linear regulator](https://www.ti.com/product/UA78M) with a 2.0 V dropout. Internal rail will be ~3.0 V. You can also power the Nano via USB. In that case, the power goes via a (Schottky) diode, with a voltage drop of ~0.3 V, so the main 5V rail will see ~4.7 V. (conversely, if you need the rail to be exactly 5.0 V, you need to either feed regulated 5.0 V to the +5V pin, or feed 5.0 V plus at least the given voltage drop plus a bit of margin to VIN.) ---
**Author:** ![Dud](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/dud/32/610_2.png) [@Dud](https://lookmumnocomputer.discourse.group/u/Dud)\ **Post date:** [May 3, 2020, 10:21am UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795/2 "2020-05-03T10:21:56Z")
Indeed on the Big Button and the Sequencer the regulated current is connected in Vin. I don’t think I would take them apart to change because it still works well like that, but it’s very good to know for my next Arduino-based constructions thank you ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [May 3, 2020, 11:29am UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795/3 "2020-05-03T11:29:34Z")
> [@fredrik](#): > > It has a dropout of ~15% of the input voltage Not sure what you mean by that and I don’t see the answer in the datasheet. I guess I’m asking what you mean by “dropout”. ---
**Author:** ![fredrik](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/fredrik/32/682_2.png) [@fredrik](https://lookmumnocomputer.discourse.group/u/fredrik)\ **Post date:** [May 3, 2020, 11:34am UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795/4 "2020-05-03T11:34:53Z")
Well, dropout (Vdo) equivalent, if you want to be picky 🙂. Vout is Vin\*Dmax where Dmax is typically 85% (yes, it [took me a while](https://lookmumnocomputer.discourse.group/t/big-button-diy-build-verified/323/90) to spot that too). I translated that to equivalent Vdo to keep things consistent. ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [May 3, 2020, 11:52am UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795/5 "2020-05-03T11:52:14Z")
Ah, I see — this part doesn’t have a fixed output voltage, you select it with an external voltage divider, and that can be up to 85% of the input voltage. Dmax is the maximum duty cycle. I was confused because I was thinking of fixed voltage regulators. ---
**Author:** ![Jos](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/jos/32/151_2.png) [@Jos](https://lookmumnocomputer.discourse.group/u/Jos)\ **Post date:** [May 4, 2020, 9:38pm UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795/6 "2020-05-04T21:38:00Z")
Thank you good Sir, for pointing out that the VIN and +5V pin serve a different purpose. I had an Arduino Nano resetting erratically, and I discovered that I had used the wrong pin to supply 5V to it. ---
**Author:** ![Doolang](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/doolang/32/44_2.png) [@Doolang](https://lookmumnocomputer.discourse.group/u/Doolang)\ **Post date:** [May 5, 2020, 4:08am UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795/7 "2020-05-05T04:08:58Z")
So, I’ve noticed the Big Button doesn’t have enough voltage out to trigger pretty much any drum module I have other than MI Braids. Could changing to 5v make a difference in this case? I was going to attempt to add some op amps to boost the signal., but this would be easier. Probably wishful thinkin”. ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [May 5, 2020, 4:22am UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795/8 "2020-05-05T04:22:05Z")
What voltage do you have now? Putting the output of the regulator onto the +5V pin instead of the VIN pin should give you ~5V gates which _ought_ to trigger any well designed module. “Ought”. “Well designed”. But if not, boosting an anemic gate shouldn’t be too hard to do. A transistor and a couple resistors may be all you need. ---
**Author:** ![sebastian](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sebastian/32/39_2.png) [@sebastian](https://lookmumnocomputer.discourse.group/u/sebastian)\ **Post date:** [May 7, 2020, 1:06pm UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795/9 "2020-05-07T13:06:18Z")
I did also do this mistake on my stripboard for a little arduino synth (basically a clone of a [ginkosynthese seeds](https://www.ginkosynthese.com/product/1070494/seeds-assembled)) And I am wondering now if that may be the issue with my tuning issues… maybe it’s something different, but I could imagine that having a different reference voltage could be a problem here… ---
**Author:** ![Doolang](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/doolang/32/44_2.png) [@Doolang](https://lookmumnocomputer.discourse.group/u/Doolang)\ **Post date:** [May 8, 2020, 10:46pm UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795/11 "2020-05-08T22:46:39Z")
Happen to have any plans or a link for building that? ---
**Author:** ![sebastian](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/sebastian/32/39_2.png) [@sebastian](https://lookmumnocomputer.discourse.group/u/sebastian)\ **Post date:** [May 9, 2020, 2:08pm UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795/12 "2020-05-09T14:08:05Z")
It’s basically this for the output ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/9/9b938a2197c26dc85722a36616bced21fdd0526d.jpeg) Just the things on pin D11. left wire goes to the output jack. The code is in the First link. From this you can make your inputs and potentiometers ---
**Author:** ![Doolang](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/doolang/32/44_2.png) [@Doolang](https://lookmumnocomputer.discourse.group/u/Doolang)\ **Post date:** [May 9, 2020, 7:13pm UTC](https://lookmumnocomputer.discourse.group/t/design-glitches-arduino-nano-supply-voltage/795/13 "2020-05-09T19:13:24Z")
I got part of that. Could you elaborate a bit on the build? Not sure what I’m seeing above. Where do pots and jacks go? Did you find a layout for this somewhere? It’s pretty cool.