on SurfBoard SIP Adapter

with a Potentiometer Dimmer Circuit

This design eliminates the need to etch a circuit board for the small surface mount chip. Peripheral components are large "through hole" items soldered together on a blank board.

Results for Max 1674 are similar.

i, amps
(two white leds in parallel) |
dV, volts, across
R=.333 ohms |
dV led, volts |

0 | 0 | 2.40 |

.010 | .0033 | 3.09 |

.020 | .0066 | 3.25 |

.050 | .0167 | 3.55 |

i, amps
(1 watt Luxeon Star) |
dV across
R=.333 ohms |
Vled |

0 | 0 | 2.40 |

.100 | .033 | 2.87 |

.200 | .066 | 2.99 |

.275 | .092 | 3.08 |

.300 | .100 | 3.10 |

.325 | .108 | 3.12 |

.350 | .117 | 3.14 |

note: R is three 1 ohm resistors in parallel.

1/R = (1/1) + (1/1) + (1/1) = 3, so R = .333 ohms

Output Voltage IC Operating Temperature, Degrees C Degrees F 2.58 38 100 2.94 46 114 3.11 54 129 From Max1797 and Max 1674 data sheet:

Ambient temperature range is -40 C to 85 C, with a maximum junction temperature of 150 C

Efficiency:dVin = .185 volts = I R

I = dV/R = .185/.333 = .555 amps

V bat (2C nimh) under load = 2.34 volts after going through R = .333 ohms

Vout to led under load = 3.15 volts, I led = .365 amps (extrapolated from data above)

P = V I

Pout/Pin = (3.15)(.365)/(2.34)(.555) = .885