Raise the bridge or lower the water?
Posted: Mon Dec 14, 2015 12:38 pm
I have an old vacuum cleaner with a beater brush that I had to rebuild about two years ago. (a plastic on plastic bushing wore out from a couple decades of use).. It works fine now and no cyclones or v6 electric motors are involved. It has a feature that i almost forgot about, red and green lamps that indicate if the vacuum is still picking up dirt even if carpet looks clean... kind of slick feature, that I rediscovered when I put a battery in it a couple months ago,,, IIRC I put a new battery in my smoke alarm, and put the used battery in my dirt detector, but now it is dead as a door nail (3V).
Oddly this line cord vacuum uses a 9V battery for this feature, I was suspicious that the circuit may leak current when off.. but no, however when turned on it draws about 20mA from a fresh 9V battery... that is a bunch of current from a 250mAh battery.
So do I re-engineer the detector and display to reduce current draw, or add an AC-DC supply to the vacuum. Even if i reduce the current draw in half that is still not great battery life...these generally use a lamp and optical sensor and latch the lamp output when any dirt blocks and perturbs the light pickup. This is surprisingly sensitive.
I found a 300ma DC PS on the WWW for $2.79
but with $6.50 shipping 
(I probably have an old charger sitting around somewhere that puts out enough power,,, I can add a diode and cap if charger is AC.)
Probably a little Rube Goldberg to tap into the vacuum cleaners line cord, but I can kluge the PS on the outside of the vacuum or inside by the bag compartment if it doesn't get too hot... It doesn't need to look pretty...
I just put a new battery in it so I don't have to make a decisions for a while.
JR
Oddly this line cord vacuum uses a 9V battery for this feature, I was suspicious that the circuit may leak current when off.. but no, however when turned on it draws about 20mA from a fresh 9V battery... that is a bunch of current from a 250mAh battery.
So do I re-engineer the detector and display to reduce current draw, or add an AC-DC supply to the vacuum. Even if i reduce the current draw in half that is still not great battery life...these generally use a lamp and optical sensor and latch the lamp output when any dirt blocks and perturbs the light pickup. This is surprisingly sensitive.
I found a 300ma DC PS on the WWW for $2.79
but with $6.50 shipping (I probably have an old charger sitting around somewhere that puts out enough power,,, I can add a diode and cap if charger is AC.) Probably a little Rube Goldberg to tap into the vacuum cleaners line cord, but I can kluge the PS on the outside of the vacuum or inside by the bag compartment if it doesn't get too hot... It doesn't need to look pretty...
I just put a new battery in it so I don't have to make a decisions for a while.
JR