Help with 24 led light powered by 12 Volt car battery

[campus189]

Tried on ac volts, pressed range button till it displayed mV on display then pressed Hz button.
I'm getting numbers all over the place...

Tried alternating between pins 3 & 4 as well as both sides of C2, all erratic numbers, nothing consistent.

If you want to give up on this, i'll understand
Getting me upset now

 

[KJ6EAD]

If it's unstable on the 400mV range, it may work better on 4V.

 

[campus189]

If it's unstable on the 400mV range, it may work better on 4V.

Heck, I'm trying everything with no consistent numbers.
I have tried AC & DV
I'll try again in the morning

 

[KJ6EAD]

I checked the spec's on your meter. It needs a bigger signal (500mV) than what's available to read Hz. :sad: The other option would be to measure the capacitance of C2 (power off). I would expect a value around 1-2nF.

 

[campus189]

For some reason I cant get a reading from C2 at all.
Used Ohms setting, got nothing.
Worked on all the other SMD resistors, just not C2 itself.

 

[KJ6EAD]

It's a capacitor, not a resistor.

 

[campus189]

Yes, I know

Having a heck of a time getting any reading from it

When 1st connecting I get a reading of 32.0 M Ohms & it drops like a countdown timer.
The numbers just keep going down.
If I break the connection & reconnect, It starts out at 32. M Ohms.

Re edit....

Hit the select button for nF scale
1st reading -1.84nF
2nd reading -1.93nF
3rd Reading -1.76nF
Hope this helps

 

[KJ6EAD]

That's a reasonable number. The nearest standard value would be 1.8nF which makes the operating frequency ≈21kHz. Let me do some calculating now.

 

[campus189]

Sorry for all the difficulties
New meter, taking a while to figure out ,lol

 

[KJ6EAD]

It should be possible to get enough current by reducing the value of C2 to 220pF which will increase the operating frequency to 75kHz but if that doesn't work, you'll have to increase the size of the inductor. You might find it easier to change the inductor anyway.

 

[campus189]

So, something like this? I take it ?


50v is the lowest I can find

 

[KJ6EAD]

Yes, that's the type, though I can't verify the size (you have the board :wink. 50V is normal for capacitors of that type.

 

[campus189]

Ordered them, when they are installed, I will post results here.
Thanks

 

[campus189]

Ok, replaced with 220pF

 

[KJ6EAD]

What was the result?

 

[campus189]

Having a hard time getting a consistent reading

However draw is now 181mA

 

[KJ6EAD]

Is the inductor getting hot?

 

[campus189]

Is the inductor getting hot?

Sorry for delay in posting. Working double shifts

With 1.5 Ohm resistor
Inductor @ 90 Degrees Fahrenheit
132.7 mA draw
3.0v @ led

Without 1.5 Ohm resistor
Inductor @ 155 Degrees Fahrenheit
190 mA draw
3.2v @ led

Hope this helps

 

[KJ6EAD]

Since the increased frequency is just generating more heat in the inductor, the only thing left to do is change the inductor to a larger value. I'd try 220µH.

This would be a good type if it will fit on the boards: **broken link removed**

Otherwise, something like this: **broken link removed**

You're looking for a 1.5A current rating.

 

[xaccto]

just some notes:
these converters should already be running about 70kHz.
The only chance of measuring the frequency digitally is at pin 3, but it is a sawtooth waveform offset from 0volt, meter may have trouble
reading it....
If you want to increase freq, (and increase current) then you should decrease inductance and you may get lower coil resistance.
try using this equation
Lmin = (Vin -Vsat(sw) -Vout) / Ipk(sw) ) * ton

What current and voltage are you trying to achieve now for the converter?