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Project:SpeedAdjustableBikeLight: Difference between revisions

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Project:SpeedAdjustableBikeLight (view source)

Revision as of 00:41, 5 May 2012

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→‎Voltage regulator for the MCU
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==Voltage regulator for the MCU==
==Voltage regulator for the MCU==
Needs to operate of a widely varied supply voltage. The dynamo generates a voltage proportional to the bike speed. Potentially reaching hundreds of volts. And the higher the voltage climbs, the more power I can use in the LEDs! Many components to deal with 0.5A are specced at about 40 to 60V - so that is a very high limit for the working voltage. A chain of 6 LEDs would need 24v. My plans are for 3 LEDs in a chain - so 20V is a good target.
Needs to operate of a widely varied supply voltage. The dynamo generates a voltage proportional to the bike speed. Potentially reaching hundreds of volts. And the higher the voltage climbs, the more power I can use in the LEDs! Many components to deal with 0.5A are specced at about 40 to 60V - so that is a very high limit for the working voltage. A chain of 6 LEDs would need 24v. My plans are for 3 LEDs in a chain - so 20V is a good target.
MCU Vcc of 3V (supporting 10MHz clock) these are some possible regulators.
* [http://uk.farnell.com/national-semiconductor/lm2936mp-3-0-nopb/ic-ldo-volt-reg-3v-50ma-sot-223/dp/1496125 3.0v, 200mV drop out, 50 mA, max 40v supply] from a 3.2V diode bridge supply :). It is a 4 pin SMD device for £1.60.
* [http://uk.farnell.com/national-semiconductor/lp2980im5-3-0-nopb/ic-ldo-volt-reg-3v-50ma-5-sot-23/dp/1559574 3.0v, 120mV drop out, 50mA, 16V max supply] will do above from a 3.12V supply, but restricts me to chains of fewer than four LEDs. £0.46
* [http://uk.farnell.com/on-semiconductor/lp2950cz-3-0g/ic-ldo-volt-reg-3v-0-1a-to-92-3/dp/1354344 3v, 350mV drop out, 100mA, 30V max supply] is a small 3 pin through hole package for £0.46. Required voltage is now 3.35V :(.
MCU Vcc of 2.5V (max clock of 8Mhz)
* [http://uk.farnell.com/linear-technology/lt1761es5-2-5-pbf/ic-ldo-volt-reg-2-5v-0-1a-5-tsot/dp/1531492 a 2.5V, 300mV drop out, 100mA, 20V max power supply] will allow operation at 2.8V:).


==voltage regulator==
==voltage regulator==
Daveb
153

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