Driver Ckt

[yatishw]

HI,
I need CKT to Drive series of LEDs (6/8 nos) through NO/NC contact with no supply flow through NO/NC contact

 

[Reloadron]

You aren't telling anyone anything? Maybe it is just me but your ststement:

I need CKT to Drive series of LEDs (6/8 nos) through NO/NC contact with no supply flow through NO/NC contact

makes absolutely no sense. What LEDs? What are the LED ratings like voltage & current? Normally Open / Normally closed with no supply flow? What do you mean?

Ron

 

[yatishw]

I want to turn on LEDs with trigger from equipment. Equipment normally has 'Normally Open' contact when it turns to 'Close' LED should be turned ON. But i don't want any supply driven through equipment.

 

[colin55]

You need an external supply and treat the no contacts as a switch.

 

[UnloadedQ]

Can't be done without some current flow, but that current can me miniscule for the N.O. contacts. I assume they are all sharing the one common terminal and have N.O. connections on other terminals. This is common on a lot of Fire Alarm panels and CNC machine controllers. These contacts are usually either rated for 100mA to 10A and from +5 to +50 volts DC. High voltage and high current outputs usually don't have a common terminal for the contacts.

If you can live with approximately 10mA of current flow at 9VDC, use a 9V battery and connect the negative (-) terminal of the battery to the common. Connect each cathode of the LEDs to the contacts. Connect each LED anode to a 1/4 Watt resistor (see below). Connect the other end of all the resistors together. Connect the common resistor joint to the positive (+) terminal of the battery. If you need a longer running affair, use a 5 or 12V wall bug rated for at least 1/2A (500mA). The value of the resistor is then (VDC - VLED) / 0.01 VDC is the supply voltage, VLED is the LED voltage (1.8 for Red, 2.9 for Green, 3.9 for Blue) and the 0.01 is 10mA. Using a 5V wall bug, this works out to 330 Ohms for Red, 220 for Green and 110 Ohms for Blue - be careful, blue and green LEDs are super efficient, so 1K to 3,3K might be enough .

I can post a circuit using a transistor if less than 10mA of current is needed.