Milliamps and voltage help please

[Robin Hewitt]

Problem with a 12 Volt battery is you will get over voltage when fully charged. 9 Volts really is the best bet, unless you pop in a regulator.

Can you get a 9 Volt regulator or do they leap from 6 to 12? 12 would very quickly have the same problem, even if low drop out.

[irving2008]

Problem with a 12 Volt battery is you will get over voltage when fully charged. 9 Volts really is the best bet, unless you pop in a regulator.

Can you get a 9 Volt regulator or do they leap from 6 to 12? 12 would very quickly have the same problem, even if low drop out.

Yep, LM2940CT-9 Buy Low Dropout Voltage Regulators 1A,9V,LDO Voltage Regulator,LM2940CT-9.0 National Semiconductor LM2940CT-9.0/NOPB online from RS for next day delivery. 9v out @ 1A max, max 0.2v dropout @ 100mA, typ 0.5v @ 1A. Only £1.33 each. They do a 10v one as well.

As an alternative MC2941 http://www.rapidonline.com/Electroni...egulator-65305 @ £1.75 will also do the same, but is programmable for any output voltage with 2 resistors.

Either will handle 12v -> 9v @ 400mA with no heatsink (tho case will be > 90degC so hot!) but a small clip on heatsink would be advisable (or just a couple of sq in of ally) if using a lead acid cell or other battery thats at 13.6v fully charged