James Mc Auley
Posts: 2
Joined: Tue Jul 17, 2007 3:21 pm

How to reduce Amperage on 12VDC adapter from 500mA to 50mA?

Postby James Mc Auley » Tue Jul 17, 2007 3:40 pm

Could anyone please advise me if and how, I could easily adapt a 12VDC adapter currently rated at 500 mA to provide 12V DC with an output of 50mA max???
The adapter is intended to replace a lost adapter for powering a cmos camera.

Any advice would be very much appreciated and might even be of benefit to rural folk in one little area of Cambodia if we can get it going.
Fingers crossed,
Thanks,
James

Craig_Bridge
Former Expert
Posts: 1297
Joined: Mon Oct 16, 2006 11:47 am

Postby Craig_Bridge » Wed Jul 18, 2007 7:16 am

No modifications are required beyond making sure the connector and polarity is correct.

An adapter that delivers 12 VDC rated at 500mA maximum current load is capable of delivering from 0 to 500 mA at 12 VDC will happily supply 0 to 50 mA at 12 VDC.

-Craig
-Craig

James Mc Auley
Posts: 2
Joined: Tue Jul 17, 2007 3:21 pm

Thank you for the advice.....one final question please...

Postby James Mc Auley » Wed Jul 18, 2007 12:45 pm

Many thanks for the reply Craig.

We will go with this and see what happens... A last request for your advice before I proceed please: Is there a risk of damaging the cmos camera using the higher rated adapter ie 500mA. It is a mini-camera.

We have little choice at the minute here in any case, so I will find out shortly....
Cheers Craig,
James

Craig_Bridge
Former Expert
Posts: 1297
Joined: Mon Oct 16, 2006 11:47 am

Postby Craig_Bridge » Thu Jul 19, 2007 5:48 am

If you get the polarity reversed, there is significant risk to the camera.

As long as you get the polarity correct and the voltage ratings match which you previously stated were both 12 VDC, the is very little risk in normal operation.

The only additional risks are secondary behaviors like: "Should there be an unrelated circuitry failure in the camera, will 500 mA cause more additional damage than 50 mA might?" This is a non-trivial kind of question that is next to impossible to answer without a lot of destructive type testing using identical pieces of equipment.

12 VDC * 500 mA = 6W. 7.5 W decorative bulbs (older style "Christmas tree" light sets) can produce enough heat to burn your fingers, melt plastic, and catch paper on fire so if something bad happens to the circuitry, so there is probably an increased risk.

How do you mitigate the additional risks, don't leave it plugged in when not in use. Don't leave it unattended. Basic common safety practices for any electrical equipment.
-Craig


Return to “Physical Science”