LED-Circuits 4


Posted on Feb 6, 2014

This is a constant current source using a FET. This is the most simple replacement to series resistor to limit current. The N-Channel FET BF256C can give 15mA current. Simple Methods Before you get to use chips, experiment with some methods, which will help you learn about the LEDs better. The first is just One Resistor in series. This is to Limit


LED-Circuits 4
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the max current in a Series LED Chain. If you have a Regulated Supply with a Fixed Voltage, then you can use this method. Let us take a 12V SMPS, Each HB White LED has a drop of Read More This circuit is derived from a Siemens Application Note 1974. This circuit uses common components of today. The circuit is here as it is of high educational value. I have not tested it. You can simulate and test` or wire it up and try` and let me know how it worked. The Circuit is also a simple analog to digital converter. You can use optos in place of LEDs. T1 and T2 make a differential amplifier. T3, T4 and T5 driving the LEDs are comparators. Now to learn more on how they work you have to study circuits at 4QD-TEC Read More This Circuit helps in the monitoring of mains supply voltage. It does not use a isolation step down transformer. This has to be constructed only by skilled people with knowledge of safety requirements. C1 limits the current and drops most of the voltage. The zener regulated supply is for the chip. C2 can be raised to 220uF or more if required. The bar mode display may consume more power. R2-R3-R5-R6 form a voltage divider to get a sample of the input voltage, D11-C3 get the DC value. Adjust R5 preset with a log Plastic tweaker to get the 5th led Read More This Circuit helps in the monitoring of mains supply voltage. It does not use a isolation step down transformer. This has to be constructed only by skilled people...




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