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IC to protect against voltage faults?

M

Mike V.

Jan 1, 1970
0
I've heard somewhere of a circuit (or IC?) that will turn off your
voltage source to a motor if the microcontroller that controls the
system malfunctions (e.g. latches up). If a square wave is not
continuously applied, then the voltage turns off. For example, in the
case of a latched-up micro, then the voltage source supplying the
motor will get switched off. Is there any commercial IC to accomplish
this? If not, I think it was on Electronics Design magazine, but I
have no idea which issue it is.
 
M

Martin Riddle

Jan 1, 1970
0
The Dallas ds1232(?) comes to mind, but its a reset chip, uc supervisor.
You can also use a retriggerable one shot (74123) and trigger it via an interrupt routine. This you can set the time-out to your
liking.

Cheers
 
B

Ban

Jan 1, 1970
0
Mike said:
I've heard somewhere of a circuit (or IC?) that will turn off your
voltage source to a motor if the microcontroller that controls the
system malfunctions (e.g. latches up). If a square wave is not
continuously applied, then the voltage turns off. For example, in the
case of a latched-up micro, then the voltage source supplying the
motor will get switched off. Is there any commercial IC to accomplish
this? If not, I think it was on Electronics Design magazine, but I
have no idea which issue it is.

Do you mean a watchdog timer? Google for it, there are hundreds around. It
will give out a reset signal, which you can route to any convenient points
in your circuit.
 
M

Mike V.

Jan 1, 1970
0
Ban said:
Do you mean a watchdog timer? Google for it, there are hundreds around. It
will give out a reset signal, which you can route to any convenient points
in your circuit.

Martin and Ban, it's not a voltage supervisor nor watchdog that I have
in mind. I don't want to reset the microcontroller due to a low
voltage or watchdog timeout. However, I want to do something similiar
to hardware that controls whether a voltage source to the motor is
turned on or off. If the micro latches up, and the motor is turned on
at full speed, then I can cause physical damage with a runaway motor.
 
J

Joerg

Jan 1, 1970
0
Hi Mike,

If this is a cost sensitive application you could do it discrete. Use
the square wave pulses to keep a capacitor charged which in turn keeps a
FET conducting. Then when the signal disappears a bleeder resistor (or
the uC port itself via the charge resistor) discharges the cap and the
FET turns off. This would not be a very graceful turn-off but it might
suffice in some applications. Turn on and turn off times can be chosen
by the respective RC ratios. Sometimes a diode in the charge up path is
needed depending on the duty cycle of the "uC alive" indicator signal.

Regards, Joerg
 
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