I recently salvaged a mc34063 from a damaged car charger. I experimented with various configurations. I currently have it set up with an external npn. The resistors that attatch to pin 5 dont seem to be changing the output voltage. The only thing that does is when i change the resistor that goes from 2 to ground. I can post the exact component values later today, but i know offhand that im using a 220 uh inductor and thrle resistors on pin 5 are configured for 5 volts (1000 and 3300 ohms) but it usually reads about 3 to 4 or 6.5 to 7.3 volts. Any ideas?

 

Post a schematic.

 

L1 is 220 uH
R3 is 2.2 ohms
C3 is 1 nF
C2 is 1 or 2 mF
R4 is 1000 ohms

R1 is 1000 ohms
R2 is 3300 ohms
But I've also tried
R1 3300 ohms
R2 10000 ohms

 

Looks like output should be 5.375V. What is the load?

 

With the values drawn, the output is 5V,
The formula is 1.25 X ( 1+R2/R1)

So make R2 variable to alter the output.

 

I've been using a 200 ohm resistor as a load, but it does the same thing without a load. I've also been using 9 volts input instead of 12, but 12 yields the same voltage.

 

With the values drawn, the output is 5V,
The formula is 1.25 X ( 1+R2/R1)

So make R2 variable to alter the output.

I have a potentiometer lying around. Won't hurt to try it.

 

Potentiometer (0ish to 100000 ohms) in series with r2 did nothing.

 

Unloaded, the circuit jumps to 6 or 7 volts

 

Unloaded, the circuit jumps to 6 or 7 volts

Are you certain the regulator still works?

Is the filter cap 1000uF (1mF)?

An oscilloscope is handy for troubleshooting switching regulator problems. Do you have one available?

 

The stabilizer capacitor is either 1000 or 2000 microfarads. The 34063 was working a few days ago. Who knows though. I got it from a busted car usb charger. The only part on it that was broken was a punctured capacitor. I can order another one on amazon if I need to though.

 

uraniumhexoflorite

Binary compounds (contains only two types of elements) end in "-ide"

"Hexa-" is the prefix for 6.

And fluoride has a "u".

That said, I like your moniker. There is very interesting chemistry and physics associated with the volatile fluoride compounds.

 

The 34063 was working last week in an external pnp setup. Ill try it out again if i get some spare time today.

 

Using this circuit, i managed to get 5.61 volts out. R1 is 1k ohms and R2 is 3.3k ohms. The odd thing is that when I put 9 volts and 18 volts through, it did perfectly, but when I put 18 volts through an lm7812 and then put the resulting 12 volts through the circuit, the voltage started at 5.61, but then quickly dipped to between 3 or 4 volts. The LM7812 puts out a constant 12.01 volts. Could it be the LM not supplying enough current?

 

The current doesn't seem to be the problem. With a 200 ohm load on the converter, it raws about 20 ma from two 9 volts in series (18 volts), but draws 30 ma from the LM7812 (12 volts). Any ideas on why the voltage drops when the LM is used, but not when the batteries are used?