Lynxmotion Tech Support

hi there,


Lately I run in a little problem; botboard pin 10 ( I use it as a PWM output ) doesn't give any output signal anymore ( I had my scoopy on it)Pin 10 and Pin 11 both do the same; I use a simple test program now.. Pin 11 keeps working normal, but Pin 10 died.. And the processor it self seems to give smoke signals after a while.. ( I tought to see it one time)

On both Pins are two BS170's parallel connected. Trough them I power two 12V motors ( one BS170 is just to light for both motors)

If i would turn the processor now on, with everything connected, Pin 10 would work for a while.. after half a minute the output signal is compleet gone. Also when I dont connect anything, only scope the signal then the same thing happens. (Pin 11 keeps working normal at all time.) At all times on both pins the same electronic circuit was connected.
here are the things that I can think of that could cause the break down.

1. The output current is to big.
2. By mistake the Pin got connected to ground.
3. By mistake the Pin got connected to 12V.

I already ordered a new one, but I dont wanne put it in before im sure that it will not happen again..

Does anybody has a clue about what caussed it? or had the same problem as well?


Many thanks in advance!

Robert

Post your circuit.

Do you have a series resistor in lead to output pin?

Alan KM6VV

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Alans suggestion is probably the best option. Add a current limiting resistor. Should also protect against possible over voltages as well to some extent. I've seen pins killed but never saw one work and then fail and then work again later.

_________________
Basicmicro

here is the circuit:


its a pretty straight forward circuit, founded all over the net. On most pages on the net "they" also say that the resistor in serie with the BS170 is not needed cause the input has already a high resistor value. I dont know anymore why i choosed a 15K resistor..

I tried it now again, but now the output is really gone.. a little bit of the pwm signal is still visable, so its still not totally gone...??


thnx for the quick reply!

well, as nobody ever experienced the same thing.. then ill just put a new processor in when its arrives.

just some info:

I had the working Pin running half the day with the circuit above. I only removed the resistor, so putted the BS170's straight to the pin,
it keeps working fine..


Robert

Not going to use the resistors?

Alan KM6VV

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Yes I will, I will go with a 10K resistor, and maybe a diode in serie as well, gonna try that on the broken atom.. you think it will bring something? The diode i mean..

Robert

Probably don't need the diode.

Alan KM6VV

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