7812 and 7805 for powering a stamp and 2 IC''s
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Hi,
I'm using a 7812 regulator to power a stamp from a 20v source. I'm
also using a 7805 to power to IC's from the 12V from the 7812.
My problem is that my 5v from the 7805 keeps drifting low, it starts
at around 4.5 and will drift slowly down to 3.0v . I can't figure out
why this is happening, I've tried other 7805's and I get the same
result. The circuit works fine off my bench 5v supply. I'm thinking
that this could be happening because I'm not drawing enough current
that it can't keep a stable voltage with a real low power draw.
The only thing the 7805 is powering is 2 IC's (7 seg driver, RS232
level converter) 2 digit 7 seg display and one bi-color LED. I'm
guessing my total current load is less than 100ma perhaps more like
50ma.
Is their a minimum current load for the 7805 or 7812 regulators?
Should I just hang a shunt resistor on the 5v to load it down?
Thanks for you help
Tim
I'm using a 7812 regulator to power a stamp from a 20v source. I'm
also using a 7805 to power to IC's from the 12V from the 7812.
My problem is that my 5v from the 7805 keeps drifting low, it starts
at around 4.5 and will drift slowly down to 3.0v . I can't figure out
why this is happening, I've tried other 7805's and I get the same
result. The circuit works fine off my bench 5v supply. I'm thinking
that this could be happening because I'm not drawing enough current
that it can't keep a stable voltage with a real low power draw.
The only thing the 7805 is powering is 2 IC's (7 seg driver, RS232
level converter) 2 digit 7 seg display and one bi-color LED. I'm
guessing my total current load is less than 100ma perhaps more like
50ma.
Is their a minimum current load for the 7805 or 7812 regulators?
Should I just hang a shunt resistor on the 5v to load it down?
Thanks for you help
Tim