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Help, accidentally connected 24v to a 12v ip camera and now it won't turn on.

Fedx

Nov 11, 2020
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Accidentally connected a 12v IP camera to a 24v poe port and I think I screw it because it won't trun on. Which components should I check first? Picture of PCB in the link attached. (Red is positive and green is gnd) thanks
gTfJgyb


https://ibb.co/gTfJgyb
 

Martaine2005

May 12, 2015
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You should have no problem connecting a 24V device to 12V. It simply may not work and obvious polarity is a factor. Please tell us more.

Martin
 

Fedx

Nov 11, 2020
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You should have no problem connecting a 24V device to 12V. It simply may not work and obvious polarity is a factor. Please tell us more.

Martin

Hi, thanks for replying. The camera is a chinese 36x optical zoom 5 mp ip camera from ebay, its not natively POE supported but the seller told me to buy a POE splitter. I used the camera with its own 12v 4 amp adapter and a cat6 cable for 2 days without any problems but today i wanted to use the poe splitter so i connected everything and plugged my utp cable to my ubiquiti 150w switch, the problem is that the port was setup as 24v passive, after that when i connect the 12v adapter the camera wont turn on and the blue LED inside the adapter starts flashing. As soon as i disconnect the camera the LED stays on, i tried other devices with the adapter and its working fine. Thanks
 

Harald Kapp

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You should have no problem connecting a 24V device to 12V.
But he connected a 12 V camera to 24 V. If he's lucky, only a fuse has blown. But the flashing LED indicates that something else has happened. I guess there is a short circuit in the camera that leads to overcurrent which in turn makes the power supply LED go flashing.
@Fedx : can you open the camera and look for obvious signs of destruction? Maybe take photos an upload them for inspection.
 

Fedx

Nov 11, 2020
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hello, i already took the camera apart but i don't see anything burned or damaged. I tried attaching the image in the first post but i guess it failed so i left a link to the image. I'm trying to reattach the image in this post. I desoldered the AMS117 regulator which btw there are 2 regulators one on top of the other (soldered to the same pads) but i keep getting the failure so i'm hopping that the only components fried are the diodes (i saw 2 M7 1 M3 and 1 that said MB or BM) i'm no electrical engineer so any help or tips would be greatly appreciated since i really like electronics:) i have a reflow station and a good soldering iron and a medium/advanced soldering skills so i would be able to pull out components and solder them back. Thanks!
 

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Harald Kapp

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No obvious signs of destruction visible.
Start by checking the electrolytic capacitors. They are rated 16 V and may have been damaged by 24 V. Although they do not the show the typical signs of overload (blown up cases, leaking electrolyte).
Remove all cables from the PCB except to power input to limit the possible sources of failure to this pcb.
 

Fedx

Nov 11, 2020
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No obvious signs of destruction visible.
Start by checking the electrolytic capacitors. They are rated 16 V and may have been damaged by 24 V. Although they do not the show the typical signs of overload (blown up cases, leaking electrolyte).
Remove all cables from the PCB except to power input to limit the possible sources of failure to this pcb.
Hi, i desoldered the first diode that is marked as "BM" the pcb slot is TVS1 and now when i connect the camera it turns on and the power supply is working fine now (solid blue led not flashing anymore as before) so i guess i need to replace it. Any tips on how to find the exact replacement? Thanks
 

Fedx

Nov 11, 2020
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My . . .my . . .MY ! . . . . . you really DODGED a BIG bullet on that one !

That would appear to be a Transient Voltage Supressor installed across the supply line.
Check out Littelfuse as the BM marking code is referring to one of their 15V units
Make REFERENCE to their SMF series @

https://www.littelfuse.com/~/media/...es/littelfuse_tvs_diode_smf_datasheet.pdf.pdf


73's de Edd . . . . .



.
phew! I hope it was just that component because everything else seems to be working fine, i will try to get a replacement by any chance do you know which kind of devices mainly have those diodes in? I looked all around my arduinos, sensors and in a wireless router but couldn't find a similar diode hehehe
 

73's de Edd

Aug 21, 2015
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I don't think that you will be finding a "freebie" in any other "things" that you have laying around.
 
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