L298 exploding, after having worked perfectly

Dave schrieb:
> What are the most probable reasons for burning the L298? (sense,
> clock???)

Your diodes are ok? A missing diode kills a L298 with ease.
L298 mounted on Heatspreader?
Same Supply after changing case?
:-)

Yes, the L298s are mounted on heatspreader, supply is the same as 
before. I checked the diodes with a multimeter. They were permeable from 
one side and blocked from the other. Seem to be normal, but maybe I 
remove them and check them individually.

Thank you

Dave

Yes, they are isolated. I mounted a seperate heatsink on every L298. 
There is no connection.

Thanks for the tipp

Well, I think I have to reassemble the boards and make sure everything 
works fine again?? Maybe it's a wrong connected voltageconnection or a 
problem with the diodes.

The heatsinks are not connected and not mounted in the case. They are 
freestanding in the case.

Thanks for all your support, guys. I'm gonna test it again (and burn 
more L298?? ;-) ).

I can't see the problem right now, let's hope it will work again. From 
the outside everything seems to be ok!

Dave

Thank you for your guesses and help

I reassembled the boards and the cables/connections, and that time I 
checked everything more than twice (make sure that there is no unwanted 
connecion). I think too that there was a problem somehow with ground or 
just something badly connected.


I was really scared to test them again because when they explode it is 
quite load (I use a 24V/10A power supply)
but finally I did it the controllers are working perfectly again. ;-)

Thanks for all

The next time I am more carefull when changing the case.

Dave

The power supply is an industrial supply (TRACO). It has a fuse for 10A. 
On the controller boards I have fuses too : 5A

I don't have the right fuses at home right now, but I will buy some 3A 
fuses soon.

Do you think it's better to switsch on the L298s over enable input 
instead of directly plugging in the power supply(enable always on high)?


Thanks

schodavi schrub:
> Do you think it's better to switsch on the L298s over enable input
> instead of directly plugging in the power supply(enable always on high)?

Datasheet [1] suggests (page 7/application information):

1

Turn-On and Turn-Off : Before to Turn-ON the Sup-

2

ply Voltage and before to Turn it OFF, the Enable in-

3

put must be driven to the Low state.

I guess weird things can happen if you don't. Like escaping magic smoke 
;-)

HTH

[1] 
http://www.datasheetarchive.com/pdf-datasheets/Datasheets-5/DSA-95442.html

g457 schrieb:
> Datasheet [1] suggests (page 7/application information):Turn-On and Turn-Off : 
Before to Turn-ON the Sup-
> ply Voltage and before to Turn it OFF, the Enable in-
> put must be driven to the Low state.
> I guess weird things can happen if you don't. Like escaping magic smoke
> ;-)


You are right, but before/during the explosions, I was always switching 
on and off the L298 via enable input. Just today after the reassemble I 
forgot it and directly switched on the power supply. But it didn't cause 
any damage at all.

This is probably a safety feature for people who are using simpler power 
supply (which can have a voltage top when switching on/off (induction). 
Mine was really expensive (but I got it for free from a friend ;-)

PS: I have a current-limited power supply but the problem is that it 
isn't really powerful.  Maybe I have to buy an additional (better) one??

PS: There was a lot of noise from the choppers during operation, so I 
replaced some GND - wires with thicker ones. Now the noise is much lower 
(but still there of course). I think it was a problem with GND 
connection or supply voltage wrongly connected. Finally it is working 
now. I also added a mechanical switch to manually control the enable 
inputs.

That's it. Now I can do some milling again ;-)!

Thanks for the great support and all your help.