Jump to content
spirilis

12V MOSFET Cape

Recommended Posts

Ok so here's a project I did to scratch my own itch... I have two surveillance cameras outside that, while they do have WiFi, they suck. One of them seems to lose connectivity and go out to lunch on a whim, the other is a bit better but a lot better if the first cam is shut off. My long-term plan is to run ethernet to them, use PoE injector dongles to supply their power, and have a BBB plus small ethernet switch provide a WiFi-to-Ethernet bridge outside my house. With the BBB having the ability to power-cycle the cameras if they misbehave.

That last point...... brings me to this. Featuring the Fairchild FDS6675BZ P-channel MOSFET (PowerTrench), it allows 12Vin and switches up to 4 12V outputs. Header on the lower left is meant for a 5V regulator (I have some switching buck-converter regulators -- see http://www.mouser.com/ProductDetail/Murata-Power-Solutions/OKI-78SR-5-15-W36-C/?qs=sGAEpiMZZMtwaiKVUtQsNemMZL4TplJBqOl7845nWHA%3d ) which supplies the 'Bone.

post-1-1426469113339_thumb.jpg

The switching regulator I use for the bone works at 7-36Vin, but the FDS6675BZ has a D-S breakdown of -30V and gate-source of +/-25V, so I wouldn't use this for anything over 20V. My surveillance cams all have 12V adapters anyhow so that's what I'm using.

Main 12V rail PCB trace was spec'd for roughly 5A worth of load from input to far end. FETs rated 11A I think.

PCBs are available for sale if anyone's interested (got 9 extras)! PM me. $5+shipping/board (shipping is usually $3 for USPS+tracking, $2 without tracking to USA). If anyone wants one fully assembled, let me know and I'll come up with a suitable price for those... I don't have extra parts in stock to do them all up atm so it'd require a mouser order to stock up first.

FYI there are EEPROM pads on the back although I don't populate them for my own uses. There is a resistor array (10K x 4) on there that I will populate since I have a bazillion of them in my parts bin and not everyone keeps those around. The rest (C2 0.1uF and R8, R9 4.7K I2C pullups) are 0805-sized SMD pads, along with the SOIC-8 EEPROM footprint.

Share this post


Link to post
Share on other sites

Finally soldered the cape up completely & powered it using a 12V lead-acid battery:

 

post-4-142646911337_thumb.jpg

 

Should have tried a better angle to get the blue LEDs, but, it did indeed boot up per the power LED and GPIO LED blink patterns.  Didn't have my console or network hooked up, just wanted to make sure the power supply circuit worked :)

(note how my WiFi dongle and SD cards were removed in case I fried something... LOL)

 

Next task is to test the switching with GPIOs.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...