Vb = 4v
Va = 9v
Ic = 280 mA (while in LOW state)
Ic = 0.05 mA (while in High Z state)
if this helps at all
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Vb = 4v
Va = 9v
Ic = 280 mA (while in LOW state)
Ic = 0.05 mA (while in High Z state)
if this helps at all
|
You need to use an NPN transistor to drive R3 not the PIC.
Because the PIC is powered from 4V the voltage on its pins cannot exceed 4.6v due to internal protection diodes. This means that even when in its hi-z state current will still be flowing via R3 which would explain why you stil have current flowing even when it is supposed to be off.
Keith
www.diyha.co.uk
www.kat5.tv
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Keith is 100% correct. The base of Q2 would need to be at the same level as Va in order for it to switch off. 0.6v or more below Va would mean that it's biased on.
You will find that in its current form Q2 is actually always on.
Trent Jackson
Last edited by T.Jackson; - 8th April 2007 at 16:07.
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I'll try that solution as soon as i can and get back to you to see if it worked out. but everything seems logical thanks.
jose
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The NPN Transistor driving R3 works fine. thank you all for your help it is greatly appreciated!
jose
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if you put a resistor on the battery for a short period you can decrease surface charge a lot and get an even more accurate reading (closer to actual charge held) on the battery
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