Observatory 12v power change?

[Demon Barber]

Hi Michael,just seen your post,i have used this bench power supply for five years with no problems at all ,plenty of reserve capacity for any upgrades in the future.

Link here: https://www.rapidonline.com/rapid-sps-9250-209mg-smps-switch-mode-power-supply-15v-25a-with-digital-display-85-1824

There is plenty of room in the casing to the rear of the unit to add XLR Sockets.

I can highly recommend this product.

Regards

Mike

[JonC]

Just spotted his, and thought it might be handy for power distribution, about £15 from hobbyking, they are pretty good for parts relating to charging and anything 12V. Bit of taps to cover the LEDS would be needed!

https://hobbyking.com/en_us/hobbyking-powerstrip-fuse-protected-power-distribution-board.html

 

 

[michaelmorris]

Thanks for the link to the power distribution panel.  I'm actually putting together my own 12v power distribution hub which is going to be put in the same box as an Arduino-based focuser controller.

It will have a 12v input and 6 x switched 12v outputs.   I have a question about wiring up this power distribution system, is there any virtue in having fuses in this system?  If so, should I have separate fuses for each outlet?

Thanks

[Physopto]

3 hours ago, michaelmorris said:

Thanks for the link to the power distribution panel.  I'm actually putting together my own 12v power distribution hub which is going to be put in the same box as an Arduino-based focuser controller.

It will have a 12v input and 6 x switched 12v outputs.   I have a question about wiring up this power distribution system, is there any virtue in having fuses in this system?  If so, should I have separate fuses for each outlet?

Thanks

I would allways use a fused output for each channel. You then can match the fuse size in mA or Amps  to the item powered by that socket. Also use a fuse  from the live output to everything at either a battery or a mains power supply to limit the overall output. A power supply is limited by its own actual output, but a battery can supply much more current especially if it is a large size (say 100 Ah), enough to fry any wiring and equipment since the short circuit current can be in the hundreds of amps. just a note LiFePo4 types even if small can supply massive currents as the internal resistances are very low.

Derek

[patm]

Ditto on what Physopto said! Fuse everything and choose fuses that are close (but not under) the equipment rating. Fuses can be fast or slow blow so make sure you get fast for expensive electronics. Slow blow is better for inductive loads (motors, transformers, anything that has a big inrush current when first started). Your "main" fuse (between battery and distribution device) should also be slow blow since the device fuses will protect each device.

Here's a war story!

I worked at an ice rink for many years. They bought an Ice Bear electric resurfacer (same idea as a Zamboni). Each wheel has its own drive motor and speed detection bearing. The drivers noticed some jerkiness at times and reported it but nobody considered it a big problem. One day POOF! It died on the ice with a big bunch of sparks and billowing smoke. Turned out the speed detecting bearings went bad and were giving different amounts of current. Eventually the far exceeded the rating of the wiring and fried the entire harness ($60,000 to replace and 9 weeks waiting for one to be made and shipped from Europe).

We discovered it has a single slow blow main fuse but no other current protection at all on the motor legs of the harness. Considering the price of one of these things is well over $100k you would have thought they'd spend a few hundred more to protect each motor leg.

[michaelmorris]

Thanks guys.

So I assume I would need fuses like this.

http://www.ebay.co.uk/itm/5-X-20mm-x-5mm-Fast-Acting-Quick-Blow-Glass-Fuses-1A-to-5A-Superior-Quality-/302183013823?var=&hash=item465b82ddbf:m:mzWGXoMb708Tu0Fl8Q9GOoA

Rather than blade fuses like these

http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p3984.m570.l1311.R1.TR12.TRC2.A0.H0.X1a.TRS0&_nkw=1+amp+fuse&_sacat=0

Is this correct?

[patm]

Those non-clear round fuses are for high voltage and a total waste of money below 120V. You could go with the round fuses and inline holders or with the newer automotive fuses. Just make sure the fuses are covered in some way. Glass/metal exposed to the sky can have shorts due to condensation which doesn't necessarily harm anything but the fuse may not blow until well beyond its rating. While very unlikely you can also get an arc from a short which throws off sparks and sparks can cause fires. Electrical code everywhere demands connections to be in rated enclosures; not so much on low voltage systems but why lose a telescope/obs/house to save a measly few dollars?

By enclosure I don't necessarily mean a big box. Lots of inline fuse holders have nice drip proof tubes you put fuses into and cost just a few dollars.