Fuse on inputs of Pixie 4 & Pixie 8 boards

[MattJ]

Hi Folks

I think I've missed an important component in building my first controllers. 

I have the regulated 12V output from my power supply running directly to the input on the pixie boards.

I was reading some stuff about power injection (next project) and it made me think about fuses on the input to the pixie board. 

Do I need to - or should I as a good practice - include an inline ATC fuse on the +ve input to the pixie controller. 

If so, what size fuse is needed? The Pixie Specs (page 46) say that Pixie 4 has a max draw of 16A and pixie 8 has a max draw of 32A, but has dual 12V input.

So if I put a 20A inline fuse on the Pixie 4 and a 20A fuse on each of the inputs to the Pixie 8... I'm good... right?

Thanks in advance!

Cheers MattJ

[k6ccc]

You can, but I think most of us don't.  If you put a fuse at or near the input to the Pixie, the only thing you are protecting against is a massive short in the Pixie itself or the PC board in the Pixie shorting to a metal enclosure.  The power supply is most likely fused (often hidden on the board - not overly user accessible) so that will protect the wiring between the power supply and the Pixie.  The one exception to this is if you are powering multiple controllers off of a really large power supply (battery comes to mind), then yes, I would fuse it as close to the power source as possible.  A car sized battery can source hundreds or thousands of amps, so yes, you want to protect your wiring for that.

Many of us have the power supply in the same enclosure as the controller, so there is not much to protect.  I have a couple places where there is many feet of heavy wire from a power supply to a controller (longest is almost 60 feet), so yes, I fuse that near the power source.

 

[TheDucks]

You must be looking at  2nd Gen Pixies (have fuses at the Outputs. (Gen 1 fused the input).

If you have a solid (good) board mount and protection, it may be moot to fuse the input.  BUT absolutely fuse the injections  AND break the + (ONLY) lead between sections to prevent back feed

Fusing protects the wire and traces

[MattJ]

3 hours ago, TheDucks said:

If you have a solid (good) board mount and protection, it may be moot to fuse the input.  BUT absolutely fuse the injections  AND break the + (ONLY) lead between sections to prevent back feed

Jim + TheDucks - Thank you both. Yes PS is in the same enclosure as the pixie board I would consider both well mounted and protected.

100% will fuse the injections. A realization that a fuse there was a must, was what lead me to this question.

A big "10-4" on breaking ONLY the +ve.

I was following this link posted by somebody last year. Good info 

https://www.doityourselfchristmas.com/wiki/index.php?title=Power_Injection

I'm waiting for a few more connectors to come in the mail and then we'll see if this flies... or fries! ;)

[MattJ]

In the end - I fused the 12V power injection line only and it all seems to be working fine. 

On a string of 133 CCBIIs on a 15ft extension, my voltage had dropped to 8.1 volts after the last bulb. I injected the power after the first 50 CCBs and, with that power injection, the voltage only drops to 11.4 volts after the last bulb!!

Now my days are merry and bright and all my Christmases are white (and not an off pink color!) ;)

Thanks folks