Arduino pro mini - program failure at 9V - Page 1
Forum section: electronics / general

author: mtdoc
author_rank: Super Contributor
timestamp: October 25, 2015, 07:19:37 pm
content: So I'm putting together a Star Wars Jawa costume for one of my sons for Halloween. I decided to jazz it up with some LEDs and for the sake of speed and simplicity resorted to using one ofthese Pro Minis- doing a slight modification ofthe stock "Knight Rider 3" sketch- just adding a momentary switch to be able to turn on the effect.For some reason the sketch will not run when the supply voltage is greater than about 8 volts. I plan on powering it with a 9V battery. The problem was easily solved with a voltage divider but I don't understand why it wouldn't work with 9V. I've powered several Pro Mini projects with 9v in the past without issue.I'm sure there's a simple explanation that my amateur brain is missing. Thanks to anyone who can enlighten me.

author: dadler
author_rank: Unknown
timestamp: October 25, 2015, 07:27:50 pm
content: How much current is your circuit pulling?

author: miceuz
author_rank: Frequent Contributor
timestamp: October 25, 2015, 07:30:36 pm
content: Check the voltage on the output of the regulator. Usually regulators on those boards are swept from a factory floor somewhere and don't meet specs at all. As a workaround, get yourself a dc - dc buck module from the same source and power the Arduino board via it to 5V directly.

author: mtdoc
author_rank: Super Contributor
timestamp: October 25, 2015, 07:31:53 pm
content: Quote from: dadler on October 25, 2015, 07:27:50 pm20-30mA

author: mtdoc
author_rank: Super Contributor
timestamp: October 25, 2015, 07:37:51 pm
content: Quote from: miceuz on October 25, 2015, 07:30:36 pmThat's a good point. I should have thought to check that - it didn't occur to me that a faulty regulator would cause that kind of failure (though it should have. I'll look at that the next time I fire it up.I solved the issue with a voltage divider dropping the battery voltage to 7.5V or so. It only has to work for a few hours on Halloween....

author: LabSpokane
author_rank: Super Contributor
timestamp: October 25, 2015, 10:21:32 pm
content: Have any 78XX series voltage regulators lying around?

author: miceuz
author_rank: Frequent Contributor
timestamp: October 26, 2015, 10:52:26 am
content: Quote from: mtdoc on October 25, 2015, 07:37:51 pmVoltage divider is a pretty lame solution - it's either very high impedance (can not provide enough current) or very wasteful. Just use an LM7805 and power arduino directly to 5V pin.BTW, how are you switching LEDs? Sourcing current from Arduino pin?

author: obiwanjacobi
author_rank: Super Contributor
timestamp: October 26, 2015, 11:30:01 am
content: You are powering it on the RAW pin, right....(just checking)

author: mtdoc
author_rank: Super Contributor
timestamp: October 26, 2015, 04:49:41 pm
content: Quote from: miceuz on October 26, 2015, 10:52:26 amI agree - it's not the optimal solution. But the whole idea of this was just a very small, quick solution to fit in a very small form factor - to be strapped to a 9 yr old's arm for a few hours of trick or treating. I've got a whole bin of voltage regulators but using one would mean a bigger form factor.QuoteYep - see the "knight rider" link in my first post.This is not intended to be a finely engineered project - just something I put together in an hour one evening.Thanks for everyone's ideas.

author: mtdoc
author_rank: Super Contributor
timestamp: October 26, 2015, 04:50:59 pm
content: Quote from: obiwanjacobi on October 26, 2015, 11:30:01 amYep. Thanks.

author: Seekonk
author_rank: Super Contributor
timestamp: October 26, 2015, 06:12:12 pm
content: Nice to know it will still work to that voltage and not explode. I was given an item with a 3.3V micro in it that didn't work. I powered it up to 12 volts and did some testing. The 3.3 regulator was supplying 11V to the micro. Replaced the regulator and it has worked fine ever since. Never thought that was possible for a 3.3V device to survive that much voltage.

author: LabSpokane
author_rank: Super Contributor
timestamp: October 26, 2015, 06:23:21 pm
content: MtdocIf you need it, I can send you an APM out of my stash. It would likely make it there before the end of the week.

author: mtdoc
author_rank: Super Contributor
timestamp: October 26, 2015, 06:29:34 pm
content: Quote from: LabSpokane on October 26, 2015, 06:23:21 pmThanks for the offer. I actually have a stash of them. This one is actually working fine with my current bodge solution - so I haven't been bothered to change it out.

author: Wilksey
author_rank: Super Contributor
timestamp: October 26, 2015, 06:38:43 pm
content: Does the micro power up or does the regulator go into "over voltage protection" mode?