L
Lord Garth
Guest
<hboothe@gte.net> wrote in message
news:1110984084.204853.29530@f14g2000cwb.googlegroups.com...
close to 2.4 volts open circuit. That means without anything attached
to the output of the voltage regulator. Given an input of 13.8V and an
output of 2.4V, that means the 317 is going to loose 11.4 volts across
itself. It will need a heatsink since that is quit a bit of difference.
Make it
reasonably large.
Now that you have created the proper voltage, you can regulate the current.
The second regulator will loose some voltage across itself as well so be
prepared to go back and adjust the voltage regulator to make up for the loss
on the current regulator. Ultimately, you should read the output of the
open circuit current regulator to be close to 2.4 volts and if connected to
a battery, the current should be limited to 120mA for a .1C assuming 1200mAH
sub C cells.
You need both conditions to do this properly.
Too high of a voltage applied across the battery will damage that battery.
The way one sets up bench power supply is to adjust the open circuit voltage
and then set the current limit to zero, short the supply and SLOWLY turn up
the
current limit until the desired level is reached.
news:1110984084.204853.29530@f14g2000cwb.googlegroups.com...
The chargers output voltage is not 'stiff' so you need to measureHey, Garth, the voltage across the positive and negative leads of the
charger (while actually charging) is 2.6v (which I think means that I'm
sinking all available voltage EXCEPT 2.6 volts. The voltage across the
leads of the device with the driver NOT attached, so it's open circuit
potential is 13.6 (approx.) volts. I ran the unit for a while last
night without the housing of the driver getting hot or even warm, but
the LM317 sure gets hot. I set one device up as a constant voltage
device, as I think I mentioned in one of my posts and it got hot, too.
I still don't know if I should be setting this thing up as a constant
voltage or a constant current device, or if I should be looking for
some different technology to do this. If it's constant current, won't
it do just that, remain constant so, say the driver's battery is
getting fully charged so it's current tries to drop (it's drawing less
current), won't the setup of the LM317 as a constant current device
just increase voltage to still manage the same amount of current
output? With the constant voltage device it would seem like it
couldn't increase the current because it can't increase the voltage, so
that might be better, but it was getting hot, too.
The heat tells me that maybe the problem is inherent to this device
trying to dissipate/sink the difference between a 13.8v car system and
a 2.4v driver. It would help if I knew a lot more about electronics,
and it's frustrating not knowing this stuff any better than I do; I
fear that my ingnorance may be preventing me from seeing or
understanding some simple thing that would make this clear.
Anyway, thanks for your help and time.
--HC
close to 2.4 volts open circuit. That means without anything attached
to the output of the voltage regulator. Given an input of 13.8V and an
output of 2.4V, that means the 317 is going to loose 11.4 volts across
itself. It will need a heatsink since that is quit a bit of difference.
Make it
reasonably large.
Now that you have created the proper voltage, you can regulate the current.
The second regulator will loose some voltage across itself as well so be
prepared to go back and adjust the voltage regulator to make up for the loss
on the current regulator. Ultimately, you should read the output of the
open circuit current regulator to be close to 2.4 volts and if connected to
a battery, the current should be limited to 120mA for a .1C assuming 1200mAH
sub C cells.
You need both conditions to do this properly.
Too high of a voltage applied across the battery will damage that battery.
The way one sets up bench power supply is to adjust the open circuit voltage
and then set the current limit to zero, short the supply and SLOWLY turn up
the
current limit until the desired level is reached.