why did I blow my power adapter??

[max90272]

Hi there,
Couple things...probably related. I'm building a stepper motor driver on a breadboard and somehow the zener diode gets SUPER hot.. I mean it goes from red to almost black.. Is this normal... Then, I blew my 12v power adapter?? What are the reasons why a power converter blows?
Thank you in advance. I am a beginner.

 

[Nigel Goodwin]

Sounds like you wired things wrong, or designed it wrong - the zener obviously went S/C and blew the PSU.

 

[RODALCO]

You probably overloaded the power supply. Polarity of zener wrong ?

Draw the circuit which you were connecting to your PSU.

 

[crutschow]

Zener connected directly to power supply with no limiting resistor?

 

[picbits]

Zener connected directly to power supply with no limiting resistor?

^^^ My money is on that (or the wrong value limiting resistor)

 

[audioguru]

Of course the output of the 12V power supply was shorted by the lower voltage zener diode. Then both got SUPER hot.

 

[max90272]

Why did I blow my power supply (part 2)?

Hi there,
Thank you all who tried to give me some tips yesterday in regards to why my zener diode was super hot, and ultimately why I blew up my 12v power adapter...

I have checked that there is indeed resistor between PSU and diode, and direction of zener diode seems fine (the black line on the + side, right?)

So i decided to take a picture of my breadboard and post it here in hopes that someone can tell me what i am doing wrong. The first file is the schematic that I followed (stepper motor driver) and the other 2 are from my breadboard with a close up on the zener diode. Of course, if you have a lot of time and feel like checking my whole connections, I would really appreciate it also.

One more thing, you will see that the gentlemen who created this schematic decided to use a light bulb as resistor right before going into the + of motor. He said that this way, if you need more current (for bigger motor), you can just change the bulb for a 20w instead of a 4w bulb.

So when i blew my psu, I was running 12v 200ma with an 18watts bulb. The bulb lit up and the motor was buzzing. Then nothing but a burning smell!!!!!

Thank you for your help.
MAX

 

[Nigel Goodwin]

Looking at your breadboard layout it seems to me that you've connected the zener diode directly across the supply, with the resistor doing nothing.

 

[arhi]

that resistor is there just for show afaic. the breadboard is shorting it out, so the circuit is running without resistor to limit the current and the rest you already know, magic smoke ..

EDIT: nigel was faster

 

[max90272]

Why did i blow power supply (part2)

Hi there,
Thank you all who tried to give me some tips yesterday in regards to why my zener diode was super hot, and ultimately why I blew up my 12v power adapter...

I have checked that there is indeed resistor between PSU and diode, and direction of zener diode seems fine (the black line on the + side, right?)

So i decided to take a picture of my breadboard and post it here in hopes that someone can tell me what i am doing wrong. The first file is the schematic that I followed (stepper motor driver) and the other 2 are from my breadboard with a close up on the zener diode. Of course, if you have a lot of time and feel like checking my whole connections, I would really appreciate it also.

One more thing, you will see that the gentlemen who created this schematic decided to use a light bulb as resistor right before going into the + of motor. He said that this way, if you need more current (for bigger motor), you can just change the bulb for a 20w instead of a 4w bulb.

So when i blew my psu, I was running 12v 200ma with an 18watts bulb. The bulb lit up and the motor was buzzing. Then nothing but a burning smell!!!!!

Thank you for your help.

 

[audioguru]

I told you so.
The 12V from the supply is directly across the 6.2V zener diode. The 1k series resistor is not in series with the zener diode.

Why is there a 6.2V zener diode? The CD4xxx ICs work fine when their supply is as high as 18V.

 

[Torben]

Hi Max,

The resistor is doing nothing in that circuit. Check the second photo. The zener is a direct short from +V to gnd and the resistor legs are shorted together.

Put the resistor with one leg on +V and the other leg into an unused row of holes on the breadboard. Then put the zener with the cathode to another pin on the same row of holes, and the anode to the gnd line.

There may be other problems but that's the first biggie I see.


Torben

 

[audioguru]

Double post deleted.

 

[audioguru]

Continued on his second thread.

 

[audioguru]

why are there two threads about this simple problem?

 

[max90272]

Audioguru, there is 2 threads because the first one was placed under someone else's thread by mistake. My apologies, I am new at these forums (and at electronic as you can see). I will try erase the other one.

Torben, thank you for being so clear. When you are a beginner like myself, you need to put it in very precise words which you did wonderfully. I will check that tonight.

Thank you again.
MAX

 

[picbits]

I told you so.
The 12V from the supply is directly across the 6.2V zener diode. The 1k series resistor is not in series with the zener diode.

Why is there a 6.2V zener diode? The CD4xxx ICs work fine when their supply is as high as 18V.

More than likely to stop the gates of the Fets being driven with too high a voltage from the CDxxx ICs

 

[max90272]

Thank you all for the tips.
TORBEN, i did what you said and it all worked out. Clearly I've got basic eletro concepts to grasp properly...

Now i gotta try the control my stepper. It's all over the place.. buzzing and turning... Perhaps some settings in the software (KCAM).
THX

 

[Hero999]

So when i blew my psu, I was running 12v 200ma with an 18watts bulb. The bulb lit up and the motor was buzzing. Then nothing but a burning smell!!!!!

So you overloaded your wimpy 2.4W 12V PSU with an 18W bulb, plus a motor? Of course the PSU will blow up, it's being severely overloaded!