emergency lamp circuit problem


Posted on Feb 4, 2014

I think the zener diode is not producing enough current on its breakdown state to turn on the transistor. I tried removing the resistor R2 but still won`t work. Can you help me how to make this work First, the zener looks like the voltage selection might be too high. depending on the tolerance of the zener it may not regulate the o


emergency lamp circuit problem
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utput voltage because the drop is too high so it never conducts. This might work as long as the zener is the right voltage though. Third, T2 may have to be a higher current transistor or Darlington if the LEDs combined current draw is significant. There`s no current rating for the LEDs so it is hard to tell. And when T2 is a single transistor we`d have to see if R15 is low enough to turn it on properly. My circuit designs should be regarded as experimental. Although they work in simulation, their component values may need altering or additional components may be necessary when the circuits are built. Due safety precautions should be taken with any circuit involving mains voltage or electrostatic-sensitive components. But as is, R15 may have to be lowered in value because the min gain of the BD140 is spec`d quite low, and i see now that the LEDs are probably EACH being driven at around 50ma, so that`s 600ma collector current roughly. In addition to that, a resistor across the input of the LM317 is a good idea too to make sure T2 turns on fully. With R16 a lower value and VR1 adjusted all the way up, the 6v, 4. 5AHr battery might charge OK. The zener will prevent overcharging if it is sized right, but then again i would not want my battery charging all the time as many of these lights (including commercial units) do. The battery dries up. Well, we have on the one hand the fact that we need to charge the battery with a decent...




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