Hi All ,

i have made a mistake and need to discuss the result with you ,

i have made a new pcb for controlling stepper motor but i forgot to put the diode between the emitter and the collector of the TIP120

that burnt the microcontroller 16f84a

could you please tell me what is the purpose of the diode in the tip120

and how my microcontroller burnt although i have the buffer 4050

what will happen when i neglect it

here is the original the schematic in case you would like to see it

http://www.imagesco.com/articles/picstepper/03.html

 

According to your link:-

From this it looks like you risk destroying the transistors, what makes you think you "burnt" the uC?

 

Maybe I'm misreading it, but I thought that meant the exact opposite: that on transistors *without* the internal diode, you'd risk blowing the transistors, but that the TIP120s include it internally and so should be safe. The second paragraph on the linked page has a sentence in boldface specifically stating that you don't need to include the snubber diodes.

So I don't know yet what's wrong here, but I'd look somewhere else first.


Torben

 

It's far better to put a diode across each of the stepper motor coils.

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those diodes are there to clamp the collector to diode voltage drop. i WOULD PREFER THE DIODES TO BE PUT ACROSS THE COIL as opposed to across the transistor. the question that remains are the diodes fast enough to do the job. if not then the C to B breakdown ocured blowing the whole thing. OR maybe the diodes cannot absorbe the energy from the coil then blewy.

 

maybe you lost the ground of 7805, I'm just guessing .

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I'd check the PCB for errors. I use AVR, mostly Attiny13L, which at 88 cents each, and still learning... I tend to abuse the hell out of them, and haven't damaged one yet.

 

i have one fact now , my microcontrollelr is over......but i wonder why that had happened although i have this stupid IC4050

i have another PCB for the same schematic , it works very well , without the diodes i think all will go wrong like the state i'm in .

have another question : what if i have a stepper motor needs 12 volt , can i cnonnect it's fifth terminal to this 12 Volt ..

or what i have to do

thanks you

 

Are you using the 4050 as buffer between the PIC output and the TIP120's
If Yes, the 4050 isnt suitable for a 12V base connection to the TIP120!!!

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/