“How to test LED screen?”

[Peter Chiu]

Re: “How to test LED screen?”

Appreciated for your information.

I came to the office at 5:30 am, I need to modifier 220v (input power) V A meter to dc 12v
and I need to finish this LED tester today, by change to IGBT and some breadboard test and modification.

The prototype look like this (Pics). I call it Mutualism or Parasitism circuits
Bacillary, I will use all my junks to build one.

Yes,LED tester parasite in Samsung 55' LED TV power supply.

An adjustable DC voltage 0-340v ,LED screen tester, with PFC ,IGBT, with DC 0-600v voltage and 0-10A DC current meter....................(i ordered this one) DC 0-600V 10A Voltmeter Ammeter LCD Panel Amp Digital Volt Gauge meter 12V/24V [ D85-3051]

PFC: IC used this one

{Self-talk} Samsung power board BN44-00499A ....%$#%#^%#^....... because I have more than 10 of them.... %$@#%$@^^ ..... Ebay about $5.69.....^$&$&^$.........Yes, I don't know how they pay the shipping ....... ^%#^%....... ^%#^%#^.......
http://www.ebay.com/itm/SAMSUNG-UN55...item27fc681108

Won't reply till tomorrow.

[budm]

Re: “How to test LED screen?”

Why would you need PFC? the testing current is less than 1A (100~300mA range is what you will reading) so you should get meter with better resolution. 100mA at 200V (if the LED needs that high) is only 20W.
As printed on that BN44-00499A, the LED drive volage is 331V @289mA. The outputs are for driving one long strings of LED as you can see that the connector CNL802:

PIN 1 (D1+) & 2 (D1+) are tied together for the Anode of the LED string #1.
PIN 3 N.C.
PIN 4 (D1-) the Cathode of string #1 is connected to pin 6 (D2+) which is Anode of the LED string #2
PIN 5 N.C.
PIN 7 N.C.

PIN 8 (D2-) & 9 (D2-) are tied together, it is the Cathode of the string #2 which is connected 5 current sensing resistors (RL884~888) connected in parallel to the GND return (normally there will be POWER MOSFET connected in series with the sensing resistors and driven by PWM to maintain constant current.
The meter input will have to be isolated from circuit GND, if the power for the meter is not isolated.

[Peter Chiu]

Re: “How to test LED screen?”

PFC is free, come with power board

LED 2 groups 4+3=7

4 strips LEDs each strip has 14 LEDs total on this group LED are 56 LEDs
3 strips LEDs each strip has 14 LEDs total on this group LED are 42 LEDs
7 strips LEDs each strip has 14 LEDs total screen are 98 LEDs
I did light up the screen.

LX27901 is the LED driver IC ,check menu is really helpful.

https://www.google.com/search?q=LX27..._sm=0&ie=UTF-8

2 hours work on meter, I got it work , but I can't read...

How did you power the meter? from power board 12v ...........................

Wow..........Time is running out

[budm]

Re: “How to test LED screen?”

How did you power the meter? it has to be isolated power otherwise you will not be able to measure the current. You need two meters, the isolated AMP meter, and the Voltmeter.
Just think of it as having two FLUKES which runs on batteries so it is isolated, but if you use the power from the board, it is not isolated and I doubt that the meter uses differential probe method.
You did not put the LCD back in place correctly or contaminate the connections that is why the digits are missing.

[Peter Chiu]

Re: “How to test LED screen?”

You did not put the LCD back in place correctly or contaminate the connections that is why the digits are missing.

You're right again.... I did put up side down...now ...is ok........ Thanks......

The meter now, I tested on DC12v ..... the transformer is AC 220V to AC 6v, 12v


But this meter only up to DC199.90V so i order another one.

Look carefully I maybe put the reflector the wrong way, too .who care ......I need to keep going on.....

[budm]

Re: “How to test LED screen?”

98 LEDs x 3.3Vf (typical) = 323.4V, the board spec is 331V so the LEDS are connetced in series to form one long string of LEDs.

[budm]

Re: “How to test LED screen?”

You did not put the LCD back in place correctly or contaminate the connections that is why the digits are missing.

You're right again.... I did put up side down...now ...is ok........ Thanks......

The meter now, I tested on DC12v ..... the transformer is AC220 to AC 6v, 12v

Now check the input (measuring ports) to see any of them are tie to the power supply GND.
So you removed the transformer which is needed to isolated the meter circuit?

[Peter Chiu]

Re: “How to test LED screen?”

Update:

I put meter up side down , it's OK, I will change to other one,late.

Shock twice by DC 394 V, now breadboard time....

[budm]

Re: “How to test LED screen?”

What is that 084 V reading from?
https://www.badcaps.net/forum/attach...2&d=1429895219

[Peter Chiu]

Re: “How to test LED screen?”

8.4 V (from 9V battery) , I use the Samsung power board DC12v(marked 13V )
to power the meter.

the cable is AC cable,which I moved away , to have space to hot glue the meter.

the 500k potentiometer I found burned out light dimmer exactly 500k ohm with switch so I can on/off the power.

[budm]

Re: “How to test LED screen?”

Do you have the meter info that you can upload?

[vinceroger69]

Re: “How to test LED screen?”

maybe this one using post 21 DC 0-600V 10A Voltmeter Ammeter LCD Panel Amp Digital Volt Gauge meter 12V/24V [ D85-3051]
http://www.ebay.com/itm/DC-0-600V-20...-/281631696703

[budm]

Re: “How to test LED screen?”

If that is the one then the max measured Voltage is only 40V per graph 3, and the current mode return is connected to power supply - which is circuit GND of the SAMSUNG POWER supply board.
He also need to watch out where the meter is inserted into the circuit to measure the current.

[Peter Chiu]

Re: “How to test LED screen?”

[Music] https://www.youtube.com/watch?v=qRlGFXl_e1E

IGBT i used from this board ( pic 1) U can find any one but Vce>450V
RJP63F3DPP-M0
Silicon N Channel IGBT
High Speed Power Switching

[budm]

Re: “How to test LED screen?”

100K resistor there, really?
You should analyze and understand the circuit.

[Peter Chiu]

Re: “How to test LED screen?”

You show me, one guy put 100k resistor and 12 zener diodes..
Adjustable voltage 0-354V with my old meter.and 3.3 ohm current limite R need to modified to adjustable . if you have parts, took about an hour to built it .

He said ,I don't believe, so I change 47k look picture..

[The video is belong to my experiment, I have slightly modified the circuit to maintenance 300VDC, I add a 100K resistor in between B+ and 500K , and i add a 24V x 12 = 294V zener parrallel with 500K.

I didn’t use MOSFET because i don’t have on hand i ‘m using FGA25N120ANTD 1200V 25A IGBT , i think any MOSFET will work as long as the Vds can withstand 400V and above.

I’m Using the transformer is design for valve/tube amplifier, having output 230V and 6.3V, the 6.3V winding i use to power the digital voltmeter for voltage and current as well.. the current actually is 1V meter with 1 ohm resistor in low side sense as shunt.]

[budm]

Re: “How to test LED screen?”

Lets see now, 354Vdc output from the main filter cap C1 feeds in to 100K resistor, so at worst case if everything on the right side of the resistor are shorted out to ground return, how much current will be flowing through the resistor? You know simple Ohms law, right? The 3.3 Ohm is not going to do much of the current limiting.
Tell me what you get from your calculation.
Even at 47K, what do you think the current will be?
It really does not matter what you are using in place of the MOSFET at this point, look that resistor (100K, or 47K) you put in the circuit.

[Peter Chiu]

Re: “How to test LED screen?”

[Problem] votage can change from 0V to 350V (DC) but not enough current?

I short the 47k still no enough current . I can't light up 10w LED, stop at dc 7.5V?
can i use 1 ohm? is that Q2 BE reach 0.7 then current limited circuit is on.

I change to 1ohm still the same ,maybe I need to use IRF740

next will change 470k .Maybe R1 not pass enough current ,


Good news change to 1 ohm IGBT shot right away.

[budm]

Re: “How to test LED screen?”

Like I said, did you look at the circuit and understand what that resistor (100K, 47K) does to the circuit? Calculate the maximum current will be allowed to flow?
Simple Ohms law. If you cannot figure that out then you should not even try.

[Peter Chiu]

Re: “How to test LED screen?”

change IGBT everything is ok then I bypass the 47k .....everything go back to original.....
the problem is the led burn out right away.....and the IGBT shorted again. because like U said, current limit is very important I just turn a little the voltage up a lot,10 turns controller may be need...
47k maybe important to limit the current ,otherwise the circuit is simple but easy to run wide , I think that's why? that guy put 100k and 12 zener diodes.

I do have IRF740 in stock (we fix car amp) will try it.
When my hand turn (from 0 to 350v ) is very easy to over drive LED (led is a diode,run wild).

that's why, they sale the tester 1-180v (they voltage is 240v), can drive 1-100 LEDs and you need to turn knob to change current.
[Tips] To drive LED best is current source.
http://en.wikipedia.org/wiki/Current_source

And I think, I hate him.