Antique LED tester II

[budm]

Re: Antique LED tester II

Look at your graph scale again, your Volt scale is not right (it is set as linear scale) but you place your Voltage reading at the wrong point on the graph. Your first division represents 0 ~ 264.6, so the next one will be 264.6 + 264.6 = 529.2V, you have it down as 279.4V, the next one will be 529.2 + 264.6 = 794.2V, so on and so on.
100ma 264.6v
150ma 279.4v current is increased by 50% but not the Vf
200ma 287.5v current is increased by 50% but not the Vf
250ma 287.5v typo, should be 294.7 per graph, look at the percentage.
300ma 294.7v typo, should be 302.0 per graph, , look at the percentage.
350ma 302.0v

[eccerr0r]

Re: Antique LED tester II

That makes more sense now, I didn't even notice the errors in the data table.

The graph should be exponential, but it doesn't show it. Even with a resistor, it should still show a slight exponential aspect in it though the resistor will mute the exponential nature.

So if the table is supposed to be

100mA 264.6V (base)
150mA 279.4V (+50mA +14.8V)
200mA 287.5V (+50mA +8.1V)
250mA 294.7V (+50mA +7.2V)
300mA 302.0V (+50mA +7.3V)

If it is exponential as they teach diodes to be, voltage delta should be going down significantly as the current goes up if the independent variable is current. Except for that last sample, the delta appears to be dropping - so this is weakly exponential. There's not enough accurate data to discern exponential versus quadratic however...

[budm]

Re: Antique LED tester II

"200ma 287.5v current is increased by 50% but not the Vf" My typo on this one, I copy and pasted and forget to change the percentage, 150mA to 200mA is 33.33% increase in current.

[capwizard]

Re: Antique LED tester II

MY BAD

This can prove that I am not a robot but the point is that Antique LED tester's current can be adjusted to very precise, because I saw that variac coil is very thick, I thought it was very difficult to adjust Precise current
.
should be this:
100mA 264.6V
150mA 279.4V
200mA 287.5V
250mA 294.7V
300mA 302.0V

but, inside the I-V chart input is correct.

I have an idea, because the high voltage transformer is not easy to find, can i use MOT to make Antique LED tester?

how about this picture 3,4,5,6) programmable variac!

Automatic variac

+ Automatic generation of voltage, no more manual regulation

+ Programmable fixed output voltage 0-300V

+ Programmable fluctuated output voltage 0-300V with 10 speed selectable

+ Separate voltage jump mode

+ Separate switching on/off mode

+ Multi-channel automatic test and judgement

+ RS232/RS485/USB optional

[eccerr0r]

Re: Antique LED tester II

Your graph is still deceptive because the X axis is not linearly spaced. Try setting the graphing program to a scatter chart instead of a line graph if your graphing program can't deal with drawing the horizontal axis as the dependent variable.

But anyway, all you need is a high voltage range CC/CV PSU. You set the current limit to 100mA and the PSU would automatically choose the voltage to pass that much current. No variac needed. A regular bench CC/CV PSU lights discrete LEDs just fine though if it has a large capacitor output it can damage LEDs. (I've used my homemade bench psu to light LEDs without resistors just depending on CC mode, but the main problem being that it's tough to set it to 10mA as I was too cheap to add coarse/fine controls... The larger LEDs that can handle 100mA are easier to light without frying.)

[capwizard]

Re: Antique LED tester II

Money, money, money. Must be funny. In the rich man's world. Money, money, money. Always sunny. In the rich man's world. Aha- aha..... I did check the prices of Laboratory high voltage cc cc power supplies are very expensive.

My next project will be: I want to use a microwave transformer to make the simplest and most dangerous led tester for Africans.

[budm]

Re: Antique LED tester II

So how expensive is the VARIAC you trying to use? You should come up with the BOM so you can see what the material cost will be.

[eccerr0r]

Re: Antique LED tester II

New variacs are not cheap, think of all the copper and iron in it... Also consider the cost of shipping these due to weight. So considering Africans, this is fallacious concern.

You don't need a transformer except for isolation. All you need is a low capacitance dropper doubler circuit, this should be sufficient to light LEDs.

[capwizard]

Re: Antique LED tester II

My sweet dream is broken. you are right, old TV power supply maybe cheaper, I will save this MOT for my next project plasma cutter.

[capwizard]

Re: Antique LED tester II

Update

I made LR8k4 a PCB for heat dissipation. PCB is from LED Strip.

[budm]

Re: Antique LED tester II

https://www.badcaps.net/forum/attach...0&d=1553784372
Only 4.44ma of current?
https://cdn.badcaps-static.com/pdfs/...f24c969b6b.pdf
BTW, the output should be at the ADJ pin, see fig 3-4, you also need some caps.

[capwizard]

Re: Antique LED tester II

I= 1.20v/270ohm = 0.0044A= 4.4ma

But the reality is 10 ma and I didn't know why?

[budm]

Re: Antique LED tester II

That because that connection you made where the output is connected to is wrong, look at your schematic again and then the spec sheet of the IC, the math does not lie, the wrong connection you made is what giving you wrong current.
Always check your works when it does not come out as calculated.

[capwizard]

Re: Antique LED tester II

I double checked, the connections are right?

[budm]

Re: Antique LED tester II

Not component problem, look at your schematic and the spec sheet and see how the constant current connection should be for the output compared to your schematic. The output should be connected to the ADJ pin for it to be constant current source.

[budm]

Re: Antique LED tester II

See how the CC source connection.

[capwizard]

Re: Antique LED tester II

I tried this manufacturer circuit ( picture 4) and I used120ohm has no current output. I even changed new LR8 still the same.

I remember before I used a breadboard to do the experience and that was the best result.

[budm]

Re: Antique LED tester II

I use that CC in hundreds of project, no problem. That CC circuit is common circuit.

[capwizard]

Re: Antique LED tester II

Thank you Mr. budm

This circuit will give a very accurate current limit, my LED current meter hook up has a problem. I used multimeter which has a very accurate reading.

[budm]

Re: Antique LED tester II

Thank you Mr. budm

This circuit will give a very accurate current limit, my current meter hook up has a problem. I used multimeter which has a very accurate reading.

So are you suing this circuit?
https://www.badcaps.net/forum/attach...0&d=1553801842

BTW:"I tried this manufacturer circuit ( picture 4) and I used 120ohm has no current output." So No current and No output Voltage, correct?