Question for the electrically minded

[Tony P]

I have one of those Tamiya work benches with the LED lights. I have been using batteries (4xDsize) but want to now use the power adapter option. The instructions say that the power source should be 6V DC at 800MA. Now I have a non-regulating power source that is 6V DC at 1A. Although, when I use this, the LEDS are not as bright as when I use the batteries. Can anyone explain the reason? Is the increase of 200MA the reason? Would a 6V DC 800MA adapter cure the problem? I’d like to avoid having to buy a new adapter but if I can’t get away with the 1A example, than 800MA it has to be.

Thanks in advance.

Tony

[mkimages]

No electrical expert by any means, but my guess would be that your 6V power supply is actually putting out less than 6V. The 800MA requirement of the lamp tells how much current that it draws. Having more than 800 (in your case 1000) simply means that your supply can give more than the lamp wants to take, no problem. If a supply is rated less than the appliance it's hooked to, then you wind up with the supply overheating as it tries to deliver more current than it's capable of.

If you have access to a voltmeter you can check that the supply is in-fact putting out 6 Volts.

Mark

[Alex.B]

I agree 100% with mkimages!

Test your power supply with a voltmeter, and discover the real outpout of it.

And usually, more cheaper the power adaptors are... more difference you have between what is written on the box, and what it really gives.

But is most common the inverse problem, that the little thing gives you more V than what it is supposed to do. I have one that should be 12 V, 8oo mA....

but it's real output is 18 V !!!

[72linerlover]

Hi guys.

There are two factors, beside the effective output voltage, that affect the efficiency of lighting leds.

1. Most of power units provide pulsating current because the mains AC is not rectified in a pure DC output. What is given is the positive and the negative semi wave of the AC. This means that your DC output varies from 0 to +3 and –3 V with the same frequency of the mains. Advanced DC supplies have capacitors inside that perform an almost pure DC.

2 Lighting leds require stabilized voltage. This is sure with batteries, but, once again, more expensive DC supplies solve the problem.

An other fact to point out is that the open circuit measured voltage is always higher than what you measure with the load connected.

As far as I know

Regards

Euge

edited for typo in bold

Edited April 8, 2010 by 72linerlover