Help with 24 led light powered by 12 Volt car battery

[campus189]

I actually just ordered some 3X2 PCB's & I Plan on trying that.
But want to figure this out first

 

[KJ6EAD]

I had hoped we wouldn't run into a current limit problem when we changed the voltage but we did. The easiest way to increase the limit is by reducing the value of the current sense resistor (R1 on your converters). It's 0.22Ω now. You could try reducing it to 0.18Ω or even 0.15Ω. If that doesn't have enough effect, increasing the frequency by reducing the value of the timing capacitor (C2 on your converters) may be enough. If neither of these works, the inductance of L1 would have to be increased. I don't know what the value of your timing capacitor or inductor are presently so it's impossible to determine the effects accurately beyond an educated guess.

You don't have to replace R1 to test some lower values. You can do it by holding another resistor in parallel with it temporarily to reduce the value. For example, a 1Ω resistor in parallel with 0.22Ω would make 0.18Ω and 0.47Ω in parallel with 0.22Ω would make 0.15Ω. You can hold a regular through hole resistor in place by hand since body resistance is high enough to not affect the value.

 

[campus189]

I have 1.5Ω & 1.2Ω resistors, just don't have any 1Ω resistors

I will sort through my resistors & see what I can find & post back results

Wondering if I would have better luck starting with new LEDs rather than messed up ones,lol

**broken link removed**

 

[KJ6EAD]

You could use the 1.2Ω with the 0.22Ω. That would make it 0.185Ω. This is just to see if the current comes up enough to notice.

 

[campus189]

You could use the 1.2Ω with the 0.22Ω. That would make it 0.185Ω. This is just to see if the current comes up enough to notice.

I will do that..
I'll post back results shortly..
Thanks

---------- Post added at 16:41 ---------- Previous post was at 15:33 ----------

Ok,

Tried 1.2Ω with the 0.22Ω.(R1) in parallel.

No change on mA

 

[campus189]

Looks like I fried one of the converters
Down to 6 of them now,lol
Reversed polarity connecting to breadboard

 

[KJ6EAD]

Don't discard the fried converters. The most valuable part of them is the circuit board itself since you can populate it with whatever parts you want to get the desired step-down converter.

Speaking of redesign, since your converter won't source enough current as it is, could you measure it's frequency (probably around 30 kHz)? This can be read across the timing capacitor (C2).

 

[campus189]

You want to measure the good pcb & not the fried one I take it?

 

[KJ6EAD]

You want to measure the good pcb & not the fried one I take it?

Yes, of course. While you're at it, do your inductors have any numbers marked on them?

 

[campus189]

Inductor doesn't have any numbers.
Just the capacitors & diode have numbers

 

[campus189]

Ok, Tried to measure capacitance.
Only has two capacitors.
Discharged the capacitors

C-1 25v 22 uf can't get any reading at all from any of the capacitors on any of the pcb's
c-3 10v 220 uf all pcb's measure between 6.25-6.30

**broken link removed**

 

[KJ6EAD]

Frequency (Hz), not capacitance. Unit must be powered up. C2 is the small ceramic chip capacitor circled in the photo.

 

[campus189]

Holy crap I'm retarded,lol
The other side of the PCB has writing that states C1 & C3
All at 60Hz..
Thanks

 

[KJ6EAD]

Frequency measured at C2?

 

[campus189]

Frequency measured at C2?

yes Frequency measured at C2- 60Hz

 

[KJ6EAD]

That's just the line frequency of your household power. Either you're doing something wrong or your meter is unable.

 

[campus189]

Well, I did follow directions in manual...

Unless the meter is messed up It's brand new.

**broken link removed****broken link removed**

 

[KJ6EAD]

Your meter setup is correct (I have the pdf file of the manual). You need to put the leads on both sides of C2 while the converter is running. These are the same nodes in the circuit as pins 3 & 4 of the IC.

 

[campus189]

Your meter setup is correct (I have the pdf file of the manual). You need to put the leads on both sides of C2 while the converter is running. These are the same nodes in the circuit as pins 3 & 4 of the IC.

Exactly what I did bud
I put leads on both sides of C2 while it was running.
I even reversed test leads to make sure.
No difference

You don't suppose a load on the dc to dc converter would make a difference do you?

Does this help?
DC/DC Converter (Integrated Switch) - Inverting Regulator - MC34063A - TI.com
https://focus.ti.com/lit/ds/symlink/mc34063a.pdf
**broken link removed**

Are you saying to measure pins on the chip?

Switching Frequency(Max)(kHz):100

 

[KJ6EAD]

Exactly what I did bud
I put leads on both sides of C2 while it was running.

Funny, sorry to be so unnecessarily explicit. :wink:

You don't suppose a load on the dc to dc converter would make a difference do you?

No.

Does this help?

No. I have all the datasheets and application notes.

Are you saying to measure pins on the chip?

Pins 3 & 4 are the same circuit nodes as the ends of C2, so either will do.

It must be a meter thing. Try setting your meter on AC Volts on the 400mV or 4V range, then pressing the Hz button.