A load absorbs 250mA at 12V and i need to generate voltage sags of 800ms on the 12V power supply.
With a NE555 as a monostable, i get a positive pulse of 800ms.
This pulse is the input of a NPN BC639 that reverse its polarity on its collector, connected to the 12V with a 220 Ogn resistor.
The pulse is then applied to the base of a BU810 (NPN).
The 250mA load is connected between +12V and the BU810 collector, used as a switch.
The emitters are connected to 0V (GND).
I expected to have a good switching on the collector of the BU810, from saturation to interdiction,
but with a scope on the collector i see something different.
As the picture shows, the ON OFF transition is very smoothing: something is not working well
but i don't understand what.
The load is an electronic board with some electrolytic capacitors on the +12V power supply (120uF).
It could be schematized as a resistor with a capacitor in parallel.
With a NE555 as a monostable, i get a positive pulse of 800ms.
This pulse is the input of a NPN BC639 that reverse its polarity on its collector, connected to the 12V with a 220 Ogn resistor.
The pulse is then applied to the base of a BU810 (NPN).
The 250mA load is connected between +12V and the BU810 collector, used as a switch.
The emitters are connected to 0V (GND).
I expected to have a good switching on the collector of the BU810, from saturation to interdiction,
but with a scope on the collector i see something different.
As the picture shows, the ON OFF transition is very smoothing: something is not working well
but i don't understand what.
The load is an electronic board with some electrolytic capacitors on the +12V power supply (120uF).
It could be schematized as a resistor with a capacitor in parallel.
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