I just fried my nano!

Hi everyone, I was just after some advice after seeing my nano go u in smoke: Basically I am running a project which controls a micro servo and a couple of LEDs on separate digital outputs. There is also a couple of switches on separate digital pins and an RFID-20 tag reader. The project has been working perfectly whilst being powered via the USB port. Problems started when I used a 9v battery connected to VIN. The servo seemed to be struggling and doing weird things, but everything else was ok if I disconnected the servo. I thought that maybe the 9v battery was not man enough for the job, so instead I swapped it for a 12v 1A supply into the VIN. This caused the same problem so I swapped back to the battery. I was just resetting the nano when I heard the dreaded pop followed by smoke. Pretty certain i have fried the regulator, as the nano still has limited life via the USB. Can anyone see where I may have been going wrong as I assumed that the VIN could take up to 20V DC and then it would be regulated back to a usable 5v. I bought the nano new from ebayhttp://www.ebay.co.uk/itm/320853660843?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_3567wt_891 for not a lot of money and wonder whether its just a cheap Chinese clone with a rubbish regulator or if these micro servo's draw too much for the nano 5V output to supply.

Any help or comments would be appreciated, as I don't want to fry another one!

You were powering the servo from the 5V line? That would certainly overload the regulator and put spikes on the 5V line.

Don’t power motors or servos from the 5V line ever - motors put high voltage spikes and draw large currents - leading to logic chips either blowing or reseting. Use a separate supply for servos - 6V battery pack is commonly used.

The on-board regulator can take 20V on the input for light loads, but with a servo it’ll have to pass an amp or two when the servo is active, and from a 12V PSU there’s 7V to drop across the regulator. 7V x 1A = 7W = fried instantly. With a regulator you have to not draw too much current, not feed it too high a voltage, and not dissipate too much power in it. All 3 are vital.

You could have used a separate 5V regulator on a heatsink for the servo for instance, or a DC-DC converter with extra output decoupling, the nano’s regulator is not large enough to dissipate much power - it should have simply shutdown though, so I’m rather surprised it blew.

Hi MarkT, Thanks ever so much for enlightening me on the subject. I was aware about voltage spike from motors causing problems but didnt realise it also applied to tiny servos. I have also had a recollection that I may have manually moved the servo arm pretty quickly whilst it was connected to the nano. Could this have sent a spike? I must have just assumed because most of the servo tutorials power the servos straight from the arduino 5v, I assumed that the nano could cope with the same setup. Is the nano regulator inferior because its smaller and would a duemilenove cope better? I have desoldered the nano from the PCB again now to reveal a nice hole in the top of the regulator so I think is defo toast! The project I am doing requires that I use battery power to control the whole thing. Is there anything that you could recommend to power the servos that doesn't take up much space (ideally about the size of a 9v battery).also do you know of a part suitable part number for the regulator? Sorry for all the questions, but your advice is very much appreciated!

Thanks in advance.

Hi

I drive my motors with this layout. http://www.arduino.cc/playground/uploads/Learning/relays.pdf

I change the relay to a motor and it works perfekt. And i can use an external power supply/battery to drive the motors. (large transistor rekommended)

Maybe its different for servos but some usefull info.