S8V3A Step UP Step Down regulator problems

Well I just ordered and received 5 of these regulators and I wanted to say thanks for the super fast shipping. I have used the other 5V boost regulator NCP1402 with great success on a geiger counter using a 3.7V 3000mah lipo battery with a USB charging circuit. It works flawlessly as the Geiger runs great at 5 volts.

For this regulator my plans were to use it with 4 eneloops in series and because when they are fully charged, they can measure as high as 5.8 volts, and the uc on the board of my geiger counter maxes out at 5.5v or there abouts, so I wanted to have a regulator to keep it from going up or going down in voltage and keep it at a steady 5.5 volts.

Well, after installing it as I believe it should have been and setting the voltage to 5.5, I began to smell that horrible plastic burn smell that we all dread, and sure enough I think my GC is fried. The chip and many of the components on the board were all super hot, even the regulator was hot enough to fry an egg on it. Now nothing is working on the circuit even after waiting for it to cool down.

I don’t know why this happened, as I did make sure of hooking it up in the correct polarity. Maybe 300mah is too much for it? I don’t know cause the other reg was working fine and it is 200mah.

Now I am worried about trying it again as I have another kit that needs a regulator, but I wanted to boost the voltage up to 9 volts as that is what drives that geiger counter.

Please advise, help!

As it turns out, that one regulator out of 5 was a defective one, because the second one I hooked up is working as designed. It is not hot at all either. The defective one only went up to 5 or 6 volts, and this one goes all the way up to 12V. Hopefully the other 3 are good too. I guess maybe I deserve a replacement from Pololu?

Also, good news on the dead Geiger. I replaced two out of three chips on the board and its starting to come back to life. I have the last one on order as I didn’t have a spare mega AT 328. Hopefully, after that it will be as good as new. To be continued.

Just in case anyone else was following along, Dave and I discussed this issue via email. I ended up recommending that he use one of our boost regulators (791 or 799) if he wanted to boost to 9 V (so that the output voltage is always higher than the input voltage), since the boost regulators are somewhat more efficient than the step-up/step-down regulator.

- Kevin