Lead Acid Battery
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Do I need a regulator or something similar between my lead acid battery and what I am powering?
Hey,
I have a 12V DC Lead Acid Battery and I am using it to power 2 x 6V pumps that I will power in series - I am just wondering if I need something between the battery and the pumps? like a regulator?
Could something please recommend an appropriate circuit set up and the more detail the better, as I really have no clue myself!
Thanks,
Jen
The pumps use the same voltage but different current levels, will this be a problem?
A fuse is a good idea in case there's a fault. Not 100% sure on what it's rating would need to be because motors draw more when starting then when running. 12V automotive fuses should be cheep enough to determine experimentally which fuse wont blow under normal running conditions
As BillRuss said, one motor could end up taking the lions share of the voltage and that could cause problems. As each motor is 6V and the supply is 12, ideally the voltage between the motors should be at a voltage half way between that of the supply. If this voltage is higher or lower than it should be ie 6V , it's probably best to shut the circuit down. Easiest way of doing this would be to provide a low resistance path and blow the fuse ie a crowbar circuit A voltage that is exactly half way between the supply voltage can be produced by a potential divider. Perhaps connect the coil of highly rated relay between the potential divider, and in between the motors. If the voltage across the coil is sufficient a current will flow, and the relay should shut. If the relay's contacts are across the supply (AFTER the fuse and wired to short the supply) closing the relay should hopefully blow the fuse under the fault condition of "unequal voltage across the motors".
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Same voltage/different current means different resistance as R=V/I. As wired in series the current flow has to be the same through both pumps. The only way the pumps can equalise the current flow is by altering the voltage drop across themselves. The pump which normally draw more current, will try to draw less current, by droping less voltage (V=IR). The pump which normally draw less current (the higher resistance one) will increase the voltage drop across itself in an attempt to draw more current, and become overloaded.
So yes it's likely to be a problem if the motors are ran in series off 12V !
You should be able to use a buck converter to half the voltage, and then run the motors in parrallel from it's output.
http://en.wikipedia.org/wiki/Buck_converter
555 astable "square wave" generate should provide the 50% duty cycle needed as a drive signals for halving a voltage
http://en.wikipedia.org/wiki/555_timer_IC#Astable_mode
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