electrickery

[andy230]

hello all.  Stupid question time!

Solar shed, runnning on a 12v supply.  Option to step up to 240v to run strip lights etc.

I have been trying not to use the 240v lights as figured it was wasteful stepping up to 240v (costs 1A).  Then a 60w tube (@12v) = 5A.

I think my 4x12w (thus 1A each) 12v lights may use more power than my 240v strip, even including losses.  There is a small basic charge indicator on the solar power control module.  I think its effectively an ammeter/ voltmeter?

No load= green light= plenty of charge in the battery
4x 12v lights= orange light.  Switch off, goes green again
1x 240v strip= light stays green.

See what I'm saying??

To cut this very long and boring story short, how do I measure current drawn from the 12v supply?  I remember that voltage is measured ROUND the supply.  But is current to be measured IN SERIES??

ie do I connect my multimeter in-line in the postitive side of the circuit, just after the battery.  Can my little multimeter handle a 5A load thru those wee probe wires??

Thank you for advice on how not to give maplins another £20 for a new multimeter...!

a

[Andy M]

An Ammeter goes in the circuit, so yes in series. Good Multimeter wires will handle 5A, so if yours came via Maplins it'll do the job.

Andy

[andy230]

cheers andy   

[Steve Lake]

Hi Andy.....I think you are calculating your consumption for the strip light a bit off center....it is rated at 60w....240v (not 12) thus (using P=VxC) transposed to C=P/V = 0.25A plus your convertion penalty of 1A...total of 1.25A.....which is why your green light stays on...so you can run a second strip light now!!!
cheers
steve

[guest288]

Either that or use some compact fluro's- we're installing some at work at the mo- 230volt GU10 type lamps but instead of halogen they are fluorescents. 50 watt halogen equivolent in these things consumes 11 watts, about 20 seconds startup time but if you left them on constantly they would last 1.7 years! Also as a plus, they emit very little heat compared to a halogen. They use the equivolent of 0.0478A once running. Also they're available in different shades of white...

Try this site:   www.megemanuk.com

Regards, Dave

[andy230]

Hi Andy.....I think you are calculating your consumption for the strip light a bit off center....it is rated at 60w....240v (not 12) thus (using P=VxC) transposed to C=P/V = 0.25A plus your convertion penalty of 1A...total of 1.25A.....which is why your green light stays on...so you can run a second strip light now!!!
cheers
steve

Yep, I hear what you're saying steve, but its still gonna come back to a 12v supply innit??.

Anyway, will post current draw (for the truely bored) after I check it out tonight

cheers! 

a

[Steve Lake]

bet it's a tad over 2 amps......pint?

[andy230]

its NO amps apparently...  think the multimeters shagged.

I even changed the fuse (protects to 10A DC input of the meter) still nothing.

Voltmeter and Ohmmeter works.  But can't get any of the ammeter functions to work...  Oh well, makes no difference, I just wanted to know which was more effective use of my (limited) power.  The 240v fluo tubes certainly give better light.

The ammeter...It never goes in series...  (Or maybe it DID, once, and thats why its goosed?!)

a

[Steve Lake]

series it is Andy.....if it's fused, should be ok...assuming correct rating of fuse.....flourescent will use less power

[guest288]

Sounds like you've done the fuse- you may have one in each of the leads, other than that, it'll be in the meter itself. Try RS components for replacement meter fuses.