hp f2105 conversion to smd led

[budm]

Re: hp f2105 conversion to smd led

You should set your meter to DC AMP and put it in series with the LEDs to see how much current you are actually drawing through the LEDs.

[klein]

Re: hp f2105 conversion to smd led

they started to flicker at 4.5v and came on dim at 5v
both sets hooked together drew .74 amps on 12.v

[budm]

Re: hp f2105 conversion to smd led

That is a lot of current, that is about 9 Watts, does not sound right. Can I get some info about these LED strings?

[tom66]

Re: hp f2105 conversion to smd led

9W sounds fine for a 21" screen. Much better than 30~40W CCFL.

[budm]

Re: hp f2105 conversion to smd led

I do not drive white LED with steady 350mA, I pulse it. So I am not sure what kind of LED these are, never seen LED suppliers for the products I design that make LED that can handle steady state current that high and no heat sink.

[tom66]

Re: hp f2105 conversion to smd led

You can get 700mA and 350mA LEDs. Likely they are 700mA LEDs in 5050 form factor. They will need good cooling, or they could fail.

[klein]

Re: hp f2105 conversion to smd led

here is a pic of three i cut off the strip it needed to be shorter this is all i know about them. other than they are 12v dc

[budm]

Re: hp f2105 conversion to smd led

http://www.birddogdistributing.com/1...5050-Tri-chip/
SMD-5050 (Super Bright):
Cut Interveral: 4 inch (every 3 LED's)
Bulbs:150 Super bright LED's
Power Consumption: 2.2 Watts per foot (12 LEDs)
Waterproof.

https://cdn.badcaps-static.com/pdfs/...2ed2570c0c.pdf

[klein]

Re: hp f2105 conversion to smd led

i went back in my account and found this from the seller

Waterproof
Led Color: Cool White
Strip length: 0.5m
Size (L * W * H): 500 * 10 * 2.2 mm;
LED type: SMD5050;
LED quantity: 30 pieces / 0.5 m;
Beam angle: 120 °;
Operating voltage: 12 V DC;
Current: 600mA (0.5M);
Power: ≤ 7.2W (0.5M)
Operating temperature: -20 ° to 50 °

[budm]

Re: hp f2105 conversion to smd led

30 LED @ 600mA min 7.2Watts 12VDC? So it has 3 LEDs (connected in series with current limiting resistor) per string, 10 strings in parallel, so 60mA of current per string. You are getting about 320mA per string. Spec that I saw in the link is 150mA max steady state (you can have 3 LEDs in series with 150mA flowing through the string but no head room). So Iam not sure what is going on. I think it may be over driven.

[klein]

Re: hp f2105 conversion to smd led

right now on my work bench with the voltage regulator working both strings are drawing .73 amps isn't that 730 ma ? and the regulator is rated 1 amp oh and there were three leds cut off each string .


so there is 24 5050 leds drawing .73 amps on 12v dc right ?

[budm]

Re: hp f2105 conversion to smd led

That is what I am trying to read the spec ypu provided, it shows 30 LEDS (0.5Meter):
And it only draws 0.6A (600mA).
Spec if you drive ALL 30 LEDs:
LED type: SMD5050;
LED quantity: 30 pieces / 0.5 m;
Beam angle: 120 °;
Operating voltage: 12 V DC;
Current: 600mA (0.5M);
Power: ≤ 7.2W (0.5M)
You are only driving 2 strings (3 LEDs per string) and it draws 0.73A (730mA) total for total of 6 LEDs. so it is drawing 365mA per string, 9Watts of power for just two strings. That does not make sense since 30 LEDs ( 10 strings, 3 LEDs per string) only uses 600mA, ~7Watts.
Am I correct that you are measuring current draw of TWO LEDs strings, each string has 3 LEDs? If you are not using all 30 LEDs, then the power consumption cannot be higher than using all 30 LEDs according to the spec.

[klein]

Re: hp f2105 conversion to smd led

try it with 54 lol see if it works out, two strings of 30 leds - 3 leds from each string leaves 54 leds in two strings

[budm]

Re: hp f2105 conversion to smd led

They can only have 3 LEDs per string for it to work at 12VDC, they cannot have 30 LEDs in series since 12V will not be enough to forward bias the LED on which is about 3~3.25V. So 30 LEDs in series will need power supply higher than 98V.

http://www.maximintegrated.com/app-n...ex.mvp/id/3070

[klein]

Re: hp f2105 conversion to smd led

i am assuming there are two rails running inside theses strings of leds from one end to the other, and every led picks up 12v through one resister my thinking is each 5050 smd is really three leds in one chip.

the break every three chips is just connivance you can cut on the line and solder to the little pads, i think you can buy these in a 16' roll thus shortening up a string where ever there is a place to cut, these end up every three leds about every two inches.