Power supply HELP!

[LewisM]

I know NOTHING about electronics. NOTHING! Maybe enough to get myself into serious trouble.

Anyway, I had my usual mount power supply go last night. Went to replace it at Jaycar today, and ended up with a switching 12VDC/10A supply.

Now, the rated supply for the mount I use is 12-14VDC, with 3A - will the mount only draw the amperage it needs, or is plugging in a 10A supply going to make the motor board fry?

I can change it over for a 12VDC/2.5A supply instead for the same price :) But my LIMITED understanding of amperage says if a supply can give 10A, but the unit only needs 2 A, then it should be fine and the power supply will be more efficient

HELP - want to get this finalised today

[AndrewJ]

Gday Lewis

Current ( amps ) will only get pulled as required.
The general equation for Power used is P = VI ( where V = voltage and I = current )
If your mount only requires a set power to run it, and you have a fixed voltage, then the current drawn will be proportional to power used.
The one caveat with a more powerful supply is if something goes wrong, it CAN supply more current, which is why you use a fuse :-)
A battery is far worse here as some batteries can supply many hundreds of amps if you get a short, whereas a plugpack cant.

As to efficiency being better, thats harder to determine, as the efficiency of many switchmode units is a function of their loading. That said, the difference between the 2 would probably be negligible for the use involved. soo the 10A unit will be fine.

Andrew

[The_bluester]

One of these?

http://www.jaycar.com.au/Power-Products-Electrical/Power-Supply/Laboratory-Bench/13-8-Volt-10-Amp-DC-Power-Supply/p/MP3097

I would not worry, the supply rating is the maximum output the supply can support, if you only use 3A that is not a problem.

I am using one of these

http://www.jaycar.com.au/Power-Products-Electrical/Power-Supply/Laboratory-Bench/13-8VDC-0-to-12-Amp-Regulated-Power-Supply/p/MP3079

And actually it is the other way around efficiency wise, if you run the supply at a very low percentage of its rated output then there is comparatively greater losses in the supply itself. Whenever I finally manage to build an obs I will probably need more than 12A but until then it makes no sense to pay the money for it, my current gear would draw 5A max and about 3A continuous with the heaters going.

[LewisM]

No, I almost did, but went with this instead:

http://www.jaycar.com.au/Power-Products-Electrical/Plugpacks/Desktop---DC-Output/120W-12VDC-10A-Desktop-Style-Switchmode-Power-Supply/p/MP3241

Wanted to avoid the possibility of pulling the banana clips out.

[AndrewJ]

Gday Lewis

Just for info, nearly all banana plug connectors also unscrew such that you can use spade lugs etc to get a solid join that wont pull out.

Andrew

[The_bluester]

I went the other way and have it in a small enclosure with a small SLA battery. That way if I have a mains interruption the battery floats me over it. I just charge the battery properly now and again with a good multi stage charger to keep it in decent condition.

[LewisM]

Thanks everyone. Very much appreciated.

[LewisM]

New supply works a charm.

I tried charging the old battery for an entire day and night. Disconnected, and it started beeping immediately, so either the recharge circuit is damaged, or the batteries themselves are past use by date. The light on it still works (these are Super Cheap Auto jump packs), so will be handy for setting up and packing up. Connected the multimeter, and was getting VERY inconsistent and low results

[ZeroID]

That battery is dud Lewis, no good hanging on to it. You'll charge it up and go to use it a day later and it will be dead or last about 5 mins. I don't need to do setup or knock down in the Ob but I bought a $15 Led shed light from Bunnings which has a couple of AAA batteries in and after nearly 18 months it is still going. It only gets about 10 mins use at shutdown time but specs say it should give 80 hours from 1 set of batteries. It just hangs on a handy hook inside the door.

[LewisM]

I wrapped some red duct tape around it so as to differentiate it from the GOOD car jump pack. That way, I know to ONLY use it as a light source.

May disassemble it to reduce it to components.