LED Backlight Tester model A : The world first battery TV led tester

[budm]

Re: LED Backlight Tester model A : The world first battery TV led tester

I bet if you measure the current when using your tester with 1 LED an when with one big LED string I am sure the current will not be the same and that is problem with simple Voltage supply instead of constant current power supply, and if the string has shorted LED's the you cannot really calculate how many there are in the string.
BTW, what do you mean "yes, its light was very dim. 84*3.3=277.6v and 184v These two have great differences!" You actually measure Vf of 277.6V on the good LED string? 184V at how many mA? I have a feeling that you are driving the LED striking at a lot less than 30mA, power at 184V @30mA = 5.5 Watts! Guess how much current you will be drawing from 1.5V power supply? Does your power supply really has that much power? You need to monitor the LED current.

[capwizard]

Re: LED Backlight Tester model A : The world first battery TV led tester

You're right on.
One led. I tested was 3.2v then went down to 2.7v. Picture1 and 2.

Picture 5 is comparison of two testers. I found out if led tester voltage unstable is the indicator for bad LEDs.

Both Samsung are UN60J620DAFXZA I will open the blinking one to see what's happen.

[capwizard]

Re: LED Backlight Tester model A : The world first battery TV led tester

I opened the blinking panel. let's see what was happened inside. exactly like I predicted those leds were bad. It needs change all the LED strips. 31 leds were good. 53 leds were no good.

[budm]

Re: LED Backlight Tester model A : The world first battery TV led tester

Are those current readings really 0.63mA and 0.1mA? way low.

[budm]

Re: LED Backlight Tester model A : The world first battery TV led tester

https://www.badcaps.net/forum/attach...0&d=1548260585
Are you actually drive the LED's with 100mA with your little testers?

[capwizard]

Re: LED Backlight Tester model A : The world first battery TV led tester

https://www.badcaps.net/forum/attach...0&d=1548260585
Are you actually drive the LED's with 100mA with your little testers?

Small tester only gave 1 to 2 mA. 100ma is another tester. Look at left down Conner tester is over there. Picture1
This is the tester you taught me to use dim contral to change current. I still working on it. Thank you.

[capwizard]

Re: LED Backlight Tester model A : The world first battery TV led tester

Are those current readings really 0.63mA and 0.1mA? way low.

Yes fist read 3.1v at 0.63mA then dropped to 2.7v at 0.1ma. I try to improve that in the future.

[eccerr0r]

Re: LED Backlight Tester model A : The world first battery TV led tester

Those bug zappers are fun, though the one I have is on the order of 1KV or so, at least if it was higher, it'd cause the output capacitor to self destruct. Pretty much a high voltage "joule thief"...

Also note that at least the bug zapper I have, uses 2 "D" (UM1) cells, it's only got a "stun" setting. Run it long enough or a small bug, the bug will die, but usually the first zap is just a stun... I've had flies and moths get back up and fly once more after them getting stunned by the zap.

The death rate for small bugs like mosquitoes have been nearly consistently kill. And the *really* small bugs like gnats sometimes pass through without getting zapped.

[capwizard]

Re: LED Backlight Tester model A : The world first battery TV led tester

I use disposable camera strobe power supplies. 1.5V to around 300VDC.
You can add turns to the primary if you want to run off a higher voltage
I ditch the big electrolytic, and use a smaller 1uF 300V cap.

You can add turns to the primary if you want to run off a higher voltage.

Sorry, I didn't pay attention to this at first time then I found out that is very useful and important tips because I only thought about to reduce the secondary coils turns can low down high voltage but most time transformer's secondary coils are deep inside.

What I'm trying to say is, add truns to Transformer is more easier than reduce the turns, after the HV transformer was done.

This might solve the problem of insufficient current to my Martin TV LED Tester model A.

[budm]

Re: LED Backlight Tester model A : The world first battery TV led tester

The current capability of the power supply has to do with the driver circuit, the transformer rating (I.E. you have 1KVA, adding more turn will not make it more power), the output circuit. Your bug zapper has high output Z.


https://community.keysight.com/commu...haracteristics

https://community.keysight.com/commu...c-power-supply

http://powersupply.blogs.keysight.co...impedance.html

https://cdn.badcaps-static.com/pdfs/...12379bb449.pdf

https://cdn.badcaps-static.com/pdfs/...276779faf1.pdf

https://cdn.badcaps-static.com/pdfs/...992d99cd1e.pdf



https://cdn.badcaps-static.com/pdfs/...4ed2a3b0ab.pdf

https://cdn.badcaps-static.com/pdfs/...f69b3363f8.pdf

[capwizard]

Re: LED Backlight Tester model A : The world first battery TV led tester

The current capability of the power supply has to do with the driver circuit

Bug zapper has a very high voltage output (800v-1000v) even i cut the power source down to 1.5v and took away voltage tripler circuit.

use Bug zipper as an LED tester needs to add a potentiometer in the base of the transistor to limited the output voltage to 300v, for safe to touch, in the meantime it drop down the output current also.

The most ideal method is a customized transformer for this application.


ps: thank you for the Transformer information. I have read it twice.

........................................................................................
references

For a transistor to conduct, the base emitter junction is forward biased. The forward biased voltage causes carriers injected from the emitter into the base (resulting in collector current) and injected from the base back into emitter (resulting in base current).

So for a change in base current, the base and emitter biased voltage must also be changed. In other words, the change in base current actually change the base emitter biased voltage. This change in biased voltage also affects the collector current. Since emitter current is the sum of base current and collector current, it is not hard to see the change in base current affects the emitter current.

We know :

Ie=Ib+Ic

Ie=Ib+ẞ*Ib

Ie=Ib(1+ẞ), or

ΔIe=ΔIb(1+ẞ)

[capwizard]

Re: LED Backlight Tester model A : The world first battery TV led tester

Continue above post

If you want to make more efficiency transformer yourself, there are several videos below for reference.

Which one is better mini inverter !!!! D882 (or) irfz44n mosfet(or)mosquito bat???
https://www.youtube.com/watch?v=V_R5V3uBTVc

How to Make AA (1.5V) Battery to 220V AC Inverter DIY-Circuit!
https://www.youtube.com/watch?v=_sqnCsHDoR8&t=36s

1.5v to 220v inverter
https://www.youtube.com/watch?v=MBiiWmHQUEE

1.5V, 3.7V to 220V inverter | DC to AC inverter
https://www.youtube.com/watch?v=6mq6p3zF5UY