12vDC to 5vDC 2A converter supply?

[Omaroo (Chris Malikoff)]

Hi all

I'm looking for a place that might sell DC to DC converters with 12v input and 5v output able to handle at least 2 amps but preferably 3. Jaycars' seem to top out at 600ma which is no good. Anyone know of anywhere? I'm trying to make a 12v DC power supply for my SBIG ST.

[pmrid (Peter)]

This is only half an answer I'm afraid but it might be of some help anyway.
I bought a DC to DC converter recently from Super Cheap Auto. The input is 12V DC and the output is variable up to (I think) 19 which is what I wanted to run an old ASUS laptop - which it does very niucely thank you. I haven't got it near me at the moment so I can't tell you any more than that - but it may well be worth a quick visit to your friendly neighbourhood SCA sto0re.

[Omaroo (Chris Malikoff)]

Thanks Peter - I'll have a look on my way past today!

[Omaroo (Chris Malikoff)]

I've been alerted to the TO-220 package adjustable regulators from Jaycar that adjust from 1.2vDC to 13vDC with the help of a couple of resistors of specific values placed across a couple of the legs. Looks like they will supply 3A reliably, so this is great. Only thing is that the data sheet does mention variations at low temperature (which they classify as 0Deg C) so does anyone have any experience with these units in low temp conditions with a device hanhing off that wants to eat 2A at precisely 5vDC?

[bojan]

It will be OK.
The only issue is power dissipation, you will have up to 21W (7V voltage drop x 3A = 21W).
Make sure you mount it on a large heatsink.

However, I think you may be much better off with 12V -> 240V inverter (just make sure it is true sinusoidal output).

Then you can use 240/5V adapters and whatever else goes on 240V.
Your battery will last longer, as there will be no unnecessary dissipation (like with linear regulators) - those inverters (and switch mode power adapters) are very efficient.

[acropolite (Phil)]

I've been alerted to the TO-220 package adjustable regulators from Jaycar that adjust from 1.2vDC to 13vDC with the help of a couple of resistors of specific values placed across a couple of the legs. Looks like they will supply 3A reliably

As bojan pointed out dissipation is very high at maximum current, meaning that these regulators are extremely inefficient. It's also necessary to have a voltage differential, i.e. to get 12 volts output you will probably need 5 Volts higher or more (17+ volts), you can't get 12 Volts from a 12 V supply with a linear regulator.

[MrB (Simon)]

Jaycar has a 25W 12v power supply that outputs multiple voltages. Cat# MP3038.
Unfortunatelly, there's no 5v output, but there is a 4.5v and a 6v.
Do you have a spec sheet for your SBIG?, check if it has min-max voltage ranges.
I'll pull one from the shelf tomorrow and play around with it.

[Omaroo (Chris Malikoff)]

Thanks for the help fellas.

I'm going to power the SBIG from a 12v 80AH deep cycle. I'd use an inverter Bojan, except that the power supply I recieved with the camera is a 120vAC jobbie, not 240. I could use a 240-120 step-down after the inverter but think that there'd be a few inefficiencies creeping in.

I'm now thinking that an AT power supply from a PC might do the job. It needs +5vDC @2A and +/-12vDC at 0.5A. They're nice and regulated switch-mode units and have plenty of power in reserve. Running off my 500W pure sine wave inverter it should work nicely.... I think.

[MrB (Simon)]

Heh, Jaycar has a 12v operated 205W ATX power supply available, cat XC4876
Link

[rsbfoto]

Hi,

I am using power supplies like sold from this company http://www.micropowerdirect.com/ and the model is from one of these http://www.micropowerdirect.com/Page...0Enclosed.html

http://www.micropowerdirect.com/Page...%20MPE25S.html

http://www.micropowerdirect.com/PDF%...-Datasheet.pdf

I know this is an American company but those are built in Taiwan or China

http://www.agspecinfo.com/pdfs/H/HF10W-SL.PDF

They surely must be sold by somebody in Australia

Here you can see them in my control board of my pier

http://www.rainerehlert.com/ObsReal14/Remoto/ROR-20.jpg

[mrsnipey]

You could build one fairly easily using an LM350 which is able to handle over 3 Amps according to the spec sheet. I've only ever used the LM7805 but it has a rating of < 1 amp.

http://www.fairchildsemi.com/ds/LM/LM350.pdf

[rsbfoto]

Hi,

Here http://www.oceancontrols.com.au/ is a supplier of the power supplies I recommended

http://www.oceancontrols.com.au/powe...r_supplies.htm